selective oxidation reduction: Topics by Science.gov

Sample records for selective oxidation reduction

NOX REMOVAL WITH COMBINED SELECTIVE CATALYTIC REDUCTION AND SELECTIVE NONCATALYTIC REDUCTION: PILOT- SCALE TEST RESULTS

EPA Science Inventory

Pilot-scale tests were conducted to develop a combined nitrogen oxide (NOx) reduction technology using both selective catalytic reduction (SCR) and selective noncatalytic reduction (SNCR). A commercially available vanadium-and titatnium-based composite honeycomb catalyst and enh...
INDUSTRIAL BOILER RETROFIT FOR NOX CONTROL: COMBINED SELECTIVE NONCATALYTIC REDUCTION AND SELECTIVE CATALYTIC REDUCTION

EPA Science Inventory

The paper describes retrofitting and testing a 590 kW (2 MBtu/hr), oil-fired, three-pass, fire-tube package boiler with a combined selective noncatalytic reduction (SNCR) and selective catalytic reduction (SCR) system. The system demonstrated 85% nitrogen oxides (NOx) reduction w...
Treatment of power utilities exhaust

DOEpatents

Koermer, Gerald [Basking Ridge, NJ

2012-05-15

Provided is a process for treating nitrogen oxide-containing exhaust produced by a stationary combustion source by the catalytic reduction of nitrogen oxide in the presence of a reductant comprising hydrogen, followed by ammonia selective catalytic reduction to further reduce the nitrogen oxide level in the exhaust.
Highly Selective TiN-Supported Highly Dispersed Pt Catalyst: Ultra Active toward Hydrogen Oxidation and Inactive toward Oxygen Reduction.

PubMed

Luo, Junming; Tang, Haibo; Tian, Xinlong; Hou, Sanying; Li, Xiuhua; Du, Li; Liao, Shijun

2018-01-31

The severe dissolution of the cathode catalyst, caused by an undesired oxygen reduction reaction at the anode during startup and shutdown, is a fatal challenge to practical applications of polymer electrolyte membrane fuel cells. To address this important issue, according to the distinct structure-sensitivity between the σ-type bond in H 2 and the π-type bond in O 2 , we design a HD-Pt/TiN material by highly dispersing Pt on the TiN surface to inhibit the unwanted oxygen reduction reaction. The highly dispersed Pt/TiN catalyst exhibits excellent selectivity toward hydrogen oxidation and oxygen reduction reactions. With a Pt loading of 0.88 wt %, our catalyst shows excellent hydrogen oxidation reaction activity, close to that of commercial 20 wt % Pt/C catalyst, and much lower oxygen reduction reaction activity than the commercial 20 wt % Pt/C catalyst. The lack of well-ordered Pt facets is responsible for the excellent selectivity of the HD-Pt/TiN materials toward hydrogen oxidation and oxygen reduction reactions. Our work provides a new and cost-effective solution to design selective catalysts toward hydrogen oxidation and oxygen reduction reactions, making the strategy of using oxygen-tolerant anode catalyst to improve the stability of polymer electrolyte membrane fuel cells during startup and shutdown more affordable and practical.
Efficient photocatalytic selective nitro-reduction and C-H bond oxidation over ultrathin sheet mediated CdS flowers.

PubMed

Pahari, Sandip Kumar; Pal, Provas; Srivastava, Divesh N; Ghosh, Subhash Ch; Panda, Asit Baran

2015-06-28

We report here a visible light driven selective nitro-reduction and oxidation of saturated sp(3) C-H bonds using ultrathin (0.8 nm) sheet mediated uniform CdS flowers as catalyst under a household 40 W CFL lamp and molecular oxygen as oxidant. The CdS flowers were synthesized using a simple surfactant assisted hydrothermal method.
MERCURY OXIDATION PROMOTED BY A SELECTIVE CATALYTIC REDUCTION CATALYST UNDER SIMULATED POWDER RIVER BASIN COAL COMBUSTION CONDITIONS

EPA Science Inventory

A bench-scale reactor consisting of a natural gas burner and an electrically heated reactor housing a selective catalytic reduction (SCR) catalyst was constructed for studying elemental mercury oxidation under SCR conditions. A low sulfur Power River Basin (PRB) coal combustion ...
Optimizing C–C Coupling on Oxide-Derived Copper Catalysts for Electrochemical CO 2 Reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lum, Yanwei; Yue, Binbin; Lobaccaro, Peter

Here, copper electrodes, prepared by reduction of oxidized metallic copper, have been reported to exhibit higher activity for the electrochemical reduction of CO 2 and better selectivity toward C 2 and C 3 (C 2+) products than metallic copper that has not been preoxidized. We report here an investigation of the effects of four different preparations of oxide-derived electrocatalysts on their activity and selectivity for CO 2 reduction, with particular attention given to the selectivity to C 2+ products. All catalysts were tested for CO 2 reduction in 0.1 M KHCO 3 and 0.1 M CsHCO 3 at applied voltagesmore » in the range from –0.7 to –1.0 V vs RHE. The best performing oxide-derived catalysts show up to ~70% selectivity to C 2+ products and only ~3% selectivity to C 1 products at –1.0 V vs RHE when CsHCO 3 is used as the electrolyte. In contrast, the selectivity to C 2+ products decreases to ~56% for the same catalysts tested in KHCO 3. By studying all catalysts under identical conditions, the key factors affecting product selectivity could be discerned. These efforts reveal that the surface area of the oxide-derived layer is a critical parameter affecting selectivity. A high selectivity to C 2+ products is attained at an overpotential of –1 V vs RHE by operating at a current density sufficiently high to achieve a moderately high pH near the catalyst surface but not so high as to cause a significant reduction in the local concentration of CO 2. On the basis of recent theoretical studies, a high pH suppresses the formation of C 1 relative to C 2+ products. At the same time, however, a high local CO 2 concentration is necessary for the formation of C 2+ products.« less
Optimizing C–C Coupling on Oxide-Derived Copper Catalysts for Electrochemical CO 2 Reduction

DOE PAGES

Lum, Yanwei; Yue, Binbin; Lobaccaro, Peter; ...

2017-07-06

Here, copper electrodes, prepared by reduction of oxidized metallic copper, have been reported to exhibit higher activity for the electrochemical reduction of CO 2 and better selectivity toward C 2 and C 3 (C 2+) products than metallic copper that has not been preoxidized. We report here an investigation of the effects of four different preparations of oxide-derived electrocatalysts on their activity and selectivity for CO 2 reduction, with particular attention given to the selectivity to C 2+ products. All catalysts were tested for CO 2 reduction in 0.1 M KHCO 3 and 0.1 M CsHCO 3 at applied voltagesmore » in the range from –0.7 to –1.0 V vs RHE. The best performing oxide-derived catalysts show up to ~70% selectivity to C 2+ products and only ~3% selectivity to C 1 products at –1.0 V vs RHE when CsHCO 3 is used as the electrolyte. In contrast, the selectivity to C 2+ products decreases to ~56% for the same catalysts tested in KHCO 3. By studying all catalysts under identical conditions, the key factors affecting product selectivity could be discerned. These efforts reveal that the surface area of the oxide-derived layer is a critical parameter affecting selectivity. A high selectivity to C 2+ products is attained at an overpotential of –1 V vs RHE by operating at a current density sufficiently high to achieve a moderately high pH near the catalyst surface but not so high as to cause a significant reduction in the local concentration of CO 2. On the basis of recent theoretical studies, a high pH suppresses the formation of C 1 relative to C 2+ products. At the same time, however, a high local CO 2 concentration is necessary for the formation of C 2+ products.« less
Effect of preparation procedures on catalytic activity and selectivity of copper-based mixed oxides in selective catalytic oxidation of ammonia into nitrogen and water vapour

NASA Astrophysics Data System (ADS)

Jabłońska, Magdalena; Nocuń, Marek; Gołąbek, Kinga; Palkovits, Regina

2017-11-01

The selective oxidation of ammonia into nitrogen and water vapour (NH3-SCO) was studied over Cu-Mg(Zn)-Al-(Zr) mixed metal oxides, obtained by coprecipitation and their subsequent calcination. The effect of acid-base properties of Cu-Mg-Al-Ox on catalytic activity was investigated by changing the Mg/Al molar ratio. Other Cu-containing oxides were prepared by rehydration of calcined Mg-Al hydrotalcite-like compounds or thermal decomposition of metal nitrate precursors. XRD, BET, NH3-TPD, H2-TPR, XPS, FTIR with adsorption of pyridine and CO as well as TEM techniques were used for catalysts characterization. The results of catalytic tests revealed a crucial role of easily reducible highly dispersed copper oxide species to obtain enhanced activity and N2 selectivity in NH3-SCO. The selective catalytic reduction of NO by NH3 (NH3-SCR) and in situ DRIFT of NH3 sorption indicated that NH3-SCO proceeds according to the internal selective catalytic reduction mechanism (i-SCR).
Two component-three dimensional catalysis

DOEpatents

Schwartz, Michael; White, James H.; Sammells, Anthony F.

2002-01-01

This invention relates to catalytic reactor membranes having a gas-impermeable membrane for transport of oxygen anions. The membrane has an oxidation surface and a reduction surface. The membrane is coated on its oxidation surface with an adherent catalyst layer and is optionally coated on its reduction surface with a catalyst that promotes reduction of an oxygen-containing species (e.g., O.sub.2, NO.sub.2, SO.sub.2, etc.) to generate oxygen anions on the membrane. The reactor has an oxidation zone and a reduction zone separated by the membrane. A component of an oxygen containing gas in the reduction zone is reduced at the membrane and a reduced species in a reactant gas in the oxidation zone of the reactor is oxidized. The reactor optionally contains a three-dimensional catalyst in the oxidation zone. The adherent catalyst layer and the three-dimensional catalyst are selected to promote a desired oxidation reaction, particularly a partial oxidation of a hydrocarbon.
Partially oxidized iridium clusters within dendrimers: size-controlled synthesis and selective hydrogenation of 2-nitrobenzaldehyde

NASA Astrophysics Data System (ADS)

Higaki, Tatsuya; Kitazawa, Hirokazu; Yamazoe, Seiji; Tsukuda, Tatsuya

2016-06-01

Iridium clusters nominally composed of 15, 30 or 60 atoms were size-selectively synthesized within OH-terminated poly(amidoamine) dendrimers of generation 6. Spectroscopic characterization revealed that the Ir clusters were partially oxidized. All the Ir clusters efficiently converted 2-nitrobenzaldehyde to anthranil and 2-aminobenzaldehyde under atmospheric hydrogen at room temperature in toluene via selective hydrogenation of the NO2 group. The selectivity toward 2-aminobenzaldehyde over anthranil was improved with the reduction of the cluster size. The improved selectivity is ascribed to more efficient reduction than intramolecular heterocyclization of a hydroxylamine intermediate on smaller clusters that have a higher Ir(0)-phase population on the surface.Iridium clusters nominally composed of 15, 30 or 60 atoms were size-selectively synthesized within OH-terminated poly(amidoamine) dendrimers of generation 6. Spectroscopic characterization revealed that the Ir clusters were partially oxidized. All the Ir clusters efficiently converted 2-nitrobenzaldehyde to anthranil and 2-aminobenzaldehyde under atmospheric hydrogen at room temperature in toluene via selective hydrogenation of the NO2 group. The selectivity toward 2-aminobenzaldehyde over anthranil was improved with the reduction of the cluster size. The improved selectivity is ascribed to more efficient reduction than intramolecular heterocyclization of a hydroxylamine intermediate on smaller clusters that have a higher Ir(0)-phase population on the surface. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr01460g
COST OF SELECTIVE CATALYTIC REDUCTION (SCR) APPLICATION FOR NOX CONTROL ON COAL-FIRED BOILERS

EPA Science Inventory

The report provides a methodology for estimating budgetary costs associated with retrofit applications of selective catalytic reduction (SCR) technology on coal-fired boilers. SCR is a postcombustion nitrogen oxides (NOx) control technology capable of providing NOx reductions >90...
COST OF SELECTIVE CATALYTIC REDUCTION (SCR) APPLICATION FOR NOX CONTROL ON COAL-FIRED BOILERS

EPA Science Inventory

The report provides a methodology for estimating budgetary costs associ-ated with retrofit applications of selec-tive catalytic reduction (SCR) technology on coal-fired boilers. SCR is a post-combustion nitrogen oxides (NOX) con-trol technology capable of providing NOX reductions...
In-situ sequential laser transfer and laser reduction of graphene oxide films

NASA Astrophysics Data System (ADS)

Papazoglou, S.; Petridis, C.; Kymakis, E.; Kennou, S.; Raptis, Y. S.; Chatzandroulis, S.; Zergioti, I.

2018-04-01

Achieving high quality transfer of graphene on selected substrates is a priority in device fabrication, especially where drop-on-demand applications are involved. In this work, we report an in-situ, fast, simple, and one step process that resulted in the reduction, transfer, and fabrication of reduced graphene oxide-based humidity sensors, using picosecond laser pulses. By tuning the laser illumination parameters, we managed to implement the sequential printing and reduction of graphene oxide flakes. The overall process lasted only a few seconds compared to a few hours that our group has previously published. DC current measurements, X-Ray Photoelectron Spectroscopy, X-Ray Diffraction, and Raman Spectroscopy were employed in order to assess the efficiency of our approach. To demonstrate the applicability and the potential of the technique, laser printed reduced graphene oxide humidity sensors with a limit of detection of 1700 ppm are presented. The results demonstrated in this work provide a selective, rapid, and low-cost approach for sequential transfer and photochemical reduction of graphene oxide micro-patterns onto various substrates for flexible electronics and sensor applications.
Formation of Copper Catalysts for CO 2 Reduction with High Ethylene/Methane Product Ratio Investigated with In Situ X-ray Absorption Spectroscopy

DOE PAGES

Eilert, André; Roberts, F. Sloan; Friebel, Daniel; ...

2016-04-04

Nanostructured copper cathodes are among the most efficient and selective catalysts to date for making multicarbon products from the electrochemical carbon dioxide reduction reaction (CO 2RR). We report an in situ X-ray absorption spectroscopy investigation of the formation of a copper nanocube CO 2RR catalyst with high activity that highly favors ethylene over methane production. The results show that the precursor for the copper nanocube formation is copper(I)-oxide, not copper(I)-chloride as previously assumed. A second route to an electrochemically similar material via a copper(II)–carbonate/hydroxide is also reported. In conclusion, this study highlights the importance of using oxidized copper precursors formore » constructing selective CO 2 reduction catalysts and shows the precursor oxidation state does not affect the electrocatalyst selectivity toward ethylene formation.« less
Pyroprocessing of Oxidized Sodium-Bonded Fast Reactor Fuel -- an Experimental Study of Treatment Options for Degraded EBR-II Fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

S. D. Herrmann; L. A. Wurth; N. J. Gese

An experimental study was conducted to assess pyrochemical treatment options for degraded EBR-II fuel. As oxidized material, the degraded fuel would need to be converted back to metal to enable electrorefining within an existing electrometallurgical treatment process. A lithium-based electrolytic reduction process was studied to assess the efficacy of converting oxide materials to metal with a particular focus on the impact of zirconium oxide and sodium oxide on this process. Bench-scale electrolytic reduction experiments were performed in LiCl-Li2O at 650 °C with combinations of manganese oxide (used as a surrogate for uranium oxide), zirconium oxide, and sodium oxide. The experimentalmore » study illustrated how zirconium oxide and sodium oxide present different challenges to a lithium-based electrolytic reduction system for conversion of select metal oxides to metal.« less
ON-LINE DEOXYGENATION IN REDUCTIVE (AND OXIDATIVE) AMPEROMETRIC DETECTION: ENVIRONMENTAL APPLICATIONS IN THE LIQUID CHROMATOGRAPHY OF ORGANIC PEROXIDES

EPA Science Inventory

Cyclic voltammetry was used qualitatively to characterize and determine the feasibility of the oxidation and reduction of selected organic peroxides and hydroperoxides at a glassy carbon electrode. Organic peroxides were determined using reversed-phase high-performance liquid chr...
Ce-Sn binary oxide catalyst for the selective catalytic reduction of NOx by NH3

NASA Astrophysics Data System (ADS)

Liu, Zhiming; Feng, Xu; Zhou, Zizheng; Feng, Yongjun; Li, Junhua

2018-01-01

Ce-Sn binary oxide catalysts prepared by the hydrothermal method have been investigated for the selective catalytic reduction (SCR) of NOx with NH3. Compared with pure CeO2 and SnO2, Ce-Sn binary oxide catalyst showed significantly higher NH3-SCR activity. Moreover, Ce-Sn catalyst showed high resistance against H2O and SO2. The high catalytic performance of Ce-Sn binary oxide is attributed to the synergetic effect between Ce and Sn species, which not only enhances the redox property of the catalyst but also increases the Lewis acidity, thus promoting the adsorption and activation of NH3 species, which contributes to improving the NH3-SCR performance.
Stability of Residual Oxides in Oxide-Derived Copper Catalysts for Electrochemical CO2 Reduction Investigated with 18 O Labeling.

PubMed

Lum, Yanwei; Ager, Joel W

2018-01-08

Oxide-derived (OD) Cu catalysts have high selectivity towards the formation of multi-carbon products (C 2 /C 3 ) for aqueous electrochemical CO 2 reduction (CO 2 R). It has been proposed that a large fraction of the initial oxide can be surprisingly resistant to reduction, and these residual oxides play a crucial catalytic role. The stability of residual oxides was investigated by synthesizing 18 O-enriched OD Cu catalysts and testing them for CO 2 R. These catalysts maintain a high selectivity towards C 2 /C 3 products (ca. 60 %) for up to 5 h in 0.1 m KHCO 3 at -1.0 V vs. RHE. However, secondary-ion mass spectrometry measurements show that only a small fraction (<1 %) of the original 18 O content remains, showing that residual oxides are not present in significant amounts during CO 2 R. Furthermore, we show that OD Cu can reoxidize rapidly, which could compromise the accuracy of ex situ methods for determining the true oxygen content. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
HYBRID SNCR-SCR TECHNOLOGIES FOR NOX CONTROL: MODELING AND EXPERIMENT

EPA Science Inventory

The hybrid process of homogeneous gas-phase selective non-catalytic reduction (SNCR) followed by selective catalytic reduction (SCR) of nitric oxide (NO) was investigated through experimentation and modeling. Measurements, using NO-doped flue gas from a gas-fired 29 kW test combu...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Eilert, André; Roberts, F. Sloan; Friebel, Daniel

Nanostructured copper cathodes are among the most efficient and selective catalysts to date for making multicarbon products from the electrochemical carbon dioxide reduction reaction (CO 2RR). We report an in situ X-ray absorption spectroscopy investigation of the formation of a copper nanocube CO 2RR catalyst with high activity that highly favors ethylene over methane production. The results show that the precursor for the copper nanocube formation is copper(I)-oxide, not copper(I)-chloride as previously assumed. A second route to an electrochemically similar material via a copper(II)–carbonate/hydroxide is also reported. In conclusion, this study highlights the importance of using oxidized copper precursors formore » constructing selective CO 2 reduction catalysts and shows the precursor oxidation state does not affect the electrocatalyst selectivity toward ethylene formation.« less
Surface Selective Oxide Reduction During the Intercritical Annealing of Medium Mn Steel

NASA Astrophysics Data System (ADS)

Jo, Kyoung Rae; Cho, Lawrence; Oh, Jong Han; Kim, Myoung Soo; Kang, Ki Cheol; De Cooman, Bruno C.

2017-08-01

Third generation advanced high-strength steels achieve an excellent strength-ductility balance using a cost-effective alloy composition. During the continuous annealing of medium Mn steel, the formation of an external selective oxide layer of MnO has a negative impact on the coating quality after galvanizing. A procedure to reduce the selective oxide was therefore developed. It involves annealing in the temperature range of 1073 K to 1323 K (800 °C to 1050 °C) in a HNx gas atmosphere. Annealing at higher temperatures and the use of larger H2 volume fractions are shown to make the gas atmosphere reducing with respect to MnO. The reduction of the surface MnO layer was observed by SEM, GDOES, and cross-sectional TEM analysis.
Impacts of halogen additions on mercury oxidation, in a slipstream selective catalyst reduction (SCR), reactor when burning sub-bituminous coal.

PubMed

Cao, Yan; Gao, Zhengyang; Zhu, Jiashun; Wang, Quanhai; Huang, Yaji; Chiu, Chengchung; Parker, Bruce; Chu, Paul; Pant, Wei-Ping

2008-01-01

This paper presents a comparison of impacts of halogen species on the elemental mercury (Hg(0)) oxidation in a real coal-derived flue gas atmosphere. It is reported there is a higher percentage of Hg(0) in the flue gas when burning sub-bituminous coal (herein Powder River Basin (PRB) coal) and lignite, even with the use of selective catalytic reduction (SCR). The higher Hg(0)concentration in the flue gas makes it difficult to use the wet-FGD process for the mercury emission control in coal-fired utility boilers. Investigation of enhanced Hg(0) oxidation by addition of hydrogen halogens (HF, HCl, HBr, and HI) was conducted in a slipstream reactor with and without SCR catalysts when burning PRB coal. Two commercial SCR catalysts were evaluated. SCR catalyst no. 1 showed higher efficiencies of both NO reduction and Hg(0) oxidation than those of SCR catalyst no. 2. NH3 addition seemed to inhibit the Hg(0) oxidation, which indicated competitive processes between NH3 reduction and Hg(0) oxidation on the surface of SCR catalysts. The hydrogen halogens, in the order of impact on Hg(0) oxidation, were HBr, HI, and HCl or HF. Addition of HBr at approximately 3 ppm could achieve 80% Hg(0) oxidation. Addition of HI at approximately 5 ppm could achieve 40% Hg(0) oxidation. In comparison to the empty reactor, 40% Hg(0) oxidation could be achieved when HCl addition was up to 300 ppm. The enhanced Hg(0) oxidation by addition of HBr and HI seemed not to be correlated to the catalytic effects by both evaluated SCR catalysts. The effectiveness of conversion of hydrogen halogens to halogen molecules or interhalogens seemed to be attributed to their impacts on Hg(0) oxidation.
Effect of Precursor Selection on the Photocatalytic Performance of Indium Oxide Nanomaterials for Gas-Phase CO 2 Reduction

DOE PAGES

Hoch, Laura B.; He, Le; Qiao, Qiao; ...

2016-06-01

Nonstoichiometric indium oxide nanoparticles, In 2O 3–x(OH)y, have been shown to function as active photocatalysts for gas-phase CO 2 reduction under simulated solar irradiation. We demonstrate that the choice of starting material has a strong effect on the photocatalytic activity of indium oxide nanoparticles. We also examine three indium oxide materials prepared via the thermal decomposition of either indium(III) hydroxide or indium(III) nitrate and correlate their stability and photocatalytic activity to the number and type of defect present in the material. Furthermore, we use 13CO 2 isotope-tracing experiments to clearly identify the origins of the observed carbon-containing products. Significantly, wemore » find that the oxidizing nature of the precursor anion has a substantial impact on the defect formation within the sample. Our study demonstrates the importance of surface defects in designing an active heterogeneous photocatalyst and provides valuable insight into key parameters for the precursor design, selection, and performance optimization of materials for gas-phase CO 2 reduction.« less
Carbon-neutral energy cycles using alcohols.

PubMed

Fukushima, Takashi; Kitano, Sho; Hata, Shinichi; Yamauchi, Miho

2018-01-01

We demonstrated carbon-neutral (CN) energy circulation using glycolic acid ( GC )/oxalic acid ( OX ) redox couple. Here, we report fundamental studies on both catalyst search for power generation process, i.e. GC oxidation, and elemental steps for fuel generation process, i.e. OX reduction, in CN cycle. The catalytic activity test on various transition metals revealed that Rh, Pd, Ir, and Pt have preferable features as a catalyst for electrochemical oxidation of GC . A carbon-supported Pt catalyst in alkaline conditions exhibited higher activity, durability, and product selectivity for electrooxidation of GC rather than those in acidic media. The kinetic study on OX reduction clearly indicated that OX reduction undergoes successive two-electron reductions to form GC . Furthermore, application of TiO 2 catalysts with large specific area for electrochemical reduction of OX facilitates the selective formation of GC .
Carbon-neutral energy cycles using alcohols

PubMed Central

Fukushima, Takashi; Kitano, Sho; Hata, Shinichi; Yamauchi, Miho

2018-01-01

Abstract We demonstrated carbon-neutral (CN) energy circulation using glycolic acid (GC)/oxalic acid (OX) redox couple. Here, we report fundamental studies on both catalyst search for power generation process, i.e. GC oxidation, and elemental steps for fuel generation process, i.e. OX reduction, in CN cycle. The catalytic activity test on various transition metals revealed that Rh, Pd, Ir, and Pt have preferable features as a catalyst for electrochemical oxidation of GC. A carbon-supported Pt catalyst in alkaline conditions exhibited higher activity, durability, and product selectivity for electrooxidation of GC rather than those in acidic media. The kinetic study on OX reduction clearly indicated that OX reduction undergoes successive two-electron reductions to form GC. Furthermore, application of TiO2 catalysts with large specific area for electrochemical reduction of OX facilitates the selective formation of GC. PMID:29511392
INVESTIGATION OF SELECTIVE CATALYTIC REDUCTION IMPACT ON MERCURY SPECIATION UNDER SIMULATED NOX EMISSION CONTROL CONDITIONS

EPA Science Inventory

Selective catalytic reduction (SCR) technology is being increasingly applied for controlling emissions of nitrogen oxides (NOx) from coal-fired boilers. Some recent field and pilot studies suggest that the operation of SCR could affect the chemical form of mercury in the coal com...
Low-cost optical fabrication of flexible copper electrode via laser-induced reductive sintering and adhesive transfer

NASA Astrophysics Data System (ADS)

Back, Seunghyun; Kang, Bongchul

2018-02-01

Fabricating copper electrodes on heat-sensitive polymer films in air is highly challenging owing to the need of expensive copper nanoparticles, rapid oxidation of precursor during sintering, and limitation of sintering temperature to prevent the thermal damage of the polymer film. A laser-induced hybrid process of reductive sintering and adhesive transfer is demonstrated to cost-effectively fabricate copper electrode on a polyethylene film with a thermal resistance below 100 °C. A laser-induced reductive sintering process directly fabricates a high-conductive copper electrode onto a glass donor from copper oxide nanoparticle solution via photo-thermochemical reduction and agglomeration of copper oxide nanoparticles. The sintered copper patterns were transferred in parallel to a heat-sensitive polyethylene film through self-selective surface adhesion of the film, which was generated by the selective laser absorption of the copper pattern. The method reported here could become one of the most important manufacturing technologies for fabricating low-cost wearable and disposable electronics.
System for trapping and storing gases for subsequent chemical reduction to solids

DOEpatents

Vogel, John S [San Jose, CA; Ognibene, Ted J [Oakland, CA; Bench, Graham S [Livermore, CA; Peaslee, Graham F [Holland, MI

2009-11-03

A system for quantitatively reducing oxide gases. A pre-selected amount of zinc is provided in a vial. A tube is provided in the vial. The zinc and the tube are separated. A pre-selected amount of a catalyst is provided in the tube. Oxide gases are injected into the vial. The vial, tube, zinc, catalyst, and the oxide gases are cryogenically cooled. At least a portion of the vial, tube, zinc, catalyst, and oxide gases are heated.
System and method for controlling ammonia levels in a selective catalytic reduction catalyst using a nitrogen oxide sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

A system according to the principles of the present disclosure includes an air/fuel ratio determination module and an emission level determination module. The air/fuel ratio determination module determines an air/fuel ratio based on input from an air/fuel ratio sensor positioned downstream from a three-way catalyst that is positioned upstream from a selective catalytic reduction (SCR) catalyst. The emission level determination module selects one of a predetermined value and an input based on the air/fuel ratio. The input is received from a nitrogen oxide sensor positioned downstream from the three-way catalyst. The emission level determination module determines an ammonia level basedmore » on the one of the predetermined value and the input received from the nitrogen oxide sensor.« less
Selective reduction of N-oxides to amines: application to drug metabolism.

PubMed

Kulanthaivel, Palaniappan; Barbuch, Robert J; Davidson, Rita S; Yi, Ping; Rener, Gregory A; Mattiuz, Edward L; Hadden, Chad E; Goodwin, Lawrence A; Ehlhardt, William J

2004-09-01

Phase I oxidative metabolism of nitrogen-containing drug molecules to their corresponding N-oxides is a common occurrence. There are instances where liquid chromatography/tandem mass spectometry techniques are inadequate to distinguish this pathway from other oxidation processes, including C-hydroxylations and other heteroatom oxidations, such as sulfur to sulfoxide. Therefore, the purpose of the present study was to develop and optimize an efficient and practical chemical method to selectively convert N-oxides to their corresponding amines suitable for drug metabolism applications. Our results indicated that efficient conversion of N-oxides to amines could be achieved with TiCl(3) and poly(methylhydrosiloxane). Among them, we found TiCl(3) to be a facile and easy-to-use reagent, specifically applicable to drug metabolism. There are a few reports describing the use of TiCl(3) to reduce N-O bonds in drug metabolism studies, but this methodology has not been widely used. Our results indicated that TiCl(3) is nearly as efficient when the reductions were carried out in the presence of biological matrices, including plasma and urine. Finally, we have shown a number of examples where TiCl(3) can be successfully used to selectively reduce N-oxides in the presence of sulfoxides and other labile groups.
Stabilized tin-oxide-based oxidation/reduction catalysts

NASA Technical Reports Server (NTRS)

Watkins, Anthony Neal (Inventor); Oglesby, Donald M. (Inventor); Gulati, Suresh T. (Inventor); Summers, Jerry C. (Inventor); Schryer, David R. (Inventor); Davis, Patricia P. (Inventor); Leighty, Bradley D. (Inventor); Jordan, Jeffrey D. (Inventor); Schryer, Jacqueline L. (Inventor)

2008-01-01

The invention described herein involves a novel approach to the production of oxidation/reduction catalytic systems. The present invention serves to stabilize the tin oxide reducible metal-oxide coating by co-incorporating at least another metal-oxide species, such as zirconium. In one embodiment, a third metal-oxide species is incorporated, selected from the group consisting of cerium, lanthanum, hafnium, and ruthenium. The incorporation of the additional metal oxide components serves to stabilize the active tin-oxide layer in the catalytic process during high-temperature operation in a reducing environment (e.g., automobile exhaust). Moreover, the additional metal oxides are active components due to their oxygen-retention capabilities. Together, these features provide a mechanism to extend the range of operation of the tin-oxide-based catalyst system for automotive applications, while maintaining the existing advantages.
Method For Selective Catalytic Reduction Of Nitrogen Oxides

DOEpatents

Mowery-Evans, Deborah L.; Gardner, Timothy J.; McLaughlin, Linda I.

2005-02-15

A method for catalytically reducing nitrogen oxide compounds (NO.sub.x, defined as nitric oxide, NO, +nitrogen dioxide, NO.sub.2) in a gas by a material comprising a base metal consisting essentially of CuO and Mn, and oxides of Mn, on an activated metal hydrous metal oxide support, such as HMO:Si. A promoter, such as tungsten oxide or molybdenum oxide, can be added and has been shown to increase conversion efficiency. This method provides good conversion of NO.sub.x to N.sub.2, good selectivity, good durability, resistance to SO.sub.2 aging and low toxicity compared with methods utilizing vanadia-based catalysts.
Method for selective catalytic reduction of nitrogen oxides

DOEpatents

Mowery-Evans, Deborah L [Broomfield, CO; Gardner, Timothy J [Albuquerque, NM; McLaughlin, Linda I [Albuquerque, NM

2005-02-15

A method for catalytically reducing nitrogen oxide compounds (NO.sub.x, defined as nitric oxide, NO, +nitrogen dioxide, NO.sub.2) in a gas by a material comprising a base metal consisting essentially of CuO and Mn, and oxides of Mn, on an activated metal hydrous metal oxide support, such as HMO:Si. A promoter, such as tungsten oxide or molybdenum oxide, can be added and has been shown to increase conversion efficiency. This method provides good conversion of NO.sub.x to N.sub.2, good selectivity, good durability, resistance to SO.sub.2 aging and low toxicity compared with methods utilizing vanadia-based catalysts.
Single-Atom Catalyst of Platinum Supported on Titanium Nitride for Selective Electrochemical Reactions.

PubMed

Yang, Sungeun; Kim, Jiwhan; Tak, Young Joo; Soon, Aloysius; Lee, Hyunjoo

2016-02-05

As a catalyst, single-atom platinum may provide an ideal structure for platinum minimization. Herein, a single-atom catalyst of platinum supported on titanium nitride nanoparticles were successfully prepared with the aid of chlorine ligands. Unlike platinum nanoparticles, the single-atom active sites predominantly produced hydrogen peroxide in the electrochemical oxygen reduction with the highest mass activity reported so far. The electrocatalytic oxidation of small organic molecules, such as formic acid and methanol, also exhibited unique selectivity on the single-atom platinum catalyst. A lack of platinum ensemble sites changed the reaction pathway for the oxygen-reduction reaction toward a two-electron pathway and formic acid oxidation toward direct dehydrogenation, and also induced no activity for the methanol oxidation. This work demonstrates that single-atom platinum can be an efficient electrocatalyst with high mass activity and unique selectivity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Effects of dew point on selective oxidation of TRIP steels containing Si, Mn, and B

NASA Astrophysics Data System (ADS)

Lee, Suk-Kyu; Kim, Jong-Sang; Choi, Jin-Won; Kang, Namhyun; Cho, Kyung-Mox

2011-04-01

The selective oxidation of Si, Mn, and B on TRIP steel surfaces is a widely known phenomenon that occurs during heat treatment. However, the relationship between oxide formation and the annealing factors is not completely understood. This study examines the effect of the annealing conditions (dew point and annealing temperature) on oxide formation. A low dew point of -40 °C leads to the formation of Si-based oxides on the surface. A high dew point of -20 °C changes the oxide type to Mn-based oxides because the formation of Si oxides on the surface is suppressed by internal oxidation. Mn-based oxides exhibit superior wettability due to aluminothermic reduction during galvanizing.
Methodology for the effective stabilization of tin-oxide-based oxidation/reduction catalysts

NASA Technical Reports Server (NTRS)

Jordan, Jeffrey D. (Inventor); Schryer, David R. (Inventor); Leighty, Bradley D. (Inventor); Watkins, Anthony N. (Inventor); Summers, Jerry C. (Inventor); Davis, Patricia P. (Inventor); Oglesby, Donald M. (Inventor); Schryer, Jacqueline L. (Inventor); Gulati, Suresh T. (Inventor)

2011-01-01

The invention described herein involves a novel approach to the production of oxidation/reduction catalytic systems. The present invention serves to stabilize the tin oxide reducible metal-oxide coating by co-incorporating at least another metal-oxide species, such as zirconium. In one embodiment, a third metal-oxide species is incorporated, selected from the group consisting of cerium, lanthanum, hafnium, and ruthenium. The incorporation of the additional metal oxide components serves to stabilize the active tin-oxide layer in the catalytic process during high-temperature operation in a reducing environment (e.g., automobile exhaust). Moreover, the additional metal oxides are active components due to their oxygen-retention capabilities. Together, these features provide a mechanism to extend the range of operation of the tin-oxide-based catalyst system for automotive applications, while maintaining the existing advantages.
Oxidase catalysis via aerobically generated hypervalent iodine intermediates

NASA Astrophysics Data System (ADS)

Maity, Asim; Hyun, Sung-Min; Powers, David C.

2018-02-01

The development of sustainable oxidation chemistry demands strategies to harness O2 as a terminal oxidant. Oxidase catalysis, in which O2 serves as a chemical oxidant without necessitating incorporation of oxygen into reaction products, would allow diverse substrate functionalization chemistry to be coupled to O2 reduction. Direct O2 utilization suffers from intrinsic challenges imposed by the triplet ground state of O2 and the disparate electron inventories of four-electron O2 reduction and two-electron substrate oxidation. Here, we generate hypervalent iodine reagents—a broadly useful class of selective two-electron oxidants—from O2. This is achieved by intercepting reactive intermediates of aldehyde autoxidation to aerobically generate hypervalent iodine reagents for a broad array of substrate oxidation reactions. The use of aryl iodides as mediators of aerobic oxidation underpins an oxidase catalysis platform that couples substrate oxidation directly to O2 reduction. We anticipate that aerobically generated hypervalent iodine reagents will expand the scope of aerobic oxidation chemistry in chemical synthesis.
Structural and surface changes of cobalt modified manganese oxide during activation and ethanol steam reforming reaction

NASA Astrophysics Data System (ADS)

Gac, Wojciech; Greluk, Magdalena; Słowik, Grzegorz; Turczyniak-Surdacka, Sylwia

2018-05-01

Surface and structural changes of unmodified manganese and cobalt-manganese oxide during activation and ethanol steam reforming reaction conditions (ESR) were studied by means of X-ray diffraction, X-ray photoelectron spectroscopy, temperature-programmed reduction/oxidation (TPR/TPO) and transmission electron microscopy. It was shown that synthesis of cobalt manganese oxide by the redox precipitation method led to the formation of strongly dispersed cobalt ionic species within cryptomelane-based manganese oxide structure. Development of large cube-like MnO nanoparticles with spherical cobalt metallic crystallites decorated by manganese oxide on the high oxidation state and potassium species was observed during reduction. Cobalt manganese catalyst showed high initial activity and selectivity to H2 and CO2 in ethanol stem reforming reaction in the range of 390-480 °C. The drop of ethanol conversion and changes of selectivity with the time-on-stream were observed. An increase of reaction temperature led to intensification of deactivation phenomena. TEM studies evidenced coexistence of Co and CoOx nanoparticles formed under ethanol steam reforming conditions, partially covered by filamentous and encapsulating carbonaceous deposits.
Recent progress and perspectives in the photocatalytic CO2 reduction of Ti-oxide-based nanomaterials

NASA Astrophysics Data System (ADS)

Sohn, Youngku; Huang, Weixin; Taghipour, Fariborz

2017-02-01

The conversion of CO2 with H2O to valuable chemicals and fuels is a new solution to current environmental and energy problems, and the high energy barrier of these reactions can be overcome by the input of solar and electrical energy. However, the reduction efficiencies and selectivities of these reactions are insufficient for practical use, and significant effort and strategy are required to overcome the many obstacles preventing the large-scale application of photocatalytic CO2 reduction. This article reviews recent progress in CO2 reduction using titanium oxide-based materials and various strategic factors for increasing photocatalytic efficiency. This article also highlights non-titanium-oxide catalysts, the photoelectrocatalytic reduction of CO2, and other recent review articles concerning the recycling of CO2 to value-added carbon compounds.

Tetraalykylammonium polyoxoanionic oxidation catalysts

DOEpatents

Ellis, Paul E.; Lyons, James E.; Myers, Jr., Harry K.; Shaikh, Shahid N.

1998-01-01

Alkanes are catalytically oxidized in air or oxygen using iron-substituted polyoxoanions (POAs) of the formula: H.sub.e-z ›(n-C.sub.4 H.sub.9).sub.4 N!.sub.z (XM.sub.11 M'O.sub.39).sup.-e The M' (e.g., iron(III)/iron(II)) reduction potential of the POAs is affected by selection of the central atom X and the framework metal M, and by the number of tetrabutyl-ammonium groups. Decreased Fe(III)/Fe(II) reduction potential has been found to correlate to increased oxidation activity.
Tetraalklylammonium polyoxoanionic oxidation catalysts

DOEpatents

Ellis, P.E.; Lyons, J.E.; Myers, H.K. Jr.; Shaikh, S.N.

1998-10-06

Alkanes are catalytically oxidized in air or oxygen using iron-substituted polyoxoanions (POAs) of the formula: H{sub e{minus}z}[(n-C{sub 4}H{sub 9}){sub 4}N]{sub z}(XM{sub 11}M{prime}O{sub 39}){sup {minus}e}. The M{prime} (e.g., iron(III)/iron(II)) reduction potential of the POAs is affected by selection of the central atom X and the framework metal M, and by the number of tetrabutyl-ammonium groups. Decreased Fe(III)/Fe(II) reduction potential has been found to correlate to increased oxidation activity.
Investigation of selective catalytic reduction impact on mercury speciation under simulated NOx emission control conditions.

PubMed

Lee, Chun W; Srivastava, Ravi K; Ghorishi, S Behrooz; Hastings, Thomas W; Stevens, Frank M

2004-12-01

Selective catalytic reduction (SCR) technology increasingly is being applied for controlling emissions of nitrogen oxides (NOx) from coal-fired boilers. Some recent field and pilot studies suggest that the operation of SCR could affect the chemical form of mercury (Hg) in coal combustion flue gases. The speciation of Hg is an important factor influencing the control and environmental fate of Hg emissions from coal combustion. The vanadium and titanium oxides, used commonly in the vanadia-titania SCR catalyst for catalytic NOx reduction, promote the formation of oxidized mercury (Hg2+). The work reported in this paper focuses on the impact of SCR on elemental mercury (Hg0) oxidation. Bench-scale experiments were conducted to investigate Hg0 oxidation in the presence of simulated coal combustion flue gases and under SCR reaction conditions. Flue gas mixtures with different concentrations of hydrogen chloride (HCl) and sulfur dioxide (SO2) for simulating the combustion of bituminous coals and subbituminous coals were tested in these experiments. The effects of HCl and SO2 in the flue gases on Hg0 oxidation under SCR reaction conditions were studied. It was observed that HCl is the most critical flue gas component that causes conversion of Hg0 to Hg2+ under SCR reaction conditions. The importance of HCl for Hg0 oxidation found in the present study provides the scientific basis for the apparent coal-type dependence observed for Hg0 oxidation occurring across the SCR reactors in the field.
Chemoselective reduction and oxidation of ketones in water through control of the electron transfer pathway

PubMed Central

Kim, Sun Min; Yoo, Ho Sung; Hosono, Hideo; Yang, Jung Woon; Kim, Sung Wng

2015-01-01

The selective synthesis of different products from the same starting materials in water, which is the most abundant solvent in nature, is a crucial issue as it maximizes the utilization of materials. Realizing such reactions for ketones is of considerable importance because numerous organic functionalities can be obtained via nucleophilic addition reactions. Herein, we report chemoselective reduction and oxidation reactions of 1,2-diketones in water, which initiates anionic electron transfer from the inorganic electride [Ca24Al28O64]4+·4e−, through controlling the pathway of the electrons to substrates. The generation of different radical species for transient intermediates was the key process required to control the reaction selectivity, which was achieved by reacting the anionic electrons with either diketones or O2, leading to the formation of ketyl dianion and superoxide radicals in the reduction and oxidation reactions, respectively. This methodology that utilizes electrides may provide an alternative to the pulse radiolysis of water in synthetic chemistry. PMID:26020413
Combustion in a multiburner furnace with selective flow of oxygen

DOEpatents

Bool, III, Lawrence E.; Kobayashi, Hisashi

2004-03-02

Improved operational characteristics such as improved fuel efficiency, reduction of NOx formation, reduction of the amount of unburned carbon in the ash, and lessened tendency to corrosion at the tube wall, in a multi-burner furnace are obtained by reducing the flow rate of combustion air to the burners and selectively individually feeding oxidant to only some of the burners.
XANES study of elemental mercury oxidation over RuO 2/TiO 2 and selective catalytic reduction catalysts for mercury emissions control

DOE PAGES

Liu, Zhouyang; Li, Can; Sriram, Vishnu; ...

2016-07-25

Linear combination fitting of the X-ray Absorption Near Edge Spectroscopy (XANES) was used to quantify oxidized mercury species over RuO 2/TiO 2 and Selective Catalytic Reduction (SCR) catalysts under different simulated flue gas conditions. Halogen gases play a major role in mercury oxidation. In the absence of halogen gas, elemental mercury can react with sulfur that is contained in both the RuO2/TiO2 and SCR catalysts to form HgS and HgSO 4. In the presence of HCl or HBr gas, HgCl 2 or HgBr 2 is the main oxidized mercury species. When both HCl and HBr gases are present, HgBr2 ismore » the preferred oxidation product and no HgCl 2 can be found. The formation of HgO and HgS cannot be neglected with or without halogen gas. Other simulated flue gas components such as NO, NH 3, SO 2 and CO 2 do not have significant effect on oxidized mercury speciation when halogen gas is present.« less
Selective catalytic reduction system and process for control of NO.sub.x emissions in a sulfur-containing gas stream

DOEpatents

Sobolevskiy, Anatoly

2015-08-11

An exhaust gas treatment process, apparatus, and system for reducing the concentration of NOx, CO and hydrocarbons in a gas stream, such as an exhaust stream (29), via selective catalytic reduction with ammonia is provided. The process, apparatus and system include a catalytic bed (32) having a reducing only catalyst portion (34) and a downstream reducing-plus-oxidizing portion (36). Each portion (34, 36) includes an amount of tungsten. The reducing-plus-oxidizing catalyst portion (36) advantageously includes a greater amount of tungsten than the reducing catalyst portion (36) to markedly limit ammonia salt formation.
Highly selective plasma-activated copper catalysts for carbon dioxide reduction to ethylene

DOE PAGES

Mistry, Hemma; Varela, Ana Sofia; Bonifacio, Cecile S.; ...

2016-06-30

There is an urgent need to develop technologies that use renewable energy to convert waste products such as carbon dioxide into hydrocarbon fuels. Carbon dioxide can be electrochemically reduced to hydrocarbons over copper catalysts, although higher efficiency is required. We have developed oxidized copper catalysts displaying lower overpotentials for carbon dioxide electroreduction and record selectivity towards ethylene (60%) through facile and tunable plasma treatments. Herein we provide insight into the improved performance of these catalysts by combining electrochemical measurements with microscopic and spectroscopic characterization techniques. Operando X-ray absorption spectroscopy and cross-sectional scanning transmission electron microscopy show that copper oxides aremore » surprisingly resistant to reduction and copper + species remain on the surface during the reaction. Furthermore, our results demonstrate that the roughness of oxide-derived copper catalysts plays only a partial role in determining the catalytic performance, while the presence of copper + is key for lowering the onset potential and enhancing ethylene selectivity.« less
Isothermal Oxidation of Magnetite to Hematite in Air and Cyclic Reduction/Oxidation Under Carbon Looping Combustion Conditions

NASA Astrophysics Data System (ADS)

Simmonds, Tegan; Hayes, Peter C.

2017-12-01

In the carbon looping combustion process the oxygen carrier is regenerated through oxidation in air; this process has been simulated by the oxidation of dense synthetic magnetite for selected temperatures and times. The oxidation of magnetite in air is shown to occur through the formation of dense hematite layers on the particle surface. This dense hematite forms through lath type shear transformations or solid-state diffusion through the product layer. Cyclic reduction in CO-CO2/oxidation in air of hematite single crystals has been carried out under controlled laboratory conditions at 1173 K (900 °C). It has been shown that the initial reduction step is critical to determining the product microstructure, which consists of gas pore dendrites in the magnetite matrix with blocky hematite formed on the pore surfaces. The progressive growth of the magnetite layer with the application of subsequent cycles appears to continue until no original hematite remains, after which physical disintegration of the particles takes place.
Descriptors and Thermodynamic Limitations of Electrocatalytic Carbon Dioxide Reduction on Rutile Oxide Surfaces.

PubMed

Bhowmik, Arghya; Vegge, Tejs; Hansen, Heine A

2016-11-23

A detailed understanding of the electrochemical reduction of CO 2 into liquid fuels on rutile metal oxide surfaces is developed by using DFT calculations. We consider oxide overlayer structures on RuO 2 (1 1 0) surfaces as model catalysts to elucidate the trends and limitations in the CO 2 reduction reaction (CO2RR) based on thermodynamic analysis. We aim to specify the requirements for CO2RR catalysts to establish adsorbate scaling relations and use these to derive activity volcanoes. Computational results show that the OH* binding free energy is a good descriptor of the thermodynamic limitations and it defines the left leg of the activity volcano for CO2RR. HCOOH* is a key intermediate for products formed through further reduction, for example, methanediol, methanol, and methane. The surfaces that do not bind HCOOH* are selective towards formic acid (HCOOH) production, but hydrogen evolution limits their suitability. We determine the ideal binding free energy for H* and OH* to facilitate selective CO2RR over H 2 /CO evolution to be ΔG B [H]>0.5 eV and -0.5 eV<ΔG B [OH]<0.1 eV. The Re-containing overlayers considered in this work display excellent promise for selectivity, although they are active at a highly reducing potential. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Selective hydrodeoxygenation of cyclic vicinal diols to cyclic alcohols over tungsten oxide-palladium catalysts.

PubMed

Amada, Yasushi; Ota, Nobuhiko; Tamura, Masazumi; Nakagawa, Yoshinao; Tomishige, Keiichi

2014-08-01

Hydrodeoxygenation of cyclic vicinal diols such as 1,4-anhydroerythritol was conducted over catalysts containing both a noble metal and a group 5-7 transition-metal oxide. The combination of Pd and WOx allowed the removal of one of the two OH groups selectively. 3-Hydroxytetrahydrofuran was obtained from 1,4-anhydroerythritol in 72 and 74% yield over WOx -Pd/C and WOx -Pd/ZrO2 , respectively. The WOx -Pd/ZrO2 catalyst was reusable without significant loss of activity if the catalyst was calcined as a method of regeneration. Characterization of WOx -Pd/C with temperature-programmed reduction, X-ray diffraction, and transmission electron microscopy/energy-dispersive X-ray spectroscopy suggested that Pd metal particles approximately 9 nm in size were formed on amorphous tungsten oxide particles. A reaction mechanism was proposed on the basis of kinetics, reaction results with tungsten oxides under an atmosphere of Ar, and density functional theory calculations. A tetravalent tungsten center (W(IV) ) was formed by reduction of WO3 with the Pd catalyst and H2 , and this center served as the reductant for partial hydrodeoxygenation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Isolation of the Copper Redox Steps in the Standard Selective Catalytic Reduction on Cu-SSZ-13

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paolucci, Christopher; Verma, Anuj A.; Bates, Shane A.

2014-10-27

Operando X-ray absorption experiments and density functional theory (DFT) calculations are reported that elucidate the role of copper redox chemistry in the selective catalytic reduction (SCR) of NO over Cu-exchanged SSZ-13. Catalysts prepared to contain only isolated, exchanged CuII ions evidence both CuII and CuI ions under standard SCR conditions at 473 K. Reactant cutoff experiments show that NO and NH3 together are necessary for CuII reduction to CuI. DFT calculations show that NO-assisted NH3 dissociation is both energetically favorable and accounts for the observed CuII reduction. The calculations predict in situ generation of Brønsted sites proximal to CuI uponmore » reduction, which we quantify in separate titration experiments. Both NO and O2 are necessary for oxidation of CuI to CuII, which DFT suggests to occur by a NO2 intermediate. Reaction of Cu-bound NO2 with proximal NH4 + completes the catalytic cycle. N2 is produced in both reduction and oxidation half-cycles.« less
Isolation of the Copper Redox Steps in the Standard Selective Catalytic Reduction on Cu-SSZ-13

DOE Office of Scientific and Technical Information (OSTI.GOV)

Paolucci, Christopher; Verma, Anuj A.; Bates, Shane A.

2014-09-12

Operando X-ray absorption experiments and density functional theory (DFT) calculations are reported that elucidate the role of copper redox chemistry in the selective catalytic reduction (SCR) of NO over Cu-exchanged SSZ-13. Catalysts prepared to contain only isolated, exchanged CuII ions evidence both CuII and CuI ions under standard SCR conditions at 473 K. Reactant cutoff experiments show that NO and NH3 together are necessary for CuII reduction to CuI. DFT calculations show that NO-assisted NH3 dissociation is both energetically favorable and accounts for the observed CuII reduction. The calculations predict in situ generation of Brønsted sites proximal to CuI uponmore » reduction, which we quantify in separate titration experiments. Both NO and O2 are necessary for oxidation of CuI to CuII, which DFT suggests to occur by a NO2 intermediate. Reaction of Cu-bound NO2 with proximal NH4 + completes the catalytic cycle. N2 is produced in both reduction and oxidation half-cycles.« less
Continuous flow reduction of artemisinic acid utilizing multi-injection strategies-closing the gap towards a fully continuous synthesis of antimalarial drugs.

PubMed

Pieber, Bartholomäus; Glasnov, Toma; Kappe, C Oliver

2015-03-09

One of the rare alternative reagents for the reduction of carbon-carbon double bonds is diimide (HN=NH), which can be generated in situ from hydrazine hydrate (N2H4⋅H2O) and O2. Although this selective method is extremely clean and powerful, it is rarely used, as the rate-determining oxidation of hydrazine in the absence of a catalyst is relatively slow using conventional batch protocols. A continuous high-temperature/high-pressure methodology dramatically enhances the initial oxidation step, at the same time allowing for a safe and scalable processing of the hazardous reaction mixture. Simple alkenes can be selectively reduced within 10-20 min at 100-120 °C and 20 bar O2 pressure. The development of a multi-injection reactor platform for the periodic addition of N2H4⋅H2O enables the reduction of less reactive olefins even at lower reaction temperatures. This concept was utilized for the highly selective reduction of artemisinic acid to dihydroartemisinic acid, the precursor molecule for the semisynthesis of the antimalarial drug artemisinin. The industrially relevant reduction was achieved by using four consecutive liquid feeds (of N2H4⋅H2O) and residence time units resulting in a highly selective reduction within approximately 40 min at 60 °C and 20 bar O2 pressure, providing dihydroartemisinic acid in ≥93% yield and ≥95% selectivity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Progress of reduction of graphene oxide by ascorbic acid

NASA Astrophysics Data System (ADS)

De Silva, K. Kanishka H.; Huang, Hsin-Hui; Yoshimura, Masamichi

2018-07-01

Graphene oxide (GO) and reduced graphene oxide (RGO) are in greater demand in many research fields. As a result, the synthesis of these materials on a large scale in a costeffective manner is more concerned for numerous applications. In the present work, GO was synthesized by oxidizing natural graphite and reduced by ascorbic acid (AA), which is a green reductant. The reduced products obtained at different time periods were in detail characterized by UV-Visible spectroscopy, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared (ATR-FT-IR) spectroscopy, Raman spectroscopy, thermogravimetric analysis (TGA), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Results showed that the oxidation of graphite has given highly oxidized GO with a 9.30 Å interlayer space and about 33% of oxygen atomic percentage. Until 50 min of the reduction, both GO and RGO coexist. The reduction rate is fast within the first 30 min. In addition, the suitability of natural graphite over synthetic graphite for the synthesis of GO is shown. The findings of this work pave the way to select GO and RGO for applications of interest in a cheap, green and efficient manner.
Oxidation of ultrathin GaSe

DOE PAGES

Thomas Edwin Beechem; McDonald, Anthony E.; Ohta, Taisuke; ...

2015-10-26

Oxidation of exfoliated gallium selenide (GaSe) is investigated through Raman, photoluminescence, Auger, and X-ray photoelectron spectroscopies. Photoluminescence and Raman intensity reductions associated with spectral features of GaSe are shown to coincide with the emergence of signatures emanating from the by-products of the oxidation reaction, namely, Ga 2Se 3 and amorphous Se. Furthermore, photoinduced oxidation is initiated over a portion of a flake highlighting the potential for laser based patterning of two-dimensional heterostructures via selective oxidation.
Site-selective oxidation, amination and epimerization reactions of complex polyols enabled by transfer hydrogenation

NASA Astrophysics Data System (ADS)

Hill, Christopher K.; Hartwig, John F.

2017-12-01

Polyoxygenated hydrocarbons that bear one or more hydroxyl groups comprise a large set of natural and synthetic compounds, often with potent biological activity. In synthetic chemistry, alcohols are important precursors to carbonyl groups, which then can be converted into a wide range of oxygen- or nitrogen-based functionality. Therefore, the selective conversion of a single hydroxyl group in natural products into a ketone would enable the selective introduction of unnatural functionality. However, the methods known to convert a simple alcohol, or even an alcohol in a molecule that contains multiple protected functional groups, are not suitable for selective reactions of complex polyol structures. We present a new ruthenium catalyst with a unique efficacy for the selective oxidation of a single hydroxyl group among many in unprotected polyol natural products. This oxidation enables the introduction of nitrogen-based functional groups into such structures that lack nitrogen atoms and enables a selective alcohol epimerization by stepwise or reversible oxidation and reduction.
Solid state proton and electron mediating membrane and use in catalytic membrane reactors

DOEpatents

White, James H.; Schwartz, Michael; Sammells, Anthony F.

1998-01-01

This invention provides catalytic proton and electron mediating membranes useful in catalytic reactors. The membranes have an oxidation and a reduction surface and comprise a single-phase mixed metal oxide material of the formula: AB.sub.1-x B'.sub.x O.sub.3-y wherein A is selected from Ca, Sr or Ba ions; B is selected from Ce, Tb, Pr, or Th ions; B' is selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, Ga, or In ions, or combinations thereof; and x is greater than or equal to 0.02 and less than or equal to 0.5. The membranes can further comprise a catalyst on either the oxidation or reduction surface, or both. Membranes include those which are fabricated-by combining powders of metal oxides or metal carbonates of metal A ion, metal B ion and metal B' ion such that the stoichiometric ratio A:B:B' is 1:1-x:x where 0.2.ltoreq..times.0.5, repeatedly calcining and milling the combined powders until a single-phase material is obtained and pressing and sintering the singlephase material to obtain a membrane.
Solid state proton and electron mediating membrane and use in catalytic membrane reactors

DOEpatents

White, J.H.; Schwartz, M.; Sammells, A.F.

1998-10-13

This invention provides catalytic proton and electron mediating membranes useful in catalytic reactors. The membranes have an oxidation and a reduction surface and comprise a single-phase mixed metal oxide material of the formula: AB{sub 1{minus}x}B{prime}{sub x}O{sub 3{minus}y} wherein A is selected from Ca, Sr or Ba ions; B is selected from Ce, Tb, Pr, or Th ions; B{prime} is selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Al, Ga, or In ions, or combinations thereof; and x is greater than or equal to 0.02 and less than or equal to 0.5. The membranes can further comprise a catalyst on either the oxidation or reduction surface, or both. Membranes include those which are fabricated by combining powders of metal oxides or metal carbonates of metal A ion, metal B ion and metal B{prime} ion such that the stoichiometric ratio A:B:B{prime} is 1:1{minus}x:x where 0.2{<=}{times}0.5, repeatedly calcining and milling the combined powders until a single-phase material is obtained and pressing and sintering the single phase material to obtain a membrane. 6 figs.
RP-UHPLC-UV-ESI-MS/MS analysis of LPMO generated C4-oxidized gluco-oligosaccharides after non-reductive labeling with 2-aminobenzamide.

PubMed

Frommhagen, Matthias; van Erven, Gijs; Sanders, Mark; van Berkel, Willem J H; Kabel, Mirjam A; Gruppen, Harry

2017-08-07

Lytic polysaccharide monooxygenases (LPMOs) are able to cleave recalcitrant polysaccharides, such as cellulose, by oxidizing the C1 and/or C4 atoms. The analysis of the resulting products requires a variety of analytical techniques. Up to now, these techniques mainly focused on the identification of non-oxidized and C1-oxidized oligosaccharides. The analysis of C4-oxidized gluco-oligosaccharides is mostly performed by using high pressure anion exchange chromatography (HPAEC). However, the alkaline conditions used during HPAEC analysis lead to tautomerization of C4-oxidized gluco-oligosaccharides, which limits the use of this technique. Here, we describe the use of reverse phase-ultra high performance liquid chromatography (RP-UHPLC) in combination with non-reductive 2-aminobenzamide (2-AB) labeling. Non-reductive 2-AB labeling enabled separation of C4-oxidized gluco-oligosaccharides from their non-oxidized counterparts. Moreover, RP-UHPLC does not require buffered mobile phases, which reduce mass spectrometry (MS) sensitivity. The latter is seen as an advantage over other techniques such as hydrophilic interaction liquid chromatography and porous graphitized carbon coupled to MS. RP-UHPLC coupled to UV detection and mass spectrometry allowed the identification of both labeled non-oxidized and C4-oxidized oligosaccharides. Non-reductive labeling kept the ketone at the C4-position of LPMO oxidized oligosaccharides intact, while selective reducing agents such as sodium triacetoxyborohydride (STAB) reduced this ketone group. Our results show that RP-UHPLC-UV-ESI-MS in combination with non-reductively 2-AB labeling is a suitable technique for the separation and identification of LPMO-generated C4-oxidized gluco-oligosaccharides. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

EVALUATION AND MITIGATION OF VISIBLE ACIDIC AEROSOL PLUMES FROM COAL FIRED POWER BOILERS

EPA Science Inventory

The formation of sulfur trioxide during the combustion of coal can increase significantly following the installation and operation of selective catalytic reduction systems for reduction of nitrogen oxides. This can in turn lead to adverse environmental impacts, including visible...
Functionalized Cobalt Triarylcorrole Covalently Bonded with Graphene Oxide: A Selective Catalyst for the Two- or Four-Electron Reduction of Oxygen.

PubMed

Tang, Jijun; Ou, Zhongping; Guo, Rui; Fang, Yuanyuan; Huang, Dong; Zhang, Jing; Zhang, Jiaoxia; Guo, Song; McFarland, Frederick M; Kadish, Karl M

2017-08-07

A cobalt triphenylcorrole (CorCo) was covalently bonded to graphene oxide (GO), and the resulting product, represented as GO-CorCo, was characterized by UV-vis, FT-IR, and micro-Raman spectroscopy as well as by HRTEM, TGA, XRD, XPS, and AFM. The electrocatalytic activity of GO-CorCo toward the oxygen reduction reaction (ORR) was then examined in air-saturated 0.1 M KOH and 0.5 M H 2 SO 4 solutions by cyclic voltammetry and linear sweep voltammetry using a rotating disk electrode and/or a rotating ring-disk electrode. An overall 4-electron reduction of O 2 is obtained in alkaline media while under acidic conditions a 2-electron process is seen. The ORR results thus indicate that covalently bonded GO-CoCor can be used as a selective catalyst for either the 2- or 4-electron reduction of oxygen, the prevailing reaction depending upon the acidity of the solution.
75 FR 63259 - Standards of Performance for New Stationary Sources and Emission Guidelines for Existing Sources...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-10-14

... Thermal Oxidizer SBA Small Business Administration SCR Selective Catalytic Reduction SNCR Selective Non...). Finally, on June 4, 2010, EPA proposed a definition of non- hazardous solid waste (75 FR 31844) under the...
Agents for replacement of NAD+/NADH system in enzymatic reactions

DOEpatents

Fish, Richard H.; Kerr, John B.; Lo, Christine H.

2004-04-06

Novel agents acting as co-factors for replacement of NAD(P).sup.+ /NAD(P)H co-enzyme systems in enzymatic oxido-reductive reactions. Agents mimicking the action of NAD(P).sup.+ /NAD(P)H system in enzymatic oxidation/reduction of substrates into reduced or oxidized products. A method for selection and preparation of the mimicking agents for replacement of NAD(P).sup.+ /NAD(P)H system and a device comprising co-factors for replacement of NAD(P).sup.+ /NAD(P)H system.
The Variation of Catalyst and Carrier Gas on Anisole Deoxygenation Reaction

NASA Astrophysics Data System (ADS)

Ariyani, D.; Dwi Nugrahaningtyas, Khoirina; Heraldy, E.

2018-03-01

This research aims to determine the best catalyst and carrier gas in anisole deoxygenation reaction. The reaction was carried out over a flow system with a variation of catalyst CoMo A (CoMo/USY reduction), CoMo B (CoMo/USY oxidation-reduction), and CoMo C (CoMo/ZAA oxidation-reduction). In addition, variation of carrier gas nitrogen and hydrogen was investigated. The result was analyzed using Gas Chromatography-Mass Spectroscopy (GC-MS). The deoxygenation anisole result showed that CoMo A catalyst with hydrogen as the carrier gas has the highest total product yield (50.72 %), intermediate product yield (38.49 % in phenol and 6.99 % in benzaldehyde), and deoxygenation yield (5.24 %). The CoMo C catalyst exhibited the most selective deoxygenation product. The nitrogen carrier gas with the CoMo C catalyst has the best selectivity of benzene product (93.92 %).
POWER PLANT EVALUATION OF THE EFFECT OF SCR TECHNOLOGY ON MERCURY

EPA Science Inventory

The paper presents results of research on the impact that selective catalytic reduction (SCR) systems have on speciation and total emissions of mercury. Although SCR systems are designed to reduce nitrogen oxides (NOx), they may oxidize elemental mercury (Hg0) to Hg2+, which is m...
STUDY OF MERCURY OXIDATION BY SCR CATALYST IN AN ENTRAINED-FLOW REACTOR UNDER SIMULATED PRB CONDITIONS

EPA Science Inventory

A bench-scale entrained-flow reactor system was constructed for studying elemental mercury oxidation under selective catalytic reduction (SCR) reaction conditions. Simulated flue gas was doped with fly ash collected from a subbituminous Powder River Basin (PRB) coal-fired boiler ...
Anion exchange membranes for electrochemical oxidation-reduction energy storage system

NASA Technical Reports Server (NTRS)

Odonnell, P. M.; Sheibley, D. W.; Gahn, R. F.

1977-01-01

Oxidation-reduction couples in concentrated solutions separated by appropriate ion selective membranes were considered as an attractive approach to bulk electrical energy storage. A key problem is the development of the membrane. Several promising types of anionic membranes are discussed which were developed and evaluated for redox energy storage systems. The copolymers of ethyleneglycoldimethacrylate with either 2-vinylpyridine or vinylbenzl chloride gave stable resistance values compared to the copolymer of vinylbenzlchloride and divinylbenzene which served as the baseline membrane. A polyvinylchloride film aminated with tetraethylenepentamine had a low resistance but a high ion transfer rate. A slurry coated vinylpyridine had the lowest ion transfer rate. All these membranes functioned well in laboratory cells at ambient temperatures with the acidic chloride oxidant/reductant system, Fe 3, Fe 2/Ti 3, Ti 4.
Role of acetate and nitrates in the selective catalytic reduction of NO by propene over alumina catalyst as investigated by FTIR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shimizu, Kenichi; Kawabata, Hisaya; Satsuma, Atsushi

1999-06-24

It is widely accepted that selective catalytic reduction (SCR) of NO by hydrocarbons is a potential method to remove NO{sub x} practically in excess O{sub 2}. Although many studies on SCR are related to zeolitic catalysts, metal oxides are also of importance as promising SCR catalysts due to their high durability. Among oxide catalysts, {gamma}-Al{sub 2}O{sub 3} is one of the most active single oxides for SCR. The mechanism of the selective catalytic reduction (SCR) of NO by C{sub 3}H{sub 6} on Al{sub 2}O{sub 3} was investigated using in situ IR spectroscopy. Attention was focused on the reactivity of themore » adsorbed acetate and nitrates on the Al{sub 2}O{sub 3} surface. IR spectra showed that the reaction starts with the nitrates formation from NO + O{sub 2} followed by its reaction with C{sub 3}H{sub 6} to form acetate, which becomes the predominant surface species in the steady-state condition. The acetate band, which was stable in He or NO, significantly decreased when the flowing gas was switched to NO + O{sub 2}. A complementary set of experiments monitoring gas composition showed that N{sub 2} and CO{sub x} were produced by the reaction of acetate with NO + O{sub 2}. The rate of acetate consumption in NO + O{sub 2} exhibited the same order of magnitude as the NO reduction rate, indicating that the acetate is active as a reductant and takes part in the N{sub 2} formation. Nitrates can oxidize both C{sub 3}H{sub 6} and acetate, and are mostly reduced to N{sub 2}. A proposed reaction scheme explains the role of O{sub 2} in facilitating SCR of NO.« less
Selective catalytic reduction manages ships' emissions

DOE Office of Scientific and Technical Information (OSTI.GOV)

McMahon, K.R.

1994-10-01

Ships employed by USS-Posco Industries are the first seagoing vessels that use selective catalytic reduction in marine diesel engine design, resulting in a 90 percent reduction of nitrogen oxide emissions. The vessels, which deliver semifinished steel coils, or hot bands'', to the company's terminal in the San Francisco Bay area, were commissioned for $120 million by Pohang Iron and Steel Co. Ltd., one of UPI's parent companies. Installing the catalytic reduction equipment cost $12 million. As anticipated, NOx concentrations were reduced between 90 percent and 95 percent. However, achieving high mass NOx reduction proved more difficult, because exhaust gas hadmore » to be maintained within the desired temperature range.« less
Nickel-catalyzed synthesis of diarylamines via oxidatively induced C-N bond formation at room temperature.

PubMed

Ilies, Laurean; Matsubara, Tatsuaki; Nakamura, Eiichi

2012-11-02

A nickel-catalyzed oxidative coupling of zinc amides with organomagnesium compounds selectively produces diarylamines under mild reaction conditions, with tolerance for chloride, bromide, hydroxyl, ester, and ketone groups. A diamine is bis-monoarylated. A bromoaniline undergoes N-arylation followed by Kumada-Tamao-Corriu coupling in one pot. The reaction may proceed via oxidatively induced reductive elimination of a nickel species.
Effects of copper loading on NH3-SCR and NO oxidation over Cu impregnated CHA zeolite

DOE PAGES

Akter, Nusnin; Chen, Xianyin; Parise, John; ...

2017-11-25

Cu/CHA catalysts with various Cu loadings (0.5 wt%–6.0 wt%) were synthesized via incipient wetness impregnation. The catalysts were then applied to the selective catalytic reduction (SCR) of NO with NH 3 and NO oxidation reaction. XRD and N 2 adsorption-desorption data showed that CHA structure was maintained with the incorporation of Cu, while specific surface areas decreased with increasing Cu loading. At intermediate Cu loading, 4 wt%, the highest NH 3-SCR activity was observed with ~98% N2 selectivity from 150°C to 300°C. Small amounts of water, 2%, slightly increased NO conversion in addition to the remarkable N 2O and NOmore » 2 reduction at high temperature. Water effects are attributed to the improved Cu ion reducibility and mobility. NO oxidation results provided no relation between NO 2 formation and SCR activity. Physicochemical properties, NO conversion, N 2 selectivity, and activation energy data showed that impregnated samples’ molecular structure and catalytic activity are comparable to the conventional ion-exchanged (IE) samples’ ones.« less
Gas-phase mercury reduction to measure total mercury in the flue gas of a coal-fired boiler.

PubMed

Meischen, Sandra J; Van Pelt, Vincent J; Zarate, Eugene A; Stephens, Edward A

2004-01-01

Gaseous elemental and total (elemental + oxidized) mercury (Hg) in the flue gas from a coal-fired boiler was measured by a modified ultraviolet (UV) spectrometer. Challenges to Hg measurement were the spectral interferences from other flue gas components and that UV measures only elemental Hg. To eliminate interference from flue gas components, a cartridge filled with gold-coated sand removed elemental Hg from a flue gas sample. The Hg-free flue gas was the reference gas, eliminating the spectral interferences. To measure total Hg by UV, oxidized Hg underwent a gas-phase, thermal-reduction in a quartz cell heated to 750 degrees C. Simultaneously, hydrogen was added to flash react with the oxygen present forming water vapor and preventing Hg re-oxidation as it exits the cell. Hg concentration results are in parts per billion by volume Hg at the flue gas oxygen concentration. The modified Hg analyzer and the Ontario Hydro method concurrently measured Hg at a field test site. Measurements were made at a 700-MW steam turbine plant with scrubber units and selective catalytic reduction. The flue gas sampled downstream of the selective catalytic reduction contained 2100 ppm SO2 and 75 ppm NOx. Total Hg measured by the Hg analyzer was within 20% of the Ontario Hydro results.
A three-dimensional interpenetrating electrode of reduced graphene oxide for selective detection of dopamine.

PubMed

Yu, Xiaowen; Sheng, Kaixuan; Shi, Gaoquan

2014-09-21

Electrochemical detection of dopamine plays an important role in medical diagnosis. In this paper, we report a three-dimensional (3D) interpenetrating graphene electrode fabricated by electrochemical reduction of graphene oxide for selective detection of dopamine. This electrochemically reduced graphene oxide (ErGO) electrode was used directly without further functionalization or blending with other functional materials. This electrode can efficiently lower the oxidation potential of ascorbic acid; thus, it is able to selectively detect dopamine in the presence of ascorbic acid and uric acid. The ErGO-based biosensor exhibited a linear response towards dopamine in the concentration range of 0.1-10 μM with a low detection limit of 0.1 μM. Furthermore, this electrode has good reproducibility and environmental stability, and can be used to analyse real samples.
Reduced graphene oxide supported gold nanoparticles for electrocatalytic reduction of carbon dioxide

NASA Astrophysics Data System (ADS)

Saquib, Mohammad; Halder, Aditi

2018-02-01

Electrochemical reduction of carbon dioxide is one of the methods which have the capability to recycle CO2 into valuable products for energy and industrial applications. This research article describes about a new electrocatalyst "reduced graphene oxide supported gold nanoparticles" for selective electrochemical conversion of carbon dioxide to carbon monoxide. The main aim for conversion of CO2 to CO lies in the fact that the latter is an important component of syn gas (a mixture of hydrogen and carbon monoxide), which is then converted into liquid fuel via well-known industrial process called Fischer-Tropsch process. In this work, we have synthesized different composites of the gold nanoparticles supported on defective reduced graphene oxide to evaluate the catalytic activity of reduced graphene oxide (RGO)-supported gold nanoparticles and the role of defective RGO support towards the electrochemical reduction of CO2. Electrochemical and impedance measurements demonstrate that higher concentration of gold nanoparticles on the graphene support led to remarkable decrease in the onset potential of 240 mV and increase in the current density for CO2 reduction. Lower impedance and Tafel slope values also clearly support our findings for the better performance of RGOAu than bare Au for CO2 reduction.
Ferrate(VI) enhanced photocatalytic oxidation of pollutants in aqueous TiO2 suspensions.

PubMed

Sharma, Virender K; Graham, Nigel J D; Li, Xiang-Zhong; Yuan, Bao-Ling

2010-02-01

Photocatalytic oxidation using UV irradiation of TiO(2) has been studied extensively and has many potential industrial applications, including the degradation of recalcitrant contaminants in water and wastewater treatment. A limiting factor in the oxidation process is the recombination of conduction band electrons (e(-)(cb)) with electron holes (h(vb)(+)) on the irradiated TiO(2) surface; thus, in aqueous conditions, the presence of an effective electron scavenger will be beneficial to the efficiency of the oxidation process. Ferrate (FeO(4)(2-)) has received much recent attention as a water treatment chemical since it behaves simultaneously as an oxidant and coagulant. The combination of ferrate [Fe(VI)] with UV/TiO(2) photocatalysis offers an oxidation synergism arising from the Fe(VI) scavenging of e(-)(cb) and the corresponding beneficial formation of Fe(V) from the Fe(VI) reduction. This paper reviews recent studies concerning the photocatalytic oxidation of problematic pollutants with and without ferrate. The paper reviews the published results of laboratory experiments designed to follow the photocatalytic degradation of selected contaminants of environmental significance and the influence of the experimental conditions (e.g. pH, reactant concentrations and dissolved oxygen). The specific compounds are as follows: ammonia, cyanate, formic acid, bisphenol-A, dibutyl- and dimethyl-phthalate and microcystin-LR. The principal focus in these studies has been on the rates of reaction rather than on reaction pathways and products. The presence of UV/TiO(2) accelerates the chemical reduction of ferrate, and the reduction rate decreases with pH owing to deprotonation of ferrate ion. For all the selected contaminant substances, the photocatalytic oxidation rate was greater in the presence of ferrate, and this was believed to be synergistic rather than additive. The presence of dissolved oxygen in solution reduced the degradation rate of dimethyl phthalate in the ferrate/photocatalysis system. In the study of microcystin-LR, it was evident that an optimal ferrate concentration exists, whereby higher Fe(VI) concentrations above the optimum leads to a reduction in microcystin-LR degradation. In addition, the rate of microcystin-LR degradation was found to be strongly dependent on pH and was greatest at pH 6. The initial rate of photocatalytic reduction under different conditions was analysed using a Langmuirian form. Decrease in rates in the presence of dissolved oxygen may be due to competition between oxygen and ferrate as electron scavengers and to non-productive radical species interactions. The reaction between ferrate(VI) and microcystins-LR in the pH range of 6.0-10.0 is most likely controlled by the protonated Fe(VI) species, HFeO(4)(-). The photocatalytic oxidation of selected, recalcitrant contaminants was found to be significantly greater in the presence of ferrate, arising from the role of ferrate in inhibiting the h(vb)(+)-e(-)(cb) pair recombination on TiO(2) surfaces and the corresponding generation of highly oxidative Fe(V) species. The performance of the ferrate/photocatalysis system is strongly influenced by the reaction conditions, particularly the pH and dissolved oxygen concentration, arising from the complex nature of the interactions between the catalyst and the solution. Overall, the treatment performance of the Fe(VI)-TiO(2)-UV system is generally superior to alternative chemical oxidation methods. The formation of intermediate Fe(V) species in the photocatalytic reduction of ferrate(VI) requires confirmation, and a method involving electron paramagnetic resonance spectroscopy could be applied for this. The reactivity of Fe(V) with the selected contaminants is required in order to better understand the role of ferrate in the Fe(VI)-TiO(2)-UV oxidation system. To increase the practical utility of the system, it is recommended that future studies involving the photocatalytic oxidation of pollutants in the presence of ferrate(VI) should focus on developing modified TiO(2) surfaces that are photocatalytic under visible light conditions.
STUDY OF THE EFFECT OF CHLORINE ADDITION ON MERCURY OXIDATION BY SCR CATALYST UNDER SIMULATED SUBBITUMINOUS COAL FLUE GAS

EPA Science Inventory

An entrained flow reactor is used to study the effect of addition of chlorine-containing species on the oxidation of elemental mercury (Hgo)by a selective catalytic reduction (SCR) catalyst in simulated subbituminous coal combustion flue gas. The combustion flue gas was doped wit...
Electrolytic oxide reduction system

DOEpatents

Wiedmeyer, Stanley G; Barnes, Laurel A; Williamson, Mark A; Willit, James L; Berger, John F

2015-04-28

An electrolytic oxide reduction system according to a non-limiting embodiment of the present invention may include a plurality of anode assemblies, a plurality of cathode assemblies, and a lift system configured to engage the anode and cathode assemblies. The cathode assemblies may be alternately arranged with the anode assemblies such that each cathode assembly is flanked by two anode assemblies. The lift system may be configured to selectively engage the anode and cathode assemblies so as to allow the simultaneous lifting of any combination of the anode and cathode assemblies (whether adjacent or non-adjacent).
Reduction-oxidation Enabled Glass-ceramics to Stainless Steel Bonding Part I: screening of doping oxidants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dai, Steve Xunhu

Lithium silicate-based glass-ceramics with high coefficients of thermal expansion, designed to form matched hermetic seals in 304L stainless steel housing, show little evidence of interfacial chemical bonding, despite extensive inter-diffusion at the glass-ceramic-stainless steel (GC-SS) interface. A series of glass-ceramic compositions modified with a variety of oxidants, AgO, FeO, NiO, PbO, SnO, CuO, CoO, MoO 3 and WO 3, are examined for the feasibility of forming bonding oxides through reduction-oxidation (redox) at the GC-SS interface. The oxidants were selected according to their Gibbs free energy to allow for oxidation of Cr/Mn/Si from stainless steel, and yet to prevent a reductionmore » of P2O5 in the glass-ceramic where the P 2O 5 is to form Li 3PO 4 nuclei for growth of high expansion crystalline SiO 2 phases. Other than the CuO and CoO modified glass-ceramics, bonding from interfacial redox reactions were not achieved in the modified glass-ceramics, either because of poor wetting on the stainless steel or a reduction of the oxidants at the surface of glass-ceramic specimens rather than the GC-SS interface.« less
Investigation of Mixed Oxide Catalysts for NO Oxidation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szanyi, Janos; Karim, Ayman M.; Pederson, Larry R.

2014-12-09

The oxidation of engine-generated NO to NO2 is an important step in the reduction of NOx in lean engine exhaust because NO2 is required for the performance of the LNT technology [2], and it enhances the activities of ammonia selective catalytic reduction (SCR) catalysts [1]. In particular, for SCR catalysts an NO:NO2 ratio of 1:1 is most effective for NOx reduction, whereas for LNT catalysts, NO must be oxidized to NO2 before adsorption on the storage components. However, NO2 typically constitutes less than 10% of NOx in lean exhaust, so catalytic oxidation of NO is essential. Platinum has been foundmore » to be especially active for NO oxidation, and is widely used in DOC and LNT catalysts. However, because of the high cost and poor thermal durability of Pt-based catalysts, there is substantial interest in the development of alternatives. The objective of this project, in collaboration with partner General Motors, is to develop mixed metal oxide catalysts for NO oxidation, enabling lower precious metal usage in emission control systems. [1] M. Koebel, G. Madia, and M. Elsener, Catalysis Today 73, 239 (2002). [2] C. H. Kim, G. S. Qi, K. Dahlberg, and W. Li, Science 327, 1624 (2010).« less

Measurement of regulated and unregulated exhaust emissions from a lawn mower with and without an oxidizing catalyst: a comparison of two different fuels.

