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Sample records for molecular sieve catalyst

  1. Catalytic cracking catalysts using silicoaluminophosphate molecular sieves

    SciTech Connect

    Pellet, R.J.; Coughlin, P.K.; Staniulis, M.T.; Long, G.N.; Rabo, J.A.

    1987-05-19

    A cracking catalyst is described comprising: a silicoaluminophosphate molecular sieve of U.S. Pat. No. 4,440,871 characterized in its calcined form by an adsorption of isobutane of at least 2 percent by weight at a pressure of 500 torr and a temperature of 20/sup 0/C and having an effective amount of the cations associated with the silicoaluminophosphate molecular sieve selected from the group consisting of H+, ammonium, Group IIA, groups IIIB to VIIB, cerium, lanthanum, praseodymium, neodymium, and promethium.

  2. Octahedral molecular sieve sorbents and catalysts

    DOEpatents

    Li, Liyu [Richland, WA; King, David L [Richland, WA

    2010-04-20

    Octahedral molecular sieve sorbents and catalysts are disclosed, including silver hollandite and cryptomelane. These materials can be used, for example, to catalyze the oxidation of CO.sub.x (e.g., CO), NO.sub.x (e.g., NO), hydrocarbons (e.g., C.sub.3H.sub.6) and/or sulfur-containing compounds. The disclosed materials also may be used to catalyze other reactions, such as the reduction of NO.sub.2. In some cases, the disclosed materials are capable of sorbing certain products from the reactions they catalyze. Silver hollandite, in particular, can be used to remove a substantial portion of certain sulfur-containing compounds from a gas or liquid by catalysis and/or sorption. The gas or liquid can be, for example, natural gas or a liquid hydrocarbon.

  3. Catalytic Transformation of Bio-oil to Olefins with Molecular Sieve Catalysts

    NASA Astrophysics Data System (ADS)

    Huang, Wei-wei; Gong, Fei-yan; Zhai, Qi; Li, Quan-xin

    2012-08-01

    Catalytic conversion of bio-oil into light olefins was performed by a series of molecular sieve catalysts, including HZSM-5, MCM-41, SAPO-34 and Y-zeolite. Based on the light olefins yield and its carbon selectivity, the production of light olefins decreased in the following order: HZSM-5>SAPO-34>MCM-41> Y-zeolite. The highest olefins yield from bio-oil using HZSM-5 catalyst reached 0.22 kg/kgbio-oil with carbon selectivity of 50.7% and a nearly complete bio-oil conversion. The reaction conditions and catalyst characterization were investigated in detail to reveal the relationship between the catalyst structure and the production of olefins. The comparison between the pyrolysis and catalytic pyrolysis of bio-oil was also performed.

  4. [Synergetic effects of silicon carbide and molecular sieve loaded catalyst on microwave assisted catalytic oxidation of toluene].

    PubMed

    Wang, Xiao-Hui; Bo, Long-Li; Liu, Hai-Nan; Zhang, Hao; Sun, Jian-Yu; Yang, Li; Cai, Li-Dong

    2013-06-01

    Molecular sieve loaded catalyst was prepared by impregnation method, microwave-absorbing material silicon carbide and the catalyst were investigated for catalytic oxidation of toluene by microwave irradiation. Research work examined effects of silicon carbide and molecular sieve loading Cu-V catalyst's mixture ratio as well as mixed approach changes on degradation of toluene, and characteristics of catalyst were measured through scanning electron microscope, specific surface area test and X-ray diffraction analysis. The result showed that the fixed bed reactor had advantages of both thermal storage property and low-temperature catalytic oxidation when 20% silicon carbide was filled at the bottom of the reactor, and this could effectively improve the utilization of microwave energy as well as catalytic oxidation efficiency of toluene. Under microwave power of 75 W and 47 W, complete-combustion temperatures of molecular sieve loaded Cu-V catalyst and Cu-V-Ce catalyst to toluene were 325 degrees C and 160 degrees C, respectively. Characteristics of the catalysts showed that mixture of rare-earth element Ce increased the dispersion of active components in the surface of catalyst, micropore structure of catalyst effectively guaranteed high adsorption capacity for toluene, while amorphous phase of Cu and V oxides increased the activity of catalyst greatly. PMID:23947020

  5. Preparation and application of zirconium sulfate supported on SAPO-34 molecular sieve as solid acid catalyst for esterification

    SciTech Connect

    Xu, Dongyan Ma, Hong; Cheng, Fei

    2014-05-01

    Graphical abstract: - Highlights: • SAPO-34 supported zirconium sulfate solid acid catalyst was prepared. • Esterification of acetic acid with ethanol can be catalyzed by ZS/SAPO-34. • The hydration of ZS is vital to the acidic property and catalytic performance. • The ZS/SAPO-34 catalyst treated at 200 °C shows good reusability. - Abstract: Zirconium sulfate (ZS) was supported on SAPO-34 molecular sieve by using an incipient wetness impregnation method with zirconium sulfate as the precursor. The as-prepared catalysts were used as solid acid catalyst for esterification reaction of acetic acid with ethanol. The influence of calcination temperature on the acidic property, catalytic activity, and reusability of ZS/SAPO-34 catalysts were mainly investigated. FT-IR, SEM, EDS and TG analysis have been carried out to demonstrate the characteristics of ZS/SAPO-34 catalysts. It was found that the 30 wt%ZS/SAPO-34 catalysts display the property of superacid irrespective of calcination temperature. The ZS/SAPO-34 catalyst treated at 200 °C can enhance the interaction between the supported ZS and SAPO-34 and keep the catalyst remaining substantially active after several reaction cycles. However, further increasing calcination temperature will cause the transfer of ZS from hydrate to anhydrous phase, and thus the decrease of activity.

  6. Current Understanding of Cu-Exchanged Chabazite Molecular Sieves for Use as Commercial Diesel Engine DeNOx Catalysts

    SciTech Connect

    Gao, Feng; Kwak, Ja Hun; Szanyi, Janos; Peden, Charles HF

    2013-11-03

    Selective catalytic reduction (SCR) of NOx with ammonia using metal-exchanged molecular sieves with a chabazite (CHA) structure has recently been commercialized on diesel vehicles. One of the commercialized catalysts, i.e., Cu-SSZ-13, has received much attention for both practical and fundamental studies. For the latter, the particularly well-defined structure of this zeolite is allowing long-standing issues of the catalytically active site for SCR in metal-exchanged zeolites to be addressed. In this review, recent progress is summarized with a focus on two areas. First, the technical significance of Cu-SSZ-13 as compared to other Cu-ion exchanged zeolites (e.g., Cu-ZSM-5 and Cu-beta) is highlighted. Specifically, the much enhanced hydrothermal stability for Cu-SSZ-13 compared to other zeolite catalysts is addressed via performance measurements and catalyst characterization using several techniques. The enhanced stability of Cu-SSZ-13 is rationalized in terms of the unique small pore structure of this zeolite catalyst. Second, the fundamentals of the catalytically active center; i.e., the chemical nature and locations within the SSZ-13 framework are presented with an emphasis on understanding structure-function relationships. For the SCR reaction, traditional kinetic studies are complicated by intra-particle diffusion limitations. However, a major side reaction, nonselective ammonia oxidation by oxygen, does not suffer from mass-transfer limitations at relatively low temperatures due to significantly lower reaction rates. This allows structure-function relationships that are rather well understood in terms of Cu ion locations and redox properties. Finally, some aspects of the SCR reaction mechanism are addressed on the basis of in-situ spectroscopic studies.

  7. Titanium(IV) in the organic-structure-directing-agent-free synthesis of hydrophobic and large-pore molecular sieves as redox catalysts.

    PubMed

    Wang, Jingui; Yokoi, Toshiyuki; Kondo, Junko N; Tatsumi, Takashi; Zhao, Yanli

    2015-08-10

    Titanium(IV) incorporated into the framework of molecular sieves can be used as a highly active and sustainable catalyst for the oxidation of industrially important organic molecules. Unfortunately, the current process for the incorporation of titanium(IV) requires a large amount of expensive organic molecules used as organic-structure-directing agents (OSDAs), and this significantly increases the production costs and causes environmental problems owing to the removal of OSDAs by pyrolysis. Herein, an OSDA-free process was developed to incorporate titanium(IV) into BEA-type molecular sieves for the first time. More importantly, the hydrophobic environment and the robust, 3 D, and large pore structure of the titanium(IV)-incorporated molecular sieves fabricated from the OSDA-free process created a catalyst that was extremely active and selective for the epoxidation of bulky cyclooctene in comparison to Ti-incorporated BEA-type molecular sieves synthesized with OSDAs and commercial titanosilicate TS-1. PMID:26073555

  8. Space station molecular sieve development

    NASA Technical Reports Server (NTRS)

    Chang, C.; Rousseau, J.

    1986-01-01

    An essential function of a space environmental control system is the removal of carbon dioxide (CO2) from the atmosphere to control the partial pressure of this gas at levels lower than 3 mm Hg. The use of regenerable solid adsorbents for this purpose was demonstrated effectively during the Skylab mission. Earlier sorbent systems used zeolite molecular sieves. The carbon molecular sieve is a hydrophobic adsorbent with excellent potential for space station application. Although carbon molecular sieves were synthesized and investigated, these sieves were designed to simulate the sieving properties of 5A zeolite and for O2/N2 separation. This program was designed to develop hydrophobic carbon molecular sieves for CO2 removal from a space station crew environment. It is a first phase effort involved in sorbent material development and in demonstrating the utility of such a material for CO2 removal on space stations. The sieve must incorporate the following requirements: it must be hydrophobic; it must have high dynamic capacity for carbon dioxide at the low partial pressure of the space station atmosphere; and it must be chemiclly stable and will not generate contaminants.

  9. Molecular Sieve Regeneration System (MSRS)

    SciTech Connect

    Nasise, J.E.; Anderson, J.L. ); Naruse, Y. )

    1992-01-01

    A Molecular Sieve Regeneration System (MSRS) was added to the existing Tritium Waste Treatment system (TWT) within the Tritium Systems Test Assembly (TSTA) at Los Alamos National Laboratory. The Department of Energy (DOE) no longer allows inventory by difference'' for radioactive wastes that are to be buried. The MSRS was designed and built to comply with this requirement. Within the TWT, water is generated by the catalytic conversion of hydrogen isotopes and removed by molecular sieve trapping prior to release to the environment. Molecular sieve regeneration is required to remove the trapped water and to rejuvenate the beds. The MSRS permits the collection and direct tritium assay of regenerated tritiated water from molecular sieve beds. This paper describes the MSRS in detail and how it is interfaced with the TWT.

  10. Molecular Sieve Regeneration System (MSRS)

    SciTech Connect

    Nasise, J.E.; Anderson, J.L.; Naruse, Y.

    1992-03-01

    A Molecular Sieve Regeneration System (MSRS) was added to the existing Tritium Waste Treatment system (TWT) within the Tritium Systems Test Assembly (TSTA) at Los Alamos National Laboratory. The Department of Energy (DOE) no longer allows ``inventory by difference`` for radioactive wastes that are to be buried. The MSRS was designed and built to comply with this requirement. Within the TWT, water is generated by the catalytic conversion of hydrogen isotopes and removed by molecular sieve trapping prior to release to the environment. Molecular sieve regeneration is required to remove the trapped water and to rejuvenate the beds. The MSRS permits the collection and direct tritium assay of regenerated tritiated water from molecular sieve beds. This paper describes the MSRS in detail and how it is interfaced with the TWT.

  11. Synthesis and application of different phthalocyanine molecular sieve catalyst for oxidative desulfurization

    SciTech Connect

    Zhao, Na; Li, Siwen; Wang, Jinyi; Zhang, Ronglan; Gao, Ruimin; Zhao, Jianshe; Wang, Junlong

    2015-05-15

    M{sub 2}(PcAN){sub 2} (M=Fe, Co, Ni, Cu, Zn and Mn) anchored onto W-HZSM-5 (M{sub 2}(PcAN){sub 2}–W-HZSM-5) or the M{sub 2}(PcTN){sub 2} doping W-HZSM-5 (M{sub 2}(PcTN){sub 2}/W-HZSM-5) were prepared and their catalytic performances were tested for oxidative desulfurization in the presence of oxygen. Thiophene (T), benzothiophene (BT), and dibenzothiophene (DBT) were considered as sulfur compounds. Among zeolite-based catalysts, the Cu{sub 2}(PcAN){sub 2}–W-HZSM-5 and Cu{sub 2}(PcTN){sub 2}/W-HZSM-5 showed superior desulfurization performance and the activity of selectivity followed the order: T>BT>DBT. The effects of phthalocyanine concentration were studied by UV–Vis and calcination temperature was obtained by TG-DSC for Cu{sub 2}(PcTN){sub 2}/W-HZSM-5. Catalysts were characterized by EA, IR, XRD, SEM, TEM, ICP, and N{sub 2} adsorption. Reaction time, temperature and the amount of catalyst were investigated as the important parameters for optimization of the reaction. Furthermore, a possible process of oxidative desulfurization and the reaction products were proposed. - Graphical abstract: The ODS reaction schematic shows the reaction mechanism of ultra-deep desulfurization. The sulfur compounds are oxidized to their corresponding sulfoxides or sulfones through the use of oxygen and catalysts. The reaction process of ultra-deep desulfurization. - Highlights: • A kind of novel catalyst for deep desulfurization was synthesized. • Cu{sub 2}(PcAN){sub 2}–W-HZSM-5 exhibits excellent catalytic performance for desulfurization. • The reaction conditions that affect desulfurization efficiency are investigated. • The reaction process of model sulfur compounds is proposed.

  12. Synthesis and application of different phthalocyanine molecular sieve catalyst for oxidative desulfurization

    NASA Astrophysics Data System (ADS)

    Zhao, Na; Li, Siwen; Wang, Jinyi; Zhang, Ronglan; Gao, Ruimin; Zhao, Jianshe; Wang, Junlong

    2015-05-01

    M2(PcAN)2 (M=Fe, Co, Ni, Cu, Zn and Mn) anchored onto W-HZSM-5 (M2(PcAN)2-W-HZSM-5) or the M2(PcTN)2 doping W-HZSM-5 (M2(PcTN)2/W-HZSM-5) were prepared and their catalytic performances were tested for oxidative desulfurization in the presence of oxygen. Thiophene (T), benzothiophene (BT), and dibenzothiophene (DBT) were considered as sulfur compounds. Among zeolite-based catalysts, the Cu2(PcAN)2-W-HZSM-5 and Cu2(PcTN)2/W-HZSM-5 showed superior desulfurization performance and the activity of selectivity followed the order: T>BT>DBT. The effects of phthalocyanine concentration were studied by UV-Vis and calcination temperature was obtained by TG-DSC for Cu2(PcTN)2/W-HZSM-5. Catalysts were characterized by EA, IR, XRD, SEM, TEM, ICP, and N2 adsorption. Reaction time, temperature and the amount of catalyst were investigated as the important parameters for optimization of the reaction. Furthermore, a possible process of oxidative desulfurization and the reaction products were proposed.

  13. Niobate-based octahedral molecular sieves

    DOEpatents

    Nenoff, Tina M.; Nyman, May D.

    2006-10-17

    Niobate-based octahedral molecular sieves having significant activity for multivalent cations and a method for synthesizing such sieves are disclosed. The sieves have a net negatively charged octahedral framework, comprising niobium, oxygen, and octahedrally coordinated lower valence transition metals. The framework can be charge balanced by the occluded alkali cation from the synthesis method. The alkali cation can be exchanged for other contaminant metal ions. The ion-exchanged niobate-based octahedral molecular sieve can be backexchanged in acidic solutions to yield a solution concentrated in the contaminant metal. Alternatively, the ion-exchanged niobate-based octahedral molecular sieve can be thermally converted to a durable perovskite phase waste form.

  14. Niobate-based octahedral molecular sieves

    DOEpatents

    Nenoff, Tina M.; Nyman, May D.

    2003-07-22

    Niobate-based octahedral molecular sieves having significant activity for multivalent cations and a method for synthesizing such sieves are disclosed. The sieves have a net negatively charged octahedral framework, comprising niobium, oxygen, and octahedrally coordinated lower valence transition metals. The framework can be charge balanced by the occluded alkali cation from the synthesis method. The alkali cation can be exchanged for other contaminant metal ions. The ion-exchanged niobate-based octahedral molecular sieve can be backexchanged in acidic solutions to yield a solution concentrated in the contaminant metal. Alternatively, the ion-exchanged niobate-based octahedral molecular sieve can be thermally converted to a durable perovskite phase waste form.

  15. Carbon fiber composite molecular sieves

    SciTech Connect

    Burchell, T.D.; Rogers, M.R.; Williams, A.M.

    1996-06-01

    The removal of CO{sub 2} is of significance in several energy applications. The combustion of fossil fuels, such as coal or natural gas, releases large volumes of CO{sub 2} to the environment. Several options exist to reduce CO{sub 2} emissions, including substitution of nuclear power for fossil fuels, increasing the efficiency of fossil plants and capturing the CO{sub 2} prior to emission to the environment. All of these techniques have the attractive feature of limiting the amount of CO{sub 2} emitted to the atmosphere, but each has economic, technical, or societal limitations. In the production of natural gas, the feed stream from the well frequently contains contaminants and diluents which must be removed before the gas can enter the pipeline distribution system. Notable amongst these diluent gasses is CO{sub 2}, which has no calorific value. Currently, the pipeline specification calls for <2 mol % CO{sub 2} in the gas. Gas separation is thus a relevant technology in the field of energy production. A novel separation system based on a parametric swing process has been developed that utilizes the unique combination of properties exhibited by our carbon fiber composite molecular sieve (CFCMS).

  16. Enhanced Molecular Sieve CO2 Removal Evaluation

    NASA Technical Reports Server (NTRS)

    Rose, Susan; ElSherif, Dina; MacKnight, Allen

    1996-01-01

    The objective of this research is to quantitatively characterize the performance of two major types of molecular sieves for two-bed regenerative carbon dioxide removal at the conditions compatible with both a spacesuit and station application. One sorbent is a zeolite-based molecular sieve that has been substantially improved over the materials used in Skylab. The second sorbent is a recently developed carbon-based molecular sieve. Both molecular sieves offer the potential of high payoff for future manned missions by reducing system complexity, weight (including consumables), and power consumption in comparison with competing concepts. The research reported here provides the technical data required to improve CO2 removal systems for regenerative life support systems for future IVA and EVA missions.

  17. Synthesis of biological molecules on molecular sieves.

    PubMed

    Poncelet, G; Van Assche, A T; Fripiat, J J

    1975-07-01

    Catalytic properties of aluminosilicates may play a role in the synthesis of biological molecules from simple gaseous molecules commonly found in planetary atmospheres. Urea, amino acids and UV absorbing substances have been obtained by heating CO and NH3 with Linde molecular sieves saturated with Ca+2, NH4+ or Fe+3. The yields of amino acids produced have been determined by an amino acid analyzer. The quantity of urea produced largely depends on the nature of the saturating cation. Experiments using 14CO confirm that the amino acids are not due to contaminants adsorbed on the surface of the molecular sieves. PMID:171609

  18. Molecular sieving silica membrane fabrication process

    DOEpatents

    Raman, Narayan K.; Brinker, Charles Jeffrey

    1998-01-01

    A process for producing a molecular sieve silica membrane comprising depositing a hybrid organic-inorganic polymer comprising at least one organic constituent and at least one inorganic constituent on a porous substrate material and removing at least a portion of the at least one organic constituent of the hybrid organic-inorganic polymer, forming a porous film.

  19. Molecular sieving silica membrane fabrication process

    DOEpatents

    Raman, Narayan K.; Brinker, Charles Jeffrey

    1999-01-01

    A process for producing a molecular sieve silica membrane comprising depositing a hybrid organic-inorganic polymer comprising at least one organic constituent and at least one inorganic constituent on a porous substrate material and removing at least a portion of the at least one organic constituent of the hybrid organic-inorganic polymer, forming a porous film.

  20. Molecular sieving silica membrane fabrication process

    DOEpatents

    Raman, N.K.; Brinker, C.J.

    1999-08-10

    A process is described for producing a molecular sieve silica membrane comprising depositing a hybrid organic-inorganic polymer comprising at least one organic constituent and at least one inorganic constituent on a porous substrate material and removing at least a portion of the at least one organic constituent of the hybrid organic-inorganic polymer, forming a porous film. 11 figs.

  1. Coal-based carbons with molecular sieve properties

    SciTech Connect

    El-Wakil, A.M.; Youssef, A.M.; Tollan, K.A. )

    1991-01-01

    Carbon molecular sieves are used extensively in gas chromatography for the separation of permanent gases and light hydrocarbons. Carbon molecular sieves also find commercial application for the manufacture of pure hydrogen from hydrogen-rich gases such as coke-oven gas, and for the separation of air by the pressure-swing adsorption technique. The objective of this investigation was to prepare carbons from Maghara coal, recently available on the commercial market. Coal-based carbons, if they possess molecular sieve properties, are superior to molecular sieve carbons from agricultural by-products because they have more satisfactory mechanical properties.

  2. [Removal Characteristics of Elemental Mercury by Mn-Ce/molecular Sieve].

    PubMed

    Tan, Zeng-qiang; Niu, Guo-ping; Chen, Xiao-wen; An, Zhen

    2015-06-01

    The impregnation method was used to support molecular sieve with active manganese and cerium components to obtain a composite molecular sieve catalyst. The mercury removal performance of the catalyst was studied with a bench-scale setup. XPS analysis was used to characterize the sample before and after the modification in order to study the changes in the active components of the catalyst prepared. The results showed that the catalyst carrying manganese and cerium components had higher oxidation ability of elemental mercury in the temperature range of 300 degrees C - 450 degrees C, especially at 450 degrees C, the oxidation efficiency of elemental mercury was kept above 80%. The catalyst had more functional groups that were conducive to the oxidation of elemental mercury, and the mercury removal mainly depended on the chemical adsorption. The SO2 and NO in flue gas could inhibit the oxidation of elemental mercury to certain extent. PMID:26387298

  3. Adsorption of gases on carbon molecular sieves

    SciTech Connect

    Vyas, S.N.; Patwardhan, S.R.; Vijayalakshmi, S. . Dept. of Chemical Engineering); Ganesh, K.S. )

    1994-12-01

    Adsorption on carbon molecular sieves (CMS) prepared by coke deposition has become an interesting area of adsorption due to its microporous nature and favorable separation factor on size and shape selectivity basis for many gaseous systems. In the present work CMS was synthesized from coconut shell through three major steps, namely, carbonization, activation, and coke deposition by hydrocarbon cracking. The crushed, washed, and sieved granules of coconut shell (particle size 2--3 mm) were pretreated with sodium silicate solution and oven-dried at 150 C to create the inorganic sites necessary for coke deposition. Carbonization and activation of the dried granules were carried out at 800 C, for 30 min each. The activated char thus produced was subjected to hydrocarbon cracking at 600 C for periods varying from 30 to 180 min. The product samples were characterized in terms of adsorption isotherm, kinetic adsorption curve, surface area, pore volume, pore size distribution, and characteristic energy for adsorption by using O[sub 2], N[sub 2], C[sub 2]H[sub 2], CO[sub 2], C[sub 3]H[sub 6], and CH[sub 4].

  4. Shape-selective sieving layers on an oxide catalyst surface.

    PubMed

    Canlas, Christian P; Lu, Junling; Ray, Natalie A; Grosso-Giordano, Nicolas A; Lee, Sungsik; Elam, Jeffrey W; Winans, Randall E; Van Duyne, Richard P; Stair, Peter C; Notestein, Justin M

    2012-12-01

    New porous materials such as zeolites, metal-organic frameworks and mesostructured oxides are of immense practical utility for gas storage, separations and heterogeneous catalysis. Their extended pore structures enable selective uptake of molecules or can modify the product selectivity (regioselectivity or enantioselectivity) of catalyst sites contained within. However, diffusion within pores can be problematic for biomass and fine chemicals, and not all catalyst classes can be readily synthesized with pores of the correct dimensions. Here, we present a novel approach that adds reactant selectivity to existing, non-porous oxide catalysts by first grafting the catalyst particles with single-molecule sacrificial templates, then partially overcoating the catalyst with a second oxide through atomic layer deposition. This technique is used to create sieving layers of Al(2)O(3) (thickness, 0.4-0.7 nm) with 'nanocavities' (<2 nm in diameter) on a TiO(2) photocatalyst. The additional layers result in selectivity (up to 9:1) towards less hindered reactants in otherwise unselective, competitive photocatalytic oxidations and transfer hydrogenations. PMID:23174984

  5. Shape-selective sieving layers on an oxide catalyst surface

    NASA Astrophysics Data System (ADS)

    Canlas, Christian P.; Lu, Junling; Ray, Natalie A.; Grosso-Giordano, Nicolas A.; Lee, Sungsik; Elam, Jeffrey W.; Winans, Randall E.; van Duyne, Richard P.; Stair, Peter C.; Notestein, Justin M.

    2012-12-01

    New porous materials such as zeolites, metal-organic frameworks and mesostructured oxides are of immense practical utility for gas storage, separations and heterogeneous catalysis. Their extended pore structures enable selective uptake of molecules or can modify the product selectivity (regioselectivity or enantioselectivity) of catalyst sites contained within. However, diffusion within pores can be problematic for biomass and fine chemicals, and not all catalyst classes can be readily synthesized with pores of the correct dimensions. Here, we present a novel approach that adds reactant selectivity to existing, non-porous oxide catalysts by first grafting the catalyst particles with single-molecule sacrificial templates, then partially overcoating the catalyst with a second oxide through atomic layer deposition. This technique is used to create sieving layers of Al2O3 (thickness, 0.4-0.7 nm) with ‘nanocavities’ (<2 nm in diameter) on a TiO2 photocatalyst. The additional layers result in selectivity (up to 9:1) towards less hindered reactants in otherwise unselective, competitive photocatalytic oxidations and transfer hydrogenations.

  6. Silicotitanate molecular sieve and condensed phases

    DOEpatents

    Nenoff, Tina M.; Nyman, May D.

    2002-01-01

    A new microporous crystalline molecular sieve material having the formula Cs.sub.3 TiSi.sub.3 O.sub.95.cndot.3H.sub.2 O and its hydrothermally condensed phase, Cs.sub.2 TiSi.sub.6 O.sub.15, are disclosed. The microporous material can adsorb divalent ions of radionuclides or other industrial metals such as chromium, nickel, lead, copper, cobalt, zinc, cadmium, barium, and mercury, from aqueous or hydrocarbon solutions. The adsorbed metal ions can be leached out for recovery purposes or the microporous material can be hydrothermally condensed to a radiation resistant, structurally and chemically stable phase which can serve as a storage waste form for radionuclides.

  7. Copper crystallite in carbon molecular sieves for selective oxygen removal

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K. (Inventor); Seshan, Panchalam K. (Inventor)

    1993-01-01

    Carbon molecular sieves modified by the incorporation of finely divided elemental copper useful for the selective sorption of oxygen at elevated temperatures. The carbon molecular sieves can be regenerated by reduction with hydrogen. The copper modified carbon molecular sieves are prepared by pyrolysis of a mixture of a copper-containing material and polyfurfuryl alcohol to form a sorbent precursor. The sorbent precursors are then heated and reduced to produce copper modified carbon molecular sieves. The copper modified carbon molecular sieves are useful for sorption of all concentrations of oxygen at temperatures up to about 200.degree. C. They are also useful for removal of trace amount of oxygen from gases at temperatures up to about 600.degree. C.

  8. Copper modified carbon molecular sieves for selective oxygen removal

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K. (Inventor); Seshan, Panchalam K. (Inventor)

    1992-01-01

    Carbon molecular sieves modified by the incorporation of finely divided elemental copper useful for the selective sorption of oxygen at elevated temperatures. The carbon molecular sieves can be regenerated by reduction with hydrogen. The copper modified carbon molecular sieves are prepared by pyrolysis of a mixture of a copper-containing material and polyfunctional alcohol to form a sorbent precursor. The sorbent precursors are then heated and reduced to produce copper modified carbon molecular sieves. The copper modified carbon molecular sieves are useful for sorption of all concentrations of oxygen at temperatures up to about 200.degree. C. They are also useful for removal of trace amount of oxygen from gases at temperatures up to about 600.degree. C.

  9. 21 CFR 173.40 - Molecular sieve resins.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...) The molecular sieve resins consist of purified dextran having an average molecular weight of 40,000, cross-linked with epichlorohydrin in a ratio of 1 part of dextran to 10 parts of epichlorohydrin,...

  10. 21 CFR 173.40 - Molecular sieve resins.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...) The molecular sieve resins consist of purified dextran having an average molecular weight of 40,000, cross-linked with epichlorohydrin in a ratio of 1 part of dextran to 10 parts of epichlorohydrin,...

  11. Porous Organic Cage Thin Films and Molecular-Sieving Membranes.

    PubMed

    Song, Qilei; Jiang, Shan; Hasell, Tom; Liu, Ming; Sun, Shijing; Cheetham, Anthony K; Sivaniah, Easan; Cooper, Andrew I

    2016-04-01

    Porous organic cage molecules are fabricated into thin films and molecular-sieving membranes. Cage molecules are solution cast on various substrates to form amorphous thin films, with the structures tuned by tailoring the cage chemistry and processing conditions. For the first time, uniform and pinhole-free microporous cage thin films are formed and demonstrated as molecular-sieving membranes for selective gas separation. PMID:26800019

  12. A 99 percent purity molecular sieve oxygen generator

    NASA Technical Reports Server (NTRS)

    Miller, G. W.

    1991-01-01

    Molecular sieve oxygen generating systems (MSOGS) have become the accepted method for the production of breathable oxygen on military aircraft. These systems separate oxygen for aircraft engine bleed air by application of pressure swing adsorption (PSA) technology. Oxygen is concentrated by preferential adsorption in nitrogen in a zeolite molecular sieve. However, the inability of current zeolite molecular sieves to discriminate between oxygen and argon results in an oxygen purity limitations of 93-95 percent (both oxygen and argon concentrate). The goal was to develop a new PSA process capable of exceeding the present oxygen purity limitations. A novel molecular sieve oxygen concentrator was developed which is capable of generating oxygen concentrations of up to 99.7 percent directly from air. The process is comprised of four absorbent beds, two containing a zeolite molecular sieve and two containing a carbon molecular sieve. This new process may find use in aircraft and medical breathing systems, and industrial air separation systems. The commercial potential of the process is currently being evaluated.

  13. Antibacterial mesoporous molecular sieves modified with polymeric N-halamine.

    PubMed

    Wang, Yingfeng; Li, Lin; Liu, Ying; Ren, Xuehong; Liang, Jie

    2016-12-01

    In this research, a new kind of porous N-halamine material with high antibacterial efficacies was prepared. Poly [5,5-dimethyl-3-(3'-triethoxysilylpropyl)-hydantoin] (PSPH), an N-halamine precursor, was synthesized and grafted onto the surface of mesoporous molecular sieves (SBA-15). The mesoporous molecular sieves modified with the N-halamine polymer could be rendered biocidal upon exposure to dilute household bleach. The modified mesoporous molecular sieves were characterized by SEM, TEM, FTIR, XPS, TGA, XRD and BET analysis. It was found that the PSPH has been successfully grafted on the surface of mesoporous molecular sieves, and the morphology and structure of the modified mesoporous molecular sieves were slightly affected. The N-halamine modified mesoporous molecular sieves showed excellent antibacterial property, and inactivated 100% of S. aureus and E. coli O157:H7 with 8.05 and 7.92 log reductions within 1min of contact, respectively. The modified SBA-15 with high-antibacterial efficiency has potential application in water treatment and biomaterials areas. PMID:27612805

  14. Molecular Sieve Bench Testing and Computer Modeling

    NASA Technical Reports Server (NTRS)

    Mohamadinejad, Habib; DaLee, Robert C.; Blackmon, James B.

    1995-01-01

    The design of an efficient four-bed molecular sieve (4BMS) CO2 removal system for the International Space Station depends on many mission parameters, such as duration, crew size, cost of power, volume, fluid interface properties, etc. A need for space vehicle CO2 removal system models capable of accurately performing extrapolated hardware predictions is inevitable due to the change of the parameters which influences the CO2 removal system capacity. The purpose is to investigate the mathematical techniques required for a model capable of accurate extrapolated performance predictions and to obtain test data required to estimate mass transfer coefficients and verify the computer model. Models have been developed to demonstrate that the finite difference technique can be successfully applied to sorbents and conditions used in spacecraft CO2 removal systems. The nonisothermal, axially dispersed, plug flow model with linear driving force for 5X sorbent and pore diffusion for silica gel are then applied to test data. A more complex model, a non-darcian model (two dimensional), has also been developed for simulation of the test data. This model takes into account the channeling effect on column breakthrough. Four FORTRAN computer programs are presented: a two-dimensional model of flow adsorption/desorption in a packed bed; a one-dimensional model of flow adsorption/desorption in a packed bed; a model of thermal vacuum desorption; and a model of a tri-sectional packed bed with two different sorbent materials. The programs are capable of simulating up to four gas constituents for each process, which can be increased with a few minor changes.

  15. Manganese oxide octahedral molecular sieve K-OMS-2 as catalyst in post plasma-catalysis for trichloroethylene degradation in humid air.

    PubMed

    Nguyen Dinh, M T; Giraudon, J-M; Vandenbroucke, A M; Morent, R; De Geyter, N; Lamonier, J-F

    2016-08-15

    The total oxidation of trichloroethylene (TCE) in air at low relative humidity (RH=10%) in the presence of CO2 (520ppmv) was investigated in function of energy density using an atmospheric pressure negative DC luminescent glow discharge combined with a cryptomelane catalyst positioned downstream of the plasma reactor at a temperature of 150°C. When using Non-Thermal Plasma (NTP) alone, it is found a low COx (x=1-2) yield in agreement with the detection of gaseous polychlorinated by-products in the outlet stream as well as ozone which is an harmful pollutant. Introduction of cryptomelane enhanced trichloroethylene removal, totally inhibited plasma ozone formation and increased significantly the COx yield. The improved performances of the hybrid system were mainly ascribed to the total destruction of plasma generated ozone on cryptomelane surface to produce active oxygen species. Consequently these active oxygen species greatly enhanced the abatement of the plasma non-reacted TCE and completely destroyed the hazardous plasma generated polychlorinated intermediates. The facile redox of Mn species associated with oxygen vacancies and mobility as well as the textural properties of the catalyst might also contribute as a whole to the efficiency of the process. PMID:27107238

  16. Catalytic Reforming of Lignin-Derived Bio-Oil Over a Nanoporous Molecular Sieve Silicoaluminophosphate-11.

    PubMed

    Park, Y K; Kang, Hyeon Koo; Jang, Hansaem; Suh, Dong Jin; Park, Sung Hoon

    2016-05-01

    Catalytic pyrolysis of lignin, a major constituent of biomass, was performed. A nanoporous molecular sieve silicoaluminophosphate-11 (SAPO-11) was selected as catalyst. Thermogravimetric analysis showed that 500 degrees C was the optimal pyrolysis temperature. Pyrolyzer-gas chromatography/mass spectroscopy was used to investigate the pyrolysis product distribution. Production of phenolics, the dominant product from the pyrolysis of lignin, was promoted by the increase in the catalyst dose. In particular, low-molecular-mass phenolics were produced more over SAPO-11, while high-molecular-mass phenolics and double-bond-containing phenolics were produced less. The fraction of aromatic compounds, including benzene, toluene, xylene, and ethylbenzene, was also increased by catalytic reforming. The catalytic effects were more pronounced when the catalyst/biomass ratio was increased. The enhanced production of aromatic compounds by an acidic catalyst obtained in this study is in good agreement with the results of previous studies. PMID:27483769

  17. Molecular Sieve Regeneration System for assaying HTO from detritiation systems

    SciTech Connect

    Nasise, J.E.; Anderson, J.L.; Naruse, Y.

    1992-07-01

    A Molecular Sieve Regeneration System (MSRS) is being added to the existing Tritium Waste Treatment system (TWT) within the Tritium Systems Test Assembly (TSTA) at the Los Alamos National Laboratory. This system is an upgrade to the TWT to provide accurate measurements of the liquid waste generated from this system. Within the TWT, hydrogen isotopes are removed from the effluent gas stream by the catalytic conversion to water and the subsequent removal of water by molecular sieve trapping prior to the release to the environment. Within the TWT and similar systems, molecular sieve regeneration is required to rejuvenate the beds. The major difference of the MSRS and other regeneration systems is the capability of direct assay of long-term storage waste containers. This is accomplished with loop-flow regeneration, water collection, and tritiated water assay by scintillation and calorimetric techniques. This paper describes the MSRS in detail and how it is interfaced with the Tritium Waste Treatment system.

  18. Molecular Sieve Regeneration System for assaying HTO from detritiation systems

    SciTech Connect

    Nasise, J.E.; Anderson, J.L. ); Naruse, Y. )

    1992-01-01

    A Molecular Sieve Regeneration System (MSRS) is being added to the existing Tritium Waste Treatment system (TWT) within the Tritium Systems Test Assembly (TSTA) at the Los Alamos National Laboratory. This system is an upgrade to the TWT to provide accurate measurements of the liquid waste generated from this system. Within the TWT, hydrogen isotopes are removed from the effluent gas stream by the catalytic conversion to water and the subsequent removal of water by molecular sieve trapping prior to the release to the environment. Within the TWT and similar systems, molecular sieve regeneration is required to rejuvenate the beds. The major difference of the MSRS and other regeneration systems is the capability of direct assay of long-term storage waste containers. This is accomplished with loop-flow regeneration, water collection, and tritiated water assay by scintillation and calorimetric techniques. This paper describes the MSRS in detail and how it is interfaced with the Tritium Waste Treatment system.

  19. Carbon molecular sieves for air separation from Nomex aramid fibers.

    PubMed

    Villar-Rodil, Silvia; Martínez-Alonso, Amelia; Tascón, Juan M D

    2002-10-15

    Activated carbon fibers prepared from aramid fibers have proved to possess outstanding homogeneity in pore size, most of all when Nomex aramid fiber is used as precursor. Taking advantage of this feature, microporous carbon molecular sieves for air separation have been prepared through carbon vapor deposition of benzene on Nomex-derived carbon fibers activated to two different burnoff degrees. Carbon molecular sieves with good selectivity for this separation and showing acceptable adsorption capacities were obtained from ACFs activated to the two burnoff degrees chosen. PMID:12702417

  20. Double rotation NMR studies of zeolites and aluminophosphate molecular sieves

    SciTech Connect

    Jelinek, R. |

    1993-07-01

    Goal is to study the organization and structures of guest atoms and molecules and their reactions on internal surfaces within pores of zeolites and aluminophosphate molecular sieves. {sup 27}Al and {sup 23}Na double rotation NMR (DOR) is used since it removes the anisotropic broadening in NMR spectra of quadrupolar nuclei, thus increasing resolution. This work concentrates on probing aluminum framework atoms in aluminophosphate molecular sieves and sodium extra framework cations in porous aluminosilicates. In aluminophosphates, ordering and electronic environments of the framework {sup 27}Al nuclei are modified upon adsorption of water molecules within the channels; a relation is sought between the sieve channel topology and the organization of adsorbed water, as well as the interaction between the Al nuclei and the water molecules. Extra framework Na{sup +} cations are directly involved in adsorption processes and reactions in zeolite cavities.

  1. Improved light olefin yield from methyl bromide coupling over modified SAPO-34 molecular sieves.

    PubMed

    Zhang, Aihua; Sun, Shouli; Komon, Zachary J A; Osterwalder, Neil; Gadewar, Sagar; Stoimenov, Peter; Auerbach, Daniel J; Stucky, Galen D; McFarland, Eric W

    2011-02-21

    As an alternative to the partial oxidation of methane to synthesis gas followed by methanol synthesis and the subsequent generation of olefins, we have studied the production of light olefins (ethylene and propylene) from the reaction of methyl bromide over various modified microporous silico-aluminophosphate molecular-sieve catalysts with an emphasis on SAPO-34. Some comparisons of methyl halides and methanol as reaction intermediates in their conversion to olefins are presented. Increasing the ratio of Si/Al and incorporation of Co into the catalyst framework improved the methyl bromide yield of light olefins over that obtained using standard SAPO-34. PMID:21203621

  2. Decolorization / deodorization of zein via activated carbons and molecular sieves

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective is to evaluate a series of granular media consisting of activated carbons and molecular sieves in a batch process for the purpose of clarifying and removal of color and odor components from yellow zein dispersed in an aqueous alcohol medium. The major contributors of yellow zein is du...

  3. 21 CFR 173.40 - Molecular sieve resins.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... gram of dry resin (expressed in terms of water regain), and a particle size of 10 to 300 microns. (b) The molecular sieve resins are thoroughly washed with potable water prior to their first use in... purification of partially delactosed whey. The gel bed shall be maintained in a sanitary manner in...

  4. Molecular Sieves: Porous Organic Cage Thin Films and Molecular-Sieving Membranes (Adv. Mater. 13/2016).

    PubMed

    Song, Qilei; Jiang, Shan; Hasell, Tom; Liu, Ming; Sun, Shijing; Cheetham, Anthony K; Sivaniah, Easan; Cooper, Andrew I

    2016-04-01

    Porous organic cage molecules are a new class of molecular materials that combine microporosity and solution-processability. On page 2629, E. Sivaniah, A. I. Cooper, and co-workers demonstrate solution processing of cage molecules into thin films with tunable structures. For the first time, cage molecules are fabricated into continuous and pinhole-free microporous molecular-sieving membranes, as confirmed by selective gas transport in terms of high permeance and molecular selectivity. Image credit: Adam Kewley. PMID:27037946

  5. Titanium modified {beta} and MCM-41 molecular sieves K

    SciTech Connect

    Reddy, K.M.; Reddy, J.S.; Dicko, A.

    1995-12-01

    Ti modified large Pore {beta} zeolite and mesoporous MCM-41 molecular sieve were synthesized using hydrothermal procedures. Several other Ti-{beta} zeolites were prepared by treating a {beta} zeolite (Si/Al = 100) with ammonium titanyl oxalate solution. All samples were characterized by atomic absorption, XRD, IR, UV-Vis, Raman and XPS. The presence of tetrahedral Ti was evidenced particularly by the presence of a 212 nm absorption band in the UV-Vis spectra and a Ti(2p{sub 3/2}) binding energy of 459.5 eV. All samples were tested for the hydroxylation of hexane, benzene and phenol, and also for the epoxidation of 1-hexene. High catalytic activity was found only for the epoxidation reaction. Previous reports showed that, contrary to TS-1 and TS-2 zeolites, Ti modified {beta} (M.E. Davis et al. Prepr. Div. Petrol. Chem. 1993, p.769) and ZSM-48 (A. Sayari et at Catal. Lett. 23 (1994) 175) zeolites are poor hydroxylation catalysts in the presence of H{sub 2}O{sub 2}. In a paper devoted to Ti-MCM-41, Corma et al. (Chem. Commun. 1994, 147) reported only on the 1-hexene epoxidation. However, in the presence of excess H{sub 2}O{sub 2}, Pinnavaia et al. (Nature 368 (1994) 321) found that Ti-MCM-41 exhibits significant catalytic activity in the hydroxylation of benzene and substituted phenol. This behavior may indicate that in TS-1 and TS-2, Ti has a different local environment.

  6. Carbon fiber composite molecular sieve electrically regenerable air filter media

    DOEpatents

    Wilson, Kirk A.; Burchell, Timothy D.; Judkins, Roddie R.

    1998-01-01

    An electrically regenerable gas filter system includes a carbon fiber composite molecular sieve (CFCMS) filter medium. After a separate medium-efficiency pre-filter removes particulate from the supply airstream, the CFCMS filter sorbs gaseous air pollutants before the air is recirculated to the space. When saturated, the CFCMS media is regenerated utilizing a low-voltage current that is caused to pass through the filter medium.

  7. Carbon fiber composite molecular sieve electrically regenerable air filter media

    DOEpatents

    Wilson, K.A.; Burchell, T.D.; Judkins, R.R.

    1998-10-27

    An electrically regenerable gas filter system includes a carbon fiber composite molecular sieve (CFCMS) filter medium. After a separate medium-efficiency pre-filter removes particulate from the supply air stream, the CFCMS filter sorbs gaseous air pollutants before the air is recirculated to the space. When saturated, the CFCMS media is regenerated utilizing a low-voltage current that is caused to pass through the filter medium. 3 figs.

  8. NMR of small solutes in liquid crystals and molecular sieves

    NASA Astrophysics Data System (ADS)

    Ylihautala, Mika Petri

    The present thesis deals with the nuclear magnetic resonance (NMR) spectroscopy of small solutes applied to the studies of liquid crystals and molecular sieves. In this method, changes induced by the investigated environment to the static spectral parameters (i.e. nuclear shielding, indirect and direct spin-spin coupling and quadrupole coupling) of the solute are measured. The nuclear shielding of dissolved noble gases is utilized for the studies of thermotropic liquid crystals. The relation between the symmetry properties of mesophases and the nuclear shielding is described. The different interaction mechanisms perturbing the observed noble gas nuclear shielding are discussed, particularly, the role of long-range attractive van der Waals interactions is brought out. The suitability of the noble gas NMR spectroscopy to the studies of Iyotropic liquid crystals is investigated in terms of nuclear shielding and quadrupole coupling interactions. In molecular sieve systems, the effect of inter- and intracrystalline motions of solutes on their NMR spectra is discussed. A novel method for the measurement of the intracrystalline motions is developed. The distinctions in the 13C shielding of methane adsorbed in AlPO4-11 and SAPO-11, two structurally similar molecular sieves differing in composition, are indicated.

  9. Titanium-containing mesoporous molecular sieves for catalytic oxidation of aromatic compounds

    NASA Astrophysics Data System (ADS)

    Tanev, Peter T.; Chibwe, Malama; Pinnavaia, Thomas J.

    1994-03-01

    TITANIUM silicalite is an effective molecular-sieve catalyst for the selective oxidation of alkanes, the hydroxylation of phenol and the epoxidation of alkenes in the presence of H2O2 (refs 1-3). The range of organic compounds that can be oxidized is greatly limited, however, by the relatively small pore size (about 0.6 nm) of the host framework4. Large-pore (mesoporous) silica-based molecular sieves have been prepared recently by Kresge et all5-7 and Kuroda et al 8.; the former used a templating approach in which the formation of an inorganic mesoporous structure is assisted by self-organization of surfactants, and the latter involved topochemical rearrangement of a layered silica precursor. Here we describe the use of the templating approach to synthesize mesoporous silica-based molecular sieves partly substituted with titanium-large-pore analogues of titanium silicalite. We find that these materials show selective catalytic activity towards the oxidation of 2,6-ditert-butyl phenol to the corresponding quinone and the conversion of benzene to phenol.

  10. A controllable molecular sieve for Na+ and K+ ions.

    PubMed

    Gong, Xiaojing; Li, Jichen; Xu, Ke; Wang, Jianfeng; Yang, Hui

    2010-02-17

    The selective rate of specific ion transport across nanoporous material is critical to biological and nanofluidic systems. Molecular sieves for ions can be achieved by steric and electrical effects. However, the radii of Na(+) and K(+) are quite similar; they both carry a positive charge, making them difficult to separate. Biological ionic channels contain precisely arranged arrays of amino acids that can efficiently recognize and guide the passage of K(+) or Na(+) across the cell membrane. However, the design of inorganic channels with novel recognition mechanisms that control the ionic selectivity remains a challenge. We present here a design for a controllable ion-selective nanopore (molecular sieve) based on a single-walled carbon nanotube with specially arranged carbonyl oxygen atoms modified inside the nanopore, which was inspired by the structure of potassium channels in membrane spanning proteins (e.g., KcsA). Our molecular dynamics simulations show that the remarkable selectivity is attributed to the hydration structure of Na(+) or K(+) confined in the nanochannels, which can be precisely tuned by different patterns of the carbonyl oxygen atoms. The results also suggest that a confined environment plays a dominant role in the selectivity process. These studies provide a better understanding of the mechanism of ionic selectivity in the KcsA channel and possible technical applications in nanotechnology and biotechnology, including serving as a laboratory-in-nanotube for special chemical interactions and as a high-efficiency nanodevice for purification or desalination of sea and brackish water. PMID:20102186

  11. Evaluation of Strontium Selectivity by Sandia Octahedral Molecular Sieves (SOMS).

    SciTech Connect

    Rigali, Mark J.; Stewart, Thomas Austin

    2016-01-01

    Sandia National Laboratories has collaborated with Pleasanton Ridge Research Company (PRRC) to determine whether Sandia Octahedral Molecular Sieves (SOMS) and modified SOMs materials can be synthesized in large batches and produced in granular form. Sandia National Laboratories tested these SOMS and its variants based in aqueous chemical environments for an application-based evaluation of material performance as a sorbent. Testing focused primarily on determining the distribution coefficients (K d ) and chemical selectivity SOMs for alkali earth (Sr) ions in aqueous and dilute seawater solutions. In general the well-crystallized SOMS materials tested exhibited very high K d values (>10 6 ) in distilled water but K d values dropped substantially (%7E10 2 -10 3 ) in the dilute seawater (3%). However, one set of SOMS samples (1.4.2 and 1.4.6) provided by PRRC yielded relatively high K d (approaching 10 4 ) in dilute seawater. Further examination of these samples by scanning electron microscopy (SEM) revealed the presence of at least two phases at least one of which may be accounting for the improved K d values in dilute seawater. Evaluation of Strontium Selectivity by Sandia Octahedral Molecular Sieves (SOMS) January 20, 2016

  12. Method of recovering adsorbed liquid compounds from molecular sieve columns

    DOEpatents

    Burkholder, Harvey R.; Fanslow, Glenn E.

    1983-01-01

    Molecularly adsorbed volatile liquid compounds are recovered from molecular sieve adsorbent columns by directionally applying microwave energy to the bed of the adsorbent to produce a mixed liquid-gas effluent. The gas portion of the effluent generates pressure within the bed to promote the discharge of the effluent from the column bottoms. Preferably the discharged liquid-gas effluent is collected in two to three separate fractions, the second or intermediate fraction having a substantially higher concentration of the desorbed compound than the first or third fractions. The desorption does not need to be assisted by passing a carrier gas through the bed or by applying reduced pressure to the outlet from the bed.

  13. Method of recovering adsorbed liquid compounds from molecular sieve columns

    DOEpatents

    Burkholder, H.R.; Fanslow, G.E.

    1983-12-20

    Molecularly adsorbed volatile liquid compounds are recovered from molecular sieve adsorbent columns by directionally applying microwave energy to the bed of the adsorbent to produce a mixed liquid-gas effluent. The gas portion of the effluent generates pressure within the bed to promote the discharge of the effluent from the column bottoms. Preferably the discharged liquid-gas effluent is collected in two to three separate fractions, the second or intermediate fraction having a substantially higher concentration of the desorbed compound than the first or third fractions. The desorption does not need to be assisted by passing a carrier gas through the bed or by applying reduced pressure to the outlet from the bed. 8 figs.

  14. Carbon dioxide sorption in a nanoporous octahedral molecular sieve

    NASA Astrophysics Data System (ADS)

    Williamson, Izaak; Nelson, Eric B.; Li, Lan

    2015-08-01

    We have performed first-principles density functional theory calculations, incorporated with van der Waals interactions, to study CO2 adsorption and diffusion in nanoporous solid—OMS-2 (Octahedral Molecular Sieve). We found the charge, type, and mobility of a cation, accommodated in a porous OMS-2 material for structural stability, can affect not only the OMS-2 structural features but also CO2 sorption performance. This paper targets K+, Na+, and Ba2+ cations. First-principles energetics and electronic structure calculations indicate that Ba2+ has the strongest interaction with the OMS-2 porous surface due to valence electrons donation to the OMS-2 and molecular orbital hybridization. However, the Ba-doped OMS-2 has the worst CO2 uptake capacity. We also found evidence of sorption hysteresis in the K- and Na-doped OMS-2 materials.

  15. Transformation of metal-organic frameworks for molecular sieving membranes.

    PubMed

    Li, Wanbin; Zhang, Yufan; Zhang, Congyang; Meng, Qin; Xu, Zehai; Su, Pengcheng; Li, Qingbiao; Shen, Chong; Fan, Zheng; Qin, Lei; Zhang, Guoliang

    2016-01-01

    The development of simple, versatile strategies for the synthesis of metal-organic framework (MOF)-derived membranes are of increasing scientific interest, but challenges exist in understanding suitable fabrication mechanisms. Here we report a route for the complete transformation of a series of MOF membranes and particles, based on multivalent cation substitution. Through our approach, the effective pore size can be reduced through the immobilization of metal salt residues in the cavities, and appropriate MOF crystal facets can be exposed, to achieve competitive molecular sieving capabilities. The method can also be used more generally for the synthesis of a variety of MOF membranes and particles. Importantly, we design and synthesize promising MOF membranes candidates that are hard to achieve through conventional methods. For example, our CuBTC/MIL-100 membrane exhibits 89, 171, 241 and 336 times higher H2 permeance than that of CO2, O2, N2 and CH4, respectively. PMID:27090597

  16. Transformation of metal-organic frameworks for molecular sieving membranes

    PubMed Central

    Li, Wanbin; Zhang, Yufan; Zhang, Congyang; Meng, Qin; Xu, Zehai; Su, Pengcheng; Li, Qingbiao; Shen, Chong; Fan, Zheng; Qin, Lei; Zhang, Guoliang

    2016-01-01

    The development of simple, versatile strategies for the synthesis of metal-organic framework (MOF)-derived membranes are of increasing scientific interest, but challenges exist in understanding suitable fabrication mechanisms. Here we report a route for the complete transformation of a series of MOF membranes and particles, based on multivalent cation substitution. Through our approach, the effective pore size can be reduced through the immobilization of metal salt residues in the cavities, and appropriate MOF crystal facets can be exposed, to achieve competitive molecular sieving capabilities. The method can also be used more generally for the synthesis of a variety of MOF membranes and particles. Importantly, we design and synthesize promising MOF membranes candidates that are hard to achieve through conventional methods. For example, our CuBTC/MIL-100 membrane exhibits 89, 171, 241 and 336 times higher H2 permeance than that of CO2, O2, N2 and CH4, respectively. PMID:27090597

  17. Transformation of metal-organic frameworks for molecular sieving membranes

    NASA Astrophysics Data System (ADS)

    Li, Wanbin; Zhang, Yufan; Zhang, Congyang; Meng, Qin; Xu, Zehai; Su, Pengcheng; Li, Qingbiao; Shen, Chong; Fan, Zheng; Qin, Lei; Zhang, Guoliang

    2016-04-01

    The development of simple, versatile strategies for the synthesis of metal-organic framework (MOF)-derived membranes are of increasing scientific interest, but challenges exist in understanding suitable fabrication mechanisms. Here we report a route for the complete transformation of a series of MOF membranes and particles, based on multivalent cation substitution. Through our approach, the effective pore size can be reduced through the immobilization of metal salt residues in the cavities, and appropriate MOF crystal facets can be exposed, to achieve competitive molecular sieving capabilities. The method can also be used more generally for the synthesis of a variety of MOF membranes and particles. Importantly, we design and synthesize promising MOF membranes candidates that are hard to achieve through conventional methods. For example, our CuBTC/MIL-100 membrane exhibits 89, 171, 241 and 336 times higher H2 permeance than that of CO2, O2, N2 and CH4, respectively.

  18. Hydroxylation of phenol over MeAPO molecular sieves synthesized by vapor phase transport

    NASA Astrophysics Data System (ADS)

    Shao, Hui; Chen, Jingjing; Chen, Xia; Leng, Yixin; Zhong, Jing

    2016-07-01

    In this study, MeAPO-25 (Me = Fe, Cu, Mn) molecular sieves were first synthesized by a vapor phase transport method using tetramethyl guanidine as the template and applied to hydroxylation of phenol. The zeolites were characterized by XRD, SEM, FT-IR, and DR UV-Vis. As a result, MeAPO-21 and MeAPO-15 were synthesized by changing the Me/Al ratio. UV-Visible diffuse reflectance study suggested incorporation of heteroatoms into the framework and FT-IR study also supported these data. Effects of heteroatoms, contents of Me in MeAPO-25, reaction temperature, phenol/H2O2 mole ratios, reaction time and concentration of catalyst on the conversion of phenol, as well as on the selectivity were studied. FeAPO-25 exhibited a high catalytic activity at the mole ratio of FeO and Al2O3 equal to 0.1 in the synthesis gel, giving the phenol conversion of 88.75% and diphenols selectivity of 66.23% at 60°C within 3 h [ n(phenol)/ n(H2O2) = 0.75, m(FeAPO-25)/ m(phenol) = 7.5%]. Experimental results indicated that the FeAPO-25 molecular sieve was a fairly promising candidate for the application in hydroxylation of phenol.

  19. Investigation of Y/SBA Composite Molecular Sieves Morphology Control and Catalytic Performance for n-Pentane Aromatization.

    PubMed

    Shi, Chun-Wei; Wu, Wen-Yuan; Li, Shuai; Bian, Xue; Zhao, Shan-Lin; Pei, Ming-Yuan

    2016-01-01

    Using Y molecular sieve as the core, Y/SBA-15 composite molecular sieves were prepared by different crystallization methods in the paper. The growth process and morphologies of the composite molecular sieves were controlled by adjusting the synthesis factors. The structures and acidity of two kinds of composite molecular sieves were characterized by X-ray diffraction (XRD), N2 adsorption/desorption, transmission electron microscopy (TEM), and NH3-TPD. The catalysis performances of the composite molecular sieves were investigated in the aromatization reaction of n-pentane. The results indicated that the desired core-shell composite molecular sieves were obtained when the crystallization conditions were 36 hours, 100 °C and secondary crystallization. The aromatization results showed that core-shell composite molecular sieves had better selectivity for producing high application value xylenes compared to mixed-crystal composite molecular sieves. PMID:27029526

  20. Investigation of Y/SBA Composite Molecular Sieves Morphology Control and Catalytic Performance for n-Pentane Aromatization

    PubMed Central

    Shi, Chun-Wei; Wu, Wen-Yuan; Li, Shuai; Bian, Xue; Zhao, Shan-lin; Pei, Ming-Yuan

    2016-01-01

    Using Y molecular sieve as the core, Y/SBA-15 composite molecular sieves were prepared by different crystallization methods in the paper. The growth process and morphologies of the composite molecular sieves were controlled by adjusting the synthesis factors. The structures and acidity of two kinds of composite molecular sieves were characterized by X-ray diffraction (XRD), N2 adsorption/desorption, transmission electron microscopy (TEM), and NH3-TPD. The catalysis performances of the composite molecular sieves were investigated in the aromatization reaction of n-pentane. The results indicated that the desired core-shell composite molecular sieves were obtained when the crystallization conditions were 36 hours, 100 °C and secondary crystallization. The aromatization results showed that core-shell composite molecular sieves had better selectivity for producing high application value xylenes compared to mixed-crystal composite molecular sieves. PMID:27029526

  1. Catalyzing the oxidation of sulfamethoxazole by permanganate using molecular sieves supported ruthenium nanoparticles.

    PubMed

    Zhang, Jing; Sun, Bo; Huang, Yuying; Guan, Xiaohong

    2015-12-01

    This study developed a heterogeneous catalytic permanganate oxidation system with three molecular sieves, i.e., nanosized ZSM-5 (ZSM-5A), microsized ZSM-5 (ZSM-5B) and MCM-41, supported ruthenium nanoparticles as catalyst, denoted as Ru/ZSM-5A, Ru/ZSM-5B and Ru/MCM-41, respectively. The presence of 0.5gL(-1) Ru/ZSM-5A, Ru/ZSM-5B and Ru/MCM-41 increased the oxidation rate of sulfamethoxazole (SMX) by permanganate at pH 7.0 by 27-1144 times. The catalytic performance of Ru catalysts toward SMX oxidation by permanganate was strongly dependent on Ru loading on the catalysts. The X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses confirmed that Ru catalyst acted as an electron shuttle in catalytic permanganate oxidation process. Ru(III) deposited on the surface of catalysts was oxidized by permanganate to its higher oxidation state Ru(VII), which could work as a co-oxidant with permanganate to decompose SMX and was then reduced to its initial tri-valence. During the successive runs, Ru/ZSM-5A could not maintain its catalytic activity due to the deposition of MnO2, which was the reductive product of permanganate, onto the surface of Ru/ZSM-5A. Thus, the regeneration of partially deactivated Ru catalysts by reductant NH2OH⋅HCl or ascorbic acid was proposed. Ru/ZSM-5A regenerated by NH2OH⋅HCl displayed comparable catalytic ability to its virgin counterpart, while ascorbic acid could not completely remove the deposited MnO2. A trace amount of leaching of Ru into the reaction solution was also observed, which would be ameliorated by improving the preparation conditions in the future study. PMID:26196405

  2. Use of Carbon Fiber Composite Molecular Sieves for Air Separation

    SciTech Connect

    Baker, Frederick S; Contescu, Cristian I; Gallego, Nidia C; Burchell, Timothy D

    2005-09-01

    A novel adsorbent material, 'carbon fiber composite molecular sieve' (CFCMS), has been developed by the Oak Ridge National Laboratory. Its features include high surface area, large pore volume, and a rigid, permeable carbon structure that exhibits significant electrical conductivity. The unique combination of high adsorptive capacity, permeability, good mechanical properties, and electrical conductivity represents an enabling technology for the development of novel gas separation and purification systems. In this context, it is proposed that a fast-cycle air separation process that exploits a kinetic separation of oxygen and nitrogen should be possible using a CFCMS material coupled with electrical swing adsorption (ESA). The adsorption of O{sub 2}, N{sub 2}, and CO{sub 2} on activated carbon fibers was investigated using static and dynamic techniques. Molecular sieving effects in the activated carbon fiber were highlighted by the adsorption of CO{sub 2}, a more sensitive probe molecule for the presence of microporosity in adsorbents. The kinetic studies revealed that O2 was more rapidly adsorbed on the carbon fiber than N{sub 2}, and with higher uptake under equilibrium conditions, providing the fiber contained a high proportion of very narrow micropores. The work indicated that CFCMS is capable of separating O{sub 2} and N{sub 2} from air on the basis of the different diffusion rates of the two molecules in the micropore network of the activated carbon fibers comprising the composite material. In response to recent enquires from several potential users of CFCMS materials, attention has been given to the development of a viable continuous process for the commercial production of CFCMS material. As part of this effort, work was implemented on characterizing the performance of lignin-based activated carbon fiber, a potentially lower cost fiber than the pitch-based fibers used for CFCMS production to date. Similarly, to address engineering issues, measurements were

  3. Fringe field NMR diffusometry of anomalous self-diffusion in molecular sieves

    NASA Astrophysics Data System (ADS)

    Ylihautala, Mika; Jokisaari, Jukka; Fischer, Elmar; Kimmich, Rainer

    1998-06-01

    Superconducting magnet fringe field NMR diffusometry is applied to an adsorbate-molecular sieve system in order to obtain intracrystalline self-diffusion of adsorbed molecules. Effects of self-diffusion, exchange, relaxation, and dipolar correlation are discussed. The proper equations for one- and two-dimensional anomalous self-diffusion with and without macroscopic order are derived. The method is applied to investigate methane self-diffusion in the molecular sieve silicoaluminophosphate, type 11 (SAPO-11). It is concluded that the nature of the methane displacements in the sieve channels is single-file self-diffusion.

  4. Isotherms for Water Adsorption on Molecular Sieve 3A: Influence of Cation Composition

    DOE PAGESBeta

    Lin, Ronghong; Ladshaw, Austin; Nan, Yue; Liu, Jiuxu; Yiacoumi, Sotira; Tsouris, Costas; DePaoli, David W.; Tavlarides, Lawrence L.

    2015-06-16

    This study is part of our continuing efforts to address engineering issues related to the removal of tritiated water from off-gases produced in used nuclear fuel reprocessing facilities. In the current study, adsorption equilibrium of water on molecular sieve 3A beads was investigated. Adsorption isotherms for water on the UOP molecular sieve 3A were measured by a continuous-flow adsorption system at 298, 313, 333, and 353 K. Experimental data collected were analyzed by the Generalized Statistical Thermodynamic Adsorption (GSTA) isotherm model. The K+/Na+ molar ratio of this particular type of molecular sieve 3A was ~4:6. Our results showed that themore » GSTA isotherm model worked very well to describe the equilibrium behavior of water adsorption on molecular sieve 3A. The optimum number of parameters for the current experimental data was determined to be a set of four equilibrium parameters. This result suggests that the adsorbent crystals contain four energetically distinct adsorption sites. In addition, it was found that water adsorption on molecular sieve 3A follows a three-stage adsorption process. This three-stage adsorption process confirmed different water adsorption sites in molecular sieve crystals. In addition, the second adsorption stage is significantly affected by the K+/Na+ molar ratio. In this stage, the equilibrium adsorption capacity at a given water vapor pressure increases as the K+/Na+ molar ratio increases.« less

  5. Isotherms for Water Adsorption on Molecular Sieve 3A: Influence of Cation Composition

    SciTech Connect

    Lin, Ronghong; Ladshaw, Austin; Nan, Yue; Liu, Jiuxu; Yiacoumi, Sotira; Tsouris, Costas; DePaoli, David W.; Tavlarides, Lawrence L.

    2015-06-16

    This study is part of our continuing efforts to address engineering issues related to the removal of tritiated water from off-gases produced in used nuclear fuel reprocessing facilities. In the current study, adsorption equilibrium of water on molecular sieve 3A beads was investigated. Adsorption isotherms for water on the UOP molecular sieve 3A were measured by a continuous-flow adsorption system at 298, 313, 333, and 353 K. Experimental data collected were analyzed by the Generalized Statistical Thermodynamic Adsorption (GSTA) isotherm model. The K+/Na+ molar ratio of this particular type of molecular sieve 3A was ~4:6. Our results showed that the GSTA isotherm model worked very well to describe the equilibrium behavior of water adsorption on molecular sieve 3A. The optimum number of parameters for the current experimental data was determined to be a set of four equilibrium parameters. This result suggests that the adsorbent crystals contain four energetically distinct adsorption sites. In addition, it was found that water adsorption on molecular sieve 3A follows a three-stage adsorption process. This three-stage adsorption process confirmed different water adsorption sites in molecular sieve crystals. In addition, the second adsorption stage is significantly affected by the K+/Na+ molar ratio. In this stage, the equilibrium adsorption capacity at a given water vapor pressure increases as the K+/Na+ molar ratio increases.

  6. Synthetic Zeolites and Other Microporous Oxide Molecular Sieves

    NASA Astrophysics Data System (ADS)

    Sherman, John D.

    1999-03-01

    Use of synthetic zeolites and other microporous oxides since 1950 has improved insulated windows, automobile air-conditioning, refrigerators, air brakes on trucks, laundry detergents, etc. Their large internal pore volumes, molecular-size pores, regularity of crystal structures, and the diverse framework chemical compositions allow "tailoring" of structure and properties. Thus, highly active and selective catalysts as well as adsorbents and ion exchangers with high capacities and selectivities were developed. In the petroleum refining and petrochemical industries, zeolites have made possible cheaper and lead-free gasoline, higher performance and lower-cost synthetic fibers and plastics, and many improvements in process efficiency and quality and in performance. Zeolites also help protect the environment by improving energy efficiency, reducing automobile exhaust and other emissions, cleaning up hazardous wastes (including the Three Mile Island nuclear power plant and other radioactive wastes), and, as specially tailored desiccants, facilitating the substitution of new refrigerants for the ozone-depleting chlorofluorocarbons banned by the Montreal Protocol.

  7. Synthetic zeolites and other microporous oxide molecular sieves.

    PubMed

    Sherman, J D

    1999-03-30

    Use of synthetic zeolites and other microporous oxides since 1950 has improved insulated windows, automobile air-conditioning, refrigerators, air brakes on trucks, laundry detergents, etc. Their large internal pore volumes, molecular-size pores, regularity of crystal structures, and the diverse framework chemical compositions allow "tailoring" of structure and properties. Thus, highly active and selective catalysts as well as adsorbents and ion exchangers with high capacities and selectivities were developed. In the petroleum refining and petrochemical industries, zeolites have made possible cheaper and lead-free gasoline, higher performance and lower-cost synthetic fibers and plastics, and many improvements in process efficiency and quality and in performance. Zeolites also help protect the environment by improving energy efficiency, reducing automobile exhaust and other emissions, cleaning up hazardous wastes (including the Three Mile Island nuclear power plant and other radioactive wastes), and, as specially tailored desiccants, facilitating the substitution of new refrigerants for the ozone-depleting chlorofluorocarbons banned by the Montreal Protocol. PMID:10097059

  8. Synthetic zeolites and other microporous oxide molecular sieves

    PubMed Central

    Sherman, John D.

    1999-01-01

    Use of synthetic zeolites and other microporous oxides since 1950 has improved insulated windows, automobile air-conditioning, refrigerators, air brakes on trucks, laundry detergents, etc. Their large internal pore volumes, molecular-size pores, regularity of crystal structures, and the diverse framework chemical compositions allow “tailoring” of structure and properties. Thus, highly active and selective catalysts as well as adsorbents and ion exchangers with high capacities and selectivities were developed. In the petroleum refining and petrochemical industries, zeolites have made possible cheaper and lead-free gasoline, higher performance and lower-cost synthetic fibers and plastics, and many improvements in process efficiency and quality and in performance. Zeolites also help protect the environment by improving energy efficiency, reducing automobile exhaust and other emissions, cleaning up hazardous wastes (including the Three Mile Island nuclear power plant and other radioactive wastes), and, as specially tailored desiccants, facilitating the substitution of new refrigerants for the ozone-depleting chlorofluorocarbons banned by the Montreal Protocol. PMID:10097059

  9. A systematic investigation of the preparation and properties of composite carbon molecular sieves containing inorganic oxides

    NASA Technical Reports Server (NTRS)

    Foley, Henry C.

    1990-01-01

    The objective of this research is to define the methodology for the preparation and characterization of new carbon-based molecular sieves with composite structures. Carbon molecular sieves have found increasing application in the field of separation and purification of gases. These materials are relatively easy to prepare and their surfaces can be modified to some extent. It is expected that by combining inorganic oxides with the carbonaceous structure one can begin to design composite materials with a wider range of possible chemical and physical properties. In this way, the IOM-CMS materials may confer distinct advantages over pure carbon molecular sieves, not just for separation, but also for catalysis. The most recent results in the design and characterization of these IOM-CMS materials are reviewed and summarized. Directions for further research are also presented.

