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Sample records for 2 wet catalytic

  1. Catalytic wet peroxide oxidation of phenol solutions over CuO/CeO2 systems.

    PubMed

    Massa, Paola; Ivorra, Fernando; Haure, Patricia; Fenoglio, Rosa

    2011-06-15

    Three 5% CuO/CeO(2) catalysts were synthesized by sol-gel, precipitation and combustion methods, followed by incipient wetness impregnation with copper nitrate. The samples were characterized by XRD, TPR, BET and tested for the catalytic wet peroxide oxidation of a phenol solution (5 g/L). The reaction took place in a batch reactor at atmospheric pressure, in a temperature range of 60-80°C, during 4h. Phenol conversion, H(2)O(2) consumption, pH and chemical oxygen demand were determined. The reaction temperature and the catalyst loading did improve the phenol and the H(2)O(2) conversions. The effect on the selectivity towards complete mineralization was less marked, with levels among 60-70%. Stepwise addition of H(2)O(2) was also tested.

  2. Catalytic wet peroxide oxidation of phenol solutions over CuO/CeO2 systems.

    PubMed

    Massa, Paola; Ivorra, Fernando; Haure, Patricia; Fenoglio, Rosa

    2011-06-15

    Three 5% CuO/CeO(2) catalysts were synthesized by sol-gel, precipitation and combustion methods, followed by incipient wetness impregnation with copper nitrate. The samples were characterized by XRD, TPR, BET and tested for the catalytic wet peroxide oxidation of a phenol solution (5 g/L). The reaction took place in a batch reactor at atmospheric pressure, in a temperature range of 60-80°C, during 4h. Phenol conversion, H(2)O(2) consumption, pH and chemical oxygen demand were determined. The reaction temperature and the catalyst loading did improve the phenol and the H(2)O(2) conversions. The effect on the selectivity towards complete mineralization was less marked, with levels among 60-70%. Stepwise addition of H(2)O(2) was also tested. PMID:21489687

  3. Catalytic wet air oxidation of carboxylic acids on TiO{sub 2}-supported ruthenium catalysts

    SciTech Connect

    Beziat, J.C.; Besson, M.; Gallezot, P.; Durecu, S.

    1999-02-15

    The total oxidation of aqueous solutions of carboxylic acids by air was studied in a slurry reactor over the temperature range 180--100 C and oxygen partial pressure of 0.3--1.8 MPa in the presence of a 2.8%Ru/TiO{sub 2} catalyst. The influence of various parameters is presented: the catalytic wet air oxidation of succinic acid is 0 order with respect to succinic acid; the order with respect to oxygen pressure is 0.4, and the activation energy is ca. 125 kJ/mol. It was found that acetic acid, which is one of the intermediates, and CO{sub 2} have no retarding effect on the total organic carbon abatement rate of succinic acid. Substitution of one hydrogen atom of the methyl group in acetic acid by Cl, OH, or NH{sub 2} gives an increase of the oxidation rate. However, it was proposed that the low activity of acetic acid oxidation is due not only to the difficulty to oxidize the methyl group, but also to the low adsorption coefficient of acetic acid on ruthenium surface. Inorganic salts, such as sodium chloride, only slightly decrease the oxidation rate of acetic acid. The absence of metal ions (Ru, Ti) in the effluents after reaction and the absence of particle sintering indicate also a high stability of the catalyst under the conditions employed. The catalyst can be recycled without loss of activity after the second run. The activity becomes stable after the attainment of a steady-state coverage of the Ru particles by oxygen. The study of the effect of reduction-oxidation treatments of the catalyst showed that the activity depends on the oxidation state of the surface.

  4. Catalytic wet air oxidation of phenol using CeO2 as the catalyst. Kinetic study and mechanism development.

    PubMed

    Chang, Dong-Jang; Lin, Shiow-Shyung; Chen, Chun-Liang; Wang, Shu-Pin; Ho, Wei-Lun

    2002-08-01

    Using a CeO2 catalyst prepared from CeCl3.7H2O under high thermal impact, the catalytic wet air oxidation (CWAO) of phenol was effectively implemented. With initial phenol concentrations of between (400 and 2500) mg/L, and at a temperature of 160 degrees C, the rate of phenol conversion increased with increased catalyst loading (0.2g/L-1.0g/L) and oxygen pressure (0.5 MPa-1.5 MPa). Even at an initial concentration of 2500 mg/L, conversion of phenol was as high as 95% after 3 h reaction. The effect of phenol concentration, catalyst loading, and oxygen pressure on the initial rate of phenol conversion was evaluated in a kinetic study. The initial rate equation derived from kinetic study is: Ro=k1 x [Ph]1.3-1.4 x W0.5-0.6 x PO2(0.9-1.1), where k1 is a rate constant, and [Ph], W and PO2 refer to phenol concentration, catalyst loading and oxygen pressure, respectively. A free-radical involved reaction mechanism was proposed and an initial rate expression based on this mechanism was derived: Ro = k2 x [Ph]1.5 x W0.5, where k2 is also a rate constant. Fitting of experimental data with the theoretically derived initial rate equation resulted in good correlation: the coefficient is greater than 0.99.

  5. Treatment of aniline by catalytic wet air oxidation: comparative study over CuO/CeO2 and NiO/Al2O3.

    PubMed

    Ersöz, Gülin; Atalay, Süheyda

    2012-12-30

    The treatment of aniline by catalytic wet air oxidation (CWAO) was studied in a bubble reactor. The experiments were performed to investigate the effects of catalyst loading, temperature, reaction time, air flow rate, and pressure on aniline removal. The catalytic effects of the prepared nanostructured catalysts, CuO/CeO(2) (10% wt) and NiO/Al(2)O(3) (10% wt), on the CWAO treatment efficiency were also examined and compared. The prepared catalysts seem to be active having an aniline removal of 45.7% with CuO/CeO(2) and 41.9% with NiO/Al(2)O(3). The amount of N(2) formed was approximately the same for both of the catalysts.

  6. Treatment of aniline by catalytic wet air oxidation: comparative study over CuO/CeO2 and NiO/Al2O3.

    PubMed

    Ersöz, Gülin; Atalay, Süheyda

    2012-12-30

    The treatment of aniline by catalytic wet air oxidation (CWAO) was studied in a bubble reactor. The experiments were performed to investigate the effects of catalyst loading, temperature, reaction time, air flow rate, and pressure on aniline removal. The catalytic effects of the prepared nanostructured catalysts, CuO/CeO(2) (10% wt) and NiO/Al(2)O(3) (10% wt), on the CWAO treatment efficiency were also examined and compared. The prepared catalysts seem to be active having an aniline removal of 45.7% with CuO/CeO(2) and 41.9% with NiO/Al(2)O(3). The amount of N(2) formed was approximately the same for both of the catalysts. PMID:23041516

  7. Catalytic wet air oxidation on a Ru/TiO{sub 2} catalyst in a trickle-bed reactor

    SciTech Connect

    Beziat, J.C.; Besson, M.; Gallezot, P.; Durecu, S.

    1999-04-01

    The catalytic wet air oxidation of oxygenated pollutants has been investigated in a co-current downflow trickle-bed reactor, over a temperature range 423--473 K at a total pressure of 5 MPa, using a 2.8% Ru/TiO{sub 2} catalyst. When the catalyst was employed under integral conditions (high catalyst mass/liquid flow ratio, approximate residence time of 5.1 h g{sub Ru}/L ) it was possible to convert 5 g/L aqueous solutions of cyclohexanol, succinic acid, and acetic acid into CO{sub 2} and H{sub 2}O. Experimental kinetic data were measured, in the reactor operating differentially at 463 K, at different conversions of succinic acid obtained at each step of the successive recycling of the reaction medium. The intermediate compounds detected were identified as acrylic and acetic acid. For the six main reactions identified, the reaction rates were described by Langmuir-Hinshelwood type rate equations, assuming competitive adsorption of liquid-phase components. The comparison of the experimental data with kinetic modeling showed an excellent agreement. The model indicates a very low adsorption of acetic acid (K{sub ACE} {le} 0.005 L/mmol) compared to succinic and acrylic acid (K{sub SUC} = 0.13 and K{sub ACR} = 0.16 L/mmol), even though the kinetic constants were of the same order of magnitude. Long-term experiments with this catalyst demonstrate its stability under the reaction conditions used.

  8. Post-treatment of biologically treated wastewater containing organic contaminants using a sequence of H2O2 based advanced oxidation processes: photolysis and catalytic wet oxidation.

    PubMed

    Rueda-Márquez, J J; Sillanpää, M; Pocostales, P; Acevedo, A; Manzano, M A

    2015-03-15

    In this paper the feasibility of a multi-barrier treatment (MBT) for the regeneration of synthetic industrial wastewater (SIWW) was evaluated. Industrial pollutants (orange II, phenol, 4-chlorophenol and phenanthrene) were added to the effluent of municipal wastewater treatment plant. The proposed MBT begins with a microfiltration membrane pretreatment (MF), followed by hydrogen peroxide photolysis (H2O2/UVC) and finishing, as a polishing step, with catalytic wet peroxide oxidation (CWPO) using granular activated carbon (GAC) at ambient conditions. During the microfiltration step (0.7 μm) the decrease of suspended solids concentration, turbidity and Escherichia coli in treated water were 88, 94 and 99%, respectively. Also, the effluent's transmittance (254 nm) was increased by 14.7%. Removal of more than 99.9% of all added pollutants, mineralization of 63% of organic compounds and complete disinfection of total coliforms were reached during the H2O2/UVC treatment step (H2O2:TOC w/w ratio = 5 and an UVC average dose accumulated by wastewater 8.80 WUVC s cm(-2)). The power and efficiency of the lamp, the water transmittance and photoreactor geometry are taken into account and a new equation to estimate the accumulated dose in water is suggested. Remaining organic pollutants with a higher oxidation state of carbon atoms (+0.47) and toxic concentration of residual H2O2 were present in the effluent of the H2O2/UVC process. After 2.3 min of contact time with GAC at CWPO step, 90 and 100% of total organic carbon and residual H2O2 were removed, respectively. Also, the wastewater toxicity was studied using Vibrio fischeri and Sparus aurata larvae. The MBT operational and maintenance costs (O&M) was estimated to be 0.59 € m(-3). PMID:25600300

  9. Post-treatment of biologically treated wastewater containing organic contaminants using a sequence of H2O2 based advanced oxidation processes: photolysis and catalytic wet oxidation.

    PubMed

    Rueda-Márquez, J J; Sillanpää, M; Pocostales, P; Acevedo, A; Manzano, M A

    2015-03-15

    In this paper the feasibility of a multi-barrier treatment (MBT) for the regeneration of synthetic industrial wastewater (SIWW) was evaluated. Industrial pollutants (orange II, phenol, 4-chlorophenol and phenanthrene) were added to the effluent of municipal wastewater treatment plant. The proposed MBT begins with a microfiltration membrane pretreatment (MF), followed by hydrogen peroxide photolysis (H2O2/UVC) and finishing, as a polishing step, with catalytic wet peroxide oxidation (CWPO) using granular activated carbon (GAC) at ambient conditions. During the microfiltration step (0.7 μm) the decrease of suspended solids concentration, turbidity and Escherichia coli in treated water were 88, 94 and 99%, respectively. Also, the effluent's transmittance (254 nm) was increased by 14.7%. Removal of more than 99.9% of all added pollutants, mineralization of 63% of organic compounds and complete disinfection of total coliforms were reached during the H2O2/UVC treatment step (H2O2:TOC w/w ratio = 5 and an UVC average dose accumulated by wastewater 8.80 WUVC s cm(-2)). The power and efficiency of the lamp, the water transmittance and photoreactor geometry are taken into account and a new equation to estimate the accumulated dose in water is suggested. Remaining organic pollutants with a higher oxidation state of carbon atoms (+0.47) and toxic concentration of residual H2O2 were present in the effluent of the H2O2/UVC process. After 2.3 min of contact time with GAC at CWPO step, 90 and 100% of total organic carbon and residual H2O2 were removed, respectively. Also, the wastewater toxicity was studied using Vibrio fischeri and Sparus aurata larvae. The MBT operational and maintenance costs (O&M) was estimated to be 0.59 € m(-3).

  10. Degradation process analysis of the azo dyes by catalytic wet air oxidation with catalyst CuO/γ-Al2O3.

    PubMed

    Hua, Li; Ma, Hongrui; Zhang, Lei

    2013-01-01

    Three azo dyes (Methyl Orange, Direct Brown and Direct Green) were treated by catalytic wet air oxidation (CWAO) with the catalysts CuO/γ-Al(2)O(3) prepared by consecutive impregnation. The relationship of decolorization extent, chemical oxygen demand (COD) removal extent and total organic carbon (TOC) in dye solution were investigated. The results indicated that the CuO/γ-Al(2)O(3) catalyst had excellent catalytic activity in treating azo dyes. Almost 99% of color and 70% of TOC were removed in 2h. The high removal extent of color and TOC indicated that the CWAO obtained perfect decomposition for pollutants. The degradation pathway of azo dyes was analyzed by UV-Vis, FTIR and MS. According to the examined results, the hydroxyl ((·)OH) radicals induced strong oxidizing effects in the target solution and destroyed the chromophoric groups of azo-benzene conjugated of the molecular structure. Considering characteristics of the dye structure, the azo bond (-N=N-) would first be attacked by the hydroxyl radical and other free radicals. With the continuous oxidization and the long reaction time at high temperature, these intermediates could be oxidized to the final oxidation products, such as water and carbon dioxide. PMID:22795071

  11. Catalytic wet air oxidation of chlorophenols over supported ruthenium catalysts.

    PubMed

    Li, Ning; Descorme, Claude; Besson, Michèle

    2007-07-31

    A series of noble metal (Pt, Pd, Ru) loaded zirconia catalysts were evaluated in the catalytic wet air oxidation (CWAO) of mono-chlorophenols (2-CP, 3-CP, 4-CP) under relatively mild reaction conditions. Among the investigated noble metals, Ru appeared to be the best to promote the CWAO of CPs as far as incipient-wetness impregnation was used to prepare all the catalysts. The position of the chlorine substitution on the aromatic ring was also shown to have a significant effect on the CP reactivity in the CWAO over 3wt.% Ru/ZrO(2). 2-CP was relatively easier to degradate compared to 3-CP and 4-CP. One reason could be the higher adsorption of 2-CP on the catalyst surface. Further investigations suggested that 3wt.% Ru/ZrO(2) is a very efficient catalyst in the CWAO of 2-CP as far as high 2-CP conversion and TOC abatement could still be reached at even lower temperature (393K) and lower total pressure (3MPa). Additionally, the conversion of 2-CP was demonstrated to increase with the initial pH of the 2-CP solution. The dechlorination reaction is promoted at higher pH. In all cases, the adsorption of the reactants and the reaction intermediates was shown to play a major role. All parameters that would control the molecule speciation in solution or the catalyst surface properties would have a key effect. PMID:17513043

  12. Catalytic wet air oxidation for the treatment of emulsifying wastewater.

    PubMed

    Zhao, Jian-Fu; Chen, Ling; Lu, Yi-Cheng; Tang, Wen-Wei

    2005-01-01

    The wet air oxidation (WAO) and catalytic WAO (CWAO) of the high strength emulsifying wastewater containing nonionic surfactants have been investigated in terms of COD and TOC removal. The WAO and homogeneous CWAO processes were carried out at the temperature from 433 K to 513 K, with initial oxygen pressure 1.2 MPa. It was found that homogeneous catalyst copper(Cu(NO3)2) had an fairly good catalytic activity for the WAO process, and the oxidation was catalyzed when the temperature was higher than 473 K. Moreover, several heterogeneous catalysts were proved to be effective for the WAO process. At the temperature 473 K, after 2 h reaction, WAO process could achieve about 75% COD removal and 66% TOC removal, while catalysts Cu/Al2O3 and Mn-Ce/Al2O3 elevated the COD removal up to 86%--89% and that of TOC up to 82%. However, complete elimination of COD and TOC was proved to be difficult even the best non-noble catalyst was used. Therefore, the effluent from WAO or CWAO process need to be further disposed. The bioassay proved that the effluent from WAO process was amenable to the biochemical method. PMID:16158582

  13. Scale-up of catalytic wet oxidation under moderate conditions

    SciTech Connect

    Harf, J.; Hug, A.; Vogel, F.; Rohr, P.R. von

    1999-05-01

    The Catalytic Wet Oxidation with pure oxygen is a suitable treatment process for the degradation of organic matter in wastewaters and sludges. The applied moderate reaction conditions lead only to a partial oxidation of the organics. Therefore the resulting process water has to be purified in a biological treatment plant. In this study, experimental data collected during the wet oxidation of phenol and sewage sludge in a laboratory batch reactor as well as in a pilot plant are presented. A generalized kinetic model combined with a residence time analysis allows to predict accurately the degradation of organic matter in the pilot plant. The wet oxidation of wastewaters and sewage sludge was realized in one single plant concept. Treating suspended or diluted organic wastes produces a highly biodegradable process water containing low molecular oxidation products. The investigated Catalytic Wet Oxidation of sewage sludge generates a residual solid complying with the European quality standards of disposal concerning leachability and organic content. Due to its low capital and operating costs, the Catalytic Wet Oxidation process constitutes an acceptable alternative to incineration for the disposal of sludges.

  14. Wet peroxide oxidation and catalytic wet oxidation of stripped sour water produced during oil shale refining.

    PubMed

    Prasad, Jaidev; Tardio, James; Jani, Harit; Bhargava, Suresh K; Akolekar, Deepak B; Grocott, Stephen C

    2007-07-31

    Catalytic wet oxidation (CWO) and wet peroxide oxidation (WPO) of stripped sour water (SSW) from an oil shale refinery was investigated. Greater than 70% total organic carbon (TOC) removal from SSW was achieved using Cu(NO(3))(2) catalysed WO under the following conditions using a glass lined reaction vessel: 200 degrees C, pO(2)=0.5MPa, 3h, [Cu(NO(3))(2)]=67mmol/L. Significant TOC removal ( approximately 31%) also occurred in the system without added oxygen. It is proposed that this is predominantly due to copper catalysed oxidative decarboxylation of organics in SSW based on observed changes in copper oxidation state. Greater than 80% TOC removal was achieved using WPO under the following conditions: 150 degrees C, t=1.5h, [H(2)O(2)]=64g/L. Significantly more TOC could be removed from SSW by adding H(2)O(2) in small doses as opposed to adding the same total amount in one single dose. It was concluded that WPO was a far more effective process for removing odorous compounds from SSW.

  15. [Degradation of beta-naphthol by catalytic wet air oxidation].

    PubMed

    Liu, Jie; Yu, Chao-Ying; Zhao, Pei-Qing; Chen, Ge-Xin

    2012-11-01

    A series of MnO(x)/nano-TiO2 catalysts were prepared and their application in degradation of beta-naphthol by catalytic wet air oxidation (CWAO) was investigated. The catalysts preparation conditions, reaction conditions and its stability were tested. The catalysts had been characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and temperature-programmed reduction (TPR) measurements. The results showed that the decrease of the COD removal for the degradation of beta-naphthol at high Mn loading was due to the aggregation of the highly dispersed Mn species and the formation of the correlated crystals. The decline of the COD removal at high calcination temperature was probably attributed to the weak electron transfer between Mn2O3 and MnO2 and the formation of the inactive Mn2O3. The COD removal had been falling slightly when the catalyst was used 6 times, and this was likely related to the decrease of the diffraction peaks. The catalyst had a high activity when the Mn loading (mass fraction) was 4% and the calcination temperature was 450 degrees C. The COD removal was up to 96.4% at 110 degrees C and 0.5 MPa with this catalyst. The COD removal of 92.4% could be obtained with the MnO(x)/nano-TiO2 catalyst was recycled 6 times. The Mn leaching at 50, 80, 110 and 150 degrees C were all less than 9.3 mg x L(-1) by means of Atomic Absorption Spectroscopy (AAS). The probable degradation pathway was proposed according to some publications.

  16. Catalytic wet air oxidation of high concentration pharmaceutical wastewater.

    PubMed

    Zhan, Wei; Wang, Xiaocong; Li, Daosheng; Ren, Yongzheng; Liu, Dongqi; Kang, Jianxiong

    2013-01-01

    In this study, we investigated the pretreatment of a high concentration pharmaceutical wastewater by catalytic wet air oxidation (CWAO) process. Different experiments were conducted to investigate the effects of the catalyst type, operating temperature, initial system pH, and oxygen partial pressure on the oxidation of the wastewater. Results show that the catalysts prepared by the co-precipitation method have better catalytic activity compared to others. Chemical oxygen demand (COD) conversion increased with the increase in temperature from 160 to 220 °C and decreased with the increase in pH. Moreover, the effect of the oxygen partial pressure on the COD conversion was significant only during the first 20 min of the reaction. Furthermore, the biodegradability of the wastewater improved greatly after CWAO, the ratio of BOD5/COD increased less than 0.1-0.75 when treated at 220 °C (BOD: biochemical oxygen demand). PMID:23676399

  17. Catalytic wet air oxidation of high concentration pharmaceutical wastewater.

    PubMed

    Zhan, Wei; Wang, Xiaocong; Li, Daosheng; Ren, Yongzheng; Liu, Dongqi; Kang, Jianxiong

    2013-01-01

    In this study, we investigated the pretreatment of a high concentration pharmaceutical wastewater by catalytic wet air oxidation (CWAO) process. Different experiments were conducted to investigate the effects of the catalyst type, operating temperature, initial system pH, and oxygen partial pressure on the oxidation of the wastewater. Results show that the catalysts prepared by the co-precipitation method have better catalytic activity compared to others. Chemical oxygen demand (COD) conversion increased with the increase in temperature from 160 to 220 °C and decreased with the increase in pH. Moreover, the effect of the oxygen partial pressure on the COD conversion was significant only during the first 20 min of the reaction. Furthermore, the biodegradability of the wastewater improved greatly after CWAO, the ratio of BOD5/COD increased less than 0.1-0.75 when treated at 220 °C (BOD: biochemical oxygen demand).

  18. Process of forming catalytic surfaces for wet oxidation reactions

    NASA Technical Reports Server (NTRS)

    Jagow, R. B. (Inventor)

    1977-01-01

    A wet oxidation process was developed for oxidizing waste materials, comprising dissolved ruthenium salt in a reactant feed stream containing the waste materials. The feed stream is introduced into a reactor, and the reactor contents are then raised to an elevated temperature to effect deposition of a catalytic surface of ruthenium black on the interior walls of the reactor. The feed stream is then maintained in the reactor for a period of time sufficient to effect at least partial oxidation of the waste materials.

  19. Evolution of toxicity upon wet catalytic oxidation of phenol.

    PubMed

    Santos, A; Yustos, P; Quintanilla, A; García-Ochoa, F; Casas, J A; Rodríguez, J J

    2004-01-01

    This work reports on the evolution of the toxicity of phenol-containing simulated wastewater upon catalytic wet oxidation with a commercial copper-based catalyst (Engelhard Cu-0203T). The results of the study show that this catalyst enhances detoxification, in addition to its effect on the oxidation rate. The EC50 values of the intermediates identified throughout the oxidation route of phenol have been determined and used to predict the evolution of toxicity upon oxidation. The predicted values have been compared with the ones measured directly from the aqueous solution during the oxidation process. To learn about the evolution of toxicity through out the routes of phenol oxidation, experiments have been performed with simulated wastewaters containing separately phenol, catechol, and hydroquinone as original pollutants. The significant increase of toxicity observed during the early stages of phenol oxidation is not directly related to the development of the brown color that derives mainly from catechol oxidation. This increase of toxicity is caused by the formation of hydroquinone and p-benzoquinone as intermediates, the former showing the highest toxicity. Furthermore, synergistic effects, giving rise to a significant increase of toxicity, have been observed. These effects derive from the interactions among copper leached from the catalyst and catechol, hydroquinone, and p-benzoquinone and demand that close attention be paid to this potential problem in catalytic wet oxidation. PMID:14740728

  20. Degradation of paracetamol by catalytic wet air oxidation and sequential adsorption - Catalytic wet air oxidation on activated carbons.

    PubMed

    Quesada-Peñate, I; Julcour-Lebigue, C; Jáuregui-Haza, U J; Wilhelm, A M; Delmas, H

    2012-06-30

    The concern about the fate of pharmaceutical products has raised owing to the increasing contamination of rivers, lakes and groundwater. The aim of this paper is to evaluate two different processes for paracetamol removal. The catalytic wet air oxidation (CWAO) of paracetamol on activated carbon was investigated both as a water treatment technique using an autoclave reactor and as a regenerative treatment of the carbon after adsorption in a sequential fixed bed process. Three activated carbons (ACs) from different source materials were used as catalysts: two microporous basic ACs (S23 and C1) and a meso- and micro-porous acidic one (L27). During the first CWAO experiment the adsorption capacity and catalytic performance of fresh S23 and C1 were higher than those of fresh L27 despite its higher surface area. This situation changed after AC reuse, as finally L27 gave the best results after five CWAO cycles. Respirometry tests with activated sludge revealed that in the studied conditions the use of CWAO enhanced the aerobic biodegradability of the effluent. In the ADOX process L27 also showed better oxidation performances and regeneration efficiency. This different ageing was examined through AC physico-chemical properties.

  1. Development of a catalytic system for gasification of wet biomass

    SciTech Connect

    Elliott, D.C.; Sealock, L.J.; Phelps, M.R.; Neuenschwander, G.G.; Hart, T.R.

    1993-08-01

    A gasification system is under development at Pacific Northwest Laboratory that can be used with high-moisture biomass feedstocks. The system operates at 350 C and 205 atm using a liquid water phase as the processing medium. Since a pressurized system is used, the wet biomass can be fed as a slurry to the reactor without drying. Through the development of catalysts, a useful processing system has been produced. This paper includes assessment of processing test results of different catalysts. Reactor system results including batch, bench-scale continuous, and engineering-scale processing results are presented to demonstrate the applicability of this catalytic gasification system to biomass. The system has utility both for direct conversion of biomass to fuel gas or as a wastewater cleanup system for treatment of unconverted biomass from bioconversion processes. By the use of this system high conversion of biomass to fuel gas can be achieved. Medium-Btu is the primary product. Potential exists for recovery/recycle of some of the unreacted inorganic components from the biomass in the aqueous byproduct stream.

  2. The applicability of the catalytic wet-oxidation to CELSS

    NASA Technical Reports Server (NTRS)

    Takahashi, Y.; Nitta, K.; Ohya, H.; Oguchi, M.

    1987-01-01

    The wet oxidation catalysis of Au, Pd, Pt, Rh or Ru on a ceramic honeycomb carrier was traced in detail by 16 to 20 repetitive batch tests each. As a result, Pt or Pd on a honeycomb carrier was shown to catalyze complete nitrogen gasification as N2. Though the catalysts which realize both complete nitrogen gasification and complete oxidation could not be found, the Ru+Rh catalyst was found to be most promising. Ru honeycomb catalyzed both nitrification and nitrogen gasification.

  3. Catalytic Wet Gasification of Municipal and Animal Wastes

    SciTech Connect

    Ro, Kyoung S.; Cantrell, Keri; Elliott, Douglas C.; Hunt, Patrick G.

    2007-02-21

    Applicability of wet gasification technology for various animal and municipal wastes was examined. Wet gasification of swine manure and raw sewage sludge generated high number of net energies. Furthermore, the moisture content of these wastes is ideal for current wet gasification technology. Significant quantities of water must be added to dry feedstock wastes such as poultry litter, feedlot manures and MSW to make the feedstock pumpable. Because of their high ash contents, MSW and unpaved feedlot manure would not generate positive energy return from wet gasification. The costs of a conceptual wet gasification manure management system for a model swine farm were significantly higher than that of the anaerobic lagoon system. However, many environmental advantages of the wet gasification system were identified, which might reduce the costs significantly. Due to high sulfur content of the wastes, pretreatment to prevent the poisoning of catalysts is critically needed.

  4. Catalytic wet oxidation of thiocyanate with homogeneous copper(II) sulphate catalyst.

    PubMed

    Collado, Sergio; Laca, Adriana; Díaz, Mario

    2010-05-15

    The wet oxidation of thiocyanate has been investigated in a semi-batch reactor at temperatures between 423 and 473 K and pressures between 6.1 x 10(3) and 1.0 x 10(4)kPa in the presence of copper(II) sulphate as catalyst. The effects of copper concentration, initial thiocyanate concentration, pressure and temperature on the reaction rate were analyzed and the main products of reaction were identified. A kinetic model for the Cu-catalyzed reaction is here proposed, including temperature, oxygen concentration, and the reduction of Cu(2+) to Cu(+) that gives an accurate prediction of the oxidation process under the assayed conditions. A mechanistic model based on the formation of a transition complex between a copper cation and two thiocyanate anions has been proposed for the catalytic wet oxidation.

  5. Low-temperature catalytic gasification of wet industrial wastes

    SciTech Connect

    Elliott, D C; Neuenschwander, G G; Baker, E G; Sealock, Jr, L J; Butner, R S

    1991-04-01

    Bench-scale reactor tests are in progress at Pacific Northwest Laboratory to develop a low-temperature, catalytic gasification system. The system, licensed under the trade name Thermochemical Environmental Energy System (TEES{reg sign}), is designed for treating a wide variety of feedstocks ranging from dilute organics in water to waste sludges from food processing. This report describes a test program which used a continuous-feed tubular reactor. This test program is an intermediate stage in the process development. The reactor is a laboratory-scale version of the commercial concept as currently envisioned by the process developers. An energy benefit and economic analysis was also completed on the process. Four conceptual commercial installations of the TEES process were evaluated for three food processing applications and one organic chemical manufacturing application. Net energy production (medium-Btu gas) was achieved in all four cases. The organic chemical application was found to be economically attractive in the present situation. Based on sensitivity studies included in the analysis, the three food processing cases will likely become attractive in the near future as waste disposal regulations tighten and disposal costs increase. 21 refs., 2 figs., 9 tabs.

  6. Catalytic wet oxidation of phenol: kinetics of phenol uptake.

    PubMed

    Santos, A; Yustos, P; Durbán, B; García-Ochoa, F

    2001-07-01

    Catalytic phenol oxidation in aqueous phase under intermediate temperature and pressure has been carried out in order to determine the kinetic model of phenol uptake rate. The catalyst employed here was a commercial one based on copper supplied by Engelhard (Cu-0203T). Operational variables have been studied in the following ranges: temperature from 127 to 180 degrees C, oxygen pressure from 3.2 to 16 bar, initial phenol concentration from 680 to 1200 ppm, and catalyst concentration from 0 to 1550 g/L of liquid phase. Because of the wide interval here employed for the catalyst concentration, two experimental setups have been used: a basket stirred tank reactor (BSTR) with the liquid phase in batch and an integral fixed-bed reactor (FBR) with co-current upflow of gas and liquid phases. An important influence of the reaction in the bulk liquid was obtained in both types of reactor. This fact has been taken into account in the kinetic model according to different approaches. The first approach was a breakup of the reaction rate in two kinetic expressions, considering the homogeneous and heterogeneous contribution separately; the second approach was empirical where the reaction rate is a potential function of the catalyst concentration. It was found that the extent of reaction in the bulk liquid is also influenced by the catalyst concentration and that the first approach is not able to adequately predict the experimental results. Finally a kinetic model, based on the second approach, was discriminated, with a power law for the catalyst concentration with an order about 0.4. This model fits quite well the experimental data obtained in both experimental setups, BSTR and FBR, throughout the wide range of variables studied.

  7. Post-treatment of refinery wastewater effluent using a combination of AOPs (H2O2 photolysis and catalytic wet peroxide oxidation) for possible water reuse. Comparison of low and medium pressure lamp performance.

    PubMed

    Rueda-Márquez, J J; Levchuk, I; Salcedo, I; Acevedo-Merino, A; Manzano, M A

    2016-03-15

    The main aim of this work was to study the feasibility of multi-barrier treatment (MBT) consisting of filtration, hydrogen peroxide photolysis (H2O2/UVC) and catalytic wet peroxide oxidation (CWPO) for post-treatment of petroleum refinery effluent. Also the possibility of water reuse or safe discharge was considered. The performance of MBT using medium (MP) and low (LP) pressure lamps was compared as well as operation and maintenance (O&M) cost. Decomposition of organic compounds was followed by means of gas chromatography-mass spectrometry (GC-MS), total organic carbon (TOC) and chemical oxygen demand (COD) analysis. After filtration step (25 μm) turbidity and concentration of suspended solids decreased by 92% and 80%, respectively. During H2O2/UVC process with LP lamp at optimal conditions (H2O2:TOC ratio 8 and UVC dose received by water 5.28 WUVC s cm(-2)) removal of phenolic compounds, TOC and COD was 100%, 52.3% and 84.3%, respectively. Complete elimination of phenolic compounds, 47.6% of TOC and 91% of COD was achieved during H2O2/UVC process with MP lamp at optimal conditions (H2O2:TOC ratio 5, UVC dose received by water 6.57 WUVC s cm(-2)). In order to compare performance of H2O2/UVC treatment with different experimental set up, the UVC dose required for removal of mg L(-1) of COD was suggested as a parameter and successfully applied. The hydrophilicity of H2O2/UVC effluent significantly increased which in turn enhanced the oxidation of organic compounds during CWPO step. After H2O2/UVC treatment with LP and MP lamps residual H2O2 concentration was 160 mg L(-1) and 96.5 mg L(-1), respectively. Remaining H2O2 was fully consumed during subsequent CWPO step (6 and 3.5 min of contact time for LP and MP, respectively). Total TOC and COD removal after MBT was 94.7% and 92.2% (using LP lamp) and 89.6% and 95%, (using MP lamp), respectively. The O&M cost for MBT with LP lamp was estimated to be 0.44 € m(-3) while with MP lamp it was nearly five

  8. Thermal and sonochemical synthesis of porous (Ce,Zr)O2 mixed oxides from metal β-diketonate precursors and their catalytic activity in wet air oxidation process of formic acid.

    PubMed

    Cau, Camille; Guari, Yannick; Chave, Tony; Larionova, Joulia; Nikitenko, Sergey I

    2014-07-01

    Porous (Ce0.5Zr0.5)O2 solid solutions were prepared by thermolysis (T=285 °C) or sonolysis (20 kHz, I=32 W cm(-2), Pac=0.46 W mL(-1), T=200 °C) of Ce(III) and Zr(IV) acetylacetonates in oleylamine or hexadecylamine under argon followed by heat treatment of the precipitates obtained in air at 450 °C. Transmission Electron Microscopy images of the samples show nanoparticles of ca. 4-6 nm for the two synthetic approaches. The powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray and μ-Raman spectroscopy of solids obtained after heat treatment indicate the formation of (Ce0.5Zr0.5)O2 solid solutions with a metastable tetragonal crystal structure for the two synthetic routes. The specific surface area of the samples varies between 78 and 149 m(2) g(-1) depending on synthesis conditions. The use of Barrett-Joyner-Halenda and t-plot methods reveal the formation of mixed oxides with a hybrid morphology that combines mesoporosity and microporosity regardless of the method of preparation. Platinum nanoparticles were deposited on the surface of the mixed oxides by sonochemical reduction of Pt(IV). It was found that the materials prepared by sonochemistry exhibit better resistance to dissolution during the deposition process of platinum. X-ray photoelectron spectroscopy analysis shows the presence of Pt(0) and Pt(II) on the surface of mixed oxides. Porous (Ce0.5Zr0.5)O2 mixed oxides loaded with 1.5%wt. platinum exhibit high activity in catalytic wet air oxidation of formic acid at 40 °C.

  9. Integrated catalytic wet air oxidation and biological treatment of wastewater from Vitamin B 6 production

    NASA Astrophysics Data System (ADS)

    Kang, Jianxiong; Zhan, Wei; Li, Daosheng; Wang, Xiaocong; Song, Jing; Liu, Dongqi

    This study investigated the feasibility of coupling a catalytic wet air oxidation (CWAO), with CuO/Al 2O 3 as catalyst, and an anaerobic/aerobic biological process to treat wastewater from Vitamin B 6 production. Results showed that the CWAO enhanced the biodegradability (BOD 5/COD) from 0.10 to 0.80. The oxidized effluents with COD of 10,000 mg l -1 was subjected to subsequent continuous anaerobic/aerobic oxidation, and 99.3% of total COD removal was achieved. The quality of the effluent obtained met the discharge standards of water pollutants for pharmaceutical industry Chemical Synthesis Products Category (GB21904-2008), and thereby it implies that the integrated CWAO and anaerobic/aerobic biological treatment may offer a promising process to treat wastewater from Vitamin B 6 production.

  10. Catalytic oxidation with Al-Ce-Fe-PILC as a post-treatment system for coffee wet processing wastewater.

    PubMed

    Sanabria, Nancy R; Peralta, Yury M; Montañez, Mardelly K; Rodríguez-Valencia, Nelson; Molina, Rafael; Moreno, Sonia

    2012-01-01

    The effluent from the anaerobic biological treatment of coffee wet processing wastewater (CWPW) contains a non-biodegradable compound that must be treated before it is discharged into a water source. In this paper, the wet hydrogen peroxide catalytic oxidation (WHPCO) process using Al-Ce-Fe-PILC catalysts was researched as a post-treatment system for CWPW and tested in a semi-batch reactor at atmospheric pressure and 25 °C. The Al-Ce-Fe-PILC achieved a high conversion rate of total phenolic compounds (70%) and mineralization to CO(2) (50%) after 5 h reaction time. The chemical oxygen demand (COD) of coffee processing wastewater after wet hydrogen peroxide catalytic oxidation was reduced in 66%. The combination of the two treatment methods, biological (developed by Cenicafé) and catalytic oxidation with Al-Ce-Fe-PILC, achieved a 97% reduction of COD in CWPW. Therefore, the WHPCO using Al-Ce-Fe-PILC catalysts is a viable alternative for the post-treatment of coffee processing wastewater.

  11. Ultrasound assisted catalytic wet peroxide oxidation of phenol: kinetics and intraparticle diffusion effects.

    PubMed

    Nikolopoulos, Apostolos N; Igglessi-Markopoulou, Olga; Papayannakos, Nikolaos

    2006-01-01

    The combination of ultrasound irradiation and catalytic wet peroxide oxidation was used as a means to degrade phenol. Direct and indirect irradiation were employed, while experiments in the absence of ultrasound were used as reference. A mixed (Al-Fe) pillared clay named FAZA, was used as a catalyst in the form of powder, extrudates and crushed extrudates. Ultrasound was found to clearly enhance the extrudates performance, increasing the conversion at 4h by more than 6 times under direct and almost 11 times under indirect irradiation. This observation is attributed to the reduction of diffusion resistance within the catalyst pores. The overall sonication-catalytic wet peroxide oxidation process appears very promising for environmental purposes. PMID:16223693

  12. Catalytic wet peroxide oxidation of azo dye (Congo red) using modified Y zeolite as catalyst.

    PubMed

    Kondru, Arun Kumar; Kumar, Pradeep; Chand, Shri

    2009-07-15

    The present study explores the degradation of azo dye (Congo red) by catalytic wet peroxide oxidation using Fe exchanged commercial Y zeolite as a catalyst. The effects of various operating parameters like temperature, initial pH, hydrogen peroxide concentration and catalyst loading on the removal of dye, color and COD from an aqueous solution were studied at atmospheric pressure. The percent removals of dye, color and COD at optimum pH(0) 7, 90 degrees C using 0.6 ml H(2)O(2)/350 ml solution and 1g/l catalyst was 97% (in 4h), 100% (in 45 min) and 58% (in 4h), respectively. The % dye removal has been found to be less in comparison to % color removal at all conditions, e.g. dye removal in 45 min and at above conditions was 82%, whereas the color removal was 100%. The results indicate that the Fe exchanged Y zeolite is a promising catalyst for dye removal. Fe exchanged catalyst is characterized using XRD, SEM/EDAX, surface area analyzer and FTIR. Though the dye, color and COD removals were maximum at pH(0) 2 but as the leaching of Fe from the catalyst was more in acidic pH range, pH(0) 7 was taken as operating pH due to almost comparable removals as of pH(0) 2 and no leaching of Fe ions. PMID:19135790

  13. Chloride ions promoted the catalytic wet peroxide oxidation of phenol over clay-based catalysts.

    PubMed

    Zhou, Shiwei; Zhang, Changbo; Xu, Rui; Gu, Chuantao; Song, Zhengguo; Xu, Minggang

    2016-01-01

    Catalytic wet peroxide oxidation (CWPO) of phenol over clay-based catalysts in the presence and absence of NaCl was investigated. Changes in the H2O2, Cl(-), and dissolved metal ion concentration, as well as solution pH during phenol oxidation, were also studied. Additionally, the intermediates formed during phenol oxidation were detected by liquid chromatography-mass spectroscopy and the chemical bonding information of the catalyst surfaces was analyzed by X-ray photoelectron spectroscopy (XPS). The results showed that the presence of Cl(-) increased the oxidation rate of phenol to 155%, and this phenomenon was ubiquitous during the oxidation of phenolic compounds by H2O2 over clay-based catalysts. Cl(-)-assisted oxidation of phenol was evidenced by several analytical techniques such as mass spectroscopy (MS) and XPS, and it was hypothesized that the rate-limiting step was accelerated in the presence of Cl(-). Based on the results of this study, the CWPO technology appears to be promising for applications in actual saline phenolic wastewater treatment. PMID:26942523

  14. SPONTANEOUS CATALYTIC WET AIR OXIDATION DURING PRE-TREATMENT OF HIGH-LEVEL RADIOACTIVE WASTE SLUDGE

    SciTech Connect

    Koopman, D.; Herman, C.; Pareizs, J.; Bannochie, C.; Best, D.; Bibler, N.; Fellinger, T.

    2009-10-01

    Savannah River Remediation, LLC (SRR) operates the Defense Waste Processing Facility for the U.S. Department of Energy at the Savannah River Site. This facility immobilizes high-level radioactive waste through vitrification following chemical pretreatment. Catalytic destruction of formate and oxalate ions to carbon dioxide has been observed during qualification testing of non-radioactive analog systems. Carbon dioxide production greatly exceeded hydrogen production, indicating the occurrence of a process other than the catalytic decomposition of formic acid. Statistical modeling was used to relate the new reaction chemistry to partial catalytic wet air oxidation of both formate and oxalate ions driven by the low concentrations of palladium, rhodium, and/or ruthenium in the waste. Variations in process conditions led to increases or decreases in the total oxidative destruction, as well as partially shifting the preferred species undergoing destruction from oxalate ion to formate ion.

  15. Catalytic wet oxidation of the pretreated synthetic pulp and paper mill effluent under moderate conditions.

    PubMed

    Garg, Anurag; Mishra, I M; Chand, Shri

    2007-01-01

    In the present study, catalytic wet oxidation (CWO) was investigated for the destruction of organic pollutants in the thermally pretreated effluent from a pulp and paper mill under moderate temperature and pressure conditions. The thermal pretreatment studies were conducted at atmospheric pressure and 368K using copper sulfate as a catalyst. The thermal pretreatment reduced COD by about 61%. The filtrate of the thermal pretreatment step was used at pH 8.0 for CWO at 383-443K temperature and a total pressure of 0.85MPa for 4h. Catalysts used for the reaction include copper sulfate, 5% CuO/95% activated carbon, 60% CuO/40% MnO(2), and 60% CuO/40% CeO(2). Maximum COD reduction was found to be 89% during CWO step using 5% CuO/95% activated carbon with a catalyst loading of 8gl(-1) at 443K and 0.85MPa total pressure. Overall COD reduction for the pretreatment and the CWO was found to be 96%. Besides this, 60% CuO/40% CeO(2) catalyst also exhibited the similar activity as that of obtained with 5% CuO/95% activated carbon catalyst at 423K temperature and 0.85MPa total pressure. The pH of the solution during the experimental runs decreases initially due to the formation of carboxylic acid and then increases due to the decomposition of acids.

  16. Degradation of 4-hydroxybenzoic acid by combined ultrasound irradiation and catalytic wet peroxide oxidation.

    PubMed

    Nikolopoulos, Apostolos N; Igglessi-Markopoulou, Olga; Papayannakos, Nikolaos

    2004-05-01

    The aim of this study is to explore the potential benefits from the combined use of ultrasound irradiation and catalytic wet peroxide oxidation for the degradation of 4-hydroxybenzoic acid (4-HBA). The target compound degradation was studied under direct and indirect sonication, while silent conditions were employed as reference. The catalyst, a mixed (Al-Fe) pillared clay named FAZA, was in the form of powder and of extrudates. In the case of extrudates it was observed that ultrasound improves the catalyst performance due to reduction of diffusion resistance, thereby increasing the conversion after 4 h by 12-15 times. Increasing the initial concentration of 4-HBA was found to lead to lower conversion. The combined ultrasonic/catalytic process appears very promising for environmental applications. PMID:15081978

  17. Tough and catalytically active hybrid biofibers wet-spun from nanochitin hydrogels.

    PubMed

    Das, Paramita; Heuser, Thomas; Wolf, Andrea; Zhu, Baolei; Demco, Dan Eugen; Ifuku, Shinsuke; Walther, Andreas

    2012-12-10

    Sustainable alternatives for high-performance and functional materials based on renewable resources are intensely needed as future alternatives for present-day, fossil-based materials. Nanochitin represents an emerging class of highly crystalline bionanoparticles with high intrinsic mechanical properties and the ability for conjugation into functional materials owing to reactive amine and hydroxyl groups. Herein we demonstrate that hydrogels containing surface-deacetylated chitin nanofibrils of micrometer length and average diameters of 9 nm, as imaged by cryogenic transmission electron microscopy, can be wet-spun into macrofibers via extrusion in a coagulation bath, a simple low energy and large-scale processing route. The resulting biofibers display attractive mechanical properties with a large plastic region of about 12% in strain, in which frictional sliding of nanofibrils allows dissipation of fracture energy and enables a high work-of-fracture of near 10 MJ/m3. We further show how to add functionality to these macrofibers by exploiting the amine functions of the surface chitosan groups to host catalytically active noble metal nanoparticles, furnishing biobased, renewable catalytic hybrids. These inorganic/organic macrofibers can be used repeatedly for fast catalytic reductions of model compounds without loss of activity, rendering the concept of hybridized chitin materials interesting as novel bioderived supports for nanoparticle catalysts. PMID:23102411

  18. Homogeneous catalytic wet-air oxidation for the treatment of textile wastewater

    SciTech Connect

    Lei, L. Chen, G.; Hu, X.; Yue, P.L.

    2000-04-01

    An extensive series of experiments was performed to identify suitable catalysts to increase the reaction rate of wet-air oxidation of textile wastewater t relatively mild temperatures an pressures. Wastewater types treated included natural-fiber desizing wastewater, synthetic-fiber desizing wastewater, and printing and dyeing wastewater. Experimental results indicated that all catalysts tested in this investigation significantly increased the chemical oxygen demand (COD) and total organic carbon (TOC) removal rates and total COD and TOC removals. Of all catalysts tested, copper salts were the most effective. Anions in the slat solutions played a role in the catalytic process. Nitrate ions were more effective than sulfate ions. Similarly, copper nitrates were more effective than copper sulfates. A mixture of salts containing different metals performed better than any single salt.

  19. Treatment of municipal landfill leachate by catalytic wet air oxidation: Assessment of the role of operating parameters by factorial design

    SciTech Connect

    Anglada, Angela; Urtiaga, Ane; Ortiz, Inmaculada; Diamadopoulos, Evan

    2011-08-15

    Highlights: > Landfill leachates can be treated effectively by catalytic wet oxidation. > Addition of H{sub 2}O{sub 2} in the presence of transition metals promotes degradation. > Factorial design evaluates the statistically significant operating conditions. > H{sub 2}O{sub 2}, reaction time and temperature are critical in determining performance. - Abstract: The wet air oxidation (WAO) of municipal landfill leachate catalyzed by cupric ions and promoted by hydrogen peroxide was investigated. The effect of operating conditions such as WAO treatment time (15-30 min), temperature (160-200 deg. C), Cu{sup 2+} concentration (250-750 mg L{sup -1}) and H{sub 2}O{sub 2} concentration (0-1500 mg L{sup -1}) on chemical oxygen demand (COD) removal was investigated by factorial design considering a two-stage, sequential process comprising the heating-up of the reactor and the actual WAO. The leachate, at an initial COD of 4920 mg L{sup -1}, was acidified to pH 3 leading to 31% COD decrease presumably due to the coagulation/precipitation of colloidal and other organic matter. During the 45 min long heating-up period of the WAO reactor under an inert atmosphere, COD removal values up to 35% (based on the initial COD value) were recorded as a result of the catalytic decomposition of H{sub 2}O{sub 2} to reactive hydroxyl radicals. WAO at 2.5 MPa oxygen partial pressure advanced treatment further; for example, 22 min of oxidation at 200 deg. C, 250 mg L{sup -1} Cu{sup 2+} and 0-1500 mg L{sup -1} H{sub 2}O{sub 2} resulted in an overall (i.e. including acidification and heating-up) COD reduction of 78%. Amongst the operating variables in question, temperature had the strongest influence on both the heating-up and WAO stages, while H{sub 2}O{sub 2} concentration strongly affected the former and reaction time the latter. Nonetheless, the effects of temperature and H{sub 2}O{sub 2} concentration were found to depend on the concentration levels of catalyst as suggested by the

  20. Low-temperature catalytic gasification of wet industrial wastes. FY 1991--1992 interim report

    SciTech Connect

    Elliott, D.C.; Neuenschwander, G.G.; Hart, T.R.; Phelps, M.R.; Sealock, L.J. Jr.

    1993-07-01

    A catalytic gasification system operating in a pressurized water environment has been developed and refined at Pacific Northwest Laboratory (PNL) for over 12 years. Initial experiments were aimed at developing kinetics information for steam gasification of biomass in the presence of catalysts. The combined use of alkali and metal catalysts was reported for gasification of biomass and its components at low temperatures (350{degrees}C to 450{degrees}C). From the fundamental research evolved the concept of a pressurized, catalytic gasification system for converting wet biomass feedstocks to fuel gas. Extensive batch reactor testing and limited continuous reactor system (CRS) testing were undertaken in the development of this system under sponsorship of the US Department of Energy. A wide range of biomass feedstocks were tested, and the importance of the nickel metal catalyst was identified. Specific use of this process for treating food processing wastes was also studied. The concept application was further expanded to encompass cleanup of hazardous wastewater streams, and results were reported for batch reactor tests and continuous reactor tests. Ongoing work at PNL focuses on refining the catalyst and scaling the system to long-term industrial needs. The process is licensed as the Thermochemical Environmental Energy System (TEES{reg_sign}) to Onsite*Ofsite, Inc., of Duarte, California. This report is a follow-on to the 1989--90 interim report [Elliott et al. 1991], which reviewed the results of the studies conducted with a fixed-bed, continuous-feed, tubular reactor. The discussion here provides an overview of experiments on the wide range of potential feedstock materials conducted in a batch reactor; development of new catalyst materials; and tests performed in continuous-flow reactors at three scales. The appendices contain the history and background of the process development, as well as more detailed descriptions and results of the recent studies.

  1. Unprecedented Catalytic Wet Oxidation of Glucose to Succinic Acid Induced by the Addition of n-Butylamine to a Ru(III) Catalyst.

    PubMed

    Podolean, Iunia; Rizescu, Cristina; Bala, Camelia; Rotariu, Lucian; Parvulescu, Vasile I; Coman, Simona M; Garcia, Hermenegildo

    2016-09-01

    A new pathway for the catalytic wet oxidation (CWO) of glucose is described. Employing a cationic Ru@MNP catalyst, succinic acid is obtained in unprecedently high yield (87.5 %) for a >99.9 % conversion of glucose, most probably through a free radical mechanism combined with catalytic didehydroxylation of vicinal diols and hydrogenation of the resulted unsaturated intermediate. PMID:27511900

  2. Catalytic wet peroxide oxidation of aniline in wastewater using copper modified SBA-15 as catalyst.

    PubMed

    Kong, Liming; Zhou, Xiang; Yao, Yuan; Jian, Panming; Diao, Guowang

    2016-01-01

    SBA-15 mesoporous molecular sieves modified with copper (Cu-SBA-15) were prepared by pH-adjusting hydrothermal method and characterized by X-ray diffraction, BET, transmission electron microscopy, UV-Vis and (29)Si MAS NMR. The pH of the synthesis gel has a significant effect on the amount and the dispersion of copper on SBA-15. The Cu-SBA-15(4.5) (where 4.5 denotes the pH value of the synthesis gel) modified with highly dispersed copper was used as catalyst for the oxidation of aniline by H2O2. The Cu-SBA-15(4.5) shows a higher catalytic activity compared to CuO on the surface of SBA-15. The influences of reaction conditions, such as initial pH of the aqueous solutions, temperature, as well as the dosages of H2O2 and catalyst were investigated. Under weakly alkaline aqueous solution conditions, the aniline conversion, the H2O2 decomposition and the total organic carbon (TOC) removal could be increased significantly compared to the acid conditions. The percentage of leaching Cu(2+) could be decreased from 45.0% to 3.66% when the initial pH of solution was increased from 5 to 10. The TOC removal could be enhanced with the increases of temperature, H2O2 and catalyst dosage, but the aniline conversion and H2O2 decomposition change slightly with further increasing dosage of catalyst and H2O2. At 343 K and pH 8.0, 100% aniline conversion and 66.9% TOC removal can be achieved under the conditions of 1.0 g/L catalyst and 0.05 mol/L H2O2 after 180 min. Although copper might be slightly leached from catalyst, the homogeneous Cu(2+) contribution to the whole catalytic activity is unimportant, and the highly dispersed copper on SBA-15 plays a dominant role.

  3. Bench-scale reactor tests of low temperature, catalytic gasification of wet industrial wastes

    SciTech Connect

    Elliot, D.C.; Baker, E.G.; Butner, R.S.; Sealock, L.J. Jr. )

    1993-02-01

    Bench-scale reactor tests are under way at Pacific Northwest Laboratory to develop a low temperature, catalytic gasification system. The system, licensed under the trade name Thermochemical Environmental Energy System (TEES[reg sign]), is designed for to a wide variety of feedstocks ranging from dilute organics in water to waste sludges from food processing. The current research program is focused on the use of a continuous feed, tubular reactor. The catalyst is nickel metal on an inert support. Typical results show that feedstocks such as solutions of 2 percent para-cresol or 5 percent and 10 percent lactose in water or cheese whey can be processed to [gt] 99 percent reduction of chemical oxygen demand (COD) at a rate of up to 2 L/hr. The estimated residence lime is less than 5 min at 360C and 3,000 psig, not including 1 to 2 min required in the preheating zone of the reactor. The liquid hourly space velocity has been varied from 1.8 to 2.9 L feedstock/L catalyst/hr depending on the feedstock. The product fuel gas contains 40 percent to 55 percent methane, 35 percent to 50 percent carbon dioxide, and 5 percent to 10 percent hydrogen with as much as 2 percent ethane, but less than 0.1 percent ethylene or carbon monoxide, and small amounts of higher hydrocarbons. The byproduct water stream carries residual organics amounting to less than 500 mg/L COD.

  4. Bench-scale reactor tests of low-temperature, catalytic gasification of wet, industrial wastes

    SciTech Connect

    Elliott, D.C.; Neuenschwander, G.G.; Baker, E.G.; Butner, R.S.; Sealock, L.J.

    1990-04-01

    Bench-scale reactor tests are under way at Pacific Northwest Laboratory to develop a low-temperature, catalytic gasification system. The system, licensed under the trade name Thermochemical Environmental Energy System (TEES{reg sign}), is designed for to a wide variety of feedstocks ranging from dilute organics in water to waste sludges from food processing. The current research program is focused on the use of a continuous-feed, tubular reactor. The catalyst is nickel metal on an inert support. Typical results show that feedstocks such as solutions of 2% para-cresol or 5% and 10% lactose in water or cheese whey can be processed to >99% reduction of chemical oxygen demand (COD) at a rate of up to 2 L/hr. The estimated residence time is less than 5 min at 360{degree}C and 3000 psig, not including 1 to 2 min required in the preheating zone of the reactor. The liquid hourly space velocity has been varied from 1.8 to 2.9 L feedstock/L catalyst/hr depending on the feedstock. The product fuel gas contains 40% to 55% methane, 35% to 50% carbon dioxide, and 5% to 10% hydrogen with as much as 2% ethane, but less than 0.1% ethylene or carbon monoxide, and small amounts of higher hydrocarbons. The byproduct water stream carries residual organics amounting to less than 500 mg/L COD. 9 refs., 1 fig., 4 tabs.

  5. Development of the Monolith Froth Reactor for Catalytic Wet Oxidation of CELSS Model Wastes

    NASA Technical Reports Server (NTRS)

    Fisher, John W.; Abraham, Martin

    1993-01-01

    The aqueous phase oxidation of acetic acid, used as a model compound for the treatment of CELSS (Controlled Ecological Life Support System) waste, was carried out in the monolith froth reactor which utilizes two-phase flow in the monolith channels. The catalytic oxidation of acetic acid was carried out over a Pt/Al2O3 catalyst at temperatures and pressures below the critical point of water. The effect of externally controllable parameters (temperature, liquid flow rate, distributor plate orifice size, pitch, and catalyst distance from the distributor plate) on the rate of acetic acid oxidation was investigated. Results indicate reaction rate increased with increasing temperature and exhibited a maximum with respect to liquid flow rate. The apparent activation energy calculated from reaction rate data was 99.7 kJ/mol. This value is similar to values reported for the oxidation of acetic acid in other systems and is comparable to intrinsic values calculated for oxidation reactions. The kinetic data were modeled using simple power law kinetics. The effect of "froth" feed system characteristics was also investigated. Results indicate that the reaction rate exhibits a maximum with respect to distributor plate orifice size, pitch, and catalyst distance from the distributor plate. Fundamental results obtained were used to extrapolate where the complete removal of acetic acid would be obtained and for the design and operation of a full scale CELSS treatment system.

  6. Development of the Monolith Froth Reactor for Catalytic Wet Oxidation of CELSS Model Wastes

    NASA Technical Reports Server (NTRS)

    Abraham, Martin; Fisher, John W.

    1995-01-01

    The aqueous phase oxidation of acetic acid, used as a model compound for the treatment of CELSS (Controlled Ecological Life Support System) waste, was carried out in the monolith froth reactor which utilizes two-phase flow in the monolith channels. The catalytic oxidation of acetic acid was carried out over a Pt/Al2O3 catalyst, prepared at The University of Tulsa, at temperatures and pressures below the critical point of water. The effect of externally controllable parameters (temperature, liquid flow rate, distributor plate orifice size, pitch, and catalyst distance from the distributor plate) on the rate of acetic acid oxidation was investigated. Results indicate reaction rate increased with increasing temperature and exhibited a maximum with respect to liquid flow rate. The apparent activation energy calculated from reaction rate data was 99.7 kJ/mol. This value is similar to values reported for the oxidation of acetic acid in other systems and is comparable to intrinsic values calculated for oxidation reactions. The kinetic data were modeled using simple power law kinetics. The effect of "froth" feed system characteristics was also investigated. Results indicate that the reaction rate exhibits a maximum with respect to distributor plate orifice size, pitch, and catalyst distance from the distributor plate. Fundamental results obtained were used to extrapolate where the complete removal of acetic acid would be obtained and for the design and operation of a full scale CELSS treatment system.

  7. Low-temperature catalytic gasification of wet industrial wastes. FY 1993--1994 interim report

    SciTech Connect

    Elliott, D.C.; Hart, T.R.; Neuenschwander, G.G.; Deverman, G.S.; Werpy, T.A.; Phelps, M.R.; Baker, E.G.; Sealock, L.J. Jr.

    1995-03-01

    Process development research is continuing on a low-temperature, catalytic gasification system that has been demonstrated to convert organics in water (dilute or concentrated) to useful and environmentally safe gases. The system, licensed under the trade name Thermochemical Environmental Energy System (TEESO), treats a wide variety of feedstocks ranging from hazardous organics in water to waste sludges from food processing. The current research program is focused on the use of continuous-feed, tubular reactors systems for testing catalysts and feedstocks in the process. A range of catalysts have been tested, including nickel and other base metals, as well as ruthenium and other precious metals. Results of extensive testing show that feedstocks, ranging from 2% para-cresol in water to potato waste and spent grain, can be processed to > 99% reduction of chemical oxygen demand (COD). The product fuel gas contains from 40% up to 75% methane, depending on the feedstock. The balance of the gas is mostly carbon dioxide with < 5% hydrogen and usually < 1% ethane and higher hydrocarbons. The byproduct water stream carries residual organics from 10 to 1,000 mg/l COD, depending on the feedstock. The level of development of TEES has progressed to the initial phases of industrial process demonstration. Testing of industrial waste streams is under way at both the bench scale and engineering scale of development.

  8. Project WET Curriculum and Activity Guide 2.0

    ERIC Educational Resources Information Center

    Project WET Foundation, 2011

    2011-01-01

    The "Project WET Curriculum and Activity Guide 2.0" continues Project WET's dedication to 21st-century, cutting-edge water education. Now in full color, Guide 2.0 offers new activities on topics such as National Parks and storm water, fully revised and updated activities from the original Guide and the very best activities gathered from all of…

  9. Reactive wetting properties of TiO2 nanoparticles predicted by ab initio molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Brandt, Erik G.; Agosta, Lorenzo; Lyubartsev, Alexander P.

    2016-07-01

    Small-sized wet TiO2 nanoparticles have been investigated by ab initio molecular dynamics simulations. Chemical and physical adsorption of water on the TiO2-water interface was studied as a function of water content, ranging from dry nanoparticles to wet nanoparticles with monolayer coverage of water. The surface reactivity was shown to be a concave function of water content and driven by surface defects. The local coordination number at the defect was identified as the key factor to decide whether water adsorption proceeds through dissociation or physisorption on the surface. A consistent picture of TiO2 nanoparticle wetting at the microscopic level emerges, which corroborates existing experimental data and gives further insight into the molecular mechanisms behind nanoparticle wetting. These calculations will facilitate the engineering of metal oxide nanoparticles with a controlled catalytic water activity.Small-sized wet TiO2 nanoparticles have been investigated by ab initio molecular dynamics simulations. Chemical and physical adsorption of water on the TiO2-water interface was studied as a function of water content, ranging from dry nanoparticles to wet nanoparticles with monolayer coverage of water. The surface reactivity was shown to be a concave function of water content and driven by surface defects. The local coordination number at the defect was identified as the key factor to decide whether water adsorption proceeds through dissociation or physisorption on the surface. A consistent picture of TiO2 nanoparticle wetting at the microscopic level emerges, which corroborates existing experimental data and gives further insight into the molecular mechanisms behind nanoparticle wetting. These calculations will facilitate the engineering of metal oxide nanoparticles with a controlled catalytic water activity. Electronic supplementary information (ESI) available: Simulation data on equilibration of energies and structures (root-mean-square-deviations and

  10. Development of a Catalytic Wet Air Oxidation Method to Produce Feedstock Gases from Waste Polymers

    NASA Technical Reports Server (NTRS)

    Kulis, Michael J.; Guerrero-Medina, Karen J.; Hepp, Aloysius F.

    2012-01-01

    Given the high cost of space launch, the repurposing of biological and plastic wastes to reduce the need for logistical support during long distance and long duration space missions has long been recognized as a high priority. Described in this paper are the preliminary efforts to develop a wet air oxidation system in order to produce fuels from waste polymers. Preliminary results of partial oxidation in near supercritical water conditions are presented. Inherent corrosion and salt precipitation are discussed as system design issues for a thorough assessment of a second generation wet air oxidation system. This work is currently being supported by the In-Situ Resource Utilization Project.

  11. WetLab-2: Wet Lab RNA SmartCycler Providing PCR Capability on ISS

    NASA Technical Reports Server (NTRS)

    Parra, Macarena; Schonfeld, Julie

    2015-01-01

    The WetLab-2 system will provide sample preparation and qRT-PCR analysis on-board the ISS, a capability to enable using the ISS as a real laboratory. The system will be validated on SpX-7, and is planned for its first PI use on SpX-9.

  12. Degradation of cationic red GTL by catalytic wet air oxidation over Mo-Zn-Al-O catalyst under room temperature and atmospheric pressure.

    PubMed

    Xu, Yin; Li, Xiaoyi; Cheng, Xiang; Sun, Dezhi; Wang, Xueye

    2012-03-01

    To overcome the drawback of catalytic wet air oxidation (CWAO) with high temperature and high pressure, the catalytic activity of Mo-Zn-Al-O catalyst for degradation of cationic red GTL under room temperature and atmospheric pressure was investigated. Mo-Zn-Al-O catalyst was prepared by coprecipitation and impregnation. XRD, TG-DTG, and XPS were used to characterize the resulting sample. Central composition design using response surface methodology was employed to optimize correlation of factors on the decolorization of cationic red GTL. The results show that the optimal conditions of pH value, initial concentration of dye and catalyst dosage were found to be 4.0, 85 mg/L and 2.72 g/L, respectively, for maximum decolorization of 80.1% and TOC removal of 50.9%. Furthermore, the reaction on the Mo-Zn-Al-O catalyst and degradation mechanism of cationic red GTL was studied by Electron spin resonance (ESR) and GC-MS technique. The possible reaction mechanism was that the Mo-Zn-Al-O catalyst can efficiently react with adsorbed oxygen/H(2)O to produce ·OH and (1)O(2) and finally induce the degradation of cationic red GTL. GC-MS analysis of the degradation products indicates that cationic red GTL was initiated by the cleavage of -N ═ N- and the intermediates were further oxidized by ·OH or (1)O(2).

  13. Sewage-sludge-derived carbonaceous materials for catalytic wet hydrogen peroxide oxidation of m-cresol in batch and continuous reactors.

    PubMed

    Yu, Yang; Wei, Huangzhao; Yu, Li; Wang, Wei; Zhao, Ying; Gu, Bin; Sun, Chenglin

    2016-01-01

    In this study, four sewage-sludge-derived carbonaceous materials (SWs) were evaluated for their catalytic wet hydrogen peroxide oxidation (CWPO) performance of m-cresol in batch reactor and continuous reactor, respectively. The SWs were produced by carbonization (SW); carbonization with the addition of CaO (CaO-SW); HNO3 pretreatment (HNO3-SW) and steam activation (Activated-SW). The properties of SW catalysts were assessed by thermogravimetric analysis, Brunauer-Emmett-Teller, Fourier Transform Infrared Spectroscopy, X-ray Fluorescence, Scanning electron microscopy, energy dispersive X-ray analysis and zeta potential. The results showed that SW treated by HNO3 (HNO3-SW) had a high conversion of m-cresol in batch reactor and continuous reactor, respectively. Under the conditions of batch reaction (Cm-cresol = 100 mg L(-1), CH2O2 = 15.7 mmol L(-1), initial pH=7.0, 0.5 g L(-1) catalyst, 80°C, 180 min adsorption and 210 min oxidation), the conversion of m-cresol reached 100% and total organic carbon removal was 67.1%. It had a high catalytic activity and stability on the treatment of m-cresol in CWPO for more than 1100 h. Furthermore, a possible reaction mechanism for the oxidation of m-cresol to 2-methyl-p-benzoquinone by CWPO was proposed.

  14. Ni/MgAlO regeneration for catalytic wet air oxidation of an azo-dye in trickle-bed reaction.

    PubMed

    Vallet, Ana; Ovejero, Gabriel; Rodríguez, Araceli; Peres, José A; García, Juan

    2013-01-15

    Active nickel catalysts (7 wt%) supported over Mg-Al mixed oxides have been recently developed and it has also been demonstrated that they are also highly selective in Catalytic Wet air Oxidation (CWAO) of dyes. CWAO of Chromotrope 2R (C2R) has been studied using a trickle bed reactor employing temperatures from 100 to 180 °C, liquid flow rates from 0.1 to 0.7 mL min(-1) and initial dye concentration from 10 to 50 ppm. Total pressure and air flow were 25 bar and 300 mL min(-1), respectively. The catalyst showed a very stable activity up to 24 h on stream with an average TOC conversion of 82% at 150 °C and T(r)=0.098 g(Ni) min mL(-1). After the reaction, a 1.1 wt% C of carbonaceous deposit is formed onto the catalyst and a diminution of 30% of the surface area with respect of the fresh catalyst was observed. An increase in the space time gave higher TOC conversions up to T(r)=0.098 g(Ni) min mL(-1), attaining values of 80% at 180 °C. The performance of TOC and dye removal does not decrease after two regeneration cycles. In total, a 57 h effective reaction has been carried out with no loss of catalytic activity. PMID:23246939

  15. Application of sludge-based carbonaceous materials in a hybrid water treatment process based on adsorption and catalytic wet air oxidation.

    PubMed

    Julcour Lebigue, Carine; Andriantsiferana, Caroline; N'Guessan Krou; Ayral, Catherine; Mohamed, Elham; Wilhelm, Anne-Marie; Delmas, Henri; Le Coq, Laurence; Gerente, Claire; Smith, Karl M; Pullket, Suangusa; Fowler, Geoffrey D; Graham, Nigel J D

    2010-12-01

    This paper describes a preliminary evaluation of the performance of carbonaceous materials prepared from sewage sludges (SBCMs) in a hybrid water treatment process based on adsorption and catalytic wet air oxidation; phenol was used as the model pollutant. Three different sewage sludges were treated by either carbonisation or steam activation, and the physico-chemical properties of the resultant carbonaceous materials (e.g. hardness, BET surface area, ash and elemental content, surface chemistry) were evaluated and compared with a commercial reference activated carbon (PICA F22). The adsorption capacity for phenol of the SBCMs was greater than suggested by their BET surface area, but less than F22; a steam activated, dewatered raw sludge (SA_DRAW) had the greatest adsorption capacity of the SBCMs in the investigated range of concentrations (<0.05 mol L(-1)). In batch oxidation tests, the SBCMs demonstrated catalytic behaviour arising from their substrate adsorptivity and metal content. Recycling of SA_DRAW in successive oxidations led to significant structural attrition and a hardened SA_DRAW was evaluated, but found to be unsatisfactory during the oxidation step. In a combined adsorption-oxidation sequence, both the PICA carbon and a selected SBCM showed deterioration in phenol adsorption after oxidative regeneration, but a steady state performance was reached after 2 or 3 cycles.

  16. TiO2-sludge carbon enhanced catalytic oxidative reaction in environmental wastewaters applications.

    PubMed

    Athalathil, Sunil; Erjavec, Boštjan; Kaplan, Renata; Stüber, Frank; Bengoa, Christophe; Font, Josep; Fortuny, Agusti; Pintar, Albin; Fabregat, Azael

    2015-12-30

    The enhanced oxidative potential of sludge carbon/TiO2 nano composites (SNCs), applied as heterogeneous catalysts in advanced oxidation processes (AOPs), was studied. Fabrification of efficient SNCs using different methods and successful evaluation of their catalytic oxidative activity is reported for the first time. Surface modification processes of hydrothermal deposition, chemical treatment and sol-gel solution resulted in improved catalytic activity and good surface chemistry of the SNCs. The solids obtained after chemical treatment and hydrothermal deposition processes exhibit excellent crystallinity and photocatalytic activity. The highest photocatalytic rate was obtained for the material prepared using hydrothermal deposition technique, compared to other nanocomposites. Further, improved removal of bisphenol A (BPA) from aqueous phase by means of catalytic ozonation and catalytic wet air oxidation processes is achieved over the solid synthesized using chemical treatment method. The present results demonstrate that the addition of TiO2 on the surface of sludge carbon (SC) increases catalytic oxidative activity of SNCs. The latter produced from harmful sludge materials can be therefore used as cost-effective and efficient sludge derived catalysts for the removal of hazardous pollutants.

  17. [CuO-Ru/Al2O3 catalytic ozonation of acetophenone in water].

    PubMed

    Zhang, Hua; Shi, Rui; Zang, Xing-jie; Tong, Shao-ping; Ma, Chun-an

    2010-03-01

    Two-component CuO-Ru based on active Al2O3 (CuO-Ru/Al2O3) catalyst was prepared by incipient wetness impregnation and used to catalytic ozonation of acetophenone (AP). The results showed that doping Ru could significantly improve the catalytic activity of CuO/Al2O3. For example, the COD removal rates of AP solution after 30 min by ozonation alone, CuO/Al2O3/O3, and CuO-Ru/Al2O3/O3 were 6.3%, 20.0% and 54.0%, respectively. The change of pH almost had no affect on degradation efficiency of AP. However, a comparison of COD removal between ozonation alone and catalytic ozonation indicated that CuO-Ru/Al2O3 catalyst was more suitable for application in neutral or acidic condition. CuO-Ru/Al2O3 catalyst could accelerate decomposition rate of ozone in water, and its decomposition rate constant reached 2.58 x 10(-3) s(-1) while that of ozone alone in double-water was 1.19 x 10(-3) s(-1). The experimental result of t-butanol indicated that CuO-Ru/Al2O3 catalytic ozonation of AP followed a radical-type mechanism. PMID:20358832

  18. Electrochemical, H2O2-Boosted Catalytic Oxidation System

    NASA Technical Reports Server (NTRS)

    Akse, James R.; Thompson, John O.; Schussel, Leonard J.

    2004-01-01

    An improved water-sterilizing aqueous-phase catalytic oxidation system (APCOS) is based partly on the electrochemical generation of hydrogen peroxide (H2O2). This H2O2-boosted system offers significant improvements over prior dissolved-oxygen water-sterilizing systems in the way in which it increases oxidation capabilities, supplies H2O2 when needed, reduces the total organic carbon (TOC) content of treated water to a low level, consumes less energy than prior systems do, reduces the risk of contamination, and costs less to operate. This system was developed as a variant of part of an improved waste-management subsystem of the life-support system of a spacecraft. Going beyond its original intended purpose, it offers the advantage of being able to produce H2O2 on demand for surface sterilization and/or decontamination: this is a major advantage inasmuch as the benign byproducts of this H2O2 system, unlike those of systems that utilize other chemical sterilants, place no additional burden of containment control on other spacecraft air- or water-reclamation systems.

  19. WO3/CeO2/TiO2 Catalysts for Selective Catalytic Reduction of NO(x) by NH3: Effect of the Synthesis Method.

    PubMed

    Michalow-Mauke, Katarzyna A; Lu, Ye; Ferri, Davide; Graule, Thomas; Kowalski, Kazimierz; Elsener, Martin; Kröcher, Oliver

    2015-01-01

    WO3/CeO2/TiO2, CeO2/TiO2 and WO3/TiO2 catalysts were prepared by wet impregnation. CeO2/TiO2 and WO3/TiO2 showed activity towards the selective catalytic reduction (SCR) of NO(x) by NH3, which was significantly improved by subsequent impregnation of CeO/TiO2 with WO3. Catalytic performance, NH3 oxidation and NH3 temperature programmed desorption of wet-impregnated WO3/CeO2/TiO2 were compared to those of a flame-made counterpart. The flame-made catalyst exhibits a peculiar arrangement of W-Ce-Ti-oxides that makes it very active for NH3-SCR. Catalysts prepared by wet impregnation with the aim to mimic the structure of the flame-made catalyst were not able to fully reproduce its activity. The differences in the catalytic performance between the investigated catalysts were related to their structural properties and the different interaction of the catalyst components.

  20. SWI/SNF mutant cancers depend upon catalytic and non–catalytic activity of EZH2

    PubMed Central

    Kim, Kimberly H.; Kim, Woojin; Howard, Thomas P.; Vazquez, Francisca; Tsherniak, Aviad; Wu, Jennifer N.; Wang, Weishan; Haswell, Jeffrey R.; Walensky, Loren D.; Hahn, William C.; Orkin, Stuart H.; Roberts, Charles W. M.

    2016-01-01

    Human cancer genome sequencing has recently revealed that genes encoding subunits of SWI/SNF chromatin remodeling complexes are frequently mutated across a wide variety of cancers, and several subunits of the complex have been shown to have bona fide tumor suppressor activity1. However, whether mutations in SWI/SNF subunits result in shared dependencies is unknown. Here we show that EZH2, a catalytic subunit of the Polycomb repressive complex 2 (PRC2), is essential in all tested cancer cell lines and xenografts harboring mutations of the SWI/SNF subunits ARID1A, PBRM1, and SMARCA4, which are several of the most frequently mutated SWI/SNF subunits in human cancer but that co–occurrence of a Ras pathway mutation correlates with abrogation of this dependence. Surprisingly, we demonstrate that SWI/SNF mutant cancer cells are primarily dependent upon a non–catalytic role of EZH2 in stabilization of the PRC2 complex, and only partially dependent on EZH2 histone methyltransferase activity. These results not only reveal a shared dependency of cancers with genetic alterations in SWI/SNF subunits, but also suggest that EZH2 enzymatic inhibitors now in clinical development may not fully suppress the oncogenic activity of EZH2. PMID:26552009

  1. SWI/SNF-mutant cancers depend on catalytic and non-catalytic activity of EZH2.

    PubMed

    Kim, Kimberly H; Kim, Woojin; Howard, Thomas P; Vazquez, Francisca; Tsherniak, Aviad; Wu, Jennifer N; Wang, Weishan; Haswell, Jeffrey R; Walensky, Loren D; Hahn, William C; Orkin, Stuart H; Roberts, Charles W M

    2015-12-01

    Human cancer genome sequencing has recently revealed that genes that encode subunits of SWI/SNF chromatin remodeling complexes are frequently mutated across a wide variety of cancers, and several subunits of the complex have been shown to have bona fide tumor suppressor activity. However, whether mutations in SWI/SNF subunits result in shared dependencies is unknown. Here we show that EZH2, a catalytic subunit of the polycomb repressive complex 2 (PRC2), is essential in all tested cancer cell lines and xenografts harboring mutations of the SWI/SNF subunits ARID1A, PBRM1, and SMARCA4, which are several of the most frequently mutated SWI/SNF subunits in human cancer, but that co-occurrence of a Ras pathway mutation is correlated with abrogation of this dependence. Notably, we demonstrate that SWI/SNF-mutant cancer cells are primarily dependent on a non-catalytic role of EZH2 in the stabilization of the PRC2 complex, and that they are only partially dependent on EZH2 histone methyltransferase activity. These results not only reveal a shared dependency of cancers with genetic alterations in SWI/SNF subunits, but also suggest that EZH2 enzymatic inhibitors now in clinical development may not fully suppress the oncogenic activity of EZH2.

  2. Catalytic wet air oxidation of bisphenol A solution in a batch-recycle trickle-bed reactor over titanate nanotube-based catalysts.

    PubMed

    Kaplan, Renata; Erjavec, Boštjan; Senila, Marin; Pintar, Albin

    2014-10-01

    Catalytic wet air oxidation (CWAO) is classified as an advanced oxidation process, which proved to be highly efficient for the removal of emerging organic pollutant bisphenol A (BPA) from water. In this study, BPA was successfully removed in a batch-recycle trickle-bed reactor over bare titanate nanotube-based catalysts at very short space time of 0.6 min gCAT g(-1). The as-prepared titanate nanotubes, which underwent heat treatment at 600 °C, showed high activity for the removal of aqueous BPA. Liquid-phase recycling (5- or 10-fold recycle) enabled complete BPA conversion already at 200 °C, together with high conversion of total organic carbon (TOC), i.e., 73 and 98 %, respectively. The catalyst was chemically stable in the given range of operating conditions for 189 h on stream.

  3. Catalytic behaviour and copper leaching of Cu0.10Zn0.90Al1.90Fe0.10O4 spinel for catalytic wet air oxidation of phenol.

    PubMed

    Xu, Aihua; Sun, Chenglin

    2012-06-01

    A Cu0.10Zn0.90Al1.90Fe0.10O4 spinel catalyst prepared by the sol-gel method was tested for catalytic wet air oxidation (CWAO) of phenol. The catalyst showed high activity for phenol degradation. During successive test at 170 degrees C, 100% phenol conversion and 95% chemical oxygen demand (COD) removal were observed. Results from scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) indicated that the catalyst structure remained unchanged during reaction. From the analysis of temperature programmed reduction (TPR), diffuse reflectance UV-Vis spectra (DR UV-Vis) and activity assay at basic solution pH, it can be suggested that the highly dispersed copper ions on the catalyst surface were almost completely dissolved into the reaction solution, whereas the tetra-coordinated copper ions were not only stable against leaching but also active towards phenol degradation.