PubMed

Christensen, A; Westerholm, R; Almén, J

2001-06-01

Relatively few emission characterization studies have been made on small engines used in garden equipment. The present investigation focuses on exhaust characterization from a lawn mower engine fueled with two different fuels in combination with and without an oxidizing catalyst. The compounds measured in the exhaust are carbon monoxide, hydrocarbons, nitrogen oxides, particulates, polycyclic aromatic hydrocarbons, methane, ethane, ethene, ethanol, and nitrous oxide. A significant reduction can be achieved by the use of a catalyst. By selection of the fuel, a significant reduction of certain carcinogenic compounds ("probably carcinogenic to humans" according to the IARC; benzo[a]pyrene and benzo[a]anthracene) may be achieved. The highest reduction improvement is achieved through the combination of an environmentally improved fuel, i.e., alkylate fuel, and a catalyst system. The data presented show that emissions from lawn mower engines are still relatively large although there is the potential for further improvements.
IDENTIFICATION AND RESPONSES TO POTENTIAL EFFECTS OF SCR AND WET SCRUBBERS ON SUBMICRON PARTICULATE EMISSIONS AND PLUME CHARACTERISTICS

EPA Science Inventory

Applications of selective catalytic reduction (SCR) systems and wet flue gas desulfurization (FGD) scrubbers on coal-fired boilers have led to substantial reductions in emissions of nitrogen oxides (NOX) and sulfur dioxide (SO2). However, observations of pilot- and full-scale tes...
76 FR 32886 - Control of Emissions From New Highway Vehicles and Engines; Guidance on EPA's Certification...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-07

... production is accounted for in API's certification program and that the follow-up audit program is showing... Selective Catalytic Reduction Technology AGENCY: Environmental Protection Agency (EPA). ACTION: Request for... reduction (SCR) technology to meet emission standards for oxides of nitrogen (NO X ). This draft guidance...
Development and characterization of reduced graphene oxide films for transient electronics

NASA Astrophysics Data System (ADS)

Sheikh, Rasel; Bhatkar, Omkar; Smith, David; Rizvi, Reza

2018-03-01

Emerging interests in hardware security as well as environmental concerns have given rise to the field of transient or temporary electronics, which can be decommissioned by an external stimulus with minimal impact to the surrounding environment. In this study, an all graphene based film is produced by a one-step deposition process. The conversion of graphene oxide (GO) to reduced graphene oxide (rGO) depends on an interfacial reduction reaction. Control of processing conditions such as the underlying substrate, pH of GO and the film drying environment results in an ability to tailor the internal architecture of the films and their electronic properties. Furthermore, the ability to create masks for selective reduction of GO during deposition was also demonstrated, which was used to create intricate yet well-defined patterns and connections required in electronic circuits and devices. All graphene based freestanding films with selectively reduced GO were used in transient electronics application as circuitry and RFID tag patterns.
Mercury oxidation promoted by a selective catalytic reduction catalyst under simulated Powder River Basin coal combustion conditions.

PubMed

Lee, Chun W; Serre, Shannon D; Zhao, Yongxin; Lee, Sung Jun; Hastings, Thomas W

2008-04-01

A bench-scale reactor consisting of a natural gas burner and an electrically heated reactor housing a selective catalytic reduction (SCR) catalyst was constructed for studying elemental mercury (Hg(o)) oxidation under SCR conditions. A low sulfur Powder River Basin (PRB) subbituminous coal combustion fly ash was injected into the entrained-flow reactor along with sulfur dioxide (SO2), nitrogen oxides (NOx), hydrogen chloride (HCl), and trace Hg(o). Concentrations of Hg(o) and total mercury (Hg) upstream and downstream of the SCR catalyst were measured using a Hg monitor. The effects of HCl concentration, SCR operating temperature, catalyst space velocity, and feed rate of PRB fly ash on Hg(o) oxidation were evaluated. It was observed that HCl provides the source of chlorine for Hg(o) oxidation under simulated PRB coal-fired SCR conditions. The decrease in Hg mass balance closure across the catalyst with decreasing HCl concentration suggests that transient Hg capture on the SCR catalyst occurred during the short test exposure periods and that the outlet speciation observed may not be representative of steady-state operation at longer exposure times. Increasing the space velocity and operating temperature of the SCR led to less Hg(o) oxidized. Introduction of PRB coal fly ash resulted in slightly decreased outlet oxidized mercury (Hg2+) as a percentage of total inlet Hg and correspondingly resulted in an incremental increase in Hg capture. The injection of ammonia (NH3) for NOx reduction by SCR was found to have a strong effect to decrease Hg oxidation. The observations suggest that Hg(o) oxidation may occur near the exit region of commercial SCR reactors. Passage of flue gas through SCR systems without NH3 injection, such as during the low-ozone season, may also impact Hg speciation and capture in the flue gas.
Selective extraction of metal ions with polymeric extractants by ion exchange/redox

DOEpatents

Alexandratos, Spiro D.

1987-01-01

The specification discloses a method for the extraction of metal ions having a reduction potential of above about +0.3 from an aqueous solution. The method includes contacting the aqueous solution with a polymeric extractant having primary phosphinic acid groups, secondary phosphine oxide groups, or both phosphinic acid and phosphine oxide groups.
Reductive reactivity of iron(III) oxides in the east china sea sediments: characterization by selective extraction and kinetic dissolution.

PubMed

Chen, Liang-Jin; Zhu, Mao-Xu; Yang, Gui-Peng; Huang, Xiang-Li

2013-01-01

Reactive Fe(III) oxides in gravity-core sediments collected from the East China Sea inner shelf were quantified by using three selective extractions (acidic hydroxylamine, acidic oxalate, bicarbonate-citrate buffered sodium dithionite). Also the reactivity of Fe(III) oxides in the sediments was characterized by kinetic dissolution using ascorbic acid as reductant at pH 3.0 and 7.5 in combination with the reactive continuum model. Three parameters derived from the kinetic method: m 0 (theoretical initial amount of ascorbate-reducible Fe(III) oxides), k' (rate constant) and γ (heterogeneity of reactivity), enable a quantitative characterization of Fe(III) oxide reactivity in a standardized way. Amorphous Fe(III) oxides quantified by acidic hydroxylamine extraction were quickly consumed in the uppermost layer during early diagenesis but were not depleted over the upper 100 cm depth. The total amounts of amorphous and poorly crystalline Fe(III) oxides are highly available for efficient buffering of dissolved sulfide. As indicated by the m 0, k' and γ, the surface sediments always have the maximum content, reactivity and heterogeneity of reactive Fe(III) oxides, while the three parameters simultaneously downcore decrease, much more quickly in the upper layer than at depth. Albeit being within a small range (within one order of magnitude) of the initial rates among sediments at different depths, incongruent dissolution could result in huge discrepancies of the later dissolution rates due to differentiating heterogeneity, which cannot be revealed by selective extraction. A strong linear correlation of the m 0 at pH 3.0 with the dithionite-extractable Fe(III) suggests that the m 0 may represent Fe(III) oxide assemblages spanning amorphous and crystalline Fe(III) oxides. Maximum microbially available Fe(III) predicted by the m 0 at pH 7.5 may include both amorphous and a fraction of other less reactive Fe(III) phases.
Reductive Reactivity of Iron(III) Oxides in the East China Sea Sediments: Characterization by Selective Extraction and Kinetic Dissolution

PubMed Central

Chen, Liang-Jin; Zhu, Mao-Xu; Yang, Gui-Peng; Huang, Xiang-Li

2013-01-01

Reactive Fe(III) oxides in gravity-core sediments collected from the East China Sea inner shelf were quantified by using three selective extractions (acidic hydroxylamine, acidic oxalate, bicarbonate-citrate buffered sodium dithionite). Also the reactivity of Fe(III) oxides in the sediments was characterized by kinetic dissolution using ascorbic acid as reductant at pH 3.0 and 7.5 in combination with the reactive continuum model. Three parameters derived from the kinetic method: m 0 (theoretical initial amount of ascorbate-reducible Fe(III) oxides), k′ (rate constant) and γ (heterogeneity of reactivity), enable a quantitative characterization of Fe(III) oxide reactivity in a standardized way. Amorphous Fe(III) oxides quantified by acidic hydroxylamine extraction were quickly consumed in the uppermost layer during early diagenesis but were not depleted over the upper 100 cm depth. The total amounts of amorphous and poorly crystalline Fe(III) oxides are highly available for efficient buffering of dissolved sulfide. As indicated by the m 0, k′ and γ, the surface sediments always have the maximum content, reactivity and heterogeneity of reactive Fe(III) oxides, while the three parameters simultaneously downcore decrease, much more quickly in the upper layer than at depth. Albeit being within a small range (within one order of magnitude) of the initial rates among sediments at different depths, incongruent dissolution could result in huge discrepancies of the later dissolution rates due to differentiating heterogeneity, which cannot be revealed by selective extraction. A strong linear correlation of the m 0 at pH 3.0 with the dithionite-extractable Fe(III) suggests that the m 0 may represent Fe(III) oxide assemblages spanning amorphous and crystalline Fe(III) oxides. Maximum microbially available Fe(III) predicted by the m 0 at pH 7.5 may include both amorphous and a fraction of other less reactive Fe(III) phases. PMID:24260377
Photoredox-catalyzed Direct Reductive Amination of Aldehydes without an External Hydrogen/Hydride Source.

PubMed

Alam, Rauful; Molander, Gary A

2018-05-04

The direct reductive amination of aromatic aldehydes has been realized using a photocatalyst under visible light irradiation. The single electron oxidation of an in situ formed aminal species generates the putative α-amino radical that eventually delivers the reductive amination product. This method is operationally simple, highly selective, and functional group tolerant, which allows the direct synthesis of benzylic amines by a unique mechanistic pathway.
Development of Teaching Material Oxidation-Reduction Reactions through Four Steps Teaching Material Development (4S TMD)

NASA Astrophysics Data System (ADS)

Syamsuri, B. S.; Anwar, S.; Sumarna, O.

2017-09-01

This research aims to develop oxidation-reduction reactions (redox) teaching material used the Four Steps Teaching Material Development (4S TMD) method consists of four steps: selection, structuring, characterization and didactical reduction. This paper is the first part of the development of teaching material that includes selection and structuring steps. At the selection step, the development of teaching material begins with the development concept of redox based on curriculum demands, then the development of fundamental concepts sourced from the international textbook, and last is the development of values or skills can be integrated with redox concepts. The results of this selection step are the subject matter of the redox concept and values can be integrated with it. In the structuring step was developed concept map that provide on the relationship between redox concepts; Macro structure that guide systematic on the writing of teaching material; And multiple representations which are the development of teaching material that connection between macroscopic, submicroscopic, and symbolic level representations. The result of the two steps in this first part of the study produced a draft of teaching material. Evaluation of the draft of teaching material is done by an expert lecturer in the field of chemical education to assess the feasibility of teaching material.
System and method for selective catalytic reduction of nitrogen oxides in combustion exhaust gases

DOEpatents

Sobolevskiy, Anatoly; Rossin, Joseph A

2014-04-08

A multi-stage selective catalytic reduction (SCR) unit (32) provides efficient reduction of NOx and other pollutants from about 50-550.degree. C. in a power plant (19). Hydrogen (24) and ammonia (29) are variably supplied to the SCR unit depending on temperature. An upstream portion (34) of the SCR unit catalyzes NOx+NH.sub.3 reactions above about 200.degree. C. A downstream portion (36) catalyzes NOx+H.sub.2 reactions below about 260.degree. C., and catalyzes oxidation of NH.sub.3, CO, and VOCs with oxygen in the exhaust above about 200.degree. C., efficiently removing NOx and other pollutants over a range of conditions with low slippage of NH.sub.3. An ammonia synthesis unit (28) may be connected to the SCR unit to provide NH.sub.3 as needed, avoiding transport and storage of ammonia or urea at the site. A carbonaceous gasification plant (18) on site may supply hydrogen and nitrogen to the ammonia synthesis unit, and hydrogen to the SCR unit.
Oxidative stress and protein aggregation during biological aging.

PubMed

Squier, T C

2001-09-01

Biological aging is a fundamental process that represents the major risk factor with respect to the development of cancer, neurodegenerative, and cardiovascular diseases in vertebrates. It is, therefore, evident that the molecular mechanisms of aging are fundamental to understand many disease processes. In this regard, the oxidation and nitration of intracellular proteins and the formation of protein aggregates have been suggested to underlie the loss of cellular function and the reduced ability of senescent animals to withstand physiological stresses. Since oxidatively modified proteins are thermodynamically unstable and assume partially unfolded tertiary structures that readily form aggregates, it is likely that oxidized proteins are intermediates in the formation of amyloid fibrils. It is, therefore, of interest to identify oxidatively sensitive protein targets that may play a protective role through their ability to down-regulate energy metabolism and the consequent generation of reactive oxygen species (ROS). In this respect, the maintenance of cellular calcium gradients represents a major energetic expense, which links alterations in intracellular calcium levels to ATP utilization and the associated generation of ROS through respiratory control mechanisms. The selective oxidation or nitration of the calcium regulatory proteins calmodulin and Ca-ATPase that occurs in vivo during aging and under conditions of oxidative stress may represent an adaptive response to oxidative stress that functions to down-regulate energy metabolism and the associated generation of ROS. Since these calcium regulatory proteins are also preferentially oxidized or nitrated under in vitro conditions, these results suggest an enhanced sensitivity of these critical calcium regulatory proteins, which modulate signal transduction processes and intracellular energy metabolism, to conditions of oxidative stress. Thus, the selective oxidation of critical signal transduction proteins probably represents a regulatory mechanism that functions to minimize the generation of ROS through respiratory control mechanisms. The reduction of the rate of ROS generation, in turn, will promote cellular survival under conditions of oxidative stress, when reactive oxygen and nitrogen species overwhelm cellular antioxidant defense systems, by minimizing the non-selective oxidation of a range of biomolecules. Since protein aggregation occurs if protein repair and degradative systems are unable to act upon oxidized proteins and restore cellular function, the reduction of the oxidative load on the cell by the down-regulation of the electron transport chain functions to minimize protein aggregation. Thus, ROS function as signaling molecules that fine-tune cellular metabolism through the selective oxidation or nitration of calcium regulatory proteins in order to minimize wide-spread oxidative damage and protein aggregation. Oxidative damage to cellular proteins, the loss of calcium homeostasis and protein aggregation contribute to the formation of amyloid deposits that accumulate during biological aging. Critical to understand the relationship between these processes and biological aging is the identification of oxidatively sensitive proteins that modulate energy utilization and the associated generation of ROS. In this latter respect, oxidative modifications to the calcium regulatory proteins calmodulin (CaM) and the sarco/endoplasmic reticulum Ca-ATPase (SERCA) function to down-regulate ATP utilization and the associated generation of ROS associated with replenishing intracellular ATP through oxidative phosphorylation. Reductions in the rate of ROS generation, in turn, will minimize protein oxidation and facilitate intracellular repair and degradative systems that function to eliminate damaged and partially unfolded proteins. Since the rates of protein repair or degradation compete with the rate of protein aggregation, the modulation of intracellular calcium concentrations and energy metabolism through the selective oxidation or nitration of critical signal transduction proteins (i.e. CaM or SERCA) is thought to maintain cellular function by minimizing protein aggregation and amyloid formation. Age-dependent increases in the rate of ROS generation or declines in cellular repair or degradation mechanisms will increase the oxidative load on the cell, resulting in corresponding increases in the concentrations of oxidized proteins and the associated formation of amyloid.
Effect of the Mn oxidation state and lattice oxygen in Mn-based TiO2 catalysts on the low-temperature selective catalytic reduction of NO by NH3.

PubMed

Lee, Sang Moon; Park, Kwang Hee; Kim, Sung Su; Kwon, Dong Wook; Hong, Sung Chang

2012-09-01

TiO2-supported manganese oxide catalysts formed using different calcination temperatures were prepared by using the wet-impregnation method and were investigated for their activity in the low-temperature selective catalytic reduction (SCR) of NO by NH3 with respect to the Mn valence and lattice oxygen behavior. The surface and bulk properties of these catalysts were examined using Brunauer-Emmett-Teller (BET) surface area, X-ray diffraction (XRD), temperature-programmed reduction (TPR), and temperature-programmed desorption (TPD). Catalysts prepared using lower calcination temperatures, which contained Mn4+ displayed high SCR activity at low temperatures and possessed several acid sites and active oxygen. The TPD analysis determined that the Brönsted and Lewis acid sites in the Mn/TiO2 catalysts were important for the low-temperature SCR at 80-160 and 200-350 degrees C, respectively. In addition, the available lattice oxygen was important for attaining high NO to NO2 oxidation at low temperatures. Recently, various Mn catalysts have been evaluated as SCR catalysts. However, there have been no studies on the relationship of adsorption and desorption properties and behavior of lattice oxygen according to the valence state for manganese oxides (MnO(x)). Therefore, in this study, the catalysts were prepared by the wet-impregnation method at different calcination temperatures in order to show the difference of manganese oxidation state. These catalysts were then characterized using various physicochemical techniques, including BET, XRD, TPR, and TPD, to understand the structure, oxidation state, redox properties, and adsorption and desorption properties of the Mn/TiO2 catalysts.
Transformation of mercury speciation through the SCR system in power plants.

PubMed

Yang, Hong-min; Pan, Wei-ping

2007-01-01

Coal-fired utility boilers are now identified as the largest source of mercury in the United States. There is speculation that the installation of selective catalytic reduction (SCR) system for reduction of NOx can also prompt the oxidation and removal of mercury. In this paper, tests at six full-scale power plants with similar type of the SCR systems are conducted to investigate the effect of the SCR on the transformation of mercury speciation. The results show that the SCR system can achieve more than 70%-80% oxidation of elemental mercury and enhance the mercury removal ability in these units. The oxidation of elemental mercury in the SCR system strongly depends on the coal properties and the operation conditions of the SCR systems. The content of chloride in the coal is the key factor for the oxidization process and the maximum oxidation of elemental mercury is found when chloride content changes from 400 to 600 ppm. The sulfur content is no significant impact on oxidation of elemental mercury.
Physicochemical properties of manganese oxides obtained via the sol-gel method: The reduction of potassium permanganate by polyvinyl alcohol

NASA Astrophysics Data System (ADS)

Ivanets, A. I.; Prozorovich, V. G.; Krivoshapkina, E. F.; Kuznetsova, T. F.; Krivoshapkin, P. V.; Katsoshvili, L. L.

2017-08-01

Experimental data on the sol-gel synthesis of manganese oxides formed during the reduction of potassium permanganate by polyvinyl alcohol in an aqueous medium are presented. The physicochemical properties of the obtained manganese oxide systems that depend on the conditions of the synthesis are studied by means of DTA, XRD, SEM, and the low temperature adsorption-desorption of nitrogen. It is found that the obtained samples have a mesoporous structure and predominantly consist of double potassium-manganese oxide K2Mn4O8 with a tunnel structure and impurities of oxides such as α-MnO2, MnO, α-Mn2O3, and Mn5O8. It is shown that the proposed method of synthesis allows us to regulate the size and volume of mesopores and, to a lesser extent, the texture of the obtained oxides, which can be considered promising sorbents for the selective extraction of strontium and cesium ions from multicomponent aqueous solutions.
In situ IR studies of Co and Ce doped Mn/TiO2 catalyst for low-temperature selective catalytic reduction of NO with NH3

NASA Astrophysics Data System (ADS)

Qiu, Lu; Pang, Dandan; Zhang, Changliang; Meng, Jiaojiao; Zhu, Rongshu; Ouyang, Feng

2015-12-01

The Mn-Co-Ce/TiO2 catalyst was prepared by wet co-impregnation method for selective catalytic reduction of NO by NH3 in the presence of oxygen. The adsorption and co-adsorption of NH3, NO and O2 on catalysts were investigated by in situ FTIR spectroscopy. The results suggested that addition of cobalt and cerium oxides increased the numbers of acid and redox sites. Especially, the cobalt oxide produced lots of Brønsted acid sites, which favor to the adsorption of coordinated NH3 through NH3 migration. Ce addition improved amide ions formation to reach best NO reduction selectivity. A mechanistic pathway over Mn-Co-Ce/TiO2 was proposed. At low-temperature SCR reaction, coordinated NH3 reacted with NO2-, and amide reacted with NO (ad) or NO (g) to form N2. NO2 was related to the formation of nitrite on Co-contained catalysts and the generation of sbnd NH2- on Ce-contained catalysts. At high temperature, the other branch reaction also occurred between the coordinated NH3 and nitrate species, resulting in N2O yield increase.
Structure Characterization and Catalytic Properties of Cr2O3 Doped with MgO Supported on MgF2

NASA Astrophysics Data System (ADS)

Goslar, J.; Wojciechowska, M.; Zieliński, M.; Tomska-Foralewska, I.; Przystajko, W.

2006-08-01

A characterization of double oxide systems containing Cr2O3 doped with MgO and supported on MgF2 was carried out. The catalysts were prepared by impregnation and co-impregnation methods and characterized by the Brunauer-Emmett-Teller method, EPR, and temperature programmed reduction. The results proved the interactions between supported oxides and the presence of spinel-like phase after treatment at 400 ºC. Magnesium oxide clearly influences the catalytic activity as well as selectivity of chromium catalysts supported on MgF2. The MgO-Cr2O3/MgF2 systems were active and selective in the reaction of CO oxidation at the room temperature and in the dehydrogenation of cyclohexene.
Enantiocomplementary Yarrowia lipolytica Oxidoreductases: Alcohol Dehydrogenase 2 and Short Chain Dehydrogenase/Reductase

PubMed Central

Napora-Wijata, Kamila; Strohmeier, Gernot A.; Sonavane, Manoj N.; Avi, Manuela; Robins, Karen; Winkler, Margit

2013-01-01

Enzymes of the non-conventional yeast Yarrowia lipolytica seem to be tailor-made for the conversion of lipophilic substrates. Herein, we cloned and overexpressed the Zn-dependent alcohol dehydrogenase ADH2 from Yarrowia lipolytica in Escherichia coli. The purified enzyme was characterized in vitro. The substrate scope for YlADH2 mediated oxidation and reduction was investigated spectrophotometrically and the enzyme showed a broader substrate range than its homolog from Saccharomyces cerevisiae. A preference for secondary compared to primary alcohols in oxidation direction was observed for YlADH2. 2-Octanone was investigated in reduction mode in detail. Remarkably, YlADH2 displays perfect (S)-selectivity and together with a highly (R)-selective short chain dehydrogenase/ reductase from Yarrowia lipolytica it is possible to access both enantiomers of 2-octanol in >99% ee with Yarrowia lipolytica oxidoreductases. PMID:24970175
Enantiocomplementary Yarrowia lipolytica Oxidoreductases: Alcohol Dehydrogenase 2 and Short Chain Dehydrogenase/Reductase.

PubMed

Napora-Wijata, Kamila; Strohmeier, Gernot A; Sonavane, Manoj N; Avi, Manuela; Robins, Karen; Winkler, Margit

2013-08-12

Enzymes of the non-conventional yeast Yarrowia lipolytica seem to be tailor-made for the conversion of lipophilic substrates. Herein, we cloned and overexpressed the Zn-dependent alcohol dehydrogenase ADH2 from Yarrowia lipolytica in Escherichia coli. The purified enzyme was characterized in vitro. The substrate scope for YlADH2 mediated oxidation and reduction was investigated spectrophotometrically and the enzyme showed a broader substrate range than its homolog from Saccharomyces cerevisiae. A preference for secondary compared to primary alcohols in oxidation direction was observed for YlADH2. 2-Octanone was investigated in reduction mode in detail. Remarkably, YlADH2 displays perfect (S)-selectivity and together with a highly (R)-selective short chain dehydrogenase/ reductase from Yarrowia lipolytica it is possible to access both enantiomers of 2-octanol in >99% ee with Yarrowia lipolytica oxidoreductases.
CO2-Free Power Generation on an Iron Group Nanoalloy Catalyst via Selective Oxidation of Ethylene Glycol to Oxalic Acid in Alkaline Media

NASA Astrophysics Data System (ADS)

Matsumoto, Takeshi; Sadakiyo, Masaaki; Ooi, Mei Lee; Kitano, Sho; Yamamoto, Tomokazu; Matsumura, Syo; Kato, Kenichi; Takeguchi, Tatsuya; Yamauchi, Miho

2014-07-01

An Fe group ternary nanoalloy (NA) catalyst enabled selective electrocatalysis towards CO2-free power generation from highly deliverable ethylene glycol (EG). A solid-solution-type FeCoNi NA catalyst supported on carbon was prepared by a two-step reduction method. High-resolution electron microscopy techniques identified atomic-level mixing of constituent elements in the nanoalloy. We examined the distribution of oxidised species, including CO2, produced on the FeCoNi nanoalloy catalyst in the EG electrooxidation under alkaline conditions. The FeCoNi nanoalloy catalyst exhibited the highest selectivities toward the formation of C2 products and to oxalic acid, i.e., 99 and 60%, respectively, at 0.4 V vs. the reversible hydrogen electrode (RHE), without CO2 generation. We successfully generated power by a direct EG alkaline fuel cell employing the FeCoNi nanoalloy catalyst and a solid-oxide electrolyte with oxygen reduction ability, i.e., a completely precious-metal-free system.

Spectroscopic and electrochemical characterization of some Schiff base metal complexes containing benzoin moiety

NASA Astrophysics Data System (ADS)

El-Shahawi, M. S.; Al-Jahdali, M. S.; Bashammakh, A. S.; Al-Sibaai, A. A.; Nassef, H. M.

2013-09-01

The ligation behavior of bis-benzoin ethylenediamine (B2ED) and benzoin thiosemicarbazone (BTS) Schiff bases towards Ru3+, Rh3+, Pd2+, Ni2+ and Cu2+ were determined. The bond length of M-N and spectrochemical parameters (10Dq, β, B and LFSE) of the complexes were evaluated. The redox characteristics of selected complexes were explored by cyclic voltammetry (CV) at Pt working electrode in non aqueous solvents. Au mesh (100 w/in.) optically transparent thin layer electrode (OTTLE) was also used for recording thin layer CV for selected Ru complex. Oxidation of some complexes occurs in a consecutive chemical reaction of an EC type mechanism. The characteristics of electron transfer process of the couples M2+/M3+ and M3+/M4+ (M = Ru3+, Rh3+) and the stability of the complexes towards oxidation and/or reduction were assigned. The nature of the electroactive species and reduction mechanism of selected electrode couples were assigned.
Effect of dipolar fields, surface termination, and surface orientation on photochemical reactions on transition metal oxides

NASA Astrophysics Data System (ADS)

Giocondi, Jennifer Lynn

Experiments have been conducted to determine the effects of dipolar fields, surface termination, and surface orientation on the photochemical reactivity of several transition metal oxides. These compounds include BaTiO3, SrTiO3, BaTi4O9, Sr2Nb2O 7, and Sr2Ta2O7 which were studied as polycrystalline ceramics, single crystals, micron-sized faceted particles, or some combination of these forms. The reduction of Ag+ from an aqueous AgNO3 solution (Ag0 product) and the oxidation of Pb2+ from an aqueous lead acetate solution (PbO 2 product) were selected as probe reactions because they leave insoluble products on the oxide surfaces. The reactivity of ferroelectric BaTiO3 was dominated by the effect of dipolar fields on the transport of photogenerated charge carriers. Silver was reduced on domains with a positive surface charge while lead was oxidized on domains with a negative surface charge. This reactivity implies that the dipolar field in individual domains drives photogenerated charge carriers to oppositely charged surfaces. This reaction mechanism results in a physical separation of the photogenerated charge carriers and the locations of the oxidation and reduction half reactions on the catalyst surface. Experiments performed on polycrystalline ceramics, single crystals, and micron-sized particles all showed this domain specific reactivity. SrTiO3 has the ideal cubic perovskite structure from which the tetragonally distorted ferroelectric BaTiO3 phase is derived. Polished and annealed surfaces of randomly oriented grain surfaces were bound by some combination of the following three planes: {110}, {111}, and a complex facet inclined approximately 24° from {100}. Surfaces with the complex {100} facet were found to be the most active for Ag reduction. Single crystal studies also showed that the nonpolar (100) surface is the most reactive and that the composition of the termination layer does not influence this reaction. However, the polar (111) and (110) surfaces had a non-uniform distribution of reaction products. For these orientations, the location of the reduction and oxidation reactions is determined by the chemical and charge terminations of the different terraces or facets. The reactivity for silver reduction on the faceted particles is ranked as (100) > (111) > (110) while the (100) surface was least reactive for lead oxidation. Overall, these results show that the photochemical reactivity of SrTiO3 is anisotropic and that on polar surfaces, dipolar fields arising from charged surface domains influence the transport of photogenerated charge carriers and promote spatially selective oxidation and reduction reactions. (Abstract shortened by UMI.)
Coupled Metal/Oxide Catalysts with Tunable Product Selectivity for Electrocatalytic CO2 Reduction.

PubMed

Huo, Shengjuan; Weng, Zhe; Wu, Zishan; Zhong, Yiren; Wu, Yueshen; Fang, Jianhui; Wang, Hailiang

2017-08-30

One major challenge to the electrochemical conversion of CO 2 to useful fuels and chemical products is the lack of efficient catalysts that can selectively direct the reaction to one desirable product and avoid the other possible side products. Making use of strong metal/oxide interactions has recently been demonstrated to be effective in enhancing electrocatalysis in the liquid phase. Here, we report one of the first systematic studies on composition-dependent influences of metal/oxide interactions on electrocatalytic CO 2 reduction, utilizing Cu/SnO x heterostructured nanoparticles supported on carbon nanotubes (CNTs) as a model catalyst system. By adjusting the Cu/Sn ratio in the catalyst material structure, we can tune the products of the CO 2 electrocatalytic reduction reaction from hydrocarbon-favorable to CO-selective to formic acid-dominant. In the Cu-rich regime, SnO x dramatically alters the catalytic behavior of Cu. The Cu/SnO x -CNT catalyst containing 6.2% of SnO x converts CO 2 to CO with a high faradaic efficiency (FE) of 89% and a j CO of 11.3 mA·cm -2 at -0.99 V versus reversible hydrogen electrode, in stark contrast to the Cu-CNT catalyst on which ethylene and methane are the main products for CO 2 reduction. In the Sn-rich regime, Cu modifies the catalytic properties of SnO x . The Cu/SnO x -CNT catalyst containing 30.2% of SnO x reduces CO 2 to formic acid with an FE of 77% and a j HCOOH of 4.0 mA·cm -2 at -0.99 V, outperforming the SnO x -CNT catalyst which only converts CO 2 to formic acid in an FE of 48%.
Selective CO Production by Photoelectrochemical Methane Oxidation on TiO2.

PubMed

Li, Wei; He, Da; Hu, Guoxiang; Li, Xiang; Banerjee, Gourab; Li, Jingyi; Lee, Shin Hee; Dong, Qi; Gao, Tianyue; Brudvig, Gary W; Waegele, Matthias M; Jiang, De-En; Wang, Dunwei

2018-05-23

The inertness of the C-H bond in CH 4 poses significant challenges to selective CH 4 oxidation, which often proceeds all the way to CO 2 once activated. Selective oxidation of CH 4 to high-value industrial chemicals such as CO or CH 3 OH remains a challenge. Presently, the main methods to activate CH 4 oxidation include thermochemical, electrochemical, and photocatalytic reactions. Of them, photocatalytic reactions hold great promise for practical applications but have been poorly studied. Existing demonstrations of photocatalytic CH 4 oxidation exhibit limited control over the product selectivity, with CO 2 as the most common product. The yield of CO or other hydrocarbons is too low to be of any practical value. In this work, we show that highly selective production of CO by CH 4 oxidation can be achieved by a photoelectrochemical (PEC) approach. Under our experimental conditions, the highest yield for CO production was 81.9%. The substrate we used was TiO 2 grown by atomic layer deposition (ALD), which features high concentrations of Ti 3+ species. The selectivity toward CO was found to be highly sensitive to the substrate types, with significantly lower yield on P25 or commercial anatase TiO 2 substrates. Moreover, our results revealed that the selectivity toward CO also depends on the applied potentials. Based on the experimental results, we proposed a reaction mechanism that involves synergistic effects by adjacent Ti sites on TiO 2 . Spectroscopic characterization and computational studies provide critical evidence to support the mechanism. Furthermore, the synergistic effect was found to parallel heterogeneous CO 2 reduction mechanisms. Our results not only present a new route to selective CH 4 oxidation, but also highlight the importance of mechanistic understandings in advancing heterogeneous catalysis.
Simultaneous removal of nitrogen oxides and sulfur oxides from combustion gases

DOEpatents

Clay, David T.; Lynn, Scott

1976-10-19

A process for the simultaneous removal of sulfur oxides and nitrogen oxides from power plant stack gases comprising contacting the stack gases with a supported iron oxide catalyst/absorbent in the presence of sufficient reducing agent selected from the group consisting of carbon monoxide, hydrogen, and mixtures thereof, to provide a net reducing atmosphere in the SO.sub.x /NO.sub.x removal zone. The sulfur oxides are removed by absorption substantially as iron sulfide, and nitrogen oxides are removed by catalytic reduction to nitrogen and ammonia. The spent iron oxide catalyst/absorbent is regenerated by oxidation and is recycled to the contacting zone. Sulfur dioxide is also produced during regeneration and can be utilized in the production of sulfuric acid and/or sulfur.
Alternative mechanistic explanation for ligand-dependent selectivities in copper-catalyzed N- and O-arylation reactions.

PubMed

Yu, Hai-Zhu; Jiang, Yuan-Ye; Fu, Yao; Liu, Lei

2010-12-29

The ligand-dependent selectivities in Ullmann-type reactions of amino alcohols with iodobenzene by β-diketone- and 1,10-phenanthroline-ligated Cu(I) complexes were recently explained by the single-electron transfer and iodine atom transfer mechanisms (Jones, G. O., Liu, P., Houk, K. N., and Buchwald, S. L. J. Am. Chem. Soc. 2010, 132, 6205.). The present study shows that an alternative, oxidative addition/reductive elimination mechanism may also explain the selectivities. Calculations indicate that a Cu(I) complex with a negatively charged β-diketone ligand is electronically neutral, so that oxidative addition of ArI to a β-diketone-ligated Cu(I) prefers to occur (and occur readily) in the absence of the amino alcohol. Thus, coordination of the amino alcohol in its neutral form can only occur at the Cu(III) stage where N-coordination is favored over O-coordination. The coordination step is the rate-limiting step and the outcome is that N-arylation is favored with the β-diketone ligand. On the other hand, a Cu(I) complex with a neutral 1,10-phenanthroline ligand is positively charged, so that oxidative addition of ArI to a 1,10-phenanthroline-ligated Cu(I) has to get assistance from a deprotonated amino alcohol substrate. This causes oxidative addition to become the rate-limiting step in the 1,10-phenanthroline-mediated reaction. The immediate product of the oxidative addition step is found to undergo facile reductive elimination to provide the arylation product. Because O-coordination of a deprotonated amino alcohol is favored over N-coordination in the oxidative addition transition state, O-arylation is favored with the 1,10-phenanthroline ligand.
Tuning of CO2 Reduction Selectivity on Metal Electrocatalysts.

PubMed

Wang, Yuhang; Liu, Junlang; Wang, Yifei; Al-Enizi, Abdullah M; Zheng, Gengfeng

2017-11-01

Climate change, caused by heavy CO 2 emissions, is driving new demands to alleviate the rising concentration of atmospheric CO 2 levels. Enlightened by the photosynthesis of green plants, photo(electro)chemical catalysis of CO 2 reduction, also known as artificial photosynthesis, is emerged as a promising candidate to address these demands and is widely investigated during the past decade. Among various artificial photosynthetic systems, solar-driven electrochemical CO 2 reduction is widely recognized to possess high efficiencies and potentials for practical application. The efficient and selective electroreduction of CO 2 is the key to the overall solar-to-chemical efficiency of artificial photosynthesis. Recent studies show that various metallic materials possess the capability to play as electrocatalysts for CO 2 reduction. In order to achieve high selectivity for CO 2 reduction products, various efforts are made including studies on electrolytes, crystal facets, oxide-derived catalysts, electronic and geometric structures, nanostructures, and mesoscale phenomena. In this Review, these methods for tuning the selectivity of CO 2 electrochemical reduction of metallic catalysts are summarized. The challenges and perspectives in this field are also discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Cermets and method for making same

DOEpatents

Aaron, W. Scott; Kinser, Donald L.; Quinby, Thomas C.

1983-01-01

The present invention is directed to a method for making a wide variety of general-purpose cermets and for radioactive waste disposal from ceramic powders prepared from urea-dispersed solutions containing various metal values. The powders are formed into a compact and subjected to a rapid temperature increase in a reducing atmosphere. During this reduction, one or more of the more readily reducible oxides in the compact is reduced to a selected substoichiometric state at a temperature below the eutectic phase for that particular oxide or oxides and then raised to a temperature greater than the eutectic temperature to provide a liquid phase in the compact prior to the reduction of the liquid phase forming oxide to solid metal. This liquid phase forms at a temperature below the melting temperature of the metal and bonds together the remaining particulates in the cermet to form a solid polycrystalline cermet.
Interaction at the silicon/transition metal oxide heterojunction interface and its effect on the photovoltaic performance.

PubMed

Liang, Zhimin; Su, Mingze; Zhou, Yangyang; Gong, Li; Zhao, Chuanxi; Chen, Keqiu; Xie, Fangyan; Zhang, Weihong; Chen, Jian; Liu, Pengyi; Xie, Weiguang

2015-11-07

The interfacial reaction and energy level alignment at the Si/transition metal oxide (TMO, including MoO3-x, V2O5-x, WO3-x) heterojunction are systematically investigated. We confirm that the interfacial reaction appears during the thermal deposition of TMO, with the reaction extent increasing from MoO3-x, to V2O5-x, and to WO3-x. The reaction causes the surface oxidation of silicon for faster electron/hole recombination, and the reduction of TMO for effective hole collection. The photovoltaic performance of the Si/TMO heterojunction devices is affected by the interface reaction. MoO3-x are the best hole selecting materials that induce least surface oxidation but strongest reduction. Compared with H-passivation, methyl group passivation is an effective way to reduce the interface reaction and improve the interfacial energy level alignment for better electron and hole collection.
Electrochemistry in the mimicry of oxidative drug metabolism by cytochrome P450s.

PubMed

Nouri-Nigjeh, Eslam; Bischoff, Rainer; Bruins, Andries P; Permentier, Hjalmar P

2011-05-01

Prediction of oxidative drug metabolism at the early stages of drug discovery and development requires fast and accurate analytical techniques to mimic the in vivo oxidation reactions by cytochrome P450s (CYP). Direct electrochemical oxidation combined with mass spectrometry, although limited to the oxidation reactions initiated by charge transfer, has shown promise in the mimicry of certain CYP-mediated metabolic reactions. The electrochemical approach may further be utilized in an automated manner in microfluidics devices facilitating fast screening of oxidative drug metabolism. A wide range of in vivo oxidation reactions, particularly those initiated by hydrogen atom transfer, can be imitated through the electrochemically-assisted Fenton reaction. This reaction is based on O-O bond activation in hydrogen peroxide and oxidation by hydroxyl radicals, wherein electrochemistry is used for the reduction of molecular oxygen to hydrogen peroxide, as well as the reduction of Fe(3+) to Fe(2+). Metalloporphyrins, as surrogates for the prosthetic group in CYP, utilizing metallo-oxo reactive species, can also be used in combination with electrochemistry. Electrochemical reduction of metalloporphyrins in solution or immobilized on the electrode surface activates molecular oxygen in a manner analogous to the catalytical cycle of CYP and different metalloporphyrins can mimic selective oxidation reactions. Chemoselective, stereoselective, and regioselective oxidation reactions may be mimicked using electrodes that have been modified with immobilized enzymes, especially CYP itself. This review summarizes the recent attempts in utilizing electrochemistry as a versatile analytical and preparative technique in the mimicry of oxidative drug metabolism by CYP. © 2011 Bentham Science Publishers Ltd.
Magnetic cobaltic nanoparticle-anchored carbon nanocomposite derived from cobalt-dipicolinic acid coordination polymer: An enhanced catalyst for environmental oxidative and reductive reactions.

PubMed

Wu, Chang-Hsun; Lin, Jyun-Ting; Lin, Kun-Yi Andrew

2018-05-01

Direct carbonization of cobalt complexes represents as a convenient approach to prepare magnetic carbon/cobalt nanocomposites (MCCNs) as heterogeneous environmental catalysts. However, most of MCCNs derived from consist of sheet-like carbon matrices with very sparse cobaltic nanoparticles (NPs), making them exhibit relatively low catalytic activities, porosity and magnetism. In this study, dipicolinic acid (DPA) is selected to prepare a 3-dimensional cobalt coordination polymer (CoDPA). MCCN derived from CoDPA can consist of a porous carbon matrix embedded with highly-dense Co 0 and Co 3 O 4 NPs. This magnetic Co 0 /Co 3 O 4 NP-anchored carbon composite (MCNC) appears as a promising heterogeneous catalyst for oxidative and reductive environmental catalytic reactions. As peroxymonosulfate (PMS) activation is selected as a model catalytic oxidative reaction, MCNC exhibits a much higher catalytic activity than Co 3 O 4 , a benchmark catalyst for PMS activation. The reductive catalytic activity of MCNC is demonstrated through 4-nitrophenol (4-NP) reduction in the presence of NaBH 4 . MCNC could rapidly react with NaBH 4 to generate H 2 for hydrogenation of 4-NP to 4-aminophenol (4-AP). In comparison with other precious metallic catalysts, MCNC also shows a relatively high catalytic activity. These results indicate that MCNC is a conveniently prepared and highly effective and stable carbon-supported cobaltic heterogeneous catalyst for versatile environmental catalytic applications. Copyright © 2018 Elsevier Inc. All rights reserved.
Cerium Oxide Nanoparticles Decorated Graphene Nanosheets for Selective Detection of Dopamine.

PubMed

Nayak, Pranati; Santhosh, P N; Ramaprabhu, S

2015-07-01

The fabrication of a novel amperometric biosensor based on selective determination of dopamine (DA) using nafion coated cerium oxide nanoparticles (NPs) decorated graphene nanosheets (CeO2-HEG-nafion) as a transducer candidate is reported. Graphene was synthesized by hydrogen exfoliation technique. Decoration of CeO2NPs over graphene nanosheets was done by chemical reduction method. The electrochemical impedance spectroscopy (EIS) study shows the enhanced electron transfer kinetics of the composite compared to HEG modified and bare glassy carbon electrode (GCE). The response of the composite towards dopamine displays a lower oxidation potential of 0.23 V and a high oxidation current. The sensor exhibits linearity from 10 µM to 780 µM with a detection limit of 1 µM. In the presence of nafion, it shows excellent selectivity for coexisting interference species like Ascorbic acid (AA) and Uric acid (UA). The excellent performance of the biosensor can be attributed to large active surface area, enhanced electron transfer kinetics and high catalytic activity of the composite.
Coupling catalytic hydrolysis and oxidation of HCN over HZSM-5 modified by metal (Fe,Cu) oxides

NASA Astrophysics Data System (ADS)

Hu, Yanan; Liu, Jiangping; Cheng, Jinhuan; Wang, Langlang; Tao, Lei; Wang, Qi; Wang, Xueqian; Ning, Ping

2018-01-01

In this work, a series of metal oxides (Fe,Cu) modified HZSM-5 catalysts were synthesized by incipient-wetness impregnation method and then characterized by XRD, N2 adsorption-desorption, H2-TPR, NH3-TPD, UV-vis, FT-IR and XPS measurements. The catalytic hydrolysis and oxidation behaviors toward HCN were investigated. The results indicated that the Fe-Cu/HZSM-5 catalysts exhibited more excellent performence on coupling catalytic hydrolysis and oxidation of HCN than HZSM-5, Fe/HZSM-5, Cu/HZSM-5, and both nearly 100% HCN conversion and 80% N2 selectivity were obtained at about 250 °C. The improved catalytic performance could be ascribed to the creation of highly dispersed iron and copper composites on the surface of the HZSM-5 support, the excellent redox and regulated acid properties of the active ingredients. Moreover, the highly N2 selectivity could be attributed to the good interaction between the Fe and Cu nanocomposites which was facilitated to the NH3-SCR (selective catalytic reduction of NO by NH3) reaction.
Selective CO2 conversion to formate conjugated with H2O oxidation utilizing semiconductor/complex hybrid photocatalysts.

PubMed

Sato, Shunsuke; Arai, Takeo; Morikawa, Takeshi; Uemura, Keiko; Suzuki, Tomiko M; Tanaka, Hiromitsu; Kajino, Tsutomu

2011-10-05

Photoelectrochemical reduction of CO(2) to HCOO(-) (formate) over p-type InP/Ru complex polymer hybrid photocatalyst was highly enhanced by introducing an anchoring complex into the polymer. By functionally combining the hybrid photocatalyst with TiO(2) for water oxidation, selective photoreduction of CO(2) to HCOO(-) was achieved in aqueous media, in which H(2)O was used as both an electron donor and a proton source. The so-called Z-scheme (or two-step photoexcitation) system operated with no external electrical bias. The selectivity for HCOO(-) production was >70%, and the conversion efficiency of solar energy to chemical energy was 0.03-0.04%.
Improving the oxidation resistance and stability of Ag nanoparticles by coating with multilayered reduced graphene oxide

NASA Astrophysics Data System (ADS)

Li, Yahui; Zhang, Huayu; Wu, Bowen; Guo, Zhuo

2017-12-01

A kind of coating nanostructure, Ag nanoparticles coated with multilayered reduced graphene oxide (RGO), is fabricated by employing a three-step reduction method in an orderly manner, which is significantly different from the conventional structures that are simply depositing or doping with Ag nanoparticles on RGO via chemical reduction. The as-prepared nanostructure is investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), selected-area electronic diffraction (SEAD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The results show that the obtained Ag/RGO nanostructure is observed to be a perfect coating structure with well dispersed Ag particles, which is responsible for the remarkable oxidation resistance. The results of XPS spectra indicate the content of metallic Ag is far greater than that of Ag oxides despite of prolonged exposure to the air, which fully demonstrate the excellent stability of thus coating nanostructure.
One-Electron Reduction of Penicillins in Relation to the Oxidative Stress Phenomenon

PubMed Central

Szabó, László; Tóth, Tünde; Takács, Erzsébet; Wojnárovits, László

2015-01-01

Certain bactericidal antibiotics target mitochondrial components and, due to the leakage of electrons from the electron transport chain, one-electron reduction might occur that can lead to intermediates passing the electron to suitable acceptors. This study aimed at investigating the one-electron reduction mechanism of selected penicillin derivatives using pulse radiolysis techniques. Penicillins can accommodate the electron on each of their carbonyl carbon. Ketyl radicals are thus produced, which are reducing agents with possibility to interact with suitable biomolecules. A detailed mechanism of the reduction is reported. PMID:26690427
Biology Notes.

ERIC Educational Resources Information Center

School Science Review, 1982

1982-01-01

Describes laboratory procedures, demonstrations, and classroom activities/materials, including use of dwarf cichlids (fishes) in secondary school biology, teaching edge effects on stomatal diffusion, computer program on effects of selection on gene frequencies, biological oxidation/reduction reactions, short cuts with Drosophila, computer program…
Controlled, Stepwise Reduction and Band Gap Manipulation of Graphene Oxide.

PubMed

Mathkar, Akshay; Tozier, Dylan; Cox, Paris; Ong, Peijie; Galande, Charudatta; Balakrishnan, Kaushik; Leela Mohana Reddy, Arava; Ajayan, Pulickel M

2012-04-19

Graphene oxide (GO) has drawn tremendous interest as a tunable precursor in numerous areas, due to its readily manipulable surface. However, its inhomogeneous and nonstoichiometric structure makes achieving chemical control a major challenge. Here, we present a room-temperature based, controlled method for the stepwise reduction of GO, with evidence of sequential removal of each organic moiety. By analyzing signature infrared absorption frequencies, we identify the carbonyl group as the first to be reduced, while the tertiary alcohol takes the longest to be completely removed from the GO surface. Controlled reduction allows for progressive tuning of the optical gap from 3.5 eV down to 1 eV, while XPS spectra show a concurrent increase in the C/O ratio. This study is the first step toward selectively enhancing the chemical homogeneity of GO, thus providing greater control over its structure, and elucidating the order of removal of functional groups and hydrazine-vapor reduction.
Reducing diesel NOx and PM emissions of diesel buses and trucks.

DOT National Transportation Integrated Search

2008-07-01

The objective of the present investigation was development of a high efficiency : selective catalytic reduction (SCR) system for reducing diesel nitrogen oxides (NOx) and : particulate matters of diesel trucks. The investigation was divided into two ...
EVALUATION OF SIMULTANEOUS SO2/NOX CONTROL TECHNOLOGY

EPA Science Inventory

The report gives results of work concentrating on characterizing three process operational parameters of a technology that combines sorbent injection and selective non-catalytic reduction for simultaneous sulfur dioxide/nitrogen oxide (SO2/NOx) removal from coal-fired industrial ...

Spectroscopic and electrochemical characterization of some Schiff base metal complexes containing benzoin moiety.

PubMed

El-Shahawi, M S; Al-Jahdali, M S; Bashammakh, A S; Al-Sibaai, A A; Nassef, H M

2013-09-01

The ligation behavior of bis-benzoin ethylenediamine (B2ED) and benzoin thiosemicarbazone (BTS) Schiff bases towards Ru(3+), Rh(3+), Pd(2+), Ni(2+) and Cu(2+) were determined. The bond length of M-N and spectrochemical parameters (10Dq, β, B and LFSE) of the complexes were evaluated. The redox characteristics of selected complexes were explored by cyclic voltammetry (CV) at Pt working electrode in non aqueous solvents. Au mesh (100 w/in.) optically transparent thin layer electrode (OTTLE) was also used for recording thin layer CV for selected Ru complex. Oxidation of some complexes occurs in a consecutive chemical reaction of an EC type mechanism. The characteristics of electron transfer process of the couples M(2+)/M(3+) and M(3+)/M(4+) (M=Ru(3+), Rh(3+)) and the stability of the complexes towards oxidation and/or reduction were assigned. The nature of the electroactive species and reduction mechanism of selected electrode couples were assigned. Copyright © 2013 The Authors. Published by Elsevier B.V. All rights reserved.
CO2-Free Power Generation on an Iron Group Nanoalloy Catalyst via Selective Oxidation of Ethylene Glycol to Oxalic Acid in Alkaline Media

PubMed Central

Matsumoto, Takeshi; Sadakiyo, Masaaki; Ooi, Mei Lee; Kitano, Sho; Yamamoto, Tomokazu; Matsumura, Syo; Kato, Kenichi; Takeguchi, Tatsuya; Yamauchi, Miho

2014-01-01

An Fe group ternary nanoalloy (NA) catalyst enabled selective electrocatalysis towards CO2-free power generation from highly deliverable ethylene glycol (EG). A solid-solution-type FeCoNi NA catalyst supported on carbon was prepared by a two-step reduction method. High-resolution electron microscopy techniques identified atomic-level mixing of constituent elements in the nanoalloy. We examined the distribution of oxidised species, including CO2, produced on the FeCoNi nanoalloy catalyst in the EG electrooxidation under alkaline conditions. The FeCoNi nanoalloy catalyst exhibited the highest selectivities toward the formation of C2 products and to oxalic acid, i.e., 99 and 60%, respectively, at 0.4 V vs. the reversible hydrogen electrode (RHE), without CO2 generation. We successfully generated power by a direct EG alkaline fuel cell employing the FeCoNi nanoalloy catalyst and a solid-oxide electrolyte with oxygen reduction ability, i.e., a completely precious-metal-free system. PMID:25004118
Preparation of highly active manganese oxides supported on functionalized MWNTs for low temperature NOx reduction with NH3

NASA Astrophysics Data System (ADS)

Pourkhalil, Mahnaz; Moghaddam, Abdolsamad Zarringhalam; Rashidi, Alimorad; Towfighi, Jafar; Mortazavi, Yadollah

2013-08-01

Manganese oxide catalysts (MnOx) supported on functionalized multi-walled carbon nanotubes (FMWNTs) for low temperature selective catalytic reduction (LTSCR) of nitrogen oxides (NOx) with NH3 in the presence of excess O2 were prepared by the incipient wetness impregnation method. These catalysts were characterized by N2 adsorption, Fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM), X-ray diffraction (XRD), thermal gravimetric analysis (TGA) and H2-temperature programmed reduction (H2-TPR) methods. The effects of reaction temperature, MnOx loading, calcination temperature and calcination time were investigated. The presence of surface nitrate species under moderate calcination conditions may play a favorable role in the LTSCR of NOx with NH3. Under the reaction conditions of 200 °C, 1 bar, NO = NH3 = 900 ppm, O2 = 5 vol%, GHSV = 30,000 h-1 and 12 wt% MnOx, NOx conversion and N2 selectivity were 97% and 99.5%, respectively. The SCR activity was reduced in the presence of 100 ppm SO2 and 2.5 vol% H2O from 97% to 92% within 6 h at 200 °C, however such an effect was shown to be reversible by exposing the catalyst to a helium flow for 2 h at 350 °C due to thermal decomposition of ammonium sulphate salts.
Mitochondrial oxidative phosphorylation efficiency is upregulated during fasting in two major oxidative tissues of ducklings.

PubMed

Monternier, Pierre-Axel; Teulier, Loïc; Drai, Jocelyne; Bourguignon, Aurore; Collin-Chavagnac, Delphine; Hervant, Frédéric; Rouanet, Jean-Louis; Roussel, Damien

2017-10-01

Fasted endothermic vertebrates must develop physiological responses to maximize energy conservation and survival. The aim of this study was to determine the effect of 1-wk. fasting in 5-wk. old ducklings (Cairina moschata) from whole-body resting metabolic rate and body temperature to metabolic phenotype of tissues and mitochondrial coupling efficiency. At the level of whole organism, the mass-specific metabolic rate of ducklings was decreased by 40% after 1-wk. of fasting, which was associated with nocturnal Tb declines and shallow diurnal hypothermia during fasting. At the cellular level, fasting induced a large reduction in liver, gastrocnemius (oxidative) and pectoralis (glycolytic) muscle masses together with a fuel selection towards lipid oxidation and ketone body production in liver and a lower glycolytic phenotype in skeletal muscles. At the level of mitochondria, fasting induced a reduction of oxidative phosphorylation activities and an up-regulation of coupling efficiency (+30% on average) in liver and skeletal muscles. The present integrative study shows that energy conservation in fasted ducklings is mainly achieved by an overall reduction in mitochondrial activity and an increase in mitochondrial coupling efficiency, which would, in association with shallow hypothermia, increase the conservation of endogenous fuel stores during fasting. Copyright © 2017 Elsevier Inc. All rights reserved.
Silver Nanoparticles with Surface-Bonded Oxygen for Highly Selective CO 2 Reduction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jiang, Kun; Kharel, Priti; Peng, Yande

Here, the surface electronic structures of catalysts need to be carefully engineered in CO 2 reduction reaction (CO 2RR), where the hydrogen evolution side reaction usually takes over under a significant overpotential, and thus dramatically lows the reaction selectivity. Surface oxides can play a critical role in tuning the surface oxidation state of metal catalysts for a proper binding with CO 2RR reaction intermediates, which may significantly improve the catalyst activity and selectivity. Here, we demonstrate the importance of surface-bonded oxygen on silver nanoparticles in altering the reaction pathways and improving the CO 2RR performances. A comparative investigation on air-annealedmore » Ag (Air-Ag) catalyst with or without the post-treatment of H 2 thermal annealing (H 2-Ag) was performed. In Air-Ag, the subsurface chemically bonded O species (O-Ag δ+) was identified by angle resolved X-ray photoelectron spectroscopy and X-ray absorption spectroscopy techniques, and contributed to the improved CO selectivity rather than H 2 in CO 2RR electrolysis. As a result, while the maximal CO Faradaic efficiency of H 2-Ag is at ~ 30 %, the Air-Ag catalyst presented a high CO selectivity of more than 90 % under a current density of ~ 21 mA/cm 2.« less
Silver Nanoparticles with Surface-Bonded Oxygen for Highly Selective CO 2 Reduction

DOE PAGES

Jiang, Kun; Kharel, Priti; Peng, Yande; ...

2017-09-12

Here, the surface electronic structures of catalysts need to be carefully engineered in CO 2 reduction reaction (CO 2RR), where the hydrogen evolution side reaction usually takes over under a significant overpotential, and thus dramatically lows the reaction selectivity. Surface oxides can play a critical role in tuning the surface oxidation state of metal catalysts for a proper binding with CO 2RR reaction intermediates, which may significantly improve the catalyst activity and selectivity. Here, we demonstrate the importance of surface-bonded oxygen on silver nanoparticles in altering the reaction pathways and improving the CO 2RR performances. A comparative investigation on air-annealedmore » Ag (Air-Ag) catalyst with or without the post-treatment of H 2 thermal annealing (H 2-Ag) was performed. In Air-Ag, the subsurface chemically bonded O species (O-Ag δ+) was identified by angle resolved X-ray photoelectron spectroscopy and X-ray absorption spectroscopy techniques, and contributed to the improved CO selectivity rather than H 2 in CO 2RR electrolysis. As a result, while the maximal CO Faradaic efficiency of H 2-Ag is at ~ 30 %, the Air-Ag catalyst presented a high CO selectivity of more than 90 % under a current density of ~ 21 mA/cm 2.« less
Hydrophobic Catalysts For Removal Of NOx From Flue Gases

NASA Technical Reports Server (NTRS)

Sharma, Pramod K.; Hickey, Gregory S.; Voecks, Gerald E.

1995-01-01

Improved catalysts for removal of nitrogen oxides (NO and NO2) from combustion flue gases formulated as composites of vanadium pentoxide in carbon molecular sieves. Promotes highly efficient selective catalytic reduction of NOx at relatively low temperatures while not being adversely affected by presence of water vapor and sulfur oxide gases in flue gas. Apparatus utilizing catalyst of this type easily integrated into exhaust stream of power plant to remove nitrogen oxides, generated in combustion of fossil fuels and contribute to formation of acid rain and photochemical smog.
Experimental characterization of enhanced SNCR process with carbonaceous gas additives.

PubMed

Yao, Ting; Duan, Yufeng; Yang, Zhizhong; Li, Yuan; Wang, Linwei; Zhu, Chun; Zhou, Qiang; Zhang, Jun; She, Min; Liu, Meng

2017-06-01

Carbonaceous gases such as CO and alkanes are commonly used as additives to enhance the selective non-catalytic reduction (SNCR) performance due to their high reducibility. This study compared the effect of CO and CH 4 on NO reduction in a tubular reactor with simulated flue gas. The enhancement of C 3 H 8 on SNCR process was tested at extremely low temperature, i.e. 650 °C. Experimental results suggested that reactions between NH 3 and SO 2 were favored at low temperatures and the competition for NH 3 between SO 2 and NO was influenced by gas additives. A maximum downward shift of 25 °C and 100 °C in temperature window for 50% NO reduction efficiency was obtained with the addition of CO and CH 4 , respectively. Considerable CO emission was observed with addition of CH 4 . The addition of CH 4 contributed to the formation of a self-accelerating reaction route within NO/O 2 /NH 3 SNCR reaction system. NO 2 produced from NO accelerates the oxidation of CH 4 to CO, while the oxidation of CH 4 returns to enhance the NO reduction globally. Optimal NO reduction of 44% was achieved with addition of C 3 H 8 at 650 °C. Substantial portion of C 3 H 8 was partially oxidized to CO and the remaining was converted into C 2 H 4 and C 3 H 6 during the SNCR process. Oxidative dehydrogenation of C 3 H 8 was involved. High reactivity of C 3 H 6 and C 2 H 4 favored the further oxidation and cracking to produce CO. These differences in oxidation behavior significantly influence the promotion capacities of CO, CH 4 and C 3 H 8 for NO reduction. Copyright © 2017 Elsevier Ltd. All rights reserved.
Preferentially Oriented Ag Nanocrystals with Extremely High Activity and Faradaic Efficiency for CO2 Electrochemical Reduction to CO.

PubMed

Peng, Xiong; Karakalos, Stavros G; Mustain, William E

2018-01-17

Selective electrochemical reduction of CO 2 is one of the most important processes to study because of its promise to convert this greenhouse gas to value-added chemicals at low cost. In this work, a simple anodization treatment was devised that first oxidizes Ag to Ag 2 CO 3 , then uses rapid electrochemical reduction to create preferentially oriented nanoparticles (PONs) of metallic Ag (PON-Ag) with high surface area as well as high activity and very high selectivity for the reduction of CO 2 to CO. The PON-Ag catalyst was dominated by (110) and (100) orientation, which allowed PON-Ag to achieve a CO Faradaic efficiency of 96.7% at an operating potential of -0.69 V vs RHE. This performance is not only significantly higher than that of polycrystalline Ag (60% at -0.87 V vs RHE) but also represents one of the best combinations of activity and selectivity achieved to date - all with a very simple, scalable approach to electrode fabrication.
Compact, Lightweight, Ceramic Matrix Composite (CMC) Based Acoustic Liners for Reducing Subsonic Jet Aircraft Engine Noise

NASA Technical Reports Server (NTRS)

Kiser, J. Douglas; Grady, Joseph E.; Miller, Christopher J.; Hultgren, Lennart S.; Jones, Michael G.

2016-01-01

Recent developments have reduced fan and jet noise contributions to overall subsonic aircraft jet-engine noise. Now, aircraft designers are turning their attention toward reducing engine core noise. The NASA Glenn Research Center and NASA Langley Research Center have teamed to investigate the development of a compact, lightweight acoustic liner based on oxide/oxide ceramic matrix composite (CMC) materials. The NASA team has built upon an existing oxide/oxide CMC sandwich structure concept that provides monotonal noise reduction. Oxide/oxide composites have good high temperature strength and oxidation resistance, which could allow them to perform as core liners at temperatures up to 1000C (1832F), and even higher depending on the selection of the composite constituents. NASA has initiated the evaluation of CMC-based liners that use cells of different lengths (variable-depth channels) or effective lengths to achieve broadband noise reduction. Reducing the overall liner thickness is also a major goal, to minimize the volume occupied by the liner. As a first step toward demonstrating the feasibility of our concepts, an oxide/oxide CMC acoustic testing article with different channel lengths was tested. Our approach, summary of test results, current status, and goals for the future are reported.
In situ supported MnOx-CeOx on carbon nanotubes for the low-temperature selective catalytic reduction of NO with NH3

NASA Astrophysics Data System (ADS)

Zhang, Dengsong; Zhang, Lei; Shi, Liyi; Fang, Cheng; Li, Hongrui; Gao, Ruihua; Huang, Lei; Zhang, Jianping

2013-01-01

The MnOx and CeOx were in situ supported on carbon nanotubes (CNTs) by a poly(sodium 4-styrenesulfonate) assisted reflux route for the low-temperature selective catalytic reduction (SCR) of NO with NH3. X-Ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed desorption (NH3-TPD) have been used to elucidate the structure and surface properties of the obtained catalysts. It was found that the in situ prepared catalyst exhibited the highest activity and the most extensive operating-temperature window, compared to the catalysts prepared by impregnation or mechanically mixed methods. The XRD and TEM results indicated that the manganese oxide and cerium oxide species had a good dispersion on the CNT surface. The XPS results demonstrated that the higher atomic concentration of Mn existed on the surface of CNTs and the more chemisorbed oxygen species exist. The H2-TPR results suggested that there was a strong interaction between the manganese oxide and cerium oxide on the surface of CNTs. The NH3-TPD results demonstrated that the catalysts presented a larger acid amount and stronger acid strength. In addition, the obtained catalysts exhibited much higher SO2-tolerance and improved the water-resistance as compared to that prepared by impregnation or mechanically mixed methods.The MnOx and CeOx were in situ supported on carbon nanotubes (CNTs) by a poly(sodium 4-styrenesulfonate) assisted reflux route for the low-temperature selective catalytic reduction (SCR) of NO with NH3. X-Ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), X-ray photoelectron spectroscopy (XPS), H2 temperature-programmed reduction (H2-TPR) and NH3 temperature-programmed desorption (NH3-TPD) have been used to elucidate the structure and surface properties of the obtained catalysts. It was found that the in situ prepared catalyst exhibited the highest activity and the most extensive operating-temperature window, compared to the catalysts prepared by impregnation or mechanically mixed methods. The XRD and TEM results indicated that the manganese oxide and cerium oxide species had a good dispersion on the CNT surface. The XPS results demonstrated that the higher atomic concentration of Mn existed on the surface of CNTs and the more chemisorbed oxygen species exist. The H2-TPR results suggested that there was a strong interaction between the manganese oxide and cerium oxide on the surface of CNTs. The NH3-TPD results demonstrated that the catalysts presented a larger acid amount and stronger acid strength. In addition, the obtained catalysts exhibited much higher SO2-tolerance and improved the water-resistance as compared to that prepared by impregnation or mechanically mixed methods. Electronic supplementary information (ESI) available: SEM images and EDS analysis, TEM images, and XPS spectrum of samples. See DOI: 10.1039/c2nr33006g
Sequential reductive and oxidative conditions used to biodegradation of organochlorine pesticides by native bacteria.

NASA Astrophysics Data System (ADS)

Kopytko, M.; Correa-Torres, S. N.; Plata, A.

2016-07-01

Despite restrictions and bans on the use of many organochlorine pesticides in the 1970s and 1980s, they continue to persist in the environment today. This is the case of Agustin Codazzi, Cesar where the organochlorine pesticides were buried without control in the soil in 1999, after being banned their use. Nowadays is necessary to find the best method, which allows remediation of this soils. Reductive dechlorination is the first and limiting step in the metabolism of many organochlorine pesticides by anaerobic bacteria. In this study the reductive conditions were enhanced by addition of biogas as an auxiliary electron donors.The soil sample was taken from the zone at Agustin Codazzi, Cesar, and their characteristics correspond to a loam soil with low nutrient and slight compaction. The experimental tests were performed by varying the exposure time of a reducer to oxidative environment. Reductive conditions were enhanced by methane from biogas and oxidative environment was generated by air blown to stimulate a metabolic process of the soil native bacteria. Removals between 70 and 78.9% of compounds such as 4,4'-DDT, 4, 4'-DDD, 4,4'-DDE, Endrin and Trans- Chlordane, detected by gas chromatography analysis, were achieved under reductive/oxidative conditions during 120 days. Furthermore, bacterial strains capable of degrading organochlorine pesticides were selected from the native bacteria, and identified by the purified and identified based on its morphological characteristics and 16S rDNA sequencing.
Cocatalysts in Semiconductor-based Photocatalytic CO2 Reduction: Achievements, Challenges, and Opportunities.

PubMed

Ran, Jingrun; Jaroniec, Mietek; Qiao, Shi-Zhang

2018-02-01

Ever-increasing fossil-fuel combustion along with massive CO 2 emissions has aroused a global energy crisis and climate change. Photocatalytic CO 2 reduction represents a promising strategy for clean, cost-effective, and environmentally friendly conversion of CO 2 into hydrocarbon fuels by utilizing solar energy. This strategy combines the reductive half-reaction of CO 2 conversion with an oxidative half reaction, e.g., H 2 O oxidation, to create a carbon-neutral cycle, presenting a viable solution to global energy and environmental problems. There are three pivotal processes in photocatalytic CO 2 conversion: (i) solar-light absorption, (ii) charge separation/migration, and (iii) catalytic CO 2 reduction and H 2 O oxidation. While significant progress is made in optimizing the first two processes, much less research is conducted toward enhancing the efficiency of the third step, which requires the presence of cocatalysts. In general, cocatalysts play four important roles: (i) boosting charge separation/transfer, (ii) improving the activity and selectivity of CO 2 reduction, (iii) enhancing the stability of photocatalysts, and (iv) suppressing side or back reactions. Herein, for the first time, all the developed CO 2 -reduction cocatalysts for semiconductor-based photocatalytic CO 2 conversion are summarized, and their functions and mechanisms are discussed. Finally, perspectives in this emerging area are provided. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Oxidative coupling of methane using inorganic membrane reactor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, Y.H.; Moser, W.R.; Dixon, A.G.

1995-12-31

The goal of this research is to improve the oxidative coupling of methane in a catalytic inorganic membrane reactor. A specific target is to achieve conversion of methane to C{sub 2} hydrocarbons at very high selectivity and relatively higher yields than in fixed bed reactors by controlling the oxygen supply through the membrane. A membrane reactor has the advantage of precisely controlling the rate of delivery of oxygen to the catalyst. This facility permits balancing the rate of oxidation and reduction of the catalyst. In addition, membrane reactors minimize the concentration of gas phase oxygen thus reducing non selective gasmore » phase reactions, which are believed to be a main route for formation of CO{sub x} products. Such gas phase reactions are a cause for decreased selectivity in oxidative coupling of methane in conventional flow reactors. Membrane reactors could also produce higher product yields by providing better distribution of the reactant gases over the catalyst than the conventional plug flow reactors. Modeling work which aimed at predicting the observed experimental trends in porous membrane reactors was also undertaken in this research program.« less
Effect of water on hydrogen permeability

NASA Technical Reports Server (NTRS)

Hulligan, David; Tomazic, William A.

1987-01-01

Doping of hydrogen with CO and CO2 was developed to reduce hydrogen permeation in Stirling engines by forming a low permeability oxide coating on the inner surface of the heater head tubes. Although doping worked well, under certain circumstances the protective oxide could be chemically reduced by the hydrogen in the engine. Some oxygen is required in the hydrogen to prevent reduction. Eventually, all the oxygen in the hydrogen gas - whatever its source - shows up as water. This is the result of hydrogen reducing the CO, CO2, or the protective inner surface oxides. This water can condense in the engine system under the right conditions. If the concentration of water vapor is reduced to a low enough level, the hydrogen can chemically reduce the oxide coating, resulting in an increase in permeability. This work was done to define the minimum water content required to avoid this reduction in the oxide coating. The results of this testing show that a minimum of approximately 750 ppm water is required to prevent an increase in permeability of CG-27, a high temperature metal alloy selected for Stirling engine heater tubes.
Chemical properties which control selectivity and efficacy of aromatic N-oxide bioreductive drugs.

PubMed Central

Wardman, P.; Priyadarsini, K. I.; Dennis, M. F.; Everett, S. A.; Naylor, M. A.; Patel, K. B.; Stratford, I. J.; Stratford, M. R.; Tracy, M.

1996-01-01

Pulse radiolysis was used to generate radicals from one electron reduction of 1,2,4-benzotriazine-1,4-dioxides (derivatives of tirapazamine), and of imidazo [1,2-a]quinoxaline-4-oxides (analogues of RB90740), which have selective toxicity towards hypoxic cells. Radicals from the mono N-oxides (from the latter compounds) react with oxygen approximately 10-40 times faster than does the tirapazamine radical. Radicals from the tirapazamine analogues studied react with oxygen up to approximately 10 times slower than tirapazamine radicals. The quinoxaline N-oxide radicals are involved in prototropic equilibria with pK(a) values (5.5 to 7.4) spanning that reported for tirapazamine (6.0). Generation of radicals radiolytically in the presence of H donors (formate, 2-propanol, deoxyribose) indicate a chain reaction ascribed to H abstraction by the drug radical. The protonated drug radical is much more reactive than the radical anion (H abstraction rate constant approximately equal to 10(2) - 10(3) dm3 mol-1 s-1). Chain termination is ascribed to drug radical-radical reactions, i.e. radical stability in anoxia, with rate constants 2k approximately equal to 1 x 10(7) to 2 x 10(8) dm3 mol-1 s-1 at pH approximately 7.4. Estimates of the reduction potentials of the drug-radical couples in water at pH 7 for two of the mono-N-oxides were in the range-0.7 to 0.8 V vs NHE at pH 7. PMID:8763850
Catalytic Activation of Nitrogen Dioxide for Selective Synthesis of Nitroorganics

DTIC Science & Technology

2015-01-15

observed, with C-P and C-C reductive elimination of ancillary phosphine ligands taking place preferentially, though traces of nitroarene are...reductive elimination) as well as some phosphine oxide. Thermolysis of (Ph3P)Pd(IPr)(C6H4CH3)(NO2) gives unusual C–C reductive elimination of the...N-heterocyclic carbene to give the imidazolium salt [CH3C6H4–IPr]NO2. Only in the case of the bis(diphenylphosphino) ferrocene complex [Fe(C5H4PPh2
Oxidative shielding and the cost of reproduction.

PubMed

Blount, Jonathan D; Vitikainen, Emma I K; Stott, Iain; Cant, Michael A

2016-05-01

Life-history theory assumes that reproduction and lifespan are constrained by trade-offs which prevent their simultaneous increase. Recently, there has been considerable interest in the possibility that this cost of reproduction is mediated by oxidative stress. However, empirical tests of this theory have yielded equivocal support. We carried out a meta-analysis to examine associations between reproduction and oxidative damage across markers and tissues. We show that oxidative damage is positively associated with reproductive effort across females of various species. Yet paradoxically, categorical comparisons of breeders versus non-breeders reveal that transition to the reproductive state is associated with a step-change reduction in oxidative damage in certain tissues and markers. Developing offspring may be particularly sensitive to harm caused by oxidative damage in mothers. Therefore, such reductions could potentially function to shield reproducing mothers, gametes and developing offspring from oxidative insults that inevitably increase as a consequence of reproductive effort. According to this perspective, we hypothesise that the cost of reproduction is mediated by dual impacts of maternally-derived oxidative damage on mothers and offspring, and that mothers may be selected to diminish such damage. Such oxidative shielding may explain why many existing studies have concluded that reproduction has little or no oxidative cost. Future advance in life-history theory therefore needs to take account of potential transgenerational impacts of the mechanisms underlying life-history trade-offs. © 2015 Cambridge Philosophical Society.
Effect of selective catalytic reduction (SCR) on fine particle emission from two coal-fired power plants in China

NASA Astrophysics Data System (ADS)

Li, Zhen; Jiang, Jingkun; Ma, Zizhen; Wang, Shuxiao; Duan, Lei

2015-11-01

Nitrogen oxides (NOx) emission abatement of coal-fired power plants (CFPPs) requires large-scaled installation of selective catalytic reduction (SCR), which would reduce secondary fine particulate matter (PM2.5) (by reducing nitrate aerosol) in the atmosphere. However, our field measurement of two CFPPs equipped with SCR indicates a significant increase of SO42- and NH4+ emission in primary PM2.5, due to catalytic enhancement of SO2 oxidation to SO3 and introducing of NH3 as reducing agent. The subsequent formation of (NH4)2SO4 or NH4HSO4 aerosol is commonly concentrated in sub-micrometer particulate matter (PM1) with a bimodal pattern. The measurement at the inlet of stack also showed doubled primary PM2.5 emission by SCR operation. This effect should therefore be considered when updating emission inventory of CFPPs. By rough estimation, the enhanced primary PM2.5 emission from CFPPs by SCR operation would offset 12% of the ambient PM2.5 concentration reduction in cities as the benefit of national NOx emission abatement, which should draw attention of policy-makers for air pollution control.
Preservation of organic matter in nontronite against iron redox cycling.

NASA Astrophysics Data System (ADS)

Zeng, Q.

2015-12-01

It is generally believed that clay minerals can protect organic matter from degradation in redox active environments, but both biotic and abiotic factors can influence the redox process and thus potentially change the clay-organic associations. However, the specific mechanisms involved in this process remain poorly understood. In this study, a model organic compound, 12-Aminolauric acid (ALA) was selected to intercalate into the structural interlayer of nontronite (an iron-rich smectite, NAu-2) to form an ALA-intercalated NAu-2 composite (ALA-NAu-2). Shawanella putrefaciens CN32 and sodium dithionite were used to reduce structural Fe(III) to Fe(II) in NAu-2 and ALA-NAu-2. The bioreduced ALA-NAu-2 was subsequently re-oxidized by air. The rates and extents of bioreduction and air re-oxidation were determined with wet chemistry methods. ALA release from ALA-NAu-2 via redox process was monitored. Mineralogical changes after iron redox cycle were investigated with X-ray diffraction, infrared spectroscopy, and scanning and transmission electron microscopy. At the beginning stage of bioreduction, S. putrefaciens CN32 reduced Fe(III) from the edges of nontronite and preferentially reduced and dissolved small and poorly crystalline particles, and released ALA, resulting a positive correlation between ALA release and iron reduction extent (<12%). The subsequent bioreduction (reduction extent ranged from 12~30%) and complete air re-oxidation showed no effect on ALA release. These results suggest that released ALA was largely from small and poorly crystalline NAu-2 particles. In contrast to bioreduction, chemical reduction did not exhibit any selectivity in reducing ALA-NAu-2 particles, and a considerable amount of reductive dissolution was responsible for a large amount of ALA release (>80%). Because bacteria are the principal agent for mediating redox process in natural environments, our results demonstrated that the structural interlayer of smectite can serve as a potential shelter to protect organic matter from oxidation.

Single-Step Laser-Assisted Graphene Oxide Reduction and Nonlinear Optical Properties Exploration via CW Laser Excitation

NASA Astrophysics Data System (ADS)

Ghasemi, Fatemeh; Razi, Sepehr; Madanipour, Khosro

2018-02-01

The synthesis of reduced graphene oxide using pulsed laser irradiation is experimentally investigated. For this purpose, various irradiation conditions were selected and the chemical features of the different products were explored using ultraviolet-visible, Fourier transform infrared and Raman spectroscopy techniques. Moreover, the nonlinear optical properties of the synthesized products were assessed by using open and closed aperture Z-scan techniques, in which continuous wave laser irradiating at 532-nm wavelength was utilized as the exciting source. The results clearly revealed that the degree of graphene oxide reduction not only depends on the amount of the irradiation dose (energy of the laser beam × exposure time) but also on the light source wavelength. Furthermore, strong dependency between the nonlinear optical properties of the products and the amount of the de-oxygenation was observed. The experimental results are discussed in detail.
High Temperature Modification of SNCR Technology and its Impact on NOx Removal Process

NASA Astrophysics Data System (ADS)

Blejchař, Tomáš; Konvička, Jaroslav; von der Heide, Bernd; Malý, Rostislav; Maier, Miloš

2018-06-01

SNCR (Selective non-catalytic reduction) Technology is currently being used to reach the emission limit for nitrogen oxides at fossil fuel fired power plant and/or heating plant and optimum temperature for SNCR process is in range 850 - 1050°C. Modified SNCR technology is able to reach reduction 60% of nitrogen oxides at temperature up to 1250°C. So the technology can also be installed where the flue gas temperature is too high in combustion chamber. Modified SNCR was tested using generally known SNCR chemistry implemented in CFD (Computation fluid dynamics) code. CFD model was focused on detail simulation of reagent injection and influence of flue gas temperature. Than CFD simulation was compared with operating data of boiler where the modified SNCR technology is installed. By comparing the experiment results with the model, the effect on nitrous oxides removal process and temperature of flue gas at the injection region.
Enhanced catalytic and dopamine sensing properties of electrochemically reduced conducting polymer nanocomposite doped with pure graphene oxide.

PubMed

Wang, Wenting; Xu, Guiyun; Cui, Xinyan Tracy; Sheng, Ge; Luo, Xiliang

2014-08-15

Significantly enhanced catalytic activity of a nanocomposite composed of conducting polymer poly (3,4-ethylenedioxythiophene) (PEDOT) doped with graphene oxide (GO) was achieved through a simple electrochemical reduction process. The nanocomposite (PEDOT/GO) was electrodeposited on an electrode and followed by electrochemical reduction, and the obtained reduced nanocomposite (PEDOT/RGO) modified electrode exhibited lowered electrochemical impedance and excellent electrocatalytic activity towards the oxidation of dopamine. Based on the excellent catalytic property of PEDOT/RGO, an electrochemical sensor capable of sensitive and selective detection of DA was developed. The fabricated sensor can detect DA in a wide linear range from 0.1 to 175μM, with a detection limit of 39nM, and it is free from common interferences such as uric acid and ascorbic acid. Copyright © 2014 Elsevier B.V. All rights reserved.
Thermal Analysis on the Pyrolysis of Tetrabromobisphenol A and Electric Arc Furnace Dust Mixtures

NASA Astrophysics Data System (ADS)

Al-Harahsheh, Mohammad; Al-Otoom, Awni; Al-Jarrah, Muhannad; Altarawneh, Mohammednoor; Kingman, Sam

2018-02-01

The pyrolysis of Tetrabromobisphenol A (TBBPA) mixed with electric arc furnace dust (EAFD) was studied using thermogravimetric analysis (TGA) and theoretically analyzed using thermodynamic equilibrium calculations. Mixtures of both materials with varying TBBPA loads (1:1 and 1:3) were prepared and pyrolyzed in a nitrogen atmosphere under dynamic heating conditions at heating rates of 5 and 10 °C/min. The mixtures degraded through several steps, including decomposition of TBBPA yielding mainly HBr, bromination of metal oxides, followed by their evaporation in the sequence of CuBr3, ZnBr2, PbBr2, FeBr2, MnBr2, KBr, NaBr, CaBr2, and MgBr2, and finally reduction of the remaining metal oxides by the char formed from decomposition of TBBPA. Thermodynamic calculations suggest the possibility of selective bromination of zinc and lead followed by their evaporation, leaving iron in its oxide form, while the char formed may serve as a reduction agent for iron oxides into metallic iron. However, at higher TBBPA volumes, iron bromide forms, which can also be evaporated at a temperature higher than those of ZnBr2 and PbBr2. Results from this work provide practical insight into selective recovery of valuable metals from EAFD while at the same time recycling the hazardous bromine content in TBBPA.
A multiherbal formulation influencing immune response in vitro.