  10. In-situ preparation of functionalized molecular sieve material and a methodology to remove template

    PubMed Central

    Yadav, Rekha; Ahmed, Maqsood; Singh, Arvind Kumar; Sakthivel, Ayyamperumal

    2016-01-01

    A series of diaminosilane-functionalized silicoaluminophosphate molecular sieve (SAPO-37) was prepared by in-situ synthesis, and a novel method was developed for the selective removal of structure directing agent (SDA)/template from the functionalized SAPO-37.The complete removal of the SDA was evident according to FT-IR, TGA, 13C MAS-NMR and elemental analysis. The developed method was found to be efficient for removal of template from microporous molecular sieve viz., SAPO-37 and can be applied for other microporous molecular sieves such as SAPO-5, SAPO-40, etc. The powder XRD pattern of the template-removed samples showed a highly crystalline SAPO-37 phase. Argentometric titration revealed that more than 90% of diamine functionality exposed on the surface was accessible for catalytic applications. The resultant materials showed promising activity for ring opening of epoxide with aniline to yield β-amino-alcohol. PMID:26960707

  11. In-situ preparation of functionalized molecular sieve material and a methodology to remove template.

    PubMed

    Yadav, Rekha; Ahmed, Maqsood; Singh, Arvind Kumar; Sakthivel, Ayyamperumal

    2016-01-01

    A series of diaminosilane-functionalized silicoaluminophosphate molecular sieve (SAPO-37) was prepared by in-situ synthesis, and a novel method was developed for the selective removal of structure directing agent (SDA)/template from the functionalized SAPO-37.The complete removal of the SDA was evident according to FT-IR, TGA, (13)C MAS-NMR and elemental analysis. The developed method was found to be efficient for removal of template from microporous molecular sieve viz., SAPO-37 and can be applied for other microporous molecular sieves such as SAPO-5, SAPO-40, etc. The powder XRD pattern of the template-removed samples showed a highly crystalline SAPO-37 phase. Argentometric titration revealed that more than 90% of diamine functionality exposed on the surface was accessible for catalytic applications. The resultant materials showed promising activity for ring opening of epoxide with aniline to yield β-amino-alcohol. PMID:26960707

  12. In-situ preparation of functionalized molecular sieve material and a methodology to remove template

    NASA Astrophysics Data System (ADS)

    Yadav, Rekha; Ahmed, Maqsood; Singh, Arvind Kumar; Sakthivel, Ayyamperumal

    2016-03-01

    A series of diaminosilane-functionalized silicoaluminophosphate molecular sieve (SAPO-37) was prepared by in-situ synthesis, and a novel method was developed for the selective removal of structure directing agent (SDA)/template from the functionalized SAPO-37.The complete removal of the SDA was evident according to FT-IR, TGA, 13C MAS-NMR and elemental analysis. The developed method was found to be efficient for removal of template from microporous molecular sieve viz., SAPO-37 and can be applied for other microporous molecular sieves such as SAPO-5, SAPO-40, etc. The powder XRD pattern of the template-removed samples showed a highly crystalline SAPO-37 phase. Argentometric titration revealed that more than 90% of diamine functionality exposed on the surface was accessible for catalytic applications. The resultant materials showed promising activity for ring opening of epoxide with aniline to yield β-amino-alcohol.

  13. Synthesis and physicochemical properties of Zr-MCM-41 mesoporous molecular sieves and Pt/H{sub 3}PW{sub 12}O{sub 40}/Zr-MCM-41 catalysts

    SciTech Connect

    Chen, L.F. Wang, J.A.; Norena, L.E.; Aguilar, J.; Navarrete, J.; Salas, P.; Montoya, J.A.; Del Angel, P.

    2007-10-15

    For the first time, modifications of the surface and framework of Si-MCM-41 by depositing a heteropolyacid on the surface and by introducing foreign Zr{sup 4+} ions into the framework are investigated. The Zr-modified Si-MCM-41 mesoporous materials (hereafter referred as WSZn, n=Si/Zr=25, 15, 8, 4) were synthesized through a surfactant-templated preparation approach, using low-cost fumed silica as the Si precursor. After impregnation with 25 wt% of H{sub 3}PW{sub 12}O{sub 40}, the surface Broensted acidity of the Pt/H{sub 3}PW{sub 12}O{sub 40}/WSZn catalysts was greatly enhanced by 2-10 times relative to the bare WSZn support. Two kinds of supported heteropolyacids were formed: (i) bulk-like heteropolyacid crystals with unchanged Keggin structures, and (ii) highly dispersed heteropolyacid with distorted Keggin units. The formation of various kinds of heteropolyacid structures is closely related to the interaction between the heteropolyanions and the hydroxyl groups in the host support. - Graphical abstract: Modifications of the surface and framework of Si-MCM-41 by depositing a heteropolyacid on the surface and by introducing foreign Zr{sup 4+} ions into the framework are investigated. Broensted acidity of the Pt/H{sub 3}PW{sub 12}O{sub 40}/Zr-MCM-41 catalysts was greatly enhanced by 2-10 times relative to the bare Zr-MCM-41 support.

  14. Update on N2O4 Molecular Sieving with 3A Material at NASA/KSC

    NASA Technical Reports Server (NTRS)

    Davis, Chuck; Dorn, Claudia

    2000-01-01

    During its operational life, the Shuttle Program has experienced numerous failures in the Nitrogen Tetroxide (N2O4) portion of Reaction Control System (RCS), many of which were attributed to iron-nitrate contamination. Since the mid-1980's, N2O4 has been processed through a molecular sieve at the N2O4 manufacturer's facility which results in an iron content typically less than 0.5 parts-per-million-by-weight (ppmw). In February 1995, a Tiger Team was formed to attempt to resolve the iron nitrate problem. Eighteen specific actions were recommended as possibly reducing system failures. Those recommended actions include additional N2O4 molecular sieving at the Shuttle launch site. Testing at NASA White Sands Test Facility (WSTF) determined an alternative molecular sieve material could also reduce the water-equivalent content (free water and HNO3) and thereby further reduce the natural production of iron nitrate in N2O4 while stored in iron-alloy storage tanks. Since April '96, NASA Kennedy Space Center (KSC) has been processing N2O4 through the alternative molecular sieve material prior to delivery to Shuttle launch pad N2O4 storage tanks. A new, much larger capacity molecular sieve unit has also been used. This paper will evaluate the effectiveness of N2O4 molecular sieving on a large-scale basis and attempt to determine if the resultant lower-iron and lower-water content N2O4 maintains this new purity level in pad storage tanks and shuttle flight systems.

  15. Low temperature VOC combustion over manganese, Cobalt and Zinc ALPO(4) Molecular sieves. Semi-annual, March 1, 1996 - Aug. 31, 1996

    SciTech Connect

    Das, K.; Sheehan, D.G.; Szostak, R.

    1996-12-31

    A functional fixed bed continuous flow catalytic reactor was constructed for conducting experiments on the catalytic destruction of VOCs using cobalt and manganese containing aluminophosphate catalysts (MeAPOs). The reactor was also interfaced to a Gas Chromatograph in order to facilitate on line product analysis. As preliminary catalytic experiments, a cobalt exchanged form of large pore zeolite Y was used as a reference catalyst for the oxidation of methylene chloride (CH{sub 2}Cl{sub 2}). At 350{degrees}C, the catalyst was effective in partial conversion of this feed stream of VOC to CO{sub 2}. Optimization of reaction conditions are currently underway in order to obtain higher conversion levels. The effect of variations in reaction conditions such as reactant flow rate, reaction temperature and catalyst compositions are currently been investigated. In the next phase of this project, the Co-exchanged Y zeolite will be substituted by the MeAPOs catalysts and the reactivities of the latter will be assessed. The potential of the MeAPOs to function as oxidation catalysts was evaluated in the liquid phase conversion of phenol to hydroquinone and catechol. The percentage conversion and product yield were significant and varied depending on the metal type and content of the molecular sieve framework. Conversion levels were also dependent on molecular sieve pore dimensions as the medium pore MeAPO-11 was more active than the larger pore MeAPO-5 or MeAPO-36.

  16. Application of 3A molecular sieve layer in dye-sensitized solar cells

    SciTech Connect

    Yan, Yuan; Wang, Jinzhong E-mail: qingjiang.yu@hit.edu.cn; Yu, Qingjiang E-mail: qingjiang.yu@hit.edu.cn; Huang, Yuewu; Chang, Quanhong; Hao, Chunlei; Jiao, Shujie; Gao, Shiyong; Li, Hongtao; Wang, Dongbo

    2014-08-25

    3A molecular sieve layer was used as dehydration and electronic-insulation layer on the TiO{sub 2} electrode of dye-sensitized solar cells. This layer diminished the effect of water in electrolyte efficiently and enhanced the performance of cells. The conversion efficiency increased from 9.58% to 10.2%. The good moisture resistance of cells was attributed to the three-dimensional interconnecting structure of 3A molecular sieve with strong adsorption of water molecule. While the performance enhancement benefited from the suppression of the charge recombination of electronic-insulation layer and scattering effect of large particles.

  17. Overtone and combination tone bands in the DRIFT spectra of molecular sieves

    NASA Astrophysics Data System (ADS)

    Peuker, Ch.; Splett, Ch.

    1993-03-01

    The DRIFT spectra of molecular sieves of type A, X, ZSM-5 and SAPO are measured. It is demonstrated that in some cases the overtone and combination tone bands of the lattice vibrations may be used for characterizing the structure of molecular sieves. For instance crystal phase transition due to thermal or hydrothermal treatment, can easily be studied in the region between 2500 and 1500 cm -1. In general the variations in the spectra of the samples due to structural distortion are less significant in the overtone and combination tone bands than in fundamental ones.

  18. CTR Fuel recovery system using regeneration of a molecular sieve drying bed

    DOEpatents

    Folkers, Charles L.

    1981-01-01

    A primary molecular sieve drying bed is regenerated by circulating a hot inert gas through the heated primary bed to desorb water held on the bed. The inert gas plus water vapor is then cooled and passed through an auxiliary molecular sieve bed which adsorbs the water originally desorbed from the primary bed. The main advantage of the regeneration technique is that the partial pressure of water can be reduced to the 10.sup.-9 atm. range. This is significant in certain CTR applications where tritiated water (T.sub.2 O, HTO) must be collected and kept at very low partial pressure.

  19. Development of design information for molecular-sieve type regenerative CO2-removal systems

    NASA Technical Reports Server (NTRS)

    Wright, R. M.; Ruder, J. M.; Dunn, V. B.; Hwang, K. C.

    1973-01-01

    Experimental and analytic studies were conducted with molecular sieve sorbents to provide basic design information, and to develop a system design technique for regenerable CO2-removal systems for manned spacecraft. Single sorbate equilibrium data were obtained over a wide range of conditions for CO2, water, nitrogen, and oxygen on several molecular sieve and silica gel sorbents. The coadsorption of CO2 with water preloads, and with oxygen and nitrogen was experimentally evaluated. Mass-transfer, and some limited heat-transfer performance evaluations were accomplished under representative operating conditions, including the coadsorption of CO2 and water. CO2-removal system performance prediction capability was derived.

  20. Characterization of Se-loaded molecular sieves A, X, Y, AlPO-5, and mordenite

    SciTech Connect

    Parise, J.B.; MacDougall, J.E.; Herron, N.; Farlee, R.; Sleight, A.W.; Ying Wang; Bein, T.; Moller, K.; Moroney, L.M.

    1988-01-27

    Selenium has been successfully loaded into molecular sieves A, X, Y, AlPO-5, and mordenite, and the products were characterized by using EXAFS, solid-state NMR, and diffuse-reflectance techniques. This study reveals selenium is predominantly of the trigonal (helical chains) form in all but the A sample, where only the Se/sub 8/-crown ring form is found. A mixture of allotropes and helical chains occupy the large 3D-pore and channel systems of molecular sieves X and Y; however, a single, probably fixed-pitch helical-chain allotrope occupies the more constrained 12-membered-ring channels found in mordenite and AlPO-5. The high degree of order in these last two sieves is reflected in a strong second-shell feature in the EXAFS spectra. 22 refs., 12 figs., 3 tabs.

  1. [Preparation and evaluation of novel mesoporous molecular sieve of baicalin surface molecularly imprinted polymers].

    PubMed

    Gu, Xia-li; He, Hong-liang; Shi, Li-ying; Gao, Yan-kun; Chen, Li-na

    2015-05-01

    Taking mesoporous molecular sieve MCM-41 as a substrate, baicalin (BA) as template, acrylamide (AM) as the functional monomer, ethylene glycol dimethacrylate (EGDMA) as a cross-linking agent, ethanol as solvent, under thermal polymerization initiator of azobis isobutyronitrilo (AIBN) , a kind of selective recognition of baicalin surface molecularly imprinted polymer was synthesized. The surface morphologies and characteristics of the MIPs were characterized by infrared spectroscopy (IR) and transmission electron microscope (TEM). The adsorption properties of polymer microsphere for the template were tested by the dynamic adsorption equilibrium experiments and static adsorption equilibrium experiments. The experiment showed that the imprinting process was successfully and the well-ordered one-dimensional pore structure of MCM-41 was still preserved. Furthermore, molecularly imprinted polymers had higher selective ability for BA, then provided a new method for the efficient separation and enrichment of baicalin active ingredients from medicinal plants Scutellaria baicalensis. PMID:26323135

  2. Textural mesoporosity and the catalytic activity of mesoporous molecular sieves with wormhole framework structures

    SciTech Connect

    Pauly, T.R.; Liu, Y.; Pinnavaia, T.J.; Billinge, S.J.L.; Rieker, T.P.

    1999-09-29

    Three different water-alcohol cosolvent systems were used to assemble mesoporous molecular sieve silicas with wormhole framework structures (previously denoted HMS silicas) from an electrically neutral amine surfactant (S{degree}) and a silicon alkoxide precursor (I{degree}). The fundamental particle size and associated textural (interparticle) porosity of the disordered structures were correlated with the solubility of the surfactant in the water-alcohol cosolvents used for the S{degree}I{degree} assembly process. Polar cosolvents containing relatively low volume fractions of C{sub n}H{sub 2n+1}OH alcohols (n = 1--3) gave heterogeneous surfactant emulsions that assembled intergrown aggregates of small primary particles with high textural pore volumes (designated HMS-HTx). Conversely, three-dimensional, monolithic particles with little or no textural porosity (designated HMS-LTx) were formed from homogeneous surfactant solutions in lower polarity cosolvents. Aluminum substituted AL-HMS-HTx analogues with high textural porosity and improved framework accessibility also were shown to be much more efficient catalysts than AL-HMS-LTx or monolithic forms of hexagonal AL-MCM-41 for the sterically demanding condensed phase alkylation of 2,4-di-tert-butylphenol with cinnamyl alcohol. Transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) studies verified the textural differences between wormhole HMS and electrostatically assembled hexagonal MCM-41 and SBA-3 molecular sieves. Power law fits to the scattering data indicated a surface fractal (D{sub s} = 2.76) for HMS-HTx, consistent with rough surfaces. A second power law at lower-q indicated the formation of a mass fractal (D{sub m} = 1.83) consistent with branching of small fundamental particles. Hexagonal MCM-41 and SBA-3 silicas, on the other hand, exhibited scattering properties consistent with moderately rough surfaces (D{sub s} = 2.35 and 2.22, respectively) and large particle diameters ({much

  3. Drying R-407C and R-410A refrigerant blends with molecular sieve desiccants

    SciTech Connect

    Cohen, A.P.; Tucker, D.M.

    1998-10-01

    The hydrofluorocarbon (HFC) R-32 (CF{sub 2}H{sub 2}) is a component of refrigerant blends in the 407 and 410 series being tested and commercialized for use as replacements for R-502 and the hydrochlorofluorocarbon (HCFC) R-22. The molecular sieve desiccants used with chlorofluorocarbon (CFC) and HCFC mineral oil systems in the past have achieved high water capacity by excluding the refrigerant and adsorbing only the water. Unfortunately, R-32 is adsorbed on commercial type 3A molecular sieve desiccant products. The result of this adsorption is a loss of water capacity when drying R-32 compared to drying R-22 or R-502 and a reduced level of chemical compatibility of the desiccant with the refrigerant. Some compressor manufacturers are seeking a water concentration as low as 10 mg/kg (ppm[wt]) in the circulating refrigerant of polyolester-lubricated refrigerating equipment using these HFC blends. This paper compares unmodified commercial type 3A molecular sieve desiccants with a recently developed, modified 3A molecular sieve that excludes R-32. The modified 3A has better chemical compatibility with R-32 and high water capacity in liquid R-407C and R-410A. The drying rates of the two desiccants in R-407C and R-410A are similar. Data and test methods are reported on refrigerant adsorption, water capacity, drying rate, and chemical compatibility.

  4. A reconstruction strategy to synthesize mesoporous SAPO molecular sieve single crystals with high MTO catalytic activity.

    PubMed

    Wang, Chan; Yang, Miao; Li, Mingrun; Xu, Shutao; Yang, Yue; Tian, Peng; Liu, Zhongmin

    2016-05-11

    Mesoporous SAPO-34 single crystals with tunable porosity and Si content have been fast synthesized within 4 hours by a reconstruction strategy, which show excellent hydrothermal stability and MTO catalytic activity. This new strategy is further proven to be applicable to prepare other mesoporous SAPO molecular sieve single crystals. PMID:27101359

  5. Molecular sieve generation of aviator's oxygen: Performance of a prototype system under simulated flight conditions.

    PubMed

    Miller, R L; Ikels, K G; Lamb, M J; Boscola, E J; Ferguson, R H

    1980-07-01

    The molecular sieve method of generating an enriched-oxygen breathing gas is one of several candidate onboard oxygen generation (OBOG) systems under joint Army-Navy-Air Force development for application in tactical aircraft. The performance of a nominal two-man-capacity molecular sieve oxygen generation system was characterized under simulated flight conditions. Data are given on the composition of the molecular sieve-generated breathing gas (oxygen, nitrogen, carbon dioxide, and argon) as a function of inlet air pressure, altitude, breathing gas flow rate, and ambient temperature. The maximum oxygen concentration observed was 95%, with the balance argon. At low demand flow rates and certain conditions of pressure and altitude, the argon enrichment factor exceeded that of oxygen giving a maximum argon concentration of 6.6% with the balance oxygen. The structural integrity of the unit was verified by vibration and centrifuge testing. The performance of the molecular sieve unit is discussed in the context of aircraft operating envelopes using both diluter-demand and 100% delivery subsystems. PMID:6774707

  6. Experiments for the Undergraduate Laboratory that Illustrate the Size-Exclusion Properties of Zeolite Molecular Sieves

    ERIC Educational Resources Information Center

    Cooke, Jason; Henderson, Eric J.

    2009-01-01

    Experiments are presented that demonstrate the size-exclusion properties of zeolites and reveal the reason for naming zeolites "molecular sieves". If an IR spectrometer is available, the adsorption or exclusion of alcohols of varying sizes from dichloromethane or chloroform solutions can be readily demonstrated by monitoring changes in the…

  7. EVALUATION OF MOLECULAR SIEVES FOR SAMPLING N0X EMISSIONS AT ELECTRIC UTILITY PLANTS

    EPA Science Inventory

    A field study was conducted to evaluate the use of molecular sieves for collection of NOx (NO + NO2) emissions from utility boilers. It was found that NOx could be collected efficiently (99%) at sample flow rates of 1 L/min over 20- to 40-min sampling periods at the NOx levels en...

  8. Low Temperature VOC Combustion Over Manganese, Cobalt and Zinc AlPO{sub 4} Molecular Sieves

    SciTech Connect

    Szostak, R.

    1997-03-31

    The objective of this project is to prepare manganese, cobalt and zinc containing AlPO{sub 4} molecular sieves and evaluate their catalytic activities for the removal of low levels of volatile organic compounds (VOCs) from gas streams. This report highlights our research activities for period October 1,1996 to March 31, 1997.

  9. Probing the structure of metal-substituted molecular sieves by solid-state NMR

    SciTech Connect

    Labouriau, A.; Crawford, S.N.; Ott, K.; Earl, W.L.

    1998-08-01

    Paramagnetic metal ions exert large influences on the NMR spectra of neighboring nuclei. The authors are using these effects to probe metal sites in zeolites and AlPO{sub 4} molecular sieves. In particular, they are studying [Co]-AlPO{sub 4}-5 because similar cobalt substituted AlPO{sub 4} sieves are reported in the literature. They have extended that work to probe the titanium zeolite TS-1 by comparing spectra of normal TS-1 to samples where the titanium has been reduced to the paramagnetic Ti{sup 3+}. This promises to be a useful technique for determining framework substitution in many zeolite systems.

  10. Molecular water oxidation catalyst

    DOEpatents

    Gratzel, Michael; Munavalli, Shekhar; Pern, Fu-Jann; Frank, Arthur J.

    1993-01-01

    A dimeric composition of the formula: ##STR1## wherein L', L", L'", and L"" are each a bidentate ligand having at least one functional substituent, the ligand selected from bipyridine, phenanthroline, 2-phenylpyridine, bipyrimidine, and bipyrazyl and the functional substituent selected from carboxylic acid, ester, amide, halogenide, anhydride, acyl ketone, alkyl ketone, acid chloride, sulfonic acid, phosphonic acid, and nitro and nitroso groups. An electrochemical oxidation process for the production of the above functionally substituted bidentate ligand diaqua oxo-bridged ruthenium dimers and their use as water oxidation catalysts is described.

  11. Controlled thermal oxidative crosslinking of polymers of intrinsic microporosity towards tunable molecular sieve membranes

    NASA Astrophysics Data System (ADS)

    Song, Qilei; Cao, Shuai; Pritchard, Robyn H.; Ghalei, Behnam; Al-Muhtaseb, Shaheen A.; Terentjev, Eugene M.; Cheetham, Anthony K.; Sivaniah, Easan

    2014-09-01

    Organic open frameworks with well-defined micropore (pore dimensions below 2 nm) structure are attractive next-generation materials for gas sorption, storage, catalysis and molecular level separations. Polymers of intrinsic microporosity (PIMs) represent a paradigm shift in conceptualizing molecular sieves from conventional ordered frameworks to disordered frameworks with heterogeneous distributions of microporosity. PIMs contain interconnected regions of micropores with high gas permeability but with a level of heterogeneity that compromises their molecular selectivity. Here we report controllable thermal oxidative crosslinking of PIMs by heat treatment in the presence of trace amounts of oxygen. The resulting covalently crosslinked networks are thermally and chemically stable, mechanically flexible and have remarkable selectivity at permeability that is three orders of magnitude higher than commercial polymeric membranes. This study demonstrates that controlled thermochemical reactions can delicately tune the topological structure of channels and pores within microporous polymers and their molecular sieving properties.

  12. Synthesis of an extra-large molecular sieve using proton sponges as organic structure-directing agents

    PubMed Central

    Martínez-Franco, Raquel; Moliner, Manuel; Yun, Yifeng; Sun, Junliang; Wan, Wei; Zou, Xiaodong; Corma, Avelino

    2013-01-01

    The synthesis of crystalline microporous materials containing large pores is in high demand by industry, especially for the use of these materials as catalysts in chemical processes involving bulky molecules. An extra-large–pore silicoaluminophosphate with 16-ring openings, ITQ-51, has been synthesized by the use of bulky aromatic proton sponges as organic structure-directing agents. Proton sponges show exceptional properties for directing extra-large zeolites because of their unusually high basicity combined with their large size and rigidity. This extra-large–pore material is stable after calcination, being one of the very few examples of hydrothermally stable molecular sieves containing extra-large pores. The structure of ITQ-51 was solved from submicrometer-sized crystals using the rotation electron diffraction method. Finally, several hypothetical zeolites related to ITQ-51 have been proposed. PMID:23431186

  13. Reverse osmosis molecular differentiation of organic liquids using carbon molecular sieve membranes.

    PubMed

    Koh, Dong-Yeun; McCool, Benjamin A; Deckman, Harry W; Lively, Ryan P

    2016-08-19

    Liquid-phase separations of similarly sized organic molecules using membranes is a major challenge for energy-intensive industrial separation processes. We created free-standing carbon molecular sieve membranes that translate the advantages of reverse osmosis for aqueous separations to the separation of organic liquids. Polymer precursors were cross-linked with a one-pot technique that protected the porous morphology of the membranes from thermally induced structural rearrangement during carbonization. Permeation studies using benzene derivatives whose kinetic diameters differ by less than an angstrom show kinetically selective organic liquid reverse osmosis. Ratios of single-component fluxes for para- and ortho-xylene exceeding 25 were observed and para- and ortho- liquid mixtures were efficiently separated, with an equimolar feed enriched to 81 mole % para-xylene, without phase change and at ambient temperature. PMID:27540170

  14. Framework redox sites in nanoporous molecular sieve catalyst

    NASA Astrophysics Data System (ADS)

    Nguyen, Khanh Dieu Hong

    The work described in this thesis is concerned with the characterisation of metal ions substituted nanosporous materials. The first chapter deals with the introduction to nanoporous materials, with historical background, structural chemistry, synthetic methods and catalytic applications. The second chapter describes the experiment techniques for synthesis and characterization throughout this work with background of theory, applications, equipment used and useful information achieved from each technique. Chapter 3 deals with the study of cobalt ions substituted microporous aluminophosphate material. Here the main aim is to understand the effect of synthesis condition used in preparing CoAlPO-34, CoSAPO-34 and SAPO-34 materials on the particle size, nano-structure stability and more importantly the oxidation-reduction chemistry of cobalt ions. XRD, SEM, EDX and in situ XRD/EXAFS techniques were used to charactersize the materials in detail. It was found, using microscopy and in situ XRD/EXAFS technique, that when CoAlPO or CoSAPO-34 materials are prepared around pH 7.5, the system has small particles, with good structural stability and complete redox chemistry of cobalt ions. Chapter 4 describes the results obtained from the in situ studies of iron substituted A1PO-5. A1PO-5 samples were synthesized by the hydrothermal reaction of a gel mixture with different templates and different Fe content. These materials were studied using XRD, SEM, EDX and in situ XRD/EXAFS. Here the aim is to investigate the influence of structure directing organic template on the state of iron in the as-synthesised and calcined form. It was found that, depending on the nature of template, the coordination of Fe(III) ions change from octahedral to tetrahedral at different temperature. In situ studies of the reactivity of Ti(IV) species in the titanosilicate TS-1 material was studied using X-ray absorption near edge structure and they are described in the chapter 5. A comparison between the amorphous titanosilicate and crystalline TS-1 was made and it was found that titanium ions in amorphous material reacts much more readily with water molecules compared to crystalline counter part and this correlates with the hydrophobic character of crystalline TS-1 material. In the final chapter, 6, a brief summary and conclusions obtained from the work described in the results chapter as well as future works are given.

  15. Catalytic degradation of Acid Orange 7 by manganese oxide octahedral molecular sieves with peroxymonosulfate under visible light irradiation.

    PubMed

    Duan, Lian; Sun, Binzhe; Wei, Mingyu; Luo, Shilu; Pan, Fei; Xu, Aihua; Li, Xiaoxia

    2015-03-21

    In this paper, the photodegradation of Acid Orange 7 (AO7) in aqueous solutions with peroxymonosulfate (PMS) was studied with manganese oxide octahedral molecular sieves (OMS-2) as the catalyst. The activities of different systems including OMS-2 under visible light irradiation (OMS-2/Vis), OMS-2/PMS and OMS-2/PMS/Vis were evaluated. It was found that the efficiency of OMS-2/PMS was much higher than that of OMS-2/Vis and could be further enhanced by visible light irradiation. The catalyst also exhibited stable performance for multiple runs. Results from ESR and XPS analyses suggested that the highly catalytic activity of the OMS-2/PMS/Vis system possible involved the activation of PMS to sulfate radicals meditated by the redox pair of Mn(IV)/Mn(III) and Mn(III)/Mn(II), while in the OMS-2/PMS system, only the redox reaction between Mn(IV)/Mn(III) occurred. Several operational parameters, such as dye concentration, catalyst load, PMS concentration and solution pH, affected the degradation of AO7. PMID:25528234

  16. 21 CFR 173.40 - Molecular sieve resins.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... purified dextran having an average molecular weight of 40,000, cross-linked with epichlorohydrin in a ratio of 1 part of dextran to 10 parts of epichlorohydrin, to give a stable three dimensional...

  17. Toward Molecular Catalysts by Computer

    SciTech Connect

    Raugei, Simone; DuBois, Daniel L.; Rousseau, Roger J.; Chen, Shentan; Ho, Ming-Hsun; Bullock, R. Morris; Dupuis, Michel

    2015-02-17

    Rational design of molecular catalysts requires a systematic approach to designing ligands with specific functionality and precisely tailored electronic and steric properties. It then becomes possible to devise computer protocols to predict accurately the required properties and ultimately to design catalysts by computer. In this account we first review how thermodynamic properties such as oxidation-reduction potentials (E0), acidities (pKa), and hydride donor abilities (ΔGH-) form the basis for a systematic design of molecular catalysts for reactions that are critical for a secure energy future (hydrogen evolution and oxidation, oxygen and nitrogen reduction, and carbon dioxide reduction). We highlight how density functional theory allows us to determine and predict these properties within “chemical” accuracy (~ 0.06 eV for redox potentials, ~ 1 pKa unit for pKa values, and ~ 1.5 kcal/mol for hydricities). These quantities determine free energy maps and profiles associated with catalytic cycles, i.e. the relative energies of intermediates, and help us distinguish between desirable and high-energy pathways and mechanisms. Good catalysts have flat profiles that avoid high activation barriers due to low and high energy intermediates. We illustrate how the criterion of a flat energy profile lends itself to the prediction of design points by computer for optimum catalysts. This research was carried out in the Center for Molecular Electro-catalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory (PNNL) is operated for the DOE by Battelle.

  18. Synthesis of a specified, silica molecular sieve by using computationally predicted organic structure-directing agents.

    PubMed

    Schmidt, Joel E; Deem, Michael W; Davis, Mark E

    2014-08-01

    Crystalline molecular sieves are used in numerous applications, where the properties exploited for each technology are the direct consequence of structural features. New materials are typically discovered by trial and error, and in many cases, organic structure-directing agents (OSDAs) are used to direct their formation. Here, we report the first successful synthesis of a specified molecular sieve through the use of an OSDA that was predicted from a recently developed computational method that constructs chemically synthesizable OSDAs. Pentamethylimidazolium is computationally predicted to have the largest stabilization energy in the STW framework, and is experimentally shown to strongly direct the synthesis of pure-silica STW. Other OSDAs with lower stabilization energies did not form STW. The general method demonstrated here to create STW may lead to new, simpler OSDAs for existing frameworks and provide a way to predict OSDAs for desired, theoretical frameworks. PMID:24961789

  19. Evaluation of RTV as a Moldable Matrix When Combined With Molecular Sieve and Organic Hydrogen Getter

    SciTech Connect

    Knight, J. A.

    2011-12-01

    This work was undertaken in an effort to develop a combined RTV 615/3Å molecular sieve/DEB molded component. A molded RTV 615/3Å molecular sieve component is currently in production, and an RTV 615/DEB component was produced in the past. However, all three materials have never before been combined in a single production part, and this is an opportunity to create a new component capable of being molded to shape, performing desiccation, and hydrogen gettering. This analysis looked at weapons system parameters and how they might influence part design. It also looked at material processing and how it related to mixing, activating a dessicant, and hydrogen uptake testing.

  20. Synthesis of highly selective zeolite topology molecular sieve for adsorption of benzene gas

    NASA Astrophysics Data System (ADS)

    Wei, Lin; Chen, Yunlin; Zhang, Baoping; Zu, Zhinan

    2013-02-01

    Shangdong fly ash (SFA), Fangshan fly ash (FFA) and Heilongjiang fly ash (HFA) were selected as the raw materials to be used for synthesis of highly selective zeolite topology molecular sieve. Twice foaming method was studied in terms of synthetic zeolite. The experimental products were characterized by means of X-ray fluorescence (XRF), scanning electron microscope (SEM), X-ray diffraction (XRD), and automated surface area & pore size analyser. The results indicated that 10 M NaOH was chosen as modification experiment condition to process SFA. Crystallization temperature and time were 140 °C and 8 h, respectively. Zeolite topology molecular sieve was prepared with Si/Al molar ratio of 7.9, and its adsorption ratio of benzene gas was up to 66.51%.

  1. Activation of methane by transition metal-substituted aluminophosphate molecular sieves

    DOEpatents

    Iton, Lennox E.; Maroni, Victor A.

    1991-01-01

    Aluminophosphate molecular sieves substituted with cobalt, manganese or iron and having the AlPO.sub.4 -34 or AlPO.sub.4 -5, or related AlPO.sub.4 structure activate methane starting at approximately 350.degree. C. Between 400.degree. and 500.degree. C. and at methane pressures .ltoreq.1 atmosphere the rate of methane conversion increases steadily with typical conversion efficiencies at 500.degree. C. approaching 50% and selectivity to the production of C.sub.2+ hydrocarbons approaching 100%. The activation mechanism is based on reduction of the transition metal(III) form of the molecular sieve to the transition metal(II) form with accompanying oxidative dehydrogenation of the methane. Reoxidation of the - transition metal(II) form to the transition metal(III) form can be done either chemically (e.g., using O.sub.2) or electrochemically.

  2. Removal of Nitrogen Oxides in Diesel Engine Exhaust by Plasma Assisted Molecular Sieves

    NASA Astrophysics Data System (ADS)

    Rajanikanth, B. S.; Ravi, V.

    2002-08-01

    This paper reports the studies conducted on removal of oxides of nitrogen (NOx) from diesel engine exhaust using electrical discharge plasma combined with adsorbing materials such as molecular sieves. This study is being reported for the first time. The exhaust is taken from a diesel engine of 6 kW under no load conditions. The characteristic behavior of a pulse energized dielectric barrier discharge reactor in the diesel exhaust treatment is reported. The NOx removal was not significant (36%) when the reactor without any packing was used. However, when the reactor was packed with molecular sieves (MS -3A, -4A & -13X), the NOx removal efficiency was increased to 78% particularly at a temperature of 200 °C. The studies were conducted at different temperatures and the results were discussed.

  3. Design Through Simulation of a Molecular Sieve Column for Treatment of MON-3

    NASA Technical Reports Server (NTRS)

    Swartz, A. Ben; Wilson, D. B.

    1999-01-01

    The presence of water in propellant-grade MON-3 is a concern in the Aerospace Industry. NASA Johnson Space Center (JSC), White Sands Test Facility (WSTF) Propulsion Department has evaluated many types of molecular sieves for control of iron, the corrosion product of water in Mixed Oxides of Nitrogen (MON-3). In 1995, WSTF initiated laboratory and pilot-scale testing of molecular sieve type 3A for removal of water and iron. These tests showed sufficient promise that a series of continuous recycle tests were conducted at WSTF. Periodic samples of the circulating MON-3 solution were analyzed for water (wt %) and iron (ppm, wt). This test column was modeled as a series of transfer units; i. e., each unit represented the height equivalent of a theoretical plate. Such a model assumes there is equilibrium between the adsorbent material and the effluent stream from the unit. Operational and design parameters were derived based on the simulation results. These parameters were used to predict the design characteristics of a proposed molecular sieve column for removal of water and iron from MON-3 at the NASA Kennedy Space Center (KSC). In addition, these parameters were used to simulate a small, single-pass operation column at KSC currently used for treating MON-3. The results of this work indicated that molecular sieve type 3A in 1/16 in. diameter pellets, in a column 2.5 ft. in diameter, 18 ft. in height, and operated at 25 gpm is adequate for the required removal of water and iron from MON-3.

  4. A 1-D Model of the 4 Bed Molecular Sieve of the Carbon Dioxide Removal Assembly

    NASA Technical Reports Server (NTRS)

    Coker, Robert; Knox, Jim

    2015-01-01

    Developments to improve system efficiency and reliability for water and carbon dioxide separation systems on crewed vehicles combine sub-scale systems testing and multi-physics simulations. This paper describes the development of COMSOL simulations in support of the Life Support Systems (LSS) project within NASA's Advanced Exploration Systems (AES) program. Specifically, we model the 4 Bed Molecular Sieve (4BMS) of the Carbon Dioxide Removal Assembly (CDRA) operating on the International Space Station (ISS).

  5. Carbon-fiber composite molecular sieves for gas separation

    SciTech Connect

    Jagtoyen, M.; Derbyshire, F.

    1996-08-01

    This report describes continuing work on the activation and characterization of formed carbon fiber composites. The composites are produced at the Oak Ridge National Laboratory (ORNL) and activated at the Center for Applied Energy Research (CAER) using steam, CO{sub 2}, or O{sub 2} at different conditions of temperature and time, and with different furnace configurations. The general aims of the project are to produce uniformly activated samples with controlled pore structures for specialist applications such as gas separation and water treatment. In previous work the authors reported that composites produced from isotropic pitch fibers weighing up to 25g can be uniformly activated through the appropriate choice of reaction conditions and furnace configurations. They have now succeeded in uniformly activating composites of dimensions up to 12 x 7 x 6 cm, or up to about 166 gram - a scale-up factor of about six. Part of the work has involved the installation of a new furnace that can accommodate larger composites. Efforts were made to achieve uniform activation in both steam and CO{sub 2}. The authors have also succeeded in producing materials with very uniform and narrow pore size distributions by using a novel method involving low temperature oxygen chemisorption in combination with heat treatment in N{sub 2} at high temperatures. Work has also started on the activation of PAN based carbon fibers and fiber composites with the aim of producing composites with wide pore structures for use as catalyst supports. So far activation of the PAN fiber composites supplied by ORNL has been difficult which is attributed to the low reactivity of the PAN fibers. As a result, studies are now being made of the activation of the PAN fibers to investigate the optimum carbonization and activation conditions for PAN based fibers.

  6. A Pervaporation Study of Ammonia Solutions Using Molecular Sieve Silica Membranes

    PubMed Central

    Yang, Xing; Fraser, Thomas; Myat, Darli; Smart, Simon; Zhang, Jianhua; Diniz da Costa, João C.; Liubinas, Audra; Duke, Mikel

    2014-01-01

    An innovative concept is proposed to recover ammonia from industrial wastewater using a molecular sieve silica membrane in pervaporation (PV), benchmarked against vacuum membrane distillation (VMD). Cobalt and iron doped molecular sieve silica-based ceramic membranes were evaluated based on the ammonia concentration factor downstream and long-term performance. A modified low-temperature membrane evaluation system was utilized, featuring the ability to capture and measure ammonia in the permeate. It was found that the silica membrane with confirmed molecular sieving features had higher water selectivity over ammonia. This was due to a size selectivity mechanism that favoured water, but blocked ammonia. However, a cobalt doped silica membrane previously treated with high temperature water solutions demonstrated extraordinary preference towards ammonia by achieving up to a 50,000 mg/L ammonia concentration (a reusable concentration level) measured in the permeate when fed with 800 mg/L of ammonia solution. This exceeded the concentration factor expected by the benchmark VMD process by four-fold, suspected to be due to the competitive adsorption of ammonia over water into the silica structure with pores now large enough to accommodate ammonia. However, this membrane showed a gradual decline in selectivity, suspected to be due to the degradation of the silica material/pore structure after several hours of operation. PMID:24957120

  7. Aminopropyl-modified mesoporous molecular sieves as efficient adsorbents for removal of auxins

    NASA Astrophysics Data System (ADS)

    Moritz, Michał; Geszke-Moritz, Małgorzata

    2015-03-01

    In the present study, mesoporous siliceous materials grafted with 3-aminopropyltriethoxysilane (APTES) were examined as sorbents for removal of chosen plant growth factors (auxins) such as 1-naphthaleneacetic acid (NAA), indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA). Four different types of mesoporous molecular sieves including SBA-15, PHTS, SBA-16 and MCF have been prepared via non-ionic surfactant-assisted soft templating method. Silica molecular sieves were thoroughly characterized by nitrogen adsorption-desorption analysis, powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and Fourier-transform infrared spectroscopy (FT-IR). The maximum adsorption capacity (Qmax) for NAA, IAA and IBA was in the range from 51.0 to 140.8 mg/g and from 4.3 to 7.3 mg/g for aminopropyl-modified adsorbents and pure silicas, respectively. The best adsorption performance was observed for IAA entrapment using both APTES-functionalized SBA-15 and MCF matrices (Qmax of 140.8 and 137.0 mg/g, respectively) which can be ascribed to their larger pore volumes and pore diameters. Moreover, these silicas were characterized by the highest adsorption efficiency exceeding 90% at low pollutant concentration. The experimental points for adsorption of plant growth factors onto aminopropyl-modified mesoporous molecular sieves fitted well to the Langmuir equation.

  8. Advanced Nanostructured Molecular Sieves for Energy Efficient Industrial Separations

    SciTech Connect

    Kunhao Li, Michael Beaver

    2012-01-18

    Due to the very small relative volatility difference between propane and propylene, current propane/propylene separation by distillation requires very tall distillation towers (150-250 theoretical plates) and large reflux ratios (up to 15), which is considered to be the most energy consuming large-scale separation process. Adsorptive separation processes are widely considered to be more energy-efficient alternatives to distillation. However, slow diffusion kinetics/mass transport rate through the adsorbent bed often limits the performance of such processes, so further improvements are possible if intra-particle mass transfer rates can be improved. Rive Technology, Inc. is developing and commercializing its proprietary mesoporous zeolite technology for catalysis and separation. With well-controlled intracrystalline mesoporosity, diffusion kinetics through such mesoporous zeolite based catalysts is much improved relative to conventional zeolites, leading to significantly better product selectivity. This 'proof-of-principle' project (DE-EE0003470) is intended to demonstrate that Rive mesoporous zeolite technology can be extended and applied in adsorptive propane/propylene separation and lead to significant energy saving compared to the current distillation process. In this project, the mesoporous zeolite Y synthesis technology was successfully extended to X and A zeolites that are more relevant to adsorbent applications. Mesoporosity was introduced to zeolite X and A for the first time while maintaining adequate adsorption capacity. Zeolite adsorbents were tested for liquid phase separation performance using a pulse flow test unit and the test results show that the separation selectivity of the mesoporous zeolite adsorbent is much closer to optimal for a Simulated Moving Bed (SMB) separation process and the enhanced mesoporosity lead to >100% increase of overall mass transport rate for propane and propylene. These improvements will significantly improve the

  9. Synthesis of 4 A˚ single-walled carbon nanotubes in catalytic Si-substituted AlPO4-5 molecular sieves

    NASA Astrophysics Data System (ADS)

    Li, Z. M.; Zhai, J. P.; Liu, H. J.; Li, I. L.; Chan, C. T.; Sheng, Ping; Tang, Z. K.

    2004-08-01

    4Å single-walled carbon nanotubes (SWCNs) were fabricated using Si-substituted AlPO4-5 (SAPO-5) molecular sieves as the template. In comparison with neutral AlPO4-5, the SAPO-5 framework plays an important role as a catalyst in pyrolyzing the hydrocarbon molecules, owing to the Bønsted acid sites. The first-principles calculation shows the Si decoration to be very favorable to the formation of carbon nanotubes in the SAPO-5 channels. The resulting SWCNs have better quality than those fabricated without Si doping, evidenced by clearer and stronger radial breathing modes in the Raman spectra.

  10. A novel molecular sieve supporting material for enhancing activity and stability of Ag3PO4 photocatalyst

    NASA Astrophysics Data System (ADS)

    Wu, Qiang; Wang, Peifu; Niu, Futao; Huang, Cunping; Li, Yang; Yao, Weifeng

    2016-08-01

    A small-pore silicon-substituted silicon aluminum phosphate (SAPO-34) molecular sieve, for the first time, is reported to significantly increase both the activity and life span of Ag3PO4 photocatalyst for visible-light degradation of methylene blue (MB) and rhodamine B (RhB). Results show that 60 wt.% Ag3PO4/SAPO-34 exhibits the highest photocatalytic degradation efficiencies for both MB (91.0% degradation within 2.0 min) and RhB (91.0% degradation within 7.0 min). In comparison, pure Ag3PO4 powder photocatalyst requires 8.0 min and 12.0 min for decomposing 91.0% of MB and RhB, respectively. During MB degradation the rate constant for 60 wt.% Ag3PO4/SAPO-34 increases 317.2% in comparison with the rate constant of pure Ag3PO4. This activity is also much higher than literature reported composite or supported Ag3PO4 photocatalysts. In three photocatalytic runs for the degradation of RhB, the rate constant for 60 wt.% Ag3PO4/SAPO-34 reduces from 0.33 to 0.18 min-1 (45.5% efficiency loss). In contrast, the rate constant of pure Ag3PO4 catalyst decreases from 0.2 to 0.07 min-1 (80.0% efficiency loss). All experimental results have shown that small pores and zero light absorption loss of SAPO-34 molecular sieves minimize Ag3PO4 loading, enhance photocatalytic activity and prolong the lifespan of Ag3PO4 photocatalyst.

  11. Investigations to improve carbon dioxide control with amine and molecular sieve type sorbers

    NASA Technical Reports Server (NTRS)

    Bertrand, J. F.; Brose, H. F.; Kester, F. L.; Lunde, P. J.

    1972-01-01

    The optimization trends and operating parameters of an integral molecular sieve bed heat exchanger were investigated. The optimum combination of substrate and coating for the HS-B porous polymer was determined based on the CO2 dynamic capacity in the presence of water vapor. Full size HS-B canister performance was evaluated. An Amine CO2 Concentrator utilizing IR-45 sorber material and available Manned Orbiting Laboratory hardware was designed, fabricated and tested for use as an experiment in the NASA 90-day space simulator test of 1970. It supported four men in the simulator for 71 days out of the 90-day test duration.

  12. Synthesis, characterization, and pulsed laser ablation of molecular sieves for thin film applications

    NASA Astrophysics Data System (ADS)

    Munoz, Trinidad, Jr.

    1998-12-01

    Molecular sieves are one class of crystalline low density metal oxides which are made up of one-, two-, and three dimensional pores and/or cages. We have investigated the synthesis and characterization of metal substituted aluminophosphates and all silica molecular sieves for thin film applications. A new copper substituted aluminophosphate, CuAPO-5 has been synthesized and characterized using x-ray powder diffraction, FT-IR spectroscopy and scanning electron microscopy. Electron spin resonance and electron spin echo modulation provided supporting evidence of framework incorporation of Cu(II) ions. Thus, an exciting addition has been added to the family of metal substituted aluminophosphates where substitution of the metal has been demonstrated as framework species. Also presented here is the synthesis and characterization of an iron substituted aluminophosphate, FeAPO-5, and an all silica zeolite, UTD-1 for thin film applications. Pulsed laser ablation has been employed as the technique to generate thin films. Here an excimer laser (KrFsp*, 248 nm) was used to deposit the molecular sieves on a variety of substrates including polished silicon, titanium nitride, and porous stainless steel disks. The crystallinity of the deposited films was enhanced by a post hydrothermal treatment. A vapor phase treatment of the laser deposited FeAPO-5 films has been shown to increase the crystallinity of the film without increasing film thickness. Thin films of the FeAPO-5 molecular sieves were subsequently used as the dielectric phase in capacitive type chemical sensors. The capacitance change of the FeAPO-5 devices to the relative moisture makes them potential humidity sensors. The all silica zeolite UTD-1 thin films were deposited on polished silicon and porous supports. A brief post hydrothermal treatment of the laser deposited films deposited on polished silicon and porous metal supports resulted in oriented film growth lending these films to applications in gas separations

  13. 13C NMR spectroscopy of methane adsorbed in SAPO-11 molecular sieve

    NASA Astrophysics Data System (ADS)

    Koskela, Tuomas; Ylihautala, Mika; Vaara, Juha; Jokisaari, Jukka

    1996-10-01

    Static 13C and 13C-{ 1H} NMR spectra of carbon-13 enriched methane ( 13CH 4) adsorbed into SAPO-11 molecular sieve were recorded at variable temperatures. Moreover, the corresponding MAS NMR spectra were measured. These experiments reveal a temperature-dependent, anisotropic and asymmetric 13C nuclear shielding tensor. Ab initio model calculations of methane in the field of a positive point charge suggest that the deformation of the shielding tensor may be related to the interaction between the methane molecule and the charge-compensating protons. A comparison with existing Xe data is made.

  14. Redox chemistry of gaseous reactants inside photoexcited FeAlPO{sub 4} molecular sieve

    SciTech Connect

    Ulagappan, N.; Frei, H.

    2000-01-27

    The reactivity of ligand-to-metal charge transfer excited Fe centers of FeAlPO{sub 4}-5 molecular sieve at the gas-micropore interface has been probed by in situ FT-IR spectroscopy. Laser light in the region 350--430 nm was used to excite the metal centers, and reaction was induced between methanol or 2-propanol and O{sub 2}. Acetone and H{sub 2}O are the observed products of the 2-propanol + O{sub 2} system, while the reaction of methanol with O{sub 2} yields formic acid, methyl formate, and H{sub 2}O as final products. These originate from secondary thermal reaction of initially produced formaldehyde and hydrogen peroxide. The primary step of the proposed mechanism involves one-electron reduction of O{sub 2} by transient Fe{sup +II} under concurrent donation of an electron to be hole of framework oxygen by the alcohol molecule. The efficient reaction suggests that the photoreduced Fe center of the molecular sieve has a substantially stronger reducing power than the conduction band electrons of dense-phase Fe{sub 2}O{sub 3} semiconductor particles.

  15. Platinum–nickel frame within metal-organic framework fabricated in situ for hydrogen enrichment and molecular sieving

    PubMed Central

    Li, Zhi; Yu, Rong; Huang, Jinglu; Shi, Yusheng; Zhang, Diyang; Zhong, Xiaoyan; Wang, Dingsheng; Wu, Yuen; Li, Yadong

    2015-01-01

    Developing catalysts that provide the effective activation of hydrogen and selective absorption of substrate on metal surface is crucial to simultaneously improve activity and selectivity of hydrogenation reaction. Here we present an unique in situ etching and coordination synthetic strategy for exploiting a functionalized metal-organic framework to incorporate the bimetallic platinum–nickel frames, thereby forming a frame within frame nanostructure. The as-grown metal-organic framework serves as a ‘breath shell' to enhance hydrogen enrichment and activation on platinum–nickel surface. More importantly, this framework structure with defined pores can provide the selective accessibility of molecules through its one-dimensional channels. In a mixture containing four olefins, the composite can selectively transport the substrates smaller than its pores to the platinum–nickel surface and catalyse their hydrogenation. This molecular sieve effect can be also applied to selectively produce imines, which are important intermediates in the reductive imination of nitroarene, by restraining further hydrogenation via cascade processes. PMID:26391605

  16. Platinum-nickel frame within metal-organic framework fabricated in situ for hydrogen enrichment and molecular sieving

    NASA Astrophysics Data System (ADS)

    Li, Zhi; Yu, Rong; Huang, Jinglu; Shi, Yusheng; Zhang, Diyang; Zhong, Xiaoyan; Wang, Dingsheng; Wu, Yuen; Li, Yadong

    2015-09-01

    Developing catalysts that provide the effective activation of hydrogen and selective absorption of substrate on metal surface is crucial to simultaneously improve activity and selectivity of hydrogenation reaction. Here we present an unique in situ etching and coordination synthetic strategy for exploiting a functionalized metal-organic framework to incorporate the bimetallic platinum-nickel frames, thereby forming a frame within frame nanostructure. The as-grown metal-organic framework serves as a `breath shell' to enhance hydrogen enrichment and activation on platinum-nickel surface. More importantly, this framework structure with defined pores can provide the selective accessibility of molecules through its one-dimensional channels. In a mixture containing four olefins, the composite can selectively transport the substrates smaller than its pores to the platinum-nickel surface and catalyse their hydrogenation. This molecular sieve effect can be also applied to selectively produce imines, which are important intermediates in the reductive imination of nitroarene, by restraining further hydrogenation via cascade processes.

  17. Cryogenic adsorption of low-concentration hydrogen on charcoal, 5A molecular sieve, sodalite, ZSM-5 and Wessalith DAY

    SciTech Connect

    Willms, R.S.

    1993-12-01

    The separation of low-concentration hydrogen isotopes from helium is a processing step that is required for ceramic lithium breeding blanket processing. Cryogenic adsorption is one method of effecting this separation. In this study live adsorbents were considered for this purpose: charcoal, 5A molecular sieve, UOP S-115, ZSM-5 and Wessalith DAY. The first two adsorbents exhibit good equilibrium loadings and are shown to be quite effective at adsorbing low-concentration hydrogen isotopes. The latter three adsorbents display considerably lower equilibrium loadings. This study concludes that by using either charcoal or 5A molecular sieve, cryogenic adsorption would be an effective means of separating hydrogen isotopes from helium.

  18. A portable molecular-sieve-based CO2 sampling system for radiocarbon measurements

    NASA Astrophysics Data System (ADS)

    Palonen, V.

    2015-12-01

    We have developed a field-capable sampling system for the collection of CO2 samples for radiocarbon-concentration measurements. Most target systems in environmental research are limited in volume and CO2 concentration, making conventional flask sampling hard or impossible for radiocarbon studies. The present system captures the CO2 selectively to cartridges containing 13X molecular sieve material. The sampling does not introduce significant under-pressures or significant losses of moisture to the target system, making it suitable for most environmental targets. The system also incorporates a significantly larger sieve container for the removal of CO2 from chambers prior to the CO2 build-up phase and sampling. In addition, both the CO2 and H2O content of the sample gas are measured continuously. This enables in situ estimation of the amount of collected CO2 and the determination of CO2 flux to a chamber. The portable sampling system is described in detail and tests for the reliability of the method are presented.

  19. A portable molecular-sieve-based CO2 sampling system for radiocarbon measurements.

    PubMed

    Palonen, V

    2015-12-01

    We have developed a field-capable sampling system for the collection of CO2 samples for radiocarbon-concentration measurements. Most target systems in environmental research are limited in volume and CO2 concentration, making conventional flask sampling hard or impossible for radiocarbon studies. The present system captures the CO2 selectively to cartridges containing 13X molecular sieve material. The sampling does not introduce significant under-pressures or significant losses of moisture to the target system, making it suitable for most environmental targets. The system also incorporates a significantly larger sieve container for the removal of CO2 from chambers prior to the CO2 build-up phase and sampling. In addition, both the CO2 and H2O content of the sample gas are measured continuously. This enables in situ estimation of the amount of collected CO2 and the determination of CO2 flux to a chamber. The portable sampling system is described in detail and tests for the reliability of the method are presented. PMID:26724067

  20. A portable molecular-sieve-based CO{sub 2} sampling system for radiocarbon measurements

    SciTech Connect

    Palonen, V.

    2015-12-15

    We have developed a field-capable sampling system for the collection of CO{sub 2} samples for radiocarbon-concentration measurements. Most target systems in environmental research are limited in volume and CO{sub 2} concentration, making conventional flask sampling hard or impossible for radiocarbon studies. The present system captures the CO{sub 2} selectively to cartridges containing 13X molecular sieve material. The sampling does not introduce significant under-pressures or significant losses of moisture to the target system, making it suitable for most environmental targets. The system also incorporates a significantly larger sieve container for the removal of CO{sub 2} from chambers prior to the CO{sub 2} build-up phase and sampling. In addition, both the CO{sub 2} and H{sub 2}O content of the sample gas are measured continuously. This enables in situ estimation of the amount of collected CO{sub 2} and the determination of CO{sub 2} flux to a chamber. The portable sampling system is described in detail and tests for the reliability of the method are presented.

  1. Exploring meso-/microporous composite molecular sieves with core-shell structures.

    PubMed

    Qian, Xufang F; Li, Bin; Hu, Yuanyuan Y; Niu, Guoxing X; Zhang, D Yahong H; Che, Renchao C; Tang, Yi; Su, Dangsheng S; Asiri, Abdullah M; Zhao, Dongyuan Y

    2012-01-16

    A series of core-shell-structured composite molecular sieves comprising zeolite single crystals (i.e., ZSM-5) as a core and ordered mesoporous silica as a shell were synthesized by means of a surfactant-directed sol-gel process in basic medium by using cetyltrimethylammonium bromide (CTAB) as a template and tetraethylorthosilicate (TEOS) as silica precursor. Through this coating method, uniform mesoporous silica shells closely grow around the anisotropic zeolite single crystals, the shell thickness of which can easily be tuned in the range of 15-100 nm by changing the ratio of TEOS/zeolite. The obtained composite molecular sieves have compact meso-/micropore junctions that form a hierarchical pore structure from ordered mesopore channels (2.4-3.0 nm in diameter) to zeolite micropores (≈0.51 nm). The short-time kinetic diffusion efficiency of benzene molecules within pristine ZSM-5 (≈7.88×10(-19)  m(2)  s(-1)) is almost retainable after covering with 75 nm-thick mesoporous silica shells (≈7.25×10(-19)  m(2)  s(-1)), which reflects the greatly opened junctions between closely connected mesopores (shell) and micropores (core). The core-shell composite shows greatly enhanced adsorption capacity (≈1.35 mmol  g(-1)) for large molecules such as 1,3,5-triisopropylbenzene relative to that of pristine ZSM-5 (≈0.4 mmol  g(-1)) owing to the mesoporous silica shells. When Al species are introduced during the coating process, the core-shell composite molecular sieves demonstrate a graded acidity distribution from weak acidity of mesopores (predominant Lewis acid sites) to accessible strong acidity of zeolite cores (Lewis and Brønsted acid sites). The probe catalytic cracking reaction of n-dodecane shows the superiority of the unique core-shell structure over pristine ZSM-5. Insight into the core-shell composite structure with hierarchical pore and graded acidity distribution show great potential for petroleum catalytic processes. PMID

  2. Titanium-containing zeolites and microporous molecular sieves as photovoltaic solar cells.

    PubMed

    Atienzar, Pedro; Valencia, Susana; Corma, Avelino; García, Hermenegildo

    2007-05-14

    Four titanium-containing zeolites and microporous molecular sieves differing on the crystal structure and particle size (Ti/Beta, Ti/Beta-60, TS-1 and ETS-10) are prepared, and their activity for solar cells after incorporating N3 (a commercially available ruthenium polypyridyl dye) is tested. All the zeolites exhibit photovoltaic activity, and the photoresponse is quite independent of the zeolite pore dimensions or particle size. The photoresponse increases with titanium content in the range 1-7% wt. In this way, cells are obtained that have open-circuit voltage Voc=560 mV and maximum short-circuit photocurrent density Isc=100 microA, measured for 1x1 cm2 surfaces with a solar simulator at 1000 W through and AM 1.5 filter. These values are promising and comparable to those obtained for current dye-sensitized titania solar cells. PMID:17410619

  3. Inorganic fluoride uptake as a measure of relative compatibility of molecular sieve desiccants with fluorocarbon refrigerants

    SciTech Connect

    Cohen, A.P.; Blackwell, C.S.

    1995-12-31

    The fluoride content of molecular sieve desiccants after exposure to R-32 in compatibility tests indicates the extent of the reaction of refrigerant with desiccant. The objective is to determine this fluoride content in a way that reports fluorine that has reacted with the desiccant, not fluorine that is present as adsorbed refrigerant. A conditioning procedure is described to remove adsorbed refrigerant by displacement with water vapor. The efficacy of this procedure is substantiated by {sup 19}F NMR spectroscopy. The conditioned desiccant undergoes pyrohydrolysis at a high temperature (975 C, 1787 F) to remove reacted fluorine as HF. Fluoride is determined in the resulting condensate using an ion-selective electrode. The ability of this technique to report accurate fluoride values is confirmed with standard reference materials.

  4. Efficient adsorption of phenanthrene by simply synthesized hydrophobic MCM-41 molecular sieves

    NASA Astrophysics Data System (ADS)

    Hu, Yun; He, Yinyun; Wang, Xiaowen; Wei, Chaohai

    2014-08-01

    Hydrophobic molecular sieve MCM-41 including surfactant template was synthesized by a simple method. The adsorption properties of this material toward phenanthrene were studied. The effects of adsorbent dose and pH value on the adsorption process as well as the adsorption mechanism and reuse performance were investigated. The template-containing MCM-41 showed a significant adsorption for phenanthrene, due to its hydrophobicity created by the surfactant template in MCM-41. The solution pH had little effect on the adsorption capacity. The adsorption kinetic could be fitted well with pseudo-second-order kinetic model. The adsorption equilibrium was fitted well by the linear model, and the adsorption process followed the liquid/solid phase distribution mechanism. The thermodynamic results indicated that the adsorption was a spontaneous and exothermic process.

  5. Production of carbon molecular sieves from Illinois coal. Technical report, March 1, 1994--May 31, 1994

    SciTech Connect

    Lizzio, A.A.; Rostam-Abadi, M.; Feizoulof, C.A.; Vyas, S.N.

    1994-09-01

    Carbon molecular sieves (CMS) have become an increasingly important class of adsorbents for use in gas separation and recovery processes. The overall objective of this project is to determine whether Illinois coal is a suitable feedstock for the production of CMS and to evaluate the potential application of the products in commercial gas separation processes. The full potential of these materials in commercial gas separations has yet to be realized. In Phase II, the optimal char preparation conditions determined in Phase I are being applied to production of larger quantities of CMS in a 2 in. ID batch fluidized-bed reactor (FBR) and a 4 in. ID continuous rotary tube kiln (RTK). In the previous reporting period, an invention disclosure describing a novel CMS preparation technique (oxygen deposition) was prepared and submitted to Research Corporation Technologies for evaluation. During this reporting period, work continued on the development of the oxygen deposition process. Carbon deposition as a means to narrow pore size was also investigated. Pound quantities of CMS were prepared from IBC-102 coal in the TRK. A meeting was arranged between the ISGS and Carbo Tech Industieservice GmbH, one of two companies in the world that produce CMS from coal, to discuss possible shipment of Illinois coal to Germany for CMS production. A secrecy agreement between the ISGS and Carbo Tech is in preparation. Several large scale char production runs using Industry Mine coal were conducted in an 18 in. ID batch and 8 in. ID continuous RTK at Allis Mineral Systems, Milwaukee, WI. The molecular sieve properties of the chars have yet to be determined.

  6. The combined use of ultrasound and molecular sieves improves the synthesis of ethyl butyrate catalyzed by immobilized Thermomyces lanuginosus lipase.

    PubMed

    Paludo, Natalia; Alves, Joana S; Altmann, Cintia; Ayub, Marco A Z; Fernandez-Lafuente, Roberto; Rodrigues, Rafael C

    2015-01-01

    In this work, the combined use of ultrasound energy and molecular sieves was investigated for the synthesis of ethyl butyrate, ester with mango and banana notes, catalyzed by the immobilized lipase from Thermomyces lanuginosus (Lipozyme TL-IM). Initially, the best concentrations of biocatalysts (35%) and butyric acid (0.7M) were tested using ultrasound as an alternative to mechanical agitation. The amount of acid in the reaction could be increased by 2-fold when compared to previous works where mechanical agitation was used. In the next step, substrate molar ratio and reaction temperature were optimized and the best conditions were at their lowest levels: 1:1 (acid:alcohol), and 30°C, reaching 61% of conversion in 6h. Molecular sieves (3Å) were added to optimized reaction medium in order to remove the formed water and improve the maximum yield. The reaction yield increased 1.5 times, reaching 90% of conversion in 6h, when 60mg of molecular sieves per mmol of butyric acid was used. Finally, the reuse of Lipozyme TL-IM for the ultrasound-assisted synthesis of ethyl butyrate was verified for 10 batches, without any appreciable loss of activity, whereas in systems using mechanical agitation, the biocatalyst was completely inactivated after 5 batches. These results suggest that the combined use of ultrasound and molecular sieves greatly improve esterification reactions by stabilizing the enzyme and increasing yields. PMID:24844439

  7. Carbon Molecular Sieve Membrane as a True One Box Unit for Large Scale Hydrogen Production

    SciTech Connect

    Liu, Paul

    2012-05-01

    IGCC coal-fired power plants show promise for environmentally-benign power generation. In these plants coal is gasified to syngas then processed in a water gas-shift (WGS) reactor to maximize the hydrogen/CO{sub 2} content. The gas stream can then be separated into a hydrogen rich stream for power generation and/or further purified for sale as a chemical and a CO{sub 2} rich stream for the purpose of carbon capture and storage (CCS). Today, the separation is accomplished using conventional absorption/desorption processes with post CO{sub 2} compression. However, significant process complexity and energy penalties accrue with this approach, accounting for ~20% of the capital cost and ~27% parasitic energy consumption. Ideally, a one-box process is preferred in which the syngas is fed directly to the WGS reactor without gas pre-treatment, converting the CO to hydrogen in the presence of H{sub 2}S and other impurities and delivering a clean hydrogen product for power generation or other uses. The development of such a process is the primary goal of this project. Our proposed "one-box" process includes a catalytic membrane reactor (MR) that makes use of a hydrogen-selective, carbon molecular sieve (CMS) membrane, and a sulfur-tolerant Co/Mo/Al{sub 2}O{sub 3} catalyst. The membrane reactor's behavior has been investigated with a bench top unit for different experimental conditions and compared with the modeling results. The model is used to further investigate the design features of the proposed process. CO conversion >99% and hydrogen recovery >90% are feasible under the operating pressures available from IGCC. More importantly, the CMS membrane has demonstrated excellent selectivity for hydrogen over H{sub 2}S (>100), and shown no flux loss in the presence of a synthetic "tar"-like material, i.e., naphthalene. In summary, the proposed "one-box" process has been successfully demonstrated with the bench-top reactor. In parallel we have successfully designed and

  8. Low temperature VOC combustion over manganese, cobalt and zinc AlPO{sub 4} molecular sieves. Semi-annual report-1, September 1, 1995--February 29, 1996

    SciTech Connect

    Szostak, R.

    1997-06-01

    The objective of this project is to prepare manganese, cobalt and zinc containing AlPO{sub 4} large pore molecular sieves of structure type -36 and evaluate their ability to function as successful oxidation catalysts for the removal of low levels of VOC`s from gas streams. The tasks to be accomplished are as follows: (1) To develop reliable synthesis methods that produce the large pore metal aluminophosphates containing manganese, cobalt and zinc in their framework. (2) To characterize these materials to determine phase purity and the location of the incorporated metal in the framework. Characterization will also include the nature of the active sites within the structures and the effect manganese, cobalt and zinc has on the structures` acidity. (3) To screen the material for their catalytic activity in the oxidation of hydrocarbons and aromatics. This report gives a summary of the status of the project as of 28th February 1996.

  9. Nanoscopic imaging of meso-tetraalkylporphyrins prepared in high yields enabled by Montmorrilonite K10 and 3A molecular sieves.

    PubMed

    Plamont, Rémi; Kikkawa, Yoshihiro; Takahashi, Mayuko; Kanesato, Masatoshi; Giorgi, Michel; Chan Kam Shun, Anita; Roussel, Christian; Balaban, Teodor Silviu

    2013-08-19

    We have developed a high-yielding synthesis of meso-tetraalkylporphyrins, which previously have been obtained only in lower yields. By employing Montmorrilonite K10 as the acid catalyst and 3 Å molecular sieves as the dehydrating agent, yields that reached 70 % could be achieved with some aliphatic aldehydes. The free-base porphyrins with decyl (C10) or longer chains were imaged at the single-molecule level at the solvent/surface interface. Highly oriented pyrolytic graphite (HOPG) was used as a π-stacking surface, whereas 1-phenyloctane and 1-phenylnonane were used as solvents. An odd-even effect was observed from C13 to C16. For C13 a single-crystal X-ray structure allowed an unprecedented insight into how packing from two dimensions is expanded into a three-dimensional crystal lattice. PMID:23839774

  10. The effects of zeolite molecular sieve based surface treatments on the properties of wool fabrics

    NASA Astrophysics Data System (ADS)

    Carran, Richard S.; Ghosh, Arun; Dyer, Jolon M.

    2013-12-01

    Wool is a natural composite fiber, with keratin and keratin-associated proteins as the key molecular components. The outermost surface of wool fibers comprises a hydrophobic lipid layer that can lead to unsatisfactory processing and properties of fabric products. In this study, molecular sieve 5A, a Na+ and Ca2+ exchanged type A zeolite with a 1:1 Si:Al ratio was integrated onto the surface of wool using 3-mercaptopropyl trimethoxy silane. The resultant surface morphology, hydrophilicity and mechanical performance of the treated wool fabrics were then evaluated. Notably, the surface hydrophilicity of wool was observed to increase dramatically. When wool was treated with a dispersion of 2 wt% acetic acid, 2.5 wt% zeolite and 0.3 wt% or more silane, the water contact angle was observed to decrease from an average value of 148° to 0° over a period of approximately 30 s. Scanning electron microscopic imaging indicated good coverage of the wool surface with zeolite particles, with infrared spectroscopic evaluation indicating strong bonding of the dealuminated zeolite to wool keratins. This application of zeolite showed no adverse effects on the tensile and other mechanical properties of the fabric. This study indicates that zeolite-based treatment is a potentially efficient approach to increasing the surface hydrophilicity and modifying other key surface properties of wool and wool fabrics.