  4. Catalytic behaviour and copper leaching of Cu0.10Zn0.90Al1.90Fe0.10O4 spinel for catalytic wet air oxidation of phenol.

    PubMed

    Xu, Aihua; Sun, Chenglin

    2012-06-01

    A Cu0.10Zn0.90Al1.90Fe0.10O4 spinel catalyst prepared by the sol-gel method was tested for catalytic wet air oxidation (CWAO) of phenol. The catalyst showed high activity for phenol degradation. During successive test at 170 degrees C, 100% phenol conversion and 95% chemical oxygen demand (COD) removal were observed. Results from scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD) indicated that the catalyst structure remained unchanged during reaction. From the analysis of temperature programmed reduction (TPR), diffuse reflectance UV-Vis spectra (DR UV-Vis) and activity assay at basic solution pH, it can be suggested that the highly dispersed copper ions on the catalyst surface were almost completely dissolved into the reaction solution, whereas the tetra-coordinated copper ions were not only stable against leaching but also active towards phenol degradation. PMID:22856307

  5. Forsterite Carbonation in Wet Supercritical CO2 and Sodium Citrate

    NASA Astrophysics Data System (ADS)

    Qiu, L.; Schaef, T.; Wang, Z.; Miller, Q.; McGrail, P.

    2013-12-01

    Lin Qiu1*, Herbert T. Schaef2, Zhengrong Wang1, Quin R.S. Miller3, BP McGrail2 1. Yale University, New Haven, CT, USA 2. Pacific Northwest National Laboratory, Richland, WA, USA 3. University of Wyoming, Laramie, WY, USA Geologic reservoirs for managing carbon emissions (mostly CO2) have expanded over the last 5 years to include unconventional formations including basalts and fractured shales. Recently, ~1000 metric tons of CO2 was injected into the Columbia River Basalt (CRB) in Eastern Washington as part of the Wallula Pilot Project, Big Sky Regional Carbon Partnership. Based on reservoir conditions, the injected CO2 is present as a supercritical fluid that dissolves into the formation water over time, and reacts with basalt components to form carbonate minerals. In this paper, we discuss mineral transformation reactions occurring when the forsterite (Mg2SiO4) is exposed to wet scCO2 in equilibrium with pure water and sodium citrate solutions. Forsterite was selected as it is an important olivine group mineral present in igneous and mafic rocks. Citrate was selected as it has been shown to enhance mineral dissolution and organic ligands are possible degradation products of the microbial communities present in the formational waters of the CRB. For the supercritical phase, transformation reactions were examined by in situ high pressure x-ray diffraction (HXRD) in the presence of supercritical carbon dioxide (scCO2) in contact with water and sodium citrate solutions at conditions relevant to carbon sequestration. Experimental results show close-to-complete dissolution of forsterite in contact with scCO2 equilibrated with pure water for 90 hours (90 bar and 50°C). Under these conditions, thin films of water coated the mineral surface, providing a mechanism for silicate dissolution and transport of cations necessary for carbonate formation. The primary crystalline component initially detected with in situ HXRD was the hydrated magnesium carbonate, nesquehonite [Mg

  6. 40 CFR Table 2 to Subpart Eeee of... - Operating Limits for Incinerators and Wet Scrubbers

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Wet Scrubbers 2 Table 2 to Subpart EEEE of Part 60 Protection of Environment ENVIRONMENTAL PROTECTION..., Subpt. EEEE, Table 2 Table 2 to Subpart EEEE of Part 60—Operating Limits for Incinerators and Wet... establish these operating limits And monitoring using these minimum frequencies Data measurement...

  7. Development studies for a novel wet oxidation process. Phase 2

    SciTech Connect

    1994-07-01

    DETOX{sup SM} is a catalyzed wet oxidation process which destroys organic materials in an acidic water solution of iron at 373 to 473 K. The solution can be used repeatedly to destroy great amounts of organic materials. Since the process is conducted in a contained vessel, air emissions from the process can be well controlled. The solution is also capable of dissolving and concentrating many heavy and radioactive metals for eventual stabilization and disposal. The Phase 2 effort for this project is site selection and engineering design for a DETOX demonstration unit. Site selection was made using a set of site selection criteria and evaluation factors. A survey of mixed wastes at DOE sites was conducted using the Interim Mixed Waste Inventory Report. Sites with likely suitable waste types were identified. Potential demonstration sites were ranked based on waste types, interest, regulatory needs, scheduling, ability to provide support, and available facilities. Engineering design for the demonstration unit is in progress and is being performed by Jacobs Applied Technology. The engineering design proceeded through preliminary process flow diagrams (PFDs), calculation of mass and energy balances for representative waste types, process and instrumentation diagrams (P and IDs), preparation of component specifications, and a firm cost estimate for fabrication of the demonstration unit.

  8. Second GEWEX/GLASS Global Soil Wetness Project (GSWP2)

    NASA Astrophysics Data System (ADS)

    Dirmeyer, P. A.; Oki, T.

    2002-05-01

    The Second Global Soil Wetness Project (GSWP2) is a land-surface modeling activity of the Global Land-Atmosphere System Study (GLASS) and the International Satellite Land-Surface Climatology Project (ISLSCP), both contributing projects of the Global Energy and Water Cycle Experiment (GEWEX). The first phase of GSWP2, a global 10-year multi-model simulation and comparison using the ISLSCP Initiative II data set (1986-1995), begins later this year. In addition to providing a large-scale test-bed for comparison of land surface schemes (LSSs), several sub-projects are proposed. Estimates of continental and global-scale surface energy and water budgets will be calculated, and inter-model uncertainties will be established. The ability of multiple LSSs to simulate large-scale interannual variations will be investigated. GSWP2 will serve as a global platform for the application of remote sensing to LSS calibration, validation and assimilation. Sensitivity of simulated fluxes and state variables to uncertainties in atmospheric forcings, soil, and vegetation parameters will be examined. The ability of simple and intermediate models to replicate the behavior of complex LSSs will be explored, as a tool for better understanding of surface processes. In situ validation of LSSs with data from numerous field campaigns conducted during the 10-year period will also be possible. GSWP2 will also explore promising new data management technologies, including the capability to perform model integration and analysis with distributed data sets, reducing the data management burden on participants. A subsequent continental phase will focus on North America, and will also investigate issues of aggregation (from 1/8 degree to 1 degree).

  9. Catalytic Reduction of CO2 by Renewable Organohydrides.

    PubMed

    Lim, Chern-Hooi; Holder, Aaron M; Hynes, James T; Musgrave, Charles B

    2015-12-17

    Dihydropyridines are renewable organohydride reducing agents for the catalytic reduction of CO2 to MeOH. Here we discuss various aspects of this important reduction. A centerpiece, which illustrates various general principles, is our theoretical catalytic mechanism for CO2 reduction by successive hydride transfers (HTs) and proton transfers (PTs) from the dihydropyridine PyH2 obtained by 1H(+)/1e(-)/1H(+)/1e(-) reductions of pyridine. The Py/PyH2 redox couple is analogous to NADP(+)/NADPH in that both are driven to effect HTs by rearomatization. High-energy radical intermediates and their associated high barriers/overpotentials are avoided because HT involves a 2e(-) reduction. A HT-PT sequence dictates that the reduced intermediates be protonated prior to further reduction for ultimate MeOH formation; these protonations are aided by biased cathodes that significantly lower the local pH. In contrast, cathodes that efficiently reduce H(+) such as Pt and Pd produce H2 and create a high interfacial pH, both obstructing dihydropyridine production and formate protonation and thus ultimately CO2 reduction by HTPTs. The role of water molecule proton relays is discussed. Finally, we suggest future CO2 reduction strategies by organic (photo)catalysts. PMID:26722706

  10. Elucidating dz2 orbital selective catalytic activity in brownmillerite Ca2Mn2O5

    NASA Astrophysics Data System (ADS)

    Lu, Yue; Lu, Feng; Yang, Zhi; Wu, Jie; Yu, Hongyun; Xie, Xinjian; Xu, Jianping; Cheng, Fangyi; Chen, Jun; Xiong, Ka; Liu, Hui; Wang, Wei-Hua; Zhao, Jianzhou; Wang, Weichao

    2016-09-01

    3d-orbital filling in transition metal oxide is crucial to govern the catalytic activity in oxygen evolution reduction, nevertheless, it is not fundamentally accessible why specific orbital occupation produces a highest catalytic performance. Here, we utilize brownmillerite Ca2Mn2O5 to clarify the orbital selective catalytic behavior due to the crystal field splitting and on-site coulomb interactions. Within density functional theory plus dynamical mean field theory, Ca2Mn2O5 shows a paramagnetic Mott insulating behavior at room temperature, consistent with optical adsorption spectra and magnetic susceptibility. As the center of the dz2 orbital locates in the lower Hubbard sub-band, the unit occupation on dz2 orbital provides a moderate bonding with external O* species to cause a high catalytic activity of Ca2Mn2O5 with a square pyramid crystal field. Such concept of unit occupation of dz2 near Fermi level could be extended to other crystal fields for future design of oxide catalysts.

  11. ENHANCED CONTROL OF MERCURY BY WET FLUE GAS DESULFURIZATION SYSTEMS--SITE 2 RESULTS

    SciTech Connect

    G. Blythe; S. Miller; C. Richardson; K. Searcy

    2000-06-01

    The U.S. Department of Energy and EPRI are co-funding this project to improve the control of mercury emissions from coal-fired power plants equipped with wet flue gas desulfurization (FGD) systems. The project is investigating catalytic oxidation of vapor-phase elemental mercury to a form that is more effectively captured in wet FGD systems. If successfully developed, the process could be applicable to over 90,000 MW of utility generating capacity with existing FGD systems, and to future FGD installations. Field tests are being conducted to determine whether candidate catalyst materials remain active towards mercury oxidation after extended flue gas exposure. Catalyst life will have a large impact on the cost effectiveness of this potential process. A mobile catalyst test unit is being used to test the activity of four different catalysts for a period of up to six months at each of three utility sites. Catalyst testing at the first site, which fires Texas lignite, was completed in December 1998. Testing at the second test site, which fires a Powder River Basin subbituminous coal, was completed in the fall of 1999, and testing at the third site, which fires a high-sulfur bituminous coal, will begin in 2000. This technical note reports results from Site 2; results from Site 1 were reported in a previous technical note. At Site 2, catalysts were tested in several forms, including powders dispersed in sand bed reactors and in commercial forms such as extruded beads and coated honeycomb structures. This technical note presents results from Site 2 for both the sand bed reactors and commercial catalyst forms. Field testing is being supported by laboratory tests to screen catalysts for activity at specific flue gas compositions, to investigate catalyst deactivation mechanisms and to investigate methods for regenerating spent catalysts. Laboratory results related to the Site 2 field effort are also included and discussed in this technical note. Preliminary economics, based

  12. ENHANCED CONTROL OF MERCURY BY WET FLUE GAS DESULFURIZATION SYSTEMS--SITE 2 RESULTS

    SciTech Connect

    G. Blythe; S. Miller; C. Richardson; K. Searcy

    2000-02-01

    The U.S. Department of Energy and EPRI are co-funding this project to improve the control of mercury emissions from coal-fired power plants equipped with wet flue gas desulfurization (FGD) systems. The project is investigating catalytic oxidation of vapor-phase elemental mercury to a form that is more effectively captured in wet FGD systems. If successfully developed, the process could be applicable to over 90,000 MW of utility generating capacity with existing FGD systems, and to future FGD installations. Field tests are being conducted to determine whether candidate catalyst materials remain active towards mercury oxidation after extended flue gas exposure. Catalyst life will have a large impact on the cost effectiveness of this potential process. A mobile catalyst test unit is being used to test the activity of four different catalysts for a period of up to six months at each of three utility sites. Catalyst testing at the first site, which fires Texas lignite, was completed in December 1998. Testing at the second test site, which fires a Powder River Basin subbituminous coal, was completed in the fall of 1999, and testing at the third site, which fires a high-sulfur bituminous coal, will begin in early 2000. This technical note reports results from Site 2; results from Site 1 were reported in a previous technical note. At Site 2, catalysts were tested in several forms, including powders dispersed in sand bed reactors and in more commercially viable forms such as extruded beads and coated honeycomb structures. This technical note presents results from Site 2 for both the sand bed reactors and commercial catalyst forms. Site 3 results are not yet available, but should be available late in the year 2000. Field testing is being supported by laboratory tests to screen catalysts for activity at specific flue gas compositions, to investigate catalyst deactivation mechanisms and to investigate methods for regenerating spent catalysts. Laboratory results related to the

  13. Break up of connected non-wetting phase during CO2-brine and N2-water drainage core floods

    NASA Astrophysics Data System (ADS)

    Reynolds, C. A.; Krevor, S. C.

    2014-12-01

    We present evidence of a transition from connected to unconnected non-wetting phase flow during drainage in CO2-brine and N2-water core floods. Connected non-wetting phase flow is controlled by heterogeneity in the pore space, with non-wetting phase pathways developing in regions of lower capillary entry pressure. During unconnected non-wetting phase flow, pore space heterogeneity has no impact on fluid flow paths and relative permeability is controlled by fluid properties such as interfacial tension. The transition is observed through a shift in relative permeability curves, maps of steady state saturation and fluid arrangement during relative permeability measurements, and pore scale observations. The transition can be achieved either by modifying the pressure, temperature and salinity conditions of a core flood to increase the wetting phase viscosity, or by increasing the wetting or non-wetting phase flow rate. We suggest the viscous pressure in the wetting phase has a strong impact on the flow behaviour and fluid arrangement during multiphase flow, even at conditions where the flow is traditionally considered to be capillary dominated. Figure 1. Wetting and non-wetting phase capillary number [1] plotted for 7 CO2-brine and one N2-water core floods at temperatures and pressures of 38-91°C and 10.3-20.7 MPa and brine molalities of 0-5 mol kg-1. Saturation maps at a steady state saturation of Sw = 56 % are shown for connected and disconnected non-wetting phase flow. Non-wetting phase relative permeability changes from low endpoint at high irreducible water saturation during connected flow to a high end point relative permeability and low irreducible water saturation during disconnected non-wetting phase flow. [1] Datta, S. S., J.-B. Dupin, and D. A. Weitz. "Fluid breakup during simultaneous two-phase flow through a three-dimensional porous medium." Physics of Fluids (1994-present) 26.6 (2014).

  14. 40 CFR Table 2 to Subpart Uuu of... - Operating Limits for Metal HAP Emissions From Catalytic Cracking Units

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Emissions From Catalytic Cracking Units 2 Table 2 to Subpart UUU of Part 63 Protection of Environment... Petroleum Refineries: Catalytic Cracking Units, Catalytic Reforming Units, and Sulfur Recovery Units Pt. 63... Catalytic Cracking Units As stated in § 63.1564(a)(2), you shall meet each operating limit in the...

  15. 40 CFR Table 2 to Subpart Uuu of... - Operating Limits for Metal HAP Emissions From Catalytic Cracking Units

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Emissions From Catalytic Cracking Units 2 Table 2 to Subpart UUU of Part 63 Protection of Environment... Petroleum Refineries: Catalytic Cracking Units, Catalytic Reforming Units, and Sulfur Recovery Units Pt. 63... Catalytic Cracking Units As stated in § 63.1564(a)(2), you shall meet each operating limit in the...

  16. Soil CO2 Fluxes Following Wetting Events: Field Observations and Modeling

    NASA Astrophysics Data System (ADS)

    O'Donnell, F. C.; Caylor, K. K.

    2009-12-01

    Carbon exchange data from eddy flux towers in drylands suggest that the Birch Effect, a pulse of soil CO2 efflux triggered by the first rain following a dry period, may contribute significantly to the annual carbon budget of these ecosystems. Laboratory experiments on dryland soils have shown that microbes adapted to live in arid ecosystems may be able to remain dormant in dry soil for much longer than expected and an osmotic shock response to sudden increases in soil water potential may play a role in the Birch Effect. However, little has been done to understand how a dry soil profile responds to a rainfall event. We measured soil CO2 production during experimental wetting events in treatment plots at a site on the Botswana portion of the Kalahari Transect (KT). We buried small, solid-state sensors that continuously measure CO2 concentration in the soil air space at four depths and the soil surface and applied wetting treatments intended to simulate typical rainfall for the region to the plots, including single 10 mm wettings (the mean storm depth for the KT), single 20 mm wettings, and repeated 10 mm wettings. We solved a finite difference approximation of the governing equation for CO2 in the soil airspace to determine the source rate of CO2 during and after the wetting treatments, using Richard’s equation to approximate the change in air-filled porosity due to infiltrating water. The wetting treatments induced a rapid spike in the source rate of CO2 in the soil, the timing and magnitude of which were consistent with laboratory experiments that observed a microbial osmotic shock response. The source rate averaged over the first three hours after wetting showed that a 20 mm wetting produced a larger response than the 10 mm wettings. It also showed that a second wetting event produced a smaller response than the first and though it was not significant, an upward trend in response was apparent through the two month period. These results suggest that there may be

  17. Computational evaluation of factors governing catalytic 2-keto acid decarboxylation.

    PubMed

    Wu, Di; Yue, Dajun; You, Fengqi; Broadbelt, Linda J

    2014-06-01

    Recent advances in computational approaches for creating pathways for novel biochemical reactions has motivated the development of approaches for identifying enzyme-substrate pairs that are attractive candidates for effecting catalysis. We present an improved structural-based strategy to probe and study enzyme-substrate binding based on binding geometry, energy, and molecule characteristics, which allows for in silico screening of structural features that imbue higher catalytic potential with specific substrates. The strategy is demonstrated using 2-keto acid decarboxylation with various pairs of 2-keto acids and enzymes. We show that this approach fitted experimental values for a wide range of 2-keto acid decarboxylases for different 2-keto acid substrates. In addition, we show that the structure-based methods can be used to select specific enzymes that may be promising candidates to catalyze decarboxylation of certain 2-keto acids. The key features and principles of the candidate enzymes evaluated by the strategy can be used to design novel biosynthesis pathways, to guide enzymatic mutation or to guide biomimetic catalyst design.

  18. Capillary Trapping of CO2 in Oil Reservoirs: Observations in a Mixed-Wet Carbonate Rock.

    PubMed

    Al-Menhali, Ali S; Krevor, Samuel

    2016-03-01

    Early deployment of carbon dioxide storage is likely to focus on injection into mature oil reservoirs, most of which occur in carbonate rock units. Observations and modeling have shown how capillary trapping leads to the immobilization of CO2 in saline aquifers, enhancing the security and capacity of storage. There are, however, no observations of trapping in rocks with a mixed-wet-state characteristic of hydrocarbon-bearing carbonate reservoirs. Here, we found that residual trapping of supercritical CO2 in a limestone altered to a mixed-wet state with oil was significantly less than trapping in the unaltered rock. In unaltered samples, the trapping of CO2 and N2 were indistinguishable, with a maximum residual saturation of 24%. After the alteration of the wetting state, the trapping of N2 was reduced, with a maximum residual saturation of 19%. The trapping of CO2 was reduced even further, with a maximum residual saturation of 15%. Best-fit Land-model constants shifted from C = 1.73 in the water-wet rock to C = 2.82 for N2 and C = 4.11 for the CO2 in the mixed-wet rock. The results indicate that plume migration will be less constrained by capillary trapping for CO2 storage projects using oil fields compared with those for saline aquifers.

  19. Residual Supercritical CO2 Saturation in an Oil-wet Sandstone: a Pore-scale Analysis

    NASA Astrophysics Data System (ADS)

    Rahman, T.; Lebedev, M.; Barifcani, A.; Iglauer, S.

    2015-12-01

    Residual supercritical CO2 (scCO2) in an oil-wet Bentheimer sandstone was imaged at high 3D resolution (3.4μm)3 with an x-ray micro-computed tomograph (μCT). The residual saturation measured (SCO2,r = 12%) was significantly lower than in an analogue strongly water-wet plug (SCO2,r = 35%). The residual CO2 was split into many small disconnected clusters, and the cluster size distributions followed a power law correlation, similar to those reported for water-wet rock. However, the CO2 was more frequently located in smaller pores than in the analogue water-wet case. On the μCT images we were able to measure scCO2-water interfacial areas and capillary pressures of each CO2 bubble in-situ. These capillary pressures (Pc) showed a distribution function which ranged from -1 MPa to +1 MPa, and peaked at Pc = 0. This variation in Pc will influence the mass transfer process (of CO2 into water) as it changes the chemical potential; but it is clear that the interfacial areas are large and thus provide a good basis for dissolution trapping. Overall we conclude that oil-wet storage rock has a significantly lower capillary trapping capacity, although we still observed residual CO2 at the pore-scale.

  20. Residual trapping of supercritical CO2 in oil-wet sandstone.

    PubMed

    Rahman, Taufiq; Lebedev, Maxim; Barifcani, Ahmed; Iglauer, Stefan

    2016-05-01

    Residual trapping, a key CO2 geo-storage mechanism during the first decades of a sequestration project, immobilizes micrometre sized CO2 bubbles in the pore network of the rock. This mechanism has been proven to work in clean sandstones and carbonates; however, this mechanism has not been proven for the economically most important storage sites into which CO2 will be initially injected at industrial scale, namely oil reservoirs. The key difference is that oil reservoirs are typically oil-wet or intermediate-wet, and it is clear that associated pore-scale capillary forces are different. And this difference in capillary forces clearly reduces the capillary trapping capacity (residual trapping) as we demonstrate here. For an oil-wet rock (water contact angle θ=130°) residual CO2 saturation SCO2,r (≈8%) was approximately halved when compared to a strongly water-wet rock (θ=0°; SCO2,r≈15%). Consequently, residual trapping is less efficient in oil-wet reservoirs.

  1. 40 CFR Table 2 to Subpart Eeee of... - Operating Limits for Incinerators and Wet Scrubbers

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 7 2014-07-01 2014-07-01 false Operating Limits for Incinerators and Wet Scrubbers 2 Table 2 to Subpart EEEE of Part 60 Protection of Environment ENVIRONMENTAL PROTECTION..., Subpt. EEEE, Table 2 Table 2 to Subpart EEEE of Part 60—Operating Limits for Incinerators and...

  2. 40 CFR Table 2 to Subpart Eeee of... - Operating Limits for Incinerators and Wet Scrubbers

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Operating Limits for Incinerators and Wet Scrubbers 2 Table 2 to Subpart EEEE of Part 60 Protection of Environment ENVIRONMENTAL PROTECTION..., Subpt. EEEE, Table 2 Table 2 to Subpart EEEE of Part 60—Operating Limits for Incinerators and...

  3. 40 CFR Table 2 to Subpart Eeee of... - Operating Limits for Incinerators and Wet Scrubbers

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 7 2013-07-01 2013-07-01 false Operating Limits for Incinerators and Wet Scrubbers 2 Table 2 to Subpart EEEE of Part 60 Protection of Environment ENVIRONMENTAL PROTECTION..., Subpt. EEEE, Table 2 Table 2 to Subpart EEEE of Part 60—Operating Limits for Incinerators and...

  4. 40 CFR Table 2 to Subpart Eeee of... - Operating Limits for Incinerators and Wet Scrubbers

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 7 2012-07-01 2012-07-01 false Operating Limits for Incinerators and Wet Scrubbers 2 Table 2 to Subpart EEEE of Part 60 Protection of Environment ENVIRONMENTAL PROTECTION..., Subpt. EEEE, Table 2 Table 2 to Subpart EEEE of Part 60—Operating Limits for Incinerators and...

  5. Catalytic Decomposition of 2,3-Dihydrobenzofuran to Monocyclic Compounds Over Palladium Catalysts Supported on Sulfonated Ordered Mesoporous Carbon.

    PubMed

    Kim, Jeong Kwon; Park, Hai Woong; Hong, Ung Gi; Lee, Yoon Jae; Song, In Kyu

    2015-11-01

    Ordered mesoporous carbon (OMC) was sulfonated at different temperature (OMC-SO3H-X, X = 125, 150, 175, 200, and 225 degrees C) in order to provide acid sites to OMC. Palladium catalysts were then supported on OMC-SO3H-X by an incipient wetness impregnation method for use in the catalytic decomposition of 2,3-dihydrobenzofuran to monocyclic compounds. 2,3-Dihydrobenzofuran was used as a lignin model compound for representing β-5 linkage of lignin. In the catalytic decomposition of 2,3-dihydrobenzofuran over Pd/OMC-SO3H-X, ethylcyclohexane and 2-ethlyphenol were mainly produced. Conversion of 2,3-dihydrobenzofuran and total yield for main products (ethylcyclohexane and 2-ethylphenol) were closely related to the acidity of the catalysts. Conversion of 2,3-dihydrobenzofuran and total. yield for main products increased with increasing acidity of Pd/OMC-SO3H-X catalysts. Among the catalysts tested, Pd/OMC-SO3H-150 with the largest acidity showed the highest conversion of 2,3-dihydrobenzofuran and the highest total yield for main products. PMID:26726658

  6. 40 CFR Table 2 to Subpart Cccc of... - Operating Limits for Wet Scrubbers

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Table 2 to Subpart CCCC of Part 60 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED..., Subpt. CCCC, Table 2 Table 2 to Subpart CCCC of Part 60—Operating Limits for Wet Scrubbers For these operatingparameters You must establish these operating limits And monitoring using these minimum frequencies...

  7. Catalytic performance of Fe3O4-CoO/Al2O3 catalyst in ozonation of 2-(2,4-dichlorophenoxy)propionic acid, nitrobenzene and oxalic acid in water.

    PubMed

    Tong, Shaoping; Shi, Rui; Zhang, Hua; Ma, Chunan

    2010-01-01

    Fe3O4-CoO/Al2O3 catalyst was prepared by incipient wetness impregnation using Fe(NO3)3 x 9H2O and Co(NO3)2 x 6H2O as the precursors, and its catalytic performance was investigated in ozonation of 2-(2,4-dichlorophenoxy)propionic acid (2,4-DP), nitrobenzene and oxalic acid. The experimental results indicated that Fe3O4-CoO/Al2O3 catalyst enabled an interesting improvement of ozonation efficiency during the degradation of each organic pollutant, and the Fe3O4-CoO/Al2O3 catalytic ozonation system followed a radical-type mechanism. The kinetics of ozonation alone and Fe3O4-CoO/Al2O3 catalytic ozonation of three organic pollutants in aqueous solution were discussed under the mere consideration of direct ozone reaction and OH radical reaction to well investigate its performance. In the catalytic ozonation of 2,4-DP, the apparent reaction rate constants (k) were determined to be 1.456 x 10(-2) min(-1) for ozonation alone and 4.740 x 10(-2) min(-1) for O3/Fe3O4-CoO/Al203. And O3/Fe3O4-CoO/Al2O3 had a larger R(ct) (6.614 x 10(-9)) calculated by the relative method than O3 did (1.800 x 10(-9)), showing O3/Fe3O4-CoO/Al2O3 generated more hydroxyl radical. Similar results were also obtained in the catalytic ozonation of nitrobenzene and oxalic acid. The above results demonstrated that the catalytic performance of Fe3O4-CoO/Al2O3 in ozonation of studied organic substance was universal to a certain degree. PMID:21235195

  8. Conducting On-orbit Gene Expression Analysis on ISS: WetLab-2

    NASA Technical Reports Server (NTRS)

    Parra, Macarena; Almeida, Eduardo; Boone, Travis; Jung, Jimmy; Lera, Matthew P.; Ricco, Antonio; Souza, Kenneth; Wu, Diana; Richey, C. Scott

    2013-01-01

    WetLab-2 will enable expanded genomic research on orbit by developing tools that support in situ sample collection, processing, and analysis on ISS. This capability will reduce the time-to-results for investigators and define new pathways for discovery on the ISS National Lab. The primary objective is to develop a research platform on ISS that will facilitate real-time quantitative gene expression analysis of biological samples collected on orbit. WetLab-2 will be capable of processing multiple sample types ranging from microbial cultures to animal tissues dissected on orbit. WetLab-2 will significantly expand the analytical capabilities onboard ISS and enhance science return from ISS.

  9. Effect of core-shell structure and chitosan addition on catalytic activities of copper-containing silica-aluminosilicate composites in deNO(x) reaction by H2.

    PubMed

    Chamnankid, Busaya; Samanpratan, Rattanaporn; Kongkachuichay, Paisan

    2012-12-01

    Mesoporous silica-aluminosilicate composites were used as supports for selective catalytic reduction of NO by H2 using copper catalyst. Effect of loading techniques and structures of the supports on the catalytic performance were investigated. The nature, the oxidation state of copper, the structural properties and the morphology of the catalysts were characterized by means of UV-vis spectra, Fourier Transform Infrared Spectroscopy (FTIR), nitrogen sorption, and transmission electron microscopy, respectively. By using substitution technique, the copper(II) species were introduced into the silica-aluminosilicate framework by replacing aluminum atoms that located in the tetrahedral coordination. On the other hand, by using incipient wetness impregnation method, the copper species were deposited on the surface of composite materials. Upon testing their performances in deNO(x) reaction, the catalysts prepared by incipient wetness impregnation method showed higher catalytic activity than those prepared by substitution technique in any copper content. The core-shell structure was able to enhance the catalytic performance. It was found that, among the tested catalysts, the 1.5% Cu loaded core-shell mesoporous silica aluminosilicate composites prepared by an incipient wetness impregnation yielded the highest NO conversion of approximately 59%. However, the addition of chitosan creating macroporosity and controlling the uniform small clusters did not improve the catalytic performance. PMID:23447996

  10. Wet foams hydrophobized by amphiphiles to give Al2O3 porous ceramics

    NASA Astrophysics Data System (ADS)

    Pokhrel, Ashish; Park, Jung Gyu; Kim, Ik Jin

    2012-05-01

    Wet chemical method to prepare ceramic foams with antecedent stability using inorganic particles (Al2O3,SiO2 etc.) which are in situ hydrophobized upon adsorption of short-chain amphiphilic molecules in the wet state and heightened mechanical property in the sintered state was developed. These wet foams are stable over several days and show no bubble coarsening nor drainage or creaming. This long-term stability is achieved through the irreversible adsorption of partially hydrophobized colloidal particles to the air-water interface using short-chain amphiphiles to in situ modify the wetting behavior of the particle surface based on the observations of Pickering emulsions. As a result, the suspension is foamed homogeneously throughout its entire volume and porous bulk materials can be produced upon drying and sintering. Wet foams featuring average bubble sizes between 30 and 300μm and sintered foams with porosity from 50 to 85% were obtained by adjusting the amphiphile - particle concentration, and additives in the initial suspension. Cells were mostly closed with an average size of approximately 150 μm. Single cells were separated by walls with minimum thicknesses of 1-3 μm.

  11. [Catalytic degradation of naphthalene by CuO (-CeO2)/Al2O3].

    PubMed

    Zha, Jian; Zhou, Hong-Cang; He, Du-Liang; Shan, Long; Zhang, Lu; Xie, Jie

    2014-10-01

    Three catalysts CuO/Al2O3, CeO2/Al2O3 and CuO-CeO2/Al2O3 were prepared by the impregnation method. The textural and structural properties of the synthesized catalysts were characterized by N2 adsorption/desorption, SEM and XRD, and the effect of active ingredients, flow rate and reaction temperature on catalytic degradation of naphthalene (NaP) were investigated in fixed-bed reactor. The experimental results show that the prepared 18% CeO2/Al2O3 has a low catalytic activity of NaP. Nevertheless, both 18% CuO/Al2O3 and 9% CuO-9% CeO2/Al2O3 exhibit high catalytic activity whose removal efficiencies at 300°C can reach 91% and 89%, respectively. Besides, compared with CuO/Al2O3, CuO-CeO2/Al2O3 possesses a higher low-temperature activity. Furthermore, the variation of flow rates has little effect on the performance of two catalysts.

  12. [Catalytic degradation of naphthalene by CuO (-CeO2)/Al2O3].

    PubMed

    Zha, Jian; Zhou, Hong-Cang; He, Du-Liang; Shan, Long; Zhang, Lu; Xie, Jie

    2014-10-01

    Three catalysts CuO/Al2O3, CeO2/Al2O3 and CuO-CeO2/Al2O3 were prepared by the impregnation method. The textural and structural properties of the synthesized catalysts were characterized by N2 adsorption/desorption, SEM and XRD, and the effect of active ingredients, flow rate and reaction temperature on catalytic degradation of naphthalene (NaP) were investigated in fixed-bed reactor. The experimental results show that the prepared 18% CeO2/Al2O3 has a low catalytic activity of NaP. Nevertheless, both 18% CuO/Al2O3 and 9% CuO-9% CeO2/Al2O3 exhibit high catalytic activity whose removal efficiencies at 300°C can reach 91% and 89%, respectively. Besides, compared with CuO/Al2O3, CuO-CeO2/Al2O3 possesses a higher low-temperature activity. Furthermore, the variation of flow rates has little effect on the performance of two catalysts. PMID:25693411

  13. [Wet work].

    PubMed

    Kieć-Swierczyńska, Marta; Chomiczewska, Dorota; Krecisz, Beata

    2010-01-01

    Wet work is one of the most important risk factors of occupational skin diseases. Exposure of hands to the wet environment for more than 2 hours daily, wearing moisture-proof protective gloves for a corresponding period of time or necessity to wash hands frequently lead to the disruption of epidermal stratum corneum, damage to skin barrier function and induction of irritant contact dermatitis. It may also promote penetration of allergens into the skin and increase the risk of sensitization to occupational allergens. Exposure to wet work plays a significant role in occupations, such as hairdressers and barbers, nurses and other health care workers, cleaning staff, food handlers and metalworkers. It is more common among women because many occupations involving wet work are female-dominated. The incidence of wet-work-induced occupational skin diseases can be reduced by taking appropriate preventive measures. These include identification of high-risk groups, education of workers, organization of work enabling to minimize the exposure to wet work, use of personal protective equipment and skin care after work.

  14. Electrogeneration of H(2) for Pd-catalytic hydrodechlorination of 2,4-dichlorophenol in groundwater.

    PubMed

    Zheng, Mingming; Bao, Jianguo; Liao, Peng; Wang, Kun; Yuan, Songhu; Tong, Man; Long, Huayun

    2012-06-01

    A novel electrolytic groundwater remediation process, which used the H(2) continuously generated at cathode to achieve in situ catalytic hydrodechlorination, was developed for the treatment of 2,4-dichlorophenol (2,4-DCP) in groundwater. Catalytic hydrodechlorination using Pd supported on bamboo charcoal and external H(2) showed that 2,4-DCP was completely dechlorinated to phenol within 30 min at pH ≤ 5.5. In a divided electrolytic system, the catalytic hydrodechlorination of 2,4-DCP in cathodic compartment by H(2) generated at the cathode under 20 and 50 mA reached 100% at 120 and 60 min, respectively. Two column experiments with influent pHs of 5.5 (unconditioned) and 2 were conducted to evaluate the feasibility of this process. The 2,4-DCP removal efficiencies were about 63% and nearly 100% at influent pHs of 5.5 and 2, respectively. Phenol was solely produced by 2,4-DCP hydrodechlorination, and was subsequently degraded at the anode. A low pH could enhance the hydrodechlorination, but was not necessarily required. This study provides the preliminary results of a novel effective electrolytic process for the remediation of groundwater contaminated by chlorinated aromatics.

  15. Synthesis and visible-light-induced catalytic activity of Ag2S-coupled TiO2 nanoparticles and nanowires

    NASA Astrophysics Data System (ADS)

    Xie, Yi; Heo, Sung Hwan; Kim, Yong Nam; Yoo, Seung Hwa; Cho, Sung Oh

    2010-01-01

    We present the synthesis and visible-light-induced catalytic activity of Ag2S-coupled TiO2 nanoparticles (NPs) and TiO2 nanowires (NWs). Through a simple wet chemical process from a mixture of peroxo titanic acid (PTA) solution, thiourea and AgAc, a composite of Ag2S NPs and TiO2 NPs with sizes of less than 7 nm was formed. When the NP composite was further treated with NaOH solution followed by annealing at ambient conditions, a new nanocomposite material comprising Ag2S NPs on TiO2 NWs was created. Due to the coupling with such a low bandgap material as Ag2S, the TiO2 nanocomposites could have a visible-light absorption capability much higher than that of pure TiO2. As a result, the synthesized Ag2S/TiO2 nanocomposites exhibited much higher catalytic efficiency for the decomposition of methyl orange than commercial TiO2 (Degussa P25, Germany) under visible light.

  16. Catalytic [3 + 2] Cycloaddition through Ring Cleavage of Simple Cyclopropanes with Isocyanates.

    PubMed

    Tsunoi, Shinji; Maruoka, Yoshiaki; Suzuki, Itaru; Shibata, Ikuya

    2015-08-21

    The catalytic synthesis of γ-butyrolactams was established via [3 + 2]-cycloaddition of cyclopropanes with isocyanates. An organotin iodide ate complex, MgBr(+)[Bu2SnBrI2](-), was employed as an effective catalyst. Simple cyclopropanes that lack aryl or vinyl substituents were useful precursors. Even acyl cyclopropanes were applicable. The hybrid characteristics of a tin complex, acidic MgBr(+) with nucleophilic tin iodide, was responsible for the catalytic reaction.

  17. Catalytic [3 + 2] Cycloaddition through Ring Cleavage of Simple Cyclopropanes with Isocyanates.

    PubMed

    Tsunoi, Shinji; Maruoka, Yoshiaki; Suzuki, Itaru; Shibata, Ikuya

    2015-08-21

    The catalytic synthesis of γ-butyrolactams was established via [3 + 2]-cycloaddition of cyclopropanes with isocyanates. An organotin iodide ate complex, MgBr(+)[Bu2SnBrI2](-), was employed as an effective catalyst. Simple cyclopropanes that lack aryl or vinyl substituents were useful precursors. Even acyl cyclopropanes were applicable. The hybrid characteristics of a tin complex, acidic MgBr(+) with nucleophilic tin iodide, was responsible for the catalytic reaction. PMID:26247349

  18. Effect of calcination method on the product distribution from catalytic degradation of polystyrene in the presence of 1% Pd/Al2O3 catalysts

    NASA Astrophysics Data System (ADS)

    Ramli, Anita; Kun, Lim Sheo; Kait, Chong Fai; Yahya, Noorhana; Daud, Hanita

    2012-11-01

    Incipient wetness impregnation method was used to prepare 1% Pd/Al2O3 catalyst which was calcined at 500 °C for 16 hr as well as in a domestic microwave at 650W for 5 and 10 min. These catalysts were tested in the catalytic degradation of polystyrene (PS) into liquid fuels at catalyst to PS ratio of 0.2 (w/w). The organic liquid product (OLP) collected was analysed using Gas Chromatography (GC). Results show that the conventional calcined catalyst gives petrol as the main product while kerosene was the main product for the microwave calcined catalysts.

  19. Designing Catalytic Monoliths For Closed-Cycle CO2 Lasers

    NASA Technical Reports Server (NTRS)

    Guinn, Keith; Herz, Richard K.; Goldblum, Seth; Noskowski, ED

    1992-01-01

    LASCAT (Design of Catalytic Monoliths for Closed-Cycle Carbon Dioxide Lasers) computer program aids in design of catalyst in monolith by simulating effects of design decisions on performance of laser. Provides opportunity for designer to explore tradeoffs among activity and dimensions of catalyst, dimensions of monolith, pressure drop caused by flow of gas through monolith, conversion of oxygen, and other variables. Written in FORTRAN 77.

  20. Catalytic decomposition of N2O on ordered crystalline metal oxides.

    PubMed

    Ma, Zhen; Ren, Yu; Lu, Yanbin; Bruce, Peter G

    2013-07-01

    The synthesis of mesoporous metal oxides using mesoporous silicas or carbons as hard templates has attracted growing interest recently, but the catalytic application of mesoporous metal oxides has not been studied sufficiently. In addition, few publications have compared the catalytic performance of a series of mesoporous metal oxides in the same reaction, and little is known about the influence of preparation details of mesoporous metal oxides on catalytic activity. Herein, ordered crystalline mesoporous metal oxides (i.e., CeO2, Co3O4, Cr2O3, CuO, alpha-Fe2O3, beta-MnO2, Mn2O3, Mn3O4, NiO) prepared using mesoporous SiO2 (KIT-6) as a hard template were tested in the decomposition of N2O, an environmental pollutant, and the catalytic performance was compared with that of commercial metal oxides with low surface areas. In particular, mesoporous Co3O4, beta-MnO2, and NiO showed high N2O conversions at 350 degrees C. The influence of preparation parameters of mesoporous Co3O4 on catalytic activity was then studied in more detail. Mesoporous Co3O4 samples with different pore sizes and wall thicknesses were prepared using KIT-6 synthesized under different hydrothermal or calcination temperatures. Interestingly, the catalytic activities of different mesoporous Co3O4 samples were found to be influenced by these preparation details. PMID:23901535

  1. Catalytic performance of carbon nanotubes in H2O2 decomposition: experimental and quantum chemical study.

    PubMed

    Voitko, Katerina; Tóth, Ajna; Demianenko, Evgenij; Dobos, Gábor; Berke, Barbara; Bakalinska, Olga; Grebenyuk, Anatolij; Tombácz, Etelka; Kuts, Volodymyr; Tarasenko, Yurij; Kartel, Mykola; László, Krisztina

    2015-01-01

    The catalytic performance of multi-walled carbon nanotubes (MWCNTs) with different surface chemistry was studied in the decomposition reaction of H2O2 at various values of pH and temperature. A comparative analysis of experimental and quantum chemical calculation results is given. It has been shown that both the lowest calculated activation energy (∼18.9 kJ/mol) and the highest rate constant correspond to the N-containing CNT. The calculated chemisorption energy values correlate with the operation stability of MWCNTs. Based on the proposed quantum chemical model it was found that the catalytic activity of carbon materials in electron transfer reactions is controlled by their electron donor capability.

  2. Efficient catalytic decomposition of CO2 to CO and O2 over Pd/ mixed-conducting oxide catalyst in an oxygen-permeable membrane reactor.

    PubMed

    Jin, Wanqin; Zhang, Chun; Chang, Xianfeng; Fan, Yiqun; Xing, Weihong; Xu, Nanping

    2008-04-15

    The thermal decomposition of CO2 to CO and O2 is a potential route for the consumption and utilization of CO2. However, this reaction is limited by both the thermodynamic equilibrium and the kinetic barrier. In this study, we reported an innovative catalytic process to decompose CO2 in an oxygen-permeation membrane reactor packed with a mixed-conducting oxide supported noble metal catalyst, or Pd/SrCo0.4Fe0.5Zr0.1O3-delta (Pd/ SCFZ), which is of high activity in the decomposition of CO2 into CO and O2. Pd/SCFZ catalyst was prepared by incipient wetness impregnation of the SCFZ powders with an aqueous solution of PdCl2, and the CO2 sorption/desorption property was examined by in situ Fourier transform infrared spectroscopy and temperature-programmed desorption-mass spectrometry technologies. It was shown that there appeared a typical of bridged carbonyls (Pd-CO) on the surface of the Pd/SCFZ catalyst formed after CO2 decomposition. Both CO2 and CO could be detected in the species desorbed from Pd/SCFZ catalyst, which implied that the Pd/SCFZ catalyst could effectively activate the CO2 molecule. During the catalytic process, furthermore, the activity of the Pd/SCFZ catalyst can self-regenerate by removing the produced lattice oxygen through the dense oxygen-permeable ceramic membrane. At 900 degrees C, this catalytic process attains 100% of CO formation selectivity at 15.8% of CO2 conversions. PMID:18497167

  3. [Experiment study on the aqueous removal of SO2 by Mn2+ catalytic ozonation].

    PubMed

    Ma, Shuang-Chen; Su, Min; Ma, Jing-Xiang; Sun, Yun-Xue; Jin, Xin; Zhao, Yi

    2009-11-01

    The removal of SO2 by Mn2+ catalytic aqueous ozonation was investigated by experiment, so as to find the effects of Mn2+ for aqueous removal of SO2 by ozonation. The concentration curve of ozone was drawn by standard iodine method. The operating factors included mole ratio of ozone to sulfur dioxide and concentration of Mn2+. When absorption solution has no Mn2+, the removal efficiency of SO2 was 35% at [O3 ]/[SO2 ] = 0.5,but the efficiency was 70% when Mn2+ was put into absorption solution at the same value of [O3 ]/[SO2].With the increasing of [3O]/[SO2], the removal efficiency of SO2 increases. And as concentration of Mn2+ increases, the efficiency also increases. There is an appropriate concentration range which is 1.2 x 10(-2)-1.2 x 10(-1) mol/L for Mn2+.

  4. Catalytic nanoreactors in continuous flow: hydrogenation inside single-walled carbon nanotubes using supercritical CO2.

    PubMed

    Chamberlain, Thomas W; Earley, James H; Anderson, Daniel P; Khlobystov, Andrei N; Bourne, Richard A

    2014-05-25

    One nanometre wide carbon nanoreactors are utilised as the reaction vessel for catalytic chemical reactions on a preparative scale. Sub-nanometre ruthenium catalytic particles which are encapsulated solely within single-walled carbon nanotubes offering a unique reaction environment are shown to be active when embedded in a supercritical CO2 continuous flow reactor. A range of hydrogenation reactions were tested and the catalyst displayed excellent stability over extended reaction times.

  5. Fabrication development and preliminary characterization of Li 2TiO 3 pebbles by wet process

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Kunihiko; Kawamura, Hiroshi; Fuchinoue, Katsuhiro; Sawada, Hiroshi; Watarumi, Kazutoshi

    1998-10-01

    Lithium titanate (Li 2TiO 3) has attracted attention of many researchers because of easy tritium recovery at low temperature, high chemical stability, etc. The application of small Li 2TiO 3 spheres has been proposed in some designs of fusion blanket. Although, the wet process and sol-gel method are the most advantageous as a fabrication method of Li 2TiO 3 pebbles from points of mass production, and of reprocessing necessary for effective use of resources and reduction of radioactive wastes. However, the fabrication of Li 2TiO 3 pebbles by the wet process has not been established. Therefore, in this study, fabrication development and preliminary characterization of Li 2TiO 3 pebbles by the wet process were performed, noting the aging and sintering conditions in the fabrication process of gel-spheres. At the best condition, Li 2TiO 3 pebbles with the target density of 80-85%T.D. were obtained.

  6. Effects of Particle Size on the Gas Sensitivity and Catalytic Activity of In2O3

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoshui; Gu, Ruiqin; Zhao, Jinling; Jin, Guixin; Zhao, Mengke; Xue, Yongliang

    2015-10-01

    Nanosized In2O3 powders with different particle sizes were prepared by the microemulsion synthetic method. The effects of particle size on the gas-sensing and catalytic properties of the as-prepared In2O3 were investigated. Reductions in particle size to nanometer levels improved the sensitivity and catalytic activity of In2O3 to i-C4H10 and C2H5OH. The sensitivity of nanosized In2O3 (<42 nm) sensors to i-C4H10, H2 and C2H5OH was 2-4 times higher than that of chemically precipitated In2O3 (130 nm) sensor. A nearly linear relationship was observed between the catalytic activity and specific surface area of In2O3 for the oxidation of i-C4H10 and C2H5OH at 275 °C. The relationship between gas sensitivity and catalytic activity was further discussed. The results of this work reveal that catalytic activity plays a key role in enhancing the sensitivity of gas-sensing materials.

  7. The catalytic role of the M2 metal ion in PP2Cα.

    PubMed

    Pan, Chang; Tang, Jun-yi; Xu, Yun-fei; Xiao, Peng; Liu, Hong-da; Wang, Hao-an; Wang, Wen-bo; Meng, Fan-guo; Yu, Xiao; Sun, Jin-peng

    2015-01-01

    PP2C family phosphatases (the type 2C family of protein phosphatases; or metal-dependent phosphatase, PPM) constitute an important class of signaling enzymes that regulate many fundamental life activities. All PP2C family members have a conserved binuclear metal ion active center that is essential for their catalysis. However, the catalytic role of each metal ion during catalysis remains elusive. In this study, we discovered that mutations in the structurally buried D38 residue of PP2Cα (PPM1A) redefined the water-mediated hydrogen network in the active site and selectively disrupted M2 metal ion binding. Using the D38A and D38K mutations of PP2Cα as specific tools in combination with enzymology analysis, our results demonstrated that the M2 metal ion determines the rate-limiting step of substrate hydrolysis, participates in dianion substrate binding and stabilizes the leaving group after P-O bond cleavage. The newly characterized catalytic role of the M2 metal ion in this family not only provides insight into how the binuclear metal centers of the PP2C phosphatases are organized for efficient catalysis but also helps increase our understanding of the function and substrate specificity of PP2C family members. PMID:25708299

  8. The catalytic role of the M2 metal ion in PP2

    NASA Astrophysics Data System (ADS)

    Pan, Chang; Tang, Jun-Yi; Xu, Yun-Fei; Xiao, Peng; Liu, Hong-Da; Wang, Hao-An; Wang, Wen-Bo; Meng, Fan-Guo; Yu, Xiao; Sun, Jin-Peng

    2015-02-01

    PP2C family phosphatases (the type 2C family of protein phosphatases; or metal-dependent phosphatase, PPM) constitute an important class of signaling enzymes that regulate many fundamental life activities. All PP2C family members have a conserved binuclear metal ion active center that is essential for their catalysis. However, the catalytic role of each metal ion during catalysis remains elusive. In this study, we discovered that mutations in the structurally buried D38 residue of PP2Cα (PPM1A) redefined the water-mediated hydrogen network in the active site and selectively disrupted M2 metal ion binding. Using the D38A and D38K mutations of PP2Cα as specific tools in combination with enzymology analysis, our results demonstrated that the M2 metal ion determines the rate-limiting step of substrate hydrolysis, participates in dianion substrate binding and stabilizes the leaving group after P-O bond cleavage. The newly characterized catalytic role of the M2 metal ion in this family not only provides insight into how the binuclear metal centers of the PP2C phosphatases are organized for efficient catalysis but also helps increase our understanding of the function and substrate specificity of PP2C family members.

  9. Photocatalytic and thermal catalytic oxidation of acetaldehyde on Pt/TiO{sub 2}

    SciTech Connect

    Falconer, J.L.; Magrini-Bair, K.A.

    1998-10-01

    Low concentrations of acetaldehyde in air (60 ppm) were oxidized over TiO{sub 2} (Degussa P25) and 0.5% Pt/TiO{sub 2} catalysts from 24 to 200 C by photocatalytic and thermal catalytic reactions. On Pt/TiO{sub 2}, the contribution by photocatalytic oxidation (PCO) is a maximum at 140 C, where conversion is 2.8 times that at 24 C. Titania without Pt deactivates rapidly during PCO at elevated temperature due to a thermal catalytic reaction that takes place in parallel with PCO, but the addition of Pt dramatically slows deactivation. Apparently, Pt supplies spillover oxygen onto the TiO{sub 2}, and the oxygen oxidizes the acetaldehyde decomposition products in a dark reaction. Deactivated TiO{sub 2} without Pt was regenerated by PCO at room temperature. Seven distinct reactions (photocatalytic and thermal catalytic) are identified on Pt/TiO{sub 2}.

  10. Enhanced NO{sub x} removal in wet scrubbers using metal chelates. Final report, Volume 2

    SciTech Connect

    1992-12-01

    Successful pilot plant tests of simultaneous removal of SO{sub 2} and NO{sub x} in a wet lime flue gas desulfurization system were concluded in December. The test, at up to 1.5 MW(e) capacity, were conducted by the Cincinnati Gas and Electric Company and Dravo Lime Company for the US Department of Energy at a pilot plant facility at the Miami Fort station of CG&E near Cincinnati, Ohio. The pilot plant scrubbed a slipstream of flue gas from Unit 7 a 530 MW coal-fired electric generating unit. Tests were conducted in three phases between April and December. The technology tested was wet scrubbing with Thiosorbic{reg_sign} magnesium-enhanced lime for SO{sub 2} removal and simultaneous NO scrubbing with ferrous EDTA, a metal chelate. Magnesium-enhanced lime-based wet scrubbing is used at 20 full-scale high-sulfur coal-fired electric generating units with a combined capacity of 8500 MW. Ferrous EDTA reacts with nitric oxide, NO, which comprises about 96% of NO{sub x} from coal-fired boilers. In this report, although not precise, NO and NO{sub x} are used interchangeably. A major objective of the tests was to combine NO{sub x} removal using ferrous EDTA, a developing technology, with SO{sub 2} removal using wet lime FGD, already in wide commercial use. If successful, this could allow wide application of this NO{sub x} removal technology. Volume 2 covers: description and results of NO{sub x} removal tests; and description and results of waste characterization studies.

  11. Theoretical models of catalytic domains of protein phosphatases 1 and 2A with Zn2+ and Mn2+ metal dications and putative bioligands in their catalytic centers.

    PubMed

    Woźniak-Celmer, E; Ołdziej, S; Ciarkowski, J

    2001-01-01

    The oligomeric metalloenzymes protein phosphatases dephosphorylate OH groups of Ser/Thr or Tyr residues of proteins whose actions depend on the phosphorus signal. The catalytic units of Ser/Thr protein phosphatases 1, 2A and 2B (PP1c, PP2Ac and PP2Bc, respectively), which exhibit about 45% sequence similarity, have their active centers practically identical. This feature strongly suggests that the unknown structure of PP2Ac could be successfully homology-modeled from the known structures of PP1c and/or PP2Bc. Initially, a theoretical model of PP1c was built, including a phosphate and a metal dication in its catalytic site. The latter was modeled, together with a structural hydroxyl anion, as a triangular pseudo-molecule (Zno or Mno), composed of two metal cations (double Zn2+ or Mn2+, respectively) and the OH- group. To the free PP1c two inhibitor sequences R29RRRPpTPAMLFR40 of DARPP-32 and R30RRRPpTPATLVLT42 of Inhibitor-1, and two putative substrate sequences LRRApSVA and QRRQRKpRRTI were subsequently docked. In the next step, a free PP2Ac model was built via homology re-modeling of the PP1c template and the same four sequences were docked to it. Thus, together, 20 starting model complexes were built, allowing for combination of the Zno and Mno pseudo-molecules, free enzymes and the peptide ligands docked in the catalytic sites of PP1c and PP2Ac. All models were subsequently subjected to 250-300 ps molecular dynamics using the AMBER 5.0 program. The equilibrated trajectories of the final 50 ps were taken for further analyses. The theoretical models of PP1c complexes, irrespective of the dication type, exhibited increased mobilities in the following residue ranges: 195-200, 273-278, 287-209 for the inhibitor sequences and 21-25, 194-200, 222-227, 261, 299-302 for the substrate sequences. Paradoxically, the analogous PP2Ac models appeared much more stable in similar simulations, since only their "prosegment" residues 6-10 and 14-18 exhibited an increased mobility

  12. [Selective catalytic oxidation of H2S over supported Fe catalysts on CeO2-intercalated laponite clay].

    PubMed

    Sun, Chao; Zhang, Xin; Hao, Zheng-Ping; Dou, Guang-Yu; Sun, Chun-Bao

    2014-05-01

    A series of Fe/CeO2-intercalated clay catalysts were synthesized successfully, the physicochemical properties of the catalysts were characterized by XRD, BET, XRF, TG, FT-IR, O2-TPD, H2-TPR and XPS methods. The catalytic performances for selective catalytic oxidation of H2S were further investigated, all catalysts exhibited high catalytic activities. Among them 5% Fe/Ce-Lap presented the best activity at 180 degreeC and the maximum sulfur yield was up to 96% due to the interaction between iron and cerium, which improved the redox ability of Fe3+ . Moreover, the strong oxygen adsorption capacity and the well dispersion of iron species improved the catalytic performance efficiently.

  13. Pore Scale Observations of Trapped CO2 in Mixed-Wet Carbonate Rock: Applications to Storage in Oil Fields.

    PubMed

    Al-Menhali, Ali S; Menke, Hannah P; Blunt, Martin J; Krevor, Samuel C

    2016-09-20

    Geologic CO2 storage has been identified as a key to avoiding dangerous climate change. Storage in oil reservoirs dominates the portfolio of existing projects due to favorable economics. However, in an earlier related work ( Al-Menhali and Krevor Environ. Sci. Technol. 2016 , 50 , 2727 - 2734 ) , it was identified that an important trapping mechanism, residual trapping, is weakened in rocks with a mixed wetting state typical of oil reservoirs. We investigated the physical basis of this weakened trapping using pore scale observations of supercritical CO2 in mixed-wet carbonates. The wetting alteration induced by oil provided CO2-wet surfaces that served as conduits to flow. In situ measurements of contact angles showed that CO2 varied from nonwetting to wetting throughout the pore space, with contact angles ranging 25° < θ < 127°; in contrast, an inert gas, N2, was nonwetting with a smaller range of contact angle 24° < θ < 68°. Observations of trapped ganglia morphology showed that this wettability allowed CO2 to create large, connected, ganglia by inhabiting small pores in mixed-wet rocks. The connected ganglia persisted after three pore volumes of brine injection, facilitating the desaturation that leads to decreased trapping relative to water-wet systems.

  14. Pore Scale Observations of Trapped CO2 in Mixed-Wet Carbonate Rock: Applications to Storage in Oil Fields.

    PubMed

    Al-Menhali, Ali S; Menke, Hannah P; Blunt, Martin J; Krevor, Samuel C

    2016-09-20

    Geologic CO2 storage has been identified as a key to avoiding dangerous climate change. Storage in oil reservoirs dominates the portfolio of existing projects due to favorable economics. However, in an earlier related work ( Al-Menhali and Krevor Environ. Sci. Technol. 2016 , 50 , 2727 - 2734 ) , it was identified that an important trapping mechanism, residual trapping, is weakened in rocks with a mixed wetting state typical of oil reservoirs. We investigated the physical basis of this weakened trapping using pore scale observations of supercritical CO2 in mixed-wet carbonates. The wetting alteration induced by oil provided CO2-wet surfaces that served as conduits to flow. In situ measurements of contact angles showed that CO2 varied from nonwetting to wetting throughout the pore space, with contact angles ranging 25° < θ < 127°; in contrast, an inert gas, N2, was nonwetting with a smaller range of contact angle 24° < θ < 68°. Observations of trapped ganglia morphology showed that this wettability allowed CO2 to create large, connected, ganglia by inhabiting small pores in mixed-wet rocks. The connected ganglia persisted after three pore volumes of brine injection, facilitating the desaturation that leads to decreased trapping relative to water-wet systems. PMID:27533473

  15. Ag–Fe2O3 nanocomposites with enhanced catalytic activity for reduction of 4-nitrophenol

    NASA Astrophysics Data System (ADS)

    Liu, Shiben; Chen, Yingjie; Dong, Lifeng

    2016-07-01

    Hybrid nanostructures can be multifunctional and even possess enhanced properties. Ag–Fe2O3 nanocomposites and Ag nanoparticles (NPs) were fabricated and applied to catalyze the reduction of 4-nitrophenol. Compared with Ag NPs, Ag–Fe2O3 nanocomposites demonstrated enhanced catalytic activities. Furthermore, due to their magnetic properties, Ag–Fe2O3 nanocomposites could be easily separated from the reaction mixture and recycled through an external magnetic field. These findings will help us design hybrid nanostructures with catalytic activity and explore other potential applications of magnetic nanocomposites.

  16. Electrochemical fabrication of Cu(OH) 2 and CuO nanostructures and their catalytic property

    NASA Astrophysics Data System (ADS)

    Ming, Hai; Pan, Keming; Liu, Yang; Li, Haitao; He, Xiaodie; Ming, Jun; Ma, Zheng; Kang, Zhenhui

    2011-07-01

    In this paper, we reported an anodization method for the fabrication of novel uniform Cu(OH) 2 nanowires, CuO nanoparticles, and CuO shuttle-like nanoparticles with advanced structures. The possible formation mechanism of Cu(OH) 2 nanowires, CuO nanoparticles, and CuO shuttle-like nanoparticles was proposed. The good catalytic properties of CuO nanoparticles converted from Cu(OH) 2 nanowires and the CuO shuttle-like nanoparticles were confirmed by evaluating their catalytic ability on the C-N cross coupling of amines with iodobenzene.

  17. [Preparation, characterization and three way catalytic performance for Pd/CZ/Al2O3 catalyst].

    PubMed

    Fang, Shi-Ping; Chen, Hong-De; Tian, Qun; Yao, Qing; Han, Yun

    2005-09-01

    Pd/CZ/Al2O3 catalyst was prepared by impregnating a noble metal solution to the support CZ/Al2O3 which was prefabricated by co-impregnation. The investigation results show that Pd/CZ/Al2O3 has a superior three-way catalytic performance, which is comparable to Pd/CZ for the fresh sample and a better one after thermal ageing. Based on the XRD, BET and TPR characterizations, the internal relationship between catalytic performance, composition and structure was discussed. The relatively high activity after thermal ageing is ascribed to the maintenance of the Strong Metal-Support Interaction (SMSI).

  18. Electronic Coupling and Catalytic Effect on H2 Evolution of MoS2/Graphene Nanocatalyst

    PubMed Central

    Liao, Ting; Sun, Ziqi; Sun, Chenghua; Dou, Shi Xue; Searles, Debra J.

    2014-01-01

    Inorganic nano-graphene hybrid materials that are strongly coupled via chemical bonding usually present superior electrochemical performance. However, how the chemical bond forms and the synergistic catalytic mechanism remain fundamental questions. In this study, the chemical bonding of the MoS2 nanolayer supported on vacancy mediated graphene and the hydrogen evolution reaction of this nanocatalyst system were investigated. An obvious reduction of the metallic state of the MoS2 nanolayer is noticed as electrons are transferred to form a strong contact with the reduced graphene support. The missing metallic state associated with the unsaturated atoms at the peripheral sites in turn modifies the hydrogen evolution activity. The easiest evolution path is from the Mo edge sites, with the presence of the graphene resulting in a decrease in the energy barrier from 0.17 to 0.11 eV. Evolution of H2 from the S edge becomes more difficult due to an increase in the energy barrier from 0.43 to 0.84 eV. The clarification of the chemical bonding and catalytic mechanisms for hydrogen evolution using this strongly coupled MoS2/graphene nanocatalyst provide a valuable source of reference and motivation for further investigation for improved hydrogen evolution using chemically active nanocoupled systems. PMID:25174324

  19. Hg2+ reduction and re-emission from simulated wet flue gas desulfurization liquors.

    PubMed

    Wo, Jingjing; Zhang, Meng; Cheng, Xiaoya; Zhong, Xiaohang; Xu, Jiang; Xu, Xinhua

    2009-12-30

    In this study, considering that Hg(2+) in wet flue gas desulfurization (FGD) systems can easily be reduced and then released into atmosphere, causing secondary pollution, the researches about Hg(2+) reduction and Hg(0) re-emission mechanism were carried out. The effects of several experimental parameters on the reduction were studied, including initial pH, temperature, and concentrations of Cl(-) and S(IV). Our experimental results indicated that Cl(-) had a restraining effect on the Hg(2+) reduction and Hg(0) re-emission, after 24h reaction, only 20.5% of Hg(2+) was reduced with 100mM Cl(-) in simulated desulfurization solution. Cl(-) can slow Hg(2+) reduction and Hg(0) re-emissions dramatically through changing reaction mechanism, with formation of new intermediate: ClHgSO(3)(-), which can decompose to Hg(0), but much more slowly than Hg(SO(3))(2)(2-) or HgSO(3). Simulating the conditions of the practical application (initial pH 5, T=50 degrees C, S(IV)=5 mM, Cl(-)=100 mM), we also found that Ca(2+), NO(3)(-), F(-), etc. all had obvious effects on reduction rates. Based on the material balance and characteristic of the reactants, the reduction emission mechanism of Hg(2+) has been established, providing theoretical basis for industrial application of mercury control in wet FGD systems. PMID:19699584

  20. Effect of the Addition of CeO2 to Iron Phosphate Glass for Catalytic Applications.

    PubMed

    Chung, Jae-Yeop; Kim, Jong-Hwan; Choi, Su-Yeon; Ryu, Bong-Ki

    2015-10-01

    We investigated the effect of CeO2 content on the catalytic behavior and chemical properties of the (100 - x)(80P2O5-20Fe2O3)-xCeO2 (x = 0, 4, 8, 12, 16, 20 and 24 wt%) glass system. Using thermogravimetric analysis, we confirmed that the catalytic activity increased until a CeO2 content of 16 wt%, beyond which, it decreased. The reasons for the change in the catalytic properties of the glass samples were determined using Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and density analyses. It was confirmed using the FT-IR and XPS-01s spectra that CeO2 acts as a network modifier in iron phosphate glass. When the CeO2 content is above 16 wt%, the number of non-bridging oxygen atoms decreases with increasing CeO2 content. For these reasons, the catalytic properties decrease when the CeO2 content is more than 16 wt%. From the dissolution rate measurements, it can be observed that cerium-iron phosphate has a high water resistance. Also, as we expected, it can be confirmed that the chemical durability is improved with increasing CeO2 content.

  1. Conversion of Acetic Acid from the Catalytic Pyrolysis of Xylan Over CeO2.

    PubMed

    Lee, Heejin; Ko, Jeong Huy; Kwon, Woo Hyun; Park, Young-Kwon

    2016-05-01

    CeO2 was synthesized hydrothermally in supercritical water and applied to the catalytic pyrolysis of xylan. Acetic acid, which is the main component in bio-oil produced from the non-catalytic pyrolysis of xylan, deteriorates the fuel quality of the oil. Catalysis over CeO2 effectively converted the acetic acid to ketone species, such as acetone, thereby reducing the acidity of the oil considerably. The content of aromatics in bio-oil was also increased substantially by catalysis. PMID:27483777

  2. Catalytic oxidation of formaldehyde over Pt/Fe2O3 catalysts prepared by different method

    NASA Astrophysics Data System (ADS)

    An, Nihong; Wu, Ping; Li, Suying; Jia, Mingjun; Zhang, Wenxiang

    2013-11-01

    Iron oxide supported platinum catalysts were prepared by different methods, including co-precipitation, impregnation and colloid deposition methods. The catalytic properties of these catalysts were investigated for the complete oxidation of formaldehyde. It is found that the catalyst prepared by colloid deposition method (Pt/Fe2O3-CD) exhibited relatively high catalytic activity, which could completely oxidize HCHO even at room temperature. Based on a variety of physical-chemical characterization results, it is proposed that the presence of suitable interaction between Pt particles and iron oxide supports (i.e., PtOFe), which would influence the structure and properties of iron oxide supports, should play a positive role in determining the catalytic activity of Pt/Fe2O3-CD catalyst.

  3. Catalytic C6 functionalization of 2,3-disubstituted indoles by scandium triflate.

    PubMed

    Liu, Hua; Zheng, Chao; You, Shu-Li

    2014-02-01

    We report herein an unprecedented direct catalytic C6 functionalization reaction of 2,3-disubstituted indoles with various N-Ts aziridines catalyzed by Sc(OTf)3 under mild conditions. Mechanistic studies revealed that a kinetically favored but reversible formal [3 + 2] annulation occurs initially. The direct C6 functionalization, although having a relatively higher energetic barrier, delivers the thermodynamically favorable products.

  4. In Situ Infrared Spectroscopic Study of Forsterite Carbonation in Wet Supercritical CO2

    SciTech Connect

    Loring, John S.; Thompson, Christopher J.; Wang, Zheming; Joly, Alan G.; Sklarew, Deborah S.; Schaef, Herbert T.; Ilton, Eugene S.; Rosso, Kevin M.; Felmy, Andrew R.

    2011-07-19

    Carbonation reactions are central to the prospect of CO2 trapping by mineralization in geologic reservoirs. In contrast to the relevant aqueous-mediated reactions, little is known about the propensity for carbonation in the long-term partner fluid: water-containing supercritical carbon dioxide (‘wet’ scCO2). We employed in situ mid-infrared spectroscopy to follow the reaction of a model silicate mineral (forsterite, Mg2SiO4) for 24 hr with wet scCO2 at 50°C and 180 atm, using water concentrations corresponding to 0%, 55%, 95%, and 136% saturation. Results show a dramatic dependence of reactivity on water concentration and the presence of liquid water on the forsterite particles. Exposure to neat scCO2 showed no detectable carbonation reaction. At 55% and 95% water saturation, a liquid-like thin water film was detected on the forsterite particles; less than 1% of the forsterite transformed, mostly within the first 3 hours of exposure to the fluid. At 136% saturation, where an (excess) liquid water film approximately several nanometers thick was intentionally condensed on the forsterite, the carbonation reaction proceeded continuously for 24 hr with 10% to 15% transformation. Our collective results suggest constitutive links between water concentration, water film formation, reaction rate and extent, and reaction products in wet scCO2.

  5. Impact of repeated dry-wet cycles on soil CO2 efflux in a beech forest

    NASA Astrophysics Data System (ADS)

    Leitner, Sonja; Saronjic, Nermina; Kobler, Johannes; Holtermann, Christian; Zechmeister-Boltenstern, Sophie; Zimmermann, Michael

    2015-04-01

    Climate change research predicts that both frequency and intensity of weather extremes such as severe droughts and heavy rainfall events will increase in mid Europe over the next decades. Because soil moisture is one of the major factors controlling microbially-driven soil processes, a changed moisture regime will impact soil organic matter (SOM) decomposition and nutrient cycling. This in turn can lead to feedback effects between altered precipitation and changed soil CO2 fluxes which can intensify climate change. Soil microorganisms can go into a state of dormancy or form inactive cysts to protect themselves from osmotic stress during soil drying. However, severe droughts increase microbial mortality which slows down SOM decomposition and decreases soil CO2 efflux. The rewetting of dry soil, on the other hand, causes large CO2 emissions, which is also known as the "Birch effect". Until today it is not clear whether these CO2 peaks outweigh the drought-induced decrease of total CO2 efflux. To investigate the impact of repeated dry-wet cycles on soil CO2 efflux we are conducting a precipitation manipulation experiment in a temperate Austrian beech forest. Roofs exclude rainfall and simulate drought periods, and heavy rainfall events are simulated with a sprinkler system. We apply repeated dry-wet cycles in two intensities: one treatment receives 6 cycles of 1 month drought followed by 75mm irrigation, and a parallel treatment receives 3 cycles of 2 months drought followed by 150mm irrigation. Soil CO2 efflux is constantly monitored with an automated flux chamber system, and environmental parameters are recorded via dataloggers. Our results show that droughts significantly reduce soil CO2 effluxes, and that the reductions depend on the length of the drought periods, with longer droughts leading to stronger reductions of CO2 effluxes. In the first 24 to 48h after rewetting, CO2 emissions strongly increased, and then slowly decreased again. Soil CO2 efflux was

  6. Thickness dependent wetting properties and surface free energy of HfO2 thin films

    NASA Astrophysics Data System (ADS)

    Zenkin, Sergei; Belosludtsev, Alexandr; Kos, Šimon; Čerstvý, Radomír; Haviar, Stanislav; Netrvalová, Marie

    2016-06-01

    We show here that intrinsic hydrophobicity of HfO2 thin films can be easily tuned by the variation of film thickness. We used the reactive high-power impulse magnetron sputtering for preparation of high-quality HfO2 films with smooth topography and well-controlled thickness. Results show a strong dependence of wetting properties on the thickness of the film in the range of 50-250 nm due to the dominance of the electrostatic Lifshitz-van der Waals component of the surface free energy. We have found the water droplet contact angle ranging from ≈120° for the thickness of 50 nm to ≈100° for the thickness of 2300 nm. At the same time the surface free energy grows from ≈25 mJ/m2 for the thickness of 50 nm to ≈33 mJ/m2 for the thickness of 2300 nm. We propose two explanations for the observed thickness dependence of the wetting properties: influence of the non-dominant texture and/or non-monotonic size dependence of the particle surface energy.

  7. Tunable Molecular MoS2 Edge-Site Mimics for Catalytic Hydrogen Production.

    PubMed

    Garrett, Benjamin R; Polen, Shane M; Click, Kevin A; He, Mingfu; Huang, Zhongjie; Hadad, Christopher M; Wu, Yiying

    2016-04-18

    Molybdenum sulfides represent state-of-the-art, non-platinum electrocatalysts for the hydrogen evolution reaction (HER). According to the Sabatier principle, the hydrogen binding strength to the edge active sites should be neither too strong nor too weak. Therefore, it is of interest to develop a molecular motif that mimics the catalytic sites structurally and possesses tunable electronic properties that influence the hydrogen binding strength. Furthermore, molecular mimics will be important for providing mechanistic insight toward the HER with molybdenum sulfide catalysts. In this work, a modular method to tune the catalytic properties of the S-S bond in MoO(S2)2L2 complexes is described. We studied the homogeneous electrocatalytic hydrogen production performance metrics of three catalysts with different bipyridine substitutions. By varying the electron-donating abilities, we present the first demonstration of using the ligand to tune the catalytic properties of the S-S bond in molecular MoS2 edge-site mimics. This work can shed light on the relationship between the structure and electrocatalytic activity of molecular MoS2 catalysts and thus is of broad importance from catalytic hydrogen production to biological enzyme functions. PMID:27022836

  8. Core-shell nanospheres Pt@SiO2 for catalytic hydrogen production

    NASA Astrophysics Data System (ADS)

    Hu, Yujuan; Wang, Yuqing; Lu, Zhang-Hui; Chen, Xiangshu; Xiong, Lihua

    2015-06-01

    Ultrafine platinum nanoparticles (NPs) embedded in silica nanospheres (Pt@SiO2) have been synthesized in a NP-5/cyclohexane reversed-micelle system followed by NaBH4 reduction. The as-synthesized core-shell nanocatalysts Pt@SiO2 were characterized by scanning electron microscopy, transmission electron microscopes, X-ray powder diffraction analysis, energy dispersive X-ray spectrometer and nitrogen adsorption-desorption investigations. Interestingly, the as-synthesized core-shell nanocatalysts Pt@SiO2 showed an excellent catalytic performance in hydrogen generation from the hydrolysis of ammonia borane (BH3NH3, AB) at room temperature. Especially, the catalytic performance of the Pt@SiO2 remained almost unchanged after the five recycles and even after the heat treatment (673 K), because the silica shells inhibit aggregation or deformation of the metal cores. Besides, the kinetic studies showed that the catalytic hydrolysis of AB was first order with respect to the catalyst concentration and zero order with respect to the substrate concentration, respectively. The excellent catalytic activity and stability of Pt@SiO2 can make it have a bright future in the practical application.

  9. Structure of the catalytic domain of glucuronoyl esterase Cip2 from Hypocrea jecorina

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The structure of the catalytic domain of glucuronoyl esterase Cip2 from the fungus Hypocrea jecorina was determined at a resolution of 1.9 Angstroms. This is the first structure of the newly established carbohydrate esterase family 15. The structure has revealed the residues Ser278–His411–Glu301 pre...

  10. Fundamentals and Catalytic Applications of CeO2-Based Materials.

    PubMed

    Montini, Tiziano; Melchionna, Michele; Monai, Matteo; Fornasiero, Paolo

    2016-05-25

    Cerium dioxide (CeO2, ceria) is becoming an ubiquitous constituent in catalytic systems for a variety of applications. 2016 sees the 40(th) anniversary since ceria was first employed by Ford Motor Company as an oxygen storage component in car converters, to become in the years since its inception an irreplaceable component in three-way catalysts (TWCs). Apart from this well-established use, ceria is looming as a catalyst component for a wide range of catalytic applications. For some of these, such as fuel cells, CeO2-based materials have almost reached the market stage, while for some other catalytic reactions, such as reforming processes, photocatalysis, water-gas shift reaction, thermochemical water splitting, and organic reactions, ceria is emerging as a unique material, holding great promise for future market breakthroughs. While much knowledge about the fundamental characteristics of CeO2-based materials has already been acquired, new characterization techniques and powerful theoretical methods are deepening our understanding of these materials, helping us to predict their behavior and application potential. This review has a wide view on all those aspects related to ceria which promise to produce an important impact on our life, encompassing fundamental knowledge of CeO2 and its properties, characterization toolbox, emerging features, theoretical studies, and all the catalytic applications, organized by their degree of establishment on the market.

  11. Modelling ignition characteristics of rich H2/O2 mixture in a monolithic catalytic reactor

    NASA Technical Reports Server (NTRS)

    Tien, Ta-Ching; T'Ien, James S.

    1988-01-01

    Ignition of rich hydrogen-oxygen mixture in a monolithic catalytic reactor is studied using a transient combustion model. The model assumes a quasi-steady gas phase and a thermally-thin substrate. The ignition time lag is due to the thermal inertia of the substrate. One-step global chemical reaction is assumed both on the surface and in the gas phase. An effectiveness factor is introduced to account for the transition from a kinetically-limited catalytic surface reaction to a diffusion-limit one during ignition. Results presented include a catalytic ignition boundary, ignition delay time and the transient response in the catalytic bed.

  12. Catalytic reaction of 3-phenyl-2-propyn-1-ol with alcohols

    SciTech Connect

    Grigoryan, S.G.; Avetisyan, K.G.; Matnishyan, A.A.

    1987-01-10

    The cyclic ketal 2,5-dimethyl-2,5-bis(3-phenyl-2-propynyloxy)-1,4-dioxane was obtained by the reaction of 3-phenyl-2-propyn-1=ol with propargyl alcohol in the presence of the HgO-BF/sub 3/ O(C/sub 2/H/sub 5/)/sub 2/ catalytic system. The transformation of 3-phenyl-2-propyn-1-ol and its ethers in methanol and ethanol by the action of the above-mentioned catalytic system leads to 1-phenyl-3-alkoxy-1-propanone, 1-phenyl-1,1,3-trialkoxypropane, and 1-phenyl-2-propen-1-one. The intermediate organomercury compound, which is the product from regioselective addition of mercuric oxide and the saturated alcohol at the triple bond, was isolated. Its protodemercuration led to the above-mentioned linear products. The formation of the cyclic ketal is presumably due to the preferred formation of mercury bis-hydroxypropargylide.

  13. The short-chain oxidoreductase Q9HYA2 from Pseudomonas aeruginosa PAO1 contains an atypical catalytic center.

    PubMed

    Huether, Robert; Mao, Qilong; Duax, William L; Umland, Timothy C

    2010-05-01

    The characteristic oxidation or reduction reaction mechanisms of short-chain oxidoreductase (SCOR) enzymes involve a highly conserved Asp-Ser-Tyr-Lys catalytic tetrad. The SCOR enzyme Q9HYA2 from the pathogenic bacterium Pseudomonas aeruginosa was recognized to possess an atypical catalytic tetrad composed of Lys118-Ser146-Thr159-Arg163. Orthologs of Q9HYA2 containing the unusual catalytic tetrad along with conserved substrate and cofactor recognition residues were identified in 27 additional species, the majority of which are bacterial pathogens. However, this atypical catalytic tetrad was not represented within the Protein Data Bank. The crystal structures of unligated and NADPH-complexed Q9HYA2 were determined at 2.3 A resolution. Structural alignment to a polyketide ketoreductase (KR), a typical SCOR, demonstrated that Q9HYA2's Lys118, Ser146, and Arg163 superimposed upon the KR's catalytic Asp114, Ser144, and Lys161, respectively. However, only the backbone of Q9HYA2's Thr159 overlapped KR's catalytic Tyr157. The Thr159 hydroxyl in apo Q9HYA2 is poorly positioned for participating in catalysis. In the Q9HYA2-NADPH complex, the Thr159 side chain was modeled in two alternate rotamers, one of which is positioned to interact with other members of the tetrad and the bound cofactor. A chloride ion is bound at the position normally occupied by the catalytic tyrosine hydroxyl. The putative active site of Q9HYA2 contains a chemical moiety at each catalytically important position of a typical SCOR enzyme. This is the first observation of a SCOR protein with this alternate catalytic center that includes threonine replacing the catalytic tyrosine and an ion replacing the hydroxyl moiety of the catalytic tyrosine.