PubMed

Menghini, L; Leporini, L; Scanu, N; Pintore, G; Ferrante, C; Recinella, L; Orlando, G; Vacca, M; Brunetti, L

2012-02-01

Aim of this study was to evaluate the effects of phytocomplexes of Uncaria, Shiitake and Ribes in terms of viability and inflammatory response on immune cell-derived cultures. Standardized extracts of Uncaria, Shitake and Ribes and their commercial formulation were tested on cell lines PBMC, U937 and macrophage. The activity was evaluated in terms of cell viability (MTT test), variations of oxidative marker release (ROS and PGE2) and modulatory effects on immune response (gene expression of IL-6, IL-8 and TNFα, RT-PCR). Cell viability was not affected by extracts, except subtle variations observed only at higher doses (>250 µg/mL). The extract mixture was well tolerated, with no effects on cell viability up to doses of 500 µg/mL. Pre-treatment of macrophages with subtoxic doses of the extracts reduced the basal release of oxidative markers and enhanced the cell response to exogenous oxidant stimulation, as revealed by ROS and PGE2 release reduction. The same treatment on macrophage resulted in a selective modulation of the immune response, as shown by an increase of IL-6 mRNA and, partially, IL-8 mRNA, while a reduction was observed for TNFα mRNA. Data confirm that extracts and their formulations can act as regulator of the immune system with mechanisms involving the oxidative stress and the release of selected proinflammatory cytokines.
Selective liquid phase oxidation of benzyl alcohol to benzaldehyde by tert-butyl hydroperoxide over γ-Al2O3 supported copper and gold nanoparticles

NASA Astrophysics Data System (ADS)

Ndolomingo, Matumuene Joe; Meijboom, Reinout

2017-03-01

Benzyl alcohol oxidation to benzaldehyde was performed by tert-butyl hydroperoxide (TBHP) in the absence of any solvent using γ-Al2O3 supported copper and gold nanoparticles. Li2O and ionic liquids were used as additive and stabilizers for the synthesis of the catalysts. The physico-chemical properties of the catalysts were characterized by atomic absorption spectroscopy (AAS), X-ray diffraction spectroscopy (XRD), N2 absorption/desorption (BET), transmission electron microscopy (TEM), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and temperature programmed reduction (TPR), whereas, the oxidation reaction was followed by gas chromatography with a flame ionization detector (GC-FID). The as prepared catalysts exhibited good catalytic performance in terms of conversion and selectivity towards benzaldehyde. The performance of the Au-based catalysts is significantly higher than that of the Cu-based catalysts. For both Cu and Au catalysts, the conversion of benzyl alcohol increased as the reaction proceeds, while the selectivity for benzaldehyde decreased. Moreover, the catalysts can be easily recycled and reused with neither significant loss of activity nor selectivity. A kinetic study for the Cu and Au-catalyzed oxidation of benzyl alcohol to benzyldehyde is reported. The rate at which the oxidation of benzyl alcohol is occurring as a function of catalyst and oxidant amounts was investigated, with the apparent rate constant, kapp being proportional to the amount of nano catalyst and oxygen present in the system.
Regeneration of sulfated metal oxides and carbonates

DOEpatents

Hubble, Bill R.; Siegel, Stanley; Cunningham, Paul T.

1978-03-28

Alkali metal or alkaline earth metal carbonates such as calcium carbonate and magnesium carbonate found in dolomite or limestone are employed for removal of sulfur dioxide from combustion exhaust gases. The sulfated carbonates are regenerated to oxides through use of a solid-solid reaction, particularly calcium sulfide with calcium sulfate to form calcium oxide and sulfur dioxide gas. The regeneration is performed by contacting the sulfated material with a reductant gas such as hydrogen within an inert diluent to produce calcium sulfide in mixture with the sulfate under process conditions selected to permit the sulfide-sulfate, solid-state reaction to occur.
Thermodynamic analysis of the selective chlorination of electric arc furnace dust.

PubMed

Pickles, C A

2009-07-30

The remelting of automobile scrap in an electric arc furnace (EAF) results in the production of a dust, which contains high concentrations of the oxides of zinc, iron, calcium and other metals. Typically, the lead and zinc are of commercial value, while the other metals are not worth recovering. At the present time, EAF dusts are treated in high temperature Waelz rotary kiln-type processes, where the lead and zinc oxides are selectively reduced and simultaneously reoxidized and a crude zinc oxide is produced. Another alternative processing route is selective chlorination, in which the non-ferrous metals are preferentially chlorinated to their gaseous chlorides and in this manner separated from the iron. In the present research, a detailed thermodynamic analysis of this chlorination process has been performed and the following factors were investigated; temperature, amount of chlorine, lime content, silica content, presence of an inert gas and the oxygen potential. High lead and zinc recoveries as gaseous chlorides could be achieved but some of the iron oxide was also chlorinated. Additionally, the calcium oxide in the dust consumes chlorine, but this can be minimized by adding silica, which results in the formation of stable calcium silicates. The optimum conditions were determined for a typical dust composition. The selectivities achieved with chlorination were lower than those for reduction, as reported in the literature, but there are other advantages such as the potential recovery of copper.
Vapor Phase Hydrogenolysis of Furanics Utilizing Reduced Cobalt Mixed Metal Oxide Catalysts

DOE PAGES

Sulmonetti, Taylor P.; Hu, Bo; Ifkovits, Zachary; ...

2017-03-21

Vapor phase hydrogenolysis of both furfuryl alcohol and furfural were investigated over reduced Co based mixed metal oxides derived from the calcination of a layered double hydroxide precursor. Although a reduced cobalt aluminate sample displays promising selectivity towards 2-methylfuran (2-MF) production, the addition of an Fe dopant into the oxide matrix significantly enhances the activity and selectivity per gram of catalyst. Approximately 82% 2-MF yield is achieved at high conversion when furfuryl alcohol is fed into the reactor at 180 °C over the reduced 3Co-0.25Fe-0.75Al catalyst. Based on structural characterization studies including TPR, XPS, and in-situ XAS it is suggestedmore » that Fe facilitates the reduction of Co, allowing for formation of more metallic species. Altogether, this study demonstrates that non-precious metal catalysts offer promise for the selective conversion of a key biomass oxygenate to a proposed fuel additive.« less
Electroreduction of carbon monoxide to liquid fuel on oxide-derived nanocrystalline copper.

PubMed

Li, Christina W; Ciston, Jim; Kanan, Matthew W

2014-04-24

The electrochemical conversion of CO2 and H2O into liquid fuel is ideal for high-density renewable energy storage and could provide an incentive for CO2 capture. However, efficient electrocatalysts for reducing CO2 and its derivatives into a desirable fuel are not available at present. Although many catalysts can reduce CO2 to carbon monoxide (CO), liquid fuel synthesis requires that CO is reduced further, using H2O as a H(+) source. Copper (Cu) is the only known material with an appreciable CO electroreduction activity, but in bulk form its efficiency and selectivity for liquid fuel are far too low for practical use. In particular, H2O reduction to H2 outcompetes CO reduction on Cu electrodes unless extreme overpotentials are applied, at which point gaseous hydrocarbons are the major CO reduction products. Here we show that nanocrystalline Cu prepared from Cu2O ('oxide-derived Cu') produces multi-carbon oxygenates (ethanol, acetate and n-propanol) with up to 57% Faraday efficiency at modest potentials (-0.25 volts to -0.5 volts versus the reversible hydrogen electrode) in CO-saturated alkaline H2O. By comparison, when prepared by traditional vapour condensation, Cu nanoparticles with an average crystallite size similar to that of oxide-derived copper produce nearly exclusive H2 (96% Faraday efficiency) under identical conditions. Our results demonstrate the ability to change the intrinsic catalytic properties of Cu for this notoriously difficult reaction by growing interconnected nanocrystallites from the constrained environment of an oxide lattice. The selectivity for oxygenates, with ethanol as the major product, demonstrates the feasibility of a two-step conversion of CO2 to liquid fuel that could be powered by renewable electricity.
Potential bile acid metabolites. XV. Synthesis of 4 beta-hydroxylated bile acids; unique bile acids in human fetal bile.

PubMed

Iida, T; Momose, T; Chang, F C; Goto, J; Nambara, T

1989-12-01

The 4 beta-hydroxylated derivatives of lithocholic, deoxycholic, chenodeoxycholic, and cholic acids were synthesized from their respective parent compounds. The principal reactions employed were 1) beta-face cis-dihydroxylation of delta 3 intermediates with osmium tetroxide-N-methylmorpholine N-oxide, 2) selective cathylation of vicinal 3 beta,4 beta-diols followed by oxidation of the resulting 4 beta-monocathylates, or direct selective oxidation at C-3 of 3 beta,4 beta-diols with pyridinium chlorochromate, and 3) stereoselective reduction of the 3-oxo compounds with tert-butylamine-borane complex. The results of analysis of the prepared 4 beta-hydroxylated bile acids with a diequatorial trans-glycol structure and their 3 beta-epimers by proton and carbon-13 nuclear magnetic resonance spectroscopies are briefly discussed along with the mass spectrometric properties.
Production of nitrous oxide from anaerobic digester centrate and its use as a co-oxidant of biogas to enhance energy recovery.

PubMed

Scherson, Yaniv D; Woo, Sung-Geun; Criddle, Craig S

2014-05-20

Coupled Aerobic-anoxic Nitrous Decomposition Operation (CANDO) is a new process for wastewater treatment that removes nitrogen from wastewater and recovers energy from the nitrogen in three steps: (1) NH4(+) oxidation to NO2(-); (2) NO2(-) reduction to N2O gas; and (3) N2O conversion to N2 with energy production. In this work, we optimize Steps 1 and 2 for anaerobic digester centrate, and we evaluate Step 3 for a full-scale biogas-fed internal combustion engine. Using a continuous stirred reactor coupled to a bench-scale sequencing batch reactor, we observed sustained partial oxidation of NH4(+) to NO2(-) and sustained (3 months) partial reduction of NO2(-) to N2O (75-80% conversion, mass basis), with >95% nitrogen removal (Step 2). Alternating pulses of acetate and NO2(-) selected for Comamonas (38%), Ciceribacter (16%), and Clostridium (11%). Some species stored polyhydroxybutyrate (PHB) and coupled oxidation of PHB to reduction of NO2(-) to N2O. Some species also stored phosphorus as polyphosphate granules. Injections of N2O into a biogas-fed engine at flow rates simulating a full-scale system increased power output by 5.7-7.3%. The results underscore the need for more detailed assessment of bioreactor community ecology and justify pilot- and full-scale testing.
Isolation of microorganisms involved in reduction of crystalline iron(III) oxides in natural environments

PubMed Central

Hori, Tomoyuki; Aoyagi, Tomo; Itoh, Hideomi; Narihiro, Takashi; Oikawa, Azusa; Suzuki, Kiyofumi; Ogata, Atsushi; Friedrich, Michael W.; Conrad, Ralf; Kamagata, Yoichi

2015-01-01

Reduction of crystalline Fe(III) oxides is one of the most important electron sinks for organic compound oxidation in natural environments. Yet the limited number of isolates makes it difficult to understand the physiology and ecological impact of the microorganisms involved. Here, two-stage cultivation was implemented to selectively enrich and isolate crystalline iron(III) oxide reducing microorganisms in soils and sediments. Firstly, iron reducers were enriched and other untargeted eutrophs were depleted by 2-years successive culture on a crystalline ferric iron oxide (i.e., goethite, lepidocrocite, hematite, or magnetite) as electron acceptor. Fifty-eight out of 136 incubation conditions allowed the continued existence of microorganisms as confirmed by PCR amplification. High-throughput Illumina sequencing and clone library analysis based on 16S rRNA genes revealed that the enrichment cultures on each of the ferric iron oxides contained bacteria belonging to the Deltaproteobacteria (mainly Geobacteraceae), followed by Firmicutes and Chloroflexi, which also comprised most of the operational taxonomic units (OTUs) identified. Venn diagrams indicated that the core OTUs enriched with all of the iron oxides were dominant in the Geobacteraceae while each type of iron oxides supplemented selectively enriched specific OTUs in the other phylogenetic groups. Secondly, 38 enrichment cultures including novel microorganisms were transferred to soluble-iron(III) containing media in order to stimulate the proliferation of the enriched iron reducers. Through extinction dilution-culture and single colony isolation, six strains within the Deltaproteobacteria were finally obtained; five strains belonged to the genus Geobacter and one strain to Pelobacter. The 16S rRNA genes of these isolates were 94.8–98.1% identical in sequence to cultured relatives. All the isolates were able to grow on acetate and ferric iron but their physiological characteristics differed considerably in terms of growth rate. Thus, the novel strategy allowed to enrich and isolate novel iron(III) reducers that were able to thrive by reducing crystalline ferric iron oxides. PMID:25999927
Isolation of microorganisms involved in reduction of crystalline iron(III) oxides in natural environments.

PubMed

Hori, Tomoyuki; Aoyagi, Tomo; Itoh, Hideomi; Narihiro, Takashi; Oikawa, Azusa; Suzuki, Kiyofumi; Ogata, Atsushi; Friedrich, Michael W; Conrad, Ralf; Kamagata, Yoichi

2015-01-01

Reduction of crystalline Fe(III) oxides is one of the most important electron sinks for organic compound oxidation in natural environments. Yet the limited number of isolates makes it difficult to understand the physiology and ecological impact of the microorganisms involved. Here, two-stage cultivation was implemented to selectively enrich and isolate crystalline iron(III) oxide reducing microorganisms in soils and sediments. Firstly, iron reducers were enriched and other untargeted eutrophs were depleted by 2-years successive culture on a crystalline ferric iron oxide (i.e., goethite, lepidocrocite, hematite, or magnetite) as electron acceptor. Fifty-eight out of 136 incubation conditions allowed the continued existence of microorganisms as confirmed by PCR amplification. High-throughput Illumina sequencing and clone library analysis based on 16S rRNA genes revealed that the enrichment cultures on each of the ferric iron oxides contained bacteria belonging to the Deltaproteobacteria (mainly Geobacteraceae), followed by Firmicutes and Chloroflexi, which also comprised most of the operational taxonomic units (OTUs) identified. Venn diagrams indicated that the core OTUs enriched with all of the iron oxides were dominant in the Geobacteraceae while each type of iron oxides supplemented selectively enriched specific OTUs in the other phylogenetic groups. Secondly, 38 enrichment cultures including novel microorganisms were transferred to soluble-iron(III) containing media in order to stimulate the proliferation of the enriched iron reducers. Through extinction dilution-culture and single colony isolation, six strains within the Deltaproteobacteria were finally obtained; five strains belonged to the genus Geobacter and one strain to Pelobacter. The 16S rRNA genes of these isolates were 94.8-98.1% identical in sequence to cultured relatives. All the isolates were able to grow on acetate and ferric iron but their physiological characteristics differed considerably in terms of growth rate. Thus, the novel strategy allowed to enrich and isolate novel iron(III) reducers that were able to thrive by reducing crystalline ferric iron oxides.
Selective Catalytic Reduction over Cu/SSZ-13: Linking Homo- and Heterogeneous Catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, Feng; Mei, Donghai; Wang, Yilin

Active centers in Cu/SSZ-13 selective catalytic reduction (SCR) catalysts have been recently identified as isolated Cu2+ and [CuII(OH)]+ ions. A redox reaction mechanism has also been established, where Cu-ions cycle between CuI and CuII oxidation states during SCR reaction. While the mechanism for the reduction half-cycle (CuII CuI) is reasonably well understood, that for the oxidation half-cycle (CuI CuII) remains an unsettled debate. Herein we report detailed reaction kinetics on low-temperature standard NH3-SCR, supplemented by DFT calculations, as strong evidence that the low-temperature oxidation half-cycle occurs with the participation of two isolated CuI ions, via formation of a transient [CuI(NH3)2]+-O2-[CuI(NH3)2]+more » intermediate. The feasibility of this reaction mechanism is confirmed from DFT calculations, and the simulated energy barrier and rate constants are consistent with experimental findings. Significantly, the low-temperature standard SCR mechanism proposed here provides full consistency with low-temperature SCR kinetics. The authors gratefully acknowledge the US Department of Energy (DOE), Energy Efficiency and Renewable Energy, Vehicle Technologies Office for the support of this work. The research described in this paper was performed in the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle.« less
Phosphine-functionalized graphene oxide, a high-performance electrocatalyst for oxygen reduction reaction

NASA Astrophysics Data System (ADS)

Ensafi, Ali A.; Golbon Haghighi, Mohsen; Jafari-Asl, Mehdi

2018-01-01

Here, a new approach for the synthesis of phosphine-functionalized graphene oxide (GO-PPh2) was developed. Using a simple method, diphenylphosphine group was linked to the hydroxyl group of OH-functionalized graphene that existing at the graphene surface. The electrochemical activity of GO-PPh2 for electrochemical oxygen reduction was checked. The results demonstrated that the new carbon hybrid material has a powerful potential for electrochemical oxygen reduction reaction (ORR). Moreover, GO-PPh2 as an electrocatalyst for ORR exhibited tolerance for methanol or ethanol as a result of crossover effect. In comparison with commercial Pt/C and Pt/rGO electrocatalysts, results showed that GO-PPh2 has a much higher selectivity, better durability, and much better electrochemical stability towards the ORR. The proposed method based on GO-PPh2 introduce an efficient electrocatalyst for further application in fuel cells.
Enhanced Air Stability in REPb3 (RE = Rare Earths) by Dimensional Reduction Mediated Valence Transition.

PubMed

Subbarao, Udumula; Sarkar, Sumanta; Jana, Rajkumar; Bera, Sourav S; Peter, Sebastian C

2016-06-06

We conceptually selected the compounds REPb3 (RE = Eu, Yb), which are unstable in air, and converted them to the stable materials in ambient conditions by the chemical processes of "nanoparticle formation" and "dimensional reduction". The nanoparticles and the bulk counterparts were synthesized by the solvothermal and high-frequency induction furnace heating methods, respectively. The reduction of the particle size led to the valence transition of the rare earth atom, which was monitored through magnetic susceptibility and X-ray absorption near edge spectroscopy (XANES) measurements. The stability was checked by X-ray diffraction and thermogravimetric analysis over a period of seven months in oxygen and argon atmospheres and confirmed by XANES. The nanoparticles showed outstanding stability toward aerial oxidation over a period of seven months compared to the bulk counterpart, as the latter one is more prone to the oxidation within a few days.
"Outer-sphere to inner-sphere" redox cycling for ultrasensitive immunosensors.

PubMed

Akanda, Md Rajibul; Choe, Yu-Lim; Yang, Haesik

2012-01-17

This paper reports chemical-chemical (CC) and electrochemical-chemical-chemical (ECC) redox cycling, for use in ultrasensitive biosensor applications. A triple chemical amplification approach using an enzymatic reaction, CC redox cycling, and ECC redox cycling is applied toward electrochemical immunosensors of cardiac troponin I. An enzymatic reaction, in which alkaline phosphatase converts 4-aminophenyl phosphate to 4-aminophenol (AP), triggers CC redox cycling in the presence of an oxidant and a reductant, and electrochemical signals are measured with ECC redox cycling after an incubation period of time in an air-saturated solution. To obtain high, selective, and reproducible redox cycling without using redox enzymes, two redox reactions [the reaction between AP and the oxidant and the reaction between the oxidized form of AP (4-quinone imine, QI) and the reductant] should be fast, but an unwanted reaction between the oxidant and reductant should be very slow. Because species that undergo outer-sphere reactions (OSR-philic species) react slowly with species that undergo inner-sphere reactions (ISR-philic species), highly OSR-philic Ru(NH(3))(6)(3+) and highly ISR-philic tris(2-carboxyethyl)phosphine (TCEP) are chosen as the oxidant and reductant, respectively. The OSR- and ISR-philic QI/AP couple allows fast redox reactions with both the OSR-philic Ru(NH(3))(6)(3+) and the ISR-philic TCEP. Highly OSR-philic indium-tin oxide (ITO) electrodes minimize unwanted electrochemical reactions with highly ISR-philic species. Although the formal potential of the Ru(NH(3))(6)(3+)/Ru(NH(3))(6)(2+) couple is lower than that of the QI/AP couple, the endergonic reaction between Ru(NH(3))(6)(3+) and AP is driven by the highly exergonic reaction between TCEP and QI (via a coupled reaction mechanism). Overall, the "outer-sphere to inner-sphere" redox cycling in the order of highly OSR-philic ITO, highly OSR-philic Ru(NH(3))(6)(3+)/Ru(NH(3))(6)(2+) couple, OSR- and ISR-philic QI/AP couple, and highly ISR-philic TCEP allows high, selective, and reproducible signal amplification. The electrochemical data obtained by chronocoulometry permit a lower detection limits than those obtained by cyclic voltammetry. The detection limit of an immunosensor for troponin I in serum, calculated from the anodic charges in chronocoulometry, is ca. 10 fg/mL.
Issues Concerning the Oxidation of Ni(Pt)Ti Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Smialek, James

2011-01-01

The oxidation behavior of the Ni-30Pt-50Ti high temperature shape memory alloy is compared to that of conventional NiTi nitinol SMAs. The oxidation rates were 1/4 those of NiTi under identical conditions. Ni-Ti-X SMAs are dominated by TiO2 scales, but, in some cases, the activation energy diverges for unexplained reasons. Typically, islands of metallic Ni or Pt(Ni) particles are embedded in lower scale layers due to rapid selective growth of TiO2 and low oxygen potential within the scale. The blocking effect of Pt-rich particles and lower diffusivity of Pt-rich depletion zones are proposed to account for the reduction in oxidation rates.
Catalyst and method for reduction of nitrogen oxides

DOEpatents

Ott, Kevin C [Los Alamos, NM

2008-05-27

A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).

Catalyst and method for reduction of nitrogen oxides

DOEpatents

Ott, Kevin C [Los Alamos, NM

2008-08-19

A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).
Catalyst for reduction of nitrogen oxides

DOEpatents

Ott, Kevin C.

2010-04-06

A Selective Catalytic Reduction (SCR) catalyst was prepared by slurry coating ZSM-5 zeolite onto a cordierite monolith, then subliming an iron salt onto the zeolite, calcining the monolith, and then dipping the monolith either into an aqueous solution of manganese nitrate and cerium nitrate and then calcining, or by similar treatment with separate solutions of manganese nitrate and cerium nitrate. The supported catalyst containing iron, manganese, and cerium showed 80 percent conversion at 113 degrees Celsius of a feed gas containing nitrogen oxides having 4 parts NO to one part NO.sub.2, about one equivalent ammonia, and excess oxygen; conversion improved to 94 percent at 147 degrees Celsius. N.sub.2O was not detected (detection limit: 0.6 percent N.sub.2O).
Application of silica-supported Fe-Cu nanoparticles in the selective hydrogenation of p-dinitrobenzene to p-phenylenediamine

NASA Astrophysics Data System (ADS)

Shesterkina, A. A.; Shuvalova, E. V.; Kirichenko, O. A.; Strelkova, A. A.; Nissenbaum, V. D.; Kapustin, G. I.; Kustov, L. M.

2017-02-01

Supported bimetallic Fe-Cu/SiO2 materials are synthesized, and their catalytic activity in hydrogenation of dinitrobenzene to phenylenediamine at 145-180°C and 1.3 MPa hydrogen pressure is studied for the first time. The best results (89% selectivity toward p-phenylenediamine at complete conversion of p-dinitrobenzene) are obtained for the sample synthesized via co-deposition with subsequent calcination at 300°C. The sample contains 7% iron and 3% copper. The formation of separate phases of metal oxides (for the catalysts prepared by impregnation) and mixed bimetallic oxide phases (in case of co-deposition procedure) in calcined samples is revealed via thermoprogrammed reduction with hydrogen.
Effect Of Oxidation On Chromium Leaching And Redox Capacity Of Slag-Containing Waste Forms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Almond, P. M.; Stefanko, D. B.; Langton, C. A.

2013-03-01

The rate of oxidation is important to the long-term performance of reducing salt waste forms because the solubility of some contaminants, e.g., technetium, is a function of oxidation state. TcO 4 - in the salt solution is reduced to Tc(IV) and has been shown to react with ingredients in the waste form to precipitate low solubility sulfide and/or oxide phases [Shuh, et al., 1994, Shuh, et al., 2000, Shuh, et al., 2003]. Upon exposure to oxygen, the compounds containing Tc(IV) oxidize to the pertechnetate ion, Tc(VII)O 4 -, which is very soluble. Consequently the rate of technetium oxidation front advancementmore » into a monolith and the technetium leaching profile as a function of depth from an exposed surface are important to waste form performance and ground water concentration predictions. An approach for measuring contaminant oxidation rate (effective contaminant specific oxidation rate) based on leaching of select contaminants of concern is described in this report. In addition, the relationship between reduction capacity and contaminant oxidation is addressed. Chromate was used as a non-radioactive surrogate for pertechnetate in simulated waste form samples. Depth discrete subsamples were cut from material exposed to Savannah River Site (SRS) field cured conditions. The subsamples were prepared and analyzed for both reduction capacity and chromium leachability. Results from field-cured samples indicate that the depth at which leachable chromium was detected advanced further into the sample exposed for 302 days compared to the sample exposed to air for 118 days (at least 50 mm compared to at least 20 mm). Data for only two exposure time intervals is currently available. Data for additional exposure times are required to develop an equation for the oxidation front progression. Reduction capacity measurements (per the Angus-Glasser method, which is a measurement of the ability of a material to chemically reduce Ce(IV) to Ce(III) in solution) performed on depth discrete samples could not be correlated with the amount of chromium leached from the depth discrete subsamples or with the oxidation front inferred from soluble chromium (i.e., effective Cr oxidation front). Exposure to oxygen (air or oxygen dissolved in water) results in the release of chromium through oxidation of Cr(III) to highly soluble chromate, Cr(VI). Residual reduction capacity in the oxidized region of the test samples indicates that the remaining reduction capacity is not effective in re-reducing Cr(VI) in the presence of oxygen. Consequently, this method for determining reduction capacity may not be a good indicator of the effective contaminant oxidation rate in a relatively porous solid (40 to 60 volume percent porosity). The chromium extracted in depth discrete samples ranged from a maximum of about 5.8 % at about 5 mm (118 day exposure) to about 4 % at about 10 mm (302 day exposure). The use of reduction capacity as an indicator of long-term performance requires further investigation. The carbonation front was also estimated to have advanced to at least 28 mm in 302 days based on visual observation of gas evolution during acid addition during the reduction capacity measurements. Depth discrete sampling of materials exposed to realistic conditions in combination with short term leaching of crushed samples has potential for advancing the understanding of factors influencing performance and will support conceptual model development.« less
Study on the poisoning effect-of non-vanadium catalysts by potassium

NASA Astrophysics Data System (ADS)

Zeng, Huanmu; Liu, Ying; Yu, Xiaowei; Lin, Yasi

2018-02-01

The poisoning effect of catalyst by alkali metals is one of the problems in the selective catalytic reduction (SCR) of NO by NH3. Serious deactivation by alkali poisoning have been proved to take place in the commercial vanadium catalyst. Recently, non-vanadium catalysts such as copper oxides, manganese oxides, chromium oxides and cerium oxides have attracted special attentions in SCR application. However, their tolerance in the presence of alkali metals is still doubtful. In this paper, copper oxides, manganese oxides, chromium oxides and cerium oxides supported on TiO2 nanoparticle was prepared by impregnating method. Potassium nitrate was chosen as the precursor of poisoner. Catalytic activities of these catalysts were evaluated before and after the addition of potassium. Some characterization methods including X-ray diffraction and temperature programmed desorption was utilized to reveal the main reason of alkali deactivation.
Selective catalytic reduction system and process for treating NOx emissions using a palladium and rhodium or ruthenium catalyst

DOEpatents

Sobolevskiy, Anatoly [Orlando, FL; Rossin, Joseph A [Columbus, OH; Knapke, Michael J [Columbus, OH

2011-07-12

A process for the catalytic reduction of nitrogen oxides (NOx) in a gas stream (29) in the presence of H.sub.2 is provided. The process comprises contacting the gas stream with a catalyst system (38) comprising zirconia-silica washcoat particles (41), a pre-sulfated zirconia binder (44), and a catalyst combination (40) comprising palladium and at least one of rhodium, ruthenium, or a mixture of ruthenium and rhodium.
Oxidative Polyoxometalates Modified Graphitic Carbon Nitride for Visible-Light CO2 Reduction.

PubMed

Zhou, Jie; Chen, Weichao; Sun, Chunyi; Han, Lu; Qin, Chao; Chen, Mengmeng; Wang, Xinlong; Wang, Enbo; Su, Zhongmin

2017-04-05

Developing a photocatalysis system for converting CO 2 to valuable fuels or chemicals is a promising strategy to address global warming and fossil fuel consumption. Exploring photocatalysts with high-performance and low-cost has been two ultimate goals toward photoreduction of CO 2 . Herein, noble-metal-free polyoxometalates (Co4) with oxidative ability was first introduced into g-C 3 N 4 resulted in inexpensive hybrid materials (Co4@g-C 3 N 4 ) with staggered band alignment. The staggered composited materials show a higher activity of CO 2 reduction than bare g-C 3 N 4 . An optimized Co4@g-C 3 N 4 hybrid sample exhibited a high yield (107 μmol g -1 h -1 ) under visible-light irradiation (λ ≥ 420 nm), meanwhile maintaining high selectivity for CO production (94%). After 10 h of irradiation, the production of CO reached 896 μmol g -1 . Mechanistic studies revealed the introduction of Co4 not only facilitate the charge transfer of g-C 3 N 4 but greatly increased the surface catalytic oxidative ability. This work creatively combined g-C 3 N 4 with oxidative polyoxometalates which provide novel insights into the design of low-cost photocatalytic materials for CO 2 reduction.
Selective CO2 reduction conjugated with H2O oxidation utilizing semiconductor/metal-complex hybrid photocatalysts

NASA Astrophysics Data System (ADS)

Morikawa, T.; Sato, S.; Arai, T.; Uemura, K.; Yamanaka, K. I.; Suzuki, T. M.; Kajino, T.; Motohiro, T.

2013-12-01

We developed a new hybrid photocatalyst for CO2 reduction, which is composed of a semiconductor and a metal complex. In the hybrid photocatalyst, ΔG between the position of conduction band minimum (ECBM) of the semiconductor and the CO2 reduction potential of the complex is an essential factor for realizing fast electron transfer from the conduction band of semiconductor to metal complex leading to high photocatalytic activity. On the basis of this concept, the hybrid photocatalyst InP/Ru-complex, which functions in aqueous media, was developed. The photoreduction of CO2 to formate using water as an electron donor and a proton source was successfully achieved as a Z-scheme system by functionally conjugating the InP/Ru-complex photocatalyst for CO2 reduction with a TiO2 photocatalyst for water oxidation. The conversion efficiency from solar energy to chemical energy was ca. 0.04%, which approaches that for photosynthesis in a plant. Because this system can be applied to many other inorganic semiconductors and metal-complex catalysts, the efficiency and reaction selectivity can be enhanced by optimization of the electron transfer process including the energy-band configurations, conjugation conformations, and catalyst structures. This electrical-bias-free reaction is a huge leap forward for future practical applications of artificial photosynthesis under solar irradiation to produce organic species.
Catalyst for selective NO.sub.x reduction using hydrocarbons

DOEpatents

Marshall, Christopher L [Naperville, IL; Neylon, Michael K [Naperville, IL

2007-05-22

A two phase catalyst is disclosed with one or more transition metals such as Cu, Co, Fe, Ag and Mo supported on a molecular sieve having a pore size not greater than 8 .ANG. along with a stabilizing oxide of one or more of the oxides of Zr, Mo, V, Nb or the rare earths coating the molecular sieve. A method of preparing the two phase catalyst and using same to remediate NO.sub.x in combustion gases is also described.
Influence on the oxidative potential of a heavy-duty engine particle emission due to selective catalytic reduction system and biodiesel blend.

PubMed

Godoi, Ricardo H M; Polezer, Gabriela; Borillo, Guilherme C; Brown, Andrew; Valebona, Fabio B; Silva, Thiago O B; Ingberman, Aline B G; Nalin, Marcelo; Yamamoto, Carlos I; Potgieter-Vermaak, Sanja; Penteado Neto, Renato A; de Marchi, Mary Rosa R; Saldiva, Paulo H N; Pauliquevis, Theotonio; Godoi, Ana Flavia L

2016-08-01

Although the particulate matter (PM) emissions from biodiesel fuelled engines are acknowledged to be lower than those of fossil diesel, there is a concern on the impact of PM produced by biodiesel to human health. As the oxidative potential of PM has been suggested as trigger for adverse health effects, it was measured using the Electron Spin Resonance (OP(ESR)) technique. Additionally, Energy Dispersive X-ray Fluorescence Spectroscopy (EDXRF) was employed to determine elemental concentration, and Raman Spectroscopy was used to describe the amorphous carbon character of the soot collected on exhaust PM from biodiesel blends fuelled test-bed engine, with and without Selective Catalytic Reduction (SCR). OP(ESR) results showed higher oxidative potential per kWh of PM produced from a blend of 20% soybean biodiesel and 80% ULSD (B20) engine compared with a blend of 5% soybean biodiesel and 95% ULSD (B5), whereas the SCR was able to reduce oxidative potential for each fuel. EDXRF data indicates a correlation of 0.99 between concentration of copper and oxidative potential. Raman Spectroscopy centered on the expected carbon peaks between 1100cm(-1) and 1600cm(-1) indicate lower molecular disorder for the B20 particulate matter, an indicative of a more graphitic carbon structure. The analytical techniques used in this study highlight the link between biodiesel engine exhaust and increased oxidative potential relative to biodiesel addition on fossil diesel combustion. The EDXRF analysis confirmed the prominent role of metals on free radical production. As a whole, these results suggest that 20% of biodiesel blends run without SCR may pose an increased health risk due to an increase in OH radical generation. Copyright © 2015 Elsevier B.V. All rights reserved.
Methane Oxidation to Methanol Catalyzed by Cu-Oxo Clusters Stabilized in NU-1000 Metal-Organic Framework.

PubMed

Ikuno, Takaaki; Zheng, Jian; Vjunov, Aleksei; Sanchez-Sanchez, Maricruz; Ortuño, Manuel A; Pahls, Dale R; Fulton, John L; Camaioni, Donald M; Li, Zhanyong; Ray, Debmalya; Mehdi, B Layla; Browning, Nigel D; Farha, Omar K; Hupp, Joseph T; Cramer, Christopher J; Gagliardi, Laura; Lercher, Johannes A

2017-08-02

Copper oxide clusters synthesized via atomic layer deposition on the nodes of the metal-organic framework (MOF) NU-1000 are active for oxidation of methane to methanol under mild reaction conditions. Analysis of chemical reactivity, in situ X-ray absorption spectroscopy, and density functional theory calculations are used to determine structure/activity relations in the Cu-NU-1000 catalytic system. The Cu-loaded MOF contained Cu-oxo clusters of a few Cu atoms. The Cu was present under ambient conditions as a mixture of ∼15% Cu + and ∼85% Cu 2+ . The oxidation of methane on Cu-NU-1000 was accompanied by the reduction of 9% of the Cu in the catalyst from Cu 2+ to Cu + . The products, methanol, dimethyl ether, and CO 2 , were desorbed with the passage of 10% water/He at 135 °C, giving a carbon selectivity for methane to methanol of 45-60%. Cu oxo clusters stabilized in NU-1000 provide an active, first generation MOF-based, selective methane oxidation catalyst.
Evaluation of SSME test data reduction methods

NASA Technical Reports Server (NTRS)

Santi, L. Michael

1994-01-01

Accurate prediction of hardware and flow characteristics within the Space Shuttle Main Engine (SSME) during transient and main-stage operation requires a significant integration of ground test data, flight experience, and computational models. The process of integrating SSME test measurements with physical model predictions is commonly referred to as data reduction. Uncertainties within both test measurements and simplified models of the SSME flow environment compound the data integration problem. The first objective of this effort was to establish an acceptability criterion for data reduction solutions. The second objective of this effort was to investigate the data reduction potential of the ROCETS (Rocket Engine Transient Simulation) simulation platform. A simplified ROCETS model of the SSME was obtained from the MSFC Performance Analysis Branch . This model was examined and tested for physical consistency. Two modules were constructed and added to the ROCETS library to independently check the mass and energy balances of selected engine subsystems including the low pressure fuel turbopump, the high pressure fuel turbopump, the low pressure oxidizer turbopump, the high pressure oxidizer turbopump, the fuel preburner, the oxidizer preburner, the main combustion chamber coolant circuit, and the nozzle coolant circuit. A sensitivity study was then conducted to determine the individual influences of forty-two hardware characteristics on fourteen high pressure region prediction variables as returned by the SSME ROCETS model.
Promotion effect of H2 on ethanol oxidation and NOx reduction with ethanol over Ag/Al2O3 catalyst.

PubMed

Yu, Yunbo; Li, Yi; Zhang, Xiuli; Deng, Hua; He, Hong; Li, Yuyang

2015-01-06

The catalytic partial oxidation of ethanol and selective catalytic reduction of NOx with ethanol (ethanol-SCR) over Ag/Al2O3 were studied using synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry (PIMS). The intermediates were identified by PIMS and their photoionization efficiency (PIE) spectra. The results indicate that H2 promotes the partial oxidation of ethanol to acetaldehyde over Ag/Al2O3, while the simultaneously occurring processes of dehydration and dehydrogenation were inhibited. H2 addition favors the formation of ammonia during ethanol-SCR over Ag/Al2O3, the occurrence of which creates an effective pathway for NOx reduction by direct reaction with NH3. Simultaneously, the enhancement of the formation of ammonia benefits its reaction with surface enolic species, resulting in producing -NCO species again, leading to enhancement of ethanol-SCR over Ag/Al2O3 by H2. Using VUV-PIMS, the reactive vinyloxy radical was observed in the gas phase during the NOx reduction by ethanol for the first time, particularly in the presence of H2. Identification of such a reaction occurring in the gas phase may be crucial for understanding the reaction pathway of HC-SCR over Ag/Al2O3.
In vitro knockout of human p47phox blocks superoxide anion production and LDL oxidation by activated human monocytes.

PubMed

Bey, E A; Cathcart, M K

2000-03-01

We previously reported that superoxide dismutase (SOD) blocked human monocyte oxidation of LDL and therefore concluded that superoxide anion (O(2)(.-)) was required for oxidation. Others, however, have suggested that SOD may inhibit by mechanisms alternative to the dismutation of O(2)(.-). This study definitively addresses the involvement of O(2)(.-) in monocyte oxidation of LDL. Using an antisense ODN designed to target p47phox mRNA, we found that treatment of monocytes with antisense ODN caused a substantial and selective decrease in expression of p47phox protein, whereas sense ODN was without effect. Corresponding functional assays demonstrated that antisense ODN inhibited production of O(2)(.-). As sense ODN caused no inhibition of O(2)(.-) production, these results suggested that inhibition of p47phox expression caused reduction in O(2)(.-) production. Evaluation of the contribution of O(2)(.-) production to monocyte-mediated oxidation of LDL lipids confirmed that O(2)(.-) production is required for LDL lipid oxidation as antisense ODN treatment significantly inhibited LDL oxidation whereas sense ODN treatment caused no inhibition. This is the first report of the reduction of NADPH oxidase activity in intact human monocytes by directly targeting the mRNA of a significant member of this enzyme complex. Our results provide convincing data that O(2)(.-) is indeed required for monocyte-mediated LDL oxidation.
Evaluation of eutrophication of Ostravice river depending on the chemical and physical parameters

NASA Astrophysics Data System (ADS)

Hlavac, A.; Melcakova, I.; Novakova, J.; Svehlakova, H.; Slavikova, L.; Klimsa, L.; Bartkova, M.

2017-10-01

The main objective of this study was to evaluate which selected environmental parameters in rivers affect the concentration of chlorophyll a and the distribution of macrozoobenthos. The data were collected on selected profiles of the Ostravice mountain river in the Moravian-Silesian Region. The examined chemical and physical parameters include dissolved oxygen (DO), flow rate, oxidation-reduction potential (ORP), conductivity, temperature, pH, total nitrogen and phosphorus concentration.
Partially oxidized atomic cobalt layers for carbon dioxide electroreduction to liquid fuel.

PubMed

Gao, Shan; Lin, Yue; Jiao, Xingchen; Sun, Yongfu; Luo, Qiquan; Zhang, Wenhua; Li, Dianqi; Yang, Jinlong; Xie, Yi

2016-01-07

Electroreduction of CO2 into useful fuels, especially if driven by renewable energy, represents a potentially 'clean' strategy for replacing fossil feedstocks and dealing with increasing CO2 emissions and their adverse effects on climate. The critical bottleneck lies in activating CO2 into the CO2(•-) radical anion or other intermediates that can be converted further, as the activation usually requires impractically high overpotentials. Recently, electrocatalysts based on oxide-derived metal nanostructures have been shown to enable CO2 reduction at low overpotentials. However, it remains unclear how the electrocatalytic activity of these metals is influenced by their native oxides, mainly because microstructural features such as interfaces and defects influence CO2 reduction activity yet are difficult to control. To evaluate the role of the two different catalytic sites, here we fabricate two kinds of four-atom-thick layers: pure cobalt metal, and co-existing domains of cobalt metal and cobalt oxide. Cobalt mainly produces formate (HCOO(-)) during CO2 electroreduction; we find that surface cobalt atoms of the atomically thin layers have higher intrinsic activity and selectivity towards formate production, at lower overpotentials, than do surface cobalt atoms on bulk samples. Partial oxidation of the atomic layers further increases their intrinsic activity, allowing us to realize stable current densities of about 10 milliamperes per square centimetre over 40 hours, with approximately 90 per cent formate selectivity at an overpotential of only 0.24 volts, which outperforms previously reported metal or metal oxide electrodes evaluated under comparable conditions. The correct morphology and oxidation state can thus transform a material from one considered nearly non-catalytic for the CO2 electroreduction reaction into an active catalyst. These findings point to new opportunities for manipulating and improving the CO2 electroreduction properties of metal systems, especially once the influence of both the atomic-scale structure and the presence of oxide are mechanistically better understood.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Mistry, Hemma; Varela, Ana Sofia; Bonifacio, Cecile S.

There is an urgent need to develop technologies that use renewable energy to convert waste products such as carbon dioxide into hydrocarbon fuels. Carbon dioxide can be electrochemically reduced to hydrocarbons over copper catalysts, although higher efficiency is required. We have developed oxidized copper catalysts displaying lower overpotentials for carbon dioxide electroreduction and record selectivity towards ethylene (60%) through facile and tunable plasma treatments. Herein we provide insight into the improved performance of these catalysts by combining electrochemical measurements with microscopic and spectroscopic characterization techniques. Operando X-ray absorption spectroscopy and cross-sectional scanning transmission electron microscopy show that copper oxides aremore » surprisingly resistant to reduction and copper + species remain on the surface during the reaction. Furthermore, our results demonstrate that the roughness of oxide-derived copper catalysts plays only a partial role in determining the catalytic performance, while the presence of copper + is key for lowering the onset potential and enhancing ethylene selectivity.« less
Graphene oxide nanoplatforms to enhance catalytic performance of iron phthalocyanine for oxygen reduction reaction in bioelectrochemical systems

NASA Astrophysics Data System (ADS)

Costa de Oliveira, Maida Aysla; Mecheri, Barbara; D'Epifanio, Alessandra; Placidi, Ernesto; Arciprete, Fabrizio; Valentini, Federica; Perandini, Alessando; Valentini, Veronica; Licoccia, Silvia

2017-07-01

We report the development of electrocatalysts based on iron phthalocyanine (FePc) supported on graphene oxide (GO), obtained by electrochemical oxidation of graphite in aqueous solution of LiCl, LiClO4, and NaClO4. Structure, surface chemistry, morphology, and thermal stability of the prepared materials were investigated by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, atomic force microscopy (AFM), thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS). The catalytic activity toward oxygen reduction reaction (ORR) at neutral pH was evaluated by cyclic voltammetry. The experimental results demonstrate that the oxidation degree of GO supports affects the overall catalytic activity of FePc/GO, due to a modulation effect of the interaction between FePc and the basal plane of GO. On the basis of electrochemical, spectroscopic, and morphological investigations, FePc/GO_LiCl was selected to be assembled at the cathode side of a microbial fuel cell prototype, demonstrating a good electrochemical performance in terms of voltage and power generation.
System and method for regeneration and recirculation of a reducing agent using highly exothermic reactions induced by mixed industrial slags

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nakano, Jinichiro; Bennett, James P.; Nakano, Anna

Embodiments relate to systems and methods for regenerating and recirculating a CO, H.sub.2 or combinations thereof utilized for metal oxide reduction in a reduction furnace. The reduction furnace receives the reducing agent, reduces the metal oxide, and generates an exhaust of the oxidized product. The oxidized product is transferred to a mixing vessel, where the oxidized product, a calcium oxide, and a vanadium oxide interact to regenerate the reducing agent from the oxidized product. The regenerated reducing agent is transferred back to the reduction furnace for continued metal oxide reductions.
Necessary and sufficient conditions for the successful three-phase photocatalytic reduction of CO2 by H2O over heterogeneous photocatalysts.

PubMed

Teramura, Kentaro; Tanaka, Tsunehiro

2018-03-28

Artificial photosynthesis has recently drawn an increasing amount of attention due to the fact that it allows for direct solar-to-chemical energy conversion. However, one of the basic steps of this process, namely the reduction of CO2 by H2O to afford O2 and CO2 reduction products (CO2RPs) such as HCOOH, CO, HCHO, CH3OH, and CH4, is very difficult to achieve. In contrast to the CO2 reduction in plants and homogenous systems, the reduction of CO2 to CO2RPs over heterogeneous photocatalysts was challenged by the competing reduction of H+ to H2. Unfortunately, most of the research performed so far has focused only on the reduction of CO2, rather than the characterization of the H2O oxidation and H2 production. Moreover, the fact that the heterogeneous photocatalytic reduction of CO2 into CO2RPs by H2O should satisfy several selectivity criteria has often been ignored. Herein, we propose three such evaluation criteria, namely (1) the origin of carbon in CO2RPs (determined using isotopically labeled CO2 (13CO2)), (2) the relative amount of H2 and CO2RPs produced, and (3) the amount of O2 produced by the oxidation of H2O. If all these criteria are satisfied, i.e., the carbons of CO2RPs originate from CO2, the amount of H2 produced is negligible, and a stoichiometric amount of O2 is produced by the oxidation of H2O, then CO2 introduced into the gas phase is believed to be reduced by H2O to CO2RPs in the aqueous phase.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, T.; Griffin, A. M.; Gorski, C. A.

Dissimilatory microbial reduction of solid-phase Fe(III)-oxides and Fe(III)-bearing phyllosilicates (Fe(III)-phyllosilicates) is an important process in anoxic soils, sediments, and subsurface materials. Although various studies have documented the relative extent of microbial reduction of single-phase Fe(III)-oxides and Fe(III)-phyllosilicates, detailed information is not available on interaction between these two processes in situations where both phases are available for microbial reduction. The goal of this research was to use the model dissimilatory iron-reducing bacterium (DIRB) Geobacter sulfurreducens to study Fe(III)-oxide vs. Fe(III)-phyllosilicate reduction in a range of subsurface materials and Fe(III)-oxide stripped versions of the materials. Low temperature (12K) Mossbauer spectroscopy was usedmore » to infer changes in the relative abundances of Fe(III)-oxide, Fe(III)-phyllosilicate, and phyllosilicate-associated Fe(II) (Fe(II)-phyllosilicate). A Fe partitioning model was employed to analyze the fate of Fe(II) and assess the potential for abiotic Fe(II)-catalyzed reduction of Fe(III)-phyllosilicates. The results showed that in most cases Fe(III)- oxide utilization dominated (70-100 %) bulk Fe(III) reduction activity, and that electron transfer from oxide-derived Fe(II) played only a minor role (ca. 10-20 %) in Fe partitioning. In addition, the extent of Fe(III)-oxide reduction was positively correlated to surface area-normalized cation exchange capacity and the phyllosilicate-Fe(III)/total Fe(III) ratio, which suggests that the phyllosilicates in the natural sediments promoted Fe(III)-oxide reduction by binding of oxide-derived Fe(II), thereby enhancing Fe(III)-oxide reduction by reducing or delaying the inhibitory effect that Fe(II) accumulation on oxide and DIRB cell surfaces has on Fe(III)-oxide reduction. In general our results suggest that although Fe(III)-oxide reduction is likely to dominate bulk Fe(III) reduction in most subsurface sediments, Fe(II) binding by phyllosilicates is likely to play a key role in controlling the long-term kinetics of Fe(III)-oxide reduction.« less
Catalyst for elemental sulfur recovery process

DOEpatents

Flytzani-Stephanopoulos, M.; Liu, W.

1995-01-24

A catalytic reduction process is described for the direct recovery of elemental sulfur from various SO[sub 2]-containing industrial gas streams. The catalytic process provides high activity and selectivity, as well as stability in the reaction atmosphere, for the reduction of SO[sub 2] to elemental sulfur product with carbon monoxide or other reducing gases. The reaction of sulfur dioxide and reducing gas takes place over a metal oxide composite catalyst having one of the following empirical formulas: [(FO[sub 2])[sub 1[minus]n](RO)[sub n
A dual-plate ITO-ITO generator-collector microtrench sensor: surface activation, spatial separation and suppression of irreversible oxygen and ascorbate interference.

PubMed

Hasnat, Mohammad A; Gross, Andrew J; Dale, Sara E C; Barnes, Edward O; Compton, Richard G; Marken, Frank

2014-02-07

Generator-collector electrode systems are based on two independent working electrodes with overlapping diffusion fields where chemically reversible redox processes (oxidation and reduction) are coupled to give amplified current signals. A generator-collector trench electrode system prepared from two tin-doped indium oxide (ITO) electrodes placed vis-à-vis with a 22 μm inter-electrode gap is employed here as a sensor in aqueous media. The reversible 2-electron anthraquinone-2-sulfonate redox system is demonstrated to give well-defined collector responses even in the presence of oxygen due to the irreversible nature of the oxygen reduction. For the oxidation of dopamine on ITO, novel "Piranha-activation" effects are observed and chemically reversible generator-collector feedback conditions are achieved at pH 7, by selecting a more negative collector potential, again eliminating possible oxygen interference. Finally, dopamine oxidation in the presence of ascorbate is demonstrated with the irreversible oxidation of ascorbate at the "mouth" of the trench electrode and chemically reversible oxidation of dopamine in the trench "interior". This spatial separation of chemically reversible and irreversible processes within and outside the trench is discussed as a potential in situ microscale sensing and separation tool.
Controllable synthesis of palladium nanocubes/reduced graphene oxide composites and their enhanced electrocatalytic performance

NASA Astrophysics Data System (ADS)

Zhang, Yuting; Huang, Qiwei; Chang, Gang; Zhang, Zaoli; Xia, Tiantian; Shu, Honghui; He, Yunbin

2015-04-01

Homogeneous distribution of cube-shaped Pd nanocrystals on the surface of reduced graphene oxide is obtained via a facile one-step method by employing AA and KBr as the reductant and capping agent, respectively. The experimental factors affecting the morphology and structure of Pd nanoparticles have been systematically investigated to explore the formation mechanism of Pd nanocubes (PdNCs). It is revealed that PdNCs enclosed by active {100} facets with an average side length of 15 nm were successfully synthesized on the surface of reduced graphene oxide. KBr plays the role for facet selection by surface passivation and AA controls the reduction speed of Pd precursors, both of which govern the morphology changes of palladium nanoparticles. In the further electrochemical evaluations, the Pd nanocubes/reduced graphene oxide composites show better electrocatalytic activity and stability towards the electro-oxidation of ethanol than both reduced graphene oxide supported Pd nanoparticles and free-standing PdNCs. It could be attributed to the high electrocatalytic activity of the dominated active {100} crystal facets of Pd nanocubes and the enhanced electron transfer of graphene. The developed approach provide a versatile way for shape-controlled preparation of noble metal nanoparticles, which can work as novel electrocatalysts in the application of direct alcohols fuel cells.
Contaminant removal from enclosed atmospheres by regenerable adsorbents

NASA Technical Reports Server (NTRS)

Goldsmith, R. L.; Mcnulty, K. J.; Freedland, G. M.; Turk, A.; Nwankwo, J.

1974-01-01

A system for removing contaminants from spacecraft atmospheres was studied, which utilizes catalyst-impregnated activated carbon followed by in-situ regeneration by low-temperature catalytic oxidation of the adsorbed contaminants. Platinum was deposited on activated carbon by liquid phase impregnation with chloroplatinic acid, followed by drying and high-temperature reduction. Results were obtained for the seven selected spacecraft contaminants by means of three experimental test systems. The results indicate that the contaminants could be removed by oxidation with very little loss in adsorptive capacity. The advantages of a catalyst-impregnated carbon for oxidative regeneration are found to be significant enough to warrent its use.
Comparison of Two Preparation Methods on Catalytic Activity and Selectivity of Ru-Mo/HZSM5 for Methane Dehydroaromatization

DOE PAGES

Petkovic, Lucia M.; Ginosar, Daniel M.

2014-01-01

Catalytic performance of Mo/HZSM5 and Ru-Mo/HZSM5 catalysts prepared by vaporization-deposition of molybdenum trioxide and impregnation with ammonium heptamolybdate was analyzed in terms of catalyst activity and selectivity, nitrogen physisorption analyses, temperature-programmed oxidation of carbonaceous residues, and temperature-programmed reduction. Vaporization-deposition rendered the catalyst more selective to ethylene and coke than the catalyst prepared by impregnation. This result was assigned to lower interaction of molybdenum carbide with the zeolite acidic sites.
Chemoselective catalytic conversion of glycerol as a biorenewable source to valuable commodity chemicals.

PubMed

Zhou, Chun-Hui Clayton; Beltramini, Jorge N; Fan, Yong-Xian; Lu, G Q Max

2008-03-01

New opportunities for the conversion of glycerol into value-added chemicals have emerged in recent years as a result of glycerol's unique structure, properties, bioavailability, and renewability. Glycerol is currently produced in large amounts during the transesterification of fatty acids into biodiesel and as such represents a useful by-product. This paper provides a comprehensive review and critical analysis on the different reaction pathways for catalytic conversion of glycerol into commodity chemicals, including selective oxidation, selective hydrogenolysis, selective dehydration, pyrolysis and gasification, steam reforming, thermal reduction into syngas, selective transesterification, selective etherification, oligomerization and polymerization, and conversion of glycerol into glycerol carbonate.
Nox control for high nitric oxide concentration flows through combustion-driven reduction

DOEpatents

Yeh, James T.; Ekmann, James M.; Pennline, Henry W.; Drummond, Charles J.

1989-01-01

An improved method for removing nitrogen oxides from concentrated waste gas streams, in which nitrogen oxides are ignited with a carbonaceous material in the presence of substoichiometric quantities of a primary oxidant, such as air. Additionally, reductants may be ignited along with the nitrogen oxides, carbonaceous material and primary oxidant to achieve greater reduction of nitrogen oxides. A scrubber and regeneration system may also be included to generate a concentrated stream of nitrogen oxides from flue gases for reduction using this method.
Stereoselective oxidation of aliphatic diols and reduction of hydroxy-ketones with galactitol dehydrogenase from Rhodobacter sphaeroides D.

PubMed

Kohring, G W; Wiehr, P; Jeworski, M; Giffhorn, F

2003-01-01

From the Rhodobacter sphaeroides mutant D a galactitol dehydrogenase (GDH) was isolated and characterized in an earlier investigation (1). The enzyme expressed activity with a wide spread substrate spectrum, like sugars, sugar alcohols, secondary alcohols or the corresponding ketones and it can be used for the production of the rare sugar L-tagatose by regioselective oxidation of galactitol (2). This study focuses on the preparation of optically pure aliphatic diols by oxidation of one enantiomer or stereospecific reduction of keto-alcohols and diketones. The oxidation of 1,2-propanediol, 1,2-butanediol, 1,2-pentanediol and 1,2-hexanediol occurred highly specific with the S-enantiomer leaving the R-enantiomer of the diols in the reaction vessel. Also (S)-1,2,6-hexanetriol was oxidized by GDH to 1,6-dihydroxy-2-hexanone. The Km values of these reactions decreased with increasing length of the carbon chain. Reduction of hydroxyacetone or 1-hydroxy-2-butanone resulted in an excess of 93% (S)-1,2-propanediol and more than 98% of (S)-1,2-butanediol, respectively. The diketone 2,3-hexanedione was only reduced to (2R,3S)-2,3-hexanediol, one of the possible four configurations. The wide substrate spectrum on one hand and the selectivity in the reaction on the other hand make GDH a very interesting enzyme for the production of optically pure building blocks in the chemical synthesis of bioactive compounds.
Role of ligands in permanganate oxidation of organics.

PubMed

Jiang, Jin; Pang, Su-Yan; Ma, Jun

2010-06-01

We previously demonstrated that several ligands such as phosphate, pyrophosphate, EDTA, and humic acid could significantly enhance permanganate oxidation of triclosan (one phenolic biocide), which was explained by the contribution of ligand-stabilized reactive manganese intermediates in situ formed upon permanganate reduction. To further understand the underlying mechanism, we comparatively investigated the influence of ligands on permanganate oxidation of bisphenol A (BPA, one phenolic endocrine-disrupting chemical), carbamazepine (CBZ, a pharmaceutical containing the olefinic group), and methyl p-tolyl sulfoxide (TMSO, a typical oxygen-atom acceptor). Selected ligands exerted oxidation enhancement for BPA but had negligible influence for CBZ and TMSO. This was mainly attributed to the effects of identified Mn(III) complexes, which would otherwise disproportionate spontaneously in the absence of ligands. The one-electron oxidant Mn(III) species exhibited no reactivity toward CBZ and TMSO for which the two-electron oxygen donation may be the primary oxidation mechanism but readily oxidized BPA. The latter case was a function of pH, the complexing ligand, and the molar [Mn(III)]:[ligand] ratio, generally consistent with the patterns of ligand-affected permanganate oxidation. Moreover, the combination of the one-electron reduction of Mn(III) (Mn(III) + e(-) -->Mn(II)) and the Mn(VII)/Mn(II) reaction in excess ligands (Mn(VII) + 4Mn(II) ----> (ligands) 5Mn(III)) suggested a catalytic role of the Mn(III)/Mn(II) pair in permanganate oxidation of some phenolics in the presence of ligands.
Mössbauer study of iron-based perovskite-type materials as potential catalysts for ethyl acetate oxidation

NASA Astrophysics Data System (ADS)

Paneva, D.; Dimitrov, M.; Velinov, N.; Kolev, H.; Kozhukharov, V.; Tsoncheva, T.; Mitov, I.

2010-03-01

La-Sr-Fe perovskite-type oxides were prepared by the nitrate-citrate method. The basic object of this study is layered Ruddlesden-Popper phase LaSr3Fe3O10. The phase composition and structural properties of the obtained materials are investigated by Mössbauer spectroscopy, X-ray diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS) and temperature programmed reduction (TPR). The preliminary catalytic tests show a high potential of these materials for volatile organic compounds (VOCs) elimination as they possess high conversion ability and selectivity to total oxidation of ethyl acetate. Catalytic performance of LaSr3Fe3O10 is depended on the stability of structure and Fe4+-oxidation state.
Dopant selection for control of charge carrier density and mobility in amorphous indium oxide thin-film transistors: Comparison between Si- and W-dopants

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mitoma, Nobuhiko, E-mail: MITOMA.Nobuhiko@nims.go.jp, E-mail: TSUKAGOSHI.Kazuhito@nims.go.jp; Kizu, Takio; Lin, Meng-Fang

The dependence of oxygen vacancy suppression on dopant species in amorphous indium oxide (a-InO{sub x}) thin film transistors (TFTs) is reported. In a-InO{sub x} TFTs incorporating equivalent atom densities of Si- and W-dopants, absorption of oxygen in the host a-InO{sub x} matrix was found to depend on difference of Gibbs free energy of the dopants for oxidation. For fully oxidized films, the extracted channel conductivity was higher in the a-InO{sub x} TFTs containing dopants of small ionic radius. This can be explained by a reduction in the ionic scattering cross sectional area caused by charge screening effects.
Comparison of preparation methods for ceria catalyst and the effect of surface and bulk sulfates on its activity toward NH3-SCR.

PubMed

Chang, Huazhen; Ma, Lei; Yang, Shijian; Li, Junhua; Chen, Liang; Wang, Wei; Hao, Jiming

2013-11-15

A series of CeO2 catalysts prepared with sulfate (S) and nitrate (N) precursors by hydrothermal (H) and precipitation (P) methods were investigated in selective catalytic reduction of NOx by NH3 (NH3-SCR). The catalytic activity of CeO2 was significantly affected by the preparation methods and the precursor type. CeO2-SH, which was prepared by hydrothermal method with cerium (IV) sulfate as a precursor, showed excellent SCR activity and high N2 selectivity in the temperature range of 230-450 °C. Based on the results obtained by temperature-programmed reduction (H2-TPR), transmission infrared spectra (IR) and thermal gravimetric analysis (TGA), the excellent performance of CeO2-SH was correlated with the surface sulfate species formed in the hydrothermal reaction. These results indicated that sulfate species bind with Ce(4+) on the CeO2-SH catalyst, and the specific sulfate species, such as Ce(SO4)2 or CeOSO4, were formed. The adsorption of NH3 was promoted by these sulfate species, and the probability of immediate oxidation of NH3 to N2O on Ce(4+) was reduced. Accordingly, the selective oxidation of NH3 was enhanced, which contributed to the high N2 selectivity in the SCR reaction. However, the location of sulfate on the CeO2-SP catalyst was different. Plenty of sulfate species were likely deposited on CeO2-SP surface, covering the active sites for NO oxidation, which resulted in poor SCR activity in the test temperature range. Moreover, the resistance to alkali metals, such as Na and K, was improved over the CeO2-SH catalyst. Copyright © 2013 Elsevier B.V. All rights reserved.
SCR atmosphere induced reduction of oxidized mercury over CuO-CeO2/TiO2 catalyst.

PubMed

Li, Hailong; Wu, Shaokang; Wu, Chang-Yu; Wang, Jun; Li, Liqing; Shih, Kaimin

2015-06-16

CuO-CeO2/TiO2 (CuCeTi) catalyst synthesized by a sol-gel method was employed to investigate mercury conversion under a selective catalytic reduction (SCR) atmosphere (NO, NH3 plus O2). Neither NO nor NH3 individually exhibited an inhibitive effect on elemental mercury (Hg(0)) conversion in the presence of O2. However, Hg(0) conversion over the CuCeTi catalyst was greatly inhibited under SCR atmosphere. Systematic experiments were designed to investigate the inconsistency and explore the in-depth mechanisms. The results show that the copresence of NO and NH3 induced reduction of oxidized mercury (Hg(2+), HgO in this study), which offset the effect of catalytic Hg(0) oxidation, and hence resulted in deactivation of Hg(0) conversion. High NO and NH3 concentrations with a NO/NH3 ratio of 1.0 facilitated Hg(2+) reduction and therefore lowered Hg(0) conversion. Hg(2+) reduction over the CuCeTi catalyst was proposed to follow two possible mechanisms: (1) direct reaction, in which NO and NH3 react directly with HgO to form N2 and Hg(0); (2) indirect reaction, in which the SCR reaction consumed active surface oxygen on the CuCeTi catalyst, and reduced species on the CuCeTi catalyst surface such as Cu2O and Ce2O3 robbed oxygen from adjacent HgO. Different from the conventionally considered mechanisms, that is, competitive adsorption responsible for deactivation of Hg(0) conversion, this study reveals that oxidized mercury can transform into Hg(0) under SCR atmosphere. Such knowledge is of fundamental importance in developing efficient and economical mercury control technologies for coal-fired power plants.
Ionic liquids as an electrolyte for the electro synthesis of organic compounds.

PubMed

Kathiresan, Murugavel; Velayutham, David

2015-12-25

The use of ionic liquids (ILs) as a solvent and an electrolyte for electro organic synthesis has been reviewed. To date several ILs exist, however the ILs based on tetraalkylammonium, pyrrolidinium, piperidinium and imidazolium cations with BF4(-), PF6(-), and TFSI anions have been widely used and explored the most. Electro organic synthesis in ionic liquid media leading to the synthesis of a wide range of organic compounds has been discussed. Anodic oxidation or cathodic reduction will generate radical cation or anion intermediates, respectively. These radicals can undergo self coupling or coupling with other molecules yielding organic compounds of interest. The cation of the IL is known to stabilize the radical anion extensively. This stabilization effect has a specific impact on the electrochemical CO2 reduction and coupling to various organics. The relative stability of the intermediates in IL leads to the formation of specific products in higher yields. Electrochemical reduction of imidazolium or thiazolium based ILs generates N-heterocyclic carbenes that have been shown to catalyze a wide range of base or nucleophile catalyzed organic reactions in IL media, an aspect that falls into the category of organocatalysis. Electrochemical fluorination or selective electrochemical fluorination is another fascinating area that delivers selectively fluorinated organic products in Et3N·nHF or Et4NF·nHF adducts (IL) via anodic oxidation. Oxidative polymerization in ILs has been explored the most; although morphological changes were observed compared to the conventional methods, polymers were obtained in good yields and in some cases ILs were used as dopants to improve the desired properties.
Analysis of long-term bacterial vs. chemical Fe(III) oxide reduction kinetics

NASA Astrophysics Data System (ADS)

Roden, Eric E.

2004-08-01

Data from studies of dissimilatory bacterial (10 8 cells mL -1 of Shewanella putrefaciens strain CN32, pH 6.8) and ascorbate (10 mM, pH 3.0) reduction of two synthetic Fe(III) oxide coated sands and three natural Fe(III) oxide-bearing subsurface materials (all at ca. 10 mmol Fe(III) L -1) were analyzed in relation to a generalized rate law for mineral dissolution (J t/m 0 = k'(m/m 0) γ, where J t is the rate of dissolution and/or reduction at time t, m 0 is the initial mass of oxide, and m/m 0 is the unreduced or undissolved mineral fraction) in order to evaluate changes in the apparent reactivity of Fe(III) oxides during long-term biological vs. chemical reduction. The natural Fe(III) oxide assemblages demonstrated larger changes in reactivity (higher γ values in the generalized rate law) compared to the synthetic oxides during long-term abiotic reductive dissolution. No such relationship was evident in the bacterial reduction experiments, in which temporal changes in the apparent reactivity of the natural and synthetic oxides were far greater (5-10 fold higher γ values) than in the abiotic reduction experiments. Kinetic and thermodynamic considerations indicated that neither the abundance of electron donor (lactate) nor the accumulation of aqueous end-products of oxide reduction (Fe(II), acetate, dissolved inorganic carbon) are likely to have posed significant limitations on the long-term kinetics of oxide reduction. Rather, accumulation of biogenic Fe(II) on residual oxide surfaces appeared to play a dominant role in governing the long-term kinetics of bacterial crystalline Fe(III) oxide reduction. The experimental findings together with numerical simulations support a conceptual model of bacterial Fe(III) oxide reduction kinetics that differs fundamentally from established models of abiotic Fe(III) oxide reductive dissolution, and indicate that information on Fe(III) oxide reactivity gained through abiotic reductive dissolution techniques cannot be used to predict long-term patterns of reactivity toward enzymatic reduction at circumneutral pH.
Environmental and economic evaluation of selective non-catalytic reduction of nitrogen oxides

NASA Astrophysics Data System (ADS)

Parchevskii, V. M.; Shchederkina, T. E.; Proshina, A. O.

2017-11-01

There are two groups of atmosphere protecting measures: technology (primary) and treatment (secondary). When burning high-calorie low-volatile brands of coals in the furnaces with liquid slag removal to achieve emission standards required joint use of these two methods, for example, staged combustion and selective non-catalytic reduction recovery (SNCR). For the economically intelligent combination of these two methods it is necessary to have information not only about the environmental performance of each method, but also the operating costs per unit of reduced emission. The authors of this report are made an environmental-economic analysis of SNCR on boiler Π-50P Kashirskaya power station. The obtained results about the dependence of costs from the load of the boiler and the mass emissions of nitrogen oxides then approximates into empirical formulas, is named as environmental and economic characteristics, which is suitable for downloading into controllers and other control devices for subsequent implementation of optimal control of emissions to ensure compliance with environmental regulations at the lowest cost at any load of the boiler.
A review of carbon-based and non-carbon-based catalyst supports for the selective catalytic reduction of nitric oxide

PubMed Central

Anthonysamy, Shahreen Binti Izwan; Afandi, Syahidah Binti; Khavarian, Mehrnoush

2018-01-01

Various types of carbon-based and non-carbon-based catalyst supports for nitric oxide (NO) removal through selective catalytic reduction (SCR) with ammonia are examined in this review. A number of carbon-based materials, such as carbon nanotubes (CNTs), activated carbon (AC), and graphene (GR) and non-carbon-based materials, such as Zeolite Socony Mobil–5 (ZSM-5), TiO2, and Al2O3 supported materials, were identified as the most up-to-date and recently used catalysts for the removal of NO gas. The main focus of this review is the study of catalyst preparation methods, as this is highly correlated to the behaviour of NO removal. The general mechanisms involved in the system, the Langmuir–Hinshelwood or Eley–Riedeal mechanism, are also discussed. Characterisation analysis affecting the surface and chemical structure of the catalyst is also detailed in this work. Finally, a few major conclusions are drawn and future directions for work on the advancement of the SCR-NH3 catalyst are suggested. PMID:29600136
A review of carbon-based and non-carbon-based catalyst supports for the selective catalytic reduction of nitric oxide.

PubMed

Anthonysamy, Shahreen Binti Izwan; Afandi, Syahidah Binti; Khavarian, Mehrnoush; Mohamed, Abdul Rahman Bin

2018-01-01

Various types of carbon-based and non-carbon-based catalyst supports for nitric oxide (NO) removal through selective catalytic reduction (SCR) with ammonia are examined in this review. A number of carbon-based materials, such as carbon nanotubes (CNTs), activated carbon (AC), and graphene (GR) and non-carbon-based materials, such as Zeolite Socony Mobil-5 (ZSM-5), TiO 2 , and Al 2 O 3 supported materials, were identified as the most up-to-date and recently used catalysts for the removal of NO gas. The main focus of this review is the study of catalyst preparation methods, as this is highly correlated to the behaviour of NO removal. The general mechanisms involved in the system, the Langmuir-Hinshelwood or Eley-Riedeal mechanism, are also discussed. Characterisation analysis affecting the surface and chemical structure of the catalyst is also detailed in this work. Finally, a few major conclusions are drawn and future directions for work on the advancement of the SCR-NH 3 catalyst are suggested.
Perovskite nanocomposites as effective CO2-splitting agents in a cyclic redox scheme

PubMed Central

Zhang, Junshe; Haribal, Vasudev; Li, Fanxing

2017-01-01

We report iron-containing mixed-oxide nanocomposites as highly effective redox materials for thermochemical CO2 splitting and methane partial oxidation in a cyclic redox scheme, where methane was introduced as an oxygen “sink” to promote the reduction of the redox materials followed by reoxidation through CO2 splitting. Up to 96% syngas selectivity in the methane partial oxidation step and close to complete conversion of CO2 to CO in the CO2-splitting step were achieved at 900° to 980°C with good redox stability. The productivity and production rate of CO in the CO2-splitting step were about seven times higher than those in state-of-the-art solar-thermal CO2-splitting processes, which are carried out at significantly higher temperatures. The proposed approach can potentially be applied for acetic acid synthesis with up to 84% reduction in CO2 emission when compared to state-of-the-art processes. PMID:28875171

Efficient and Selective Electrochemical and Photoelectrochemical Reduction of 5-Hydroxymethylfurfural to 2,5-Bis(hydroxymethyl)furan using Water as the Hydrogen Source

DOE PAGES

Roylance, John J.; Kim, Tae Woo; Choi, Kyoung-Shin

2016-02-17

Reductive biomass conversion has been conventionally conducted using H 2 gas under high-temperature and-pressure conditions. Here, efficient electrochemical reduction of 5-hydroxymethylfurfural (HMF), a key intermediate for biomass conversion, to 2,5-bis(hydroxymethyl)furan (BHMF), an important monomer for industrial processes, was demonstrated using Ag catalytic electrodes. This process uses water as the hydrogen source under ambient conditions and eliminates the need to generate and consume H 2 for hydrogenation, providing a practical and efficient route for BHMF production. By systematic investigation of HMF reduction on the Ag electrode surface, BHMF production was achieved with the Faradaic efficiency and selectivity nearing 100%, and plausiblemore » reduction mechanisms were also elucidated. Furthermore, construction of a photoelectrochemical cell (PEC) composed of an n-type BiVO 4 semiconductor anode, which uses photogenerated holes for water oxidation, and a catalytic Ag cathode, which uses photoexcited electrons from BiVO 4 for the reduction of HMF to BHMF, was demonstrated to utilize solar energy to significantly decrease the external voltage necessary for HMF reduction. This shows the possibility of coupling electrochemical HMF reduction and solar energy conversion, which can provide more efficient and environmentally benign routes for reductive biomass conversion.« less
Lithium metal reduction of plutonium oxide to produce plutonium metal

DOEpatents

Coops, Melvin S.

1992-01-01

A method is described for the chemical reduction of plutonium oxides to plutonium metal by the use of pure lithium metal. Lithium metal is used to reduce plutonium oxide to alpha plutonium metal (alpha-Pu). The lithium oxide by-product is reclaimed by sublimation and converted to the chloride salt, and after electrolysis, is removed as lithium metal. Zinc may be used as a solvent metal to improve thermodynamics of the reduction reaction at lower temperatures. Lithium metal reduction enables plutonium oxide reduction without the production of huge quantities of CaO--CaCl.sub.2 residues normally produced in conventional direct oxide reduction processes.
Selective CO{sub 2} reduction conjugated with H{sub 2}O oxidation utilizing semiconductor/metal-complex hybrid photocatalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Morikawa, T., E-mail: morikawa@mosk.tytlabs.co.jp; Sato, S., E-mail: morikawa@mosk.tytlabs.co.jp; Arai, T., E-mail: morikawa@mosk.tytlabs.co.jp

2013-12-10

We developed a new hybrid photocatalyst for CO{sub 2} reduction, which is composed of a semiconductor and a metal complex. In the hybrid photocatalyst, ΔG between the position of conduction band minimum (E{sub CBM}) of the semiconductor and the CO{sub 2} reduction potential of the complex is an essential factor for realizing fast electron transfer from the conduction band of semiconductor to metal complex leading to high photocatalytic activity. On the basis of this concept, the hybrid photocatalyst InP/Ru-complex, which functions in aqueous media, was developed. The photoreduction of CO{sub 2} to formate using water as an electron donor andmore » a proton source was successfully achieved as a Z-scheme system by functionally conjugating the InP/Ru-complex photocatalyst for CO{sub 2} reduction with a TiO{sub 2} photocatalyst for water oxidation. The conversion efficiency from solar energy to chemical energy was ca. 0.04%, which approaches that for photosynthesis in a plant. Because this system can be applied to many other inorganic semiconductors and metal-complex catalysts, the efficiency and reaction selectivity can be enhanced by optimization of the electron transfer process including the energy-band configurations, conjugation conformations, and catalyst structures. This electrical-bias-free reaction is a huge leap forward for future practical applications of artificial photosynthesis under solar irradiation to produce organic species.« less
Selective detection of vapor phase hydrogen peroxide with phthalocyanine chemiresistors.

PubMed

Bohrer, Forest I; Colesniuc, Corneliu N; Park, Jeongwon; Schuller, Ivan K; Kummel, Andrew C; Trogler, William C

2008-03-26

The use of hydrogen peroxide as a precursor to improvised explosives has made its detection a topic of critical importance. Chemiresistor arrays comprised of 50 nm thick films of metallophthalocyanines (MPcs) are redox selective vapor sensors of hydrogen peroxide. Hydrogen peroxide is shown to decrease currents in cobalt phthalocyanine sensors while it increases currents in nickel, copper, and metal-free phthalocyanine sensors; oxidation and reduction of hydrogen peroxide via catalysis at the phthalocyanine surface are consistent with the pattern of sensor responses. This represents the first example of MPc vapor sensors being oxidized and reduced by the same analyte by varying the metal center. Consequently, differential analysis by redox contrast with catalytic amplification using a small array of sensors may be used to uniquely identify peroxide vapors. Metallophthalocyanine chemiresistors represent an improvement over existing peroxide vapor detection technologies in durability and selectivity in a greatly decreased package size.
Effect of thermal insulation on the electrical characteristics of NbOx threshold switches

NASA Astrophysics Data System (ADS)

Wang, Ziwen; Kumar, Suhas; Wong, H.-S. Philip; Nishi, Yoshio

2018-02-01

Threshold switches based on niobium oxide (NbOx) are promising candidates as bidirectional selector devices in crossbar memory arrays and building blocks for neuromorphic computing. Here, it is experimentally demonstrated that the electrical characteristics of NbOx threshold switches can be tuned by engineering the thermal insulation. Increasing the thermal insulation by ˜10× is shown to produce ˜7× reduction in threshold current and ˜45% reduction in threshold voltage. The reduced threshold voltage leads to ˜5× reduction in half-selection leakage, which highlights the effectiveness of reducing half-selection leakage of NbOx selectors by engineering the thermal insulation. A thermal feedback model based on Poole-Frenkel conduction in NbOx can explain the experimental results very well, which also serves as a piece of strong evidence supporting the validity of the Poole-Frenkel based mechanism in NbOx threshold switches.
Efficient selective catalytic reduction of NO by novel carbon-doped metal catalysts made from electroplating sludge.

PubMed

Zhang, Jia; Zhang, Jingyi; Xu, Yunfeng; Su, Huimin; Li, Xiaoman; Zhou, Ji Zhi; Qian, Guangren; Li, Li; Xu, Zhi Ping

2014-10-07

Electroplating sludges, once regarded as industrial wastes, are precious resources of various transition metals. This research has thus investigated the recycling of an electroplating sludge as a novel carbon-doped metal (Fe, Ni, Mg, Cu, and Zn) catalyst, which was different from a traditional carbon-supported metal catalyst, for effective NO selective catalytic reduction (SCR). This catalyst removed >99.7% NO at a temperature as low as 300 °C. It also removed NO steadily (>99%) with a maximum specific accumulative reduced amount (MSARA) of 3.4 mmol/g. Gas species analyses showed that NO removal was accompanied by evolving N2 and CO2. Moreover, in a wide temperature window, the sludge catalyst showed a higher CO2 selectivity (>99%) than an activated carbon-supported metal catalyst. Structure characterizations revealed that carbon-doped metal was transformed to metal oxide in the sludge catalyst after the catalytic test, with most carbon (2.33 wt %) being consumed. These observations suggest that NO removal over the sludge catalyst is a typical SCR where metals/metal oxides act as the catalytic center and carbon as the reducing reagent. Therefore, our report probably provides an opportunity for high value-added utilizations of heavy-metal wastes in mitigating atmospheric pollutions.
Electrochemically Switchable Polymeric Membrane Ion-Selective Electrodes.

PubMed

Zdrachek, Elena; Bakker, Eric

2018-06-07

We present here for the first time a solid contact ion-selective electrode suitable for the simultaneous sensing of cations (tetrabutylammonium) and anions (hexafluorophosphate), achieved by electrochemical switching. The membrane is based on a thin plasticized polyurethane membrane deposited on poly(3-octylthiophene) (POT) and contains a cation exchanger and lipophilic electrolyte (ETH 500). The cation exchanger is initially in excess; the ion-selective electrode exhibits an initial potentiometric response to cations. During an oxidative current pulse, POT is converted into POT + , which results in the expulsion of cations from the membrane followed by the extraction of anions from the sample solution to fulfill the electroneutrality condition. This creates a defined excess of lipophilic cation in the membrane, resulting in a potentiometric anion response. A reductive current pulse restores the original cation response by triggering the conversion of POT + back into POT, which is accompanied by the expulsion of anions from the membrane and the extraction of cations from the sample solution. Various current pulse magnitudes and durations are explored, and the best results in terms of response slope values and signal stability were observed with an oxidation current pulse of 140 μA cm -2 applied for 8 s and a reduction current pulse of -71 μA cm -2 applied for 8 s.
Solar photocatalytic treatment of synthetic municipal wastewater.

PubMed

Kositzi, M; Poulios, I; Malato, S; Caceres, J; Campos, A

2004-03-01

The photocatalytic organic content reduction of a selected synthetic municipal wastewater by the use of heterogeneous and homogeneous photocatalytic methods under solar irradiation has been studied at a pilot-plant scale at the Plataforma Solar de Almeria. In the case of heterogeneous photocatalysis the effect of catalysts and oxidants concentration on the decomposition degree of the wastewater was examined. By an accumulation energy of 50 kJL(-1) the synergetic effect of 0.2 gL(-1)TiO(2) P-25 with hydrogen peroxide (H(2)O(2)) and Na(2)S(2)O(8) leads to a 55% and 73% reduction of the initial organic carbon content, respectively. The photo-fenton process appears to be more efficient for this type of wastewater in comparison to the TiO(2)/oxidant system. An accumulation energy of 20 kJL(-1) leads to 80% reduction of the organic content. The presence of oxalate in the Fe(3+)/H(2)O(2) system leads to an additional improvement of the photocatalytic efficiency.
Multi-electron oxygen reduction by a hybrid visible-light-photocatalyst consisting of metal-oxide semiconductor and self-assembled biomimetic complex.

PubMed

Naya, Shin-ichi; Niwa, Tadahiro; Negishi, Ryo; Kobayashi, Hisayoshi; Tada, Hiroaki

2014-12-08

Adsorption experiments and density functional theory (DFT) simulations indicated that Cu(acac)2 is chemisorbed on the monoclinic sheelite (ms)-BiVO4 surface to form an O2-bridged binuclear complex (OBBC/BiVO4) like hemocyanin. Multi-electron reduction of O2 is induced by the visible-light irradiation of the OBBC/BiVO4 in the same manner as a blue Cu enzyme. The drastic enhancement of the O2 reduction renders ms-BiVO4 to work as a good visible-light photocatalyst without any sacrificial reagents. As a model reaction, we show that this biomimetic hybrid photocatalyst exhibits a high level of activity for the aerobic oxidation of amines to aldehydes in aqueous solution and imines in THF solution at 25 °C giving selectivities above 99% under visible-light irradiation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Hydrogen Oxidation-Selective Electrocatalysis by Fine Tuning of Pt Ensemble Sites to Enhance the Durability of Automotive Fuel Cells.

