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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. Metal supports for exhaust gas catalysts

    SciTech Connect

    Nonnenmann, M.

    1985-01-01

    Since 1979, metal supports as pre-catalysts have been mass-produced and installed in export models of German automobiles bound for the United States and Japan. The close-to-engine installation directly behind the exhaust manifold places specially high demands on the thermal and mechanical durability of the metal supports. Sueddeutsche Kuehlerfabrik Behr produces these metal supports under the name of ''Metalit''. The development, properties and special advantages of these metal supports are covered. The successful use of hundreds of thousands of metal supports, a number of automobile manufacturers are working on programs to employ the Metalit concept for primary catalysts.

  4. Methane activation on supported transition metal catalysts

    NASA Astrophysics Data System (ADS)

    Carstens, Jason Ned

    At present, there is considerable interest in utilizing methane more efficiently as both a fuel source and as a starting material for the production of other, more valuable products. However, methane is a very stable molecule with strong C-H bonds that are difficult to break. This makes methane combustion or the formation of carbon-carbon bonds quite difficult. The present work focuses on the use of supported transition metal catalysts as a means of activating methane (i.e. breaking C-H bonds) at low temperatures to produce valuable products or energy. The conversion of methane into higher hydrocarbons. A low temperature (<750 K), direct process to effectively convert methane into higher hydrocarbons would be quite desirable. Such a process is thermodynamically feasible if the reaction is broken up into two separate steps. The first step is the adsorption of methane onto a transition metal catalyst at temperatures above about 600 K to produce a surface carbon species. The second step is a low temperature (<373 K) hydrogenation to convert the carbon species into higher hydrocarbons. T. Koerts et al. have pursued this approach by dissociatively absorbing methane onto silica supported transition metal catalysts at temperatures ranging between 573 K and 773 K. The result was a surface carbonaceous species and hydrogen. In the second step, the carbonaceous intermediates produced small alkanes upon hydrogenation around 373 K. A maximum yield to higher hydrocarbons of 13% was obtained on a ruthenium catalyst. The present study was conducted to further investigate the nature of the carbonaceous species reported by Koerts. Methane combustion. This investigation was conducted in an effort to better understand the mechanism of methane combustion on Pd catalysts. In the first part of this study, temperature programmed reduction (TPR) was used to investigate the oxidation and reduction dynamics of a 10 wt% Pd/ZrOsb2 catalyst used for methane combustion. TPR experiments indicate

  5. 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.

  6. Metal-Support Cooperative Catalysts for Environmentally Benign Molecular Transformations.

    PubMed

    Kaneda, Kiyotomi; Mitsudome, Takato

    2017-01-01

    Metal-support cooperative catalysts have been developed for sustainable and environmentally benign molecular transformations. The active metal centers and supports in these catalysts could cooperatively activate substrates, resulting in high catalytic performance for liquid-phase reactions under mild conditions. These catalysts involved hydrotalcite-supported gold and silver nanoparticles with high catalytic activity for organic reactions such as aerobic oxidation, oxidative carbonylation, and chemoselective reduction of epoxides to alkenes and nitrostyrenes to aminostyrenes using alcohols and CO/H2 O as reducing reagents. This high catalytic performance was due to cooperative catalysis between the metal nanoparticles and basic sites of the hydrotalcite support. To increase the metal-support cooperative effect, core-shell nanostructured catalysts consisting of gold or silver nanoparticles in the core and ceria supports in the shell were designed. These core-shell nanocomposite catalysts were effective for the chemoselective hydrogenation of nitrostyrenes to aminostyrenes, unsaturated aldehydes to allyl alcohols, and alkynes to alkenes using H2 as a clean reductant. In addition, these solid catalysts could be recovered easily from the reaction mixture by simple filtration, and were reusable with high catalytic activity. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. 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

  8. Electronic metal-support interactions in single-atom catalysts.

    PubMed

    Hu, Pingping; Huang, Zhiwei; Amghouz, Zakariae; Makkee, Michiel; Xu, Fei; Kapteijn, Freek; Dikhtiarenko, Alla; Chen, Yaxin; Gu, Xiao; Tang, Xingfu

    2014-03-24

    The synthesis of single-atom catalysts and the control of the electronic properties of catalytic sites to arrive at superior catalysts is a major challenge in heterogeneous catalysis. A stable supported single-atom silver catalyst with a controllable electronic state was obtained by anti-Ostwald ripening. An electronic perturbation of the catalytic sites that is induced by a subtle change in the structure of the support has a strong influence on the intrinsic reactivity. The higher depletion of the 4d electronic state of the silver atoms causes stronger electronic metal-support interactions, which leads to easier reducibility and higher catalytic activity. These results may improve our understanding of the nature of electronic metal-support interactions and lead to structure-activity correlations.

  9. Supported Dendrimer-Encapsulated Metal Clusters: Toward Heterogenizing Homogeneous Catalysts.

    PubMed

    Ye, Rong; Zhukhovitskiy, Aleksandr V; Deraedt, Christophe V; Toste, F Dean; Somorjai, Gabor A

    2017-08-15

    Recyclable catalysts, especially those that display selective reactivity, are vital for the development of sustainable chemical processes. Among available catalyst platforms, heterogeneous catalysts are particularly well-disposed toward separation from the reaction mixture via filtration methods, which renders them readily recyclable. Furthermore, heterogeneous catalysts offer numerous handles-some without homogeneous analogues-for performance and selectivity optimization. These handles include nanoparticle size, pore profile of porous supports, surface ligands and interface with oxide supports, and flow rate through a solid catalyst bed. Despite these available handles, however, conventional heterogeneous catalysts are themselves often structurally heterogeneous compared to homogeneous catalysts, which complicates efforts to optimize and expand the scope of their reactivity and selectivity. Ongoing efforts in our laboratories are aimed to address the above challenge by heterogenizing homogeneous catalysts, which can be defined as the modification of homogeneous catalysts to render them in a separable (solid) phase from the starting materials and products. Specifically, we grow the small nanoclusters in dendrimers, a class of uniform polymers with the connectivity of fractal trees and generally radial symmetry. Thanks to their dense multivalency, shape persistence, and structural uniformity, dendrimers have proven to be versatile scaffolds for the synthesis and stabilization of small nanoclusters. Then these dendrimer-encapsulated metal clusters (DEMCs) are adsorbed onto mesoporous silica. Through this method, we have achieved selective transformations that had been challenging to accomplish in a heterogeneous setting, e.g., π-bond activation and aldol reactions. Extensive investigation into the catalytic systems under reaction conditions allowed us to correlate the structural features (e.g., oxidation states) of the catalysts and their activity. Moreover, we have

  10. Metal Phosphate-Supported Pt Catalysts for CO Oxidation

    PubMed Central

    Qian, Xiaoshuang; Qin, Hongmei; Meng, Tao; Lin, Yi; Ma, Zhen

    2014-01-01

    Oxides (such as SiO2, TiO2, ZrO2, Al2O3, Fe2O3, CeO2) have often been used to prepare supported Pt catalysts for CO oxidation and other reactions, whereas metal phosphate-supported Pt catalysts for CO oxidation were rarely reported. Metal phosphates are a family of metal salts with high thermal stability and acid-base properties. Hydroxyapatite (Ca10(PO4)6(OH)2, denoted as Ca-P-O here) also has rich hydroxyls. Here we report a series of metal phosphate-supported Pt (Pt/M-P-O, M = Mg, Al, Ca, Fe, Co, Zn, La) catalysts for CO oxidation. Pt/Ca-P-O shows the highest activity. Relevant characterization was conducted using N2 adsorption-desorption, inductively coupled plasma (ICP) atomic emission spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), CO2 temperature-programmed desorption (CO2-TPD), X-ray photoelectron spectroscopy (XPS), and H2 temperature-programmed reduction (H2-TPR). This work furnishes a new catalyst system for CO oxidation and other possible reactions. PMID:28788293

  11. Metal-support effects on acetone hydrogenation over platinum catalysts

    SciTech Connect

    Sen, B.; Vannice, M.A. )

    1988-09-01

    Acetone hydrogenation was studied over Pt/TiO{sub 2}, Pt/{eta}-Al{sub 2}O{sub 3}, Pt/SiO{sub 2}, Pt powder, and Pt/Au catalysts to test the hypothesis that the metal-support effect responsible for higher CO hydrogenation rates over certain metal/TiO{sub 2} catalysts represents a phenomenon capable of activating carbonyl bonds in general. Compared with the other catalysts, the high-temperature reduced (HTR) Pt/TiO{sub 2} samples had turnover frequencies more than 500 times higher than those of unsupported Pt and Pt/SiO{sub 2} catalysts, and the specific activity (per g Pt) of the Pt/TiO{sub 2} catalyst was 10 times that of a Pt/SiO{sub 2} catalyst with comparable dispersion. Complete hydrogenation to C{sub 3}H{sub 8} and H{sub 2}O occurred only on large, unsupported Pt crystallites; however, partial hydrogenation to isopropyl alcohol appeared to be structure insensitive and activation energies were similar over all catalysts, as were pressure dependencies, which associates the higher activity with a larger preexponential factor. Only one Langmuir-Hinshelwood model provided a rate expression consistent with experimental results - that which assumed competitive adsorption of H{sub 2} and acetone on the same sites and addition of the second H atom as the rate-determining step. This model is consistent with previous TPD, IR, and EELs studies and is also substantiated by theoretical calculations based on the bond-order conservation method. The much higher activities over Pt/TiO{sub 2} catalysts are attributed to an increase in the active site concentration in the Pt-titania interface region. These special sites are presumed to be defects on the titania surface near the Pt that can activate the carbonyl bond in the presence of atomic hydrogen provided by the Pt. 131 refs.

  12. Metal-support interaction on cobalt based FT catalysts - a DFT study of model inverse catalysts.

    PubMed

    van Heerden, Tracey; van Steen, Eric

    2017-04-28

    It is challenging to isolate the effect of metal-support interactions on catalyst reaction performance. In order to overcome this problem, inverse catalysts can be prepared in the laboratory and characterized and tested at relevant conditions. Inverse catalysts are catalysts where the precursor to the catalytically active phase is bonded to a support-like ligand. We can then view the metal-support interaction as a ligand interaction with the support acting as a supra-molecular ligand. Importantly, laboratory studies have shown that these ligands are still present after reduction of the catalyst. By varying the quantity of these ligands present on the surface, insight into the positive effect SMSI have during a reaction is gained. Here, we present a theoretical study of mono-dentate alumina support based ligands, adsorbed on cobalt surfaces. We find that the presence of the ligand may significantly affect the morphology of a cobalt crystallite. With Fischer-Tropsch synthesis in mind, the CO dissociation is used as a probe reaction, with the ligand assisting the dissociation, making it feasible to dissociate CO on the dense fcc Co(111) surface. The nature of the interaction between the ligand and the probe molecule is characterized, showing that the support-like ligands' metal centre is directly interacting with the probe molecule.

  13. Reaction and spectroscopic study of supported metal oxide catalysts

    NASA Astrophysics Data System (ADS)

    Ramani, Narayanan C.

    The role of surface structure, cation reducibility, surface acidity and the effect of the support was examined in the reaction of 1-butene over well characterized, supported metal oxide catalysts. Cr, Mo and W oxides supported on SiOsb2 were used to study the effect of structure, surface acidity and cation reducibility in the isomerization and selective oxidation of 1-butene. Supported oxides of Mo on TiOsb2,\\ Alsb2Osb3 and SiOsb2 were used to understand the role of the support in the selective oxidation of 1-butene. The surface acidity of SiOsb2 supported Cr, Mo, W and V oxide catalysts was examined by pyridine adsorption. Existing theoretical models of acidity were compared against experimental data. Over Mo(VI)/SiOsb2 and W(VI)/SiOsb2, isomerization through both a Bronsted catalyzed pathway and an allylic pathway were observed, while only the allylic pathway was observed over Cr(VI)/SiOsb2. The greater reducibility of the Cr cation compared to Mo and W cations was identified as the reason for the allylic pathway being dominant over Cr(VI)/SiOsb2. Cation reducibility was again seen to play an important role in the selective oxidation of 1-butene over SiOsb2 supported metal oxides. The turn over frequencies for 1,3-butadiene formation followed the trend in red-ox ability, with Cr > Mo > W. The activity to 1,3-butadiene formation did not change with increasing weight loading of Mo over TiOsb2 and Alsb2Osb3 supports. An analysis of the turn over frequencies of the supports and the supported cations revealed that a support effect, through the bridging oxygen ligand, dominated the intrinsic cation reducibility of Mo for these catalysts. The existence of Bronsted acidity over SiOsb2 supported Cr, Mo and V oxides was shown by an analysis of the OH region of the infrared spectrum, and by the adsorption of 1-butene and pyridine. Existing theoretical models for Bronsted acidity over supported metal oxides were shown to be inadequate to describe the observed results over

  14. Adsorbate-mediated strong metal-support interactions in oxide-supported Rh catalysts.

    PubMed

    Matsubu, John C; Zhang, Shuyi; DeRita, Leo; Marinkovic, Nebojsa S; Chen, Jingguang G; Graham, George W; Pan, Xiaoqing; Christopher, Phillip

    2017-02-01

    The optimization of supported metal catalysts predominantly focuses on engineering the metal site, for which physical insights based on extensive theoretical and experimental contributions have enabled the rational design of active sites. Although it is well known that supports can influence the catalytic properties of metals, insights into how metal-support interactions can be exploited to optimize metal active-site properties are lacking. Here we utilize in situ spectroscopy and microscopy to identify and characterize a support effect in oxide-supported heterogeneous Rh catalysts. This effect is characterized by strongly bound adsorbates (HCOx) on reducible oxide supports (TiO2 and Nb2O5) that induce oxygen-vacancy formation in the support and cause HCOx-functionalized encapsulation of Rh nanoparticles by the support. The encapsulation layer is permeable to reactants, stable under the reaction conditions and strongly influences the catalytic properties of Rh, which enables rational and dynamic tuning of CO2-reduction selectivity.

  15. Adsorbate-mediated strong metal-support interactions in oxide-supported Rh catalysts

    NASA Astrophysics Data System (ADS)

    Matsubu, John C.; Zhang, Shuyi; Derita, Leo; Marinkovic, Nebojsa S.; Chen, Jingguang G.; Graham, George W.; Pan, Xiaoqing; Christopher, Phillip

    2016-09-01

    The optimization of supported metal catalysts predominantly focuses on engineering the metal site, for which physical insights based on extensive theoretical and experimental contributions have enabled the rational design of active sites. Although it is well known that supports can influence the catalytic properties of metals, insights into how metal-support interactions can be exploited to optimize metal active-site properties are lacking. Here we utilize in situ spectroscopy and microscopy to identify and characterize a support effect in oxide-supported heterogeneous Rh catalysts. This effect is characterized by strongly bound adsorbates (HCOx) on reducible oxide supports (TiO2 and Nb2O5) that induce oxygen-vacancy formation in the support and cause HCOx-functionalized encapsulation of Rh nanoparticles by the support. The encapsulation layer is permeable to reactants, stable under the reaction conditions and strongly influences the catalytic properties of Rh, which enables rational and dynamic tuning of CO2-reduction selectivity.

  16. Adsorbate-mediated strong metal-support interactions in oxide-supported Rh catalysts

    NASA Astrophysics Data System (ADS)

    Matsubu, John C.; Zhang, Shuyi; Derita, Leo; Marinkovic, Nebojsa S.; Chen, Jingguang G.; Graham, George W.; Pan, Xiaoqing; Christopher, Phillip

    2017-02-01

    The optimization of supported metal catalysts predominantly focuses on engineering the metal site, for which physical insights based on extensive theoretical and experimental contributions have enabled the rational design of active sites. Although it is well known that supports can influence the catalytic properties of metals, insights into how metal-support interactions can be exploited to optimize metal active-site properties are lacking. Here we utilize in situ spectroscopy and microscopy to identify and characterize a support effect in oxide-supported heterogeneous Rh catalysts. This effect is characterized by strongly bound adsorbates (HCOx) on reducible oxide supports (TiO2 and Nb2O5) that induce oxygen-vacancy formation in the support and cause HCOx-functionalized encapsulation of Rh nanoparticles by the support. The encapsulation layer is permeable to reactants, stable under the reaction conditions and strongly influences the catalytic properties of Rh, which enables rational and dynamic tuning of CO2-reduction selectivity.

  17. Control of metal nanocrystal size reveals metal-support interface role for ceria catalysts.

    PubMed

    Cargnello, Matteo; Doan-Nguyen, Vicky V T; Gordon, Thomas R; Diaz, Rosa E; Stach, Eric A; Gorte, Raymond J; Fornasiero, Paolo; Murray, Christopher B

    2013-08-16

    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.

  18. 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.

  19. Studies of Immobilized Homogeneous Metal Catalysts on Silica Supports

    SciTech Connect

    Stanger, Keith James

    2003-01-01

    The tethered, chiral, chelating diphosphine rhodium complex, which catalyzes the enantioselective hydrogenation of methyl-α-acetamidocinnamate (MAC), has the illustrated structure as established by 31P 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]4, [Rh(COD)2]+BF4-, [Rh(COD)Cl]2, and RhCl3• 3H2O, adsorbed on SiO2 are optimally activated for toluene hydrogenation by pretreatment with H2 at 200 C. The same complexes on Pd-SiO2 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(CH2)3s-]Re(O)(Me)(PPh3) 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.

  20. 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.

  1. Strong Metal-Support Interactions (smsi) in Model Titania-Supported Rhodium Catalysts.

    NASA Astrophysics Data System (ADS)

    Sadeghi, Hassan Roger

    Model catalysts consisting of rhodium particles supported on well characterized, single crystal rutile substrates were used to study the nature of strong metal -support interactions (SMSI) in supported catalyst systems. The use of single crystal supports eliminates many of the complications inherent with powder supported catalysts and greatly simplifies the interpretation of experimental data. A variety of surface sensitive electron spectroscopic techniques, including ultraviolet and x-ray photoemission (UPS and XPS), electron energy loss (ELS) and Auger spectroscopies, low energy electron diffraction (LEED), combined with chemisorption measurements were applied to rhodium on titania model catalysts in order to separate the various phenomena that contribute to SMSI. The properties of the clean titania supports have been determined, including the dynamics of oxidation of reduced surfaces. Model catalysts were then prepared by thermal evaporation of rhodium onto these supports. The high temperature reduction procedures that produce the SMSI state on powder supported catalysts have been used on the model catalysts, and Auger sputter profiles indicate that during high temperature reduction (HTR) a suboxide of titanium migrates onto the rhodium particles, thus blocking carbon monoxide chemisorption. Removal of the suboxide layer by ion bombardment restores the normal chemisorption properties of the catalyst. Model rhodium on titania catalysts fabricated on both fully oxidized and on partially reduced single crystal supports have also been used. In this way it is possible to observe support-to-metal charge transfer in the absence of the encapsulation that accompanies HTR. The experimental results show that reduced titania species and rhodium interact with each other through a partially ionic bond, with electronic charge transferred from the reduced titanium cations to the rhodium. This bonding interaction is part of the driving force that leads to encapsulation of the

  2. 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.

  3. Supported liquid metal catalysts: Popping up to the surface

    NASA Astrophysics Data System (ADS)

    Rupprechter, Günther

    2017-09-01

    Merging the advantages of homogeneous and heterogeneous catalysts is a useful strategy for creating improved catalytic systems. Now, a concept has been developed that uses single Pd atoms -- supported within liquid alloy droplets -- that emerge from the droplet subsurface and interior to react with molecules approaching from the gas phase.

  4. Electrochemical dopamine sensor based on P-doped graphene: Highly active metal-free catalyst and metal catalyst support.

    PubMed

    Chu, Ke; Wang, Fan; Zhao, Xiao-Lin; Wang, Xin-Wei; Tian, Ye

    2017-12-01

    Heteroatom doping is an effective strategy to enhance the catalytic activity of graphene and its hybrid materials. Despite a growing interest of P-doped graphene (P-G) in energy storage/generation applications, P-G has rarely been investigated for electrochemical sensing. Herein, we reported the employment of P-G as both metal-free catalyst and metal catalyst support for electrochemical detection of dopamine (DA). As a metal-free catalyst, P-G exhibited prominent DA sensing performances due to the important role of P doping in improving the electrocatalytic activity of graphene toward DA oxidation. Furthermore, P-G could be an efficient supporting material for loading Au nanoparticles, and resulting Au/P-G hybrid showed a dramatically enhanced electrocatalytic activity and extraordinary sensing performances with a wide linear range of 0.1-180μM and a low detection limit of 0.002μM. All these results demonstrated that P-G might be a very promising electrode material for electrochemical sensor applications. Copyright © 2017 Elsevier B.V. All rights reserved.

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

    SciTech Connect

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

    2012-02-07

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

  6. 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.

  7. 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.

  8. Characterization of the metal-support interface in supported metal and supported metal complex catalysts. [Final report

    SciTech Connect

    Gates, B.C.

    1992-12-31

    Re and Ir carbonyls, and other compounds, were chosen as precursors. MgO, La{sub 2}O{sub 3}, zeolite NaX and KL, among others, were chosen as supports. EXAFS was used to study the metal-support interactions. Structures formed on almost fully dehydroxylated MgO by HRe(CO){sub 5}, and on MgO by Ir{sub 4}(CO){sub 12}, were studied. A metal-oxygen distance of 2.15 {angstrom} holds in for the metal-support interface in oxide-supported metal clusters following reduction in H{sub 2} above 450 C; for reduction below 350 C, the distance is 2.5--2.7 {angstrom}.

  9. Synthesis and stabilization of supported metal catalysts by atomic layer deposition.

    PubMed

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

    2013-08-20

    Supported metal nanoparticles are among the most important catalysts for many practical reactions, including petroleum refining, automobile exhaust treatment, and Fischer-Tropsch synthesis. The catalytic performance strongly depends on the size, composition, and structure of the metal nanoparticles, as well as the underlying support. Scientists have used conventional synthesis methods including impregnation, ion exchange, and deposition-precipitation to control and tune these factors, to establish structure-performance relationships, and to develop better catalysts. Meanwhile, chemists have improved the stability of metal nanoparticles against sintering by the application of protective layers, such as polymers and oxides that encapsulate the metal particle. This often leads to decreased catalytic activity due to a lack of precise control over the thickness of the protective layer. A promising method of catalyst synthesis is atomic layer deposition (ALD). ALD is a variation on chemical vapor deposition in which metals, oxides, and other materials are deposited on surfaces by a sequence of self-limiting reactions. The self-limiting character of these reactions makes it possible to achieve uniform deposits on high-surface-area porous solids. Therefore, design and synthesis of advanced catalysts on the nanoscale becomes possible through precise control over the structure and composition of the underlying support, the catalytic active sites, and the protective layer. In this Account, we describe our advances in the synthesis and stabilization of supported metal catalysts by ALD. After a short introduction to the technique of ALD, we show several strategies for metal catalyst synthesis by ALD that take advantage of its self-limiting feature. Monometallic and bimetallic catalysts with precise control over the metal particle size, composition, and structure were achieved by combining ALD sequences, surface treatments, and deposition temperature control. Next, we describe

  10. 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.

  11. Gallium-rich Pd-Ga phases as supported liquid metal catalysts

    NASA Astrophysics Data System (ADS)

    Taccardi, N.; Grabau, M.; Debuschewitz, J.; Distaso, M.; Brandl, M.; Hock, R.; Maier, F.; Papp, C.; Erhard, J.; Neiss, C.; Peukert, W.; Görling, A.; Steinrück, H.-P.; Wasserscheid, P.