  14. Catalytic characterization of human microsomal glutathione S-transferase 2: identification of rate-limiting steps.

    PubMed

    Ahmad, Shabbir; Niegowski, Damian; Wetterholm, Anders; Haeggström, Jesper Z; Morgenstern, Ralf; Rinaldo-Matthis, Agnes

    2013-03-12

    Microsomal glutathione S-transferase 2 (MGST2) is a 17 kDa trimeric integral membrane protein homologous to leukotriene C4 synthase (LTC4S). MGST2 has been suggested to catalyze the biosynthesis of the pro-inflammatory mediator leukotriene C4 (LTC4) in cells devoid of LTC4S. A detailed biochemical study of MGST2 is critical for the understanding of its cellular function and potential role as an LTC4-producing enzyme. Here we have characterized the substrate specificity and catalytic properties of purified MGST2 by steady-state and pre-steady-state kinetic experiments. In comparison with LTC4S, which has a catalytic efficiency of 8.7 × 10(5) M(-1) s(-1), MGST2, with a catalytic efficiency of 1.8 × 10(4) M(-1) s(-1), is considerably less efficient in producing LTC4. However, the two enzymes display a similar KM(LTA4) of 30-40 μM. While LTC4S has one activated glutathione (GSH) (forming a thiolate) per enzyme monomer, the MGST2 trimer seems to display only third-of-the-sites reactivity for thiolate activation, which in part would explain its lower catalytic efficiency. Furthermore, MGST2 displays GSH-dependent peroxidase activity of ∼0.2 μmol min(-1) mg(-1) toward several lipid hydroperoxides. MGST2, but not LTC4S, is efficient in catalyzing conjugation of the electrophilic substrate 1-chloro-2,4-dinitrobenzene (CDNB) and the lipid peroxidation product 4-hydroxy-2-nonenal with GSH. Using stopped-flow pre-steady-state kinetics, we have characterized the full catalytic reaction of MGST2 with CDNB and GSH as substrates, showing an initial rapid equilibrium binding of GSH followed by thiolate formation. Burst kinetics for the CDNB-GSH conjugation step was observed only at low GSH concentrations (thiolate anion formation becoming rate-limiting under these conditions). Product release is rapid and does not limit the overall reaction. Therefore, in general, the chemical conjugation step is rate-limiting for MGST2 at physiological GSH concentrations. MGST2 and LTC4S

  15. Catalytic reduction of CN-, CO, and CO2 by nitrogenase cofactors in lanthanide-driven reactions.

    PubMed

    Lee, Chi Chung; Hu, Yilin; Ribbe, Markus W

    2015-01-19

    Nitrogenase cofactors can be extracted into an organic solvent to catalyze the reduction of cyanide (CN(-)), carbon monoxide (CO), and carbon dioxide (CO2) without using adenosine triphosphate (ATP), when samarium(II) iodide (SmI2) and 2,6-lutidinium triflate (Lut-H) are employed as a reductant and a proton source, respectively. Driven by SmI2, the cofactors catalytically reduce CN(-) or CO to C1-C4 hydrocarbons, and CO2 to CO and C1-C3 hydrocarbons. The C-C coupling from CO2 indicates a unique Fischer-Tropsch-like reaction with an atypical carbonaceous substrate, whereas the catalytic turnover of CN(-), CO, and CO2 by isolated cofactors suggests the possibility to develop nitrogenase-based electrocatalysts for the production of hydrocarbons from these carbon-containing compounds.

  16. LOXL2 catalytically inactive mutants mediate epithelial-to-mesenchymal transition.

    PubMed

    Cuevas, Eva P; Moreno-Bueno, Gema; Canesin, Giacomo; Santos, Vanesa; Portillo, Francisco; Cano, Amparo

    2014-02-15

    Lysyl-oxidase-like 2 (LOXL2) is a member of the lysyl oxidase family that catalyzes the cross-linking of collagens or elastins in the extracellular matrix, thus regulating the tensile strength of tissues. However, many reports have suggested different intracellular roles for LOXL2, including the ability to regulate gene transcription and tumor progression. We previously reported that LOXL2 mediates epithelial-to-mesenchymal transition (EMT) by Snail1-dependent and independent mechanisms, related to E-cadherin silencing and downregulation of epidermal differentiation and cell polarity components, respectively. Whether or not the catalytic activity of LOXL2 is required to induce/sustain EMT is actually unknown. Here we show that LOXL2 catalytic inactive mutants collaborate with Snail1 in E-cadherin gene repression to trigger EMT and, in addition, promote FAK/Src pathway activation to support EMT. These findings reveal a non-conventional role of LOXL2 on regulating epithelial cell plasticity.

  17. Catalytic trifluoromethylation of aryl- and vinylboronic acids by 2-cyclopropyl-1-(trifluoromethyl)benzo[b]thiophenium triflate.

    PubMed

    Arimori, Sadayuki; Shibata, Norio

    2015-04-01

    Catalytic trifluoromethylation of aryl- and vinylboronic acids by 2-cyclopropyl-1-(trifluoromethyl)benzo[b]thiophenium triflate is described. In the presence of a catalytic amount of CuOAc and 2,4,6-collidine in ethyl acetate, the reaction proceeded in good to high yields for various substrates under mild reaction conditions at room temperature. PMID:25783441

  18. Inverse algorithms for 2D shallow water equations in presence of wet dry fronts: Application to flood plain dynamics

    NASA Astrophysics Data System (ADS)

    Monnier, J.; Couderc, F.; Dartus, D.; Larnier, K.; Madec, R.; Vila, J.-P.

    2016-11-01

    The 2D shallow water equations adequately model some geophysical flows with wet-dry fronts (e.g. flood plain or tidal flows); nevertheless deriving accurate, robust and conservative numerical schemes for dynamic wet-dry fronts over complex topographies remains a challenge. Furthermore for these flows, data are generally complex, multi-scale and uncertain. Robust variational inverse algorithms, providing sensitivity maps and data assimilation processes may contribute to breakthrough shallow wet-dry front dynamics modelling. The present study aims at deriving an accurate, positive and stable finite volume scheme in presence of dynamic wet-dry fronts, and some corresponding inverse computational algorithms (variational approach). The schemes and algorithms are assessed on classical and original benchmarks plus a real flood plain test case (Lèze river, France). Original sensitivity maps with respect to the (friction, topography) pair are performed and discussed. The identification of inflow discharges (time series) or friction coefficients (spatially distributed parameters) demonstrate the algorithms efficiency.

  19. Human liver glucuronate 2-sulphatase. Purification, characterization and catalytic properties.

    PubMed Central

    Freeman, C; Hopwood, J J

    1989-01-01

    Human glucuronate 2-sulphatase (GAS), which is involved in the degradation of the glycosaminoglycans heparan sulphate and chondroitin 6-sulphate, was purified almost 2,000,000-fold to homogeneity in 8% yield from liver with a four-step six-column procedure, which consists of a concanavalin A-Sepharose/Blue A-agarose coupled step, a DEAE-Sephacel/octyl-Sepharose coupled step, CM-Sepharose chromatography and gel-permeation chromatography. Although more than 90% of GAS activity had a pI of greater than 7.5, other forms with pI values of 5.8, 5.3, 4.7 and less than 4.0 were also present. The pI greater than 7.5 form of GAS had a native molecular mass of 63 kDa. SDS/polyacrylamide-gel-electrophoretic analysis resulted in two polypeptide subunits of molecular mass 47 and 19.5 kDa. GAS was active towards disaccharide substrates derived from heparin [O-(beta-glucuronic acid 2-sulphate)-(1----4)-O-(2,5)-anhydro[1-3H]mannitol 6-sulphate (GSMS)] and chondroitin 6-sulphate [O-(beta-glucuronic acid 2-sulphate-(1----3)-O-(2,5)-anhydro[1-3H]talitol 6-sulphate (GSTS)]. GAS activity towards GSMS and GSTS was at pH optima of 3.2 and 3.0 respectively with apparent Km values of 0.3 and 0.6 microM respectively and corresponding Vmax values of 12.8 and 13.7 mumol/min per mg of protein respectively. Sulphate and phosphate ions are potent inhibitors of enzyme activity. Cu2+ ions stimulated, whereas EDTA inhibited enzyme activity. It was concluded that GAS is required together with a series of other exoenzyme activities in the lysosomal degradation of glycosaminoglycans containing glucuronic acid 2-sulphate residues. Images Fig. 5. PMID:2497731

  20. Human Brown Fat Inducible Thioesterase Variant 2 (BFIT2) Cellular Localization and Catalytic Function#

    PubMed Central

    Chen, Danqi; Latham, John; Zhao, Hong; Bisoffi, Marco; Farelli, Jeremiah; Dunaway-Mariano, Debra

    2014-01-01

    The mammalian brown fat inducible thioesterase variant 2 (BFIT2), also known as ACOT11, is a multi-modular protein containing two consecutive hotdog-fold domains and a C-terminal steroidogenic acute regulatory protein related lipid transfer (START) domain (StarD14). In this study, we demonstrate that the N-terminal region of human BFIT2 (hBFIT2) constitutes a mitochondrial location signal sequence, which undergoes mitochondria-dependent posttranslational cleavage. The mature hBFIT2 is shown to be located in the mitochondrial matrix whereas the paralog “cytoplasmic acetyl-CoA hydrolase” (CACH, also known as ACOT12) was found in the cytoplam. In-vitro activity analysis of full-length hBFIT2 isolated from stably transfected HEK293 cells demonstrates selective thioesterase activity directed towards long chain fatty acyl-CoA thioesters, thus distinguishing BFIT2 catalytic function from that of CACH. The results from a protein-lipid overlay test indicate that the hBFIT2 StarD14 domain binds phosphatidylinositol 4-phosphate. PMID:22897136

  1. Catalytic combustion of toluene on Pd/CeO2-TiO2 catalysts.

    PubMed

    Chen, Yu-Wen; Lee, Der-Shing

    2013-03-01

    Pd/TiO2 and Pd/CeO2 were reported to be very active to destruct toluene. Combination of TiO2 and CeO2 is an interesting candidate to achieve a catalyst with higher activity. In this study, a series of Pd/CeO2-TiO2 catalysts with various Pd loadings were prepared. CeO2-TiO2 was prepared by impregnation of aqueous solution of cerium nitrate into TiO2 support. It was then calcined at 400 degrees C. Pd was loaded by incipient-wetness impregnation method. The Pd loadings in all samples were fixed at 0.5 wt.%. The catalysts were characterized by powder X-ray diffraction, transmission electron microscopy, high resolution transmission electron microscopy, temperature-programmed reduction of hydrogen, and X-ray photoelectron spectroscopy. The catalysts were tested for total oxidation of toluene. The feed concentration of toluene was 8.564 g/m3 (2085 ppm), with GHSV = 10,000 h(-1). Pd particle sizes were 3-5 nm and well-dispersed on the support. CeO2 on TiO2 was easier to reduce than the bulk CeO2, therefore it could enhance the activity of VOC destruction. Pd/CeO2-TiO2 was more active than Pd/CeO2 and Pd/TiO2. Pd/CeO2-TiO2 with Ce/Ti ratio of 2/8 was very active for toluene destruction, due to its lower oxygen reduction temperature of ceria and higher concentration of Pd(0). PMID:23755662

  2. Effect of Calcination Temperature on Surface Oxygen Vacancies and Catalytic Performance Towards CO Oxidation of Co3O4 Nanoparticles Supported on SiO2

    NASA Astrophysics Data System (ADS)

    Li, Jin-bing; Jiang, Zhi-quan; Qian, Kun; Huang, Wei-xin

    2012-02-01

    Co3O4/SiO2 catalysts for CO oxidation were prepared by conventional incipient wetness impregnation followed by calcination at various temperatures. Their structures were characterized with X-ray diffraction (XRD), laser Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR) and X-ray absorption fine structure (XAFS) spectroscopy. Both XRD and Raman spectroscopy only detect the existence of Co3O4 crystallites in all catalysts. However, XPS results indicate that excess Co2+ ions are present on the surface of Co3O4 in Co3O4(200)/SiO2 as compared with bulk Co3O4. Meanwhile, TPR results suggest the presence of surface oxygen vacancies on Co3O4 in Co3O4(200)/SiO2, and XAFS results demonstrate that Co3O4 in Co3O4(200)/SiO2 contains excess Co2+. Increasing calcination temperature results in oxidation of excess Co2+ and the decrease of the concentration of surface oxygen vacancies, consequently the formation of stoichiometric Co3O4 on supported catalysts. Among all Co3O4/SiO2 catalysts, Co3O4(200)/SiO2 exhibits the best catalytic performance towards CO oxidation, demonstrating that excess Co2+ and surface oxygen vacancies can enhance the catalytic activity of Co3O4 towards CO oxidation. These results nicely demonstrate the effect of calcination temperature on the structure and catalytic performance towards CO oxidation of silica-supported Co3O4 catalysts and highlight the important role of surface oxygen vacancies on Co3O4.

  3. Catalyst performance and mechanism of catalytic combustion of dichloromethane (CH2Cl2) over Ce doped TiO2.

    PubMed

    Cao, Shuang; Wang, Haiqiang; Yu, Feixiang; Shi, Mengpa; Chen, Shuang; Weng, Xiaole; Liu, Yue; Wu, Zhongbiao

    2016-02-01

    TiO2 and Ce/TiO2 were synthesized and subsequently used for the catalytic combustion of DCM. TiO2 had abundant Lewis acid sites and was responsible for the adsorption and the rupture of C-Cl bonds. However, TiO2 tended to be inactivated because of chloride poisoning due to the adsorption and accumulation of Cl species over the surface. While, Ce/TiO2 obtained total oxidation of CH2Cl2 at 335°C and exhibited stable DCM removal activity on 100h long-time stability tests at 330°C without any catalyst deactivation. The doped cerium generated Ce(3+) chemical states and surface active oxygen, and therefore played important roles from two aspects as follows. First of all, the poisoning of Cl for Ce/TiO2 was inhibited to some extent by CeO2 due to the rapid removal of Cl on the surface of CeO2, which has been verified by NH3-IR characterization. In the other hand, CeO2 enhanced the further deep oxidation of C-H from byproducts and retained the certain oxidation of CO to CO2. Based on the DRIFT characterization and the catalysts activity tests, a two-step reaction pathway for the catalytic combustion of DCM on Ce/TiO2 catalyst was proposed. PMID:26550781

  4. Catalyst performance and mechanism of catalytic combustion of dichloromethane (CH2Cl2) over Ce doped TiO2.

    PubMed

    Cao, Shuang; Wang, Haiqiang; Yu, Feixiang; Shi, Mengpa; Chen, Shuang; Weng, Xiaole; Liu, Yue; Wu, Zhongbiao

    2016-02-01

    TiO2 and Ce/TiO2 were synthesized and subsequently used for the catalytic combustion of DCM. TiO2 had abundant Lewis acid sites and was responsible for the adsorption and the rupture of C-Cl bonds. However, TiO2 tended to be inactivated because of chloride poisoning due to the adsorption and accumulation of Cl species over the surface. While, Ce/TiO2 obtained total oxidation of CH2Cl2 at 335°C and exhibited stable DCM removal activity on 100h long-time stability tests at 330°C without any catalyst deactivation. The doped cerium generated Ce(3+) chemical states and surface active oxygen, and therefore played important roles from two aspects as follows. First of all, the poisoning of Cl for Ce/TiO2 was inhibited to some extent by CeO2 due to the rapid removal of Cl on the surface of CeO2, which has been verified by NH3-IR characterization. In the other hand, CeO2 enhanced the further deep oxidation of C-H from byproducts and retained the certain oxidation of CO to CO2. Based on the DRIFT characterization and the catalysts activity tests, a two-step reaction pathway for the catalytic combustion of DCM on Ce/TiO2 catalyst was proposed.

  5. Catalytic deactivation on methane steam reforming catalysts. 2. Kinetic study

    SciTech Connect

    Agnelli, M.E.; Ponzi, E.N.; Yeramian, A.A.

    1987-08-01

    The kinetics of methane steam reforming reaction over an alumina-supported nickel catalyst was investigated at a temperature range of 640-740/sup 0/C in a flow reactor at atmospheric pressure. The experiments were performed varying the inlet concentration of methane, hydrogen, and water. A kinetic scheme of the Houghen-Watson type was satisfactorily proposed assuming the dissociative adsorption of CH/sub 4/ as the rate-limiting step, but this kinetic scheme can be easily replaced by a first-order kinetics (r/sub CH/4/sub / = kapparho/sub CH/4/sub /) for engineering purposes. Catalyst activation with H/sub 2/ and N/sub 2/ mixtures or with the reactant mixture results in the same extent of reaction.

  6. Catalytic Thr or Ser Residue Modulates Structural Switches in 2-Cys Peroxiredoxin by Distinct Mechanisms

    PubMed Central

    Tairum, Carlos A.; Santos, Melina Cardoso; Breyer, Carlos A.; Geyer, R. Ryan; Nieves, Cecilia J.; Portillo-Ledesma, Stephanie; Ferrer-Sueta, Gerardo; Toledo, José Carlos; Toyama, Marcos H.; Augusto, Ohara; Netto, Luis E. S.; de Oliveira, Marcos A.

    2016-01-01

    Typical 2-Cys Peroxiredoxins (2-Cys Prxs) reduce hydroperoxides with extraordinary rates due to an active site composed of a catalytic triad, containing a peroxidatic cysteine (CP), an Arg, and a Thr (or Ser). 2-Cys Prx are involved in processes such as cancer; neurodegeneration and host-pathogen interactions. During catalysis, 2-Cys Prxs switch between decamers and dimers. Analysis of 2-Cys Prx structures in the fully folded (but not locally unfolded) form revealed a highly conserved, non-conventional hydrogen bond (CH-π) between the catalytic triad Thr of a dimer with an aromatic residue of an adjacent dimer. In contrast, structures of 2-Cys Prxs with a Ser in place of the Thr do not display this CH-π bond. Chromatographic and structural data indicate that the Thr (but not Ser) destabilizes the decamer structure in the oxidized state probably through steric hindrance. As a general trend, mutations in a yeast 2-Cys Prx (Tsa1) favoring the dimeric state also displayed a decreased catalytic activity. Remarkably, yeast naturally contains Thr-Ser variants (Tsa1 and Tsa2, respectively) with distinct oligomeric stabilities in their disulfide states. PMID:27629822

  7. Au@TiO2 double-shelled octahedral nanocages with improved catalytic properties.

    PubMed

    Lv, Xiaoming; Zhu, Yihua; Jiang, Hongliang; Zhong, Hua; Yang, Xiaoling; Li, Chunzhong

    2014-10-28

    A novel and facile strategy has been successfully developed to synthesize uniform gold@titanium dioxide octahedral nanocages (Au@TiO2), which have a well-defined double-shelled structure with Au as the internal shell and TiO2 as the external shell. The unique Au@TiO2 double-shelled octahedral nanocages were elaborately fabricated by a Cu2O-templated strategy combining with spatially confined galvanic replacement. The formation process of these delicate hierarchical octahedral architectures is discussed in detail. The catalytic performance of the Au@TiO2 double-shelled octahedral nanocages was investigated using the reduction of 4-nitrophenol as a model reaction. The mesoporous structure of both the Au and TiO2 shells provides direct access for the reactant molecules to diffuse and subsequently interact with the Au shell. This novel catalyst shows excellent and stable activity for the catalytic reduction of 4-nitrophenol, which can be recycled for ten successive cycles of the reaction with a conversion efficiency of more than 90%. The superior catalytic activity attributes to mesoporous double shells, enhanced synergistic effects between the Au and TiO2 shells and the unique properties of the octahedral structure. More importantly, the as-obtained Au@TiO2 double-shelled octahedral nanocages also show potential applications in solar cells, organocatalysis and water splitting. PMID:25166883

  8. Catalytic Thr or Ser Residue Modulates Structural Switches in 2-Cys Peroxiredoxin by Distinct Mechanisms.

    PubMed

    Tairum, Carlos A; Santos, Melina Cardoso; Breyer, Carlos A; Geyer, R Ryan; Nieves, Cecilia J; Portillo-Ledesma, Stephanie; Ferrer-Sueta, Gerardo; Toledo, José Carlos; Toyama, Marcos H; Augusto, Ohara; Netto, Luis E S; de Oliveira, Marcos A

    2016-09-15

    Typical 2-Cys Peroxiredoxins (2-Cys Prxs) reduce hydroperoxides with extraordinary rates due to an active site composed of a catalytic triad, containing a peroxidatic cysteine (CP), an Arg, and a Thr (or Ser). 2-Cys Prx are involved in processes such as cancer; neurodegeneration and host-pathogen interactions. During catalysis, 2-Cys Prxs switch between decamers and dimers. Analysis of 2-Cys Prx structures in the fully folded (but not locally unfolded) form revealed a highly conserved, non-conventional hydrogen bond (CH-π) between the catalytic triad Thr of a dimer with an aromatic residue of an adjacent dimer. In contrast, structures of 2-Cys Prxs with a Ser in place of the Thr do not display this CH-π bond. Chromatographic and structural data indicate that the Thr (but not Ser) destabilizes the decamer structure in the oxidized state probably through steric hindrance. As a general trend, mutations in a yeast 2-Cys Prx (Tsa1) favoring the dimeric state also displayed a decreased catalytic activity. Remarkably, yeast naturally contains Thr-Ser variants (Tsa1 and Tsa2, respectively) with distinct oligomeric stabilities in their disulfide states.

  9. Catalytic Thr or Ser Residue Modulates Structural Switches in 2-Cys Peroxiredoxin by Distinct Mechanisms.

    PubMed

    Tairum, Carlos A; Santos, Melina Cardoso; Breyer, Carlos A; Geyer, R Ryan; Nieves, Cecilia J; Portillo-Ledesma, Stephanie; Ferrer-Sueta, Gerardo; Toledo, José Carlos; Toyama, Marcos H; Augusto, Ohara; Netto, Luis E S; de Oliveira, Marcos A

    2016-01-01

    Typical 2-Cys Peroxiredoxins (2-Cys Prxs) reduce hydroperoxides with extraordinary rates due to an active site composed of a catalytic triad, containing a peroxidatic cysteine (CP), an Arg, and a Thr (or Ser). 2-Cys Prx are involved in processes such as cancer; neurodegeneration and host-pathogen interactions. During catalysis, 2-Cys Prxs switch between decamers and dimers. Analysis of 2-Cys Prx structures in the fully folded (but not locally unfolded) form revealed a highly conserved, non-conventional hydrogen bond (CH-π) between the catalytic triad Thr of a dimer with an aromatic residue of an adjacent dimer. In contrast, structures of 2-Cys Prxs with a Ser in place of the Thr do not display this CH-π bond. Chromatographic and structural data indicate that the Thr (but not Ser) destabilizes the decamer structure in the oxidized state probably through steric hindrance. As a general trend, mutations in a yeast 2-Cys Prx (Tsa1) favoring the dimeric state also displayed a decreased catalytic activity. Remarkably, yeast naturally contains Thr-Ser variants (Tsa1 and Tsa2, respectively) with distinct oligomeric stabilities in their disulfide states. PMID:27629822

  10. Wet chemical techniques for passivation of YBa2Cu3O7(7-x)

    NASA Technical Reports Server (NTRS)

    Vasquez, R. P.; Foote, M. C.; Hunt, B. D.

    1989-01-01

    Wet chemical techniques are described for treatment of YBa2Cu3O(7-x) surfaces, resulting in the formation of native compounds with little or no reactivity to water. Promising native compounds include CuI, BaSO4, CuS, Cu2S, and the oxalates, all of which are either insoluble or have very low solubility in water. Treatment with dilute HI results in the formation of a native iodide film which is 80-90 percent CuI with small amounts of YI3 and BaI2. Treatment with dilute H2SO4 results in the formation of a film which is 95 percent BaSO4 and 5 percent Y2(SO4)3. Cu2S is formed on the surface with a dilute Na2S solution. An oxalate film with equal amounts of Y2(C2O4)3 and BaC2O4 results from treatment with dilute oxalic acid. X-ray photoelectron spectra show no significant changes when the sulfide, sulfate, or oxalate films are dipped in water, while the iodide film shows evidence of Cu(OH)2 formation.

  11. Catalytic ozonation of petroleum refinery wastewater utilizing Mn-Fe-Cu/Al2O 3 catalyst.

    PubMed

    Chen, Chunmao; Yoza, Brandon A; Wang, Yandan; Wang, Ping; Li, Qing X; Guo, Shaohui; Yan, Guangxu

    2015-04-01

    There is of great interest to develop an economic and high-efficient catalytic ozonation system (COS) for the treatment of biologically refractory wastewaters. Applications of COS require options of commercially feasible catalysts. Experiments in the present study were designed to prepare and investigate a novel manganese-iron-copper oxide-supported alumina-assisted COS (Mn-Fe-Cu/Al2O3-COS) for the pretreatment of petroleum refinery wastewater. The highly dispersed composite metal oxides on the catalyst surface greatly promoted the performance of catalytic ozonation. Hydroxyl radical mediated oxidation is a dominant reaction in Mn-Fe-Cu/Al2O3-COS. Mn-Fe-Cu/Al2O3-COS enhanced COD removal by 32.7% compared with a single ozonation system and by 8-16% compared with Mn-Fe/Al2O3-COS, Mn-Cu/Al2O3-COS, and Fe-Cu/Al2O3-COS. The O/C and H/C ratios of oxygen-containing polar compounds significantly increased after catalytic ozonation, and the biodegradability of petroleum refinery wastewater was significantly improved. This study illustrates potential applications of Mn-Fe-Cu/Al2O3-COS for pretreatment of biologically refractory wastewaters.

  12. Catalytic ozonation of petroleum refinery wastewater utilizing Mn-Fe-Cu/Al2O 3 catalyst.

    PubMed

    Chen, Chunmao; Yoza, Brandon A; Wang, Yandan; Wang, Ping; Li, Qing X; Guo, Shaohui; Yan, Guangxu

    2015-04-01

    There is of great interest to develop an economic and high-efficient catalytic ozonation system (COS) for the treatment of biologically refractory wastewaters. Applications of COS require options of commercially feasible catalysts. Experiments in the present study were designed to prepare and investigate a novel manganese-iron-copper oxide-supported alumina-assisted COS (Mn-Fe-Cu/Al2O3-COS) for the pretreatment of petroleum refinery wastewater. The highly dispersed composite metal oxides on the catalyst surface greatly promoted the performance of catalytic ozonation. Hydroxyl radical mediated oxidation is a dominant reaction in Mn-Fe-Cu/Al2O3-COS. Mn-Fe-Cu/Al2O3-COS enhanced COD removal by 32.7% compared with a single ozonation system and by 8-16% compared with Mn-Fe/Al2O3-COS, Mn-Cu/Al2O3-COS, and Fe-Cu/Al2O3-COS. The O/C and H/C ratios of oxygen-containing polar compounds significantly increased after catalytic ozonation, and the biodegradability of petroleum refinery wastewater was significantly improved. This study illustrates potential applications of Mn-Fe-Cu/Al2O3-COS for pretreatment of biologically refractory wastewaters. PMID:25649390

  13. Synthesis of chitosan supported palladium nanoparticles and its catalytic activity towards 2-nitrophenol reduction

    NASA Astrophysics Data System (ADS)

    Dhanavel, S.; Nivethaa, E. A. K.; Esther, G.; Narayanan, V.; Stephen, A.

    2016-05-01

    Chitosan supported Palladium nanoparticles were synthesized by a simple cost effective chemical reduction method using NaBH4. The prepared nanocomposite was characterized by X-Ray diffraction analysis, FESEM and Energy dispersive spectroscopy analysis of X-rays (EDAX). The catalytic performance of the nanocomposite was evaluated on the reduction of 2-Nitrophenol to the 2-Amino phenol with rate constant 1.08 × 10-3 S-1 by NaBH4 using Spectrophotometer.

  14. An investigation on NO removal by wet scrubbing using NaClO2 seawater solution.

    PubMed

    Han, Zhitao; Yang, Shaolong; Zheng, Dekang; Pan, Xinxiang; Yan, Zhijun

    2016-01-01

    The experiments were conducted to investigate the NO removal by wet scrubbing using NaClO2 seawater solution in a cyclic scrubbing mode. Results show that, when the concentration of NaClO2 in scrubbing solution is higher than 10 mM, a complete removal of NO can be achieved during the cyclic scrubbing process. The breakthrough time for seawater with 15 mM NaClO2 is enhanced by 34.3 % compared with that for NaClO2 freshwater. The extension of the breakthrough time for NaClO2 seawater is mainly ascribed to the improved utilization of NaClO2 in the solution. The good buffering ability of seawater could suppress the acidic decomposition of NaClO2 into ClO2 effectively. The analysis of reaction products indicates that the main anions in the spent liquor are chloride ions and nitrate ions. The calculation of NaClO2 utilization according to the ion chromatography also agrees well with the experimental results of breakthrough times. PMID:27386234

  15. Forsterite Carbonation in Wet-scCO2: Dependence on Adsorbed Water Concentration

    NASA Astrophysics Data System (ADS)

    Loring, J.; Benezeth, P.; Qafoku, O.; Thompson, C.; Schaef, T.; Bonneville, A.; McGrail, P.; Felmy, A.; Rosso, K.

    2013-12-01

    Capturing and storing CO2 in basaltic formations is one of the most promising options for mitigating atmospheric CO2 emissions resulting from the burning of fossil fuels. These geologic reservoirs have high reactive potential for CO2-mineral trapping due to an abundance of divalent-cation containing silicates, such as forsterite (Mg2SiO4). Recent studies have shown that carbonation of these silicates under wet scCO2 conditions, e. g. encountered near a CO2 injection well, proceeds along a different pathway and is more effective than in CO2-saturated aqueous fluids. The presence of an adsorbed water film on the forsterite surface seems to be key to reactivity towards carbonation. In this study, we employed in situ high pressure IR spectroscopy to investigate the dependence of adsorbed water film thickness on forsterite carbonation chemistry. Post reaction ex situ SEM, TEM, TGA, XRD, and NMR measurements will also be discussed. Several IR titrations were performed of forsterite with water at 50 °C and 90 bar scCO2. Aliquots of water were titrated at 4-hour reaction-time increments. Once a desired total water concentration was reached, data were collected for about another 30 hours. One titration involved 10 additions, which corresponds to 6.8 monolayers of adsorbed water. Clearly, a carbonate was precipitating, and its spectral signature matched magnesite. Another titration involved 8 aliquots, or up to 4.4 monolayers of water. The integrated absorbance under the CO stretching bands of carbonate as a function of time after reaching 4.4 monolayers showed an increase and then a plateau. We are currently unsure of the identity of the carbonate that precipitated, but it could be an amorphous anhydrous phase or magnesite crystals with dimensions of only several nanometers. A third titration only involved 3 additions, or up to 1.6 monolayers of water. The integrated absorbance under the CO stretching bands of carbonate as a function of time after reaching 1.6 monolayers

  16. The catalytic activity of Ag2S-montmorillonites as peroxidase mimetic toward colorimetric detection of H2O2.

    PubMed

    Liu, Qingyun; Jiang, Yanling; Zhang, Leyou; Zhou, Xinpei; Lv, Xintian; Ding, Yanyuan; Sun, Lifang; Chen, Pengpeng; Yin, Hailiang

    2016-08-01

    Nanocomposites based on silver sulfide (Ag2S) and Ca-montmorillonite (Ca(2+)-MMT) were synthesized by a simple hydrothermal method. The nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Fourier transform infrared spectra (FTIR). The as-prepared Ag2S-MMT nanocomposites were firstly demonstrated to possess intrinsic peroxidase-like activity and could rapidly catalytically oxidize the substrate 3,3',5,5'-tetramethylbenzidine (TMB) in the presence of H2O2 to produce a blue product which can be seen by the naked eye in only one minute. The experimental results revealed that the Ag2S-MMT nanocomposites exhibit higher thermal durance. Based on the TMB-H2O2 catalyzed color reaction, the Ag2S-MMT nanocomposites were exploited as a new type of biosensor for detection and estimation of H2O2 through a simple, cheap and selective colorimetric method. PMID:27157733

  17. Boryl-mediated reversible H2 activation at cobalt: catalytic hydrogenation, dehydrogenation, and transfer hydrogenation.

    PubMed

    Lin, Tzu-Pin; Peters, Jonas C

    2013-10-16

    We describe the synthesis of a cobalt(I)-N2 complex (2) supported by a meridional bis-phosphino-boryl (PBP) ligand. Complex 2 undergoes a clean reaction with 2 equiv of dihydrogen to afford a dihydridoboratocobalt dihydride (3). The ability of boron to switch between a boryl and a dihydridoborate conformation makes possible the reversible conversion of 2 and 3. Complex 3 reacts with HMe2N-BH3 to give a hydridoborane cobalt tetrahydridoborate complex. We explore this boryl-cobalt system in the context of catalytic olefin hydrogenation as well as amine-borane dehydrogenation/transfer hydrogenation. PMID:24079337

  18. Hydrodechlorination catalytic activity of gold nanoparticles supported on TiO 2 modified SBA-15 investigated by IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Hannus, I.; Búza, M.; Beck, A.; Guczi, L.; Sáfrán, G.

    2009-04-01

    The hydrodechlorination catalytic activity of gold nanoparticles on SBA-15 silica modified by TiO 2 promoters has been investigated. Comparing the hydrodechlorination catalytic activity platinum nanoparticles supported on TiO 2 catalyst was used in the hydrodechlorination of CCl 4 as model compound. The IR spectroscopic experimental results showed that the gold nanoparticles have higher catalytic activity, than platinum ones. The two samples were tested also in CO oxidation, in which Au/TiO 2/SBA-15 possess also somewhat higher activity than Pt/TiO 2.

  19. [Current research situation of H2S selective catalytic oxidation technologies and catalysts].

    PubMed

    Hao, Zheng-ping; Dou, Guang-yu; Zhang, Xin; Qu, Si-qiu

    2012-08-01

    This review summarizes and discusses different selective catalytic oxidation technologies and various catalysts for removing H2S, the undesirable byproduct of the fluid catalytic cracking (FCC) processing. Currently the selective oxidation technologies used include Superclaus, Euroclaus, Clinsulf-Do, BSR/Hi-Activity, Selectox and Modop techniques, which have various characteristics and application areas. Catalysts for H2S selective oxidation mainly contain the following systems: carbon, supported SiC, zeolite, oxide, and pillared clay. Former studies focused on carbon and oxide systems. The research interest on zeolite system decreased in recent years, while SiC is regarded as a typical support with great potential for this reaction and continues to be attractive. Pillared clay system is at the preliminary research stage, and is still far from practical application.

  20. Isolated metal active site concentration and stability control catalytic CO2 reduction selectivity.

    PubMed

    Matsubu, John C; Yang, Vanessa N; Christopher, Phillip

    2015-03-01

    CO2 reduction by H2 on heterogeneous catalysts is an important class of reactions that has been studied for decades. However, atomic scale details of structure-function relationships are still poorly understood. Particularly, it has been suggested that metal particle size plays a unique role in controlling the stability of CO2 hydrogenation catalysts and the distribution of active sites, which dictates reactivity and selectivity. These studies often have not considered the possible role of isolated metal active sites in the observed dependences. Here, we utilize probe molecule diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) with known site-specific extinction coefficients to quantify the fraction of Rh sites residing as atomically dispersed isolated sites (Rhiso), as well as Rh sites on the surface of Rh nanoparticles (RhNP) for a series of TiO2 supported Rh catalysts. Strong correlations were observed between the catalytic reverse water gas shift turn over frequency (TOF) and the fraction of Rhiso sites and between catalytic methanation TOF and the fraction of RhNP sites. Furthermore, it was observed that reaction condition-induced disintegration of Rh nanoparticles, forming Rhiso active sites, controls the changing reactivity with time on stream. This work demonstrates that isolated atoms and nanoparticles of the same metal on the same support can exhibit uniquely different catalytic selectivity in competing parallel reaction pathways and that disintegration of nanoparticles under reaction conditions can play a significant role in controlling stability.

  1. Isolated metal active site concentration and stability control catalytic CO2 reduction selectivity.

    PubMed

    Matsubu, John C; Yang, Vanessa N; Christopher, Phillip

    2015-03-01

    CO2 reduction by H2 on heterogeneous catalysts is an important class of reactions that has been studied for decades. However, atomic scale details of structure-function relationships are still poorly understood. Particularly, it has been suggested that metal particle size plays a unique role in controlling the stability of CO2 hydrogenation catalysts and the distribution of active sites, which dictates reactivity and selectivity. These studies often have not considered the possible role of isolated metal active sites in the observed dependences. Here, we utilize probe molecule diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) with known site-specific extinction coefficients to quantify the fraction of Rh sites residing as atomically dispersed isolated sites (Rhiso), as well as Rh sites on the surface of Rh nanoparticles (RhNP) for a series of TiO2 supported Rh catalysts. Strong correlations were observed between the catalytic reverse water gas shift turn over frequency (TOF) and the fraction of Rhiso sites and between catalytic methanation TOF and the fraction of RhNP sites. Furthermore, it was observed that reaction condition-induced disintegration of Rh nanoparticles, forming Rhiso active sites, controls the changing reactivity with time on stream. This work demonstrates that isolated atoms and nanoparticles of the same metal on the same support can exhibit uniquely different catalytic selectivity in competing parallel reaction pathways and that disintegration of nanoparticles under reaction conditions can play a significant role in controlling stability. PMID:25671686

  2. Solid-phase reduction of Cr2O3 under chemical catalytic conditions

    NASA Astrophysics Data System (ADS)

    Simonov, V. K.; Grishin, A. M.

    2016-06-01

    The kinetics of the solid-phase reduction of Cr2O3 with carbon under chemical catalytic action on the reacting system is studied. A significant intensification of the process in the presence of small amounts of potassium and sodium salts is established. The concepts of the catalyst action mechanism are considered and experimentally substantiated. Manufacture of iron-chromium master alloys with a restricted content of carbon can be organized at low temperatures, and they can be used in steelmaking.

  3. Study of the dynamics of the MoO2-Mo2C system for catalytic partial oxidation reactions

    NASA Astrophysics Data System (ADS)

    Cuba Torres, Christian Martin

    On a global scale, the energy demand is largely supplied by the combustion of non-renewable fossil fuels. However, their rapid depletion coupled with environmental and sustainability concerns are the main drivers to seek for alternative energetic strategies. To this end, the sustainable generation of hydrogen from renewable resources such as biodiesel would represent an attractive alternative solution to fossil fuels. Furthermore, hydrogen's lower environmental impact and greater independence from foreign control make it a strong contender for solving this global problem. Among a wide variety of methods for hydrogen production, the catalytic partial oxidation offers numerous advantages for compact and mobile fuel processing systems. For this reaction, the present work explores the versatility of the Mo--O--C catalytic system under different synthesis methods and reforming conditions using methyl oleate as a surrogate biodiesel. MoO2 exhibits good catalytic activity and exhibits high coke-resistance even under reforming conditions where long-chain oxygenated compounds are prone to form coke. Moreover, the lattice oxygen present in MoO2 promotes the Mars-Van Krevelen mechanism. Also, it is introduced a novel beta-Mo2C synthesis by the in-situ formation method that does not utilize external H2 inputs. Herein, the MoO 2/Mo2C system maintains high catalytic activity for partial oxidation while the lattice oxygen serves as a carbon buffer for preventing coke formation. This unique feature allows for longer operation reforming times despite slightly lower catalytic activity compared to the catalysts prepared by the traditional temperature-programmed reaction method. Moreover, it is demonstrated by a pulse reaction technique that during the phase transformation of MoO2 to beta-Mo2C, the formation of Mo metal as an intermediate is not responsible for the sintering of the material wrongly assumed by the temperature-programmed method.

  4. TiO2 nanoparticles doped SiO2 films with ordered mesopore channels: a catalytic nanoreactor.

    PubMed

    Saha, Jony; Mitra, Anuradha; Dandapat, Anirban; De, Goutam

    2014-04-01

    Titanium dioxide (TiO2) incorporated ordered 2D hexagonal mesoporous silica (SiO2) films on a glass substrate were fabricated for use as a catalytic nanoreactor. Films were prepared using a tetraethyl orthosilicate (TEOS) derived SiO2 sol and a commercially available dispersion of TiO2 nanoparticles (NPs) in the presence of pluronic P123 as the structure directing agent. The effect of TiO2 doping (4-10 mol% with respect to the equivalent SiO2) into the ordered mesoporous SiO2 matrix was thoroughly investigated. The undoped SiO2 film showed a mesostructural transformation after heat-treatment at 350 °C whereas incorporation of TiO2 restricted such a transformation. Among all the TiO2 incorporated films, TEM showed that the 7 equivalent mol% TiO2 doped SiO2 film (ST-7) had an optimal composition which could retain the more organized 2D hexagonal (space group p6mm)-like mesostructures after heat-treatment. The catalytic activities of the TiO2 doped (4-10 mol%) films were investigated for the reduction of toxic KMnO4 in an aqueous medium. ST-7 film showed the maximum catalytic activity, as well as reusability. A TEM study on the resultant solution after KMnO4 reduction revealed the formation of MnO2 nanowires. It was understood that the embedded TiO2 NPs bonded SiO2 matrix increased the surface hydroxyl groups of the composite films resulting in the generation of acidic sites. The catalytic process can be explained by this enhanced surface acidity. The mesoporous channel of the ST-7 films with TiO2 doping can be used as a nanoreactor to form extremely thin MnO2 nanowires.

  5. Supercritical CO{sub 2} mediated synthesis and catalytic activity of graphene/Pd nanocomposites

    SciTech Connect

    Tang, Lulu; Nguyen, Van Hoa; Shim, Jae-Jin

    2015-11-15

    Highlights: • RGO/Pd composite was efficiently prepared via a facile method in supercritical CO{sub 2}. • Graphene sheets were coated uniformly with Pd nanoparticles with a size of ∼8 nm. • Composites exhibited excellent catalytic activity in the Suzuki reaction even after 10 cycles. - Abstract: Graphene sheets were decorated with palladium nanoparticles using a facile and efficient method in supercritical CO{sub 2}. The nanoparticles were formed on the graphene sheets by the simple hydrogen reduction of palladium(II) hexafluoroacetylacetonate precursor in supercritical CO{sub 2}. The product was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Highly dispersed nanoparticles with various sizes and shapes adhered well to the graphene sheets. The composites showed high catalytic activities for the Suzuki reaction under aqueous and aerobic conditions within 5 min. The effects of the different Pd precursor loadings on the catalytic activities of the composites were also examined.

  6. Influence of Water on the Interfacial Nanostructure and Wetting of [Rmim][NTf2] Ionic Liquids at Mica Surfaces.

    PubMed

    Wang, Zhantao; Li, Hua; Atkin, Rob; Priest, Craig

    2016-09-01

    The effect of water concentration on the interfacial nanostructure and wetting behavior of a family of ionic liquids (ILs), 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [Rmim][NTf2], at the surface of mica was investigated by contact angle measurement and atomic force microscopy (AFM). AFM reveals that interfacial layers of ILs observed at the surface of mica for "dry" ILs are not present for water-saturated ILs. The interaction of the IL ions of [Rmim][NTf2] with water molecules through hydrogen bonding is suspected to disrupt IL ion layering and precursor film growth on mica. Without the IL precursor film, contact angle relaxation of "wet" ILs on mica is less significant and ambient vapor adsorption becomes more important in determining the macroscopic wetting behavior. PMID:27486675

  7. Influence of Water on the Interfacial Nanostructure and Wetting of [Rmim][NTf2] Ionic Liquids at Mica Surfaces.

    PubMed

    Wang, Zhantao; Li, Hua; Atkin, Rob; Priest, Craig

    2016-09-01

    The effect of water concentration on the interfacial nanostructure and wetting behavior of a family of ionic liquids (ILs), 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [Rmim][NTf2], at the surface of mica was investigated by contact angle measurement and atomic force microscopy (AFM). AFM reveals that interfacial layers of ILs observed at the surface of mica for "dry" ILs are not present for water-saturated ILs. The interaction of the IL ions of [Rmim][NTf2] with water molecules through hydrogen bonding is suspected to disrupt IL ion layering and precursor film growth on mica. Without the IL precursor film, contact angle relaxation of "wet" ILs on mica is less significant and ambient vapor adsorption becomes more important in determining the macroscopic wetting behavior.

  8. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

    PubMed Central

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-01-01

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate. PMID:26235671

  9. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2.

    PubMed

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-08-03

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate.

  10. Suppressed N2O formation during NH3 selective catalytic reduction using vanadium on zeolitic microporous TiO2

    NASA Astrophysics Data System (ADS)

    Lee, Seung Gwan; Lee, Hyun Jeong; Song, Inhak; Youn, Seunghee; Kim, Do Heui; Cho, Sung June

    2015-08-01

    Emission of N2O from mobile and off-road engine is now being currently regulated because of its high impact compared to that of CO2, thereby implying that N2O formation from the exhaust gas after-treatment system should be suppressed. Selective catalytic reduction using vanadium supported TiO2 catalyst in mobile and off-road engine has been considered to be major source for N2O emission in the system. Here we have demonstrated that vanadium catalyst supported on zeolitic microporous TiO2 obtained from the hydrothermal reaction of bulk TiO2 at 400 K in the presence of LiOH suppresses significantly the N2O emission compared to conventional VOx/TiO2 catalyst, while maintaining the excellent NOx reduction, which was ascribed to the location of VOx domain in the micropore of TiO2, resulting in the strong metal support interaction. The use of zeolitic microporous TiO2 provides a new way of preparing SCR catalyst with a high thermal stability and superior catalytic performance. It can be also extended further to the other catalytic system employing TiO2-based substrate.

  11. Wet chemical methods for producing mixing crystalline phase ZrO2 thin film

    NASA Astrophysics Data System (ADS)

    Pakma, Osman; Özdemir, Cengiz; Kariper, İ. Afşin; Özaydın, Cihat; Güllü, Ömer

    2016-07-01

    The aim of the study is to develop a more economical and easier method for obtaining ZrO2 thin films at lower temperature, unlike the ones mentioned in the literature. For this purpose, wet chemical synthesis methods have been tested and XRD, UV-VIS and SEM analysis of ZrO2 thin films have been performed. At the end of the analysis, we identified the best method and it has been found that the features of the films produced with this method were better than the films produced by using different reagents, as well as the films reported in the literature. Especially it has been observed that the transmittance of the film produced with this method were higher and better than the films in the literature and the others. In addition, refractive index of the film produced with this method was observed to be lower. Moreover, by using the same method Al/ZrO2/p-Si structure has been obtained and it has been compared with Al/p-Si reference structure in terms of electrical parameters.

  12. Structural, catalytic and magnetic properties of Cu1-XCoXFe2O4

    NASA Astrophysics Data System (ADS)

    Briceño, Sarah; Castillo, Hector Del; Sagredo, V.; Bramer-Escamilla, Werner; Silva, Pedro

    2012-12-01

    Copper substituted cobalt ferrite Cu1-XCoXFe2O4 (0 ≤x ≤ 1) have been synthesized using sol-gel auto combustion method with citric acid as fuel. Structural identification, magnetic and catalytic properties were investigated using thermogravimetric and differential thermal analysis, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry and their application in the selective catalytic reduction of NOx were studied. Analysis of structural properties reveals that all samples have cubic spinel structure. Room temperature magnetic hysteresis measurements as a function of magnetic field infer that the magnetic properties decrease with Cu2+ doping which may be due to the difference of the magnetic moment of Cu2+ and Co2+ ions. The higher activity of the samples in NO selective reduction to N2 occurs at 350 °C, reaching a maximum of 38% NO conversion and 95% of selective conversion to N2. The compositions containing both Cu2+ and Co2+ ions are more active to the products selectivity to N2, suggesting a synergistic effect on the active surface of ferrite and the effect of Co2+ is more pronounced than Cu2+ towards NO conversion.

  13. Operation regimes in catalytic combustion: H{sub 2}/air mixtures near Pt

    SciTech Connect

    Park, Y.K.; Bui, P.A.; Vlachos, D.G.

    1998-09-01

    The influence of a platinum catalyst on flammability limits and operation windows for catalytic and catalyst-assisted homogeneous oxidation is studied, for the first time to the authors` knowledge, as a function of H{sub 2} in air composition in a stagnation-point flow geometry. The results show that the coupling between the homogeneous and heterogeneous chemistries leads to relatively easy startup, the coexistence of catalytically (partially) and homogeneously (completely) ignited branches under certain conditions, and the expansion of the fuel-lean and rich flammability limits. A strategy to attain virtually any desired operation regime is discussed. It is shown that synergism between homogeneous and heterogeneous chemistries leads to higher combustion efficiency and lower fuel emissions at elevated temperatures for fuel-lean mixtures only. Analysis of the flammability limits indicates that heat generated by surface reactions is primarily responsible for expansion of the flammability limits. Finally, a direct transition to flames occurs over a wide range of composition upon catalytic ignition in the absence of surface heat loss.

  14. Fabrication of Ag/TiO2 nanotube array with enhanced photo-catalytic degradation of aqueous organic pollutant

    NASA Astrophysics Data System (ADS)

    Ma, Jie; Yang, Mingxuan; Sun, Yiran; Li, Chenlu; Li, Qiang; Gao, Fangfang; Yu, Fei; Chen, Junhong

    2014-04-01

    In this paper, the fabrication of Ag/TiO2 nanotube arrays and their photo-catalytic activity have been studied. The SEM, TEM and XRD were performed to characterize the morphology and crystalline phase of the TiO2 nanotube array and Ag/TiO2 nanotube array. Ag nanoparticles with different loadings, which are aimed to suppress the electron-hole recombination so as to enhance the photo-catalytic oxidation efficiency, were systematically coated onto TiO2 nanotubes. The photo-catalytic activity of these nano-materials was evaluated by the degradation of two different pollutants: methyl orange and glyphosate. The effects of various parameters, such as the amount of the photo-catalyst, the illumination time, and pH value on the photo-catalytic oxidation activity, were studied.

  15. Synthesis of TiO2 Nanofluids by Wet Mechanochemical Process

    NASA Astrophysics Data System (ADS)

    Harjanto, S.; Sutanto, H.; Setiaji, R.; Yuwono, A. H.; Ferdian, D.

    2011-12-01

    Nanofluids have been developed in a search of new coolants with higher thermal conductivity compared to the conventional coolants, such as water or ethylene glycol. This research is conducted to observe the main characteristics, such as particle size, suspension stability, and thermal conductivity, of nanofluids produced from wet mechanochemical process with the addition of 0.02 vol% oleic acid. Milling process was conducted in conventional planetary ball mill for 15 hours. The results showed that nanoparticle was formed from micron size raw materials and dan dispersed simultaneously in water. Particle size distribution of particles which are less than 100 nm size were in the range of 51-100%. The ratio of thermal conductivity enhancement of the 1% vol TiO2 nanofluids compared with water without surfactant is 1.1. The ratio of thermal conductivity of TiO2 nanofluids increases in higher concentration of nanofluids. Oleic acid addition increases the particle stability of nanofluids and its ratio of thermal conductivity.

  16. Identification of the Catalytic Mg2+ Ion in the HDV Ribozyme

    PubMed Central

    Chen, Ji; Ganguly, Abir; Miswan, Zulaika; Hammes-Schiffer, Sharon; Bevilacqua, Philip C.; Golden, Barbara L.

    2013-01-01

    The hepatitis delta virus ribozyme catalyzes an RNA cleavage reaction using a catalytic nucleobase and a divalent metal ion. The catalytic base, C75, serves as a general acid and has a pKa shifted towards neutrality. Less is known about the role of metal ions in the mechanism. A recent crystal structure of the pre-cleavage ribozyme identified a Mg2+ ion that interacts through its partial hydration sphere with the G25•U20 reverse wobble. In addition, this Mg2+ ion is in position to directly coordinate the nucleophile, the 2’-hydroxyl of U(-1), suggesting it can serve as a Lewis acid to facilitate deprotonation of the 2’-hydroxyl. To test the role of the active site Mg2+ ion, we replaced the G25•U20 reverse wobble with an isosteric A25•C20 reverse wobble. This change was found to significantly reduce the negative potential at the active site, as supported by electrostatics calculations, suggesting that active site Mg2+ binding could be adversely affected by the mutation. Kinetic analysis and molecular dynamics of the A25•C20 double mutant suggest that this variant stably folds into an active structure. However, pH-rate profiles of the double mutant are inverted relative to the profiles for wild-type ribozyme, suggesting that the A25•C20 double mutant has lost the active site metal ion. Overall, these studies support a model wherein the partially hydrated Mg2+ positioned at the G25•U20 reverse wobble is catalytic and could serve as a Lewis acid, a Brønsted base, or both to facilitate deprotonation of the nucleophile. PMID:23311293

  17. Switchable catalytic DNA catenanes.

    PubMed

    Hu, Lianzhe; Lu, Chun-Hua; Willner, Itamar

    2015-03-11

    Two-ring interlocked DNA catenanes are synthesized and characterized. The supramolecular catenanes show switchable cyclic catalytic properties. In one system, the catenane structure is switched between a hemin/G-quadruplex catalytic structure and a catalytically inactive state. In the second catenane structure the catenane is switched between a catalytically active Mg(2+)-dependent DNAzyme-containing catenane and an inactive catenane state. In the third system, the interlocked catenane structure is switched between two distinct catalytic structures that include the Mg(2+)- and the Zn(2+)-dependent DNAzymes. PMID:25642796

  18. The Synthesis and Characterization of Multifunctional Titania-based Materials for the Photo/Thermal Catalytic Reduction of CO2

    NASA Astrophysics Data System (ADS)

    Schwartzenberg, Kevin

    The work presented in this dissertation is aimed at improving our understanding of the fundamental processes required for the photocatalytic reduction of CO2. A QCM reactor system for measuring CO2 adsorption under a range of conditions was designed, constructed, and characterized. Measurements on catalyst films revealed sufficient sensitivity to detect CO2 adsorption on the order of 0.1 molecules/nm2. Adsorption experiments were repeatable across multiple measurements for the same film. However, variation across multiple films prepared using the same mass of catalyst highlights the large contribution of surface roughness to frequency response and the importance of uniform, reproducible film preparation. The design of a multifunctional photo/thermal catalyst was explored through the concept of MnOx-TiO2 composites with thermally generated oxygen vacancies as the active sites for CO2 activation. MnOx-TiO 2 were prepared by incipient wetness impregnation of titania supports with one of two Mn precursors, and were characterized and screened for catalytic activity. The results were compared with predictions from theoretical modeling studies. Through TPR, UV-vis spectroscopy, and XANES, it was observed that a Mn(NO 3)2•4H2O precursor led to bulk-like domains of MnOx whereas a Mn(CH3COO)2•4H2O precursor led to a dispersed surface oxide. This precursor effect was less pronounced on rutile than on anatase support. As predicted by theory, the MnOx-TiO 2 exhibited the reversible generation of oxygen vacancies at mild temperatures (< 300°C) and a red shift in the band gap for anatase-supported composites. A similar red shift was not observed for rutile-supported materials. In screening reactions, however, neither CO nor other products were detected by GC. In-situ FTIR experiments also failed to show evidence of nonvolatile CO2 reduction products. However, several carbonate, bicarbonate, and carboxylate species were observed, confirming the interaction of CO 2 with oxygen

  19. Catalytic processes during preferential oxidation of CO in H 2-rich streams over catalysts based on copper-ceria

    NASA Astrophysics Data System (ADS)

    Gamarra, D.; Hornés, A.; Koppány, Zs.; Schay, Z.; Munuera, G.; Soria, J.; Martínez-Arias, A.

    Nanostructured catalysts based on combinations between oxidised copper and cerium entities prepared by two different methods (impregnation of ceria and coprecipitation of the two components within reverse microemulsions) have been examined with respect to their catalytic performance for preferential oxidation of CO in a H 2-rich stream (CO-PROX). Correlations between their catalytic and redox properties are established on the basis of parallel analyses of temperature programmed reduction results employing both H 2 and CO as reactants as well as by XPS. Although general catalytic trends can be directly correlated with the redox properties observed upon separate interactions with each of the two reductants (CO and H 2), the existence of interferences between both reductants must be considered to complete details for such activity/redox correlation. Differences in the nature of the active oxidised copper-cerium contacts present in each case determine the catalytic properties of these systems for the CO-PROX process.

  20. Evaluation of thermal catalytic decomposition of organic compounds with TiO2 by packed-capillary gas chromatography.

    PubMed

    Ueta, Ikuo; Mizuguchi, Ayako; Tani, Kazue; Kawakubo, Susumu; Saito, Yoshihiro

    2014-01-01

    A novel method for evaluating the thermal catalytic decomposition of organic compounds on a solid acid catalyst was developed using a capillary gas chromatography-flame ionization detector (GC-FID) equipped with a packed-capillary column. The thermal catalytic decomposition of various organic compounds was investigated by introducing gaseous or liquid organic compounds into a heated test tube packed with TiO2 particles. The resulting carbon monoxide (CO) and carbon dioxide (CO2) in the test tube were determined in a conventional capillary GC system with a methanizer after separation on a packed-capillary column. In the packed-capillary GC system, several parameters affecting thermal catalytic reactions of various organic compounds were successfully evaluated, such as the type of the catalysts and the effect of catalytic temperatures. Finally, a sequential decomposition of organic compounds was confirmed in the heated reaction tube packed with TiO2 particles. PMID:24614737

  1. High Resolution Crystal Structure of the Catalytic Domain of ADAMTS-5 (Aggrecanase-2)

    SciTech Connect

    Shieh, Huey-Sheng; Mathis, Karl J.; Williams, Jennifer M.; Hills, Robert L.; Wiese, Joe F.; Benson, Timothy E.; Kiefer, James R.; Marino, Margaret H.; Carroll, Jeffery N.; Leone, Joseph W.; Malfait, Anne-Marie; Arner, Elizabeth C.; Tortorella, Micky D.; Tomasselli, Alfredo

    2008-06-30

    Aggrecanase-2 (a disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS-5)), a member of the ADAMTS protein family, is critically involved in arthritic diseases because of its direct role in cleaving the cartilage component aggrecan. The catalytic domain of aggrecanase-2 has been refolded, purified, and crystallized, and its three-dimensional structure determined to 1.4{angstrom} resolution in the presence of an inhibitor. A high resolution structure of an ADAMTS/aggrecanase protein provides an opportunity for the development of therapeutics to treat osteoarthritis.

  2. Superiority of wet-milled over dry-milled superfine powdered activated carbon for adsorptive 2-methylisoborneol removal.

    PubMed

    Pan, Long; Matsui, Yoshihiko; Matsushita, Taku; Shirasaki, Nobutaka

    2016-10-01

    Superfine powdered activated carbon (SPAC), which is produced from conventionally sized powdered activated carbon (PAC) by wet milling in a bead mill, has attracted attention for its high adsorptive removal ability in both research and practice. In this study, the performance of dry-milled SPAC was investigated. 2-Methylisoborneol (MIB), an earthy-musty compound commonly targeted by water treatment systems, was used as the target adsorbate. Dry-milled SPAC exhibited lower adsorptive removal of MIB than wet-milled SPAC, even when both SPACs were produced from the same PAC and were composed of particles of the same size. One reason for the lower removal of MIB by the dry-milled SPAC was a higher degree of aggregation in the dry-milled SPAC after production; as a result the apparent particle size of dry-milled SPAC was larger than that of wet-milled SPAC. The dry-milled SPAC was also more negatively charged than the wet-milled SPAC, and, owing to its higher repulsion, it was more amenable to dispersion by ultrasonication. However, even after the dry-milled SPAC was ultrasonicated so that its apparent particle size was similar to or less than that of the wet-milled SPAC, the dry-milled SPAC was still inferior in adsorptive removal to the wet-milled SPAC. Therefore, another reason for the lower adsorptive removal of dry-milled SPAC was its lower equilibrium adsorption capacity due to the oxidation during the milling. The adsorption kinetics by SPACs with different degrees of particle aggregation were successfully simulated by a pore diffusion model and a fractal aggregation model. PMID:27403874

  3. SO 2 adsorption capacity of K 2CO 3-impregnated activated carbon as a function of K 2CO 3 content loaded by soaking and incipient wetness

    NASA Astrophysics Data System (ADS)

    Fortier, H.; Zelenietz, C.; Dahn, T. R.; Westreich, P.; Stevens, D. A.; Dahn, J. R.

    2007-01-01

    The SO 2 adsorption capacity of K 2CO 3-impregnated activated carbons, prepared by soaking carbon in large volumes of K 2CO 3 in solution of various concentrations, varies linearly with respect to the loading of K 2CO 3 on the carbon up to about 12% K 2CO 3 by weight. Above 12%, the capacity for SO 2 levels out and then decreases. This suggests that at high loadings the K 2CO 3 either aggregates and/or blocks pores of the activated carbon. In contrast, the adsorption capacity of carbons prepared by repeatedly (maximum of three times total) loading K 2CO 3 via incipient wetness is much larger than that of the soaked samples, up to 70% more, when the loading of K 2CO 3 is greater than 12%. Static and dynamic adsorption, DSC, SEM, EDX and incipient wetness studies of the samples show that the impregnant aggregates but does not block carbon pores.

  4. Synthesis of Au-SiO2 Composite Nanospheres and Their Catalytic Activity.

    PubMed

    Dexuan, Wang; Guian, Li; Qingyan, Han; Ziqiang, Wang; Liping, Pan; Zhonayue, Zhang; Hairong, Zhenq

    2016-04-01

    We report a simple and environmentally friendly approach to the synthesis of Au-SiC2 composite nanospheres. Our method presents a route for the decoration of preformed amine functionalized SiO2 nanospheres by in situ formation of Au nanoparticles at three different concentrations of Au precursor (HAuCl4). Herein, the silane coupling agent (KH-550) is used as an intermediary to connect the Au nanoparticles to the surfaces of the SiO2 nanospheres, which helps avoid the aggregation of Au nanoparticles. The crystal structure, chemical elements, morphology and catalytic properties of the Au-SiO2 composite nanospheres were analyzed by transmission electron microscopy (TEM), X-Ray powder diffraction (XRD), UV-vis-spectrophotometer (UV-vis) and X-ray photoelectron spectroscopy (XPS). The analytical results demonstrate that the Au nanoparticles (4-9 nm) were homogeneously distributed on the surface of the SiO2 nanospheres, which had a good FCC crystal structure. Moreover, the Au-SiO2 composite nanospheres exhibited good catalytic properties, measured by their ability to reduce organic dyes. The Au-SiO2 composite nanospheres are promising candidates for applications in catalysis and wastewater treatment. PMID:27451717

  5. LOXL2 catalytically inactive mutants mediate epithelial-to-mesenchymal transition.

    PubMed

    Cuevas, Eva P; Moreno-Bueno, Gema; Canesin, Giacomo; Santos, Vanesa; Portillo, Francisco; Cano, Amparo

    2014-01-01

    Lysyl-oxidase-like 2 (LOXL2) is a member of the lysyl oxidase family that catalyzes the cross-linking of collagens or elastins in the extracellular matrix, thus regulating the tensile strength of tissues. However, many reports have suggested different intracellular roles for LOXL2, including the ability to regulate gene transcription and tumor progression. We previously reported that LOXL2 mediates epithelial-to-mesenchymal transition (EMT) by Snail1-dependent and independent mechanisms, related to E-cadherin silencing and downregulation of epidermal differentiation and cell polarity components, respectively. Whether or not the catalytic activity of LOXL2 is required to induce/sustain EMT is actually unknown. Here we show that LOXL2 catalytic inactive mutants collaborate with Snail1 in E-cadherin gene repression to trigger EMT and, in addition, promote FAK/Src pathway activation to support EMT. These findings reveal a non-conventional role of LOXL2 on regulating epithelial cell plasticity. PMID:24414204

  6. Wet air oxidation of pretreatment of pharmaceutical wastewater by Cu2+ and [PxWmOy]q- co-catalyst system.

    PubMed

    Wang, Guowen; Wang, Dong; Xu, Xiaochen; Liu, Lifen; Yang, Fenglin

    2012-05-30

    This study concentrates on the pretreatment of real wastewater using catalytic wet air oxidation (CWAO). WO(3-) and PO(4)(3-) contained in fosfomycin pharmaceutical wastewater (FPW) and Cu(2+) contained in berberine pharmaceutical wastewater (BPW) were studied as CWAO influent. Mixture of this two streams were reused to form Cu(2+) and [P(x)W(m)O(y)](q-), namely polyoxometalates (POMs) as co-catalyst system to treat themselves. Experiments were conducted to investigate the effects of the initial oxygen pressure and temperature on the COD (chemical oxygen demand), TOC (total organic carbon) removal and biodegradable enhancement, it was discovered that over 40% of COD and TOC removal can be easily realized in an hour of WAO oxidation at 523 K, 1.4 MPa. The BOD(5)/COD (BOD(5), biochemical oxygen demand in 5 days) of this two pharmaceutical mixture ascended from nonexistent to maximum 0.41 depends on the optimal FPW:BPW volume ratio 4:1, to compose POM co-catalyst system. Organic pollutants were incompletely oxidized to propionic acid and other intermediates. Some properties (e.g., TGA, IR, XRF) of POM catalyst separated from effluent, were obtained to provide additional information. PMID:22494900

  7. Initial Wetting and Spreading Rates Between SiC and CaO-SiO2-MnO Slag

    NASA Astrophysics Data System (ADS)

    Park, Jungseon; Jeon, Junmo; Lee, Kyuyoung; Park, Joo Hyun; Chung, Yongsug

    2016-06-01

    The wetting of CaO-SiO2-MnO slag on silicon carbide was studied with a variety of slag compositions at 1823 K (1550 °C). Wetting experiments were performed by the dispensed drop technique. We observed complete wetting of the slag on SiC (within 1 second) without a bubble reaction regardless of the basicity (=CaO/SiO2 = C/S ratio). However, after 8 seconds, the bubble reaction was observed under conditions of C/S = 0.8 and 1.1, whereas it was not observed at temperatures lower than 1823 K (1550 °C). The contact angle was independent of MnO content, while the spreading rate increased with the increasing MnO content at the early stage of wetting. Inertial force acts on the early stage of spreading, and viscous force acts with lower MnO content due to higher viscosity. The low-viscosity slag did not fit with the nonreactive viscous model. However, the high-viscosity slag fitted the model well.

  8. Effect of ZrO{sub 2}-doping of nanosized Fe{sub 2}O{sub 3}/MgO system on its structural, surface and catalytic properties

    SciTech Connect

    Hassan, Neveen A.; El-Molla, Sahar A.; Mohamed, Ghada M.; Fagal, Gehan A.

    2012-09-15

    Highlights: ► Preparation and characterization nano-sized ZrO{sub 2}-doped Fe{sub 2}O{sub 3}/MgO system. ► Pure and doped solids calcined at 500 and 700 °C are mesoporous adsorbents. ► ZrO{sub 2}-doping increased the lattice constant “a” of MgO lattice to an extent proportional to the amount of ZrO{sub 2} added. ► The catalytic activity in H{sub 2}O{sub 2} decomposition was found to increase as a function of dopant concentration. -- Abstract: Fe{sub 2}O{sub 3}/MgO system was prepared by wet impregnation method followed by treatment with different amounts of Zr-dopant salt then heating at 500 and 700 °C. The dopant concentrations were 0.48, 0.95 and 1.4 mol% ZrO{sub 2}. Pure and variously doped solids were characterized using XRD, N{sub 2}-adsorption isotherms carried out at −196 °C and catalytic decomposition of H{sub 2}O{sub 2} in aqueous solution at 25–35 °C. The results revealed that the nanosized MgO phase was only detected in the diffractograms of pure and doped solids calcined at 500 °C. Heating pure and doped solids at 700 °C produced nanosized MgFe{sub 2}O{sub 4} phase together with MgO phase. Pure and ZrO{sub 2}-doped solids calcined at 500 and 700 °C are mesoporous adsorbents. The doping process brought about a measurable decrease in the S{sub BET} of Fe{sub 2}O{sub 3}/MgO system with subsequent increase in its catalytic activity. The catalytic activity of the investigated system toward H{sub 2}O{sub 2} decomposition, expressed as reaction rate constant per unit surface area was found to increase as a function of dopant concentration. The maximum increase in the reaction rate constant per unit surface area measured for the reaction carried out at 30 °C attained 125% for the heavily doped samples. This significant increase was based on the catalytic activity of pure catalyst sample measured under the same conditions.

  9. Structure of the catalytic domain of the hepatitis C virus NS2-3 protease

    SciTech Connect

    Lorenz,I.; Marcotrigiano, J.; Dentzer, T.; Rice, C.

    2006-01-01

    Hepatitis C virus is a major global health problem affecting an estimated 170 million people worldwide. Chronic infection is common and can lead to cirrhosis and liver cancer. There is no vaccine available and current therapies have met with limited success. The viral RNA genome encodes a polyprotein that includes two proteases essential for virus replication. The NS2-3 protease mediates a single cleavage at the NS2/NS3 junction, whereas the NS3-4A protease cleaves at four downstream sites in the polyprotein. NS3-4A is characterized as a serine protease with a chymotrypsin-like fold, but the enzymatic mechanism of the NS2-3 protease remains unresolved. Here we report the crystal structure of the catalytic domain of the NS2-3 protease at 2.3 Angstroms resolution. The structure reveals a dimeric cysteine protease with two composite active sites. For each active site, the catalytic histidine and glutamate residues are contributed by one monomer, and the nucleophilic cysteine by the other. The carboxy-terminal residues remain coordinated in the two active sites, predicting an inactive post-cleavage form. Proteolysis through formation of a composite active site occurs in the context of the viral polyprotein expressed in mammalian cells. These features offer unexpected insights into polyprotein processing by hepatitis C virus and new opportunities for antiviral drug design.

  10. Investigation of Potassium Feldspar Reactivity in Wet Supercritical CO2 by In Situ Infrared Spectroscopy

    NASA Astrophysics Data System (ADS)

    Thompson, C.; Widener, C.; Schaef, T.; Loring, J.; McGrail, B. P.

    2014-12-01

    Capture and subsequent storage of CO2 in deep geologic reservoirs is progressively being considered as a viable approach to reduce anthropogenic greenhouse gas emissions. In the long term, injected CO2 may become permanently entrapped as silicate minerals react with CO2 enriched fluids to form stable carbonate minerals. Potassium feldspars are highly abundant in the earth's crust and are present in the caprocks and storage formations of many target reservoirs. While the dissolution kinetics and carbonation reactions of feldspars have been well studied in the aqueous phase, comparatively little work has focused on K-feldspar reactivity in the CO2-rich fluid. In this study, we used in situ infrared spectroscopy to investigate the carbonation reactions of natural microcline samples. Experiments were carried out at 50 °C and 91 bar by circulating dry or wet supercritical CO2 (scCO2) past a thin film of powdered sample. Water concentrations ranged from 0% to 125% relative to saturation, and transmission-mode absorbance spectra were recorded as a function of time for 48 hours. No discernible reaction was detected when the samples were exposed to anhydrous scCO2. However, in fully water-saturated scCO2, a thin film of liquid-like water was observed on the samples' surfaces, and up to 0.6% of the microcline was converted to a carbonate phase. Potassium carbonate is the most likely reaction product, but minor amounts of sodium carbonate and siderite may also have formed from minor sample impurities. The extent of reaction appears to be related to the thickness of the water film and is likely a consequence of the film's ability to solvate and transport ions in the vicinity of the mineral surface. Other features observed in the spectra correspond to microcline dissolution and precipitation of amorphous silica. Implications about the role of water in these reactions and the relative effectiveness of alkali feldspars for mineral trapping of CO2 will be discussed.

  11. Investigation of Plagioclase Reactivity in Wet Supercritical CO2 by In Situ Infrared Spectroscopy

    NASA Astrophysics Data System (ADS)

    Thompson, C.; Gauglitz, K.; Loring, J.; Schaef, T.; Miller, Q.; Johnson, K. T.; Wang, Z.; Rosso, K. M.; McGrail, P.

    2013-12-01

    Increasingly, CO2 capture and subsequent storage in deep geologic reservoirs is being implemented as a viable approach for reducing anthropogenic emissions of CO2 into the atmosphere. Several mechanisms may act to secure the injected CO2, including hydrodynamic confinement, dissolution into reservoir fluids, retention of CO2 as a separate phase in pore spaces, and carbonation of reservoir minerals. This latter mechanism is the most permanent, but it requires the presence of reactive minerals and potentially significant amounts of time for the reactions to proceed. Plagioclase feldspars are highly abundant in the earth's crust and are present in the caprocks and storage formations of many target reservoirs. Although the dissolution kinetics and carbonation reactions of feldspars have been well studied in the aqueous phase, comparatively little work has focused on plagioclase reactivity in the CO2-rich fluid at conditions relevant to geologic carbon sequestration. In this study, we used in situ infrared spectroscopy to investigate the carbonation potential of a powdered plagioclase sample similar to labradorite [(Ca,Na)(Al,Si)4O8] that had been isolated from a Hawaiian basalt. Experiments were carried out at 50 °C and 91 bar by circulating a stream of dry or wet supercritical CO2 (scCO2) past a sample overlayer deposited on the window of a high-pressure infrared flow cell. Water concentrations ranged from 0% to 125% relative to saturation, and transmission-mode absorbance spectra were recorded as a function of time for 24 hours. In experiments with excess water, a controlled temperature gradient was used to intentionally condense a film of liquid water on the overlayers' surfaces. No discernible reaction was detected when the samples were exposed to anhydrous scCO2. When water was added, a thin film of liquid-like water was observed on the samples' surfaces, and up to 0.3% of the plagioclase was converted to a carbonate phase. Calcite is the most likely reaction

  12. Evaluation of wet tantalum capacitors after exposure to extended periods of ripple current, volume 2

    NASA Technical Reports Server (NTRS)

    Ward, C. M.

    1975-01-01

    The application of tantalum capacitors in the Viking Lander includes dc voltage and ripple current electrical stress, high temperature during nonoperating times (sterilization), and high vibration and shock loads. The capacitors must survive these severe environments without any degradation if reliable performance is to be achieved. A test program was established to evaluate both wet-slug tantalum and wet-foil capacitors under conditions accurately duplicating actual Viking applications. Test results of the electrical performance characteristics during extended periods of ripple current, the characteristics of the internal silver migration as a function of extended periods of ripple current, and the existence of any memory characteristics are presented.

  13. One-pot, one-step, catalytic synthesis of 2,5-diformylfuran from fructose

    NASA Astrophysics Data System (ADS)

    Tao, Furong; Cui, Yuezhi; Yang, Pengfei; Gong, Yinghua

    2014-07-01

    MIL-101, a chromium-based metal-organic framework, is known for its very large pore size, large surface area and good stability. However, application of this material in catalysis is still limited. In this paper, a simple and practical catalytic method for the preparation 2,5-diformylfuran (DFF) directly from fructose was investigated. 5% Pd-V(3: 2)@MIL-101 was evaluated as a potential and effective catalyst for the direct oxidation of fructose. The amount of the catalyst, reaction time and temperature had a large effect on the reaction. At the optimized reaction conditions, when the reaction was conducted at 140°C for 600 min, 1 atm oxygen pressure, the yield of DFF reached 34%, fructose conversion was up to 100%. In our system, the main side products were 5-formyl-2-furancarboxylic acid (FFCA) and 2,5-furandicarboxylic acid (FDCA), which are the products of deep oxidation of DFF. This simple and effective catalytic system may be valuable to facilitate energy-efficient conversion of fructose into biofuels and platform chemicals.

  14. Synthesis, spectroscopic and catalytic properties of some new boron hybrid molecule derivatives by BF2 and BPh2 chelation

    NASA Astrophysics Data System (ADS)

    Kilic, Ahmet; Alcay, Ferhat; Aydemir, Murat; Durgun, Mustafa; Keles, Armagan; Baysal, Akın

    2015-05-01

    A new series of Schiff base ligands (L1-L3) and their corresponding fluorine/phenyl boron hybrid complexes [LnBF2] and [LnBPh2] (n = 1, 2 or 3) have been synthesized and well characterized by both analytical and spectroscopic methods. The Schiff base ligands and their corresponding fluorine/phenyl boron hybrid complexes have been characterized by NMR (1H, 13C and 19F), FT-IR, UV-Vis, LC-MS, and fluorescence spectroscopy as well as melting point and elemental analysis. The fluorescence efficiencies of phenyl chelate complexes are greatly red-shifted compared to those of the fluorine chelate analogs based on the same ligands, presumably due to the large steric hindrance and hard π → π∗ transition of the diphenyl boron chelation, which can effectively prevent molecular aggregation. The boron hybrid complexes were applied to the transfer hydrogenation of acetophenone derivatives to 1-phenylethanol derivatives in the presence of 2-propanol as the hydrogen source. The catalytic studies showed that boron hybrid complexes are good catalytic precursors for transfer hydrogenation of aromatic ketones in 0.1 M iso-PrOH solution. Also, we have found that both steric and electronic factors have a significant impact on the catalytic properties of this class of molecules.

  15. Catalytic combustion of benzene over CuO-CeO2 mixed oxides.

    PubMed

    Jung, Won Young; Lim, Kwon-Taek; Hong, Seong-Soo

    2014-11-01

    Catalytic combustion of benzene over CuO-CeO2 mixed oxides has been investigated. The CuO-CeO2 mixed oxides were prepared by the combustion method using malic acid as an organic fuel and characterized by XRD, XPS and TPR. For the CuO-CeO2 catalyst with a Cu/(Cu + Ce) molar ratio of more than 0.4, highly dispersed copper oxide species were shown at 2θ = 35.5 degrees and 38.8 degrees. The CuO-CeO2 catalyst prepared using 2.0 M malic acid showed the highest activity, with conversion reaching nearly 100% at 350 degrees C. In addition, the highest activity is shown on Cu0.40 (the index denotes the molar ratio Cu/(Cu + Ce)) sample and then it decreases on Cu0.5 and Cu0.7 samples. PMID:25958554

  16. Catalytic Hydrothermal Gasification of Wet Biomass Feedstock

    SciTech Connect

    2006-04-01

    Industries and municipalities generate substantial amounts of biomass as high-moisture waste streams, such as animal manure, food processing sludge, stillage from ethanol production, and municipal wastewater sludge.

  17. Catalytic behavior of AMoO{sub x} (A = Ba, Sr) in oxidation of 2-propanol

    SciTech Connect

    Kubo, Jun Ueda, Wataru

    2009-04-02

    Perovskite-type oxides, BaMoO{sub 3} and SrMoO{sub 3}, were prepared by reduction of scheelite-type oxides, BaMoO{sub 4} and SrMoO{sub 4}, in H{sub 2} flow at 873 K and characterized by XRD, TG, SEM, TPR, NH{sub 3}-TPD, UV-vis DRS and BET measurement. The catalytic activity of these alkaline-earth molybdenum oxide catalysts was tested for oxidation of 2-propanol with gaseous oxygen under atmospheric pressure. Dehydration to propylene was mainly promoted over the scheelite-type with Mo{sup 6+}, while oxidative dehydrogenation to acetone was mainly promoted over the perovskite-type with Mo{sup 4+}, and selectivity to acetone was much higher over BaMoO{sub 3} than over SrMoO{sub 3}. Both perovskite-type oxide catalysts underwent oxidation to some degree during the catalytic reaction, so that they also contained some Mo{sup 6+}. We concluded that the high selectivity to acetone resulting from oxidative dehydrogenation during 2-propanol conversion is related to the constantly changing oxidation state of the catalyst, resulting in coexistence of Mo{sup 6+} octahedra and Mo{sup 4+} octahedra on the AMoO{sub 3} oxides.

  18. Antibiotic Binding Drives Catalytic Activation of Aminoglycoside Kinase APH(2″)-Ia.

    PubMed

    Caldwell, Shane J; Huang, Yue; Berghuis, Albert M

    2016-06-01

    APH(2″)-Ia is a widely disseminated resistance factor frequently found in clinical isolates of Staphylococcus aureus and pathogenic enterococci, where it is constitutively expressed. APH(2″)-Ia confers high-level resistance to gentamicin and related aminoglycosides through phosphorylation of the antibiotic using guanosine triphosphate (GTP) as phosphate donor. We have determined crystal structures of the APH(2″)-Ia in complex with GTP analogs, guanosine diphosphate, and aminoglycosides. These structures collectively demonstrate that aminoglycoside binding to the GTP-bound kinase drives conformational changes that bring distant regions of the protein into contact. These changes in turn drive a switch of the triphosphate cofactor from an inactive, stabilized conformation to a catalytically competent active conformation. This switch has not been previously reported for antibiotic kinases or for the structurally related eukaryotic protein kinases. This catalytic triphosphate switch presents a means by which the enzyme can curtail wasteful hydrolysis of GTP in the absence of aminoglycosides, providing an evolutionary advantage to this enzyme.

  19. MnO2/CeO2 for catalytic ultrasonic decolorization of methyl orange: Process parameters and mechanisms.

    PubMed

    Zhao, He; Zhang, Guangming; Chong, Shan; Zhang, Nan; Liu, Yucai

    2015-11-01

    MnO2/CeO2 catalyst was prepared and characterized by means of Brunauer-Emmet-Teller (BET) method, X-ray diffraction (XRD) and scanning electron microscope (SEM). The characterization showed that MnO2/CeO2 had big specific surface area and MnO2 was dispersed homogeneously on the surface of CeO2. Excellent degradation efficiency of methyl orange was achieved by MnO2/CeO2 catalytic ultrasonic process. Operating parameters were studied and optimized. The optimal conditions were 10 min of ultrasonic irradiation, 1.0 g/L of catalyst dose, 2.6 of pH value and 1.3 W/ml of ultrasonic density. Under the optimal conditions, nearly 90% of methyl orange was removed. The mechanism of methyl orange degradation was further studied. The decolorization mechanism in the ultrasound-MnO2/CeO2 system was quite different with that in the ultrasound-MnO2 system. Effects of manganese and cerium in catalytic ultrasonic process were clarified. Manganese ions in solution contributed to generating hydroxyl free radical. MnO2/CeO2 catalyst strengthened the oxidation ability of ultrasound and realized complete decolorization of methyl orange.

  20. Yolk-shell Fe(0)@SiO2 nanoparticles as nanoreactors for fenton-like catalytic reaction.

    PubMed

    Liu, Chao; Li, Jiansheng; Qi, Junwen; Wang, Jing; Luo, Rui; Shen, Jinyou; Sun, Xiuyun; Han, Weiqing; Wang, Lianjun

    2014-08-13

    Yolk-shell nanoparticles (YSNs) with active metal cores have shown promising applications in nanoreactors with excellent catalytic performance. In this work, Fe(0)@SiO2 YSNs were synthesized by a sequential "two-solvents" impregnation-reduction approach. Specifically, FeSO4 aqueous solution was introduced into the preformed hollow mesoporous silica spheres (HMSS), dispersed in n-hexane, via a "two-solvent" impregnation way. Subsequently, aqueous solution of sodium borohydride (NaBH4) was introduced into the cavity of HMSS by the same way, leading to the formation of Fe core inside the HMSS through the reaction between Fe(2+) and NaBH4. The resulting Fe(0)@SiO2 YSNs possess distinctive structures, including active cores, accessible mesoporous channels, protective shells, and hollow cavities. To present the catalytic performance of YSNs nanoreactors, Fenton-like catalytic oxidation of phenol was chosen as the model catalysis reaction. In addition to the Fe(0)@SiO2 YSNs, two other materials were also applied to the catalytic system for comparison, including Fe@SiO2 composites with iron nanoparticles sticking on the outer shells of HMSS (Fe@SiO2-DI) and bare iron nanoparticles without HMSS (bare Fe(0)), respectively. The catalytic results show that Fe(0)@SiO2 YSNs exhibit higher catalytic rate toward phenol removal at 2-fold and 4-fold as compared to that of Fe@SiO2-DI and bare Fe(0), indicating the outstanding catalytic property of YSNs nanoreactors. To further clarify the relationship between catalytic properties and structural characteristics, the adsorption experiments of the three samples were also performed in the absence of H2O2. Other than catalytic results, Fe(0)@SiO2 YSNs show slightly higher adsorption efficiency than the other two samples, indicating the accessibility of nanoreactors. This result demonstrates that the removal of phenol in the oxidation system of Fe(0)@SiO2 YSNs may have contributed to the structure-enhanced effect of YSNs as nanoreactors.

  1. Catalytic ozonation of 2,4-dichlorophenoxyacetic acid using alumina in the presence of a radical scavenger.

    PubMed

    Guzman-Perez, Carlos A; Soltan, Jafar; Robertson, Jared

    2012-01-01

    Using a laboratory-scale mixed reactor, the performance of alumina in degrading 2,4-Dichlorophenoxyacetic acid with ozone in the presence of tert-butyl alcohol radical scavenger was studied. The operating variables investigated were the dose of alumina catalyst and solution pH. Results showed that using ozone and alumina leads to a significant increase in 2,4-D removal in comparison to non-catalytic ozonation and adsorption processes. The observed reaction rate constants (k(obs)) for 2,4-D during ozonation were found to increase linearly with increasing catalyst dose. At pH 5, the k(obs) value increased from 19.3 to 26 M(-1) s(-1) and 67 M(-1) s(-1) when varying the alumina dose from 1 to 2 and 4 g L(-1), respectively. As pH was increased, higher reaction rates were observed for both non-catalytic ozonation and catalytic ozonation processes. Thus, at pH 3 and using a catalyst dose of 8 g L(-1), the k(obs) values for non-catalytic ozonation and catalytic ozonation processes were 3.4 and 58.9 M(-1) s(-1), respectively, whereas at pH 5 reaction rate constants of 6.5 and 128.5 M(-1) s(-1) were observed, respectively. Analysis of total organic carbon suggested that catalytic ozonation with alumina achieved a considerable level of mineralization of 2,4-D. Adsorption of 2,4-D on alumina was found to play an important role in the catalytic ozonation process.

  2. Catalytic conversion of alcohols. 28. Product selectivities for 2-methylcyclohexanol conversion with metal oxide catalysts

    SciTech Connect

    Dabbagh, H.A.; Hughes, C.G.; Davis, B.H. )

    1992-02-01

    Metal oxides exhibit a range of selectivities (dehydration percentage, alkene distribution and alcohol isomerization) for the conversion of a 2-methylcyclohexanol isomer. For many metal oxide catalysts, trans-2-methylcyclohexanol produces a predominance of the less stable 3-methylcyclohexene isomer. The grouping of metal oxides based on the production of the less stable alkene isomers from 2-octanol is similar to that for trans-2-methlycyclohexanol. It is proposed that the same catalytic properties determine the selectivity for both reactants: for smaller metal cations the product selectivity is determined by steric crowding in the transition state, and for the larger cations the product selectivity is determined by the basicity of the oxygen anion and the relative acidity of the {beta}-hydrogens that are eliminated to produce water.

  3. A Catalytic Sensor for Measurement of Radical Density in CO2 Plasmas

    PubMed Central

    Vesel, Alenka; Zaplotnik, Rok; Iacono, Jonathan; Balat-Pichelin, Marianne; Mozetic, Miran

    2012-01-01

    A catalytic sensor for the measurement of radical density in weakly ionized CO2 plasmas, created in a low-pressure electrodeless discharge, is presented. The CO2 plasma was created in a 4 cm wide borosilicate glass tube inside a copper coil connected to a radio frequency generator operating at 27.12 MHz with a nominal power of 250 W. The dissociation fraction of the CO2 molecules was measured in the early afterglow at pressures ranging from 10 Pa to 100 Pa, and at distances of up to 35 cm along the gas stream from the glowing plasma. The radical density peaked (2 × 1020 m−3) at 80 Pa. The density quickly decreased with increasing distance from the glowing plasma despite a rather large drift velocity. The dissociation fraction showed similar behavior, except that the maximum was obtained at somewhat lower pressure. The results were explained by rather intense surface recombination of radicals. PMID:23443372

  4. PREFACE: Dynamics of wetting Dynamics of wetting

    NASA Astrophysics Data System (ADS)

    Grest, Gary S.; Oshanin, Gleb; Webb, Edmund B., III

    2009-11-01

    Capillary phenomena associated with fluids wetting other condensed matter phases have drawn great scientific interest for hundreds of years; consider the recent bicentennial celebration of Thomas Young's paper on equilibrium contact angles, describing the geometric shape assumed near a three phase contact line in terms of the relevant surface energies of the constituent phases [1]. Indeed, nearly a century has passed since the seminal papers of Lucas and Washburn, describing dynamics of capillary imbibition [2, 3]. While it is generally appreciated that dynamics of fluid wetting processes are determined by the degree to which a system is out of capillary equilibrium, myriad complications exist that challenge the fundamental understanding of dynamic capillary phenomena. The topic has gathered much interest from recent Nobel laureate Pierre-Gilles de Gennes, who provided a seminal review of relevant dissipation mechanisms for fluid droplets spreading on solid surfaces [4] Although much about the dynamics of wetting has been revealed, much remains to be learned and intrinsic technological and fundamental interest in the topic drives continuing high levels of research activity. This is enabled partly by improved experimental capabilities for resolving wetting processes at increasingly finer temporal, spatial, and chemical resolution. Additionally, dynamic wetting research advances via higher fidelity computational modeling capabilities, which drive more highly refined theory development. The significance of this topic both fundamentally and technologically has resulted in a number of reviews of research activity in wetting dynamics. One recent example addresses the evaluation of existing wetting dynamics theories from an experimentalist's perspective [5]. A Current Opinion issue was recently dedicated to high temperature capillarity, including dynamics of high temperature spreading [6]. New educational tools have recently emerged for providing instruction in wetting

  5. Effect of MnO2 morphology on the catalytic oxidation of toluene over Ag/MnO2 catalysts

    NASA Astrophysics Data System (ADS)

    Li, Jiamin; Qu, Zhenping; Qin, Yuan; Wang, Hui

    2016-11-01

    The Ag/MnO2 catalysts with different morphologies (wire-like, rod-like and tube-like) are used as toluene oxidation catalysts in an attempt to investigate how the structures of support affect the interaction of Ag and MnO2, and thus the toluene catalytic activity. Analysis by TEM, H2-TPR and XPS measurements reveals that the structures of MnO2 influence the particle size and dispersion of silver particles and the combination of silver particles with MnO2. Meanwhile, the addition of Ag regulates the performance of MnO2. The small particle size and hemispherically shaped Ag particles are easily to form and homogeneously dispersed on the surface of wire-like MnO2. And this specific form of Ag shows the strongest interaction with MnO2, which promotes the low-temperature reducibility of support and generated more lattice oxygen in metal oxides. The Ag/MnO2 nanowires sample exhibits the highest reactivity for toluene oxidation with a complete conversion at 220 °C. Therefore, the excellent catalytic performance of Ag/MnO2 nanowires catalyst for toluene oxidation is clearly connected with the interaction between the Ag and MnO2, which is determined by the morphology of MnO2 support.

  6. 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.

  7. Mechanistic Insights into Hydride Transfer for Catalytic Hydrogenation of CO2 with Cobalt Complexes

    SciTech Connect

    Kumar, Neeraj; Camaioni, Donald M.; Dupuis, Michel; Raugei, Simone; Appel, Aaron M.

    2014-08-21

    The catalytic hydrogenation of CO2 to formate by Co(dmpe)2H can proceeds via direct hydride transfer or via CO2 coordination to Co followed by reductive elimination of formate. Both pathways have activation barriers consistent with experiment (~17.5 kcal/mol). Controlling the basicity of Co by ligand design is key to improve catalysis. The research by N.K., D.M.C. and A.M.A. was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. The research by S.R. and M.D. 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. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for the DOE by Battelle.

  8. (Catalytic mechanism of hydrogenase from aerobic N sub 2 -fixing microorganisms)

    SciTech Connect

    Arp, D.J.

    1990-01-01

    Hydrogenases are enzymes which catalyze reactions involving dihydrogen. They serve integral roles in a number of microbial metabolic pathways. Our research is focussed on investigations of the catalytic mechanism of the hydrogenases found in aerobic, N{sub 2}-fixing microorganisms such as Azotobacter vinelandii and the agronomically important Bradyrhizobium japonicum as well as microorganisms with similar hydrogenases. The hydrogenases isolated from these microorganisms are Ni- and Fe-containing heterodimers. Our work has focussed on three areas during the last grant period. In all cases, a central theme has been the role of inhibitors in the characteristics under investigation. In addition, a number of collaborative efforts have yielded interesting results. In metalloenzymes such as hydrogenase, inhibitors often influence the activity of the enzyme through ligand interactions with redox centers, often metals, within the enzyme. Therefore, investigations of the ability of various compounds to inhibit an enzyme's activity, as well as the mechanism of inhibition, can provide insight into the catalytic mechanism of the enzyme as well as the role of various redox centers in catalysis. We have investigated in detail four inhibitors of A. vinelandii and the results are summarized here. The influence of these inhibitors on the spectral properties of the enzyme are summarized. Electron paramagnetic resonance and ultraviolet spectra investigations are discussed. 9 figs.

  9. 49 CFR 173.244 - Bulk packaging for certain pyrophoric liquids (Division 4.2), dangerous when wet (Division 4.3...

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... (Division 4.2), dangerous when wet (Division 4.3) materials, and poisonous liquids with inhalation hazards...), dangerous when wet (Division 4.3) materials, and poisonous liquids with inhalation hazards (Division 6.1... apply: (i) Division 6.1 Hazard Zone A materials must be transported in tank cars having a test...

  10. Morphology control of ceria nanocrystals for catalytic conversion of CO2 with methanol

    NASA Astrophysics Data System (ADS)

    Wang, Shengping; Zhao, Lifang; Wang, Wei; Zhao, Yujun; Zhang, Guanglin; Ma, Xinbin; Gong, Jinlong

    2013-05-01

    This paper describes the synthesis of ceria catalysts with octahedron, nanorod, nanocube and spindle-like morphologies via a template-free hydrothermal method. The surface morphologies, crystal plane and physical-chemical structures were investigated via field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and temperature-programmed desorption of ammonia and carbon dioxide (NH3-TPD and CO2-TPD). The catalytic performance over these ceria catalysts with different exposed planes were tested for dimethyl carbonate (DMC) synthesis from CO2 and methanol. The results showed that the spindle-like CeO2 showed the highest DMC yields, followed by nano-rods, nano-cubes and nano-octahedrons. A synergism among the exposed (111) plane, defect sites, and acid-basic sites was proposed to be crucial to obtaining the high reactivity of DMC formation.This paper describes the synthesis of ceria catalysts with octahedron, nanorod, nanocube and spindle-like morphologies via a template-free hydrothermal method. The surface morphologies, crystal plane and physical-chemical structures were investigated via field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and temperature-programmed desorption of ammonia and carbon dioxide (NH3-TPD and CO2-TPD). The catalytic performance over these ceria catalysts with different exposed planes were tested for dimethyl carbonate (DMC) synthesis from CO2 and methanol. The results showed that the spindle-like CeO2 showed the highest DMC yields, followed by nano-rods, nano-cubes and nano-octahedrons. A synergism among the exposed (111) plane, defect sites, and acid-basic sites was proposed to be crucial to obtaining the high reactivity of DMC formation. Electronic supplementary information (ESI) available. See DOI

  11. Predicting CYP2C19 catalytic parameters for enantioselective oxidations using artificial neural networks and a chirality code.

    PubMed

    Hartman, Jessica H; Cothren, Steven D; Park, Sun-Ha; Yun, Chul-Ho; Darsey, Jerry A; Miller, Grover P

    2013-07-01

    Cytochromes P450 (CYP for isoforms) play a central role in biological processes especially metabolism of chiral molecules; thus, development of computational methods to predict parameters for chiral reactions is important for advancing this field. In this study, we identified the most optimal artificial neural networks using conformation-independent chirality codes to predict CYP2C19 catalytic parameters for enantioselective reactions. Optimization of the neural networks required identifying the most suitable representation of structure among a diverse array of training substrates, normalizing distribution of the corresponding catalytic parameters (k(cat), K(m), and k(cat)/K(m)), and determining the best topology for networks to make predictions. Among different structural descriptors, the use of partial atomic charges according to the CHelpG scheme and inclusion of hydrogens yielded the most optimal artificial neural networks. Their training also required resolution of poorly distributed output catalytic parameters using a Box-Cox transformation. End point leave-one-out cross correlations of the best neural networks revealed that predictions for individual catalytic parameters (k(cat) and K(m)) were more consistent with experimental values than those for catalytic efficiency (k(cat)/K(m)). Lastly, neural networks predicted correctly enantioselectivity and comparable catalytic parameters measured in this study for previously uncharacterized CYP2C19 substrates, R- and S-propranolol. Taken together, these seminal computational studies for CYP2C19 are the first to predict all catalytic parameters for enantioselective reactions using artificial neural networks and thus provide a foundation for expanding the prediction of cytochrome P450 reactions to chiral drugs, pollutants, and other biologically active compounds.

  12. Removal of formaldehyde over Mn(x)Ce(1)-(x)O(2) catalysts: thermal catalytic oxidation versus ozone catalytic oxidation.

    PubMed

    Li, Jia Wei; Pan, Kuan Lun; Yu, Sheng Jen; Yan, Shaw Yi; Chang, Moo Been

    2014-12-01

    Mn(x)Ce(1)-(x)O(2) (x: 0.3-0.9) prepared by Pechini method was used as a catalyst for the thermal catalytic oxidation of formaldehyde (HCHO). At x=0.3 and 0.5, most of the manganese was incorporated in the fluorite structure of CeO(2) to form a solid solution. The catalytic activity was best at x=0.5, at which the temperature of 100% removal rate is the lowest (270°C). The temperature for 100% removal of HCHO oxidation is reduced by approximately 40°C by loading 5wt.% CuO(x) into Mn(0.5)Ce(0.5)O(2). With ozone catalytic oxidation, HCHO (61 ppm) in gas stream was completely oxidized by adding 506 ppm O₃over Mn(0.5)Ce(0.5)O(2) catalyst with a GHSV (gas hourly space velocity) of 10,000 hr⁻¹ at 25°C. The effect of the molar ratio of O(3) to HCHO was also investigated. As O(3)/HCHO ratio was increased from 3 to 8, the removal efficiency of HCHO was increased from 83.3% to 100%. With O(3)/HCHO ratio of 8, the mineralization efficiency of HCHO to CO(2) was 86.1%. At 25°C, the p-type oxide semiconductor (Mn(0.5)Ce(0.5)O(2)) exhibited an excellent ozone decomposition efficiency of 99.2%, which significantly exceeded that of n-type oxide semiconductors such as TiO(2), which had a low ozone decomposition efficiency (9.81%). At a GHSV of 10,000 hr⁻¹, [O(3)]/[HCHO]=3 and temperature of 25°C, a high HCHO removal efficiency (≥ 81.2%) was maintained throughout the durability test of 80 hr, indicating the long-term stability of the catalyst for HCHO removal.

  13. Lipocalin 2 alleviates iron toxicity by facilitating hypoferremia of inflammation and limiting catalytic iron generation.

    PubMed

    Xiao, Xia; Yeoh, Beng San; Saha, Piu; Olvera, Rodrigo Aguilera; Singh, Vishal; Vijay-Kumar, Matam

    2016-06-01

    Iron is an essential transition metal ion for virtually all aerobic organisms, yet its dysregulation (iron overload or anemia) is a harbinger of many pathologic conditions. Hence, iron homeostasis is tightly regulated to prevent the generation of catalytic iron (CI) which can damage cellular biomolecules. In this study, we investigated the role of iron-binding/trafficking innate immune protein, lipocalin 2 (Lcn2, aka siderocalin) on iron and CI homeostasis using Lcn2 knockout (KO) mice and their WT littermates. Administration of iron either systemically or via dietary intake strikingly upregulated Lcn2 in the serum, urine, feces, and liver of WT mice. However, similarly-treated Lcn2KO mice displayed elevated CI, augmented lipid peroxidation and other indices of organ damage markers, implicating that Lcn2 responses may be protective against iron-induced toxicity. Herein, we also show a negative association between serum Lcn2 and CI in the murine model of dextran sodium sulfate (DSS)-induced colitis. The inability of DSS-treated Lcn2KO mice to elicit hypoferremic response to acute colitis, implicates the involvement of Lcn2 in iron homeostasis during inflammation. Using bone marrow chimeras, we further show that Lcn2 derived from both immune and non-immune cells participates in CI regulation. Remarkably, exogenous rec-Lcn2 supplementation suppressed CI levels in Lcn2KO serum and urine. Collectively, our results suggest that Lcn2 may facilitate hypoferremia, suppress CI generation and prevent iron-mediated adverse effects. PMID:27007712

  14. Maintaining the genuine structure of 2D materials and catalytic nanoparticles at atomic resolution.

    PubMed

    Calderon, H A; Kisielowski, C; Specht, P; Barton, B; Godinez-Salomon, F; Solorza-Feria, O

    2015-01-01

    The recent development of atomic resolution, low dose-rate electron microscopy allows investigating 2D materials as well as catalytic nano particles without compromising their structural integrity. For graphene and a variety of nanoparticle compositions, it is shown that a critical dose rate exists of <100 e(-)/Å(2) s at 80 keV of electron acceleration that allows maintaining the genuine object structures including their surfaces and edges even if particles are only 3 nm large or smaller. Moreover, it is demonstrated that electron beam-induced phonon excitation from outside the field of view contributes to a contrast degradation in recorded images. These degradation effects can be eliminated by delivering electrons onto the imaged area, only, by using a Nilsonian illumination scheme in combination with a suitable aperture at the electron gun/monochromator assembly.

  15. Catalytic liquid-phase oxidation of acetaldehyde to acetic acid over a Pt/CeO2-ZrO2-SnO2/γ-alumina catalyst.

    PubMed

    Choi, Pil-Gyu; Ohno, Takanobu; Masui, Toshiyuki; Imanaka, Nobuhito

    2015-10-01

    Pt/CeO2-ZrO2-SnO2/γ-Al2O3 catalysts were prepared by co-precipitation and wet impregnation methods for catalytic oxidation of acetaldehyde to acetic acid in water. In the present catalysts, Pt and CeO2-ZrO2-SnO2 were successfully dispersed on the γ-Al2O3 support. Dependences of platinum content and reaction time on the selective oxidation of acetaldehyde to acetic acid were investigated to optimize the reaction conditions for obtaining both high acetaldehyde conversion and highest selectivity to acetic acid. Among the catalysts, a Pt(6.4wt.%)/Ce0.68Zr0.17Sn0.15O2.0(16wt.%)/γ-Al2O3 catalyst showed the highest acetaldehyde oxidation activity. On this catalyst, acetaldehyde was completely oxidized after the reaction at 0°C for 8hr, and the selectivity to acetic acid reached to 95% and higher after the reaction for 4hr and longer.

  16. Influence of He/O 2 atmospheric pressure plasma jet treatment on subsequent wet desizing of polyacrylate on PET fabrics

    NASA Astrophysics Data System (ADS)

    Li, Xuming; Lin, Jun; Qiu, Yiping

    2012-01-01

    The influence of He/O2 atmospheric pressure plasma jet (APPJ) treatment on subsequent wet desizing of polyacrylate on PET fabrics was studied in the present paper. Weight loss results indicated that the weight loss increased with an increase of plasma treatment time. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) showed an increased surface roughness after the plasma treatment. SEM also showed that the fiber surfaces were as clean as unsized fibers after 35 s treatment followed by NaHCO3 desizing. X-ray photoelectron spectroscopy (XPS) analysis indicated that oxygen-based functional groups increased for the plasma treated polyacrylate sized fabrics. The percent desizing ratio (PDR) results showed that more than 99% PDR was achieved after 65 s plasma treatment followed by a 5 min NaHCO3 desizing. Compared to conventional wet desizing, indicating that plasma treatment could significantly reduce desizing time.

  17. Heterogeneous catalytic oxidation of As(III) on nonferrous metal oxides in the presence of H2O2.

    PubMed

    Kim, Dong-hyo; Bokare, Alok D; Koo, Min suk; Choi, Wonyong

    2015-03-17

    The oxidation of As(III) (arsenite) to As(V) (arsenate), a critical pretreatment process for total arsenic removal, is easily achieved using chemical oxidation methods. Hydrogen peroxide (H2O2) is widely used as an environmentally benign oxidant but its practical use for the arsenite oxidation is limited by the strong pH dependence and slow oxidation kinetics. This study demonstrated that H2O2-induced oxidation of As(III) can be markedly enhanced in the presence of nonferrous metal oxides (e.g., WO3, TiO2, ZrO2) as a heterogeneous catalyst working over a wide pH range in ambient reaction conditions. In particular, TiO2 is an ideal catalyst because it is not only active and stable but also easily available and inexpensive. Although the photocatalytic oxidation of As(III) on TiO2 was intensively studied, the thermal catalytic activities of TiO2 and other nonferrous metal oxides for the arsenic oxidation have been little investigated. The heterogeneous oxidation rate increased with increasing the TiO2 surface area and [H2O2] and weakly depended on pH whereas the homogeneous oxidation by H2O2 alone was favored only at alkaline condition. The oxidation rate in the TiO2/H2O2 system was not reduced at all in the absence of dioxygen. It was not retarded at all by OH radical scavengers but markedly inhibited by hydroperoxyl radical scavengers. It is proposed that the surface complexation of H2O2 on TiO2 induces the generation of the surface hydroperoxyl radical through an inner-sphere electron transfer, which subsequently reacts with As(III). The catalytic activity of TiO2 was maintained without showing any sign of deactivation. The heterogeneous catalytic oxidation is proposed as a viable method for the preoxidation treatment of As(III)-contaminated water under ambient conditions. PMID:25695481

  18. Novel preparation of highly dispersed Ni2P embedded in carbon framework and its improved catalytic performance

    NASA Astrophysics Data System (ADS)

    Wang, Shan; Wang, Kang; Wang, Xitao

    2016-11-01

    Highly dispersed Ni2P embedded in carbon framework with different phosphidation temperature was prepared through carbonizing Ni-alginate gel and followed by phosphidation with PPh3 in liquid phase. The significant effects of phosphidation temperature on Ni2P particle size and catalytic properties for isobutane dehydrogenation to isobutene were investigated. The results showed that Ni2P catalyst derived from the Ni-alginate gel (Ni2P-ADC), consisting of Ni2P particles embedded in carbon walls, possessed smaller particle size and more active site compared with Ni2P catalyst supported on active carbon (Ni2P/AC) prepared by impregnation method. The Ni2P-ADC catalyst phosphorized at 578 K for 3 h exhibited the highest catalytic performance, with the corresponding selectivity of isobutene approaching 89% and conversion approaching 15% after reaction for 4.5 h at 833 K, whereas Ni2P/AC catalyst prepared by impregnation method displays a much lower catalytic activity. The improved catalytic performance of the Ni2P-ADC can be ascribed to the smaller and highly dispersed Ni2P particles incorporated into carbon framework resulting from Ni-alginate gel.

  19. (Catalytic mechanism of hydrogenase from aerobic N sub 2 -fixing microorganisms)

    SciTech Connect

    Arp, D.J.

    1991-01-01

    The results of this DOE-sponsored project have contributed to our understanding of the catalytic mechanism of A. vinelandii hydrogenase. A group of inhibitors have been characterized. These provide information about the different types of redox clusters involved in catalysis and the roles of each. One group has already used acetylene in a study of three desulfovibrian hydrogenases and shown that only the NiFe hydrogenases are inhibited. We have characterized a number of spectral properties of A. vinelandii hydrogenase. The EPR signals associated with this hydrogenase in the reduced state are reminiscent of other NiFe dimeric hydrogenases such as A. eutrophus, but distinctly difference from others such as D. gigas and Chromatium vinosum. Thus, while the NiFe dimeric hydrogenases are now recognized as a large group of similar enzymes, there are differences in the spectral and catalytic properties which are not explained by their similar redox inventories, identical subunit structures, immunological cross reactivity and conserved sequences. The inhibitors we have characterized are also proving of value in the spectral characterizations. Surprisingly, we only see a significant EP signal attributable to Ni after the enzyme has been inactivated with O{sub 2} and then reduced (though not reactivated). No spectral perterbations (EPR or UV-V is) of active enzyme can be attributed to binding of H{sub 2}, even though H{sub 2} clearly binds to this form of the enzyme. Acetylene, which does not substantially perterb the EPR signal of active hydrogenase, does result in a new absorption envelope in the UV-V is spectrum. Overall, the results of this project have revealed the complex interactions of the redox clusters in catalysis through studies of inhibitor mechanisms and spectral properties. 14 refs., 9 figs.

  20. Fe2O3 particles as superior catalysts for low temperature selective catalytic reduction of NO with NH3.

    PubMed

    Wang, Xiaobo; Gui, Keting

    2013-12-01

    Fe2O3 particle catalysts were experimentally studied in the low temperature selective catalytic reduction (SCR) of NO with NH3. The effects of reaction temperature, oxygen concentration, [NH3]/[NO] molar ratio and residence time on SCR activity were studied. It was found that Fe2O3 catalysts had high activity for the SCR of NO with NH3 in a broad temperature range of 150-270 degrees C, and more than 95% NO conversion was obtained at 180 degrees C when the molar ratio [NH3]/[NO] = 1, the residence time was 0.48 seconds and O2 volume fraction was 3%. In addition, the effect of SO2 on SCR catalytic activity was also investigated at the temperature of 180 degrees C. The results showed that deactivation of the Fe2O3 particles occurred due to the presence of SO2 and the NO conversion decreased from 99.2% to 58% in 240 min, since SO2 gradually decreased the catalytic activity of the catalysts. In addition, X-ray diffraction, Thermogravimetric analysis and Fourier transform infrared spectroscopy were used to characterize the fresh and deactivated Fe2O3 catalysts. The results showed that the deactivation caused by SO2 was due to the formation of metal sulfates and ammonium sulfates on the catalyst surface during the de-NO reaction, which could cause pore plugging and result in suppression of the catalytic activity.

  1. Study on the mechanism of NH3-selective catalytic reduction over CuCexZr1-x/TiO2

    NASA Astrophysics Data System (ADS)

    Chen, Xujuan; Sun, Xiaoliang; Gong, Cairong; Lv, Gang; Song, Chonglin

    2016-06-01

    Copper-cerium-zirconium catalysts loaded on TiO2 prepared by a wet impregnation method were investigated for NH3-selective catalytic reduction (SCR) of NOx. The reaction mechanism was proposed on the basis of results from in situ diffuse reflectance infrared transform spectroscopy (DRIFT). When NH3 is introduced, ammonia bonded to Lewis acid sites is more stable over CuCe0.25Zr0.75/TiO2 at high temperature, while Brønsted acid sites are more important than Lewis acid sites at low temperature. For the NH3+NO+O2 co-adsorption, NH3 species occupy most of activity sites on CuCe0.25Zr0.75/TiO2 catalyst, and mainly exist in the forms of NH4 + (at low temperature) and NH3 coordinated (at high temperature), playing a crucial role in the NH3-SCR process. Two different reaction routes, the L-H mechanism at low temperature (< 200°C) and the E-R mechanism at high temperature (> 200°C), are presented for the SCR reaction over CuCe0.25Zr0.75/TiO2 catalyst.

  2. High NO2/NOx emissions downstream of the catalytic diesel particulate filter: An influencing factor study.

    PubMed

    He, Chao; Li, Jiaqiang; Ma, Zhilei; Tan, Jianwei; Zhao, Longqing

    2015-09-01

    Diesel vehicles are responsible for most of the traffic-related nitrogen oxide (NOx) emissions, including nitric oxide (NO) and nitrogen dioxide (NO2). The use of after-treatment devices increases the risk of high NO2/NOx emissions from diesel engines. In order to investigate the factors influencing NO2/NOx emissions, an emission experiment was carried out on a high pressure common-rail, turbocharged diesel engine with a catalytic diesel particulate filter (CDPF). NO2 was measured by a non-dispersive ultraviolet analyzer with raw exhaust sampling. The experimental results show that the NO2/NOx ratios downstream of the CDPF range around 20%-83%, which are significantly higher than those upstream of the CDPF. The exhaust temperature is a decisive factor influencing the NO2/NOx emissions. The maximum NO2/NOx emission appears at the exhaust temperature of 350°C. The space velocity, engine-out PM/NOx ratio (mass based) and CO conversion ratio are secondary factors. At a constant exhaust temperature, the NO2/NOx emissions decreased with increasing space velocity and engine-out PM/NOx ratio. When the CO conversion ratios range from 80% to 90%, the NO2/NOx emissions remain at a high level.

  3. Methodology to assay CYP2E1 mixed function oxidase catalytic activity and its induction

    PubMed Central

    Cederbaum, Arthur I.

    2014-01-01

    The cytochrome P450 mixed function oxidase enzymes are the major catalysts involved in drug metabolism. There are many forms of P450. CYP2E1 metabolizes many toxicologically important compounds including ethanol and is active in generating reactive oxygen species. Since several of the contributions in the common theme series “Role of CYP2E1 and Oxidative/Nitrosative Stress in the Hepatotoxic Actions of Alcohol” discuss CYP2E1, this methodology review describes assays on how CYP2E1 catalytic activity and its induction by ethanol and other inducers can be measured using substrate probes such as the oxidation of para-nitrophenol to para-nitrocatechol and the oxidation of ethanol to acetaldehyde. Approaches to validate that a particular reaction e.g. oxidation of a drug or toxin is catalyzed by CYP2E1 or that induction of that reaction is due to induction of CYP2E1 are important and specific examples using inhibitors of CYP2E1, anti-CYP2E1 IgG or CYP2E1 knockout and knockin mice will be discussed. PMID:25454746

  4. High NO2/NOx emissions downstream of the catalytic diesel particulate filter: An influencing factor study.

    PubMed

    He, Chao; Li, Jiaqiang; Ma, Zhilei; Tan, Jianwei; Zhao, Longqing

    2015-09-01

    Diesel vehicles are responsible for most of the traffic-related nitrogen oxide (NOx) emissions, including nitric oxide (NO) and nitrogen dioxide (NO2). The use of after-treatment devices increases the risk of high NO2/NOx emissions from diesel engines. In order to investigate the factors influencing NO2/NOx emissions, an emission experiment was carried out on a high pressure common-rail, turbocharged diesel engine with a catalytic diesel particulate filter (CDPF). NO2 was measured by a non-dispersive ultraviolet analyzer with raw exhaust sampling. The experimental results show that the NO2/NOx ratios downstream of the CDPF range around 20%-83%, which are significantly higher than those upstream of the CDPF. The exhaust temperature is a decisive factor influencing the NO2/NOx emissions. The maximum NO2/NOx emission appears at the exhaust temperature of 350°C. The space velocity, engine-out PM/NOx ratio (mass based) and CO conversion ratio are secondary factors. At a constant exhaust temperature, the NO2/NOx emissions decreased with increasing space velocity and engine-out PM/NOx ratio. When the CO conversion ratios range from 80% to 90%, the NO2/NOx emissions remain at a high level. PMID:26354692

  5. Synergistic Ion-Binding Catalysis Demonstrated via an Enantioselective, Catalytic [2,3]-Wittig Rearrangement

    PubMed Central

    2016-01-01

    Sigmatropic rearrangements number among the most powerful complexity-building transformations in organic synthesis but have remained largely insensitive to enantioselective catalysis due to the diffuse nature of their transition structures. Here, we describe a synergistic ion-binding strategy for asymmetric catalysis of anionic sigmatropic rearrangements. This approach is demonstrated with the enantioselective [2,3]-Wittig rearrangement of α-allyloxy carbonyl compounds to afford highly enantioenriched homoallylic alcohol products. Chiral thiourea catalysts are shown to engage reactive anions and their countercations through a cooperative set of attractive, noncovalent interactions. Catalyst structure–reactivity–selectivity relationship studies and computational analyses provide insight into catalyst–substrate interactions responsible for enantioinduction and allude to the potential generality of this catalytic strategy. PMID:27413786

  6. Synthesis, characterization, electronic structure and catalytic activity of new ruthenium carbonyl complexes of N-[(2-pyridyl)methylidene]-2-aminothiazole

    NASA Astrophysics Data System (ADS)

    Kundu, Subhankar; Sarkar, Deblina; Jana, Mahendra Sekhar; Pramanik, Ajoy Kumar; Jana, Subrata; Mondal, Tapan Kumar

    2013-03-01

    Reaction of ruthenium carbonyls, [Ru(CO)2Cl2]n/[Ru(CO)4I2] with bidentate Schiffs base ligands derived by the condensation of pyridine-2-carboxaldehyde with 2-aminothiazole in a 1:1 mole ratio in acetonitrile led to the formation of complexes having general formula [Ru(CO)2(L)X2] (X = Cl (1) and I (2)) (L = N-[(2-pyridyl)methylidene]-2-aminothiazole). The compounds have been characterized by various analytical and spectroscopic (IR, electronic and 1H NMR) studies. In acetonitrile solution the complexes exhibit a weak broad metal-ligand to ligand charge transfer (MLLCT) band along with ILCT transitions. The compounds are emissive in room temperature upon excitation in the ILCT band. The complexes exhibit a quasi-reversible one electron Ru(II)/Ru(III) oxidation couple at 1.44 V for 1 and 0.94 V for 2. Catalytic activity of these compounds is investigated to the oxidation of PhCH2OH to PhCHO, 2-butanol (C4H9OH) to 2-butanone, 1-phenylethanol (PhC2H4OH) to acetophenone, cyclopentanol (C5H9OH) to cyclopentanone, cyclohexanol to cyclohexanone, cycloheptanol to cycloheptanone and cycloctanol to cycloctanone using N-methylmorpholine-N-oxide (NMO) as oxidant. The catalytic efficiency of 2 is greater than complex 1 and well correlate with the metal oxidation potential of the complexes. DFT, NBO and TDDFT calculations are employed to explain the structural and electronic features and to support the spectroscopic assignments.

  7. Atmospheric trace elements at Enewetak Atoll: 2. Transport to the ocean by wet and dry deposition

    NASA Astrophysics Data System (ADS)

    Arimoto, R.; Duce, R. A.; Ray, B. J.; Unni, C. K.

    1985-02-01

    The concentrations of trace elements in precipitation and dry deposition are presented for samples collected at Enewetak Atoll (11°N, 162° E) during SEAREX experiments in 1979. The concentrations of Al, Sc, Mn, Fe, Co, and Th in rain are dominated by crustal material, and for these elements, wet deposition evidently exceeds dry deposition. For most of these elements the present rates of atmospheric deposition at Enewetak are similar to their mean rate of accumulation in sediments over the past 5-10,000 years, suggesting that the air-to-sea exchange of particles is closely tied to the sedimentary cycle of the mid-Pacific. Noncrustal sources govern the concentrations of Pb, Zn, Cu, Se, and Cd in wet and dry deposition samples. Analyses of dry deposition collected from a flat plastic plate indicate that the amount of material recycled from the sea surface varies markedly between samples, and even though these estimates do not necessarily reflect the dry deposition to the ocean surface, the results suggest that recycled sea spray often amounts to more than 50% of the total dry deposition of the enriched elements. Recycled sea spray also makes up a significant fraction of the total wet deposition of the enriched elements. The net deposition rates of elements such as Cu and Zn are greater than or equal to their inputs from vertical mixing, but the net deposition of Pb clearly exceeds the input from upwelling. The current net deposition rates of the enriched elements are also similar to their rates of removal to sediments. These results indicate that air-sea exchange processes may significantly affect the chemistry of trace metals in the open ocean.

  8. Wetting of sodium on β''-Al2O3/YSZ composites for low temperature planar sodium-metal halide batteries

    SciTech Connect

    Reed, David; Coffey, Greg; Mast, Eric; Canfield, Nathan; Mansurov, Jirgal; Lu, Xiaochuan; Sprenkle, Vince

    2013-04-01

    Wetting of Na on B”-Al2O3/YSZ composites was investigated using the sessile drop technique. The effects of moisture and surface preparation were studied at low temperatures. Electrical conductivity of Na/B”-Al2O3-YSZ/Na cells was also investigated at low temperatures and correlated to the wetting behavior. The use of planar B”-Al2O3 substrates at low temperature with low cost polymeric seals is realized due to improved wetting at low temperature and conductivity values consistent with the literature.

  9. Anchoring noble metal nanoparticles on CeO2 modified reduced graphene oxide nanosheets and their enhanced catalytic properties.

    PubMed

    Ji, Zhenyuan; Shen, Xiaoping; Xu, Yuling; Zhu, Guoxing; Chen, Kangmin

    2014-10-15

    The strategy of structurally integrating noble metal, metal oxide, and graphene is expected to offer prodigious opportunities toward emerging functions of graphene-based nanocomposites. In this study, we develop a facile two-step approach to disperse noble metal (Pt and Au) nanoparticles on the surface of CeO2 functionalized reduced graphene oxide (RGO) nanosheets. It is shown that Pt and Au with particle sizes of about 5 and 2nm are well dispersed on the surface of RGO/CeO2. The reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) by NaBH4 was used as a model reaction to quantitatively evaluate the catalytic properties of the as-synthesized RGO/Pt/CeO2 and RGO/Au/CeO2 ternary nanocomposites. In such triple-component catalysts, CeO2 nanocrystals provide unique and critical roles for optimizing the catalytic performance of noble metallic Pt and Au, allowing them to express enhanced catalytic activities in comparison with RGO/Pt and RGO/Au catalysts. In addition, a possible mechanism for the enhanced catalytic activities of the RGO/Pt/CeO2 and RGO/Au/CeO2 ternary catalysts in the reduction of 4-NP is proposed. It is expected that our prepared graphene-based triple-component composites, which inherit peculiar properties of graphene, metal oxide, and noble metal, are attractive candidates for catalysis and other applications.

  10. Pd-catalytic hydrodechlorination of chlorinated hydrocarbons in groundwater using H2 produced by a dual-anode system.

    PubMed

    Xie, Shiwei; Yuan, Songhu; Liao, Peng; Jia, Mengqi; Wang, Yin

    2015-12-01

    Water electrolysis has been employed for in situ supplying H2 to Pd-catalytic treatment of groundwater, but the treatment efficiency is greatly inhibited by the concomitant production of O2. In this study, a new dual-anode system is proposed to improve the efficiency. An inert anode and an iron anode are used simultaneously to produce O2 and Fe(II), respectively. The quick oxidative precipitation of Fe(II) by O2 removes both Fe(II) and O2, improving the utilization of cathodic H2 for the subsequent Pd-catalytic hydrodechlorination. Feasibility tests in the lab show that Pd-catalytic hydrodechlorination of trichloroethylene (TCE) was considerably increased by the addition of an iron anode to the conventional two-electrode system. Scale-up tests at an abandoned chemical site demonstrated that chlorobenzenes in the groundwater were largely hydrodechlorinated to benzene, showing a maximum efficiency with the currents of 0.24 and 0.16 A applied to the inert and iron anodes, respectively, at the flow rate of 6 L/h. In a 3-month intermittent field test, Pd normalized rate constants of hydrodechlorinating three chlorobenzenes are comparable to the conventional means of H2 supply, while the cost for hydrodechlorination normalized by one mole [H] is much lower. The dual-anode system is an effective means to supplying H2 in situ for Pd-catalytic treatment.

  11. Water and temperature effects on photo-selective catalytic reduction of nitric oxide on Pd-loaded TiO2 photocatalyst.

    PubMed

    Lasek, Janusz; Yu, Yi-Hui; Wu, Jeffrey C S

    2012-09-01

    Photo-selective catalytic reduction (photo-SCR) of nitric oxide (NO) was studied in the presence of water. The incipient wetness impregnation was applied to prepare 1 wt% PdO/TiO2 photocatalyst. Steady-state photoreaction was carried out in a continuous-flow photoreactor with 0.55-1.6 v% water at 30-120 degrees C under UV-light intensity of approximately 200mW/cm(2). The C3H8/NO molar ratio in the feed ranged from 0.8 - 16.8 at a volume hourly space velocity (VHSV) from 330-1090 h(-1). The result indicates that the increase of temperature has played an important role in inhibiting NO transformation to NO2 under the humid condition. Another important factor for maximizing denitrification (reduction of nitrogen oxides, DeNOx) efficiency was C3H8/NO ratio. An increase of temperature at a suitable C3H8/NO ratio can minimize NO2 formation, which can lead to high NO removal efficiency of more than 90% at a temperature of 70-100 degrees C. In addition, the mechanism of palladium transformation during photoreaction is proposed, to explain the influence of Pd on the improvement of NO removal. PMID:23240208

  12. Visible light plasmonic heating of Au-ZnO for the catalytic reduction of CO2

    DOE PAGESBeta

    Wang, Congjun; Ranasingha, Oshadha; Natesakhawat, Sittichai; Ohodnicki, Paul R.; Andio, Mark; Lewis, James P.; Matranga, Christopher

    2013-01-01

    Plasmonic excitation of Au nanoparticles attached to the surface of ZnO catalysts using low power 532 nm laser illumination leads to significant heating of the catalyst and the conversion of CO2 and H2 reactants to CH4 and CO products. Temperature-calibrated Raman spectra of ZnO phonons show that intensity-dependent plasmonic excitation can controllably heat Au–ZnO from 30 to ~600 °C and simultaneously tune the CH4 : CO product ratio. The laser induced heating and resulting CH4 : CO product distribution agrees well with predictions from thermodynamic models and temperature-programmed reaction experiments indicating that the reaction is a thermally driven process resultingmore » from the plasmonic heating of the Au-ZnO. The apparent quantum yield for CO2 conversion under continuous wave (cw) 532 nm laser illumination is 0.030%. The Au-ZnO catalysts are robust and remain active after repeated laser exposure and cycling. The light intensity required to initiate CO2 reduction is low ( ~2.5 x 105 W m-2) and achievable with solar concentrators. Our results illustrate the viability of plasmonic heating approaches for CO2 utilization and other practical thermal catalytic applications.« less

  13. Precise tuning of the charge transfer kinetics and catalytic properties of MoS2 materials via electrochemical methods.

    PubMed

    Chia, Xinyi; Ambrosi, Adriano; Sedmidubský, David; Sofer, Zdeněk; Pumera, Martin

    2014-12-22

    MoS2 has become particularly popular for its catalytic properties towards the hydrogen evolution reaction (HER). It has been shown that the metallic 1T phase of MoS2 , obtained by chemical exfoliation after lithium intercalation, possesses enhanced catalytic activity over the semiconducting 2H phase due to the improved conductivity properties which facilitate charge-transfer kinetics. Here we demonstrate a simple electrochemical method to precisely tune the electron-transfer kinetics as well as the catalytic properties of both exfoliated and bulk MoS2 -based films. A controlled reductive or oxidative electrochemical treatment can alter the surface properties of the film with consequently improved or hampered electrochemical and catalytic properties compared to the untreated film. Density functional theory calculations were used to explain the electrochemical activation of MoS2 . The electrochemical tuning of electrocatalytic properties of MoS2 opens the doors to scalable and facile tailoring of MoS2 -based electrochemical devices.

  14. Numerical solution of 2D wet steam flow with non-equilibrium condensation and real thermodynamics

    SciTech Connect

    Hric, V.; Halama, J.

    2015-03-10

    An approach to modeling of wet steam flow with non-equilibrium condensation phenomenon is presented. The first part of our flow model is homogeneous Euler system of transport equations for mass, momentum and total energy of wet steam (mixture). The additional second part describes liquid phase via non-homogeneous system of transport equations for moments of droplets number distribution function and relies on corrected classical nucleation theory. Moment equations are closed by linearization of droplet growth rate model. All necessary relations for thermodynamic properties of steam are provided by IAPWS set of equations. However, properties of condensate are simply modeled by liquid saturation data. Two real equations of state are implemented. Recently developed CFD formulation for entropy (does not require iteration process) and so-called IAPWS special gas equation for Helmholtz energy (one iteration loop is necessary). Flow model is validated on converging-diverging supersonic nozzle with Barschdorff geometry. Simulations were performed by in-house CFD code based on finite volume method and stiff character of equations was solved by symmetrical time operator splitting. Achieved results satisfactorily agreed with experimental data.

  15. Wetting of mono and few-layered WS2 and MoS2 films supported on Si/SiO2 substrates.

    PubMed

    Chow, Philippe K; Singh, Eklavya; Viana, Bartolomeu Cruz; Gao, Jian; Luo, Jian; Li, Jing; Lin, Zhong; Elías, Ana L; Shi, Yunfeng; Wang, Zuankai; Terrones, Mauricio; Koratkar, Nikhil

    2015-03-24

    The recent interest and excitement in graphene has also opened up a pandora's box of other two-dimensional (2D) materials and material combinations which are now beginning to come to the fore. One family of these emerging 2D materials is transition metal dichalcogenides (TMDs). So far there is very limited understanding on the wetting behavior of "monolayer" TMD materials. In this study, we synthesized large-area, continuous monolayer tungsten disulfide (WS2) and molybdenum disulfide (MoS2) films on SiO2/Si substrates by the thermal reduction and sulfurization of WO3 and MO3 thin films. The monolayer TMD films displayed an advancing water contact angle of ∼83° as compared to ∼90° for the bulk material. We also prepared bilayer and trilayer WS2 films and studied the transition of the water contact angle with increasing number of layers. The advancing water contact angle increased to ∼85° for the bilayer and then to ∼90° for the trilayer film. Beyond three layers, there was no significant change in the measured water contact angle. This type of wetting transition indicates that water interacts to some extent with the underlying silica substrate through the monolayer TMD sheet. The experimentally observed wetting transition with numbers of TMD layers lies in-between the predictions of one continuum model that considers only van der Waals attractions and another model that considers only dipole-dipole interactions. We also explored wetting as a function of aging. A clean single-layer WS2 film (without airborne contaminants) was shown to be strongly hydrophilic with an advancing water contact angle of ∼70°. However, over time, the sample ages as hydrocarbons and water present in air adsorb onto the clean WS2 sheet. After ∼7 days, the aging process is completed and the advancing water contact angle of the aged single-layer WS2 film stabilizes at ∼83°. These results suggest that clean (i.e., nonaged) monolayer TMDs are hydrophilic materials. We further

  16. Combustion of CH4/H2/air mixtures in catalytic microreactors.

    PubMed

    Specchia, Stefania; Vella, Luigi D; Burelli, Sara; Saracco, Guido; Specchia, Vito

    2009-03-23

    The combustion of CH(4)/H(2)/HC mixtures in a very small space represents an alternative, innovative way to produce thermal/electrical energy. Pd/NiCrO(4) catalysts are lined on SiC monoliths via in situ solution combustion synthesis (SCS), and the monoliths are then tested by feeding CH(4), H(2), and lean CH(4)/H(2) mixtures into a lab-scale test rig at an output thermal power of 7.6 MW(th) m(-3). In all cases, the combustion temperature shifts to values lower than those observed in non-catalytic combustion. When the power density is kept constant (by adding H(2) to the gas mixture), the value of CH(4)-T(50) (the half-conversion temperature of CH(4)) decreases relative to that of pure CH(4), and the slope of the conversion curve becomes steeper. The higher the H(2) concentration is, the higher the reactivity of the mixture towards CH(4) oxidation-probably due to a higher production of H(2) reactive radicals (OH).

  17. Designing CuOx Nanoparticle-Decorated CeO2 Nanocubes for Catalytic Soot Oxidation: Role of the Nanointerface in the Catalytic Performance of Heterostructured Nanomaterials.

    PubMed

    Sudarsanam, Putla; Hillary, Brendan; Mallesham, Baithy; Rao, Bolla Govinda; Amin, Mohamad Hassan; Nafady, Ayman; Alsalme, Ali M; Reddy, B Mahipal; Bhargava, Suresh K

    2016-03-01

    This work investigates the structure-activity properties of CuOx-decorated CeO2 nanocubes with a meticulous scrutiny on the role of the CuOx/CeO2 nanointerface in the catalytic oxidation of diesel soot, a critical environmental problem all over the world. For this, a systematic characterization of the materials has been undertaken using transmission electron microscopy (TEM), transmission electron microscopy-energy-dispersive X-ray spectroscopy (TEM-EDS), high-angle annular dark-field-scanning transmission electron microscopy (HAADF-STEM), scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS), X-ray diffraction (XRD), Raman, N2 adsorption-desorption, and X-ray photoelectron spectroscopy (XPS) techniques. The TEM images show the formation of nanosized CeO2 cubes (∼25 nm) and CuOx nanoparticles (∼8.5 nm). The TEM-EDS elemental mapping images reveal the uniform decoration of CuOx nanoparticles on CeO2 nanocubes. The XPS and Raman studies show that the decoration of CuOx on CeO2 nanocubes leads to improved structural defects, such as higher concentrations of Ce(3+) ions and abundant oxygen vacancies. It was found that CuOx-decorated CeO2 nanocubes efficiently catalyze soot oxidation at a much lower temperature (T50 = 646 K, temperature at which 50% soot conversion is achieved) compared to that of pristine CeO2 nanocubes (T50 = 725 K) under tight contact conditions. Similarly, a huge 91 K difference in the T50 values of CuOx/CeO2 (T50 = 744 K) and pristine CeO2 (T50 = 835 K) was found in the loose-contact soot oxidation studies. The superior catalytic performance of CuOx-decorated CeO2 nanocubes is mainly attributed to the improved redox efficiency of CeO2 at the nanointerface sites of CuOx-CeO2, as evidenced by Ce M5,4 EELS analysis, supported by XRD, Raman, and XPS studies, a clear proof for the role of nanointerfaces in the performance of heterostructured nanocatalysts. PMID:26886079

  18. Designing CuOx Nanoparticle-Decorated CeO2 Nanocubes for Catalytic Soot Oxidation: Role of the Nanointerface in the Catalytic Performance of Heterostructured Nanomaterials.

    PubMed

    Sudarsanam, Putla; Hillary, Brendan; Mallesham, Baithy; Rao, Bolla Govinda; Amin, Mohamad Hassan; Nafady, Ayman; Alsalme, Ali M; Reddy, B Mahipal; Bhargava, Suresh K

    2016-03-01

    This work investigates the structure-activity properties of CuOx-decorated CeO2 nanocubes with a meticulous scrutiny on the role of the CuOx/CeO2 nanointerface in the catalytic oxidation of diesel soot, a critical environmental problem all over the world. For this, a systematic characterization of the materials has been undertaken using transmission electron microscopy (TEM), transmission electron microscopy-energy-dispersive X-ray spectroscopy (TEM-EDS), high-angle annular dark-field-scanning transmission electron microscopy (HAADF-STEM), scanning transmission electron microscopy-electron energy loss spectroscopy (STEM-EELS), X-ray diffraction (XRD), Raman, N2 adsorption-desorption, and X-ray photoelectron spectroscopy (XPS) techniques. The TEM images show the formation of nanosized CeO2 cubes (∼25 nm) and CuOx nanoparticles (∼8.5 nm). The TEM-EDS elemental mapping images reveal the uniform decoration of CuOx nanoparticles on CeO2 nanocubes. The XPS and Raman studies show that the decoration of CuOx on CeO2 nanocubes leads to improved structural defects, such as higher concentrations of Ce(3+) ions and abundant oxygen vacancies. It was found that CuOx-decorated CeO2 nanocubes efficiently catalyze soot oxidation at a much lower temperature (T50 = 646 K, temperature at which 50% soot conversion is achieved) compared to that of pristine CeO2 nanocubes (T50 = 725 K) under tight contact conditions. Similarly, a huge 91 K difference in the T50 values of CuOx/CeO2 (T50 = 744 K) and pristine CeO2 (T50 = 835 K) was found in the loose-contact soot oxidation studies. The superior catalytic performance of CuOx-decorated CeO2 nanocubes is mainly attributed to the improved redox efficiency of CeO2 at the nanointerface sites of CuOx-CeO2, as evidenced by Ce M5,4 EELS analysis, supported by XRD, Raman, and XPS studies, a clear proof for the role of nanointerfaces in the performance of heterostructured nanocatalysts.

  19. Catalytic Deoxygenation of 1,2-Propanediol to Give n-Propanol

    SciTech Connect

    Schlaf, Marcel; Ghosh, Prasenjit; Fagan, Paul J.; Hauptman, Elisabeth; Bullock, R. Morris

    2009-03-01

    Catalytic deoxygenation of 1,2-propanediol has been studied as a model the for deoxygenation of polyols and other biomass-derived compounds. Deoxygenation of 1,2-propanediol (1.0 M in sulfolane) catalyzed by {[Cp*Ru(CO)2]2(μ-H)}+OTf – (0.5 mol %) at 110 °C under H2 (750 psi) in the presence of HOTf (60 mM) gives n-propanol (54 %) as the major product, indicating a high selectivity for deoxygenation of the internal OH over the terminal OH of the diol. Di-n propyl ether forms through condensation of n-propanol with itself, and propylene glycol propyl ether arises from condensation of n-propanol with the starting material diol, giving a total of up to 80 % yield for deoxygenation / hydrogenation products under these conditions. The deoxygenation of 1,2-propanediol is strongly influenced by the concentration of acid, giving faster rates and proceeding to higher conversions as the concentration of HOTf is increased. There is little or no dependence of the rate on the pressure of H2. Propionaldehyde was observed as an intermediate, being formed through acid-catalyzed dehydration of 1,2-propanediol. This aldehyde is hydrogenated to n-propanol through an ionic pathway involving protonation of the aldehyde, followed by hydride transfer from the neutral hydride, Cp*Ru(CO)2H. The proposed mechanism for the deoxygenation/hydrogenation reaction involves formation of a highly acidic dihydrogen complex, [Cp*Ru(CO)22-H2)]+OTf-. Regeneration of the dihydrogen complex occurs through reaction of Cp*Ru(CO)2OTf with H2. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  20. Detailed characterization of the cooperative mechanism of Ca(2+) binding and catalytic activation in the Ca(2+) transport (SERCA) ATPase.

    PubMed

    Zhang, Z; Lewis, D; Strock, C; Inesi, G; Nakasako, M; Nomura, H; Toyoshima, C

    2000-08-01

    Expression of heterologous SERCA1a ATPase in Cos-1 cells was optimized to yield levels that account for 10-15% of the microsomal protein, as revealed by protein staining on electrophoretic gels. This high level of expression significantly improved our characterization of mutants, including direct measurements of Ca(2+) binding by the ATPase in the absence of ATP, and measurements of various enzyme functions in the presence of ATP or P(i). Mutational analysis distinguished two groups of amino acids within the transmembrane domain: The first group includes Glu771 (M5), Thr799 (M6), Asp800 (M6), and Glu908 (M8), whose individual mutations totally inhibit binding of the two Ca(2+) required for activation of one ATPase molecule. The second group includes Glu309 (M4) and Asn796 (M6), whose individual or combined mutations inhibit binding of only one and the same Ca(2+). The effects of mutations of these amino acids were interpreted in the light of recent information on the ATPase high-resolution structure, explaining the mechanism of Ca(2+) binding and catalytic activation in terms of two cooperative sites. The Glu771, Thr799, and Asp800 side chains contribute prominently to site 1, together with less prominent contributions by Asn768 and Glu908. The Glu309, Asn796, and Asp800 side chains, as well as the Ala305 (and possibly Val304 and Ile307) carbonyl oxygen, contribute to site 2. Sequential binding begins with Ca(2+) occupancy of site 1, followed by transition to a conformation (E') sensitive to Ca(2+) inhibition of enzyme phosphorylation by P(i), but still unable to utilize ATP. The E' conformation accepts the second Ca(2+) on site 2, producing then a conformation (E' ') which is able to utilize ATP. Mutations of residues (Asp813 and Asp818) in the M6/M7 loop reduce Ca(2+) affinity and catalytic turnover, suggesting a strong influence of this loop on the correct positioning of the M6 helix. Mutation of Asp351 (at the catalytic site within the cytosolic domain

  1. A Bioinspired Catalytic Aerobic Oxidative C–H Functionalization of Primary Aliphatic Amines: Synthesis of 1,2-Disubstituted Benzimidazoles

    PubMed Central

    Nguyen, Khac Minh Huy; Largeron, Martine

    2015-01-01

    Aerobic oxidative C–H functionalization of primary aliphatic amines has been accomplished with a biomimetic cooperative catalytic system to furnish 1,2-disubstituted benzimidazoles that play an important role as drug discovery targets. This one-pot atom-economical multistep process, which proceeds under mild conditions, with ambient air and equimolar amounts of each coupling partner, constitutes a convenient environmentally friendly strategy to functionalize non-activated aliphatic amines that remain challenging substrates for non-enzymatic catalytic aerobic systems. PMID:26206475

  2. Aerobic oxidative amidation of aromatic and cinnamic aldehydes with secondary amines by CuI/2-pyridonate catalytic system.

    PubMed

    Zhu, Mingwen; Fujita, Ken-ichi; Yamaguchi, Ryohei

    2012-10-19

    A simple and convenient CuI/2-pyridonate catalytic system for the oxidative amidation of aldehydes with secondary amines has been developed. With this system, a variety of useful arylamides have been synthesized in moderate to good yields in the presence of small amount of copper catalyst and the pyridonate ligand, generating only water as a coproduct. Synthesis of cinnamamides was also achieved by the reactions of cinnamaldehydes with secondary amines in moderate yields. Air was successfully employed as a green oxidant in this catalytic system, achieving a safe and atom-efficient system for the synthesis of amides. PMID:23006061

  3. [Catalytic Degradation of Diclofenac Sodium over the Catalyst of 3D Flower-like alpha-FeOOH Synergized with H2O2 Under Visible Light Irradiation].

    PubMed

    Xu, Jun-ge; Li, Yun-qin; Huang, Hua-shan; Yuan, Bao-ling; Cui, Hao-jie; Fu, Ming-lai

    2015-06-01

    Three dimensional (3D) flower-like alpha-FeOOH nanomaterials were prepared by oil bath reflux method using FeSO4, urea, ethanol and water, and the products which were characterized by XRD, FT-IR and SEM techniques. The SEM images showed that the 3D flower-like samples consisted of nanorods with a length of 400-500 nm and a diameter of 40-60 nm. The catalytic performance of the samples was evaluated by catalytic degradation of diclofenac sodium using H2O2 as the oxidant under simulated visible light. The results showed that the as-prepared samples presented high efficient catalytic performances, and more than 99% of the initial diclofenac sodium (30 mg x L(-1)) was degraded in 90 min. A radical mechanism can be proposed for the catalytic degradation of diclofenac sodium solution. PMID:26387316

  4. [Catalytic Degradation of Diclofenac Sodium over the Catalyst of 3D Flower-like alpha-FeOOH Synergized with H2O2 Under Visible Light Irradiation].

    PubMed

    Xu, Jun-ge; Li, Yun-qin; Huang, Hua-shan; Yuan, Bao-ling; Cui, Hao-jie; Fu, Ming-lai

    2015-06-01

    Three dimensional (3D) flower-like alpha-FeOOH nanomaterials were prepared by oil bath reflux method using FeSO4, urea, ethanol and water, and the products which were characterized by XRD, FT-IR and SEM techniques. The SEM images showed that the 3D flower-like samples consisted of nanorods with a length of 400-500 nm and a diameter of 40-60 nm. The catalytic performance of the samples was evaluated by catalytic degradation of diclofenac sodium using H2O2 as the oxidant under simulated visible light. The results showed that the as-prepared samples presented high efficient catalytic performances, and more than 99% of the initial diclofenac sodium (30 mg x L(-1)) was degraded in 90 min. A radical mechanism can be proposed for the catalytic degradation of diclofenac sodium solution.

  5. Spectroscopic and catalytic properties of Rhus vernicifera laccase depleted in type 2 copper.

    PubMed

    Reinhammar, B; Oda, Y

    1979-10-01

    1. The type 2 copper in Rhus vernicifera laccase was completely removed without loss of other types of copper. The properties of this protein derivative and the role of type 2 copper in the catalytic action of laccase was investigated. 2. The molar extinction coefficient at 614 nm of the blue chromophore decreases from 5700 to 4700 cm-1 on removal of type 2 copper. There are no apparent absorption changes at other wavelengths in the visible or near ultraviolet region when this copper is taken away. The electron-paramagnetic-resonance (epr) parameter A parallel and the linewidth of type 1 Cu2+ decreases on removal of type 2 copper. 3. The rate of reduction of type 1 Cu2+ is not affected by removal of type 2 copper but the reduction of the two-electron acceptor is greatly impaired. These results strongly support the idea that type 1 Cu2+ is the primary site for electron transfer between substrate and enzyme and that the two-electron acceptor in the native enzyme is reduced by simultaneous electron transfer from reduced types 1 and 2 copper. 4. Reoxidation of types 1 and 3 copper and the formation of the oxygen intermediate are the same processes in native and type-2-depleted enzyme. These observations suggests that type 2 copper is not involved in the formation and rapid decay of the oxygen intermediate and that it is not necessary for the stabilization of this intermediate. 5. Two new epr signals are observed on reoxidation of reduced type-2-depleted laccase. One is temporarily formed on re-reduction of reoxidized enzyme and it is suggested that it might arise from copper, possibly type 3 copper. The other one is stable for hours and it is proposed that it might come from a modified oxygen intermediate. PMID:228004

  6. Selective catalytic reduction of NO{sub 2} with urea in nanocrystalline NaY zeolite

    SciTech Connect

    Gonghu Li; Conrad A. Jones; Vicki H. Grassian; Sarah C. Larsen

    2005-09-10

    In this study, the selective catalytic reduction (SCR) of NO{sub 2} with urea in nanocrystalline NaY zeolite was investigated with in situ transmission Fourier transform infrared (FTIR) spectroscopy and solid-state nuclear magnetic resonance spectroscopy. At T=473 K, the reaction rate for urea-SCR of NO{sub 2} in nanocrystalline NaY zeolite was significantly greater than that in commercial NaY zeolite with a larger crystal size. In addition, a dramatic decrease in the concentration of undesirable surface species, including biuret and cyanuric acid, was observed in nanocrystalline NaY compared with commercial NaY after urea-SCR of NO{sub 2} at T=473 K. The increased reactivity for urea-SCR of NO{sub 2} was attributed to silanol groups and extra-framework aluminum species located on the external surface of nanocrystalline NaY. Specifically, NOx storage as nitrate and nitrite on the internal zeolite surface was coupled to reactive deNOx sites on the external surface. Isotopic labeling combined with IR analysis suggest that NN bond formation involved both an N-atom originating from NO{sub 2} and an N-atom originating from urea. This is the first clear example demonstrating that the increased external surface area (up to 40% of total surface area) of nanocrystalline zeolites can be used as a reactive surface with unique active sites for catalysis.

  7. In situ catalytic growth of large-area multilayered graphene/MoS2 heterostructures

    PubMed Central

    Fu, Wei; Du, Fei-Hu; Su, Juan; Li, Xin-Hao; Wei, Xiao; Ye, Tian-Nan; Wang, Kai-Xue; Chen, Jie-Sheng

    2014-01-01

    Stacking various two-dimensional atomic crystals on top of each other is a feasible approach to create unique multilayered heterostructures with desired properties. Herein for the first time, we present a controlled preparation of large-area graphene/MoS2 heterostructures via a simple heating procedure on Mo-oleate complex coated sodium sulfate under N2 atmosphere. Through a direct in situ catalytic reaction, graphene layer has been uniformly grown on the MoS2 film formed by the reaction of Mo species with S pecies, which is from the carbothermal reduction of sodium sulfate. Due to the excellent graphene “painting” on MoS2 atomic layers, the significantly shortened lithium ion diffusion distance and the markedly enhanced electronic conductivity, these multilayered graphene/MoS2 heterostructures exhibit high specific capacity, unprecedented rate performance and outstanding cycling stability, especially at a high current density, when used as an anode material for lithium batteries. This work provides a simple but efficient route for the controlled fabrication of large-area multilayered graphene/metal sulfide heterostructures with promising applications in battery manufacture, electronics or catalysis. PMID:24728289

  8. Principles of water oxidation and O2-based hydrocarbon transformation by multinuclear catalytic sites

    SciTech Connect

    Musaev, Djamaladdin G; Hill, Craig L; Morokuma, Keiji

    2014-10-28

    Abstract The central thrust of this integrated experimental and computational research program was to obtain an atomistic-level understanding of the structural and dynamic factors underlying the design of catalysts for water oxidation and selective reductant-free O2-based transformations. The focus was on oxidatively robust polyoxometalate (POM) complexes in which a catalytic active site interacts with proximal metal centers in a synergistic manner. Thirty five publications in high-impact journals arose from this grant. I. Developing an oxidatively and hydrolytically stable and fast water oxidation catalyst (WOC), a central need in the production of green fuels using water as a reductant, has proven particularly challenging. During this grant period we have designed and investigated several carbon-free, molecular (homogenous), oxidatively and hydrolytically stable WOCs, including the Rb8K2[{Ru4O4(OH)2(H2O)4}(γ-SiW10O36)2]·25H2O (1) and [Co4(H2O)2(α-PW9O34)2]10- (2). Although complex 1 is fast, oxidatively and hydrolytically stable WOC, Ru is neither abundant nor inexpensive. Therefore, development of a stable and fast carbon-free homogenous WOC, based on earth-abundant elements became our highest priority. In 2010, we reported the first such catalyst, complex 2. This complex is substantially faster than 1 and stable under homogeneous conditions. Recently, we have extended our efforts and reported a V2-analog of the complex 2, i.e. [Co4(H2O)2(α-VW9O34)2]10- (3), which shows an even greater stability and reactivity. We succeeded in: (a) immobilizing catalysts 1 and 2 on the surface of various electrodes, and (b) elucidating the mechanism of O2 formation and release from complex 1, as well as the Mn4O4L6 “cubane” cluster. We have shown that the direct O-O bond formation is the most likely pathway for O2 formation during water oxidation catalyzed by 1. II. Oxo transfer catalysts that contain two proximal and synergistically interacting redox active metal

  9. Influence of catalyst synthesis method on selective catalytic reduction (SCR) of NO by NH3 with V2O5-WO3/TiO2 catalysts

    DOE PAGESBeta

    He, Yuanyuan; Ford, Michael E.; Zhu, Minghui; Liu, Qingcai; Tumuluri, Uma; Wu, Zili; Wachs, Israel E.

    2016-04-14

    We compared the molecular structures, surface acidity and catalytic activity for NO/NH3/O2 SCR of V2O5-WO3/TiO2 catalysts for two different synthesis methods: co-precipitation of aqueous vanadium and tungsten oxide precursors with TiO(OH)2 and by incipient wetness impregnation of the aqueous precursors on a reference crystalline TiO2 support (P25; primarily anatase phase). Bulk analysis by XRD showed that co-precipitation results in small and/or poorly ordered TiO2(anatase) particles and that VOx and WOx do not form solid solutions with the bulk titania lattice. Surface analysis of the co-precipitated catalyst by High Sensitivity-Low Energy Ion Scattering (HS-LEIS) confirms that the VOx and WOx aremore » surface segregated for the co-precipitated catalysts. In situ Raman and IR spectroscopy revealed that the vanadium and tungsten oxide components are present as surface mono-oxo O = VO3 and O = WO4 sites on the TiO2 supports. Co-precipitation was shown for the first time to also form new mono-oxo surface VO4 and WO4 sites that appear to be anchored at surface defects of the TiO2 support. IR analysis of chemisorbed ammonia showed the presence of both surface NH3* on Lewis acid sites and surface NH4+* on Brønsted acid sites. TPSR spectroscopy demonstrated that the specific SCR kinetics was controlled by the redox surface VO4 species and that the surface kinetics was independent of TiO2 synthesis method or presence of surface WO5 sites. SCR reaction studies revealed that the surface WO5 sites possess minimal activity below ~325 °C and their primary function is to increase the adsorption capacity of ammonia. A relationship between the SCR activity and surface acidity was not found. The SCR reaction is controlled by the surface VO4 sites that initiate the reaction at ~200 °C. The co-precipitated catalysts were always more active than the corresponding impregnated catalysts. Finally, we ascribe the higher activity of the co-precipitated catalysts to the presence of

  10. Probing Hot Electron Flow Generated on Pt Nanoparticles with Au/TiO2 Schottky Diodes during Catalytic CO Oxidation

    SciTech Connect

    Park, Jeong Y.; Lee, Hyunjoo; Renzas, J. Russell; Zhang, Yawen; Somorjai, G.A.

    2008-05-01

    Hot electron flow generated on colloid platinum nanoparticles during exothermic catalytic carbon monoxide oxidation was directly detected with Au/TiO{sub 2} diodes. Although Au/TiO{sub 2} diodes are not catalytically active, platinum nanoparticles on Au/TiO{sub 2} exhibit both chemicurrent and catalytic turnover rate. Hot electrons are generated on the surface of the metal nanoparticles and go over the Schottky energy barrier between Au and TiO{sub 2}. The continuous Au layer ensures that the metal nanoparticles are electrically connected to the device. The overall thickness of the metal assembly (nanoparticles and Au thin film) is comparable to the mean free path of hot electrons, resulting in ballistic transport through the metal. The chemicurrent and chemical reactivity of nanoparticles with citrate, hexadecylamine, hexadecylthiol, and TTAB (Tetradecyltrimethylammonium Bromide) capping agents were measured during catalytic CO oxidation at pressures of 100 Torr O{sub 2} and 40 Torr CO at 373-513 K. We found that chemicurrent yield varies with each capping agent, but always decreases with increasing temperature. We suggest that this inverse temperature dependence is associated with the influence of charging effects due to the organic capping layer during hot electron transport through the metal-oxide interface.

  11. 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...

  12. Catalytic activity in lithium-treated core–shell MoOx/MoS2 nanowires

    DOE PAGESBeta

    Cummins, Dustin R.; Martinez, Ulises; Kappera, Rajesh; Voiry, Damien; Martinez-Garcia, Alejandro; Jasinski, Jacek; Kelly, Dan; Chhowalla, Manish; Mohite, Aditya D.; Sunkara, Mahendra K.; et al

    2015-09-22

    Significant interest has grown in the development of earth-abundant and efficient catalytic materials for hydrogen generation. Layered transition metal dichalcogenides present opportunities for efficient electrocatalytic systems. Here, we report the modification of 1D MoOx/MoS2 core–shell nanostructures by lithium intercalation and the corresponding changes in morphology, structure, and mechanism of H2 evolution. The 1D nanowires exhibit significant improvement in H2 evolution properties after lithiation, reducing the hydrogen evolution reaction (HER) onset potential by ~50 mV and increasing the generated current density by ~600%. The high electrochemical activity in the nanowires results from disruption of MoS2 layers in the outer shell, leadingmore » to increased activity and concentration of defect sites. This is in contrast to the typical mechanism of improved catalysis following lithium exfoliation, i.e., crystal phase transformation. As a result, these structural changes are verified by a combination of Raman and X-ray photoelectron spectroscopy (XPS).« less

  13. Dependence of Localized Electronic Structure on Ligand Configuration in the [2Fe] Hydrogenase Catalytic Core^*

    NASA Astrophysics Data System (ADS)

    Chang, Christopher H.; Kim, Kwiseon

    2007-03-01

    The [FeFe] hydrogenase enzyme is found in a variety of organisms, including Archaea, Eubacteria, and green algae^1,2, and crystallographically determined atomic position data is available for two examples. The biologically unusual catalytic H-cluster, responsible for proton reduction to H2 in vivo, is conserved in the known structures and includes two bis-thiolato bridged iron ions with extensive cyano- and carbonyl ligation. To address the configurational specificity of the diatomic ligand ligation, density functional theoretical calculations were done on [2Fe] core models of the active center, with varying CO and CN^- ligation patterns. Bonding in each complex has been characterized within the Natural Bond Orbital formalism. The effect of ligand configuration on bonding and charge distribution as well as Kohn-Sham orbital structure will be presented. [1] M. Forestier, P. King, L. Zhang, M. Posewitz, S. Schwarzer, T. Happe, M.L. Ghirardi, and M. Seibert, Eur. J. Biochem. 270, 2750 (2003). [2] Posewitz, M.C., P.W. King, S.L. Smolinski, R.D. Smith, II, A.R. Ginley, M.L. Ghirardi, and M. Seibert, Biochem. Soc. Trans. 33, 102 (2005). ^*This work was supported by the US DOE-SC-BES Hydrogen Fuels Initiative, and done in collaboration with the NREL Chemical and Biosciences Center.

  14. Preparation and Acid Catalytic Activity of TiO2 Grafted Silica MCM-41 with Sulfate Treatment

    NASA Astrophysics Data System (ADS)

    Guo, Dai-shi; Ma, Zi-feng; Yin, Chun-sheng; Jiang, Qi-zhong

    2008-02-01

    TiO2 grafted silica MCM-41 catalyst with and without sulfate treatment were prepared. The structural and acid properties of these materials were investigated by XRD, N2 adsorption-desorption, element analysis, thermal analysis, Raman and FTIR measurements. Their acid-catalytic activities were evaluated using the cyclization reaction of pseudoionone. It was found that the obtained materials possess well-ordered mesostructure, and the grafted TiO2 components were in highly dispersed amorphous form. T/MCM41 without sulfation contained only Lewis acid sites, while Brønsted and Lewis acidities were remarkably improved for the sulfated materials ST/MCM41 and d-ST/MCM41. T/MCM-41 was not active for the cyclization reaction of pseudoionone, but ST/MCM-41 and d-ST/MCM-41 possessed favorable catalytic activities. The catalytic performance of ST/MCM-41 was comparable with that of the commercial solid acid catalyst of Amberlyst-15, and better than that of d-ST/MCM-41, although the latter underwent a second TiO2 grafting process and accordingly had higher Ti and S content. The specific surface structure of Si-O-Ti-O-S=O in ST/MCM-41 and the bilateral induction effect of Si and S=O on Si-O-Ti bonds were speculated to account for its higher acid catalytic activity.

  15. Workshop on early Mars: How warm and how wet, part 2?

    NASA Technical Reports Server (NTRS)

    Squyres, S. (Editor); Kasting, J. (Editor)

    1993-01-01

    In 1992 the MSATT program conducted a workshop on modeling of the Martian climate. At that workshop it became clear that a serious problem had arisen concerning the early climate of Mars. Based on the evidence for smallscale fluvial activity, the view had been widely held that early in its history Mars had a climate that was much warmer and wetter than today's. However, most plausible recent climate models have fallen far short of the warm temperatures often inferred from the geologic evidence. Moreover, recent geophysical work has suggested that early geothermal warming may also have played a significant role in allowing fluvial activity. In order to address the issue of just how warm and how wet early Mars was, a workshop was convened in July of 1993, in Breckenridge, Colorado. The results of the workshop are reported here.

  16. Catalytic oxidation of HCN over a 0.5% Pt/Al2O3 catalyst

    SciTech Connect

    Zhao, Haibo; Tonkyn, Russell G; Barlow, Stephan E; Koel, Bruce E; Peden, Charles HF

    2006-03-27

    The adsorption of HCN on, its catalytic oxidation with 6% O2 over 0.5% Pt/Al2O3, and the subsequent oxidation of strongly bound chemisorbed species upon heating were investigated. The observed N-containing products were N2O, NO and NO2, and some residual adsorbed N-containing species were oxidized to NO and NO2 during subsequent temperature programmed oxidation. Because N-atom balance could not be obtained after accounting for the quantities of each of these product species, we propose that N2 and was formed. Both the HCN conversion and the selectivity towards different N-containing products depend strongly on the reaction temperature and the composition of the reactant gas mixture. In particular, total HCN conversion reaches 95% above 250 C. Furthermore, the temperature of maximum HCN conversion to N2O is located between 200 and 250 C, while raising the reaction temperature increases the proportion of NOx in the products. The co-feeding of H2O and C3H6 had little, if any effect on the total HCN conversion, but C3H6 addition did increase the conversion to NO and decrease the conversion to NO2, perhaps due to the competing presence of adsorbed fragments of reductive C3H6. Evidence is also presented that introduction of NO and NO2 into the reactant gas mixture resulted in additional reaction pathways between these NOx species and HCN that provide for lean-NOx reduction coincident with HCN oxidation.

  17. Catalytic decomposition of Ba(NO3)2 on Pt(111)

    SciTech Connect

    Mudiyanselage, Kumudu; Weaver, Jason F.; Szanyi, Janos

    2011-04-07

    The decomposition of Ba(NO3)2 formed on BaO/Pt(111) (Pt(111) surface is partially covered by BaO) in the presence of CO was studied using temperature programmed desorption (TPD), infrared reflection absorption (IRA) and X-ray photoelectron (XP) spectroscopies. The exposure of BaO/Pt(111) to elevated NO2 pressure (1.0×10-4 Torr) at 450 K leads to the formation of Ba(NO3)2, chemisorbed O (OPt) and Pt-oxide-like domains. During TPD, the Ba(NO3)2 begins to thermally decompose near 490 K, releasing NO and NO2 with the maximum NOx desorption rate seen at 605 K. The OPt species formed following the exposure of BaO/Pt(111) to NO2 react with CO to release CO2 at 450 K. The consumption of OPt during CO oxidation initiates the migration of O from the Pt-oxide-like domains to the chemisorbed phase, where the CO oxidation reaction occurs. Therefore, the removal of OPt by CO leads to the reduction of oxidized Pt, and to the formation of metallic Pt(111) domains, where, subsequently, catalytic decomposition of Ba(NO3)2 can take place. The Pt-catalyzed decomposition of Ba(NO3)2 occurs readily at 450 K, a temperature much lower than the onset of the decomposition temperature of Ba(NO3)2 in the presence of oxidized Pt. This work was supported by the US Department of Energy Basic Energy Sciences' Chemical Sciences, Geosciences & Biosciences Division. Pacific Northwest National Laboratory is operated by Battelle for the US Department of Energy.

  18. Thermal catalytic oxidation of octachloronaphthalene over anatase TiO2 nanomaterial and its hypothesized mechanism

    PubMed Central

    Su, Guijin; Li, Qianqian; Lu, Huijie; Zhang, Lixia; Huang, Linyan; Yan, Li; Zheng, Minghui

    2015-01-01

    As an environmentally-green technology, thermal catalytic oxidation of octachloronaphthalene (CN-75) over anatase TiO2 nanomaterials was investigated at 300 °C. A wide range of oxidation intermediates, which were investigated using various techniques, could be of three types: naphthalene-ring, single-benzene-ring, and completely ring-opened products. Reactive oxygen species on anatase TiO2 surface, such as O2−• and O2−, contributed to oxidative degradation. Based on these findings, a novel oxidation degradation mechanism was proposed. The reaction at (101) surface of anatase TiO2 was used as a model. The naphthalene-ring oxidative products with chloronaphthols and hydroxyl-pentachloronaphthalene-dione, could be formed via attacking the carbon of naphthalene ring at one or more positions by nucleophilic O2−. Lateral cleavage of the naphthalene ring at different C1-C10 and C4-C9, C1-C2 and C4-C9, C1-C2 or and C3-C4 bond positions by electrophilic O2−• could occur. This will lead to the formation of tetrachlorophenol, tetrachloro-benzoic acid, tetrachloro-phthalaldehyde, and tetrachloro-acrolein-benzoic acid, partially with further transformation into tetrachlorobenzene-dihydrodiol and tetrachloro-salicylic acid. Unexpectedly, the symmetric half section of CN-75 could be completely remained with generating the intricate oxidative intermediates characteristically containing tetrachlorobenzene structure. Complete cleavage of naphthalene ring could produce the ring-opened products, such as formic and acetic acids. PMID:26643373

  19. Thermal catalytic oxidation of octachloronaphthalene over anatase TiO2 nanomaterial and its hypothesized mechanism

    NASA Astrophysics Data System (ADS)

    Su, Guijin; Li, Qianqian; Lu, Huijie; Zhang, Lixia; Huang, Linyan; Yan, Li; Zheng, Minghui

    2015-12-01

    As an environmentally-green technology, thermal catalytic oxidation of octachloronaphthalene (CN-75) over anatase TiO2 nanomaterials was investigated at 300 °C. A wide range of oxidation intermediates, which were investigated using various techniques, could be of three types: naphthalene-ring, single-benzene-ring, and completely ring-opened products. Reactive oxygen species on anatase TiO2 surface, such as O2-• and O2-, contributed to oxidative degradation. Based on these findings, a novel oxidation degradation mechanism was proposed. The reaction at (101) surface of anatase TiO2 was used as a model. The naphthalene-ring oxidative products with chloronaphthols and hydroxyl-pentachloronaphthalene-dione, could be formed via attacking the carbon of naphthalene ring at one or more positions by nucleophilic O2-. Lateral cleavage of the naphthalene ring at different C1-C10 and C4-C9, C1-C2 and C4-C9, C1-C2 or and C3-C4 bond positions by electrophilic O2-• could occur. This will lead to the formation of tetrachlorophenol, tetrachloro-benzoic acid, tetrachloro-phthalaldehyde, and tetrachloro-acrolein-benzoic acid, partially with further transformation into tetrachlorobenzene-dihydrodiol and tetrachloro-salicylic acid. Unexpectedly, the symmetric half section of CN-75 could be completely remained with generating the intricate oxidative intermediates characteristically containing tetrachlorobenzene structure. Complete cleavage of naphthalene ring could produce the ring-opened products, such as formic and acetic acids.

  20. In Situ CO2 Efflux from Leaf Litter Layer Showed Large Temporal Variation Induced by Rapid Wetting and Drying Cycle

    PubMed Central

    Ataka, Mioko; Kominami, Yuji; Yoshimura, Kenichi; Miyama, Takafumi; Jomura, Mayuko; Tani, Makoto

    2014-01-01

    We performed continuous and manual in situ measurements of CO2 efflux from the leaf litter layer (RLL) and water content of the leaf litter layer (LWC) in conjunction with measurements of soil respiration (RS) and soil water content (SWC) in a temperate forest; our objectives were to evaluate the response of RLL to rainfall events and to assess temporal variation in its contribution to RS. We measured RLL in a treatment area from which all potential sources of CO2 except for the leaf litter layer were removed. Capacitance sensors were used to measure LWC. RLL increased immediately after wetting of the leaf litter layer; peak RLL values were observed during or one day after rainfall events and were up to 8.6-fold larger than RLL prior to rainfall. RLL declined to pre-wetting levels within 2–4 day after rainfall events and corresponded to decreasing LWC, indicating that annual RLL is strongly influenced by precipitation. Temporal variation in the observed contribution of RLL to RS varied from nearly zero to 51%. Continuous in situ measurements of LWC and CO2 efflux from leaf litter only, combined with measurements of RS, can provide robust data to clarify the response of RLL to rainfall events and its contribution to total RS. PMID:25271761

  1. Simultaneous treatment of NO and SO2 with aqueous NaClO2 solution in a wet scrubber combined with a plasma electrostatic precipitator.

    PubMed

    Park, Hyun-Woo; Choi, Sooseok; Park, Dong-Wha

    2015-03-21

    NO and SO2 gases that are generally produced in thermal power plants and incinerators were simultaneously removed by using a wet scrubber combined with a plasma electrostatic precipitator. The wet scrubber was used for the absorption and oxidation of NO and SO2, and non-thermal plasma was employed for the electrostatic precipitation of aerosol particles. NO and SO2 gases were absorbed and oxidized by aerosol particles of NaClO2 solution in the wet scrubber. NO and SO2 reacted with the generated NaClO2 aerosol particles, NO2 gas, and aqueous ions such as NO2(-), NO3(-), HSO3(-), and SO4(2-). The aerosol particles were negatively charged and collected on the surface of grounded anode in the plasma electrostatic precipitator. The NO and SO2 removal efficiencies of the proposed system were 94.4% and 100% for gas concentrations of 500 mg/m(3) and a total gas flow rate of 60 Nm(3)/h, when the molar flow rate of NaClO2 and the gas-liquid contact time were /min and 1.25 s, respectively. The total amount and number of aerosol particles in the exhaust gas were reduced to 7.553 μg/m(3) and 210/cm(3) at the maximum plasma input power of 68.8 W, which are similar to the values for clean air.

  2. Highly selective catalytic reduction of NO via SO2/H2O-tolerant spinel catalysts at low temperature.

    PubMed

    Cai, Xuanxuan; Sun, Wei; Xu, Chaochao; Cao, Limei; Yang, Ji

    2016-09-01

    Selective catalytic reduction of NO X by hydrogen (H2-SCR) in the presence of oxygen has been investigated over the NiCo2O4 and Pd-doped NiCo2O4 catalysts under varying conditions. The catalysts were prepared by a sol-gel method in the presence of oxygen within 50-350 °C and were characterized using XRD, BET, EDS, XPS, Raman, H2-TPR, and NH3-TPD analysis. The results demonstrated that the doped Pd could improve the catalyst reducibility and change the surface acidity and redox properties, resulting in a higher catalytic performance. The performance of NiCo1.95Pd0.05O4 was consistently better than that of NiCo2O4 within the 150-350 °C range at a gas hourly space velocity (GHSV) of 4800 mL g(-1) h(-1), with a feed stream containing 1070 ppm NO, 10,700 ppm H2, 2 % O2, and N2 as balance gas. The effects of GHSV, NO/H2 ratios, and O2 feed concentration on the NO conversion over the NiCo2O4 and NiCo1.95Pd0.05O4 catalysts were also investigated. The two samples similarly showed that an increase in GHSV from 4800 to 9600 mL h(-1) g(-1), the NO/H2 ratio from 1:10 to 1:1, and the O2 content from 0 to 6 % would result in a decrease in NO conversion. In addition, 2 %, 5 %, and 8 % H2O into the feed gas had a slightly negative influence on SCR activity over the two catalysts. The effect of SO2 on the SCR activity indicated that the NiCo1.95Pd0.05O4 possesses better SO2 tolerance than NiCo2O4 catalyst does. Graphical abstract The NiCo1.95Pd0.05O4 catalyst achieved over 90 % NO conversion with N2 selectivity of 100 % in the 200∼250 °C range than the maximum 40.5 % NO conversion over NiCo2O4 with N2 selectivity of approximately 80 % in 350 °C.

  3. Highly selective catalytic reduction of NO via SO2/H2O-tolerant spinel catalysts at low temperature.

    PubMed

    Cai, Xuanxuan; Sun, Wei; Xu, Chaochao; Cao, Limei; Yang, Ji

    2016-09-01

    Selective catalytic reduction of NO X by hydrogen (H2-SCR) in the presence of oxygen has been investigated over the NiCo2O4 and Pd-doped NiCo2O4 catalysts under varying conditions. The catalysts were prepared by a sol-gel method in the presence of oxygen within 50-350 °C and were characterized using XRD, BET, EDS, XPS, Raman, H2-TPR, and NH3-TPD analysis. The results demonstrated that the doped Pd could improve the catalyst reducibility and change the surface acidity and redox properties, resulting in a higher catalytic performance. The performance of NiCo1.95Pd0.05O4 was consistently better than that of NiCo2O4 within the 150-350 °C range at a gas hourly space velocity (GHSV) of 4800 mL g(-1) h(-1), with a feed stream containing 1070 ppm NO, 10,700 ppm H2, 2 % O2, and N2 as balance gas. The effects of GHSV, NO/H2 ratios, and O2 feed concentration on the NO conversion over the NiCo2O4 and NiCo1.95Pd0.05O4 catalysts were also investigated. The two samples similarly showed that an increase in GHSV from 4800 to 9600 mL h(-1) g(-1), the NO/H2 ratio from 1:10 to 1:1, and the O2 content from 0 to 6 % would result in a decrease in NO conversion. In addition, 2 %, 5 %, and 8 % H2O into the feed gas had a slightly negative influence on SCR activity over the two catalysts. The effect of SO2 on the SCR activity indicated that the NiCo1.95Pd0.05O4 possesses better SO2 tolerance than NiCo2O4 catalyst does. Graphical abstract The NiCo1.95Pd0.05O4 catalyst achieved over 90 % NO conversion with N2 selectivity of 100 % in the 200∼250 °C range than the maximum 40.5 % NO conversion over NiCo2O4 with N2 selectivity of approximately 80 % in 350 °C. PMID:27301438

  4. Facet-dependent catalytic activity of Cu2O nanocrystals in the one-pot synthesis of 1,2,3-triazoles by multicomponent click reactions.

    PubMed

    Chanda, Kaushik; Rej, Sourav; Huang, Michael H

    2013-11-18

    We report the highly facet-dependent catalytic activity of Cu2O nanocubes, octahedra, and rhombic dodecahedra for the multicomponent direct synthesis of 1,2,3-triazoles from the reaction of alkynes, organic halides, and NaN3. The catalytic activities of clean surfactant-removed Cu2O nanocrystals with the same total surface area were compared. Rhombic dodecahedral Cu2O nanocrystals bounded by {110} facets were much more catalytically active than Cu2O octahedra exposing {111} facets, whereas Cu2O nanocubes displayed the slowest catalytic activity. The superior catalytic activity of Cu2O rhombic dodecahedra is attributed to the fully exposed surface Cu atoms on the {110} facet. A large series of 1,4-disubstituted 1,2,3-triazoles have been synthesized in excellent yields with high regioselectivity under green conditions by using these rhombic dodecahedral Cu2O catalysts, including the synthesis of rufinamide, an antiepileptic drug, demonstrating the potential of these nanocrystals as promising heterogeneous catalysts for other important coupling reactions. PMID:24127396

  5. Structure, bonding, and catalytic activity of monodisperse, transition-metal-substituted CeO2 nanoparticles.

    PubMed

    Elias, Joseph S; Risch, Marcel; Giordano, Livia; Mansour, Azzam N; Shao-Horn, Yang

    2014-12-10

    We present a simple and generalizable synthetic route toward phase-pure, monodisperse transition-metal-substituted ceria nanoparticles (M0.1Ce0.9O2-x, M = Mn, Fe, Co, Ni, Cu). The solution-based pyrolysis of a series of heterobimetallic Schiff base complexes ensures a rigorous control of the size, morphology and composition of 3 nm M0.1Ce0.9O2-x crystallites for CO oxidation catalysis and other applications. X-ray absorption spectroscopy confirms the dispersion of aliovalent (M(3+) and M(2+)) transition metal ions into the ceria matrix without the formation of any bulk transition metal oxide phases, while steady-state CO oxidation catalysis reveals an order of magnitude increase in catalytic activity with copper substitution. Density functional calculations of model slabs of these compounds confirm the stabilization of M(3+) and M(2+) in the lattice of CeO2. These results highlight the role of the host CeO2 lattice in stabilizing high oxidation states of aliovalent transition metal dopants that ordinarily would be intractable, such as Cu(3+), as well as demonstrating a rational approach to catalyst design. The current work demonstrates, for the first time, a generalizable approach for the preparation of transition-metal-substituted CeO2 for a broad range of transition metals with unparalleled synthetic control and illustrates that Cu(3+) is implicated in the mechanism for CO oxidation on CuO-CeO2 catalysts. PMID:25406101

  6. The effectiveness of wet cupping vs. venesection on arterial O2 saturation level of cigarette smokers: A randomized controlled clinical trial

    PubMed Central

    D, Hekmatpou; L, Moeini; S, Haji-Nadali

    2013-01-01

    Objective: Wet cupping is a traditional bloodletting method recommended for controlling of respiratory disease complications. This study aimed to compare the efficacy of wet cupping vs. venesection on arterial O2 saturation level of smokers. Methods: This is a randomized controlled clinical trial which started with simple sampling of smokers. After administering spirometery, participants (N = 110 male smokers) with positive pulmonary function test (PFT), who manifested Chronic Obstructive Pulmonary Disease (COPD), were randomly assigned to intervention and control groups. The two groups were assessed in terms of demographic data, rate of hemoglobin (Hb), hematocrit (Hct), and arterial O2 saturation. Then, the intervention participants underwent wet cupping whereas venesection was performed on the control participants. At four stages after the two treatments, pulse oximetery was performed. Data was analyzed using SPSS (Version 17). Results: Result shows that mean arterial O2 sat level increased at three stages, namely before, immediately after, and 6 and 12 hrs after these two treatments (p ≤ 0.001). This indicates that wet cupping and venesection alike were effective on O2 sat level in the two groups, but the increasing pattern was maintained 12 hrs afterward only in those participants who had received wet cupping (p ≤ 0.001). Moreover, the results of repeated measure ANOVA between the two groups at the four stages showed that there were significant differences between the means of O2 saturation level at the 6- and 12-hrs stages (F = 66.92, p ≤ 0.001). Conclusion: Wet cupping caused a continued O2 saturation in the intervention group even up to 12 hrs afterward. Participants expressed liveliness and improved respiration after wet cupping. Therefore, wet cupping is recommended for promoting the health of cigarette smokers. PMID:24550951

  7. Synthesis of nanostructured framework of novel ZnBaO2 nanopowder via wet chemical approach and hepatocytotoxicity response

    NASA Astrophysics Data System (ADS)

    Athar, Taimur; Vishwakarma, Sandeep Kumar; Alabass, Razzaq; Alqaralosy, Ahmed; Khan, Aleem Ahmed

    2016-08-01

    Wet synthetic process is an effective and facile method at low cost, environmentally benign process for easy scaling-up and then used for fabrication of multi-utility devices. Self-assembling of nanobrick leads to architecture framework with new functional properties which help to make its vast applications as nanodevices with their intrinsic shape, size and functional properties. The bimetallic oxide nanostructure with phase structure was characterized by FTIR, UV-visible electronic absorption, XRD, thermal studies, SEM, TEM, DLS and fluorescence. Nanocrystalline ZnBaO2 powder can be used due to its chemical stability and excellent transmission in the visible region. It was observed that the annealing rate plays an important role to redefine the structural and other physicochemical properties which finally help to change gel into crystalline functional properties with porosity. Wet chemical approach can be used for the synthesis of other metal oxide nanopowders which can be easily scale up for production level. Along with synthesis and characterization, we also assessed biological responses of human hepatocytes exposed to ZnBaO2 nanopowder. Cell membrane permeability and ammonia detoxification were investigated against various concentrations of nanoparticles on in vitro cultured hepatocytes. Our results suggest that low concentrations (<40 μg/ml) of ZnBaO2 nanopowder have no cytotoxic effect on hepatocytes viability, proliferation and detoxification, whereas concentrations above 40 μg/ml depict significant toxicity on cells.

  8. Essential biphasic role for JAK3 catalytic activity in IL-2 receptor signaling

    PubMed Central

    Smith, Geoffrey A.; Uchida, Kenji; Weiss, Arthur; Taunton, Jack

    2016-01-01

    To drive lymphocyte proliferation and differentiation, common γ-chain (γc) cytokine receptors require hours to days of sustained stimulation. While JAK1 and JAK3 kinases are found together in all γc-receptor complexes, it is not known how their respective catalytic activities contribute to signaling over time. Here, we dissect the temporal requirements for JAK3 kinase activity with a selective covalent inhibitor (JAK3i). By monitoring STAT5 phosphorylation over 20 hours in IL-2-stimulated CD4+ T cells, we document a previously unappreciated second wave of signaling that is much more sensitive to JAK3i than the first wave. Selective inhibition of this second wave is sufficient to block cyclin expression and S-phase entry. An inhibitor-resistant JAK3 mutant (Cys905Ser) rescued all effects of JAK3i in isolated T cells and in mice. Our chemical genetic toolkit elucidates a biphasic requirement for JAK3 kinase activity in IL-2-driven T-cell proliferation and will find broad utility in studies of γc-receptor signaling. PMID:27018889

  9. Nanostructured Samarium Doped Fluorapatites and Their Catalytic Activity towards Synthesis of 1,2,4-Triazoles.

    PubMed

    Gangu, Kranthi Kumar; Maddila, Suresh; Maddila, Surya Narayana; Jonnalagadda, Sreekantha B

    2016-01-01

    An investigation was conducted into the influence of the amino acids as organic modifiers in the facile synthesis of metal incorporated fluorapatites (FAp) and their properties. The nanostructured Sm doped fluorapatites (Sm-FAp) were prepared by a co-precipitation method using four different amino acids, namely glutamic acid, aspartic acid, glycine and histidine. The materials were characterized by various techniques including X-ray diffraction (XRD), Fourier transform infra-red spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), high resolution transmission electron microscopy (HR-TEM), N₂-adsorption/desorption isotherm, temperature programmed desorption (TPD) and fluorescence spectrophotometry. Under similar conditions, Sm-FAp prepared using different amino acids exhibited distinctly different morphological structures, surface area and pore properties. Their activity as catalysts was assessed and Sm-FAp/Glycine displayed excellent efficiency in the synthesis of 1,2,4-triazole catalyzing the reaction between 2-nitrobenzaldehyde and thiosemicarbazide with exceptional selectivity and 98% yield in a short time interval (10 min). The study provides an insight into the role of organic modifiers as controllers of nucleation, growth and aggregation which significantly influence the nature and activity of the catalytic sites on Sm-FAp. Sm-FAp could also have potential as photoactive material. PMID:27669208

  10. Nuclear localization of catalytically active MMP-2 in endothelial cells and neurons

    PubMed Central

    Sinha, Satyesh K; Asotra, Kamlesh; Uzui, Hiroyasu; Nagwani, Santosh; Mishra, Vivek; Rajavashisth, Tripathi B

    2014-01-01

    From microscopic organelles and sub-cellular domains to the level of whole tissues, organs, and body parts, living organisms must continuously maintain and renovate structural components. Matrix metalloproteinases (MMPs) comprise a family of over two dozen Zn-dependent endopeptidases thought to be primary effectors of extracellular tissue renewal and remodeling processes. Endogenous inhibitors, particularly the tissue inhibitors of MMPs (TIMPs), counteract MMP-2 proteolytic activity, but also participate in conversion of several pro-MMPs to proteolytically active forms. Numerous pathologies are characterized by imbalances in activities of MMPs relative to TIMPs. MMPs are synthesized and stored in cytoplasmic domains prior to secretion or expression in cell surface-associated form. Several proteases have been identified in cell nuclei, but their functions, regulation, and substrates remain largely unknown. Here we showed that the catalytically active gelatinase MMP-2 is expressed in nuclei of endothelial cells and neurons, but not in glial or Schwannoma cell lines, in a pattern resembling nuclear speckles, and colocalizes with TIMP-1. PMID:24489995

  11. Uniform Ni/SiO2@Au magnetic hollow microspheres: rational design and excellent catalytic performance in 4-nitrophenol reduction.

    PubMed

    Zhang, Shenghuan; Gai, Shili; He, Fei; Dai, Yunlu; Gao, Peng; Li, Lei; Chen, Yujin; Yang, Piaoping

    2014-06-21

    A unique and rational design was presented to fabricate Ni/SiO2@Au magnetic hollow microspheres (MHMs) with interesting structures and well-dispersed metal nanoparticles. Hierarchical nickel silicate hollow microspheres were synthesized using silica colloidal spheres as a chemical template. Then, Ni/SiO2 MHMs with well-dispersed Ni nanoparticles were prepared via an in situ reduction approach. Ni/SiO2@Au MHMs were finally obtained by immobilizing uniform Au nanoparticles onto Ni/SiO2 support through a low-temperature chemical reduction process. It was found that Ni/SiO2@Au MHMs inherit the shape and uniformity of the original silica scaffold, and Ni NPs and Au NPs, which were less than 5 nm in size, were well dispersed on the mesoporous silica shell with narrow size distribution. Both Ni/SiO2 and Ni/SiO2@Au MHMs showed excellent catalytic activity in the 4-nitrophenol reduction reaction. Importantly, introduction of a small amount of Au NPs onto Ni/SiO2 MHMs markedly improved the catalytic activity. In particular, Ni/SiO2@Au MHMs showed high conversion even after re-use for several cycles with magnetic separation. The unique structure, high catalytic performance, and ease of separation make Ni/SiO2@Au MHMs highly promising candidates for diverse applications.

  12. Catalytic conversion of furfural into a 2,5-furandicarboxylic acid-based polyester with total carbon utilization.

    PubMed

    Pan, Tao; Deng, Jin; Xu, Qing; Zuo, Yong; Guo, Qing-Xiang; Fu, Yao

    2013-01-01

    One divided into two combined into one: The catalytic conversion of furfural into a 2,5-furandicarboxylic acid-based polyester, linked by the disproportionation of furoate to furan and 2,5-furandicarboxylate, is reported. In this manner, all carbons are utilized, demonstrating the success of combining a platform molecule from C(5) sugars (furfural) to one from C(6) sugars (2,5-FDCA). PMID:23239596

  13. Mn-Promoted Co3O4/TiO2 as an efficient catalyst for catalytic oxidation of dibromomethane (CH2Br2).

    PubMed

    Mei, Jian; Zhao, Songjian; Huang, Wenjun; Qu, Zan; Yan, Naiqiang

    2016-11-15

    Brominated hydrocarbon is the typical pollutant in the exhaust gas from the synthesis process of Purified Terephthalic Acid (PTA), which may cause various environmental problems once emitted into atmosphere. Dibromomethane (DBM) was employed as the model compound in this study, and a series of TiO2-supported manganese and cobalt oxide catalysts with different Mn/Co molar ratio were prepared by the impregnation method and used for catalytic oxidation of DBM. It was found that the addition of Mn significantly enhanced the catalytic performance of Co/TiO2 catalyst. Among all the prepared catalysts, Mn(1)-Co/TiO2 (Mn/Co molar ratio was 1) catalyst exhibited the highest activity with T90 at about 325°C and good stability maintained for at least 30h at 500ppm DBM and 10% O2 at GHSV=60,000h(-1), and the final products in the reaction were COx, HBr and Br2, without the formation of Br-containing organics. The high activity and high stability might be attributed to the redox cycle (Co(2+)+Mn(4+)↔Co(3+)+Mn(3+)) over Mn-promoted Co3O4/TiO2 catalyst. Based on the results of in situ DRIFT studies and analysis of products, a plausible reaction mechanism for catalytic oxidation of DBM over Mn-Co/TiO2 catalysts was also proposed. PMID:27388418

  14. Mn-Promoted Co3O4/TiO2 as an efficient catalyst for catalytic oxidation of dibromomethane (CH2Br2).

    PubMed

    Mei, Jian; Zhao, Songjian; Huang, Wenjun; Qu, Zan; Yan, Naiqiang

    2016-11-15

    Brominated hydrocarbon is the typical pollutant in the exhaust gas from the synthesis process of Purified Terephthalic Acid (PTA), which may cause various environmental problems once emitted into atmosphere. Dibromomethane (DBM) was employed as the model compound in this study, and a series of TiO2-supported manganese and cobalt oxide catalysts with different Mn/Co molar ratio were prepared by the impregnation method and used for catalytic oxidation of DBM. It was found that the addition of Mn significantly enhanced the catalytic performance of Co/TiO2 catalyst. Among all the prepared catalysts, Mn(1)-Co/TiO2 (Mn/Co molar ratio was 1) catalyst exhibited the highest activity with T90 at about 325°C and good stability maintained for at least 30h at 500ppm DBM and 10% O2 at GHSV=60,000h(-1), and the final products in the reaction were COx, HBr and Br2, without the formation of Br-containing organics. The high activity and high stability might be attributed to the redox cycle (Co(2+)+Mn(4+)↔Co(3+)+Mn(3+)) over Mn-promoted Co3O4/TiO2 catalyst. Based on the results of in situ DRIFT studies and analysis of products, a plausible reaction mechanism for catalytic oxidation of DBM over Mn-Co/TiO2 catalysts was also proposed.

  15. Mixing in a three-phase system: Enhanced production of oil-wet reservoirs by CO2 injection

    NASA Astrophysics Data System (ADS)

    Jiménez-Martínez, Joaquín.; Porter, Mark L.; Hyman, Jeffrey D.; Carey, J. William; Viswanathan, Hari S.

    2016-01-01

    We recreate three-phase reservoir conditions (high-pressure/temperature) using a microfluidics system and show that the use of scCO2 for restimulation operations, such as hydraulic fracturing, can enhance mixing and production. The results inform hydrocarbon extraction from deep shale formations, which has recently generated an energy boom that has lowered hydrocarbon costs. However, production decreases rapidly and methods to increase efficiency or allow restimulation of wells are needed. In our experiments, the presence of residual brine from initial production creates spatiotemporal variability in the system that causes the injected scCO2 to more effectively interact-mix with trapped hydrocarbon, thereby increasing recovery. We apply volume-averaging techniques to upscale brine saturation, which allows us to analyze the complex three-phase system in the framework of well characterized two-phase systems. The upscaled three-phase system behaves like a two-phase system: greater mixing with larger non-wetting content and higher heterogeneity. The results are contrary to previous observations in water-wet systems.

  16. Additives affecting properties of β-Li2TiO3 pebbles in a modified indirect wet chemistry process

    NASA Astrophysics Data System (ADS)

    Yu, Cheng-Long; Liu, Wei; Yang, Long-Tao; Wang, Dao-Yi; Wu, Kang; Zhang, Zeng-Ping; Wang, Xiu-Feng; Yanagisawa, Kazumichi

    2016-11-01

    Lithium metatitanate (β-Li2TiO3) pebbles were fabricated via the modified indirect wet chemistry method. Effect of varied additives, as polyvinyl alcohol, glycerol, and agar on the properties evolution was investigated. The highest density is obtained by adding 2 wt% (weight percent) polyvinyl alcohol, 3 wt% glycerol, and 3 wt% agar, respectively. β-Li2TiO3 pebbles with relative sintered density of 92.4%T.D. (Theoretical Density), the ratio of the intensity of diffraction peak (002) to that of (-133) of about 2.93, about 1.58 mm in diameter, a better sphericity of 1.02, the particle size of 5-6 μm, and the well-developed surface layered structure are successfully fabricated with 3 wt% glycerol. Glycerol is beneficial to improving the properties by other fabrication method as well.

  17. [Low-temperature catalytic reduction of NO over Fe-MnOx-CeO2/ZrO2 catalyst].

    PubMed

    Liu, Rong; Yang, Zhi-Qin

    2012-06-01

    Fe-MnOx-CeO2/ZrO2 catalysts were prepared through impregnation method with nanometer ZrO2 as a carrier and used in selective catalytic reduction of NO with NH3 at low temperature. Effects of active component ratio and loading of promoter on the catalyst activity were investigated. The catalysts were characterized by means of XRD, SEM, EDS and BET. The effects of temperature, SO2 and H2O on NO conversion were studied and the results showed that in the absence of SO2 and H2O, the catalyst of 8% Fe-10% MnOx-CeO2/ZrO2 had good activity and stability as well as the NOx removal efficiency reached 85.23% at 120 degrees C and 92.0% at 180 degrees C. The presence of SO2 and H2O results in the catalyst deactivated. Properties of the catalyst on different reaction stages were characterized by FT-IR to study the inactivation mechanism of the catalyst. The results showed that the catalyst deactivation was due to the deposition of ammonium sulfate on the catalyst and the sulphation of the catalyst.

  18. Catalytic activities of Werner protein are affected by adduction with 4-hydroxy-2-nonenal

    PubMed Central

    Czerwińska, Jolanta; Poznański, Jarosław; Dębski, Janusz; Bukowy, Zuzanna; Bohr, Vilhelm A.; Tudek, Barbara; Speina, Elżbieta

    2014-01-01

    4-Hydroxy-2-nonenal (HNE) is a reactive α,β-unsaturated aldehyde generated during oxidative stress and subsequent peroxidation of polyunsaturated fatty acids. Here, Werner protein (WRN) was identified as a novel target for modification by HNE. Werner syndrome arises through mutations in the WRN gene that encodes the RecQ DNA helicase which is critical for maintaining genomic stability. This hereditary disease is associated with chromosomal instability, premature aging and cancer predisposition. WRN appears to participate in the cellular response to oxidative stress and cells devoid of WRN display elevated levels of oxidative DNA damage. We demonstrated that helicase/ATPase and exonuclease activities of HNE-modified WRN protein were inhibited both in vitro and in immunocomplexes purified from the cell extracts. Sites of HNE adduction in human WRN were identified at Lys577, Cys727, His1290, Cys1367, Lys1371 and Lys1389. We applied in silico modeling of the helicase and RQC domains of WRN protein with HNE adducted to Lys577 and Cys727 and provided a potential mechanism of the observed deregulation of the protein catalytic activities. In light of the obtained results, we postulate that HNE adduction to WRN is a post-translational modification, which may affect WRN conformational stability and function, contributing to features and diseases associated with premature senescence. PMID:25170083

  19. Simultaneous catalytic removal of NO and N{sub 2}O using Fe-MFI

    SciTech Connect

    Koegel, M.; Turek, T.; Moennig, R.; Schwieger, W.; Tissler, A.

    1999-03-10

    Fe-MFI preparations active for the reduction of nitric oxide and nitrous oxide with hydrocarbons have been prepared by solid-state ion-exchange in the presence of air. While nitrous oxide can be removed by a variety of reducing agents, C{sub 3} hydrocarbons, especially propane, are suitable for the catalytic reduction of nitric oxide. The reduction of nitrous oxide was always enhanced by increasing temperature, whereas maximum NO conversions were observed at temperatures around 300 C. The addition of up to 7% of water was found to decrease the achievable conversions of the nitrogen oxides moderately. The activity for the removal of nitrous oxide was strongly inhibited in the presence of NO, probably via an intermediate formed from NO{sub 2} and the hydrocarbon. On the other hand, the observed NO conversions were not affected by the presence of nitrous oxide. In all cases, considerable amounts of carbon monoxide were formed from the hydrocarbons. It could be shown that the degree of ion-exchange achievable during the solid-state procedure is limited. At iron contents exceeding Fe/Al = 0.5, Fe ions are no longer being introduced into the zeolite. The excess iron is being precipitated as hematite, which is inactive in the reduction of both nitric oxide and nitrous oxide.

  20. Persistent DNA binding, cleavage performance and eco-friendly catalytic nature of novel complexes having 2-aminobenzophenone precursor.

    PubMed

    Muniyandi, Vellaichamy; Pravin, Narayanaperumal; Subbaraj, Paramasivam; Raman, Natarajan

    2016-03-01

    This paper describes the synthesis of four novel bidentate metal(II) complexes having 2-aminobenzophenone precursor and a co-ligand (anthranilic acid). They are characterized by the usual spectral and analytical data. They adopt octahedral geometrical arrangements around the metal ions which have been confirmed by electronic absorption data. Moreover, the EPR study of Cu(II) complex has provided supportive evidence to the conclusion drawn on the basis of electronic spectrum and magnetic moment value. Powder XRD and SEM studies show that all the complexes are microcrystalline with homogenous morphology. The interaction of these complexes with CT-DNA has been explored by UV-absorption, fluorescence, viscosity, CV and CD techniques which reveal that the complexes could bind to CT-DNA through intercalation. The oxidative cleavage of the metal complexes with pBR322 DNA has also been investigated by gel electrophoresis. Moreover, the antimicrobial bustle shows that all metal chelates have superior activity than the free Schiff base ligand. The catalytic activity of the complexes has been evaluated towards the oxidation of aniline. All the complexes exhibit significant catalytic activity. Among them Cu(II) complex exhibits better catalytic activity than others. This catalytic process occurs at room temperature and it proceeds in water medium which suggests that this is an eco-friendly process. PMID:26784572

  1. Oxidation of nitrogen oxide in hybrid plasma-catalytic reactors based on DBD and Fe2O3

    NASA Astrophysics Data System (ADS)

    Jõgi, Indrek; Erme, Kalev; Haljaste, Ants; Laan, Matti

    2013-02-01

    In the present study, Fe2O3 was used as catalyst for the removal of NO in a hybrid plasma- catalytic reactor. The catalyst was located either directly inside the hybrid plasma-catalytic reactor or in a separate catalytic reactor, which followed ozone producing and injecting plasma reactor. Ozone production in such a reactor was dependent on the state of the electrode surface. The fresh catalyst ensured an order of magnitude smaller ozone concentration in the outlet of the hybrid reactor. After a short treatment of the catalyst with NO2, its ability to destroy ozone diminished but was regained after heating of the reactor up to 100 °C. Similarly to earlier results obtained with TiO2, the removal of NO in the hybrid reactor with Fe2O3 was enhanced compared to that in an ordinary plasma reactor. In the ozone injection reactor, oxidation of NO to NO2 took place with considerably higher efficiency compared to the hybrid reactor. The use of catalyst in the ozonation stage further improved the oxidation of NO2 to N2O5. The time-dependence effects of NO removal during plasma and ozone oxidation were explained by reactions between NO2 adsorbed on surface, with surface-bound NO3 and gas phase NO as the reaction product. Contribution to the Topical Issue "13th International Symposium on High Pressure Low Temperature Plasma Chemistry (Hakone XIII)", Edited by Nicolas Gherardi, Henryca Danuta Stryczewska and Yvan Ségui.

  2. On the reactivity of plasma-treated photo-catalytic TiO2 surfaces for oxidation of C2H2 and CO

    NASA Astrophysics Data System (ADS)

    Lopatik, D.; Marinov, D.; Guaitella, O.; Rousseau, A.; Röpcke, J.

    2013-06-01

    The objective of this study is to understand fundamental aspects of interactions of plasmas with catalytic surfaces. Based on this approach the reactivity of plasma treated and stimulated catalytic surfaces of TiO2 is studied by analysing the oxidation (i) of C2H2 to CO and CO2 and (ii) of CO to CO2. The inner surface of a Pyrex discharge tube is coated with TiO2 films impregnated with TiO2 nanoparticles, which provides a surface area of about 4 m2. In addition to the exposure of the TiO2 surface by low-pressure radio-frequency plasmas using O2, Ar or N2 (f = 13.56 MHz, p = 0.53 mbar, P = 17 W) the surfaces are stimulated by heating and UV radiation treatment. The temporal development of the concentrations of the precursor gases C2H2 or CO and of the reaction products is monitored using quantum cascade laser absorption spectroscopy, which provides multi-component detection in the mid-infrared spectral range. The C2H2 concentration was found to be nearly constant over time after a pre-treatment with Ar or N2 discharges using an initial gas mixture of 1% C2H2 in Ar. However, a strong decay of the concentration of C2H2 is observed for pure O2 plasma pre-treatment. In general, the decay is found to be nearly exponential with time constant in the order of about 10 min. The reactive adsorption of C2H2 molecules on the inner surface of the tube reactor showed a density of about 7.5 × 1012 C2H2 molecules cm-2. This behaviour demonstrates that the reaction (O_{ads} +C_{2} H_{2})_{{TiO}_{2}} produces some adsorbed intermediates, which can be thermally or photo-catalytically oxidized to CO2. In contrast, when 1% CO in Ar is used as an initial gas mixture no adsorption processes on the TiO2 surface could be detected. An effective destruction of CO took part via photo-catalytic oxidation.

  3. Remarkable promotion effect of trace sulfation on OMS-2 nanorod catalysts for the catalytic combustion of ethanol.

    PubMed

    Zhang, Jie; Zhang, Changbin; He, Hong

    2015-09-01

    OMS-2 nanorod catalysts were synthesized by a hydrothermal redox reaction method using MnSO4 (OMS-2-SO4) and Mn(CH3COO)2 (OMS-2-AC) as precursors. SO4(2-)-doped OMS-2-AC catalysts with different SO4(2-) concentrations were prepared next by adding (NH4)2SO4 solution into OMS-2-AC samples to investigate the effect of the anion SO4(2-) on the OMS-2-AC catalyst. All catalysts were then tested for the catalytic oxidation of ethanol. The OMS-2-SO4 catalyst synthesized demonstrated much better activity than OMS-2-AC. The SO4(2-) doping greatly influenced the activity of the OMS-2-AC catalyst, with a dramatic promotion of activity for suitable concentration of SO4(2-) (SO4/catalyst=0.5% W/W). The samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectroscopy (ICP-OES), NH3-TPD and H2-TPR techniques. The results showed that the presence of a suitable amount of SO4(2-) species in the OMS-2-AC catalyst could decrease the Mn-O bond strength and also enhance the lattice oxygen and acid site concentrations, which then effectively promoted the catalytic activity of OMS-2-AC toward ethanol oxidation. Thus it was confirmed that the better catalytic performance of OMS-2-SO4 compared to OMS-2-AC is due to the presence of some residual SO4(2-) species in OMS-2-SO4 samples. PMID:26354694

  4. Study on the catalytic activity of vanadium doped TiO2: Anatase-to-rutile phase transition

    NASA Astrophysics Data System (ADS)

    Zhang, Huiming; Bian, He; Zhang, Shiguo

    2016-01-01

    The catalytic activity of vanadium doped TiO2 in the ethylbenzene oxidative dehydrogenation with CO2 was studied experimentally and theoretically. The experimental results showed that the reduction of ethylbenzene conversion and the styrene selectivity was caused by the transition of anatase to rutile phase. Theoretical results showed that the transition of the anatase to rutile phase was mainly caused by vanadium ions and oxygen vacancies.

  5. 2',6'-Dihalostyrylanilines, pyridines, and pyrimidines for the inhibition of the catalytic subunit of methionine S-adenosyltransferase-2.

    PubMed

    Sviripa, Vitaliy M; Zhang, Wen; Balia, Andrii G; Tsodikov, Oleg V; Nickell, Justin R; Gizard, Florence; Yu, Tianxin; Lee, Eun Y; Dwoskin, Linda P; Liu, Chunming; Watt, David S

    2014-07-24

    Inhibition of the catalytic subunit of the heterodimeric methionine S-adenosyl transferase-2 (MAT2A) with fluorinated N,N-dialkylaminostilbenes (FIDAS agents) offers a potential avenue for the treatment of liver and colorectal cancers where upregulation of this enzyme occurs. A study of structure-activity relationships led to the identification of the most active compounds as those with (1) either a 2,6-difluorostyryl or 2-chloro-6-fluorostyryl subunit, (2) either an N-methylamino or N,N-dimethylamino group attached in a para orientation relative to the 2,6-dihalostyryl subunit, and (3) either an N-methylaniline or a 2-(N,N-dimethylamino)pyridine ring. These modifications led to FIDAS agents that were active in the low nanomolar range, that formed water-soluble hydrochloride salts, and that possessed the desired property of not inhibiting the human hERG potassium ion channel at concentrations at which the FIDAS agents inhibit MAT2A. The active FIDAS agents may inhibit cancer cells through alterations of methylation reactions essential for cancer cell survival and growth.

  6. Cobalt-Catalyzed [2π + 2π] Cycloadditions of Alkenes: Scope, Mechanism, and Elucidation of Electronic Structure of Catalytic Intermediates.

    PubMed

    Schmidt, Valerie A; Hoyt, Jordan M; Margulieux, Grant W; Chirik, Paul J

    2015-06-24

    Aryl-substituted bis(imino)pyridine cobalt dinitrogen compounds, ((R)PDI)CoN2, are effective precatalysts for the intramolecular [2π + 2π] cycloaddition of α,ω-dienes to yield the corresponding bicyclo[3.2.0]heptane derivatives. The reactions proceed under mild thermal conditions with unactivated alkenes, tolerating both amine and ether functional groups. The overall second order rate law for the reaction, first order with respect to both the cobalt precatalyst and the substrate, in combination with electron paramagnetic resonance (EPR) spectroscopic studies established the catalyst resting state as dependent on the identity of the precatalyst and diene substrate. Planar S = ½ κ(3)-bis(imino)pyridine cobalt alkene and tetrahedral κ(2)-bis(imino)pyridine cobalt diene complexes were observed by EPR spectroscopy and in the latter case structurally characterized. The hemilabile chelate facilitates conversion of a principally ligand-based singly occupied molecular orbital (SOMO) in the cobalt dinitrogen and alkene compounds to a metal-based SOMO in the diene intermediates, promoting C-C bond-forming oxidative cyclization. Structure-activity relationships on bis(imino)pyridine substitution were also established with 2,4,6-tricyclopentyl-substituted aryl groups, resulting in optimized catalytic [2π + 2π] cycloaddition. The cyclopentyl groups provide a sufficiently open metal coordination sphere that encourages substrate coordination while remaining large enough to promote a challenging, turnover-limiting C(sp(3))-C(sp(3)) reductive elimination. PMID:26030841

  7. Cobalt-Catalyzed [2π + 2π] Cycloadditions of Alkenes: Scope, Mechanism, and Elucidation of Electronic Structure of Catalytic Intermediates.

    PubMed

    Schmidt, Valerie A; Hoyt, Jordan M; Margulieux, Grant W; Chirik, Paul J

    2015-06-24

    Aryl-substituted bis(imino)pyridine cobalt dinitrogen compounds, ((R)PDI)CoN2, are effective precatalysts for the intramolecular [2π + 2π] cycloaddition of α,ω-dienes to yield the corresponding bicyclo[3.2.0]heptane derivatives. The reactions proceed under mild thermal conditions with unactivated alkenes, tolerating both amine and ether functional groups. The overall second order rate law for the reaction, first order with respect to both the cobalt precatalyst and the substrate, in combination with electron paramagnetic resonance (EPR) spectroscopic studies established the catalyst resting state as dependent on the identity of the precatalyst and diene substrate. Planar S = ½ κ(3)-bis(imino)pyridine cobalt alkene and tetrahedral κ(2)-bis(imino)pyridine cobalt diene complexes were observed by EPR spectroscopy and in the latter case structurally characterized. The hemilabile chelate facilitates conversion of a principally ligand-based singly occupied molecular orbital (SOMO) in the cobalt dinitrogen and alkene compounds to a metal-based SOMO in the diene intermediates, promoting C-C bond-forming oxidative cyclization. Structure-activity relationships on bis(imino)pyridine substitution were also established with 2,4,6-tricyclopentyl-substituted aryl groups, resulting in optimized catalytic [2π + 2π] cycloaddition. The cyclopentyl groups provide a sufficiently open metal coordination sphere that encourages substrate coordination while remaining large enough to promote a challenging, turnover-limiting C(sp(3))-C(sp(3)) reductive elimination.

  8. Characterization of an Fe≡N-NH2 Intermediate Relevant to Catalytic N2 Reduction to NH3

    PubMed Central

    Connor, Bridget A.; Gunderson, William A.; Zhang, Limei; Hoffman, Brian M.; Peters, Jonas C.

    2015-01-01

    The ability of certain transition metals to mediate the reduction of N2 to NH3 has attracted broad interest in the biological and inorganic chemistry communities. Early transition metals such as Mo and W readily bind N2 and mediate its protonation at one or more N atoms to furnish M(NxHy) species that can be characterized and, in turn, extrude NH3. By contrast, the direct protonation of Fe-N2 species to Fe(NxHy) products that can be characterized has been elusive. Herein we show that addition of acid at low temperature to [(TPB)Fe(N2)][Na(12-crown-4)] results in a new S = 1/2 Fe species. EPR, ENDOR, Mössbauer, and EXAFS analysis, coupled with a DFT study, unequivocally assign this new species as [(TPB)Fe≡N-NH2]+, a doubly protonated hydrazido(2-) complex featuring an Fe-to-N triple bond. This unstable species offers strong evidence that the first steps in Fe-mediated nitrogen reduction by [(TPB)Fe(N2)][Na(12-crown-4)] can proceed along a distal or `Chatt-type' pathway. A brief discussion of whether subsequent catalytic steps may involve early or late stage cleavage of the N-N bond, as would be found in limiting distal or alternating mechanisms, respectively, is also provided. PMID:26000443

  9. Non-catalytic transfer hydrogenation in supercritical CO2 for coal liquefaction

    NASA Astrophysics Data System (ADS)

    Elhussien, Hussien

    This thesis presents the results of the investigation on developing and evaluating a low temperature (<150°C) non - catalytic process using a hydrogen transfer agent (instead of molecu-lar hydrogen) for coal dissolution in supercritical CO2. The main idea behind the thesis was that one hydrogen atom from water and one hydrogen atom from the hydrogen transfer agent (HTA) were used to hydrogenate the coal. The products of coal dissolution were non-polar and polar while the supercritical CO2, which enhanced the rates of hydrogenation and dissolution of the non-polar molecules and removal from the reaction site, was non-polar. The polar modifier (PM) for CO2 was added to the freed to aid in the dissolution and removal of the polar components. The addition of a phase transfer agent (PTA) allowed a seamless transport of the ions and by-product between the aqueous and organic phases. DDAB, used as the PTA, is an effective phase transfer catalyst and showed enhancement to the coal dissolution process. COAL + DH- +H 2O → COAL.H2 + DHO-- This process has a great feature due to the fact that the chemicals were obtained without requir-ing to first convert coal to CO and H2 units as in indirect coal liquefaction. The experiments were conducted in a unique reactor set up that can be connected through two lines. one line to feed the reactor with supercritical CO 2 and the other connected to gas chromatograph. The use of the supercritical CO2 enhanced the solvent option due to the chemical extraction, in addition to the low environmental impact and energy cost. In this thesis the experiment were conducted at five different temperatures from atmos-pheric to 140°C, 3000 - 6000 psi with five component of feed mixture, namely water, HTA, PTA, coal, and PM in semi batch vessels reactor system with a volume of 100 mL. The results show that the chemicals were obtained without requiring to first convert coal to CO and H2 units as in indirect coal liquefaction. The results show that

  10. Z-selective, catalytic internal alkyne semihydrogenation under H2/CO mixtures by a niobium(III) imido complex.

    PubMed

    Gianetti, Thomas L; Tomson, Neil C; Arnold, John; Bergman, Robert G

    2011-09-28

    The discovery of a Nb(III)-mediated catalytic hydrogenation of internal alkynes to (Z)-alkenes that proceeds through an unprecedented mechanism is reported. The mechanistic proposal involves initial reduction of the alkyne by the Nb(III) complex (BDI)Nb(N(t)Bu)(CO)(2) to provide a Nb(V) metallacyclopropene, itself capable of σ-bond metathesis reactivity with H(2). The resulting alkenyl hydride species then undergoes reductive elimination to provide the (Z)-alkene product and regenerate a metal complex in the Nb(III) oxidation state. Support for the proposed mechanism is derived from (i) the dependence of the product selectivity on the relative concentrations of CO and H(2), (ii) the isolation of complexes closely related to those proposed to be part of the catalytic cycle, (iii) H/D crossover experiments, and (iv) DFT studies of multiple possible reaction pathways.

  11. Why is silver catalytically active for NO reduction? A unique pathway via an inverted (NO)2 dimer.

    PubMed

    Liu, Zhi-Pan; Jenkins, Stephen J; King, David A

    2004-06-16

    NO reduction on the noble metal Ag has been studied using density functional theory calculations. It was found that monomeric NO dissociation is subject to prohibitive barriers on Ag metal and is thus unlikely to account for the experimental observations for NO reduction over Ag-based catalysts. For the first time, a mechanism via an inverted (NO)(2) dimer is identified, which can explain both the high activity and the selectivity of this catalytic system. N(2)O is the major reduction product of the inverted (NO)(2) dimer, in accord with experiment. The physical origin of the Ag metallic state as a good catalyst is furthermore identified: Ag surfaces, including small clusters, have little or no covalent bonding ability but can bond ionically with adsorbates. We conclude that the variation of the ionic bonding strength of Ag toward different reactants determines its catalytic selectivity.

  12. Analysis of the Sensitivity of GEM-MACH PM2.5 Forecasts to the Representation of Wet and Dry Deposition Processes

    NASA Astrophysics Data System (ADS)

    Pavlovic, Radenko; Gong, Wanmin; Moran, Mike; Menard, Sylvain; Anselmo, David; Davignon, Didier

    2014-05-01

    Environment Canada produces 48-hour operational air quality forecasts for Canada twice daily (at 00 and 12 UTC). At the core of the forecast system is the GEM-MACH model, an on-line coupled meteorology and chemistry model that considers gas-phase, aqueous-phase, and heterogeneous chemistry and a number of size-resolved particulate matter (PM) processes, including wet and dry deposition. Predicting PM concentrations, especially for fine particular matter (PM2.5), remains a challenge for air quality models. In this poster we analyze the maximum sensitivity of predicted PM2.5 concentrations to the representation of both wet and dry deposition. For wet deposition, both in-cloud and below-cloud scavenging are considered. An analysis of the impact of wet and dry deposition on PM2.5 concentrations was performed using GEM-MACH model output over the summer and winter seasons of 2012 for a base case and two sensitivity runs, one in which the parameterization of dry deposition was turned off and one in which the parameterization of wet deposition was turned off. The results obtained show that the predicted wet deposition of PM2.5 over North America is generally greater than predicted dry deposition, but both processes can reduce predicted PM2.5 concentration by 25% or more on average. However, the impact of both processes varies significantly from one region to another and is strongly dependent on modelled meteorology, especially the occurrence of precipitation. These results suggest that the details of the treatments of wet and dry deposition of PM2.5 do matter and can enhance or detract from model performance.

  13. Plant carbon-nutrient interactions control CO{sub 2} exchange in Alaskan wet sedge tundra ecosystems

    SciTech Connect

    Johnson, L.C.; Shaver, G.R.; Cades, D.H.; Rastetter, E.; Nadelhoffer, K.; Giblin, A.; Laundre, J.; Stanley, A.

    2000-02-01

    The authors explored the long-term (8-yr) effects of separate field manipulations of temperature and nutrient availability on carbon balance in wet sedge tundra near the Arctic Long Term Ecological Research (LTER) site at Toolik Lake, Alaska. Their goals were (1) to assess the relative importance of chronic warming (with field greenhouses) and increased N and P availability (by fertilization) in controlling gross ecosystem photosynthesis, ecosystem respiration, and ultimately ecosystem C balance; and (2) to attempt to partition ecosystem responses to these treatments between plant and soil contributions. The authors present results of the effects of these manipulations on whole-system CO{sub 2} exchange over seasonal and duel cycles, and on nonrhizosphere soil microbial respiration using in situ soil incubations.

  14. 2D/2D nano-hybrids of γ-MnO₂ on reduced graphene oxide for catalytic ozonation and coupling peroxymonosulfate activation.

    PubMed

    Wang, Yuxian; Xie, Yongbing; Sun, Hongqi; Xiao, Jiadong; Cao, Hongbin; Wang, Shaobin

    2016-01-15

    Two-dimensional reduced graphene oxide (2D rGO) was employed as both a shape-directing medium and support to fabricate 2D γ-MnO2/2D rGO nano-hybrids (MnO2/rGO) via a facile hydrothermal route. For the first time, the 2D/2D hybrid materials were used for catalytic ozonation of 4-nitrophenol. The catalytic efficiency of MnO2/rGO was much higher than either MnO2 or rGO only, and rGO was suggested to play the role for promoting electron transfers. Quenching tests using tert-butanol, p-benzoquinone, and sodium azide suggested that the major radicals responsible for 4-nitrophenol degradation and mineralization are O2(-) and (1)O2, but not ·OH. Reusability tests demonstrated a high stability of the materials in catalytic ozonation with minor Mn leaching below 0.5 ppm. Degradation mechanism, reaction kinetics, reusability and a synergistic effect between catalytic ozonation and coupling peroxymonosulfate (PMS) activation were also discussed.

  15. Influence of optical band gap and particle size on the catalytic properties of Sm/SnO2-TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Javaid, Shaghraf; Farrukh, Muhammad Akhyar; Muneer, Iqra; Shahid, Maryam; Khaleeq-ur-Rahman, Muhammad; Umar, Akrajas Ali

    2015-06-01

    In this work, samarium (Sm) supported on tin oxide-titanium oxide (SnO2/TiO2) nanoparticles (Sm/SnO2-TiO2) were synthesized by sol-gel, ultrasonic and hydrothermal methods; and the optical and catalytic properties of Sm/SnO2-TiO2 nanoparticles was observed. Effect of synthetic methods on nanoparticles size and percentage composition of anatase and rutile phase in TiO2 was evaluated. The Sm/SnO2-TiO2 nanoparticles were characterized by Transmission Electron Microscopy, Scanning Electron Microscopy, Energy Dispersive X-ray spectroscopy, Powder X-ray Diffraction, Thermogravimetric Analysis and Fourier Transmission Infrared Spectroscopy. However, UV-Vis and solid phase spectroscopy were used to determine the catalytic efficiency and optical band gap, respectively. It was found out that nanoparticles synthesized by sol-gel and hydrothermal method have small optical band gap as compare to nanoparticles synthesized by ultrasonic method and ultimately showed more catalytic activity toward degradation of dye due to red shift in the optical band gap (shifting of wavelength to visible region). A direct relationship between particle size and optical band gap was investigated. It was observed that Sm reduced the optical band gap and increased catalytic efficiency when supported on SnO2/TiO2.

  16. Communications: Electron polarization critically stabilizes the Mg2+ complex in the catalytic core domain of HIV-1 integrase

    NASA Astrophysics Data System (ADS)

    Lu, Yunpeng; Mei, Ye; Zhang, John Z. H.; Zhang, Dawei

    2010-04-01

    In this paper, we present a detailed dynamics study of the catalytic core domain (CCD) of HIV-1 integrase using both polarized and nonpolarized force fields. The numerical results reveal the critical role of protein polarization in stabilizing Mg2+ coordination complex in CCD. Specifically, when nonpolarized force field is used, a remarkable drift of the Mg2+ complex away from its equilibrium position is observed, which causes the binding site blocked by the Mg2+ complex. In contrast, when polarized force field is employed in MD simulation, HIV-1 integrase CCD structure is stabilized and both the position of the Mg2+ complex and the binding site are well preserved. The detailed analysis shows the transition of α-helix to 310-helix adjacent to the catalytic loop (residues 139-147), which correlates with the dislocation of the Mg2+ complex. The current study demonstrates the importance of electronic polarization of protein in stabilizing the metal complex in the catalytic core domain of HIV-1 integrase.

  17. Two sites of action for PLD2 inhibitors: The enzyme catalytic center and an allosteric, phosphoinositide biding pocket.

    PubMed

    Ganesan, Ramya; Mahankali, Madhu; Alter, Gerald; Gomez-Cambronero, Julian

    2015-03-01

    Phospholipase D (PLD) has been implicated in many physiological functions, such as chemotaxis and phagocytosis, as well as pathological functions, such as cancer cell invasion and metastasis. New inhibitors have been described that hamper the role of PLD in those pathologies but their site of action is not known. We have characterized the biochemical and biological behavior of the PLD1/2 dual inhibitor 5-Fluoro-2-indolyl des-chlorohalopemide (FIPI), and the specific PLD2 inhibitor, N-[2-[1-(3-Fluorophenyl)-4-oxo-1,3,-8-triazaspiro[4.5]dec-8-yl]ethyl]-2-naphthalenecarboxamide (NFOT), and found that both FIPI and NFOT are mixed-kinetics inhibitors. Mutagenesis studies indicate that FIPI binds at S757 of PLD2, which is within the HKD2 catalytic site of the enzyme, whereas NFOT binds to PLD2 at two different sites, one being at S757/S648 and another to an allosteric site that is a natural site occupied by PIP2 (R210/R212). This latter site, along with F244/L245/L246, forms a hydrophobic pocket in the PH domain. The mechanism of action of FIPI is a direct effect on the catalytic site (and as such inhibits both PLD1 and PLD2 isoforms), whereas PLD2 affects both the catalytic site (orthosteric) and blocks PIP2 binding to PLD2 (allosteric), which negates the natural enhancing role of PIP2. Moreover, NFOT prevents cell invasion of cancer cells, which does not occur in cells overexpressing PLD2-F244A/L245A/L246A, or PLD2-R210A/R212A, or PLD2-S757/S648 mutants. This study provides new specific knowledge of enzyme regulation and mechanisms of activation and inhibition of PLD2 that are necessary to understand its role in cell signaling and to develop new inhibitors for cancer cell invasion and metastasis.

  18. Differences between the catalytic properties of recombinant human PC2 and endogenous rat PC2.

    PubMed Central

    Bailyes, E M; Shennan, K I; Usac, E F; Arden, S D; Guest, P C; Docherty, K; Hutton, J C

    1995-01-01

    Human prohormone convertase PC2 was expressed in Xenopus oocytes and its properties were compared with those of the Type-2 endopeptidase of rat insulin secretory granules, previously identified as PC2 [Bennett, Bailyes, Nielson, Guest, Rutherford, Arden and Hutton (1992) J. Biol. Chem. 267, 15229-15236]. Recombinant PC2 had the same substrate specificity as the Type-2 endopeptidase, cleaving at the CA-junction (Lys64, Arg65) of human des-31,32-proinsulin to generate insulin; little activity was found toward human des-64,65-proinsulin or proinsulin itself. Recombinant PC2 was maximally active in 5-7 mM Ca2+ (K0.5 = 1.6 mM) whereas the Type-2 endopeptidase was maximally active in 0.5-1 mM Ca2+ (K0.5 = 40 microM). Both enzymes had a pH optimum of 5.0-5.5 but the Type-2 endopeptidase was active over a wider pH range. Two molecular forms of recombinant PC2 (71 kDa and 68 kDa) were found, both had an intact C-terminus but differed by the presence of the propeptide. The endogenous PC2 comprised several overlapping forms (size range 64-68 kDa), approximately two-thirds of which lacked C-terminal immunoreactivity. Part of the size difference between recombinant and endogenous PC2 was attributable to differences in N-glycosylation. The different post-translational proteolytic modifications of recombinant and endogenous PC2 did not account for the different pH and Ca2+ sensitivities shown by the enzymes. A modulating effect of carbohydrate on enzyme activity could not be excluded. Images Figure 2 Figure 3 Figure 5 Figure 6 Figure 7 PMID:7626024

  19. Efficient Catalytic Electrode for CO2 Reduction Realized by Physisorbing Ni(cyclam) Molecules with Hydrophobicity Based on Hansen's Theory.

    PubMed

    Murase, Masakazu; Kitahara, Gaku; Suzuki, Tomiko M; Ohta, Riichiro

    2016-09-21

    An electrochemical electrode physisorbed with Ni(cyclam) complex molecules containing tetraphenylborate ions (BPh4(-)) as counteranions shows catalytic activity for the reduction reaction of CO2 to CO in an aqueous electrolyte, superior to that of an electrode physisorbed with conventional [Ni(cyclam)]Cl2 complex molecules. The BPh4(-)-containing Ni(cyclam) is inferred as having high hydrophobicity based on its Hansen solubility parameter (HSP), with an interaction sphere excluding HSPs of water in a three-dimensional vector space. The high hydrophobicity of BPh4(-)-containing Ni(cyclam) molecules inhibits their dissolution into aqueous electrolyte and retains their immobilization onto the electrode surface, which we believe to result in the improved catalytic activity of the electrode physisorbed with them. HSP analysis also provides an optimized mixing ratio of solvents dissolving BPh4(-)-containing Ni(cyclam) molecules. PMID:27606702

  20. Halogen poisoning effect of Pt-TiO2 for formaldehyde catalytic oxidation performance at room temperature

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaofeng; Cheng, Bei; Yu, Jiaguo; Ho, Wingkei

    2016-02-01

    Catalytic decomposition of formaldehyde (HCHO) at room temperature is an important method for HCHO removal. Pt-based catalysts are the optimal catalyst for HCHO decomposition at room temperature. However, the stability of this catalyst remains unexplored. In this study, Pt-TiO2 (Pt-P25) catalysts with and without adsorbed halogen ions (including F-, Cl-, Br-, and I-) were prepared through impregnation and ion modification. Pt-TiO2 samples with adsorbed halogen ions exhibited reduced catalytic activity for formaldehyde decomposition at room temperature compared with the Pt-TiO2 sample; the catalytic activity followed the order of F-Pt-P25, Cl-Pt-P25, Br-Pt-P25, and I-Pt-P25. Characterization results (including XRD, TEM, HRTEM, BET, XPS, and metal dispersion) showed that the adsorbed halogen ions can poison Pt nanoparticles (NPs), thereby reducing the HCHO oxidation activity of Pt-TiO2. The poison mechanism is due to the strong adsorption of halogen ions on the surface of Pt NPs. The adsorbed ions form coordination bonds with surface Pt atoms by transferring surplus electrons into the unoccupied 5d orbit of the Pt atom, thereby inhibiting oxygen adsorption and activation of the Pt NP surface. Moreover, deactivation rate increases with increasing diameter of halogen ions. This study provides new insights into the fabrication of high-performance Pt-based catalysts for indoor air purification.

  1. Effects of SO2 on selective catalytic reduction of NO with NH3 over a TiO2 photocatalyst

    NASA Astrophysics Data System (ADS)

    Yamamoto, Akira; Teramura, Kentaro; Hosokawa, Saburo; Tanaka, Tsunehiro

    2015-04-01

    The effect of SO2 gas was investigated on the activity of the photo-assisted selective catalytic reduction of nitrogen monoxide (NO) with ammonia (NH3) over a TiO2 photocatalyst in the presence of excess oxygen (photo-SCR). The introduction of SO2 (300 ppm) greatly decreased the activity of the photo-SCR at 373 K. The increment of the reaction temperature enhanced the resistance to SO2 gas, and at 553 K the conversion of NO was stable for at least 300 min of the reaction. X-ray diffraction, FTIR spectroscopy, thermogravimetry and differential thermal analysis, x-ray photoelectron spectroscopy (XPS), elemental analysis and N2 adsorption measurement revealed that the ammonium sulfate species were generated after the reaction. There was a strong negative correlation between the deposition amount of the ammonium sulfate species and the specific surface area. Based on the above relationship, we concluded that the deposition of the ammonium sulfate species decreased the specific surface area by plugging the pore structure of the catalyst, and the decrease of the specific surface area resulted in the deactivation of the catalyst.

  2. Catalytic Hydrogenation of Organic Compounds without H2 Supply: An Electrochemical System

    ERIC Educational Resources Information Center

    Navarro, Daniela Maria do Amaral Ferraz; Navarro, Marcelo

    2004-01-01

    An experiment developed for an undergraduate organic chemistry laboratory course that can be used to introduce the catalytic hydrogenation reaction, catalysis electrochemical principles and gas chromatography is presented. The organic compounds hydrogenated by the electrocatalytic hydrogenation (ECH) process were styrene, benzaldehyde and…

  3. Catalytic Rearrangement of 2-Alkoxy Diallyl Alcohols: Access to Polysubstituted Cyclopentenones.

    PubMed

    Lempenauer, Luisa; Duñach, Elisabet; Lemière, Gilles

    2016-03-18

    A catalytic rearrangement of diallyl alcohols comprising a cyclic enol ether has been developed using very mild conditions. Bismuth(III) triflate was found to be a very active catalyst for the ring rearrangement of a range of tertiary allylic alcohols to efficiently afford polysubstituted cyclopentenones with a high degree of diastereoselectivity. PMID:26927227

  4. Diastereodivergent Catalytic Asymmetric Michael Addition of 2-Oxindoles to α,β-Unsaturated Ketones by Chiral Diamine Catalysts.

    PubMed

    Wei, Yuan; Wen, Shigang; Liu, Zunwu; Wu, Xinxin; Zeng, Bubing; Ye, Jinxing

    2015-06-01

    A diastereodivergent catalytic asymmetric Michael addition of 2-oxindoles to α,β-unsaturated ketones has been successfully developed with two complementary chiral diamine catalysts, affording chiral 3,3-disubstituted oxindoles with two adjacent chiral centers. Diastereodivergence has been realized through modifying substrates and utilizing different catalysts. Either anti-or syn-configured products possessing vicinal quaternary and tertiary stereogenic centers were produced with high enantioselectivities. PMID:25973971

  5. Efficient synthesis of biazoles by aerobic oxidative homocoupling of azoles catalyzed by a copper(I)/2-pyridonate catalytic system.

    PubMed

    Zhu, Mingwen; Fujita, Ken-ichi; Yamaguchi, Ryohei

    2011-12-28

    A highly efficient and convenient CuCl/2-pyridonate catalytic system for oxidative homocoupling of azoles affording a biazole product has been developed. With this system, a variety of biazoles have been effectively synthesized in good to excellent yields in the presence of a very small amount of copper catalyst (1.0 mol%). It was feasible to employ air as a green oxidant. PMID:22076830

  6. Catalytic decomposition of petroleum into natural gas

    SciTech Connect

    Mango, F.D.; Hightower, J.

    1997-12-01

    Petroleum is believed to be unstable in the earth, decomposing to lighter hydrocarbons at temperatures > 150{degrees}C. Oil and gas deposits support this view: gas/oil ratios and methane concentrations tend to increase with depth above 150{degrees}C. Although oil cracking is suggested and receives wide support, laboratory pyrolysis does not give products resembling natural gas. Moreover, it is doubtful that the light hydrocarbons in wet gas (C{sub 2}-C{sub 4}) could decompose over geologic time to dry gas (>95% methane) without catalytic assistance. We now report the catalytic decomposition of crude oil to a gas indistinguishable from natural gas. Like natural gas in deep basins, it becomes progressively enriched in methane: initially 90% (wet gas) to a final composition of 100% methane (dry gas). To our knowledge, the reaction is unprecedented and unexpectedly robust (conversion of oil to gas is 100% in days, 175{degrees}C) with significant implications regarding the stability of petroleum in sedimentary basins. The existence or nonexistence of oil in the deep subsurface may not depend on the thermal stability of hydrocarbons as currently thought. The critical factor could be the presence of transition metal catalysts which destabilize hydrocarbons and promote their decomposition to natural gas.

  7. NASA Aerospace Flight Battery Program: Wet Life of Nickel-Hydrogen (Ni-H2) Batteries. Volume 1, Part 3

    NASA Technical Reports Server (NTRS)

    Jung, David S.; Lee, Leonine S.; Manzo, Michelle A.

    2010-01-01

    This NASA Aerospace Flight Battery Systems Working Group was chartered within the NASA Engineering and Safety Center (NESC). The Battery Working Group was tasked to complete tasks and to propose proactive work to address battery related, agency-wide issues on an annual basis. In its first year of operation, this proactive program addressed various aspects of the validation and verification of aerospace battery systems for NASA missions. Studies were performed, issues were discussed and in many cases, test programs were executed to generate recommendations and guidelines to reduce risk associated with various aspects of implementing battery technology in the aerospace industry. This document contains Part 3 - Volume I: Wet Life of Nickel-Hydrogen (Ni-H2) Batteries of the program's operations.

  8. Binary and Ternary Catalytic Systems for Olefin Metathesis Based on MoCl5/SiO2

    NASA Astrophysics Data System (ADS)

    Bykov, Victor I.; Belyaev, Boris A.; Butenko, Tamara A.; Finkelshtein, Eugene Sh.

    Kinetics of α-olefin metathesis in the presence of binary (MoCl5/ SiO2-Me4Sn) and ternary catalytic systems (MoCl5/SiO2-Me4Sn-ECl4, E = Si or Ge) was studied. Specifically, kinetics and reactivity of 1-decene, 1-octene, and 1-hexene in the metathesis reaction at 27°C and 50°C in the presence of MoCl5/ SiO2-SnMe4 were examined and evaluated in detail. It was shown that experimental data comply well with the simple kinetic equation for the rate of formation of symmetrical olefins with allowance for the reverse reaction and catalyst deactivation: r = left( {k_1 \\cdot c_α - k_{ - 1} \\cdot c_s } right) \\cdot e^{ - k_d \\cdot tilde n_{tot} } . The coefficients for this equation were determined, and it was shown that these α-olefins had practically the same reactivity. It was found that reactivation in the course of metathesis took place due to the addition of a third component (silicon tetrachloride or germanium tetrachloride in combination with tetramethyltin) to a partially deactivated catalyst. The number of active centers was determined (5-6% of the amount of Mo) and the mechanisms of formation, deactivation, and reactivation were proposed for the binary and ternary catalytic systems. The role of individual components of the catalytic systems was revealed.

  9. Detailed study of the plasma-activated catalytic generation of ammonia in N2-H2 plasmas

    NASA Astrophysics Data System (ADS)

    van Helden, J. H.; Wagemans, W.; Yagci, G.; Zijlmans, R. A. B.; Schram, D. C.; Engeln, R.; Lombardi, G.; Stancu, G. D.; Röpcke, J.

    2007-02-01

    We investigated the efficiency and formation mechanism of ammonia generation in recombining plasmas generated from mixtures of N2 and H2 under various plasma conditions. In contrast to the Haber-Bosch process, in which the molecules are dissociated on a catalytic surface, under these plasma conditions the precursor molecules, N2 and H2, are already dissociated in the gas phase. Surfaces are thus exposed to large fluxes of atomic N and H radicals. The ammonia production turns out to be strongly dependent on the fluxes of atomic N and H radicals to the surface. By optimizing the atomic N and H fluxes to the surface using an atomic nitrogen and hydrogen source ammonia can be formed efficiently, i.e., more than 10% of the total background pressure is measured to be ammonia. The results obtained show a strong similarity with results reported in literature, which were explained by the production of ammonia at the surface by stepwise addition reactions between adsorbed nitrogen and hydrogen containing radicals at the surface and incoming N and H containing radicals. Furthermore, our results indicate that the ammonia production is independent of wall material. The high fluxes of N and H radicals in our experiments result in a passivated surface, and the actual chemistry, leading to the formation of ammonia, takes place in an additional layer on top of this passivated surface.

  10. Catalytic combustion of soot particulates over rare-earth substituted Ln2Sn2O7 pyrochlores (Ln=La, Nd and Sm).

    PubMed

    Wang, Zhongpeng; Zhu, Hongjian; Ai, Lijie; Liu, Xuhui; Lv, Min; Wang, Liguo; Ma, Zhenmin; Zhang, Zhaoliang

    2016-09-15

    Catalytic combustion is one of the most promising methods for diesel soot removal. Ln2Sn2O7 pyrochlores substituted with different rare-earth (RE) elements (Ln=La, Nd and Sm) were prepared through co-precipitation method for catalytic combustion of soot particulates. The structural, textural and redox properties, together with the oxygen vacancy of the catalysts were investigated systematically. Their catalytic activities were evaluated by both temperature-programmed oxidation and isothermal reaction techniques. With the increasing in RE ionic radius (r), the SnO bond strength in Ln2Sn2O7 pyrochlores evaluated from the stretching IR band was decreased, resulting in the improved reducibility and enhanced oxygen vacancies of catalysts. The increase of oxygen vacancy concentration was further confirmed by photoluminescence (PL) investigations wherein upon excitation with UV radiation, the pyrochlores nanoparticles exhibited strong and sharp transition at 408nm attributed to oxygen vacancies. Catalytic combustion and isothermal reactions revealed that the ignition activity (ignition temperature, T5) and the intrinsic activity (turnover frequency, TOF) were shown to depend correlatedly on redox properties and oxygen vacancy concentrations, both of which were influenced by the substitution of different RE elements. Among the pyrochlore oxides, the as-synthesized La2Sn2O7 sample displayed relatively the highest ignition activity and the largest intrinsic activity with TOF of 2.33×10(-3)s(-1).

  11. Catalytic combustion of soot particulates over rare-earth substituted Ln2Sn2O7 pyrochlores (Ln=La, Nd and Sm).

    PubMed

    Wang, Zhongpeng; Zhu, Hongjian; Ai, Lijie; Liu, Xuhui; Lv, Min; Wang, Liguo; Ma, Zhenmin; Zhang, Zhaoliang

    2016-09-15

    Catalytic combustion is one of the most promising methods for diesel soot removal. Ln2Sn2O7 pyrochlores substituted with different rare-earth (RE) elements (Ln=La, Nd and Sm) were prepared through co-precipitation method for catalytic combustion of soot particulates. The structural, textural and redox properties, together with the oxygen vacancy of the catalysts were investigated systematically. Their catalytic activities were evaluated by both temperature-programmed oxidation and isothermal reaction techniques. With the increasing in RE ionic radius (r), the SnO bond strength in Ln2Sn2O7 pyrochlores evaluated from the stretching IR band was decreased, resulting in the improved reducibility and enhanced oxygen vacancies of catalysts. The increase of oxygen vacancy concentration was further confirmed by photoluminescence (PL) investigations wherein upon excitation with UV radiation, the pyrochlores nanoparticles exhibited strong and sharp transition at 408nm attributed to oxygen vacancies. Catalytic combustion and isothermal reactions revealed that the ignition activity (ignition temperature, T5) and the intrinsic activity (turnover frequency, TOF) were shown to depend correlatedly on redox properties and oxygen vacancy concentrations, both of which were influenced by the substitution of different RE elements. Among the pyrochlore oxides, the as-synthesized La2Sn2O7 sample displayed relatively the highest ignition activity and the largest intrinsic activity with TOF of 2.33×10(-3)s(-1). PMID:27295323

  12. Uniform Ni/SiO2@Au magnetic hollow microspheres: rational design and excellent catalytic performance in 4-nitrophenol reduction

    NASA Astrophysics Data System (ADS)

    Zhang, Shenghuan; Gai, Shili; He, Fei; Dai, Yunlu; Gao, Peng; Li, Lei; Chen, Yujin; Yang, Piaoping

    2014-05-01

    A unique and rational design was presented to fabricate Ni/SiO2@Au magnetic hollow microspheres (MHMs) with interesting structures and well-dispersed metal nanoparticles. Hierarchical nickel silicate hollow microspheres were synthesized using silica colloidal spheres as a chemical template. Then, Ni/SiO2 MHMs with well-dispersed Ni nanoparticles were prepared via an in situ reduction approach. Ni/SiO2@Au MHMs were finally obtained by immobilizing uniform Au nanoparticles onto Ni/SiO2 support through a low-temperature chemical reduction process. It was found that Ni/SiO2@Au MHMs inherit the shape and uniformity of the original silica scaffold, and Ni NPs and Au NPs, which were less than 5 nm in size, were well dispersed on the mesoporous silica shell with narrow size distribution. Both Ni/SiO2 and Ni/SiO2@Au MHMs showed excellent catalytic activity in the 4-nitrophenol reduction reaction. Importantly, introduction of a small amount of Au NPs onto Ni/SiO2 MHMs markedly improved the catalytic activity. In particular, Ni/SiO2@Au MHMs showed high conversion even after re-use for several cycles with magnetic separation. The unique structure, high catalytic performance, and ease of separation make Ni/SiO2@Au MHMs highly promising candidates for diverse applications.A unique and rational design was presented to fabricate Ni/SiO2@Au magnetic hollow microspheres (MHMs) with interesting structures and well-dispersed metal nanoparticles. Hierarchical nickel silicate hollow microspheres were synthesized using silica colloidal spheres as a chemical template. Then, Ni/SiO2 MHMs with well-dispersed Ni nanoparticles were prepared via an in situ reduction approach. Ni/SiO2@Au MHMs were finally obtained by immobilizing uniform Au nanoparticles onto Ni/SiO2 support through a low-temperature chemical reduction process. It was found that Ni/SiO2@Au MHMs inherit the shape and uniformity of the original silica scaffold, and Ni NPs and Au NPs, which were less than 5 nm in size, were well

  13. Au-nanocrystals-decorated δ-MnO2 as an efficient catalytic cathode for high-performance Li-O2 batteries

    NASA Astrophysics Data System (ADS)

    Liu, Shuangyu; Wang, Guoqing; Tu, Fangfang; Xie, Jian; Yang, Hui Ying; Zhang, Shichao; Zhu, Tiejun; Cao, Gaoshao; Zhao, Xinbing

    2015-05-01

    A Li-O2 battery works based on the reversible formation and decomposition of Li2O2, which is insulating and highly reactive. Designing a catalytic cathode capable of controlling Li2O2 growth recently became a challenge to overcome this barrier. In this work, we present a new design of catalytic cathode by growing porous Au/δ-MnO2 electrocatalyst directly on a conductive substrate. We found that Au/δ-MnO2 can catalyze the directed growth of Li2O2 into a thin/small form, only inside porous δ-MnO2, and along the surface of δ-MnO2 sheets. We proposed the catalytic mechanism of Au/δ-MnO2, where Au plays a critical role in catalyzing the nucleation, crystallization and conformal growth of Li2O2 on δ-MnO2 sheets. Li-O2 batteries with an Au/δ-MnO2 catalytic cathode showed excellent electrochemical performance due to this favorable Li2O2 growth habit. The battery yielded a high capacity of 10 600 mA h g-1 with a low polarization of 0.91 V at 100 mA g-1. Superior cycling stability could be achieved in both capacity-limited (500 mA h g-1, 165 times at 400 mA g-1) and unlimited (ca. 3000 mA h g-1, 50 cycles at 800 mA g-1) modes.A Li-O2 battery works based on the reversible formation and decomposition of Li2O2, which is insulating and highly reactive. Designing a catalytic cathode capable of controlling Li2O2 growth recently became a challenge to overcome this barrier. In this work, we present a new design of catalytic cathode by growing porous Au/δ-MnO2 electrocatalyst directly on a conductive substrate. We found that Au/δ-MnO2 can catalyze the directed growth of Li2O2 into a thin/small form, only inside porous δ-MnO2, and along the surface of δ-MnO2 sheets. We proposed the catalytic mechanism of Au/δ-MnO2, where Au plays a critical role in catalyzing the nucleation, crystallization and conformal growth of Li2O2 on δ-MnO2 sheets. Li-O2 batteries with an Au/δ-MnO2 catalytic cathode showed excellent electrochemical performance due to this favorable Li2O2 growth

  14. Wet-season spatial variability in N2O emissions from a tea field in subtropical central China

    NASA Astrophysics Data System (ADS)

    Fu, X.; Liu, X.; Li, Y.; Shen, J.; Wang, Y.; Zou, G.; Li, H.; Song, L.; Wu, J.

    2015-06-01

    Tea fields emit large amounts of nitrous oxide (N2O) to the atmosphere. Obtaining accurate estimations of N2O emissions from tea-planted soils is challenging due to strong spatial variability. We examined the spatial variability in N2O emissions from a red-soil tea field in Hunan Province, China, on 22 April 2012 (in a wet season) using 147 static mini chambers approximately regular gridded in a 4.0 ha tea field. The N2O fluxes for a 30 min snapshot (10:00-10:30 a.m.) ranged from -1.73 to 1659.11 g N ha-1 d-1 and were positively skewed with an average flux of 102.24 g N ha-1 d-1. The N2O flux data were transformed to a normal distribution by using a logit function. The geostatistical analyses of our data indicated that the logit-transformed N2O fluxes (FLUX30t) exhibited strong spatial autocorrelation, which was characterized by an exponential semivariogram model with an effective range of 25.2 m. As observed in the wet season, the logit-transformed soil ammonium-N (NH4Nt), soil nitrate-N (NO3Nt), soil organic carbon (SOCt) and total soil nitrogen (TSNt) were all found to be significantly correlated with FLUX30t (r = 0.57-0.71, p < 0.001). Three spatial interpolation methods (ordinary kriging, regression kriging and cokriging) were applied to estimate the spatial distribution of N2O emissions over the study area. Cokriging with NH4Nt and NO3Nt as covariables (r = 0.74 and RMSE = 1.18) outperformed ordinary kriging (r = 0.18 and RMSE = 1.74), regression kriging with the sample position as a predictor (r = 0.49 and RMSE = 1.55) and cokriging with SOCt as a covariable (r = 0.58 and RMSE = 1.44). The predictions of the three kriging interpolation methods for the total N2O emissions of 4.0 ha tea field ranged from 148.2 to 208.1 g N d-1, based on the 30 min snapshots obtained during the wet season. Our findings suggested that to accurately estimate the total N2O emissions over a region, the environmental variables (e.g., soil properties) and the current land use pattern

  15. Wet-season spatial variability of N2O emissions from a tea field in subtropical central China

    NASA Astrophysics Data System (ADS)

    Fu, X.; Liu, X.; Li, Y.; Shen, J.; Wang, Y.; Zou, G.; Li, H.; Song, L.; Wu, J.

    2015-01-01

    Tea fields emit large amounts of nitrous oxide (N2O) to the atmosphere. Obtaining accurate estimations of N2O emissions from tea-planted soils is challenging due to strong spatial variability. We examined the spatial variability of N2O emissions from a red-soil tea field in Hunan province, China, on 22 April 2012 (in a wet season) using 147 static mini chambers approximately regular gridded in a 4.0 ha tea field. The N2O fluxes for a 30 min snapshot (10-10.30 a.m.) ranged from -1.73 to 1659.11 g N ha-1 d-1 and were positively skewed with an average flux of 102.24 g N ha-1 d-1. The N2O flux data were transformed to a normal distribution by using a logit function. The geostatistical analyses of our data indicated that the logit-transformed N2O fluxes (FLUX30t) exhibited strong spatial autocorrelation, which was characterized by an exponential semivariogram model with an effective range of 25.2 m. As observed in the wet season, the logit-transformed soil ammonium-N (NH4Nt), soil nitrate-N (NO3Nt), soil organic carbon (SOCt), total soil nitrogen (TSNt) were all found to be significantly correlated with FLUX30t (r=0.57-0.71, p<0.001). Three spatial interpolation methods (ordinary kriging, regression kriging and cokriging) were applied to estimate the spatial distribution of N2O emissions over the study area. Cokriging with NH4Nt and NO3Nt as covariables (r= 0.74 and RMSE =1.18) outperformed ordinary kriging (r= 0.18 and RMSE =1.74), regression kriging with the sample position as a predictor (r= 0.49 and RMSE =1.55) and cokriging with SOCt as a covariable (r= 0.58 and RMSE =1.44). The predictions of the three kriging interpolation methods for the total N2O emissions of the 4.0 ha tea field ranged from 148.2 to 208.1 g N d-1, based on the 30 min snapshots obtained during the wet season. Our findings suggested that to accurately estimate the total N2O emissions over a region, the environmental variables (e.g., soil properties) and the current land use pattern (e.g., tea

  16. Enhanced Intrinsic Catalytic Activity of λ-MnO2 by Electrochemical Tuning and Oxygen Vacancy Generation.

    PubMed

    Lee, Sanghan; Nam, Gyutae; Sun, Jie; Lee, Jang-Soo; Lee, Hyun-Wook; Chen, Wei; Cho, Jaephil; Cui, Yi

    2016-07-18

    Chemically prepared λ-MnO2 has not been intensively studied as a material for metal-air batteries, fuel cells, or supercapacitors because of their relatively poor electrochemical properties compared to α- and δ-MnO2 . Herein, through the electrochemical removal of lithium from LiMn2 O4 , highly crystalline λ-MnO2 was prepared as an efficient electrocatalyst for the oxygen reduction reaction (ORR). The ORR activity of the material was further improved by introducing oxygen vacancies (OVs) that could be achieved by increasing the calcination temperature during LiMn2 O4 synthesis; a concentration of oxygen vacancies in LiMn2 O4 could be characterized by its voltage profile as the cathode in a lithiun-metal half-cell. λ-MnO2-z prepared with the highest OV exhibited the highest diffusion-limited ORR current (5.5 mA cm(-2) ) among a series of λ-MnO2-z electrocatalysts. Furthermore, the number of transferred electrons (n) involved in the ORR was >3.8, indicating a dominant quasi-4-electron pathway. Interestingly, the catalytic performances of the samples were not a function of their surface areas, and instead depended on the concentration of OVs, indicating enhancement in the intrinsic catalytic activity of λ-MnO2 by the generation of OVs. This study demonstrates that differences in the electrochemical behavior of λ-MnO2 depend on the preparation method and provides a mechanism for a unique catalytic behavior of cubic λ-MnO2 . PMID:27254822

  17. Catalytic performance and catalyst structure of nickel-magnesia catalysts for CO{sub 2} reforming of methane

    SciTech Connect

    Chen, Y.G.; Tomishige, Keiichi; Yokoyama, Kota; Fujimoto, Kaoru

    1999-06-10

    The catalytic performance of nickel-magnesia catalysts in CO{sub 2} reforming of methane and the factors influencing carbon deposition during the reaction were investigated by a comparative study of reduced Ni{sub x}Mg{sub 1{minus}x}O solid solution and magnesia-supported Ni metal (Ni/MgO) catalysts. Reduced NI{sub x}Mg{sub 1{minus}x}O solid solution catalysts generally showed higher resistance to carbon formation than Ni/MgO. From the combination of catalytic properties with the characterization results of XRD, TEM, FTIR, and dispersion measurements, it was found that the excellent anticoking performance of reduced solid solution catalyst with low Ni content is attributable to high dispersion of reduced Ni species, basicity of support surface, and nickel-support interaction.

  18. Selective catalytic reduction performance project at Public Services Electric and Gas Company`s Mercer Generating Station Unit 2

    SciTech Connect

    Wallace, A.J.; Gibbons, F.X.; Knell, E.W.; Johnson, R.E.

    1996-01-01

    PSE&G, Wahlco, and Siemens have successfully demonstrated the technical feasibility of a Post Combustion NO{sub x} Reduction System on a 321 MW net coal-fired utility boiler at PSE&G`s Mercer Station Unit 2. The program featured a selective catalytic reduction (SCR) reactor in a horizontal flue gas duct and an air heater SCR (AHSCR). Predicted performance of the In-Duct SCR was confirmed. The AHSCR was shown to be an effective means to enhance overall system performance as compared to an In-Duct SCR alone. Selective Non-Catalytic Reduction (SNCR) was also tested in combination with the SCR/AHSCR system using aqueous ammonia as a common reduction agent. Ammonia based jet mixing SNCR and the use of an ammonia injection grid was found to be the operation of choice in the NH{sub 3} based SNCR/SCR Hybrid NO{sub x} reduction system.

  19. Orbiter catalytic/noncatalytic heat transfer as evidenced by heating to contaminated surfaces on STS-2 and STS-3

    NASA Technical Reports Server (NTRS)

    Throckmorton, D. A.; Zoby, E. V.; Hamilton, H. H., II

    1983-01-01

    During that portion of Space Shuttle orbiter entry when significant aerodynamic heat transfer occurs, the flow over the vehicle is in chemical nonequilibrium. The parameter which most significantly influences the level of surface heat transfer in such a flow field is the catalytic efficiency of the surface with respect to the recombination of dissociated oxygen atoms. Significant, and instantaneous, changes were observed in the level of heat transfer at several lower surface centerline locations on STS-2 and STS-3. This phenomenon apparently resulted from a sudden change in the surface catalytic efficiency at these locations due to contamination of the surface by metallic oxides. As a result, data obtained from affected measurements cannot be considered as benchmark data with which to attempt to characterize nonequilibrium heat transfer to the orbiter's lower surface centerline.

  20. ADVANCED BYPRODUCT RECOVERY: DIRECT CATALYTIC REDUCTION OF SO2 TO ELEMENTAL SULFUR

    SciTech Connect

    Robert S. Weber

    1999-05-01

    Arthur D. Little, Inc., together with its commercialization partner, Engelhard Corporation, and its university partner Tufts, investigated a single-step process for direct, catalytic reduction of sulfur dioxide from regenerable flue gas desulfurization processes to the more valuable elemental sulfur by-product. This development built on recently demonstrated SO{sub 2}-reduction catalyst performance at Tufts University on a DOE-sponsored program and is, in principle, applicable to processing of regenerator off-gases from all regenerable SO{sub 2}-control processes. In this program, laboratory-scale catalyst optimization work at Tufts was combined with supported catalyst formulation work at Engelhard, bench-scale supported catalyst testing at Arthur D. Little and market assessments, also by Arthur D. Little. Objectives included identification and performance evaluation of a catalyst which is robust and flexible with regard to choice of reducing gas. The catalyst formulation was improved significantly over the course of this work owing to the identification of a number of underlying phenomena that tended to reduce catalyst selectivity. The most promising catalysts discovered in the bench-scale tests at Tufts were transformed into monolith-supported catalysts at Engelhard. These catalyst samples were tested at larger scale at Arthur D. Little, where the laboratory-scale results were confirmed, namely that the catalysts do effectively reduce sulfur dioxide to elemental sulfur when operated under appropriate levels of conversion and in conditions that do not contain too much water or hydrogen. Ways to overcome those limitations were suggested by the laboratory results. Nonetheless, at the end of Phase I, the catalysts did not exhibit the very stringent levels of activity or selectivity that would have permitted ready scale-up to pilot or commercial operation. Therefore, we chose not to pursue Phase II of this work which would have included further bench-scale testing

  1. Near-Monodisperse Ni-Cu Bimetallic Nanocrystals of Variable Composition: Controlled Synthesis and Catalytic Activity for H2 Generation

    SciTech Connect

    Zhang, Yawen; Huang, Wenyu; Habas, Susan E.; Kuhn, John N.; Grass, Michael E.; Yamada, Yusuke; Yang, Peidong; Somorjai, Gabor A.

    2008-07-22

    Near-monodisperse Ni{sub 1-x}Cu{sub x} (x = 0.2-0.8) bimetallic nanocrystals were synthesized by a one-pot thermolysis approach in oleylamine/1-octadecene, using metal acetylacetonates as precursors. The nanocrystals form large-area 2D superlattices, and display a catalytic synergistic effect in the hydrolysis of NaBH{sub 4} to generate H{sub 2} at x = 0.5 in a strongly basic medium. The Ni{sub 0.5}Cu{sub 0.5} nanocrystals show the lowest activation energy, and also exhibit the highest H{sub 2} generation rate at 298 K.

  2. 40 CFR Table 2 to Subpart III of... - Operating Limits for Wet Scrubbers

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Table 2 to Subpart III of Part 62 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... Commenced Construction On or Before November 30, 1999 Pt. 62, Subpt. III, Table 2 Table 2 to Subpart III of... operating limits And monitor using these minimum frequencies Data measurement Data recording Averaging...

  3. A comparison of TiO2 nanoparticles and nanotubes for catalytic gas phase destruction of H2S gas at high temperatures.

    PubMed

    Shahzad, Naeem; Hussain, Syed Tajammul; Siddiqua, Asima; Baig, Muhammad Anwar

    2012-06-01

    Reduction of H2S gas over Sulphur doped TiO2 nanoparticles and TiO2 nanotubes was studied in this work. Fixed bed catalytic system was used for the catalytic reduction of H2S gas at a high temperature of 450 degrees C under laboratory conditions. 99.97% reduction was achieved using S-doped TiO2. 2.89% Sulphur was adsorbed on S-doped TiO2 nanoparticles in the form of Ti(SO4)2, while 95.6% reduction was achieved in case of TiO2 nanotubes and the sulphur adsorption was 2.67%. The XRD, SEM, and EDX techniques were carried out to characterize the nanoparticles and nanotubes, while gas reduction analysis was carried out using GC-MS for gas samples. PMID:22905577

  4. Photocatalytic activities of wet oxidation synthesized ZnO and ZnO-TiO2 thick porous films

    NASA Astrophysics Data System (ADS)

    Chen, Ruiqun; Han, Jie; Yan, Xiaodong; Zou, Chongwen; Bian, Jiming; Alyamani, Ahmed; Gao, Wei

    2011-05-01

    Highly porous zinc oxide (ZnO) film was produced by using reactive magnetron sputtering zinc target followed by wet oxidation. Titanium dioxide (TiO2) was mixed to the porous films by using either TiO2 target magnetron sputter deposition or sol-spin method. The film thickness could reach 50 μm with uniform porosity. On the sputtering prepared ZnO-TiO2 film surface, fine nanorods with small anatase TiO2 nano-clusters on the tips were observed by SEM and TEM, and the titanium (Ti) composition was determined by XPS as 0.37%. The sol-spin treatment could increase the Ti composition to 4.9%, with reduced pore size compared to the untreated ZnO porous film. Photoluminescence measurements showed that the Ti containing porous film has strong ultraviolet-visible light emission. In the photo-catalysis testing, ZnO and ZnO-TiO2 have similar photo-catalysis activity under 365 nm UV irradiation, but under visible light, the photocatalysis activities of ZnO-TiO2 films were twice higher than that of ZnO porous film, implying promising applications of this porous oxide composite for industrial and dairy farm wastewater treatment.

  5. Active carbons obtained from bituminous coal for NO{sub 2} removal under dry and wet conditions at room temperature

    SciTech Connect

    Robert Pietrzak

    2009-07-15

    The adsorption of NO{sub 2} on active carbons obtained from Polish bituminous coal was studied. Carbonaceous adsorbents were obtained by pyrolysis of coal at 500, 600, and 700{sup o}C followed by activation with KOH at 700 {sup o}C. Adsorption of NO{sub 2} was carried out from dry and moist (70% humidity) air. The surface structure and chemistry of the initial and exhausted adsorbents were analyzed using adsorption of nitrogen, Boehm method, and elemental and thermal analyses. All adsorbents obtained were found to have acidic surfaces. The best NO{sub 2} sorption capacity in both dry and wet conditions was obtained for the active carbon pyrolyzed at 700{sup o}C, with respective values of 25.0 and 43.5 mg/g, respectively. For all materials a considerable amount of NO{sub 2} was reduced to NO. Differential thermogravimetry curves of samples after exposure to NO{sub 2} showed two new peaks, the first at 90-180{sup o}C, assigned to the removal of physically adsorbed NO{sub 2} and NO, and the second at 200-400{sup o}C, assigned to the decomposition of potassium nitrates and nitrites. 48 refs., 6 figs., 5 tabs.

  6. Selective catalytic reduction of NO with NH3 over V2O5 supported on TiO2 and Al2O3: A comparative study

    NASA Astrophysics Data System (ADS)

    Huang, Xianming; Zhang, Shule; Chen, Huinan; Zhong, Qin

    2015-10-01

    This study aimed at investigating the interaction of V2O5 species with TiO2 and Al2O3 supports to understand the effect of supports on SCR reaction. Analysis by XRD, BET, UV-vis, and DFT theoretical calculations, XPS, EPR and in situ DRIFT showed that the two kinds of supports could interact with V2O5. The interaction of electron excitation and charge transfer of supports to V2O5 species was important to the formation of the reduced V2O5. These aspects increased the formation of superoxide ions that could improve the NO oxidation over V2O5/TiO2. It was responsible for the higher SCR catalytic activity of V2O5/TiO2 than V2O5/Al2O3.

  7. Changes in wetting properties of silica surface treated with DPPC in the presence of phospholipase A 2 enzyme

    NASA Astrophysics Data System (ADS)

    Wiącek, Agnieszka Ewa

    2010-10-01

    Wetting properties of silica plates contacted with dipalmitoylphosphatidylcholine (DPPC) or DPPC/enzyme (phospholipase PLA 2) in NaCl solution were determined by thin layer wicking and with a help of Washburn equation. The wicking experiments were performed both for bare plates and the silica plates precontacted overnight with the probe liquid saturated vapors the silica plates, as well as untreated and DPPC (or DPPC/enzyme) treated. Adsorption of DPPC on original silica plates increases a bit hydrophobic character of silica surface in such a way that hydrocarbon chains are directed outwards and the polar part towards the silica surface. However, after the enzyme action the products of DPPC hydrolysis by PLA 2 (palmitic acid and lysophosphatidylcholine) increase again hydrophilic character of silica surface (an increase in acid-base interactions, γsAB). The changes of silica surface wettability are evidently dependent on the time of enzyme contacting with DPPC in NaCl solution. Although, the changes of total surface free energy of silica after treatment with DPPC/enzyme solution are minor about 2-6 mJ/m 2, the changes of the electron-donor ( γs-) and Lifshitz-van der Waals ( γsLW) component of the surface free energy are noticeable. Despite, these results are somehow preliminary, it seems that thin layer wicking method is an interesting tool for investigation of the effect of adsorbed DPPC on hydrophobicity/hydrophilicity of silica surface and influence of enzyme PLA 2 action.

  8. Dependence of Protein Adsorption on Wetting Behavior of UHMWPE-HA-Al2O3-CNT Hybrid Biocomposites

    NASA Astrophysics Data System (ADS)

    Gupta, Ankur; Tripathi, Garima; Basu, Bikramjit; Balani, Kantesh

    2012-04-01

    Ultrahigh-molecular-weight polyethylene (UHMWPE) is used as an articulating surface in total hip and knee joint replacement. In order to enhance long-term durability/wear resistance properties, UHMWPE-based polymer-ceramic hybrid composites are being developed. Surface properties such as wettability and protein adsorption alter with reinforcement or with change in surface chemistry. From this perspective, the wettability and protein adsorption behavior of compression-molded UHMWPE-hydroxyapatite (HA)-aluminum oxide (Al2O3)-carbon nanotube (CNT) composites were analyzed in conjunction with surface roughness. The combined effect of Al2O3 and CNT shows enhancement of the contact angle by ~37° compared with the surface of the UHMWPE matrix reinforced with HA. In reference to unreinforced UHMWPE, protein adsorption density also increased by ~230% for 2 wt.%HA-5 wt.%Al2O3-2 wt.%CNT addition to UHMWPE. An important conclusion is that the polar and dispersion components of the surface free energy play a significant role in wetting and protein adsorption than do the total free energy or chemistry of the surface. The results of this study have major implications for the biocompatibility of these newly developed biocomposites.

  9. Effect of structure and surface properties on the catalytic activity of nanodiamond in the conversion of 1,2-dichloroethane

    NASA Astrophysics Data System (ADS)

    Tveritinova, E. A.; Zhitnev, Yu. N.; Kulakova, I. I.; Maslakov, K. I.; Nesterova, E. A.; Kharlanov, A. N.; Ivanov, A. S.; Savilov, S. V.; Lunin, V. V.

    2015-04-01

    The catalytic activity of a detonation nanodiamond and its Ni-containing forms in the conversion of 1,2-dichloroethane is studied and compared with the activity of other carbon and nanocarbon materials: carbon nanotubes, "Dalan" synthetic diamond, and fluorinated graphite. The surface and structure of the carbon materials are characterized using XRD, diffuse reflectance IR spectroscopy, XPS, BET, and TPR. The catalytic properties of the materials are studied using the pulsed microcatalytic method. It is found that the synthetic diamond, the nanodiamond, and its Ni-containing forms are catalysts for dichloroethane conversion in a nitrogen atmosphere, where the main product is ethylene. It is noted that the catalytic activity of deactivated diamond catalysts is restored after hydrogen treatment. It is shown that the carbon structure of the nanodiamond and the "Dalan" synthetic diamond with hydrogen groups located on it plays a key role in the dichloroethane conversion. It is found that the nanodiamond acts simultaneously as a catalyst and an adsorbent of chlorine-containing products of dichloroethane conversion.

  10. Catalytic hydrodechlorination of PCDD/Fs from condensed water with Pd/γ-Al2O3.

    PubMed

    Liu, Mei-Chen; Chang, Shu-Hao; Chang, Moo-Been

    2016-07-01

    A continuous pyrolysis system (CPS) with effective air pollution control devices (APCDs) is designed and constructed to remediate the soil containing high-concentration PCDD/Fs. The quench tower of the APCDs system can capture the pollutants of high boiling points from the flue gas of CPS and produces condensed water of high PCDD/Fs concentration (16-44 ng I-TEQ/L), and needs further treatment. First, the result of activated carbon adsorption test displays the PCDD/Fs toxicity concentration of effluents meet the regulatory standards as the liquid to solid ratio is controlled at 3: 1. However, large amount of activated carbon need to achieve the high removal efficiency leads to high cost, so catalytic hydrodechlorination technology with Pd/Al2O3 as catalyst is applied to treat the condensed water. The PCDD/Fs mass removal efficiency achieved without the reducing agent is 53.21% with the operating time of 180 min. As 5% reducing agent (methanol) is added, the removal efficiency increases to 71.86%. In addition, to better understand the differences between molecular hydrogen and hydrogen donor, the condensed water was pre-aerated with hydrogen and catalytic hydrodechlorination test with palladium as catalyst was conducted. The results show that the PCDD/Fs mass removal efficiency increases to 97.34% with the operating time of 180 min, demonstrating the high PCDD/Fs removal efficiency of catalytic hydrodechlorination. PMID:27088535

  11. Comparative Reactivity Study of Forsterite and Antigorite in Wet Supercritical CO2 by In Situ Infrared Spectroscopy

    SciTech Connect

    Thompson, Christopher J.; Loring, John S.; Rosso, Kevin M.; Wang, Zheming

    2013-10-01

    The carbonation reactions of forsterite (Mg2SiO4) and antigorite [Mg3Si2O5(OH)4], representatives of olivine and serpentine minerals, in dry and wet supercritical carbon dioxide (scCO2) at conditions relevant to geologic carbon sequestration (35 °C and 100 bar) were studied by in-situ Fourier transform infrared (FT-IR) spectroscopy. Our results confirm that water plays a critical role in the reactions between metal silicate minerals and scCO2. For neat scCO2, no reaction was observed in 24 hr for either mineral. When water was added to the scCO2, a thin water film formed on the minerals’ surfaces, and the reaction rates and extents increased as the water saturation level was raised from 54% to 116% (excess water). For the first time, the presence of bicarbonate, a key reaction intermediate for metal silicate reactions with scCO2, was observed in a heterogeneous system where mineral solids, an adsorbed water film, and bulk scCO2 co-exist. In excess-water experiments, approximately 4% of forsterite and less than 2% of antigorite transformed into hydrated Mg-carbonates. A precipitate similar to nesquehonite (MgCO3•3H2O) was observed for forsterite within 6 hr of reaction time, but no such precipitate was formed from antigorite until after water was removed from the scCO2 following a 24-hr reaction period. The reduced reactivity and carbonate-precipitation behavior of antigorite was attributed to slower, incongruent dissolution of the mineral and lower concentrations of Mg2+ and HCO3- in the water film. The in situ measurements employed in this work make it possible to quantify metal carbonate precipitates and key reaction intermediates such as bicarbonate for the investigation of carbonation reaction mechanisms relevant to geologic carbon sequestration.

  12. Wet chemical synthesis and self-assembly of SnS2 nanoparticles on TiO2 for quantum dot-sensitized solar cells.

    PubMed

    Tsukigase, Hiroki; Suzuki, Yoshikazu; Berger, Marie-Hélène; Sagawa, Takashi; Yoshikawa, Susumu

    2011-04-01

    SnS2 nanoparticles were synthesized through a simple wet chemical process at room temperature. The SnS2 nanoparticles were approximately spherical in shape and had diameter about 3-4 nm. SnS2-sensitized TiO2 electrodes were fabricated by the immersion of chemically modified TiO2 to well-dispersed SnS2 solution for 72 h (i.e., self-assembly method.) SnS2-sensitized TiO2 electrodes were applied in quantum dot-sensitized solar cells (QDSSCs). Under AM1.5 irradiation with 100 mW/cm2 light intensity (at 1 sun), the short-circuit current density (J(sc)), the open-circuit voltage (V(oc)), the fill factor (FF), and the energy conversion efficiency (eta) were 0.47 mA/cm2, 0.29 V, 0.58 and 0.081%, respectively.

  13. Catalytic methods using molecular oxygen for treatment of PMMS and ECLSS waste streams, volume 2

    NASA Technical Reports Server (NTRS)

    Akse, James R.

    1992-01-01

    Catalytic oxidation has proven to be an effective addition to the baseline sorption, ion exchange water reclamation technology which will be used on Space Station Freedom (SSF). Low molecular weight, polar organics such as alcohols, aldehydes, ketones, amides, and thiocarbamides which are poorly removed by the baseline multifiltration (MF) technology can be oxidized to carbon dioxide at low temperature (121 C). The catalytic oxidation process by itself can reduce the Total Organic Carbon (TOC) to below 500 ppb for solutions designed to model these waste waters. Individual challenges by selected contaminants have shown only moderate selectivity towards particular organic species. The combined technology is applicable to the more complex waste water generated in the Process Materials Management System (PMMS) and Environmental Control and Life Support System (ECLSS) aboard SSF. During the phase 3 Core Module Integrated Facility (CMIF) water recovery tests at NASA MSFC, real hygiene waste water and humidity condensate were processed to meet potable specifications by the combined technology. A kinetic study of catalytic oxidation demonstrates that the Langmuir-Hinshelwood rate equation for heterogeneous catalysts accurately represent the kinetic behavior. From this relationship, activation energy and rate constants for acetone were determined.

  14. Catalytic oxidation of 2-Propanol over (Cr,Mn,Fe)-Pt/gamma-Al2O3 bimetallic catalysts and modeling of experimental results by artificial neural networks.

    PubMed

    Niaei, A; Salari, D; Aghazadeh, F; Caylak, N; Sepehrianazar, A

    2010-01-01

    The catalytic activity of transition metals (Cr,Mn,Fe) supported on the Pt/gamma -Al(2)O(3) industrial catalyst was investigated to bring about the complete oxidation of 2-Propanol. Catalytic studies were carried out under atmospheric pressure in a fixed bed reactor. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and ICP-AES techniques were used to characterize a series of catalysts. Results showed that the Pt-Mn/gamma -Al(2)O(3) (3.88 wt.%Mn) at calcination temperature of 300 degrees C was the most promising catalyst based on activity, which might be contributed to the quantity of manganese loading, the favorable synergetic effects between Pt and Mn and the well-dispersed bimetallic phase. An artificial neural networks (ANN) model was developed to predict the performance of catalytic oxidation process over Pt-Mn/gamma -Al(2)O(3) bimetallic catalyst based on experimental data. For this purpose the Levenberg-Marquardt (LM) learning algorithm was employed to train the model by using laboratory experimental data. A comparison between the predicted results of the designed ANN model and experimental data was also conducted. The developed model can describe the catalytic oxidation over bimetallic catalysts under different conditions. PMID:20390890

  15. E2 superfamily of ubiquitin-conjugating enzymes: constitutively active or activated through phosphorylation in the catalytic cleft

    PubMed Central

    Valimberti, Ilaria; Tiberti, Matteo; Lambrughi, Matteo; Sarcevic, Boris; Papaleo, Elena

    2015-01-01

    Protein phosphorylation is a modification that offers a dynamic and reversible mechanism to regulate the majority of cellular processes. Numerous diseases are associated with aberrant regulation of phosphorylation-induced switches. Phosphorylation is emerging as a mechanism to modulate ubiquitination by regulating key enzymes in this pathway. The molecular mechanisms underpinning how phosphorylation regulates ubiquitinating enzymes, however, are elusive. Here, we show the high conservation of a functional site in E2 ubiquitin-conjugating enzymes. In catalytically active E2s, this site contains aspartate or a phosphorylatable serine and we refer to it as the conserved E2 serine/aspartate (CES/D) site. Molecular simulations of substrate-bound and -unbound forms of wild type, mutant and phosphorylated E2s, provide atomistic insight into the role of the CES/D residue for optimal E2 activity. Both the size and charge of the side group at the site play a central role in aligning the substrate lysine toward E2 catalytic cysteine to control ubiquitination efficiency. The CES/D site contributes to the fingerprint of the E2 superfamily. We propose that E2 enzymes can be divided into constitutively active or regulated families. E2s characterized by an aspartate at the CES/D site signify constitutively active E2s, whereas those containing a serine can be regulated by phosphorylation. PMID:26463729

  16. Highly active Ag clusters stabilized on TiO2 nanocrystals for catalytic reduction of p-nitrophenol

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Zhao, Zhe; Ou, Dingrong; Tu, Baofeng; Cui, Daan; Wei, Xuming; Cheng, Mojie

    2016-11-01

    Ag/TiO2 nanocomposites comprising of Ag clusters on TiO2 nanocrystal surfaces are of great significance in catalysts and advanced functional materials. Herein a novel method to synthesize Ag/TiO2 nanocomposites with Ag clusters under 2 nm on TiO2 nanocrystal surfaces have been developed. The success of this method relies on a silver mirror reaction in toluene, which refers to the reduction of silver-dodecylamine complexes by acetaldehyde in the presence of mono-dispersed TiO2 nanocrystals. The prepared Ag/TiO2 nanocomposites have been characterized by FT-IR spectra, UV-vis absorption spectra, X-ray diffraction (XRD) analysis, ultra high resolution scanning electron microscope (Ultra-HRSEM), high resolution transmission electron microscope (HRTEM) and X-ray photoelectron spectra (XPS). Catalytic activity of Ag/TiO2 nanocomposites is evaluated for the reduction of p-nitrophenol (4-NP) into p-aminophenol (4-AP) by NaBH4. Results demonstrate that Ag/TiO2 nanocomposites have shown an outstanding catalytic activity as well as a good stability in successive reduction of 4-NP. Noticeably, TOF of Ag/TiO2-0.75 nanocomposites obtained in this work is the highest among Ag based catalysts previously reported.

  17. 2-Aminoethanol-mediated wet chemical synthesis of ZnO nanostructures

    NASA Astrophysics Data System (ADS)

    Naz, Tehmina; Afzal, Adeel; Siddiqi, Humaira M.; Akhtar, Javeed; Habib, Amir; Banski, Mateusz; Podhorodecki, Artur

    2015-04-01

    The synthesis of ZnO nanostructures via co-precipitation of Zn(NO3)2·2H2O in 2-aminoethanol under different reaction conditions is presented. The effect of temperature and time on crystal structure, size, morphology, and optical properties of ZnO nanopowders is studied. XRD analyses demonstrate that single crystalline wurtzite ZnO nanostructures are instantaneously formed at higher temperature, or at low temperature with growth times equal to 2 h. However, the mean crystallite size increases as a function of reaction temperature and growth time. XRD and SEM results reveal that ZnO nuclei grow along favored crystallographic planes [wurtzite (101)] in 2-aminoethanol to form single crystalline nanorods. The optical band-gap energies of ZnO crystallites measured from their UV absorption spectra increase from 3.31 to 3.52 eV with decreasing particle size. ZnO nanopowders also exhibit good photoluminescent characteristics with strong UV and weak visible (violet, blue) light emissions corresponding to surface defects and oxygen vacancies in ZnO products.

  18. O/W/O double emulsion-assisted synthesis and catalytic properties of CeO 2 hollow microspheres

    NASA Astrophysics Data System (ADS)

    Zhang, DongEn; Xie, Qing; Wang, MingYan; Zhang, XiaoBo; Li, ShanZhong; Han, GuiQuan; Ying, AiLing; Chen, AiMei; Gong, JunYan; Tong, ZhiWei

    2010-09-01

    CeO 2 hollow microspheres have been fabricated through a simple thermal decomposition of precursor approach. The precursor with an average size of 10 μm was prepared in a reverse microemulsions containing Ce(NO 3) 3·6H 2O and CO(NH 2) 2 at 160 °C. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscope (TEM), selected area electron diffraction (SAED) and scanning electron microscopy (SEM). The possible formation mechanism of hollow spheres was discussed. In addition, the CeO 2 hollow microspheres modified glassy carbon electrode exhibit excellent sensing performance towards methyl orange, which provide a new application of CeO 2 hollow spheres. The catalytic activity of CeO 2 hollow spheres on the thermal decomposition of ammonium perchlorate (AP) also was investigated by TGA. The catalytic performance of CeO 2 hollow spheres is superior to that of commercial CeO 2 powder.

  19. High-temperature hydrothermal synthesis of crystalline mesoporous TiO2 with superior photo catalytic activities

    NASA Astrophysics Data System (ADS)

    Liu, Fujian; Liu, Chun-Lin; Hu, Baowei; Kong, Wei-Ping; Qi, Chen-Ze

    2012-07-01

    Mesoporous titanium dioxide with crystalline mesopore walls (M-TiO2-ns) have been successfully synthesized through the self-assembly of poly 4-Vinylpyridine template and tetrabutyl titanate precursor based on their complex bond interaction under high temperature (180 °C) hydrothermal conditions. X-ray diffraction shows that M-TiO2-ns have highly crystalline mesopore walls with anatase phase characters; N2 sorption-desorption isotherms, SEM and TEM images show that M-TiO2-ns have high BET surface areas (85 and 120 m2/g, respectively), large pore volumes (0.32 and 0.34 cm3/g, respectively) and crystalline mesopore walls, which exhibit monolithic morphology with crystal sizes around 3-5 μm. Interestingly, M-TiO2-ns exhibit much higher catalytic activities and good recyclability in both induced reduction of decabromodiphenyl and oxidation of Rhodamine B under UV light than those of nonporous crystalline TiO2 and M-TiO2 templated by hydrocarbon surfactant of F127, which is even comparable with that of commercial P25. Combination of the unique characters such as crystallinity, stable mesostructure, large BET surface areas and superior photo catalytic activities make M-TiO2-ns a kind of potentially important material for removing of organic pollutions in environment through green photo irradiation processes.

  20. Investigation of Mineral Transformations in Wet Supercritical CO2 by Electron Microscopy

    SciTech Connect

    Arey, Bruce W.; Kovarik, Libor; Wang, Zheming; Felmy, Andrew R.

    2011-10-10

    The capture and storage of carbon dioxide and other greenhouse gases in deep geologic formations represents one of the most promising options for mitigating the impacts of greenhouse gases on global warming. In this regard, mineral-fluid interactions are of prime importance since such reactions can result in the long term sequestration of CO2 by trapping in mineral phases. Recently it has been recognized that interactions with neat to water-saturated non-aqueous fluids are of prime importance in understanding mineralization reactions since the introduced CO2 is likely to contain water initially or soon after injection and the supercritical CO2 (scCO2) is less dense than the aqueous phase which can result in a buoyant scCO2 plume contacting the isolating caprock. As a result, unraveling the molecular/microscopic mechanisms of mineral transformation in neat to water saturated scCO2 has taken on an added important. In this study, we are examining the interfacial reactions of the olivine mineral forsterite (Mg2SiO4) over a range of water contents up to and including complete water saturation in scCO2. The surface precipitates that form on the reacted forsterite grains are extremely fragile and difficult to experimentally characterize. In order to address this issue we have developed experimental protocols for preparing and imaging electron-transparent samples from fragile structures. These electron-transparent samples are then examined using a combination of STEM/EDX, FIB-TEM, and helium ion microscope (HIM) imaging (Figures 1-3). This combination of capabilities has provided unique insight into the geochemical processes that occur on scCO2 reacted mineral surfaces. The experimental procedures and protocols that have been developed also have useful applications for examining fragile structures on a wide variety of materials. This research was performed using EMSL, a national scientific user facility sponsored by the Department of Energy's Office of Biological and

  1. Crystallization and preliminary crystallographic studies of the catalytic subunits of human pyruvate dehydrogenase phosphatase isoforms 1 and 2

    PubMed Central

    Kato, Junko; Kato, Masato

    2010-01-01

    Pyruvate dehydrogenase phosphatase (PDP) is a mitochondrial serine phos­phatase that activates phosphorylated pyruvate dehydrogenase complex by dephosphorylation. In humans, two PDP isoforms (1 and 2) have been identified. PDP1 is composed of a catalytic subunit (PDP1c) and a regulatory subunit (PDP1r), whereas PDP2 consists of only a catalytic subunit (PDP2c). Both PDP1c and PDP2c have been crystallized individually and complete X-ray diffraction data sets have been collected to 2.45 and 2.0 Å resolution, respectively. The PDP1c crystals belonged to space group P41212 or P43212, with unit-cell parameters a = b = 65.1, c = 216.1 Å. The asymmetric unit is expected to contain one molecule, with a Matthews coefficient V M of 2.56 Å3 Da−1. The PDP2c crystals belonged to space group P212121, with unit-cell parameters a = 53.6, b = 69.1, c = 109.7 Å. The asymmetric unit is expected to contain one molecule, with a Matthews coefficient V M of 1.91 Å3 Da−1. PMID:20208177

  2. CO2 retention with minimal symptoms but severe dysfunction during wet simulated dives to 6.8 atm abs.

    PubMed

    Warkander, D E; Norfleet, W T; Nagasawa, G K; Lundgren, C E

    1990-11-01

    During wet dives in a hyperbaric chamber to 6.8 atm abs (690 kPa), air breathing subjects were experimentally exposed to external breathing resistance. Two of them were, unbeknownst to themselves, severely incapacitated. In the first incident the subject had been exercising for 25 min (end-tidal PCO2 60-65 mmHg, 7.3-8.0 kPa) when the breathing resistance was rapidly increased from low to very high (requiring pressure swings of 80 cmH2O, 8 kPa, peak to peak). He functioned normally (end-tidal PCO2 72 mmHg, 9.6 kPa) for about 100 s but 20 s later he was confused and irrational. After being extracted from the water (end-tidal PCO2 above 90 mmHg, 12 kPa), he lost consciousness for about 60 s. In the second incident the subject was exercising and breathing against a high resistance (pressure swings of 50-55 cmH2O, 5.0-5.6 kPa). His end-tidal PCO2 was high (65-68 mmHg, 8.7-9.3 kPa) throughout the exercise period, and after 24 min he reported mild dyspnea. A few seconds later he became confused. In other experiments both subjects voluntarily terminated experiments when the breathing resistance became overwhelming. These 2 subjects generally had high end-tidal PCO2 levels, but 1 other subject with end-tidal PCO2 levels in the same range never experienced any problems. These incidents indicate that severe hypercapnia does not necessarily correlate with dyspnea and that severe disturbances in mental function due to hypercapnia can develop suddenly when high breathing resistance is encountered in diving.

  3. Molecular modeling studies of interfacial reactions in wet supercritical CO2.

    NASA Astrophysics Data System (ADS)

    Glezakou, V.; McGrail, B. P.; Windisch, C. F.; Schaef, H. T.; Martin, P.

    2011-12-01

    In the recent years, Carbon Capture and Sequestration (CCS) technologies have gained considerable momentum in a globally organized effort to mitigate greenhouse emissions and adverse climate change. Co-sequestration refers to the capture and geologic sequestration of carbon dioxide and minor contaminants (sulfur compounds, NOx, Hg, etc.) in subsurface formations. Cosequestration offers the potential to make carbon management more economically acceptable to industry relative to sequestration of pure CO2. This may be achieved through significant savings in plant (and retrofit) capital cost, operating cost, and energy savings as well by eliminating the need for one or more individual pollutant capture systems (such as SO2 scrubbers). The latter point is important because co-sequestration may result in a net positive impact to the environment through avoided loss of power generation capacity from parasitic loads and reduced fuel needs. This paper will discuss our research on modeling, imaging and characterization of cosequestration processes and reactivity at a fundamental level. Our work examines the interactions of CO2-rich fluids with metal and mineral surfaces, and how these are affected by the presence of other gas components (e.g. SO2, H2O or NOx) commonly present in the CO2 streams. We have found that reactivity is also affected by the composition of the surface or, less obviously, by the surface exposed, for example, (104) vs (100 )of carbonate minerals. We combine experimental techniques such as XRD and Raman spectroscopy, which can detect and follow reactive processes, with ab initio modeling methods based on density functional theory, to establish a reliable correspondence between theory and experiment with predictive capability. Analysis of our molecular dynamics simulations, reveals structural information and vibrational density of states that can directly compare with XRD measurements and vibrational spectroscopy. While reactivity in CO2-containing

  4. The effect of B2O3 flux on growth NLBCO superconductor by solid state reaction and wet-mixing methods

    NASA Astrophysics Data System (ADS)

    Suharta, W. G.; Wendri, N.; Ratini, N.; Suarbawa, K. N.

    2016-03-01

    The synthesis of B2O3 flux substituted NLBCO superconductor NdBa1.75La0.25Cu3O7-∂ has been done using solid state reaction and wet-mixing methods in order to obtain homogeneous crystals and single phase. From DTA/TGA characteritations showed the synthesis process by wet-mixing requires a lower temperature than the solid state reaction in growing the superconductor NdBa1.75La0.25Cu3O7-∂. Therefore, in this research NdBa1.75La0.25Cu3O7-∂ sample calcinated at 650°C for wet-mixing method and 820°C for solid state reaction methods. The all samples was sintered at 950°C for ten hours. Crystallinity of the sample was confirmed using X-ray techniques and generally obtained sharp peaks that indicates the sample already well crystallized. Search match analyses for diffraction data gave weight fractions of impurity phase of the solid state reaction method higher than wet-mixing method. In this research showed decreasing the price of the lattice parameter about 1% with the addition of B2O3 flux for the both synthesis process and 2% of wet mixing process for all samples. Characterization using scanning electron microscopy (SEM) showed the distribution of crystal zise for wet-mixing method more homogeneous than solid state reaction method, with he grain size of samples is around 150-250 nm. The results of vibrating sample magnetometer (VSM) showed the paramagnetic properties for all samples.

  5. Effects of increased nutrients and warming on CO{sub 2} exchanges in Alaskan wet sedge tundras: Mechanism of response

    SciTech Connect

    Johnson, L.C.; Shaver, G.R.; Cades, D.C.

    1995-06-01

    We measured ecosystem- and leaf-level CO{sub 2} exchanges in Alaskan wet sedge tundra that had been warmed or fertilized for 6 years. Gross ecosystem photosynthesis (GEP), both diurnally and seasonally, was nearly double in N+P fertilizer additions. With N+P additions, GEP greatly exceeded ecosystem respiration, thereby increasing ecosystem C storage. Warming for 6 years (in a field greenhouse) had little effect on GEP, ecosystem respiration, or ecosystem C storage compared to controls.(Controls stored {approximately}90 gC m{sup -2} season{sup -1}.) In the N+P additions, higher canopy photosynthetic rates (P{sub max}) under saturating light conditions accounted for the higher GEP; under low light, GEP was similar among treatments. The increased canopy P{sub max} with N+P additions was due more to increased leaf mass than to increased photosynthesis per unit leaf area. Ecosystem respiration (plant plus microbial) strongly increased in response to greater nutrient availability. This increase was due to a stimulation of plant respiration (mostly aboveground) because the microbial component of the gaseous CO{sub 2} flux was small and unresponsive to treatments. In summary, ecosystem response to increased nutrients appears to be primarily dominated by aboveground plant response.

  6. Nanocrystalline sol-gel TiO{sub 2}-SnO{sub 2} coatings: Preparation, characterization and photo-catalytic performance

    SciTech Connect

    Kaleji, Behzad Koozegar; Sarraf-Mamoory, Rasoul

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer SnO{sub 2} additive enhanced significantly photo-catalytic properties of TiO{sub 2} based thin film for remove of organic compounds. Black-Right-Pointing-Pointer Structural and optical properties are dependent on dopant concentration. Black-Right-Pointing-Pointer TiO{sub 2}-SnO{sub 2} nanocrystalline thin film is promising for photocatalytic properties in visible light. -- Abstract: In this study, preparation of SnO{sub 2} (0-30 mol% SnO{sub 2})-TiO{sub 2} dip-coated thin films on glazed porcelain substrates via sol-gel process has been investigated. The effects of SnO{sub 2} on the structural, optical, and photo-catalytic properties of applied thin films have been studied by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Surface topography and surface chemical state of thin films were examined by atomic force microscopy and X-ray photoelectron spectroscopy. XRD patterns showed an increase in peak intensities of the rutile crystalline phase by increasing the SnO{sub 2} content. The prepared Sn doped TiO{sub 2} photo-catalyst films showed optical absorption in the visible light area exhibited excellent photo-catalytic ability for the degradation of methylene blue under visible light irradiation. Best photo-catalytic activity of Sn doped TiO{sub 2} thin films was measured in the TiO{sub 2}-15 mol% SnO{sub 2} sample by the Sn{sup 4+} dopants presented substitution Ti{sup 4+} into the lattice of TiO{sub 2} increasing the surface oxygen vacancies and the surface hydroxyl groups.

  7. In Situ X-Ray Diffraction Study of Na+ Saturated Montmorillonite Exposed to Variably Wet Super Critical CO2

    SciTech Connect

    Ilton, Eugene S.; Schaef, Herbert T.; Qafoku, Odeta; Rosso, Kevin M.; Felmy, Andrew R.

    2012-04-03

    Reactions involving variably hydrated super critical CO{sub 2} (scCO{sub 2}) and a Na saturated dioctahedral smectite (Na-STX-1) were examined by in situ high-pressure x-ray diffraction at 50 C and two different pressures (90 and 180 bars); conditions that are relevant to long term geologic storage of CO{sub 2}. Both hydration and dehydration reactions were rapid with appreciable reaction occurring in minutes and near steady state within an hour. Hydration occurred stepwise as a function of increasing H{sub 2}O in the system; 1W, 2W-3W, and >3W clay hydration states were stable from {approx} 1.5-30%, {approx} 31-55 < 64%, and {ge} {approx} 71% H{sub 2}O saturation in scCO{sub 2}, respectively. Exposure of sub 1W clay to anhydrous scCO{sub 2} caused interlayer expansion, not contraction as expected for dehydration. In contrast, control experiments using pressurized N{sub 2} and similar initial conditions as in the scCO{sub 2} study, showed little to no change in the d{sub 001} spacing, or hydration states, of the clay. Comparison of the N{sub 2} and scCO{sub 2} experiments indicates that the induced changes are not a pressure effect, but rather are due to the intrinsic properties of scCO{sub 2}. A salient implication for CO{sub 2} sequestration and cap rock integrity is that clays can dehydrate when exposed to wet scCO{sub 2}. For example, the {approx} 3W clay hydration state appears to be unstable and the structure will collapse by {approx} 3 {angstrom} in the c* direction, or {approx} 15%, if exposed to scCO{sub 2} at less than or equal to about 64% H{sub 2}O saturation. Further, the evidence suggests that CO{sub 2} intercalated the interlayer region of the sub 1W clay which might provide a secondary trapping mechanism for CO{sub 2}.

  8. Preliminary results on yield and CO2 fluxes when using alternate wetting and drying on different varieties of European rice

    NASA Astrophysics Data System (ADS)

    Oliver, Viktoria; Monaco, Stefano; Volante, Andrea; Cochrane, Nicole; Gennaro, Massimo; Orasen, Gabriele; Valè, Giampiero; Price, Adam; Arn Teh, Yit

    2016-04-01

    In Europe, rice is grown (467 000 ha) under permanently flooded conditions (PF) using irrigation waters of major rivers. Climate change, which has led to a greater fluctuation in river flows, is a major challenge to rice production systems, which depend on large and consistent water supplies. This challenge will become more acute in the future, with more frequent extreme weather (e.g. drought) predicted under climate change and increased demands for rice. Alternate wetting and drying (AWD) is a system in where irrigation is applied to obtain 2-5 cm of field water depth, after which the soil is allowed to drain naturally to typically 15 cm below the surface before re-wetting once more. Preliminary studies suggest that AWD can reduce water use by up 30 %, with no net loss in yield but significantly reducing CH4 emissions. However, uncertainties still remain as to the impacts of AWD on CO2 exchange, N2O fluxes, and plant acclimation responses to a fluctuating water regime. For example, CO2 emissions could potentially increase in AWD due to higher rates of soil organic matter decomposition when the fields are drained. The work presented here evaluated the impacts of AWD on the productivity and yield of twelve varieties of European rice, whilst simultaneously measuring CO2 exchange, N2O fluxes, and plant biomass allocation patterns under different treatment regimes. Field experiments were conducted in the Piedmont region (northern Italy Po river plain) in a loamy soil during the growing season of 2015 in a 2-factor paired plot design, with water treatment (AWD, PF) and variety (12 European varieties) as factors (n=4 per variety per treatment). The varieties chosen were commercially important cultivars from across the rice growing regions of Europe (6 Italian, 3 French, 3 Spanish). Light and dark CO2 fluxes were measured six times over the growing season, using an infra-red gas analyzer. Environmental variables (soil moisture, temperature, water table depth, water

  9. Preliminary results on yield and CO2 fluxes when using alternate wetting and drying on different varieties of European rice

    NASA Astrophysics Data System (ADS)

    Oliver, Viktoria; Monaco, Stefano; Volante, Andrea; Cochrane, Nicole; Gennaro, Massimo; Orasen, Gabriele; Valè, Giampiero; Price, Adam; Arn Teh, Yit

    2016-04-01

    In Europe, rice is grown (467 000 ha) under permanently flooded conditions (PF) using irrigation waters of major rivers. Climate change, which has led to a greater fluctuation in river flows, is a major challenge to rice production systems, which depend on large and consistent water supplies. This challenge will become more acute in the future, with more frequent extreme weather (e.g. drought) predicted under climate change and increased demands for rice. Alternate wetting and drying (AWD) is a system in where irrigation is applied to obtain 2-5 cm of field water depth, after which the soil is allowed to drain naturally to typically 15 cm below the surface before re-wetting once more. Preliminary studies suggest that AWD can reduce water use by up 30 %, with no net loss in yield but significantly reducing CH4 emissions. However, uncertainties still remain as to the impacts of AWD on CO2 exchange, N2O fluxes, and plant acclimation responses to a fluctuating water regime. For example, CO2 emissions could potentially increase in AWD due to higher rates of soil organic matter decomposition when the fields are drained. The work presented here evaluated the impacts of AWD on the productivity and yield of twelve varieties of European rice, whilst simultaneously measuring CO2 exchange, N2O fluxes, and plant biomass allocation patterns under different treatment regimes. Field experiments were conducted in the Piedmont region (northern Italy Po river plain) in a loamy soil during the growing season of 2015 in a 2-factor paired plot design, with water treatment (AWD, PF) and variety (12 European varieties) as factors (n=4 per variety per treatment). The varieties chosen were commercially important cultivars from across the rice growing regions of Europe (6 Italian, 3 French, 3 Spanish). Light and dark CO2 fluxes were measured six times over the growing season, using an infra-red gas analyzer. Environmental variables (soil moisture, temperature, water table depth, water

  10. Identification of Fragile Microscopic Structures during Mineral Transformations in Wet Supercritical CO2

    SciTech Connect

    Arey, Bruce W.; Kovarik, Libor; Qafoku, Odeta; Wang, Zheming; Hess, Nancy J.; Felmy, Andrew R.

    2013-04-01

    In this study we examine the nature of highly fragile reaction products that form in low water content super critical carbon dioxide (scCO2) using a combination of scanning electron microscopy/focus ion beam (SEM/FIB), confocal Raman spectroscopy, helium ion microscopy (HeIM), and transmission electron microscopy (TEM). HeIM images show these precipitates to be fragile rosettes that can readily decompose even under slight heating from an electron beam. Using the TEM revealed details on the interfacial structure between the newly formed surface precipitates and the underlying initial solid phases. The detailed microscopic analysis revealed that the growth of the precipitates either followed a tip growth mechanism with precipitates forming directly on the forsterite surface if the initial solid was non-porous (natural forsterite) or growth from the surface of the precipitates where fluid was conducted through the porous (nanoforsterite) agglomerates to the growth center. The mechanism of formation of the hydrated/hydroxylated magnesium carbonate compound (HHMC) phases offers insight into the possible mechanisms of carbonate mineral formation from scCO2 solutions which has recently received a great deal of attention as the result of the potential for CO2 to act as an atmospheric greenhouse gas and impact overall global warming. The techniques used here to examine these fragile structures an also be used to examine a wide range of fragile material surfaces. SEM and FIB technologies have now been brought together in a single instrument, which represents a powerful combination for the studies in biological, geological and materials science.

  11. WetLab-2: Tools for Conducting On-Orbit Quantitative Real-Time Gene Expression Analysis on ISS

    NASA Technical Reports Server (NTRS)

    Parra, Macarena; Almeida, Eduardo; Boone, Travis; Jung, Jimmy; Schonfeld, Julie

    2014-01-01

    The objective of NASA Ames Research Centers WetLab-2 Project is to place on the ISS a research platform capable of conducting gene expression analysis via quantitative real-time PCR (qRT-PCR) of biological specimens sampled or cultured on orbit. The project has selected a Commercial-Off-The-Shelf (COTS) qRT-PCR system, the Cepheid SmartCycler and will fly it in its COTS configuration. The SmartCycler has a number of advantages including modular design (16 independent PCR modules), low power consumption, rapid ramp times and the ability to detect up to four separate fluorescent channels at one time enabling multiplex assays that can be used for normalization and to study multiple genes of interest in each module. The team is currently working with Cepheid to enable the downlink of data from the ISS to the ground and provide uplink capabilities for programming, commanding, monitoring, and instrument maintenance. The project has adapted commercial technology to design a module that can lyse cells and extract RNA of sufficient quality and quantity for use in qRT-PCR reactions while using a housekeeping gene to normalize RNA concentration and integrity. The WetLab-2 system is capable of processing multiple sample types ranging from microbial cultures to animal tissues dissected on-orbit. The ability to conduct qRT-PCR on-orbit eliminates the confounding effects on gene expression of reentry stresses and shock acting on live cells and organisms or the concern of RNA degradation of fixed samples. The system can be used to validate terrestrial analyses of samples returned from ISS by providing on-orbit gene expression benchmarking prior to sample return. The ability to get on orbit data will provide investigators with the opportunity to adjust experiment parameters for subsequent trials based on the real-time data analysis without need for sample return and re-flight. Researchers will also be able to sample multigenerational changes in organisms. Finally, the system can be

  12. Tritium release kinetics from Li 2TiO 3 pebbles as prepared by soft-wet-chemistry

    NASA Astrophysics Data System (ADS)

    Casadio, S.; van der Laan, J. G.; Alvani, C.; Magielsen, A. J.; Stijkel, M. P.

    2004-08-01

    Lithium meta titanate pebbles has been prepared from agglomeration-sintering powders which were obtained by Li-Ti-peroxo-complex solution precursor (Li 2TiO 3 dissolved at room temperature in H 2O + 40% H 2O 2 and stabilized with citric acid). Through this wet route Li 2TiO 3 pebbles with high density(˜92% of T.D.) has been obtained and the tritium release behavior has been tested `in-pile' by the EXOTIC-8.9 experiment (˜440 days of irradiation at full power in the high neutron flux of HFR-Petten). Tritium residence times ( τ) in the pebbles has been measured during irradiation between 550 and 400 °C and He + 0.1%H 2 purge gas composition. By a thermally activated process (activation energy=111 kJ/mol) with 410 °C as minimum temperature the tritium residence time is found to be about 1 day, which places this specimen in a good ranking position among those tested by the EXOTIC-series. A clear increase of the tritium release rate has been observed by increased H 2 concentration (up to 1%) in the He purge. Out-of-pile ramp-annealing tritium desorption (TPD) tests on short-time irradiated pebbles has been also performed by various devices and conditions. The kinetic parameters from the TPD investigation gave consistent results with those characterizing the equilibrium times of tritium release rate after the gas composition and temperature transients imposed on the specimen during the in-pile experiment.

  13. Catalytic fast pyrolysis of cellulose and biomass to produce levoglucosenone using magnetic SO4(2-)/TiO2-Fe3O4.

    PubMed

    Lu, Qiang; Ye, Xiao-ning; Zhang, Zhi-bo; Dong, Chang-qing; Zhang, Ying

    2014-11-01

    Magnetic superacid (SO4(2-)/TiO2-Fe3O4) was prepared for catalytic fast pyrolysis of cellulose and poplar wood to produce levoglucosenone (LGO). Its catalytic activity was evaluated via pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments, and compared with the non-magnetic SO4(2-)/TiO2, phosphoric acid (H3PO4) and sulfur acid (H2SO4) catalysts. Moreover, the LGO yield was quantitatively determined. The results indicated that the magnetic SO4(2-)/TiO2-Fe3O4 was effective to selectively produce LGO from both cellulose and poplar wood. Its catalytic capability was a little better than the non-magnetic SO4(2-)/TiO2 and H3PO4, and much better than the H2SO4. The maximal LGO yields from both cellulose and poplar wood were obtained at 300 °C with the feedstock/catalyst ratio of 1/1, reaching as high as 15.43 wt% from cellulose and 7.06 wt% from poplar wood, respectively. PMID:25173471

  14. Structure of the catalytic sites in Fe/N/C-catalysts for O2-reduction in PEM fuel cells.

    PubMed

    Kramm, Ulrike I; Herranz, Juan; Larouche, Nicholas; Arruda, Thomas M; Lefèvre, Michel; Jaouen, Frédéric; Bogdanoff, Peter; Fiechter, Sebastian; Abs-Wurmbach, Irmgard; Mukerjee, Sanjeev; Dodelet, Jean-Pol

    2012-09-01

    Fe-based catalytic sites for the reduction of oxygen in acidic medium have been identified by (57)Fe Mössbauer spectroscopy of Fe/N/C catalysts containing 0.03 to 1.55 wt% Fe, which were prepared by impregnation of iron acetate on carbon black followed by heat-treatment in NH(3) at 950 °C. Four different Fe-species were detected at all iron concentrations: three doublets assigned to molecular FeN(4)-like sites with their ferrous ions in a low (D1), intermediate (D2) or high (D3) spin state, and two other doublets assigned to a single Fe-species (D4 and D5) consisting of surface oxidized nitride nanoparticles (Fe(x)N, with x≤ 2.1). A fifth Fe-species appears only in those catalysts with Fe-contents ≥0.27 wt%. It is characterized by a very broad singlet, which has been assigned to incomplete FeN(4)-like sites that quickly dissolve in contact with an acid. Among the five Fe-species identified in these catalysts, only D1 and D3 display catalytic activity for the oxygen reduction reaction (ORR) in the acid medium, with D3 featuring a composite structure with a protonated neighbour basic nitrogen and being by far the most active species, with an estimated turn over frequency for the ORR of 11.4 e(-) per site per s at 0.8 V vs. RHE. Moreover, all D1 sites and between 1/2 and 2/3 of the D3 sites are acid-resistant. A scheme for the mechanism of site formation upon heat-treatment is also proposed. This identification of the ORR-active sites in these catalysts is of crucial importance to design strategies to improve the catalytic activity and stability of these materials.

  15. Structure of the catalytic sites in Fe/N/C-catalysts for O2-reduction in PEM fuel cells

    PubMed Central

    Kramm, Ulrike I.; Herranz, Juan; Larouche, Nicholas; Arruda, Thomas M.; Lefèvre, Michel; Jaouen, Frédéric; Bogdanoff, Peter; Fiechter, Sebastian; Abs-Wurmbach, Irmgard; Mukerjee, Sanjeev; Dodelet, Jean-Pol

    2012-01-01

    Fe-based catalytic sites for the reduction of oxygen in acidic medium have been identified by 57Fe Mössbauer spectroscopy of Fe/N/C catalysts containing 0.03 to 1.55 wt% Fe, which were prepared by impregnation of iron acetate on carbon black followed by heat-treatment in NH3 at 950°C. Four different Fe-species were detected at all iron concentrations: three doublets assigned to molecular FeN4-like sites with their ferrous ion in low (D1), medium (D2) or high spin state (D3), and two other doublets assigned to a single Fe-species (D4 and D5) consisting of surface oxidized nitride nanoparticles (FexN, with x≤2.1). A fifth Fe-species appears only in those catalysts with Fe-contents ≥ 0.27 wt%. It is characterized by a very broad singlet, which has been assigned to incomplete FeN4-like sites that quickly dissolve in contact with an acid. Among the five Fe-species identified in these catalysts, only D1 and D3 display catalytic activity for the oxygen reduction reaction (ORR) in the acid medium, with D3 featuring a composite structure with a protonated neighbour basic nitrogen and being by far the most active species, with an estimated turn over frequency for the ORR of 11.4 e− site−1 s−1 at 0.8V vs RHE. Moreover, all D1 sites and between 1/2 to 2/3 of the D3 sites are acid-resistant. A scheme for the mechanism of site formation upon heat-treatment is also proposed. This identification of the ORR-active sites in these catalysts is of crucial importance to design strategies to improve the catalytic activity and stability of these materials. PMID:22824866

  16. Investigation of ZnCo2O4-Pt hybrids with different morphologies towards catalytic CO oxidation.

    PubMed

    Wang, Fan; Wang, Xiao; Liu, Dapeng; Zhen, Jiangman; Li, Junqi; Zhang, Hongjie

    2015-12-28

    In this work, three kinds of ZnCo2O4 morphologies, that is, rod, plate and sphere, have been successfully prepared and further used to support Pt nanoparticles (NPs) via in situ deposition. The as-prepared ZnCo2O4-Pt hybrid nanomaterials were then carefully characterized by SEM, TEM, XRD, XPS, ICP EDX, and N2 adsorption measurement in great detail. Besides, the three catalysts were also evaluated by the model reaction of catalytic CO oxidation. After comparing the difference in the three kinds of morphologies, we have tried to clarify the reason for their different catalytic performances. As a result, the ZnCo2O4-Pt sphere was found to be the most active, attaining 100% CO conversion at a relatively low temperature of 140 °C, because more Pt NPs are prone to distribution on the surface of ZnCo2O4 spheres than the other ones. The following cycling tests confirm the excellent stability of the as-prepared ZnCo2O4-Pt samples. PMID:26596247

  17. Investigation of catalytic reduction and filter techniques for simultaneous measurements of NO, NO2, and HNO3 in the stratosphere

    NASA Technical Reports Server (NTRS)

    Wendt, J.; Fabian, Peter; Flentje, G.; Kourtidis, K.

    1994-01-01

    A concept for measuring stratospheric NOy-species is presented which utilizes the catalytic reduction of NO2 and HNO3 over heated metal catalysts and the chemisorption of HNO3 on Nylon. Using the Max Planck Institute for Aeronomy (MPAE) chemiluminescent balloon-borne sonde, stratospheric NO and NO2 profiles have been measured since 1983. NO is detected by chemiluminescence produced in reaction with O3 while NO2 needs first to be converted to NO over a heated stainless steel catalyst. To improve this technique for simultaneously measuring HNO3, the catalytic reduction of NO2 and HNO3 over several metal catalysts and the chemisorption of NO2 and HNO3 on Nylon have been investigated in laboratory tests. The results of these tests under simulated stratospheric conditions are presented in detail in this paper. They demonstrate that the simultaneous measurement of NO, NO2 and HNO3 is indeed possible with the combination of stainless steel or Au as a catalyst and a nylon filter.

  18. CeO2 doped anatase TiO2 with exposed (001) high energy facets and its performance in selective catalytic reduction of NO by NH3

    NASA Astrophysics Data System (ADS)

    Wang, Haiqiang; Cao, Shuang; Fang, Zheng; Yu, Feixiang; Liu, Yue; Weng, Xiaole; Wu, Zhongbiao

    2015-03-01

    Ceria doped on anatase TiO2 with high energy (001) facets was synthesized in this paper, which was subsequently utilized for selective catalytic reduction (SCR) of NO by NH3. After subjected to a range of analytical techniques, such as XRD, BET, TEM, XPS ESR, H2-TPR and NH3-TPD, it was found that compared with Ce/P25 catalyst, the presence of (001) facets over the TiO2 support had yielded a remarkably high activity at 390-490 °C for NO removal. The unique feature of active-energy (001) facets had enhanced the thermal stability of CeO2 whilst the presence of Ti3+ over the TiO2 surface had effectively facilitated the SCR process, both of which resulted in the remarkable catalytic performance for the catalyst.

  19. Catalytic formal [2+2+1] synthesis of pyrroles from alkynes and diazenes via TiII/TiIV redox catalysis

    NASA Astrophysics Data System (ADS)

    Gilbert, Zachary W.; Hue, Ryan J.; Tonks, Ian A.

    2016-01-01

    Pyrroles are structurally important heterocycles. However, the synthesis of polysubstituted pyrroles is often challenging. Here, we report a multicomponent, Ti-catalysed formal [2+2+1] reaction of alkynes and diazenes for the oxidative synthesis of penta- and trisubstituted pyrroles: a nitrenoid analogue to classical Pauson-Khand-type syntheses of cyclopentenones. Given the scarcity of early transition-metal redox catalysis, preliminary mechanistic studies are presented. Initial stoichiometric and kinetic studies indicate that the mechanism of this reaction proceeds through a formally TiII/TiIV redox catalytic cycle, in which an azatitanacyclobutene intermediate, resulting from [2+2] alkyne + Ti imido coupling, undergoes a second alkyne insertion followed by reductive elimination to yield pyrrole and a TiII species. The key component for catalytic turnover is the reoxidation of the TiII species to a TiIV imido via the disproportionation of an η2-diazene-TiII complex.

  20. Catalytic formal [2+2+1] synthesis of pyrroles from alkynes and diazenes via Ti(II)/Ti(IV) redox catalysis.

    PubMed

    Gilbert, Zachary W; Hue, Ryan J; Tonks, Ian A

    2016-01-01

    Pyrroles are structurally important heterocycles. However, the synthesis of polysubstituted pyrroles is often challenging. Here, we report a multicomponent, Ti-catalysed formal [2+2+1] reaction of alkynes and diazenes for the oxidative synthesis of penta- and trisubstituted pyrroles: a nitrenoid analogue to classical Pauson-Khand-type syntheses of cyclopentenones. Given the scarcity of early transition-metal redox catalysis, preliminary mechanistic studies are presented. Initial stoichiometric and kinetic studies indicate that the mechanism of this reaction proceeds through a formally Ti(II)/Ti(IV) redox catalytic cycle, in which an azatitanacyclobutene intermediate, resulting from [2+2] alkyne + Ti imido coupling, undergoes a second alkyne insertion followed by reductive elimination to yield pyrrole and a Ti(II) species. The key component for catalytic turnover is the reoxidation of the Ti(II) species to a Ti(IV) imido via the disproportionation of an η(2)-diazene-Ti(II) complex.

  1. Defect-induced wetting on BaF 2(111) and CaF 2(111) at ambient conditions

    NASA Astrophysics Data System (ADS)

    Cardellach, M.; Verdaguer, A.; Fraxedas, J.

    2011-12-01

    The interaction of water with freshly cleaved (111) surfaces of isostructural BaF2 and CaF2 single crystals at ambient conditions (room temperature and under controlled humidity) has been studied using scanning force microscopy in different operation modes and optical microscopy. Such surfaces exhibit contrasting behaviors for both materials: while on BaF2(111) two-dimensional water layers are formed after accumulation at step edges, CaF2(111) does not promote the formation of such layers. We attribute such opposed behavior to lattice match (mismatch) between hexagonal water ice and the hexagonal (111) surfaces of BaF2(CaF2). Optical microscope images reveal that this behavior also determines the way the surfaces become wetted at a macroscopic level.

  2. Alternate wetting and drying of rice reduced CH4 emissions but triggered N2O peaks in a clayey soil of central Italy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Reducing CH4 and N2O emissions from rice cropping systems while sustaining production levels with less water requires a better understanding of the key processes involved. Alternate wetting and drying (AWD) irrigation is one promising practice that has been shown to reduce CH4 emissions. However, li...

  3. Catalytic evaluation of promoted CeO2-ZrO2 by transition, alkali, and alkaline-earth metal oxides for diesel soot oxidation.

    PubMed

    Alinezhadchamazketi, Ali; Khodadadi, Abas Ali; Mortazavi, Yadollah; Nemati, Ahmad

    2013-12-01

    Series of mixed metal oxides were synthesized by gel-combustion method and their catalytic activities for soot oxidation were investigated. The catalysts were M-Ce-Zr (M = Mn, Cu, Fe, K, Ba, Sr), and xK-20Mn-Ce-Zr (x = 0, 5, 10, 20), they were characterized by XRD, SEM, TPR and BET surface area techniques. The results of soot temperature programmed oxidation (TPO) in an O2 oxidizing atmosphere indicate that K-Ce-Zr has the highest catalytic activity for soot oxidation under loose contact condition, due to enhancement of the soot and catalyst contacts. On the other hand, under a tight contact condition, Mn-Ce-Zr and Cu-Ce-Zr nano-composites have high activities for soot oxidation and lower the soot TPO peak temperatures by about 280 and 270 degrees C, respectively, as compared to non-catalytic soot oxidation. Furthermore, the addition of up to 10 wt.% potassium oxides into Mn-Ce-Zr increases its catalytic activity and further reduces the soot TPO peak temperature by about 40 degrees C under loose contact condition.

  4. Synthesis, crystal structure and catalytic behavior of homo- and heteronuclear coordination polymers [M(tdc)(bpy)] (M2+ = Fe2+, Co2+, Zn2+, Cd2+; tdc2- = 2,5-thiophenedicarboxylate).

    PubMed

    Kettner, Florian; Worch, Christian; Moellmer, Jens; Gläser, Roger; Staudt, Reiner; Krautscheid, Harald

    2013-08-01

    A series of isostructural 3D coordination polymers (3)∞[M(tdc)(bpy)] (M(2+) = Zn(2+), Cd(2+), Co(2+), Fe(2+); tdc(2-) = 2,5-thiophenedicarboxylate; bpy = 4,4'-bipyridine) was synthesized and characterized by X-ray diffraction, thermal analysis, and gas adsorption measurements. The materials show high thermal stability up to approximately 400 °C and a solvent induced phase transition. Single crystal X-ray structure determination was successfully performed for all compounds after the phase transition. In the zinc-based coordination polymer, various amounts of a second type of metal ions such as Co(2+) or Fe(2+) could be incorporated. Furthermore, the catalytic behavior of the homo- and heteronuclear 3D coordination polymers in an oxidation model reaction was investigated.

  5. Synthesis, Characterization and Catalytic Properties of Attapulgite/CeO2 Nanocomposite Films for Decomposition of Rhodamine B.

    PubMed

    Lu, Xiaowang; Li, Xiazhang; Qian, Junchao; Chen, Feng; Chen, Zhigang

    2015-08-01

    ATP(attapulgite)/CeO2 nanocomposite films were prepared on the glass substrates via a sol-gel and dip-coating route. The ATP/CeO2 nanocomposite films were characterized by Powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS), transmission electron microscopy (TEM), atomic force microscopy (AFM) and fourier transform infrared spectroscopy (FT-IR). The results showed that the ATP/CeO2 nanocomposite films were free from cracks and the nanoparticles were attached onto the surface of attapulgite. The ATP/CeO2 nanocomposite films displayed excellent catalytic activity for decomposition of Rhodamine B. The COD (chemical oxygen demand) removal rate of rhodamine B using ATP/CeO2 nanocomposite films as catalyst reached as high as 94% when the weight ratio of ATP to CeO2 was 2:1.

  6. Dispersion and activity of molybdena-alumina catalysts prepared by impregnation and solid/solid wetting methods

    SciTech Connect

    Reddy, B.M.; Reddy, E.P.; Srinivas, S.T. )

    1992-07-01

    Alumina-supported molybdena catalysts were prepared by both the standard incipient wetness method and by mixing MoO{sub 3} and Al{sub 2}O{sub 3} (solid/solid wetting), followed by thermal treatment of 500 C under dry or wet O{sub 2} atmospheric conditions. These catalysts were characterized by means of O{sub 2} chemisorption at {minus}78 C, CO{sub 2} uptake at ambient temperature, X-ray diffraction (XRD), and electron spin resonance (ESR) techniques. Activities of the catalysts were determined for partial oxidation of methanol and hydrodesulfurization of thiophene at atmospheric pressure. XRD results suggest high dispersion of Mo-oxide on alumina support irrespective of their method of preparation. However, O{sub 2} and CO{sub 2} uptake measurements reveal partial coverage of the Al{sub 2}O{sub 3} support surface by the Mo-oxide phase and appear to depend on the gas atmosphere (wet or dry O{sub 2}) during heat treatments in case of solid/solid wetting method. ESR, oxygen and carbon dioxide uptakes and the catalytic properties clearly demonstrate that spontaneous spreading of MoO{sub 3} on the Al{sub 2}O{sub 3} support at 500 C in the presence of wet O{sub 2} is a most effective alternative method for preparing molybdenum-alumina catalysts.

  7. Recovery of SO2 and MgO from By-Products of MgO Wet Flue Gas Desulfurization.

    PubMed

    Yan, Liyun; Lu, Xiaofeng; Wang, Quanhai; Guo, Qiang

    2014-11-01

    An industrial demonstration unit using natural gas as a heat source was built to calcine the by-products of MgO wet flue gas desulfurization from power plants; influencing factors on the SO2 content in calciner gas were comprehensively analyzed; and an advantageous recycling condition of MgO and SO2 from by-products was summarized. Results showed that the SO2 content in the calciner gas was increased by more than 10 times under a lower excess air coefficient, a higher feed rate, a lower crystal water in by-products, and a higher feed port position. For the tests conducted under the excess air coefficient above and below one, the effect of the furnace temperature on the SO2 content in the calciner gas was reversed. Results of activity analysis indicate that particles of MgO generated under the calcination temperature of 900-1,000°C had a high activity. In contrast, due to the slight sintering, MgO generated under the calcination temperature of 1,100°C had a low activity. To recycle SO2 as well as MgO, a temperature range of 900-927°C for TE103 is proposed. These studies will prompt the desulfurization market diversification, reduce the sulfur's dependence on imports for making sulfuric acid, be meaningful to balance the usage of the natural resource in China, and be regarded as a reference for the development of this technology for other similar developing countries.

  8. Recovery of SO2 and MgO from By-Products of MgO Wet Flue Gas Desulfurization

    PubMed Central

    Yan, Liyun; Lu, Xiaofeng; Wang, Quanhai; Guo, Qiang

    2014-01-01

    Abstract An industrial demonstration unit using natural gas as a heat source was built to calcine the by-products of MgO wet flue gas desulfurization from power plants; influencing factors on the SO2 content in calciner gas were comprehensively analyzed; and an advantageous recycling condition of MgO and SO2 from by-products was summarized. Results showed that the SO2 content in the calciner gas was increased by more than 10 times under a lower excess air coefficient, a higher feed rate, a lower crystal water in by-products, and a higher feed port position. For the tests conducted under the excess air coefficient above and below one, the effect of the furnace temperature on the SO2 content in the calciner gas was reversed. Results of activity analysis indicate that particles of MgO generated under the calcination temperature of 900–1,000°C had a high activity. In contrast, due to the slight sintering, MgO generated under the calcination temperature of 1,100°C had a low activity. To recycle SO2 as well as MgO, a temperature range of 900–927°C for TE103 is proposed. These studies will prompt the desulfurization market diversification, reduce the sulfur's dependence on imports for making sulfuric acid, be meaningful to balance the usage of the natural resource in China, and be regarded as a reference for the development of this technology for other similar developing countries. PMID:25371652

  9. Catalytic Asymmetric Synthesis of Cyclopentyl β-Amino Esters by [3+2] Cycloaddition of Enecarbamates with Electrophilic Metalloenolcarbene Intermediates.

    PubMed

    Deng, Yongming; Yglesias, Matthew V; Arman, Hadi; Doyle, Michael P

    2016-08-16

    Chiral cyclopentyl β-amino esters are formed catalytically by [3+2] cycloaddition reactions of enecarbamates with electrophilic metalloenolcarbenes in high yield with up to 98 % ee and excellent diastereocontrol. Use of β-silyl-substituted enoldiazoacetates with a chiral dirhodium catalyst and trans-β-arylvinylcarbamates are optimal for this transformation, which occurs with hydrogen-bond association between the vinylcarbamate and the intermediate metalloenolcarbene. Reductive conversion of the protected amino esters forms highly functionalized cyclopentyl β-amino acids and 3-aminocyclopentanones.

  10. A Redox 2-Cys Mechanism Regulates the Catalytic Activity of Divergent Cyclophilins1[W

    PubMed Central

    Campos, Bruna Medéia; Sforça, Mauricio Luis; Ambrosio, Andre Luis Berteli; Domingues, Mariane Noronha; Brasil de Souza, Tatiana de Arruda Campos; Barbosa, João Alexandre Ribeiro Gonçalvez; Leme, Adriana Franco Paes; Perez, Carlos Alberto; Whittaker, Sara Britt-Marie; Murakami, Mario Tyago; Zeri, Ana Carolina de Matos; Benedetti, Celso Eduardo

    2013-01-01

    The citrus (Citrus sinensis) cyclophilin CsCyp is a target of the Xanthomonas citri transcription activator-like effector PthA, required to elicit cankers on citrus. CsCyp binds the citrus thioredoxin CsTdx and the carboxyl-terminal domain of RNA polymerase II and is a divergent cyclophilin that carries the additional loop KSGKPLH, invariable cysteine (Cys) residues Cys-40 and Cys-168, and the conserved glutamate (Glu) Glu-83. Despite the suggested roles in ATP and metal binding, the functions of these unique structural elements remain unknown. Here, we show that the conserved Cys residues form a disulfide bond that inactivates the enzyme, whereas Glu-83, which belongs to the catalytic loop and is also critical for enzyme activity, is anchored to the divergent loop to maintain the active site open. In addition, we demonstrate that Cys-40 and Cys-168 are required for the interaction with CsTdx and that CsCyp binds the citrus carboxyl-terminal domain of RNA polymerase II YSPSAP repeat. Our data support a model where formation of the Cys-40-Cys-168 disulfide bond induces a conformational change that disrupts the interaction of the divergent and catalytic loops, via Glu-83, causing the active site to close. This suggests a new type of allosteric regulation in divergent cyclophilins, involving disulfide bond formation and a loop-displacement mechanism. PMID:23709667

  11. Rapid 2D incoherent mirror fabrication by laser interference lithography and wet etching for III-V MQW solar cells

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Freundlich, Alex

    2016-03-01

    Optimization of non-planar antireflective coating and back- (or front-) surface texturing are widely studied as advanced light management approach to further reduce the reflection losses and increase the sunlight absorption path in solar cells. Rear reflectors have been developed from coherent mirrors to incoherent mirrors in order to further increase light path, which can significantly improve the efficiency and allow for much thinner devices. A Lambertian surface, which has the most random texture, can theoretically raise the light path to 4n2 times that of a smooth surface. It's a challenge however to fabricate ideal Lambertian texture, especially in a fast and low cost way. In this work, a method is developed to overcome this challenge that combines the use of laser interference lithography (LIL) and selective wet etching. This approach allows for a rapid (10 min) wafer scale (3 inch wafer) texture processing with sub-wavelength (nano)-scale control of the pattern and the pitch. The technique appears as being particularly attractive for the development of ultrathin III-V devices, or in overcoming the weak sub-bandgap absorption in devices incorporating quantum dots or quantum wells. The structure of the device is demonstrated, without affecting active layers.