PubMed

Yun, Su-Won; Park, Shin-Ae; Kim, Tae-June; Kim, Jun-Hyuk; Pak, Gi-Woong; Kim, Yong-Tae

2017-02-08

A simple, inexpensive approach is proposed for enhancing the durability of automotive proton exchange membrane fuel cells by selective promotion of the hydrogen oxidation reaction (HOR) and suppression of the oxygen reduction reaction (ORR) at the anode in startup/shutdown events. Dodecanethiol forms a self-assembled monolayer (SAM) on the surface of Pt particles, thus decreasing the number of Pt ensemble sites. Interestingly, by controlling the dodecanethiol concentration during SAM formation, the number of ensemble sites can be precisely optimized such that it is sufficient for the HOR but insufficient for the ORR. Thus, a Pt surface with an SAM of dodecanethiol clearly effects HOR-selective electrocatalysis. Clear HOR selectivity is demonstrated in unit cell tests with the actual membrane electrode assembly, as well as in an electrochemical three-electrode setup with a thin-film rotating disk electrode configuration. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Target-directed catalytic metallodrugs

PubMed Central

Joyner, J.C.; Cowan, J.A.

2013-01-01

Most drugs function by binding reversibly to specific biological targets, and therapeutic effects generally require saturation of these targets. One means of decreasing required drug concentrations is incorporation of reactive metal centers that elicit irreversible modification of targets. A common approach has been the design of artificial proteases/nucleases containing metal centers capable of hydrolyzing targeted proteins or nucleic acids. However, these hydrolytic catalysts typically provide relatively low rate constants for target inactivation. Recently, various catalysts were synthesized that use oxidative mechanisms to selectively cleave/inactivate therapeutic targets, including HIV RRE RNA or angiotensin converting enzyme (ACE). These oxidative mechanisms, which typically involve reactive oxygen species (ROS), provide access to comparatively high rate constants for target inactivation. Target-binding affinity, co-reactant selectivity, reduction potential, coordination unsaturation, ROS products (metal-associated vs metal-dissociated; hydroxyl vs superoxide), and multiple-turnover redox chemistry were studied for each catalyst, and these parameters were related to the efficiency, selectivity, and mechanism(s) of inactivation/cleavage of the corresponding target for each catalyst. Important factors for future oxidative catalyst development are 1) positioning of catalyst reduction potential and redox reactivity to match the physiological environment of use, 2) maintenance of catalyst stability by use of chelates with either high denticity or other means of stabilization, such as the square planar geometric stabilization of Ni- and Cu-ATCUN complexes, 3) optimal rate of inactivation of targets relative to the rate of generation of diffusible ROS, 4) targeting and linker domains that afford better control of catalyst orientation, and 5) general bio-availability and drug delivery requirements. PMID:23828584
Pyroprocessing of oxidized sodium-bonded fast reactor fuel - An experimental study of treatment options for degraded EBR-II fuel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hermann, S.D.; Gese, N.J.; Wurth, L.A.

An experimental study was conducted to assess pyrochemical treatment options for degraded EBR-II fuel. As oxidized material, the degraded fuel would need to be converted back to metal to enable electrorefining within an existing electro-metallurgical treatment process. A lithium-based electrolytic reduction process was studied to assess the efficacy of converting oxide materials to metal with a particular focus on the impact of zirconium oxide and sodium oxide on this process. Bench-scale electrolytic reduction experiments were performed in LiCl-Li{sub 2}O at 650 C. degrees with combinations of manganese oxide (used as a surrogate for uranium oxide), zirconium oxide, and sodium oxide.more » In the absence of zirconium or sodium oxide, the electrolytic reduction of MnO showed nearly complete conversion to metal. The electrolytic reduction of a blend of MnO-ZrO{sub 2} in LiCl - 1 wt% Li{sub 2}O showed substantial reduction of manganese, but only 8.5% of the zirconium was found in the metal phase. The electrolytic reduction of the same blend of MnO-ZrO{sub 2} in LiCl - 1 wt% Li{sub 2}O - 6.2 wt% Na{sub 2}O showed substantial reduction of manganese, but zirconium reduction was even less at 2.4%. This study concluded that ZrO{sub 2} cannot be substantially reduced to metal in an electrolytic reduction system with LiCl - 1 wt% Li{sub 2}O at 650 C. degrees due to the perceived preferential formation of lithium zirconate. This study also identified a possible interference that sodium oxide may have on the same system by introducing a parasitic and cyclic reaction of dissolved sodium metal between oxidation at the anode and reduction at the cathode. When applied to oxidized sodium-bonded EBR-II fuel (e.g., U-10Zr), the prescribed electrolytic reduction system would not be expected to substantially reduce zirconium oxide, and the accumulation of sodium in the electrolyte could interfere with the reduction of uranium oxide, or at least render it less efficient.« less
Pyrometallurgical Extraction of Valuable Elements in Ni-Metal Hydride Battery Electrode Materials

NASA Astrophysics Data System (ADS)

Jiang, Yin-ju; Deng, Yong-chun; Bu, Wen-gang

2015-10-01

Gas selective reduction-oxidation (redox) and melting separation were consecutively applied to electrode materials of AB5-type Ni-metal hydride batteries leading to the production of a Ni-Co alloy and slag enriched with rare earth oxides (REO). In the selective redox process, electrode materials were treated with H2/H2O at 1073 K and 1173 K (800 °C and 900 °C). Active elements such as REs, Al, and Mn were oxidized whereas relatively inert elements such as Ni and Co were transformed into their elemental states in the treated materials. SiO2 and Al2O3 powders were added into the treated materials as fluxes which were then melted at 1823 K (1550 °C) to yield a Ni-Co alloy and a REO-SiO2-Al2O3-MnO slag. The high-purity Ni-Co alloy produced can be used as a raw material for AB5-type hydrogen-storage alloy. The REO content in slag was very high, i.e., 48.51 pct, therefore it can be used to recycle rare earth oxides.
Size-selective reactivity of subnanometer Ag 4 and Ag 16 clusters on a TiO 2 surface

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Po-Tuan; Tyo, Eric C.; Hayashi, Michitoshi

Size-selected Ag 4 and Ag 16 clusters on a titania surface have been studied for their potential in CO oxidation using theoretical calculations and X-ray absorption near edge spectroscopy. The first peak at the measured Ag K-edge of Ag 16@TiO 2 is more prominent in air than in carbon monoxide environment, but no variation was found between the spectra of Ag 4@TiO 2 in air and in carbon monoxide environments. Density functional theory calculations show a preference for molecular oxygen adsorption for Ag 4@TiO 2 and that for a dissociative one on Ag 16@TiO 2, while carbon monoxide reactions withmore » adsorbed oxygen reduced the Ag 16@TiO 2 cluster. The dissociated oxygen atoms increased the oxidation state of Ag 16 cluster and resulted in the prominent first peak in Ag K-edge spectrum in quasi-particle theory calculations, with the subsequent carbon monoxide oxidation reversing the character of Ag K-edge spectrum associated with the reduction of the cluster. Finally, the results provide insight into the size selectivity of supported subnanometer silver clusters in their interactions with oxygen and carbon monoxide, with implications on the cluster catalytic properties in oxidative reactions.« less
Size-selective reactivity of subnanometer Ag 4 and Ag 16 clusters on a TiO 2 surface

DOE PAGES

Chen, Po-Tuan; Tyo, Eric C.; Hayashi, Michitoshi; ...

2017-03-08

Size-selected Ag 4 and Ag 16 clusters on a titania surface have been studied for their potential in CO oxidation using theoretical calculations and X-ray absorption near edge spectroscopy. The first peak at the measured Ag K-edge of Ag 16@TiO 2 is more prominent in air than in carbon monoxide environment, but no variation was found between the spectra of Ag 4@TiO 2 in air and in carbon monoxide environments. Density functional theory calculations show a preference for molecular oxygen adsorption for Ag 4@TiO 2 and that for a dissociative one on Ag 16@TiO 2, while carbon monoxide reactions withmore » adsorbed oxygen reduced the Ag 16@TiO 2 cluster. The dissociated oxygen atoms increased the oxidation state of Ag 16 cluster and resulted in the prominent first peak in Ag K-edge spectrum in quasi-particle theory calculations, with the subsequent carbon monoxide oxidation reversing the character of Ag K-edge spectrum associated with the reduction of the cluster. Finally, the results provide insight into the size selectivity of supported subnanometer silver clusters in their interactions with oxygen and carbon monoxide, with implications on the cluster catalytic properties in oxidative reactions.« less
Oxidative deamination of alicyclic primary amines by liver microsomes from rats and rabbits.

PubMed

Kurebayashi, H; Tanaka, A; Yamaha, T; Tatahashi, A

1988-09-01

1. Substrate selectivity and species difference in the oxidative deamination of the alicyclic primary amines, cyclopentylamine, cyclohexylamine, cycloheptylamine, 1- and 2-aminoindane, and 1- and 2-aminotetralin were studied using liver microsomes from rats and rabbits. 2. The deamination rates of the amines were much greater with liver microsomes from rabbits than from rats. Substrate selectivity resulted in much faster deamination of 1-aminoindane and 1-aminotetralin than of the corresponding 2-amino compounds, especially in rats. 3. When 1-aminoindane and 1-aminotetralin were incubated with rat liver microsomes and NADPH under 18O2, oxygen-18 was incorporated into the deaminated products, 1-indanone and 1-tetralone. The carbinolamine is a key intermediate in the oxidative deamination by rat liver microsomes, indicating the contribution of cytochrome P-450-dependent alpha-C-oxidation to the reaction. 4. Alicyclic primary amines gave type II binding spectra with rat and rabbit liver microsomes, but the spectra appeared to contain type I components. 5. The ratios of the alcohols, cyclohexanol, 2-tetralol and 2-indanol in the deaminated products were high in both rats and rabbits. The ketones were precursors of the alcohols, and substrate selectivity in reduction of the alicyclic ketones with NADPH was similar in both species.
Methods of selectively incorporating metals onto substrates

DOEpatents

Ernst; Richard D. , Eyring; Edward M. , Turpin; Gregory C. , Dunn; Brian C.

2008-09-30

A method for forming multi-metallic sites on a substrate is disclosed and described. A substrate including active groups such as hydroxyl can be reacted with a pretarget metal complex. The target metal attached to the active group can then be reacted with a secondary metal complex such that an oxidation-reduction (redox) reaction occurs to form a multi-metallic species. The substrate can be a highly porous material such as aerogels, xerogels, zeolites, and similar materials. Additional metal complexes can be reacted to increase catalyst loading or control co-catalyst content. The resulting compounds can be oxidized to form oxides or reduced to form metals in the ground state which are suitable for practical use.
Activation of peroxisome proliferator-activated receptor δ induces fatty acid β-oxidation in skeletal muscle and attenuates metabolic syndrome

PubMed Central

Tanaka, Toshiya; Yamamoto, Joji; Iwasaki, Satoshi; Asaba, Hiroshi; Hamura, Hiroki; Ikeda, Yukio; Watanabe, Mitsuhiro; Magoori, Kenta; Ioka, Ryoichi X.; Tachibana, Keisuke; Watanabe, Yuichiro; Uchiyama, Yasutoshi; Sumi, Koichi; Iguchi, Haruhisa; Ito, Sadayoshi; Doi, Takefumi; Hamakubo, Takao; Naito, Makoto; Auwerx, Johan; Yanagisawa, Masashi; Kodama, Tatsuhiko; Sakai, Juro

2003-01-01

In this study, we defined the role of peroxisome proliferator-activated receptor β/δ (PPARδ) in metabolic homeostasis by using subtype selective agonists. Analysis of rat L6 myotubes treated with the PPARδ subtype-selective agonist, GW501516, by the Affymetrix oligonucleotide microarrays revealed that PPARδ controls fatty acid oxidation by regulating genes involved in fatty acid transport, β-oxidation, and mitochondrial respiration. Similar PPARδ-mediated gene activation was observed in the skeletal muscle of GW501516-treated mice. Accordingly, GW501516 treatment induced fatty acid β-oxidation in L6 myotubes as well as in mouse skeletal muscles. Administration of GW501516 to mice fed a high-fat diet ameliorated diet-induced obesity and insulin resistance, an effect accompanied by enhanced metabolic rate and fatty acid β-oxidation, proliferation of mitochondria, and a marked reduction of lipid droplets in skeletal muscles. Despite a modest body weight change relative to vehicle-treated mice, GW501516 treatment also markedly improved diabetes as revealed by the decrease in plasma glucose and blood insulin levels in genetically obese ob/ob mice. These data suggest that PPARδ is pivotal to control the program for fatty acid oxidation in the skeletal muscle, thereby ameliorating obesity and insulin resistance through its activation in obese animals. PMID:14676330
Silk provides a new avenue for third generation biosensors: Sensitive, selective and stable electrochemical detection of nitric oxide.

PubMed

Musameh, Mustafa M; Dunn, Christopher J; Uddin, Md Hemayet; Sutherland, Tara D; Rapson, Trevor D

2018-04-30

Using heme entrapped in recombinant silk films, we have produced 3rd generation biosensors, which allow direct electron transfer from the heme center to an electrode avoiding the need for electron mediators. Here, we demonstrate the use of these heme-silk films for the detection of nitric oxide (NO) at nanomolar levels in the presence and absence of oxygen. The sensor was prepared by drop-casting a silk solution on a glassy carbon electrode modified with multiwalled carbon nanotubes (MWCNT) followed by infusion with heme. The sensor was characterized by cyclic voltammetry and showed well defined and reversible Fe + / Fe 3+ redox couple activity, with NO detection by oxidation at potentials above +0.45V or reduction at potentials below - 0.7V. Evaluation of the effect of pH on the sensor response to NO reduction indicated a maximum response at pH 3. The sensor showed good linearity in the concentration range from 19 to 190nM (R 2 = 0.99) with a detection limit of 2nM. The sensor had excellent selectivity towards NO with no or negligible interference from oxygen, nitrite, nitrate, dopamine and ascorbic acid and retained 86% of response after 2 months of operation and storage at room temperature. Crown Copyright © 2017. Published by Elsevier B.V. All rights reserved.
An Investigation of the Use of Computer-Aided-Instruction in Teaching Students How to Solve Selected Multistep General Chemistry Problems.

ERIC Educational Resources Information Center

Grandey, Robert C.

The development of computer-assisted instructional lessons on the following three topics is discussed: 1) the mole concept and chemical formulas, 2) concentration of solutions and quantities from chemical equations, and 3) balancing equations for oxidation-reduction reactions. Emphasis was placed on developing computer routines which interpret…

Oxidation of N-nitrosodimethylamine (NDMA) precursors with ozone and chlorine dioxide: kinetics and effect on NDMA formation potential.

PubMed

Lee, Changha; Schmidt, Carsten; Yoon, Jeyong; von Gunten, Urs

2007-03-15

The oxidation of N-nitrosodimethylamine (NDMA) precursors chlorine dioxide (ClO2). Second-order rate constants for the reactions of model NDMA precursors (dimethylamine (DMA) and 7 tertiary amines) with ozone (kapp at pH 7 = 2.4 x 10(-1) to 2.3 x 10(9) M(-1) s(-1)), ClO2 (kapp at pH 7 = 6.7 x 10(-3) to 3.0 x 10(7) M(-1) s(-1)), and hydroxyl radical (*OH) (kapp at pH 7 = 6.2 x 10(7) to 1.4 x 10(10) M(-1) s(-1)) were determined, which showed that the selected NDMA precursors, with the exception of dimethylformamide (DMFA) can be completely transformed via their direct reaction with ozone. During ozonation, DMFA may be partially transformed through oxidation by the secondary oxidant *OH. ClO2 was also shown to effectively transform most of the precursors, with the exceptions of DMA and DMFA. In the second part of the study, the NDMA formation potentials (NDMA-FP) in synthetic and natural waters were measured with and without pre-oxidation with ozone and ClO2. A significant reduction in the NDMA-FPs was observed after complete transformation of the model NDMA precursors. Ozonation generally led to more effective reduction of the NDMA-FP than ClO2. For most of the precursors, the formation of DMA could account for the NDMA-FPs remaining after complete transformation of the model NDMA precursors. In contrast, dimethylethanolamine and dimethyldithiocarbamate yielded other NDMA precursors (not DMA) as their oxidation products. Pre-oxidation by ozone and ClO2 of several natural waters showed behavior similar to that of the oxidation of model NDMA precursors with a reduction of the NDMA-FP by 32-94% for various natural water sources.
Stereoselective isoxazolidine synthesis via copper-catalyzed alkene aminooxygenation.

PubMed

Karyakarte, Shuklendu D; Smith, Thomas P; Chemler, Sherry R

2012-09-07

Isoxazolidines are useful in organic synthesis, drug discovery, and chemical biology endeavors. A new stereoselective synthesis of methyleneoxy-substituted isoxazolidines is disclosed. The method involves copper-catalyzed aminooxygenation/cyclization of N-sulfonyl-O-butenyl hydroxylamines in the presence of (2,2,6,6-tetramethylpiperidin-1-yl)oxyl radical (TEMPO) and O(2) and provides substituted isoxazolidines in excellent yields and diastereoselectivities. We also demonstrate selective mono N-O reduction followed by oxidation of the remaining N-O bond to reveal a 2-amino-γ-lactone. Reduction of the γ-lactone reveals the corresponding aminodiol.
Effects of Borax on the Reduction of Pre-oxidized Panzhihua Ilmenite

NASA Astrophysics Data System (ADS)

Guo, Yufeng; Zheng, Fuqiang; Jiang, Tao; Chen, Feng; Wang, Shuai; Qiu, Guanzhou

2018-01-01

The effects of borax (sodium borate) on the enhancement reduction of pre-oxidized Panzhihua ilmenite were investigated. The effects of borax on the mineral phase transformation, microstructures, crystal cell parameter, melting point and Mg distribution were studied to reveal the mechanism of enhancement reduction. Under the constant reduction conditions, the borax could reduce the reduction activation energy of pre-oxidized ilmenite. The reduction kinetics analysis indicated that the reduction rate was controlled by interfacial chemical reaction. The reduction activation energy of the pre-oxidized ilmenite with 4% borax was 80.263 kJ/mol, which was 28.585 kJ/mol less than that of the pre-oxidized ilmenite without borax. Borax could eliminate the migration of Mg into the reduced particle center. The crystal cell parameter of the reduced product was increased by adding borax. Borax could improve the growth of dendritic crystals in the pre-oxidized ilmenite.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Winter, Lea R.; Gomez, Elaine; Yan, Binhang

CO 2 hydrogenation over Fe-modified Ni/CeO 2 catalysts was investigated in a batch reactor using time-resolved in situ FTIR spectroscopy. Low loading of Ni/CeO 2 was associated with high selectivity to CO over CH 4, while higher Ni loading improved CO 2 hydrogenation activity with a reduced CO selectivity. X-ray absorption near-edge structure (XANES) analysis revealed Ni to be metallic for all catalysts including the CO-selective low loading 0.5% Ni catalyst, suggesting that the selectivity trend is due to structural rather than oxidation state effects. The loading amount of 1.5% Ni was selected for co-impregnation with Fe, based on themore » significant shift in product selectivity towards CH 4 for that loading amount, in order to shift the selectivity towards CO while maintaining high activity. Temperature programmed reduction (TPR) results indicated bimetallic interactions between Ni and Fe, and XANES analysis showed that about 70% of Fe in the bimetallic catalysts was oxidized. The Ni-Fe catalysts demonstrated improved selectivity towards CO without significantly compromising activity, coupling the high activity of Ni catalysts and the high CO selectivity of Fe. The general trends in Ni loading and bimetallic modification should guide efforts to develop non-precious metal catalysts for the selective production of CO by CO 2 hydrogenation.« less
Nanocarbon/oxide composite catalysts for bifunctional oxygen reduction and evolution in reversible alkaline fuel cells: A mini review

NASA Astrophysics Data System (ADS)

Chen, Mengjie; Wang, Lei; Yang, Haipeng; Zhao, Shuai; Xu, Hui; Wu, Gang

2018-01-01

A reversible fuel cell (RFC), which integrates a fuel cell with an electrolyzer, is similar to a rechargeable battery. This technology lies on high-performance bifunctional catalysts for the oxygen reduction reaction (ORR) in the fuel cell mode and the oxygen evolution reaction (OER) in the electrolyzer mode. Current catalysts are platinum group metals (PGM) such as Pt and Ir, which are expensive and scarce. Therefore, it is highly desirable to develop PGM-free catalysts for large-scale application of RFCs. In this mini review, we discussed the most promising nanocarbon/oxide composite catalysts for ORR/OER bifunctional catalysis in alkaline media, which is mainly based on our recent progress. Starting with the effectiveness of selected oxides and nanocarbons in terms of their activity and stability, we outlined synthetic methods and the resulting structures and morphologies of catalysts to provide a correlation between synthesis, structure, and property. A special emphasis is put on understanding of the possible synergistic effect between oxide and nanocarbon for enhanced performance. Finally, a few nanocomposite catalysts are discussed as typical examples to elucidate the rules of designing highly active and durable bifunctional catalysts for RFC applications.
Selective catalytic two-step process for ethylene glycol from carbon monoxide

PubMed Central

Dong, Kaiwu; Elangovan, Saravanakumar; Sang, Rui; Spannenberg, Anke; Jackstell, Ralf; Junge, Kathrin; Li, Yuehui; Beller, Matthias

2016-01-01

Upgrading C1 chemicals (for example, CO, CO/H2, MeOH and CO2) with C–C bond formation is essential for the synthesis of bulk chemicals. In general, these industrially important processes (for example, Fischer Tropsch) proceed at drastic reaction conditions (>250 °C; high pressure) and suffer from low selectivity, which makes high capital investment necessary and requires additional purifications. Here, a different strategy for the preparation of ethylene glycol (EG) via initial oxidative coupling and subsequent reduction is presented. Separating coupling and reduction steps allows for a completely selective formation of EG (99%) from CO. This two-step catalytic procedure makes use of a Pd-catalysed oxycarbonylation of amines to oxamides at room temperature (RT) and subsequent Ru- or Fe-catalysed hydrogenation to EG. Notably, in the first step the required amines can be efficiently reused. The presented stepwise oxamide-mediated coupling provides the basis for a new strategy for selective upgrading of C1 chemicals. PMID:27377550
The anaerobic degradation of organic matter in Danish coastal sediments - Iron reduction, manganese reduction, and sulfate reduction

NASA Technical Reports Server (NTRS)

Canfield, Donald E.; Thamdrup, BO; Hansen, Jens W.

1993-01-01

A combination of porewater and solid phase analysis as well as a series of sediment incubations are used to quantify organic carbon oxidation by dissimilatory Fe reduction, Mn reduction, and sulfate reduction, in sediments from the Skagerrak (located off the northeast coast of Jutland, Denmark). Solid phase data are integrated with incubation results to define the zones of the various oxidation processes. At S(9), surface Mn enrichments of up to 3.5 wt pct were found, and with such a ready source of Mn, dissimilatory Mn reduction was the only significant anaerobic process of carbon oxidation in the surface 10 cm of the sediment. At S(4) and S(6), active Mn reduction occurred; however, most of the Mn reduction may have resulted from the oxidation of acid volatile sulfides and Fe(2+) rather than by a dissimilatory sulfate. Dissolved Mn(2+) was found to completely adsorb onto sediment containing fully oxidized Mn oxides.
OXIDATION-REDUCTION POTENTIAL MEASUREMENTS OF IMPORTANT OXIDANTS IN DRINKING WATER

EPA Science Inventory

Oxidation-reduction (redox) reactions are important in drinking water treatment and distribution. Oxidation-reduction potential (ORP) measurements of water reflect the tendency of major constituents in the water to accept or lose electrons. Although ORP measurements are valuable...
Influence of adsorption versus coprecipitation on the retention of rice straw-derived dissolved organic carbon and subsequent reducibility of Fe-DOC systems

NASA Astrophysics Data System (ADS)

Sodano, Marcella; Lerda, Cristina; Martin, Maria; Celi, Luisella; Said-Pullicino, Daniel

2016-04-01

The dissimilatory reduction of Fe oxides is the main organic C-consuming process in paddy soils under anoxic conditions. The contribution of Fe(III) reduction to anaerobic C mineralization depends on many factors, but most importantly on the bioavailability of labile organic matter and a reducible Fe pool as electron donors and acceptors, respectively. On the other hand, the strong affinity of these minerals for organic matter and their capability of protecting it against microbial decomposition is well known. Natural Fe oxides in these soils may therefore play a key role in determining the C source/sink functions of these agro-ecosystems. Apart from contributing to C stabilization, the interaction between Fe oxides and dissolved organic C (DOC) may influence the structure and reactivity of these natural oxides, and selectively influence the chemical properties of DOC. Indeed, Fe-DOC associations may not only reduce the availability of DOC, but may also limit the microbial reduction of Fe oxides under anoxic conditions. In fact, the accessibility of these minerals to microorganisms, extracellular enzymes, redox active shuttling compound or reducing agents may be impeded by the presence of sorbed organic matter. In soils that are regularly subjected to fluctuations in redox conditions the interaction between DOC and Fe oxides may not only involve organic coatings on mineral surfaces, but also Fe-DOC coprecipitates that form during the rapid oxidation of soil solutions containing important amounts of DOC and Fe(II). However, little is known on how these processes influence DOC retention, and the structure and subsequent reducibility of these Fe-DOC associations. We hypothesized that the nature and extent of the interaction between DOC and Fe oxides may influence the accessibility of the bioavailable Fe pool and consequently its reducibility. We tested this hypothesis by synthesizing a series of Fe-DOC systems with increasing C:Fe ratios prepared by either surface adsorption or coprecipitation, DOC was obtained by incubating a suspension of rice straw in water (straw-solution ratio of 1:30) under oxic conditions at 25° C for 30 days to simulate the decomposition of rice straw in the field. Increasing amounts of DOC were equilibrated (pH = 6) with a known mass of ferrihydrite (initial molar C:Fe ratios of 1, 5 and 10) to obtain surface coated Fe-DOC systems with increasing C loading. On the other hand, coprecipitates with similar initial C:Fe ratios were obtained by oxidation of a Fe(II) solution in the presence of increasing amounts of DOC at pH = 6. A natural Fe-DOC coprecipitate was also obtained by in situ sampling of a paddy soil solution from the topsoil during a cropping season, and subsequent oxidation in the laboratory. The surface and chemical properties of all substrates were subsequently evaluated and compared. We hereby present the first results of the influence of adsorption vs coprecipitation on the selective retention of DOC, structure and surface charge, as well as their susceptibility to chemical reduction with ascorbic acid.
Selective inhibition of extracellular oxidants liberated from human neutrophils--A new mechanism potentially involved in the anti-inflammatory activity of hydroxychloroquine.

PubMed

Jančinová, Viera; Pažoureková, Silvia; Lucová, Marianna; Perečko, Tomáš; Mihalová, Danica; Bauerová, Katarína; Nosáľ, Radomír; Drábiková, Katarína

2015-09-01

Hydroxychloroquine is used in the therapy of rheumatoid arthritis or lupus erythematosus. Although these diseases are often accompanied by activation of neutrophils, there are still few data relating to the impact of hydroxychloroquine on these cells. We investigated the effect of orally administered hydroxychloroquine on neutrophil oxidative burst in rats with adjuvant arthritis. In human neutrophils, extra- and intracellular formation of oxidants, mobilisation of intracellular calcium and the phosphorylation of proteins regulating NADPH oxidase assembly were analysed. Administration of hydroxychloroquine decreased the concentration of oxidants in blood of arthritic rats. The inhibition was comparable with the reference drug methotrexate, yet it was not accompanied by a reduction in neutrophil count. When both drugs were co-applied, the effect became more pronounced. In isolated human neutrophils, treatment with hydroxychloroquine resulted in reduced mobilisation of intracellular calcium, diminished concentration of external oxidants and in decreased phosphorylation of Ca(2+)-dependent protein kinase C isoforms PKCα and PKCβII, which regulate activation of NADPH oxidase on plasma membrane. On the other hand, no reduction was observed in intracellular oxidants or in the phosphorylation of p40(phox) and PKCδ, two proteins directing the oxidase assembly to intracellular membranes. Hydroxychloroquine reduced neutrophil-derived oxidants potentially involved in tissue damage and protected those capable to suppress inflammation. The observed effects may represent a new mechanism involved in the anti-inflammatory activity of this drug. Copyright © 2015 Elsevier B.V. All rights reserved.
Selective catalytic reduction of nitrogen oxides over a modified silicoaluminophosphate commercial zeolite.

PubMed

Petitto, Carolina; Delahay, Gérard

2018-03-01

Nitrogen oxides (NO x : NO, NO 2 ) are a concern due to their adverse health effects. Diesel engine transport sector is the major emitter of NO x . The regulations have been strengthened and to comply with them, one of the two methods commonly used is the selective catalytic reduction of NO x by NH 3 (NH 3 -SCR), NH 3 being supplied by the in-situ hydrolysis of urea. Efficiency and durability of the catalyst for this process are highly required. Durability is evaluated by hydrothermal treatment of the catalysts at temperature above 800°C. In this study, very active catalysts for the NH 3 -SCR of NO x were prepared by using a silicoaluminophosphate commercial zeolite as copper host structure. Characterizations by X-ray diffraction (XRD), scanning electron microscopy (SEM) and temperature programmed desorption of ammonia (NH 3 -TPD) showed that this commercial zeolite was hydrothermally stable up to 850°C and, was able to retain some structural properties up to 950°C. After hydrothermal treatment at 850°C, the NO x reduction efficiency into NH 3 -SCR depends on the copper content. The catalyst with a copper content of 1.25wt.% was the most active. The difference in activity was much more important when using NO than the fast NO/NO 2 reaction mixture. Copyright © 2017. Published by Elsevier B.V.
RELATIONSHIPS BETWEEN OXIDATION-REDUCTION, OXIDANT, AND PH IN DRINKING WATER

EPA Science Inventory

Oxidation and reduction (redox) reactions are very important in drinking water. Oxidation-reduction potential (ORP) measurements reflect the redox state of water. Redox measurements are not widely made by drinking water utilities in part because they are not well understood. The ...
Chlorobenzene degeradation by non-thermal plasma combined with EG-TiO2/ZnO as a photocatalyst: Effect of photocatalyst on CO2 selectivity and byproducts reduction.

PubMed

Ghorbani Shahna, Farshid; Bahrami, Abdulrahman; Alimohammadi, Iraj; Yarahmadi, Rassuol; Jaleh, Babak; Gandomi, Mastaneh; Ebrahimi, Hossein; Ad-Din Abedi, Kamal

2017-02-15

The non-thermal plasma (NTP) technique, which suffers from low selectivity in complete oxidation of volatile organic compounds to CO 2 and H 2 O, creates unwanted and harmful byproducts. NTP in concert with photocatalyst can resolve this limitation due to additional oxidation. TiO 2 and ZnO nanoparticles were coated on the surface of the expanded graphite and placed downstream of the NTP reactor under UV light. In this study, to compare the performance of NTP and the combined system, chlorobenzene removal, selectivity of CO 2 and byproducts formation were investigated. The results showed that the combined system enhanced both the removal efficiency and CO 2 selectivity. The output gas of the NTP reactor contained chlorobenzene, phosgene, O 3 , NO, NO 2 , CO, CO 2 , HCL and CL. The bulk of these byproducts was oxidized on the surface of the nanocomposite; as a result, the content of the byproducts in the output gas of the combined system decreased dramatically. The removal efficiency and CO 2 selectivity increased by rising the applied voltage and residence time because the collision between active species and pollutant molecules increases. Based on these results, the combined system is preferred due to a higher performance and lower formation of harmful byproducts. Copyright © 2016 Elsevier B.V. All rights reserved.
Disguised as a Sulfate Reducer: Growth of the Deltaproteobacterium Desulfurivibrio alkaliphilus by Sulfide Oxidation with Nitrate

PubMed Central

Thorup, Casper; Schramm, Andreas

2017-01-01

ABSTRACT This study demonstrates that the deltaproteobacterium Desulfurivibrio alkaliphilus can grow chemolithotrophically by coupling sulfide oxidation to the dissimilatory reduction of nitrate and nitrite to ammonium. Key genes of known sulfide oxidation pathways are absent from the genome of D. alkaliphilus. Instead, the genome contains all of the genes necessary for sulfate reduction, including a gene for a reductive-type dissimilatory bisulfite reductase (DSR). Despite this, growth by sulfate reduction was not observed. Transcriptomic analysis revealed a very high expression level of sulfate-reduction genes during growth by sulfide oxidation, while inhibition experiments with molybdate pointed to elemental sulfur/polysulfides as intermediates. Consequently, we propose that D. alkaliphilus initially oxidizes sulfide to elemental sulfur, which is then either disproportionated, or oxidized by a reversal of the sulfate reduction pathway. This is the first study providing evidence that a reductive-type DSR is involved in a sulfide oxidation pathway. Transcriptome sequencing further suggests that nitrate reduction to ammonium is performed by a novel type of periplasmic nitrate reductase and an unusual membrane-anchored nitrite reductase. PMID:28720728
On a new ironmaking process to produce hydrogen and reduce energy consumption

NASA Astrophysics Data System (ADS)

Corbari, Rodrigo

The primary purpose of the present work is to compute the volume and composition of the products of a theoretical charring unit for high volatile coals. In particular, the compositions of volatile gas and char and the hydrogen yield of the process. The volume of oxygen necessary to supply the energy for the process was also calculated. The model consists of materials and energy balance equations and local thermodynamic equilibrium. The model was combined with experimental results relating the effect of temperature on the extent of devolatilization and chemistry evolution of coal. Results of the model indicated that temperature plays a major role defining the quantities and composition of charring products. The H2 concentration of the volatile gas increased from about 16vol% at 700°C to 47vol% at 900°C, leveling off at approximately 52vol% at 1100°C. The hydrogen yield of the process increased from 7 to 60 percent at 700°C and 1100°C respectively. For a typical high volatile coal considered, the volume of gas generated varied from about 210 to 780 liters/kg-coal(STP) according to temperature and fraction of solids combusted. The char becomes enriched in carbon and depleted in hydrogen as temperature is increased. As much as 97 percent of the hydrogen in coal is removed at 1100°C. In the second part of this study, the kinetics of reduction of iron oxide fines with simulated smelter gas was experimentally studied by thermogravimetry. An equimolar CO/CO2 mixture was selected to simulate the off-gas of a smelter operating with char at 50 percent post combustion. Reduction temperatures ranged from 590°C to 1000°C. Under these conditions, reduction was limited to wustite. Results indicated that the reduction kinetics and dominating reaction mechanism varied with temperature, extent of reduction and type of iron oxide employed. Reduction from hematite to wustite proceeded in two consecutive reaction steps with magnetite as an intermediate oxide. The first reduction step, hematite to magnetite, was fast and controlled by external gas mass transfer independently of type of iron oxide and temperature employed in this work. The second reduction step, magnetite to wustite, was the overall reaction controlling step. The reduction mechanism varied with temperature and type of iron oxide. For moderately porous oxide fines (VALE and Taconite ores), the magnetite to wustite reduction followed a uniform internal reaction regime, where the chemical reaction at the gas-solid surface is the slowest step. For highly porous oxide (PAH), the magnetite to wustite reduction step was controlled by external gas mass transfer above 700°C. Below that, a mixed regime involving external gas mass transfer and limited mixed control, which comprises pore diffusion and chemical reaction, took place. The rate equations for this mixed control reaction mechanism were developed and the limited mixed control rate constant (klm) was computed. For denser oxides under uniform internal reaction, the product of the rate constant and pore surface area (k·S) was calculated. The final part of this research focused on the study of the mechanisms contributing for the distribution of sulfur in the smelter process. A methodology was developed for this purpose, which computes the sulfur concentration and distribution between the metal, slag and gas phases of the smelter for selected case scenarios. The model assumed the smelter as an ideal continuous stirred reactor under steady state conditions. Sulfur in the gas phase resulted from slag desulfurization by reaction with gas and the direct transfer of sulfur from coal or char. In general, it was found that a large fraction of sulfur leaves the smelter with the gas when coal or char is the only sulfur input to the process. However, the predominant mechanism for transfer of sulfur into the gas depended on process operating conditions. The effect of recycling sulfur back into the smelter was also evaluated. This is important when sulfur leaving with the smelter gas is captured by pre-reduced iron oxide or by dust particles and re-introduced in the process. In general, the more sulfur is recycled into the smelter, the higher the metal and slag sulfur concentration. However, the increasing sulfur content of metal and slag when sulfur is recycled may be partially counter-balanced by the use of char in place of coal. (Abstract shortened by UMI.)
Electrodeposition of nano-sized bismuth on copper foil as electrocatalyst for reduction of CO2 to formate

NASA Astrophysics Data System (ADS)

Lv, Weixin; Zhou, Jing; Bei, Jingjing; Zhang, Rui; Wang, Lei; Xu, Qi; Wang, Wei

2017-01-01

Electrochemical reduction of carbon dioxide (CO2) to formate is energetically inefficient because high overpotential is required for reduction of CO2 to formate on most traditional catalysts. In this paper, a novel nano-sized Bi-based electrocatalyst deposited on a Cu foil has been synthesized, which can be used as a cathode for electrochemical reduction of CO2 to formate with a low overpotential (0.69 V) and a high selectivity (91.3%). The electrocatalyst can show excellent catalytic performance toward reduction of CO2 which can probably be attributed to the nano-sized structure and the surface oxide layer. The energy efficiency for reduction of CO2 to formate can reach to 50% when an IrxSnyRuzO2/Ti electrode is used as anode, it is one of the highest values found in the literatures and very practicable for sustainable fuel synthesis.
RELATIONSHIPS BETWEEN OXIDATION-REDUCTION POTENTIAL, OXIDANT, AND PH IN DRINKING WATER

EPA Science Inventory

Oxidation and reduction (redox) reactions are very important in drinking water. Oxidation-reduction potential (ORP) measurements reflect the redox state of water. Redox measurements are not widely made by drinking water utilities in part because they are not well understood. The ...
The effect of oxidizing water on metallic restorations in the mouth: in vitro reduction behavior of oxidizing water.

PubMed

Nishida, T

1997-03-01

Mouth-rinsing with oxydized water which contains electrolytically generated chlorine is known to hinder dental plaque formation and growth, but it also accelerates the deterioration of metallic restorations in the mouth. The present work consists of an in vitro study to elucidate the electrochemical reactions involved in the reduction of oxydized water on dental alloys through a systematic investigation of the potentiostatic polarization behavior of dental alloy electrodes. The five dental alloys selected for investigation were gold alloy, gold alloy containing platinum, silver-palladium-gold alloy, conventional amalgam and high copper amalgam. The corrosion potentials of all dental alloy electrodes were shown to be more noble in oxydized water than in 0.1N sodium chloride solution. The potential differences between the corrosion potentials were relatively small in the case of amalgam electrodes. The polarization curves for all of the dental alloy electrodes in oxydized water revealed reduction currents of chlorine, hypochlorous acid, dissolved oxygen and oxonium ion. The reduction of chlorine and hypochlorous acid started at a more noble potential than that of dissolved oxygen. The dental alloys studied, except the amalgams, did not dissolve excessively at the corrosion potentials in oxydized water.
Elemental sulfur recovery process

DOEpatents

Flytzani-Stephanopoulos, M.; Zhicheng Hu.

1993-09-07

An improved catalytic reduction process for the direct recovery of elemental sulfur from various SO[sub 2]-containing industrial gas streams. The catalytic process provides combined high activity and selectivity for the reduction of SO[sub 2] to elemental sulfur product with carbon monoxide or other reducing gases. The reaction of sulfur dioxide and reducing gas takes place over certain catalyst formulations based on cerium oxide. The process is a single-stage, catalytic sulfur recovery process in conjunction with regenerators, such as those used in dry, regenerative flue gas desulfurization or other processes, involving direct reduction of the SO[sub 2] in the regenerator off gas stream to elemental sulfur in the presence of a catalyst. 4 figures.
Efficient solar-assisted O2 reduction by a cofacial iron porphyrin dimer integrated to a p-CuBi2O4 photocathode prepared by a simple novel method.

PubMed

Zahran, Zaki N; Mohamed, Eman A; Naruta, Yoshinori; Haleem, Ashraf

2017-10-04

A cofacial iron porphyrin hetero-dimer, Fe2TPFPP-TMP showed high electro-catalytic activity, selectivity, and stability for the O2 reduction to H2O both in homogeneous non-aqueous and heterogeneous neutral aqueous solutions. Moreover, when it is integrated to FTO/p-CuBi2O4 (FTO = fluorine doped tin oxide) photocathode prepared by a simple novel method, a remarkable efficient solar-assisted O2 reduction is achieved in neutral potassium phosphate (KPi) or basic NaOH solutions saturated with O2. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Elemental sulfur recovery process

DOEpatents

Flytzani-Stephanopoulos, Maria; Hu, Zhicheng

1993-01-01

An improved catalytic reduction process for the direct recovery of elemental sulfur from various SO.sub.2 -containing industrial gas streams. The catalytic process provides combined high activity and selectivity for the reduction of SO.sub.2 to elemental sulfur product with carbon monoxide or other reducing gases. The reaction of sulfur dioxide and reducing gas takes place over certain catalyst formulations based on cerium oxide. The process is a single-stage, catalytic sulfur recovery process in conjunction with regenerators, such as those used in dry, regenerative flue gas desulfurization or other processes, involving direct reduction of the SO.sub.2 in the regenerator off gas stream to elemental sulfur in the presence of a catalyst.
Disguised as a Sulfate Reducer: Growth of the Deltaproteobacterium Desulfurivibrio alkaliphilus by Sulfide Oxidation with Nitrate.

PubMed

Thorup, Casper; Schramm, Andreas; Findlay, Alyssa J; Finster, Kai W; Schreiber, Lars

2017-07-18

This study demonstrates that the deltaproteobacterium Desulfurivibrio alkaliphilus can grow chemolithotrophically by coupling sulfide oxidation to the dissimilatory reduction of nitrate and nitrite to ammonium. Key genes of known sulfide oxidation pathways are absent from the genome of D. alkaliphilus Instead, the genome contains all of the genes necessary for sulfate reduction, including a gene for a reductive-type dissimilatory bisulfite reductase (DSR). Despite this, growth by sulfate reduction was not observed. Transcriptomic analysis revealed a very high expression level of sulfate-reduction genes during growth by sulfide oxidation, while inhibition experiments with molybdate pointed to elemental sulfur/polysulfides as intermediates. Consequently, we propose that D. alkaliphilus initially oxidizes sulfide to elemental sulfur, which is then either disproportionated, or oxidized by a reversal of the sulfate reduction pathway. This is the first study providing evidence that a reductive-type DSR is involved in a sulfide oxidation pathway. Transcriptome sequencing further suggests that nitrate reduction to ammonium is performed by a novel type of periplasmic nitrate reductase and an unusual membrane-anchored nitrite reductase. IMPORTANCE Sulfide oxidation and sulfate reduction, the two major branches of the sulfur cycle, are usually ascribed to distinct sets of microbes with distinct diagnostic genes. Here we show a more complex picture, as D. alkaliphilus , with the genomic setup of a sulfate reducer, grows by sulfide oxidation. The high expression of genes typically involved in the sulfate reduction pathway suggests that these genes, including the reductive-type dissimilatory bisulfite reductases, are also involved in as-yet-unresolved sulfide oxidation pathways. Finally, D. alkaliphilus is closely related to cable bacteria, which grow by electrogenic sulfide oxidation. Since there are no pure cultures of cable bacteria, D. alkaliphilus may represent an exciting model organism in which to study the physiology of this process. Copyright © 2017 Thorup et al.
Thermodynamic Versus Surface Area Control of Microbial Fe(III) Oxide Reduction Kinetics

NASA Astrophysics Data System (ADS)

Roden, E. E.

2003-12-01

Recent experimental studies of synthetic and natural Fe(III) oxide reduction permit development of conceptual and quantitative models of enzymatic Fe(III) oxide reduction at circumneutral pH that can be compared to and contrasted with established models of abiotic mineral dissolution. The findings collectively support a model for controls on enzymatic reduction that differs fundamentally from those applied to abiotic reductive dissolution as a result of two basic phenomena: (1) the relatively minor influence of oxide mineralogical and thermodynamic properties on surface area-normalized rates of enzymatic reduction compared to abiotic reductive dissolution; and (2) the major limitation which sorption and/or surface precipitation of biogenic Fe(II) on residual oxide and Fe(III)-reducing bacterial cell surfaces poses to enzymatic electron transfer in the presence of excess electron donor. Parallel studies with two major Fe(III)-reducing bacteria genera (Shewanella and Geobacter) lead to common conclusions regarding the importance of these phenomena in regulating the rate and long-term extent of Fe(III) oxide reduction. Although the extent to which these phenomena can be traced to underlying kinetic vs. thermodynamic effects cannot be resolved with current information, models in which rates of enzymatic reduction are limited kinetically by the abundance of "available" oxide surface sites (as controlled by oxide surface area and the abundance of surface-bound Fe(II)) provide an adequate macroscopic description of controls on the initial rate and long-term extent of oxide reduction. In some instances, thermodynamic limitation posed by the accumulation of aqueous reaction end-products (i.e. Fe(II) and alkalinity) must also be invoked to explain observed long-term patterns of reduction. In addition, the abundance of Fe(III)-reducing microorganisms plays an important role in governing rates of reduction and needs to be considered in models of Fe(III) reduction in nonsteady-state systems, e.g. subsurface environments in which Fe(III) reduction is stimulated by contamination with organics or for the purposes of metal/radionuclide bioremediation.
Candida parapsilosis: A versatile biocatalyst for organic oxidation-reduction reactions.

PubMed

Chadha, Anju; Venkataraman, Sowmyalakshmi; Preetha, Radhakrishnan; Padhi, Santosh Kumar

2016-10-01

This review highlights the importance of the biocatalyst, Candida parapsilosis for oxidation and reduction reactions of organic compounds and establishes its versatility to generate a variety of chiral synthons. Appropriately designed reactions using C. parapsilosis effect efficient catalysis of organic transformations such as deracemization, enantioselective reduction of prochiral ketones, imines, and kinetic resolution of racemic alcohols via selective oxidation. This review includes the details of these biotransformations, catalyzed by whole cells (wild type and recombinant strains), purified enzymes (oxidoreductases) and immobilized whole cells of C. parapsilosis. The review presents a bioorganic perspective as it discusses the chemo, regio and stereoselectivity of the biocatalyst along with the structure of the substrates and optical purity of the products. Fermentation scale biocatalysis using whole cells of C. parapsilosis for several biotransformations to synthesize important chiral synthons/industrial chemicals is included. A comparison of C. parapsilosis with other whole cell biocatalysts for biocatalytic deracemization and asymmetric reduction of carbonyl and imine groups in the synthesis of a variety of enantiopure products is presented which will provide a basis for the choice of a biocatalyst for a desired organic transformation. Thus, a wholesome perspective on the present status of C. parapsilosis mediated organic transformations and design of new reactions which can be considered for large scale operations is provided. Taken together, C. parapsilosis can now be considered a 'reagent' for the organic transformations discussed here. Copyright © 2016 Elsevier Inc. All rights reserved.
One-Step Laser Patterned Highly Uniform Reduced Graphene Oxide Thin Films for Circuit-Enabled Tattoo and Flexible Humidity Sensor Application.

PubMed

Park, Rowoon; Kim, Hyesu; Lone, Saifullah; Jeon, Sangheon; Kwon, Young Woo; Shin, Bosung; Hong, Suck Won

2018-06-06

The conversion of graphene oxide (GO) into reduced graphene oxide (rGO) is imperative for the electronic device applications of graphene-based materials. Efficient and cost-effective fabrication of highly uniform GO films and the successive reduction into rGO on a large area is still a cumbersome task through conventional protocols. Improved film casting of GO sheets on a polymeric substrate with quick and green reduction processes has a potential that may establish a path to the practical flexible electronics. Herein, we report a facile deposition process of GO on flexible polymer substrates to create highly uniform thin films over a large area by a flow-enabled self-assembly approach. The self-assembly of GO sheets was successfully performed by dragging the trapped solution of GO in confined geometry, which consisted of an upper stationary blade and a lower moving substrate on a motorized translational stage. The prepared GO thin films could be selectively reduced and facilitated from the simple laser direct writing process for programmable circuit printing with the desired configuration and less sample damage due to the non-contact mode operation without the use of photolithography, toxic chemistry, or high-temperature reduction methods. Furthermore, two different modes of the laser operating system for the reduction of GO films turned out to be valuable for the construction of novel graphene-based high-throughput electrical circuit boards compatible with integrating electronic module chips and flexible humidity sensors.
Reduction of antibiotic resistance genes in municipal wastewater effluent by advanced oxidation processes.

PubMed

Zhang, Yingying; Zhuang, Yao; Geng, Jinju; Ren, Hongqiang; Xu, Ke; Ding, Lili

2016-04-15

This study investigated the reduction of antibiotic resistance genes (ARGs), intI1 and 16S rRNA genes, by advanced oxidation processes (AOPs), namely Fenton oxidation (Fe(2+)/H2O2) and UV/H2O2 process. The ARGs include sul1, tetX, and tetG from municipal wastewater effluent. The results indicated that the Fenton oxidation and UV/H2O2 process could reduce selected ARGs effectively. Oxidation by the Fenton process was slightly better than that of the UV/H2O2 method. Particularly, for the Fenton oxidation, under the optimal condition wherein Fe(2+)/H2O2 had a molar ratio of 0.1 and a H2O2 concentration of 0.01molL(-1) with a pH of 3.0 and reaction time of 2h, 2.58-3.79 logs of target genes were removed. Under the initial effluent pH condition (pH=7.0), the removal was 2.26-3.35 logs. For the UV/H2O2 process, when the pH was 3.5 with a H2O2 concentration of 0.01molL(-1) accompanied by 30min of UV irradiation, all ARGs could achieve a reduction of 2.8-3.5 logs, and 1.55-2.32 logs at a pH of 7.0. The Fenton oxidation and UV/H2O2 process followed the first-order reaction kinetic model. The removal of target genes was affected by many parameters, including initial Fe(2+)/H2O2 molar ratios, H2O2 concentration, solution pH, and reaction time. Among these factors, reagent concentrations and pH values are the most important factors during AOPs. Copyright © 2016 Elsevier B.V. All rights reserved.
Selective detection and recovery of gold at tannin-immobilized non-conducting electrode.

PubMed

Banu, Khaleda; Shimura, Takayoshi; Sadeghi, Saman

2015-01-01

A tannin-immobilized glassy carbon electrode (TIGC) was prepared via electrochemical oxidation of the naturally occurring polyphenolic mimosa tannin, which generated a non-conducting polymeric film (NCPF) on the electrode surface. The fouling of the electrode surface by the electropolymerized film was evaluated by monitoring the electrode response of ferricyanide ions as a redox marker. The NCPF was permselective to HAuCl4, and the electrochemical reduction of HAuCl4 to metallic gold at the TIGC electrode was evaluated by recording the reduction current during cyclic voltammetry measurement. In the mixed electrolyte containing HAuCl4 along with FeCl3 and/or CuCl2, the NCPF remained selective toward the electrochemical reduction of HAuCl4 into the metallic state. The chemical reduction of HAuCl4 into metallic gold was also observed when the NCPF was inserted into an acidic gold solution overnight. The adsorption capacity of Au(III) on tannin-immobilized carbon fiber was 29±1.45 mg g(-1) at 60°C. In the presence of excess Cu(II) and Fe(III), tannin-immobilized NCPF proved to be an excellent candidate for the selective detection and recovery of gold through both electrochemical and chemical processes. Copyright © 2014 Elsevier B.V. All rights reserved.
Enhanced nitrogen selectivity for nitrate reduction on Cu-nZVI by TiO2 photocatalysts under UV irradiation

NASA Astrophysics Data System (ADS)

Krasae, Nalinee; Wantala, Kitirote

2016-09-01

The aims of this work were to study the effect of Cu-nZVI with and without TiO2 on nitrate reduction and to study the pathway of nitrate reduction utilizing to nitrogen gas. The chemical and physical properties of Cu-nZVI and Cu-nZVI/TiO2 such as specific surface area, crystalline phase, oxidation state of Cu and Fe and morphology were determined by N2 adsorption-desorption Brunauer-Emmett-Teller (BET) analytical technique, X-ray diffraction (XRD), X-ray Absorption Near Edge Structure (XANES) technique and Transmittance Electron Microscopy (TEM). The full factorial design (FFD) was used in this experiment for the effect of Cu-nZVI with and without TiO2, where the initial solution pH was varied at 4, 5.5, and 7 and initial nitrate concentration was varied at 50, 75, and 100 ppm. Finally, the pathway of nitrate reduction was examined to calculate the nitrogen gas selectivity. The specific area of Cu-nZVI and Cu-nZVI/TiO2 was found to be about 4 and 36 m2/g, respectively. The XRD pattern of Fe0 in Cu-nZVI was found at 45° (2θ), whereas Cu-nZVI/TiO2 cannot be observed. TEM images can confirm the position of the core and the shell of nZVI for Fe0 and ferric oxide. Cu-nZVI/TiO2 proved to have higher activity in nitrogen reduction performance than that without TiO2 and nitrate can be completely degraded in both of solution pH of 4 and 7 in 75 ppm of initial nitrate concentration. It can be highlighted that the nitrogen gas selectivity of Cu-nZVI/TiO2 greater than 82% was found at an initial solution pH of 4 and 7. The main effects of Cu-nZVI with and without TiO2 and the initial nitrate concentration on nitrate reduction were significant. The interaction between solution pH and initial nitrate concentration and the interaction of all effects at a reaction time of 15 min on nitrate reduction were also significant.
C-MEMS for bio-sensing applications

NASA Astrophysics Data System (ADS)

Song, Yin; Agrawal, Richa; Wang, Chunlei

2015-05-01

Developing highly sensitive, selective, and reproducible miniaturized bio-sensing platforms require reliable biointerface which should be compatible with microfabrication techniques. In this study, we have fabricated pyrolyzed carbon arrays with high surface area as a bio-sensing electrode, and developed the surface functionalization methods to increase biomolecules immobilization efficiency and further understand electrochemical phenomena at biointerfaces. The carbon microelectrode arrays with high aspect ratio have been fabricated by carbon microelectromechanical systems (C-MEMS) and nanomaterials such as graphene have been integrated to further increase surface area. To achieve the efficient covalent immobilization of biomolecules, various oxidation and reduction functionalization methods have been investigated. The oxidation treatment in this study includes vacuum ultraviolet, electrochemical activation, UV/Ozone and oxygen RIE. The reduction treatment includes direct amination and diazonium grafting. The developed bio-sensing platform was then applied for several applications, such as: DNA sensor; H2O2 sensor; aptamer sensor and HIV sensor.
Oxidation-reduction catalyst and its process of use

NASA Technical Reports Server (NTRS)

Schryer, Jacqueline L. (Inventor); Oglesby, Donald M. (Inventor); Jordan, Jeffrey D. (Inventor); Watkins, Anthony Neal (Inventor)

2008-01-01

This invention relates generally to a ruthenium stabilized oxidation-reduction catalyst useful for oxidizing carbon monoxide, and volatile organic compounds, and reducing nitrogen oxide species in oxidizing environments, substantially without the formation of toxic and volatile ruthenium oxide species upon said oxidizing environment being at high temperatures.
Tuning Ni-catalyzed CO 2 hydrogenation selectivity via Ni-ceria support interactions and Ni-Fe bimetallic formation

DOE PAGES

Winter, Lea R.; Gomez, Elaine; Yan, Binhang; ...

2017-10-16

CO 2 hydrogenation over Fe-modified Ni/CeO 2 catalysts was investigated in a batch reactor using time-resolved in situ FTIR spectroscopy. Low loading of Ni/CeO 2 was associated with high selectivity to CO over CH 4, while higher Ni loading improved CO 2 hydrogenation activity with a reduced CO selectivity. X-ray absorption near-edge structure (XANES) analysis revealed Ni to be metallic for all catalysts including the CO-selective low loading 0.5% Ni catalyst, suggesting that the selectivity trend is due to structural rather than oxidation state effects. The loading amount of 1.5% Ni was selected for co-impregnation with Fe, based on themore » significant shift in product selectivity towards CH 4 for that loading amount, in order to shift the selectivity towards CO while maintaining high activity. Temperature programmed reduction (TPR) results indicated bimetallic interactions between Ni and Fe, and XANES analysis showed that about 70% of Fe in the bimetallic catalysts was oxidized. The Ni-Fe catalysts demonstrated improved selectivity towards CO without significantly compromising activity, coupling the high activity of Ni catalysts and the high CO selectivity of Fe. The general trends in Ni loading and bimetallic modification should guide efforts to develop non-precious metal catalysts for the selective production of CO by CO 2 hydrogenation.« less
Calibration of redox potential in sperm wash media and evaluation of oxidation-reduction potential values in various assisted reproductive technology culture media using MiOXSYS system.

PubMed

Panner Selvam, M K; Henkel, R; Sharma, R; Agarwal, A

2018-03-01

Oxidation-reduction potential describes the balance between the oxidants and antioxidants in fluids including semen. Various artificial culture media are used in andrology and IVF laboratories for sperm preparation and to support the development of fertilized oocytes under in vitro conditions. The composition and conditions of these media are vital for optimal functioning of the gametes. Currently, there are no data on the status of redox potential of sperm processing and assisted reproduction media. The purpose of this study was to compare the oxidation-reduction potential values of the different media and to calibrate the oxidation-reduction potential values of the sperm wash medium using oxidative stress inducer cumene hydroperoxide and antioxidant ascorbic acid. Redox potential was measured in 10 different media ranging from sperm wash media, freezing media and assisted reproductive technology one-step medium to sequential media. Oxidation-reduction potential values of the sequential culture medium and one-step culture medium were lower and significantly different (p < 0.05) from the sperm wash media. Calibration of the sperm wash media using the oxidant cumene hydroperoxide and antioxidant ascorbic acid demonstrated that oxidation-reduction potential and the concentration of oxidant or antioxidant are logarithmically dependent. This study highlights the importance of calibrating the oxidation-reduction potential levels of the sperm wash media in order to utilize it as a reference value to identify the physiological range of oxidation-reduction potential that does not have any adverse effect on normal physiological sperm function. © 2017 American Society of Andrology and European Academy of Andrology.
Gold nanoparticles supported on titanium dioxide: an efficient catalyst for highly selective synthesis of benzoxazoles and benzimidazoles.

PubMed

Tang, Lin; Guo, Xuefeng; Yang, Yu; Zha, Zhenggen; Wang, Zhiyong

2014-06-11

A highly efficient and selective reaction for the synthesis of 2-substituted benzoxazoles and benzimidazoles catalyzed by Au/TiO2 has been developed via two hydrogen-transfer processes. This reaction has a good tolerance to air and water, a wide substrate scope, and represents a new avenue for practical C-N and C-O bond formation. More importantly, no additional additives, oxidants and reductants are required for the reaction and the catalyst can be recovered and reused readily.
Melamine-Schiff base/manganese complex with denritic structure: An efficient catalyst for oxidation of alcohols and one-pot synthesis of nitriles.

PubMed

Kazemnejadi, Milad; Nikookar, Mahsa; Mohammadi, Mohammad; Shakeri, Alireza; Esmaeilpour, Mohsen

2018-05-18

Efficient and selective oxidation of alcohol to the corresponding carbonyl and/or nitrile was carried out by a new water-soluble melamine-based dendritic Mn(III) complex (Melamine-Mn (III)-Schiff base complex) in the presence of 2,4,6-trichloro-1,3,5-triazine (TCT) and O 2 at room temperature. Also, the oxidation of amine to the corresponding nitrile with high selectivity and conversion was performed at room temperature using the current method and high amounts of turnover frequencies (TOFs) were obtained for reactions. This system was also applicable for direct preparation of oxime through oxidation of alcohol. The catalyst was characterized by Fourier-transform infrared (FTIR), ultraviolet-visible (UV-Vis), thermogravimetric analysis (TGA), energy-dispersive X-ray (EDX), X-ray photoelectron spectroscopy (XPS), CHN and inductively coupled plasma (ICP) analyses. Also, oxidation/reduction behavior of the catalyst was studied by cyclic voltammetry (CV). Moreover, chemoselectivity of the catalyst was discussed with various combinations. The water-soluble catalyst could be recycled from the reaction mixture and reused for several times with a very low losing in efficiency. The recovered catalyst was also investigated with various analyses. Finally, gram scale preparation of nitrile was evaluated by present method. Copyright © 2018 Elsevier Inc. All rights reserved.
Pathways of organic carbon oxidation in three continental margin sediments

NASA Technical Reports Server (NTRS)

Canfield, D. E.; Jorgensen, B. B.; Fossing, H.; Glud, R.; Gundersen, J.; Ramsing, N. B.; Thamdrup, B.; Hansen, J. W.; Nielsen, L. P.; Hall, P. O.

1993-01-01

We have combined several different methodologies to quantify rates of organic carbon mineralization by the various electron acceptors in sediments from the coast of Denmark and Norway. Rates of NH4+ and Sigma CO2 liberation sediment incubations were used with O2 penetration depths to conclude that O2 respiration accounted for only between 3.6-17.4% of the total organic carbon oxidation. Dentrification was limited to a narrow zone just below the depth of O2 penetration, and was not a major carbon oxidation pathway. The processes of Fe reduction, Mn reduction and sulfate reduction dominated organic carbon mineralization, but their relative significance varied depending on the sediment. Where high concentrations of Mn-oxide were found (3-4 wt% Mn), only Mn reduction occurred. With lower Mn oxide concentrations more typical of coastal sediments, Fe reduction and sulfate reduction were most important and of a similar magnitude. Overall, most of the measured O2 flux into the sediment was used to oxidized reduced inorganic species and not organic carbon. We suspect that the importance of O2 respiration in many coastal sediments has been overestimated, whereas metal oxide reduction (both Fe and Mn reduction) has probably been well underestimated.
Critical role of intercalated water for electrocatalytically active nitrogen-doped graphitic systems

DOE PAGES

Martinez, Ulises; Dumont, Joseph H.; Holby, Edward F.; ...

2016-03-18

Graphitic materials are very essential in energy conversion and storage because of their excellent chemical and electrical properties. The strategy for obtaining functional graphitic materials involves graphite oxidation and subsequent dissolution in aqueous media, forming graphene-oxide nanosheets (GNs). Restacked GNs contain substantial intercalated water that can react with heteroatom dopants or the graphene lattice during reduction. We demonstrate that removal of intercalated water using simple solvent treatments causes significant structural reorganization, substantially affecting the oxygen reduction reaction (ORR) activity and stability of nitrogen-doped graphitic systems. Amid contrasting reports describing the ORR activity of GN-based catalysts in alkaline electrolytes, we demonstratemore » superior activity in an acidic electrolyte with an onset potential of ~0.9 V, a half-wave potential (E ½) of 0.71 V, and a selectivity for four-electron reduction of >95%. Finally and further, durability testing showed E ½ retention >95% in N 2- and O 2-saturated solutions after 2000 cycles, demonstrating the highest ORR activity and stability reported to date for GN-based electrocatalysts in acidic media.« less
Morphological Control of Au Dendrite Electrocatalysts for CO2 Reduction

NASA Astrophysics Data System (ADS)

Nesbitt, Nathan T.; Ma, Ming; Carter, Brittany E.; D'Imperio, Luke A.; Naughton, Jeffrey R.; Courtney, Dave T.; Shepard, Steve; Burns, Michael J.; Smith, Wilson A.; Naughton, Michael J.

Au has demonstrated the highest catalytic selectivity, activity, and stability for CO2 reduction to CO of any metal, but the mechanism for this performance remains unclear. Studies of nanoparticle films have shown that higher index facets have improved performance, but the preeminent nanoparticle films, from oxide-derived Au, lack well-defined facets and morphological stability to illuminate their enabling mechanism. More recent work has shown Au needles with a sub 5 nm radius of curvature have excellent performance and stability, independent of crystal facet. The same studies, however, still show calculations expecting a facet dependance. Here we demonstrate a facile and novel dendrite fabrication process with tunable morphology. The dendrites show high catalytic selectivity, activity, and stability for CO2 reduction to CO, along with morphological stability after 18 hours of operation, allowing correlation between morphology and performance. The influence of exposed facets will be discussed. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. (DGE-1258923).
Near-infrared selective dynamic windows controlled by charge transfer impedance at the counter electrode.

PubMed

Pattathil, Praveen; Scarfiello, Riccardo; Giannuzzi, Roberto; Veramonti, Giulia; Sibillano, Teresa; Qualtieri, Antonio; Giannini, Cinzia; Cozzoli, P Davide; Manca, Michele

2016-12-08

Recent developments in the exploitation of transparent conductive oxide nanocrystals paved the way to the realization of a new class of electrochemical systems capable of selectively shielding the infrared heat loads carried by sunlight and prospected the blooming of a key enabling technology to be implemented in the next generation of "zero-energy" building envelopes. Here we report the fabrication of a set of electrochromic devices embodying an engineered nanostructured electrode made by high aspect-ratio tungsten oxide nanorods, which allow for selectively and dynamically controlling sunlight transmission over the near-infrared to visible range. Varying the intensity of applied voltage makes the spectral response of the device change across three different optical regimes, namely fully transparent, near-infrared only blocking and both visible and near-infrared blocking. It is demonstrated that the degree of reversible modulation of the thermal radiation entering the glazing element can approach a remarkable 85%, accompanied by only a modest reduction in the luminous transmittance.
In-Situ Optical Studies of Oxidation/Reduction Kinetics on SOFC Cermet Anodes

DTIC Science & Technology

2010-12-28

DATES COVERED (From - To) 1/29/10-9/30/10 4. TITLE AND SUBTITLE In situ optical studies of oxidation/reduction kinetics on SOFC cermet anodes 5a...0572 In-situ Optical Studies of Oxidation/Reduction Kinetics on SOFC Cermet Anodes Department of Chemistry and Biochemistry Montana State University...of Research In-situ Optical Studies of Oxidation/Reduction Kinetics on SOFC Cermet Anodes Principal Investigator Robert Walker Organization
Biomineralization associated with microbial reduction of Fe3+ and oxidation of Fe2+ in solid minerals

USGS Publications Warehouse

Zhang, G.; Dong, H.; Jiang, H.; Kukkadapu, R.K.; Kim, J.; Eberl, D.; Xu, Z.

2009-01-01

Iron-reducing and oxidizing microorganisms gain energy through reduction or oxidation of iron, and by doing so play an important role in the geochemical cycling of iron. This study was undertaken to investigate mineral transformations associated with microbial reduction of Fe3+ and oxidation of Fe2+ in solid minerals. A fluid sample from the 2450 m depth of the Chinese Continental Scientific Drilling project was collected, and Fe3+-reducing and Fe2+-oxidizing microorganisms were enriched. The enrichment cultures displayed reduction of Fe3+ in nontronite and ferric citrate, and oxidation of Fe2+ in vivianite, siderite, and monosulfide (FeS). Additional experiments verified that the iron reduction and oxidation was biological. Oxidation of FeS resulted in the formation of goethite, lepidocrocite, and ferrihydrite as products. Although our molecular microbiological analyses detected Thermoan-aerobacter ethanolicus as a predominant organism in the enrichment culture, Fe3+ reduction and Fe2+ oxidation may be accomplished by a consortia of organisms. Our results have important environmental and ecological implications for iron redox cycling in solid minerals in natural environments, where iron mineral transformations may be related to the mobility and solubility of inorganic and organic contaminants.

Selective dissolution followed by EDDS washing of an e-waste contaminated soil: Extraction efficiency, fate of residual metals, and impact on soil environment.

PubMed

Beiyuan, Jingzi; Tsang, Daniel C W; Valix, Marjorie; Zhang, Weihua; Yang, Xin; Ok, Yong Sik; Li, Xiang-Dong

2017-01-01

To enhance extraction of strongly bound metals from oxide minerals and organic matter, this study examined the sequential use of reductants, oxidants, alkaline solvents and organic acids followed by a biodegradable chelating agent (EDDS, [S,S]-ethylene-diamine-disuccinic-acid) in a two-stage soil washing. The soil was contaminated by Cu, Zn, and Pb at an e-waste recycling site in Qingyuan city, China. In addition to extraction efficiency, this study also examined the fate of residual metals (e.g., leachability, bioaccessibility, and distribution) and the soil quality parameters (i.e., cytotoxicity, enzyme activities, and available nutrients). The reductants (dithionite-citrate-bicarbonate and hydroxylamine hydrochloride) effectively extracted metals by mineral dissolution, but elevated the leachability and bioaccessibility of metals due to the transformation from Fe/Mn oxides to labile fractions. Subsequent EDDS washing was found necessary to mitigate the residual risks. In comparison, prior washing by oxidants (persulphate, hypochlorite, and hydrogen peroxide) was marginally useful because of limited amount of soil organic matter. Prior washing by alkaline solvents (sodium hydroxide and sodium bicarbonate) was also ineffective due to metal precipitation. In contrast, prior washing by low-molecular-weight organic acids (citrate and oxalate) improved the extraction efficiency. Compared to hydroxylamine hydrochloride, citrate and oxalate induced lower cytotoxicity (Microtox) and allowed higher enzyme activities (dehydrogenase, acid phosphatase, and urease) and soil nutrients (available nitrogen and phosphorus), which would facilitate reuse of the treated soil. Therefore, while sequential washing proved to enhance extraction efficacy, the selection of chemical agents besides EDDS should also include the consideration of effects on metal leachability/bioaccessibility and soil quality. Copyright © 2016 Elsevier Ltd. All rights reserved.
Systems-level computational modeling demonstrates fuel selection switching in high capacity running and low capacity running rats

PubMed Central

Qi, Nathan R.

2018-01-01

High capacity and low capacity running rats, HCR and LCR respectively, have been bred to represent two extremes of running endurance and have recently demonstrated disparities in fuel usage during transient aerobic exercise. HCR rats can maintain fatty acid (FA) utilization throughout the course of transient aerobic exercise whereas LCR rats rely predominantly on glucose utilization. We hypothesized that the difference between HCR and LCR fuel utilization could be explained by a difference in mitochondrial density. To test this hypothesis and to investigate mechanisms of fuel selection, we used a constraint-based kinetic analysis of whole-body metabolism to analyze transient exercise data from these rats. Our model analysis used a thermodynamically constrained kinetic framework that accounts for glycolysis, the TCA cycle, and mitochondrial FA transport and oxidation. The model can effectively match the observed relative rates of oxidation of glucose versus FA, as a function of ATP demand. In searching for the minimal differences required to explain metabolic function in HCR versus LCR rats, it was determined that the whole-body metabolic phenotype of LCR, compared to the HCR, could be explained by a ~50% reduction in total mitochondrial activity with an additional 5-fold reduction in mitochondrial FA transport activity. Finally, we postulate that over sustained periods of exercise that LCR can partly overcome the initial deficit in FA catabolic activity by upregulating FA transport and/or oxidation processes. PMID:29474500
1. West facade of Plutonium Concentration Facility (Building 233S), ReductionOxidation ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. West facade of Plutonium Concentration Facility (Building 233-S), Reduction-Oxidation Building (REDOX-202-S) to the right. Looking east. - Reduction-Oxidation Complex, Plutonium Concentration Facility, 200 West Area, Richland, Benton County, WA
Interactions between microbial iron reduction and metal geochemistry: effect of redox cycling on transition metal speciation in iron bearing sediments.

PubMed

Cooper, D Craig; Picardal, Flynn F; Coby, Aaron J

2006-03-15

Microbial iron reduction is an important biogeochemical process that can affect metal geochemistry in sediments through direct and indirect mechanisms. With respectto Fe(III) (hydr)oxides bearing sorbed divalent metals, recent reports have indicated that (1) microbial reduction of goethite/ferrihydrite mixtures preferentially removes ferrihydrite, (2) this process can incorporate previously sorbed Zn(II) into an authigenic crystalline phase that is insoluble in 0.5 M HCl, (3) this new phase is probably goethite, and (4) the presence of nonreducible minerals can inhibit this transformation. This study demonstrates that a range of sorbed transition metals can be selectively sequestered into a 0.5 M HCl insoluble phase and that the process can be stimulated through sequential steps of microbial iron reduction and air oxidation. Microbial reduction experiments with divalent Cd, Co, Mn, Ni, Pb, and Zn indicate that all metals save Mn experienced some sequestration, with the degree of metal incorporation into the 0.5 M HCl insoluble phase correlating positively with crystalline ionic radius at coordination number = 6. Redox cycling experiments with Zn adsorbed to synthetic goethite/ferrihydrite or iron-bearing natural sediments indicate that redox cycling from iron reducing to iron oxidizing conditions sequesters more Zn within authigenic minerals than microbial iron reduction alone. In addition, the process is more effective in goethite/ferrihydrite mixtures than in iron-bearing natural sediments. Microbial reduction alone resulted in a -3x increase in 0.5 M HCl insoluble Zn and increased aqueous Zn (Zn-aq) in goethite/ferrihydrite, but did not significantly affect Zn speciation in natural sediments. Redox cycling enhanced the Zn sequestration by approximately 12% in both goethite/ferrihydrite and natural sediments and reduced Zn-aq to levels equal to the uninoculated control in goethite/ferrihydrite and less than the uninoculated control in natural sediments. These data suggest that in situ redox cycling may serve as an effective method for
Radiolytic Gas-Driven Cryovolcanism in the Outer Solar System

NASA Technical Reports Server (NTRS)

Cooper, John F.; Cooper, Paul D.; Sittler, Edward C.; Sturner, Steven J.; Rymer, Abigail M.; Hill, Matthew E.

2007-01-01

Water ices in surface crusts of Europa, Enceladus, Saturn's main rings, and Kuiper Belt Objects can become heavily oxidized from radiolytic chemical alteration of near-surface water ice by space environment irradiation. Oxidant accumulations and gas production are manifested in part through observed H2O2 on Europa. tentatively also on Enceladus, and found elsewhere in gaseous or condensed phases at moons and rings of Jupiter and Saturn. On subsequent chemical contact in sub-surface environments with significant concentrations of primordially abundant reductants such as NH3 and CH4, oxidants of radiolytic origin can react exothermically to power gas-driven cryovolcanism. The gas-piston effect enormously amplifies the mass flow output in the case of gas formation at basal thermal margins of incompressible fluid reservoirs. Surface irradiation, H2O2 production, NH3 oxidation, and resultant heat, gas, and gas-driven mass flow rates are computed in the fluid reservoir case for selected bodies. At Enceladus the oxidant power inputs are comparable to limits on nonthermal kinetic power for the south polar plumes. Total heat output and plume gas abundance may be accounted for at Enceladus if plume activity is cyclic in high and low "Old Faithful" phases, so that oxidants can accumulate during low activity phases. Interior upwelling of primordially abundant NH3 and CH4 hydrates is assumed to resupply the reductant fuels. Much lower irradiation fluxes on Kuiper Belt Objects require correspondingly larger times for accumulation of oxidants to produce comparable resurfacing, but brightness and surface composition of some objects suggest that such activity may be ongoing.
Efficacy of a solution-based approach for making sodalite waste forms for an oxide reduction salt utilized in the reprocessing of used uranium oxide fuel

NASA Astrophysics Data System (ADS)

Riley, Brian J.; Pierce, David A.; Frank, Steven M.; Matyáš, Josef; Burns, Carolyne A.

2015-04-01

This paper describes the various approaches evaluated for making solution-derived sodalite with a LiCl-Li2O oxide reduction salt selected to dissolve used uranium oxide fuel so the uranium can be recovered and recycled. The approaches include modified sol-gel and solution-based synthesis processes. As-made products were mixed with 5 and 10 mass% of a Na2O-B2O3-SiO2 glass binder and these, along with product without a binder, were heated using either a cold-press-and-sinter method or hot uniaxial pressing. The results demonstrate the limitation of sodalite yield due to the fast intermediate reactions between Na+ and Cl- to form halite in solution and Li2O and SiO2 to form lithium silicates (e.g., Li2SiO3 or Li2Si2O5) in the calcined and sintered pellets. The results show that pellets can be made with high sodalite fractions in the crystalline product (∼92 mass%) and low porosities using a solution-based approach and this LiCl-Li2O salt but that the incorporation of Li into the sodalite is low.
1,2-Dibenzyltetradimethylamido-Dimolybdenum and -Ditungsten (M=M) Compounds and Their Reactions with Carbon Dioxide and 1,3-Diaryltriazines. A Radical Difference.

DTIC Science & Technology

1982-07-07

solution of a mixture of these Mo2- and MoW-containing compounds selectively precipitated the heterobimetallic single elec- tron oxidation product MoW...3.5 and reduction, using 0$ powdered zinc in acetonitrile at 25°C, yielded the heterobimetallic quadruply bonded compound MoW(O2CBu t )4. Katovic, V
Human reductive halothane metabolism in vitro is catalyzed by cytochrome P450 2A6 and 3A4.

PubMed

Spracklin, D K; Thummel, K E; Kharasch, E D

1996-09-01

The anesthetic halothane undergoes extensive oxidative and reductive biotransformation, resulting in metabolites that cause hepatotoxicity. Halothane is reduced anaerobically by cytochrome P450 (P450) to the volatile metabolites 2-chloro-1,1-difluoroethene (CDE) and 2-chloro-1,1,1-trifluoroethane (CTE). The purpose of this investigation was to identify the human P450 isoform(s) responsible for reductive halothane metabolism. CDE and CTE formation from halothane metabolism by human liver microsomes was determined by GC/MS analysis. Halothane metabolism to CDE and CTE under reductive conditions was completely inhibited by carbon monoxide, which implicates exclusively P450 in this reaction. Eadie-Hofstee plots of both CDE and CTE formation were nonlinear, suggesting multiple P450 isoform involvement. Microsomal CDE and CTE formation were each inhibited 40-50% by P450 2A6-selective inhibitors (coumarin and 8-methoxypsoralen) and 55-60% by P450 3A4-selective inhibitors (ketoconazole and troleandomycin). P450 1A-, 2B6-, 2C9/10-, and 2D6-selective inhibitors (7,8-benzoflavone, furafylline, orphenadrine, sulfaphenazole, and quinidine) had no significant effect on reductive halothane metabolism. Measurement of product formation catalyzed by a panel of cDNA-expressed P450 isoforms revealed that maximal rates of CDE formation occurred with P450 2A6, followed by P450 3A4. P450 3A4 was the most effective catalyst of CTE formation. Among a panel of 11 different human livers, there were significant linear correlations between the rate of CDE formation and both 2A6 activity (r = 0.64, p < 0.04) and 3A4 activity (r = 0.64, p < 0.03). Similarly, there were significant linear correlations between CTE formation and both 2A6 activity (r = 0.55, p < 0.08) and 3A4 activity (r = 0.77, p < 0.005). The P450 2E1 inhibitors 4-methylpyrazole and diethyldithiocarbamate inhibited CDE and CTE formation by 20-45% and 40-50%, respectively; however, cDNA-expressed P450 2E1 did not catalyze significant amounts of CDE or CTE production, and microsomal metabolite formation was not correlated with P450 2E1 activity. This investigation demonstrated that human liver microsomal reductive halothane metabolism is catalyzed predominantly by P450 2A6 and 3A4. This isoform selectivity for anaerobic halothane metabolism contrasts with that for oxidative human halothane metabolism, which is catalyzed predominantly by P450 2E1.
Selective oxidation of methanol and ethanol on supported ruthenium oxide clusters at low temperatures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Haichao; Iglesia, Enrique

RuO2 domains supported on SnO2, ZrO2, TiO2, Al2O3, and SiO2 catalyze the oxidative conversion of methanol to formaldehyde, methylformate, and dimethoxymethane with unprecedented rates and high combined selectivity (>99 percent) and yield at low temperatures (300-400 K). Supports influence turnover rates and the ability of RuO2 domains to undergo redox cycles required for oxidation turnovers. Oxidative dehydrogenation turnover rates and rates of stoichiometric reduction of RuO2 in H2 increased in parallel when RuO2 domains were dispersed on more reducible supports. These support effects, the kinetic effects of CH3OH and O2 on reaction rates, and the observed kinetic isotope effects withmore » CH3OD and CD3OD reactants are consistent with a sequence of elementary steps involving kinetically relevant H-abstraction from adsorbed methoxide species using lattice oxygen atoms and with methoxide formation in quasi-equilibrated CH3OH dissociation on nearly stoichiometric RuO2 surfaces. Anaerobic transient experiments confirmed that CH3OH oxidation to HCHO requires lattice oxygen atoms and that selectivities are not influenced by the presence of O2. Residence time effects on selectivity indicate that secondary HCHO-CH3OH acetalization reactions lead to hemiacetal or methoxymethanol intermediates that convert to dimethoxymethane in reactions with CH3OH on support acid sites or dehydrogenate to form methylformate on RuO2 and support redox sites. These conclusions are consistent with the tendency of Al2O3 and SiO2 supports to favor dimethoxymethane formation, while SnO2, ZrO2, and TiO2 preferentially form methylformate. These support effects on secondary reactions were confirmed by measured CH3OH oxidation rates and selectivities on physical mixtures of supported RuO2 catalysts and pure supports. Ethanol also reacts on supported RuO2 domains to form predominately acetaldehyde and diethoxyethane at 300-400 K. The bifunctional nature of these reaction pathways and the remarkable ability of RuO2-based catalysts to oxidize CH3OH to HCHO at unprecedented low temperatures introduce significant opportunities for new routes to complex oxygenates, including some containing C-C bonds, using methanol or ethanol as intermediates derived from natural gas or biomass.« less
Persulfate activation by subsurface minerals.