    2017-09-01

    A strategy to develop improved catalysts is to create systems that merge the advantages of heterogeneous and molecular catalysis. One such system involves supported liquid-phase catalysts, which feature a molecularly defined, catalytically active liquid film/droplet layer adsorbed on a porous solid support. In the past decade, this concept has also been extended to supported ionic liquid-phase catalysts. Here we develop this idea further and describe supported catalytically active liquid metal solutions (SCALMS). We report a liquid mixture of gallium and palladium deposited on porous glass that forms an active catalyst for alkane dehydrogenation that is resistant to coke formation and is thus highly stable. X-ray diffraction and X-ray photoelectron spectroscopy, supported by theoretical calculations, confirm the liquid state of the catalytic phase under the reaction conditions. Unlike traditional heterogeneous catalysts, the supported liquid metal reported here is highly dynamic and catalysis does not proceed at the surface of the metal nanoparticles, but presumably at homogeneously distributed metal atoms at the surface of a liquid metallic phase.

  12. Graphene supported non-precious metal-macrocycle catalysts for oxygen reduction reaction in fuel cells

    NASA Astrophysics Data System (ADS)

    Choi, Hyun-Jung; Ashok Kumar, Nanjundan; Baek, Jong-Beom

    2015-04-01

    Fuel cells are promising alternative energy devices owing to their high efficiency and eco-friendliness. While platinum is generally used as a catalyst for the oxygen reduction reaction (ORR) in a typical fuel cell, limited reserves and prohibitively high costs limit its future use. The development of non-precious and durable metal catalysts is being constantly conceived. Graphene has been widely used as a substrate for metal catalysts due to its unique properties, thus improving stability and ORR activities. In this feature, we present an overview on the electrochemical characteristics of graphene supported non-precious metal containing macrocycle catalysts that include metal porphyrin and phthalocyanine derivatives. Suggested research and future development directions are discussed.

  13. Carbonyl clusters of transition metals on oxide supports as heterogeneous catalysts for hydrocarbon synthesis

    SciTech Connect

    Kuznetsov, B.N.; Koval`chuk, V.I.

    1995-05-01

    The methods of preparation of heterogeneous catalysts by immobilization of carbonyl clusters of transition metals on oxide supports, as well as the study of the state of supported compounds and their catalytic properties in CO hydrogenation and olefin hydroformulation are briefly reviewed.

  14. Transition metal complexes supported on metal-organic frameworks for heterogeneous catalysts

    DOEpatents

    Farha, Omar K.; Hupp, Joseph T.; Delferro, Massimiliano; Klet, Rachel C.

    2017-02-07

    A robust mesoporous metal-organic framework comprising a hafnium-based metal-organic framework and a single-site zirconium-benzyl species is provided. The hafnium, zirconium-benzyl metal-organic framework is useful as a catalyst for the polymerization of an alkene.

  15. 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.

  16. 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.

  17. Fundamental Studies of the Reforming of Oxygenated Compounds over Supported Metal Catalysts

    SciTech Connect

    Dumesic, James A.

    2016-01-04

    The main objective of our research has been to elucidate fundamental concepts associated with controlling the activity, selectivity, and stability of bifunctional, metal-based heterogeneous catalysts for tandem reactions, such as liquid-phase conversion of oxygenated hydrocarbons derived from biomass. We have shown that bimetallic catalysts that combine a highly-reducible metal (e.g., platinum) with an oxygen-containing metal promoter (e.g., molybdenum) are promising materials for conversion of oxygenated hydrocarbons because of their high activity for selective cleavage for carbon-oxygen bonds. We have developed methods to stabilize metal nanoparticles against leaching and sintering under liquid-phase reaction conditions by using atomic layer deposition (ALD) to apply oxide overcoat layers. We have used controlled surface reactions to produce bimetallic catalysts with controlled particle size and controlled composition, with an important application being the selective conversion of biomass-derived molecules. The synthesis of catalysts by traditional methods may produce a wide distribution of metal particle sizes and compositions; and thus, results from spectroscopic and reactions kinetics measurements have contributions from a distribution of active sites, making it difficult to assess how the size and composition of the metal particles affect the nature of the surface, the active sites, and the catalytic behavior. Thus, we have developed methods to synthesize bimetallic nanoparticles with controlled particle size and controlled composition to achieve an effective link between characterization and reactivity, and between theory and experiment. We have also used ALD to modify supported metal catalysts by addition of promoters with atomic-level precision, to produce new bifunctional sites for selective catalytic transformations. We have used a variety of techniques to characterize the metal nanoparticles in our catalysts, including scanning transmission electron

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. Alumina-supported noble metal catalysts for destructive oxidation of organic pollutants in effluent from a softwood kraft pulp mill

    SciTech Connect

    Zhang, Q.; Chuang, K.T.

    1998-08-01

    The effectiveness of alumina-supported noble metal catalysts for the destructive oxidation of organic pollutants in effluent from a softwood kraft pulp mill was evaluated in a slurry reactor at 463 K and an oxygen pressure of 1.5 MPa. The effects of catalyst preparation procedures, such as metal loading, calcination, or reduction treatment on the catalytic activities, were also tested. Alumina-supported palladium catalysts were found to be more effective than supported manganese, iron, or platinum catalysts. The rate of oxidation over Pd/alumina catalyst was significantly higher than that of the uncatalyzed reaction. Adding Ce on the alumina support was found to promote the activity of alumina-supported Pt catalyst but inhibit the activity of alumina-supported Pd catalyst. The reaction mechanisms for the catalytic wet oxidation process and the roles of Ce on catalytic activity for destructive oxidation of organic pollutants in wastewater are discussed.

  5. 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.

  6. 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.

  7. Steam dealkylation of aromatic hydrocarbons. II. Role of the support and kinetic pathway of oxygenated species in toluene steam dealkylation over group VIII metal catalysts. [Catalyst support comparison

    SciTech Connect

    Duprez, D.; Pereira, P.; Miloudi, A.; Maurel, R.

    1982-05-01

    The role of support in steam dealkylation (SDA) is studied on a series of Group VIII metal catalysts supported on alumina, silica, and titania. When possible turnover frequencies are given on the basis of the free metal fraction during the reaction, the values are generally constant with time-on-steam and represent the actual turnover frequency of the catalysts. Metals can be classified into two groups, namely, support-sensitive metals (Pt,Rh,Pd) and support-insensitive metals (Ni,Co,Ru and to a certain extent Ir). Support sensitivity is related to the oxidizability of the metallic surface. For metals of the first group, the reaction is probably governed by a noncompetitive mechanism in which the metal coverage by the oxygenated species is negligible. Kinetic derivation leads to a rate law where there is at once intervention of the support site concentration and of the specific perimeter of the metal/support interface. One can thus explain the support effect for this metal group and the slight sensitivity to the crystallite size observed in the Rh/Al/sub 2/O/sub 3/ series. For metals of the second group, a competitive mechanism probably takes place on the metal. Kinetic derivation leads to a rate law independent of the support site concentration and accounting for the slight negative order with respect to toluene as previously reported. The conspicuous parallelism between the selectivities of the various metals in SDA, in hydrodealkylation , and in hydrogenolysis is also discussed. In addition to the metal, the support and the crystallite size are determining factors of the selectivity to benzene in SDA.

  8. Highly dispersed metal catalyst

    DOEpatents

    Xiao, Xin; West, William L.; Rhodes, William D.

    2016-11-08

    A supported catalyst having an atomic level single atom structure is provided such that substantially all the catalyst is available for catalytic function. A process of forming a single atom catalyst unto a porous catalyst support is also provided.

  9. 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

  10. 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.

  11. 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.

  12. Supported noble metal catalysts in the catalytic wet air oxidation of industrial wastewaters and sewage sludges.

    PubMed

    Besson, M; Descorme, C; Bernardi, M; Gallezot, P; di Gregorio, F; Grosjean, N; Minh, D Pham; Pintar, A

    2010-12-01

    This paper reviews some catalytic wet air oxidation (CWAO) investigations of industrial wastewaters over platinum and ruthenium catalysts supported on TiO2 and ZrO2 formulated to be active and resistant to leaching, with particular focus on the stability of the catalyst. Catalyst recycling experiments were performed in batch reactors and long-term stability tests were conducted in trickle-bed reactors. The catalyst did not leach upon treatment of Kraft bleaching plant and olive oil mill effluents, and could be either recycled or used for long periods of time in continuous reactors. Conversely, these catalysts were rapidly leached when used to treat effluents from the production of polymeric membranes containing N,N-dimethylformamide. The intermediate formation of amines, such as dimethylamine and methylamine with a high complexing capacity for the metal, was shown to be responsible for the metal leaching. These heterogeneous catalysts also deactivated upon CWAO of sewage sludges due to the adsorption of the solid organic matter. Pre-sonication of the sludge to disintegrate the flocs and improve solubility was inefficient.

  13. Nanosheet Supported Single-Metal Atom Bifunctional Catalyst for Overall Water Splitting.

    PubMed

    Ling, Chongyi; Shi, Li; Ouyang, Yixin; Zeng, Xiao Cheng; Wang, Jinlan

    2017-08-09

    Nanosheet supported single-atom catalysts (SACs) can make full use of metal atoms and yet entail high selectivity and activity, and bifunctional catalysts can enable higher performance while lowering the cost than two separate unifunctional catalysts. Supported single-atom bifunctional catalysts are therefore of great economic interest and scientific importance. Here, on the basis of first-principles computations, we report a design of the first single-atom bifunctional eletrocatalyst, namely, isolated nickel atom supported on β12 boron monolayer (Ni1/β12-BM), to achieve overall water splitting. This nanosheet supported SAC exhibits remarkable electrocatalytic performance with the computed overpotential for oxygen/hydrogen evolution reaction being just 0.40/0.06 V. The ab initio molecular dynamics simulation shows that the SAC can survive up to 800 K elevated temperature, while enacting a high energy barrier of 1.68 eV to prevent isolated Ni atoms from clustering. A viable experimental route for the synthesis of Ni1/β12-BM SAC is demonstrated from computer simulation. The desired nanosheet supported single-atom bifunctional catalysts not only show great potential for achieving overall water splitting but also offer cost-effective opportunities for advancing clean energy technology.

  14. Studies of supported metal catalysts. Progress report, September 1, 1979-August 31, 1982

    SciTech Connect

    Hercules, D.M.

    1983-04-01

    The overall objective of this research was to characterize the binding of transition metals to catalytic supports, and to study speciation of these metals on supports. The accomplishments during this period fall into two categories. First, we have advanced the adapation of spectroscopic instrumentation for studying catalytic surfaces. Second, we have obtained interesting and valuable information about a variety of catalytic systems. One of the most interesting accomplishments was to demonstrate the utility of using the combination of x-ray Photoelectron Spectroscopy (ESCA), Low Energy Ion Scattering Spectroscopy (ISS) and Laser Raman Spectroscopy (LRS) to study catalytic surfaces. We have demonstrated the correlation between ESCA, EXAFS and Photoacoustic Spectroscopy (PAS) measurements on the same catalyst systems. We have been able to characterize nickel species on alumina and silica surfaces when the preparation method and nickel content of the catalysts are varied. Second, we have studied the nature of cobalt species on alumina and how these species are affected by the presence of molybdenum or zinc, or by sulfiding. Third, we have been able to study the species of molybdenum on an alumina catalyst and to determine how these species are changed by sulfiding, by the presence of cobalt or by being supported on titania. Fourth, we have studied tungsten on alumina and shown how the catalyst species for tungsten differ from those for molybdenum on the same support. Fifth, we have carried out an extensive study of photoacoustic measurements to determine the site symmetry of cobalt and nickel supported on alumina.

  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. Nanostructural and Chemical Characterization of Supported Metal Oxide Catalysts by Aberration Corrected Analytical Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Zhou, Wu

    Ox with WOx. As a consequence, the catalytic activity of the co-impregnated material is dramatically increased by more than two orders of magnitude. We further showed in Chapter 5 that the Keggin structure based on phosphotungstic acid hydrate (i.e. an ˜ 1nm P-WOx mixed oxide cluster) can be successfully immobilized on an amorphous SiO2 support surface. Such catalyst design experiments further support our postulated structure-activity model, in which WO x clusters mixed with some low valence heteroatoms are the most active entities for the methanol dehydration and n-pentane isomerization reactions. Another major theme of this thesis is the analysis of model double-supported metal oxide catalysts, in which a high surface area oxide support material (amorphous SiO2) is modified by the presence of a second metal oxide surface species (TiO2 or ZrO2) added to control the distribution and activity of the active surface WOx component. These complex double-supported metal oxide catalysts represent a very significant challenge in terms of structural characterization. A new electron microscopy characterization strategy was developed for this purpose which combined aberration corrected STEM imaging with concurrent EELS and XEDS analysis. We demonstrated that the various components in a double-supported WO3/TiO 2/SiO2 catalyst system can be effectively visualized using complementary HAADF and STEM-BF imaging within an aberration corrected STEM. Furthermore, when combined with chemical analysis by STEM-EELS and XEDS within the same STEM instrument, it is possible to map out the relative spatial distribution of all the metal oxide components within the WO3/TiO2/SiO 2 catalyst. By comparing the structures of a systematic set of WO 3/TiO2/SiO2 samples displaying high, intermediate and low activity for the methanol dehydration reaction, we showed that the acidic catalytic activity seems to benefit from having (i) a more localized electron density on the TiOx support and (ii) a larger WOx

  17. Sintering-Resistant Single-Site Nickel Catalyst Supported by Metal-Organic Framework.

    PubMed

    Li, Zhanyong; Schweitzer, Neil M; League, Aaron B; Bernales, Varinia; Peters, Aaron W; Getsoian, Andrew Bean; Wang, Timothy C; Miller, Jeffrey T; Vjunov, Aleksei; Fulton, John L; Lercher, Johannes A; Cramer, Christopher J; Gagliardi, Laura; Hupp, Joseph T; Farha, Omar K

    2016-02-17

    Developing supported single-site catalysts is an important goal in heterogeneous catalysis since the well-defined active sites afford opportunities for detailed mechanistic studies, thereby facilitating the design of improved catalysts. We present herein a method for installing Ni ions uniformly and precisely on the node of a Zr-based metal-organic framework (MOF), NU-1000, in high density and large quantity (denoted as Ni-AIM) using atomic layer deposition (ALD) in a MOF (AIM). Ni-AIM is demonstrated to be an efficient gas-phase hydrogenation catalyst upon activation. The structure of the active sites in Ni-AIM is proposed, revealing its single-site nature. More importantly, due to the organic linker used to construct the MOF support, the Ni ions stay isolated throughout the hydrogenation catalysis, in accord with its long-term stability. A quantum chemical characterization of the catalyst and the catalytic process complements the experimental results. With validation of computational modeling protocols, we further targeted ethylene oligomerization catalysis by Ni-AIM guided by theoretical prediction. Given the generality of the AIM methodology, this emerging class of materials should prove ripe for the discovery of new catalysts for the transformation of volatile substrates.

  18. Support Shape Effect in Metal Oxide Catalysis: Ceria-Nanoshape-Supported Vanadia Catalysts for Oxidative Dehydrogenation of Isobutane.

    PubMed

    Wu, Zili; Schwartz, Viviane; Li, Meijun; Rondinone, Adam J; Overbury, Steven H

    2012-06-07

    The support effect has long been an intriguing topic in catalysis research. With the advancement of nanomaterial synthesis, the availability of faceted oxide nanocrystals provides the opportunity to gain unprecedented insights into the support effect by employing these well-structured nanocrystals. In this Letter, we show by utilizing ceria nanoshapes as supports for vanadium oxide that the shape of the support poses a profound effect on the catalytic performance of metal oxide catalysts. Specifically, the activation energy of VOx/CeO2 catalysts in oxidative dehydrogenation of isobutane was found to be dependent on the shape of ceria support, rods < octahedra, closely related to the surface oxygen vacancy formation energy and the numbe of defects of the two ceria supports with different crystallographic surface planes.

  19. Support effects studied on model supported catalysts

    SciTech Connect

    Gorte, R.J.

    1993-02-01

    Composition and structure of oxide support materials can change the catalytic behavior of metal and oxide catalysts. Model catalysts are being studied in which the active phase is deposited on flat oxide substrates, with emphasis on metals catalysis for automotive emissions control and acidity in supported oxides. Research is reported in the following areas: particle-size effects, support effects on ZnO and zirconia, support effects on ceria, supported oxides, and low energy ion scattering (no results in the latter).

  20. Tuning the Selectivity of Single-Site Supported Metal Catalysts with Ionic Liquids

    DOE PAGES

    Babucci, Melike; Fang, Chia -Yu; Hoffman, Adam S.; ...

    2017-09-11

    1,3-Dialkylimidazolium ionic liquid coatings act as electron donors, increasing the selectivity for partial hydrogenation of 1,3-butadiene catalyzed by iridium complexes supported on high-surface-area γ-Al2O3. High-energy-resolution fluorescence detection X-ray absorption near-edge structure (HERFD XANES) measurements quantify the electron donation and are correlated with the catalytic activity and selectivity. Furthermore, the results demonstrate broad opportunities to tune electronic environments and catalytic properties of atomically dispersed supported metal catalysts.

  1. 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.

  2. 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.

  3. A versatile sonication-assisted deposition-reduction method for preparing supported metal catalysts for catalytic applications.

    PubMed

    Padilla, Romen Herrera; Priecel, Peter; Lin, Ming; Lopez-Sanchez, Jose Antonio; Zhong, Ziyi

    2017-03-01

    This work aims to develop a rapid and efficient strategy for preparing supported metal catalysts for catalytic applications. The sonication-assisted reduction-precipitation method was employed to prepare the heterogeneous mono- and bi-metallic catalysts for photocatalytic degradation of methyl orange (MO) and preferential oxidation (PROX) of CO in H2-rich gas. In general, there are three advantages for the sonication-assisted method as compared with the conventional methods, including high dispersion of metal nanoparticles on the catalyst support, the much higher deposition efficiency (DE) than those of the deposition-precipitation (DP) and co-precipitation (CP) methods, and the very fast preparation, which only lasts 10-20s for the deposition. In the AuPd/TiO2 catalysts series, the AuPd(3:1)/TiO2 catalyst is the most active for MO photocatalytic degradation; while for PROX reaction, Ru/TiO2, Au-Cu/SBA-15 and Pt/γ-Al2O3 catalysts are very active, and the last one showed high stability in the lifetime test. The structural characterization revealed that in the AuPd(3:1)/TiO2 catalyst, Au-Pd alloy particles were formed and a high percentage of Au atoms was located at the surface. Therefore, this sonication-assisted method is efficient and rapid in the preparation of supported metal catalysts with obvious structural characteristics for various catalytic applications.

  4. Bond cleavage of lignin model compounds into aromatic monomers using supported metal catalysts in supercritical water

    PubMed Central

    Yamaguchi, Aritomo; Mimura, Naoki; Shirai, Masayuki; Sato, Osamu

    2017-01-01

    More efficient use of lignin carbon is necessary for carbon-efficient utilization of lignocellulosic biomass. Conversion of lignin into valuable aromatic compounds requires the cleavage of C–O ether bonds and C–C bonds between lignin monomer units. The catalytic cleavage of C–O bonds is still challenging, and cleavage of C–C bonds is even more difficult. Here, we report cleavage of the aromatic C–O bonds in lignin model compounds using supported metal catalysts in supercritical water without adding hydrogen gas and without causing hydrogenation of the aromatic rings. The cleavage of the C–C bond in bibenzyl was also achieved with Rh/C as a catalyst. Use of this technique may greatly facilitate the conversion of lignin into valuable aromatic compounds. PMID:28387304

  5. Noble-metal-based catalysts supported on zeolites and macro-mesoporous metal oxide supports for the total oxidation of volatile organic compounds.

    PubMed

    Barakat, Tarek; Rooke, Joanna C; Tidahy, Haingomalala Lucette; Hosseini, Mahsa; Cousin, Renaud; Lamonier, Jean-François; Giraudon, Jean-Marc; De Weireld, Guy; Su, Bao-Lian; Siffert, Stéphane

    2011-10-17

    The use of porous materials to eliminate volatile organic compounds (VOCs) has proven very effective towards achieving sustainability and environmental protection goals. The activity of zeolites and macro-mesoporous metal-oxide supports in the total oxidation of VOCs has been investigated, with and without noble-metal deposition, to develop highly active catalyst systems where the formation of by-products was minimal. The first catalysts employed were zeolites, which offered a good activity in the oxidation of VOCs, but were rapidly deactivated by coke deposition. The effects of the acido-basicity and ionic exchange of these zeolites showed that a higher basicity was related to exchanged ions with lower electronegativities, resulting in better catalytic performances in the elimination of VOCs. Following on from this work, noble metals were deposited onto macro-mesoporous metal-oxide supports to form mono and bimetallic catalysts. These were then tested in the oxidation of toluene to study their catalytic performance and their deactivation process. PdAu/TiO(2) and PdAu/TiO(2) -ZrO(2) 80/20 catalysts demonstrated the best activity and life span in the oxidation of toluene and propene and offered the lowest temperatures for a 50 % conversion of VOCs and the lowest coke content after catalytic testing. Different characterization techniques were employed to explain the changes occurring in catalyst structure during the oxidation of toluene and propene.

  6. Development of a supported tri-metallic catalyst and evaluation of the catalytic activity in biomass steam gasification.

    PubMed

    Li, Jianfen; Xiao, Bo; Yan, Rong; Xu, Xiaorong

    2009-11-01

    A supported tri-metallic catalyst (nano-Ni-La-Fe/gamma-Al(2)O(3)) was developed for tar reduction and enhanced hydrogen production in biomass steam gasification, with focuses on preventing coke deposition and sintering effects to lengthen the lifetime of developed catalysts. The catalyst was prepared by deposition-precipitation method and characterized by various analytical approaches. Following that, the activity of catalysts in biomass steam gasification was investigated in a bench-scale combined fixed bed reactor. With presence of the catalyst, the content of hydrogen in gas products was increased to over 10 vol.%, the tar removal efficiency reached 99% at 1073 K, and more importantly the coke deposition on the catalyst surfaces and sintering effects were avoided, leading to a long lifetime of catalysts.

  7. Degradation of phenylamine by catalytic wet air oxidation using metal catalysts with modified supports.

    PubMed

    Torrellas, Silvia A; Escudero, Gabriel O; Rodriguez, Araceli R; Rodriguez, Juan G

    2015-01-01

    The effect of acid treatments with HCl and HNO3 on the surface area and surface chemistry of three granular activated carbons was studied. These supports were characterized and the hydrochloric acid treatment leads to the best activated carbon support (AC2-C). The catalytic behavior of Pt, Ru and Fe (1 wt.%) supported on granular activated carbon treated with HCl was tested in the phenylamine continuous catalytic wet air oxidation in a three-phase, high-pressure catalytic reactor over a range of reaction temperatures 130-170ºC and total pressure of 1.0-3.0 MPa at LHSV = 0.4-1 h(-1), whereas the phenylamine concentration range and the catalyst loading were 5-16 mol.m(-3) and 0.5-1.5 g, respectively. Activity as well as conversion varied as a function of the metal, the catalyst preparation method and operation conditions. Higher activities were obtained with Pt incorporated on hydrochloric acid -treated activated carbon by the ion exchange method. In steady state, approximately 98% phenylamine conversion, 77% of TOC and 94% of COD removal, was recorded at 150ºC, 11 mol m(-3) of phenylamine concentration and 1.5 g of catalyst, and the selectivity to non-organic compounds was 78%. Several reaction intermediaries were detected. A Langmuir-Hinshelwood model gave an excellent fit of the kinetic data of phenylamine continuous catalytic wet air oxidation over the catalysts of this work.

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

    PubMed

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

    2015-06-08

    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). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. 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

  10. 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.

  11. 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.