  11. A titanosilicate molecular sieve with adjustable pores for size-selective adsorption of molecules.

    PubMed

    Kuznicki, S M; Bell, V A; Nair, S; Hillhouse, H W; Jacubinas, R M; Braunbarth, C M; Toby, B H; Tsapatsis, M

    2001-08-16

    Zeolites and related crystalline microporous oxides-tetrahedrally coordinated atoms covalently linked into a porous framework-are of interest for applications ranging from catalysis to adsorption and ion-exchange. In some of these materials (such as zeolite rho) adsorbates, ion-exchange, and dehydration and cation relocation can induce strong framework deformations. Similar framework flexibility has to date not been seen in mixed octahedral/tetrahedral microporous framework materials, a newer and rapidly expanding class of molecular sieves. Here we show that the framework of the titanium silicate ETS-4, the first member of this class of materials, can be systematically contracted through dehydration at elevated temperatures to 'tune' the effective size of the pores giving access to the interior of the crystal. We show that this so-called 'molecular gate' effect can be used to tailor the adsorption properties of the materials to give size-selective adsorbents suitable for commercially important separations of gas mixtures of molecules with similar size in the 4.0 to 3.0 A range, such as that of N2/CH4, Ar/O2 and N2/O2. PMID:11507636

  12. Continuously Adjustable, Molecular-Sieving “Gate” on 5A Zeolite for Distinguishing Small Organic Molecules by Size

    PubMed Central

    Song, Zhuonan; Huang, Yi; Xu, Weiwei L.; Wang, Lei; Bao, Yu; Li, Shiguang; Yu, Miao

    2015-01-01

    Zeolites/molecular sieves with uniform, molecular-sized pores are important for many adsorption-based separation processes. Pore size gaps, however, exist in the current zeolite family. This leads to a great challenge of separating molecules with size differences at ~0.01 nm level. Here, we report a novel concept, pore misalignment, to form a continuously adjustable, molecular-sieving “gate” at the 5A zeolite pore entrance without sacrificing the internal capacity. Misalignment of the micropores of the alumina coating with the 5A zeolite pores was related with and facilely adjusted by the coating thickness. For the first time, organic molecules with sub-0.01 nm size differences were effectively distinguished via appropriate misalignment. This novel concept may have great potential to fill the pore size gaps of the zeolite family and realize size-selective adsorption separation. PMID:26358480

  13. Degradation of antibiotic amoxicillin using 1 x 1 molecular sieve-structured manganese oxide.

    PubMed

    Kuan, Wen-Hui; Hu, Ching-Yao; Liu, Bin-Sheng; Tzou, Yu-Min

    2013-01-01

    The kinetics and mechanism ofamoxicillin (AMO) degradation using a 1 x 1 molecular sieve-structured manganese oxide (MnO2) was studied. The presence of the buffer solution (i.e., NaHCO3, NaH2PO4 and KH2PO4) diminished AMO binding to MnO2, thus reducing AMO degradation in the pretest; therefore, all other experiments in this study were conducted without the addition of a buffer. Third-order rate constants, second-order on AMO and first-order on MnO2 increased with elevating pH level (2.81-7.23) from 0.54 to 9.17 M(-2) s(-1), and it decreased to 4.27 M(-2) s(-1) at pH 8.53 beyond the pk(a2) of AMO (7.3). The dissolution of the MnO2 suspension with and without AMO exhibited a similar trend; that is, Mn2+ concentration increased with decreasing pH. However, the dissolution of MnO2 with AMO was greater than that without AMO, except for the reaction occurring at pH 8.53, partially indicating that MnO2 acts as an oxidant in AMO degradation. The preliminary chromatogram data display different products with varying pH reaction s, implying that AMO elimination using this 1 x 1 molecular sieve-structured MnO2 is by adsorption as well as oxidative degradation. A complementary experiment indicates that the amount of oxidatively degraded AMO increases substantially from 65.5% at 4 h to 95% at 48 h, whereas the AMO adsorbed onto MnO2 decreases slightly from 4.5% at4 h to 2.4% at 48 h. The oxidative degradation accounted for more AMO removal than adsorption over the whole reaction course, indicating that the oxidative reaction of AMO on MnO2 dominated the AMO removal. PMID:24350501

  14. Mixed Matrix Carbon Molecular Sieve and Alumina (CMS-Al2O3) Membranes

    PubMed Central

    Song, Yingjun; Wang, David K.; Birkett, Greg; Martens, Wayde; Duke, Mikel C.; Smart, Simon; Diniz da Costa, João C.

    2016-01-01

    This work shows mixed matrix inorganic membranes prepared by the vacuum-assisted impregnation method, where phenolic resin precursors filled the pore of α-alumina substrates. Upon carbonisation, the phenolic resin decomposed into several fragments derived from the backbone of the resin matrix. The final stages of decomposition (>650 °C) led to a formation of carbon molecular sieve (CMS) structures, reaching the lowest average pore sizes of ~5 Å at carbonisation temperatures of 700 °C. The combination of vacuum-assisted impregnation and carbonisation led to the formation of mixed matrix of CMS and α-alumina particles (CMS-Al2O3) in a single membrane. These membranes were tested for pervaporative desalination and gave very high water fluxes of up to 25 kg m−2 h−1 for seawater (NaCl 3.5 wt%) at 75 °C. Salt rejection was also very high varying between 93–99% depending on temperature and feed salt concentration. Interestingly, the water fluxes remained almost constant and were not affected as feed salt concentration increased from 0.3, 1 and 3.5 wt%. PMID:27469389

  15. CIT-7, a crystalline, molecular sieve with pores bounded by 8 and 10-membered rings

    SciTech Connect

    Schmidt, Joel E.; Xie, Dan; Rea, Thomas; Davis, Mark E.

    2015-01-23

    A new crystalline molecular sieve, denoted CIT-7, is synthesized using an imidazolium-based diquaternary organic structure directing agent (OSDA). The framework structure is determined from a combination of rotation electron diffraction and synchrotron X-ray powder diffraction data. The structure has 10 crystallographically unique tetrahedral atoms (T-atoms) in the unit cell, and can be described as an ordered arrangement of the [425462] mtw building unit and a previously unreported [4452] building unit. The framework contains a 2-dimensional pore system that is bounded by 10 T-atom rings (10-ring, 5.1 Å × 6.2 Å opening) that are connected with oval 8-rings (2.9 Å × 5.5 Å opening) through medium-sized cavities (~7.9 Å) at the channel intersections. CIT-7 can be synthesized over a broad range of compositions including pure-silica and heteroatom, e.g., aluminosilicate and titanosilicate, containing variants.

  16. Tunable ionic-conductivity of collapsed Sandia octahedral molecular sieves (SOMS).

    SciTech Connect

    Pless, Jason; Nenoff, Tina Maria; Garino, Terry J.; Axness, Marlene

    2006-11-01

    This proposal focuses on the synthesis and characterization of ''tunable'' perovskite ceramics with resulting controlled strength and temperature of dielectric constants and/or with ionic conductivity. Traditional methods of synthesis involve high temperature oxide mixing and baking. We developed a new methodology of synthesis involving the (1) low temperature hydrothermal synthesis of metastable porous phases with ''tuned'' stoichiometry, and element types, and then (2) low temperature heat treatment to build exact stoichiometry perovskites, with the desired vacancy concentrations. This flexible pathway can lead to compositions and structures not attainable by conventional methods. During the course of this program, a series of Na-Nb perovskites were synthesized by calcining and collapsing microporous Sandia Octahedral Molecular Sieve (SOMS) phases. These materials were studied by various characterization techniques and conductivity measurements to better delineate stability and stoichiometry/bulk conductivity relationships. The conductivity can be altered by changing the concentration and type of the substituting framework cation(s) or by ion exchange of sodium. To date, the Na{sub 0.9}Mg{sub 0.1}Nb{sub 0.8}Ti{sub 0.2}O{sub 3-{delta}} shows the best conductivity.

  17. CIT-7, a crystalline, molecular sieve with pores bounded by 8 and 10-membered rings

    DOE PAGESBeta

    Schmidt, Joel E.; Xie, Dan; Rea, Thomas; Davis, Mark E.

    2015-01-23

    A new crystalline molecular sieve, denoted CIT-7, is synthesized using an imidazolium-based diquaternary organic structure directing agent (OSDA). The framework structure is determined from a combination of rotation electron diffraction and synchrotron X-ray powder diffraction data. The structure has 10 crystallographically unique tetrahedral atoms (T-atoms) in the unit cell, and can be described as an ordered arrangement of the [425462] mtw building unit and a previously unreported [4452] building unit. The framework contains a 2-dimensional pore system that is bounded by 10 T-atom rings (10-ring, 5.1 Å × 6.2 Å opening) that are connected with oval 8-rings (2.9 Å ×more » 5.5 Å opening) through medium-sized cavities (~7.9 Å) at the channel intersections. CIT-7 can be synthesized over a broad range of compositions including pure-silica and heteroatom, e.g., aluminosilicate and titanosilicate, containing variants.« less

  18. Passive CO{sub 2} removal using a carbon fiber composite molecular sieve

    SciTech Connect

    Burchell, T.D.; Judkins, R.R.

    1995-12-01

    Manufacture and characterization of a carbon fiber composite molecular sieve (CFCMS), and its efficacy as a CO{sub 2} gas adsorbent are reported. The CFCMS consists of an isotropic pitch derived carbon fiber and a phenolic resin derived carbon binder. Activation (selective gasification) of the CFCMS creates microporosity in the carbon fibers, yielding high micropore volumes (>0.5 cm{sup 3}/g) and BET surface areas (>1000 m{sup 2}/g). Moreover, the CFCMS material is a rigid, strong, monolith with an open structure that allows the free-flow of fluids through the material. This combination of properties provides an adsorbent material that has several distinct advantages over granular adsorbents in gas separation systems such as pressure swing adsorption (PSA) units. The results of our initial evaluations of the CO{sub 2} adsorption capacity and kinetics of CFCMS are reported. The room temperature CO{sub 2} adsorption capacity of CFCMS is >120 mg of CO{sub 2} per g of CFCMS. A proposed project is described that targets the development, over a three-year period, of a demonstration separation system based on CFCMS for the removal of CO{sub 2} from a flue gas slip stream at a coal-fired power plant. The proposed program would be conducted jointly with industrial and utility partners.

  19. Covalent anchoring of chloroperoxidase and glucose oxidase on the mesoporous molecular sieve SBA-15.

    PubMed

    Jung, Dirk; Streb, Carsten; Hartmann, Martin

    2010-01-01

    Functionalization of porous solids plays an important role in many areas, including heterogeneous catalysis and enzyme immobilization. In this study, large-pore ordered mesoporous SBA-15 molecular sieves were synthesized with tetraethyl orthosilicate (TEOS) in the presence of the non-ionic triblock co-polymer Pluronic P123 under acidic conditions. These materials were grafted with 3-aminopropyltrimethoxysilane (ATS), 3-glycidoxypropyltrimethoxysilane (GTS) and with 3-aminopropyltrimethoxysilane and glutaraldehyde (GA-ATS) in order to provide covalent anchoring points for enzymes. The samples were characterized by nitrogen adsorption, powder X-ray diffraction, solid-state NMR spectroscopy, elemental analysis, diffuse reflectance fourier transform infrared spectroscopy and diffuse reflectance UV/Vis spectroscopy. The obtained grafted materials were then used for the immobilization of chloroperoxidase (CPO) and glucose oxidase (GOx) and the resulting biocatalysts were tested in the oxidation of indole. It is found that enzymes anchored to the mesoporous host by the organic moieties can be stored for weeks without losing their activity. Furthermore, the covalently linked enzymes are shown to be less prone to leaching than the physically adsorbed enzymes, as tested in a fixed-bed reactor under continuous operation conditions. PMID:20386667

  20. Adsorbate shape selectivity: Separation of the HF/134a azeotrope over carbogenic molecular sieve

    SciTech Connect

    Hong, A.; Mariwala, R.K.; Kane, M.S.; Foley, H.C.

    1995-03-01

    Experimental evidence is provided for adsorptive shape selectivity in the separation of the azeotrope between HF and 1,1,1,2-tetrafluoroethane (134a) over pyrolyzed poly(furfuryl alcohol)-derived carbogenic molecular sieve (PPFA-CMS). The separation can be accomplished over coconut charcoal or Carbosieve G on the basis of the differences in the extent of equilibrium adsorption of HF and 134a. On these adsorbents 134a is more strongly bound than HF, thus it elutes much more slowly from the bed. The heat of adsorption for 134a in the vicinity of 200 C on Carbosieve G is {approximately}8.8 kcal/mol. In contrast, when the same azeotropic mixture is separated over PPFA-CMS prepared at 500 C, 134a is not adsorbed. As a result 134a elutes from the bed first, followed by HF. The reversal is brought about by the narrower pore size and pore size distribution of the PPFA-CMS versus that for Carbosieve G. Thus the separation over PPFA-CMS is an example of adsorbate shape selectivity and represents a limiting case of kinetic separation.

  1. Mixed Matrix Carbon Molecular Sieve and Alumina (CMS-Al2O3) Membranes.

    PubMed

    Song, Yingjun; Wang, David K; Birkett, Greg; Martens, Wayde; Duke, Mikel C; Smart, Simon; Diniz da Costa, João C

    2016-01-01

    This work shows mixed matrix inorganic membranes prepared by the vacuum-assisted impregnation method, where phenolic resin precursors filled the pore of α-alumina substrates. Upon carbonisation, the phenolic resin decomposed into several fragments derived from the backbone of the resin matrix. The final stages of decomposition (>650 °C) led to a formation of carbon molecular sieve (CMS) structures, reaching the lowest average pore sizes of ~5 Å at carbonisation temperatures of 700 °C. The combination of vacuum-assisted impregnation and carbonisation led to the formation of mixed matrix of CMS and α-alumina particles (CMS-Al2O3) in a single membrane. These membranes were tested for pervaporative desalination and gave very high water fluxes of up to 25 kg m(-2) h(-1) for seawater (NaCl 3.5 wt%) at 75 °C. Salt rejection was also very high varying between 93-99% depending on temperature and feed salt concentration. Interestingly, the water fluxes remained almost constant and were not affected as feed salt concentration increased from 0.3, 1 and 3.5 wt%. PMID:27469389

  2. Carbon molecular sieve membranes on porous composite tubular supports for high performance gas separations

    DOE PAGESBeta

    Lee, Pyung -Soo; Bhave, Ramesh R.; Nam, Seung -Eun; Kim, Daejin

    2016-01-11

    Thin carbon molecular sieve membranes (<500 nm) were fabricated inside of long geometry (9 inch) of stainless steel tubes with all welded construction. Alumina intermediate layer on porous stainless steel tube support was used to reduce effective support pore size and to provide a more uniform surface roughness. Novolac phenolic resin solution was then coated on the inside of porous stainless steel tube by slip casting while their viscosities were controlled from 5 centipoises to 30 centipoises. Carbonization was carried out at 700 °C in which thermal stress was minimized and high quality carbon films were prepared. The highest separationmore » performance characteristics were obtained using 20 cP phenolic resin solutions. The fabricated CMSM showed good separation factor for He/N2 462, CO2/N2 97, and O2/N2 15.4. As the viscosity of polymer precursor solution was reduced from 20 cP to 15 cP, gas permeance values almost doubled with somewhat lower separation factor He/N2 156, CO2/N2 88, and O2/N2 7.7.« less

  3. Studies of oxygen species in synthetic Todorokite-like manganese oxide octahedral molecular sieves

    SciTech Connect

    Yin, Yuan-Gen; Xu, Wen-Qing; Shen, Yan-Fei; Suib, S.L. ); O'Young, C.L. )

    1994-10-01

    Manganese oxide octahedral molecular sieves of 3 x 3 tunnel structure (OMS-1) doped with various cations possess high thermal stability and were studied by means of temperature-programmed desorption and reduction by H[sub 2] and CO. Different oxygen species can be discerned according to their peak positions in the temperature-programmed desorption and reduction and assigned to chemisorbed dioxygen, oxygen atoms bound to Mn[sup 2+], and those bound to Mn[sup 4+] ions in the framework. Differences in peak positions and availabilities of these species during TPD and TPR can be explained by creation of nascent Mn[sup 2+] ions during TPR. The effects of doping cations on the reactivity and availability of these oxygen species are demonstrated to be more pronounced in TPR in H[sub 2] or CO than in TPD. In some instances, the trends of changes in reactivity and availability of the oxygen species due to doping of Cu[sup 2+], Ni[sup 2+], Zn[sup 2+], and Mg[sup 2+] correlated with the changes in the heat of formation of oxides of these cations. Temperature-programmed reactions with methane show some reactivity of these doped OMS-1 materials. Pulse reactions with CO show higher reactivity of Cu-doped OM-1 than with butane. However, the recovery of Cu-doped OMS-1 by reoxidation with oxygen pulses seems rather incomplete at the same temperature. 27 refs., 9 figs.

  4. Mixed Matrix Carbon Molecular Sieve and Alumina (CMS-Al2O3) Membranes

    NASA Astrophysics Data System (ADS)

    Song, Yingjun; Wang, David K.; Birkett, Greg; Martens, Wayde; Duke, Mikel C.; Smart, Simon; Diniz da Costa, João C.

    2016-07-01

    This work shows mixed matrix inorganic membranes prepared by the vacuum-assisted impregnation method, where phenolic resin precursors filled the pore of α-alumina substrates. Upon carbonisation, the phenolic resin decomposed into several fragments derived from the backbone of the resin matrix. The final stages of decomposition (>650 °C) led to a formation of carbon molecular sieve (CMS) structures, reaching the lowest average pore sizes of ~5 Å at carbonisation temperatures of 700 °C. The combination of vacuum-assisted impregnation and carbonisation led to the formation of mixed matrix of CMS and α-alumina particles (CMS-Al2O3) in a single membrane. These membranes were tested for pervaporative desalination and gave very high water fluxes of up to 25 kg m‑2 h‑1 for seawater (NaCl 3.5 wt%) at 75 °C. Salt rejection was also very high varying between 93–99% depending on temperature and feed salt concentration. Interestingly, the water fluxes remained almost constant and were not affected as feed salt concentration increased from 0.3, 1 and 3.5 wt%.

  5. The parasitophorous vacuole membrane surrounding intracellular Toxoplasma gondii functions as a molecular sieve.

    PubMed

    Schwab, J C; Beckers, C J; Joiner, K A

    1994-01-18

    The obligate intracellular protozoan parasite Toxoplasma gondii creates and enters into a unique membrane-bounded cytoplasmic compartment, the parasitophorous vacuole, when invading mammalian host cells. By microinjecting polar fluorescent molecules into individual T. gondii-infected fibroblasts, we show here that the parasitophorous vacuole membrane (PVM) surrounding the parasite functions as a molecular sieve. Lucifer yellow (457 Da) displayed free bidirectional flux across the PVM and distinctly outlined the parasites, which did not take up the dye, within the vacuole. This dye movement was not appreciably delayed by pretreatment of cells with 5 mM probenecid or chilling the monolayer to 5 degrees C, suggesting that dye movement was due to passive permeation through a membrane pore rather than active transport. Calcein, fluo-3, and a series of fluorescein isothiocyanate-labeled peptides up to 1291 Da crossed the PVM in a size-restricted fashion. A labeled peptide of 1926 Da and labeled dextrans and proteins (> or = 3000 Da) failed to transit the PVM. This putative channel in the PVM therefore allows exchange of molecules up to 1300-1900 Da between the host cell cytoplasm and the parasitophorous vacuolar space. PMID:8290555

  6. Identification of tetrahedrally ordered Si-O-Al environments in molecular sieves by { 27Al}- 29Si REAPDOR NMR

    NASA Astrophysics Data System (ADS)

    Ganapathy, S.; Kumar, Rajiv; Montouillout, V.; Fernandez, C.; Amoureux, J. P.

    2004-05-01

    The silicon sites tetrahedrally connected to aluminum in framework positions of a molecular sieve may be identified by a selective reintroduction of the hetero-nuclear 27Al- 29Si dipolar interaction through Rotational Echo Adiabatic Passage DOuble Resonance (REAPDOR) NMR. In this rotor synchronized 29Si MAS experiment, an effective dipolar dephasing of the Si-O-Al, over Si-O-Si, environments is shown to aid in the identification of silicon sites in the immediate vicinity of aluminum. Application of the method in the structurally interesting and novel molecular sieve ETAS-10 provides valuable insights on the details of aluminum substitution in the zeolite lattice and further leads to the first direct NMR estimate of Al-Si distance ( rAl-Si=323±5 pm) in ETAS-10.

  7. Zeolitic Imidazolate Framework/Graphene Oxide Hybrid Nanosheets as Seeds for the Growth of Ultrathin Molecular Sieving Membranes.

    PubMed

    Hu, Yaoxin; Wei, Jing; Liang, Yan; Zhang, Huacheng; Zhang, Xiwang; Shen, Wei; Wang, Huanting

    2016-02-01

    A defect-free zeolitic imidazolate framework-8 (ZIF-8)/graphene oxide (GO) membrane with a thickness of 100 nm was prepared using two-dimensional (2D) ZIF-8/GO hybrid nanosheets as seeds. Hybrid nanosheets with a suitable amount of ZIF-8 nanocrystals were essential for producing a uniform seeding layer that facilitates fast crystal intergrowth during membrane formation. Moreover, the seeding layer acts as a barrier between two different synthesis solutions, and self-limits crystal growth and effectively eliminates defects during the contra-diffusion process. The resulting ultrathin membranes show excellent molecular sieving gas separation properties, such as with a high CO2 /N2 selectivity of 7.0. This 2D nano-hybrid seeding strategy can be readily extended to the fabrication of other defect-free and ultrathin MOF or zeolite molecular sieving membranes for a wide range of separation applications. PMID:26710246

  8. The reversible transition of the molecular sieve VPI-5 into ALPO -84 and the structure of ALPO -84

    NASA Astrophysics Data System (ADS)

    Vogt, Eelco T. C.; Richardson, James W.

    1990-08-01

    In this letter we describe the reversibility of the recrystallization of the aluminophosphate molecular sieve VPI-5 to ALPO -84, and the structure of ALPO -84. VPI-5 is known to contain one-dimensional circular pores circumscribed by 18 tetrahedral atoms. Upon heating in the presence of moisture it is known to recrystallize to ALPO -84. This transition now proves to be reversible. Although phase transitions of aluminophosphate molecular sieves have been described, this is the first report of such a transition being reversible. ALPO -84 is found to contain one-dimensional elliptical pores, with free diameters of 7.5 to 9.5 Å circumscribed by 14 tetrahedral atoms. This new pore system thus contains one of the largest openings described so far, second only to VPI-5.

  9. Defect-Controlled Preparation of UiO-66 Metal-Organic Framework Thin Films with Molecular Sieving Capability.

    PubMed

    Zhang, Caiqin; Zhao, Yajing; Li, Yali; Zhang, Xuetong; Chi, Lifeng; Lu, Guang

    2016-01-01

    Metal-organic framework (MOF) UiO-66 thin films are solvothermally grown on conducting substrates. The as-synthesized MOF thin films are subsequently dried by a supercritical process or treated with polydimethylsiloxane (PDMS). The obtained UiO-66 thin films show excellent molecular sieving capability as confirmed by the electrochemical studies for redox-active species with different sizes. PMID:26548455

  10. Biomass-based palm shell activated carbon and palm shell carbon molecular sieve as gas separation adsorbents.

    PubMed

    Sethupathi, Sumathi; Bashir, Mohammed Jk; Akbar, Zinatizadeh Ali; Mohamed, Abdul Rahman

    2015-04-01

    Lignocellulosic biomass has been widely recognised as a potential low-cost source for the production of high added value materials and proved to be a good precursor for the production of activated carbons. One of such valuable biomasses used for the production of activated carbons is palm shell. Palm shell (endocarp) is an abundant by-product produced from the palm oil industries throughout tropical countries. Palm shell activated carbon and palm shell carbon molecular sieve has been widely applied in various environmental pollution control technologies, mainly owing to its high adsorption performance, well-developed porosity and low cost, leading to potential applications in gas-phase separation using adsorption processes. This mini-review represents a comprehensive overview of the palm shell activated carbon and palm shell carbon molecular sieve preparation method, physicochemical properties and feasibility of palm shell activated carbon and palm shell carbon molecular sieve in gas separation processes. Some of the limitations are outlined and suggestions for future improvements are pointed out. PMID:25804669

  11. Infrared study of CO{sub 2} sorption over 'molecular basket' sorbent consisting of polyethylenimine-modified mesoporous molecular sieve

    SciTech Connect

    Wang, X.X.; Schwartz, V.; Clark, J.C.; Ma, X.L.; Overbury, S.H.; Xu, X.C.; Song, C.S.

    2009-04-15

    An infrared study has been conducted on CO{sub 2} sorption into nanoporous CO{sub 2} 'molecular basket' sorbents prepared by loading polyethylenimine (PEI) into mesoporous molecular sieve SBA-15. IR results from DRIFTS showed that a part of loaded PEI is anchored on the surface of SBA-15 through the interaction between amine groups and isolated surface silanol groups. Raising the temperature from 25 to 75{sup o}C increased the molecular flexibility of PEI loaded in the mesopore channels, which may partly contribute to the increase of CO{sub 2} sorption capacity at higher temperatures. CO{sub 2} sorption/desorption behavior studied by in situ transmission FTIR showed that CO{sub 2} is sorbed on amine sites through the formation of alkylammonium carbamates and absorbed into the multiple layers of PEI located in mesopores of SBA-15. A new observation by in situ IR is that two broad IR bands emerged at 2450 and 2160 cm{sup -1} with CO{sub 2} flowing over PEI(50)/SBA-15, which could be attributed to chemically sorbed CO{sub 2} species on PEI molecules inside the mesopores of SBA-15. The intensities of these two bands also increased with increasing CO{sub 2} exposure time and with raising CO{sub 2} sorption temperature. By comparison of the CO{sub 2} sorption rate at 25 and 75{sup o}C in terms of differential IR intensities, it was found that CO{sub 2} sorption over molecular basket sorbent includes two rate regimes which suggest two distinct steps: rapid sorption on exposed outer surface layers of PEI (controlled by sorption affinity or thermodynamics) and the diffusion and sorption inside the bulk of multiple layers of PEI (controlled by diffusion). The sorption of CO{sub 2} is reversible at 75{sup o}C.

  12. Phase behavior and molecular mobility of n -octylcyanobiphenyl confined to molecular sieves: Dependence on the pore size

    NASA Astrophysics Data System (ADS)

    Frunza, Ligia; Frunza, Stefan; Kosslick, Hendrik; Schönhals, Andreas

    2008-11-01

    The molecular dynamics of 4- n -octyl- 4' -cyanobiphenyl (8CB) confined inside the pores of a series of AlMCM-41 samples with the same structure, constant composition (Si/Al=14.7) but different pore sizes (diameter between 2.3 and 4.6nm ) was investigated by broadband dielectric spectroscopy (10-2-109Hz) in a large temperature interval. Two relaxation processes are observed: one has a bulklike behavior and is assigned to the 8CB in the pore center. The relaxation time of the second relaxation process is essentially slower than that of the former one and this process is related to the dynamics of molecules in a surface layer with a paranematic order. Both relaxation processes are specifically influenced by the interaction of the molecules with the surface and by the confinement. Above the clearing temperature the temperature dependence of the relaxation rate of the bulklike process obeys the Vogel-Fulcher-Tammann (VFT) law. The Vogel temperature increases with decreasing pore size. This is explained by increasing influence of paranematic potential of the surface layer with decreasing pore size. The temperature dependence of the relaxation rate of the surface layer follows also the VFT formula and the Vogel temperature decreases with decreasing pore size. This temperature dependence is controlled by both the interaction of the 8CB molecules with the surface via hydrogen bonding and by spatial confinement effects. To discriminate between both effects the data for the surface layer of 8CB confined to the molecular sieves are compared with results concerning 8CB adsorbed as a quasimonolayer on the surface of silica spheres of aerosil. On this basis a confinement parameter is defined and discussed.

  13. Phase behavior and molecular mobility of n-octylcyanobiphenyl confined to molecular sieves: dependence on the pore size.

    PubMed

    Frunza, Ligia; Frunza, Stefan; Kosslick, Hendrik; Schönhals, Andreas

    2008-11-01

    The molecular dynamics of 4-n-octyl-4'-cyanobiphenyl (8CB) confined inside the pores of a series of AlMCM-41 samples with the same structure, constant composition (SiAl=14.7) but different pore sizes (diameter between 2.3 and 4.6 nm) was investigated by broadband dielectric spectroscopy (10(-2)-10(9) Hz) in a large temperature interval. Two relaxation processes are observed: one has a bulklike behavior and is assigned to the 8CB in the pore center. The relaxation time of the second relaxation process is essentially slower than that of the former one and this process is related to the dynamics of molecules in a surface layer with a paranematic order. Both relaxation processes are specifically influenced by the interaction of the molecules with the surface and by the confinement. Above the clearing temperature the temperature dependence of the relaxation rate of the bulklike process obeys the Vogel-Fulcher-Tammann (VFT) law. The Vogel temperature increases with decreasing pore size. This is explained by increasing influence of paranematic potential of the surface layer with decreasing pore size. The temperature dependence of the relaxation rate of the surface layer follows also the VFT formula and the Vogel temperature decreases with decreasing pore size. This temperature dependence is controlled by both the interaction of the 8CB molecules with the surface via hydrogen bonding and by spatial confinement effects. To discriminate between both effects the data for the surface layer of 8CB confined to the molecular sieves are compared with results concerning 8CB adsorbed as a quasimonolayer on the surface of silica spheres of aerosil. On this basis a confinement parameter is defined and discussed. PMID:19113137

  14. 13C NMR of methane in an AlPO4-11 molecular sieve: Exchange effects and shielding anisotropy

    NASA Astrophysics Data System (ADS)

    Koskela, Tuomas; Ylihautala, Mika; Jokisaari, Jukka; Vaara, Juha

    1998-12-01

    13C NMR spectra of 13CH4 in an AlPO4-11 molecular sieve reveal exchange effects between adsorbed and nonadsorbed methane gas. An application of pulsed field gradients is introduced to decrease nonadsorbed and exchanging gas signals in order to extract the chemical shift anisotropy line shape of the adsorbed gas. The resulting 13C shielding anisotropy of methane is compared to existing value for methane in related SAPO-11 material. Less anisotropic shielding is observed in AlPO4-11, most likely due to the lack of charge-compensating cations.

  15. Infrared Study of CO2 Sorption over ?Molecular Basket? Sorbent Consisting of Polyethylenimine-Modified Mesoporous Molecular Sieve

    SciTech Connect

    Overbury, Steven {Steve} H; Wang, Xiaoxing; Clark, Jason; Ma, Xiaoliang; Xu, Xiaochun; Song, Chunshan; Schwartz, Viviane

    2009-01-01

    An infrared study has been conducted on CO{sub 2} sorption into nanoporous CO{sub 2} 'molecular basket' sorbents prepared by loading polyethylenimine (PEI) into mesoporous molecular sieve SBA-15. IR results from DRIFTS showed that a part of loaded PEI is anchored on the surface of SBA-15 through the interaction between amine groups and isolated surface silanol groups. Raising the temperature from 25 to 75 C increased the molecular flexibility of PEI loaded in the mesopore channels, which may partly contribute to the increase of CO{sub 2} sorption capacity at higher temperatures. CO{sub 2} sorption/desorption behavior studied by in situ transmission FTIR showed that CO{sub 2} is sorbed on amine sites through the formation of alkylammonium carbamates and absorbed into the multiple layers of PEI located in mesopores of SBA-15. A new observation by in situ IR is that two broad IR bands emerged at 2450 and 2160 cm{sup -1} with CO{sub 2} flowing over PEI(50)/SBA-15, which could be attributed to chemically sorbed CO{sub 2} species on PEI molecules inside the mesopores of SBA-15. The intensities of these two bands also increased with increasing CO{sub 2} exposure time and with raising CO{sub 2} sorption temperature. By comparison of the CO{sub 2} sorption rate at 25 and 75 C in terms of differential IR intensities, it was found that CO{sub 2} sorption over molecular basket sorbent includes two rate regimes which suggest two distinct steps: rapid sorption on exposed outer surface layers of PEI (controlled by sorption affinity or thermodynamics) and the diffusion and sorption inside the bulk of multiple layers of PEI (controlled by diffusion). The sorption of CO{sub 2} is reversible at 75 C. Comparative IR examination of the CO{sub 2} sorption/desorption spectra on dry and prewetted PEI/SBA-15 sorbent revealed that presorbed water does not significantly affect the CO{sub 2}-amine interaction patterns.

  16. N-methyldiethanolamine: a multifunctional structure-directing agent for the synthesis of SAPO and AlPO molecular sieves.

    PubMed

    Wang, Dehua; Tian, Peng; Fan, Dong; Yang, Miao; Gao, Beibei; Qiao, Yuyan; Wang, Chan; Liu, Zhongmin

    2015-05-01

    In the present study, N-methyldiethanolamine (MDEA) is demonstrated to be a multifunctional structure-directing agent for the synthesis of aluminophosphate-based molecular sieves. Four types of molecular sieves, including SAPO-34, -35, AlPO-9 and -22, are for the first time acquired with MDEA as a novel template. The phase selectivity of the present synthesis is found to be condition-dependent. SAPO-34 (CHA) crystallizes from a conventional hydrothermal system with a higher MDEA concentration. When using MDEA as both the template and solvent, pure SAPO-35 (LEV) is obtained from the synthetic gel with a high P2O5/Al2O3 ratio of (2-3), in which the concentration of MDEA could be varied in a wide range. AlPO-9 and AlPO-22 (AWW) are synthesized under the similar conditions to SAPO-35, except without the addition of Si source. The physicochemical properties of the obtained samples are investigated by XRD, XRF, SEM, N2 physisorption, TG-DSC, and various NMR spectra ((13)C, (29)Si, (27)Al and (31)P). Both SAPO-34 and SAPO-35 show good thermal stability, large surface area, and high pore volume. The catalytic performance of SAPO-34 is evaluated by the methanol-to-olefins (MTO) reaction and a good (C2H4+C3H6) selectivity of 82.7% has been achieved. PMID:25616250

  17. Time-Dependent CO[subscript 2] Sorption Hysteresis in a One-Dimensional Microporous Octahedral Molecular Sieve

    SciTech Connect

    Espinal, Laura; Wong-Ng, Winnie; Kaduk, James A.; Allen, Andrew J.; Snyder, Chad R.; Chiu, Chun; Siderius, Daniel W.; Li, Lan; Cockayne, Eric; Espinal, Anais E.; Suib, Steven L.

    2014-09-24

    The development of sorbents for next-generation CO{sub 2} mitigation technologies will require better understanding of CO{sub 2}/sorbent interactions. Among the sorbents under consideration are shape-selective microporous molecular sieves with hierarchical pore morphologies of reduced dimensionality. We have characterized the non-equilibrium CO{sub 2} sorption of OMS-2, a well-known one-dimensional microporous octahedral molecular sieve with manganese oxide framework. Remarkably, we find that the degree of CO{sub 2} sorption hysteresis increases when the gas/sorbent system is allowed to equilibrate for longer times at each pressure step. Density functional theory calculations indicate a 'gate-keeping' role of the cation in the tunnel, only allowing CO{sub 2} molecules to enter fully into the tunnel via a highly unstable transient state when CO{sub 2} loadings exceed 0.75 mmol/g. The energy barrier associated with the gate-keeping effect suggests an adsorption mechanism in which kinetic trapping of CO{sub 2} is responsible for the observed hysteretic behavior.

  18. Spray-dried powders enhance vaginal siRNA delivery by potentially modulating the mucus molecular sieve structure

    PubMed Central

    Wu, Na; Zhang, Xinxin; Li, Feifei; Zhang, Tao; Gan, Yong; Li, Juan

    2015-01-01

    Vaginal small interfering RNA (siRNA) delivery provides a promising strategy for the prevention and treatment of vaginal diseases. However, the densely cross-linked mucus layer on the vaginal wall severely restricts nanoparticle-mediated siRNA delivery to the vaginal epithelium. In order to overcome this barrier and enhance vaginal mucus penetration, we prepared spray-dried powders containing siRNA-loaded nanoparticles. Powders with Pluronic F127 (F127), hydroxypropyl methyl cellulose (HPMC), and mannitol as carriers were obtained using an ultrasound-assisted spray-drying technique. Highly dispersed dry powders with diameters of 5–15 μm were produced. These powders showed effective siRNA protection and sustained release. The mucus-penetrating properties of the powders differed depending on their compositions. They exhibited different potential of opening mesh size of molecular sieve in simulated vaginal mucus system. A powder formulation with 0.6% F127 and 0.1% HPMC produced the maximum increase in the pore size of the model gel used to simulate vaginal mucus by rapidly extracting water from the gel and interacting with the gel; the resulting modulation of the molecular sieve effect achieved a 17.8-fold improvement of siRNA delivery in vaginal tract and effective siRNA delivery to the epithelium. This study suggests that powder formulations with optimized compositions have the potential to alter the steric barrier posed by mucus and hold promise for effective vaginal siRNA delivery. PMID:26347257

  19. Activation and Micropore Structure Determination of Carbon-Fiber Composite Molecular Sieves

    SciTech Connect

    Jagtoyen, M.

    1995-01-01

    levels of burnoff above about 40%, the extent of contraction is sufficient to produce stresses that result in fracture. Activated composites have been evaluated for the separation of CH{sub 4}-CO{sub 2} mixtures, and an apparatus has been constructed specifically for this purpose. Samples activated to low burn-off (5-7% wt loss) with low surface areas (from 300-500m{sup 2}/g) give much better separation of CO{sub 2} and CH{sub 4}, than samples produced at higher burnoff, and there appears to be no benefit in producing composites at burnoffs higher than 10%. The greater separation efficiency obtained at low burnoff means that the most effective CFCMS can be produced at relatively low cost. Continuing work will attempt to define the parameters that influence this gas separation, and whether these are applicable to other gas mixtures. Five samples of CFCMS have been recently prepared for shipment to British Oxygen Corporation (BOC) for testing as molecular sieves. The samples were machined to specific dimensions at ORNL (approx. 2.5 cm diameter x 1.25 cm thick) and activated at CAER. The samples were produced to different burn-off, but all have relatively narrow pore size distributions with average pore diameters around 6A.

  20. Activation of molecular catalysts using semiconductor quantum dots

    DOEpatents

    Meyer, Thomas J.; Sykora, Milan; Klimov, Victor I.

    2011-10-04

    Photocatalytic materials based on coupling of semiconductor nanocrystalline quantum dots (NQD) and molecular catalysts. These materials have capability to drive or catalyze non-spontaneous chemical reactions in the presence of visible radiation, ultraviolet radiation, or both. The NQD functions in these materials as a light absorber and charge generator. Following light absorption, the NQD activates a molecular catalyst adsorbed on the surface of the NQD via transfer of one or more charges (either electrons or electron-holes) from the NQD to the molecular catalyst. The activated molecular catalyst can then drive a chemical reaction. A photoelectrolytic device that includes such photocatalytic materials is also described.

  1. Formation of hydroxyl-functionalized stilbenoid molecular sieves at the liquid/solid interface on top of a 1-decanol monolayer

    NASA Astrophysics Data System (ADS)

    Bellec, Amandine; Arrigoni, Claire; Douillard, Ludovic; Fiorini-Debuisschert, Céline; Mathevet, Fabrice; Kreher, David; Attias, André-Jean; Charra, Fabrice

    2014-10-01

    Specific molecular tectons can be designed to form molecular sieves through self-assembly at the solid-liquid interface. After demonstrating a model tecton bearing apolar alkyl chains, we then focus on a modified structure involving asymmetric functionalization of some alkyl chains with polar hydroxyl groups in order to get chemical selectivity in the sieving. As the formation of supramolecular self-assembled networks strongly depends on molecule-molecule, molecule-substrate and molecule-solvent interactions, we compared the tectons’ self-assembly on graphite for two types of solvent. We demonstrate the possibility to create hydroxylated stilbenoid molecular sieves by using 1-decanol as a solvent. Interestingly, with this solvent, the porous network is developed on top of a 1-decanol monolayer.

  2. In situ solid-state NMR studies of the catalytic conversion of methanol on the molecular sieve SAPO-34

    SciTech Connect

    Anderson, M.W.; Sulikowski, B.; Barrie, P.J.; Klinowski, J. )

    1990-04-05

    We have monitored the shape-selective catalytic conversion of methanol (MeOH) to low-molecular-weight olefins and aliphatics over the molecular sieve SAPO-34 using {sup 13}C and {sup 1}H magic-angle-spinning (MAS) NMR in tandem with gas chromatography. The size of the eight-membered windows in the structure limits the gas-phase products to linear C{sub 1}, C{sub 2}, and C{sub 3} species. However, the main species present in the intracrystalline space are branched C{sub 4} and C{sub 5} saturated hydrocarbons such as isobutane and isopentane: too large to leave the intracrystalline pore system they become trapped, thus imposing an additional steric constraint on the diffusion of linear hydrocarbons.

  3. Cobalt Fischer-Tropsch catalysts having improved selectivity

    DOEpatents

    Miller, James G.; Rabo, Jule A.

    1989-01-01

    The promoter(s) Mn oxide or Mn oxide and Zr oxide are added to a cobalt Fischer-Tropsch catalyst combined with the molecular sieve TC-103 or TC-123 such that the resultant catalyst demonstrates improved product selectivity, stability and catalyst life. The improved selectivity is evidenced by lower methane production, higher C5+ yield and increased olefin production.

  4. Mathematical model and calculation algorithm of micro and meso levels of separation process of gaseous mixtures in molecular sieves

    SciTech Connect

    Umarova, Zhanat; Botayeva, Saule; Yegenova, Aliya; Usenova, Aisaule

    2015-05-15

    In the given article, the main thermodynamic aspects of the issue of modeling diffusion transfer in molecular sieves have been formulated. Dissipation function is used as a basic notion. The differential equation, connecting volume flow with the change of the concentration of catchable component has been derived. As a result, the expression for changing the concentration of the catchable component and the coefficient of membrane detecting has been received. As well, the system approach to describing the process of gases separation in ultra porous membranes has been realized and micro and meso-levels of mathematical modeling have been distinguished. The non-ideality of the shared system is primarily taken into consideration at the micro-level and the departure from the diffusion law of Fick has been taken into account. The calculation method of selectivity considering fractal structure of membranes has been developed at the meso level. The calculation algorithm and its software implementation have been suggested.

  5. Mathematical model and calculation algorithm of micro and meso levels of separation process of gaseous mixtures in molecular sieves

    NASA Astrophysics Data System (ADS)

    Umarova, Zhanat; Botayeva, Saule; Yegenova, Aliya; Usenova, Aisaule

    2015-05-01

    In the given article, the main thermodynamic aspects of the issue of modeling diffusion transfer in molecular sieves have been formulated. Dissipation function is used as a basic notion. The differential equation, connecting volume flow with the change of the concentration of catchable component has been derived. As a result, the expression for changing the concentration of the catchable component and the coefficient of membrane detecting has been received. As well, the system approach to describing the process of gases separation in ultra porous membranes has been realized and micro and meso-levels of mathematical modeling have been distinguished. The non-ideality of the shared system is primarily taken into consideration at the micro-level and the departure from the diffusion law of Fick has been taken into account. The calculation method of selectivity considering fractal structure of membranes has been developed at the meso level. The calculation algorithm and its software implementation have been suggested.

  6. Integrated Testing of a 4-Bed Molecular Sieve, Air-Cooled Temperature Swing Adsorption Compressor, and Sabatier Engineering Development Unit

    NASA Technical Reports Server (NTRS)

    Knox, James C.; Miller, Lee; Campbell, Melissa; Mulloth, Lila; Varghese, Mini

    2006-01-01

    Accumulation and subsequent compression of carbon dioxide that is removed from the space cabin are two important processes involved in a closed-loop air revitalization scheme of the International Space Station (ISS). The 4-Bed Molecular Sieve (4BMS) of ISS currently operates in an open loop mode without a compressor. The Sabatier Engineering Development Unit (EDU) processes waste CO2 to provide water to the crew. This paper reports the integrated 4BMS, air-cooled Temperature Swing Adsorption Compressor (TSAC), and Sabatier EDU testing. The TSAC prototype was developed at NASA Ames Research Center (ARC). The 4BMS was modified to a functionally flight-like condition at NASA Marshall Space Flight Center (MSFC). Testing was conducted at MSFC. The paper provides details of the TSAC operation at various CO2 loadings and corresponding performance of the 4BMS and Sabatier.

  7. Modification of molecular sieves MCM-41 and SBA-15 with covalently grafted pyromellitimide and 1,4,5,8-naphthalenediimide.

    PubMed

    Trindade, Fabiane Jesus; Rey, José Fernando Queiruga; Brochsztain, Sergio

    2012-02-15

    This article describes the covalent grafting of pyromellitimide and 1,4,5,8-naphthalenediimide, which are organic semiconductors with very interesting electro-optical properties, onto the walls of mesoporous molecular sieves. The mesoporous materials MCM-41 and SBA-15 were first treated with 3-aminopropyltriethoxysilane, generating materials with a surface coverage of primary amino groups. These materials were further reacted with either pyromellitic dianhydride or 1,4,5,8-naphthalenetetracarboxylic dianhydride, generating surface-bound pyromellitimide or 1,4,5,8-naphthalenediimide, respectively. The success of the modification reactions was confirmed by elemental and thermogravimetric analyses, X-ray diffraction patterns and infrared, reflectance and fluorescence spectroscopies. The results indicated that the mesoporous structure of the new materials was preserved after the modification reactions and that the chromophores were included inside the mesoporous channels with stacked aromatic rings. PMID:22153336

  8. Small-Pore Molecular Sieves SAPO-34 with Chabazite Structure: Theoretical Study of Silicon Incorporation and Interrelated Catalytic Activity

    NASA Astrophysics Data System (ADS)

    Wang, Hong; Lewis, James; Liu, Zhongmin

    2011-03-01

    The catalytic conversion of methonal to olefin (MTO) has attracted attention both in industrial and academic fields. Strong evidence shows that small-pore molecular sieves with certain amount silicon incorporated (SAPO) present promising high catalytic activity in MTO conversion. Using DFT, we study the structural and electronic properties of chabazite SAPO-34. Although there are extensively experimental results show that silicon incorporation does not change the overall structure as the original AlPO structure, local structural changes are still created by silicon substitution, which probably accounted for the high catalytic activity. It is noted that the catalytic activity of SAPO-34 presents increasing trend along with the silicon incorporation amount increasing and maintain a flat peak even with more silicon incorporated. Hence, there is an optimal silicon incorporation amount which possibly yields the highest catalytic MTO conversion.

  9. Laboratory test and evaluation report of the essex model 60C-0037-2 molecular sieve oxygen generating system

    NASA Astrophysics Data System (ADS)

    Squire, Brendan E.; Bruckart, James E.; Quattlebaum, Martin; Johnston, Leslie W.

    1993-06-01

    The Essex Model 60C-0037-2 Molecular Sieve Oxygen Generating System was tested for environmental and electromagnetic interference/compatibility under the U.S. Army Program for Testing and Evaluation of Equipment for Aeromedical Operations. The tests were conducted using current military and industrial standards and procedures for environmental tests and electromagnetic interference/compatibility and human factors. The Essex Model 60C-0037-2 performed properly in the test environments. The oxygen concentration produced by the unit depends on the compressed air pressure, oxygen flow, and vent pressure. A separate oxygen concentration analyzer would be required to determine the oxygen concentration for patient use. The unit produces a significant amount of noise while operating.

  10. Production of carbon molecular sieves from Illinois coal; [Quarterly] technical report, September 1, 1993--November 30, 1993

    SciTech Connect

    Lizzio, A.A.; Rostam-Abadi, M.; Vyas, S.N.

    1994-03-01

    Carbon molecular sieves (CMS) have become an increasingly important class of adsorbents for use in gas separation and recovery processes. The overall objective of this project is to determine whether Illinois Basin coal is a suitable feedstock for the production of CMS and to evaluate the potential application of these products in commercial gas separation processes. In Phase I of this project, gram quantities of char were produced from IBC-102 coal in a fixed-bed reactor under a wide range of pyrolysis and activation conditions. Chars having surface areas. of 1500--2100 m{sup 2}/g were produced by chemical activation using potassium hydroxide as the activant. These high surface area chars had more than twice the adsorption capacity of commercial molecular sieves. The kinetics of adsorption of various gases, i.e., O{sub 2}, N{sub 2}, CO{sub 2}, CH{sub 4} and H{sub 2} on these chars at 25{degree}C was studied. Several chars showed good potential for efficient O{sub 2}/N{sub 2}, CO{sub 2}/CH{sub 4}, CO{sub 2}/H{sub 2} and CH{sub 4}/H{sub 2} separation; both high adsorption capacities and selectivities were achieved. The full potential of these materials in commercial gas separations has yet to be realized. In Phase II, the optimal preparation conditions determined in Phase I will be applied to production of larger quantities of CMS in a batch fluidized-bed reactor (FBR) and continuous rotary tube kiln (RTK).

  11. Production of carbon molecular sieves from Illinois coal. Final technical report, 1 September, 1992--31 August 1993

    SciTech Connect

    Lizzio, A.A.; Rostam-Abadi, M.

    1993-12-31

    Carbon molecular sieves (CMS) have become an increasingly important class of adsorbents for use in gas separation and recovery processes. The overall objective of this project is to determine whether Illinois Basin coals are a suitable feedstock for the production of CMS and to evaluate the potential application of these products in commercial gas separation processes. In Phase 1 of this project, gram quantities of char were prepared from Illinois coal in a fixed-bed reactor under a wide range of pyrolysis and activation conditions. Chars having surface areas of 1,500--2,100 m{sup 2}/g were produced by chemical activation using potassium hydroxide (KOH) as the chemical activant. These high surface area (HSA) chars had more than twice the adsorption capacity of commercial molecular sieves. The kinetics of adsorption of various gases, e.g., O{sub 2}, N{sub 2}, CO{sub 2}, CH{sub 4}, and H{sub 2}, on these chars at 25 C was determined. Several chars showed good potential for efficient O{sub 2}/N{sub 2}, CO{sub 2}/CH{sub 4} and CH{sub 4}/H{sub 2} separation. In Phase 2 of this project, larger quantities of char are being prepared from Illinois coal in a batch fluidized-bed reactor and in a continuous rotary tube kiln. The ability of these chars to separate binary gas mixtures is tested in an adsorption column/gas chromatography system. Oxygen and nitrogen breakthrough curves obtained for selected chars were compared to those of a commercial zeolite. Selected chars were subjected to a nitric acid oxidation treatment. The air separation capability of nitric acid treated char was strongly dependent on the outgassing conditions used prior to an O{sub 2}/N{sub 2} adsorption experiment. An outgassing temperature of 130--160 C produced chars with the most favorable air separation properties. 61 refs.

  12. Effect of lipase immobilization on resolution of (R, S)-2-octanol in nonaqueous media using modified ultrastable-Y molecular sieve as support.

    PubMed

    Dai, Dazhang; Xia, Liming

    2006-07-01

    The lipase from Penicillium expansum PED-03 (PEL) was immobilized onto modified ultrastable-Y (USY) molecular sieve and the resolution of (R, S)- 2-octanol was carried out in a bioreactor in nonaqueous media by the immobilized lipase. It was found that the conversion rate, enantiomeric excess (ee) value, and enantioselectivity (E) value of the resolution catalyzed by PEL immobilized on modified USY molecular sieve were much higher than those of the reaction catalyzed by free PEL and PEL immobilized on other supports. Immobilized on modified USY molecular sieve, the PEL exhibited obvious activity within a wider pH range and at a much higher temperature and showed a markedly enhanced stability against thermal inactivation, by which the suitable pH of the buffer used for immobilization could be "memorized." The conversion rate of the reaction catalyzed by PEL immobilized on modified USY molecular sieve reached 48.84%, with excellent enantioselectivity (average E value of eight batches >460) in nonaqueous media at "memorial" pH 9.5, 50 degrees C for 24 h, demonstrating a good application potential in the production of optically pure (R, S)-2-octanol. PMID:16891665

  13. Enhanced catalyst for conversion of syngas to liquid motor fuels

    DOEpatents

    Coughlin, P.K.; Rabo, J.A.

    1985-12-03

    Synthesis gas comprising carbon monoxide and hydrogen is converted to C[sub 5][sup +] hydrocarbons suitable for use as liquid motor fuels by contact with a dual catalyst system capable of enhancing the selectivity of said conversion to motor fuel range hydrocarbons and the quality of the resulting motor fuel product. The catalyst composition employs a Fischer-Tropsch catalyst, together with a co-catalyst/support component comprising a SAPO silicoaluminophosphate, non-zeolitic molecular sieve catalyst.

  14. Enhanced catalyst for conversion of syngas to liquid motor fuels

    DOEpatents

    Coughlin, Peter K.; Rabo, Jule A.

    1985-01-01

    Synthesis gas comprising carbon monoxide and hydrogen is converted to C.sub.5.sup.+ hydrocarbons suitable for use as liquid motor fuels by contact with a dual catalyst system capable of enhancing the selectivity of said conversion to motor fuel range hydrocarbons and the quality of the resulting motor fuel product. The catalyst composition employs a Fischer-Tropsch catalyst, together with a co-catalyst/support component comprising SAPO silicoaluminophosphate, non-zeolitic molecular sieve catalyst.

  15. Design strategies for the molecular level synthesis of supported catalysts.

    PubMed

    Wegener, Staci L; Marks, Tobin J; Stair, Peter C

    2012-02-21

    Supported catalysts, metal or oxide catalytic centers constructed on an underlying solid phase, are making an increasingly important contribution to heterogeneous catalysis. For example, in industry, supported catalysts are employed in selective oxidation, selective reduction, and polymerization reactions. Supported structures increase the thermal stability, dispersion, and surface area of the catalyst relative to the neat catalytic material. However, structural and mechanistic characterization of these catalysts presents a formidable challenge because traditional preparations typically afford complex mixtures of structures whose individual components cannot be isolated. As a result, the characterization of supported catalysts requires a combination of advanced spectroscopies for their characterization, unlike homogeneous catalysts, which have relatively uniform structures and can often be characterized using standard methods. Moreover, these advanced spectroscopic techniques only provide ensemble averages and therefore do not isolate the catalytic function of individual components within the mixture. New synthetic approaches are required to more controllably tailor supported catalyst structures. In this Account, we review advances in supported catalyst synthesis and characterization developed in our laboratories at Northwestern University. We first present an overview of traditional synthetic methods with a focus on supported vanadium oxide catalysts. We next describe approaches for the design and synthesis of supported polymerization and hydrogenation catalysts, using anchoring techniques which provide molecular catalyst structures with exceptional activity and high percentages of catalytically significant sites. We then highlight similar approaches for preparing supported metal oxide catalysts using atomic layer deposition and organometallic grafting. Throughout this Account, we describe the use of incisive spectroscopic techniques, including high

  16. Reduction of nitrogen oxides with catalytic acid resistant aluminosilicate molecular sieves and ammonia

    DOEpatents

    Pence, Dallas T.; Thomas, Thomas R.

    1980-01-01

    Noxious nitrogen oxides in a waste gas stream such as the stack gas from a fossil-fuel-fired power generation plant or other industrial plant off-gas stream is catalytically reduced to elemental nitrogen and/or innocuous nitrogen oxides employing ammonia as reductant in the presence of a zeolite catalyst in the hydrogen or sodium form having pore openings of about 3 to 10 A.

  17. Preparation, characterization, and catalytic performance of Ta-HMS mesoporous molecular sieve

    NASA Astrophysics Data System (ADS)

    Li, Xuefeng; Zhang, Like; Gao, Huanxin; Chen, Qingling

    2016-08-01

    Various Ta-HMS (hexagonal mesoporous silica) samples with different Ta content were hydrothermally prepared and characterized by XRD, N2-adsorption, ICP-AES, FTIR, and UV-Vis spectroscopy. The catalytic performance of the samples was also evaluated in the epoxidation of cyclohexene with cumene hydroperoxide as oxidant. The regularity of mesoporous structure decreases while more extraframe Ta ions are formed with increasing the Ta content. Ta-HMS with Ta/Si ratio of 0.015 shows the highest conversion and selectivity in the studied epoxidation reaction. The catalyst can be used for three times without significant activity loss.

  18. LOW TEMPERATURE VOC COMBUSTION OVER MANGANESE, COBALT AND ZINC ALPO4 MOLECULAR SIEVES

    SciTech Connect

    Rosemarie Szostak

    2003-03-06

    The objective of this project was to prepare microporous aluminophosphates containing magnesium, manganese, cobalt and zinc (MeAPOs) and to evaluate their performance as oxidation catalysts for the removal of low levels of volatile organic compounds (VOCs) from gas streams. The tasks to be accomplished were as follows: (1) To develop reliable synthesis methods for metal aluminophosphates containing manganese, cobalt and zinc in their framework; (2) To characterize these materials for crystallinity, phase purity, the location and nature of the incorporated metal in the framework; and (3) To evaluate the materials for their catalytic activities in the oxidation of volatile organic environmental pollutants.

  19. Catalytic cracking of HDPE wastes to liquid fuel in the presence of siliceous mesoporous molecular sieves

    NASA Astrophysics Data System (ADS)

    Ramli, Anita; Majid, Noor Diana Abdul; Yusup, Suzana

    2014-10-01

    A siliceous gel was synthesized at 80°C and aged for 5 days at 120°C before it was dried at 120°C for 16 hours and calcined at 500 and 700°C. The calcined Na-Si-MMS samples were then undergone ion exchange with ammonia solution to form NH4- Si - MMS . All samples were characterized for their physicochemical properties using nitrogen (N2) adsorption-desorption isotherm for surface area and porosity; and temperature programme desorption of ammonia (TPD-NH3) for determination of acidity. The catalytic activity of all samples was tested in pyrolysis of high density polyethylene (HDPE) waste at catalyst to HDPE ratio of 0.2. The organic liquid product (OLP) collected was analysed using gas chromatography (GC). Results show that presence of Na-Si-MMS calcined at 500°C promotes the formation of gasoline-like product while presence of Na-Si-MMS calcined at 700°C promotes the formation of both diesel-like and kerosene-like products. On the other hand, presence of all NH4-Si-MMS catalysts promotes the formation of gasoline-like product. These show that the activation process of Si-MMS has a significant effect on the production of fuel-like product from pyrolysis of HDPE.

  20. Synthesis of highly stable metal-containing extra-large-pore molecular sieves.

    PubMed

    Martínez-Franco, Raquel; Paris, Cecilia; Moliner, Manuel; Corma, Avelino

    2016-02-28

    The isomorphic substitution of two different metals (Mg and Co) within the framework of the ITQ-51 zeotype (IFO structure) using bulky aromatic proton sponges as organic structure-directing agents (OSDAs) has allowed the synthesis of different stable metal-containing extra-large-pore zeotypes with high pore accessibility and acidity. These metal-containing extra-large-pore zeolites, named MgITQ-51 and CoITQ-51, have been characterized by different techniques, such as powder X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectrometry, UV-Vis spectroscopy, temperature programmed desorption of ammonia and Fourier transform infrared spectroscopy, to study their physico-chemical properties. The characterization confirms the preferential insertion of Mg and Co atoms within the crystalline structure of the ITQ-51 zeotype, providing high Brønsted acidity, and allowing their use as efficient heterogeneous acid catalysts in industrially relevant reactions involving bulky organic molecules. PMID:26755759

  1. Controllable deformation of salt water-filled carbon nanotubes using an electric field with application to molecular sieving.

    PubMed

    Ye, Hongfei; Zheng, Yonggang; Zhang, Zhongqiang; Zhang, Hongwu; Chen, Zhen

    2016-08-01

    Precisely controlling the deformation of carbon nanotubes (CNTs) has practical application in the development of nanoscale functional devices, although it is a challenging task. Here, we propose a novel method to guide the deformation of CNTs through filling them with salt water and applying an electric field. With the electric field along the axial direction, the height of CNTs is enlarged by the axial electric force due to the internal ions and polar water molecules. Under an electric field with two mutually orthogonal components, the transverse electric force could further induce the bending deformation of CNTs. Based on the classical rod and beam theories, two mechanical models are constructed to verify and quantitatively describe the relationships between the tension and bending deformations of CNTs and the electric field intensity. Moreover, by means of the electric field-driven tension behavior of CNTs, we design a stretchable molecular sieve to control the flow rate of mixed gas and collect a single high-purity gas. The present work opens up new avenues in the design and fabrication of nanoscale controlling units. PMID:27335235

  2. Production of carbon molecular sieves from Illinois coal. [Quarterly] technical report, December 1, 1993--February 28, 1994

    SciTech Connect

    Lizzio, A.A.; Rostam-Abadi, M.; Vyas, S.N.

    1994-06-01

    Carbon molecular sieves (CMS) have become an increasingly important class of adsorbents for use in gas separation and recovery processes. The overall objective of this project is to determine whether Illinois coal is a suitable feedstock for the production of CMS and to evaluate the potential application of the products in commercial gas separation processes. In Phase I of this project, gram quantities of char were produced from IBC-102 coal in a fixed-bed reactor under a wide range of pyrolysis and activation conditions. The kinetics of adsorption of various gases, i.e., O{sub 2}, N{sub 2}, CO{sub 2}, CH{sub 4} and H{sub 2}, on these chars at 25{degree}C was studied. Several chars showed good potential for efficient O{sub 2}/N{sub 2}, CO{sub 2}/CH{sub 4}, CO{sub 2}H{sub 2} and CH{sub 4}/H{sub 2} separation; both high adsorption capacities and selectivities were achieved. The full potential of these materials in commercial gas separations has yet to be realized. In Phase II, the optimal char preparation conditions determined in Phase I are applied to production of larger quantities of CMS in a batch fluidized-bed reactor (FBR) and a continuous rotary tube kiln (RTFK).

  3. Ionothermal Synthesis of MnAPO-SOD Molecular Sieve without the Aid of Organic Structure-Directing Agents.

    PubMed

    Liu, Hao; Tian, Zhijian; Wang, Lei; Wang, Yasong; Li, Dawei; Ma, Huaijun; Xu, Renshun

    2016-02-15

    An SOD-type metalloaluminophosphate molecular sieve (denoted as SOD-Mn) was ionothermally synthesized by introducing manganese(II) cations into the reaction mixture via MnO-acid or MnO2-reductant reactions. Composition and structure analyses results show that two kinds of manganese(II) cations exist in the SOD-Mn structure. Part of the manganese(II) cations isomorphously substitute the framework aluminum(III) with a substitution degree of ∼30%. The rest of the manganese(II) cations occupy a fraction of the sod cages in their hydrated forms. A comprehensive investigation of the synthesis parameters, crystal sizes, and crystallization kinetics indicates that the in situ released hydrated manganese(II) cations direct the formation of SOD-Mn. Such structure-directing effect may be inhibited by both the fluorination of manganese(II) cations and the water accumulation during crystallization. In the fluoride anion-containing reaction mixture with a low ionic liquid content, the crystallization process is strongly suppressed, and large SOD-Mn single crystals of over 200 μm in size are yielded. SOD-Mn is free from organics and shows improved thermal stability compared with metalloaluminophosphates synthesized by using organic structure-directing agents. PMID:26821274

  4. Preparation, characterization and application of p-tert-butyl-calix[4]arene-SBA-15 mesoporous silica molecular sieves.

    PubMed

    Huang, Huayu; Zhao, Chuande; Ji, Yongsheng; Nie, Rong; Zhou, Pan; Zhang, Haixia

    2010-06-15

    p-tert-Butyl-calix[4]arene-SBA-15 mesoporous silica molecular sieves have been prepared and characterized by Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD) and nitrogen adsorption-desorption measurements. FT-IR spectra showed the presence of methylene (-CH(2)-), methyl (-CH(3)) and phenyl bands on the modified SBA-15. Powder XRD data indicated the structure of p-tert-butyl-calix[4]arene-SBA-15 remained the host SBA-15 structure. Brunauer-Emmett-Teller (BET) surface area analysis revealed a decrease in surface area and pore size. The adsorption capacity of the materials to diethylstilbestrol and bisphenol A was studied via the dynamic adsorption experiments. The maximum dynamic adsorption capacity on modified materials was 34.8 and 2.9 times higher than SBA-15 particles for diethylstilbestrol and bisphenol A, respectively. The results indicated that p-tert-butyl-calix[4]arene-SBA-15 particles could be used to the enrich the various compounds in water samples before the further analysis. PMID:20185235

  5. Diffusion of methane and carbon dioxide in carbon molecular sieve membranes by multinuclear pulsed field gradient NMR.

    PubMed

    Mueller, Robert; Kanungo, Rohit; Kiyono-Shimobe, Mayumi; Koros, William J; Vasenkov, Sergey

    2012-07-10

    Carbon molecular sieve (CMS) membranes are promising materials for energy efficient separations of light gases. In this work, we report a detailed microscopic study of carbon dioxide and methane self-diffusion in three CMS membrane derived from 6FDA/BPDA(1:1)-DAM and Matrimid polymers. In addition to diffusion of one-component sorbates, diffusion of a carbon dioxide/methane mixture was investigated. Self-diffusion studies were performed by the multinuclear (i.e., (1)H and (13)C) pulsed field gradient (PFG) NMR technique which combines the advantages of high field (17.6 T) NMR and high magnetic field gradients (up to 30 T/m). Diffusion measurements were carried out at different temperatures and for a broad range of the root-mean-square displacements of gas molecules inside the membranes. The diffusion data obtained from PFG NMR are compared with the corresponding results of membrane permeation measurements reported previously for the same membrane types. The observed differences between the transport diffusivities and self-diffusion coefficients of carbon dioxide and methane are discussed. PMID:22694169

  6. Interlinked Test Results for Fusion Fuel Processing and Blanket Tritium Recovery Systems Using Cryogenic Molecular Sieve Bed

    SciTech Connect

    Yamanishi, Toshihiko; Hayashi, Takumi; Kawamura, Yoshinori; Iwai, Yasunori; Isobe, Kanetsugu; Uzawa, Masayuki; Nishi, Masataka

    2005-07-15

    A simulated fuel processing (cryogenic distillation columns and a palladium diffuser) and CMSB (cryogenic molecular sieve bed) systems were linked together, and were operated. The validity of the CMSB was discussed through this experiment as an integrated system for the recovery of blanket tritium. A gas stream of hydrogen isotopes and He was supplied to the CMSB as the He sweep gas in blanket of a fusion reactor. After the breakthrough of tritium was observed, regeneration of the CMSB was carried out by evacuating and heating. The hydrogen isotopes were finally recovered by the diffuser. At first, only He gas was sent by the evacuating. The hydrogen isotopes gas was then rapidly released by the heating. The system worked well against the above drastic change of conditions. The amount of hydrogen isotopes gas finally recovered by the diffuser was in good agreement with that adsorbed by the CMSB. The dynamic behaviors (breakthrough and regeneration) of the system were explained well by a set of basic codes.

  7. Effects of octahedral molecular sieve on treatment performance, microbial metabolism, and microbial community in expanded granular sludge bed reactor.

    PubMed

    Pan, Fei; Xu, Aihua; Xia, Dongsheng; Yu, Yang; Chen, Guo; Meyer, Melissa; Zhao, Dongye; Huang, Ching-Hua; Wu, Qihang; Fu, Jie

    2015-12-15

    This study evaluated the effects of synthesized octahedral molecular sieve (OMS-2) nanoparticles on the anaerobic microbial community in a model digester, expanded granular sludge bed (EGSB) reactor. The addition of OMS-2 (0.025 g/L) in the EGSB reactors resulted in an enhanced operational performance, i.e., COD removal and biogas production increased by 4% and 11% respectively, and effluent volatile fatty acid (VFA) decreased by 11% relative to the control group. The Biolog EcoPlate™ test was employed to investigate microbial metabolism in the EGSB reactors. Results showed that OMS-2 not only increased the microbial metabolic level but also significantly changed the community level physiological profiling of the microorganisms. The Illumina MiSeq high-throughput sequencing of 16S rRNA gene indicated OMS-2 enhanced the microbial diversity and altered the community structure. The largest bacterial genus Lactococcus, a lactic acid bacterium, reduced from 29.3% to 20.4% by abundance in the presence of 0.25 g/L OMS-2, which may be conducive to decreasing the VFA production and increasing the microbial diversity. OMS-2 also increased the quantities of acetogenic bacteria and Archaea, and promoted the acetogenesis and methanogenesis. The X-ray photoelectron spectroscopy illustrated that Mn(IV)/Mn(III) with high redox potential in OMS-2 were reduced to Mn(II) in the EGSB reactors; this in turn affected the microbial community. PMID:26397455

  8. Controllable deformation of salt water-filled carbon nanotubes using an electric field with application to molecular sieving

    NASA Astrophysics Data System (ADS)

    Ye, Hongfei; Zheng, Yonggang; Zhang, Zhongqiang; Zhang, Hongwu; Chen, Zhen

    2016-08-01

    Precisely controlling the deformation of carbon nanotubes (CNTs) has practical application in the development of nanoscale functional devices, although it is a challenging task. Here, we propose a novel method to guide the deformation of CNTs through filling them with salt water and applying an electric field. With the electric field along the axial direction, the height of CNTs is enlarged by the axial electric force due to the internal ions and polar water molecules. Under an electric field with two mutually orthogonal components, the transverse electric force could further induce the bending deformation of CNTs. Based on the classical rod and beam theories, two mechanical models are constructed to verify and quantitatively describe the relationships between the tension and bending deformations of CNTs and the electric field intensity. Moreover, by means of the electric field-driven tension behavior of CNTs, we design a stretchable molecular sieve to control the flow rate of mixed gas and collect a single high-purity gas. The present work opens up new avenues in the design and fabrication of nanoscale controlling units.

  9. An efficient synthesis of graphenated carbon nanotubes over the tailored mesoporous molecular sieves by chemical vapor deposition

    SciTech Connect

    Atchudan, R.; Joo, Jin.; Pandurangan, A.

    2013-06-01

    Highlights: ► Tailored 3D cubic Ni/KIT-6 with large pores was synthesized successfully. ► The new hybrid g-CNTs in large scale were synthesized using Ni/KIT-6 by CVD method. ► The use of mesoporous material by CVD method would be an ideal choice to prepare g-CNTs at reasonable cost. ► This type of g-CNTs might be a new avenue for nano-electronic applications. - Abstract: The new hybrid of graphenated carbon nanotubes (g-CNTs) was superior to either CNTs or graphene. Mesoporous 3D cubic Ni/KIT-6 were synthesized hydrothermally through organic template route and then were used as catalytic template for the production of g-CNTs using acetylene as a carbon precursor by chemical vapor deposition (CVD) method. The deposited new hybrid carbon materials were purified and analyzed by various physico-chemical techniques such as XRD, TGA, SEM, TEM and Raman spectroscopy techniques. The graphitization of CNTs was confirmed by TGA and HRTEM studies. Thermal stability, surface morphology, and structural morphology of these materials were revealed by TGA, SEM and TEM analysis, respectively. Moreover, the tailored mesoporous Ni/KIT-6 molecular sieves were found to possess better quality and massive quantity of g-CNTs produced compared to other catalytic template route.

  10. Decolorization/Deodorization of Zein via Activated Carbons and Molecular Sieves

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A series of commercial activated carbons generated from different media and selective microporous zeolites with different pore sizes were used in a batch system to sequester the low molecular weight odor and color contaminants in commercial zein products. Because the adsorbents can also adsorb prot...

  11. Protein sterilization method of firefly luciferase using reduced pressure and molecular sieves

    NASA Technical Reports Server (NTRS)

    Chappelle, E. W.; Rich, E., Jr. (Inventor)

    1973-01-01

    The sterilization of the protein fruitfly luciferase under conditions that prevent denaturation is examined. Denaturation is prevented by heating the protein in contact with molecular seives and under a reduced pressure of the order of 0.00005 millimeters of mercury.

  12. Molecular sieve adsorbents and membranes for applications in the production of renewable fuels and chemicals

    NASA Astrophysics Data System (ADS)

    Ranjan, Rajiv

    Metal organic frameworks (MOF), a new class of porous materials, have emerged as promising candidate for gas storage, separation membrane and chemical sensors. We used secondary growth method to grow microporous metal organic framework (MMOF) films on porous alumina supports. Examination of the film using SEM and XRD showed that the crystals were well inter-grown and preferentially oriented. Gas permeation study showed that membranes were defect free and moderate selectivity was achieved for H2/N2 gas pairs. The next project had to do with ethanol production from lignocellulosic biomass as an alternate energy source. However, toxic inhibitors produced from the hydrolysis of biomass decrease ethanol yield during the fermentation process. We demonstrated the use of zeolites for the pretreatment of hydrolyzate in order to remove inhibitors like 5-Hydroxymethylfurfuraldehyde (HMF) and furfural from aqueous solution. Zeolites exhibit preferential adsorption of the inhibitors and in effect improve the ethanol yield during fermentation. Ideal Adsorbed Solution Theory (IAST) was also used to predict adsorption isotherms for HMF-furfural mixtures using single component adsorption data. We also studied production of HMF, a potential substitute as a building block for plastic and chemical production, from renewable biomass resources. Catalytic dehydration of fructose for HMF production faces problems like low conversion and yield. Dimethyl sulfoxide (DMSO) can be used as the solvent as well as the catalyst resulting in high HMF yield. We studied a reaction-separation system for this dehydration reaction where the product (HMF) could be recovered by selective adsorption on solid adsorbents from the reaction mixture.

  13. Catalyst for converting synthesis gas to liquid motor fuels

    DOEpatents

    Coughlin, Peter K.

    1986-01-01

    The addition of an inert metal component, such as gold, silver or copper, to a Fischer-Tropsch catalyst comprising cobalt enables said catalyst to convert synthesis gas to liquid motor fuels at about 240.degree.-370.degree. C. with advantageously reduced selectivity of said cobalt for methane in said conversion. The catalyst composition can advantageously include a support component, such as a molecular sieve, co-catalyst/support component or a combination of such support components.

  14. Exploring molecular sieve capabilities of activated carbon fibers to reduce the impact of NOM preloading on trichloroethylene adsorption

    SciTech Connect

    Tanju Karanfil; Seyed A. Dastgheib; Dina Mauldin

    2006-02-15

    Adsorption of trichloroethylene (TCE) by two activated carbon fibers ACF10 and ACF20H and two granular activated carbons, coal-based F400 and Macro preloaded with hydrophobic and transphilic fractions of natural organic matter (NOM) was examined. ACF10, the most microporous activated carbon used in this study, had over 90% of its pore volume in pores smaller than 10 {angstrom}. It also had the highest volume in pores 5-8 {angstrom}, which is the optimum pore size region for TCE adsorption, among the four activated carbons. Adsorption of NOM fractions by ACF10 was, in general, negligible. Therefore, ACF10, functioning as a molecular sieve during preloading, exhibited the least NOM uptake for each fraction, and subsequently the highest TCE adsorption. The other three sorbents had wider pore size distributions, including high volumes in pores larger than 10 {angstrom}, where NOM molecules can adsorb. As a result, they showed a higher degree of uptake for all NOM fractions, and subsequently lower adsorption capacities for TCE, as compared to ACF10. The results obtained in this study showed that understanding the interplay between the optimum pore size region for the adsorption of target synthetic organic contaminant (SOC) and the pore size region for the adsorption of NOM molecules is important for controlling NOM-SOC competitions. Experiments with different NOM fractions indicated that the degree of NOM loading is important in terms of preloading effects; however the way that the carbon pores are filled and loaded by different NOM fractions can be different and may create an additional negative impact on TCE adsorption. 40 refs., 3 figs., 2 tabs.

  15. Atmospheric weathering and silica-coated feldspar: Analogy with zeolite molecular sieves, granite weathering, soil formation, ornamental slabs, and ceramics

    PubMed Central

    Smith, Joseph V.

    1998-01-01

    Feldspar surfaces respond to chemical, biological, and mechanical weathering. The simplest termination is hydroxyl (OH), which interacts with any adsorption layer. Acid leaching of alkalis and aluminum generated a silica-rich, nanometers-thick skin on certain feldspars. Natural K, Na-feldspars develop fragile surfaces as etch pits expand into micrometer honeycombs, possibly colonized by lichens. Most crystals have various irregular coats. Based on surface-catalytic processes in molecular sieve zeolites, I proposed that some natural feldspars lose weakly bonded Al-OH (aluminol) to yield surfaces terminated by strongly bonded Si-OH (silanol). This might explain why some old feldspar-bearing rocks weather slower than predicted from brief laboratory dissolution. Lack of an Al-OH infrared frequency from a feldspar surface is consistent with such a silanol-dominated surface. Raman spectra of altered patches on acid-leached albite correspond with amorphous silica rather than hydroxylated silica–feldspar, but natural feldspar may respond differently. The crystal structure of H-exchanged feldspar provides atomic positions for computer modeling of complex ideas for silica-terminated feldspar surfaces. Natural weathering also depends on swings of temperature and hydration, plus transport of particles, molecules, and ionic complexes by rain and wind. Soil formation might be enhanced by crushing granitic outcrops to generate new Al-rich surfaces favorable for chemical and biological weathering. Ornamental slabs used by architects and monumental masons might last longer by minimizing mechanical abrasion during sawing and polishing and by silicifying the surface. Silica-terminated feldspar might be a promising ceramic surface. PMID:9520371

  16. Photocatalytic water oxidation by molecular assemblies based on cobalt catalysts.

    PubMed

    Zhou, Xu; Li, Fei; Li, Hua; Zhang, Biaobiao; Yu, Fengshou; Sun, Licheng

    2014-09-01

    Chromophore-catalyst molecular assemblies towards visible light-driven water oxidation were synthesized by covalent integration of a light-harvesting complex [Ru(bpy)3](2+) (bpy=2,2'-bipyridine) and a Co4O4 cubane water oxidation catalyst. The two components were assembled either in linear or macrocyclic configurations. In the presence of the sacrificial reagent, the Ru-Co metallocycle exhibits remarkable photocatalytic activity for oxygen evolution, which is one order of magnitude higher than that of a multicomponent system and exceeds that of a linear assembly by a factor of five, offering access to highly active photocatalyst through molecular design. PMID:25111070

  17. Synthesis and modification of mesoporous silica and the preparation of molecular sieve thin films via pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Coutinho, Decio Heringer

    2001-07-01

    describes the evaluation of the HISIV(TM) 1000 molecular sieve for TBC adsorption. The TBC equilibrium capacity was determined from a cyclohexane/TBC liquid mixture and was comparable to alumina adsorbents. Practicum One. A fluorescent diagnostic system was developed to image the inhomogeneous mixture formed as two miscible fluids mix. This diagnostic for the mixing fraction uses a commercially available CCD color camera, a polarity sensitive fluorescent probe (DCM), and the planar laser induced fluorescence (PLIF) imaging technique to track the mixing of two miscible fluids of different polarity (ethanol and decane). The DCM fluorescence spectrum shifts to the red with increasing polarity, and the CCD camera's red, green, and blue color channels serve as spectral filters for the probe's fluorescence.

  18. Dark- and photoreactions of ethanol and acetaldehyde over TiO{sub 2}/carbon molecular sieve fibers

    SciTech Connect

    Reztsova, T.; Chang, C.H.; Idriss, H.; Koresh, J.

    1999-07-01

    TiO{sub 2} has been synthesized within the pores of carbon molecular sieve fibers (CMSF) in order to grow particles of quantum size. TiO{sub 2}/CMSF characteristics were followed by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and UV-vis diffuse reflectance. XPS showed that all Ti cations are in a +4 oxidation state. The reduction profile of Ti cations (made by preferential O anion removal due to Ar{sup +} sputtering), as evidenced by Ti{sup +x}/Ti{sup +4} cations, is very similar to that already observed for well-defined TiO{sub 2} surfaces. The absence of XRD pattern indicated that TiO{sub 2} particles are in an amorphous form. UV-vis diffuse reflectance showed a considerably blue shift ({Delta}E = 0.6--0.7 eV) of the band gap of TiO{sub 2}/CMSF when compared to TiO{sub 2} (anatase). This shift translates an average particle radius of 15 {+-} 2 {angstrom}. Larger TiO{sub 2} particles, outside the CMSF nanopores, are, however, observed by TEM. Dark- and photoreactions of ethanol and acetaldehyde have been investigated over TiO{sub 2}/CMSF by steady state kinetics and temperature programmed desorption in UHV conditions, as well as in batch conditions at atmospheric pressure. UHV-steady state ethanol reactions have shown eightfold increase in the reaction rate at 573 K in the presence of UV when compared to dark reactions at the same temperatures. The rate constants ratio k{sub 2}K{sub 2}/k{sub 1}K{sub 1}, for the photoreactions of ethanol, is ca. 40 times higher for TiO{sub 2}/CMSF than for TiO{sub 2} (powder) indicating the high selectivity of the former toward total conversion of ethanol to CO{sub 2} with minor accumulation of acetaldehyde (k{sub 1}K{sub 1} and k{sub 2}K{sub 2} are the rate constants for ethanol to acetaldehyde and acetaldehyde to CO{sub 2}, respectively). Evidence of C-C bond dissociation is given by formaldehyde desorption during UV-acetaldehyde-TPD over TiO{sub 2}/CMSF under UHV conditions. Moreover, UV

  19. Evaluation of INL Supplied MOOSE/OSPREY Model: Modeling Water Adsorption on Type 3A Molecular Sieve

    SciTech Connect

    Pompilio, L. M.; DePaoli, D. W.; Spencer, B. B.

    2014-08-29

    The purpose of this study was to evaluate Idaho National Lab’s Multiphysics Object-Oriented Simulation Environment (MOOSE) software in modeling the adsorption of water onto type 3A molecular sieve (3AMS). MOOSE can be thought-of as a computing framework within which applications modeling specific coupled-phenomena can be developed and run. The application titled Off-gas SeParation and REcoverY (OSPREY) has been developed to model gas sorption in packed columns. The sorbate breakthrough curve calculated by MOOSE/OSPREY was compared to results previously obtained in the deep bed hydration tests conducted at Oak Ridge National Laboratory. The coding framework permits selection of various options, when they exist, for modeling a process. For example, the OSPREY module includes options to model the adsorption equilibrium with a Langmuir model or a generalized statistical thermodynamic adsorption (GSTA) model. The vapor solid equilibria and the operating conditions of the process (e.g., gas phase concentration) are required to calculate the concentration gradient driving the mass transfer between phases. Both the Langmuir and GSTA models were tested in this evaluation. Input variables were either known from experimental conditions, or were available (e.g., density) or were estimated (e.g., thermal conductivity of sorbent) from the literature. Variables were considered independent of time, i.e., rather than having a mass transfer coefficient that varied with time or position in the bed, the parameter was set to remain constant. The calculated results did not coincide with data from laboratory tests. The model accurately estimated the number of bed volumes processed for the given operating parameters, but breakthrough times were not accurately predicted, varying 50% or more from the data. The shape of the breakthrough curves also differed from the experimental data, indicating a much wider sorption band. Model modifications are needed to improve its utility and

  20. Preparation of amorphous sulfide sieves

    DOEpatents

    Siadati, Mohammad H.; Alonso, Gabriel; Chianelli, Russell R.

    2006-11-07

    The present invention involves methods and compositions for synthesizing catalysts/porous materials. In some embodiments, the resulting materials are amorphous sulfide sieves that can be mass-produced for a variety of uses. In some embodiments, methods of the invention concern any suitable precursor (such as thiomolybdate salt) that is exposed to a high pressure pre-compaction, if need be. For instance, in some cases the final bulk shape (but highly porous) may be same as the original bulk shape. The compacted/uncompacted precursor is then subjected to an open-flow hot isostatic pressing, which causes the precursor to decompose and convert to a highly porous material/catalyst.

  1. Supported Molecular Catalysts: Synthesis, in-situ Characterization and Performance

    SciTech Connect

    James F. Haw

    2010-12-14

    The technological advantages of solid catalysts (robustness for operation at high temperatures, lack of corrosion, and ease of separation of products) can be combined with the advantages of soluble catalysts (e.g., selectivity) by synthesis of structurally discrete, nearly uniform catalysts on supports. Our goal is to synthesize, characterize, test, and model such catalysts and their reactions, thereby opening a door to unprecedented fundamental understanding of the properties of such materials. We employ molecular chemistry in nano-scale cages of zeolites and on surfaces of tailored porous solids for the precise synthesis of catalysts with discrete, uniform, well-defined sites, primarily mononuclear metal complexes, characterizing them (sometimes in the functioning state) with a broad range of complementary experimental techniques and using computational chemistry to interpret the results, map out reaction paths, provide bases for the design of new catalysts, improve methods of data analysis, and identify key experiments. The effort is directly in support of DOE's energy, environmental, and national security missions as well as the support of DOE’s basic science mission to develop the tools and understanding needed for the success of the applied mission areas. The research is demonstrating progress in understanding, modeling, and controlling chemical reactivity at interfaces to develop a fundamental understanding of how to control catalytic reactions for a broad range of applications.

  2. Activation and micropore structure determination of carbon-fiber composite molecular sieves. Topical report, 30 March 1994--14 April 1995

    SciTech Connect

    Jagtoyen, M.; Derbyshire, F.; Kimber, G.; Fei, You Qing

    1995-05-19

    Progress in developing novel, rigid, monolithic adsorbent carbon fiber composites is described. Carbon fiber composites are activated using steam or CO{sub 2}, in order to produce uniform activation through the material and to control the pore structure and adsorptive properties. There is an overall shrinkage during activation, which is directly correlated with burnoff; burnoff above 40% results in fracture. Burnoffs higher than 10% does not produce any benefit for separation of CH{sub 4}-CO{sub 2} mixtures. Five samples of CFCMS have been prepared for testing as molecular sieves; all have relatively narrow pore size distributions with average pore diameters around 6A.

  3. Analysis of the Sensitivity of K-Type Molecular Sieve-Deposited MWNTs for the Detection of SF6 Decomposition Gases under Partial Discharge

    PubMed Central

    Zhang, Xiaoxing; Li, Xin; Luo, Chenchen; Dong, Xingchen; Zhou, Lei

    2015-01-01

    Sulfur hexafluoride (SF6) is widely utilized in gas-insulated switchgear (GIS). However, part of SF6 decomposes into different components under partial discharge (PD) conditions. Previous research has shown that the gas responses of intrinsic and 4 Å-type molecular sieve-deposited multi-wall carbon nanotubes (MWNTs) to SOF2 and SO2F2, two important decomposition components of SF6, are not obvious. In this study, a K-type molecular sieve-deposited MWNTs sensor was developed. Its gas response characteristics and the influence of the mixture ratios of gases on the gas-sensing properties were studied. The results showed that, for sensors with gas mixture ratios of 5:1, 10:1, and 20:1, the resistance change rate increased by nearly 13.0% after SOF2 adsorption, almost 10 times that of MWNTs sensors, while the sensors’ resistance change rate with a mixture ratio of 10:1 reached 17.3% after SO2F2 adsorption, nearly nine times that of intrinsic MWNT sensors. Besides, a good linear relationship was observed between concentration of decomposition components and the resistance change rate of sensors. PMID:26569245

  4. Analysis of the Sensitivity of K-Type Molecular Sieve-Deposited MWNTs for the Detection of SF₆ Decomposition Gases under Partial Discharge.

    PubMed

    Zhang, Xiaoxing; Li, Xin; Luo, Chenchen; Dong, Xingchen; Zhou, Lei

    2015-01-01

    Sulfur hexafluoride (SF6) is widely utilized in gas-insulated switchgear (GIS). However, part of SF6 decomposes into different components under partial discharge (PD) conditions. Previous research has shown that the gas responses of intrinsic and 4 Å-type molecular sieve-deposited multi-wall carbon nanotubes (MWNTs) to SOF2 and SO2F2, two important decomposition components of SF6, are not obvious. In this study, a K-type molecular sieve-deposited MWNTs sensor was developed. Its gas response characteristics and the influence of the mixture ratios of gases on the gas-sensing properties were studied. The results showed that, for sensors with gas mixture ratios of 5:1, 10:1, and 20:1, the resistance change rate increased by nearly 13.0% after SOF2 adsorption, almost 10 times that of MWNTs sensors, while the sensors' resistance change rate with a mixture ratio of 10:1 reached 17.3% after SO2F2 adsorption, nearly nine times that of intrinsic MWNT sensors. Besides, a good linear relationship was observed between concentration of decomposition components and the resistance change rate of sensors. PMID:26569245

  5. Catalyst and process for converting synthesis gas to liquid motor fuels

    DOEpatents

    Coughlin, Peter K.

    1987-01-01

    The addition of an inert metal component, such as gold, silver or copper, to a Fischer-Tropsch catalyst comprising cobalt enables said catalyst to convert synthesis gas to liquid motor fuels at about 240.degree.-370.degree. C. with advantageously reduced selectivity of said cobalt for methane in said conversion. The catalyst composition can advantageously include a support component, such as a molecular sieve, co-catalyst/support component or a combination of such support components.

  6. Enhanced catalyst for converting synthesis gas to liquid motor fuels

    DOEpatents

    Coughlin, Peter K.

    1986-01-01

    The conversion of synthesis gas to liquid molar fuels by means of a cobalt Fischer-Tropsch catalyst composition is enhanced by the addition of molybdenum, tungsten or a combination thereof as an additional component of said composition. The presence of the additive component increases the olefinic content of the hydrocarbon products produced. The catalyst composition can advantageously include a support component, such as a molecular sieve, co-catalyst/support component or a combination of such support components.

  7. The Use of Cryogenically Cooled 5A Molecular Sieves for Large Volume Reduction of Tritiated Hydrogen Gas

    SciTech Connect

    Antoniazzi, A.B.; Bartoszek, F.E.; Sherlock, A.M.

    2006-07-01

    A commercial hydrogen isotope separation system based on gas chromatography (AGC-ISS) has been built. The system operates in two modes: stripping and volume reduction. The purpose of the stripping mode is to reduce a large volume of tritiated hydrogen gas to a small volume of tritium rich hydrogen gas. The results here illustrate the effectiveness of the AGC-ISS in the stripping and volume reduction phases. Column readiness for hydrogen isotope separation is confirmed by room temperature air separation tests. Production runs were initially carried out using natural levels of deuterium (110-160 ppm) in high purity hydrogen. After completion of the deuterium/hydrogen runs the system began operations with tritiated hydrogen. The paper presents details of the AGC-ISS design and results of tritium tests. The heart of the AGC-ISS consists of two packed columns (9 m long, 3.8 cm OD) containing 5A molecular sieve material of 40/60 mesh size. Each column has 5 individually controlled heaters along the length of the column and is coiled around an inverted inner dewar. The coiled column and inner dewar are both contained within an outer dewar. In this arrangement liquid nitrogen, used to cryogenically cool the columns, flows into and out off the annular space defined by the two dewars, allowing for alternate heating and cooling cycles. Tritiated hydrogen feed is injected in batch quantities. The batch size is variable with the maximum quantity restricted by the tritium concentration in the exhausted hydrogen. The stripping operations can be carried out in full automated mode or in full manual mode. The average cycle time between injections is about 75 minutes. To date, the maximum throughput achieved is 10.5 m{sup 3}/day. A total of 37.8 m{sup 3} of tritiated hydrogen has been processed during commissioning. The system has demonstrated that venting of >99.95% of the feed gas is possible while retaining 99.98% of the tritium. At a maximum tritium concentration of {approx}7 GBq

  8. Molecular metal catalysts on supports: organometallic chemistry meets surface science.

    PubMed

    Serna, Pedro; Gates, Bruce C

    2014-08-19

    Recent advances in the synthesis and characterization of small, essentially molecular metal complexes and metal clusters on support surfaces have brought new insights to catalysis and point the way to systematic catalyst design. We summarize recent work unraveling effects of key design variables of site-isolated catalysts: the metal, metal nuclearity, support, and other ligands on the metals, also considering catalysts with separate, complementary functions on supports. The catalysts were synthesized with the goal of structural simplicity and uniformity to facilitate incisive characterization. Thus, they are essentially molecular species bonded to porous supports chosen for their high degree of uniformity; the supports are crystalline aluminosilicates (zeolites) and MgO. The catalytic species are synthesized in reactions of organometallic precursors with the support surfaces; the precursors include M(L)2(acetylacetonate)1-2, with M = Ru, Rh, Ir, or Au and the ligands L = C2H4, CO, or CH3. Os3(CO)12 and Ir4(CO)12 are used as precursors of supported metal clusters, and some such catalysts are made by ship-in-a-bottle syntheses to trap the clusters in zeolite cages. The simplicity and uniformity of the supported catalysts facilitate precise structure determinations, even in reactive atmospheres and during catalysis. The methods of characterizing catalysts in reactive atmospheres include infrared (IR), extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES), and nuclear magnetic resonance (NMR) spectroscopies, and complementary methods include density functional theory and atomic-resolution aberration-corrected scanning transmission electron microscopy for imaging of individual metal atoms. IR, NMR, XANES, and microscopy data demonstrate the high degrees of uniformity of well-prepared supported species. The characterizations determine the compositions of surface metal complexes and clusters, including the ligands and the metal

  9. Confinement of Ionic Liquids in Nanocages: Tailoring the Molecular Sieving Properties of ZIF-8 for Membrane-Based CO2 Capture.

    PubMed

    Ban, Yujie; Li, Zhengjie; Li, Yanshuo; Peng, Yuan; Jin, Hua; Jiao, Wenmei; Guo, Ang; Wang, Po; Yang, Qingyuan; Zhong, Chongli; Yang, Weishen

    2015-12-14

    Fine-tuning of effective pore size of microporous materials is necessary to achieve precise molecular sieving properties. Herein, we demonstrate that room temperature ionic liquids can be used as cavity occupants for modification of the microenvironment of MOF nanocages. Targeting CO2 capture applications, we tailored the effective cage size of ZIF-8 to be between CO2 and N2 by confining an imidazolium-based ionic liquid [bmim][Tf2 N] into ZIF-8's SOD cages by in-situ ionothermal synthesis. Mixed matrix membranes derived from ionic liquid-modified ZIF-8 exhibited remarkable combinations of permeability and selectivity that transcend the upper bound of polymer membranes for CO2 /N2 and CO2 /CH4 separation. We observed an unusual response of the membranes to varying pressure, that is, an increase in the CO2 /CH4 separation factor with pressure, which is highly desirable for practical applications in natural gas upgrading. PMID:26515558

  10. Integrated Testing of a 4-Bed Molecular Sieve and a Temperature-Swing Adsorption Compressor for Closed-Loop Air Revitalization

    NASA Technical Reports Server (NTRS)

    Knox, James C.; Mulloth, Lila M.; Affleck, David L.

    2004-01-01

    Accumulation and subsequent compression of carbon dioxide that is removed from space cabin are two important processes involved in a closed-loop air revitalization scheme of the International Space Station (ISS). The 4-Bed Molecular Sieve (4BMS) of ISS currently operates in an open loop mode without a compressor. This paper reports the integrated 4BMS and liquid-cooled TSAC testing conducted during the period of March 3 to April 18, 2003. The TSAC prototype was developed at NASA Ames Research Center (ARC). The 4BMS was modified to a functionally flight-like condition at NASA Marshall Space Flight Center (MSFC). Testing was conducted at MSFC. The paper provides details of the TSAC operation at various CO2 loadings and corresponding performance of CDRA.

  11. A New Class of Octahedral Molecular Sieve Materials for the Selective Removal and Sequestration of {sup 90}Sr{sup 2+}

    SciTech Connect

    NYMAN,MAY D.; NENOFF,TINA M.; TRIPATHI,AKHILESH; PARISE,JOHN B.; MAXWELL,ROBERT S.; HARRISON,WILLIAM T.A.

    2000-07-14

    The structure of Na{sub 16}Nb{sub 12.8}Ti{sub 3.2}O{sub 44.8}(OH){sub 3.2} {center_dot} 8H{sub 2}O, a member of a new family of Sandia Octahedral Molecular Sieves (SOMS) having a Nb/Na/M{sup IV} (M= Ti, Zr) oxide framework and exchangeable Na and water in open channels, was determined from Synchrotron X-ray data. The SOMS phases are isostructural with variable M{sup IV}:Nb(1:50--1:4) ratios. The SOMS are extremely selective for sorption of divalent cations, particularly Sr{sup 2+}. The ion-exchanged SOMS undergo direct thermal conversion to a perovskite-type phase, indicating this is a promising new method for removal and sequestration of radioactive Sr-90 from mixed nuclear wastes.

  12. Trace matrix solid phase dispersion using a molecular sieve as the sorbent for the determination of flavonoids in fruit peels by ultra-performance liquid chromatography.

    PubMed

    Cao, Wan; Hu, Shuai-Shuai; Ye, Li-Hong; Cao, Jun; Pang, Xiao-Qing; Xu, Jing-Jing

    2016-01-01

    A simple, rapid, and highly selective trace matrix solid phase dispersion (MSPD) technique, coupled with ultra-performance liquid chromatography-ultraviolet detection, was proposed for extracting flavonoids from orange fruit peel matrices. Molecular sieve SBA-15 was applied for the first time as a solid support in trace MSPD. Parameters, such as the type of dispersant, mass ratio of the sample to the dispersant, grinding time, and elution pH, were optimized in detail. The optimal extraction conditions involved dispersing a powdered fruit peel sample (25 mg) into 25mg of SBA-15 and then eluting the target analytes with 500 μL of methanol. A satisfactory linearity (r(2) > 0.9990) was obtained, and the calculated limits of detection reached 0.02-0.03 μg/mL for the compounds. The results showed that the method developed was successfully applied to determine the content of flavonoids in complex fruit peel matrices. PMID:26212999

  13. Sabatier Catalyst Poisoning Investigation

    NASA Technical Reports Server (NTRS)

    Nallette, Tim; Perry, Jay; Abney, Morgan; Knox, Jim; Goldblatt, Loel

    2013-01-01

    The Carbon Dioxide Reduction Assembly (CRA) on the International Space Station (ISS) has been operational since 2010. The CRA uses a Sabatier reactor to produce water and methane by reaction of the metabolic CO2 scrubbed from the cabin air and the hydrogen byproduct from the water electrolysis system used for metabolic oxygen generation. Incorporating the CRA into the overall air revitalization system has facilitated life support system loop closure on the ISS reducing resupply logistics and thereby enhancing longer term missions. The CRA utilizes CO2 which has been adsorbed in a 5A molecular sieve within the Carbon Dioxide Removal Assembly, CDRA. There is a potential of compounds with molecular dimensions similar to, or less than CO2 to also be adsorbed. In this fashion trace contaminants may be concentrated within the CDRA and subsequently desorbed with the CO2 to the CRA. Currently, there is no provision to remove contaminants prior to entering the Sabatier catalyst bed. The risk associated with this is potential catalyst degradation due to trace organic contaminants in the CRA carbon dioxide feed acting as catalyst poisons. To better understand this risk, United Technologies Aerospace System (UTAS) has teamed with MSFC to investigate the impact of various trace contaminants on the CRA catalyst performance at relative ISS cabin air concentrations and at about 200/400 times of ISS concentrations, representative of the potential concentrating effect of the CDRA molecular sieve. This paper summarizes our initial assessment results.

  14. Natural gas cleanup: Evaluation of a molecular sieve carbon as a pressure swing adsorbent for the separation of methane/nitrogen mixtures

    SciTech Connect

    Grimes, R.W.

    1994-06-01

    This report describes the results of a preliminary evaluation to determine the technical feasibility of using a molecular sieve carbon manufactured by the Takeda Chemical Company of Japan in a pressure owing adsorption cycle for upgrading natural gas (methane) contaminated with nitrogen. Adsorption tests were conducted using this adsorbent in two, four, and five-step adsorption cycles. Separation performance was evaluated in terms of product purity, product recovery, and sorbent productivity for all tests. The tests were conducted in a small, single-column adsorption apparatus that held 120 grams of the adsorbent. Test variables included adsorption pressure, pressurization rate, purge rate and volume, feed rate, and flow direction in the steps from which the product was collected. Sorbent regeneration was accomplished by purging the column with the feed gas mixture for all but one test series where a pure methane purge was used. The ratio between the volumes of the pressurization gas and the purge gas streams was found to be an important factor in determining separation performance. Flow rates in the various cycle steps had no significant effect. Countercurrent flow in the blow-down and purge steps improved separation performance. Separation performance appears to improve with increasing adsorption pressure, but because there are a number of interrelated variables that are also effected by pressure, further testing will be needed to verify this. The work demonstrates that a molecular sieve carbon can be used to separate a mixture of methane and nitrogen when used in a pressure swing cycle with regeneration by purge. Further work is needed to increase product purity and product recovery.

  15. Structurally Defined Molecular Hypervalent Iodine Catalysts for Intermolecular Enantioselective Reactions

    PubMed Central

    Haubenreisser, Stefan; Wöste, Thorsten H.; Martínez, Claudio; Ishihara, Kazuaki

    2015-01-01

    Abstract Molecular structures of the most prominent chiral non‐racemic hypervalent iodine(III) reagents to date have been elucidated for the first time. The formation of a chirally induced supramolecular scaffold based on a selective hydrogen‐bonding arrangement provides an explanation for the consistently high asymmetric induction with these reagents. As an exploratory example, their scope as chiral catalysts was extended to the enantioselective dioxygenation of alkenes. A series of terminal styrenes are converted into the corresponding vicinal diacetoxylation products under mild conditions and provide the proof of principle for a truly intermolecular asymmetric alkene oxidation under iodine(I/III) catalysis. PMID:26596513

  16. Solar driven water oxidation by a bioinspired manganese molecular catalyst.

    PubMed

    Brimblecombe, Robin; Koo, Annette; Dismukes, G Charles; Swiegers, Gerhard F; Spiccia, Leone

    2010-03-10

    A photoelectrochemical cell was designed that catalyzes the photooxidation of water using visible light as the sole energy source and a molecular catalyst, [Mn(4)O(4)L(6)](+) (1(+), L = bis(methoxyphenyl)phosphinate), synthesized from earth-abundant elements. The essential features include a photochemical charge separation system, [Ru(II)(bipy)(2)(bipy(COO)(2))], adhered to titania-coated FTO conductive glass, and 1(+) embedded within a proton-conducting membrane (Nafion). The complete photoanode represents a functional analogue of the water-oxidizing center of natural photosynthesis. PMID:20155923

  17. Effect of H{sub 3}PW{sub 12}O{sub 40} impregnation on Sn-MCM-41 mesoporous molecular sieves and their physico-chemical properties

    SciTech Connect

    Nedumaran, D.; Pandurangan, A.

    2015-01-15

    Graphical abstract: The wide angle XRD shows the well dispersion of HPWA in Sn-MCM-41. It enhances the total acidity of the material. The acidity of the material is correlated with sulfone selectivity. The FT-IR of dibenzothiophene and product shows the formation of sulfone (DBTO{sub 2}). - Highlights: • To enhance the total acidity of Sn-MCM-41 TPA is impregnated. • FT-IR and {sup 31}P MAS NMR confirms the HPWA intact on Sn-MCM-41. • EDAX shows the presence of W and P on Sn-MCM-41. • In ODS formation of sulfone was confirmed by FT-IR and {sup 1}H NMR. • The order of the catalytic activity of the catalysts are 18HSnM > 28HSnM > 8HSnM. - Abstract: Si-Sn-MCM-41 (Si/Sn = 110) mesoporous molecular sieve was synthesized by hydrothermal sol–gel method using cetyltrimethylammonium bromide (CTAB) as surfactant and SnCl{sub 4}·5H{sub 2}O as a metal source. To generate surface acidity of Si-Sn-MCM-41, 12-tungstophosphoric acid (HPWA) is impregnated on it. The acidity of HPWA loading on Sn-MCM-41 was investigated by temperature programmed desorption of NH{sub 3}. The diffused reflectance spectra of ultraviolet radiation, Raman spectra, FT-IR, {sup 29}Si-MAS NMR and {sup 31}P-MAS NMR techniques revealed the intact of α-Keggin anions on Sn-MCM-41. The wide angle XRD results showed that the HPWA is well dispersed on the support. The total acidity was enhanced with increase in loading of H{sub 3}PW{sub 12}O{sub 40}. The catalytic activity was examined in desulfurization of dibenzothiophene in vapor phase system. Among the catalysts 18% HPWA loaded Sn-MCM-41 showed good catalytic activity in desulfurization at 325 °C. The HPWA/Sn-MCM-41 are a suitable solid acid catalyst for converting organic sulfur into insoluble sulfone.

  18. Massively parallel mathematical sieves

    SciTech Connect

    Montry, G.R.

    1989-01-01

    The Sieve of Eratosthenes is a well-known algorithm for finding all prime numbers in a given subset of integers. A parallel version of the Sieve is described that produces computational speedups over 800 on a hypercube with 1,024 processing elements for problems of fixed size. Computational speedups as high as 980 are achieved when the problem size per processor is fixed. The method of parallelization generalizes to other sieves and will be efficient on any ensemble architecture. We investigate two highly parallel sieves using scattered decomposition and compare their performance on a hypercube multiprocessor. A comparison of different parallelization techniques for the sieve illustrates the trade-offs necessary in the design and implementation of massively parallel algorithms for large ensemble computers.

  19. Enhanced catalyst and process for converting synthesis gas to liquid motor fuels

    DOEpatents

    Coughlin, Peter K.

    1986-01-01

    The conversion of synthesis gas to liquid molar fuels by means of a cobalt Fischer-Tropsch catalyst composition is enhanced by the addition of molybdenum, tungsten or a combination thereof as an additional component of said composition. The presence of the additive component increases the olefinic content of the hydrocarbon products produced. The catalyst composition can advantageously include a support component, such as a molecular sieve, co-catalyst/support component or a combination of such support components.

  20. Nanocomposite prepared from ZnS nanoparticles and molecular sieves nanoparticles by ion exchange method: characterization and its photocatalytic activity.

    PubMed

    Pourahmad, Afshin

    2013-02-15

    In this article, we have reported synthesis of ZnS/MCM-41 nanocomposite and its photocatalytic activity. The photocatalytic activity was evaluated using basic blue 9 or methylene blue (MB) as model pollutant under UV light irradiation. The catalyst is characterized by transmission electron microscopy (TEM), UV-vis diffused reflectance spectra (UV-vis DRS), X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques. The effect of ZnS, MCM-41 support and different wt% of ZnS over the support on the photocatalytic degradation and influence of parameters such as ZnS loading, catalyst a mount, pH and initial concentration of dye on degradation are evaluated. The degradation reaction follows pseudo-first order kinetics. The effect of dosage of photocatalyst was studied in the range 0.02-5 g/L. It was seen that 0.4 g/L of photocatalyst is an optimum value for the dosage of photocatalyst. The degradation efficiency was decreased in dye concentration above 3.2 ppm for dye. In the best conditions, the degradation efficiency was obtained 0.32 ppm for methylene blue. PMID:23261613

  1. Effect of structure of the redox molecular sieve TS-1 on the oxidation of phenol, crotyl alcohol and norbornylene.

    PubMed

    Kerton, Owain J; McMorn, Paul; Bethell, Donald; King, Frank; Hancock, Frederick; Burrows, Andrew; Kiely, Christopher J; Ellwood, Simon; Hutchings, Graham

    2005-07-01

    A range of crystalline TS-1 samples with different morphologies as well as the corresponding TS-1 precursor structures have been synthesised using hydrothermal crystallisation. The materials have been characterised using powder X-ray diffraction, IR and Raman spectroscopy and electron microscopy. The materials were used as catalysts for the oxidation of crotyl alcohol, phenol and norbornylene and, in particular, the reactivity of the precursor structures was contrasted with crystalline TS-1. The oxidation of crotyl alcohol, selected as a relatively non-reactive substituted alkene, did not require the TS-1 structure for reactivity and TS-1 precursor structures are active, although crystalline TS-1 was found to be more reactive than the precursor structures. In contrast, phenol hydroxylation is only catalysed by crystalline TS-1. The reaction of phenol is observed to occur only on the exterior surface of large TS-1 crystallites. With smaller crystallites of TS-1, i.e. the size range of interest for catalysis, the rapid subsequent reaction of hydroquinone makes it difficult to determine whether reaction occurs solely on the exterior of the crystallites or at sites within the porous structure. Hence it is suggested that this reaction has limited scope as a probe reaction for the reactivity of sites within the crystallites. It is, however, feasible that phenol hydroxylation is a viable probe reaction for TS-1 type structural units. Norbornylene was studied as an example of a reactant too large to enter the internal pore structure of TS-1 and hence only reaction at pore mouths and external surface sites was possible. Larger TS-1 crystallites were more active for this substrate than suggested by surface area considerations. The results are discussed in terms of the selection of model reactions for the study of TS-1 catalysts. PMID:16189579

  2. Application of computational fluid dynamics for the simulation of cryogenic molecular sieve bed absorber of hydrogen isotopes recovery system for Indian LLCB-TBM

    SciTech Connect

    Gayathri Devi, V.; Sircar, A.; Sarkar, B.

    2015-03-15

    One of the most challenging tasks in the design of the fuel cycle system lies in the effective design of Tritium Extraction System (TES) which involves proper extraction and purification of tritium in the fuel cycle of the fusion reactor. Indian Lead Lithium cooled Ceramic Breeder Test Blanket Module (LLCB-TBM) would extract hydrogen isotopes through Cryogenic Molecular Sieve Bed (CMSB) adsorber system. A prototype Hydrogen Isotopes Recovery System (HIRS) is being developed to validate the concepts for tritium extraction by adsorption mass transfer mechanism. In this study, a design model has been developed and analyzed to simulate the adsorption mass transfer kinetics in a fixed bed adsorption column. The simulation leads primarily to effective design of HIRS, which is a state-of-the-art technology. The paper describes the process simulation approach and the results of Computational Fluid Dynamics (CFD) analysis. The effects of different operating conditions are studied to investigate their influence on the hydrogen isotopes adsorption capacity. The results of the present simulation study would be used to understand the best optimized transport phenomenon before realizing the TES as a system for LLCB-TBM. (authors)

  3. 129Xe NMR of xenon adsorbed on the molecular sieves AlPO 4-11 and SAPO-11. Chemical shift anisotropy related to the asymmetry of the adsorption zones

    NASA Astrophysics Data System (ADS)

    Springuel-Huet, M. A.; Fraissard, J.

    1989-01-01

    The form of the 129Xe NMR signal of xenon adsorbed at low concentration on the molecular sieves SAPO-11 and AlPO 4-11 corresponds to a highly anisotropic chemical shift which expresses the asymmetry of the channels in which the xenon is located. To the asymmetry of the xenon-wall interaction is added that of the xenon-xenon interaction when the channels are largely filled.

  4. A molecular catalyst for water oxidation that binds to metal oxide surfaces

    PubMed Central

    Sheehan, Stafford W.; Thomsen, Julianne M.; Hintermair, Ulrich; Crabtree, Robert H.; Brudvig, Gary W.; Schmuttenmaer, Charles A.

    2015-01-01

    Molecular catalysts are known for their high activity and tunability, but their solubility and limited stability often restrict their use in practical applications. Here we describe how a molecular iridium catalyst for water oxidation directly and robustly binds to oxide surfaces without the need for any external stimulus or additional linking groups. On conductive electrode surfaces, this heterogenized molecular catalyst oxidizes water with low overpotential, high turnover frequency and minimal degradation. Spectroscopic and electrochemical studies show that it does not decompose into iridium oxide, thus preserving its molecular identity, and that it is capable of sustaining high activity towards water oxidation with stability comparable to state-of-the-art bulk metal oxide catalysts. PMID:25757425

  5. Molecular co-catalyst accelerating hole transfer for enhanced photocatalytic H2 evolution

    PubMed Central

    Bi, Wentuan; Li, Xiaogang; Zhang, Lei; Jin, Tao; Zhang, Lidong; Zhang, Qun; Luo, Yi; Wu, Changzheng; Xie, Yi

    2015-01-01

    In artificial photocatalysis, sluggish kinetics of hole transfer and the resulting high-charge recombination rate have been the Achilles' heel of photocatalytic conversion efficiency. Here we demonstrate water-soluble molecules as co-catalysts to accelerate hole transfer for improved photocatalytic H2 evolution activity. Trifluoroacetic acid (TFA), by virtue of its reversible redox couple TFA·/TFA−, serves as a homogeneous co-catalyst that not only maximizes the contact areas between co-catalysts and reactants but also greatly promotes hole transfer. Thus K4Nb6O17 nanosheet catalysts achieve drastically increased photocatalytic H2 production rate in the presence of TFA, up to 32 times with respect to the blank experiment. The molecular co-catalyst represents a new, simple and highly effective approach to suppress recombination of photogenerated charges, and has provided fertile new ground for creating high-efficiency photosynthesis systems, avoiding use of noble-metal co-catalysts. PMID:26486863

  6. Molecular co-catalyst accelerating hole transfer for enhanced photocatalytic H2 evolution

    NASA Astrophysics Data System (ADS)

    Bi, Wentuan; Li, Xiaogang; Zhang, Lei; Jin, Tao; Zhang, Lidong; Zhang, Qun; Luo, Yi; Wu, Changzheng; Xie, Yi

    2015-10-01

    In artificial photocatalysis, sluggish kinetics of hole transfer and the resulting high-charge recombination rate have been the Achilles' heel of photocatalytic conversion efficiency. Here we demonstrate water-soluble molecules as co-catalysts to accelerate hole transfer for improved photocatalytic H2 evolution activity. Trifluoroacetic acid (TFA), by virtue of its reversible redox couple TFA./TFA-, serves as a homogeneous co-catalyst that not only maximizes the contact areas between co-catalysts and reactants but also greatly promotes hole transfer. Thus K4Nb6O17 nanosheet catalysts achieve drastically increased photocatalytic H2 production rate in the presence of TFA, up to 32 times with respect to the blank experiment. The molecular co-catalyst represents a new, simple and highly effective approach to suppress recombination of photogenerated charges, and has provided fertile new ground for creating high-efficiency photosynthesis systems, avoiding use of noble-metal co-catalysts.

  7. Microfluidic sieve valves

    SciTech Connect

    Quake, Stephen R; Marcus, Joshua S; Hansen, Carl L

    2015-01-13

    Sieve valves for use in microfluidic device are provided. The valves are useful for impeding the flow of particles, such as chromatography beads or cells, in a microfluidic channel while allowing liquid solution to pass through the valve. The valves find particular use in making microfluidic chromatography modules.

  8. Carbon fiber composite molecular sieves

    SciTech Connect

    Burchell, T.D.; Rogers, M.R.

    1997-12-01

    Monolithic adsorbents based on isotropic pitch fibers have been developed jointly by ORNL and the University of Kentucky, Center for Applied Energy Research. The monoliths are attractive for gas separation and storage applications because of their unique combination of physical properties and microporous structure. Currently at ORNL the monoliths are produced in billets that are 10 cm in diameter and 25 cm in length. The monolithic adsorbent material is being considered for guard bed applications on a natural gas (NG) powered device. In order for the material to be successful in this application, one must attain a uniform activation to modest micropore volumes throughout the large monoliths currently being produced. Here the authors report the results of a study directed toward attaining uniform activation in these billets.

  9. Research on Molecular Sieve Technology.

    ERIC Educational Resources Information Center

    Shah, Dhananjai B.; Hayhurst, David T.

    1985-01-01

    The zeolite synthesis and modification research program at Cleveland State University (Ohio) is described, including program philosophy and objectives, and research facilities. Also considers zeolite synthesis, adsorption on zeolites, kinetics of adsorption, and zeolite catalysis research. (JN)

  10. Molecular-level Design of Heterogeneous Chiral Catalysts

    SciTech Connect

    Gellman, Andrew John; Sholl, David S.; Tysoe, Wilfred T.; Zaera, Francisco

    2013-04-28

    Understanding and controlling selectivity is one of the key challenges in heterogeneous catalysis. Among problems in catalytic selectivity enantioselectivity is perhaps the most the most challenging. The primary goal of the project on “Molecular-level Design of Heterogeneous Chiral Catalysts” is to understand the origins of enantioselectivity on chiral heterogeneous surfaces and catalysts. The efforts of the project team include preparation of chiral surfaces, characterization of chiral surfaces, experimental detection of enantioselectivity on such surfaces and computational modeling of the interactions of chiral probe molecules with chiral surfaces. Over the course of the project period the team of PI’s has made some of the most detailed and insightful studies of enantioselective chemistry on chiral surfaces. This includes the measurement of fundamental interactions and reaction mechanisms of chiral molecules on chiral surfaces and leads all the way to rationale design and synthesis of chiral surfaces and materials for enantioselective surface chemistry. The PI’s have designed and prepared new materials for enantioselective adsorption and catalysis. Naturally Chiral Surfaces • Completion of a systematic study of the enantiospecific desorption kinetics of R-3-methylcyclohexanone (R-3-MCHO) on 9 achiral and 7 enantiomeric pairs of chiral Cu surfaces with orientations that span the stereographic triangle. • Discovery of super-enantioselective tartaric acid (TA) and aspartic acid (Asp) decomposition as a result of a surface explosion mechanism on Cu(643)R&S. Systematic study of super-enantiospecific TA and Asp decomposition on five enantiomeric pairs of chiral Cu surfaces. • Initial observation of the enantiospecific desorption of R- and S-propylene oxide (PO) from Cu(100) imprinted with {3,1,17} facets by L-lysine adsorption. Templated Chiral Surfaces • Initial observation of the enantiospecific desorption of R- and S-PO from Pt(111) and Pd(111

  11. Ultrasound- and Molecular Sieves-Assisted Synthesis, Molecular Docking and Antifungal Evaluation of 5-(4-(Benzyloxy)-substituted phenyl)-3-((phenylamino)methyl)-1,3,4-oxadiazole-2(3H)-thiones.

    PubMed

    Nimbalkar, Urja D; Tupe, Santosh G; Seijas Vazquez, Julio A; Khan, Firoz A Kalam; Sangshetti, Jaiprakash N; Nikalje, Anna Pratima G

    2016-01-01

    A novel series of 5-(4-(benzyloxy)substituted phenyl)-3-((phenyl amino)methyl)-1,3,4-oxadiazole-2(3H)-thione Mannich bases 6a-o were synthesized in good yield from the key compound 5-(4-(benzyloxy)phenyl)-1,3,4-oxadiazole-2(3H)-thione by aminomethylation with paraformaldehyde and substituted amines using molecular sieves and sonication as green chemistry tools. The antifungal activity of the new products was evaluated against seven human pathogenic fungal strains, namely, Candida albicans ATCC 24433, Candida albicans ATCC 10231, Candida glabrata NCYC 388, Cryptococcus neoformans ATCC 34664, Cryptococcus neoformans PRL 518, Aspergillus fumigatus NCIM 902 and Aspergillus niger ATCC 10578. The synthesized compounds 6d, 6f, 6g, 6h and 6j exhibited promising antifungal activity against the tested fungal pathogens. In molecular docking studies, derivatives 6c, 6f and 6i showed good binding at the active site of C. albicans cytochrome P450 enzyme lanosterol 14 α-demethylase. The in vitro antifungal activity results and docking studies indicated that the synthesized compounds have potential antifungal activity and can be further optimized as privileged scaffolds to design and develop potent antifungal drugs. PMID:27171073

  12. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis

    SciTech Connect

    Osseo-Asare, K.; Boakye, E.; Vaidyanathan, N.; Radovic, L.R.

    1992-04-01

    The objective of this project is to pursue the development of highly dispersed and inexpensive catalysts for improved coal solubilization and upgrading of coal liquids. A novel study of the synthesis of liquefaction catalysts of nanometer size will be carried out. It is based on the molecular design of reverse micelles (microemulsions). These surfactant-stabilized, metal-bearing microdrops offer unique opportunities for synthesizing very small particles by providing a cage-like effect that limits particle nucleation, growth and agglomeration. The emphasis will be on iron- and molybdenum-based catalysts, but the techniques to be developed should also be generally applicable. (VC)

  13. Molecular Engineering of Trifunctional Supported Catalysts for the Aerobic Oxidation of Alcohols.

    PubMed

    Fernandes, Antony E; Riant, Olivier; Jensen, Klavs F; Jonas, Alain M

    2016-09-01

    We describe a simple and general method for the preparation and molecular engineering of supported trifunctional catalysts and their application in the representative Cu/TEMPO/NMI-catalyzed aerobic oxidation of benzyl alcohol. The methodology allows in one single step to immobilize, with precise control of surface composition, both pyta, Cu(I) , TEMPO, and NMI sites on azide-functionalized silica particles. To optimize the performance of the heterogeneous trifunctional catalysts, synergistic interactions are finely engineered through modulating the degree of freedom of the imidazole site as well as tuning the relative surface composition, leading to catalysts with an activity significantly superior to the corresponding homogeneous catalytic system. PMID:27430481

  14. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis

    SciTech Connect

    Osseo-Asare, K.; Radovic, L.R.

    1991-07-01

    The objective of this project is to pursue the development of highly dispersed and inexpensive catalysts for improved coal solubilization and upgrading of coal liquids. A novel study of the synthesis of liquefaction catalysts of nanometer size will be carried out. It is based on the molecular design of reverse micelles (microemulsions). These surfactant-stabilized, metal-bearing microdrops offer unique opportunities for synthesizing very small particles by providing a cage-like effect that limits particle nucleation, growth and agglomeration. The emphasis will be on iron- and molybdenum-based catalysts, but the techniques to be developed should also be generally applicable. (VC)

  15. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis

    SciTech Connect

    Osseo-Asare, K.; Radovic, L.R.

    1991-02-01

    The objective of this project is to pursue the development of highly dispersed and inexpensive catalysts for improved coal solubilization and upgrading of coal liquids. A novel study of the synthesis of liquefaction catalysts of nanometer size will be carried out. It is based on the molecular design of reverse micelles (microemulsions). These surfactant-stabilized, metal-bearing microdrops offer unique opportunities for synthesizing very small particles by providing a cage-like effects that limits particle nucleation, growth and agglomeration. The emphasis will be on iron- and molybdenum-based catalysts, but the techniques to be developed should also be generally applicable.

  16. Metalloporphyrin catalysts for oxygen reduction developed using computer-aided molecular design

    SciTech Connect

    Ryba, G.N.; Hobbs, J.D.; Shelnutt, J.A.

    1996-04-01

    The objective of this project is the development of a new class of metalloporphyrin materials used as catalsyts for use in fuel cell applications. The metalloporphyrins are excellent candidates for use as catalysts at both the anode and cathode. The catalysts reduce oxygen in 1 M potassium hydroxide, as well as in 2 M sulfuric acid. Covalent attachment to carbon supports is being investigated. The computer-aided molecular design is an iterative process, in which experimental results feed back into the design of future catalysts.

  17. Quality of epitaxial InAs nanowires controlled by catalyst size in molecular beam epitaxy

    SciTech Connect

    Zhang, Zhi; Xu, Hong-Yi; Guo, Ya-Nan; Liao, Zhi-Ming; Lu, Zhen-Yu; Chen, Ping-Ping; Shi, Sui-Xing; Lu, Wei; Zou, Jin

    2013-08-12

    In this study, the structural quality of Au-catalyzed InAs nanowires grown by molecular beam epitaxy is investigated. Through detailed electron microscopy characterizations and analysis of binary Au-In phase diagram, it is found that defect-free InAs nanowires can be induced by smaller catalysts with a high In concentration, while comparatively larger catalysts containing less In induce defected InAs nanowires. This study indicates that the structural quality of InAs nanowires can be controlled by the size of Au catalysts when other growth conditions remain as constants.

  18. Quality of epitaxial InAs nanowires controlled by catalyst size in molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Zhang, Zhi; Lu, Zhen-Yu; Chen, Ping-Ping; Xu, Hong-Yi; Guo, Ya-Nan; Liao, Zhi-Ming; Shi, Sui-Xing; Lu, Wei; Zou, Jin

    2013-08-01

    In this study, the structural quality of Au-catalyzed InAs nanowires grown by molecular beam epitaxy is investigated. Through detailed electron microscopy characterizations and analysis of binary Au-In phase diagram, it is found that defect-free InAs nanowires can be induced by smaller catalysts with a high In concentration, while comparatively larger catalysts containing less In induce defected InAs nanowires. This study indicates that the structural quality of InAs nanowires can be controlled by the size of Au catalysts when other growth conditions remain as constants.

  19. Solar hydrogen production using carbon quantum dots and a molecular nickel catalyst.

    PubMed

    Martindale, Benjamin C M; Hutton, Georgina A M; Caputo, Christine A; Reisner, Erwin

    2015-05-13

    Carbon quantum dots (CQDs) are established as excellent photosensitizers in combination with a molecular catalyst for solar light driven hydrogen production in aqueous solution. The inexpensive CQDs can be prepared by straightforward thermolysis of citric acid in a simple one-pot, multigram synthesis and are therefore scalable. The CQDs produced reducing equivalents under solar irradiation in a homogeneous photocatalytic system with a Ni-bis(diphosphine) catalyst, giving an activity of 398 μmolH2 (gCQD)(-1) h(-1) and a "per Ni catalyst" turnover frequency of 41 h(-1). The CQDs displayed activity in the visible region beyond λ > 455 nm and maintained their full photocatalytic activity for at least 1 day under full solar spectrum irradiation. A high quantum efficiency of 1.4% was recorded for the noble- and toxic-metal free photocatalytic system. Thus, CQDs are shown to be a highly sustainable light-absorbing material for photocatalytic schemes, which are not limited by cost, toxicity, or lack of scalability. The photocatalytic hybrid system was limited by the lifetime of the molecular catalyst, and intriguingly, no photocatalytic activity was observed using the CQDs and 3d transition metal salts or platinum precursors. This observation highlights the advantage of using a molecular catalyst over commonly used heterogeneous catalysts in this photocatalytic system. PMID:25864839

  20. Preparation of Supported Metal Catalysts by Atomic and Molecular Layer Deposition for Improved Catalytic Performance

    NASA Astrophysics Data System (ADS)

    Gould, Troy D.

    Creating catalysts with enhanced selectivity and activity requires precise control over particle shape, composition, and size. Here we report the use of atomic layer deposition (ALD) to synthesize supported Ni, Pt, and Ni-Pt catalysts in the size regime (< 3 nm) where nanoscale properties can have a dramatic effect on reaction activity and selectivity. This thesis presents the first ALD synthesis of non-noble metal nanoparticles by depositing Ni on Al2O3 with two half-reactions of Ni(Cp)2 and H2. By changing the number of ALD cycles, Ni weight loadings were varied from 4.7 wt% to 16.7 wt% and the average particle sizes ranged from 2.5 to 3.3 nm, which increased the selectivity for C 3H6 hydrogenolysis by an order of magnitude over a much larger Ni/Al2O3 catalyst. Pt particles were deposited by varying the number of ALD cycles and the reaction chemistry (H2 or O 2) to control the particle size from approximately 1 to 2 nm, which allowed lower-coordinated surface atoms to populate the particle surface. These Pt ALD catalysts demonstrated some of the highest oxidative dehydrogenation of propane selectivities (37%) of a Pt catalyst synthesized by a scalable technique. Dry reforming of methane (DRM) is a reaction of interest due to the recent increased recovery of natural gas, but this reaction is hindered from industrial implementation because the Ni catalysts are plagued by deactivation from sintering and coking. This work utilized Ni ALD and NiPt ALD catalysts for the DRM reaction. These catalysts did not form destructive carbon whiskers and had enhanced reaction rates due to increased bimetallic interaction. To further limit sintering, the Ni and NiPt ALD catalysts were coated with a porous alumina matrix by molecular layer deposition (MLD). The catalysts were evaluated for DRM at 973 K, and the MLD-coated Ni catalysts outperformed the uncoated Ni catalysts in either activity (with 5 MLD cycles) or stability (with 10 MLD cycles). In summary, this thesis developed a

  1. Supported Molecular Catalysts: Synthesis, In-Situ Characterization and Performance

    SciTech Connect

    Davis, Mark E.

    2009-03-13

    The objectives of our work are: (i) to create solid catalysts with active sites that can function in a cooperative manner to enhance reactivity and selectivity, and (ii) to prepare solid catalysts that can perform multiple reactions in a network that in some cases would not be possible in solution due to the incompatibilities of the various catalytic entities (for example an acid and a base). We carried out extensive reactions to test the nature of the cooperative effect caused by thiol/sulfonic acid interactions. The acid/thiol combination provided an example where the two organic groups should be positioned as close to one another as possible. We also studied a system where this is not possible (acid-base). We investigated simultaneously incorporating acid and base groups into the same material. For the case of acid and bases, there is an optimal separation distance (too close allows for neutralization while too far eliminates any cooperative behavior).

  2. Generalized Fibonacci photon sieves.

    PubMed

    Ke, Jie; Zhang, Junyong

    2015-08-20

    We successfully extend the standard Fibonacci zone plates with two on-axis foci to the generalized Fibonacci photon sieves (GFiPS) with multiple on-axis foci. We also propose the direct and inverse design methods based on the characteristic roots of the recursion relation of the generalized Fibonacci sequences. By switching the transparent and opaque zones, according to the generalized Fibonacci sequences, we not only realize adjustable multifocal distances but also fulfill the adjustable compression ratio of focal spots in different directions. PMID:26368763

  3. Titanium compounds as catalysts of higher alpha-olefin-based super-high-molecular polymers synthesis

    NASA Astrophysics Data System (ADS)

    Konovalov, K. B.; Kazaryan, M. A.; Manzhay, V. N.; Vetrova, O. V.

    2016-01-01

    The synthesis of polymers of 10 million or more molecular weight is a difficult task even in a chemical lab. Higher α-olefin-based polymer agents of such kind have found a narrow but quite important niche, the reduction of drag in the turbulent flow of hydrocarbon fluids such as oil and oil-products. In its turn, searching for a catalytic system capable to produce molecules of such a high length and to synthesize polymers of a low molecular-mass distribution is part of a global task of obtaining a high-quality product. In this paper we had observed a number of industrial catalysts with respect to their suitability for higher poly-α- olefins synthesis. A number samples representing copolymers of 1-hexene with 1-decene obtained on a previous generation catalyst, a microsphere titanium chloride catalytic agent had been compared to samples synthesized using a titanium-magnesium catalyst both in solution and in a polymer medium.

  4. Electrochemical CO2 Reduction to Hydrocarbons on a Heterogeneous Molecular Cu Catalyst in Aqueous Solution.

    PubMed

    Weng, Zhe; Jiang, Jianbing; Wu, Yueshen; Wu, Zishan; Guo, Xiaoting; Materna, Kelly L; Liu, Wen; Batista, Victor S; Brudvig, Gary W; Wang, Hailiang

    2016-07-01

    Exploration of heterogeneous molecular catalysts combining the atomic-level tunability of molecular structures and the practical handling advantages of heterogeneous catalysts represents an attractive approach to developing high-performance catalysts for important and challenging chemical reactions such as electrochemical carbon dioxide reduction which holds the promise for converting emissions back to fuels utilizing renewable energy. Thus, far, efficient and selective electroreduction of CO2 to deeply reduced products such as hydrocarbons remains a big challenge. Here, we report a molecular copper-porphyrin complex (copper(II)-5,10,15,20-tetrakis(2,6-dihydroxyphenyl)porphyrin) that can be used as a heterogeneous electrocatalyst with high activity and selectivity for reducing CO2 to hydrocarbons in aqueous media. At -0.976 V vs the reversible hydrogen electrode, the catalyst is able to drive partial current densities of 13.2 and 8.4 mA cm(-2) for methane and ethylene production from CO2 reduction, corresponding to turnover frequencies of 4.3 and 1.8 molecules·site(-1)·s(-1) for methane and ethylene, respectively. This represents the highest catalytic activity to date for hydrocarbon production over a molecular CO2 reduction electrocatalyst. The unprecedented catalytic performance is attributed to the built-in hydroxyl groups in the porphyrin structure and the reactivity of the copper(I) metal center. PMID:27310487

  5. Dynamic Structural Changes in a Molecular Zeolite-Supported Iridium Catalyst for Ethene Hydrogenation

    SciTech Connect

    Uzun, Alper; Gates, Bruce C.

    2009-11-16

    The structure of a catalyst often changes as a result of changes in the reactive environment during operation. Examples include changes in bulk phases, extended surface structures, and nanoparticle morphologies; now we report real-time characterization of changes in the structure of a working supported catalyst at the molecular level. Time-resolved extended X-ray absorption fine structure (EXAFS) data demonstrate the reversible interconversion of mononuclear iridium complexes and tetrairidium clusters inside zeolite Y cages, with the structure controlled by the C{sub 2}H{sub 4}/H{sub 2} ratio during ethene hydrogenation at 353 K. The data demonstrate break-up of tetrairidium clusters into mononuclear complexes indicated by a decrease in the Ir-Ir coordination number in ethene-rich feed. When the feed composition was switched to first equimolar and then to a H{sub 2}-rich (C{sub 2}H{sub 4}/H{sub 2} = 0.3) feed, the EXAFS spectra show the reformation of tetrairidium clusters as the Ir-Ir coordination number increased again. When the feed composition was cycled from ethene-rich to H{sub 2}-rich, the predominant species in the catalyst cycled accordingly. Evidence confirming the structural change is provided by IR spectra of iridium carbonyls formed by probing of the catalyst with CO. The data are the first showing how to tune the structure of a solid catalyst at the molecular scale by choice of the reactant composition.

  6. A Pt/Al2O3-supported metal-organic framework film as the size-selective core-shell hydrogenation catalyst.

    PubMed

    Aguado, Sonia; El-Jamal, Sawsan; Meunier, Frederic; Canivet, Jerome; Farrusseng, David

    2016-06-01

    The substituted imidazolate-based MOF (SIM-1) easily forms a homogeneous layer at the surface of millimetric platinum-loaded alumina beads. This new core-shell SIM-1@Pt/Al2O3 catalyst shows the fine molecular sieving effect for the Pt-catalyzed hydrogenation of carbon-carbon double bonds. PMID:27172134

  7. Broad pore channels as molecular highways in nanoporous catalysts: Multiscale modeling, optimization and applications

    NASA Astrophysics Data System (ADS)

    Wang, Gang

    Porous catalysts are widely used in many applications, ranging from petroleum refining to fuel cells and emission control. Nanoporous catalysts like zeolites often have an extremely large internal surface area (e.g., 1000m 2/g), which is beneficial because catalytic reactions occur on the surface. However, their small pore size leads to slow molecular transport and pore blocking, limiting the efficient use of the catalytic material. This indicates that, apart from the nanopores where reactions actually occur, a "distribution" network of broad pore channels is needed for molecules to quickly move in and out of the catalyst. Despite considerable experimental efforts in the introduction of broad pore channels into nanoporous catalysts in a controllable way, the following generic question remains: which broad pore channel network should be included in a nanoporous catalyst for optimal catalyst performance? To this end, model-based optimizations were used to optimize hierarchically structured porous catalysts, containing both broad pore channels and nanopores. Extensive optimizations showed that, for a single, isothermal reaction, the nanoporous walls (i.e., the nanoporous catalytic material between two neighboring broad pore channels) should be sufficiently thin so that diffusion limitations vanish inside them. It was found that the optimal catalytic performance is dictated by the generalized distributor Thiele modulus, which is defined in a way analogous to the generalized Thiele modulus, but using the molecular diffusivity in the broad pore channels, rather than the effective diffusivity in the nanopores. The use of hierarchically structured porous catalysts was demonstrated for power plant deNOx catalysis and autothermal reforming of methane. For deNOx catalysis, overall catalytic activity in a mesoporous deNOx catalyst with a median pore size of 32.5 nm could be increased by a factor of 1.8-2.8 simply by introducing 8-22mum broad pore channels (occupying 20-40% of

  8. Surface Interaction and Quantum Kinetic Molecular Sieving for H2 and D2 Adsorption on a Mixed-Metal-Organic Framework Material

    SciTech Connect

    Chen, Banglin; Zhaou, Xuebo; Putkham, Apipong; Hong, Kunlun; Labkovsky, Emil B; Hurtado, Eric J; Fletcher, Ashleigh J; Thomas, K Mark

    2008-01-01

    two types of pores, a slow component with high activation energy (13.35 {+-} 0.59 kJ mol{sup -1}) for the narrow pores and a faster component with low activation energy (8.56 0.41 kJ mol{sup -1}). The D{sub 2} adsorption kinetic constants for both components were significantly faster than the corresponding H{sub 2} kinetics for specific pressure increments and had slightly lower activation energies than the corresponding values for H{sub 2} adsorption. The kD{sub 2}/kH{sub 2} ratio for the slow component was 1.62 {+-} 0.07, while the fast component was 1.38 {+-} 0.04 at 77.3 K, and the corresponding ratios were smaller at 87.3 K. These observations of kinetic isotope quantum molecular sieving in porous materials are due to the larger zero-point energy for the lighter H{sub 2}, resulting in slower adsorption kinetics compared with the heavier D{sub 2}. The results show that a combination of open metal centers and confinement in ultramicroporosity leads to a high enthalpy for H{sub 2} adsorption over a wide range of surface coverage and quantum effects influence diffusion of H{sub 2} and D{sub 2} in pores in M{prime}MOF 1.

  9. Development of group IV molecular catalysts for high temperature ethylene-α-olefin copolymerization reactions.

    PubMed

    Klosin, Jerzy; Fontaine, Philip P; Figueroa, Ruth

    2015-07-21

    This Account describes our research related to the development of molecular catalysts for solution phase olefin polymerization. Specifically, a series of constrained geometry and nonmetallocene (imino-amido-type) complexes were developed for high temperature olefin polymerization reactions. We have discovered many highly active catalysts that are capable of operating at temperatures above 120 °C and producing copolymers with a useful range of molecular weights (from medium to ultrahigh depending on precatalyst identity and polymerization conditions) and α-olefin incorporation capability. Constrained geometry catalysts (CGCs) exhibit very high activities and are capable of producing a variety of copolymers including ethylene-propylene and ethylene-1-octene copolymers at high reactor temperatures. Importantly, CGCs have much higher reactivity toward α-olefins than classical Ziegler-Natta catalysts, thus allowing for the production of copolymers with any desired level of comonomer. In search of catalysts with improved performance, we discovered 3-amino-substituted indenyl-based CGCs that exhibit the highest activity and produce copolymers with the highest molecular weight within this family of catalysts. Phenanthrenyl-based CGCs were found to be outstanding catalysts for the effective production of high styrene content ethylene-styrene copolymers under industrially relevant conditions. In contrast to CGC ligands, imino-amido-type ligands are bidentate and monoionic, leading to the use of trialkyl group IV precatalysts. The thermal instability of imino-amido complexes was addressed by the development of imino-enamido and amidoquinoline complexes, which are not only thermally very robust, but also produce copolymers with higher molecular weights, and exhibit improved α-olefin incorporation. Imido-amido and imino-enamido catalysts undergo facile chain transfer reactions with metal alkyls, as evidenced by a sharp decrease in polymer molecular weight when the

  10. Molecular metal-Oxo catalysts for generating hydrogen from water

    SciTech Connect

    Long, Jeffrey R; Chang, Christopher J; Karunadasa, Hemamala I

    2015-02-24

    A composition of matter suitable for the generation of hydrogen from water is described, the positively charged cation of the composition having the general formula [(PY5W.sub.2)MO].sup.2+, wherein PY5W.sub.2 is (NC.sub.5XYZ)(NC.sub.5H.sub.4).sub.4C.sub.2W.sub.2, M is a transition metal, and W, X, Y, and Z can be H, R, a halide, CF.sub.3, or SiR.sub.3, where R can be an alkyl or aryl group. The two accompanying counter anions, in one embodiment, can be selected from the following Cl.sup.-, I.sup.-, PF.sub.6.sup.-, and CF.sub.3SO.sub.3.sup.-. In embodiments of the invention, water, such as tap water containing electrolyte or straight sea water can be subject to an electric potential of between 1.0 V and 1.4 V relative to the standard hydrogen electrode, which at pH 7 corresponds to an overpotential of 0.6 to 1.0 V, with the result being, among other things, the generation of hydrogen with an optimal turnover frequency of ca. 1.5 million mol H.sub.2/mol catalyst per h.

  11. Molecular molybdenum persulfide and related catalysts for generating hydrogen from water

    DOEpatents

    Long, Jeffrey R.; Chang, Christopher J.; Karunadasa, Hemamala I.; Majda, Marcin

    2016-04-19

    New metal persulfido compositions of matter are described. In one embodiment the metal is molybdenum and the metal persulfido complex mimics the structure and function of the triangular active edge site fragments of MoS.sub.2, a material that is the current industry standard for petroleum hydro desulfurization, as well as a promising low-cost alternative to platinum for electrocatalytic hydrogen production. This molecular [(PY5W.sub.2)MoS.sub.2].sup.x+ containing catalyst is capable of generating hydrogen from acidic-buffered water or even seawater at very low overpotentials at a turnover frequency rate in excess of 500 moles H.sub.2 per mole catalyst per second, with a turnover number (over a 20 hour period) of at least 19,000,000 moles H.sub.2 per mole of catalyst.

  12. Selective oxidation of cyclohexane on a novel catalyst Mg-Cu/SBA-15 by molecular oxygen.

    PubMed

    Duan, Xiaogang; Liu, Weimin; Yue, Lumin; Fu, Wei; Ha, Minh Ngoc; Li, Jun; Lu, Guanzhong

    2015-10-21

    The novel catalysts xMg-2.3Cu/SBA-15 with copper and magnesium oxide co-supported on mesoporous silica were synthesized by an impregnation method. The newly synthesized catalysts were characterized using a series of techniques such as BET, XRD, H2-TPR, UV-vis, XPS, EDS and TEM. The catalytic performance was evaluated by using selective oxidation of cyclohexane with molecular oxygen as the oxidant in a solvent free system. The incorporation of magnesium improved the dispersion of copper oxide and prevented the deep oxidation of cyclohexanol and cyclohexanone. The selectivity of K/A oil was up to 99.3% with 12% conversion of cyclohexane over the 1.2Mg-2.3Cu/SBA-15 catalyst. To our knowledge, this is the best result for the heterogeneous oxidation of cyclohexane by O2. PMID:26388454

  13. Hydrophobic Catalysts For Removal Of NOx From Flue Gases

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  14. Visible-light-driven selective oxidation of benzyl alcohol and thioanisole by molecular ruthenium catalyst modified hematite.

    PubMed

    Bai, Lichen; Li, Fei; Wang, Yong; Li, Hua; Jiang, Xiaojuan; Sun, Licheng

    2016-08-11

    Molecular ruthenium catalysts were found to selectively catalyze the oxidation of thioanisole to sulfoxide with a yield up to 100% in the presence of visible light and sacrificial reagents when they were anchored onto hematite powder. The composite photocatalysts also showed about 5 times higher efficiencies in benzyl alcohol oxidation than the system composed of dispersed molecular catalysts and hematite particles in aqueous solution. A photoelectrochemical cell based on a molecular catalyst modified hematite photoanode was further fabricated, which exhibited high activity towards the oxidation of organic substrates. PMID:27411498

  15. Integration of molecular and enzymatic catalysts on graphene for biomimetic generation of antithrombotic species

    NASA Astrophysics Data System (ADS)

    Xue, Teng; Peng, Bo; Xue, Min; Zhong, Xing; Chiu, Chin-Yi; Yang, Si; Qu, Yongquan; Ruan, Lingyan; Jiang, Shan; Dubin, Sergey; Kaner, Richard B.; Zink, Jeffrey I.; Meyerhoff, Mark E.; Duan, Xiangfeng; Huang, Yu

    2014-02-01

    The integration of multiple synergistic catalytic systems can enable the creation of biocompatible enzymatic mimics for cascading reactions under physiologically relevant conditions. Here we report the design of a graphene-haemin-glucose oxidase conjugate as a tandem catalyst, in which graphene functions as a unique support to integrate molecular catalyst haemin and enzymatic catalyst glucose oxidase for biomimetic generation of antithrombotic species. Monomeric haemin can be conjugated with graphene through π-π interactions to function as an effective catalyst for the oxidation of endogenous L-arginine by hydrogen peroxide. Furthermore, glucose oxidase can be covalently linked onto graphene for local generation of hydrogen peroxide through the oxidation of blood glucose. Thus, the integrated graphene-haemin-glucose oxidase catalysts can readily enable the continuous generation of nitroxyl, an antithrombotic species, from physiologically abundant glucose and L-arginine. Finally, we demonstrate that the conjugates can be embedded within polyurethane to create a long-lasting antithrombotic coating for blood-contacting biomedical devices.

  16. Local Platinum Environments in a Solid Analogue of the Molecular Periana Catalyst

    DOE PAGESBeta

    Soorholtz, Mario; Jones, Louis C.; Samuelis, Dominik; Weidenthaler, Claudia; White, Robin J.; Titirici, Maria-Magdalena; Cullen, David A.; Zimmermann, Tobias; Antonietti, Markus; Maier, Joachim; et al

    2016-02-16

    Combining advantages of homogeneous and heterogeneous catalysis by incorporating active species on a solid support is often an effective strategy for improving overall catalyst performance, although the influences of the support are generally challenging to establish, especially at a molecular level. In this paper, we report the local compositions, and structures of platinum species incorporated into covalent triazine framework (Pt-CTF) materials, a solid analogue of the molecular Periana catalyst, Pt(bpym)Cl2, both of which are active for the selective oxidation of methane in the presence of concentrated sulfuric acid. By using a combination of solid-state 195Pt nuclear magnetic resonance (NMR) spectroscopy,more » aberration-corrected scanning transmission electron microscopy (AC-STEM), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS), important similarities and differences are observed between the Pt-CTF and Periana catalysts, which are likely related to their respective macroscopic reaction properties. In particular, wide-line solid-state 195Pt NMR spectra enable direct measurement, identification, and quantification of distinct platinum species in as-synthesized and used Pt-CTF catalysts. The results indicate that locally ordered and disordered Pt sites are present in as-synthesized Pt-CTF, with the former being similar to one of the two crystallographically distinct Pt sites in crystalline Pt(bpym)Cl2. A distribution of relatively disordered Pt moieties is also present in the used catalyst, among which are the principal active sites. Similarly XAS shows good agreement between the measured data of Pt-CTF and a theoretical model based on Pt(bpym)Cl2. Analyses of the absorption spectra of Pt-CTF used for methane oxidation suggests ligand exchange, as predicted for the molecular catalyst. XPS analyses of Pt(bpym)Cl2, Pt-CTF, as well as the unmodified ligands, further corroborate platinum coordination by pyridinic N atoms

  17. Reactivity and Selectivity of Heterogenized Homogeneous Catalysts: Insights from Molecular Simulations

    NASA Astrophysics Data System (ADS)

    Malek, Kourosh; van Santen, Rutger A.

    Immobilized metal complexes on nanoporous materials have recently been proposed as a novel class of heterogeneous enantioselective catalyst for epoxidation of unfunctionalized olefins as well as hydrogenation, alkylation, and nitroaldol reactions. The porous hosted materials affect catalytic performance due to a cooperative interaction among the nanoporous solid, immobilizing linker, and metal complex asymmetry. The effects of mesoporous materials and immobilizing agents on chiral catalysis are not well understood, however, the catalysts confined in nanopores show comparable or even higher conversions and enantioselectivity compared to their homogeneous counterparts. This chapter highlights major scientific problems for fundamental understanding and design of heterogenized homogeneous catalysts. It describes in detail the pivotal role of a sound framework in physical theory and molecular modeling in systematic efforts towards better materials and catalytic performance optimization. The common threads of the various topics addressed is the wide range of scales that has to be considered in establishing relations between structure, physicochemical properties, and catalytic performance. Physical theory and modeling employ a variety of methods, encompassing ab-initio calculations, molecular simulations, and the continuum model of transport and reaction in nanoporous materials. We particularly describe how molecular simulations can be used to investigate the origin of enantioselectivity of an anchored metal complex in nanoporous materials. These studies provide new insights into the steric effects that relate to choices of substrate and linker and to the interplay with mesopore confinement. We also bring detailed example of employing molecular simulations to unravel the catalytic properties of metallomacrocyclics for the electrochemical reduction of molecular oxygen in aqueous media. We rationalize the importance of immobilization and show how it relates to the steric

  18. Covalent Immobilization of a Molecular Catalyst on Cu2O Photocathodes for CO2 Reduction.

    PubMed

    Schreier, Marcel; Luo, Jingshan; Gao, Peng; Moehl, Thomas; Mayer, Matthew T; Grätzel, Michael

    2016-02-17

    Sunlight-driven CO2 reduction is a promising way to close the anthropogenic carbon cycle. Integrating light harvester and electrocatalyst functions into a single photoelectrode, which converts solar energy and CO2 directly into reduced carbon species, is under extensive investigation. The immobilization of rhenium-containing CO2 reduction catalysts on the surface of a protected Cu2O-based photocathode allows for the design of a photofunctional unit combining the advantages of molecular catalysts with inorganic photoabsorbers. To achieve large current densities, a nanostructured TiO2 scaffold, processed at low temperature, was deposited on the surface of protected Cu2O photocathodes. This led to a 40-fold enhancement of the catalytic photocurrent as compared to planar devices, resulting in the sunlight-driven evolution of CO at large current densities and with high selectivity. Potentiodynamic and spectroelectrochemical measurements point toward a similar mechanism for the catalyst in the bound and unbound form, whereas no significant production of CO was observed from the scaffold in the absence of a molecular catalyst. PMID:26804626

  19. Turnover of Soluble Proteins in the Wheat Sieve Tube

    PubMed Central

    Fisher, Donald B.; Wu, Yujia; Ku, Maurice S. B.

    1992-01-01

    Although the enucleate conducting cells of the phloem are incapable of protein synthesis, phloem exudates characteristically contain low concentrations of soluble proteins. The role of these proteins and their movement into and out of the sieve tubes poses important questions for phloem physiology and for cell-to-cell protein movement via plasmodesmata. The occurrence of protein turnover in sieve tubes was investigated by [35S]methionine labeling and by the use of aphid stylets to sample the sieve tube contents at three points along a source-to-sink pathway (flag leaf to grains) in wheat plants (Triticum aestivum L.). Protein concentration and composition were similar at all sampling sites. The kinetics of 35S-labeling of protein suggested a basically source-to-sink pattern of movement for many proteins. However, an appreciable amount of protein synthesis and, presumably, removal also occurred along the path. This movement appeared to be protein specific and not based on passive molecular sieving. The results have important implications for the transport capacities of plasmodesmata between sieve tubes and companion cells. The observations considerably expand the possible basis for ongoing sieve tube-companion cell interactions and, perhaps, interaction between sources and sinks. Images Figure 2 Figure 3 Figure 4 Figure 5 Figure 8 Figure 10 Figure 11 Figure 12 PMID:16653142

  20. Photoswitching a molecular catalyst to regulate CO2 hydrogenation.

    PubMed

    Priyadarshani, Nilusha; Ginovska, Bojana; Bays, J Timothy; Linehan, John C; Shaw, Wendy J

    2015-09-01

    Inspired by nature's ability to regulate catalysis using physiological stimuli, azobenzene was incorporated into Rh(bis)diphosphine CO2 hydrogenation catalysts to photoinitiate structural changes to modulate the resulting catalytic activity. The rhodium bound diphosphine ligands (P(Ph2)-CH2-N(R)-CH2-P(Ph2)) contain the terminal amine of a non-natural amino acid, with the R-group being either β-alanine (β-Ala) or γ-aminobutyric acid (GABA). For both β-Ala and GABA containing complexes, the carboxylic acids of the amino acids were coupled to the amines of diaminoazobenzene, creating a complex consisting of a rhodium bound to a photo-responsive tetradentate ligand. The photo-induced cis-trans isomerization of the azobenzene-containing complexes imposes structural changes on these complexes, as evidenced by NMR studies. We found that the CO2 hydrogenation activity for the β-Ala bound rhodium complex is 40% faster at 27 °C with the light on, i.e. azobenzene in the cis-conformation (TOF = 16 s(-1)) than when the complex was in the dark and the azobenzene in the trans-conformation (TOF = 11 s(-1)). In contrast the γ-aminobutyric acid containing rhodium complex has the same rate (TOF ∼17 s(-1)) with the azobenzene in either the cis or the trans-conformation at 27 °C. The corresponding (bis)diphosphine complexes without the attached azobenzene were also prepared, characterized, and catalytically tested for comparison, and have TOF's of 30 s(-1). Computational studies were undertaken to evaluate if the difference in rate between the cis- and trans-azobenzene isomers for the β-Ala bound rhodium complex were due to structural differences. These computational investigations revealed major structural changes between all cis- and trans-azobenzene structures, but only minor structural changes that would be unique to the β-Ala bound rhodium complex. We postulate that the different rates between the cis- and trans-azobenzene β-Ala bound containing rhodium complexes are

  1. Immobilization of a Molecular Ruthenium Catalyst on Hematite Nanorod Arrays for Water Oxidation with Stable Photocurrent.

    PubMed

    Fan, Ke; Li, Fusheng; Wang, Lei; Daniel, Quentin; Chen, Hong; Gabrielsson, Erik; Sun, Junliang; Sun, Licheng

    2015-10-12

    Photoelectrochemical (PEC) cells for light-driven water splitting are prepared using hematite nanorod arrays on conductive glass as the photoanode. These devices improve the photocurrent of the hematite-based photoanode for water splitting, owing to fewer surface traps and decreased electron recombination resulting from the one-dimensional structure. By employing a molecular ruthenium co-catalyst, which contains a strong 2,6-pyridine-dicarboxylic acid anchoring group at the hematite photoanode, the photocurrent of the PEC cell is enhanced with high stability for over 10 000 s in a 1 m KOH solution. This approach can pave a route for combining one-dimensional nanomaterials and molecular catalysts to split water with high efficiency and stability. PMID:26315677

  2. Immobilization of a molecular catalyst on carbon nanotubes for highly efficient electro-catalytic water oxidation.

    PubMed

    Li, Fusheng; Li, Lin; Tong, Lianpeng; Daniel, Quentin; Göthelid, Mats; Sun, Licheng

    2014-11-21

    Electrochemically driven water oxidation has been performed using a molecular water oxidation catalyst immobilized on hybrid carbon nanotubes and nano-material electrodes. A high turnover frequency (TOF) of 7.6 s(-1) together with a high catalytic current density of 2.2 mA cm(-2) was successfully obtained at an overpotential of 480 mV after 1 h of bulk electrolysis. PMID:25265253

  3. Carbogenic molecular sieves for reaction and separation by design: A novel approach to shape selective super base, super acid and catalytic membranes. Final report

    SciTech Connect

    Foley, Henry C.

    2002-03-18

    This report details the findings of three years of research plus one year of a no-cost extension. Primary results are the work with supported nanoporous carbon membranes for separation and reaction as well as with cesium-nanoporous carbon catalysts. The work resulted in 17 plus 2 papers (2 are in progress) and partial or full support for five Ph.D. students. Two patents were filed based on this research.

  4. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis

    SciTech Connect

    Osseo-Asare, K.; Boakye, E.; Vaidyanathan, N.; Radovic, L.R.

    1991-10-01

    The objective of this project is to pursue the development of highly dispersed and inexpensive catalysts for improved coal solubilization and upgrading of coal liquids. A novel study of the synthesis of liquefaction catalysts of nanometer size will be carried out. It is based on the molecular design of reverse micelles (microemulsions). These surfactant-stabilized, metalbearing microdrops offer unique opportunities for synthesizing very small particles by providing a cage-like effect that limits particle nucleation, growth and agglomeration. The emphasis will be on iron- and molybdenum-based catalysts, but the techniques to be developed should also be generally applicable. The size of these very small and monodispersed particles will be accurately determined both separately and after in situ and ex situ coal impregnation. The as-prepared nanoparticles as well as the catalyst-impregnated coal or char matrix will be characterized using the following techniques: dynamic light scattering, x-ray diffraction, x-ray photoelectron spectroscopy, scanning and/or transmission electron microscopy, and selective chemisorption.

  5. Distinguishing molecular environments in supported Pt catalysts and their influences on activity and selectivity

    NASA Astrophysics Data System (ADS)

    Jones, Louis Chin

    This thesis entails the synthesis, automated catalytic testing, and in situ molecular characterization of supported Pt and Pt-alloy nanoparticle (NP) catalysts, with emphasis on how to assess the molecular distributions of Pt environments that are affecting overall catalytic activity and selectivity. We have taken the approach of (a) manipulating nucleation and growth of NPs using oxide supports, surfactants, and inorganic complexes to create Pt NPs with uniform size, shape, and composition, (b) automating batch and continuous flow catalytic reaction tests, and (c) characterizing the molecular environments of Pt surfaces using in situ infrared (IR) spectroscopy and solid-state 195Pt NMR. The following will highlight the synthesis and characterization of Ag-doped Pt NPs and their influence on C 2H2 hydrogenation selectivity, and the implementation of advanced solid-state 195Pt NMR techniques to distinguish how distributions of molecular Pt environments vary with nanoparticle size, support, and surface composition.

  6. Modified silica-based heterogeneous catalysts for etherification of glycerol

    NASA Astrophysics Data System (ADS)

    Gholami, Zahra; Abdullah, Ahmad Zuhairi; Gholami, Fatemeh; Vakili, Mohammadtaghi

    2015-07-01

    The advent of mesoporous silicas such as MCM-41 has provided new opportunities for research into supported metal catalysis. The loading of metals into framework structures and particularly into the pores of porous molecular sieves, has long been of interest because of their potential catalytic activity. Stable heterogeneous mesoporous basic catalysts were synthesized by wet impregnation of MCM-41 with calcium nitrate and lanthanum nitrate. The surface and structural properties of the prepared catalysts were characterized using BET surface analysis, SEM and TEM. MCM-41 and modified MCM-41 were used in the solventless etherification of glycerol to produce diglycerol as the desired product. The reaction was performed at 250 °C for 8 h, and catalyst activity was evaluated. Catalytic etherification over the 20%Ca1.6La0.6/MCM-41 catalyst resulted in the highest glycerol conversion of 91% and diglycerol yield of 43%.

  7. Modified silica-based heterogeneous catalysts for etherification of glycerol

    SciTech Connect

    Gholami, Zahra; Abdullah, Ahmad Zuhairi Gholami, Fatemeh; Vakili, Mohammadtaghi

    2015-07-22

    The advent of mesoporous silicas such as MCM-41 has provided new opportunities for research into supported metal catalysis. The loading of metals into framework structures and particularly into the pores of porous molecular sieves, has long been of interest because of their potential catalytic activity. Stable heterogeneous mesoporous basic catalysts were synthesized by wet impregnation of MCM-41 with calcium nitrate and lanthanum nitrate. The surface and structural properties of the prepared catalysts were characterized using BET surface analysis, SEM and TEM. MCM-41 and modified MCM-41 were used in the solventless etherification of glycerol to produce diglycerol as the desired product. The reaction was performed at 250 °C for 8 h, and catalyst activity was evaluated. Catalytic etherification over the 20%Ca{sub 1.6}La{sub 0.6}/MCM-41 catalyst resulted in the highest glycerol conversion of 91% and diglycerol yield of 43%.

  8. Enhanced Photochemical Hydrogen Production by a Molecular Diiron Catalyst Incorporated into a Metal-Organic Framework

    SciTech Connect

    Pullen, Sonja; Fei, Honghan; Orthaber, Andreas; Cohen, Seth M.; Ott, Sascha

    2013-12-04

    A molecular proton reduction catalyst [FeFe](dcbdt)(CO)6 (1, dcbdt = 1,4-dicarboxylbenzene-2,3-dithiolate) with structural similarities to [FeFe]-hydrogenase active sites has been incorporated into a highly robust Zr(IV)-based metal–organic framework (MOF) by postsynthetic exchange (PSE). The PSE protocol is crucial as direct solvothermal synthesis fails to produce the functionalized MOF. The molecular integrity of the organometallic site within the MOF is demonstrated by a variety of techniques, including X-ray absorption spectroscopy. In conjunction with [Ru(bpy)3]2+ as a photosensitizer and ascorbate as an electron donor, MOF-[FeFe](dcbdt)(CO)6 catalyzes photochemical hydrogen evolution in water at pH 5. The immobilized catalyst shows substantially improved initial rates and overall hydrogen production when compared to a reference system of complex 1 in solution. Improved catalytic performance is ascribed to structural stabilization of the complex when incorporated in the MOF as well as the protection of reduced catalysts 1 and 12– from undesirable charge recombination with oxidized ascorbate.

  9. Improved Fischer-Tropsch Synthesis catalysts for indirect coal liquefaction

    SciTech Connect

    Tong, G.T.; Wilson, R.B.; McCarty, J.G.

    1987-01-01

    The monoruthenium cluster catalyst with a molecular sieve support and the tetraruthenium cluster catalyst with a sodium-Y zeolite support have been examined for Fischer-Tropsch Synthesis (FTS) performance at high pressure (6.9 MPa) in a slurry reactor and compared with conventional ruthenium with an alumina support and clean fused iron catalysts. Of the four catalysts tested, only the conventional ruthenium catalyst exhibited a chain growth factor of 0.88 and a methane selectivity of 6.6%, which are typical of slurry reactor results reported for iron catalysts under similar conditions. The other three catalysts tested showed low chain growth factors (ranging from 0.44 to 0.57) and high methane selectivity (ranging from 20 to 32%). A cobalt catalyst with approximately 50% sulfur coverage was prepared and tested for FTS activity and selectivity at ambient pressure and compared with the FTS performance of the clean and fully sulfided cobalt catalysts. The introduction of sulfur caused a decrease in methane selectivity and an increase in olefin selectivity with only a moderate decline in activity. 1 ref., 2 tabs.

  10. Bio-Inspired Molecular Catalysts for Hydrogen Oxidation and Hydrogen Production

    SciTech Connect

    Ho, Ming-Hsun; Chen, Shentan; Rousseau, Roger J.; Dupuis, Michel; Bullock, R. Morris; Raugei, Simone

    2013-06-03

    Recent advances in Ni-based bio-inspired catalysts obtained in the Center for Molecular Electrocatalysis, an Energy Frontier Research Center (EFRC) at the Pacific Northwest National Laboratory, demonstrated the possibility of cleaving H2 or generating H2 heterolytically with turnover frequencies comparable or superior to those of hydrogenase enzymes. In these catalysts the transformation between H2 and protons proceeds via an interplay between proton, hydride and electron transfer steps and involves the interaction of a dihydrogen molecule with both a Ni(II) center and with pendant amine bases incorporated in a six-membered ring, which act as proton relays. These catalytic platforms are well designed in that when protons are correctly positioned (endo) toward the Raugei-ACS-Books.docxPrinted 12/18/12 2 metal center, catalysis proceeds at very high rates. We will show that the proton removal (for H2 oxidation) and proton delivery (for H2 production) are often the rate determining steps. Furthermore, the presence of multiple protonation sites gives rise to reaction intermediates with protons not correctly positioned (exo relative to the metal center). These isomers are easily accessible kinetically and are detrimental to catalysis because of the slow isomerization processes necessary to convert them to the catalytically competent endo isomers. In this chapter we will review the major findings of our computational investigation on the role of proton relays for H2 chemistry and provide guidelines for the design of new catalysts. This research was carried out in 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 is operated for the U.S. Department of Energy by Battelle. Computational resources were provided at W. R. Wiley Environmental Molecular Science Laboratory (EMSL), a Raugei-Bio-Inspired Molecular-Catalysts-for-Hydrogen- Oxidation

  11. Itegrated Test and Evaluation of a 4-Bed Molecular Sieve (4BMS) Carbon Dioxide Removtal System (CDRA), Mechanical Compressor Engineering Development Unit (EDU), and Sabitier Engineering Development Unit (EDU)

    NASA Technical Reports Server (NTRS)

    Knox, James C.; Campbell, Melissa; Murdoch, Karen; Miller, Lee A.; Jeng, Frank

    2005-01-01

    Currently on the International Space Station s (ISS) U.S. Segment, carbon dioxide (CO2) scrubbed from the cabin by a 4-Bed Molecular Sieve (4BMS) Carbon Dioxide Removal Assembly (CDRA) is vented overboard as a waste product. Likewise, the product hydrogen (H2) that will be generated by the Oxygen Generation Assembly (OGA) planned for installation will also be vented. A flight experiment has been proposed that will take the waste CO2 removed from the cabin, and via the catalytic Sabatier process, reduce it with waste H2 to generate water and methane. The water produced may provide cost and logistics savings for ISS by reducing the amount of water periodically re-supplied to orbit. To make this concept viable, a mechanical piston compressor and accumulator were developed for collecting and storing the CO2 from the CDRA. The compressor, accumulator and Sabatier system would be packaged together as one unit and referred to as the Carbon Dioxide Reduction Assembly (CRA). Testing was required to evaluate the performance of a 4BMS CDRA, compressor, accumulator, and Sabatier performance along with their operating rules when integrated together. This had been numerically modeled and simulated; however, testing was necessary to verify the results from the engineering analyses. Testing also allowed a better understanding of the practical inefficiencies and control issues involved in a fully integrated system versus the theoretical ideals in the model. This paper presents and discusses the results of an integrated engineering development unit test.

  12. Supported Molecular Iridium Catalysts: Resolving Effects of Metal Nuclearity and Supports as Ligands

    SciTech Connect

    Lu, Jing; Serna, Pedro; Aydin, Cerem; Browning, Nigel D.; Gates, Bruce C.

    2012-02-07

    The performance of a supported catalyst is influenced by the size and structure of the metal species, the ligands bonded to the metal, and the support. Resolution of these effects has been lacking because of the lack of investigations of catalysts with uniform and systematically varied catalytic sites. We now demonstrate that the performance for ethene hydrogenation of isostructural iridium species on supports with contrasting properties as ligands (electron-donating MgO and electron-withdrawing HY zeolite) can be elucidated on the basis of molecular concepts. Spectra of the working catalysts show that the catalytic reaction rate is determined by the dissociation of H{sub 2} when the iridium, either as mono- or tetra-nuclear species, is supported on MgO and is not when the support is the zeolite. The neighboring iridium sites in clusters are crucial for activation of both H{sub 2} and C{sub 2}H{sub 4} when the support is MgO but not when it is the zeolite, because the electron-withdrawing properties of the zeolite support enable even single site-isolated Ir atoms to bond to both C{sub 2}H{sub 4} and H{sub 2} and facilitate the catalysis.

  13. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis. Technical progress report, October--December 1991

    SciTech Connect

    Osseo-Asare, K.; Boakye, E.; Vaidyanathan, N.; Radovic, L.R.

    1992-04-01

    The objective of this project is to pursue the development of highly dispersed and inexpensive catalysts for improved coal solubilization and upgrading of coal liquids. A novel study of the synthesis of liquefaction catalysts of nanometer size will be carried out. It is based on the molecular design of reverse micelles (microemulsions). These surfactant-stabilized, metal-bearing microdrops offer unique opportunities for synthesizing very small particles by providing a cage-like effect that limits particle nucleation, growth and agglomeration. The emphasis will be on iron- and molybdenum-based catalysts, but the techniques to be developed should also be generally applicable. (VC)

  14. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis. Technical progress report, April--June 1991

    SciTech Connect

    Osseo-Asare, K.; Radovic, L.R.

    1991-07-01

    The objective of this project is to pursue the development of highly dispersed and inexpensive catalysts for improved coal solubilization and upgrading of coal liquids. A novel study of the synthesis of liquefaction catalysts of nanometer size will be carried out. It is based on the molecular design of reverse micelles (microemulsions). These surfactant-stabilized, metal-bearing microdrops offer unique opportunities for synthesizing very small particles by providing a cage-like effect that limits particle nucleation, growth and agglomeration. The emphasis will be on iron- and molybdenum-based catalysts, but the techniques to be developed should also be generally applicable. (VC)

  15. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis. Technical progress report, October--December 1990

    SciTech Connect

    Osseo-Asare, K.; Radovic, L.R.

    1991-02-01

    The objective of this project is to pursue the development of highly dispersed and inexpensive catalysts for improved coal solubilization and upgrading of coal liquids. A novel study of the synthesis of liquefaction catalysts of nanometer size will be carried out. It is based on the molecular design of reverse micelles (microemulsions). These surfactant-stabilized, metal-bearing microdrops offer unique opportunities for synthesizing very small particles by providing a cage-like effects that limits particle nucleation, growth and agglomeration. The emphasis will be on iron- and molybdenum-based catalysts, but the techniques to be developed should also be generally applicable.

  16. Highly efficient bioinspired molecular Ru water oxidation catalysts with negatively charged backbone ligands.

    PubMed

    Duan, Lele; Wang, Lei; Li, Fusheng; Li, Fei; Sun, Licheng

    2015-07-21

    -coordinate Ru(IV) species was isolated as a reaction intermediate, shedding light on the reaction mechanisms of Ru-catalyzed water oxidation chemistry. Auxiliary ligands have dramatic effects on the water oxidation catalysis in terms of the reactivity and the reaction mechanism. For instance, Ru-bda (H2bda = 2,2'-bipyridine-6,6'-dicarboxylic acid) water oxidation catalysts catalyze Ce(IV)-driven water oxidation extremely fast via the radical coupling of two Ru(V)═O species, while Ru-pda (H2pda = 1,10-phenanthroline-2,9-dicarboxylic acid) water oxidation catalysts catalyze the same reaction slowly via water nucleophilic attack on a Ru(V)═O species. With a number of active Ru catalysts in hands, light driven water oxidation was accomplished using catalysts with low catalytic onset potentials. The structures of molecular catalysts could be readily tailored to introduce additional functional groups, which favors the fabrication of state-of-the-art Ru-based water oxidation devices, such as electrochemical water oxidation anodes and photo-electrochemical anodes. The development of efficient water oxidation catalysts has led to a step forward in the sustainable energy system. PMID:26131964

  17. Cadherin selectivity filter regulates endothelial sieving properties

    PubMed Central

    Quadri, Sadiqa K.; Sun, Li; Islam, Mohammad Naimul; Shapiro, Lawrence; Bhattacharya, Jahar

    2013-01-01

    The molecular basis of endothelial protein sieving, the critical vascular barrier function that restricts flow of large plasma proteins into tissues while allowing small molecules and water to pass, is not understood. Here, we address this issue using a novel assay to detect macromolecular penetrance at microdomains of endothelial adherens junctions. Adherens junctions, as detected by cadherin-GFP expression, were distributed in the cell perimeter as high- or low-density segments. Low but not high-density segments permitted penetrance of a 70-kDa fluorescent dextran, a molecule of equivalent size to albumin. Expression of a cadherin mutant that abrogates strand–swap adhesive binding in the cadherin EC1 ectodomain, or alternatively of an α-actinin-1 mutant that inhibits F-actin bundling, increased both cadherin mobility and 70 kDa dextran penetrance at high-density segments. These findings suggest that adhesive interactions in the cadherin EC1 domain, which underlie adherens junction structure, are critical determinants of endothelial macromolecular sieving. PMID:23033075

  18. Molecular dissociation in the presence of catalysts: interpreting bond breaking as a quantum dynamical phase transition

    NASA Astrophysics Data System (ADS)

    Ruderman, A.; Dente, A. D.; Santos, E.; Pastawski, H. M.

    2015-08-01

    In this work we show that molecular chemical bond formation and dissociation in the presence of the d-band of a metal catalyst can be described as a quantum dynamical phase transition (QDPT). This agrees with DFT calculations that predict sudden jumps in some observables as the molecule breaks. According to our model this phenomenon emerges because the catalyst provides for a non-Hermitian Hamiltonian. We show that when the molecule approaches the surface, as occurs in the Heyrovsky reaction of H2, the bonding H2 orbital has a smooth crossover into a bonding molecular orbital built with the closest H orbital and the surface metal d-states. The same occurs for the antibonding state. Meanwhile, two resonances appear within the continuous spectrum of the d-band, which are associated with bonding and antibonding orbitals between the furthest H atom and the d-states at the second metallic layer. These move toward the band center, where they collapse into a pure metallic resonance and an almost isolated H orbital. This phenomenon constitutes a striking example of the non-trivial physics enabled when one deals with non-Hermitian Hamiltonian beyond the usual wide band approximation.

  19. Dye-sensitised semiconductors modified with molecular catalysts for light-driven H2 production.

    PubMed

    Willkomm, Janina; Orchard, Katherine L; Reynal, Anna; Pastor, Ernest; Durrant, James R; Reisner, Erwin

    2016-01-01

    The development of synthetic systems for the conversion of solar energy into chemical fuels is a research goal that continues to attract growing interest owing to its potential to provide renewable and storable energy in the form of a 'solar fuel'. Dye-sensitised photocatalysis (DSP) with molecular catalysts is a relatively new approach to convert sunlight into a fuel such as H2 and is based on the self-assembly of a molecular dye and electrocatalyst on a semiconductor nanoparticle. DSP systems combine advantages of both homogenous and heterogeneous photocatalysis, with the molecular components providing an excellent platform for tuning activity and understanding performance at defined catalytic sites, whereas the semiconductor bridge ensures favourable multi-electron transfer kinetics between the dye and the fuel-forming electrocatalyst. In this tutorial review, strategies and challenges for the assembly of functional molecular DSP systems and experimental techniques for their evaluation are explained. Current understanding of the factors governing electron transfer across inorganic-molecular interfaces is described and future directions and challenges for this field are outlined. PMID:26584204

  20. Multiprocessing the Sieve of Eratosthenes

    SciTech Connect

    Bokhari, S.H.

    1987-04-01

    More than two thousand years ago, Eratosthenes of Cyrene described a procedure for finding all prime numbers in a given range. This straightforward algorithm, known as the Sieve of Eratosthenes, is to this day the only procedure for finding prime numbers. In recent years it has been of interest to computer scientists and engineers because it serves as a convenient benchmark against which to measure some aspects of a computer's performance. Specifically, the Sieve tests the power of a machine (or of a compiler) to access a very large array in memory rapidly and repeatedly. This power is clearly influenced by memory access time, the speed at which indexing is done, and the overhead of looping. The parallel version of the Sieve is very useful as a test of some of the capabilities of a parallel machine. The parallel algorithm is straightforward, and so is the process for checking the final results. However, the efficient implementation of the algorithm on a real parallel machine, especially in the dynamic load-balancing case, requires thoughtful design.

  1. A molecular ruthenium catalyst with water-oxidation activity comparable to that of photosystem II

    NASA Astrophysics Data System (ADS)

    Duan, Lele; Bozoglian, Fernando; Mandal, Sukanta; Stewart, Beverly; Privalov, Timofei; Llobet, Antoni; Sun, Licheng

    2012-05-01

    Across chemical disciplines, an interest in developing artificial water splitting to O2 and H2, driven by sunlight, has been motivated by the need for practical and environmentally friendly power generation without the consumption of fossil fuels. The central issue in light-driven water splitting is the efficiency of the water oxidation, which in the best-known catalysts falls short of the desired level by approximately two orders of magnitude. Here, we show that it is possible to close that ‘two orders of magnitude’ gap with a rationally designed molecular catalyst [Ru(bda)(isoq)2] (H2bda = 2,2‧-bipyridine-6,6‧-dicarboxylic acid; isoq = isoquinoline). This speeds up the water oxidation to an unprecedentedly high reaction rate with a turnover frequency of >300 s-1. This value is, for the first time, moderately comparable with the reaction rate of 100-400 s-1 of the oxygen-evolving complex of photosystem II in vivo.

  2. Efficient and selective molecular catalyst for the CO2-to-CO electrochemical conversion in water

    PubMed Central

    Costentin, Cyrille; Robert, Marc; Savéant, Jean-Michel; Tatin, Arnaud

    2015-01-01

    Substitution of the four paraphenyl hydrogens of iron tetraphenylporphyrin by trimethylammonio groups provides a water-soluble molecule able to catalyze the electrochemical conversion of carbon dioxide into carbon monoxide. The reaction, performed in pH-neutral water, forms quasi-exclusively carbon monoxide with very little production of hydrogen, despite partial equilibration of CO2 with carbonic acid—a low pKa acid. This selective molecular catalyst is endowed with a good stability and a high turnover frequency. On this basis, prescribed composition of CO–H2 mixtures can be obtained by adjusting the pH of the solution, optionally adding an electroinactive buffer. The development of these strategies will be greatly facilitated by the fact that one operates in water. The same applies for the association of the cathode compartment with a proton-producing anode by means of a suitable separator. PMID:26038542

  3. Molecular dissociation in presence of a catalyst: II. The bond breaking role of the transition from virtual to localized states

    NASA Astrophysics Data System (ADS)

    Ruderman, A.; Dente, A. D.; Santos, E.; Pastawski, H. M.

    2016-08-01

    We address a molecular dissociation mechanism that is known to occur when a H2 molecule approaches a catalyst with its molecular axis parallel to the surface. It is found that molecular dissociation is a form of quantum dynamical phase transition associated to an analytic discontinuity of quite unusual nature: the molecule is destabilized by the transition from non-physical virtual states into actual localized states. Current description complements our recent results for a molecule approaching the catalyst with its molecular axis perpendicular to the surface (Ruderman et al 2015 J. Phys.: Condens. Matter 27 315501). Also, such a description can be seen as a further successful implementation of a non-Hermitian Hamiltonian in a well defined model.

  4. Clean Donor Oxidation Enhances the H2 Evolution Activity of a Carbon Quantum Dot-Molecular Catalyst Photosystem.

    PubMed

    Martindale, Benjamin C M; Joliat, Evelyne; Bachmann, Cyril; Alberto, Roger; Reisner, Erwin

    2016-08-01

    Carbon quantum dots (CQDs) are new-generation light absorbers for photocatalytic H2 evolution in aqueous solution, but the performance of CQD-molecular catalyst systems is currently limited by the decomposition of the molecular component. Clean oxidation of the electron donor by donor recycling prevents the formation of destructive radical species and non-innocent oxidation products. This approach allowed a CQD-molecular nickel bis(diphosphine) photocatalyst system to reach a benchmark lifetime of more than 5 days and a record turnover number of 1094±61 molH2  (molNi )(-1) for a defined synthetic molecular nickel catalyst in purely aqueous solution under AM1.5G solar irradiation. PMID:27355200

  5. From porphyrins to pyrphyrins: adsorption study and metalation of a molecular catalyst on Au(111).

    PubMed

    Mette, Gerson; Sutter, Denys; Gurdal, Yeliz; Schnidrig, Stephan; Probst, Benjamin; Iannuzzi, Marcella; Hutter, Jürg; Alberto, Roger; Osterwalder, Jürg

    2016-04-14

    The molecular ligand pyrphyrin, a tetradentate bipyridine based macrocycle, represents an interesting but widely unexplored class of molecules. It resembles the well-known porphyrin, but consists of pyridyl subunits instead of pyrroles. Metal complexes based on pyrphyrin ligands have recently shown promise as water reduction catalysts in homogeneous photochemical water splitting reactions. In this study, the adsorption and metalation of pyrphyrin on a single crystalline Au(111) surface is investigated in an ultrahigh vacuum by means of scanning tunneling microscopy, low-energy electron diffraction, X-ray photoelectron spectroscopy and density functional theory. Pyrphyrin coverages of approximately one monolayer and less are obtained by sublimation of the molecules on the substrate kept at room temperature. The molecules self-assemble in two distinct phases of long-range molecular ordering depending on the surface coverage. The deposition of cobalt metal and subsequent annealing lead to the formation of Co-ligated pyrphyrin molecules accompanied by a pronounced change of the molecular self-assembly. Electronic structure calculations taking the herringbone reconstruction of Au(111) into account show that the molecules are physisorbed, but preferred adsorption sites are identified where Co and the N atoms of the two terminal cyano groups are optimally coordinated to the surface Au atoms. An intermediate state of the metalation reaction is observed and the reaction steps for the Co metalation of pyrphyrin molecules on Au(111) are established in a joint experimental and computational effort. PMID:27006307

  6. Toward Photochemical Water Splitting Using Band-Gap-Narrowed Semiconductors and Transition-Metal Based Molecular Catalysts

    SciTech Connect

    Muckerman,J.T.; Rodriguez, J.A.; Fujita, E.

    2009-06-07

    We are carrying out coordinated theoretical and experimental studies of toward photochemical water splitting using band-gap-narrowed semiconductors (BGNSCs) with attached multi-electron molecular water oxidation and hydrogen production catalysts. We focus on the coupling between the materials properties and the H{sub 2}O redox chemistry, with an emphasis on attaining a fundamental understanding of the individual elementary steps in the following four processes: (1) Light-harvesting and charge-separation of stable oxide or oxide-derived semiconductors for solar-driven water splitting, including the discovery and characterization of the behavior of such materials at the aqueous interface; (2) The catalysis of the four-electron water oxidation by dinuclear hydroxo transition-metal complexes with quinonoid ligands, and the rational search for improved catalysts; (3) Transfer of the design principles learned from the elucidation of the DuBois-type hydrogenase model catalysts in acetonitrile to the rational design of two-electron hydrogen production catalysts for aqueous solution; (4) Combining these three elements to examine the function of oxidation catalysts on BGNSC photoanode surfaces and hydrogen production catalysts on cathode surfaces at the aqueous interface to understand the challenges to the efficient coupling of the materials functions.

  7. Roles of molecular hydrogen and a hydrogen donor solvent in the cracking of moal model compounds with dispersed catalysts

    SciTech Connect

    Suzuki, Toshimitsu; Ikenaga, Na-oki; Sakota, Takahiro

    1994-12-31

    It is of great importance to evaluate quantitative hydrogen transfer process by using coal model compounds with a hydrogen-donor solvent. Cronauer el al. showed that in the cracking of benzyl phenyl ether the hydrogen required to stabilize free radicals comes from a donor solvent or intramolecular rearrangement and not from gaseous hydrogen in the absence of a catalyst. Korobkov et al. and Schlosberg et al. showed that the thermolysis of benzyl phenyl ether and dibenzyl ether were accomplished by intramolecular rearrangements. Yokokawa et al. reported that tetralin retarded the catalyzed hydrocracking of coal model compounds containing C-C and C-O bonds. However, few studies dealt with quantitative discussion in the hydrogen transfer process from a hydrogen-donor solvent or molecular hydrogen to free radicals derived from a model compound except a series of studies by Nicole and co-workers. On the other hand, it is well known that the amount of naphthalene produced from tetralin decreases after the liquefaction of coal in tetralin with catalyst as compared to the liquefaction in the absence of catalysts. To account for this, two mechanisms are proposed. One is that the catalyst hydrogenates naphthalene produced from tetralin, and the other is that the catalyst promotes the direct hydrogen transfer from molecular hydrogen to free radicals. The purpose of this work is to elucidate the role of catalyst and tetralin by means of the quantitative treatment of the hydrogen transfer reaction stabilizing thermally decomposed free radicals. Cracking of benzyl phenyl ether (BPE), dibenzyl ether (DBE), 1,2-diphenylethane, and 1,3-diphenylpropane was studied in tetralin in the presence of highly disposed catalyst.

  8. A patterned anisotropic nanofluidic sieving structure for continuous-flow separation of DNA and proteins

    PubMed Central

    Fu, Jianping; Schoch, Reto B.; Stevens, Anna L.; Tannenbaum, Steven R.; Han, Jongyoon

    2008-01-01

    Microfabricated regular sieving structures hold great promise as an alternative to gels to improve biomolecule separation speed and resolution. In contrast to disordered gel porous networks, these regular structures also provide well-defined environments ideal for study of molecular dynamics in confining spaces. However, previous regular sieving structures have been limited for separation of long DNA molecules, and separation of smaller, physiologically-relevant macromolecules, such as proteins, still remains as a challenge. Here we report a microfabricated anisotropic sieving structure consisting of a two-dimensional periodic nanofluidic filter array (Anisotropic Nanofilter Array: ANA). The designed structural anisotropy in the ANA causes different-sized or -charged biomolecules to follow distinct trajectories, leading to efficient separation. Continuous-flow size-based separation of DNA and proteins as well as electrostatic separation of proteins were achieved, thus demonstrating the potential of the ANA as a generic molecular sieving structure for an integrated biomolecule sample preparation and analysis system. PMID:18654231

  9. Stille Catalyst-Transfer Polycondensation Using Pd-PEPPSI-IPr for High-Molecular-Weight Regioregular Poly(3-hexylthiophene).

    PubMed

    Qiu, Yunyan; Mohin, Jacob; Tsai, Chia-Hua; Tristram-Nagle, Stephanie; Gil, Roberto R; Kowalewski, Tomasz; Noonan, Kevin J T

    2015-05-01

    A commercially available palladium N-heterocyclic carbene (Pd-NHC) precatalyst is used to initiate chain-growth polymerization of 2-bromo-3-hexyl-5-trimethylstannylthiophene. The molecular weight of the resultant poly(3-hexylthiophene) can be modulated (7 to 73 kDa, Đ = 1.14 to 1.53) by varying the catalyst concentration. Mass spectrometry data confirm control over the polymer end groups and (1)H NMR spectroscopy reveals that the palladium catalyst is capable of "ring-walking". A linear relationship between Mn and monomer conversion is observed. Atomic force microscopy and X-ray scattering verify the regioregular nature of the resultant polythiophene. PMID:25757046

  10. Multiprocessing the Sieve of Eratosthenes

    NASA Technical Reports Server (NTRS)

    Bokhari, S.

    1986-01-01

    The Sieve of Eratosthenes for finding prime numbers in recent years has seen much use as a benchmark algorithm for serial computers while its intrinsically parallel nature has gone largely unnoticed. The implementation of a parallel version of this algorithm for a real parallel computer, the Flex/32, is described and its performance discussed. It is shown that the algorithm is sensitive to several fundamental performance parameters of parallel machines, such as spawning time, signaling time, memory access, and overhead of process switching. Because of the nature of the algorithm, it is impossible to get any speedup beyond 4 or 5 processors unless some form of dynamic load balancing is employed. We describe the performance of our algorithm with and without load balancing and compare it with theoretical lower bounds and simulated results. It is straightforward to understand this algorithm and to check the final results. However, its efficient implementation on a real parallel machine requires thoughtful design, especially if dynamic load balancing is desired. The fundamental operations required by the algorithm are very simple: this means that the slightest overhead appears prominently in performance data. The Sieve thus serves not only as a very severe test of the capabilities of a parallel processor but is also an interesting challenge for the programmer.

  11. 08-ERD-071 Final Report: New Molecular Probes and Catalysts for Bioenergy Research

    SciTech Connect

    Thelen, M P; Rowe, A A; Siebers, A K; Jiao, Y

    2011-03-07

    A major thrust in bioenergy research is to develop innovative methods for deconstructing plant cell wall polymers, such as cellulose and lignin, into simple monomers that can be biologically converted to ethanol and other fuels. Current techniques for monitoring a broad array of cell wall materials and specific degradation products are expensive and time consuming. To monitor various polymers and assay their breakdown products, molecular probes for detecting specific carbohydrates and lignins are urgently needed. These new probes would extend the limited biochemical techniques available, and enable realtime imaging of ultrastructural changes in plant cells. Furthermore, degradation of plant biomass could be greatly accelerated by the development of catalysts that can hydrolyze key cell wall polysaccharides and lignin. The objective of this project was to develop cheap and efficient DNA reagents (aptamers) used to detect and quantify polysaccharides, lignin, and relevant products of their breakdown. A practical goal of the research was to develop electrochemical aptamer biosensors, which could be integrated into microfluidic devices and used for high-throughput screening of enzymes or biological systems that degrade biomass. Several important model plant cell wall polymers and compounds were targeted for specific binding and purification of aptamers, which were then tested by microscopic imaging, circular dichroism, surface plasmon resonance, fluorescence anisotropy, and electrochemical biosensors. Using this approach, it was anticiated that we could provide a basis for more efficient and economically viable biofuels, and the technologies established could be used to design molecular tools that recognize targets sought in medicine or chemical and biological defense projects.

  12. From porphyrins to pyrphyrins: adsorption study and metalation of a molecular catalyst on Au(111)

    NASA Astrophysics Data System (ADS)

    Mette, Gerson; Sutter, Denys; Gurdal, Yeliz; Schnidrig, Stephan; Probst, Benjamin; Iannuzzi, Marcella; Hutter, Jürg; Alberto, Roger; Osterwalder, Jürg

    2016-04-01

    The molecular ligand pyrphyrin, a tetradentate bipyridine based macrocycle, represents an interesting but widely unexplored class of molecules. It resembles the well-known porphyrin, but consists of pyridyl subunits instead of pyrroles. Metal complexes based on pyrphyrin ligands have recently shown promise as water reduction catalysts in homogeneous photochemical water splitting reactions. In this study, the adsorption and metalation of pyrphyrin on a single crystalline Au(111) surface is investigated in an ultrahigh vacuum by means of scanning tunneling microscopy, low-energy electron diffraction, X-ray photoelectron spectroscopy and density functional theory. Pyrphyrin coverages of approximately one monolayer and less are obtained by sublimation of the molecules on the substrate kept at room temperature. The molecules self-assemble in two distinct phases of long-range molecular ordering depending on the surface coverage. The deposition of cobalt metal and subsequent annealing lead to the formation of Co-ligated pyrphyrin molecules accompanied by a pronounced change of the molecular self-assembly. Electronic structure calculations taking the herringbone reconstruction of Au(111) into account show that the molecules are physisorbed, but preferred adsorption sites are identified where Co and the N atoms of the two terminal cyano groups are optimally coordinated to the surface Au atoms. An intermediate state of the metalation reaction is observed and the reaction steps for the Co metalation of pyrphyrin molecules on Au(111) are established in a joint experimental and computational effort.The molecular ligand pyrphyrin, a tetradentate bipyridine based macrocycle, represents an interesting but widely unexplored class of molecules. It resembles the well-known porphyrin, but consists of pyridyl subunits instead of pyrroles. Metal complexes based on pyrphyrin ligands have recently shown promise as water reduction catalysts in homogeneous photochemical water splitting

  13. Comparative Modal Analysis of Sieve Hardware Designs

    NASA Technical Reports Server (NTRS)

    Thompson, Nathaniel

    2012-01-01

    The CMTB Thwacker hardware operates as a testbed analogue for the Flight Thwacker and Sieve components of CHIMRA, a device on the Curiosity Rover. The sieve separates particles with a diameter smaller than 150 microns for delivery to onboard science instruments. The sieving behavior of the testbed hardware should be similar to the Flight hardware for the results to be meaningful. The elastodynamic behavior of both sieves was studied analytically using the Rayleigh Ritz method in conjunction with classical plate theory. Finite element models were used to determine the mode shapes of both designs, and comparisons between the natural frequencies and mode shapes were made. The analysis predicts that the performance of the CMTB Thwacker will closely resemble the performance of the Flight Thwacker within the expected steady state operating regime. Excitations of the testbed hardware that will mimic the flight hardware were recommended, as were those that will improve the efficiency of the sieving process.

  14. An artificial compound eye of photon Sieves

    NASA Astrophysics Data System (ADS)

    Jiang, Wenbo; Hu, Song; He, Yu; Bu, Yun

    2015-11-01

    The compound eye of insects has numerous extraordinary optical performances, such as minimum chromatic aberration, wide-angle field of view, and high sensitivity to the incidence light. Inspired by these unique performances, we present a novel artificial compound eye of photon sieves in this paper, where the photon sieves play the roles of insects' ommatidia. These photon sieves have the same focal length. The incidence light can be focused into the same focal plane and produce the superposition effect, the utilization ratio of energy can be largely improved. Through the numerical simulation, the results show that this novel structure has similar focusing performance with the conventional photon sieves, but has higher utilization ratio of energy and wider angle field of view than that of the conventional photon sieves. Our findings provide a new direction for optics and biology researchers, which will be beneficial for medical imaging, astronomy, etc.

  15. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis. Technical progress report, July--September 1993

    SciTech Connect

    Boakye, E.; Vittal, M.; Osseo-Asare, K.

    1993-10-01

    The objective of this project is to pursue the development of highly dispersed and inexpensive catalysts for improved coal solubilization and upgrading of coal liquids. A novel study of the synthesis of liquefaction catalysts of manometer size is being carried out. It is based on the molecular design of inverse micelles (microemulsions). These surfactant-stabilized, metal-bearing microdrops offer unique opportunities for synthesizing very small particles by providing a cage-like effect that limits particle nucleation, growth and agglomeration. The emphasis is on molybdenum- and iron-based catalysts, but the techniques being developed should also be generally applicable. The size of these very small and monodispersed particles will be accurately determined both separately and after in situ and ex situ coal impregnation. The as-prepared nanoparticles as well as the catalyst-impregnated coal matrix are characterized using a battery of techniques, including dynamic light scattering, x-ray diffraction and transmission electron microscopy. Catalytic activity tests are conducted under standardized coal liquefaction conditions. The effects of particle size of these unsupported catalysts on the product yield and distribution during conversion of a bituminous and a subbituminous coal are being determined.

  16. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis. Technical progress report, January 1993--March 1993

    SciTech Connect

    Boakye, E.; Vittal, M.; Osseo-Asare, K.

    1993-04-01

    The objective of this project is to pursue the development of highly dispersed and inexpensive catalysts for improved coal solubilization and upgrading of coal liquids. A novel study of the synthesis of liquefaction catalysts of manometer size is being carried out. It is based on the molecular design of reverse micelles (microemulsions). These surfactant-stabilized, metal-bearing microdrops offer unique opportunities for synthesizing very small particles by providing a cage-like effect that limits particle nucleation, growth and agglomeration. The emphasis is on molybdenum- and iron-based catalysts, but the techniques being developed should also be generally applicable. The size of these very small and monodispersed particles will be accurately determined both separately and after in situ and ex situ coal impregnation. The as-prepared nanoparticles as well as the catalyst-impregnated coal or char matrix are characterized using a battery of techniques, including dynamic light scattering, x-ray diffraction and transmission electron microscopy. Catalytic activity tests are conducted under standardized coal liquefaction conditions. The effect of particle size of these unsupported catalysts on the product yield and distribution during conversion of a bituminous and a subbituminous coal are being determined. This quarter, the solubilization of ammonium tetrathiomolybdate and the synthesis of molybdenum sulfide in several microemulsion systems is discussed.

  17. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis. Technical progress report, January 1992--March 1992

    SciTech Connect

    Osseo-Asare, K.; Boakye, E.; Radovic, L.R.

    1992-05-01

    The objective of this project is to pursue the development of highly dispersed and inexpensive catalysts for improved coal solubilization and upgrading of coal liquids. A novel study of the synthesis of liquefaction catalysts of manometer size will be carried out. It is based on the molecular design of reverse micelles (microemulsions). These surfactant-stabilized, metal-bearing microdrops offer unique opportunities for synthesizing very small particles by providing a cage-like effect that limits particle nucleation, growth and agglomeration. The emphasis will be on iron- and molybdenum-based catalysts, but the techniques to be developed should also be generally applicable. The size of these very small and monodispersed particles will be accurately determined both separately and after in situ and ex situ coal impregnation. The as-prepared nanoparticles as well as the catalyst-impregnated coal or char matrix will be characterized using the following techniques: dynamic light scattering, x-ray diffraction, x-ray photoelectron spectroscopy, scanning and/or transmission electron microscopy, and selective chemisorption. Catalytic activity tests will be conducted under standardized conditions in both hydrogenation and hydrodesulfurization reactions. The effect of particle size of these unsupported catalysts on the product yield and distribution during liquefaction of a bituminous and a subbituminous coal will thus be quantitatively determined.

  18. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis. Technical progress report, July 1992--September 1992

    SciTech Connect

    Boakye, E.; Vittal, M.; Osseo-Asare, K.

    1992-10-01

    The objective of this project is to pursue the development of highly dispersed and inexpensive catalysts for improved coal solubilization and upgrading of coal liquids. A novel study of the synthesis of liquefaction catalysts of manometer size will be carried out. It is based on the molecular design of reverse micelles (microemulsions). These surfactant-stabilized, metal-bearing microdrops offer unique opportunities for synthesizing very small particles by providing a cage-like effect that limits particle. nucleation, growth and agglomeration. The emphasis will be on iron- and molybdenum-based catalysts, but the techniques to be developed should also be generally applicable. The size of these very small and monodispersed particles will be accurately determined both separately and after in situ and ex situ coal impregnation. The as-prepared nanoparticles as well as the catalyst-impregnated coal or char matrix will be characterized using the following techniques: dynamic light scattering, x-ray diffraction, x-ray photoelectron spectroscopy, scanning and/or transmission electron microscopy, and selective chemisorption. Catalytic activity tests will be conducted under standardized conditions in both hydrogenation and hydrodesulfurization reactions. The effect of particle size of these unsupported catalysts on the product yield and distribution during liquefaction of a bituminous and a subbituminous coal will thus be quantitatively determined.

  19. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis. Technical progress report, April 1992--June 1992

    SciTech Connect

    Osseo-Asare, K.; Boakye, E.; Radovic, L.R.

    1992-07-01

    The objective of this project is to pursue the development of highly dispersed and inexpensive catalysts for improved coal solubilization and upgrading of coal liquids. A novel study of the synthesis of liquefaction catalysts of manometer size will be carried out. It is based on the molecular design of reverse micelles (microemulsions). These surfactant-stabilized, metal-bearing microdrops offer unique opportunities for synthesizing very small particles by providing a cage-like effect that limits particle nucleation, growth and agglomeration. The emphasis will be on iron- and molybdenum-based catalysts, but the techniques to be developed should also be generally applicable. The size of these very small and monodispersed particles will be accurately determined both separately and after in situ and ex situ coal impregnation. The as-prepared nanoparticles as well as the catalyst-impregnated coal or char matrix will be characterized using the following techniques: dynamic light scattering, x-ray diffraction, x-ray photoelectron spectroscopy, scanning and/or transmission electron microscopy, and selective chemisorption. Catalytic activity tests will be conducted under standardized conditions in both hydrogenation and hydrodesulfurization reactions. The effect of particle size of these unsupported catalysts on the product yield and distribution during liquefaction of a bituminous and a subbituminous coal will thus be quantitatively determined.This quarter, the effect of ammonium tetrathiomolybdate concentration on the synthesis of molybdenum sulfide in the 0.15 M NP-5/cyclohexane/water microemulsion system is discussed.

  20. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis. Technical progress report, October 1992--December 1992

    SciTech Connect

    Boakye, E.; Vittal, M.; Osseo-Asare, K.

    1993-02-01

    The objective of this project is to pursue the development of highly dispersed and inexpensive catalysts for improved coal solubilization and upgrading of coal liquids. A novel study of the synthesis of liquefaction catalysts of manometer size is being carried out. It is based on the molecular design of reverse micelles (microemulsions). These surfactant-stabilized, metal-bearing microdrops offer unique opportunities for synthesizing very small particles by providing a cage-like effect that limits particle nucleation, growth and agglomeration. The emphasis is on molybdenum- and iron-based catalysts, but the techniques being developed should also be generally applicable. The size of these very small and monodispersed particles will be accurately determined both separately and after in situ and ex situ coal impregnation. The as-prepared nanoparticles as well as the catalyst-impregnated coal or char matrix are characterized using a battery of techniques, including dynamic light scattering, x-ray diffraction and transmission electron microscopy. Catalytic activity tests are conducted under standardized coal liquefaction conditions. The effect of particle size of these unsupported catalysts on the product yield and distribution during conversion of a bituminous and a subbituminous coal are being determined.In this quarter, the synthesis of molybdenum sulfide in a microemulsion system with an alcohol-to-surfactant mass ratio of 3.5 is reported.

  1. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis. Technical progress report, April 1993--June 1993

    SciTech Connect

    Boakye, E.; Vittal, M.; Osseo-Asare, K.

    1993-07-01

    The objective of this project is to pursue the development of highly dispersed and inexpensive catalysts for improved coal solubilization and upgrading of coal liquids. A novel study of the synthesis of liquefaction catalysts of manometer size is being carried out. It is based on the molecular design of inverse micelles (microemulsions). These surfactant-stabilized, metal-bearing microdrops offer unique opportunities for synthesizing very small particles by providing a cage-like effect that limits particle nucleation, growth and agglomeration. The emphasis is on molybdenum- and iron-based catalysts, but the techniques being developed should also be generally applicable. The size of these very small and monodispersed particles will be accurately determined both separately and after in situ and ex situ coal impregnation. The as-prepared nanoparticles as well as the catalyst-impregnated coal matrix are characterized using a battery of techniques, including g dynamic light scattering, x-ray diffraction and transmission electron microscopy. Catalytic activity tests are conducted under standardized coal liquefaction conditions. The effects of particle size of these unsupported catalysts on the product yield and distribution during conversion of a bituminous and a subbituminous coal are being determined. This report discusses molybdenum sulfide particle synthesis, characterization, and microemulsion characterization.

  2. Oxygen Tolerance of a Molecular Engineered Cathode for Hydrogen Evolution Based on a Cobalt Diimine-Dioxime Catalyst.

    PubMed

    Kaeffer, Nicolas; Morozan, Adina; Artero, Vincent

    2015-10-29

    We report here that a bioinspired cobalt diimine-dioxime molecular catalyst for hydrogen evolution immobilized onto carbon nanotube electrodes proves tolerant toward oxygen. The cobalt complex catalyzes O2 reduction with an onset potential of +0.55 V vs RHE. In this process, a mixture of water and hydrogen peroxide is produced in a 3:1 ratio. Our study evidences that such side-reductions have little impact on effectiveness of proton reduction by the grafted molecular catalyst which still displays good activity for H2 evolution in the presence of O2. The presence of O2 in the media is not detrimental toward H2 evolution under the conditions used, which simulate turn-on conditions of a water-splitting device. PMID:25993343

  3. Bioinspired Molecular Co-Catalysts Bonded to a Silicon Photocathode for Solar Hydrogen Evolution

    SciTech Connect

    Hou, Yidong

    2011-11-08

    The production of fuels from sunlight represents one of the main challenges in the development of a sustainable energy system. Hydrogen is the simplest fuel to produce and although platinum and other noble metals are efficient catalysts for photoelectrochemical hydrogen evolution earth-abundant alternatives are needed for large-scale use. We show that bioinspired molecular clusters based on molybdenum and sulphur evolve hydrogen at rates comparable to that of platinum. The incomplete cubane-like clusters (Mo{sub 3}S{sub 4}) efficiently catalyse the evolution of hydrogen when coupled to a p-type Si semiconductor that harvests red photons in the solar spectrum. The current densities at the reversible potential match the requirement of a photoelectrochemical hydrogen production system with a solar-to-hydrogen efficiency in excess of 10% (ref. 16). The experimental observations are supported by density functional theory calculations of the Mo{sub 3}S{sub 4} clusters adsorbed on the hydrogen-terminated Si(100) surface, providing insights into the nature of the active site.

  4. Bioinspired molecular co-catalysts bonded to a silicon photocathode for solar hydrogen evolution.

    PubMed

    Hou, Yidong; Abrams, Billie L; Vesborg, Peter C K; Björketun, Mårten E; Herbst, Konrad; Bech, Lone; Setti, Alessandro M; Damsgaard, Christian D; Pedersen, Thomas; Hansen, Ole; Rossmeisl, Jan; Dahl, Søren; Nørskov, Jens K; Chorkendorff, Ib

    2011-06-01

    The production of fuels from sunlight represents one of the main challenges in the development of a sustainable energy system. Hydrogen is the simplest fuel to produce and although platinum and other noble metals are efficient catalysts for photoelectrochemical hydrogen evolution, earth-abundant alternatives are needed for large-scale use. We show that bioinspired molecular clusters based on molybdenum and sulphur evolve hydrogen at rates comparable to that of platinum. The incomplete cubane-like clusters (Mo(3)S(4)) efficiently catalyse the evolution of hydrogen when coupled to a p-type Si semiconductor that harvests red photons in the solar spectrum. The current densities at the reversible potential match the requirement of a photoelectrochemical hydrogen production system with a solar-to-hydrogen efficiency in excess of 10%. The experimental observations are supported by density functional theory calculations of the Mo(3)S(4) clusters adsorbed on the hydrogen-terminated Si(100) surface, providing insights into the nature of the active site. PMID:21516095

  5. A Frontier Molecular Orbital determination of the active sites on dispersed metal catalysts

    SciTech Connect

    Augustine, R.L.; Lahanas, K.M.

    1992-01-01

    An angular overlap calculation has been used to determine the s, p and d orbital energy levels of the different types of surface sites present on a dispersed metal catalysts. The basis for these calculations is the reported finding that a large number of catalyzed reactions take place on single atom active sites on the metal surface. Thus, these sites can be considered as surface complexes made up of the central active atom surrounded by near-neighbor metal atom ligands'' with localized surface orbitals perturbed only by these ligands''. These complexes'' are based on a twelve coordinate species with the ligands'' attached to the t{sub 2g} orbitals and the coordinate axes coincident with the direction of the e{sub g} orbitals on the central atom. These data can permit a Frontier Molecular Orbital treatment of specific site activities as long as the surface orbital availability for overlap with adsorbed substrates is considered along with its energy value and symmetry.

  6. A Frontier Molecular Orbital determination of the active sites on dispersed metal catalysts

    SciTech Connect

    Augustine, R.L.; Lahanas, K.M.

    1992-11-01

    An angular overlap calculation has been used to determine the s, p and d orbital energy levels of the different types of surface sites present on a dispersed metal catalysts. The basis for these calculations is the reported finding that a large number of catalyzed reactions take place on single atom active sites on the metal surface. Thus, these sites can be considered as surface complexes made up of the central active atom surrounded by near-neighbor metal atom ``ligands`` with localized surface orbitals perturbed only by these ``ligands``. These ``complexes`` are based on a twelve coordinate species with the ``ligands`` attached to the t{sub 2g} orbitals and the coordinate axes coincident with the direction of the e{sub g} orbitals on the central atom. These data can permit a Frontier Molecular Orbital treatment of specific site activities as long as the surface orbital availability for overlap with adsorbed substrates is considered along with its energy value and symmetry.

  7. Electrochemical driven water oxidation by molecular catalysts in situ polymerized on the surface of graphite carbon electrode.

    PubMed

    Wang, Lei; Fan, Ke; Daniel, Quentin; Duan, Lele; Li, Fusheng; Philippe, Bertrand; Rensmo, Håkan; Chen, Hong; Sun, Junliang; Sun, Licheng

    2015-05-01

    A simple strategy to immobilize highly efficient ruthenium based molecular water-oxidation catalysts on the basal-plane pyrolytic graphite electrode (BPG) by polymerization has been demonstrated. The electrode 1@BPG has obtained a high initial turnover frequency (TOF) of 10.47 s(-1) at ∼700 mV overpotential, and a high turnover number (TON) up to 31600 in 1 h electrolysis. PMID:25854858

  8. Production of High Molecular Weight Organic Compounds on the Surfaces of Amorphous Iron Silicate Catalysts: Implications for Organic Synthesis in the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Gilmour, I.; Hill, H. G. M.; Pearson, V. K.; Sephton, M. A.; Nuth, J. A., III

    2002-01-01

    The high molecular weight organic products of Fischer-Tropsch/Haber-Bosch syntheses on the surfaces of Fe-silicate catalysts have been studied by GCMS. Additional information is contained in the original extended abstract.

  9. Synthesis and characterization of catalysts and electrocatalysts using combinatorial methods

    NASA Astrophysics Data System (ADS)

    Ramanathan, Ramnarayanan

    This thesis documents attempts at solving three problems. Bead-based parallel synthetic and screening methods based on matrix algorithms were developed. The method was applied to search for new heterogeneous catalysts for dehydrogenation of methylcyclohexane. The most powerful use of the method to date was to optimize metal adsorption and evaluate catalysts as a function of incident energy, likely to be important in the future, should availability of energy be an optimization parameter. This work also highlighted the importance of order of addition of metal salts on catalytic activity and a portion of this work resulted in a patent with UOP LLC, Desplaines, Illinois. Combinatorial methods were also investigated as a tool to search for carbon-monoxide tolerant anode electrocatalysts and methanol tolerant cathode electrocatalysts, resulting in discovery of no new electrocatalysts. A physically intuitive scaling criterion was developed to analyze all experiments on electrocatalysts, providing insight for future experiments. We attempted to solve the CO poisoning problem in polymer electrolyte fuel cells using carbon molecular sieves as a separator. This approach was unsuccessful in solving the CO poisoning problem, possibly due to the tendency of the carbon molecular sieves to concentrate CO and CO 2 in pore walls.

  10. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis. Technical progress report, July--September 1991

    SciTech Connect

    Osseo-Asare, K.; Boakye, E.; Vaidyanathan, N.; Radovic, L.R.

    1991-10-01

    The objective of this project is to pursue the development of highly dispersed and inexpensive catalysts for improved coal solubilization and upgrading of coal liquids. A novel study of the synthesis of liquefaction catalysts of nanometer size will be carried out. It is based on the molecular design of reverse micelles (microemulsions). These surfactant-stabilized, metalbearing microdrops offer unique opportunities for synthesizing very small particles by providing a cage-like effect that limits particle nucleation, growth and agglomeration. The emphasis will be on iron- and molybdenum-based catalysts, but the techniques to be developed should also be generally applicable. The size of these very small and monodispersed particles will be accurately determined both separately and after in situ and ex situ coal impregnation. The as-prepared nanoparticles as well as the catalyst-impregnated coal or char matrix will be characterized using the following techniques: dynamic light scattering, x-ray diffraction, x-ray photoelectron spectroscopy, scanning and/or transmission electron microscopy, and selective chemisorption.

  11. Tuning the properties of copper-based catalysts based on molecular in situ studies of model systems.

    PubMed

    Stacchiola, Darío J

    2015-07-21

    Studying catalytic processes at the molecular level is extremely challenging, due to the structural and chemical complexity of the materials used as catalysts and the presence of reactants and products in the reactor's environment. The most common materials used on catalysts are transition metals and their oxides. The importance of multifunctional active sites at metal/oxide interfaces has been long recognized, but a molecular picture of them based on experimental observations is only recently emerging. The initial approach to interrogate the surface chemistry of catalysts at the molecular level consisted of studying metal single crystals as models for reactive metal centers, moving later to single crystal or well-defined thin film oxides. The natural next iteration consisted in the deposition of metal nanoparticles on well-defined oxide substrates. Metal nanoparticles contain undercoordinated sites, which are more reactive. It is also possible to create architectures where oxide nanoparticles are deposited on top of metal single crystals, denominated inverse catalysts, leading in this case to a high concentration of reactive cationic sites in direct contact with the underlying fully coordinated metal atoms. Using a second oxide as a support (host), a multifunctional configuration can be built in which both metal and oxide nanoparticles are located in close proximity. Our recent studies on copper-based catalysts are presented here as an example of the application of these complementary model systems, starting from the creation of undercoordinated sites on Cu(111) and Cu2O(111) surfaces, continuing with the formation of mixed-metal copper oxides, the synthesis of ceria nanoparticles on Cu(111) and the codeposition of Cu and ceria nanoparticles on TiO2(110). Catalysts have traditionally been characterized before or after reactions and analyzed based on static representations of surface structures. It is shown here how dynamic changes on a catalyst's chemical state

  12. Current Issues in Molecular Catalysis Illustrated by Iron Porphyrins as Catalysts of the CO2-to-CO Electrochemical Conversion.

    PubMed

    Costentin, Cyrille; Robert, Marc; Savéant, Jean-Michel

    2015-12-15

    Recent attention aroused by the reduction of carbon dioxide has as main objective the production of useful products, the "solar fuels", in which solar energy would be stored. One route to this goal is the design of photochemical schemes that would operate this conversion using directly sun light energy. An indirect approach consists in first converting sunlight energy into electricity then using it to reduce CO2 electrochemically. Conversion of carbon dioxide into carbon monoxide is thus a key step through the classical dihydrogen-reductive Fischer-Tropsch chemistry. Direct and catalytic electrochemical CO2 reduction already aroused active interest during the 1980-1990 period. The new wave of interest for these matters that has been growing since 2012 is in direct conjunction with modern energy issues. Among molecular catalysts, electrogenerated Fe(0) porphyrins have proved to be particularly efficient and robust. Recent progress in this field has closely associated the search of more and more efficient catalysts in the iron porphyrin family with an unprecedentedly rigorous deciphering of mechanisms. Accordingly, the coupling of proton transfer with electron transfer and breaking of one of the two C-O bonds of CO2 have been the subjects of relentless scrutiny and mechanistic analysis with systematic investigation of the degree of concertedness of these three events. Catalysis of the electrochemical CO2-to-CO conversion has thus been a good testing ground for the mechanism diagnostic strategies and the all concerted reactivity model proposed then. The role of added Brönsted acids, both as H-bond providers and proton donors, has been elucidated. These efforts have been a preliminary to the inclusion of the acid functionalities within the catalyst molecule, giving rise to considerable increase of the catalytic efficiency. The design of more and more efficient catalysts made it necessary to propose "catalytic Tafel plots" relating the turnover frequency to the

  13. From molecular complexes to complex metallic nanostructures--2H solid-state NMR studies of ruthenium-containing hydrogenation catalysts.

    PubMed

    Gutmann, Torsten; del Rosal, Iker; Chaudret, Bruno; Poteau, Romuald; Limbach, Hans-Heinrich; Buntkowsky, Gerd

    2013-09-16

    In the last years, the combination of (2)H solid-state NMR techniques with quantum-chemical calculations has evolved into a powerful spectroscopic tool for the characterization of the state of hydrogen on the surfaces of heterogeneous catalysts. In the present minireview, a brief summary of this development is given, in which investigations of the structure and dynamics of hydrogen in molecular complexes, clusters and nanoparticle systems are presented, aimed to understand the reaction mechanisms on the surface of hydrogenation catalysts. The surface state of deuterium/hydrogen is analyzed employing a combination of variable-temperature (2)H static and magic-angle spinning (MAS) solid-state NMR techniques, in which the dominant quadrupolar interactions of deuterium give information on the binding situation and local symmetry of deuterium/hydrogen on molecular species. Using a correlation database from molecular complexes and clusters, the possibility to distinguish between terminal Ru-D, bridged Ru2-D, three-fold Ru3-D, and interstitial Ru6-D is demonstrated. Combining these results with quantum-chemical density functional theory (DFT) calculations allows the interpretation of (2)H solid-state data of complex "real world" nanostructures, which yielded new insights into reaction pathways at the molecular level. PMID:23658058

  14. A Bioinspired Molecular Polyoxometalate Catalyst with Two Cobalt(II) Oxide Cores for Photocatalytic Water Oxidation.

    PubMed

    Wei, Jie; Feng, Yingying; Zhou, Panpan; Liu, Yan; Xu, Jingyin; Xiang, Rui; Ding, Yong; Zhao, Chongchao; Fan, Linyuan; Hu, Changwen

    2015-08-24

    To overcome the bottleneck of water splitting, the exploration of efficient, selective, and stable water oxidation catalysts (WOCs) is crucial. We report an all-inorganic, oxidatively and hydrolytically stable WOC based on a polyoxometalate [(A-α-SiW9 O34)2Co8(OH)6(H2O)2(CO3)3](16-) (Co8 POM). As a cobalt(II)-based cubane water oxidation catalyst, Co8POM embeds double Co(II)4O3 cores. The self-assembled catalyst is similar to the oxygen evolving complex (OEC) of photosystem II (PS II). Using [Ru(bpy)3](2+) as a photosensitizer and persulfate as a sacrificial electron acceptor, Co8POM exhibits excellent water oxidation activity with a turnover number (TON) of 1436, currently the highest among bioinspired catalysts with a cubical core, and a high initial turnover frequency (TOF). Investigation by several spectroscopy, spectrometry, and other techniques confirm that Co8POM is a stable and efficient catalyst for visible light-driven water oxidation. The results offer a useful insight into the design of water oxidation catalysts. PMID:26130568

  15. Process and catalyst for converting synthesis gas to liquid hydrocarbon mixture

    DOEpatents

    Rao, V. Udaya S.; Gormley, Robert J.

    1987-01-01

    Synthesis gas containing CO and H.sub.2 is converted to a high-octane hydrocarbon liquid in the gasoline boiling point range by bringing the gas into contact with a heterogeneous catalyst including, in physical mixture, a zeolite molecular sieve, cobalt at 6-20% by weight, and thoria at 0.5-3.9% by weight. The contacting occurs at a temperature of 250.degree.-300.degree. C., and a pressure of 10-30 atmospheres. The conditions can be selected to form a major portion of the hydrocarbon product in the gasoline boiling range with a research octane of more than 80 and less than 10% by weight aromatics.

  16. Generation of optical vortices by apodized photon sieves

    NASA Astrophysics Data System (ADS)

    Sun, Hai-bin; Wang, Xing-hai; Chen, Jun; Sun, Ping

    2016-05-01

    As a novel diffractive optical element, photon sieve has good focusing properties. We propose a method to verify the focusing properties by using apodized photon sieves. The apodized photon sieve is obtained by using a Gaussian window function to modulate the general photon sieve. Focusing properties of apodized photon sieve are studied by numerical simulations and experiments. It shows that photon sieves have good focusing ability, and the focusing ability of the photon sieve on the focal plane is stronger than that on other image planes. The experimental results also demonstrate that photon sieves can be used to generate optical vortices. The existence of optical vortices is confirmed by the formation of fork fringes. This apodized photon sieve is expected to have some practical applications in focusing analysis, optical imaging, and optical communication.

  17. Multicomponent redox catalysts for reduction of large biological molecules using molecular hydrogen as the reductant

    SciTech Connect

    Chao, S.; Simon, R.A.; Mallouk, T.E.; Wrighton, M.S.

    1988-03-30

    One-electron reduction of the large biological molecules horse heart cytochrome c, sperm whale myoglobin, and horseradish peroxidase using H/sub 2/ as the reductant can be catalyzed by two-component, high surface area heterogeneous catalysts. The catalysts can be prepared by first functionalizing high surface area SiO/sub 2/ with a polycationic polymer into which is dispersed MCl/sub 4//sup 2 -/ (M = Pd, Pt). Reduction with H/sub 2/ yields elemental Pd or Pt dispersed in the polymer. The particles are finally functionalized with a redox polymer derived from hydrolysis of Si(OR)/sub 3/ groups of an N,N'-dialkyl-4,4'-bipyridinium- or from a cobalticenium-based monomer. The two components of the heterogeneous catalysts are the buried noble metal capable of activating the H/sub 2/ and the redox polymer, which can equilibrate both with the noble metal and with the large biological molecule. Reduction of the large biological molecules in aqueous solution can be effected at room temperature and 1 atm H/sub 2/ using the catalysts under conditions where the biological materials would not be reducible with H/sub 2/ alone or when the noble metal alone would be used as the catalyst.

  18. Tetranuclear vanadium complex, (VO)(4)(hpic)(4): a recyclable catalyst for oxidation of benzyl alcohols with molecular oxygen.

    PubMed

    Kodama, Shintaro; Ueta, Yukihiro; Yoshida, Jun; Nomoto, Akihiro; Yano, Shigenobu; Ueshima, Michio; Ogawa, Akiya

    2009-11-28

    Vanadium(iv) complexes bearing 3-hydroxypicolinic acid (H(2)hpic) as ligands, VO(Hhpic)(2) (1) and the cyclic tetramer (VO)(4)(hpic)(4) (2), have excellent catalytic ability for the oxidation of a variety of primary and secondary benzyl alcohols with molecular oxygen in acetonitrile or protic solvents such as ethanol and water, affording the corresponding aldehydes and ketones, respectively. Construction of multi-nuclear complexes by the selection of ligands attains higher turnover numbers and recycling of the catalyst. PMID:19885511

  19. Catalyst-free growth of Bi{sub 2}Te{sub 3} nanostructures by molecular beam epitaxy

    SciTech Connect

    Harrison, S. E.; Schönherr, P.; Hesjedal, T.; Huo, Y.; Harris, J. S.

    2014-10-13

    We present the catalyst-free growth of binary Bi{sub 2}Te{sub 3} topological insulator nanostructures on c-plane sapphire substrates by molecular beam epitaxy. Dense arrays of single-crystalline nanostructures, growing along the [110] direction, are obtained for substrate temperatures ranging from ∼180 °C to 260 °C. The growth rate and shape of the nanostructures are highly temperature-dependent. The microscopic study of the nanostructures and their relationship to the underlying Bi{sub 2}Te{sub 3} thin film gives an insight into the growth mechanism.

  20. Efficient and limiting reactions in aqueous light-induced hydrogen evolution systems using molecular catalysts and quantum dots.

    PubMed

    Gimbert-Suriñach, Carolina; Albero, Josep; Stoll, Thibaut; Fortage, Jérôme; Collomb, Marie-Noëlle; Deronzier, Alain; Palomares, Emilio; Llobet, Antoni

    2014-05-28

    Hydrogen produced from water and solar energy holds much promise for decreasing the fossil fuel dependence. It has recently been proven that the use of quantum dots as light harvesters in combination with catalysts is a valuable strategy to obtain photogenerated hydrogen. However, the light to hydrogen conversion efficiency of these systems is reported to be lower than 40%. The low conversion efficiency is mainly due to losses occurring at the different interfacial charge-transfer reactions taking place in the multicomponent system during illumination. In this work we have analyzed all the involved reactions in the hydrogen evolution catalysis of a model system composed of CdTe quantum dots, a molecular cobalt catalyst and vitamin C as sacrificial electron donor. The results demonstrate that the electron transfer from the quantum dots to the catalyst occurs fast enough and efficiently (nanosecond time scale), while the back electron transfer and catalysis are much slower (millisecond and microsecond time scales). Further improvements of the photodriven proton reduction should focus on the catalytic rate enhancement, which should be at least in the hundreds of nanoseconds time scale. PMID:24799030

  1. Direct Methylation of Amines with Carbon Dioxide and Molecular Hydrogen using Supported Gold Catalysts.

    PubMed

    Du, Xian-Long; Tang, Gao; Bao, Hong-Liang; Jiang, Zheng; Zhong, Xin-Hua; Su, Dang Sheng; Wang, Jian-Qiang

    2015-10-26

    The N-methylation of amines with CO2 and H2 is an important step in the synthesis of bioactive compounds and chemical intermediates. The first heterogeneous Au catalyst is reported for this methylation reaction with good to excellent yields. The average turnover frequency (TOF) based on surface Au atoms is 45 h(-1) , which is the highest TOF value ever reported for the methylation of aniline with CO2 and H2 . Furthermore, the catalyst is tolerant toward a variety of amines, which includes aromatic, aliphatic, secondary, and primary amines. Preliminary mechanistic studies suggest that the N-alkyl formamide might be an intermediate in the N-methylation of amine process. Moreover, through a one-pot process, it is possible to convert primary amines, aldehydes, and CO2 into unsymmetrical tertiary amines with H2 as a reductant in the presence of the Au catalyst. PMID:26364582

  2. Elucidating molecular iridium water oxidation catalysts using metal-organic frameworks: a comprehensive structural, catalytic, spectroscopic, and kinetic study.

    PubMed

    Wang, Cheng; Wang, Jin-Liang; Lin, Wenbin

    2012-12-01

    As a new class of porous, crystalline, molecular materials, metal-organic frameworks (MOFs) have shown great promise as recyclable and reusable single-site solid catalysts. Periodic order and site isolation of the catalytic struts in MOFs facilitate the studies of their activities and reaction mechanisms. Herein we report the construction of two highly stable MOFs (1 and 2) using elongated dicarboxylate bridging ligands derived from Cp*Ir(L)Cl complexes (L = dibenzoate-substituted 2,2'-bipyridine, bpy-dc, or dibenzoate-substituted 2-phenylpyridine, ppy-dc) and Zr(6)O(4)(OH)(4)(carboxylate)(12) cuboctahedral secondary building units (SBUs) and the elucidation of water oxidation pathways of the Cp*Ir(L)Cl catalysts using these MOFs. We carried out detailed kinetic studies of Ce(4+)-driven water oxidation reactions (WORs) catalyzed by the MOFs using UV-vis spectroscopy, phosphorescent oxygen detection, and gas chromatographic analysis. These results confirmed not only water oxidation activity of the MOFs but also indicated oxidative degradation of the Cp* rings during the WOR. The (bpy-dc)Ir(H(2)O)(2)XCl (X is likely a formate or acetate group) complex resulted from the oxidative degradation process was identified as a competent catalyst responsible for the water oxidation activity of 1. Further characterization of the MOFs recovered from WORs using X-ray photoelectron, diffuse-reflectance UV-vis absorption, luminescence, and infrared spectroscopies supported the identity of (bpy-dc)Ir(H(2)O)(2)XCl as an active water oxidation catalyst. Kinetics of MOF-catalyzed WORs were monitored by Ce(4+) consumptions and fitted with a reaction-diffusion model, revealing an intricate relationship between reaction and diffusion rates. Our work underscores the opportunity in using MOFs as well-defined single-site solid catalytic systems to reveal mechanistic details that are difficult to obtain for their homogeneous counterparts. PMID:23136923

  3. A Systematic Comparative Study of Hydrogen-Evolving Molecular Catalysts in Aqueous Solutions.

    PubMed

    Roy, Souvik; Bacchi, Marine; Berggren, Gustav; Artero, Vincent

    2015-11-01

    We describe here a systematic, reliable, and fast screening method that allows the comparison of H2-forming catalysts that work under aqueous conditions with two readily prepared chemical reductants and two commonly used photosensitizers. This method uses a Clark-type microsensor for H2 detection and complements previous methods based on rotating disk electrode measurements. The efficiencies of a series of H2 -producing catalysts based on Co, Ni, Fe, and Pt were investigated in aqueous solutions under thermal conditions with europium(II) reductants and under photochemical conditions in the presence of two different photosensitizers {[Ru(bipy)3]Cl2(bipy=2,2-bipyridine) and eosin-Y} and sacrificial electron donors (ascorbate and triethanolamine, respectively). The majority of catalysts tested were active only under specific conditions. However, our results also demonstrate the impressive versatility of a group of Co catalysts, which were able to produce H2 under different reducing conditions and at various pH values. In particular, a cobaloxime, [Co(dmgH)2(H2O)2] (dmgH2 =dimethylglyoxime), and a cobalt tetraazamacrocyclic complex, {Co(CR)Cl2}(+) [CR=2,12-dimethyl-3,7,11,17-tetraazabicylo(11.3.1)heptadeca-1(17),2,11,13,15-pentaene], displayed excellent catalytic rates under the studied conditions, and the best rates were observed under thermal conditions. PMID:26383700

  4. SEORious business: structural proteins in sieve tubes and their involvement in sieve element occlusion.

    PubMed

    Knoblauch, Michael; Froelich, Daniel R; Pickard, William F; Peters, Winfried S

    2014-04-01

    The phloem provides a network of sieve tubes for long-distance translocation of photosynthates. For over a century, structural proteins in sieve tubes have presented a conundrum since they presumably increase the hydraulic resistance of the tubes while no potential function other than sieve tube or wound sealing in the case of injury has been suggested. Here we summarize and critically evaluate current speculations regarding the roles of these proteins. Our understanding suffers from the suggestive power of images; what looks like a sieve tube plug on micrographs may not actually impede translocation very much. Recent reports of an involvement of SEOR (sieve element occlusion-related) proteins, a class of P-proteins, in the sealing of injured sieve tubes are inconclusive; various lines of evidence suggest that, in neither intact nor injured plants, are SEORs determinative of translocation stoppage. Similarly, the popular notion that P-proteins serve in the defence against phloem sap-feeding insects is unsupported by empirical facts; it is conceivable that in functional sieve tubes, aphids actually could benefit from inducing a plug. The idea that rising cytosolic Ca(2+) generally triggers sieve tube blockage by P-proteins appears widely accepted, despite lacking experimental support. Even in forisomes, P-protein assemblages restricted to one single plant family and the only Ca(2+)-responsive P-proteins known, the available evidence does not unequivocally suggest that plug formation is the cause rather than a consequence of translocation stoppage. We conclude that the physiological roles of structural P-proteins remain elusive, and that in vivo studies of their dynamics in continuous sieve tube networks combined with flow velocity measurements will be required to (hopefully) resolve this scientific roadblock. PMID:24591057

  5. Methanol Oxidative Dehydrogenation on Oxide Catalysts: Molecular and Dissociative Routes and Hydrogen Addition Energies as Descriptors of Reactivity

    SciTech Connect

    Deshlahra, Prashant; Iglesia, Enrique

    2014-11-13

    The oxidative dehydrogenation (ODH) of alkanols on oxide catalysts is generally described as involving H-abstraction from alkoxy species formed via O–H dissociation. Kinetic and isotopic data cannot discern between such routes and those involving kinetically-relevant H-abstraction from undissociated alkanols. Here, we combine such experiments with theoretical estimates of activation energies and entropies to show that the latter molecular routes prevail over dissociative routes for methanol reactions on polyoxometalate (POM) clusters at all practical reaction temperatures. The stability of the late transition states that mediate H-abstraction depend predominantly on the stability of the O–H bond formed, making H-addition energies (HAE) accurate and single-valued descriptors of reactivity. Density functional theory-derived activation energies depend linearly on HAE values at each O-atom location on clusters with a range of composition (H3PMo12, H4SiMo12, H3PW12, H4PV1Mo11, and H4PV1W11); both barriers and HAE values reflect the lowest unoccupied molecular orbital energy of metal centers that accept the electron and the protonation energy of O-atoms that accept the proton involved in the H-atom transfer. Bridging O-atoms form O–H bonds that are stronger than those of terminal atoms and therefore exhibit more negative HAE values and higher ODH reactivity on all POM clusters. For each cluster composition, ODH turnover rates reflect the reactivity-averaged HAE of all accessible O-atoms, which can be evaluated for each cluster composition to provide a rigorous and accurate predictor of ODH reactivity for catalysts with known structure. These relations together with oxidation reactivity measurements can then be used to estimate HAE values and to infer plausible structures for catalysts with uncertain active site structures.

  6. Novel, benign, solid catalysts for the oxidation of hydrocarbons.

    PubMed

    Ratnasamy, Paul; Raja, Robert; Srinivas, Darbha

    2005-04-15

    The catalytic properties of two classes of solid catalysts for the oxidation of hydrocarbons in the liquid phase are discussed: (i) microporous solids, encapsulating transition metal complexes in their cavities and (ii) titanosilicate molecular sieves. Copper acetate dimers encapsulated in molecular sieves Y, MCM-22 and VPI-5 use dioxygen to regioselectively ortho-hydroxylate L-tyrosine to L-dopa, phenol to catechol and cresols to the corresponding o-dihydroxy and o-quinone compounds. Monomeric copper phthalocyanine and salen complexes entrapped in zeolite-Y oxidize methane to methanol, toluene to cresols, naphthalene to naphthols, xylene to xylenols and phenol to diphenols. Trimeric mu3-oxo-bridged Co/Mn cluster complexes, encapsulated inside Y-zeolite, oxidize para-xylene, almost quantitatively, to terephthalic acid. In almost all cases, the intrinsic catalytic activity (turnover frequency) of the metal complex is enhanced very significantly, upon encapsulation in the porous solids. Spectroscopic and electrochemical studies suggest that the geometric distortions of the complex on encapsulation change the electron density at the metal ion site and its redox behaviour, thereby influencing its catalytic activity and selectivity in oxidation reactions. Titanosilicate molecular sieves can oxidize hydrocarbons using dioxygen when loaded with transition metals like Pd, Au or Ag. The structure of surface Ti ions and the type of oxo-Ti species generated on contact with oxidants depend on several factors including the method of zeolite synthesis, zeolite structure, solvent, temperature and oxidant. Although, similar oxo-Ti species are present on all the titanosilicates, their relative concentrations vary among different structures and determine the product selectivity. PMID:15901549

  7. Activation of molecular oxygen and the nature of the active oxygen species for CO oxidation on oxide supported Au catalysts.

    PubMed

    Widmann, D; Behm, R J

    2014-03-18

    Although highly dispersed Au catalysts with Au nanoparticles (NPs) of a few nanometers in diameter are well-known for their high catalytic activity for several oxidation and reduction reactions already at rather low temperatures for almost 30 years, central aspects of the reaction mechanism are still unresolved. While most studies focused on the active site, the active Au species, and the effect of the support material, the most crucial step during oxidation reactions, the activation of molecular oxygen and the nature of the resulting active oxygen species (Oact), received more attention just recently. This is topic of this Account, which focuses on the formation, location, and nature of the Oact species present on metal oxide supported Au catalysts under typical reaction conditions, at room temperature and above. It is mainly based on quantitative temporal analysis of products (TAP) reactor measurements, which different from most spectroscopic techniques are able to detect and quantify these species even at the extremely low concentrations present under realistic reaction conditions. Different types of pulse experiments were performed, during which the highly dispersed, realistic powder catalysts are exposed to very low amounts of reactants, CO and/or O2, in order to form and reactively remove Oact species and gain information on their formation, nature, and the active site for Oact formation. Our investigations have shown that the active oxygen species for CO oxidation on Au/TiO2 for reaction at 80 °C and higher is a highly stable atomic species, which at 80 °C is formed only at the perimeter of the Au-oxide interface and whose reactive removal by CO is activated, but not its formation. From these findings, it is concluded that surface lattice oxygen represents the Oact species for the CO oxidation. Accordingly, the CO oxidation proceeds via a Au-assisted Mars-van Krevelen mechanism, during which surface lattice oxygen close to the Au NPs is removed by reaction

  8. 7 CFR 801.8 - Tolerances for sieves.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ....3 percent, mean deviation from standard sieve using barley ±0.5 percent, mean deviation from standard sieve using barley 55/64×3/4 inch slotted ±0.5 percent, mean deviation from standard sieve using barley ±0.7 percent, mean deviation from standard sieve using barley 6/64×3/4 inch slotted ±0.7...

  9. 7 CFR 801.8 - Tolerances for sieves.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ....3 percent, mean deviation from standard sieve using barley ±0.5 percent, mean deviation from standard sieve using barley 55/64×3/4 inch slotted ±0.5 percent, mean deviation from standard sieve using barley ±0.7 percent, mean deviation from standard sieve using barley 6/64×3/4 inch slotted ±0.7...

  10. 7 CFR 801.8 - Tolerances for sieves.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ....3 percent, mean deviation from standard sieve using barley ±0.5 percent, mean deviation from standard sieve using barley 55/64×3/4 inch slotted ±0.5 percent, mean deviation from standard sieve using barley ±0.7 percent, mean deviation from standard sieve using barley 6/64×3/4 inch slotted ±0.7...

  11. 7 CFR 801.8 - Tolerances for sieves.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ....3 percent, mean deviation from standard sieve using barley ±0.5 percent, mean deviation from standard sieve using barley 55/64×3/4 inch slotted ±0.5 percent, mean deviation from standard sieve using barley ±0.7 percent, mean deviation from standard sieve using barley 6/64×3/4 inch slotted ±0.7...

  12. 7 CFR 801.8 - Tolerances for sieves.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ....3 percent, mean deviation from standard sieve using barley ±0.5 percent, mean deviation from standard sieve using barley 55/64×3/4 inch slotted ±0.5 percent, mean deviation from standard sieve using barley ±0.7 percent, mean deviation from standard sieve using barley 6/64×3/4 inch slotted ±0.7...

  13. A Molecular Copper Catalyst for Hydrogenation of CO­2 to Formate

    SciTech Connect

    Zall, Christopher M.; Linehan, John C.; Appel, Aaron M.

    2015-09-04

    There is widespread interest in the hydrogenation of CO2 to energy-rich products such as formate. However, first-row transition metal complexes that catalyze the hydrogenation of CO2 to formate remain rare. Copper phosphine complexes are widely used in the reduction of organic substrates but have not previously been used as catalysts for the conversion of H2 and CO2 to formate. Here we demonstrate that the triphosphine-ligated copper(I) complex LCu(MeCN)PF6 is an active catalyst for CO2 hydrogenation in the presence of a suitable base. Screening of bases and studies of catalytic reactions by in operando spectroscopy revealed important and unusual roles for the base in promoting H2 activation and turnover.

  14. Efficient disproportionation of formic acid to methanol using molecular ruthenium catalysts.

    PubMed

    Savourey, Solène; Lefèvre, Guillaume; Berthet, Jean-Claude; Thuéry, Pierre; Genre, Caroline; Cantat, Thibault

    2014-09-22

    The disproportionation of formic acid to methanol was unveiled in 2013 using iridium catalysts. Although attractive, this transformation suffers from very low yields; methanol was produced in less than 2% yield, because the competitive dehydrogenation of formic acid (to CO2 and H2) is favored. We report herein the efficient and selective conversion of HCOOH to methanol in 50% yield, utilizing ruthenium(II) phosphine complexes under mild conditions. Experimental and theoretical (DFT) results show that different convergent pathways are involved in the production of methanol, depending on the nature of the catalyst. Reaction intermediates have been isolated and fully characterized and the reaction chemistry of the resulting ruthenium complexes has been studied. PMID:25088282

  15. Recent Improvements To the Sieve of Eratosthenes.

    ERIC Educational Resources Information Center

    Quesada, Antonio R.

    1997-01-01

    Presents recently developed generalizations to the sieve of Eratosthenes, showing the principles underlying these improvements, which increase its efficiency without changing too much of its simplicity. Offers several possibilities to propose good investigations for students to explore, find patterns, and make generalizations. (JRH)

  16. Ni-based heterogeneous catalyst from a designed molecular precursor for the efficient electrochemical water oxidation.

    PubMed

    Kuznetsov, Denis A; Konev, Dmitry V; Komarova, Natal'ya S; Ionov, Andrey M; Mozhchil, Rais N; Fedyanin, Ivan V

    2016-07-28

    Bimetallic Ni-Mo alkoxide was synthesized and exploited as the single-source precursor for the solution-processed deposition of the mixed-oxide layers on different conducting surfaces. Upon potential cycling in 1 M NaOH, these composites convert, in situ, into highly porous NiOx/NiOOH catalysts characterized by the high electrocatalytic activity for water oxidation under both basic (pH 13.6) and near neutral (pH 9.2) conditions. PMID:27354324

  17. Factorization using the quadratic sieve algorithm

    SciTech Connect

    Davis, J.A.; Holdridge, D.B.

    1983-12-01

    Since the cryptosecurity of the RSA two key cryptoalgorithm is no greater than the difficulty of factoring the modulus (product of two secret primes), a code that implements the Quadratic Sieve factorization algorithm on the CRAY I computer has been developed at the Sandia National Laboratories to determine as sharply as possible the current state-of-the-art in factoring. Because all viable attacks on RSA thus far proposed are equivalent to factorization of the modulus, sharper bounds on the computational difficulty of factoring permit improved estimates for the size of RSA parameters needed for given levels of cryptosecurity. Analysis of the Quadratic Sieve indicates that it may be faster than any previously published general purpose algorithm for factoring large integers. The high speed of the CRAY I coupled with the capability of the CRAY to pipeline certain vectorized operations make this algorithm (and code) the front runner in current factoring techniques.

  18. Factorization using the quadratic sieve algorithm

    SciTech Connect

    Davis, J.A.; Holdridge, D.B.

    1983-01-01

    Since the cryptosecurity of the RSA two key cryptoalgorithm is no greater than the difficulty of factoring the modulus (product of two secret primes), a code that implements the Quadratic Sieve factorization algorithm on the CRAY I computer has been developed at the Sandia National Laboratories to determine as sharply as possible the current state-of-the-art in factoring. Because all viable attacks on RSA thus far proposed are equivalent to factorization of the modulus, sharper bounds on the computational difficulty of factoring permit improved estimates for the size of RSA parameters needed for given levels of cryptosecurity. Analysis of the Quadratic Sieve indicates that it may be faster than any previously published general purpose algorithm for factoring large integers. The high speed of the CRAY I coupled with the capability of the CRAY to pipeline certain vectorized operations make this algorithm (and code) the front runner in current factoring techniques.

  19. Molecular modification of proanthocyanidins.

    PubMed

    Huo, Qing; Kong, Xiangye; Yang, Xiaofang; Wang, Yue; Ma, Lingling; Luo, Min; Xu, Diandou

    2016-07-01

    Regioselective enzymatic acylation of proanthocyanidin is proposed and investigated as a method by which to improve the solubility of proanthocyanidins in the oil phase and maintain its oxidation resistance. Experimental results indicate that butanol functions as the best solvent in the studied reaction, in which Lipase Novozym435 is used as biological catalyst enzyme and the molar ratio of lauric acid to proanthocyanidins is 4:1. To increase the esterification conversion, we propose the addition of molecular sieve at 5 h. The product was separated by TLC, and results indicate an optimal solvent ratio of ethyl acetate: petroleum ether: acetic acid = 2:3:0.5. This condition can effectively separate the ester and proanthocyanidins, achieving an esterification yield of 60.9%. PMID:27459598

  20. Water reduction by a p-GaInP2 photoelectrode stabilized by an amorphous TiO2 coating and a molecular cobalt catalyst

    NASA Astrophysics Data System (ADS)

    Gu, Jing; Yan, Yong; Young, James L.; Steirer, K. Xerxes; Neale, Nathan R.; Turner, John A.

    2016-04-01

    Producing hydrogen through solar water splitting requires the coverage of large land areas. Abundant metal-based molecular catalysts offer scalability, but only if they match noble metal activities. We report on a highly active p-GaInP2 photocathode protected through a 35-nm TiO2 layer functionalized by a cobaloxime molecular catalyst (GaInP2-TiO2-cobaloxime). This photoelectrode mediates H2 production with a current density of ~9 mA cm-2 at a potential of 0 V versus RHE under 1-sun illumination at pH 13. The calculated turnover number for the catalyst during a 20-h period is 139,000, with an average turnover frequency of 1.9 s-1. Bare GaInP2 shows a rapid current decay, whereas the GaInP2-TiO2-cobaloxime electrode shows <=5% loss over 20 min, comparable to a GaInP2-TiO2-Pt catalyst particle-modified interface. The activity and corrosion resistance of the GaInP2-TiO2-cobaloxime photocathode in basic solution is made possible by an atomic layer-deposited TiO2 and an attached cobaloxime catalyst.

  1. Water reduction by a p-GaInP2 photoelectrode stabilized by an amorphous TiO2 coating and a molecular cobalt catalyst.

    PubMed

    Gu, Jing; Yan, Yong; Young, James L; Steirer, K Xerxes; Neale, Nathan R; Turner, John A

    2016-04-01

    Producing hydrogen through solar water splitting requires the coverage of large land areas. Abundant metal-based molecular catalysts offer scalability, but only if they match noble metal activities. We report on a highly active p-GaInP2 photocathode protected through a 35-nm TiO2 layer functionalized by a cobaloxime molecular catalyst (GaInP2-TiO2-cobaloxime). This photoelectrode mediates H2 production with a current density of ∼9 mA cm(-2) at a potential of 0 V versus RHE under 1-sun illumination at pH 13. The calculated turnover number for the catalyst during a 20-h period is 139,000, with an average turnover frequency of 1.9 s(-1). Bare GaInP2 shows a rapid current decay, whereas the GaInP2-TiO2-cobaloxime electrode shows ≤5% loss over 20 min, comparable to a GaInP2-TiO2-Pt catalyst particle-modified interface. The activity and corrosion resistance of the GaInP2-TiO2-cobaloxime photocathode in basic solution is made possible by an atomic layer-deposited TiO2 and an attached cobaloxime catalyst. PMID:26689139

  2. Water reduction by a p-GaInP2 photoelectrode stabilized by an amorphous TiO2 coating and a molecular cobalt catalyst

    SciTech Connect

    Gu, Jing; Yan, Yong; Young, James L.; Steirer, K. Xerxes; Neale, Nathan R.; Turner, John A.

    2015-12-21

    Producing hydrogen through solar water splitting requires the coverage of large land areas. Abundant metal-based molecular catalysts offer scalability, but only if they match noble metal activities. We report on a highly active p-GaInP2 photocathode protected through a 35-nm TiO2 layer functionalized by a cobaloxime molecular catalyst (GaInP2-TiO2-cobaloxime). This photoelectrode mediates H2 production with a current density of ~9"0mA"0cm-2 at a potential of 0"0V versus RHE under 1-sun illumination at pH"013. The calculated turnover number for the catalyst during a 20-h period is 139,000, with an average turnover frequency of 1.9"0s-1. Bare GaInP2 shows a rapid current decay, whereas the GaInP2-TiO2-cobaloxime electrode shows catalyst particle-modified interface. The activity and corrosion resistance of the GaInP2-TiO2-cobaloxime photocathode in basic solution is made possible by an atomic layer-deposited TiO2 and an attached cobaloxime catalyst.

  3. Solid Molecular Phosphine Catalysts for Formic Acid Decomposition in the Biorefinery.

    PubMed

    Hausoul, Peter J C; Broicher, Cornelia; Vegliante, Roberta; Göb, Christian; Palkovits, Regina

    2016-04-25

    The co-production of formic acid during the conversion of cellulose to levulinic acid offers the possibility for on-site hydrogen production and reductive transformations. Phosphorus-based porous polymers loaded with Ru complexes exhibit high activity and selectivity in the base-free decomposition of formic acid to CO2 and H2 . A polymeric analogue of 1,2-bis(diphenylphosphino)ethane (DPPE) gave the best results in terms of performance and stability. Recycling tests revealed low levels of leaching and only a gradual decrease in the activity over seven runs. An applicability study revealed that these catalysts even facilitate selective removal of formic acid from crude product mixtures arising from the synthesis of levulinic acid. PMID:27043017

  4. MCM-41-supported cobalt-molybdenum catalysts for deep hydrodesulfurization of diesel and jet fuel feedstocks

    NASA Astrophysics Data System (ADS)

    Turaga, Uday Tsrpr

    Regulatory issues require new catalysts for the deep hydrodesulfurization (HDS) of refractory polyaromatic sulfur compounds such as 4,6-dimethyldibenzothiophene (4,6-DMDBT) present in diesel and jet fuel. Molybdenum sulfide (MoS2 ) supported on mesoporous molecular sieve MCM-41 and promoted by cobalt was hypothesized to have superior activity for deep HDS because of MCM-41's (1) high surface area and uniform mesopores and (2) superior acidity as compared to conventional supports such as gamma-alumina (gamma-Al 2O3). This study examines the role of MCM-41 as a support for new cobalt (Co)-molybdenum (Mo) HDS catalysts. At CoO-MoO3 loadings typical of commercially available HDS catalysts, MCM-41-supported catalysts were only slightly better. At higher loadings---27.0% (by weight) MoO3 and 5.8% CoO---MCM-41-supported catalysts were twice more active than the commercial catalyst. This difference in activities is related to the degree of MoS2 stacking. Remarkable increase in the conversion of 4,6-DMDBT was observed over MCM-41-supported catalysts with decreasing SiO2/Al2O 3 ratio. More significantly, the SiO2/Al2O 3 ratio of MCM-41 has a profound effect on product distribution and catalyst selectivity. Irrespective of CoO-MoO3 loading, catalysts using MCM-41 with a SiO2/Al2O3 ratio of 50 convert more of 4,6-DMDBT through the highly desirable hydrogenolysis pathway. The acidity of these catalysts was measured and correlated to their selectivities for hydrogenolysis and hydrocracking. Co-Mo/MCM-41 continued to demonstrate activities twice that of the commercial catalyst for the HDS of 4,6-DMDBT in petroleum-derived feedstocks such as light cycle oil. However, for a blend of coal- and petroleum-derived feedstocks, nitrogen from the coal-derived liquid inhibited both catalysts for the HDS of 4,6-DMDBT. Basic nitrogen, e.g., quinoline, significantly retards the HDS of 4,6-DMDBT over both catalysts. Non-basic carbazole, on the other hand, inhibited the MCM-41-supported

  5. Sieve Tube Geometry in Relation to Phloem Flow

    PubMed Central

    Mullendore, Daniel L.; Windt, Carel W.; Van As, Henk; Knoblauch, Michael

    2010-01-01

    Sieve elements are one of the least understood cell types in plants. Translocation velocities and volume flow to supply sinks with photoassimilates greatly depend on the geometry of the microfluidic sieve tube system and especially on the anatomy of sieve plates and sieve plate pores. Several models for phloem translocation have been developed, but appropriate data on the geometry of pores, plates, sieve elements, and flow parameters are lacking. We developed a method to clear cells from cytoplasmic constituents to image cell walls by scanning electron microscopy. This method allows high-resolution measurements of sieve element and sieve plate geometries. Sieve tube–specific conductivity and its reduction by callose deposition after injury was calculated for green bean (Phaseolus vulgaris), bamboo (Phyllostachys nuda), squash (Cucurbita maxima), castor bean (Ricinus communis), and tomato (Solanum lycopersicum). Phloem sap velocity measurements by magnetic resonance imaging velocimetry indicate that higher conductivity is not accompanied by a higher velocity. Studies on the temporal development of callose show that small sieve plate pores might be occluded by callose within minutes, but plants containing sieve tubes with large pores need additional mechanisms. PMID:20354199

  6. Photocatalytic water oxidation via combination of BiVO4-RGO and molecular cobalt catalysts.

    PubMed

    Wang, Yong; Li, Fei; Li, Hua; Bai, Lichen; Sun, Licheng

    2016-02-18

    A BiVO4-reduced graphene oxide (RGO) composite in conjugation with the cubic molecular complex Co4O4(O2CMe)4(py)4 (py = pyridine) has been found to be highly efficient towards visible light-driven water oxidation. A 4-fold enhancement in the average oxygen evolution rate and 100% yield based on the consumption of the sacrificial electron acceptor were obtained upon the addition of molecular cocatalysts to BiVO4-RGO in pure water. PMID:26795211

  7. MgCl(2).6PhCH2OH--a new molecular adduct as support material for Ziegler-Natta catalyst: synthesis, characterization and catalytic activity.

    PubMed

    Gnanakumar, Edwin S; Thushara, K S; Bhange, Deu S; Mathew, Renny; Ajithkumar, T G; Rajamohanan, P R; Bhaduri, Sumit; Gopinath, Chinnakonda S

    2011-11-01

    Benzyl alcohol has been used to prepare a single phase MgCl(2).6BzOH molecular adduct as a support for an ethylene polymerization catalyst (Ziegler catalyst). The structural, spectroscopic and morphological aspects of the MgCl(2).6BzOH molecular adduct and the Ziegler catalyst have been thoroughly studied by various physicochemical characterization techniques. The presence of MgO(6) octahedrons due to the interaction of Mg(2+) with six -OH groups of the benzyl alcohol is confirmed from a Raman feature at 703 cm(-1), and structural studies. The supported catalyst activity has been evaluated for the ethylene polymerization reaction. The lower polymerization activity of the titanated Ziegler-Natta catalyst compared with a standard catalyst is attributed to the strong interaction of titanium chloride with the support and associated electronic factors. PMID:21909567

  8. Studies on KIT-6 Supported Cobalt Catalyst for Fischer–Tropsch Synthesis

    SciTech Connect

    Gnanamani, M.; Jacobs, G; Graham, U; Ma, W; Pendyala, V; Ribeiro, M; Davis, B

    2010-01-01

    KIT-6 molecular sieve was used as a support to prepare cobalt catalyst for Fischer-Tropsch synthesis (FTS) using an incipient wetness impregnation method to produce cobalt loadings of 15 and 25 wt%. The catalysts were characterized by BET surface area, X-ray diffraction, scanning transmission election microscopy (STEM), extended X-ray absorption fine spectroscopy and X-ray absorption near edge spectroscopy. The catalytic properties for FTS were evaluated using a 1L CSTR reactor. XRD, pore size distribution, and STEM analysis indicate that the KIT-6 mesostructure remains stable during and after cobalt impregnation and tends to form smaller cobalt particles, probably located inside the mesopores. The mesoporous KIT-6 exhibited a slightly higher cobalt dispersion compared to amorphous SiO{sub 2} supported catalyst. With the higher Co loading (25 wt%) on KIT-6, partial structural collapse was observed after the FTS reaction. Compared to an amorphous SiO{sub 2} supported cobalt catalyst, KIT-6 supported cobalt catalyst displayed higher methane selectivity at a similar Co loading, likely due to diffusion effects.

  9. Alternative catalyst and exhaust gas sensor work at Argonne National Laboratory

    SciTech Connect

    Iton, L.E.; Maroni, V.A.; Dieckman, S.L.; Sheen, S.H.; Raptis, A.C.

    1994-12-31

    Research programs at Argonne National Laboratory in the areas of automobile emissions monitoring and control are described. The mandate to improve automobile efficiency while reducing Pollution requires the development of new catalysts for exhaust emissions control that are capable of functioning efficiently under lean-burn engine operating conditions. It is also desirable that the use of expensive noble metal catalysts be avoided. NO{sub x} emissions will not be efficiently controlled by the current three-way, supported noble metal catalysts under lean-burn conditions. New catalysts are being sought that could effect the selective catalytic reduction (SCR) of NO{sub x} by exhaust hydrocarbons in the presence of oxygen. Molecular sieve zeolites of the ZSM-5 and ferrierite types, ion-exchanged with copper ions, are the best of the catalysts known to effect this chemistry, but the mechanism of the SCR is still not understood. In this project the authors will first undertake the investigation of the SCR of NO using model reactions to test postulated mechanistic pathways. Initial experiments have been devised to investigate the possible participation of metal alkyl complexes, metal oxime complexes, N-alkyl-N-nitroso-alkylaminato-metal complexes, and metal nitrile complexes in the zeolites. ANL will also develop microsensors, based on surface acoustic wave (SAW) chemical sensing techniques, and a micro mass-spectrometer (MS) for tailpipe or engine-out emission monitoring. The sensor configurations and sensing techniques of the proposed SAW and micro-MS are described.

  10. Direct amidation of carboxylic acids catalyzed by ortho-iodo arylboronic acids: catalyst optimization, scope, and preliminary mechanistic study supporting a peculiar halogen acceleration effect.

    PubMed

    Gernigon, Nicolas; Al-Zoubi, Raed M; Hall, Dennis G

    2012-10-01

    The importance of amides as a component of biomolecules and synthetic products motivates the development of catalytic, direct amidation methods employing free carboxylic acids and amines that circumvent the need for stoichiometric activation or coupling reagents. ortho-Iodophenylboronic acid 4a has recently been shown to catalyze direct amidation reactions at room temperature in the presence of 4A molecular sieves as dehydrating agent. Herein, the arene core of ortho-iodoarylboronic acid catalysts has been optimized with regards to the electronic effects of ring substitution. Contrary to the expectation, it was found that electron-donating substituents are preferable, in particular, an alkoxy substituent positioned para to the iodide. The optimal new catalyst, 5-methoxy-2-iodophenylboronic acid (MIBA, 4f), was demonstrated to be kinetically more active than the parent des-methoxy catalyst 4a, providing higher yields of amide products in shorter reaction times under mild conditions at ambient temperature. Catalyst 4f is recyclable and promotes the formation of amides from aliphatic carboxylic acids and amines, and from heteroaromatic carboxylic acids and other functionalized substrates containing moieties like a free phenol, indole and pyridine. Mechanistic studies demonstrated the essential role of molecular sieves in this complex amidation process. The effect of substrate stoichiometry, concentration, and measurement of the catalyst order led to a possible catalytic cycle based on the presumed formation of an acylborate intermediate. The need for an electronically enriched ortho-iodo substituent in catalyst 4f supports a recent theoretical study (Marcelli, T. Angew. Chem. Int. Ed.2010, 49, 6840-6843) with a purported role for the iodide as a hydrogen-bond acceptor in the orthoaminal transition state. PMID:23013456

  11. Ultrasound assisted synthesis of methyl butyrate using heterogeneous catalyst.

    PubMed

    Dange, P N; Kulkarni, A V; Rathod, V K

    2015-09-01

    Ultrasound assisted esterification of butyric acid with methanol was investigated in an ultrasound irradiated isothermal batch reactor using acid ion-exchange resin (amberlyst-15) as a catalyst. Effect of parameters such as temperature (323-353 K), catalyst loading (0-8.5%w/w), alcohol to acid ratio, M (2-6), ultrasound power (0-145 W), duty cycle (0-85%) and amount of molecular sieves added (0-11%w/w) on the rate of reaction was studied. At optimized parameters, a maximum conversion of 91.64% was obtained in 120 min in presence of ultrasound. Experimental kinetic data were correlated by using Eley-Rideal (ER) and Langmuir-Hinshelwood-Hougen-Watson (LHH W) models taking into account reverse reaction. Studies showed that single site LHHW with reactants and products both adsorbing on catalyst surface was most suited for the obtained experimental data. Activation energy determined based on heterogeneous kinetics was in the range 49.31-57.54 kJ/mol while it was 18.29 kJ/mol using homogeneous model. PMID:25825149

  12. Control of carbon monoxide (CO) from automobile exhaust by a dealuminated zeolite supported regenerative MnCo2O4 catalyst.

    PubMed

    Arun, P S; Ranjith, B P; Shibli, S M A

    2013-03-19

    We synthesized MnCo(2)O(4) catalyst with very high porosity on the surface of dealuminated zeolite molecular sieves (DAZMS) for CO oxidation under actual automobile conditions. The MnCo(2)O(4) catalyst was selected on the basis of preliminary DFT study using the software ADF BAND. The MnCo(2)O(4) catalyst had comparatively higher CO adsorption energy and very low oxygen vacancy formation energy. The synthesized MnCo(2)O(4)/DAZMS catalyst was characterized by XRD, XRF, BET, SEM, and Confocal Microscopy. The Confocal microscopic analysis revealed that porosity of the dealuminated zeolite surface was significantly enhanced after the catalyst loading process. The completely precious metal free and DAZMS-supported catalyst exhibited excellent CO oxidation ability with renewed activity for seven months under actual automobile conditions with reference to normal and cold start conditions. The synthesized MnCo(2)O(4)/DAZMS not only exhibited surprisingly high catalytic activity for CO oxidation at a temperature resembling a cold start period but was also sufficiently stable/active under actual automobile conditions and ambient conditions containing large amounts of CO,H(2)O,CO(2), and NO(x) at 155-715 °C. These significant results revealed the flexible use of the present catalyst system for a wide variety of automobiles from a small gasoline-fuelled vehicle to a large diesel-fuelled vehicle that may produce high CO-content exhaust. PMID:23406461

  13. Novel fine-disperse bimetallic Pt-Pd/Al2O3 catalysts for glycerol oxidation with molecular oxygen

    NASA Astrophysics Data System (ADS)

    Dubencovs, K.; Chornaja, S.; Sproge, E.; Kampars, V.; Markova, D.; Kulikova, L.; Serga, V.; Cvetkovs, A.

    2013-12-01

    Using extractive-pyrolytic method several Pt-Pd bimetallic catalysts supported on plasma-processed alumina nanopowder were synthesized. Pt-Pd loading and glycerol oxidation process parameter influence on catalyst activity and selectivity was determined oxidizing glycerol in mild conditions. Novel bimetallic catalysts in neutral water solutions were practically inactive (glycerol conversion was only 3%) whereas in alkaline solutions they were active and selective to glyceric acid. Using 1.2%Pt-1.2%Pd/Al2O3 catalyst glyceric acid was obtained with 65% selectivity (glycerol conversion was 96%). It was shown that novel fine-disperse bimetallic Pt-Pd/Al2O3 catalysts were more active compared to analogous monometallic Pt/Al2O3 and Pd/Al2O3 catalysts.

  14. Photoswitching a Molecular Catalyst to Regulate CO2 Hydrogenation

    SciTech Connect

    Priyadarshani, Nilusha; Ginovska-Pangovska, Bojana; Bays, J. Timothy; Linehan, John C.; Shaw, Wendy J.

    2015-07-24

    Inspired by nature’s ability to regulate catalysis using physiological stimuli, azobenzene was incorporated into Rh(bis)diphosphine CO2 hydrogenation catalysts to photoinitiate structural changes to modulate the resulting catalytic activity. The rhodium bound diphosphine ligands (P(Ph2)-CH2-N(R) CH2-P(Ph2)) contain the terminal amine of a non-natural amino acid, either β-alanine (β-Ala) or γ-aminobutyric acid (GABA). For both β-ala and GABA containing complexes, the carboxylic acids of the amino acids were coupled to the amines of diaminoazobenzene, creating a rhodium bound trans-spanning tetraphosphine complex. The photo-induced cis-trans isomerization of the azobenzene-containing complexes imposes structural changes on these complexes, as evidenced by 1H NMR. We found that the CO2 hydrogenation activity for the β-ala bound Rh complex is 40% faster with azobenzene in the cis configuration (16 s-1) than in the trans conformation (11 s-1), while the γ-aminobutyric acid containing Rh complex has the same rate (~17 s-1) in either the cis or the trans configuration at 27 °C. The corresponding complexes without the attached azobenzene were also prepared, characterized, and catalytically tested for comparison, and have rates of 30 s-1. Computational studies were undertaken to evaluate the difference in rate between the cis and trans isomers for the β-Ala bound Rh complex, and revealed major structural changes between all cis and trans structures, but only minor structural changes that would be unique to the β-Ala bound Rh complex. We postulate that the slower rate of the azobenzene-containing β-Ala bound Rh complex is due to subtle changes in the bite angle arising from steric strain due to the trans-spanning azobenzene, altering hydricity and consequently rate. This work was supported by the US Department of Energy, Office of Science, Office of Basic Energy

  15. Nickel complex with internal bases as efficient molecular catalyst for photochemical H2 production.

    PubMed

    Yang, Yong; Wang, Mei; Xue, Liqin; Zhang, Fengbo; Chen, Lin; Ahlquist, Mårten S G; Sun, Licheng

    2014-10-01

    A Ni complex with internal bases that contain bipyridine-derived ligands, [Ni(L)2 (H2 O)2 ](BF4 )2 ([1](BF4 )2 , L=2-(2-pyridyl)-1,8-naphthyridine), and a reference complex that bears analogous bipyridine-derived ligands but without an internal base, [Ni(L')3 ](BF4 )2 ([2](BF4 )2 , L'=2-(2-pyridyl)quinoline), were synthesized and characterized. The electrochemical properties of these complexes were studied in CH3 CN, H2 O, and a mixture of EtOH/H2 O. The fluorescence spectroscopic studies suggest that both dynamic and the sphere-of-action static quenching exist in the fluorescein Fl(2-) /[1](2+) and Fl(2-) /[2](2+) systems. These noble-metal-free molecular systems were studied for photocatalytic H2 generation. Under optimal conditions, the turnover number of H2 evolution reaches 3230 based on [1](2+) , whereas [2](2+) displays only approximately one third of the turnover of [1](2+) . A plausible mechanism for the catalytic H2 generation by [1](2+) is presented based on DFT calculations. PMID:25179906

  16. Clad photon sieve for generating localized hollow beams

    NASA Astrophysics Data System (ADS)

    Cheng, Yiguang; Tong, Junmin; Zhu, Jiangping; Liu, Junbo; Hu, Song; He, Yu

    2016-02-01

    A novel photon sieve structure called clad photon sieve is proposed to generate localized hollow beams and its design principle and focusing properties are studied. The clad photon sieve is composed of the internal zone and external zone with pinholes being positioned on the dark zones. Pinholes in the internal zone and in the external zone give destructive interference to the focus, leading to localized hollow beams being generated on the focal plane. Focusing properties of clad photon sieve with different focal lengths, zone numbers and modulation factors are also studied by theoretical calculations, numerical simulations and experiments, showing that the central dark spot size can be controlled by the focal length and rings number, and the intensity of the central dark spot varies with different modulation factors related with the internal zone and the external zone. This photon sieve can be useful for trapping and manipulating of particles and cooling of atoms.

  17. Sieving wastewater--cellulose recovery, economic and energy evaluation.

    PubMed

    Ruiken, C J; Breuer, G; Klaversma, E; Santiago, T; van Loosdrecht, M C M

    2013-01-01

    Application of fine-mesh sieves (<0.35 mm) as pretreatment for municipal biological wastewater treatment gives an opportunity to recover resources and increase sustainability of wastewater treatment processes. Sieves are traditionally used for single stage mechanical treatment (typical mesh of 0.35 mm) or in combination with an MBR (typical mesh >0.7 mm). When sieves with a mesh of 0.35 mm are used on raw sewage we observed that cellulose fibres mainly originating from toilet paper are removed efficiently from the influent with a high recovery and purity. The application of sieves as pretreatment for conventional activated sludge processes has been evaluated based on pilot plant research at three WWTPs in the Netherlands. With sieving applied to the dry weather flow only the overall energy usage of the WWTP including sludge treatment can be decreased by at least 40% with a payback time of 7 years. PMID:23121895

  18. Subnanometer Two-Dimensional Graphene Oxide Channels for Ultrafast Gas Sieving.

    PubMed

    Shen, Jie; Liu, Gongping; Huang, Kang; Chu, Zhenyu; Jin, Wanqin; Xu, Nanping

    2016-03-22

    Two-dimensional (2D) materials with atomic thickness and extraordinary physicochemical properties exhibit unique mass transport behaviors, enabling them as emerging nanobuilding blocks for separation membranes. Engineering 2D materials into membrane with subnanometer apertures for precise molecular sieving remains a great challenge. Here, we report rational-designing external forces to precisely manipulate nanoarchitecture of graphene oxide (GO)-assembled 2D channels with interlayer height of ∼0.4 nm for fast transporting and selective sieving gases. The external forces are synergistic to direct the GO nanosheets stacking so as to realize delicate size-tailoring of in-plane slit-like pores and plane-to-plane interlayer-galleries. The 2D channels endow GO membrane with excellent molecular-sieving characteristics that offer 2-3 orders of magnitude higher H2 permeability and 3-fold enhancement in H2/CO2 selectivity compared with commercial membranes. Formation mechanism of 2D channels is proposed on the basis of the driving forces, nanostructures, and transport behaviors. PMID:26866661

  19. Open flow hot isostatic pressing assisted synthesis of highly porous materials and catalysts

    NASA Astrophysics Data System (ADS)

    Siadati, Mohammad Hossein

    Open-flow hot isostatic pressing (OFHIP) technique is applied for synthesizing molecular sieves and highly porous catalytic materials. First, the isostatic pressure is applied to the starting material/catalyst precursor, and then heat is applied. Under this condition, as the organic components gradually decompose and leave the material, the voids left behind are immediately filled/replaced by the gas (pressure medium) in flow. This substitution warrants the preservation as well as the uniformity of the voids/pores. The result is a very porous material with very uniform pore size distribution. Another advantage is the production of the catalyst directly from the precursor, in the absence of solvent (neat), rendering the process simpler and less costly than previous processes. The entire process takes place under flow of the gas that is used as medium to develop the isostatic pressure. Consequently, the entire process, as well as the final product produced, is devoid of any undesirable residues. This endeavor also introduces a viable technique for mass-producing porous materials/catalysts. The resulting materials are termed "amorphous sulfide sieves" to reflect their unique properties that include high surface area, narrow pore size distribution and high activity. The catalysts are potentially licensable to all petroleum and petroleum chemical companies for a wide variety of environmental and product improvement purposes. The results obtained on unpromoted samples synthesized at 300°C indicate that as the synthesis pressure is increased, both surface area and catalytic activity of the materials produced increase. The increase in activity k value from 3 to 6 x 10-7 mol/g.s corresponds to increase in pressure from 100 to 800 psi, respectively. The N2 gas used as pressure medium results in highly porous materials but low activity. H 2 seems to be the ideal gas for both pressure medium and reducing agent. Co-promoted catalysts synthesized at 1400 psi and 300°C show

  20. Oxidation catalyst

    DOEpatents

    Ceyer, Sylvia T.; Lahr, David L.

    2010-11-09

    The present invention generally relates to catalyst systems and methods for oxidation of carbon monoxide. The invention involves catalyst compositions which may be advantageously altered by, for example, modification of the catalyst surface to enhance catalyst performance. Catalyst systems of the present invention may be capable of performing the oxidation of carbon monoxide at relatively lower temperatures (e.g., 200 K and below) and at relatively higher reaction rates than known catalysts. Additionally, catalyst systems disclosed herein may be substantially lower in cost than current commercial catalysts. Such catalyst systems may be useful in, for example, catalytic converters, fuel cells, sensors, and the like.

  1. Continuous-Flow Bioseparation Using Microfabricated Anisotropic Nanofluidic Sieving Structures

    PubMed Central

    Fu, Jianping; Mao, Pan; Han, Jongyoon

    2010-01-01

    The anisotropic nanofluidic filter (nanofilter) array (ANA) is a unique molecular sieving structure for separating biomolecules. Here we describe fabrication of planar and vertical ANA chips and how to perform continuous-flow bioseparation using them. This protocol is most useful for bioengineers that are interested in developing automated multistep chip-based bioanalysis systems and assumes prior cleanroom microfabrication knowledge. The ANA consists of a two-dimensional periodic nanofilter array, and the designed structural anisotropy of the ANA causes different sized- or charged-biomolecules to follow distinct trajectories under applied electric fields, leading to efficient continuous-flow separation. Using microfluidic channels surrounding the ANA, the fractionated biomolecule streams are collected and routed to different fluid channels or reservoirs for convenient sample recovery and downstream bioanalysis. The ANA is physically robust and can be reused repeatedly. Compared to conventional gel-based separation techniques, the ANA offers the potential for faster separation, higher throughput, and more convenient sample recovery. PMID:19876028

  2. Surface-inspired molecular vanadium oxide catalysts for the oxidative dehydrogenation of alcohols: evidence for metal cooperation and peroxide intermediates.

    PubMed

    Werncke, C Gunnar; Limberg, Christian; Knispel, Christina; Mebs, Stefan

    2011-10-17

    On the basis that thiacalix[4]arene (H(4)T4A) complex (PPh(4) )(2) [H(2)T4A(VO(2))](2) (Ia) was found to be an adequate functional model for surface species occurring on vanadium oxide based catalysts and itself catalyses the oxidative dehydrogenation (ODH) of alcohols, an analogue containing 2,2'-thiobis(2,4-di-tert-butylphenolate), (S)L(2-), as ligand, namely, (PPh(4))(2)[(S)LVO(2)](2) (II) was investigated in the same context. Despite the apparent similarity of Ia and II, studies on II revealed several novel insights, which are also valuable in connection with surfaces of vanadia catalysts: 1) For Ia and II similar turnover numbers (TONs) were found for the ODH of activated alcohols, which indicates that the additional OH units inherent to Ia do not contribute particularly to the activity of this complex, for instance, through prebinding of the alcohol. 2) On dissolution II enters into an equilibrium with a monomeric form, which is the predominant species in solution; nevertheless, ODH proceeds exclusively at the dimeric form, and this stresses the need for cooperation of two vanadium centres. 3) By omitting O(2) from the system during the oxidation of 9-fluorenol, the reduced form of the catalyst could be isolated and fully characterised (including single-crystal X-ray analysis). The corresponding intermediate had been elusive in case of thiacalixarene system Ia. 4) Reoxidation was found to proceed via a peroxide intermediate that also oxidises one alcohol equivalent. As the peroxide can also perform mono- and dioxygenation of the thioether group in II, after a number of turnovers the active catalyst contains a sulfone group. The reduced form of this ultimate catalyst was also isolated and structurally characterised. Possible implications of 1)-4) for the function of heterogeneous vanadia catalysts are discussed. PMID:21915928

  3. Separation of branched hexane isomers using zeolite molecular sieves

    SciTech Connect

    Huddersman, K.; Klimczyk, M.

    1996-02-01

    A range of small, medium and large pore zeolite, and their modified forms are studied for their ability to separate di- from monobranched isomers of hexane. The separation studies are carried out using high-temperature (250--350 C) gas chromatography. Beta(H,Ba) is found to be the most effective separator of 2,3-dimethylbutane and 3-methyl-pentane and is therefore studied for its sorption capacities toward the two hexane isomers. This work is directed to the improvement of the quality of petrol by separating hydrocarbon mixtures using zeolites. Since maximum hydrocarbon branching is desirable in petrol (hydrocarbons with a branching structure burn more efficiently and thus have a higher octane rating), catalytic isomerization is used to isomerize straight-chain hydrocarbons to their mono- or dibranched isomers.

  4. Molecular sieve sensors for selective detection at the nanogram level

    DOEpatents

    Bein, Thomas; Brown, Kelly D.; Frye, Gregory C.; Brinker, Charles J.

    1992-01-01

    The invention relates to a selective chemical sensor for selective detection of chemical entities even at the nanogram level. The invention further relates to methods of using the sensor. The sensor comprises: (a) a piezoelectric substrate capable of detecting mass changes resulting from adsorption of material thereon; and (b) a coating applied to the substrate, which selectively sorbs chemical entities of a size smaller than a preselected magnitude.

  5. 21 CFR 173.40 - Molecular sieve resins.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... give a stable three dimensional structure. The resins have a pore size of 2.0 to 3.0 milliliters per gram of dry resin (expressed in terms of water regain), and a particle size of 10 to 300 microns....

  6. Carbon-fiber composite molecular sieves for gas separation

    SciTech Connect

    Jagtoyen, M.; Derbyshire, F.; Kimber, G.; Fei, Y.Q.

    1995-08-01

    The progress of research in the development of novel, rigid, monolithic adsorbent carbon fiber composites is described. Carbon fiber composites are produced at ORNL and activated at the CAER using steam or CO{sub 2} under different conditions, with the aims of producing a uniform degree of activation through the material, and of closely controlling pore structure and adsorptive properties The principal focus of the work to date has been to produce materials with narrow porosity for use in gas separations.

  7. Quantum-size effects in the titanosilicate molecular sieve

    NASA Astrophysics Data System (ADS)

    Borello, Enzo; Lamberti, Carlo; Bordiga, Silvia; Zecchina, Adriano; Areán, Carlos Otero

    1997-10-01

    The recently synthesized Engelhard titanosilicate (ETS-10) represents a material which contains in the structure well defined atomic ⋯O-Ti-O-Ti-O⋯ quantum wires embedded in a highly insulating siliceous matrix. We report and discuss the UV-Vis spectrum of this material and compare the experimentally determined optical band gap with the results predicted by simple modeling of a titanium oxide semiconductor wire unidimensionally confined by an infinite potential barrier.

  8. Novel nanodispersed coal liquefaction catalysts: Molecular design via microemulsion-based synthesis. Final technical report, October 1990--December 1994

    SciTech Connect

    Osseo-Asare, K.; Boakye, E.; Vittal, M.

    1995-04-01

    This report described the synthesis of Molybdenum Sulfides in microemulsions by acidification of ammonium tetrathiomolybdate. Molybdenum Sulfides have been shown to be potential coal liquefaction catalysts. The importance of particle size, temperature effects, and coal surface chemistry to impregnation are discussed.

  9. Solar Hydrogen Production Using Molecular Catalysts Immobilized on Gallium Phosphide (111)A and (111)B Polymer-Modified Photocathodes.

    PubMed

    Beiler, Anna M; Khusnutdinova, Diana; Jacob, Samuel I; Moore, Gary F

    2016-04-20

    We report the immobilization of hydrogen-producing cobaloxime catalysts onto p-type gallium phosphide (111)A and (111)B substrates via coordination to a surface-grafted polyvinylimidazole brush. Successful grafting of the polymeric interface and subsequent assembly of cobalt-containing catalysts are confirmed using grazing angle attenuated total reflection Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Photoelectrochemical testing in aqueous conditions at neutral pH shows that cobaloxime modification of either crystal face yields a similar enhancement of photoperformance, achieving a greater than 4-fold increase in current density and associated rates of hydrogen production as compared to results obtained using unfunctionalized electrodes tested under otherwise identical conditions. Under simulated solar illumination (100 mW cm(-2)), the catalyst-modified photocathodes achieve a current density ≈ 1 mA cm(-2) when polarized at 0 V vs the reversible hydrogen electrode reference and show near-unity Faradaic efficiency for hydrogen production as determined by gas chromatography analysis of the headspace. This work illustrates the modularity and versatility of the catalyst-polymer-semiconductor approach for directly coupling light harvesting to fuel production and the ability to export this chemistry across distinct crystal face orientations. PMID:26998554

  10. Unraveling a Single-Step Simultaneous Two-Electron Transfer Process from Semiconductor to Molecular Catalyst in a CoPy/CdS Hybrid System for Photocatalytic H2 Evolution under Strong Alkaline Conditions.

    PubMed

    Xu, Yuxing; Ye, Yun; Liu, Taifeng; Wang, Xiuli; Zhang, Bingqing; Wang, Mei; Han, Hongxian; Li, Can

    2016-08-31

    Electron transfer processes from semiconductor to molecular catalysts was studied in a model hybrid photocatalytic hydrogen evolution system composed of [Co((III))(dmgH)2PyCl] (CoPy) and CdS under different pH conditions. Thermodynamic and kinetic studies revealed that photocatalytic H2 evolution under high pH conditions (pH 13.5) can only account for the thermodynamically more favorable single-step simultaneous two-electron transfer from photoirradiated CdS to Co(III)Py to produce unavoidable intermediate Co(I)Py, rather than a two-step successive one-electron transfer process. This finding not only provides new insight into the charge transfer processes between semiconductors and molecular catalysts but also opens up a new avenue for the assembly and optimization of semiconductor-molecular catalyst hybrid systems processed through multielectron transfer processes. PMID:27529565

  11. Mesh Algorithms for PDE with Sieve I: Mesh Distribution

    DOE PAGESBeta

    Knepley, Matthew G.; Karpeev, Dmitry A.

    2009-01-01

    We have developed a new programming framework, called Sieve, to support parallel numerical partial differential equation(s) (PDE) algorithms operating over distributed meshes. We have also developed a reference implementation of Sieve in C++ as a library of generic algorithms operating on distributed containers conforming to the Sieve interface. Sieve makes instances of the incidence relation, or arrows, the conceptual first-class objects represented in the containers. Further, generic algorithms acting on this arrow container are systematically used to provide natural geometric operations on the topology and also, through duality, on the data. Finally, coverings and duality are used to encode notmore » only individual meshes, but all types of hierarchies underlying PDE data structures, including multigrid and mesh partitions. In order to demonstrate the usefulness of the framework, we show how the mesh partition data can be represented and manipulated using the same fundamental mechanisms used to represent meshes. We present the complete description of an algorithm to encode a mesh partition and then distribute a mesh, which is independent of the mesh dimension, element shape, or embedding. Moreover, data associated with the mesh can be similarly distributed with exactly the same algorithm. The use of a high level of abstraction within the Sieve leads to several benefits in terms of code reuse, simplicity, and extensibility. We discuss these benefits and compare our approach to other existing mesh libraries.« less

  12. A carbon-free polyoxometalate molecular catalyst with a cobalt-arsenic core for visible light-driven water oxidation.

    PubMed

    Chen, Wei-Chao; Wang, Xin-Long; Qin, Chao; Shao, Kui-Zhan; Su, Zhong-Min; Wang, En-Bo

    2016-07-21

    A carbon-free, stable, homogeneous water oxidation catalyst based on the unique hepta-nuclear cobalt-arsenic core ("fused" double-quasi-cubane) and polyoxometalate ligands, Na12[{Co(II)7As(III)6O9(OH)6}(A-α-SiW9O34)2]·8H2O (1), was synthesized, thoroughly characterized and employed to catalyze water oxidation under visible-light-driven conditions. PMID:27383015

  13. Photochemical hydrogen production from water catalyzed by CdTe quantum dots/molecular cobalt catalyst hybrid systems.

    PubMed

    Han, Kai; Wang, Mei; Zhang, Shuai; Wu, Suli; Yang, Yong; Sun, Licheng

    2015-04-25

    A hybrid system with a coordinative interaction between a cobalt complex of a N2S2-tetradentate ligand and CdTe quantum dots displayed a high activity (initial TOF 850 h(-1)) and improved stability (TON 1.44 × 10(4) based on catalyst over 30 h) for the photochemical H2 generation from water, with a quantum efficiency of 5.32% at 400 nm. PMID:25800286

  14. Manganese dioxide as a new cathode catalyst in microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Hu, Boxun; Suib, Steven; Lei, Yu; Li, Baikun

    This study focused on manganese oxides with a cryptomelane-type octahedral molecular sieve (OMS-2) structure to replace platinum as a cathode catalyst in microbial fuel cells (MFCs). Undoped (ud-OSM-2) and three catalysts doped with cobalt (Co-OMS-2), copper (Cu-OMS-2), and cerium (Ce-OMS-2) to enhance their catalytic performances were investigated. The novel OMS-2 cathodes were examined in granular activated carbon MFC (GACMFC) with sodium acetate as the anode reagent and oxygen in air as the cathode reagent. The results showed that after 400 h of operation, the Co-OMS-2 and Cu-OMS-2 exhibited good catalytic performance in an oxygen reduction reaction (ORR). The voltage of the Co-OMS-2 GACMFC was 217 mV, and the power density was 180 mW m -2. The voltage of the Cu-OMS-2 GACMFC was 214 mV and the power density was 165 mW m -2. The internal resistance (R in) of the OMS-2 GACMFCs (18 ± 1 Ω) was similar to that of the platinum GACMFCs (17 Ω). Furthermore, the degradation rates of organic substrates in the OMS-2 GACMFCs were twice those in the platinum GACMFCs, which enhance their wastewater treatment efficiencies. This study indicated that using OMS-2 manganese oxides to replace platinum as a cathodic catalyst enhances power generation, increases contaminant removal, and substantially reduces the cost of MFCs.

  15. Understanding the Electronic Structure of 4d Metal Complexes: From Molecular Spinors to L-Edge Spectra of a di-Ru Catalyst

    SciTech Connect

    Alperovich, Igor; Smolentsev, Grigory; Moonshiram, Dooshaye; Jurss, Jonah W.; Concepcion, Javier J.; Meyer, Thomas J.; Soldatov, Alexander; Pushkar, Yulia

    2015-09-17

    L{sub 2,3}-edge X-ray absorption spectroscopy (XAS) has demonstrated unique capabilities for the analysis of the electronic structure of di-Ru complexes such as the blue dimer cis,cis-[Ru{sub 2}{sup III}O(H{sub 2}O){sub 2}(bpy){sub 4}]{sup 4+} water oxidation catalyst. Spectra of the blue dimer and the monomeric [Ru(NH{sub 3}){sub 6}]{sup 3+} model complex show considerably different splitting of the Ru L{sub 2,3} absorption edge, which reflects changes in the relative energies of the Ru 4d orbitals caused by hybridization with a bridging ligand and spin-orbit coupling effects. To aid the interpretation of spectroscopic data, we developed a new approach, which computes L{sub 2,3}-edges XAS spectra as dipole transitions between molecular spinors of 4d transition metal complexes. This allows for careful inclusion of the spin-orbit coupling effects and the hybridization of the Ru 4d and ligand orbitals. The obtained theoretical Ru L{sub 2,3}-edge spectra are in close agreement with experiment. Critically, existing single-electron methods (FEFF, FDMNES) broadly used to simulate XAS could not reproduce the experimental Ru L-edge spectra for the [Ru(NH{sub 3}){sub 6}]{sup 3+} model complex nor for the blue dimer, while charge transfer multiplet (CTM) calculations were not applicable due to the complexity and low symmetry of the blue dimer water oxidation catalyst. We demonstrated that L-edge spectroscopy is informative for analysis of bridging metal complexes. The developed computational approach enhances L-edge spectroscopy as a tool for analysis of the electronic structures of complexes, materials, catalysts, and reactive intermediates with 4d transition metals.

  16. Molecular separation method and apparatus

    DOEpatents

    Villa-Aleman, E.

    1996-04-09

    A method and apparatus are disclosed for separating a gaseous mixture of chemically identical but physically different molecules based on their polarities. The gaseous mixture of molecules is introduced in discrete quantities into the proximal end of a porous glass molecular sieve. The molecular sieve is exposed to microwaves to excite the molecules to a higher energy state from a lower energy state, those having a higher dipole moment being excited more than those with a lower energy state. The temperature of the sieve kept cold by a flow of liquid nitrogen through a cooling jacket so that the heat generated by the molecules colliding with the material is transferred away from the material. The molecules thus alternate between a higher energy state and a lower one, with the portion of molecules having the higher dipole moment favored over the others. The former portion can then be extracted separately from the distal end of the molecular sieve. 2 figs.

  17. Hybrid photocathodes for solar fuel production: coupling molecular fuel-production catalysts with solid-state light harvesting and conversion technologies

    PubMed Central

    Cedeno, Diana; Krawicz, Alexandra; Moore, Gary F.

    2015-01-01

    Artificial photosynthesis is described as the great scientific and moral challenge of our time. We imagine a future where a significant portion of our energy is supplied by such technologies. However, many scientific, engineering and policy challenges must be addressed for this realization. Scientific challenges include the development of effective strategies to couple light absorption, electron transfer and catalysis for efficient conversion of light energy to chemical energy as well as the construction and study of structurally diverse assemblies to carry out these processes. In this article, we review recent efforts from our own research to develop a modular approach to interfacing molecular fuel-production catalysts to visible-light-absorbing semiconductors and discuss the role of the interfacing material as a protection layer for the catalysts as well as the underpinning semiconductor. In concluding, we briefly discuss the potential benefits of a globally coordinated project on artificial photosynthesis that interfaces teams of scientists, engineers and policymakers. Further, we offer cautions that such a large interconnected organization should consider. This article is inspired by, and draws largely from, an invited presentation given by the corresponding author at the Royal Society at Chicheley Hall, home of the Kavli Royal Society International Centre, Buckinghamshire on the themed meeting topic: ‘Do we need a global project on artificial photosynthesis?’ PMID:26052422

  18. Electrocatalytic and Solar-Driven CO2 Reduction to CO with a Molecular Manganese Catalyst Immobilized on Mesoporous TiO2.

    PubMed

    Rosser, Timothy E; Windle, Christopher D; Reisner, Erwin

    2016-06-20

    Electrocatalytic CO2 reduction to CO was achieved with a novel Mn complex, fac-[MnBr(4,4'-bis(phosphonic acid)-2,2'-bipyridine)(CO)3 ] (MnP), immobilized on a mesoporous TiO2 electrode. A benchmark turnover number of 112±17 was attained with these TiO2 |MnP electrodes after 2 h electrolysis. Post-catalysis IR spectroscopy demonstrated that the molecular structure of the MnP catalyst was retained. UV/vis spectroscopy confirmed that an active Mn-Mn dimer was formed during catalysis on the TiO2 electrode, showing the dynamic formation of a catalytically active dimer on an electrode surface. Finally, we combined the light-protected TiO2 |MnP cathode with a CdS-sensitized photoanode to enable solar-light-driven CO2 reduction with the light-sensitive MnP catalyst. PMID:27110904

  19. Hybrid photocathodes for solar fuel production: coupling molecular fuel-production catalysts with solid-state light harvesting and conversion technologies.

    PubMed

    Cedeno, Diana; Krawicz, Alexandra; Moore, Gary F

    2015-06-01

    Artificial photosynthesis is described as the great scientific and moral challenge of our time. We imagine a future where a significant portion of our energy is supplied by such technologies. However, many scientific, engineering and policy challenges must be addressed for this realization. Scientific challenges include the development of effective strategies to couple light absorption, electron transfer and catalysis for efficient conversion of light energy to chemical energy as well as the construction and study of structurally diverse assemblies to carry out these processes. In this article, we review recent efforts from our own research to develop a modular approach to interfacing molecular fuel-production catalysts to visible-light-absorbing semiconductors and discuss the role of the interfacing material as a protection layer for the catalysts as well as the underpinning semiconductor. In concluding, we briefly discuss the potential benefits of a globally coordinated project on artificial photosynthesis that interfaces teams of scientists, engineers and policymakers. Further, we offer cautions that such a large interconnected organization should consider. This article is inspired by, and draws largely from, an invited presentation given by the corresponding author at the Royal Society at Chicheley Hall, home of the Kavli Royal Society International Centre, Buckinghamshire on the themed meeting topic: 'Do we need a global project on artificial photosynthesis?' PMID:26052422

  20. Widely tunable alloy composition and crystal structure in catalyst-free InGaAs nanowire arrays grown by selective area molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Treu, J.; Speckbacher, M.; Saller, K.; Morkötter, S.; Döblinger, M.; Xu, X.; Riedl, H.; Abstreiter, G.; Finley, J. J.; Koblmüller, G.

    2016-02-01

    We delineate the optimized growth parameter space for high-uniformity catalyst-free InGaAs nanowire (NW) arrays on Si over nearly the entire alloy compositional range using selective area molecular beam epitaxy. Under the required high group-V fluxes and V/III ratios, the respective growth windows shift to higher growth temperatures as the Ga-content x(Ga) is tuned from In-rich to Ga-rich InGaAs NWs. Using correlated x-ray diffraction, transmission electron microscopy, and micro-photoluminescence spectroscopy, we identify structural defects to govern luminescence linewidths in In-rich (x(Ga) < 0.4) and Ga-rich (x(Ga) > 0.6) NWs, whereas limitations at intermediate Ga-content (0.4 < x(Ga) < 0.6) are mainly due to compositional inhomogeneities. Most remarkably, the catalyst-free InGaAs NWs exhibit a characteristic transition in crystal structure from wurtzite to zincblende (ZB) dominated phase near x(Ga) ˜ 0.4 that is further reflected in a cross-over from blue-shifted to red-shifted photoluminescence emission relative to the band edge emission of the bulk ZB InGaAs phase.

  1. Correlation and Prediction of Redox Potentials of Hydrogen Evolution Mononuclear Cobalt Catalysts via Molecular Electrostatic Potential: A DFT Study.

    PubMed

    Anjali, Bai Amutha; Sayyed, Fareed Bhasha; Suresh, Cherumuttathu H

    2016-02-25

    Reduction potentials (E(0)) of six mononuclear cobalt catalysts (1-6) for hydrogen evolution reaction and electron donating/withdrawing effect of nine X-substituents on their macrocyclic ligand are reported at solvation effect-included B3P86/6-311+G** level of density functional theory. The electrostatic potential at the Co nucleus (VCo) is found to be a powerful descriptor of the electronic effect experienced by Co from the ligand environment. The VCo values vary substantially with respect to the nature of macrocycle, type of apical ligands, nature of substituent and oxidation state of the metal center. Most importantly, VCo values of both the oxidized and reduced states of all the six complexes show strong linear correlation with E(0). The correlation plots between VCo and E(0) provide an easy-to-interpret graphical interpretation and quantification of the effect of ligand environment on the reduction potential. Further, on the basis of a correlation between the relative VCo and relative E(0) values of a catalyst with respect to the CF3-substituted reference system, the E(0) of any X-substituted 1-6 complexes is predicted. PMID:26836251

  2. A Ru-Co hybrid material based on a molecular photosensitizer and a heterogeneous catalyst for light-driven water oxidation.

    PubMed

    Wang, Hong-Yan; Liu, Jia; Zhu, Jiefang; Styring, Stenbjörn; Ott, Sascha; Thapper, Anders

    2014-02-28

    A novel approach to anchor a molecular photosensitizer onto a heterogeneous water oxidation catalyst via coordination bonds is presented. A photosensitizer (1) based on [Ru(bpy)3](2+) and decorated with two methylenediphosphonate (M2P) groups has been designed and synthesized for this purpose. The M2P groups in complex 1 allow for coordination of cobalt ions to afford a novel molecular-heterogeneous hybrid material P1. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize P1 as an amorphous, non-uniform material that contains Ru and Co in a ratio of 1 : 2. A suspension of P1 in a buffered aqueous solution is active as a light-driven water oxidation catalyst in the presence of persulfate (S2O8(2-)) as electron acceptor. The yield of oxygen is higher when P1 is prepared in situ by mixing and illuminating 1 and Co(2+) in the presence of S2O8(2-). After oxygen evolution ceases, a second material P2 can be isolated from the reaction mixture. P2 is characterized by a lower Ru content than P1, and contains Co in a higher oxidation state. Interestingly, P2 as a freshly prepared suspension is also active for light-driven water oxidation. It is shown that 1 resides in the interior of P1 and P2, and is thus in a location where undesirable quenching pathways of the photo-excited state of 1 limit the oxygen production yields for both P1 and P2. PMID:24419175

  3. Ultra-broadband achromatic imaging with diffractive photon sieves

    PubMed Central

    Zhao, Xiaonan; Hu, Jingpei; Lin, Yu; Xu, Feng; Zhu, Xiaojun; Pu, Donglin; Chen, Linsen; Wang, Chinhua

    2016-01-01

    Diffractive optical elements suffer from large chromatic aberration due to the strong wavelength-dependent nature in diffraction phenomena, and therefore, diffractive elements can work only at a single designed wavelength, which significantly limits the applications of diffractive elements in imaging. Here, we report on a demonstration of a wavefront coded broadband achromatic imaging with diffractive photon sieves. The broadband diffraction imaging is implemented with a wavefront coded pinhole pattern that generates equal focusing power for a wide range of operating wavelength in a single thin-film element without complicated auxiliary optical system. Experimental validation was performed using an UV-lithography fabricated wavefront coded photon sieves. Results show that the working bandwidth of the wavefront coded photon sieves reaches 28 nm compared with 0.32 nm of the conventional one. Further demonstration of the achromatic imaging with a bandwidth of 300 nm is also performed with a wavefront coded photon sieves integrated with a refractive element. PMID:27328713

  4. Ultra-broadband achromatic imaging with diffractive photon sieves.

    PubMed

    Zhao, Xiaonan; Hu, Jingpei; Lin, Yu; Xu, Feng; Zhu, Xiaojun; Pu, Donglin; Chen, Linsen; Wang, Chinhua

    2016-01-01

    Diffractive optical elements suffer from large chromatic aberration due to the strong wavelength-dependent nature in diffraction phenomena, and therefore, diffractive elements can work only at a single designed wavelength, which significantly limits the applications of diffractive elements in imaging. Here, we report on a demonstration of a wavefront coded broadband achromatic imaging with diffractive photon sieves. The broadband diffraction imaging is implemented with a wavefront coded pinhole pattern that generates equal focusing power for a wide range of operating wavelength in a single thin-film element without complicated auxiliary optical system. Experimental validation was performed using an UV-lithography fabricated wavefront coded photon sieves. Results show that the working bandwidth of the wavefront coded photon sieves reaches 28 nm compared with 0.32 nm of the conventional one. Further demonstration of the achromatic imaging with a bandwidth of 300 nm is also performed with a wavefront coded photon sieves integrated with a refractive element. PMID:27328713

  5. Methanol conversion to light olefins over nanostructured CeAPSO-34 catalyst: Thermodynamic analysis of overall reactions and effect of template type on catalytic properties and performance

    SciTech Connect

    Aghamohammadi, Sogand; Haghighi, Mohammad; Charghand, Mojtaba

    2014-02-01

    Graphical abstract: In this research nanostructured CeAPSO-34 was synthesized to explore the effect of TEAOH and morpholine on its physiochemical properties and MTO performance. Prepared catalysts were characterized with XRD, FESEM, BET, FTIR and NH3-TPD techniques. The results indicated that the nature of the template determines the physiochemical properties of CeAPSO-34 due to different rate of crystal growth. The catalyst obtained by using morpholine showed longer life time as well as sustaining light olefins selectivity at higher values. Furthermore, a comprehensive thermodynamic analysis of overall reactions network was carried out to address the major channels of methanol to olefins conversion. - Highlights: • Introduction of Ce into SAPO-34 framework. • Comparison of CeAPSO-34 synthesized using morpholine and TEAOH. • The nature of the template determines the physiochemical properties of CeAPSO-34. • Morpholine enhances catalyst lifetime in MTO process. • Presenting a complete reaction network for MTO process. - Abstract: TEAOH and morpholine were employed in synthesis of nanostructured CeAPSO-34 molecular sieve and used in methanol to olefins conversion. Prepared samples were characterized by XRD, FESEM, EDX, BET, FTIR and NH{sub 3}-TPD techniques. XRD patterns reflected the higher crystallinity of the catalyst synthesized with morpholine. The FESEM results indicated that the nature of the template determines the morphology of nanostructured CeAPSO-34 due to different rate of crystal growth. There was a meaningful difference in the strength of both strong and weak acid sites for CeAPSO-34 catalysts synthesized with TEAOH and morpholine templates. The catalyst synthesized with morpholine showed higher desorption temperature of both weak and strong acid sites evidenced by NH{sub 3}-TPD characterization. The catalyst obtained using morpholine template had the longer lifetime and sustained desired light olefins at higher values. A comprehensive

  6. Sieve Element Ca2+ Channels as Relay Stations between Remote Stimuli and Sieve Tube Occlusion in Vicia faba[W

    PubMed Central

    Furch, Alexandra C.U.; van Bel, Aart J.E.; Fricker, Mark D.; Felle, Hubert H.; Fuchs, Maike; Hafke, Jens B.

    2009-01-01

    Damage induces remote occlusion of sieve tubes in Vicia faba by forisome dispersion, triggered during the passage of an electropotential wave (EPW). This study addresses the role of Ca2+ channels and cytosolic Ca2+ elevation as a link between EPWs and forisome dispersion. Ca2+ channel antagonists affect the initial phase of the EPW as well as the prolonged plateau phase. Resting levels of sieve tube Ca2+ of ∼50 nM were independently estimated using Ca2+-selective electrodes and a Ca2+-sensitive dye. Transient changes in cytosolic Ca2+ were observed in phloem tissue in response to remote stimuli and showed profiles similar to those of EPWs. The measured elevation of Ca2+ in sieve tubes was below the threshold necessary for forisome dispersion. Therefore, forisomes need to be associated with Ca2+ release sites. We found an association between forisomes and endoplasmic reticulum (ER) at sieve plates and pore-plasmodesma units where high-affinity binding of a fluorescent Ca2+ channel blocker mapped an increased density of Ca2+ channels. In conclusion, propagation of EPWs in response to remote stimuli is linked to forisome dispersion through transiently high levels of parietal Ca2+, release of which depends on both plasma membrane and ER Ca2+ channels. PMID:19602624

  7. High-Resolution Solar Imaging With Photon Sieves

    NASA Astrophysics Data System (ADS)

    Oktem, F. S.; Kamalabadi, F.; Davila, J. M.

    2014-12-01

    A photon sieve is a modification of a Fresnel zone plate in which open zones are replaced by a large number of circular holes. This lightweight optical device offers a superior image forming capability compared with the Fresnel zone plate, and is specially suited to observations at UV and x-ray wavelengths where refractive lenses are not available due to strong absorption of materials, and reflective mirrors are difficult to manufacture to achieve near diffraction-limited resolution. At these shorter wavelengths, photon sieves enable diffraction-limited imaging performance with relaxed manufacturing tolerances, and simple and low-cost fabrication. In this work, we present a new photon sieve imaging modality that, unlike previous designs, takes advantage of chromatic aberration. The fact that different wavelengths are focused at different distances from photon sieve is exploited to develop a novel multi-spectral imaging technique. The idea is to use a photon sieve imaging system with a moving detector which records images at different planes. Each measurement consists of superimposed images of different wavelengths, with each individual image being either in focus or out of focus. For spatially incoherent illumination, we study the problem of recovering the individual images from these superimposed measurements. We first formulate the discrete forward problem using the closed-form Fresnel imaging formulas. The inverse problem is then a multi-frame deconvolution problem involving multiple objects, and is formulated as a maximum posterior estimation problem. The resulting nonlinear optimization problem is solved using a fixed-point iterative algorithm. In contrast to traditional spectral imagers employing a series of wavelength filters, the proposed technique relies on a simple optical system, but incorporates powerful image processing methods to form spectral images computationally. In addition to diffraction-limited high spatial resolution enabled by photon sieves

  8. Electrocatalytic oxidation of glucose by rhodium porphyrin-functionalized MWCNT electrodes: application to a fully molecular catalyst-based glucose/O2 fuel cell.

    PubMed

    Elouarzaki, Kamal; Le Goff, Alan; Holzinger, Michael; Thery, Jessica; Cosnier, Serge

    2012-08-29

    This paper details the electrochemical investigation of a deuteroporphyrin dimethylester (DPDE) rhodium(III) ((DPDE)Rh(III)) complex, immobilized within a MWCNT/Nafion electrode, and its integration into a molecular catalysis-based glucose fuel cell. The domains of present (DPDE)Rh(I), (DPDE)Rh-H, (DPDE)Rh(II), and (DPDE)Rh(III) were characterized by surface electrochemistry performed at a broad pH range. The Pourbaix diagrams (plots of E(1/2) vs pH) support the stability of (DPDE)Rh(II) at intermediate pH and the predominance of the two-electron redox system (DPDE)Rh(I)/(DPDE)Rh(III) at both low and high pH. This two-electron system is especially involved in the electrocatalytic oxidation of alcohols and was applied to the glucose oxidation. The catalytic oxidation mechanism exhibits an oxidative deactivation coupled with a reductive reactivation mechanism, which has previously been observed for redox enzymes but not yet for a metal-based molecular catalyst. The MWCNT/(DPDE)Rh(III) electrode was finally integrated in a novel design of an alkaline glucose/O(2) fuel cell with a MWCNT/phthalocyanin cobalt(II) (CoPc) electrode for the oxygen reduction reaction. This nonenzymatic molecular catalysis-based glucose fuel cell exhibits a power density of P(max) = 0.182 mW cm(-2) at 0.22 V and an open circuit voltage (OCV) of 0.64 V. PMID:22816654

  9. Molecular engineering of porous silica using aryl templates

    DOEpatents

    Loy, D.A.; Shea, K.J.

    1994-06-14

    A process is described for manipulating the porosity of silica using a series of organic template groups covalently incorporated into the silicate matrix. The templates in the bridged polysilsesquioxanes are selectively removed from the material by oxidation with oxygen plasma or other means, leaving engineered voids or pores. The size of these pores is dependent upon the length or size of the template or spacer. The size of the templates is measured in terms of Si-Si distances which range from about 0.67 nm to 1.08 nm. Changes introduced by the loss of the templates result in a narrow range of micropores (i.e. <2 nm). Both aryl and alkyl template groups are used as spacers. Novel microporous silica materials useful as molecular sieves, desiccants, and catalyst supports are produced. 3 figs.

  10. The feasibility of images reconstructed with the method of sieves

    SciTech Connect

    Veklerov, E.; Llacer, J.

    1989-04-01

    The concept of sieves has been applied with the Maximum likelihood Estimator (MLE) to image reconstruction. While it makes it possible to recover smooth images consistent with the data, the degree of smoothness provided by it is arbitrary. It is shown that the concept of feasibility is able to resolve this arbitrariness. By varying the values of parameters determining the degree of smoothness, one can generate images on both sides of the feasibility region, as well as within the region. Feasible images recovered by using different sieve parameters are compared with feasible results of other procedures. One- and two-dimensional examples using both simulated and real data sets are considered. 12 refs., 3 figs., 2 tabs.

  11. Focusing properties of phase-only generalized Fibonacci photon sieves

    NASA Astrophysics Data System (ADS)

    Ke, Jie; Zhang, Junyong

    2016-06-01

    We propose a new algorithm to extend the standard Fibonacci photon sieve to the phase-only generalized Fibonacci photon sieve (GFiPS) and find that the focusing properties of the phase-only GFiPS are only relevant to the characteristic roots of the recursion relation of the generalized Fibonacci sequences. By switching the transparent and opaque zones on the basis of the generalized Fibonacci sequences, we not only realize adjustable bifocal lengths, but also give their corresponding analytic expressions. Besides, we investigate a special phase-only GFiPS, a spiral-phase GFiPS, which can present twin vortices along the axial coordinate. Compared with the single focusing system, bifocal system can be exploited to enhance the processing speed, and offer a broad range of applications, such as direct laser writing, optical tweezers or atom trapping and paralleled fluorescence microscope.

  12. SUT2, a Putative Sucrose Sensor in Sieve Elements

    PubMed Central

    Barker, Laurence; Kühn, Christina; Weise, Andreas; Schulz, Alexander; Gebhardt, Christiane; Hirner, Brigitte; Hellmann, Hanjo; Schulze, Waltraud; Ward, John M.; Frommer, Wolf B.

    2000-01-01

    In leaves, sucrose uptake kinetics involve high- and low-affinity components. A family of low- and high-affinity sucrose transporters (SUT) was identified. SUT1 serves as a high-affinity transporter essential for phloem loading and long-distance transport in solanaceous species. SUT4 is a low-affinity transporter with an expression pattern overlapping that of SUT1. Both SUT1 and SUT4 localize to enucleate sieve elements of tomato. New sucrose transporter–like proteins, named SUT2, from tomato and Arabidopsis contain extended cytoplasmic domains, thus structurally resembling the yeast sugar sensors SNF3 and RGT2. Features common to these sensors are low codon bias, environment of the start codon, low expression, and lack of detectable transport activity. In contrast to LeSUT1, which is induced during the sink-to-source transition of leaves, SUT2 is more highly expressed in sink than in source leaves and is inducible by sucrose. LeSUT2 protein colocalizes with the low- and high-affinity sucrose transporters in sieve elements of tomato petioles, indicating that multiple SUT mRNAs or proteins travel from companion cells to enucleate sieve elements. The SUT2 gene maps on chromosome V of potato and is linked to a major quantitative trait locus for tuber starch content and yield. Thus, the putative sugar sensor identified colocalizes with two other sucrose transporters, differs from them in kinetic properties, and potentially regulates the relative activity of low- and high-affinity sucrose transport into sieve elements. PMID:10899981

  13. A differential delay equation arising from the sieve of Eratosthenes

    NASA Technical Reports Server (NTRS)

    Cheer, A. Y.; Goldston, D. A.

    1990-01-01

    Consideration is given to the differential delay equation introduced by Buchstab (1937) in connection with an asymptotic formula for the uncanceled terms in the sieve of Eratosthenes. Maier (1985) used this result to show there is unexpected irreqularity in the distribution of primes in short intervals. The function omega(u) is studied in this paper using numerical and analytical techniques. The results are applied to give some numerical constants in Maier's theorem.

  14. Predictability sieve, pointer states, and the classicality of quantum trajectories

    SciTech Connect

    Dalvit, D. A. R.; Zurek, W. H.; Dziarmaga, J.

    2005-12-15

    We study various measures of classicality of the states of open quantum systems subject to decoherence. Classical states are expected to be stable in spite of decoherence, and are thought to leave conspicuous imprints on the environment. Here these expected features of environment-induced superselection are quantified using four different criteria: predictability sieve (which selects states that produce least entropy), purification time (which looks for states that are the easiest to find out from the imprint they leave on the environment), efficiency threshold (which finds states that can be deduced from measurements on a smallest fraction of the environment), and purity loss time (that looks for states for which it takes the longest to lose a set fraction of their initial purity). We show that when pointer states--the most predictable states of an open quantum system selected by the predictability sieve--are well defined, all four criteria agree that they are indeed the most classical states. We illustrate this with two examples: an underdamped harmonic oscillator, for which coherent states are unanimously chosen by all criteria, and a free particle undergoing quantum Brownian motion, for which most criteria select almost identical Gaussian states (although, in this case, the predictability sieve does not select well defined pointer states)

  15. 3D Oxidized Graphene Frameworks for Efficient Nano Sieving.

    PubMed

    Pawar, Pranav Bhagwan; Saxena, Sumit; Badhe, Dhanashree Kamlesh; Chaudhary, Raghvendra Pratap; Shukla, Shobha

    2016-01-01

    The small size of Na(+) and Cl(-) ions provides a bottleneck in desalination and is a challenge in providing alternatives for continuously depleting fresh water resources. Graphene by virtue of its structural properties has the potential to address this issue. Studies have indicated that use of monolayer graphene can be used to filter micro volumes of saline solution. Unfortunately it is extremely difficult, resource intensive and almost impractical with current technology to fabricate operational devices using mono-layered graphene. Nevertheless, graphene based devices still hold the key to solve this problem due to its nano-sieving ability. Here we report synthesis of oxidized graphene frameworks and demonstrate a functional device to desalinate and purify seawater from contaminants including Na(+) and Cl(-) ions, dyes and other microbial pollutants. Micro-channels in these frameworks help in immobilizing larger suspended solids including bacteria, while nano-sieving through graphene enables the removal of dissolved ions (e.g. Cl(-)). Nano-sieving incorporated with larger frameworks has been used in filtering Na(+) and Cl(-) ions in functional devices. PMID:26892277

  16. 3D Oxidized Graphene Frameworks for Efficient Nano Sieving

    PubMed Central

    Pawar, Pranav Bhagwan; Saxena, Sumit; Badhe, Dhanashree Kamlesh; Chaudhary, Raghvendra Pratap; Shukla, Shobha

    2016-01-01

    The small size of Na+ and Cl− ions provides a bottleneck in desalination and is a challenge in providing alternatives for continuously depleting fresh water resources. Graphene by virtue of its structural properties has the potential to address this issue. Studies have indicated that use of monolayer graphene can be used to filter micro volumes of saline solution. Unfortunately it is extremely difficult, resource intensive and almost impractical with current technology to fabricate operational devices using mono-layered graphene. Nevertheless, graphene based devices still hold the key to solve this problem due to its nano-sieving ability. Here we report synthesis of oxidized graphene frameworks and demonstrate a functional device to desalinate and purify seawater from contaminants including Na+ and Cl− ions, dyes and other microbial pollutants. Micro-channels in these frameworks help in immobilizing larger suspended solids including bacteria, while nano-sieving through graphene enables the removal of dissolved ions (e.g. Cl−). Nano-sieving incorporated with larger frameworks has been used in filtering Na+ and Cl− ions in functional devices. PMID:26892277

  17. Bimetallic Catalysts.

    ERIC Educational Resources Information Center

    Sinfelt, John H.

    1985-01-01

    Chemical reaction rates can be controlled by varying composition of miniscule clusters of metal atoms. These bimetallic catalysts have had major impact on petroleum refining, where work has involved heterogeneous catalysis (reacting molecules in a phase separate from catalyst.) Experimentation involving hydrocarbon reactions, catalytic…

  18. Oxyhydrochlorination catalyst

    DOEpatents

    Taylor, Charles E.; Noceti, Richard P.

    1992-01-01

    An improved catalyst and method for the oxyhydrochlorination of methane is disclosed. The catalyst includes a pyrogenic porous support on which is layered as active material, cobalt chloride in major proportion, and minor proportions of an alkali metal chloride and of a rare earth chloride. On contact of the catalyst with a gas flow of methane, HCl and oxygen, more than 60% of the methane is converted and of that converted more than 40% occurs as monochloromethane. Advantageously, the monochloromethane can be used to produce gasoline boiling range hydrocarbons with the recycle of HCl for further reaction. This catalyst is also of value for the production of formic acid as are analogous catalysts with lead, silver or nickel chlorides substituted for the cobalt chloride.

  19. Reactions of aqueous glucose solution over solid-acid Y-zeolite catalyst at 110-160 C

    SciTech Connect

    Lourvanij, K.; Rorrer, G.L. )

    1993-01-01

    Reactions of glucose with solid-acid Y-zeolite catalyst were studied to see if this heterogeneous system could produce oxygenated hydrocarbons by shape-selective, acid-catalyzed processes at fairly low temperatures. Experimentally, aqueous solutions of glucose (12 wt %) were reacted with HY-zeolite powder in a well-mixed batch reactor at temperatures ranging from 110 to 160 C and catalyst concentrations ranging from 2 to 20 g/150 ml. Unreacted glucose and oxygenated hydrocarbon products were measured by HPLC as a function of reaction time (0-24 h) and process conditions. Glucose conversions of 100% were obtained at 160 C after an 8-h reaction time. The apparent activation energy based on glucose conversion was 23.25 [plus minus] 0.40 kcal/mol. Several acid-catalyzed reactions were identified, including isomerization of glucose to fructose, partial dehydration of glucose to 5-(hydroxymethyl)furfural (HMF), rehydration and cleavage of HMF to formic acid and 4-oxo-pentanoic acid, and carbonization . Polymers of HMF and seven minor additional products in the lower molecular weight organic acids/aldehydes/ketones elution range were also isolated by HPLC. High yields of organic acids relative to HMF and lowered selectivity of HMF in the bulk phase relative to the homogeneous acid-catalyzed reaction suggests the possibility of molecular sieving reactions within the Y-zeolite in addition to reactions on the outer surface of the Y-zeolite particle.

  20. Iron Pentapyridyl Complexes as Molecular Water Oxidation Catalysts: Strong Influence of a Chloride Ligand and pH in Altering the Mechanism.

    PubMed

    Das, Biswanath; Orthaber, Andreas; Ott, Sascha; Thapper, Anders

    2016-05-23

    The development of molecular water oxidation catalysts based on earth-abundant, non-noble metals is essential for artificial photosynthesis research. Iron, which is the most abundant transition metal in the earth's crust, is a prospective candidate for this purpose. Herein, we report two iron complexes based on the polypyridyl ligand Py5OH (Py5OH=pyridine-2,6-diylbis [di(pyridin-2-yl)methanol]) that can catalyse water oxidation to produce O2 in Ru(III) -induced (at pH 8, highest turnover number (TON)=26.5; turnover frequency (TOF)=2.2 s(-1) ), Ce(IV) -induced (at pH≈1.5 highest TON=16; TOF=0.75 s(-1) ) and photo-induced (at pH 8, highest TON=43.5; TOF=0.6 s(-1) ) reactions. A chloride ligand in one of the iron complexes is shown to affect the activity strongly, improve stability and, thereby, the performance at pH 8 but it inhibits oxygen evolution at pH≈1.5. The observations are consistent with a change in mechanism for catalytic water oxidation with the Fe(Py5OH) complexes between acidic (Ce(IV) ) and near-neutral pH (Ru(III) ). PMID:27114078

  1. Probing the smallest molecular model of MoS2 catalyst: S2 units in the MoS(-/0 (n = 1-5) clusters.

    PubMed

    Wang, Bin; Wu, Ni; Zhang, Xiao-Bin; Huang, Xin; Zhang, Yong-Fan; Chen, Wen-Kai; Ding, Kai-Ning

    2013-07-11

    Density functional theory (DFT) and coupled cluster theory (CCSD(T)) calculations are carried out to investigate the electronic and structural properties of a series of monomolybdenum sulfide clusters, MoSn(-/0) (n = 1-5). Generalized Koopmans' theorem is applied to predict the vertical detachment energies and simulate the photoelectron spectra (PES). We found that the additional sulfur atoms have a tendency to successively occupy the terminal sites in the sequential sulfidation until the Mo reaches its maximum oxidation sate of +6. After that, the polysulfide ligands (viz., S2 and S3) emerge in the MoS4 and MoS5(-/0) clusters. The MoS4 (C2, (1)A) is predicted to be the ground state and may be used as a neutral model for the sulfur-rich edge sites of the fresh MoS2 catalysts. Molecular orbital analyses are performed to analyze the chemical bonding in the monomolybdenum sulfide clusters and to elucidate their electronic and structural evolution. PMID:23767784

  2. What did Erwin mean? The physics of information from the materials genomics of aperiodic crystals and water to molecular information catalysts and life.

    PubMed

    Varn, D P; Crutchfield, J P

    2016-03-13

    Erwin Schrödinger famously and presciently ascribed the vehicle transmitting the hereditary information underlying life to an 'aperiodic crystal'. We compare and contrast this, only later discovered to be stored in the linear biomolecule DNA, with the information-bearing, layered quasi-one-dimensional materials investigated by the emerging field of chaotic crystallography. Despite differences in functionality, the same information measures capture structure and novelty in both, suggesting an intimate coherence between the information character of biotic and abiotic matter-a broadly applicable physics of information. We review layered solids and consider three examples of how information- and computation-theoretic techniques are being applied to understand their structure. In particular, (i) we review recent efforts to apply new kinds of information measures to quantify disordered crystals; (ii) we discuss the structure of ice I in information-theoretic terms; and (iii) we recount recent investigations into the structure of tris(bicyclo[2.1.1]hexeno)benzene, showing how an information-theoretic analysis yields additional insight into its structure. We then illustrate a new Second Law of Thermodynamics that describes information processing in active low-dimensional materials, reviewing Maxwell's Demon and a new class of molecular devices that act as information catalysts. Lastly, we conclude by speculating on how these ideas from informational materials science may impact biology. PMID:26857672

  3. Efficient new ribozyme mimics: direct mapping of molecular design principles from small molecules to macromolecular, biomimetic catalysts

    PubMed Central

    Putnam, William C.; Daniher, Andrew T.; Trawick, Bobby N.; Bashkin, James K.

    2001-01-01

    Dramatic improvements in ribozyme mimics have been achieved by employing the principles of small molecule catalysis to the design of macromolecular, biomimetic reagents. Ribozyme mimics derived from the ligand 2,9-dimethylphenanthroline (neocuproine) show at least 30-fold improvements in efficiency at sequence-specific RNA cleavage when compared with analogous o-phenanthroline- and terpyridine-derived reagents. The suppression of hydroxide-bridged dimers and the greater activation of coordinated water by Cu(II) neocuproine (compared with the o-phananthroline and terpyridine complexes) better allow Cu(II) to reach its catalytic potential as a biomimetic RNA cleavage agent. This work demonstrates the direct mapping of molecular design principles from small-molecule cleavage to macromolecular cleavage events, generating enhanced biomimetic, sequence-specific RNA cleavage agents. PMID:11353090

  4. Polymerization catalyst

    SciTech Connect

    Graves, V.

    1987-05-12

    A process is described for polymerizing at least one alpha olefin under conditions characteristic of Ziegler polymerization wherein the polymerization is conducted in the presence of a catalyst system which comprises: a supported catalyst prepared under anhydrous conditions by the sequential steps of: preparing a slurry of inert particulate support material; adding to the slurry a solution of an organomagnesium compound; adding to the slurry and reacting a solution of a zirconium halide compound, hafnium compound or mixtures thereof; adding to the slurry and reacting a halogenator; adding to the slurry and reacting a tetravalent titanium halide compound; and recovering solid catalyst.

  5. Polymerization catalyst

    SciTech Connect

    Graves, V.

    1986-10-21

    A process is described for polymerizing at least one alpha-olefin under conditions characteristic of Ziegler polymerization wherein the polymerization is conducted in the presence of a catalyst comprising: a supported catalyst prepared under anhydrous conditions by the steps of: (1) sequentially; (a) preparing a slurry of inert particulate support material; (b) adding to the slurry a solution of an organomagnesium compound; (c) adding to the slurry and reacting a solution of zirconium compound; and (2) thereafter; (d) adding to the slurry and reacting a halogenator; (e) adding to the slurry and reacting a tetravalent titanium compound; (f) recovering solid catalyst; and an organoaluminum compound.

  6. Molecular models of site-isolated cobalt, rhodium, and iridium catalysts supported on zeolites: Ligand bond dissociation energies

    DOE PAGESBeta

    Chen, Mingyang; Serna, Pedro; Lu, Jing; Gates, Bruce C.; Dixon, David A.

    2015-09-28

    The chemistry of zeolite-supported site-isolated cobalt, rhodium, and iridium complexes that are essentially molecular was investigated with density functional theory (DFT) and the results compared with experimentally determined spectra characterizing rhodium and iridium species formed by the reactions of Rh(C2H4)2(acac) and Ir(C2H4)2(acac) (acac = acetylacetonate) with acidic zeolites such as dealuminated HY zeolite. The experimental results characterize ligand exchange reactions and catalytic reactions of adsorbed ligands, including olefin hydrogenation and dimerization. Two molecular models were used to characterize various binding sites of the metal complexes in the zeolites, and the agreement between experimental and calculated infrared frequencies and metal-ligand distancesmore » determined by extended X-ray absorption fine structure spectroscopy was generally very good. The calculated structures and energies indicate a metal-support-oxygen (M(I)-O) coordination number of two for most of the supported complexes and a value of three when the ligands include the radicals C2H5 or H. The results characterizing various isomers of the supported metal complexes incorporating hydrocarbon ligands indicate that some carbene and carbyne ligands could form. Ligand bond dissociation energies (LDEs) are reported to explain the observed reactivity trends. The experimental observations of a stronger M-CO bond than M-(C2H4) bond for both Ir and Rh match the calculated LDEs, which show that the single-ligand LDEs of the mono and dual-ligand complexes for CO are similar to 12 and similar to 15 kcal/mol higher in energy (when the metal is Rh) and similar to 17 and similar to 20 kcal/mol higher (when the metal is Ir) than the single-ligand LDEs of the mono and dual ligand complexes for C2H4, respectively. The results provide a foundation for the prediction of the catalytic properties of numerous supported metal complexes, as summarized in detail here.« less

  7. Molecular models of site-isolated cobalt, rhodium, and iridium catalysts supported on zeolites: Ligand bond dissociation energies

    SciTech Connect

    Chen, Mingyang; Serna, Pedro; Lu, Jing; Gates, Bruce C.; Dixon, David A.

    2015-09-28

    The chemistry of zeolite-supported site-isolated cobalt, rhodium, and iridium complexes that are essentially molecular was investigated with density functional theory (DFT) and the results compared with experimentally determined spectra characterizing rhodium and iridium species formed by the reactions of Rh(C2H4)2(acac) and Ir(C2H4)2(acac) (acac = acetylacetonate) with acidic zeolites such as dealuminated HY zeolite. The experimental results characterize ligand exchange reactions and catalytic reactions of adsorbed ligands, including olefin hydrogenation and dimerization. Two molecular models were used to characterize various binding sites of the metal complexes in the zeolites, and the agreement between experimental and calculated infrared frequencies and metal-ligand distances determined by extended X-ray absorption fine structure spectroscopy was generally very good. The calculated structures and energies indicate a metal-support-oxygen (M(I)-O) coordination number of two for most of the supported complexes and a value of three when the ligands include the radicals C2H5 or H. The results characterizing various isomers of the supported metal complexes incorporating hydrocarbon ligands indicate that some carbene and carbyne ligands could form. Ligand bond dissociation energies (LDEs) are reported to explain the observed reactivity trends. The experimental observations of a stronger M-CO bond than M-(C2H4) bond for both Ir and Rh match the calculated LDEs, which show that the single-ligand LDEs of the mono and dual-ligand complexes for CO are similar to 12 and similar to 15 kcal/mol higher in energy (when the metal is Rh) and similar to 17 and similar to 20 kcal/mol higher (when the metal is Ir) than the single-ligand LDEs of the mono and dual ligand complexes for C2H4, respectively. The results provide a foundation for the prediction

  8. DOE Award No. DE-FC36-03GO13108 NOVEL NON-PRECIOUS METAL CATALYSTS FOR PEMFC: CATALYST SELECTION THROUGH MOLECULAR MODELING AND DURABILITY STUDIES Final Report (September 2003 – October 2008)

    SciTech Connect

    Branko N. Popov

    2009-03-03

    The objective of this project is to develop novel non-precious metal electrocatalysts for oxygen reduction reaction (ORR), and demonstrate the potential of the catalysts to perform at least as good as conventional Pt catalysts currently in use in polymer electrolyte membrane fuel cell (PEMFC) with a cost at least 50 % less than a target of 0.2 g (Pt loading)/peak kW and with durability > 2,000 h operation with less than 10 % power degradation. A novel nitrogen-modified carbon-based catalyst was obtained by modifying carbon black with nitrogen-containing organic precursor in the absence of transition metal precursor. The catalyst shows the onset potential of approximately 0.76 V (NHE) for ORR and the amount of H2O2 of approximately 3% at 0.5 V (NHE). Furthermore, a carbon composite catalyst was achieved through the high-temperature pyrolysis of the precursors of transition metal (Co and Fe) and nitrogen supported on the nitrogen-modified carbon-based catalyst, followed by chemical post-treatment. This catalyst showed an onset potential for ORR as high as 0.87 V (NHE), and generated less than 1 % of H2O2. The PEM fuel cell exhibited a current density of 2.3 A cm-2 at 0.2 V for a catalyst loading of 6.0 mg cm-2. No significant performance degradation was observed for 480 h continuous operation. The characterization studies indicated that the metal-nitrogen chelate complexes decompose at the temperatures above 800 oC. During the pyrolysis, the transition metals facilitate the incorporation of pyridinic and graphitic nitrogen groups into the carbon matrix, and the carbon surface modified with nitrogen is active for ORR. In order to elucidate the role of transition metal precursor played in the formation of active sites in the non-precious metal catalysts, a novel ruthenium-based chelate (RuNx) catalyst was synthesized by using RuCl3 and propylene diammine as the Ru and N precursors, respectively, followed by high-temperature pyrolysis. This catalyst exhibited comparable

  9. DOE Award No. DE-FC36-03GO13108 NOVEL NON-PRECIOUS METAL CATALYSTS FOR PEMFC: CATALYST SELECTION THROUGH MOLECULAR MODELING AND DURABILITY STUDIES Final Report (September 2003 – October 2008)

    SciTech Connect

    Branko N. Popov

    2009-02-20

    The objective of this project is to develop novel non-precious metal electrocatalysts for oxygen reduction reaction (ORR), and demonstrate the potential of the catalysts to perform at least as good as conventional Pt catalysts currently in use in polymer electrolyte membrane fuel cell (PEMFC) with a cost at least 50 % less than a target of 0.2 g (Pt loading)/peak kW and with durability > 2,000 h operation with less than 10 % power degradation. A novel nitrogen-modified carbon-based catalyst was obtained by modifying carbon black with nitrogen-containing organic precursor in the absence of transition metal precursor. The catalyst shows the onset potential of approximately 0.76 V (NHE) for ORR and the amount of H2O2 of approximately 3% at 0.5 V (NHE). Furthermore, a carbon composite catalyst was achieved through the high-temperature pyrolysis of the precursors of transition metal (Co and Fe) and nitrogen supported on the nitrogen-modified carbon-based catalyst, followed by chemical post-treatment. This catalyst showed an onset potential for ORR as high as 0.87 V (NHE), and generated less than 1 % of H2O2. The PEM fuel cell exhibited a current density of 2.3 A cm-2 at 0.2 V for a catalyst loading of 6.0 mg cm-2. No significant performance degradation was observed for 480 h continuous operation. The characterization studies indicated that the metal-nitrogen chelate complexes decompose at the temperatures above 800 oC. During the pyrolysis, the transition metals facilitate the incorporation of pyridinic and graphitic nitrogen groups into the carbon matrix, and the carbon surface modified with nitrogen is active for ORR. In order to elucidate the role of transition metal precursor played in the formation of active sites in the non-precious metal catalysts, a novel ruthenium-based chelate (RuNx) catalyst was synthesized by using RuCl3 and propylene diammine as the Ru and N precursors, respectively, followed by high-temperature pyrolysis. This catalyst exhibited comparable

  10. Nios II hardware acceleration of the epsilon quadratic sieve algorithm

    NASA Astrophysics Data System (ADS)

    Meyer-Bäse, Uwe; Botella, Guillermo; Castillo, Encarnacion; García, Antonio

    2010-04-01

    The quadratic sieve (QS) algorithm is one of the most powerful algorithms to factor large composite primes used to break RSA cryptographic systems. The hardware structure of the QS algorithm seems to be a good fit for FPGA acceleration. Our new ɛ-QS algorithm further simplifies the hardware architecture making it an even better candidate for C2H acceleration. This paper shows our design results in FPGA resource and performance when implementing very long arithmetic on the Nios microprocessor platform with C2H acceleration for different libraries (GMP, LIP, FLINT, NRMP) and QS architecture choices for factoring 32-2048 bit RSA numbers.

  11. A differential delay equation arising from the sieve of Eratosthenes

    NASA Astrophysics Data System (ADS)

    Cheer, A. Y.; Goldston, D. A.

    1990-07-01

    The differential delay equation defined by ω (u) = 1/u for 1 ≤ u ≤ 2 and (uω (u))' = ω (u - 1) for u ≥ 2 was introduced by Buchstab in connection with an asymptotic formula for the number of uncanceled terms in the sieve of Eratosthenes. Maier has recently used this result to show there is unexpected irregularity in the distribution of primes in short intervals. The function ω (u) is studied in this paper using numerical and analytical techniques. The results are applied to give some numerical constants in Maier's theorem.

  12. Centrifugal Size-Separation Sieve for Granular Materials

    NASA Technical Reports Server (NTRS)

    Walton, Otis (Inventor); Dreyer, Christopher (Inventor); Riedel, Edward (Inventor)

    2015-01-01

    A centrifugal sieve and method utilizes centrifugal force in rapidly-rotated cylindrical or conical screens as the primary body force contributing to size segregation. Within the centrifugal acceleration field, vibration and/or shearing flows are induced to facilitate size segregation and eventual separation of the fines from the coarse material. Inside a rotating cylindrical or conical screen, a separately-rotated screw auger blade can be used to transport material along the rotating cylinder or conical wall and to induce shearing in the material.

  13. Photo-oxidation catalysts

    DOEpatents

    Pitts, J. Roland; Liu, Ping; Smith, R. Davis

    2009-07-14

    Photo-oxidation catalysts and methods for cleaning a metal-based catalyst are disclosed. An exemplary catalyst system implementing a photo-oxidation catalyst may comprise a metal-based catalyst, and a photo-oxidation catalyst for cleaning the metal-based catalyst in the presence of light. The exposure to light enables the photo-oxidation catalyst to substantially oxidize absorbed contaminants and reduce accumulation of the contaminants on the metal-based catalyst. Applications are also disclosed.

  14. Solar-Driven Reduction of Aqueous Protons Coupled to Selective Alcohol Oxidation with a Carbon Nitride–Molecular Ni Catalyst System

    PubMed Central

    2016-01-01

    Solar water-splitting represents an important strategy toward production of the storable and renewable fuel hydrogen. The water oxidation half-reaction typically proceeds with poor efficiency and produces the unprofitable and often damaging product, O2. Herein, we demonstrate an alternative approach and couple solar H2 generation with value-added organic substrate oxidation. Solar irradiation of a cyanamide surface-functionalized melon-type carbon nitride (NCNCNx) and a molecular nickel(II) bis(diphosphine) H2-evolution catalyst (NiP) enabled the production of H2 with concomitant selective oxidation of benzylic alcohols to aldehydes in high yield under purely aqueous conditions, at room temperature and ambient pressure. This one-pot system maintained its activity over 24 h, generating products in 1:1 stoichiometry, separated in the gas and solution phases. The NCNCNx–NiP system showed an activity of 763 μmol (g CNx)−1 h–1 toward H2 and aldehyde production, a Ni-based turnover frequency of 76 h–1, and an external quantum efficiency of 15% (λ = 360 ± 10 nm). This precious metal-free and nontoxic photocatalytic system displays better performance than an analogous system containing platinum instead of NiP. Transient absorption spectroscopy revealed that the photoactivity of NCNCNx is due to efficient substrate oxidation of the material, which outweighs possible charge recombination compared to the nonfunctionalized melon-type carbon nitride. Photoexcited NCNCNx in the presence of an organic substrate can accumulate ultralong-lived “trapped electrons”, which allow for fuel generation in the dark. The artificial photosynthetic system thereby catalyzes a closed redox cycle showing 100% atom economy and generates two value-added products, a solar chemical, and solar fuel. PMID:27337491

  15. Solar-Driven Reduction of Aqueous Protons Coupled to Selective Alcohol Oxidation with a Carbon Nitride-Molecular Ni Catalyst System.

    PubMed

    Kasap, Hatice; Caputo, Christine A; Martindale, Benjamin C M; Godin, Robert; Lau, Vincent Wing-Hei; Lotsch, Bettina V; Durrant, James R; Reisner, Erwin

    2016-07-27

    Solar water-splitting represents an important strategy toward production of the storable and renewable fuel hydrogen. The water oxidation half-reaction typically proceeds with poor efficiency and produces the unprofitable and often damaging product, O2. Herein, we demonstrate an alternative approach and couple solar H2 generation with value-added organic substrate oxidation. Solar irradiation of a cyanamide surface-functionalized melon-type carbon nitride ((NCN)CNx) and a molecular nickel(II) bis(diphosphine) H2-evolution catalyst (NiP) enabled the production of H2 with concomitant selective oxidation of benzylic alcohols to aldehydes in high yield under purely aqueous conditions, at room temperature and ambient pressure. This one-pot system maintained its activity over 24 h, generating products in 1:1 stoichiometry, separated in the gas and solution phases. The (NCN)CNx-NiP system showed an activity of 763 μmol (g CNx)(-1) h(-1) toward H2 and aldehyde production, a Ni-based turnover frequency of 76 h(-1), and an external quantum efficiency of 15% (λ = 360 ± 10 nm). This precious metal-free and nontoxic photocatalytic system displays better performance than an analogous system containing platinum instead of NiP. Transient absorption spectroscopy revealed that the photoactivity of (NCN)CNx is due to efficient substrate oxidation of the material, which outweighs possible charge recombination compared to the nonfunctionalized melon-type carbon nitride. Photoexcited (NCN)CNx in the presence of an organic substrate can accumulate ultralong-lived "trapped electrons", which allow for fuel generation in the dark. The artificial photosynthetic system thereby catalyzes a closed redox cycle showing 100% atom economy and generates two value-added products, a solar chemical, and solar fuel. PMID:27337491

  16. Molecular separation method and apparatus

    DOEpatents

    Villa-Aleman, Eliel

    1996-01-01

    A method and apparatus for separating a gaseous mixture of chemically identical but physically different molecules based on their polarities. The gaseous mixture of molecules is introduced in discrete quantities into the proximal end of a porous glass molecular. The molecular sieve is exposed to microwaves to excite the molecules to a higher energy state from a lower energy state, those having a higher dipole moment being excited more than those with a lower energy state. The temperature of the sieve kept cold by a flow of liquid nitrogen through a cooling jacket so that the heat generated by the molecules colliding with the material is transferred away from the material. The molecules thus alternate between a higher energy state and a lower one, with the portion of molecules having the higher dipole moment favored over the others. The former portion can then be extracted separately from the distal end of the molecular sieve.

  17. 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. PMID:26227827

  18. PILLARED CLAYS AS SUPERIOR CATALYSTS FOR SELECTIVE CATALYTIC REDUCTION OF NITRIC OXIDE

    SciTech Connect

    R. T. Yang; R.Q. Long

    1999-03-31

    In the last annual reports, we reported Cu-exchanged pillared clays as superior selective catalytic reduction (SCR) catalysts. During the past year we explored the possibilities with MCM-41, a new class of molecular sieve. In this report, Rh exchanged Al-MCM-41 is studied for the SCR of NO by C{sub 3}H{sub 6} in the presence of excess oxygen. It shows a high activity in converting NO to N{sub 2} and N{sub 2}O at low temperatures. In situ FT-IR studies indicate that Rh-NO{sup +} species (1910-1898 cm{sup {minus}1}) is formed on the Rh-Al-MCM-41 catalyst in flowing NO/He, NO+O{sub 2}/He and NO+C{sub 3}H{sub 6}+O{sub 2}/He at 100-350 C. This species is quite active in reacting with propylene and/or propylene adspecies (e.g., {pi}-C{sub 3}H{sub 5}, polyene, etc.) at 250 C in the presence/absence of oxygen, leading to the formation of the isocyanate species (Rh-NCO, at 2174 cm{sup {minus}1}), CO and CO{sub 2}. Rh-NCO is also detected under reaction conditions. A possible reaction pathway for reduction of NO by C{sub 3}H{sub 6} is proposed. In the SCR reaction, Rh-NO{sup +} and propylene adspecies react to generate the Rh-NCO species, then Rh-NCO reacts with O{sub 2}, NO and NO{sub 2} to produce N{sub 2}, N{sub 2}O and CO{sub 2}. Rh-NO{sup +} and Rh-NCO species are two main intermediates for the SCR reaction on Rh-Al-MCM-41 catalyst.

  19. Fractionation of distillers dried grains with solubles (DDGS) by sieving and winnowing.

    PubMed

    Liu, KeShun

    2009-12-01

    Four commercial samples of distillers dried grains with solubles (DDGS) were sieved. All sieved fractions except for the pan fraction, constituting about 90% of original mass, were then winnowed with an air blast seed cleaner. Sieving was effective in producing fractions with varying composition. As the particle size decreased, protein and ash contents increased, and total carbohydrate (CHO) decreased. Winnowing sieved fractions was also effective in shifting composition, particularly for larger particle classes. Heavy sub-fractions were enriched in protein, oil and ash, while light sub-fractions were enriched for CHO. For protein, the combination of the two procedures resulted in a maximum 56.4% reduction in a fraction and maximum 60.2% increase in another fraction. As airflow velocity increased, light sub-fraction mass increased, while the compositional difference between the heavy and light sub-fractions decreased. Winnowing three times at a lower velocity was as effective as winnowing one time at a medium velocity. Winnowing the whole DDGS was much less effective than winnowing sieved fractions in changing composition, but sieving winnowed fractions was more effective than sieving whole DDGS. The two combination sequences gave comparable overall effects but sieving followed by winnowing is recommended because it requires less time. Regardless of combinational sequence, the second procedure was more effective in shifting composition than the first procedure. PMID:19692227

  20. Synthesis and Evaluation of Cu-SAPO-34 Catalysts for Ammonia Selective Catalytic Reduction. 1. Aqueous Solution Ion Exchange

    SciTech Connect

    Gao, Feng; Walter, Eric D.; Washton, Nancy M.; Szanyi, Janos; Peden, Charles HF

    2013-09-06

    SAPO-34 molecular sieves are synthesized using various structure directing agents (SDAs). Cu-SAPO-34 catalysts are prepared via aqueous solution ion exchange. Catalysts are characterized with surface area/pore volume measurements, temperature programmed reduction (TPR), electron paramagnetic resonance (EPR) and nuclear magnetic resonance (NMR) spectroscopies. Catalytic properties are examined using standard ammonia selective catalytic reduction (NH3-SCR) and ammonia oxidation reactions. During solution ion exchange, different SAPO-34 samples undergo different extent of structural damage via irreversible hydrolysis. Si content within the samples (i.e., Al-O-Si bond density) and framework stress are key factors that affect irreversible hydrolysis. Even using very dilute Cu acetate solutions, it is not possible to generate Cu-SAPO-34 samples with only isolated Cu2+ ions. Small amounts of CuOx species always coexist with isolated Cu2+ ions. Highly active and selective Cu-SAPO-34 catalysts for NH3-SCR are readily generated using this synthesis protocol, even for SAPO-34 samples that degrade substantially during solution ion exchange. High-temperature aging is found to improve the catalytic performance. This is likely due to reduction of intracrystalline mass-transfer limitations via formation of additional porosity in the highly defective SAPO-34 particles formed after ion exchange. The authors gratefully acknowledge the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy, Office of Vehicle Technologies for the support of this work. The research described in this paper was performed at the Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory (PNNL). PNNL is operated for the US DOE by Battelle Memorial Institute under contract number DE-AC05-76RL01830.

  1. A rhenium complex doped in a silica molecular sieve for molecular oxygen sensing: Construction and characterization.

    PubMed

    Yang, Xiaozhou; Li, Yanxiao

    2016-01-15

    This paper reported a diamine ligand and its Re(I) complex for potential application in oxygen sensing. The novelty of this diamine ligand localized at its increased conjugation chain which had a typical electron-withdrawing group of 1,3,4-oxadiazole. Electronic distribution of excited electrons and their lifetime were supposed to be increased, favoring oxygen sensing collision. This hypothesis was confirmed by single crystal analysis, theoretical calculation and photophysical measurement. It was found that this Re(I) complex had a long-lived emission peaking at 545 nm, favoring sensing application. By doping this complex into a silica matrix MCM-41, oxygen sensing performance and mechanism of the resulting composites were discussed in detail. Non-linear Stern-Volmer working curves were observed with maximum sensitivity of 5.54 and short response time of ~6 s. PMID:26478986

  2. A rhenium complex doped in a silica molecular sieve for molecular oxygen sensing: Construction and characterization

    NASA Astrophysics Data System (ADS)

    Yang, Xiaozhou; Li, Yanxiao

    2016-01-01

    This paper reported a diamine ligand and its Re(I) complex for potential application in oxygen sensing. The novelty of this diamine ligand localized at its increased conjugation chain which had a typical electron-withdrawing group of 1,3,4-oxadiazole. Electronic distribution of excited electrons and their lifetime were supposed to be increased, favoring oxygen sensing collision. This hypothesis was confirmed by single crystal analysis, theoretical calculation and photophysical measurement. It was found that this Re(I) complex had a long-lived emission peaking at 545 nm, favoring sensing application. By doping this complex into a silica matrix MCM-41, oxygen sensing performance and mechanism of the resulting composites were discussed in detail. Non-linear Stern-Volmer working curves were observed with maximum sensitivity of 5.54 and short response time of ~ 6 s.

  3. Hydride mobility in trinuclear sulfido clusters with the core [Rh3(μ-H)(μ3-S)2]: molecular models for hydrogen migration on metal sulfide hydrotreating catalysts.

    PubMed

    Jiménez, M Victoria; Lahoz, Fernando J; Lukešová, Lenka; Miranda, José R; Modrego, Francisco J; Nguyen, Duc H; Oro, Luis A; Pérez-Torrente, Jesús J

    2011-07-11

    The treatment of [{Rh(μ-SH){P(OPh)(3)}(2)}(2)] with [{M(μ-Cl)(diolef)}(2)] (diolef=diolefin) in the presence of NEt(3) affords the hydrido-sulfido clusters [Rh(3)(μ-H)(μ(3)-S)(2)(diolef){P(OPh)(3)}(4)] (diolef=1,5-cyclooctadiene (cod) for 1, 2,5-norbornadiene (nbd) for 2, and tetrafluorobenzo[5,6]bicyclo[2.2.2]octa-2,5,7-triene (tfb) for 3) and [Rh(2)Ir(μ-H)(μ(3)-S)(2)(cod){P(OPh)(3)}(4)] (4). Cluster 1 can be also obtained by treating [{Rh(μ-SH){P(OPh)(3)}(2)}(2)] with [{Rh(μ-OMe)(cod)}(2)], although the main product of the reaction with [{Ir(μ-OMe)(cod)}(2)] was [RhIr(2)(μ-H)(μ(3)-S)(2)(cod)(2){P(OPh)(3)}(2)] (5). The molecular structures of clusters 1 and 4 have been determined by X-ray diffraction methods. The deprotonation of a hydrosulfido ligand in [{Rh(μ-SH)(CO)(PPh(3))}(2)] by [M(acac)(diolef)] (acac=acetylacetonate) results in the formation of hydrido-sulfido clusters [Rh(3)(μ-H)(μ(3)-S)(2)(CO)(2) (diolef)(PPh(3))(2)] (diolef=cod for 6, nbd for 7) and [Rh(2)Ir(μ-H)(μ(3)-S)(2)(CO)(2)(cod)(PPh(3))(2)] (8). Clusters 1-3 and 5 exist in solution as two interconverting isomers with the bridging hydride ligand at different edges. Cluster 8 exists as three isomers that arise from the disposition of the PPh(3) ligands in the cluster (cis and trans) and the location of the hydride ligand. The dynamic behaviour of clusters with bulky triphenylphosphite ligands, which involves hydrogen migration from rhodium to sulfur with a switch from hydride to proton character, is significant to understand hydrogen diffusion on the surface of metal sulfide hydrotreating catalysts. PMID:21633978

  4. Catalyst activator

    DOEpatents

    McAdon, Mark H.; Nickias, Peter N.; Marks, Tobin J.; Schwartz, David J.

    2001-01-01

    A catalyst activator particularly adapted for use in the activation of metal complexes of metals of Group 3-10 for polymerization of ethylenically unsaturated polymerizable monomers, especially olefins, comprising two Group 13 metal or metalloid atoms and a ligand structure including at least one bridging group connecting ligands on the two Group 13 metal or metalloid atoms.

  5. A Sieving ANN for Emotion-Based Movie Clip Classification

    NASA Astrophysics Data System (ADS)

    Watanapa, Saowaluk C.; Thipakorn, Bundit; Charoenkitkarn, Nipon

    Effective classification and analysis of semantic contents are very important for the content-based indexing and retrieval of video database. Our research attempts to classify movie clips into three groups of commonly elicited emotions, namely excitement, joy and sadness, based on a set of abstract-level semantic features extracted from the film sequence. In particular, these features consist of six visual and audio measures grounded on the artistic film theories. A unique sieving-structured neural network is proposed to be the classifying model due to its robustness. The performance of the proposed model is tested with 101 movie clips excerpted from 24 award-winning and well-known Hollywood feature films. The experimental result of 97.8% correct classification rate, measured against the collected human-judges, indicates the great potential of using abstract-level semantic features as an engineered tool for the application of video-content retrieval/indexing.

  6. Biofuel Manufacturing from Woody Biomass: Effects of Sieve Size Used in Biomass Size Reduction

    PubMed Central

    Zhang, Meng; Song, Xiaoxu; Deines, T. W.; Pei, Z. J.; Wang, Donghai

    2012-01-01

    Size reduction is the first step for manufacturing biofuels from woody biomass. It is usually performed using milling machines and the particle size is controlled by the size of the sieve installed on a milling machine. There are reported studies about the effects of sieve size on energy consumption in milling of woody biomass. These studies show that energy consumption increased dramatically as sieve size became smaller. However, in these studies, the sugar yield (proportional to biofuel yield) in hydrolysis of the milled woody biomass was not measured. The lack of comprehensive studies about the effects of sieve size on energy consumption in biomass milling and sugar yield in hydrolysis process makes it difficult to decide which sieve size should be selected in order to minimize the energy consumption in size reduction and maximize the sugar yield in hydrolysis. The purpose of this paper is to fill this gap in the literature. In this paper, knife milling of poplar wood was conducted using sieves of three sizes (1, 2, and 4 mm). Results show that, as sieve size increased, energy consumption in knife milling decreased and sugar yield in hydrolysis increased in the tested range of particle sizes. PMID:22665985

  7. Clast-contact conglomerates in submarine canyons: possible subaqueous sieve deposits

    SciTech Connect

    Fitzgerald, M.S.

    1987-05-01

    Thick, coarse, clast-contact conglomerates in submarine canyon fill have previously been attributed to rock-fall, grain-flow, or winnowing processes. However, these processes do not adequately explain some thick conglomeratic sequences. The proposed process of subaqueous sieve deposition could account for these clast-contact conglomerates. Subaerial sieve deposition has been documented on small-scale fan models and on alluvial fans. A subaerial sieve deposit begins as a debris flow which at some point freezes up. The matrix is then lost by subsequent filtration or outflow, and the emplacement of a clast-contact gravel ensues. A subaqueous sieve deposit would be slightly modified in that the matrix would not be lost by filtration into the submarine canyon floor, but rather by outflow at the terminus of the lobe immediately after deposition, or possibly from the top and/or sides of the freezing flow mass during transport. Besides forming in submarine canyons, subaqueous sieve deposits might also occur in paralic, submarine fan channel, and base-of-the-slope settings. In substantiating the existence of subaqueous sieve deposits, the sedimentary structures and grain-size data from recent sieve deposits on alluvial fans are compared to those of ancient submarine canyon deposits. Numerous similarities are found supporting this new method of deposition. Some discrepancies are encountered, but these are expected due to modifications caused by an aqueous medium.

  8. Catalyst suppliers consolidate further, offer more catalysts

    SciTech Connect

    Rhodes, A.K.

    1995-10-02

    The list of suppliers of catalysts to the petroleum refining industry has decreased by five since Oil and Gas Journal`s survey of refining catalysts and catalytic additives was last published. Despite the consolidation, the list of catalyst designations has grown to about 950 in this latest survey, compared to 820 listed in 1993. The table divides the catalysts by use and gives data on their primary differentiating characteristics, feedstock, products, form, bulk density,catalyst support, active agents, availability, and manufactures.

  9. Qualitative extension of the EC' Zone Diagram to a molecular catalyst for a multi-electron, multi-substrate electrochemical reaction.

    PubMed

    Martin, Daniel J; McCarthy, Brian D; Rountree, Eric S; Dempsey, Jillian L

    2016-06-14

    The EC' Zone Diagram, introduced by Savéant and Su over 30 years ago, has been used to classify voltammetric responses for electrocatalytic systems. With a single H2-evolving catalyst, Co(dmgBF2)2(CH3CH)2 (dmgBF2 = difluoroboryl-dimethylglyoxime), and a series of para-substituted anilinium acids, experimental conditions were carefully tuned to access to each region of the classic zone diagram. Close scrutiny revealed the extent to which the kinetic (λ) and excess (γ) factors could be experimentally controlled and used to access a variety of waveforms for this ECEC' catalytic system. It was found that most of the tunable experimental parameters (such as catalyst concentration, scan rate, and substrate concentration) predicted in the EC' Zone Diagram could be extended to a multi-electron system and produced similarly-shaped waveforms with some deviations. Tuning of a single catalyst across every region of the classic zone diagram has previously been prevented due to the seven orders of magnitude that need to be traversed across the kinetic parameter; however, the cobalt catalyst in this study provided unique control of this parameter. By varying the acids used as the proton source, the rate constants for protonation were tuned via a pKa-dependent linear free energy relationship. PMID:26998812

  10. Hydrocracking catalyst

    SciTech Connect

    Hilfman, L.; O'Hara, M.

    1980-07-01

    A description is given of a process for the conversion of heavy hydrocarbon oil boiling above about 650/sup 0/F into lower boiling hydrocarbons, which comprises hydrocracking the heavy oil in admixture with hydrogen and in contact with a catalyst with comprising a ra re earth exchange metal component and a platinum group metal component supported on a mixture of ziegler alumina and a zeolite.

  11. Electrooxidation of Ethanol and Methanol Using the Molecular Catalyst [{Ru4O4(OH)2(H2O)4}(γ-SiW10O36)2](10.).

    PubMed

    Liu, YuPing; Zhao, Shu-Feng; Guo, Si-Xuan; Bond, Alan M; Zhang, Jie; Zhu, Guibo; Hill, Craig L; Geletii, Yurii V

    2016-03-01

    Highly efficient electrocatalytic oxidation of ethanol and methanol has been achieved using the ruthenium-containing polyoxometalate molecular catalyst, [{Ru4O4(OH)2(H2O)4}(γ-SiW10O36)2](10-) ([1(γ-SiW10O36)2](10-)). Voltammetric studies with dissolved and surface-confined forms of [1(γ-SiW10O36)2](10-) suggest that the oxidized forms of 1 can act as active catalysts for alcohol oxidation in both aqueous (over a wide pH range covering acidic, neutral, and alkaline) and alcohol media. Under these conditions, the initial form of 1 also exhibits considerable reactivity, especially in neutral solution containing 1.0 M NaNO3. To identify the oxidation products, preparative scale bulk electrolysis experiments were undertaken. The products detected by NMR, gas chromatography (GC), and GC-mass spectrometry from oxidation of ethanol are 1,1-diethoxyethane and ethyl acetate formed from condensation of acetaldehyde or acetic acid with excess ethanol. Similarly, the oxidation of methanol generates formaldehyde and formic acid which then condense with methanol to form dimethoxymethane and methyl formate, respectively. These results demonstrate that electrocatalytic oxidation of ethanol and methanol occurs via two- and four-electron oxidation processes to yield aldehydes and acids. The total faradaic efficiencies of electrocatalytic oxidation of both alcohols exceed 94%. The numbers of aldehyde and acid products per catalyst were also calculated and compared with the literature reported values. The results suggest that 1 is one of the most active molecular electrocatalysts for methanol and ethanol oxidation. PMID:26848832

  12. Design, in vitro and in vivo assessment of a multi-channel sieve electrode with integrated multiplexer

    NASA Astrophysics Data System (ADS)

    Ramachandran, Anup; Schuettler, Martin; Lago, Natalia; Doerge, Thomas; Koch, Klaus Peter; Navarro, Xavier; Hoffmann, Klaus-Peter; Stieglitz, Thomas

    2006-06-01

    This paper reports on the design, in vitro and in vivo investigation of a flexible, lightweight, polyimide based implantable sieve electrode with a hybrid assembly of multiplexers and polymer encapsulation. The integration of multiplexers enables us to connect a large number of electrodes on the sieve using few input connections. The implant assembly of the sieve electrode with the electronic circuitry was verified by impedance measurement. The 27 platinum electrodes of the sieve were coated with platinum black to reduce the electrode impedance. The impedance magnitude of the electrode sites on the sieve (geometric surface area 2200 µm2) was |Zf=1kHz| = 5.7 kΩ. The sieve electrodes, encased in silicone, have been implanted in the transected sciatic nerve of rats. Initial experiments showed that axons regenerated through the holes of the sieve and reinnervated distal target organs. Nerve signals were recorded in preliminary tests after 3-7 months post-implantation.

  13. Ultraviolet Raman spectroscopy of catalysts: Adsorption and coke formation in zeolites and vibrational spectra of supported metal oxides

    NASA Astrophysics Data System (ADS)

    Chua, Yek Tann

    2001-10-01

    The primary goal of this dissertation is to study the physicochemical and catalytic properties of zeolites and supported metal oxide catalysts using UV Raman spectroscopy. In order to reduce the thermal degradation and possible photodecomposition of adsorbates by UV radiation, we have developed a novel fluidized bed method for measuring the UV Raman spectra of catalysts and adsorbates. The UV Raman spectra of various organic compounds adsorbed in zeolites H-USY and H-ZSM-5 are recorded. When measurements are performed on stationary and spinning samples, the Raman spectra show the presence of coke, a typical end product of heat and photochemistry. In contrast, the Raman peaks of the unreacted adsorbates dominate the spectra measured using the fluidized bed method. These results indicate that the fluidized bed technique is a good method for measuring UV Raman spectra of catalysts and adsorbates. The formation of coke in the methanol-to-gasoline conversion over zeolite H-ZSM-5 causes deactivation of the catalyst. To gain insight into the formation of coke, we have studied this reaction using UV Raman spectroscopy. The Raman spectral changes suggest coke is produced from conjugated olefins via cyclopentadiene intermediates. Aromatic compounds in gasoline may also be produced from cyclopentadienes. The adsorbate-induced structural changes of zeolites may alter the molecular sieving characteristics of these materials which ultimately affect their performance as catalysts and adsorbents. We have quantified the adsorbate-induced structural changes of zeolite H-RHO using UV Raman spectroscopy. The Raman spectra of the zeolite after the adsorption of water, methanol or acetonitrile are consistent with an increase in the average T-O-T angle of the zeolite of 5-8°. The adsorption of ammonia, on the other hand, decreases the average T-O-T angle by 5°. Because of certain advantages of UV Raman spectroscopy over visible Raman spectroscopy, recently there is a strong interest in

  14. Magnetic and Mössbauer study of metal-zeolite interaction in catalysts

    NASA Astrophysics Data System (ADS)

    Pannaparayil, Thomas; Oskooie-Tabrizi, M.; Lo, C.; Mulay, L. N.; Melson, G. A.; Rao, V. U. S.

    1984-03-01

    Molecular sieve aluminosilicates, such as ZSM-5 and mordenite, when impregnated with highly dispersed Fe, yield catalysts for the selective conversion of coal-derived syngas (CO+H2) to liquid hydrocarbon fuels. Fe performs the primary Fischer-Tropsch (FT) syngas to yield light olefins which are converted by the acidic (H+) and shape-selective function of the zeolite to high octane gasoline components. The physical aspects of the Fe-mordenite interaction studied by magnetic measurements, Mössbauer, and IR spectroscopy are reported and correlations with the catalytic properties are drawn. Mordenite samples with [SiO2/Al2O3] ratio in the range 12 - 60 were impregnated with 15 wt. % Fe using Fe3(CO)12; decarbonylation yielded superparamagmetic dispersions of γ-Fe2O3, in the range 1.4-5.0 nm; the smallest particles were obtained for a ratio=17. Hydrogen chemisorption also revealed a similar trend in Fe dispersions. No samples, other than the one with a ratio=60 and containing the largest particles could be carbided under usual conditions. The acidity of the mordenite and the aromatics fraction in liquid hydrocarbons from syngas conversion also showed maxima at a ratio=17. The presence of a strong metal-support interaction between Fe and mordenite was thus influenced by the varying ratios in the mordenite in a manner that paralleled the acidity and catalytic activity.

  15. [Enhanced electro-catalytic oxidation of dye wastewater with FePMo12 adopted catalyst].

    PubMed

    Wang, Li; Yue, Lin; Guo, Jian-Bo; Yang, Jing-Liang; Lian, Jing; Luo, Xiao; Wang, Kai-Hong

    2014-05-01

    Electrochemical oxidation degradation of azo dyes has become a widely used method in recent years. Iron phosphomolybdate (FePMo12) was synthesized with molybdophosphoric acid and ferric salt. Morphology and microstructure of catalyst were chararerized by IR spectrometry and X-ray diffraction. The heteropolyanion showed a Keggin structure. Electrochemical oxidation of acid red 3R was investigated in the presence of FePMo12 supported on modified 4A molecular sieve (4A) as packing materials in the reactor. The results showed that the optimal technological conditions for decolorization of acid red 3R simulated wastewater were as follows: active component load 3% , electrolytic voltage 22 V, initial pH 4, air-flow 0.08 m3 h- ', electrode span 3.0 cm. Under the opñrrizd conditions, the decolorization efficiency, COD and TOC removal efficiencies reached 75.3% , 65.4% and 46.0% after 90 min, respectively. With the addition of NaCI to the dyes solution during electrolysis, the decolorization efficiency increased, while the effect of Na2SO4 on the degradation was negative. The efficiency of degradation and mineralization of the acid red 3R were estimated based on the absorbance measurements by UV-vis. It shows that the conjugated structure of dye was destroyed primarily. PMID:25055676

  16. Dr. Grant Heikan examines lunar material in sieve from sample container

    NASA Technical Reports Server (NTRS)

    1969-01-01

    Dr. Grant Heikan, Manned Spacecraft Center and a Lunar Sample preliminary Examination Team member, examines lunar material in a sieve from the bulk sample container which was opened in the Biopreparation Laboratory of the Lunar Receiving Laboratory.

  17. Centrifugal Sieve for Gravity-Level-Independent Size Segregation of Granular Materials

    NASA Technical Reports Server (NTRS)

    Walton, Otis R.; Dreyer, Christopher; Riedel, Edward

    2013-01-01

    Conventional size segregation or screening in batch mode, using stacked vibrated screens, is often a time-consuming process. Utilization of centrifugal force instead of gravity as the primary body force can significantly shorten the time to segregate feedstock into a set of different-sized fractions. Likewise, under reduced gravity or microgravity, a centrifugal sieve system would function as well as it does terrestrially. When vibratory and mechanical blade sieving screens designed for terrestrial conditions were tested under lunar gravity conditions, they did not function well. The centrifugal sieving design of this technology overcomes the issues that prevented sieves designed for terrestrial conditions from functioning under reduced gravity. These sieves feature a rotating outer (cylindrical or conical) screen wall, rotating fast enough for the centrifugal forces near the wall to hold granular material against the rotating screen. Conventional centrifugal sieves have a stationary screen and rapidly rotating blades that shear the granular solid near the stationary screen, and effect the sieving process assisted by the airflow inside the unit. The centrifugal sieves of this new design may (or may not) have an inner blade or blades, moving relative to the rotating wall screen. Some continuous flow embodiments would have no inner auger or blades, but achieve axial motion through vibration. In all cases, the shearing action is gentler than conventional centrifugal sieves, which have very high velocity differences between the stationary outer screen and the rapidly rotating blades. The new design does not depend on airflow in the sieving unit, so it will function just as well in vacuum as in air. One advantage of the innovation for batch sieving is that a batch-mode centrifugal sieve may accomplish the same sieving operation in much less time than a conventional stacked set of vibrated screens (which utilize gravity as the primary driving force for size separation

  18. Sieve of Eratosthenes benchmarks for the Z8 FORTH microcontroller

    SciTech Connect

    Edwards, R.

    1989-02-01

    This report presents benchmarks for the Z8 FORTH microcontroller system that ORNL uses extensively in proving concepts and developing prototype test equipment for the Smart House Project. The results are based on the sieve of Eratosthenes algorithm, a calculation used extensively to rate computer systems and programming languages. Three benchmark refinements are presented,each showing how the execution speed of a FORTH program can be improved by use of a particular optimization technique. The last version of the FORTH benchmark shows that optimization is worth the effort: It executes 20 times faster than the Gilbreaths' widely-published FORTH benchmark program. The National Association of Home Builders Smart House Project is a cooperative research and development effort being undertaken by American home builders and a number of major corporations serving the home building industry. The major goal of the project is to help the participating organizations incorporate advanced technology in communications,energy distribution, and appliance control products for American homes. This information is provided to help project participants use the Z8 FORTH prototyping microcontroller in developing Smart House concepts and equipment. The discussion is technical in nature and assumes some experience with microcontroller devices and the techniques used to develop software for them. 7 refs., 5 tabs.

  19. [Catalyst research]. Final Report

    SciTech Connect

    Ian P Rothwell; David R McMillin

    2005-03-14

    Research results are the areas of catalyst precursor synthesis, catalyst fluxionality, catalyst stability, polymerization of {alpha}-olefins as well as the chemistry of Group IV and Group V metal centers with aryloxide and arylsulfide ligands.

  20. A sieving method for collecting the metacercariae of trematode parasites from freshwater fish.

    PubMed

    Fan, P C; Wu, C C; Huang, P; Yen, C W

    2002-03-01

    This study describes a sieving method for the collection of metacercariae from frozen (-20 degrees C) freshwater fish. Digested fish tissue is filtered through a series of sieves; the crude filtrate is then centrifuged. Centrifugation produces a sediment from which metacercariae can be removed. Half of the metracercariae that were obtained from the fish meat that had been frozen for 10 days (-20 degrees C) were dead; the other half were alive and some larvae were moving slowly. PMID:12118453

  1. Molecular Insight in Structure and Activity of Highly Efficient, Low-Ir Ir-Ni Oxide Catalysts for Electrochemical Water Splitting (OER).

    PubMed

    Reier, Tobias; Pawolek, Zarina; Cherevko, Serhiy; Bruns, Michael; Jones, Travis; Teschner, Detre; Selve, Sören; Bergmann, Arno; Nong, Hong Nhan; Schlögl, Robert; Mayrhofer, Karl J J; Strasser, Peter

    2015-10-14

    Mixed bimetallic oxides offer great opportunities for a systematic tuning of electrocatalytic activity and stability. Here, we demonstrate the power of this strategy using well-defined thermally prepared Ir-Ni mixed oxide thin film catalysts for the electrochemical oxygen evolution reaction (OER) under highly corrosive conditions such as in acidic proton exchange membrane (PEM) electrolyzers and photoelectrochemical cells (PEC). Variation of the Ir to Ni ratio resulted in a volcano type OER activity curve with an unprecedented 20-fold improvement in Ir mass-based activity over pure Ir oxide. In situ spectroscopic probing of metal dissolution indicated that, against common views, activity and stability are not directly anticorrelated. To uncover activity and stability controlling parameters, the Ir-Ni mixed thin oxide film catalysts were characterized by a wide array of spectroscopic, microscopic, scattering, and electrochemical techniques in conjunction with DFT theoretical computations. By means of an intuitive model for the formation of the catalytically active state of the bimetallic Ir-Ni oxide surface, we identify the coverage of reactive surface hydroxyl groups as a suitable descriptor for the OER activity and relate it to controllable synthetic parameters. Overall, our study highlights a novel, highly active oxygen evolution catalyst; moreover, it provides novel important insights into the structure and performance of bimetallic oxide OER electrocatalysts in corrosive acidic environments. PMID:26355767

  2. Aphid salivary proteases are capable of degrading sieve-tube proteins.

    PubMed

    Furch, Alexandra C U; van Bel, Aart J E; Will, Torsten

    2015-02-01

    Sieve tubes serve as transport conduits for photo-assimilates and other resources in angiosperms and are profitable targets for piercing-sucking insects such as aphids. Sieve-tube sap also contains significant amounts of proteins with diverse functions, for example in signalling, metabolism, and defence. The identification of salivary proteases in Acyrthosiphon pisum led to the hypothesis that aphids might be able to digest these proteins and by doing so suppress plant defence and access additional nitrogen sources. Here, the scarce knowledge of proteases in aphid saliva is briefly reviewed. In order to provide a better platform for discussion, we conducted a few tests on in vitro protease activity and degradation of sieve-tube sap proteins of Cucurbita maxima by watery saliva. Inhibition of protein degradation by EDTA indicates the presence of different types of proteases (e.g. metalloproteses) in saliva of A. pisum. Proteases in the watery saliva from Macrosiphum euphorbiae and A. pisum were able to degrade the most abundant phloem protein, which is phloem protein 1. Our results provide support for the breakdown of sieve-element proteins by aphid saliva in order to suppress/neutralize the defence responses of the plant and to make proteins of sieve-tube sap accessible as a nitrogen source, as is discussed in detail. Finally, we discuss whether glycosylation of sieve-element proteins and the presence of protease inhibitors may confer partial protection against the proteolytic activity of aphid saliva. PMID:25540441

  3. Sieve efficiency in benthic sampling as related to chironomid head capsule width

    USGS Publications Warehouse

    Hudson, Patrick L.; Adams, Jean V.

    1998-01-01

    The width of the head capsule in chironomid larvae is the most important morphometric character controlling retention of specimens in sieving devices. Knowledge of the range in size of these widths within any chironomid community is fundamental to sampling and interpreting the resulting data. We present the head capsule widths of 30 species of chironomids and relate their size distribution to loss or retention in several experiments using graded sieve sizes. Based on our measurements and those found in the literature we found the head capsule width of fourth instars in half the chironomids species to be less than 350 I?m. Many species may never be collected with the commonly used U.S. Standard No. 30 sieve (589 I?m), and the No. 60 (246 I?m) screen appears to retain most species only qualitatively. We found 70 to 90% of the chironomid larvae and 19 to 34% of their biomass can pass through a No. 80 sieve (177 I?m). The implications of sieve loss and other factors affecting sieving efficiency are discussed.

  4. P-proteins in Arabidopsis are heteromeric structures involved in rapid sieve tube sealing

    PubMed Central

    Jekat, Stephan B.; Ernst, Antonia M.; von Bohl, Andreas; Zielonka, Sascia; Twyman, Richard M.; Noll, Gundula A.; Prüfer, Dirk

    2013-01-01

    Structural phloem proteins (P-proteins) are characteristic components of the sieve elements in all dicotyledonous and many monocotyledonous angiosperms. Tobacco P-proteins were recently confirmed to be encoded by the widespread sieve element occlusion (SEO) gene family, and tobacco SEO proteins were shown to be directly involved in sieve tube sealing thus preventing the loss of photosynthate. Analysis of the two Arabidopsis SEO proteins (AtSEOa and AtSEOb) indicated that the corresponding P-protein subunits do not act in a redundant manner. However, there are still pending questions regarding the interaction properties and specific functions of AtSEOa and AtSEOb as well as the general function of structural P-proteins in Arabidopsis. In this study, we characterized the Arabidopsis P-proteins in more detail. We used in planta bimolecular fluorescence complementation assays to confirm the predicted heteromeric interactions between AtSEOa and AtSEOb. Arabidopsis mutants depleted for one or both AtSEO proteins lacked the typical P-protein structures normally found in sieve elements, underlining the identity of AtSEO proteins as P-proteins and furthermore providing the means to determine the role of Arabidopsis P-proteins in sieve tube sealing. We therefore developed an assay based on phloem exudation. Mutants with reduced AtSEO expression levels lost twice as much photosynthate following injury as comparable wild-type plants, confirming that Arabidopsis P-proteins are indeed involved in sieve tube sealing. PMID:23840197

  5. PILLARED CLAYS AS SUPERIOR CATALYSTS FOR SELECTIVE CATALYTIC REDUCTION OF NITRIC OXIDE

    SciTech Connect

    R. Q. LONG; R.T. YANG

    1998-09-30

    Selective catalytic reduction (SCR) of NO{sub x} by hydrocarbons was investigated on Pt doped MCM-41 and copper ion and/or cerium ion-exchanged Al-MCM-41 in the presence of excess oxygen. It was found that Pt/MCM-41 provided the highest specific NO reduction rates as compared with other Pt doped catalysts reported in the literature, such as Pt/Al{sub 2}O{sub 3} and Pt/ZSM-5. For different hydrocarbons, the catalytic activity decreased according to the sequence of C{sub 3}H{sub 6} {approx} C{sub 2}H{sub 4} >> C{sub 3}H{sub 8} > CH{sub 4}. This catalyst was also stable in the presence of H{sub 2}O and SO{sub 2}. Cu exchanged Al-MCM-41 and cerium promoted Cu-Al-MCM-41 (i.e., Ce-Cu-Al-MCM-41) were also found to be active in this reaction. Higher NO{sub x} conversions to N2 were obtained on the Ce-Cu-Al-MCM-41 as compared with Cu-Al-MCM-41. The activity of Ce-Cu-Al-MCM-41 was approximately the same as that of Cu-ZSM-5; but the former had a wider temperature window. TPR results indicated that only isolated Cu{sup 2+} and Cu{sup +} ions were detected in the Cu{sup 2+}-exchanged Al-MCM-41 samples, which may play an important role in the selective catalytic reduction of NO{sub x} to N{sub 2}. After some cerium ions were introduced into Cu-Al-MCM-41, Cu{sup 2+} in the molecular sieve became more easily reducible by H{sub 2}. This may be related to the increase of catalytic activity of NO{sub x} reduction by ethylene.

  6. Tuning Pore Size in Square-Lattice Coordination Networks for Size-Selective Sieving of CO2.

    PubMed

    Chen, Kai-Jie; Madden, David G; Pham, Tony; Forrest, Katherine A; Kumar, Amrit; Yang, Qing-Yuan; Xue, Wei; Space, Brian; Perry, John J; Zhang, Jie-Peng; Chen, Xiao-Ming; Zaworotko, Michael J

    2016-08-22

    Porous materials capable of selectively capturing CO2 from flue-gases or natural gas are of interest in terms of rising atmospheric CO2 levels and methane purification. Size-exclusive sieving of CO2 over CH4 and N2 has rarely been achieved. Herein we show that a crystal engineering approach to tuning of pore-size in a coordination network, [Cu(quinoline-5-carboxyate)2 ]n (Qc-5-Cu) ena+bles ultra-high selectivity for CO2 over N2 (SCN ≈40 000) and CH4 (SCM ≈3300). Qc-5-Cu-sql-β, a narrow pore polymorph of the square lattice (sql) coordination network Qc-5-Cu-sql-α, adsorbs CO2 while excluding both CH4 and N2 . Experimental measurements and molecular modeling validate and explain the performance. Qc-5-Cu-sql-β is stable to moisture and its separation performance is unaffected by humidity. PMID:27439315

  7. Vascular Cell Induction Culture System Using Arabidopsis Leaves (VISUAL) Reveals the Sequential Differentiation of Sieve Element-Like Cells.

    PubMed

    Kondo, Yuki; Nurani, Alif Meem; Saito, Chieko; Ichihashi, Yasunori; Saito, Masato; Yamazaki, Kyoko; Mitsuda, Nobutaka; Ohme-Takagi, Masaru; Fukuda, Hiroo

    2016-06-01

    Cell differentiation is a complex process involving multiple steps, from initial cell fate specification to final differentiation. Procambial/cambial cells, which act as vascular stem cells, differentiate into both xylem and phloem cells during vascular development. Recent studies have identified regulatory cascades for xylem differentiation. However, the molecular mechanism underlying phloem differentiation is largely unexplored due to technical challenges. Here, we established an ectopic induction system for phloem differentiation named Vascular Cell Induction Culture System Using Arabidopsis Leaves (VISUAL). Our results verified similarities between VISUAL-induced Arabidopsis thaliana phloem cells and in vivo sieve elements. We performed network analysis using transcriptome data with VISUAL to dissect the processes underlying phloem differentiation, eventually identifying a factor involved in the regulation of the master transcription factor gene APL Thus, our culture system opens up new avenues not only for genetic studies of phloem differentiation, but also for future investigations of multidirectional differentiation from vascular stem cells. PMID:27194709

  8. Pillared montmorillonite catalysts for coal liquefaction

    SciTech Connect

    Sharma, R.K.; Olson, E.S.

    1994-12-31

    Pillared clays contain large micropores and have considerable potential for catalytic hydrogenation and cleavage of coal macromolecules. Pillared montmorillonite-supported catalysts were prepared by the intercalation of polynuclear hydroxychromium cations and subsequent impregnation of nickel and molybdenum. Infrared and thermogravimetric studies of pyridine-adsorbed catalysts indicated the presence of both Lewis and Bronsted acid sites. Thus, the catalysts have both acidic properties that can aid in hydrocracking and cleavage of carbon-heteroatom bonds as well as hydrogen-activating bimetallic sites. These catalysts were applied to the hydrodesulfurization and liquefaction of coal-derived intermediates. The reactions of model organosulfur compounds and coal liquids were carried out at 300{degrees}-400{degrees}C for 3 hours in the presence of 1000 psi of molecular hydrogen. Reaction products were analyzed by GC/FT-IR/MS/AED. The catalysts have been found to be very effective in removing sulfur from model compounds as well as liquefaction products.

  9. Hydrocracking with new solid acid catalysts: Model compounds studies

    SciTech Connect

    Sharma, R.K.; Diehl, J.W.; Olson, E.S. )

    1990-01-01

    Two new solid acid catalysts have been prepared by supporting zinc chloride on silica gel and acid-exchanged montmorillonite. The acid properties of these catalysts were determined by Hammett indicator method which showed that highly Bronsted acidic sites were present. SEM/EDS studies indicated a uniform distribution of silicon, zinc, and chlorine in the silica gel-zinc chloride catalyst. The activities of these catalysts in the hydrocracking of bibenzyl, polybenzyl, alkylbenzenes, and other heteroatom substituted aromatics were investigated. Their results with model compounds account for the effectiveness of these solid acid catalysts for conversion of coals to lower molecular weight materials.

  10. Electrochemical catalyst recovery method

    DOEpatents

    Silva, L.J.; Bray, L.A.

    1995-05-30

    A method of recovering catalyst material from latent catalyst material solids includes: (a) combining latent catalyst material solids with a liquid acid anolyte solution and a redox material which is soluble in the acid anolyte solution to form a mixture; (b) electrochemically oxidizing the redox material within the mixture into a dissolved oxidant, the oxidant having a potential for oxidation which is effectively higher than that of the latent catalyst material; (c) reacting the oxidant with the latent catalyst material to oxidize the latent catalyst material into at least one oxidized catalyst species which is soluble within the mixture and to reduce the oxidant back into dissolved redox material; and (d) recovering catalyst material from the oxidized catalyst species of the mixture. The invention is expected to be particularly useful in recovering spent catalyst material from petroleum hydroprocessing reaction waste products having adhered sulfides, carbon, hydrocarbons, and undesired metals, and as well as in other industrial applications. 3 figs.

  11. Electrochemical catalyst recovery method

    DOEpatents

    Silva, Laura J.; Bray, Lane A.

    1995-01-01

    A method of recovering catalyst material from latent catalyst material solids includes: a) combining latent catalyst material solids with a liquid acid anolyte solution and a redox material which is soluble in the acid anolyte solution to form a mixture; b) electrochemically oxidizing the redox material within the mixture into a dissolved oxidant, the oxidant having a potential for oxidation which is effectively higher than that of the latent catalyst material; c) reacting the oxidant with the latent catalyst material to oxidize the latent catalyst material into at least one oxidized catalyst species which is soluble within the mixture and to reduce the oxidant back into dissolved redox material; and d) recovering catalyst material from the oxidized catalyst species of the mixture. The invention is expected to be particularly useful in recovering spent catalyst material from petroleum hydroprocessing reaction waste products having adhered sulfides, carbon, hydrocarbons, and undesired metals, and as well as in other industrial applications.

  12. A kinetic study of plutonium dioxide dissolution in hydrochloric acid using iron (II) as an electron transfer catalyst

    SciTech Connect

    Fife, K.W.

    1996-09-01

    Effective dissolution of plutonium dioxide has traditionally been accomplished by contact with strong nitric acid containing a small amount of fluoride at temperatures of {approximately} 100 C. In spite of these aggressive conditions, PuO{sub 2} dissolution is sometimes incomplete requiring additional contact with the solvent. This work focused on an alternative to conventional dissolution in nitric acid where an electron transfer catalyst, Fe(II), was used in hydrochloric acid. Cyclic voltammetry was employed as an in-situ analytical technique for monitoring the dissolution reaction rate. The plutonium oxide selected for this study was decomposed plutonium oxalate with > 95% of the material having a particle diameter (< 70 {micro}m) as determined by a scanning laser microscopy technique. Attempts to dry sieve the oxide into narrow size fractions prior to dissolution in the HCl-Fe(II) solvent system failed, apparently due to significant interparticle attractive forces. Although sieve splits were obtained, subsequent scanning laser microscopy analysis of the sieve fractions indicated that particle segregation was not accomplished and the individual sieve fractions retained a particle size distribution very similar to the original powder assemblage. This phenomena was confirmed through subsequent dissolution experiments on the various screen fractions which illustrated no difference in kinetic behavior between the original oxide assemblage and the sieve fractions.

  13. Long-Life Catalyst

    NASA Technical Reports Server (NTRS)

    1999-01-01

    STC Catalysts, Inc. (SCi) manufactures a noble metal reducible oxide catalyst consisting primarily of platinum and tin dioxide deposited on a ceramic substrate. It is an ambient temperature oxidation catalyst that was developed primarily for Carbon Dioxide Lasers.The catalyst was developed by the NASA Langley Research Center for the Laser Atmospheric Wind Sounder Program (LAWS) which was intended to measure wind velocity on a global basis. There are a number of NASA owned patents covering various aspects of the catalyst.

  14. Methods of producing epoxides from alkenes using a two-component catalyst system

    DOEpatents

    Kung, Mayfair C.; Kung, Harold H.; Jiang, Jian

    2013-07-09

    Methods for the epoxidation of alkenes are provided. The methods include the steps of exposing the alkene to a two-component catalyst system in an aqueous solution in the presence of carbon monoxide and molecular oxygen under conditions in which the alkene is epoxidized. The two-component catalyst system comprises a first catalyst that generates peroxides or peroxy intermediates during oxidation of CO with molecular oxygen and a second catalyst that catalyzes the epoxidation of the alkene using the peroxides or peroxy intermediates. A catalyst system composed of particles of suspended gold and titanium silicalite is one example of a suitable two-component catalyst system.

  15. Improving the Photocatalytic Reduction of CO2 to CO through Immobilisation of a Molecular Re Catalyst on TiO2

    PubMed Central

    Windle, Christopher D; Pastor, Ernest; Reynal, Anna; Whitwood, Adrian C; Vaynzof, Yana; Durrant, James R; Perutz, Robin N; Reisner, Erwin

    2015-01-01

    The photocatalytic activity of phosphonated Re complexes, [Re(2,2′-bipyridine-4,4′-bisphosphonic acid) (CO)3(L)] (ReP; L=3-picoline or bromide) immobilised on TiO2 nanoparticles is reported. The heterogenised Re catalyst on the semiconductor, ReP–TiO2 hybrid, displays an improvement in CO2 reduction photocatalysis. A high turnover number (TON) of 48 molCO molRe−1 is observed in DMF with the electron donor triethanolamine at λ>420 nm. ReP–TiO2 compares favourably to previously reported homogeneous systems and is the highest TON reported to date for a CO2-reducing Re photocatalyst under visible light irradiation. Photocatalytic CO2 reduction is even observed with ReP–TiO2 at wavelengths of λ>495 nm. Infrared and X-ray photoelectron spectroscopies confirm that an intact ReP catalyst is present on the TiO2 surface before and during catalysis. Transient absorption spectroscopy suggests that the high activity upon heterogenisation is due to an increase in the lifetime of the immobilised anionic Re intermediate (t50 %>1 s for ReP–TiO2 compared with t50 %=60 ms for ReP in solution) and immobilisation might also reduce the formation of inactive Re dimers. This study demonstrates that the activity of a homogeneous photocatalyst can be improved through immobilisation on a metal oxide surface by favourably modifying its photochemical kinetics. PMID:25639778

  16. Improving the photocatalytic reduction of CO2 to CO through immobilisation of a molecular Re catalyst on TiO2.

    PubMed

    Windle, Christopher D; Pastor, Ernest; Reynal, Anna; Whitwood, Adrian C; Vaynzof, Yana; Durrant, James R; Perutz, Robin N; Reisner, Erwin

    2015-02-23

    The photocatalytic activity of phosphonated Re complexes, [Re(2,2'-bipyridine-4,4'-bisphosphonic acid) (CO)3(L)] (ReP; L = 3-picoline or bromide) immobilised on TiO2 nanoparticles is reported. The heterogenised Re catalyst on the semiconductor, ReP-TiO2 hybrid, displays an improvement in CO2 reduction photocatalysis. A high turnover number (TON) of 48 molCO molRe(-1) is observed in DMF with the electron donor triethanolamine at λ>420 nm. ReP-TiO2 compares favourably to previously reported homogeneous systems and is the highest TON reported to date for a CO2-reducing Re photocatalyst under visible light irradiation. Photocatalytic CO2 reduction is even observed with ReP-TiO2 at wavelengths of λ>495 nm. Infrared and X-ray photoelectron spectroscopies confirm that an intact ReP catalyst is present on the TiO2 surface before and during catalysis. Transient absorption spectroscopy suggests that the high activity upon heterogenisation is due to an increase in the lifetime of the immobilised anionic Re intermediate (t50% >1 s for ReP-TiO2 compared with t50% = 60 ms for ReP in solution) and immobilisation might also reduce the formation of inactive Re dimers. This study demonstrates that the activity of a homogeneous photocatalyst can be improved through immobilisation on a metal oxide surface by favourably modifying its photochemical kinetics. PMID:25639778

  17. ''KN'' series cracking catalysts

    SciTech Connect

    Klapstov, V.F.; Khlebrikova, M.A.; Maslova, A.A.; Nefedov, B.K.

    1986-09-01

    The basic directions in improving high-activity zeolitic cracking catalysts at the present stage are improvements in the resistance to attrition and increases in the bulk density of the catalysts, along with a changeover to relatively waste-free catalyst manufacturing technology. Catalysts of the ''KN'' series have been synthesized recently with improved quality characteristics. Low-waste technology is used in manufacturing them. Data are presented which show that the KN catalysts are better than the other Soviet catalysts. The starting materials and reagents in preparing the KN catalysts are technical alumina, rare-earth element nitrates, a natural component (such as clay conforming to specification TU-21-25-146-75), sodium hydroxide, and granulated sodium silicate. The preparation of the KN catalysts is described and no silica gel is used in manufacturing the KN series catalyst, in contrast to the RSG-6Ts catalyst. The use of KN series catalysts in place of KMTsR in catalytic cracking units will result in an increase in the naphtha yield by at least 20% by weight, as well as a reduction of the catalyst consumption by a factor of 2-3. A changeover to the commerical production of this catalyst will make it possible to reduce saline waste by a factor of 8-10 and reduce the catalyst cost by a factor of 1.5-2.

  18. Laser Diffraction Techniques Replace Sieving for Lunar Soil Particle Size Distribution Data

    NASA Technical Reports Server (NTRS)

    Cooper, Bonnie L.; Gonzalez, C. P.; McKay, D. S.; Fruland, R. L.

    2012-01-01

    Sieving was used extensively until 1999 to determine the particle size distribution of lunar samples. This method is time-consuming, and requires more than a gram of material in order to obtain a result in which one may have confidence. This is demonstrated by the difference in geometric mean and median for samples measured by [1], in which a 14-gram sample produced a geometric mean of approx.52 micrometers, whereas two other samples of 1.5 grams resulted in gave means of approx.63 and approx.69 micrometers. Sample allocations for sieving are typically much smaller than a gram, and many of the sample allocations received by our lab are 0.5 to 0.25 grams in mass. Basu [2] has described how the finest fraction of the soil is easily lost in the sieving process, and this effect is compounded when sample sizes are small.

  19. Live Imaging of Companion Cells and Sieve Elements in Arabidopsis Leaves

    PubMed Central

    Cayla, Thibaud; Batailler, Brigitte; Le Hir, Rozenn; Revers, Frédéric; Anstead, James A.; Thompson, Gary A.; Grandjean, Olivier; Dinant, Sylvie

    2015-01-01

    The phloem is a complex tissue composed of highly specialized cells with unique subcellular structures and a compact organization that is challenging to study in vivo at cellular resolution. We used confocal scanning laser microscopy and subcellular fluorescent markers in companion cells and sieve elements, for live imaging of the phloem in Arabidopsis leaves. This approach provided a simple framework for identifying phloem cell types unambiguously. It highlighted the compactness of the meshed network of organelles within companion cells. By contrast, within the sieve elements, unknown bodies were observed in association with the PP2-A1:GFP, GFP:RTM1 and RTM2:GFP markers at the cell periphery. The phloem lectin PP2-A1:GFP marker was found in the parietal ground matrix. Its location differed from that of the P-protein filaments, which were visualized with SEOR1:GFP and SEOR2:GFP. PP2-A1:GFP surrounded two types of bodies, one of which was identified as mitochondria. This location suggested that it was embedded within the sieve element clamps, specific structures that may fix the organelles to each another or to the plasma membrane in the sieve tubes. GFP:RTM1 was associated with a class of larger bodies, potentially corresponding to plastids. PP2-A1:GFP was soluble in the cytosol of immature sieve elements. The changes in its subcellular localization during differentiation provide an in vivo blueprint for monitoring this process. The subcellular features obtained with these companion cell and sieve element markers can be used as landmarks for exploring the organization and dynamics of phloem cells in vivo. PMID:25714357

  20. Computational image formation with photon sieves for milli-arcsecond solar imaging

    NASA Astrophysics Data System (ADS)

    Oktem, Figen S.; Kamalabadi, Farzad; Davila, Joseph

    2016-07-01

    A photon sieve is a modification of a Fresnel zone plate in which open zones are replaced by a large number of circular holes. This diffractive imaging element is specially suited to observations at UV and x-ray wavelengths where refractive lenses are not available due to strong absorption of materials, and reflective mirrors are difficult to manufacture with sufficient surface figure accuracy to achieve diffraction-limited resolution. On the other hand, photon sieves enable diffraction-limited imaging with much more relaxed tolerances than conventional imaging technology. In this presentation, we present the capabilities of an instrument concept that is based on computational image formation with photon sieves. The instrument enables high-resolution spectral imaging by distributing the imaging task between a photon sieve system and a computational method. A photon sieve coupled with a moving detector provides measurements from multiple planes. Then computational image formation, which involves deconvolution, is performed in a Bayesian estimation framework to reconstruct the multi-spectral images from these measurements. In addition to diffraction-limited high spatial resolution enabled by photon sieves, this instrument can also achieve higher spectral resolution than the conventional spectral imagers, since the technique offers the possibility of separating nearby spectral components that would not otherwise be possible using wavelength filters. Here, the promising capabilities and the imaging performance are shown for imaging the solar corona at EUV wavelengths. The effectiveness of various potential observing scenarios, the effects of interfering emission lines, and the appropriate form of the cost function for image deconvolution are examined.

  1. MassSieve: panning MS/MS peptide data for proteins.

    PubMed

    Slotta, Douglas J; McFarland, Melinda A; Markey, Sanford P

    2010-08-01

    We present MassSieve, a Java-based platform for visualization and parsimony analysis of single and comparative LC-MS/MS database search engine results. The success of mass spectrometric peptide sequence assignment algorithms has led to the need for a tool to merge and evaluate the increasing data set sizes that result from LC-MS/MS-based shotgun proteomic experiments. MassSieve supports reports from multiple search engines with differing search characteristics, which can increase peptide sequence coverage and/or identify conflicting or ambiguous spectral assignments. PMID:20564260

  2. Chronic recording of regenerating VIIIth nerve axons with a sieve electrode

    NASA Technical Reports Server (NTRS)

    Mensinger, A. F.; Anderson, D. J.; Buchko, C. J.; Johnson, M. A.; Martin, D. C.; Tresco, P. A.; Silver, R. B.; Highstein, S. M.

    2000-01-01

    A micromachined silicon substrate sieve electrode was implanted within transected toadfish (Opsanus tau) otolith nerves. High fidelity, single unit neural activity was recorded from seven alert and unrestrained fish 30 to 60 days after implantation. Fibrous coatings of genetically engineered bioactive protein polymers and nerve guide tubes increased the number of axons regenerating through the electrode pores when compared with controls. Sieve electrodes have potential as permanent interfaces to the nervous system and to bridge missing connections between severed or damaged nerves and muscles. Recorded impulses might also be amplified and used to control prosthetic devices.

  3. Bidirectional Translocation of Sugars in Sieve Tubes of Squash Plants 1

    PubMed Central

    Trip, P.; Gorham, P. R.

    1968-01-01

    Two streams of sugars moving in opposite directions in the petiole of a half-grown leaf were demonstrated by feeding tritiated glucose to a fully grown leaf of a squash plant (Cucurbita melopepo Bailey) and 14CO2 to the half-grown one. Autoradiographic evidence indicates that the movement of both streams occurred within the same sieve tubes. The data do not fit the mass flow theory of translocation which requires unidirectional flow of sugar solution in the lumen of the sieve tube. Images PMID:16656856

  4. Microfluidic sieve using intertwined, free-standing carbon nanotube mesh as active medium

    DOEpatents

    Bakajin, Olgica; Noy, Aleksandr

    2007-11-06

    A microfluidic sieve having a substrate with a microfluidic channel, and a carbon nanotube mesh. The carbon nanotube mesh is formed from a plurality of intertwined free-standing carbon nanotubes which are fixedly attached within the channel for separating, concentrating, and/or filtering molecules flowed through the channel. In one embodiment, the microfluidic sieve is fabricated by providing a substrate having a microfluidic channel, and growing the intertwined free-standing carbon nanotubes from within the channel to produce the carbon nanotube mesh attached within the channel.

  5. Catalysts and process for liquid hydrocarbon fuel production

    DOEpatents

    White, Mark G.; Ranaweera, Samantha A.; Henry, William P.

    2016-08-02

    The present invention provides a novel process and system in which a mixture of carbon monoxide and hydrogen synthesis gas, or syngas, is converted into hydrocarbon mixtures composed of high quality distillates, gasoline components, and lower molecular weight gaseous olefins in one reactor or step. The invention utilizes a novel supported bimetallic ion complex catalyst for conversion, and provides methods of preparing such novel catalysts and use of the novel catalysts in the process and system of the invention.

  6. Lewis Base Catalysts 6: Carbene Catalysts

    PubMed Central

    Moore, Jennifer L.

    2013-01-01

    The use of N-heterocyclic carbenes as catalysts for organic transformations has received increased attention in the past 10 years. A discussion of catalyst development and nucleophilic characteristics precedes a description of recent advancements and new reactions using N-heterocyclic carbenes in catalysis. PMID:21494949

  7. Model Catalysts: Simulating the Complexities of Heterogeneous Catalysts

    NASA Astrophysics Data System (ADS)

    Gao, Feng; Goodman, D. Wayne

    2012-05-01

    Surface-science investigations have contributed significantly to heterogeneous catalysis in the past several decades. Fundamental studies of reactive systems on metal single crystals have aided researchers in understanding the effect of surface structure on catalyst reactivity and selectivity for a number of important reactions. Recently, model systems, consisting of metal clusters deposited on planar oxide surfaces, have facilitated the study of metal particle-size and support effects. These model systems not only are useful for carrying out kinetic investigations, but are also amenable to surface spectroscopic techniques, thus enabling investigations under realistic pressures and at working temperatures. By combining surface-science characterization methods with kinetic measurements under realistic working conditions, researchers are continuing to advance the molecular-level understanding of heterogeneous catalysis and are narrowing the pressure and material gap between model and real-world catalysts.

  8. The use of poly(2-acrylamido-2-methyl-1-propanesulfonic acid) polymers as spacers for isotachophoresis in sieving gel matrices.

    PubMed

    Bellini, M P; Manchester, K L

    1999-03-01

    The electric field strength gradients generated in isotachophoresis (ITP) may be used for the separation of biomolecules. Poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (polyAMPS) polymers of a uniform distribution of molecular mass were synthesized and used as novel spacers in ITP. Since these polymeric spacers are strongly acidic species, their ionic charges remain constant over a wide pH range, so that their ionic mobilities are governed solely by their molecular masses and not by the pH of the milieu. A modification of ITP known as telescope electrophoresis was used to separate a number of acidic dyes of varying ionic mobility, using polyAMPS polymers as spacers. The resolution obtained was superior to that obtained by polyacrylamide gel electrophoresis (PAGE), due to the focusing effect of the electric field strength gradient. Since these novel polymeric spacers are designed to operate within sieving medium, it was decided to test their suitability for the separation of DNA molecules. DNA molecules up to 1000 bp long were successfully resolved, with a similar resolution to that obtained with conventional PAGE. PMID:10036157

  9. Effect of barley roller milling on fractionation of flour using sieving and air classification

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Separation of hulls prior to fermentation of barley flour could increase fuel ethanol productivity and the hulls would be an additional coproduct. In a recent study, it was found that the Elusieve process, a combination of sieving and elutriation (air classification) was effective in separating hul...

  10. Separation of fiber from distillers dried grains (DDG) using sieving and elutriation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We recently developed a new process that combined sieving and elutriation (upward air flow) to separate fiber from distillers dried grains and solubles (DDGS). The current study was designed to evaluate the elusieve process for the first time using distillers dried grains (DDG) instead of DDGS. Be...

  11. Importance of neutralization sieve analyses when seeking correlates of HIV-1 vaccine efficacy

    PubMed Central

    Montefiori, David C

    2014-01-01

    This commentary describes a rationale for the use of breakthrough viruses from clinical trial participants to assess neutralizing antibodies as a correlate of HIV-1 vaccine efficacy. The rationale is based on principles of a genetic sieve analysis, where the 2 analyses may be cooperative for delineating neutralizing antibodies as a mechanistic correlate of protection. PMID:25424964

  12. Alternative sieving method for extraction of light filth from cheeses: collaborative study.

    PubMed

    Nakashima, M J

    1994-01-01

    A collaborative study was conducted on an alternative sieving method for the extraction of light filth from cheeses. The alternative method was developed that is applicable to broad variety of cheeses. A 225 g test portion is dispersed in a solution of 5.7% HCl, Igepal CO-730, and Igepal DM-710. Digested cheese is wet-sieved on a No. 230 sieve. The residue is treated with Tergitol Anionic 4, transferred to 1% sodium lauryl sulfate solution, heated, and maintained at 65 degrees-75 degrees C for 10 min. The residue is washed with these 2 surfactants a maximum of 4 times until it is reduced to an amount that is filterable. The residue is filtered and the filter papers are examined microscopically at a magnification of ca 30x. Average recoveries by 9 collaborators for 3 spike levels of rat hairs (5, 10, and 15) were 80, 68, and 81%, respectively; for insect fragments (5, 15, and 30) recoveries were 97, 90, and 92%, respectively. The alternative sieving method for extraction of light filth from cheeses has been adopted first action by AOAC INTERNATIONAL. PMID:7950417

  13. Structure-Property Relationships of Inorganically Surface-Modified Zeolite Molecular Sieves for Nanocomposite Membrane Fabrication

    SciTech Connect

    Lydon, Megan E; Unocic, Kinga A; Jones, Christopher W; Nair, Sankar

    2012-01-01

    A multiscale experimental study of the structural, compositional, and morphological characteristics of aluminosilicate (LTA) and pure-silica (MFI) zeolite materials surface-modified with MgO{sub x}H{sub y} nanostructures is presented. These characteristics are correlated with the suitability of such materials in the fabrication of LTA/Matrimid mixed-matrix membranes (MMMs) for CO{sub 2}/CH{sub 4} separations. The four functionalization methods studied in this work produce surface nanostructures that may appear superficially similar under SEM observation but in fact differ considerably in shape, size, surface coverage, surface area/roughness, degree of attachment to the zeolite surface, and degree of zeolite pore blocking. The evaluation of these characteristics by a combination of TEM, HRTEM, N{sub 2} physisorption, multiscale compositional analysis (XPS, EDX, and ICP-AES elemental analysis), and diffraction (ED and XRD) allows improved understanding of the origin of disparate gas permeation properties observed in MMMs made with four types of surface-modified zeolite LTA materials, as well as a rational selection of the method expected to result in the best enhancement of the desired properties (in the present case, CO{sub 2}/CH{sub 4} selectivity increase without sacrificing permeability). A method based on ion exchange of the LTA with Mg{sup 2+}, followed by base-induced precipitation and growth of MgOxHy nanostructures, deemed 'ion exchange functionalization' here, offers modified particles with the best overall characteristics resulting in the most effective MMMs. LTA/Matrimid MMMs containing ion exchange functionalized particles had a considerably higher CO{sub 2}/CH{sub 4} selectivity (40) than could be obtained with the other functionalization techniques (30), while maintaining a CO{sub 2} permeability of 10 barrers. A parallel study on pure silica MFI surface nanostructures is also presented to compare and contrast with the zeolite LTA case.

  14. Novel insights into RNP granules by employing the trypanosome's microtubule skeleton as a molecular sieve

    PubMed Central

    Fritz, Melanie; Vanselow, Jens; Sauer, Nadja; Lamer, Stephanie; Goos, Carina; Siegel, T. Nicolai; Subota, Ines; Schlosser, Andreas; Carrington, Mark; Kramer, Susanne

    2015-01-01

    RNP granules are ribonucleoprotein assemblies that regulate the post-transcriptional fate of mRNAs in all eukaryotes. Their exact function remains poorly understood, one reason for this is that RNP granule purification has not yet been achieved. We have exploited a unique feature of trypanosomes to prepare a cellular fraction highly enriched in starvation stress granules. First, granules remain trapped within the cage-like, subpellicular microtubule array of the trypanosome cytoskeleton while soluble proteins are washed away. Second, the microtubules are depolymerized and the granules are released. RNA sequencing combined with single molecule mRNA FISH identified the short and highly abundant mRNAs encoding ribosomal mRNAs as being excluded from granules. By mass spectrometry we have identified 463 stress granule candidate proteins. For 17/49 proteins tested by eYFP tagging we have confirmed the localization to granules, including one phosphatase, one methyltransferase and two proteins with a function in trypanosome life-cycle regulation. The novel method presented here enables the unbiased identification of novel RNP granule components, paving the way towards an understanding of RNP granule function. PMID:26187993

  15. Novel insights into RNP granules by employing the trypanosome's microtubule skeleton as a molecular sieve.

    PubMed

    Fritz, Melanie; Vanselow, Jens; Sauer, Nadja; Lamer, Stephanie; Goos, Carina; Siegel, T Nicolai; Subota, Ines; Schlosser, Andreas; Carrington, Mark; Kramer, Susanne

    2015-09-18

    RNP granules are ribonucleoprotein assemblies that regulate the post-transcriptional fate of mRNAs in all eukaryotes. Their exact function remains poorly understood, one reason for this is that RNP granule purification has not yet been achieved. We have exploited a unique feature of trypanosomes to prepare a cellular fraction highly enriched in starvation stress granules. First, granules remain trapped within the cage-like, subpellicular microtubule array of the trypanosome cytoskeleton while soluble proteins are washed away. Second, the microtubules are depolymerized and the granules are released. RNA sequencing combined with single molecule mRNA FISH identified the short and highly abundant mRNAs encoding ribosomal mRNAs as being excluded from granules. By mass spectrometry we have identified 463 stress granule candidate proteins. For 17/49 proteins tested by eYFP tagging we have confirmed the localization to granules, including one phosphatase, one methyltransferase and two proteins with a function in trypanosome life-cycle regulation. The novel method presented here enables the unbiased identification of novel RNP granule components, paving the way towards an understanding of RNP granule function. PMID:26187993

  16. Adsorption of CO 2, CH 4 and N 2 on ordered mesoporous silica molecular sieve

    NASA Astrophysics Data System (ADS)

    Liu, Xiuwu; Li, Jingwen; Zhou, Li; Huang, Desheng; Zhou, Yaping

    2005-11-01

    Five samples of ordered mesoporous silica SBA-15 were synthesized. Its pore size was in the range 5-9 nm, and the specific surface area was in the range 500-900 m 2/g, which was controlled by the temperature and time of aging on crystallization. Adsorption isotherms of CO 2, CH 4 and N 2 on the samples were collected at 298 K, and the adsorption rates of the gases were also compared for different pressures. It was concluded that SBA-15 with the textural property studied was a good adsorbent for the separation of carbon dioxide from its mixture with methane and nitrogen.

  17. Microwave-assisted fast vapor-phase transport synthesis of MnAPO-5 molecular sieves

    SciTech Connect

    Shao Hui; Yao Jianfeng; Ke Xuebin; Zhang Lixiong Xu Nanping

    2009-04-02

    MnAPO-5 was prepared by a microwave-assisted vapor-phase transport method at 180 deg. C in short times. The products were characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectra, UV-vis spectroscopic measurement, NH{sub 3}-temperature-programmed desorption and esterification reaction. It was found that dry gels prepared with aluminum isopropoxide, phosphoric acid and manganese acetate could be transferred to MnAPO-5 in the vapors of triethylamine and water by the microwave-assisted vapor-phase transport method at 180 deg. C for less than 30 min. The crystallization time was greatly reduced by the microwave heating compared with the conventional heating. The resulting MnAPO-5 exhibited much smaller particle sizes, higher surface areas and slightly higher catalytic activity in the esterification of acetic acid and butyl alcohol than those prepared by the conventional vapor-phase transport method and hydrothermal synthesis.

  18. Catalytic properties of molecular sieves MCM41 type doped with heteropolyacids for ethanol oxidation

    NASA Astrophysics Data System (ADS)

    Popa, A.; Sasca, V.; Halasz, J.

    2008-12-01

    Keggin type heteropolyacids (HPAs) have been used in acid-catalysed reactions as well as oxidation reactions both in the heterogeneous and homogeneous systems. In order to be more effective for catalytic reactions, HPAs are usually impregnated on different porous materials with high surface area. The structure and texture of H 3PMo 12O 40 and H 4PVMo 11O 40 supported on Al-MCM41 and Fe-MCM41 were studied by XRD, low-temperature nitrogen adsorption and thermal analysis. Catalytic properties of prepared samples were studied by using a reactant pulse method at different temperatures. The ethanol conversion proceeds by two main pathways: an oxidehydrogenation reaction on redox catalytic centers, and a dehydration reaction on acidic centers, respectively. The favourable effect of HPAs deposition on Al-MCM41 and Fe-MCM41 supports for oxidehydrogenation pathway to acetaldehyde results from the examination of apparent activation energies Ea and reaction rate values. An evidenced decreasing of Ea was obtained for acetaldehyde formation in the case of Fe-MCM41-supported HPM (25 kJ/mole) comparatively with pure HPM (56.6 kJ/mole). For all reaction temperatures, the reaction rates of acetaldehyde formation are with one order of magnitude higher for supported samples than unsupported ones.

  19. Textural and structural properties and surface acidity characterization of mesoporous silica-zirconia molecular sieves

    NASA Astrophysics Data System (ADS)

    Rodríguez-Castellón, E.; Jiménez-López, A.; Maireles-Torres, P.; Jones, D. J.; Rozière, J.; Trombetta, M.; Busca, G.; Lenarda, M.; Storaro, L.

    2003-11-01

    Homogeneous mesoporous zirconium-containing MCM-41 type silica were prepared by supramolecular templating and their textural and structural properties were studied using powder X-ray diffraction, N 2 porosimetry, atomic force microscopy, EXAFS, XPS, and UV-VIS-NIR diffuse reflectance spectroscopy. Their acid properties were also studied by using IR spectroscopy and by the use of catalytic tests such as the decomposition of isopropanol and the isomerization of 1-butene. The materials prepared show a good degree of crystallinity with a regular ordering of the pores into a hexagonal arrangement and high thermal stability. The specific surface area of the prepared materials decreases as the zirconium content rises. Zirconium atoms are in coordination 7 to 8 and located at the surface of the pores such that a high proportion of the oxygen atoms bonded to zirconium corresponds to surface non-condensed oxygen atoms. Both facts are responsible for the acid properties of the solids that show weak Brønsted and medium strong Lewis acidity.

  20. Optimization of Manganese Reduction in Biotreated POME onto 3A Molecular Sieve and Clinoptilolite Zeolites.

    PubMed

    Jami, Mohammed S; Rosli, Nurul-Shafiqah; Amosa, Mutiu K

    2016-06-01

    Availability of quality-certified water is pertinent to the production of food and pharmaceutical products. Adverse effects of manganese content of water on the corrosion of vessels and reactors necessitate that process water is scrutinized for allowable concentration levels before being applied in the production processes. In this research, optimization of the adsorption process conditions germane to the removal of manganese from biotreated palm oil mill effluent (BPOME) using zeolite 3A subsequent to a comparative adsorption with clinoptilolite was studied. A face-centered central composite design (FCCCD) of the response surface methodology (RSM) was adopted for the study. Analysis of variance (ANOVA) for response surface quadratic model revealed that the model was significant with dosage and agitation speed connoting the main significant process factors for the optimization. R(2) of 0.9478 yielded by the model was in agreement with predicted R(2). Langmuir and pseudo-second-order suggest the adsorption mechanism involved monolayer adsorption and cation exchanging. PMID:26556067

  1. Structural charge transfer in the aluminophosphate molecular sieves by diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Zanjanchi, M. A.; Rashidi, M. K.

    1999-05-01

    Influence of water adsorption in AlPO-5, SAPO-5, AlPO-11 and SAPO-11 has been studied with UV diffuse reflectance spectroscopy. The observed UV absorption spectra in the as-synthesized, template free and hydrated materials are related to the charge transfer processes between aluminum and oxygen atoms of the aluminophosphate and water molecules. As-synthesised materials show two distinct and well-defined bands at about 220 and 260-280 nm correlated to framework aluminum and organic templates, respectively. Upon calcination, the band of occluded template disappears and the band assigned to the framework aluminum shifts at about 240 nm. When the calcined samples are completely hydrated, broadening of the aluminum charge transfer band is observed. This is due to coordination of water molecules to the part of the framework aluminum. Broadening occurs more in AlPO-5 possibly because of higher water capacity and homogenity with respect to SAPO-5.

  2. IR spectroscopic study of hydroxyl groups of molecular sieves in the fundamental and combination tone regions

    NASA Astrophysics Data System (ADS)

    Löffler, E.; Zscherpel, U.; Peuker, Ch.; Staudte, B.

    1993-03-01

    The fundamental and combination vibrations of hydroxyl groups in zeolites (Y, ZSM-5) and silicoaluminophosphates (SAPO-5, -17, -34) are investigated. The influence of adsorbed molecules (C 6F 6, n-hexane) on the combination vibrations is also studied. Finally, remarks on quantitative evaluation of DRIFT spectra of NaHZSM-5 containing different amounts of bridging OH groups are given.

  3. System for reactivating catalysts

    SciTech Connect

    Ginosar, Daniel M.; Thompson, David N.; Anderson, Raymond P.

    2010-03-02

    A method of reactivating a catalyst, such as a solid catalyst or a liquid catalyst is provided. The method comprises providing a catalyst that is at least partially deactivated by fouling agents. The catalyst is contacted with a fluid reactivating agent that is at or above a critical point of the fluid reactivating agent and is of sufficient density to dissolve impurities. The fluid reactivating agent reacts with at least one fouling agent, releasing the at least one fouling agent from the catalyst. The at least one fouling agent becomes dissolved in the fluid reactivating agent and is subsequently separated or removed from the fluid reactivating agent so that the fluid reactivating agent may be reused. A system for reactivating a catalyst is also disclosed.

  4. Molecular simulations and experimental studies of zeolites

    NASA Astrophysics Data System (ADS)

    Moloy, Eric C.

    Zeolites are microporous aluminosilicate tetrahedral framework materials that have symmetric cages and channels with open-diameters between 0.2 and 2.0 nm. Zeolites are used extensively in the petrochemical industries for both their microporosity and their catalytic properties. The role of water is paramount to the formation, structure, and stability of these materials. Zeolites frequently have extra-framework cations, and as a result, are important ion-exchange materials. Zeolites also play important roles as molecular sieves and catalysts. For all that is known about zeolites, much remains a mystery. How, for example, can the well established metastability of these structures be explained? What is the role of water with respect to the formation, stabilization, and dynamical properties? This dissertation addresses these questions mainly from a modeling perspective, but also with some experimental work as well. The first discussion addresses a special class of zeolites: pure-silica zeolites. Experimental enthalpy of formation data are combined with molecular modeling to address zeolitic metastability. Molecular modeling is used to calculate internal surface areas, and a linear relationship between formation enthalpy and internal surface areas is clearly established, producing an internal surface energy of approximately 93 mJ/m2. Nitrate bearing sodalite and cancrinite have formed under the caustic chemical conditions of some nuclear waste processing centers in the United States. These phases have fouled expensive process equipment, and are the primary constituents of the resilient heels in the bottom of storage tanks. Molecular modeling, including molecular mechanics, molecular dynamics, and density functional theory, is used to simulate these materials with respect to structure and dynamical properties. Some new, very interesting results are extracted from the simulation of anhydrous Na6[Si6Al 6O24] sodalite---most importantly, the identification of two distinct

  5. Catalysts and process for liquid hydrocarbon fuel production

    SciTech Connect

    White, Mark G; Liu, Shetian

    2014-12-09

    The present invention provides a novel process and system in which a mixture of carbon monoxide and hydrogen synthesis gas, or syngas, is converted into hydrocarbon mixtures composed of high quality gasoline components, aromatic compounds, and lower molecular weight gaseous olefins in one reactor or step. The invention utilizes a novel molybdenum-zeolite catalyst in high pressure hydrogen for conversion, as well as a novel rhenium-zeolite catalyst in place of the molybdenum-zeolite catalyst, and provides for use of the novel catalysts in the process and system of the invention.

  6. Catalyst patterning for nanowire devices

    NASA Technical Reports Server (NTRS)

    Li, Jun (Inventor); Cassell, Alan M. (Inventor); Han, Jie (Inventor)

    2004-01-01

    Nanowire devices may be provided that are based on carbon nanotubes or single-crystal semiconductor nanowires. The nanowire devices may be formed on a substrate. Catalyst sites may be formed on the substrate. The catalyst sites may be formed using lithography, thin metal layers that form individual catalyst sites when heated, collapsible porous catalyst-filled microscopic spheres, microscopic spheres that serve as masks for catalyst deposition, electrochemical deposition techniques, and catalyst inks. Nanowires may be grown from the catalyst sites.

  7. Systematic preparation of selective heterogeneous catalysts

    SciTech Connect

    Augustine, R.L.

    1991-11-07

    The Single Turnover (STO) procedure, involving pulses of hydrogen and 1-butene, was developed for studying the types of active sites present on supported metal catalysts. The STO procedure was used to study direct saturated sites and other topics. Frontier molecular orbital studies were also made.

  8. Enhanced catalyst-free nucleation of GaN nanowires on amorphous Al{sub 2}O{sub 3} by plasma-assisted molecular beam epitaxy

    SciTech Connect

    Sobanska, Marta Klosek, Kamil; Borysiuk, Jolanta; Kret, Slawomir; Tchutchulasvili, Giorgi; Gieraltowska, Sylwia; Zytkiewicz, Zbigniew R.

    2014-01-28

    We report on plasma-assisted molecular beam epitaxial growth of GaN nanowires (NWs) on Si(111) substrates with a thin amorphous Al{sub 2}O{sub 3} buffer layer deposited by atomic layer deposition. Comparison of nucleation kinetics shows that presence of amorphous Al{sub 2}O{sub 3} buffer significantly enhances spontaneous nucleation of GaN NWs. Slower nucleation was observed on partially amorphous silicon nitride films. No growth of NWs was found on sapphire substrate under the same growth conditions which we explain by a low density of defects on monocrystalline substrate surface where NWs may nucleate. Our finding shows that tuning of substrate microstructure is an efficient tool to control rate of self-induced nucleation of GaN NWs.

  9. Textured catalysts and methods of making textured catalysts

    DOEpatents

    Werpy, Todd; Frye, Jr., John G.; Wang, Yong; Zacher, Alan H.

    2007-03-06

    A textured catalyst having a hydrothermally-stable support, a metal oxide and a catalyst component is described. Methods of conducting aqueous phase reactions that are catalyzed by a textured catalyst are also described. The invention also provides methods of making textured catalysts and methods of making chemical products using a textured catalyst.

  10. Oxidative demethylation of 2-picolines on vanadium oxide catalysts

    SciTech Connect

    Suvorov, B.V.; Glubokovskikh, L.K.; Demin, V.V.; Kan, I.I.

    1988-07-10

    One of the known methods for the preparation of pyridine is based on the dealkylation of alkylpyridines in the presence of vanadium-containing catalysts, molecular oxygen and steam. By using the oxidative demethylation of 2-picoline in the presence of steam on a fused vanadium(V) oxide, pyridine can be obtained in a yield of up to 88% of theory. To lower the consumption of vanadium(V) oxide and increase the thermostability of the catalyst, they studied the possible use of V/sub 2/O/sub 5/ catalysts on various carriers (diatomite, silica gel, porcelain balls), including the industrially produced brand SVD and SVS catalysts. The SVS brand catalyst has a satisfactory activity and selectivity in the oxidation demethylation of 2-picoline into pyridine. Under optimal conditions, pyridine is formed on this catalyst in a yield of 88% of the theoretical.

  11. OHMS**: Phytoplasmas dictate changes in sieve-element ultrastructure to accommodate their requirements for nutrition, multiplication and translocation

    PubMed Central

    Musetti, Rita; Pagliari, Laura; Buxa, Stefanie V.; Degola, Francesca; De Marco, Federica; Loschi, Alberto; Kogel, Karl-Heinz; van Bel, Aart J. E.

    2016-01-01

    ABSTRACT Phytoplasmas are among the most recently discovered plant pathogenic microorganisms so, many traits of the interactions with host plants and insect vectors are still unclear and need to be investigated. At now, it is impossible to determine the precise sequences leading to the onset of the relationship with the plant host cell. It is still unclear how phytoplasmas, located in the phloem sieve elements, exploit host cell to draw nutrition for their metabolism, growth and multiplication. In this work, basing on microscopical observations, we give insight about the structural interactions established by phytoplasmas and the sieve element plasma membrane, cytoskeleton, sieve endoplasmic reticulum, speculating about a possible functional role. PMID:26795235

  12. The surface chemistry of iron Fischer-Tropsch catalysts

    SciTech Connect

    Dwyer, D.J.; Hardenburgh, J.H.

    1986-04-01

    The indirect conversion of coal to liquid hydrocarbons via steam gasification followed by synthesis gas (CO/H/sub 2/) chemistry has been the subject of intensive study for a number of decades. A key technological challenge facing researchers in this area is control over the product distribution during the hydrocarbon synthesis step. In the case of iron Fischer-Tropsch catalysts, it has been known that the addition of alkali to the metal catalyst has a significant impact on the product distribution. Iron catalysts treated with alkali produce less methane more alkenes and higher molecular weight products. In spite of numerous investigations, the details of this promotional effect are not understood on a molecular level. To explore the role of alkali in the surface chemistry of iron catalysts, the authors have carried out a combined surface science and catalytic kinetic study of a model iron catalyst with and without surface alkali.

  13. Sieve-based relation extraction of gene regulatory networks from biological literature

    PubMed Central

    2015-01-01

    Background Relation extraction is an essential procedure in literature mining. It focuses on extracting semantic relations between parts of text, called mentions. Biomedical literature includes an enormous amount of textual descriptions of biological entities, their interactions and results of related experiments. To extract them in an explicit, computer readable format, these relations were at first extracted manually from databases. Manual curation was later replaced with automatic or semi-automatic tools with natural language processing capabilities. The current challenge is the development of information extraction procedures that can directly infer more complex relational structures, such as gene regulatory networks. Results We develop a computational approach for extraction of gene regulatory networks from textual data. Our method is designed as a sieve-based system and uses linear-chain conditional random fields and rules for relation extraction. With this method we successfully extracted the sporulation gene regulation network in the bacterium Bacillus subtilis for the information extraction challenge at the BioNLP 2013 conference. To enable extraction of distant relations using first-order models, we transform the data into skip-mention sequences. We infer multiple models, each of which is able to extract different relationship types. Following the shared task, we conducted additional analysis using different system settings that resulted in reducing the reconstruction error of bacterial sporulation network from 0.73 to 0.68, measured as the slot error rate between the predicted and the reference network. We observe that all relation extraction sieves contribute to the predictive performance of the proposed approach. Also, features constructed by considering mention words and their prefixes and suffixes are the most important features for higher accuracy of extraction. Analysis of distances between different mention types in the text shows that our choice

  14. Chemical Posttranslational Modification with Designed Rhodium(II) Catalysts.

    PubMed

    Martin, S C; Minus, M B; Ball, Z T

    2016-01-01

    Natural enzymes use molecular recognition to perform exquisitely selective transformations on nucleic acids, proteins, and natural products. Rhodium(II) catalysts mimic this selectivity, using molecular recognition to allow selective modification of proteins with a variety of functionalized diazo reagents. The rhodium catalysts and the diazo reactivity have been successfully applied to a variety of protein folds, the chemistry succeeds in complex environments such as cell lysate, and a simple protein blot method accurately assesses modification efficiency. The studies with rhodium catalysts provide a new tool to study and probe protein-binding events, as well as a new synthetic approach to protein conjugates for medical, biochemical, or materials applications. PMID:27586326

  15. Methods of making textured catalysts

    DOEpatents

    Werpy, Todd; Frye, Jr., John G.; Wang, Yong; Zacher, Alan H.

    2010-08-17

    A textured catalyst having a hydrothermally-stable support, a metal oxide and a catalyst component is described. Methods of conducting aqueous phase reactions that are catalyzed by a textured catalyst are also described. The invention also provides methods of making textured catalysts and methods of making chemical products using a textured catalyst.

  16. Catalyst Alloys Processing

    NASA Astrophysics Data System (ADS)

    Tan, Xincai

    2014-10-01

    Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

  17. Roles of adsorption sites in electron transfer from CdS quantum dots to molecular catalyst cobaloxime studied by time-resolved spectroscopy.

    PubMed

    Ye, Yun; Xu, Yuxing; Huang, Lei; Fan, Dayong; Feng, Zhaochi; Wang, Xiuli; Li, Can

    2016-06-29

    Electron transfer from CdS quantum dots (QDs) to cobaloxime (Co(dmgH)2pyCl) is demonstrated by transient absorption spectroscopy (TAS), and further confirmed using photoluminescence (PL) techniques. The analysis of the PL quenching results offers a novel way to understand the roles of the surface adsorption sites of CdS QDs in the performance of charge transfer in the CdS QDs-cobaloxime hybrid system. Two types of quenching dynamics reveal that there are two different adsorption modes of cobaloxime on the CdS QD surface. When cobaloxime substitutes the surface capping ligands of CdS QDs under low cobaloxime concentrations, the transfer is nearly unfavorable for both the free and trapped electrons. When cobaloxime occupies the surface defect sites of the CdS QDs under high cobaloxime concentrations, the transfer of both the free and trapped electrons is very effective, with an extremely high quenching rate constant of ∼10(12) M(-1) s(-1). Therefore, controlling the molecular adsorption sites and adjusting the surface defect properties of semiconductor QDs provide a strategy to improve the electron transfer efficiency of the QDs-cobaloxime photocatalytic system. PMID:27306688

  18. Catalyst enhances Claus operations

    SciTech Connect

    Dupin, T.; Voizin, R.

    1982-11-01

    An improved Claus catalyst offers superior activity that emphasizes hydrolysis of CS/sub 2/ in the first converter. The catalyst is insensitive to oxygen action at concentrations generally found in Claus gas feeds. It also has an excellent resistance to hydrothermal shocks that may occur during shutdown of the sulfur line. Collectively, these properties make this catalyst the most active formula now available for optimum Claus yields and COS/CS/sub 2/ hydrolysis conversion.

  19. Mesoporous catalysts, supports and catalytic membranes based on MCM-41. Final report for the period January 15,2000 - January 14, 2001

    SciTech Connect

    Haller, Gary L.

    2001-07-01

    The research had two objectives: to understand the effect of pore size on the chemistry and activity of active sites, and to investigate both the pore size and anchoring effect of Me-MCM-41 on Pt clusters (where Me is a metal incorporated in silica-based MCM-41). The focus is not on the effect of pore size on transport of reactants and products, but on how the local radius of curvature might affect the properties of a foreign ion embedded in a silicon wall that acts as a catalytic site or anchor for the catalytic site. The mesoporous molecular sieve, MCM-41, allows the variation of pore size with constant composition and pore geometry so these new materials allow this scientific question to be addressed for the first time. For the anchoring effect, concentration was on Sn-MCM-41 to prepare Pt/Sn-MCM-41 catalysts, by characterizing these and by testing them with probe reforming reactions (dehydrogenation, isomerization and aromatization). Although this is a final report on activity January 15, 2000 - January 14, 2001, this was a continuation of work initiated in the three-year grant period January 15, 1997 - January 14, 2000, so the summary of progress for these three years is appended for completeness.

  20. Capture and isotopic exchange method for water and hydrogen isotopes on zeolite catalysts up to technical scale for pre-study of processing highly tritiated water

    SciTech Connect

    Michling, R.; Braun, A.; Cristescu, I.; Dittrich, H.; Gramlich, N.; Lohr, N.; Glugla, M.; Shu, W.; Willms, S.

    2015-03-15

    Highly tritiated water (HTW) may be generated at ITER by various processes and, due to the excessive radio toxicity, the self-radiolysis and the exceedingly corrosive property of HTW, a potential hazard is associated with its storage and process. Therefore, the capture and exchange method for HTW utilizing Molecular Sieve Beds (MSB) was investigated in view of adsorption capacity, isotopic exchange performance and process parameters. For the MSB, different types of zeolite were selected. All zeolite materials were additionally coated with platinum. The following work comprised the selection of the most efficient zeolite candidate based on detailed parametric studies during the H{sub 2}/D{sub 2}O laboratory scale exchange experiments (about 25 g zeolite per bed) at the Tritium Laboratory Karlsruhe (TLK). For the zeolite, characterization analytical techniques such as Infrared Spectroscopy, Thermogravimetry and online mass spectrometry were implemented. Followed by further investigation of the selected zeolite catalyst under full technical operation, a MSB (about 22 kg zeolite) was processed with hydrogen flow rates up to 60 mol*h{sup -1} and deuterated water loads up to 1.6 kg in view of later ITER processing of arising HTW. (authors)