PubMed

Ahmad, Mushtaque; Teel, Amy L; Watts, Richard J

2010-06-25

Persulfate dynamics in the presence of subsurface minerals was investigated as a basis for understanding persulfate activation for in situ chemical oxidation (ISCO). The mineral-mediated decomposition of persulfate and generation of oxidants and reductants was investigated with four iron and manganese oxides and two clay minerals at both low pH (<7) and high pH (>12). The manganese oxide birnessite was the most effective initiator of persulfate for degrading the oxidant probe nitrobenzene, indicating that oxidants are generated at both low and high pH regimes. The iron oxide goethite was the most effective mineral for degrading the reductant probe hexachloroethane. A natural soil and two soil fractions were used to confirm persulfate activation by synthetic minerals. The soil and soil fractions did not effectively promote the generation of oxidants or reductants. However, soil organic matter was found to promote reductant generation at high pH. The results of this research demonstrate that synthetic iron and manganese oxides can activate persulfate to generate reductants and oxidants; however, iron and manganese oxides in the natural soil studied do not show the same reactivity, most likely due to the lower masses of the metal oxides in the soil relative to the masses studied in isolated mineral systems. 2010. Published by Elsevier B.V.
Fabrication of selectively functionalized-graphene reinforced copper phthalocyanine nanocomposites with low dielectric loss and high dielectric constant

NASA Astrophysics Data System (ADS)

Wang, Zicheng; Wei, Renbo; Liu, Xiaobo

2017-01-01

A novel kind of selectively functionalized-graphene reinforced copper phthalocyanine (RGO-O-CuPc) nanocomposites was successfully fabricated through a facile and effective three-step method, involving preferential surficial modification and reduction of graphene oxide (GO) sheets, and followed by incorporating with CuPc via in situ polymerization. The results of SEM, AFM, XPS, FTIR, XRD and UV-vis confirmed that GO was effectively surficial functionalized by a ring-open covalent reaction between amino in 3-aminophenoxyphthalonitrile (3-APN) and epoxy groups on the GO sheets, and partly reduced back to graphene under solvothermal conditions. And the RGO-O-CuPc was successfully fabricated by self-assembling of CuPc molecule on graphene sheets via in situ polymerization. As a consequence, the selective surface functionalization and solvothermal reduction of GO facilitated the improvement in the dielectric constant and AC conductivity, and the decrease in the dielectric loss of the graphene/CuPc nanocomposites.
Decontamination of metals using chemical etching

DOEpatents

Lerch, Ronald E.; Partridge, Jerry A.

1980-01-01

The invention relates to chemical etching process for reclaiming contaminated equipment wherein a reduction-oxidation system is included in a solution of nitric acid to contact the metal to be decontaminated and effect reduction of the reduction-oxidation system, and includes disposing a pair of electrodes in the reduced solution to permit passage of an electrical current between said electrodes and effect oxidation of the reduction-oxidation system to thereby regenerate the solution and provide decontaminated equipment that is essentially radioactive contamination-free.
Breakfast skipping in prepubertal obese children: hormonal, metabolic and cognitive consequences.

PubMed

Maffeis, C; Fornari, E; Surano, M G; Comencini, E; Corradi, M; Tommasi, M; Fasan, I; Cortese, S

2012-03-01

Skipping breakfast influences cognitive performance. The aim of our study was to investigate the relationship between the variation of hormonal and metabolic postprandial parameters induced by breakfast consumption or fasting and cognitive performance in obese children. Cross-sectional study for repeated measures. Memory and attention assessment tests, hormones and nutrient oxidation were measured before and after consuming breakfast vs fasting in 10 prepubertal obese children. Fasting induced a significant (P<0.05) increase of the Overall Index of the Continuous Performance Test II (a global index of inattention) and the Test of Memory and Learning Word Selective Reminding (a test of verbal memory), whereas no changes were found after breakfast. Fasting was associated with a reduction of insulin and an increase in glucagon, with no changes in glucose. The increase in inattention was associated with a reduction of carbohydrate oxidation (ρ=-0.66, P<0.05). We found no difference in the area under the curve of peptide YY and glucagon-like peptide-1 after breakfast or fasting, whereas Ghrelin was significantly lower. No association between postprandial hormone variation and cognitive performance was found. Attention and visual memory performance in the morning were reduced when the children skipped breakfast. No association was found with hormones or metabolic changes, but we did find an association with a reduction of carbohydrate oxidation. Nevertheless, these preliminary findings need confirmation in larger sample size.
Combination of biodiesel-ethanol-diesel fuel blend and SCR catalyst assembly to reduce emissions from a heavy-duty diesel engine.

PubMed

Shi, Xiaoyan; Yu, Yunbo; He, Hong; Shuai, Shijin; Dong, Hongyi; Li, Rulong

2008-01-01

In this study, the efforts to reduce NOx and particulate matter (PM) emissions from a diesel engine using both ethanol-selective catalytic reduction (SCR) of NOx over an Ag/Al2O3 catalyst and a biodiesel-ethanol-diesel fuel blend (BE-diesel) on an engine bench test are discussed. Compared with diesel fuel, use of BE-diesel increased PM emissions by 14% due to the increase in the soluble organic fraction (SOF) of PM, but it greatly reduced the Bosch smoke number by 60%-80% according to the results from 13-mode test of European Stationary Cycle (ESC) test. The SCR catalyst was effective in NOx reduction by ethanol, and the NOx conversion was approximately 73%. Total hydrocarbons (THC) and CO emissions increased significantly during the SCR of NOx process. Two diesel oxidation catalyst (DOC) assemblies were used after Ag/Al2O3 converter to remove CO and HC. Different oxidation catalyst showed opposite effect on PM emission. The PM composition analysis revealed that the net effect of oxidation catalyst on total PM was an integrative effect on SOF reduction and sulfate formation of PM. The engine bench test results indicated that the combination of BE-diesel and a SCR catalyst assembly could provide benefits for NOx and PM emissions control even without using diesel particle filters (DPFs).
Kinetic Coupling of Water Splitting and Photoreforming on SrTiO 3 -Based Photocatalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sanwald, Kai E.; Berto, Tobias F.; Jentys, Andreas

Coupling the anodic half-reactions of overall water splitting and oxygenate photoreforming (i.e., proton reduction and oxygenate oxidations) on Al-doped SrTiO3 decorated with a co-catalyst enables efficient photocatalytic H2 generation along with oxygenate conversion without accumulating undesired intermediates such as formaldehyde. The net H2-evolution rates result from the interplay between water oxidation, oxygenate oxidation, and the back-reaction of H2 and O2 to water. When the latter pathway is quantitatively suppressed (e.g., on RhCrOx co-catalyst or in excess of oxygenated hydrocarbons), the initial H2-evolution rates are independent of the oxygenate nature and concentration. This is a consequence of the reduction equivalents formore » H2-evolution provided by water oxidation compensating changes in the rates of oxygenate conversion. Thus, under conditions of suppressed back-reaction, water and oxygenate oxidations have equal quantum efficiencies. The selectivities to water and oxygenate oxidation depend on oxygenate nature and concentration. Transformations mediated by indirect hole transfer dominate as a result of the water oxidation at the anode and the associated intermediates generated in O2-evolution catalysis (e.g. ·OH, ·O and ·OOH). On the undecorated semiconductor, the O2 produced during overall water splitting is reductively activated to participate in glycerol oxidation without consuming evolved H2. Acknowledgements The authors would like to thank ESRF in Grenoble, France, for providing beam time at the ID26 station for XAFS experiments. K.E.S. gratefully acknowledges financial support by the Fond der Chemischen Industrie (FCI). J.A.L. and O.Y.G. acknowledge support for his contribution by the Laboratory Directed Research and Development Program at Pacific Northwest National Laboratory, a multi-program national laboratory operated by Battelle for the U.S. Department of Energy. The authors thank Xaver Hecht for BET measurements, Martin Neukamm for SEM and AAS measurements and Dr. Udishnu Sanyal for TEM imaging. Christine Schwarz is acknowledged for technical assistance in NMR experiments.« less
Geochemical controls on microbial nitrate-dependent U(IV) oxidation

USGS Publications Warehouse

Senko, John M.; Suflita, Joseph M.; Krumholz, Lee R.

2005-01-01

After reductive immobilization of uranium, the element may be oxidized and remobilized in the presence of nitrate by the activity of dissimilatory nitrate-reducing bacteria. We examined controls on microbially mediated nitrate-dependent U(IV) oxidation in landfill leachate-impacted subsurface sediments. Nitrate-dependent U(IV)-oxidizing bacteria were at least two orders of magnitude less numerous in these sediments than glucose- or Fe(II)-oxidizing nitrate-reducing bacteria and grew more slowly than the latter organisms, suggesting that U(IV) is ultimately oxidized by Fe(III) produced by nitrate-dependent Fe(II)-oxidizing bacteria or by oxidation of Fe(II) by nitrite that accumulates during organotrophic dissimilatory nitrate reduction. We examined the effect of nitrate and reductant concentration on nitrate-dependent U(IV) oxidation in sediment incubations and used the initial reductive capacity (RDC = [reducing equivalents] - [oxidizing equivalents]) of the incubations as a unified measurement of the nitrate or reductant concentration. When we lowered the RDC with progressively higher nitrate concentrations, we observed a corresponding increase in the extent of U(IV) oxidation, but did not observe this relationship between RDC and U(IV) oxidation rate, especially when RDC > 0, suggesting that nitrate concentration strongly controls the extent, but not the rate of nitrate-dependent U(IV) oxidation. On the other hand, when we raised the RDC in sediment incubations with progressively higher reductant (acetate, sulfide, soluble Fe(II), or FeS) concentrations, we observed progressively lower extents and rates of nitrate-dependent U(IV) oxidation. Acetate was a relatively poor inhibitor of nitrate-dependent U(IV) oxidation, while Fe(II) was the most effective inhibitor. Based on these results, we propose that it may be possible to predict the stability of U(IV) in a bioremediated aquifer based on the geochemical characteristics of that aquifer.
Ceruloplasmin copper induces oxidant damage by a redox process utilizing cell-derived superoxide as reductant

NASA Technical Reports Server (NTRS)

Mukhopadhyay, C. K.; Fox, P. L.

1998-01-01

Oxidative damage by transition metals bound to proteins may be an important pathogenic mechanism. Ceruloplasmin (Cp) is a Cu-containing plasma protein thought to be involved in oxidative modification of lipoproteins. We have previously shown that Cp increased cell-mediated low-density lipoprotein (LDL) oxidation by a process requiring cell-derived superoxide, but the underlying chemical mechanism(s) is (are) unknown. We now show that superoxide reduction of Cp Cu is a critical reaction in cellular LDL oxidation. By bathocuproine disulfonate (BCS) binding and by superoxide utilization, we showed that exogenous superoxide reduces a single Cp Cu atom, the same Cu required for LDL oxidation. The Cu atom remained bound to Cp during the redox cycle. Three avenues of evidence showed that vascular cells reduce Cp Cu by a superoxide-dependent process. The 2-fold higher rate of Cp Cu reduction by smooth muscle cells (SMC) compared to endothelial cells (EC) was consistent with their relative rates of superoxide release. Furthermore, Cp Cu reduction by cells was blocked by Cu,Zn superoxide dismutase (SOD1). Finally, the level of superoxide produced by EC and SMC was sufficient to cause the amount of Cu reduction observed. An important role of Cp Cu reduction in LDL oxidation was suggested by results showing that SOD1 inhibited Cp Cu reduction and LDL oxidation by SMC with equal potency, while tumor necrosis factor-alpha stimulated both processes. In summary, these results show that superoxide is a critical cellular reductant of divalent transition metals involved in oxidation, and that protein-bound Cu is a substrate for this reaction. The role of these mechanisms in oxidative processes in vivo has yet to be defined.
Oxidation-Reduction Resistance of Advanced Copper Alloys

NASA Technical Reports Server (NTRS)

Greenbauer-Seng, L. (Technical Monitor); Thomas-Ogbuji, L.; Humphrey, D. L.; Setlock, J. A.

2003-01-01

Resistance to oxidation and blanching is a key issue for advanced copper alloys under development for NASA's next generation of reusable launch vehicles. Candidate alloys, including dispersion-strengthened Cu-Cr-Nb, solution-strengthened Cu-Ag-Zr, and ODS Cu-Al2O3, are being evaluated for oxidation resistance by static TGA exposures in low-p(O2) and cyclic oxidation in air, and by cyclic oxidation-reduction exposures (using air for oxidation and CO/CO2 or H2/Ar for reduction) to simulate expected service environments. The test protocol and results are presented.
Photoinduced Cross-Linking of Dynamic Poly(disulfide) Films via Thiol Oxidative Coupling.

PubMed

Feillée, Noémi; Chemtob, Abraham; Ley, Christian; Croutxé-Barghorn, Céline; Allonas, Xavier; Ponche, Arnaud; Le Nouen, Didier; Majjad, Hicham; Jacomine, Léandro

2016-01-01

Initially developed as an elastomer with an excellent record of barrier and chemical resistance properties, poly(disulfide) has experienced a revival linked to the dynamic nature of the S-S covalent bond. A novel photobase-catalyzed oxidative polymerization of multifunctional thiols to poly(disulfide) network is reported. Based solely on air oxidation, the single-step process is triggered by the photodecarboxylation of a xanthone acetic acid liberating a strong bicyclic guanidine base. Starting with a 1 μm thick film based on trithiol poly(ethylene oxide) oligomer, the UV-mediated oxidation of thiols to disulfides occurs in a matter of minutes both selectively, i.e., without overoxidation, and quantitatively as assessed by a range of spectroscopic techniques. Thiolate formation and film thickness determine the reaction rates and yield. Spatial control of the photopolymerization serves to generate robust micropatterns, while the reductive cleavage of S-S bridges allows the recycling of 40% of the initial thiol groups. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Vapor phase hydrogenation of furfural over nickel mixed metal oxide catalysts derived from layered double hydroxides

DOE PAGES

Sulmonetti, Taylor P.; Pang, Simon H.; Claure, Micaela Taborga; ...

2016-03-09

The hydrogenation of furfural is investigated over various reduced nickel mixed metal oxides derived from layered double hydroxides (LDHs) containing Ni-Mg-Al and Ni-Co-Al. Upon reduction, relatively large Ni(0) domains develop in the Ni-Mg-Al catalysts, whereas in the Ni-Co-Al catalysts smaller metal particles of Ni(0) and Co(0), potentially as alloys, are formed, as evidenced by XAS, XPS, STEM and EELS. All the reduced Ni catalysts display similar selectivities towards major hydrogenation products (furfuryl alcohol and tetrahydrofurfuryl alcohol), though the side products varied with the catalyst composition. The 1.1Ni-0.8Co-Al catalyst showed the greatest activity per titrated site when compared to the othermore » catalysts, with promising activity compared to related catalysts in the literature. In conclusion, the use of base metal catalysts for hydrogenation of furanic compounds may be a promising alternative to the well-studied precious metal catalysts for making biomass-derived chemicals if catalyst selectivity can be improved in future work by alloying or tuning metal-oxide support interactions.« less

Vapor phase hydrogenation of furfural over nickel mixed metal oxide catalysts derived from layered double hydroxides

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sulmonetti, Taylor P.; Pang, Simon H.; Claure, Micaela Taborga

2016-05-01

The hydrogenation of furfural is investigated over various reduced nickel mixed metal oxides derived from layered double hydroxides (LDHs) containing Ni-Mg-Al and Ni-Co-Al. Upon reduction, relatively large Ni(0) domains develop in the Ni-Mg-Al catalysts, whereas in the Ni-Co-Al catalysts smaller metal particles of Ni(0) and Co(0), potentially as alloys, are formed, as evidenced by XAS, XPS, STEM and EELS. All the reduced Ni catalysts display similar selectivities towards major hydrogenation products (furfuryl alcohol and tetrahydrofurfuryl alcohol), though the side products varied with the catalyst composition. The 1.1Ni-0.8Co-Al catalyst showed the greatest activity per titrated site when compared to the othermore » catalysts, with promising activity compared to related catalysts in the literature. The use of base metal catalysts for hydrogenation of furanic compounds may be a promising alternative to the well-studied precious metal catalysts for making biomass-derived chemicals if catalyst selectivity can be improved in future work by alloying or tuning metal-oxide support interactions.« less
Understanding the Broad Substrate Repertoire of Nitroreductase Based on Its Kinetic Mechanism*

PubMed Central

Pitsawong, Warintra; Hoben, John P.; Miller, Anne-Frances

2014-01-01

The oxygen-insensitive nitroreductase from Enterobacter cloacae (NR) catalyzes two-electron reduction of nitroaromatics to the corresponding nitroso compounds and, subsequently, to hydroxylamine products. NR has an unusually broad substrate repertoire, which may be related to protein dynamics (flexibility) and/or a simple non-selective kinetic mechanism. To investigate the possible role of mechanism in the broad substrate repertoire of NR, the kinetics of oxidation of NR by para-nitrobenzoic acid (p-NBA) were investigated using stopped-flow techniques at 4 °C. The results revealed a hyperbolic dependence on the p-NBA concentration with a limiting rate of 1.90 ± 0.09 s−1, indicating one-step binding before the flavin oxidation step. There is no evidence for a distinct binding step in which specificity might be enforced. The reduction of p-NBA is rate-limiting in steady-state turnover (1.7 ± 0.3 s−1). The pre-steady-state reduction kinetics of NR by NADH indicate that NADH reduces the enzyme with a rate constant of 700 ± 20 s−1 and a dissociation constant of 0.51 ± 0.04 mm. Thus, we demonstrate simple transient kinetics in both the reductive and oxidative half-reactions that help to explain the broad substrate repertoire of NR. Finally, we tested the ability of NR to reduce para-hydroxylaminobenzoic acid, demonstrating that the corresponding amine does not accumulate to significant levels even under anaerobic conditions. Thus E. cloacae NR is not a good candidate for enzymatic production of aromatic amines. PMID:24706760
Continued development of abradable gas path seals. [for gas turbine engines

NASA Technical Reports Server (NTRS)

Shiembob, L. T.

1975-01-01

Major program objectives were the continued development of NiCrAlY feltmetal and honeycomb systems for knife edge seal applications in the 1144 to 1366 K temperature range, and to initiate abradable seal material evaluation for blade tip seal applications in the 1366 to 1589 K temperature range. Larger fiber size, higher density feltmetal showed greatly improved erosion resistance with a slight reduction in abradability compared to the baseline feltmetal. Pack aluminide coating of the honeycomb extended the oxidation resistance and slightly improved the abradability of this material. Evaluation through selected abradability, erosion and oxidation testing, and pertinent metallography led to selection of a plasma sprayed yttria stabilized zirconia (ZrO2)/CoCrAlY layered system as the system with the most potential to meet the 1589 K requirement for blade tip seals. This system demonstrated structural integrity, erosion resistance, and some degree of abradability.
A novel green approach for reduction of free standing graphene oxide: electrical and electronic structural investigations.

PubMed

Saravanan, K; Panigrahi, B K; Suresh, K; Sundaravel, B; Magudapathy, P; Gupta, Mukul

2018-08-24

Ion beam irradiation technique has been proposed, for efficient, fast and eco-friendly reduction of graphene oxide (GO), as an alternative to the conventional methods. 5 MeV, Au + ion beam has been used to reduce the free standing GO flake. Both electronic and nuclear energy loss mechanisms of the irradiation process play a major role in removal of oxygen moieties and recovery of graphene network. Atomic resolution scanning tunnelling microscopy analysis of the irradiated GO flake shows the characteristic honeycomb structure of graphene. X-ray absorption near edge structure analysis at C K-edge reveals that the features of the irradiated GO flake resemble the few layer graphene. Resonant Rutherford backscattering spectrometry analysis evidenced an enhanced C/O ratio of ∼23 in the irradiated GO. In situ sheet resistance measurements exhibit a sharp decrease of resistance (few 100 s of Ω) at a fluence of 6.5 × 10 14 ions cm -2 . Photoluminescence spectroscopic analysis of irradiated GO shows a sharp blue emission, while pristine GO exhibits a broad emission in the visible-near IR region. Region selective reduction, tunable electrical and optical properties by controlling C/O ratio makes ion irradiation as a versatile tool for the green reduction of GO for diverse applications.
Change of Cu+ species and synergistic effect of copper and cerium during reduction-oxidation treatment for preferential CO oxidation

NASA Astrophysics Data System (ADS)

Zhang, Hao; Zhao, Xiaozhou; Wang, Shuang; Zeng, Shanghong; Su, Haiquan

2018-05-01

The CuO-CeO2@SiO2 catalyst with flower-sphere morphology was prepared by the impregnation method and then experienced the reduction-oxidation treatment at different temperatures. The multi-technique characterization shows that the reduction-oxidation treatment can remodel CuO, improve textural and surface properties and change Cu+ content and synergistic effect of copper and cerium. The importance of this work lies in the fact that the decrease of Cu+ content and synergistic effect of copper and cerium that occurs in the reduction-oxidation process results in the decrease of catalytic activity over the CuO-CeO2@SiO2 catalyst for preferential CO oxidation. The process of reaction in rich-hydrogen streams is equivalent to a reduction procedure which decreases Cu+ content and synergistic effect of copper and cerium.
CMOS compatible electrode materials selection in oxide-based memory devices

NASA Astrophysics Data System (ADS)

Zhuo, V. Y.-Q.; Li, M.; Guo, Y.; Wang, W.; Yang, Y.; Jiang, Y.; Robertson, J.

2016-07-01

Electrode materials selection guidelines for oxide-based memory devices are constructed from the combined knowledge of observed device operation characteristics, ab-initio calculations, and nano-material characterization. It is demonstrated that changing the top electrode material from Ge to Cr to Ta in the Ta2O5-based memory devices resulted in a reduction of the operation voltages and current. Energy Dispersed X-ray (EDX) Spectrometer analysis clearly shows that the different top electrode materials scavenge oxygen ions from the Ta2O5 memory layer at various degrees, leading to different oxygen vacancy concentrations within the Ta2O5, thus the observed trends in the device performance. Replacing the Pt bottom electrode material with CMOS compatible materials (Ru and Ir) further reduces the power consumption and can be attributed to the modification of the Schottky barrier height and oxygen vacancy concentration at the electrode/oxide interface. Both trends in the device performance and EDX results are corroborated by the ab-initio calculations which reveal that the electrode material tunes the oxygen vacancy concentration via the oxygen chemical potential and defect formation energy. This experimental-theoretical approach strongly suggests that the proper selection of CMOS compatible electrode materials will create the critical oxygen vacancy concentration to attain low power memory performance.
Effect of selective versus non-selective cyclooxygenase inhibitors on ischemia-reperfusion-induced hepatic injury in rats.

PubMed

Abdel-Gaber, Seham A; Ibrahim, Mohamed A; Amin, Entesar F; Ibrahim, Salwa A; Mohammed, Rehab K; Abdelrahman, Aly M

2015-08-01

Ischemia-reperfusion (IR) injury represents an important pathological process of liver injury during major hepatic surgery. The role of cyclooxygenase (COX) enzymes in the pathogenesis of ischemia-reperfusion (IR)-induced liver injury is not clear. This study investigated the effect of a selective COX-2 inhibitor, celecoxib, versus non-selective, indomethacin, on hepatic IR injury in rats. Hepatic IR was induced in adult male rats. The animals were divided into 4 groups: normal control (sham group), IR non-treated group; IR-indomethacin-treated group; and IR-celecoxib-treated group. Liver injury was evaluated by serum alanine aminotransferase (ALT) and a histopathological examination of liver tissues. Hepatic tissue content of oxidative stress parameters glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase, malondialdehyde (MDA), nitric oxide (NO) and the inflammatory marker, tumor necrosis factor-alpha, (TNF-α) were measured. Moreover, the immunohistochemical detection of endothelial NO synthase (eNOS), inducible NO synthase (iNOS), and caspase-3 in the hepatic tissue was performed. Celecoxib, but not indomethacin, significantly attenuated hepatic IR injury as evidenced by reduction in serum ALT as well as by improvement in the histopathological scoring. Such effect was associated with attenuation in oxidative stress and TNF-α, along with modulation of immunohistochemical expression of eNOS, iNOS and caspase-3 in the hepatic tissue. The present study concluded that selective COX-2 inhibition (but not non-selective), is hepatoprotective against liver IR injury; indicating a differential role of COX-1 versus COX-2. Modulation of iNOS, eNOS and caspase-3 might participate in the protective effect of selective COX-2-inhibitors. Copyright © 2015 Elsevier Inc. All rights reserved.
Formation of NO + and its possible roles during the selective catalytic reduction of NOx with NH 3 on Cu-CHA catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Hai-Ying; Kollar, Marton; Wei, Zhehao

The catalytic activities of small-pore Cu-CHA and large-pore Cu-BEA catalysts for the selective catalytic reduction of NO with NH 3 were measured at a very high flow rate. Cu-CHA clearly exhibited much higher intrinsic SCR activity and lower N 2O selectivity. In situ DRIFT spectra were recorded during the adsorption and desorption following NO and (NO+O 2) exposure to fully oxidized samples in a flow cell. The results are in agreement with what we have reported previously based on in situ transmission IR studies of partially reduced samples. Both suggest that different SCR reaction pathways might exist on these twomore » catalysts and that NO + could be an important reaction intermediate for Cu-CHA. Detailed IR studies with various isotopically labeled gas mixtures of (NO+O 2), ( 15NO+O 2), (NO+ 18O 2) and ( 15N 18O+O 2) were conducted to understand the origin of the surface adsorption complexes on Cu-CHA. Formation of NO + was not the consequence of a simple charge transfer reaction, NO+Cu 2+=NO+ + Cu +. Instead, O 2 was found to be essential in changing the oxidation state of N from +2 to +3 although it did not participate in new N$-$O bond formation. In conclusion, the majority of the adsorbed NO + maintained its isotopic origin of the feed gas.« less
Copper nanoparticle ensembles for selective electroreduction of CO 2 to C 2-C 3 products

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kim, Dohyung; Kley, Christopher S.; Li, Yifan

Direct conversion of carbon dioxide to multicarbon products remains as a grand challenge in electrochemical CO 2 reduction. Various forms of oxidized copper have been demonstrated as electrocatalysts that still require large overpotentials. Here in this paper, we show that an ensemble of Cu nanoparticles (NPs) enables selective formation of C 2–C 3 products at low overpotentials. Densely packed Cu NP ensembles underwent structural transformation during electrolysis into electrocatalytically active cube-like particles intermixed with smaller nanoparticles. Ethylene, ethanol, and n-propanol are the major C 2–C 3 products with onset potential at -0.53 V (vs. reversible hydrogen electrode, RHE) and Cmore » 2–C 3 faradaic efficiency (FE) reaching 50% at only -0.75 V. Thus, the catalyst exhibits selective generation of C 2–C 3 hydrocarbons and oxygenates at considerably lowered overpotentials in neutral pH aqueous media. In addition, this approach suggests new opportunities in realizing multicarbon product formation from CO 2, where the majority of efforts has been to use oxidized copper-based materials. Robust catalytic performance is demonstrated by 10 h of stable operation with C 2–C 3 current density 10 mA/cm 2 (at -0.75 V), rendering it attractive for solar-to-fuel applications. Lastly, Tafel analysis suggests reductive CO coupling as a rate determining step for C 2 products, while n-propanol (C 3) production seems to have a discrete pathway.« less
Copper nanoparticle ensembles for selective electroreduction of CO 2 to C 2-C 3 products

DOE PAGES

Kim, Dohyung; Kley, Christopher S.; Li, Yifan; ...

2017-09-18

Direct conversion of carbon dioxide to multicarbon products remains as a grand challenge in electrochemical CO 2 reduction. Various forms of oxidized copper have been demonstrated as electrocatalysts that still require large overpotentials. Here in this paper, we show that an ensemble of Cu nanoparticles (NPs) enables selective formation of C 2–C 3 products at low overpotentials. Densely packed Cu NP ensembles underwent structural transformation during electrolysis into electrocatalytically active cube-like particles intermixed with smaller nanoparticles. Ethylene, ethanol, and n-propanol are the major C 2–C 3 products with onset potential at -0.53 V (vs. reversible hydrogen electrode, RHE) and Cmore » 2–C 3 faradaic efficiency (FE) reaching 50% at only -0.75 V. Thus, the catalyst exhibits selective generation of C 2–C 3 hydrocarbons and oxygenates at considerably lowered overpotentials in neutral pH aqueous media. In addition, this approach suggests new opportunities in realizing multicarbon product formation from CO 2, where the majority of efforts has been to use oxidized copper-based materials. Robust catalytic performance is demonstrated by 10 h of stable operation with C 2–C 3 current density 10 mA/cm 2 (at -0.75 V), rendering it attractive for solar-to-fuel applications. Lastly, Tafel analysis suggests reductive CO coupling as a rate determining step for C 2 products, while n-propanol (C 3) production seems to have a discrete pathway.« less
Formation of NO + and its possible roles during the selective catalytic reduction of NOx with NH 3 on Cu-CHA catalysts

DOE PAGES

Chen, Hai-Ying; Kollar, Marton; Wei, Zhehao; ...

2017-12-21

The catalytic activities of small-pore Cu-CHA and large-pore Cu-BEA catalysts for the selective catalytic reduction of NO with NH 3 were measured at a very high flow rate. Cu-CHA clearly exhibited much higher intrinsic SCR activity and lower N 2O selectivity. In situ DRIFT spectra were recorded during the adsorption and desorption following NO and (NO+O 2) exposure to fully oxidized samples in a flow cell. The results are in agreement with what we have reported previously based on in situ transmission IR studies of partially reduced samples. Both suggest that different SCR reaction pathways might exist on these twomore » catalysts and that NO + could be an important reaction intermediate for Cu-CHA. Detailed IR studies with various isotopically labeled gas mixtures of (NO+O 2), ( 15NO+O 2), (NO+ 18O 2) and ( 15N 18O+O 2) were conducted to understand the origin of the surface adsorption complexes on Cu-CHA. Formation of NO + was not the consequence of a simple charge transfer reaction, NO+Cu 2+=NO+ + Cu +. Instead, O 2 was found to be essential in changing the oxidation state of N from +2 to +3 although it did not participate in new N$-$O bond formation. In conclusion, the majority of the adsorbed NO + maintained its isotopic origin of the feed gas.« less
CuO based catalysts on modified acidic silica supports tested in the de-NOx reduction.

PubMed

Bennici, Simona; Gervasini, Antonella; Lazzarin, Marta; Ragaini, Vittorio

2005-03-01

A series of dispersed CuO catalysts supported on modified silica supports with Al2O3 (SA), TiO2 (ST), and ZrO2 (SZ) were prepared optimising the adsorption method of copper deposition assisted by ultrasound treatment, already reported in a previous paper (S. Bennici, A. Gervasini, V. Ragaini, Ultrason. Sonochem. 10 (2003) 61). The obtained catalysts were characterized in their bulk (atomic absorption, X-ray diffraction, temperature programmed reduction) and surface (N2 adsorption, X-ray photoelectron spectroscopy, scanning electron microscopy) properties. The morphology of the finished materials was not deeply modified compared with that of the relevant supports. The employed complemented techniques evidenced a well dispersed CuO phase with a copper-support interaction on the most acidic supports (SA and SZ). The catalyst performances were studied in the reaction of selective catalytic reduction of NOx with ethene in oxidizing atmosphere in a flow apparatus under variable times (0.360-0.072 s) and temperatures (200-450 degrees C). The catalysts prepared on the most acidic supports (SA and SZ) were the most active and selective towards N2 formation. They showed a particular interesting activity in the reaction of NO2 reduction besides that of NO reduction.
[Ecological security of wastewater treatment processes: a review].

PubMed

Yang, Sai; Hua, Tao

2013-05-01

Though the regular indicators of wastewater after treatment can meet the discharge requirements and reuse standards, it doesn't mean the effluent is harmless. From the sustainable point of view, to ensure the ecological and human security, comprehensive toxicity should be considered when discharge standards are set up. In order to improve the ecological security of wastewater treatment processes, toxicity reduction should be considered when selecting and optimizing the treatment processes. This paper reviewed the researches on the ecological security of wastewater treatment processes, with the focus on the purposes of various treatment processes, including the processes for special wastewater treatment, wastewater reuse, and for the safety of receiving waters. Conventional biological treatment combined with advanced oxidation technologies can enhance the toxicity reduction on the base of pollutants removal, which is worthy of further study. For the process aimed at wastewater reuse, the integration of different process units can complement the advantages of both conventional pollutants removal and toxicity reduction. For the process aimed at ecological security of receiving waters, the emphasis should be put on the toxicity reduction optimization of process parameters and process unit selection. Some suggestions for the problems in the current research and future research directions were put forward.
Supported Pd nanoclusters with enhanced hydrogen spillover for NOx removal via H2-SCR: the elimination of "volcano-type" behaviour.

PubMed

Peng, Zhezhe; Li, Zongyuan; Liu, Yun-Quan; Yan, Shuai; Tong, Jianing; Wang, Duo; Ye, Yueyuan; Li, Shuirong

2017-05-30

A rational design of a Pd catalyst with highly dispersed Pd nanoclusters on an Al doped ceria-based oxide for low temperature selective catalytic reduction of NO x by hydrogen with excess O 2 was achieved. The supported Pd nanocluster shows a high hydrogen spillover ability and a NO x conversion of >84% within 100-300 °C.
Effect of oxidation and catalytic reduction of trace organic contaminants on their activated carbon adsorption.

PubMed

Schoutteten, Klaas V K M; Hennebel, Tom; Dheere, Ellen; Bertelkamp, Cheryl; De Ridder, David J; Maes, Synthia; Chys, Michael; Van Hulle, Stijn W H; Vanden Bussche, Julie; Vanhaecke, Lynn; Verliefde, Arne R D

2016-12-01

The combination of ozonation and activated carbon (AC) adsorption is an established technology for removal of trace organic contaminants (TrOCs). In contrast to oxidation, reduction of TrOCs has recently gained attention as well, however less attention has gone to the combination of reduction with AC adsorption. In addition, no literature has compared the removal behavior of reduction vs. ozonation by-products by AC. In this study, the effect of pre-ozonation vs pre-catalytic reduction on the AC adsorption efficiency of five TrOCs and their by-products was compared. All compounds were susceptible to oxidation and reduction, however the catalytic reductive treatment proved to be a slower reaction than ozonation. New oxidation products were identified for dinoseb and new reduction products were identified for carbamazepine, bromoxynil and dinoseb. In terms of compatibility with AC adsorption, the influence of the oxidative and reductive pretreatments proved to be compound dependent. Oxidation products of bromoxynil and diatrizoic acid adsorbed better than their parent TrOCs, but oxidation products of atrazine, carbamazepine and dinoseb showed a decreased adsorption. The reductive pre-treatment showed an enhanced AC adsorption for dinoseb and a major enhancement for diatrizoic acid. For atrazine and bromoxynil, no clear influence on adsorption was noted, while for carbamazepine, the reductive pretreatment resulted in a decreased AC affinity. It may thus be concluded that when targeting mixtures of TrOCs, a trade-off will undoubtedly have to be made towards overall reactivity and removal of the different constituents, since no single treatment proves to be superior to the other. Copyright © 2016 Elsevier Ltd. All rights reserved.
Complexation facilitated reduction of aromatic N-oxides by aqueous Fe(II)-tiron complex: reaction kinetics and mechanisms.

PubMed

Chen, Yiling; Zhang, Huichun

2013-10-01

Rapid reduction of carbadox (CDX), olaquindox and several other aromatic N-oxides were investigated in aqueous solution containing Fe(II) and tiron. Consistent with previous work, the 1:2 Fe(II)-tiron complex, FeL2(6-), is the dominant reactive species as its concentration linearly correlates with the observed rate constant kobs under various conditions. The N-oxides without any side chains were much less reactive, suggesting direct reduction of the N-oxides is slow. UV-vis spectra suggest FeL2(6-) likely forms 5- or 7-membered rings with CDX and olaquindox through the N and O atoms on the side chain. The formed inner-sphere complexes significantly facilitated electron transfer from FeL2(6-) to the N-oxides. Reduction products of the N-oxides were identified by HPLC/QToF-MS to be the deoxygenated analogs. QSAR analysis indicated neither the first electron transfer nor N-O bond cleavage is the rate-limiting step. Calculations of the atomic spin densities of the anionic N-oxides confirmed the extensive delocalization between the aromatic ring and the side chain, suggesting complex formation can significantly affect the reduction kinetics. Our results suggest the complexation facilitated N-oxide reduction by Fe(II)-tiron involves a free radical mechanism, and the subsequent deoxygenation might also benefit from the weak complexation of Fe(II) with the N-oxide O atom.
Antioxidant enzymes as redox-based biomarkers: a brief review.

PubMed

Yang, Hee-Young; Lee, Tae-Hoon

2015-04-01

The field of redox proteomics focuses to a large extent on analyzing cysteine oxidation in proteins under different experimental conditions and states of diseases. The identification and localization of oxidized cysteines within the cellular milieu is critical for understanding the redox regulation of proteins under physiological and pathophysiological conditions, and it will in turn provide important information that are potentially useful for the development of novel strategies in the treatment and prevention of diseases associated with oxidative stress. Antioxidant enzymes that catalyze oxidation/reduction processes are able to serve as redox biomarkers in various human diseases, and they are key regulators controlling the redox state of functional proteins. Redox regulators with antioxidant properties related to active mediators, cellular organelles, and the surrounding environments are all connected within a network and are involved in diseases related to redox imbalance including cancer, ischemia/reperfusion injury, neurodegenerative diseases, as well as normal aging. In this review, we will briefly look at the selected aspects of oxidative thiol modification in antioxidant enzymes and thiol oxidation in proteins affected by redox control of antioxidant enzymes and their relation to disease.
Inverted bulk-heterojunction organic solar cells with the transfer-printed anodes and low-temperature-processed ultrathin buffer layers

NASA Astrophysics Data System (ADS)

Itoh, Eiji; Sakai, Shota; Fukuda, Katsutoshi

2018-03-01

We studied the effects of a hole buffer layer [molybdenum oxide (MoO3) and natural copper oxide layer] and a low-temperature-processed electron buffer layer on the performance of inverted bulk-heterojunction organic solar cells in a device consisting of indium-tin oxide (ITO)/poly(ethylene imine) (PEI)/titanium oxide nanosheet (TiO-NS)/poly(3-hexylthiopnehe) (P3HT):phenyl-C61-butyric acid methylester (PCBM)/oxide/anode (Ag or Cu). The insertion of ultrathin TiO-NS (˜1 nm) and oxide hole buffer layers improved the open circuit voltage V OC, fill factor, and rectification properties owing to the effective hole blocking and electron transport properties of ultrathin TiO-NS, and to the enhanced work function difference between TiO-NS and the oxide hole buffer layer. The insertion of the TiO-NS contributed to the reduction in the potential barrier at the ITO/PEI/TiO-NS/active layer interface for electrons, and the insertion of the oxide hole buffer layer contributed to the reduction in the potential barrier for holes. The marked increase in the capacitance under positive biasing in the capacitance-voltage characteristics revealed that the combination of TiO-NS and MoO3 buffer layers contributes to the selective transport of electrons and holes, and blocks counter carriers at the active layer/oxide interface. The natural oxide layer of the copper electrode also acts as a hole buffer layer owing to the increase in the work function of the Cu surface in the inverted cells. The performance of the cell with evaporated MoO3 and Cu layers that were transfer-printed to the active layer was almost comparable to that of the cell with MoO3 and Ag layers directly evaporated onto the active layer. We also demonstrated comparable device performance in the cell with all-printed MoO3 and low-temperature-processed silver nanoparticles as an anode.
Magnesiothermic reduction for direct synthesis of Ti-Nb alloy at 1073 K (800 °C)

NASA Astrophysics Data System (ADS)

Choi, Kyunsuk; Lee, Kwang Hee; Ali, Basit; Choi, Sang-Hoon; Park, Kyoung-Tae; Sohn, Il

2017-09-01

Direct fabrication of titanium (Ti) and niobium (Nb) alloys by direct magnesiothermic reduction from the respective initial metal oxides and complex oxides has been studied. TiO2, Nb2O5, and complex TiNb2O7 oxides were used as raw materials with Mg used as a reductant. To ensure a high chemical potential of the reactants to drive the spontaneous magnesiothermic reduction of the oxide mixtures, excess Mg five times higher than the required stoichiometric molar ratio was added. Samples were heated in a glove box under recycled and purified Ar atmosphere at 1073 K (800 °C) for 10 h. After the reduction of TiO2, intermediate oxide phases of Ti6O could still be observed, but reduction of Nb2O5 and TiNb2O7 showed metallic Nb and Ti-Nb to be present with negligible oxides according to the scanning electron microscope-energy dispersive spectroscopy and x ray diffraction analysis. This indicated that direct fabrication of Ti-Nb alloys through a complex TiNb2O7 oxide is possible and can be more efficient than alloying pure metallic elements of Ti and Nb.
A universal entropy-driven mechanism for thioredoxin–target recognition

PubMed Central

Palde, Prakash B.; Carroll, Kate S.

2015-01-01

Cysteine residues in cytosolic proteins are maintained in their reduced state, but can undergo oxidation owing to posttranslational modification during redox signaling or under conditions of oxidative stress. In large part, the reduction of oxidized protein cysteines is mediated by a small 12-kDa thiol oxidoreductase, thioredoxin (Trx). Trx provides reducing equivalents for central metabolic enzymes and is implicated in redox regulation of a wide number of target proteins, including transcription factors. Despite its importance in cellular redox homeostasis, the precise mechanism by which Trx recognizes target proteins, especially in the absence of any apparent signature binding sequence or motif, remains unknown. Knowledge of the forces associated with the molecular recognition that governs Trx–protein interactions is fundamental to our understanding of target specificity. To gain insight into Trx–target recognition, we have thermodynamically characterized the noncovalent interactions between Trx and target proteins before S-S reduction using isothermal titration calorimetry (ITC). Our findings indicate that Trx recognizes the oxidized form of its target proteins with exquisite selectivity, compared with their reduced counterparts. Furthermore, we show that recognition is dependent on the conformational restriction inherent to oxidized targets. Significantly, the thermodynamic signatures for multiple Trx targets reveal favorable entropic contributions as the major recognition force dictating these protein–protein interactions. Taken together, our data afford significant new insight into the molecular forces responsible for Trx–target recognition and should aid the design of new strategies for thiol oxidoreductase inhibition. PMID:26080424

Growth and surface modification of LaFeO3 thin films induced by reductive annealing

NASA Astrophysics Data System (ADS)

Flynn, Brendan T.; Zhang, Kelvin H. L.; Shutthanandan, Vaithiyalingam; Varga, Tamas; Colby, Robert J.; Oleksak, Richard P.; Manandhar, Sandeep; Engelhard, Mark H.; Chambers, Scott A.; Henderson, Michael A.; Herman, Gregory S.; Thevuthasan, Suntharampillai

2015-03-01

The mixed electronic and ionic conductivity of perovskite oxides has enabled their use in diverse applications such as automotive exhaust catalysts, solid oxide fuel cell cathodes, and visible light photocatalysts. The redox chemistry at the surface of perovskite oxides is largely dependent on the oxidation state of the metal cations as well as the oxide surface stoichiometry. In this study, LaFeO3 (LFO) thin films grown on yttria-stabilized zirconia (YSZ) was characterized using both bulk and surface sensitive techniques. A combination of in situ reflection high-energy electron diffraction (RHEED), X-ray diffraction (XRD), and Rutherford backscattering spectrometry (RBS) demonstrated that the film is primarily textured in the [1 0 0] direction and is stoichiometric. High-resolution transmission electron microscopy measurements show regions that are dominated by [1 0 0] oriented LFO grains that are oriented with respect to the substrates lattice. However, selected regions of the film show multiple domains of grains that are not [1 0 0] oriented. The film was annealed in an ultra-high vacuum chamber to simulate reducing conditions and studied by angle-resolved X-ray photoelectron spectroscopy (XPS). Iron was found to exist as Fe(0), Fe(II), and Fe(III) depending on the annealing conditions and the depth within the film. A decrease in the concentration of surface oxygen species was correlated with iron reduction. These results should help guide and enhance the design of LFO materials for catalytic applications.
Oxidative stress, redox stress or redox success?

PubMed

Gutteridge, John M C; Halliwell, Barry

2018-05-09

The first life forms evolved in a highly reducing environment. This reduced state is still carried by cells today, which makes the concept of "reductive stress" somewhat redundant. When oxygen became abundant on the Earth, due to the evolution of photosynthesis, life forms had to adapt or become extinct. Living organisms did adapt, proliferated and an explosion of new life forms resulted, using reactive oxygen species (ROS) to drive their evolution. Adaptation to oxygen and its reduction intermediates necessitated the simultaneous evolution of select antioxidant defences, carefully regulated to allow ROS to perform their major roles. Clearly this "oxidative stress" did not cause a major problem to the evolution of complex life forms. Why not? Iron and oxygen share a close relationship in aerobic evolution. Iron is used in proteins to transport oxygen, promote electron transfers, and catalyse chemical reactions. In all of these functions, iron is carefully sequestered within proteins and restricted from reacting with ROS, this sequestration being one of our major antioxidant defences. Iron was abundant to life forms before the appearance of oxygen. However, oxygen caused its oxidative precipitation from solution and thereby decreased its bioavailability and thus the risk of iron-dependent oxidative damage. Micro-organisms had to adapt and develop strategies involving siderophores to acquire iron from the environment and eventually their host. This battle for iron between bacteria and animal hosts continues today, and is a much greater daily threat to our survival than "oxidative stress" and "redox stress". Copyright © 2018. Published by Elsevier Inc.
Effects of Low-temperature Pre-oxidation on the Titanomagnetite Ore Structure and Reduction Behaviors in a Fluidized Bed

NASA Astrophysics Data System (ADS)

Adetoro, Ajala Adewole; Sun, Haoyan; He, Shengyi; Zhu, Qingshan; Li, Hongzhong

2018-04-01

With respect to high efficient utilization of low-grade iron ore resource, the behavior of low-temperature "973 K to 1123 K (700 °C to 850 °C)" oxidation, on the phase transition of SA TTM ore (South African titanomagnetite), and its effect on subsequent reduction was investigated. The results showed that hematite and rutile are the oxidation product below 1048 K (775 °C), while pseudobrookite is the stable phase above 1073 K (800 °C). With the increase in temperature and oxidation time, there is a competitive relationship between the amount of hematite and pseudobrookite generated. The reduction efficiency of SA TTM was significantly improved by oxidation pretreatment, primarily due to the dissociation of titania-ferrous oxides to more easily reducible hematite. But the generation of pseudobrookite phase decreases the amount of free hematite available for reduction, which weakens the improvement effect of pre-oxidation. The equilibrium relationship between the metallization degree and the gas reduction potential for TTM ore with pre-oxidation treatment has been built. Finally, the reduction metallization degree for the first and second step can be improved averagely by 16.67 and 3.45 pct, respectively, for sample pre-oxidized at 1098 K (825 °C) for 15 and 90 minutes, while 26.96 and 7.4 pct, improvement is achieved for sample pre-oxidized at a lower temperature of 1048 K (775 °C) for 120 minutes.
Oxidation-reduction potential and lipid oxidation in ready-to-eat blue mussels in red sauce: criteria for package design.

PubMed

Bhunia, Kanishka; Ovissipour, Mahmoudreza; Rasco, Barbara; Tang, Juming; Sablani, Shyam S

2017-01-01

Ready-to-eat in-package pasteurized blue mussels in red sauce requires refrigerated storage or in combination with an aerobic environment to prevent the growth of anaerobes. A low barrier packaging may create an aerobic environment; however, it causes lipid oxidation in mussels. Thus, evaluation of the oxidation-reduction potential (Eh) (aerobic/anaerobic nature of food) and lipid oxidation is essential. Three packaging materials with oxygen transmission rate (OTR) of 62 (F-62), 40 (F-40) and 3 (F-3) cm 3 m -2 day -1 were selected for this study. Lipid oxidation was measured by color changes in thiobarbituric acid reactive substances (TBARS) at 532 nm (TBARS@532) and 450 nm (TBARS@450). Significantly higher (P < 0.05) TBARS@532 was found in mussels packaged in higher OTR film. TBARS@450 in mussels packaged with F-62 and F-40 gradually increased during refrigerated storage (3.5 ± 0.5 °C), but remained constant after 20 days of storage for mussels packaged with F-3. The Eh of pasteurized sauce was not significantly affected (P > 0.05) by OTR and remained negative (< -80 mV) during storage. Negative Eh values can support the growth of anaerobes such as Clostridium botulinum. The headspace oxygen concentration was reduced by about 50% from its initial value during pasteurization, and then further declined during storage. The headspace oxygen concentration was higher in trays packaged with higher OTR film. Mussels packed with high OTR film showed higher lipid oxidation, indicating that high barrier film is required for packaging of mussels. Pasteurized mussels must be kept in refrigerated storage to prevent growth of anaerobic proteolytic C. botulinum spores under temperature abuse. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.
Genome Scale Mutational Analysis of Geobacter sulfurreducens Reveals Distinct Molecular Mechanisms for Respiration and Sensing of Poised Electrodes versus Fe(III) Oxides.

PubMed

Chan, Chi Ho; Levar, Caleb E; Jiménez-Otero, Fernanda; Bond, Daniel R

2017-10-01

Geobacter sulfurreducens generates electrical current by coupling intracellular oxidation of organic acids to the reduction of proteins on the cell surface that are able to interface with electrodes. This ability is attributed to the bacterium's capacity to respire other extracellular electron acceptors that require contact, such as insoluble metal oxides. To directly investigate the genetic basis of electrode-based respiration, we constructed Geobacter sulfurreducens transposon-insertion sequencing (Tn-Seq) libraries for growth, with soluble fumarate or an electrode as the electron acceptor. Libraries with >33,000 unique insertions and an average of 9 insertions/kb allowed an assessment of each gene's fitness in a single experiment. Mutations in 1,214 different genomic features impaired growth with fumarate, and the significance of 270 genes unresolved by annotation due to the presence of one or more functional homologs was determined. Tn-Seq analysis of -0.1 V versus standard hydrogen electrode (SHE) electrode-grown cells identified mutations in a subset of genes encoding cytochromes, processing systems for proline-rich proteins, sensory networks, extracellular structures, polysaccharides, and metabolic enzymes that caused at least a 50% reduction in apparent growth rate. Scarless deletion mutants of select genes identified via Tn-Seq revealed a new putative porin-cytochrome conduit complex ( extABCD ) crucial for growth with electrodes, which was not required for Fe(III) oxide reduction. In addition, four mutants lacking components of a putative methyl-accepting chemotaxis-cyclic dinucleotide sensing network ( esnABCD ) were defective in electrode colonization but grew normally with Fe(III) oxides. These results suggest that G. sulfurreducens possesses distinct mechanisms for recognition, colonization, and reduction of electrodes compared to Fe(III) oxides. IMPORTANCE Since metal oxide electron acceptors are insoluble, one hypothesis is that cells sense and reduce metals using the same molecular mechanisms used to form biofilms on electrodes and produce electricity. However, by simultaneously comparing thousands of Geobacter sulfurreducens transposon mutants undergoing electrode-dependent respiration, we discovered new cytochromes and chemosensory proteins supporting growth with electrodes that are not required for metal respiration. This supports an emerging model where G. sulfurreducens recognizes surfaces and forms conductive biofilms using mechanisms distinct from those used for growth with metal oxides. These findings provide a possible explanation for studies that correlate electricity generation with syntrophic interspecies electron transfer by Geobacter and reveal many previously unrecognized targets for engineering this useful capability in other organisms. Copyright © 2017 Chan et al.
Direct chemical reduction of neptunium oxide to neptunium metal using calcium and calcium chloride

DOE PAGES

Squires, Leah N.; Lessing, Paul

2016-01-13

A process of direct reduction of neptunium oxide to neptunium metal using calcium metal as the reducing agent is discussed. After reduction of the oxide to metal, the metal is separated by density from the other components of the reaction mixture and can easily removed upon cooling. Furthermore, the direct reduction technique consistently produces high purity (98%–99% pure) neptunium metal.
Selective Extraction of Uranium from Liquid or Supercritical Carbon Dioxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farawila, Anne F.; O'Hara, Matthew J.; Wai, Chien M.

2012-07-31

Current liquid-liquid extraction processes used in recycling irradiated nuclear fuel rely on (1) strong nitric acid to dissolve uranium oxide fuel, and (2) the use of aliphatic hydrocarbons as a diluent in formulating the solvent used to extract uranium. The nitric acid dissolution process is not selective. It dissolves virtually the entire fuel meat which complicates the uranium extraction process. In addition, a solvent washing process is used to remove TBP degradation products, which adds complexity to the recycling plant and increases the overall plant footprint and cost. A liquid or supercritical carbon dioxide (l/sc -CO2) system was designed tomore » mitigate these problems. Indeed, TBP nitric acid complexes are highly soluble in l/sc -CO2 and are capable of extracting uranium directly from UO2, UO3 and U3O8 powders. This eliminates the need for total acid dissolution of the irradiated fuel. Furthermore, since CO2 is easily recycled by evaporation at room temperature and pressure, it eliminates the complex solvent washing process. In this report, we demonstrate: (1) A reprocessing scheme starting with the selective extraction of uranium from solid uranium oxides into a TBP-HNO3 loaded Sc-CO2 phase, (2) Back extraction of uranium into an aqueous phase, and (3) Conversion of recovered purified uranium into uranium oxide. The purified uranium product from step 3 can be disposed of as low level waste, or mixed with enriched uranium for use in a reactor for another fuel cycle. After an introduction on the concept and properties of supercritical fluids, we first report the characterization of the different oxides used for this project. Our extraction system and our online monitoring capability using UV-Vis absorbance spectroscopy directly in sc-CO2 is then presented. Next, the uranium extraction efficiencies and kinetics is demonstrated for different oxides and under different physical and chemical conditions: l/sc -CO2 pressure and temperature, TBP/HNO3 complex used, reductant or complexant used for selectivity, and ionic liquids used as supportive media. To complete the extraction and recovery cycle, we then demonstrate uranium back extraction from the TBP loaded sc-CO2 phase into an aqueous phase and the characterization of the uranium complex formed at the end of this process. Another aspect of this project was to limit proliferation risks by either co-extracting uranium and plutonium, or by leaving plutonium behind by selectively extracting uranium. We report that the former is easily achieved, since plutonium is in the tetravalent or hexavalent oxidation state in the oxidizing environment created by the TBP-nitric acid complex, and is therefore co-extracted. The latter is more challenging, as a reductant or complexant to plutonium has to be used to selectively extract uranium. After undertaking experiments on different reducing or complexing systems (e.g., AcetoHydroxamic Acid (AHA), Fe(II), ascorbic acid), oxalic acid was chosen as it can complex tetravalent actinides (Pu, Np, Th) in the aqueous phase while allowing the extraction of hexavalent uranium in the sc-CO2 phase. Finally, we show results using an alternative media to commonly used aqueous phases: ionic liquids. We show the dissolution of uranium in ionic liquids and its extraction using sc-CO2 with and without the presence of AHA. The possible separation of trivalent actinides from uranium is also demonstrated in ionic liquids using neodymium as a surrogate and diglycolamides as the extractant.« less
Iron oxides stimulate sulfate-driven anaerobic methane oxidation in seeps

DOE PAGES

Sivan, Orit; Antler, Gilad; Turchyn, Alexandra V.; ...

2014-09-22

Seep sediments are dominated by intensive microbial sulfate reduction coupled to the anaerobic oxidation of methane (AOM). Through geochemical measurements of incubation experiments with methane seep sediments collected from Hydrate Ridge, we provide insight into the role of iron oxides in sulfate-driven AOM. Seep sediments incubated with 13C-labeled methane showed co-occurring sulfate reduction, AOM, and methanogenesis. The isotope fractionation factors for sulfur and oxygen isotopes in sulfate were about 40‰ and 22‰, respectively, reinforcing the difference between microbial sulfate reduction in methane seeps versus other sedimentary environments (for example, sulfur isotope fractionation above 60‰ in sulfate reduction coupled to organicmore » carbon oxidation or in diffusive sedimentary sulfate–methane transition zone). The addition of hematite to these microcosm experiments resulted in significant microbial iron reduction as well as enhancing sulfate-driven AOM. The magnitude of the isotope fractionation of sulfur and oxygen isotopes in sulfate from these incubations was lowered by about 50%, indicating the involvement of iron oxides during sulfate reduction in methane seeps. The similar relative change between the oxygen versus sulfur isotopes of sulfate in all experiments (with and without hematite addition) suggests that oxidized forms of iron, naturally present in the sediment incubations, were involved in sulfate reduction, with hematite addition increasing the sulfate recycling or the activity of sulfur-cycling microorganisms by about 40%. Furthermore, these results highlight a role for natural iron oxides during bacterial sulfate reduction in methane seeps not only as nutrient but also as stimulator of sulfur recycling.« less
The Reduction of Aqueous Metal Species on the Surfaces of Fe(II)-Containing Oxides: The Role of Surface Passivation

USGS Publications Warehouse

White, A.F.; Peterson, M.L.

1998-01-01

The reduction of aqueous transition metal species at the surfaces of Fe(II)- containing oxides has important ramifications in predicting the transport behavior in ground water aquifers. Experimental studies using mineral suspensions and electrodes demonstrate that structural Fe(II) heterogeneously reduces aqueous ferric, cupric, vanadate and chromate ions on magnetite and ilmenite surfaces. The rates of metal reduction on natural oxides is strongly dependent on the extent of surface passivation and redox conditions in the weathering environment. Synchrotron studies show that surface oxidation of Fe(II)-containing oxide minerals decreases their capacity for Cr(VI) reduction at hazardous waste disposal sites.
One-pot synthesis of hierarchical FeZSM-5 zeolites from natural aluminosilicates for selective catalytic reduction of NO by NH3

PubMed Central

Yue, Yuanyuan; Liu, Haiyan; Yuan, Pei; Yu, Chengzhong; Bao, Xiaojun

2015-01-01

Iron-modified ZSM-5 zeolites (FeZSM-5s) have been considered to be a promising catalyst system to reduce nitrogen oxide emissions, one of the most important global environmental issues, but their synthesis faces enormous economic and environmental challenges. Herein we report a cheap and green strategy to fabricate hierarchical FeZSM-5 zeolites from natural aluminosilicate minerals via a nanoscale depolymerization-reorganization method. Our strategy is featured by neither using any aluminum-, silicon-, or iron-containing inorganic chemical nor involving any mesoscale template and any post-synthetic modification. Compared with the conventional FeZSM-5 synthesized from inorganic chemicals with the similar Fe content, the resulting hierarchical FeZSM-5 with highly-dispersed iron species showed superior catalytic activity in the selective catalytic reduction of NO by NH3. PMID:25791958
One-pot low-temperature green synthesis of magnetic graphene nanocomposite for the selective reduction of nitrobenzene

NASA Astrophysics Data System (ADS)

Haridas, Vijayasree; Sugunan, Sankaran; Narayanan, Binitha N.

2018-06-01

In the present study, a green one-pot low-temperature method is adopted for the synthesis of a novel magnetic graphene nanocomposite catalyst. Graphene preparation is performed without employing any oxidizing agents or corrosive chemicals, under mild sonication in isopropyl alcohol - water mixture. Monolayered nanoplatelets of graphene are obtained in the green solvent mixture and the composite material is found to be ferromagnetic in nature, obvious from the vibrating sample magnetometric measurements. Fe in the nanocomposite exists in two different forms i.e., α-Fe2O3 and α-FeOOH, as evident from the material characterization results. The graphene nanocomposite is found to be highly efficient in the selective reduction of nitrobenzene to aniline under solvent free reaction conditions and magnetic separation of this fine nanomaterial from the reaction mixture is successfully carried out. The catalyst is efficiently reusable till five repeated cycles.
Synthesis of 19-hydroxyaldosterone and the 3 beta-hydroxy-5-ene analog of aldosterone, active mineralocorticoids.

PubMed

Harnik, M; Kashman, Y; Aharonowitz, Y; Morris, D J

1985-08-01

19-Hydroxyaldosterone (20) and the 3 beta-hydroxy-5-ene analog of aldosterone (HAA) (8) were synthesized from 21-acetoxy-4-pregnene-3,20-dion-20-ethylene ketal-18, 11 beta-lactone (2) as follows: the double bond was transposed from the 4,5 to the 5,6-position by enol acetylation to 3, followed by sodium borohydride reduction. Further reduction of the resulting lactone 4a with diisobutylaluminum hydride (DIBAH) furnished the 20-ketal of HAA 6, from which free HAA (8) and the 18,21-anhydro compound 7 were obtained by acid treatment. The [1H]NMR spectrum of 8 in CDCl3 showed it to be a mixture of two isomeric forms. Correlation with the known aldosterone-gamma-etiolactone (10) was established by periodate oxidation of HAA to the corresponding etiolactone 9 followed by chromic acid oxidation. The preparation of 20 was next effected in the following manner: the diacetate 4b was converted into the 6 beta, 19-oxido compound 13b by addition of hypobromous acid followed by the hypoiodite reaction of the bromohydrin 11. Mild saponification of 13b lead to the corresponding diol 13a, and was followed by selective oxidation to the 3-one 14, readily dehydrobrominated to 15a. Reductive ring opening furnished a mixture of the 19,21-diol 16a and its 5-ene isomer 16b, which was directly converted to the diketal 17. Reduction with DIBAH gave the hemiacetal 18, and hydrolysis of the latter 19-hydroxyaldosterone (20) as a water-soluble solid, accompanied by the 18,21-anhydro compound 19. 19-Hydroxyaldosterone exists in CHCl3 and water as a mixture of mainly two isomers. Periodate oxidation furnished the etiolactone 21. Preliminary results indicate that HAA and 19-hydroxyaldosterone are active mineralocorticoids in the Kagawa bioassay and short-circuit current measurements.
Application of green chemistry techniques to prepare electrocatalysts for direct methanol fuel cells.

PubMed

Shimizu, Kenichi; Wang, Joanna S; Wai, Chien M

2010-03-25

A series of green techniques for synthesizing carbon nanotube-supported platinum nanoparticles and their high electrocatalytic activity toward methanol fuel cell applications are reported. The techniques utilize either the supercritical fluid carbon dioxide or water as a medium for depositing platinum nanoparticles on surfaces of multiwalled or single-walled carbon nanotubes. The catalytic properties of the carbon nanotubes-supported Pt nanoparticle catalysts prepared by four different techniques are compared for anodic oxidation of methanol and cathodic reduction of oxygen using cyclic voltammetry. One technique using galvanic exchange of Pt(2+) in water with zerovalent iron present on the surfaces of as-grown single-walled carbon nanotubes produces a Pt catalyst that shows an unusually high catalytic activity for reduction of oxygen but a negligible activity for oxidation of methanol. This fuel-selective catalyst may have a unique application as a cathode catalyst in methanol fuel cells to alleviate the problems caused by crossover of methanol through the polymer electrolyte membrane.
Material and system for catalytic reduction of nitrogen oxide in an exhaust stream of a combustion process

DOEpatents

Gardner, Timothy J.; Lott, Stephen E.; Lockwood, Steven J.; McLaughlin, Linda I.

1998-01-01

A catalytic material of activated hydrous metal oxide doped with platinum, palladium, or a combination of these, and optionally containing an alkali or alkaline earth metal, that is effective for NO.sub.X reduction in an oxidizing exhaust stream from a combustion process is disclosed. A device for reduction of nitrogen oxides in an exhaust stream, particularly an automotive exhaust stream, the device having a substrate coated with the activated noble-metal doped hydrous metal oxide of the invention is also provided.
Environmentally Responsible Redox Chemistry: An Example of Convenient Oxidation Methodology without Chromium Waste

ERIC Educational Resources Information Center

Crumbie, Robyn L.

2006-01-01

The reactions use recyclable Magtrieve as the oxidant in a simple reaction sequence illustrating the reciprocity of oxidation and reduction processes. The reciprocity of oxidation and reduction reactions are explored while undertaking the reactions in an environmentally friendly manner.
Selective Oxidation and Reactive Wetting During Hot-Dip Galvanizing of a 1.0 pct Al-0.5 pct Si TRIP-Assisted Steel

NASA Astrophysics Data System (ADS)

Bellhouse, E. M.; McDermid, J. R.

2012-07-01

Selective oxidation and reactive wetting during continuous galvanizing were studied for a low-alloy transformation induced plasticity (TRIP)-assisted steel with 0.2 pct C, 1.5 pct Mn, 1.0 pct Al and 0.5 pct Si. Three process atmospheres were tested during annealing prior to galvanizing: 220 K (-53 °C) dew point (dp) N2-20 pct H2, 243 K (-30 °C) dp N2-5 pct H2 and 278 K (+5 °C) dp N2-5 pct H2. The process atmosphere oxygen partial pressure affected the oxide chemistry, morphology and thickness. For the 220 K (-53 °C) dp and 243 K (-30 °C) dp process atmospheres, film and nodule-type manganese, silicon and aluminum containing oxides were observed at the surface. For the 278 K (+5 °C) dp atmosphere, MnO was observed at the grain boundaries and as thicker localized surface films. Oxide morphology, thickness and chemistry affected reactive wetting, with complete wetting being observed for the 220 K (-53 °C) dp and 243 K (-30 °C) dp process atmospheres and incomplete reactive wetting being observed for the 278 K (+5 °C) dp atmosphere. Complete reactive wetting for the 220 K (-53 °C) dp and 243 K (-30 °C) dp process atmospheres was attributed to a combination of zinc bridging of oxides, aluminothermic reduction of surface oxides and wetting of the oxides. Incomplete wetting for the 278 K (+5 °C) dp atmosphere was attributed to localized thick MnO films.
Catalyst for elemental sulfur recovery process

DOEpatents

Flytzani-Stephanopoulos, Maria; Liu, Wei

1995-01-01

A catalytic reduction process for the direct recovery of elemental sulfur from various SO.sub.2 -containing industrial gas streams. The catalytic process provides high activity and selectivity, as well as stability in the reaction atmosphere, for the reduction of SO.sub.2 to elemental sulfur product with carbon monoxide or other reducing gases. The reaction of sulfur dioxide and reducing gas takes place over a metal oxide composite catalyst having one of the following empirical formulas: [(OF.sub.2).sub.1-n (RO.sub.1)n].sub.1-k M.sub.k, [(FO.sub.2).sub.1-n (RO.sub.1.5).sub.n ].sub.1-k M.sub.k, or [Ln.sub.x Zr.sub.1-x O.sub.2-0.5x ].sub.1-k M.sub.k wherein FO.sub.2 is a fluorite-type oxide; RO represents an alkaline earth oxide; RO.sub.1.5 is a Group IIIB or rare earth oxide; Ln is a rare earth element having an atomic number from 57 to 65 or mixtures thereof; M is a transition metal or a mixture of transition metals; n is a number having a value from 0.0 to 0.35; k is a number having a value from 0.0 to about 0.5; and x is a number having a value from about 0.45 to about 0.55.
Cyclic interconversion of methionine containing peptide between oxidized and reduced phases monitored by reversed-phase HPLC and ESI-MS/MS.

PubMed

Jin, Yulong; Huang, Yanyan; Xie, Yunfeng; Hu, Wenbing; Wang, Fuyi; Liu, Guoquan; Zhao, Rui

2012-01-30

The cyclic oxidation and reduction of methionine (Met) containing peptides and proteins play important roles in biological system. This work was contributed to analysis the cyclic oxidation and reduction processes of a methionine containing peptide which is very likely to relate in the cell signal transduction pathways. To mimic the biological oxidation condition, hydrogen peroxide was used as the reactive oxygen species to oxidize the peptide. Reversed-phase high-performance liquid chromatography and mass spectrometry were employed to monitor the reactions and characterize the structural changes of the products. A rapid reduction procedure was developed by simply using KI as the reductant, which is green and highly efficient. By investigation of the cyclic oxidation and reduction process, our work provides a new perspective to study the function and mechanism of Met containing peptides and proteins during cell signaling processes as well as diseases. Copyright © 2011 Elsevier B.V. All rights reserved.
Nitrogen-doped diamond electrode shows high performance for electrochemical reduction of nitrobenzene.

PubMed

Zhang, Qing; Liu, Yanming; Chen, Shuo; Quan, Xie; Yu, Hongtao

2014-01-30

Effective electrode materials are critical to electrochemical reduction, which is a promising method to pre-treat anti-oxidative and bio-refractory wastewater. Herein, nitrogen-doped diamond (NDD) electrodes that possess superior electrocatalytic properties for reduction were fabricated by microwave-plasma-enhanced chemical vapor deposition technology. Nitrobenzene (NB) was chosen as the probe compound to investigate the material's electro-reduction activity. The effects of potential, electrolyte concentration and pH on NB reduction and aniline (AN) formation efficiencies were studied. NDD exhibited high electrocatalytic activity and selectivity for reduction of NB to AN. The NB removal efficiency and AN formation efficiency were 96.5% and 88.4% under optimal conditions, respectively; these values were 1.13 and 3.38 times higher than those of graphite electrodes. Coulombic efficiencies for NB removal and AN formation were 27.7% and 26.1%, respectively; these values were 4.70 and 16.6 times higher than those of graphite electrodes under identical conditions. LC-MS analysis revealed that the dominant reduction pathway on the NDD electrode was NB to phenylhydroxylamine (PHA) to AN. Copyright © 2013 Elsevier B.V. All rights reserved.
Nitrous oxide and methane emissions and nitrous oxide isotopic composition from waste incineration in Switzerland.

PubMed

Harris, Eliza; Zeyer, Kerstin; Kegel, Rainer; Müller, Beat; Emmenegger, Lukas; Mohn, Joachim

2015-01-01

Solid waste incineration accounts for a growing proportion of waste disposal in both developed and developing countries, therefore it is important to constrain emissions of greenhouse gases from these facilities. At five Swiss waste incineration facilities with grate firing, emission factors for N2O and CH4 were determined based on measurements of representative flue gas samples, which were collected in Tedlar bags over a one year period (September 2010-August 2011) and analysed with FTIR spectroscopy. All five plants burn a mixture of household and industrial waste, and two of the plants employ NOx removal through selective non-catalytic reduction (SNCR) while three plants use selective catalytic reduction (SCR) for NOx removal. N2O emissions from incineration plants with NOx removal through selective catalytic reduction were 4.3 ± 4.0g N2O tonne(-1) waste (wet) (hereafter abbreviated as t(-1)) (0.4 ± 0.4 g N2O GJ(-1)), ten times lower than from plants with selective non-catalytic reduction (51.5 ± 10.6g N2O t(-1); 4.5 ± 0.9g N2O GJ(-1)). These emission factors, which are much lower than the value of 120g N2O t(-1) (10.4g N2O GJ(-1)) used in the 2013 Swiss national greenhouse gas emission inventory, have been implemented in the most recent Swiss emission inventory. In addition, the isotopic composition of N2O emitted from the two plants with SNCR, which had considerable N2O emissions, was measured using quantum cascade laser spectroscopy. The isotopic site preference of N2O - the enrichment of (14)N(15)NO relative to (15)N(14)NO - was found to be 17.6 ± 0.8‰, with no significant difference between the two plants. Comparison to previous studies suggests SP of 17-19‰ may be characteristic for N2O produced from SNCR. Methane emissions were found to be insignificant, with a maximum emission factor of 2.5 ± 5.6g CH4 t(-1) (0.2 ± 0.5g CH4 GJ(-1)), which is expected due to high incinerator temperatures and efficient combustion. Copyright © 2014 Elsevier Ltd. All rights reserved.

Hydrogen and formate oxidation coupled to dissimilatory reduction of iron or manganese by Alteromonas putrefaciens

USGS Publications Warehouse

Lovley, D.R.; Phillips, E.J.P.; Lonergan, D.J.

1989-01-01

The ability of Alteromonas putrefaciens to obtain energy for growth by coupling the oxidation of various electron donors to dissimilatory Fe(III) or Mn(IV) reduction was investigated. A. putrefaciens grew with hydrogen, formate, lactate, or pyruvate as the sole electron donor and Fe(III) as the sole electron acceptor. Lactate and pyruvate were oxidized to acetate, which was not metabolized further. With Fe(III) as the electron acceptor, A. putrefaciens had a high affinity for hydrogen and formate and metabolized hydrogen at partial pressures that were 25-fold lower than those of hydrogen that can be metabolized by pure cultures of sulfate reducers or methanogens. The electron donors for Fe(III) reduction also supported Mn(IV) reduction. The electron donors for Fe(III) and Mn(IV) reduction and the inability of A. putrefaciens to completely oxidize multicarbon substrates to carbon dioxide distinguish A. putrefaciens from GS-15, the only other organism that is known to obtain energy for growth by coupling the oxidation of organic compounds to the reduction of Fe(III) or Mn(IV). The ability of A. putrefaciens to reduce large quantities of Fe(III) and to grow in a defined medium distinguishes it from a Pseudomonas sp., which is the only other known hydrogen-oxidizing, Fe(III)-reducing microorganism. Furthermore, A. putrefaciens is the first organism that is known to grow with hydrogen as the electron donor and Mn(IV) as the electron acceptor and is the first organism that is known to couple the oxidation of formate to the reduction of Fe(III) or Mn(IV). Thus, A. putrefaciens provides a much needed microbial model for key reactions in the oxidation of sediment organic matter coupled to Fe(III) and Mn(IV) reduction.
Evaluation of Treatment Technologies for Wastewater from Insensitive Munitions Production. Phase 1: Technology Down-Selection

DTIC Science & Technology

2013-11-01

the AOP reactor according to the target process formulation. Gases were vented to a GAC vessel. ERDC/EL TR-13-20 94 10.2.2 Results and Discussion...destructive and filtration methods such as biological treatment (destructive), chemical reduction (destructive), reverse osmosis (RO)/nano- filtration ... filtration ), and advanced oxidation processes (destructive). A comprehensive evaluation of alternatives relies on a detailed list of criteria, allowing for
Industrial Processes to Reduce Generation of Hazardous Waste at DoD Facilities. Phase 2 Report. Evaluation of 18 Case Studies.

DTIC Science & Technology

1985-07-15

oxidize 13 .. . . . . . .- .. . ..-.-........ ~ -. trivalent chromium to hexavalent chromium and to selectively precipitate cation impurities from the...plating facilities. Chromium must be reduced to its trivalent state before it can be removed by precipitation as a hydroxide. Reduction is normally...conversion of hexavalent to trivalent chromium prior to precipitation. Trivalent solutions are typically less concentrated (22 g/L versus 150 g/L for
Dissimilatory reduction of nitrate and nitrite in the bovine rumen: nitrous oxide production and effect of acetylene.

PubMed

Kaspar, H F; Tiedje, J M

1981-03-01

15N tracer methods and gas chromatography coupled to an electron capture detector were used to investigate dissimilatory reduction of nitrate and nitrite by the rumen microbiota of a fistulated cow. Ammonium was the only 15N-labeled end product of quantitative significance. Only traces of nitrous oxide were detected as a product of nitrate reduction; but in experiments with nitrite, up to 0.3% of the added nitrogen accumulated as nitrous oxide, but it was not further reduced. Furthermore, when 13NO3- was incubated with rumen microbiota virtually no [13N]N2 was produced. Acetylene partially inhibited the reduction of nitrite to ammonium as well as the formation of nitrous oxide. It is suggested that in the rumen ecosystem nitrous oxide is a byproduct of dissimilatory nitrite reduction to ammonium rather than a product of denitrification and that the latter process is absent from the rumen habitat.
Evaluation of selected chemical processes for production of low-cost silicon

NASA Technical Reports Server (NTRS)

Blocher, J. M., Jr.; Browning, M. F.; Wilson, W. J.; Carmichael, D. C.

1976-01-01

Plant construction costs and manufacturing costs were estimated for the production of solar-grade silicon by the reduction of silicon tetrachloride in a fluidized bed of seed particles, and several modifications of the iodide process using either thermal decomposition on heated filaments (rods) or hydrogen reduction in a fluidized bed of seed particles. Energy consumption data for the zinc reduction process and each of the iodide process options are given and all appear to be acceptable from the standpoint of energy pay back. Information is presented on the experimental zinc reduction of SiCl4 and electrolytic recovery of zinc from ZnCl2. All of the experimental work performed thus far has supported the initial assumption as to technical feasibility of producing semiconductor silicon by the zinc reduction or iodide processes proposed. The results of a more thorough thermodynamic evaluation of the iodination of silicon oxide/carbon mixtures are presented which explain apparent inconsistencies in an earlier cursory examination of the system.
In situ redox manipulation of subsurface sediments from Fort Lewis, Washington: Iron reduction and TCE dechlorination mechanisms

DOE Office of Scientific and Technical Information (OSTI.GOV)

JE Szecsody; JS Fruchter; DS Sklarew

2000-03-21

Pacific Northwest National Laboratory (PNNL) conducted a bench-scale study to determine how effective chemically treated Ft. Lewis sediments can degrade trichloroethylene (TCE). The objectives of this experimental study were to quantify: (1) sediment reduction and oxidation reactions, (2) TCE degradation reactions, and (3) other significant geochemical changes that occurred. Sediment reduction and oxidation were investigated to determine the mass of reducible iron in the Ft. Lewis sediments and the rate of this reduction and subsequent oxidation at different temperatures. The temperature dependence was needed to be able to predict field-scale reduction in the relatively cold ({approximately}11 C) Ft. Lewis aquifer.more » Results of these experiments were used in conjunction with other geochemical and hydraulic characterization to design the field-scale injection experiment and predict barrier longevity. For example, the sediment reduction rate controls the amount of time required for the dithionite solution to fully react with sediments. Sediment oxidation experiments were additionally conducted to determine the oxidation rate and provide a separate measure of the mass of reduced iron. Laboratory experiments that were used to meet these objectives included: (1) sediment reduction in batch (static) systems, (2) sediment reduction in 1-D columns, and (3) sediment oxidation in 1-D columns. Multiple reaction modeling was conducted to quantify the reactant masses and reaction rates.« less
Dissimilatory Fe(III) and Mn(IV) reduction.

PubMed Central

Lovley, D R

1991-01-01

The oxidation of organic matter coupled to the reduction of Fe(III) or Mn(IV) is one of the most important biogeochemical reactions in aquatic sediments, soils, and groundwater. This process, which may have been the first globally significant mechanism for the oxidation of organic matter to carbon dioxide, plays an important role in the oxidation of natural and contaminant organic compounds in a variety of environments and contributes to other phenomena of widespread significance such as the release of metals and nutrients into water supplies, the magnetization of sediments, and the corrosion of metal. Until recently, much of the Fe(III) and Mn(IV) reduction in sedimentary environments was considered to be the result of nonenzymatic processes. However, microorganisms which can effectively couple the oxidation of organic compounds to the reduction of Fe(III) or Mn(IV) have recently been discovered. With Fe(III) or Mn(IV) as the sole electron acceptor, these organisms can completely oxidize fatty acids, hydrogen, or a variety of monoaromatic compounds. This metabolism provides energy to support growth. Sugars and amino acids can be completely oxidized by the cooperative activity of fermentative microorganisms and hydrogen- and fatty-acid-oxidizing Fe(III) and Mn(IV) reducers. This provides a microbial mechanism for the oxidation of the complex assemblage of sedimentary organic matter in Fe(III)- or Mn(IV)-reducing environments. The available evidence indicates that this enzymatic reduction of Fe(III) or Mn(IV) accounts for most of the oxidation of organic matter coupled to reduction of Fe(III) and Mn(IV) in sedimentary environments. Little is known about the diversity and ecology of the microorganisms responsible for Fe(III) and Mn(IV) reduction, and only preliminary studies have been conducted on the physiology and biochemistry of this process. PMID:1886521
High-Potential Electrocatalytic O2 Reduction with Nitroxyl/NOx Mediators: Implications for Fuel Cells and Aerobic Oxidation Catalysis

PubMed Central

2015-01-01

Efficient reduction of O2 to water is a central challenge in energy conversion and many aerobic oxidation reactions. Here, we show that the electrochemical oxygen reduction reaction (ORR) can be achieved at high potentials by using soluble organic nitroxyl and nitrogen oxide (NOx) mediators. When used alone, neither organic nitroxyls, such as 2,2,6,6-tetramethyl-1-piperidinyl-N-oxyl (TEMPO), nor NOx species, such as sodium nitrite, are effective ORR mediators. The combination of nitroxyl/NOx species, however, mediates sustained O2 reduction with overpotentials as low as 300 mV in acetonitrile containing trifluoroacetic acid. Mechanistic analysis of the coupled redox reactions supports a process in which the nitrogen oxide catalyst drives aerobic oxidation of a nitroxyl mediator to an oxoammonium species, which then is reduced back to the nitroxyl at the cathode. The electrolysis potential is dictated by the oxoammonium/nitroxyl reduction potential. The overpotentials accessible with this ORR system are significantly lower than widely studied molecular metal-macrocycle ORR catalysts and benefit from the mechanism-based specificity for four-electron reduction of oxygen to water mediated by NOx species, together with kinetically efficient reduction of oxidized NOx species by TEMPO and other organic nitroxyls. PMID:27162977
Electric coupling between distant nitrate reduction and sulfide oxidation in marine sediment

PubMed Central

Marzocchi, Ugo; Trojan, Daniela; Larsen, Steffen; Louise Meyer, Rikke; Peter Revsbech, Niels; Schramm, Andreas; Peter Nielsen, Lars; Risgaard-Petersen, Nils

2014-01-01

Filamentous bacteria of the Desulfobulbaceae family can conduct electrons over centimeter-long distances thereby coupling oxygen reduction at the surface of marine sediment to sulfide oxidation in deeper anoxic layers. The ability of these cable bacteria to use alternative electron acceptors is currently unknown. Here we show that these organisms can use also nitrate or nitrite as an electron acceptor thereby coupling the reduction of nitrate to distant oxidation of sulfide. Sulfidic marine sediment was incubated with overlying nitrate-amended anoxic seawater. Within 2 months, electric coupling of spatially segregated nitrate reduction and sulfide oxidation was evident from: (1) the formation of a 4–6-mm-deep zone separating sulfide oxidation from the associated nitrate reduction, and (2) the presence of pH signatures consistent with proton consumption by cathodic nitrate reduction, and proton production by anodic sulfide oxidation. Filamentous Desulfobulbaceae with the longitudinal structures characteristic of cable bacteria were detected in anoxic, nitrate-amended incubations but not in anoxic, nitrate-free controls. Nitrate reduction by cable bacteria using long-distance electron transport to get privileged access to distant electron donors is a hitherto unknown mechanism in nitrogen and sulfur transformations, and the quantitative importance for elements cycling remains to be addressed. PMID:24577351
Mechanistic investigation of Fe(III) oxide reduction by low molecular weight organic sulfur species

NASA Astrophysics Data System (ADS)

Eitel, Eryn M.; Taillefert, Martial

2017-10-01

Low molecular weight organic sulfur species, often referred to as thiols, are known to be ubiquitous in aquatic environments and represent important chemical reductants of Fe(III) oxides. Thiols are excellent electron shuttles used during dissimilatory iron reduction, and in this capacity could indirectly affect the redox state of sediments, release adsorbed contaminants via reductive dissolution, and influence the carbon cycle through alteration of bacterial respiration processes. Interestingly, the reduction of Fe(III) oxides by thiols has not been previously investigated in environmentally relevant conditions, likely due to analytical limitations associated with the detection of thiols and their oxidized products. In this study, a novel electrochemical method was developed to simultaneously determine thiol/disulfide pair concentrations in situ during the reduction of ferrihydrite in batch reactors. First order rate laws with respect to initial thiol concentration were confirmed for Fe(III) oxyhydroxide reduction by four common thiols: cysteine, homocysteine, cysteamine, and glutathione. Zero order was determined for both Fe(III) oxyhydroxide and proton concentration at circumneutral pH. A kinetic model detailing the molecular mechanism of the reaction was optimized with proposed intermediate surface structures. Although metal oxide overall reduction rate constants were inversely proportional to the complexity of the thiol structure, the extent of metal reduction increased with structure complexity, indicating that surface complexes play a significant role in the ability of these thiols to reduce iron. Taken together, these results demonstrate the importance of considering the molecular reaction mechanism at the iron oxide surface when investigating the potential for thiols to act as electron shuttles during dissimilatory iron reduction in natural environments.
Oxidation and reduction behaviors of a prototypic MgO-PuO2-x inert matrix fuel

NASA Astrophysics Data System (ADS)

Miwa, Shuhei; Osaka, Masahiko

2017-04-01

Oxidation and reduction behaviors of prototypic MgO-based inert matrix fuels (IMFs) containing PuO2-x were experimentally investigated by means of thermogravimetry. The oxidation and reduction kinetics of the MgO-PuO2-x specimen were determined. The oxidation and reduction rates of the MgO-PuO2-x were found to be low compared with those of PuO2-x. It is note that the changes in O/Pu ratios of MgO-PuO2-x from stoichiometry were smaller than those of PuO2-x at high oxygen partial pressure.
Direct electrochemical reduction of solid uranium oxide in molten fluoride salts

NASA Astrophysics Data System (ADS)

Gibilaro, Mathieu; Cassayre, Laurent; Lemoine, Olivier; Massot, Laurent; Dugne, Olivier; Malmbeck, Rikard; Chamelot, Pierre

2011-07-01

The direct electrochemical reduction of UO 2 solid pellets was carried out in LiF-CaF 2 (+2 mass.% Li 2O) at 850 °C. An inert gold anode was used instead of the usual reactive sacrificial carbon anode. In this case, oxidation of oxide ions present in the melt yields O 2 gas evolution on the anode. Electrochemical characterisations of UO 2 pellets were performed by linear sweep voltammetry at 10 mV/s and reduction waves associated to oxide direct reduction were observed at a potential 150 mV more positive in comparison to the solvent reduction. Subsequent, galvanostatic electrolyses runs were carried out and products were characterised by SEM-EDX, EPMA/WDS, XRD and microhardness measurements. In one of the runs, uranium oxide was partially reduced and three phases were observed: nonreduced UO 2 in the centre, pure metallic uranium on the external layer and an intermediate phase representing the initial stage of reduction taking place at the grain boundaries. In another run, the UO 2 sample was fully reduced. Due to oxygen removal, the U matrix had a typical coral-like structure which is characteristic of the pattern observed after the electroreduction of solid oxides.
Oxidant Induced Changes in Mitochondria and Calcium Dynamicsin the Pathophysiology of Alzheimer's Disease

PubMed Central

Gibson, Gary E.; Karuppagounder, Saravanan S.; Shi, Qingli

2009-01-01

Considerable data supports the hypothesis that mitochondrial abnormalities link gene defects and/or environmental insults to the neurodegenerative process The interaction of oxidants with calcium and the mitochondrial enzymes of the tricarboxylic acid (TCA) cycle are central to that relationship. Abnormalities that were discovered in brains or fibroblasts from patients with Alzheimer's Disease (AD) have been modeled in vitro and in vivo to assess their pathophysiological importance and to determine how they might be reversed. The conclusions are consistent with the hypothesis that the AD-related abnormalities result from oxidative stress. The selection of compounds for reversal is complex because the actions of the relevant compounds vary under different conditions such as cell redox states and acute vs chronic changes. However, the models that have been developed are useful for testing the effectiveness of the potential medications. The results suggest that the reversal of the mitochondrial deficits and a reduction in oxidative stress will reduce the clinical and pathological changes and benefit patients. PMID:19076444
Minimizing analyte electrolysis in electrospray ionization mass spectrometry using a redox buffer coated emitter electrode

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peintler-Krivan, Emese; Van Berkel, Gary J; Kertesz, Vilmos

2010-01-01

An emitter electrode with an electroactive poly(pyrrole) (PPy) polymer film coating was constructed for use in electrospray ionization mass spectrometry (ESI-MS). The PPy film acted as a surface-attached redox buffer limiting the interfacial potential of the emitter electrode. While extensive oxidation of selected analytes (reserpine and amodiaquine) was observed in positive ion mode ESI using a bare metal (gold) emitter electrode, the oxidation was suppressed for these same analytes when using the PPy-coated electrode. A semi-quantitative relationship between the rate of oxidation observed and the interfacial potential of the emitter electrode was shown. The redox buffer capacity, and therefore themore » lifetime of the redox buffering effect, correlated with the oxidation potential of the analyte and with the magnitude of the film charge capacity. Online reduction of the PPy polymer layer using negative ion mode ESI between analyte injections was shown to successfully restore the redox buffering capacity of the polymer film to its initial state.« less
Emission Control Technologies for Thermal Power Plants

NASA Astrophysics Data System (ADS)

Nihalani, S. A.; Mishra, Y.; Juremalani, J.

2018-03-01

Coal thermal power plants are one of the primary sources of artificial air emissions, particularly in a country like India. Ministry of Environment and Forests has proposed draft regulation for emission standards in coal-fired power plants. This includes significant reduction in sulphur-dioxide, oxides of nitrogen, particulate matter and mercury emissions. The first step is to evaluate the technologies which represent the best selection for each power plant based on its configuration, fuel properties, performance requirements, and other site-specific factors. This paper will describe various technology options including: Flue Gas Desulfurization System, Spray Dryer Absorber (SDA), Circulating Dry Scrubber (CDS), Limestone-based Wet FGD, Low NOX burners, Selective Non Catalytic Reduction, Electrostatic Precipitator, Bag House Dust Collector, all of which have been evaluated and installed extensively to reduce SO2, NOx, PM and other emissions. Each control technology has its advantages and disadvantages. For each of the technologies considered, major features, potential operating and maintenance cost impacts, as well as key factors that contribute to the selection of one technology over another are discussed here.
In vitro enzymatic reduction kinetics of mineral oxides by membrane fractions from Shewanella oneidensis MR-1

NASA Astrophysics Data System (ADS)

Ruebush, Shane S.; Icopini, Gary A.; Brantley, Susan L.; Tien, Ming

2006-01-01

This study documents the first example of in vitro solid-phase mineral oxide reduction by enzyme-containing membrane fractions. Previous in vitro studies have only reported the reduction of aqueous ions. Total membrane (TM) fractions from iron-grown cultures of Shewanella oneidensis MR-1 were isolated and shown to catalyze the reduction of goethite, hematite, birnessite, and ramsdellite/pyrolusite using formate. In contrast, nicotinamide adenine dinucleotide (NADH) and succinate cannot function as electron donors. The significant implications of observations related to this cell-free system are: (i) both iron and manganese mineral oxides are reduced by the TM fraction, but aqueous U(VI) is not; (ii) TM fractions from anaerobically grown, but not aerobically grown, cells can reduce the mineral oxides; (iii) electron shuttles and iron chelators are not needed for this in vitro reduction, documenting conclusively that reduction can occur by direct contact with the mineral oxide; (iv) electron shuttles and EDTA stimulate the in vitro Fe(III) reduction, documenting that exogenous molecules can enhance rates of enzymatic mineral reduction; and (v) multiple membrane components are involved in solid-phase oxide reduction. The membrane fractions, consisting of liposomes of cytoplasmic and outer membrane segments, contain at least 100 proteins including the enzyme that oxidizes formate, formate dehydrogenase. Mineral oxide reduction was inhibited by the addition of detergent Triton X-100, which solubilizes membranes and their associated proteins, consistent with the involvement of multiple electron carriers that are disrupted by detergent addition. In contrast, formate dehydrogenase activity was not inhibited by Triton X-100. The addition of anthraquinone-2,6-disulfonate (AQDS) and menaquinone-4 was unable to restore activity; however, menadione (MD) restored 33% of the activity. The addition of AQDS and MD to reactions without added detergent increased the rate of goethite reduction. The Michaelis-Menten Km values of 71 ± 22 m 2/L for hematite and 50 ± 16 m 2/L for goethite were calculated as a function of surface area of the two insoluble minerals. Vmax was determined to be 123 ± 14 and 156 ± 13 nmol Fe(II)/min/mg of TM protein for hematite and goethite, respectively. These values are consistent with in vivo rates of reduction reported in the literature. These observations are consistent with our conclusion that the enzymatic reduction of mineral oxides is an effective probe that will allow elucidation of molecular chemistry of the membrane-mineral interface where electron transfer occurs.
Variation of iron redox kinetics and its relation with molecular composition of standard humic substances at circumneutral pH.

PubMed

Lee, Ying Ping; Fujii, Manabu; Kikuchi, Tetsuro; Terao, Koumei; Yoshimura, Chihiro

2017-01-01

Oxidation and reduction kinetics of iron (Fe) and proportion of steady-state Fe(II) concentration relative to total dissolved Fe (steady-state Fe(II) fraction) were investigated in the presence of various types of standard humic substances (HS) with particular emphasis on the photochemical and thermal reduction of Fe(III) and oxidation of Fe(II) by dissolved oxygen (O2) and hydrogen peroxide (H2O2) at circumneutral pH (pH 7-8). Rates of Fe(III) reduction were spectrophotometrically determined by a ferrozine method under the simulated sunlight and dark conditions, whereas rates of Fe(II) oxidation were examined in air-saturated solution using luminol chemiluminescence technique. The reduction and oxidation rate constants were determined to substantially vary depending on the type of HS. For example, the first-order rate constants varied by up to 10-fold for photochemical reduction and 7-fold for thermal reduction. The degree of variation in Fe(II) oxidation was larger for the H2O2-mediated reaction compared to the O2-mediated reaction (e.g., 15- and 3-fold changes for the former and latter reactions, respectively, at pH 8). The steady-state Fe(II) fraction under the simulated sunlight indicated that the Fe(II) fraction varies by up to 12-fold. The correlation analysis indicated that variation of Fe(II) oxidation is significantly associated with aliphatic content of HS, suggesting that Fe(II) complexation by aliphatic components accelerates Fe(II) oxidation. The reduction rate constant and steady-state Fe(II) fractions in the presence of sunlight had relatively strong positive relations with free radical content of HS, possibly due to the reductive property of radical semiquinone in HS. Overall, the findings in this study indicated that the Fe reduction and oxidation kinetics and resultant Fe(II) formation are substantially influenced by chemical properties of HS.
Microbial Manganese and Sulfate Reduction in Black Sea Shelf Sediments

PubMed Central

Thamdrup, Bo; Rosselló-Mora, Ramón; Amann, Rudolf

2000-01-01

The microbial ecology of anaerobic carbon oxidation processes was investigated in Black Sea shelf sediments from mid-shelf with well-oxygenated bottom water to the oxic-anoxic chemocline at the shelf-break. At all stations, organic carbon (Corg) oxidation rates were rapidly attenuated with depth in anoxically incubated sediment. Dissimilatory Mn reduction was the most important terminal electron-accepting process in the active surface layer to a depth of ∼1 cm, while SO42− reduction accounted for the entire Corg oxidation below. Manganese reduction was supported by moderately high Mn oxide concentrations. A contribution from microbial Fe reduction could not be discerned, and the process was not stimulated by addition of ferrihydrite. Manganese reduction resulted in carbonate precipitation, which complicated the quantification of Corg oxidation rates. The relative contribution of Mn reduction to Corg oxidation in the anaerobic incubations was 25 to 73% at the stations with oxic bottom water. In situ, where Mn reduction must compete with oxygen respiration, the contribution of the process will vary in response to fluctuations in bottom water oxygen concentrations. Total bacterial numbers as well as the detection frequency of bacteria with fluorescent in situ hybridization scaled to the mineralization rates. Most-probable-number enumerations yielded up to 105 cells of acetate-oxidizing Mn-reducing bacteria (MnRB) cm−3, while counts of Fe reducers were <102 cm−3. At two stations, organisms affiliated with Arcobacter were the only types identified from 16S rRNA clone libraries from the highest positive MPN dilutions for MnRB. At the third station, a clone type affiliated with Pelobacter was also observed. Our results delineate a niche for dissimilatory Mn-reducing bacteria in sediments with Mn oxide concentrations greater than ∼10 μmol cm−3 and indicate that bacteria that are specialized in Mn reduction, rather than known Mn and Fe reducers, are important in this niche. PMID:10877783
Proposal of New Rewritable Printing Media Using Electrophoresis and Confirmation of Its Mechanism

NASA Astrophysics Data System (ADS)

Hoshino, Yasushi; Ogura, Masahiro; Sano, Takayuki

2004-10-01

A new rewritable printing media using electrophoresis and selective heating is proposed to contribute to the reduction in paper consumption by printers. The mechanism is that when a heated part of the rewritable media is melted, white particles in that part of the media are able to move by electrophoresis. The media is initialized by heating its entire surface under the condition of voltage application and imaging is carried out by selective heating under the condition of an applied reversed-polarity voltage. Using a mixture system of carnauba wax and particles coated with titanium oxide (TiO2), the feasibility of the mechanism is confirmed.
Ammonia- and nitrite-oxidizing bacterial communities in a pilot-scale chloraminated drinking water distribution system.

PubMed

Regan, John M; Harrington, Gregory W; Noguera, Daniel R

2002-01-01

Nitrification in drinking water distribution systems is a common operational problem for many utilities that use chloramines for secondary disinfection. The diversity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in the distribution systems of a pilot-scale chloraminated drinking water treatment system was characterized using terminal restriction fragment length polymorphism (T-RFLP) analysis and 16S rRNA gene (ribosomal DNA [rDNA]) cloning and sequencing. For ammonia oxidizers, 16S rDNA-targeted T-RFLP indicated the presence of Nitrosomonas in each of the distribution systems, with a considerably smaller peak attributable to Nitrosospira-like AOB. Sequences of AOB amplification products aligned within the Nitrosomonas oligotropha cluster and were closely related to N. oligotropha and Nitrosomonas ureae. The nitrite-oxidizing communities were comprised primarily of Nitrospira, although Nitrobacter was detected in some samples. These results suggest a possible selection of AOB related to N. oligotropha and N. ureae in chloraminated systems and demonstrate the presence of NOB, indicating a biological mechanism for nitrite loss that contributes to a reduction in nitrite-associated chloramine decay.

Post Quench Ductility Evaluation of Zircaloy-4 and Select Iron Alloys under Design Basis and Extended LOCA Conditions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Yong; Keiser, James R; Terrani, Kurt A

2014-01-01

Oxidation experiments were conducted at 1200 C in flowing steam with tubing specimens of Zircaloy-4, 317, 347 stainless steels, and the commercial FeCrAl alloy APMT. The purpose was to determine the oxidation behavior and post quench ductility of these alloys under postulated loss-of-coolant accident conditions. The parabolic rate constant for Zircaloy-4 tubing samples at 1200 were determined to be k = 2.173 107 g2/cm4/s C, in excellent agreement with the Cathcart-Pawel correlation. The APMT alloy experienced the slowest oxidation rate among all materials examined in this work. The ductility of post quenched samples was evaluated by ring compression tests atmore » 135 C. For Zircaloy-4, the ductile to brittle transition occurs at an equivalent cladding reacted (ECR) of 19.3%. SS-347 was still ductile after being oxidized for 2400 s (CP-ECR 50%), but the maximum load was reduced significantly owing to the metal layer thickness reduction. No ductility decrease was observed for the post-quenched APMT samples oxidized up to four hours.« less
Post-quench ductility evaluation of Zircaloy-4 and select iron alloys under design basis and extended LOCA conditions

NASA Astrophysics Data System (ADS)

Yan, Y.; Keiser, J. R.; Terrani, K. A.; Bell, G. L.; Snead, L. L.

2014-05-01

Oxidation experiments were conducted at 1200 °C in flowing steam with tubing specimens of Zircaloy-4, 317, 347 stainless steels, and the commercial FeCrAl alloy APMT. The purpose was to determine the oxidation behavior and post-quench ductility under postulated and extended LOCA conditions. The parabolic rate constant for Zircaloy-4 tubing samples at 1200 °C was determined to be k = 2.173 × 107 g2/cm4/s, in excellent agreement with the Cathcart-Pawel correlation. The APMT alloy experienced the slowest oxidation rate among all materials examined in this work. The ductility of post-quenched samples was evaluated by ring compression tests at 135 °C. For Zircaloy-4, the ductile to brittle transition occurs at an equivalent cladding reacted (ECR) of 19.3%. SS-347 was still ductile after being oxidized for 2400 s (CP-ECR ≈ 50%), but the maximum load was reduced significantly owing to the metal layer thickness reduction. No ductility decrease was observed for the post-quenched APMT samples oxidized up to 4 h.
Ammonia- and Nitrite-Oxidizing Bacterial Communities in a Pilot-Scale Chloraminated Drinking Water Distribution System

PubMed Central

Regan, John M.; Harrington, Gregory W.; Noguera, Daniel R.

2002-01-01

Nitrification in drinking water distribution systems is a common operational problem for many utilities that use chloramines for secondary disinfection. The diversity of ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB) in the distribution systems of a pilot-scale chloraminated drinking water treatment system was characterized using terminal restriction fragment length polymorphism (T-RFLP) analysis and 16S rRNA gene (ribosomal DNA [rDNA]) cloning and sequencing. For ammonia oxidizers, 16S rDNA-targeted T-RFLP indicated the presence of Nitrosomonas in each of the distribution systems, with a considerably smaller peak attributable to Nitrosospira-like AOB. Sequences of AOB amplification products aligned within the Nitrosomonas oligotropha cluster and were closely related to N. oligotropha and Nitrosomonas ureae. The nitrite-oxidizing communities were comprised primarily of Nitrospira, although Nitrobacter was detected in some samples. These results suggest a possible selection of AOB related to N. oligotropha and N. ureae in chloraminated systems and demonstrate the presence of NOB, indicating a biological mechanism for nitrite loss that contributes to a reduction in nitrite-associated chloramine decay. PMID:11772611
Comparison of different wastewater treatments for removal of selected endocrine-disruptors from paper mill wastewaters.

PubMed

Balabanič, Damjan; Hermosilla, Daphne; Merayo, Noemí; Klemenčič, Aleksandra Krivograd; Blanco, Angeles

2012-01-01

There is increasing concern about chemical pollutants that have the ability to mimic hormones, the so-called endocrine-disrupting compounds (EDCs). One of the main reasons for concern is the possible effect of EDCs on human health. EDCs may be released into the environment in different ways, and one of the most significant sources is industrial wastewater. The main objective of this research was to evaluate the treatment performance of different wastewater treatment procedures (biological treatment, filtration, advanced oxidation processes) for the reduction of chemical oxygen demand and seven selected EDCs (dimethyl phthalate, diethyl phthalate, dibutyl phthalate, benzyl butyl phthalate, bis(2-ethylhexyl) phthalate, bisphenol A and nonylphenol) from wastewaters from a mill producing 100 % recycled paper. Two pilot plants were running in parallel and the following treatments were compared: (i) anaerobic biological treatment followed by aerobic biological treatment, ultrafiltration and reverse osmosis (RO), and (ii) anaerobic biological treatment followed by membrane bioreactor and RO. Moreover, at lab-scale, four different advanced oxidation processes (Fenton reaction, photo-Fenton reaction, photocatalysis with TiO(2), and ozonation) were applied. The results indicated that the concentrations of selected EDCs from paper mill wastewaters were effectively reduced (100 %) by both combinations of pilot plants and photo-Fenton oxidation (98 %), while Fenton process, photocatalysis with TiO(2) and ozonation were less effective (70 % to 90 %, respectively).
Oxidation and Reduction Reactions in Organic Chemistry

ERIC Educational Resources Information Center

Shibley, Ivan A., Jr.; Amaral, Katie E.; Aurentz, David J.; McCaully, Ronald J.

2010-01-01

A variety of approaches to the concept of oxidation and reduction appear in organic textbooks. The method proposed here is different than most published approaches. The oxidation state is calculated by totaling the number of heterogeneous atoms, [pi]-bonds, and rings. A comparison of the oxidation states of reactant and product determine what type…
Results of the pollution reduction technology program for turboprop engines

NASA Technical Reports Server (NTRS)

Mularz, E. J.

1976-01-01

A program was performed to evolve and demonstrate advanced combustor technology aimed at achieving the 1979 EPA standards for turboprop engines (Class P2). The engine selected for this program was the 501-D22A turboprop. Three combustor concepts were designed and tested in a combustor rig at the exact combustor operating conditions of the 50-D22A engine over the EPA landing-takeoff cycle. Each combustor concept exhibited pollutant emissions well below the EPA standards, achieving substantial reductions in unburned hydrocarbons, carbon monoxide, and smoke emissions compared with emissions from the production combustor of this engine. Oxides of nitrogen emissions remained well below the EPA standards, also.
Selectivity shifting behavior of Pd nanoparticles loaded zinc stannate/zinc oxide (Zn2SnO4/ZnO) nanowires sensors

NASA Astrophysics Data System (ADS)

Arafat, M. M.; Ong, J. Y.; Haseeb, A. S. M. A.

2018-03-01

In this research, the gas sensing behavior of Pd nanoparticles loaded zinc stannate/zinc oxide (Zn2SnO4/ZnO) nanowires were investigated. The Zn2SnO4/ZnO nanowires were grown on Au interdigitated alumina substrate by carbon assisted thermal evaporation process. Pd nanoparticles were loaded on the Zn2SnO4/ZnO nanowires by wet reduction process. The nanowires were characterized by X-ray diffractometer, field emission scanning electron microscope and energy dispersive X-ray spectroscope. The Zn2SnO4/ZnO and Pd nanoparticles loaded Zn2SnO4/ZnO nanowires were investigated for detecting H2, H2S and C2H5OH gases in N2 background. Results revealed that the average diameter and length of as-grown Zn2SnO4/ZnO nanowires were 74 nm and 30 μm, respectively. During wet reduction process,Pd particles having size of 20-60 nm were evenly distributed on the Zn2SnO4/ZnO nanowires. The Zn2SnO4/ZnO nanowires based sensors showed selective response towards C2H5OH whereas Pd nanoparticles loaded Zn2SnO4/ZnO nanowires showed selective response towards H2. The recovery time of the sensors reduced with Pd loading on Zn2SnO4/ZnO nanowires. A mechanism is proposed to elucidate the gas sensing mechanism of Pd nanoparticles loaded Zn2SnO4/ZnO nanowires.
Ammonia reactions with the stored oxygen in a commercial lean NO x trap catalyst

DOE PAGES

Bartova, Sarka; Mracek, David; Koci, Petr; ...

2014-10-12

Ammonia is an important intermediate of the NO x reduction in a NO x storage and reduction catalyst (aka lean NO x trap). NH 3 formed under rich conditions in the reduced front part of the catalyst is transported by convection downstream to the unregenerated (still oxidized) zone of the catalyst, where it further reacts with the stored oxygen and NO x. In this paper, the kinetics and selectivity of NH 3 reactions with the stored oxygen are studied in detail with a commercial Ba-based NO x storage catalyst containing platinum group metals (PGM), Ba and Ce oxides. Furthermore, steady-statemore » NH 3 decomposition, NH 3 oxidation by O 2 and NO, and N 2O decomposition are examined in light-off experiments. Periodic lean/rich cycling is measured first with O 2 and NH 3, and then with NO x + O 2 and NH 3 to discriminate between the NH 3 reactions with the stored oxygen and the stored NO x. The reaction of NH 3 with the stored O 2 is highly selective towards N 2, however a certain amount of NO x and N 2O is also formed. The formed NO x by-product is efficiently adsorbed on the NO x storage sites such that the NO x is not detected at the reactor outlet except at high temperatures. The stored NO x reacts with NH 3 feed in the next rich phase, contributing to the N 2O formation. Water inhibits the reactions of NH 3 with the stored oxygen. On the contrary, the presence of CO 2 increases the NH 3 consumption. Furthermore, CO 2 is able to provide additional oxygen for NH 3 oxidation, forming –CO in analogy to the reverse water gas shift reaction.« less
Analysis of flavin oxidation and electron-transfer inhibition in Plasmodium falciparum dihydroorotate dehydrogenase.

PubMed

Malmquist, Nicholas A; Gujjar, Ramesh; Rathod, Pradipsinh K; Phillips, Margaret A

2008-02-26

Plasmodium falciparum dihydroorotate dehydrogenase (pfDHODH) is a flavin-dependent mitochondrial enzyme that provides the only route to pyrimidine biosynthesis in the parasite. Clinically significant inhibitors of human DHODH (e.g., A77 1726) bind to a pocket on the opposite face of the flavin cofactor from dihydroorotate (DHO). This pocket demonstrates considerable sequence variability, which has allowed species-specific inhibitors of the malarial enzyme to be identified. Ubiquinone (CoQ), the physiological oxidant in the reaction, has been postulated to bind this site despite a lack of structural evidence. To more clearly define the residues involved in CoQ binding and catalysis, we undertook site-directed mutagenesis of seven residues in the structurally defined A77 1726 binding site, which we term the species-selective inhibitor site. Mutation of several of these residues (H185, F188, and F227) to Ala substantially decreased the affinity of pfDHODH-specific inhibitors (40-240-fold). In contrast, only a modest increase in the Kmapp for CoQ was observed, although mutation of Y528 in particular caused a substantial reduction in kcat (40-100-fold decrease). Pre-steady-state kinetic analysis by single wavelength stopped-flow spectroscopy showed that the mutations had no effect on the rate of the DHO-dependent reductive half-reaction, but most reduced the rate of the CoQ-dependent flavin oxidation step (3-20-fold decrease), while not significantly altering the Kdox for CoQ. As with the mutants, inhibitors that bind this site block the CoQ-dependent oxidative half-reaction without affecting the DHO-dependent step. These results identify residues involved in inhibitor binding and electron transfer to CoQ. Importantly, the data provide compelling evidence that the binding sites for CoQ and species-selective site inhibitors do not overlap, and they suggest instead that inhibitors act either by blocking the electron path between flavin and CoQ or by stabilizing a conformation that excludes CoQ binding.
Sulfate reduction and oxic respiration in marine sediments: implications for organic carbon preservation in euxinic environments

NASA Technical Reports Server (NTRS)

Canfield, D. E.; DeVincenzi, D. L. (Principal Investigator)

1989-01-01

Compilations have been made of sulfate reduction rates and oxic respiration rates over the entire range of marine sedimentation rates, and sedimentary environments, including several euxinic sites. These data show, consistent with the findings of Jorgensen (1982, Nature, 296, 643-645), that sulfate reduction and oxic respiration oxidize equal amounts of organic carbon in nearshore sediments. As sedimentation rates decrease, oxic respiration, becomes progressively more important, and in deep-sea sediments 100-1000 times more organic carbon is oxidized by oxic respiration than by sulfate reduction. By contrast, nearly as much organic carbon is oxidized by sulfate reduction in euxinic sediments as is oxidized by the sum of sulfate reduction and oxic respiration in normal marine sediments of similar deposition rate. This observation appears at odds with the enhanced preservation of organic carbon observed in euxinic sediments. However, only small reductions in (depth-integrated) organic carbon decomposition rates (compared to normal marine) are required to give both high organic carbon concentrations and enhanced carbon preservation in euxinic sediments. Lower rates of organic carbon decomposition (if only by subtle amounts) are explained by the diminished ability of anaerobic bacteria to oxidize the full suite of sedimentary organic compounds.
Annual Reporting of Monitoring at Morrill, Kansas in 2015

DOE Office of Scientific and Technical Information (OSTI.GOV)

LaFreniere, Lorraine M.

In September 2005, the CCC/USDA initiated periodic sampling of groundwater, in accord with a program (Argonne 2005b) approved by the KDHE (2005), to monitor carbon tetrachloride concentrations in the groundwater. Under the KDHE-approved monitoring plan (Argonne 2005b), groundwater was sampled twice yearly for VOCs analyses through 2011. During the initial two years of monitoring, analysis for selected geochemical parameters was also conducted to aid in the evaluation of possible natural contaminant degradation (reductive dechlorination) processes in the subsurface environment. Consistently low levels of dissolved oxygen (DO) and oxidation-reduction potential (ORP) at monitoring well MW1D (in the deepest portion of themore » contaminated aquifer) and the presence of chloroform (the primary degradation product of carbon tetrachloride) suggested that some degree of reductive dechlorination was occurring.« less
Effects of the state of Co species in Co/Al2O3 catalysts on the catalytic performance of propane dehydrogenation

NASA Astrophysics Data System (ADS)

Li, Xiuyi; Wang, Pengzhao; Wang, Haoren; Li, Chunyi

2018-05-01

In this paper, the Co/Al2O3 catalyst was prepared by incipient wetness impregnation method, and different post treatment methods were used to promote its dehydrogenation properties. Interestingly, we found that Co/Al2O3 catalysts with different post treatment protocols exhibited totally different catalytic behaviors in propane dehydrogenation. Fresh catalyst showed an induction period and was highly active for pyrolysis and coking at 10-30 min of reaction. The pre-reduction led to complete pyrolysis and coking at the beginning of reaction. However, the re-oxidation treatment gave a high selectivity (∼93.0%) to propylene at the whole process. XRD, H2-TPR, XPS, TEM and hydrogen chemisorption investigations showed that the post treatment has a great impact on the state of cobalt species and the performance of propane dehydrogenation over Co/Al2O3 catalysts. Specifically, the poorly dispersed metal Co led to pyrolysis and coking, while highly dispersed metal Co were responsible for the dehydrogenation of propane. The large Co3O4 particles (DFresh = 33.68 nm) result in the large metal Co grains (DPre-reduced = 24.90 nm) after the reduction or reaction process. While during the re-oxidization process, the surface metal Co was re-oxidized in a mild environment and got re-dispersion (DRe-oxidized = 6.07 nm). And the surface cobalt oxides layer is more readily to be reduced to metal Co during the reaction thus leading to the shortened induction period.
Evidence for the Existence of Autotrophic Nitrate-Reducing Fe(II)-Oxidizing Bacteria in Marine Coastal Sediment

PubMed Central

Laufer, Katja; Røy, Hans; Jørgensen, Bo Barker

2016-01-01

ABSTRACT Nitrate-reducing Fe(II)-oxidizing microorganisms were described for the first time ca. 20 years ago. Most pure cultures of nitrate-reducing Fe(II) oxidizers can oxidize Fe(II) only under mixotrophic conditions, i.e., when an organic cosubstrate is provided. A small number of nitrate-reducing Fe(II)-oxidizing cultures have been proposed to grow autotrophically, but unambiguous evidence for autotrophy has not always been provided. Thus, it is still unclear whether or to what extent Fe(II) oxidation coupled to nitrate reduction is an enzymatically catalyzed and energy-yielding autotrophic process or whether Fe(II) is abiotically oxidized by nitrite from heterotrophic nitrate reduction. The aim of the present study was to find evidence for the existence of autotrophic nitrate-reducing Fe(II) oxidizers in coastal marine sediments. Microcosm incubations showed that with increasing incubation times, the stoichiometric ratio of reduced nitrate/oxidized Fe(II) [NO3−reduced/Fe(II)oxidized] decreased, indicating a decreasing contribution of heterotrophic denitrification and/or an increasing contribution of autotrophic nitrate-reducing Fe(II) oxidation over time. After incubations of sediment slurries for >10 weeks, nitrate-reducing activity ceased, although nitrate was still present. This suggests that heterotrophic nitrate reduction had ceased due to the depletion of readily available organic carbon. However, after the addition of Fe(II) to these batch incubation mixtures, the nitrate-reducing activity resumed, and Fe(II) was oxidized, indicating the activity of autotrophic nitrate-reducing Fe(II) oxidizers. The concurrent reduction of 14C-labeled bicarbonate concentrations unambiguously proved that autotrophic C fixation occurred during Fe(II) oxidation and nitrate reduction. Our results clearly demonstrated that autotrophic nitrate-reducing Fe(II)-oxidizing bacteria were present in the investigated coastal marine sediments. IMPORTANCE Twenty years after the discovery of nitrate-reducing Fe(II) oxidizers, it is still controversially discussed whether autotrophic nitrate-reducing Fe(II)-oxidizing microorganisms exist and to what extent Fe(II) oxidation in this reduction/oxidation process is enzymatically catalyzed or which role abiotic side reactions of Fe(II) with reactive N species play. Most pure cultures of nitrate-reducing Fe(II) oxidizers are mixotrophic; i.e., they need an organic cosubstrate to maintain their activity over several cultural transfers. For the few existing autotrophic isolates and enrichment cultures, either the mechanism of nitrate-reducing Fe(II) oxidation is not known or evidence for their autotrophic lifestyle is controversial. In the present study, we provide evidence for the existence of autotrophic nitrate-reducing Fe(II) oxidizers in coastal marine sediments. The evidence is based on stoichiometries of nitrate reduction and Fe(II) oxidation determined in microcosm incubations and the incorporation of carbon from CO2 under conditions that favor the activity of nitrate-reducing Fe(II) oxidizers. PMID:27496777
Competition for ammonia influences the structure of chemotrophic communities in geothermal springs.

PubMed

Hamilton, Trinity L; Koonce, Evangeline; Howells, Alta; Havig, Jeff R; Jewell, Talia; de la Torre, José R; Peters, John W; Boyd, Eric S

2014-01-01

Source waters sampled from Perpetual Spouter hot spring (pH 7.03, 86.4°C), Yellowstone National Park, WY, have low concentrations of total ammonia, nitrite, and nitrate, suggesting nitrogen (N) limitation and/or tight coupling of N cycling processes. Dominant small-subunit rRNA sequences in Perpetual Spouter source sediments are closely affiliated with the ammonia-oxidizing archaeon "Candidatus Nitrosocaldus yellowstonii" and the putatively nitrogen-fixing (diazotrophic) bacterium Thermocrinis albus, respectively, suggesting that these populations may interact at the level of the bioavailable N pool, specifically, ammonia. This hypothesis was evaluated by using a combination of geochemical, physiological, and transcriptomic analyses of sediment microcosms. Amendment of microcosms with allylthiourea, an inhibitor of ammonia oxidation, decreased rates of acetylene reduction (a proxy for N2 fixation) and nitrite production (a proxy for ammonia oxidation) and decreased transcript levels of structural genes involved in both nitrogen fixation (nifH) and ammonia oxidation (amoA). In contrast, amendment of microcosms with ammonia stimulated nitrite production and increased amoA transcript levels while it suppressed rates of acetylene reduction and decreased nifH transcript levels. Sequencing of amplified nifH and amoA transcripts from native sediments, as well as microcosms, at 2 and 4 h postamendment, indicates that the dominant and responsive populations involved in ammonia oxidation and N2 fixation are closely affiliated with Ca. Nitrosocaldus yellowstonii and T. albus, respectively. Collectively, these results suggest that ammonia-oxidizing archaea, such as Ca. Nitrosocaldus yellowstonii, have an apparent affinity for ammonia that is higher than that of the diazotrophs present in this ecosystem. Depletion of the bioavailable N pool through the activity of ammonia-oxidizing archaea likely represents a strong selective pressure for the inclusion of organisms capable of nitrogen fixation in geothermal communities. These observations help to explain the strong pattern in the codistribution of ammonia-oxidizing archaea and diazotrophs in circumneutral-to-alkaline geothermal springs.
Competition for Ammonia Influences the Structure of Chemotrophic Communities in Geothermal Springs

PubMed Central

Hamilton, Trinity L.; Koonce, Evangeline; Howells, Alta; Havig, Jeff R.; Jewell, Talia; de la Torre, José R.; Peters, John W.

2014-01-01

Source waters sampled from Perpetual Spouter hot spring (pH 7.03, 86.4°C), Yellowstone National Park, WY, have low concentrations of total ammonia, nitrite, and nitrate, suggesting nitrogen (N) limitation and/or tight coupling of N cycling processes. Dominant small-subunit rRNA sequences in Perpetual Spouter source sediments are closely affiliated with the ammonia-oxidizing archaeon “Candidatus Nitrosocaldus yellowstonii” and the putatively nitrogen-fixing (diazotrophic) bacterium Thermocrinis albus, respectively, suggesting that these populations may interact at the level of the bioavailable N pool, specifically, ammonia. This hypothesis was evaluated by using a combination of geochemical, physiological, and transcriptomic analyses of sediment microcosms. Amendment of microcosms with allylthiourea, an inhibitor of ammonia oxidation, decreased rates of acetylene reduction (a proxy for N2 fixation) and nitrite production (a proxy for ammonia oxidation) and decreased transcript levels of structural genes involved in both nitrogen fixation (nifH) and ammonia oxidation (amoA). In contrast, amendment of microcosms with ammonia stimulated nitrite production and increased amoA transcript levels while it suppressed rates of acetylene reduction and decreased nifH transcript levels. Sequencing of amplified nifH and amoA transcripts from native sediments, as well as microcosms, at 2 and 4 h postamendment, indicates that the dominant and responsive populations involved in ammonia oxidation and N2 fixation are closely affiliated with Ca. Nitrosocaldus yellowstonii and T. albus, respectively. Collectively, these results suggest that ammonia-oxidizing archaea, such as Ca. Nitrosocaldus yellowstonii, have an apparent affinity for ammonia that is higher than that of the diazotrophs present in this ecosystem. Depletion of the bioavailable N pool through the activity of ammonia-oxidizing archaea likely represents a strong selective pressure for the inclusion of organisms capable of nitrogen fixation in geothermal communities. These observations help to explain the strong pattern in the codistribution of ammonia-oxidizing archaea and diazotrophs in circumneutral-to-alkaline geothermal springs. PMID:24242238
Microbial reduction of manganese oxides - Interactions with iron and sulfur

NASA Technical Reports Server (NTRS)

Myers, Charles R.; Nealson, Kenneth H.

1988-01-01

Alteromonas putrefaciens (strain MR-1) is capable of rapid Mn(IV) reduction under conditions of neutral pH and temperatures characteristic of the Oneida Lake, New York, sediments from which it was isolated. MR-1 also reduces Fe(3+) to Fe(2+), and disproportionates thiosulfate to sulfide and sulfite; independently, the Fe(2+) and sulfide act as rapid reductants of Mn. The addition of Fe(3+) or thiosulfate to cultures of MR-1 in the presence of oxidized Mn increases the rate and the extent of Mn reduction relative to that observed in the absence of Fe(3+) or thiosulfate. Furthermore, when Fe(3+) and Mn oxides are present conjointly, Fe(2+) does not appear until the reduction of the oxidized Mn is complete. These results demonstrate that the observed rates of Fe(2+) and sulfide production may underestimate the total rates of Fe and sulfate reduction in those environments containing oxidized Mn. These results also demonstrate the potential impact that a single microbe can exert on sediment geochemistry, and provide the basis for preliminary models of the complexity of microbial and geochemical interactions that occur.
Removal of PCBs in contaminated soils by means of chemical reduction and advanced oxidation processes.

PubMed

Rybnikova, V; Usman, M; Hanna, K

2016-09-01

Although the chemical reduction and advanced oxidation processes have been widely used individually, very few studies have assessed the combined reduction/oxidation approach for soil remediation. In the present study, experiments were performed in spiked sand and historically contaminated soil by using four synthetic nanoparticles (Fe(0), Fe/Ni, Fe3O4, Fe3 - x Ni x O4). These nanoparticles were tested firstly for reductive transformation of polychlorinated biphenyls (PCBs) and then employed as catalysts to promote chemical oxidation reactions (H2O2 or persulfate). Obtained results indicated that bimetallic nanoparticles Fe/Ni showed the highest efficiency in reduction of PCB28 and PCB118 in spiked sand (97 and 79 %, respectively), whereas magnetite (Fe3O4) exhibited a high catalytic stability during the combined reduction/oxidation approach. In chemical oxidation, persulfate showed higher PCB degradation extent than hydrogen peroxide. As expected, the degradation efficiency was found to be limited in historically contaminated soil, where only Fe(0) and Fe/Ni particles exhibited reductive capability towards PCBs (13 and 18 %). In oxidation step, the highest degradation extents were obtained in presence of Fe(0) and Fe/Ni (18-19 %). The increase in particle and oxidant doses improved the efficiency of treatment, but overall degradation extents did not exceed 30 %, suggesting that only a small part of PCBs in soil was available for reaction with catalyst and/or oxidant. The use of organic solvent or cyclodextrin to improve the PCB availability in soil did not enhance degradation efficiency, underscoring the strong impact of soil matrix. Moreover, a better PCB degradation was observed in sand spiked with extractable organic matter separated from contaminated soil. In contrast to fractions with higher particle size (250-500 and <500 μm), no PCB degradation was observed in the finest fraction (≤250 μm) having higher organic matter content. These findings may have important practical implications to promote successively reduction and oxidation reactions in soils and understand the impact of soil properties on remediation performance.
High-Potential Electrocatalytic O2 Reduction with Nitroxyl / NOx Mediators: Implications for Fuel Cells and Aerobic Oxidation Catalysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gerken, James B.; Stahl, Shannon S.

2015-07-15

Efficient reduction of O2 to water is a central challenge in energy conversion and aerobic oxidation catalysis. In the present study, we investigate the electrochemical reduction of O2 with soluble organic nitroxyl and nitrogen oxide (NOx) mediators. When used alone, neither organic nitroxyls, such as TEMPO (2,2,6,6-tetramethyl-1-piperidinyl-N-oxyl), nor NOx species, such as sodium nitrite, are effective mediators of electrochemical O2 reduction. The combination of nitroxyl/NOx species, however, mediates sustained O2 reduction at electrochemical potentials of 0.19–0.33 V (vs. Fc/Fc+) in acetonitrile containing trifluoroacetic acid. Mechanistic analysis of the coupled redox reactions supports a process in which the nitrogen oxide catalystmore » drives aerobic oxidation of a nitroxyl mediator to an oxoammonium species, which then is reduced back to the nitroxyl at the cathode. The electrolysis potential is dictated by the oxoammonium/nitroxyl reduction potential. The high potentials observed with this ORR system benefit from the mechanism-based specificity for four-electron reduction of oxygen to water mediated by NOx species, together with kinetically efficient reduction of oxidized NOx species by TEMPO and other organic nitroxyls. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center, funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.« less
Visualizing the Cu/Cu2(O) Interface Transition in Nanoparticles with Environmental Scanning Transmission Electron Microscopy.

PubMed

LaGrow, Alec P; Ward, Michael R; Lloyd, David C; Gai, Pratibha L; Boyes, Edward D

2017-01-11

Understanding the oxidation and reduction mechanisms of catalytically active transition metal nanoparticles is important to improve their application in a variety of chemical processes. In nanocatalysis the nanoparticles can undergo oxidation or reduction in situ, and thus the redox species are not what are observed before and after reactions. We have used the novel environmental scanning transmission electron microscope (ESTEM) with 0.1 nm resolution in systematic studies of complex dynamic oxidation and reduction mechanisms of copper nanoparticles. The oxidation of copper has previously been reported to be dependent on its crystallography and its interaction with the substrate. By following the dynamic oxidation process in situ in real time with high-angle annular dark-field imaging in the ESTEM, we use conditions ideal to track the oxidation front as it progresses across a copper nanoparticle by following the changes in the atomic number (Z) contrast with time. The oxidation occurs via the nucleation of the oxide phase (Cu 2 O) from one area of the nanoparticle which then progresses unidirectionally across the particle, with the Cu-to-Cu 2 O interface having a relationship of Cu{111}//Cu 2 O{111}. The oxidation kinetics are related to the temperature and oxygen pressure. When the process is reversed in hydrogen, the reduction process is observed to be similar to the oxidation, with the same crystallographic relationship between the two phases. The dynamic observations provide unique insights into redox mechanisms which are important to understanding and controlling the oxidation and reduction of copper-based nanoparticles.
Modified fly ash from municipal solid waste incineration as catalyst support for Mn-Ce composite oxides

NASA Astrophysics Data System (ADS)

Chen, Xiongbo; Liu, Ying; Yang, Ying; Ren, Tingyan; Pan, Lang; Fang, Ping; Chen, Dingsheng; Cen, Chaoping

2017-08-01

Fly ash from municipal solid waste incineration was modified by hydrothermal treatment and used as catalyst support for Mn-Ce composite oxides. The prepared catalyst showed good activity for the selective catalytic reduction (SCR) of NO by NH3. A NO conversion of 93% could be achieved at 300 °C under a GHSV of 32857 h-1. With the help of characterizations including XRD, BET, SEM, TEM, XPS and TPR, it was found that hydrothermal treatment brought a large surface area and abundant mesoporous to the modified fly ash, and Mn-Ce composite oxides were highly dispersed on the surface of the support. These physical and chemical properties were the intrinsic reasons for the good SCR activity. This work transformed fly ash into high value-added products, providing a new approach to the resource utilization and pollution control of fly ash.

Understanding Nitrifier Denitrification: How far are we?

NASA Astrophysics Data System (ADS)

Wrage-Mönnig, N.

2014-12-01

Nitrifier denitrification is the oxidation of ammonia (NH3) via hydroxylamine (NH2OH) to nitrite (NO2-) and subsequent reduction of NO2- via nitric oxide (NO) to the greenhouse gas nitrous oxide (N2O) and possibly to dinitrogen (N2) by autotrophic nitrifiers. Especially in recent years, a lot of research has been conducted on this pathway. Under some conditions, it might dominate the N2O production from soils. Methods for studying nitrifier denitrification include selective inhibition, stable isotope and isotopomer methods, molecular and modelling approaches. They are applied from pure culture and pot studies to the field scale, trying to improve our knowledge of the conditions and factors controlling nitrifier denitrification. But how far are we? What have we learned so far and what remains to be discovered? With this contribution, I am trying to give an update of our understanding of this less well-known but important pathway.
Demonstration of an N7 integrated fab process for metal oxide EUV photoresist

NASA Astrophysics Data System (ADS)

De Simone, Danilo; Mao, Ming; Kocsis, Michael; De Schepper, Peter; Lazzarino, Frederic; Vandenberghe, Geert; Stowers, Jason; Meyers, Stephen; Clark, Benjamin L.; Grenville, Andrew; Luong, Vinh; Yamashita, Fumiko; Parnell, Doni

2016-03-01

Inpria has developed a directly patternable metal oxide hard-mask as a robust, high-resolution photoresist for EUV lithography. In this paper we demonstrate the full integration of a baseline Inpria resist into an imec N7 BEOL block mask process module. We examine in detail both the lithography and etch patterning results. By leveraging the high differential etch resistance of metal oxide photoresists, we explore opportunities for process simplification and cost reduction. We review the imaging results from the imec N7 block mask patterns and its process windows as well as routes to maximize the process latitude, underlayer integration, etch transfer, cross sections, etch equipment integration from cross metal contamination standpoint and selective resist strip process. Finally, initial results from a higher sensitivity Inpria resist are also reported. A dose to size of 19 mJ/cm2 was achieved to print pillars as small as 21nm.
Feasible metabolisms in high pH springs of the Philippines

PubMed Central

Cardace, Dawn; Meyer-Dombard, D'Arcy R.; Woycheese, Kristin M.; Arcilla, Carlo A.

2015-01-01

A field campaign targeting high pH, H2-, and CH4-emitting serpentinite-associated springs in the Zambales and Palawan Ophiolites of the Philippines was conducted in 2012-2013, and enabled description of several springs sourced in altered pillow basalts, gabbros, and peridotites. We combine field observations of pH, temperature, conductivity, dissolved oxygen, and oxidation-reduction potential with analyses of major ions, dissolved inorganic carbon, dissolved organic carbon, and dissolved gas phases in order to model the activities of selected phases important to microbial metabolism, and to rank feasible metabolic reactions based on energy yield. We document changing geochemical inventories in these springs between sampling years, and examine how the environment supports or prevents the function of certain microbial metabolisms. In all, this geochemistry-based assessment of feasible metabolisms indicates methane cycling, hydrogen oxidation, some iron and sulfur metabolisms, and ammonia oxidation are feasible reactions in this continental site of serpentinization. PMID:25713561
Feasible metabolisms in high pH springs of the Philippines.

PubMed

Cardace, Dawn; Meyer-Dombard, D'Arcy R; Woycheese, Kristin M; Arcilla, Carlo A

2015-01-01

A field campaign targeting high pH, H2-, and CH4-emitting serpentinite-associated springs in the Zambales and Palawan Ophiolites of the Philippines was conducted in 2012-2013, and enabled description of several springs sourced in altered pillow basalts, gabbros, and peridotites. We combine field observations of pH, temperature, conductivity, dissolved oxygen, and oxidation-reduction potential with analyses of major ions, dissolved inorganic carbon, dissolved organic carbon, and dissolved gas phases in order to model the activities of selected phases important to microbial metabolism, and to rank feasible metabolic reactions based on energy yield. We document changing geochemical inventories in these springs between sampling years, and examine how the environment supports or prevents the function of certain microbial metabolisms. In all, this geochemistry-based assessment of feasible metabolisms indicates methane cycling, hydrogen oxidation, some iron and sulfur metabolisms, and ammonia oxidation are feasible reactions in this continental site of serpentinization.
Suppression of H-/O2- exchange by incorporated nitride anions in the perovskite lattice

NASA Astrophysics Data System (ADS)

Takeiri, Fumitaka; Yajima, Takeshi; Yamamoto, Takafumi; Kobayashi, Yoji; Matsui, Toshiaki; Hester, James; Kageyama, Hiroshi

2017-12-01

We investigate the low temperature anion exchange behavior of hydride and oxide in perovskite oxynitrides. CaH2 reduction of (Sr1-xLax)Ti(O3-xNx) (0
REPEATED REDUCTIVE AND OXIDATIVE TREATMENTS ON GRANULAR ACTIVATED CARBON

EPA Science Inventory

Fenton oxidation and Fenton oxidation preceded by reduction solutions were applied to granular activated carbon (GAC) to chemically regenerate the adsorbent. No adsorbate was present on the GAC so physicochemical effects from chemically aggressive regeneration of the carbon coul...
Oxidation and reduction in irradiated binary crystals of resorcinol and progesterone

NASA Astrophysics Data System (ADS)

Box, Harold C.; Budzinski, Edwin E.

1985-12-01

The binary single crystals of resorcinol and progesterone were x-irradiated at 4.2 K. The semiquinone of resorcinol was generated by radiation induced oxidation. The oxidation and reduction products were identified from ESR and ENDOR measurements. (AIP)
Study on emission characteristics and reduction strategy of nitrous oxide during wastewater treatment by different processes.

PubMed

Sun, Shichang; Bao, Zhiyuan; Sun, Dezhi

2015-03-01

Given the inexorable increase in global wastewater treatment, increasing amounts of nitrous oxide are expected to be emitted from wastewater treatment plants and released to the atmosphere. It has become imperative to study the emission and control of nitrous oxide in the various wastewater treatment processes currently in use. In the present investigation, the emission characteristics and the factors affecting the release of nitrous oxide were studied via full- and pilot-scale experiments in anoxic-oxic, sequencing batch reactor and oxidation ditch processes. We propose an optimal treatment process and relative strategy for nitrous oxide reduction. Our results show that both the bio-nitrifying and bio-denitrifying treatment units in wastewater treatment plants are the predominant sites for nitrous oxide production in each process, while the aerated treatment units are the critical sources for nitrous oxide emission. Compared with the emission of nitrous oxide from the anoxic-oxic (1.37% of N-influent) and sequencing batch reactor (2.69% of N-influent) processes, much less nitrous oxide (0.25% of N-influent) is emitted from the oxidation ditch process, which we determined as the optimal wastewater treatment process for nitrous oxide reduction, given the current technologies. Nitrous oxide emissions differed with various operating parameters. Controlling the dissolved oxygen concentration at a proper level during nitrification and denitrification and enhancing the utilization rate of organic carbon in the influent for denitrification are the two critical methods for nitrous oxide reduction in the various processes considered.
Fe(III) oxides accelerate microbial nitrate reduction and electricity generation by Klebsiella pneumoniae L17.

PubMed

Liu, Tongxu; Li, Xiaomin; Zhang, Wei; Hu, Min; Li, Fangbai

2014-06-01

Klebsiella pneumoniae L17 is a fermentative bacterium that can reduce iron oxide and generate electricity under anoxic conditions, as previously reported. This study reveals that K. pneumoniae L17 is also capable of dissimilatory nitrate reduction, producing NO2(-), NH4(+), NO and N2O under anoxic conditions. The presence of Fe(III) oxides (i.e., α-FeOOH, γ-FeOOH, α-Fe2O3 and γ-Fe2O3) significantly accelerates the reduction of nitrate and generation of electricity by K. pneumoniae L17, which is similar to a previous report regarding another fermentative bacterium, Bacillus. No significant nitrate reduction was observed upon treatment with Fe(2+) or α-FeOOH+Fe(2+), but a slight facilitation of nitrate reduction and electricity generation was observed upon treatment with L17+Fe(2+). This result suggests that aqueous Fe(II) or mineral-adsorbed Fe(II) cannot reduce nitrate abiotically but that L17 can catalyze the reduction of nitrate and generation of electricity in the presence of Fe(II) (which might exist as cell surface-bound Fe(II)). To rule out the potential effect of Fe(II) produced by L17 during microbial iron reduction, treatments with the addition of TiO2 or Al2O3 instead of Fe(III) oxides also exhibited accelerated microbial nitrate reduction and electricity generation, indicating that cell-mineral sorption did account for the acceleration effect. However, the acceleration caused by Fe(III) oxides is only partially attributed to the cell surface-bound Fe(II) and cell-mineral sorption but may be driven by the iron oxide conduction band-mediated electron transfer from L17 to nitrate or an electrode, as proposed previously. The current study extends the diversity of bacteria of which nitrate reduction and electricity generation can be facilitated by the presence of iron oxides and confirms the positive role of Fe(III) oxides on microbial nitrate reduction and electricity generation by particular fermentative bacteria in anoxic environments. Copyright © 2014 Elsevier Inc. All rights reserved.
Dye-controlled interfacial electron transfer for high-current indium tin oxide photocathodes.

PubMed

Huang, Zhongjie; He, Mingfu; Yu, Mingzhe; Click, Kevin; Beauchamp, Damian; Wu, Yiying

2015-06-01

Efficient sensitized photocathodes are highly desired for solar fuels and tandem solar cells, yet the development is hindered by the scarcity of suitable p-type semiconductors. The generation of high cathodic photocurrents by sensitizing a degenerate n-type semiconductor (tin-doped indium oxide; ITO) is reported. The sensitized mesoporous ITO electrodes deliver cathodic photocurrents of up to 5.96±0.19 mA cm(-2), which are close to the highest record in conventional p-type sensitized photocathodes. This is realized by the rational selection of dyes with appropriate energy alignments with ITO. The energy level alignment between the highest occupied molecular orbital of the sensitizer and the conduction band of ITO is crucial for efficient hole injection. Transient absorption spectroscopy studies demonstrate that the cathodic photocurrent results from reduction of the photoexcited sensitizer by free electrons in ITO. Our results reveal a new perspective toward the selection of electrode materials for sensitized photocathodes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Antioxidant enzymes as redox-based biomarkers: a brief review

PubMed Central

Yang, Hee-Young; Lee, Tae-Hoon

2015-01-01

The field of redox proteomics focuses to a large extent on analyzing cysteine oxidation in proteins under different experimental conditions and states of diseases. The identification and localization of oxidized cysteines within the cellular milieu is critical for understanding the redox regulation of proteins under physiological and pathophysiological conditions, and it will in turn provide important information that are potentially useful for the development of novel strategies in the treatment and prevention of diseases associated with oxidative stress. Antioxidant enzymes that catalyze oxidation/reduction processes are able to serve as redox biomarkers in various human diseases, and they are key regulators controlling the redox state of functional proteins. Redox regulators with antioxidant properties related to active mediators, cellular organelles, and the surrounding environments are all connected within a network and are involved in diseases related to redox imbalance including cancer, ischemia/reperfusion injury, neurodegenerative diseases, as well as normal aging. In this review, we will briefly look at the selected aspects of oxidative thiol modification in antioxidant enzymes and thiol oxidation in proteins affected by redox control of antioxidant enzymes and their relation to disease. [BMB Reports 2015; 48(4): 200-208] PMID:25560698
TEMPO-oxidized cellulose nanofibers

NASA Astrophysics Data System (ADS)

Isogai, Akira; Saito, Tsuguyuki; Fukuzumi, Hayaka

2011-01-01

Native wood celluloses can be converted to individual nanofibers 3-4 nm wide that are at least several microns in length, i.e. with aspect ratios >100, by TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl radical)-mediated oxidation and successive mild disintegration in water. Preparation methods and fundamental characteristics of TEMPO-oxidized cellulose nanofibers (TOCN) are reviewed in this paper. Significant amounts of C6 carboxylate groups are selectively formed on each cellulose microfibril surface by TEMPO-mediated oxidation without any changes to the original crystallinity (~74%) or crystal width of wood celluloses. Electrostatic repulsion and/or osmotic effects working between anionically-charged cellulose microfibrils, the ζ-potentials of which are approximately -75 mV in water, cause the formation of completely individualized TOCN dispersed in water by gentle mechanical disintegration treatment of TEMPO-oxidized wood cellulose fibers. Self-standing TOCN films are transparent and flexible, with high tensile strengths of 200-300 MPa and elastic moduli of 6-7 GPa. Moreover, TOCN-coated poly(lactic acid) films have extremely low oxygen permeability. The new cellulose-based nanofibers formed by size reduction process of native cellulose fibers by TEMPO-mediated oxidation have potential application as environmentally friendly and new bio-based nanomaterials in high-tech fields.
On the annealing-induced enhancement of the interface properties of NiO:Cu/wet-SiOx/n-Si tunnelling junction solar cells

NASA Astrophysics Data System (ADS)

Yang, Xueliang; Liu, Wei; Chen, Jingwei; Sun, Yun

2018-04-01

Using metal oxides to form a carrier-selective interface on crystalline silicon (c-Si) has recently generated considerable interest for use with c-Si photovoltaics because of the potential to reduce cost. n-type oxides, such as MoO3, V2O5, and WO3, have been widely studied. In this work, a p-type oxide, Cu-doped NiO (NiO:Cu), is explored as a transparent hole-selective contact to n-Si. An ultrathin SiOx layer, fabricated by a wet-chemical method (wet-SiOx), is introduced at the NiO:Cu/n-Si interface to achieve a tunnelling junction solar cell. Interestingly, it was observed that the interface quality of the NiO:Cu/wet-SiOx/n-Si heterojunction was dramatically enhanced by post-deposition annealing (PDA) at a temperature of 200 °C. Our device exhibits an improved power conversion efficiency of 10.8%, which is the highest efficiency among NiO/Si heterojunction photo-electric devices to date. It is demonstrated that the 200 °C PDA treatment enhances the built-in field by a reduction in the interface density of states (Dit) but does not influence the work function of the NiO:Cu thin layer. This stable work function after the PDA treatment is in conflict with the changed built-in field according to the Schottky model. Thus, the Bardeen model is introduced for this physical insight: the enhancement of the built-in field originates from the unpinning of the Fermi levels of NiO:Cu and n-Si by the interface state reduction.
A survey of analytical methods employed for monitoring of Advanced Oxidation/Reduction Processes for decomposition of selected perfluorinated environmental pollutants.

PubMed

Trojanowicz, Marek; Bobrowski, Krzysztof; Szostek, Bogdan; Bojanowska-Czajka, Anna; Szreder, Tomasz; Bartoszewicz, Iwona; Kulisa, Krzysztof

2018-01-15

The monitoring of Advanced Oxidation/Reduction Processes (AO/RPs) for the evaluation of the yield and mechanisms of decomposition of perfluorinated compounds (PFCs) is often a more difficult task than their determination in the environmental, biological or food samples with complex matrices. This is mostly due to the formation of hundreds, or even thousands, of both intermediate and final products. The considered AO/RPs, involving free radical reactions, include photolytic and photocatalytic processes, Fenton reactions, sonolysis, ozonation, application of ionizing radiation and several wet oxidation processes. The main attention is paid to the most commonly occurring PFCs in the environment, namely PFOA and PFOS. The most powerful and widely exploited method for this purpose is without a doubt LC/MS/MS, which allows the identification and trace quantitation of all species with detectability and resolution power depending on the particular instrumental configurations. The GC/MS is often employed for the monitoring of volatile fluorocarbons, confirming the formation of radicals in the processes of C‒C and C‒S bonds cleavage. For the direct monitoring of radicals participating in the reactions of PFCs decomposition, the molecular spectrophotometry is employed, especially electron paramagnetic resonance (EPR). The UV/Vis spectrophotometry as a detection method is of special importance in the evaluation of kinetics of radical reactions with the use of pulse radiolysis methods. The most commonly employed for the determination of the yield of mineralization of PFCs is ion-chromatography, but there is also potentiometry with ion-selective electrode and the measurements of general parameters such as Total Organic Carbon and Total Organic Fluoride. The presented review is based on about 100 original papers published in both analytical and environmental journals. Copyright © 2017 Elsevier B.V. All rights reserved.
Electrochemical determination of 2,4,6-trinitrophenol using a hybrid film composed of a copper-based metal organic framework and electroreduced graphene oxide.

PubMed

Wang, Yong; Cao, Wei; Wang, Luyao; Zhuang, Qianfen; Ni, Yongnian

2018-06-04

A metal organic framework (MOF) of the type copper(II)-1,3,5-benzenetricarboxylic acid (Cu-BTC) was electrodeposited on electroreduced graphene oxide (ERGO) placed on a glassy carbon electrode (GCE). The modified GCE was used for highly sensitive electrochemical determination of 2,4,6-trinitrophenol (TNP). The fabrication process of the modified electrode was characterized by scanning electron microscopy and electrochemical impedance spectroscopy. Differential pulse voltammetry (DPV) demonstrates that the Cu-BTC/ERGO/GCE gives stronger signals for TNP reduction than Cu-BTC/GCE or ERGO/GCE alone. DPV also shows TNP to exhibit three reduction peaks, the first at a potential of -0.42 V (vs. SCE). This potential was selected because the other three similarly-structured compounds (2-nitrophenol, 4-nitrophenol, 2,4-dinitrophenol) do not give a signal at this potential. Response is linear in the 0.2 to 10 μM TNP concentration range, with a 0.1 μM detection limit (at S/N = 3) and a 15.98 μA∙μM -1 ∙cm -2 sensitivity under optimal conditions. The applicability of the sensor was evaluated by detecting TNP in spiked tap water and lake water samples. Recoveries ranged between 95 and 101%. Graphical abstract Schematic presentation of an electrochemical sensor that was fabricated by electrodeposition of the metal-organic framework (MOF) of copper(II)-1,3,5-benzenetricarboxylic acid (Cu-BTC) onto the surface of electroreduced graphene oxide (ERGO) modified glassy carbon electrode (GCE). It was applied to sensitive and selective detection of 2,4,6-trinitrophenol (TNP).
Manganese oxide/poly(3,4-ethylenedioxythiophene) hybrid electrocatalysts for the oxygen reduction reaction in alkaline fuel cells

DOE PAGES

Lambert, Timothy N.; Vigil, Julian A.

2016-08-22

Manganese oxide/poly(3,4-ethylene-dioxythiophene) (MnO x/ PEDOT) nanostructured hybrid thin films were prepared using a simple anodic electrodeposition process from aqueous solution, and then tested for oxygen reduction reaction (ORR) activity in alkaline electrolyte using rotating disk electrode and rotating ring disk electrode methods. MnO x/PEDOT provided improvements over MnO x-only and PEDOT-only control films, with > 0.2 V decrease in onset and half-wave overpotentials, and > 1.5 times increase in terminal current density. The MnO x/PEDOT film exhibited only a slightly lower n value (n = 3.86-3.92) than the 20% Pt/C benchmark electrocatalyst (n = 3.98) across all potentials. MnO x/PEDOTmore » also displayed a more positive half-wave potential and superior electrocatalytic selectivity for the ORR upon methanol exposure than 20% Pt/C. Here, the high activity and synergism of MnO x/PEDOT towards the ORR is attributed to effective intermixing/dispersion of the two materials, intimate substrate contact with improved charge transfer processes attained by co-electrodepositing MnO x with PEDOT and due to the increase in Mn 3+ content at the surface of the oxide.« less
Fabrication of Highly Sensitive Nonenzymatic Electrochemical H₂O₂ Sensor Based on Pt Nanoparticles Anchored Reduced Graphene Oxide.

PubMed

Dhara, Keerthy; Ramachandran, T; Nair, Bipin G; Babu, T G Satheesh

2018-06-01

A highly sensitive nonenzymatic hydrogen peroxide (H2O2) sensor was fabricated using platinum nanoparticles decorated reduced graphene oxide (Pt/rGO) nanocomposite. The Pt/rGO nanocomposite was prepared by single-step chemical reduction method. Nanocomposite was characterized by various analytical techniques including Raman spectroscopy, X-ray diffraction, field emission scanning electron microscope and high-resolution transmission electron microscopy. Screen printed electrodes (SPEs) were fabricated and the nanocomposite was cast on the working area of the SPE. Cyclic voltammetry and amperometry demonstrated that the Pt/rGO/SPE displayed much higher electrocatalytic activity towards the reduction of H2O2 than the other modified electrodes. The sensor exhibited wide linear detection range (from 10 μM to 8 mM), very high sensitivity of 1848 μA mM-1 cm-2 and a lower limit of detection of 0.06 μM. The excellent performance of Pt/rGO/SPE sensor were attributed to the reduced graphene oxide being used as an effective matrix to load a number of Pt nanoparticles and the synergistic amplification effect of the two kinds of nanomaterials. Moreover, the sensor showed remarkable features such as good reproducibility, repeatability, long-term stability, and selectivity.
Single-Atom Catalysts of Precious Metals for Electrochemical Reactions.

PubMed

Kim, Jiwhan; Kim, Hee-Eun; Lee, Hyunjoo

2018-01-10

Single-atom catalysts (SACs), in which metal atoms are dispersed on the support without forming nanoparticles, have been used for various heterogeneous reactions and most recently for electrochemical reactions. In this Minireview, recent examples of single-atom electrocatalysts used for the oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), hydrogen evolution reaction (HER), formic acid oxidation reaction (FAOR), and methanol oxidation reaction (MOR) are introduced. Many density functional theory (DFT) simulations have predicted that SACs may be effective for CO 2 reduction to methane or methanol production while suppressing H 2 evolution, and those cases are introduced here as well. Single atoms, mainly Pt single atoms, have been deposited on TiN or TiC nanoparticles, defective graphene nanosheets, N-doped covalent triazine frameworks, graphitic carbon nitride, S-doped zeolite-templated carbon, and Sb-doped SnO 2 surfaces. Scanning transmission electron microscopy, extended X-ray absorption fine structure measurement, and in situ infrared spectroscopy have been used to detect the single-atom structure and confirm the absence of nanoparticles. SACs have shown high mass activity, minimizing the use of precious metal, and unique selectivity distinct from nanoparticle catalysts owing to the absence of ensemble sites. Additional features that SACs should possess for effective electrochemical applications were also suggested. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.
Manganese oxide/poly(3,4-ethylenedioxythiophene) hybrid electrocatalysts for the oxygen reduction reaction in alkaline fuel cells

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lambert, Timothy N.; Vigil, Julian A.

Manganese oxide/poly(3,4-ethylene-dioxythiophene) (MnO x/ PEDOT) nanostructured hybrid thin films were prepared using a simple anodic electrodeposition process from aqueous solution, and then tested for oxygen reduction reaction (ORR) activity in alkaline electrolyte using rotating disk electrode and rotating ring disk electrode methods. MnO x/PEDOT provided improvements over MnO x-only and PEDOT-only control films, with > 0.2 V decrease in onset and half-wave overpotentials, and > 1.5 times increase in terminal current density. The MnO x/PEDOT film exhibited only a slightly lower n value (n = 3.86-3.92) than the 20% Pt/C benchmark electrocatalyst (n = 3.98) across all potentials. MnO x/PEDOTmore » also displayed a more positive half-wave potential and superior electrocatalytic selectivity for the ORR upon methanol exposure than 20% Pt/C. Here, the high activity and synergism of MnO x/PEDOT towards the ORR is attributed to effective intermixing/dispersion of the two materials, intimate substrate contact with improved charge transfer processes attained by co-electrodepositing MnO x with PEDOT and due to the increase in Mn 3+ content at the surface of the oxide.« less
Investigation of NOx Removal from Small Engine Exhaust

NASA Technical Reports Server (NTRS)

Akyurtlu, Ates; Akyurtlu, Jale F.

1999-01-01

Contribution of emissions from small engines to the air pollution is significant. Due to differences in operating conditions and economics, the pollution control systems designed for automobiles will be neither suitable nor economically feasible for use on small engines. The objective of this project was to find a catalyst for the removal of NOx from the exhaust of small engines which use a rich air to fuel ratio. The desired catalyst should be inexpensive so that the cost of the pollution control unit will be only a small fraction of the total equipment cost. The high cost of noble metals makes them too expensive for use as NOx catalyst for small engines. Catalytic reduction of Nitrogen Oxide (NO) can also be accomplished by base-metal oxide catalysts. The main disadvantage of base-metal catalysts is their deactivation by poisons and high temperatures. Requirements for the length of the life of the small engine exhaust catalysts are much less than those for automobile exhaust catalysts. Since there is no oxygen in the exhaust gases, reduction selectivity is not a problem. Also, the reducing exhaust gases might help prevent the harmful interactions of the catalyst with the support. For these reasons only the supported metal oxide catalysts were investigated in this project.

The effect of low-fat beef patties formulated with a low-energy fat analogue enriched in long-chain polyunsaturated fatty acids on lipid oxidation and sensory attributes.

PubMed

Alejandre, Marta; Passarini, Denis; Astiasarán, Iciar; Ansorena, Diana

2017-12-01

A new low-energy gelled emulsion containing algae oil was developed as animal fat replacer. Its stability was evaluated under different storage conditions: 4V (4°C/vacuum), 4NV (4°C/no vacuum), 25V (25°C/vacuum) and 25NV (25°C/no vacuum). According to moisture, hardness, color and lipid oxidation data, 4°C under vacuum (4V) was selected as the best condition. Once the gelled emulsion was characterized, its effectiveness as fat analogue was demonstrated in beef patties. Reformulated patties were produced with 100% of animal fat replacement and compared to conventional patties (9%fat). A 70%fat reduction was achieved in the new patties, mainly due to a reduction in the saturated fatty acids. Also, decreased n-6 (76%lower content) and increased eicosapentaenoic and docosahexaenoic acids (55%higher content) were noticed in the new formulation. The incorporation of the gelled emulsion containing reduced amount of n-6 fatty acids and increased amounts of long chain n-3 fatty acids (EPA+DHA) reduced the oxidation status of the patties and their sensory evaluation resulted in acceptable scores. Copyright © 2017 Elsevier Ltd. All rights reserved.
Dissimilatory reduction of nitrate and nitrite in the bovine rumen: nitrous oxide production and effect of acetylene.

PubMed Central

Kaspar, H F; Tiedje, J M

1981-01-01

15N tracer methods and gas chromatography coupled to an electron capture detector were used to investigate dissimilatory reduction of nitrate and nitrite by the rumen microbiota of a fistulated cow. Ammonium was the only 15N-labeled end product of quantitative significance. Only traces of nitrous oxide were detected as a product of nitrate reduction; but in experiments with nitrite, up to 0.3% of the added nitrogen accumulated as nitrous oxide, but it was not further reduced. Furthermore, when 13NO3- was incubated with rumen microbiota virtually no [13N]N2 was produced. Acetylene partially inhibited the reduction of nitrite to ammonium as well as the formation of nitrous oxide. It is suggested that in the rumen ecosystem nitrous oxide is a byproduct of dissimilatory nitrite reduction to ammonium rather than a product of denitrification and that the latter process is absent from the rumen habitat. PMID:7224631
Method of treating intermetallic alloy hydrogenation/oxidation catalysts for improved impurity poisoning resistance, regeneration and increased activity

DOEpatents

Wright, Randy B.

1992-01-01

Alternate, successive high temperature oxidation and reduction treatments, in either order, of intermetallic alloy hydrogenation and intermetallic alloy oxidation catalysts unexpectedly improves the impurity poisoning resistance, regeneration capacity and/or activity of the catalysts. The particular alloy, and the final high temperature treatment given alloy (oxidation or reduction) will be chosen to correspond to the function of the catalyst (oxidation or hydrogenation).
Cast Stone Oxidation Front Evaluation: Preliminary Results For Samples Exposed To Moist Air

DOE Office of Scientific and Technical Information (OSTI.GOV)

Langton, C. A.; Almond, P. M.

The rate of oxidation is important to the long-term performance of reducing salt waste forms because the solubility of some contaminants, e.g., technetium, is a function of oxidation state. TcO{sub 4}{sup -} in the salt solution is reduced to Tc(IV) and has been shown to react with ingredients in the waste form to precipitate low solubility sulfide and/or oxide phases. Upon exposure to oxygen, the compounds containing Tc(IV) oxidize to the pertechnetate ion, Tc(VII)O{sub 4}{sup -}, which is very soluble. Consequently the rate of technetium oxidation front advancement into a monolith and the technetium leaching profile as a function ofmore » depth from an exposed surface are important to waste form performance and ground water concentration predictions. An approach for measuring contaminant oxidation rate (effective contaminant specific oxidation rate) based on leaching of select contaminants of concern is described in this report. In addition, the relationship between reduction capacity and contaminant oxidation is addressed. Chromate (Cr(VI) was used as a non-radioactive surrogate for pertechnetate, Tc(VII), in Cast Stone samples prepared with 5 M Simulant. Cast Stone spiked with pertechnetate was also prepared and tested. Depth discrete subsamples spiked with Cr were cut from Cast Stone exposed to Savannah River Site (SRS) outdoor ambient temperature fluctuations and moist air. Depth discrete subsamples spiked with Tc-99 were cut from Cast Stone exposed to laboratory ambient temperature fluctuations and moist air. Similar conditions are expected to be encountered in the Cast Stone curing container. The leachability of Cr and Tc-99 and the reduction capacities, measured by the Angus-Glasser method, were determined for each subsample as a function of depth from the exposed surface. The results obtained to date were focused on continued method development and are preliminary and apply to the sample composition and curing / exposure conditions described in this report. The Cr oxidation front (depth to which soluble Cr was detected) for the Cast Stone sample exposed for 68 days to ambient outdoor temperatures and humid air (total age of sample was 131 days) was determined to be about 35 mm below the top sample surface exposed. The Tc oxidation front, depth at which Tc was insoluble, was not determined. Interpretation of the results indicates that the oxidation front is at least 38 mm below the exposed surface. The sample used for this measurement was exposed to ambient laboratory conditions and humid air for 50 days. The total age of the sample was 98 days. Technetium appears to be more easily oxidized than Cr in the Cast Stone matrix. The oxidized forms of Tc and Cr are soluble and therefore leachable. Longer exposure times are required for both the Cr and Tc spiked samples to better interpret the rate of oxidation. Tc spiked subsamples need to be taken further from the exposed surface to better define and interpret the leachable Tc profile. Finally Tc(VII) reduction to Tc(IV) appears to occur relatively fast. Results demonstrated that about 95 percent of the Tc(VII) was reduced to Tc(IV) during the setting and very early stage setting for a Cast Stone sample cured 10 days. Additional testing at longer curing times is required to determine whether additional time is required to reduce 100 % of the Tc(VII) in Cast Stone or whether the Tc loading exceeded the ability of the waste form to reduce 100 % of the Tc(VII). Additional testing is required for samples cured for longer times. Depth discrete subsampling in a nitrogen glove box is also required to determine whether the 5 percent Tc extracted from the subsamples was the result of the sampling process which took place in air. Reduction capacity measurements (per the Angus-Glasser method) performed on depth discrete samples could not be correlated with the amount of chromium or technetium leached from the depth discrete subsamples or with the oxidation front inferred from soluble chromium and technetium (i.e., effective Cr and Tc oxidation fronts). Residual reduction capacity in the oxidized region of the test samples indicates that the remaining reduction capacity is not effective in re-reducing Cr(VI) or Tc(VII) in the presence of oxygen. Depth discrete sampling and leaching is a useful for evaluating Cast Stone and other chemically reducing waste forms containing ground granulated blast furnace slag (GGBFS) or other reduction / sequestration reagents to control redox sensitive contaminant chemistry and leachability in the near surface disposal environment. Based on results presented in this report, reduction capacity measured by the Angus-Glasser Ce(IV) method is not an appropriate or meaningful parameter for determining or predicting Tc and Cr oxidation / retentions, speciation, or solubilities in cementitious materials such as Cast Stone. A model for predicting Tc(IV) oxidation to soluble Tc(VII) should consider the waste form porosity (pathway for oxygen ingress), oxygen source, and the contaminant specific oxidation rates and oxidation fronts. Depth discrete sampling of materials exposed to realistic conditions in combination with short term leaching of crushed samples has potential for advancing the understanding of factors influencing performance. This information can be used to support conceptual model development.« less
Bacterial manganese reduction and growth with manganese oxide as the sole electron acceptor

NASA Technical Reports Server (NTRS)

Myers, Charles R.; Nealson, Kenneth H.

1988-01-01

Microbes that couple growth to the reduction of manganese could play an important role in the biogeochemistry of certain anaerobic environments. Such a bacterium, Alteromonas putrefaciens MR-1, couples its growth to the reduction of manganese oxides only under anaerobic conditions. The characteristics of this reduction are consistent with a biological, and not an indirect chemical, reduction of manganese, which suggest that this bacterium uses manganic oxide as a terminal electron acceptor. It can also utilize a large number of other compounds as terminal electron acceptors; this versatility could provide a distinct advantage in environments where electron-acceptor concentrations may vary.
Fischer-Tropsch Cobalt Catalyst Improvements with the Presence of TiO2, La2O3, and ZrO2 on an Alumina Support

NASA Technical Reports Server (NTRS)

Klettlinger, Jennifer Lindsey Suder

2012-01-01

The objective of this study was to evaluate the effect of titanium oxide, lanthanum oxide, and zirconium oxide on alumina supported cobalt catalysts. The hypothesis was that the presence of lanthanum oxide, titanium oxide, and zirconium oxide would reduce the interaction between cobalt and the alumina support. This was of interest because an optimized weakened interaction could lead to the most advantageous cobalt dispersion, particle size, and reducibility. The presence of these oxides on the support were investigated using a wide range of characterization techniques such as SEM, nitrogen adsorption, x-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed reduction after reduction (TPR-AR), and hydrogen chemisorptions/pulse reoxidation. Results indicated that both La2O3 and TiO2 doped supports facilitated the reduction of cobalt oxide species in reference to pure alumina supported cobalt catalysts, however further investigation is needed to determine the effect of ZrO2 on the reduction profile. Results showed an increased corrected cluster size for all three doped supported catalysts in comparison to their reference catalysts. The increase in reduction and an increase in the cluster size led to the conclusion that the support-metal interaction weakened by the addition of TiO2 and La2O3. It is also likely that the interaction decreased upon presence of ZrO2 on the alumina, but further research is necessary. Preliminary results have indicated that the alumina-supported catalysts with titanium oxide and lanthanum oxide present are of interest because of the weakened cobalt support interaction. These catalysts showed an increased extent of reduction, therefore more metallic cobalt is present on the support. However, whether or not there is more cobalt available to participate in the Fischer-Tropsch synthesis reaction (cobalt surface atoms) depends also on the cluster size. On one hand, increasing cluster size alone tends to decrease the active site density; on the other hand, by increasing the size of the cobalt clusters, there is less likelihood of forming oxidized cobalt complexes (cobalt aluminate) during Fischer-Tropsch synthesis. Thus, from the standpoint of stability, improving the extent of reduction while increasing the particle size slightly may be beneficial for maintaining the sites, even if there is a slight decrease in overall initial active site density.
Anaerobic Redox Cycling of Iron by Freshwater Sediment Microorganisms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weber, Karrie A.; Urrutia, Matilde M.; Churchill, Perry F.

2006-01-01

The potential for microbially-mediated anaerobic redox cycling of iron (Fe) was examined in a first-generation enrichment culture of freshwater wetland sediment microorganisms. MPN enumerations revealed the presence of significant populations of Fe(III)-reducing (ca. 108 cells mL-1) and Fe(II)-oxidizing, nitrate-reducing organisms (ca. 105 cells mL-1) in the sediment used to inoculate the enrichment cultures. Nitrate reduction commenced immediately following inoculation of acetate-containing (ca. 1 mM) medium with a small quantity (1% vol/vol) of wetland sediment, and resulted in the transient accumulation of NO2- and production of a mixture of end-products including NH4+. Fe(III) oxide (high surface area goethite) reduction took placemore » - after NO3- was depleted and continued until all the acetate was utilized. Addition of NO3 after Fe(III) reduction ceased resulted in the immediate oxidation of Fe(II) coupled to reduction of + NO3-to NH4 . No significant NO2- accumulation was observed during nitrate-dependent Fe(II) oxidation. No Fe(II) oxidation occurred in pasteurized controls. Microbial community structure in the enrichment was monitored by DGGE analysis of PCR amplified 16s rDNA and RT-PCR amplified 16S rRNA, as well as by construction of 16S rDNA clone libraries for four different time points during the experiment. Strong similarities in dominant members of the microbial community were observed in the Fe(III) reduction and nitrate-dependent Fe(II) oxidation phases of the experiment, specifically the common presence of organisms closely related (= 95% sequence similarity) to the genera Geobacter and Dechloromonas. These results indicate that the wetland sediments contained organisms such as Geobacter sp. which are capable of both + dissimilatory Fe(III) reduction and oxidation of Fe(II) with reduction of NO3-reduction to NH4 . Our findings suggest that microbially-catalyzed nitrate-dependent Fe(II) oxidation has the potential to contribute to a dynamic anaerobic Fe redox cycle in freshwater sediments.« less
Selective photocatalytic reduction of CO2 by H2O/H2 to CH4 and CH3OH over Cu-promoted In2O3/TiO2 nanocatalyst

NASA Astrophysics Data System (ADS)

Tahir, Muhammad; Tahir, Beenish; Saidina Amin, Nor Aishah; Alias, Hajar

2016-12-01

Photocatalytic CO2 reduction by H2O and/or H2 reductant to selective fuels over Cu-promoted In2O3/TiO2 photocatalyst has been investigated. The samples, prepared via a simple and direct sol-gel method, were characterized by XRD, SEM, TEM, XPS, N2 adsorption-desorption, UV-vis diffuse reflectance, Raman and PL spectroscopy. Cu and In loaded into TiO2, oxidized as Cu2+ and In3+, promoted efficient separation of photo-generated electron/hole pairs (e-/h+). The results indicate that the reduction rate of CO2 by H2O to CH4 approached to 181 μmol g-1 h-1 using 0.5% Cu-3% In2O3/TiO2 catalyst, a 1.53 fold higher than the production rate over the 3% In2O3/TiO2 and 5 times the amount produced over the pure TiO2. In addition, Cu was found to promote efficient production of CH3OH and yield rate reached to 68 μmol g-1 h-1 over 1% Cu-3% In2O3/TiO2 catalyst. This improvement was attributed to charge transfer property and suppressed recombination rate by Cu-metal. More importantly, H2 reductant was less favorable for CH4 production, yet a significant amount of CH4 and CH3OH were obtained using a mixture of H2O/H2 reductant. Therefore, Cu-loaded In2O3/TiO2 catalyst has shown to be capable for methanol production, whereas product selectivity was greatly depending on the amount of Cu-loading and the type of reductant. A photocatalytic reaction mechanism was proposed to understand the experimental results over the Cu-loaded In2O3/TiO2 catalyst.
Multi-stage catalyst systems and uses thereof

DOEpatents

Ozkan, Umit S [Worthington, OH; Holmgreen, Erik M [Columbus, OH; Yung, Matthew M [Columbus, OH

2009-02-10

Catalyst systems and methods provide benefits in reducing the content of nitrogen oxides in a gaseous stream containing nitric oxide (NO), hydrocarbons, carbon monoxide (CO), and oxygen (O.sub.2). The catalyst system comprises an oxidation catalyst comprising a first metal supported on a first inorganic oxide for catalyzing the oxidation of NO to nitrogen dioxide (NO.sub.2), and a reduction catalyst comprising a second metal supported on a second inorganic oxide for catalyzing the reduction of NO.sub.2 to nitrogen (N.sub.2).
A review on photocatalytic CO2 reduction using perovskite oxide nanomaterials

NASA Astrophysics Data System (ADS)

Zeng, Sheng; Kar, Piyush; Thakur, Ujwal Kumar; Shankar, Karthik

2018-02-01

As the search for efficient catalysts for CO2 photoreduction continues, nanostructured perovskite oxides have emerged as a class of high-performance photocatalytic materials. The perovskite oxide candidates for CO2 photoreduction are primarily nanostructured forms of titanates, niobates, tantalates and cobaltates. These materials form the focus of this review article because they are much sought-after due to their nontoxic nature, adequate chemical stability, and tunable crystal structures, bandgaps and surface energies. As compared to conventional semiconductors and nanomaterial catalysts, nanostructured perovskite oxides also exhibit an extended optical-absorption edge, longer charge carrier lifetimes, and favorable band-alignment with respect to reduction potential of activated CO2 and reduction products of the same. While CO2 reduction product yields of several hundred μmol-1 h-1 are observed with many types of perovskite oxide nanomaterials in stand-alone forms, yield of such quantities are not common with semiconductor nanomaterials of other types. In this review, we present current state-of-the-art synthesis methods to form perovskite oxide nanomaterials, and procedures to engineer their bandgaps. This review also presents a comprehensive summary and discussion on crystal structures, defect distribution, morphologies and electronic properties of the perovskite oxides, and correlation of these properties to CO2 photoreduction performance. This review offers researchers key insights for developing advanced perovskite oxides in order to further improve the yields of CO2 reduction products.
Tin in a chondritic interplanetary dust particle

NASA Technical Reports Server (NTRS)

Rietmeijer, Frans J. M.

1989-01-01

Submicron platey Sn-rich grains are present in chondritic porous interplanetary dust particle (IDP) W7029 A and it is the second occurrence of a tin mineral in a stratospheric micrometeorite. Selected Area Electron Diffraction data for the Sn-rich grains match with Sn2O3 and Sn3O4. The oxide(s) may have formed in the solar nebula when tin metal catalytically supported reduction of CO or during flash heating on atmospheric entry of the IDP. The presence of tin is consistent with enrichments for other volatile trace elements in chondritic IDPs and may signal an emerging trend toward nonchondritic volatile element abundances in chondritic IDPs. The observation confirms small-scale mineralogical heterogeneity in fine-grained chondritic porous interplanetary dust.
Lead-acid battery construction

NASA Technical Reports Server (NTRS)

Rowlette, John J. (Inventor)

1988-01-01

The power characteristics of a lead-acid battery are improved by incorporating a dispersion of 1 to 10% by weight of a thermodynamically stable conductivity additive, such as conductive tin oxide coated glass fibers (34) of filamentary glass wool (42) in the positive active layer (32) carried on the grid (30) of the positive plate (16). The avoiding of positive plate reversal to prevent reduction of the tin oxide is accomplished by (a) employing an oversized positive plate and pre-charging it; (b) by pre-discharging the negative plate; and/or (c) by placing a circuit breaker (26) in combination with the plates (16, 18) and terminals (22, 24) to remove the load when the voltage of the positive plate falls below a pre-selected level.
Microbial oxidation of soluble sulfide in produced water from the Bakkeen Sands

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gevertz, D.; Zimmerman, S.; Jenneman, G.E.

1995-12-31

The presence of soluble sulfide in produced water results in problems for the petroleum industry due to its toxicity, odor, corrosive nature, and potential for wellbore plugging. Sulfide oxidation by indigenous nitrate-reducing bacteria (NRB) present in brine collected from wells at the Coleville Unit (CVU) in Saskatchewan, Canada, was investigated. Sulfide oxidation took place readily when nitrate and phosphate were added to brine enrichment cultures, resulting in a decrease in sulfide levels of 99-165 ppm to nondetectable levels (< 3.3 ppm). Produced water collected from a number of producing wells was screened to determine the time required for complete sulfidemore » oxidation, in order to select candidate wells for treatment. Three wells were chosen, based on sulfide removal in 48 hours or less. These wells were treated down the backside of the annulus with a solution containing 10 mM KNO{sub 3} and 100 {mu}M NaH{sub 2}PO{sub 4}. Following a 24- to 72-hour shut-in, reductions in pretreatment sulfide levels of greater than 90% were observed for two of the wells, as well as sustained sulfide reductions of 50% for at least two days following startup. NRB populations in the produced brine were observed to increase significantly following treatment, but no significant increases in sulfate-reducing bacteria were observed. These results demonstrate the technical feasibility of stimulating indigenous populations of NRB to remediate and control sulfide in produced brine.« less
Roles of Cationic and Elemental Calcium in the Electro-Reduction of Solid Metal Oxides in Molten Calcium Chloride

NASA Astrophysics Data System (ADS)

Qiu, Guohong; Jiang, Kai; Ma, Meng; Wang, Dihua; Jin, Xianbo; Chen, George Z.

2007-06-01

Previous work, mainly from this research group, is re-visited on electrochemical reduction of solid metal oxides, in the form of compacted powder, in molten CaCl2, aiming at further understanding of the roles of cationic and elemental calcium. The discussion focuses on six aspects: 1.) debate on two mechanisms proposed in the literature, i. e. electro-metallothermic reduction and electro-reduction (or electro-deoxidation), for the electrolytic removal of oxygen from solid metals or metal oxides in molten CaCl2; 2.) novel metallic cavity working electrodes for electrochemical investigations of compacted metal oxide powders in high temperature molten salts assisted by a quartz sealed Ag/AgCl reference electrode (650 ºC- 950 ºC); 3.) influence of elemental calcium on the background current observed during electrolysis of solid metal oxides in molten CaCl2; 4.) electrochemical insertion/ inclusion of cationic calcium into solid metal oxides; 5.) typical features of cyclic voltammetry and chronoamperometry (potentiostatic electrolysis) of metal oxide powders in molten CaCl2; and 6.) some kinetic considerations on the electrolytic removal of oxygen.
Oxidation of aromatic contaminants coupled to microbial iron reduction

USGS Publications Warehouse

Lovley, D.R.; Baedecker, M.J.; Lonergan, D.J.; Cozzarelli, I.M.; Phillips, E.J.P.; Siegel, D.I.

1989-01-01

THE contamination of sub-surface water supplies with aromatic compounds is a significant environmental concern1,2. As these contaminated sub-surface environments are generally anaerobic, the microbial oxidation of aromatic compounds coupled to nitrate reduction, sulphate reduction and methane production has been studied intensively1-7. In addition, geochemical evidence suggests that Fe(III) can be an important electron acceptor for the oxidation of aromatic compounds in anaerobic groundwater. Until now, only abiological mechanisms for the oxidation of aromatic compounds with Fe(III) have been reported8-12. Here we show that in aquatic sediments, microbial activity is necessary for the oxidation of model aromatic compounds coupled to Fe(III) reduction. Furthermore, a pure culture of the Fe(III)-reducing bacterium GS-15 can obtain energy for growth by oxidizing benzoate, toluene, phenol or p-cresol with Fe(III) as the sole electron acceptor. These results extend the known physiological capabilities of Fe(III)-reducing organisms and provide the first example of an organism of any type which can oxidize an aromatic hydrocarbon anaerobically. ?? 1989 Nature Publishing Group.
Liquid-phase and solid-phase microwave irradiations for reduction of graphite oxide

NASA Astrophysics Data System (ADS)

Zhao, Na; Wen, Chen-Yu; Zhang, David Wei; Wu, Dong-Ping; Zhang, Zhi-Bin; Zhang, Shi-Li

2014-12-01

In this paper, two microwave irradiation methods: (i) liquid-phase microwave irradiation (MWI) reduction of graphite oxide suspension dissolved in de-ionized water and N, N-dimethylformamide, respectively, and (ii) solid-phase MWI reduction of graphite oxide powder have been successfully carried out to reduce graphite oxide. The reduced graphene oxide products are thoroughly characterized by scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectral analysis, Raman spectroscopy, UV-Vis absorption spectral analysis, and four-point probe conductivity measurements. The results show that both methods can efficiently remove the oxygen-containing functional groups attached to the graphite layers, though the solid-phase MWI reduction method can obtain far more efficiently a higher quality-reduced graphene oxide with fewer defects. The I(D)/I(G) ratio of the solid-phase MWI sample is as low as 0.46, which is only half of that of the liquid-phase MWI samples. The electrical conductivity of the reduced graphene oxide by the solid method reaches 747.9 S/m, which is about 25 times higher than that made by the liquid-phase method.
Highly efficient visible light photocatalytic reduction of CO2 to hydrocarbon fuels by Cu-nanoparticle decorated graphene oxide.

PubMed

Shown, Indrajit; Hsu, Hsin-Cheng; Chang, Yu-Chung; Lin, Chang-Hui; Roy, Pradip Kumar; Ganguly, Abhijit; Wang, Chen-Hao; Chang, Jan-Kai; Wu, Chih-I; Chen, Li-Chyong; Chen, Kuei-Hsien

2014-11-12

The production of renewable solar fuel through CO2 photoreduction, namely artificial photosynthesis, has gained tremendous attention in recent times due to the limited availability of fossil-fuel resources and global climate change caused by rising anthropogenic CO2 in the atmosphere. In this study, graphene oxide (GO) decorated with copper nanoparticles (Cu-NPs), hereafter referred to as Cu/GO, has been used to enhance photocatalytic CO2 reduction under visible-light. A rapid one-pot microwave process was used to prepare the Cu/GO hybrids with various Cu contents. The attributes of metallic copper nanoparticles (∼4-5 nm in size) in the GO hybrid are shown to significantly enhance the photocatalytic activity of GO, primarily through the suppression of electron-hole pair recombination, further reduction of GO's bandgap, and modification of its work function. X-ray photoemission spectroscopy studies indicate a charge transfer from GO to Cu. A strong interaction is observed between the metal content of the Cu/GO hybrids and the rates of formation and selectivity of the products. A factor of greater than 60 times enhancement in CO2 to fuel catalytic efficiency has been demonstrated using Cu/GO-2 (10 wt % Cu) compared with that using pristine GO.
TiO2@Pt@CeO2 nanocomposite as a bifunctional catalyst for enhancing photo-reduction of Cr (VI) and photo-oxidation of benzyl alcohol.

PubMed

Li, Shunxing; Cai, Jiabai; Wu, Xueqing; Liu, Biwen; Chen, Qiaoying; Li, Yuehai; Zheng, Fengying

2018-03-15

An solar-light-driven and bifunctional photocatalyst was designed for photo-reduction of Cr(VI) and selective photo-oxidation of benzyl alcohol into benzaldehyde in the presence of water under ambient conditions. Double-shelled and sandwiched TiO 2 @Pt@CeO 2 hollow spheres were prepared by using functionalized polystyrene spheres, sol-gel, hydrothermal reaction, and calcination. The Pt nanoparticles (NPs) were controllably loaded between the TiO 2 shell and CeO 2 shell. Under solar-light irradiation, the photo-reduction rate of Cr(VI) (μmol h -1 ) was in the order of TiO 2 @Pt@CeO 2 (1.901) > TiO 2 @CeO 2 (1.424) > TiO 2 (1.040) > CeO 2 (0.992). Among the above-mentioned photocatalysts, the conversion rate of benzyl alcohol for TiO 2 @Pt@CeO 2 was also the best. These results were attributed to the combination of TiO 2 and CeO 2 as photocatalyst and oxygen buffer, the double-shelled and sandwiched nanostructure, and the addition of Pt NPs as cocatalyst and electron trap site, which could store and shuttle photo-generated electrons, reduce the recombination of the electron-hole, and then enhance photo-generation of active radicals. This conclusion was verified by the electron paramagnetic resonance (EPR) spectroscopy. Considering the versatile combination of photocatalyst, oxygen buffer and cocatalyst, this work could provide new insights into the design of high-performance bifunctional photocatalysts for heavy metal removal and selective synthesis. Copyright © 2017 Elsevier B.V. All rights reserved.
Pt-Doped NiFe₂O₄ Spinel as a Highly Efficient Catalyst for H₂ Selective Catalytic Reduction of NO at Room Temperature.

PubMed

Sun, Wei; Qiao, Kai; Liu, Ji-Yuan; Cao, Li-Mei; Gong, Xue-Qing; Yang, Ji

2016-04-11

H2 selective catalytic reduction (H2-SCR) has been proposed as a promising technology for controlling NOx emission because hydrogen is clean and does not emit greenhouse gases. We demonstrate that Pt doped into a nickel ferrite spinel structure can afford a high catalytic activity of H2-SCR. A superior NO conversion of 96% can be achieved by employing a novel NiFe1.95Pt0.05O4 spinel-type catalyst at 60 °C. This novel catalyst is different from traditional H2-SCR catalysts, which focus on the role of metallic Pt species and neglect the effect of oxidized Pt states in the reduction of NO. The obtained Raman and XPS spectra indicate that Pt in the spinel lattice has different valence states with Pt(2+) occupying the tetrahedral sites and Pt(4+) residing in the octahedral ones. These oxidation states of Pt enhance the back-donation process, and the lack of filling electrons of the 5d band causes Pt to more readily hybridize with the 5σ orbital of the NO molecule, especially for octahedral Pt(4+), which enhances the NO chemisorption on the Pt sites. We also performed DFT calculations to confirm the enhancement of adsorption of NO onto Pt sites when doped into the Ni-Fe spinel structure. The prepared Pt/Ni-Fe catalysts indicate that increasing the dispersity of Pt on the surfaces of the individual Ni-Fe spinel-type catalysts can efficiently promote the H2-SCR activity. Our demonstration provides new insight into designing advanced catalysts for H2-SCR.
Selective catalytic reduction of NOx with NH3 over iron-cerium-tungsten mixed oxide catalyst prepared by different methods

NASA Astrophysics Data System (ADS)

Xiong, Zhi-bo; Liu, Jing; Zhou, Fei; Liu, Dun-yu; Lu, Wei; Jin, Jing; Ding, Shi-fa

2017-06-01

A series of magnetic Fe0.85Ce0.10W0.05Oz catalysts were synthesized by three different methods(Co-precipitation(Fe0.85Ce0.10W0.05Oz-CP), Hydrothermal treatment assistant critic acid sol-gel method(Fe0.85Ce0.10W0.05Oz-HT) and Microwave irradiation assistant critic acid sol-gel method(Fe0.85Ce0.10W0.05Oz-MW)), and the catalytic activity was evaluated for selective catalytic reduction of NO with NH3. The catalyst was characterized by XRD, N2 adsorption-desorption, XPS, H2-TPR and NH3-TPD. Among the tested catalysts, Fe0.85Ce0.10W0.05Oz-MW shows the highest NOx conversion over per gram in unit time with NOx conversion of 60.8% at 350 °C under a high gas hourly space velocity of 1,200,000 ml/(g h). Different from Fe0.85Ce0.10W0.05Oz-CP catalyst, there exists a large of iron oxide crystallite(γ-Fe2O3 and α-Fe2O3) scattered in Fe0.85Ce0.10W0.05Oz catalysts prepared through hydrothermal treatment or microwave irradiation assistant critic acid sol-gel method, and higher iron atomic concentration on their surface. And Fe0.85Ce0.10W0.05Oz-MW shows higher surface absorbed oxygen concentration and better dispersion compared with Fe0.85Ce0.10W0.05Oz-HT catalyst. These features were favorable for the high catalytic performance of NO reduction with NH3 over Fe0.85Ce0.10W0.05Oz-MW catalyst.

Regulation of cell function by methionine oxidation and reduction

PubMed Central

Hoshi, Toshinori; Heinemann, Stefan H

2001-01-01

Reactive oxygen species (ROS) are generated during normal cellular activity and may exist in excess in some pathophysiological conditions, such as inflammation or reperfusion injury. These molecules oxidize a variety of cellular constituents, but sulfur-containing amino acid residues are especially susceptible. While reversible cysteine oxidation and reduction is part of well-established signalling systems, the oxidation and the enzymatically catalysed reduction of methionine is just emerging as a novel molecular mechanism for cellular regulation. Here we discuss how the oxidation of methionine to methionine sulfoxide in signalling proteins such as ion channels affects the function of these target proteins. Methionine sulfoxide reductase, which reduces methionine sulfoxide to methionine in a thioredoxin-dependent manner, is therefore not only an enzyme important for the repair of age- or degenerative disease-related protein modifications. It is also a potential missing link in the post-translational modification cycle involved in the specific oxidation and reduction of methionine residues in cellular signalling proteins, which may give rise to activity-dependent plastic changes in cellular excitability. PMID:11179387
Structural changes in graphene oxide thin film by electron-beam irradiation

NASA Astrophysics Data System (ADS)

Tyagi, Chetna; Lakshmi, G. B. V. S.; Kumar, Sunil; Tripathi, Ambuj; Avasthi, D. K.

2016-07-01

Although we have a whole class of 2D materials, graphene has drawn much attention for its excellent electronic, optical, thermal and mechanical properties. Recent researches have shown its large scale production by the reduction of graphene oxide either thermally, chemically or electrochemically. Although the structure of graphene oxide is inhomogeneous and hence complicated due to the presence of organic moieties e.g. epoxy, carboxylic acid, hydroxyl groups etc., its properties can be tuned by reduction according to desired application. The aim of this work is to synthesize continuous thin film of graphene oxide using commercially available graphene oxide solution and to study its reduction by 25 keV electron beam irradiation at fluences varying from 2 × 1011 to 2 × 1013 e-/cm2. Our studies using X-ray diffraction, Raman microscopy and UV-Vis spectroscopy showed that electron-beam irradiation is an effective tool for reduction of graphene oxide and for tuning its band gap.
Method of treating intermetallic alloy hydrogenation/oxidation catalysts for improved impurity poisoning resistance, regeneration and increased activity

DOEpatents

Wright, R.B.

1992-01-14

Alternate, successive high temperature oxidation and reduction treatments, in either order, of intermetallic alloy hydrogenation and intermetallic alloy oxidation catalysts unexpectedly improves the impurity poisoning resistance, regeneration capacity and/or activity of the catalysts. The particular alloy, and the final high temperature treatment given alloy (oxidation or reduction) will be chosen to correspond to the function of the catalyst (oxidation or hydrogenation). 23 figs.
Evolution of thermal stress and failure probability during reduction and re-oxidation of solid oxide fuel cell

NASA Astrophysics Data System (ADS)

Wang, Yu; Jiang, Wenchun; Luo, Yun; Zhang, Yucai; Tu, Shan-Tung

2017-12-01

The reduction and re-oxidation of anode have significant effects on the integrity of the solid oxide fuel cell (SOFC) sealed by the glass-ceramic (GC). The mechanical failure is mainly controlled by the stress distribution. Therefore, a three dimensional model of SOFC is established to investigate the stress evolution during the reduction and re-oxidation by finite element method (FEM) in this paper, and the failure probability is calculated using the Weibull method. The results demonstrate that the reduction of anode can decrease the thermal stresses and reduce the failure probability due to the volumetric contraction and porosity increasing. The re-oxidation can result in a remarkable increase of the thermal stresses, and the failure probabilities of anode, cathode, electrolyte and GC all increase to 1, which is mainly due to the large linear strain rather than the porosity decreasing. The cathode and electrolyte fail as soon as the linear strains are about 0.03% and 0.07%. Therefore, the re-oxidation should be controlled to ensure the integrity, and a lower re-oxidation temperature can decrease the stress and failure probability.
In Situ UV-Visible Assessment of Iron-Based High-Temperature Water-Gas Shift Catalysts Promoted with Lanthana: An Extent of Reduction Study

DOE PAGES

Hallac, Basseem B.; Brown, Jared C.; Stavitski, Eli; ...

2018-02-04

Here, the extent of reduction of unsupported iron-based high-temperature water-gas shift catalysts with small (<5 wt %) lanthana contents was studied using UV-visible spectroscopy. Temperature- programmed reduction measurements showed that lanthana content higher than 0.5 wt % increased the extent of reduction to metallic Fe, while 0.5 wt % of lanthana facilitated the reduction to Fe 3O 4. In situ measurements on the iron oxide catalysts using mass and UV-visible spectroscopies permitted the quantification of the extent of reduction under temperature-programmed reduction and high-temperature water-gas shift conditions. The oxidation states were successfully calibrated against normalized absorbance spectra of visible lightmore » using the Kubelka-Munk theory. The normalized absorbance relative to the fully oxidized Fe 2O 3 increased as the extent of reduction increased. XANES suggested that the average bulk iron oxidation state during the water-gas shift reaction was Fe +2.57 for the catalyst with no lanthana and Fe +2.54 for the catalysts with 1 wt % lanthana. However, the UV-vis spectra suggest that the surface oxidation state of iron would be Fe +2.31 for the catalyst with 1 wt % lanthana if the oxidation state of iron in the catalyst with 0 wt % lanthana were Fe +2.57. The findings of this paper emphasize the importance of surface sensitive UV-visible spectroscopy for determining the extent of catalyst reduction during operation. Furthermore, the paper highlights the potential to use bench-scale UV-visible spectroscopy to study the surface chemistry of catalysts instead of less-available synchrotron X-ray radiation facilities.« less
In Situ UV-Visible Assessment of Iron-Based High-Temperature Water-Gas Shift Catalysts Promoted with Lanthana: An Extent of Reduction Study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hallac, Basseem B.; Brown, Jared C.; Stavitski, Eli

Here, the extent of reduction of unsupported iron-based high-temperature water-gas shift catalysts with small (<5 wt %) lanthana contents was studied using UV-visible spectroscopy. Temperature- programmed reduction measurements showed that lanthana content higher than 0.5 wt % increased the extent of reduction to metallic Fe, while 0.5 wt % of lanthana facilitated the reduction to Fe 3O 4. In situ measurements on the iron oxide catalysts using mass and UV-visible spectroscopies permitted the quantification of the extent of reduction under temperature-programmed reduction and high-temperature water-gas shift conditions. The oxidation states were successfully calibrated against normalized absorbance spectra of visible lightmore » using the Kubelka-Munk theory. The normalized absorbance relative to the fully oxidized Fe 2O 3 increased as the extent of reduction increased. XANES suggested that the average bulk iron oxidation state during the water-gas shift reaction was Fe +2.57 for the catalyst with no lanthana and Fe +2.54 for the catalysts with 1 wt % lanthana. However, the UV-vis spectra suggest that the surface oxidation state of iron would be Fe +2.31 for the catalyst with 1 wt % lanthana if the oxidation state of iron in the catalyst with 0 wt % lanthana were Fe +2.57. The findings of this paper emphasize the importance of surface sensitive UV-visible spectroscopy for determining the extent of catalyst reduction during operation. Furthermore, the paper highlights the potential to use bench-scale UV-visible spectroscopy to study the surface chemistry of catalysts instead of less-available synchrotron X-ray radiation facilities.« less
Reduction of metal oxides through mechanochemical processing

DOEpatents

Froes, Francis H.; Eranezhuth, Baburaj G.; Senkov, Oleg N.

2000-01-01

The low temperature reduction of a metal oxide using mechanochemical processing techniques. The reduction reactions are induced mechanically by milling the reactants. In one embodiment of the invention, titanium oxide TiO.sub.2 is milled with CaH.sub.2 to produce TiH.sub.2. Low temperature heat treating, in the range of 400.degree. C. to 700.degree. C., can be used to remove the hydrogen in the titanium hydride.
In Situ Generation of Pd-Pt Core-Shell Nanoparticles on Reduced Graphene Oxide (Pd@Pt/rGO) Using Microwaves: Applications in Dehalogenation Reactions and Reduction of Olefins.

PubMed

Goswami, Anandarup; Rathi, Anuj K; Aparicio, Claudia; Tomanec, Ondrej; Petr, Martin; Pocklanova, Radka; Gawande, Manoj B; Varma, Rajender S; Zboril, Radek

2017-01-25

Core-shell nanocatalysts are a distinctive class of nanomaterials with varied potential applications in view of their unique structure, composition-dependent physicochemical properties, and promising synergism among the individual components. A one-pot microwave (MW)-assisted approach is described to prepare the reduced graphene oxide (rGO)-supported Pd-Pt core-shell nanoparticles, (Pd@Pt/rGO); spherical core-shell nanomaterials (∼95 nm) with Pd core (∼80 nm) and 15 nm Pt shell were nicely distributed on the rGO matrix in view of the choice of reductant and reaction conditions. The well-characterized composite nanomaterials, endowed with synergism among its components and rGO support, served as catalysts in aromatic dehalogenation reactions and for the reduction of olefins with high yield (>98%), excellent selectivity (>98%) and recyclability (up to 5 times); both Pt/rGO and Pd/rGO and even their physical mixtures showed considerably lower conversions (20 and 57%) in dehalogenation of 3-bromoaniline. Similarly, in the reduction of styrene to ethylbenzene, Pd@Pt core-shell nanoparticles (without rGO support) possess considerably lower conversion (60%) compared to Pd@Pt/rGO. The mechanism of dehalogenation reactions with Pd@Pt/rGO catalyst is discussed with the explicit premise that rGO matrix facilitates the adsorption of the reducing agent, thus enhancing its local concentration and expediting the hydrazine decomposition rate. The versatility of the catalyst has been validated via diverse substrate scope for both reduction and dehalogenation reactions.
Selective autocatalytic reduction of NO from sintering flue gas by the hot sintered ore in the presence of NH3.

PubMed

Chen, Wangsheng; Luo, Jing; Qin, Linbo; Han, Jun

2015-12-01

In this paper, the selective autocatalytic reduction of NO by NH3 combined with multi-metal oxides in the hot sintered ore was studied, and the catalytic activity of the hot sintered ore was investigated as a function of temperature, NH3/NO ratio, O2 content, H2O and SO2. The experimental results indicated that the hot sintered ore, when combined with NH3, had a maximum denitration efficiency of 37.67% at 450 °C, 3000 h(-1) gas hourly space velocity (GHSV) and a NH3/NO ratio of 0.4/1. Additionally, it was found that O2 played an important role in removing NOx. However, high O2 content had a negative effect on NO reduction. H2O was found to promote the denitration efficiency in the absence of SO2, while SO2 inhibited the catalytic activity of the sintered ore. In the presence of H2O and SO2, the catalytic activity of the sintered ore was dramatically suppressed. Copyright © 2015 Elsevier Ltd. All rights reserved.
Selective photocatalytic reduction of CO2 to methanol in CuO-loaded NaTaO3 nanocubes in isopropanol

PubMed Central

Xiang, Tianyu; Chen, Jingshuai; Wang, Yuwen; Yin, Xiaohong; Shao, Xiao

2016-01-01

Summary A series of NaTaO3 photocatalysts were prepared with Ta2O5 and NaOH via a hydrothermal method. CuO was loaded onto the surface of NaTaO3 as a cocatalyst by successive impregnation and calcination. The obtained photocatalysts were characterized by XRD, SEM, UV–vis, EDS and XPS and used to photocatalytically reduce CO2 in isopropanol. This worked to both absorb CO2 and as a sacrificial reagent to harvest CO2 and donate electrons. Methanol and acetone were generated as the reduction product of CO2 and the oxidation product of isopropanol, respectively. NaTaO3 nanocubes loaded with 2 wt % CuO and synthesized in 2 mol/L NaOH solution showed the best activity. The methanol and acetone yields were 137.48 μmol/(g·h) and 335.93 μmol/(g·h), respectively, after 6 h of irradiation. Such high activity could be attributed to the good crystallinity, morphology and proper amount of CuO loading, which functioned as reductive sites for selective formation of methanol. The reaction mechanism was also proposed and explained by band theory. PMID:27335766
Promotional Effects of In on Non-Oxidative Methane Transformation Over Mo-ZSM-5

DOE PAGES

Zhang, Yang; Kidder, Michelle; Ruther, Rose E.; ...

2016-08-16

In this paper, we present a new class of catalysts, InMo-ZSM- 5, which can be prepared by indium impregnation of Mo-ZSM- 5. The incorporation of indium dramatically decreases coke formation during methane dehydroaromatization. The benzene and C 2 hydrocarbons selectivity among total hydrocarbons over InMo-ZSM- 5 remains comparable to that of Mo-ZSM- 5 despite reduced methane conversion due to decreased coke formation. We found 1 wt% indium to be optimal loading for reducing coke selectivity to half that of Mo-ZSM- 5. Characterization methods were not helpful in discerning the interaction of In with Mo but experiments with bimetallic 1In2Mo-ZSM- 5more » and mechanical mixture 1In+2Mo-ZSM- 5 suggest that In and Mo need to be in close proximity to suppress coke formation. Finally, this is supported by temperature programmed reduction experiments which show that In incorporation leads to lower Mo reduction temperature in In2Mo-ZMS- 5.« less
A Perspective on the Selective Catalytic Reduction (SCR) of NO with NH 3 by Supported V 2O 5 –WO 3/TiO 2 Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lai, Jun-Kun; Wachs, Israel E.

We report the selective catalytic reduction (SCR) of NO x with NH 3 to harmless N 2 and H 2O plays a crucial role in reducing highly undesirable NO x acid gas emissions from large utility boilers, industrial boilers, municipal waste plants, and incinerators. The supported V 2O 5 –WO 3/TiO 2 catalysts have become the most widely used industrial catalysts for these SCR applications since introduction of this technology in the early 1970s. Lastly, this Perspective examines the current fundamental understanding and recent advances of the supported V 2O 5 –WO 3/TiO 2 catalyst system: (i) catalyst synthesis, (ii)more » molecular structures of titaniasupported vanadium and tungsten oxide species, (iii) surface acidity, (iv) catalytic active sites, (v) surface reaction intermediates, (vi) reaction mechanism, (vii) ratedetermining- step, and (viii) reaction kinetics.« less
A Perspective on the Selective Catalytic Reduction (SCR) of NO with NH 3 by Supported V 2O 5 –WO 3/TiO 2 Catalysts

DOE PAGES

Lai, Jun-Kun; Wachs, Israel E.

2018-06-04

We report the selective catalytic reduction (SCR) of NO x with NH 3 to harmless N 2 and H 2O plays a crucial role in reducing highly undesirable NO x acid gas emissions from large utility boilers, industrial boilers, municipal waste plants, and incinerators. The supported V 2O 5 –WO 3/TiO 2 catalysts have become the most widely used industrial catalysts for these SCR applications since introduction of this technology in the early 1970s. Lastly, this Perspective examines the current fundamental understanding and recent advances of the supported V 2O 5 –WO 3/TiO 2 catalyst system: (i) catalyst synthesis, (ii)more » molecular structures of titaniasupported vanadium and tungsten oxide species, (iii) surface acidity, (iv) catalytic active sites, (v) surface reaction intermediates, (vi) reaction mechanism, (vii) ratedetermining- step, and (viii) reaction kinetics.« less
Oxide reduction during triggered-lightning fulgurite formation

NASA Astrophysics Data System (ADS)

Jones, B. E.; Jones, K. S.; Rambo, K. J.; Rakov, V. A.; Jerald, J.; Uman, M. A.

2005-03-01

In this study triggered-lightning induced fulgurites were formed in 99.9% pure binary oxides of manganese (MnO) and nickel (NiO) in order to study oxide reduction mechanisms. The fulgurite formation process involved packing the oxide in PVC holders and using the standard rocket-and-wire technique to trigger a lightning strike through the oxide at the International Center for Lightning Research and Testing in Camp Blanding, Florida. These two oxides were chosen from the thermodynamic extrapolation of the oxide stability using the Ellingham Diagram. This diagram indicates that NiO is significantly less stable than MnO. Fulgurites from the pure oxides were analyzed in a scanning electron microscope (SEM); secondary electron images, backscattered images and energy dispersive spectroscopy (EDS) were used to determine the microstructure and composition of the fulgurites. SEM/EDS analysis of the NiO and MnO prior to fulgurite formation confirmed they were pure binary oxides with no metallic contamination. After fulgurite formation, it was found that the nickel oxide fulgurite contained metallic nickel particles; the manganese oxide fulgurite showed no metallic phase formation. Transmission electron microscopy (TEM) examination confirmed that the MnO was a pure oxide with no sign of metallic phase formation. However, TEM results of the NiO showed that approximately 50% of the NiO was reduced to metallic face-centered cubic Ni. The Ni and NiO were observed to be coherent with the [1 0 0]Ni//[1 0 0]NiO and [1 1 0]Ni//[1 1 0]NiO. These results are consistent with the aforementioned thermodynamic stability calculations and show that the presence of carbonaceous material or mixtures of oxides is not necessary for oxide reduction during fulgurite formation. These studies do not rule out the possibility that electrolysis plays a role in oxide reduction. However, these fulgurites were made simultaneously during the same lightning strike and therefore were subjected to the same electrical current, and thus it is proposed the thermodynamic stability of the oxide must play a role in oxide reduction.
Technology innovations and experience curves for nitrogen oxides control technologies.

PubMed

Yeh, Sonia; Rubin, Edward S; Taylor, Margaret R; Hounshell, David A

2005-12-01

This paper reviews the regulatory history for nitrogen oxides (NOx) pollutant emissions from stationary sources, primarily in coal-fired power plants. Nitrogen dioxide (NO2) is one of the six criteria pollutants regulated by the 1970 Clean Air Act where National Ambient Air Quality Standards were established to protect public health and welfare. We use patent data to show that in the cases of Japan, Germany, and the United States, innovations in NOx control technologies did not occur until stringent government regulations were in place, thus "forcing" innovation. We also demonstrate that reductions in the capital and operation and maintenance (O&M) costs of new generations of high-efficiency NOx control technologies, selective catalytic reduction (SCR), are consistently associated with the increasing adoption of the control technology: the so-called learning-by-doing phenomena. The results show that as cumulative world coal-fired SCR capacity doubles, capital costs decline to approximately 86% and O&M costs to 58% of their original values. The observed changes in SCR technology reflect the impact of technological advance as well as other factors, such as market competition and economies of scale.
Bimetallic Platinum-Rhodium Alloy Nanodendrites as Highly Active Electrocatalyst for the Ethanol Oxidation Reaction.

PubMed

Bai, Juan; Xiao, Xue; Xue, Yuan-Yuan; Jiang, Jia-Xing; Zeng, Jing-Hui; Li, Xi-Fei; Chen, Yu

2018-06-13

Rationally designing and manipulating composition and morphology of precious metal-based bimetallic nanostructures can markedly enhance their electrocatalytic performance, including selectivity, activity, and durability. We herein report the synthesis of bimetallic PtRh alloy nanodendrites (ANDs) with tunable composition by a facile complex-reduction synthetic method under hydrothermal conditions. The structural/morphologic features, formation mechanism, and electrocatalytic performance of PtRh ANDs are investigated thoroughly by various physical characterization and electrochemical methods. The preformed Rh crystal nuclei effectively catalyze the reduction of Pt 2+ precursor, resulting in PtRh alloy generation due to the catalytic growth and atoms interdiffusion process. The Pt atoms deposition distinctly interferes in Rh atoms deposition on Rh crystal nuclei, resulting in dendritic morphology of PtRh ANDs. For the ethanol oxidation reaction (EOR), PtRh ANDs display the chemical composition and solution pH co-dependent electrocatalytic activity. Because of the alloy effect and particular morphologic feature, Pt 1 Rh 1 ANDs with optimized composition exhibit better reactivity and stability for the EOR than commercial Pt nanocrystals electrocatalyst.
A Fungal P450 (CYP5136A3) Capable of Oxidizing Polycyclic Aromatic Hydrocarbons and Endocrine Disrupting Alkylphenols: Role of Trp129 and Leu324

PubMed Central

Syed, Khajamohiddin; Porollo, Aleksey; Lam, Ying Wai; Yadav, Jagjit S.

2011-01-01

The model white rot fungus Phanerochaete chrysosporium, which is known for its versatile pollutant-biodegradation ability, possesses an extraordinarily large repertoire of P450 monooxygenases in its genome. However, the majority of these P450s have hitherto unknown function. Our initial studies using a genome-wide gene induction strategy revealed multiple P450s responsive to individual classes of xenobiotics. Here we report functional characterization of a cytochrome P450 monooxygenase, CYP5136A3 that showed common responsiveness and catalytic versatility towards endocrine-disrupting alkylphenols (APs) and mutagenic/carcinogenic polycyclic aromatic hydrocarbons (PAHs). Using recombinant CYP5136A3, we demonstrated its oxidation activity towards APs with varying alkyl side-chain length (C3-C9), in addition to PAHs (3–4 ring size). AP oxidation involves hydroxylation at the terminal carbon of the alkyl side-chain (ω-oxidation). Structure-activity analysis based on a 3D model indicated a potential role of Trp129 and Leu324 in the oxidation mechanism of CYP5136A3. Replacing Trp129 with Leu (W129L) and Phe (W129F) significantly diminished oxidation of both PAHs and APs. The W129L mutation caused greater reduction in phenanthrene oxidation (80%) as compared to W129F which caused greater reduction in pyrene oxidation (88%). Almost complete loss of oxidation of C3-C8 APs (83–90%) was observed for the W129L mutation as compared to W129F (28–41%). However, the two mutations showed a comparable loss (60–67%) in C9-AP oxidation. Replacement of Leu324 with Gly (L324G) caused 42% and 54% decrease in oxidation activity towards phenanthrene and pyrene, respectively. This mutation also caused loss of activity towards C3-C8 APs (20–58%), and complete loss of activity toward nonylphenol (C9-AP). Collectively, the results suggest that Trp129 and Leu324 are critical in substrate recognition and/or regio-selective oxidation of PAHs and APs. To our knowledge, this is the first report on an AP-oxidizing P450 from fungi and on structure-activity relationship of a eukaryotic P450 for fused-ring PAHs (phenanthrene and pyrene) and AP substrates. PMID:22164262
Tribological Properties of Structural Ceramics

NASA Technical Reports Server (NTRS)

Buckley, Donald H.; Miyoshi, Kazuhisa

1987-01-01

Paper discusses tribological properties of structural ceramics. Function of tribological research is to bring about reduction in adhesion, friction, and wear of mechanical components; to prevent failures; and to provide long, reliable component life, through judicious selection of materials, operating parameters, and lubricants. Paper reviews adhesion, friction, wear, and lubrication of ceramics; anisotropic friction and wear behavior; and effects of surface films and interactions between ceramics and metals. Analogies with metals are made. Both oxide and nonoxide ceramics, including ceramics used as high temperature lubricants, are dicussed.
Fast and fully-scalable synthesis of reduced graphene oxide

NASA Astrophysics Data System (ADS)

Abdolhosseinzadeh, Sina; Asgharzadeh, Hamed; Seop Kim, Hyoung

2015-05-01

Exfoliation of graphite is a promising approach for large-scale production of graphene. Oxidation of graphite effectively facilitates the exfoliation process, yet necessitates several lengthy washing and reduction processes to convert the exfoliated graphite oxide (graphene oxide, GO) to reduced graphene oxide (RGO). Although filtration, centrifugation and dialysis have been frequently used in the washing stage, none of them is favorable for large-scale production. Here, we report the synthesis of RGO by sonication-assisted oxidation of graphite in a solution of potassium permanganate and concentrated sulfuric acid followed by reduction with ascorbic acid prior to any washing processes. GO loses its hydrophilicity during the reduction stage which facilitates the washing step and reduces the time required for production of RGO. Furthermore, simultaneous oxidation and exfoliation significantly enhance the yield of few-layer GO. We hope this one-pot and fully-scalable protocol paves the road toward out of lab applications of graphene.
Stereospecific 1,4-addition to an alpha,beta-unsaturated steroidal epoxide: syntheses of new 15-oxygenated sterols.

PubMed

Parish, E J; Tsuda, M; Schroepfer, G J

1988-11-01

3 beta-Benzoyloxy-14 alpha,15 alpha-epoxy-5 alpha-cholest-7-ene (1) is a key intermediate in the synthesis of C-7 and C-15 oxygenated sterols. Treatment of 1 with benzoyl chloride resulted in the formation of 3 beta,15 alpha-bis-benzoyloxy-7 alpha-chloro-5 alpha-cholest-8(14)-ene (2). Reaction of 2 with LiAlH4 or LiAlD4 resulted in the formation of 5 alpha-cholest-7-ene-3 beta,15 alpha-diol (3a) or [14 alpha-2H]5 alpha-cholest-7-ene-3 beta,15 alpha-diol (3b). Diol 3b was selectively oxidized by Ag2CO3/celite to [14 alpha-2H]5 alpha-cholest-7-en-15 alpha-ol-3-one (4). Treatment of 1 with MeMgI/CuI gave 7 alpha-methyl-5 alpha-cholest-8(14)-ene-3 beta,15 alpha-diol (5). Selective oxidation of 5 with pyridinium chlorochromate (PCC)/pyridine or oxidation with PCC resulted in the formation of 7 alpha-methyl-5 alpha-cholest-8(14)-en-3 beta-ol-15-one (6) and 7 alpha-methyl-5 alpha-cholest-8(14)-ene-3,15-dione, respectively. Reduction of 6 with LiAlH4 yielded 5 and 7 alpha-methyl-5 alpha-cholest-8(14)-ene-3 beta,15 beta-diol (6). Reaction of 1 with benzoic acid/pyridine gave 3 beta,7 alpha-bis-benzoyloxy-5 alpha-cholest-8(14)-en-15 alpha-ol (9). Treatment of 9 with LiAlH4 or ethanolic KOH resulted in the formation of 5 alpha-cholest-8(14)-ene-3 beta,7 alpha,15 alpha-triol (10). Dibenzoate 9, upon brief treatment with mineral acid, gave 3 beta-benzoyloxy-5 alpha-cholest-8(14)-ene-15-one (11). Oxidation of 9 with PCC yielded 3 beta,7 alpha-bis-benzoyloxy-5 alpha-cholest-8(14)-ene-15-one (12). Ketone 12 was also prepared by the selective hydride reduction of 5 alpha-cholest-8(14)-en-7 alpha-ol-3,15-dione (13) to give 5 alpha-cholest-8(14)-ene-3 beta,7 alpha-diol-15-one (14), which was then treated with benzoyl chloride to produce 12.

Phyto-reduction of graphene oxide using the aqueous extract of Eichhornia crassipes (Mart.) Solms

NASA Astrophysics Data System (ADS)

Firdhouse, M. Jannathul; Lalitha, P.

2014-10-01

The aqueous extract of Eichhornia crassipes was used as reductant to produce graphene from graphene oxide by refluxing method. The complete reduction of graphene oxide was monitored using UV-Vis spectrophotometer. Characterization of graphene was made through FTIR, XRD, and Raman spectroscopy analysis. The stability of graphene was studied by thermal gravimetric analysis and zeta potential measurements. The nature and surface morphology of the synthesized graphene was analyzed by transmission electron microscopy. The production of graphene using phytoextract as reductant emphasizes on the facile method of synthesis and greener nanotechnology.
Investigation of the reduction process of dopamine using paired pulse voltammetry

PubMed Central

Kim, Do Hyoung; Oh, Yoonbae; Shin, Hojin; Blaha, Charles D.; Bennet, Kevin E.; Lee, Kendall H.; Kim, In Young; Jang, Dong Pyo

2014-01-01

The oxidation of dopamine (DA) around +0.6V potential in anodic sweep and its reduction around −0.1V in cathodic sweep at a relatively fast scanning rate (300 V/s or greater) have been used for identification of DA oxidation in fast-scan cyclic voltammetry (FSCV). However, compared to the oxidation peak of DA, the reduction peak has not been fully examined in analytical studies, although it has been used as one of the representative features to identify DA. In this study, the reduction process of DA was investigated using paired pulse voltammetry (PPV), which consists of two identical triangle-shaped waveforms, separated by a short interval at the holding potential. Especially, the discrepancies between the magnitude of the oxidation and reduction peaks of DA were investigated based on three factors: (1) the instant desorption of the DA oxidation product (dopamine-o-quinone: DOQ) after production, (2) the effect of the holding potential on the reduction process, and (3) the rate-limited reduction process of DA. For the first test, the triangle waveform FSCV experiment was performed on DA with various scanrates (from 400 to 1000 V/s) and durations of switching potentials of the triangle waveform (from 0.0 to 6.0 ms) in order to vary the duration between the applied oxidation potential at +0.6V and the reduction potential at −0.2V. As a result, the ratio of reduction over oxidation peak current response decreased as the duration became longer. To evaluate the effect of holding potentials during the reduction process, FSCV experiments were conducted with holding potential from 0.0V to −0.8V. We found that more negative holding potentials lead to larger amount of reduction process. For evaluation of the rate-limited reduction process of DA, PPV with a 1Hz repetition rate and various delays (2, 8, 20, 40 and 80ms) between the paired scans were utilized to determine how much reduction process occurred during the holding potential (−0.4V). These tests showed that relatively large amounts of DOQ are reduced to DA during the holding potential. The rate-limited reduction process was also confirmed with the increase of reduction in a lower pH environment. In addition to the mechanism of the reduction process of DA, we found that the differences between the responses of primary and secondary pulses in PPV were mainly dependent on the rate-limited reduction process during the holding potential. In conclusion, the reduction process may be one of the important factors to be considered in the kinetic analysis of DA and other electroactive species in brain tissue and in the design of new types of waveform in FSCV. PMID:24926227
Combination for electrolytic reduction of alumina

DOEpatents

Brown, Craig W.; Brooks, Richard J.; Frizzle, Patrick B.; Juric, Drago D.

2002-04-30

An electrolytic bath for use during the electrolytic reduction of alumina to aluminum. The bath comprises molten electrolyte having the following ingredients: AlF.sub.3 and at least one salt selected from the group consisting of NaF, KF, and LiF; and about 0.004 wt. % to about 0.2 wt. %, based on total weight of the molten electrolyte, of at least one transition metal or at least one compound of the metal or both. The compound is, a fluoride; oxide, or carbonate. The metal is nickel, iron, copper, cobalt, or molybdenum. The bath is employed in a combination including a vessel for containing the bath and at least one non-consumable anode and at least one dimensionally stable cathode in the bath. Employing the instant bath during electrolytic reduction of alumina to aluminum improves the wetting of aluminum on a cathode by reducing or eliminating the formation of non-metallic deposits on the cathode.
Elevated acetate concentrations in the rhizosphere of Spartina alterniflora and potential influences on sulfate reduction

NASA Technical Reports Server (NTRS)

Hines, Mark E.; Tugel, Joyce B.; Giblin, A. E.; Banta, G. T.; Hobbie, J. E.

1992-01-01

Acetate is important in anaerobic metabolism of non-vegetated sediments but its role in salt marsh soils was not investigated thoroughly. Acetate concentrations, oxidation (C-14) and SO4(2-) reduction (S-35) were measured in S. alterniflora soils in NH and MA. Pore water from cores contained greater than 0.1 mM acetate and in some instances greater than 1.0 mM. Non-destructive samples contained less than 0.01 mM. Acetate was associated with roots and concentrations were highest during vegetative growth and varied with changes in plant physiology. Acetate turnover was very low whether whole core or slurry incubations were used. Radiotracers injected directly into soils yielded rates of SO4(2-) reduction and acetate oxidation not significantly different from core incubation techniques. Regardless of incubation method, acetate oxidation did not account for a significant percentage of SO4(2-) reduction. These results differ markedly from data for non-vegetated coastal sediments where acetate levels are low, oxidation rate constants are high and acetate oxidation rates greatly exceed rates of SO4(2-) reduction. The discrepancy between rates of acetate oxidation and SO4(2-) reduction in marsh soils may be due either to the utilization of substrates other than acetate by SO4(2-) reducers or artifacts associated with measurements of organic utilization by rhizosphere bacteria.
Following the movement of Cu ions in a SSZ-13 zeolite during dehydration, reduction and adsorption: a combined in situ TP-XRD, XANES/DRIFTS study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kwak, Ja Hun; Varga, Tamas; Peden, Charles HF

2014-05-05

Cu-SSZ-13 has been shown to possess high activity and superior N2 formation selectivity in the selective catalytic reduction of NOx under oxygen rich conditions. Here, a combination of synchrotron-based (XRD and XANES) and vibrational (DRIFTS) spectroscopy tools have been used to follow the changes in the location and coordination environment of copper ions in a Cu-SSZ-13 zeolite during calcinations, reduction with CO, and adsorption of CO and H2O. XANES spectra collected during these procedures provides critical information not only on the variation in the oxidation state of the copper species in the zeolite structure, but also on the changes inmore » the coordination environment around these ions as they interact with the framework, and with different adsorbates (H2O and CO). Time-resolved XRD data indicate the movement of copper ions and the consequent variation of the unit cell parameters during dehydration. DRIFT spectra provide information about the adsorbed species present in the zeolite, as well as the oxidation states of and coordination environment around the copper ions. A careful analysis of the asymmetric T-O-T vibrations of the CHA framework perturbed by copper ions in different coordination environments proved to be especially informative. The results of this study will aid the identification of the location, coordination and oxidation states of copper ions obtained during in operando catalytic studies. Financial support was provided by the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Vehicle Technologies Program. Part of this work (sample preparation) was performed in the Environmental Molecular Sciences Laboratory (EMSL) at Pacific Northwest National Laboratory (PNNL). The EMSL is a national scientific user facility supported by the US DOE, Office of Biological and Environmental Research. PNNL is a multi-program national laboratory operated for the US DOE by Battelle. All of the spectroscopy work reported here was carried out at the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory (BNL). NSLS is a national scientific user facility supported by the US DOE.« less
A Mechanistic Investigation of Nitrogen Evolution and Corrosion with Oxy-Combustion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dale Tree; Andrew Mackrory; Thomas Fletcher

A premixed, staged, down-fired, pulverized coal reactor and a flat flame burner were used to study the evolution of nitrogen in coal contrasting differences in air and oxy-combustion. In the premixed reactor, the oxidizer was staged to produce a fuel rich zone followed by a burnout zone. The initial nominal fuel rich zone stoichiometric ratio (S.R.) of 0.85 selected produced higher NO reductions in the fuel rich region under oxy-combustion conditions. Air was found to be capable of similar NO reductions when the fuel rich zone was at a much lower S.R. of 0.65. At a S.R. of 0.85, oxy-combustionmore » was measured to have higher CO, unburned hydrocarbons, HCN and NH{sub 3} in the fuel rich region than air at the same S.R. There was no measured difference in the initial formation of NO. The data suggest devolatilization and initial NO formation is similar for the two oxidizers when flame temperatures are the same, but the higher CO{sub 2} leads to higher concentrations of CO and nitrogen reducing intermediates at a given equivalence ratio which increases the ability of the gas phase to reduce NO. These results are supported by flat flame burner experiments which show devolatilization of nitrogen from the coal and char to be similar for air and oxy-flame conditions at a given temperature. A model of premixed combustion containing devolatilization, char oxidation and detailed kinetics captures most of the trends seen in the data. The model suggests CO is high in oxy-combustion because of dissociation of CO{sub 2}. The model also predicts a fraction (up to 20%, dependent on S.R.) of NO in air combustion can be formed via thermal processes with the source being nitrogen from the air while in oxy-combustion equilibrium drives a reduction in NO of similar magnitude. The data confirm oxy-combustion is a superior oxidizer to air for NO control because NO reduction can be achieved at higher S.R. producing better char burnout in addition to NO from recirculated flue gas being reduced as it passes back through the flame.« less
Vertical variability of arsenic concentrations under the control of iron-sulfur-arsenic interactions in reducing aquifer systems

NASA Astrophysics Data System (ADS)

Pi, Kunfu; Wang, Yanxin; Postma, Dieke; Ma, Teng; Su, Chunli; Xie, Xianjun

2018-06-01

High spatial variability of arsenic (As) concentration in geogenic As-contaminated groundwater has been commonly observed worldwide, but the underlying reasons remain not well understood. Selecting a sulfate-containing, As-affected aquifer at the Datong Basin, northern China as the study area and combining hydrogeochemical investigation and sediment extraction with reactive transport modeling, this work elucidated the roles of Fe-S-As interactions in regulating the vertical variation of As concentration in the groundwater. Dissolved As concentration varied between 0.05 and 18 μmol/L, but generally increased in the depth of 20-25 m and then decreased in 25-30 m. The high-As groundwater contained low Fe(II) (<0.007 mmol/L) and up to 15 μmol/L sulfide, in contrary to the S/SE Asian deltas/floodplains where high Fe(II) and As jointly occur in the groundwater devoid of sulfate reduction. The reductive dissolution of As-bearing Fe(III) oxides coupled to the degradation of organic matter with an estimated maximum rate of 0.22 mmol C/L/yr, mainly accounted for the depth-dependent increase of As concentration in the upper part of the shallow aquifer (<25 m deep). However, the decreasing reactivity of Fe(III) oxides together with the increase of pH over depth rendered the majority of electrons being transferred to sulfate reduction. The Fe(II) sulfides formed as a consequence not only helped to restrict the build-up of Fe(II) in the groundwater but also probably co-precipitated As to prompt As decrease in the depth of 25-30 m. Arsenite adsorbed on remaining Fe(III) oxides and newly-formed Fe(II) sulfides is another important pool of As in the aquifer, which varies in response to the extents of Fe(III)-oxide and sulfate reduction and consequently alters As distribution coefficient between the solid and the aqueous phases. This study highlights the importance of coupled geochemical cycling of Fe, S and As for As mobilization and reveals how it regulates As partitioning between groundwater and sediments.
Evaluation of selected chemical processes for production of low-cost silicon. Quarterly progress report, 15 Dec 1975--31 Mar 1976

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blocher, J.M. Jr; Browning, M.F.; Wilson, W.J.

1976-04-08

Plant construction costs and manufacturing costs were estimmated for the production of solar-grade silicon by the reduction of silicon tetrachloride in a fluidized bed of seed particles, and several modifications of the iodide process using either thermal decomposition on heated filaments (rods) or hydrogen reduction in a fluidized bed of seed particles. Energy consumption data for the zinc reduction process and each of the iodide process options are given and all appear to be acceptable from the standpoint of energy pay back. Information is presented on the experimental zinc reduction of SiCl4 and electrolytic recovery of zinc from ZnCl2. Allmore » of the experimental work performed thus far has supported the initial assumption as to technical feasibility of producing semiconductor silicon by the zinc reduction or iodide processes proposed. The results of a more thorough thermodynamic evaluation of the iodination of silicon oxide/carbon mixtures are presented which explain apparent inconsistencies in an earlier cursory examination of the system.« less
Study on the influences of reduction temperature on nickel-yttria-stabilized zirconia solid oxide fuel cell anode using nickel oxide-film electrode

NASA Astrophysics Data System (ADS)

Jiao, Zhenjun; Ueno, Ai; Suzuki, Yuji; Shikazono, Naoki

2016-10-01

In this study, the reduction processes of nickel oxide at different temperatures were investigated using nickel-film anode to study the influences of reduction temperature on the initial performances and stability of nickel-yttria-stabilized zirconia anode. Compared to conventional nickel-yttria-stabilized zirconia composite cermet anode, nickel-film anode has the advantage of direct observation at nickel-yttria-stabilized zirconia interface. The microstructural changes were characterized by scanning electron microscopy. The reduction process of nickel oxide is considered to be determined by the competition between the mechanisms of volume reduction in nickel oxide-nickel reaction and nickel sintering. Electrochemical impedance spectroscopy was applied to analyze the time variation of the nickel-film anode electrochemical characteristics. The anode performances and microstructural changes before and after 100 hours discharging and open circuit operations were analyzed. The degradation of nickel-film anode is considered to be determined by the co-effect between the nickel sintering and the change of nickel-yttria-stabilized zirconia interface bonding condition.
Activity and selectivity of photocatalysts in photodegradation of phenols.

PubMed

Emeline, A V; Zhang, X; Murakami, T; Fujishima, A

2012-04-15

Photodegradation of phenol and 4-chlorophenol over six different TiO(2) samples was tested in order to establish whether an interconnection between the activity and selectivity of photocatalysts exists. The obtained experimental data were analyzed using correlation analysis. Some correlations between the activity in phenol(s) photodegradation and selectivity toward formation of primary intermediate products were established. The type of correlations depends on the type of studied photoreactions. The discussion of the observed correlations between the activity and selectivity of photocatalysts is given in terms of the difference of surface concentrations of electrons and holes and corresponding surface active sites which might be dependent on the types of dominating surface faces. On the basis of the obtained results of correlation analysis it was assumed that a higher activity of photocatalysts could be achieved provided that both reduction and oxidation reaction pathways occur with equally high efficiency. Copyright Â© 2011 Elsevier B.V. All rights reserved.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Tao; Kukkadapu, Ravi K.; Griffin, Aron M.

Fe(III)-oxides and Fe(III)-bearing phyllosilicates are the two major iron sources utilized as electron acceptors by dissimilatory iron-reducing bacteria (DIRB) in anoxic soils and sediments. Although there have been many studies of microbial Fe(III)-oxide and Fe(III)-phyllosilicate reduction with both natural and specimen materials, no controlled experimental information is available on the interaction between these two phases when both are available for microbial reduction. In this study, the model DIRB Geobacter sulfurreducens was used to examine the pathways of Fe(III) reduction in Fe(III)-oxide stripped subsurface sediment that was coated with different amounts of synthetic high surface area goethite. Cryogenic (12K) 57Fe Mössbauermore » spectroscopy was used to determine changes in the relative abundances of Fe(III)-oxide, Fe(III)-phyllosilicate, and phyllosilicate-associated Fe(II) (Fe(II)-phyllosilicate) in bioreduced samples. Analogous Mössbauer analyses were performed on samples from abiotic Fe(II) sorption experiments in which sediments were exposed to a quantity of exogenous soluble Fe(II) (FeCl22H2O) comparable to the amount of Fe(II) produced during microbial reduction. A Fe partitioning model was developed to analyze the fate of Fe(II) and assess the potential for abiotic Fe(II)-catalyzed reduction of Fe(III)-phyllosilicatesilicates. The microbial reduction experiments indicated that although reduction of Fe(III)-oxide accounted for virtually all of the observed bulk Fe(III) reduction activity, there was no significant abiotic electron transfer between oxide-derived Fe(II) and Fe(III)-phyllosilicatesilicates, with 26-87% of biogenic Fe(II) appearing as sorbed Fe(II) in the Fe(II)-phyllosilicate pool. In contrast, the abiotic Fe(II) sorption experiments showed that 41 and 24% of the added Fe(II) engaged in electron transfer to Fe(III)-phyllosilicate surfaces in synthetic goethite-coated and uncoated sediment. Differences in the rate of Fe(II) addition and system redox potential may account for the microbial and abiotic reaction systems. Our experiments provide new insight into pathways for Fe(III) reduction in mixed Fe(III)-oxide/Fe(III)-phyllosilicate assemblages, and provide key mechanistic insight for interpreting microbial reduction experiments and field data from complex natural soils and sediments.« less
Nitrous oxide causes a regulated hypothermia: rats select a cooler ambient temperature while becoming hypothermic.

PubMed

Ramsay, Douglas S; Seaman, Jana; Kaiyala, Karl J

2011-04-18

An initial administration of 60% nitrous oxide (N(2)O) evokes hypothermia in rats and if the administration continues for more than 1-2h, acute tolerance typically develops such that the initial reduction in core temperature (Tc) reverses and Tc recovers toward control values. Calorimeter studies at normal ambient temperature indicate that hypothermia results from a transient reduction in heat production (HP) combined with an elevation in heat loss. Acute tolerance develops primarily due to progressive increases in HP. Our aim was to determine whether rats provided a choice of ambient temperatures would behaviorally facilitate or oppose N(2)O-induced hypothermia. A gas-tight thermally-graded alleyway (range, 6.7-37.0°C) enabled male Long-Evans rats (n=12) to select a preferred ambient temperature during a 5-hour steady-state administration of 60% N(2)O and a separate paired control gas exposure (order counterbalanced). Tc was measured telemetrically from a sensor surgically implanted into the peritoneal cavity >7days before testing. Internal LED lighting maintained the accustomed day:night cycle (light cycle 0700-1900h) during sessions lasting 45.5h. Rats entered the temperature gradient at 1100h, and the 5-h N(2)O or control gas period did not start until 23h later to provide a long habituation/training period. Food and water were provided ad libitum at the center of the alleyway. The maximum decrease of mean Tc during N(2)O administration occurred at 0.9h and was -2.05±0.25°C; this differed significantly (p<0.0001) from the corresponding Tc change at 0.9h during control gas administration (0.01±0.14°C). The maximum decrease of the mean selected ambient temperature during N(2)O administration occurred at 0.7h and was -13.58±1.61°C; this differed significantly (p<0.0001) from the corresponding mean change in the selected ambient temperature at 0.7h during control gas administration (0.30±1.49°C). N(2)O appears to induce a regulated hypothermia because the selection of a cool ambient temperature facilitates the reduction in Tc. The recovery of Tc during N(2)O administration (i.e., acute tolerance development) could have been facilitated by selection of ambient temperatures that were warmer than those chosen during control administrations, but interestingly, this did not occur. Copyright © 2011 Elsevier Inc. All rights reserved.
Nitrous Oxide Causes a Regulated Hypothermia: Rats Select a Cooler Ambient Temperature While Becoming Hypothermic

PubMed Central

Ramsay, Douglas S.; Seaman, Jana; Kaiyala, Karl J.

2011-01-01

An initial administration of 60% nitrous oxide (N2O) evokes hypothermia in rats and if the administration continues for more than 1 – 2 hours, acute tolerance typically develops such that the initial reduction in core temperature (Tc) reverses and Tc recovers toward control values. Calorimeter studies at normal ambient temperature indicate that hypothermia results from a transient reduction in heat production (HP) combined with an elevation in heat loss. Acute tolerance develops primarily due to progressive increases in HP. Our aim was to determine whether rats provided a choice of ambient temperatures would behaviorally facilitate or oppose N2O -induced hypothermia. A gas-tight thermally-graded alleyway (range, 6.7 – 37.0°C) enabled male Long-Evans rats (n=12) to select a preferred ambient temperature during a 5-hour steady-state administration of 60% N2O and a separate paired control gas exposure (order counterbalanced). Tc was measured telemetrically from a sensor surgically implanted into the peritoneal cavity > 7 days before testing. Internal LED lighting maintained the accustomed day:night cycle (light cycle 0700 – 1900 h) during sessions lasting 45.5 hours. Rats entered the temperature gradient at 1100 h, and the 5-h N2O or control gas period did not start until 23 hours later to provide a long habituation / training period. Food and water were provided ad libitum at the center of the alleyway. The maximum decrease of mean Tc during N2O administration occurred at 0.9 h and was −2.05 ± 0.25°C; this differed significantly (p<0.0001) from the corresponding Tc change at 0.9 h during control gas administration (0.01 ± 0.14°C). The maximum decrease of mean selected ambient temperature during N2O administration occurred at 0.7 h and was −13.58 ± 1.61°C; this differed significantly (p < 0.0001) from the corresponding mean change in selected ambient temperature at 0.7 h during control gas administration (0.30 ± 1.49°C). N2O appears to induce a regulated hypothermia because the selection of a cool ambient temperature facilitates the reduction in Tc. The recovery of Tc during N2O administration (i.e., acute tolerance development) could have been facilitated by selection of ambient temperatures that were warmer than those chosen during control administrations, but interestingly, this did not occur. PMID:21184766
Plasma-assisted oxide removal from ruthenium-coated EUV optics

NASA Astrophysics Data System (ADS)

Dolgov, A.; Lee, C. J.; Bijkerk, F.; Abrikosov, A.; Krivtsun, V. M.; Lopaev, D.; Yakushev, O.; van Kampen, M.

2018-04-01

An experimental study of oxide reduction at the surface of ruthenium layers on top of multilayer mirrors and thin Ru/Si films is presented. Oxidation and reduction processes were observed under conditions close to those relevant for extreme ultraviolet lithography. The oxidized ruthenium surface was exposed to a low-temperature hydrogen plasma, similar to the plasma induced by extreme ultraviolet radiation. The experiments show that hydrogen ions are the main reducing agent. Furthermore, the addition of hydrogen radicals increases the reduction rate beyond that expected from simple flux calculations. We show that low-temperature hydrogen plasmas can be effective for reducing oxidized top surfaces. Our proof-of-concept experiments show that an in situ, EUV-generated plasma cleaning technology is feasible.
Enhanced Lifetime of Polymer Solar Cells by Surface Passivation of Metal Oxide Buffer Layers.

PubMed

Venkatesan, Swaminathan; Ngo, Evan; Khatiwada, Devendra; Zhang, Cheng; Qiao, Qiquan

2015-07-29

The role of electron selective interfaces on the performance and lifetime of polymer solar cells were compared and analyzed. Bilayer interfaces consisting of metal oxide films with cationic polymer modification namely poly ethylenimine ethoxylated (PEIE) were found to enhance device lifetime compared to bare metal oxide films when used as an electron selective cathode interface. Devices utilizing surface-modified metal oxide layers showed enhanced lifetimes, retaining up to 85% of their original efficiency when stored in ambient atmosphere for 180 days without any encapsulation. The work function and surface potential of zinc oxide (ZnO) and ZnO/PEIE interlayers were evaluated using Kelvin probe and Kelvin probe force microscopy (KPFM) respectively. Kelvin probe measurements showed a smaller reduction in work function of ZnO/PEIE films compared to bare ZnO films when aged in atmospheric conditions. KPFM measurements showed that the surface potential of the ZnO surface drastically reduces when stored in ambient air for 7 days because of surface oxidation. Surface oxidation of the interface led to a substantial decrease in the performance in aged devices. The enhancement in the lifetime of devices with a bilayer interface was correlated to the suppressed surface oxidation of the metal oxide layers. The PEIE passivated surface retained a lower Fermi level when aged, which led to lower trap-assisted recombination at the polymer-cathode interface. Further photocharge extraction by linearly increasing voltage (Photo-CELIV) measurements were performed on fresh and aged samples to evaluate the field required to extract maximum charges. Fresh devices with a bare ZnO cathode interlayer required a lower field than devices with ZnO/PEIE cathode interface. However, aged devices with ZnO required a much higher field to extract charges while aged devices with ZnO/PEIE showed a minor increase compared to the fresh devices. Results indicate that surface modification can act as a suitable passivation layer to suppress oxidation in metal oxide thin films for enhanced lifetime in inverted organic solar cells.
Intra-puff CO and CO 2 measurements of cigarettes with iron oxide cigarette paper using quantum cascade laser spectroscopy

NASA Astrophysics Data System (ADS)

Crawford, Danielle R.; Parrish, Milton E.; Gee, Diane L.; Harward, Charles N.

2007-05-01

The objective of this research was to apply Fourier transform infrared spectroscopy (FTIR) and tunable infrared laser differential absorption spectroscopy (TILDAS) for measuring selected gaseous constituents in mainstream (MS) and sidestream (SS) smoke for experimental cigarettes designed to reduce MS CO using iron oxide cigarette papers. These two complimentary analytical techniques are well suited for providing per puff smoke deliveries and intra-puff evolution profiles in cigarette smoke respectively. The quad quantum cascade (QC) laser high resolution infrared spectroscopy system has the necessary temporal and spectral resolution and whole smoke analysis capabilities to provide detailed information for CO and CO 2 as they are being formed in both MS and SS smoke. The QC laser system has an optimal data rate of 20 Hz and a unique puffing system, with a square wave shaped puff, that allows whole smoke to enter an 18 m, 0.3 L multi-pass gas cell in real time (0.1 s cell response time) requiring no syringe or Cambridge filter pad. Another similar multi-pass gas cell with a 36 m pathlength simultaneously monitors the sidestream cigarette smoke. The smoke from experimental cigarettes manufactured with two types of iron oxide papers were compared to the smoke from cigarettes manufactured similarly without iron oxide in the paper using both instrument systems. The delivery per puff determined by the QC laser method agreed with FTIR results. MS CO intra-puff evolution profiles for iron oxide prototype cigarettes demonstrated CO reduction when compared to cigarettes without iron oxide paper. Additionally, both CO and CO 2 intra-puff evolution profiles of the cigarettes with iron oxide paper showed a significant reduction at the initial portion of the 2 s puff not observed in the non-iron oxide prototype cigarettes. This effect also was observed for ammonia and ethylene, suggesting that physical parameters such as paper porosity and burn rate are important. The SS CO and CO 2 deliveries for the experimental cigarettes evaluated remained unaffected. The iron oxide paper technology remains under development and continues to be evaluated.
Intra-puff CO and CO2 measurements of cigarettes with iron oxide cigarette paper using quantum cascade laser spectroscopy.

PubMed

Crawford, Danielle R; Parrish, Milton E; Gee, Diane L; Harward, Charles N

2007-05-01

The objective of this research was to apply Fourier transform infrared spectroscopy (FTIR) and tunable infrared laser differential absorption spectroscopy (TILDAS) for measuring selected gaseous constituents in mainstream (MS) and sidestream (SS) smoke for experimental cigarettes designed to reduce MS CO using iron oxide cigarette papers. These two complimentary analytical techniques are well suited for providing per puff smoke deliveries and intra-puff evolution profiles in cigarette smoke respectively. The quad quantum cascade (QC) laser high resolution infrared spectroscopy system has the necessary temporal and spectral resolution and whole smoke analysis capabilities to provide detailed information for CO and CO(2) as they are being formed in both MS and SS smoke. The QC laser system has an optimal data rate of 20 Hz and a unique puffing system, with a square wave shaped puff, that allows whole smoke to enter an 18 m, 0.3 L multi-pass gas cell in real time (0.1s cell response time) requiring no syringe or Cambridge filter pad. Another similar multi-pass gas cell with a 36 m pathlength simultaneously monitors the sidestream cigarette smoke. The smoke from experimental cigarettes manufactured with two types of iron oxide papers were compared to the smoke from cigarettes manufactured similarly without iron oxide in the paper using both instrument systems. The delivery per puff determined by the QC laser method agreed with FTIR results. MS CO intra-puff evolution profiles for iron oxide prototype cigarettes demonstrated CO reduction when compared to cigarettes without iron oxide paper. Additionally, both CO and CO(2) intra-puff evolution profiles of the cigarettes with iron oxide paper showed a significant reduction at the initial portion of the 2 s puff not observed in the non-iron oxide prototype cigarettes. This effect also was observed for ammonia and ethylene, suggesting that physical parameters such as paper porosity and burn rate are important. The SS CO and CO(2) deliveries for the experimental cigarettes evaluated remained unaffected. The iron oxide paper technology remains under development and continues to be evaluated.
A Comparative Study of N2O Formation during the Selective Catalytic Reduction of NOx with NH3 on Zeolite Supported Cu Catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Hai-Ying; Wei, Zhehao; Kollar, Marton

A comparative study was carried out on a small-pore CHA.Cu and a large-pore BEA.Cu zeolite catalyst to understand the lower N2O formation on small-pore zeolite supported Cu catalysts in the selective catalytic reduction (SCR) of NOx with NH3. On both catalysts, the N2O yield increases with an increase in the NO2/NOx ratios of the feed gas, suggesting N2O formation via the decomposition of NH4NO3. Temperature-programmed desorption experiments reveal that NH4NO3 is more stable on CHA.Cu than on BEA.Cu. In situ FTIR spectra following stepwise (NO2 + O2) and (15NO + NH3 + O2) adsorption and reaction, and product distribution analysismore » using isotope-labelled reactants, unambiguously prove that surface nitrate groups are essential for the formation of NH4NO3. Furthermore, CHA.Cu is shown to be considerably less active than BEA.Cu in catalyzing NO oxidation and the subsequent formation of surface nitrate groups. Both factors, i.e., (1) the higher thermal stability of NH4NO3 on CHA.Cu, and (2) the lower activity for this catalyst to catalyze NO oxidation and the subsequent formation of surface nitrates, likely contribute to the higher SCR selectivity with less N2O formation on this catalyst as compared to BEA.Cu. The latter is determined as the primary reason since surface nitrates are the source that leads to the formation of NH4NO3 on the catalysts.« less
Evaluation of oxidative stress markers in obstructive sleep apnea syndrome and additional antioxidant therapy: a review article.

PubMed

Lira, Amanda Bastos; de Sousa Rodrigues, Célio Fernando

2016-12-01

The hypoxia and reoxygenation cycles in obstructive sleep apnea syndrome (OSAS) cause a change in the oxidative balance, leading to the formation of reactive oxygen species capable of reacting with other organic molecules impairing their functions. This study aimed to determine the best markers of oxidative stress in OSAS and what better antioxidant agent to be used to treat the disease. Searches were conducted in three different databases (PubMed, LILACS, SCIELO), using as descriptors the terms obstructive sleep apnea, oxidative stress, and antioxidant therapy. A total of 120 articles were found but only those considered of interest to the research were selected. Thus, 10 articles were included for further analysis regarding the biomarkers of oxidative stress in OSAS, and 6 articles to evaluate the antioxidant most often used for demonstration of efficacy. The thioredoxin, malondialdehyde, superoxide dysmutase, and reduced iron were the most commonly used biomarkers and showed a more consistent relationship between increased oxidative stress and OSAS. As antioxidant therapy, vitamin C and N-acetylcysteine (NAC) presented interesting results as a reduction of oxidative stress, which may become an alternative to the complementary treatment of OSAS. This review's findings agree mostly to measure that the markers of oxidative stress in OSAS may be a contributing aspect to assessment and monitoring of patient, and the antioxidant therapy appears to be beneficial in the treatment of OSAS.
Proton translocation coupled to trimethylamine N-oxide reduction in anaerobically grown Escherichia coli.

PubMed Central

Takagi, M; Tsuchiya, T; Ishimoto, M

1981-01-01

Proton translocation coupled to trimethylamine N-oxide reduction was studied in Escherichia coli grown anaerobically in the presence of trimethylamine N-oxide. Rapid acidification of the medium was observed when trimethylamine N-oxide was added to anaerobic cell suspensions of E. coli K-10. Acidification was sensitive to the proton conductor 3,5-di-tert-butyl-4-hydroxybenzylidenemalononitrile (SF6847). No pH change was shown in a strain deficient in trimethylamine N-oxide reductase activity. The apparent H+/trimethylamine N-oxide ratio in cells oxidizing endogenous substrates was 3 to 4 g-ions of H+ translocated per mol of trimethylamine N-oxide added. The addition of trimethylamine N-oxide and formate to ethylenediaminetetraacetic acid-treated cell suspension caused fluorescence quenching of 3,3'-dipropylthiacarbocyanine [diS-C3-(5)], indicating the generation of membrane potential. These results indicate that the reduction of trimethylamine N-oxide in E. coli is catalyzed by an anaerobic electron transfer system, resulting in formation of a proton motive force. Trimethylamine N-oxide reductase activity and proton extrusion were also examined in chlorate-resistant mutants. Reduction of trimethylamine N-oxide occurred in chlC, chlG, and chlE mutants, whereas chlA, chlB, and chlD mutants, which are deficient in the molybdenum cofactor, could not reduce it. Protons were extruded in chlC and chlG mutants, but not in chlA, chlB, and chlD mutants. Trimethylamine N-oxide reductase activity in a chlD mutant was restored to the wild-type level by the addition of 100 microM molybdate to the growth medium, indicating that the same molybdenum cofactor as used by nitrate reductase is required for the trimethylamine N-oxide reductase system. PMID:7031034

Tuning the nonlinear optical absorption of reduced graphene oxide by chemical reduction.

PubMed

Shi, Hongfei; Wang, Can; Sun, Zhipei; Zhou, Yueliang; Jin, Kuijuan; Redfern, Simon A T; Yang, Guozhen

2014-08-11

Reduced graphene oxides with varying degrees of reduction have been produced by hydrazine reduction of graphene oxide. The linear and nonlinear optical properties of both graphene oxide as well as the reduced graphene oxides have been measured by single beam Z-scan measurement in the picosecond region. The results reveal both saturable absorption and two-photon absorption, strongly dependent on the intensity of the pump pulse: saturable absorption occurs at lower pump pulse intensity (~1.5 GW/cm2 saturation intensity) whereas two-photon absorption dominates at higher intensities (≥5.7 GW/cm2). Intriguingly, we find that the two-photon absorption coefficient (from 1.5 cm/GW to 4.5cm/GW) and the saturation intensity (from 1 GW/cm2 to 2 GW/cm2) vary with chemical reduction, which is ascribed to the varying concentrations of sp2 domains and sp2 clusters in the reduced graphene oxides. Our results not only provide an insight into the evolution of the nonlinear optical coefficient in reduced graphene oxide, but also suggest that chemical engineering techniques may usefully be applied to tune the nonlinear optical properties of various nano-materials, including atomically thick graphene sheets.
Large Scale Reduction of Graphite Oxide Project

NASA Technical Reports Server (NTRS)

Calle, Carlos; Mackey, Paul; Falker, John; Zeitlin, Nancy

2015-01-01

This project seeks to develop an optical method to reduce graphite oxide into graphene efficiently and in larger formats than currently available. Current reduction methods are expensive, time-consuming or restricted to small, limited formats. Graphene has potential uses in ultracapacitors, energy storage, solar cells, flexible and light-weight circuits, touch screens, and chemical sensors. In addition, graphite oxide is a sustainable material that can be produced from any form of carbon, making this method environmentally friendly and adaptable for in-situ reduction.
Anaerobic oxidation of toluene, phenol, and p-cresol by the dissimilatory iron-reducing organism, GS-15

USGS Publications Warehouse

Lovley, D.R.; Lonergan, D.J.

