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Sample records for metal catalyst supported

  1. Supported molten-metal catalysts

    DOEpatents

    Datta, Ravindra; Singh, Ajeet; Halasz, Istvan; Serban, Manuela

    2001-01-01

    An entirely new class of catalysts called supported molten-metal catalysts, SMMC, which can replace some of the existing precious metal catalysts used in the production of fuels, commodity chemicals, and fine chemicals, as well as in combating pollution. SMMC are based on supporting ultra-thin films or micro-droplets of the relatively low-melting (<600.degree. C.), inexpensive, and abundant metals and semimetals from groups 1, 12, 13, 14, 15 and 16, of the periodic table, or their alloys and intermetallic compounds, on porous refractory supports, much like supported microcrystallites of the traditional solid metal catalysts. It thus provides orders of magnitude higher surface area than is obtainable in conventional reactors containing molten metals in pool form and also avoids corrosion. These have so far been the chief stumbling blocks in the application of molten metal catalysts.

  2. Supported metal alloy catalysts

    DOEpatents

    Barrera, Joseph; Smith, David C.

    2000-01-01

    A process of preparing a Group IV, V, or VI metal carbonitride including reacting a Group IV, V, or VI metal amide complex with ammonia to obtain an intermediate product; and, heating the intermediate product to temperatures and for times sufficient to form a Group IV, V, or VI metal carbonitride is provided together with the product of the process and a process of reforming an n-alkane by use of the product.

  3. Supported Molten Metal Catalysis. A New Class of Catalysts

    SciTech Connect

    Ravindra Datta; Ajeet Singh; Manuela Serban; Istvan Halasz

    2006-06-02

    We describe a new class of heterogeneous catalysts called supported molten metal catalysis (SMMC), in which molten metal catalysts are dispersed as nanodroplets on the surface of porous supports, allowing much larger active surface area than is possible in conventional contacting techniques for catalytic metals that are molten under reaction conditions, thus greatly enhancing their activity and potential utility. Specific examples of different types of reactions are provided to demonstrate the broad applicability of the technique in designing active, selective, and stable new catalysts. It is shown that dispersing the molten metal on a support in the suggested manner can enhance the rate of a reaction by three to four orders of magnitude as a result of the concomitant increase in the active surface area. New reaction examples include {gamma}-Al{sub 2}O{sub 3} supported molten Te (melting point 450 C) and Ga (MP 30 C) catalysts for bifunctional methylcyclohexane dehydrogenation. These catalysts provide activity similar to conventional Pt-based catalysts for this with better resistance to coking. In addition, results are described for a controlled pore glass supported molten In (MP 157 C) catalyst for the selective catalytic reduction of NO with ethanol in the presence of water, demonstrating activities superior to conventional catalysts for this reaction. A discussion is also provided on the characterization of the active surface area and dispersion of these novel supported catalysts. It is clear based on the results described that the development of new active and selective supported molten metal catalysts for practical applications is entirely plausible.

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

    PubMed

    Serna, Pedro; Gates, Bruce C

    2014-08-19

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

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

    PubMed

    Serna, Pedro; Gates, Bruce C

    2014-08-19

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

  6. Preparation and evaluation of novel hydrous metal oxide (HMO)-supported noble metal catalysts

    SciTech Connect

    Gardner, T.J.; McLaughlin, L.I.; Evans, L.R.; Datye, A.K.

    1998-04-01

    Hydrous Metal Oxides (HMOs) are chemically synthesized materials that, because of their high cation exchange capacity, possess a unique ability to allow the preparation of highly dispersed supported-metal catalyst precursors with high metal loadings. This study evaluates high weight loading Rh/HMO catalysts with a wide range of HMO support compositions, including hydrous titanium oxide (HTO), silica-doped hydrous titanium oxide (HTO:Si), hydrous zirconium oxide (HZO), and silica-doped hydrous zirconium oxide (HZO:Si), against conventional oxide-supported Rh catalysts with similar weight loadings and support chemistries. Catalyst activity measurements for a structure-sensitive model reaction (n-butane hydrogenolysis) as a function of catalyst activation conditions show superior activity and stability for the ZrO{sub 2}, HZO, and HZO:Si supports, although all of the Rh/HMO catalysts have high ethane selectivity indicative of high Rh dispersion. For the TiO{sub 2}-, HTO-, and HTO:Si supported Rh catalysts, a significant loss of both catalyst activity and Rh dispersion is observed at more aggressive activation conditions, consistent with TiO{sub x} migration associated with SMSI phenomena. Of all the Rh/HMO catalysts, the Rh/HZO:Si catalysts appear to offer the best tradeoff in terms of high Rh dispersion, high activity, and high selectivity.

  7. Control of Metal Nanocrystal Size Reveals Metal-Support Interface Role for Ceria Catalysts

    SciTech Connect

    Cargnello, M; Doan-Nguyen, VVT; Gordon, TR; Diaz, RE; Stach, EA; Gorte, RJ; Fornasiero, P; Murray, CB

    2013-08-15

    Interactions between ceria (CeO2) and supported metals greatly enhance rates for a number of important reactions. However, direct relationships between structure and function in these catalysts have been difficult to extract because the samples studied either were heterogeneous or were model systems dissimilar to working catalysts. We report rate measurements on samples in which the length of the ceria-metal interface was tailored by the use of monodisperse nickel, palladium, and platinum nanocrystals. We found that carbon monoxide oxidation in ceria-based catalysts is greatly enhanced at the ceria-metal interface sites for a range of group VIII metal catalysts, clarifying the pivotal role played by the support.

  8. Studies of Immobilized Homogeneous Metal Catalysts on Silica Supports

    SciTech Connect

    Keith James Stanger

    2003-05-31

    The tethered, chiral, chelating diphosphine rhodium complex, which catalyzes the enantioselective hydrogenation of methyl-{alpha}-acetamidocinnamate (MAC), has the illustrated structure as established by {sup 31}P NMR and IR studies. Spectral and catalytic investigations also suggest that the mechanism of action of the tethered complex is the same as that of the untethered complex in solution. The rhodium complexes, [Rh(COD)H]{sub 4}, [Rh(COD){sub 2}]{sup +}BF{sub 4}{sup -}, [Rh(COD)Cl]{sub 2}, and RhCl{sub 3} {center_dot} 3H{sub 2}O, adsorbed on SiO{sub 2} are optimally activated for toluene hydrogenation by pretreatment with H{sub 2} at 200 C. The same complexes on Pd-SiO{sub 2} are equally active without pretreatments. The active species in all cases is rhodium metal. The catalysts were characterized by XPS, TEM, DRIFTS, and mercury poisoning experiments. Rhodium on silica catalyzes the hydrogenation of fluorobenzene to produce predominantly fluorocyclohexane in heptane and 1,2-dichloroethane solvents. In heptane/methanol and heptane/water solvents, hydrodefluorination to benzene and subsequent hydrogenation to cyclohexane occurs exclusively. Benzene inhibits the hydrodefluorination of fluorobenzene. In DCE or heptane solvents, fluorocyclohexane reacts with hydrogen fluoride to form cyclohexene. Reaction conditions can be chosen to selectively yield fluorocyclohexane, cyclohexene, benzene, or cyclohexane. The oxorhenium(V) dithiolate catalyst [-S(CH{sub 2}){sub 3}s-]Re(O)(Me)(PPh{sub 3}) was modified by linking it to a tether that could be attached to a silica support. Spectroscopic investigation and catalytic oxidation reactivity showed the heterogenized catalyst's structure and reactivity to be similar to its homogeneous analog. However, the immobilized catalyst offered additional advantages of recyclability, extended stability, and increased resistance to deactivation.

  9. Predicting catalyst-support interactions between metal nanoparticles and amorphous silica supports

    NASA Astrophysics Data System (ADS)

    Ewing, Christopher S.; Veser, Götz; McCarthy, Joseph J.; Lambrecht, Daniel S.; Johnson, J. Karl

    2016-10-01

    Metal-support interactions significantly affect the stability and activity of supported catalytic nanoparticles (NPs), yet there is no simple and reliable method for estimating NP-support interactions, especially for amorphous supports. We present an approach for rapid prediction of catalyst-support interactions between Pt NPs and amorphous silica supports for NPs of various sizes and shapes. We use density functional theory calculations of 13 atom Pt clusters on model amorphous silica supports to determine linear correlations relating catalyst properties to NP-support interactions. We show that these correlations can be combined with fast discrete element method simulations to predict adhesion energy and NP net charge for NPs of larger sizes and different shapes. Furthermore, we demonstrate that this approach can be successfully transferred to Pd, Au, Ni, and Fe NPs. This approach can be used to quickly screen stability and net charge transfer and leads to a better fundamental understanding of catalyst-support interactions.

  10. Evaluation of some new zeolite-supported metal catalysts for synthesis gas conversion

    SciTech Connect

    Melson, G.A.; Crawford, J.E.; Crites, J.W.; Mbadcam, K.J.; Rao, V.U.S.; Stencel, J.M.

    1982-03-01

    The use of bifunctional zeolite-based catalysts for the conversion of synthesis gas (carbon monoxide and hydrogen) to gasoline range hydrocarbons has recently attracted much attention. For example, the combination of metal oxides with the medium pore (about 6A) zeolite ZSM-5 and the use of a metal nitrate impregnated ZSM-5 catalyst have been shown to produce gasoline range hydrocarbons containing a high percentage of aromatics from synthesis gas. The production of gasoline range hydrocarbons which have a high olefin content has also been reported by using iron or cobalt impregnated ZSM-5 catalysts. The efficiency and selectivity of supported metal heterogeneous catalysts is closely related to the dispersion and particle size of the metal component and to the nature of the interaction between the metal and the support. For a particular metal, catalytic activity may be varied by changing the metal dispersion and the support, thus, the method of synthesis and any pre-treatment of the catalyst is important in the overall process of catalyst evaluation. Supported metal catalysts have traditionally been prepared by impregnation techniques that involve treatment of a support with an aqueous solution of a metal salt followed by calcination. In the Fe/ZSM-5, system, the decomposition of the iron nitrate during calcination usually produces iron oxides of relatively large crystallite size. This work was initiated in an attempt to produce highly dispersed, thermally stable supported metal catalysts which may be effective for synthesis gas conversion.

  11. A new model describing the metal-support interaction in noble metal catalysts

    SciTech Connect

    Mojet, B.L.; Koningsberger, D.C.; Miller, J.T.; Ramaker, D.E.

    1999-09-10

    The catalytic activity and spectroscopic properties of supported noble metal catalysts are strongly influenced by the acidity/alkalinity of the support but are relatively independent of the metal (Pd or Pt) or the type of support (zeolite LTL or SiO{sub 2}). As the alkalinity of the support increases, the TOF of the metal particles for neopentane hydrogenolysis decreases. At the same time, there is a decrease in the XPS binding energy and a shift from linear to bridge bonded CO in the IR spectra. Analysis of the shape resonance in XANES spectra indicates that in the presence of chemisorbed hydrogen the difference in energy between the Pt-H antibonding orbital and the Fermi level decreases as the alkalinity of the support increases. Based on the results from the IR, XPS, and shape resonance data a new model is proposed in which the interaction between the metal and support leads to a shift in the energy of the metal valence orbitals. The EXAFS structural analysis indicates that the small metal particles are in contact only with the oxide ions of the support. Finally, a new spectroscopic characterization, Atomic XAFS, is presented which provides new insights into the origin of the electronic changes in the metal. As the alkalinity of the support increases, there is decrease in the metal ionization potential. The primary interaction is a Coulomb attraction between metal particle and support oxygen ions, which affects the metal interatomic potential. This model for the metal-support interaction explicitly excludes the need for electron transfer, and it can account for all observed changes in the catalytic, electronic, and structural properties of the supported metal particles induced by support acidity ranging from acidic to neutral to alkaline.

  12. Process of making supported catalyst

    DOEpatents

    Schwarz, James A.; Subramanian, Somasundaram

    1992-01-01

    Oxide supported metal catalysts have an additional metal present in intimate association with the metal catalyst to enhance catalytic activity. In a preferred mode, iridium or another Group VIII metal catalyst is supported on a titania, alumina, tungsten oxide, silica, or composite oxide support. Aluminum ions are readsorbed onto the support and catalyst, and reduced during calcination. The aluminum can be added as aluminum nitrate to the iridium impregnate solution, e.g. chloroiridic acid.

  13. CO oxidation studies over supported noble metal catalysts and single crystals: A review

    NASA Technical Reports Server (NTRS)

    Boecker, Dirk; Gonzalez, Richard D.

    1987-01-01

    The catalytic oxidation of CO over noble metal catalysts is reviewed. Results obtained on supported noble metal catalysts and single crystals both at high pressures and under UHV conditions are compared. The underlying causes which result in surface instabilities and multiple steady-state oscillations are considered, in particular, the occurrence of hot spots. CO islands of reactivity, surface oxide formation and phase transformations under oscillatory conditions are discussed.

  14. Supported metal catalysts for alcohol/sugar alcohol steam reforming

    SciTech Connect

    Davidson, Stephen; Zhang, He; Sun, Junming; Wang, Yong

    2014-08-21

    Despite extensive studies on hydrogen production via steam reforming of alcohols and sugar alcohols, catalysts typically suffer a variety of issues from poor hydrogen selectivity to rapid deactivation. Here, we summarize recent advances in fundamental understanding of functionality and structure of catalysts for alcohol/sugar alcohol steam reforming, and provide perspectives on further development required to design highly efficient steam reforming catalysts.

  15. Oxide-supported metal carbonyls: novel catalysts for the liquefaction of coal. Final technical report

    SciTech Connect

    Melson, G.A.

    1985-01-01

    Coal liquefaction, hydrodesulfurization (HDS), and hydrodenitrogenation (HDN) catalysts have been investigated increasingly in recent years because of the need to understand how to develop more selective and stable materials for coal utilization. One catalyst that has been used extensively for HDS and subjected to numerous characterization and model reaction studies is Co-Mo/Al/sub 2/O/sub 3/. In these studies, the catalyst preparation technique has usually involved the incipient-wetness impregnation of ..gamma..-Al/sub 2/O/sub 3/ with ammonium molybdates and cobalt nitrates. Such a technique leads to a variety of surface species, bulk-like and monolayer forms, which have been described and can be controlled by alterations in the preparation techniques and materials. However, certain structural and chemical factors of the catalysts, e.g., Co and Mo reducibility and dispersion or surface speciation at low and high metal concentrations, seem to be independent of such alterations. To investigate whether these factors can be affected by preparation techniques and to develop oxide-supported, metal catalysts having controlled metal dispersions and speciation, a catalyst preparation technique using metal carbonyls with an extraction process to metal-load oxide supports has been developed (J.E. Crawford, G.A. Melson, L.E. Makovsky, F.R. Brown, J. Catal., 83: 454 (1983)). This report discusses the surface and bulk characterization, and presents initial HDS and liquefaction results, for these catalysts. 7 refs., 4 figs., 1 tab.

  16. Towards stable catalysts by controlling collective properties of supported metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Prieto, Gonzalo; Zečević, Jovana; Friedrich, Heiner; de Jong, Krijn P.; de Jongh, Petra E.

    2013-01-01

    Supported metal nanoparticles play a pivotal role in areas such as nanoelectronics, energy storage/conversion and as catalysts for the sustainable production of fuels and chemicals. However, the tendency of nanoparticles to grow into larger crystallites is an impediment for stable performance. Exemplarily, loss of active surface area by metal particle growth is a major cause of deactivation for supported catalysts. In specific cases particle growth might be mitigated by tuning the properties of individual nanoparticles, such as size, composition and interaction with the support. Here we present an alternative strategy based on control over collective properties, revealing the pronounced impact of the three-dimensional nanospatial distribution of metal particles on catalyst stability. We employ silica-supported copper nanoparticles as catalysts for methanol synthesis as a showcase. Achieving near-maximum interparticle spacings, as accessed quantitatively by electron tomography, slows down deactivation up to an order of magnitude compared with a catalyst with a non-uniform nanoparticle distribution, or a reference Cu/ZnO/Al2O3 catalyst. Our approach paves the way towards the rational design of practically relevant catalysts and other nanomaterials with enhanced stability and functionality, for applications such as sensors, gas storage, batteries and solar fuel production.

  17. Towards stable catalysts by controlling collective properties of supported metal nanoparticles.

    PubMed

    Prieto, Gonzalo; Zečević, Jovana; Friedrich, Heiner; de Jong, Krijn P; de Jongh, Petra E

    2013-01-01

    Supported metal nanoparticles play a pivotal role in areas such as nanoelectronics, energy storage/conversion and as catalysts for the sustainable production of fuels and chemicals. However, the tendency of nanoparticles to grow into larger crystallites is an impediment for stable performance. Exemplarily, loss of active surface area by metal particle growth is a major cause of deactivation for supported catalysts. In specific cases particle growth might be mitigated by tuning the properties of individual nanoparticles, such as size, composition and interaction with the support. Here we present an alternative strategy based on control over collective properties, revealing the pronounced impact of the three-dimensional nanospatial distribution of metal particles on catalyst stability. We employ silica-supported copper nanoparticles as catalysts for methanol synthesis as a showcase. Achieving near-maximum interparticle spacings, as accessed quantitatively by electron tomography, slows down deactivation up to an order of magnitude compared with a catalyst with a non-uniform nanoparticle distribution, or a reference Cu/ZnO/Al(2)O(3) catalyst. Our approach paves the way towards the rational design of practically relevant catalysts and other nanomaterials with enhanced stability and functionality, for applications such as sensors, gas storage, batteries and solar fuel production. PMID:23142841

  18. Silica coated noble metal nanoparticle hydrosols as supported catalyst precursors.

    PubMed

    Kong, Tung Shing Adam; Yu, Kai Man Kerry; Tsang, Shik Chi

    2006-04-01

    Synthesis of well-defined nanoparticles has been intensively pursued not only for their fundamental scientific interest, but also for many technological applications. One important development of the nanomaterial is in the area of chemical catalysis. We have now developed a new aqueous-based method for the synthesis of silica encapsulated noble metal nanoparticles in controlled dimensions. Thus, colloid stable silica encapsulated approximately 5 nm platinum nanoparticle is synthesized by a multi-step method. The thickness of the silica coating could be controlled using a different amount of silica precursor. These particles supported on a high surface area alumina are also demonstrated to display a superior hydrogenation activity and stability against metal sintering after thermal activation.

  19. Crystalline titanate catalyst supports

    DOEpatents

    Anthony, Rayford G.; Dosch, Robert G.

    1993-01-01

    A series of new crystalline titanates (CT) are shown to have considerable potential as catalyst supports. For Pd supported catalyst, the catalytic activity for pyrene hydrogenation was substantially different depending on the type of CT, and one was substantially more active than Pd on hydrous titanium oxide (HTO). For 1-hexene hydrogenation the activities of the new CTs were approximately the same as for the hydrous metal oxide supports.

  20. Crystalline titanate catalyst supports

    DOEpatents

    Anthony, R.G.; Dosch, R.G.

    1993-01-05

    A series of new crystalline titanates (CT) are shown to have considerable potential as catalyst supports. For Pd supported catalyst, the catalytic activity for pyrene hydrogenation was substantially different depending on the type of CT, and one was substantially more active than Pd on hydrous titanium oxide (HTO). For 1-hexene hydrogenation the activities of the new CTs were approximately the same as for the hydrous metal oxide supports.

  1. H2-SCR at low temperatures on noble metal supported catalysts

    NASA Astrophysics Data System (ADS)

    Mihet, Maria; Lazar, Mihaela Diana; Almasan, V.; Mirel, V.

    2012-02-01

    The selective catalytic reduction of NO using hydrogen as reducing agent (H2-SCR) is investigated on alumina supported noble metal catalysts at low temperatures (<350°C). Three noble metal supported catalysts (Pt/Al2O3, Pd/Al2O3, and Rh/Al2O3 with 1 wt.% metal loading), prepared by the incipient wetness impregnation method, were characterized by N2 adsorption-desorption at -196°C, NO-TPD, and H2-TPD. Catalytic activity tests of the investigated noble metal catalysts were performed under plug flow conditions, using a feed stream of 0.5% NO, 0.60% H2 and Ar as balance gas, at temperatures below 350°C, and a GHSV of 4500 h-1. Pt/Al2O3 and Pd/Al2O3 proved to be the most active catalysts for H2-SCR in terms of NO conversion, while the Pd catalyst showed the best N2 selectivity and N2 yield. NO conversion > 95% and N2 selectivity above 80% were obtained for each catalyst at 200°C.

  2. High quality syngas production from microwave pyrolysis of rice husk with char-supported metallic catalysts.

    PubMed

    Zhang, Shuping; Dong, Qing; Zhang, Li; Xiong, Yuanquan

    2015-09-01

    This study aimed to obtain the maximum possible gas yield and the high quality syngas production from microwave pyrolysis of rice husk with rice husk char and rice husk char-supported metallic (Ni, Fe and Cu) catalysts. The rice husk char-supported metallic catalysts had developed pore structure and catalytic activity for gas productions and tar conversion. The temperature-rising characteristic, product yields, properties of gas products and tar conversion mechanisms were investigated. It was found that three rice husk char-supported metallic catalysts improved the microwave absorption capability and increased heating rate and final temperature. Rice husk char-supported Ni catalyst presented most effective effects on gas production, e.g. the gas yield is 53.9%, and the volume concentration of desired syngas is 69.96%. Rice husk char-supported Ni and Fe catalysts played pivotal roles in tar conversion that less heavy compounds can be detected along with the reduction of organic compound number.

  3. A combinatorial study on catalytic synergism in supported metal catalysts for fuel cell technology

    NASA Astrophysics Data System (ADS)

    Kobayashi, Tetsuhiko; Ueda, Atsushi; Yamada, Yusuke; Shioyama, Hiroshi

    2004-02-01

    In order to accelerate the catalyst development for the increasing demand on the fuel cell technology, it has been attempted to adopt a combinatorial approach. The catalytic synergism, often observed on the supported metal catalysts for the fuel cell utilization, has been subjected to study. It is proposed herein that not only a comparison of catalysts in one reaction, but also the comparison of interrelated reactions by use of a common catalyst library brings about important information to elucidate the catalytic synergism. Preliminary results of the comparison between the water-gas shift reaction and the steam reforming of MeOH on a given set of catalyst library are presented. An important indicator to predict the serendipitous synergism is expected to be obtained from such information by use of artificial intelligence.

  4. Self-Supporting Metal-Organic Layers as Single-Site Solid Catalysts.

    PubMed

    Cao, Lingyun; Lin, Zekai; Peng, Fei; Wang, Weiwei; Huang, Ruiyun; Wang, Cheng; Yan, Jiawei; Liang, Jie; Zhang, Zhiming; Zhang, Teng; Long, Lasheng; Sun, Junliang; Lin, Wenbin

    2016-04-11

    Metal-organic layers (MOLs) represent an emerging class of tunable and functionalizable two-dimensional materials. In this work, the scalable solvothermal synthesis of self-supporting MOLs composed of [Hf6O4(OH)4(HCO2)6] secondary building units (SBUs) and benzene-1,3,5-tribenzoate (BTB) bridging ligands is reported. The MOL structures were directly imaged by TEM and AFM, and doped with 4'-(4-benzoate)-(2,2',2''-terpyridine)-5,5''-dicarboxylate (TPY) before being coordinated with iron centers to afford highly active and reusable single-site solid catalysts for the hydrosilylation of terminal olefins. MOL-based heterogeneous catalysts are free from the diffusional constraints placed on all known porous solid catalysts, including metal-organic frameworks. This work uncovers an entirely new strategy for designing single-site solid catalysts and opens the door to a new class of two-dimensional coordination materials with molecular functionalities.

  5. Supported transition-metal oxide catalysts for reduction of sulfur dioxide with hydrogen to elemental sulfur.

    PubMed

    Chen, Chun-Liang; Wang, Ching-Huei; Weng, Hung-Shan

    2004-08-01

    This work is for the purpose to find a high performance catalyst for the catalytic reduction of SO2 with H2 as a reducing agent. NiO/gamma-Al2O3 catalyst was found to be the most active catalyst among the seven gamma-Al2O3-supported metal-oxide catalysts tested. With NiO as the active species, of the supports tested, gamma-Al2O3 was the most suitable one and the optimal Ni content was 16 wt%. Using this NiO/gamma-Al2O3 catalyst, we found that the optimal feed ratio of H2/SO2 is 2:1 and the catalyst presulfided with H2 + H2S exhibits a higher performance than that pretreated with H2 or He. XRD patterns reveal that the nickel oxide experienced a transformation to Ni3S2 and NiS, and then to NiS2, the most active nickel sulfide, during the reaction process. The reason for the highest catalyst activity of 16 wt% Ni was attributed to the largest amount of NiS2. Water vapor in the feed gas reactant caused inhibition of catalyst activity, whereas H2S promoted the reduction of SO2. These phenomena were rationalized with the aid of Claus reaction. PMID:15212907

  6. Monodisperse metal nanoparticle catalysts on silica mesoporous supports: synthesis, characterizations, and catalytic reactions

    SciTech Connect

    Somorjai, G.A.

    2009-09-14

    The design of high performance catalyst achieving near 100% product selectivity at maximum activity is one of the most important goals in the modern catalytic science research. To this end, the preparation of model catalysts whose catalytic performances can be predicted in a systematic and rational manner is of significant importance, which thereby allows understanding of the molecular ingredients affecting the catalytic performances. We have designed novel 3-dimensional (3D) high surface area model catalysts by the integration of colloidal metal nanoparticles and mesoporous silica supports. Monodisperse colloidal metal NPs with controllable size and shape were synthesized using dendrimers, polymers, or surfactants as the surface stabilizers. The size of Pt, and Rh nanoparticles can be varied from sub 1 nm to 15 nm, while the shape of Pt can be controlled to cube, cuboctahedron, and octahedron. The 3D model catalysts were generated by the incorporation of metal nanoparticles into the pores of mesoporous silica supports via two methods: capillary inclusion (CI) and nanoparticle encapsulation (NE). The former method relies on the sonication-induced inclusion of metal nanoparticles into the pores of mesoporous silica, whereas the latter is performed by the encapsulation of metal nanoparticles during the hydrothermal synthesis of mesoporous silica. The 3D model catalysts were comprehensively characterized by a variety of physical and chemical methods. These catalysts were found to show structure sensitivity in hydrocarbon conversion reactions. The Pt NPs supported on mesoporous SBA-15 silica (Pt/SBA-15) displayed significant particle size sensitivity in ethane hydrogenolysis over the size range of 1-7 nm. The Pt/SBA-15 catalysts also exhibited particle size dependent product selectivity in cyclohexene hydrogenation, crotonaldehyde hydrogenation, and pyrrole hydrogenation. The Rh loaded SBA-15 silica catalyst showed structure sensitivity in CO oxidation reaction. In

  7. Surface/structure functionalization of copper-based catalysts by metal-support and/or metal-metal interactions

    NASA Astrophysics Data System (ADS)

    Konsolakis, Michalis; Ioakeimidis, Zisis

    2014-11-01

    Cu-based catalysts have recently attracted great attention both in catalysis and electro-catalysis fields due to their excellent catalytic performance and low cost. Given that their performance is determined, to a great extent, by Cu sites local environment, considerable efforts have been devoted on the strategic modifications of the electronic and structural properties of Cu sites. In this regard, the feasibility of tuning the local structure of Cu entities by means of metal-support or metal-metal interactions is investigated. More specifically, the physicochemical properties of Cu entities are modified by employing: (i) different oxides (CeO2, La2O3, Sm2O3), or (ii) ceria-based mixed oxides (Ce1-xSmxOδ) as supporting carriers, and (iii) a second metal (Cobalt) adjacent to Cu (bimetallic Cu-Co/CeO2). A characterization study, involving BET, XRD, TPR, and XPS, reveal that significant modifications on structural, redox and electronic properties of Cu sites can be induced by adopting either different oxide carriers or bimetallic complexes. Fundamental insights into the tuning of Cu local environment by metal-support or metal-metal interactions are provided, paving the way for real-life industrial applications.

  8. CeO2 nanorods-supported transition metal catalysts for CO oxidation.

    PubMed

    Mock, Samantha A; Sharp, Shannon E; Stoner, Thomas R; Radetic, Michael J; Zell, Elizabeth T; Wang, Ruigang

    2016-03-15

    A catalytically active oxide support in combination with metal catalysts is required in order to achieve better low temperature activity and selectivity. Here, we report that CeO2 nanorods with a superior surface oxygen release/storage capability were used as an active support of transition metal (TM) catalysts (Mn, Fe, Co, Ni, Cu) for CO oxidation reaction. The as-prepared CeO2 nanorods supported 10 wt% TM catalysts were highly active for CO oxidation at low temperature, except for the Fe sample. It is found that the 10%Cu-CeO2 catalyst performed best, and it provided a lower light-off temperature with T50 (50% conversion) at 75 °C and T100 (100% conversion) of CO to CO2 at 194 °C. The atomic level surface structure of CeO2 nanorods was investigated in order to understand the improved low temperature catalytic activity. The richness of surface roughness and various defects (voids, lattice distortion, bending, steps, twinning) on CeO2 nanorods could facilitate oxygen release and storage. According to XRD and Raman analysis, copper species migrate into the bulk CeO2 nanorods to a greater degree. Since CO adsorbed over the surface of the catalyst/support is detrimental to its catalytic activity, the surface defects on the CeO2 nanorods and CeO2-TM interactions were critical to the enhanced activity.

  9. CeO2 nanorods-supported transition metal catalysts for CO oxidation.

    PubMed

    Mock, Samantha A; Sharp, Shannon E; Stoner, Thomas R; Radetic, Michael J; Zell, Elizabeth T; Wang, Ruigang

    2016-03-15

    A catalytically active oxide support in combination with metal catalysts is required in order to achieve better low temperature activity and selectivity. Here, we report that CeO2 nanorods with a superior surface oxygen release/storage capability were used as an active support of transition metal (TM) catalysts (Mn, Fe, Co, Ni, Cu) for CO oxidation reaction. The as-prepared CeO2 nanorods supported 10 wt% TM catalysts were highly active for CO oxidation at low temperature, except for the Fe sample. It is found that the 10%Cu-CeO2 catalyst performed best, and it provided a lower light-off temperature with T50 (50% conversion) at 75 °C and T100 (100% conversion) of CO to CO2 at 194 °C. The atomic level surface structure of CeO2 nanorods was investigated in order to understand the improved low temperature catalytic activity. The richness of surface roughness and various defects (voids, lattice distortion, bending, steps, twinning) on CeO2 nanorods could facilitate oxygen release and storage. According to XRD and Raman analysis, copper species migrate into the bulk CeO2 nanorods to a greater degree. Since CO adsorbed over the surface of the catalyst/support is detrimental to its catalytic activity, the surface defects on the CeO2 nanorods and CeO2-TM interactions were critical to the enhanced activity. PMID:26745742

  10. Ethanol oxidation on metal oxide-supported platinum catalysts

    SciTech Connect

    L. M. Petkovic 090468; Sergey N. Rashkeev; D. M. Ginosar

    2009-09-01

    Ethanol is a renewable fuel that can be used as an additive to gasoline (or its substitute) with the advantage of octane enhancement and reduced carbon monoxide exhaust emissions. However, on Ethanol is a renewable fuel that can be used as an additive to gasoline (or its substitute) with the advantage of octane enhancement and reduced carbon monoxide exhaust emissions. However, on the standard three-way catalysts, the conversion of unburned ethanol is low because both ethanol and some of its partially oxidized derivatives are highly resistant to oxidation. A combination of first-principles density-functional theory (DFT) based calculations and in-situ diffuse reflectance infrared spectroscopy (DRIFTS) analysis was applied to uncover some of the fundamental phenomena associated with ethanol oxidation on Pt containing catalysts. In particular, the objective was to analyze the role of the oxide (i.e., ?-Al2O3 or SiO2) substrate on the ethanol oxidation activity. The results showed that Pt nanoparticles trap and accumulate oxygen at their surface and perimeter sites and play the role of “stoves” that burn ethanol molecules and their partially oxidized derivatives to the “final” products. The ?-Al2O3 surfaces provided higher mobility of the fragments of ethanol molecules than the SiO2 surface and hence increased the supply rate of these objects to the Pt particles. This will in turn produce a higher conversion rate of unburned ethanol.and some of its partially oxidized derivatives are highly resistant to oxidation. A combination of first-principles density-functional theory (DFT) based calculations and in-situ diffuse reflectance infrared spectroscopy (DRIFTS) analysis was applied to uncover some of the fundamental phenomena associated with ethanol oxidation on Pt containing catalysts. In particular, the objective was to analyze the role of the oxide (i.e., ?-Al2O3 or SiO2) substrate on the ethanol oxidation activity. The results showed that Pt nanoparticles

  11. Supported oxorhenate catalysts prepared by thermal spreading of metal Re 0 for methanol conversion to methylal

    NASA Astrophysics Data System (ADS)

    Sécordel, Xavier; Yoboué, Anthony; Cristol, Sylvain; Lancelot, Christine; Capron, Mickaël; Paul, Jean-François; Berrier, Elise

    2011-10-01

    TiO 2-anatase and SiO 2 supported oxorhenate catalysts were prepared by an original and simple technique based on the oxidative dispersion of metallic rhenium under dry conditions. The dispersion process of the supported oxorhenate phase as a function of the rhenium coverage and the support properties are discussed on the base of in situ characterization. The structures of the as prepared catalysts were found to be comparable to those of materials prepared using the incipient wetness impregnation technique. The absence of water in the preparation technique has made it possible to highlight the role of the hydration level on the rhenium oxide volatilization. The as-prepared Re/TiO 2 catalysts were found to be effective for the direct conversion of methanol to methylal.

  12. Supported transition metal catalysts for para- to ortho-hydrogen conversion

    NASA Technical Reports Server (NTRS)

    Brooks, Christopher J.; Wang, Wei; Eyman, Darrell P.

    1994-01-01

    The main goal of this study was to develop and improve on existing catalysts for the conversion of ortho- to para-hydrogen. Starting with a commercially available Air Products nickel silicate, which had a beta value of 20, we were trying to synthesize catalysts that would be an improvement to AP. This was accomplished by preparing silicates with various metals as well as different preparation methods. We also prepared supported ruthenium catalysts by various techniques using several metal precursors to improve present technology. What was also found was that the activation conditions prior to catalytic testing was highly important for both the silicates and the supported ruthenium catalysts. While not the initial focus of the research, we made some interesting observations into the adsorption of H2 on ruthenium. This helped us to get a better understanding of how ortho- to para-H2 conversion takes place, and what features in a catalyst are important to optimize activity. Reactor design was the final area in which some interesting conclusions were drawn. As discussed earlier, the reactor catalyst bed must be constructed using straight 1/8 feet OD stainless steel tubing. It was determined that the use of 1/4 feet OD tubing caused two problems. First, the radius from the center of the bed to the wall was too great for thermal equilibrium. Since the reaction of ortho- to para-H2 is exothermic, the catalyst bed center was warmer than the edges. Second, the catalyst bed was too shallow using a 1/4 feet tube. This caused reactant blow-by which was thought to decrease the measured activity when the flow rate was increased. The 1/8 feet tube corrected both of these concerns.

  13. 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.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

    Gould, Troy D.

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

  16. Hydrodenitrogenation of decahydroquinoline, cyclohexylamine and O-propylaniline over carbon-supported transition metal sulfide catalysts

    SciTech Connect

    Eijsbouts, S.; Sudhakar, C.; de Beer, V.H.J.; Prins, R. )

    1991-02-01

    Carbon-supported transition metal sulfide (TMS) catalysts were prepared by impregnation of an activated carbon support with aqueous solutions of first-, second-, and third-row (group V-VIII) transition metal salts followed by drying and in situ sulfidation. Their activity for the hydrodenitrogenation of decahydroquinoline (5.2-5.5 MPa, 623-653 K), cyclohexylamine (4.8-5.5 MPa, 543-653 K), and o-propylaniline (5.1-5.5 MPa, 593-653 K) was tested in microautoclaves. When plotted versus the position of the transition metal in the Periodic System, the conversions of all three N-containing reactants to hydrocarbons over the first-row transition metal sulfides formed U-shaped curves with a minimum at Mn, while V had the highest conversion. The decahydroquinoline and cyclohexylamine conversions to hydrocarbons over the second- and third-row TMS formed volcano curves with maxima at Rh and Ir, respectively. Disproportionation reactions were found to be important side reactions in the cyclohexylamine hydrodenitrogenation. The activities of the second-row transition metal sulfides for the conversion of 0-propylaniline formed a volcano curve with a maximum at Ru or Rh sulfide, whereas the activities of the third-row transition metal sulfides formed a strongly distorted volcano curve. All catalysts and especially Re sulfide had a very high selectivity for propylbenzene.

  17. Carrier effects of active carbon for methanol carbonylation with supported transition metal catalysts

    SciTech Connect

    Fujimoto, K.; Omata, K.; Yagita, H.

    1996-10-01

    Transition metals such as nickel or noble metals showed excellent catalytic activities for the vapor phase carbonylation of methanol to acetic acid. Reaction proceeded via the carbonylation of methanol to methyl acetate and its successive carbonylation to acetic acid anhydride followed by the hydrolysis. Under slightly pressurized conditions and at around 250{degrees}C methanol was completely carbonylated to acetic acid with the selectivity of 97% or higher. Also, other group 8 metals including noble metals showed excellent catalytic activity only when they were supported on active carbon, whose activity, ordered by strength of metal-halogen bonding showed a volcano-shape relationship with the peak at Rh. The role of active carbon as the active carrier was clarified by kinetics and catalyst characterization which showed that active carbon promoted the reductive elimination of intermediate for acetic acid formation by donating electron from carbon to nickel species.

  18. Periodic trends in the hydrodenitrogenation activity of carbon-supported transition metal sulfide catalysts

    SciTech Connect

    Eijsbouts, S.; De Beer, V.H.J.; Prins, R.

    1988-01-01

    Periodic trends of transition metals for the catalysis of reactions such as hydrogenation, hydrogenolysis, isomerization and hydrogen oxidation have been well studied. When activity versus position of the transition metal in the periodic table is plotted, quite often these trends are manifested in the form of so-called volcano-type curves. In the present study, the authors have chosen the HDN of quinoline at moderately high pressure as a model reaction, and they have used the same carbon-supported transition metal sulfide catalysts studied by Vissers et al. Results are shown for the following transition metals: V, Cr, Mn, Fe, Co, Ni, Mo, Ru, Rh, Pd, W, Re, Os, Ir, and Pt. 9 references.

  19. Metal (Fe, Co, Ni) supported on different aluminas as Fischer-Tropsch catalyst

    NASA Astrophysics Data System (ADS)

    Dahlan, Marsih, I. Nyoman; Makertihartha, I. G. B. N.; Praserthdam, Piyasan; Panpranot, Joongjai; Ismunandar

    2015-09-01

    This research aimed to compare the physico-chemical properties of the same metal M (M = iron, cobalt, nickel) supported on aluminas with different morphology and pore size as Fischer-Tropsch catalyst. The aluminas applied as support were alumina synthesized through hydrothermal process, alumina formed by pretreatment of catapal and commercial alumina which named as Ahy, Aca, and Aco respectively. Ahy has uniform morphology of nanotubes while Aca and Aco showed non-uniform morphology of particle lumps. The particle lumps of Aca were larger than those of Aco. Ahy, Aca, and Aco respectively has average pore diameter of 2.75, 2.86 and 2.9 nm. Metals were deposited on the supports by incipient-wetness impregnation method. The catalysts were characterized by XRD, H2-TPR, and H2 chemisorption. Catalyst acitivity test for Fischer-Tropsch reaction was carried out in a micro reactor at 200 °C and 1 atm, and molar ratio of H2/CO = 2:1. The metal oxide particle size increased in the order M/Aco < M/Aca < M/Ahy. The catalysts reducibility also increased according to the order M/Aco < M/Aca < M/Ahy suggesting that the larger metal oxide particles are more reducible. The number of active site was not proportional to the reducibility because during the reduction, larger metal oxide particles were converted into larger metal particles. On the other hand, the number of active sites was inversely proportional to the particle sizes. The number of active site increased in the order M/Ahy < M/Aco < M/Aca. The catalytic activity also increased in the following order M/Ahy < M/Aco < M/Aca. The activity per active site increased according to the order M/Aca < M/Aco < M/Ahy meaning that for M/Ahy, a little increase in active site will lead to a significance increase in catalytic activity. It showed that Ahy has potential for the better support.

  20. Metal (Fe, Co, Ni) supported on different aluminas as Fischer-Tropsch catalyst

    SciTech Connect

    Dahlan; Marsih, I. Nyoman Ismunandar; Makertihartha, I. G. B. N.; Praserthdam, Piyasan; Panpranot, Joongjai

    2015-09-30

    This research aimed to compare the physico-chemical properties of the same metal M (M = iron, cobalt, nickel) supported on aluminas with different morphology and pore size as Fischer-Tropsch catalyst. The aluminas applied as support were alumina synthesized through hydrothermal process, alumina formed by pretreatment of catapal and commercial alumina which named as Ahy, Aca, and Aco respectively. Ahy has uniform morphology of nanotubes while Aca and Aco showed non-uniform morphology of particle lumps. The particle lumps of Aca were larger than those of Aco. Ahy, Aca, and Aco respectively has average pore diameter of 2.75, 2.86 and 2.9 nm. Metals were deposited on the supports by incipient-wetness impregnation method. The catalysts were characterized by XRD, H{sub 2}-TPR, and H{sub 2} chemisorption. Catalyst acitivity test for Fischer-Tropsch reaction was carried out in a micro reactor at 200 °C and 1 atm, and molar ratio of H{sub 2}/CO = 2:1. The metal oxide particle size increased in the order M/Aco < M/Aca < M/Ahy. The catalysts reducibility also increased according to the order M/Aco < M/Aca < M/Ahy suggesting that the larger metal oxide particles are more reducible. The number of active site was not proportional to the reducibility because during the reduction, larger metal oxide particles were converted into larger metal particles. On the other hand, the number of active sites was inversely proportional to the particle sizes. The number of active site increased in the order M/Ahy < M/Aco < M/Aca. The catalytic activity also increased in the following order M/Ahy < M/Aco < M/Aca. The activity per active site increased according to the order M/Aca < M/Aco < M/Ahy meaning that for M/Ahy, a little increase in active site will lead to a significance increase in catalytic activity. It showed that Ahy has potential for the better support.

  1. Decomposition of hexachlorobenzene over Al2O3 supported metal oxide catalysts.

    PubMed

    Zhang, Lifei; Zheng, Minghui; Zhang, Bing; Liu, Wenbin; Gao, Lirong; Ba, Te; Ren, Zhiyuan; Su, Guijin

    2008-01-01

    Decomposition of hexachlorobenzene (HCB) was investigated over several metal oxides (i.e., MgO, CaO, BaO, La2O3, CeO2, MnO2, Fe2O3, and Co3O4) supported on Al2O3, which was achieved in closed system at a temperature of 300 degrees C. Catalysts were prepared by incipient wetness impregnation with different metal oxides loading and impregnating solvents. The decomposition efficiency of different catalysts for this reaction depends on the nature of the metal oxide used, and Al2O3 supported La2O3 was found to be the most active one. Pentachlorobenzene (PeCB), and all tetrachlorobenzene (TeCB), trichlorobenzene (TrCB), and dichlorobenzene (DCB) isomers were detected after the decomposition reaction, indicating that the decomposition was mainly a dechlorination process. The detection of all lower chlorinated benzenes suggested the complexity of decomposition and the presence of more than one dechlorination pathway. PMID:19209643

  2. Noble metal ionic catalysts.

    PubMed

    Hegde, M S; Madras, Giridhar; Patil, K C

    2009-06-16

    Because of growing environmental concerns and increasingly stringent regulations governing auto emissions, new more efficient exhaust catalysts are needed to reduce the amount of pollutants released from internal combustion engines. To accomplish this goal, the major pollutants in exhaust-CO, NO(x), and unburned hydrocarbons-need to be fully converted to CO(2), N(2), and H(2)O. Most exhaust catalysts contain nanocrystalline noble metals (Pt, Pd, Rh) dispersed on oxide supports such as Al(2)O(3) or SiO(2) promoted by CeO(2). However, in conventional catalysts, only the surface atoms of the noble metal particles serve as adsorption sites, and even in 4-6 nm metal particles, only 1/4 to 1/5 of the total noble metal atoms are utilized for catalytic conversion. The complete dispersion of noble metals can be achieved only as ions within an oxide support. In this Account, we describe a novel solution to this dispersion problem: a new solution combustion method for synthesizing dispersed noble metal ionic catalysts. We have synthesized nanocrystalline, single-phase Ce(1-x)M(x)O(2-delta) and Ce(1-x-y)Ti(y)M(x)O(2-delta) (M = Pt, Pd, Rh; x = 0.01-0.02, delta approximately x, y = 0.15-0.25) oxides in fluorite structure. In these oxide catalysts, Pt(2+), Pd(2+), or Rh(3+) ions are substituted only to the extent of 1-2% of Ce(4+) ion. Lower-valent noble metal ion substitution in CeO(2) creates oxygen vacancies. Reducing molecules (CO, H(2), NH(3)) are adsorbed onto electron-deficient noble metal ions, while oxidizing (O(2), NO) molecules are absorbed onto electron-rich oxide ion vacancy sites. The rates of CO and hydrocarbon oxidation and NO(x) reduction (with >80% N(2) selectivity) are 15-30 times higher in the presence of these ionic catalysts than when the same amount of noble metal loaded on an oxide support is used. Catalysts with palladium ion dispersed in CeO(2) or Ce(1-x)Ti(x)O(2) were far superior to Pt or Rh ionic catalysts. Therefore, we have demonstrated that the

  3. Role of metal-support interactions on the activity of Pt and Rh catalysts for reforming methane and butane.

    SciTech Connect

    Rossignol, C.; Krause, T.; Krumpelt, M.

    2002-01-11

    For residential fuel cell systems, reforming of natural gas is one option being considered for providing the H{sub 2} necessary for the fuel cell to operate. Industrially, natural gas is reformed using Ni-based catalysts supported on an alumina substrate, which has been modified to inhibit coke formation. At Argonne National Laboratory, we have developed a new family of catalysts derived from solid oxide fuel cell technology for reforming hydrocarbon fuels to generate H{sub 2}. These catalysts consist of a transition metal supported on an oxide-ion-conducting substrate, such as ceria, that has been doped with a small amount of a non-reducible element, such as gadolinium, samarium, or zirconium. Unlike alumina, the oxide-ion-conducting substrate has been shown to induce strong metal-support interactions. Metal-support interactions are known to play an important role in influencing the catalytic activity of many metals supported on oxide supports. Based on results from temperature-programmed reduction/oxidation and kinetic reaction studies, this paper discusses the role of the metal and the substrate in the metal-support interactions, and how these interactions influence the activity and the selectivity of the catalyst in reforming methane and butane to hydrogen for use in fuel cell power systems.

  4. Environmentally Friendly Carbon-Preserving Recovery of Noble Metals From Supported Fuel Cell Catalysts.

    PubMed

    Latsuzbaia, R; Negro, E; Koper, G J M

    2015-06-01

    The dissolution of noble-metal catalysts under mild and carbon-preserving conditions offers the possibility of in situ regeneration of the catalyst nanoparticles in fuel cells or other applications. Here, we report on the complete dissolution of the fuel cell catalyst, platinum nanoparticles, under very mild conditions at room temperature in 0.1 M HClO4 and 0.1 M HCl by electrochemical potential cycling between 0.5-1.1 V at a scan rate of 50 mV s(-1) . Dissolution rates as high as 22.5 μg cm(-2) per cycle were achieved, which ensured a relatively short dissolution timescale of 3-5 h for a Pt loading of 0.35 mg cm(-2) on carbon. The influence of chloride ions and oxygen in the electrolyte on the dissolution was investigated, and a dissolution mechanism is proposed on the basis of the experimental observations and available literature results. During the dissolution process, the corrosion of the carbon support was minimal, as observed by X-ray photoelectron spectroscopy (XPS).

  5. Environmentally Friendly Carbon-Preserving Recovery of Noble Metals From Supported Fuel Cell Catalysts.

    PubMed

    Latsuzbaia, R; Negro, E; Koper, G J M

    2015-06-01

    The dissolution of noble-metal catalysts under mild and carbon-preserving conditions offers the possibility of in situ regeneration of the catalyst nanoparticles in fuel cells or other applications. Here, we report on the complete dissolution of the fuel cell catalyst, platinum nanoparticles, under very mild conditions at room temperature in 0.1 M HClO4 and 0.1 M HCl by electrochemical potential cycling between 0.5-1.1 V at a scan rate of 50 mV s(-1) . Dissolution rates as high as 22.5 μg cm(-2) per cycle were achieved, which ensured a relatively short dissolution timescale of 3-5 h for a Pt loading of 0.35 mg cm(-2) on carbon. The influence of chloride ions and oxygen in the electrolyte on the dissolution was investigated, and a dissolution mechanism is proposed on the basis of the experimental observations and available literature results. During the dissolution process, the corrosion of the carbon support was minimal, as observed by X-ray photoelectron spectroscopy (XPS). PMID:25959077

  6. Vapor-phase catalytic oxidesulfurization (ODS) of organosulfur compounds over supported metal oxide catalysts

    NASA Astrophysics Data System (ADS)

    Choi, Sukwon

    Sulfur in transportation fuels remains a leading source of SOx emissions from vehicle engines and is a major source of air pollution. The very low levels of sulfur globally mandated for transportation fuels in the near future cannot be achieved by current practices of hydrodesulfurization (HDS) for sulfur removal, which operate under severe conditions (high T, P) and use valuable H2. Novel vapor-phase catalytic oxidesulfurization (ODS) processes of selectively oxidizing various organosulfur compounds (carbonyl sulfide, carbon disulfide, methanethiol, dimethyl sulfide (DMS), dimethyl disulfide (DMDS), thiophene, 2,5-dimenthylthiophene) typically found in various industrial streams (e.g., petroleum refining, pulp and paper) into valuable chemical intermediates (H 2CO, CO, H2, maleic anhydride and concentrated SO2) has been extensively studied. This research has primarily focused on establishing the fundamental kinetics and mechanisms of these selective oxidation reactions over well-defined supported metal oxide catalysts. The selective oxidation reactions of COS + O2 → CO + SO2; 2CS2 + 5O2 → 2CO + 4SO2; CH3SH + 2O 2 → H2CO + SO2 + H2O; C4 H4S + 3O2 → C4H2O 3 + H2O + SO2; were studied. Raman spectroscopy revealed that the supported metal oxide phases were 100% dispersed on the oxide substrate. All the catalysts were highly active and selective for the oxidesulfurization of carbonyl sulfide, carbon disulfide, methanethiol, and thiophene between 290--330°C, 230--270°C, 350--400°C, and 250--400°C, respectively and did not deactivate. The TOFs (turnover frequency, normalized activity per active catalytic site) for all ODS reactions over supported vanadia catalysts, only containing molecularly dispersed surface vanadia species, varied within one order of magnitude and revealed the V-O-Support bridging bond was involved in the critical rate-determining kinetic steps. The surface reaction mechanism for each reaction was revealed by in situ IR (infrared) and

  7. Dynamical Observation and Detailed Description of Catalysts under Strong Metal-Support Interaction.

    PubMed

    Zhang, Shuyi; Plessow, Philipp N; Willis, Joshua J; Dai, Sheng; Xu, Mingjie; Graham, George W; Cargnello, Matteo; Abild-Pedersen, Frank; Pan, Xiaoqing

    2016-07-13

    Understanding the structures of catalysts under realistic conditions with atomic precision is crucial to design better materials for challenging transformations. Under reducing conditions, certain reducible supports migrate onto supported metallic particles and create strong metal-support states that drastically change the reactivity of the systems. The details of this process are still unclear and preclude its thorough exploitation. Here, we report an atomic description of a palladium/titania (Pd/TiO2) system by combining state-of-the-art in situ transmission electron microscopy and density functional theory (DFT) calculations with structurally defined materials, in which we visualize the formation of the overlayers at the atomic scale under atmospheric pressure and high temperature. We show that an amorphous reduced titania layer is formed at low temperatures, and that crystallization of the layer into either mono- or bilayer structures is dictated by the reaction environment and predicted by theory. Furthermore, it occurs in combination with a dramatic reshaping of the metallic surface facets.

  8. Dynamical Observation and Detailed Description of Catalysts under Strong Metal-Support Interaction.

    PubMed

    Zhang, Shuyi; Plessow, Philipp N; Willis, Joshua J; Dai, Sheng; Xu, Mingjie; Graham, George W; Cargnello, Matteo; Abild-Pedersen, Frank; Pan, Xiaoqing

    2016-07-13

    Understanding the structures of catalysts under realistic conditions with atomic precision is crucial to design better materials for challenging transformations. Under reducing conditions, certain reducible supports migrate onto supported metallic particles and create strong metal-support states that drastically change the reactivity of the systems. The details of this process are still unclear and preclude its thorough exploitation. Here, we report an atomic description of a palladium/titania (Pd/TiO2) system by combining state-of-the-art in situ transmission electron microscopy and density functional theory (DFT) calculations with structurally defined materials, in which we visualize the formation of the overlayers at the atomic scale under atmospheric pressure and high temperature. We show that an amorphous reduced titania layer is formed at low temperatures, and that crystallization of the layer into either mono- or bilayer structures is dictated by the reaction environment and predicted by theory. Furthermore, it occurs in combination with a dramatic reshaping of the metallic surface facets. PMID:27280326

  9. Combined homogeneous and heterogeneous catalysts. Rhodium and platinum isocyanide complexes tethered on silica-supported metal heterogeneous catalysts: Arene and cyclohexanone hydrogenation

    SciTech Connect

    Gao, H.; Angelici, R.J. |

    1999-03-15

    Rhodium and platinum isocyanide complexes RhCl(CO)[CN(CH{sub 2}){sub 3}Si(OC{sub 2}H{sub 5}){sub 3}]{sub 2} (Rh-CNR{sub 2}), RhCl[CN(CH{sub 2}){sub 3}Si(OC{sub 2}H{sub 5}){sub 3}]{sub 3} (Rh-CNR{sub 3}), and PtCl{sub 2}[CN(CH{sub 2}){sub 3}Si(OC{sub 2}H{sub 5}){sub 3}]{sub 2} (Pt-CNR{sub 2}) were tethered to the silica-supported metal heterogeneous catalysts M-SiO{sub 2} (M = Pd, Pt, Ru) to give the TCSM (tethered complex on supported metal) catalysts Rh-CNR{sub 2}/Pd-SiO{sub 2}, Rh-CNR{sub 3}/M-SiO{sub 2} (M = Pd, Pt, Ru), and Pt-CNR{sub 2}/Pd-SiO{sub 2}. These TCSM catalysts were used to catalyze the hydrogenation of arenes (Rh-CNR{sub 2}/Pd-SiO{sub 2} and Rh-CNR{sub 3}/M-SiO{sub 2}) and cyclohexanone (Pt-CNR{sub 2}/Pd-SiO{sub 2}) under the mild conditions of 40 C and 1 atm. They exhibit activities that are higher than those of the separate homogeneous rhodium (or platinum) isocyanide complex, the separate silica-supported metal heterogeneous catalyst, or the rhodium (or platinum) complex catalyst tethered on just SiO{sub 2}. The activities of the TCSM catalysts are strongly affected by the nature and loading of the supported metal in the catalyst. Among the three silica-supported metal M-SiO{sub 2} (M = Pd, Pt, Ru) catalysts, the rhodium complex Rh-CNR{sub 3} tethered on Pd-SiO{sub 2} exhibits the highest activity for the hydrogenation of toluene (TOF = 5.5 mol H{sub 2}/(mol Rh min) and TO = 2,420 mol H{sub 2}/mol Rh during 8.5 h). The Rh-CNR{sub 3}/Pd-SiO{sub 2} catalyst with 10 wt % Pd is more active than its counterparts with higher or lower palladium loadings. IR (DRIFT) spectral studies of the TCSM catalysts before and after being used for toluene hydrogenation show that the isocyanide ligands remain coordinated to the rhodium (or platinum) center even after extended use. Atomic emission spectroscopic analysis of hydrogenation solutions shows that there is no rhodium (or platinum) leaching into the solutions.

  10. Graphene-supported ultrafine metal nanoparticles encapsulated by mesoporous silica: robust catalysts for oxidation and reduction reactions.

    PubMed

    Shang, Lu; Bian, Tong; Zhang, Baihui; Zhang, Donghui; Wu, Li-Zhu; Tung, Chen-Ho; Yin, Yadong; Zhang, Tierui

    2014-01-01

    Graphene nanosheet-supported ultrafine metal nanoparticles encapsulated by thin mesoporous SiO2 layers were prepared and used as robust catalysts with high catalytic activity and excellent high-temperature stability. The catalysts can be recycled and reused in many gas- and solution-phase reactions, and their high catalytic activity can be fully recovered by high-temperature regeneration, should they be deactivated by feedstock poisoning. In addition to the large surface area provided by the graphene support, the enhanced catalytic performance is also attributed to the mesoporous SiO2 layers, which not only stabilize the ultrafine metal nanoparticles, but also prevent the aggregation of the graphene nanosheets. The synthetic strategy can be extended to other metals, such as Pd and Ru, for preparing robust catalysts for various reactions.

  11. Transition metal sulfide loaded catalyst

    DOEpatents

    Maroni, V.A.; Iton, L.E.; Pasterczyk, J.W.; Winterer, M.; Krause, T.R.

    1994-04-26

    A zeolite-based catalyst is described for activation and conversion of methane. A zeolite support includes a transition metal (Mo, Cr or W) sulfide disposed within the micropores of the zeolite. The catalyst allows activation and conversion of methane to C[sub 2]+ hydrocarbons in a reducing atmosphere, thereby avoiding formation of oxides of carbon.

  12. Transition metal sulfide loaded catalyst

    DOEpatents

    Maroni, Victor A.; Iton, Lennox E.; Pasterczyk, James W.; Winterer, Markus; Krause, Theodore R.

    1994-01-01

    A zeolite based catalyst for activation and conversion of methane. A zeolite support includes a transition metal (Mo, Cr or W) sulfide disposed within the micropores of the zeolite. The catalyst allows activation and conversion of methane to C.sub.2 + hydrocarbons in a reducing atmosphere, thereby avoiding formation of oxides of carbon.

  13. Supported catalyst of increased resistance to poisons useful for hydrotreating metal containing oil fractions

    SciTech Connect

    Toulhoat, H.; Dupin, T.; Jacquin, Y.

    1985-02-12

    A catalyst for use in the hydrotreatment of hydrocarbons comprises a carrier and at least one catalytic metal selected from vanadium, molybdenum, tungsten, nickel, cobalt and/or iron; this catalyst is in the form of a plurality of juxtaposed agglomerates of acicular platelets, oriented radially to each other. It is prepared from agglomerates of activated alumina subjected to reaction with an acid and a compound providing an anion able to combine with aluminum ions in solution.

  14. Thin film hydrous metal oxide catalysts

    DOEpatents

    Dosch, Robert G.; Stephens, Howard P.

    1995-01-01

    Thin film (<100 nm) hydrous metal oxide catalysts are prepared by 1) synthesis of a hydrous metal oxide, 2) deposition of the hydrous metal oxide upon an inert support surface, 3) ion exchange with catalytically active metals, and 4) activating the hydrous metal oxide catalysts.

  15. Supported oxorhenate catalysts prepared by thermal spreading of metal Re{sup 0} for methanol conversion to methylal

    SciTech Connect

    Secordel, Xavier; Yoboue, Anthony; Cristol, Sylvain; Lancelot, Christine; Capron, Mickael; Paul, Jean-Francois; Berrier, Elise

    2011-10-15

    TiO{sub 2}-anatase and SiO{sub 2} supported oxorhenate catalysts were prepared by an original and simple technique based on the oxidative dispersion of metallic rhenium under dry conditions. The dispersion process of the supported oxorhenate phase as a function of the rhenium coverage and the support properties are discussed on the base of in situ characterization. The structures of the as prepared catalysts were found to be comparable to those of materials prepared using the incipient wetness impregnation technique. The absence of water in the preparation technique has made it possible to highlight the role of the hydration level on the rhenium oxide volatilization. The as-prepared Re/TiO{sub 2} catalysts were found to be effective for the direct conversion of methanol to methylal. - Graphical Abstract: Evolution of the 900-1000 cm{sup -1} region of the Raman spectrum of a mixture of metal rhenium with anatase TiO{sub 2} K03 upon heating in pure O{sub 2}. Highlights: > Supported rhenium catalysts can be easily prepared from metal Re. > This dry process is mainly a CVD immediately followed by rhenium deposition. > Hydration of the oxorhenate phase is dependent on the support.

  16. Nanostructured catalyst supports

    SciTech Connect

    Zhu, Yimin; Goldman, Jay L.; Qian, Baixin; Stefan, Ionel C.

    2015-09-29

    The present invention relates to SiC nanostructures, including SiC nanopowder, SiC nanowires, and composites of SiC nanopowder and nanowires, which can be used as catalyst supports in membrane electrode assemblies and in fuel cells. The present invention also relates to composite catalyst supports comprising nanopowder and one or more inorganic nanowires for a membrane electrode assembly.

  17. Nanostructured catalyst supports

    DOEpatents

    Zhu, Yimin; Goldman, Jay L.; Qian, Baixin; Stefan, Ionel C.

    2012-10-02

    The present invention relates to SiC nanostructures, including SiC nanopowder, SiC nanowires, and composites of SiC nanopowder and nanowires, which can be used as catalyst supports in membrane electrode assemblies and in fuel cells. The present invention also relates to composite catalyst supports comprising nanopowder and one or more inorganic nanowires for a membrane electrode assembly.

  18. Infrared investigations on metal-support interactions in Ni-SiO{sub 2} catalyst precursors: Role of silica

    SciTech Connect

    Ghuge, K.D.; Babu, G.P.

    1995-02-01

    In a Ni-silica catalyst system prepared by the precipitation/deposition method the silica is reported to play a role in forming the {open_quotes}support{close_quotes} to nickel carbonate (or hydroxide) species. The support formed is identified as various types of nickel silicate species and also as the species comprising -Ni-O-Si- linkages. Further, the support is shown to (i) provide the definite porous structure to the catalyst and (ii) influence the reducibility of nickel species. Also, in nickel catalyst system prepared by impregnation method, formation of silicate species on surface and its influence on reduction of nickel and restriction in metal sintering is well established. However, the mechanism of silica conversion to support species and influence on metal dispersion, the formation of a definite porous network and catalytic activity in Ni-silica catalyst system prepared by precipitation is not well established. In this paper Ni-silica catalyst precursors were prepared by adding separate solutions of nickel sulfate and sodium carbonate simultaneously to the precipitation vessel containing a silica slurry as described by Nitta et al. and maintaining a SiO{sub 2}/Ni ratio of 0.5, precipitation temperature = 92{degrees}C, and pH = 8.5. 15 refs., 1 fig., 1 tab.

  19. Rapid and scalable reduction of dense surface-supported metal-oxide catalyst with hydrazine vapor.

    PubMed

    Pint, Cary L; Kim, Seung Min; Stach, Eric A; Hauge, Robert H

    2009-07-28

    An efficient technique using hydrazine (N(2)H(4)) vapor as an agent for the rapid reduction of high-density layers of catalytic nanoparticles is demonstrated. With as little as 10 mTorr hydrazine bled into a thermal chemical vapor deposition (CVD) apparatus, efficient reduction of metal-oxide catalyst particles is achieved more rapidly than when using atomic hydrogen as the reducing agent. Postreduction catalyst imaging emphasizes the differences in nanoparticle formation under different reduction environments, with the most uniform and compact catalyst size distribution observed following hydrazine exposure. Low-temperature reduction studies suggest that as little as 15 s N(2)H(4) exposure at temperatures of 350 °C can yield a reduced catalyst layer preceding the synthesis of dense, aligned arrays of single-walled carbon nanotubes (SWNT) with uniform height. This work demonstrates a simple route toward scalable, vapor transport reduction of metal-oxide catalyst relevant to a number of catalytic applications, including the synthesis and selective synthesis of aligned SWNT arrays.

  20. Effect of the metal support interactions on the physicochemical and magnetic properties of Ni catalysts

    NASA Astrophysics Data System (ADS)

    Gómez-Polo, C.; Gil, A.; Korili, S. A.; Pérez-Landázabal, J. I.; Recarte, V.; Trujillano, R.; Vicente, M. A.

    2007-09-01

    In this work, the effect of the preparation method on the physicochemical and magnetic properties of nickel-containing catalysts is analysed. The catalysts were prepared by two methods, incipient wetness impregnation and precipitation-deposition using two commercial oxides, γ-Al 2O 3 (Rhône-Poulenc) and SiO 2 (AF125, Kali Chemie) as supports. The precursors were dried at 393 K for 16 h and then calcined at 823 K for 4 h. The physicochemical characterization of the catalysts included nitrogen adsorption, X-ray diffraction (XRD), temperature-programmed reduction (TPR) and chemical analysis. A SQUID magnetometer was employed in the magnetic characterization. The basic compositional and structural characteristics of these Ni-based nanoporous catalysts are analysed in relation to their magnetic response.

  1. Thermal stability and hcp-fcc allotropic transformation in supported Co metal catalysts probed near operando by ferromagnetic NMR.

    PubMed

    Andreev, Andrey S; d'Espinose de Lacaillerie, Jean-Baptiste; Lapina, Olga B; Gerashenko, Alexander

    2015-06-14

    Despite the fact that cobalt based catalysts are used at the industrial scale for Fischer-Tropsch synthesis, it is not yet clear which cobalt metallic phase is actually at work under operando conditions and what is its state of dispersion. As it turns out, the different phases of metallic cobalt, fcc and hcp, give rise to distinct ferromagnetic nuclear magnetic resonance. Furthermore, within one Co metal particle, the occurrence of several ferromagnetic domains of limited sizes can be evidenced by the specific resonance of Co in multi-domain particles. Consequently, by ferromagnetic NMR, one can follow quantitatively the sintering and phase transitions of dispersed Co metal particles in supported catalysts under near operando conditions. The minimal size probed by ferromagnetic Co NMR is not precisely known but is considered to be in the order of 10 nm for supported Co particles at room temperature and increases to about 35 nm at 850 K. Here, in Co metal Fischer-Tropsch synthesis catalysts supported on β-SiC, the resonances of the fcc multi-domain, fcc single-domain and hcp Co were clearly distinguished. A careful rationalization of their frequency and width dependence on temperature allowed a quantitative analysis of the spectra in the temperature range of interest, thus reflecting the state of the catalysts under near operando conditions that is without the uncertainty associated with prior quenching. The allotropic transition temperature was found to start at 600-650 K, which is about 50 K below the bulk transition temperature. The phase transition was fully reversible and a significant part of the hcp phase was found to be stable up to 850 K. This anomalous behavior that was observed without quenching might prove to be crucial to understand and model active species not only in catalysts but also in battery materials.