  12. Metal-support effects on intramolecular selectivity during acetophenone hydrogenation over Pt catalysts

    SciTech Connect

    Lin, S.D.; Sanders, D.K.; Vannice, M.A. )

    1994-05-01

    The choice of support to disperse a metal can have a significant effect in certain reactions, and one of the best examples of metal-support interactions (MSI) is the hydrogenation of C[double bond]O bonds over noble metals such as Pt. It was first shown that the turnover frequency (TOF) for CH[sub 4] formation on Pt from CO and H[sub 2] could be increased by two orders of magnitude using TiO[sub 2] as a support. This reaction is structure insensitive and the TOF is independent of crystallite size. The explanation the authors have preferred for this behavior is the creation of special sites at the metal-support interface which interact with the oxygen end of the molecule to enhance the reactivity of the C[double bond]O bond towards hydrogen. As further support of this concept, the hydrogenation of acetone to isopropanol also showed marked enhancements in TOF (ca. 500-fold) over Pt/TiO[sub 2] catalysts, and the intramolecular selectivity during crotonaldehyde hydrogenation was altered by favoring hydrogenation of the carbonyl bond compared to the C[double bond]C double bond to increase the crotyl alcohol/butyraldehyde product ratio. The next step in examining the influence of MSI on intramolecular selectivity was a comparison of the rates of hydrogenation of a carbonyl bond vs an aromatic ring, and acetophenone (C[sub 6]H[sub 5]COCH[sub 3]) represents one of the simplest molecules containing these two types of bond systems which also has a high enough vapor pressure to allow a vapor-phase reaction to be utilized. These results are reported here. 34 refs., 1 fig., 2 tabs.

  13. 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.

  14. 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.

  15. Reforming with a catalyst containing a group VIII noble metal a group VIII non-noble metal and gallium on separate support particles

    SciTech Connect

    Sorrentino, C. M.; Bertolacini, R. J.; Pellet, R. J.

    1984-11-13

    The catalyst comprises a physical particle-form mixture of a Componet A, a Component B, and a Component C, said Component A comprising at least one Group VIII noble metal, preferably platinum, deposed on a solid catalyst support material providing acidic catalytic sites, said Component B comprising a small amount of a non-noble metal of Group VIII selected from cobalt, nickel, and mixtures thereof, preferably cobalt, on a solid catalyst support material providing acidic catalytic sites, said Component C comprising a small amount of gallium deposed on a solid catalyst support material providing acidic catalytic sites, and said catalyst having been prepared by thoroughly and intimately blending finely-divided particles of said Component A, B, and C to provide a thoroughly-blended composite. The catalyst can be employed suitably in a hydrocarbon conversion process. In particular, the catalyst can be employed in a process for the reforming of a hydrocarbon stream, which process comprises contacting said stream in a reforming zone under reforming conditions and in the presence of hydrogen with said catalyst. The process can be used advantageously to reform a hydrocarbon stream that contains up to 80 ppm sulfur.

  16. 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.

  17. Nanostructured catalyst supports

    DOEpatents

    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.

  18. Oxidation catalysts on alkaline earth supports

    DOEpatents

    Mohajeri, Nahid

    2017-03-21

    An oxidation catalyst includes a support including particles of an alkaline earth salt, and first particles including a palladium compound on the support. The oxidation catalyst can also include precious metal group (PMG) metal particles in addition to the first particles intermixed together on the support. A gas permeable polymer that provides a continuous phase can completely encapsulate the particles and the support. The oxidation catalyst may be used as a gas sensor, where the first particles are chemochromic particles.

  19. Steam reforming of biomass gasification tar using benzene as a model compound over various Ni supported metal oxide catalysts.

    PubMed

    Park, Hyun Ju; Park, Sung Hoon; Sohn, Jung Min; Park, Junhong; Jeon, Jong-Ki; Kim, Seung-Soo; Park, Young-Kwon

    2010-01-01

    The steam reforming of benzene as a model compound of biomass gasification tar was carried out over various Ni/metal oxide catalysts. The effects of the support, temperature, Ni-precursor, Ni loading and reaction time were examined, and their catalytic performance was compared with that of a commercial Ni catalyst. Among the Ni/metal oxide catalysts used, 15 wt% Ni/CeO(2)(75%)-ZrO(2)(25%) showed the highest catalytic performance owing to its greater redox characteristics and increased surface area, irrespective of the reaction temperature. The catalytic activity of 15 wt% Ni/CeO(2)(75%)-ZrO(2)(25%) was higher than that of the commercial Ni catalyst. Moreover, the catalyst activity was retained due to its excellent resistance to coke deposition even after 5h. The Ni-precursor played a critical role in the catalytic activity. With the exception of nickel nitrate, all the Ni-precursors (chloride and sulfate) caused deactivation of the catalyst.

  20. 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.

  1. 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.

  2. Mechanochemical synthesis of graphene oxide-supported transition metal catalysts for the oxidation of isoeugenol to vanillin.

    PubMed

    Franco, Ana; De, Sudipta; Balu, Alina M; Garcia, Araceli; Luque, Rafael

    2017-01-01

    Vanillin is one of the most commonly used natural products, which can also be produced from lignin-derived feedstocks. The chemical synthesis of vanillin is well-established in large-scale production from petrochemical-based starting materials. To overcome this problem, lignin-derived monomers (such as eugenol, isoeugenol, ferulic acid etc.) have been effectively used in the past few years. However, selective and efficient production of vanillin from these feedstocks still remains an issue to replace the existing process. In this work, new transition metal-based catalysts were proposed to investigate their efficiency in vanillin production. Reduced graphene oxide supported Fe and Co catalysts showed high conversion of isoeugenol under mild reaction conditions using H2O2 as oxidizing agent. Fe catalysts were more selective as compared to Co catalysts, providing a 63% vanillin selectivity at 61% conversion in 2 h. The mechanochemical process was demonstrated as an effective approach to prepare supported metal catalysts that exhibited high activity for the production of vanillin from isoeugenol.

  3. 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.

  4. Insight into the influence of addition of a second metal Fe and supports with different morphology on H2 dissociation over Ni/MgO catalysts

    NASA Astrophysics Data System (ADS)

    Liu, Hongyan; Li, Kai; Zhang, Riguang; Ling, Lixia; Wang, Baojun

    2017-12-01

    The effect of addition of a second metal to activation component and the support with different morphology on H2 dissociation on Ni/MgO catalyst was investigated using density functional theory. The results show that after addition of a second metal Fe, the metal-support interaction is increased in perfect MgO supported Ni catalyst while it is decreased in defective MgO supported Ni catalyst. Although the change is difference between metal-support interaction, the ability of H2 dissociation is increased on the two surfaces. Analyzing those results from addition of Fe, Co and Cu to Ni/MgO, one can conclude that it is neither too strong nor too weak (i.e., medium) interaction between metal and support that favors to improve the catalyst performance.

  5. 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. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  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. Sintering-resistant Single-Site Nickel Catalyst Supported by Metal-Organic Framework

    SciTech Connect

    Li, Zhanyong; Schweitzer, Neil; League, Aaron; Bernales Candia, Sandra Varinia; Peters, Aaron; Getsoian, Andrew G.; Wang, Timothy; Miller, Jeffrey T.; Vjunov, Aleksei; Fulton, John L.; Lercher, Johannes A.; Cramer, Christopher J.; Gagliardi, Laura; Hupp, Joseph; Farha, Omar

    2016-02-17

    Developing supported single-site catalysts is an important goal in heterogeneous catalysis, since the well-defined active sites afford opportunities for detailed mechanistic studies, thereby facilitating the design of improved catalysts. We present herein a method for installing Ni ions uniformly and precisely on the node of a Zr-based MOF, NU-1000, in high density and large quantity (denoted as Ni-AIM) using atomic layer deposition (ALD) in a metal–organic framework (MOF) (AIM). Ni-AIM is demonstrated to be an efficient gas-phase hydrogenation catalyst upon activation. The structure of the active sites in Ni-AIM is proposed, revealing its single-site nature. More importantly, due to the organic linker used to construct the MOF support, the Ni ions stay isolated throughout the hydrogenation catalysis, in accord with its long-term stability. A quantum chemical characterization of the catalyst and the catalytic process complements the experimental results. With validation of computational modeling protocols, we further targeted ethylene oligomerization catalysis by Ni-AIM guided by theoretical prediction. Given the generality of the AIM methodology, this emerging class of materials should prove ripe for the discovery of new catalysts for the transformation of volatile substrates.

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

    PubMed

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

    2016-01-31

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

  9. 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

  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. 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.

  13. Metal catalysts supported on activated carbon fibers for removal of polycyclic aromatic hydrocarbons from incineration flue gas.

    PubMed

    Lin, Chiou-Liang; Cheng, Yu-Hsiang; Liu, Zhen-Shu; Chen, Jian-Yuan

    2011-12-15

    The aim of this research was to use metal catalysts supported on activated carbon fibers (ACFs) to remove 16 species of polycyclic aromatic hydrocarbons (PAHs) from incineration flue gas. We tested three different metal loadings (0.11 wt%, 0.29 wt%, and 0.34 wt%) and metals (Pt, Pd, and Cu), and two different pretreatment solutions (HNO(3) and NaOH). The results demonstrated that the ACF-supported metal catalysts removed the PAHs through adsorption and catalysis. Among the three metals, Pt was most easily adsorbed on the ACFs and was the most active in oxidation of PAHs. The mesopore volumes and density of new functional groups increased significantly after the ACFs were pretreated with either solutions, and this increased the measured metal loading in HNO(3)-0.48% Pd/ACFs and NaOH-0.52% Pd/ACFs. These data confirm that improved PAH removal can be achieved with HNO(3)-0.48% Pd/ACFs and NaOH-0.52% Pd/ACFs.

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

    SciTech Connect

    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

    2016-03-08

    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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Evaluation of Silica-Supported Metal and Metal Phosphide Nanoparticle Catalysts for the Hydrodeoxygenation of Guaiacol Under Ex Situ Catalytic Fast Pyrolysis Conditions

    DOE PAGES

    Griffin, Michael B.; Baddour, Frederick G.; Habas, Susan E.; ...

    2015-09-30

    A series of metal and metal phosphide catalysts were investigated for the hydrodeoxygenation of guaiacol under ex situ catalytic fast pyrolysis (CFP) conditions (350 °C, 0.5 MPa, 12 H2:1 guaiacol, weight hourly space velocity 5 h$-$1). Ligand-capped Ni, Pt, Rh, Ni2P, and Rh2P nanoparticles (NPs) were prepared using solution-phase synthesis techniques and dispersed on a silica support. For the metal phosphide NP-catalysts, a synthetic route that relies on the decomposition of a single molecular precursor was employed. The reactivity of the NP-catalysts was compared to a series of reference materials including Ni/SiO2 and Pt/SiO2 prepared using incipient wetness (IW) impregnationmore » and a commercial (com) Pt/SiO2 catalyst. The NP-Ni/SiO2 catalyst exhibited the largest reduction in the oxygen mol% of the organic phase and outperformed the IW-Ni/SiO2 material. Although it was less active for guaiacol conversion than NP-Ni/SiO2, NP-Rh2P/SiO2 demonstrated the largest production of completely deoxygenated products and the highest selectivity to anisole, benzene, and cyclohexane, suggesting that it is a promising catalyst for deoxygenation of aryl-OH bonds. Finally, the com-Pt/SiO2 and IW-Pt/SiO2 catalyst exhibited the highest normalized rate of guaiacol conversion per m2 and per gram of active phase, respectively, but did not produce any completely deoxygenated products.« less

  1. Evaluation of Silica-Supported Metal and Metal Phosphide Nanoparticle Catalysts for the Hydrodeoxygenation of Guaiacol Under Ex Situ Catalytic Fast Pyrolysis Conditions

    SciTech Connect

    Griffin, Michael B.; Baddour, Frederick G.; Habas, Susan E.; Ruddy, Daniel A.; Schaidle, Joshua A.

    2015-09-30

    A series of metal and metal phosphide catalysts were investigated for the hydrodeoxygenation of guaiacol under ex situ catalytic fast pyrolysis (CFP) conditions (350 °C, 0.5 MPa, 12 H2:1 guaiacol, weight hourly space velocity 5 h$-$1). Ligand-capped Ni, Pt, Rh, Ni2P, and Rh2P nanoparticles (NPs) were prepared using solution-phase synthesis techniques and dispersed on a silica support. For the metal phosphide NP-catalysts, a synthetic route that relies on the decomposition of a single molecular precursor was employed. The reactivity of the NP-catalysts was compared to a series of reference materials including Ni/SiO2 and Pt/SiO2 prepared using incipient wetness (IW) impregnation and a commercial (com) Pt/SiO2 catalyst. The NP-Ni/SiO2 catalyst exhibited the largest reduction in the oxygen mol% of the organic phase and outperformed the IW-Ni/SiO2 material. Although it was less active for guaiacol conversion than NP-Ni/SiO2, NP-Rh2P/SiO2 demonstrated the largest production of completely deoxygenated products and the highest selectivity to anisole, benzene, and cyclohexane, suggesting that it is a promising catalyst for deoxygenation of aryl-OH bonds. Finally, the com-Pt/SiO2 and IW-Pt/SiO2 catalyst exhibited the highest normalized rate of guaiacol conversion per m2 and per gram of active phase, respectively, but did not produce any completely deoxygenated products.

  2. Support effects studied on model supported catalysts. Progress report

    SciTech Connect

    Gorte, R.J.

    1993-02-01

    Composition and structure of oxide support materials can change the catalytic behavior of metal and oxide catalysts. Model catalysts are being studied in which the active phase is deposited on flat oxide substrates, with emphasis on metals catalysis for automotive emissions control and acidity in supported oxides. Research is reported in the following areas: particle-size effects, support effects on ZnO and zirconia, support effects on ceria, supported oxides, and low energy ion scattering (no results in the latter).

  3. Characterization of catalysts with metal-support effects and of the species adsorbed on their surfaces

    NASA Astrophysics Data System (ADS)

    Vannice, M. A.

    1985-06-01

    The influence of crystallite size and the support on heats of adsorption of H2, CO, and O2 on Pt and Pd are reported. Isothermal, integral heats of adsorption have been measured for H2 and CO adsorption on Pt and Pd dispersed on four supports, SiO2, Al2O3, and SiO2-Al2O3. These values were determined at 215K and 300 to 320K. Results are presented. For support Pt the heats of adsorption were highest on Pt/SiO2 and lowest on Pt/TiO2. However, a clear trend existed between heats of adsorption and Pt exposed with large Pt crystallites having the highest values. The Pd catalysts exhibited behavior different than those for the Pt catalysts in two major aspects. First, the heats of adsorption values tended to increase somewhat as crystallite sizes became very small. Second, the high temperature reduction step did not decrease the heats of adsorption values as significantly for Pd/TiO2.

  4. Catalytic hydrothermal treatment of pulping effluent using a mixture of Cu and Mn metals supported on activated carbon as catalyst.

    PubMed

    Yadav, Bholu Ram; Garg, Anurag

    2016-10-01

    The present study was performed to investigate the performance of activated carbon-supported copper and manganese base catalyst for catalytic wet oxidation (CWO) of pulping effluent. CWO reaction was performed in a high pressure reactor (capacity = 0.7 l) at temperatures ranging from 120 to 190 °C and oxygen partial pressures of 0.5 to 0.9 MPa with the catalyst concentration of 3 g/l for 3 h duration. With Cu/Mn/AC catalyst at 190 °C temperature and 0.9 MPa oxygen partial pressures, the maximum chemical oxygen demand (COD), total organic carbon (TOC), lignin, and color removals of 73, 71, 86, and 85 %, respectively, were achieved compared to only 52, 51, 53, and 54 % removals during the non-catalytic process. Biodegradability (in terms of 5-day biochemical oxygen demand (BOD5) to COD ratio) of the pulping effluent was improved to 0.38 from an initial value of 0.16 after the catalytic reaction. The adsorbed carbonaceous fraction on the used catalyst was also determined which contributed meager TOC reduction of 3-4 %. The leaching test showed dissolution of the metals (i.e., Cu and Mn) from the catalysts in the wastewater during CWO reaction at 190 °C temperature and 0.9 MPa oxygen partial pressures. In the future, the investigations should focus on the catalyst reusability.

  5. 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.

  6. Ligand-Free Noble Metal Nanocluster Catalysts on Carbon Supports via “Soft” Nitriding

    PubMed Central

    Liu, Ben; Yao, Huiqin; Song, Wenqiao; Jin, Lei; Mosa, Islam M.; Rusling, James F.; Suib, Steven L.; He, Jie

    2016-01-01

    We report a robust, universal “soft” nitriding method to grow in situ ligand-free ultrasmall noble metal nanocatalysts (UNMN; e.g., Au, Pd, and Pt) onto carbon. Using low-temperature urea pretreatment at 300 °C, soft nitriding enriches nitrogen-containing species on the surface of carbon supports and enhances the affinity of noble metal precursors onto these supports. We demonstrated sub-2-nm, ligand-free UNMNs grown in situ on seven different types of nitrided carbons with no organic ligands via chemical reduction or thermolysis. Ligand-free UNMNs supported on carbon showed superior electrocatalytic activity for methanol oxidation compared to counterparts with surface capping agents or larger nanocrystals on the same carbon supports. Our method is expected to provide guidelines for the preparation of ligand-free UNMNs on a variety of supports and, additionally, to broaden their applications in energy conversion and electrochemical catalysis. PMID:27014928

  7. 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.

  8. 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.

  9. Influence of the reduction temperature on the structure of the metal particles and the metal-support interface of Pt/γ-Al 2O 3 catalysts

    NASA Astrophysics Data System (ADS)

    Koningsberger, D. C.; Vaarkamp, M.

    1995-02-01

    The structure of the metal particles and the metal-support interface of a Pt/γ-Al 2O 3 catalyst was determined by EXAFS after low temperature reduction (LTR: 300°C) and high temperature reduction (HTR:450°C). The clusters have excellent thermal stability as the particle size remains 12 atoms per cluster upon increasing the reduction temperature from 300°C to 450°C. However, the structure of the metal-support interface is a strong function of the reduction temperature. After LTR and in the presence of chemisorbed hydrogen the metal particles are at a distance of 2.68 Å from the support oxygen ions. This long PtO distance is due to the presence of hydrogen between the platinum atoms and the support. Increasing the reduction temperature results in the removal of hydrogen from the metal-support interface, simultaneously placing the metal particles in direct contact with the support oxygen atoms at a distance of 2.28 Å. The release of interfacial hydrogen during high temperature reduction is changing the metal-support interaction, which in turn changes the electron density distribution in the metal particles. The electronic and thereby the catalytic properties of the platinum metal particles are therefore a function of the reduction temperature. The results show that the influence of the reduction temperature on the structure of the metal-support interface of platinum particles on a amorphous support is similar to platinum particles which reside in cavities of zeolites.

  10. Fine-Tuning the Activity of Metal-Organic Framework-Supported Cobalt Catalysts for the Oxidative Dehydrogenation of Propane.

    PubMed

    Li, Zhanyong; Peters, Aaron W; Platero-Prats, Ana E; Liu, Jian; Kung, Chung-Wei; Noh, Hyunho; DeStefano, Matthew R; Schweitzer, Neil M; Chapman, Karena W; Hupp, Joseph T; Farha, Omar K

    2017-10-04

    Few-atom cobalt-oxide clusters, when dispersed on a Zr-based metal-organic framework (MOF) NU-1000, have been shown to be active for the oxidative dehydrogenation (ODH) of propane at low temperatures (< 230 °C), affording a selective and stable propene production catalyst. In our current work, a series of promoter ions with varying Lewis acidity, including Ni(II), Zn(II), Al(III), Ti(IV) and Mo(VI), are anchored as metal-oxide,hydroxide clusters to NU-1000 followed by Co(II) ion deposition, yielding a series of NU-1000-supported bimetallic-oxo,hydroxo,aqua clusters. Using difference envelope density (DED) analyses, the spatial locations of the promoter ions and catalytic cobalt ions are determined. For all samples the promoter ions are sited between pairs of Zr6 nodes along the MOF c axis whereas the location of the cobalt ions varies with the promoter ions. These NU-1000-supported bimetallic-oxide clusters are active for propane ODH after thermal activation under O2 to open a cobalt coordination site and to oxidize Co(II) to Co(III), as evidenced by operando X-ray absorption spectroscopy at the Co K-edge. In accord with the decreasing Lewis acidity of the promoter ion, catalytic activity increases in the order: Mo(VI)supported heterogeneous catalysts. Coupled with mechanistic studies-computational or experimental-this ability may translate into informed prediction of improved catalysts for propane ODH and other chemical reactions.

  11. In situ-generated metal oxide catalyst during CO oxidation reaction transformed from redox-active metal-organic framework-supported palladium nanoparticles

    PubMed Central

    2012-01-01

    The preparation of redox-active metal-organic framework (ra-MOF)-supported Pd nanoparticles (NPs) via the redox couple-driven method is reported, which can yield unprotected metallic NPs at room temperature within 10 min without the use of reducing agents. The Pd@ra-MOF has been exploited as a precursor of an active catalyst for CO oxidation. Under the CO oxidation reaction condition, Pd@ra-MOF is transformed into a PdOx-NiOy/C nanocomposite to generate catalytically active species in situ, and the resultant nanocatalyst shows sustainable activity through synergistic stabilization. PMID:22898143

  12. New insights into selective heterogeneous nucleation of metal nanoparticles on oxides by microwave-assisted reduction: rapid synthesis of high-activity supported catalysts.

    PubMed

    Anumol, Erumpukuthickal Ashok; Kundu, Paromita; Deshpande, Parag Arvind; Madras, Giridhar; Ravishankar, Narayanan

    2011-10-25

    Microwave-based methods are widely employed to synthesize metal nanoparticles on various substrates. However, the detailed mechanism of formation of such hybrids has not been addressed. In this paper, we describe the thermodynamic and kinetic aspects of reduction of metal salts by ethylene glycol under microwave heating conditions. On the basis of this analysis, we identify the temperatures above which the reduction of the metal salt is thermodynamically favorable and temperatures above which the rates of homogeneous nucleation of the metal and the heterogeneous nucleation of the metal on supports are favored. We delineate different conditions which favor the heterogeneous nucleation of the metal on the supports over homogeneous nucleation in the solvent medium based on the dielectric loss parameters of the solvent and the support and the metal/solvent and metal/support interfacial energies. Contrary to current understanding, we show that metal particles can be selectively formed on the substrate even under situations where the temperature of the substrate is lower than that of the surrounding medium. The catalytic activity of the Pt/CeO(2) and Pt/TiO(2) hybrids synthesized by this method for H(2) combustion reaction shows that complete conversion is achieved at temperatures as low as 100 °C with Pt-CeO(2) catalyst and at 50 °C with Pt-TiO(2) catalyst. Our method thus opens up possibilities for rational synthesis of high-activity supported catalysts using a fast microwave-based reduction method.

  13. Toluene decomposition by DBD-type plasma combined with metal oxide catalysts supported on ferroelectric materials.

    PubMed

    Jeong, Jin Guk; Lee, Hyeong Seok; Kang, Youngjin; Lee, Ki Bong; Yoo, Jung Whan

    2013-06-01

    We investigated toluene decomposition with a single-stage plasma catalytic system operated at atmospheric pressure and working at reduced temperature (T < 75 degrees C), where a synergistic catalyst was integrated on ferroelectric BaTiO3 beads with a high dielectric constant. The catalyst species were characterized by FE-SEM and XPS before and after the experiment. The MnO2/BaTiO3 catalyst showed high stability in igniting plasma during destruction of toluene for 230 hours in a lifetime test.

  14. Gaseous fuel production from nonrecyclable paper wastes by using supported metal catalysts in high-temperature liquid water.

    PubMed

    Yamaguchi, Aritomo; Hiyoshi, Norihito; Sato, Osamu; Bando, Kyoko K; Shirai, Masayuki

    2010-06-21

    Paper wastes are used for the production of gaseous fuels over supported metal catalysts. The gasification of the nonrecyclable paper wastes, such as shredded documents and paper sludge, is carried out in high-temperature liquid water. The order of the catalytic activity for the gasification is found to be ruthenium>rhodium>platinum>palladium. A charcoal-supported ruthenium catalyst (Ru/C) is the most effective for the gasification of paper and cellulose. Paper wastes are gasified to a limited degree (32.6 carbon %) for 30 min in water at 523 K to produce methane and carbon dioxide, with a small amount of hydrogen. At 573 K, more complete gasification with almost 100 carbon % is achieved within 10 min in water. At 523 K, the gas yield of paper gasification over Ru/C is higher than that of cellulose powder. The gas yields are increased by ball-milling treatment of the recycled paper and cellulose powder. Printed paper wastes are also gasified at 523 K in water.

  15. Non-Noble Metal Nanoparticles Supported by Postmodified Porous Organic Semiconductors: Highly Efficient Catalysts for Visible-Light-Driven On-Demand H2 Evolution from Ammonia Borane.

    PubMed

    Zhang, Hao; Gu, Xiaojun; Song, Jin; Fan, Na; Su, Haiquan

    2017-09-27

    From the viewpoint of controlling the visible-light-driven activities of catalysts containing metal nanoparticles (NPs) by tuning the microstructures of semiconducting supports, we employed a postsynthetic thermal modification approach to prepare carbon nitride (C3N4) species featuring different microstructures and then we synthesized Co and Ni NPs supported by these C3N4 species, which were used to catalyze the room-temperature H2 evolution from ammonia borane (NH3BH3). The systematic investigation showed that the catalysts had different activities under light irradiation. Compared with the pristine C3N4-based catalyst, all the modified C3N4-based catalysts had enhanced activities. The highest active Co catalyst with a total turnover frequency of 93.8 min(-1) was successfully obtained, which exceeded the values of all the reported heterogeneous noble metal-free catalysts. The structure characterizations indicated that the postmodified porous C3N4 species had the different band structures, photoluminescence lifetime, and photocurrent density under visible light irradiation, leading to the different separation efficiency of photogenerated charge carriers. These characteristics helped us regulate the electronic characteristics of Co and Ni NPs in the supported catalysts and then led to the significantly different and enhanced activity in the visible-light-driven H2 evolution.

  16. 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.

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

    SciTech Connect

    Boszormenyi, Istvan

    1991-05-01

    This (<100Å) 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 x 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 cm2 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.

  18. 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.

  19. The role of metal-support interaction for CO-free hydrogen from low temperature ethanol steam reforming on Rh-Fe catalysts.

    PubMed

    Choong, Catherine K S; Chen, Luwei; Du, Yonghua; Schreyer, Martin; Daniel Ong, S W; Poh, Chee Kok; Hong, Liang; Borgna, Armando

    2017-02-08

    Rh-Fe catalysts supported on Ca-Al2O3, MgO and ZrO2 were evaluated in ethanol steam reforming at 623 K and compared to Rh catalysts on the same supports without iron promotion. The metal-support interaction among the three entities, i.e. Rh ↔ Fe2O3 ← support (ZrO2, MgO and Ca-Al2O3) was investigated using H2-chemisorption, TEM, XPS and in situ techniques such as DRIFTS, temperature-resolved XRD and XAS. As compared to the unpromoted Rh catalysts on the same supports, the CO selectivity is depressed in the presence of iron on Rh/MgO and Rh/Ca-Al2O3, the latter being significantly superior. The role of metal-support interaction for CO-free hydrogen generation was unravelled using a combination of techniques. It was found that the reducibility of iron oxide determines the extent of the strong metal support interaction between Rh and Fe2O3 and the reducibility of iron oxide was affected by the support. On Rh-Fe/Ca-Al2O3, a good balance of the interaction between Rh, Fe2O3 and Ca-Al2O3 prevents strong metal support interaction between Rh and Fe2O3 and thus promotes CO elimination via water-gas-shift reaction on Rh-FexOy sites.

  20. High-temperature catalytic reforming of n-hexane over supported and core-shell Pt nanoparticle catalysts: role of oxide-metal interface and thermal stability.

    PubMed

    An, Kwangjin; Zhang, Qiao; Alayoglu, Selim; Musselwhite, Nathan; Shin, Jae-Youn; Somorjai, Gabor A

    2014-08-13

    Designing catalysts with high thermal stability and resistance to deactivation while simultaneously maintaining their catalytic activity and selectivity is of key importance in high-temperature reforming reactions. We prepared Pt nanoparticle catalysts supported on either mesoporous SiO2 or TiO2. Sandwich-type Pt core@shell catalysts (SiO2@Pt@SiO2 and SiO2@Pt@TiO2) were also synthesized from Pt nanoparticles deposited on SiO2 spheres, which were encapsulated by either mesoporous SiO2 or TiO2 shells. n-Hexane reforming was carried out over these four catalysts at 240-500 °C with a hexane/H2 ratio of 1:5 to investigate thermal stability and the role of the support. For the production of high-octane gasoline, branched C6 isomers are more highly desired than other cyclic, aromatic, and cracking products. Over Pt/TiO2 catalyst, production of 2-methylpentane and 3-methylpentane via isomerization was increased selectively up to 420 °C by charge transfer at Pt-TiO2 interfaces, as compared to Pt/SiO2. When thermal stability was compared between supported catalysts and sandwich-type core@shell catalysts, the Pt/SiO2 catalyst suffered sintering above 400 °C, whereas the SiO2@Pt@SiO2 catalyst preserved the Pt nanoparticle size and shape up to 500 °C. The SiO2@Pt@TiO2 catalyst led to Pt nanoparticle sintering due to incomplete protection of the TiO2 shells during the reaction at 500 °C. Interestingly, over the Pt/TiO2 catalyst, the average size of Pt nanoparticles was maintained even after 500 °C without sintering. In situ ambient pressure X-ray photoelectron spectroscopy demonstrated that the Pt/TiO2 catalyst did not exhibit TiO2 overgrowth on the Pt surface or deactivation by Pt sintering up to 600 °C. The extraordinarily high stability of the Pt/TiO2 catalyst promoted high reaction rates (2.0 μmol · g(-1) · s(-1)), which was 8 times greater than other catalysts and high isomer selectivity (53.0% of C6 isomers at 440 °C). By the strong metal-support interaction

  1. Transition-Metal-Controlled Inorganic Ligand-Supported Non-Precious Metal Catalysts for the Aerobic Oxidation of Amines to Imines.

    PubMed

    Yu, Han; Zhai, Yongyan; Dai, Guoyong; Ru, Shi; Han, Sheng; Wei, Yongge

    2017-08-21

    Most state-of-art transition-metal catalysts usually require organic ligands, which are essential for controlling the reactivity and selectivity of reactions catalyzed by transition metals. However, organic ligands often suffer from severe problems including cost, toxicity, air/moisture sensitivity, and being commercially unavailable. Herein, we show a simple, mild, and efficient aerobic oxidation procedure of amines using inorganic ligand-supported non-precious metal catalysts 1, (NH4 )n [MMo6 O18 (OH)6 ] (M=Cu(2+) ; Fe(3+) ; Co(3+) ; Ni(2+) ; Zn(2+) , n=3 or 4), synthesized by a simple one-step method in water at 100 °C, demonstrating that the catalytic activity and selectivity can be significantly improved by changing the central metal atom. In the presence of these catalysts, the catalytic oxidation of primary and secondary amines, as well as the coupling of alcohols and amines, can smoothly proceed to afford various imines with O2 (1 atm) as the sole oxidant. In particular, the catalysts 1 have transition-metal ion core, and the planar arrangement of the six Mo(VI) centers at their highest oxidation states around the central heterometal can greatly enhance the Lewis acidity of catalytically active sites, and also enable the electrons in the center to delocalize onto the six edge-sharing MO6 units, in the same way as ligands in traditional organometallic complexes. The versatility of this methodology maybe opens a path to catalytic oxidation through inorganic ligand-coordinated metal catalysis. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. The influence of the nature of the metal on the performance of cerium oxide supported catalysts in the partial oxidation of ethanol

    NASA Astrophysics Data System (ADS)

    Mattos, L. V.; Noronha, F. B.

    This work studied the effect of the nature of the metal on the performance of Co/CeO 2, Pd/CeO 2 and Pt/CeO 2 catalysts in the partial oxidation of ethanol. Infrared spectroscopy of adsorbed ethanol and temperature programmed desorption of ethanol were performed in order to establish the reaction mechanism. Catalytic experiments revealed that the product distribution is strongly affected by the nature of the metal. Acetaldehyde was practically the only product formed on a Co/CeO 2 catalyst while methane was also produced on Pt/CeO 2 and Pd/CeO 2 catalysts. These results were explained through a reaction mechanism proposed by the characterization techniques. Co/CeO 2 and Pt/CeO 2 catalysts show mainly ethoxy species at room temperature whereas acetate species is mainly formed on the Pd/CeO 2 catalyst. The ethoxy species can undergo further dehydrogenation and desorb as acetaldehyde. This effect is more significant with the Co/CeO 2 catalyst and could explain the higher selectivity to acetaldehyde observed on supported Co and Pt catalysts.

  3. Support effects studied on model supported catalysts

    SciTech Connect

    Gorte, R.G.

    1991-11-01

    We are studying model catalysts in which the active phase is deposited onto flat oxide substrates in order to understand how a catalyst is affected by its support. We have examined the following growth and stability of titania overlayers which had been vapor deposited onto a Rh foil; the growth of Pt films on ZnO(0001)Zn and O(0001)O and compared the results to those obtained for Pt on {alpha}-Al{sub 2}O{sub 3}(0001). Samples were prepared by vapor deposition of Pt onto flat substrates in ultra high vacuum, and metal coverages were measured using a quartz-crystal, film thickness monitor; the structure and CO adsorption properties of Pt films vapor deposited onto a ZrO{sub 2}(100) crystal; the deposition of Rh on a ZrO{sub 2}(100) crystal; The absorption of NO on Pt particles supported on CeO{sub 2}, {alpha}-Al{sub 2}O{sub 3}(0001), and the Zn- and O-polar surfaces of ZnO(0001). We have investigated supported oxides in order to understand the acidic properties that have been reported for monolayer oxides. Our first studies were of amorphous, silicalumina catalysts. Finally, we have also begun to prepare model supported oxides in order to be able to used spectroscopic methods to characterize the sites formed on these materials. Our first studies were of niobia deposition on oxidized Al films and on an {alpha}-Al{sub 2}O{sub 3}(0001) crystal.

  4. Direct fabrication of metal-free hollow graphene balls with a self-supporting structure as efficient cathode catalysts of fuel cell

    NASA Astrophysics Data System (ADS)

    Lu, Yanqi; Liu, Mingda; Nie, Huagui; Gu, Cancan; Liu, Ming; Yang, Zhi; Yang, Keqin; Chen, Xi'an; Huang, Shaoming

    2016-06-01

    Despite the good progress in developing carbon catalysts for oxygen reduction reaction (ORR), the current metal-free carbon catalysts are still far from satisfactory for large-scale applications of fuel cell. Developing hollow graphene balls with a self-supporting structure is considered to be an ideal method to inhibit graphene stacking and improve their catalytic performance. Herein, we fabricated metal-free hollow graphene balls with a self-supporting structure, through using a new strategy that involves direct metal-free catalytic growth from assembly of SiO2 spheres. To our knowledge, although much researches involving the synthesis of graphene balls have been reported, investigations into the direct metal-free catalytic growth of hollow graphene balls are rare. Furthermore, the electrocatalytic performance shows that the resulting hollow graphene balls have significantly high catalytic activity. More importantly, such catalysts also possess much improved stability and better methanol tolerance in alkaline media during the ORR compared with commercial Pt/C catalysts. The outstanding performances coupled with an easy and inexpensive preparing method indicated the great potential of the hollow graphene balls with a self-supporting structure in large-scale applications of fuel cell.

  5. Evaluation of the role of the metal-support interfacial centers in the dry reforming of methane on alumina-supported rhodium catalysts

    SciTech Connect

    Ferreira-Aparicio, P.; Fernandez-Garcia, M.; Guerrero-Ruiz, A.; Rodriguez-Ramos, I.

    2000-03-10

    The reforming of CH{sub 4} with CO{sub 2} (dry reforming) has been studied on a series of Al{sub 2}O{sub 3}-supported Rh-Cu catalysts. The reaction has been found to proceed on these systems through a bifunctional mechanism, in which the activation on methane takes place on the rhodium phase while carbon dioxide is activated on the support surface via formate intermediates. The addition of a metal, such as copper, inactive for methane activation, has allowed the authors to evaluate the role of the interfacial Rh-Al{sub 2}O{sub 3} sites in the reaction. The presence of copper reduces the stability of the catalysts, though it does not have any effect on the initial activity per surface exposed site. It indicates that the dry reforming of methane is not a structure-sensitive reaction and that catalytic activity, largely affected by the alumina support, is dependent on the number of surface exposed rhodium centers.

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

    PubMed Central

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

    2013-01-01

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

  7. 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.

  8. Mesoporous zeolite-supported noble metal catalysts for low-temperature hydrogenation of aromatics in distillate fuels

    SciTech Connect

    Reddy, K.M.; Song, C.

    1996-12-31

    The present work is concerned with deep hydrogenation of aromatics in distillate fuels at low temperatures using mesoporous zeolite-supported noble metal catalysts. This work is a part of our on-going effort to develop advanced thermally stable jet fuels from coal-derived liquids and petroleum. Saturation of naphthalene and its derivatives from only reduces aromatics contents of jet fuels, but also generates decalins which show much higher thermal stability than long-chain alkanes in jet fuels at high temperature. This work also has a bearing on developing new catalytic processes for low-temperature hydrogenation of distillate fuels. The Clean Air Act Amendments of 1990 and new regulations call for the production and use of more environmentally friendly transportation fuels with lower contents of sulfur and aromatics. High aromatic content in distillate fuels lowers the fuel quality and contributes significantly to the formation of environmentally harmful emissions. California Air Resources Board (CARB) has passed legislative measures to limit the sulfur and aromatic contents of diesel fuel to 0.05 wt% and 10 vol%, respectively, effective October 1993. Currently, conventional hydrotreating technology is adapted for aromatics saturation. Some studies have shown that complete hydrogenation of aromatics is not possible owing to equilibrium limitations under typical hydrotreating conditions, and existing middle distillate hydrotreaters designed to reduce sulfur and nitrogen levels would lower the diesel aromatics only marginally.

  9. 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.

  10. Separately supported polymetallic reforming catalyst

    SciTech Connect

    Kresge, C. T.; Krishnamurthy, S.; McHale, W. D.

    1985-01-15

    There is provided, in accordance with the present invention, a catalyst composition made up of a mixture of two components, one component comprising a minor proportion of platinum and rhenium on a support and the second component comprising a minor proportion of iridium and rhenium on a separate support. A process for reforming a charge stock, such as naphtha, utilizing such catalyst is also provided.

  11. An efficient noble-metal-free supported copper catalyst for selective nitrocyclohexane hydrogenation to cyclohexanone oxime.

    PubMed

    Zhang, Qian-Qian; Dong, Jing; Liu, Yong-Mei; Cao, Yong; He, He-Yong; Wang, Yang-Dong

    2017-03-07

    It was shown for the first time that cyclohexanone oxime (CHO) can be selectively produced by heterogeneous copper-catalyzed hydrogenative transformation of nitrocyclohexane (NC). The combination of Cu(0) and Cu(+) and their cooperative interaction with weakly acidic SiO2 supports elicited a significantly unique and selective catalysis in the hydrogenation of NC to CHO.

  12. First-row transition metal hydrogenation and hydrosilylation catalysts

    DOEpatents

    Trovitch, Ryan J.; Mukhopadhyay, Tufan K.; Pal, Raja; Levin, Hagit Ben-Daat; Porter, Tyler M.; Ghosh, Chandrani

    2017-07-18

    Transition metal compounds, and specifically transition metal compounds having a tetradentate and/or pentadentate supporting ligand are described, together with methods for the preparation thereof and the use of such compounds as hydrogenation and/or hydrosilylation catalysts.

  13. 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. 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. 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.

  14. 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.

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

    DOE PAGES

    Johnson, Robert L.; Perras, Frédéric A.; Kobayashi, Takeshi; ...

    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.

  16. 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.

  17. 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.

  18. 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.

  19. Nanoporous PtFe Nanoparticles Supported on N-Doped Porous Carbon Sheets Derived from Metal-Organic Frameworks as Highly Efficient and Durable Oxygen Reduction Reaction Catalysts.

    PubMed

    Yang, Kang; Jiang, Peng; Chen, Jitang; Chen, Qianwang

    2017-09-05

    Designing and exploring catalysts with high activity and stability for oxygen reduction reaction (ORR) at the cathode in acidic environments is imperative for the industrialization of proton exchange membrane fuel cells (PEMFCs). Theoretical calculations and experiments have demonstrated that alloying Pt with a transition metal can not only cut down the usage of scarce Pt metal but also improve performance of mass activity compared with pure Pt. Herein, we exhibit the preparation of nanoporous PtFe nanoparticles (np-PtFe NPs) supported on N-doped porous carbon sheets (NPCS) via facile in situ thermolysis of a Pt-modified Fe-based metal-organic framework (MOF). The np-PtFe/NPCS exhibit a more positive half-wave potential (0.92 V) compared with commercial Pt/C catalyst (0.883 V). The nanoporous structure allows our catalyst to possess high mass activity, which is found to be 0.533 A·mgPt(-1) and 3.04 times better than that of Pt/C (0.175 A·mgPt(-1)). Moreover, the conversion of PtFe NPs from porous to hollow structure can maintain the activity of electrocatalyst. Our strategy provides a facile design and synthesis process of noble-transition metal alloy electrocatalysts via noble metal modified MOFs as precursors.

  20. 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.

  1. Microbial recovery of metals from spent catalysts

    SciTech Connect

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

    1990-01-01

    The second quarter of 1990 was one of peripheral progress on the project of reclaiming molybdenum and nickel from spent coal liquefaction catalysts. We defined some important parameters for future research and we were able to clear up ambiguities in some of the past approaches and the problems uniquely associated with the ability of T. ferrooxidans to leach both Ni{sup ++} and molybdate from spent, alumina supported catalyst from the Wilsonville pilot project. We were also able to show the T. ferrooxidans was very sensitive to molybdate and extremely sensitive to tungstate, but showed relatively little sensitivity for the related elements chromate, vanadate and for the catalyst associated metal, Ni{sup ++}. There appears to be no negative synergistic effects between Ni{sup ++} and molybdate for growth, which bodies well for processes to reclaim both these metals from spent coal liquefaction catalysts. We have shown that T. ferrooxidans is indeed capable of leaching molybdate and Ni{sup ++} from spent catalysts if the catalyst is washed extensively with both an organic solvent such as tetrahydrofuran to remove the oily contaminants and an aqueous acidic medium to remove readily solubilized N{sup ++} and molybdate. It is possible to extract into an acidic medium enough molybdate from THF washed spent catalyst within 24 hr to completely inhibit the growth of all tested T. ferrooxidans strains. The stage is now set for the development of a molybdate tolerant strain to be used for actual leaching of the spent catalyst. We are currently seeking simpler ways of pretreating the raw spent catalyst in order to make it more amenable to microbial leaching and possibly produce an economic and feasible technology.

  2. 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.

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

    SciTech Connect

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

    2016-06-03

    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){sub 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 m{sup 2}/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.

  4. Clay complexes support HDS catalyst.

    SciTech Connect

    Marshall, C. L.; Carrado, K.; Chemical Engineering

    2000-01-01

    Hydroprocessing represents a crucial component of petroleum refining operations both in terms of environmental and economic considerations. Regulations concerning maximum amount of sulfur content of gasoline and emissions of sulfur-oxide compounds upon combustion are becoming more and more stringent. One 1994-2000 focus of Argonne National Laboratory (ANL) has been the development of catalysts for hydrodesulfurization (HDS). Typical HDS catalysts are comprised of Co-Mo sulfides or Ni-Mo sulfides on an alumina support. Modification of the pore structure of the support has generated great attention among researchers. Most desulfurization test reactions have used dibenzothiophene (DBT) as the model compound to test various configurations of support material with Co-Mo-S and Ni-Mo-S catalysts. In this testing, the desired product would be biphenyl and hydrogen sulfide (H{sub 2}S). A competing reaction creates cyclohexylbenzene by saturating one aromatic ring prior to desulfurization. Ring saturation requires more costly hydrogen and is not desirable. Fortunately, a more effective catalyst for adding hydrogen at the sulfur site with hydrogenating the aromatic rings has been found. However, this has only been tested on DBT. HDS uses various types of catalysts to add hydrogen to reduce unwanted sulfur compounds. Typically this requires expensive, high-pressure, high-temperature equipment to produce the environmentally friendly low-sulfur fuels. ANL scientists identified several new desulfurization catalysts with improved HDS activity and selectivity. From these new catalysts, it may be possible to achieve HDS processing at lower temperature and pressure. The catalysts used for HDS at ANL are various clay complexes. Natural clays have a history of use in the hydroprocessing industry since they are abundant and inexpensive. ANL's approach is to create synthetic organo-clay complexes (SOCC). An advantage of SOCCs is that the pore size and distribution can be controlled by

  5. Tuning the Selectivity of Catalytic Carbon Dioxide Hydrogenation over Iridium/Cerium Oxide Catalysts with a Strong Metal-Support Interaction.

    PubMed

    Li, Siwei; Xu, Yao; Chen, Yifu; Li, Weizhen; Lin, Lili; Li, Mengzhu; Deng, Yuchen; Wang, Xiaoping; Ge, Binghui; Yang, Ce; Yao, Siyu; Xie, Jinglin; Li, Yongwang; Liu, Xi; Ma, Ding

    2017-08-28

    A one-step ligand-free method based on an adsorption-precipitation process was developed to fabricate iridium/cerium oxide (Ir/CeO2 ) nanocatalysts. Ir species demonstrated a strong metal-support interaction (SMSI) with the CeO2 substrate. The chemical state of Ir could be finely tuned by altering the loading of the metal. In the carbon dioxide (CO2 ) hydrogenation reaction it was shown that the chemical state of Ir species-induced by a SMSI-has a major impact on the reaction selectivity. Direct evidence is provided indicating that a single-site catalyst is not a prerequisite for inhibition of methanation and sole production of carbon monoxide (CO) in CO2 hydrogenation. Instead, modulation of the chemical state of metal species by a strong metal-support interaction is more important for regulation of the observed selectivity (metallic Ir particles select for methane while partially oxidized Ir species select for CO production). The study provides insight into heterogeneous catalysts at nano, sub-nano, and atomic scales. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. 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.

  7. 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.

  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. Spiral waves over metal catalysts

    NASA Astrophysics Data System (ADS)

    Karma, Alain; Zou, Xiaoqin

    1992-09-01

    Selection formulas for the wavelength and frequency of uniformly rotating spiral waves are derived for the general class of three-variable models of single-diffusive excitable-oscillatory media and applied to make quantitative predictions that could be experimentally tested for the model proposed by Sales, Turner, and Maple [Surf. Sci. 114, 381 (1982)] to describe the oscillatory oxidation of CO over polycrystalline metal catalysts.

  10. 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.

  11. 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.

  12. XPS studies of Pt catalysts supported on porous carbon

    SciTech Connect

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

    2016-05-23

    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 sp{sup 2} and sp{sup 3} 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.

  13. 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.

  14. Cobalt phosphide nanowall arrays supported on carbon cloth: an efficient monolithic non-noble-metal hydrogen evolution catalyst.

    PubMed

    Yang, Libin; Wang, Kunyang; Du, Gu; Zhu, Wenxin; Cui, Liang; Zhang, Chengxiao; Sun, Xuping; Asiri, Abdullah M

    2016-11-25

    Hydrogen has been considered as an ideal energy carrier for replacing fossil fuels to mitigate global energy crises. Hydrolysis of sodium borohydride (NaBH4) is simple and effective for hydrogen production but needs active and durable catalysts to accelerate the kinetics. In this paper, we demonstrate that cobalt phosphide nanowall arrays supported on carbon cloth (CoP NAs/CC) efficiently catalyze the hydrolytic dehydrogenation of NaBH4 with an activation energy of 42.1 kJ mol(-1) in alkaline media. These monolithic CoP NAs/CC show a maximum hydrogen generation rate of [Formula: see text] and are robust with superior durability and reusability. They are also excellent in activity and durability for electrochemical hydrogen evolution in 1.0 M KOH, with the need of an overpotential of only 80 mV to drive 10 mA cm(-2). They offer us a promising low-cost hydrogen-generating catalyst for applications.

  15. Cobalt phosphide nanowall arrays supported on carbon cloth: an efficient monolithic non-noble-metal hydrogen evolution catalyst

    NASA Astrophysics Data System (ADS)

    Yang, Libin; Wang, Kunyang; Du, Gu; Zhu, Wenxin; Cui, Liang; Zhang, Chengxiao; Sun, Xuping; Asiri, Abdullah M.

    2016-11-01

    Hydrogen has been considered as an ideal energy carrier for replacing fossil fuels to mitigate global energy crises. Hydrolysis of sodium borohydride (NaBH4) is simple and effective for hydrogen production but needs active and durable catalysts to accelerate the kinetics. In this paper, we demonstrate that cobalt phosphide nanowall arrays supported on carbon cloth (CoP NAs/CC) efficiently catalyze the hydrolytic dehydrogenation of NaBH4 with an activation energy of 42.1 kJ mol-1 in alkaline media. These monolithic CoP NAs/CC show a maximum hydrogen generation rate of 5960 {{ml}} {{{\\min }}}-1 {{{{g}}}-1}({{CoP})} and are robust with superior durability and reusability. They are also excellent in activity and durability for electrochemical hydrogen evolution in 1.0 M KOH, with the need of an overpotential of only 80 mV to drive 10 mA cm-2. They offer us a promising low-cost hydrogen-generating catalyst for applications.

  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. Titanium dioxide as a catalyst support in heterogeneous catalysis.

    PubMed

    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.

  18. 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.

  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. Environmentally friendly one-pot synthesis of alpha-alkylated nitriles using hydrotalcite-supported metal species as multifunctional solid catalysts.

    PubMed

    Motokura, Ken; Fujita, Noriaki; Mori, Kohsuke; Mizugaki, Tomoo; Ebitani, Kohki; Jitsukawa, Koichiro; Kaneda, Kiyotomi

    2006-11-06

    A ruthenium-grafted hydrotalcite (Ru/HT) and hydrotalcite-supported palladium nanoparticles (Pd(nano)/HT) are easily prepared by treating basic layered double hydroxide, hydrotalcite (HT, Mg(6)Al(2)(OH)(16)CO(3)) with aqueous RuCl(3)n H(2)O and K(2)[PdCl(4)] solutions, respectively, using surface impregnation methods. Analysis by means of X-ray diffraction, and energy-dispersive X-ray, electron paramagnetic resonance, and X-ray absorption fine structure spectroscopies proves that a monomeric Ru(IV) species is grafted onto the surface of the HT. Meanwhile, after reduction of a surface-isolated Pd(II) species, highly dispersed Pd nanoclusters with a mean diameter of about 70 A is observed on the Pd(nano)/HT surface by transmission electron microscopy analysis. These hydrotalcite-supported metal catalysts can effectively promote alpha-alkylation reactions of various nitriles with primary alcohols or carbonyl compounds through tandem reactions consisting of metal-catalyzed oxidation and reduction, and an aldol reaction promoted by the base sites of the HT. In these catalytic alpha-alkylations, homogeneous bases are unnecessary and the only by-product is water. Additionally, these catalyst systems are applicable to one-pot syntheses of glutaronitrile derivatives.

  1. Metal-organic-framework-derived carbons: Applications as solid-base catalyst and support for Pd nanoparticles in tandem catalysis

    DOE PAGES

    Li, Xinle; Zhang, Biying; Fang, Yuhui; ...

    2017-02-11

    Here, the facile pyrolysis of a bipyridyl metal-organic framework, MOF-253, produces N-doped porous carbons (Cz-MOF-253), which exhibit excellent catalytic activity in the Knoevenagel condensation reaction and outperform other nitrogen-containing MOF-derived carbons. More importantly, by virtue of their high Lewis basicity and porous nature, Cz-MOF-253-supported Pd nanoparticles (Pd/Cz-MOF-253-800) show excellent performance in a one-pot sequential Knoevenagel condensation-hydrogenation reaction.

  2. 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.

  3. Catalyst support effects on hydrogen spillover

    NASA Astrophysics Data System (ADS)

    Karim, Waiz; Spreafico, Clelia; Kleibert, Armin; Gobrecht, Jens; Vandevondele, Joost; Ekinci, Yasin; van Bokhoven, Jeroen A.

    2017-01-01

    Hydrogen spillover is the surface migration of activated hydrogen atoms from a metal catalyst particle, on which they are generated, onto the catalyst support. The phenomenon has been much studied and its occurrence on reducible supports such as titanium oxide is established, yet questions remain about whether hydrogen spillover can take place on nonreducible supports such as aluminium oxide. Here we use the enhanced precision of top-down nanofabrication to prepare controlled and precisely tunable model systems that allow us to quantify the efficiency and spatial extent of hydrogen spillover on both reducible and nonreducible supports. We place multiple pairs of iron oxide and platinum nanoparticles on titanium oxide and aluminium oxide supports, varying the distance between the pairs from zero to 45 nanometres with a precision of one nanometre. We then observe the extent of the reduction of the iron oxide particles by hydrogen atoms generated on the platinum using single-particle in situ X-ray absorption spectromicroscopy applied simultaneously to all particle pairs. The data, in conjunction with density functional theory calculations, reveal fast hydrogen spillover on titanium oxide that reduces remote iron oxide nanoparticles via coupled proton-electron transfer. In contrast, spillover on aluminium oxide is mediated by three-coordinated aluminium centres that also interact with water and that give rise to hydrogen mobility competing with hydrogen desorption; this results in hydrogen spillover about ten orders of magnitude slower than on titanium oxide and restricted to very short distances from the platinum particle. We anticipate that these observations will improve our understanding of hydrogen storage and catalytic reactions involving hydrogen, and that our approach to creating and probing model catalyst systems will provide opportunities for studying the origin of synergistic effects in supported catalysts that combine multiple functionalities.

  4. Alkene Metalates as Hydrogenation Catalysts.

    PubMed

    Büschelberger, Philipp; Gärtner, Dominik; Reyes-Rodriguez, Efrain; Kreyenschmidt, Friedrich; Koszinowski, Konrad; Jacobi von Wangelin, Axel; Wolf, Robert

    2017-03-02

    First-row transition-metal complexes hold great potential as catalysts for hydrogenations and related reductive reactions. Homo- and heteroleptic arene/alkene metalates(1-) (M=Co, Fe) are a structurally distinct catalyst class with good activities in hydrogenations of alkenes and alkynes. The first syntheses of the heteroleptic cobaltates [K([18]crown-6)][Co(η(4) -cod)(η(2) -styrene)2 ] (5) and [K([18]crown-6)][Co(η(4) -dct)(η(4) -cod)] (6), and the homoleptic complex [K(thf)2 ][Co(η(4) -dct)2 ] (7; dct=dibenzo[a,e]cyclooctatetraene, cod=1,5-cyclooctadiene), are reported. For comparison, two cyclopentadienylferrates(1-) were synthesized according to literature procedures. The isolated and fully characterized monoanionic complexes were competent precatalysts in alkene hydrogenations under mild conditions (2 bar H2 , r.t., THF). Mechanistic studies by NMR spectroscopy, ESI mass spectrometry, and poisoning experiments documented the operation of a homogeneous mechanism, which was initiated by facile redox-neutral π-ligand exchange with the substrates followed by H2 activation. The substrate scope of the investigated precatalysts was also extended to polar substrates (ketones and imines).

  5. Effect of support and second metal in catalytic in-situ generation of hydrogen peroxide by Pd-supported catalysts: application in the removal of organic pollutants by means of the Fenton process.

    PubMed

    Contreras, S; Yalfani, M S; Medina, F; Sueiras, J E

    2011-01-01

    A catalytic system for the generation of H2O2 from formic acid and oxygen at ambient conditions has been developed. Pd-supported catalysts (Pd/C, Pd/TiO2 and Pd/Al2O3) have been tested, showing that for bulk purposes Pd/Al2O3 is more favourable while for in-situ applications Pd/TiO2 seems to be preferable. However, when these catalysts were tested in the in-situ H2O2 generation for the oxidation of phenol by means of the Fenton process (in the presence of ferrous ion), Pd/TiO2 did not demonstrate the expected results, whereas Pd/Al2O3 showed to be an efficient catalyst. Therefore, Pd/Al2O3 is offered as a good catalyst for Fenton's reactions with in-situ generated H2O2. In order to optimize the operating cost of the process, different initial concentrations of formic acid have been tested with Pd/Al2O3, and it has been seen that lowering the initial amount of formic acid favours the efficiency of the process. The effect of the addition of a second metallic (Pt, Au, Fe, Cu) active phase was studied. Concerning H2O2 generation, best results were obtained with a Pd-Au catalyst for bulk production (long time) while for in-situ application Pd-Fe showed interesting results. The Pd-Fe catalyst also performed similarly to the semi-heterogeneous Fenton system involving Pd/Al2O3 and ferrous ion in the degradation of phenol. Therefore, Pd-Fe catalyst offered an interesting prospect for making a full heterogeneous catalyst for Fenton reaction involving in-situ generation of H2O2.

  6. Effect of counterpart metals in carbon-supported Pt-based catalysts prepared using radiation chemical method

    NASA Astrophysics Data System (ADS)

    Okazaki, Tomohisa; Seino, Satoshi; Matsuura, Yoshiyuki; Otake, Hiroaki; Kugai, Junichiro; Ohkubo, Yuji; Nitani, Hiroaki; Nakagawa, Takashi; Yamamoto, Takao A.

    2017-04-01

    The process of nanoparticle formation by radiation chemical synthesis in a heterogeneous system has been investigated. Carbon-supported Pt-based bimetallic nanoparticles were synthesized using a high-energy electron beam. Rh, Cu, Ru, and Sn were used as counterpart metals. The nanoparticles were characterized by inductively coupled plasma atomic emission spectrometry, transmission electron microscopy, X-ray diffraction, and X-ray absorption spectroscopy. PtRh formed a uniform random alloy nanoparticle, while Cu partially formed an alloy with Pt and the remaining Cu existed as CuO. PtRu formed an alloy structure with a composition distribution of a Pt-rich core and Ru-rich shell. No alloying was observed in PtSn, which had a Pt-SnO2 structure. The alloy and oxide formation mechanisms are discussed considering the redox potentials, the standard enthalpy of oxide formation, and the solid solubilities of Pt and the counterpart metals.

  7. Metal nanoparticles as a conductive catalyst

    DOEpatents

    Coker, Eric N [Albuquerque, NM

    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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Fundamental studies of supported bimetallic catalysts by NMR spectroscopy

    SciTech Connect

    Savargaonkar, Nilesh

    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.

  13. Hydroliquefaction of coal with supported catalysts: 1980 status review

    SciTech Connect

    Polinski, Leon M.; Stiegel, Gary J.; Tischer, Richard E.

    1981-06-01

    The objectives of the program have been to determine catalyst deactivation kinetic models and catalyst deactivation modes for supported Co-Mo and Ni-Mo catalysts used primarily in coal liquefaction via the H-COAL process. Emphasis has been on developing methods to increase catalyst usage by determining how to decrease catalyst replacement rates in the process and how to decrease catalyst poisoning. An important conclusion reached via model analysis and verified by experiment is that larger diameter (1/16 in.) catalysts resist poisoning deactivation much more than smaller (1/32 in.) catalysts over extended periods (60 to 110 hours) of time. If this trend can be verified, it gives a powerful tool for reducing catalyst replacement rate in the H-COAL ebullated bed system by factors of 2 or more. A second conclusion is that poisoning of catalysts occurs by several possible mechanisms or modes. Indirect or direct evidence of all these modes can be presented, though the relative importance of each mechanism has not been established. The modes include (a) poisoning by coking - with gradual increase in C/H ratio (more refractory coke) with time, (b) poisoning by metallization (selective/non-selective adsorption of inorganics such as Ti and Fe on the catalyst), (c) sintering - increase in larger pores/decrease in surface area, and (d) parallel poisoning by irreversible nitrogen compound adsorption.

  14. 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.

  15. 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.

  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. Carbon-based metal-free catalysts

    NASA Astrophysics Data System (ADS)

    Liu, Xien; Dai, Liming

    2016-11-01

    Metals and metal oxides are widely used as catalysts for materials production, clean energy generation and storage, and many other important industrial processes. However, metal-based catalysts suffer from high cost, low selectivity, poor durability, susceptibility to gas poisoning and have a detrimental environmental impact. In 2009, a new class of catalyst based on earth-abundant carbon materials was discovered as an efficient, low-cost, metal-free alternative to platinum for oxygen reduction in fuel cells. Since then, tremendous progress has been made, and carbon-based metal-free catalysts have been demonstrated to be effective for an increasing number of catalytic processes. This Review provides a critical overview of this rapidly developing field, including the molecular design of efficient carbon-based metal-free catalysts, with special emphasis on heteroatom-doped carbon nanotubes and graphene. We also discuss recent advances in the development of carbon-based metal-free catalysts for clean energy conversion and storage, environmental protection and important industrial production, and outline the key challenges and future opportunities in this exciting field.

  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. Probing specific oxides as potential supports for metal/oxide model catalysts: MgO(111) polar film

    NASA Astrophysics Data System (ADS)

    Grigorkina, G. S.; Ramonova, A. G.; Kibizov, D. D.; Kozyrev, E. N.; Zaalishvili, V. B.; Fukutani, K.; Magkoev, T. T.

    2017-05-01

    The growth of thermally evaporated magnesium oxide thin film on Mo(110) substrate in ultra-high vacuum was studied by means of Auger electron spectroscopy (AES), low-energy electron diffraction (LEED) and work function (WF) measurements. It is shown that at a growth rate of c.a. 0.1 monolayer per minute and the substrate temperature of 600 K the film acquires the MgO(111) structure. This structure begins to form at two monolayers and holds up to six monolayers. At higher thickness the film disorders due to weakening of the ordering effect of the isosymmetric Mo(110) support. Adsorption of CO and H2 on the formed MgO(111) film cooled down to 90 K was studied by means of ultraviolet photoelectron spectroscopy (UPS) and reflection absorption infrared spectroscopy (RAIRS) and compared with in-situ obtained results for CO on Pt(111). Comparison of UPS data of CO on MgO(111) and Pt(111) in combination with RAIRS results reveals quite different bonding mechanisms on the metal and the oxide supports. The main feature of CO on MgO(111) is quite high intensity of CO stretch vibration, considerably exceeding that on amorphous MgO, and comparable to that of CO on Pt(111). This is presumably due to the electrostatic effect of the uncompensated microscopic dipole moment of ultrathin MgO(111) film on the enhancing of CO dynamical dipole moment. Adsorption of H2 dramatically reduces the CO stretch intensity as a possible result of removing of dipole moment of MgO(111) surface by hydrogen and (CO+H2) interaction.

  1. 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%).

  2. Catalyst support structure, catalyst including the structure, reactor including a catalyst, and methods of forming same

    DOEpatents

    Van Norman, Staci A.; Aston, Victoria J.; Weimer, Alan W.

    2017-05-09

    Structures, catalysts, and reactors suitable for use for a variety of applications, including gas-to-liquid and coal-to-liquid processes and methods of forming the structures, catalysts, and reactors are disclosed. The catalyst material can be deposited onto an inner wall of a microtubular reactor and/or onto porous tungsten support structures using atomic layer deposition techniques.

  3. Carbon nanotube synthesis with different support materials and catalysts

    NASA Astrophysics Data System (ADS)

    Gümüş, Fatih; Yuca, Neslihan; Karatepe, Nilgün

    2013-09-01

    Having remarkable characteristics, carbon nanotubes (CNTs) have attracted a lot of interest. Their mechanical, electrical, thermal and chemical properties make CNTs suitable for several applications such as electronic devices, hydrogen storage, textile, drug delivery etc. CNTs have been synthesized by various methods, such as arc discharge, laser ablation and catalytic chemical vapor deposition (CCVD). In comparison with the other techniques, CCVD is widely used as it offers a promising route for mass production. High capability of decomposing hydrocarbon formation is desired for the selected catalysts. Therefore, transition metals which are in the nanometer scale are the most effective catalysts. The common transition metals that are being used are Fe, Co, Ni and their binary alloys. The impregnation of the catalysts over the support material has a crucial importance for the CNT production. In this study, the influence of the support materials on the catalytic activity of metals was investigated. CNTs have been synthesized over alumina (Al2O3), silica (SiO2) and magnesium oxide (MgO) supported Fe, Co, Fe-Co catalysts. Catalyst - support material combinations have been investigated and optimum values for each were compared. Single walled carbon nanotubes (SWCNTs) were produced at 800°C. The duration of synthesis was 30 minutes for all support materials. The synthesized materials were characterized by thermal gravimetric analysis (TGA), Raman spectroscopy and transmission electron microscopy.

  4. Preparation of Supported Palladium Catalysts using Deep Eutectic Solvents.

    PubMed

    Iwanow, Melanie; Finkelmeyer, Jasmin; Söldner, Anika; Kaiser, Manuela; Gärtner, Tobias; Sieber, Volker; König, Burkhard

    2017-09-12

    Deep eutectic solvents (DESs) dissolve metal salts or oxides and are used as solvent and carbon source for the preparation of supported palladium catalysts. After dissolving of the palladium salt in the DES, the pyrolysis of the mixture under nitrogen atmosphere yields catalytically active palladium on supporting material composed of carbon, nitrogen and oxygen (CNO) by a simple single step preparation method without further activation. The catalysts were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET) and CHNS/O elementary analysis. The amount of functional groups on the surface of the supporting material was determined by Boehm titrations. Moreover, the activity of the prepared catalysts was evaluated in the hydrogenation of linear alkenes and compared with a commercial Pd/C catalyst. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Influence of the hydrogen uptake by the support on metal-support interactions in catalysts. Comparison of the Rh/TiO/sub 2/ and Rh/SrTiO/sub 3/ systems

    SciTech Connect

    Sanz, J.; Rojo, J.M.; Malet, P.; Munuera, G.; Blasco, M.T.; Conesa, J.C.; Soria, J.

    1985-12-05

    Samples of Rh/TiO/sub 2/ and Rh/SrTiO/sub 3/ catalysts subjected to thermal treatments under H/sub 2/ and in vacuo have been examined by NMR, EPR, and quantitative adsorption techniques in order to ascertain the dependence of SMSI effects on hydrogen strongly adsorbed at high temperatures. Loss of H/sub 2/ chemisorption capacity upon high-temperature reduction (monitored directly by NMR of metal-adsorbed hydrogen) occurs only in Rh/TiO/sub 2/, and is accompanied by extensive incorporation of hydrogen in the support in form of hydride-type species. Both effects are reversed by high-temperature outgassing, while the amount of EPR-detected Ti/sup 3 +/ increases. It is concluded that support-held hydrogen produces SMSI-type effects in Rh/TiO/sub 2/ that cannot be explained by a conventional support reduction mechanism (generation of Ti/sup 3 +/ and anion vacancies) or by coverage of the metal with TiO/sub x/ species migrating from the support. Electronic changes (rehybridization) induced in the small metal particles by interaction with highly reduced species generated at the support are proposed as a possible source of SMSI behavior that can be reversed by outgassing or oxidation more easily than coverage by TiO/sub x/ entities. 40 references, 8 figures.

  6. 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.

  7. Tuning the properties of metal-organic framework nodes as supports of single-site iridium catalysts: node modification by atomic layer deposition of aluminium.

    PubMed

    Yang, Dong; Momeni, Mohammad R; Demir, Hakan; Pahls, Dale R; Rimoldi, Martino; Wang, Timothy C; Farha, Omar K; Hupp, Joseph T; Cramer, Christopher J; Gates, Bruce C; Gagliardi, Laura

    2017-09-08

    The metal-organic framework NU-1000, with Zr6-oxo, hydroxo, and aqua nodes, was modified by incorporation of hydroxylated Al(iii) ions by ALD-like chemistry with [Al(CH3)2(iso-propoxide)]2 followed by steam (ALD = atomic layer deposition). Al ions were installed to the extent of approximately 7 per node. Single-site iridium diethylene complexes were anchored to the nodes of the modified and unmodified MOFs by reaction with Ir(C2H4)2(acac) (acac = acetylacetonate) and converted to Ir(CO)2 complexes by treatment with CO. Infrared spectra of these supported complexes show that incorporation of Al weakened the electron donor tendency of the MOF. Correspondingly, the catalytic activity of the initial supported iridium complexes for ethylene hydrogenation increased, as did the selectivity for ethylene dimerization. The results of density functional theory calculations with a simplified model of the nodes incorporating Al(iii) ions are in qualitative agreement with some catalyst performance data.

  8. Complete oxidation of ethylene over supported gold nanoparticle catalysts.

    PubMed

    Ahn, Ho-Geun; Choi, Byoung-Min; Lee, Do-Jin

    2006-11-01

    Complete oxidation of ethylene was performed over supported noble metals or transition metals oxide catalysts and on monoliths under atmospheric pressure. Gold nanoparticles on Al2O3 or MxOy(M = Mo, Fe, Mn) were prepared by impregnation, coprecipitation, deposition, and dispersion methods. Nanoparticles prepared by impregnation method were irregular and very large above 25 nm, but those by coprecipitation and deposition method were uniformly nanosized at 4-5 nm. The gold nanoparticle were outstandingly active in catalyzing oxidation of ethylene. The activity order of these catalysts with preparation methods was deposition > coprecipitation > impregnation, and Au/Co3O4 prepared by deposition method showed the best performance in ethylene oxidation. The addition of gold particles to MxOy/Al2O3 catalyst enhanced the ethylene oxidation activity significantly. The main role of the gold nanoparticles apparently was to promote dissociative adsorption of oxygen and to enhance the reoxidation of the catalyst.

  9. Nanoengineering Catalyst Supports via Layer-by Layer Surface Functionalization

    SciTech Connect

    Yan, Wenfu; Mahurin, Shannon Mark; Overbury, Steven {Steve} H; Dai, Sheng

    2006-01-01

    Recent progress in the layer-by-layer surface modification of oxides for the preparation of highly active and stable gold nanocatalysts is briefly reviewed. Through a layer-by-layer surface modification approach, the surfaces of various catalyst supports including both porous and nonporous silica materials and TiO{sub 2} nanoparticles were modified with monolayers or multilayers of distinct metal oxide ultra-thin films. The surface-modified materials were used as supports for Au nanoparticles, resulting in highly active nanocatalysts for low-temperature CO oxidation. Good stability against sintering under high-temperature treatment was achieved for a number of the Au catalysts through surface modification of the support material. The surface modification of supports can be a viable route to control both the composition and structure of support and nanoparticle interfaces, thereby tailoring the stability and activity of the supported catalyst systems.

  10. NiCo2O4 spinel/ordered mesoporous carbons as noble-metal free electrocatalysts for oxygen reduction reaction and the influence of structure of catalyst support on the electrochemical activity of NiCo2O4

    NASA Astrophysics Data System (ADS)

    Bo, Xiangjie; Zhang, Yufan; Li, Mian; Nsabimana, Anaclet; Guo, Liping

    2015-08-01

    Three ordered mesoporous carbons (OMCs) with different structures are used as catalyst supports for growth of NiCo2O4 spinel. The high surface area of OMCs provides more active sites to adsorb metal precursors. The porous structure confines the growth of NiCo2O4 and supplies more efficient transport passage for reactant molecules to access the active sites. Due to the structural characteristics of OMCs and catalytic properties of NiCo2O4, NiCo2O4/OMCs composites are highly active, cheap, and selective noble metal-free electrocatalysts for the oxygen reduction reaction (ORR) in alkaline solution. The electrochemical activity of NiCo2O4 supported on three OMCs with different structures, surface areas, pore sizes, pore volumes, and defective sites is studied. NiCo2O4/OMCs composites may be further used as efficient and inexpensive noble metal-free ORR catalysts in alkaline solution.

  11. Ceramic wash-coat for catalyst support

    DOEpatents

    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.

  12. 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.

  13. 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

  14. 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

  15. New catalysts for coal processing: Metal carbides and nitrides

    SciTech Connect

    S. Ted Oyama; David F. Cox

    1999-12-03

    The subject of this research project was to investigate the catalytic properties of a new class of materials, transition metal carbides and nitrides, for treatment of coal liquid and petroleum feedstocks. The main objectives were: (1) preparation of catalysts in unsupported and supported form; (2) characterization of the materials; (3) evaluation of their catalytic properties in HDS and HDN; (4) measurement of the surface properties; and (5) observation of adsorbed species. All of the objectives were substantially carried out and the results will be described in detail below. The catalysts were transition metal carbides and nitrides spanning Groups 4--6 in the Periodic Table. They were chosen for study because initial work had shown they were promising materials for hydrotreating. The basic strategy was first to prepare the materials in unsupported form to identify the most promising catalyst, and then to synthesize a supported form of the material. Already work had been carried out on the synthesis of the Group VI compounds Mo{sub 2}C, Mo{sub 2}N, and WC, and new methods were developed for the Group V compounds VC and NbC. All the catalysts were then evaluated in a hydrotreating test at realistic conditions. It was found that the most active catalyst was Mo{sub 2}C, and further investigations of the material were carried out in supported form. A new technique was employed for the study of the bulk and surface properties of the catalysts, near edge x-ray absorption spectroscopy (NEXAFS), that fingerprinted the electronic structure of the materials. Finally, two new research direction were explored. Bimetallic alloys formed between two transition metals were prepared, resulting in catalysts having even higher activity than Mo{sub 2}C. The performance of the catalysts in hydrodechloration was also investigated.

  16. Single-layer transition metal sulfide catalysts

    DOEpatents

    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.

  17. 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...

  18. 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...

  19. 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).

  20. 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.; ...

    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

  1. 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.

  2. 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.

  3. Catalysts comprising magnesium and a transition metal

    SciTech Connect

    Bujadoux, K.

    1984-10-09

    A catalyst comprising the product obtained by bringing into contact a compound of magnesium comprising at least one species selected from the group consisting of magnesium monohalides (MgX), halo-magnesium hydrides (HMgX) and magnesium hydride (MgH/sub 2/), X being a halogen and the said species MgX or HMgX being obtained by thermal decomposition of a powdery organo-magnesium halide R/sub 1/MgX wherein R/sub 1/ is an organic radical; and at least one halide of a transistion metal selected from the group consisting of titanium and vanadium, the valency of said metal in said halide being lower than or equal to 3, the quantities being such that the atomic ratio of magnesium to said transistion metal is between 1 and 25, and a catalyst system including the catalyst that is suitable for use in the polymerization of olefins and particularly ethylene.

  4. Computational Study on M1/POM Single-Atom Catalysts (M = Cu, Zn, Ag, and Au; POM = [PW12O40](3-)): Metal-Support Interactions and Catalytic Cycle for Alkene Epoxidation.

    PubMed

    Liu, Chun-Guang; Jiang, Meng-Xu; Su, Zhong-Min

    2017-09-05

    Geometrical structures, metal-support interactions, and infrared (IR) spectroscopy of a series of M1/POM (M = Cu, Zn, Ag, and Au; POM = [PW12O40](3-)) single-atom catalysts (SACs), and catalytic cycle for alkene epoxidation catalyzed by M1/POM SACs were studied using density functional theory (DFT) calculations. The calculations demonstrate that the most probable anchoring sties for the isolated single atoms studied here in the M1/POM SACs are the fourfold hollow sites on the surface of POM support. The bonding interaction between single metal atom and surface of POM support comes from the molecular orbitals with a mixture of d atomic orbital of metal and 2p group orbital of surface oxygen atoms of POM cage. The calculated adsorption energy of isolated metal atoms in these M1/POM SACs indicates that the early transition metals (Cu and Zn) have high thermal stability. The DFT-derived IR spectra show that the four characteristic peaks of free Keggin-type POM structure split into six because of introduction of isolated metal atom. Compared with other metal atoms, the Zn1/POM SAC has the high reactivity for activity of dioxygen molecule, because the dioxygen moiety in Zn1/POM SAC displays O2(-)· radical feature with [POM(4-)·Zn(2+)O2(-)·](3-) configuration. Finally, a catalytic cycle for ethylene epoxidation by O2 catalyzed by Zn1/POM SAC was proposed based on our DFT calculations. Supported noble-metal SACs are among the most important catalysts currently. However, noble metals are expensive and of limited supply. Development of non-noble-metal SACs is of essential importance. Therefore, the reported Zn1/POM SAC would be very useful to guide the search for SACs into non-noble metals.

  5. 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).

  6. 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.

  7. 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.

  8. 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.

  9. New applications of noble metal catalysts in hydrocracking

    SciTech Connect

    Mitchell, D.H.G.; Bertram, R.V.; Dencker, G.D.

    1995-09-01

    The paper explores how a noble metal hydrocracking catalyst functions stably in a hydrogen sulfide and ammonia environment and, in particular, how the physical positioning of the noble metal molecules affects catalyst performance. A commercial example, HC-28 catalyst in the Unicracking unit at Marathon Oil Refinery in Robinson, Illinois, demonstrates the success of the noble metal catalyst approach for naphtha production. In addition, a new Unicracking catalyst, HC-35, which uses a noble metal component to produce high-quality middle distillates, is introduced. The paper also shows how refiners may derive increased economic and operational benefits from their catalyst investment by using the latest developments in reactor internals design.

  10. 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.

  11. Catalysis science of supported vanadium oxide catalysts.

    PubMed

    Wachs, Israel E

    2013-09-07

    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).

  12. Long Range Materials Research. Appendix 1. Synthesis and Characterization of Supported Organometallic Rhodium (I) Catalysts

    DTIC Science & Technology

    1974-06-30

    support organo - metallic homogeneous catalysts on inert supports. This thesis describes the synthesis of a new chelating ligand for binding...homogeneous catalysts to silica surfaces, a now method using poisons for distinguishing con- ventional heterogeneous catal’,sts from the newer supported organo ...Homogeneous HIydrogenation by Rhodium(l) Complexes Homogeneous catalysts have both served and plagued alchemists and chemists since work began with solutions

  13. 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.

  14. Stable metal–organic framework-supported niobium catalysts

    DOE PAGES

    Ahn, Sol; Thornburg, Nicholas E.; Li, Zhanyong; ...

    2016-10-31

    In this study by developing structurally well-defined, supported oxide catalysts remains a significant challenge. Here, we report the grafting of Nb(V) oxide sites onto the nodes of the Zr-based metal organic framework (MOF) NU-1000 as a stable, well-defined catalyst support. Nb(V) oxide was deposited with loadings up to 1.6 mmol/g via two post-synthetic methods: atomic layer deposition in a MOF (AIM), and solution-phase grafting in a MOF (SIM). Difference envelope density (DED) measurements indicated that the two synthetic methods resulted in different local structures of the Nb(V) ions within NU-1000. Despite their high Nb(V) loadings, which were equivalent to >60%more » surface coverage, nearly all Nb(V) sites of the MOF-supported catalysts were active sites for alkene epoxidation, as confirmed by phenylphosphonic acid titration. The MOF-supported catalysts were more selective than the control Nb-ZrO2 catalyst for cyclohexene epoxidation with aqueous H2O2, and were far more active on a gravimetric basis.« less

  15. Stable metal–organic framework-supported niobium catalysts

    SciTech Connect

    Ahn, Sol; Thornburg, Nicholas E.; Li, Zhanyong; Wang, Timothy C.; Gallington, Leighanne C.; Chapman, Karena W.; Notestein, Justin M.; Hupp, Joseph T.; Farha, Omar K.

    2016-10-31

    In this study by developing structurally well-defined, supported oxide catalysts remains a significant challenge. Here, we report the grafting of Nb(V) oxide sites onto the nodes of the Zr-based metal organic framework (MOF) NU-1000 as a stable, well-defined catalyst support. Nb(V) oxide was deposited with loadings up to 1.6 mmol/g via two post-synthetic methods: atomic layer deposition in a MOF (AIM), and solution-phase grafting in a MOF (SIM). Difference envelope density (DED) measurements indicated that the two synthetic methods resulted in different local structures of the Nb(V) ions within NU-1000. Despite their high Nb(V) loadings, which were equivalent to >60% surface coverage, nearly all Nb(V) sites of the MOF-supported catalysts were active sites for alkene epoxidation, as confirmed by phenylphosphonic acid titration. The MOF-supported catalysts were more selective than the control Nb-ZrO2 catalyst for cyclohexene epoxidation with aqueous H2O2, and were far more active on a gravimetric basis.

  16. Various conformations of carbon nanocoils prepared by supported Ni-Fe/molecular sieve catalyst.

    PubMed

    Yang, Shaoming; Chen, Xiuqin; Takeuchi, K; Motojima, Seiji

    2006-01-01

    The carbon nanocoils with various kinds of conformations were prepared by the catalytic pyrolysis of acetylene using the Ni metal catalyst supported on molecular Sieves which was prepared using Fe-containing kaolin as the raw material. There are four kinds of carbon nanocoils conformations produced by this catalyst. The influences of reaction temperature and gas conditions on the conformations of the nanocoils were investigated and the reasons of forming nano-size coils were discussed by comparison with pure Ni metal catalyst.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. Alkaline earth metal catalysts for asymmetric reactions.

    PubMed

    Kobayashi, Shū; Yamashita, Yasuhiro

    2011-01-18

    The group 2 alkaline earth metals calcium (Ca), strontium (Sr), and barium (Ba) are among the most common elements on Earth, abundant in both the sea and the Earth's crust. Although they are familiar in our daily lives, their application to organic synthesis has, so far, been limited. Some particularly useful properties of these elements include (i) low electronegativity, (ii) a stable oxidation state of +2, meaning that they can potentially form two covalent bonds with anions, and (iii) the ability to occupy a variety of coordination sites due to their large ionic radius. Furthermore, the alkaline earth metals, found between the group 1 and group 3 elements, show mild but significant Lewis acidity, which can be harnessed to control coordinative molecules via a Lewis acid-base interaction. Taken together, these characteristics make the metals Ca, Sr, and Ba very promising components of highly functionalized acid-base catalysts. In this Account, we describe the development of chiral alkaline earth metal catalysts for asymmetric carbon-carbon bond-forming reactions. Recently prepared chiral alkaline earth metal complexes have shown high diastereo- and enantioselectivities in fundamental and important chemical transformations. We chose chiral bisoxazoline (Box) derivatives bearing a methylene tether as a ligand for chiral modification. These molecules are very useful because they can covalently coordinate to alkaline earth metals in a bidentate fashion through deprotonation of the tether portion. It was found that chiral calcium-Box complexes could successfully promote catalytic asymmetric 1,4-addition and [3 + 2] cycloaddition reactions with high diastereo- and enantioselectivities. Both the calcium-Box complexes and chiral strontium-bis-sulfonamide and chiral barium-BINOLate complexes could catalyze asymmetric 1,4-addition reactions with high enantioselectivities. Furthermore, we designed a calcium-neutral coordinative ligand complex as a new type of chiral alkaline

  3. Templating Routes to Supported Oxide Catalysts by Design

    SciTech Connect

    Notestein, Justin M.

    2016-09-08

    The rational design and understanding of supported oxide catalysts requires at least three advancements, in order of increasing complexity: the ability to quantify the number and nature of active sites in a catalytic material, the ability to place external controls on the number and structure of these active sites, and the ability to assemble these active sites so as to carry out more complex functions in tandem. As part of an individual investigator research program that is integrated with the Northwestern University Institute for Catalysis in Energy Processes (ICEP) as of 2015, significant advances were achieved in these three areas. First, phosphonic acids were utilized in the quantitative assessment of the number of active and geometrically-available sites in MOx-SiO2 catalysts, including nanocrystalline composites, co-condensed materials, and grafted structures, for M=Ti, Zr, Hf, Nb, and Ta. That work built off progress in understanding supported Fe, Cu, and Co oxide catalysts from chelating and/or multinuclear precursors to maximize surface reactivity. Secondly, significant progress was made in the new area of using thin oxide overcoats containing ‘nanocavities’ from organic templates as a method to control the dispersion and thermal stability of subsequently deposited metal nanoparticles or other catalytic domains. Similar methods were used to control surface reactivity in SiO2-Al2O3 acid catalysts and to control reactant selectivity in Al2O3-TiO2 photocatalysts. Finally, knowledge gained from the first two areas has been combined to synthesize a tandem catalyst for hydrotreating reactions and an orthogonal tandem catalyst system where two subsequent reactions in a reaction network are independently controlled by light and heat. Overall, work carried out under this project significantly advanced the knowledge of synthesis-structure-function relationships in supported

  4. A new type of strong metal-support interaction and the production of H2 through the transformation of water on Pt/CeO2(111) and Pt/CeO(x)/TiO2(110) catalysts.

    PubMed

    Bruix, Albert; Rodriguez, José A; Ramírez, Pedro J; Senanayake, Sanjaya D; Evans, Jaime; Park, Joon B; Stacchiola, Dario; Liu, Ping; Hrbek, Jan; Illas, Francesc

    2012-05-30

    The electronic properties of Pt nanoparticles deposited on CeO(2)(111) and CeO(x)/TiO(2)(110) model catalysts have been examined using valence photoemission experiments and density functional theory (DFT) calculations. The valence photoemission and DFT results point to a new type of "strong metal-support interaction" that produces large electronic perturbations for small Pt particles in contact with ceria and significantly enhances the ability of the admetal to dissociate the O-H bonds in water. When going from Pt(111) to Pt(8)/CeO(2)(111), the dissociation of water becomes a very exothermic process. The ceria-supported Pt(8) appears as a fluxional system that can change geometry and charge distribution to accommodate adsorbates better. In comparison with other water-gas shift (WGS) catalysts [Cu(111), Pt(111), Cu/CeO(2)(111), and Au/CeO(2)(111)], the Pt/CeO(2)(111) surface has the unique property that the admetal is able to dissociate water in an efficient way. Furthermore, for the codeposition of Pt and CeO(x) nanoparticles on TiO(2)(110), we have found a transfer of O from the ceria to Pt that opens new paths for the WGS process and makes the mixed-metal oxide an extremely active catalyst for the production of hydrogen.

  5. Dry reforming of methane on a highly-active Ni-CeO2 catalyst: Effects of metal-support interactions on C–H bond breaking

    DOE PAGES

    Liu, Zongyuan; Grinter, David C.; Lustemberg, Pablo G.; ...

    2016-05-04

    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 onmore » Ni/CeO2–x(111). At 700 K, under methane dry reforming conditions, no signals for adsorbed CHx or C species are detected in the C1s XPS region. As a result, the reforming of methane proceeds in a clean and efficient way.« less

  6. 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.

  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. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

    SciTech Connect

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

    2016-05-01

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

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

    SciTech Connect

    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 other 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.

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

    DOE PAGES

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

    2016-03-09

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

  12. 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.

  13. 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.

  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. Self-supported spinel FeCo2O4 nanowire array: an efficient non-noble-metal catalyst for the hydrolysis of NaBH4 toward on-demand hydrogen generation

    NASA Astrophysics Data System (ADS)

    Hao, Shuai; Yang, Libin; Cui, Liang; Lu, Wenbo; Yang, Yingchun; Sun, Xuping; Asiri, Abdullah M.

    2016-11-01

    NaBH4 has been considered as one of the most advantageous candidates for chemical hydrogen storage, but it is still a huge challenge to design efficient non-noble-metal catalysts for on-demand hydrogen generation from NaBH4 hydrolysis. In this paper, we demonstrate for the first time that a spinel FeCo2O4 nanowire array supported on carbon cloth (FeCo2O4 NA/CC) behaves as an efficient earth-abundant catalyst toward NaBH4 hydrolysis in alkaline solutions with an activation energy of 44.98 kJ mol-1. Such FeCo2O4 NA/CC offers a hydrogen generation rate of 2551 ml min-1 g-1 under ambient conditions, with good stability and reusability. Its use as an ON/OFF switch for on-demand hydrogen generation is also demonstrated successfully.

  16. 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.

  17. 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.

  18. Metal Fluorides, Metal Chlorides and Halogenated Metal Oxides as Lewis Acidic Heterogeneous Catalysts. Providing Some Context for Nanostructured Metal Fluorides.

    PubMed

    Lennon, David; Winfield, John M

    2017-01-28

    Aspects of the chemistry of selected metal fluorides, which are pertinent to their real or potential use as Lewis acidic, heterogeneous catalysts, are reviewed. Particular attention is paid to β-aluminum trifluoride, aluminum chlorofluoride and aluminas γ and η, whose surfaces become partially fluorinated or chlorinated, through pre-treatment with halogenating reagents or during a catalytic reaction. In these cases, direct comparisons with nanostructured metal fluorides are possible. In the second part of the review, attention is directed to iron(III) and copper(II) metal chlorides, whose Lewis acidity and potential redox function have had important catalytic implications in large-scale chlorohydrocarbons chemistry. Recent work, which highlights the complexity of reactions that can occur in the presence of supported copper(II) chloride as an oxychlorination catalyst, is featured. Although direct comparisons with nanostructured fluorides are not currently possible, the work could be relevant to possible future catalytic developments in nanostructured materials.

  19. 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.

  20. 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; ...

    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

  1. Combustion of chlorinated VOC on nanostructured chromia aerogel as catalyst and catalyst support.

    PubMed

    Rotter, H; Landau, M V; Herskowitz, M

    2005-09-01

    The chromia-based catalysts have been reported to combine the high activity and resistance to deactivation in oxidative removal of chlorinated VOC. However, their activity is limited by the low amount of chromia that can be deposited on supports maintaining the optimal state of surface species and high surface area. The pure nanostructured chromia was used as a catalytically active support for noble metals and transition-metal oxide oxidation catalysts. High efficiency of Pt-promoted CrOOH aerogel with surface area of 500 m2*g(-1) was demonstrated in full combustion of 1,2-dichloroethane (DCE) and chlorobenzene (CB). At gas hour space velocity (GHSV) of 46 000 h(-1), the total conversion to CO2/H2O/HCl was achieved at 330 degrees C (DCE) and 380 degrees C (CB). The combustion rate constants measured at standard conditions with 0.5% Pt/CrOOH catalyst were 1 or 2 orders of magnitude higher than measured with 15%Cr2O3/Al2O3 or 0.5%Pt/Al2O3, respectively. The effects of Pt, Au, Mn, and Ce additives on the performance of CrOOH aerogel in combustion of chlorinated VOC were analyzed related to the materials structure.

  2. 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

  3. 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

  4. Synthesis of bioethanol from biomass-derived syngas over carbon nanotube/silica supported catalyst.

    PubMed

    Feng, Wei; Yao, Jianqiang; Wu, Hailiang; Ji, Peijun

    2012-01-01

    Multi-walled carbon nanotubes (MWNTs) were functionalized with pyrogallol and used in a composite with silica as a support for a Cu-Co based catalyst. The catalysts were characterized using X-ray diffraction, transmission electron microscopy, and H(2) temperature programmed reduction. The effects of pyrogallol and the weight ratio of silica to MWNTs on the performance of the catalyst were studied in a fixed bed reactor. The increase of the amount of MWNTs in the catalyst support was found to favor decreased methanol production and increased production of C2+ alcohols. Using pyrogallol in catalyst preparation was also found to increase the production of C2+ alcohols. It was concluded that pyrogallol improves the distribution and uniformity of metal particles on the support, decreases the size of metal particles and increasing the rate of catalytic reduction.

  5. Peptide-templated noble metal catalysts: syntheses and applications.

    PubMed

    Wang, Wei; Anderson, Caleb F; Wang, Zongyuan; Wu, Wei; Cui, Honggang; Liu, Chang-Jun

    2017-05-01

    Noble metal catalysts have been widely used in many applications because of their high activity and selectivity. However, a controllable preparation of noble metal catalysts still remains as a significant challenge. To overcome this challenge, peptide templates can play a critical role in the controllable syntheses of catalysts owing to their flexible binding with specific metallic surfaces and self-assembly characteristics. By employing peptide templates, the size, shape, facet, structure, and composition of obtained catalysts can all be specifically controlled under the mild synthesis conditions. In addition, catalysts with spherical, nanofiber, and nanofilm structures can all be produced by associating with the self-assembly characteristics of peptide templates. Furthermore, the peptide-templated noble metal catalysts also reveal significantly enhanced catalytic behaviours compared with conventional catalysts because the electron conductivity, metal dispersion, and reactive site exposure can all be improved. In this review, we summarize the research progresses in the syntheses of peptide-templated noble metal catalysts. The applications of the peptide-templated catalysts in organic reactions, photocatalysis, and electrocatalysis are discussed, and the relationship between structure and activity of these catalysts are addressed. Future opportunities, including new catalytic materials designed by using biological principles, are indicated to achieve selective, eco-friendly, and energy neutral synthesis approaches.

  6. Peptide-templated noble metal catalysts: syntheses and applications

    PubMed Central

    Wang, Wei; Anderson, Caleb F.; Wang, Zongyuan; Wu, Wei

    2017-01-01

    Noble metal catalysts have been widely used in many applications because of their high activity and selectivity. However, a controllable preparation of noble metal catalysts still remains as a significant challenge. To overcome this challenge, peptide templates can play a critical role in the controllable syntheses of catalysts owing to their flexible binding with specific metallic surfaces and self-assembly characteristics. By employing peptide templates, the size, shape, facet, structure, and composition of obtained catalysts can all be specifically controlled under the mild synthesis conditions. In addition, catalysts with spherical, nanofiber, and nanofilm structures can all be produced by associating with the self-assembly characteristics of peptide templates. Furthermore, the peptide-templated noble metal catalysts also reveal significantly enhanced catalytic behaviours compared with conventional catalysts because the electron conductivity, metal dispersion, and reactive site exposure can all be improved. In this review, we summarize the research progresses in the syntheses of peptide-templated noble metal catalysts. The applications of the peptide-templated catalysts in organic reactions, photocatalysis, and electrocatalysis are discussed, and the relationship between structure and activity of these catalysts are addressed. Future opportunities, including new catalytic materials designed by using biological principles, are indicated to achieve selective, eco-friendly, and energy neutral synthesis approaches. PMID:28507701

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

    SciTech Connect

    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.

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

    DOE PAGES

    Kandemir, Timur; Friedrich, Matthias; Parker, Stewart F.; ...

    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.

  9. 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.

  10. Adsorbate-mediated strong metal–support interactions in oxide-supported Rh catalysts

    DOE PAGES

    Matsubu, John C.; Zhang, Shuyi; DeRita, Leo; ...

    2016-09-19

    The optimization of supported metal catalysts predominantly focuses on engineering the metal site, for which physical insights based on extensive theoretical and experimental contributions have enabled the rational design of active sites. Although it is well known that supports can influence the catalytic properties of metals, insights into how metal–support interactions can be exploited to optimize metal active-site properties are lacking. Here in this paper, we utilize in situ spectroscopy and microscopy to identify and characterize a support effect in oxide-supported heterogeneous Rh catalysts. This effect is characterized by strongly bound adsorbates (HCOx) on reducible oxide supports (TiO2 and Nb2O5)more » that induce oxygen-vacancy formation in the support and cause HCOx-functionalized encapsulation of Rh nanoparticles by the support. The encapsulation layer is permeable to reactants, stable under the reaction conditions and strongly influences the catalytic properties of Rh, which enables rational and dynamic tuning of CO2-reduction selectivity.« less

  11. Adsorbate-mediated strong metal–support interactions in oxide-supported Rh catalysts

    SciTech Connect

    Matsubu, John C.; Zhang, Shuyi; DeRita, Leo; Marinkovic, Nebojsa S.; Chen, Jingguang G.; Graham, George W.; Pan, Xiaoqing; Christopher, Phillip

    2016-09-19

    The optimization of supported metal catalysts predominantly focuses on engineering the metal site, for which physical insights based on extensive theoretical and experimental contributions have enabled the rational design of active sites. Although it is well known that supports can influence the catalytic properties of metals, insights into how metal–support interactions can be exploited to optimize metal active-site properties are lacking. Here in this paper, we utilize in situ spectroscopy and microscopy to identify and characterize a support effect in oxide-supported heterogeneous Rh catalysts. This effect is characterized by strongly bound adsorbates (HCOx) on reducible oxide supports (TiO2 and Nb2O5) that induce oxygen-vacancy formation in the support and cause HCOx-functionalized encapsulation of Rh nanoparticles by the support. The encapsulation layer is permeable to reactants, stable under the reaction conditions and strongly influences the catalytic properties of Rh, which enables rational and dynamic tuning of CO2-reduction selectivity.

  12. Non-Noble Metal Oxide Catalysts for Methane Catalytic Combustion: Sonochemical Synthesis and Characterisation

    PubMed Central

    Jędrzejczyk, Roman J.; Dziedzicka, Anna; Kuterasiński, Łukasz; Sitarz, Maciej

    2017-01-01

    The aim of this study was to obtain nanocrystalline mixed metal-oxide–ZrO2 catalysts via a sonochemically-induced preparation method. The effect of a stabiliser’s addition on the catalyst parameters was investigated by several characterisation methods including X-ray Diffraction (XRD), nitrogen adsorption, X-ray fluorescence (XRF), scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and µRaman. The sonochemical preparation method allowed us to manufacture the catalysts with uniformly dispersed metal-oxide nanoparticles at the support surface. The catalytic activity was tested in a methane combustion reaction. The activity of the catalysts prepared by the sonochemical method was higher than that of the reference catalysts prepared by the incipient wetness method without ultrasonic irradiation. The cobalt and chromium mixed zirconia catalysts revealed their high activities, which are comparable with those presented in the literature. PMID:28686190

  13. Recent Development of Palladium-Supported Catalysts for Chemoselective Hydrogenation.

    PubMed

    Monguchi, Yasunari; Ichikawa, Tomohiro; Sajiki, Hironao

    2017-01-01

    This paper describes practical and selective hydrogenation methodologies using heterogeneous palladium catalysts. Chemoselectivity develops dependent on the catalyst activity based on the characteristic of the supports, derived from structural components, functional groups, and/or morphologies. We especially focus on our recent development of heterogeneous palladium catalysts supported on chelate resin, ceramic, and spherically shaped activated carbon. In addition, the application of flow technology for chemoselective hydrogenation using the palladium catalysts immobilized on molecular sieves 3A and boron nitride is outlined.

  14. 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.

  15. 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''.

  16. 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.

  17. Engineering catalyst microenvironments for metal-catalyzed hydrogenation of biologically derived platform chemicals.

    PubMed

    Schwartz, Thomas J; Johnson, Robert L; Cardenas, Javier; Okerlund, Adam; Da Silva, Nancy A; Schmidt-Rohr, Klaus; Dumesic, James A

    2014-11-17

    It is shown that microenvironments formed around catalytically active sites mitigate catalyst deactivation by biogenic impurities that are present during the production of biorenewable chemicals from biologically derived species. Palladium and ruthenium catalysts are inhibited by the presence of sulfur-containing amino acids; however, these supported metal catalysts are stabilized by overcoating with poly(vinyl alcohol) (PVA), which creates a microenvironment unfavorable for biogenic impurities. Moreover, deactivation of Pd catalysts by carbon deposition from the decomposition of highly reactive species is suppressed by the formation of bimetallic PdAu nanoparticles. Thus, a PVA-overcoated PdAu catalyst was an order of magnitude more stable than a simple Pd catalyst in the hydrogenation of triacetic acid lactone, which is the first step in the production of biobased sorbic acid. A PVA-overcoated Ru catalyst showed a similar improvement in stability during lactic acid hydrogenation to propylene glycol in the presence of methionine.

  18. 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. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. 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.

  20. 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.

  1. Comparison of nickel molybdenum hydrous metal oxides with commercial catalysts for HDS/HDN of coal liquids

    SciTech Connect

    Lott, S.E.; Gardner, T.J.; McLaughlin, L.I.; Oelfke, J.B.

    1994-06-01

    Improved efficiency in direct coal liquefaction processes can be obtained by developing catalysts with better activity, selectivity, and life. In previous exploratory research at Sandia National Laboratories, catalysts prepared via hydrous metal oxide (HMO) ion exchangers have been shown to have potential for application to a number of reactions associated with the conversion of coal to liquid fuels. In the present effort, one member of this class of catalysts, hydrous titanium oxide (HTO), has been used to develop catalysts for hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) of coal liquids. For HYD of pyrone, unsupported NiMoHTO catalysts performed better than commercial benchmark catalysts on either a catalyst weight or active metals basis. In a side-by-side comparison of supported NiMoHTO catalysts with commercial counterparts, the supported NiMoHTO catalysts outperformed the Shell 324 and Amocat 1C catalysts for HYD of pyrene. For HDS/HDN of coal liquids, the supported and bulk forms of the NiMoHTO catalysts equaled the performance of the commercial catalysts at 500, 1000, and 1500 psig while containing less active metals. Possible reasons for the high activity of the NiMoHTO catalysts are a high dispersion of the active MoS{sub 2} phase and a high acidity of the bulk NiMoHTO.

  2. 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).

  3. Nano-ceramic support materials for low temperature fuel cell catalysts

    NASA Astrophysics Data System (ADS)

    Lv, Haifeng; Mu, Shichun

    2014-04-01

    Low temperature fuel cells (LTFCs) have received broad attention due to their low operating temperature, virtually zero emissions, high power density and efficiency. However, the limited stability of the catalysts is a critical limitation to the large scale commercialization of LTFCs. State of the art carbon supports undergo corrosion under harsh chemical and electrochemical oxidation conditions, which results in performance degradation of catalysts. Therefore, non-carbon materials which are highly oxidation resistant under strongly oxidizing conditions of LTFCs are ideal alternative supports. This minireview highlights the advances and scenarios in using nano-ceramics as supports to enhance the stability of catalysts, the solutions to improve electrical conductivity of nano-ceramic materials, and the synergistic effects between metal catalyst and support to help improve the catalytic activity and CO/SO2 tolerance of catalysts.

  4. Nano-ceramic support materials for low temperature fuel cell catalysts.

    PubMed

    Lv, Haifeng; Mu, Shichun

    2014-05-21

    Low temperature fuel cells (LTFCs) have received broad attention due to their low operating temperature, virtually zero emissions, high power density and efficiency. However, the limited stability of the catalysts is a critical limitation to the large scale commercialization of LTFCs. State of the art carbon supports undergo corrosion under harsh chemical and electrochemical oxidation conditions, which results in performance degradation of catalysts. Therefore, non-carbon materials which are highly oxidation resistant under strongly oxidizing conditions of LTFCs are ideal alternative supports. This minireview highlights the advances and scenarios in using nano-ceramics as supports to enhance the stability of catalysts, the solutions to improve electrical conductivity of nano-ceramic materials, and the synergistic effects between metal catalyst and support to help improve the catalytic activity and CO/SO2 tolerance of catalysts.

  5. Metallic bionanocatalysts: potential applications as green catalysts and energy materials.

    PubMed

    Macaskie, Lynne E; Mikheenko, Iryna P; Omajai, Jacob B; Stephen, Alan J; Wood, Joseph

    2017-08-22

    Microbially generated or supported nanocatalysts have potential applications in green chemistry and environmental application. However, precious (and base) metals biorefined from wastes may be useful for making cheap, low-grade catalysts for clean energy production. The concept of bionanomaterials for energy applications is reviewed with respect to potential fuel cell applications, bio-catalytic upgrading of oils and manufacturing 'drop-in fuel' precursors. Cheap, effective biomaterials would facilitate progress towards dual development goals of sustainable consumption and production patterns and help to ensure access to affordable, reliable, sustainable and modern energy. © 2017 The Authors. Microbial Biotechnology published by John Wiley & Sons Ltd and Society for Applied Microbiology.

  6. Method of making metal-polymer composite catalysts

    DOEpatents

    Zelena, Piotr [Los Alamos, NM; Bashyam, Rajesh [Los Alamos, NM

    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.

  7. Selective recovery of catalyst layer from supporting matrix of ceramic-honeycomb-type automobile catalyst.

    PubMed

    Kim, Wantae; Kim, Boungyoung; Choi, Doyoung; Oki, Tatsuya; Kim, Sangbae

    2010-11-15

    Natural resources of platinum group metals (PGMs) are limited and their demand is increasing because of their extensive uses in industrial applications. The low rate of production of PGMs due to low concentration in the related natural ores and high cost of production have made the recovery of PGMs from previously discarded catalytic converters a viable proposition. The ceramic-honeycomb-type automobile catalytic converter contains appreciable amount of PGMs. These valuable substances, which are embedded in the catalyst layer and covered on the surface of the supporting matrix, were selectively recovered by attrition scrubbing. The attrition scrubbing was effective for the selective recovery of catalyst layer. The process was convinced as the comminution and separation process by physical impact and shearing action between particles in the scrubbing vessel. The catalyst layer was dislodged from the surface of the supporting matrix into fine particles by attrition scrubbing. The recovery of Al(2)O(3) and total PGMs in the fraction less than 300 μm increased with the residence time whereas their contents in the recovered materials slightly decreased. The interparticle scrubbing became favorable when the initial input size increased. However, the solid/liquid ratio in the mixing vessel was slightly affected by the low density of converter particles.

  8. Hydrodechlorination of Tetrachloromethane over Palladium Catalysts Supported on Mixed MgF₂-MgO Carriers.

    PubMed

    Bonarowska, Magdalena; Wojciechowska, Maria; Zieliński, Maciej; Kiderys, Angelika; Zieliński, Michał; Winiarek, Piotr; Karpiński, Zbigniew

    2016-11-25

    Pd/MgO, Pd/MgF₂ and Pd/MgO-MgF₂ catalysts were investigated in the reaction of CCl₄ hydrodechlorination. All the catalysts deactivated in time on stream, but the degree of deactivation varied from catalyst to catalyst. The MgF₂-supported palladium with relatively large metal particles appeared the best catalyst, characterized by good activity and selectivity to C₂-C₅ hydrocarbons. Investigation of post-reaction catalyst samples allowed to find several details associated with the working state of hydrodechlorination catalysts. The role of support acidity was quite complex. On the one hand, a definite, although not very high Lewis acidity of MgF₂ is beneficial for shaping high activity of palladium catalysts. The MgO-MgF₂ support characterized by stronger Lewis acidity than MgF₂ contributes to very good catalytic activity for a relatively long reaction period (~5 h) but subsequent neutralization of stronger acid centers (by coking) eliminates them from the catalyst. On the other hand, the role of acidity evolution, which takes place when basic supports (like MgO) are chlorided during HdCl reactions, is difficult to assess because different events associated with distribution of chlorided support species, leading to partial or even full blocking of the surface of palladium, which plays the role of active component in HdCl reactions.

  9. Pd-Pt Catalysts on Fluorinated Alumina Support Studied by X-Ray Absorption Fine Structure

    NASA Astrophysics Data System (ADS)

    Yan, Wensheng; Li, Zhongrui; Wei, Zheng; Wei, Shiqiang

    2007-02-01

    A series of bi-metallic Pd-Pt catalysts supported on both pristine and fluorinated alumina supports were investigated with x-ray absorption spectroscopy. It was found that Pd and Pt form small alloy particles on the pristine alumina support; the composition and the cluster size of the PdPt bimetallic alloys, and the electronic properties of the metals were significantly altered on the fluorinated support. The remarkable increase in sulfur tolerance of the PdPt metallic clusters supported on the fluorine pretreated alumina can be attributed to an electronic depletion of the metals, large particle size and direct participation of the acid sites in the reaction.

  10. The effects of deposition methods for metal catalyst formation in carbon nanotubes growth

    NASA Astrophysics Data System (ADS)

    Isa, Siti S. Mat; Ramli, Muhammad M.

    2014-10-01

    In this study, we examine the effect of two different metal catalyst deposition methods in carbon nanotubes (CNT) growth for interconnect application. Metal support layer, which is Titanium Nitride (TiN) was first deposited on Silicon Dioxide (SiO2) pads, Then, nickel (Ni) catalyst was deposited, first; by sputtering technique to form uniform thin film, and second; by cluster tool where spherical metal catalyst was formed. These metal catalysts were annealed at 400 °C, 500 °C and 600 °C. The image shows that the number of Ni particles for cluster techniques was higher than thin film sample. While, the average diameter of particles for thin film samples were higher than that in cluster samples. For the CNT growth, the density of the growth was believed to be higher for thin film samples than cluster samples. Raman spectroscopy was used to investigate the quality of CNT.

  11. Oxygen electro-reduction catalysts for self-assembly on supports

    NASA Astrophysics Data System (ADS)

    Dougan, Jennifer; Panton, Raquel; Cheng, Qiling; Gervasio, Don F.

    2005-01-01

    A new strategy for making low cost, catalytic electrodes is being developed for fuel-cells and electrochemical sensors. The strategy is to synthesize a macrocyclic catalyst derivatized with a functional group (like phosphate or carboxylate), which has affinity for a metal-oxide/metal surface. The purpose of the functional group is to anchor the modified catalyst to the metal surface, thereby promoting the formation of a self-assembled monolayer (SAM) of catalyst on a metal support. Syntheses are given for new ferrocene compounds and metallo porphyrins with anchor groups. The ferrocenes, which are relatively easy to synthesize, were made to learn how to form a stable SAM on a metal-oxide/metal surface. The metallo porphyrins were made for catalyzing oxygen electro-reduction with no platinum. Strategies for attaining an ideal catalytic electrode are discussed.

  12. Enhanced Activity of Supported Ni Catalysts Promoted by Pt for Rapid Reduction of Aromatic Nitro Compounds

    PubMed Central

    Shang, Huishan; Pan, Kecheng; Zhang, Lu; Zhang, Bing; Xiang, Xu

    2016-01-01

    To improve the activities of non-noble metal catalysts is highly desirable and valuable to the reduced use of noble metal resources. In this work, the supported nickel (Ni) and nickel-platinum (NiPt) nanocatalysts were derived from a layered double hydroxide/carbon composite precursor. The catalysts were characterized and the role of Pt was analysed using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS) mapping, and X-ray photoelectron spectroscopy (XPS) techniques. The Ni2+ was reduced to metallic Ni0 via a self-reduction way utilizing the carbon as a reducing agent. The average sizes of the Ni particles in the NiPt catalysts were smaller than that in the supported Ni catalyst. The electronic structure of Ni was affected by the incorporation of Pt. The optimal NiPt catalysts exhibited remarkably improved activity toward the reduction of nitrophenol, which has an apparent rate constant (Ka) of 18.82 × 10−3 s−1, 6.2 times larger than that of Ni catalyst and also larger than most of the reported values of noble-metal and bimetallic catalysts. The enhanced activity could be ascribed to the modification to the electronic structure of Ni by Pt and the effect of exposed crystal planes. PMID:28335231

  13. Enhanced Activity of Supported Ni Catalysts Promoted by Pt for Rapid Reduction of Aromatic Nitro Compounds.

    PubMed

    Shang, Huishan; Pan, Kecheng; Zhang, Lu; Zhang, Bing; Xiang, Xu

    2016-06-04

    To improve the activities of non-noble metal catalysts is highly desirable and valuable to the reduced use of noble metal resources. In this work, the supported nickel (Ni) and nickel-platinum (NiPt) nanocatalysts were derived from a layered double hydroxide/carbon composite precursor. The catalysts were characterized and the role of Pt was analysed using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), energy dispersive X-ray spectroscopy (EDS) mapping, and X-ray photoelectron spectroscopy (XPS) techniques. The Ni(2+) was reduced to metallic Ni⁰ via a self-reduction way utilizing the carbon as a reducing agent. The average sizes of the Ni particles in the NiPt catalysts were smaller than that in the supported Ni catalyst. The electronic structure of Ni was affected by the incorporation of Pt. The optimal NiPt catalysts exhibited remarkably improved activity toward the reduction of nitrophenol, which has an apparent rate constant (Ka) of 18.82 × 10(-3) s(-1), 6.2 times larger than that of Ni catalyst and also larger than most of the reported values of noble-metal and bimetallic catalysts. The enhanced activity could be ascribed to the modification to the electronic structure of Ni by Pt and the effect of exposed crystal planes.

  14. Studies of supported hydrodesulfurization catalysts. Final technical report

    SciTech Connect

    Hercules, D.M.

    1995-10-26

    This report describes a series of studies on the following: Mo/titania and Mo/alumina catalysts for thiophene hydrodesulfurization; absorption of metal oxyanion on alumina; particle size effects for Co/silica catalyst for CO hydrogenation; correlation of Mo oxidation states with benzene hydrogenation activity; factor analysis for curve fitting Mo ESCA spectra; and quantitative Raman and ESCA characterization of W/titania catalysts. 27 refs.

  15. Dearomatization of jet fuel on irradiated platinum-supported catalyst

    NASA Astrophysics Data System (ADS)

    Múčka, V.; Ostrihoňová, A.; Kopernický, I.; Mikula, O.

    The effect of ionizing radiation ( 60Co γ-rays) on Pt-supported catalyst used for the dearomatization of jet fuel with distillation in the range 395-534 K has been studied. Pre-irradiation of the catalyst with doses in the range 10 2-5 × 10 4 Gy leads to the partial catalyst activation. Irradiation of the catalyst enhances its resistance to catalyst poisons, particularly to sulphur-compounds, and this is probably the reason for its catalytic activity being ˜60-100% greater than that of un-irradiated catalyst. Optimum conditions for dearomatization on the irradiated catalyst were found and, by means of a rotary three-factorial experiment, it was shown that these lie at lower temperatures and lower pressures than those for un-irradiated catalyst.

  16. Laser synthesis of Pt, Pd, CoO and Pd-CoO nanoparticle catalysts supported on graphene

    NASA Astrophysics Data System (ADS)

    Moussa, Sherif; Abdelsayed, Victor; Samy El-Shall, M.

    2011-07-01

    We have developed a facile laser reduction method for the synthesis of transition metal nanoparticle catalysts supported on reduced graphene oxide (RGO) sheets. Using 532 or 355 nm laser irradiation of a mixture of graphene oxide and metal ion precursors in water, we report the photocatalytic reduction of the metal ions simultaneously with the partial reduction of GO, and the synthesis of metal nanoparticle catalysts well-dispersed and supported on the reduced GO. The Pd-CoO composite nanoparticles were found to have significantly enhanced activity for CO oxidation over both the Pd and the CoO catalysts. The simple synthesis method without chemical reducing agents, the formation of alloy nanoparticles with variable catalyst loading and composition, and the low cost of GO could enhance the commercial viability of these supported catalysts.

  17. An exploratory program for using hydrous metal oxide ion exchangers as Fischer-Tropsch catalysts

    SciTech Connect

    Lynch, A.W.; Dosch, R.G.; Sault, A.G.

    1990-01-01

    The purpose of this program is to investigate the potential of hydrous metal oxide (HMO) ion exchangers, invented at Sandia National Laboratories, as Fischer-Tropsch (F-T) catalysts. Metals known to be active in F-T synthesis (e.g. Fe, Co) were ion exchanged on hydrous metal oxide supports. Although HMO catalysts based on Zr, Nb, and Ta have been investigated in direct coal liquefaction studies, this effect focused on formulations based on the hydrous titanium oxide (HTO) system. The program has the goals of developing a catalyst with (1) high activity, (2) selectively to fuel range or other useful products, and (3) better properties for use in slurry reactors. The program has three main tasks: (1) catalyst synthesis, to develop methods for preparing catalysts having desirable F-T properties, (2) characterization, to investigate catalysts proving to have desirable properties by a variety of analytical techniques to determine correlations between activity and material properties and (3) testing to determine activity and selectivity of catalysts. This paper discussed results of activity testing of Ruhrchemie catalyst and some catalyst formulations prepared using ion exchange on hydrous titanium oxide and precipitation. For example, at 250{degree}C the Ruhrchemie catalyst converts {approximately}50% of the syngas feed to reaction products. In comparison, iron catalysts prepared by ion exchange and precipitation had conversions ranging from 20 to 50% over a temperature range of 250 to 275{degree}C of the syngas feed. In addition, results are Auger surface analysis of Ruhrchemie catalyst are presented. 6 refs., 2 figs., 2 tabs.

  18. 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.

  19. Comparative Study of Catalysts containing Transition Metals in Production of Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Vesselényi, I.; Niesz, K.; Kónya, Z.; Nagy, J. B.; Kiricsi, I.

    2002-10-01

    For production of multiwall carbon nanotubes (MWNT) by catalytic chemical vapour deposition (CCVD) different transition metals supported on amorphous or crystalline oxides such as silica, alumina or zeolites were used. In several cases both the productivity of catalysts and the quality of MWNT are improved by using bimetallic catalysts such as Co-Fe, Co-V etc. In this publication we report the results in comparison of mono and bimetallic catalysts of Co, Fe, Ni and V supported on alumina, zeolite 13X-FAU and zeolite ZSM-5-MFI.

  20. Ionic-liquid-supported (ILS) catalysts for asymmetric organic synthesis.

    PubMed

    Ni, Bukuo; Headley, Allan D

    2010-04-19

    The asymmetric synthesis of compounds that contain new C-C and C-O bonds remains one of the most important types of synthesis in organic chemistry. Over the years, many different types of catalysts have been designed and used effectively to carry out such transformations. Ionic-liquid-supported (ILS) catalysts represent a new and very effective class of catalysts that are used to facilitate the asymmetric synthesis of such compounds. There are many advantages to using ILS catalysts; they are nontoxic, environmentally benign, and, most important, recyclable. An overview of the design, synthesis, mode of action, and effectiveness of this class of catalysts is reported.

  1. Characterizing substrate–surface interactions on alumina-supported metal catalysts by dynamic nuclear polarization-enhanced double-resonance NMR spectroscopy [Characterizing substrate-surface interactions on alumina supported metal catalysts by DNP-enhanced double-resonance NMR spectroscopy

    DOE PAGES

    Perras, Frederic A.; Padmos, J. Daniel; Johnson, Robert L.; ...

    2017-01-23

    The characterization of nanometer-scale interactions between carbon-containing substrates and alumina surfaces is of paramount importance to industrial and academic catalysis applications, but it is also very challenging. Here, we demonstrate that dynamic nuclear polarization surface-enhanced NMR spectroscopy (DNP SENS) allows the unambiguous description of the coordination geometries and conformations of the substrates at the alumina surface through high-resolution measurements of 13C–27Al distances. We apply this new technique to elucidate the molecular-level geometry of 13C-enriched methionine and natural abundance poly(vinyl alcohol) adsorbed on γ-Al2O3-supported Pd catalysts, and we support these results with element-specific X-ray absorption near-edge measurements. Furthermore, this work clearlymore » demonstrates a surprising bimodal coordination of methionine at the Pd–Al2O3 interface.« less

  2. Development of catalytically active and highly stable catalyst supports for polymer electrolyte membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Kim, Taekeun; Xie, Tianyuan; Jung, Wonsuk; Gadala-Maria, Francis; Ganesan, Prabhu; Popov, Branko N.

    2015-01-01

    Novel procedures are developed for the synthesis of highly stable carbon composite catalyst supports (CCCS-800 °C and CCCS-1100 °C) and an activated carbon composite catalyst support (A-CCCS). These supports are synthesized through: (i) surface modification with acids and inclusion of oxygen groups, (ii) metal-catalyzed pyrolysis, and (iii) chemical leaching to remove excess metal used to dope the support. The procedure results in increasing carbon graphitization and inclusion of non-metallic active sites on the support surface. Catalytic activity of CCCS indicates an onset potential of 0.86 V for the oxygen reduction reaction (ORR) with well-defined kinetic and mass-transfer regions and ∼2.5% H2O2 production in rotating ring disk electrode (RRDE) studies. Support stability studies at 1.2 V constant potential holding for 400 h indicate high stability for the 30% Pt/A-CCCS catalyst with a cell potential loss of 27 mV at 800 mA cm-2 under H2-air, 32% mass activity loss, and 30% ECSA loss. Performance evaluation in polymer electrolyte membrane (PEM) fuel cell shows power densities (rated) of 0.18 and 0.23 gPt kW-1 for the 30% Pt/A-CCCS and 30% Pt/CCCS-800 °C catalysts, respectively. The stabilities of various supports developed in this study are compared with those of a commercial Pt/C catalyst.

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

    SciTech Connect

    Wu, Xi.

    1990-09-21

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

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

    DOEpatents

    Marks, Tobin J [Evanston, IL; Rodriguez, Brandon A [Evanston, IL; Delferro, Massimiliano [Chicago, IL

    2012-08-07

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

  5. A Catalyst for Collaboration: Supporting Technology in Teaching through Partnerships.

    ERIC Educational Resources Information Center

    Alway, Mark; Lewis, Tom; Macklin, Scott

    The Web-based Catalyst Initiative was created at the University of Washington (UW) to support innovation in teaching through technology. The approach utilizes participatory design techniques in the development of next generation technologies in order to scale beyond early to second wave adopters. Catalyst is the product of a support strategy that…

  6. Doped palladium containing oxidation catalysts

    SciTech Connect

    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.

  7. 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).

  8. 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

  9. 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

    2014-04-03

    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.

  10. Single-Atom Catalysts of Precious Metals for Electrochemical Reactions.

    PubMed

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

    2017-09-11

    Single-atom catalysts (SACs), in which metal atoms are dispersed on the support without forming nanoparticles, have been used for various heterogeneous reactions and most recently for electrochemical reactions. In this Minireview, recent examples of single-atom electrocatalysts used for the oxygen reduction reaction (ORR), hydrogen oxidation reaction (HOR), hydrogen evolution reaction (HER), formic acid oxidation reaction (FAOR), and methanol oxidation reaction (MOR) are introduced. Many density functional theory (DFT) simulations have predicted that SACs may be effective for CO2 reduction to methane or methanol production while suppressing H2 evolution, and those cases are introduced here as well. Single atoms, mainly Pt single atoms, have been deposited on TiN or TiC nanoparticles, defective graphene nanosheets, N-doped covalent triazine frameworks, graphitic carbon nitride, S-doped zeolite-templated carbon, and Sb-doped SnO2 surfaces. Scanning transmission electron microscopy, extended X-ray absorption fine structure measurement, and in situ infrared spectroscopy have been used to detect the single-atom structure and confirm the absence of nanoparticles. SACs have shown high mass activity, minimizing the use of precious metal, and unique selectivity distinct from nanoparticle catalysts owing to the absence of ensemble sites. Additional features that SACs should possess for effective electrochemical applications were also suggested. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. 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)

  12. 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.

  13. Hydrogenation of artemisinin to dihydroartemisinin over heterogeneous metal catalysts

    NASA Astrophysics Data System (ADS)

    Kristiani, Anis; Pertiwi, Ralentri; Adilina, Indri Badria

    2017-01-01

    A series of heterogeneous metal catalysts of Ni, Pd, and Pt, both of synthesized and commercial catalysts were used for hydrogenation of artemisinin to dihydroartemisinin. Their catalytic properties were determsined by Surface Area Analyzer and Thermogravimetry Analyzer. The catalytic properties in various reaction conditions in terms of temperature, pressure, reaction time and reactant/catalyst ratio were also studied. The results catalytic activity tests showed that synthesized catalysts of Ni/zeolite, Ni-Sn/zeolite, Ni/bentonite and Ni-Sn/bentonite were not able to produced dihydroartemisinin and deoxyartemisinin was mainly formed. Meanwhile, commercial catalysts of Ni skeletal, Pd/activated charcoal and Pt/activated charcoal yielded the desired dihydroartemisinin product. Ni skeletal commercial catalyst gave the best performance of hydrogenation artemisinin to dihydroartemisinin in room temperature and low H2 pressure.

  14. 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.

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

    PubMed

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

    2014-10-07

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

  16. 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

  17. The role of catalyst support in carbon nanotube synthesis

    NASA Astrophysics Data System (ADS)

    Siska, Andrea; Hernadi, Klara; Kiricsi, Imre; Rojik, Imre; Nagy, Janos B.

    1998-08-01

    Acetylene decomposition over supported cobalt (or iron) catalysts proved to be an effective method for the preparation of well-graphitized carbon nanotubes. Compared to other techniques, catalytic synthesis is operated under relatively mild reaction conditions (700 °C, atmospheric pressure) and experimental apparatus is very simple. In order to improve catalyst performance, we try to understand the reaction mechanism. Catalysts were prepared by the impregnation method using different materials as catalyst support. Physico-chemical characterization of the samples were carried out by XRD, IR, etc. Surface acidity was measured by pyridine adsorption technique. Catalyst samples were tested in the decomposition of acetylene in a fixed bed flow reactor at 722 °C. The quantity of carbon deposit was weighted (catalyst activity). The quality of carbon nanotubes produced was characterized by means of transmission electron microscopy.

  18. Membrane fuel cell cathode catalysts based on titanium oxide supported platinum nanoparticles.

    PubMed

    Gebauer, Christian; Jusys, Zenonas; Wassner, Maximilian; Hüsing, Nicola; Behm, R Jürgen

    2014-07-21

    The potential of platinum catalysts supported on pure, nitrogen-, or carbon-doped titania for application in the oxygen reduction reaction (ORR), as a cathode catalyst in polymer electrolyte membrane fuel cells, is investigated. The oxide supports are synthesized by using a sol-gel route. Modification with nitrogen and carbon doping is achieved by thermal decomposition of urea and the structure-directing agent P123. Platinum nanoparticles are prepared by reduction of a Pt(IV) salt in ethylene glycol and subsequently immobilized on different support materials. Structural and electronic properties of the support materials and the resulting catalysts are characterized by various methods, including X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. These results and electrochemical characterization of the support materials and platinum nanoparticle catalysts indicate distinct support effects in the catalysts. The electrocatalytic performance of these catalysts in the ORR, as determined in rotating ring disc electrode measurements, is promising. Also here, distinct support effects can be identified. Correlations with the structural/electronic and the electrochemical properties are discussed, as well as the role of metal-support interactions.

  19. 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.

  20. Dynamic structural disorder in supported nanoscale catalysts

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    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.

  1. 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.

  2. 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.

  3. 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

  4. Titania-Supported Catalysts for Levulinic Acid Hydrogenation: Influence of Support and its Impact on γ-Valerolactone Yield.

    PubMed

    Ruppert, A M; Grams, J; Jędrzejczyk, M; Matras-Michalska, J; Keller, N; Ostojska, K; Sautet, P

    2015-05-11

    A series of titania-supported ruthenium and platinum catalysts was investigated in the levulinic acid hydrogenation towards γ-valerolactone, a key reaction for the catalytic transformation of biomass. It was shown that various morphologies and phases of titania strongly influence the physicochemical and catalytic properties of supported Ru and Pt catalysts in different ways. In the case of the catalyst supported on mixed TiO2 phases, Ru particles are exclusively located on the minority rutile crystallites, whereas such an effect was not observed for platinum. The platinum catalyst activity could be increased when the metal was dispersed on the large surface-area anatase, which was not the case for ruthenium as a result of its agglomeration on this support. The activity of ruthenium on anatase could be increased in two ways: a) when RuO2 formation during catalyst preparation was avoided; b) when pure anatase support material was modified so that it exhibited no microporosity. The obtained results allow a better understanding of the role of the support for Ru and Pt catalysts.

  5. 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

    2015-11-04

    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.

  6. 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.

  7. X-ray characterization of platinum group metal catalysts

    NASA Astrophysics Data System (ADS)

    Peterson, Eric J.

    Platinum group metals (PGMs) are used extensively as catalysts, employed in several sectors of the world energy economy. Fuel cells employing PGM catalysts show promise as power sources in the proposed hydrogen economy, using alcohols as hydrogen storage media. Currently, the most economically important application for PGMs is for the mitigation of emissions from internal combustion engines via catalytic converters. In all applications, efficient use of these expensive metals to fabricate robust catalysts is of the utmost importance. Understanding the catalyst structure/property relationship is the key to the improvement of existing catalysts and the discovery of new catalysts. For example, catalyst particle size can have profound effects on catalyst activity, as in the case of gold nanoparticles. Catalyst particle size control and stability is also important for the efficient use of PGM metals and catalyst deactivation prevention. The challenge is to identify and characterize structural features and determine if and how these features may relate to catalytic properties. The ultimate goal is to simultaneously measure catalyst structural characteristics and catalytic properties under operando conditions, unambiguously establishing the structure/property link. X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) are important techniques used for the characterization of PGM catalysts. Microstructural information such as crystallite size, as small as ~ 1 nm, and microstrain can be obtained from Bragg diffraction peak shapes in X-ray diffraction patterns, and long range crystal structure information is found in the intensities and positions of these peaks. In contrast, X-ray absorption spectroscopy provides information about the chemical state and local structure of selected atoms. From the average nearest neighbor coordination numbers, crystallite sizes can also be inferred, with particularly high sensitivity in the sub-nm size range. Electron microscopy

  8. 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

  9. 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.

  10. Hydrous metal oxide catalysts for oxidation of hydrocarbons

    SciTech Connect

    Miller, J.E.; Dosch, R.G.; McLaughlin, L.I.

    1993-07-01

    This report describes work performed at Sandia under a CRADA with Shell Development of Houston, Texas aimed at developing hydrous metal oxide (HMO) catalysts for oxidation of hydrocarbons. Autoxidation as well as selective oxidation of 1-octene was studied in the presence of HMO catalysts based on known oxidation catalysts. The desired reactions were the conversion of olefin to epoxides, alcohols, and ketones, HMOs seem to inhibit autoxidation reactions, perhaps by reacting with peroxides or radicals. Attempts to use HMOs and metal loaded HMOs as epoxidation catalysts were unsuccessful, although their utility for this reaction was not entirely ruled out. Likewise, alcohol formation from olefins in the presence of HMO catalysts was not achieved. However, this work led to the discovery that acidified HMOs can lead to carbocation reactions of hydrocarbons such as cracking. An HMO catalyst containing Rh and Cu that promotes the reaction of {alpha}-olefins with oxygen to form methyl ketones was identified. Although the activity of the catalyst is relatively low and isomerization reactions of the olefin simultaneously occur, results indicate that these problems may be addressed by eliminating mass transfer limitations. Other suggestions for improving the catalyst are also made. 57 refs.

  11. 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.

  12. 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

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

    DOEpatents

    Ragle, Christie Susan [Havana, IL; Silver, Ronald G [Peoria, IL; Zemskova, Svetlana Mikhailovna [Edelstein, IL; Eckstein, Colleen J [Metamora, IL

    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.

  14. 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.

  15. Characterisation of the surface of freshly prepared precious metal catalysts.

    PubMed

    Parker, Stewart F; Adroja, Devashibhai; Jiménez-Ruiz, Mónica; Tischer, Markus; Möbus, Konrad; Wieland, Stefan D; Albers, Peter

    2016-07-14

    A combination of electron microscopy, X-ray and neutron spectroscopies and computational methods has provided new insights into the species present on the surface of freshly prepared precious metal catalysts. The results show that in all cases, at least half of the surface is metallic or nearly so, with the remainder covered by oxygen, largely as hydroxide. Water is also present and is strongly held; weeks of pumping under high vacuum is insufficient to remove it. The hydroxyls are reactive as shown by their reaction with or displacement by CO and can be removed by hydrogenation. This clearly has implications for how precious metal catalysts are activated after preparation.

  16. 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

    2016-07-04

    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.

  17. 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.

  18. KF-loaded mesoporous Mg-Fe bi-metal oxides: high performance transesterification catalysts for biodiesel production.

    PubMed

    Tao, Guiju; Hua, Zile; Gao, Zhe; Zhu, Yan; Zhu, Yan; Chen, Yu; Shu, Zhu; Zhang, Lingxia; Shi, Jianlin

    2013-09-21

    Using newly developed mesoporous Mg-Fe bi-metal oxides as supports, a novel kind of high performance transesterification catalysts for biodiesel production has been synthesized. More importantly, the impregnation solvent was for the first time found to substantially affect the structures and catalytic performances of the resultant transesterification catalysts.

  19. 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.

  20. 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.

  1. Hydrodechlorination of polychlorinated molecules using transition metal phosphide catalysts.

    PubMed

    Cecilia, J A; Infantes-Molina, A; Rodríguez-Castellón, E

    2015-10-15

    Ni2P and CoP catalysts (5 wt.% of metal) supported on a commercial SiO2 were tested in the gas phase catalytic hydrodechlorination (HDCl) of mono (chlorobenzene-ClB) and polychlorobenzenes (PCBs) (1,2- dichlorobenzene (1,2-DClB), 1,3-dichlorobenzene (1,3-DClB), 1,4-dichlorobenzene (1,4-DClB), and 1,2,4-trichlorobenzene (1,2,4-TClB)) at atmospheric pressure. It was investigated how the number and position of chlorine atoms in the molecule influence the HDCl activity. The prepared catalysts were characterized by X-ray diffraction (XRD), CO chemisorption, N2 adsorption-desorption at -196°C, and X-ray photoelectron spectroscopy (XPS). Characterization results indicated better active phase dispersion and greater amount of P on the Ni2P catalyst surface. Catalytic results showed that the Ni2P was more active and stable in this type of reactions. The hydrodechlorination activity decreased by increasing the number of chlorine atoms in the molecule and chlorine substituents in close proximity. The observed trend in the HDCl activity was: ClB>1,4-DClB>1,3-DClB>1,2-DClB>1,2,4-TClB. The exception was the catalytic response after 24h on stream observed for the Ni2P in the HDCl reaction of 1,2,4-TClB, which was equal to that observed for the 1,4-DClB molecule, and also yielding benzene as the main reaction product. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Nafion induced surface confinement of oxygen in carbon-supported oxygen reduction catalysts

    SciTech Connect

    Chlistunoff, Jerzy; Sansinena, Jose -Maria

    2016-11-17

    We studied the surface confinement of oxygen inside layers of Nafion self-assembled on carbon-supported oxygen reduction reaction (ORR) catalysts. It is demonstrated that oxygen accumulates in the hydrophobic component of the polymer remaining in contact with the carbon surface. Furthermore, the amount of surface confined oxygen increases with the degree of carbon surface graphitization, which promotes the self-assembly of the polymer. Planar macrocyclic ORR catalysts possessing a delocalized system of π electrons such as Co and Fe porphyrins and phthalocyanines have virtually no effect on the surface confinement of oxygen, in accordance with their structural similarity to graphitic carbon surfaces where they adsorb. Platinum particles in carbon-supported ORR catalysts with high metal contents (20%) disrupt the self-assembly of Nafion and virtually eliminate the oxygen confinement, but the phenomenon is still observed for low Pt loading (4.8%) catalysts.

  3. Nafion induced surface confinement of oxygen in carbon-supported oxygen reduction catalysts

    DOE PAGES

    Chlistunoff, Jerzy; Sansinena, Jose -Maria

    2016-11-17

    We studied the surface confinement of oxygen inside layers of Nafion self-assembled on carbon-supported oxygen reduction reaction (ORR) catalysts. It is demonstrated that oxygen accumulates in the hydrophobic component of the polymer remaining in contact with the carbon surface. Furthermore, the amount of surface confined oxygen increases with the degree of carbon surface graphitization, which promotes the self-assembly of the polymer. Planar macrocyclic ORR catalysts possessing a delocalized system of π electrons such as Co and Fe porphyrins and phthalocyanines have virtually no effect on the surface confinement of oxygen, in accordance with their structural similarity to graphitic carbon surfacesmore » where they adsorb. Platinum particles in carbon-supported ORR catalysts with high metal contents (20%) disrupt the self-assembly of Nafion and virtually eliminate the oxygen confinement, but the phenomenon is still observed for low Pt loading (4.8%) catalysts.« less

  4. 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…

  5. 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…

  6. 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.

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

    PubMed

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

    2016-06-25

    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.

  8. 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...

  9. Design of hybrid titania nanocrystallites as supports for gold catalysts.

    PubMed

    Mendez, Violaine; Caps, Valérie; Daniele, Stéphane

    2009-06-07

    Citrate-functionalized titania nanocrystallites are successfully synthesized from a heteroleptic titanium alkoxide precursor in a low temperature, hydrolytic process and used as gold catalyst supports for CO oxidation and aerobic stilbene epoxidation.

  10. 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...

  11. 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.

  12. 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.

  13. Microbial recovery of metals from spent catalysts. Quarterly report, July--September 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. 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. 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.

  14. High-quality bio-oil from one-pot catalytic hydrocracking of kraft lignin over supported noble metal catalysts in isopropanol system.

    PubMed

    Yang, Jing; Zhao, Liang; Liu, Shaotong; Wang, Yuanyuan; Dai, Liyi

    2016-07-01

    Catalytic hydrocracking of kraft lignin was carried out in isopropanol system and an orthogonal array design (OAD) was employed to optimize the experimental conditions. GC-MS/FID, elemental analysis, GPC and (1)H-(13)C HSQC NMR were carried out for entire investigation of the liquid products. The results indicated that the hydrocracking process was thermally controlled and catalysts showed significant influences on the product distributions. Comparing with Pd/C, Pt/C and Ru/C, Rh/C inhibited the self-condensation of isopropanol and reduced the formation of oxygenic-chain compounds. The excellent catalytic activity for phenols conversion was obtained over Rh/C. The routes of oxygenic-chain compounds formation and phenol conversion were proposed in detail. The least oxygenic-chain compounds formation, the highest phenols conversion (93.4%), the lowest O/C ratio (0.094) and the highest HHV (37.969MJ/kg) provided the possibility of the high quality bio-oil obtained over Rh/C in isopropanol medium. Copyright © 2016 Elsevier Ltd. All rights reserved.

  15. 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.

  16. 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.

  17. 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

    2016-08-30

    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.

  18. 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.

  19. Tungsten materials as durable catalyst supports for fuel cell electrodes

    NASA Astrophysics Data System (ADS)

    Perchthaler, M.; Ossiander, T.; Juhart, V.; Mitzel, J.; Heinzl, C.; Scheu, C.; Hacker, V.

    2013-12-01

    Durable platinum catalyst support materials, e.g. tungsten carbide (WC), tungsten oxide (WOx) and self-synthesized tungsten oxide (WOxs) were evaluated for the use in High-Temperature Proton Exchange Fuel Cells (HT-PEM) based on phosphoric acid doped polybenzimidazole as electrolyte. The support materials and the catalyst loaded support materials were characterized ex-situ by cyclic voltammetry in HClO4, potential cycling, CO-stripping, electron microscopy and X-ray diffraction measurements. The tungsten oxide and tungsten carbide based supported catalysts were compared to High Surface Area Carbon (HSAC), each coated with platinum via the same in-house manufacturing procedures. The in-house manufacturing procedures resulted in catalyst particle sizes on HSAC of 3-4 nm with a uniform distribution. The in-situ Potential Cycling experiments of WOx or WOxs supported catalysts showed much lower degradation rates compared to High Surface Area Carbons. The formation of WOx species on WC was proven by ex- and in-situ cyclic voltammetric studies and thermogravimetric analyses. X-ray diffraction, ex-situ cyclic voltammetry and in-situ cyclic voltammetry showed that WOx is formed from WC as starting material under oxidizing conditions. Finally a 1000 h durability test with WOx as catalyst support material on the anode was done in a HT-PEM fuel cell with reformed methanol on the anode.

  20. 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.

  1. Highly Efficient Transition Metal Nanoparticle Catalysts in Aqueous Solutions.

    PubMed

    Wang, Changlong; Ciganda, Roberto; Salmon, Lionel; Gregurec, Danijela; Irigoyen, Joseba; Moya, Sergio; Ruiz, Jaime; Astruc, Didier

    2016-02-24

    A ligand design is proposed for transition metal nanoparticle (TMNP) catalysts in aqueous solution. Thus, a tris(triazolyl)-polyethylene glycol (tris-trz-PEG) amphiphilic ligand, 2, is used for the synthesis of very small TMNPs with Fe, Co, Ni, Cu, Ru, Pd, Ag, Pt, and Au. These TMNP-2 catalysts were evaluated and compared for the model 4-nitrophenol reduction, and proved to be extremely efficient. High catalytic efficiencies involving the use of only a few ppm metal of PdNPs, RuNPs, and CuNPs were also exemplified in Suzuki-Miyaura, transfer hydrogenation, and click reactions, respectively.

  2. 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.

  3. Characteristics of Polyaniline Cobalt Supported Catalysts for Epoxidation Reactions

    PubMed Central

    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. PMID:24701183

  4. Catalytic performance of activated carbon supported cobalt catalyst for CO2 reforming of CH4.

    PubMed

    Zhang, Guojie; Su, Aiting; Du, Yannian; Qu, Jiangwen; Xu, Ying

    2014-11-01

    Syngas production by CO2 reforming of CH4 in a fixed bed reactor was investigated over a series of activated carbon (AC) supported Co catalysts as a function of Co loading (between 15 and 30wt.%) and calcination temperature (Tc=300, 400 or 500°C). The catalytic performance was assessed through CH4 and CO2 conversions and long-term stability. XRD and SEM were used to characterize the catalysts. It was found that the stability of Co/AC catalysts was strongly dependent on the Co loading and calcination temperature. For the loadings (25wt.% for Tc=300°C), stable activities have been achieved. The loading of excess Co (>wt.% 25) causes negative effects not only on the performance of the catalysts but also on the support surface properties. In addition, the experiment showed that ultrasound can enhance and promote dispersion of the active metal on the carrier, thus improving the catalytic performance of the catalyst. The catalyst activity can be long-term stably maintained, and no obvious deactivation has been observed in the first 2700min. After analyzing the characteristics, a reaction mechanism for CO2 reforming of CH4 over Co/AC catalyst was proposed. Copyright © 2014 Elsevier Inc. All rights reserved.

  5. Synthesis and Characterization of Organo-Rare-Earth Metal Monoalkyl Complexes Supported by Carbon σ-Bonded Indolyl Ligands: High Specific Isoprene 1,4-Cis Polymerization Catalysts.

    PubMed

    Guo, Liping; Zhu, Xiancui; Zhang, Guangchao; Wei, Yun; Ning, Lixin; Zhou, Shuangliu; Feng, Zhijun; Wang, Shaowu; Mu, Xiaolong; Chen, Jun; Jiang, Yuzhe

    2015-06-15

    A series of N-protected 3-imino-functionalized indolyl ligands 1-R-3-(R'N═CH)C8H5N [R = Bn, R' = 2,6-(i)Pr2C6H3 (HL(1)); R = CH3, R' = 2,6-(i)Pr2C6H3 (HL(2)); R = Bn, R' = (t)Bu (HL(3))] and 1-CH3-2-(2,6-(i)Pr2C6H3N═CH)C8H5N (HL(4)) was prepared via reactions of N-protected indolyl aldehydes with corresponding amines. The C-H σ-bond metathesis followed by alkane elimination reactions between RE(CH2SiMe3)3(thf)2 and HL(1)-HL(3) afforded the carbon σ-bonded indolyl-ligated rare-earth metal monoalkyl complexes. Reactions of RE(CH2SiMe3)3(thf)2 with 2 equiv of HL(1) or HL(2) gave the carbon σ-bonded indolyl-ligated rare-earth metal monoalkyl complexes L(1)2RECH2SiMe3 (RE = Y(1), Er(2), