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Sample records for bimetallic dispersed catalysts

  1. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction

    SciTech Connect

    Song, Chunshan; Schobert, H.H.

    1993-02-01

    Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that catalysts are superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires intimate contact between the catalyst and coal. This research is a fundamental and exploratory study on catalytic coal liquefaction, with the emphasis on the development of novel bimetallic dispersed catalysts for temperature-programmed liquefaction. The ultimate goal of the present research is to develop novel catalytic hydroliquefaction process using highly active dispersed catalysts. The primary objective of this research is to develop novel bimetallic dispersed catalysts from organometallic molecular that can be used in low precursors concentrations (< 1 %) but exhibit high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. The major technical approaches are, first, to prepare the desired heteronuclear organometallic molecules as catalyst precursors that contain covalently bound, two different metal atoms and sulfur in a single molecule. Such precursors will generate finely dispersed bimetallic catalysts such as Fe-Mo, Co-Mo and Ni-Mo binary sulfides upon thermal decomposition. The second major technical approach is to perform the liquefaction of coals unpregnated with the organometallic precursors under temperature-programmed conditions, where the programmed heat-up serves as a step for both catalyst activation and coal pretreatment or preconversion. Two to three different complexes for each of the Fe-Mo, Co-Mo, and Ni-Mo combinations will be prepared. Initial catalyst screening tests will be conducted using a subbituminous coal and a bituminous coal. Effects of coal rank and solvents will be examined with the selected bimetallic catalysts which showed much higher activity than the dispersed catalysts from conventional precursors.

  2. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction

    SciTech Connect

    Chunshan, Song; Kirby, S.; Schmidt, E.

    1995-12-31

    The objective of this project is to explore bimetallic dispersed catalysts for more efficient coal liquefaction. Coal liquefaction involves cleavage of methylene, dimethylene and ether bridges connecting various aromatic units and the reactions of various oxygen functional groups. This paper describes recent results on (1) hydrodeoxygenation of O-containing polycyclic model compounds using novel organometallic catalyst precursors; and (2) activity and selectivity of dispersed Fe catalysts from organometallic and inorganic precursors for hydrocracking of 4-(1-naphthylmethyl) bibenzyl. The results showed that some iron containing catalysts have higher activity in the sulfur-free form, contrary to conventional wisdom. Adding sulfur to Fe precursors with Cp-ligands decreased the activity of the resulting catalyst. This is in distinct contrast to the cases with iron pentacarbonyl and superfine Fe{sub 2}O{sub 3}, where S addition increased their catalytic activity substantially. A positive correlation between sulfur addition and increased activity can be seen, but a reversed trend between Fe cluster size and hydrocracking conversion could be observed, for carbonyl-type Fe precursors. It is apparent that the activity and selectivity of Fe catalysts for NMBB conversion depends strongly on both the type of ligand environment, the oxidation state and the number of intermetal bonds in the molecular precursor.

  3. 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…

  4. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Final report

    SciTech Connect

    Chunshan Song; Schobert, H.H.; Parfitt, D.P.

    1997-11-01

    Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that dispersed catalysts are superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires intimate contact between the catalyst and coal. This research is a fundamental and exploratory study on catalytic coal liquefaction, with the emphasis on exploring novel bimetallic dispersed catalysts for coal liquefaction and the effectiveness of temperature-programmed liquefaction using dispersed catalysts. The primary objective of this research was to explore novel bimetallic dispersed catalysts from organometallic molecular precursors, that could be used in low concentrations but exhibit relatively high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. We have synthesized and tested various catalyst precursors in liquefaction of subbituminous and bituminous coals and in model compound studies to examine how do the composition and structure of the catalytic precursors affect their effectiveness for coal liquefaction under different reaction conditions, and how do these factors affect their catalytic functions for hydrogenation of polyaromatic hydrocarbons, for cleavage of C-C bonds in polycyclic systems such as 4-(1-naphthylmethyl)bibenzyl, for hydrogenolysis of C-O bond such as that in dinaphthylether, for hydrodeoxygenation of phenolic compounds and other oxygen-containing compounds such as xanthene, and for hydrodesulfurization of polycyclic sulfur compounds such as dibenzothiophene. The novel bimetallic and monometallic precursors synthesized and tested in this project include various Mo- and Fe-based compounds.

  5. Model hydrocracking reactions over monometallic and bimetallic dispersed catalysts

    SciTech Connect

    Schmidt, E.; Song, C.

    1994-12-31

    Coal liquefaction involves the cleavage of methylene and dimethylene bridges connecting polycyclic aromatic units. The selected compound for model reactions is 4-(1-naphthylmethyl)bibenzyl (NMBB). This work describes the synthesis and screening of several metallic complex precursors as dispersed catalysts for hydrocracking of NMBB.

  6. 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.

  7. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, October--December 1992

    SciTech Connect

    Song, Chunshan; Schobert, H.H.

    1993-02-01

    Development of new catalysts is a promising approach to more efficient coal liquefaction. It has been recognized that catalysts are superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires intimate contact between the catalyst and coal. This research is a fundamental and exploratory study on catalytic coal liquefaction, with the emphasis on the development of novel bimetallic dispersed catalysts for temperature-programmed liquefaction. The ultimate goal of the present research is to develop novel catalytic hydroliquefaction process using highly active dispersed catalysts. The primary objective of this research is to develop novel bimetallic dispersed catalysts from organometallic molecular that can be used in low precursors concentrations (< 1 %) but exhibit high activity for efficient hydroliquefaction of coals under temperature-programmed conditions. The major technical approaches are, first, to prepare the desired heteronuclear organometallic molecules as catalyst precursors that contain covalently bound, two different metal atoms and sulfur in a single molecule. Such precursors will generate finely dispersed bimetallic catalysts such as Fe-Mo, Co-Mo and Ni-Mo binary sulfides upon thermal decomposition. The second major technical approach is to perform the liquefaction of coals unpregnated with the organometallic precursors under temperature-programmed conditions, where the programmed heat-up serves as a step for both catalyst activation and coal pretreatment or preconversion. Two to three different complexes for each of the Fe-Mo, Co-Mo, and Ni-Mo combinations will be prepared. Initial catalyst screening tests will be conducted using a subbituminous coal and a bituminous coal. Effects of coal rank and solvents will be examined with the selected bimetallic catalysts which showed much higher activity than the dispersed catalysts from conventional precursors.

  8. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, April--June 1993

    SciTech Connect

    Song, Chunshan; Parfitt, D.P.; Schobert, H.H.

    1993-08-01

    The ultimate goal of the present research is to develop novel catalytic hydroliquefaction process using highly active dispersed catalysts. The primary objective of this research is to develop novel bimetallic dispersed catalysts from organometallic molecular precursors, that can be used in low concentrations (bimetallic dispersed catalysts for liquefaction of a Montana subbituminous coal (DECS-9) at the loading level of 0.5 wt% Mo on dmmf coal. It was found that the structure of the precursors, in particular the ligands to the metal species, affect the activity of the resulting catalyst significantly. Among the M-M` type precursors tested, Mo-Co thiocubane, Mo{sub 2}Co{sub 2}S{sub 4}(Cp){sub 2}(CO){sub 2} [Cp = cyclopentadiene], designated as MoCo-TC2, produced in-situ the best catalyst The performance of the Mo-Co bimetallic catalyst was further enhanced by using temperature programmed (TPL) conditions consisting of a low temperature soaking at 200{degrees}C, programmed heat-up to 400 or 425{degrees}C followed by a 30 minutes hold. The pro ed heat-up serves as an in-situ activation of catalyst and coal pretreatment, which contributes to more effective hydrogenation of reactive fragments at high temperature.

  9. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, October--December 1993

    SciTech Connect

    Schmidt, E.; Kirby, S.; Song, Chunshan; Schobert, H.H.

    1994-04-01

    Development of new catalysts is a promising approach to more, efficient coal liquefaction. It has been recognized that dispersed catalysts can be superior to supported catalysts for primary liquefaction of coals, because the control of initial coal dissolution or depolymerization requires infinite contact between the catalyst and coal. The primary objective of this research is to explore the potential of bimetallic dispersed catalysts from heterometallic molecular precursors in their use in model compound liquefaction reactions. This quarterly report describes the use of three precursors in model compound reactions. The first catalyst is a heterometallic complex consisting of two transition metals, Mo and Ni, and sulfur in a single molecule. The second is a thiocubane type complex consisting of cobalt, molybdenum and sulfur. The third is a thiocubane type cluster consisting of iron and sulfur and the fourth, the pure inorganic salt ammonium tetrathiomolybdate (ATM). It was found that the structure and the ligands in the model complexes affect the activity of the resulting catalyst significantly. The optimum reaction at a pressure of 6.9 MPa hydrogen gas varied for different catalysts. The bimetallic catalysts generated in situ from the organometallic precursor are more active than monometallic catalysts like ATTM and the thiocubane type cluster Fe{sub 4}. Main products are hydrogenated phenanthrene derivatives, like DBP, THP, sym-OHP, cis- and trans-unsym-OHP with minor isomerization products such as sym-OHA. Our results indicate that other transition metal and ligand combinations in the organometallic precursors and the use of another model compound could result in substantially higher conversion activity.

  10. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, January--March, 1994

    SciTech Connect

    Schmidt, E.; Song, C.; Schobert, H.H.

    1994-06-01

    Coal liquefaction involves cleavage of methylene and dimethylene bridges connecting polycyclic aromatic units. The selected compound for model coal liquefaction reactions is 4-(1-naphthylmethyl)bibenzyl (NMBB). This report describes the synthesis and screening of several hetero- and homometallic complexes as precursors of dispersed catalysts for hydrocracking of NMBB. Experiments were carried out at 400 C for 30 min under 6.9 MPa H{sub 2} pressure. (NH{sub 4}){sub 2}MoS{sub 4} and MoCl{sub 3} converted NMBB predominantly into naphthalene and 4-methylbibenzyl. Small amounts of secondary products were formed by hydrogenation and fragmentation of the primary products. Lewis acid-type MoCl{sub 3} catalyst gave lower selectivity to the primary products, with relatively larger amounts of methyltetrahydronaphthalene- and methylnaphthalene-derivatives. In contrast, the bimetallic catalyst precursors Cp{sub 2}Co {sub 2}Mo{sub 2} (CO){sub 2}S{sub 4} and (Ph{sub 4}P){sub 2}(Ni(MoS{sub 4})) inflict less fragmentation and less hydrogenation of primary cleavage products. Cp{sub 2}Co{sub 2}Mo{sub 2}(CO){sub 2}S{sub 4} converted a substantial amount of starting material even at 350 C; whereas, a noncatalytic run under the same conditions showed only small conversion. Inorganic and bimetallic catalyst precursors gave similar conversions. Greater product selectivity can be achieved by means of organometallic precursors and low severity reaction condition. Mo(CO){sub 6} and Co{sub 2}(CO){sub 8}/Mo(CO){sub 6} gave similar conversion as the bimetallic catalyst precursors. The addition of sulfur to the combination Co{sub 2}(CO){sub 8}/Mo(CO){sub 6} gave significant higher conversion but reduced generally the yield of hydrogenation products.

  11. Catalysis on singly dispersed bimetallic sites

    NASA Astrophysics Data System (ADS)

    Zhang, Shiran; Nguyen, Luan; Liang, Jin-Xia; Shan, Junjun; Liu, Jingyue; Frenkel, Anatoly I.; Patlolla, Anitha; Huang, Weixin; Li, Jun; Tao, Franklin

    2015-08-01

    A catalytic site typically consists of one or more atoms of a catalyst surface that arrange into a configuration offering a specific electronic structure for adsorbing or dissociating reactant molecules. The catalytic activity of adjacent bimetallic sites of metallic nanoparticles has been studied previously. An isolated bimetallic site supported on a non-metallic surface could exhibit a distinctly different catalytic performance owing to the cationic state of the singly dispersed bimetallic site and the minimized choices of binding configurations of a reactant molecule compared with continuously packed bimetallic sites. Here we report that isolated Rh1Co3 bimetallic sites exhibit a distinctly different catalytic performance in reduction of nitric oxide with carbon monoxide at low temperature, resulting from strong adsorption of two nitric oxide molecules and a nitrous oxide intermediate on Rh1Co3 sites and following a low-barrier pathway dissociation to dinitrogen and an oxygen atom. This observation suggests a method to develop catalysts with high selectivity.

  12. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, July--September 1994

    SciTech Connect

    Schmidt, E.; Kirby, S.; Song, Chunshan; Schobert, H.H.

    1994-11-01

    Coal liquefaction involves cleavage of methylene and dimethylene bridges connecting polycyclic aromatic units and the reactions of various oxygen functional groups. The selected compound for model coal liquefaction reactions are 4-(l-naphthylmethyl)bibenzyl (NMBB) and anthrone. This report describes (1) the synthesis and screening of selected iron carbonyl complexes as precursors of dispersed catalysts for hydrocracking of NMBB, and (2) the hydrogenation and hydrodeoxygenation reactions of anthrone. Experiments were carried out at 400{degree}C (for NMBB) or at both 300{degree}C and 400{degree}C (for anthrone) for 30 min under 6.9 MPa H{sub 2} pressure. All catalyst precursors converted NMBB predominately into naphthalene and 4-methylbibenzyl. Small amounts of secondary products were formed by hydrogenation, isomerization and fragmentation of the primary products. The greatest activity among the tested catalysts was found using iron pentacarbonyl with added sulfur. Increasing cluster size lead to decreased activity. The beneficial effect of sulfur was also demonstrated in a reaction of iron pentacarbonyl and NMBB. A sulfur-free run showed substantially smaller conversion, whereas an experiment with added sulfur gave considerably higher conversion. Again, the same trend between cluster size and catalyst activity was observed. The objective of examining oxygen-containing compounds is to investigate the possibility of reduced oxygen functionality in the products of a reaction performed under liquefaction conditions, with the use of highly dispersed catalysts from monometallic and bimetallic organometallic precursors. Both the Ni-Mo and CoMo-T2 precursors showed an increase in the yield of non-0-containing products, compared to a non-catalytic reaction or one using a standard inorganic catalyst precursor, ammonium tetrathiomolybdate (ATTM).

  13. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, October 1994--December 1994

    SciTech Connect

    Schmidt, E.; Kirby, S.; Song, Chunshan

    1995-02-01

    Coal liquefaction involves cleavage of methylene and dimethylene and ether-type bridges connecting polycyclic aromatic units. The selected compounds for model coal liquefaction reactions are 4-(l-naphthylmethyl)bibenzyl (NMBB) and several oxygen-containing compounds. This report mainly describes the synthesis and screening of selected iron and molybdenum compounds as precursors of dispersed catalysts for hydrocracking of NMBB and oxygen-containing compounds. Experiments using NMBB were carried out at 400{degrees}C for 30 min. under 6.9 MPa H{sub 2} pressure. All catalyst precursors converted NMBB predominately into naphthalene and 4-methylbibenzyl. Generally, ferrocene demonstrated very low activity as catalyst. Even sulfur addition did not increase activity. Hydrated iron sulfate FeSO{sub 4} x 7 H{sub 2}O gave similar conversion like ferrocene. In order to clarify the effect of sulfur alone on model compound conversion, NMBB was treated with sulfur in concentrations of 1.2 to 3.4 wt %, corresponding to conditions present in catalytic runs with sulfur. It was found that increasing sulfur concentrations lead to higher NMBB conversion. Furthermore, sulfur had a permanent influence on the reactor walls. It reacted with the transition metals in the steel to form a microscopic black iron sulfide layer on the surface, which could not be removed mechanically. Non catalytic runs after experiments with added sulfur yielded higher conversion than a normal run with a new reactor. The objective of the work on oxygen-compounds is to investigate the utility of highly dispersed catalysts, from organometallic precursors, in the removal of heteroatom functionality from the products of a reaction performed under liquefaction conditions. The bimetallic catalytic precursor CoMo-T2 exhibited a sizable increase in the yield of non-O-containing products, compared to the run using a standard inorganic catalyst precursor (ATTM) or a non-catalytic reaction.

  14. Structural analysis of polymer-protected Pd/Pt bimetallic clusters as dispersed catalysts by using extended x-ray absorption fine structure spectroscopy

    SciTech Connect

    Toshima, Naoki; Harada, Masafumi; Yonezawa, Tetsu; Kushihashi, Kakuta; Asakura, Kiyotaka )

    1991-09-19

    Extended X-ray absorption fine structure (EXAFS) was applied to the determination of the structure of colloidal dispersions of the poly (N-vinyl-2-pyrrolidone)-protected palladium/platinum bimetallic clusters, which work as the catalysts for selective partial hydrogenation of 1,3-cyclooctadiene to cyclooctene. The catalytic activity was found to depend on the structure of the bimetallic clusters. The EXAFS data on the Pd/Pt (4/1) bimetallic clusters, which are the most active catalysts, indicate a Pt core structure, in which the 42 Pd atoms are on the surface of the cluster particle and 13 Pt atoms are at the center of the particle, forming a core. In contrast, the Pd/Pt (1/1) bimetallic clusters are suggested to have a modified Pt core structure, in which 28 Pt atoms connect directly with each other, being located both in the core and on the surface, and 27 Pd atoms form three islands on the surface of the cluster particle. These bimetallic clusters work as active catalysts for selective hydrogenation of olefins, selective partial hydrogenation of diene to monoene, and visible light-induced hydrogen generation from water.

  15. Bimetallic catalysts for hydrogen generation.

    PubMed

    Wei, Zhehao; Sun, Junming; Li, Yan; Datye, Abhaya K; Wang, Yong

    2012-12-21

    Research interest in bimetallic catalysts is mainly due to their tunable chemical/physical properties by a number of parameters like composition and morphostructure. In catalysis, numerous bimetallic catalysts have been shown to exhibit unique properties which are distinct from those of their monometallic counterparts. To meet the growing energy demand while mitigating the environmental concerns, numerous endeavors have been made to seek green and sustainable energy resources, among which hydrogen has been identified as the most promising one with bimetallic catalysts playing important roles. This tutorial review intends to summarize recent progress in bimetallic catalysts for hydrogen production, specifically focusing on that of reforming technologies as well as the relevant processes like water-gas shift (WGS) and CO preferential oxidation (PROX), and emphasizing on the fundamental understanding of the nature of catalytic sites responsible for generating high purity hydrogen and minimizing carbon monoxide formation. Meanwhile, some important synthesis and characterization methods of bimetallic catalysts developed so far are also summarized. PMID:23011345

  16. Catalysis on singly dispersed bimetallic sites.

    PubMed

    Zhang, Shiran; Nguyen, Luan; Liang, Jin-Xia; Shan, Junjun; Liu, Jingyue Jimmy; Frenkel, Anatoly I; Patlolla, Anitha; Huang, Weixin; Li, Jun; Tao, Franklin Feng

    2015-01-01

    A catalytic site typically consists of one or more atoms of a catalyst surface that arrange into a configuration offering a specific electronic structure for adsorbing or dissociating reactant molecules. The catalytic activity of adjacent bimetallic sites of metallic nanoparticles has been studied previously. An isolated bimetallic site supported on a non-metallic surface could exhibit a distinctly different catalytic performance owing to the cationic state of the singly dispersed bimetallic site and the minimized choices of binding configurations of a reactant molecule compared with continuously packed bimetallic sites. Here we report that isolated Rh1Co3 bimetallic sites exhibit a distinctly different catalytic performance in reduction of nitric oxide with carbon monoxide at low temperature, resulting from strong adsorption of two nitric oxide molecules and a nitrous oxide intermediate on Rh1Co3 sites and following a low-barrier pathway dissociation to dinitrogen and an oxygen atom. This observation suggests a method to develop catalysts with high selectivity. PMID:26294191

  17. Dispersion enhanced metal/zeolite catalysts

    DOEpatents

    Sachtler, Wolfgang M. H.; Tzou, Ming-Shin; Jiang, Hui-Jong

    1987-01-01

    Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

  18. Dispersion enhanced metal/zeolite catalysts

    DOEpatents

    Sachtler, W.M.H.; Tzou, M.S.; Jiang, H.J.

    1987-03-31

    Dispersion stabilized zeolite supported metal catalysts are provided as bimetallic catalyst combinations. The catalyst metal is in a reduced zero valent form while the dispersion stabilizer metal is in an unreduced ionic form. Representative catalysts are prepared from platinum or nickel as the catalyst metal and iron or chromium dispersion stabilizer.

  19. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, January--March, 1995

    SciTech Connect

    Song, C.; Kirby, S. Schmidt, E.; Schobert, H.H.

    1995-05-01

    Coal liquefaction involves cleavage of methylene, dimethylene and ether bridges connecting polycyclic aromatic units and the reactions of various oxygen functional groups. The selected compound for model coal liquefaction reactions are 4-(1-naphthylmethyl)bibenzyl (NMBB) and anthrone. This report describes hydrodeoxygenation of O-containing polycyclic model compounds using novel organometallic catalyst precursors and activity and selectivity of dispersed Fe catalysts from organometallic and inorganic precursors for hydrocracking of 4-(1-Naphthylmethyl) bibenzyl. For hydrodeoxygenation, model compound studies were performed using multi-ring systems, or those of comparable molecular weight, to investigate the capabilities of the dispersed catalysts. The model compounds selected include anthrone (carbonyl); dinaphthyl ether (aryl-aryl ether); xanthene (heterocyclic ether); and 2,6-di-t-butyl-4-methylphenol (hydroxyl). The catalyst precursors used were (NH{sub 4}){sub 2}MoS{sub 4}, [Ph{sub 4}P]{sub 2}[Ni(MoS{sub 4}){sub 2}] and Cp{sub 2}Co{sub 2}Mo{sub 2}(CO){sub 2}S{sub 4}. To examine what determines the activity and selectivity of Fe catalysts for hydrogenation and hydrocracking, various molecular precursors with Fe in different chemical environments have been tested in this work to help understand the influence of precursor structure and the effect of sulfur addition on the activity and selectivity of resulting Fe catalysts in model reactions of 4-(naphthylmethyl)bibenzyl. The authors have examined various precursors, including a thiocubane type cluster Cp{sub 4}Fe{sub 4}S{sub 4}, a cyclopentadienyliron dicarbonyl dimer Cp{sub 2}Fe{sub 2}(CO){sub 4}, ferrocene Cp{sub 2}Fe, a series of carbonyl precursors including Fe(CO){sub 5}, Fe{sub 2}(CO){sub 9}, and Fe{sub 3}(CO){sub 12}, and superfine iron oxide with average particle size of 30 {angstrom}.

  20. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, April 1994--June 1994

    SciTech Connect

    Schmidt, E.; Song, C.; Schobert, H.H.

    1994-07-01

    Coal liquefaction involves cleavage of methylene and dimethylene bridges connecting polycyclic aromatic units. The selected compound for model coal liquefaction reactions is 4-(1-naphthylmethyl)bibenzyl (NMBB). This report describes the synthesis and screening of several iron containing complexes as precursors of dispersed catalysts for hydrocracking of NMBB. Experiments were carried out at 400{degrees}C for 30 min under 6.9 MPa H{sub 2} pressure. All catalyst precursors converted NMBB predominately into naphthalene and 4-methylbibenzyl. Small amounts of secondary products were formed by hydrogenation, isomerization and fragmentation of the primary products. The greatest activity among the tested catalysts was found using superfine iron oxide with added sulfur. An experiment of the high surface Fe{sub 2}O{sub 3} without added sulfur gave only moderate conversion. Organometallics with relatively high volatility show higher activity than the inorganic system iron oxide. The thiocubane type cluster Cp{sub 4}Fe{sub 4}S{sub 4} showed the lowest activity. The beneficial effect of sulfur was also demonstrated in a reaction of iron pentacarbonyl and NMBB. A sulfur-free run showed substantially smaller conversion, whereas an experiment with added sulfur gave 15.6 % higher conversion. The catalytic activity of Cp{sub 2}Fe{sub 2}(CO){sub 4} is the highest among the sulfur-free catalyst precursors.

  1. Fundamental investigations of supported monometallic and bimetallic catalysts by proton magnetic resonance spectroscopy

    SciTech Connect

    Wu, Xi.

    1990-09-21

    Proton magnetic resonance spectroscopy, or nuclear magnetic resonance (NMR) of hydrogen, has been applied to investigate silica-supported Group VIII monometallic and Group VIII-Group IB bimetallic catalysts and alumina- and silica-supported platinum-rhenium bimetallic catalysts. Two adsorbed states of hydrogen, i.e., irreversible and reversible hydrogen, on the surfaces of monometallic Ru, Pt, and Cu particles and bimetallic Ru-Group Ib, Pt-Group Ib, and Pt-Re particles were observed directly via proton NMR. The same amounts of the irreversible hydrogen adsorbed on pure Ru catalysts were measured by both proton NMR and the volumetric technique. The electronic environments on surfaces of monometallic catalysts are sensitive to changes in metal dispersion, state of adsorbed hydrogen, and residual chlorine. Surface compositions for the Ru--Cu and Pt--Cu bimetallic catalysts were determined by NMR of adsorbed hydrogen. 297 refs., 96 figs., 19 tabs.

  2. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Quarterly technical progress report, July--September 1995

    SciTech Connect

    Song, Chunshan; Schmidt, E.; Schobert, H.H.

    1996-01-01

    Coal liquefaction involves cleavage of methylene, dimethylene and ether bridges connecting polycyclic aromatic units and the reactions of various oxygen functional groups. Here in this quarterly, we report on the hydrocracking of 4-(l-naphthylmethyl)bibenzyl in the presence of iron (Fe) catalysts and sulfur and residual wall catalytic effect. Catalytic hydrocracking of 4-(1-naphthylmethyl)bibenzyl (NMBB) predominantly yielded naphthalene and 4-methylbibenzyl. Various iron compounds were examined as catalyst precursors. Sulfur addition to most catalyst precursors led to substantially higher catalyst activity and higher conversion. NMBB was also treated with sulfur in the absence of iron compounds, in concentrations of 1.2-3.4 wt%, corresponding to the conditions present in reactions with added iron compounds. Increasing sulfur concentrations led to higher NMBB conversions. Furthermore, sulfur had a permanent effect on the reactor walls. A black sulfide layer formed on the surface which could not be removed mechanically. The supposed non-catalytic reactions done in the same reactor but after experiments with added sulfur showed higher conversions than comparable experiments done in new reactors. This wall catalytic effect can be reduced by treating the sulfided reactors with hydrochloric acid. The results of this work demonstrate the significant effect of sulfur addition and sulfur-induced residual wall effects on carbon-carbon bond cleavage and hydrogenation of aromatics.

  3. Novel bimetallic dispersed catalysts for temperature-programmed coal liquefaction. Technical progress report, October 1995--December 1995

    SciTech Connect

    Song, C.; Cooke, W.S.; Schmidt, E.; Schobert, H.H.

    1996-02-01

    Coal liquefaction involves cleavage of methylene, dimethylene and ether bridges connecting polycyclic aromatic units and the reactions of various oxygen functional groups. Here in this quarterly, we report on the catalytic effects of several molybdenum-, cobalt-, and iron-containing compounds in the reactions of dibenzothiophene (DBT) with hydrogen under conditions related to coal liquefaction. The catalytic effects of several molybdenum-, cobalt-, and iron-containing compounds have been examined in the hydrogenation and hydrodesulfurization reactions of dibenzothiophene (DBT) under conditions related to coal liquefaction. The metal compounds are candidate catalyst precursors for direct coal liquefaction. The reactions were carried out in batch microautoclave reactors at 400{degrees}C for 30 minutes with 6.9 MPa (cold) hydrogen pressure, and tridecane solvent. A metal loading of 0.5 mol% resulted in low conversion and only hydrogenation. Addition of sulfur in 4:1 molar ratio led only to a minor increase in conversion and hydrodesulfurization. The use of a higher boiling solvent (octadecane vs. tridecane) was beneficial in providing increased conversion, hydrodesulfurization, and hydrogenation. An increase in metal compound loading to 36.2 mol% led to a dramatic increase in conversion, hydrodesulfurization, and hydrocracking. Molybdenum hexacarbonyl at 36 mol% loading, with added sulfur at 6:1 ratio and octadecane solvent, gave 100% conversion of dibenzothiophene to other products with 100% hydrodesulfurization. Ammonium tetrathiomolybdate and molybdenum(III) chloride are less active under similar conditions. A cobalt-molybdenum thiocubane complex gave unexpectedly low conversions. Iron and cobalt carbonyls also provided very low conversions, even with added sulfur.

  4. Neutral bimetallic transition metal phenoxyiminato catalysts and related polymerization methods

    DOEpatents

    Marks, Tobin J.; Rodriguez, Brandon A.; Delferro, Massimiliano

    2012-08-07

    A catalyst composition comprising a neutral bimetallic diphenoxydiiminate complex of group 10 metals or Ni, Pd or Pt is disclosed. The compositions can be used for the preparation of homo- and co-polymers of olefinic monomer compounds.

  5. Direct decomposition of methane over SBA-15 supported Ni, Co and Fe based bimetallic catalysts

    NASA Astrophysics Data System (ADS)

    Pudukudy, Manoj; Yaakob, Zahira; Akmal, Zubair Shamsul

    2015-03-01

    Thermocatalytic decomposition of methane is an alternative route for the production of COx-free hydrogen and carbon nanomaterials. In this work, a set of novel Ni, Co and Fe based bimetallic catalysts supported over mesoporous SBA-15 was synthesized by a facile wet impregnation route, characterized for their structural, textural and reduction properties and were successfully used for the methane decomposition. The fine dispersion of metal oxide particles on the surface of SBA-15, without affecting its mesoporous texture was clearly shown in the low angle X-ray diffraction patterns and the transmission electron microscopy (TEM) images. The nitrogen sorption analysis showed the reduced specific surface area and pore volume of SBA-15, after metal loading due to the partial filling of hexagonal mesopores by metal species. The results of methane decomposition experiments indicated that all of the bimetallic catalysts were highly active and stable for the reaction at 700 °C even after 300 min of time on stream (TOS). However, a maximum hydrogen yield of ∼56% was observed for the NiCo/SBA-15 catalyst within 30 min of TOS. A high catalytic stability was shown by the CoFe/SBA-15 catalyst with 51% of hydrogen yield during the course of reaction. The catalytic stability of the bimetallic catalysts was attributed to the formation of bimetallic alloys. Moreover, the deposited carbons were found to be in the form of a new set of hollow multi-walled nanotubes with open tips, indicating a base growth mechanism, which confirm the selectivity of SBA-15 supported bimetallic catalysts for the formation of open tip carbon nanotubes. The Raman spectroscopic and thermogravimetric analysis of the deposited carbon nanotubes over the bimetallic catalysts indicated their higher graphitization degree and oxidation stability.

  6. The catalytic behavior of precisely synthesized Pt–Pd bimetallic catalysts for use as diesel oxidation catalysts

    DOE PAGESBeta

    Wong, Andrew P.; Kyriakidou, Eleni A.; Toops, Todd J.; Regalbuto, John R.

    2016-04-17

    The demands of stricter diesel engine emission regulations have created challenges for current exhaust systems. With advances in low-temperature internal combustion engines and their operations, advances must also be made in vehicle exhaust catalysts. Most current diesel oxidation catalysts use heavy amounts of precious group metals (PGMs) for hydrocarbon (HC), CO, and NO oxidation. These catalysts are expensive and are most often synthesized with poor bimetallic interaction and dispersion. In this paper, the goal was to study the effect of aging on diesel emission abatement of Pt–Pd bimetallic nanoparticles precisely prepared with different morphologies: well dispersed core–shell vs. well dispersedmore » homogeneously alloyed vs. poorly dispersed, poorly alloyed particles. Alumina and silica supports were studied. Particle morphology and dispersion were analyzed before and after hydrothermal treatments by XRD, EDX, and STEM. Reactivity as a function of aging was measured in simulated diesel engine exhaust. While carefully controlled bimetallic catalyst nanoparticle structure has a profound influence on initial or low temperature catalytic activity, the differences in behavior disappear with higher temperature aging as thermodynamic equilibrium is achieved. The metallic character of Pt-rich alumina-supported catalysts is such that behavior rather closely follows the Pt–Pd metal phase diagram. Nanoparticles disparately composed as well-dispersed core–shell (via seq-SEA), well-dispersed homogeneously alloyed (via co-SEA), and poorly dispersed, poorly alloyed (via co-DI) end up as well alloyed, large particles of almost the same size and activity. With Pd-rich systems, the oxidation of Pd also figures into the equilibrium, such that Pd-rich oxide phases appear in the high temperature forms along with alloyed metal cores. Finally, the small differences in activity after high temperature aging can be attributed to the synthesis methods, sequential SEA and co

  7. The synergistic effect in the Fe-Co bimetallic catalyst system for the growth of carbon nanotube forests

    SciTech Connect

    Hardeman, D.; Esconjauregui, S. Cartwright, R.; D'Arsié, L.; Robertson, J.; Bhardwaj, S.; Cepek, C.; Oakes, D.; Clark, J.; Ducati, C.

    2015-01-28

    We report the growth of multi-walled carbon nanotube forests employing an active-active bimetallic Fe-Co catalyst. Using this catalyst system, we observe a synergistic effect by which—in comparison to pure Fe or Co—the height of the forests increases significantly. The homogeneity in the as-grown nanotubes is also improved. By both energy dispersive spectroscopy and in-situ x-ray photoelectron spectroscopy, we show that the catalyst particles consist of Fe and Co, and this dramatically increases the growth rate of the tubes. Bimetallic catalysts are thus potentially useful for synthesising nanotube forests more efficiently.

  8. Controlled Surface Segregation Leads to Efficient Coke-Resistant Nickel/Platinum Bimetallic Catalysts for the Dry Reforming of Methane

    SciTech Connect

    Li, Lidong; Zhou, Lu; Ould-Chikh, Samy; Anjum, Dalaver H.; Kanoun, Mohammed B.; Scaranto, Jessica; Hedhili, Mohamed N.; Khalid, Syed; Laveille, Paco V.; Lawrence D'Souza; Clo, Alain; Basset, Jean-Marie

    2015-02-03

    The surface composition and structure are of vital importance for heterogeneous catalysts, especially for bimetallic catalysts, which often vary as a function of reaction conditions (known as surface segregation). The preparation of bimetallic catalysts with controlled metal surface composition and structure is very challenging. In this study, we synthesize a series of Ni/Pt bimetallic catalysts with controlled metal surface composition and structure using a method derived from surface organometallic chemistry. Moreover, the evolution of the surface composition and structure of the obtained bimetallic catalysts under simulated reaction conditions is investigated by various techniques, which include CO-probe IR spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, extended X-ray absorption fine structure analysis, X-ray absorption near-edge structure analysis, XRD, and X-ray photoelectron spectroscopy. It is demonstrated that the structure of the bimetallic catalyst is evolved from Pt monolayer island-modified Ni nanoparticles to core–shell bimetallic nanoparticles composed of a Ni-rich core and a Ni/Pt alloy shell upon thermal treatment. The catalysts are active for the dry reforming of methane, and their catalytic activities, stabilities, and carbon formation vary with their surface composition and structure.

  9. On factors controlling activity of submonolayer bimetallic catalysts: Nitrogen desorption

    SciTech Connect

    Guo, Wei; Vlachos, Dionisios G.

    2014-01-07

    We model N{sub 2} desorption on submonolayer bimetallic surfaces consisting of Co clusters on Pt(111) via first-principles density functional theory-based kinetic Monte Carlo simulations. We find that submonolayer structures are essential to rationalize the high activity of these bimetallics in ammonia decomposition. We show that the N{sub 2} desorption temperature on Co/Pt(111) is about 100 K higher than that on Ni/Pt(111), despite Co/Pt(111) binding N weaker at low N coverages. Co/Pt(111) has substantially different lateral interactions than single metals and Ni/Pt. The lateral interactions are rationalized with the d-band center theory. The activity of bimetallic catalysts is the result of heterogeneity of binding energies and reaction barriers among sites, and the most active site can differ on various bimetallics. Our results are in excellent agreement with experimental data and demonstrate for the first time that the zero-coverage descriptor, used until now, for catalyst activity is inadequate due not only to lacking lateral interactions but importantly to presence of multiple sites and a complex interplay of thermodynamics (binding energies, occupation) and kinetics (association barriers) on those sites.

  10. Microstructural characterization of bimetallic Ni-Pt catalysts supported on SiO 2

    NASA Astrophysics Data System (ADS)

    Arenas-Alatorre, J.; Avalos-Borja, M.; Díaz, G.

    2002-04-01

    A set of Pt, Ni and a bimetallic Ni50Pt50 catalysts supported on SiO2 of low and high surface area (S=50 and 200 m2/g) with a total metal loading of 2 wt.% was characterized by high-resolution electron microscopy (HREM), conventional transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS) and computational techniques such as digital processing and image simulation. Special attention was placed to the identification of intermetallic phases in the Ni50Pt50/SiO2 sample. Catalysts were prepared by impregnation and submitted to calcination-reduction activation treatments. For all the set, the increase in support's surface area led to an improvement of the metal dispersion. TEM and HREM images showed significant differences in the shape and crystalline lattice of the Pt and Ni particles in the monometallic samples taken as reference. While in Pt/SiO2 catalyst we identified only reduced Pt particles, in Ni/SiO2 some NiO particles were detected. HREM characterization of the Ni50Pt50 catalysts showed that many particles have defects such as twinning and dislocations. Cubo-octahedral shapes were predominant in the bimetallic catalyst. Crystal lattice and angles measurements were consistent with the identification of NiPt and/or Ni3Pt intermetallic phases. Superlattice structures were also identified and confirmed by image simulation. EDS analysis on a particle by particle basis confirmed that in bimetallic catalysts supported in SiO2 of low and high surface area, particles were present consisting of Ni-rich, nominal and Pt-rich metal compositions. Pt-only particles were found but no Ni-only particles were detected. Among the possibilities, NiPt and Ni3Pt compositions were identified.

  11. Bimetallic catalysts for upgrading of biomass to fuels and chemicals.

    PubMed

    Alonso, David Martin; Wettstein, Stephanie G; Dumesic, James A

    2012-12-21

    Research interest in biomass conversion to fuels and chemicals has increased significantly in the last decade as the necessity for a renewable source of carbon has become more evident. Accordingly, many different reactions and processes to convert biomass into high-value products and fuels have been proposed in the literature. Special attention has been given to the conversion of lignocellulosic biomass, which does not compete with food sources and is widely available as a low cost feedstock. In this review, we start with a brief introduction on lignocellulose and the different chemical structures of its components: cellulose, hemicellulose, and lignin. These three components allow for the production of different chemicals after fractionation. After a brief overview of the main reactions involved in biomass conversion, we focus on those where bimetallic catalysts are playing an important role. Although the reactions are similar for cellulose and hemicellulose, which contain C(6) and C(5) sugars, respectively, different products are obtained, and therefore, they have been reviewed separately. The third major fraction of lignocellulose that we address is lignin, which has significant challenges to overcome, as its structure makes catalytic processing more challenging. Bimetallic catalysts offer the possibility of enabling lignocellulosic processing to become a larger part of the biofuels and renewable chemical industry. This review summarizes recent results published in the literature for biomass upgrading reactions using bimetallic catalysts. PMID:22872312

  12. Bimetallic complexes and polymerization catalysts therefrom

    DOEpatents

    Patton, Jasson T.; Marks, Tobin J.; Li, Liting

    2000-11-28

    Group 3-6 or Lanthanide metal complexes possessing two metal centers, catalysts derived therefrom by combining the same with strong Lewis acids, Bronsted acid salts, salts containing a cationic oxidizing agent or subjected to bulk electrolysis in the presence of compatible, inert non-coordinating anions and the use of such catalysts for polymerizing olefins, diolefins and/or acetylenically unsaturated monomers are disclosed.

  13. Selective Hydrogenation of Phenylacetylene on Bimetallic Cu-Pd and Cu-Pt Catalysts

    NASA Astrophysics Data System (ADS)

    Cladaras, George

    /Pd species are alloyed and well-dispersed on the surface of the nanoparticles. The bimetallic catalysts were tested for the liquid phase hydrogenation of phenylacetylene and were compared to their monometallic analogs for reactivity and selectivity. Both the Pt-Cu and Pd-Cu bimetallic catalysts display a significant improvement of the selectivity to styrene, especially at high conversions. Based on the rate data, activation energy measurements and the model study done in UHV, it is concluded that the reaction mechanism has been altered in the bimetallic samples. Pt and Pd serve as sites for molecular hydrogen dissociation to hydrogen atoms, which in turn spillover onto the Cu surface where the hydrogenation reaction occurs. In summary, this work has demonstrated how Pd-Cu and Pt-Cu bimetallic catalysts can serve as both active and highly selective hydrogenation catalysts, where the Pd and Pt entities promote the hydrogenation activity of a Cu surface which maintains high selectivity for phenylacetylene hydrogenation to styrene.

  14. Fundamental studies of supported bimetallic catalysts by NMR spectroscopy

    SciTech Connect

    Savargaonkar, N.

    1996-10-17

    Various hydrogenation reactions on transition metals are important commercially whereas certain hydrogenolysis reactions are useful from fundamental point of view. Understanding the hydrogen mobility and kinetics of adsorption-desorption of hydrogen is important in understanding the mechanisms of such reactions involving hydrogen. The kinetics of hydrogen chemisorption was studied by means of selective excitation NMR on silica supported Pt, Rh and Pt-Rh catalysts. The activation energy of hydrogen desorption was found to be lower on silica supported Pt catalysts as compared to Rh and Pt-Rh catalysts. It was found that the rates of hydrogen adsorption and desorption on Pt-Rh catalyst were similar to those on Rh catalyst and much higher as compared to Pt catalyst. The Ru-Ag bimetallic system is much simpler to study than the Pt-Rh system and serves as a model system to characterize more complicated systems such as the K/Ru system. Ag was found to decrease the amounts of adsorbed hydrogen and the hydrogen-to-ruthenium stoichiometry. Ag reduced the populations of states with low and intermediate binding energies of hydrogen on silica supported Ru catalyst. The rates of hydrogen adsorption and desorption were also lower on silica supported Ru-Ag catalyst as compared to Ru catalyst. This report contains introductory information, the literature review, general conclusions, and four appendices. An additional four chapters and one appendix have been processed separately for inclusion on the data base.

  15. The selective hydrogenation of crotonaldehyde over bimetallic catalysts

    SciTech Connect

    Schoeb, A.M.

    1997-02-01

    The selective hydrogenation of crotonaldehyde has been investigated over a monometallic Pt/SiO{sub 2} catalyst and platinum bimetallic catalysts where the second metal was either silver, copper, or tin. The effects of addition of a second metal to the Pt/SiO{sub 2} system on the selectivity to crotyl alcohol were investigated. The Pt-Sn bimetallic catalysts were characterized by hydrogen chemisorption, {sup 1}H NMR and microcalorimetry. The Pt-Ag/SiO{sub 2} and Pt-Cu/SiO{sub 2} catalysts were characterized by hydrogen chemisorption. Pt-Sn/SiO{sub 2} catalysts selectively hydrogenated crotonaldehyde to crotyl alcohol and the method of preparation of these catalysts affected the selectivity. The most selective Pt-Sn/SiO{sub 2} catalysts for the hydrogenation of crotonaldehyde to crotyl alcohol were those in which the Sn precursor was dissolved in a HCl solution. Sn increased both the rate of formation of butyraldehyde and the rate of formation of crotyl alcohol. The Pt/SiO{sub 2}, Pt-Ag/SiO{sub 2} and Pt-Cu/SiO{sub 2} catalysts produced only butyraldehyde. Initial heats of adsorption ({approximately}90 kJ/mol) measured using microcalorimetry were not affected by the presence of Sn on Pt. We can conclude that there is no through metal electronic interaction between Pt and Sn at least with respect to hydrogen surface bonds since the Pt and Pt-Sn at least with respect to hydrogen surface bonds since the Pt and Pt-Sn had similar initial heats of adsorption coupled with the invariance of the {sup 1}H NMR Knight shift.

  16. Bimetallic dendrimer-encapsulated nanoparticles as catalysts: a review of the research advances.

    PubMed

    Peng, Xiaohong; Pan, Qinmin; Rempel, Garry L

    2008-08-01

    Bimetallic dendrimer-encapsulated nanoparticles (DENs) are important materials, because they have demonstrated improvement in performance compared to the monometallic DENs in many systems when they are used as catalysts. This tutorial review focuses on the recent research advances in bimetallic DENs with respect to their synthesis, characterization, and applications as catalysts. Bimetallic DENs can be made mainly via three routes: co-complexation, sequential loading, and partial displacement. The research in bimetallic DENs has been significantly promoted by the advancement of characterization instruments. The performances of bimetallic DENs as homogeneous and heterogeneous catalysts in organic synthesis have been compared with both monometallic DENs and their physical mixtures. It is concluded that the synergistic electronic effect in bimetallic nanoparticles enhances their catalytic activities. PMID:18648686

  17. Bimetallic ruthenium-copper nanoparticles embedded in mesoporous carbon as an effective hydrogenation catalyst.

    PubMed

    Liu, Jiajia; Zhang, Li Li; Zhang, Jiatao; Liu, Tao; Zhao, X S

    2013-11-21

    Bimetallic ruthenium-copper nanoparticles embedded in the pore walls of mesoporous carbon were prepared via a template route and evaluated in terms of catalytic properties in D-glucose hydrogenation. The existence of bimetallic entities was supported by Ru L3-edge and Cu K-edge X-ray absorption results. The hydrogen spillover effect of the bimetallic catalyst on the hydrogenation reaction was evidenced by the results of both hydrogen and carbon monoxide chemisorptions. The bimetallic catalyst displayed a higher catalytic activity than the single-metal catalysts prepared using the same approach, namely ruthenium or copper nanoparticles embedded in the pore walls of mesoporous carbon. This improvement was due to the changes in the geometric and electronic structures of the bimetallic catalyst because of the presence of the second metal. PMID:24072134

  18. Bimetallic ruthenium-copper nanoparticles embedded in mesoporous carbon as an effective hydrogenation catalyst

    NASA Astrophysics Data System (ADS)

    Liu, Jiajia; Zhang, Li Li; Zhang, Jiatao; Liu, Tao; Zhao, X. S.

    2013-10-01

    Bimetallic ruthenium-copper nanoparticles embedded in the pore walls of mesoporous carbon were prepared via a template route and evaluated in terms of catalytic properties in d-glucose hydrogenation. The existence of bimetallic entities was supported by Ru L3-edge and Cu K-edge X-ray absorption results. The hydrogen spillover effect of the bimetallic catalyst on the hydrogenation reaction was evidenced by the results of both hydrogen and carbon monoxide chemisorptions. The bimetallic catalyst displayed a higher catalytic activity than the single-metal catalysts prepared using the same approach, namely ruthenium or copper nanoparticles embedded in the pore walls of mesoporous carbon. This improvement was due to the changes in the geometric and electronic structures of the bimetallic catalyst because of the presence of the second metal.Bimetallic ruthenium-copper nanoparticles embedded in the pore walls of mesoporous carbon were prepared via a template route and evaluated in terms of catalytic properties in d-glucose hydrogenation. The existence of bimetallic entities was supported by Ru L3-edge and Cu K-edge X-ray absorption results. The hydrogen spillover effect of the bimetallic catalyst on the hydrogenation reaction was evidenced by the results of both hydrogen and carbon monoxide chemisorptions. The bimetallic catalyst displayed a higher catalytic activity than the single-metal catalysts prepared using the same approach, namely ruthenium or copper nanoparticles embedded in the pore walls of mesoporous carbon. This improvement was due to the changes in the geometric and electronic structures of the bimetallic catalyst because of the presence of the second metal. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr03813k

  19. High-performance PdRu bimetallic catalyst supported on mesoporous silica nanoparticles for phenol hydrogenation

    NASA Astrophysics Data System (ADS)

    Huang, Chao; Yang, Xu; Yang, Hui; Huang, Peiyan; Song, Huiyu; Liao, Shijun

    2014-10-01

    A high-performance PdRu bimetallic catalyst supported on mesoporous silica nanoparticles (MSN), PdRu/MSN, was prepared by a facile impregnation-hydrogen reduction method. It was found that PdRu/MSN showed 5 times higher activity than that of Pd/MSN towards the liquid-phase hydrogenation of phenol. The catalysts were characterized comprehensively by multiple techniques, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and hydrogen temperature program reduction (TPR). It was revealed that adding Ru could effectively improve the Pd dispersion and promote the electronic interaction between the Pd and Ru, both of which contribute to enhancing the catalytic activity.

  20. Patched bimetallic surfaces are active catalysts for ammonia decomposition

    PubMed Central

    Guo, Wei; Vlachos, Dionisios G.

    2015-01-01

    Ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material's structure. Core–shell or surface-segregated bimetallic nanoparticles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core–shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N−H bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design. PMID:26443525

  1. Patched bimetallic surfaces are active catalysts for ammonia decomposition

    SciTech Connect

    Guo, Wei; Vlachos, Dionisios G.

    2015-10-07

    In this study, ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material’s structure. Core–shell or surface-segregated bimetallic nanoparticles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core–shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N-H bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design.

  2. An in-depth understanding of the bimetallic effects and coked carbon species on an active bimetallic Ni(Co)/Al2O3 dry reforming catalyst.

    PubMed

    Liao, Xin; Gerdts, Rihards; Parker, Stewart F; Chi, Lina; Zhao, Yongxiang; Hill, Martyn; Guo, Junqiu; Jones, Martin O; Jiang, Zheng

    2016-06-29

    Ni/Al2O3, Co/Al2O3 and bimetallic Ni(Co)/Al2O3 catalysts were prepared using an impregnation method and employed in CO2 dry reforming of methane under coking-favored conditions. The spent catalysts were carefully characterized using typical characterization technologies and inelastic neutron scattering spectroscopy. The bimetallic catalyst exhibited a superior activity and anti-coking performance compared to Ni/Al2O3, while the most resistant to coking behavior was Co/Al2O3. The enhanced activity of the Ni(Co)/Al2O3 bimetallic catalyst is attributed to the reduced particle size of metallic species and resistance to forming stable filamentous carbon. The overall carbon deposition on the spent bimetallic catalyst is comparable to that of the spent Ni/Al2O3 catalyst, whereas the carbon deposited on the bimetallic catalyst is mainly less-stable carbonaceous species as confirmed by SEM, TPO, Raman and INS characterization. This study provides an in depth understanding of alloy effects in catalysts, the chemical nature of coked carbon on spent Ni-based catalysts and, hopefully, inspires the creative design of a new bimetallic catalyst for dry reforming reactions. PMID:27326792

  3. Effect of Bimetallic Ni-Cr Catalysts for Steam-CO2 Reforming of Methane at High Pressure.

    PubMed

    Choi, Bong Kwan; Park, Yoon Hwa; Moon, Dong Ju; Park, Nam Cook; Kim, Young Chul

    2015-07-01

    The present work was to carry out the development of high performance Ni-based catalyst for Steam-CO2 reforming of methane (SCR) which is suitable for Fischer-Tropsch synthesis of GTL- FPSO (floating, production, storage and offloading) process. The bimetallic Ni-Cr catalysts were prepared by co-impregnation method. The Ni and Cr loading amount were fixed at 12 wt% and 3~7 wt%, respectively. The catalytic reaction was conducted at 900 °C and 20 bar with reactant feed ratio of CH4:CO2:H2O:Ar = 1:0.8:1.3:1 and GHSV = 25,000 h(-1). The Cr-modified Ni/γ-Al2O3 catalyst was characterized by BET surface area analysis, X-ray diffraction (XRD), H2-temperature programmed reduction (TPR), H2-chmisorption, CO2-temperature programmed desorption (TPD) and Transmission electron microscopy(TEM). To confirm the amount and type of the carbon deposition, the used catalysts were examined by Thermogravitic analysis (TGA) and Field emission-scanning microscopy/Energy dispersive X-ray analysis (FE-SEM/EDX). It was found that the bimetallic Ni-Cr catalyst exhibits highly dispersed Ni particles with strong metal-to-support interaction (SMSI) as well as excellent catalytic activity, resulting in the suppression of Ni sintering and carbon deposition. PMID:26373119

  4. Efficient sulfur-tolerant bimetallic catalysts for hydrogen generation from diesel fuel

    NASA Astrophysics Data System (ADS)

    Cheekatamarla, Praveen K.; Lane, Alan M.

    Catalytic autothermal reforming (ATR) of synthetic diesel and JP8 over supported metal catalysts has been investigated in the present study. Bimetallic catalysts exhibited superior performance compared to the commercial catalyst and the monometallic counterparts. BET, temperature-programmed desorption (TPD), temperature-programmed reduction (TPR) and XPS were utilized for characterizing these formulations, which showed that the enhanced stability is due to a strong metal-metal and metal-support interaction in the catalyst.

  5. NOVEL SUPPORTED BIMETALLIC CARBIDE CATALYSTS FOR COPROCESSING OF COAL WITH WASTE METERIALS

    SciTech Connect

    S. Ted Oyama; David F. Cox; Chunshan Song; Fred Allen; Weilin Wang; Viviane Schwartz; Xinqin Wang; Jianli Yang

    2001-01-01

    The overall objectives of this project are to explore the potential of novel monometallic and bimetallic Mo-based carbide catalysts for heavy hydrocarbon coprocessing, and to understand the fundamental chemistry related to the reaction pathways of coprocessing and the role of the catalysts in the conversion of heavy hydrocarbon resources into liquid fuels based on the model compound reactions.

  6. Patched bimetallic surfaces are active catalysts for ammonia decomposition

    DOE PAGESBeta

    Guo, Wei; Vlachos, Dionisios G.

    2015-10-07

    In this study, ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material’s structure. Core–shell or surface-segregated bimetallic nanoparticles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core–shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N-Hmore » bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design.« less

  7. Support Effect on the Low-Temperature Hydrogenation of Benzene over PtCo Bimetallic and the Corresponding Monometallic Catalysts

    SciTech Connect

    Lu, S.; Lonergan, W; Zhu, Y; Xie, Y; Chen, J

    2009-01-01

    PtCo bimetallic and Co, Pt monometallic catalysts supported on ?-Al2O3, SiO2, TiO2 and activated carbon (AC) were prepared and evaluated for the hydrogenation of benzene at relatively low temperatures (343 K) and atmospheric pressure. Results from flow reactor studies showed that supports strongly affected the catalytic properties of different bimetallic catalysts. AC supported PtCo bimetallic catalysts exhibited significantly better performance than the other bimetallic catalysts, and all the bimetallic catalysts possessed higher activity than the corresponding monometallic catalysts. Results from CO chemisorption and H2-temperature-programmed reduction (H2-TPR) studies suggested that different catalysts possessed different properties in chemisorption capacity and reduction behavior, and AC supported PtCo catalysts possessed significantly higher CO chemisorption capacity compared to the other catalysts. Extended X-ray absorption fine structure (EXAFS) and transmission electron microscopy (TEM) analysis provided additional information regarding the formation of Pt-Co bimetallic bonds and metallic particle size distribution in the PtCo bimetallic catalysts on different supports.

  8. Synergistic Effects in Bimetallic Palladium-Copper Catalysts Improve Selectivity in Oxygenate Coupling Reactions.

    PubMed

    Goulas, Konstantinos A; Sreekumar, Sanil; Song, Yuying; Kharidehal, Purnima; Gunbas, Gorkem; Dietrich, Paul J; Johnson, Gregory R; Wang, Y C; Grippo, Adam M; Grabow, Lars C; Gokhale, Amit A; Toste, F Dean

    2016-06-01

    Condensation reactions such as Guerbet and aldol are important since they allow for C-C bond formation and give higher molecular weight oxygenates. An initial study identified Pd-supported on hydrotalcite as an active catalyst for the transformation, although this catalyst showed extensive undesirable decarbonylation. A catalyst containing Pd and Cu in a 3:1 ratio dramatically decreased decarbonylation, while preserving the high catalytic rates seen with Pd-based catalysts. A combination of XRD, EXAFS, TEM, and CO chemisorption and TPD revealed the formation of CuPd bimetallic nanoparticles with a Cu-enriched surface. Finally, density functional theory studies suggest that the surface segregation of Cu atoms in the bimetallic alloy catalyst produces Cu sites with increased reactivity, while the Pd sites responsible for unselective decarbonylation pathways are selectively poisoned by CO. PMID:27195582

  9. From First Principles Design to Realization of Bimetallic Catalysts for Ultrahigh Selectivity - Final Project Report

    SciTech Connect

    Richard M. Crooks

    2007-04-11

    (A) Synthesis, Characterization, and Fundamental Properties of Bimetallic DENs. AuAg alloy and core/shell bimetallic DENs were synthesized and characterized. Selective extraction was used as a structural characterization tool for these bimetallic nanoparticles. This is significant because there are few easily accessible methods for structure elucidation of bimetallic nanoparticles in this size regime. As a first step towards the synthesis of catalytically active, bimetallic heterogeneous materials we reported the incorporation of Au and Pd monometallic DENs and AuPd bimetallic DENs into amorphous titania networks. The compositional fidelity of the original DENs, and to some extent their size, is retained following dendrimer removal. Gas-phase catalytic activity for CO oxidation is higher for the bimetallic catalysts than for the corresponding Pd-only and Au-only monometallics. (B) Electrocatalysts based on dendrimer-encapsulated nanoparticles. Platinum dendrimer-encapsulated nanoparticles (DENs) were prepared within fourth-generation, hydroxyl-terminated, poly(amidoamine) dendrimers and immobilized on glassy carbon electrodes using an electrochemical immobilization strategy. X-ray photoelectron spectroscopy, electron microscopy, and electrochemical experiments confirm that the Pt DENs are about 1.4 nm in diameter and that they remain within the dendrimer following surface immobilization. The resulting Pt DEN films were electrocatalytically active for the oxygen reduction reaction (ORR). The films are also robust, surviving up to 50 consecutive cyclic voltammograms and sonication. Monometallic Pd DENs were also prepared and found to have little catalytic activity for the ORR. However, PtPd bimetallic DENs had catalytic activity nearly identical to that found for Pt-only DENs. This indicates an overall catalytic enhancement for the bimetallic electrocatalysts.

  10. Catalytic oxidation of 2-Propanol over (Cr,Mn,Fe)-Pt/gamma-Al2O3 bimetallic catalysts and modeling of experimental results by artificial neural networks.

    PubMed

    Niaei, A; Salari, D; Aghazadeh, F; Caylak, N; Sepehrianazar, A

    2010-01-01

    The catalytic activity of transition metals (Cr,Mn,Fe) supported on the Pt/gamma -Al(2)O(3) industrial catalyst was investigated to bring about the complete oxidation of 2-Propanol. Catalytic studies were carried out under atmospheric pressure in a fixed bed reactor. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and ICP-AES techniques were used to characterize a series of catalysts. Results showed that the Pt-Mn/gamma -Al(2)O(3) (3.88 wt.%Mn) at calcination temperature of 300 degrees C was the most promising catalyst based on activity, which might be contributed to the quantity of manganese loading, the favorable synergetic effects between Pt and Mn and the well-dispersed bimetallic phase. An artificial neural networks (ANN) model was developed to predict the performance of catalytic oxidation process over Pt-Mn/gamma -Al(2)O(3) bimetallic catalyst based on experimental data. For this purpose the Levenberg-Marquardt (LM) learning algorithm was employed to train the model by using laboratory experimental data. A comparison between the predicted results of the designed ANN model and experimental data was also conducted. The developed model can describe the catalytic oxidation over bimetallic catalysts under different conditions. PMID:20390890

  11. XPS/STM study of model bimetallic Pd-Au/HOPG catalysts

    NASA Astrophysics Data System (ADS)

    Bukhtiyarov, Andrey V.; Prosvirin, Igor P.; Bukhtiyarov, Valerii I.

    2016-03-01

    The preparation of model bimetallic Pd-Au/HOPG catalysts has been investigated using scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) techniques. Initially, model "core-shell" type Pd-Au/HOPG catalysts with similar particle size distribution (5-8 nm), but with different densities of particle locations on the HOPG surface and Pd/Au atomic ratios are prepared. Further, their thermal stability is studied within a temperature range of 50-500 °C at UHV conditions. It has been shown that annealing the model catalysts at a temperature range of 300-400 °C leads to formation of Pd-Au alloyed particles. Enhancement of heating temperature up to 500 °C results in sintering of bimetallic nanoparticles. Contribution of different parameters controlling the properties of Pd-Au alloyed particles has been discussed.

  12. Efficient method for the conversion of agricultural waste into sugar alcohols over supported bimetallic catalysts.

    PubMed

    Tathod, Anup P; Dhepe, Paresh L

    2015-02-01

    Promoter effect of Sn in the PtSn/γ-Al2O3 (AL) and PtSn/C bimetallic catalysts is studied for the conversion of variety of substrates such as, C5 sugars (xylose, arabinose), C6 sugars (glucose, fructose, galactose), hemicelluloses (xylan, arabinogalactan), inulin and agricultural wastes (bagasse, rice husk, wheat straw) into sugar alcohols (sorbitol, mannitol, xylitol, arabitol, galactitol). In all the reactions, PtSn/AL showed enhanced yields of sugar alcohols by 1.5-3 times than Pt/AL. Compared to C, AL supported bimetallic catalysts showed prominent enhancement in the yields of sugar alcohols. Bimetallic catalysts characterized by X-ray diffraction study revealed the stability of catalyst and absence of alloy formation thereby indicating that Pt and Sn are present as individual particles in PtSn/AL. The TEM analysis also confirmed stability of the catalysts and XPS study disclosed formation of electron deficient Sn species which helps in polarizing carbonyl bond to achieve enhanced hydrogenation activity. PMID:25453932

  13. Nanosegregated bimetallic oxide anode catalyst for proton exchange membrane electrolyzer

    DOEpatents

    Danilovic, Nemanja; Kang, Yijin; Markovic, Nenad; Stamenkovic, Vojislav; Myers, Deborah J.; Subbaraman, Ram

    2016-08-23

    A surface segregated bimetallic composition of the formula Ru.sub.1-xIr.sub.x wherein 0.1.ltoreq.x.ltoreq.0.75, wherein a surface of the material has an Ir concentration that is greater than an Ir concentration of the material as a whole is provided. The surface segregated material may be produced by a method including heating a bimetallic composition of the formula Ru.sub.1-xIr.sub.x, wherein 0.1.ltoreq.x.ltoreq.0.75, at a first temperature in a reducing environment, and heating the composition at a second temperature in an oxidizing environment. The surface segregated material may be utilized in electrochemical devices.

  14. Characterization of CeO2-Supported Cu-Pd Bimetallic Catalyst for the Oxygen-Assisted Water-Gas Shift Reaction

    SciTech Connect

    Fox, Elise; Velu, Subramani; Engelhard, Mark H.; Chin, Ya-Huei; Miller, Jeffrey T.; Kropf, Jeremy; Song, Chunshan

    2008-12-10

    This study was focused to investigate the roles of Cu and Pd in CuPd/CeO2 bimetallic catalysts containing 20-30 wt% Cu and 0.5-1 wt% Pd used in the oxygen-assisted water-gas shift (OWGS) reaction employing a combined bulk and surface characterization techniques such as XRD, TPR, CO chemisorption, and in-situ XPS. The catalytic activity for CO conversion and the stability of catalyst during on-stream operation increased by the addition of Cu to Pd/CeO2 or Pd to Cu/CeO2 monometallic catalysts, especially when the OWGS reaction was performed under low temperatures, below 200oC. The bimetallic catalyst after leaching with nitric acid retained about 60% of its original activity. The TPR of monometallic Cu/CeO2 showed reduction of CuO supported on CeO2 in two distinct regions, around 150 and 250oC. The high temperature peak disappeared and reduction occurred in a single step around 150oC upon Pd addition. The Pd dispersion decreased from 38.5% for Pd/CeO2 to below 1% for CuPd/CeO2 bimetallic catalyst. In-situ XPS studies showed a shift in Cu 2p peaks toward lower binding energy (BE) with concommitant shift in the Pd 3d peaks toward higher BE. Addition of Pd decreased the surface Cu concentration while the concentration of Pd remained unaltered. All these observations indicated the formation of Cu-Pd surface alloy. The valence band XP spectra collected below 10 eV corroborated the core level XP spectra and indicated that Cu is mainly involved in the catalytic reaction. The improved catalytic activity and stability of CuPd/CeO2 bimetallic catalyst was attributed to the alloy formation.

  15. Kinetics of oxygen-enhanced water gas shift on bimetallic catalysts and the roles of metals and support

    NASA Astrophysics Data System (ADS)

    Kugai, Junichiro

    dissociation and/or the subsequent reaction with chemisorbed CO as well as Pd keeps Cu in reduced state. Cu was found to keep Pd dispersed, suppress H2 activation on Pd, and facilitate CO 2 desorption from catalyst surface. While composition and structure of metal have large impacts on OWGS performance, CeO2 was shown to create new sites for H2O activation at metal-ceria interfacial region in concert with metal. These new sites strongly activate H2O to drive OWGS and WGS compared to the pure metallic sites which are present in majority on Al2O3-supported catalyst. The observed two regimes of turnover rate, the one dependent on catalyst surface area and the other independent of surface area, strongly suggested bifunctional reaction pathway where the reaction rate is determined by activation of H2O and by association of chemisorbed CO and H 2O. The associative route was also evidenced by pulse response study where the reaction occurs only when CO and H2O pulses are supplied together, and thus pre-adsorbed species such as formate and carbonate identified by FT-IR are proven to be spectators. No correlation between WGS rate and isotopic exchange rate of molecularly adsorbed D2O with H 2 showed H2O dissociation is necessary for WGS to occur. Long duration tests revealed CeO2-supported Pd-Cu, Pt-Cu and Cu catalysts are stable in OWGS condition compared to Pt, Pd, and Al 2O3-supported Pd-Cu catalysts which exhibited continuous deactivation during about 70 hours of test. The addition of Cu prevents agglomeration of monometallic Pd and carbonate formation on monometallic Pt during the reaction. The better activity and stability of Pd-Cu and Pt-Cu bimetallic catalysts in the realistic OWGS condition were ascribed to the unique active sites consisting of highly dispersed Pd in Cu or Pt in Cu on CeO2, which are good for H2O activation with low reaction inhibition by the product gases. Pt monometallic catalyst showed and highest activity in OWGS in the absence of product gases, but this

  16. Structural characterization of bimetallic Pd-Cu vapor derived catalysts

    NASA Astrophysics Data System (ADS)

    Balerna, Antonella; Evangelisti, Claudio; Psaro, Rinaldo; Fusini, Graziano; Carpita, Adriano

    2016-05-01

    Pd-Cu bimetallic Solvated Metal Atoms (SMA) were synthesized by metal vapor synthesis technique and supported on PVPy resin. Since the catalytic activity, of the Pd-Cu system turned out to be quite high also compared to the corresponding monometallic system, a structural characterization, using electron microscopy techniques and X-ray Absorption Fine Structure spectroscopy, was performed. HRTEM analysis showed the presence of Pd particles distributed in a narrow range with a mean diameter of about 2.5 nm while the XAFS analysis, confirmed the presence of the Pd nanoparticles but revealed also some alloying with Cu atoms.

  17. High viscosity to highly dispersed PtPd bimetallic nanocrystals for enhanced catalytic activity and stability.

    PubMed

    Ying, Jie; Hu, Zhi-Yi; Yang, Xiao-Yu; Wei, Hao; Xiao, Yu-Xuan; Janiak, Christoph; Mu, Shi-Chun; Tian, Ge; Pan, Mu; Van Tendeloo, Gustaaf; Su, Bao-Lian

    2016-07-01

    A facile high-viscosity-solvent method is presented to synthesize PtPd bimetallic nanocrystals highly dispersed in different mesostructures (2D and 3D structures), porosities (large and small pore sizes), and compositions (silica and carbon). Further, highly catalytic activity, stability and durability of the nanometals have been proven in different catalytic reactions. PMID:27222099

  18. On the properties of silica-supported bimetallic Fe-Cu catalysts. Part 1. Preparation and characterization

    SciTech Connect

    Wielers, A.F.H.; Hop, C.E.C.A.; van Beijnum, J.; Geus, J.W. ); van der Kraan, A.M. )

    1990-02-01

    In this work a series of silica-supported bimetallic iron-copper catalysts has been prepared and characterized. The bimetallic catalysts were prepared via homogeneous deposition-precipitation involving a procedure in which first copper ions (as copper hydrosilicate) and consecutively iron(III) ions (as goethite) are precipitated onto the support. The results show that copper facilitates the reduction of iron(III) to iron(II) (which is present as iron(II)silicate) as well as the reduction to zero-valent iron. In the reduced iron/copper catalyst zero-valent iron is present as monometallic {alpha}-Fe particles and as iron clusters in bimetallic Fe-Cu particles. The relative amounts of the various iron species vary with the overall composition. Whereas the surfaces of the freshly reduced bimetallic particles are not extensively enriched in one of the constituents, prolonged CO exposure at room temperature leads to a considerable iron enrichment.

  19. Experimental and computational investigations of sulfur-resistant bimetallic catalysts for reforming of biomass gasification products

    SciTech Connect

    Rangan, Meghana; Yung, Matthew M.; Medlin, J. William

    2011-11-17

    A combination of density functional theory (DFT) calculations and experimental studies of supported catalysts was used to identify H{sub 2}S-resistant biomass gasification product reforming catalysts. DFT calculations were used to search for bimetallic, nickel-based (1 1 1) surfaces with lower sulfur adsorption energies and enhanced ethylene adsorption energies. These metrics were used as predictors for H{sub 2}S resistance and activity toward steam reforming of ethylene, respectively. Relative to Ni, DFT studies found that the Ni/Sn surface alloy exhibited enhanced sulfur resistance and the Ni/Ru system exhibited an improved ethylene binding energy with a small increase in sulfur binding energy. A series of supported bimetallic nickel catalysts was prepared and screened under model ethylene reforming conditions and simulated biomass tar reforming conditions. The observed experimental trends in activity were consistent with theoretical predictions, with observed reforming activities in the order Ni/Ru > Ni > Ni/Sn. Interestingly, Ni/Ru showed a high level of resistance to sulfur poisoning compared with Ni. This sulfur resistance can be partly explained by trends in sulfur versus ethylene binding energy at different types of sites across the bimetallic surface.

  20. Mono- and bimetallic Rh and Pt NSR-catalysts prepared by controlled deposition of noble metals on support or storage component

    PubMed Central

    Büchel, Robert; Pratsinis, Sotiris E.; Baiker, Alfons

    2013-01-01

    Mono- and bimetallic Rh and Pt based NOx storage-reduction (NSR) catalysts, where the noble metals were deposited on the Al2O3 support or BaCO3 storage component, have been prepared using a twin flame spray pyrolysis setup. The catalysts were characterized by nitrogen adsorption, CO chemisorption combined with diffuse reflectance infrared Fourier transform spectroscopy, X-ray diffraction, and scanning transmission electron microscopy combined with energy dispersive X-ray spectroscopy. The NSR performance of the catalysts was investigated by fuel lean/rich cycling in the absence and presence of SO2 (25 ppm) as well as after H2 desulfation at 750 °C. The performance increased when Rh was located on BaCO3 enabling good catalyst regeneration during the fuel rich phase. Best performance was observed for bimetallic catalysts where the noble metals were separated, with Pt on Al2O3 and Rh on BaCO3. The Rh-containing catalysts generally showed much higher tolerance to SO2 during fuel rich conditions and lost only little activity during thermal aging at 750 °C. PMID:23741085

  1. Exceptional methanol electro-oxidation activity by bimetallic concave and dendritic Pt-Cu nanocrystals catalysts

    NASA Astrophysics Data System (ADS)

    Wang, Ying-Xia; Zhou, Hui-Jing; Sun, Ping-Chuan; Chen, Tie-Hong

    2014-01-01

    PtCux (x = 1, 2 and 3) bimetallic nanocrystals with concave surface and dendritic morphology were prepared and used as electrocatalysts in methanol oxidation reaction (MOR) for polymer electrolyte membrane fuel cells. The bimetallic nanocrystals were synthesized via one-pot co-reduction of H2PtCl6 and Cu(acac)2 by oleylamine and polyvinyl pyrrolidone (PVP) in an autoclave at 180 °C. The concave dendritic bimetallic nanostructure consisted of a core rich in Cu and nanodendrites rich in Pt, which was formed via galvanic replacement of Cu by Pt. It was found that PVP played an important role in initiating, facilitating, and directing the replacement reaction. The electrochemical properties of the PtCux were characterized by cyclic voltammetry (CV) and chronoamperometry (CA). The concave dendritic PtCu2/C nanocrystals exhibited exceptionally high activity and strong poisoning resistance in MOR. At 0.75 V (vs. reversible hydrogen electrode, RHE) the mass activity and specific activity of PtCu2/C were 3.3 and 4.1 times higher than those of the commercial Pt/C catalysts, respectively. The enhanced catalytic activity could be attributed to the unique concave dendritic morphology of the bimetallic nanocrystals.

  2. Enantioselective polymerization of epoxides using biaryl-linked bimetallic cobalt catalysts: a mechanistic study.

    PubMed

    Ahmed, Syud M; Poater, Albert; Childers, M Ian; Widger, Peter C B; LaPointe, Anne M; Lobkovsky, Emil B; Coates, Geoffrey W; Cavallo, Luigi

    2013-12-18

    The enantioselective polymerization of propylene oxide (PO) using biaryl-linked bimetallic salen Co catalysts was investigated experimentally and theoretically. Five key aspects of this catalytic system were examined: (1) the structural features of the catalyst, (2) the regio- and stereoselectivity of the chain-growth step, (3) the probable oxidation and electronic state of Co during the polymerization, (4) the role of the cocatalyst, and (5) the mechanism of monomer enchainment. Several important insights were revealed. First, density functional theory (DFT) calculations provided detailed structural information regarding the regio- and stereoselective chain-growth step. Specifically, the absolute stereochemistry of the binaphthol linker determines the enantiomer preference in the polymerization, and the interaction between the salen ligand and the growing polymer chain is a fundamental aspect of enantioselectivity. Second, a new bimetallic catalyst with a conformationally flexible biphenol linker was synthesized and found to enantioselectively polymerize PO, though with lower enantioselectivity than the binaphthol linked catalysts. Third, DFT calculations revealed that the active form of the catalyst has two active exo anionic ligands (chloride or carboxylate) and an endo polymer alkoxide which can ring-open an adjacent cobalt-coordinated epoxide. Fourth, calculations showed that initiation is favored by an endo chloride ligand, while propagation is favored by the presence of two exo carboxylate ligands. PMID:24199614

  3. Characterization of Na+- beta-Zeolite Supported Pd and Pd Ag Bimetallic Catalysts using EXAFS, TEM and Flow Reactor

    SciTech Connect

    Huang,W.; Lobo, R.; Chen, J.

    2008-01-01

    Flow reactor studies of the selective hydrogenation of acetylene in the presence of ethylene have been performed on Na+ exchanged {beta}-zeolite supported Pd, Ag and PdAg catalysts, as an extension of our previous batch reactor studies [W. Huang, J.R. McCormick, R.F. Lobo, J.G. Chen, J. Catal. 246 (2007) 40-51]. Results from flow reactor studies show that the PdAg/Na+-{beta}-zeolite bimetallic catalyst has lower activity than Pd/Na+-{beta}-zeolite monometallic catalyst, while Ag/Na+-{beta}-zeolite does not show any activity for acetylene hydrogenation. However, the selectivity for the PdAg bimetallic catalyst is much higher than that for either the Pd catalyst or Ag catalyst. The selectivity to byproduct (ethane) is greatly inhibited on the PdAg bimetallic catalyst as well. The results from the current flow reactor studies confirmed the pervious results from batch reactor studies [W. Huang, J.R. McCormick, R.F. Lobo, J.G. Chen, J. Catal. 246 (2007) 40-51]. In addition, we used transmission electron microscope (TEM), extended X-ray absorption fine structure (EXAFS), and FTIR of CO adsorption to confirm the formation of Pd-Ag bimetallic alloy in the PdAg/Na+-{beta}-zeolite catalyst.

  4. Growth and characterization of CNT Forests using Bimetallic Nanoparticles as Catalyst

    NASA Astrophysics Data System (ADS)

    Lee, Kyung-Hwan; Sra, A.; Jang, H.; Choi, B.; Overzet, L.; Lee, G.; Yang, D.

    2008-10-01

    We study the growth of Multiwall carbon nanotubes (MWCNT) using bimetallic nanoparticles (NP) as catalyst rather than zerovalent metal ions such as Fe, Ni, Co. One advantage of using bimetallic NP is that both the size and shape and composition (atomic ordering) can be controlled. We will describe a simple method of producing bimetallic Fe-Pt, Fe-Co alloy nanoparticles and compare MWCNT growth using them to Fe catalyst growth. The synthesis of Fe, Fe-Pt, Fe-Co NP was carried out using a bottom-up polyol process. Subsequent growth of MWCNT forests was accomplished by PECVD using acetylene as precursor. TEM and SEM analysis of the sample cross-section grown at substrate temperature of 680 ^oC indicates that the diameters of the CNTs are ˜ 10-20 nm while height of the forest varies from 30 μm for Fe to 5 μm for Fe-Pt and 80-100 μm for Fe-Co. The number of walls in the CNTs and the graphitization content could be manipulated by varying the temperature (increasing to 760 ^oC) or by pre-treatment of the nanoparticles with oxygen plasma.

  5. Understanding and controlling nanoporosity formation for improving the stability of bimetallic fuel cell catalysts.

    PubMed

    Gan, Lin; Heggen, Marc; O'Malley, Rachel; Theobald, Brian; Strasser, Peter

    2013-03-13

    Nanoporosity is a frequently reported phenomenon in bimetallic particle ensembles used as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. It is generally considered a favorable characteristic, because it increases the catalytically active surface area. However, the effect of nanoporosity on the intrinsic activity and stability of a nanoparticle electrocatalyst has remained unclear. Here, we present a facile atmosphere-controlled acid leaching technique to control the formation of nanoporosity in Pt-Ni bimetallic nanoparticles. By statistical analysis of particle size, composition, nanoporosity, and atomic-scale core-shell fine structures before and after electrochemical stability test, we uncover that nanoporosity formation in particles larger than ca. 10 nm is intrinsically tied to a drastic dissolution of Ni and, as a result of this, a rapid drop in intrinsic catalytic activity during ORR testing, translating into severe catalyst performance degradation. In contrast, O2-free acid leaching enabled the suppression of nanoporosity resulting in more solid core-shell particle architectures with thin Pt-enriched shells; surprisingly, such particles maintained high intrinsic activity and improved catalytic durability under otherwise identical ORR tests. On the basis of these findings, we suggest that catalytic stability could further improve by controlling the particle size below ca. 10 nm to avoid nanoporosity. Our findings provide an explanation for the degradation of bimetallic particle ensembles and show an easy to implement pathway toward more durable fuel cell cathode catalysts. PMID:23360425

  6. Reverse Micelle Synthesis and Characterization of Supported Pt/Ni Bimetallic Catalysts on gamma-Al2O3

    SciTech Connect

    B Cheney; J Lauterbach; J Chen

    2011-12-31

    Reverse micelle synthesis was used to improve the nanoparticle size uniformity of bimetallic Pt/Ni nanoparticles supported on {gamma}-Al{sub 2}O{sub 3}. Two impregnation methods were investigated to optimize the use of the micelle method: (1) step-impregnation, where Ni nanoparticles were chemically reduced in microemulsion and then supported, followed by Pt deposition using incipient wetness impregnation, and (2) co-impregnation, where Ni and Pt were chemically reduced simultaneously in microemulsion and then supported. Transmission electron microscopy (TEM) was used to characterize the particle size distribution. Atomic absorption spectroscopy (AAS) was used to perform elemental analysis of bimetallic catalysts. Extended X-ray absorption fine structure (EXAFS) measurements were utilized to confirm the formation of the Pt-Ni bimetallic bond in the step-impregnated catalyst. CO pulse chemisorption and Fourier transform infrared spectroscopy (FTIR) studies of 1,3-butadiene hydrogenation in a batch reactor were performed to determine the catalytic activity. Step-impregnated Pt/Ni catalyst demonstrated enhanced hydrogenation activity over the parent monometallic Pt and Ni catalysts due to bimetallic bond formation. The catalyst synthesized using co-impregnation showed no enhanced activity, behaving similarly to monometallic Ni. Overall, our results indicate that reverse micelle synthesis combined with incipient wetness impregnation produced small, uniform nanoparticles with bimetallic bonds that enhanced hydrogenation activity.

  7. Spectroscopic and Computational Insights on Catalytic Synergy in Bimetallic Aluminophosphate Catalysts.

    PubMed

    Potter, Matthew E; Paterson, A James; Mishra, Bhoopesh; Kelly, Shelly D; Bare, Simon R; Corà, Furio; Levy, Alan B; Raja, Robert

    2015-07-01

    A combined electronic structure computational and X-ray absorption spectroscopy study was used to investigate the nature of the active sites responsible for catalytic synergy in Co-Ti bimetallic nanoporous frameworks. Probing the nature of the molecular species at the atomic level has led to the identification of a unique Co-O-Ti bond, which serves as the loci for the superior performance of the bimetallic catalyst, when compared with its analogous monometallic counterpart. The structural and spectroscopic features associated with this active site have been characterized and contrasted, with a view to affording structure-property relationships, in the wider context of designing sustainable catalytic oxidations with porous solids. PMID:26076192

  8. Strategies for designing supported gold-palladium bimetallic catalysts for the direct synthesis of hydrogen peroxide.

    PubMed

    Edwards, Jennifer K; Freakley, Simon J; Carley, Albert F; Kiely, Christopher J; Hutchings, Graham J

    2014-03-18

    Hydrogen peroxide is a widely used chemical but is not very efficient to make in smaller than industrial scale. It is an important commodity chemical used for bleaching, disinfection, and chemical manufacture. At present, manufacturers use an indirect process in which anthraquinones are sequentially hydrogenated and oxidized in a manner that hydrogen and oxygen are never mixed. However, this process is only economic at a very large scale producing a concentrated product. For many years, the identification of a direct process has been a research goal because it could operate at the point of need, producing hydrogen peroxide at the required concentration for its applications. Research on this topic has been ongoing for about 100 years. Until the last 10 years, catalyst design was solely directed at using supported palladium nanoparticles. These catalysts require the use of bromide and acid to arrest peroxide decomposition, since palladium is a very active catalyst for hydrogen peroxide hydrogenation. Recently, chemists have shown that supported gold nanoparticles are active when gold is alloyed with palladium because this leads to a significant synergistic enhancement in activity and importantly selectivity. Crucially, bimetallic gold-based catalysts do not require the addition of bromide and acids, but with carbon dioxide as a diluent its solubility in the reaction media acts as an in situ acid promoter, which represents a greener approach for peroxide synthesis. The gold catalysts can operate under intrinsically safe conditions using dilute hydrogen and oxygen, yet these catalysts are so active that they can generate peroxide at commercially significant rates. The major problem associated with the direct synthesis of hydrogen peroxide concerns the selectivity of hydrogen usage, since in the indirect process this factor has been finely tuned over decades of operation. In this Account, we discuss how the gold-palladium bimetallic catalysts have active sites for the

  9. Bimetallic PtSn/C catalysts obtained via SOMC/M for glycerol steam reforming.

    PubMed

    Pastor-Pérez, Laura; Merlo, Andrea; Buitrago-Sierra, Robison; Casella, Mónica; Sepúlveda-Escribano, Antonio

    2015-12-01

    A detailed study on the preparation of bimetallic PtSn/C catalysts using surface-controlled synthesis methods, and on their catalytic performance in the glycerol steam reforming reaction has been carried out. In order to obtain these well-defined bimetallic phases, techniques derived from Surface Organometallic Chemistry on Metals (SOMC/M) were used. The preparation process involved the reaction between an organometallic compound ((C4H9)4Sn) and a supported transition metal (Pt) in a H2 atmosphere. Catalysts with Sn/Pt atomic ratios of 0.2, 0.3, 0.5, and 0.7 were obtained, and characterized using several techniques: ICP, H2 chemisorption, TEM and XPS. These systems were tested in the glycerol steam reforming varying the reaction conditions (glycerol concentration and reaction temperature). The best performance was observed for the catalysts with the lowest tin contents (PtSn0.2/C and PtSn0.3/C). It was observed that the presence of tin increased the catalysts' stability when working under more severe reaction conditions. PMID:26283100

  10. Using supported Au nanoparticles as starting material for preparing uniform Au/Pd bimetallic catalysts

    SciTech Connect

    Villa, Alberto; Prati, Laura; Su, Dangshen; Wang, Di; Veith, Gabriel M

    2010-01-01

    One of the best methods for producing bulk homogeneous (composition) supported bimetallic AuPd clusters involves the immobilization of a protected Au seed followed by the addition of Pd. This paper investigates the importance of this gold seed in controlling the resulting bimetallic AuPd clusters structures, sizes and catalytic activities by investigating three different gold seeds. Uniform Au-Pd alloy were obtained when a steric/electrostatic protecting group, poly(vinyl alcohol) (PVA), was used to form the gold clusters on activated carbon (AC). In contrast Au/AC precursors prepared using Au nanoparticles with only electrostatic stabilization (tetrakis(hydroxypropyl)phosphonium chloride (THPC)), or no stabilization (magnetron sputtering) produced inhomogeneous alloys and segregation of the gold and palladium. The uniform alloyed catalyst (Pd{at}Au{sub PVA}/AC) is the most active and selective catalyst, while the inhomogenous catalysts are less active and selective. Further study of the PVA protected Au clusters revealed that the amount of PVA used is also critical for the preparation of uniform alloyed catalyst, their stability, and their catalytic activity.

  11. Designing Bimetallic Co-Catalysts: A Party of Two.

    PubMed

    Aronovitch, Eran; Kalisman, Philip; Mangel, Shai; Houben, Lothar; Amirav, Lilac; Bar-Sadan, Maya

    2015-09-17

    The enhanced catalytic properties of bimetallic particles has made them the focus of extensive research. We compare the photocatalytic activity for hydrogen production of core-shell structures of Au@Pd and Au@(Au/Pd alloy) on seeded rods of CdSe@CdS and show that Au@alloy was superior toward hydrogen production. Our finding reveals that the promotion effects of Au in Pd originate both from the alteration of the electronic structure by the Au core as well as by the atomic rearrangement of the surface. Long-term monitoring of the activity of the photocatalysts offered insights into the dynamic processes during the illumination showing that the tip morphology influenced the stability of the hybrid structures. The Au core served as a physical barrier, protecting the CdS rod against cation exchange reactions with the Pd. The coupling of these factors to achieve synergistic effects is therefore a prime aspect in the rational design of efficient cocatalysts. PMID:26722753

  12. Alkoxylation using modified calcium-containing bimetallic or polymetallic catalysts

    SciTech Connect

    King, S.W.

    1992-05-19

    This patent describes a method for providing an alkoxylation catalyst. It comprises reacting or solubilizing, at least partially, calcium metal or a calcium-containing compound, by mixing with an activator or solubilizing thereby forming a calcium-containing reacting a divalent or polyvalent metal or a divalent or polyvalent metal-containing compound wherein the divalent or polyvalent metal is selected from the group consisting of beryllium, magnesium, strontium, barium, lanthanum, titanium, zirconium, hafnium, niobium, tantalum, molybdenum, tungsten, iron, cobalt, nickel, copper, zinc, boron, gallium, silicon, germanium tin, phosphorus, antimony, sulfur, selenium, tellurium, cerium and thorium with an organic compound having at least one active hydrogen to produce a divalent or polyvalent metal-containing composition: reacting the calcium-containing composition with the divalent or polyvalent metal-containing composition under effective reaction conditions to produce a catalyst precursor composition; and reacting the catalyst precursor composition with a divalent or polyvalent oxyacid or a divalent or polyvalent metal salt of an oxyacid or mixtures thereof under effective reaction conditions to produce the alkoxylation catalyst.

  13. Final technical report. Bimetallic complexes as methanol oxidation catalysts

    SciTech Connect

    McElwee-White, Lisa

    2002-01-21

    Our work on the electrocatalyzed oxidation of methanol was initially motivated by the interest in methanol as an anodic reactant in fuel cells. The literature on electrochemical oxidation of alcohols can be roughly grouped into two sets: fuel cell studies and inorganic chemistry studies. Work on fuel cells primarily focuses on surface-catalyzed oxidation at bulk metal anodes, usually Pt or Pt/Ru alloys. In the surface science/electrochemistry approach to these studies, single molecule catalysts are generally not considered. In contrast, the inorganic community investigates the electrooxidation of alcohols in homogeneous systems. Ruthenium complexes have been the most common catalysts in these studies. The alcohol substrates are typically either secondary alcohols (e.g., isopropanol) such that the reaction stops after 2 e{sup -} oxidation to the aldehyde and 4 e{sup -} oxidation to the carboxylic acid can be observed. Methanol, which can also undergo 6 e{sup -} oxidation to CO{sub 2}, rarely appears in the homogeneous catalysis studies. Surface studies have shown that two types of metal centers with different functions result in more effective catalysts than a single metal; however, application of this concept to homogeneous systems has not been demonstrated. The major thrust of the work is to apply this insight from the surface studies to homogeneous catalysis. Even though homogeneous systems would not be appropriate models for active sites on Pt/Ru anodes, it is possible that heterobimetallic catalysts could also utilize two metal centers for different roles. Starting from that perspective, this work involves the preparation and investigation of heterobinuclear catalysts for the electrochemical oxidation of methanol.

  14. Synthesis and Characterization of Cluster-Derived Supported Bimetallic Catalysts

    SciTech Connect

    Adams, Richard D; Amiridis, Michael D

    2008-10-10

    New procedures have been developed for synthesizing di- and tri-metallic cluster complexes. The chemical properties of the new complexes have been investigated, particularly toward the activation of molecular hydrogen. These complexes were then converted into bi- and tri-metallic nanoparticles on silica and alumina supports. These nanoparticles were characterized by electron microscopy and were then tested for their ability to produce catalytic hydrogenation of unsaturated hydrocarbons and for the preferential oxidation of CO in the presence of hydrogen. The bi- and tri-metallic nanoparticles exhibited far superior activity and selectivity as hydrogenation catalysts when compared to the individual metallic components. It was found that the addition of tin greatly improved the selectivity of the catalysts for the hydrogenation of polyolefins. The addition of iron improves the catalysts for the selective oxidation of CO by platinum in the presence of hydrogen. The observations should lead to the development of lower cost routes to molecules that can be used to produce polymers and plastics for use by the general public and for procedures to purify hydrogen for use as an alternative energy in the hydrogen economy of the future.

  15. Novel supported bimetallic carbide catalysts for coprocessing of coal with waste materials

    SciTech Connect

    S.T. Oyama; D.F. Cox; C. Song; F. Allen

    1999-12-15

    In this reporting period the authors have continued their investigation of bimetallic nitride and carbide compounds for use in coprocessing of coal and waste plastics or rubber. Following up on their finding of a class of bimetallic nitrides, reported in the last period, they now report on a new family of bimetallic oxycarbides M{sup I}-M{sup II}-O-C (M{sup I} = Mo, W; M{sup II} = V, Nb, Cr, Fe, Co, Ni). They have carried out a preliminary test of the compounds with a model coal liquid feed and find that, in general, these carbides are even more active than the nitrides. They have identified Nb-Mo-O-C as the most promising catalyst, and this catalyst together with Mo{sub 2}C, the most active single-metal carbide are being investigated for the coprocessing reaction. Comparison is made to standard sulfide catalysts. The latter reaction is carried out in batch autoclave systems, so that preliminary tests are first carried out with a simpler five-component feedstock. The feedstock is a multi-component model mixture that simulates the combined feed of coal and waste materials. The idea is to use different compounds that are specific for each reaction type but have no overlapping products. The proposed design involves a 5-component mixture containing: 4-(1-naphthylmethyl)bibenzyl, abbreviated as NMBB, pyrene, tetradecane, dibenzothiophene and quinoline. NMBB simulates the aromatic-aliphatic as well as aliphatic-aliphatic C-C bonds in coal and in some aromatic plastics such as polystyrene. This compound has been used as a probe molecule in previous studies. Pyrene represents polyaromatic structures in coal, while tetradecane is representative of polyethylene-type plastics in chemical reactivity. Dibenzothiophene and quinoline provide sulfur and nitrogen content.

  16. Correlating Extent of Pt–Ni Bond Formation with Low-temperature Hydrogenation of Benzene and 1,3-butadiene over Supported Pt/Ni Bimetallic Catalysts

    SciTech Connect

    Lonergan, W.; Vlachos, D; Chen, J

    2010-01-01

    Low-temperature hydrogenation of benzene and 1,3-butadiene on supported Pt/Ni catalysts have been used as probe reactions to correlate hydrogenation activity with the extent of Pt-Ni bimetallic bond formation. Pt/Ni bimetallic and Pt and Ni monometallic catalysts were supported on {gamma}-Al{sub 2}O{sub 3} using incipient wetness impregnation. Two sets of bimetallic catalysts were synthesized: one set to study the effect of metal atomic ratio and the other to study the effect of impregnation sequence. Fourier transform infrared spectroscopy (FTIR) CO adsorption studies were performed to characterize the surface composition of the bimetallic nanoparticles, and transmission electron microscopy (TEM) was utilized to characterize the particle size distribution. Batch reactor studies with FTIR demonstrated that all bimetallic catalysts outperformed monometallic catalysts for both benzene and 1,3-butadiene hydrogenation. Within the two sets of bimetallic catalysts, it was found that catalysts with a smaller Pt:Ni ratio possessed higher hydrogenation activity and that catalysts synthesized using co-impregnation had greater activity than sequentially impregnated catalysts. Extended X-ray absorption fine structure (EXAFS) measurements were performed in order to verify the extent of Pt-Ni bimetallic bond formation, which was found to correlate with the hydrogenation activity.

  17. CATALYSIS SCIENCE INITIATIVE: From First Principles Design to Realization of Bimetallic Catalysts for Enhanced Selectivity

    SciTech Connect

    MAVRIKAKIS, MANOS DUMESIC, JAMES A.

    2007-05-03

    In this project, we have integrated state-of-the-art Density Functional Theory (DFT) models of heterogeneous catalytic processes with high-throughput screening of bimetallic catalytic candidates for important industrial problems. We have studied a new class of alloys characterized by a surface composition different from the bulk composition, and investigated their stability and activity for the water-gas shift reaction and the oxygen reduction reaction. The former reaction is an essential part of hydrogen production; the latter is the rate-limiting step in low temperature H2 fuel cells. We have identified alloys that have remarkable stability and activity, while having a much lower material cost for both of these reactions. Using this knowledge of bimetallic interactions, we have also made progress in the industrially relevant areas of carbohydrate reforming and conversion of biomass to liquid alkanes. One aspect of this work is the conversion of glycerol (a byproduct of biodiesel production) to synthesis gas. We have developed a bifunctional supported Pt catalyst that can cleave the carbon-carbon bond while also performing the water-gas shift reaction, which allows us to better control the H2:CO ratio. Knowledge gained from the theoretical metal-metal interactions was used to develop bimetallic catalysts that perform this reaction at low temperature, allowing for an efficient coupling of this endothermic reaction with other reactions, such as Fischer-Tropsch or methanol synthesis. In our work on liquid alkane production from biomass, we have studied deactivation and selectivity in these areas as a function of metal-support interactions and reaction conditions, with an emphasis on the bifunctionality of the catalysts studied. We have identified a stable, active catalyst for this process, where the selectivity and yield can be controlled by the reaction conditions. While complete rational design of catalysts is still elusive, this work demonstrates the power of

  18. Low-temperature aqueous-phase reforming of ethanol on bimetallic PdZn catalysts

    SciTech Connect

    Xiong, Haifeng; DelaRiva, Andrew; Wang, Yong; Dayte, Abhaya

    2015-01-01

    Bimetallic PdZn catalysts supported on carbon black (CB) and carbon nanotubes (CNTs) were found to be selective for CO-free H-2 production from ethanol at low temperature (250 degrees C). On Pd, the H-2 yield was low (similar to 0.3 mol H-2/mol ethanol reacted) and the CH4/CO2 ratio was high (similar to 1.7). Addition of Zn to Pd formed the intermetallic PdZn beta phase (atomic ratio of Zn to Pd is 1) with increased H-2 yield (similar to 1.9 mol H-2/mol ethanol reacted) and CH4/CO2 ratio of <1. The higher H-2 yield and low CH4 formation was related to the improved dehydrogenation activity of the L1(0) PdZn beta phase. The TOF increased with particle size and the CNTs provided the most active and selective catalysts, which may be ascribed to pore-confinement effects. Furthermore, no significant changes in either the supports or the PdZn beta particles was found after aqueous-phase reforming (APR) indicating that the metal nanoparticles and the carbon support are hydrothermally stable in the aqueous phase at elevated temperatures and pressures (>200 degrees C, 65 bar). No CO was detected for all the catalysts performed in aqueous-phase reaction, indicating that both monometallic Pd and bimetallic PdZn catalysts have high water-gas shift activity during APR. However, the yield of H-2 is considerably lower than the theoretical value of 6 H-2 per mole ethanol which is due to the presence of oxygenated products and methane on the PdZn catalysts.

  19. Optimization of Single and Bimetallic Noble Metal Catalysts by Strong Electrostatic Adsorption

    NASA Astrophysics Data System (ADS)

    Barnes, Sean E.

    Heterogeneous catalysts are used in over 90% of chemical processes today. These small metal particles maximize the number of active sites present, which leads to cheaper, more effective catalysts. However, the preparation of heterogeneous catalysts is still a "dark art". An alternate to dry impregnation is the method of Strong Electrostatic Adsorption (SEA). In this method the surface hydroxyl groups of the support can either protonate or deprotonate depending on the pH of the contacting solution. These surface groups then can then attract oppositely charged metal precursors. Preparation of catalysts by SEA leads to the anchoring of small, well dispersed, highly active metal particles. The aim of this work is to optimize the preparation via SEA of various supported catalysts systems, particularly Pt/carbon, Au supported on a variety of materials, and Au-Pd/carbon. Carbon supported metal catalysts are becoming increasingly important not just as electro catalyst in fuel cells, but for many aqueous phase biomass conversion reactions.

  20. Structure and Reactivity Investigations on Supported Bimetallic Au-Ni Catalysts Used for Hydrocarbon Steam Reforming

    SciTech Connect

    Chin, Ya-Huei; King, David L.; Roh, Hyun-Seog; Wang, Yong; Heald, S.

    2006-12-10

    The addition of small quantities of gold to the surface of supported nickel catalysts has been described as a means to retard carbon formation during hydrocarbon steam reforming. Calculations by others have indicated that gold locates at the most catalytically active (step and edge) sites that also serve as nucleation sites for carbon formation. In this paper we describe experiments to characterize the Ni-Au interactions on bimetallic Au-Ni/MgAl2O4 catalysts at various Ni and Au loadings. The catalyst structure was investigated using EXAFS/XANES spectroscopy and adsorption-desorption measurements with H2 and N2O. Evidence for surface alloy formation is provided in the Ni K and Au LIII edge EXAFS measurements of Au-promoted 8.8%Ni/MgAl2O4, especially at Au loadings ?0.2 wt.%. At higher Au concentrations, there is evidence for a combination of alloy and segregated Au species. H2 chemisorption and N2O temperature programmed desorption (TPD) measurements showed a significant decrease in total surface sites, or surface site reactivity, on Au modified Ni/MgAl2O4 catalyst. The XANES structure is consistent with perturbation of the electronic structure of both the Ni and Au atoms as a result of alloy formation. TGA studies with steam/n-butane feed confirmed the ability of Au to retard coke deposition under low S/C reforming conditions, although carbon formation was not fully suppressed. When testing for methane steam reforming, a lower initial activity and deactivation rate resulted from Au promotion of the Ni catalyst. However, both catalysts showed a declining activity with time. The lack of a direct correlation between the surface characterization results and catalytic activity is most likely a result of decreasing effectiveness of the surface alloy with increasing temperature.

  1. Nickel-cobalt bimetallic anode catalysts for direct urea fuel cell

    NASA Astrophysics Data System (ADS)

    Xu, Wei; Zhang, Huimin; Li, Gang; Wu, Zucheng

    2014-08-01

    Nickel is an ideal non-noble metal anode catalyst for direct urea fuel cell (DUFC) due to its high activity. However, there exists a large overpotential toward urea electrooxidation. Herein, NiCo/C bimetallic nanoparticles were prepared with various Co contents (0, 10, 20, 30 and 40 wt%) to improve the activity. The best Co ratio was 10% in the aspect of cell performance, with a maximum power density of 1.57 mW cm-2 when 0.33 M urea was used as fuel, O2 as oxidant at 60°C. The effects of temperature and urea concentration on DUFC performance were investigated. Besides, direct urine fuel cell reaches a maximum power density of 0.19 mW cm-2 with an open circuit voltage of 0.38 V at 60°C.

  2. Nickel-cobalt bimetallic anode catalysts for direct urea fuel cell

    PubMed Central

    Xu, Wei; Zhang, Huimin; Li, Gang; Wu, Zucheng

    2014-01-01

    Nickel is an ideal non-noble metal anode catalyst for direct urea fuel cell (DUFC) due to its high activity. However, there exists a large overpotential toward urea electrooxidation. Herein, NiCo/C bimetallic nanoparticles were prepared with various Co contents (0, 10, 20, 30 and 40 wt%) to improve the activity. The best Co ratio was 10% in the aspect of cell performance, with a maximum power density of 1.57 mW cm−2 when 0.33 M urea was used as fuel, O2 as oxidant at 60°C. The effects of temperature and urea concentration on DUFC performance were investigated. Besides, direct urine fuel cell reaches a maximum power density of 0.19 mW cm−2 with an open circuit voltage of 0.38 V at 60°C. PMID:25168632

  3. Bimetallic complexes of spiro-azacrown ligands as catalysts of phosphoester and phosphoric anhydride cleavage.

    PubMed

    Wang, Qi; Mikkola, Satu; Lönnberg, Harri

    2004-09-01

    The ability of bimetallic homo- and heteronuclear complexes of two spiro-linked ligands, viz. a biazacrown (i.e., 2,6,10,14,18,22-hexaazaspiro[11.11]tricosane (1)) and an azacrown-crown ether (i.e., 14,17,20,23,26-pentaoxa-2,6,10-triaza-spiro[11.15]heptacosane (2)), to promote the cleavage of the phosphoester linkage of dinucleoside 3',5'-phosphates and the phosphoric anhydride bridge of dinucleoside 5',5'-triphosphates was studied. In both reactions, the bimetallic homonuclear Cu2+ and Zn2+ complexes were better catalysts than their monometallic counterparts. The acceleration was two- to five-fold with the phosphoester cleavage and 3- to 20-fold with the phosphoric anhydride cleavage. Interestingly, the most-efficient catalyst of the phosphoester cleavage was the heterodinuclear Ni2+,Zn2+ complex of 1, the catalytic activity of which was up to 5- and 100-fold that of the homodinuclear Zn2+ and Ni2+ complexes, respectively. Moreover, this cooperative acceleration was observed to depend on the identity of the 5'-linked nucleoside: 3',5'-UpU and 3',5'-ApU were cleaved much faster than 3',5'-UpA, and no cooperative acceleration was observed with 3',5'-ApA. The reaction was second-order in hydroxide ion concentration, suggesting that a double deprotonation took place on going from the initial to the transition state. Evidently, in addition to deprotonation of the attacking 2'-OH group, N(3)H of the 5'-linked uridine was displaced by one of the metal ions of the cleaving agent. With the phosphoric anhydride cleavage, no similar cooperativity of two different metal ions was observed, but the greatest rate-acceleration was achieved with the homodinuclear Cu2+ complexes. PMID:17191909

  4. Synthesis of Bimetallic Ni-Cr Nano-Oxides as Catalysts for Methanol Oxidation in NaOH Solution.

    PubMed

    Gu, Yingying; Luo, Jing; Liu, Yicheng; Yang, Haihong; Ouyang, Ruizhou; Miao, Yuqing

    2015-05-01

    Bimetallic Ni-Cr nano-oxide catalysts were synthesized by thermal decomposition method and were investigated as the anode electrocatalysts for the oxidation of methanol. The catalysts were characterized by X-ray diffraction and transmission electron microscopy. The electroactivity of the catalysts towards methanol oxidation in a solution containing 0.25 M NaOH and 1.0 M MeOH was examined using cyclic voltammetry and chronoamperometry. The results indicate that a mixture of rhombohedral-structured NiO and Cr2O3 nanocrystals generated at the calcination temperature of 500-700 degrees C while octahedral-structured spinel NiCr2O4 formed at higher temperature. The influence of metallic molar ratio on the electrocatalytic performance of the catalysts was studied. The Ni-Cr nano-oxides prepared at comparatively low temperature displayed significantly higher catalytic activity and durability in alkaline solution toward electrooxidation of methanol compared with the pure nano NiO. The results indicate a synergy effect between NiO and Cr2O3 enhancing the electrocatalytic properties of the bimetallic Ni-Cr nano-oxide catalysts. Meanwhile, NiCr2O4 hardly increased the activity and durability of the catalyst. In addition, the Ni-Cr catalyst also exhibited excellent stability and good reproducibility. Therefore, Ni-Cr nano-oxide catalyst may be a suitable and cheap electrocatalyst for methanol oxidation in alkaline medium. PMID:26505000

  5. Titania-supported bimetallic catalysts combined with HZSM-5 for Fischer-Tropsch synthesis

    SciTech Connect

    Jothimurugesan, K.; Gangwal, S.K.

    1998-04-01

    The Fischer-Tropsch synthesis (FTS) can convert coal or natural gas derived synthesis gas (CO + H{sub 2}) to liquid fuels and high-value chemicals. Fischer-Tropsch synthesis was studied in a fixed-bed reactor over single-metal and bimetallic alloy catalysts, selected from Co, Ni, and Fe, supported on TiO{sub 2} at a total metal loading of 10 wt%. The catalysts, prepared by incipient wetness impregnation using nitrate precursors, were tested as is and in combination with a HZSM-5 zeolite. The test conditions were 1 MPa, 250 C, H{sub 2}/CO = 1, and weight hourly space velocity (WHSV) = 0.77 h{sup {minus}1}. Alloying of metals resulted in a significant enhancement in CO conversion without an increase in methane selectivity. A 50:50 weight ratio Co-Ni catalyst physically mixed with HZSM-5 (5% Co-5% Ni/TiO{sub 2} + HZSM-5) gave the highest CO conversion (45.2%) at the conditions tested. This compares to conversion of 8.9% and 10.5% with Co-only and Ni-only catalysts, respectively. Mixing the Co-Ni catalyst with HZSM-5 resulted in a significant reduction in methane selectivity and a significant increase in C{sub 4}{sup +} selectivity. The aromatic fraction increased from 1.5 to 8.1 wt%, the C{sub 2}{sup +} olefins were nearly eliminated, and i-C{sub 4}H{sub 10} increased from 2.3 to 58.5 wt % in the C{sub 4} fraction.

  6. NiW and NiRu Bimetallic Catalysts for Ethylene Steam Reforming: Alternative Mechanisms for Sulfur Resistance

    SciTech Connect

    Rangan, M.; Yung, M. M.; Medlin, J. W.

    2012-06-01

    Previous investigations of Ni-based catalysts for the steam reforming of hydrocarbons have indicated that the addition of a second metal can reduce the effects of sulfur poisoning. Two systems that have previously shown promise for such applications, NiW and NiRu, are considered here for the steam reforming of ethylene, a key component of biomass derived tars. Monometallic and bimetallic Al{sub 2}O{sub 3}-supported Ni and W catalysts were employed for ethylene steam reforming in the presence and absence of sulfur. The NiW catalysts were less active than Ni in the absence of sulfur, but were more active in the presence of 50 ppm H{sub 2}S. The mechanism for the W-induced improvements in sulfur resistance appears to be different from that for Ru in NiRu. To probe reasons for the sulfur resistance of NiRu, the adsorption of S and C{sub 2}H{sub 4} on several bimetallic NiRu alloy surfaces ranging from 11 to 33 % Ru was studied using density functional theory (DFT). The DFT studies reveal that sulfur adsorption is generally favored on hollow sites containing Ru. Ethylene preferentially adsorbs atop the Ru atom in all the NiRu (111) alloys investigated. By comparing trends across the various bimetallic models considered, sulfur adsorption was observed to be correlated with the density of occupied states near the Fermi level while C{sub 2}H{sub 4} adsorption was correlated with the number of unoccupied states in the d-band. The diverging mechanisms for S and C{sub 2}H{sub 4} adsorption allow for bimetallic surfaces such as NiRu that enhance ethylene binding without accompanying increases in sulfur binding energy. In contrast, bimetallics such as NiSn and NiW appear to decrease the affinity of the surface for both the reagent and the poison.

  7. Preparation and characterization of bi-metallic nanoparticle catalyst having better anti-coking properties using reverse micelle technique

    NASA Astrophysics Data System (ADS)

    Zacharia, Thomas

    Energy needs are rising on an exponential basis. The mammoth energy sources like coal, natural gas and petroleum are the cause of pollution. The large outcry for an alternate energy source which is environmentally friendly and energy efficient is heard during the past few years. This is where “Clean-Fuel” like hydrogen gained its ground. Hydrogen is mainly produced by steam methane reforming (SMR). An alternate sustainable process which can reduce the cost as well as eliminate the waste products is Tri-reforming. In both these reforming processes nickel is used as catalyst. However as the process goes on the catalyst gets deactivated due to coking on the catalytic surface. This goal of this thesis work was to develop a bi-metallic catalyst which has better anti-coking properties compared to the conventional nickel catalyst. Tin was used to dope nickel. It was found that Ni3Sn complex around a core of Ni is coking resistant compared to pure nickel catalyst. Reverse micelle synthesis of catalyst preparation was used to control the size and shape of catalytic particles. These studies will benefit researches on hydrogen production and catalyst manufactures who work on different bi-metallic combinations.

  8. Highly dispersed catalysts for coal liquefaction

    SciTech Connect

    Hirschon, A.S.; Wilson, R.B. Jr.

    1992-06-08

    Iron and molybdenum complexes were studied as precursors to high dispersion catalysts for coal liquefaction. The precursors were either organometallic complexes or water soluble salts and were impregnated into coals of various ranks. The molybdenum catalysts were found to be very effective for conversion of an Illinois {number sign}6 bituminous coal whereas the iron catalysts were not. In contrast, the iron catalysts were found to be very effective for lignite conversions. A H-donor and a non-donor conversion system were compared, using tetralin and n-hexadecane, respectively. In each case the organometallic precursor gave greater yields of toluene soluble material, with differences being most dramatic in the hexadecane system. The yields using the organometallic molybdenum precursors in hexadecane were found to be almost as great as those in the tetralin system, indicating that good catalyst precursors do not require donor solvents. The impregnation techniques were evaluated by comparing conversion yields and analyzing the products using Field Ionization Mass Spectroscopy (f.i.m.s) and FT-IR.

  9. Pd-Au bimetallic catalysts: understanding alloy effects from planar models and (supported) nanoparticles.

    SciTech Connect

    Gao, Feng; Goodman, Wayne D.

    2012-12-21

    Pd-Au bimetallic catalysts often display enhanced catalytic activities and selectivities compared with Pd-alone catalysts. This enhancement is often caused by two alloy effects, i.e., ensemble and ligand effects. The ensemble effect is dilution of surface Pd by Au. With increasing surface Au coverages, contiguous Pd ensembles disappear and isolated Pd ensembles form. For certain reactions, for example vinyl acetate synthesis, this effect is responsible for reaction rate enhancement via the formation of highly active surface sites, e.g., isolated Pd pairs. The disappearance of contiguous Pd ensembles also switches off side reactions catalyzed by these sites. This explains selectivity increase of certain reactions, for example direct H2O2 synthesis. The ligand effect is electronic perturbation of Au to Pd. By direct charge transfer or affecting bond length, the ligand effect causes the Pd d band to be more filled and the d-band center away from the Fermi level. Both changes make Pd more "atomic like" therefore binding reactants and products weaker. For certain reactions, this eliminates the so-called "self poisoning" and enhances activity/selectivity.

  10. Structural analysis of palladium-decorated gold nanoparticles as colloidal bimetallic catalysts.

    SciTech Connect

    Fang, Y. L.; Miller, J. T.; Guo, N.; Heck, K. N.; Alvarez, P. J. J.; Wong, M. S.

    2011-02-02

    Bimetallic palladium-decorated gold nanoparticle (Pd/Au NP) catalysts are significantly more active than palladium-only catalysts, but the mechanism for enhancement is not completely clear for most reactions, like the aqueous-phase hydrodechlorination of trichloroethene. In this study, we conducted X-ray absorption spectroscopy on carbon-supported Pd/Au NPs to obtain information about the local atomic environment (i.e., oxidation states, coordination numbers, and bond distances) of the two metals under different treatment conditions. The as-synthesized NPs were confirmed to have a Pd-shell/Au-core nanostructure, in which the Pd was found as surface ensembles. Upon exposure to room temperature in air, a portion of the Pd, but not the Au, was oxidized. In comparison, nearly the entire surface of monometallic Pd NPs was oxidized, suggesting that Au in Pd/Au NPs imparts oxidation resistance to Pd atoms. The surface Pd was found randomly distributed, presumably as a PdAu surface alloy, after reduction at 300 C. X-ray absorption spectroscopy provides direct evidence for the Pd-shell/Au-core structure of Pd/Au NPs, and suggests that metallic Pd in the Pd/Au NPs is a source for higher catalytic activity for aqueous-phase trichloroethene hydrodechlorination.

  11. Catalytic activity of bimetallic catalysts highly sensitive to the atomic composition and phase structure at the nanoscale

    NASA Astrophysics Data System (ADS)

    Shan, Shiyao; Petkov, Valeri; Prasai, Binay; Wu, Jinfang; Joseph, Pharrah; Skeete, Zakiya; Kim, Eunjoo; Mott, Derrick; Malis, Oana; Luo, Jin; Zhong, Chuan-Jian

    2015-11-01

    The ability to determine the atomic arrangement in nanoalloy catalysts and reveal the detailed structural features responsible for the catalytically active sites is essential for understanding the correlation between the atomic structure and catalytic properties, enabling the preparation of efficient nanoalloy catalysts by design. Herein we describe a study of CO oxidation over PdCu nanoalloy catalysts focusing on gaining insights into the correlation between the atomic structures and catalytic activity of nanoalloys. PdCu nanoalloys of different bimetallic compositions are synthesized as a model system and are activated by a controlled thermochemical treatment for assessing their catalytic activity. The results show that the catalytic synergy of Pd and Cu species evolves with both the bimetallic nanoalloy composition and temperature of the thermochemical treatment reaching a maximum at a Pd : Cu ratio close to 50 : 50. The nanoalloys are characterized structurally by ex situ and in situ synchrotron X-ray diffraction, including atomic pair distribution function analysis. The structural data show that, depending on the bimetallic composition and treatment temperature, PdCu nanoalloys adopt two different structure types. One features a chemically ordered, body centered cubic (B2) type alloy consisting of two interpenetrating simple cubic lattices, each occupied with Pd or Cu species alone, and the other structure type features a chemically disordered, face-centered cubic (fcc) type of alloy wherein Pd and Cu species are intermixed at random. The catalytic activity for CO oxidation is strongly influenced by the structural features. In particular, it is revealed that the prevalence of chemical disorder in nanoalloys with a Pd : Cu ratio close to 50 : 50 makes them superior catalysts for CO oxidation in comparison with the same nanoalloys of other bimetallic compositions. However, the catalytic synergy can be diminished if the Pd50Cu50 nanoalloys undergo phase

  12. Facile Synthesis of Porous Dendritic Bimetallic Platinum-Nickel Nanocrystals as Efficient Catalysts for the Oxygen Reduction Reaction.

    PubMed

    Eid, Kamel; Wang, Hongjing; Malgras, Victor; Alothman, Zeid Abdullah; Yamauchi, Yusuke; Wang, Liang

    2016-05-01

    Certain bimetallic nanocrystals (NCs) possess promising catalytic properties for electrochemical energy conversion. Herein, we report a facile method for the one-step synthesis of porous dendritic PtNi NCs in aqueous solution at room temperature that contrasts with the traditional multistep thermal decomposition approach. The dendritic PtNi NCs assembled by interconnected arms are efficient catalysts for the oxygen reduction reaction. This direct and efficient method is favorable for the up-scaled synthesis of active catalysts used in electrochemical applications. PMID:26879517

  13. Highly Dispersed Metal Catalyst for Fuel Cell Electrodes

    SciTech Connect

    2009-03-01

    This factsheet describes a study that will bring industrial catalyst experience to fuel cell research. Specifically, industrial catalysts, such as those used in platforming, utilize precious metal platinum as an active component in a finely dispersed form.

  14. Designing supported palladium-on-gold bimetallic nano-catalysts for controlled hydrogenation of acetylene in large excess of ethylene

    NASA Astrophysics Data System (ADS)

    Malla, Pavani

    Ethylene is used as a starting point for many chemical intermediates in the petrochemical industry. It is predominantly produced through steam cracking of higher hydrocarbons (ethane, propane, butane, naphtha, and gas oil). During the cracking process, a small amount of acetylene is produced as a side product. However, acetylene must be removed since it acts as a poison for ethylene polymerization catalysts at even ppm concentrations (>5 ppm). Thus, the selective hydrogenation of acetylene to ethylene is an important process for the purification of ethylene. Conventional, low weight loading Pd catalysts are used for this selective reaction in high concentration ethylene streams. Gold was initially considered to be catalytically inactive for a long time. This changed when gold was seen in the context of the nanometric scale, which has indeed shown it to have excellent catalytic activity as a homogeneous or a heterogeneous catalyst. Gold is proved to have high selectivity to ethylene but poor at conversion. Bimetallic Au and Pd catalysts have exhibited superior activity as compared to Pd particles in semi-hydrogenation. Hydrogenation of acetylene was tested using this bimetallic combination. The Pd-on-Au bimetallic catalyst structure provides a new synthesis approach in improving the catalytic properties of monometallic Pd materials. TiO 2 as a support material and 0.05%Pd loading on 1%Au on titania support and used different treatment methods like washing plasma and reduction between the two metal loadings and was observed under 2:1 ratio. In my study there were two set of catalysts which were prepared by a modified incipient wetness impregnation technique. Out of all the reaction condition the catalyst which was reduced after impregnating gold and then impregnating palladium which was further treated in non-thermal hydrogen plasma and then pretreated in hydrogen till 250°C for 1 hour produced the best activity of 76% yield at 225°C. Stability tests were conducted

  15. Combination of supported bimetallic rhodium-molybdenum catalyst and cerium oxide for hydrogenation of amide

    NASA Astrophysics Data System (ADS)

    Nakagawa, Yoshinao; Tamura, Riku; Tamura, Masazumi; Tomishige, Keiichi

    2015-02-01

    Hydrogenation of cyclohexanecarboxamide to aminomethylcyclohexane was conducted with silica-supported bimetallic catalysts composed of noble metal and group 6-7 elements. The combination of rhodium and molybdenum with molar ratio of 1:1 showed the highest activity. The effect of addition of various metal oxides was investigated on the catalysis of Rh-MoOx/SiO2, and the addition of CeO2 much increased the activity and selectivity. Higher hydrogen pressure and higher reaction temperature in the tested range of 2-8 MPa and 393-433 K, respectively, were favorable in view of both activity and selectivity. The highest yield of aminomethylcyclohexane obtained over Rh-MoOx/SiO2 + CeO2 was 63%. The effect of CeO2 addition was highest when CeO2 was not calcined, and CeO2 calcined at >773 K showed a smaller effect. The use of CeO2 as a support rather decreased the activity in comparison with Rh-MoOx/SiO2. The weakly-basic nature of CeO2 additive can affect the surface structure of Rh-MoOx/SiO2, i.e. reducing the ratio of Mo-OH/Mo-O- sites.

  16. General Method for Determination of the Surface Composition in Bimetallic Nanoparticle Catalysts from the L Edge X-ray Absorption Near-Edge Spectra

    SciTech Connect

    Wu, Tiapin; Childers, David; Gomez, Carolina; Karim, Ayman M.; Schweitzer, Neil; Kropf, Arthur; Wang, Hui; Bolin, Trudy B.; Hu, Yongfeng; Kovarik, Libor; Meyer, Randall; Miller, Jeffrey T.

    2012-10-08

    Bimetallic PtPd on silica nano-particle catalysts have been synthesized and their average structure determined by Pt L3 and Pd K-edge extended X-ray absorption finestructure (EXAFS) spectroscopy. The bimetallic structure is confirmed from elemental line scans by STEM for the individual 1-2 nm sized particles. A general method is described to determine the surface composition in bimetallic nanoparticles even when both metals adsorb, for example, CO. By measuring the change in the L3 X-ray absorption near-edge structure (XANES) spectra with and without CO in bimetallic particles and comparing these changes to those in monometallic particles of known size the fraction of surface atoms can be determined. The turnover rates (TOR) and neopentane hydrogenolysis and isomerization selectivities based on the surface composition suggest that the catalytic and spectroscopic properties are different from those in monometallic nano-particle catalysts. At the same neo-pentane conversion, the isomerization selectivity is higher for the PtPd catalyst while the TOR is lower than that of both Pt and Pd. As with the catalytic performance, the infrared spectra of adsorbed CO are not a linear combination of the spectra on monometallic catalysts. Density functional theory calculations indicate that the Pt-CO adsorption enthalpy increases while the Pd-CO bond energy decreases. The ability to determine the surface composition allows for a better understanding of the spectroscopic and catalytic properties of bimetallic nanoparticle catalysts.

  17. Facile synthesis of Pd-based bimetallic nanocrystals and their application as catalysts for methanol oxidation reaction

    NASA Astrophysics Data System (ADS)

    Xi, Pinxian; Cao, Yang; Yang, Fengchun; Ma, Cai; Chen, Fengjuan; Yu, Sha; Wang, Shuai; Zeng, Zhengzhi; Zhang, Xin

    2013-06-01

    We employed an efficient and facile route to synthesise monodisperse Pd-based bimetallic nanocrystals (MPd: M = Cu, Co and Ni) via a controlled co-reduction of Pd(ii) chloride and M(ii) nitrate at 200-230 °C in the presence of oleylamine (OAm). These monodisperse Pd-based nanocrystals have small dimensions, unique structures and homogeneous morphology, thus exhibit efficient catalytic activities for methanol oxidation in alkaline solution, which is much better than commercial Pd/C with same amount of palladium. The catalytic activities of these nanocrystals followed the order of NiPd/C > CoPd/C > CuPd/C > commercial Pd/C, due to the different synergistic effects. Our results show that these Pd-based bimetallic nanocrystals can be promising as practical catalysts for methanol oxidation reactions and other catalytic reactions in further investigations.We employed an efficient and facile route to synthesise monodisperse Pd-based bimetallic nanocrystals (MPd: M = Cu, Co and Ni) via a controlled co-reduction of Pd(ii) chloride and M(ii) nitrate at 200-230 °C in the presence of oleylamine (OAm). These monodisperse Pd-based nanocrystals have small dimensions, unique structures and homogeneous morphology, thus exhibit efficient catalytic activities for methanol oxidation in alkaline solution, which is much better than commercial Pd/C with same amount of palladium. The catalytic activities of these nanocrystals followed the order of NiPd/C > CoPd/C > CuPd/C > commercial Pd/C, due to the different synergistic effects. Our results show that these Pd-based bimetallic nanocrystals can be promising as practical catalysts for methanol oxidation reactions and other catalytic reactions in further investigations. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr00912b

  18. Platinum-palladium bimetallic nanoparticles on graphitic carbon nitride modified carbon black: A highly electroactive and durable catalyst for electrooxidation of alcohols

    NASA Astrophysics Data System (ADS)

    Qian, Huayu; Chen, Shouwen; Fu, Yongsheng; Wang, Xin

    2015-12-01

    A composite catalyst consisting of Pt-Pd bimetallic nanoparticles (NPs) and graphitic carbon nitride (g-C3N4) modified carbon black (CB) is designed and fabricated by a facile two-step approach. The resulting catalyst exhibits unprecedented high catalytic activity and excellent long-term stability for electrooxidation of alcohols (methanol, ethanol, ethylene glycol and glycerol) in alkaline media. The superior electrochemical performance of the composite catalyst is attributed to the specific characteristics of the unique nanostructure and the synergistic effects of individual components, including the complementary roles of Pt (dehydrogenation site) and Pd (removal of CO-like species), the template effect of the planar amino group of g-C3N4 for the dispersed decoration of Pt-Pd NPs, the high specific surface area of CB for the rapid diffusion of electrolyte and removal of the carbonaceous intermediates, as well as the structural stability of the support based on covalent interaction between g-C3N4 and CB for maintaining the durability of the catalytic system.

  19. Catalytic activity of bimetallic catalysts highly sensitive to the atomic composition and phase structure at the nanoscale.

    PubMed

    Shan, Shiyao; Petkov, Valeri; Prasai, Binay; Wu, Jinfang; Joseph, Pharrah; Skeete, Zakiya; Kim, Eunjoo; Mott, Derrick; Malis, Oana; Luo, Jin; Zhong, Chuan-Jian

    2015-12-01

    The ability to determine the atomic arrangement in nanoalloy catalysts and reveal the detailed structural features responsible for the catalytically active sites is essential for understanding the correlation between the atomic structure and catalytic properties, enabling the preparation of efficient nanoalloy catalysts by design. Herein we describe a study of CO oxidation over PdCu nanoalloy catalysts focusing on gaining insights into the correlation between the atomic structures and catalytic activity of nanoalloys. PdCu nanoalloys of different bimetallic compositions are synthesized as a model system and are activated by a controlled thermochemical treatment for assessing their catalytic activity. The results show that the catalytic synergy of Pd and Cu species evolves with both the bimetallic nanoalloy composition and temperature of the thermochemical treatment reaching a maximum at a Pd : Cu ratio close to 50 : 50. The nanoalloys are characterized structurally by ex situ and in situ synchrotron X-ray diffraction, including atomic pair distribution function analysis. The structural data show that, depending on the bimetallic composition and treatment temperature, PdCu nanoalloys adopt two different structure types. One features a chemically ordered, body centered cubic (B2) type alloy consisting of two interpenetrating simple cubic lattices, each occupied with Pd or Cu species alone, and the other structure type features a chemically disordered, face-centered cubic (fcc) type of alloy wherein Pd and Cu species are intermixed at random. The catalytic activity for CO oxidation is strongly influenced by the structural features. In particular, it is revealed that the prevalence of chemical disorder in nanoalloys with a Pd : Cu ratio close to 50 : 50 makes them superior catalysts for CO oxidation in comparison with the same nanoalloys of other bimetallic compositions. However, the catalytic synergy can be diminished if the Pd50Cu50 nanoalloys undergo

  20. Application of a Re-Pd bimetallic catalyst for treatment of perchlorate in waste ion-exchange regenerant brine.

    PubMed

    Liu, Jinyong; Choe, Jong Kwon; Sasnow, Zachary; Werth, Charles J; Strathmann, Timothy J

    2013-01-01

    Concentrated sodium chloride (NaCl) brines are often used to regenerate ion-exchange (IX) resins applied to treat drinking water sources contaminated with perchlorate (ClO(4)(-)), generating large volumes of contaminated waste brine. Chemical and biological processes for ClO(4)(-) reduction are often inhibited severely by high salt levels, making it difficult to recycle waste brines. Recent work demonstrated that novel rhenium-palladium bimetallic catalysts on activated carbon support (Re-Pd/C) can efficiently reduce ClO(4)(-) to chloride (Cl(-)) under acidic conditions, and here the applicability of the process for treating waste IX brines was examined. Experiments conducted in synthetic NaCl-only brine (6-12 wt%) showed higher Re-Pd/C catalyst activity than in comparable freshwater solutions, but the rate constant for ClO(4)(-) reduction measured in a real IX waste brine was found to be 65 times lower than in the synthetic NaCl brine. Through a series of experiments, co-contamination of the IX waste brine by excess NO(3)(-) (which the catalyst reduces principally to NH(4)(+)) was found to be the primary cause for deactivation of the Re-Pd/C catalyst, most likely by altering the immobilized Re component. Pre-treatment of NO(3)(-) using a different bimetallic catalyst (In-Pd/Al(2)O(3)) improved selectivity for N(2) over NH(4)(+) and enabled facile ClO(4)(-) reduction by the Re-Pd/C catalyst. Thus, sequential catalytic treatment may be a promising strategy for enabling reuse of waste IX brine containing NO(3)(-) and ClO(4)(-). PMID:23084116

  1. Low-temperature 1 3-butadiene Hydrogenation over Supported Pt/3d/gamma-Al2O3 Bimetallic Catalysts

    SciTech Connect

    W Lonergan; X Xing; R Zheng; S Qi; B Huang; J Chen

    2011-12-31

    Low-temperature 1,3-butadiene hydrogenation is used as a probe reaction to investigate the hydrogenation activity over several {gamma}-Al{sub 2}O{sub 3} supported Pt/3d (3d = Co, Ni, Cu) bimetallic catalysts. Batch and flow reactor studies are employed to quantify the kinetic activity and steady-state conversion, respectively, of each catalyst. Transmission electron microscopy (TEM) is utilized to characterize particle sizes and extended X-ray absorption fine structure (EXAFS) measurements are performed to verify the Pt-3d bimetallic bond formation. Pulse carbon monoxide chemisorption measurements are also performed to characterize the number of active sites. Additionally, density functional theory (DFT) calculations are included to determine the binding energies of 1,3-butadiene and atomic hydrogen on the corresponding model surfaces. The binding energies of the adsorbates are found to correlate with the hydrogenation activity, allowing for use of such correlation to potentially predict hydrogenation catalysts with enhanced activity based on the binding energies of the adsorbates of interest.

  2. Direct hydrogenation of biomass-derived butyric acid to n-butanol over a ruthenium-tin bimetallic catalyst.

    PubMed

    Lee, Jong-Min; Upare, Pravin P; Chang, Jong-San; Hwang, Young Kyu; Lee, Jeong Ho; Hwang, Dong Won; Hong, Do-Young; Lee, Seung Hwan; Jeong, Myung-Geun; Kim, Young Dok; Kwon, Young-Uk

    2014-11-01

    Catalytic hydrogenation of organic carboxylic acids and their esters, for example, cellulosic ethanol from fermentation of acetic acid and hydrogenation of ethyl acetate is a promising possibility for future biorefinery concepts. A hybrid conversion process based on selective hydrogenation of butyric acid combined with fermentation of glucose has been developed for producing biobutanol. ZnO-supported Ru-Sn bimetallic catalysts exhibits unprecedentedly superior performance in the vapor-phase hydrogenation of biomass-derived butyric acid to n-butanol (>98% yield) for 3500 h without deactivation. PMID:25123894

  3. The atomic structural dynamics of γ-Al2O3 supported Ir-Pt nanocluster catalysts prepared from a bimetallic molecular precursor: a study using aberration-corrected electron microscopy and X-ray absorption spectroscopy.

    PubMed

    Small, Matthew W; Sanchez, Sergio I; Menard, Laurent D; Kang, Joo H; Frenkel, Anatoly I; Nuzzo, Ralph G

    2011-03-16

    This study describes a prototypical, bimetallic heterogeneous catalyst: compositionally well-defined Ir-Pt nanoclusters with sizes in the range of 1-2 nm supported on γ-Al(2)O(3). Deposition of the molecular bimetallic cluster [Ir(3)Pt(3)(μ-CO)(3)(CO)(3)(η-C(5)Me(5))(3)] on γ-Al(2)O(3), and its subsequent reduction with hydrogen, provides highly dispersed supported bimetallic Ir-Pt nanoparticles. Using spherical aberration-corrected scanning transmission electron microscopy (C(s)-STEM) and theoretical modeling of synchrotron-based X-ray absorption spectroscopy (XAS) measurements, our studies provide unambiguous structural assignments for this model catalytic system. The atomic resolution C(s)-STEM images reveal strong and specific lattice-directed strains in the clusters that follow local bonding configurations of the γ-Al(2)O(3) support. Combined nanobeam diffraction (NBD) and high-resolution transmission electron microscopy (HRTEM) data suggest the polycrystalline γ-Al(2)O(3) support material predominantly exposes (001) and (011) surface planes (ones commensurate with the zone axis orientations frequently exhibited by the bimetallic clusters). The data reveal that the supported bimetallic clusters exhibit complex patterns of structural dynamics, ones evidencing perturbations of an underlying oblate/hemispherical cuboctahedral cluster-core geometry with cores that are enriched in Ir (a result consistent with models based on surface energetics, which favor an ambient cluster termination by Pt) due to the dynamical responses of the M-M bonding to the specifics of the adsorbate and metal-support interactions. Taken together, the data demonstrate that strong temperature-dependent charge-transfer effects occur that are likely mediated variably by the cluster-support, cluster-adsorbate, and intermetallic bonding interactions. PMID:21341654

  4. Synergy between Two Metal Catalysts: A Highly Active Silica-Supported Bimetallic W/Zr Catalyst for Metathesis of n-Decane.

    PubMed

    Samantaray, Manoja K; Dey, Raju; Kavitake, Santosh; Abou-Hamad, Edy; Bendjeriou-Sedjerari, Anissa; Hamieh, Ali; Basset, Jean-Marie

    2016-07-13

    A well-defined, silica-supported bimetallic precatalyst [≡Si-O-W(Me)5≡Si-O-Zr(Np)3] (4) has been synthesized for the first time by successively grafting two organometallic complexes [W(Me)6 (1) followed by ZrNp4 (2)] on a single silica support. Surprisingly, multiple-quantum NMR characterization demonstrates that W and Zr species are in close proximity to each other. Hydrogenation of this bimetallic catalyst at room temperature showed the easy formation of zirconium hydride, probably facilitated by tungsten hydride which was formed at this temperature. This bimetallic W/Zr hydride precatalyst proved to be more efficient (TON = 1436) than the monometallic W hydride (TON = 650) in the metathesis of n-decane at 150 °C. This synergy between Zr and W suggests that the slow step of alkane metathesis is the C-H bond activation that occurs on Zr. The produced olefin resulting from a β-H elimination undergoes easy metathesis on W. PMID:27248839

  5. Enhanced performance of the catalytic conversion of allyl alcohol to 3-hydroxypropionic acid using bimetallic gold catalysts.

    PubMed

    Falletta, Ermelinda; Della Pina, Cristina; Rossi, Michele; He, Qian; Kiely, Christopher J; Hutchings, Graham J

    2011-01-01

    One of the strategic building blocks in organic synthesis is 3-hydroxypropionic acid, which is particularly important for the manufacture of high performance polymers. However, to date, despite many attempts using both biological and chemical routes, no large scale effective process for manufacturing 3-hydroxypropionic acid has been developed. One potentially useful starting point is from allyl alcohol, as this can be obtained in principle from the dehydration of glycerol, thereby presenting a bio-renewable green pathway to this important building block. The catalytic transformation of allyl alcohol to 3-hydroxypropionic acid presents interesting challenges in catalyst design, particularly with respect to the control of selectivity among the products that can be expected, as acrylic acid, acrolein and glyceric acid can also be formed. In this paper, we present a novel eco-sustainable catalytic pathway leading to 3-hydroxypropionic acid, which highlights the outstanding potential of gold-based and bimetallic catalysts in the aerobic oxidation of allyl alcohol. PMID:22455056

  6. Selective aerobic oxidation of 1,3-propanediol to 3-hydroxypropanoic acid using hydrotalcite supported bimetallic gold nanoparticle catalyst in water

    NASA Astrophysics Data System (ADS)

    Mohammad, Mujahid; Nishimura, Shun; Ebitani, Kohki

    2015-02-01

    Selective oxidation of 1,3-propanediol (1,3-PD) to 3-hydroxypropanoic acid (3-HPA), an important industrial building block, was successfully achieved using hydrotalcite-supported bimetallic Au nanoparticle catalysts in water at 343 K under aerobic and base-free conditions. The highest yield of 42% with 73% selectivity towards 3-HPA was afforded by 1wt% Au0.8Pd0.2-PVP/HT catalyst.

  7. Aqueous Phase Glycerol Reforming by PtMo Bimetallic Nano-Particle Catalyst: Product Selectivity and Structural Characterization

    SciTech Connect

    Stach E. A.; Dietrich, P.J.; Lobo-Lapidus, R.J.; Wu, T.; Sumer, A.; Akatay, M.C.; Fingland, B.R.; Guo, N.; Dumesic, J.A.; Marshall, C.L.; Jellinek, J.; Delgass, W.N.; Ribeiro, F.H.; Miller, J.T.

    2012-03-01

    A carbon supported PtMo aqueous phase reforming catalyst for producing hydrogen from glycerol was characterized by analysis of the reaction products and pathway, TEM, XPS and XAS spectroscopy. Operando X-ray absorption spectroscopy (XAS) indicates the catalyst consists of bimetallic nano-particles with a Pt rich core and a Mo rich surface. XAS of adsorbed CO indicates that approximately 25% of the surface atoms are Pt. X-ray photoelectron spectroscopy indicates that there is unreduced and partially reduced Mo oxide (MoO{sub 3} and MoO{sub 2}), and Pt-rich PtMo bimetallic nano-particles. The average size measured by transmission electron microscopy of the fresh PtMo nano-particles is about 2 nm, which increases in size to 5 nm after 30 days of glycerol reforming at 31 bar and 503 K. The catalyst structure differs from the most energetically stable structure predicted by density functional theory (DFT) calculations for metallic Pt and Mo atoms. However, DFT indicates that for nano-particles composed of metallic Pt and Mo oxide, the Mo oxide is at the particle surface. Subsequent reduction would lead to the experimentally observed structure. The aqueous phase reforming reaction products and intermediates are consistent with both C-C and C-OH bond cleavage to generate H{sub 2}/CO{sub 2} or the side product CH{sub 4}. While the H{sub 2} selectivity at low conversion is about 75%, cleavage of C-OH bonds leads to liquid products with saturated carbon atoms. At high conversions (to gas), these will produced additional CH{sub 4} reducing the H{sub 2} yield and selectivity.

  8. Greatly improved electrochemical performance of lithium-oxygen batteries with a bimetallic platinum-copper alloy catalyst

    NASA Astrophysics Data System (ADS)

    Lee, Minwook; Hwang, Yubin; Yun, Kyung-Han; Chung, Yong-Chae

    2015-08-01

    Research on the cathode catalysts of lithium-oxygen (Li-O2) batteries is one of the most important branches to commercialize these batteries to overcome the sluggish kinetics during both the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER). In this study, a high performance catalyst based on a bimetallic Pt-Cu alloy is investigated for Li-O2 batteries using first-principles calculation. The theoretical prediction shows that the Pt-Cu alloy is much more effective than the pure Pt according to the electrochemical performance. In particular, the effectiveness of the catalytic property is maximized in the case of the PtCu (111) surface which greatly reduces the large overpotentials of the original Li-O2 batteries during the OER/ORR. It is identified for the first time that the charge overpotentials are affected mainly by the inherent surface charge character of the alloy catalyst. It is observed that the more negatively charged PtCu (111) surface can act as a weakly positively charged surface for the adsorption of Li-O intermediates and thus result in weak ionic bonding of the intermediates on the surface. As a result, the dominant factor improving the catalytic performance is clearly demonstrated, providing insight into the design of an efficient catalyst for Li-O2 battery technologies.

  9. Immobilization of ultrafine bimetallic Ni-Pt nanoparticles inside the pores of metal-organic frameworks as efficient catalysts for dehydrogenation of alkaline solution of hydrazine.

    PubMed

    Cao, Nan; Yang, Lan; Dai, Hongmei; Liu, Teng; Su, Jun; Wu, Xiaojun; Luo, Wei; Cheng, Gongzhen

    2014-10-01

    We report a facile liquid impregnation approach for immobilization of ultrafine bimetallic Ni-Pt nanoparticles (NPs) inside the pores of MIL-101. The methods of powder X-ray diffraction, N2 physisorption, X-ray photoelectron spectroscopy, transmission electron microscopy, and inductively coupled plasma-atomic emission spectroscopy were employed to characterize the NiPt@MIL-101 catalysts and further indicated the as-synthesized Ni-Pt NPs were confined in the pores of MIL-101. These as-synthesized bimetallic NiPt@MIL-101 NPs exhibit exceedingly high catalytic activity, selectivity, and durability toward hydrogen generation from alkaline solution of hydrazine. PMID:25197778

  10. Highly stable bimetallic AuIr/TiO2 catalyst: physical origin of the intrinsic stability against sintering

    NASA Astrophysics Data System (ADS)

    Marinero, Ernesto; Han, Chan Wan; Majundar, Paulami; Aguilar-Tapia, Antonio; Zanella, Rodolfo; Greeley, Jeffrey; Otarlan, Volkan

    It has been a long-lived research topic in the field of heterogeneous catalysis to find a way to stabilizing supported Au catalysts against sintering. Herein, we report highly stable AuIr bimetallic nanoparticles on TiO2 synthesized by sequential deposition-precipitation. To understand the physical origin of the high stability AuIr/TiO2 system, we have used scanning transmission electron microscopy (STEM), STEM-tomography and density functional theory (DFT) calculations. 3D structures of AuIr/TiO2 obtained by STEM-tomography indicate that AuIr nanoparticles on TiO2 have intrinsically lower free energy and less driving force for sintering than Au nanoparticles. DFT calculations on segregation behavior of AuIr slabs on TiO2 showed that the presence of Ir near the TiO2 surface increases the adhesion energy of the bimetallic slabs to the TiO2 and the attractive interactions between Ir and TiO2 lead to higher stability of the AuIr nanoparticles compared to Au nanoparticles.

  11. Highly dispersive PdCoB catalysts for dechlorination of chlorophenols.

    PubMed

    Liu, Xuchen; Wang, Xingyi

    2014-06-15

    Highly dispersive PdCoB nano-particles were prepared by precipitation-reduction with NaBH4 at 273 K. Characterization showed that the dispersion of amorphous alloy PdCoB nano-particles increased with decrease in both Pd/Co ratio and preparation temperature. The size of PdCoB-L(273) (Pd/Co ratio of 0.0005) nano-particles prepared at 273 K was 5 nm and BET specific surface area was estimated to be 177 m(2)/g, much higher than those of bimetallic catalysts reported in literature. During the hydrodechlorination of 4-chlorophenol, PdCoB catalysts were effective within pH range from 2.5 to 11. The activity of PdCoB can be promoted by the increase in B/Co ratio on the surface. PdCoB-L(273) sample presented the highest efficiency, and the reaction constants described in different terms for 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol were much higher than those obtained over PdFe in literature, probably ascribed to smaller particle sizes, less agglomerations and strong synergistic effect between Pd, Co and B species. PMID:24768961

  12. Pumice-supported Pd-Pt bimetallic catalysts: Synthesis, structural characterization, and liquid-phase hydrogenation of 1,3-cyclooctadiene

    SciTech Connect

    Deganello, G.; Duca, D.; Liotta, L.F.; Martorana, A.; Venezia, M.; Benedetti, A.; Fagherazz, G.

    1995-01-01

    A series of pumice-supported palladium-platinum bimetallic catalysts were prepared and investigated by X-ray scattering (WAXS and SAXS) and XPS techniques. An alloy Pd-Pt was formed. The less abundant metal was found to segregate to the surface. The catalysts were tested in the liquid-phase hydrogenation of 1,3-cyclooctadiene to cyclooctene, and compared with similarly prepared pumice-supported palladium and platinum catalysts and other supported Pd-Pt catalysts reported in the literature. The addition of platinum reduces the activity and the selectivity of the palladium catalysts. Differences between the activity of these pumice-supported catalysts and the activity of previously described Pd and Pd-Pt catalysts on other supports, are attributed to the presence, in the latter, of diffusional processes. 50 refs., 4 figs. 2 tabs.

  13. Dispersed catalysts for co-processing and coal liquefaction

    SciTech Connect

    Bockrath, B.; Parfitt, D.; Miller, R.

    1995-12-31

    The basic goal is to improve dispersed catalysts employed in the production of clean fuels from low value hydrocarbons. The immediate objective is to determine how the properties of the catalysts may be altered to match the demands placed on them by the properties of the feedstock, the qualities of the desired end products, and the economic constraints put upon the process. Several interrelated areas of the application of dispersed catalysts to co-processing and coal conversion are under investigation. The first involves control of the selectivity of MoS{sub 2} catalysts for HDN, HDS, and hydrogenation of aromatics. A second area of research is the development and use of methods to evaluate dispersed catalysts by means of activity and selectivity tests. A micro-flow reactor has been developed for determining intrinsic reactivities using model compounds, and will be used to compare catalysts prepared in different ways. Micro-autoclaves will also be used to develop data in batch experiments at higher partial pressures of hydrogen. The third area under investigation concerns hydrogen spillover reactions between MoS{sub 2} catalysts and carbonaceous supports. Preliminary results obtained by monitoring H{sub 2}/D{sub 2} exchange reactions with a pulse-flow microreactor indicate the presence of spillover between MoS{sub 2} and a graphitic carbon. A more complete study will be made at a later stage of the project. Accomplishments and conclusions are discussed.

  14. Photochemical route for synthesizing atomically dispersed palladium catalysts.

    PubMed

    Liu, Pengxin; Zhao, Yun; Qin, Ruixuan; Mo, Shiguang; Chen, Guangxu; Gu, Lin; Chevrier, Daniel M; Zhang, Peng; Guo, Qing; Zang, Dandan; Wu, Binghui; Fu, Gang; Zheng, Nanfeng

    2016-05-13

    Atomically dispersed noble metal catalysts often exhibit high catalytic performances, but the metal loading density must be kept low (usually below 0.5%) to avoid the formation of metal nanoparticles through sintering. We report a photochemical strategy to fabricate a stable atomically dispersed palladium-titanium oxide catalyst (Pd1/TiO2) on ethylene glycolate (EG)-stabilized ultrathin TiO2 nanosheets containing Pd up to 1.5%. The Pd1/TiO2 catalyst exhibited high catalytic activity in hydrogenation of C=C bonds, exceeding that of surface Pd atoms on commercial Pd catalysts by a factor of 9. No decay in the activity was observed for 20 cycles. More important, the Pd1/TiO2-EG system could activate H2 in a heterolytic pathway, leading to a catalytic enhancement in hydrogenation of aldehydes by a factor of more than 55. PMID:27174982

  15. Selectivity, activity, and metal-support interactions of Rh bimetallic catalysts. Progress report, 15 November 1981-15 August 1982

    SciTech Connect

    Haller, G L

    1982-08-01

    We report on a detailed investigation of the effect of TiO/sub 2/ support on Rh-Ag interaction as exhibited in catalytic activity. The temporal evolution of activity over Rh-Ag/TiO/sub 2/ for ethane hydrogenolysis and hydrogen chemisorption as a function of temperature, Ag to Rh ratio, the Rh particle size, Rh loading, and ambient gas were studied. Preliminary extended x-ray absorption fine structure (EXAFS) analysis of Rh/TiO/sub 2/ catalysts indicate that 100% exposed (dispersed) catalyst prepared by ion exchange may be atomically dispersed after low temperature reduction. 7 figures, 1 table.

  16. Homogeneously dispersed multimetal oxygen-evolving catalysts.

    PubMed

    Zhang, Bo; Zheng, Xueli; Voznyy, Oleksandr; Comin, Riccardo; Bajdich, Michal; García-Melchor, Max; Han, Lili; Xu, Jixian; Liu, Min; Zheng, Lirong; García de Arquer, F Pelayo; Dinh, Cao Thang; Fan, Fengjia; Yuan, Mingjian; Yassitepe, Emre; Chen, Ning; Regier, Tom; Liu, Pengfei; Li, Yuhang; De Luna, Phil; Janmohamed, Alyf; Xin, Huolin L; Yang, Huagui; Vojvodic, Aleksandra; Sargent, Edward H

    2016-04-15

    Earth-abundant first-row (3d) transition metal-based catalysts have been developed for the oxygen-evolution reaction (OER); however, they operate at overpotentials substantially above thermodynamic requirements. Density functional theory suggested that non-3d high-valency metals such as tungsten can modulate 3d metal oxides, providing near-optimal adsorption energies for OER intermediates. We developed a room-temperature synthesis to produce gelled oxyhydroxides materials with an atomically homogeneous metal distribution. These gelled FeCoW oxyhydroxides exhibit the lowest overpotential (191 millivolts) reported at 10 milliamperes per square centimeter in alkaline electrolyte. The catalyst shows no evidence of degradation after more than 500 hours of operation. X-ray absorption and computational studies reveal a synergistic interplay between tungsten, iron, and cobalt in producing a favorable local coordination environment and electronic structure that enhance the energetics for OER. PMID:27013427

  17. Highly Dispersed Alloy Catalyst for Durability

    SciTech Connect

    Vivek S. Murthi; Izzo, Elise; Bi, Wu; Guerrero, Sandra; Protsailo, Lesia

    2013-01-08

    Achieving DOE's stated 5000-hr durability goal for light-duty vehicles by 2015 will require MEAs with characteristics that are beyond the current state of the art. Significant effort was placed on developing advanced durable cathode catalysts to arrive at the best possible electrode for high performance and durability, as well as developing manufacturing processes that yield significant cost benefit. Accordingly, the overall goal of this project was to develop and construct advanced MEAs that will improve performance and durability while reducing the cost of PEMFC stacks. The project, led by UTC Power, focused on developing new catalysts/supports and integrating them with existing materials (membranes and gas diffusion layers (GDLs)) using state-of-the-art fabrication methods capable of meeting the durability requirements essential for automotive applications. Specifically, the project work aimed to lower platinum group metals (PGM) loading while increasing performance and durability. Appropriate catalysts and MEA configuration were down-selected that protects the membrane, and the layers were tailored to optimize the movements of reactants and product water through the cell to maximize performance while maintaining durability.

  18. Ultrasound enhanced heterogeneous activation of peroxydisulfate by bimetallic Fe-Co/GAC catalyst for the degradation of Acid Orange 7 in water.

    PubMed

    Cai, Chun; Wang, Liguo; Gao, Hong; Hou, Liwei; Zhang, Hui

    2014-06-01

    Bimetallic Fe-Co/GAC (granular activated carbon) was prepared and used as heterogeneous catalyst in the ultrasound enhanced heterogeneous activation of peroxydisulfate (PS, S2O(2-)8) process. The effect of initial pH, PS concentration, catalyst addition and stirring rate on the decolorization of Acid Orange 7 (AO7) was investigated. The results showed that the decolorization efficiency increased with an increase in PS concentration from 0.3 to 0.5 g/L and an increase in catalyst amount from 0.5 to 0.8 g/L. But further increase in PS concentration and catalyst addition would result in an unpronounced increase in decolorization efficiency. In the range of 300 to 900 r/min, stirring rate had little effect on AO7 decolorization. The catalyst stability was evaluated by measuring decolorization efficiency for four successive cycles. PMID:25079835

  19. Synthesis of supported bimetallic nanoparticles with controlled size and composition distributions for active site elucidation

    SciTech Connect

    Hakim, Sikander H.; Sener, Canan; Alba Rubio, Ana C.; Gostanian, Thomas M.; O'neill, Brandon J; Ribeiro, Fabio H.; Miller, Jeffrey T.; Dumesic, James A

    2015-08-01

    Elucidation of active sites in supported bimetallic catalysts is complicated by the high level of dispersity in the nanoparticle size and composition that is inherent in conventional methods of catalyst preparation. We present a synthesis strategy that leads to highly dispersed, bimetallic nanoparticles with uniform particle size and composition by means of controlled surface reactions. We demonstrate the synthesis of three systems, RhMo, PtMo, and RhRe, consisting of a highly reducible metal with an oxophilic promoter. These catalysts are characterized by FTIR, CO chemisorption, STEM/EDS, TPR, and XAS analysis. The catalytic properties of these bimetallic nanoparticles were probed for the selective CO hydrogenolysis of (hydroxymethyl)tetrahydropyran to produce 1,6 hexanediol. Based on the characterization results and reactivity trends, the active sites in the hydrogenolysis reaction are identified to be small ensembles of the more noble metal (Rh, Pt) adjacent to highly reduced moieties of the more oxophilic metal (Mo, Re).

  20. Effect of dispersing agent in heating process for high dispersion of coal liquefaction catalyst

    SciTech Connect

    Okada, Y.; Haneda, M.; Inokuchi, K.; Aihara, Y.; Imada, K.; Kai, T.; Sakaki, T.; Shibata, M.

    1999-07-01

    This work deals with one proposal concerning the improvement of catalytic activity on coal liquefaction. It is known that pyrite (FeS{sub 2}) transform into pyrrhotite (Fe{sub 1{minus}x}S) and aggregate at the heating process on coal liquefaction. The aggregation of liquefaction catalyst decreases the specific surface area, and causes the decline in catalytic activity. The authors investigated the effects of dispersing agent on the morphological change and the dispersing state of liquefaction catalyst at the rapid heating process. For the liquefaction tests with added dispersing agent, the product yields were compared with the results of other tests.

  1. Selective Oxidation of 1,6-Hexanediol to 6-Hydroxycaproic Acid over Reusable Hydrotalcite-Supported Au-Pd Bimetallic Catalysts.

    PubMed

    Tuteja, Jaya; Nishimura, Shun; Choudhary, Hemant; Ebitani, Kohki

    2015-06-01

    Selective oxidation of 1,6-hexanediol into 6-hydroxycaproic acid was achieved over hydrotalcite-supported Au-Pd bimetallic nanoparticles as heterogeneous catalyst using aqueous H2 O2 . N,N-dimethyldodecylamine N-oxide (DDAO) was used as an efficient capping agent. Spectroscopic analyses by UV/Vis, TEM, XPS, and X-ray absorption spectroscopy suggested that interactions between gold and palladium atoms are responsible for the high activity of the reusable Au40 Pd60 -DDAO/HT catalyst. PMID:25990616

  2. Bimetallic catalysts for CO.sub.2 hydrogenation and H.sub.2 generation from formic acid and/or salts thereof

    DOEpatents

    Hull, Jonathan F.; Himeda, Yuichiro; Fujita, Etsuko; Muckeman, James T.

    2015-08-04

    The invention relates to a ligand that may be used to create a catalyst including a coordination complex is formed by the addition of two metals; Cp, Cp* or an unsubstituted or substituted .pi.-arene; and two coordinating solvent species or solvent molecules. The bimetallic catalyst may be used in the hydrogenation of CO.sub.2 to form formic acid and/or salts thereof, and in the dehydrogenation of formic acid and/or salts thereof to form H.sub.2 and CO.sub.2.

  3. Homogeneously dispersed, multimetal oxygen-evolving catalysts

    DOE PAGESBeta

    Zhang, Bo; Zheng, Xueli; Voznyy, Oleksandr; Comin, Riccardo; Bajdich, Michal; Garcia-Melchor, Max; Han, Lili; Xu, Jixian; Liu, Min; Zheng, Lirong; et al

    2016-03-24

    Earth-abundant first-row (3d) transition-metal-based catalysts have been developed for the oxygen-evolution reaction (OER); however, they operate at overpotentials significantly above thermodynamic requirements. Density functional theory suggested that non-3d high-valency metals such as tungsten can modulate 3d metal oxides, providing near-optimal adsorption energies for OER intermediates. We developed a room-temperature synthesis to produce gelled oxy-hydroxide materials with an atomically homogeneous metal distribution. These gelled FeCoW oxy-hydroxide exhibits the lowest overpotential (191 mV) reported at 10 mA per square centimeter in alkaline electrolyte. Here, the catalyst shows no evidence of degradation following more than 500 hours of operation. X-ray absorption and computationalmore » studies reveal a synergistic interplay between W, Fe and Co in producing a favorable local coordination environment and electronic structure that enhance the energetics for OER.« less

  4. Molecular Level Control Through Dual Site Participation Using Bimetallic Catalysts - Final Report

    SciTech Connect

    d'Itri, Julie, L.; Kovalchuk, Vladimir, I.

    2010-02-08

    The overall goal of this research program was to explore the hypothesis that it is possible to design a bimetallic surface such that each metal catalyzes different elementary reaction steps in an overall reaction pathway. A corollary to this hypothesis is that the different ensemble size requirements for an elementary reaction step can be used to force an elementary reaction step to occur on only one of the metals. The research program involved a combination of materials synthesis, chemical kinetics experiments, spectroscopic studies and computational investigations. The major outcome of this research program was the development and dissemination of the Dual Site Model, for which chlorocarbon reactions in the presence of hydrogen were used as model systems.

  5. The Effects of Oxide Supports on the Low Temperature Hydrogenation Activity of Acetone over Pt/Ni Bimetallic Catalysts on SiO2 gamma-Al2O3 and TiO2

    SciTech Connect

    S Qi; B Cheney; R Zheng; W Lonergan; W Yu; J Chen

    2011-12-31

    Low temperature (308 K) hydrogenation of acetone was used as a probe reaction to investigate the support effect on the hydrogenation activity of Pt/Ni bimetallic catalysts supported on TiO{sub 2}, SiO{sub 2} and {gamma}-Al{sub 2}O{sub 3}. The oxide supports significantly affected the catalytic properties of Pt/Ni catalysts, in which Pt/Ni/SiO2 bimetallic catalysts exhibited significantly higher activity than the other two bimetallic catalysts. TEM measurements revealed that the three supported Pt/Ni bimetallic catalysts have similar particle size distribution, while CO chemisorption measurements showed very different chemisorption capacity. Extended X-Ray absorption fine structure (EXAFS) measurements of the Pt L{sub III}-edge indicated that Pt atoms were fully reduced and the Pt-Ni bimetallic bonds were formed on all three catalysts. The extent of Pt-Ni bond formation followed the trend of SiO{sub 2} > {gamma}-Al{sub 2}O{sub 3} > TiO{sub 2}, which correlated very well with the hydrogenation activity.

  6. Driving the Oxygen Evolution Reaction by Nonlinear Cooperativity in Bimetallic Coordination Catalysts.

    PubMed

    Wurster, Benjamin; Grumelli, Doris; Hötger, Diana; Gutzler, Rico; Kern, Klaus

    2016-03-23

    Developing efficient catalysts for electrolysis, in particular for the oxygen evolution in the anodic half cell reaction, is an important challenge in energy conversion technologies. By taking inspiration from the catalytic properties of single-atom catalysts and metallo-proteins, we exploit the potential of metal-organic networks as electrocatalysts in the oxygen evolution reaction (OER). A dramatic enhancement of the catalytic activity toward the production of oxygen by nearly 2 orders of magnitude is demonstrated for novel heterobimetallic organic catalysts compared to metallo-porphyrins. Using a supramolecular approach we deliberately place single iron and cobalt atoms in either of two different coordination environments and observe a highly nonlinear increase in the catalytic activity depending on the coordination spheres of Fe and Co. Catalysis sets in at about 300 mV overpotential with high turnover frequencies that outperform other metal-organic catalysts like the prototypical hangman porphyrins. PMID:26937997

  7. Use of dispersed catalysts for direct coal liquefaction

    SciTech Connect

    Hirschon, A.S.; Kim, S.; Wilson, R.B.; Ghaly, O.

    1996-12-31

    With dwindling supplies of petroleum products, efforts to utilize alternative energy feedstocks such as coal, is essential. Several areas in coal conversion technology have been identified that, if improved, could make coal liquefaction more cost competitive with petroleum. The objectives of this project are to address possible improvements in the economics by utilizing low-rank coals, new precursors to dispersed catalysts, and processing variations such as using syngas atmospheres. The purpose of the dispersed catalysts is to better control retrogressive reactions and avoid char formation, while the purpose of the carbon monoxide atmosphere is to improve the economics by simplifying or totally eliminating a separate water-gas-shift step, and perhaps help remove oxygen in the product slate. These possible improvements are being examined and evaluated for potential use in a 2-stage liquefaction process with the goal of converting coal to distillable liquids at a cost competitive to petroleum of $25/bbl. To evaluate our catalysts and process conditions, we used three types of laboratory-scale operations. In the first operation, we compared the reaction chemistry of various ranks of coals and catalysts in synthetic solvents such as hexadecane. This method allowed us to better compare our catalysts without the complications of solvent initiated chemistry. Once the catalysts were tested in this manner, they were examined for the conversions of a Black Thunder subbituminous coal using a recycle vehicle derived from the same coal as the solvent. Finally, we upgraded selected first-stage conversion products using a conventional hydrotreating catalyst to compare with recent results in two-stage coal liquefaction development. The results were evaluated for economic feasibility through a subcontract with Bechtel Corp.

  8. Carbon-Supported bimetallic Pd-Fe catalysts for vapor-phase hydrodeoxygenation of guaiacol

    SciTech Connect

    Sun, Junming; Karim, Ayman M.; Zhang, He; Kovarik, Libor; Li, Xiaohong S.; Hensley, Alyssa; McEwen, Jean-Sabin; Wang, Yong

    2013-10-01

    Abstract Carbon supported metal catalysts (Cu/C, Fe/C, Pd/C, Pt/C, PdFe/C and Ru/C) have been prepared, characterized and tested for vapor-phase hydrodeoxygenation (HDO) of guaiacol (GUA) at atmospheric pressure. Phenol was the major intermediate on all catalysts. Over the noble metal catalysts saturation of the aromatic ring was the major pathway observed at low temperature (250 °C), forming predominantly cyclohexanone and cyclohexanol. Substantial ring opening reaction was observed on Pt/C and Ru/C at higher reaction temperatures (e.g., 350 °C). Base metal catalysts, especially Fe/C, were found to exhibit high HDO activity without ring-saturation or ring-opening with the main products being benzene, phenol along with small amounts of cresol, toluene and trimethylbenzene (TMB). A substantial enhancement in HDO activity was observed on the PdFe/C catalysts. Compared with Fe/C, the yield to oxygen-free aromatic products (i.e., benzene/toluene/TMB) on PdFe/C increased by a factor of four at 350 °C, and by approximately a factor of two (83.2% versus 43.3%) at 450 °C. The enhanced activity of PdFe/C is attributed to the formation of PdFe alloy as evidenced by STEM, EDS and TPR.

  9. Method of making maximally dispersed heterogeneous catalysts

    DOEpatents

    Jennison, Dwight R.

    2005-11-15

    A method of making a catalyst with monolayer or sub-monolayer metal by controlling the wetting characteristics on the support surface and increasing the adhesion between the catalytic metal and an oxide layer. There are two methods that have been demonstrated by experiment and supported by theory. In the first method, which is useful for noble metals as well as others, a negatively-charged species is introduced to the surface of a support in sub-ML coverage. The layer-by-layer growth of metal deposited onto the oxide surface is promoted because the adhesion strength of the metal-oxide interface is increased. This method can also be used to achieve nanoislands of metal upon sub-ML deposition. The negatively-charged species can either be deposited onto the oxide surface or a compound can be deposited that dissociates on, or reacts with, the surface to form the negatively-charged species. The deposited metal adatoms can thereby bond laterally to the negatively-charged species as well as vertically to the oxide surface. Thus the negatively-charged species serve as anchors for the metal. In the second method, a chemical reaction that occurs when most metals are deposited on a fully hydroxylated oxide surface is used to create cationic metal species that bind strongly both to the substrate and to metallic metal atoms. These are incorporated into the top layer of the substrate and bind strongly both to the substrate and to metallic metal atoms. In this case, these oxidized metal atoms serve as the anchors. Here, as in the previous method, nanoislands of catalytic metal can be achieved to increase catalytic activity, or monolayers or bilayers of reactive metal can also be made.

  10. Glucose microfluidic fuel cell based on silver bimetallic selective catalysts for on-chip applications

    NASA Astrophysics Data System (ADS)

    Cuevas-Muñiz, F. M.; Guerra-Balcázar, M.; Esquivel, J. P.; Sabaté, N.; Arriaga, L. G.; Ledesma-García, J.

    2012-10-01

    A glucose microfluidic fuel cell with outstanding performance at zero flow condition is presented. Polarization tests showed that bimetallic materials based in silver (AuAg/C as anode, PtAg/C as cathode) exhibit tolerance to byproducts and crossover effect. This allowed achieving one of the highest power densities reported for glucose fuel cells, up to a value of 630 μW cm-2 using two separated laminar flows of reactants. Furthermore, the tolerance to crossover effect caused by the selectivity of PtAg/C to oxygen reduction reaction in presence of glucose permitted using a single flow containing a mixture of glucose/oxygen, yielding a performance as high as 270 μW cm-2. Microfluidic fuel cell was further evaluated with a simulated body fluid solution that contained salts commonly present in the human blood plasma, reaching a power of 240 μW cm-2 at zero flow. These results envisage the incorporation of this fuel cell as a portable power source in Lab-on-a-Chip devices without the need of external pumps.

  11. Method for dispersing catalyst onto particulate material and product thereof

    DOEpatents

    Utz, Bruce R.; Cugini, Anthony V.

    1992-01-01

    A method for dispersing finely divided catalyst precursors onto the surface of coal or other particulate material includes the steps of forming a wet paste mixture of the particulate material and a liquid solution containing a dissolved transition metal salt, for instance a solution of ferric nitrate. The wet paste mixture is in a state of incipient wetness with all of this solution adsorbed onto the surfaces of the particulate material without the presence of free moisture. On adding a precipitating agent such as ammonia, a catalyst precursor such as hydrated iron oxide is deposited on the surfaces of the coal. The catalyst is activated by converting it to the sulfide form for the hydrogenation or direct liquefaction of the coal.

  12. Formation and characterization of highly-dispersed metal colloid catalysts

    SciTech Connect

    Wilcoxon, J.; Martino, A.; Nigrey, P.; Sylwester, A.; Klavetter, E.; Baughman, R.

    1991-01-01

    The objective of this research is to explore the feasibility of using small metal colloids, in microemulsions, as catalysts. The product of this work will be a new concept for tailoring highly dispersed materials to specific catalytic reactions. The knowledge gained from the proposed research will be broadly applicable to variety of reactions, including hydrogenation, synthesis gas conversion, and hydrogen conversion. To achieve this objective, a plan has been formulated to prepare and characterize catalyst particles in organic solvents and to explore the use of catalyst particles. In this paper, we will discuss the use of inverse micelles to solubilize significant quantities of metal compounds in hydrocarbon solvents and their reduction, decomposition, and sulfidation to give colloidal catalytic materials. We will also discuss in detail the characterization of these materials, present preliminary results for the catalytic hydropyrolysis of coals, and discuss the results of our evaluation of selected metal colloids in catalytic hydrogenation of pyrene. 9 refs., 3 tabs.

  13. Surface Modified Coals for Enhanced Catalyst Dispersion and Liquefaction

    SciTech Connect

    Yaw D. Yeboah

    1998-12-04

    The aim of this study is to enhance catalyst loading and dispersion in coal for improved liquefaction by preadsorption of surfactants and catalysts on to the coal. During this reporting period, liquefaction experiments were conducted with the raw coal and catalyst loaded samples. Pretreatment of the coal and catalyst-loaded samples were done using the surfactants presented in previous reports. Liquefaction samples were tested using 6.6 g of solvent, 3.3 g coal, 6.9 MPa ambient hydrogen pressure, 425 0 C and 30 minutes. The liquid and solid products were removed from the reactor using tetrahydrofuran (THF). Coal conversions were calculated based on THF and heptane solubility. The results showed that in the absence of a catalyst, 33.8% heptane solubles was obtained with the parent coal compared to 27.8% and 27.3% with the SDS and DDAB surfactants. The presence of molybdenum, as expected, resulted in enhanced heptane solubles with or without surfactants. In the absence of surfactants, 50% heptane solubles was obtained compared to 40-47% with surfactants. Thus, it appears that pretreatment, unexpectedly, had a negative effect on liquefaction activity. It is unclear if the observed differences in results are significant. Clearly, additional experiments are needed before any firm deductions and conclusions can be drawn from the results.

  14. Catalyst dispersion and activity under conditions of temperature- staged liquefaction

    SciTech Connect

    Davis, A.; Schobert, H.H.; Mitchell, G.D.; Artok, L.

    1991-09-01

    The general objectives of this research are (1) to investigate the use of highly dispersed catalysts for the pretreatment of coal by mild hydrogenation, (2) to identify the active forms of the catalysts under reaction conditions and (3) to clarify the mechanisms of catalysis. The ultimate objective is to ascertain if mild catalytic hydrogenation resulting in very limited or no coal solubilization is an advantageous pretreatment for the transformation of coal into transportable fuels. The experimental program will focus upon the development of effective methods of impregnating coal with catalysts, evaluating the conditions under which the catalysts are most active and establishing the relative impact of improved impregnation on conversion and product distributions obtained from coal hydrogenation. Liquefaction experiments of solvent-treated and untreated Blind Canyon (DECS-6) and Texas lignite (DECS-1) have been performed using ammonium tetrathiomolybdate (ATTM) and bis (dicarbonylcyclopentadienyl) iron (CPI) as catalyst precursors using temperature-staged conditions (275{degrees}C, 30 min; 425{degrees}C, 30 min). Solid state {sup 13}C NMR analysis was carried out for each coal and for selected residues. 12 refs., 14 figs., 9 tabs.

  15. Low-Temperature 1,3-Butadiene Hydrogenation over Supported Pt/3d/gamma-Al2O3 Bimetallic Catalysts

    SciTech Connect

    Lonergan, William W; Xing, X; Zheng, Renyang; Qi, Suitao; Huang, B; Chen, Jingguang

    2011-02-02

    Low-temperature 1,3-butadiene hydrogenation is used as a probe reaction to investigate the hydrogenation activity over several γ-Al{sub 2}O{sub 3} supported Pt/3d (3d = Co, Ni, Cu) bimetallic catalysts. Batch and flow reactor studies are employed to quantify the kinetic activity and steady-state conversion, respectively, of each catalyst. Transmission electron microscopy (TEM) is utilized to characterize particle sizes and extended X-ray absorption fine structure (EXAFS) measurements are performed to verify the Pt–3d bimetallic bond formation. Pulse carbon monoxide chemisorption measurements are also performed to characterize the number of active sites. Additionally, density functional theory (DFT) calculations are included to determine the binding energies of 1,3-butadiene and atomic hydrogen on the corresponding model surfaces. The binding energies of the adsorbates are found to correlate with the hydrogenation activity, allowing for use of such correlation to potentially predict hydrogenation catalysts with enhanced activity based on the binding energies of the adsorbates of interest.

  16. Oxidation of ethyl acetate by a high performance nanostructure (Ni, Mn)-Ag/ZSM-5 bimetallic catalysts and development of an artificial neural networks predictive modeling.

    PubMed

    Jodaei, Azadeh; Salari, Darush; Niaei, Ali; Khatamian, Masumeh; Hosseini, Seyed Ali

    2011-01-01

    The catalytic oxidation of ethyl acetate in low concentration was investigated over mono-metallic Ag/ZSM5 and bimetallic (Ni, Mn)-Ag/ZSM-5 catalysts. Catalytic studies were carried out in a catalytic fixed bed reactor under atmospheric pressure. The sequence of catalytic activity was as follows: Ni-Ag-ZSM-5 > Mn-Ag-ZSM-5 > Ag-ZSM-5 > H-ZSM-5. The catalysts were characterized by ICP-AES, X-ray diffraction (XRD), low temperature nitrogen adsorption, NH(3)-TPD, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and diffuse reflectance UV-vis spectra (UV-vis). An artificial neural networks (ANN) model was developed to predict the performance of catalytic oxidation process over bimetallic Ni-Ag/ZSM-5 catalyst based on experimental data. For this purpose the standard feed forward back propagation algorithm was employed to train the model by using laboratory experimental data. A good agreement was resulted between experimental results and those obtained by ANN. Following order for variables effects on conversion yield of ethyl acetate was predicted by ANN model: reaction temperature (32.99%) > Ag loading (27.38%) > initial ethyl acetate concentration (23.58%) > Ni loading (16.05%). PMID:21104495

  17. Synthesis of triazoles from nonactivated terminal alkynes via the three-component coupling reaction using a Pd(0)-Cu(I) bimetallic catalyst.

    PubMed

    Kamijo, Shin; Jin, Tienan; Huo, Zhibao; Yamamoto, Yoshinori

    2003-07-01

    The synthesis of triazoles via the three-component coupling reaction of unactivated terminal alkynes, allyl carbonate, and trimethylsiyl azide under the Pd(0)-Cu(I) bimetallic catalyst is developed. The reaction most probably proceeds through the formation of a pi-allylpalladium azide complex and a copper-acetylide followed by a successive [3 + 2] cycloaddition. The deallylation of the resulting allyltriazoles proceeds very easily by the Ru-catalyzed isomerization followed by the ozonolysis of the resulting propenyltriazoles to give the triazoles in high yields. PMID:12822981

  18. From First Principles Design to Realization of Bimetallic Catalysts for Enhanced Selectivity

    SciTech Connect

    Lobo, Raul F.; Crooks, Richard M.; Mavrikakis, Manos

    2014-04-08

    “Catalysis by design” has been a dream for decades. To specify the composition and structure of matter to effect a desired catalytic transformation with desired and predicted rate and selectivity remains a monumental challenge, especially in heterogeneous catalysis. Our research thrusts have been chosen not only for their practical and scientific relevance, e.g. for more efficient and sustainable chemicals and fuels production, but also because they provide a foundation for developing and exploring broadly applicable principles and strategies for catalyst design.

  19. SURFACE-MODIFIED COALS FOR ENHANCED CATALYST DISPERSION AND LIQUEFACTION

    SciTech Connect

    Dr. Yaw D. Yeboah

    1999-09-01

    This is the final report of the Department of Energy Sponsored project DE-FGF22-95PC95229 entitled, surface modified coals for enhanced catalyst dispersion and liquefaction. The aims of the study were to enhance catalyst loading and dispersion in coal for improved liquefaction by preadsorption of surfactants and catalysts on the coal and to train and educate minority scientists in catalysts and separation science. Illinois No. 6 Coal (DEC-24) was selected for the study. The surfactants investigated included dodecyl dimethyl ethyl ammonium bromide (DDAB), a cationic surfactant, sodium dodecyl sulfate, an anionic surfactant, and Triton x-100, a neutral surfactant. Ammonium molybdate tetrahydrate was used as the molybdenum catalyst precursor. Zeta potential, BET, FTIR, AFM, UV-Vis and luminescence intensity measurements were undertaken to assess the surface properties and the liquefaction activities of the coal. The parent coal had a net negative surface charge over the pH range 2-12. However, in the presence of DDAB the negativity of the surface charge decreased. At higher concentrations of DDAB, a positive surface charge resulted. In contrast to the effect of DDAB, the zeta potential of the coal became more negative than the parent coal in the presence of SDS. Adsorption of Triton reduced the net negative charge density of the coal samples. The measured surface area of the coal surface was about 30 m{sup 2}/g compared to 77m{sup 2}/g after being washed with deionized water. Addition of the surfactants decreased the surface area of the samples. Adsorption of the molybdenum catalyst increased the surface area of the coal sample. The adsorption of molybdenum on the coal was significantly promoted by preadsorption of DDAB and SDS. Molybdenum adsorption showed that, over a wide range of concentrations and pH values, the DDAB treated coal adsorbed a higher amount of molybdenum than the samples treated with SDS. The infrared spectroscopy (FTIR) and the atomic force

  20. The role of metals and influence of oxygen on ceria supported copper-palladium bimetallic catalysts for the oxygen-assisted water-gas shift reaction

    NASA Astrophysics Data System (ADS)

    Fox, Elise Bickford

    This study was focused to investigate the roles of Cu and Pd in CuPd/CeO 2 bimetallic catalysts containing 30 wt% Cu and 1 wt% Pd used in the oxygen-assisted water-gas shift (OWGS) reaction employing combined bulk and surface characterization techniques such as X-ray diffraction (XRD), temperature programmed reduction (TPR), CO chemisorption, and in-situ X-ray photoelectron spectroscopy (XPS). The role of oxygen in aiding the water-gas shift reaction was also studied to determine an overall mechanism for the water-gas shift reaction. The catalytic activity for CO conversion and the stability of catalyst during on-stream operation increased upon adding Pd to Cu/CeO2 monometallic catalysts, especially when the OWLS reaction was performed under low temperatures. In-situ XPS studies of reduced catalysts showed the existence of Cu and Pd in their metallic states. The spectra also showed a shift in Cu 2p peaks toward lower binding energy with concommitant shift in the Pd 3d peaks toward higher BE. Addition of Pd decreased the surface Cu concentration while the concentration of Pd remained unaltered. The improved catalytic activity and stability of CuPd/CeO2 bimetallic catalyst was attributed to the Cu-Pd interaction. When the catalyst series was reduced in-situ under UHV conditions in the XPS chamber in order to better understand the metal-support interactions, it was found that the addition of 1%Pd to the Cu/CeO2 catalyst would greatly improve the reduction properties of the Cu and Ce under UHV conditions. When compared with results from the oxygen-assisted water-gas-shift reaction, it was found that the increased reduction from the addition of Pd aided in the reaction. When reaction kinetics of the water-gas shift and the oxygen-assisted water-gas shift reaction were examined, it was found that the addition of a small amount of air improved the overall reaction kinetics. In general, the activation energies decreased for the catalyst series when air was added to the

  1. Surface modified coals for enhanced catalyst dispersion and liquefaction

    SciTech Connect

    Dr. Yaw D. Yeboah

    1998-10-29

    The aim of the study is to enhance catalyst loading and dispersion in coal for improved liquefaction by preadsorption of surfactants and catalysts on to the coal. During this reporting period, zeta potential measurements were conducted to assess the surface charge on the raw, pretreated and catalyzed coal samples. The surface area, transmission spectroscopy and luminescence intensity of the raw coal and pretreated coal samples were also determined to assess the quality of the coal surface. Across a broad range of pH values, the raw coal had an overall negative charge. Coal treated with anionic surfactant SDS maintained an overall net negative surface negative charge. The interaction between the coal and cationic surfactant DDAB caused the opposite effect resulting in a more positive coal surface charge. Although one would have expected little or no effect of the neutral surfactant Triton X-100, there appears to be some difference in the results of the raw coal and the coal treated with Triton X-100. The authors believe that the Triton not only binds to the nonpolar sites but also has a strong affinity for the polar sites through electrostatic bonding and interaction between the hydrophobic tails. The addition of molybdenum to coal pretreated with DDAB caused a reduction in the positive charge of the coal surface probably due to possible ionic interaction between the coal surface, the surfactant and the catalyst. The adsorption isotherm of the coal was characteristic of isotherms for porous samples and the surface area of the coal increased from 30 m{sup 2}/g to 77 m{sup 2}/g when washed with deionized water. This suggests coal washing may be one method of increasing the surface area for surfactant adsorption. Although the transmission measurements provided valuable information about the coal it resulted in little information on the amount of adsorbed Triton. However, the maximum solid-liquid ratio for optimum surfactant loading of Triton X-100 was determined via

  2. Bimetallic Ni-Rh catalysts with low amounts of Rh for the steam and autothermal reforming of n-butane for fuel-cell applications.

    SciTech Connect

    Ferrandon, M.; Kropf, A. J.; Krause, T.; Chemical Sciences and Engineering Division

    2010-05-15

    Mono-metallic nickel and rhodium catalysts and bimetallic Ni-Rh catalysts supported on La-Al{sub 2}O{sub 3}, CeZrO{sub 2} and CeMgOx were prepared and evaluated for catalyzing the steam and autothermal reforming of n-butane. The binary Ni-Rh supported on La-Al{sub 2}O{sub 3} catalysts with low weight loading of rhodium exhibited higher H{sub 2} yields than Ni or Rh alone. The Ni-Rh/CeZrO{sub 2} catalyst exhibited higher performance and no coke formation, compared to the same metals on other supports. A NiAl{sub 2}O{sub 4} spinel phase was obtained on all Ni and Ni-Rh catalysts supported on La-Al{sub 2}O{sub 3}. The presence of rhodium stabilized the spinel phase as well as NiOx species upon reforming while Ni alone was mostly reduced into metallic species. Extended X-ray absorption fine-structure analysis showed evidence of Ni-Rh alloy during preparation and even further after an accelerated aging at 900C in a H{sub 2}/H{sub 2}O atmosphere.

  3. Tuning selectivity of electrochemical reactions by atomically dispersed platinum catalyst

    PubMed Central

    Choi, Chang Hyuck; Kim, Minho; Kwon, Han Chang; Cho, Sung June; Yun, Seongho; Kim, Hee-Tak; Mayrhofer, Karl J. J.; Kim, Hyungjun; Choi, Minkee

    2016-01-01

    Maximum atom efficiency as well as distinct chemoselectivity is expected for electrocatalysis on atomically dispersed (or single site) metal centres, but its realization remains challenging so far, because carbon, as the most widely used electrocatalyst support, cannot effectively stabilize them. Here we report that a sulfur-doped zeolite-templated carbon, simultaneously exhibiting large sulfur content (17 wt% S), as well as a unique carbon structure (that is, highly curved three-dimensional networks of graphene nanoribbons), can stabilize a relatively high loading of platinum (5 wt%) in the form of highly dispersed species including site isolated atoms. In the oxygen reduction reaction, this catalyst does not follow a conventional four-electron pathway producing H2O, but selectively produces H2O2 even over extended times without significant degradation of the activity. Thus, this approach constitutes a potentially promising route for producing important fine chemical H2O2, and also offers opportunities for tuning the selectivity of other electrochemical reactions on various metal catalysts. PMID:26952517

  4. Tuning selectivity of electrochemical reactions by atomically dispersed platinum catalyst

    NASA Astrophysics Data System (ADS)

    Choi, Chang Hyuck; Kim, Minho; Kwon, Han Chang; Cho, Sung June; Yun, Seongho; Kim, Hee-Tak; Mayrhofer, Karl J. J.; Kim, Hyungjun; Choi, Minkee

    2016-03-01

    Maximum atom efficiency as well as distinct chemoselectivity is expected for electrocatalysis on atomically dispersed (or single site) metal centres, but its realization remains challenging so far, because carbon, as the most widely used electrocatalyst support, cannot effectively stabilize them. Here we report that a sulfur-doped zeolite-templated carbon, simultaneously exhibiting large sulfur content (17 wt% S), as well as a unique carbon structure (that is, highly curved three-dimensional networks of graphene nanoribbons), can stabilize a relatively high loading of platinum (5 wt%) in the form of highly dispersed species including site isolated atoms. In the oxygen reduction reaction, this catalyst does not follow a conventional four-electron pathway producing H2O, but selectively produces H2O2 even over extended times without significant degradation of the activity. Thus, this approach constitutes a potentially promising route for producing important fine chemical H2O2, and also offers opportunities for tuning the selectivity of other electrochemical reactions on various metal catalysts.

  5. Biosupported Bimetallic Pd Au Nanocatalysts for Dechlorination of Environmental Contaminants

    SciTech Connect

    De Corte, S.; Fitts, J.; Hennebel, T.; Sabbe, T.; Bliznuk, V.; Verschuere, S.; van der Lelie, D.; Verstraete, W.; Boon, N.

    2011-08-30

    Biologically produced monometallic palladium nanoparticles (bio-Pd) have been shown to catalyze the dehalogenation of environmental contaminants, but fail to efficiently catalyze the degradation of other important recalcitrant halogenated compounds. This study represents the first report of biologically produced bimetallic Pd/Au nanoparticle catalysts. The obtained catalysts were tested for the dechlorination of diclofenac and trichloroethylene. When aqueous bivalent Pd(II) and trivalent Au(III) ions were both added to concentrations of 50 mg L{sup -1} and reduced simultaneously by Shewanella oneidensis in the presence of H{sub 2}, the resulting cell-associated bimetallic nanoparticles (bio-Pd/Au) were able to dehalogenate 78% of the initially added diclofenac after 24 h; in comparison, no dehalogenation was observed using monometallic bio-Pd or bio-Au. Other catalyst-synthesis strategies did not show improved dehalogenation of TCE and diclofenac compared with bio-Pd. Synchrotron-based X-ray diffraction, (scanning) transmission electron microscopy and energy dispersive X-ray spectroscopy indicated that the simultaneous reduction of Pd and Au supported on cells of S. oneidensis resulted in the formation of a unique bimetallic crystalline structure. This study demonstrates that the catalytic activity and functionality of possibly environmentally more benign biosupported Pd-catalysts can be improved by coprecipitation with Au.

  6. Sulfur poisoning of CeO[subscript 2]-Al[subscript 2]O[subscript 3]-supported mono- and bi-metallic Ni and Rh catalysts in steam reforming of liquid hydrocarbons at low and high temperatures

    SciTech Connect

    Xie, Chao; Chen, Yongsheng; Li, Yan; Wang, Xiaoxing; Song, Chunshan

    2010-12-01

    In order to develop a better understanding on sulfur poisoning of reforming catalysts in fuel processing for hydrogen production, steam reforming of liquid hydrocarbons was performed over CeO{sub 2}-Al{sub 2}O{sub 3} supported monometallic Ni and Rh and bimetallic Rh-Ni catalysts at 550 and 800 C. XANES was used to identify the sulfur species in the used catalysts and to study their impacts on the metal surface properties probed by XPS. It was found that both monometallic catalysts rapidly deactivated at 550 C, and showed poor sulfur tolerance. Although ineffective for the Ni catalyst, increasing the temperature to 800 C dramatically improved the sulfur tolerance of the Rh catalyst. XANES revealed that metal sulfide and organic sulfide are the dominant sulfur species on the used Ni catalyst, while sulfonate and sulfate predominate on the used Rh catalyst. The presence of sulfur induced severe carbon deposition on the Ni catalyst at 800 C. The superior sulfur tolerance of the Rh catalyst at 800 C may be associated with its capability in sulfur oxidation. It is likely that the formation of the oxygen-shielded sulfur structure of sulfonate and sulfate can suppress the poisoning impact of sulfur on Rh by inhibiting direct rhodium-sulfur interaction. Moreover, XPS indicated that the metal surface properties of the Rh catalysts after the reaction without and with sulfur at 800 C are similar, suggesting that sulfur poisoning on Rh was mitigated under the high-temperature condition. Although the Rh-Ni catalyst exhibited better sulfur tolerance than the monometallic catalysts at 550 C, its catalytic performance was inferior compared with the Rh catalyst in the sulfur-containing reaction at 800 C probably due to the severe carbon deposition on the bimetallic catalyst.

  7. Advanced liquefaction using coal swelling and catalyst dispersion techniques

    SciTech Connect

    Curtis, C.W. ); Gutterman, C. ); Chander, S. )

    1992-08-26

    Research in this project centers upon developing a new approach to the direct liquefaction of coal to produce an all-distillate product slate at a sizable cost reduction over current technology. The approach integrates all aspects of the coal liquefaction process including coal selection, pretreatment, coal swelling with catalyst impregnation, coal liquefaction experimentation, product recovery with characterization, alternate bottoms processing, and a technical assessment including an economic evaluation. The project is being carried out under contract to the United States Department of Energy. On May 28, 1992, the Department of Energy authorized starting the experimental aspects of this projects; therefore, experimentation at Amoco started late in this quarterly report period. Research contracts with Auburn University, Pennsylvania State University, and Foster Wheeler Development Corporation were signed during June, 1992, so their work was just getting underway. Their work will be summarized in future quarterly reports. A set of coal samples were sent to Hazen Research for beneficiation. The samples were received and have been analyzed. The literature search covering coal swelling has been up-dated, and preliminary coal swelling experiments were carried out. Further swelling experimentation is underway. An up-date of the literature on the liquefaction of coal using dispersed catalysts is nearing completion; it will be included in the next quarterly report.

  8. Catalytic remediation of 2-propanol on Pt-Mn/γ-Al2O3 bimetallic catalyst during catalytic combustion--experimental study and response surface methodology (RSM) modeling.

    PubMed

    Salari, Dariush; Niaei, Aligholi; Aghazadeh, Faezeh; Hosseini, Seyed Ali; Seyednajafi, Fardin

    2012-01-01

    Process and composition variables of catalytic oxidation of 2-propanol on Pt-Mn/γ-Al(2)O(3) bimetallic catalysts were optimized and modeled by response surface methodology (RSM). 31 factorial experiments were designed by setting four factors at five levels: X (1) = amount of manganese loading (wt.% Mn = 1, 3, 5, 7, 9); X (2) = reaction temperature (25, 50, 75, 100, 125°C); X (3) = calcination temperature (200, 300, 400, 500, 600°C) and X (4) = calcination time (2, 3, 4, 5, 6 h). A second-order polynomial model and response surface were developed for 2-propanol conversion. The optimum conditions for 2-propanol complete conversion were 4.8wt.% manganese loading, 4h calcination time with 75°C and 395°C for reaction and calcination temperatures, respectively. A good correlation was found between experimental and predicted responses, confirming the reliability of the model. PMID:22320686

  9. Heterogenized Bimetallic Pd-Pt-Fe3O4 Nanoflakes as Extremely Robust, Magnetically Recyclable Catalysts for Chemoselective Nitroarene Reduction.

    PubMed

    Byun, Sangmoon; Song, Yeami; Kim, B Moon

    2016-06-15

    A very simple synthesis of bimetallic Pd-Pt-Fe3O4 nanoflake-shaped alloy nanoparticles (NPs) for cascade catalytic reactions such as dehydrogenation of ammonia-borane (AB) followed by the reduction of nitro compounds (R-NO2) to anilines or alkylamines (R-NH2) in methanol at ambient temperature is described. The Pd-Pt-Fe3O4 NPs were easily prepared via a solution phase hydrothermal method involving the simple one-pot coreduction of potassium tetrachloroplatinate (II) and palladium chloride (II) in polyvinylpyrrolidone with subsequent deposition on commercially available Fe3O4 NPs. The bimetallic Pd-Pt alloy NPs decorated on Fe3O4 NPs provide a unique synergistic effect for the catalysis of cascade dehydrogenation/reduction. Various nitroarene derivatives were reduced to anilines with very specific chemoselectivity in the presence of other reducible functional groups. The bimetallic Pd-Pt-Fe3O4 NPs provide a unique synergistic effect for the catalysis of cascade dehydrogenation/reduction. The nitro reduction proceeded in 5 min with nearly quantitative conversions and yields. Furthermore, the magnetically recyclable nanocatalysts were readily separated using an external magnet and reused up to 250 times without any loss of catalytic activity. A larger scale (10 mmol) reaction was also successfully performed with >99% yield. This efficient, recyclable Pd-Pt-Fe3O4 NPs system can therefore be repetitively utilized for the reduction of various nitro-containing compounds. PMID:27191706

  10. Surface structure and reaction property of CuCl2-PdCl2 bimetallic catalyst in methanol oxycarbonylation: A DFT approach

    NASA Astrophysics Data System (ADS)

    Meng, Qingsen; Wang, Shengping; Shen, Yongli; Yan, Bing; Wu, Yuanxin; Ma, Xinbin

    2014-02-01

    Surface structure of CuCl2-PdCl2 bimetallic catalyst (Wacker-type catalyst) was built employing density functional theory (DFT) calculations, and the reaction mechanism of methanol oxycarbonylation over the CuCl2-PdCl2 surfaces was also investigated. On the CuCl2-PdCl2 surface, the active site for methanol oxidation was confirmed as Cu-Cl-Cu (Pd). Comparing with pure CuCl2 surface, the introduction of Pd atom causes the electron repopulation on the surface and lowers the energy barrier for methanol oxidation, but the number of the active site decreases with the increasing of Pd doping volume. Agreed with previous experimental results, the Pd site is most favorable for the CO insertion, indicated by the lowest activation barrier for the formation of COOCH3 on Pd atom. The lowest energy barrier for the formation of DMC appears when COOCH3 species adsorbed on Pd atom and methoxyl adsorbed on Cu atoms, which is 0.42 eV. Finally, the reconstruction of the unsaturated surface is a spontaneous and exothermic process. Comparing with other surfaces, the rate-limiting step, methanol oxidation, on CuCl2-PdCl2 surface with Pd/Cu = 1:17 has the lowest energy barrier, which is agreed with the experimental observation that PdCl2-CuCl2 catalyst with Pd/Cu = 1:20 has the favorable activity. The adsorbed methoxyl will further lower the activation barrier of methanol oxidation, which is agreed with experimental observation that the Wacker-type catalysts have an induction period in the methanol oxidative carbonylation system.

  11. Effect of Reaction Temperature in the Selective Synthesis of Single Wall Carbon Nanotubes (SWNT) on a Bimetallic CoCr-MCM-41 Catalyst

    SciTech Connect

    Zoican Loebick, C.; Abanulo, D; Majewska, M; Haller, G; Pfefferle, L

    2010-01-01

    Synthesis of single wall carbon nanotubes (SWNT) on a CoCr-MCM-41 bimetallic catalyst by CO disproportionation has been carried out at five different temperatures between 500 and 900 C. A series of methods have been employed for a comprehensive assessment effect of temperature on the size-controllability of the catalyst particles and the morphology of the resultant SWNT. By extended fine structure X-ray absorption, thermogravimetric analysis, resonance Raman spectroscopy, photoluminescence excitation (PLE) mapping and transmission electron microscopy we found an optimal synthesis temperature window between 600 and 800 C. In this window, modifying the reaction temperature leads to significant changes in the SWNT yield, diameter and chirality distribution. Decrease in reaction temperature favored the selective synthesis of very small diameter carbon nanotubes (as low as 0.6 nm). Chirality dependence of SWNT on temperature has been measured by PLE. A progressive suppression of larger diameter SWNT identities in the measured SWNT population was noted when reaction temperature decreased. In the measured PL maps, two near armchair structures (6,5) and (7,3) were dominant at 600 and 700 C.

  12. Insight on the Interaction of Methanol-Selective Oxidation Intermediates with Au- or/and Pd-Containing Monometallic and Bimetallic Core@Shell Catalysts.

    PubMed

    Czelej, Kamil; Cwieka, Karol; Colmenares, Juan Carlos; Kurzydlowski, Krzysztof J

    2016-08-01

    Using density functional theory (DFT), the interaction of crucial molecules involved in the selective partial oxidation of methanol to methyl formate (MF) with monometallic Au and Pd and bimetallic Au/Pd and Pd/Au core@shell catalysts is systematically investigated. The core@shell structures modeled in this study consist of Au(111) and Pd(111) cores covered by a monolayer of Pd and Au, respectively. Our results indicate that the adsorption strength of the molecules examined as a function of catalytic surface decreases in the order of Au/Pd(111) > Pd(111) > Au(111) > Pd/Au(111) and correlates well with the d-band center model. The preadsorption of oxygen is found to have a positive impact on the selective partial oxidation reaction because of the stabilization of CH3OH and HCHO on the catalyst surface and the simultaneous intensification of MF desorption. On the basis of a dynamical matrix approach combined with statistical thermodynamics, we propose a simple route for evaluating the Gibbs free energy of adsorption as a function of temperature. This method allows us to anticipate the relative temperature stability of molecules involved in the selective partial oxidation of methanol to MF in terms of catalytic surface. PMID:27373791

  13. The formation of silica, alumina and zirconia supported high surface area monometallic and bimetallic catalysts. Progress report

    SciTech Connect

    Gonzalez, R.D.

    1993-12-01

    During the current granting period, 12/01/92--11/30/93, studies have progressed along four fronts: (1) Preparation of high surface area Pt/SiO{sub 2} catalysts; (2) preparation of high surface area Pt/Al{sub 2}O{sub 3} catalysts; (3) preparation of high surface area promoted zirconia superacid catalysts and, (4) stabilization and sintering of porous Pt/SiO{sub 2} catalysts. In addition to these current studies a major review article on previously funded DOE research has been completed and will appear in Catalysis Reviews. Results of these studies are briefly described.

  14. One step electrochemical synthesis of bimetallic PdAu supported on nafion–graphene ribbon film for ethanol electrooxidation

    SciTech Connect

    Shendage, Suresh S. Singh, Abilash S.; Nagarkar, Jayashree M.

    2015-10-15

    Highlights: • Electrochemical deposition of bimetallic PdAu NPs. • Highly loaded PdAu NPs are obtained. • Nafion–graphene supported PdAu NPs shows good activity for ethanol electrooxidation. - Abstract: A nafion–graphene ribbon (Nf–GR) supported bimetallic PdAu nanoparticles (PdAu/Nf–GR) catalyst was prepared by electrochemical codeposition of Pd and Au at constant potential. The prepared catalyst was characterized by scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), transmission electron microscopy (TEM) and X-ray diffraction analysis (XRD). The average particle size of PdAu nanoparticles (NPs) determined from XRD was 3.5 nm. The electrocatalytic activity of the PdAu/Nf–GR catalyst was examined by cyclic voltametry. It was observed that the as prepared catalyst showed efficient activity and good stability for ethanol electrooxidation in alkaline medium.

  15. Applications of extended X-ray absorption fine-structure spectroscopy to studies of bimetallic nanoparticle catalysts.

    PubMed

    Frenkel, Anatoly I

    2012-12-21

    Extended X-ray absorption fine structure (EXAFS) spectroscopy has been used to study short range order in heterometallic alloys for almost four decades. In this critical review, experimental, theoretical and data analytical approaches are revisited to examine their power, and limitations, in studies of bimetallic nanocatalysts. This article covers the basics of EXAFS experiments, data analysis, and modelling of nanoscale clusters. It demonstrates that, in the best case scenario, quantitative information about the nanocatalyst's size, shape, details of core-shell architecture, as well as static and dynamic disorder in metal-metal bond lengths can be obtained. The article also emphasizes the main challenge accompanying such insights: the need to account for the statistical nature of the EXAFS technique, and discusses corrective strategies. PMID:22833100

  16. Effect of promoter and noble metals and suspension pH on catalytic nitrate reduction by bimetallic nanoscale Fe(0) catalysts.

    PubMed

    Bae, Sungjun; Hamid, Shanawar; Jung, Junyoung; Sihn, Youngho; Lee, Woojin

    2016-05-01

    Experiments were conducted to investigate the effect of experimental factors (types of promotor and noble metals, H2 injection, and suspension pH) on catalytic nitrate reduction by bimetallic catalysts supported by nanoscale zero-valent iron (NZVI). NZVI without H2 injection showed 71% of nitrate reduction in 1 h. Cu/NZVI showed the almost complete nitrate reduction (96%) in 1 h, while 67% of nitrate was reduced by Ni/NZVI. The presence of noble metals (Pd and Pt) on Cu/NZVI without H2 injection resulted in the decrease of removal efficiency to 89% and 84%, respectively, due probably to the electron loss of NZVI for formation of metallic Pd and Pt. H2 injection into Cu-Pd/NZVI suspension significantly improved both catalytic nitrate reduction (>97% in 30 min) and N2 selectivity (18%), indicating that adsorbed H on active Pd sites played an important role for the enhanced nitrate reduction and N2 selectivity. The rapid passivation of NZVI surface resulted in a dramatic decrease in nitrate reduction (79-28%) with an increase in N2 selectivity (8-66%) as the suspension pH increased from 8 to 10. PMID:26512419

  17. Fabrication of PdCo Bimetallic Nanoparticles Anchored on Three-Dimensional Ordered N-Doped Porous Carbon as an Efficient Catalyst for Oxygen Reduction Reaction.

    PubMed

    Xue, Hairong; Tang, Jing; Gong, Hao; Guo, Hu; Fan, Xiaoli; Wang, Tao; He, Jianping; Yamauchi, Yusuke

    2016-08-17

    PdCo bimetallic nanoparticles (NPs) anchored on three-dimensional (3D) ordered N-doped porous carbon (PdCo/NPC) were fabricated by an in situ synthesis. Within this composite, N-doped porous carbon (NPC) with an ordered mesoporous structure possesses a high surface area (659.6 m(2) g(-1)), which can facilitate electrolyte infiltration. NPC also acts as a perfect 3D conductive network, guaranteeing fast electron transport. In addition, homogeneously distributed PdCo alloy NPs (∼15 nm) combined with the doping of the N element can significantly improve the electrocatalytic activity for the oxygen reduction reaction (ORR). Due to the structural and material superiority, although the weight percentage of PdCo NPs (∼8 wt%) is much smaller than that of commercial Pt/C (20 wt%), the PdCo/NPC catalyst exhibits similar excellent electrocatalytic activity; however, its superior durability and methanol-tolerance ability of the ORR are as great as those of commercial Pt/C in alkaline media. PMID:27441490

  18. Fabrication and application of amperometric glucose biosensor based on a novel PtPd bimetallic nanoparticle decorated multi-walled carbon nanotube catalyst.

    PubMed

    Chen, Kuan-Jung; Lee, Chia-Feng; Rick, John; Wang, Shih-Han; Liu, Chung-Chiun; Hwang, Bing-Joe

    2012-03-15

    A sensitive, selective and stable amperometric glucose biosensor employing novel PtPd bimetallic nanoparticles decorated on multi-walled carbon nanotubes (PtPd-MWCNTs) was investigated. PtPd-MWCNTs were prepared by a modified Watanabe method, and characterized by XRD and TEM. The biosensor was constructed by immobilizing the PtPd-MWCNTs catalysts in a Nafion film on a glassy carbon electrode. An inner Nafion film coating was used to eliminate common interferents such as uric acid, ascorbic acid and fructose. Finally, a highly porous surface with an orderly three-dimensional network enzyme layer (CS-GA-GOx) was fabricated by electrodeposition. The resulting biosensor exhibited a good response to glucose with a wide linear range (0.062-14.07 mM) and a low detection limit 0.031 mM. The biosensor also showed a short response time (within 5 s), and a high sensitivity (112 μA mM(-1)cm(-2)). The Michaelis-Menten constant (K(m)) was determined as 3.3 mM. In addition, the biosensor exhibited high reproducibility, good storage stability and satisfactory anti-interference ability. The applicability of the biosensor to actual serum sample analysis was also evaluated. PMID:22277115

  19. Dynamic Structural Changes of SiO₂ Supported Pt-Ni Bimetallic Catalysts over Redox Treatments Revealed by NMR and EPR

    SciTech Connect

    Xu, Suochang; Walter, Eric D.; Zhao, Zhenchao; Hu, Mary Y.; Han, Xiuwen; Hu, Jian Z.; Bao, Xinhe

    2015-08-18

    SiO2 supported Pt-Ni bimetallic catalysts with different nickel loadings were prepared and their structural changes after redox treatments were studied by XRD, NMR, and EPR. It is found that the paramagnetic Ni species are mainly located on the surface of silica lattice. The relaxation of detected 29Si nuclei in our samples is mainly governed by a spin-diffusion mechanism. The paramagnetic effects are reflected in the spin-lattice relaxation of Q4 species, with the oxidized samples presenting faster relaxation rates than the corresponding reduced ones. Meanwhile the Q3 species, which are in close contact with the paramagnetic nickel ions, are “spectrally invisible”. In reducing atmosphere Ni gradually diffuses into Pt NPs to form PtNi alloys. While under oxidization treatment, the alloyed Ni atoms migrate outward from the core of Pt NPs and are oxidized. The main EPR spectrum results from reduced nickel species, and the reduced samples show stronger EPR signal than the corresponding oxidized ones. However, in the reduced samples, the superparamagnetic or ferromagnetic metallic Ni particles were inside the PtNi NPs, making their influence on the 29Si relaxation in the SiO2 support weaker than the oxidized samples.

  20. Uninterrupted galvanic reaction for scalable and rapid synthesis of metallic and bimetallic sponges/dendrites as efficient catalysts for 4-nitrophenol reduction.

    PubMed

    Barman, Barun Kumar; Nanda, Karuna Kar

    2015-03-01

    Here, we demonstrate an uninterrupted galvanic replacement reaction (GRR) for the synthesis of metallic (Ag, Cu and Sn) and bimetallic (Cu-M, M=Ag, Au, Pt and Pd) sponges/dendrites by sacrificing the low reduction potential metals (Mg in our case) in acidic medium. The acidic medium prevents the oxide formation on Mg surface and facilitates the uninterrupted reaction. The morphology of dendritic/spongy structures is controlled by the volume of acid used for this reaction. The growth mechanism of the spongy/dendritic microstructures is explained by diffusion-limited aggregate model (DLA), which is also largely affected by the volume of acid. The significance of this method is that the yield can be easily predicted, which is a major challenge for the commercialization of the products. Furthermore, the synthesis is complete in 1-2 minutes at room temperature. We show that the sponges/dendrites efficiently act as catalysts to reduce 4-nitrophenol (4-NP) to 4-aminophenol (4-AP) using NaBH4-a widely studied conversion process. PMID:25628256

  1. Rare earth-modified kaolin/NaY-supported Pd-Pt bimetallic catalyst for the catalytic combustion of benzene.

    PubMed

    Zuo, Shufeng; Sun, Xuejie; Lv, Ningning; Qi, Chenze

    2014-08-13

    A new type of porous kaolin/NaY composite (KL-NY) with a large specific surface area and large pore sizes was synthesized through a one-step crystallization process, and rare earth-modified KL-NY-supported Pd-Pt catalysts were studied for benzene combustion. The results indicated that the pore volume and specific surface area of KL-NY after calcination and crystallization were 0.298 cm(3)/g and 365 m(2)/g, respectively, exhibiting appropriate pore structure and good thermal stability. Catalysts with rare earth metals greatly enhanced the activity of Pd/KL-NY, and the addition of Pt and Ce into the Pd catalyst improved the catalytic activity as well as the stability. The catalyst with an optimal Ce content and Pt/Pd molar ratio (0.2%Pd-Pt (6:1)/6%Ce/KL-NY) demonstrated the best activity for the complete oxidation of benzene at 230 °C, and the catalyst above maintained the 100% benzene conversion for 960 h. PMID:25057756

  2. Bimetallic junctions

    NASA Technical Reports Server (NTRS)

    Arcella, F. G.; Lessmann, G. G.; Lindberg, R. A. (Inventor)

    1977-01-01

    The formation of voids through interdiffusion in bimetallic welded structures exposed to high operating temperatures is inhibited by utilizing an alloy of the parent materials in the junction of the parent materials or by preannealing the junction at an ultrahigh temperature. These methods are also used to reduce the concentration gradient of a hardening agent.

  3. Sulfided heterogeneous, bimetallic RuMo catalysts derived from mixtures of Ru{sub 3}(CO){sub 12} (or RuCl{sub 3}) and a molybdenum heteropolyanion. The reactions of ethanol with tetrahydroquinoline

    SciTech Connect

    Koo, Sang-Man; Ryan, D.; Laine, R.M.

    1992-09-01

    Efforts have been made to develop Ru/Mo bimetallic catalyst systems for hydrodenitrogenation (HDN) of tetrahydroquinoline (THQ)- In the course of these studies, it was discovered that in ethanol, under H{sub 2} and in the presence Of CS2, Precatalyst solutions containing Ru [as Ru{sub 3} (CO){sub 12} or RuCl{sub 3}] and Mo [as the H{sub 3}PMO{sub 12}0{sub 40} heteropolyanion (HPA)] decompose to form bimetallic, sulfided particles. Particle diameters run from 0.1 to 5 {mu}m depending on the rate of stirring. Catalyst particles with sizes ranging from 0.1--1 {mu}m can be prepared reproducibly. BET measured surface areas for these size particles ranged from 2 to 20 m2/g. These sulfided particles were found to catalyze, at temperatures of 200--250{degrees}C and hydrogen pressures of 200--1000 psig H{sub 2}, the N-ethylation of THQ to form NEt-THQ; rather than the formation of propylcyclohexane or propylbenzene, reaction products expected for HDN of THQ. Monometallic heterogeneous catalysts prepared from the individual precatalyst complexes, under identical conditions, show minimal activity for N-ethylation by comparison with the bimetallic catalyst. In the absence of H{sub 2}, the reaction proceeds such that THQ is converted to Q, N-EtTHQ, N-C{sub 6}H{sub 9}-THQ, and N-C{sub 6}H{sub 13}-THQ. The latter products appear to arise via acetaldehyde, formed as an intermediate by dehydrogenation of ethanol. Acetaldehyde either condenses with THQ to form N-Et-THQ, or self condenses (aldol condensation) prior to reaction with THQ thereby giving higher homolog alkylation products.

  4. Sulfided heterogeneous, bimetallic RuMo catalysts derived from mixtures of Ru sub 3 (CO) sub 12 (or RuCl sub 3 ) and a molybdenum heteropolyanion. The reactions of ethanol with tetrahydroquinoline

    SciTech Connect

    Koo, Sang-Man; Ryan, D.; Laine, R.M.

    1992-01-01

    Efforts have been made to develop Ru/Mo bimetallic catalyst systems for hydrodenitrogenation (HDN) of tetrahydroquinoline (THQ)- In the course of these studies, it was discovered that in ethanol, under H{sub 2} and in the presence Of CS2, Precatalyst solutions containing Ru (as Ru{sub 3} (CO){sub 12} or RuCl{sub 3}) and Mo (as the H{sub 3}PMO{sub 12}0{sub 40} heteropolyanion (HPA)) decompose to form bimetallic, sulfided particles. Particle diameters run from 0.1 to 5 {mu}m depending on the rate of stirring. Catalyst particles with sizes ranging from 0.1--1 {mu}m can be prepared reproducibly. BET measured surface areas for these size particles ranged from 2 to 20 m2/g. These sulfided particles were found to catalyze, at temperatures of 200--250{degrees}C and hydrogen pressures of 200--1000 psig H{sub 2}, the N-ethylation of THQ to form NEt-THQ; rather than the formation of propylcyclohexane or propylbenzene, reaction products expected for HDN of THQ. Monometallic heterogeneous catalysts prepared from the individual precatalyst complexes, under identical conditions, show minimal activity for N-ethylation by comparison with the bimetallic catalyst. In the absence of H{sub 2}, the reaction proceeds such that THQ is converted to Q, N-EtTHQ, N-C{sub 6}H{sub 9}-THQ, and N-C{sub 6}H{sub 13}-THQ. The latter products appear to arise via acetaldehyde, formed as an intermediate by dehydrogenation of ethanol. Acetaldehyde either condenses with THQ to form N-Et-THQ, or self condenses (aldol condensation) prior to reaction with THQ thereby giving higher homolog alkylation products.

  5. Propane dehydrogenation over Pt-Cu bimetallic catalysts: the nature of coke deposition and the role of copper.

    PubMed

    Han, Zhiping; Li, Shuirong; Jiang, Feng; Wang, Tuo; Ma, Xinbin; Gong, Jinlong

    2014-09-01

    This paper describes an investigation of the promotional effect of Cu on the catalytic performance of Pt/Al2O3 catalysts for propane dehydrogenation. We have shown that Pt/Al2O3 catalysts possess higher propylene selectivity and lower deactivation rate as well as enhanced anti-coking ability upon Cu addition. The optimized loading content of Cu is 0.5 wt%, which increases the propylene selectivity to 90.8% with a propylene yield of 36.5%. The origin of the enhanced catalytic performance and anti-coking ability of the Pt-Cu/Al2O3 catalyst is ascribed to the intimate interaction between Pt and Cu, which is confirmed by the change of particle morphology and atomic electronic environment of the catalyst. The Pt-Cu interaction inhibits propylene adsorption and elevates the energy barrier of C-C bond rupture. The inhibited propylene adsorption diminishes the possibility of coke formation and suppresses the cracking reaction towards the formation of lighter hydrocarbons on Pt-Cu/Al2O3, while a higher energy barrier for C-C bond cleavage suppresses the methane formation. PMID:24933477

  6. Propane dehydrogenation over Pt-Cu bimetallic catalysts: the nature of coke deposition and the role of copper

    NASA Astrophysics Data System (ADS)

    Han, Zhiping; Li, Shuirong; Jiang, Feng; Wang, Tuo; Ma, Xinbin; Gong, Jinlong

    2014-08-01

    This paper describes an investigation of the promotional effect of Cu on the catalytic performance of Pt/Al2O3 catalysts for propane dehydrogenation. We have shown that Pt/Al2O3 catalysts possess higher propylene selectivity and lower deactivation rate as well as enhanced anti-coking ability upon Cu addition. The optimized loading content of Cu is 0.5 wt%, which increases the propylene selectivity to 90.8% with a propylene yield of 36.5%. The origin of the enhanced catalytic performance and anti-coking ability of the Pt-Cu/Al2O3 catalyst is ascribed to the intimate interaction between Pt and Cu, which is confirmed by the change of particle morphology and atomic electronic environment of the catalyst. The Pt-Cu interaction inhibits propylene adsorption and elevates the energy barrier of C-C bond rupture. The inhibited propylene adsorption diminishes the possibility of coke formation and suppresses the cracking reaction towards the formation of lighter hydrocarbons on Pt-Cu/Al2O3, while a higher energy barrier for C-C bond cleavage suppresses the methane formation.

  7. Chirality specific and spatially uniform synthesis of single-walled carbon nanotubes from a sputtered Co-W bimetallic catalyst

    NASA Astrophysics Data System (ADS)

    An, Hua; Kumamoto, Akihito; Takezaki, Hiroki; Ohyama, Shinnosuke; Qian, Yang; Inoue, Taiki; Ikuhara, Yuichi; Chiashi, Shohei; Xiang, Rong; Maruyama, Shigeo

    2016-07-01

    Synthesis of single-walled carbon nanotubes (SWNTs) with well-defined atomic arrangements has been widely recognized in the past few decades as the biggest challenge in the SWNT community, and has become a bottleneck for the application of SWNTs in nano-electronics. Here, we report a selective synthesis of (12, 6) SWNTs with an enrichment of 50%-70% by chemical vapor deposition (CVD) using sputtered Co-W as a catalyst. This is achieved under much milder reduction and growth conditions than those in the previous report using transition-metal molecule clusters as catalyst precursors (Nature, 2014, 510, 522). Meanwhile, in-plane transmission electron microscopy unambiguously identified an intermediate structure of Co6W6C, which is strongly associated with selective growth. However, most of the W atoms disappear after a 5 min CVD growth, which implies that anchoring W may be important in this puzzling Co-W system.Synthesis of single-walled carbon nanotubes (SWNTs) with well-defined atomic arrangements has been widely recognized in the past few decades as the biggest challenge in the SWNT community, and has become a bottleneck for the application of SWNTs in nano-electronics. Here, we report a selective synthesis of (12, 6) SWNTs with an enrichment of 50%-70% by chemical vapor deposition (CVD) using sputtered Co-W as a catalyst. This is achieved under much milder reduction and growth conditions than those in the previous report using transition-metal molecule clusters as catalyst precursors (Nature, 2014, 510, 522). Meanwhile, in-plane transmission electron microscopy unambiguously identified an intermediate structure of Co6W6C, which is strongly associated with selective growth. However, most of the W atoms disappear after a 5 min CVD growth, which implies that anchoring W may be important in this puzzling Co-W system. Electronic supplementary information (ESI) available: Raman spectroscopy (G-band) of SWNTs grown from Co and Co-W catalyst; Kataura plot for chirality

  8. Chirality specific and spatially uniform synthesis of single-walled carbon nanotubes from a sputtered Co-W bimetallic catalyst.

    PubMed

    An, Hua; Kumamoto, Akihito; Takezaki, Hiroki; Ohyama, Shinnosuke; Qian, Yang; Inoue, Taiki; Ikuhara, Yuichi; Chiashi, Shohei; Xiang, Rong; Maruyama, Shigeo

    2016-08-14

    Synthesis of single-walled carbon nanotubes (SWNTs) with well-defined atomic arrangements has been widely recognized in the past few decades as the biggest challenge in the SWNT community, and has become a bottleneck for the application of SWNTs in nano-electronics. Here, we report a selective synthesis of (12, 6) SWNTs with an enrichment of 50%-70% by chemical vapor deposition (CVD) using sputtered Co-W as a catalyst. This is achieved under much milder reduction and growth conditions than those in the previous report using transition-metal molecule clusters as catalyst precursors (Nature, 2014, 510, 522). Meanwhile, in-plane transmission electron microscopy unambiguously identified an intermediate structure of Co6W6C, which is strongly associated with selective growth. However, most of the W atoms disappear after a 5 min CVD growth, which implies that anchoring W may be important in this puzzling Co-W system. PMID:27412697

  9. Development of a PtSn bimetallic catalyst for direct fuel cells using bio-butanol fuel.

    PubMed

    Puthiyapura, V K; Brett, D J L; Russell, A E; Lin, W F; Hardacre, C

    2015-09-01

    Pt and PtSn catalysts were studied for n-butanol electro-oxidation at various temperatures. PtSn showed a higher activity towards butanol electro-oxidation compared to Pt in acidic media. The onset potential for n-butanol oxidation on PtSn is ∼520 mV lower than that found on Pt, and significantly lower activation energy was found for PtSn compared with that for Pt. PMID:26214283

  10. Catalyst dispersion and activity under conditions of temperature-staged liquefaction. Final report

    SciTech Connect

    Davis, A.; Schobert, H.H.; Mitchell, G.D.; Artok, L.

    1993-02-01

    This research program involves the investigation of the use of highly dispersed catalyst precursors for the pretreatment of coals by mild hydrogenation. During the course of this effort solvent preswelling of the coal was evaluated as a means of deeply impregnating catalysts into coal, active phases of catalysts under reaction conditions were studied and the impact of these techniques were evaluated during pretreatment and temperature-staged liquefaction. Two coals, a Texas subbituminous and a Utah high volatile A bituminous, were used to examine the effects of solvent swelling pretreatment and catalyst impregnation on conversion behavior at 275{degrees}C, representative of the first, low-temperature stage in a temperature-staged liquefaction reaction. Ferrous sulfate, iron pentacarbonyl, ammonium tetrathiomolybdate, and molybdenum hexacarbonyl were used as catalyst precursors. Without swelling pretreatment, impregnation of both coals increased conversion, mainly through increased yields of preasphaltenes.

  11. Catalyst dispersion and activity under conditions of temperature-staged liquefaction

    SciTech Connect

    Davis, A.; Schobert, H.H.; Mitchell, G.D.; Artok, L.

    1993-02-01

    This research program involves the investigation of the use of highly dispersed catalyst precursors for the pretreatment of coals by mild hydrogenation. During the course of this effort solvent preswelling of the coal was evaluated as a means of deeply impregnating catalysts into coal, active phases of catalysts under reaction conditions were studied and the impact of these techniques were evaluated during pretreatment and temperature-staged liquefaction. Two coals, a Texas subbituminous and a Utah high volatile A bituminous, were used to examine the effects of solvent swelling pretreatment and catalyst impregnation on conversion behavior at 275[degrees]C, representative of the first, low-temperature stage in a temperature-staged liquefaction reaction. Ferrous sulfate, iron pentacarbonyl, ammonium tetrathiomolybdate, and molybdenum hexacarbonyl were used as catalyst precursors. Without swelling pretreatment, impregnation of both coals increased conversion, mainly through increased yields of preasphaltenes.

  12. Chemisorption and diffusion of atomic hydrogen in and on cluster models of Pd, Rh, and bimetallic PdSn, RhSn, and RhZn catalysts

    SciTech Connect

    Rochefort, A.; Andzelm, J.; Salahub, D.R. ); Russo, N. )

    1990-11-07

    Results of LCGTO-MCP-LSD (Linear Combination of Gaussian Type Orbitals-Model Core Potential-Local Spin Density) calculations are reported for chemisorption and for bulk and surface diffusion of atomic hydrogen on clusters simulating the (111) and (100) surfaces of pure transition metals (Pd and Rh) and bimetallic catalysts (PdSn, RhSn, and RhZn). The replacement of a Pd or Rh atom near the hydrogen atom by Sn decreases the binding energy for hydrogen adsorption. In particular, the decrease is most pronounced when the non-transition metal lies in the first surface layer (e.g. 3.8 eV (2.4 eV) for Pd (PdSn) and 4.1 eV (2.8 eV) for Rh (RhSn)) but is also significant when the non-transition metal is placed as a second neighbor (e.g. 3.8 eV (3.1 eV) for Pd(PdSn) and 4.1 eV (2.9 eV) for Rh(RhSn)). For Zn substitution the behavior is less regular, one case of an increase in binding energy has been found. The presence of Sn or Zn on the surface significantly increases the equilibrium bond distances (e.g. 1.76 {angstrom} for Pd{sub 3}Pd vs 1.93 {angstrom} for Pd{sub 2}SnPd) and decreases the hydrogen perpendicular vibrational frequencies (e.g. 1166 cm{sup {minus}1} for Pd{sub 3}Pd vs 988 cm{sup {minus}1} for Pd{sub 2}SnPd).

  13. Hydrodesulfurization of dibenzothiophene over Mo-based dispersed catalysts

    SciTech Connect

    Song, C.; Cooke, W.S.; Eckhardt, S.

    1995-12-31

    The hydrodesulfurization (HDS) and hydrocracking (HC) activity and selectivity of several Mo-based catalyst precursors have been examined in model compound reactions of dibenzothiophene (DBT). Reactions were carried out at 400{degrees}C with 6.9 MN of H{sub 2} for 30 min. A metal loading of 0.5 mol% (based on DBT) in tridecane as solvent resulted in a low conversion rate and only hydrogenation products. Even the addition of sulfur to the catalyst in a 4:1 molar ratio only led to a minor increase in conversion and HDS. However, a change in the molar ratio of solvent to model compound from 1:1 to 19:1 and a metal loading of 33.16 mol% lead to a dramatic increase in conversion, HDS, and HC. Furthermore, the use of higher boiling point solvents such as hexadecane and octadecane had a beneficial effect on both HDS and HC. The addition of sulfur in a 6:1 ratio of S:metal to the higher-metal-loaded runs had varying effects that were dependent upon the catalyst used.

  14. The calculation of surface orbital energies for specific types of active sites on dispersed metal catalysts

    SciTech Connect

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

    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 dispersed metal catalysts. 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.

  15. The calculation of surface orbital energies for specific types of active sites on dispersed metal catalysts

    SciTech Connect

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

    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 dispersed metal catalysts. 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.

  16. Synthesis of highly dispersed and active palladium/carbon nanofiber catalyst for formic acid electrooxidation

    NASA Astrophysics Data System (ADS)

    Qin, Yuan-Hang; Yue-Jiang; Yang, Hou-Hua; Zhang, Xin-Sheng; Zhou, Xing-Gui; Niu, Li; Yuan, Wei-Kang

    2011-05-01

    Highly dispersed and active palladium/carbon nanofiber (Pd/CNF) catalyst is synthesized by NaBH4 reduction with trisodium citrate as the stabilizing agent. The obtained Pd/CNF catalyst is characterized by high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD). The results show that the Pd nanoparticles with an average particle size of ca. 3.8 nm are highly dispersed on the CNF support even with a small ratio of citrate to Pd precursor, which is believed to be due to the pH adjustment of citrate stabilized colloidal Pd nanoparticles. The cyclic voltammetry and chronoamperometry techniques show that the obtained Pd/CNF catalyst exhibits good catalytic activity and stability for the electrooxidation of formic acid.

  17. Combustion of chlorinated volatile organic compounds (VOCs) using bimetallic chromium-copper supported on modified H-ZSM-5 catalyst.

    PubMed

    Abdullah, Ahmad Zuhairi; Bakar, Mohamad Zailani Abu; Bhatia, Subhash

    2006-02-28

    The paper reports on the performance of chromium or/and copper supported on H-ZSM-5(Si/Al = 240) modified with silicon tetrachloride (Cr1.5/SiCl4-Z, Cu1.5/SiCl4-Z and Cr1.0Cu0.5/SiCl4-Z) as catalysts in the combustion of chlorinated VOCs (Cl-VOCs). A reactor operated at a gas hourly space velocity (GHSV) of 32,000 h(-1), a temperature between 100 and 500 degrees C with 2500 ppm of dichloromethane (DCM), trichloromethane (TCM) and trichloroethylene (TCE) is used for activity studies. The deactivation study is conducted at a GHSV of 3800 h(-1), at 400 degrees C for up to 12 h with a feed concentration of 35,000 ppm. Treatment with silicon tetrachloride improves the chemical resistance of H-ZSM-5 against hydrogen chloride. TCM is more reactive compared to DCM but it produces more by-products due to its high chlorine content. The stabilization of TCE is attributed to resonance effects. Water vapor increases the carbon dioxide yield through its role as hydrolysis agent forming reactive carbocations and acting as hydrogen-supplying agent to suppress chlorine-transfer reactions. The deactivation of Cr1.0Cu0.5/SiCl4-Z is mainly due to the chlorination of its metal species, especially with higher Cl/H feed. Coking is limited, particularly with DCM and TCM. In accordance with the Mars-van Krevelen model, the weakening of overall metal reducibility due to chlorination leads to a loss of catalytic activity. PMID:16310938

  18. Deoxyribonucleic acid-directed growth of well dispersed nickel-palladium-platinum nanoclusters on graphene as an efficient catalyst for ethanol electrooxidation

    NASA Astrophysics Data System (ADS)

    Ma, Jingwen; Wang, Jun; Zhang, Guanghui; Fan, Xiaobin; Zhang, Guoliang; Zhang, Fengbao; Li, Yang

    2015-03-01

    Trimetallic NiPdPt alloy nanoclusters with diameter of about 10 nm are successfully dispersed on the deoxyribonucleic acid-modified reduced graphene oxide (DNA-rGO) by using NaBH4 as reductant. The prepared NiPdPt nanoclusters grown on DNA-rGO (NiPdPt/DNA-rGO) composite are used as electrocatalysts for ethanol electrooxidation in alkaline solution. Cyclic voltammetry and chronoamperometry are used to investigate the electrochemical activities and stabilities of the catalysts. The Ni1Pd1Pt1/DNA-rGO (molar ratio of Ni, Pd, Pt is 1:1:1) has extraordinary electrocataltic activity, with their mass current density reaching 3.4 A mg-1metal and better stability. As compared with the bimetallic counterparts and NiPdPt grown on multi-wall carbon nanotubes, Ni1Pd1Pt1/DNA-rGO retains the highest mass current density after a 2000 s current-time test at 0 V.

  19. Bimetallic catalyst for synthesizing quasi-aligned, well-graphitized multiwalled carbon nanotube bundles on a large scale by the catalytic chemical vapor deposition method.

    PubMed

    Mukhopadhyay, Kingsuk; Mathur, Gyanesh Narayan

    2002-04-01

    An effective method of growth by catalytic chemical vapor deposition (CCVD) to get a large-scale yield of carbon nanotubes is reported. In this method, acetylene is decomposed catalytically over well-dispersed metal particles (Co-Fe and Co-Ni) embedded in commercially available zeolite at a lower temperature (600-700 degrees C). The two binary-metal catalysts (Co-Fe and Co-Ni) used are compared by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Crucial reaction parameters, such as reaction time, temperature, and the effect of purity of gas to obtain optimum production of the nanotubes, both qualitatively and quantitatively, are also reported. PMID:12908309

  20. Highly dispersed catalysts for coal liquefaction. Quarterly report No. 3, February 23, 1992--May 22, 1992

    SciTech Connect

    Hirschon, A.S.; Wilson, R.B. Jr.

    1992-06-08

    Iron and molybdenum complexes were studied as precursors to high dispersion catalysts for coal liquefaction. The precursors were either organometallic complexes or water soluble salts and were impregnated into coals of various ranks. The molybdenum catalysts were found to be very effective for conversion of an Illinois {number_sign}6 bituminous coal whereas the iron catalysts were not. In contrast, the iron catalysts were found to be very effective for lignite conversions. A H-donor and a non-donor conversion system were compared, using tetralin and n-hexadecane, respectively. In each case the organometallic precursor gave greater yields of toluene soluble material, with differences being most dramatic in the hexadecane system. The yields using the organometallic molybdenum precursors in hexadecane were found to be almost as great as those in the tetralin system, indicating that good catalyst precursors do not require donor solvents. The impregnation techniques were evaluated by comparing conversion yields and analyzing the products using Field Ionization Mass Spectroscopy (f.i.m.s) and FT-IR.

  1. Homogeneous Pt-bimetallic Electrocatalysts

    SciTech Connect

    Wang, Chao; Chi, Miaofang; More, Karren Leslie; Markovic, Nenad; Stamenkovic, Vojislav

    2011-01-01

    Alloying has shown enormous potential for tailoring the atomic and electronic structures, and improving the performance of catalytic materials. Systematic studies of alloy catalysts are, however, often compromised by inhomogeneous distribution of alloying components. Here we introduce a general approach for the synthesis of monodispersed and highly homogeneous Pt-bimetallic alloy nanocatalysts. Pt{sub 3}M (where M = Fe, Ni, or Co) nanoparticles were prepared by an organic solvothermal method and then supported on high surface area carbon. These catalysts attained a homogeneous distribution of elements, as demonstrated by atomic-scale elemental analysis using scanning transmission electron microscopy. They also exhibited high catalytic activities for the oxygen reduction reaction (ORR), with improvement factors of 2-3 versus conventional Pt/carbon catalysts. The measured ORR catalytic activities for Pt{sub 3}M nanocatalysts validated the volcano curve established on extended surfaces, with Pt{sub 3}Co being the most active alloy.

  2. Hydrogenation of nitrocompounds with supported palladium catalysts: influence of metal dispersion and nitrocompound nature

    SciTech Connect

    Carturan, G.; Facchin, G.; Cocco, G.; Navazio, G.; Gubitosa, G.

    1983-07-01

    Nitrobenzene, Et-NO/sub 2/, and t-Bu-NO/sub 2/ are hydrogenated to corresponding amines using Pd catalysts in n-octane suspension at 90/sup 0/C and at constant H/sub 2/ pressure. Nitrobenzene reduction to aniline has been studied with several Pd catalysts having a different degree of metal dispersion determined by X-ray methods and chemisorption analysis. Results indicate that the process is a structure sensitive reaction; a peculiar lowering in catalytic activity as the degree of Pd dispersion increases is observed. This fact is discussed in terms of metallic surface oxidation due to the sorbed nitrocompound. Hydrogenation kinetic patterns change with the nature of the nitrocompound. Reduction of Et-NO/sub 2/ and t-Bu-NO/sub 2/ depends on substrate concentration, while nitrobenzene hydrogenation is independent of this parameter. The relevant kinetic experiments allow the formulation of a general reaction mechanism accounting for the different kinetic patterns observed on changing the substrate. The discussion illustrates the possibility that in nitrocompound reduction with metal catalysts the rate determining step may be hydrogenation of the metallic surface oxidized by the sorbed nitrocompound.

  3. Influence of the support on the activity and selectivity of high dispersion Fe catalysts in the Fischer-Tropsch reaction

    SciTech Connect

    Cagnoli, M.V.; Marchetti, S.G.; Gallegos, N.G.; Alvarez, A.M.; Mercader, R.C.; Yeramian, A.A. Facultad de Ciencias Exactas, La Plata )

    1990-05-01

    In order to study the influence of the support on high dispersion catalysts used for the CO hydrogenation reaction, two catalysts, Fe/SiO{sub 2} and Fe/Al{sub 2}O{sub 3}, were prepared by the dry impregnation method. Selective chemisorption of CO, volumetric oxidation, and Moessbauer spectroscopy were used to determine the Fe species present as well as the metallic crystal size, the degree of dispersion, and the reduction percentage. The presence of small Fe{sup 0} crystallites with high dispersion was determined in both catalysts. Reaction rates were measured in a differential reactor and significant differences, about one order of magnitude less for the Al{sub 2}O{sub 3} than for the SiO{sub 2} supported catalysts, were found in the methane turnover frequencies. They are attributed to the interaction between the metal and the supports. The selectivity differences is also discussed in connection with distinct surface properties.

  4. Highly dispersed catalysts for coal liquefaction. Phase 1 final report, August 23--November 22, 1994

    SciTech Connect

    Hirschon, A.S.; Wilson, R.B.; Ghaly, O.

    1995-03-22

    The ultimate goal of this project is to develop novel processes for making the conversion of coal into distillable liquids competitive to that of petroleum products in the range of $25/bbl. The objectives of Phase 1 were to determine the utility of new precursors to highly dispersed catalysts for use of syngas atmospheres in coal liquefaction, and to estimate the effect of such implementation on the cost of the final product. The project is divided into three technical tasks. Tasks 1 and 2 are the analyses and liquefaction experiments, respectively, and Task 3 deals with the economic effects of using these methods during coal liquefaction. Results are presented on the following: Analytical Support--screening tests and second-stage conversions; Laboratory-Scale Operations--catalysts, coal conversion in synthetic solvents, Black Thunder screening studies, and two-stage liquefaction experiments; and Technical and economic Assessment--commercial liquefaction plant description, liquefaction plant cost; and economic analysis.

  5. Synthesis and Characterization of Cu-Pt Bimetallic Nanoparticles

    NASA Astrophysics Data System (ADS)

    Zheng, Xusheng; Liu, Shoujie; Chen, Xing; Cheng, Jie; Si, Cheng; Pan, Zhiyun; Marcelli, Augosto; Chu, Wangsheng; Wu, Ziyu

    2013-04-01

    Pt-based alloys have recently triggered a lot of attentions due to their important potential industrial applications. They provide great opportunities for the development of low-cost and high-performance fuel-cell catalysts. Many studies have already pointed out the excellent physico-chemical properties of Pt-based alloys, intimately related to their internal structure. Great efforts have been spent to characterize shape, homogeneity, dispersion, alloying extent and kinetic growth of Pt-based nano-particles. Here, we present Cu-Pt bimetallic nano-particles synthesized by the thermal decomposition method under oleylamine and OE coordination. HRTEM images show that Cu-Pt nanostructures having size of about 1.2 nm includes about 35 atoms capped by the surfactant with OA. Accurate structural information of this system has been obtained by XRD and XAFS. A charge transfer mechanism has been observed and Pt occupied Cu sites in these Cu-Pt nanoparticles.

  6. Synthesis, Characterization, and Catalytic Performance of Highly Dispersed Vandium Grafted SBA-15 Catalyst

    SciTech Connect

    Du,G.; Lim, S.; Pinault, M.; Wang, C.; Fang, F.; Pfefferle, L.; Hall, G.

    2008-01-01

    Vanadium oxide grafted on mesoporous silica SBA-15 has been synthesized using a controlled grafting process. Its structure has been thoroughly investigated using different characterization techniques, including N2-physisorption, X-ray diffraction, transmission electron microscopy (TEM), Raman spectroscopy, H2 temperature-programmed reduction, X-ray absorption near-edge structure (XANES), and extended X-ray absorption fine structure (EXAFS). The spectroscopic results revealed that under dehydrated conditions, the grafted vanadium domains are highly dispersed on the SBA-15 surface, composed predominately of isolated VO4 units with distorted tetrahedral coordination. The suggested ({triple_bond}SiO)3V{double_bond}O sites on the silica surface include one short bond ({approx}1.54 Angstroms) and three long bonds (1.74 Angstroms). Methanol oxidation was used as a chemical probe reaction to examine the catalytic properties of these catalysts. At low vanadium loading, the vanadium species grafted on the surface show structural properties similar to those of vanadium-incorporated MCM-41 catalyst. However, the present mesoporous V-SBA-15 catalysts in the oxidation of methanol to formaldehyde show remarkable catalytic performance compared with that of VOx/SBA-15 catalysts synthesized through a conventional wet impregnation method, which has been attributed to the homogeneous dispersion and uniformity of the catalytic vanadium species achieved on the SBA-15 support with large pore diameter and surface area. The acidic properties of V-SBA-15 was investigated by pyridine temperature-programmed desorption, which indicated the existence of both Lewis and Broensted acid sites of the surface.

  7. Preparation of active HDS catalysts by controlling the dispersion of active species

    NASA Astrophysics Data System (ADS)

    Inamura, Kazuhiro; Uchikawa, Kei; Matsuda, Satoshi; Akai, Yoshio

    1997-11-01

    It is demonstrated that the structural control of the metal ion precursors in the impregnating solution by adding the chelating agents is effective to prepare the higher active CoMo supported on alumina catalysts ( Co-Mo/Al 2O 3) for hydrodesulfurization (HDS). Coordination structures of the Co and Mo complexes in the CoMo impregnating solution and distributions of the Co and Mo complexes were evaluated by spectroscopic characterization techniques and by using a computational calculation, respectively. An addition of a chelating agent, such as NTA (nitrilotriacetic acid) and Glu (L-glutamic acid), in the CoMo solution results in the selective formation of the Co complexes, while the amount of the Mo complex is negligibly small at the practical pH of 9.2. The addition of the chelating agent increases the thiophene HDS activity of the sulfided catalysts typically by 50%, compared with that prepared without the chelating agent. Dispersion results of Co and Mo species on both oxidic and sulfided catalysts indicate that the higher HDS activity is explained by the higher degree of surface exposure of Co sites (namely the dispersion of Co) rather than that of Mo sites. The selective formation of the Co-chelate complexes keeps Co ions stable in solution up to high concentration. Furthermore, the Co complexes are estimated to be stable on the support even in the initial step of calcination, which would depress the formation of crystalline Co compounds, such as CoAl 2O 4 and CoMoO 4. These effects result in the higher dispersion of the active Co surface species.

  8. High dispersed catalysts for coal liquefaction. Quarterly report No. 7, February 23, 1993--May 22, 1993

    SciTech Connect

    Hirschon, A.S.; Wilson, R.B.

    1993-08-19

    The objectives of this project are to study the effect of pretreatment methods on the two-stage liquefaction process. In particular, the effects of dispersed catalysts and carbon monoxide atmospheres on a coal liquefaction process. The project is divided into three technical tasks. Task 1 involves the analyses of the liquefaction products derived from liquefaction experiments using the catalysts Fe(CO){sub 5} and the sulfated iron catalyst, Fe{sub 2}O{sub 3}{center_dot}SO{sub 4}. We also analyzed the products derived from treating the recycle vehicle under coal liquefaction conditions with no coal or catalyst present, and found that the toluene and THF fractions had low H/C ratios. No CO or CO{sub 2} gases were detected after reaction, although considerable amount of methane gas was produced, suggesting that during the liquefaction runs the carbon oxides are produced only from the coal, as expected, but that methane gas is produced both from the recycle solvent and the coal. We now have more information about the recycle solvent from Wilsonville, who report that the residue was 63%, composed of 45% resid and 18% insoluble inorganic (CI), and a distilable portion of 37% (1050{degrees}F). During this quarter we compared coal conversions using Fe(CO){sub 5} with CO and H{sub 2}/CO atmospheres and determined the effect of using sulfated iron (Fe{sub 2}O{sub 3}{center_dot}SO{sub 4}) as a conversion catalyst. Also, the coal liquefaction recycle vehicle was subjected to coal product distribution. We found that the Fe(CO){sub 5} under a pure hydrogen atmosphere gave better conversions than under a CO/H{sub 2} atmosphere in terms of oils and asphaltenes but was equal in terms of overall conversion into soluble fractions.

  9. Bimetallic Pt-Au nanocatalysts electrochemically deposited on graphene and their electrocatalytic characteristics towards oxygen reduction and methanol oxidation.

    PubMed

    Hu, Yaojuan; Zhang, Hua; Wu, Ping; Zhang, Hui; Zhou, Bo; Cai, Chenxin

    2011-03-01

    The burgeoning demand for clean and energy-efficient fuel cell system requires electrocatalysts to deliver greater activity and selectivity. Bimetallic catalysts have proven superior to single metal catalysts in this respect. This work reports the preparation, characterization, and electrocatalytic characteristics of a new bimetallic nanocatalyst. The catalyst, Pt-Au-graphene, was synthesized by electrodeposition of Pt-Au nanostructures on the surface of graphene sheets, and characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), X-ray powder diffraction (XRD), and voltammetry. The morphology and composition of the nanocatalyst can be easily controlled by adjusting the molar ratio between Pt and Au precursors. The electrocatalytic characteristics of the nanocatalysts for the oxygen reduction reaction (ORR) and the methanol oxidation reaction (MOR) were systematically investigated by cyclic voltammetry. The Pt-Au-graphene catalysts exhibits higher catalytic activity than Au-graphene and Pt-graphene catalysts for both the ORR and the MOR, and the highest activity is obtained at a Pt/Au molar ratio of 2:1. Moreover, graphene can significantly enhance the long-term stability of the nanocatalyst toward the MOR by effectively removing the accumulated carbonaceous species formed in the oxidation of methanol from the surface of the catalyst. Therefore, this work has demonstrated that a higher performance of ORR and the MOR could be realized at the Pt-Au-graphene electrocatalyst while Pt utilization also could be greatly diminished. This method may open a general approach for the morphology-controlled synthesis of bimetallic Pt-M nanocatalysts, which can be expected to have promising applications in fuel cells. PMID:21229152

  10. Catalyst dispersion and activity under conditions of temperature- staged liquefaction. [Catalyst precursors for molybdenum-based catalyst and iron-based catalyst

    SciTech Connect

    Davis, A.; Schobert, H.H.; Mitchell, G.D.; Artok, L.

    1992-07-01

    Two coals, a Texas subbituminous C and a Utah high volatile A bituminous, were used to examine the effects of solvent swelling and catalyst impregnation on liquefaction conversion behavior in temperature staged reactions for 30 minutes each at 275{degree} and 425{degree}C in H{sub 2} and 95:5 H{sub 2}:H{sub 2}S atmospheres. Methanol, pyridine, tetrahydrofuran, and tetrabutylammonium hydroxide were used as swelling agents. Molybdenum-based catalyst precursors were ammonium tetrathiomolybdate, molybdenum trisulfide, molybdenum hexacarbonyl, and bis(tricarbonylcyclopentadienyl-molybdenum). Ferrous sulfate and bis(dicarbonylcyclo-pentadienyliron) served as iron-based catalyst precursors. In addition, ion exchange was used for loading iron onto the subbituminous coal. For most experiments, liquefaction in H{sub 2}:H{sub 2}S was superior to that in H{sub 2}, regardless of the catalyst precursor. The benefit of the H{sub 2}S was greater for the subbituminous, presumably because of its higher iron content relative to the hvab coal. Tetrabutylammonium hydroxide was the only swelling agent to enhance conversion of the hvab coal significantly; it also caused a remarkable increase in conversion of the subbituminous coal. The combined application of solvent swelling and catalyst impregnation also improves liquefaction, mainly through increased oil yields from the hvab coal and increased asphaltenes from the subbituminous. A remarkable effect from use of ammonium tetrathiomolybdate as a catalyst precursor is substantial increase in pristane and phytane yields. Our findings suggest that these compounds are, at least in part, bound to the coal matrix.

  11. Chemistry of bimetallic and alloy surfaces

    SciTech Connect

    Koel, B.E.

    1991-10-18

    In the first funding period, we continued our work on elucidating the underlying principles that govern chemical reactions occurring on bimetallic and alloy surfaces. Our goal is to aid in the atomic level explanation of the reactivity and selectivity of alloy and bimetallic cluster catalysts and to provide a fundamental basis for the design of new catalysts with improved performance. Our approach is to use a battery of surface science methods to obtain fundamental data on the thermochemistry and kinetics of the adsorption and reaction of molecules on extensively characterized, single-crystal bimetallic surfaces. We measure changes in chemisorption bond strengths, adsorption site distributions, and hydrocarbon fragment stability and reactivity and correlate these results with the geometric and electronic structure of the metal atoms on the surface. Often, our aim is to carefully design experiments that isolate the several factors (e.g., ensemble and ligand effects) that control surface chemistry and catalysis on bimetallic and alloy surfaces in order to better understand the importance of each contribution. Some of the highlights and noteworthy accomplishments made during the first period of this grant are given.

  12. Chemistry of bimetallic and alloys surfaces

    SciTech Connect

    Koel, B.E.

    1991-10-18

    We have continued our work on elucidating the underlying principles that govern chemical reactions occurring on bimetallic and alloy surfaces. Our goal is to aid in the atomic level explanation of the reactivity and selectivity of alloy and bimetallic cluster catalysts and to provide a fundamental basis for the design of new catalysts with improved performance. Our approach is to use a battery of surface science methods to obtain fundamental data on the thermochemistry and kinetics of the adsorption and reaction of molecules on extensively characterized, single-crystal bimetallic surfaces. We measure changes in chemisorption bond strength, adsorption site distributions, and hydrocarbon fragment stability and reactivity and correlate these results with the geometric and electronic structure of the metal atoms on the surface. Often, our aim is to carefully design experiments that isolate the several factors (e.g., ensemble and ligand effects) that control surface chemistry and catalysis on bimetallic and alloy surfaces in order to better understand the importance of each contribution. In the past 18 months, we have continued to study how alkali promoters strongly affect the reactions of hydrocarbons on Pt and Ni surfaces by altering the electronic structure and inducing significant site-blocking effects. We have shown that bismuth coadsorption provides benchmark data on ensemble sizes required for chemical reactions on Pt and Ni surfaces. Surface alloys of Sn/Pt are being used for detailed probing of ensemble sizes and also reactive site requirements. 22 refs.

  13. Bimetallic Wiregauze Supported Pt-Ru Nanocatalysts for Hydrogen Mitigation.

    PubMed

    Sanap, Kiran K; Varma, S; Waghmode, S B; Sharma, P; Manoj, N; Vatsa, R K; Bharadwaj, S R

    2015-05-01

    Passive autocatalytic recombiner (PAR) is one of the most suitable devices for mitigation of hydrogen, generated in nuclear power plant under accidental conditions. For this purpose we report development of stainless steel wire gauze supported Pt-Ru nanoparticles as catalysts. Simultaneous electroless deposition has been employed for the synthesis of the catalysts. Pt-Ru based bimetallic catalysts were characterized for their rate of coating kinetics, noble metal loading, phase purity by XRD and surface morphology by SEM, TEM and elemental analysis by SIMS. Developed catalysts were found to be active for efficient recombination of hydrogen and oxygen in air as well as in presence of various prospective poisons like CO2, CH4, CO and relative humidity. Pt-Ru based bimetallic catalyst with 0.9% loading was found to be active for CO poisoning up to 400 ppm of CO. PMID:26504972

  14. Highly Dispersed Pseudo-Homogeneous and Heterogeneous Catalysts Synthesized via Inverse Micelle Solutions for the Liquefaction of Coal

    SciTech Connect

    Hampden-Smith, M.; Kawola, J.S.; Martino, A.; Sault, A.G.; Yamanaka, S.A.

    1999-01-05

    The mission of this project was to use inverse micelle solutions to synthesize nanometer sized metal particles and test the particles as catalysts in the liquefaction of coal and other related reactions. The initial focus of the project was the synthesis of iron based materials in pseudo-homogeneous form. The frost three chapters discuss the synthesis, characterization, and catalyst testing in coal liquefaction and model coal liquefaction reactions of iron based pseudo-homogeneous materials. Later, we became interested in highly dispersed catalysts for coprocessing of coal and plastic waste. Bifunctional catalysts . to hydrogenate the coal and depolymerize the plastic waste are ideal. We began studying, based on our previously devised synthesis strategies, the synthesis of heterogeneous catalysts with a bifunctional nature. In chapter 4, we discuss the fundamental principles in heterogeneous catalysis synthesis with inverse micelle solutions. In chapter 5, we extend the synthesis of chapter 4 to practical systems and use the materials in catalyst testing. Finally in chapter 6, we return to iron and coal liquefaction now studied with the heterogeneous catalysts.

  15. Synthesis of higher alcohols over highly dispersed Cu-Fe based catalysts derived from layered double hydroxides.

    PubMed

    Han, Xinyou; Fang, Kegong; Zhou, Juan; Zhao, Lu; Sun, Yuhan

    2016-05-15

    Highly dispersed Cu-Fe based catalysts with Fe/Cu molar ratios ranging from 0.2 to 1 were prepared via thermal decomposition of layered double hydroxides (LDHs) precursors and tested for higher alcohol synthesis (HAS) via CO hydrogenation. The catalysts were characterized using different techniques such as XRD, TEM, XPS, and H2-TPR. It was demonstrated that the Cu and Fe ions were highly dispersed in the brucite-like layers of the LDHs. With increased Fe/Cu atomic ratio, the tetrahedrally coordinated Cu ion content, Cu reduction temperatures, and the spacing of layers initially increase until the Fe/Cu ratio reaches 0.5 and then decrease. In addition to the catalytic evaluation for CO hydrogenation and catalyst characterization, the relationships between the physical-chemical properties of the catalysts and their catalytic performances were also investigated. It was also found that the alcohols/hydrocarbons ratios correlate linearly with the tetrahedrally coordinated Cu ion content. Moreover, higher reduction temperatures of Cu species as well as larger spacing between the layers in the catalyst are favorable for the synthesis of alcohols. The incorporation of a suitable amount of Fe is beneficial for the production of higher alcohols, with the best catalytic performance (alcohol selectivity of 20.77% and C2+ alcohol selectivity of 48.06%) obtained from a Fe/Cu atomic ratio of 0.5. PMID:26943001

  16. Structure-Property Relationship in Metal Carbides and Bimetallic Alloys

    SciTech Connect

    Chen, Jingguan

    2014-03-04

    The primary objective of our DOE/BES sponsored research is to use carbide and bimetallic catalysts as model systems to demonstrate the feasibility of tuning the catalytic activity, selectivity and stability. Our efforts involve three parallel approaches, with the aim at studying single crystal model surfaces and bridging the “materials gap” and “pressure gap” between fundamental surface science studies and real world catalysis. The utilization of the three parallel approaches has led to the discovery of many intriguing catalytic properties of carbide and bimetallic surfaces and catalysts. During the past funding period we have utilized these combined research approaches to explore the possibility of predicting and verifying bimetallic and carbide combinations with enhanced catalytic activity, selectivity and stability.

  17. Promotion of the electrocatalytic activity of a bimetallic platinum-ruthenium catalyst by repetitive redox treatments for direct methanol fuel cell

    NASA Astrophysics Data System (ADS)

    Huang, Sheng-Yang; Yeh, Chuin-Tih

    Pt-Ru/C catalyst (12 wt%) was prepared by the incipient wetness impregnation method followed by a redox heat-treatment. Transmission electron microscopy (TEM) results revealed uniformly distributed metallic crystallites of Pt-Ru alloy nanoparticles (d PtRu = 2.1 ± 1.0 nm). The effect of redox treatments of the impregnated catalysts on methanol oxidation reaction (MOR) was examined by cyclic voltammetry (CV). The MOR activity of the PtRu/C was significantly improved after each oxidation step of the redox treatment cycles. The enhanced catalytic activity was found to be quite stable in chronoamperometry (CA) measurements. CV, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD) results strongly suggested that the improved catalytic activity was due to the formation of a stable c-RuO x (x = 2-3) domain during the oxidation treatments. A bifunctional based mechanism was proposed for the MOR on the oxidized PtRu/C catalysts. Formation of Ru-OH species on the surface of c-RuO x domains was suggested as stale sites for the oxidation of carbon monoxide adsorbed on the Pt catalytic sites.

  18. A facile reflux procedure to increase active surface sites form highly active and durable supported palladium@platinum bimetallic nanodendrites

    NASA Astrophysics Data System (ADS)

    Wang, Qin; Li, Yingjun; Liu, Baocang; Xu, Guangran; Zhang, Geng; Zhao, Qi; Zhang, Jun

    2015-11-01

    A series of well-dispersed bimetallic Pd@Pt nanodendrites uniformly supported on XC-72 carbon black are fabricated by using different capping agents. These capping agents are essential for the branched morphology control. However, the surfactant adsorbed on the nanodendrites surface blocks the access of reactant molecules to the active surface sites, and the catalytic activities of these bimetallic nanodendrites are significantly restricted. Herein, a facile reflux procedure to effectively remove the capping agent molecules without significantly affecting their sizes is reported for activating supported nanocatalysts. More significantly, the structure and morphology of the nanodendrites can also be retained, enhancing the numbers of active surface sites, catalytic activity and stability toward methanol and ethanol electro-oxidation reactions. The as-obtained hot water reflux-treated Pd@Pt/C catalyst manifests superior catalytic activity and stability both in terms of surface and mass specific activities, as compared to the untreated catalysts and the commercial Pt/C and Pd/C catalysts. We anticipate that this effective and facile removal method has more general applicability to highly active nanocatalysts prepared with various surfactants, and should lead to improvements in environmental protection and energy production.

  19. 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.

  20. 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.

  1. Formation of Catalyst Model Dispersed of Pd on a thin MgO(100)

    NASA Astrophysics Data System (ADS)

    Baara, F.; Chemam, A.

    2016-04-01

    The nucleation kinetics or the formation of a catalyst model dispersed for the system Pd/thin MgO (100) are calculated by developing many programs using Fortran software. This simulation is based upon parameters studied in situ by transmission electron microscopy (TEM), related to the first quantitative study on the nucleation and the growth. Palladium nanoparticles deposited on thin MgO are tested in the temperature range 573-1073 K and deposition time of 1000 s. The nucleation kinetics are interpreted according to the theory of random nucleation. The general scheme is consisting of three stages namely, nucleation, growth and coalescence. The saturation density of clusters decreases when the substrate temperature increases following Arrhenius law. This behavior is in agreement with a recent AFM study for Ag/MgO and Au/MgO. The phenomenon of coalescence is explained via island migration process. It is shown that the coalescence occurs more rapidly when the substrate temperature is high.

  2. A photoactive bimetallic framework for direct aminoformylation of nitroarenes

    EPA Science Inventory

    A bimetallic catalyst, AgPd@g-C3N4, was synthesized by immobilizing silver and palladium nanoparticles over the surface of graphitic carbon nitride (g-C3N4) and its utility was demonstrated for the concerted aminoformylation of aromatic nitro compounds under visible light conditi...

  3. Adsorption of CO on Ni/Cu(110) bimetallic surfaces

    NASA Astrophysics Data System (ADS)

    Demirci, E.; Carbogno, C.; Groß, A.; Winkler, A.

    2009-08-01

    The adsorption behavior of CO on bimetallic Ni/Cu(110) surfaces has been studied experimentally by thermal-desorption spectroscopy and theoretically by density-functional theory (DFT) calculations. The bimetallic surfaces were produced either by evaporation of nickel or by decomposition of Ni(CO)4 on Cu(110). Adsorption of CO at 180 K on such a bimetallic surface yields three new adsorption states with adsorption energies between that of CO on clean Cu(110) and clean Ni(110). The new desorption peaks from the bimetallic surface, designated as β1-β3 , can be observed at 250, 300, and 360 K, respectively. These new states are most pronounced when (1)/(2) monolayer of nickel is present on the copper surface. DFT calculations, using the Vienna ab initio simulation package code, were performed to identify the most probable Ni/Cu atomic arrangements at the bimetallic surface to reconcile with the experimental results. It turned out that CO adsorption on nickel dimers consisting of in-surface and adjacent subsurface atoms can best explain the observed experimental data. The result shows that CO adsorption is determined by local (geometric) effects rather than by long-range (electronic) effects. These findings should contribute to a better understanding of tailoring catalytic processes with the help of bimetallic catalysts.

  4. Ultrasound enhanced heterogeneous activation of peroxymonosulfate by a bimetallic Fe-Co/SBA-15 catalyst for the degradation of Orange II in water.

    PubMed

    Cai, Chun; Zhang, Hui; Zhong, Xing; Hou, Liwei

    2015-01-01

    Mesoporous silica SBA-15 supported iron and cobalt (Fe-Co/SBA-15) was prepared and used as catalyst in the ultrasound (US) enhanced heterogeneous activation of peroxymonosulfate (PMS, HSO5(-)) process. The effects of some important reaction parameters on the removal of Orange II by US/Fe-Co/SBA-15/PMS process were investigated. The results indicated that the removal rate of Orange II was not significantly affected by the initial pH, and it increased with the higher PMS concentration, reaction temperature, Fe-Co/SBA-15 dosage and ultrasonic power. Furthermore, sulfate radicals (SO4(-)) were assumed to be the dominating reactive species for the Orange II decolorization. Moreover, the Fe-Co/SBA-15 catalyst showed high activity during the repeated experiments. The intermediate products were identified by GC-MS, thereby a plausible degradation pathway is proposed. In addition, the chemical oxygen demand (COD) removal efficiencies at 2 and 24h were 56.8% and 80.1%, respectively and the corresponding total organic carbon (TOC) removal efficiencies were 33.8 and 53.3%. Finally, toxicity tests with activated sludge showed that the toxicity of the solution increased during the first stage and then decreased significantly with the progress of the oxidation. PMID:25262480

  5. Facile Synthesis of Worm-like Micelles by Visible Light Mediated Dispersion Polymerization Using Photoredox Catalyst.

    PubMed

    Yeow, Jonathan; Xu, Jiangtao; Boyer, Cyrille

    2016-01-01

    Presented herein is a protocol for the facile synthesis of worm-like micelles by visible light mediated dispersion polymerization. This approach begins with the synthesis of a hydrophilic poly(oligo(ethylene glycol) methyl ether methacrylate) (POEGMA) homopolymer using reversible addition-fragmentation chain-transfer (RAFT) polymerization. Under mild visible light irradiation (λ = 460 nm, 0.7 mW/cm(2)), this macro-chain transfer agent (macro-CTA) in the presence of a ruthenium based photoredox catalyst, Ru(bpy)3Cl2 can be chain extended with a second monomer to form a well-defined block copolymer in a process known as Photoinduced Electron Transfer RAFT (PET-RAFT). When PET-RAFT is used to chain extend POEGMA with benzyl methacrylate (BzMA) in ethanol (EtOH), polymeric nanoparticles with different morphologies are formed in situ according to a polymerization-induced self-assembly (PISA) mechanism. Self-assembly into nanoparticles presenting POEGMA chains at the corona and poly(benzyl methacrylate) (PBzMA) chains in the core occurs in situ due to the growing insolubility of the PBzMA block in ethanol. Interestingly, the formation of highly pure worm-like micelles can be readily monitored by observing the onset of a highly viscous gel in situ due to nanoparticle entanglements occurring during the polymerization. This process thereby allows for a more reproducible synthesis of worm-like micelles simply by monitoring the solution viscosity during the course of the polymerization. In addition, the light stimulus can be intermittently applied in an ON/OFF manner demonstrating temporal control over the nanoparticle morphology. PMID:27340940

  6. Electrocatalytic hydrodehalogenation of atrazine in aqueous solution by Cu@Pd/Ti catalyst.

    PubMed

    Chen, Ya-Li; Xiong, Lu; Song, Xiang-Ning; Wang, Wei-Kang; Huang, Yu-Xi; Yu, Han-Qing

    2015-04-01

    Electrocatalytic hydrodehalogenation is a cost-effective approach to degrade halogenated organic pollutants in groundwater, and Pd-based catalysts have been found to be an efficient cathode material for this purpose. In this work, a novel Cu@Pd bimetallic catalyst loaded on Ti plate was prepared via combined electrodeposition and galvanic replacement for electrocatalytic hydrodehalogenation of atrazine, a typical halogenated pollutant. The obtained bimetallic catalyst with uniformly dispersed Pd nanoparticles possessed a large electrochemically active surface area of 572 cm2. The Cu@Pd/Ti cathode exhibited a higher electrocatalytic efficiency towards atrazine reduction than the individual Pd/Ti or Cu/Ti cathodes, and achieved up to 91.5% within 120 min under a current density of 1 mA cm(-2). Such an electrocatalytic reduction followed pseudo-first-order kinetics with a rate constant of 0.0214 min(-1). Atrazine was selectively transformed to dechlorinated atrazine, and its degradation pathway was identified. Current density was found to have a critical influence on the atrazine reduction due to the competitive hydrogen evolution reaction at a higher current density. The fabricated bimetallic catalyst also exhibited a good stability. This work provides an efficient and stable electrocatalyst for chlorinated contaminate removal and groundwater remediation. PMID:25697805

  7. One-step preparation of highly dispersed metal-supported catalysts by fluidized-bed MOCVD for carbon nanotube synthesis

    NASA Astrophysics Data System (ADS)

    Xu, Chunbao; Zhu, Jesse

    2004-11-01

    A new technique of fluidized-bed metal-organic chemical vapour deposition (FB-MOCVD) is developed as a one-step method to prepare highly dispersed metal-supported catalysts for carbon nanotube synthesis. By using ultrafine powder of gamma-alumina (70 nm Sauter mean in size) as the support with Fe(CO)5 and Mo(CO)6 as the metal precursors, Fe/Al2O3, Mo/Al2O3 and Fe-Mo/Al2O3 catalysts have been prepared in an FB-MOCVD reactor. Compared with the conventional catalyst-preparation methods such as impregnation, ion exchange, co-precipitation and co-crystallization, the one-step FB-MOCVD technique is advantageous in many aspects. These include eliminating the solid-liquid separation and the subsequent operations of drying and high-temperature calcination/reduction, thus minimizing the aggregation or the crystalline size-growing problem for the supported metal particles caused by these operations. The metal-supported catalysts obtained by FB-MOCVD are characterized with various techniques including ICP-AES, SEM-EDX, XRD and nitrogen isothermal adsorption. Some catalysts are selected and used for carbon nanotube synthesis by CVD from acetylene (C2H2) in a fluidized bed at 650 or 850 °C. The formation of the entangled multi-walled carbon nanotubes (MWNTs), around 50 nm in outer diameter and 10 nm in inner diameter, and several to tens of microns in length, has been confirmed by the TEM and SEM analyses. High CNT selectivity ({\\ge }95{%} ) with the carbon yield ranging widely from about 10% to over 60%, depending on the type of catalyst used and the CNT deposition temperature, has been demonstrated with TGA tests.

  8. Moessbauer spectroscopic investigations of bimetallic FeCo, FeNi, and FeRu model catalysts supported on magnesium hydroxide carbonate

    SciTech Connect

    Nagorny, K.; Bubert, S.

    1987-11-01

    FeCo, FeNi, and FeRu alloys supported on basic magnesium carbonate have been prepared by precipitation from salt solutions at 340 K onto the support using ion exchange and have been subsequently annealed for 20 h under argon. The reduction, oxidation, and sintering behavior of the samples under H/sub 2/ or CO exposure has been investigated at 723 K by means of Moessbauer spectroscopy. The comparison of the resonance absorption areas of the spectra taken at 4 and 295 K allowed the calculation of the Debye temperatures and Debye-Waller factors of the different components. From the Debye-Waller factors the relative fractions could be extrapolated to the conditions at 0 K. The kinetics of the H/sub 2/ exposure showed an increase in the reduction velocity as well as in the degree of reduction in the sequence FeCo < FeNi < FeRu. Above a critical particle diameter a phase separation occurred because of the segregation of an iron-rich phase at the surface of the alloy particles. The kinetics of the CO exposure demonstrated that with FeCo clusters iron(III) surface oxide layers form, whereas with FeNi clusters iron(II) surface oxide layers are generated. FeCo clusters with a cobalt content of 25% form only unstable surface carbides, whereas clusters with a cobalt content of about 5% form stable bulk carbides. The velocity of carbide formation increases with decreasing particle size. Based on the present data a model is proposed which explains the behavior of FeMe/magnesium hydroxide carbonates catalysts in H/sub 2/ and CO atmospheres.

  9. Structural Characterization of Bimetallic Nanocrystal Electrocatalysts

    SciTech Connect

    Cullen, David A

    2016-01-01

    Late transition metal nanocrystals find applications in heterogeneous catalysis such as plasmon-enhanced catalysis and as electrode materials for fuel cells, a zero-emission and sustainable energy technology. Their commercial viability for automotive transportation has steadily increased in recent years, almost exclusively due to the discovery of more efficient bimetallic nanocatalysts for the oxygen reduction reaction (ORR) at the cathode. Despite improvements to catalyst design, achieving high activity while maintaining durability is essential to further enhance their performance for this and other important applications in catalysis. Electronic effects arising from the generation of metal-metal interfaces, from plasmonic metals, and from lattice distortions, can vastly improve sorption properties at catalytic surfaces, while increasing durability.[1] Multimetallic lattice-strained nanoparticles are thus an interesting opportunity for fundamental research.[2,3] A colloidal synthesis approach is demonstrated to produce AuPd alloy and Pd@Au core-shell nanoicosahedra as catalysts for electro-oxidations. The nanoparticles are characterized using aberration-corrected scanning transmission electron microscopy (ac-STEM) and large solid angle energy dispersive X-ray spectroscopy (EDS) on an FEI Talos 4-detector STEM/EDS system. Figure 1 shows bright-field (BF) and high-angle annular dark-field (HAADF) ac-STEM images of the alloy and core-shell nanoicosahedra together with EDS line-scans and elemental maps. These structures are unique in that the presence of twin boundaries, alloying, and core-shell morphology could create highly strained surfaces and interfaces. The shell thickness of the core-shell structures observed in HAADF-STEM images is tuned by adjusting the ratio between metal precursors (Figure 2a-f) to produce shells ranging from a few to several monolayers. Specific activity was measured in ethanol electro-oxidation to examine the effect of shell thickness on

  10. Novel Bimettallic Dispersed Catalysts for Temperature-Programmed Coal Liquefaction: Technical progress report January--March 1996

    SciTech Connect

    Song, C.; Schmidt, E.; Schobert, H.H.

    1996-06-01

    Coal liquefaction may involve cleavage of methylene, dimethylene and ether bridges connecting polycyclic aromatic units and the reactions of various oxygen functional groups. Here in this quarterly, we report on the effects of dispersed Mo catalysts and H{sub 2}O addition on hydrogenation and C-C bond hydrocracking of 4-(1- naphthylmethyl)bibenzyl, abbreviated as NMBB. Recent research in this laboratory has demonstrated a strong synergistic effect between a dispersed Mo sulfide catalyst and water in low-severity coal liquefaction reaction. This finding prompted us to examine the effects of dispersed Mo catalysts and H{sub 2}O addition on hydrogenation and C-C bond hydrocracking of 4-(1-naphthylmethyl)bibenzyl, NMBB. Batch studied in microautoclave reactors at 350 and 400{degrees}C for 30 min revealed that active catalysts can be generated in situ from either ammonium tetrathiomolybdate (ATTM) or Mo(CO){sub 6} under the reaction conditions (350 or 400{degrees}C, 30 min), with the main catalysis of the latter for NMBB hydrogenation, but the former for C-C bond cleavage. Water may have strong promoting effect on NMBB conversion in catalytic runs, depending on the conditions. At 350{degrees}C a 50% increase in NMBB conversion was observed upon H{sub 2}O addition to the run using ATTM (1 wt % Mo) as catalyst. However, at 400{degrees}C no major difference in conversion or product distribution was found. Runs of NMBB at 350{degrees}C using Mo(CO){sub 6} lead to tetrahydro-NMBB-derivatives and few cleavage products. Water added to Mo(CO){sub 6} suppressed hydrogenation. The combination of Mo(CO){sub 6} and S lead to almost complete conversion of NMBB. A run with Mo(CO){sub 6}/S/H{sub 2}O gave similar results. It appears that water can increase NMBB conversion with ATTM at 350{degrees}C but decreased conversion for runs at 400{degrees}C. Also contained in this report is mechanistic discussion for hydrocracking and hydrogenation of NMBB.

  11. Small-sized and highly dispersed Pt nanoparticles loading on graphite nanoplatelets as an effective catalyst for methanol oxidation

    NASA Astrophysics Data System (ADS)

    Zhang, Genlei; Yang, Zhenzhen; Huang, Chengde; Zhang, Wen; Wang, Yuxin

    2015-05-01

    A series of high loading Pt nanoparticles (NPs) with a small particle size uniformly dispersed on graphite nanoplatelets (GNPs) have been synthesized in the presence of an imidazolium-based ionic liquid (Pt/I-IL (x)/GNPs). I-IL, an amphoteric ion used as an additive agent to stabilize Pt NPs, can also prevent the aggregation of the GNPs. The results obtained from X-ray diffraction, transmission electron microscopy and electrochemical testing showed that the I-IL assisted synthesis method resulted in size reduction of Pt NPs, an improvement of Pt dispersion on GNPs, and the identification of the relationships between the mean size of Pt NPs and the volume of I-IL. Among all as-prepared Pt/GNP catalysts with or without I-IL assisted, the sample with 10 microliters of I-IL assisted (Pt/I-IL (10)/GNPs) exhibits the highest electrocatalytic activity and the best stability toward the methanol oxidation reaction. Moreover, the Pt/I-IL (10)/GNP catalyst markedly outperforms the commercial Pt/C from Johnson Matthey in terms of both methanol oxidation activity and stability, revealed by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy.A series of high loading Pt nanoparticles (NPs) with a small particle size uniformly dispersed on graphite nanoplatelets (GNPs) have been synthesized in the presence of an imidazolium-based ionic liquid (Pt/I-IL (x)/GNPs). I-IL, an amphoteric ion used as an additive agent to stabilize Pt NPs, can also prevent the aggregation of the GNPs. The results obtained from X-ray diffraction, transmission electron microscopy and electrochemical testing showed that the I-IL assisted synthesis method resulted in size reduction of Pt NPs, an improvement of Pt dispersion on GNPs, and the identification of the relationships between the mean size of Pt NPs and the volume of I-IL. Among all as-prepared Pt/GNP catalysts with or without I-IL assisted, the sample with 10 microliters of I-IL assisted (Pt/I-IL (10)/GNPs) exhibits the

  12. The chemical properties of bimetallic surfaces: Importance of ensemble and electronic effects in the adsorption of sulfur and SO 2

    NASA Astrophysics Data System (ADS)

    Rodriguez, José A.

    The understanding of the interaction of sulfur with bimetallic surfaces is a critical issue for preventing the deactivation of hydrocarbon reforming catalysts and for the design of better hydrodesulfurization catalysts. The alloying or combination of two metals can lead to materials with special chemical properties due to an interplay of “ensemble” and “electronic” effects. In recent years, several new interesting phenomena have been discovered when studying the interaction of sulfur with bimetallic surfaces using the modern techniques of surface science. Very small amounts of sulfur are able to induce dramatic changes in the morphology of bimetallic surfaces that combine noble metals (Cu, Ag, Au) and transition metals. This phenomenon can lead to big modifications in the activity and selectivity of bimetallic catalysts used for hydrocarbon reforming. In many cases, bimetallic bonding produces a significant redistribution of charge around the bonded metals. The electronic perturbations associated with the formation of a heteronuclear metal-metal bond can affect the reactivity of the bonded metals toward sulfur. This can be a very important issue to consider when trying to minimize the negative effects of sulfur poisoning (Sn/Pt versus Ag/Pt and Cu/Pt catalysts) or when trying to improve the performance of desulfurization catalysts (Co/Mo and Ni/Mo systems). Clearly much more work is necessary in this area, but new concepts are emerging that can be useful for designing more efficient bimetallic catalysts.

  13. Studies of Pt-Sn/Al sub 2 O sub 3 catalysts prepared by Pt and Sn coevaporation (Solvated Metal Atom Dispersion)

    SciTech Connect

    Li, Yongxi; Klabunde, K.J. )

    1990-11-01

    Metal atoms of Pt and Sn have been solvated at low temperatures, and these solvated metal atoms have been used for depositing Pt-Sn bimetallic particles on Al{sub 2}O{sub 3} (full SMAD methods). Spectroscopic investigations with XPS, XRD, EXAFS, and Moessbauer have confirmed the presence of very small and/or amorphous Pt-Sn particles. Catalytic performance tests show that these particles are active for dehydrocyclization reactions, but depress unwanted hydrogenolysis reactions. These results, compared with results for conventionally prepared and half-SMAD methods (Sn{sup 0} on performed Pt particles), show that Sn{sup 0} within and on Pt particles has a significant effect on catalyst performance, and suggest that such performance can be predictably modified by using the correct preparation procedure (SMAD or conventional). The effect of tin is also perhaps now better understood due to these results.

  14. Advanced liquefaction using coal swelling and catalyst dispersion techniques. Quarterly technical progress report, July--September 1992

    SciTech Connect

    Curtis, C.W.; Gutterman, C.; Chander, S.

    1992-12-31

    The experimental study of coal swelling ratios have been determined with a wide variety of solvents. Only marginal levels of coal swelling were observed for the hydrocarbon solvents, but high levels were found with solvents having heteroatom functionality. Blends were superior to pure solvents. The activity of various catalyst precursors for pyrene hydrogenation and coal conversion was measured. Higher coal conversions were observed for the S0{sub 2}-treated coal than the raw coal, regardless of catalyst type. Coal conversions were highest for Molyvan-L, molybdenum naphthenate, and nickel octoate, respectively. Bottoms processing consists of a combination of the ASCOT process coupling solvent deasphalting with delayed coking. Initial results indicate that a blend of butane and pentane used near the critical temperature of butane is the best solvent blend for producing a yield/temperature relationship of proper sensitivity and yet retaining an asphalt phase of reasonable viscosity. The literature concerning coal swelling, both alone and in combination with coal liquefaction, and the use of dispersed or unsupported catalysts in coal liquefaction has been updated.

  15. Small-sized and highly dispersed Pt nanoparticles loading on graphite nanoplatelets as an effective catalyst for methanol oxidation.

    PubMed

    Zhang, Genlei; Yang, Zhenzhen; Huang, Chengde; Zhang, Wen; Wang, Yuxin

    2015-06-14

    A series of high loading Pt nanoparticles (NPs) with a small particle size uniformly dispersed on graphite nanoplatelets (GNPs) have been synthesized in the presence of an imidazolium-based ionic liquid (Pt/I-IL (x)/GNPs). I-IL, an amphoteric ion used as an additive agent to stabilize Pt NPs, can also prevent the aggregation of the GNPs. The results obtained from X-ray diffraction, transmission electron microscopy and electrochemical testing showed that the I-IL assisted synthesis method resulted in size reduction of Pt NPs, an improvement of Pt dispersion on GNPs, and the identification of the relationships between the mean size of Pt NPs and the volume of I-IL. Among all as-prepared Pt/GNP catalysts with or without I-IL assisted, the sample with 10 microliters of I-IL assisted (Pt/I-IL (10)/GNPs) exhibits the highest electrocatalytic activity and the best stability toward the methanol oxidation reaction. Moreover, the Pt/I-IL (10)/GNP catalyst markedly outperforms the commercial Pt/C from Johnson Matthey in terms of both methanol oxidation activity and stability, revealed by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. PMID:25986338

  16. Heterogeneous Catalysis on Atomically Dispersed Supported Metals: CO2 Reduction on Multifunctional Pd Catalysts

    SciTech Connect

    Kwak, Ja Hun; Kovarik, Libor; Szanyi, Janos

    2013-11-01

    Temperature programmed reaction and scanning transmission electron microscopy experiments were applied to prove the requirement of two different catalyst functionalities for the reduction of CO2 with hydrogen on Pd/Al2O3 and Pd/MWCNT catalysts. The research described in this paper was supported by the Laboratory Directed Research and Development (LDRD) program of the Pacific Northwest National Laboratory (PNNL) and 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 PNNL. PNNL is operated for the US DOE by Battelle Memorial Institute.

  17. Nitrogen-Doped Ordered Mesoporous Carbon Supported Bimetallic PtCo Nanoparticles for Upgrading of Biophenolics.

    PubMed

    Wang, Guang-Hui; Cao, Zhengwen; Gu, Dong; Pfänder, Norbert; Swertz, Ann-Christin; Spliethoff, Bernd; Bongard, Hans-Josef; Weidenthaler, Claudia; Schmidt, Wolfgang; Rinaldi, Roberto; Schüth, Ferdi

    2016-07-25

    Hydrodeoxygenation (HDO) is an attractive route for the upgrading of bio-oils produced from lignocellulose. Current catalysts require harsh conditions to effect HDO, decreasing the process efficiency in terms of energy and carbon balance. Herein we report a novel and facile method for synthesizing bimetallic PtCo nanoparticle catalysts (ca. 1.5 nm) highly dispersed in the framework of nitrogen-doped ordered mesoporous carbon (NOMC) for this reaction. We demonstrate that NOMC with either 2D hexagonal (p6m) or 3D cubic (Im3‾ m) structure can be easily synthesized by simply adjusting the polymerization temperature. We also demonstrate that PtCo/NOMC (metal loading: Pt 9.90 wt %; Co 3.31 wt %) is a highly effective catalyst for HDO of phenolic compounds and "real-world" biomass-derived phenolic streams. In the presence of PtCo/NOMC, full deoxygenation of phenolic compounds and a biomass-derived phenolic stream is achieved under conditions of low severity. PMID:27294563

  18. Bimetallic nanoparticles: Preparation, properties, and biomedical applications.

    PubMed

    Nasrabadi, Hamid Tayefi; Abbasi, Elham; Davaran, Soodabeh; Kouhi, Mohammad; Akbarzadeh, Abolfazl

    2016-01-01

    Many studies of non-supported bimetallic nanoparticle (BMNP) dispersions, stabilized by ligands or polymers, and copolymers, were started only about 10 years ago. Several preparative procedures have been proposed, and full characterizations on BMNPs have been approved. Studies on BMNPs received huge attention from both scientific and technological communities because most of the NPs' catalytic activity depends on their structural aspects. In this study, we focus on the preparation, properties, and bio-application of BMNPs and introduction of the recent advance in these NPs. PMID:25203939

  19. Dispersed metal cluster catalysts by design. Synthesis, characterization, structure, and performance

    SciTech Connect

    Arslan, Ilke; Dixon, David A.; Gates, Bruce C.; Katz, Alexander

    2015-09-30

    To understand the class of metal cluster catalysts better and to lay a foundation for the prediction of properties leading to improved catalysts, we have synthesized metal catalysts with well-defined structures and varied the cluster structures and compositions systematically—including the ligands bonded to the metals. These ligands include supports and bulky organics that are being tuned to control both the electron transfer to or from the metal and the accessibility of reactants to influence catalytic properties. We have developed novel syntheses to prepare these well-defined catalysts with atomic-scale control the environment by choice and placement of ligands and applied state-of-the art spectroscopic, microscopic, and computational methods to determine their structures, reactivities, and catalytic properties. The ligands range from nearly flat MgO surfaces to enveloping zeolites to bulky calixarenes to provide controlled coverages of the metal clusters, while also enforcing unprecedented degrees of coordinative unsaturation at the metal site—thereby facilitating bonding and catalysis events at exposed metal atoms. With this wide range of ligand properties and our arsenal of characterization tools, we worked to achieve a deep, fundamental understanding of how to synthesize robust supported and ligand-modified metal clusters with controlled catalytic properties, thereby bridging the gap between active site structure and function in unsupported and supported metal catalysts. We used methods of organometallic and inorganic chemistry combined with surface chemistry for the precise synthesis of metal clusters and nanoparticles, characterizing them at various stages of preparation and under various conditions (including catalytic reaction conditions) and determining their structures and reactivities and how their catalytic properties depend on their compositions and structures. Key characterization methods included IR, NMR, and EXAFS spectroscopies to identify

  20. Monolayer dispersion of NiO in NiO/Al2O3 catalysts probed by positronium atom

    NASA Astrophysics Data System (ADS)

    Zhang, H. J.; Chen, Z. Q.; Wang, S. J.

    2012-01-01

    NiO/Al2O3 catalysts with different NiO loadings were prepared by impregnation method. The monolayer dispersion capacity of NiO is determined to be about 9 wt.% through XRD quantitative phase analysis. Positron lifetime spectra measured for NiO/Al2O3 catalysts comprise two long and two short lifetime components, where the long lifetimes τ3 and τ4 correspond to ortho-positronium (o-Ps) annihilation in microvoids and large pores, respectively. With increasing loading of NiO from 0 to 9 wt.%, τ4 drops drastically from 88 to 38 ns. However, when the NiO loading is higher than 9 wt.%, τ4 shows a slower decrease. Variation of λ4 (1/τ4) as a function of the NiO content can be well fitted by two straight lines with different slopes. The relative intensity of τ4 also shows a fast decrease followed by a slow decrease for the NiO content lower and higher than 9 wt.%, respectively. The coincidence Doppler broadening measurements reveal a continuous increase of S parameter with increasing NiO loading up to 9 wt.% and then a decrease afterwards. This is due to the variation in intensity of the narrow component contributed by the annihilation of para-positronium (p-Ps). Our results show that the annihilation behavior of positronium is very sensitive to the dispersion state of NiO on the surface of γ-Al2O3. When the NiO loading is lower than monolayer dispersion capacity, spin conversion of positronium induced by NiO is the dominant effect, which causes decrease of the longest lifetime and its intensity but increase of the narrow component intensity. After the NiO loading is higher than monolayer dispersion capacity, the spin conversion effect becomes weaker and inhibition of positronium formation by NiO is strengthened, which results in decrease of both the long lifetime intensity and the narrow component intensity. The reaction rate constant is determined to be (1.50 ± 0.04) × 1010 g mol-1s-1 and (3.43 ± 0.20) × 109 g mol-1 s-1 for NiO content below and above

  1. Dispersal

    USGS Publications Warehouse

    2001-01-01

    The ability of species to migrate and disperse is a trait that has interested ecologists for many years. Now that so many species and ecosystems face major environmental threats from habitat fragmentation and global climate change, the ability of species to adapt to these changes by dispersing, migrating, or moving between patches of habitat can be crucial to ensuring their survival. This book provides a timely and wide-ranging overview of the study of dispersal and incorporates much of the latest research. The causes, mechanisms, and consequences of dispersal at the individual, population, species and community levels are considered. The potential of new techniques and models for studying dispersal, drawn from molecular biology and demography, is also explored. Perspectives and insights are offered from the fields of evolution, conservation biology and genetics. Throughout the book, theoretical approaches are combined with empirical data, and care has been taken to include examples from as wide a range of species as possible.

  2. Clustering of metal atoms in organic media. II. Effect of support on nickel catalysts prepared by solvated metal atom dispersion (SMAD)

    SciTech Connect

    Matsuo, K.; Klabunde, K.J.

    1982-02-26

    Highly dispersed Ni/support catalysts were prepared from toluene-solvated nickel atoms (solvated metal atom dispersed or SMAD). Catalysts were prepared on MgO, Al/sub 2/O/sub 3/, SiO/sub 2/, and carbon, and their activities were tested for hydrogenolysis of methylcyclopentane, hydrogenation of toluene, dehydrogenation of isopropyl alcohol, and methanation of carbon monoxide. Conventional catalysts were also studied and compared with the SMAD systems. The effect of the support on SMAD catalyst activities was minimal for hydrogenolysis of methylcyclopentane, hydrogenation of toluene, and dehydration of isopropyl alcohol. However, conventional catalysts showed a significant effect of support when these reactions were studied. This difference between SMAD and conventional catalysts is attributed to the presence of an insulating layer of carbonaceous species between Ni and the support in the SMAD systems. Conversely, catalyst activity for methanation of carbon monoxide was significantly affected by support, especially MgO. This phenomenon reflects a synergistic effect of MgO when Ni is present, where CO can be adsorbed readily on MgO which apparently aids in the initial CO reduction step. The SMAD method in combination with high surface area supports yields highly dispersed catalysts with very small particle sizes. Carbon, a support with a particularly high surface area, allows formation of the smallest particle sizes, and this phenomenon is believed to indicate a direct dependency ofmetal particle size on the surface area of the support. The implications of this finding on the mechanism of particle formation are discussed, as well as the observation of optimum nickel particle size effects for the reactions studied. 5 figures, 4 tables.

  3. Earth abundant bimetallic nanoparticles for heterogeneous catalysis

    NASA Astrophysics Data System (ADS)

    Senn, Jonathan F., Jr.

    Polymer exchange membrane fuel cells have the potential to replace current fossil fuel-based technologies in terms of emissions and efficiency, but CO contamination of H2 fuel, which is derived from steam methane reforming, leads to system inefficiency or failure. Solutions currently under development are bimetallic nanoparticles comprised of earth-abundant metals in different architectures to reduce the concentration of CO by PROX during fuel cell operation. Chapter One introduces the Pt-Sn and Co-Ni bimetallic nanoparticle systems, and the intermetallic and core-shell architectures of interest for catalytic evaluation. Application, theory, and studies associated with the efficacy of these nanoparticles are briefly reviewed. Chapter Two describes the concepts of the synthetic and characterization methods used in this work. Chapter Three presents the synthetic, characterization, and catalytic findings of this research. Pt, PtSn, PtSn2, and Pt 3Sn nanoparticles have been synthesized and supported on gamma-Al2O3. Pt3Sn was shown to be an effective PROX catalyst in various gas feed conditions, such as the gas mixture incorporating 0.1% CO, which displayed a light-off temperatures of ˜95°C. Co and Ni monometallic and CoNi bimetallic nanoparticles have been synthesized and characterized, ultimately leading to the development of target Co Ni core-shell nanoparticles. Proposed studies of catalytic properties of these nanoparticles in preferential oxidation of CO (PROX) reactions will further elucidate the effects of different crystallographic phases, nanoparticle-support interactions, and architecture on catalysis, and provide fundamental understanding of catalysis with nanoparticles composed of earth abundant metals in different architectures.

  4. Versatile and efficient catalysts for energy and environmental processes: Mesoporous silica containing Au, Pd and Au-Pd

    NASA Astrophysics Data System (ADS)

    da Silva, Anderson G. M.; Fajardo, Humberto V.; Balzer, Rosana; Probst, Luiz F. D.; Lovón, Adriana S. P.; Lovón-Quintana, Juan J.; Valença, Gustavo P.; Schreine, Wido H.; Robles-Dutenhefner, Patrícia A.

    2015-07-01

    We described a versatile approach for the synthesis of Au/MCM-41, Pd/MCM-41 and Au-Pd/MCM-41 by the direct incorporation of the noble metals into the MCM-41 framework. The structural, textural and chemical properties were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), N2-adsorption (BET and BJH methods), H2-chemisorption, small angle X-ray scattering (SAXS), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS). The nanomaterials, being comprised of Au, Pd and Au-Pd nanoparticles and possessing high surface areas were applied as versatile and efficient catalysts in benzene, toluene and o-xylene (BTX) oxidation and in the steam reforming of ethanol for hydrogen production. The results revealed that the catalytic behavior in both processes was influenced by the experimental conditions and the nature of the catalyst employed. The Au-Pd/MCM-41 catalyst was the most active in the BTX total oxidation. On the basis of characterization data, it was proposed that the close contact between Pd and Au and the higher dispersion of Pd may be responsible for the enhanced activity of the bimetallic catalyst. However, the strong interaction between the noble metals did not improve the performance of the bimetallic catalyst in ethanol steam reforming, the Pd/MCM-41 catalyst being the most active and selective for hydrogen production.

  5. Advanced liquefaction using coal swelling and catalyst dispersion techniques. Quarterly technical progress report, April--June 1992

    SciTech Connect

    Curtis, C.W.; Gutterman, C.; Chander, S.

    1992-08-26

    Research in this project centers upon developing a new approach to the direct liquefaction of coal to produce an all-distillate product slate at a sizable cost reduction over current technology. The approach integrates all aspects of the coal liquefaction process including coal selection, pretreatment, coal swelling with catalyst impregnation, coal liquefaction experimentation, product recovery with characterization, alternate bottoms processing, and a technical assessment including an economic evaluation. The project is being carried out under contract to the United States Department of Energy. On May 28, 1992, the Department of Energy authorized starting the experimental aspects of this projects; therefore, experimentation at Amoco started late in this quarterly report period. Research contracts with Auburn University, Pennsylvania State University, and Foster Wheeler Development Corporation were signed during June, 1992, so their work was just getting underway. Their work will be summarized in future quarterly reports. A set of coal samples were sent to Hazen Research for beneficiation. The samples were received and have been analyzed. The literature search covering coal swelling has been up-dated, and preliminary coal swelling experiments were carried out. Further swelling experimentation is underway. An up-date of the literature on the liquefaction of coal using dispersed catalysts is nearing completion; it will be included in the next quarterly report.

  6. Advanced liquefaction using coal swelling and catalyst dispersion techniques. Quarterly progress report, July--September 1993

    SciTech Connect

    Curtis, C.W.; Gutterman, C.; Chander, S.

    1993-12-31

    The overall objective of this project is to develop a new approach for the direct liquefaction of coal to produce an all-distillate product slate at a sizable cost reduction over current technology. The approach integrates coal selection, pretreatment, coal swelling with catalyst impregnation, liquefaction, product recovery with characterization, alternate bottoms processing, and carrying out a technical assessment including an economic evaluation. The primary coal of this program, Black Thunder subbituminous coal, can be effectively beneficiated to about 3.5 wt % ash using aqueous sulfurous acid pretreatment. This treated coal can be further beneficiated to about 2 wt % ash using commercially available procedures. All three coals used in this study (Black Thunder, Burning Star bituminous, and Martin Lake lignite) are effectively swelled by a number of solvents. The most effective solvents are those having hetero-functionality. laboratory- and bench-scale liquefaction experimentation is underway using swelled and catalyst impregnated coal samples. Higher coal conversions were observed for the SO{sub 2}-treated subbituminous coal than the raw coal, regardless of catalyst type. Conversions of swelled coal were highest when Molyvan L, molybdenum naphthenate, and nickel octoate, respectively, were added to the liquefaction solvent. The study of bottoms processing consists of combining the ASCOT process which consists of coupling solvent deasphalting with delayed coking to maximize the production of coal-derived liquids while rejecting solids within the coke drum. The asphalt production phase has been completed; representative product has been evaluated. The solvent system for the deasphalting process has been established. Two ASCOT tests produced overall liquid yields (63.3 wt % and 61.5 wt %) that exceeded the combined liquid yields from the vacuum tower and ROSE process.

  7. Facile synthesis of Cu-Pd bimetallic multipods for application in cyclohexane oxidation.

    PubMed

    Zhang, Zhuo-Qun; Huang, Jianliu; Zhang, Lan; Sun, Mei; Wang, You-Cheng; Lin, Yue; Zeng, Jie

    2014-10-31

    The synergy between Cu and Pd makes Cu-Pd bimetallic nanocrystals interesting materials for investigation. The scarcity of shapes of Cu-Pd bimetallic nanocrystals motivated us to explore highly branched structures, which may promote a wide range of applications. In this communication, we report a facile synthesis of Cu-Pd bimetallic multipods (19.2 ± 1.2 nm), on branches of which some high-index facets were exposed. Modification of reaction parameters concerning capping agents and reductant led to the formation of other shapes, including sphere-like nanocrystals (SNCs). When loaded onto TiO2, the as-prepared Cu-Pd bimetallic multipods exhibited excellent catalytic activity for the oxidation of cyclohexane by hydrogen peroxide and higher selectivity towards cyclohexanone than monometallic catalysts and SNCs/TiO2. PMID:25297725

  8. Facile synthesis of Cu-Pd bimetallic multipods for application in cyclohexane oxidation

    NASA Astrophysics Data System (ADS)

    Zhang, Zhuo-Qun; Huang, Jianliu; Zhang, Lan; Sun, Mei; Wang, You-Cheng; Lin, Yue; Zeng, Jie

    2014-10-01

    The synergy between Cu and Pd makes Cu-Pd bimetallic nanocrystals interesting materials for investigation. The scarcity of shapes of Cu-Pd bimetallic nanocrystals motivated us to explore highly branched structures, which may promote a wide range of applications. In this communication, we report a facile synthesis of Cu-Pd bimetallic multipods (19.2 ± 1.2 nm), on branches of which some high-index facets were exposed. Modification of reaction parameters concerning capping agents and reductant led to the formation of other shapes, including sphere-like nanocrystals (SNCs). When loaded onto TiO2, the as-prepared Cu-Pd bimetallic multipods exhibited excellent catalytic activity for the oxidation of cyclohexane by hydrogen peroxide and higher selectivity towards cyclohexanone than monometallic catalysts and SNCs/TiO2.

  9. Well-dispersed Pt cubes on porous Cu foam: high-performance catalysts for the electrochemical oxidation of glucose in neutral media.

    PubMed

    Niu, Xiangheng; Lan, Minbo; Zhao, Hongli; Chen, Chen

    2013-07-15

    The investigation of highly efficient catalysts for the electrochemical oxidation of glucose is the most critical challenge to commercialize nonenzymatic glucose sensors, which display a few attractive superiorities including the sufficient stability of their properties and the desired reproducibility of results over enzyme electrodes. Herein we propose a new and very promising catalyst: Pt cubes well-dispersed on the porous Cu foam, for the the electrochemical oxidation reaction of glucose in neutral media. The catalyst is fabricated in situ on a homemade screen-printed carbon electrode (SPCE) substrate through initially synthesizing the three-dimensional (3D) porous Cu foam using a hydrogen evolution assisted electrodeposition strategy, followed by electrochemically reducing the platinic precursor simply and conveniently. Field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) proofs demonstrate that Pt cubes, with an average size (the distance of opposite faces) of 185.1 nm, highly dispersed on the macro/nanopore integrated Cu foam support can be reproducibly obtained. The results of electrochemical tests indicate that the cubic Pt-based catalyst exhibits significant enhancement on the catalytic activity towards the electrooxidation of glucose in the presence of chloride ions, providing a specific activity 6.7 times and a mass activity 5.3 times those of commercial Pt/C catalysts at -0.4 V (vs. Ag/AgCl). In addition, the proposed catalyst shows excellent stability of performance, with only a 2.8% loss of electrocatalytic activity after 100 repetitive measurements. PMID:23744705

  10. Sonochemically synthesized mono and bimetallic Au-Ag reduced graphene oxide based nanocomposites with enhanced catalytic activity.

    PubMed

    Neppolian, Bernaurdshaw; Wang, Chang; Ashokkumar, Muthupandian

    2014-11-01

    Graphene oxide (GO) supported Ag and Au mono-metallic and Au-Ag bimetallic catalysts were synthesized using a sonochemical method. Bimetallic catalysts containing different weight ratios of Au and Ag were loaded onto GO utilizing a low frequency horn-type ultrasonicator. High frequency ultrasonication was used to efficiently reduce Ag(I) and Au(III) ions in the presence of polyethylene glycol and 2-propanol. Transmission electron microscopy (TEM-EDX) and X-ray photoelectron spectroscopy were used to analyze the morphology, size, shape and chemical oxidation states of the prepared metallic catalysts on GO. The catalytic efficiency of the prepared catalysts were compared using 4-nitrophenol (4-NP) reduction reaction and the subsequent formation of 4-aminophenol (4-AP) that was also monitored using UV-vis spectrophotometry. The results revealed that Au-Ag-GO bimetallic catalysts showed high activity for the conversion of 4-NP to 4-AP than their monometallic counterparts. Amongst different weight ratios (1:1, 1:2 and 2:1) between Au and Ag, the 1:2 (Au:Ag) catalyst exhibited very good catalytic performance for the conversion of 4-NP to 4-AP. A total reduction of 4-NP took place within a short period of time if Au-GO was reduced first followed by Ag reduction, whereas a lower reduction rate was observed if Ag-GO was reduced first. The same trend was observed for all the ratios of bimetallic catalysts prepared by this method. The initial unfavorable reduction potential of Ag(I) is likely to be responsible for the above order. It was found that applying dual frequency ultrasonication was a highly effective way of preparing bimetallic catalysts requiring relatively low levels of added chemicals and producing bimetallic catalysts with GO with improved catalytic efficiency. PMID:24582660

  11. Enhanced electrochemical methanation of carbon dioxide with a dispersible nanoscale copper catalyst.

    PubMed

    Manthiram, Karthish; Beberwyck, Brandon J; Alivisatos, A Paul

    2014-09-24

    Although the vast majority of hydrocarbon fuels and products are presently derived from petroleum, there is much interest in the development of routes for synthesizing these same products by hydrogenating CO2. The simplest hydrocarbon target is methane, which can utilize existing infrastructure for natural gas storage, distribution, and consumption. Electrochemical methods for methanizing CO2 currently suffer from a combination of low activities and poor selectivities. We demonstrate that copper nanoparticles supported on glassy carbon (n-Cu/C) achieve up to 4 times greater methanation current densities compared to high-purity copper foil electrodes. The n-Cu/C electrocatalyst also exhibits an average Faradaic efficiency for methanation of 80% during extended electrolysis, the highest Faradaic efficiency for room-temperature methanation reported to date. We find that the level of copper catalyst loading on the glassy carbon support has an enormous impact on the morphology of the copper under catalytic conditions and the resulting Faradaic efficiency for methane. The improved activity and Faradaic efficiency for methanation involves a mechanism that is distinct from what is generally thought to occur on copper foils. Electrochemical data indicate that the early steps of methanation on n-Cu/C involve a pre-equilibrium one-electron transfer to CO2 to form an adsorbed radical, followed by a rate-limiting non-electrochemical step in which the adsorbed CO2 radical reacts with a second CO2 molecule from solution. These nanoscale copper electrocatalysts represent a first step toward the preparation of practical methanation catalysts that can be incorporated into membrane-electrode assemblies in electrolyzers. PMID:25137433

  12. Highly Stable and Active Catalyst for Sabatier Reactions

    NASA Technical Reports Server (NTRS)

    Hu, Jianli; Brooks, Kriston P.

    2012-01-01

    Highly active Ru/TiO2 catalysts for Sabatier reaction have been developed. The catalysts have shown to be stable under repeated shutting down/startup conditions. When the Ru/TiO2 catalyst is coated on the engineered substrate Fe-CrAlY felt, activity enhancement is more than doubled when compared with an identically prepared engineered catalyst made from commercial Degussa catalyst. Also, bimetallic Ru-Rh/TiO2 catalysts show high activity at high throughput.

  13. Atomic layer deposition-Sequential self-limiting surface reactions for advanced catalyst "bottom-up" synthesis

    NASA Astrophysics Data System (ADS)

    Lu, Junling; Elam, Jeffrey W.; Stair, Peter C.

    2016-06-01

    Catalyst synthesis with precise control over the structure of catalytic active sites at the atomic level is of essential importance for the scientific understanding of reaction mechanisms and for rational design of advanced catalysts with high performance. Such precise control is achievable using atomic layer deposition (ALD). ALD is similar to chemical vapor deposition (CVD), except that the deposition is split into a sequence of two self-limiting surface reactions between gaseous precursor molecules and a substrate. The unique self-limiting feature of ALD allows conformal deposition of catalytic materials on a high surface area catalyst support at the atomic level. The deposited catalytic materials can be precisely constructed on the support by varying the number and type of ALD cycles. As an alternative to the wet-chemistry based conventional methods, ALD provides a cycle-by-cycle "bottom-up" approach for nanostructuring supported catalysts with near atomic precision. In this review, we summarize recent attempts to synthesize supported catalysts with ALD. Nucleation and growth of metals by ALD on oxides and carbon materials for precise synthesis of supported monometallic catalyst are reviewed. The capability of achieving precise control over the particle size of monometallic nanoparticles by ALD is emphasized. The resulting metal catalysts with high dispersions and uniformity often show comparable or remarkably higher activity than those prepared by conventional methods. For supported bimetallic catalyst synthesis, we summarize the strategies for controlling the deposition of the secondary metal selectively on the primary metal nanoparticle but not on the support to exclude monometallic formation. As a review of the surface chemistry and growth behavior of metal ALD on metal surfaces, we demonstrate the ways to precisely tune size, composition and structure of bimetallic metal nanoparticles. The cycle-by-cycle "bottom up" construction of bimetallic (or multiple

  14. Synthesis of highly stable, water-dispersible copper nanoparticles as catalysts for nitrobenzene reduction.

    PubMed

    Kaur, Ravneet; Giordano, Cristina; Gradzielski, Michael; Mehta, Surinder K

    2014-01-01

    We report an aqueous-phase synthetic route to copper nanoparticles (CuNPs) using a copper-surfactant complex and tests of their catalytic efficiency for a simple nitrophenol reduction reaction under atmospheric conditions. Highly stable, water-dispersed CuNPs were obtained with the aid of polyacrylic acid (PAA), but not with other dispersants like surfactants or polymethacrylic acid (PMAA). The diameter of the CuNPs could be controlled in the range of approximately 30-85 nm by modifying the ratio of the metal precursor to PAA. The catalytic reduction of p-nitrophenol to p-aminophenol takes place at the surface of CuNPs at room temperature and was accurately monitored by UV/Vis spectroscopy. The catalytic efficiency was found to be remarkably high for these PAA-capped CuNPs, given the fact that at the same time PAA is efficiently preventing their oxidation as well. The activity was found to increase as the size of the CuNPs decreased. It can therefore be concluded that the synthesized CuNPs are catalytically highly efficient in spite of the presence of a protective PAA coating, which provides them with a long shelf life and thereby enhances the application potential of these CuNPs. PMID:24124135

  15. Hydrogasification of carbon adsorbed on sulfur-poisoned dispersed metal catalysts. Final report

    SciTech Connect

    McCarty, J.G.; Wood, B.J.

    1993-12-01

    The temperature programmed reaction of 1- to 10-atom hydrogen (TPRH) with carbon deposited on alumina supported Ni, Ru, and Co and on fused Fe catalysts has been developed to examine the effect of sulfur poisoning on coking rates and the nature of the deposited carbon. A new procedure, passivation by carbon deposition on clean reduced metals and low temperature (20--50 C) exposure to recirculate dilute H{sub 2}S with moderate 0.1 atm partial pressure of CO{sub 2} was used to slow the rate of sulfur chemisorption. This method facilitated slow uniform sulfur chemisorption to fractional saturation coverages. Fractional sulfur poisoning generally blocked sites of active surface carbon (or hydrocarbon fragments) while suppressing rates of hydrogasification as shown by the increasing temperatures in the TPRH hydrogasification rate versus temperature spectra. Fractional sulfur poisoning (e.g., half saturation) appears to inhibit H{sub 2} gasification with surface carbon surprisingly without strongly affecting catalytic activity. Sulfur poisoning to saturation levels (defined here as {approximately}1 ppm H{sub 2}S in 1-atm H{sub 2} at 500 C) always results in complete loss of activity and is also marked by the growth of a very unreactive form of carbon.

  16. Structure and Activity of Pt-Ni Catalysts Supported on Modified Al2O3 for Ethanol Steam Reforming.

    PubMed

    Navarro, R M; Sanchez-Sanchez, M C; Fierro, J L G

    2015-09-01

    Modification of alumina with La-, Ce-, Zr- and Mg-oxides was studied with the aim to use them as supports of bimetallic Pt-Ni catalysts for the steam reforming of ethanol. Activity results showed that modifications of Al2O3 support with the incorporation of La, Ce, Zr or Mg oxides play an essential role in the catalytic behaviour of PtNi catalysts. Bimetallic PtNi catalyst supported on bare Al2O3 showed evolution of the reaction products with time on stream consisting in the increase of C2H4 production with concomitant decrease of CH4 and CO2 production. The addition of Mg or Zr to γ-A1203 did not inhibit the appearance of ethylene but delayed its production. In the case of Ce- or La-supported catalysts, the product selectivities were stable with time-on-stream, with no changes being observed in the product distribution for 24 h. Characterization results showed that La- and Ce-containing supports improves the Pt and Ni metal exposure values. The better stability achieved for Ce and La containing catalysts was inferred to be related with a participation/assistance of lanthanum and cerium entities in the gasification of coke deposits together with a modification of Pt and Ni dispersion which lower the probability of the nucleation of coke precursors on their surfaces. PMID:26716216

  17. Shape-controlled synthesis of Au-Pd bimetallic nanocrystals for catalytic applications.

    PubMed

    Zhang, Lei; Xie, Zhaoxiong; Gong, Jinlong

    2016-07-21

    Au-Pd nanostructured materials have been recognized as important heterogeneous catalysts in various reactions, due to their superior activities caused by the ensemble and ligand effects. In recent years, shape-controlled synthesis of noble metal nanocrystals (NCs) provided a brand-new insight for improving the performance of catalysts. The electronic properties and catalytic activities of Au-Pd NCs could be optimized by tuning their shape and composition engineering. This review describes recent progress in the design and synthesis of shape-controlled Au-Pd bimetallic NCs and their emerging catalytic applications. The review starts with a general discussion of various applications of Au-Pd catalysts and the significance of preparing shape-controlled Au-Pd NCs, followed by an overview of synthetic strategies for two different structures of Au-Pd bimetallic catalysts: a core-shell structure and an alloy structure. We also put forward the key factors for the preparation of Au-Pd core-shell and alloy structures. Additionally, we discussed the unique optical properties and structural effects of shape-controlled Au-Pd NCs. These recent advancements in the methodology development of Au-Pd bimetallic NCs offer numerous insights for generating Au-Pd NCs with a number of unique geometries in the future. Furthermore, the systematic synthesis of core-shell or alloy structures would provide insights for the preparation of other bimetallic NCs. PMID:27095006

  18. Synthesis of subnanometer-diameter vertically aligned single-walled carbon nanotubes with copper-anchored cobalt catalysts

    NASA Astrophysics Data System (ADS)

    Cui, Kehang; Kumamoto, Akihito; Xiang, Rong; An, Hua; Wang, Benjamin; Inoue, Taiki; Chiashi, Shohei; Ikuhara, Yuichi; Maruyama, Shigeo

    2016-01-01

    We synthesize vertically aligned single-walled carbon nanotubes (VA-SWNTs) with subnanometer diameters on quartz (and SiO2/Si) substrates by alcohol CVD using Cu-anchored Co catalysts. The uniform VA-SWNTs with a nanotube diameter of 1 nm are synthesized at a CVD temperature of 800 °C and have a thickness of several tens of μm. The diameter of SWNTs was reduced to 0.75 nm at 650 °C with the G/D ratio maintained above 24. Scanning transmission electron microscopy energy-dispersive X-ray spectroscopy (EDS-STEM) and high angle annular dark field (HAADF-STEM) imaging of the Co/Cu bimetallic catalyst system showed that Co catalysts were captured and anchored by adjacent Cu nanoparticles, and thus were prevented from coalescing into a larger size, which contributed to the small diameter of SWNTs. The correlation between the catalyst size and the SWNT diameter was experimentally clarified. The subnanometer-diameter and high-quality SWNTs are expected to pave the way to replace silicon for next-generation optoelectronic and photovoltaic devices.We synthesize vertically aligned single-walled carbon nanotubes (VA-SWNTs) with subnanometer diameters on quartz (and SiO2/Si) substrates by alcohol CVD using Cu-anchored Co catalysts. The uniform VA-SWNTs with a nanotube diameter of 1 nm are synthesized at a CVD temperature of 800 °C and have a thickness of several tens of μm. The diameter of SWNTs was reduced to 0.75 nm at 650 °C with the G/D ratio maintained above 24. Scanning transmission electron microscopy energy-dispersive X-ray spectroscopy (EDS-STEM) and high angle annular dark field (HAADF-STEM) imaging of the Co/Cu bimetallic catalyst system showed that Co catalysts were captured and anchored by adjacent Cu nanoparticles, and thus were prevented from coalescing into a larger size, which contributed to the small diameter of SWNTs. The correlation between the catalyst size and the SWNT diameter was experimentally clarified. The subnanometer-diameter and high

  19. Synthesis and characteristics of Ag/Pt bimetallic nanocomposites by arc-discharge solution plasma processing.

    PubMed

    Pootawang, Panuphong; Saito, Nagahiro; Takai, Osamu; Lee, Sang-Yul

    2012-10-01

    Arc discharge in solution, generated by applying a high voltage of unipolar pulsed dc to electrodes of Ag and Pt, was used as a method to form Ag/Pt bimetallic nanocomposites via electrode erosion by the effects of the electric arc at the cathode (Ag rod) and the sputtering at the anode (Pt rod). Ag/Pt bimetallic nanocomposites were formed as colloidal particles dispersed in solution via the reduction of hydrogen radicals generated during discharge without the addition of chemical precursor or reducing agent. At a discharge time of 30 s, the fine bimetallic nanoparticles with a mean particle size of approximately 5 nm were observed by transmission electron microscopy (TEM). With increasing discharge time, the bimetallic nanoparticle size tended to increase by forming an agglomeration. The presence of the relatively small amount of Pt dispersed in the Ag matrix could be observed by the analytical mapping mode of energy-dispersive x-ray spectroscopy and high-resolution TEM. This demonstrated that the synthesized particle was in the form of a nanocomposite. No contamination of other chemical substances was detected by x-ray photoelectron spectroscopy. Hence, solution plasma could be a clean and simple process to effectively synthesize Ag/Pt bimetallic nanocomposites and it is expected to be widely applicable in the preparation of several types of nanoparticle. PMID:22968093

  20. Platinum-cobalt bimetallic nanoparticles in hollow carbon nanospheres for hydrogenolysis of 5-hydroxymethylfurfural

    NASA Astrophysics Data System (ADS)

    Wang, Guang-Hui; Hilgert, Jakob; Richter, Felix Herrmann; Wang, Feng; Bongard, Hans-Josef; Spliethoff, Bernd; Weidenthaler, Claudia; Schüth, Ferdi

    2014-03-01

    The synthesis of 2,5-dimethylfuran (DMF) from 5-hydroxymethylfurfural (HMF) is a highly attractive route to a renewable fuel. However, achieving high yields in this reaction is a substantial challenge. Here it is described how PtCo bimetallic nanoparticles with diameters of 3.6 ± 0.7 nm can solve this problem. Over PtCo catalysts the conversion of HMF was 100% within 10 min and the yield to DMF reached 98% after 2 h, which substantially exceeds the best results reported in the literature. Moreover, the synthetic method can be generalized to other bimetallic nanoparticles encapsulated in hollow carbon spheres.

  1. INTERACTION OF SULPHUR WITH BIMETALLIC SURFACES: EFFECTS OF STRUCTURAL, ELECTRONIC AND CHEMICAL PROPERTIES.

    SciTech Connect

    RODRIGUEZ,J.A.; HRBEK,J.

    2001-10-04

    In recent years, several new interesting phenomena have been discovered when studying the interaction of sulphur with bimetallic surfaces using the modern techniques of surface science. Very small amounts of sulphur can induce dramatic changes in the morphology of bimetallic surfaces. The electronic perturbations associated with the formation of a heteronuclear metal-metal bond affect the reactivity of the bonded metals toward sulphur. This can be a very important issue to consider when trying to minimize the negative effects of sulphur poisoning or dealing with the design of desulfurization catalysts.

  2. Effects of dispersed Mo catalysts and H{sub 2}O addition on hydrogenation and hydrocracking of 4-(1-naphthylmethyl)bibenzyl

    SciTech Connect

    Schmidt, E.; Song, C.

    1995-12-31

    Recent research in our group has demonstrated a strong synergistic effect between a dispersed Mo sulfide catalyst and water in low-severity coal liquefaction reaction. This paper reports our results on the effects of dispersed Mo catalysts and H{sub 2}O addition on hydrogenation and C-C bond hydrocracking of 4-(1-naphthylmethyl)bibenzyl, abbreviated as NMBB. Batch studies in micro reactors at 350 and 400{degrees}C for 30 min (initial cold H{sub 2} pressure of 6.9 MPa) revealed that active catalysts can be generated in situ from either ammonium tetrathiomolybdate (ATTM) or Mo(CO){sub 6} under the reaction conditions (350 or 400{degrees}C, 30 min), with the main catalysis of the latter for NMBB hydrogenation, but the former for C-C bond cleavage. Water may have strong promoting effect on NMBB conversion in catalytic runs, depending on the conditions. At 350{degrees}C a 50% increase in NMBB conversion was observed upon H{sub 2}O addition to the run using ATTM (1 wt% Mo) as catalyst. However, at 400{degrees}C no major difference in conversion or product distribution was found. Runs of NMBB at 350{degrees}C using Mo(CO){sub 6} lead to tetrahydro-NMBB-derivatives and few cleavage products. Water added to Mo(CO){sub 6} suppressed hydrogenation. The combination of Mo(CO){sub 6} and S lead to almost complete conversion of NMBB. A run with Mo(CO){sub 6}/S/H{sub 2}O gave similar results. It appears that water can increase NMBB conversion with metal sulfide catalysts within a certain temperature range.

  3. Biosynthesis of Pd-Au alloys on carbon fiber paper: Towards an eco-friendly solution for catalysts fabrication

    NASA Astrophysics Data System (ADS)

    Zhuang, Zechao; Wang, Feifeng; Naidu, Ravendra; Chen, Zuliang

    2015-09-01

    Bimetallic nanomaterials with enhanced activity and stability have been extensively studied as emerging catalysts for hydrogen evolution reaction (HER). Expensive and environmentally unfriendly chemical synthesis routes inhibit their large-scale applications. In this work, we developed a facile and green synthesis of Pd-Au alloy nanoparticles (NPs) dispersed on carbon fiber paper (CFP) by plant-mediated bioreduction coupled with self-assembly. Engineering the morphology and composition of bimetallic catalysts synthesized by plant extracts on complex substrate is achieved. The resulting NPs are uniform in shape and have a spherical morphology with an average diameter of ∼180 nm, in which the molar ratio of Au/Pd is near 75:25 and the catalysts loading is about 0.5 mg cm-2. The Pd-Au/CFP hybrid electrode exhibits an excellent HER performance with a Tafel slope of 47 mV dec-1 and an exchange current density of 0.256 mA cm-2. Electrochemical stability tests through long-term potential cycles and potentiostatic electrolysis further confirm the high durability of the electrode. This development offers an efficient and eco-friendly catalysts synthesis route for constructing water-splitting cells and other electrocatalytic devices.

  4. X-ray characterization of platinum group metal catalysts

    NASA Astrophysics Data System (ADS)

    Peterson, Eric J.

    complements information obtained from both XRD and XAS. With aberration-corrected HAADF, particles ranging from sub-nm-size down to clusters of a few atoms and isolated single-atoms can be routinely imaged. A challenge to the interpretation of these images is the characterization of mixed atomic species, in this case, palladium and lanthanum. In this work we show for the first time that quantitative chemical identification of atomically-dispersed mixtures of palladium and lanthanum in an industrially relevant catalyst (palladium on lanthanum-stabilized gamma-alumina) can be obtained through image intensity analysis. Using these techniques we have characterized the state of bimetallic fuel cell catalysts, ex situ, and have examined the state of Pd catalysts under operando CO oxidation conditions.

  5. Stellated Ag-Pt bimetallic nanoparticles: An effective platform for catalytic activity tuning

    PubMed Central

    Liu, Hui; Ye, Feng; Yao, Qiaofeng; Cao, Hongbin; Xie, Jianping; Lee, Jim Yang; Yang, Jun

    2014-01-01

    The usefulness of Pt-based nanomaterials for catalysis can be greatly enhanced by coupling morphology engineering to the strategic presence of a second or even third metal. Here we demonstrate the design and preparation of stellated Ag-Pt bimetallic nanoparticles where significant activity difference between the methanol oxidation reaction (MOR) and the oxygen reduction reaction (ORR) may be realized by relegating Ag to the core or by hollowing out the core. In particular the stellated Pt surface, with an abundance of steps, edges, corner atoms, and {111} facets, is highly effective for the ORR but is ineffective for MOR. MOR activity is only observed in the presence of a Ag core through electronic coupling to the stellated Pt shell. The bimetallic Ag-Pt stellates therefore demonstrate the feasibility of tuning a Pt surface for two very different structure sensitive catalytic reactions. Stellated bimetallics may therefore be an effective platform for highly tunable catalyst designs. PMID:24495979

  6. Stellated Ag-Pt bimetallic nanoparticles: An effective platform for catalytic activity tuning

    NASA Astrophysics Data System (ADS)

    Liu, Hui; Ye, Feng; Yao, Qiaofeng; Cao, Hongbin; Xie, Jianping; Lee, Jim Yang; Yang, Jun

    2014-02-01

    The usefulness of Pt-based nanomaterials for catalysis can be greatly enhanced by coupling morphology engineering to the strategic presence of a second or even third metal. Here we demonstrate the design and preparation of stellated Ag-Pt bimetallic nanoparticles where significant activity difference between the methanol oxidation reaction (MOR) and the oxygen reduction reaction (ORR) may be realized by relegating Ag to the core or by hollowing out the core. In particular the stellated Pt surface, with an abundance of steps, edges, corner atoms, and {111} facets, is highly effective for the ORR but is ineffective for MOR. MOR activity is only observed in the presence of a Ag core through electronic coupling to the stellated Pt shell. The bimetallic Ag-Pt stellates therefore demonstrate the feasibility of tuning a Pt surface for two very different structure sensitive catalytic reactions. Stellated bimetallics may therefore be an effective platform for highly tunable catalyst designs.

  7. Preparation and Characterization of Polymer-Stabilized Ruthenium-Platinum and Ruthenium-Palladium Bimetallic Colloids and Their Catalytic Properties for Hydrogenation of o-Chloronitrobenzene.

    PubMed

    Liu; Yu; Liu; Zheng

    1999-06-15

    Colloidal dispersions of poly(N-vinyl-2-pyrrolidone) (PVP)-stabilized ruthenium-platinum and ruthenium-palladium bimetallic colloids were prepared by NaBH4 reduction of the corresponding mixed-metal salts at room temperature and characterized by TEM, XPS, and XRD. The resulting bimetallic colloids were used as catalysts for the selective hydrogenation of o-chloronitrobenzene (o-CNB) in methanol at 303 K under 0.1 MPa of hydrogen. It was observed that the catalytic performance of PVP-stabilized ruthenium-platinum colloids (PVP-Ru/Pt) and ruthenium-palladium colloids (PVP-Ru/Pd) was dependent on their compositions and could be remarkably affected by some added metal cations. In the presence of cobalt ion, nearly 100% selectivity to o-chloroaniline (o-CAN) was achieved over PVP-Ru/Pt colloids at 100% conversion of o-CNB, with an activity two orders of magnitude higher than that of monometallic PVP-Ru colloid. Copyright 1999 Academic Press. PMID:10339363

  8. Enhanced Activity of CuCeO Catalysts for CO Oxidation: Influence of Cu2O and the Dispersion of Cu2O, CuO, and CeO2.

    PubMed

    Wang, Zhenhua; Li, Ren; Chen, Qianwang

    2015-08-01

    CuCeO catalysts prepared by a hydrothermal method with subsequent calcination are tested for the catalytic oxidation of CO. This synthesis method leads to a homogeneous dispersion of Cu2 O, CuO, and CeO2 in the catalysts. The composition of the catalysts is determined by the molar ratio of the metals, the hydrothermal process, and calcination temperature and influences the catalytic performance. The catalyst containing Cu2 O exhibits high catalytic activity with almost 100 % CO conversion at 105 °C and shows excellent stability with the conversion ratio not decreasing after four months of storage. PMID:26017784

  9. Antibacterial activity of graphene supported FeAg bimetallic nanocomposites.

    PubMed

    Ahmad, Ayyaz; Qureshi, Abdul Sattar; Li, Li; Bao, Jie; Jia, Xin; Xu, Yisheng; Guo, Xuhong

    2016-07-01

    We report the simple one pot synthesis of iron-silver (FeAg) bimetallic nanoparticles with different compositions on graphene support. The nanoparticles are well dispersed on the graphene sheet as revealed by the TEM, XRD, and Raman spectra. The antibacterial activity of graphene-FeAg nanocomposite (NC) towards Bacillus subtilis, Escherichia coli, and Staphylococcus aureus was investigated by colony counting method. Graphene-FeAg NC demonstrates excellent antibacterial activity as compared to FeAg bimetallic without graphene. To understand the antibacterial mechanism of the NC, oxidative stress caused by reactive oxygen species (ROS) and the glutathione (GSH) oxidation were investigated in the system. It has been observed that ROS production and GSH oxidation are concentration dependent while the increase in silver content up to 50% generally enhances the ROS production while ROS decreases on further increase in silver content. Graphene loaded FeAg NC demonstrates higher GSH oxidation capacity than bare FeAg bimetallic nanocomposite. The mechanism study suggests that the antibacterial activity is probably due to membrane and oxidative stress produced by the nanocomposites. The possible antibacterial pathway mainly includes the non-ROS oxidative stress (GSH oxidation) while ROS play minor role. PMID:27038914

  10. Advanced liquefaction using coal swelling and catalyst dispersion techniques. Quarterly technical progress report No. 7, April 1993--June 1993

    SciTech Connect

    Curtis, C.W.; Chander, S.; Gutterman, C.

    1994-09-01

    The overall objective of this project is to develop a new approach for the direct liquefaction of coal to produce an all-distillate product slate at a sizable cost reduction over current technology. The approach integrates coal selection, pretreatment, coal swelling with catalyst impregnation, liquefaction, product recovery with characterization, alternate bottoms processing, and carrying out a technical assessment including an economic evaluation. The project is being carried out under contract to the United States Department of Energy. All three coals used in this study (Black Thunder, Burning Star bituminous, and Martin Lake lignite) are effectively swelled by a number of solvents. The most effective solvents are those having hetero-functionality. In addition, a synergistic effect has been demonstrated, in which solvent blends are more effective for coal swelling than the pure solvents alone. Therefore, it will be necessary to use only low levels of swelling agents and yet promote the impregnation of catalyst precursors. The rate of the impregnation of catalyst precursors into swollen coal increases greatly as the effectiveness of the solvent to swell the coal increases. This effect is also demonstrated by improved catalyst precursor impregnation with increased contact temperature. Laboratory- and bench-scale liquefaction experimentation is underway using swelled and catalyst impregnated coal samples. Higher coal conversions were observed for the SO{sub 2}-treated coal than the raw coal, regardless of catalyst type. Conversions of swelled coal were highest when Molyvan-L, molybdenum naphthenate, and nickel octoate, respectively, were added to the liquefaction solvent.