1990-01-01

The dissimilatory Fe(III) reducer, GS-15, is the first microorganism known to couple the oxidation of aromatic compounds to the reduction of Fe(III) and the first example of a pure culture of any kind known to anaerobically oxidize an aromatic hydrocarbon, toluene. In this study, the metabolism of toluene, phenol, and p-cresol by GS-15 was investigated in more detail. GS-15 grew in an anaerobic medium with toluene as the sole electron donor and Fe(III) oxide as the electron acceptor. Growth coincided with Fe(III) reduction. [ring-14C]toluene was oxidized to 14CO2, and the stoichiometry of 14CO2 production and Fe(III) reduction indicated that GS-15 completely oxidized toluene to carbon dioxide with Fe(III) as the electron acceptor. Magnetite was the primary iron end product during toluene oxidation. Phenol and p-cresol were also completely oxidized to carbon dioxide with Fe(III) as the sole electron acceptor, and GS-15 could obtain energy to support growth by oxidizing either of these compounds as the sole electron donor. p-Hydroxybenzoate was a transitory extracellular intermediate of phenol and p-cresol metabolism but not of toluene metabolism. GS-15 oxidized potential aromatic intermediates in the oxidation of toluene (benzylalcohol and benzaldehyde) and p-cresol (p-hydroxybenzylalcohol and p-hydroxybenzaldehyde). The metabolism described here provides a model for how aromatic hydrocarbons and phenols may be oxidized with the reduction of Fe(III) in contaminated aquifers and petroleum-containing sediments.
Oxidation state and interfacial effects on oxygen vacancies in tantalum pentoxide

DOE PAGES

Bondi, Robert J.; Marinella, Matthew J.

2015-02-28

First-principles density-functional theory (DFT) calculations are used to study the atomistic structure, structural energetics, and electron density near the O monovacancy (V O n; n=0,1+,2+) in both bulk, amorphous tantalum pentoxide (a-Ta 2O 5) and also at vacuum and metallic Ta interfaces. We calculate multivariate vacancy formation energies to evaluate stability as a function of oxidation state, distance from interface plane, and Fermi energy. V O n of all oxidation states preferentially segregate at both Ta and vacuum interfaces, where the metallic interface exhibits global formation energy minima. In a-Ta 2O 5, V O 0 are characterized by structural contractionmore » and electron density localization, while V O 2+ promote structural expansion and are depleted of electron density. In contrast, interfacial V O 0 and V O 2+ show nearly indistinguishable ionic and electronic signatures indicative of a reduced V O center. Interfacial V O 2+ extract electron density from metallic Ta indicating V O 2+ is spontaneously reduced at the expense of the metal. This oxidation/reduction behavior suggests careful selection and processing of both oxide layer and metal electrodes for engineering memristor device operation.« less
Enhancing mercury removal across air pollution control devices for coal-fired power plants by desulfurization wastewater evaporation.

PubMed

Bin, Hu; Yang, Yi; Cai, Liang; Yang, Linjun; Roszak, Szczepan

2017-10-09

Desulfurization wastewater evaporation technology is used to enhance the removal of gaseous mercury (Hg) in conventional air pollution control devices (APCDs) for coal-fired power plants. Studies have affirmed that gaseous Hg is oxidized and removed by selective catalytic reduction (SCR), an electrostatic precipitator (ESP) and wet ﬂue gas desulfurization (WFGD) in a coal-fired thermal experiment platform with WFGD wastewater evaporation. Effects of desulfurization wastewater evaporation position, evaporation temperature and chlorine ion concentration on Hg oxidation were studied as well. The Hg 0 oxidation efﬁciency was increased ranging from 30% to 60%, and the gaseous Hg removal efficiency was 62.16% in APCDs when wastewater evaporated before SCR. However, the Hg 0 oxidation efﬁciency was 18.99% and the gaseous Hg removal efficiency was 40.19% in APCDs when wastewater evaporated before ESP. The results show that WFGD wastewater evaporation before SCR is beneficial to improve the efficiency of Hg oxidized and removed in APCDs. Because Hg 2+ can be easily removed in ACPDs and WFGD wastewater in power plants is enriched with chlorine ions, this method realizes WFGD wastewater zero discharge and simultaneously enhances Hg removal in APCDs.
Methane-Oxidizing Enzymes: An Upstream Problem in Biological Gas-to-Liquids Conversion

PubMed Central

Lawton, Thomas J.; Rosenzweig, Amy C.

2017-01-01

Biological conversion of natural gas to liquids (Bio-GTL) represents an immense economic opportunity. In nature, aerobic methanotrophic bacteria and anaerobic archaea are able to selectively oxidize methane using methane monooxygenase (MMO) and methyl coenzyme M reductase (MCR) enzymes. Although significant progress has been made toward genetically manipulating these organisms for biotechnological applications, the enzymes themselves are slow, complex, and not recombinantly tractable in traditional industrial hosts. With turnover numbers of 0.16–13 s−1, these enzymes pose a considerable upstream problem in the biological production of fuels or chemicals from methane. Methane oxidation enzymes will need to be engineered to be faster to enable high volumetric productivities; however, efforts to do so and to engineer simpler enzymes have been minimally successful. Moreover, known methane-oxidizing enzymes have different expression levels, carbon and energy efficiencies, require auxiliary systems for biosynthesis and function, and vary considerably in terms of complexity and reductant requirements. The pros and cons of using each methane-oxidizing enzyme for Bio-GTL are considered in detail. The future for these enzymes is bright, but a renewed focus on studying them will be critical to the successful development of biological processes that utilize methane as a feedstock. PMID:27366961
Methane-Oxidizing Enzymes: An Upstream Problem in Biological Gas-to-Liquids Conversion.

PubMed

Lawton, Thomas J; Rosenzweig, Amy C

2016-08-03

Biological conversion of natural gas to liquids (Bio-GTL) represents an immense economic opportunity. In nature, aerobic methanotrophic bacteria and anaerobic archaea are able to selectively oxidize methane using methane monooxygenase (MMO) and methyl coenzyme M reductase (MCR) enzymes. Although significant progress has been made toward genetically manipulating these organisms for biotechnological applications, the enzymes themselves are slow, complex, and not recombinantly tractable in traditional industrial hosts. With turnover numbers of 0.16-13 s(-1), these enzymes pose a considerable upstream problem in the biological production of fuels or chemicals from methane. Methane oxidation enzymes will need to be engineered to be faster to enable high volumetric productivities; however, efforts to do so and to engineer simpler enzymes have been minimally successful. Moreover, known methane-oxidizing enzymes have different expression levels, carbon and energy efficiencies, require auxiliary systems for biosynthesis and function, and vary considerably in terms of complexity and reductant requirements. The pros and cons of using each methane-oxidizing enzyme for Bio-GTL are considered in detail. The future for these enzymes is bright, but a renewed focus on studying them will be critical to the successful development of biological processes that utilize methane as a feedstock.
High basal metabolic rate does not elevate oxidative stress during reproduction in laboratory mice.

PubMed

Brzęk, Paweł; Książek, Aneta; Ołdakowski, Łukasz; Konarzewski, Marek

2014-05-01

Increased oxidative stress (OS) has been suggested as a physiological cost of reproduction. However, previous studies reported ambiguous results, with some even showing a reduction of oxidative damage during reproduction. We tested whether the link between reproduction and OS is mediated by basal metabolic rate (BMR), which has been hypothesized to affect both the rate of radical oxygen species production and antioxidative capacity. We studied the effect of reproduction on OS in females of laboratory mice divergently selected for high (H-BMR) and low (L-BMR) BMR, previously shown to differ with respect to parental investment. Non-reproducing L-BMR females showed higher oxidative damage to lipids (quantified as the level of malondialdehyde in internal organ tissues) and DNA (quantified as the level of 8-oxodG in blood serum) than H-BMR females. Reproduction did not affect oxidative damage to lipids in either line; however, it reduced damage to DNA in L-BMR females. Reproduction increased catalase activity in liver (significantly stronger in L-BMR females) and decreased it in kidneys. We conclude that the effect of reproduction on OS depends on the initial variation in BMR and varies between studied internal organs and markers of OS.
Thiamine deficiency induces oxidative stress and exacerbates the plaque pathology in Alzheimer’s mouse model

PubMed Central

Karuppagounder, Saravanan S.; Xu, Hui; Shi, Qingli; Chen, Lian H.; Pedrini, Steve; Pechman, David; Baker, Harriet; Beal, M. Flint; Gandy, Sam E.; Gibson, Gary E.

2009-01-01

Mitochondrial dysfunction, oxidative stress and reductions in thiamine-dependent enzymes have been implicated in multiple neurological disorders including Alzheimer's disease (AD). Experimental thiamine deficiency (TD) is an established model for reducing the activities of thiamine-dependent enzymes in brain. TD diminishes thiamine dependent enzymes throughout the brain, but produces a time-dependent selective neuronal loss, glial activation, inflammation, abnormalities in oxidative metabolism and clusters of degenerating neurites in only specific thalamic regions. The present studies tested how TD alters brain pathology in Tg19959 transgenic mice over expressing a double mutant form of the amyloid precursor protein (APP). TD exacerbated amyloid plaque pathology in transgenic mice and enlarged the area occupied by plaques in cortex, hippocampus and thalamus by 50%, 200% and 200%, respectively. TD increased Aβ1–42 levels by about three-fold, β-CTF (C99) levels by 33% and β-secretase (BACE1) protein levels by 43%. TD induced inflammation in areas of plaque formation. Thus, the induction of mild impairment of oxidative metabolism, oxidative stress and inflammation induced by TD alters metabolism of APP and/or Aβ and promotes accumulation of plaques independent of neuron loss or neuritic clusters. PMID:18406011
Exsolution of Iron-Titanium Oxides in Magnetite in Miller Range (MIL) 03346 Nakhlite: Evidence for Post Crystallization Reduction in the Nakhlite Cumulate Pile

NASA Technical Reports Server (NTRS)

Righter, Kevin; Keller, L. P.; Rahman, Z.; Christoffersen, R.

2012-01-01

MIL 03346 is one of the most mesostasis-rich nakhlites [1] and thought to have equilibrated at oxygen fugacities near the fayalite-magnetite-quartz oxygen (FMQ) buffer ([2,3]). Studies of FeTi oxides in nakhlites have led to additional constraints on their equilibration temperatures and fO2s [4,5,6,7]. Comparison of these results to fO2s calculated for shergottites indicates that nakhlites are among the most oxidized samples from the martian meteorite suite [2]. The mesostasis of MIL 03346 contains skeletal titanomagnetite. Several scientists noticed several years ago (e.g. [8]) that this titanomagnetite contains very fine oxidation-driven exsolution lamellae (Figure 1). However, the lamellae are so small that they cannot be characterized by electron microprobe analysis (EMPA). Here we select several areas for focused ion beam (FIB) extraction, prepare transmission electron microscopy (TEM) foils, and identify and analyze the lamellae using TEM at the Johnson Space Center (JSC). The resulting analyses are combined with previous work on nakhlites to interpret the thermal and oxidation history of this meteorite group.
A rapid room temperature chemical route for the synthesis of graphene: metal-mediated reduction of graphene oxide.

PubMed

Dey, Ramendra Sundar; Hajra, Saumen; Sahu, Ranjan K; Raj, C Retna; Panigrahi, M K

2012-02-07

A rapid and facile route for the synthesis of reduced graphene oxide sheets (rGOs) at room temperature by the chemical reduction of graphene oxide using Zn/acid in aqueous solution is demonstrated. This journal is © The Royal Society of Chemistry 2012
Removal of oxides from alkali metal melts by reductive titration to electrical resistance-change end points

DOEpatents

Tsang, Floris Y.

1980-01-01

Alkali metal oxides dissolved in alkali metal melts are reduced with soluble metals which are converted to insoluble oxides. The end points of the reduction is detected as an increase in electrical resistance across an alkali metal ion-conductive membrane interposed between the oxide-containing melt and a material capable of accepting the alkali metal ions from the membrane when a difference in electrical potential, of the appropriate polarity, is established across it. The resistance increase results from blocking of the membrane face by ions of the excess reductant metal, to which the membrane is essentially non-conductive.
The light-induced reduction of horizontal cell receptive field size in the goldfish retina involves nitric oxide.

PubMed

Daniels, Bryan A; Baldridge, William H

2011-03-01

Horizontal cells of the vertebrate retina have large receptive fields as a result of extensive gap junction coupling. Increased ambient illumination reduces horizontal cell receptive field size. Using the isolated goldfish retina, we have assessed the contribution of nitric oxide to the light-dependent reduction of horizontal cell receptive field size. Horizontal cell receptive field size was assessed by comparing the responses to centered spot and annulus stimuli and from the responses to translated slit stimuli. A period of steady illumination decreased the receptive field size of horizontal cells, as did treatment with the nitric oxide donor (Z)-1-[N-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate (100 μM). Blocking the endogenous production of nitric oxide with the nitric oxide synthase inhibitor, N(G)-nitro-L-arginine methyl ester (1 mM), decreased the light-induced reduction of horizontal cell receptive field size. These findings suggest that nitric oxide is involved in light-induced reduction of horizontal cell receptive field size. Copyright © Cambridge University Press, 2011
Chemical modification of cellulose-rich fibres to clarify the influence of the chemical structure on the physical and mechanical properties of cellulose fibres and thereof made sheets.

PubMed

López Durán, Verónica; Larsson, Per A; Wågberg, Lars

2018-02-15

Despite the different chemical approaches used earlier to increase the ductility of fibre-based materials, it has not been possible to link the chemical modification to their mechanical performance. In this study, cellulose fibres have been modified by periodate oxidation, alone or followed either by borohydride reduction, reductive amination or chlorite oxidation. In addition, TEMPO oxidation, and TEMPO oxidation in combination with periodate oxidation and further reduction with sodium borohydride have also been studied. The objective was to gain understanding of the influence of different functional groups on the mechanical and structural properties of handsheets made from the modified fibres. It was found that the modifications studied improved the tensile strength of the fibres to different extents, but that only periodate oxidation followed by borohydride reduction provided more ductile fibre materials. Changes in density, water-holding capacity and mechanical performance were also quantified and all are dependent on the functional group introduced. Copyright © 2017 Elsevier Ltd. All rights reserved.
H2S adsorption and decomposition on the gradually reduced α-Fe2O3(001) surface: A DFT study

NASA Astrophysics Data System (ADS)

Lin, Changfeng; Qin, Wu; Dong, Changqing

2016-11-01

Reduction of iron based desulfurizer occurs during hot gas desulfurization process, which will affect the interaction between H2S and the desulfurizer surface. In this work, a detailed adsorption behavior and dissociation mechanism of H2S on the perfect and reduced α-Fe2O3(001) surfaces, as well as the correlation between the interaction characteristic and reduction degree of iron oxide, have been studied by using periodic density functional theory (DFT) calculations. Results demonstrate that H2S firstly chemisorbs on surface at relatively higher oxidation state (reduction degree χ < 33%), then dissociative adsorption occurs and becomes the main adsorption type after χ > 33%. Reduction of iron oxide benefits the H2S adsorption. Further, dissociation processes of H2S via molecular and dissociative adsorption were investigated. Results show that after reduction of Fe2O3 into the oxidation state around FeO and Fe, the reduced surface exhibits very strong catalytic capacity for H2S decomposition into S species. Meanwhile, the overall dissociation process on all surfaces is exothermic. These results provide a fundamental understanding of reduction effect of iron oxide on the interaction mechanism between H2S and desulfurizer surface, and indicate that rational control of reduction degree of desulfurizer is essential for optimizing the hot gas desulfurization process.
Preparation and characterization of PANI@G/CWO nanocomposite for enhanced 2-nitrophenol sensing

NASA Astrophysics Data System (ADS)

Khan, Anish; Khan, Aftab Aslam Parwaz; Rahman, Mohammed M.; Asiri, Abdullah M.; Inamuddin; Alamry, Khalid A.; Hameed, Salem A.

2018-03-01

A new material by polymer insertion via graphene oxide into cerium tungstate was prepared by very simple oxidation-reduction method. Aniline polymerization was done on the surface of graphene oxide (GO) which was reduced to graphene (G) simultaneously mixed with separately prepared inorganic matrices of cerium tungstate (Ce2(WO4)3 (CWO)). PANI@G/CWO was characterized by various spectroscopic methods as SEM, FTIR, TGA, XRD and XPS to confirm its possibilities. Selective 2-nitrophenol sensor was fabricated on flat glassy carbon electrode (GCE) and PANI@G/CWO nanocomposites in the form of thin layer. It was found excellent sensitivity as well as long life spam with broad dynamic concentration range (LDR) that showed efficient electrochemical performance towards 2-nitrophenol on fabricated chemical sensor by PANI@G/CWO. The linear calibration curve (r2 = 0.9914) with wide range of 2-nitrophenol concentration (1.0 nM-1.0 mM) was found having the detection limit of 0.87 nM while the sensitivity of the sensor was around 1.229 μ A μM-1 cm-2. It was introduced a new route for the development of a versatile phenolic sensor based on PANI@G/CWO nanocomposites by I-V method that is proved more selective and sensitive for environmental toxic materials.
Impact of Fuel Metal Impurities on the Durability of a Light-Duty Diesel Aftertreatment System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Williams, A.; Burton, J.; McCormick, R. L.

2013-04-01

Alkali and alkaline earth metal impurities found in diesel fuels are potential poisons for diesel exhaust catalysts. A set of diesel engine production exhaust systems was aged to 150,000 miles. These exhaust systems included a diesel oxidation catalyst, selective catalytic reduction (SCR) catalyst, and diesel particulate filter (DPF). Four separate exhaust systems were aged, each with a different fuel: ultralow sulfur diesel containing no measureable metals, B20 (a common biodiesel blend) containing sodium, B20 containing potassium, and B20 containing calcium, which were selected to simulate the maximum allowable levels in B100 according to ASTM D6751. Analysis included Federal Test Proceduremore » emissions testing, bench-flow reactor testing of catalyst cores, electron probe microanalysis (EPMA), and measurement of thermo-mechanical properties of the DPFs. EPMA imaging found that the sodium and potassium penetrated into the washcoat, while calcium remained on the surface. Bench-flow reactor experiments were used to measure the standard nitrogen oxide (NOx) conversion, ammonia storage, and ammonia oxidation for each of the aged SCR catalysts. Vehicle emissions tests were conducted with each of the aged catalyst systems using a chassis dynamometer. The vehicle successfully passed the 0.2 gram/mile NOx emission standard with each of the four aged exhaust systems.« less
Global Emissions of Nitrous Oxide: Key Source Sectors, their Future Activities and Technical Opportunities for Emission Reduction

NASA Astrophysics Data System (ADS)

Winiwarter, W.; Höglund-Isaksson, L.; Klimont, Z.; Schöpp, W.; Amann, M.

2017-12-01

Nitrous oxide originates primarily from natural biogeochemical processes, but its atmospheric concentrations have been strongly affected by human activities. According to IPCC, it is the third largest contributor to the anthropogenic greenhouse gas emissions (after carbon dioxide and methane). Deep decarbonization scenarios, which are able to constrain global temperature increase within 1.5°C, require strategies to cut methane and nitrous oxide emissions on top of phasing out carbon dioxide emissions. Employing the Greenhouse gas and Air pollution INteractions and Synergies (GAINS) model, we have estimated global emissions of nitrous oxide until 2050. Using explicitly defined emission reduction technologies we demonstrate that, by 2030, about 26% ± 9% of the emissions can be avoided assuming full implementation of currently existing reduction technologies. Nearly a quarter of this mitigation can be achieved at marginal costs lower than 10 Euro/t CO2-eq with the chemical industry sector offering important reductions. Overall, the largest emitter of nitrous oxide, agriculture, also provides the largest emission abatement potentials. Emission reduction may be achieved by precision farming methods (variable rate technology) as well as by agrochemistry (nitrification inhibitors). Regionally, the largest emission reductions are achievable where intensive agriculture and industry are prevalent (production and application of mineral fertilizers): Centrally Planned Asia including China, North and Latin America, and South Asia including India. Further deep cuts in nitrous oxide emissions will require extending reduction efforts beyond strictly technological solutions, i.e., considering behavioral changes, including widespread adoption of "healthy diets" minimizing excess protein consumption.
A Facile Electrochemical Preparation of Reduced Graphene Oxide@Polydopamine Composite: A Novel Electrochemical Sensing Platform for Amperometric Detection of Chlorpromazine

NASA Astrophysics Data System (ADS)

Palanisamy, Selvakumar; Thirumalraj, Balamurugan; Chen, Shen-Ming; Wang, Yi-Ting; Velusamy, Vijayalakshmi; Ramaraj, Sayee Kannan

2016-09-01

We report a novel and sensitive amperometric sensor for chlorpromazine (CPZ) based on reduced graphene oxide (RGO) and polydopamine (PDA) composite modified glassy carbon electrode. The RGO@PDA composite was prepared by electrochemical reduction of graphene oxide (GO) with PDA. The RGO@PDA composite modified electrode shows an excellent electro-oxidation behavior to CPZ when compared with other modified electrodes such as GO, RGO and GO@PDA. Amperometric i-t method was used for the determination of CPZ. Amperometry result shows that the RGO@PDA composite detects CPZ in a linear range from 0.03 to 967.6 μM. The sensor exhibits a low detection limit of 0.0018 μM with the analytical sensitivity of 3.63 ± 0.3 μAμM-1 cm-2. The RGO@PDA composite shows its high selectivity towards CPZ in the presence of potentially interfering drugs such as metronidazole, phenobarbital, chlorpheniramine maleate, pyridoxine and riboflavin. In addition, the fabricated RGO@PDA modified electrode showed an appropriate recovery towards CPZ in the pharmaceutical tablets.
Validation of optimization strategies using the linear structured production chains

NASA Astrophysics Data System (ADS)

Kusiak, Jan; Morkisz, Paweł; Oprocha, Piotr; Pietrucha, Wojciech; Sztangret, Łukasz

2017-06-01

Different optimization strategies applied to sequence of several stages of production chains were validated in this paper. Two benchmark problems described by ordinary differential equations (ODEs) were considered. A water tank and a passive CR-RC filter were used as the exemplary objects described by the first and the second order differential equations, respectively. Considered in the work optimization problems serve as the validators of strategies elaborated by the Authors. However, the main goal of research is selection of the best strategy for optimization of two real metallurgical processes which will be investigated in an on-going projects. The first problem will be the oxidizing roasting process of zinc sulphide concentrate where the sulphur from the input concentrate should be eliminated and the minimal concentration of sulphide sulphur in the roasted products has to be achieved. Second problem will be the lead refining process consisting of three stages: roasting to the oxide, oxide reduction to metal and the oxidizing refining. Strategies, which appear the most effective in considered benchmark problems will be candidates for optimization of the mentioned above industrial processes.

Arsenic toxicity induced endothelial dysfunction and dementia: Pharmacological interdiction by histone deacetylase and inducible nitric oxide synthase inhibitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, Bhupesh, E-mail: drbhupeshresearch@gmail.com; Sharma, P.M.

Arsenic toxicity has been reported to damage all the major organs including the brain and vasculature. Dementia including Alzheimer's disease (AD) and vascular dementia (VaD) are posing greater risk to the world population as it is now increasing at a faster rate. We have investigated the role of sodium butyrate, a selective histone deacetylase (HDAC) inhibitor and aminoguanidine, a selective inducible nitric oxide synthase (iNOS) inhibitor in pharmacological interdiction of arsenic toxicity induced vascular endothelial dysfunction and dementia in rats. Arsenic toxicity was done by administering arsenic drinking water to rats. Morris water-maze (MWM) test was used for assessment ofmore » learning and memory. Endothelial function was assessed using student physiograph. Oxidative stress (aortic superoxide anion, serum and brain thiobarbituric acid reactive species, brain glutathione) and nitric oxide levels (serum nitrite/nitrate) were also measured. Arsenic treated rats have shown impairment of endothelial function, learning and memory, reduction in serum nitrite/nitrate and brain GSH levels along with increase in serum and brain TBARS. Sodium butyrate as well as aminoguanidine significantly convalesce arsenic induced impairment of learning, memory, endothelial function, and alterations in various biochemical parameters. It may be concluded that arsenic induces endothelial dysfunction and dementia, whereas, sodium butyrate, a HDAC inhibitor as well as aminoguanidine, a selective iNOS inhibitor may be considered as potential agents for the management of arsenic induced endothelial dysfunction and dementia. - Highlights: • As has induced endothelial dysfunction (Edf) and vascular dementia (VaD). • As has increased oxidative stress, AChE activity and decreased serum NO. • Inhibitors of HDAC and iNOS have attenuated As induced Edf and VaD. • Both the inhibitors have attenuated As induced biochemical changes. • Inhibitor of HDAC and iNOS has shown good potential in As induced VaD.« less
Selective downregulation of mitochondrial electron transport chain activity and increased oxidative stress in human atrial fibrillation.

PubMed

Emelyanova, Larisa; Ashary, Zain; Cosic, Milanka; Negmadjanov, Ulugbek; Ross, Gracious; Rizvi, Farhan; Olet, Susan; Kress, David; Sra, Jasbir; Tajik, A Jamil; Holmuhamedov, Ekhson L; Shi, Yang; Jahangir, Arshad

2016-07-01

Mitochondria are critical for maintaining normal cardiac function, and a deficit in mitochondrial energetics can lead to the development of the substrate that promotes atrial fibrillation (AF) and its progression. However, the link between mitochondrial dysfunction and AF in humans is still not fully defined. The aim of this study was to elucidate differences in the functional activity of mitochondrial oxidative phosphorylation (OXPHOS) complexes and oxidative stress in right atrial tissue from patients without (non-AF) and with AF (AF) who were undergoing open-heart surgery and were not significantly different for age, sex, major comorbidities, and medications. The overall functional activity of the electron transport chain (ETC), NADH:O2 oxidoreductase activity, was reduced by 30% in atrial tissue from AF compared with non-AF patients. This was predominantly due to a selective reduction in complex I (0.06 ± 0.007 vs. 0.09 ± 0.006 nmol·min(-1)·citrate synthase activity(-1), P = 0.02) and II (0.11 ± 0.012 vs. 0.16 ± 0.012 nmol·min(-1)·citrate synthase activity(-1), P = 0.003) functional activity in AF patients. Conversely, complex V activity was significantly increased in AF patients (0.21 ± 0.027 vs. 0.12 ± 0.01 nmol·min(-1)·citrate synthase activity(-1), P = 0.005). In addition, AF patients exhibited a higher oxidative stress with increased production of mitochondrial superoxide (73 ± 17 vs. 11 ± 2 arbitrary units, P = 0.03) and 4-hydroxynonenal level (77.64 ± 30.2 vs. 9.83 ± 2.83 ng·mg(-1) protein, P = 0.048). Our findings suggest that AF is associated with selective downregulation of ETC activity and increased oxidative stress that can contribute to the progression of the substrate for AF. Copyright © 2016 the American Physiological Society.
Transition Metal Oxides for the Oxygen Reduction Reaction: Influence of the Oxidation States of the Metal and its Position on the Periodic Table.

PubMed

Toh, Rou Jun; Sofer, Zdeněk; Pumera, Martin

2015-11-16

Electrocatalysts have been developed to meet the needs and requirements of renewable energy applications. Metal oxides have been well explored and are promising for this purpose, however, many reports focus on only one or a few metal oxides at once. Herein, thirty metal oxides, which were either commercially available or synthesized by a simple and scalable method, were screened for comparison with regards to their electrocatalytic activity towards the oxygen reduction reaction (ORR). We show that although manganese, iron, cobalt, and nickel oxides generally displayed the ability to enhance the kinetics of oxygen reduction under alkaline conditions compared with bare glassy carbon, there is no significant correlation between the position of a metal on the periodic table and the electrocatalytic performance of its respective metal oxides. Moreover, it was also observed that mixed valent (+2, +3) oxides performed the poorest, compared with their respective pure metal oxides. These findings may be of paramount importance in the field of renewable energy. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Controlling Hexavalent Americium – A Centerpiece to a Compact Nuclear Fuel Cycle

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shafer /Braley, Jenifer; Nash, Kenneth L; Lumetta, Gregg

2014-10-01

Closing the nuclear fuel cycle could be simplified by recovering the actinides U through Am as a group. This could be achieved by converting U, Np, Pu and Am to the hexavalent state. Uranium, Np and Pu are readily oxidized to the hexavalent state. Generation of hexavalent Am in acidic solutions is more difficult, as the standard reduction potential of the Am(VI) /Am(III) couple (+1.68 V in 1 M HClO4) is well outside of the electrochemical stability window of water. While the oxidation and separation of Am has been demonstrated under laboratory conditions, several issues could plague scale up andmore » implementation of this separation with used fuel. Two primary concerns are considered. The first issue concerns the stability of the oxidized Am. The second involves the undesirable co-extraction of tetravalent f-elements with the hexavalent actinides. To address the first concern regarding Am redox instability, Am reduction will be monitored under a variety of different conditions to establish the means of improving the stability of Am(VI) in the organic phase. Identifying the components contributing most significantly to its reduction will allow thoughtful modification of the process. To address the second concern, we propose to apply branched chain extractants to separate hexavalent actinides from tetravalent f-elements. Both branched monoamide and organophosphorus extractants have demonstrated significant selectivity for UO22+ versus Th4+, with separation factors generally on the order of 100. The efforts of this two-pronged research program should represent a significant step forward in the development of aqueous separations approaches designed to recover the U-Am actinides based on the availability of the hexavalent oxidation state. For the purposes of this proposal, separations based on this approach will be called SAn(VI) separations, indicating the Separation of An(VI).« less
Mechanistic Investigation of Ethanol SCR of NOx over Ag/Al2O3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, William L; Fisher, Galen; Toops, Todd J

2012-01-01

A 2 wt.% Ag/{gamma}-Al{sub 2}O{sub 3} catalyst was studied for the ethanol selective catalytic reduction of NO{sub x} from 200 to 550 C and space velocities between 30,000 h{sup -1} and 140,000 h{sup -1}. Peak NO{sub x} conversions reached 85% at 400 C, and an activation energy was determined to be 57 kJ/mol with a feed of ethanol to NO{sub x} or HC{sub 1}/NO{sub x} = 3. Up to 80% of the NO is oxidized to NO{sub 2} at 250 C, but overall NO{sub x} conversion is only 15%. Interestingly, ethanol oxidation occurs at much lower temperatures than NO{sub x}more » reduction; at 250 C, ethanol oxidation is 80% when flowing ethanol + NO + O{sub 2}. This increased reactivity, compared to only 15% when flowing only ethanol + O{sub 2}, combined with the observation that NO is not oxidized to NO{sub 2} in the absence of ethanol illustrates a synergistic relationship between the reactants. To further investigate this chemistry, a series of DRIFTS experiments were performed. To form nitrates/nitrites on the catalysts it was necessary to include ethanol in the feed with NO. These nitrates/nitrites were readily formed when flowing NO{sub 2} over the catalyst. It is proposed that ethanol adsorbs through an ethoxy-intermediate that results in atomic hydrogen on the surface. This hydrogen aids the release of NO{sub 2} from Ag to the gas-phase which, can be subsequently adsorbed at {gamma}-Al{sub 2}O{sub 3} sites away from Ag. The disappearance of these nitrates/nitrites at higher temperatures proceeds in parallel with the increase in NO{sub x} reduction reactivity between 300 and 350 C observed in the kinetic study. It is therefore proposed that the consumption of nitrates is involved in the rate determining step for this reaction.« less
Mechanism of sodium chloride in promoting reduction of high-magnesium low-nickel oxide ore

PubMed Central

Zhou, Shiwei; Wei, Yonggang; Li, Bo; Wang, Hua; Ma, Baozhong; Wang, Chengyan

2016-01-01

Sodium chloride has been proved that it is an effective promoter for the reduction of high-magnesium, low-nickel oxide ore. The aim of current work is to clarify the promotion behavior of sodium chloride in the roasting reduction process. The influence of moisture on the reduction of ore in the presence of sodium chloride is studied to get clear comprehension of promotion process. In the presence of moisture, the HCl is produced by pyrohydrolysis of sodium chloride for chlorinating nickel and iron oxides, moreover, interactions between metallic oxides and sodium chloride are also a way for chlorination at high temperature (>802 °C); subsequently, the metal chloride would be reduced by reductant. In the absence of moisture, the magnetic separation results show that the recoveries of iron and nickel have a significant increase; moreover, olivine structure would be destroyed gradually with the increase of roasting temperature in the action of sodium chloride, and the sodium chloride existed in high-magnesium, low-nickel oxide ore could make the NiO isolate from NiO-bearing minerals. The NiO reacts with Fe2O3 at high temperature to form NiFe2O4, which is conductive to the formation of Ni-Fe alloy during the reduction process. PMID:27374991
Mechanism of sodium chloride in promoting reduction of high-magnesium low-nickel oxide ore.

PubMed

Zhou, Shiwei; Wei, Yonggang; Li, Bo; Wang, Hua; Ma, Baozhong; Wang, Chengyan

2016-07-04

Sodium chloride has been proved that it is an effective promoter for the reduction of high-magnesium, low-nickel oxide ore. The aim of current work is to clarify the promotion behavior of sodium chloride in the roasting reduction process. The influence of moisture on the reduction of ore in the presence of sodium chloride is studied to get clear comprehension of promotion process. In the presence of moisture, the HCl is produced by pyrohydrolysis of sodium chloride for chlorinating nickel and iron oxides, moreover, interactions between metallic oxides and sodium chloride are also a way for chlorination at high temperature (>802 °C); subsequently, the metal chloride would be reduced by reductant. In the absence of moisture, the magnetic separation results show that the recoveries of iron and nickel have a significant increase; moreover, olivine structure would be destroyed gradually with the increase of roasting temperature in the action of sodium chloride, and the sodium chloride existed in high-magnesium, low-nickel oxide ore could make the NiO isolate from NiO-bearing minerals. The NiO reacts with Fe2O3 at high temperature to form NiFe2O4, which is conductive to the formation of Ni-Fe alloy during the reduction process.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Gangopadhyay, Arup; McWatt, D. G.; Zdrodowski, R. J.

Engine oils play a critical role in friction reduction. Improvements in engine oil technology steadily improved fuel economy as the industry moved through ILSAC GF-1 to GF-5 specifications. These improvements were influenced by changes in base oil chemistry, development of new friction modifiers and their treat levels, and the total additive package consisting of various other components. However, the improvements are incremental and further fuel consumption reduction opportunities are becoming more challenging. Polyalkylene glycol (PAG) based engine oils are being explored as a step forward for significant fuel consumption reduction. Although PAG fluids are used in many industrial applications, itsmore » application as an engine oil has been explored in a limited way. The objective of this project is to deep dive in exploring the applicability of PAG technology in engine oil, understanding the benefits, and limitations, elucidating the mechanism(s) for friction benefits, if any, and finally recommending how to address any limitations. The project was designed in four steps, starting with selection of lubricant technology, followed by friction and wear evaluations in laboratory bench tests which are relatively simple and inexpensive and also served as a screener for further evaluation. Selected formulations were chosen for more complex engine component level tests i.e., motored valvetrain friction and wear, piston ring friction using a motored single cylinder, and motored engine tests. A couple of formulations were further selected based on component level tests for engine dyno tests i.e., Sequence VID (ASTM D6709) for fuel economy, Sequence IVA (ASTM D6891) for valvetrain wear, and Sequence VG (ASTM D6593) for sludge and varnish protection. These are some of the industry standard tests required for qualifying engine oils. Out of these tests, a single PAG oil was selected for chassis roll dynamometer tests for fuel economy and emission measurements using FTP (Federal Test Procedure) metro/highway cycles. Five different PAG chemistries were selected by varying the starting alcohol, the oxide monomers (ethylene oxide, propylene oxide, or butylene oxide), capped or uncapped, homopolymer or random copolymer. All formulations contained a proprietary additive package and one which contained additional antiwear and friction modifier additives. Laboratory bench tests (Pin-on-Disk, High Frequency Reciprocating Rig (HFRR), Block-on-Ring, Mini-Traction Machine (MTM) identified formulations having friction, wear, and load carrying characteristics similar to or better than baseline GF-5 SAE 5W-20 oil. Motored valvetrain and motored piston ring friction tests showed nearly 50% friction reduction for some of the PAG formulations compared to GF-5 SAE 5W-20 oil. Motored engine tests showed up to 15% friction benefit over GF-5 SAE 5W-20 oil. It was observed that friction benefits are more related to PAG base oil chemistry than their lower viscosity compared to GF-5 SAE 5W-20 oil. Analysis of wear surfaces from laboratory bench tests and bucket tappets from motored valvetrain tests confirmed the presence of PAG molecules. The adsorption of these polar molecules is believed to be reason for friction reduction. However, the wear surfaces also had thin tribo-film derived from additive components. The tribo-film consisting of phosphates, sulfides, and molybdenum disulfide (when molybdenum additive was present) were observed for both GF-5 SAE 5W-20 and PAG fluids. However, when using PAG fluids, motored valvetrain tests showed high initial wear, which is believed to be due to delay in protective tribo-film formation. After the initial wear, the wear rate of PAG fluids was comparable to GF-5 SAE 5W-20 oil. The PAG oil containing additional antiwear and friction reducing additives showed low initial wear as expected. However, when this oil was evaluated in Sequence IVA test, it showed initially low wear comparable to GF-5 oil but wear accelerated with oil aging indicating rapid deterioration of additive components. ASTM Sequence VG test showed good sludge protection capability but failed to meet varnish rating for GF-5 requirement. Chassis roll dynamometer tests with PAG oil 15-1 showed about 1% fuel economy benefit over GF-5 SAE 5W-20 oil in EPA city cycles only and when the oil was slightly aged (500 miles). No fuel economy benefits could be observed in combined EPA metro/highway cycles. Also, no fuel economy benefit could be observed with continued (500- 10000 miles) oil aging. However, the emission level was comparable to the reference oil and was within EPA limits. Analysis of the PAG oil following tests showed low iron content although additive components were significantly degraded. The results indicate that PAG fluids have significant friction reduction potential but there are challenges with wear and varnish protection capabilities. These limitations are primarily because the selected additive components were chosen to provide a fluid with no metal content that forms little or no sulphated ash. Significant development work is needed to identify additive components compatible with PAG chemistry including their solubility in PAG oil. Miscibility of PAG fluids with mineral base oil is another challenge for oil change service. There is PAG chemistry (oil soluble PAG, OSP) which is soluble in mineral oils but the formulation explored in this investigation did not show significant friction reduction in motored engine tests. Again, highlighting the need for additive development for specific PAG chemistry. The thermal oxidation behavior of these oils has not been explored in this investigation and needs attention.« less
Performance evaluation of the UV/H2O2 process on selected nitrogenous organic compounds: reductions of organic contents vs. corresponding C-, N-DBPs formations.

PubMed

Chen, Huei-Wen; Chen, Chia-Yang; Wang, Gen-Shuh

2011-10-01

The presence of various organic contaminants in water sources is of concern due to their direct threats to human health and potential to react with disinfectants to form carcinogenic byproducts including trihalomethanes, haloacetic acids and nitrosamines in finished water. This study applied both medium-pressure and low-pressure ultraviolet light coupled with hydrogen peroxide (UV/H2O2) to evaluate its efficacy for degradation of selected nitrogenous organic compounds and corresponding disinfection byproduct (DBP) formation. Six organic compounds were chosen as target precursors based on their nitrogen contents and molecular structures. The results showed that higher oxidation capacity resulted in better reduction of organic matters and DBP formation potentials (DBPFPs). However, insufficient contact time and oxidant doses could lead to a rise of DBPFPs in the early stages of UV/H2O2 reactions. A greater percentage removal was achieved for organic carbon than organic nitrogen after UV/H2O2 treatment, especially for compounds with complicated structure such as diltiazem. During the UV/H2O2 treatment, the intermediate products include tertiary amine, dimethyl amine (DMA) or DMA-like structures, which are N-nitrosodimethylamine (NDMA) precursors after chlorination or chloramination. Furthermore, it was observed that using dissolved organic nitrogen and DMA to predict NDMAFP could lead to biased conclusions because of the complex nature of nitrogenous matters in aqueous environments. Copyright © 2011 Elsevier Ltd. All rights reserved.
DOE Office of Scientific and Technical Information (OSTI.GOV)

Squires, Leah N.; Lessing, Paul

A process of direct reduction of neptunium oxide to neptunium metal using calcium metal as the reducing agent is discussed. After reduction of the oxide to metal, the metal is separated by density from the other components of the reaction mixture and can easily removed upon cooling. Furthermore, the direct reduction technique consistently produces high purity (98%–99% pure) neptunium metal.
Formation of Green Rust and Immobilization of Nickel in Response to Bacterial Reduction of Hydrous Ferric Oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parmar, N.; Gorby, Yuri A.; Beveridge, Terrance J.

This investigation documents the formation of Green Rust (GR) and immobilization of Ni2+ in response to bacterial reduction of hydrous ferric oxide (HFO) reduction experiments provided evidence that the solid-phase partitioning of Ni2+ in GR extended from equilibrium solid-solution behavior.
Uniformity index measurement technology using thermocouples to improve performance in urea-selective catalytic reduction systems

NASA Astrophysics Data System (ADS)

Park, Sangki; Oh, Jungmo

2018-05-01

The current commonly used nitrogen oxides (NOx) emission reduction techniques employ hydrocarbons (HCs), urea solutions, and exhaust gas emissions as the reductants. Two of the primary denitrification NOx (DeNOx) catalyst systems are the HC-lean NOx trap (HC-LNT) catalyst and urea-selective catalytic reduction (urea-SCR) catalyst. The secondary injection method depends on the type of injector, injection pressure, atomization, and spraying technique. In addition, the catalyst reaction efficiency is directly affected by the distribution of injectors; hence, the uniformity index (UI) of the reductant is very important and is the basis for system optimization. The UI of the reductant is an indicator of the NOx conversion efficiency (NCE), and good UI values can reduce the need for a catalyst. Therefore, improving the UI can reduce the cost of producing a catalytic converter, which are expensive due to the high prices of the precious metals contained therein. Accordingly, measurement of the UI is an important process in the development of catalytic systems. Two of the commonly used methods for measuring the reductant UI are (i) measuring the exhaust emissions at many points located upstream/downstream of the catalytic converter and (ii) acquisition of a reductant distribution image on a section of the exhaust pipe upstream of the catalytic converter. The purpose of this study is to develop a system and measurement algorithms to measure the exothermic response distribution in the exhaust gas as the reductant passes through the catalytic converter of the SCR catalyst system using a set of thermocouples downstream of the SCR catalyst. The system is used to measure the reductant UI, which is applied in real-time to the actual SCR system, and the results are compared for various types of mixtures for various engine operating conditions and mixer types in terms of NCE.
Mechanisms for chelator stimulation of microbial Fe(III) -oxide reduction

USGS Publications Warehouse

Lovley, D.R.; Woodward, J.C.

1996-01-01

The mechanisms by which nitrilotriacetic acid (NTA) stimulated Fe(III) reduction in sediments from a petroleum-contaminated aquifer were investigated in order to gain insight into how added Fe(III) chelators stimulate the activity of hydrocarbon-degrading, Fe(III)-reducing microorganisms in these sediments, and how naturally occurring Fe(III) chelators might promote Fe(III) reduction in aquatic sediments. NTA solubilized Fe(III) from the aquifer sediments. NTA stimulation of microbial Fe(III) reduction did not appear to be the result of making calcium, magnesium, potassium, or trace metals more available to the microorganisms. Stimulation of Fe(III) reduction could not be attributed to NTA serving as a source of carbon or fixed nitrogen for Fe(III)-reducing bacteria as NTA was not degraded in the sediments. Studies with the Fe(III)-reducing microorganism, Geobacter metallireducens, and pure Fe(III)-oxide forms, demonstrated that NTA stimulated the reduction of a variety of Fe(III) forms, including highly crystalline Fe(III)-oxides such as goethite and hematite. The results suggest that NTA solubilization of insoluble Fe(III)-oxide is an important mechanism for the stimulation of Fe(III) reduction by NTA in aquifer sediments.
Electrical characterization of reduced graphene oxide (rGO) on organic thin film transistor (OTFT)

NASA Astrophysics Data System (ADS)

Musa, Nurhazwani; Halim, Nurul Farhanah Ab.; Ahmad, Mohd Noor; Zakaria, Zulkhairi; Hashim, Uda

2017-03-01

A green method and eco-friendly solution were used to chemically reduce graphene oxide (GO) to graphene using green reductant. In this study, graphene oxide (GO) were prepared by using Tours method. Then, reduced graphene oxides (rGO) were prepared by using three typical reduction agents: L-ascorbic acid (L-AA), formamidinesulfinic acid (FAS) and sodium sulfite (Na2SO3). The reduced materials were characterized by Fourier transform infrared spectroscopy (FTIR), Thermo gravimetric analysis (TGA) and X-ray diffraction (XRD). Graphene based organic thin film transistor (G-OTFT) was prepared by a spin coating and thermal evaporation technique. The electrical characterization of G-OTFT was analyzed by using semiconductor parameter analyzer (SPA). The G-OTFT devices show p-type semiconducting behaviour. This article focuses on the synthesis and reduction of graphene oxide using three different reductants in order to maximise its electrical conductivity. The rGO product demonstrated a good electrical conductivity performance with highly sensitivity sensor.
Synthesis Gas Conversion over Rh-Based Catalysts Promoted by Fe and Mn

DOE PAGES

Liu, Yifei; Göeltl, Florian; Ro, Insoo; ...

2017-06-13

Rh/SiO2 catalysts promoted with Fe and Mn are selective for synthesis gas conversion to oxygenates and light hydrocarbons at 523 K and 580 psi. Selective anchoring of Fe and Mn species on Rh nanoparticles was achieved by controlled surface reactions and was evidenced by ultraviolet–visible absorption spectroscopy, scanning transmission electron microscopy, and inductively coupled plasma absorption emission spectroscopy. The interaction between Rh and Fe promotes the selective production of ethanol through hydrogenation of acetaldehyde and enhances the selectivity toward C2 oxygenates, which include ethanol and acetaldehyde. The interaction between Rh and Mn increases the overall reaction rate and the selectivitymore » toward C2+ hydrocarbons. The combination of Fe and Mn on Rh/SiO2 results in trimetallic Rh-Fe-Mn catalysts that surpass the performance of their bimetallic counterparts. The highest selectivities toward ethanol (36.9%) and C2 oxygenates (39.6%) were achieved over the Rh-Fe-Mn ternary system with a molar ratio of 1:0.15:0.10, as opposed to the selectivities obtained over Rh/SiO2, which were 3.5% and 20.4%, respectively. The production of value-added oxygenates and C2+ hydrocarbons over this trimetallic catalyst accounted for 55% of the total products. X-ray photoelectron spectroscopy measurements suggest that significant fractions of the Fe and Mn species exist as metallic iron and manganese oxides on the Rh surface upon reduction. These findings are rationalized by density functional theory (DFT) calculations, which reveal that the exact state of metals on the surfaces is condition-dependent, with Mn present as Mn(I) and Mn(II) oxide on the Rh (211) step edges and Fe present as Fe(I) oxide on the step edge and metallic subsurface iron on both Rh steps and terraces. CO Fourier transform infrared spectroscopy and DFT calculations suggest that the binding of CO to Rh (211) step edges modified by Fe and/or manganese oxide is altered in comparison to CO adsorption on a clean Rh (211) surface. These results suggest that Mn2Ox species and Fe and Fe2O modify bonding at Rh step edges and shift reaction selectivity away from CH4.« less
Investigation on the Oxidation and Reduction of Titanium in Molten Salt with the Soluble TiC Anode

NASA Astrophysics Data System (ADS)

Wang, Shulan; Wan, Chaopin; Liu, Xuan; Li, Li

2015-12-01

To reveal the oxidation process of titanium from TiC anode and the reduction mechanism of titanium ions in molten NaCl-KCl, the polarization curve of TiC anode in molten NaCl-KCl and cyclic voltammograms of the molten salt after polarization were studied. Investigation on the polarization curve shows that titanium can be oxidized and dissociated from the TiC anode at very low potential. The cyclic voltammograms demonstrated that the reduction reaction of titanium ions in the molten salt is a one-step process. By potentiostatic electrolysis, dendritic titanium is obtained on the steel plate. The work promotes the understanding on the process of electrochemical oxidization/dissociation of titanium from TiC anode and the reduction mechanism of titanium ions in molten salt.
The Interface Between Chemical and Oxide Materials in the DSPEC

NASA Astrophysics Data System (ADS)

Meyer, Thomas; Alibabaei, Leila; Sherman, Benjamin; Sheridan, Matthew; Ashford, Dennis; Lapides, Alex; Brennaman, Kyle; Nayak, Animesh; Roy, Subhangi

Significant challenges exist for both chemical and oxide materials in the Dye Sensitized Photoelectrosynthesis Cell (DSPEC) for water oxidation or CO2 reduction. They arise from light absorption, the energetics of electron or hole injection, the accumulation of multiple redox equivalents at catalysts for water oxidation or water/CO2 reduction in competition with back electron transfer, and sustained, long term performance. These challenges are being met by the use of a variety of chromophores (metal complexes, organic dyes, porphyrins), broad application of nanoparticle mesoscopic oxide films, atomic layer deposition (ALD) to prepare core/shell and stabilizing overlayer structures, and recent advances in the molecular catalysis of water oxidation and CO2 reduction. UNC EFRC Center for Solar Fuels, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001011.
Reduction of renal mass is lethal in mice lacking vimentin. Role of endothelin-nitric oxide imbalance.

PubMed Central

Terzi, F; Henrion, D; Colucci-Guyon, E; Federici, P; Babinet, C; Levy, B I; Briand, P; Friedlander, G

1997-01-01

Modulation of vascular tone by chemical and mechanical stimuli is a crucial adaptive phenomenon which involves cytoskeleton elements. Disruption, by homologous recombination, of the gene encoding vimentin, a class III intermediate filament protein mainly expressed in vascular cells, was reported to result in apparently normal phenotype under physiological conditions. In this study, we evaluated whether the lack of vimentin affects vascular adaptation to pathological situations, such as reduction of renal mass, a pathological condition which usually results in immediate and sustained vasodilation of the renal vascular bed. Ablation of 3/4 of renal mass was constantly lethal within 72 h in mice lacking vimentin (Vim-/-), whereas no lethality was observed in wild-type littermates. Death in Vim-/- mice resulted from end-stage renal failure. Kidneys from Vim-/- mice synthesized more endothelin, but less nitric oxide (NO), than kidneys from normal animals. In vitro, renal resistance arteries from Vim-/- mice were selectively more sensitive to endothelin, less responsive to NO-dependent vasodilators, and exhibited an impaired flow (shear stress)- induced vasodilation, which is NO dependent, as compared with those from normal littermates. Finally, in vivo administration of bosentan, an endothelin receptor antagonist, totally prevented lethality in Vim-/- mice. These results suggest that vimentin plays a key role in the modulation of vascular tone, possibly via the tuning of endothelin-nitric oxide balance. PMID:9294120
Recent biocatalytic oxidation–reduction cascades

PubMed Central

Schrittwieser, Joerg H; Sattler, Johann; Resch, Verena; Mutti, Francesco G; Kroutil, Wolfgang

2011-01-01

The combination of an oxidation and a reduction in a cascade allows performing transformations in a very economic and efficient fashion. The challenge is how to combine an oxidation with a reduction in one pot, either by running the two reactions simultaneously or in a stepwise fashion without isolation of intermediates. The broader availability of various redox enzymes nowadays has triggered the recent investigation of various oxidation–reduction cascades. PMID:21130024
Iron and manganese in anaerobic respiration: environmental significance, physiology, and regulation

NASA Technical Reports Server (NTRS)

Nealson, K. H.; Saffarini, D.

1994-01-01

Dissimilatory iron and/or manganese reduction is known to occur in several organisms, including anaerobic sulfur-reducing organisms such as Geobacter metallireducens or Desulfuromonas acetoxidans, and facultative aerobes such as Shewanella putrefaciens. These bacteria couple both carbon oxidation and growth to the reduction of these metals, and inhibitor and competition experiments suggest that Mn(IV) and Fe(III) are efficient electron acceptors similar to nitrate in redox abilities and capable of out-competing electron acceptors of lower potential, such as sulfate (sulfate reduction) or CO2 (methanogenesis). Field studies of iron and/or manganese reduction suggest that organisms with such metabolic abilities play important roles in coupling the oxidation of organic carbon to metal reduction under anaerobic conditions. Because both iron and manganese oxides are solids or colloids, they tend to settle downward in aquatic environments, providing a physical mechanism for the movement of oxidizing potential into anoxic zones. The resulting biogeochemical metal cycles have a strong impact on many other elements including carbon, sulfur, phosphorous, and trace metals.

Transition Metal Ions in Zeolites: Coordination and activation of O2

PubMed Central

Smeets, Pieter J.; Woertink, Julia S.; Sels, Bert F.; Solomon, Edward I.; Schoonheydt, Robert A.

2010-01-01

Zeolites containing transition metal ions (TMI) often show promising activity as heterogeneous catalysts in pollution abatement and selective oxidation reactions. In this paper, two aspects of research on the TMI Cu, Co and Fe in zeolites are discussed: (i) coordination to the lattice and (ii) activated oxygen species. At low loading, TMI preferably occupy exchange sites in six-membered oxygen rings (6MR) where the TMI preferentially coordinate with the oxygen atoms of Al tetrahedra. High TMI loadings result in a variety of TMI species formed at the zeolite surface. Removal of the extra-lattice oxygens during high temperature pretreatments can result in auto-reduction. Oxidation of reduced TMI sites often results in the formation of highly reactive oxygen species. In Cu-ZSM-5, calcination with O2 results in the formation of a species, which was found to be a crucial intermediate in both the direct decomposition of NO and N2O and the selective oxidation of methane into methanol. An activated oxygen species, called α-oxygen, is formed in Fe-ZSM5 and reported to be the active site in the partial oxidation of methane and benzene into methanol and phenol, respectively. However, this reactive α-oxygen can only be formed with N2O, not with O2. O2 activated Co intermediates in Faujasite (FAU) zeolites can selectively oxidize α-pinene and epoxidize styrene. In Co-FAU, CoIII superoxo and peroxo complexes are suggested to be the active cores, whereas in Cu and Fe-ZSM-5 various monomeric and dimeric sites have been proposed, but no consensus has been obtained. Very recently, the active site in Cu-ZSM-5 was identified as a bent [Cu-O-Cu]2+ core (Proc. Natl. Acad. Sci. USA 2009, 106, 18908-18913). Overall, O2 activation depends on the interplay of structural factors such as type of zeolite, size of the channels and cages and chemical factors such as Si/Al ratio and the nature, charge and distribution of the charge balancing cations. The presence of several different TMI sites hinders the direct study of the spectroscopic features of the active site. Spectroscopic techniques capable of selectively probing these sites, even if they only constitute a minor fraction of the total amount of TMI sites, are thus required. Fundamental knowledge of the geometric and electronic structure of the reactive active site can help in the design of novel selective oxidation catalysts. PMID:20380459
Selective thermal oxidation of hydrocarbons in zeolites by oxygen

DOEpatents

Frei, Heinz; Blatter, Fritz; Sun, Hai

2000-01-01

A process for selective thermal oxidation of hydrocarbons adsorbed onto zeolite matrices. A highly selective thermal oxidation of unsubstituted or alkyl substituted alkanes, alkenes, aromatics and cycloalkyls is carried out in solvent free zeolites under dark thermal conditions. The process oxidizes hydrocarbons almost completely selectively without substantial production of byproducts.
Catalytic oxidation of Hg(0) by MnOx-CeO2/γ-Al2O3 catalyst at low temperatures.

PubMed

Wang, Pengying; Su, Sheng; Xiang, Jun; You, Huawei; Cao, Fan; Sun, Lushi; Hu, Song; Zhang, Yun

2014-04-01

MnOx-CeO2/γ-Al2O3 (MnCe) selective catalytic reduction (SCR) catalysts prepared by sol-gel method were employed for low-temperature Hg(0) oxidation on a fixed-bed experimental setup. BET, XRD and XPS were used to characterize the catalysts. MnCe catalysts exhibited high Hg(0) oxidation activity at low temperatures (100-250 °C) under the simulated flue gas (O2, CO2, NO, SO2, HCl, H2O and balanced with N2). Only a small decrease in mercury oxidation was observed in the presence of 1200 ppm SO2, which proved that the addition of Ce helped resist SO2 poisoning. An enhancing effect of NO was observed due to the formation of multi-activity NOx species. The presence of HCl alone had excellent Hg(0) oxidation ability, while 10 ppm HCl plus 5% O2 further increased Hg(0) oxidation efficiency to 100%. Hg(0) oxidation on the MnCe catalyst surface followed the Langmiur-Hinshelwood mechanism, where reactions took place between the adsorbed active species and adsorbed Hg(0) to form Hg(2+). NH3 competed with Hg(0) for active sites on the catalyst surface, hence inhibiting Hg(0) oxidation. This study shows the feasibility of a single-step process integrating low-temperature SCR and Hg(0) oxidation from the coal combustion flue gas. Copyright © 2013 Elsevier Ltd. All rights reserved.
L-Selenomethionine Does not Protect Against Testosterone Plus 17β-Estradiol-Induced Oxidative Stress and Pre-Neoplastic Lesions in the Prostate of NBL Rats

PubMed Central

Özten, Nur; Schlicht, Michael; Diamond, Alan M.; Bosland, Maarten C.

2014-01-01

Previous animal studies examining dietary selenium effects on prostatic carcinogenesis did not show preventive benefit, including one study in a rat model involving testosterone (T) and estradiol (E2)-induced prostatic oxidative stress. Here, we examined modulation of T+E2-induced prostatic oxidative stress, dysplasia, and inflammation by L-selenomethionine at 1.5 or 3.0 mg selenium/kg in NIH-07 diet in Nbl/Crl rats treated with T+E2 for 16 weeks. Hormone treatment increased immunohistochemical staining for 8-hydroxydeoxyguanosine (8-OHdG) in the prostatic sites of T+E2-induced preneoplasia (p<0.05), but selenomethionine did not attenuate 8-OHdG staining and dysplasia in the lateral prostate. Glutathione-peroxidase activity and mRNA expression were induced by T+E2 (p<0.05–p<0.0001) but not changed by selenomethionine. Selenomethionine did not cause significant responses in expression and activity of glutathione-peroxidase and MnSOD, except for a reduction of MnSOD protein expression in the lateral prostate (p<0.01). The absence of reduction of oxidative stress and dysplasia and the minimal effects on antioxidant enzymes caused by selenomethionine are consistent with the null effects observed in selenium supplementation animal studies and clinical trials. Significant (p<0.01) opposite apoptosis/cell proliferation balance responses to selenomethionine and to T+E2 occurred in the lateral and dorsal prostate, explaining why T+E2 induces lesions selectively in the lateral lobe of NBL rats. PMID:24773027
L-selenomethionine does not protect against testosterone plus 17β-estradiol-induced oxidative stress and preneoplastic lesions in the prostate of NBL rats.

PubMed

Özten, Nur; Schlicht, Michael; Diamond, Alan M; Bosland, Maarten C

2014-01-01

Previous animal studies examining dietary selenium effects on prostatic carcinogenesis did not show preventive benefit, including 1 study in a rat model involving testosterone (T) and estradiol (E2)-induced prostatic oxidative stress. Here, we examined modulation of T + E2-induced prostatic oxidative stress, dysplasia, and inflammation by L-selenomethionine at 1.5 or 3.0 mg selenium/kg in NIH-07 diet in Noble (Nbl)/Crl rats treated with T + E2 for 16 wk. Hormone treatment increased immunohistochemical staining for 8-hydroxydeoxyguanosine (8-OHdG) in the prostatic sites of T + E2-induced preneoplasia (P < 0.05), but selenomethionine did not attenuate 8-OHdG staining and dysplasia in the lateral prostate. Glutathione-peroxidase activity (P < 0.05) and mRNA expression were induced by T + E2 (P < 0.0001) but not changed by selenomethionine. Selenomethionine did not cause significant responses in expression and activity of glutathione-peroxidase and MnSOD, except for a reduction of MnSOD protein expression in the lateral prostate (P < 0.01). The absence of reduction of oxidative stress and dysplasia and the minimal effects on antioxidant enzymes caused by selenomethionine are consistent with the null effects observed in selenium supplementation animal studies and clinical trials. Significant (P < 0.01) opposite apoptosis/cell proliferation balance responses to selenomethionine and to T + E2 occurred in the lateral and dorsal prostate, explaining why T + E2 induces lesions selectively in the lateral lobe of NBL rats.
Assessing the effectiveness of chemical treatment with nanomaterials in improving the quality of different industrial effluents =

NASA Astrophysics Data System (ADS)

Nogueira, Veronica Ines Jesus Oliveira

Industrial activities are the major sources of pollution in all environments. Depending on the type of industry, various levels of organic and inorganic pollutants are being continuously discharged into the environment. Although, several kinds of physical, chemical, biological or the combination of methods have been proposed and applied to minimize the impact of industrial effluents, few have proved to be totally effective in terms of removal rates of several contaminants, toxicity reduction or amelioration of physical and chemical properties. Hence, it is imperative to develop new and innovative methodologies for industrial wastewater treatment. In this context nanotechnology arises announcing the offer of new possibilities for the treatment of wastewaters mainly based on the enhanced physical and chemical proprieties of nanomaterials (NMs), which can remarkably increase their adsorption and oxidation potential. Although applications of NMs may bring benefits, their widespread use will also contribute for their introduction into the environment and concerns have been raised about the intentional use of these materials. Further, the same properties that make NMs so appealing can also be responsible for producing ecotoxicological effects. In a first stage, with the objective of selecting NMs for the treatment of organic and inorganic effluents we first assessed the potential toxicity of nanoparticles of nickel oxide (NiO) with two different sizes (100 and 10-20 nm), titanium dioxide (TiO2, < 25 nm) and iron oxide (Fe2O3, ≈ 85x425 nm). The ecotoxicological assessment was performed with a battery of assays using aquatic organisms from different trophic levels. Since TiO2 and Fe2O3 were the NMs that presented lower risks to the aquatic systems, they were selected for the second stage of this work. Thus, the two NMs pre-selected were tested for the treatment of olive mill wastewater (OMW). They were used as catalyst in photodegradation systems (TiO2/UV, Fe2O3/UV, TiO2/H2O2/UV and Fe2O3/H2O2/UV). The treatments with TiO2 or Fe2O3 combined with H2O2 were the most efficient in ameliorating some chemical properties of the effluent. Regarding the toxicity to V. fischeri the highest reduction was recorded for the H2O2/UV system, without NMs. Afterwards a sequential treatment using photocatalytic oxidation with NMs and degradation with white-rot fungi was applied to OMW. This new approach increased the reduction of chemical oxygen demand, phenolic content and ecotoxicity to V. fischeri. However, no reduction in color and aromatic compounds was achieved after 21 days of biological treatment. The photodegradation systems were also applied to treat the kraft pulp mill and mining effluents. For the organic effluent the combination NMs and H2O2 had the best performances in reduction the chemical parameters as well in terms of toxicity reduction. However, for the mine effluent the best (TiO2/UV and Fe2O3/UV) were only able to significantly remove three metals (Zn, Al and Cd). Nonetheless the treatments were able of reducing the toxicity of the effluent. As a final stage, the toxicity of solid wastes formed during wastewater treatment with NMs was assessed with Chironomus riparius larvae, a representative species of the sediment compartment. Certain solid wastes showed the potential to negatively affect C. riparius survival and growth, depending on the type of effluent treated. This work also brings new insights to the use of NMs for the treatment of industrial wastewaters. Although some potential applications have been announced, many evaluations have to be performed before the upscaling of the chemical treatments with NMs.
In vitro metabolism of a novel JNK inhibitor tanzisertib: interspecies differences in oxido-reduction and characterization of enzymes involved in metabolism.

PubMed

Atsriku, Christian; Hoffmann, Matthew; Moghaddam, Mehran; Kumar, Gondi; Surapaneni, Sekhar

2015-01-01

1. In vitro metabolism of Tanzisertib [(1S,4R)-4-(9-((S)tetrahydrofuran-3-yl)-8-(2,4,6-trifluorophenylamino)-9H-purin-2-ylamino) cyclohexanol], a potent, selective c-Jun amino-terminal kinase (JNK) inhibitor, was investigated in mouse, rat, rabbit, dog, monkey and human hepatocytes over 4 h. The extent of metabolism of [(14)C]tanzisertib was variable, with <10% metabolized in dog and human, <20% metabolized in rabbit and monkey and >75% metabolized in rat and mouse. Primary metabolic pathways in human and dog hepatocytes, were direct glucuronidation and oxidation of cyclohexanol to a keto metabolite, which was subsequently reduced to parent or cis-isomer, followed by glucuronidation. Rat and mouse produced oxidative metabolites and cis-isomer, including direct glucuronides and sulfates of tanzisertib and cis-isomer. 2. Enzymology of oxido-reductive pathways revealed that human aldo-keto reductases AKR1C1, 1C2, 1C3 and 1C4 were responsible for oxido-reduction of tanzisertib, CC-418424 and keto tanzisertib. Characterizations of enzyme kinetics revealed that AKR1C4 had a high affinity for reduction of keto tanzisertib to tanzisertib compared to other isoforms. These results demonstrate unique stereoselectivity of the reductive properties documented by human AKR1C enzymes for the same substrate. 3. Characterization of UGT isoenzymes in glucuronidation of tanzisertib and CC-418424 revealed that, tanzisertib glucuronide was catalyzed by: UGT1A1, 1A4, 1A10 and 2B4, while CC-418424 glucuronidation was catalyzed by UGT2B4 and 2B7.
Plasma in-liquid method for reduction of zinc oxide in zinc nanoparticle synthesis

NASA Astrophysics Data System (ADS)

Amaliyah, Novriany; Mukasa, Shinobu; Nomura, Shinfuku; Toyota, Hiromichi; Kitamae, Tomohide

2015-02-01

Metal air-batteries with high-energy density are expected to be increasingly applied in electric vehicles. This will require a method of recycling air batteries, and reduction of metal oxide by generating plasma in liquid has been proposed as a possible method. Microwave-induced plasma is generated in ethanol as a reducing agent in which zinc oxide is dispersed. Analysis by energy-dispersive x-ray spectrometry (EDS) and x-ray diffraction (XRD) reveals the reduction of zinc oxide. According to images by transmission electron microscopy (TEM), cubic and hexagonal metallic zinc particles are formed in sizes of 30 to 200 nm. Additionally, spherical fiber flocculates approximately 180 nm in diameter are present.
Adsorbate-mediated strong metal–support interactions in oxide-supported Rh catalysts

DOE PAGES

Matsubu, John C.; Zhang, Shuyi; DeRita, Leo; ...

2016-09-19

The optimization of supported metal catalysts predominantly focuses on engineering the metal site, for which physical insights based on extensive theoretical and experimental contributions have enabled the rational design of active sites. Although it is well known that supports can influence the catalytic properties of metals, insights into how metal–support interactions can be exploited to optimize metal active-site properties are lacking. Here in this paper, we utilize in situ spectroscopy and microscopy to identify and characterize a support effect in oxide-supported heterogeneous Rh catalysts. This effect is characterized by strongly bound adsorbates (HCO x) on reducible oxide supports (TiO 2more » and Nb 2O 5) that induce oxygen-vacancy formation in the support and cause HCO x-functionalized encapsulation of Rh nanoparticles by the support. The encapsulation layer is permeable to reactants, stable under the reaction conditions and strongly influences the catalytic properties of Rh, which enables rational and dynamic tuning of CO 2-reduction selectivity.« less
The effect of heat treatment on the performance of the Ni/(Zr-Sm oxide) catalysts for carbon dioxide methanation

NASA Astrophysics Data System (ADS)

Takano, Hiroyuki; Izumiya, Koichi; Kumagai, Naokazu; Hashimoto, Koji

2011-07-01

The active catalysts for methane formation from the gas mixture of CO 2 + 4H 2 with almost 100% methane selectivity were prepared by reduction of the oxide mixture of NiO and ZrO 2 prepared by calcination of aqueous ZrO 2 sol with Sm(NO 3) 3 and Ni(NO 3) 2. The 50 at%Ni-50 at%(Zr-Sm oxide) catalyst consisting of 50 at%Ni-50 at%(Zr + Sm) with Zr/Sm = 5 calcined at 650 or 800 °C showed the highest activity for methanation. The active catalysts were Ni supported on tetragonal ZrO 2, and the activity for methanation increased by an increase in inclusion of Sm 3+ ions substituting Zr 4+ ions in the tetragonal ZrO 2 lattice as a result of an increase in calcination temperature. However, the increase in calcination temperature decreased BET surface area, metal dispersion and hydrogen uptake due to grain growth. Thus, the optimum calcination temperature existed.
Decoration of reduced graphene oxide with rhodium nanoparticles for the design of a sensitive electrochemical enzyme biosensor for 17β-estradiol.

PubMed

Povedano, Eloy; Cincotto, Fernando H; Parrado, Concepción; Díez, Paula; Sánchez, Alfredo; Canevari, Thiago C; Machado, Sergio A S; Pingarrón, José M; Villalonga, Reynaldo

2017-03-15

A novel nanocomposite material consisting of reduced graphene oxide/Rh nanoparticles was prepared by a one-pot reaction process. The strategy involved the simultaneous reduction of RhCl 3 and graphene oxide with NaBH 4 and the in situ deposition of the metal nanoparticles on the 2D carbon nanomaterial planar sheets. Glassy carbon electrode coated with this nanocomposite was employed as nanostructured support for the cross-linking of the enzyme laccase with glutaraldehyde to construct a voltammperometric biosensor for 17β-estradiol in the 0.9-11 pM range. The biosensor showed excellent analytical performance with high sensitivity of 25.7AµM -1 cm -1 , a very low detection limit of 0.54pM and high selectivity. The biosensor was applied to the rapid and successful determination of the hormone in spiked synthetic and real human urine samples. Copyright © 2016 Elsevier B.V. All rights reserved.
Modularity of nitrogen-oxide reducing soil bacteria: linking phenotype to genotype.

PubMed

Roco, Constance A; Bergaust, Linda L; Bakken, Lars R; Yavitt, Joseph B; Shapleigh, James P

2017-06-01

Model denitrifiers convert NO3- to N 2 , but it appears that a significant fraction of natural populations are truncated, conducting only one or two steps of the pathway. To better understand the diversity of partial denitrifiers in soil and whether discrepancies arise between the presence of known N-oxide reductase genes and phenotypic features, bacteria able to reduce NO3- to NO2- were isolated from soil, N-oxide gas products were measured for eight isolates, and six were genome sequenced. Gas phase analyses revealed that two were complete denitrifiers, which genome sequencing corroborated. The remaining six accumulated NO and N 2 O to varying degrees and genome sequencing of four indicated that two isolates held genes encoding nitrate reductase as the only dissimilatory N-oxide reductase, one contained genes for both nitrate and nitric oxide reductase, and one had nitrate and nitrite reductase. The results demonstrated that N-oxide production was not always predicted by the genetic potential and suggested that partial denitrifiers could be readily isolated among soil bacteria. This supported the hypothesis that each N-oxide reductase could provide a selectable benefit on its own, and therefore, reduction of nitrate to dinitrogen may not be obligatorily linked to complete denitrifiers but instead a consequence of a functionally diverse community. © 2016 Society for Applied Microbiology and John Wiley & Sons Ltd.
Oxidative damage of mitochondrial proteins contributes to fruit senescence: a redox proteomics analysis.

PubMed

Qin, Guozheng; Meng, Xianghong; Wang, Qing; Tian, Shiping

2009-05-01

Oxidative damage to mitochondria caused by reactive oxygen species (ROS) has been implicated in the process of senescence as well as a number of senescence-related disorders in a variety of organisms. Whereas mitochondrial DNA was shown to be oxidatively modified during cellular senescence, mitochondrial protein oxidation is not well-understood. With the use of high-resolution, two-dimensional gel electrophoresis coupled with immunoblotting, we show here that protein carbonylation, a widely used marker of protein oxidation, increased in mitochondria during the senescence of peach fruit. Specific mitochondrial proteins including outer membrane transporter (voltage-dependent anion-selective channel, VDAC), tricarboxylic acid cycle enzymes (malate dehydrogenase and aconitase), and antioxidant proteins (manganese superoxide dismutase, MnSOD) were found as the targets. The oxidative modification was concomitant with a change of VDAC function and loss of catalytic activity of malate dehydrogenase and MnSOD, which in turn facilitated the release of superoxide radicals in mitochondria. Reduction of ROS content by lowering the environmental temperature prevented the accumulation of protein carbonylation in mitochondria and retarded fruit senescence, whereas treatment of fruit with H2O2 had the opposite effect. Our data suggest that oxidative damage of specific mitochondrial proteins may be responsible for impairment of mitochondrial function, thus, leading to fruit senescence. Proteomics analysis of mitochondrial redox proteins provides considerable information on the molecular mechanisms involved in the progression of fruit senescence.
Reduction of Vanadium Oxide (VOx) under High Vacuum Conditions as Investigated by X-Ray Photoelectron Spectroscopy

NASA Astrophysics Data System (ADS)

Chourasia, A.

2015-03-01

Vanadium oxide thin films were formed by depositing thin films of vanadium on quartz substrates and oxidizing them in an atmosphere of oxygen. The deposition was done by the e-beam technique. The oxide films were annealed at different temperatures for different times under high vacuum conditions. The technique of x-ray photoelectron spectroscopy has been employed to study the changes in the oxidation states of vanadium and oxygen in such films. The spectral features in the vanadium 2p, oxygen 1s, and the x-ray excited Auger regions were investigated. The Auger parameter has been utilized to study the changes. The complete oxidation of elemental vanadium to V2O5 was observed to occur at 700°C. At any other temperature, a mixture of oxides consisting of V2O5 and VO2 was observed in the films. Annealing of the films resulted in the gradual loss of oxygen followed by reduction in the oxidation state from +5 to 0. The reduction was observed to depend upon the annealing temperature and the annealing time. Organized Research, TAMU-Commerce.
Difference of nitrogen-cycling microbes between shallow bay and deep-sea sediments in the South China Sea.

PubMed

Yu, Tiantian; Li, Meng; Niu, Mingyang; Fan, Xibei; Liang, Wenyue; Wang, Fengping

2018-01-01

In marine sediments, microorganisms are known to play important roles in nitrogen cycling; however, the composition and quantity of microbes taking part in each process of nitrogen cycling are currently unclear. In this study, two different types of marine sediment samples (shallow bay and deep-sea sediments) in the South China Sea (SCS) were selected to investigate the microbial community involved in nitrogen cycling. The abundance and composition of prokaryotes and seven key functional genes involved in five processes of the nitrogen cycle [nitrogen fixation, nitrification, denitrification, dissimilatory nitrate reduction to ammonium (DNRA), and anaerobic ammonia oxidation (anammox)] were presented. The results showed that a higher abundance of denitrifiers was detected in shallow bay sediments, while a higher abundance of microbes involved in ammonia oxidation, anammox, and DNRA was found in the deep-sea sediments. Moreover, phylogenetic differentiation of bacterial amoA, nirS, nosZ, and nrfA sequences between the two types of sediments was also presented, suggesting environmental selection of microbes with the same geochemical functions but varying physiological properties.
Antioxidants and Coronary Artery Disease: From Pathophysiology to Preventive Therapy

PubMed Central

Leopold, Jane A.

2014-01-01

Oxidant stress in the cardiovascular system may occur when antioxidant capacity is insufficient to reduce reactive oxygen species and other free radicals. Oxidant stress has been linked to the pathogenesis of atherosclerosis and incident coronary artery disease. As a result of this connection, early observational studies focused on dietary antioxidants, such as β-carotene, α-tocopherol, and ascorbic acid, and demonstrated an inverse relationship between intake of these antioxidants and major adverse cardiovascular events. These findings supported a number of randomized trials of selected antioxidants as primary and secondary prevention to decrease cardiac risk; however, many of these studies reported disappointing results with little or no observed risk reduction in antioxidant treated patients. Several plausible explanations for these findings have been suggested, including incorrect antioxidant choice or dose, synthetic versus dietary antioxidant as the intervention, and patient selection, all of which will be important to consider when designing future clinical trials. This review will focus on the contemporary evidence that is the basis for our current understanding of the role of antioxidants in cardiovascular disease prevention. PMID:25369999
In situ X-ray powder diffraction studies of the synthesis of graphene oxide and formation of reduced graphene oxide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Storm, Mie Møller, E-mail: mmst@dtu.dk; Johnsen, Rune E.; Norby, Poul

2016-08-15

Graphene oxide (GO) and reduced graphene oxide (rGO) are important materials in a wide range of fields. The modified Hummers methods, for synthesizing GO, and subsequent thermal reduction to rGO, are often employed for production of rGO. However, the mechanism behinds these syntheses methods are still unclear. We present an in situ X-ray diffraction study of the synthesis of GO and thermal reduction of GO. The X-ray diffraction revealed that the Hummers method includes an intercalation state and finally formation of additional crystalline material. The formation of GO is observed during both the intercalation and the crystallization stage. During thermalmore » reduction of GO three stages were observed: GO, a disordered stage, and the rGO stage. The appearance of these stages depends on the heating ramp. The aim of this study is to provide deeper insight into the chemical and physical processes during the syntheses. - Graphical abstract: In situ X-ray diffraction results for of the modified Hummers synthesis and the thermal reduction of graphene oxide, revealing three stages for both syntheses as well as new GO diffraction peaks and unidentified crystalline material for the Hummers synthesis and a disordered stage for the thermal reduction of graphene oxide. Display Omitted - Highlights: • Hummers synthesis consists of three stages: dissolution, intercalation and crystal. • GO is produced early on during the synthesis and display new diffraction peaks. • An unidentified triclinic phase is observed for the Hummers synthesis. • Thermal reduction of GO display three stages: GO, a disordered stage and rGO. • In situ XRD indicate reformation of rGO even for fast heated thermal reduction.« less
Comparative studies on single-layer reduced graphene oxide films obtained by electrochemical reduction and hydrazine vapor reduction

NASA Astrophysics Data System (ADS)

Wang, Zhijuan; Wu, Shixin; Zhang, Juan; Chen, Peng; Yang, Guocheng; Zhou, Xiaozhu; Zhang, Qichun; Yan, Qingyu; Zhang, Hua

2012-02-01

The comparison between two kinds of single-layer reduced graphene oxide (rGO) sheets, obtained by reduction of graphene oxide (GO) with the electrochemical method and hydrazine vapor reduction, referred to as E-rGO and C-rGO, respectively, is systematically studied. Although there is no morphology difference between the E-rGO and C-rGO films adsorbed on solid substrates observed by AFM, the reduction process to obtain the E-rGO and C-rGO films is quite different. In the hydrazine vapor reduction, the nitrogen element is incorporated into the obtained C-rGO film, while no additional element is introduced to the E-rGO film during the electrochemical reduction. Moreover, Raman spectra show that the electrochemical method is more effective than the hydrazine vapor reduction method to reduce the GO films. In addition, E-rGO shows better electrocatalysis towards dopamine than does C-rGO. This study is helpful for researchers to understand these two different reduction methods and choose a suitable one to reduce GO based on their experimental requirements.
The vertical distribution of prokaryotes in the surface sediment of Jiaolong cold seep at the northern South China Sea.

PubMed

Wu, Yuzhi; Qiu, Jian-Wen; Qian, Pei-Yuan; Wang, Yong

2018-05-01

In deep-sea cold seeps, microbial communities are shaped by geochemical components in seepage solutions. In the present study, we report the composition of microbial communities and potential metabolic activities in the surface sediment of Jiaolong cold seep at the northern South China Sea. Pyrosequencing of 16S rRNA gene amplicons revealed that a majority of the microbial inhabitants of the surface layers (0-6 cm) were sulfur oxidizer bacteria Sulfurimonas and archaeal methane consumer ANME-1, while sulfate reducer bacteria SEEP-SRB1, ANME-1 and ANME-2 dominated the bottom layers (8-14 cm). The potential ecological roles of the microorganisms were further supported by the presence of functional genes for methane oxidation, sulfur oxidation, sulfur reduction and nitrate reduction in the metagenomes. Metagenomic analysis revealed a significant correlation between coverage of 16S rRNA gene of sulfur oxidizer bacteria, functional genes involved in sulfur oxidation and nitrate reduction in different layers, indicating that sulfur oxidizing may be coupled to nitrate reducing at the surface layers of Jiaolong seeping site. This is probably related to the sulfur oxidizers of Sulfurimonas and Sulfurovum, which may be the capacity of nitrate reduction or associated with unidentified syntrophic nitrate-reducing microbes in the surface of the cold seep.
Synthesis of graphene oxide and reduced graphene oxide by needle platy natural vein graphite

NASA Astrophysics Data System (ADS)

Rathnayake, R. M. N. M.; Wijayasinghe, H. W. M. A. C.; Pitawala, H. M. T. G. A.; Yoshimura, Masamichi; Huang, Hsin-Hui

2017-01-01

Among natural graphite varieties, needle platy vein graphite (NPG) has very high purity. Therefore, it is readily used to prepare graphene oxide (GO) and reduced graphene oxide (rGO). In this study, GO and rGO were prepared using chemical oxidation and reduction process, respectively. The synthesized materials were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared (FTIR) spectroscopy. XRD studies confirmed the increase of the interlayer spacing of GO and rGO in between 3.35 to 8.66 A°. AFM studies showed the layer height of rGO to be 1.05 nm after the reduction process. TEM micrographs clearly illustrated that the prepared GO has more than 25 layers, while the rGO has only less than 15 layers. Furthermore, the effect of chemical oxidation and reduction processes on surface morphology of graphite were clearly observed in FESEM micrographs. The calculated RO/C of GO and rGO using XPS analysis are 5.37% and 1.77%, respectively. The present study revealed the successful and cost effective nature of the chemical oxidation, and the reduction processes for the production of GO and rGO out of natural vein graphite.

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