  12. Catalytic decomposition of gaseous 1,2-dichlorobenzene over CuOx/TiO₂ and CuOx/TiO₂-CNTs catalysts: Mechanism and PCDD/Fs formation.

    PubMed

    Wang, Qiu-lin; Huang, Qun-xing; Wu, Hui-fan; Lu, Sheng-yong; Wu, Hai-long; Li, Xiao-dong; Yan, Jian-hua

    2016-02-01

    Gaseous 1,2-dichlorobenzene (1,2-DCBz) was catalytically decomposed in a fixed-bed catalytic reactor using composite copper-based titanium oxide (CuOx/TiO2) catalysts with different copper ratios. Carbon nanotubes (CNTs) were introduced to produce novel CuOx/TiO2-CNTs catalysts by the sol-gel method. The catalytic performances of CuOx/TiO2 and CuOx/TiO2-CNTs on 1,2-DCBz oxidative destruction under different temperatures (150-350 °C) were experimentally examined and the correlation between catalyst structure and catalytic activity was characterized and the role of oxygen in catalytic reaction was discussed. Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) generation during 1,2-DCBz catalytic oxidation by CuOx/TiO2-CNTs composite catalyst was also examined. Results indicate that the 1,2-DCBz destruction/removal efficiencies of CuOx (4 wt%)/TiO2 catalyst at 150 °C and 350 °C with a GHSV of 3400 h(-1) are 59% and 94% respectively and low-temperature (150 °C) catalytic activity of CuOx/TiO2 on 1,2-DCBz oxidation can be improved from 59 to 77% when CNTs are introduced. Furthermore, oxygen either in catalyst or from reaction atmosphere is indispensible in reaction. The former is offered to activate and oxidize the 1,2-DCBz adsorbed on catalyst, thus can be generally consumed during reaction and the oxygen content in catalyst is observed lost from 39.9 to 35.0 wt% after reacting under inert atmosphere; the latter may replenish the vacancy in catalyst created by the consumed oxygen thus extends the catalyst life and raises the destruction/removal efficiency. The introduction of CNTs also increases the Cu(2+)/Cu(+) ratio, chemisorbed oxygen concentration and surface lattice oxygen binding energy which are closely related with catalytic activity. PCDD/Fs is confirmed to be formed when 1,2-DCBz catalytically oxidized by CuOx/TiO2-CNTs composite catalyst with sufficient oxygen (21%), proper temperature (350 °C) and high concentration of 1,2-DCBz feed (120 ppm

  13. Comparative Reactivity Study of Natural Silicate Minerals in Wet Supercritical CO2 By In Situ Infrared Spectroscopy

    NASA Astrophysics Data System (ADS)

    Thompson, C.; Schaef, T.; Miller, Q. R.; Loring, J. S.; Wang, Z.; Johnson, K. T.; McGrail, P.

    2012-12-01

    Long-term storage of CO2 in deep geologic reservoirs is one of the strategies being developed and implemented for reducing anthropogenic emissions of CO2 into the atmosphere. Reservoirs containing basalt or peridotite have the potential to permanently entrap the CO2 as silicate minerals react with the CO2 and formation waters to form stable carbonate minerals. Although the relevant reactions have been well studied in the aqueous phase, comparatively little work has focused on silicate mineral reactivity in the CO2-rich fluid containing dissolved water at conditions relevant to geologic carbon sequestration. In this study, we used in situ infrared spectroscopy to investigate the carbonation of naturally occurring samples of San Carlos olivine (Mg2SiO4), Bramble enstatite (MgSiO3), and a Hawaiian picritic basalt rich in olivine. To enhance reactivity, subsamples were micronized to obtain higher surface area materials, in the range of 14 to 23 m2g-1. Experiments were carried out at 50 °C and 91 bar by circulating a stream of dry or wet supercritical CO2 (scCO2) past a sample overlayer deposited on the window of a high-pressure infrared flow cell. Water concentrations ranged from 0% to 135% relative to saturation, and transmission-mode absorbance spectra were recorded as a function of time for 24 hours. In experiments with excess water, a controlled temperature gradient was used to intentionally condense a film of liquid water on the overlayers' surfaces. No discernible reaction was detected when the samples were exposed to dry scCO2. When water was added to the scCO2, a thin film of liquid-like water formed on the surfaces of each sample, followed by spectral evidence of carbonation. The extents of reaction were dependent on both the thickness of the water films and the materials being tested. The thinnest water film was associated with the Bramble enstatite, which also appeared minimally reactive. The Hawaiian picritic basalt was slightly more reactive but contained

  14. The effect of microstructural properties of CoCr2O4 spinel oxides on catalytic combustion of dichloromethane

    NASA Astrophysics Data System (ADS)

    Liu, Jing-Di; Zhang, Ting-Ting; Jia, Ai-Pin; Luo, Meng-Fei; Lu, Ji-Qing

    2016-04-01

    It was found that a series of spinel CoCr2O4 oxides were very active and selective for dichloromethane combustion, and the best performance was obtained on a catalyst calcined at 600 °C (with a areal specific reaction rate of 3.41 × 10-8 molCH2Cl2 s-1 m-2 at 220 °C). Quantitative analyses revealed that Cr3+/Cr6+ cations could partially substitute Co3+ cations in the octahedral sites of the spinel oxide at high-temperature calcination and thus to enhanced reducibility and surface acidity of the oxide, which synergistically governed the observed catalytic behaviors. Moreover, it was found that high valent Cr species (Cr6+) played very important role in the reaction, with a much higher turnover frequency (2.2 × 10-3 s-1) than that of the Cr3+ (0.56 × 10-3 s-1).

  15. Synthesis and characterization of Cu2O/Au and its application in catalytic reduction of 4-nitrophenol

    NASA Astrophysics Data System (ADS)

    Guo, X. H.; Ma, J. Q.; Ge, H. G.

    2015-08-01

    Monodispersed Cu2O spherical colloids with diameter of about 300 nm were prepared by a facile additive-assisted complex-precursor solution method. Core-shell structure Cu2O/Au composites, constructed by spherical Cu2O core and Au nanoparticles shell, were obtained via galvanic replacement method. The morphology, microstructure and optical properties of the Cu2O/Au composites were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectra and ultraviolet-visible absorption. The results showed that Au NPs with an average size of 12 nm were uniformly distributed on the surface of the Cu2O spheres with size about 300 nm. Cu2O/Au composites exhibit high catalytic activity toward 4-NP reduction at room temperature.

  16. The effect of several parameters on catalytic denitrification of water by the use of H2 in the presence of O2 over metal supported catalysts.

    PubMed

    Theologides, C P; Savva, P G; Olympiou, G G; Pantelidou, N A; Constantinou, B K; Chatziiona, V K; Valanidou, L Y; Piskopianou, C T; Costa, C N

    2013-01-01

    The present paper involves a detailed study of the selective catalytic reduction of nitrates in aqueous mediums by the use of H2 in the presence of O2 over monometallic and bimetallic supported catalysts. In this study, an attempt has been made to improve the denitrification efficiency (XNO3(-), SN2) of several catalysts by regulating some experimental parameters that are involved in the process. Therefore, the effects of the type of reactor (semi-batch reactor vs continuous flow reactor), the nature of the active phase (Pd, Cu, and Pd-Cu) and the particle size of γ-Al2O3 spheres (particle diameter = 1.8 mm and 3 mm) on catalytic activity and reaction selectivity, as well as the adsorption capacity of γ-Al2O3 spheres for nitrates, were examined. As the review indicates, most of the research has so far been conducted on batch or semi-batch reactors. This study successfully demonstrates the benefits of using a continuous flow reactor in terms of catalytic activity (XNO3(-), %) and reaction selectivity (SN2, %). Another important aspect of this study is the crucial role of bimetallic Pd-Cu clusters for the prevention of NH4(+) formation. Moreover, the use of 1.8 mm diameter γ-Al2O3 spheres as a support was proved to significantly enhance the catalytic performance of bimetallic Pd-Cu catalysts towards nitrate reduction compared to 3 mm diameter γ-Al2O3 spheres. This difference may be attributed to mass (NO3(-), OH(-)) transfer effects (external mass transfer phenomena). PMID:24292483

  17. PREFACE: Wetting: introductory note

    NASA Astrophysics Data System (ADS)

    Herminghaus, S.

    2005-03-01

    The discovery of wetting as a topic of physical science dates back two hundred years, to one of the many achievements of the eminent British scholar Thomas Young. He suggested a simple equation relating the contact angle between a liquid surface and a solid substrate to the interfacial tensions involved [1], γlg cos θ = γsg - γsl (1) In modern terms, γ denotes the excess free energy per unit area of the interface indicated by its indices, with l, g and s corresponding to the liquid, gas and solid, respectively [2]. After that, wetting seems to have been largely ignored by physicists for a long time. The discovery by Gabriel Lippmann that θ may be tuned over a wide range by electrochemical means [3], and some important papers about modifications of equation~(1) due to substrate inhomogeneities [4,5] are among the rare exceptions. This changed completely during the seventies, when condensed matter physics had become enthusiastic about critical phenomena, and was vividly inspired by the development of the renormalization group by Kenneth Wilson [6]. This had solved the long standing problem of how to treat fluctuations, and to understand the universal values of bulk critical exponents. By inspection of the critical exponents of the quantities involved in equation~(1), John W Cahn discovered what he called critical point wetting: for any liquid, there should be a well-defined transition to complete wetting (i.e., θ = 0) as the critical point of the liquid is approached along the coexistence curve [7]. His paper inspired an enormous amount of further work, and may be legitimately viewed as the entrance of wetting into the realm of modern physics. Most of the publications directly following Cahn's work were theoretical papers which elaborated on wetting in relation to critical phenomena. A vast amount of interesting, and in part quite unexpected, ramifications were discovered, such as the breakdown of universality in thin film systems [8]. Simultaneously, a number

  18. A PTPN11 allele encoding a catalytically impaired SHP2 protein in a patient with a Noonan syndrome phenotype

    PubMed Central

    Edwards, Jonathan J.; Martinelli, Simone; Pannone, Luca; Lo, Ivan Fai-Man; Shi, Lisong; Edelmann, Lisa; Tartaglia, Marco; Luk, Ho-Ming; Gelb, Bruce D.

    2014-01-01

    The RASopathies are a relatively common group of phenotypically similar and genetically related autosomal dominant genetic syndromes caused by missense mutations affecting genes participating in the RAS/mitogen-activated protein kinase (MAPK) pathway that include Noonan syndrome (NS) and Noonan syndrome with multiple lentigines (NSML, formerly LEOPARD syndrome). NS and NSML can be difficult to differentiate during infancy, but the presence of multiple lentigines, café au lait spots, and specific cardiac defects facilitate the diagnosis. Furthermore, individual PTPN11 missense mutations are highly specific to each syndrome and engender opposite biochemical alterations on the function of SHP-2, the protein product of that gene. Here, we report on a 5-year-old male with two de novo PTPN11 mutations in cis, c.1471C>T (p.Pro491Ser) and c.1492C>T (p.Arg498Trp), which are associated with NS and NSML, respectively. This boy’s phenotype is intermediate between NS and NSML with facial dysmorphism, short stature, mild global developmental delay, pulmonic stenosis and deafness but absence of café au lait spots or lentigines. The double-mutant SHP-2 was found to be catalytically impaired. This raises the question of whether clinical differences between NS and NSML can be ascribed solely to the relative SHP-2 catalytic activity. PMID:24891296

  19. Few-Layer MoSe2 Possessing High Catalytic Activity towards Iodide/Tri-iodide Redox Shuttles

    PubMed Central

    Lee, Lawrence Tien Lin; He, Jian; Wang, Baohua; Ma, Yaping; Wong, King Young; Li, Quan; Xiao, Xudong; Chen, Tao

    2014-01-01

    Due to the two-dimensional confinement of electrons, single- and few-layer MoSe2 nanostructures exhibit unusual optical and electrical properties and have found wide applications in catalytic hydrogen evolution reaction, field effect transistor, electrochemical intercalation, and so on. Here we present a new application in dye-sensitized solar cell as catalyst for the reduction of I3− to I− at the counter electrode. The few-layer MoSe2 is fabricated by surface selenization of Mo-coated soda-lime glass. Our results show that the few-layer MoSe2 displays high catalytic efficiency for the regeneration of I− species, which in turn yields a photovoltaic energy conversion efficiency of 9.00%, while the identical photoanode coupling with “champion” electrode based on Pt nanoparticles on FTO glass generates efficiency only 8.68%. Thus, a Pt- and FTO-free counter electrode outperforming the best conventional combination is obtained. In this electrode, Mo film is found to significantly decrease the sheet resistance of the counter electrode, contributing to the excellent device performance. Since all of the elements in the electrode are of high abundance ratios, this type of electrode is promising for the fabrication of large area devices at low materials cost. PMID:24525919

  20. Low-temperature gas from marine shales: wet gas to dry gas over experimental time

    PubMed Central

    2009-01-01

    Marine shales exhibit unusual behavior at low temperatures under anoxic gas flow. They generate catalytic gas 300° below thermal cracking temperatures, discontinuously in aperiodic episodes, and lose these properties on exposure to trace amounts of oxygen. Here we report a surprising reversal in hydrocarbon generation. Heavy hydrocarbons are formed before light hydrocarbons resulting in wet gas at the onset of generation grading to dryer gas over time. The effect is moderate under gas flow and substantial in closed reactions. In sequential closed reactions at 100°C, gas from a Cretaceous Mowry shale progresses from predominately heavy hydrocarbons (66% C5, 2% C1) to predominantly light hydrocarbons (56% C1, 8% C5), the opposite of that expected from desorption of preexisting hydrocarbons. Differences in catalyst substrate composition explain these dynamics. Gas flow should carry heavier hydrocarbons to catalytic sites, in contrast to static conditions where catalytic sites are limited to in-place hydrocarbons. In-place hydrocarbons and their products should become lighter with conversion thus generating lighter hydrocarbon over time, consistent with our experimental results. We recognize the similarities between low-temperature gas generation reported here and the natural progression of wet gas to dry gas over geologic time. There is now substantial evidence for natural catalytic activity in source rocks. Natural gas at thermodynamic equilibrium and the results reported here add to that evidence. Natural catalysis provides a plausible and unique explanation for the origin and evolution of gas in sedimentary basins. PMID:19900271

  1. Low-temperature gas from marine shales: wet gas to dry gas over experimental time.

    PubMed

    Mango, Frank D; Jarvie, Daniel M

    2009-01-01

    Marine shales exhibit unusual behavior at low temperatures under anoxic gas flow. They generate catalytic gas 300 degrees below thermal cracking temperatures, discontinuously in aperiodic episodes, and lose these properties on exposure to trace amounts of oxygen. Here we report a surprising reversal in hydrocarbon generation. Heavy hydrocarbons are formed before light hydrocarbons resulting in wet gas at the onset of generation grading to dryer gas over time. The effect is moderate under gas flow and substantial in closed reactions. In sequential closed reactions at 100 degrees C, gas from a Cretaceous Mowry shale progresses from predominately heavy hydrocarbons (66% C5, 2% C1) to predominantly light hydrocarbons (56% C1, 8% C5), the opposite of that expected from desorption of preexisting hydrocarbons. Differences in catalyst substrate composition explain these dynamics. Gas flow should carry heavier hydrocarbons to catalytic sites, in contrast to static conditions where catalytic sites are limited to in-place hydrocarbons. In-place hydrocarbons and their products should become lighter with conversion thus generating lighter hydrocarbon over time, consistent with our experimental results. We recognize the similarities between low-temperature gas generation reported here and the natural progression of wet gas to dry gas over geologic time. There is now substantial evidence for natural catalytic activity in source rocks. Natural gas at thermodynamic equilibrium and the results reported here add to that evidence. Natural catalysis provides a plausible and unique explanation for the origin and evolution of gas in sedimentary basins.

  2. Wetting or non-wetting liquid?

    NASA Astrophysics Data System (ADS)

    Karmakov, Iordan

    2000-11-01

    What factors determine whether or not a particular liquid will wet a particular surface? Is it possible for a meniscus in a capillary to become convex from concave? What would you have to do to flatten it out? In university courses in physics there is often a lack of example or comment concerning the influence of temperature on the characteristics of liquid surface tension. For example, would temperature be a factor in changing wetting? This article describes an experiment that illustrates the conversion of isopropyl alcohol from a wetting state to a non-wetting state as a result of the influence of temperature on the characteristics of the liquid.

  3. Preliminary X-ray crystallographic studies of BthTX-II, a myotoxic Asp49-phospholipase A{sub 2} with low catalytic activity from Bothrops jararacussu venom

    SciTech Connect

    Corrêa, L. C.; Marchi-Salvador, D. P.; Cintra, A. C. O.; Soares, A. M.

    2006-08-01

    A myotoxic Asp49-PLA{sub 2} with low catalytic activity from B. jararacussu (BthTX-II) was crystallized in the monoclinic crystal system; a complete X-ray diffraction data set was collected and a molecular-replacement solution was obtained. The oligomeric structure of BthTX-II resembles those of the Asp49-PLA{sub 2} PrTX-III and all bothropic Lys49-PLA{sub 2}s. For the first time, a complete X-ray diffraction data set has been collected from a myotoxic Asp49-phospholipase A{sub 2} (Asp49-PLA{sub 2}) with low catalytic activity (BthTX-II from Bothrops jararacussu venom) and a molecular-replacement solution has been obtained with a dimer in the asymmetric unit. The quaternary structure of BthTX-II resembles the myotoxin Asp49-PLA{sub 2} PrTX-III (piratoxin III from B. pirajai venom) and all non-catalytic and myotoxic dimeric Lys49-PLA{sub 2}s. In contrast, the oligomeric structure of BthTX-II is different from the highly catalytic and non-myotoxic BthA-I (acidic PLA{sub 2} from B. jararacussu). Thus, comparison between these structures should add insight into the catalytic and myotoxic activities of bothropic PLA{sub 2}s.

  4. Catalytic properties of NiSO{sub 4}/ZrO{sub 2} promoted with Fe{sub 2}O{sub 3} for acid catalysis

    SciTech Connect

    Sohn, Jong Rack . E-mail: jrsohn@knu.ac.kr; Lim, Jun Seob

    2006-07-13

    A series of catalysts, NiSO{sub 4}/Fe{sub 2}O{sub 3}-ZrO{sub 2}, for acid catalysis were prepared by the impregnation method, where support, Fe{sub 2}O{sub 3}-ZrO{sub 2} was prepared by the co-precipitation method using a mixed aqueous solution of zirconium oxychloride and iron nitrate solution followed by adding an aqueous ammonia solution. No diffraction line of nickel sulfate was observed up to 20 wt.%, indicating good dispersion of nickel sulfate on the surface of Fe{sub 2}O{sub 3}-ZrO{sub 2}. The addition of nickel sulfate (or Fe{sub 2}O{sub 3}) to ZrO{sub 2} shifted the phase transition of ZrO{sub 2} from amorphous to tetragonal to higher temperature because of the interaction between nickel sulfate (or Fe{sub 2}O{sub 3}) and ZrO{sub 2}. 15-NiSO{sub 4}/Fe{sub 2}O{sub 3}-ZrO{sub 2} containing 15 wt.% NiSO{sub 4} and 5 mol% Fe{sub 2}O{sub 3}, and calcined at 700 deg. C exhibited maximum catalytic activities for both reactions, 2-propanol dehydration and cumene dealkylation. The catalytic activities for both reactions were correlated with the acidity of catalysts measured by the ammonia chemisorption method. The addition of Fe{sub 2}O{sub 3} up to 5 mol% enhanced the acidity, thermal property, and catalytic activities of NiSO{sub 4}/Fe{sub 2}O{sub 3}-ZrO{sub 2} gradually due to the interaction between Fe{sub 2}O{sub 3} and ZrO{sub 2} and consequent formation of Fe-O-Zr bond.

  5. Variation in foliar respiration and wood CO2 efflux rates among species and canopy layers in a wet tropical forest.

    PubMed

    Asao, Shinichi; Bedoya-Arrieta, Ricardo; Ryan, Michael G

    2015-02-01

    area to mass, can be extrapolated to the stand using total wood surface area. The temperature response of foliar respiration was similar for three of the four species, and wood CO2 efflux was similar between wet and dry seasons. For these species and this forest, vertical sampling may yield more accurate estimates than would temporal sampling. PMID:25597756

  6. Changes in wetting properties of alumina surface treated with DPPC in the presence of phospholipase A2 enzyme.

    PubMed

    Wiącek, Agnieszka Ewa

    2011-10-01

    Wetting properties of commercial Al(2)O(3) plates contacted with dipalmitoylphosphatidylcholine (DPPC) or DPPC+enzyme (phospholipase PLA(2)) in NaCl solution were determined by thin layer wicking and with the help of Washburn equation. Van Oss et al.'s approach to interfacial free energy interactions was applied to determining the solid surface free energy components. Wicking experiments were performed both for bare and alumina plates precontacted overnight with the probe liquid saturated vapours, as well as the untreated and DPPC (or DPPC+PLA(2)) treated alumina plates. For this purpose the penetration rates of n-octane, water and formamide were measured. From these experiments it resulted that original alumina surface is strongly polar with electron-donor interactions originating from the surface hydroxyl groups. Adsorption of DPPC on Al(2)O(3) plates slightly increased the hydrophobic character of the alumina surface (considerable decrease of the electron-donor, γ(s)(-) parameter and γ(s)(AB) component was visible) in such a way that the hydrocarbon chains were directed outwards and the polar part towards the alumina surface. However, after the enzyme action the products of DPPC hydrolysis by PLA(2) (palmitic acid and lysophosphatidylcholine) increased again the hydrophilic character of Al(2)O(3) surface (a minor increase in γ(s)(AB) component and drastic increase of the electron-donor γ(s)(-) parameter was noticeable). After treatment with DPPC or DPPC+enzyme PLA(2) solution the changes of the total surface free energy of alumina and its Lifshits-van der Waals (γ(s)(LW)) component were in the range 7-10 mJ/m(2), but the most considerable and delivering more interesting information were the changes of the electron-donor (γ(s)(-)) parameter ranging from 27 to 35 mJ/m(2). Moreover, the changes of the alumina surface wettability were dependent on the time of the enzyme contacting with DPPC in NaCl solution. On the basis of the obtained results it seems that

  7. Variation in foliar respiration and wood CO2 efflux rates among species and canopy layers in a wet tropical forest.

    PubMed

    Asao, Shinichi; Bedoya-Arrieta, Ricardo; Ryan, Michael G

    2015-02-01

    area to mass, can be extrapolated to the stand using total wood surface area. The temperature response of foliar respiration was similar for three of the four species, and wood CO2 efflux was similar between wet and dry seasons. For these species and this forest, vertical sampling may yield more accurate estimates than would temporal sampling.

  8. Catalytic Cycle Employing a TEMPO-Anion Complex to Obtain a Secondary Mg-O2 Battery.

    PubMed

    Shiga, Tohru; Hase, Yoko; Yagi, Yusuke; Takahashi, Naoko; Takechi, Kensuke

    2014-05-15

    Nonaqueous Mg-O2 batteries are suitable only as primary cells because MgO precipitates formed during discharging are not decomposed electrochemically at ambient temperatures. To address this problem, the present study examined the ability of the 2,2,6,6-tetramethylpiperidine-oxyl (TEMPO)-anion complex to catalyze the decomposition of MgO. It was determined that this complex was capable of chemically decomposing MgO at 60 °C. A catalytic cycle for the realization of a rechargeable Mg-O2 electrode was designed by combining the decomposition of MgO via the TEMPO-anion complex and the TEMPO-redox couple. This work also demonstrates that a nonaqueous Mg-O2 battery incorporating acrylate polymer having TEMPO side units in the cathode shows evidence of being rechargeable.

  9. Prospects for improving CO2 fixation in C3-crops through understanding C4-Rubisco biogenesis and catalytic diversity.

    PubMed

    Sharwood, Robert E; Ghannoum, Oula; Whitney, Spencer M

    2016-06-01

    By operating a CO2 concentrating mechanism, C4-photosynthesis offers highly successful solutions to remedy the inefficiency of the CO2-fixing enzyme Rubisco. C4-plant Rubisco has characteristically evolved faster carboxylation rates with low CO2 affinity. Owing to high CO2 concentrations in bundle sheath chloroplasts, faster Rubisco enhances resource use efficiency in C4 plants by reducing the energy and carbon costs associated with photorespiration and lowering the nitrogen investment in Rubisco. Here, we show that C4-Rubisco from some NADP-ME species, such as maize, are also of potential benefit to C3-photosynthesis under current and future atmospheric CO2 pressures. Realizing this bioengineering endeavour necessitates improved understanding of the biogenesis requirements and catalytic variability of C4-Rubisco, as well as the development of transformation capabilities to engineer Rubisco in a wider variety of food and fibre crops. PMID:27131319

  10. Catalytic activity of nuclear PLC-beta(1) is required for its signalling function during C2C12 differentiation.

    PubMed

    Ramazzotti, Giulia; Faenza, Irene; Gaboardi, Gian Carlo; Piazzi, Manuela; Bavelloni, Alberto; Fiume, Roberta; Manzoli, Lucia; Martelli, Alberto M; Cocco, Lucio

    2008-11-01

    Here we report that PLC-beta(1) catalytic activity plays a role in the increase of cyclin D3 levels and induces the differentiation of C2C12 skeletal muscle cells. PLC-beta(1) mutational analysis revealed the importance of His(331) and His(378) for the catalysis. The expression of PLC-beta(1) and cyclin D3 proteins is highly induced during the process of skeletal myoblast differentiation. We have previously shown that PLC-beta(1) activates cyclin D3 promoter during the differentiation of myoblasts to myotubes, indicating that PLC-beta(1) is a crucial regulator of the mouse cyclin D3 gene. We show that after insulin treatment cyclin D3 mRNA levels are lower in cells overexpressing the PLC-beta(1) catalytically inactive form in comparison to wild type cells. We describe a novel signalling pathway elicited by PLC-beta(1) that modulates AP-1 activity. Gel mobility shift assay and supershift performed with specific antibodies indicate that the c-jun binding site is located in a cyclin D3 promoter region specifically regulated by PLC-beta(1) and that c-Jun binding activity is significantly increased by insulin and PLC-beta(1) overexpression. Mutation of AP-1 site decreased the basal cyclin D3 promoter activity and eliminated its induction by insulin and PLC-beta(1). These results hint at the fact that PLC-beta(1) catalytic activity signals a c-jun/AP-1 target gene, i.e. cyclin D3, during myogenic differentiation.

  11. From hydrogenases to noble metal-free catalytic nanomaterials for H2 production and uptake.

    PubMed

    Le Goff, Alan; Artero, Vincent; Jousselme, Bruno; Tran, Phong Dinh; Guillet, Nicolas; Métayé, Romain; Fihri, Aziz; Palacin, Serge; Fontecave, Marc

    2009-12-01

    Interconversion of water and hydrogen in unitized regenerative fuel cells is a promising energy storage framework for smoothing out the temporal fluctuations of solar and wind power. However, replacement of presently available platinum catalysts by lower-cost and more abundant materials is a requisite for this technology to become economically viable. Here, we show that the covalent attachment of a nickel bisdiphosphine-based mimic of the active site of hydrogenase enzymes onto multiwalled carbon nanotubes results in a high-surface area cathode material with high catalytic activity under the strongly acidic conditions required in proton exchange membrane technology. Hydrogen evolves from aqueous sulfuric acid solution with very low overvoltages (20 millivolts), and the catalyst exhibits exceptional stability (more than 100,000 turnovers). The same catalyst is also very efficient for hydrogen oxidation in this environment, exhibiting current densities similar to those observed for hydrogenase-based materials.

  12. The Origin of the Catalytic Activity of a Metal Hydride in CO2 Reduction.

    PubMed

    Kato, Shunsuke; Matam, Santhosh Kumar; Kerger, Philipp; Bernard, Laetitia; Battaglia, Corsin; Vogel, Dirk; Rohwerder, Michael; Züttel, Andreas

    2016-05-10

    Atomic hydrogen on the surface of a metal with high hydrogen solubility is of particular interest for the hydrogenation of carbon dioxide. In a mixture of hydrogen and carbon dioxide, methane was markedly formed on the metal hydride ZrCoHx in the course of the hydrogen desorption and not on the pristine intermetallic. The surface analysis was performed by means of time-of-flight secondary ion mass spectroscopy and near-ambient pressure X-ray photoelectron spectroscopy, for the in situ analysis. The aim was to elucidate the origin of the catalytic activity of the metal hydride. Since at the initial stage the dissociation of impinging hydrogen molecules is hindered by a high activation barrier of the oxidised surface, the atomic hydrogen flux from the metal hydride is crucial for the reduction of carbon dioxide and surface oxides at interfacial sites. PMID:27061237

  13. Catalytic activity of an in vivo tumor targeted anti-CEA scFv::carboxypeptidase G2 fusion protein.

    PubMed

    Bhatia, J; Sharma, S K; Chester, K A; Pedley, R B; Boden, R W; Read, D A; Boxer, G M; Michael, N P; Begent, R H

    2000-02-15

    Antibody-directed enzyme prodrug therapy (ADEPT) targets an enzyme selectively to a tumor where it converts a relatively non-toxic prodrug to a potent cytotoxic drug. Previous clinical work using antibody-enzyme chemical conjugates has been limited by the moderate efficiency of tumor targeting of these molecules. To address this a recombinant fusion protein composed of MFE-23, an anti-carcinoembryonic antigen (CEA) single chain Fv (scFv) antibody, fused to the amino-terminus of the enzyme carboxypeptidase G2 (CPG2) has been constructed to achieve ADEPT in CEA-producing tumors. MFE-23::CPG2 fusion protein was overexpressed in Escherichia coli and purified using CEA affinity chromatography. Efficacy of MFE-23::CPG2 delivery to tumors in vivo was assessed by measuring catalytic activity after intravenous injection of purified MFE-23::CPG2 into nude mice bearing CEA-positive LS174T human colon adenocarcinoma xenografts. Recombinant MFE-23::CPG2 cleared rapidly from circulation and catalytic activity in extracted tissues showed tumor to plasma ratios of 1.5:1 (6 hr), 10:1 (24 hr), 19:1 (48 hr) and 12:1 (72 hr). (125)I-MFE-23::CPG2 was retained in kidney, liver and spleen but MFE-23::CPG2 catalytic activity was not, resulting in excellent tumor to normal tissue enzyme ratios 48 hr after injection. These were 371:1 (tumor to liver), 450:1 (tumor to lung), 562:1 (tumor to kidney), 1,477:1 (tumor to colon) and 1,618:1 (tumor to spleen). Favorable tumor : normal tissue ratios occurred at early time points when there was still 21% (24 hr) and 9.5% (48 hr) of the injected activity present per gram of tumor tissue. The high tumor concentrations and selective tumor retention of active enzyme delivered by MFE-23::CPG2 establish that this recombinant fusion protein has potential to give improved clinical efficiency for ADEPT.

  14. Wetting of Porous Solids.

    PubMed

    Patkar, Saket; Chaudhuri, Parag

    2013-01-10

    This paper presents a simple, three stage method to simulate the mechanics of wetting of porous solid objects, like sponges and cloth, when they interact with a fluid. In the first stage, we model the absorption of fluid by the object when it comes in contact with the fluid. In the second stage, we model the transport of absorbed fluid inside the object, due to diffusion, as a flow in a deforming, unstructured mesh. The fluid diffuses within the object depending on saturation of its various parts and other body forces. Finally, in the third stage, over-saturated parts of the object shed extra fluid by dripping. The simulation model is motivated by the physics of imbibition of fluids into porous solids in the presence of gravity. It is phenomenologically capable of simulating wicking and imbibition, dripping, surface flows over wet media, material weakening and volume expansion due to wetting. The model is inherently mass conserving and works for both thin 2D objects like cloth and for 3D volumetric objects like sponges. It is also designed to be computationally efficient and can be easily added to existing cloth, soft body and fluid simulation pipelines. PMID:23319518

  15. Wetting of porous solids.

    PubMed

    Patkar, Saket; Chaudhuri, Parag

    2013-09-01

    This paper presents a simple, three stage method to simulate the mechanics of wetting of porous solid objects, like sponges and cloth, when they interact with a fluid. In the first stage, we model the absorption of fluid by the object when it comes in contact with the fluid. In the second stage, we model the transport of absorbed fluid inside the object, due to diffusion, as a flow in a deforming, unstructured mesh. The fluid diffuses within the object depending on saturation of its various parts and other body forces. Finally, in the third stage, oversaturated parts of the object shed extra fluid by dripping. The simulation model is motivated by the physics of imbibition of fluids into porous solids in the presence of gravity. It is phenomenologically capable of simulating wicking and imbibition, dripping, surface flows over wet media, material weakening, and volume expansion due to wetting. The model is inherently mass conserving and works for both thin 2D objects like cloth and for 3D volumetric objects like sponges. It is also designed to be computationally efficient and can be easily added to existing cloth, soft body, and fluid simulation pipelines. PMID:23846102

  16. Luminescent property and catalytic activity of Ru(II) carbonyl complexes containing N, O donor of 2-hydroxy-1-naphthylideneimines

    NASA Astrophysics Data System (ADS)

    Sivagamasundari, M.; Ramesh, R.

    2007-05-01

    The reaction of the chelating ligands (obtained by the condensation of 2-hydroxy-1-naphthaldehyde with various primary amines) with [RuHCl(CO)(EPh 3) 2(B)] (where E = P; B = PPh 3, py or pip: E = As; B = AsPh 3) in benzene afforded new stable ruthenium(II) carbonyl complexes of the general formula [Ru(Cl)(CO)(EPh 3)(B)(L)] (L = anion of bidentate Schiff bases). The structure of the new complexes was investigated using elemental analyses, spectral (FT-IR, UV-vis and 1H NMR) and electrochemical studies and is found to be octahedral. All the metal complexes exhibit characteristic MLCT absorption and luminescence bands in the visible region. The luminescence efficiency of the ruthenium(II) complexes was explained based on the ligand environment around the metal ion. These complexes catalyze oxidation of primary and secondary alcohols into their corresponding carbonyl compounds in the presence of N-methylmorpholine- N-oxide (NMO) as the source of oxygen. The formation of high valent Ru IVdbnd O species as a catalytic intermediate is proposed for the catalytic process.

  17. Catalytic dechlorination of 2,4-dichlorophenol by Pd/Fe bimetallic nanoparticles in the presence of humic acid.

    PubMed

    Zhang, Zhen; Shen, Qiaohui; Cissoko, Naman; Wo, Jingjing; Xu, Xinhua

    2010-10-15

    Pd/Fe bimetallic nanoparticles were synthesized for treatment of 2,4-dichlorophenol (2,4-DCP) in the presence of humic acid (HA), in order to understand their applicability for in situ remediation of groundwater. In this case, 2,4-DCP was catalytically dechlorinated to form the final products--phenol (P) via two intermediates, namely o-chlorophenol (o-CP) and p-chlorophenol (p-CP). We demonstrated that the carbon mass balances during the dechlorination were in the range of 82-91%, and other carbons were absorbed on the surface of Pd/Fe bimetallic nanoparticles. Our results suggest the dechlorination reaction of 2,4-DCP by Pd/Fe bimetallic nanoparticles in the presence of HA followed pseudo-first-order kinetics. HA competed for reaction sites on the Pd/Fe bimetallic nanoparticles with 2,4-DCP, and thus reduced the efficiency and rate of the dechlorination of 2,4-DCP. Efficiencies of dechlorination and phenol formations increased significantly as the Pd content increased from 0.10 wt.%, 0.15 wt.% to 0.20 wt.%, the removal percentage of 2,4-DCP increased from 70.4%, 98.4% to 99.4% within 300 min, respectively, the nitrate (NO(3)(-)) content in water also has a significant impact on 2,4-DCP dechlorination efficiency. Our results show that no other intermediates were generated besides Cl(-), o-CP, p-CP and phenol during the catalytic dechlorination of 2,4-DCP.

  18. Catalytic degradation of gaseous benzene by using TiO2/goethite immobilized on palygorskite: Preparation, characterization and mechanism

    NASA Astrophysics Data System (ADS)

    Ma, Jianzhong; Zhu, Chengzhu; Lu, Jun; Liu, Haibo; Huang, Li; Chen, Tianhu; Chen, Dong

    2015-11-01

    The nano-TiO2/goethite/palygorskite catalysts were prepared by sol-gel method. The morphology and structure of the catalysts were analyzed by X-ray diffraction (XRD), UV-Vis reflection spectrometer, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and N2 adsorption-desorption measurement. The results indicated that the self-made catalysts had excellent catalytic performance on gaseous benzene degradation. In the case of benzene concentration at 30 mg/m3, the degradation efficiency, over TiO2/goethite/palygorskite composite with mass ratio of 10:5:5, reached 70.4% after 180 min 254 nm UV irradiation. The reaction mechanism and kinetics study showed that palygorskite/goethite/TiO2 composites photocatalytic degradation benzene was mainly caused by oxidizing property of electron-holes and oxygen synergy effect.

  19. Photochemical and electrochemical catalytic reduction of CO2 with NHC-containing dicarbonyl rhenium(i) bipyridine complexes.

    PubMed

    Maurin, Antoine; Ng, Chi-On; Chen, Lingjing; Lau, Tai-Chu; Robert, Marc; Ko, Chi-Chiu

    2016-10-01

    The electrochemical and photochemical catalytic reductions of CO2 using N,O and N,S-NHC-containing dicarbonyl rhenium(i) bipyridine complexes have been investigated. By replacing the carbonyl ligand in tricarbonyl rhenium(i) complexes with a weaker π-accepting ligand, the characteristic MLCT transitions shifted to lower energy. This makes photocatalysts capable of harvesting low-energy visible light for catalyzing CO2 reduction. A detailed study revealed that these dicarbonyl rhenium(i) complexes are also highly selective for photocatalysis of CO2 to CO with a good quantum efficiency (10%), similar to that of the tricarbonyl rhenium(i) complex analogues. From the electrochemical study, it was observed that the catalysts efficiently produce CO from CO2 with high turnover frequency and good stability over time.

  20. The catalytic effect of water, water dimers and water trimers on H2S + (3)O2 formation by the HO2 + HS reaction under tropospheric conditions.

    PubMed

    Zhang, Tianlei; Yang, Chen; Feng, Xukai; Kang, Jiaxin; Song, Liang; Lu, Yousong; Wang, Zhiyin; Xu, Qiong; Wang, Wenliang; Wang, Zhuqing

    2016-06-29

    In this article, the reaction mechanisms of H2S + (3)O2 formation by the HO2 + HS reaction without and with catalyst X (X = H2O, (H2O)2 and (H2O)3) have been investigated theoretically at the CCSD(T)/6-311++G(3df,2pd)//B3LYP/6-311+G(2df,2p) level of theory, coupled with rate constant calculations by using conventional transition state theory. Our results show that in the presence of catalyst X (X = H2O, (H2O)2 and (H2O)3) into the channel of H2S + (3)O2 formation, the reactions between the SH radical and HO2(H2O)n (n = 1-3) complexes are more favorable than the corresponding reactions of the HO2 radical with HS(H2O)n (n = 1-3) complexes due to the lower barrier of the former reactions and the higher concentrations of HO2(H2O)n (n = 1-3) complexes. Meanwhile, the catalytic effect of water, water dimers and water trimers is mainly taken from the contribution of a single water vapor molecule, since the total effective rate constant of HO2H2O + HS and H2OHO2 + HS reactions was, respectively, larger by 7-9 and 9-12 orders of magnitude than that of SH + HO2(H2O)2 and SH + HO2(H2O)3 reactions. Besides, the enhancement factor of water vapor is only 0.37% at 240 K, while at high temperatures, such as 425 K, the positive water vapor effect is enhanced up to 38.00%, indicating that at high temperatures the positive water effect is obvious under atmospheric conditions. Overall, these results show how water and water clusters catalyze the gas phase reactions under atmospheric conditions.

  1. MCM-41 supported 12-tungstophosphoric acid mesoporous materials: Preparation, characterization, and catalytic activities for benzaldehyde oxidation with H2O2

    NASA Astrophysics Data System (ADS)

    Chen, Ya; Zhang, Xiao-Li; Chen, Xi; Dong, Bei-Bei; Zheng, Xiu-Cheng

    2013-10-01

    Mesoporous molecular sieves MCM-41 and bulk 12-tungstophosphoric acid (HPW) were synthesized and employed to prepare 5-45 wt.% HPW/MCM-41 mesoporous materials. Characterization results suggested the good dispersion of HPW within MCM-41 when the loading of HPW was less than 35 wt.% and HPW/MCM-41 retained the typical mesopore structure of the supports. The results of the catalytic oxidation of benzaldehyde to benzoic acid with 30% H2O2, in the absence of any organic solvent and co-catalysts, indicated that HPW/MCM-41 was an efficient catalyst and 30 wt.% HPW/MCM-41 sample exhibited the highest catalytic activity among these materials.

  2. The application of Cu/SiO2 catalytic system in chemical mechanical planarization based on the stability of SiO2 sol

    NASA Astrophysics Data System (ADS)

    Yan, Li; Yuling, Liu; Aochen, Wang; Zhixin, Yang; Mingbin, Sun; Chuan, Cheng; Yufeng, Zhang; Nannan, Zhang

    2014-06-01

    There is a lot of hydroxyl on the surface of nano SiO2 sol used as an abrasive in the chemical mechanical planarization (CMP) process, and the chemical reaction activity of the hydroxyl is very strong due to the nano effect. In addition to providing a mechanical polishing effect, SiO2 sol is also directly involved in the chemical reaction. The stability of SiO2 sol was characterized through particle size distribution, zeta potential, viscosity, surface charge and other parameters in order to ensure that the chemical reaction rate in the CMP process, and the surface state of the copper film after CMP was not affected by the SiO2 sol. Polarization curves and corrosion potential of different concentrations of SiO2 sol showed that trace SiO2 sol can effectively weaken the passivation film thickness. In other words, SiO2 sol accelerated the decomposition rate of passive film. It was confirmed that the SiO2 sol as reactant had been involved in the CMP process of copper film as reactant by the effect of trace SiO2 sol on the removal rate of copper film in the CMP process under different conditions. In the CMP process, a small amount of SiO2 sol can drastically alter the chemical reaction rate of the copper film, therefore, the possibility that Cu/SiO2 as a catalytic system catalytically accelerated the chemical reaction in the CMP process was proposed. According to the van't Hoff isotherm formula and the characteristics of a catalyst which only changes the chemical reaction rate with out changing the total reaction standard Gibbs free energy, factors affecting the Cu/SiO2 catalytic reaction were derived from the decomposition rate of Cu (OH)2 and the pH value of the system, and then it was concluded that the CuSiO3 as intermediates of Cu/SiO2 catalytic reaction accelerated the chemical reaction rate in the CMP process. It was confirmed that the Cu/SiO2 catalytic system generated the intermediate of the catalytic reaction (CuSiO3) in the CMP process through the removal

  3. Catalytic decomposition of 4-phenoxyphenol to aromatics over Pd/Cs(x)H3.0-x PW12O40/activated carbon aerogel (X = 2.0-3.0).

    PubMed

    Park, Hai Woong; Hong, Ung Gi; Lee, Yoon Jae; Choi, Jung Ho; Song, In Kyu

    2013-12-01

    Cesium-exchanged heteropolyacid (Cs(x)H3.0-xPW12O40) was impregnated onto activated carbon aerogel (ACA) with a variation of cesium content (X = 2.0, 2.3, 2.5, 2.7, and 3.0) in order to provide acid sites to ACA. Palladium catalysts were then supported on Cs(x)H3.0-xPW12O40-impregnated activated carbon aerogel (Pd/Cs(x)H3.0-xPW12O40/ACA, X = 2.0-3.0) by an incipient wetness impregnation method for use in the decomposition of lignin model compound to aromatics. 4-Phenoxyphenol was used as a lignin model compound for representing 4-O-5 linkage of lignin. In the catalytic decomposition of 4-phenoxyphenol over Pd/Cs(X)H3.0-xPW12O40/ACA, cyclohexanol, benzene, and phenol were mainly produced. Conversion of 4-phenoxyphenol and total yield for main products (cyclohexanol, benzene, and phenol) were closely related to the acidity of Pd/Cs(x)H3.0-xPW12O40/ACA. Conversion of 4-phenoxyphenol and total yield for main products increased with increasing acidity of Pd/Cs(x)H3.0-xPW12O40/ACA. Among the catalysts tested, Pd/Cs2.5H0.5PW12O40/ACA catalyst with the largest acidity showed the highest conversion of 4-phenoxyphenol and total yield for main products. Therefore, it is concluded that acidity of catalysts would be an important factor determining the catalytic performance in the decomposition of 4-phenoxyphenol. PMID:24266173

  4. Catalytic effect of nanogold on Cu(II)-N2H4 reaction and its application to resonance scattering immunoassay.

    PubMed

    Jiang, Zhiliang; Liao, Xianjiu; Deng, Anping; Liang, Aihui; Li, Jishun; Pan, Hongcheng; Li, Jianfu; Wang, Sumei; Huang, Yujuan

    2008-11-15

    In the medium of EDTA-NaOH, nanogold strongly catalyzed the slow reaction between hydrazine (N2H4) and Cu(II) to form Cu particles, which exhibited a strong resonance scattering (RS) peak at 602 nm. The increased RS intensity at 602 nm (DeltaI(RS)) was linear to the nanogold concentration in the range of 0.008-2.64 nM, with a detection limit of 1.0 pM Au. The rate equation obtained by the initial rate procedure was V(Cu) = K(Cu)[C(Cu(II))](2)C(OH)(1)C(Au)(1)C(N2)H4(1), with an apparent activation energy of 38 kJ x mol(-1), and the catalytic reaction mechanism was also discussed. An immunonanogold-catalytic resonance scattering spectral (RSS) assay was established for detection of microalbumin (Malb), using 10 nm nanogold to label goat antihuman Malb to obtain an immunonanogold probe (AuMalb) for Malb. In pH 5.0 citric acid-Na2HPO4 buffer solution, the AuMalb aggregated nonspecifically. Upon addition of Malb, it reacted with the probe to form dispersive AuMalb-Malb immunocomplex in the solution. After centrifugation, the supernatant containing AuMalb-Malb was obtained, and exhibited a catalytic effect on the reaction of N2H4-Cu(II) to produce large Cu particles that resulted in the I(602 nm) increasing. The increased RS intensity at 602 nm (DeltaI(602 nm)) was linear to Malb concentration (C(Malb)) in the range of 0.4 to 460 pg x mL(-1), with the regression equation of DeltaI(602 nm) = 0.3713 C(Malb) + 7.2, correlation coefficient of 0.9981 and detection limit of 0.1 pg x mL(-1) Malb. The proposed method was applied to detect Malb in healthy human urine samples, with satisfactory results.

  5. Presence of glycerol masks the effects of phosphorylation on the catalytic efficiency of cytosolic phospholipase A2.

    PubMed

    Burke, J R; Guenther, M G; Witmer, M R; Tredup, J A; Hail, M E; Micanovic, R; Villafranca, J J

    1997-05-01

    Cytosolic phospholipase A2 catalyzes the selective release of arachidonic acid from the sn-2 position of phospholipids and is believed to play a key cellular role in the generation of arachidonic acid. The enzymatic activity of cPLA2 is affected by several mechanisms, including substrate presentation and the phosphorylation state of the enzyme. Using covesicles of 1-palmitoy1-2-arachidonoyl-[arachidonoyl-1-14C]-8n-glycero-3 -phosphocholine and 1,2-dimyristoyl-phosphatidylmethanol as substrate, the effects of phosphorylation on the interfacial binding and catalytic constants were investigated. Phosphorylated and dephosphorylated enzyme forms were shown to have identical values of 2.6 microM for KMapp, an equilibrium dissociation constant which consists of the intrinsic dissociation constant from the lipid/water interface (Ks) and the dissociation constant for phospholipid from the active site (KM*). Moreover, the values of KM* for phosphorylated and dephosphorylated enzyme did not differ significantly (0.4 +/- 0.1 and 0.2 +/- 0.1, respectively). However, dephosphorylation of the enzyme reduced the value of kcat by 39%. The phosphorylation state of the enzyme had no effect on either the cooperativity shown by this enzyme or the thermal stability of the enzyme. Surprisingly, the presence of glycerol (4 M) masks the effect of phosphorylation on kcat. Instead, glycerol increased the value of kcat by 440% for the phosphorylated enzyme and by 760% for the dephosphorylated form. Moreover, addition of glycerol had only small effects on KMapp. the increase in the kcat upon addition of glycerol results from a substantial decrease in the activation energy from 29.4 to 14.8 kcal. mol-1. To determine whether the effects of phosphorylation of the enzyme or addition of glycerol are unique to this artificial substrate, membranes from U937 cells were isolated and used as substrate. With these membranes, the dephosphorylated enzyme was only 21% less active than the phosphorylated

  6. Catalytic Subunit 1 of Protein Phosphatase 2A Is a Subunit of the STRIPAK Complex and Governs Fungal Sexual Development

    PubMed Central

    Beier, Anna; Krisp, Christoph; Wolters, Dirk A.

    2016-01-01

    ABSTRACT The generation of complex three-dimensional structures is a key developmental step for most eukaryotic organisms. The details of the molecular machinery controlling this step remain to be determined. An excellent model system to study this general process is the generation of three-dimensional fruiting bodies in filamentous fungi like Sordaria macrospora. Fruiting body development is controlled by subunits of the highly conserved striatin-interacting phosphatase and kinase (STRIPAK) complex, which has been described in organisms ranging from yeasts to humans. The highly conserved heterotrimeric protein phosphatase PP2A is a subunit of STRIPAK. Here, catalytic subunit 1 of PP2A was functionally characterized. The Δpp2Ac1 strain is sterile, unable to undergo hyphal fusion, and devoid of ascogonial septation. Further, PP2Ac1, together with STRIPAK subunit PRO22, governs vegetative and stress-related growth. We revealed in vitro catalytic activity of wild-type PP2Ac1, and our in vivo analysis showed that inactive PP2Ac1 blocks the complementation of the sterile deletion strain. Tandem affinity purification, followed by mass spectrometry and yeast two-hybrid analysis, verified that PP2Ac1 is a subunit of STRIPAK. Further, these data indicate links between the STRIPAK complex and other developmental signaling pathways, implying the presence of a large interconnected signaling network that controls eukaryotic developmental processes. The insights gained in our study can be transferred to higher eukaryotes and will be important for understanding eukaryotic cellular development in general. PMID:27329756

  7. Catalytic behavior and synergistic effect of nanostructured mesoporous CuO-MnOx-CeO2 catalysts for chlorobenzene destruction

    NASA Astrophysics Data System (ADS)

    He, Chi; Yu, Yanke; Shen, Qun; Chen, Jinsheng; Qiao, Nanli

    2014-04-01

    Mesoporous CuO-MnOx-CeO2 composite metal oxides with different copper and manganese loadings were prepared by a urea-assistant hydrothermal method, and were further adopted for the complete catalytic combustion of chlorobenzene. The effects of reaction conditions such as inlet reagent concentration and water feed concentration on chlorobenzene combustion were also studied. The structure and textural properties of the synthesized catalysts were characterized via the XRD, N2 adsorption/desorption, FE-SEM, TEM, H2-TPR, O2-TPD, and XPS techniques. The characterization results reveal that the presence of a small amount of Mn species can facilitate the incorporation of Cu and Mn ions into ceria lattice to form Cu-Mn-Ce-O solid solution. The synergistic effect of Cu and Mn species can reduce the redox potential of the composite catalysts, and produce large amounts of oxygen vacancies in the interface of CuOx, MnOx, and CeO2 oxides. The catalyst with Cu/Mn atomic ratio of 1/1 exhibits the best chlorobenzene elimination capability, oxidizing about 95% of the inlet chlorobenzene at 264 °C with CO2 selectivity higher than 99.5%. The concentration and mobility of the chemically adsorbed oxygen are vital for the effective removal of surface Cl species, which inhibits the dissociation of oxygen molecules and decreases the reducibility of the copper and manganese species. It can be rationally concluded that the superior catalytic performance and durability of the mesoporous CuO-MnOx-CeO2 composite oxides are primarily attributed to the higher surface oxygen concentration and better active oxygen mobility.

  8. WO3/CeO2-ZrO2, a promising catalyst for selective catalytic reduction (SCR) of NOx with NH3 in diesel exhaust.

    PubMed

    Li, Ye; Cheng, Hao; Li, Deyi; Qin, Yongsheng; Xie, Yuming; Wang, Shudong

    2008-03-28

    A WO3/CeO2-ZrO2 catalyst system was discovered for selective catalytic reduction of NOx with NH3; the catalyst (10 wt% WO3 loading) showed nearly 100% NOx conversion in a temperature range of 200-500 degrees C, at a space velocity of 90 000 h(-1) in a simulated diesel exhaust containing 550 ppm NOx (NO : NO2 feed ratio at 1.0), 10 vol% H2O and 10 vol% CO2; the catalyst also exhibited high temperature stability.

  9. ASBESTOS EXPOSURES DURING ROUTINE FLOOR TILE MAINTENANCE. PART 2: ULTRA HIGH SPEED BURNISHING AND WET-STRIPPING

    EPA Science Inventory

    This study was conducted to evaluate airborne asbestos concentrations during ultra high speed (UHS) burnishing and wet-stripping of asbestos-containing resilient floor tile under two levels of floor care condition (poor and good). Airborne asbestos concentrations were measured by...

  10. Measuring the Absorption Rate of CO2 in Nonaqueous CO2-Binding Organic Liquid Solvents with a Wetted-Wall Apparatus.

    PubMed

    Mathias, Paul M; Zheng, Feng; Heldebrant, David J; Zwoster, Andy; Whyatt, Greg; Freeman, Charles M; Bearden, Mark D; Koech, Phillip

    2015-11-01

    The kinetics of the absorption of CO2 into two nonaqueous CO2-binding organic liquid (CO2 BOL) solvents were measured at T=35, 45, and 55 °C with a wetted-wall column. Selected CO2 loadings were run with a so-called "first-generation" CO2 BOL, comprising an independent base and alcohol, and a "second-generation" CO2 BOL, in which the base and alcohol were conjoined. Liquid-film mass-transfer coefficient (k'g ) values for both solvents were measured to be comparable to values for monoethanolamine and piperazine aqueous solvents under a comparable driving force, in spite of far higher solution viscosities. An inverse temperature dependence of the k'g value was also observed, which suggests that the physical solubility of CO2 in organic liquids may be making CO2 mass transfer faster than expected. Aspen Plus software was used to model the kinetic data and compare the CO2 absorption behavior of nonaqueous solvents with that of aqueous solvent platforms. This work continues our development of the CO2 BOL solvents. Previous work established the thermodynamic properties related to CO2 capture. The present paper quantitatively studies the kinetics of CO2 capture and develops a rate-based model.

  11. Measuring the Absorption Rate of CO2 in Nonaqueous CO2-Binding Organic Liquid Solvents with a Wetted-Wall Apparatus.

    PubMed

    Mathias, Paul M; Zheng, Feng; Heldebrant, David J; Zwoster, Andy; Whyatt, Greg; Freeman, Charles M; Bearden, Mark D; Koech, Phillip

    2015-11-01

    The kinetics of the absorption of CO2 into two nonaqueous CO2-binding organic liquid (CO2 BOL) solvents were measured at T=35, 45, and 55 °C with a wetted-wall column. Selected CO2 loadings were run with a so-called "first-generation" CO2 BOL, comprising an independent base and alcohol, and a "second-generation" CO2 BOL, in which the base and alcohol were conjoined. Liquid-film mass-transfer coefficient (k'g ) values for both solvents were measured to be comparable to values for monoethanolamine and piperazine aqueous solvents under a comparable driving force, in spite of far higher solution viscosities. An inverse temperature dependence of the k'g value was also observed, which suggests that the physical solubility of CO2 in organic liquids may be making CO2 mass transfer faster than expected. Aspen Plus software was used to model the kinetic data and compare the CO2 absorption behavior of nonaqueous solvents with that of aqueous solvent platforms. This work continues our development of the CO2 BOL solvents. Previous work established the thermodynamic properties related to CO2 capture. The present paper quantitatively studies the kinetics of CO2 capture and develops a rate-based model. PMID:26377774

  12. Influence of chirality on catalytic generation of nitric oxide and platelet behavior on selenocystine immobilized TiO2 films

    PubMed Central

    Fan, Yonghong; Pan, Xiaxin; Wang, Ke; Wu, Sisi; Han, Honghong; Yang, Ping; Luo, Rifang; Wang, Hong; Huang, Nan; Tan, Wei; Weng, Yajun

    2016-01-01

    As nitric oxide (NO) plays vital roles in the cardiovascular system, incorporating this molecule into cardiovascular stents is considered as an effective method. In the present study, selenocystine with different chirality (i.e., l- and d-selenocystine) was used as the catalytic molecule immobilized on TiO2 films for decomposing endogenous NO donor. The influences of surface chirality on NO release and platelet behavior were evaluated. Results show that although the amount of immobilized l-selenocystine on the surface was nearly the same as that of immobilized d-selenocystine, in vitro catalytic NO release tests showed that l-selenocystine immobilized surfaces were more capable of catalyzing the decomposition of S-nitrosoglutathione and thus generating more NO. Accordingly, l-selenocystine immobilized surfaces demonstrated significantly increased inhibiting effects on the platelet adhesion and activation, when compared to d-selenocystine immobilized ones. Measurement of the cGMP concentration of platelets further confirmed that surface chirality played an important role in regulating NO generation and platelet behaviors. Additionally, using bovine serum albumin and fibrinogen as model proteins, the protein adsorption determined with quartz crystal microbalance showed that the l-selenocystine immobilized surface enhanced protein adsorption. In conclusion, surface chirality significantly influences protein adsorption and NO release, which may have significant implications in the design of NO-generating cardiovascular stents. PMID:27153116

  13. Catalytic combustion over hexaaluminates

    SciTech Connect

    Ramesh, K.S.; Kingsley, J.J.; Hubler, T.L.; McCready, D.E.; Cox, J.L.

    1997-12-31

    Combustion is the oldest and most extensively used process for the production of light, heat, and energy utilization. Mankind has sought to control combustion since prehistoric times to more effectively utilize the combustible material, control the products of combustion, and harness the energy released during combustion. Catalysts provide the means to control the reactions of combustion beyond what can be achieved in the homogeneous gas phase (1). Catalysts also enable operation outside the range of flammability limits and control atmospheric pollutants of combustion, mainly NO{sub x}, carbon monoxide, and particles of incomplete combustion (soot). The major technical difficulty that has hindered widespread application of catalytic combustion devices is their poor performance, particularly durability of their ceramic substrates and catalytically active phases in the high temperature environment. Catalytic combustion of hydrocarbons over metals and metal oxide catalysts has been explored extensively. Recent reviews of materials for high temperature catalytic combustion have been provided by Marcus et al. (2) and Trim (3). Hexaaluminates which show good thermal stability above 1200{degrees}C are one class of metal oxides receiving consideration for application in high temperature combustion devices. Matsuda et al. (4) have developed thermally stable La-hexaaluminates with the same layer structure as Ba-hexaaluminate and have investigated their catalytic application. Machida et al. (5-7) have investigated the catalytic properties of a number of hexaaluminates of BaMAl{sub 11}O{sub 19-{alpha}}(M=Cr, Mn,Fe,Co,Ni). Here we report the synthesis, properties and catalytic combustion of some new hexaaluminates.

  14. Si doping influence on the catalytic performance of Pt/TiO2 mesoporous film catalyst for low-temperature methanol combustion

    NASA Astrophysics Data System (ADS)

    Zheng, Zhangzhang; Wang, Xiaohong; Liu, Jun; Xiao, Jinhua; Hu, Zhiyu

    2014-08-01

    A series of Si-doped mesoporous TiO2 thin films with anatase phase were synthesized and used as the supporters of Pt catalyst for low-temperature catalytic combustion of gaseous methanol. The introduced Pt ions were processed by a simple photo-reduction method. The catalytic performance of thin film catalysts with different Si doping content were measured by gas chromatography method. It was found that the catalytic performance of Pt/TiO2 can be improved a lot by Si doping and the optimized value of Si/Ti ratio is 0.1. At this point, Pt/TiO2 exhibited the best catalytic activity towards methanol combustion reaching up to 92.8% at 100 °C. This conversion rate was 13.2% higher than that of the catalyst without doping. Moreover, the mechanism for Si affecting on the catalytic performance was proposed based on the XRD, FT-IR, SEM, TEM, N2 adsorption-desorption and XPS characterizations.

  15. Determinants of ligand binding and catalytic activity in the myelin enzyme 2′,3′-cyclic nucleotide 3′-phosphodiesterase

    PubMed Central

    Raasakka, Arne; Myllykoski, Matti; Laulumaa, Saara; Lehtimäki, Mari; Härtlein, Michael; Moulin, Martine; Kursula, Inari; Kursula, Petri

    2015-01-01

    2′,3′-cyclic nucleotide 3′-phosphodiesterase (CNPase) is an enzyme highly abundant in the central nervous system myelin of terrestrial vertebrates. The catalytic domain of CNPase belongs to the 2H phosphoesterase superfamily and catalyzes the hydrolysis of nucleoside 2′,3′-cyclic monophosphates to nucleoside 2′-monophosphates. The detailed reaction mechanism and the essential catalytic amino acids involved have been described earlier, but the roles of many amino acids in the vicinity of the active site have remained unknown. Here, several CNPase catalytic domain mutants were studied using enzyme kinetics assays, thermal stability experiments, and X-ray crystallography. Additionally, the crystal structure of a perdeuterated CNPase catalytic domain was refined at atomic resolution to obtain a detailed view of the active site and the catalytic mechanism. The results specify determinants of ligand binding and novel essential residues required for CNPase catalysis. For example, the aromatic side chains of Phe235 and Tyr168 are crucial for substrate binding, and Arg307 may affect active site electrostatics and regulate loop dynamics. The β5-α7 loop, unique for CNPase in the 2H phosphoesterase family, appears to have various functions in the CNPase reaction mechanism, from coordinating the nucleophilic water molecule to providing a binding pocket for the product and being involved in product release. PMID:26563764

  16. Enhanced Control of Mercury and other HAP by Innovative Modifications to Wet FGD Processes

    SciTech Connect

    Hargrove, O. W.; Carey, T. R.; Richardson, C. F.; Skarupa, R. C.; Meserole, F. B.; Rhudy, R. G.; Brown, Thomas D.

    1997-07-01

    The overall objective of this project was to learn more about controlling emissions of hazardous air pollutants (HAPs) from coal-fired power plants that are equipped with wet flue gas desulfurization (FGD) systems. The project was included by FETC as a Phase I project in its Mega-PRDA program. Phase I of this project focused on three research areas. These areas in order of priority were: (1) Catalytic oxidation of vapor-phase elemental mercury; (2) Enhanced particulate-phase HAPs removal by electrostatic charging of liquid droplets; and (3) Enhanced mercury removal by addition of additives to FGD process liquor. Mercury can exist in two forms in utility flue gas--as elemental mercury and as oxidized mercury (predominant form believed to be HgCl{sub 2}). Previous test results have shown that wet scrubbers effectively remove the oxidized mercury from the gas but are ineffective in removing elemental mercury. Recent improvements in mercury speciation techniques confirm this finding. Catalytic oxidation of vapor-phase elemental mercury is of interest in cases where a wet scrubber exists or is planned for SO{sub 2} control. If a low-cost process could be developed to oxidize all of the elemental mercury in the flue gas, then the maximum achievable mercury removal across the existing or planned wet scrubber would increase. Other approaches for improving control of HAPs included a method for improving particulate removal across the FGD process and the use of additives to increase mercury solubility. This paper discusses results related only to catalytic oxidation of elemental mercury.

  17. [Preparation of Cu/ZrO2/S2O8(2-)/gamma-Al2O3 solid acid catalyst and its catalytic activity to selective reduction of NO].

    PubMed

    Guo, Xi-kun; Wang, Xiao-ming

    2008-06-01

    Cu/ZrO2/S2O8(2-)/gamma-Al2O3 solid acid catalyst was prepared by loading of (NH4)2S2O8, ZrOCl2, and Cu(NO3)2 onto gamma-Al2O3 step by step, which was obtained from calcining of pseudoboehmite. The catalytic property of Cu/ZrO2/S2O8(2-)/gamma-Al2O3 on the selective reduction of NO by C3H6 in excess oxygen was investigated. The relationship between the structure and the catalytic property of Cu/ZrO2/S2O8(2-)/gamma-Al2O3 catalyst was also explored by means of SEM, XRD, Py-IR and TPR. The experimental results of catalytic activity of the title catalyst indicated that the maximum conversion rate of NO could reach 82.9% in the absence of water and was up to 80.2% even in the presence of 10% water vapor. The results of the structural characterization toward the catalyst showed that S2O8(2-) and ZrO2 could restrain the sinteration of gamma-Al2O3 particles and the formation of CuAl2O4 spinelle, and also facilitate the formation of new acidic sites (Brönsted acid) and the enhance of the acidity on the surface of the catalyst. In addition, ZrO2 could increase the reducibility of Cu on the catalyst. Consequently, the catalytic activity and hydrothermal stability of the catalyst were improved effectively.

  18. 2D co-catalytic MoS2 nanosheets embedded with 1D TiO2 nanoparticles for enhancing photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Ren, Xiaohui; Qi, Xiang; Shen, Yongzhen; Xiao, Si; Xu, Guanghua; Zhang, Zhen; Huang, Zongyu; Zhong, Jianxin

    2016-08-01

    2D photocatalytic TiO2/MoS2 hybrid nanosheets (HNs) have been prepared via a facile hydrothermal process. X-ray diffraction patterns and Raman spectra are carried out and confirm a well crystalized anatase and 2H-MoS2 hybridization. Additional morphological and microstructural tests verify a distinct MoS2 framework, indicating the relatively stability of the MoS2 nanosheet platform with a high specific surface area. UV-vis spectra and electrochemical impedance spectra exhibit an enhanced light absorption ability and conductivity of TiO2/MoS2 compared to that of just TiO2. Photoelectrochemical (PEC) tests also demonstrate the photocurrent of 20 : 1 TiO2/MoS2 HNs is greatly improved compared to that of as-prepared TiO2. The saturation current density is about 33 µA cm-2 when the applied potential is 0.2 V, which is nearly twice that of pure TiO2 and four times as high as 5 : 1 TiO2/MoS2 HNs and 1 : 1 TiO2/MoS2 HNs. Besides that, the duration test exhibits no detectable distinction after processing 25 cycles. The improved photocatalytic activities are perhaps derived from the high conductivity and the increased active sites for the introduction of co-catalytic MoS2 nanosheets as well as the positive synergetic effect between the TiO2 and MoS2. This work demonstrates that the as-prepared TiO2/MoS2 HNs may have a great potential application in PEC hydrogen production.

  19. 2D co-catalytic MoS2 nanosheets embedded with 1D TiO2 nanoparticles for enhancing photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Ren, Xiaohui; Qi, Xiang; Shen, Yongzhen; Xiao, Si; Xu, Guanghua; Zhang, Zhen; Huang, Zongyu; Zhong, Jianxin

    2016-08-01

    2D photocatalytic TiO2/MoS2 hybrid nanosheets (HNs) have been prepared via a facile hydrothermal process. X-ray diffraction patterns and Raman spectra are carried out and confirm a well crystalized anatase and 2H-MoS2 hybridization. Additional morphological and microstructural tests verify a distinct MoS2 framework, indicating the relatively stability of the MoS2 nanosheet platform with a high specific surface area. UV–vis spectra and electrochemical impedance spectra exhibit an enhanced light absorption ability and conductivity of TiO2/MoS2 compared to that of just TiO2. Photoelectrochemical (PEC) tests also demonstrate the photocurrent of 20 : 1 TiO2/MoS2 HNs is greatly improved compared to that of as-prepared TiO2. The saturation current density is about 33 µA cm‑2 when the applied potential is 0.2 V, which is nearly twice that of pure TiO2 and four times as high as 5 : 1 TiO2/MoS2 HNs and 1 : 1 TiO2/MoS2 HNs. Besides that, the duration test exhibits no detectable distinction after processing 25 cycles. The improved photocatalytic activities are perhaps derived from the high conductivity and the increased active sites for the introduction of co-catalytic MoS2 nanosheets as well as the positive synergetic effect between the TiO2 and MoS2. This work demonstrates that the as-prepared TiO2/MoS2 HNs may have a great potential application in PEC hydrogen production.

  20. Mild activation of CeO2-supported gold nanoclusters and insight into the catalytic behavior in CO oxidation.

    PubMed

    Li, Weili; Ge, Qingjie; Ma, Xiangang; Chen, Yuxiang; Zhu, Manzhou; Xu, Hengyong; Jin, Rongchao

    2016-01-28

    We report a new activation method and insight into the catalytic behavior of a CeO2-supported, atomically precise Au144(SR)60 nanocluster catalyst (where thiolate -SR = -SCH2CH2Ph) for CO oxidation. An important finding is that the activation of the catalyst is closely related to the production of active oxygen species on CeO2, rather than ligand removal of the Au144(SR)60 clusters. A mild O2 pretreatment (at 80 °C) can activate the catalyst, and the addition of reductive gases (CO or H2) can enhance the activation effects of O2 pretreatment via a redox cycle in which CO could reduce the surface of CeO2 to produce oxygen vacancies-which then adsorb and activate O2 to produce more active oxygen species. The CO/O2 pulse experiments confirm that CO is adsorbed on the cluster catalyst even with ligands on, and active oxygen species present on the surface of the pretreated catalyst reacts with CO pulses to generate CO2. The Au144(SR)60/CeO2 exhibits high CO oxidation activity at 80 °C without the removal of thiolate ligands. The surface lattice-oxygen of the support CeO2 possibly participates in the oxidation of CO over the Au144(SR)60/CeO2 catalyst.

  1. Mild activation of CeO2-supported gold nanoclusters and insight into the catalytic behavior in CO oxidation.

    PubMed

    Li, Weili; Ge, Qingjie; Ma, Xiangang; Chen, Yuxiang; Zhu, Manzhou; Xu, Hengyong; Jin, Rongchao

    2016-01-28

    We report a new activation method and insight into the catalytic behavior of a CeO2-supported, atomically precise Au144(SR)60 nanocluster catalyst (where thiolate -SR = -SCH2CH2Ph) for CO oxidation. An important finding is that the activation of the catalyst is closely related to the production of active oxygen species on CeO2, rather than ligand removal of the Au144(SR)60 clusters. A mild O2 pretreatment (at 80 °C) can activate the catalyst, and the addition of reductive gases (CO or H2) can enhance the activation effects of O2 pretreatment via a redox cycle in which CO could reduce the surface of CeO2 to produce oxygen vacancies-which then adsorb and activate O2 to produce more active oxygen species. The CO/O2 pulse experiments confirm that CO is adsorbed on the cluster catalyst even with ligands on, and active oxygen species present on the surface of the pretreated catalyst reacts with CO pulses to generate CO2. The Au144(SR)60/CeO2 exhibits high CO oxidation activity at 80 °C without the removal of thiolate ligands. The surface lattice-oxygen of the support CeO2 possibly participates in the oxidation of CO over the Au144(SR)60/CeO2 catalyst. PMID:26750474

  2. Structural Basis on the Catalytic Reaction Mechanism of Novel 1,2-Alpha L-Fucosidase (AFCA) From Bifidobacterium Bifidum

    SciTech Connect

    Nagae, M.; Tsuchiya, A.; Katayama, T.; Yamamoto, K.; Wakatsuki, S.; Kato, R.

    2009-06-03

    1,2-alpha-L-fucosidase (AfcA), which hydrolyzes the glycosidic linkage of Fucalpha1-2Gal via an inverting mechanism, was recently isolated from Bifidobacterium bifidum and classified as the first member of the novel glycoside hydrolase family 95. To better understand the molecular mechanism of this enzyme, we determined the x-ray crystal structures of the AfcA catalytic (Fuc) domain in unliganded and complexed forms with deoxyfuconojirimycin (inhibitor), 2'-fucosyllactose (substrate), and L-fucose and lactose (products) at 1.12-2.10 A resolution. The AfcA Fuc domain is composed of four regions, an N-terminal beta region, a helical linker, an (alpha/alpha)6 helical barrel domain, and a C-terminal beta region, and this arrangement is similar to bacterial phosphorylases. In the complex structures, the ligands were buried in the central cavity of the helical barrel domain. Structural analyses in combination with mutational experiments revealed that the highly conserved Glu566 probably acts as a general acid catalyst. However, no carboxylic acid residue is found at the appropriate position for a general base catalyst. Instead, a water molecule stabilized by Asn423 in the substrate-bound complex is suitably located to perform a nucleophilic attack on the C1 atom of L-fucose moiety in 2'-fucosyllactose, and its location is nearly identical near the O1 atom of beta-L-fucose in the products-bound complex. Based on these data, we propose and discuss a novel catalytic reaction mechanism of AfcA.

  3. Three-phase catalytic system of H2O, ionic liquid, and VOPO4-SiO2 solid acid for conversion of fructose to 5-hydroxymethylfurfural.

    PubMed

    Tian, Chengcheng; Zhu, Xiang; Chai, Song-Hai; Wu, Zili; Binder, Andrew; Brown, Suree; Li, Lin; Luo, Huimin; Guo, Yanglong; Dai, Sheng

    2014-06-01

    Efficient transformation of biomass-derived feedstocks to chemicals and fuels remains a daunting challenge in utilizing biomass as alternatives to fossil resources. A three-phase catalytic system, consisting of an aqueous phase, a hydrophobic ionic-liquid phase, and a solid-acid catalyst phase of nanostructured vanadium phosphate and mesostructured cellular foam (VPO-MCF), is developed for efficient conversion of biomass-derived fructose to 5-hydroxymethylfurfural (HMF). HMF is a promising, versatile building block for production of value-added chemicals and transportation fuels. The essence of this three-phase system lies in enabling the isolation of the solid-acid catalyst from the aqueous phase and regulation of its local environment by using a hydrophobic ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf2N]). This system significantly inhibits the side reactions of HMF with H2O and leads to 91 mol % selectivity to HMF at 89 % of fructose conversion. The unique three-phase catalytic system opens up an alternative avenue for making solid-acid catalyst systems with controlled and locally regulated microenvironment near catalytically active sites by using a hydrophobic ionic liquid. PMID:24729382

  4. Three-phase catalytic system of H2O, ionic liquid, and VOPO4-SiO2 solid acid for conversion of fructose to 5-hydroxymethylfurfural.

    PubMed

    Tian, Chengcheng; Zhu, Xiang; Chai, Song-Hai; Wu, Zili; Binder, Andrew; Brown, Suree; Li, Lin; Luo, Huimin; Guo, Yanglong; Dai, Sheng

    2014-06-01

    Efficient transformation of biomass-derived feedstocks to chemicals and fuels remains a daunting challenge in utilizing biomass as alternatives to fossil resources. A three-phase catalytic system, consisting of an aqueous phase, a hydrophobic ionic-liquid phase, and a solid-acid catalyst phase of nanostructured vanadium phosphate and mesostructured cellular foam (VPO-MCF), is developed for efficient conversion of biomass-derived fructose to 5-hydroxymethylfurfural (HMF). HMF is a promising, versatile building block for production of value-added chemicals and transportation fuels. The essence of this three-phase system lies in enabling the isolation of the solid-acid catalyst from the aqueous phase and regulation of its local environment by using a hydrophobic ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf2N]). This system significantly inhibits the side reactions of HMF with H2O and leads to 91 mol % selectivity to HMF at 89 % of fructose conversion. The unique three-phase catalytic system opens up an alternative avenue for making solid-acid catalyst systems with controlled and locally regulated microenvironment near catalytically active sites by using a hydrophobic ionic liquid.

  5. Photo-catalytic degradation of toxic dye amaranth on TiO(2)/UV in aqueous suspensions.

    PubMed

    Gupta, Vinod K; Jain, Rajeev; Mittal, Alok; Saleh, Tawfik A; Nayak, Arunima; Agarwal, Shilpi; Sikarwar, Shalini

    2012-01-01

    The photo-catalytic degradation of an azo dye - Amaranth (AM) - has been investigated in TiO(2)/UV aqueous suspensions. The results obtained from the experiments during H(2)O(2)/TiO(2) addition show that the highest decolorization rate is provided by the combination of (UV+TiO(2)+H(2)O(2)). The decolorization efficiencies were 17%, 26%, 38% and 64% in the runs UV, UV+H(2)O(2), UV+TiO(2) and (UV+TiO(2)+H(2)O(2)) after approximately 100 min illumination periods, respectively. The observed dye degradation rates followed pseudo-first order kinetics with respect to the substrate concentration under the experimental conditions used. Different experimental conditions, such as temperature, pH and presence of electron acceptor were investigated. The temperature effect was investigated at the range of 293-313 K and it was observed that decolorization rate increased by the increase in temperature. Chemical oxygen demand and dye absorbance of the photodegraded dye solution substantially decreased. Effect of pH was also investigated and it was observed that the lower the pH the higher the degradation. In addition, an enhancement in the photodegradation rate was observed by the addition of hydrogen peroxide as an electron acceptor. The adsorption trends of Amaranth at various initial concentrations followed the Langmuir isotherm trend. This work adds to the global discussion on the role of the advanced oxidation processes in water treatment.

  6. Photo-catalytic degradation of toxic dye amaranth on TiO(2)/UV in aqueous suspensions.

    PubMed

    Gupta, Vinod K; Jain, Rajeev; Mittal, Alok; Saleh, Tawfik A; Nayak, Arunima; Agarwal, Shilpi; Sikarwar, Shalini

    2012-01-01

    The photo-catalytic degradation of an azo dye - Amaranth (AM) - has been investigated in TiO(2)/UV aqueous suspensions. The results obtained from the experiments during H(2)O(2)/TiO(2) addition show that the highest decolorization rate is provided by the combination of (UV+TiO(2)+H(2)O(2)). The decolorization efficiencies were 17%, 26%, 38% and 64% in the runs UV, UV+H(2)O(2), UV+TiO(2) and (UV+TiO(2)+H(2)O(2)) after approximately 100 min illumination periods, respectively. The observed dye degradation rates followed pseudo-first order kinetics with respect to the substrate concentration under the experimental conditions used. Different experimental conditions, such as temperature, pH and presence of electron acceptor were investigated. The temperature effect was investigated at the range of 293-313 K and it was observed that decolorization rate increased by the increase in temperature. Chemical oxygen demand and dye absorbance of the photodegraded dye solution substantially decreased. Effect of pH was also investigated and it was observed that the lower the pH the higher the degradation. In addition, an enhancement in the photodegradation rate was observed by the addition of hydrogen peroxide as an electron acceptor. The adsorption trends of Amaranth at various initial concentrations followed the Langmuir isotherm trend. This work adds to the global discussion on the role of the advanced oxidation processes in water treatment. PMID:23177765

  7. Visible light photo-catalytic activity of C-PVA/TiO2 composites for degrading rhodamine B

    NASA Astrophysics Data System (ADS)

    Yang, Haigang; Zhang, Jianling; Song, Yuanqing; Xu, Shoubin; Jiang, Long; Dan, Yi

    2015-01-01

    In this article, a novel visible light (VL) active photo-catalyst, calcinated-poly (vinyl alcohol) (C-PVA)/TiO2 composites, was prepared by calcinating the films on glass substrates obtained from TiO2 sol and initially thermally treated PVA solution. The results showed that the C-PVA with conjugated C=C bonds was doped onto the surface of TiO2 and expanded the photo-response from ultraviolet spectrum of the TiO2 to VL spectrum of the composites; meanwhile, the photo-luminescence of C-PVA was quenched by TiO2, indicating charge transfer between C-PVA and TiO2. The C-PVA/TiO2 composites showed improved adsorption and photo-catalytic performances toward rhodamine B (RhB) compared to TiO2. When the mass feed ratio (P/T) of polymer (P) to TiO2 (T) increased from 1:10 to 1:2, the equilibrium adsorption ratio of C-PVA/TiO2 composites toward RhB continuously increased from 8.2 to 21.6%; while the VL photo-degradation ratio of RhB increased at first, achieving maximum value (92.2%) at P/T = 1:6, and then decreased consecutively. SEM images showed that there were lots of aggregates of TiO2 and C-PVA on the surface of the composites. Moreover, the morphologies of those aggregates were related to the value of P/T, and the dispersion of TiO2 in the C-PVA matrix was best while P/T = 1:6. The photo-catalytic activity of C-PVA/TiO2 composites was closely correlated to aggregate states of C-PVA and TiO2, while the adsorption performance was contributed to the exposed C-PVA on the surface of C-PVA/TiO2 composites.

  8. Enhanced control of mercury and other HAPs by innovative modifications to wet FGD processes. First quarter 1996 technical progress report

    SciTech Connect

    Carey, T.R.; Hargrove, O.W.

    1996-06-03

    The overall objective of this project is to learn more about controlling emissions of hazardous air pollutants (HAPs) from coal- fired power plants that are equipped with wet flue gas desulfurization (FGD) systems. This project focuses on three research areas: (1) catalytic oxidation of vapor-phase elemental mercury, (2) enhanced particulate-phase HAPs removal by electrostatic charging of liquid droplets, and (3) enhanced mercury removal by additional of additives to FGD process liquor.

  9. Catalytic Activity and Thermal Stability of Arc Plasma Deposited Pt Nano-Particles on CeO2-Al2O3.

    PubMed

    Jeong, Young Eun; Kumar, Pullur Anil; Choi, Hee Lack; Lee, Kwan-Young; Ha, Heon Phil

    2015-11-01

    In this study, catalytic activity and thermal stability of the arc plasma deposited (APD) Pt nano-particles on A12O3 and CeO2-Al2O3 were compared with that of the conventionally prepared Pt/Al2O3. All the catalysts were characterized by BET-surface area, transmission electron microscopy, X-ray photoelectron spectroscopy, CO-pulse chemisorption, H2-temperarture programmed reduction and X-ray absorption near edge spectroscopy. Through the quantum chemical calculations of different metal oxide support, CeO2 was identified as a suitable anchoring material with high energy level between the Pt species (Pt(0) and PtO(x)) on ceria. Subsequently, the results of XPS and XANES revealed the presence of abundant Pt(0) metal species in APD catalysts. The addition of ceria to Al2O3 support enhanced the dispersion of Pt nano-particles. The H2-TPR of Pt/CeO2-Al2O3 (APD) catalyst showed high-temperature reduction peaks corresponding to the interaction of Pt with ceria on alumina by Pt-O-Ce. Consequently, the Pt nano-particles deposited on CeO2-Al2O3 by APD attained strong thermal resistance at high temperatures. In addition, superior catalytic activities for CO and C3H6 oxidation and NO(x) reduction were obtained for the Pt/CeO2- Al2O3 (APD) catalyst.

  10. Attributes for MRB_E2RF1 Catchments by Major River Basins in the Conterminous United States: Average Atmospheric (Wet) Deposition of Inorganic Nitrogen, 2002

    USGS Publications Warehouse

    Wieczorek, Michael E.; LaMotte, Andrew E.

    2010-01-01

    This tabular data set represents the average atmospheric (wet) deposition, in kilograms per square kilometer, of inorganic nitrogen for the year 2002 compiled for every catchment for MRB_E2RF1 of Major River Basins (MRBs, Crawford and others, 2006). The source data set for wet deposition was from the USGS's raster data set atmospheric (wet) deposition of inorganic nitrogen for 2002 (Gronberg, 2005). The MRB_E2RF1 catchments are based on a modified version of the U.S. Environmental Protection Agency's (USEPA) ERF1_2 and include enhancements to support national and regional-scale surface-water quality modeling (Nolan and others, 2002; Brakebill and others, 2011). Data were compiled for every catchment of MRB_E2RF1 catchments for the conterminous United States covering New England and Mid-Atlantic (MRB1), South Atlantic-Gulf and Tennessee (MRB2), the Great Lakes, Ohio, Upper Mississippi, and Souris-Red-Rainy (MRB3), the Missouri (MRB4), the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf (MRB5), the Rio Grande, Colorado, and the Great basin (MRB6), the Pacific Northwest (MRB7) river basins, and California (MRB8).

  11. Enuresis (Bed-Wetting)

    MedlinePlus

    ... their development. Bed-wetting is more common among boys than girls. What causes bed-wetting? A number of things ... valves in boys or in the ureter in girls or boys Abnormalities in the spinal cord A small bladder ...

  12. Catalytic Hydrotreatment of Humins in Mixtures of Formic Acid/2-Propanol with Supported Ruthenium Catalysts.

    PubMed

    Wang, Yuehu; Agarwal, Shilpa; Kloekhorst, Arjan; Heeres, Hero Jan

    2016-05-10

    The catalytic hydrotreatment of humins, which are the solid byproducts from the conversion of C6 sugars (glucose, fructose) into 5-hydroxymethylfurfural (HMF) and levulinic acid (LA), by using supported ruthenium catalysts has been investigated. Reactions were carried out in a batch setup at elevated temperatures (400 °C) by using a hydrogen donor (formic acid (FA) in isopropanol (IPA) or hydrogen gas), with humins obtained from d-glucose. Humin conversions of up to 69 % were achieved with Ru/C and FA, whereas the performance for Ru on alumina was slightly poorer (59 % humin conversion). Humin oils were characterized by using a range of analytical techniques (GC, GC-MS, GCxGC, gel permeation chromatography) and were shown to consist of monomers, mainly alkyl phenolics (>45 % based on compounds detectable by GC) and higher oligomers. A reaction network for the reaction is proposed based on structural proposals for humins and the main reaction products. PMID:26836970

  13. Reversibly Trapping Visible Laser Light through the Catalytic Photo-oxidation of I(-) by Ru(bpy)3(2+).

    PubMed

    Morim, Derek R; Vargas-Baca, Ignacio; Saravanamuttu, Kalaichelvi

    2016-04-21

    A Gaussian, visible laser beam traveling in a hydrogel doped with NaI and Ru(bpy)3Cl2 spontaneously transforms into a localized, self-trapped beam, which propagates without diverging through the medium. The catalytic, laser-light-induced oxidation of I(-) by [Ru(bpy)3](2+) generates I3(-) species, which create a refractive index increase along the beam path. The result is a cylindrical waveguide, which traps the optical field as bound modes and suppresses natural diffraction. When the beam is switched off, diffusion of I3(-) erases the waveguide within minutes and the system reverts to its original composition, enabling regeneration of the self-trapped beam. Our findings demonstrate reversible self-trapping for the first time in a precisely controllable, molecular-level photoreaction and could open routes to circuitry-free photonics devices powered by the interactions of switchable self-trapped beams. PMID:27035609

  14. Interaction of nickel deposits with catalytic metals on CoMo/Al[sub 2]O[sub 3] hydrometallation catalysts

    SciTech Connect

    Zhao, Xinjin; Wei, J. )

    1994-06-01

    Deactivation of hydrometallation catalyst has been studied extensively due to the demand for the processing of increasing amounts of resid and low quality crude oils. However, the interaction between metal deposits and the catalyst are not well understood. In this regard, the structures of nickel deposits on sulfided CoMo/Al[sub 2]O[sub 3] hydrodemetallation catalyst surface were characterized by using scanning transmission electron microscopy and high-resolution transmission electron microscopy techniques to study the interaction between the deposits and catalytic components. The deposits were found in crystallite form of nickel sulfide (Ni[sub 7]S[sub 6]) on the catalyst surface. Within the crystallites cobalt is uniformly distributed. Molybdenum is only partially associated with the nickel deposits as a segregated surface layer of molybdenum sulfide (MoS[sub 2]). For crystallites smaller than about 15 nm, the extent of segregation decreases. About 75% of the molybdenum is not directly associated with nickel deposits. Extensive cover-up of molybdenum by nickel deposits was not observed, and is not the main reason of catalyst deactivation. It was found that nickel deposits migrated towards cobalt sites even though molybdenum sites were the active sites for the hydrometallation reaction. Structure affinity favored the formation of solid solution between cobalt and nickel sulfides, which was the driving force for the association between nickel and cobalt on the catalyst surface. Microscopic characterization showed that deposition of nickel sulfide on the catalyst surface enhanced the mobility of the catalytic components MoS[sub 2]. Coalescence of MoS[sub 2] leads to significant reduction of accessible molybdenum sulfide sites, and is the main reason for the deactivation of hydrodemetallation catalyst. 29 refs., 14 figs., 3 tabs.

  15. Method for recovering catalytic elements from fuel cell membrane electrode assemblies

    DOEpatents

    Shore, Lawrence; Matlin, Ramail; Heinz, Robert

    2012-06-26

    A method for recovering catalytic elements from a fuel cell membrane electrode assembly is provided. The method includes converting the membrane electrode assembly into a particulate material, wetting the particulate material, forming a slurry comprising the wetted particulate material and an acid leachate adapted to dissolve at least one of the catalytic elements into a soluble catalytic element salt, separating the slurry into a depleted particulate material and a supernatant containing the catalytic element salt, and washing the depleted particulate material to remove any catalytic element salt retained within pores in the depleted particulate material.

  16. In situ FT-IR studies on the mechanism of selective catalytic reduction of NOx by propene over SnO2/Al2O3 catalyst.

    PubMed

    Liu, Zhiming; Woo, Seong Ihl; Lee, Won Su

    2006-12-28

    The mechanism of the selective catalytic reduction (SCR) of NOx by propene over SnO2/Al2O3 catalyst in the presence of oxygen has been investigated using in situ Fourier transform infrared (FT-IR) spectroscopy. In situ IR measurements indicate that acetate and formate, which are the derivatives of the partial oxidation of propene, play a crucial role in the formation of NCO by reacting with the reactive monodentate nitrate species. The resulting NCO species subsequently reacts with NOx to form N2. The presence of oxygen substantially contributes to the partial oxidation of propene and thus shows a promoting effect for the NOx reduction.

  17. Iron, lanthanum and manganese oxides loaded on gamma-AI2O3 for selective catalytic reduction of NO with NH3 at low temperature.

    PubMed

    Zhao, Weiwei; Li, Caiting; Lu, Pei; Wen, Qingbo; Zhao, Yapei; Zhang, Xing; Fan, Chunzhen; Tao, Shasha

    2013-01-01

    A series of Mn/Al2O3, La-Mn/Al2O3 and Fe-La-Mn/Al2O3 catalysts were prepared by an impregnation method and investigated for selective catalytic reduction of NO with NH3 at low temperature. The experimental results revealed that NO conversion over La-Mn/Al2O3 was obviously improved after La doping. Addition of Fe increased both NO conversion and the resistance to H2O and SO2. The catalyst Fe0.04La0.03Mn0.06/Al2O3 with a load mass of MnO2 = 6%, La2O3 = 3% and Fe2O3 = 4% exhibited relatively high catalytic activity and yielded 98% NO conversion at 260 degrees with a space velocity of 15,000 h(-1). Meanwhile, the catalytic activity was slightly decreased in the presence of H2O and SO2. Moreover, the catalysts were characterized by N2 adsorption measurement, X-ray diffraction and X-ray photoelectron spectroscopy. The results showed that the doping of La enhanced the dispersion and oxidation states of Mn on the surface of Al2O3. On the surface of the Fe0.04La0.03Mn0.06/Al2O3 catalyst, La was highly dispersed and a mixed oxidation state of Mn existed, while iron ions were only in the Fe3+ state. The mechanism of selective catalytic reduction over these catalysts is also discussed. In this experiment, metal oxides loaded on the support were catalytic centres which served as electron transfer during NO reduction. The electron transfer between Mn3+ and Fe3+ might also exist and the mixture oxidation states of Mn on the surface of the Fe0.04La0.03Mn0.06/Al2O3 catalyst contributed to the SCR activity.

  18. Pd-Re/Al{sub 2}O{sup 3}: Characterization and catalytic activity in hydrodechlorination of CCl{sub 2}F{sub 2}

    SciTech Connect

    Malinowski, A.; Juszczyk, W.; Bonarowska, M.; Pielaszek, J.; Karpinski, Z.

    1998-07-25

    A series of alumina-supported Pd-Re catalysts were prepared and characterized using X-ray diffraction, chemisorption, and temperature-programmed methods. A different stability of Pd(-Re)-hydride phases was exploited; i.e., the amount and decomposition temperatures of the {beta}-hydride phases for different Pd{sub x}Re{sub 1{minus}x}/Al{sub 2}O{sub 3} catalysts were found strongly correlated with x, suggesting a considerable extent of interaction between Pd and Re in reduced Pd-Re/Al{sub 2}O{sub 3} catalysts. The results from other characterization methods render a similar conclusion. The Pd-Re/Al{sub 2}O{sub 3} catalysts were tested in the reaction of hydrodechlorination of CCl{sub 2}F{sub 2}. Rhenium appeared inactive in this reaction. Adding Re to Pd/Al{sub 2}O{sub 3} introduces substantial changes in the catalytic behavior. All Pd-Re bimetallic samples strongly deactivated with time-on-stream, whereas the activity of Pd/Al{sub 2}O{sub 3}, after an initial increase, was fairly stable. Selectivity patterns for the bimetallic samples also differed from that of palladium, showing the increase in the selectivity to methane during the stabilization period. The steady-state activity of Pd-rich (up to 25 at% Re) bimetallic samples was much lower than that of Pd; however, it slightly increased with further Re addition, reaching a mild maximum at 50 at% Re. Such an activity pattern resembles very much the behavior of alumina-supported Pt-Re catalysts in hydrocarbon conversions. The selectivity towards CH{sub 2}F{sub 2} changed only slightly with the bimetallic composition. X-ray diffraction indicated the presence of carbon dissolved in Pd or Pd-rich phases in spent Pd-Re/Al{sub 2}O{sub 3} catalysts. Differences in lattice parameter of the carbonized phases depended on the nominal composition of Pd-Re, verifying a considerable extent of Pd-Re mixing in the supported catalysts. The results of catalytic screening are compatible with such a conclusion.

  19. High catalytic activity of oriented 2.0.0 copper(I) oxide grown on graphene film

    PubMed Central

    Primo, Ana; Esteve-Adell, Ivan; Blandez, Juan F.; Dhakshinamoorthy, Amarajothi; Álvaro, Mercedes; Candu, Natalia; Coman, Simona M.; Parvulescu, Vasile I.; García, Hermenegildo

    2015-01-01

    Metal oxide nanoparticles supported on graphene exhibit high catalytic activity for oxidation, reduction and coupling reactions. Here we show that pyrolysis at 900 °C under inert atmosphere of copper(II) nitrate embedded in chitosan films affords 1.1.1 facet-oriented copper nanoplatelets supported on few-layered graphene. Oriented (1.1.1) copper nanoplatelets on graphene undergo spontaneous oxidation to render oriented (2.0.0) copper(I) oxide nanoplatelets on few-layered graphene. These films containing oriented copper(I) oxide exhibit as catalyst turnover numbers that can be three orders of magnitude higher for the Ullmann-type coupling, dehydrogenative coupling of dimethylphenylsilane with n-butanol and C–N cross-coupling than those of analogous unoriented graphene-supported copper(I) oxide nanoplatelets. PMID:26509224

  20. High catalytic activity of oriented 2.0.0 copper(I) oxide grown on graphene film

    NASA Astrophysics Data System (ADS)

    Primo, Ana; Esteve-Adell, Ivan; Blandez, Juan F.; Dhakshinamoorthy, Amarajothi; Álvaro, Mercedes; Candu, Natalia; Coman, Simona M.; Parvulescu, Vasile I.; García, Hermenegildo

    2015-10-01

    Metal oxide nanoparticles supported on graphene exhibit high catalytic activity for oxidation, reduction and coupling reactions. Here we show that pyrolysis at 900 °C under inert atmosphere of copper(II) nitrate embedded in chitosan films affords 1.1.1 facet-oriented copper nanoplatelets supported on few-layered graphene. Oriented (1.1.1) copper nanoplatelets on graphene undergo spontaneous oxidation to render oriented (2.0.0) copper(I) oxide nanoplatelets on few-layered graphene. These films containing oriented copper(I) oxide exhibit as catalyst turnover numbers that can be three orders of magnitude higher for the Ullmann-type coupling, dehydrogenative coupling of dimethylphenylsilane with n-butanol and C-N cross-coupling than those of analogous unoriented graphene-supported copper(I) oxide nanoplatelets.

  1. Catalytic actions of alkaline salts in reactions between 1,2,3,4-butanetetracarboxylic acid and cellulose: II. Esterification.

    PubMed

    Ji, Bolin; Tang, Peixin; Yan, Kelu; Sun, Gang

    2015-11-01

    1,2,3,4-Butanetetracarboxylic acid (BTCA) reacts with cellulose in two steps with catalysis of alkaline salts such as sodium hypophosphite: anhydride formation and esterification of anhydride with cellulose. The alkali metal ions were found effective in catalyzing formation of BTCA anhydride in a previous report. In this work, catalytic functions of the alkaline salts in the esterification reaction between BTCA anhydride and cellulose were investigated. Results revealed that acid anions play an important role in the esterification reaction by assisting removal of protons on intermediates and completion of the esterification between cellulose and BTCA. Besides, alkaline salts with lower pKa1 values of the corresponding acids are more effective ones for the reaction since addition of these salts could lead to lower pH values and higher acid anion concentrations in finishing baths. The mechanism explains the results of FTIR and wrinkle recovery angles of the fabrics cured under different temperatures and times.

  2. High catalytic activity of oriented 2.0.0 copper(I) oxide grown on graphene film.

    PubMed

    Primo, Ana; Esteve-Adell, Ivan; Blandez, Juan F; Dhakshinamoorthy, Amarajothi; Álvaro, Mercedes; Candu, Natalia; Coman, Simona M; Parvulescu, Vasile I; García, Hermenegildo

    2015-01-01

    Metal oxide nanoparticles supported on graphene exhibit high catalytic activity for oxidation, reduction and coupling reactions. Here we show that pyrolysis at 900 °C under inert atmosphere of copper(II) nitrate embedded in chitosan films affords 1.1.1 facet-oriented copper nanoplatelets supported on few-layered graphene. Oriented (1.1.1) copper nanoplatelets on graphene undergo spontaneous oxidation to render oriented (2.0.0) copper(I) oxide nanoplatelets on few-layered graphene. These films containing oriented copper(I) oxide exhibit as catalyst turnover numbers that can be three orders of magnitude higher for the Ullmann-type coupling, dehydrogenative coupling of dimethylphenylsilane with n-butanol and C-N cross-coupling than those of analogous unoriented graphene-supported copper(I) oxide nanoplatelets. PMID:26509224

  3. Cloning and characterization of homeologous cellulose synthase catalytic subunit 2 genes from allotetraploid cotton (Gossypium hirsutum L.)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cellulose synthase catalytic subunits (CesAs) are the catalytic sites within a multisubunit complex for cellulose biosynthesis in plants. CesAs have been extensively studied in diploid plants, but are not well characterized in polyploid plants. Gossypium hirsutum is an allotetraploid cotton specie...

  4. Parallel measurements of organic and elemental carbon dry (PM1, PM2.5) and wet (rain, snow, mixed) deposition into the Baltic Sea.

    PubMed

    Witkowska, Agnieszka; Lewandowska, Anita; Falkowska, Lucyna M

    2016-03-15

    Parallel studies on organic and elemental carbon in PM1 and PM2.5 aerosols and in wet deposition in various forms of its occurrence were conducted in the urbanised coastal zone of the Baltic Sea. The carbon load introduced into the sea water was mainly affected by the form of precipitation. Dry deposition load of carbon was on average a few orders of magnitude smaller than wet deposition. The suspended organic carbon was more effectively removed from the air with rain than snow, while an inverse relationship was found for elemental carbon. However the highest flux of water insoluble organic carbon was recorded in precipitation of a mixed nature. The atmospheric cleaning of highly dissolved organic carbon was observed to be the most effective on the first day of precipitation, while the hydrophobic elemental carbon was removed more efficiently when the precipitation lasted longer than a day.

  5. Selective catalytic reduction of sulfur dioxide to elemental sulfur. Quarterly technical progress report No. 2, October--December 1992

    SciTech Connect

    Liu, Wei; Flytzani-Stephanopoulos, M.; Sarofim, A.F.

    1992-12-31

    Elemental sulfur recovery from SO{sub 2}-containing gas streams is highly attractive as it produces a saleable. Product and no waste to dispose of. However, commercially available schemes are complex and involve multi-stage reactors, such as, most notably in the Resox (reduction of SO{sub 2} with coke) and Claus plants(reaction of SO{sub 2} with H{sub 2}S over catalyst). This project win investigate a cerium oxide catalyst for the single-stage selective reduction SO{sub 2} to elemental sulfur by a reductant, such as carbon monoxide. Cerium oxide has been identified as a superior catalyst for SO{sub 2} reduction by CO to elemental sulfur because of its high activity and high selectivity to sulfur over COS over a wide temperature range(400--650C). Kinetic and parametric studies of SO{sub 2} reduction planned over various CeO{sub 2}-formulations will provide the necessary basis for development of a simplified process, a single-stage elemental sulfur recovery scheme from variable concentration gas streams. A first apparent application is treatment of regenerator off-gases in power plants using regenerative flue gas desulfurization. Such a simple catalytic converter may offer the long-sought ``Claus-alternative`` for coal-fired power plant applications.

  6. Understanding of catalytic behaviors of TiO2/CuOx catalysts

    SciTech Connect

    Kim H. Y.; Liu, P.

    2013-09-08

    Aiming to reveal the catalysis at the metal-oxide and oxide-oxide interfaces,1,2 the water-gas shift reaction (WGS, CO + H2O and #61664; CO2 + H2) and CO oxidation (2CO + O2 and #61664; 2CO2) at the interface of the Cu(111) and Cu2O(111) supported TiO2 clusters were studied based on DFT calculations

  7. Highly efficient degradation of 4-nitrophenol over the catalyst of Mn2O3/AC by microwave catalytic oxidation degradation method.

    PubMed

    Yin, Cheng; Cai, Jinjun; Gao, Lingfei; Yin, Jingya; Zhou, Jicheng

    2016-03-15

    A new microwave catalytic oxidation process based on two kinds of catalysts, the commercially available activated carbon (AC) and Mn2O3 nanoparticle modified AC (Mn2O3/AC), was reported for the degradation of 4-nitrophenol (4-NP) without adding any oxidant. Effects of microwave power, catalyst dosage, irradiation time, and initial concentration for the degradation efficiency were studied. Results indicated that catalyst of Mn2O3/AC showed much higher catalytic activity than pure AC and Mn2O3 particles. Significantly, 4-NP degradation efficiency reached 99.6%, corresponding to 93.5% TOC removal under optimal conditions with microwave power of 400W, Mn2O3/AC dosage of 2g, reaction time of 5min, and initial concentration of 100mg/L. Hydroxyl radicals (OH) generated during catalytic reaction is the main oxidant, and O2 can not effectively improve removal rate. We proposed the microwave 'photoelectric effect' to interpret the generation of OH in view that microwave irradiation can directly excite the catalyst to produce electron-hole pairs and then transform H2O into OH on the surface of catalyst in solution. The obtained kinetic equation for microwave catalytic oxidation degradation of 4-NP was in line with pseudo-first-order kinetic model, that is, apparent rate constant increased as microwave power density increase.

  8. Highly efficient degradation of 4-nitrophenol over the catalyst of Mn2O3/AC by microwave catalytic oxidation degradation method.

    PubMed

    Yin, Cheng; Cai, Jinjun; Gao, Lingfei; Yin, Jingya; Zhou, Jicheng

    2016-03-15

    A new microwave catalytic oxidation process based on two kinds of catalysts, the commercially available activated carbon (AC) and Mn2O3 nanoparticle modified AC (Mn2O3/AC), was reported for the degradation of 4-nitrophenol (4-NP) without adding any oxidant. Effects of microwave power, catalyst dosage, irradiation time, and initial concentration for the degradation efficiency were studied. Results indicated that catalyst of Mn2O3/AC showed much higher catalytic activity than pure AC and Mn2O3 particles. Significantly, 4-NP degradation efficiency reached 99.6%, corresponding to 93.5% TOC removal under optimal conditions with microwave power of 400W, Mn2O3/AC dosage of 2g, reaction time of 5min, and initial concentration of 100mg/L. Hydroxyl radicals (OH) generated during catalytic reaction is the main oxidant, and O2 can not effectively improve removal rate. We proposed the microwave 'photoelectric effect' to interpret the generation of OH in view that microwave irradiation can directly excite the catalyst to produce electron-hole pairs and then transform H2O into OH on the surface of catalyst in solution. The obtained kinetic equation for microwave catalytic oxidation degradation of 4-NP was in line with pseudo-first-order kinetic model, that is, apparent rate constant increased as microwave power density increase. PMID:26642442

  9. Catalytic coal liquefaction process

    DOEpatents

    Garg, D.; Sunder, S.

    1986-12-02

    An improved process for catalytic solvent refining or hydroliquefaction of non-anthracitic coal at elevated temperatures under hydrogen pressure in a solvent comprises using as catalyst a mixture of a 1,2- or 1,4-quinone and an alkaline compound, selected from ammonium, alkali metal, and alkaline earth metal oxides, hydroxides or salts of weak acids. 1 fig.

  10. Catalytic coal liquefaction process

    DOEpatents

    Garg, Diwakar; Sunder, Swaminathan

    1986-01-01

    An improved process for catalytic solvent refining or hydroliquefaction of non-anthracitic coal at elevated temperatures under hydrogen pressure in a solvent comprises using as catalyst a mixture of a 1,2- or 1,4-quinone and an alkaline compound, selected from ammonium, alkali metal, and alkaline earth metal oxides, hydroxides or salts of weak acids.

  11. The catalytic region and PEST domain of PTPN18 distinctly regulate the HER2 phosphorylation and ubiquitination barcodes.

    PubMed

    Wang, Hong-Mei; Xu, Yun-Fei; Ning, Shang-Lei; Yang, Du-Xiao; Li, Yi; Du, Yu-Jie; Yang, Fan; Zhang, Ya; Liang, Nan; Yao, Wei; Zhang, Ling-Li; Gu, Li-Chuan; Gao, Cheng-Jiang; Pang, Qi; Chen, Yu-Xin; Xiao, Kun-Hong; Ma, Rong; Yu, Xiao; Sun, Jin-Peng

    2014-09-01

    The tyrosine phosphorylation barcode encoded in C-terminus of HER2 and its ubiquitination regulate diverse HER2 functions. PTPN18 was reported as a HER2 phosphatase; however, the exact mechanism by which it defines HER2 signaling is not fully understood. Here, we demonstrate that PTPN18 regulates HER2-mediated cellular functions through defining both its phosphorylation and ubiquitination barcodes. Enzymologic characterization and three crystal structures of PTPN18 in complex with HER2 phospho-peptides revealed the molecular basis for the recognition between PTPN18 and specific HER2 phosphorylation sites, which assumes two distinct conformations. Unique structural properties of PTPN18 contribute to the regulation of sub-cellular phosphorylation networks downstream of HER2, which are required for inhibition of HER2-mediated cell growth and migration. Whereas the catalytic domain of PTPN18 blocks lysosomal routing and delays the degradation of HER2 by dephosphorylation of HER2 on pY(1112), the PEST domain of PTPN18 promotes K48-linked HER2 ubiquitination and its rapid destruction via the proteasome pathway and an HER2 negative feedback loop. In agreement with the negative regulatory role of PTPN18 in HER2 signaling, the HER2/PTPN18 ratio was correlated with breast cancer stage. Taken together, our study presents a structural basis for selective HER2 dephosphorylation, a previously uncharacterized mechanism for HER2 degradation and a novel function for the PTPN18 PEST domain. The new regulatory role of the PEST domain in the ubiquitination pathway will broaden our understanding of the functions of other important PEST domain-containing phosphatases, such as LYP and PTPN12. PMID:25081058

  12. Vanadium complexes having [VO]2+, [VO]3+ and [VO2]+ cores with hydrazones of 2,6-diformyl-4-methylphenol: synthesis, characterization, reactivity, and catalytic potential.

    PubMed

    Maurya, Mannar R; Haldar, Chanchal; Kumar, Amit; Kuznetsov, Maxim L; Avecilla, Fernando; Costa Pessoa, João

    2013-09-01

    The Schiff bases H3dfmp(L)2 obtained by the condensation of 2,6-diformyl-4-methylphenol and hydrazones [L = isonicotinoylhydrazide (inh), nicotinoylhydrazide (nah) and benzoylhydrazide (bhz)] are prepared and characterized. By reaction of [V(IV)O(acac)2] and the H3dfmp(L)2 in methanol the V(IV)O-complexes [V(IV)O{Hdfmp(inh)2}(H2O)] (1), [V(IV)O{Hdfmp(nah)2}(H2O)] (2) and [V(IV)O{Hdfmp(bhz)2}(H2O)] (3) were obtained. Upon their aerial oxidation in methanol [V(V)O(OMe)(MeOH){Hdfmp(inh)2}] (4), [V(V)O(OMe)(MeOH){Hdfmp(nah)2}] (5) and [V(V)O(OMe)(MeOH){Hdfmp(bhz)2}] (6) were isolated. In the presence of KOH, oxidation of 1-3 results in the formation of [V(V)O2{H2dfmp(inh)2}]n·5H2O (7), K[V(V)O2{Hdfmp(nah)2}] (8) and K[V(V)O2{Hdfmp(bhz)2}] (9). All compounds are characterized in the solid state and in solution, namely by spectroscopic techniques (IR, UV-Vis, EPR, (1)H, (13)C and (51)V NMR), and DFT is also used to calculate the V(IV) hyperfine coupling constants of V(IV)-compounds and (51)V NMR chemical shifts of several V(V)-species and assign them to those formed in solution. Single crystal X-ray analysis of [V(V)O(OMe)(MeOH){Hdfmp(bhz)2}] (6) and [V(V)O2{H2dfmp(inh)2}]n·5H2O (7) confirm the coordination of the ligand in the dianionic (ONO(2-)) enolate tautomeric form, one of the hydrazide moieties remaining non-coordinated. In the case of 7 the free N(pyridine) atom of the inh moiety coordinates to the other vanadium center yielding a polynuclear complex in the solid state. It is also demonstrated that the V(V)O2-complexes are catalyst precursors in the oxidative bromination of styrene by H2O2, therefore acting as functional models of vanadium dependent haloperoxidases. Plausible intermediates involved in the catalytic process are established by UV-Vis, (51)V NMR and DFT studies. PMID:23680862

  13. Catalytic hydrogenation activity and electronic structure determination of bis(arylimidazol-2-ylidene)pyridine cobalt alkyl and hydride complexes.

    PubMed

    Yu, Renyuan Pony; Darmon, Jonathan M; Milsmann, Carsten; Margulieux, Grant W; Stieber, S Chantal E; DeBeer, Serena; Chirik, Paul J

    2013-09-01

    The bis(arylimidazol-2-ylidene)pyridine cobalt methyl complex, ((iPr)CNC)CoCH3, was evaluated for the catalytic hydrogenation of alkenes. At 22 °C and 4 atm of H2 pressure, ((iPr)CNC)CoCH3 is an effective precatalyst for the hydrogenation of sterically hindered, unactivated alkenes such as trans-methylstilbene, 1-methyl-1-cyclohexene, and 2,3-dimethyl-2-butene, representing one of the most active cobalt hydrogenation catalysts reported to date. Preparation of the cobalt hydride complex, ((iPr)CNC)CoH, was accomplished by hydrogenation of ((iPr)CNC)CoCH3. Over the course of 3 h at 22 °C, migration of the metal hydride to the 4-position of the pyridine ring yielded (4-H2-(iPr)CNC)CoN2. Similar alkyl migration was observed upon treatment of ((iPr)CNC)CoH with 1,1-diphenylethylene. This reactivity raised the question as to whether this class of chelate is redox-active, engaging in radical chemistry with the cobalt center. A combination of structural, spectroscopic, and computational studies was conducted and provided definitive evidence for bis(arylimidazol-2-ylidene)pyridine radicals in reduced cobalt chemistry. Spin density calculations established that the radicals were localized on the pyridine ring, accounting for the observed reactivity, and suggest that a wide family of pyridine-based pincers may also be redox-active.

  14. Visible light plasmonic heating of Au-ZnO for the catalytic reduction of CO2

    SciTech Connect

    Wang, Congjun; Ranasingha, Oshadha; Natesakhawat, Sittichai; Ohodnicki, Paul R.; Andio, Mark; Lewis, James P.; Matranga, Christopher

    2013-01-01

    Plasmonic excitation of Au nanoparticles attached to the surface of ZnO catalysts using low power 532 nm laser illumination leads to significant heating of the catalyst and the conversion of CO2 and H2 reactants to CH4 and CO products. Temperature-calibrated Raman spectra of ZnO phonons show that intensity-dependent plasmonic excitation can controllably heat Au–ZnO from 30 to ~600 °C and simultaneously tune the CH4 : CO product ratio. The laser induced heating and resulting CH4 : CO product distribution agrees well with predictions from thermodynamic models and temperature-programmed reaction experiments indicating that the reaction is a thermally driven process resulting from the plasmonic heating of the Au-ZnO. The apparent quantum yield for CO2 conversion under continuous wave (cw) 532 nm laser illumination is 0.030%. The Au-ZnO catalysts are robust and remain active after repeated laser exposure and cycling. The light intensity required to initiate CO2 reduction is low ( ~2.5 x 105 W m-2) and achievable with solar concentrators. Our results illustrate the viability of plasmonic heating approaches for CO2 utilization and other practical thermal catalytic applications.

  15. Development Status of the WetLab-2 Project: New Tools for On-orbit Real-time Quantitative Gene Expression.

    NASA Technical Reports Server (NTRS)

    Jung, Jimmy; Parra, Macarena P.; Almeida, Eduardo; Boone, Travis; Chinn, Tori; Ricco, Antonio; Souza, Kenneth; Hyde, Liz; Rukhsana, Yousuf; Richey, C. Scott

    2013-01-01

    The primary objective of NASA Ames Research Centers WetLab-2 Project is to place on the ISS a research platform to facilitate gene expression analysis via quantitative real-time PCR (qRT-PCR) of biological specimens grown or cultured on orbit. The WetLab-2 equipment will be capable of processing multiple sample types ranging from microbial cultures to animal tissues dissected on-orbit. In addition to the logistical benefits of in-situ sample processing and analysis, conducting qRT-PCR on-orbit eliminates the confounding effects on gene expression of reentry stresses and shock acting on live cells and organisms. The system can also validate terrestrial analyses of samples returned from ISS by providing quantitative on-orbit gene expression benchmarking prior to sample return. The ability to get on orbit data will provide investigators with the opportunity to adjust experimental parameters for subsequent trials based on the real-time data analysis without need for sample return and re-flight. Finally, WetLab-2 can be used for analysis of air, surface, water, and clinical samples to monitor environmental contaminants and crew health. The verification flight of the instrument is scheduled to launch on SpaceX-5 in Aug. 2014.Progress to date: The WetLab-2 project completed a thorough study of commercially available qRT-PCR systems and performed a downselect based on both scientific and engineering requirements. The selected instrument, the Cepheid SmartCycler, has advantages including modular design (16 independent PCR modules), low power consumption, and rapid ramp times. The SmartCycler has multiplex capabilities, assaying up to four genes of interest in each of the 16 modules. The WetLab-2 team is currently working with Cepheid to modify the unit for housing within an EXPRESS rack locker on the ISS. This will enable the downlink of data to the ground and provide uplink capabilities for programming, commanding, monitoring, and instrument maintenance. The project is

  16. Enhanced catalytic complete oxidation of 1,2-dichloroethane over mesoporous transition metal-doped γ-Al2O3.

    PubMed

    Khaleel, Abbas; Nawaz, Muhammad

    2015-03-01

    High-surface-area mesoprous powders of γ-Al2O3 doped with Cu2+, Cr3+, and V3+ ions were prepared via a modified sol-gel method and were investigated as catalysts for the oxidation of chlorinated organic compounds. The composites retained high surface areas and pore volumes comparable with those of undoped γ-Al2O3 and the presence of the transition metal ions enhanced their surface acidic properties. The catalytic activity of the prepared catalysts in the oxidation of 1,2-dichloroethane (DCE) was studied in the temperature range of 250-400°C. The catalytic activity and product selectivity were strongly dependent on the presence and the type of dopant ion. While Cu2+- and Cr3+-containing catalysts showed 100% conversion at 300°C and 350°C, V3+-containing catalyst showed considerably lower conversion. Furthermore, while the major products of the reactions over γ-alumina were vinyl chloride (C2H3Cl) and hydrogen chloride (HCl) at all temperatures, Cu- and Cr-doped catalysts showed significantly stronger capability for deep oxidation to CO2. PMID:25766029

  17. New Rh2(II,II) Architecture for the Catalytic Reduction of H⁺.

    PubMed

    White, Travis A; Witt, Suzanne E; Li, Zhanyong; Dunbar, Kim R; Turro, Claudia

    2015-10-19

    Formamidinate-bridged Rh2(II,II) complexes containing diimine ligands of the formula cis-[Rh2(II,II)(μ-DTolF)2(NN)2](2+) (Rh2-NN2), where DTolF = p-ditolylformamidinate and NN = dppn (benzo[i]dipyrido[3,2-a:2',3'-h]quinoxaline), dppz (dipyrido[3,2-a:2',3'-c]phenazine), and phen (1,10-phenanthroline), electrocatalytically reduce H(+) to H2 in DMF solutions containing CH3COOH at a glassy carbon electrode. Cathodic scans in the absence of acid display a Rh(III,II/II,II) reduction at -0.90 V vs Fc(+)/Fc followed by NN(0/-) reduction at -1.13, -1.36, and -1.65 V for Rh2-dppn2, Rh2-dppz2, and Rh2-phen2, respectively. Upon the addition of acid, Rh2-dppn2 and Rh2-dppz2 undergo reduction-protonation-reduction at each pyrazine-containing NN ligand prior to the Rh2(II,II/II,I) reduction. The Rh2(II,I) species is then protonated at one of the metal centers, resulting in the formation of the corresponding Rh2(II,III)-hydride. In the case of Rh2-phen2, the reduction of the phen ligand is followed by intramolecular electron transfer to the Rh2(II,II) core in the presence of protons to form a Rh2(II,III)-hydride species. Further reduction and protonation at the Rh2 core for all three complexes rapidly catalyzes H2 formation with varied calculated turnover frequencies (TOF) and overpotential values (η): 2.6 × 10(4) s(-1) and 0.56 V for Rh2-dppn, 2.8 × 10(4) s(-1) and 0.50 V for Rh2-dppz2, and 5.9 × 10(4) s(-1) and 0.64 V for Rh2-phen2. Bulk electrolysis confirmed H2 formation, and further CH3COOH addition regenerates H2 production, attesting to the robust nature of the architecture. The cis-[Rh2(II,II)(μ-DTolF)2(NN)2](2+) architecture benefits by combining electron-rich formamidinate bridges, a redox-active Rh2(II,II) core, and electron-accepting NN diimine ligands to allow for the electrocatalysis of H(+) substrate to H2 fuel.

  18. Structural definition of the active site and catalytic mechanism of 3,4-dihydroxy-2-butanone 4-phosphate synthase

    SciTech Connect

    Liao, D.-I.; Zheng, Y.-J.; Viitanen, P.V.; Jordan, D.B.

    2010-03-08

    X-ray crystal structures of L-3,4-dihydroxy-2-butanone-4-phosphate synthase from Magnaporthe grisea are reported for the E-SO{sub 4}{sup 2-}, E-{sub 4}{sup 2-}-Mg{sup 2+}, E-SO{sub 4}{sup 2-}-Mn{sup 2+}, E-SO{sub 4}{sup 2-}-Mn{sup 2+}-glycerol, and E-SO{sub 4}{sup 2-}-Zn{sup 2+} complexes with resolutions that extend to 1.55, 0.98, 1.60, 1.16, and 1.00 {angstrom}, respectively. Active-site residues of the homodimer are fully defined. The structures were used to model the substrate ribulose 5-phosphate in the active site with the phosphate group anchored at the sulfate site and the placement of the ribulose group guided by the glycerol site. The model includes two Mg{sup 2+} cations that bind to the oxygen substituents of the C2, C3, C4, and phosphate groups of the substrate, the side chains of Glu37 and His153, and water molecules. The position of the metal cofactors and the substrate's phosphate group are further stabilized by an extensive hydrogen-bond and salt-bridge network. On the basis of their proximity to the substrate's reaction participants, the imidazole of an Asp99-His136 dyad from one subunit, the side chains of the Asp41, Cys66, and Glu174 residues from the other subunit, and Mg{sup 2+}-activated water molecules are proposed to serve specific roles in the catalytic cycle as general acid-base functionalities. The model suggests that during the 1,2-shift step of the reaction, the substrate's C3 and C4 hydroxyl groups are cis to each other. A cis transition state is calculated to have an activation barrier that is 2 kcal/mol greater than that of the trans transition state in the absence of the enzyme.

  19. Promotion effects of SiO2 or/and Al2O3 doped CeO2/TiO2 catalysts for selective catalytic reduction of NO by NH3.

    PubMed

    Zhao, Wenru; Tang, Yu; Wan, Yaping; Li, Liang; Yao, Si; Li, Xiaowei; Gu, Jinlou; Li, Yongsheng; Shi, Jianlin

    2014-08-15

    A series of the CeO2-based catalysts loaded on TiO2, TiO2-SiO2, TiO2-Al2O3, and TiO2-SiO2-Al2O3 supports were prepared by incipient impregnation method for the selective catalytic reduction (SCR) of NO by NH3 in the presence of oxygen. The SCR activities of the catalysts with different supports increases in the order of Ce/TiO2 < Ce/TiO2-20SiO2 ≈ Ce/TiO2-3.5Al2O3 < Ce/TiO2-20SiO2-3.5Al2O3. The Ce/TiO2-20SiO2-3.5Al2O3 catalyst showed 100% NO conversion in the temperature range of 250-425°C and 100% N2 selectivity in the whole temperature range. The catalytic activity of Ce/TiO2-20SiO2-3.5Al2O3 exhibited good stability and strong resistance to SO2 and H2O poisoning. The co-introduction of SiO2 and Al2O3 into TiO2 could increase the amount of chemisorbed oxygen and Lewis acid sites on the surface of catalyst, which should be responsible for the excellent SCR activity.

  20. Mild activation of CeO2-supported gold nanoclusters and insight into the catalytic behavior in CO oxidation

    NASA Astrophysics Data System (ADS)

    Li, Weili; Ge, Qingjie; Ma, Xiangang; Chen, Yuxiang; Zhu, Manzhou; Xu, Hengyong; Jin, Rongchao

    2016-01-01

    We report a new activation method and insight into the catalytic behavior of a CeO2-supported, atomically precise Au144(SR)60 nanocluster catalyst (where thiolate -SR = -SCH2CH2Ph) for CO oxidation. An important finding is that the activation of the catalyst is closely related to the production of active oxygen species on CeO2, rather than ligand removal of the Au144(SR)60 clusters. A mild O2 pretreatment (at 80 °C) can activate the catalyst, and the addition of reductive gases (CO or H2) can enhance the activation effects of O2 pretreatment via a redox cycle in which CO could reduce the surface of CeO2 to produce oxygen vacancies--which then adsorb and activate O2 to produce more active oxygen species. The CO/O2 pulse experiments confirm that CO is adsorbed on the cluster catalyst even with ligands on, and active oxygen species present on the surface of the pretreated catalyst reacts with CO pulses to generate CO2. The Au144(SR)60/CeO2 exhibits high CO oxidation activity at 80 °C without the removal of thiolate ligands. The surface lattice-oxygen of the support CeO2 possibly participates in the oxidation of CO over the Au144(SR)60/CeO2 catalyst.We report a new activation method and insight into the catalytic behavior of a CeO2-supported, atomically precise Au144(SR)60 nanocluster catalyst (where thiolate -SR = -SCH2CH2Ph) for CO oxidation. An important finding is that the activation of the catalyst is closely related to the production of active oxygen species on CeO2, rather than ligand removal of the Au144(SR)60 clusters. A mild O2 pretreatment (at 80 °C) can activate the catalyst, and the addition of reductive gases (CO or H2) can enhance the activation effects of O2 pretreatment via a redox cycle in which CO could reduce the surface of CeO2 to produce oxygen vacancies--which then adsorb and activate O2 to produce more active oxygen species. The CO/O2 pulse experiments confirm that CO is adsorbed on the cluster catalyst even with ligands on, and active oxygen

  1. Wetting in Color

    NASA Astrophysics Data System (ADS)

    Burgess, Ian Bruce

    Colorimetric litmus tests such as pH paper have enjoyed wide commercial success due to their inexpensive production and exceptional ease of use. However, expansion of colorimetry to new sensing paradigms is challenging because macroscopic color changes are seldom coupled to arbitrary differences in the physical/chemical properties of a system. In this thesis I present in detail the development of Wetting in Color Technology, focusing primarily on its application as an inexpensive and highly selective colorimetric indicator for organic liquids. The technology exploits chemically-encoded inverse-opal photonic crystals to control the infiltration of fluids to liquid-specific spatial patterns, projecting minute differences in liquids' wettability to macroscopically distinct, easy-to-visualize structural color patterns. It is shown experimentally and corroborated with theoretical modeling using percolation theory that the high selectivity of wetting, upon-which the sensitivity of the indicator relies, is caused by the highly symmetric structure of our large-area, defect-free SiO2 inverse-opals. The regular structure also produces a bright iridescent color, which disappears when infiltrated with liquid - naturally coupling the optical and fluidic responses. Surface modification protocols are developed, requiring only silanization and selective oxidation, to facilitate the deterministic design of an indicator that differentiates a broad range of liquids. The resulting tunable, built-in horizontal and vertical chemistry gradients allow the wettability threshold to be tailored to specific liquids across a continuous range, and make the readout rely only on countable color differences. As wetting is a generic fluidic phenomenon, Wetting in Color technology could be suitable for applications in authentication or identification of unknown liquids across a broad range of industries. However, the generic nature of the response also ensures chemical non-specificity. It is shown

  2. Development of catalytic asymmetric 1,4-addition and [3 + 2] cycloaddition reactions using chiral calcium complexes.

    PubMed

    Tsubogo, Tetsu; Saito, Susumu; Seki, Kazutaka; Yamashita, Yasuhiro; Kobayashi, Shu

    2008-10-01

    Catalytic asymmetric 1,4-addition and [3 + 2] cycloaddition reactions using chiral calcium species prepared from calcium isopropoxide and chiral bisoxazoline ligands have been developed. Glycine Schiff bases reacted with acrylic esters to afford 1,4-addition products, glutamic acid derivatives, in high yields with high enantioselectivities. During the investigation of the 1,4-addition reactions, we unexpectedly found that a [3 + 2] cycloaddition occurred in the reactions with crotonate derivatives, affording substituted pyrrolidine derivatives in high yields with high enantioselectivities. On the basis of this finding, we investigated asymmetric [3 + 2] cycloadditions, and it was revealed that several kinds of optically active substituted pyrrolidine derivatives containing contiguous stereogenic tertiary and quaternary carbon centers were obtained with high diastereo- and enantioselectivities. In addition, optically active pyrrolidine cores of hepatitis C virus RNA-dependent polymerase inhibitors and potential effective antiviral agents have been synthesized using this [3 + 2] cycloaddition reaction. NMR spectroscopic analysis and observation of nonamplification of enantioselectivity in nonlinear effect experiments suggested that a monomeric calcium species with an anionic ligand was formed as an active catalyst. A stepwise mechanism of the [3 + 2] cycloaddition, consisting of 1,4-addition and successive intramolecular Mannich-type reaction was suggested. Furthermore, modification of the Schiff base structure resulted in a modification of the reaction course from a [3 + 2] cycloaddition to a 1,4-addition, affording 3-substituted glutamic acid derivatives with high diasterero- and enantioselectivities.

  3. Development of catalytic asymmetric 1,4-addition and [3 + 2] cycloaddition reactions using chiral calcium complexes.

    PubMed

    Tsubogo, Tetsu; Saito, Susumu; Seki, Kazutaka; Yamashita, Yasuhiro; Kobayashi, Shu

    2008-10-01

    Catalytic asymmetric 1,4-addition and [3 + 2] cycloaddition reactions using chiral calcium species prepared from calcium isopropoxide and chiral bisoxazoline ligands have been developed. Glycine Schiff bases reacted with acrylic esters to afford 1,4-addition products, glutamic acid derivatives, in high yields with high enantioselectivities. During the investigation of the 1,4-addition reactions, we unexpectedly found that a [3 + 2] cycloaddition occurred in the reactions with crotonate derivatives, affording substituted pyrrolidine derivatives in high yields with high enantioselectivities. On the basis of this finding, we investigated asymmetric [3 + 2] cycloadditions, and it was revealed that several kinds of optically active substituted pyrrolidine derivatives containing contiguous stereogenic tertiary and quaternary carbon centers were obtained with high diastereo- and enantioselectivities. In addition, optically active pyrrolidine cores of hepatitis C virus RNA-dependent polymerase inhibitors and potential effective antiviral agents have been synthesized using this [3 + 2] cycloaddition reaction. NMR spectroscopic analysis and observation of nonamplification of enantioselectivity in nonlinear effect experiments suggested that a monomeric calcium species with an anionic ligand was formed as an active catalyst. A stepwise mechanism of the [3 + 2] cycloaddition, consisting of 1,4-addition and successive intramolecular Mannich-type reaction was suggested. Furthermore, modification of the Schiff base structure resulted in a modification of the reaction course from a [3 + 2] cycloaddition to a 1,4-addition, affording 3-substituted glutamic acid derivatives with high diasterero- and enantioselectivities. PMID:18783222

  4. Synthesis and catalytic application of palladium imidazol(in)ium-2-dithiocarboxylate complexes.

    PubMed

    Champion, Martin J D; Solanki, Riten; Delaude, Lionel; White, Andrew J P; Wilton-Ely, James D E T

    2012-10-28

    The palladium(II) dimer, [Pd(C,N-C(6)H(4)CH(2)NMe(2))Cl](2) reacts with two equivalents of the NHC·CS(2) zwitterionic ligands [NHC = IPr (1,3-diisopropylimidazol-2-ylidene), ICy (1,3-dicyclohexylimidazol-2-ylidene), IMes (1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene), IDip (1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene), SIMes (1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene)] in the presence of NH(4)PF(6), to yield the cationic products [Pd(C,N-C(6)H(4)CH(2)NMe(2))(S(2)C·NHC)](+). In a similar fashion, the compounds [Pd(C,N-bzq)(S(2)C·NHC)](+) (bzq = benzo[h]quinolinyl, NHC = ICy, IMes, IDip) are obtained from the corresponding dimer [Pd(C,N-bzq)Cl](2). The bis(phosphine) compounds [Pd(S(2)C·NHC)(PPh(3))(2)](2+) (NHC = ICy, IMes, IDip, SIMes) are obtained on treatment of [PdCl(2)(PPh(3))(2)] with NHC·CS(2) zwitterions in the presence of NH(4)PF(6). The reaction of [PdCl(2)(dppf)] with IMes·CS(2) and NH(4)PF(6) provides the complex [Pd(S(2)C·IMes)(dppf)](2+). The complexes [Pd(S(2)C·NHC)(PPh(3))(2)](PF(6))(2) (NHC = IMes, IDip) were active pre-catalysts (1 mol% loading) for the conversion of benzo[h]quinoline to 10-methoxybenzo[h]quinoline in the presence of PhI(OAc)(2) and methanol. The intermediacy of [Pd(C,N-bzq)(S(2)C·NHC)](+) was supported by the high yield of 10-methoxybenzo[h]quinoline using [Pd(C,N-bzq)(S(2)C·IDip)](+) to promote the same reaction. Small amounts of 2,10-dimethoxybenzo[h]quinoline were also isolated from these reactions. Using [Pd(C,N-bzq)(S(2)C·IDip)](+) and N-chlorosuccinimide as the oxidant led to the formation of 10-chlorobenzo[h]quinoline in moderate yield from benzo[h]quinoline. The molecular structures of [Pd(S(2)C·IMes)(PPh(3))(2)](PF(6))(2) and [Pd(S(2)C·IMes)(dppf)](PF(6))(2) were determined crystallographically. PMID:22936368

  5. Catalytic Efficiency Is a Function of How Rhodium(I) (5 + 2) Catalysts Accommodate a Conserved Substrate Transition State Geometry: Induced Fit Model for Explaining Transition Metal Catalysis

    PubMed Central

    Mustard, Thomas J. L.; Wender, Paul A.; Cheong, Paul Ha-Yeon

    2015-01-01

    The origins of differential catalytic reactivities of four Rh(I) catalysts and their derivatives in the (5 + 2) cycloaddition reaction were elucidated using density functional theory. Computed free energy spans are in excellent agreement with known experimental rates. For every catalyst, the substrate geometries in the transition state remained constant (<0.1 Å RMSD for atoms involved in bond-making and -breaking processes). Catalytic efficiency is shown to be a function of how well the catalyst accommodates the substrate transition state geometry and electronics. This shows that the induced fit model for explaining biological catalysis may be relevant to transition metal catalysis. This could serve as a general model for understanding the origins of efficiencies of catalytic reactions. PMID:26146588

  6. From Mono to Tris-1,2,3-triazole-Stabilized Gold Nanoparticles and Their Compared Catalytic Efficiency in 4-Nitrophenol Reduction.

    PubMed

    Wang, Changlong; Salmon, Lionel; Li, Qian; Igartua, María Echeverría; Moya, Sergio; Ciganda, Roberto; Ruiz, Jaime; Astruc, Didier

    2016-07-01

    Mono-, bis-, and tris-1,2,3-triazole ligands are used for the stabilization of gold nanoparticles (AuNPs), and the catalytic activities of these AuNPs in 4-nitrophenol reduction by NaBH4 in water are compared as well as with polyethylene glycol 2000 (PEG)- and polyvinylpyrrolidone (PVP)-stabilized AuNPs. The excellent catalytic results specifically obtained with the tris-triazolate ligand terminated by a PEG tail are taken into account by the synergy between the weakness of the tris-triazole-AuNP bond combined with the stabilizing ligand bulk. PMID:27304517

  7. In situ loading of well-dispersed gold nanoparticles on two-dimensional graphene oxide/SiO2 composite nanosheets and their catalytic properties.

    PubMed

    Zhu, Chengzhou; Han, Lei; Hu, Peng; Dong, Shaojun

    2012-03-01

    We demonstrated a simple, in situ reduction route to the synthesis of two-dimensional graphene oxide/SiO(2) (GSCN) hybrid nanostructures consisting of Au nanoparticles (Au NPs) supported on the both sides of GSCN. The as-prepared GSCN/Au NPs hybrid nanomaterials exhibited good catalytic activity for the reduction of 4-nitrophenol. This approach provided a useful platform based on GO hybrid nanomaterials for the fabrication of GSCN/Au NPs hybrid nanomaterials, which could be very useful in catalytic applications.

  8. Catalytic reduction of SO{sub 2} with methane over molybdenum catalyst. Technical report, March 1--May 31, 1995

    SciTech Connect

    Wiltowski, T.

    1995-12-31

    One of the primary concerns in coal utilization is the emission of sulfur compounds, especially SO{sub 2}. This project deals with catalytic reduction of SO{sub 2} with methane using molybdenum sulfide catalyst supported on different activated carbons: Darco TRS, ROZ-3, and an activated carbon prepared from Illinois coal IBC-110. The work conducted during this quarter included preparation of activated carbons from Illinois coal, preparation of the catalysts on these supports, and experiments on SO{sub 2} reduction with methane at different feed ratio SO{sub 2}: CH{sub 4}. It was found that at the feed ratio 1:1, 10% MoS{sub 2} supported on Darco TRS catalyst has highest activity at low temperatures; at higher temperatures, the catalysts 15% and 20% MoS{sub 2} supported on Darco TRS exhibit high activity in both SO{sub 2} conversion (> 90%) and yield of elemental sulfur (97.4% for 20% MoS{sub 2} at 600 C). For catalyst supported on ROZ-3, this having 10% of MOS{sub 2} showed high activity in the reaction. To determine the effect of feed ratio on the reaction, the catalysts with 15% loading of MoS{sub 2} supported on Darco TRS and ROZ-3 were used. For catalyst supported on ROZ-3 activated carbon, the effect of feed ratio is dramatic, especially at the higher temperatures at which the conversion of SO{sub 2} increases more than twice when the feed contains excess of methane. For catalyst supported on Darco TRS activated carbons, there is practically no difference in SO{sub 2} conversion for feed ratios 1:1 and 1:2 (with respect for methane).

  9. Molecular identification of a calcium-inhibited catalytic subunit of casein kinase type 2 from Paramecium tetraurelia.

    PubMed

    Vetter, Daniel; Kissmehl, Roland; Treptau, Tilman; Hauser, Karin; Kellermann, Josef; Plattner, Helmut

    2003-12-01

    We have previously described the occurrence in Paramecium of a casein kinase (CK) activity (EC 2.7.1.37) with some unusual properties, including inhibition by Ca(2+) (R. Kissmehl, T. Treptau, K. Hauser, and H. Plattner, FEBS Lett. 402:227-235, 1995). We now have cloned four genes, PtCK2alpha1 to PtCK2alpha4, all of which encode the catalytic alpha subunit of type 2 CK (CK2) with calculated molecular masses ranging from 38.9 to 39.4 kDa and pI values ranging from 8.8 to 9.0. They can be classified into two groups, which differ from each other by 28% on the nucleotide level and by 18% on the derived amino acid level. One of them, PtCK2alpha3, has been expressed in Escherichia coli and characterized in vitro. As we also have observed with the isolated CK, the recombinant protein preferentially phosphorylates casein but also phosphorylates some Paramecium-specific substrates, including the exocytosis-sensitive phosphoprotein pp63/parafusin. Characteristically, Ca(2+) inhibits the phosphorylation at elevated concentrations occurring during stimulation of a cell. Reconstitution with a recombinant form of the regulatory subunit from Xenopus laevis, XlCK2beta, confirms Ca(2+) sensitivity also under conditions of autophosphorylation. This is unusual for CK2 but correlates with the presence of two EF-hand calcium-binding motifs, one of which is located in the N-terminal segment essential for constitutive activity, as well as with an aberrant composition of normally basic domains recognizing acidic substrate domains. Immunogold localization reveals a considerable enrichment in the outermost cell cortex layers, excluding cilia. We discuss a potential role of this Ca(2+)-inhibited PtCK2alpha species in a late step of signal transduction. PMID:14665457

  10. Characteristics of NOx removal combining dielectric barrier discharge plasma with selective catalytic reduction by C2H5OH

    NASA Astrophysics Data System (ADS)

    Wang, Xing-Quan; Chen, Wei; Guo, Qi-Pei; Li, Yi; Lv, Guo-Hua; Sun, Xiu-Ping; Zhang, Xian-Hui; Feng, Ke-Cheng; Yang, Si-Ze

    2009-07-01

    With the assistance of dielectric barrier discharge (DBD) plasma, selective catalytic reduction of NOx by ethanol over Ag/Al2O3 catalysts was studied. Experimental results show that NOx conversion was greatly enhanced due to the presence of DBD plasma at lower temperature. By varying the DBD voltages or power in 13 kHz frequency at different temperatures, NOx conversion was increased to 40.7% from 6.4% at 176 °C, even to 66.8% from 17.3% at 200 °C. NOx conversion could even be improved to 90% at temperature above 255 °C. It was proposed that nonthermal plasma generated by dielectric barrier discharge reactor was very effective for oxidizing NO to NO2 under excess O2 conditions, which possesses high reactivity with C2H5OH to yield CxHyNzO compound. By reacting with CxHyNzO compound and oxygen, NOx is converted to N2 at low temperatures.

  11. Kinetics of ABTS derived radical cation scavenging by bucillamine, cysteine, and glutathione. Catalytic effect of Cu(2+) ions.

    PubMed

    Valent, Ivan; Topolská, Dominika; Valachová, Katarína; Bujdák, Juraj; Šoltés, Ladislav

    2016-05-01

    Kinetics of reduction of the stable radical cation derived from 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS) in reaction with the anti-rheumatic drug bucillamine (BUC) and two reference thiols - cysteine (Cys) and glutathione (GSH) was followed spectrophotometrically in acidic medium with 10-fold molar excess of the reductant. Decay of the radical is governed by pseudo-first order kinetics with small deviation in the case of GSH. H(+) ions displayed second order inhibition of the reaction with all the studied compounds. The reaction of BUC exhibits zero order kinetics to the radical at lower acidities with a moderate acceleration of the reaction rate by H(+) ions. A significant catalytic effect of Cu(2+) ions on the reactions with all the reductants was observed. The most sensitive to Cu(2+)-catalysis was the reaction of BUC with the radical cation, while Cu(2+) ions showed much lower effect on the reaction with GSH. The presence of EDTA strongly inhibited the reactions and equalized the reaction rates for all the reductants. A Cu(I) selective chelator bathocuproine disulfonate reduced the reaction rate with Cys, but accelerated the reaction with BUC at the lower acidities. The experimental results were rationalized in the framework of the mechanism of reductive chelation. The conclusions may have important consequences for interpretation of antioxidant capacity assays, such as TEAC, utilizing the ABTS derived radical cation.

  12. Catalytic oxidation of H2 by N2O in the gas phase: O-atom transport with atomic metal cations.

    PubMed

    Blagojevic, Voislav; Bozović, Andrea; Orlova, Galina; Bohme, Diethard K

    2008-10-16

    Twenty-five atomic cations, M (+), that lie within the thermodynamic window for O-atom transport catalysis of the oxidation of hydrogen by nitrous oxide, have been checked for catalytic activity at room temperature with kinetic measurements using an inductively-coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer. Only 4 of these 25 atomic cations were seen to be catalytic: Fe (+), Os (+), Ir (+), and Pt (+). Two of these, Ir (+) and Pt (+), are efficient catalysts, while Fe (+) and Os (+) are not. Eighteen atomic cations (Cr (+), Mn (+), Co (+), Ni (+), Cu (+), Ge (+), Se (+), Mo (+), Ru (+), Rh (+), Sn (+), Te (+), Re (+), Pb (+), Bi (+), Eu (+), Tm (+), and Yb (+)) react too slowly at room temperature either in their oxidation with N 2O to form MO (+) or in the reduction of MO (+) by H 2. Many of these reactions are known to be spin forbidden and a few actually may lie outside the thermodynamic window. Three alkaline-earth metal monoxide cations, CaO (+), SrO (+), and BaO (+), were observed to favor MOH (+) formation in their reactions with H 2. A potential-energy landscape is computed for the oxidation of H 2 with N 2O catalyzed by Fe (+)( (6)D) that vividly illustrates the operation of an ionic catalyst and qualitatively accounts for the relative inefficiency of this catalyst. PMID:18808088

  13. Brucite [Mg(OH2)] Carbonation in Wet Supercritical CO2: An in situ High Pressure X-Ray Diffraction Study

    SciTech Connect

    Schaef, Herbert T.; Windisch, Charles F.; McGrail, B. Peter; Martin, Paul F.; Rosso, Kevin M.

    2011-11-01

    Understanding mechanisms and kinetics of mineral carbonation reactions relevant to sequestering carbon dioxide as a supercritical fluid (scCO2) in geologic formations is crucial to accurately predicting long-term storage risks. Most attention so far has been focused on reactions occurring between silicate minerals and rocks in the aqueous dominated CO2-bearing fluid. However, water-bearing scCO2 also comprises a reactive fluid, and in this situation mineral carbonation mechanisms are poorly understood. Using in situ high-pressure x-ray diffraction, the carbonation of brucite [Mg(OH)2] in wet scCO2 was examined at pressure (82 bar) as a function of water concentration and temperature (50 C and 75 C). Exposing brucite to anhydrous scCO2 at either temperature resulted in little or no detectable reaction over three days. However, addition of trace amounts of water resulted in partial carbonation of brucite into nesquehonite [MgCO3 3H2O] within a few hours at 50 C. By increasing water content to well above the saturation level of the scCO2, complete conversion of brucite into nesquehonite was observed. Tests conducted at 75 C resulted in the conversion of brucite into magnesite [MgCO3] instead, apparently through an intermediate nesquehonite step. Raman spectroscopy applied to brucite reacted with 18O-labeled water in scCO2 show it was incorporated into carbonate at relatively high concentration. This supports a carbonation mechanism with at least one step involving a direct reaction between the mineral and water molecules without mediation by a condensed aqueous layer.

  14. Selective catalytic reduction (SCR) of NO by urea loaded on activated carbon fibre (ACF) and CeO2/ACF at 30 degrees C: the SCR mechanism.

    PubMed

    Zeng, Zheng; Lu, Pei; Li, Caiting; Zeng, Guangming; Jiang, Xiao; Zhai, Yunbo; Fan, Xiaopeng

    2012-06-01

    Selective catalytic reduction (SCR) of NO by urea loaded on rayon-based activated carbon fibre (ACF) and CeO2/ACF (CA) was studied at ambient temperature (30 degrees C) to establish a basic scheme for its reduction. Nitric oxide was found to be reduced to N2 with urea deposited on the ACF and CA. When oxygen was present, the greater the amount of loaded urea (20-60%), the greater the NO(x) conversions, which were between 72.03% and 77.30%, whereas the NO(x) conversions were about 50% when oxygen was absent. Moreover, when the urea was loaded on CA, a catalyst containing 40% urea/ACF loaded with 10% CeO2 (UCA4) could yield a NO(x) conversion of about 80% for 24.5 h. Based on the experimental results, the catalytic mechanisms of SCR with and without oxygen are discussed. The enhancing effect of oxygen resulted from the oxidation of NO to NO2, and urea was the main reducing agent in the SCR of loaded catalysts. ACF-C was the catalytic centre in the SCR of NO of ACF, while CeO2 of urea-loaded CA was the catalytic centre.

  15. Ti or Sn doping as a way to increase activity and sulfur tolerance of Mn/CeO2 catalyst for low temperature NH3 selective catalytic reduction of NO

    NASA Astrophysics Data System (ADS)

    Xiong, Yan; Tang, Changjin; Dong, Lin

    2015-04-01

    Mn/CeO2 catalysts modified by doping of Ti or Sn were investigated for low temperature selective catalytic reduction (SCR) of NO by NH3 with the aim of studying the effects of Ti, Sn doping on the catalytic performance. Ceria-based solid solutions (Ce0.8Ti0.2O2 and Ce0.8Sn0.2O2) were synthesized via inverse co-precipitation, and used as supports to prepare MnOx/Ce0.8M0.2O2 (M =Ti4+, Sn4+) catalysts through wetness impregnation method. The results showed that doping of Ti or Sn to the CeO2 support increase the NO removal efficiency. A NO conversion of more than 90 % was obtained over the Mn/CeTi catalyst at the temperature window of 175 ~ 300 °C under a gas hourly space velocity (GHSV) of 60,000 mL•g-1•h-1. Catalysts modified by Ti and Sn were also found to obtain higher SO2 resistance than Mn/CeO2 catalyst. More than 90% NO conversion and 95% N2 selectivity could be provided by Mn/CeTi catalyst in the presence of 100 ppm SO2 at 250 °C for 10 h. A series of characterization techniques, namely XRD, BET, H2-TPR, XPS, NH3-TPD and in situ DRIFTS were used to elucidate the structure and surface properties of the obtained supports and catalysts. The results indicate that doping of Ti or Sn brings about catalysts with favorable properties such as higher BET surface area, better oxygen storage capacity and stronger surface acidity. The relative amount of Mn4+, Ce3+, adsorbed oxygen species and oxygen vacancies on the surface of catalysts are in the order of Mn/CeTi>Mn/CeSn>Mn/CeO2, which is thought to make positive a contribution to the low-temperature SCR activity. The promoted SCR activity is considered as well to be related to the dual redox cycles in Mn/CeTi (Mn4+ + Ce3+ ↔ Mn3+ + Ce4+, Ce4+ + Ti3+ ↔ Ce3+ + Ti4+) and Mn/CeSn (Mn4+ + Ce3+ ↔ Mn3+ + Ce4+, Ce4+ + Sn2+ ↔ Ce3+ + Sn4+ ) catalysts.

  16. Cu/Cu2O/CuO loaded on the carbon layer derived from novel precursors with amazing catalytic performance.

    PubMed

    Zhao, Xiaoli; Tan, Yixin; Wu, Fengchang; Niu, Hongyun; Tang, Zhi; Cai, Yaqi; Giesy, John P

    2016-11-15

    A simple, novel method for synthesis of Cu/Cu2O/CuO on surfaces of carbon (Cu/Cu2O/CuO@C) as a non-noble-metal catalyst for reduction of organic compounds is presented. Compared with noble metals, Cu/Cu2O/CuO@C particles are more efficient and less expensive. Characterization of the Cu/Cu2O/CuO@C composites by high-resolution transmission electron microscope (HRTEM), x-ray diffraction (XRD), infrared spectroscopy and Raman analysis, revealed that it was composed of graphitized carbon with numerous nanoparticles (100nm in diameter) of Cu/CuO/Cu2O that were uniformly distributed on internal and external surfaces of the carbon support. Gallic acid (GA) has been used as both organic ligand and carbon precursor with metal organic frameworks (MOFs) as the sacrificial template and metal oxide precursor in this green synthesis. The material combined the advantages of MOFs and Cu-containing materials, the porous structure provided a large contact area and channels for the pollutions, which results in more rapid catalytic degradation of pollutants and leads to greater efficiency of catalysis. The material gave excellent catalytic performance for organic dyes and phenols. In this study, Cu/Cu2O/CuO@C was used as catalytic to reduce 4-NP, which has been usually adopted as a model reaction to check the catalytic ability. Catalytic experiment results show that 4-NP was degraded approximately 3min by use of 0.04mg of catalyst and the conversion of pollutants can reach more than 99%. The catalyst exhibited little change in efficacy after being utilized five times. Rates of degradation of dyes, such as Methylene blue (MB) and Rhodamine B (RhB) and phenolic compounds such as O-Nitrophenol (O-NP) and 2-Nitroaniline (2-NA) were all similar. PMID:27450957

  17. ESSENTIAL ROLE OF SURFACE HYDROXYLS FOR THE STABILIZATION AND CATALYTIC ACTIVITY OF TiO2-SUPPORTED GOLD NANOPARTICLES

    SciTech Connect

    Veith, Gabriel M; Lupini, Andrew R; Dudney, Nancy J

    2009-01-01

    We report the investigation of titania supported gold catalysts prepared by magnetron sputtering. Catalysts grown on natural fumed titania were structurally unstable resulting in the rapid coarsening of 2.3 nm gold clusters into large ~20 nm gold clusters in a few days at room temperature under normal atmospheric conditions. However, treating the titania support powder to a mock-deposition-precipitation process, at pH 4 or pH 10, followed by the subsequent deposition of gold onto this treated powder produced a remarkable enhancement in gold particle stability and a 20-40 fold enhancement of catalytic activity respectively. This enhancement can not be attributed to the formation of oxygen vacancies on the TiO2 surface. Instead, it appears to be associated with the formation of strongly bound hydroxyl species on the TiO2 surface. The formation of surface hydroxyls during the deposition-precipitation method is coincidental and contributes significantly to the properties of Au/TiO2 catalysts.

  18. Elucidation of the Fe(IV)=O intermediate in the catalytic cycle of the halogenase SyrB2.

    PubMed

    Wong, Shaun D; Srnec, Martin; Matthews, Megan L; Liu, Lei V; Kwak, Yeonju; Park, Kiyoung; Bell, Caleb B; Alp, E Ercan; Zhao, Jiyong; Yoda, Yoshitaka; Kitao, Shinji; Seto, Makoto; Krebs, Carsten; Bollinger, J Martin; Solomon, Edward I

    2013-07-18

    Mononuclear non-haem iron (NHFe) enzymes catalyse a broad range of oxidative reactions, including halogenation, hydroxylation, ring closure, desaturation and aromatic ring cleavage reactions. They are involved in a number of biological processes, including phenylalanine metabolism, the production of neurotransmitters, the hypoxic response and the biosynthesis of secondary metabolites. The reactive intermediate in the catalytic cycles of these enzymes is a high-spin S = 2 Fe(IV)=O species, which has been trapped for a number of NHFe enzymes, including the halogenase SyrB2 (syringomycin biosynthesis enzyme 2). Computational studies aimed at understanding the reactivity of this Fe(IV)=O intermediate are limited in applicability owing to the paucity of experimental knowledge about its geometric and electronic structure. Synchrotron-based nuclear resonance vibrational spectroscopy (NRVS) is a sensitive and effective method that defines the dependence of the vibrational modes involving Fe on the nature of the Fe(IV)=O active site. Here we present NRVS structural characterization of the reactive Fe(IV)=O intermediate of a NHFe enzyme, namely the halogenase SyrB2 from the bacterium Pseudomonas syringae pv. syringae. This intermediate reacts via an initial hydrogen-atom abstraction step, performing subsequent halogenation of the native substrate or hydroxylation of non-native substrates. A correlation of the experimental NRVS data to electronic structure calculations indicates that the substrate directs the orientation of the Fe(IV)=O intermediate, presenting specific frontier molecular orbitals that can activate either selective halogenation or hydroxylation.

  19. Homogeneous catalytic O2 reduction to water by a cytochrome c oxidase model with trapping of intermediates and mechanistic insights

    PubMed Central

    Halime, Zakaria; Kotani, Hiroaki; Li, Yuqi; Fukuzumi, Shunichi; Karlin, Kenneth D.

    2011-01-01

    An efficient and selective four-electron plus four-proton (4e-/4H+) reduction of O2 to water by decamethylferrocene and trifluoroacetic acid can be catalyzed by a synthetic analog of the heme a3/CuB site in cytochrome c oxidase (6LFeCu) or its Cu-free version (6LFe) in acetone. A detailed mechanistic-kinetic study on the homogeneous catalytic system reveals spectroscopically detectable intermediates and that the rate-determining step changes from the O2-binding process at 25 °C room temperature (RT) to the O-O bond cleavage of a newly observed FeIII-OOH species at lower temperature (-60 °C). At RT, the rate of O2-binding to 6LFeCu is significantly faster than that for 6LFe, whereas the rates of the O-O bond cleavage of the FeIII-OOH species observed (-60 °C) with either the 6LFeCu or 6LFe catalyst are nearly the same. Thus, the role of the Cu ion is to assist the heme and lead to faster O2-binding at RT. However, the proximate Cu ion has no effect on the O-O bond cleavage of the FeIII-OOH species at low temperature. PMID:21808032

  20. [Effect of vanadium and tungsten loadings on the surface characteristics and catalytic activities of V2O5-WO3/TiO2 catalysts].

    PubMed

    Chen, Jian-jun; Li, Jun-hua; Ke, Rui; Kang, Shou-fang; Hao, Ji-ming

    2007-09-01

    V2O5-WO3/TiO2 catalysts with different vanadium and tungsten loadings were prepared by impregnation method. The activities of selective catalytic reduction (SCR) of NO with NH3 were measured and surface characteristics of those samples were characterized. It is found that both the surface areas and catalytic activities are influenced by vanadium loadings. When the vanadium loadings increased from 1% to 8%, the catalyst surface areas decreased by 16 m2/g, while the highest activity temperature was reduced by about 100 degrees C. Tungsten acts as stabilizer and promoter of the SCR catalyst. When the vanadium loading was 1%, an increase of tungsten loadings from 0 to 6% resulted in the decrease of the catalyst surface areas by only 3 m2/g, while the activity window was expanded to both high and low temperature range each by about 50 degrees C. Vanadium and tungsten loadings have an effect on the surface VOx, but do not change the surface crystal structure of the catalysts.

  1. Physico-Chemical Property and Catalytic Activity of a CeO2-Doped MnO(x)-TiO2 Catalyst with SO2 Resistance for Low-Temperature NH3-SCR of NO(x).

    PubMed

    Shin, Byeongkil; Chun, Ho Hwan; Cha, Jin-Sun; Shin, Min-Chul; Lee, Heesoo

    2016-05-01

    The effects of CeO2 addition on the catalytic activity and the SO2 resistance of CeO2-doped MnO(x)-TiO2 catalysts were investigated for the low-temperature selective catalytic reduction (SCR) with NH3 of NO(x) emissions in marine applications. The most active catalyst was obtained from 30 wt% CeO2-MnO(x)-TiO2 catalyst in the whole temperature range of 100-300 degrees C at a low gas hourly space velocity (GHSV) of 10,000 h(-)1, and its de-NO(x) efficiency was higher than 90% over 250 degrees C. The enhanced catalytic activity may contribute to the dispersion state and catalytic acidity on the catalyst surface, and the highly dispersed Mn and Ce on the nano-scaled TiO2 catalyst affects the increase of Lewis and Brønsted acid sites. A CeO2-rich additive on MnO(x)-TiO2 could provide stronger catalytic acid sites, associated with NH3 adsorption and the SCR performance. As the results of sulfur resistance in flue gas that contains SO2, the de-NO(x) efficiency of MnO(x)-TiO2 decreased by 15% over 200 degrees C, whereas that of 30 wt% ceria-doped catalyst increased by 14-21% over 150 degrees C. The high SO2 resistance of CeO2-MnO(x)-TiO2 catalysts that resulted from the addition of ceria suppressed the formation of Mn sulfate species, which led to deactivation on the surface of nano-catalyst. PMID:27483759

  2. Physico-Chemical Property and Catalytic Activity of a CeO2-Doped MnO(x)-TiO2 Catalyst with SO2 Resistance for Low-Temperature NH3-SCR of NO(x).

    PubMed

    Shin, Byeongkil; Chun, Ho Hwan; Cha, Jin-Sun; Shin, Min-Chul; Lee, Heesoo

    2016-05-01

    The effects of CeO2 addition on the catalytic activity and the SO2 resistance of CeO2-doped MnO(x)-TiO2 catalysts were investigated for the low-temperature selective catalytic reduction (SCR) with NH3 of NO(x) emissions in marine applications. The most active catalyst was obtained from 30 wt% CeO2-MnO(x)-TiO2 catalyst in the whole temperature range of 100-300 degrees C at a low gas hourly space velocity (GHSV) of 10,000 h(-)1, and its de-NO(x) efficiency was higher than 90% over 250 degrees C. The enhanced catalytic activity may contribute to the dispersio