  2. Effect of Metal-Support Interactions in Ni/Al2O3 Catalysts with Low Metal Loading for Methane Dry Reforming

    SciTech Connect

    Ewbank, Jessica L.; Kovarik, Libor; Diallo, Fatoumata Z.; Sievers, Carsten

    2015-03-01

    Types of nickel sites as a function of preparation method have received much attention in the literature. In this work, two preparation methods, controlled adsorption and dry impregnation, are implemented to explore the effect of preparation method on catalytic nickel centers. For controlled adsorption, optimal synthesis conditions are identified using point of zero charge measurements, pH-precipitation experiments, and adsorption isotherms to prepare a catalyst with a high dispersion and strong metal support interactions. Metal support interactions influence the types of nickel sites formed. Thus, comparison of catalysts that differ primarily in metal support interactions, strong metal support interaction (controlled adsorption) and weak metal support interactions (dry impregnation), is of great interest. It is confirmed through characterization techniques; N2 physisorption, H2 chemisorption, temperature programmed reduction (TPR), transmission electron microscopy (TEM), and x-ray photoelectron spectroscopy (XPS) that the types of nickel sites formed are indeed strongly dependent on preparation method. Methane dry reforming reactivity studies are used to demonstrate the successful application of these catalysts and further probe the types of active centers present. Combustion analysis and XPS of spent catalysts reveal different amounts and nature of carbonaceous deposits as a function of the synthesis method.

  3. Effect of plasma treatments to graphite nanofibers supports on electrochemical behaviors of metal catalyst electrodes.

    PubMed

    Lee, Hochun; Jung, Yongju; Kim, Seok

    2012-02-01

    In the present work, we had studied the graphite nanofibers as catalyst supports after a plasma treatment for studying the effect of surface modification. By controlling the plasma intensity, a surface functional group concentration was changed. The nanoparticle size, loading efficiency, and catalytic activity were studied, after Pt-Ru deposition by a chemical reduction. Pt-Ru catalysts deposited on the plasma-treated GNFs showed the smaller size, 3.58 nm than the pristine GNFs. The catalyst loading contents were enhanced with plasma power and duration time increase, meaning an enhanced catalyst deposition efficiency. Accordingly, cyclic voltammetry result showed that the specific current density was increased proportionally till 200 W and then the value was decreased. Enhanced activity of 40 (mA mg(-1)-catalyst) was accomplished at 200 W and 180 sec duration time. Consequently, it was found that the improved electroactivity was originated from the change of size or morphology of catalysts by controlling the plasma intensity. PMID:22629990

  4. Synthesis of Supported Ultrafine Non-noble Subnanometer-Scale Metal Particles Derived from Metal-Organic Frameworks as Highly Efficient Heterogeneous Catalysts.

    PubMed

    Kang, Xinchen; Liu, Huizhen; Hou, Minqiang; Sun, Xiaofu; Han, Hongling; Jiang, Tao; Zhang, Zhaofu; Han, Buxing

    2016-01-18

    The properties of supported non-noble metal particles with a size of less than 1 nm are unknown because their synthesis is a challenge. A strategy has now been created to immobilize ultrafine non-noble metal particles on supports using metal-organic frameworks (MOFs) as metal precursors. Ni/SiO2 and Co/SiO2 catalysts were synthesized with an average metal particle size of 0.9 nm. The metal nanoparticles were immobilized uniformly on the support with a metal loading of about 20 wt%. Interestingly, the ultrafine non-noble metal particles exhibited very high activity for liquid-phase hydrogenation of benzene to cyclohexane even at 80 °C, while Ni/SiO2 with larger Ni particles fabricated by a conventional method was not active under the same conditions.

  5. Transition Metal Phosphide Nanoparticles Supported on SBA-15 as Highly Selective Hydrodeoxygenation Catalysts for the Production of Advanced Biofuels.

    PubMed

    Yang, Yongxing; Ochoa-Hernández, Cristina; de la Peña O'Shea, Víctor A; Pizarro, Patricia; Coronado, Juan M; Serrano, David P

    2015-09-01

    A series of catalysts constituted by nanoparticles of transition metal (M = Fe, Co, Ni and Mo) phosphides (TMP) dispersed on SBA-15 were synthesized by reduction of the corresponding metal phosphate precursors previously impregnated on the mesostructured support. All the samples contained a metal-loading of 20 wt% and with an initial M/P mole ratio of 1, and they were characterized by X-ray diffraction (XRD), N2 sorption, H2-TPR and transmission electron microscopy (TEM). Metal phosphide nanocatalysts were tested in a high pressure continuous flow reactor for the hydrodeoxygenation (HDO) of a methyl ester blend containing methyl oleate (C17H33-COO-CH3) as main component (70%). This mixture constitutes a convenient surrogate of triglycerides present in vegetable oils, and following catalytic hydrotreating yields mainly n-alkanes. The results of the catalytic assays indicate that Ni2P/SBA-15 catalyst presents the highest ester conversion, whereas the transformation rate is about 20% lower for MoP/SBA-15. In contrast, catalysts based on Fe and Co phosphides show a rather limited activity. Hydrocarbon distribution in the liquid product suggests that both hydrodeoxygenation and decarboxylation/decarbonylation reactions occur simultaneously over the different catalysts, although MoP/SBA-15 possess a selectivity towards hydrodeoxygenation exceeding 90%. Accordingly, the catalyst based on MoP affords the highest yield of n-octadecane, which is the preferred product in terms of carbon atom economy. Subsequently, in order to conjugate the advantages of both Ni and Mo phosphides, a series of catalysts containing variable proportions of both metals were prepared. The obtained results reveal that the mixed phosphides catalysts present a catalytic behavior intermediate between those of the monometallic phosphides. Accordingly, only marginal enhancement of the yield of n-octadecane is obtained for the catalysts with a Mo/Ni ratio of 3. Nevertheless, owing to this high selectivity

  6. Transition Metal Phosphide Nanoparticles Supported on SBA-15 as Highly Selective Hydrodeoxygenation Catalysts for the Production of Advanced Biofuels.

    PubMed

    Yang, Yongxing; Ochoa-Hernández, Cristina; de la Peña O'Shea, Víctor A; Pizarro, Patricia; Coronado, Juan M; Serrano, David P

    2015-09-01

    A series of catalysts constituted by nanoparticles of transition metal (M = Fe, Co, Ni and Mo) phosphides (TMP) dispersed on SBA-15 were synthesized by reduction of the corresponding metal phosphate precursors previously impregnated on the mesostructured support. All the samples contained a metal-loading of 20 wt% and with an initial M/P mole ratio of 1, and they were characterized by X-ray diffraction (XRD), N2 sorption, H2-TPR and transmission electron microscopy (TEM). Metal phosphide nanocatalysts were tested in a high pressure continuous flow reactor for the hydrodeoxygenation (HDO) of a methyl ester blend containing methyl oleate (C17H33-COO-CH3) as main component (70%). This mixture constitutes a convenient surrogate of triglycerides present in vegetable oils, and following catalytic hydrotreating yields mainly n-alkanes. The results of the catalytic assays indicate that Ni2P/SBA-15 catalyst presents the highest ester conversion, whereas the transformation rate is about 20% lower for MoP/SBA-15. In contrast, catalysts based on Fe and Co phosphides show a rather limited activity. Hydrocarbon distribution in the liquid product suggests that both hydrodeoxygenation and decarboxylation/decarbonylation reactions occur simultaneously over the different catalysts, although MoP/SBA-15 possess a selectivity towards hydrodeoxygenation exceeding 90%. Accordingly, the catalyst based on MoP affords the highest yield of n-octadecane, which is the preferred product in terms of carbon atom economy. Subsequently, in order to conjugate the advantages of both Ni and Mo phosphides, a series of catalysts containing variable proportions of both metals were prepared. The obtained results reveal that the mixed phosphides catalysts present a catalytic behavior intermediate between those of the monometallic phosphides. Accordingly, only marginal enhancement of the yield of n-octadecane is obtained for the catalysts with a Mo/Ni ratio of 3. Nevertheless, owing to this high selectivity

  7. Support shape effect in metal oxide catalysis: ceria nanoshapes supported vanadia catalysts for oxidative dehydrogenation of iso-butane

    SciTech Connect

    Wu, Zili; Schwartz, Viviane; Li, Meijun; Rondinone, Adam Justin; Overbury, Steven {Steve} H

    2012-01-01

    The activation energy of VOx/CeO2 catalysts in oxidative dehydrogenation of iso-butane was found dependent on the shape of ceria support: rods < octahedra, closely related to the surface oxygen vacancy formation energy and defects amount of the two ceria supports with different crystallographic surface planes.

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

    NASA Astrophysics Data System (ADS)

    Kugai, Junichiro

    The post-processing of reformate is an important step in producing hydrogen (H2) with low carbon monoxide (CO) for low temperature fuel cells from syn-gas. However, the conventional process consists of three steps, i.e. two steps of water gas shift (WGS) and preferential oxidation (PROX) of CO, and it is not suitable for mobile applications due to the large volume of water gas shift (WGS) catalysts and conditioning and/or regeneration necessary for these catalysts. Aiming at replacing those three steps by a simple one-step process, small amount of oxygen was added to WGS (the reaction called oxygen-enhanced water gas shift or OWGS) to promote the reaction kinetics and low pyrophoric ceria-supported bimetallic catalysts were employed for stable performance in this reaction. Not only CO conversion, but also H2 yield was found to increase by the O2 addition on CeO2-supported catalysts. The characteristics of OWGS, high H2 production rate at 200 to 300°C at short contact time where unreacted O2 exists, evidenced the impact of O2 addition on surface species on the catalyst. Around 1.5 of reaction order in CO for various CeO2-supported metal catalysts for OWGS compared to reaction orders in CO ranging from -0.1 to 0.6 depending on metal species for WGS shows O2 addition decreases CO coverage to free up the active sites for co-reactant (H2O) adsorption and activation. Among the monometallic and bimetallic catalysts, Pt-Cu and Pd-Cu bimetallic catalysts were superior to monometallic catalysts in OWGS. These bimetallic components were found to form alloys where noble metal is surrounded mainly by Cu to have strong interaction between noble metal and copper resulting in high OWGS activity and low pyrophoric property. The metal loadings were optimized for CeO2-supported Pd-Cu bimetallic system and 2 wt% Pd with 5 -- 10 wt% Cu were found to be the optimum for the present OWGS condition. In the kinetic study, Pd in Pd-Cu was shown to increase the active sites for H2O

  9. Hydrocracking of n-decane over zeolite-supported metal sulfide catalysts. 2: Zeolite Y-supported Ni and Ni-Mo sulfides

    SciTech Connect

    Welters, W.J.J.; Waerden, O.H. van der; Beer, V.H.J. de; Santen, R.A. van

    1995-04-01

    For zeolite Y-supported nickel sulfide catalysts the influence of the metal sulfide dispersion on the hydrocracking properties for n-decane is examined. In order to obtain different nickel sulfide distributions (inside or outside the zeolite structure) and dispersions, the preparation method (impregnation of CaY or ion exchange of NaY), sulfidation procedure (direct sulfidation or sulfidation after drying), and metal loading are varied. A higher nickel sulfide surface (as measured by dynamic oxygen chemisorption) results in a strong increase of the n-decane conversion, but this is not accompanied by an improvement of the catalytic properties toward ideal hydrocracking. Additionally, some zeolite Y-supported Ni-Mo sulfide catalysts (varying in preparation method and sulfidation procedure) are tested for the hydroconversion of it-decane. However, no promoter effect could be observed. The activity of the bimetallic sulfide catalysts is always almost equal to that of the most active monometallic sulfide constituent.

  10. Catalyst system comprising a first catalyst system tethered to a supported catalyst

    DOEpatents

    Angelici, Robert J.; Gao, Hanrong

    1998-08-04

    The present invention provides new catalyst formats which comprise a supported catalyst tethered to a second and different catalyst by a suitable tethering ligand. A preferred system comprises a heterogeneous supported metal catalyst tethered to a homogeneous catalyst. This combination of homogeneous and heterogeneous catalysts has a sufficient lifetime and unusually high catalytic activity in arene hydrogenations, and potentially many other reactions as well, including, but not limited to hydroformylation, hydrosilation, olefin oxidation, isomerization, hydrocyanation, olefin metathesis, olefin polymerization, carbonylation, enantioselective catalysis and photoduplication. These catalysts are easily separated from the products, and can be reused repeatedly, making these systems very economical.

  11. Catalyst system comprising a first catalyst system tethered to a supported catalyst

    DOEpatents

    Angelici, R.J.; Gao, H.

    1998-08-04

    The present invention provides new catalyst formats which comprise a supported catalyst tethered to a second and different catalyst by a suitable tethering ligand. A preferred system comprises a heterogeneous supported metal catalyst tethered to a homogeneous catalyst. This combination of homogeneous and heterogeneous catalysts has a sufficient lifetime and unusually high catalytic activity in arene hydrogenations, and potentially many other reactions as well, including, but not limited to hydroformylation, hydrosilication, olefin oxidation, isomerization, hydrocyanidation, olefin metathesis, olefin polymerization, carbonylation, enantioselective catalysis and photoduplication. These catalysts are easily separated from the products, and can be reused repeatedly, making these systems very economical. 2 figs.

  12. Low-Temperature Synthesis of Tunable Mesoporous Crystalline Transition Metal Oxides and Applications as Au Catalyst Supports

    SciTech Connect

    Wang, Donghai; Ma, Zhen; Dai, Sheng; Liu, Jun; Nie, Zimin; Engelhard, Mark H.; Huo, Qisheng; Wang, Chong M.; Kou, Rong

    2008-09-04

    Mesoporous transition metal oxides are of great potential as catalyst supports, shape-selective catalysts, photocatalysts, and sensor materials. Previously stable crystalline mesoporous oxides were mostly obtained by thermally induced crystallization or by segregating the nanocrystals with an amorphous phase. Here we report a novel direct approach to crystalline mesoporous frameworks via the spontaneous growth and assembly of transition metal oxide nanocrystals (i.e., rutile TiO2, fluorite CeO2, cassiterite SnO2, and anatase SnxTi1-xO2) by oxidative hydrolysis and condensation in the presence of anionic surfactants. The influences of synthesis time, surfactants with different chain lengths, concentrations of the oxidant (i.e., hydrogen peroxide), and synthesis temperatures on the composition and morphologies of the resulting materials were investigated by X-ray diffraction (XRD), N2-sorption, transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). A mechanism for the templated synthesis of crystalline mesoporous metal oxides was tentatively proposed. To demonstrate the catalytic applications of these materials, gold nanoparticles were loaded on mesoporous rutile TiO2 and fluorite CeO2 supports, and their catalytic performance in CO oxidation and water-gas shift was surveyed. Au nanoparticles supported on the mesoporous crystalline metal oxides exhibit higher reactivity and excellent on-stream stability towards CO oxidation and water-gas shift reaction compared with commercial TiO2 and CeO2.

  13. Catalytically Active and Spectator Ce(3+) in Ceria-Supported Metal Catalysts.

    PubMed

    Kopelent, René; van Bokhoven, Jeroen A; Szlachetko, Jakub; Edebeli, Jacinta; Paun, Cristina; Nachtegaal, Maarten; Safonova, Olga V

    2015-07-20

    Identification of active species and the rate-determining reaction steps are crucial for optimizing the performance of oxygen-storage materials, which play an important role in catalysts lowering automotive emissions, as electrode materials for fuel cells, and as antioxidants in biomedicine. We demonstrated that active Ce(3+) species in a ceria-supported platinum catalyst during CO oxidation are short-lived and therefore cannot be observed under steady-state conditions. Using time-resolved resonant X-ray emission spectroscopy, we quantitatively correlated the initial rate of Ce(3+) formation under transient conditions to the overall rate of CO oxidation under steady-state conditions and showed that ceria reduction is a kinetically relevant step in CO oxidation, whereas a fraction of Ce(3+) was present as spectators. This approach can be applied to various catalytic processes involving oxygen-storage materials and reducible oxides to distinguish between redox and nonredox catalytic mechanisms.

  14. Catalyst Of A Metal Heteropoly Acid Salt That Is Insoluble In A Polar Solvent On A Non-Metallic Porous Support And Method Of Making

    DOEpatents

    Wang. Yong; Peden. Charles H. F.; Choi. Saemin

    2004-11-09

    The present invention includes a catalyst having (a) a non-metallic support having a plurality of pores; (b) a metal heteropoly acid salt that is insoluble in a polar solvent on the non-metallic support; wherein at least a portion of the metal heteropoly acid salt is dispersed within said plurality of pores. The present invention also includes a method of depositing a metal heteropoly acid salt that is insoluble in a polar solvent onto a non-metallic support having a plurality of pores. The method has the steps of: (a) obtaining a first solution containing a first precursor of a metal salt cation; (b) obtaining a second solution containing a second precursor of a heteropoly acid anion in a solvent having a limited dissolution potential for said first precursor; (c) impregnating the non-metallic support with the first precursor forming a first precursor deposit within the plurality of pores, forming a first precursor impregnated support; (d) heating said first precursor impregnated support forming a bonded first precursor impregnated support; (e) impregnating the second precursor that reacts with the precursor deposit and forms the metal heteropoly acid salt.

  15. Catalyst of a metal heteropoly acid salt that is insoluble in a polar solvent on a non-metallic porous support and method of making

    DOEpatents

    Wang, Yong [Richland, WA; Peden, Charles H. F. [West Richland, WA; Choi, Saemin [Richland, WA

    2002-10-29

    The present invention includes a catalyst having (a) a non-metallic support having a plurality of pores; (b) a metal heteropoly acid salt that is insoluble in a polar solvent on the non-metallic support; wherein at least a portion of the metal heteropoly acid salt is dispersed within said plurality of pores. The present invention also includes a method of depositing a metal heteropoly acid salt that is insoluble in a polar solvent onto a non-metallic support having a plurality of pores. The method has the steps of: (a) obtaining a first solution containing a first precursor of a metal salt cation; (b) obtaining a second solution containing a second precursor of a heteropoly acid anion in a solvent having a limited dissolution potential for said first precursor; (c) impregnating the non-metallic support with the first precursor forming a first precursor deposit within the plurality of pores, forming a first precursor impregnated support; (d) heating said first precursor impregnated support forming a bonded first precursor impregnated support; (e) impregnating the second precursor that reacts with the precursor deposit and forms the metal heteropoly acid salt.

  16. Method of forming supported doped palladium containing oxidation catalysts

    SciTech Connect

    Mohajeri, Nahid

    2014-04-22

    A method of forming a supported oxidation catalyst includes providing a support comprising a metal oxide or a metal salt, and depositing first palladium compound particles and second precious metal group (PMG) metal particles on the support while in a liquid phase including at least one solvent to form mixed metal comprising particles on the support. The PMG metal is not palladium. The mixed metal particles on the support are separated from the liquid phase to provide the supported oxidation catalyst.

  17. Influence of the preparation method on the surface characteristics and activity of boron-nitride-supported noble metal catalysts.

    PubMed

    Postole, Georgeta; Gervasini, Antonella; Guimon, Claude; Auroux, Aline; Bonnetot, Bernard

    2006-06-29

    In this article, we report how variations in the preparation method of boron-nitride-supported noble metal catalysts may influence the surface characteristics of the active phase and consequently the potential applications as catalysts for oxidation reactions. The deposition and the dispersion of the active phase are strongly influenced by the preparation process and in particular by the protic or aprotic solvent used as the dispersing phase; in this study, benzene, glyme, water, tetrahydrofuran, diglyme, 2-propanol, and glycol have been investigated. Characterization techniques, such as Brunauer-Emmett-Teller, X-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis, have been used to study the influence of the choice of a solvent phase on the particle size and dispersion of the metal deposited on the BN support. The modifications undergone by the support during the deposition of palladium in different solvents have also been studied. Through the use of the same deposition procedure, different noble metal coatings (Pt, Pd, Au, and Ag) have been prepared. The acidic and redox characteristics of the resulting samples were characterized by temperature-programmed reduction and adsorption microcalorimetry. The catalytic performances of these materials were tested in the total oxidation of methane in lean conditions (excess oxygen and presence of water). PMID:16800586

  18. Tuning the acid/metal balance of carbon nanofiber-supported nickel catalysts for hydrolytic hydrogenation of cellulose.

    PubMed

    Van de Vyver, Stijn; Geboers, Jan; Schutyser, Wouter; Dusselier, Michiel; Eloy, Pierre; Dornez, Emmie; Seo, Jin Won; Courtin, Christophe M; Gaigneaux, Eric M; Jacobs, Pierre A; Sels, Bert F

    2012-08-01

    Carbon nanofibers (CNFs) are a class of graphitic support materials with considerable potential for catalytic conversion of biomass. Earlier, we demonstrated the hydrolytic hydrogenation of cellulose over reshaped nickel particles attached at the tip of CNFs. The aim of this follow-up study was to find a relationship between the acid/metal balance of the Ni/CNFs and their performance in the catalytic conversion of cellulose. After oxidation and incipient wetness impregnation with Ni, the Ni/CNFs were characterized by various analytical methods. To prepare a selective Ni/CNF catalyst, the influences of the nature of oxidation agent, Ni activation, and Ni loading were investigated. Under the applied reaction conditions, the best result, that is, 76 % yield in hexitols with 69 % sorbitol selectivity at 93 % conversion of cellulose, was obtained on a 7.5 wt % Ni/CNF catalyst prepared by chemical vapor deposition of CH(4) on a Ni/γ-Al(2)O(3) catalyst, followed by oxidation in HNO(3) (twice for 1 h at 383 K), incipient wetness impregnation, and reduction at 773 K under H(2). This preparation method leads to a properly balanced Ni/CNF catalyst in terms of Ni dispersion and hydrogenation capacity on the one hand, and the number of acidic surface-oxygen groups responsible for the acid-catalyzed hydrolysis on the other.

  19. Tuning the acid/metal balance of carbon nanofiber-supported nickel catalysts for hydrolytic hydrogenation of cellulose.

    PubMed

    Van de Vyver, Stijn; Geboers, Jan; Schutyser, Wouter; Dusselier, Michiel; Eloy, Pierre; Dornez, Emmie; Seo, Jin Won; Courtin, Christophe M; Gaigneaux, Eric M; Jacobs, Pierre A; Sels, Bert F

    2012-08-01

    Carbon nanofibers (CNFs) are a class of graphitic support materials with considerable potential for catalytic conversion of biomass. Earlier, we demonstrated the hydrolytic hydrogenation of cellulose over reshaped nickel particles attached at the tip of CNFs. The aim of this follow-up study was to find a relationship between the acid/metal balance of the Ni/CNFs and their performance in the catalytic conversion of cellulose. After oxidation and incipient wetness impregnation with Ni, the Ni/CNFs were characterized by various analytical methods. To prepare a selective Ni/CNF catalyst, the influences of the nature of oxidation agent, Ni activation, and Ni loading were investigated. Under the applied reaction conditions, the best result, that is, 76 % yield in hexitols with 69 % sorbitol selectivity at 93 % conversion of cellulose, was obtained on a 7.5 wt % Ni/CNF catalyst prepared by chemical vapor deposition of CH(4) on a Ni/γ-Al(2)O(3) catalyst, followed by oxidation in HNO(3) (twice for 1 h at 383 K), incipient wetness impregnation, and reduction at 773 K under H(2). This preparation method leads to a properly balanced Ni/CNF catalyst in terms of Ni dispersion and hydrogenation capacity on the one hand, and the number of acidic surface-oxygen groups responsible for the acid-catalyzed hydrolysis on the other. PMID:22730195

  20. Formation of a ZnO overlayer in industrial Cu/ZnO/Al2 O3 catalysts induced by strong metal-support interactions.

    PubMed

    Lunkenbein, Thomas; Schumann, Julia; Behrens, Malte; Schlögl, Robert; Willinger, Marc G

    2015-04-01

    In industrially relevant Cu/ZnO/Al2 O3 catalysts for methanol synthesis, the strong metal support interaction between Cu and ZnO is known to play a key role. Here we report a detailed chemical transmission electron microscopy study on the nanostructural consequences of the strong metal support interaction in an activated high-performance catalyst. For the first time, clear evidence for the formation of metastable "graphite-like" ZnO layers during reductive activation is provided. The description of this metastable layer might contribute to the understanding of synergistic effects between the components of the Cu/ZnO/Al2 O3 catalysts. PMID:25683230

  1. Microbial recovery of metals from spent catalysts

    SciTech Connect

    Sperl, P.L.; Sperl, G.T.

    1990-01-01

    This project was initiated on October 1, 1989, for the purpose of recovering metals from spent coal liquefaction catalysts. Two catalyst types are the subject of the contract. The first is a Ni-Mo catalyst supported on alumina (Shell 324) as is used in a pilot scale coal liquefaction facility at Wilsonville, Alabama. The object of the contract is to treat these spent catalysts with microorganisms, especially Thiobacillus ferrooxidans, but also other Thiobacillus sp., to leach and remove the metals (Ni and Mo) from the spent catalysts into a form which can be readily recovered by conventional techniques.

  2. Directly-grown and square-patterned arrays of metal oxide nanowires for high-performance catalyst support platforms.

    PubMed

    Lee, Sang Ho; Lim, Eun Ja; Jo, Yong-Ryun; Kim, Bong-Joong; Kim, Won Bae

    2014-12-10

    This research reports novel and efficient electrocatalyst support systems. Tin dioxide nanowires grown directly on current collecting substances are introduced as high-performance support platforms. For this propose, palladium or platinum catalysts are impregnated on these nanowire scaffolds and exhibit improved electrocatalytic performance for methanol oxidation in alkaline and acidic environments. These nanowire support platforms could be demonstrated to maximize the electrocatalytic activity because of the effective charge transport provided by the direct connection between the nanowire supports and current collectors. More significantly, grid-patterned nanowire arrays grown directly on current collectors are, for the first time, demonstrated as a milestone to enhance the electrocatalytic performance. The empty space between the patterned nanowire arrays acts as a channel to facilitate the electrolyte diffusion. The metal catalysts incorporated into the patterned nanowire supports show an 8-fold improvement in the catalytic performance for methanol electrooxidation, most likely because of the synergetic effects of the enhanced charge transport and mass transfer attributed to the structural advantages of the patterned nanowire array supports. PMID:25405935

  3. Ultraviolet Raman spectroscopy of catalysts: Adsorption and coke formation in zeolites and vibrational spectra of supported metal oxides

    NASA Astrophysics Data System (ADS)

    Chua, Yek Tann

    2001-10-01

    The primary goal of this dissertation is to study the physicochemical and catalytic properties of zeolites and supported metal oxide catalysts using UV Raman spectroscopy. In order to reduce the thermal degradation and possible photodecomposition of adsorbates by UV radiation, we have developed a novel fluidized bed method for measuring the UV Raman spectra of catalysts and adsorbates. The UV Raman spectra of various organic compounds adsorbed in zeolites H-USY and H-ZSM-5 are recorded. When measurements are performed on stationary and spinning samples, the Raman spectra show the presence of coke, a typical end product of heat and photochemistry. In contrast, the Raman peaks of the unreacted adsorbates dominate the spectra measured using the fluidized bed method. These results indicate that the fluidized bed technique is a good method for measuring UV Raman spectra of catalysts and adsorbates. The formation of coke in the methanol-to-gasoline conversion over zeolite H-ZSM-5 causes deactivation of the catalyst. To gain insight into the formation of coke, we have studied this reaction using UV Raman spectroscopy. The Raman spectral changes suggest coke is produced from conjugated olefins via cyclopentadiene intermediates. Aromatic compounds in gasoline may also be produced from cyclopentadienes. The adsorbate-induced structural changes of zeolites may alter the molecular sieving characteristics of these materials which ultimately affect their performance as catalysts and adsorbents. We have quantified the adsorbate-induced structural changes of zeolite H-RHO using UV Raman spectroscopy. The Raman spectra of the zeolite after the adsorption of water, methanol or acetonitrile are consistent with an increase in the average T-O-T angle of the zeolite of 5-8°. The adsorption of ammonia, on the other hand, decreases the average T-O-T angle by 5°. Because of certain advantages of UV Raman spectroscopy over visible Raman spectroscopy, recently there is a strong interest in

  4. Attrition resistant catalysts and sorbents based on heavy metal poisoned FCC catalysts

    DOEpatents

    Gangwal, S.; Jothimurugesan, K.

    1999-07-27

    A heavy metal poisoned, spent FCC catalyst is treated by chemically impregnating the poisoned catalyst with a new catalytic metal or metal salt to provide an attrition resistant catalyst or sorbent for a different catalytic or absorption process, such as catalysts for Fischer-Tropsh Synthesis, and sorbents for removal of sulfur gases from fuel gases and flue-gases. The heavy metal contaminated FCC catalyst is directly used as a support for preparing catalysts having new catalytic properties and sorbents having new sorbent properties, without removing or passivating the heavy metals on the spent FCC catalyst as an intermediate step.

  5. Attrition resistant catalysts and sorbents based on heavy metal poisoned FCC catalysts

    DOEpatents

    Gangwal, Santosh; Jothimurugesan, Kandaswamy

    1999-01-01

    A heavy metal poisoned, spent FCC catalyst is treated by chemically impregnating the poisoned catalyst with a new catalytic metal or metal salt to provide an attrition resistant catalyst or sorbent for a different catalytic or absorption processes, such as catalysts for Fischer-Tropsh Synthesis, and sorbents for removal of sulfur gasses from fuel gases and flue-gases. The heavy metal contaminated FCC catalyst is directly used as a support for preparing catalysts having new catalytic properties and sorbents having new sorbent properties, without removing or "passivating" the heavy metals on the spent FCC catalyst as an intermediate step.

  6. Passivating metals on cracking catalysts

    SciTech Connect

    Mckay, D.L.

    1980-01-15

    Metals such as nickel, vanadium and iron contaminating a cracking catalyst are passivated by contacting the cracking catalyst under elevated temperature conditions with antimony selenide, antimony sulfide, antimony sulfate, bismuth selenide, bismuth sulfide, or bismuth phosphate.

  7. Interaction of carbon and sulfur on metal catalysts. Progress report

    SciTech Connect

    McCarty, J.G.

    1988-01-21

    Goal is to study selective poisoning by fractional monolayers of chemisorbed sulfur on metal catalysts. A Pt catalyst on alumina support has been synthesized. Stabilized Fe catalysts without and with half monolayers of chemicsorbed S have been prepared. These catalysts, along with a Ni-alumina reference catalyst, will be used in experimental studies. 2 figs.

  8. Comparative Study on the Sulfur Tolerance and Carbon Resistance of Supported Noble Metal Catalysts in Steam Reforming of Liquid Hydrocarbon Fuel

    SciTech Connect

    Xie, Chao; Chen, Yongsheng; Engelhard, Mark H.; Song, Chunshan

    2012-04-18

    This work was conducted to clarify the influence of the type of metal and support on the sulfur tolerance and carbon resistance of supported noble metal catalysts in steam reforming of liquid hydrocarbons. Al2O3-supported noble metal catalysts (Rh, Ru, Pt, and Pd), Rh catalysts on different supports (Al2O3, CeO2, SiO2, and MgO), and Pt catalyst supported on CeO2 and Al2O3, were examined for steam reforming of a liquid hydrocarbon fuel (Norpar13 from Exxon Mobil) at 800 C for 55 h. The results indicate that (1) Rh/Al2O3 shows higher sulfur tolerance than the Ru, Pt, and Pd catalysts on the same support; (2) both Al2O3 and CeO2 are promising supports for Rh catalyst to process sulfur-containing hydrocarbons; and (3) Pt/CeO2 exhibits better catalytic performance than Pt/Al2O3 in the reaction with sulfur. TEM results demonstrate that the metal particles in Rh/Al2O3 were better dispersed (mostly in 1-3 nm) compared with the other catalysts after reforming the sulfur-containing feed. As revealed by XPS, the binding energy of Rh 3d for Rh/Al2O3 is notably higher than that for Rh/CeO2, implying the formation of electron-deficient Rh particles in the former. The strong sulfur tolerance of Rh/Al2O3 may be related to the formation of well-dispersed electron-deficient Rh particles on the Al2O3 support. Sulfur K-edge XANES illustrates the preferential formation of sulfonate and sulfate on Rh/Al2O3, which is believed to be beneficial for improving its sulfur tolerance as their oxygen-shielded sulfur structure may hinder direct Rh-S interaction. Due to its strong sulfur tolerance, the carbon deposition on Rh/Al2O3 was significantly lower than that on the Al2O3-supported Ru, Pt, and Pd catalysts after the reaction with sulfur. The superior catalytic performance of CeO2-supported Rh and Pt catalysts in the presence of sulfur can be ascribed mainly to the promotion effect of CeO2 on carbon gasification, leading to much lower carbon deposition compared with the Rh/Al2O3, Rh/MgO, Rh

  9. Supported organoiridium catalysts for alkane dehydrogenation

    SciTech Connect

    Baker, R. Thomas; Sattelberger, Alfred P.; Li, Hongbo

    2013-09-03

    Solid supported organoiridium catalysts, a process for preparing such solid supported organoiridium catalysts, and the use of such solid supported organoiridium catalysts in dehydrogenation reactions of alkanes is provided. The catalysts can be easily recovered and recycled.

  10. Model heterogeneous acid catalysts and metal-support interactions: A combined surface science and catalysis study

    SciTech Connect

    Boszormenyi, I.

    1991-05-01

    This (<100 {Angstrom}) silica-alumina layers were tested as potential model heterogeneous acid catalysts for combined surface science and catalysis studies. Three preparation methods were used: oxidation of r3 {times} r3 R30 Al/Si(111) structure in UHV; deposition on Si(lll) from aqueous solution; and argon ion beam sputter deposition in UHV. The homogeneous thin layers are amorphous, and the chemical environment of surface atoms is similar to that of Si, Al and oxygen atoms on high surface area acid catalysts. Since the ion beam-deposited thin layer of silica-alumina has the same composition as the target zeolite this deposition method is a promising tool to prepare model catalysts using practical catalyst targets. The silica-alumina layers are active in cumene cracking, a typical acid catalyzed reaction. In order to clearly distinguish background reactions and the acid catalyzed reaction at least 20 cm{sup 2} catalyst surface area is needed. Two series of model platinum-alumina catalysts were prepared in a combined UHV -- high pressure reactor cell apparatus by depositing alumina on polycrystalline Pt foil and by vapor depositing Pt on a thin alumina layer on Au. Both model surfaces have been prepared with and without chlorine. AES, CO desorption as well as methyl cyclopentane (MCP) hydrogenolysis studies indicate that the Pt surface area is always higher if a chlorination step is involved. Selectivity patterns in MCP ring opening on ``Pt-on-alumina`` and on ``alumina-on-Pt`` are different; only the former is a linear combination of selective and statistical ring opening. Product distribution, however, changes with coverage and reaction time. The properties of the two model catalyst systems and role of chlorine in MCP hydrogenolysis are also discussed.

  11. Model heterogeneous acid catalysts and metal-support interactions: A combined surface science and catalysis study

    SciTech Connect

    Boszormenyi, I.

    1991-05-01

    This (<100 [Angstrom]) silica-alumina layers were tested as potential model heterogeneous acid catalysts for combined surface science and catalysis studies. Three preparation methods were used: oxidation of r3 [times] r3 R30 Al/Si(111) structure in UHV; deposition on Si(lll) from aqueous solution; and argon ion beam sputter deposition in UHV. The homogeneous thin layers are amorphous, and the chemical environment of surface atoms is similar to that of Si, Al and oxygen atoms on high surface area acid catalysts. Since the ion beam-deposited thin layer of silica-alumina has the same composition as the target zeolite this deposition method is a promising tool to prepare model catalysts using practical catalyst targets. The silica-alumina layers are active in cumene cracking, a typical acid catalyzed reaction. In order to clearly distinguish background reactions and the acid catalyzed reaction at least 20 cm[sup 2] catalyst surface area is needed. Two series of model platinum-alumina catalysts were prepared in a combined UHV -- high pressure reactor cell apparatus by depositing alumina on polycrystalline Pt foil and by vapor depositing Pt on a thin alumina layer on Au. Both model surfaces have been prepared with and without chlorine. AES, CO desorption as well as methyl cyclopentane (MCP) hydrogenolysis studies indicate that the Pt surface area is always higher if a chlorination step is involved. Selectivity patterns in MCP ring opening on Pt-on-alumina'' and on alumina-on-Pt'' are different; only the former is a linear combination of selective and statistical ring opening. Product distribution, however, changes with coverage and reaction time. The properties of the two model catalyst systems and role of chlorine in MCP hydrogenolysis are also discussed.

  12. Bismuth - modified supported catalysts

    SciTech Connect

    Nadirov, N.K.; Lykova, L.F.; Petrosyan, L.S.

    1985-09-01

    Bismuth was used as an additive to three-component catalysts prepared through modification of an aluminoplatinorhenium catalyst by III and IV nontransition and iron subgroup elements. Since there is conflicting information on bismuth additions, the role of bismuth in polycomponent catalysts and whether it promotes aromatization catalysts was considered. The effect of temperature on the yield of n-hexane conversion products in the presence of Pt-Re-Co-Bi/gamma-A1/sub 2/O/sub 3/ is shown. Conclusive results establish that the addition of 0.5% nickel to a 0.3 Pt-0.3 Re/gamma-A1/sub 2/O/sub 3/ catalyst (in wt.%) increased the yield of benzene from n-hexane by 5.7%. It was also shown that 0.1 to 0.25 wt.% bismuth poisons two- and three-component samples containing 0.25 to 0.3 wt.% platinum.

  13. Acid catalyzed hydrocarbon conversion processes utilizing a catalyst comprising a group ivb, vb or vib metal oxide on an inorganic refractory oxide support

    SciTech Connect

    Grenoble, D.C.; Kim, C.J.; Murrell, L.L.

    1980-11-11

    It has been discovered and forms the basis of the disclosure that various acid catalyzed hydrocarbon conversion processes such as catalytic cracking of gas oil; xylene isomerization; toluene disproportionation; dealkylation of aromatics; ethylene, butylene , isobutylene, propylene polymerization; olefin isomerization; alcohol dehydration; olefin hydration; alkylation; heavy ends cat cracking, etc. are dramatically improved insofar as percent conversion, and selectivity are concerned by the use of a catalyst selected from the group consisting of the oxides of tungsten, niobium and mixtures thereof, and tungsten or niobium oxides in combination with one or more additional metal oxides selected from the group consisting of tantalum oxide, hafnium oxide, chromium oxide, titanium oxide and zirconium oxide, supported on an inorganic refractory oxide support. These catalysts may be prepared by the methods known in the art, I.E., incipient wetness, impregnation, coprecipitation, etc. Of the metal oxide precursor onto or with the supports followed by conversion into the oxide form. Before use, the metal oxide/support combination is preferably subjected to steaming at elevated temperatures either before introduction into the reactor or in situ in the process reactor. Conventional catalytic cracking catalysts are unstable at the elevated temperatures where the metal oxide/support combinations of the present invention are uniquely stable.

  14. Pt/MgO as catalyst for hydrogenolysis reactions of C[sub 5] and C[sub 6] hydrocarbons: Evidence for metal-support interactions

    SciTech Connect

    Clarke, J.K.A.; Bradley, M.J. ); Garvie, L.A.J.; Craven, A.J.; Baird, T. )

    1993-09-01

    Pt/magnesia catalysts having high metal dispersion (av. dia. 21 [angstrom]) have been prepared employing nonaqueous impregnating solutions and an incipient wetness technique. Both chlorine-free and residual-chlorine-containing catalysts were studied, the latter being prepared from platinum (IV) chloride. Both types of catalyst are of negligible sulphur content (<2ppm). Comparison of hydrogen chemisorption and transmission electron microscopy results for both [open quotes]chlorine-free[close quotes] and chlorine-containing Pt/MgO catalysts showed that (i) chemisorption capacity was substantially as expected from TEM-derived particle size following a reduction temperature of 593 K (LTR), and (ii) chemisorption was depressed to 40% or less of expectation when a reduction temperature of 753 K (HTR) was used. Reactions of saturated hydrocarbons in a flow of hydrogen (p[sub hydrocarbon] = 8-16 Torr, balance to 760 Torr hydrogen) showed hydrogenolysis to be a prominent reaction. With LTR chlorine-free catalysts, hydrogenolysis of n-pentane was almost exclusively by central scission. The chlorine-containing HTR catalyst yielded largely terminal scission. HTR chlorine-free catalysts and LTR chlorine-containing catalysts gave an intermediate behavior. Thus, both higher reduction temperature and presence of chlorine act to move scission of the C-C chain from the center to the ends. Hydrogenolysis of neohexane showed increased direct demethanation to give n-butane with the presence of chlorine in the catalyst. Ring scission of methylcyclopentane depressed hydrogen chemisorption and the carbanionic reactivity in these cracking reactions are interpreted in terms of a moderately strong metal-support interaction with a shift of negative charge from the magnesia O[sup 2[minus

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

    PubMed

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

    2012-02-22

    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

  16. Toward Inexpensive Photocatalytic Hydrogen Evolution: A Nickel Sulfide Catalyst Supported on a High-Stability Metal-Organic Framework.

    PubMed

    Peters, Aaron W; Li, Zhanyong; Farha, Omar K; Hupp, Joseph T

    2016-08-17

    Few-atom clusters composed of nickel and sulfur have been successfully installed into the Zr(IV)-based metal-organic framework (MOF) NU-1000 via ALD-like chemistry (ALD = atomic layer deposition). X-ray photoelectron spectroscopy and Raman spectroscopy are used to determine that primarily Ni(2+) and S(2-) sites are deposited within the MOF. In a pH 7 buffered aqueous solution, the porous catalyst is able to produce H2 gas at a rate of 3.1 mmol g(-1) h(-1) upon UV irradiation, whereas no H2 is generated by irradiating bare NU-1000. Upon visible light irradiation, little H2 generation was observed; however, with the addition of an organic dye, rose bengal, NiS-AIM can catalyze the production of H2 at an enhanced rate of 4.8 mmol g(-1) h(-1). These results indicate that ALD in MOFs (AIM) can engender reactivity within high surface area supports for applications in the solar fuels field. PMID:27487409

  17. The influence of alkali metal ions in the chemisorption of CO and CO{sub 2} on supported palladium catalysts: A Fourier transform infrared spectroscopic study

    SciTech Connect

    Liotta, L.F.; Deganello, G.; Martin, G.A.

    1996-12-01

    Two series of palladium-based catalysts were compared on the basis of the adsorption of CO and CO{sub 2}, monitored by Fourier transform infrared spectroscopy. The first series is represented by a silica-supported palladium catalyst and by some catalysts derived from it by addition of different amounts of sodium ion 0 {le} R {le} 25.6, where R is the atomic ratio Na/Pd. The second series consists of palladium catalysts supported on {open_quotes}model{close_quotes} and natural pumices. The model pumices, obtained by sol-gel techniques, are silico-aluminates containing variable amounts of sodium so that the corresponding Pd catalysts have an R value in the range 0{le}R{le}6.1. In the Pd/natural pumice catalysts, changes of the atomic ratio R{prime} = (Na + K)/Pd are achieved with different palladium loadings. Despite the analogous behaviour of the catalysts of both series when R=0, the presence of increasing alkali metal ions induces different behaviour towards the adsorption of CO. On increasing R in the Na-Pd/SiO{sub 2} series there is a progressive weakening of the C-O bond to produce eventually carbonates, whereas only a decrease of the amount of adsorbed CO occurs in the Pd/model pumice series (R{le}6.1). Furthermore, only physisorbed CO bands are observed in Pd/natural pumice catalysts (R{prime}{le}17). Different behaviour is also noticed towards the adsorption of CO{sub 2}: the equilibrium CO{sub 2}(gas){r_equilibrium}CO{sub ads}+O{sub ads} occurs in the Pd/SiO{sub 2} series, in contrast to the Pd/pumice series where only carbonate species on the surface of the support are detected. 83 refs., 12 figs., 4 tabs.

  18. A La-doped Mg-Al mixed metal oxide supported copper catalyst with enhanced catalytic performance in transfer dehydrogenation of 1-decanol.

    PubMed

    Zhang, Ming; Zhao, Yajie; Liu, Qian; Yang, Lan; Fan, Guoli; Li, Feng

    2016-01-21

    In the present work, a La-doped Mg-Al mixed metal oxide supported copper catalyst (Cu/La-MgAlO) was synthesized through a layered double hydroxide precursor route. The materials were characterized by powder X-ray diffraction, transmission electron microscopy, CO2-temperature programmed desorption, Fourier transform infrared spectra of CO2 absorption, and X-ray photoelectron spectroscopy. The results revealed that the introduction of a trace amount of La could significantly improve the surface basicity of the Cu/La-MgAlO catalyst, especially strong Lewis basicity. Compared with the undoped supported Cu catalyst, Cu/La-MgAlO exhibited much higher activity and selectivity in the liquid-phase transfer dehydrogenation of 1-decanol with a 1-decanal yield up to 89%. The excellent catalytic efficiency was mainly ascribed to the surface cooperation between the Lewis basic sites and the adjacent Cu(0)/Cu(+) species. That is, basic sites, especially strong-strength basic sites, held the key to the abstraction of protons from the hydroxyl group in 1-decanol, while the adjacent Cu(0) and Cu(+) species were responsible for the hydrogen transfer and the adsorption of styrene in the transfer dehydrogenation and hydrogenation reactions, respectively. This study provides a new method for designing cost-effective supported copper-based catalysts highly efficient for the transfer dehydrogenation of primary aliphatic alcohols by modifying the surface basicity of metal oxide supports. PMID:26659760

  19. Identifying low-coverage surface species on supported noble metal nanoparticle catalysts by DNP-NMR

    SciTech Connect

    Johnson, Robert L.; Perras, Frédéric A.; Kobayashi, Takeshi; Schwartz, Thomas J.; Dumesic, James A.; Shanks, Brent H.; Pruski, Marek

    2015-11-20

    DNP-NMR spectroscopy has been applied to enhance the signal for organic molecules adsorbed on γ-Al2O3-supported Pd nanoparticles. In addition, by offering >2500-fold time savings, the technique enabled the observation of 13C-13C cross-peaks for low coverage species, which were assigned to products from oxidative degradation of methionine adsorbed on the nanoparticle surface.

  20. Identifying low-coverage surface species on supported noble metal nanoparticle catalysts by DNP-NMR

    DOE PAGES

    Johnson, Robert L.; Perras, Frédéric A.; Kobayashi, Takeshi; Schwartz, Thomas J.; Dumesic, James A.; Shanks, Brent H.; Pruski, Marek

    2015-11-20

    DNP-NMR spectroscopy has been applied to enhance the signal for organic molecules adsorbed on γ-Al2O3-supported Pd nanoparticles. In addition, by offering >2500-fold time savings, the technique enabled the observation of 13C-13C cross-peaks for low coverage species, which were assigned to products from oxidative degradation of methionine adsorbed on the nanoparticle surface.

  1. 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.

  2. Development of Novel Supported Gold Catalysts: A Materials Perspective

    SciTech Connect

    Dai, Sheng; Ma, Zhen

    2011-01-01

    Since Haruta et al. discovered that small gold nanoparticles finely dispersed on certain metal oxide supports can exhibit surprisingly high activity in CO oxidation below room temperature, heterogeneous catalysis by supported gold nanoparticles has attracted tremendous attention. The majority of publications deal with the preparation and characterization of conventional gold catalysts (e.g., Au/TiO{sub 2}), the use of gold catalysts in various catalytic reactions, as well as elucidation of the nature of the active sites and reaction mechanisms. In this overview, we highlight the development of novel supported gold catalysts from a materials perspective. Examples, mostly from those reported by our group, are given concerning the development of simple gold catalysts with single metal-support interfaces and heterostructured gold catalysts with complicated interfacial structures. Catalysts in the first category include active Au/SiO{sub 2} and Au/metal phosphate catalysts, and those in the second category include catalysts prepared by pre-modification of supports before loading gold, by post-modification of supported gold catalysts, or by simultaneous dispersion of gold and an inorganic component onto a support. CO oxidation has generally been employed as a probe reaction to screen the activities of these catalysts. These novel gold catalysts not only provide possibilities for applied catalysis, but also furnish grounds for fundamental research.

  3. Surface Chemistry and Properties of Oxides as Catalyst Supports

    SciTech Connect

    DeBusk, Melanie Moses; Narula, Chaitanya Kumar; Contescu, Cristian I

    2015-01-01

    Heterogeneous catalysis relies on metal-oxides as supports for the catalysts. Catalyst supports are an indispensable component of most heterogeneous catalysts, but the role of the support is often minimized in light of the one played by the catalytically active species it supports. The active species of supported catalysts are located on the surface of the support where their contact with liquid or gas phase reactants will be greatest. Considering that support plays a major role in distribution and stability of active species, the absorption and retention of reactive species, and in some cases in catalytic reaction, the properties and chemistry that can occur at the surface of an oxide support are important for understanding their impact on the activity of a supported catalyst. This chapter examines this rich surface chemistry and properties of oxides used as catalyst supports, and explores the influence of their interaction with the active species.

  4. Production of carbon nanotubes: Chemical vapor deposition synthesis from liquefied petroleum gas over Fe-Co-Mo tri-metallic catalyst supported on MgO

    NASA Astrophysics Data System (ADS)

    Setyopratomo, P.; Wulan, Praswasti P. D. K.; Sudibandriyo, M.

    2016-06-01

    Carbon nanotubes were produced by chemical vapor deposition method to meet the specifications for hydrogen storage. So far, the various catalyst had been studied outlining their activities, performances, and efficiencies. In this work, tri-metallic catalyst consist of Fe-Co-Mo supported on MgO was used. The catalyst was prepared by wet-impregnation method. Liquefied Petroleum Gas (LPG) was used as carbon source. The synthesis was conducted in atmospheric fixed bed reactor at reaction temperature range 750 - 850 °C for 30 minutes. The impregnation method applied in this study successfully deposed metal component on the MgO support surface. It found that the deposited metal components might partially replace Mg(OH)2 or MgO molecules in their crystal lattice. Compare to the original MgO powder; it was significant increases in pore volume and surface area has occurred during catalyst preparation stages. The size of obtained carbon nanotubes is ranging from about 10.83 nm OD/4.09 nm ID up to 21.84 nm OD/6.51 nm ID, which means that multiwall carbon nanotubes were formed during the synthesis. Yield as much as 2.35 g.CNT/g.catalyst was obtained during 30 minutes synthesis and correspond to carbon nanotubes growth rate of 0.2 μm/min. The BET surface area of the obtained carbon nanotubes is 181.13 m2/g and around 50 % of which is contributed by mesopores. Micropore with half pore width less than 1 nm contribute about 10% volume of total micro and mesopores volume of the carbon nanotubes. The existence of these micropores is very important to increase the hydrogen storage capacity of the carbon nanotubes.

  5. Rapid ether and alcohol C-O bond hydrogenolysis catalyzed by tandem high-valent metal triflate + supported Pd catalysts.

    PubMed

    Li, Zhi; Assary, Rajeev S; Atesin, Abdurrahman C; Curtiss, Larry A; Marks, Tobin J

    2014-01-01

    The thermodynamically leveraged conversion of ethers and alcohols to saturated hydrocarbons is achieved efficiently with low loadings of homogeneous M(OTf)n + heterogeneous Pd tandem catalysts (M = transition metal; OTf = triflate; n = 4). For example, Hf(OTf)4 mediates rapid endothermic ether ⇌ alcohol and alcohol ⇌ alkene equilibria, while Pd/C catalyzes the subsequent, exothermic alkene hydrogenation. The relative C-O cleavage rates scale as 3° > 2° > 1°. The reaction scope extends to efficient conversion of biomass-derived ethers, such as THF derivatives, to the corresponding alkanes. PMID:24354599

  6. Metal phthalocyanine catalysts

    DOEpatents

    Ellis, P.E. Jr.; Lyons, J.E.

    1994-10-11

    A new composition of matter is described which is an alkali metal or ammonium or tetraalkylammonium diazidoperfluorophthalocyanatoferrate. Other embodiments of the invention comprise compositions wherein the metal of the coordination complex is cobalt, manganese and chromium.

  7. Metal phthalocyanine catalysts

    DOEpatents

    Ellis, Jr., Paul E.; Lyons, James E.

    1994-01-01

    As a new composition of matter, alkali metal or ammonium or tetraalkylammonium diazidoperfluorophthalocyanatoferrate. Other embodiments of the invention comprise compositions wherein the metal of the coordination complex is cobalt, manganese and chromium.

  8. Environmental Transmission Electron Microscopy Study of the Origins of Anomalous Particle Size Distributions in Supported Metal Catalysts

    SciTech Connect

    Benavidez, Angelica D.; Kovarik, Libor; Genc, Arda; Agrawal, Nitin; Larsson, Elin M.; Hansen, Thomas W.; Karim, Ayman M.; Datye, Abhaya K.

    2012-10-31

    In this Environmental TEM (ETEM) study of supported Pt and Pd model catalysts, individual nanoparticles were tracked during heat treatments at temperatures up to 600°C in H2, O2, and vacuum. We found anomalous growth of nanoparticles occurred during the early stages of catalyst sintering wherein some particles started to grow significantly larger than the mean, resulting in a broadening of the particle size distribution. We can rule out sample non-uniformity as a cause for the growth of these large particles, since images were recorded prior to heat treatments. The anomalous growth of these particles may help explain particle size distributions in heterogeneous catalysts which often show particles that are significantly larger than the mean, resulting in a long tail to the right. It has been suggested that particle migration and coalescence could be the likely cause for the broad size distributions. This study shows that anomalous growth of nanoparticles can occur under conditions where Ostwald ripening is the primary sintering mechanism.

  9. Reaction pathways involved in CH4 conversion on Pd/Al2O3 catalysts : TAP as a powerful tool for the elucidation of the effective role of the metal/support interface

    NASA Astrophysics Data System (ADS)

    Granger, Pascal

    2016-02-01

    Temporal Analysis of Products (TAP) reactor offers an alternative to draw direct structure/activity relationships checked on Natural Gas-fuelled Vehicle (NGV) catalysts Determination of accurate kinetic constants for methane adsorption from single pulse experiments and subsequent investigation of sequential surface reactions from alternative CH4/O2 pulse experiments provides a straightforward visualization of the involvement of the metal/support interface on freshly-prepared catalysts and the loss of this effect on aged single palladium based catalysts.

  10. Supported catalyst systems and method of making biodiesel products using such catalysts

    DOEpatents

    Kim, Manhoe; Yan, Shuli; Salley, Steven O.; Ng, K. Y. Simon

    2015-10-20

    A heterogeneous catalyst system, a method of preparing the catalyst system and a method of forming a biodiesel product via transesterification reactions using the catalyst system is disclosed. The catalyst system according to one aspect of the present disclosure represents a class of supported mixed metal oxides that include at least calcium oxide and another metal oxide deposited on a lanthanum oxide or cerium oxide support. Preferably, the catalysts include CaO--CeO.sub.2ZLa.sub.2O.sub.3 or CaO--La.sub.2O.sub.3/CeO.sub.2. Optionally, the catalyst may further include additional metal oxides, such as CaO--La.sub.2O.sub.3--GdOxZLa.sub.2O.sub.3.

  11. Promotion effects in methanol synthesis over MgO-supported Fe-Ir catalysts prepared from mixed-metal clusters

    SciTech Connect

    Marengo, S.; Psaro, R.; Dossi, C.; Calmotti, S.; Della Pergola, R.

    1996-12-31

    Methanol synthesis over bimetallic FeIr/MgO, catalysts prepared from mixed-metal carbonyl clusters, was studied with the aim of clarifying the role of the Fe/Ir ratio in the precursor and the influence of process parameters. Upon impregnation, the molecular precursors are physisorbed on the magnesia surface. Active catalysts are obtained by H{sub 2} treatment of these systems at 623 K. The presence of iron in the precursor favors the formation of surface sites exhibiting marked bifunctional character, as shown by effective production of both methanol and methane in the CO hydrogenation. This promotion is strongly influenced by reaction conditions, as a consequence of the dependence of kinetic parameters on the Fe loading. Upon raising the reaction pressure, the overall CO conversion rate increases dramatically and product distribution also changes to a significant extent, methanol being the most favored product. With Fe:Ir ratio of 1:1, high methanol productivity (above 100 mol MeOH/mol{sub Ir} {center_dot}h) was obtained at 6.1 MPa and 523 K, with 91% oxygenates selectivity.

  12. 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.

  13. Reducing the Cost and Preserving the Reactivity in Noble-Metal-Based Catalysts: Oxidation of CO by Pt and Al-Pt Alloy Clusters Supported on Graphene.

    PubMed

    Koizumi, Kenichi; Nobusada, Katsuyuki; Boero, Mauro

    2016-04-01

    The oxidation mechanisms of CO to CO2 on graphene-supported Pt and Pt-Al alloy clusters are elucidated by reactive dynamical simulations. The general mechanism evidenced is a Langmuir-Hinshelwood (LH) pathway in which O2 is adsorbed on the cluster prior to the CO oxidation. The adsorbed O2 dissociates into two atomic oxygen atoms thus promoting the CO oxidation. Auxiliary simulations on alloy clusters in which other metals (Al, Co, Cr, Cu, Fe, Ni) replace a Pt atom have pointed to the aluminum doped cluster as a special case. In the nanoalloy, the reaction mechanism for CO oxidation is still a LH pathway with an activation barrier sufficiently low to be overcome at room temperature, thus preserving the catalyst efficiency. This provides a generalizable strategy for the design of efficient, yet sustainable, Pt-based catalysts at reduced cost. PMID:26878836

  14. Non-Noble-Metal Nanoparticle Supported on Metal-Organic Framework as an Efficient and Durable Catalyst for Promoting H2 Production from Ammonia Borane under Visible Light Irradiation.

    PubMed

    Wen, Meicheng; Cui, Yiwen; Kuwahara, Yasutaka; Mori, Kohsuke; Yamashita, Hiromi

    2016-08-24

    In this work, we propose a straightforward method to enhance the catalytic activity of AB dehydrogenation by using non-noble-metal nanoparticle supported on chromium-based metal-organic framework (MIL-101). It was demonstrated to be effective for hydrogen generation from ammonia borane under assistance of visible light irradiation as a noble-metal-free catalyst. The catalytic activity of metal nanoparticles supported on MIL-101 under visible light irradiation is remarkably higher than that without light irradiation. The TOFs of Cu/MIL-101, Co/MIL-101, and Ni/MIL-101 are 1693, 1571, and 3238 h(-1), respectively. The enhanced activity of catalysts can be primarily attributed to the cooperative promoting effects from both non-noble-metal nanoparticles and photoactive metal-organic framework in activating the ammonia borane molecule and strong ability in the photocatalytic production of hydroxyl radicals, superoxide anions, and electron-rich non-noble-metal nanoparticle. This work sheds light on the exploration of active non-noble metals supported on photoactive porous materials for achieving high catalytic activity of various redox reactions under visible light irradiation. PMID:27478964

  15. XPS studies of Pt catalysts supported on porous carbon

    NASA Astrophysics Data System (ADS)

    Tyagi, Deepak; Varma, Salil; Bharadwaj, S. R.

    2016-05-01

    Pt catalysts supported on porous carbon were prepared by hard templating route and used for HI decomposition reaction of Sulfur Iodine thermochemical cycle. These catalysts were characterized by X-ray photoelectron spectroscopy for oxidation state of platinum as well as nature of carbon present in the catalysts. It was found that platinum is present in metallic state and carbon is present in both sp2 and sp3 hybridization states. The catalysts were evaluated for their activity and stability for liquid phase HI decomposition reaction and it was observed that mesoporous carbon based catalysts were more active and stable under the reaction conditions.

  16. Titanium Dioxide as a Catalyst Support in Heterogeneous Catalysis

    PubMed Central

    Bagheri, Samira; Muhd Julkapli, Nurhidayatullaili; Bee Abd Hamid, Sharifah

    2014-01-01

    The lack of stability is a challenge for most heterogeneous catalysts. During operations, the agglomeration of particles may block the active sites of the catalyst, which is believed to contribute to its instability. Recently, titanium oxide (TiO2) was introduced as an alternative support material for heterogeneous catalyst due to the effect of its high surface area stabilizing the catalysts in its mesoporous structure. TiO2 supported metal catalysts have attracted interest due to TiO2 nanoparticles high activity for various reduction and oxidation reactions at low pressures and temperatures. Furthermore, TiO2 was found to be a good metal oxide catalyst support due to the strong metal support interaction, chemical stability, and acid-base property. The aforementioned properties make heterogeneous TiO2 supported catalysts show a high potential in photocatalyst-related applications, electrodes for wet solar cells, synthesis of fine chemicals, and others. This review focuses on TiO2 as a support material for heterogeneous catalysts and its potential applications. PMID:25383380

  17. 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

  18. Dehydrogenation of dimethylcyclohexanols on metallic catalysts

    SciTech Connect

    Dokuchaeva, T.G.; Sibarov, D.A.; Timofeev, V.F.; Vasil'eva, L.V.

    1985-09-01

    This work studied the dehydrogenation of dimethylclohexanols on metallic catalysts. Alumina of A-64 grade was used as the support, and the catalyst consisted mainly of dimethylclohexenes. A table shows the dependence of the degree of conversion of cyclic alcohols on the number of methyl groups in the ring h/sup -1/; H/sub 2/: feed ratio 2.0. It is concluded that the resistance of the alkylcyclohexanols studied to catalytic conversion increases with the increase of the number of substituent methyl groups in their molecules. It is also shown that nickel catalyst prepared from nickel nitrate and acetate are highly effective for production of dimethylcyclohexanones from the corresponding alcsohols. The ketone yield at 300 /SUP o/ and 80% conversion of dimethylcyclohexanol is 91-93%.

  19. Reaction Pathways Involved in CH4 Conversion on Pd/Al2O3 Catalysts: TAP as a Powerful Tool for the Elucidation of the Effective Role of the Metal/Support Interface

    PubMed Central

    Renème, Y.; Pietrzyk, S.; Dhainaut, F.; Chaar, M.; van Veen, A. C.; Granger, Pascal

    2016-01-01

    Temporal Analysis of Products (TAP) investigation on Natural Gas-fueled Vehicle (NGV) catalysts provides information related to the nature of reaction steps involved over noble metals and at the metal-support interface. The determination of accurate kinetic parameters for methane adsorption from single pulse experiments and subsequent investigation of sequential surface reactions from alternative CH4/O2 pulse experiments is the first step toward the establishment of relevant structure/activity relationships which can highlight the importance of the metal/support interface on freshly-prepared and aged single palladium based catalysts. PMID:26909345

  20. Dry Reforming of Methane on a Highly-Active Ni-CeO2 Catalyst: Effects of Metal-Support Interactions on C-H Bond Breaking.

    PubMed

    Liu, Zongyuan; Grinter, David C; Lustemberg, Pablo G; Nguyen-Phan, Thuy-Duong; Zhou, Yinghui; Luo, Si; Waluyo, Iradwikanari; Crumlin, Ethan J; Stacchiola, Dario J; Zhou, Jing; Carrasco, Javier; Busnengo, H Fabio; Ganduglia-Pirovano, M Verónica; Senanayake, Sanjaya D; Rodriguez, José A

    2016-06-20

    Ni-CeO2 is a highly efficient, stable and non-expensive catalyst for methane dry reforming at relative low temperatures (700 K). The active phase of the catalyst consists of small nanoparticles of nickel dispersed on partially reduced ceria. Experiments of ambient pressure XPS indicate that methane dissociates on Ni/CeO2 at temperatures as low as 300 K, generating CHx and COx species on the surface of the catalyst. Strong metal-support interactions activate Ni for the dissociation of methane. The results of density-functional calculations show a drop in the effective barrier for methane activation from 0.9 eV on Ni(111) to only 0.15 eV on Ni/CeO2-x (111). At 700 K, under methane dry reforming conditions, no signals for adsorbed CHx or C species are detected in the C 1s XPS region. The reforming of methane proceeds in a clean and efficient way. PMID:27144344

  1. Dry Reforming of Methane on a Highly-Active Ni-CeO2 Catalyst: Effects of Metal-Support Interactions on C-H Bond Breaking.

    PubMed

    Liu, Zongyuan; Grinter, David C; Lustemberg, Pablo G; Nguyen-Phan, Thuy-Duong; Zhou, Yinghui; Luo, Si; Waluyo, Iradwikanari; Crumlin, Ethan J; Stacchiola, Dario J; Zhou, Jing; Carrasco, Javier; Busnengo, H Fabio; Ganduglia-Pirovano, M Verónica; Senanayake, Sanjaya D; Rodriguez, José A

    2016-06-20

    Ni-CeO2 is a highly efficient, stable and non-expensive catalyst for methane dry reforming at relative low temperatures (700 K). The active phase of the catalyst consists of small nanoparticles of nickel dispersed on partially reduced ceria. Experiments of ambient pressure XPS indicate that methane dissociates on Ni/CeO2 at temperatures as low as 300 K, generating CHx and COx species on the surface of the catalyst. Strong metal-support interactions activate Ni for the dissociation of methane. The results of density-functional calculations show a drop in the effective barrier for methane activation from 0.9 eV on Ni(111) to only 0.15 eV on Ni/CeO2-x (111). At 700 K, under methane dry reforming conditions, no signals for adsorbed CHx or C species are detected in the C 1s XPS region. The reforming of methane proceeds in a clean and efficient way.

  2. Microbial recovery of metals from spent coal liquefaction catalysts

    SciTech Connect

    Sperl, P.L.; Sperl, G.T.

    1991-01-01

    This project was initiated on October 1, 1989, for the purpose of recovering metals from spent coal liquefaction catalysts. Two catalyst types are the subject of the contract. The first is a Ni-Mo catalyst supported on alumina (Shell 324) as is used in a pilot scale coal liquefaction facility at Wilsonville, Alabama. A large sample of spent catalyst has been obtained. The second material is an unsupported ammonium molybdate catalyst used in a pilot process by the Department of energy at the Pittsburgh energy Technology Center. The object of the contract is to treat these spent catalysts with microorganisms, especially Thiobacillus ferrooxidans, but also other Thiobacillus sp. and possibly Sulfolobus, to leach and remove the metals (Ni and Mo) from the spent catalysts into a form which can be readily recovered by conventional techniques.

  3. Flame made ceria supported noble metal catalysts for efficient H2 production via the water gas shift reaction

    NASA Astrophysics Data System (ADS)

    Cavusoglu, G.; Lichtenberg, H.; Gaur, A.; Goldbach, A.; Grunwaldt, J.-D.

    2016-05-01

    Rh/ceria catalysts were synthesized by flame spray pyrolysis for high temperature water gas shift (WGS) reactions. These catalysts show a high specific surface area due to a high degree of nanocrystallinity. X-ray absorption spectroscopy (XAS) unraveled the formation of small Rh particles under WGS reaction conditions. The catalytic activity was examined at atmospheric pressure by measuring CO conversion as a function of temperature. Some methane formation was observed above 310°C.

  4. Methods for making a supported iron-copper catalyst

    DOEpatents

    Dyer, Paul N.; Pierantozzi, Ronald

    1986-01-01

    A catalyst is described for the synthesis of hydrocarbons from CO+H.sub.2 utilizing a porous Al.sub.2 O.sub.3 support impregnated with iron and copper and optionally promoted with an alkali metal. The use of an Al.sub.2 O.sub.3 support results in the suppression of heavy waxes (C.sub.26 + hydrocarbons), particularly in slurry phase operation, when compared to unsupported or co-precipitated catalysts.

  5. 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.

  6. Integrated current collector and catalyst support

    DOEpatents

    Bregoli, Lawrence J.

    1985-10-22

    An integrated current collecting electrode for a molten carbonate fuel cell includes a corrugated metal conductive strip positioned in contact with a catalyst layer. The corrugations of the metal strip form a plurality of gas channels immediately adjacent the surface of the catalyst through which a reactant gas flows. Each channel is filled with a particulate material to maintain separation between the metal strip and the catalyst in ensuring gas channel integrity. The catalyst may be in the form of a compacted, particulate material provided the particle size of the material within the gas channels is larger than that of the catalyst particles to prevent catalyst migration to the metal conductor and provide reactant gas access to the catalyst layer. The gas channels formed by the corrugations of the metal strip are arranged in an offset pattern along the direction of gas flow for improved reactant gas distribution to the catalyst layer. The particulate material positioned within the gas flow channels may be a ceramic conductor such as a perovskite or a spinel for enhanced current collection.

  7. Integrated current collector and catalyst support

    DOEpatents

    Bregoli, L.J.

    1984-10-17

    An integrated current collecting electrode for a molten carbonate fuel cell includes a corrugated metal conductive strip positioned in contact with a catalyst layer. The corrugations of the metal strip form a plurality of gas channels immediately adjacent the surface of the catalyst through which a reactant gas flows. Each channel is filled with a particulate material to maintain separation between the metal strip and the catalyst in ensuring gas channel integrity. The catalyst may be in the form of a compacted, particulate material provided the particle size of the material within the gas channels is larger than that of the catalyst particles to prevent catalyst migration to the metal conductor and provide reactant gas access to the catalyst layer. The gas channels formed by the corrugations of the metal strip are arranged in an offset pattern along the direction of gas flow for improved reactant gas distribution to the catalyst layer. The particulate material positioned within the gas flow channels may be a ceramic conductor such as a perovskite or a spinel for enhanced current collection.

  8. Oxidation of methane over palladium catalysts: effect of the support.

    PubMed

    Escandón, Lara S; Ordóñez, Salvador; Vega, Aurelio; Díez, Fernando V

    2005-01-01

    This work is focused on the deep catalytic oxidation of methane over supported palladium catalysts. The influences of the metal loading, oxidation state of palladium, nature of supports, presence of promoters in the supports (for zirconia-based supports), and thermal stability have been studied experimentally. Catalysts were prepared by incipient wetness of commercially available supports with aqueous solutions of palladium nitrate. For gamma-alumina support, it was observed that the optimal amount of palladium is between 0.5% and 2%, with higher amounts leading to a loss in specific activity. Concerning the oxidation state of the catalyst, it is concluded that for all the supports tested in the present work, a reduction of the catalyst is not needed, yielding the same conversion at steady state catalysts reduced and oxidised. The thermal stability of various supported catalysts were also studied, zirconia supports being the most active. These supports, specially Y-modified zirconia support, do not suffer appreciable deactivation below 500 degrees C.

  9. Effect of Graphitic Content on Carbon Supported Catalyst Performance

    SciTech Connect

    A. Patel; K. Artyushkova; P. Atanassov; David Harvey; M. Dutta; V. Colbow; S. Wessel

    2011-07-01

    The effect of graphitic content on carbon supported platinum catalysts was investigated in order to investigate its influence on catalyst performance. Four catalysts of varying surface areas and graphitic content were analyzed using XPS, HREELS, and tested using RDE experiments. The catalysts were also heat treated at 150 C and 100%RH as means to uniformly age them. The heat treated samples were analyzed using the same methods to determine what changes had occurred due to this aging process. When compared to the BOL catalysts, heat treated catalysts displayed increased graphitic carbon and platinum metallic content, however they also showed depressed catalytic activity. The primary cause is still under investigation, though it is believed to be related to loss of amorphous carbon content.

  10. Effect of Graphitic Content on Carbon Supported Catalyst Performance

    SciTech Connect

    Patel, Anant; Artyushkova, Kateryna; Atanassov, Plamen; Harvey, David; Dutta, Monica; Colbow, Vesna

    2011-07-01

    The effect of graphitic content on carbon supported platinum catalysts was investigated in order to investigate its influence on catalyst performance. Four catalysts of varying surface areas and graphitic content were analyzed using XPS, HREELS, and tested using RDE experiments. The catalysts were also heat treated at 150oC and 100%RH as means to uniformly age them. The heat treated samples were analyzed using the same methods to determine what changes had occurred due to this aging process. When compared to the BOL catalysts, heat treated catalysts displayed increased graphitic carbon and platinum metalic content, however they also showed depressed catalytic activity. The primary cause is still under investigation, though it is believed to be related to loss of amorphous carbon content.

  11. Metal resistance of zeolitic cracking catalysts

    SciTech Connect

    Chester, A.W.

    1981-03-01

    The impregnation-cracking technique of metal poisoning provides a rapid method for determining the metal resistance of a series of cracking catalysts. The method is useful for determining the effects of changes in a closely related series of catalysts or in evaluating a wide spectrum of commercially available catalysts. Containment-yields parameters allow determination of metal resistance independently of other catalyst properties. Actual catalyst performance, as indicated by the adjusted yields, is determined by both metal resistance characteristics and inherent selectivity. The results obtained in these tests are, however, relative and are not quantitatively translatable to commercial performance. Further, the impregnation-cracking technique allows detailed examination of some of the fundamental phenomena involved in metal poisoning. The overall validity of the method for qualitatively rating metal resistance can be - and has been - verified by comparing the behavior of the same catalysts in commercial units. The effect of antimony on metal poisons in commercial units has been reported and is successfully mimicked by the laboratory method. Relative metal activities, synergistic effects and metal dependences are readily determined for catalysts of particular interest. The different relative metal (Ni and V) activities for coke and hydrogen production is of importance in unit design for high metal feedstocks. In commercial FCC units, conversion or throughput is limited by either coke or hydrogen yields. Thus, units designed for increased contaminant yields based on a Ni/V activity ratio of 4 may well be underdesigned for coke. A knowledge of catalyst metal resistance, as determined here, coupled with feedstock properties, should allow more efficient designs for cracking processes for high-metal residual feedstocks.

  12. Metal nanoparticles as a conductive catalyst

    SciTech Connect

    Coker, Eric N.

    2010-08-03

    A metal nanocluster composite material for use as a conductive catalyst. The metal nanocluster composite material has metal nanoclusters on a carbon substrate formed within a porous zeolitic material, forming stable metal nanoclusters with a size distribution between 0.6-10 nm and, more particularly, nanoclusters with a size distribution in a range as low as 0.6-0.9 nm.

  13. Loading metal nanostructures on cotton fabrics as recyclable catalysts.

    PubMed

    Yang, Baocheng; Zhao, Chunmei; Xiao, Manda; Wang, Feng; Li, Chuanhao; Wang, Jianfang; Yu, Jimmy C

    2013-04-01

    Noble metal nanostructures of varying compositions and shapes are loaded on cotton fabrics. The fabric-supported metal nanostructures can function as effective catalysts for different liquid-phase catalytic reactions. They exhibit superior recyclability, with the catalytic activities remaining nearly unchanged even after ten cycles of catalytic reactions for all of the three tested reactions.

  14. Attrition Resistant Fischer-Tropsch Catalysts Based on FCC Supports

    SciTech Connect

    Adeyiga, Adeyinka

    2010-02-05

    Commercial spent fluid catalytic cracking (FCC) catalysts provided by Engelhard and Albemarle were used as supports for Fe-based catalysts with the goal of improving the attrition resistance of typical F-T catalysts. Catalysts with the Ruhrchemie composition (100 Fe/5 Cu/4.2 K/25 spent FCC on mass basis) were prepared by wet impregnation. XRD and XANES analysis showed the presence of Fe{sub 2}O{sub 3} in calcined catalysts. FeC{sub x} and Fe{sub 3}O{sub 4} were present in the activated catalysts. The metal composition of the catalysts was analyzed by ICP-MS. F-T activity of the catalysts activated in situ in CO at the same conditions as used prior to the attrition tests was measured using a fixed bed reactor at T = 573 K, P = 1.38 MPa and H{sub 2}:CO ratio of 0.67. Cu and K promoted Fe supported over Engelhard provided spent FCC catalyst shows relatively good attrition resistance (8.2 wt% fines lost), high CO conversion (81%) and C{sub 5}+ hydrocarbons selectivity (18.3%).

  15. Spectroscopic studies of alumina-supported nickel catalysts precursors. Part I. Catalysts prepared from acidic solutions

    NASA Astrophysics Data System (ADS)

    Pasieczna-Patkowska, S.; Ryczkowski, J.

    2007-04-01

    Nickel alumina-supported catalysts were prepared from acidic solutions of nickel nitrate by the CIM and DIM methods (classical and double impregnation, respectively). The catalysts exhibited different nickel species due to the existence of various metal-support interaction strengths. As a consequence, the reducibility and other surface properties changed as a function of the preparation method. The aim of this work was to study the interaction between the metal precursor and the alumina surface by means of FT-IR (Fourier transform infrared) and FT-IR/PAS (FT-IR photoacoustic spectroscopy).

  16. High performance, high durability non-precious metal fuel cell catalysts

    DOEpatents

    Wood, Thomas E.; Atanasoski, Radoslav; Schmoeckel, Alison K.

    2016-03-15

    This invention relates to non-precious metal fuel cell cathode catalysts, fuel cells that contain these catalysts, and methods of making the same. The fuel cell cathode catalysts are highly nitrogenated carbon materials that can contain a transition metal. The highly nitrogenated carbon materials can be supported on a nanoparticle substrate.

  17. Making A Noble-Metal-On-Metal-Oxide Catalyst

    NASA Technical Reports Server (NTRS)

    Miller, Irvin M.; Davis, Patricia P.; Upchurch, Billy T.

    1989-01-01

    Catalyst exhibits superior performance in oxidation of CO in CO2 lasers. Two-step process developed for preparing platinum- or palladium-on-tin-oxide catalyst for recombination of CO and O2, decomposition products that occur in high-voltage discharge region of closed-cycle CO2 laser. Process also applicable to other noble-metal/metal-oxide combinations.

  18. Evaluation of {gamma}-MnO{sub 2} as a VOC removal catalyst: Comparison with a noble metal catalyst

    SciTech Connect

    Lahousse, C.; Bernier, A.; Grange, P.; Delmon, B.; Papaefthimiou, P.; Ioannides, T.; Verykios, X.

    1998-08-15

    The performances of two very active catalysts for VOC removal (one metal oxide and one noble metal catalyst, namely {gamma}-MnO{sub 2} and Pt/TiO{sub 2}) are compared. The comparison takes into account not only the activity but also the sensitivity to competition effects between compounds, the influence of water vapor and the stability. The metal oxide catalyst proves to be more active than the supported noble metal one. Moreover, its performance is less affected by interferences between VOC`s than those of the noble metal catalyst. Conversely, the activity of the noble metal appears slightly more stable. Both are affected by water vapor which slightly decreases their efficiency. On the metal oxide catalyst, water shortens the time needed to get a stable catalytic activity.

  19. Catalyst regeneration process including metal contaminants removal

    DOEpatents

    Ganguli, Partha S.

    1984-01-01

    Spent catalysts removed from a catalytic hydrogenation process for hydrocarbon feedstocks, and containing undesired metals contaminants deposits, are regenerated. Following solvent washing to remove process oils, the catalyst is treated either with chemicals which form sulfate or oxysulfate compounds with the metals contaminants, or with acids which remove the metal contaminants, such as 5-50 W % sulfuric acid in aqueous solution and 0-10 W % ammonium ion solutions to substantially remove the metals deposits. The acid treating occurs within the temperature range of 60.degree.-250.degree. F. for 5-120 minutes at substantially atmospheric pressure. Carbon deposits are removed from the treated catalyst by carbon burnoff at 800.degree.-900.degree. F. temperature, using 1-6 V % oxygen in an inert gas mixture, after which the regenerated catalyst can be effectively reused in the catalytic process.

  20. Ceramic wash-coat for catalyst support

    SciTech Connect

    Kulkarni, Anand A.; Subramanian, Ramesh; Sabol, Stephen M.

    2012-08-14

    A wash-coat (16) for use as a support for an active catalyst species (18) and a catalytic combustor component (10) incorporating such wash-coat. The wash-coat is a solid solution of alumina or alumina-based material (Al.sub.2O.sub.3-0-3 wt % La.sub.2O.sub.3) and a further oxide exhibiting a coefficient of thermal expansion that is lower than that exhibited by alumina. The further oxide may be silicon dioxide (2-30 wt % SiO.sub.2), zirconia silicate (2-30 wt % ZrSiO.sub.4), neodymium oxide (0-4 wt %), titania (Al.sub.2O.sub.3-3-40% TiO.sub.2) or alumina-based magnesium aluminate spinel (Al.sub.2O.sub.3-25 wt % MgO) in various embodiments. The active catalyst species may be palladium and a second metal in a concentration of 10-50% of the concentration of the palladium.

  1. Bauxite-supported Transition Metal Oxides: Promising Low-temperature and SO2-tolerant Catalysts for Selective Catalytic Reduction of NOx

    PubMed Central

    Wang, Xiuyun; Wu, Wen; Chen, Zhilin; Wang, Ruihu

    2015-01-01

    In order to develop low-temperature (below 200 °C) and SO2-tolerant catalysts for selective catalytic reduction (SCR) of NOx, a series of cheap M/bauxite (M = Mn, Ni and Cu) catalysts were prepared using bauxite as a support. Their SCR performances are much superior to typical V2O5/TiO2, the addition of M into bauxite results in significant promotion of NOx removal efficiency, especially at low temperature. Among the catalysts, Cu/bauxite exhibits wide temperature window over 50–400 °C, strong resistance against SO2 and H2O as well as good regeneration ability in SCR of NOx. NOx conversion is more than 80% at 50–200 °C, and N2 selectivity is more than 98%. Cu/bauxite can serve as a promising catalyst in SCR of NOx. PMID:25988825

  2. Bauxite-supported Transition Metal Oxides: Promising Low-temperature and SO2-tolerant Catalysts for Selective Catalytic Reduction of NOx.

    PubMed

    Wang, Xiuyun; Wu, Wen; Chen, Zhilin; Wang, Ruihu

    2015-05-19

    In order to develop low-temperature (below 200 °C) and SO2-tolerant catalysts for selective catalytic reduction (SCR) of NOx, a series of cheap M/bauxite (M = Mn, Ni and Cu) catalysts were prepared using bauxite as a support. Their SCR performances are much superior to typical V2O5/TiO2, the addition of M into bauxite results in significant promotion of NOx removal efficiency, especially at low temperature. Among the catalysts, Cu/bauxite exhibits wide temperature window over 50-400 °C, strong resistance against SO2 and H2O as well as good regeneration ability in SCR of NOx. NOx conversion is more than 80% at 50-200 °C, and N2 selectivity is more than 98%. Cu/bauxite can serve as a promising catalyst in SCR of NOx.

  3. 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.

  4. Effect of the support and the reduction temperature on the formation of metallic nickel phase in Ni/silica gel precursors of vegetable oil hydrogenation catalysts

    NASA Astrophysics Data System (ADS)

    Gabrovska, M.; Krstić, J.; Tzvetkov, P.; Tenchev, K.; Shopska, M.; Vukelić, N.; Jovanović, D.

    2011-12-01

    Ni/SiO2 materials with identical composition (SiO2/Ni = 1.0) have been synthesized by precipitation of Ni(NO3)2 · 6H2O solution with Na2CO3 solution on the silica gel, obtained at three different pH values. The present investigation was undertaken in an endeavor to study the effects of the silica gel support type and the reduction temperature on the formation and dispersion of the metallic nickel phase in the reduced Ni/SiO2 precursors of the vegetable oil hydrogenation catalyst. The physicochemical characterization of the unreduced and reduced precursors has been accomplished appropriately by powder X-ray diffraction, infrared spectroscopy, temperature programmed reduction and H2-chemisorption techniques. It can be stated that the texture peculiarities of the silica gels used as supports influence on the crystalline state and distribution of the deposited Ni-containing phases during the preparation of the precursors, on the reduction temperature of the investigated solids as well as on the bulk size and surface dispersion of the arising metallic nickel particles. It was shown that two types of Ni2+-species are formed during the synthesis procedure, namely basic nickel carbonate-like and Ni-phyllosilicate with different extent of presence, location and strength of interaction. The different location of these species is supposed to result in various strength of Ni-O and Ni-O-Si interaction, thus determining the overall reducibility of the precursors. It was specified that the Ni2+-species are strongly bonded to the surface of the silica gel obtained at neutral pH value and weakly bonded to the surface of those prepared in acidic and alkaline conditions. It was established that the precursor, derivates from the silica gel obtained at alkaline conditions, demonstrates both significant reduction of the Ni2+ ions at 430°C and finely dispersed metallic nickel particles on its surface. High dispersion of the metallic nickel might be the crucial reason for achieving of

  5. Popping of graphite oxide: application in preparing metal nanoparticle catalysts.

    PubMed

    Gao, Yongjun; Chen, Xi; Zhang, Jiaguang; Asakura, Hiroyuki; Tanaka, Tsunehiro; Teramura, Kentaro; Ma, Ding; Yan, Ning

    2015-08-26

    A popcorn-like transformation of graphite oxide (GO) is reported and used to synthesize metal nanoparticle catalysts. The popping step is unique and essential, not only generating a high-surface-area support but also partially decomposing the metal precursors to form well-separated metal oxide nuclei, which would further evolve into highly dispersed and uniform-sized nanoparticles in the subsequent reduction. PMID:26179983

  6. STRONTIUM AS AN EFFICIENT PROMOTER FOR SUPPORTED PALLADIUM HYDROGENATION CATALYSTS

    EPA Science Inventory

    The effect of strontium promotion is studied for a series of supported palladium catalysts such as Pd/zeolite-β, Pd/Al2O3, Pd/SiO2, Pd/hydrotalcite and Pd/MgO. Strontium is found to be an effective promoter for enhancing the metal area, perce...

  7. Simultaneous formation of nitrogen and sulfur-doped transition metal catalysts for oxygen reduction reaction through pyrolyzing carbon-supported copper phthalocyanine tetrasulfonic acid tetrasodium salt

    NASA Astrophysics Data System (ADS)

    Qing, Xin; Shi, Jingjing; Ma, Chengyu; Fan, Mengyang; Bai, Zhengyu; Chen, Zhongwei; Qiao, Jinli; Zhang, Jiujun

    2014-11-01

    In this work, we report a spontaneous formation of copper (Cu-N-S/C) catalysts containing both nitrogen (N) and sulfur (S) elements using a one-step pyrolysis of carbon supported copper phthalocyanine tetrasulfonic acid tetrasodium salt (CuTSPc/C). The obtained catalysts exhibit high catalytic activities for oxygen reduction reaction (ORR) in alkaline media. Through electrochemical measurements and physical characterizations, several observations are reached as follows: (1) different pyrolysis temperatures can result in different catalyst structures and performances, and the optimum pyrolysis temperature is found to be 700 °C; (2) the electron transfer number of the ORR process catalyzed by the unpyrolyzed catalyst is about 2.5, after the pyrolysis, this number is increased to 3.5, indicating that the pyrolysis process can change the ORR pathway from a 2-electron transfer dominated process to a 4-electron transfer dominated one; (3) increasing catalyst loading from 40 μg cm-2 to 505 μg cm-2 can effectively improve the catalytic ORR activity, under which the percentage of H2O2 produced decreases sharply from 39.5% to 7.8%; and (4) the Cu ion can bond on pyridinic-N, graphite-N and C-Sn-C to form Cu-N-S/C catalyst active sites, which play the key role in the ORR activity.

  8. Microbial recovery of metals from spent catalysts. [Thiobacillus sulfolobus

    SciTech Connect

    Sperl, P.L.; Sperl, G.T.

    1991-01-01

    This project was initiated on October 1, 1989, for the purpose of recovering metals from spent coal liquefaction catalysts. Two catalyst types are the subject of the contract. The first is a Ni-Mo catalyst supported on alumina (Shell 324) as is used in a pilot scale coal liquefaction facility at Wilsonville, Alabama. This plant is run and operated by Southern Clean Fuels. A large sample of spent catalyst from this facility has been obtained. The second material is an unsupported ammonium molybdate catalyst used in a pilot process by the Department of Energy at the Pittsburgh Energy Technology Center. This material was obtained in late February 1990 but has not been pursued since the No content of this particular sample is too low for the current studies and no new catalyst has since been obtained. The object of the contract is to treat these spent catalysts with microorganisms, especially Thiobacillus ferrooxidans, but also other Thiobacillus sp. and possibly Sulfolobus, to leach and remove the metals (Ni and Mo) from the spent catalysts into a form which can be readily recovered by conventional techniques.

  9. Synthesis And Characterization of Dendrimer-Derived Supported Iridium Catalysts

    SciTech Connect

    Jesus, Y.Lopez-De; Vicente, A.; Lafaye, G.; Marecot, P.; Williams, C.T.

    2009-05-19

    The synthesis of Ir/{gamma}-Al{sub 2}O{sub 3} using the dendrimer metal nanocomposites (DMN) approach is reported. Fourth generation hydroxyl-terminated polyamidoamine dendrimer was complexed with Ir{sup 3+} in aqueous solution and the process monitored using ultraviolet-visible and X-ray absorption spectroscopy. No discernible reduction of Ir{sup 3+} to form zerovalent nanoparticles was observed after bubbling hydrogen or adding NaBH{sub 4} into the complex solution. Standard wet impregnation of the DMN precursors were used to prepare Ir/{gamma}-Al{sub 2}O{sub 3}, which were compared with conventionally prepared samples. In situ transmission Fourier transform infrared spectroscopy during dendrimer thermal decomposition in different atmospheres and CO adsorption allowed for identification of catalyst activation treatments that expose the maximum metal surface area. The particle size distributions of these catalysts were investigated using high resolution transmission electron microscopy, revealing that all of the catalysts have small particle sizes (0.4-3 nm) with narrow distributions. An optimized oxidation/reduction treatment produced a DMN-derived supported catalyst with higher metallic dispersion. DMN-derived catalysts were tested for liquid-phase hydrogenation of benzonitrile, and show an increase in TOF with increasing dispersion. The selectivity toward dibenzylamine is affected by the catalyst preparation method, with the oxidation/reduction treatment resulting in lower selectivity.

  10. Au and Pt nanoparticle supported catalysts tailored for H-2 production: From models to powder catalysts

    DOE PAGES

    T. D. Nguyen-Phan; Baber, A. E.; Rodriguez, J. A.; Senanayake, S. D.

    2015-12-10

    The use of metal nanoparticles (NPs), including Au and Pt, supported over oxides has been pivotal, and is ever increasing in enabling catalytic reactions which target the production of hydrogen. We review here the most recent works pertaining to the fundamental understanding of the structure, morphology, growth, characterization, and intrinsic phenomenological properties of Au– and Pt– based catalysts that influence the reactivity and selectivity to target hydrogen production. We draw on surface science and theoretical methods of model and powder catalysts using high resolution imaging, spectroscopy, scattering experiments, and theoretical studies. Based on these insights we identify key aspects ofmore » studies of supported metal nanoparticle (NP) catalysts for several reactions. The main focus of this review is on the intersection of catalytic chemistry related to the water-gas shift (WGS), oxygenate steam reforming (OSR), and solarassisted reactions (SAR).« less

  11. Au and Pt nanoparticle supported catalysts tailored for H-2 production: From models to powder catalysts

    SciTech Connect

    T. D. Nguyen-Phan; Baber, A. E.; Rodriguez, J. A.; Senanayake, S. D.

    2015-12-10

    The use of metal nanoparticles (NPs), including Au and Pt, supported over oxides has been pivotal, and is ever increasing in enabling catalytic reactions which target the production of hydrogen. We review here the most recent works pertaining to the fundamental understanding of the structure, morphology, growth, characterization, and intrinsic phenomenological properties of Au– and Pt– based catalysts that influence the reactivity and selectivity to target hydrogen production. We draw on surface science and theoretical methods of model and powder catalysts using high resolution imaging, spectroscopy, scattering experiments, and theoretical studies. Based on these insights we identify key aspects of studies of supported metal nanoparticle (NP) catalysts for several reactions. The main focus of this review is on the intersection of catalytic chemistry related to the water-gas shift (WGS), oxygenate steam reforming (OSR), and solarassisted reactions (SAR).

  12. Electrochemical Catalyst-Support Effects and Their Stabilizing Role for IrOx Nanoparticle Catalysts during the Oxygen Evolution Reaction.

    PubMed

    Oh, Hyung-Suk; Nong, Hong Nhan; Reier, Tobias; Bergmann, Arno; Gliech, Manuel; Ferreira de Araújo, Jorge; Willinger, Elena; Schlögl, Robert; Teschner, Detre; Strasser, Peter

    2016-09-28

    Redox-active support materials can help reduce the noble-metal loading of a solid chemical catalyst while offering electronic catalyst-support interactions beneficial for catalyst durability. This is well known in heterogeneous gas-phase catalysis but much less discussed for electrocatalysis at electrified liquid-solid interfaces. Here, we demonstrate experimental evidence for electronic catalyst-support interactions in electrochemical environments and study their role and contribution to the corrosion stability of catalyst/support couples. Electrochemically oxidized Ir oxide nanoparticles, supported on high surface area carbons and oxides, were selected as model catalyst/support systems for the electrocatalytic oxygen evolution reaction (OER). First, the electronic, chemical, and structural state of the catalyst/support couple was compared using XANES, EXAFS, TEM, and depth-resolved XPS. While carbon-supported oxidized Ir particle showed exclusively the redox state (+4), the Ir/IrOx/ATO system exhibited evidence of metal/metal-oxide support interactions (MMOSI) that stabilized the metal particles on antimony-doped tin oxide (ATO) in sustained lower Ir oxidation states (Ir(3.2+)). At the same time, the growth of higher valent Ir oxide layers that compromise catalyst stability was suppressed. Then the electrochemical stability and the charge-transfer kinetics of the electrocatalysts were evaluated under constant current and constant potential conditions, where the analysis of the metal dissolution confirmed that the ATO support mitigates Ir(z+) dissolution thanks to a stronger MMOSI effect. Our findings raise the possibility that MMOSI effects in electrochemistry-largely neglected in the past-may be more important for a detailed understanding of the durability of oxide-supported nanoparticle OER catalysts than previously thought. PMID:27549910

  13. Electrochemical Catalyst-Support Effects and Their Stabilizing Role for IrOx Nanoparticle Catalysts during the Oxygen Evolution Reaction.

    PubMed

    Oh, Hyung-Suk; Nong, Hong Nhan; Reier, Tobias; Bergmann, Arno; Gliech, Manuel; Ferreira de Araújo, Jorge; Willinger, Elena; Schlögl, Robert; Teschner, Detre; Strasser, Peter

    2016-09-28

    Redox-active support materials can help reduce the noble-metal loading of a solid chemical catalyst while offering electronic catalyst-support interactions beneficial for catalyst durability. This is well known in heterogeneous gas-phase catalysis but much less discussed for electrocatalysis at electrified liquid-solid interfaces. Here, we demonstrate experimental evidence for electronic catalyst-support interactions in electrochemical environments and study their role and contribution to the corrosion stability of catalyst/support couples. Electrochemically oxidized Ir oxide nanoparticles, supported on high surface area carbons and oxides, were selected as model catalyst/support systems for the electrocatalytic oxygen evolution reaction (OER). First, the electronic, chemical, and structural state of the catalyst/support couple was compared using XANES, EXAFS, TEM, and depth-resolved XPS. While carbon-supported oxidized Ir particle showed exclusively the redox state (+4), the Ir/IrOx/ATO system exhibited evidence of metal/metal-oxide support interactions (MMOSI) that stabilized the metal particles on antimony-doped tin oxide (ATO) in sustained lower Ir oxidation states (Ir(3.2+)). At the same time, the growth of higher valent Ir oxide layers that compromise catalyst stability was suppressed. Then the electrochemical stability and the charge-transfer kinetics of the electrocatalysts were evaluated under constant current and constant potential conditions, where the analysis of the metal dissolution confirmed that the ATO support mitigates Ir(z+) dissolution thanks to a stronger MMOSI effect. Our findings raise the possibility that MMOSI effects in electrochemistry-largely neglected in the past-may be more important for a detailed understanding of the durability of oxide-supported nanoparticle OER catalysts than previously thought.

  14. Optimization of carbon-supported platinum cathode catalysts for DMFC operation.

    SciTech Connect

    Zhu, Y.; Brosha, E. L.; Zelenay, P.

    2002-01-01

    In this paper, we describe performance and optimization of carbon-supported cathode catalysts at low platinum loading. We find that at a loading below 0.6 mg cm-2 carbon-supported platinum outperforms platinum black as a DMFC cathode catalyst. A catalyst with a 1:1 volume ratio of the dry NafionTM to the electronically conducting phase (platinum plus carbon support) provides the best performance in oxygen reduction reaction. Thanks to improved catalyst utilization, carbon-supported catalysts with a platinum content varying from 40 wt% to 80 wt% deliver very good DMFC performance, even at relatively modest precious metal loadings investigated in this work.

  15. Thermodynamic Properties of Supported Catalysts

    SciTech Connect

    Gorte, Raymond J.

    2014-03-26

    The goals of this work were to develop Coulometric Titration as a method for characterizing the thermodynamic redox properties of oxides and to apply this technique to the characterization of ceria- and vanadia-based catalysts. The redox properties of ceria and vanadia are a major part of what makes these materials catalytically active but their properties are also dependent on their structure and the presence of other oxides. Quantifying these properties through the measurement of oxidation energetics was the goal of this work.

  16. Catalyst supports for polymer electrolyte fuel cells.

    PubMed

    Subban, Chinmayee; Zhou, Qin; Leonard, Brian; Ranjan, Chinmoy; Edvenson, Heather M; Disalvo, F J; Munie, Semeret; Hunting, Janet

    2010-07-28

    A major challenge in obtaining long-term durability in fuel cells is to discover catalyst supports that do not corrode, or corrode much more slowly than the current carbon blacks used in today's polymer electrolyte membrane fuel cells. Such materials must be sufficiently stable at low pH (acidic conditions) and high potential, in contact with the polymer membrane and under exposure to hydrogen gas and oxygen at temperatures up to perhaps 120 degrees C. Here, we report the initial discovery of a promising class of doped oxide materials for this purpose: Ti(1-x)M(x)O(2), where M=a variety of transition metals. Specifically, we show that Ti(0.7)W(0.3)O(2) is electrochemically inert over the appropriate potential range. Although the process is not yet optimized, when Pt nanoparticles are deposited on this oxide, electrochemical experiments show that hydrogen is oxidized and oxygen reduced at rates comparable to those seen using a commercial Pt on carbon black support. PMID:20566509

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

    SciTech Connect

    Haw, James F

    2010-12-14

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

  18. Single-layer transition metal sulfide catalysts

    SciTech Connect

    Thoma, Steven G.

    2011-05-31

    Transition Metal Sulfides (TMS), such as molybdenum disulfide (MoS.sub.2), are the petroleum industry's "workhorse" catalysts for upgrading heavy petroleum feedstocks and removing sulfur, nitrogen and other pollutants from fuels. We have developed an improved synthesis technique to produce SLTMS catalysts, such as molybdenum disulfide, with potentially greater activity and specificity than those currently available. Applications for this technology include heavy feed upgrading, in-situ catalysis, bio-fuel conversion and coal liquefaction.

  19. Hydrothermal alkali metal catalyst recovery process

    DOEpatents

    Eakman, James M.; Clavenna, LeRoy R.

    1979-01-01

    In a coal gasification operation or similar conversion process carried out in the presence of an alkali metal-containing catalyst wherein solid particles containing alkali metal residues are produced, alkali metal constituents are recovered from the particles primarily in the form of water soluble alkali metal formates by treating the particles with a calcium or magnesium-containing compound in the presence of water at a temperature between about 250.degree. F. and about 700.degree. F. and in the presence of added carbon monoxide. During the treating process the water insoluble alkali metal compounds comprising the insoluble alkali metal residues are converted into water soluble alkali metal formates. The resultant aqueous solution containing water soluble alkali metal formates is then separated from the treated particles and any insoluble materials formed during the treatment process, and recycled to the gasification process where the alkali metal formates serve as at least a portion of the alkali metal constituents which comprise the alkali metal-containing catalyst. This process permits increased recovery of alkali metal constituents, thereby decreasing the overall cost of the gasification process by reducing the amount of makeup alkali metal compounds necessary.

  20. Catalysis science of supported vanadium oxide catalysts.

    PubMed

    Wachs, Israel E

    2013-09-01

    Supported vanadium oxide catalysts contain a vanadium oxide phase deposited on a high surface area oxide support (e.g., Al2O3, SiO2, TiO2, etc.) and have found extensive applications as oxidation catalysts in the chemical, petroleum and environmental industries. This review of supported vanadium oxide catalysts focuses on the fundamental aspects of this novel class of catalytic materials (molecular structures, electronic structures, surface chemistry and structure-reactivity relationships). The molecular and electronic structures of the supported vanadium oxide phases were determined by the application of modern in situ characterization techniques (Raman, IR, UV-vis, XANES, EXAFS, solid state (51)V NMR and isotopic oxygen exchange). The characterization studies revealed that the supported vanadium oxide phase consists of two-dimensional surface vanadia sites dispersed on the oxide supports. Corresponding surface chemistry and reactivity studies demonstrated that the surface vanadia sites are the catalytic active sites for oxidation reactions by supported vanadia catalysts. Combination of characterization and reactivity studies demonstrate that the oxide support controls the redox properties of the surface vanadia sites that can be varied by as much as a factor of ~10(3).

  1. Process for Making a Noble Metal on Tin Oxide Catalyst

    NASA Technical Reports Server (NTRS)

    Davis, Patricia; Miller, Irvin; Upchurch, Billy

    2010-01-01

    To produce a noble metal-on-metal oxide catalyst on an inert, high-surface-area support material (that functions as a catalyst at approximately room temperature using chloride-free reagents), for use in a carbon dioxide laser, requires two steps: First, a commercially available, inert, high-surface-area support material (silica spheres) is coated with a thin layer of metal oxide, a monolayer equivalent. Very beneficial results have been obtained using nitric acid as an oxidizing agent because it leaves no residue. It is also helpful if the spheres are first deaerated by boiling in water to allow the entire surface to be coated. A metal, such as tin, is then dissolved in the oxidizing agent/support material mixture to yield, in the case of tin, metastannic acid. Although tin has proven especially beneficial for use in a closed-cycle CO2 laser, in general any metal with two valence states, such as most transition metals and antimony, may be used. The metastannic acid will be adsorbed onto the high-surface-area spheres, coating them. Any excess oxidizing agent is then evaporated, and the resulting metastannic acid-coated spheres are dried and calcined, whereby the metastannic acid becomes tin(IV) oxide. The second step is accomplished by preparing an aqueous mixture of the tin(IV) oxide-coated spheres, and a soluble, chloride-free salt of at least one catalyst metal. The catalyst metal may be selected from the group consisting of platinum, palladium, ruthenium, gold, and rhodium, or other platinum group metals. Extremely beneficial results have been obtained using chloride-free salts of platinum, palladium, or a combination thereof, such as tetraammineplatinum (II) hydroxide ([Pt(NH3)4] (OH)2), or tetraammine palladium nitrate ([Pd(NH3)4](NO3)2).

  2. Novel zeolite-supported rhodium catalysts for ethanol steam reforming

    NASA Astrophysics Data System (ADS)

    Campos-Skrobot, Fabiana C.; Rizzo-Domingues, Roberta C. P.; Fernandes-Machado, Nádia R. C.; Cantão, Mauricio P.

    Renewable bioethanol is an interesting hydrogen source for fuel cells through steam reforming, but its C-C bond promotes parallel reactions, mainly coke and by-products formation. In this way, good ethanol reforming catalysts are still needed, which explains current research and development efforts around the world. Most catalysts proposed for ethanol reforming are based on oxide-supported noble metals with surface area below 100 m 2 g -1 and reaction temperatures above 500 °C. Novel Rh and Rh-K catalysts supported on NaY zeolite with surface area above 440 m 2 g -1 are presented in this work. Reaction temperature was fixed at 300 °C and H 2O/EtOH molar ratio and reagent flow were varied. Ethanol conversion varied from 50 to 99%, with average increase of 50% due to K promoter, and hydrogen production yield achieved 68%.

  3. Hydrogen Production from Ethanol Steam Reforming over Supported Cobalt Catalysts

    SciTech Connect

    Lin, Sean S.-Y.; Kim, Do Heui; Ha, Su Y.

    2008-05-01

    Hydrogen production was carried out via ethanol steam reforming over supported cobalt catalysts. Wet incipient impregnation method was used to support cobalt on ZrO2, CeO2 and CeZrO4 followed by pre-reduction with H2 up to 677 °C to attain supported cobalt catalysts. It was found that the non-noble metal based 10 wt % Co/CeZrO4 is an efficient catalyst to achieve ethanol conversion of 100% and hydrogen yield of 82% (4.9 mol H2/ mol ethanol) at 450 oC , which is superior to 0.5 wt % Rh/Al2O3. The pre-reduction process is required to activate supported cobalt catalysts for high H2 yield of ethanol steam reforming. In addition, support effect is found significant for cobalt during ethanol steam reforming. 10% Co/CeO2 gave high H2 selectivity while suffered low conversion due to the poor thermal stability. In contrast to CeO2, 10 wt % Co/ZrO2 achieved high conversion while suffered lower H2 yield due to the production of methane. The synergistic effect of ZrO2 and CeO2 to promote high ethanol conversion while suppress methanation was observed when CeZrO4 was used as a support for cobalt. This synergistic effect of CeZrO4 support leads to a high hydrogen yield at low temperature for 10 wt % Co/CeZrO4 catalyst. Under the high weight hourly space velocity (WHSV) of ethanol (2.5 h-1), the hydrogen yield over 10 wt % Co/CeZrO4 was found to gradually decrease to 70% of its initial value in 6 hours possibly due to the coke formation on the catalyst.

  4. Supported Oxide Catalysts from Chelating Precursors

    NASA Astrophysics Data System (ADS)

    Prieto-Centurion, Dario

    Supported Fe catalysts and, in particular, Fe and substituted MFI zeolites have attracted industrial and academic attention due to their ability to promote selective catalytic reduction of NOx and selective partial oxidation of hydrocarbons. It is generally accepted that some form of highly dispersed, binuclear or atomically-isolated metal species are involved in the selective processes catalyzed these materials. Several studies have sought to reproduce the structures and reactivity of these substituted zeolites on dierent supports. Given that specialized reagents or preparation conditions that are required in some of these preparation methods, and that multiple surface structures are often formed, this dissertation aimed to develop a route to highly dispersed supported transition metals using commonly available reactants and synthesis routes. Described here is a straightforward and effective procedure to control dispersion and surface speciation of Fe on SiO2 and CeO2 through incipient wetness impregnation (IWI) of the support with aqueous, anionic complexes of Fe3+ and ethylenediaminetetraacetic acid (EDTA) followed by oxidative heat-treatment. On SiO2, this method preferentially creates isolated surface structures up to loading of 0.9 Fe nm-2 if using alkali counter-cations. This isolated species display classic 'single-site' behavior|constant turn over frequency (TOF) with increasing Fe surface density|in the oxidation of adamantane with H 2O2, indicating active sites are equally accessible and equally active within this range of surface density. Additionally, TOF increases linearly with electronegativity of the alkali counter-cation, suggesting electronic promotion. Conversely, IWI of unprotected Fe3+ produces agglomerates less active in this reaction. On CeO2, the sterics and negative charge imparted on Fe 3+ by EDTA4- inhibits incorporation of Fe into surface vacancies. Instead, formation of two-dimensional oligomeric structures which can undergo Fe3+-Fe2

  5. Support chemistry, surface area, and preparation effects on sulfided NiMo catalyst activity

    SciTech Connect

    Gardner, T.J.; McLaughlin, L.I.; Sandoval, R.S.

    1996-06-01

    Hydrous Metal Oxides (HMOs) are chemically synthesized materials which contain a homogeneous distribution of ion exchangeable alkali cations that provide charge compensation to the metal-oxygen framework. In terms of the major types of inorganic ion exchangers defined by Clearfield, these amorphous HMO materials are similar to both hydrous oxides and layered oxide ion exchangers (e.g., alkali metal titanates). For catalyst applications, the HMO material serves as an ion exchangeable support which facilitates the uniform incorporation of catalyst precursor species. Following catalyst precursor incorporation, an activation step is required to convert the catalyst precursor to the desired active phase. Considerable process development activities at Sandia National Laboratories related to HMO materials have resulted in bulk hydrous titanium oxide (HTO)- and silica-doped hydrous titanium oxide (HTO:Si)-supported NiMo catalysts that are more active in model reactions which simulate direct coal liquefaction (e.g., pyrene hydrogenation) than commercial {gamma}-Al{sub 2}O{sub 3}-supported NiMo catalysts. However, a fundamental explanation does not exist for the enhanced activity of these novel catalyst materials; possible reasons include fundamental differences in support chemistry relative to commercial oxides, high surface area, or catalyst preparation effects (ion exchange vs. incipient wetness impregnation techniques). The goals of this paper are to identify the key factors which control sulfided NiMo catalyst activity, including those characteristics of HTO- and HTO:Si-supported NiMo catalysts which uniquely set them apart from conventional oxide supports.

  6. N2O decomposition by mesoporous silica supported Rh catalysts.

    PubMed

    Hussain, Murid; Fino, Debora; Russo, Nunzio

    2012-04-15

    Nitrous oxide (N(2)O), a greenhouse gas produced by nitric acid and adipic acid plants, damages the ozone layer and causes many environmental problems. The potential of MCM-41, SBA-15-Conventional (SBA-15-C), SBA-15-Spherical (SBA-15-S) and KIT-6 supported Rh catalysts has been explored at specific conditions for N(2)O decomposition in order to investigate the characteristics of new catalyst supports (SBA-15-S, KIT-6) for this application. A Rh metal loading of 1 wt% was impregnated to synthesize mesoporous silica supported Rh catalysts. The catalysts were characterized by scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), N(2) adsorption/desorption, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM) and CO-chemisorption techniques. Of all the catalysts, Rh/SBA-15-S not only showed the highest activity, but also the best strength against ageing impact, O(2) inhibiting effect and long-term stability. The higher metal dispersion due to the smaller Rh particle size and a greater formation of Rh(+1) than Rh(0) or Rh(+3) on SBA-15-S compared to the other supports, favoured a higher N(2)O decomposition. The larger pore size of SBA-15-S in Rh/SBA-15-S might favour a better Rh access, diffusion and dispersion and lead to higher activity. The higher long-term stability of Rh/SBA-15-S, with preserved support characteristics, than the other supports indicates its significance.

  7. Attrition resistant gamma-alumina catalyst support

    DOEpatents

    Singleton, Alan H.; Oukaci, Rachid; Goodwin, James G.

    2006-03-14

    A .gamma.-alumina catalyst support having improved attrition resistance produced by a method comprising the steps of treating a particulate .gamma.-alumina material with an acidic aqueous solution comprising water and nitric acid and then, prior to adding any catalytic material thereto, calcining the treated .gamma.-alumina.

  8. Metal catalysts for steam reforming of tar derived from the gasification of lignocellulosic biomass.

    PubMed

    Li, Dalin; Tamura, Masazumi; Nakagawa, Yoshinao; Tomishige, Keiichi

    2015-02-01

    Biomass gasification is one of the most important technologies for the conversion of biomass to electricity, fuels, and chemicals. The main obstacle preventing the commercial application of this technology is the presence of tar in the product gas. Catalytic reforming of tar appears a promising approach to remove tar and supported metal catalysts are among the most effective catalysts. Nevertheless, improvement of catalytic performances including activity, stability, resistance to coke deposition and aggregation of metal particles, as well as catalyst regenerability is greatly needed. This review focuses on the design and catalysis of supported metal catalysts for the removal of tar in the gasification of biomass. The recent development of metal catalysts including Rh, Ni, Co, and their alloys for steam reforming of biomass tar and tar model compounds is introduced. The role of metal species, support materials, promoters, and their interfaces is described. PMID:25455089

  9. Surface-reconstructed graphite nanofibers as a support for cathode catalysts of fuel cells.

    PubMed

    Gan, Lin; Du, Hongda; Li, Baohua; Kang, Feiyu

    2011-04-01

    Graphite nanofibers (GNFs), on which surface graphite edges were reconstructed into nano-loops, were explored as a cathode catalyst support for fuel cells. The high degree of graphitization, as well as the surface-reconstructed nano-loops that possess topological defects for uniform metal deposition, resulted in an improved performance of the GNF-supported Pt catalyst. PMID:21336405

  10. Strong metal-support interactions

    NASA Technical Reports Server (NTRS)

    Vannice, M. Albert

    1987-01-01

    It has been demonstrated that synergistic metal-support effects can occur which markedly enhance specific activity and alter selectivity in certain reactions. Because of the presence of such effects in certain reactions conducted under reducing conditions (that is, under H2 pressure), but not others, the creation of unique sites at the metal-support interface seems to be the best model at the present time to explain this behavior. The postulation of these sites, which are specific for a certain reactant such as CO, provides an effective explanation for the higher methanation rates that have been reported over some catalysts. The creation of these sites in the adlineation zone is facilitated by hydrogen spillover from the metal surface, and this same process can also enhance the reduction of many oxide supports. Although oxygen spillover is much less probable due to its higher heat of adsorption, it is much less well understood and the possibility of rate enhancements in CO oxidation caused by special interface sites cannot be discounted at the present time. Consequently, this seems to be an important area of future research.

  11. Microbial recovery of metals from spent catalysts. Quarterly report, September--December 1990

    SciTech Connect

    Sperl, P.L.; Sperl, G.T.

    1990-12-31

    This project was initiated on October 1, 1989, for the purpose of recovering metals from spent coal liquefaction catalysts. Two catalyst types are the subject of the contract. The first is a Ni-Mo catalyst supported on alumina (Shell 324) as is used in a pilot scale coal liquefaction facility at Wilsonville, Alabama. The object of the contract is to treat these spent catalysts with microorganisms, especially Thiobacillus ferrooxidans, but also other Thiobacillus sp., to leach and remove the metals (Ni and Mo) from the spent catalysts into a form which can be readily recovered by conventional techniques.

  12. Resolving Interparticle Heterogeneities in Composition and Hydrogenation Performance between Individual Supported Silver on Silica Catalysts

    PubMed Central

    2015-01-01

    Supported metal nanoparticle catalysts are commonly obtained through deposition of metal precursors onto the support using incipient wetness impregnation. Typically, empirical relations between metal nanoparticle structure and catalytic performance are inferred from ensemble averaged data in combination with high-resolution electron microscopy. This approach clearly underestimates the importance of heterogeneities present in a supported metal catalyst batch. Here we show for the first time how incipient wetness impregnation leads to 10-fold variations in silver loading between individual submillimeter-sized silica support granules. This heterogeneity has a profound impact on the catalytic performance, with 100-fold variations in hydrogenation performance at the same level. In a straightforward fashion, optical microscopy interlinks single support particle level catalytic measurements to structural and compositional information. These detailed correlations reveal the optimal silver loading. A thorough consideration of catalyst heterogeneity and the impact thereof on the catalytic performance is indispensable in the development of catalysts. PMID:26618052

  13. Metal containing polymers as fuel cell catalysts

    NASA Astrophysics Data System (ADS)

    Reed, James L.

    1987-06-01

    Several aspects of the fuel cell problem were addressed in this investigation. The objective of this work was the development of a fuel cell electrode-catalyst for use in a carbon monoxide fuel cell, which would utilize polymer bound metal complexes as the catalytic species. Several commercially available polymers were examined to be used as backbones in the development of an electrode-catalyst. Polystyrene was chosen for more extensive study. The polymer was activated by complete or partial monochloromethylation of the pendant phenyls. Several schemes for binding cyclic tetradentate and bidentate ligands to the activated polymers were not obtained. The transition metals cobalt and nickel were incorporated into the polymers, and these new materials were examined. In addition, the electrochemical behavior of several metal complexes which hold potential as catalytic species was examined.

  14. Study of Supported Particle Catalysts by Electron Microscopy Methods.

    NASA Astrophysics Data System (ADS)

    Yao, Ming-Hui

    1994-01-01

    The imaging conditions for electron microscopy study of supported ultrafine particle catalysts were investigated both theoretically and experimentally. Particles supported on crystalline supports were simulated and compared in high resolution electron microscopy (HREM) plan view and profile view as a function of defocus, voltage, aperture size, and support thickness. Possibilities and techniques for improving particle visibility and resolution by selecting objective lens defocus, Fourier filtering, and profile imaging were discussed. Various microscopy techniques, including HREM, high resolution scanning electron microscopy (HRSEM) and high-angle annular dark field imaging (HAADF) were used in parallel to study supported metal particle catalysts, and relative merits and shortcomings of each method were evaluated. It was pointed out that HREM profile imaging was the most effective technique for direct observation of microstructure, especially the surface structure of supported particles, whereas HRSEM and HAADF, respectively, were preferred for characterizing the surface topology of catalyst supports and the size distribution of supported particles. The HREM profile imaging method was used to study the strong metal-support interaction on various temperature treated Pt/CeO_2, and Pt/TiO _2 samples. Ti oxide monolayer on Pt/TiO _2 was observed, and related to the suppressed hydrogenolysis activity observed after high temperature reduction. No similar surface layer was observed on Pt/CeO_2 after high temperature treatment even though the hydrogenolysis activity was also strongly suppressed. It is proposed that decoration model is the main mechanism responsible for the SMSI for Pt/TiO _2, while morphological change and epitaxial relation is the major cause for the metal-support interaction for Pt/CeO_2. As well as surface structure, surface area was also studied in detail. A procedure for measuring surface area of supported particles by TEM was developed and applied to

  15. Process for the regeneration of metallic catalysts

    DOEpatents

    Katzer, James R.; Windawi, Hassan

    1981-01-01

    A method for the regeneration of metallic hydrogenation catalysts from the class consisting of Ni, Rh, Pd, Ir, Pt and Ru poisoned with sulfur, with or without accompanying carbon deposition, comprising subjecting the catalyst to exposure to oxygen gas in a concentration of about 1-10 ppm. intermixed with an inert gas of the group consisting of He, A, Xe, Kr, N.sub.2 and air substantially free of oxygen to an extent such that the total oxygen molecule throughout is in the range of about 10 to 20 times that of the hydrogen sulfide molecular exposure producing the catalyst poisoning while maintaining the temperature in the range of about 300.degree. to 500.degree. C.

  16. The effect of several parameters on catalytic denitrification of water by the use of H2 in the presence of O2 over metal supported catalysts.

    PubMed

    Theologides, C P; Savva, P G; Olympiou, G G; Pantelidou, N A; Constantinou, B K; Chatziiona, V K; Valanidou, L Y; Piskopianou, C T; Costa, C N

    2013-01-01

    The present paper involves a detailed study of the selective catalytic reduction of nitrates in aqueous mediums by the use of H2 in the presence of O2 over monometallic and bimetallic supported catalysts. In this study, an attempt has been made to improve the denitrification efficiency (XNO3(-), SN2) of several catalysts by regulating some experimental parameters that are involved in the process. Therefore, the effects of the type of reactor (semi-batch reactor vs continuous flow reactor), the nature of the active phase (Pd, Cu, and Pd-Cu) and the particle size of γ-Al2O3 spheres (particle diameter = 1.8 mm and 3 mm) on catalytic activity and reaction selectivity, as well as the adsorption capacity of γ-Al2O3 spheres for nitrates, were examined. As the review indicates, most of the research has so far been conducted on batch or semi-batch reactors. This study successfully demonstrates the benefits of using a continuous flow reactor in terms of catalytic activity (XNO3(-), %) and reaction selectivity (SN2, %). Another important aspect of this study is the crucial role of bimetallic Pd-Cu clusters for the prevention of NH4(+) formation. Moreover, the use of 1.8 mm diameter γ-Al2O3 spheres as a support was proved to significantly enhance the catalytic performance of bimetallic Pd-Cu catalysts towards nitrate reduction compared to 3 mm diameter γ-Al2O3 spheres. This difference may be attributed to mass (NO3(-), OH(-)) transfer effects (external mass transfer phenomena). PMID:24292483

  17. Au/TiO2 supported on ferritic stainless steel monoliths as CO oxidation catalysts

    NASA Astrophysics Data System (ADS)

    Milt, V. G.; Ivanova, S.; Sanz, O.; Domínguez, M. I.; Corrales, A.; Odriozola, J. A.; Centeno, M. A.

    2013-04-01

    Metallic supported structured catalysts were obtained by washcoating AluchromYHf monoliths with an Au/TiO2 catalyst. The powder catalyst was synthesized by DAE (direct anionic exchange) method. Using this catalyst, a stable slurry was prepared and used to washcoat the monoliths. TEM and SEM studies revealed that gold nanoparticles in the Au/TiO2 powder catalyst had an average diameter of 3-4 nm, but during the preparation of the structured catalyst, aggregate Au particles of the slurry reached diameters of 9 nm. Before coating, Aluchrom YHf monoliths were thermally treated to generate a homogeneous and well-adhered oxide rough surface layer, mainly composed of α-Al2O3 whiskers, which favored the anchoring of the catalyst. The catalytic layer deposited was well attached and contained not only the Au/TiO2 catalyst but also metallic oxides formed from stainless steel components that diffused through the oxide scale. The structural characterization was performed by XRD, XRF, TEM, SEM, GD-OES and SBET. The catalytic activity of the powder and structured catalysts was tested in the oxidation of the CO reaction. Catalysts demonstrated to be active at room temperature. After a first activation run, and in spite of their larger gold particle size, the catalytic activities of the structured catalysts overcame those of the powder catalyst. This improvement is probably due to the segregation of the transition metal oxides toward the surface oxide scale.

  18. Supported fischer-tropsch catalyst and method of making the catalyst

    DOEpatents

    Dyer, Paul N.; Pierantozzi, Ronald; Withers, Howard P.

    1987-01-01

    A Fischer-Tropsch catalyst and a method of making the catalyst for a Fischer-Tropsch process utilizing the catalyst by which synthesis gas, particularly carbon-monoxide rich synthesis gas, is selectively converted to higher hydrocarbons of relatively narrow carbon number range is disclosed. In general, the selective and notably stable catalyst, consist of an inert carrier first treated with a Group IV B metal compound (such as zirconium or titanium), preferably an alkoxide compound, and subsequently treated with an organic compound of a Fischer-Tropsch metal catalyst, such as cobalt, iron or ruthenium carbonyl. Reactions with air and water and calcination are specifically avoided in the catalyst preparation procedure.

  19. 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.

  20. Role of support in the catalytic hydrogenation of benzene over ruthenium catalysts

    SciTech Connect

    Viniegra, M.; Gomez, R.; Gonzalez, R.D.

    1988-06-01

    It is generally agreed that the hydrogenation of benzene over supported noble metal catalysts is a facile reaction which is independent of particle size. Previous benzene hydrogenation studies over supported Ru catalysts have been carried out using relatively noninteractive supports such as alumina and silica. Because of the possibility that more interactive supports such as magnesia or lanthana may modify the catalytic activity of supported Ru catalysts in the hydrogenation of benzene, the authors have extended previous studies to include magnesia, silica-alumina, and graphitic carbon as support materials. 12 references.

  1. Transition Metal Phosphide Hydroprocessing Catalysts: A review

    SciTech Connect

    Oyama, S.; Gott, T; Zhao, H; Lee, Y

    2009-01-01

    The diminishing quality of oil feedstocks coupled with increasingly more stringent environmental regulations limiting the content of sulfur in transportation fuels have given rise to a need for improved hydroprocessing technology. This review begins with a summary of the major improvements in hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) catalysts and processes that have been reported in recent years. It then describes a new class of hydroprocessing catalysts, the transition metal phosphides, which have emerged as a promising group of high-activity, stable catalysts. The phosphides have physical properties resembling ceramics, so are strong and hard, yet retain electronic and magnetic properties similar to metals. Their crystal structures are based on trigonal prisms, yet they do not form layered structures like the sulfides. They display excellent performance in HDS and HDN, with the most active phosphide, Ni{sub 2}P, having activity surpassing that of promoted sulfides on the basis of sites titrated by chemisorption (CO for the phosphides, O{sub 2} for the sulfides). In the HDS of difficult heteroaromatics like 4,6-dimethyldibenzothiophene Ni{sub 2}P operates by the hydrogenation pathway, while in the HDN of substituted nitrogen compounds like 2-methylpiperidine it carries out nucleophilic substitution. The active sites for hydrogenation in Ni{sub 2}P have a square pyramidal geometry, while those for direct hydrodesulfurization have a tetrahedral geometry. Overall, Ni{sub 2}P is a promising catalyst for deep HDS in the presence of nitrogen and aromatic compounds.

  2. In-situ and theoretical studies for the dissociation of water on an active Ni/CeO₂ catalyst: Importance of strong metal-support interactions for the cleavage of O-H bonds

    DOE PAGES

    Carrasco, Javier; Rodriguez, Jose A.; Lopez-Duran, David; Liu, Zongyuan; Duchon, Tomas; Evans, Jaime; Senanayake, Sanjaya D.; Crumlin, Ethan J.; Matolin, Vladimir; Ganduglia-Pirovano, M. Veronica

    2015-03-23

    Water dissociation is crucial in many catalytic reactions on oxide-supported transition-metal catalysts. Here, supported by experimental and density-functional theory results, we elucidate the effect of the support on O-H bond cleavage activity for nickel/ceria systems. Ambient-pressure O1s photoemission spectra at low Ni loadings on CeO₂(111) reveal a substantially larger amount of OH groups as compared to the bare support. Our computed activation energy barriers for water dissociation show an enhanced reactivity of Ni adatoms on CeO₂(111) compared with pyramidal Ni₄ particles with one Ni atom not in contact with the support, and extended Ni(111) surfaces. At the origin of thismore » support effect is the ability of ceria to stabilize oxidized Ni²⁺ species by accommodating electrons in localized f-states. The fast dissociation of water on Ni/CeO₂ has a dramatic effect on the activity and stability of this system as a catalyst for the water-gas shift and ethanol steam reforming reactions.« less

  3. In-situ and theoretical studies for the dissociation of water on an active Ni/CeO₂ catalyst: Importance of strong metal-support interactions for the cleavage of O-H bonds

    SciTech Connect

    Carrasco, Javier; Rodriguez, Jose A.; Lopez-Duran, David; Liu, Zongyuan; Duchon, Tomas; Evans, Jaime; Senanayake, Sanjaya D.; Crumlin, Ethan J.; Matolin, Vladimir; Ganduglia-Pirovano, M. Veronica

    2015-03-23

    Water dissociation is crucial in many catalytic reactions on oxide-supported transition-metal catalysts. Here, supported by experimental and density-functional theory results, we elucidate the effect of the support on O-H bond cleavage activity for nickel/ceria systems. Ambient-pressure O1s photoemission spectra at low Ni loadings on CeO₂(111) reveal a substantially larger amount of OH groups as compared to the bare support. Our computed activation energy barriers for water dissociation show an enhanced reactivity of Ni adatoms on CeO₂(111) compared with pyramidal Ni₄ particles with one Ni atom not in contact with the support, and extended Ni(111) surfaces. At the origin of this support effect is the ability of ceria to stabilize oxidized Ni²⁺ species by accommodating electrons in localized f-states. The fast dissociation of water on Ni/CeO₂ has a dramatic effect on the activity and stability of this system as a catalyst for the water-gas shift and ethanol steam reforming reactions.

  4. In situ and theoretical studies for the dissociation of water on an active Ni/CeO2 catalyst: importance of strong metal-support interactions for the cleavage of O-H bonds.

    PubMed

    Carrasco, Javier; López-Durán, David; Liu, Zongyuan; Duchoň, Tomáš; Evans, Jaime; Senanayake, Sanjaya D; Crumlin, Ethan J; Matolín, Vladimir; Rodríguez, José A; Ganduglia-Pirovano, M Verónica

    2015-03-23

    Water dissociation is crucial in many catalytic reactions on oxide-supported transition-metal catalysts. Supported by experimental and density-functional theory results, the effect of the support on OH bond cleavage activity is elucidated for nickel/ceria systems. Ambient-pressure O 1s photoemission spectra at low Ni loadings on CeO2 (111) reveal a substantially larger amount of OH groups as compared to the bare support. Computed activation energy barriers for water dissociation show an enhanced reactivity of Ni adatoms on CeO2 (111) compared with pyramidal Ni4 particles with one Ni atom not in contact with the support, and extended Ni(111) surfaces. At the origin of this support effect is the ability of ceria to stabilize oxidized Ni(2+) species by accommodating electrons in localized f-states. The fast dissociation of water on Ni/CeO2 has a dramatic effect on the activity and stability of this system as a catalyst for the water-gas shift and ethanol steam reforming reactions.

  5. In situ and theoretical studies for the dissociation of water on an active Ni/CeO2 catalyst: importance of strong metal-support interactions for the cleavage of O-H bonds.

    PubMed

    Carrasco, Javier; López-Durán, David; Liu, Zongyuan; Duchoň, Tomáš; Evans, Jaime; Senanayake, Sanjaya D; Crumlin, Ethan J; Matolín, Vladimir; Rodríguez, José A; Ganduglia-Pirovano, M Verónica

    2015-03-23

    Water dissociation is crucial in many catalytic reactions on oxide-supported transition-metal catalysts. Supported by experimental and density-functional theory results, the effect of the support on OH bond cleavage activity is elucidated for nickel/ceria systems. Ambient-pressure O 1s photoemission spectra at low Ni loadings on CeO2 (111) reveal a substantially larger amount of OH groups as compared to the bare support. Computed activation energy barriers for water dissociation show an enhanced reactivity of Ni adatoms on CeO2 (111) compared with pyramidal Ni4 particles with one Ni atom not in contact with the support, and extended Ni(111) surfaces. At the origin of this support effect is the ability of ceria to stabilize oxidized Ni(2+) species by accommodating electrons in localized f-states. The fast dissociation of water on Ni/CeO2 has a dramatic effect on the activity and stability of this system as a catalyst for the water-gas shift and ethanol steam reforming reactions. PMID:25651288

  6. In situ FTIR investigation of acetic acid electrooxidation on carbon supported Pt-Sn based trimetallic catalysts: Influence of the nature of the third metal

    NASA Astrophysics Data System (ADS)

    Beyhan, Seden; Léger, Jean-Michel; Kadırgan, Figen

    2014-12-01

    The effect of adding a third metal (Ni, Co, Pd, Rh) to Pt-Sn/C catalyst has been investigated for the adsorption and oxidation of acetic acid in acidic medium using in situ Fourier transform infrared (FTIR) spectroscopy. The results showed that the decomposition of acetic acid on the surface leads to the formation of different intermediate species and products such as acetate, acetyl, carbonate, CO and CO2. The reaction pathway of CO2 production proceeds via the formation of acetyl or carbonate through surface acetate species. It has been found that the selectivity of the acetate was enhanced by the addition of any third metal. However, the presence of Pd or Co increases the relative intensity of IR band for CO2. This is probably due to success in facilitating of the Csbnd C bond cleavage of acetyl. On the other hand, the conversion of acetate to carbonate is strongly affected by the adsorbed water, as is evident from the pronounced changes in the OH stretching region with the presence of Pd or Ni.

  7. 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.

  8. Development of new transition metal oxide catalysts for the destruction of PCDD/Fs.

    PubMed

    Yu, Ming-Feng; Li, Wen-Wei; Li, Xiao-Dong; Lin, Xiao-Qing; Chen, Tong; Yan, Jian-Hua

    2016-08-01

    Various transition metal oxide and vanadium-containing multi-metallic oxide catalysts were developed for the destruction of PCDD/Fs (polychlorinated dibenzo-p-dioxins and furans). A stable PCDD/Fs generating system was installed to support the catalytic destruction tests in this study. Nano-titania supported vanadium catalyst (VOx/TiO2) showed the highest activity, followed by CeOx, MnOx, WOx and finally MoOx. Multi-metallic oxide catalysts, prepared by doping WOx, MoOx, MnOx and CeOx into VOx/TiO2 catalysts, showed different activities on the decomposition of PCDD/Fs. The highest destruction efficiency of 92.5% was observed from the destruction test over VOxCeOx/TiO2 catalyst. However, the addition of WOx and MoOx even played a negative role in multi-metallic VOx/TiO2 catalysts. Characterizations of transition metal oxides and multi-metallic VOx/TiO2 catalysts were also investigated with XRD and TPR. After the catalysts were used, the conversion from high valent metals to low valence states was observed by XPS.

  9. Development of new transition metal oxide catalysts for the destruction of PCDD/Fs.

    PubMed

    Yu, Ming-Feng; Li, Wen-Wei; Li, Xiao-Dong; Lin, Xiao-Qing; Chen, Tong; Yan, Jian-Hua

    2016-08-01

    Various transition metal oxide and vanadium-containing multi-metallic oxide catalysts were developed for the destruction of PCDD/Fs (polychlorinated dibenzo-p-dioxins and furans). A stable PCDD/Fs generating system was installed to support the catalytic destruction tests in this study. Nano-titania supported vanadium catalyst (VOx/TiO2) showed the highest activity, followed by CeOx, MnOx, WOx and finally MoOx. Multi-metallic oxide catalysts, prepared by doping WOx, MoOx, MnOx and CeOx into VOx/TiO2 catalysts, showed different activities on the decomposition of PCDD/Fs. The highest destruction efficiency of 92.5% was observed from the destruction test over VOxCeOx/TiO2 catalyst. However, the addition of WOx and MoOx even played a negative role in multi-metallic VOx/TiO2 catalysts. Characterizations of transition metal oxides and multi-metallic VOx/TiO2 catalysts were also investigated with XRD and TPR. After the catalysts were used, the conversion from high valent metals to low valence states was observed by XPS. PMID:27186687

  10. Alumoxane precursors to designer catalysts and catalyst supports: Catalytic oxidation of dichloromethane

    SciTech Connect

    Cook, R.L.; Wong, C.; Harlan, C.J.; Kareiva, A.; Barron, A.R.

    1997-12-31

    Carboxylato-alumoxanes are aluminum-oxygen macromolecules consisting of a boehmite-like core surrounded by a sheath of carboxylate groups. The alumoxanes may be processed like organic polymers yet when fired are readily transformed into ceramic oxides. The alumoxanes can be precisely doped at room temperature in aqueous solution with a range of metal cations to prepare novel catalyst and catalyst support materials. The ease of introduction of multiple cations into the alumina lattice via the alumoxane approach provides a method for fine-tuning catalyst support properties and the fabrication of new catalyst materials themselves. Manganese-doped alumina (Mn-Al{sub 2}O{sub 3}), formed via the doping of an alumoxane with Mn at room temperature, is presented as an example where the alumoxane route provides enhanced catalytic performance over traditional approaches for the low temperature catalytic oxidation of chlorinated hydrocarbons (CHCs). The Mn-Al{sub 2}O{sub 3} formed from the Mn-doped alumoxane is compared with MnO{sub 2}/Al{sub 2}O{sub 3} prepared by the incipient wetness method, and commercial Pt/Al{sub 2}O{sub 3} for the oxidation/destruction of dichloromethane (CH{sub 2}Cl{sub 2}).

  11. Characterization of Al2O3 Supported Nickel Catalysts Derived from RFNon-thermal Plasma Technology

    SciTech Connect

    Jang, Ben W; Helleson, Michael J; Shi, Chunkai; Rondinone, Adam Justin; Schwartz, Viviane; Liang, Chengdu; Overbury, Steven {Steve} H

    2008-01-01

    Catalysts derived from non-thermal plasma techniques have previously shown unusual and highly advantageous catalytic properties including room temperature reduction, unusual metal particle structure and metal-support interactions, and enhanced selectivity and stability. This study focuses on the characterization of Al2O3 supported Ni catalysts derived from the RF non-thermal plasma technique with in-situ XRD, TPR-MS and STEM and on relating the results to the enhanced activity and stability of benzene hydrogenation. The results suggest that catalysts with plasma treatments before impregnation are relatively easier to be reduced and result in better activities under mild reduction conditions. These plasma treatments stabilize the nickel particle sizes of air(B) and H2(B) catalysts at 600 C by slowing down the sintering process. Plasma treatments after the impregnation of precursors, on the other hand, tend to delay the growth of nickel particles below 600 C, forming smaller Ni particles, but with a sudden increase in particle size near 600 C. It suggests that the structure of Ni nitrate and the metal-support interaction have been altered by the plasma treatments. The reduction patterns of plasma 1 treated catalysts are, therefore, changed. The catalyst with a combination plasma treatment demonstrates that the effect of a combination plasma treatment is larger than either the plasma treatment before or after the impregnation alone. Both plasma treatments before and after the impregnation of metal precursor play important roles in modifying supported metal catalysts.

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

    DOE PAGES

    Sulmonetti, Taylor P.; Pang, Simon H.; Claure, Micaela Taborga; Lee, Sungsik; Cullen, David A.; Agrawal, Pradeep K.; Jones, Christopher W.

    2016-03-09

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

  13. Self-assembly of noble metal monolayers on transition metal carbide nanoparticle catalysts.

    PubMed

    Hunt, Sean T; Milina, Maria; Alba-Rubio, Ana C; Hendon, Christopher H; Dumesic, James A; Román-Leshkov, Yuriy

    2016-05-20

    We demonstrated the self-assembly of transition metal carbide nanoparticles coated with atomically thin noble metal monolayers by carburizing mixtures of noble metal salts and transition metal oxides encapsulated in removable silica templates. This approach allows for control of the final core-shell architecture, including particle size, monolayer coverage, and heterometallic composition. Carbon-supported Ti(0.1)W(0.9)C nanoparticles coated with Pt or bimetallic PtRu monolayers exhibited enhanced resistance to sintering and CO poisoning, achieving an order of magnitude increase in specific activity over commercial catalysts for methanol electrooxidation after 10,000 cycles. These core-shell materials provide a new direction to reduce the loading, enhance the activity, and increase the stability of noble metal catalysts.

  14. Metal Nanoparticle Catalysts for Carbon Nanotube Growth

    NASA Technical Reports Server (NTRS)

    Pierce, Benjamin F.

    2003-01-01

    Work this summer involved and new and unique process for producing the metal nanoparticle catalysts needed for carbon nanotube (CNT) growth. There are many applications attributed to CNT's, and their properties have deemed them to be a hot spot in research today. Many groups have demonstrated the versatility in CNT's by exploring a wide spectrum of roles that these nanotubes are able to fill. A short list of such promising applications are: nanoscaled electronic circuitry, storage media, chemical sensors, microscope enhancement, and coating reinforcement. Different methods have been used to grow these CNT's. Some examples are laser ablation, flame synthesis, or furnace synthesis. Every single approach requires the presence of a metal catalyst (Fe, Co, and Ni are among the best) that is small enough to produce a CNT. Herein lies the uniqueness of this work. Microemulsions (containing inverse micelles) were used to generate these metal particles for subsequent CNT growth. The goal of this summer work was basically to accomplish as much preliminary work as possible. I strived to pinpoint which variable (experimental process, metal product, substrate, method of application, CVD conditions, etc.) was the determining factor in the results. The resulting SEM images were sufficient for the appropriate comparisons to be made. The future work of this project consists of the optimization of the more promising experimental procedures and further exploration onto what exactly dictated the results.

  15. Microbial recovery of metals from spent coal liquefaction catalysts. Quarterly report, April--June 1991

    SciTech Connect

    Sperl, P.L.; Sperl, G.T.

    1991-12-31

    This project was initiated on October 1, 1989, for the purpose of recovering metals from spent coal liquefaction catalysts. Two catalyst types are the subject of the contract. The first is a Ni-Mo catalyst supported on alumina (Shell 324) as is used in a pilot scale coal liquefaction facility at Wilsonville, Alabama. A large sample of spent catalyst has been obtained. The second material is an unsupported ammonium molybdate catalyst used in a pilot process by the Department of energy at the Pittsburgh energy Technology Center. The object of the contract is to treat these spent catalysts with microorganisms, especially Thiobacillus ferrooxidans, but also other Thiobacillus sp. and possibly Sulfolobus, to leach and remove the metals (Ni and Mo) from the spent catalysts into a form which can be readily recovered by conventional techniques.

  16. Attrition resistant Fischer-Tropsch catalyst and support

    DOEpatents

    Singleton, Alan H.; Oukaci, Rachid; Goodwin, James G.

    2004-05-25

    A catalyst support having improved attrition resistance and a catalyst produced therefrom. The catalyst support is produced by a method comprising the step of treating calcined .gamma.-alumina having no catalytic material added thereto with an acidic aqueous solution having an acidity level effective for increasing the attrition resistance of the calcined .gamma.-alumina.

  17. Different routes to methanol: Inelastic neutron scattering spectroscopy of adsorbates on supported copper catalysts

    DOE PAGES

    Kandemir, Timur; Friedrich, Matthias; Parker, Stewart F.; Studt, Felix; Lennon, David; Schlögl, Robert; Behrens, Malte

    2016-04-14

    We have investigated methanol synthesis with model supported copper catalysts, Cu/ZnO and Cu/MgO, using CO/H2 and CO2/H2 as feedstocks. Under CO/H2 both catalysts show chemisorbed methoxy as a stable intermediate, the Cu/MgO catalyst also shows hydroxyls on the support. Under CO2/H2 the catalysts behave differently, in that formate is also seen on the catalyst. For the Cu/ZnO catalyst hydroxyls are present on the metal whereas for the Cu/MgO hydroxyls are found on the support. Furthermore, these results are consistent with a recently published model for methanol synthesis and highlight the key role of ZnO in the process.

  18. Different routes to methanol: inelastic neutron scattering spectroscopy of adsorbates on supported copper catalysts.

    PubMed

    Kandemir, Timur; Friedrich, Matthias; Parker, Stewart F; Studt, Felix; Lennon, David; Schlögl, Robert; Behrens, Malte

    2016-06-29

    We have investigated methanol synthesis with model supported copper catalysts, Cu/ZnO and Cu/MgO, using CO/H2 and CO2/H2 as feedstocks. Under CO/H2 both catalysts show chemisorbed methoxy as a stable intermediate, the Cu/MgO catalyst also shows hydroxyls on the support. Under CO2/H2 the catalysts behave differently, in that formate is also seen on the catalyst. For the Cu/ZnO catalyst hydroxyls are present on the metal whereas for the Cu/MgO hydroxyls are found on the support. These results are consistent with a recently published model for methanol synthesis and highlight the key role of ZnO in the process. PMID:27075638

  19. Hydrogen recombiner catalyst test supporting data

    SciTech Connect

    Britton, M.D.

    1995-01-19

    This is a data package supporting the Hydrogen Recombiner Catalyst Performance and Carbon Monoxide Sorption Capacity Test Report, WHC-SD-WM-TRP-211, Rev 0. This report contains 10 appendices which consist of the following: Mass spectrometer analysis reports: HRC samples 93-001 through 93-157; Gas spectrometry analysis reports: HRC samples 93-141 through 93-658; Mass spectrometer procedure PNL-MA-299 ALO-284; Alternate analytical method for ammonia and water vapor; Sample log sheets; Job Safety analysis; Certificate of mixture analysis for feed gases; Flow controller calibration check; Westinghouse Standards Laboratory report on Bois flow calibrator; and Sorption capacity test data, tables, and graphs.

  20. Zircon Supported Copper Catalysts for the Steam Reforming of Methanol

    NASA Astrophysics Data System (ADS)

    Widiastri, M.; Fendy, Marsih, I. N.

    2008-03-01

    Steam reforming of methanol (SRM) is known as one of the most favorable catalytic processes for producing hydrogen. Current research on zirconia, ZrO2 supported copper catalyst revealed that CuO/ZrO2 as an active catalyst for the SRM. Zircon, ZrSiO4 is available from the by-product of tin mining. In the work presented here, the catalytic properties of CuO/ZrSiO4 with various copper oxide compositions ranging from 2.70% (catalyst I), 4.12% (catalyst II), and 7.12%-mass (catalyst III), synthesized by an incipient wetness impregnation technique, were investigated to methanol conversion, selectivity towards CO formation, and effect of ZnO addition (7.83%CuO/8.01%ZnO/ZrSiO4 = catalyst V). The catalytic activity was obtained using a fixed bed reactor and the zircon supported catalyst activity was compared to those of CuO/ZnO/Al2O3 catalyst (catalyst IV) and commercial Kujang LTSC catalyst. An X-ray powder diffraction (XRD) analysis was done to identify the abundant phases of the catalysts. The catalysts topography and particle diameter were measured with scanning electron microscopy (SEM) and composition of the catalysts was measured by SEM-EDX, scanning electron microscope-energy dispersive using X-ray analysis. The results of this research provide information on the possibility of using zircon (ZrSiO4) as solid support for SRM catalysts.

  1. Stability of noble metal catalysts for the hydrogen-oxygen reaction.

    NASA Technical Reports Server (NTRS)

    Armstrong, W. E.; Jennings, T. J.; Voge, H. H.

    1972-01-01

    Stability of various supported noble metal catalysts for initiation of the hydrogen-oxygen reaction was tested by means of steam-hydrogen treatment at 1000-1200 C followed by a simple activity test. Many catalysts were stable to 1100 C, but all lost some activity at 1200 C. The most active with very good stability was an iridium/alumina catalyst of high iridium content.

  2. Selective hydrogenation of phenylacetylene on pumice-supported palladium catalysts

    SciTech Connect

    Duca, D; Liotta, L.F.; Deganello, G.

    1995-06-01

    The liquid phase, selective hydrogenation of phenylacetylene on pumice-supported palladium catalysts has been studied for a large range of metallic dispersions (14% {le} D{sub x} {le} 62%). The kinetics were analyzed by a five-parameter mathematical model. The mechanism was determined by the contribution of three basic routes involving only surface species in the rate-determining steps. The hydrogenation of phenylacetylene to styrene is {open_quotes}structure insensitive{close_quotes}. The disappearance rate constant of styrene produced from phenylacetylene is slightly lower than that of phenylacetylene and does not change in the case of the direct hydrogenation of styrene on the same Pd/pumice catalyst. However, Q{sub 3} (the ratio of adsorption constants K{sub Eb}/K{sub St}, where Eb is ethylbenzene and St is styrene), which is typical of a zero-order reaction (Q{sub 3}{r_arrow}0) in the case of the direct hydrogenation, is practically constant (Q{sub 3}{approx_equal}2) in the case of dehydrogenation of styrene produced from phenylacetylene. This is explained by the formation, in the latter case, of polymeric species or other species which are difficult to hydrogenate and by the consequent occupation of active sites so that the adsorption of styrene is inhibited. These species are also thought to be responsible for a flattening effect in the catalytic activity. Activity and selectivity data are critically analyzed and compared with those reported for other supported palladium catalysts. Since Pd/pumice catalysts also show high activity and selectivity at high metal dispersions, they could be of interest for industrial applications. 48 refs., 9 figs., 3 tabs.

  3. Synthesis, characterization and catalytic application of nanoscale metal and metal oxide heterogeneous catalysts

    NASA Astrophysics Data System (ADS)

    Wang, Xue

    Nanoscale metals or metal oxides with high surface area to volume ratios have been widely used as catalysts for various chemical reactions. A major challenge to utilize metal nanocatalysts commercially is their tendency to sinter under working reaction conditions. To overcome this, much research is being done to anchor metal nanocatalysts on various supports to prevent their agglomeration. Mesoporous silica, SBA-15 is an attractive support material candidate because of its high surface area, stable structure and chemical inertness. Scientists have anchored metal nanocatalysts onto the pore of SBA-15 and observed some improvement in the stability. However, the interactions between the nanocatalysts and SBA-15 are relatively weak and sintering still occurs resulting in a loss of activity. In order to impart enhanced robustness, a new type of stable metal/SBA-15 nanocomposite has been prepared by intercalating metal nanoparticles into the walls of mesoporous silica SBA-15 by a unique synthetic strategy using metal coordinating agents such as bis[3-(triethoxysilyl) propyl]-tetrasulfide (TESPTS). In this dissertation, systemic research on the preparation parameters and extension to other metals will be presented. The structure changes caused by addition of TESPTS to the preparation of mesoporous silica were investigated. The relationship between increasing amounts of TESPTS and the structural change was obtained. Afterwards, a new type of PdMS catalyst with Pd intercalated in the walls of SBA-15 was synthesized for the first time using a modified preparation pathway. These materials were characterized by N2 physisorption, X-ray diffraction, transmission electron microscopy and inductively coupled plasma. The PdMS system was utilized as an active and robust catalyst for Heck reactions. Notably, after the catalytic reaction, the PdMS catalysts maintained its reactivity and size without undergoing any agglomeration due to the stable nanocomposite structure. Carbon

  4. Metal nanoparticle catalysts beginning to shape-up.

    PubMed

    Roldan Cuenya, Beatriz

    2013-08-20

    The field of heterogeneous catalysis has received a remarkable amount of interest from scientific and industrial perspectives because of its enormous impact on the world's economy: more than 90% of chemical manufacturing processes use catalysts. Catalysts are also essential in converting hazardous waste into less harmful products (car exhaust) and in generating power (fuel cells). Yet in all applications, it remains a challenge to design long lasting, highly active, selective, and environmentally friendly catalytic materials and processes, ideally based on Earth-abundant elements. In addition, the field needs more satisfactory experimental and theoretical approaches to minimize trial and error experiments in catalyst development. Nanocatalysis is one area that is developing rapidly. Researchers have reported striking novel catalytic properties, including greatly enhanced reactivities and selectivities, for nanocatalysts compared to their bulk counterparts. Fully harnessing the power of nanocatalysts requires detailed understanding of the origin of their enhanced performance at the atomic level, which in turn requires fundamental knowledge of the geometric and electronic structures of these complex systems. Numerous studies report on the properties that affect the catalytic performance of metal naoparticles (NPs) such as their size, interaction with their support, and their oxidation state. Much less research elucidates the role played by the NP shape. Complicating the analysis is that the preceding parameters are not independent, since NP size and support will affect which NP shapes are most stable. In addition, we must consider the dynamic nature of NP catalysts and their response to the environment, since the working state of a NP catalyst might not be the state in which the catalyst was prepared, but rather a structural and/or chemical isomer that responded to the particular reaction conditions. In order to address the complexity of real-world catalysts

  5. Zeolite supported iron-cobalt catalysts for the Fischer-Tropsch synthesis

    SciTech Connect

    Lin, T.

    1984-01-01

    A series of Fe, Co, FeCo catalysts on Y and ZSM-5 supports, prepared by impregnation and ion exchange, has been investigated. Characterization methods utilized were x-ray diffraction, H{sub 2}/CO chemisorption, Moessbauer spectroscopy, and atomic absorption. A differential reactor and as chromatographs were also employed to analyze the reaction activity and product selectivity. (i) Y supported catalysts: The oxidation, reduction, and carburization behavior of the iron-containing catalysts were observed via Moessbauer spectra. The reversibility of FeY (ion exchange) in oxidation-reduction cycles was confirmed in this experiment. Furthermore, ion exchange catalysts (FeY, FeCoY) do not show any iron metal, alloy or carbide phase after reduction or carburization. In contrast to silica supported catalysts, FeCo/HY (impregnated) reveals a Moessbauer spectra similar to Fe/HY. A 1/1 (CO/H{sub 2}) feed was used to investigate the Fischer-Tropsch reaction at 1 atm, 250{degree}C. (ii) ZSM-5 supported catalysts: Moessbauer results indicate similar patterns for impregnated and ion-exchanged catalysts, and reaction studies reveal similar catalytic behavior for the two preparation methods. This is in contrast to the rather widely different properties of these metals resulting from impregnation or ion exchange on Y zeolite. In generation, the ZSM-5 supported metals produce higher activity and selectivity for high molecular weight materials, and are particularly identified with significant aromatic content in the production distribution.

  6. Method for preparing high activity silica supported hydrotreating catalysts

    SciTech Connect

    Thompson, M.S.

    1986-03-04

    A method is described for preparing a silica supported hydrotreating catalyst containing from about 10-25%w molybdenum and from about 1-5%w nickel and/or cobalt as hydrogenation metals. The method consists of: (a) reacting a mixture of MoCl/sub 5/ and a compound selected from the group consisting of Ni(H/sub 2/O)/sub 6/Cl/sub 2/, Co(H/sub 2/O)/sub 6/Cl/sub 2/ and mixutres in amounts to provide a desired catalytic metals concentration of the support in the presence of a solubilizing amount of acetonitrile; (b) heating the mixture to between about 25/sup 0/ and 80/sup 0/C until most of the metal compounds have reacted and/or dissolved; (c) removing any undissolved solids from the solution; (d) impregnating the dried silica support with the hydrogenation metals-containing solution in one or more steps; and (e) drying the impregnated silica support at elevated temperature.

  7. Microbial recovery of metals from spent coal liquefaction catalysts. [Thiobacillus denitrificans, Sulfolobus

    SciTech Connect

    Sperl, P.L.; Sperl, G.T.

    1991-01-01

    This project was initiated on October 1, 1989, for the purpose of recovering metals from spent coal liquefaction catalysts. The catalyst is a Ni-Mo catalyst supported on alumina (Shell 324) as is used in a pilot scale coal liquefaction facility at Wilsonville, Alabama. This plant is run and operated by Southern Clean Fuels. A large sample of spent catalyst from this facility has been obtained. The object of the contract is to treat the spent catalysts with microorganisms, especially Thiobacillus ferrooxidans, but also other Thiobacillus sp. and possibly Sulfolobus, and other potentially useful microorganisms to leach and remove the metals (Ni and Mo) form the spent catalysts into a form which can be readily recovered by conventional techniques.

  8. Microbial recovery of metals from spent coal liquefaction catalysts. Quarterly report, October--December 1991

    SciTech Connect

    Sperl, P.L.; Sperl, G.T.

    1991-12-31

    This project was initiated on October 1, 1989, for the purpose of recovering metals from spent coal liquefaction catalysts. The catalyst is a Ni-Mo catalyst supported on alumina (Shell 324) as is used in a pilot scale coal liquefaction facility at Wilsonville, Alabama. This plant is run and operated by Southern Clean Fuels. A large sample of spent catalyst from this facility has been obtained. The object of the contract is to treat the spent catalysts with microorganisms, especially Thiobacillus ferrooxidans, but also other Thiobacillus sp. and possibly Sulfolobus, and other potentially useful microorganisms to leach and remove the metals (Ni and Mo) form the spent catalysts into a form which can be readily recovered by conventional techniques.

  9. Growth of Single-Walled Carbon Nanotubes by High Melting Point Metal Oxide Catalysts

    NASA Astrophysics Data System (ADS)

    Qian, Yang; Xiang, Rong; An, Hua; Inoue, Taiki; Chiashi, Shohei; Maruyama, Shigeo

    We report on the growth of single-walled carbon nanotubes (SWNTs) from Co oxide catalysts. The concept is using the relatively lower mobility of metal oxide (than metal) to suppress catalyst aggregation at high temperatures. Compared to the SWNTs grown by pre-reduced catalysts, SWNTs grown from oxidized Co catalysts have shown narrower diameter distribution and smaller average diameter. Different growth parameters are discussed regarding the resulting morphology of SWNTs. Transmission electron microscopy (TEM) investigations reveal the information that Co catalysts are transformed to Co3O4 after reduction-calcination process. X-ray photoelectron spectroscopy (XPS) investigations indicate that Co3O4 has decomposed to CoO before growth at a typical growth temperature (800 ºC) in Ar atmosphere. We propose that CoO has higher melting point than Co and thus is more stable during the growth. Our results indicate that besides the bimetallic catalysts, monometallic catalytic system could also be useful in stabilizing the catalysts to grow chirality-specific SWNTs by transforming the relatively low melting point metal catalysts to high melting point metal oxide catalysts. Yang Qian was supported through ``Global Leader Program for Social Design and Management''.

  10. Recent Progress on Transition Metal Catalyst Separation and Recycling in ATRP.

    PubMed

    Ding, Mingqiang; Jiang, Xiaowu; Zhang, Lifen; Cheng, Zhenping; Zhu, Xiulin

    2015-10-01

    Atom transfer radical polymerization (ATRP) is a versatile and robust tool to synthesize a wide spectrum of monomers with various designable structures. However, it usually needs large amounts of transition metal as the catalyst to mediate the equilibrium between the dormant and propagating species. Unfortunately, the catalyst residue may contaminate or color the resultant polymers, which limits its application, especially in biomedical and electronic materials. How to efficiently and economically remove or reduce the catalyst residue from its products is a challenging and encouraging task. Herein, recent advances in catalyst separation and recycling are highlighted with a focus on (1) highly active ppm level transition metal or metal free catalyzed ATRP; (2) post-purification method; (3) various soluble, insoluble, immobilized/soluble, and reversible supported catalyst systems; and (4) liquid-liquid biphasic catalyzed systems, especially thermo-regulated catalysis systems.

  11. NANOSTRUCTURED METAL OXIDE CATALYSTS VIA BUILDING BLOCK SYNTHESES

    SciTech Connect

    Craig E. Barnes

    2013-03-05

    A broadly applicable methodology has been developed to prepare new single site catalysts on silica supports. This methodology requires of three critical components: a rigid building block that will be the main structural and compositional component of the support matrix; a family of linking reagents that will be used to insert active metals into the matrix as well as cross link building blocks into a three dimensional matrix; and a clean coupling reaction that will connect building blocks and linking agents together in a controlled fashion. The final piece of conceptual strategy at the center of this methodology involves dosing the building block with known amounts of linking agents so that the targeted connectivity of a linking center to surrounding building blocks is obtained. Achieving targeted connectivities around catalytically active metals in these building block matrices is a critical element of the strategy by which single site catalysts are obtained. This methodology has been demonstrated with a model system involving only silicon and then with two metal-containing systems (titanium and vanadium). The effect that connectivity has on the reactivity of atomically dispersed titanium sites in silica building block matrices has been investigated in the selective oxidation of phenols to benezoquinones. 2-connected titanium sites are found to be five times as active (i.e. initial turnover frequencies) than 4-connected titanium sites (i.e. framework titanium sites).

  12. Application of a mixed metal oxide catalyst to a metallic substrate

    NASA Technical Reports Server (NTRS)

    Sevener, Kathleen M. (Inventor); Lohner, Kevin A. (Inventor); Mays, Jeffrey A. (Inventor); Wisner, Daniel L. (Inventor)

    2009-01-01

    A method for applying a mixed metal oxide catalyst to a metallic substrate for the creation of a robust, high temperature catalyst system for use in decomposing propellants, particularly hydrogen peroxide propellants, for use in propulsion systems. The method begins by forming a prepared substrate material consisting of a metallic inner substrate and a bound layer of a noble metal intermediate. Alternatively, a bound ceramic coating, or frit, may be introduced between the metallic inner substrate and noble metal intermediate when the metallic substrate is oxidation resistant. A high-activity catalyst slurry is applied to the surface of the prepared substrate and dried to remove the organic solvent. The catalyst layer is then heat treated to bind the catalyst layer to the surface. The bound catalyst layer is then activated using an activation treatment and calcinations to form the high-activity catalyst system.

  13. [Study on the surface diffuse reflectance ultraviolet-visible spectra of the multicomponent metal catalysts].

    PubMed

    Tang, B; Jiang, Q; He, X; Shen, H

    1999-02-01

    In this paper, the surface diffuse reflectance ultraviolet-visible spectra (DRUVS) of two and three components supported metal catalysts for methanation of CO2 by hydrogenation were studied, and the relationship between the activity of catalytic-hydrogenation and the interaction among the components of the catalysts was revealed. Based on the analysis of the DRUVS of the catalysts with defferent amount of promoters in two component catalysts system, the dependence relationship between the characteristic strength of the DRUVS and the catalytic activity was worked out. PMID:15818931

  14. Heterogenization of Homogeneous Catalysts: the Effect of the Support

    SciTech Connect

    Earl, W.L.; Ott, K.C.; Hall, K.A.; de Rege, F.M.; Morita, D.K.; Tumas, W.; Brown, G.H.; Broene, R.D.

    1999-06-29

    We have studied the influence of placing a soluble, homogeneous catalyst onto a solid support. We determined that such a 'heterogenized' homogeneous catalyst can have improved activity and selectivity for the asymmetric hydrogenation of enamides to amino acid derivatives. The route of heterogenization of RhDuPhos(COD){sup +} cations occurs via electrostatic interactions with anions that are capable of strong hydrogen bonding to silica surfaces. This is a novel approach to supported catalysis. Supported RhDuPhos(COD){sup +} is a recyclable, non-leaching catalyst in non-polar media. This is one of the few heterogenized catalysts that exhibits improved catalytic performance as compared to its homogeneous analog.

  15. Method of making metal-polymer composite catalysts

    DOEpatents

    Zelena, Piotr; Bashyam, Rajesh

    2009-06-23

    A metal-polymer-carbon composite catalyst for use as a cathode electrocatalyst in fuel cells. The catalyst includes a heteroatomic polymer; a transition metal linked to the heteroatomic polymer by one of nitrogen, sulfur, and phosphorus, and a recast ionomer dispersed throughout the heteroatomic polymer-carbon composite. The method includes forming a heteroatomic polymer-carbon composite and loading the transition metal onto the composite. The invention also provides a method of making a membrane electrode assembly for a fuel cell that includes the metal-polymer-carbon composite catalyst.

  16. Resistance of KMTs-R catalyst to heavy metal poisoning

    SciTech Connect

    Karakhanov, E.A.; Bratkov, A.A.; Il'ina, L.M.; Lysenko, S.V.; Radchenko, E.D.

    1984-05-01

    This article attempts to determine the resistance of KMTs-R commercial microbead catalyst to poisoning by heavy metals by preparing samples of this catalyst with various contents of nickel. The nickel was deposited by impregnating the catalysts with a benzene solution of nickel naphthenate at the appropriate concentration. It is determined that as the content of nickel in the catalysts is increased, the feedstock conversion, the naphtha yield, and the selectivity for naphtha dropped off monotonically. The effect of antimony diamyldithiocarbamate (compound I) on the poisoning of KMTs-R catalyst by nickel is examined. The results indicate that nickel on the catalyst is passivated by compound I. It is concluded that the parameters of nickel-poisoned KMTs-R catalyst can be restored to a great degree by treatment of the poisoned catalyst with compound I.

  17. Deuterium-Labeling Study of the Hydrogenation of 2-Methylfuran and 2,5-Dimethylfuran over Carbon-Supported Noble Metal Catalysts.

    PubMed

    Kang, Jungshik; Vonderheide, Anne; Guliants, Vadim V

    2015-09-21

    2-Methylfuran and 2,5-dimethylfuran were deuterated over Pd and Pt catalysts at 90-220 °C. Furan ring saturation over a Pd/C catalyst occurred at low reaction temperatures, which led to deuterated THFs, followed by progressive D exchange in the THF ring at higher temperatures. Finally, H/D exchange occurred in the methyl groups on the THF ring. Cleavage of the C-O bond also occurred over a Pd/C catalyst at elevated temperatures, which resulted in deuterated ketones, for which all H atoms were exchanged for D. Alcohols were produced over a Pt/C catalyst at low temperatures because they are more stable than the corresponding ketones. D replaced H on all carbon atoms of the furan ring and saturated the O and C atoms of the broken C-O bond in both deuterated 2-pentanol and 2-hexanol. At low temperatures (90-105 °C), all H atoms in the deuterated alcohols were exchanged for D except for the last two hydrogen atoms on the methyl groups. PMID:26373360

  18. Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells.

    PubMed

    Mansor, Noramalina; Jorge, A Belen; Corà, Furio; Gibbs, Christopher; Jervis, Rhodri; McMillan, Paul F; Wang, Xiaochen; Brett, Daniel J L

    2014-04-01

    Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li(+)Cl(-)), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride materials are found to be more electrochemically stable compared to conventional carbon black (Vulcan XC-72R) with B-gCNM support showing the best stability. For the supported catalysts, Pt/PTI-Li(+)Cl(-) catalyst exhibits better durability with only 19% electrochemical surface area (ECSA) loss versus 36% for Pt/Vulcan after 2000 scans. Superior methanol oxidation activity is observed for all graphitic carbon nitride supported Pt catalysts on the basis of the catalyst ECSA.

  19. Graphitic Carbon Nitride Supported Catalysts for Polymer Electrolyte Fuel Cells

    PubMed Central

    2014-01-01

    Graphitic carbon nitrides are investigated for developing highly durable Pt electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). Three different graphitic carbon nitride materials were synthesized with the aim to address the effect of crystallinity, porosity, and composition on the catalyst support properties: polymeric carbon nitride (gCNM), poly(triazine) imide carbon nitride (PTI/Li+Cl–), and boron-doped graphitic carbon nitride (B-gCNM). Following accelerated corrosion testing, all graphitic carbon nitride materials are found to be more electrochemically stable compared to conventional carbon black (Vulcan XC-72R) with B-gCNM support showing the best stability. For the supported catalysts, Pt/PTI-Li+Cl– catalyst exhibits better durability with only 19% electrochemical surface area (ECSA) loss versus 36% for Pt/Vulcan after 2000 scans. Superior methanol oxidation activity is observed for all graphitic carbon nitride supported Pt catalysts on the basis of the catalyst ECSA. PMID:24748912

  20. Effect of support materials on supported platinum catalyst prepared using a supercritical fluid deposition technique and their catalytic performance for hydrogen-rich gas production from lignocellulosic biomass.

    PubMed

    Kaya, Burçak; Irmak, Sibel; Hesenov, Arif; Erbatur, Oktay; Erkey, Can

    2012-11-01

    A number of supported Pt catalysts have been prepared by supercritical carbon dioxide deposition technique using various supports. The reduction of Pt precursor to metal performed by heat treatment under nitrogen flow. The prepared catalysts were evaluated for gasification of wheat straw biomass hydrolysates and glucose solution for hydrogen-rich gas production. The activities of the catalysts were highly affected by distribution, amount and particle sizes of platinum on the support. In general carbon-based supported Pt catalysts exhibited better catalytic activity compared to other supports to be used. Compared to biomass hydrolysate feed, gasification of glucose always resulted in higher volume of gas mixture, however, hydrogen selectivity was decreased in all catalyst except multi-walled carbon nanotube. The deposition of Pt particles inner side of that support makes the large organic substrates inaccessible to reach and react with those metal particles.

  1. A Longitudinal Investigation of Relational Catalyst Support of Goal Strivings

    PubMed Central

    Tomlinson, Jennifer M.; Feeney, Brooke C.; Van Vleet, Meredith

    2015-01-01

    The goal of this work was to test a theoretical model of relational catalyst support provision that promotes thriving in non-adverse times. We tested a pathway proposed by Feeney and Collins (2014) that explains how relational catalyst support in the context of close relationships might lead to thriving. We proposed that once relational catalyst support has been received, it functions through the mechanisms of being perceived to be responsive to one’s needs and promoting perceived capability. Perceived capability should promote indices of thriving including self-esteem, goal accomplishment, growth, and specific and general availability of support. This model was supported in two studies of married couples using observational and longitudinal methods surrounding the support of goal-strivings. Results indicate that (a) partner support of goal-strivings predicted important indicators of thriving over time, and (b) both received and perceived relational catalyst support work together and play important roles in predicting these outcomes. PMID:26997969

  2. Fundamental studies of hydrogen chemisorption on supported monometallic and bimetallic catalysts using microcalorimetry

    SciTech Connect

    Narayan, R.L.

    1997-06-24

    Highly dispersed transition metal catalysts are used in numerous commercial processes such as hydrocarbon conversions. For example, the use of Pt supported on acidic alumina or silica-alumina for reforming of naphtha in the production of gasoline is well known. Another use of supported catalysts is in automobile emission control where supported Pt-Rh bimetallic catalysts are used. Supported Ru can be used in Fischer-Tropsch synthesis for the production of higher hydrocarbons from synthesis gas. While many of these catalyst systems have been in commercial operation for several decades there is still a lack of consensus regarding the exact role of the catalyst on a molecular level. In particular, little is known about the mechanisms operating on the catalyst surface at the high pressure and high temperature conditions typically used in commercial operations. This report contains the general introduction and conclusions and an appendix containing the operating instructions for a microcalorimeter. Three chapters have been processed separately. They are: the effect of K on the kinetics and thermodynamics of hydrogen adsorption on Ru/SiO{sub 2}; hydrogen adsorption states on silica supported Ru-Ag and Ru-Cu bimetallic catalysts investigated via microcalorimetry; a comparative study of hydrogen chemisorption on silica supported Ru, Rh, and Pt.

  3. Novel supports for coal liquefaction catalysts

    SciTech Connect

    Haynes, H.W. Jr.

    1992-01-01

    This research is divided into three parts: (1) Evaluation of Alkaline-Earth-Promoted CoMo/Alumina Catalysts in a Bench Scale Hydrotreater, (2) Development of a Novel Catalytic Coal Liquefaction Microreactor (CCLM) Unit, and (3) Evaluation of Novel Catalyst Preparations for Direct Coal Liquefaction. (VC)

  4. Dynamic structural disorder in supported nanoscale catalysts

    SciTech Connect

    Rehr, J. J.; Vila, F. D.

    2014-04-07

    We investigate the origin and physical effects of “dynamic structural disorder” (DSD) in supported nano-scale catalysts. DSD refers to the intrinsic fluctuating, inhomogeneous structure of such nano-scale systems. In contrast to bulk materials, nano-scale systems exhibit substantial fluctuations in structure, charge, temperature, and other quantities, as well as large surface effects. The DSD is driven largely by the stochastic librational motion of the center of mass and fluxional bonding at the nanoparticle surface due to thermal coupling with the substrate. Our approach for calculating and understanding DSD is based on a combination of real-time density functional theory/molecular dynamics simulations, transient coupled-oscillator models, and statistical mechanics. This approach treats thermal and dynamic effects over multiple time-scales, and includes bond-stretching and -bending vibrations, and transient tethering to the substrate at longer ps time-scales. Potential effects on the catalytic properties of these clusters are briefly explored. Model calculations of molecule-cluster interactions and molecular dissociation reaction paths are presented in which the reactant molecules are adsorbed on the surface of dynamically sampled clusters. This model suggests that DSD can affect both the prefactors and distribution of energy barriers in reaction rates, and thus can significantly affect catalytic activity at the nano-scale.

  5. Enhanced Oxygen Reduction Activity In Acid By Tin-Oxide Supported Au Nanoparticle Catalysts

    SciTech Connect

    Baker,W.; Pietron, J.; Teliska, M.; Bouwman, P.; Ramaker, D.; Swider-Lyons, K.

    2006-01-01

    Gold nanoparticles supported on hydrous tin-oxide (Au-SnO{sub x}) are active for the four-electron oxygen reduction reaction in an acid electrolyte. The unique electrocatalytic of the Au-SnO is confirmed by the low amount of peroxide detected with rotating ring-disk electrode voltammetry and Koutecky-Levich analysis. In comparison, 10 wt % Au supported on Vulcan carbon and SnO{sub x} catalysts both produce significant peroxide in the acid electrolyte, indicating only a two-electron reduction reaction. Characterization of the Au-SnO{sub x} catalyst reveals a high-surface area, amorphous support with 1.7 nm gold metal particles. The high catalytic activity of the Au-SnO is attributed to metal support interactions. The results demonstrate a possible path to non-Pt catalysts for proton exchange membrane fuel cell cathodes.

  6. Catalytic ammonia decomposition over industrial-waste-supported Ru catalysts

    SciTech Connect

    Pei Fang Ng; Li Li; Shaobin Wang; Zhonghua Zhu; Gaoqing Lu; Zifeng Yan

    2007-05-15

    Industrial solid wastes (fly ash and red mud, a by-product of the aluminium industry) have been employed as supports for preparation of Ru-based catalysts. Physical and chemical treatments on red mud were conducted and these modified supports were also used for preparation of Ru-based catalysts. Those Ru catalysts were characterized by various techniques such as N2 adsorption, H{sub 2} adsorption, XRD, XPS, and temperature-programmed reduction (TPR), and were then tested for catalytic ammonia decomposition to hydrogen. It was found that red-mud-supported Ru catalyst exhibits higher ammonia conversion and hydrogen production than fly-ash-supported catalyst. Heat and chemical treatments of the red mud greatly improve the catalytic activity. Moreover, a combination of acid and heat treatments produces the highest catalytic conversion of ammonia. 35 refs., 4 figs., 4 tabs.

  7. Supported, Alkali-Promoted Cobalt Oxide Catalysts for NOx Removal from Coal Combustion Flue Gases

    SciTech Connect

    Morris D. Argyle

    2005-12-31

    A series of cobalt oxide catalysts supported on alumina ({gamma}-Al{sub 2}O{sub 3}) were synthesized with varying contents of cobalt and of added alkali metals, including lithium, sodium, potassium, rubidium, and cesium. Unsupported cobalt oxide catalysts and several cobalt oxide catalysts supported ceria (CeO{sub 2}) with varying contents of cobalt with added potassium were also prepared. The catalysts were characterized with UV-visible spectroscopy and were examined for NO{sub x} decomposition activity. The CoO{sub x}/Al{sub 2}O{sub 3} catalysts and particularly the CoO{sub x}/CeO{sub 2} catalysts show N{sub 2}O decomposition activity, but none of the catalysts (unsupported Co{sub 3}O{sub 4} or those supported on ceria or alumina) displayed significant, sustained NO decomposition activity. For the Al{sub 2}O{sub 3}-supported catalysts, N{sub 2}O decomposition activity was observed over a range of reaction temperatures beginning about 723 K, but significant (>50%) conversions of N{sub 2}O were observed only for reaction temperatures >900 K, which are too high for practical commercial use. However, the CeO{sub 2}-supported catalysts display N{sub 2}O decomposition rates similar to the Al{sub 2}O{sub 3}-supported catalysts at much lower reaction temperatures, with activity beginning at {approx}573 K. Conversions of >90% were achieved at 773 K for the best catalysts. Catalytic rates per cobalt atom increased with decreasing cobalt content, which corresponds to increasing edge energies obtained from the UV-visible spectra. The decrease in edge energies suggests that the size and dimensionality of the cobalt oxide surface domains increase with increasing cobalt oxide content. The rate data normalized per mass of catalyst that shows the activity of the CeO{sub 2}-supported catalysts increases with increasing cobalt oxide content. The combination of these data suggest that supported cobalt oxide species similar to bulk Co{sub 3}O{sub 4} are inherently more active than

  8. Durability testing at 5 atmospheres of advanced catalysts and catalyst supports for gas turbine engine combustors

    NASA Technical Reports Server (NTRS)

    Olson, B. A.; Lee, H. C.; Osgerby, I. T.; Heck, R. M.; Hess, H.

    1980-01-01

    The durability of CATCOM catalysts and catalyst supports was experimentally demonstrated in a combustion environment under simulated gas turbine engine combustor operating conditions. A test of 1000 hours duration was completed with one catalyst using no. 2 diesel fuel and operating at catalytically-supported thermal combustion conditions. The performance of the catalyst was determined by monitoring emissions throughout the test, and by examining the physical condition of the catalyst core at the conclusion of the test. Tests were performed periodically to determine changes in catalytic activity of the catalyst core. Detailed parametric studies were also run at the beginning and end of the durability test, using no. 2 fuel oil. Initial and final emissions for the 1000 hours test respectively were: unburned hydrocarbons (C3 vppm):0, 146, carbon monoxide (vppm):30, 2420; nitrogen oxides (vppm):5.7, 5.6.

  9. Mesoporous Molecular Sieves as Supports for Metathesis Catalysts

    NASA Astrophysics Data System (ADS)

    Balcar, Hynek; Cejka, Jirí

    Mesoporous molecular sieves represent a new family of inorganic oxides with regular nanostructure, large surface areas, large void volumes, and narrow pore size distribution of mesopores. These materials offer new possibilities for designing highly active and selective catalysts for olefin metathesis and metathesis polymerization. Siliceous sieves MCM-41, MCM-48, SBA-15, and organized mesoporous alumina (OMA) were used as supports for preparation of new molybdenum and rhenium oxide catalysts, as well as for heterogenization of well-defined homogeneous catalysts.

  10. Graphyne-supported single Fe atom catalysts for CO oxidation.

    PubMed

    Wu, Ping; Du, Pan; Zhang, Hui; Cai, Chenxin

    2015-01-14

    Single atom catalysts (SACs) are highly desirable for the effort to maximize the efficiency of metal atom use. However, the synthesis of SACs is a major challenge that largely depends on finding an appropriate supporting substrate to achieve a well-defined and highly dispersed single atom. This work demonstrates that, based on the density functional theory (DFT) calculation, graphyne is a good substrate for single Fe atom catalysts. The Fe atom can be tightly embedded in a graphyne sheet with a high binding energy of ∼4.99 eV and a high diffusion energy barrier of ∼1.0 eV. The graphyne-supported Fe (Fe-graphyne) SAC shows high catalytic activity towards CO oxidation, which is often regarded as a prototype reaction for designing atomic-scale catalysts. We studied the adsorption characteristics of CO and O2 on Fe-graphyne SACs, and simulated the reaction mechanism of CO oxidation involving Fe-graphyne. The simulation results indicate that O2 binding on Fe-graphyne is much stronger than that of CO, and the adsorbed O2 prior to occupy the Fe atoms as the co-existence of O2 and CO. The reaction of CO oxidation by adsorbed O2 on Fe-graphyne SACs favors to proceed via the Eley-Rideal (ER) mechanism with the energy barrier of as low as ∼0.21 eV in the rate-limiting step. Calculation of the electronic density of states (DOS) of each reaction step demonstrates that the strong interaction of the O2 and Fe adatom promotes the CO oxidation on Fe-graphyne SACs. The results presented here suggest that graphyne could provide a unique platform to synthesize SACs, and the Fe-graphyne SACs could find potential use in solving the growing environmental problems caused by CO emission from automobiles and industrial processes, in removing CO contamination from vehicle exhaust and in fuel cells.

  11. Investigating the Dispersion Behavior in Solvents, Biocompatibility, and Use as Support for Highly Efficient Metal Catalysts of Exfoliated Graphitic Carbon Nitride.

    PubMed

    Ayán-Varela, M; Villar-Rodil, S; Paredes, J I; Munuera, J M; Pagán, A; Lozano-Pérez, A A; Cenis, J L; Martínez-Alonso, A; Tascón, J M D

    2015-11-01

    The liquid-phase exfoliation of graphitic carbon nitride (g-C3N4) to afford colloidal dispersions of two-dimensional flakes constitutes an attractive route to facilitate the processing and implementation of this novel material toward different technological applications, but quantitative knowledge about its dispersibility in solvents is lacking. Here, we investigate the dispersion behavior of exfoliated g-C3N4 in a wide range of solvents and evaluate the obtained results on the basis of solvent surface energy and Hildebrand/Hansen solubility parameters. Estimates of the three Hansen parameters for exfoliated g-C3N4 from the experimentally derived data yielded δD ≈ 17.8 MPa(1/2), δP ≈ 10.8 MPa(1/2), and δH ≈ 15.4 MPa(1/2). The relatively high δH value suggested that, contrary to the case of other two-dimensional materials (e.g., graphene or transition metal dichalcogenides), hydrogen-bonding plays a substantial role in the efficient interaction, and thus dispersibility, of exfoliated g-C3N4 with solvents. Such an outcome was attributed to a high density of primary and/or secondary amines in the material, the presence of which was associated with incomplete condensation of the structure. Furthermore, cell proliferation tests carried out on thin films of exfoliated g-C3N4 using murine fibroblasts suggested that this material is highly biocompatible and noncytotoxic. Finally, the exfoliated g-C3N4 flakes were used as supports in the synthesis of Pd nanoparticles, and the resulting hybrids exhibited an exceptional catalytic activity in the reduction of nitroarenes.

  12. Multi-wavelength Raman spectroscopy study of supported vanadia catalysts: Structure identification and quantification

    SciTech Connect

    Wu, Zili

    2014-10-20

    Revealing the structure of supported metal oxide catalysts is a prerequisite for establishing the structure - catalysis relationship. Among a variety of characterization techniques, multi-wavelength Raman spectroscopy, combining resonance Raman and non-resonance Raman with different excitation wavelengths, has recently emerged as a particularly powerful tool in not only identifying but also quantifying the structure of supported metal oxide clusters. In our review, we make use of two supported vanadia systems, VOx/SiO2 and VOx/CeO2, as examples to showcase how one can employ this technique to investigate the heterogeneous structure of active oxide clusters and to understand the complex interaction between the oxide clusters and the support. Moreover, the qualitative and quantitative structural information gained from the multi-wavelength Raman spectroscopy can be utilized to provide fundamental insights for designing more efficient supported metal oxide catalysts.

  13. Multi-wavelength Raman spectroscopy study of supported vanadia catalysts: Structure identification and quantification

    DOE PAGES

    Wu, Zili

    2014-10-20

    Revealing the structure of supported metal oxide catalysts is a prerequisite for establishing the structure - catalysis relationship. Among a variety of characterization techniques, multi-wavelength Raman spectroscopy, combining resonance Raman and non-resonance Raman with different excitation wavelengths, has recently emerged as a particularly powerful tool in not only identifying but also quantifying the structure of supported metal oxide clusters. In our review, we make use of two supported vanadia systems, VOx/SiO2 and VOx/CeO2, as examples to showcase how one can employ this technique to investigate the heterogeneous structure of active oxide clusters and to understand the complex interaction between themore » oxide clusters and the support. Moreover, the qualitative and quantitative structural information gained from the multi-wavelength Raman spectroscopy can be utilized to provide fundamental insights for designing more efficient supported metal oxide catalysts.« less

  14. Steam Reforming of Ethylene Glycol over MgAl₂O₄ Supported Rh, Ni, and Co Catalysts

    SciTech Connect

    Mei, Donghai; Lebarbier, Vanessa M.; Xing, Rong; Albrecht, Karl O.; Dagle, Robert A.

    2015-11-25

    Steam reforming of ethylene glycol (EG) over MgAl₂O₄ supported metal (15 wt.% Ni, 5 wt.% Rh, and 15 wt.% Co) catalysts were investigated using combined experimental and theoretical methods. Compared to highly active Rh and Ni catalysts with 100% conversion, the steam reforming activity of EG over the Co catalyst is comparatively lower with only 42% conversion under the same reaction conditions (500°C, 1 atm, 119,000 h⁻¹, S/C=3.3 mol). However, CH₄ selectivity over the Co catalyst is remarkably lower. For example, by varying the gas hour space velocity (GHSV) such that complete conversion is achieved for all the catalysts, CH₄ selectivity for the Co catalyst is only 8%, which is much lower than the equilibrium CH₄ selectivity of ~ 24% obtained for both the Rh and Ni catalysts. Further studies show that varying H₂O concentration over the Co catalyst has a negligible effect on activity, thus indicating zero-order dependence on H₂O. These experimental results suggest that the supported Co catalyst is a promising EG steam reforming catalyst for high hydrogen production. To gain mechanistic insight for rationalizing the lower CH₃ selectivity observed for the Co catalyst, the initial decomposition reaction steps of ethylene glycol via C-O, O-H, C-H, and C-C bond scissions on the Rh(111), Ni(111) and Co(0001) surfaces were investigated using density functional theory (DFT) calculations. Despite the fact that the bond scission sequence in the EG decomposition on the three metal surfaces varies, which leads to different reaction intermediates, the lower CH₄ selectivity over the Co catalyst, as compared to the Rh and Ni catalysts, is primarily due to the higher barrier for CH₄ formation. The higher S/C ratio enhances the Co catalyst stability, which can be elucidated by the facile water dissociation and an alternative reaction path to remove the CH species as a coking precursor via the HCOH formation. This work was financially supported by the United

  15. Tailoring the Catalytic Properties of Metal Nanoparticles via Support Interactions.

    PubMed

    Ahmadi, M; Mistry, H; Roldan Cuenya, B

    2016-09-01

    The development of new catalysts for energy technology and environmental remediation requires a thorough knowledge of how the physical and chemical properties of a catalyst affect its reactivity. For supported metal nanoparticles (NPs), such properties can include the particle size, shape, composition, and chemical state, but a critical parameter which must not be overlooked is the role of the NP support. Here, we highlight the key mechanisms behind support-induced enhancement in the catalytic properties of metal NPs. These include support-induced changes in the NP morphology, stability, electronic structure, and chemical state, as well as changes in the support due to the NPs. Utilizing the support-dependent phenomena described in this Perspective may allow significant breakthroughs in the design and tailoring of the catalytic activity and selectivity of metal nanoparticles. PMID:27530730

  16. 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.

  17. Doped palladium containing oxidation catalysts

    DOEpatents

    Mohajeri, Nahid

    2014-02-18

    A supported oxidation catalyst includes a support having a metal oxide or metal salt, and mixed metal particles thereon. The mixed metal particles include first particles including a palladium compound, and second particles including a precious metal group (PMG) metal or PMG metal compound, wherein the PMG metal is not palladium. The oxidation catalyst may also be used as a gas sensor.

  18. Supported organometallic catalysts for hydrogenation and Olefin Polymerization

    DOEpatents

    Marks, Tobin J.; Ahn, Hongsang

    2001-01-01

    Novel heterogeneous catalysts for the which hydrogenation of olefins and arenes with high conversion rates under ambient conditions and the polymerization of olefins have been developed. The catalysts are synthesized from Ziegler-type precatalysts by supporting them on sulfate-modified zirconia.

  19. Transition metal-free olefin polymerization catalyst

    DOEpatents

    Sen, Ayusman; Wojcinski, II, Louis M.; Liu, Shengsheng

    2001-01-01

    Ethylene and/or propylene are polymerized to form high molecular weight, linear polymers by contacting ethylene and/or propylene monomer, in the presence of an inert reaction medium, with a catalyst system which consists essentially of (1) an aluminum alkyl component, such as trimethylaluminum, triethylaluminum, triisobutylaluminum, tri-n-octylaluminum and diethylaluminum hydride and (2) a Lewis acid or Lewis acid derivative component, such as B (C.sub.6 F.sub.5).sub.3, [(CH.sub.3).sub.2 N (H) (C.sub.6 H.sub.5)].sup.+ [B (C.sub.6 F.sub.5)4].sup.-, [(C.sub.2 H.sub.5).sub.3 NH].sup.+ [B C.sub.6 F.sub.5).sub.4 ],.sup.-, [C(C.sub.6 F.sub.5).sub.3 ].sup.+ [B(C.sub.6 F.sub.5).sub.4 ].sup.-, (C.sub.2 H.sub.5).sub.2 Al(OCH.sub.3), (C.sub.2 H.sub.5).sub.2 Al(2,6-di-t-butyl-4-methylphenoxide), (C.sub.2 H.sub.5)Al(2,6 -di-t-butylphenoxide).sub.2, (C.sub.2 H.sub.5).sub.2 Al(2,6-di-t-butylphonoxide) , 2,6 -di-t-butylphenol.multidot.methylaluminoxane or an alkylaluminoxane, and which may be completely free any transition metal component(s).

  20. CO2 Hydrogenation over Oxide-Supported PtCo Catalysts: The Role of the Oxide Support in Determining the Product Selectivity.

    PubMed

    Kattel, Shyam; Yu, Weiting; Yang, Xiaofang; Yan, Binhang; Huang, Yanqiang; Wan, Weiming; Liu, Ping; Chen, Jingguang G

    2016-07-01

    By simply changing the oxide support, the selectivity of a metal-oxide catalysts can be tuned. For the CO2 hydrogenation over PtCo bimetallic catalysts supported on different reducible oxides (CeO2 , ZrO2 , and TiO2 ), replacing a TiO2 support by CeO2 or ZrO2 selectively strengthens the binding of C,O-bound and O-bound species at the PtCo-oxide interface, leading to a different product selectivity. These results reveal mechanistic insights into how the catalytic performance of metal-oxide catalysts can be fine-tuned.

  1. Durability testing of advanced catalysts and catalyst supports for gas turbine engine combustors

    NASA Technical Reports Server (NTRS)

    Heck, R. M.; Chang, M.; Hess, H. W.; Mroz, T. S.

    1979-01-01

    The paper presents new information on the durability of a CATCOM catalyst operating at low-emission combustion temperatures (about 1527 K) with a liquid fuel, No. 2 diesel. Information on the activity of No. 2 diesel after 1000 hr of aging is given. In addition, a unique in situ activity test developed for monitoring the subtle changes in the catalyst activity of the CATCOM catalyst is also detailed. The study demonstrated the feasibility of using a CATCOM catalyst in catalytically supported thermal combustion for extended operating periods

  2. The structure and activity of titania supported cobalt catalysts

    SciTech Connect

    Ho Suiwen; Houalla, M.; Hercules, D.M. ); Cruz, J.M. )

    1992-05-01

    A series of titania supported cobalt catalysts (0.5-6%) were prepared by incipient wetness impregnation, and were characterized by ESCA, XRD, and hydrogen chemisorption. After calcination at 400 C, a surface CoTiO[sub 3]-like phase was the main species present in the 0.5 and 1% cobalt catalysts. For higher cobalt loadings, discrete Co[sub 3]O[sub 4] particles were formed in addition to surface CoTiO[sub 3]. ESCA indicates that after reduction the cobalt metal particle size (6-13 nm) increases with increasing cobalt loadings, but does not vary with reduction temperature (400-500 C). Hydrogen chemisorption was found to be activated and suppressed. The extent of hydrogen chemisorption suppression increases with increasing reduction temperature and decreasing cobalt particle size. The turnover frequency (based on cobalt dispersion derived from ESCA) for benzene and CO hydrogenation decreases with increasing reduction temperature and decreasing cobalt particle size. The decline in activity correlates with the extent of suppression of H[sub 2] chemisorption. The results were interpreted in terms of a decrease in the fraction of exposed surface cobalt due to site blocking by reduced TiO[sub 3] moieties.

  3. Efficient selective catalytic reduction of NO by novel carbon-doped metal catalysts made from electroplating sludge.

    PubMed

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

    2014-10-01

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

  4. Graphene supported heterogeneous catalysts for Li-O2 batteries

    NASA Astrophysics Data System (ADS)

    Alaf, M.; Tocoglu, U.; Kartal, M.; Akbulut, H.

    2016-09-01

    In this study production and characterization of free-standing and flexible (i) graphene, (ii) α-MnO2/graphene, (iii) Pt/graphene (iv) α-MnO2/Pt/graphene composite cathodes for Li-air batteries were reported. Graphene supported heterogeneous catalysts were produced by a facile method. In order to prevent aggregation of graphene sheets and increase not only interlayer distance but also surface area, a trace amount multi-wall carbon nano tube (MWCNT) was introduced to the composite structure. The obtained composite catalysts were characterized by SEM, X-ray diffraction, N2 adsorption-desorption analyze and Raman spectroscopy. The electrochemical characterization tests including galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) measurement of catalyst were carried out by using an ECC-Air test cell. These highly active graphene supported heterogeneous composite catalysts provide competitive properties relative to other catalyst materials for Li-air batteries.

  5. Magnetic properties of nickel and cobalt catalysts supported on nanoporous oxides.

    PubMed

    Gómez-Polo, C; Gil, A; Korili, S A; Pérez-Landazabal, J I; Recarte, V; Trujillano, R; Vicente, M A

    2008-06-01

    The aim of this work is to use magnetic measurements as a research tool in the study of possible metal-support interactions in nickel and cobalt nanoporous catalysts. Several physicochemical techniques, namely nitrogen adsorption, X-ray diffraction, temperature-programmed reduction and chemical analysis, were used to analyze the role of the preparation method and the nature of the support on the existence of such metal-support interactions and to relate them with the magnetic response of these nanoporous systems. The catalysts were prepared by incipient wetness impregnation and precipitation-deposition with two commercial oxides, gamma-Al2O3 and SiO2, as supports. The magnetic behavior of the catalysts is drastically affected by the existence of interactions between the metal and the support during the preparation procedure. The samples with weak metal-support interactions have characteristic magnetic behavior of antiferromagnetic metal oxide nanoparticles, while the ones having strong interactions display spin-glass like behavior.

  6. Magnetic properties of nickel and cobalt catalysts supported on nanoporous oxides.

    PubMed

    Gómez-Polo, C; Gil, A; Korili, S A; Pérez-Landazabal, J I; Recarte, V; Trujillano, R; Vicente, M A

    2008-06-01

    The aim of this work is to use magnetic measurements as a research tool in the study of possible metal-support interactions in nickel and cobalt nanoporous catalysts. Several physicochemical techniques, namely nitrogen adsorption, X-ray diffraction, temperature-programmed reduction and chemical analysis, were used to analyze the role of the preparation method and the nature of the support on the existence of such metal-support interactions and to relate them with the magnetic response of these nanoporous systems. The catalysts were prepared by incipient wetness impregnation and precipitation-deposition with two commercial oxides, gamma-Al2O3 and SiO2, as supports. The magnetic behavior of the catalysts is drastically affected by the existence of interactions between the metal and the support during the preparation procedure. The samples with weak metal-support interactions have characteristic magnetic behavior of antiferromagnetic metal oxide nanoparticles, while the ones having strong interactions display spin-glass like behavior. PMID:18681026

  7. Durability testing at one atmosphere of advanced catalysts and catalyst supports for automotive gas turbine engine combustors, part 1

    NASA Technical Reports Server (NTRS)

    Heck, R. M.; Chang, M.; Hess, H.; Carrubba, R.

    1977-01-01

    The durability of catalysts and catalyst supports in a combustion environment was experimentally demonstrated. A test of 1000 hours duration was completed with two catalysts, using diesel fuel and operating at catalytically supported thermal combustion conditions. The performance of the catalysts was determined by monitoring emissions throughout the test, and by examining the physical condition of the catalyst core at the conclusion of the test. The test catalysts proved to be capable of low emissions operation after 1000 hours diesel aging, with no apparent physical degradation of the catalyst support.

  8. Polymer-Supported Raney Nickel Catalysts for Sustainable Reduction Reactions.

    PubMed

    Jiang, Haibin; Lu, Shuliang; Zhang, Xiaohong; Dai, Wei; Qiao, Jinliang

    2016-01-01

    Green is the future of chemistry. Catalysts with high selectivity are the key to green chemistry. Polymer-supported Raney catalysts have been found to have outstanding performance in the clean preparation of some chemicals. For example, a polyamide 6-supported Raney nickel catalyst provided a 100.0% conversion of n-butyraldehyde without producing any detectable n-butyl ether, the main byproduct in industry, and eliminated the two main byproducts (isopropyl ether and methyl-iso-butylcarbinol) in the hydrogenation of acetone to isopropanol. Meanwhile, a model for how the polymer support brought about the elimination of byproducts is proposed and confirmed. In this account the preparation and applications of polymer-supported Raney catalysts along with the corresponding models will be reviewed.

  9. Functionalized magnetic nanoparticles: A novel heterogeneous catalyst support

    EPA Science Inventory

    Functionalized magnetic nanoparticles have emerged as viable alternatives to conventional materials, as robust, high-surface-area heterogeneous catalyst supports. Post-synthetic surface modification protocol for magnetic nanoparticles has been developed that imparts desirable che...

  10. Polymer-Supported Raney Nickel Catalysts for Sustainable Reduction Reactions.

    PubMed

    Jiang, Haibin; Lu, Shuliang; Zhang, Xiaohong; Dai, Wei; Qiao, Jinliang

    2016-01-01

    Green is the future of chemistry. Catalysts with high selectivity are the key to green chemistry. Polymer-supported Raney catalysts have been found to have outstanding performance in the clean preparation of some chemicals. For example, a polyamide 6-supported Raney nickel catalyst provided a 100.0% conversion of n-butyraldehyde without producing any detectable n-butyl ether, the main byproduct in industry, and eliminated the two main byproducts (isopropyl ether and methyl-iso-butylcarbinol) in the hydrogenation of acetone to isopropanol. Meanwhile, a model for how the polymer support brought about the elimination of byproducts is proposed and confirmed. In this account the preparation and applications of polymer-supported Raney catalysts along with the corresponding models will be reviewed. PMID:27347922

  11. Alkene Isomerization Using a Solid Acid as Activator and Support for a Homogeneous Catalyst

    ERIC Educational Resources Information Center

    Seen, Andrew J.

    2004-01-01

    An upper-level undergraduate experiment that, in addition to introducing students to catalysis using an air sensitive transition-metal complex, introduces the use of a solid acid as an activator and support for the catalyst is developed. The increased stability acquired in the course of the process affords the opportunity to characterize the…

  12. Reactivity of metal catalysts in glucose-fructose conversion.

    PubMed

    Loerbroks, Claudia; van Rijn, Jeaphianne; Ruby, Marc-Philipp; Tong, Qiong; Schüth, Ferdi; Thiel, Walter

    2014-09-15

    A joint experimental and computational study on the glucose-fructose conversion in water is reported. The reactivity of different metal catalysts (CrCl3, AlCl3, CuCl2, FeCl3, and MgCl2) was analyzed. Experimentally, CrCl3 and AlCl3 achieved the best glucose conversion rates, CuCl2 and FeCl3 were only mediocre catalysts, and MgCl2 was inactive. To explain these differences in reactivity, DFT calculations were performed for various metal complexes. The computed mechanism consists of two proton transfers and a hydrogen-atom transfer; the latter was the rate-determining step for all catalysts. The computational results were consistent with the experimental findings and rationalized the observed differences in the behavior of the metal catalysts. To be an efficient catalyst, a metal complex should satisfy the following criteria: moderate Brønsted and Lewis acidity (pKa = 4-6), coordination with either water or weaker σ donors, energetically low-lying unoccupied orbitals, compact transition-state structures, and the ability for complexation of glucose. Thus, the reactivity of the metal catalysts in water is governed by many factors, not just the Lewis acidity. PMID:25156402

  13. Reactivity of metal catalysts in glucose-fructose conversion.

    PubMed

    Loerbroks, Claudia; van Rijn, Jeaphianne; Ruby, Marc-Philipp; Tong, Qiong; Schüth, Ferdi; Thiel, Walter

    2014-09-15

    A joint experimental and computational study on the glucose-fructose conversion in water is reported. The reactivity of different metal catalysts (CrCl3, AlCl3, CuCl2, FeCl3, and MgCl2) was analyzed. Experimentally, CrCl3 and AlCl3 achieved the best glucose conversion rates, CuCl2 and FeCl3 were only mediocre catalysts, and MgCl2 was inactive. To explain these differences in reactivity, DFT calculations were performed for various metal complexes. The computed mechanism consists of two proton transfers and a hydrogen-atom transfer; the latter was the rate-determining step for all catalysts. The computational results were consistent with the experimental findings and rationalized the observed differences in the behavior of the metal catalysts. To be an efficient catalyst, a metal complex should satisfy the following criteria: moderate Brønsted and Lewis acidity (pKa = 4-6), coordination with either water or weaker σ donors, energetically low-lying unoccupied orbitals, compact transition-state structures, and the ability for complexation of glucose. Thus, the reactivity of the metal catalysts in water is governed by many factors, not just the Lewis acidity.

  14. Pore structure characterization of catalyst supports via low field NMR

    SciTech Connect

    Smith, D.M.; Glaves, C.L.; Gallegos, D.P.; Brinker, C.J.

    1988-01-01

    In this paper, the application of low-field NMR to both surface area and pore structure analysis of catalyst supports will be presented. Low-field (20 MHz) spin-lattice relaxation (T/sub 1/) experiments are performed on fluids contained in alumina and silica catalyst supports. Pore size distributions (PSD) calculated from these NMR experiments are compared to those obtained from mercury porosimetry and nitrogen condensation. 18 refs., 4 figs., 2 tabs.

  15. Microbial recovery of metals from spent catalysts. Quarterly report, January--March 1991

    SciTech Connect

    Sperl, P.L.; Sperl, G.T.

    1991-12-31

    This project was initiated on October 1, 1989, for the purpose of recovering metals from spent coal liquefaction catalysts. Two catalyst types are the subject of the contract. The first is a Ni-Mo catalyst supported on alumina (Shell 324) as is used in a pilot scale coal liquefaction facility at Wilsonville, Alabama. This plant is run and operated by Southern Clean Fuels. A large sample of spent catalyst from this facility has been obtained. The second material is an unsupported ammonium molybdate catalyst used in a pilot process by the Department of Energy at the Pittsburgh Energy Technology Center. This material was obtained in late February 1990 but has not been pursued since the No content of this particular sample is too low for the current studies and no new catalyst has since been obtained. The object of the contract is to treat these spent catalysts with microorganisms, especially Thiobacillus ferrooxidans, but also other Thiobacillus sp. and possibly Sulfolobus, to leach and remove the metals (Ni and Mo) from the spent catalysts into a form which can be readily recovered by conventional techniques.

  16. Liquid phase catalytic hydrodebromination of tetrabromobisphenol A on supported Pd catalysts

    NASA Astrophysics Data System (ADS)

    Wu, Ke; Zheng, Mengjia; Han, Yuxiang; Xu, Zhaoyi; Zheng, Shourong

    2016-07-01

    Tetrabromobisphenol A (TBBPA) is a widely used brominated flame retardant and reductive debromination is an effective method for the abatement of TBBPA pollution. In this study, Pd catalysts supported on TiO2, CeO2, Al2O3 and SiO2 were prepared by the impregnation (the resulting catalyst denoted as im-Pd/support), deposition-precipitation (the resulting catalyst denoted as dp-Pd/support), and photo-deposition (the resulting catalyst denoted as pd-Pd/support) methods. The catalysts were characterized by N2 adsorption-desorption isotherm, X-ray diffraction, transmission electron microscopy, measurement of zeta potential, CO chemisorption, and X-ray photoelectron spectroscopy. The results showed that at an identical Pd loading amount (2.0 wt.%) Pd particle size in dp-Pd/TiO2 was much smaller than those in im-Pd/TiO2 and pd-Pd/TiO2. Pd particle size of the dp-Pd/TiO2 catalyst increased with Pd loading amount. Additionally, Pd particles in the dp-Pd/TiO2 catalysts were positively charged due to the strong metal-support interaction, whereas the cationization effect was gradually attenuated with the increase of Pd loading amount. For the liquid phase catalytic hydrodebromination (HDB) of TBBPA, tri-bromobisphenol A (tri-BBPA), di-bromobisphenol A (di-BBPA), and mono-bromobisphenol A (mono-BBPA) were identified as the intermediate products, indicative of a stepwise debromination process. The catalytic HDB of TBBPA followed the Langmuir-Hinshelwood model, reflecting an adsorption enhanced catalysis mechanism. At an identical Pd loading amount, the Pd catalyst supported on TiO2 exhibited a much higher catalytic activity than those on other supports. Furthermore, dp-Pd/TiO2 was found to be more active than im-Pd/TiO2 and pd-Pd/TiO2.

  17. Studies on the metal poisoning and metal resistance of zeolitic cracking catalysts

    SciTech Connect

    Chester, A.W.

    1987-05-01

    The effects of metal poisons (Ni, V) on zeolitic cracking catalyst have been investigated with the goal of developing a method for determining the inherent metal resistance of different catalyst compositions in the laboratory. Metal resistance is evaluated by determining activity and selectivity both before and after a synthetic poisoning procedure so that ''contaminant yields'' - the excess coke and hydrogen produced by metals during cracking - could be calculated. After several methods are compared, that chosen involves impregnation of steam-deactivated catalysts with a gas oil doped with metal naphthenates, followed by high-temperature cracking and regeneration.

  18. Design of a metal-promoted oxide catalyst for the selective synthesis of butadiene from ethanol.

    PubMed

    Sushkevich, Vitaly L; Ivanova, Irina I; Ordomsky, Vitaly V; Taarning, Esben

    2014-09-01

    The synthesis of buta-1,3-diene from ethanol has been studied over metal-containing (M=Ag, Cu, Ni) oxide catalysts (MO(x)=MgO, ZrO2, Nb2O5, TiO2, Al2O3) supported on silica. Kinetic study of a wide range of ethanol conversions (2-90%) allowed the main reaction pathways leading to butadiene and byproducts to be determined. The key reaction steps of butadiene synthesis were found to involve ethanol dehydrogenation, acetaldehyde condensation, and the reduction of crotonaldehyde with ethanol into crotyl alcohol. Catalyst design included the selection of active components for each key reaction step and merging of these components into multifunctional catalysts and adjusting the catalyst functions to achieve the highest selectivity. The best catalytic performance was achieved over the Ag/ZrO2/SiO2 catalyst, which showed the highest selectivity towards butadiene (74 mol%). PMID:25123990

  19. Design of a metal-promoted oxide catalyst for the selective synthesis of butadiene from ethanol.

    PubMed

    Sushkevich, Vitaly L; Ivanova, Irina I; Ordomsky, Vitaly V; Taarning, Esben

    2014-09-01

    The synthesis of buta-1,3-diene from ethanol has been studied over metal-containing (M=Ag, Cu, Ni) oxide catalysts (MO(x)=MgO, ZrO2, Nb2O5, TiO2, Al2O3) supported on silica. Kinetic study of a wide range of ethanol conversions (2-90%) allowed the main reaction pathways leading to butadiene and byproducts to be determined. The key reaction steps of butadiene synthesis were found to involve ethanol dehydrogenation, acetaldehyde condensation, and the reduction of crotonaldehyde with ethanol into crotyl alcohol. Catalyst design included the selection of active components for each key reaction step and merging of these components into multifunctional catalysts and adjusting the catalyst functions to achieve the highest selectivity. The best catalytic performance was achieved over the Ag/ZrO2/SiO2 catalyst, which showed the highest selectivity towards butadiene (74 mol%).

  20. 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

  1. Nitrogen-doped carbon nanotubes as a highly active metal-free catalyst for selective oxidation.

    PubMed

    Chizari, Kambiz; Deneuve, Adrien; Ersen, Ovidiu; Florea, Ileana; Liu, Yu; Edouard, David; Janowska, Izabela; Begin, Dominique; Pham-Huu, Cuong

    2012-01-01

    Catalytic reactions are generally carried out on supported metals or oxides, which act as an active phase and require impregnation and thermal treatment steps. During tests, the metal or oxide nanoparticles could be further sintered, which would induces deactivation. Direct incorporation of the active phase into the matrix of a support could be an elegant alternative to prevent catalyst deactivation. Here, we report that nitrogen-doped carbon nanotubes (N-CNTs) can be efficiently employed as a metal-free catalyst for oxidative reactions that allow the selective transformation of the harmful, gaseous H(2)S into solid sulfur. The catalyst exhibits a high stability during the test at high space velocity. The macroscopic shaping of the catalyst on the silicon carbide foam also increases its catalytic activity by improving the contact between the reactants and the catalyst. Such macroscopic shaping allows the avoidance of problems linked with transport and handling of nanoscopic materials and also reduces the pressure drop across the catalyst bed to a large extent.

  2. The Corrosion of PEM Fuel Cell Catalyst Supports and Its Implications for Developing Durable Catalysts

    SciTech Connect

    Shao, Yuyan; Wang, Jun; Kou, Rong; Engelhard, Mark H.; Liu, Jun; Wang, Yong; Lin, Yuehe

    2009-01-03

    Studying the corrosion behavior of catalyst support materials is of great significance for understanding the degradation of PEM fuel cell performance and developing durable catalysts. The oxidation of Vulcan carbon black (the most widely-used catalyst support for PEM fuel cells) was investigated using various electrochemical stressing methods (fixed-potential holding vs. potential step cycling), among which the potential step cycling was considered to mimic more closely the real drive cycle operation of vehicle PEM fuel cells. The oxidation of carbon was accelerated under potential step conditions as compared with the fixed-potential holding condition. Increasing potential step frequency or decreasing the lower potential limit in the potential step can further accelerate the corrosion of carbon. The accelerated corrosion of carbon black was attributed to the cycle of consumption/regeneration of some easily oxidized species. These findings are being employed to develop a test protocol for fast screening durable catalyst support.

  3. Metallic organophosphates as catalysts in asymmetric synthesis: a return journey.

    PubMed

    Parra, Alejandro; Reboredo, Silvia; Martín Castro, Ana M; Alemán, José

    2012-07-14

    This perspective article provides a general overview of the most relevant topics in the applications of chiral metallic organophosphates. A brief introduction along with a historic comparative profile of the BINOL and phosphoric acid analogues are given. Next, a selection of the most outstanding uses of the catalysts according to the employed metal is presented.

  4. Exhaust system having a gold-platinum group metal catalyst

    DOEpatents

    Ragle, Christie Susan; Silver, Ronald G.; Zemskova, Svetlana Mikhailovna; Eckstein, Colleen J.

    2012-08-07

    A method of providing an exhaust treatment device is disclosed. The method includes applying a catalyst including gold and a platinum group metal to a particulate filter. The concentration of the gold and the platinum group metal is sufficient to enable oxidation of carbon monoxide and nitric oxide.

  5. Exhaust system having a gold-platinum group metal catalyst

    DOEpatents

    Ragle, Christie Susan; Silver, Ronald G.; Zemskova, Svetlana Mikhailovna; Eckstein, Colleen J.

    2011-12-06

    A method of providing an exhaust treatment device is disclosed. The method includes applying a catalyst including gold and a platinum group metal to a particulate filter. The concentration of the gold and the platinum group metal is sufficient to enable oxidation of carbon monoxide and nitric oxide.

  6. Preparation, reduction, and chemisorption behavior or niobia-supported nickel catalysts

    SciTech Connect

    Ko, E.I.; Hupp, J.M.; Rogan, F.H.; Wagner, N.J.

    1983-11-01

    Two niobia(Nb/sub 2/O/sub 5/)-supported nickel catalysts, containing 2 and 10 wt % nickel, were prepared by incipient wetness impregnation. Subsequent to reduction in hydrogen at 573 and 773 K for 1 h, these catalysts adsorbed a smaller amount of hydrogen at room temperature than silica-supported nickel catalysts similarly prepard. The suppression in hydrogen adsorption was more pronounced for the 2 wt % sample, which had a smaller average crystallite size as determined by x-ray line broadening measurement. Thermogravimetric analysis showed a facile reduction of the nickel precursor salt to metallic nickel. The chemisorption behavior was thus ascribed to strong metal-support interactions (SMSI). These results compared with similar data preveiouly obtained for titania(TiO/sub 2/)-supported nickel catalysts showed that niobia was a more interacting support than titania for nickel, when parameters such as average crystallite size and reduction treatment were comparable. The extent of interaction appeared to correlate with the reducibility of the oxide support, although quantitative thermogravimetric measurements suggested that the amount of support being reduced was small. 29 references, 6 figures, 3 tables.

  7. Characteristics of polyaniline cobalt supported catalysts for epoxidation reactions.

    PubMed

    Kowalski, Grzegorz; Pielichowski, Jan; Grzesik, Mirosław

    2014-01-01

    A study of polyaniline (PANI) doping with various cobalt compounds, that is, cobalt(II) chloride, cobalt(II) acetate, and cobalt(II) salen, is presented. The catalysts were prepared by depositing cobalt compounds onto the polymer surface. PANI powders containing cobalt ions were obtained by one- or two-step method suspending PANI in the following acetonitrile/acetic acid solution or acetonitrile and then acetic acid solution. Moreover different ratios of Co(II) : PANI were studied. Catalysts obtained with both methods and at all ratios were investigated using various techniques including AAS and XPS spectroscopy. The optimum conditions for preparation of PANI/Co catalysts were established. Catalytic activity of polyaniline cobalt(II) supported catalysts was tested in dec-1-ene epoxidation with molecular oxygen at room temperature. The relationship between the amount of cobalt species, measured with both AAS and XPS techniques, and the activity of PANI-Co catalysts has been established.

  8. Catalytic removal of carbon monoxide over carbon supported palladium catalyst.

    PubMed

    Srivastava, Avanish Kumar; Saxena, Amit; Shah, Dilip; Mahato, T H; Singh, Beer; Shrivastava, A R; Gutch, P K; Shinde, C P

    2012-11-30

    Carbon supported palladium (Pd/C) catalyst was prepared by impregnation of palladium chloride using incipient wetness technique, which was followed by liquid phase reduction with formaldehyde. Thereafter, Pd/C catalyst was characterized using X-ray diffractometery, scanning electron microscopy, atomic absorption spectroscopy, thermo gravimetry, differential scanning calorimetry and surface characterization techniques. Catalytic removal of carbon monoxide (CO) over Pd/C catalyst was studied under dynamic conditions. Pd/C catalyst was found to be continuously converting CO to CO(2) through the catalyzed reaction, i.e., CO+1/2O(2)→CO(2). Pd/C catalyst provided excellent protection against CO. Effects of palladium wt%, CO concentration, humidity, space velocity and reaction environment were also studied on the breakthrough behavior of CO. PMID:23083941

  9. Synthesis and characterization of metal oxide promoted alumina catalyst for biofuel production

    NASA Astrophysics Data System (ADS)

    Anisuzzaman, S. M.; Krishnaiah, D.; Bono, A.; Abang, S.; Sundang, M.; Suali, E.; Lahin, F. A.; Shaik Alawodeen, A.

    2016-06-01

    Alumina has been widely used as a support in catalysis process which owing to its extremely thermal and mechanical stability, high surface area, large pore size and pore volume. The aim of this study was to synthesize calcium oxide-supported basic alumina catalysts (CaO/Al2O3) by impregnation method and to characterize the properties of the catalyst based on its surface area and porosity, functional group, surface morphology and particle size. Impregnation method was chosen for the synthesization of catalyst which involved contacting the support with the impregnating solution for a particular period of time, drying the support to remove the imbibed liquid and calcination process. In the preparation of catalyst, catalytic performance of CaO/Al2O3 catalyst was measured at different calcined temperatures (650°C, 750°C and 800°C). Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Mercury intrusion porosimetry (MIP), and particle size analyzer (Zetasizer) was used to characterize the catalyst. The highest total specific area and the total porosity of the catalyst was obtained at 750oC. FTIR analysis basically studied on the functional groups present in each catalyst synthesized, while SEM analysis was observed to have pores on its surface. Moreover, CaO/Al2O3 catalysts at 650°C produced the smallest particle size (396.1 mn), while at 750°C produced the largest particle size (712.4 mn). Thus it can be concluded that CaO/Al2O3 catalysts has great potential coimnercialization since CaO has attracted many attentions compared to other alkali earth metal oxides especially on the transesterification reaction.

  10. Corrosion-resistant catalyst supports for phosphoric acid fuel cells

    SciTech Connect

    Kosek, J.A.; Cropley, C.C.; LaConti, A.B.

    1990-01-01

    High-surface-area carbon blacks such as Vulcan XC-72 (Cabot Corp.) and graphitized carbon blacks such as 2700{degree}C heat-treated Black Pearls 2000 (HTBP) (Cabot Corp.) have found widespread applications as catalyst supports in phosphoric acid fuel cells (PAFCs). However, due to the operating temperatures and pressures being utilized in PAFCs currently under development, the carbon-based cathode catalyst supports suffer from corrosion, which decreases the performance and life span of a PAFC stack. The feasibility of using alternative, low-cost, corrosion-resistant catalyst support (CRCS) materials as replacements for the cathode carbon support materials was investigated. The objectives of the program were to prepare high-surface-area alternative supports and to evaluate the physical characteristics and the electrochemical stability of these materials. The O{sub 2} reduction activity of the platinized CRCS materials was also evaluated. 2 refs., 3 figs.

  11. Influence of sp(3)-sp(2) Carbon Nanodomains on Metal/Support Interaction, Catalyst Durability, and Catalytic Activity for the Oxygen Reduction Reaction.

    PubMed

    Campos-Roldán, Carlos A; Ramos-Sánchez, Guadalupe; Gonzalez-Huerta, Rosa G; Vargas García, Jorge R; Balbuena, Perla B; Alonso-Vante, Nicolas

    2016-09-01

    In this work, platinum nanoparticles were impregnated by two different techniques, namely the carbonyl chemical route and photodeposition, onto systematically surface-modified multiwalled carbon nanotubes. The different interactions between platinum nanoparticles with sp(2)-sp(3) carbon nanodomains were investigated. The oxidation of an adsorbed monolayer of carbon monoxide, used to probe electronic catalytic modification, suggests a selective nucleation of platinum nanoparticles onto sp(2) carbon nanodomains when photodeposition synthesis is carried out. XPS attests the catalytic center electronic modification obtained by photodeposition. DFT calculations were used to determine the interaction energy of a Pt cluster with sp(2) and sp(3) carbon surfaces as well as with oxidized ones. The interaction energy and electronic structure of the platinum cluster presents dramatic changes as a function of the support surface chemistry, which also modifies its catalytic properties evaluated by the interaction with CO. The interaction energy was calculated to be 8-fold higher on sp(3) and oxidized surfaces in comparison to sp(2) domains. Accelerated Stability Test (AST) was applied only on the electronic-modified materials to evaluate the active phase degradation and their activity toward oxygen reduction reaction (ORR). The stability of photodeposited materials is correlated with the surface chemical nature of supports indicating that platinum nanoparticles supported onto multiwalled carbon nanotubes with the highest sp(2) character show the higher stability and activity toward ORR. PMID:27494283

  12. Influence of sp(3)-sp(2) Carbon Nanodomains on Metal/Support Interaction, Catalyst Durability, and Catalytic Activity for the Oxygen Reduction Reaction.

    PubMed

    Campos-Roldán, Carlos A; Ramos-Sánchez, Guadalupe; Gonzalez-Huerta, Rosa G; Vargas García, Jorge R; Balbuena, Perla B; Alonso-Vante, Nicolas

    2016-09-01

    In this work, platinum nanoparticles were impregnated by two different techniques, namely the carbonyl chemical route and photodeposition, onto systematically surface-modified multiwalled carbon nanotubes. The different interactions between platinum nanoparticles with sp(2)-sp(3) carbon nanodomains were investigated. The oxidation of an adsorbed monolayer of carbon monoxide, used to probe electronic catalytic modification, suggests a selective nucleation of platinum nanoparticles onto sp(2) carbon nanodomains when photodeposition synthesis is carried out. XPS attests the catalytic center electronic modification obtained by photodeposition. DFT calculations were used to determine the interaction energy of a Pt cluster with sp(2) and sp(3) carbon surfaces as well as with oxidized ones. The interaction energy and electronic structure of the platinum cluster presents dramatic changes as a function of the support surface chemistry, which also modifies its catalytic properties evaluated by the interaction with CO. The interaction energy was calculated to be 8-fold higher on sp(3) and oxidized surfaces in comparison to sp(2) domains. Accelerated Stability Test (AST) was applied only on the electronic-modified materials to evaluate the active phase degradation and their activity toward oxygen reduction reaction (ORR). The stability of photodeposited materials is correlated with the surface chemical nature of supports indicating that platinum nanoparticles supported onto multiwalled carbon nanotubes with the highest sp(2) character show the higher stability and activity toward ORR.

  13. Interaction of carbon and sulfur on metal catalysts: Technical progress report

    SciTech Connect

    McCarty, J.G.; Vajo, J.

    1989-02-17

    At high coverage, sulfur generally deactivates metal catalysts, but at low coverage, chemisorbed sulfur can have a more subtle effect on catalyst activity and selectivity. The general goal of the current project is to examine fundamental aspects of selective poisoning by fractional monolayers of chemisorbed sulfur on a variety of metal catalysts used for commercially important reactions such as hydrocarbon re-forming, light alkane steam re-forming, and hydrocarbon synthesis. Specific objectives of the research program are to experimentally measure as a function of coverage the influence of chemisorbed sulfur on the thermodynamics, reactivity, and structure of surface and bulk carbon occupying both dispersed and well-characterized metal catalyst surfaces. Special methods, such as reversible sulfur chemisorption on supported metals and temperature-programmed reaction (TPR) characterization of catalyst carbon, have been developed that are well suited to examining the interaction of sulfur and carbon on metal surfaces. New analytical instruments with greatly improved sensitivity have been recently developed and applied: a helium discharge ionization detector (DID) is being used with a gas recirculation thermodynamic system, and the surface analysis by laser ionization (SALI) technique is used with surface carbon segregation systems.

  14. Pumice-supported palladium catalysts. II. Selective hydrogenation of 1,3-cyclooctadiene

    SciTech Connect

    Deganello, G.; Duca, D.; Martorana, A.; Fagherazzi, G.; Benedetti, A.

    1994-11-01

    Two series of pumice-supported palladium catalysts (W and U) have been tested in the liquid-phase selective hydrogenation of 1,3-cyclooctadiene (1,3-COD) to cyclooctene (COE). The two series of catalysts, obtained via organometallic precursors, differ in the preparation procedure. In the W series the reduced metal derives only from Pd intermediates anchored to pumice; in the U series the metal originates also from unreacted Pd(allyl){sub 2} species in solution. The U catalysts present agglomerated metal particles. The hydrogenations, free of any diffusion problems, were performed at constant pressure of hydrogen (1 atm). Analysis of the data suggests that the rate-determining step is a surface reaction involving activated 1,3-COD. Selectivity is very high since cyclooctane (COA) is detected only when all 1,3-COD is consumed. The turnover frequencies (TOF{sub 1}) of the first semihydrogenation do not change with palladium dispersion, determined from the Porod diameter D{sub p} up to D{sub x} < 35%, but thereafter they slowly decrease. Experimental evidence, such as the absence of oxidation when exposed to air and the negative shift of binding energy of the Pd 3d level in XPS measurements, indicate a different behavior of the present catalysts in comparison with other supported palladium catalysts. These differences are attributed to the presence of alkali metal ions (Na{sup +}, K{sup +}) on the pumice surface and are explained on the basis of the change in electron density and/or in the ensemble size of the supported palladium. Several interesting features and differences in activity and selectivity between the two series of catalysts can be accounted for by the presence of agglomerated palladium particles in the U series and are discussed in terms of the evolution of parameters with dispersion. 40 refs., 8 figs., 2 tabs.

  15. Characterisation of carbon supported platinum-ruthenium fuel cell catalysts of different degree of alloying

    NASA Astrophysics Data System (ADS)

    Albers, Peter W.; Weber, Winfried; Kunzmann, Kurt; Lopez, Marco; Parker, Stewart F.

    2008-12-01

    A series of PtRu/C fuel cell catalysts have been characterised by a combination of transmission electron microscopy, scanning transmission electron microscopy, energy dispersive X-ray microanalysis, X-ray diffraction and inelastic incoherent neutron scattering. The diffraction and microscopy studies show that a range of catalysts with different degrees of alloying can be obtained. It was possible to produce a strongly alloyed catalyst with average particle size below 10 nm. STEM/EDX results on the local compositions of the precious metal particles of different size and composition showed that the larger the particles the larger the Pt/Ru ratio. This indicates that ruthenium appears to prevent the agglomeration of the platinum particles to retain the smaller nanometer size. Inelastic neutron scattering spectroscopy shows that on the alloyed catalysts hydrogen occupies the threefold site, with no evidence for occupation of the on-top sites even under 800 mbar of hydrogen gas. Changes in the region of the out-of-plane C-H vibrational bands of the carbon black support indicated a contribution of the support during catalyst formation treatment by carbothermal reaction at lower temperature. Comparison of HREELS data from single crystal work and vibrational energy values from neutron spectroscopy allows to derive information on the site occupation of atomic hydrogen on finely divided precious metal particles supported on highly absorbing high surface area carbon blacks.

  16. Steam reforming of glycerol for hydrogen production over supported nickel catalysts on alumina.

    PubMed

    Choi, Ga Young; Kim, Young Chul; Moon, Dong Ju; Seo, Gon; Park, Nam Cook

    2013-01-01

    The experiment was carried out to produce hydrogen through steam reforming of glycerol over nano-sized Ni catalysts supported on alumina (Al2O3). The catalysts were characterized by BET surface area, metal dispersion, XRD, TPR, NH3-TPD and SEM. 15 wt% Ni/Al2O3 catalysts presented carbon nano fiber after the catalyst was used. However, when the Ni loading was higher than that of 15 wt%, the catalytic activity reduced, and the increase of the Ni particle size and the formation of graphitic carbon occurred. The Ni/SiO2(70)-Al2O3 with the high surface area and the small Ni particle size promoted the catalytic activity and could easily reduce from NiO to Ni, inhibiting the formation of NiAl2O4. PMID:23646792

  17. Tailoring Silica-alumina Supported Pt-Pd As Poison Tolerant Catalyst For Aromatics Hydrogenation

    SciTech Connect

    Yu, Yanzhe; Gutierrez, Oliver Y.; Haller, Gary L.; Colby, Robert J.; Kabius, Bernd C.; Rob van Veen, J. A.; Jentys, Andreas; Lercher, Johannes A.

    2013-08-01

    The tailoring of the physicochemical and catalytic properties of mono- and bimetallic Pt-Pd catalysts supported on amorphous silica-alumina is studied. Electron energy loss spectroscopy and extended X-ray absorption fine structure analyses indicated that bimetallic Pt-Pd and relatively large monometallic Pd particles were formed, whereas the X-ray absorption near edge structure provided direct evidence for the electronic deficiency of the Pt atoms. The heterogeneous distribution of metal particles was also shown by high resolution transmission electron microscopy. The average structure of the bimetallic particles (Pt-rich core and Pd-rich shell) and the presence of Pd particles led to surface Pd enrichment, which was independently shown by IR spectra of adsorbed CO. The specific metal distribution, average size, and surface composition of the Pt-Pd particles depend to a large extent on the metal precursors. In the presence of NH3 ligands, Pt-Pd particles with a fairly homogeneous bulk and surface metal distribution were formed. Also high Lewis acid site concentration of the carrier leads to more homogeneous bimetallic particles. All catalysts were active for the hydrogenation of tetralin in the absence and presence of quinoline and dibenzothiophene (DBT). Monometallic Pt catalysts had the highest hydrogenation activity in poison-free and quinoline-containing feed. When DBT was present, bimetallic Pt-Pd catalysts with the most homogenous metal distribution showed the highest activity. The higher resistance of bimetallic catalysts towards sulfur poisoning compared to their monometallic Pt counterparts results from the weakened metal-sulfur bond on the electron deficient Pt atoms. Thus, increasing the fraction of electron deficient Pt on the surface of the bimetallic particles increases the efficiency of the catalyst in the presence of sulfur.

  18. Metal salt catalysts for enhancing hydrogen spillover

    DOEpatents

    Yang, Ralph T; Wang, Yuhe

    2013-04-23

    A composition for hydrogen storage includes a receptor, a hydrogen dissociating metal doped on the receptor, and a metal salt doped on the receptor. The hydrogen dissociating metal is configured to spill over hydrogen to the receptor, and the metal salt is configured to increase a rate of the spill over of the hydrogen to the receptor.

  19. Microbial recovery of metals from spent coal liquefaction catalysts. Final report

    SciTech Connect

    Sperl, P.L.; Sperl, G.T.

    1995-07-01

    This project was initiated on October 1, 1989, for the purpose of recovering metals from spent coal liquefaction catalysts. Two catalyst types were the subject of the contract. The first was a Ni-No catalyst support on alumina (Shell 324), the catalyst used in a pilot scale coal liquefaction facility at Wilsonville, Alabama. The second material was an unsupported ammonium molybdate catalyst used in a pilot process by the Department of Energy at the Pittsburgh Energy Technology Center. This material was obtained in late February 1990 but has not been pursued since the Mo content of this particular sample was too low for the current studies and the studies at the Pittsburgh Energy Technology Center have been discontinued. The object of the contract was to treat these spent catalysts with microorganisms, especially Thiobacillus ferrooxidans , but also other Thiobacillus spp. and possibly Sulfolobus and other potential microorganisms, to leach and remove the metals (Ni and Mo) from the spent catalysts into a form which could be readily recovered by conventional techniques.

  20. Comparative Investigation of Benzene Steam Reforming over Spinel Supported Rh and Ir Catalysts

    SciTech Connect

    Mei, Donghai; Lebarbier, Vanessa M.; Rousseau, Roger; Glezakou, Vassiliki-Alexandra; Albrecht, Karl O.; Kovarik, Libor; Flake, Matt; Dagle, Robert A.

    2013-06-07

    In a combined experimental and first-principles density functional theory (DFT) study, benzene steam reforming (BSR) over MgAl2O4 supported Rh and Ir catalysts was investigated. Experimentally, it has been found that both highly dispersed Rh and Ir clusters (1-2 nm) on the MgAl2O4 spinel support are stable during the BSR in the temperature range of 700-850°C. Compared to the Ir/MgAl2O4 catalyst, the Rh/MgAl2O4 catalyst is more active with higher benzene turnover frequency and conversion. At typical steam conditions with the steam-to-carbon ratio > 12, the benzene conversion is only a weak function of the H2O concentration in the feed. This suggests that the initial benzene decomposition step rather than the benzene adsorption is most likely the rate-determined step in BSR over supported Rh and Ir catalysts. In order to understand the differences between the two catalysts, we followed with a comparative DFT study of initial benzene decomposition pathways over two representative model systems for each supported metal (Rh and Ir) catalysts. A periodic terrace (111) surface and an amorphous 50-atom metal cluster with a diameter of 1.0 nm were used to represent the two supported model catalysts under low and high dispersion conditions. Our DFT results show that the decreasing catalyst particle size enhances the benzene decomposition on supported Rh catalysts by lowering both C-C and C-H bond scission. The activation barriers of the C-C and the C-H bond scission decrease from 1.60 and 1.61 eV on the Rh(111) surface to 1.34 and 1.26 eV on the Rh50 cluster. For supported Ir catalysts, the decreasing particle size only affects the C-C scission. The activation barrier of the C-C scission of benzene decreases from 1.60 eV on the Ir(111) surface to 1.35 eV on the Ir50 cluster while the barriers of the C-H scission are practically the same. The experimentally measured higher BSR

  1. Carbon-supported platinum alloy catalysts for phenol hydrogenation for making industrial chemicals

    SciTech Connect

    Srinivas, S.T.; Song, C.

    1999-07-01

    Phenol is available in large quantities in liquids derived from coal and biomass. Phenol hydrogenation is an industrially important reaction to produce cyclohexanone and cyclohexanol. Cyclohexane, cyclohexene and benzene are obtained as minor products in this reaction. Cyclohexanone is an important intermediate in the production of caprolactam for nylon 6 and cyclohexanol for adipic acid production. In USA, cyclohexanol and cyclohexanone are produced by benzene hydrogenation to cyclohexane over nickel or noble metal catalysts, followed by oxidation of cyclohexane to produce a mixture of cyclohexanol and cyclohexanone. Then cyclohexanol is dehydrogenated in the presence of Cu-Zn catalyst to cyclohexanone. Usually phenol hydrogenation is also carried out by using Ni catalyst in liquid phase. However, a direct single-step vapor phase hydrogenation of phenol to give cyclohexanone selectively is more advantageous in terms of energy savings and process economics, since processing is simplified and the endothermic step of cyclohexanol dehydrogenation can be avoided, as demonstrated by Montedipe and Johnson Matthey using promoted Pd/Al{sub 2}O{sub 3} catalyst. While it is not the purpose of this paper to dwell on the relative merits of these routes, it is necessary to mention that while using monometallic catalysts, generally the problem of catalyst deactivation of sintering as well as coking is frequently encountered. Addition and alloying of noble metal (e.g. Pt) with a second metal can result in a catalyst with better selectivity and activity in the reaction which is more resistant to deactivation. This paper presents the results on the single-step vapor phase hydrogenation of phenol over carbon-supported Pt-M (M=Cr, V, Zr) alloy catalysts to yield mainly cyclohexanone or cyclohexanol.

  2. Structure sensitive adsorption of hydrogen on ruthenium and ruthenium-silver catalysts supported on silica

    SciTech Connect

    Kumar, N.

    1999-02-12

    Supported metal catalysts typically consist of particles with sizes less than 10 nm, and because of the small crystallite size, low coordination number sites (edges and corners) represent a significant fraction of all surface sites. Furthermore, it has been demonstrated that adsorption rates can be much greater at these low coordination sites than on basal plane sites. What has not been generally appreciated, however, is that preferential adsorption at edge and corner sites may explain the mechanism by which a promoter, or the addition of a second metal to form a bimetallic, can alter the selectivity and rate of reaction. For example, the measurements of hydrogen adsorption onto supported Ru-Ag catalysts show marked decreases in the amount of hydrogen adsorbed relative to the amount adsorbed on Ru catalysts. Although it is known that Ag does not dissociatively adsorb hydrogen, this decrease cannot be explained by a simple one-to-one site blocking mechanism unless Ag preferentially populates edges and corners, thereby reducing the number of Ru edge sites. Indeed, Monte Carlo simulations of Ru-Group IB metal catalysts predict that Group IB metal atoms preferentially populate corner and edge sites of ruthenium crystals. This evidence, taken together, suggests that adsorption occurs preferentially at Ru corner and edge sites, which act as portals onto basal planes. A model based on this portal theory for hydrogen adsorption onto supported ruthenium bimetallic catalysts has been developed using a rate equation approach. Specifically, the model accounts for the following features: (1) preferential adsorption through portals, (2) basal plane site-energy multiplicity, and (3) hydrogen spillover onto the support. A comparison of model predictions with experiment is presented for different concentration of Ag in Ru-Ag catalysts. The portal model of hydrogen adsorption can explain the observed decreased in the amount of hydrogen adsorbed on Ru-Ag catalysts. The model can be

  3. Chemoselective single-site Earth-abundant metal catalysts at metal-organic framework nodes.

    PubMed

    Manna, Kuntal; Ji, Pengfei; Lin, Zekai; Greene, Francis X; Urban, Ania; Thacker, Nathan C; Lin, Wenbin

    2016-01-01

    Earth-abundant metal catalysts are critically needed for sustainable chemical synthesis. Here we report a simple, cheap and effective strategy of producing novel earth-abundant metal catalysts at metal-organic framework (MOF) nodes for broad-scope organic transformations. The straightforward metalation of MOF secondary building units (SBUs) with cobalt and iron salts affords highly active and reusable single-site solid catalysts for a range of organic reactions, including chemoselective borylation, silylation and amination of benzylic C-H bonds, as well as hydrogenation and hydroboration of alkenes and ketones. Our structural, spectroscopic and kinetic studies suggest that chemoselective organic transformations occur on site-isolated, electron-deficient and coordinatively unsaturated metal centres at the SBUs via σ-bond metathesis pathways and as a result of the steric environment around the catalytic site. MOFs thus provide a novel platform for the development of highly active and affordable base metal catalysts for the sustainable synthesis of fine chemicals.

  4. Chemoselective single-site Earth-abundant metal catalysts at metal-organic framework nodes

    NASA Astrophysics Data System (ADS)

    Manna, Kuntal; Ji, Pengfei; Lin, Zekai; Greene, Francis X.; Urban, Ania; Thacker, Nathan C.; Lin, Wenbin

    2016-08-01

    Earth-abundant metal catalysts are critically needed for sustainable chemical synthesis. Here we report a simple, cheap and effective strategy of producing novel earth-abundant metal catalysts at metal-organic framework (MOF) nodes for broad-scope organic transformations. The straightforward metalation of MOF secondary building units (SBUs) with cobalt and iron salts affords highly active and reusable single-site solid catalysts for a range of organic reactions, including chemoselective borylation, silylation and amination of benzylic C-H bonds, as well as hydrogenation and hydroboration of alkenes and ketones. Our structural, spectroscopic and kinetic studies suggest that chemoselective organic transformations occur on site-isolated, electron-deficient and coordinatively unsaturated metal centres at the SBUs via σ-bond metathesis pathways and as a result of the steric environment around the catalytic site. MOFs thus provide a novel platform for the development of highly active and affordable base metal catalysts for the sustainable synthesis of fine chemicals.

  5. 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.

  6. Hydrogenation of coal liquid utilizing a metal carbonyl catalyst

    DOEpatents

    Feder, Harold M.; Rathke, Jerome W.

    1979-01-01

    Coal liquid having a dissolved transition metal, catalyst as a carbonyl complex such as Co.sub.2 (CO.sub.8) is hydrogenated with hydrogen gas or a hydrogen donor. A dissociating solvent contacts the coal liquid during hydrogenation to form an immiscible liquid mixture at a high carbon monoxide pressure. The dissociating solvent, e.g. ethylene glycol, is of moderate coordinating ability, while sufficiently polar to solvate the transition metal as a complex cation along with a transition metal, carbonyl anion in solution at a decreased carbon monoxide pressure. The carbon monoxide pressure is reduced and the liquids are separated to recover the hydrogenated coal liquid as product. The dissociating solvent with the catalyst in ionized form is recycled to the hydrogenation step at the elevated carbon monoxide pressure for reforming the catalyst complex within fresh coal liquid.

  7. Engineering catalytic activity via ion beam bombardment of catalyst supports for vertically aligned carbon nanotube growth

    DOE PAGES

    Islam, A. E.; Zakharov, D.; Stach, E. A.; Nikoleav, P.; Amama, P. B.; Sargent, G.; Saber, S.; Huffman, D.; Erford, M.; Semiatin, S. L.; et al

    2015-09-16

    Carbon nanotube growth depends on the catalytic activity of metal nanoparticles on alumina or silica supports. The control on catalytic activity is generally achieved by variations in water concentration, carbon feed, and sample placement on a few types of alumina or silica catalyst supports obtained via thin film deposition. We have recently expanded the choice of catalyst supports by engineering inactive substrates like c-cut sapphire via ion beam bombardment. The deterministic control on the structure and chemistry of catalyst supports obtained by tuning the degree of beam-induced damage have enabled better regulation of the activity of Fe catalysts only inmore » the ion beam bombarded areas and hence enabled controllable super growth of carbon nanotubes. A wide range of surface characterization techniques were used to monitor the catalytically active surface engineered via ion beam bombardment. The proposed method offers a versatile way to control carbon nanotube growth in patterned areas and also enhances the current understanding of the growth process. As a result, with the right choice of water concentration, carbon feed and sample placement, engineered catalyst supports may extend the carbon nanotube growth yield to a level that is even higher than the ones reported here, and thus offers promising applications of carbon nanotubes in electronics, heat exchanger, and energy storage.« less

  8. Engineering catalytic activity via ion beam bombardment of catalyst supports for vertically aligned carbon nanotube growth

    SciTech Connect

    Islam, A. E.; Zakharov, D.; Stach, E. A.; Nikoleav, P.; Amama, P. B.; Sargent, G.; Saber, S.; Huffman, D.; Erford, M.; Semiatin, S. L.; Maruyama, B.

    2015-09-16

    Carbon nanotube growth depends on the catalytic activity of metal nanoparticles on alumina or silica supports. The control on catalytic activity is generally achieved by variations in water concentration, carbon feed, and sample placement on a few types of alumina or silica catalyst supports obtained via thin film deposition. We have recently expanded the choice of catalyst supports by engineering inactive substrates like c-cut sapphire via ion beam bombardment. The deterministic control on the structure and chemistry of catalyst supports obtained by tuning the degree of beam-induced damage have enabled better regulation of the activity of Fe catalysts only in the ion beam bombarded areas and hence enabled controllable super growth of carbon nanotubes. A wide range of surface characterization techniques were used to monitor the catalytically active surface engineered via ion beam bombardment. The proposed method offers a versatile way to control carbon nanotube growth in patterned areas and also enhances the current understanding of the growth process. As a result, with the right choice of water concentration, carbon feed and sample placement, engineered catalyst supports may extend the carbon nanotube growth yield to a level that is even higher than the ones reported here, and thus offers promising applications of carbon nanotubes in electronics, heat exchanger, and energy storage.

  9. Supported catalysts using nanoparticles as the support material

    DOEpatents

    Wong, Michael S.; Wachs, Israel E.; Knowles, William V.

    2010-11-02

    A process for making a porous catalyst, comprises a) providing an aqueous solution containing a nanoparticle precursor, b) forming a composition containing nanoparticles, c) adding a first catalytic component or precursor thereof and a pore-forming agent to the composition containing nanoparticles and allowing the first catalytic component, the pore-forming agent, and the nanoparticles form an organic-inorganic structure, d) removing water from the organic-inorganic structure; and e) removing the pore-forming agent from the organic-inorganic structure so as to yield a porous catalyst.

  10. Alkaline ionic liquids applied in supported ionic liquid catalyst for selective hydrogenation of citral to citronellal

    PubMed Central

    Salminen, Eero; Virtanen, Pasi; Mikkola, Jyri-Pekka

    2014-01-01

    The challenge in preparation of ionic liquids containing a strong alkaline anion is to identify a suitable cation which can tolerate the harsh conditions induced by the anion. In this study, a commercial quaternary ammonium compound (quat) benzalkonium [ADBA] (alkyldimethylbenzylammonium) was used as a cation in the synthesis of different alkaline ionic liquids. In fact, the precursor, benzalkonium chloride, is a mixture of alkyldimethylbenzylammonium chlorides of various alkyl chain lengths and is commonly used in the formulation of various antiseptic products. The prepared ionic liquids were utilized as Supported Ionic Liquid Catalysts (SILCAs). Typically, a SILCA contains metal nanoparticles, enzymes, or metal complexes in an ionic liquid layer which is immobilized on a solid carrier material such as an active carbon cloth (ACC). The catalysts were applied in the selective hydrogenation of citral to citronellal which is an important perfumery chemical. Interestingly, 70% molar yield toward citronellal was achieved over a catalyst containing the alkaline ionic liquid benzalkonium methoxide. PMID:24790972

  11. Alkaline ionic liquids applied in supported ionic liquid catalyst for selective hydrogenation of citral to citronellal

    NASA Astrophysics Data System (ADS)

    Salminen, Eero; Virtanen, Pasi; Mikkola, Jyri-Pekka

    2014-02-01

    The challenge in preparation of ionic liquids containing a strong alkaline anion is to identify a suitable cation which can tolerate the harsh conditions induced by the anion. In this study, a commercial quaternary ammonium compound (quat) benzalkonium [ADBA] (alkyldimethylbenzylammonium) was used as a cation in the synthesis of different alkaline ionic liquids. In fact, the precursor, benzalkonium chloride, is a mixture of alkyldimethylbenzylammonium chlorides of various alkyl chain lengths and is commonly used in the formulation of various antiseptic products. The prepared ionic liquids were utilized as Supported Ionic Liquid Catalysts (SILCAs). Typically, a SILCA contains metal nanoparticles, enzymes or metal complexes in an ionic liquid layer which is immobilized on a solid carrier material such as an active carbon cloth (ACC). The catalysts were applied in the selective hydrogenation of citral to citronellal which is an important perfumery chemical. Interestingly, 70 % molar yield towards citronellal was achieved over a catalyst containing the alkaline ionic liquid benzalkonium methoxide.

  12. Alkaline ionic liquids applied in supported ionic liquid catalyst for selective hydrogenation of citral to citronellal.

    PubMed

    Salminen, Eero; Virtanen, Pasi; Mikkola, Jyri-Pekka

    2014-01-01

    The challenge in preparation of ionic liquids containing a strong alkaline anion is to identify a suitable cation which can tolerate the harsh conditions induced by the anion. In this study, a commercial quaternary ammonium compound (quat) benzalkonium [ADBA] (alkyldimethylbenzylammonium) was used as a cation in the synthesis of different alkaline ionic liquids. In fact, the precursor, benzalkonium chloride, is a mixture of alkyldimethylbenzylammonium chlorides of various alkyl chain lengths and is commonly used in the formulation of various antiseptic products. The prepared ionic liquids were utilized as Supported Ionic Liquid Catalysts (SILCAs). Typically, a SILCA contains metal nanoparticles, enzymes, or metal complexes in an ionic liquid layer which is immobilized on a solid carrier material such as an active carbon cloth (ACC). The catalysts were applied in the selective hydrogenation of citral to citronellal which is an important perfumery chemical. Interestingly, 70% molar yield toward citronellal was achieved over a catalyst containing the alkaline ionic liquid benzalkonium methoxide.

  13. The generation of efficient supported (Heterogeneous) olefin metathesis catalysts

    SciTech Connect

    Grubbs, Robert H

    2013-04-05

    Over the past decade, a new family of homogeneous metathesis catalysts has been developed that will tolerate most organic functionalities as well as water and air. These homogeneous catalysts are finding numerous applications in the pharmaceutical industry as well as in the production of functional polymers. In addition the catalysts are being used to convert seed oils into products that can substitute for those that are now made from petroleum products. Seed oils are unsaturated, contain double bonds, and are a ready source of linear hydrocarbon fragments that are specifically functionalized. To increase the number of applications in the area of biomaterial conversion to petrol chemicals, the activity and efficiency of the catalysts need to be as high as possible. The higher the efficiency of the catalysts, the lower the cost of the conversion and a larger number of practical applications become available. Active supported catalysts were prepared and tested in the conversion of seed oils and other important starting materials. The outcome of the work was successful and the technology has been transferred to a commercial operation to develop viable applications of the discovered systems. A biorefinery that converts seed oils is under construction in Indonesia. The catalysts developed in this study will be considered for the next generation of operations.

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

    PubMed

    Li, Ning; Descorme, Claude; Besson, Michèle

    2007-07-31

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

  15. Fly ash zeolite catalyst support for Fischer-Tropsch synthesis

    NASA Astrophysics Data System (ADS)

    Campen, Adam

    This dissertation research aimed at evaluating a fly ash zeolite (FAZ) catalyst support for use in heterogeneous catalytic processes. Gas phase Fischer-Tropsch Synthesis (FTS) over a fixed-bed of the prepared catalyst/FAZ support was identified as an appropriate process for evaluation, by comparison with commercial catalyst supports (silica, alumina, and 13X). Fly ash, obtained from the Wabash River Generating Station, was first characterized using XRD, SEM/EDS, particle size, and nitrogen sorption techniques. Then, a parametric study of a two-step alkali fusion/hydrothermal treatment process for converting fly ash to zeolite frameworks was performed by varying the alkali fusion agent, agent:flyash ratio, fusion temperature, fused ash/water solution, aging time, and crystallization time. The optimal conditions for each were determined to be NaOH, 1.4 g NaOH: 1 g fly ash, 550 °C, 200 g/L, 12 hours, and 48 hours. This robust process was applied to the fly ash to obtain a faujasitic zeolite structure with increased crystallinity (40 %) and surface area (434 m2/g). Following the modification of fly ash to FAZ, ion exchange of H+ for Na+ and cobalt incipient wetness impregnation were used to prepare a FTS catalyst. FTS was performed on the catalysts at 250--300 °C, 300 psi, and with a syngas ratio H2:CO = 2. The HFAZ catalyst support loaded with 11 wt% cobalt resulted in a 75 % carbon selectivity for C5 -- C18 hydrocarbons, while methane and carbon dioxide were limited to 13 and 1 %, respectively. Catalyst characterization was performed by XRD, N2 sorption, TPR, and oxygen pulse titration to provide insight to the behavior of each catalyst. Overall, the HFAZ compared well with silica and 13X supports, and far exceeded the performance of the alumina support under the tested conditions. The successful completion of this research could add value to an underutilized waste product of coal combustion, in the form of catalyst supports in heterogeneous catalytic processes.

  16. 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.

  17. 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.

  18. Hydrogenation of aniline on a low-percentage, supported rhodium catalyst

    SciTech Connect

    Ualikhanova, A.; Temirbulatova, A.E.

    1992-01-10

    The products of hydrogenation of aniline and their derivatives exhibit biological activity and are used in the pharmaceutical industry for preparation of analgesic, antipyretic, and sulfanilamide drugs. Up to 30% of the total consumption of aniline is for synthesis of drugs. Hydrogenation of aniline on platinum metals supported on carbon was studied by Rylander et al. The authors investigated the catalytic properties of rhodium supported on oxides in saturation of aniline with hydrogen in water. In most cases, the amount of noble metal in the supported catalyst was 5%. Decreasing the concentration of active phase in the catalyst is economically advantageous. The features of hydrogenation of aniline in the presence of 1% Rh/MgO in solutions with wide variation of the technological parameters of the process were investigated in the present study. 19 refs., 3 figs., 2 tabs.

  19. Strategies and applications of combinatorial methods and high throughput screening to the discovery of non-noble metal catalyst

    NASA Astrophysics Data System (ADS)

    Bricker, Maureen L.; Sachtler, J. W. Adriaan; Gillespie, Ralph D.; McGonegal, Charles P.; Vega, Honorio; Bem, Dave S.; Holmgren, Jennifer S.

    2004-02-01

    The integrated End-to-End™ combinatorial process for catalyst preparation and screening, with emphasis on its capability to vary both process and compositional parameters will be demonstrated. Additionally, each step of the combinatorial screening process has been validated against results from traditional screening methods. The greatest challenge of all has been the adherence to the core concepts of the combinatorial approach. Catalyst libraries have been made and tested for naphthalene dehydrogenation chemistry. The preparation of these libraries has included the application of high throughput techniques for: metal impregnation; catalyst finishing; catalyst screening. The catalyst screening system has been used to find a non-noble metal catalyst system that can replace Pt in dehydrogenation applications in the petroleum industry. A proprietary catalytic composition was developed for the dehydrogenation of methylcyclohexane (MCH) to toluene starting with four non-noble metals of different proportions and four different supports (alumina, titania, zirconia and silica) prepared in different ways and applying a statistical design of experiments. These data demonstrate that all steps of catalyst preparation and screening are performed in a rapid, useful, high throughput manner. Data will be presented from the catalyst screening efforts will demonstrate that optimized metal composition is dependent on the support type.

  20. Preparation of catalysts via ion-exchangeable coatings on supports

    DOEpatents

    Dosch, R.G.; Stephens, H.P.

    1986-04-09

    Disclosed are: new catalytic compositions which comprise an inert support coated with a hydrous alkali metal, alkaline earth metal, or quaternary ammonium titanate, niobate, zirconate, or tantalate, in which the alkali or alkaline earth metal or quaternary ammonium cations have been exchanged for a catalytically effective quantity of a catalytically effective metal.

  1. Stability of Supported Platinum Sulfuric Acid Decomposition Catalysts for use in Thermochemical Water Splitting Cycles

    SciTech Connect

    Daniel M. Ginosar; Lucia M. Petkovic; Anne W. Glenn; Kyle C. Burch

    2007-03-01

    The activity and stability of several metal oxide supported platinum catalysts were explored for the sulfuric acid decomposition reaction. The acid decomposition reaction is common to several sulfur based thermochemical water splitting cycles. Reactions were carried out using a feed of concentrated liquid sulfuric acid (96 wt%) at atmospheric pressure at temperatures between 800 and 850 °C and a weight hour space velocity of 52 g acid/g catalyst/hr. Reactions were run at these high space velocities such that variations in kinetics were not masked by surplus catalyst. The influence of exposure to reaction conditions was explored for three catalysts; 0.1-0.2 wt% Pt supported on alumina, zirconia and titania. The higher surface area Pt/Al2O3 and Pt/ZrO2 catalysts were found to have the highest activity but deactivated rapidly. A low surface area Pt/TiO2 catalyst was found to have good stability in short term tests, but slowly lost activity for over 200 hours of continuous operation.

  2. Oxidative dehydrogenation of ethane on dynamically rearranging supported chloride catalysts.

    PubMed

    Gärtner, Christian A; van Veen, André C; Lercher, Johannes A

    2014-09-10

    Ethane is oxidatively dehydrogenated with a selectivity up to 95% on catalysts comprising a mixed molten alkali chloride supported on a mildly redox-active Dy2O3-doped MgO. The reactive oxyanionic OCl(-) species acting as active sites are catalytically formed by oxidation of Cl(-) at the MgO surface. Under reaction conditions this site is regenerated by O2, dissolving first in the alkali chloride melt, and in the second step dissociating and replenishing the oxygen vacancies on MgO. The oxyanion reactively dehydrogenates ethane at the melt-gas phase interface with nearly ideal selectivity. Thus, the reaction is concluded to proceed via two coupled steps following a Mars-van-Krevelen-mechanism at the solid-liquid and gas-liquid interface. The dissociation of O2 and/or the oxidation of Cl(-) at the melt-solid interface is concluded to have the lowest forward rate constants. The compositions of the oxide core and the molten chloride shell control the catalytic activity via the redox potential of the metal oxide and of the OCl(-). Traces of water may be present in the molten chloride under reaction conditions, but the specific impact of this water is not obvious at present. The spatial separation of oxygen and ethane activation sites and the dynamic rearrangement of the surface anions and cations, preventing the exposure of coordinatively unsaturated cations, are concluded to be the origin of the surprisingly high olefin selectivity. PMID:25118821

  3. Catalyst support of mixed cerium zirconium titanium oxide, including use and method of making

    DOEpatents

    Willigan, Rhonda R.; Vanderspurt, Thomas Henry; Tulyani, Sonia; Radhakrishnan, Rakesh; Opalka, Susanne Marie; Emerson, Sean C.

    2011-01-18

    A durable catalyst support/catalyst is capable of extended water gas shift operation under conditions of high temperature, pressure, and sulfur levels. The support is a homogeneous, nanocrystalline, mixed metal oxide of at least three metals, the first being cerium, the second being Zr, and/or Hf, and the third importantly being Ti, the three metals comprising at least 80% of the metal constituents of the mixed metal oxide and the Ti being present in a range of 5% to 45% by metals-only atomic percent of the mixed metal oxide. The mixed metal oxide has an average crystallite size less than 6 nm and forms a skeletal structure with pores whose diameters are in the range of 4-9 nm and normally greater than the average crystallite size. The surface area of the skeletal structure per volume of the material of the structure is greater than about 240 m.sup.2/cm.sup.3. The method of making and use are also described.

  4. 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.

  5. Laser Synthesis of Supported Catalysts for Carbon Nanotubes

    NASA Technical Reports Server (NTRS)

    VanderWal, Randall L.; Ticich, Thomas M.; Sherry, Leif J.; Hall, Lee J.; Schubert, Kathy (Technical Monitor)

    2003-01-01

    Four methods of laser assisted catalyst generation for carbon nanotube (CNT) synthesis have been tested. These include pulsed laser transfer (PLT), photolytic deposition (PLD), photothermal deposition (PTD) and laser ablation deposition (LABD). Results from each method are compared based on CNT yield, morphology and structure. Under the conditions tested, the PLT was the easiest method to implement, required the least time and also yielded the best pattemation. The photolytic and photothermal methods required organometallics, extended processing time and partial vacuums. The latter two requirements also held for the ablation deposition approach. In addition to control of the substrate position, controlled deposition duration was necessary to achieve an active catalyst layer. Although all methods were tested on both metal and quartz substrates, only the quartz substrates proved to be inactive towards the deposited catalyst particles.

  6. Microbial recovery of metals from spent coal liquefaction catalysts

    SciTech Connect

    Sperl, P.L.; Sperl, G.T.

    1991-01-01

    We have defined critical areas for further study. These arise out of the basic nature of both the microorganisms and the nature of catalysts. Whereas other catalysts not employing Mo or W would probably be readily leached by T. ferrooxidans and denitrifiers, those which contain these two metals require special attention and highly tolerant strains of T. ferrooxidans but not the denitrifiers to be realistically treated microbiologically. The alternative is to develop methods for the continuous removal of Mo as it is removed from the catalyst. We have preliminary data that show this to be technically feasible. The following are areas which need detailed study: to increase the molybdate tolerance of T. ferrooxidans, and to employ the metabolic actions of other microorganisms which may be better adapted to metal tolerances and sulfide scavenging.

  7. Polymer- and silica-supported iron BPMEN-inspired catalysts for C-H bond functionalization reactions.

    PubMed

    Feng, Yan; Moschetta, Eric G; Jones, Christopher W

    2014-11-01

    Direct catalytic C-H bond functionalization is a key challenge in synthetic chemistry, with many popular C-H activation methodologies involving precious-metal catalysts. In recent years, iron catalysts have emerged as a possible alternative to the more common precious-metal catalysts, owing to its high abundance, low cost, and low toxicity. However, iron catalysts are plagued by two key factors: the ligand cost and the low turnover numbers (TONs) typically achieved. In this work, two approaches are presented to functionalize the popular N(1),N(2)-dimethyl-N(1),N(2)-bis(pyridin-2-ylmethyl)ethane-1,2-diamine (BPMEN) ligand, so that it can be supported on porous silica or polymer resin supports. Four new catalysts are prepared and evaluated in an array of catalytic C-H functionalization reactions by using cyclohexane, cyclohexene, cyclooctane, adamantane, benzyl alcohol, and cumene with aqueous hydrogen peroxide. Catalyst recovery and recycling is demonstrated by using supported catalysts, which allows for a modest increase in the TON achieved with these catalysts.

  8. Reducible oxide based catalysts

    DOEpatents

    Thompson, Levi T.; Kim, Chang Hwan; Bej, Shyamal K.

    2010-04-06

    A catalyst is disclosed herein. The catalyst includes a reducible oxide support and at least one noble metal fixed on the reducible oxide support. The noble metal(s) is loaded on the support at a substantially constant temperature and pH.

  9. 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.

  10. Metal complexes of substituted Gable porphyrins as oxidation catalysts

    DOEpatents

    Lyons, James E.; Ellis, Jr., Paul E.; Wagner, Richard W.

    1996-01-01

    Transition metal complexes of Gable porphyrins having two porphyrin rings connected through a linking group, and having on the porphyrin rings electron-withdrawing groups, such as halogen, nitro or cyano. These complexes are useful as catalysts for the oxidation of organic compounds, e.g. alkanes.

  11. Metal complexes of substituted Gable porphyrins as oxidation catalysts

    DOEpatents

    Lyons, J.E.; Ellis, P.E. Jr.; Wagner, R.W.

    1996-01-02

    Transition metal complexes of Gable porphyrins are disclosed having two porphyrin rings connected through a linking group, and having on the porphyrin rings electron-withdrawing groups, such as halogen, nitro or cyano. These complexes are useful as catalysts for the oxidation of organic compounds, e.g. alkanes.

  12. Preparation of highly dispersed NiMo catalysts supported on carbon black particles of hollow spheres

    SciTech Connect

    Sakanishi, K.; Hasuo, H.; Mochida, I.

    1995-12-01

    One of unique carbon blacks, Ketjen Black (KB) which has extremely high surface area and low specific gravity, was selected as a catalyst support to prepare a highly dispersed NiMo catalyst with the function for recovery and the high activity for hydrogenation. KB-supported NiMo catalysts were prepared by means of impregnation, ion exchange, and incipient wetness methods from various kinds and amounts of Ni and Mo salts, and their activities were examined in the hydrogenation of 1-methyinaphthalene(1-MN) using a magnetic-stirred autoclave of 50 ml capacity at 380{degrees}C for 40 min under 10 MPa H{sub 2} reaction pressure. The catalyst, prepared from (NH{sub 4}){sub 2}MoS{sub 4} and Ni(OAc){sub 2} in their methanol solution by successive impregnations of Mo10% and Ni(2 wt%) in this order supported on nitric acid-treated carbon black(KB JD-O), provided the highest conversion of 86% to methyl-tetralins. Combinations of metal salts soluble in organic solvent, impregnation solvents, and surface properties of carbon black are suggested to be important for the preparation of highly active catalysts with higher dispersions of Ni and Mo on the carbon black, because they are easily agglomerated in impregnation solvent. It is also noted that KB-supported NiMo catalysts showed much higher activity for the hydrogenation than a commercial NiMo/Al{sub 2}O{sub 3} with the smaller weight of catalyst.

  13. Crystal structures of Ziegler-Natta catalyst supports.

    PubMed

    Malizia, Federica; Fait, Anna; Cruciani, Giuseppe

    2011-12-01

    The crystal structures of three MgCl(2)·nEtOH complexes with n=1.5, 2.8, and 3.3 have been fully determined. Such complexes are the fundamental precursors for Ziegler-Natta polymerization catalysts used to produce polyolefins on a multimillion-ton scale worldwide. The ab initio structure solution showed that the structure of MgCl(2)·nEtOH complexes with n=1.5 and 2.8 are based on ribbons of metal-centered octahedra, whereas for n=3.3 this chainlike arrangement breaks into a threadlike structure of isolated octahedra linked by hydrogen bonds. A clear correlation between catalyst performance and the crystal structure of precursors has been found, and reveals the fundamental role of the latter in determining catalyst properties. The direct knowledge of building blocks in the precursor structures will help to develop more accurate models for activated catalysts. These models will not require the arbitrary and oversimplified assumption of locating the catalyst active sites on selected cut surfaces of the α-MgCl(2) crystal lattice. PMID:22052708

  14. Supporting PtRu catalysts on various types of carbon nanomaterials for fuel cell applications

    NASA Astrophysics Data System (ADS)

    Suda, Yoshiyuki; Ozaki, Masahiro; Tanoue, Hideto; Takikawa, Hirofumi; Ue, Hitoshi; Shimizu, Kazuki; Muramoto, Hirokazu

    2013-04-01

    PtRu catalysts were supported on five types of carbon nanomaterials of various shapes, sizes, and graphitic properties and the catalyst supports evaluated. The carbon nanomaterial used included three types of nanoparticles: Arc Black (AcB), Vulcan XC-72 (Vulcan) and graphene oxide (GO), and two types of nanofibers: carbon nanocoil (CNC) and carbon nanotube (CNT). Pt and Ru were supported by the reduction method using sodium borohydride. The metal catalyst loading was confirmed by thermo-gravimetric analysis (TGA), electron microscopy, and X-ray diffraction (XRD). Transmission electron microscopy (TEM) and XRD revealed that the diameter of PtRu catalyst nanoparticles loaded on reduced GO (rGO) and AcB were ~2 nm and was the smallest among all the samples. Shifts in Pt (111) XRD peaks of CNC and CNT were larger than those of AcB, Vulcan, and rGO. These results suggest that the diameters of catalyst nanoparticles became smaller by loading on the carbon nanoparticles with a large surface area including rGO, AcB, and Vulcan. Loading onto the carbon nanofibers enhanced the degree of PtRu alloying.

  15. IR and XPS study of NO and CO interaction with palladium catalysts supported on aluminosilicates

    SciTech Connect

    Venezia, A.M.; Liotta, L.F.; Deganello, G. |; Terreros, P.; Pena, M.A.; Fierro, J.L.G.

    1999-02-16

    Adsorption of CO and NO individually and as a mixture of both on palladium catalysts has been investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The effect of sodium ions has been considered by comparing Pd/SiO{sub 2} catalyst, sodium-doped Pd/SiO{sub 2}, and Pd on natural and synthetic silicoaluminates containing sodium in their bulk structure but differing in the surface area of the support. The presence of sodium induces a different adsorption behavior depending on its location, either at the surface of the catalysts or inside the support structure. As a consequence, different species are formed from the reaction between NO and CO at room temperature and at high temperature. Modification of the metal surface of the various catalysts is observed upon the gas treatments. Palladium is oxidized to a certain extent depending on the type of the catalyst support. Moreover, different chemical states of the adsorbed nitrogen species are found.

  16. Identifying the role of N-heteroatom location in the activity of metal catalysts for alcohol oxidation

    SciTech Connect

    Chan-Thaw, Carine E.; Veith, Gabriel M.; Villa, Alberto; Prati, Laura

    2015-04-02

    Here, this work focuses on understanding how the bonding of nitrogen heteroatoms contained on/in a activated carbon support influence the stability and reactivity of a supported Pd catalyst for the oxidation of alcohols in solution. The results show that simply adding N groups via solution chemistry is insufficient to improve catalytic properties. Instead a strongly bound N moiety is required to activate the catalyst and stabilize the metal particles.

  17. Nickel supported on nitrogen-doped carbon nanotubes as hydrogen oxidation reaction catalyst in alkaline electrolyte.

    PubMed

    Zhuang, Zhongbin; Giles, Stephen A; Zheng, Jie; Jenness, Glen R; Caratzoulas, Stavros; Vlachos, Dionisios G; Yan, Yushan

    2016-01-14

    The development of a low-cost, high-performance platinum-group-metal-free hydroxide exchange membrane fuel cell is hindered by the lack of a hydrogen oxidation reaction catalyst at the anode. Here we report that a composite catalyst, nickel nanoparticles supported on nitrogen-doped carbon nanotubes, has hydrogen oxidation activity similar to platinum-group metals in alkaline electrolyte. Although nitrogen-doped carbon nanotubes are a very poor hydrogen oxidation catalyst, as a support, it increases the catalytic performance of nickel nanoparticles by a factor of 33 (mass activity) or 21 (exchange current density) relative to unsupported nickel nanoparticles. Density functional theory calculations indicate that the nitrogen-doped support stabilizes the nanoparticle against reconstruction, while nitrogen located at the edge of the nanoparticle tunes local adsorption sites by affecting the d-orbitals of nickel. Owing to its high activity and low cost, our catalyst shows significant potential for use in low-cost, high-performance fuel cells.

  18. Nickel supported on nitrogen-doped carbon nanotubes as hydrogen oxidation reaction catalyst in alkaline electrolyte.

    PubMed

    Zhuang, Zhongbin; Giles, Stephen A; Zheng, Jie; Jenness, Glen R; Caratzoulas, Stavros; Vlachos, Dionisios G; Yan, Yushan

    2016-01-01

    The development of a low-cost, high-performance platinum-group-metal-free hydroxide exchange membrane fuel cell is hindered by the lack of a hydrogen oxidation reaction catalyst at the anode. Here we report that a composite catalyst, nickel nanoparticles supported on nitrogen-doped carbon nanotubes, has hydrogen oxidation activity similar to platinum-group metals in alkaline electrolyte. Although nitrogen-doped carbon nanotubes are a very poor hydrogen oxidation catalyst, as a support, it increases the catalytic performance of nickel nanoparticles by a factor of 33 (mass activity) or 21 (exchange current density) relative to unsupported nickel nanoparticles. Density functional theory calculations indicate that the nitrogen-doped support stabilizes the nanoparticle against reconstruction, while nitrogen located at the edge of the nanoparticle tunes local adsorption sites by affecting the d-orbitals of nickel. Owing to its high activity and low cost, our catalyst shows significant potential for use in low-cost, high-performance fuel cells. PMID:26762466

  19. Nickel supported on nitrogen-doped carbon nanotubes as hydrogen oxidation reaction catalyst in alkaline electrolyte

    PubMed Central

    Zhuang, Zhongbin; Giles, Stephen A.; Zheng, Jie; Jenness, Glen R.; Caratzoulas, Stavros; Vlachos, Dionisios G.; Yan, Yushan

    2016-01-01

    The development of a low-cost, high-performance platinum-group-metal-free hydroxide exchange membrane fuel cell is hindered by the lack of a hydrogen oxidation reaction catalyst at the anode. Here we report that a composite catalyst, nickel nanoparticles supported on nitrogen-doped carbon nanotubes, has hydrogen oxidation activity similar to platinum-group metals in alkaline electrolyte. Although nitrogen-doped carbon nanotubes are a very poor hydrogen oxidation catalyst, as a support, it increases the catalytic performance of nickel nanoparticles by a factor of 33 (mass activity) or 21 (exchange current density) relative to unsupported nickel nanoparticles. Density functional theory calculations indicate that the nitrogen-doped support stabilizes the nanoparticle against reconstruction, while nitrogen located at the edge of the nanoparticle tunes local adsorption sites by affecting the d-orbitals of nickel. Owing to its high activity and low cost, our catalyst shows significant potential for use in low-cost, high-performance fuel cells. PMID:26762466

  20. Nickel supported on nitrogen-doped carbon nanotubes as hydrogen oxidation reaction catalyst in alkaline electrolyte

    DOE PAGES

    Zhuang, Zhongbin; Giles, Stephen A.; Zheng, Jie; Jenness, Glen R.; Caratzoulas, Stavros; Vlachos, Dionisios G.; Yan, Yushan

    2016-01-14

    The development of a low-cost, high-performance platinum-group-metal-free hydroxide exchange membrane fuel cell is hindered by the lack of a hydrogen oxidation reaction catalyst at the anode. Here we report that a composite catalyst, nickel nanoparticles supported on nitrogen-doped carbon nanotubes, has hydrogen oxidation activity similar to platinum-group metals in alkaline electrolyte. Although nitrogen-doped carbon nanotubes are a very poor hydrogen oxidation catalyst, as a support, it increases the catalytic performance of nickel nanoparticles by a factor of 33 (mass activity) or 21 (exchange current density) relative to unsupported nickel nanoparticles. Density functional theory calculations indicate that the nitrogen-doped support stabilizesmore » the nanoparticle against reconstruction, while nitrogen located at the edge of the nanoparticle tunes local adsorption sites by affecting the d-orbitals of nickel. Here, owing to its high activity and low cost, our catalyst shows significant potential for use in low-cost, high-performance fuel cells.« less

  1. Nickel supported on nitrogen-doped carbon nanotubes as hydrogen oxidation reaction catalyst in alkaline electrolyte

    NASA Astrophysics Data System (ADS)

    Zhuang, Zhongbin; Giles, Stephen A.; Zheng, Jie; Jenness, Glen R.; Caratzoulas, Stavros; Vlachos, Dionisios G.; Yan, Yushan

    2016-01-01

    The development of a low-cost, high-performance platinum-group-metal-free hydroxide exchange membrane fuel cell is hindered by the lack of a hydrogen oxidation reaction catalyst at the anode. Here we report that a composite catalyst, nickel nanoparticles supported on nitrogen-doped carbon nanotubes, has hydrogen oxidation activity similar to platinum-group metals in alkaline electrolyte. Although nitrogen-doped carbon nanotubes are a very poor hydrogen oxidation catalyst, as a support, it increases the catalytic performance of nickel nanoparticles by a factor of 33 (mass activity) or 21 (exchange current density) relative to unsupported nickel nanoparticles. Density functional theory calculations indicate that the nitrogen-doped support stabilizes the nanoparticle against reconstruction, while nitrogen located at the edge of the nanoparticle tunes local adsorption sites by affecting the d-orbitals of nickel. Owing to its high activity and low cost, our catalyst shows significant potential for use in low-cost, high-performance fuel cells.

  2. Low Temperature Activation of Supported Metathesis Catalysts by Organosilicon Reducing Agents.

    PubMed

    Mougel, Victor; Chan, Ka-Wing; Siddiqi, Georges; Kawakita, Kento; Nagae, Haruki; Tsurugi, Hayato; Mashima, Kazushi; Safonova, Olga; Copéret, Christophe

    2016-08-24

    Alkene metathesis is a widely and increasingly used reaction in academia and industry because of its efficiency in terms of atom economy and its wide applicability. This reaction is notably responsible for the production of several million tons of propene annually. Such industrial processes rely on inexpensive silica-supported tungsten oxide catalysts, which operate at high temperatures (>350 °C), in contrast with the mild room temperature reaction conditions typically used with the corresponding molecular alkene metathesis homogeneous catalysts. This large difference in the temperature requirements is generally thought to arise from the difficulty in generating active sites (carbenes or metallacyclobutanes) in the classical metal oxide catalysts and prevents broader applicability, notably with functionalized substrates. We report here a low temperature activation process of well-defined metal oxo surface species using organosilicon reductants, which generate a large amount of active species at only 70 °C (0.6 active sites/W). This high activity at low temperature broadens the scope of these catalysts to functionalized substrates. This activation process can also be applied to classical industrial catalysts. We provide evidence for the formation of a metallacyclopentane intermediate and propose how the active species are formed.

  3. Low Temperature Activation of Supported Metathesis Catalysts by Organosilicon Reducing Agents

    PubMed Central

    2016-01-01

    Alkene metathesis is a widely and increasingly used reaction in academia and industry because of its efficiency in terms of atom economy and its wide applicability. This reaction is notably responsible for the production of several million tons of propene annually. Such industrial processes rely on inexpensive silica-supported tungsten oxide catalysts, which operate at high temperatures (>350 °C), in contrast with the mild room temperature reaction conditions typically used with the corresponding molecular alkene metathesis homogeneous catalysts. This large difference in the temperature requirements is generally thought to arise from the difficulty in generating active sites (carbenes or metallacyclobutanes) in the classical metal oxide catalysts and prevents broader applicability, notably with functionalized substrates. We report here a low temperature activation process of well-defined metal oxo surface species using organosilicon reductants, which generate a large amount of active species at only 70 °C (0.6 active sites/W). This high activity at low temperature broadens the scope of these catalysts to functionalized substrates. This activation process can also be applied to classical industrial catalysts. We provide evidence for the formation of a metallacyclopentane intermediate and propose how the active species are formed. PMID:27610418

  4. Low Temperature Activation of Supported Metathesis Catalysts by Organosilicon Reducing Agents.

    PubMed

    Mougel, Victor; Chan, Ka-Wing; Siddiqi, Georges; Kawakita, Kento; Nagae, Haruki; Tsurugi, Hayato; Mashima, Kazushi; Safonova, Olga; Copéret, Christophe

    2016-08-24

    Alkene metathesis is a widely and increasingly used reaction in academia and industry because of its efficiency in terms of atom economy and its wide applicability. This reaction is notably responsible for the production of several million tons of propene annually. Such industrial processes rely on inexpensive silica-supported tungsten oxide catalysts, which operate at high temperatures (>350 °C), in contrast with the mild room temperature reaction conditions typically used with the corresponding molecular alkene metathesis homogeneous catalysts. This large difference in the temperature requirements is generally thought to arise from the difficulty in generating active sites (carbenes or metallacyclobutanes) in the classical metal oxide catalysts and prevents broader applicability, notably with functionalized substrates. We report here a low temperature activation process of well-defined metal oxo surface species using organosilicon reductants, which generate a large amount of active species at only 70 °C (0.6 active sites/W). This high activity at low temperature broadens the scope of these catalysts to functionalized substrates. This activation process can also be applied to classical industrial catalysts. We provide evidence for the formation of a metallacyclopentane intermediate and propose how the active species are formed. PMID:27610418

  5. Low Temperature Activation of Supported Metathesis Catalysts by Organosilicon Reducing Agents

    PubMed Central

    2016-01-01

    Alkene metathesis is a widely and increasingly used reaction in academia and industry because of its efficiency in terms of atom economy and its wide applicability. This reaction is notably responsible for the production of several million tons of propene annually. Such industrial processes rely on inexpensive silica-supported tungsten oxide catalysts, which operate at high temperatures (>350 °C), in contrast with the mild room temperature reaction conditions typically used with the corresponding molecular alkene metathesis homogeneous catalysts. This large difference in the temperature requirements is generally thought to arise from the difficulty in generating active sites (carbenes or metallacyclobutanes) in the classical metal oxide catalysts and prevents broader applicability, notably with functionalized substrates. We report here a low temperature activation process of well-defined metal oxo surface species using organosilicon reductants, which generate a large amount of active species at only 70 °C (0.6 active sites/W). This high activity at low temperature broadens the scope of these catalysts to functionalized substrates. This activation process can also be applied to classical industrial catalysts. We provide evidence for the formation of a metallacyclopentane intermediate and propose how the active species are formed.

  6. Selective Ring Opening of 1-Methylnaphthalene Over NiW-Supported Catalyst Using Dealuminated Beta Zeolite.

    PubMed

    Kim, Eun-Sang; Lee, You-Jin; Kim, Jeong-Rang; Kim, Joo-Wan; Kim, Tae-Wan; Chae, Ho-Jeong; Kim, Chul-Ung; Lee, Chang-Ha; Jeong, Soon-Yong

    2016-02-01

    Nanoporous Beta zeolite was dealuminated by weak acid treatment for reducing the acidity. Bi-functional catalysts were prepared using commercial Beta zeolites and the dealuminated zeolites for acidic function, NiW for metallic function. 1-Methylnaphthalene was selected as a model compound for multi-ring aromatics in heavy oil, and its selective ring opening reaction has been investigated using the prepared bi-functional catalysts with different acidity in fixed bed reaction system. The dealuminated Beta zeolites, which crystal structure and nanoporosity were maintained, showed the higher SiO2/Al2O3 ratio and smaller acidity than their original zeolite. NiW-supported catalyst using the dealuminated Beta zeolite with SiO2/Al203 mole ratio of 55 showed the highest performance for the selective ring opening. The acidity of catalyst seemed to play an important role as active sites for the selective ring opening of 1-methylnaphthalene but there should be some optimum catalyst acidity for the reaction. The acidity of Beta zeolite could be controlled by the acid treatment and the catalyst with the optimum acidity for the selective ring opening could be prepared.

  7. Selective Ring Opening of 1-Methylnaphthalene Over NiW-Supported Catalyst Using Dealuminated Beta Zeolite.

    PubMed

    Kim, Eun-Sang; Lee, You-Jin; Kim, Jeong-Rang; Kim, Joo-Wan; Kim, Tae-Wan; Chae, Ho-Jeong; Kim, Chul-Ung; Lee, Chang-Ha; Jeong, Soon-Yong

    2016-02-01

    Nanoporous Beta zeolite was dealuminated by weak acid treatment for reducing the acidity. Bi-functional catalysts were prepared using commercial Beta zeolites and the dealuminated zeolites for acidic function, NiW for metallic function. 1-Methylnaphthalene was selected as a model compound for multi-ring aromatics in heavy oil, and its selective ring opening reaction has been investigated using the prepared bi-functional catalysts with different acidity in fixed bed reaction system. The dealuminated Beta zeolites, which crystal structure and nanoporosity were maintained, showed the higher SiO2/Al2O3 ratio and smaller acidity than their original zeolite. NiW-supported catalyst using the dealuminated Beta zeolite with SiO2/Al203 mole ratio of 55 showed the highest performance for the selective ring opening. The acidity of catalyst seemed to play an important role as active sites for the selective ring opening of 1-methylnaphthalene but there should be some optimum catalyst acidity for the reaction. The acidity of Beta zeolite could be controlled by the acid treatment and the catalyst with the optimum acidity for the selective ring opening could be prepared. PMID:27433655

  8. Supported Copper, Nickel and Copper-Nickel Nanoparticle Catalysts for Low Temperature Water-Gas-Shift Reaction

    NASA Astrophysics Data System (ADS)

    Lin, Jiann-Horng

    Hydrogen is being considered worldwide as a future replacement for gasoline, diesel fuel, natural gas in both the transportation and non-transportation sectors. Hydrogen is a versatile energy carrier that can be produced from a variety of widely available primary energy sources, including coal, natural gas, biomass, solar, wind, and nuclear power. Coal, the most abundant fossil fuel on the planet, is being looked at as the possible future major source of H2, due to the development of the integrated gasification combined cycle (IGCC) and integrated gasification fuel cell technologies (IGFC). The gasification of coal produces syngas consisting of predominately carbon monoxide and hydrogen with some remaining hydrocarbons, carbon dioxide and water. Then, the water-gas shift reaction is used to convert CO to CO2 and additional hydrogen. The present work describes the synthesis of model Cu, Ni and Cu-Ni catalysts prepared from metal colloids, and compares their behavior in the WGS reaction to that of traditional impregnation catalysts. Initially, we systematically explored the performance of traditional Cu, Ni and Cu-Ni WGS catalysts made by impregnation methods. Various bimetallic Cu-Ni catalysts were prepared by supported impregnation and compared to monometallic Cu and Ni catalysts. The presence of Cu in bimetallic catalysts suppressed undesirable methanation side reaction, while the Ni component was important for high WGS activity. Colloidal Cu, Ni and Cu-Ni alloy nanoparticles obtained by chemical reduction were deposited onto alumina to prepare supported catalysts. The resulting Cu and Ni nanoparticle catalysts were found to be 2.5 times more active in the WGS reaction per unit mass of active metal as compared to catalysts prepared by the conventional impregnation technique. The powder XRD and HAADF-STEM provided evidence supporting the formation of Cu-Ni particles containing the Cu core and Cu-Ni alloy shell. The XPS data indicated surface segregation of Cu in

  9. CATALYTIC OXIDATION OF DIMETHYL SULFIDE WITH OZONE: EFFECT OF PROMOTER AND PHYSICO-CHEMICAL PROPERTIES OF METAL OXIDE CATALYSTS

    EPA Science Inventory

    This study reports improved catalytic activities and stabilities for the oxidation of dimethyl sulfide (DMS), a major pollutant of pulp and paper mills. Ozone was used as an oxidant and Cu, Mo, V, Cr and Mn metal oxides, and mixed metal oxides support on y-alumina as catalysts ov...

  10. Toward "metalloMOFzymes": Metal-Organic Frameworks with Single-Site Metal Catalysts for Small-Molecule Transformations.

    PubMed

    Cohen, Seth M; Zhang, Zhenjie; Boissonnault, Jake A

    2016-08-01

    Metal-organic frameworks (MOFs) are being increasingly studied as scaffolds and supports for catalysis. The solid-state structures of MOFs, combined with their high porosity, suggest that MOFs may possess advantages shared by both heterogeneous and homogeneous catalysts, with few of the shortcomings of either. Herein, efforts to create single-site catalytic metal centers appended to the organic ligand struts of MOFs will be discussed. Reactions important for advanced energy applications, such as H2 production and CO2 reduction, will be highlighted. Examining how these active sites can be introduced, their performance, and their existing limitations should provide direction for design of the next generation of MOF-based catalysts for energy-relevant, small-molecule transformations. Finally, the introduction of second-sphere interactions (e.g., hydrogen bonding via squaramide groups) as a possible route to enhancing the activity of these metal centers is reported. PMID:27231968

  11. Metal-Organic Frameworks as Catalysts for Oxidation Reactions.

    PubMed

    Dhakshinamoorthy, Amarajothi; Asiri, Abdullah M; Garcia, Hermenegildo

    2016-06-01

    This Concept is aimed at describing the current state of the art in metal-organic frameworks (MOFs) as heterogeneous catalysts for liquid-phase oxidations, focusing on three important substrates, namely, alkenes, alkanes and alcohols. Emphases are on the nature of active sites that have been incorporated within MOFs and on future targets to be set in this area. Thus, selective alkene epoxidation with peroxides or oxygen catalyzed by constitutional metal nodes of MOFs as active sites are still to be developed. Moreover, no noble metal-free MOF has been reported to date that can act as a general catalyst for the aerobic oxidation of primary and secondary aliphatic alcohols. In contrast, in the case of alkanes, a target should be to tune the polarity of MOF internal pores to control the outcome of the autooxidation process, resulting in the selective formation of alcohol/ketone mixtures at high conversion.

  12. Polymer - supported cobalt (II) catalysts for the oxidation of alkenes.

    PubMed

    Błaz, Edyta; Pielichowski, Jan

    2006-01-31

    Polymer-supported heterogeneous catalysts in a form of complexes of 8-hydroxy- quinoline with cobalt acetate were synthesized. Conjugated polymers - polyaniline (PANI), poly-o-toluidine (POT), poly-o-anisidine (POA) - were used as supports. Oxidation reactions of aliphatic and aromatic hydrocarbons were carried out in the presence of molecular oxygen at atmospheric pressure and epoxides or ketones were obtained as the main products with high selectivity.

  13. Metal catalyst technique for texturing silicon solar cells

    DOEpatents

    Ruby, Douglas S.; Zaidi, Saleem H.

    2001-01-01

    Textured silicon solar cells and techniques for their manufacture utilizing metal sources to catalyze formation of randomly distributed surface features such as nanoscale pyramidal and columnar structures. These structures include dimensions smaller than the wavelength of incident light, thereby resulting in a highly effective anti-reflective surface. According to the invention, metal sources present in a reactive ion etching chamber permit impurities (e.g. metal particles) to be introduced into a reactive ion etch plasma resulting in deposition of micro-masks on the surface of a substrate to be etched. Separate embodiments are disclosed including one in which the metal source includes one or more metal-coated substrates strategically positioned relative to the surface to be textured, and another in which the walls of the reaction chamber are pre-conditioned with a thin coating of metal catalyst material.

  14. Hydrodenitrogenation of quinoline over carbon-supported transition metal sulfides

    SciTech Connect

    Eijsbouts, S.; De Beer, V.H.J.; Prins, R. )

    1991-02-01

    Transition metal sulfide (TMS) catalysts were prepared by impregnation of an activated carbon support with aqueous solutions of first-, second-, and third-row (group V-VIII) transition metal salts, drying and in situ sulfidation. The catalysts were tested in the hydrodenitrogenation of quinoline (653 K, 5.5 MPa) in microautoclaves and microflow reactors. The first-row transition metal sulfides had low quinoline conversions to hydrocarbons, and their periodic trend formed a U-shaped curve with a minimum at Mn/C and Fe/C and maxima at V/C and Ni/C. The quinoline conversions to hydrocarbons of the second- and third-row TMS formed volcano curves with maxima at Rh/C and Ir/C and with Mo/C and W/C having the lowest conversions. The transition metal sulfide catalysts with a low quinoline hydrogenation (first-row transition metal sulfides, Mo/C and W/C) also had a low quinoline conversion to hydrocarbons. The transition metal sulfides with the highest quinoline conversions to hydrocarbons (Rh/C, Pd/C, Os/C, Ir/C and Pt/C) had a very highquinoline hydrogenation and a high selectivity for propylcyclohexane. Ru/C and especially Re/C had a good quinoline conversion to hydrocarbons, but also an exceptionally high selectivity for propylbenzene.

  15. Textured catalysts and methods of making textured catalysts

    DOEpatents

    Werpy, Todd; Frye, Jr., John G.; Wang, Yong; Zacher, Alan H.

    2007-03-06

    A textured catalyst having a hydrothermally-stable support, a metal oxide and a catalyst component is described. Methods of conducting aqueous phase reactions that are catalyzed by a textured catalyst are also described. The invention also provides methods of making textured catalysts and methods of making chemical products using a textured catalyst.

  16. The effect of alkylating agents on model supported metal clusters

    SciTech Connect

    Erdem-Senatalar, A.; Blackmond, D.G.; Wender, I. . Dept. of Chemical and Petroleum Engineering); Oukaci, R. )

    1988-01-01

    Interactions between model supported metal clusters and alkylating agents were studied in an effort to understand a novel chemical trapping technique developed for identifying species adsorbed on catalyst surfaces. It was found that these interactions are more complex than had previously been suggested. Studies were completed using deuterium-labeled dimethyl sulfate (DMS), (CH{sub 3}){sub 2}SO{sub 4}, as a trapping agent to interact with the supported metal cluster ethylidyne tricobalt enneacarbonyl. Results showed that oxygenated products formed during the trapping reaction contained {minus}OCD{sub 3} groups from the DMS, indicating that the interaction was not a simple alkylation. 18 refs., 1 fig., 3 tabs.

  17. Charge Transfer and Catalysis at the Metal Support Interface

    SciTech Connect

    Baker, Lawrence Robert

    2012-07-31

    Kinetic, electronic, and spectroscopic characterization of model Pt–support systems are used to demonstrate the relationship between charge transfer and catalytic activity and selectivity. The results show that charge flow controls the activity and selectivity of supported metal catalysts. This dissertation builds on extensive existing knowledge of metal–support interactions in heterogeneous catalysis. The results show the prominent role of charge transfer at catalytic interfaces to determine catalytic activity and selectivity. Further, this research demonstrates the possibility of selectively driving catalytic chemistry by controlling charge flow and presents solid-state devices and doped supports as novel methods for obtaining electronic control over catalytic reaction kinetics.

  18. Homogeneous and Supported Niobium Catalysts as Lewis Acid and Radical Catalysts

    SciTech Connect

    Wayne Tikkanen

    2006-12-31

    The synthesis of tetrachlorotetraphenylcyclopentadienyl group 5 metal complexes has been accomplished through two routes, one a salt metathesis with lithiumtetraphenylcyclopentadiende and the other, reaction with trimethyltintetraphenylcyclopentadiene. The reactants and products have been characterized by {sup 1}H and {sup 13}C({sup 1}H) NMR spectroscopy. The niobium complex promotes the silylcyanation of butyraldehyde. The grafting of metal complexes to silica gel surfaces has been accomplished using tetrakisdimethylamidozirconium as the metal precursor. The most homogeneous binding as determined by CP-MAS {sup 13}C NMR and infrared spectroscopy was obtained with drying at 500 C at 3 mtorr vacuum. The remaining amido groups can be replaced by reaction with alcohols to generate surface bound metal alkoxides. These bound catalysts promote silylcyanation of aryl aldehydes and can be reused three times with no loss of activity.

  19. Methods of making textured catalysts

    DOEpatents

    Werpy, Todd; Frye, Jr., John G.; Wang, Yong; Zacher, Alan H.

    2010-08-17

    A textured catalyst having a hydrothermally-stable support, a metal oxide and a catalyst component is described. Methods of conducting aqueous phase reactions that are catalyzed by a textured catalyst are also described. The invention also provides methods of making textured catalysts and methods of making chemical products using a textured catalyst.

  20. Formation and Characterization of Ni Nanofiber Catalysts on Nickel Metallic Foam by Electrospinning Process.

    PubMed

    Yeom, Hee Chul; Moon, Dong Ju; Lee, Kwan Young; Kim, Sang Woo

    2015-07-01

    We report the fabrication of nickel nanofiber catalysts supported on nickel metallic foam using a modified electrospinning with a grounded rotor and sequential reduction process. The robust deposition of aligned Ni nanofibers with a uniform morphology on the highly porous surfaces of the metallic foam could be achieved by controlling electrospinning parameters such as applied voltage, tip-collector-distance (TCD), concentration of polymer, and humidity. The diameters of the obtained nanofibers decreased with increasing voltage and TCDs. The uniform and thinnest Ni nanofibers on the Ni foam were obtained at a humidity of less than 30%, 15 kV applied voltage, and 17 cm TCD when using a precursor composed of nickel nitrate salt and poly(vinyl) pyrrolidone. The Ni foam catalyst support exhibited the superior thermal conducting property than other supports of MgO-MgAl2O4, Al2O3, and SiC, enabling to a higher heat transfer during catalytic reaction. As a result, the Ni nanofiber catalyst with a high surface area and superior heat transfer performance, which is supported on the metallic foam, were successfully fabricated via a modified electrospinning for potential application of XTL process converting anything to liquids, such as for Gas-to-Liquid (GTL), Coal-to-Liquid (CTL), and Biomass-to-Liquid (BTL).

  1. Replacing precious metals with carbide catalysts for hydrogenation reactions

    DOE PAGES

    Ruijun, Hou; Chen, Jingguang G.; Chang, Kuan; Wang, Tiefeng

    2015-03-03

    Molybdenum carbide (Mo₂C and Ni/Mo₂C) catalysts were compared with Pd/SiO₂ for the hydrogenation of several diene molecules, 1,3- butadiene, 1,3- and 1,4-cyclohexadiene (CHD). Compared to Pd/SiO₂, Mo₂C showed similar hydrogenation rate for 1,3-butadiene and 1,3-CHD and even higher rate for 1,4-CHD, but with significant deactivation rate for 1,3-CHD hydrogenation. However, the hydrogenation activity of Mo₂C could be completely regenerated by H₂ treatment at 723 K for the three molecules. The Ni modified Mo₂C catalysts retained similar activity for 1,3-butadiene hydrogenation with significantly enhanced selectivity for 1-butene production. The 1-butene selectivity increased with increasing Ni loading below 15%. Among the Nimore » modified Mo₂C catalysts, 8.6%Ni/Mo₂C showed the highest selectivity to 1-butene, which was even higher selectivity than that over Pd/SiO₂. Compared to Pd/SiO₂, both Mo₂C and Ni/Mo₂C showed combined advantages in hydrogenation activity and catalyst cost reduction, demonstrating the potential to use less expensive carbide catalysts to replace precious metals for hydrogenation reactions.« less

  2. Replacing precious metals with carbide catalysts for hydrogenation reactions

    SciTech Connect

    Ruijun, Hou; Chen, Jingguang G.; Chang, Kuan; Wang, Tiefeng

    2015-03-03

    Molybdenum carbide (Mo₂C and Ni/Mo₂C) catalysts were compared with Pd/SiO₂ for the hydrogenation of several diene molecules, 1,3- butadiene, 1,3- and 1,4-cyclohexadiene (CHD). Compared to Pd/SiO₂, Mo₂C showed similar hydrogenation rate for 1,3-butadiene and 1,3-CHD and even higher rate for 1,4-CHD, but with significant deactivation rate for 1,3-CHD hydrogenation. However, the hydrogenation activity of Mo₂C could be completely regenerated by H₂ treatment at 723 K for the three molecules. The Ni modified Mo₂C catalysts retained similar activity for 1,3-butadiene hydrogenation with significantly enhanced selectivity for 1-butene production. The 1-butene selectivity increased with increasing Ni loading below 15%. Among the Ni modified Mo₂C catalysts, 8.6%Ni/Mo₂C showed the highest selectivity to 1-butene, which was even higher selectivity than that over Pd/SiO₂. Compared to Pd/SiO₂, both Mo₂C and Ni/Mo₂C showed combined advantages in hydrogenation activity and catalyst cost reduction, demonstrating the potential to use less expensive carbide catalysts to replace precious metals for hydrogenation reactions.

  3. Resonance Raman Spectroscopy of 0-A12O3- Supported Vanadium Oxide Catalysts for Butane Dehydrogenation

    SciTech Connect

    Wu, Zili; Kim, Hack-Sung; Stair, Peter

    2008-01-01

    This chapter contains sections titled: Introduction; Structure of Al{sub 2}O{sub 3}-Supported Vanadia Catalysts; Quantification of Surface VOx Species on Supported Vanadia Catalysts; Conclusion; Acknowledgements; and References.

  4. Heavy oil hydroprocessing with group VI metal slurry catalyst

    SciTech Connect

    Lopez, J.; Pasek, E.A.

    1989-08-15

    This patent describes a process comprising the preparation of a dispersed Group VIB metal sulfide hydrocarbon oil hydroprocessing catalyst. It comprises reacting ammonia and a Group of VIB metal compound in water to form an aqueous ammonium Group VIB metal compounds, reacting aqueous ammonium Group VIB metal compounds with hydrogen sulfide essentially in the absence of feed oil in a low temperature sulfiding step at a temperature in the range 70{sup 0} to 350{sup 0}F, continuing the reaction of aqueous ammonium Group VIB metal compound with hydrogen sulfide in an intermediate temperature sulfiding step at a temperature in the range 180{sup 0} to 700{sup 0}F which is higher than the temperature in the low temperature sulfiding step and essentially without feed oil, with drawing an aqueous effluent stream from the intermediate temperature sulfiding step, passing the effluent stream to a separator zone, removing ammonia from the aqueous effluent stream in the separator zone leaving a separator residue, passing the separator residue together with feed hydrocarbon oil and hydrogen sulfide to a high temperature sulfiding step at a temperature in the range 500{sup 0} to 750{sup 0}F which is higher than the temperature in the intermediate temperature sulfiding step, the residence time in each of the sulfiding steps being at least 0.02 hours, withdrawing from the high temperature sulfiding step an aqueous-oil-slurry containing dispersed group VIB metal sulfide slurry catalyst.

  5. DIRECT DECOMPOSITION OF METHANE TO HYDROGEN ON METAL LOADED ZEOLITE CATALYST

    SciTech Connect

    Lucia M. Petkovic; Daniel M. Ginosar; Kyle C. Burch; Harry W. Rollins

    2005-08-01

    The manufacture of hydrogen from natural gas is essential for the production of ultra clean transportation fuels. Not only is hydrogen necessary to upgrade low quality crude oils to high-quality, low sulfur ultra clean transportation fuels, hydrogen could eventually replace gasoline and diesel as the ultra clean transportation fuel of the future. Currently, refinery hydrogen is produced through the steam reforming of natural gas. Although efficient, the process is responsible for a significant portion of refinery CO2 emissions. This project is examining the direct catalytic decomposition of methane as an alternative to steam reforming. The energy required to produce one mole of hydrogen is slightly lower and the process does not require water-gas-shift or pressure-swing adsorption units. The decomposition process does not produce CO2 emissions and the product is not contaminated with CO -- a poison for PEM fuel cells. In this work we examined the direct catalytic decomposition of methane over a metal modified zeolite catalyst and the recovery of catalyst activity by calcination. A favorable production of hydrogen was obtained, when compared with previously reported nickel-zeolite supported catalysts. Reaction temperature had a strong influence on catalyst activity and on the type of carbon deposits. The catalyst utilized at 873 and 973 K could be regenerated without any significant loss of activity, however the catalyst utilized at 1073 K showed some loss of activity after regeneration.

  6. Surface chemistry of metal catalyst under carbon nanotube growth conditions

    NASA Astrophysics Data System (ADS)

    Back, Tyson Cody

    The catalyst nanoparticle is critical to the yield, type, and diameter in the growth and nucleation of carbon nanotubes. The objective of this study is focused on determining what changes take place with the catalyst chemistry under growth conditions typically seen in chemical vapor deposition, CVD, experiments. It is well known that catalyst poisoning can occur and in turn effects the catalytic activity of the nanoparticle. A complete description of this mechanism is as of yet undetermined. In order to elucidate this process iron films were deposited onto Si substrates that contained a support layer of Al2O3 or SiO2. These samples were investigated with various surface chemistry techniques such as X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), and electron energy loss spectroscopy (EELS). In addition, structural characteristics were investigated with scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The surface techniques were used in-situ in order to observe chemistries that might not be observable outside a CVD reactor. Two sets of experiments were performed on the silica and alumina supports. The first consisted of carbon nanotube growth at near atmospheric pressure, while the second was performed under vacuum. The oxide support was shown to have an affect on the type of nanotubes grown under identical conditions. The silica support films produced more MWNT, while the alumina support films produced more SWNT. This difference was due to the amount of ripening that takes place on the oxide supports. Also in-situ XPS revealed differences in the chemistry of iron catalyst during growth and these differences were attributed to substrate interactions between alumina and iron. Finally, in-situ XPS analysis showed no evidence of carbides or oxides acting as a catalyst during the nucleation process.

  7. Gold-supported cerium-doped NiOx catalysts for water oxidation

    NASA Astrophysics Data System (ADS)

    Ng, Jia Wei Desmond; García-Melchor, Max; Bajdich, Michal; Chakthranont, Pongkarn; Kirk, Charlotte; Vojvodic, Aleksandra; Jaramillo, Thomas F.

    2016-05-01

    The development of high-performance catalysts for the oxygen-evolution reaction (OER) is paramount for cost-effective conversion of renewable electricity to fuels and chemicals. Here we report the significant enhancement of the OER activity of electrodeposited NiOx films resulting from the combined effects of using cerium as a dopant and gold as a metal support. This NiCeOx-Au catalyst delivers high OER activity in alkaline media, and is among the most active OER electrocatalysts yet reported. On the basis of experimental observations and theoretical modelling, we ascribe the activity to a combination of electronic, geometric and support effects, where highly active under-coordinated sites at the oxide support interface are modified by the local chemical binding environment and by doping the host Ni oxide with Ce. The NiCeOx-Au catalyst is further demonstrated in a device context by pairing it with a nickel-molybdenum hydrogen evolution catalyst in a water electrolyser, which delivers 50 mA consistently at 1.5 V over 24 h of continuous operation.

  8. Gold-supported cerium-doped NiOx catalysts for water oxidation

    NASA Astrophysics Data System (ADS)

    Ng, Jia Wei Desmond; García-Melchor, Max; Bajdich, Michal; Chakthranont, Pongkarn; Kirk, Charlotte; Vojvodic, Aleksandra; Jaramillo, Thomas F.

    2016-05-01

    The development of high-performance catalysts for the oxygen-evolution reaction (OER) is paramount for cost-effective conversion of renewable electricity to fuels and chemicals. Here we report the significant enhancement of the OER activity of electrodeposited NiOx films resulting from the combined effects of using cerium as a dopant and gold as a metal support. This NiCeOx–Au catalyst delivers high OER activity in alkaline media, and is among the most active OER electrocatalysts yet reported. On the basis of experimental observations and theoretical modelling, we ascribe the activity to a combination of electronic, geometric and support effects, where highly active under-coordinated sites at the oxide support interface are modified by the local chemical binding environment and by doping the host Ni oxide with Ce. The NiCeOx–Au catalyst is further demonstrated in a device context by pairing it with a nickel–molybdenum hydrogen evolution catalyst in a water electrolyser, which delivers 50 mA consistently at 1.5 V over 24 h of continuous operation.

  9. The influence of carbon support porosity on the activity of PtRu/Sibunit anode catalysts for methanol oxidation

    NASA Astrophysics Data System (ADS)

    Rao, V.; Simonov, P. A.; Savinova, E. R.; Plaksin, G. V.; Cherepanova, S. V.; Kryukova, G. N.; Stimming, U.

    In this paper we analyse the promises of homemade carbon materials of Sibunit family prepared through pyrolysis of natural gases on carbon black surfaces as supports for the anode catalysts of direct methanol fuel cells. Specific surface area ( SBET) of the support is varied in the wide range from 6 to 415 m 2 g -1 and the implications on the electrocatalytic activity are scrutinized. Sibunit supported PtRu (1:1) catalysts are prepared via chemical route and the preparation conditions are adjusted in such a way that the particle size is constant within ±1 nm in order to separate the influence of support on the (i) catalyst preparation and (ii) fuel cell performance. Comparison of the metal surface area measured by gas phase CO chemisorption and electrochemical CO stripping indicates close to 100% utilisation of nanoparticle surfaces for catalysts supported on low (22-72 m 2 g -1) surface area Sibunit carbons. Mass activity and specific activity of PtRu anode catalysts change dramatically with SBET of the support, increasing with the decrease of the latter. 10%PtRu catalyst supported on Sibunit with specific surface area of 72 m 2 g -1 shows mass specific activity exceeding that of commercial 20%PtRu/Vulcan XC-72 by nearly a factor of 3.

  10. Metal recovery from spent refinery catalysts by means of biotechnological strategies.

    PubMed

    Beolchini, F; Fonti, V; Ferella, F; Vegliò, F

    2010-06-15

    A bioleaching study aimed at recovering metals from hazardous spent hydroprocessing catalysts was carried out. The exhaust catalyst was rich in nickel (4.5 mg/g), vanadium (9.4 mg/g) and molybdenum (4.4 mg/g). Involved microorganisms were iron/sulphur oxidizing bacteria. Investigated factors were elemental sulphur addition, ferrous iron addition and actions contrasting a possible metal toxicity (either adding powdered activated charcoal or simulating a cross current process by means of periodical filtration). Ferrous iron resulted to be essential for metal extraction: nickel and vanadium extraction yields were 83% and 90%, respectively, while about 50% with no iron. The observed values for molybdenum extraction yields were not as high as Ni and V ones (the highest values were around 30-40%). The investigated actions aimed at contrasting a possible metal toxicity resulted not to be effective; in contrast, sequential filtration of the liquor leach had a significant negative effect on metals extraction. Nickel and vanadium dissolution kinetics resulted to be significantly faster than molybdenum dissolution ones. Furthermore, a simple first order kinetic model was successfully fitted to experimental data. All the observed results supported the important role of the indirect mechanism in bioleaching of LC-Finer catalysts. PMID:20167424

  11. Coarse-pored ceramic supports for pyrolysis catalysts

    SciTech Connect

    Potapova, L.L.; Cherches, B.Kh.; Egiazarov, Yu.G.

    1988-03-20

    One promising trend in improvement of pyrolysis of hydrocarbon feedstocks is the use of heterogeneous catalysts in the process. The industrial use of highly effective catalysts would result in substantially increased product yields and in decrease of energy consumption in comparison with the requirements of drastic thermal processes. The aims of the present work were to obtain a mechanically strong coarse-pored ceramic support for pyrolysis catalysts and to study the influence of various factors on formation of its structure. The support material was made from an industrial ceramic mass of the following composition (%): koalin 30, plastic refractory clay 21, quartz 32, pegmatite 17. Various additives were used for formation of a porous structure: noncombustible highly porous (pumice, claydite), partially combustible (shungite), and completely combustible (SKT) activated carbon). The authors results show that 15 mass % of SKT carbon (particle size 0.1-0.2 mm) and 1-2 mass % of sodium trimetaphosphate should be added to the ceramic mass. The crushing strength of the resultant support samples reaches 550-630 kg/cm/sup 2/, with 34-35% porosity. Under the optimal conditions of pyrolysis of a straight-run gasoline fraction the catalyst obtained by deposition of 12 mass % of In/sub 2/O/sub 3/ and 4% K/sub 2/O on the synthesized support gives a yield of 39-41 mass % of ethylene and 61-62 mass % of unsaturated C/sub 2/-C/sub 4/ hydrocarbons, with 88-90 mass % gasification.

  12. Characterization and Hydrodesulfurization Properties of Catalysts Derived from Amorphous Metal-boron Materials

    SciTech Connect

    Parks, Greg; Pease, Melissa; Layman, Kathryn A.; Burns, Autumn W.; Bussell, Mark E.; Wang, Xianqin; Hanson, Jonathan; Rodriguez, Jose A.

    2007-01-22

    Unsupported and silica-supported amorphous metal-boron materials (Ni-B, Mo-O-B, and Ni-Mo-O-B) were prepared by NaBH4 reduction of aqueous or impregnated metal salts. The resulting materials were characterized by a range of techniques, including conventional and time-resolved X-ray diffraction. The latter technique was used to determine the onset of crystallization of the amorphous materials during annealing in He flow and to identify the phases formed. Annealing of unsupported Ni-B resulted in the crystallization of predominantly Ni3B, followed by Ni metal, whereas Ni-B/SiO2 formed Ni and then NiO. There was no evidence for crystallization of B-containing phases for Mo-O-B or Mo-O-B/SiO2 on annealing; instead, the predominant phase formed was MoO2. In general, the phases formed for Ni-Mo-O-B and Ni-Mo-O-B/SiO2 were consistent with those formed in the monometallic materials, but at higher annealing temperatures. Catalysts prepared by sulfiding Ni-B/SiO2 and Ni-Mo-O-B/SiO2 materials had significantly higher thiophene HDS activities than conventionally prepared sulfided Ni/SiO2 and Ni-Mo/SiO2 catalysts, whereas a sulfided Mo-O-B/SiO2 catalyst had a dramatically lower HDS activity than a sulfided Mo/SiO2 catalyst.

  13. Use of metal hydrous titanium oxide catalysts to enhance coal tar yield via hydropyrolysis

    SciTech Connect

    Klavetter, E.A.; Stephens, H.P.; Dosch, R.G.

    1990-01-01

    Catalytic hydropyrolysis experiments performed in this project on several US and UK coals have established that tar yields in excess of 70% (daf basis) and conversions (100%-char) in excess of 80% can be achieved from bituminous coals containing 80--84% dmmf carbon using hydrous titanium oxide (HTO) catalysts with low concentrations of active metals. Total conversion approaches the reactive maceral contents for these coals. Previously performed two-stage catalytic hydropyrolysis experiments have demonstrated that high yields of liquid products with high H/C ratios, low heteroatom contents, and a significant concentration of light naphtha can be achieved. The objectives of this research are to determine suitable methods for catalyzing the hydropyrolysis process and to investigate the reactions and mechanisms responsible for the high conversion of coal materials to distillable liquids via direct catalytic hydropyrolysis. Recently developed hydrous titanium oxide (HTO)-supported catalysts have received encouraging results in direct coal liquefaction applications. Results of hydropyrolysis experiment using Mo and Pd HTO catalysts coated directly onto the coal are presented here and compared with results from experiments using uncatalyzed coal samples and using a dispersed MoS{sub 2} catalyst. The effect of coal rank, active metals concentration, dispersion method, and metal type are discussed. 9 refs., 6 figs., 2 tabs.

  14. Transition metal catalysts for the conversion of ortho- to para-hydrogen

    SciTech Connect

    Brooks, C.J.

    1993-01-01

    The chemistry of the catalytic conversion of ortho- to para-hydrogen was pursued in this study by the preparation and characterization of transition metal silicates as well as ruthenium supported on silica. A plug flow reactor system was designed to test the conversion of ortho- to para-H[sub 2] from room temperature to [minus]196[degrees]C. This involved both the design and modification of an overall reactor system as well as individual reactor tubes. The system was calibrated to allow the measurement of conversion by thermal conductivity and measured catalytic activity such that they could be compared with other catalysts in the literature. Metal silicates of nickel, iron, chromium, and manganese were prepared by the coprecipitation or sol-gel methods. The study involved the optimization of activities at [minus]196[degrees]C by the variation of the catalyst preparation method. These changes, which increased the total surface area and total pore volume of the silicate, also increased the activity. Nitrogen adsorption confirmed the changes in the physical structure of the silicate. Ruthenium catalysts were prepared through traditional impregnation methods as well as through inpregnation of a ruthenium ammine intermediate. It was found that the traditional catalysts had a maximum activity at [approx][minus]158[degrees]C. This is most likely caused by the increasing strength of the Ru-H interaction at decreasing temperatures. Activity could be increased by heating the catalyst to high temperature and then cooling to the reaction temperature in helium. High temperature is felt to desorb a strongly bound hydrogen layer, while low temperature cooling does not allow as great of a readsorption of hydrogen. Chlorine containing precursors enhance this effect by residual surface chlorine increasing the strong H[sub 2] adsorption activation energy. Ruthenium ammine catalysts showed greatly enhanced activities relative to the traditionally prepared ruthenium catalysts.

  15. Fundamental studies of hydrogen interaction with supported meta and bimetallic catalysts

    SciTech Connect

    Bhatia, S.

    1993-12-07

    The thesis is divided into 3 parts: interaction of H with silica supported Ru catalysts (high pressure in situ NMR), in situ NMR study of H interaction with supported Ru-group IB bimetallic catalysts, and in-situ NMR study of H effects on silica-supported Pt, Rh and Ru catalysts.

  16. Process for metallization of a substrate by curing a catalyst applied thereto

    DOEpatents

    Chen, Ken S.; Morgan, William P.; Zich, John L.

    2002-10-08

    An improved additive process for metallization of substrates is described whereby a catalyst solution is applied to a surface of a substrate. Metallic catalytic clusters can be formed in the catalyst solution on the substrate surface by heating the substrate. Electroless plating can then deposit metal onto the portion of the substrate surface coated with catalyst solution. Additional metallization thickness can be obtained by electrolytically plating the substrate surface after the electroless plating step.

  17. SISGR-Fundamental Experimental and Theoretical Studies on a Novel Family of Oxide Catalyst Supports for Water Electrolysis

    SciTech Connect

    Kumta, Prashant

    2014-10-03

    Identification and development of non-noble metal based electro-catalysts or electro-catalysts with significant reduction of expensive noble metal contents (E.g. IrO2, Pt) with comparable electrochemical performance as the standard noble metal/metal oxide for proton exchange membrane (PEM) based water electrolysis would constitute a major breakthrough in the generation of hydrogen by water electrolysis. Accomplishing such a system would not only result reduction of the overall capital costs of PEM based water electrolyzers, but also help attain the targeted hydrogen production cost [< $ 3.0 / gallon gasoline equivalent (gge)] comparable to conventional liquid fuels. In line with these goals, it was demonstrated that fluorine doped IrO2 thin films and nanostructured high surface area powders display remarkably higher electrochemical activity, and comparable durability as pure IrO2 electro-catalyst for the oxygen evolution reaction (OER) in PEM based water electrolysis. Furthermore, corrosion resistant SnO2 and NbO2 support has been doped with F and coupled with IrO2 or RuO2 for use as an OER electro-catalyst. A solid solution of SnO2:F or NbO2:F with only 20 - 30 mol.% IrO2 or RuO2 yielding a rutile structure in the form of thin films and bulk nanoparticles displays similar electrochemical activity and stability as pure IrO2/RuO2. This would lead to more than 70 mol.% reduction in the noble metal oxide content. Novel nanostructured ternary (Ir,Sn,Nb)O2 thin films of different compositions FUNDAMENTAL STUDY OF NANOSTRUCTURED ELECTRO-CATALYSTS WITH REDUCED NOBLE METAL CONTENT FOR PEM BASED WATER ELECTROLYSIS 4 have also been studied. It has been shown that (Ir0.40Sn0.30Nb0.30)O2 shows similar electrochemical activity and enhanced chemical robustness as compared to pure IrO2. F doping of the ternary (Ir,Sn,Nb)O2 catalyst helps in further decreasing the noble metal oxide content of the catalyst. As a result, these reduced noble metal oxide catalyst systems would

  18. Metal Dichalcogenides Monolayers: Novel Catalysts for Electrochemical Hydrogen Production

    PubMed Central

    Pan, Hui

    2014-01-01

    Catalyst-driven electrolysis of water is considered as a “cleanest” way for hydrogen production. Finding cheap and abundant catalysts is critical to the large-scale implementation of the technology. Two-dimensional metal dichalcogenides nanostructures have attracted increasing attention because of their catalytic performances in water electrolysis. In this work, we systematically investigate the hydrogen evolution reduction of metal dichalcogenides monolayers based on density-functional-theory calculations. We find that metal disulfide monolayers show better catalytic performance on hydrogen production than other metal dichalcogenides. We show that their hydrogen evolution reduction strongly depends on the hydrogen coverage and the catalytic performance reduces with the increment of coverage because of hydrogenation-induced lower conductivity. We further show that the catalytic performance of vanadium disulfide monolayer is comparable to that of Pt at lower hydrogen coverage and the performance at higher coverage can be improved by hybridizing with conducting nanomaterials to enhance conductivity. These metal disulfide monolayers with lower overpotentials may apply to water electrolysis for hydrogen production. PMID:24967679

  19. Novel aluminosilicate hollow sphere as a catalyst support for methane decomposition to COx-free hydrogen production

    NASA Astrophysics Data System (ADS)

    Awadallah, A. E.; Ahmed, W.; El-Din, M. R. Noor; Aboul-Enein, A. A.

    2013-12-01

    Novel Ni and Co supported on aluminosilicate hollow sphere catalysts were investigated to decompose methane into CO and CO2 free hydrogen and carbon nanotube. The hollow sphere structure was prepared by reverse microemulsion method and then Ni and Co were loaded by the impregnation method. The fresh catalysts and deposited carbon were characterized by several microscopic and spectroscopic techniques. The catalytic results showed that the Co based catalyst exhibited higher activity and durability at longer reaction time, due to the higher number and distribution of metal sites. The hollow sphere structure of the support could protect the metal particles against aggregation during the catalytic reactions. Accordingly, higher metal dispersion, stabilization and catalytic performance were achieved. The formation of nickel silicate is the main reason for the lower decomposition activity of Ni based catalyst at longer reaction time. TEM and Raman spectroscopic data revealed that the Co-based catalyst produced a relatively uniform diameter of MWCNTs with higher crystallinity and graphitization degree compared to the Ni-based catalyst.

  20. 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.

  1. Pd-nanoparticle-supported, PDDA-functionalized graphene as a promising catalyst for alcohol oxidation.

    PubMed

    Bin, Duan; Ren, Fangfang; Wang, Ying; Zhai, Chunyang; Wang, Caiqin; Guo, Jun; Yang, Ping; Du, Yukou

    2015-03-01

    Poly(diallyldimethylammonium chloride) (PDDA) has been employed as a modifying material for the development of new functional materials; then, the functionalized graphene was employed as a support for Pd nanoparticles through a facile method. The structures and morphologies of the as-synthesized Pd/PDDA-graphene composites were extensively characterized by Raman spectroscopy, XRD, XPS, and TEM. Morphological observation showed that Pd NPs with average diameters of 4.4 nm were evenly deposited over the functionalized graphene sheets. Moreover, the electrochemical experiments indicated that the Pd/PDDA-graphene catalyst showed improved electrocatalytic activity toward alcohol-oxidation reactions compared to the Pd/graphene and commercial Pd/C systems, as well as previously reported Pd-based catalysts. This study demonstrates the great potential of PDDA-functionalized graphene as a support for the development of metal-graphene nanocomposites for important applications in fuel cells. PMID:25601138

  2. New catalysts for hydroprocessing: Transition metal carbides and nitrides

    SciTech Connect

    Ramanathan, S.; Oyama, S.T. |

    1995-11-02

    A series of moderate surface area transition metal carbides and nitrides of molybdenum, tungsten, vanadium, niobium, and titanium were prepared by temperature-programmed reaction of the oxide precursor with a reactant gas (20% CH{sub 4}/H{sub 2} for the carbides and 100% NH{sub 3} for the nitrides). The phase purity and composition of the samples were established by X-ray diffraction photoelectron spectroscopy (XPS), while surface properties were determined by N{sub 2} BET and CO chemisorption measurements. The catalysts were tested in three-phase trickle-bed reactor for their activity in hydrodenitrogenation (HDN), hydrodesulfurization, and hydrodeoxygenation, with particular emphasis on HDN. The catalytic tests were carried out using a model liquid feed mixture containing 3000 ppm sulfur (dibenzothiophene), 2000 ppm nitrogen (quinoline), 500 ppm oxygen (benzofuran), 20 wt% aromatics (tetralin), and balance aliphatics (tetradecane). The carbides and nitrides were found to be active for HDN of quinoline with activity following the order group 6 > group 5 > group 4. Notably, Mo{sub 2}C showed superior areal HDN activity than a commercial sulfided Ni-Mo/Al{sub 2} O{sub 3} catalyst (shell 324). The XRD analysis of the spent catalysts indicated no change in the bulk structure, while XPS results showed little incorporation of sulfur in the surface region of the catalysts, suggesting that these materials are tolerant of sulfur. 42 refs., 11 figs., 7 tabs.

  3. Noble metal-free hydrogen evolution catalysts for water splitting.

    PubMed

    Zou, Xiaoxin; Zhang, Yu

    2015-08-01

    Sustainable hydrogen production is an essential prerequisite of a future hydrogen economy. Water electrolysis driven by renewable resource-derived electricity and direct solar-to-hydrogen conversion based on photochemical and photoelectrochemical water splitting are promising pathways for sustainable hydrogen production. All these techniques require, among many things, highly active noble metal-free hydrogen evolution catalysts to make the water splitting process more energy-efficient and economical. In this review, we highlight the recent research efforts toward the synthesis of noble metal-free electrocatalysts, especially at the nanoscale, and their catalytic properties for the hydrogen evolution reaction (HER). We review several important kinds of heterogeneous non-precious metal electrocatalysts, including metal sulfides, metal selenides, metal carbides, metal nitrides, metal phosphides, and heteroatom-doped nanocarbons. In the discussion, emphasis is given to the synthetic methods of these HER electrocatalysts, the strategies of performance improvement, and the structure/composition-catalytic activity relationship. We also summarize some important examples showing that non-Pt HER electrocatalysts could serve as efficient cocatalysts for promoting direct solar-to-hydrogen conversion in both photochemical and photoelectrochemical water splitting systems, when combined with suitable semiconductor photocatalysts.

  4. Inverse oxide/metal catalysts in fundamental studies and practical applications: A perspective of recent developments

    DOE PAGES

    Rodriguez, José A.; Liu, Ping; Graciani, Jesús; Senanayake, Sanjaya D.; Grinter, David C.; Stacchiola, Dario; Hrbek, Jan; Fernández-Sanz, Javier

    2016-06-21

    Inverse oxide/metal catalysts have shown to be excellent systems for studying the role of the oxide and oxide–metal interface in catalytic reactions. These systems can have special structural and catalytic properties due to strong oxide–metal interactions difficult to attain when depositing a metal on a regular oxide support. Oxide phases that are not seen or are metastable in a bulk oxide can become stable in an oxide/metal system opening the possibility for new chemical properties. Using these systems, it has been possible to explore fundamental properties of the metal–oxide interface (composition, structure, electronic state), which determine catalytic performance in themore » oxidation of CO, the water–gas shift and the hydrogenation of CO2 to methanol. Recently, there has been a significant advance in the preparation of oxide/metal catalysts for technical or industrial applications. In conclusion, one goal is to identify methods able to control in a precise way the size of the deposited oxide particles and their structure on the metal substrate.« less

  5. Iron-based dehydrogenation catalysts supported on zirconia. I. Preparation and characterization

    SciTech Connect

    Boot, L.A.; Dillen, A.J. van; Geus, J.W.

    1996-09-15

    Zirconia-supported iron oxide catalysts were prepared by incipient wetness impregnation, followed by drying and calcination in air. Characterization of the catalysts were performed with electron microscopy combined with element analysis (HR-TEM/EDAX), X-ray diffraction (XRD), temperature-programmed reduction (TPR), and thermomagnetic analysis. A homogeneous distribution of the iron containing phase can be obtained by using the metal complexes ammonium iron (III) citrate or ammonium (III) iron EDTA. A simple salt, such as iron nitrate, proved to be less suitable for this purpose. By HR-TEM/EDAX, it was shown that coverage of the zirconia support had been accomplished. XRL showed that crystalline Fe{sub 2}O{sub 3} particles were formed at loadings {ge} 3 wt% Fe. TPR studies point to a bi-modal particle size distribution for the catalysts with 3 wt% Fe. Above this loading (>3 wt%) bulk properties prevail in TPR, whereas at lower loadings (<3 wt%) no distinct iron oxide species could be indicated. Magnetization measurements confirmed the results obtained by TPR. Catalysts prepared by coimpregnation of iron and potassium were also studied. TEM and XRD results show that a well-dispersed phase is obtained, but from XRD only potassium carbonate and no iron oxide or ferrite is evident. It was also found that the presence of potassium increases the onset of reduction of the iron phase by about 100{degrees}C. 25 refs., 11 figs., 2 tabs.

  6. Nanostructured nonprecious metal catalysts for oxygen reduction reaction.

    PubMed

    Wu, Gang; Zelenay, Piotr

    2013-08-20

    Platinum-based catalysts represent a state of the art in the electrocatalysis of oxygen reduction reaction (ORR) from the point of view of their activity and durability in harnessing the chemical energy via direct electrochemical conversion. However, because platinum is both expensive and scarce, its widespread implementation in such clean energy applications is limited. Recent breakthroughs in the synthesis of high-performance nonprecious metal catalysts (NPMCs) make replacement of Pt in ORR electrocatalysts with earth-abundant elements, such as Fe, Co, N, and C, a realistic possibility. In this Account, we discuss how we can obtain highly promising M-N-C (M: Fe and/or Co) catalysts by simultaneously heat-treating precursors of nitrogen, carbon, and transition metals at 800-1000 °C. The activity and durability of resulting catalysts depend greatly on the selection of precursors and synthesis chemistry. In addition, they correlate quite well with the catalyst nanostructure. While chemists have presented no conclusive description of the active catalytic site for this class of NPMCs, they have developed a designed approach to making active and durable materials, focusing on the catalyst nanostructure. The approach consists of nitrogen doping, in situ carbon graphitization, and the usage of graphitic structures (possibly graphene and graphene oxides) as carbon precursors. Various forms of nitrogen, particularly pyridinic and quaternary, can act as n-type carbon dopants in the M-N-C catalysts, assisting in the formation of disordered carbon nanostructures and donating electrons to the carbon. The CNx structures are likely a crucial part of the ORR active site(s). Noteworthy, the ORR activity is not necessarily governed by the amount of nitrogen, but by how the nitrogen is incorporated into the nanostructures. Apart from the possibility of a direct participation in the active site, the transition metal often plays an important role in the in situ formation of various

  7. Chemoselective single-site Earth-abundant metal catalysts at metal-organic framework nodes.

    PubMed

    Manna, Kuntal; Ji, Pengfei; Lin, Zekai; Greene, Francis X; Urban, Ania; Thacker, Nathan C; Lin, Wenbin

    2016-01-01

    Earth-abundant metal catalysts are critically needed for sustainable chemical synthesis. Here we report a simple, cheap and effective strategy of producing novel earth-abundant metal catalysts at metal-organic framework (MOF) nodes for broad-scope organic transformations. The straightforward metalation of MOF secondary building units (SBUs) with cobalt and iron salts affords highly active and reusable single-site solid catalysts for a range of organic reactions, including chemoselective borylation, silylation and amination of benzylic C-H bonds, as well as hydrogenation and hydroboration of alkenes and ketones. Our structural, spectroscopic and kinetic studies suggest that chemoselective organic transformations occur on site-isolated, electron-deficient and coordinatively unsaturated metal centres at the SBUs via σ-bond metathesis pathways and as a result of the steric environment around the catalytic site. MOFs thus provide a novel platform for the development of highly active and affordable base metal catalysts for the sustainable synthesis of fine chemicals. PMID:27574182

  8. A novel catalyst support for DMFC: Onion-like fullerenes

    NASA Astrophysics Data System (ADS)

    Xu, Bingshe; Yang, Xiaowei; Wang, Xiaomin; Guo, Junjie; Liu, Xuguang

    Onion-like fullerenes (OLFs) were employed as the support for Pt in direct methanol fuel cells (DMFCs). A Pt/OLFs catalyst was synthesized by an impregnation-reduction method. Its structure and morphology were characterized by XRD, HRTEM and XPS. The Pt nanoparticles uniformly dispersed on OLFs had an average diameter of 3.05 nm, compared to 4.10 nm in Pt/Vulcan XC-72 prepared by the same method. XPS analysis revealed that Pt/OLF contained mostly Pt(0), with traces of Pt(II) and Pt(IV). Cyclic voltammetry showed that the real surface area of the Pt/OLFs was larger than Pt/XC-72 and the electrocatalytic activity of the Pt/OLFs catalyst, from the peak current value at around 0.78 V, outperformed the Pt/Vulcan XC-72 by about 20% in the electrooxidation of methanol.

  9. REFORMULATION OF COAL-DERIVED TRANSPORTATION FUELS: SELECTIVE OXIDATION OF CARBON MONOXIDE ON METAL FOAM CATALYSTS

    SciTech Connect

    Paul Chin; George W. Roberts; James J. Spivey

    2003-12-31

    Uses for structured catalytic supports, such as ceramic straight-channel monoliths and ceramic foams, have been established for a long time. One of the most prominent examples is the washcoated ceramic monolith as a three-way catalytic converter for gasoline-powered automobiles. A distinct alternative to the ceramic monolith is the metal foam, with potential use in fuel cell-powered automobiles. The metal foams are characterized by their pores per inch (ppi) and density ({rho}). In previous research, using 5 wt% platinum (Pt) and 0.5 wt% iron (Fe) catalysts, washcoated metal foams, 5.08 cm in length and 2.54 cm in diameter, of both varying and similar ppi and {rho} were tested for their activity (X{sub CO}) and selectivity (S{sub CO}) on a CO preferential oxidation (PROX) reaction in the presence of a H{sub 2}-rich gas stream. The variances in these metal foams' activity and selectivity were much larger than expected. Other structured supports with 5 wt% Pt, 0-1 wt% Fe weight loading were also examined. A theory for this phenomenon states that even though these structured supports have a similar nominal catalyst weight loading, only a certain percentage of the Pt/Fe catalyst is exposed on the surface as an active site for CO adsorption. We will use two techniques, pulse chemisorption and temperature programmed desorption (TPD), to characterize our structured supports. Active metal count, metal dispersion, and other calculations will help clarify the causes for the activity and selectivity variations between the supports. Results on ceramic monoliths show that a higher Fe loading yields a lower dispersion, potentially because of Fe inhibition of the Pt surface for CO adsorption. This theory is used to explain the reason for activity and selectivity differences for varying ppi and {rho} metal foams; less active and selective metal foams have a lower Fe loading, which justifies their higher metal dispersion. Data on the CO desorption temperature and average metal

  10. Catalytic Transfer Hydrogenation of Furfural to Furfuryl Alcohol over Nitrogen-Doped Carbon-Supported Iron Catalysts.

    PubMed

    Li, Jiang; Liu, Jun-Ling; Zhou, Hong-Jun; Fu, Yao

    2016-06-01

    Iron-based heterogeneous catalysts, which were generally prepared by pyrolysis of iron complexes on supports at elevated temperature, were found to be capable of catalyzing the transfer hydrogenation of furfural (FF) to furfuryl alcohol (FFA). The effects of metal precursor, nitrogen precursor, pyrolysis temperature, and support on catalytic performance were examined thoroughly, and a comprehensive study of the reaction parameters was also performed. The highest selectivity of FFA reached 83.0 % with a FF conversion of 91.6 % under the optimal reaction condition. Catalyst characterization suggested that iron cations coordinated by pyridinic nitrogen functionalities were responsible for the enhanced catalytic activity. The iron catalyst could be recycled without significant loss of catalytic activity for five runs, and the destruction of the nitrogen-iron species, the presence of crystallized Fe2 O3 phase, and the pore structure change were the main reasons for catalyst deactivation. PMID:27144965

  11. Continuous preparation of carbon-nanotube-supported platinum catalysts in a flow reactor directly heated by electric current

    PubMed Central

    dos Santos, Antonio Rodolfo; Kunz, Ulrich; Turek, Thomas

    2011-01-01

    Summary In this contribution we present for the first time a continuous process for the production of highly active Pt catalysts supported by carbon nanotubes by use of an electrically heated tubular reactor. The synthesized catalysts show a high degree of dispersion and narrow distributions of cluster sizes. In comparison to catalysts synthesized by the conventional oil-bath method a significantly higher electrocatalytic activity was reached, which can be attributed to the higher metal loading and smaller and more uniformly distributed Pt particles on the carbon support. Our approach introduces a simple, time-saving and cost-efficient method for fuel cell catalyst preparation in a flow reactor which could be used at a large scale. PMID:22043252

  12. Development of Metal Substrate for Denox Catalysts and Particulate Trap

    SciTech Connect

    Pollard, Michael; Habeger, Craig; Frary, Megan; Haines, Scott; Fluharty, Amy; Dakhoul, Youssef; Carr, Michael; Park, Paul; Stefanick, Matthew; DaCosta, Herbert; Balmer-Millar, M Lou; Readey, Michael; McCluskey, Philip

    2005-12-31

    The objective of this project was to develop advanced metallic catalyst substrate materials and designs for use in off-highway applications. The new materials and designs will be used as catalyst substrates and diesel particulate traps. They will increase durability, reduce flow resistance, decrease time to light-off, and reduce cost relative to cordierite substrates. Metallic catalyst substrates are used extensively for diesel oxidation catalysts and have the potential to be used in other catalytic systems for diesel engines. Metallic substrates have many advantages over ceramic materials including improved durability and resistance to thermal shock and vibration. However, the cost is generally higher than cordierite. The most common foil material used for metallic substrates is FeCr Alloy, which is expensive and has temperature capabilities beyond what is necessary for diesel applications. The first task in the project was Identification and Testing of New Materials. In this task, several materials were analyzed to determine if a low cost substitute for FeCr Alloy was available or could be developed. Two materials were identified as having lower cost while showing no decrease in mechanical properties or oxidation resistance at the application temperatures. Also, the ability to fabricate these materials into a finished substrate was not compromised, and the ability to washcoat these materials was satisfactory. Therefore, both candidate materials were recommended for cost savings depending on which would be less expensive in production quantities. The second task dealt with the use of novel flow designs to improve the converter efficiency while possibly decreasing the size of the converter to reduce cost even more. A non-linear flow path was simulated to determine if there would be an increase in efficiency. From there, small samples were produced for bench testing. Bench tests showed that the use of non-linear channels significantly reduced the light

  13. Comparison of the Activity and the Stability in CO Oxidation of Au-Cu Catalysts Supported on TiO2 in Anatase or Rutile Phase.

    PubMed

    Zanella, Rodolfo; Bokhimi, Xim; Maturano, Viridiana; Morales, Antonio

    2015-09-01

    Au-Cu catalysts supported on anatase or rutile phases were prepared by deposition-precipitation method. The titania polymorph used as the support determined the catalytic behavior. For the Au-Cu/rutile catalysts, the metallic phase had smaller dimensions than for the Au-Cu/anatase catalysts. The catalysts supported on anatase, however, were more active and stable than those supported on rutile. A systematic study of the catalytic activity for CO oxidation as a function of the temperature of activation and the aging time was performed. The catalytic properties were correlated with the properties of the catalysts analyzed with X-ray powder diffraction, refinement of the crystalline structures with the Rietveld method, and transmission electron microscopy. When the support was anatase, a pretreatment at 400 degrees C in air led to the most active catalysts, whereas when the support was rutile, a pretreatment between 200 and 300 degrees C in air led to the most active catalysts; activation under hydrogen generated less active catalysts. The Au-Cu catalysts activated in air were more active for the oxidation of CO than the respective monometallic gold catalysts, indicating a promoting effect between gold and copper to catalyze this reaction.

  14. Non-precious metal catalysts prepared from precursor comprising cyanamide

    SciTech Connect

    Chung, Hoon Taek; Zelenay, Piotr

    2015-10-27

    Catalyst comprising graphitic carbon and methods of making thereof; said graphitic carbon comprising a metal species, a nitrogen-containing species and a sulfur containing species. A catalyst for oxygen reduction reaction for an alkaline fuel cell was prepared by heating a mixture of cyanamide, carbon black, and a salt selected from an iron sulfate salt and an iron acetate salt at a temperature of from about 700.degree. C. to about 1100.degree. C. under an inert atmosphere. Afterward, the mixture was treated with sulfuric acid at elevated temperature to remove acid soluble components, and the resultant mixture was heated again under an inert atmosphere at the same temperature as the first heat treatment step.

  15. Metallocorroles as Nonprecious-Metal Catalysts for Oxygen Reduction.

    PubMed

    Levy, Naomi; Mahammed, Atif; Kosa, Monica; Major, Dan T; Gross, Zeev; Elbaz, Lior

    2015-11-16

    The future of affordable fuel cells strongly relies on the design of earth-abundant (non-platinum) catalysts for the electrochemical oxygen reduction reaction (ORR). However, the bottleneck in the overall process occurs therein. We have examined herein trivalent Mn, Fe, Co, Ni, and Cu complexes of β-pyrrole-brominated corrole as ORR catalysts. The adsorption of these complexes on a high-surface-area carbon powder (BP2000) created a unique composite material, used for electrochemical measurements in acidic aqueous solutions. These experiments disclosed a clear dependence of the catalytic activity on the metal center of the complexes, in the order of Co>Fe>Ni>Mn>Cu. The best catalytic performance was obtained for the Co(III) corrole, whose onset potential was as positive as 0.81 V versus the reversible hydrogen electrode (RHE). Insight into the properties of these systems was gained by spectroscopic and computational characterization of the reduced and oxidized forms of the metallocorroles.

  16. Highly stable precious metal-free cathode catalyst for fuel cell application

    NASA Astrophysics Data System (ADS)

    Serov, Alexey; Workman, Michael J.; Artyushkova, Kateryna; Atanassov, Plamen; McCool, Geoffrey; McKinney, Sam; Romero, Henry; Halevi, Barr; Stephenson, Thomas

    2016-09-01

    A platinum group metal-free (PGM-free) oxygen reduction reaction (ORR) catalyst engineered for stability has been synthesized using the sacrificial support method (SSM). This catalyst was comprehensively characterized by physiochemical analyses and tested for performance and durability in fuel cell membrane electrode assemblies (MEAs). This catalyst, belonging to the family of Fe-N-C materials, is easily scalable and can be manufactured in batches up to 200 g. The fuel cell durability tests were performed in a single cell configuration at realistic operating conditions of 0.65 V, 1.25 atmgauge air, and 90% RH for 100 h. In-depth characterization of surface chemistry and morphology of the catalyst layer before and after durability tests were performed. The failure modes of the PGM-free electrodes were derived from structure-to-property correlations. It is suggested that under constant voltage operation, the performance loss results from degradation of the electrode pore structure, while under carbon corrosion accelerated test protocols the failure mode is catalyst corrosion.

  17. Metal-Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations.

    PubMed

    Zhang, Teng; Manna, Kuntal; Lin, Wenbin

    2016-03-01

    New and active earth-abundant metal catalysts are critically needed to replace precious metal-based catalysts for sustainable production of commodity and fine chemicals. We report here the design of highly robust, active, and reusable cobalt-bipyridine- and cobalt-phenanthroline-based metal-organic framework (MOF) catalysts for alkene hydrogenation and hydroboration, aldehyde/ketone hydroboration, and arene C-H borylation. In alkene hydrogenation, the MOF catalysts tolerated a variety of functional groups and displayed unprecedentedly high turnover numbers of ∼2.5 × 10(6) and turnover frequencies of ∼1.1 × 10(5) h(-1). Structural, computational, and spectroscopic studies show that site isolation of the highly reactive (bpy)Co(THF)2 species in the MOFs prevents intermolecular deactivation and stabilizes solution-inaccessible catalysts for broad-scope organic transformations. Computational, spectroscopic, and kinetic evidence further support a hitherto unknown (bpy(•-))Co(I)(THF)2 ground state that coordinates to alkene and dihydrogen and then undergoing σ-complex-assisted metathesis to form (bpy)Co(alkyl)(H). Reductive elimination of alkane followed by alkene binding completes the catalytic cycle. MOFs thus provide a novel platform for discovering new base-metal molecular catalysts and exhibit enormous potential in sustainable chemical catalysis.

  18. The promotional effect of surface defects on the catalytic performance of supported nickel-based catalysts.

    PubMed

    Li, Yizhen; Yu, Jiaying; Li, Wei; Fan, Guoli; Yang, Lan; Li, Feng

    2016-03-01

    Controlling the metal-support interactions, as well as the nature of support materials, is of vital importance for enhancing the catalytic performance of supported metal catalysts. In the present work, supported nickel nanocatalysts with abundant surface defects (e.g. oxygen vacancies, Ti(3+) species) were directly synthesized via a facile single-source Ni-Ti layered double hydroxide precursor route, and their catalytic performance in the liquid phase selective hydrogenation of chloronitrobenzenes to chloroanilines was investigated. A series of characterization techniques including XRD, TEM, STEM, PL, XPS, H2-TPR and H2 chemisorption clearly demonstrated that the resultant Ni nanoparticles were uniformly dispersed on the surface of the Ni-Ti mixed metal oxide support formed in situ, thereby leading to strong metal-support interactions and the formation of a large amount of surface oxygen vacancies and Ti(3+) species. Compared with that prepared using a conventional impregnation method, the as-formed Ni-based nanocatalysts exhibited significantly enhanced catalytic performance with a high chloroaniline yield of 99.0% under mild reaction conditions (i.e. a low hydrogen pressure of 0.2 MPa). Such an unprecedented catalytic efficiency was mainly attributed to the promotional effect of surface defects. Furthermore, the present Ni-based nanocatalysts could be reused five times without serious aggregation of active species and remarkable activity loss, indicative of high stability.

  19. Partial Oxidation of Hydrocarbons in a Segmented Bed Using Oxide-based Catalysts and Oxygen-conducting Supports

    NASA Astrophysics Data System (ADS)

    Smith, Mark W.

    Two objectives for the catalytic reforming of hydrocarbons to produce synthesis gas are investigated herein: (1) the effect of oxygen-conducting supports with partially substituted mixed-metal oxide catalysts, and (2) a segmented bed approach using different catalyst configurations. Excess carbon deposition was the primary cause of catalyst deactivation, and was the focus of the experiments for both objectives. The formation and characterization of deposited carbon was examined after reaction for one of the selected catalysts to determine the quantity and location of the carbon on the catalyst surface leading to deactivation. A nickel-substituted barium hexaaluminate (BNHA), with the formula BaAl 11.6Ni0.4O18.8, and a Rh-substituted lanthanum zirconate pyrochlore (LCZR) with the formula La1.89Ca0.11 Zr1.89Rh0.11, were combined with two different doped ceria supports. These supports were gadolinium-doped ceria (GDC) and zirconium-doped ceria (ZDC). The active catalyst phases were combined with the supports in different ratios using different synthesis techniques. The catalysts were characterized using several different techniques and were tested under partial oxidation (POX) of n-tetradecane (TD), a diesel fuel surrogate. It was found that the presence of GDC and ZDC reduced the formation of carbon for both catalysts; the optimal ratio of catalyst to support was different for the hexaaluminate and the pyrochlore; a loading of 20 wt% of the pyrochlore with ZDC produced the most stable performance in the presence of common fuel contaminants (>50 h); and, the incipient wetness impregnation synthesis method of applying the active catalyst to the support produced more stable product yields than the catalyst prepared by a solid-state mixing technique. Different hexaaluminate and pyrochlore catalysts were used in different configurations in a segmented bed approach. The first strategy was to promote the indirect reforming mechanism by placing a combustion catalyst in the

  20. NiAg catalysts prepared by reduction of Ni2+ ions in aqueous hydrazine II. Support effect.

    PubMed

    Bettahar, M M; Wojcieszak, R; Monteverdi, S

    2009-04-15

    A series of bimetallic NiAg (Ni + Ag = 1% wt) catalysts supported on amorphous silica was synthesized via chemical reduction using hydrazine as the reducing agent at 353 K. Catalysts were prepared via impregnation or precipitation technique. It was found that the reduction of the Ni(2+) ions occurred only in the presence of silver, otherwise a stable blue [Ni(N(2)H(4))(3)](2+) complex was formed. Comparisons with similar NiAg catalysts supported on crystallized silica as prepared in our previous work indicated that the Ni(2+) ions weakly interacted with acidic crystallized silica on which they were readily reduced. For both supports, the combination of silver and nickel gave rise to a synergistic effect due to the existence of NiAg groupings. The surface and catalytic properties of the metal particles formed depended on the Ni:Ag ratio, method of preparation, and acidity of the support.

  1. Magnetic Carbon Supported Palladium Nanoparticles: An Efficient and Sustainable Catalyst for Hydrogenation Reactions

    EPA Science Inventory

    Magnetic carbon supported Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; the catalyst can be used for the hydrogenation of alkenes and reduction of aryl nitro compounds.

  2. A conceptual translation of homogeneous catalysis into heterogeneous catalysis: homogeneous-like heterogeneous gold nanoparticle catalyst induced by ceria supporter.

    PubMed

    Li, Zhen-Xing; Xue, Wei; Guan, Bing-Tao; Shi, Fu-Bo; Shi, Zhang-Jie; Jiang, Hong; Yan, Chun-Hua

    2013-02-01

    Translation of homogeneous catalysis into heterogeneous catalysis is a promising solution to green and sustainable development in chemical industry. For this purpose, noble metal nanoparticles represent a new frontier in catalytic transformations. Many challenges remain for researchers to transform noble metal nanoparticles of heterogeneous catalytic active sites into ionic species of homogeneous catalytic active sites. We report here a successful design on translating homogeneous gold catalysis into a heterogeneous system with a clear understanding of the catalytic pathway. This study initiates a novel concept to immobilize a homogeneous catalyst based on electron transfer between supporting base and supported nanoparticles. Meanwhile, on the basis of theoretical calculation, it has deepened the understanding of the interactions between noble metal nanoparticles and the catalyst support.

  3. What is below the support layer affects carbon nanotube growth: an iron catalyst reservoir yields taller nanotube carpets.

    PubMed

    Shawat, E; Mor, V; Oakes, L; Fleger, Y; Pint, C L; Nessim, G D

    2014-01-01

    Here we demonstrate an approach to enhance the growth of vertically aligned carbon nanotubes (CNTs) by including a catalyst reservoir underneath the thin-film alumina catalyst underlayer. This reservoir led to enhanced CNT growth due to the migration of catalytic material from below the underlayer up to the surface through alumina pinholes during processing. This led to the formation of large Fe particles, which in turn influenced the morphology evolution of the catalytic iron surface layer through Ostwald ripening. With inclusion of this catalyst reservoir, we observed CNT growth up to 100% taller than that observed without the catalyst reservoir consistently across a wide range of annealing and growth durations. Imaging studies of catalyst layers both for different annealing times and for different alumina support layer thicknesses demonstrate that the surface exposure of metal from the reservoir leads to an active population of smaller catalyst particles upon annealing as opposed to a bimodal catalyst size distribution that appears without inclusion of a reservoir. Overall, the mechanism for growth enhancement we present here demonstrates a new route to engineering efficient catalyst structures to overcome the limitations of CNT growth processes. PMID:24323364

  4. A palladium-doped ceria@carbon core-sheath nanowire network: a promising catalyst support for alcohol electrooxidation reactions

    NASA Astrophysics Data System (ADS)

    Tan, Qiang; Du, Chunyu; Sun, Yongrong; Du, Lei; Yin, Geping; Gao, Yunzhi

    2015-08-01

    A novel palladium-doped ceria and carbon core-sheath nanowire network (Pd-CeO2@C CSNWN) is synthesized by a template-free and surfactant-free solvothermal process, followed by high temperature carbonization. This hierarchical network serves as a new class of catalyst support to enhance the activity and durability of noble metal catalysts for alcohol oxidation reactions. Its supported Pd nanoparticles, Pd/(Pd-CeO2@C CSNWN), exhibit >9 fold increase in activity toward the ethanol oxidation over the state-of-the-art Pd/C catalyst, which is the highest among the reported Pd systems. Moreover, stability tests show a virtually unchanged activity after 1000 cycles. The high activity is mainly attributed to the superior oxygen-species releasing capability of Pd-doped CeO2 nanowires by accelerating the removal of the poisoning intermediate. The unique interconnected one-dimensional core-sheath structure is revealed to facilitate immobilization of the metal catalysts, leading to the improved durability. This core-sheath nanowire network opens up a new strategy for catalyst performance optimization for next-generation fuel cells.A novel palladium-doped ceria and carbon core-sheath nanowire network (Pd-CeO2@C CSNWN) is synthesized by a template-free and surfactant-free solvothermal process, followed by high temperature carbonization. This hierarchical network serves as a new class of catalyst support to enhance the activity and durability of noble metal catalysts for alcohol oxidation reactions. Its supported Pd nanoparticles, Pd/(Pd-CeO2@C CSNWN), exhibit >9 fold increase in activity toward the ethanol oxidation over the state-of-the-art Pd/C catalyst, which is the highest among the reported Pd systems. Moreover, stability tests show a virtually unchanged activity after 1000 cycles. The high activity is mainly attributed to the superior oxygen-species releasing capability of Pd-doped CeO2 nanowires by accelerating the removal of the poisoning intermediate. The unique

  5. Multifunctionality of organometallic quinonoid metal complexes: surface chemistry, coordination polymers, and catalysts.

    PubMed

    Kim, Sang Bok; Pike, Robert D; Sweigart, Dwight A

    2013-11-19

    rhodium complex showed catalytic activity in Suzuki-Miyaura type reaction. As a result of the excellent stability of the homogeneous catalyst [(quinone)Rh(COD)](-) in water, we also successfully demonstrated catalyst recycling in 1,2- and 1,4-addition reactions. The compound [(quinone)Ir(COD)](-) showed significantly poorer catalytic activity in 1,4-addition reactions. Following upon the excellent coordination ability of the quinonoid rhodium complexes to metal centers, we synthesized organometallic coordination polymer nanocatalysts and silica gel-supported quinonoid rhodium catalysts, the latter using a surface sol-gel technique. The resulting heterogeneous catalysts showed activity in the stereospecific polymerization of phenylacetylene.

  6. Multifunctionality of organometallic quinonoid metal complexes: surface chemistry, coordination polymers, and catalysts.

    PubMed

    Kim, Sang Bok; Pike, Robert D; Sweigart, Dwight A

    2013-11-19

    rhodium complex showed catalytic activity in Suzuki-Miyaura type reaction. As a result of the excellent stability of the homogeneous catalyst [(quinone)Rh(COD)](-) in water, we also successfully demonstrated catalyst recycling in 1,2- and 1,4-addition reactions. The compound [(quinone)Ir(COD)](-) showed significantly poorer catalytic activity in 1,4-addition reactions. Following upon the excellent coordination ability of the quinonoid rhodium complexes to metal centers, we synthesized organometallic coordination polymer nanocatalysts and silica gel-supported quinonoid rhodium catalysts, the latter using a surface sol-gel technique. The resulting heterogeneous catalysts showed activity in the stereospecific polymerization of phenylacetylene. PMID:23745596

  7. Hydrogen production by steam reforming of liquefied natural gas (LNG) over nickel catalysts supported on cationic surfactant-templated mesoporous aluminas

    NASA Astrophysics Data System (ADS)

    Seo, Jeong Gil; Youn, Min Hye; Park, Sunyoung; Jung, Ji Chul; Kim, Pil; Chung, Jin Suk; Song, In Kyu

    Two types of mesoporous γ-aluminas (denoted as A-A and A-S) are prepared by a hydrothermal method under different basic conditions using cationic surfactant (cetyltrimethylammonium bromide, CTAB) as a templating agent. A-A and A-S are synthesized in a medium of ammonia solution and sodium hydroxide solution, respectively. Ni/γ-Al 2O 3 catalysts (Ni/A-A and Ni/A-S) are then prepared by an impregnation method, and are applied to hydrogen production by steam reforming of liquefied natural gas (LNG). The effect of a mesoporous γ-Al 2O 3 support on the catalytic performance of Ni/γ-Al 2O 3 is investigated. The identity of basic solution strongly affects the physical properties of the A-A and A-S supports. The high surface-area of the mesoporous γ-aluminas and the strong metal-support interaction of supported catalysts greatly enhance the dispersion of nickel species on the catalyst surface. The well-developed mesopores of the Ni/A-A and Ni/A-S catalysts prohibit the polymerization of carbon species on the catalyst surface during the reaction. In the steam reforming of LNG, both Ni/A-A and Ni/A-S catalysts give better catalytic performance than the nickel catalyst supported on commercial γ-Al 2O 3 (Ni/A-C). In addition, the Ni/A-A catalyst is superior to the Ni/A-S catalyst. The relatively strong metal-support interaction of Ni/A-A catalyst effectively suppresses the sintering of metallic nickel and the carbon deposition in the steam reforming of LNG. The large pores of the Ni/A-A catalyst also play an important role in enhancing internal mass transfer during the reaction.

  8. Low temperature oxidation using support molten salt catalysts

    DOEpatents

    Weimer, Alan W.; Czerpak, Peter J.; Hilbert, Patrick M.

    2003-05-20

    Molten salt reactions are performed by supporting the molten salt on a particulate support and forming a fluidized bed of the supported salt particles. The method is particularly suitable for combusting hydrocarbon fuels at reduced temperatures, so that the formation NO.sub.x species is reduced. When certain preferred salts are used, such as alkali metal carbonates, sulfur and halide species can be captured by the molten salt, thereby reducing SO.sub.x and HCl emissions.

  9. Single atom catalysts on amorphous supports: A quenched disorder perspective

    SciTech Connect

    Peters, Baron; Scott, Susannah L.

    2015-03-14

    Phenomenological models that invoke catalyst sites with different adsorption constants and rate constants are well-established, but computational and experimental methods are just beginning to provide atomically resolved details about amorphous surfaces and their active sites. This letter develops a statistical transformation from the quenched disorder distribution of site structures to the distribution of activation energies for sites on amorphous supports. We show that the overall kinetics are highly sensitive to the precise nature of the low energy tail in the activation energy distribution. Our analysis motivates further development of systematic methods to identify and understand the most reactive members of the active site distribution.

  10. Sustainable catalyst supports for carbon dioxide gas adsorbent

    NASA Astrophysics Data System (ADS)

    Mazlee, M. N.

    2016-07-01

    The adsorption of carbon dioxide (CO2) become the prime attention nowadays due to the fact that increasing CO2 emissions has been identified as a contributor to global climate change. Major sources of CO2 emissions are thermoelectric power plants and industrial plants which account for approximately 45% of global CO2 emissions. Therefore, it is an urgent need to develop an efficient CO2 reduction technology such as carbon capture and storage (CCS) that can reduce CO2 emissions particularly from the energy sector. A lot of sustainable catalyst supports have been developed particularly for CO2 gas adsorbent applications.

  11. A study of aluminophosphate supported Ni-Mo catalysts for hydrocracking bitumen

    SciTech Connect

    Smith, K.J.; Lewkowicz, L.; Oballa, M.C.; Krzywicki, A.

    1994-12-31

    H-Oil and LC-Fining processes utilize a combination of thermal and catalytic hydroprocessing reactions to achieve high yields of distillate in upgrading bitumen or heavy oil residua. The processes are based on a well mixed (ebullated bed) reactor from which deactivated catalyst is continuously withdrawn and fresh catalyst is added to maintain yields. Catalyst activity and lifetime are two key factors controlling the economics of these processes. Catalyst deactivation occurs due to the deposition of coke and metals on the catalyst surface. The choice of catalyst is usually a compromise between two extremes: small pore catalyst with low metals capacity but higher activity that deactivates rapidly because of metals deposition and wide pore catalyst that has high metals deposition capacity but lower activity due to low surface area. Recently, aluminophosphate materials with large pores (< 10 nm--1,000 nm) and high surface areas (100--500 m{sup 2}/g) have been reported. The actual pore size distribution and surface area obtained depend on the Al/P ratio, preparation method and the calcination procedure. These materials are also thermally stable. The purpose of the present work was to determine if such materials, as a result of their pore size distribution and surface area, could decrease the rate of catalyst deactivation, increase catalyst activity and provide sufficient pore volume for high capacity of metals deposition during the upgrading of heavy oil residue.

  12. Evaluating the potential of CNT-supported Co catalyst used for gas pollution removal in the incineration flue gas.

    PubMed

    Lu, Chi-Yuan; Tseng, Hui-Hsin; Wey, Ming-Yen; Chuang, Kui-Hao; Kuo, Jia-Hong

    2009-04-01

    This study investigated the use of Cu/Al(2)O(3), Co/Al(2)O(3), Fe/Al(2)O(3), and Ni/Al(2)O(3) catalysts for the growth of carbon nanotubes (CNTs). These CNTs were used as support for Co catalyst preparation and Co/CNT catalysts were applied to a catalytic reaction to remove BTEX, PAHs, SO(2), NO, and CO simultaneously in a pilot-scale incineration system. The analyzed results of EDS and XRD showed low metal content and good dispersion characteristics of the Al(2)O(3)-supported catalysts by excess-solution impregnation. FESEM analyzed results showed that the CNTs that were synthesized from Co, Fe, and Ni catalysts had a diameter of 20nm, whereas those synthesized from Cu/Al(2)O(3) had a diameter of 50nm. Pilot-scale test results demonstrated that the Co/CNT catalyst effectively removed air pollutants in the catalytic reaction and that there was no obvious deactivation by Pb, water vapor, and coke deposited in the process. The thermal stabilization at 250 degrees C and hydrophobicity properties of CNTs enhanced the application of CNT catalysts in flue gas.

  13. Process for metallization of a substrate by irradiative curing of a catalyst applied thereto

    DOEpatents

    Chen, Ken S.; Morgan, William P.; Zich, John L.

    1999-01-01

    An improved additive process for metallization of substrates is described whereby a catalyst solution is applied to a surface of a substrate. Metallic catalytic clusters can be formed in the catalyst solution on the substrate surface by irradiating the substrate. Electroless plating can then deposit metal onto the portion of the substrate surface having metallic clusters. Additional metallization thickness can be obtained by electrolytically plating the substrate surface after the electroless plating step.

  14. Method of inducing surface ensembles on a metal catalyst

    DOEpatents

    Miller, S.S.

    1987-10-02

    A method of inducing surface ensembles on a transition metal catalyst used in the conversion of a reactant gas or gas mixture, such as carbon monoxide and hydrogen into hydrocarbons (the Fischer-Tropsch reaction) is disclosed which comprises adding a Lewis base to the syngas (CO + H/sub 2/) mixture before reaction takes place. The formation of surface ensembles in this manner restricts the number and types of reaction pathways which will be utilized, thus greatly narrowing the product distribution and maximizing the efficiency of the Fischer-Tropsch reaction. Similarly, amines may also be produced by the conversion of reactant gas or gases, such as nitrogen, hydrogen, or hydrocarbon constituents.

  15. Growth of transition metals on cerium tungstate model catalyst layers

    NASA Astrophysics Data System (ADS)

    Skála, T.; Tsud, N.; Stetsovych, V.; Mysliveček, J.; Matolín, V.

    2016-10-01

    Two model catalytic metal/oxide systems were investigated by photoelectron spectroscopy and scanning tunneling microscopy. The mixed-oxide support was a cerium tungstate epitaxial thin layer grown in situ on the W(1 1 0) single crystal. Active particles consisted of palladium and platinum 3D islands deposited on the tungstate surface at 300 K. Both metals were found to interact weakly with the oxide support and the original chemical state of both support and metals was mostly preserved. Electronic and morphological changes are discussed during the metal growth and after post-annealing at temperatures up to 700 K. Partial transition-metal coalescence and self-cleaning from the CO and carbon impurities were observed.

  16. Growth of transition metals on cerium tungstate model catalyst layers.

    PubMed

    Skála, T; Tsud, N; Stetsovych, V; Mysliveček, J; Matolín, V

    2016-10-01

    Two model catalytic metal/oxide systems were investigated by photoelectron spectroscopy and scanning tunneling microscopy. The mixed-oxide support was a cerium tungstate epitaxial thin layer grown in situ on the W(1 1 0) single crystal. Active particles consisted of palladium and platinum 3D islands deposited on the tungstate surface at 300 K. Both metals were found to interact weakly with the oxide support and the original chemical state of both support and metals was mostly preserved. Electronic and morphological changes are discussed during the metal growth and after post-annealing at temperatures up to 700 K. Partial transition-metal coalescence and self-cleaning from the CO and carbon impurities were observed. PMID:27494195

  17. Carbon-Based Metal-Free Catalysts for Electrocatalysis beyond the ORR.

    PubMed

    Hu, Chuangang; Dai, Liming

    2016-09-19

    Besides their use in fuel cells for energy conversion through the oxygen reduction reaction (ORR), carbon-based metal-free catalysts have also been demonstrated to be promising alternatives to noble-metal/metal oxide catalysts for the oxygen evolution reaction (OER) in metal-air batteries for energy storage and for the splitting of water to produce hydrogen fuels through the hydrogen evolution reaction (HER). This Review focuses on recent progress in the development of carbon-based metal-free catalysts for the OER and HER, along with challenges and perspectives in the emerging field of metal-free electrocatalysis. PMID:27460826

  18. Carbon-Based Metal-Free Catalysts for Electrocatalysis beyond the ORR.

    PubMed

    Hu, Chuangang; Dai, Liming

    2016-09-19

    Besides their use in fuel cells for energy conversion through the oxygen reduction reaction (ORR), carbon-based metal-free catalysts have also been demonstrated to be promising alternatives to noble-metal/metal oxide catalysts for the oxygen evolution reaction (OER) in metal-air batteries for energy storage and for the splitting of water to produce hydrogen fuels through the hydrogen evolution reaction (HER). This Review focuses on recent progress in the development of carbon-based metal-free catalysts for the OER and HER, along with challenges and perspectives in the emerging field of metal-free electrocatalysis.

  19. Nano-structured noble metal catalysts based on hexametallate architecture for the reforming of hydrocarbon fuels

    DOEpatents

    Gardner, Todd H.

    2015-09-15

    Nano-structured noble metal catalysts based on hexametallate lattices, of a spinel block type, and which are resistant to carbon deposition and metal sulfide formation are provided. The catalysts are designed for the reforming of hydrocarbon fuels to synthesis gas. The hexametallate lattices are doped with noble metals (Au, Pt, Rh, Ru) which are atomically dispersed as isolated sites throughout the lattice and take the place of hexametallate metal ions such as Cr, Ga, In, and/or Nb. Mirror cations in the crystal lattice are selected from alkali metals, alkaline earth metals, and the lanthanide metals, so as to reduce the acidity of the catalyst crystal lattice and enhance the desorption of carbon deposit forming moieties such as aromatics. The catalysts can be used at temperatures as high as 1000.degree. C. and pressures up to 30 atmospheres. A method for producing these catalysts and applications of their use also is provided.

  20. Investigation on C-TiO2 nanotubes composite as Pt catalyst support for methanol electrooxidation

    NASA Astrophysics Data System (ADS)

    Sui, Xu-Lei; Wang, Zhen-Bo; Yang, Min; Huo, Li; Gu, Da-Ming; Yin, Ge-Ping

    2014-06-01

    In this paper, Pt nanoparticles have been successfully deposited on the mixture of carbon black and one-dimensional self-ordered TiO2 nanotubes (TNTs) array by a microwave-assisted polyol process to synthesize Pt/C-TNTs catalyst. TiO2 nanoparticles (TNPs) are used instead of TNTs to prepare catalyst as a reference. The obtained samples are characterized by physical characterization and electrochemical measurements. The results show that Pt nanoparticles are uniformly deposited on the three-phase interfaces between carbon and TNTs. The Pt/C-TNTs possesses substantially enhanced activity and stability in electrochemical performance. Such remarkable properties are due to the excellent composite carrier of C-TNTs: (1) TNTs has strong corrosion resistance in acidic and oxidative environment and a metal support interaction between Pt and TNTs; (2) Compared to TNPs, TNTs is more suitable for electro-catalytic field on account of its better electronic conductivity; (3) Compared to TNPs, TNTs can improve the anti-poisoning ability of catalyst for methanol oxidation. (4) Amorphous carbon can improve the dispersion of platinum particles; (5) The distribution of carbon improves the poor conductivity of TNTs. These studies indicate that Pt/C-TNTs compound is a promising catalyst for methanol electrooxidation.

  1. Comparison study of catalyst nanoparticle formation and carbon nanotube growth: Support effect

    SciTech Connect

    Wang Yunyu; Luo Zhiquan; Li Bin; Ho, Paul S.; Yao Zhen; Shi Li; Bryan, Eugene N.; Nemanich, Robert J.

    2007-06-15

    A comparison study has been conducted on the formation of catalyst nanoparticles on a high surface tension metal and low surface tension oxide for carbon nanotube (CNT) growth via catalytic chemical vapor deposition (CCVD). Silicon dioxide (SiO{sub 2}) and tantalum have been deposited as supporting layers before deposition of a thin layer of iron catalyst. Iron nanoparticles were formed after thermal annealing. It was found that densities, size distributions, and morphologies of iron nanoparticles were distinctly different on the two supporting layers. In particular, iron nanoparticles revealed a Volmer-Weber growth mode on SiO{sub 2} and a Stranski-Krastanov mode on tantalum. CCVD growth of CNTs was conducted on iron/tantalum and iron/SiO{sub 2}. CNT growth on SiO{sub 2} exhibited a tip growth mode with a slow growth rate of less than 100 nm/min. In contrast, the growth on tantalum followed a base growth mode with a fast growth rate exceeding 1 {mu}m/min. For comparison, plasma enhanced CVD was also employed for CNT growth on SiO{sub 2} and showed a base growth mode with a growth rate greater than 2 {mu}m/min. The enhanced CNT growth rate on tantalum was attributed to the morphologies of iron nanoparticles in combination with the presence of an iron wetting layer. The CNT growth mode was affected by the adhesion between the catalyst and support as well as CVD process.

  2. Resin-supported catalysts for CuAAC click reactions in aqueous or organic solvents.

    PubMed

    Presolski, Stanislav I; Mamidyala, Sreeman K; Manzenrieder, Florian; Finn, M G

    2012-10-01

    The copper-catalyzed azide-alkyne cycloaddition click reaction is a valuable process for the synthesis of libraries of drug candidates, derivatized polymers and materials, and a wide variety of other functional molecules. In some circumstances, the removal of the copper catalyst is both necessary and inconvenient. We describe here two immobilized forms of a Cu-binding ligand that has been shown to accelerate triazole formation under many different conditions, using different resin supports that are appropriate for aqueous or organic solvents. Copper leaching from these resins was modest, allowing them to be reused in many reaction/filtration cycles without recharging with metal ion. The utility of this catalyst form was demonstrated in the convenient synthesis of 20 N-acetylgalactosamine derivatives for biological testing. PMID:22946559

  3. New catalysts for coal processing: metal carbides and nitrides. Semiannual report, November 1, 1995 - July 17, 1996

    SciTech Connect

    Oyama, S. T.; Cox, D. F.

    1996-04-01

    Work involving the synthesis of monometallic transition metal carbides supported on alumina is described. The catalysts have excellent initial activity in the hydrodechlorination of CCl{sub 2}F{sub 2} (CFC 12), but deactivate with time by the deposition of carbon. Initial work on the preparation of unsupported bimetallic oxynitrides is also described.

  4. Novel growth method of carbon nanotubes using catalyst-support layer developed by alumina grit blasting.

    PubMed

    Watanabe, Hiromichi; Ishii, Juntaro; Ota, Keishin

    2016-08-19

    We propose an efficient method of growing carbon nanotube (CNT) arrays on a variety of metals, alloys, and carbon materials using chemical vapor deposition (CVD) assisted by a simple surface treatment of the materials. The main feature of this method is the application of grit blasting with fine alumina particles to the development of a catalyst-support layer required for the growth of CNTs on various conductive materials, including ultra-hard metals such as tungsten. Auger electron spectroscopy shows that grit blasting can form a non-continuous layer where alumina nanoparticles are embedded as residues in the blasting media left on the treated surfaces. This work reveals that such a non-continuous alumina layer can behave as the catalyst-support layer, which is generally prepared by sputter or a vacuum evaporation coating process that considerably restricts the practical applications of CNTs. We have attempted to grow CNTs on grit-blasted substrates of eighteen conventionally used conductive materials using CVD together with a floating iron catalyst. The proposed method was successful in growing multi-walled CNT arrays on the grit-blasted surfaces of all the examined materials, demonstrating its versatility. Furthermore, we found that the group IV metal oxide films thermally grown on the as-received substrates can support the catalytic activity of iron nanoparticles in the CVD process just as well as the alumina film developed by grit blasting. Spectral emissivity of the CNT arrays in the visible and infrared wavelength ranges has been determined to assess the applicability of the CNT arrays as a black coating media. PMID:27389659

  5. Novel growth method of carbon nanotubes using catalyst-support layer developed by alumina grit blasting

    NASA Astrophysics Data System (ADS)

    Watanabe, Hiromichi; Ishii, Juntaro; Ota, Keishin

    2016-08-01

    We propose an efficient method of growing carbon nanotube (CNT) arrays on a variety of metals, alloys, and carbon materials using chemical vapor deposition (CVD) assisted by a simple surface treatment of the materials. The main feature of this method is the application of grit blasting with fine alumina particles to the development of a catalyst-support layer required for the growth of CNTs on various conductive materials, including ultra-hard metals such as tungsten. Auger electron spectroscopy shows that grit blasting can form a non-continuous layer where alumina nanoparticles are embedded as residues in the blasting media left on the treated surfaces. This work reveals that such a non-continuous alumina layer can behave as the catalyst-support layer, which is generally prepared by sputter or a vacuum evaporation coating process that considerably restricts the practical applications of CNTs. We have attempted to grow CNTs on grit-blasted substrates of eighteen conventionally used conductive materials using CVD together with a floating iron catalyst. The proposed method was successful in growing multi-walled CNT arrays on the grit-blasted surfaces of all the examined materials, demonstrating its versatility. Furthermore, we found that the group IV metal oxide films thermally grown on the as-received substrates can support the catalytic activity of iron nanoparticles in the CVD process just as well as the alumina film developed by grit blasting. Spectral emissivity of the CNT arrays in the visible and infrared wavelength ranges has been determined to assess the applicability of the CNT arrays as a black coating media.

  6. Synthesis and characterization of molybdenum catalysts supported on γ-Al2O3-CeO2 composite oxides

    NASA Astrophysics Data System (ADS)

    Farooq, Muhammad; Ramli, Anita; Subbarao, Duvvuri

    2012-09-01

    The physical and chemical properties of a catalyst play a vital role in various industrial applications. Molybdenum catalysts supported on γ-Al2O3 and γ-Al2O3-CeO2 mixed oxides with varying loading of CeO2 (5, 10, 15, 20 wt% with respect to γ-Al2O3) were prepared by wet impregnation method. The physiochemical properties of these synthesized Mo catalysts were studied with various characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), field emission scanning electron microscopy-energy dispersive analysis (FESEM-EDX) and X-ray fluorescence spectrometer (XRF). The results showed that the addition of CeO2 into the support affected the binding energies of the elements and reducibility of the metal oxides formed after calcination of catalyst samples due to the change in metal-support interaction. Further, the characterization techniques showed that the active metal was well dispersed on the surface of support material.

  7. Method for hydrogen production and metal winning, and a catalyst/cocatalyst composition useful therefor

    DOEpatents

    Dhooge, Patrick M.

    1987-10-13

    A catalyst/cocatalyst/organics composition of matter is useful in electrolytically producing hydrogen or electrowinning metals. Use of the catalyst/cocatalyst/organics composition causes the anode potential and the energy required for the reaction to decrease. An electrolyte, including the catalyst/cocatalyst composition, and a reaction medium composition further including organic material are also described.

  8. Direct synthesis of hydrogen peroxide from H2 and O2 using supported Au-Pd catalysts.

    PubMed

    Edwards, Jennifer K; Carley, Albert F; Herzing, Andrew A; Kiely, Christopher J; Hutchings, Graham J

    2008-01-01

    The direct synthesis of H2O2 at low temperature (2 degrees C) from H2 and O2 using carbon-supported Au, Pd and Au-Pd catalysts is described and contrasted with data for TiO2, Al2O3 and Fe2O3 as supports. The Au-Pd catalysts all perform significantly better than the pure Pd/TiO2 and Au/ TiO2 materials. The Au Pd/carbon catalysts gave the highest rate of H2O2 production, and the order of reactivity observed is: carbon > TiO2 > Al2O3. Catalysts were prepared by co-impregnation of the supports using incipient wetness with aqueous solutions of PdCl2 and HAuCl4, and following calcination at 400 degrees C the catalysts were stable and could be reused several time without loss of metal. The method of preparation is critical, however, to achieve stable catalysts. No promoters are required (e.g. halides) to achieve the high rates of hydrogen peroxide synthesis. The surface and bulk composition of the gold palladium nanoparticles was investigated by STEM-XEDS spectrum imaging. For TiO2 and Al2O3 as supports the Au Pd particles were found to exhibit a core-shell structure, Pd being concentrated on the surface. In contrast, the Au-Pd/carbon catalyst exhibited Au Pd nanoparticles which were homogeneous alloys and X-ray photoelectron studies were consistent with these observations. The origin of the enhanced activity for the carbon supported catalysts is a result of higher H2 selectivity for the formation of hydrogen peroxide which is due to the surface composition and size distribution of the nanoparticles. The key problem remaining is the sequential hydrogenation of hydrogen peroxide which limits the utilisation of the direct synthesis methodology and this is discussed in detail. PMID:18447018

  9. Growth of semiconducting single-walled carbon nanotubes by using ceria as catalyst supports.

    PubMed

    Qin, Xiaojun; Peng, Fei; Yang, Feng; He, Xiaohui; Huang, Huixin; Luo, Da; Yang, Juan; Wang, Sheng; Liu, Haichao; Peng, Lianmao; Li, Yan

    2014-02-12

    The growth of semiconducting single-walled carbon nanotubes (s-SWNTs) on flat substrates is essential for the application of SWNTs in electronic and optoelectronic devices. We developed a flexible strategy to selectively grow s-SWNTs on silicon substrates using a ceria-supported iron or cobalt catalysts. Ceria, which stores active oxygen, plays a crucial role in the selective growth process by inhibiting the formation of metallic SWNTs via oxidation. The so-produced ultralong s-SWNT arrays are immediately ready for building field effect transistors. PMID:24392872

  10. An EXAFS study of oxide and suphided catalysts

    NASA Astrophysics Data System (ADS)

    Zamaraev, K. I.; Kochubey, D. I.

    1989-10-01

    This review article summarizes the results of EXAFS studies, mainly carried out in the USSR, on the structure of oxide and sulphided chemical compounds formed on surfaces of various heterogeneous catalysts. It describes supported metallic catalysts in the presence of oxygen, supported oxide catalysts at different preparation and activation conditions, and supports, modified by transition metal oxides and catalysts for hydrodesulphurization processes.

  11. Pore structure characterization of catalyst supports via low field NMR

    SciTech Connect

    Smith, D.M.; Glaves, C.L.; Gallegos, D.P. )

    1988-09-01

    The pore structures of two types of catalyst support material were studied: {gamma}-alumina and silica aerogel. The alumina samples were commercial catalyst supports made in 1/8 inch diameter pellet form by Harshaw Chemical. Aerogels were prepared by forming a gel in a two-step, base-catalyzed process using TEOS, followed by supercritical drying to form the aerogel. Two different aerogels were made, one undergoing the drying process immediately after gel formation (non-aged), and the other being aged in the gel state for two weeks in a basic solution of 0.1 molar NH{sub 4}OH at 323 K before being supercritically dried (aged). The aging process is believed to alter the aerogel pore structure. The pore size distribution of the alumina material was determined via NMR and compared to results obtained by mercury intrusion and nitrogen adsorption/condensation techniques. The pore size distributions of the two aerogel samples were measured via NMR and nitrogen adsorption/condensation; the material was too compressible for porosimetry.

  12. Noble metal nanoparticle@metal oxide core/yolk-shell nanostructures as catalysts: recent progress and perspective

    NASA Astrophysics Data System (ADS)

    Li, Guodong; Tang, Zhiyong

    2014-03-01

    Controllable integration of noble metals (e.g., Au, Ag, Pt, and Pd) and metal oxides (e.g., TiO2, CeO2, and ZrO2) into single nanostructures has attracted immense research interest in heterogeneous catalysis, because they not only combine the properties of both noble metals and metal oxides, but also bring unique collective and synergetic functions in comparison with single-component materials. Among many strategies recently developed, one of the most efficient ways is to encapsulate and protect individual noble metal nanoparticles by a metal oxide shell of a certain thickness to generate the core-shell or yolk-shell structure, which exhibits enhanced catalytic performance compared with conventional supported catalysts. In this review article, we summarize the state-of-the art progress in synthesis and catalytic application of noble metal nanoparticle@metal oxide core/yolk-shell nanostructures. We hope that this review will help the readers to obtain better insight into the design and application of well-defined nanocomposites in both the energy and environmental fields.

  13. Reverse micelle synthesis of nanoscale metal containing catalysts

    SciTech Connect

    Darab, J.G.; Fulton, J.L.; Linehan, J.C.

    1993-03-01

    The need for morphological control during the synthesis of catalyst precursor powders is generally accepted to be important. In the liquefaction of coal, for example, iron-bearing catalyst precursor particles containing individual crystallites with diameters in the 1-100 nanometer range are believed to achieve good dispersion through out the coal-solvent slurry during liquefaction 2 runs and to undergo chemical transformations to catalytically active iron sulfide phases. The production of the nanoscale powders described here employs the confining spherical microdomains comprising the aqueous phase of a modified reverse micelle (MRM) microemulsion system as nanoscale reaction vessels in which polymerization, electrochemical reduction and precipitation of solvated salts can occur. The goal is to take advantage of the confining nature of micelles to kinetically hinder transformation processes which readily occur in bulk aqueous solution in order to control the morphology and phase of the resulting powder. We have prepared a variety of metal, alloy, and metal- and mixed metal-oxide nanoscale powders from appropriate MRM systems. Examples of nanoscale powders produced include Co, Mo-Co, Ni{sub 3}Fe, Ni, and various oxides and oxyhydroxides of iron. Here, we discuss the preparation and characterization of nickel metal (with a nickel oxide surface layer) and iron oxyhydroxide MRM nanoscale powders. We have used extended x-ray absorption fine structure (EXAFS) spectroscopy to study the chemical polymerization process in situ, x-ray diffraction (XRD), scanning and transmission electron microcroscopies (SEM and TEM), elemental analysis and structural modelling to characterize the nanoscale powders produced. The catalytic activity of these powders is currently being studied.

  14. Metal/metal oxide doped oxide catalysts having high deNOx selectivity for lean NOx exhaust aftertreatment systems

    DOEpatents

    Park, Paul W.

    2004-03-16

    A lean NOx catalyst and method of preparing the same is disclosed. The lean NOx catalyst includes a ceramic substrate, an oxide support material, preferably .gamma.-alumina, deposited on the substrate and a metal promoter or dopant introduced into the oxide support material. The metal promoters or dopants are selected from the group consisting of indium, gallium, tin, silver, germanium, gold, nickel, cobalt, copper, iron, manganese, molybdenum, chromium, cerium, vanadium, oxides thereof, and combinations thereof. The .gamma.-alumina preferably has a pore volume of from about 0.5 to about 2.0 cc/g; a surface area of between about 80 to 350 m.sup.2 /g; an average pore size diameter of between about 3 to 30 nm; and an impurity level of less than or equal to 0.2 weight percent. In a preferred embodiment the .gamma.-alumina is prepared by a sol-gel method, with the metal doping of the .gamma.-alumina preferably accomplished using an incipient wetness impregnation technique.

  15. Development of heterogeneous olympic medal metal nanoparticle catalysts for environmentally benign molecular transformations based on the surface properties of hydrotalcite.

    PubMed

    Kaneda, Kiyotomi; Mitsudome, Takato; Mizugaki, Tomoo; Jitsukawa, Koichiro

    2010-12-08

    In this review, we describe the development by our research group of highly functionalized heterogeneous Olympic medal metal (gold, silver, and copper) nanoparticle catalysts using hydrotalcite as a support, aimed towards Green and Sustainable Chemistry. Olympic medal metal nanoparticles can cooperate with the basic sites on the hydrotalcite surface, providing unique and high performance catalysis in environmentally-benign organic transformations such as aerobic oxidation of alcohols, lactonization of diols and selective deoxygenation of epoxides and nitro aromatic compounds.

  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. Platinum catalysts promoted by In doped SnO2 support for methanol electrooxidation in alkaline electrolyte

    NASA Astrophysics Data System (ADS)

    Feng, Yuan-Yuan; Kong, Wei-Qing; Yin, Qian-Ying; Du, Li-Xia; Zheng, Ying-Ting; Kong, De-Sheng

    2014-04-01

    Composite metal oxides InxSnO2 are prepared with a simple hydrothermal process and used as functionalized support of Pt catalyst toward methanol electrooxidation reaction (MOR). The catalytic activity of Pt is strongly dependent on the composition of the support. Introduction of a small amount of In into SnO2 support exhibits much higher promoting effect to the Pt catalytic properties as compared with Pt/SnO2 and commercial Pt/C catalysts. The mass-specific activity (MSA) and intrinsic activity (IA) of Pt in Pt/In0.1SnO2 is 3.0 and 4.3 times that of Pt/C, respectively. Changes in Pt electronic structure arising from the interaction between Pt and the support are responsible for this improvement. Our findings clearly suggest that the composite metal oxides InxSnO2 can not only act as the catalyst support but also act as an effective promoter to Pt toward MOR, which would be promising in designing new catalysts that can replace the traditional catalytic nanostructure.

  18. Highly aligned vertical GaN nanowires using submonolayer metal catalysts

    DOEpatents

    Wang, George T.; Li, Qiming; Creighton, J. Randall

    2010-06-29

    A method for forming vertically oriented, crystallographically aligned nanowires (nanocolumns) using monolayer or submonolayer quantities of metal atoms to form uniformly sized metal islands that serve as catalysts for MOCVD growth of Group III nitride nanowires.

  19. Function of titanium oxide coated on carbon nanotubes as support for platinum catalysts

    NASA Astrophysics Data System (ADS)

    Ying, Qiling; Naidoo, Sivapregasen; Vaivars, Guntars

    2015-09-01

    This study describes the outcome of the synthesis of laboratory-made (HM) Pt monometallic, binary and ternary catalysts supported on TiO2/CNT (carbon nanotubes) and based on using the dry-mix method of organometallic chemical vapor deposition (OMCVD). These multicomponent catalysts were investigated and compared with commercial Johnson Matthey (JM) catalysts for electrochemical applications.

  20. Microcalorimetric study of silica- and zeolite-supported platinum catalysts

    SciTech Connect

    Sharma, S.B.; Dumesic, J.A. ); Miller, J.T. )

    1994-07-01

    Microcalorimetric measurements of the differential heats of hydrogen and carbon monoxide adsorption versus adsorbate coverate were made at 403 K for platinum supported on silica, magnesia/alumina, L-zeolite, Y-zeolite, and ZSM-5. The differential heats at zero coverage for hydrogen and carbon monoxide adsorption were 90 and 140 kJ/mol, respectively, for platinum supported on silica and nonacidic zeolites. The differential heats were large by approximately 20 kJ/mol for hydrogen and carbon monoxide adsorption on platinum particles supported on basis supports such as potassium/silica, magnesia/alumina, and zeolites containing basic cations (K[sup +], Ba[sup 2+]) exchanged in excess of the zeolite framework aluminum content. The microcalorimetric results suggest that the high paraffin aromatization activity and selectivity observed for L-zeolite-supported platinum catalysts do not appear to be caused solely by changes in the adsorptive properties of the cluster-size platinum particles located within the zeolite. 35 refs., 10 figs., 2 tabs.

  1. Oxidation catalysts comprising metal exchanged hexaaluminate wherein the metal is Sr, Pd, La, and/or Mn

    DOEpatents

    Wickham, David; Cook, Ronald

    2008-10-28

    The present invention provides metal-exchanged hexaaluminate catalysts that exhibit good catalytic activity and/or stability at high temperatures for extended periods with retention of activity as combustion catalysts, and more generally as oxidation catalysts, that make them eminently suitable for use in methane combustion, particularly for use in natural gas fired gas turbines. The hexaaluminate catalysts of this invention are of particular interest for methane combustion processes for minimization of the generation of undesired levels (less than about 10 ppm) of NOx species. Metal exchanged hexaaluminate oxidation catalysts are also useful for oxidation of volatile organic compounds (VOC), particularly hydrocarbons. Metal exchanged hexaaluminate oxidation catalysts are further useful for partial oxidation, particularly at high temperatures, of reduced species, particularly hydrocarbons (alkanes and alkenes).

  2. Bridging the Gap between Theory and Experiments - Nano-structural Changes in Supported Catalysts under Operating Conditions

    SciTech Connect

    Narula, Chaitanya Kumar; Allard Jr, Lawrence Frederick; Blom, Douglas Allen; Debusk, Melanie Moses

    2008-01-01

    Computational approaches have been limited to examining catalytic processes using models that have been greatly simplified in comparison to real catalysts. Experimental studies, especially on emission treatment catalysts, have primarily focused on fully formulated systems. Thus, there remains a knowledge gap between theory and experiments. We combine the power of theory and experiment for atomistic design of catalytically active sites that can translate the fundamental insights gained directly to a catalyst system suitable for technical deployment. In this article, we describe our results on a model platinum-alumina catalyst that is a common constituent of emission treatment catalysts such as three-way, NO/dx trap, oxidation, and HC-SCR catalysts. We present theoretical and experimental studies of the oxidation and reactivity of Pt catalyst clusters towards O, CO, and NO/dx. Our theoretical studies indicate that the reaction energetics are strongly dependent on the size of the clusters as well as the extent of oxidation of the clusters, and the energetics of CO and NO oxidation may be more favorable on the oxidized clusters than metallic clusters because of the weakened adsorption of O, CO and NO. Experimentally, we have observed that the aberration-corrected HA-ADF STEM images of Pt/gg-alumina support show that there are single atoms, 2-3 atom clusters, and several 10-20 atom clusters of Pt. We also found that the Pt particles size has an impact on CO oxidation initiation and completion temperatures. Substrate effects were studied for equivalent Pt particle size distributions on both gu-alumina and gg-alumina supports. Particle size effects were investigated on Pt/gg-alumina catalysts with Pt particle size distribution centered at 1 nm and 12 nm, respectively. We will describe our results on substrate and Pt particle size effects. In addition, we will also present our study of nano-structural changes in model catalysts on exposure to various reaction conditions.

  3. Microwave-assisted cross-coupling and hydrogenation chemistry by using heterogeneous transition-metal catalysts: an evaluation of the role of selective catalyst heating.

    PubMed

    Irfan, Muhammed; Fuchs, Michael; Glasnov, Toma N; Kappe, C Oliver

    2009-11-01

    The concept of specific microwave effects in solid/liquid catalytic processes resulting from the selective heating of a microwave-absorbing heterogeneous transition-metal catalyst by using 2.45 GHz microwave irradiation was evaluated. As model transformations Ni/C-, Cu/C-, Pd/C-, and Pd/Al2O3-catalyzed carbon-carbon/carbon-heteroatom cross-couplings and hydrogenation reactions were investigated. To probe the existence of specific microwave effects by means of selective catalyst heating in these transformations, control experiments comparing microwave dielectric heating and conventional thermal heating at the same reaction temperature were performed. Although the supported metal catalysts were experimentally found to be strongly microwave absorbing, for all chemistry examples investigated herein no differences in reaction rate or selectivity between microwave and conventional heating experiments under carefully controlled conditions were observed. This was true also for reactions that use low-absorbing or microwave transparent solvents, and was independent of the microwave absorbtivity of the catalyst support material. In the case of hydrogenation reactions, the stirring speed was found to be a critical factor on the mass transfer between gas and liquid phase, influencing the rate of the hydrogenation in both microwave and conventionally heated experiments.

  4. Characterization and Hydrodesulfurization Properties of Catalysts Derived from Amorphous Metal-Boron Materials

    SciTech Connect

    Parks,G.; Pease, M.; Burns, A.; Layman, K.; Bussell, M.; Wang, X.; Hanson, J.; Rodriquez, J.

    2007-01-01

    Unsupported and silica-supported amorphous metal-boron materials (Ni-B, Mo-O-B, and Ni-Mo-O-B) were prepared by NaBH{sub 4} reduction of aqueous or impregnated metal salts. The resulting materials were characterized by a range of techniques, including conventional and time-resolved X-ray diffraction. The latter technique was used to determine the onset of crystallization of the amorphous materials during annealing in He flow and to identify the phases formed. Annealing of unsupported Ni-B resulted in the crystallization of predominantly Ni{sub 3}B, followed by Ni metal, whereas Ni-B/SiO{sub 2} formed Ni and then NiO. There was no evidence for crystallization of B-containing phases for Mo-O-B or Mo-O-B/SiO{sub 2} on annealing; instead, the predominant phase formed was MoO{sub 2}. In general, the phases formed for Ni-Mo-O-B and Ni-Mo-O-B/SiO2 were consistent with those formed in the monometallic materials, but at higher annealing temperatures. Catalysts prepared by sulfiding Ni-B/SiO{sub 2} and Ni-Mo-O-B/SiO{sub 2} materials had significantly higher thiophene HDS activities than conventionally prepared sulfided Ni/SiO2 and Ni-Mo/SiO{sub 2} catalysts, whereas a sulfided Mo-O-B/SiO{sub 2} catalyst had a dramatically lower HDS activity than a sulfided Mo/SiO{sub 2} catalyst.

  5. Metallocene supported core@LDH catalysts for slurry phase ethylene polymerisation.

    PubMed

    Buffet, Jean-Charles; Byles, Coral F H; Felton, Ryan; Chen, Chunping; O'Hare, Dermot

    2016-03-14

    We report the synthesis of solid catalysts based on a zirconocene supported on either silica@AMO-LDH or zeolite@AMO-LDH for the slurry phase polymerisation of ethylene. The hybrid catalysts demonstrate synergistic effects in which the polymerisation activity is up to three times higher than the zirconocene supported on analogous single phase silica or zeolite supports.

  6. Carbon monoxide oxidation over three different states of copper: Development of a model metal oxide catalyst

    SciTech Connect

    Jernigan, G G

    1994-10-01

    Carbon monoxide oxidation was performed over the three different oxidation states of copper -- metallic (Cu), copper (I) oxide (Cu{sub 2}O), and copper (II) oxide (CuO) as a test case for developing a model metal oxide catalyst amenable to study by the methods of modern surface science and catalysis. Copper was deposited and oxidized on oxidized supports of aluminum, silicon, molybdenum, tantalum, stainless steel, and iron as well as on graphite. The catalytic activity was found to decrease with increasing oxidation state (Cu > Cu{sub 2}O > CuO) and the activation energy increased with increasing oxidation state (Cu, 9 kcal/mol < Cu{sub 2}O, 14 kcal/mol < CuO, 17 kcal/mol). Reaction mechanisms were determined for the different oxidation states. Lastly, NO reduction by CO was studied. A Cu and CuO catalyst were exposed to an equal mixture of CO and NO at 300--350 C to observe the production of N{sub 2} and CO{sub 2}. At the end of each reaction, the catalyst was found to be Cu{sub 2}O. There is a need to study the kinetics of this reaction over the different oxidation states of copper.

  7. A new bio-inspired route to metal-nanoparticle-based heterogeneous catalysts.

    PubMed

    Debecker, Damien P; Faure, Chrystel; Meyre, Marie-Edith; Derré, Alain; Gaigneaux, Eric M

    2008-10-01

    Onion-type multilamellar vesicles are made of concentric bilayers of organic surfactant and are mainly known for their potential applications in biotechnology. They can be used as microreactors for the spontaneous and controlled production of metal nanoparticles. This process does not require any thermal treatment and, hence, it is also attractive for material sciences such as heterogeneous catalysis. In this paper, silver-nanoparticle-based catalysts are prepared by transferring onion-grown silver nanoparticles onto inorganic supports. The resulting materials are active in the total oxidation of benzene, attesting that this novel bio-inspired concept is promising in inorganic catalysis. PMID:18844300

  8. Reactivity of Aryl Halides for Reductive Dehalogenation in (Sea)water Using Polymer-Supported Terpyridine Palladium Catalyst.

    PubMed

    Suzuka, Toshimasa; Sueyoshi, Hiromu; Maehara, Shohei; Ogasawara, Hiroaki

    2015-01-01

    A polymer-supported terpyridine palladium complex was prepared. The complex was found to promote hydrodechlorination of aryl chlorides with potassium formate in seawater. Generally, reductive cleavage of aryl chlorides using transition metal catalysts is more difficult than that of aryl bromides and iodides (reactivity: I > Br > Cl); however, the results obtained did not follow the general trend. Therefore, we investigated the reaction inhibition agents and found a method to remove these inhibitors. The polymeric catalysts showed high catalytic activity and high reusability for transfer reduction in seawater.

  9. Water oxidation using earth-abundant transition metal catalysts: opportunities and challenges.

    PubMed

    Kärkäs, Markus D; Åkermark, Björn

    2016-10-01

    Catalysts for the oxidation of H2O are an integral component of solar energy to fuel conversion technologies. Although catalysts based on scarce and precious metals have been recognized as efficient catalysts for H2O oxidation, catalysts composed of inexpensive and earth-abundant element(s) are essential for realizing economically viable energy conversion technologies. This Perspective summarizes recent advances in the field of designing homogeneous water oxidation catalysts (WOCs) based on Mn, Fe, Co and Cu. It reviews the state of the art catalysts, provides insight into their catalytic mechanisms and discusses future challenges in designing bioinspired catalysts based on earth-abundant metals for the oxidation of H2O.

  10. NiO as a peculiar support for metal nanoparticles in polyols oxidation

    SciTech Connect

    Villa, Alberto; Veith, Gabriel M; Ferri, Davide; Weidenkaff, Anke; Perry, Kelly A; Campisi, Sebastiano; Prati, Laura

    2013-01-01

    The peculiar influence of a NiO support was studied by preparing gold catalysts supported on NiO(1-x) TiO2(x) mixed oxides. PVA protected Au nanoparticles showed high activity when supported on NiO for the selective oxidation of glycerol and ethan-1,2-diol. A detailed characterization of the resulting Au catalysts revealed a preferential deposition of the metal nanoparticles on the NiO phase. However, the activity of Au on NiO(1-x)-TiO2(x) decreased with respect to pure NiO and the selectivity evolved with changes to the support.

  11. Metallocorroles as Nonprecious-Metal Catalysts for Oxygen Reduction.

    PubMed

    Levy, Naomi; Mahammed, Atif; Kosa, Monica; Major, Dan T; Gross, Zeev; Elbaz, Lior

    2015-11-16

    The future of affordable fuel cells strongly relies on the design of earth-abundant (non-platinum) catalysts for the electrochemical oxygen reduction reaction (ORR). However, the bottleneck in the overall process occurs therein. We have examined herein trivalent Mn, Fe, Co, Ni, and Cu complexes of β-pyrrole-brominated corrole as ORR catalysts. The adsorption of these complexes on a high-surface-area carbon powder (BP2000) created a unique composite material, used for electrochemical measurements in acidic aqueous solutions. These experiments disclosed a clear dependence of the catalytic activity on the metal center of the complexes, in the order of Co>Fe>Ni>Mn>Cu. The best catalytic performance was obtained for the Co(III) corrole, whose onset potential was as positive as 0.81 V versus the reversible hydrogen electrode (RHE). Insight into the properties of these systems was gained by spectroscopic and computational characterization of the reduced and oxidized forms of the metallocorroles. PMID:26429211

  12. Design and Preparation of Supported Au Catalyst with Enhanced Catalytic Activities by Rationally Positioning Au Nanoparticles on Anatase.

    PubMed

    Wang, Liang; Wang, Hong; Rice, Andrew E; Zhang, Wei; Li, Xiaokun; Chen, Mingshu; Meng, Xiangju; Lewis, James P; Xiao, Feng-Shou

    2015-06-18

    A synergistic effect between individual components is crucial for increasing the activity of metal/metal oxide catalysts. The greatest challenge is how to control the synergistic effect to obtain enhanced catalytic performance. Through density functional theory calculations of model Au/TiO2 catalysts, it is suggested that there is strong interaction between Au nanoparticles and Ti species at the edge/corner sites of anatase, which is favorable for the formation of stable oxygen vacancies. Motivated by this theoretical analysis, we have rationally prepared Au nanoparticles attached to edge/corner sites of anatase support (Au/TiO2-EC), confirmed by their HR-TEM images. As expected, this strong interaction is well characterized by Raman, UV-visible, and XPS techniques. Very interestingly, compared with conventional Au catalysts, Au/TiO2-EC exhibits superior catalytic activity in the oxidations using O2. Our approach to controlling Au nanoparticle positioning on anatase to obtain enhanced catalytic activity offers an efficient strategy for developing more novel supported metal catalysts.

  13. Design and Preparation of Supported Au Catalyst with Enhanced Catalytic Activities by Rationally Positioning Au Nanoparticles on Anatase.

    PubMed

    Wang, Liang; Wang, Hong; Rice, Andrew E; Zhang, Wei; Li, Xiaokun; Chen, Mingshu; Meng, Xiangju; Lewis, James P; Xiao, Feng-Shou

    2015-06-18

    A synergistic effect between individual components is crucial for increasing the activity of metal/metal oxide catalysts. The greatest challenge is how to control the synergistic effect to obtain enhanced catalytic performance. Through density functional theory calculations of model Au/TiO2 catalysts, it is suggested that there is strong interaction between Au nanoparticles and Ti species at the edge/corner sites of anatase, which is favorable for the formation of stable oxygen vacancies. Motivated by this theoretical analysis, we have rationally prepared Au nanoparticles attached to edge/corner sites of anatase support (Au/TiO2-EC), confirmed by their HR-TEM images. As expected, this strong interaction is well characterized by Raman, UV-visible, and XPS techniques. Very interestingly, compared with conventional Au catalysts, Au/TiO2-EC exhibits superior catalytic activity in the oxidations using O2. Our approach to controlling Au nanoparticle positioning on anatase to obtain enhanced catalytic activity offers an efficient strategy for developing more novel supported metal catalysts. PMID:26266615

  14. Selective oxidation of glycerol by using a hydrotalcite-supported platinum catalyst under atmospheric oxygen pressure in water.

    PubMed

    Tsuji, Akihiro; Rao, Kasanneni Tirumala Venkateswara; Nishimura, Shun; Takagaki, Atsushi; Ebitani, Kohki

    2011-04-18

    A hydrotalcite-supported platinum (Pt/HT) catalyst was found to be a highly active and selective heterogeneous catalyst for glycerol oxidation in pure water under atmospheric oxygen pressure in a high glycerol/metal molar ratio up to 3125. High selectivity toward glyceric acid (78 %) was obtained even at room temperature under air atmosphere. The Pt/HT catalyst selectively oxidized the primary hydroxyl group of 1,2-propandiol to give the corresponding carboxylic acid (lactic acid) as well as glycerol. The activity of the catalyst was greatly influenced by the Mg/Al ratio of hydrotalcite. Glycerol conversion increased with increasing the Mg/Al ratio of hydrotalcite (from trace to 56 %). X-ray absorption fine structure (XAFS) measurements indicated that the catalytic oxidation activity was proportional to the metallic platinum concentration, and more than 35 % of metallic platinum was necessary for this reaction. TEM measurements and titration analysis by using benzoic acid suggested that the solid basicity of hydrotalcite plays important roles in the precise control of platinum size and metal concentration as well as the initial promotion of alcohol oxidation.

  15. Selective oxidation of glycerol by using a hydrotalcite-supported platinum catalyst under atmospheric oxygen pressure in water.

    PubMed

    Tsuji, Akihiro; Rao, Kasanneni Tirumala Venkateswara; Nishimura, Shun; Takagaki, Atsushi; Ebitani, Kohki

    2011-04-18

    A hydrotalcite-supported platinum (Pt/HT) catalyst was found to be a highly active and selective heterogeneous catalyst for glycerol oxidation in pure water under atmospheric oxygen pressure in a high glycerol/metal molar ratio up to 3125. High selectivity toward glyceric acid (78 %) was obtained even at room temperature under air atmosphere. The Pt/HT catalyst selectively oxidized the primary hydroxyl group of 1,2-propandiol to give the corresponding carboxylic acid (lactic acid) as well as glycerol. The activity of the catalyst was greatly influenced by the Mg/Al ratio of hydrotalcite. Glycerol conversion increased with increasing the Mg/Al ratio of hydrotalcite (from trace to 56 %). X-ray absorption fine structure (XAFS) measurements indicated that the catalytic oxidation activity was proportional to the metallic platinum concentration, and more than 35 % of metallic platinum was necessary for this reaction. TEM measurements and titration analysis by using benzoic acid suggested that the solid basicity of hydrotalcite plays important roles in the precise control of platinum size and metal concentration as well as the initial promotion of alcohol oxidation. PMID:21271683

  16. Building up strain in colloidal metal nanoparticle catalysts.

    PubMed

    Sneed, Brian T; Young, Allison P; Tsung, Chia-Kuang

    2015-08-01

    The focus on surface lattice strain in nanostructures as a fundamental research topic has gained momentum in recent years as scientists investigated its significant impact on the surface electronic structure and catalytic properties of nanomaterials. Researchers have begun to tell a more complete story of catalysis from a perspective which brings this concept to the forefront of the discussion. The nano-'realm' makes the effects of surface lattice strain, which acts on the same spatial scales, more pronounced due to a higher ratio of surface to bulk atoms. This is especially evident in the field of metal nanoparticle catalysis, where displacement of atoms on surfaces can significantly alter the sorption properties of molecules. In part, the concept of strain-engineering for catalysis opened up due to the achievements that were made in the synthesis of a more sophisticated nanoparticle library from an ever-expanding set of methodologies. Developing synthesis methods for metal nanoparticles with well-defined and strained architectures is a worthy goal that, if reached, will have considerable impact in the search for catalysts. In this review, we summarize the recent accomplishments in the area of surface lattice-strained metal nanoparticle synthesis, framing the discussion from the important perspective of surface lattice strain effects in catalysis.

  17. Method for producing hydrocarbon fuels from heavy polynuclear hydrocarbons by use of molten metal halide catalyst

    DOEpatents

    Gorin, Everett

    1979-01-01

    In a process for hydrocracking heavy polynuclear carbonaceous feedstocks to produce lighter hydrocarbon fuels by contacting the heavy feedstocks with hydrogen in the presence of a molten metal halide catalyst, thereafter separating at least a substantial portion of the carbonaceous material associated with the reaction mixture from the spent molten metal halide and thereafter regenerating the metal halide catalyst, an improvement comprising contacting the spent molten metal halide catalyst after removal of a major portion of the carbonaceous material therefrom with an additional quantity of hydrogen is disclosed.

  18. CO-oxidation catalysts: Low-temperature CO oxidation over Noble-Metal Reducible Oxide (NMRO) catalysts

    NASA Technical Reports Server (NTRS)

    Herz, Richard K.

    1990-01-01

    Oxidation of CO to CO2 is an important reaction technologically and environmentally and a complex and interesting reaction scientifically. In most cases, the reaction is carried out in order to remove CO as an environmental hazard. A major application of heterogeneous catalysts is catalytic oxidation of CO in the exhaust of combustion devices. The reaction over catalysts in exhaust gas is fast and often mass-transfer-limited since exhaust gases are hot and O2/CO ratios are high. The main challenges to catalyst designers are to control thermal sintering and chemical poisoning of the active materials. The effect of the noble metal on the oxide is discussed, followed by the effect of the oxide on the noble metal, the interaction of the noble metal and oxide to form unique catalytic sites, and the possible ways in which the CO oxidation reaction is catalyzed by the NMRO materials.

  19. Textured catalysts, methods of making textured catalysts, and methods of catalyzing reactions conducted in hydrothermal conditions

    DOEpatents

    Werpy, Todd [West Richland, WA; Wang, Yong [Richland, WA

    2003-12-30

    A textured catalyst having a hydrothermally-stable support, a metal oxide and a catalyst component is described. Methods of conducting aqueous phase reactions that are catalyzed by a textured catalyst are also described. The invention also provides methods of making textured catalysts and methods of making chemical products using a textured catalyst.

  20. Chalcogen catalysts for polymer electrolyte fuel cell

    DOEpatents

    Zelenay, Piotr; Choi, Jong-Ho; Alonso-Vante, Nicolas; Wieckowski, Andrzej; Cao, Dianxue

    2010-08-24

    A methanol-tolerant cathode catalyst and a membrane electrode assembly for fuel cells that includes such a cathode catalyst. The cathode catalyst includes a support having at least one transition metal in elemental form and a chalcogen disposed on the support. Methods of making the cathode catalyst and membrane electrode assembly are also described.

  1. Chalcogen catalysts for polymer electrolyte fuel cell

    DOEpatents

    Alonso-Vante, Nicolas; Zelenay, Piotr; Choi, Jong-Ho; Wieckowski, Andrzej; Cao, Dianxue

    2009-09-15

    A methanol-tolerant cathode catalyst and a membrane electrode assembly for fuel cells that includes such a cathode catalyst. The cathode catalyst includes a support having at least one transition metal in elemental form and a chalcogen disposed on the support. Methods of making the cathode catalyst and membrane electrode assembly are also described.

  2. Efficient production of hydrogen from formic acid using a covalent triazine framework supported molecular catalyst.

    PubMed

    Bavykina, A V; Goesten, M G; Kapteijn, F; Makkee, M; Gascon, J

    2015-03-01

    A heterogeneous molecular catalyst based on Ir(III) Cp* (Cp*=pentamethylcyclopentadienyl) attached to a covalent triazine framework (CTF) is reported. It catalyses the production of hydrogen from formic acid with initial turnover frequencies (TOFs) up to 27,000 h(-1) and turnover numbers (TONs) of more than one million in continuous operation. The CTF support, with a Brunauer-Emmett-Teller (BET) surface area of 1800 m(2)  g(-1), was constructed from an optimal 2:1 ratio of biphenyl and pyridine carbonitrile building blocks. Biphenyl building blocks induce mesoporosity and, therefore, facilitate diffusion of reactants and products whereas free pyridinic sites activate formic acid towards β-hydride elimination at the metal, rendering unprecedented rates in hydrogen production. The catalyst is air stable, produces CO-free hydrogen, and is fully recyclable. Hydrogen production rates of more than 60 mol L(-1)  h(-1) were obtained at high catalyst loadings of 16 wt % Ir, making it attractive towards process intensification.

  3. Large-scale growth of hierarchical transition-metal vanadate nanosheets on metal meshes as monolith catalysts for De-NO(x) reaction.

    PubMed

    Huang, Lei; Zhao, Xin; Zhang, Lei; Shi, Liyi; Zhang, Jianping; Zhang, Dengsong

    2015-02-14

    A facile method is developed for the large-scale growth of hierarchical transition-metal (Cu, Fe, and Ni) vanadate nanosheets on corresponding metal mesh as supports. The hierarchical transition-metal vanadate nanosheets were in situ grown on the metal meshes through an orientational etching process and simultaneous nucleation and growth process. Interestingly, the morphologies of the vanadate nanosheets are governed by the balance between dissolution rate and nucleation rate. Thus, the sizes and the thicknesses of the nanosheets could be facilely controlled by the reaction duration, the acidity of the solution and the concentration of vanadate precursor. Furthermore, the hierarchical transition-metal vanadate nanosheets supported on metal meshes are used as monolith catalysts for the selective catalytic reduction (SCR) of NO with NH3. The iron mesh based monolith catalyst shows excellent de-NOx performance with high efficiency and stability in the presence of SO2 and H2O, which provide a promising monolith de-NOx catalyst for stationary source at medium temperatures.

  4. High-temperature hydrodechlorination of ozone-depleting chlorodifluoromethane (HCFC-22) on supported Pd and Ni catalysts.

    PubMed

    Ha, Jeong-Myeong; Kim, Daewoo; Kim, Jaehoon; Ahn, Byoung Sung; Kim, Yunje; Kang, Jeong Won

    2011-01-01

    The hydrodechlorination of chlorodifluoromethane (HCFC-22) was performed by a catalytic reaction and noncatalytic thermal decomposition at high temperatures of 400-800 °C. After 47 h of time-on-stream on a supported palladium (Pd) catalyst, the gas phase composition of difluoromethane (HFC-32) is 41.0%, with 4.9% of the HCFC-22 remaining, indicating the conversion of up to 95.1% of HCFC-22. The supported nickel catalyst's deactivation is significant as it exhibits the low conversion of HCFC-22 under the same reaction conditions. The deactivation of the catalyst is caused by the polymerization of adsorbed methyl radicals, which competes with the formation of HFC-32. With concentrated reactants at high reaction temperatures, there was an increase in the catalytic activity; however, unwanted tar, methane, and trifluoromethane (HFC-23) by-products are also produced. The use of catalyst suppresses the formation of these by-products. Considering the compositions of the products of the catalytic and noncatalytic reactions, we demonstrate that the use of the supported-metal catalysts and hydrogen flow suppresses tar formation and lowers the required reaction temperature.

  5. High-temperature hydrodechlorination of ozone-depleting chlorodifluoromethane (HCFC-22) on supported Pd and Ni catalysts.

    PubMed

    Ha, Jeong-Myeong; Kim, Daewoo; Kim, Jaehoon; Ahn, Byoung Sung; Kim, Yunje; Kang, Jeong Won

    2011-01-01

    The hydrodechlorination of chlorodifluoromethane (HCFC-22) was performed by a catalytic reaction and noncatalytic thermal decomposition at high temperatures of 400-800 °C. After 47 h of time-on-stream on a supported palladium (Pd) catalyst, the gas phase composition of difluoromethane (HFC-32) is 41.0%, with 4.9% of the HCFC-22 remaining, indicating the conversion of up to 95.1% of HCFC-22. The supported nickel catalyst's deactivation is significant as it exhibits the low conversion of HCFC-22 under the same reaction conditions. The deactivation of the catalyst is caused by the polymerization of adsorbed methyl radicals, which competes with the formation of HFC-32. With concentrated reactants at high reaction temperatures, there was an increase in the catalytic activity; however, unwanted tar, methane, and trifluoromethane (HFC-23) by-products are also produced. The use of catalyst suppresses the formation of these by-products. Considering the compositions of the products of the catalytic and noncatalytic reactions, we demonstrate that the use of the supported-metal catalysts and hydrogen flow suppresses tar formation and lowers the required reaction temperature. PMID:21847789

  6. TiN@nitrogen-doped carbon supported Pt nanoparticles as high-performance anode catalyst for methanol electrooxidation

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Ma, Li; Gan, Mengyu; Fu, Shenna; Zhao, Yi

    2016-08-01

    In this paper, TiN@nitrogen-doped carbons (NDC) composed of a core-shell structure are successfully prepared through self-assembly and pyrolysis treatment using γ-aminopropyltriethoxysilane as coupling agent, polyaniline as carbon and nitrogen source, respectively. Subsequently, TiN@NDC supporting Pt nanoparticles (Pt/TiN@NDC) are obtained by a microwave-assisted polyol process. The nitrogen-containing functional groups and TiN nanoparticles play a critical role in decreasing the average particle size of Pt and improving the electrocatalytic activity of Pt/TiN@NDC. Transmission electron microscope results reveal that Pt nanoparticles are uniformly dispersed in the TiN@NDC surface with a narrow particle size ranging from 1 to 3 nm in diameter. Moreover, the Pt/TiN@NDC catalyst shows significantly improved catalytic activity and high durability for methanol electrooxidation in comparison with Pt/NDC and commercial Pt/C catalysts, revealed by cyclic voltammetry and chronoamperometry. Strikingly, this novel Pt/TiN@NDC catalyst reveals a better CO tolerance related to Pt/NDC and commercial Pt/C catalysts, which due to the bifunctional mechanism and strong metal-support interaction between Pt and TiN@NDC. In addition, the probable reaction steps for the electrooxidation of CO adspecies on Pt NPs on the basis of the bifunctional mechanism are also proposed. These results indicate that the TiN@NDC is a promising catalyst support for methanol electrooxidation.

  7. TiN@nitrogen-doped carbon supported Pt nanoparticles as high-performance anode catalyst for methanol electrooxidation

    NASA Astrophysics Data System (ADS)

    Zhang, Jun; Ma, Li; Gan, Mengyu; Fu, Shenna; Zhao, Yi

    2016-08-01

    In this paper, TiN@nitrogen-doped carbons (NDC) composed of a core-shell structure are successfully prepared through self-assembly and pyrolysis treatment using γ-aminopropyltriethoxysilane as coupling agent, polyaniline as carbon and nitrogen source, respectively. Subsequently, TiN@NDC supporting Pt nanoparticles (Pt/TiN@NDC) are obtained by a microwave-assisted polyol process. The nitrogen-containing functional groups and TiN nanoparticles play a critical role in decreasing the average particle size of Pt and improving the electrocatalytic activity of Pt/TiN@NDC. Transmission electron microscope results reveal that Pt nanoparticles are uniformly dispersed in the TiN@NDC surface with a narrow particle size ranging from 1 to 3 nm in diameter. Moreover, the Pt/TiN@NDC catalyst shows significantly improved catalytic activity and high durability for methanol electrooxidation in comparison with Pt/NDC and commercial Pt/C catalysts, revealed by cyclic voltammetry and chronoamperometry. Strikingly, this novel Pt/TiN@NDC catalyst reveals a better CO tolerance related to Pt/NDC and commercial Pt/C catalysts, which due to the bifunctional mechanism and strong metal-support interaction between Pt and TiN@NDC. In addition, the probable reaction steps for the electrooxidation of CO adspecies on Pt NPs on the basis of the bifunctional mechanism are also proposed. These results indicate that the TiN@NDC is a promising catalyst support for methanol electrooxidation.

  8. Structure and Oxidation State of Silica-Supported Manganese Oxide Catalysts and Reactivity for Acetone Oxidation with Ozone

    SciTech Connect

    Reed,C.; Lee, Y.; Oyama, S.

    2006-01-01

    Silica-supported manganese oxide catalysts with loadings of 3, 10, 15, and 20 wt % (as MnO{sub 2}) were characterized with use of X-ray absorption spectroscopy and X-ray diffraction (XRD). The edge positions in the X-ray absorption spectra indicated that the oxidation state for the manganese decreased with increasing metal oxide loading from a value close to that of Mn{sub 2}O{sub 3} (+3) to a value close to that of Mn{sub 3}O{sub 4} (+2 2/3). The XRD was consistent with these results as the diffractograms for the supported catalysts of higher manganese oxide loading matched those of a Mn{sub 3}O{sub 4} reference. The reactivity of the silica-supported manganese oxide catalysts in acetone oxidation with ozone as an oxidant was studied over the temperature range of 300 to 600 K. Both oxygen and ozone produced mainly CO{sub 2} as the product of oxidation, but in the case of ozone the reaction temperature and activation energy were significantly reduced. The effect of metal oxide loading was investigated, and the activity for acetone oxidation was greater for a 10 wt % MnO{sub x}/SiO{sub 2} catalyst sample compared to a 3 wt % MnO{sub x}/SiO{sub 2} sample.

  9. Investigation of multi-metal catalysts for stable hydrogen production via urea electrolysis

    NASA Astrophysics Data System (ADS)

    King, Rebecca L.; Botte, Gerardine G.

    It has been shown that urea electrolysis is a viable method for wastewater remediation and simultaneous production of valuable hydrogen. Inexpensive nickel catalyst is optimal for the oxidation of urea in alkaline media but improvements are needed to minimize surface blockage and increase current density. Multi-metal catalysts were investigated by depositing platinum group metals on a nickel substrate. Rhodium and nickel proved synergistic to reduce surface blockage and increase catalyst stability. Rh-Ni electrodes reduced the overpotential for the electro-oxidation of urea and improved the current density by a factor of 200 compared to a Ni catalyst.

  10. Trianionic pincer and pincer-type metal complexes and catalysts.

    PubMed

    O'Reilly, Matthew E; Veige, Adam S

    2014-09-01

    Trianionic pincer and pincer-type ligands are the focus of this review. Metal ions from across the periodic table, from main group elements, transition metals, and the rare earths, are combined with trianionic pincer ligands to produce some of the most interesting complexes to appear in the literature over the past decade. This review provides a comprehensive examination of the synthesis, characterization, properties, and catalytic applications of trianionic pincer metal complexes. Some of the interesting applications employing trianionic pincer and pincer-type complexes include: (1) catalyzed aerobic oxidation, (2) alkene isomerization, (3) alkene and alkyne polymerization, (4) nitrene and carbene group transfer, (5) fundamental transformations such as oxygen-atom transfer, (6) nitrogen-atom transfer, (7) O2 activation, (8) C-H bond activation, (9) disulfide reduction, and (10) ligand centered storage of redox equivalents (i.e. redox active ligands). Expansion of the architecture, type of donor atoms, chelate ring size, and steric and electronic properties of trianionic pincer ligands has occurred rapidly over the past ten years. This review is structured according to the type of pincer donor atoms that bind to the metal ion. The type of donor atoms within trianionic pincer and pincer-type ligands to be discussed include: NCN(3-), OCO(3-), CCC(3-), redox active NNN(3-), NNN(3-), redox active ONO(3-), ONO(3-), and SNS(3-). Since this is the first review of trianionic pincer and pincer-type ligands, an emphasis is placed on providing the reader with in-depth discussion of synthetic methods, characterization data, and highlights of these complexes as catalysts. PMID:24927219

  11. Selective oxidation of methanol to hydrogen over gold catalysts promoted by alkaline-earth-metal and lanthanum oxides.

    PubMed

    Hereijgers, Bart P C; Weckhuysen, Bert M

    2009-01-01

    A series of alumina-supported gold catalysts was investigated for the CO-free production of hydrogen by partial oxidation of methanol. The addition of alkaline-earth metal oxide promoters resulted in a significant improvement of the catalytic performance. The methanol conversion was ca. 85 % with all studied catalyst materials, however, the selectivity for hydrogen increased from 15 % to 51 % when going from the unpromoted to a BaO-promoted catalyst. The formation of the undesired byproducts CO, methane, and dimethyl ether was considerably reduced as well. The observed trend in catalyst performance follows the trend in increasing basicity of the studied promoter elements, indicating a chemical effect of the promoter material. Superior catalytic performance, in terms of H(2) and CO selectivity, was obtained with a Au/La(2)O(3) catalyst. At 300 degrees C the hydrogen selectivity reached 80 % with only 2 % CO formation, and the catalyst displayed a stable performance over at least 24 h on-stream. Furthermore, the formation of CO was found to be independent of the oxygen concentration in the feed. The commercial lanthanum oxide used in this study had a low specific surface area, which led to the formation of relative large gold particles. Therefore, the catalytic activity could be enhanced by decreasing the gold particle size through deposition on lanthanum oxide supported on high-surface-area alumina.

  12. Thermal Processing Techniques to Improve Metal Sulfide Mixed Alcohol Catalyst Performance

    SciTech Connect

    Hensley, J.; Menart, M.; Costelow, K.; Thibodeaux, J.; Yung, M.

    2011-01-01

    Research over several decades by several institutions has shown that alkali-promoted metal sulfide catalysts are capable of producing mixed alcohols from syngas with high selectivity and yield. Unfortunately, process models suggest that syngas to mixed alcohol processes, and especially thermochemical biomass to mixed alcohol processes, require improvements to sulfide catalyst activity and/or selectivity for acceptable economics. These improvements, if incremental, cannot result in increased process complexity, capital expenditure, or catalyst costs. It is well accepted among catalyst researchers that thermal processing techniques like calcining and reduction can have profound effects on the properties and performance of finished catalysts, and that small variations in thermal processing do not usually affect the overall cost of the catalyst. Metal sulfide catalysts are no exception but surprisingly, little attention has been given to the effects of thermal treatment on bulk metal sulfide mixed alcohol catalysts. This presentation will discuss how parameters like temperature, dwell time, metal ratios, and purge gas affect the performance and physical properties of K-Co/Mo catalysts.

  13. Compressive strength and heavy metal leaching behaviour of mortars containing spent catalyst.

    PubMed

    Rattanasak, U; Jaturapitakkul, C; Sudaprasert, T

    2001-10-01

    This investigation was set and aimed to study the possibility of using spent catalyst as a concrete constituent which the spent catalyst was used as sand. Besides the spent catalyst was used as sand, it was also ground to very small particle size as small as that of cement and used as 20% replacement of cement by weight. Compressive strengths and leaching characteristics of lead, chromium, cadmium, and nickel in mortars containing spent catalyst and ground spent catalyst were tested. The results presented revealed that the compressive strength of mortar containing spent catalyst increased with ages. The results also indicated that the compressive strength of mortar containing spent catalyst at the proportion of 1.25 times of cement by weight was strong enough to make a concrete brick. In case of the ground spent catalyst being used to replace cement, it made the compressive strength lower than that of the standard mortar approximately 20%. The leachate results of lead and chromium from spent catalyst were lower than the allowance, but cadmium and nickel exceeded the limits. After the spent catalyst was fixed with cement, the leaching of the heavy metals did not exceed the industrial effluent standard. Therefore, the heavy metals mentioned earlier were not a problem in using spent catalyst as a concrete constituent.

  14. Structure and reactivity of alumina-supported iron catalysts for ammonia synthesis

    SciTech Connect

    Sueiras, J.E.; Homs, N.; Ramirez de la Piscina, P.; Gracia, M.; Fierro, J.L.G.

    1986-04-01

    Alumina-supported iron catalysts, obtained either by impregnation of iron from a K/sub 4/(Fe(CN)/sub 6/) aqueous solution upon several acid-modified ..gamma..-Al/sub 2/O/sub 3/ samples or by the incipient wetness method, were characterized and their activities for ammonia synthesis at atmospheric pressure and 593 K were studied. Characterization was carried out by temperature-programmed reduction (TPR), kinetics of hydrogen reduction, CO chemisorption, X-ray photoelectron spectroscopy (XPS), IR spectroscopy, and Moessbauer spectroscopy, resulting in the degree of reduction and the dispersion of the metallic phase dependent on the previous acid modification of the ..gamma..-Al/sub 2/O/sub 3/. The XPS surface composition expressed as M 2p/Al 2p (M = Fe, K) gave K 2p/Al 2p > Fe 2p/Al 2p. IR experiments, with NO as probe molecules, exhibited bands for reduced catalysts at 1778 and 1712 cm/sup -1/ whose intensity and position depended on the protonation degree of ..gamma..-Al/sub 2/O/sub 3/ and promoter content, respectively. Moessbauer spectra of the reduced samples showed the presence of surface ..cap alpha..-Fe, superparamagnetic Fe/sup 0/, Fe/sup 2 +/, Fe/sup 3 +/, and ..cap alpha..-Fe/sub 2/O/sub 3/ depending on the catalyst. Finally, the catalytic activity for ammonia synthesis was found to be dependent on the surface structure of the catalyst and hence on the method of preparation.

  15. Anchoring and promotion effects of metal oxides on silica supported catalytic gold nanoparticles.

    PubMed

    Luo, Jingjie; Ersen, Ovidiu; Chu, Wei; Dintzer, Thierry; Petit, Pierre; Petit, Corinne

    2016-11-15

    The understanding of the interactions between the different components of supported metal doped gold catalysts is of crucial importance for selecting and designing efficient gold catalysts for reactions such as CO oxidation. To progress in this direction, a unique supported nano gold catalyst Au/SS was prepared, and three doped samples (Au/SS@M) were elaborated. The samples before and after test were characterized by Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). It is found that the doping metal species prefer to be located on the surface of gold nanoparticles and that a small amount of additional reductive metal leads to more efficient reaction. During the catalytic test, the nano-structure of the metal species transforms depending on its chemical nature. This study allows one to identify and address the contribution of each metal on the CO reaction in regard to oxidative species of gold, silica and dopants. Metal doping leads to different exposure of interface sites between Au and metal oxide, which is one of the key factors for the change of the catalytic activity. The metal oxides help the activation of oxygen by two actions: mobility inside the metal bulk and transfer of water species onto of gold nanoparticles.

  16. Anchoring and promotion effects of metal oxides on silica supported catalytic gold nanoparticles.

    PubMed

    Luo, Jingjie; Ersen, Ovidiu; Chu, Wei; Dintzer, Thierry; Petit, Pierre; Petit, Corinne

    2016-11-15

    The understanding of the interactions between the different components of supported metal doped gold catalysts is of crucial importance for selecting and designing efficient gold catalysts for reactions such as CO oxidation. To progress in this direction, a unique supported nano gold catalyst Au/SS was prepared, and three doped samples (Au/SS@M) were elaborated. The samples before and after test were characterized by Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS). It is found that the doping metal species prefer to be located on the surface of gold nanoparticles and that a small amount of additional reductive metal leads to more efficient reaction. During the catalytic test, the nano-structure of the metal species transforms depending on its chemical nature. This study allows one to identify and address the contribution of each metal on the CO reaction in regard to oxidative species of gold, silica and dopants. Metal doping leads to different exposure of interface sites between Au and metal oxide, which is one of the key factors for the change of the catalytic activity. The metal oxides help the activation of oxygen by two actions: mobility inside the metal bulk and transfer of water species onto of gold nanoparticles. PMID:27501036

  17. Biphasic catalysis using amphiphilic polyphenols-chelated noble metals as highly active and selective catalysts

    PubMed Central

    Mao, Hui; Yu, Hong; Chen, Jing; Liao, Xuepin

    2013-01-01

    In the field of catalysis, it is highly desired to develop novel catalysts that combine the advantages of both homogeneous and heterogeneous catalysts. Here we disclose that the use of plant pholyphenol as amphiphilic large molecule ligand/stabilizer allows for the preparation of noble metal complex and noble metal nanoparticle catalysts. These catalysts are found to be highly selective and active in aqueous-organic biphasic catalysis of cinnamaldehyde and quinoline, and can be reused at least 3 times without significant loss of activity. Moreover, the catalytic activity and reusability of the catalysts can be rationally controlled by simply adjusting the content of polyphenols in the catalysts. Our strategy may be extended to design a wide range of aqueous-organic biphasic catalysis system. PMID:23863916

  18. Investigation of a carbon-supported quaternary PtRuSnW catalyst for direct methanol fuel cells

    NASA Astrophysics Data System (ADS)

    Aricò, A. S.; Poltarzewski, Z.; Kim, H.; Morana, A.; Giordano, N.; Antonucci, V.

    An investigation was carried out in the electro-oxidation of methanol on a carbon-supported quaternary PtRuSnW catalyst prepared by a liquid-phase reduction method. As derived by X-ray diffraction and X-ray photoelectron spectroscopy, the catalyst was composed of metallic Pt, microcrystalline RuO 2 and SnO 2 phases and amorphous WO 3/WO 2 species. The electrochemical analysis was carried out in half-cell containing sulfuric acid electrolyte as well as in a liquid methanol-fed solid polymer electrolyte single-cell. The activity of catalyst in the half-cell varied as a function of the methanol concentration, it increased with CH 3OH molarity in the activation-controlled region and showed a maximum in 2 M CH 3OH at high currents. IR-free polarization curves showed that the activity of the quaternary catalyst was superior to Pt metal/C samples having the same Pt amount. The presence of semi-insulating metal oxides such as RuO 2, SnO 2 and WO 3 on the electrode surface exhibited a significant uncompensated resistance. The single-cell performance was lower than that predicted by the half-cell experiments mainly due to the methanol cross-over through the Nafion membrane.

  19. Methanol Oxidation Using Ozone on Titania-Supported Vanadium Catalyst

    EPA Science Inventory

    Ozone-enhanced catalytic oxidation of methanol has been conducted at mild temperatures of 100 to 250NC using V2O5/TiO2 catalyst prepared by the sol-gel method. The catalyst was characterized using XRD, surface area measurements, and temperature-programmed desorption of methanol. ...

  20. Metal and Precursor Effect during 1-Heptyne Selective Hydrogenation Using an Activated Carbon as Support

    PubMed Central

    Lederhos, Cecilia R.; Badano, Juan M.; Carrara, Nicolas; Coloma-Pascual, Fernando; Almansa, M. Cristina; Liprandi, Domingo; Quiroga, Mónica

    2013-01-01

    Palladium, platinum, and ruthenium supported on activated carbon were used as catalysts for the selective hydrogenation of 1-heptyne, a terminal alkyne. All catalysts were characterized by temperature programmed reduction, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. TPR and XPS suggest that the metal in all catalysts is reduced after the pretreatment with H2 at 673 K. The TPR trace of the PdNRX catalyst shows that the support surface groups are greatly modified as a consequence of the use of HNO3 during the catalyst preparation. During the hydrogenation of 1-heptyne, both palladium catalysts were more active and selective than the platinum and ruthenium catalysts. The activity order of the catalysts is as follows: PdClRX > PdNRX > PtClRX ≫ RuClRX. This superior performance of PdClRX was attributed in part to the total occupancy of the d electronic levels of the Pd metal that is supposed to promote the rupture of the H2 bond during the hydrogenation reaction. The activity differences between PdClRX and PdNRX catalysts could be attributed to a better accessibility of the substrate to the active sites, as a consequence of steric and electronic effects of the superficial support groups. The order for the selectivity to 1-heptene is as follows: PdClRX = PdNRX > RuClRX > PtClRX, and it can be mainly attributed to thermodynamic effects. PMID:24348168

  1. Engineering Pt in ceria for a maximum metal-support interaction in catalysis.

    PubMed

    Yeung, Connie M Y; Yu, Kai Man K; Fu, Qi Jia; Thompsett, David; Petch, Michael I; Tsang, Shik Chi

    2005-12-28

    Conventional supported metal catalysts are metal nanoparticles deposited on high surface area oxide supports with a poorly defined metal-support interface. Typically, the traditionally prepared Pt/ceria catalyzes both methanation (H2/CO to CH4) and water-gas shift (CO/H2O to CO2/H2) reactions. By using simple nanochemistry techniques, we show for the first time that Pt or PtAu metal can be created inside each CeO2 particle with tailored dimensions. The encapsulated metal is shown to interact with the thin CeO2 overlayer in each single particle in an optimum geometry to create a unique interface, giving high activity and excellent selectivity for the water-gas shift reaction, but is totally inert for methanation. Thus, this work clearly demonstrates the significance of nanoengineering of a single catalyst particle by a bottom-up construction approach in modern catalyst design which could enable exploitation of catalyst site differentiation, leading to new catalytic properties. PMID:16366545

  2. Atomistic theory of Ostwald ripening and disintegration of supported metal particles under reaction conditions.

    PubMed

    Ouyang, Runhai; Liu, Jin-Xun; Li, Wei-Xue

    2013-02-01

    Understanding Ostwald ripening and disintegration of supported metal particles under operating conditions has been of central importance in the study of sintering and dispersion of heterogeneous catalysts for long-term industrial implementation. To achieve a quantitative description of these complicated processes, an atomistic and generic theory taking into account the reaction environment, particle size and morphology, and metal-support interaction is developed. It includes (1) energetics of supported metal particles, (2) formation of monomers (both the metal adatoms and metal-reactant complexes) on supports, and (3) corresponding sintering rate equations and total activation energies, in the presence of reactants at arbitrary temperature and pressure. The thermodynamic criteria for the reactant assisted Ostwald ripening and induced disintegration are formulated, and the influence of reactants on sintering kinetics and redispersion are mapped out. Most energetics and kinetics barriers in the theory can be obtained conveniently by first-principles theory calculations. This allows for the rapid exploration of sintering and disintegration of supported metal particles in huge phase space of structures and compositions under various reaction environments. General strategies of suppressing the sintering of the supported metal particles and facilitating the redispersions of the low surface area catalysts are proposed. The theory is applied to TiO(2)(110) supported Rh particles in the presence of carbon monoxide, and reproduces well the broad temperature, pressure, and particle size range over which the sintering and redispersion occurred in such experiments. The result also highlights the importance of the metal-carbonyl complexes as monomers for Ostwald ripening and disintegration of supported metal catalysts in the presence of CO. PMID:23272702

  3. Atomistic theory of Ostwald ripening and disintegration of supported metal particles under reaction conditions.

    PubMed

    Ouyang, Runhai; Liu, Jin-Xun; Li, Wei-Xue

    2013-02-01

    Understanding Ostwald ripening and disintegration of supported metal particles under operating conditions has been of central importance in the study of sintering and dispersion of heterogeneous catalysts for long-term industrial implementation. To achieve a quantitative description of these complicated processes, an atomistic and generic theory taking into account the reaction environment, particle size and morphology, and metal-support interaction is developed. It includes (1) energetics of supported metal particles, (2) formation of monomers (both the metal adatoms and metal-reactant complexes) on supports, and (3) corresponding sintering rate equations and total activation energies, in the presence of reactants at arbitrary temperature and pressure. The thermodynamic criteria for the reactant assisted Ostwald ripening and induced disintegration are formulated, and the influence of reactants on sintering kinetics and redispersion are mapped out. Most energetics and kinetics barriers in the theory can be obtained conveniently by first-principles theory calculations. This allows for the rapid exploration of sintering and disintegration of supported metal particles in huge phase space of structures and compositions under various reaction environments. General strategies of suppressing the sintering of the supported metal particles and facilitating the redispersions of the low surface area catalysts are proposed. The theory is applied to TiO(2)(110) supported Rh particles in the presence of carbon monoxide, and reproduces well the broad temperature, pressure, and particle size range over which the sintering and redispersion occurred in such experiments. The result also highlights the importance of the metal-carbonyl complexes as monomers for Ostwald ripening and disintegration of supported metal catalysts in the presence of CO.

  4. Nano-magnetite (Fe3O4) as a support for recyclable catalysts in the development of sustainable methodologies.

    PubMed

    Gawande, Manoj B; Branco, Paula S; Varma, Rajender S

    2013-04-21

    Surface functionalization of nano-magnetic nanoparticles is a well-designed way to bridge the gap between heterogeneous and homogeneous catalysis. The introduction of magnetic nanoparticles (MNPs) in a variety of solid matrices allows the combination of well-known procedures for catalyst heterogenization with techniques for magnetic separation. Magnetite is a well-known material, also known as ferrite (Fe3O4), and can be used as a versatile support for functionalization of metals, organocatalysts, N-heterocyclic carbenes, and chiral catalysts. It is used as a support for important homogeneous catalytically active metals such as Pd, Pt, Cu, Ni, Co, Ir, etc. to obtain stable and magnetically recyclable heterogeneous catalysts. Homogeneous organocatalysts can be successfully decorated with linkers/ligands on the surface of magnetite or alternatively the organocatalysts can be directly immobilized on the surface of magnetite. The functionalized magnetically retrievable catalysts or nanocatalysts that are increasingly being used in catalysis, green chemistry and pharmaceutically significant reactions are summarized in this review.

  5. Noble Metal Catalysts for Mercury Oxidation in Utility Flue Gas: Gold, Palladium and Platinum Formulations

    SciTech Connect

    Presto, A.A.; Granite, E.J

    2008-07-01

    The use of noble metals as catalysts for mercury oxidation in flue gas remains an area of active study. To date, field studies have focused on gold and palladium catalysts installed at pilot scale. In this article, we introduce bench-scale experimental results for gold, palladium and platinum catalysts tested in realistic simulated flue gas. Our initial results reveal some intriguing characteristics of catalytic mercury oxidation and provide insight for future research into this potentially important process.

  6. Renewable and metal-free carbon nanofibre catalysts for carbon dioxide reduction

    NASA Astrophysics Data System (ADS)

    Kumar, Bijandra; Asadi, Mohammad; Pisasale, Davide; Sinha-Ray, Suman; Rosen, Brian A.; Haasch, Richard; Abiade, Jeremiah; Yarin, Alexander L.; Salehi-Khojin, Amin

    2013-12-01

    The development of an efficient catalyst system for the electrochemical reduction of carbon dioxide into energy-rich products is a major research topic. Here we report the catalytic ability of polyacrylonitrile-based heteroatomic carbon nanofibres for carbon dioxide reduction into carbon monoxide, via a metal-free, renewable and cost-effective route. The carbon nanofibre catalyst exhibits negligible overpotential (0.17 V) for carbon dioxide reduction and more than an order of magnitude higher current density compared with the silver catalyst under similar experimental conditions. The carbon dioxide reduction ability of carbon nanofibres is attributed to the reduced carbons rather than to electronegative nitrogen atoms. The superior performance is credited to the nanofibrillar structure and high binding energy of key intermediates to the carbon nanofibre surfaces. The finding may lead to a new generation of metal-free and non-precious catalysts with much greater efficiency than the existing noble metal catalysts.

  7. n-hydrocarbons conversions over metal-modified solid acid catalysts

    NASA Astrophysics Data System (ADS)

    Zarubica, A.; Ranđelović, M.; Momčilović, M.; Radulović, N.; Putanov, P.

    2013-12-01

    The quality of a straight-run fuel oil can be improved if saturated n-hydrocarbons of low octane number are converted to their branched counterparts. Poor reactivity of traditional catalysts in isomerization reactions imposed the need for the development of new catalysts among which noble metal promoted acid catalysts, liquid and/or solid acid catalysts take a prominent place. Sulfated zirconia and metal promoted sulfated zirconia exhibit high activity for the isomerization of light alkanes at low temperatures. The present paper highlights the original results which indicate that the modification of sulfated zirconia by incorporation of metals (platinum and rhenium) significantly affects catalytic performances in n-hydrocarbon conversion reactions. Favourable activity/selectivity of the promoted sulfated zirconia depends on the crystal phase composition, critical crystallites sizes, platinum dispersion, total acidity and type of acidity. Attention is also paid to the recently developed solid acid catalysts used in other conversion reactions of hydrocarbons.

  8. 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.

  9. Near-ambient XPS characterization of interfacial copper species in ceria-supported copper catalysts.

    PubMed

    Monte, Manuel; Munuera, Guillermo; Costa, Dominique; Conesa, José C; Martínez-Arias, Arturo

    2015-11-28

    Catalysts based on combinations of copper and cerium oxides are interesting alternatives to noble metal ones for processes involved in the production/purification of hydrogen produced from hydrocarbons or biomass like the water-gas shift or the preferential oxidation of CO reactions. Active sites for such processes have been proposed to correspond to reduced species formed at the interface between both oxides. The present work provides direct evidence of reduced copper species located at the interface and observed during the course of near-ambient XPS experiments performed over samples of copper oxide supported on ceria nanospheres and nanocubes subjected to interaction with CO at different temperatures. The analysis of XPS results is based on DFT+U calculations employed as a complementary method for the analysis of redox properties of the catalysts and core-level shifts produced upon such redox changes. Differences observed in interfacial redox properties as a function of the ceria support morphology appear to be most useful to explain catalytic properties of this type of system for mentioned processes.

  10. Advanced cathode materials for polymer electrolyte fuel cells based on pt/ metal oxides: from model electrodes to catalyst systems.

    PubMed

    Fabbri, Emiliana; Pătru, Alexandra; Rabis, Annett; Kötz, Rüdiger; Schmidt, Thomas J

    2014-01-01

    The development of stable catalyst systems for application at the cathode side of polymer electrolyte fuel cells (PEFCs) requires the substitution of the state-of-the-art carbon supports with materials showing high corrosion resistance in a strongly oxidizing environment. Metal oxides in their highest oxidation state can represent viable support materials for the next generation PEFC cathodes. In the present work a multilevel approach has been adopted to investigate the kinetics and the activity of Pt nanoparticles supported on SnO2-based metal oxides. Particularly, model electrodes made of SnO2 thin films supporting Pt nanoparticles, and porous catalyst systems made of Pt nanoparticles supported on Sb-doped SnO2 high surface area powders have been investigated. The present results indicate that SnO2-based supports do not modify the oxygen reduction reaction mechanism on the Pt nanoparticle surface, but rather lead to catalysts with enhanced specific activity compared to Pt/carbon systems. Different reasons for the enhancement in the specific activity are considered and discussed.

  11. Nitrogen-doped carbon-supported cobalt-iron oxygen reduction catalyst

    DOEpatents

    Zelenay, Piotr; Wu, Gang

    2014-04-29

    A Fe--Co hybrid catalyst for oxygen reaction reduction was prepared by a two part process. The first part involves reacting an ethyleneamine with a cobalt-containing precursor to form a cobalt-containing complex, combining the cobalt-containing complex with an electroconductive carbon supporting material, heating the cobalt-containing complex and carbon supporting material under conditions suitable to convert the cobalt-containing complex and carbon supporting material into a cobalt-containing catalyst support. The second part of the process involves polymerizing an aniline in the presence of said cobalt-containing catalyst support and an iron-containing compound under conditions suitable to form a supported, cobalt-containing, iron-bound polyaniline species, and subjecting said supported, cobalt-containing, iron bound polyaniline species to conditions suitable for producing a Fe--Co hybrid catalyst.

  12. Role of bonding mechanisms during transfer hydrogenation reaction on heterogeneous catalysts of platinum nanoparticles supported on zinc oxide nanorods

    NASA Astrophysics Data System (ADS)

    Al-Alawi, Reem A.; Laxman, Karthik; Dastgir, Sarim; Dutta, Joydeep

    2016-07-01

    For supported heterogeneous catalysis, the interface between a metal nanoparticle and the support plays an important role. In this work the dependency of the catalytic efficiency on the bonding chemistry of platinum nanoparticles supported on zinc oxide (ZnO) nanorods is studied. Platinum nanoparticles were deposited on ZnO nanorods (ZnO NR) using thermal and photochemical processes and the effects on the size, distribution, density and chemical state of the metal nanoparticles upon the catalytic activities are presented. The obtained results indicate that the bonding at Pt-ZnO interface depends on the deposition scheme which can be utilized to modulate the surface chemistry and thus the activity of the supported catalysts. Additionally, uniform distribution of metal on the catalyst support was observed to be more important than the loading density. It is also found that oxidized platinum Pt(IV) (platinum hydroxide) provided a more suitable surface for enhancing the transfer hydrogenation reaction of cyclohexanone with isopropanol compared to zero valent platinum. Photochemically synthesized ZnO supported nanocatalysts were efficient and potentially viable for upscaling to industrial applications.

  13. Conversion of biomass-derived sorbitol to glycols over carbon-materials supported Ru-based catalysts.

    PubMed

    Guo, Xingcui; Guan, Jing; Li, Bin; Wang, Xicheng; Mu, Xindong; Liu, Huizhou

    2015-01-01

    Ruthenium (Ru) supported on activated carbon (AC) and carbon nanotubes (CNTs) was carried out in the hydrogenolysis of sorbitol to ethylene glycol (EG) and 1,2-propanediol (1,2-PD) under the promotion of tungsten (WOx) species and different bases. Their catalytic activities and glycols selectivities strongly depended on the support properties and location of Ru on CNTs, owning to the altered metal-support interactions and electronic state of ruthenium. Ru located outside of the tubes showed excellent catalytic performance than those encapsulated inside the nanotubes. Additionally, the introduction of WOx into Ru/CNTs significantly improved the hydrogenolysis activities, and a complete conversion of sorbitol with up to 60.2% 1,2-PD and EG yields was obtained on RuWOx/CNTs catalyst upon addition of Ca(OH)2. Stability study showed that this catalyst was highly stable against leaching and poisoning and could be recycled several times. PMID:26578426

  14. Conversion of biomass-derived sorbitol to glycols over carbon-materials supported Ru-based catalysts

    NASA Astrophysics Data System (ADS)

    Guo, Xingcui; Guan, Jing; Li, Bin; Wang, Xicheng; Mu, Xindong; Liu, Huizhou

    2015-11-01

    Ruthenium (Ru) supported on activated carbon (AC) and carbon nanotubes (CNTs) was carried out in the hydrogenolysis of sorbitol to ethylene glycol (EG) and 1,2-propanediol (1,2-PD) under the promotion of tungsten (WOx) species and different bases. Their catalytic activities and glycols selectivities strongly depended on the support properties and location of Ru on CNTs, owning to the altered metal-support interactions and electronic state of ruthenium. Ru located outside of the tubes showed excellent catalytic performance than those encapsulated inside the nanotubes. Additionally, the introduction of WOx into Ru/CNTs significantly improved the hydrogenolysis activities, and a complete conversion of sorbitol with up to 60.2% 1,2-PD and EG yields was obtained on RuWOx/CNTs catalyst upon addition of Ca(OH)2. Stability study showed that this catalyst was highly stable against leaching and poisoning and could be recycled several times.

  15. Conversion of biomass-derived sorbitol to glycols over carbon-materials supported Ru-based catalysts

    PubMed Central

    Guo, Xingcui; Guan, Jing; Li, Bin; Wang, Xicheng; Mu, Xindong; Liu, Huizhou

    2015-01-01

    Ruthenium (Ru) supported on activated carbon (AC) and carbon nanotubes (CNTs) was carried out in the hydrogenolysis of sorbitol to ethylene glycol (EG) and 1,2-propanediol (1,2-PD) under the promotion of tungsten (WOx) species and different bases. Their catalytic activities and glycols selectivities strongly depended on the support properties and location of Ru on CNTs, owning to the altered metal-support interactions and electronic state of ruthenium. Ru located outside of the tubes showed excellent catalytic performance than those encapsulated inside the nanotubes. Additionally, the introduction of WOx into Ru/CNTs significantly improved the hydrogenolysis activities, and a complete conversion of sorbitol with up to 60.2% 1,2-PD and EG yields was obtained on RuWOx/CNTs catalyst upon addition of Ca(OH)2. Stability study showed that this catalyst was highly stable against leaching and poisoning and could be recycled several times. PMID:26578426

  16. Process for manufacturing a supported catalyst for the hydrotreatment of hydrocarbon oils

    SciTech Connect

    Toulhoat, H.; Jacquin, Y.; Mercier, M.; Plumail, J. C.

    1985-04-09

    Supported catalysts for use in hydrocarbons hydrotreatments are made by shaping catalyst carrier, with or without catalyst precursors, into balls, calcining the balls at 300/sup 0/-1000/sup 0/ C., and crushing the calcined balls to particles whose average size is 0.2-0.8 times the average diameter of the balls. When the precursors are not present during the manufacture, they are added thereafter.

  17. Graphene-Supported Platinum Catalyst-Based Membrane Electrode Assembly for PEM Fuel Cell

    NASA Astrophysics Data System (ADS)

    Devrim, Yilser; Albostan, Ayhan

    2016-08-01

    The aim of this study is the preparation and characterization of a graphene-supported platinum (Pt) catalyst for proton exchange membrane fuel cell (PEMFC) applications. The graphene-supported Pt catalysts were prepared by chemical reduction of graphene and chloroplatinic acid (H2PtCl6) in ethylene glycol. X-ray powder diffraction, thermogravimetric analysis (TGA) and scanning electron microscopy have been used to analyze structure and surface morphology of the graphene-supported catalyst. The TGA results showed that the Pt loading of the graphene-supported catalyst was 31%. The proof of the Pt particles on the support surfaces was also verified by energy-dispersive x-ray spectroscopy analysis. The commercial carbon-supported catalyst and prepared Pt/graphene catalysts were used as both anode and cathode electrodes for PEMFC at ambient pressure and 70°C. The maximum power density was obtained for the Pt/graphene-based membrane electrode assembly (MEA) with H2/O2 reactant gases as 0.925 W cm2. The maximum current density of the Pt/graphene-based MEA can reach 1.267 and 0.43 A/cm2 at 0.6 V with H2/O2 and H2/air, respectively. The MEA prepared by the Pt/graphene catalyst shows good stability in long-term PEMFC durability tests. The PEMFC cell voltage was maintained at 0.6 V without apparent voltage drop when operated at 0.43 A/cm2 constant current density and 70°C for 400 h. As a result, PEMFC performance was found to be superlative for the graphene-supported Pt catalyst compared with the Pt/C commercial catalyst. The results indicate the graphene-supported Pt catalyst could be utilized as the electrocatalyst for PEMFC applications.

  18. Highly active and durable core-corona structured bifunctional catalyst for rechargeable metal-air battery application.

    PubMed

    Chen, Zhu; Yu, Aiping; Higgins, Drew; Li, Hui; Wang, Haijiang; Chen, Zhongwei

    2012-04-11

    A new class of core-corona structured bifunctional catalyst (CCBC) consisting of lanthanum nickelate centers supporting nitrogen-doped carbon nanotubes (NCNT) has been developed for rechargeable metal-air battery application. The nanostructured design of the catalyst allows the core and corona to catalyze the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), respectively. These materials displayed exemplary OER and ORR activity through half-cell testing, comparable to state of the art commercial lanthanum nickelate (LaNiO(3)) and carbon-supported platinum (Pt/C), with added bifunctional capabilities allowing metal-air battery rechargeability. LaNiO(3) and Pt/C are currently the most accepted benchmark electrocatalyst materials for the OER and ORR, respectively; thus with comparable activity toward both of these reactions, CCBC are presented as a novel, inexpensive catalyst component for the cathode of rechargeable metal-air batteries. Moreover, after full-range degradation testing (FDT) CCBC retained excellent activity, retaining 3 and 13 times greater ORR and OER current upon comparison to state of the art Pt/C. Zinc-air battery performances of CCBC is in good agreement with the half-cell experiments with this bifunctional electrocatalyst displaying high activity and stability during battery discharge, charge, and cycling processes. Owing to its outstanding performance toward both the OER and ORR, comparable with the highest performing commercial catalysts to date for each of the respective reaction, coupled with high stability and rechargeability, CCBC is presented as a novel class of bifunctional catalyst material that is very applicable to future generation rechargeable metal-air batteries.

  19. Highly active and durable core-corona structured bifunctional catalyst for rechargeable metal-air battery application.

    PubMed

    Chen, Zhu; Yu, Aiping; Higgins, Drew; Li, Hui; Wang, Haijiang; Chen, Zhongwei

    2012-04-11

    A new class of core-corona structured bifunctional catalyst (CCBC) consisting of lanthanum nickelate centers supporting nitrogen-doped carbon nanotubes (NCNT) has been developed for rechargeable metal-air battery application. The nanostructured design of the catalyst allows the core and corona to catalyze the oxygen evolution reaction (OER) and oxygen reduction reaction (ORR), respectively. These materials displayed exemplary OER and ORR activity through half-cell testing, comparable to state of the art commercial lanthanum nickelate (LaNiO(3)) and carbon-supported platinum (Pt/C), with added bifunctional capabilities allowing metal-air battery rechargeability. LaNiO(3) and Pt/C are currently the most accepted benchmark electrocatalyst materials for the OER and ORR, respectively; thus with comparable activity toward both of these reactions, CCBC are presented as a novel, inexpensive catalyst component for the cathode of rechargeable metal-air batteries. Moreover, after full-range degradation testing (FDT) CCBC retained excellent activity, retaining 3 and 13 times greater ORR and OER current upon comparison to state of the art Pt/C. Zinc-air battery performances of CCBC is in good agreement with the half-cell experiments with this bifunctional electrocatalyst displaying high activity and stability during battery discharge, charge, and cycling processes. Owing to its outstanding performance toward both the OER and ORR, comparable with the highest performing commercial catalysts to date for each of the respective reaction, coupled with high stability and rechargeability, CCBC is presented as a novel class of bifunctional catalyst material that is very applicable to future generation rechargeable metal-air batteries. PMID:22372510

  20. Influence of the metal precursor on the catalytic behavior of Pt/ceria catalysts in the preferential oxidation of CO in the presence of H₂ (PROX).

    PubMed

    Jardim, Erika O; Rico-Francés, Soledad; Coloma, Fernando; Anderson, James A; Silvestre-Albero, Joaquín; Sepúlveda-Escribano, Antonio

    2015-04-01

    The effect of the metal precursor (presence or absence of chlorine) on the preferential oxidation of CO in the presence of H2 over Pt/CeO2 catalysts has been studied. The catalysts are prepared using (Pt(NH3)4)(NO3)2 and H2PtCl6, as precursors, in order to ascertain the effect of the chlorine species on the chemical properties of the support and on the catalytic behavior of these systems in the PROX reaction. The results show that chloride species exert an important effect on the redox properties of the oxide support due to surface chlorination. Consequently, the chlorinated catalyst exhibits a poorer catalytic activity at low temperatures compared with the chlorine-free catalyst, and this is accompanied by a higher selectivity to CO2 even at high reaction temperatures. It is proposed that the CO oxidation mechanism follows different pathways on each catalyst.

  1. Influence of the metal precursor on the catalytic behavior of Pt/ceria catalysts in the preferential oxidation of CO in the presence of H₂ (PROX).

    PubMed

    Jardim, Erika O; Rico-Francés, Soledad; Coloma, Fernando; Anderson, James A; Silvestre-Albero, Joaquín; Sepúlveda-Escribano, Antonio

    2015-04-01

    The effect of the metal precursor (presence or absence of chlorine) on the preferential oxidation of CO in the presence of H2 over Pt/CeO2 catalysts has been studied. The catalysts are prepared using (Pt(NH3)4)(NO3)2 and H2PtCl6, as precursors, in order to ascertain the effect of the chlorine species on the chemical properties of the support and on the catalytic behavior of these systems in the PROX reaction. The results show that chloride species exert an important effect on the redox properties of the oxide support due to surface chlorination. Consequently, the chlorinated catalyst exhibits a poorer catalytic activity at low temperatures compared with the chlorine-free catalyst, and this is accompanied by a higher selectivity to CO2 even at high reaction temperatures. It is proposed that the CO oxidation mechanism follows different pathways on each catalyst. PMID:25531415

  2. Sulphur poisoning of palladium catalysts used for methane combustion: effect of the support.

    PubMed

    Escandón, Lara S; Ordóñez, Salvador; Vega, Aurelio; Díez, Fernando V

    2008-05-01

    Four different supported palladium catalysts (using alumina, silica, zirconia and titania as supports), prepared by incipient wetness impregnation, were tested as catalysts for methane oxidation in presence of sulphur dioxide. The catalyst supported on zirconia showed the best performance, whereas the silica-supported one showed the fastest deactivation. Temperature-programmed desorption experiments of the poisoned catalysts suggest that SO(2) adsorption capacity of the support plays a key role in the catalyst poisoning. In order to study the effect of promoters, expected to improve the thermal stability and thioresistance of the catalyst, commercial zirconia modified by yttrium and lantane was tested as supports. It was found that the presence of these promoters does not improve the performance of the zirconia-supported catalyst. A deactivation model -- considering two different active sites (fresh and poisoning), pseudo-first order dependence on methane concentration and poisoning rate depending on sulphur concentration and fraction of non-poisoned palladium -- was used for modelling the deactivation behaviour. PMID:17935880

  3. Sulphur poisoning of palladium catalysts used for methane combustion: effect of the support.

    PubMed

    Escandón, Lara S; Ordóñez, Salvador; Vega, Aurelio; Díez, Fernando V

    2008-05-01

    Four different supported palladium catalysts (using alumina, silica, zirconia and titania as supports), prepared by incipient wetness impregnation, were tested as catalysts for methane oxidation in presence of sulphur dioxide. The catalyst supported on zirconia showed the best performance, whereas the silica-supported one showed the fastest deactivation. Temperature-programmed desorption experiments of the poisoned catalysts suggest that SO(2) adsorption capacity of the support plays a key role in the catalyst poisoning. In order to study the effect of promoters, expected to improve the thermal stability and thioresistance of the catalyst, commercial zirconia modified by yttrium and lantane was tested as supports. It was found that the presence of these promoters does not improve the performance of the zirconia-supported catalyst. A deactivation model -- considering two different active sites (fresh and poisoning), pseudo-first order dependence on methane concentration and poisoning rate depending on sulphur concentration and fraction of non-poisoned palladium -- was used for modelling the deactivation behaviour.

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

    SciTech Connect

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

    2015-02-24

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

  5. Structural Characterization of Alumina-Supported Rh Catalysts: Effects of Ceriation and Zirconiation by using Metal–Organic Precursors

    PubMed Central

    Kroner, Anna B; Newton, Mark A; Tromp, Moniek; Russell, Andrea E; Dent, Andrew J; Evans, John

    2013-01-01

    The effects of the addition of ceria and zirconia on the structural properties of supported rhodium catalysts (1.6 and 4 wt % Rh/γ-Al2O3) are studied. Ceria and zirconia are deposited by using two preparation methods. Method I involves the deposition of ceria on γ-Al2O3 from Ce(acac)3, and the rhodium metal is subsequently added, whereas method II is based on a controlled surface reaction technique, that is, the decomposition of metal–organic M(acac)x (in which M=Ce, x=3 and M=Zr, x=4) on Rh/γ-Al2O3. The structures of the prepared catalyst materials are characterized ex situ by using N2 physisorption, transmission electron microscopy, high-angle annular dark-field scanning transmission election microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy (XPS), and X-ray absorption fine structure spectroscopy (XAFS). All supported rhodium systems readily oxidize in air at room temperature. By using ceriated and zirconiated precursors, a larger rhodium-based metallic core fraction is obtained in comparison to the undoped rhodium catalysts, suggesting that ceria and zirconia protect the rhodium particles against extensive oxidation. XPS results indicate that after the calcination and reduction treatments, a small amount of chlorine is retained on the support of all rhodium catalysts. EXAFS analysis shows significant Rh—Cl interactions for Rh/Al2O3 and Rh/CeOx/Al2O3 (method I) catalysts. After reaction with H2/He in situ, for series of samples with 1.6 wt % Rh, the EXAFS first shell analysis affords a mean size of approximately 30 atoms. A broader spread is evident with a 4 wt % rhodium loading (ca. 30–110 atoms), with the incorporation of zirconium providing the largest particle sizes. PMID:23943563

  6. Localization of alkali metal ions in sodium-promoted palladium catalysts as studied by low energy ion scattering and transmission electron microscopy

    SciTech Connect

    Liotta, L.F.; Deganello, G.; Delichere, P.

    1996-12-01

    Three series of palladium-based catalysts have been studied by Low Energy Ion Scattering (LEIS) and Transmission Electron Microscopy (TEM). The first series is comprised of Na-Pd/SiO{sub 2} catalysts, obtained by addition of palladium to a silica support and by further addition of sodium ions with a Na/Pd atomic ratio (R) equal to 0,6.4 and 25.6. The second series consists of palladium catalysts supported on natural pumice, in which, due to a different loading of supported palladium, R{prime}, the (Na+K)/Pd atomic ratio, is equal to 17.0 and 39.4. The third series is represented by two palladium-based catalysts supported on {open_quotes}model pumices,{close_quotes} synthetic silico-aluminates, obtained by sol-gel techniques, with a different amount of sodium, and R equal to 2.1 and 6.1 respectively. LEIS experiments and electron microscopy demonstrate a different location of alkali metal ions in the first two series: in the Na-Pd/SiO{sub 2} catalysts sodium is distributed in a way which is not uniform on the support and on the palladium metal, which is partly decorated with Na ions, whereas in the Pd/natural-pumice series the palladium surface is sodium-free. The results on the third series of catalysts, Pd/model pumice, are not definitive on the basis of the LEIS and TEM analyses, but by FTIR study of CO and CO{sub 2} adsorption, the decoration of palladium by sodium ions could be excluded. The results confirm the importance of the alkali metal ion location in alkali-promoted palladium catalysts and open new possibilities in the design of palladium-supported catalysts by a better control of promoter location. 18 refs., 5 figs., 2 tabs.

  7. A methodology for investigating new nonprecious metal catalysts for PEM fuel cells.

    PubMed

    Susac, D; Sode, A; Zhu, L; Wong, P C; Teo, M; Bizzotto, D; Mitchell, K A R; Parsons, R R; Campbell, S A

    2006-06-01

    This paper reports an approach to investigate metal-chalcogen materials as catalysts for the oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells. The methodology is illustrated with reference to Co-Se thin films prepared by magnetron sputtering onto a glassy-carbon substrate. Scanning Auger microscopy (SAM), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffraction (XRD) have been used, in parallel with electrochemical activity and stability measurements, to assess how the electrochemical performance relates to chemical composition. It is shown that Co-Se thin films with varying Se are active for oxygen reduction, although the open circuit potential (OCP) is lower than for Pt. A kinetically controlled process is observed in the potential range 0.5-0.7 V (vs reversible hydrogen electrode) for the thin-film catalysts studied. An initial exposure of the thin-film samples to an acid environment served as a pretreatment, which modified surface composition prior to activity measurements with the rotating disk electrode (RDE) method. Based on the SAM characterization before and after electrochemical tests, all surfaces demonstrating activity are dominated by chalcogen. XRD shows that the thin films have nanocrystalline character that is based on a Co(1-x)Se phase. Parallel studies on Co-Se powder supported on XC72R carbon show comparable OCP, Tafel region, and structural phase as for the thin-film model catalysts. A comparison for ORR activity has also been made between this Co-Se powder and a commercial Pt catalyst.

  8. Dinucleating Ligand Platforms Supporting Indium and Zinc Catalysts for Cyclic Ester Polymerization.

    PubMed

    Kremer, Alexandre B; Osten, Kimberly M; Yu, Insun; Ebrahimi, Tannaz; Aluthge, Dinesh C; Mehrkhodavandi, Parisa

    2016-06-01

    The synthesis of the first alkoxide-bridged indium complex supported by a chiral dinucleating ligand platform (1), along with its zinc analogue (2), is reported. Both complexes are synthesized in a one-pot reaction starting from a chiral dinucleating bis(diamino)phenolate ligand platform, sodium ethoxide, and respective metal salts. The dinucleating indium analogue (7) based on an achiral ligand backbone is also reported. Indium complexes bearing either the chiral or achiral ligand catalyze the ring-opening polymerization of racemic lactide (rac-LA) to afford highly heterotactic poly(lactic acid) (PLA; Pr > 0.85). The indium complex bearing an achiral ligand affords essentially atactic PLA from meso-LA. The role of the dinucleating ligand structure in catalyst synthesis and polymerization activity is discussed. PMID:27187767

  9. Effect of particle size on CO hydrogenation activity of silica supported cobalt catalysts

    SciTech Connect

    Ho, Suiwen; Houalla, M.; Hercules, D.M. )

    1990-08-09

    Two series of silica supported cobalt catalysts were prepared by incipient wetness impregnation, one by varying the calcination temperature (200-400{degree}C, 3 wt % Co) and the other by changing the cobalt loading (1-10 wt % Co). Examination by ESCA, XRD, and H{sub 2} chemisorption showed that Co{sub 3}O{sub 4} is the dominant phase. The cobalt phase is reduced to cobalt metal at 400{degree}C. The cobalt particle sizes obtained from ESCA correlated well with those derived from H{sub 2} chemisorption and XRD line broadening. The turnover frequency of Co/SiO{sub 2} for CO hydrogenation was invariant with cobalt dispersion in the range of 6-20% dispersion.

  10. 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

  11. Magnetic silica supported palladium catalyst: synthesis of allyl aryl ethers in water

    EPA Science Inventory

    A simple and benign procedure for the synthesis of aryl allyl ethers has been developed using phenols, allyl acetates and magnetically recyclable silica supported palladium catalyst in water; performance of reaction in air and easy separation of the catalyst using an external mag...

  12. Synthesis and Characterization of Carbon Nanofibers on Transition Metal Catalysts by Chemical Vapor Deposition.

    PubMed

    Hyun, Yura; Park, Eun-Sil; Mees, Karina; Park, Ho-Seon; Willert-Porada, Monika; Lee, Chang-Seop

    2015-09-01

    Carbon nanofibers were synthesized on transition metal (Fe, Co, Cu) catalysts by Chemical Vapor Deposition (CVD). The variations of thickness and surface of the fibers were investigated according to the concentration of the transition metal. In order to prepare the metal catalysts for synthesis, transition metal nitrate and copper nitrate at a weight ratio were dissolved in distilled water. The obtained catalyst precipitates were filtered and then dried for more than 24 hours at 110 degrees C. Carbon nanofibers were synthesized by using ethylene gas of carbon source by CVD after pulverization of the fully-dried catalyst precipitates. They were characterized by SEM, EDS, Raman, XRD, XPS and TG/DTA, and their specific surface area was measured by BET. The characteristics of the synthesized carbon nanofibers were greatly influenced by the concentration ratio of the metal catalysts. Especially, uniform carbon nanofibers grew when the concentration ratio of Fe and Cu was 7:3, and that of Co and Cu was 6:4. Carbon nanofibers synthesized under such concentration conditions had the best crystallizability, compared to carbon nanofibers synthesized with metal catalysts of different concentration ratios, and revealed high amorphicity as well as high specific surface area. PMID:26716326

  13. Physicochemical investigations of carbon nanofiber supported Cu / ZrO2 catalyst

    NASA Astrophysics Data System (ADS)

    Din, Israf Ud; Shaharun, Maizatul S.; Subbarao, Duvvuri; Naeem, A.

    2014-10-01

    Zirconia-promoted copper/carbon nanofiber catalysts (Cu - ZrO2/ CNF ) were prepared by the sequential deposition precipitation method. The Herringbone type of carbon nanofiber GNF-100 (Graphite nanofiber) was used as a catalyst support. Carbon nanofiber was oxidized to (CNF-O) with 5% and 65 % concentration of nitric acid (HNO3). The CNF activated with 5% HNO3 produced higher surface area which is 155 m2/g. The catalyst was characterized by X-ray Diffraction (XRD), Fourier Transform Infra-Red (FTIR) and N2 adsorption-desorption. The results showed that increase of HNO3 concentration reduced the surface area and porosity of the catalyst.

  14. Influences of synthesis methods and modifier addition on the properties of Ni-based catalysts supported on reticulated ceramic foams

    NASA Astrophysics Data System (ADS)

    Nikolić, Vesna; Kamberović, Željko; Anđić, Zoran; Korać, Marija; Sokić, Miroslav; Maksimović, Vesna

    2014-08-01

    A method of synthesizing Ni-based catalysts supported on α-Al2O3-based foams was developed. The foams were impregnated with aqueous solutions of metal chlorides under an air atmosphere using an aerosol route. Separate procedures involved calcination to form oxides and drying to obtain chlorides on the foam surface. The synthesized samples were subsequently reduced with hydrogen. With respect to the Ni/Al2O3 catalysts, the chloride reduction route enabled the formation of a Ni coating without agglomerates or cracks. Further research included catalyst modification by the addition of Pd, Cu, and Fe. The influences of the additives on the degree of reduction and on the low-temperature reduction effectiveness (533 and 633 K) were examined and compared for the catalysts obtained from oxides and chlorides. Greater degrees of reduction were achieved with chlorides, whereas Pd was the most effective modifier among those investigated. The reduction process was nearly complete at 533 K in the sample that contained 0.1wt% Pd. A lower reduction temperature was utilized, and the calcination step was avoided, which may enhance the economical and technological aspects of the developed catalyst production method.

  15. Biopolymer-supported ionic-liquid-phase ruthenium catalysts for olefin metathesis.

    PubMed

    Clousier, Nathalie; Filippi, Alexandra; Borré, Etienne; Guibal, Eric; Crévisy, Christophe; Caijo, Fréderic; Mauduit, Marc; Dez, Isabelle; Gaumont, Annie-Claude

    2014-04-01

    Original ruthenium supported ionic liquid phase (SILP) catalysts based on alginates as supports were developed for olefin metathesis reactions. The marine biopolymer, which fulfills most of the requisite properties for a support such as widespread abundance, insolubility in the majority of organic solvents, a high affinity for ionic liquids, high chemical stability, biodegradability, low cost, and easy processing, was impregnated by [bmim][PF6 ] containing an ionically tagged ruthenium catalyst. These biosourced catalysts show promising performances in ring-closing metathesis (RCM) and cross-metathesis (CM) reactions, with a high level of recyclability and reusability combined with a good reactivity. PMID:24616203

  16. Biopolymer-supported ionic-liquid-phase ruthenium catalysts for olefin metathesis.

    PubMed

    Clousier, Nathalie; Filippi, Alexandra; Borré, Etienne; Guibal, Eric; Crévisy, Christophe; Caijo, Fréderic; Mauduit, Marc; Dez, Isabelle; Gaumont, Annie-Claude

    2014-04-01

    Original ruthenium supported ionic liquid phase (SILP) catalysts based on alginates as supports were developed for olefin metathesis reactions. The marine biopolymer, which fulfills most of the requisite properties for a support such as widespread abundance, insolubility in the majority of organic solvents, a high affinity for ionic liquids, high chemical stability, biodegradability, low cost, and easy processing, was impregnated by [bmim][PF6 ] containing an ionically tagged ruthenium catalyst. These biosourced catalysts show promising performances in ring-closing metathesis (RCM) and cross-metathesis (CM) reactions, with a high level of recyclability and reusability combined with a good reactivity.

  17. Synthesis and characterization of supported polysugar-stabilized palladium nanoparticle catalysts for enhanced hydrodechlorination of trichloroethylene.

    PubMed

    Bacik, Deborah B; Zhang, Man; Zhao, Dongye; Roberts, Christopher B; Seehra, Mohinar S; Singh, Vivek; Shah, Naresh

    2012-07-27

    Palladium (Pd) nanoparticle catalysts were successfully synthesized within an aqueous phase using sodium carboxymethyl cellulose (CMC) as a capping ligand which offers a green alternative to conventional nanoparticle synthesis techniques. The CMC-stabilized Pd nanoparticles were subsequently dispersed within support materials using the incipient wetness impregnation technique for utilization in heterogeneous catalyst systems. The unsupported and supported (both calcined and uncalcined) Pd nanoparticle catalysts were characterized using transmission electron microscopy, energy dispersive x-ray spectrometry, x-ray diffraction, and Brunauer-Emmett-Teller surface area measurement and their catalytic activity toward the hydrodechlorination of trichloroethylene (TCE) in aqueous media was examined using homogeneous and heterogeneous catalyst systems, respectively. The unsupported Pd nanoparticles showed considerable activity toward the degradation of TCE, as demonstrated by the reaction kinetics. Although the supported Pd nanoparticle catalysts had a lower catalytic activity than the unsupported particles that were homogeneously dispersed in the aqueous solutions, the supported catalysts retained sufficient activity toward the degradation of TCE. In addition, the use of the hydrophilic Al(2)O(3) support material induced a mass transfer resistance to TCE that affected the initial hydrodechlorination rate. This paper demonstrates that supported Pd catalysts can be applied to the heterogeneous catalytic hydrodechlorination of TCE. PMID:22743584

  18. Synthesis and characterization of supported polysugar-stabilized palladium nanoparticle catalysts for enhanced hydrodechlorination of trichloroethylene

    NASA Astrophysics Data System (ADS)

    Bacik, Deborah B.; Zhang, Man; Zhao, Dongye; Roberts, Christopher B.; Seehra, Mohinar S.; Singh, Vivek; Shah, Naresh

    2012-07-01

    Palladium (Pd) nanoparticle catalysts were successfully synthesized within an aqueous phase using sodium carboxymethyl cellulose (CMC) as a capping ligand which offers a green alternative to conventional nanoparticle synthesis techniques. The CMC-stabilized Pd nanoparticles were subsequently dispersed within support materials using the incipient wetness impregnation technique for utilization in heterogeneous catalyst systems. The unsupported and supported (both calcined and uncalcined) Pd nanoparticle catalysts were characterized using transmission electron microscopy, energy dispersive x-ray spectrometry, x-ray diffraction, and Brunauer-Emmett-Teller surface area measurement and their catalytic activity toward the hydrodechlorination of trichloroethylene (TCE) in aqueous media was examined using homogeneous and heterogeneous catalyst systems, respectively. The unsupported Pd nanoparticles showed considerable activity toward the degradation of TCE, as demonstrated by the reaction kinetics. Although the supported Pd nanoparticle catalysts had a lower catalytic activity than the unsupported particles that were homogeneously dispersed in the aqueous solutions, the supported catalysts retained sufficient activity toward the degradation of TCE. In addition, the use of the hydrophilic Al2O3 support material induced a mass transfer resistance to TCE that affected the initial hydrodechlorination rate. This paper demonstrates that supported Pd catalysts can be applied to the heterogeneous catalytic hydrodechlorination of TCE.

  19. Ni/Fe-supported over hydrotalcites precursors as catalysts for clean and selective oxidation of Basic Yellow 11: reaction intermediates determination.

    PubMed

    Ovejero, G; Rodríguez, A; Vallet, A; García, J

    2013-01-01

    In this work, Basic Yellow 11 (BY 11) was employed as model compound to study catalytic wet air oxidation as a pre-treatment step to the conventional biological oxidation. Ni and Fe catalysts supported over hydrotalcite (HT) were prepared by incipient wetness and excess impregnation to obtain catalysts with different metal loadings (from 1 to 10 wt.%). HTs were synthesized by co-precipitation and characterized with XRD, X-ray fluorescence (XRF), BET, thermogravimetric analysis and SEM. Results showed that dye conversion increased with Ni and Fe content up to 7 wt.% and that the most effective catalyst were prepared by incipient wetness impregnation. The influence of metal loading in the catalyst, and the preparation method as well as the reaction conditions was investigated. A mechanism and reaction pathways for BY 11 during catalytic liquid phase oxidation have also been proposed.

  20. Ni/Fe-supported over hydrotalcites precursors as catalysts for clean and selective oxidation of Basic Yellow 11: reaction intermediates determination.

    PubMed

    Ovejero, G; Rodríguez, A; Vallet, A; García, J

    2013-01-01

    In this work, Basic Yellow 11 (BY 11) was employed as model compound to study catalytic wet air oxidation as a pre-treatment step to the conventional biological oxidation. Ni and Fe catalysts supported over hydrotalcite (HT) were prepared by incipient wetness and excess impregnation to obtain catalysts with different metal loadings (from 1 to 10 wt.%). HTs were synthesized by co-precipitation and characterized with XRD, X-ray fluorescence (XRF), BET, thermogravimetric analysis and SEM. Results showed that dye conversion increased with Ni and Fe content up to 7 wt.% and that the most effective catalyst were prepared by incipient wetness impregnation. The influence of metal loading in the catalyst, and the preparation method as well as the reaction conditions was investigated. A mechanism and reaction pathways for BY 11 during catalytic liquid phase oxidation have also been proposed. PMID:22960061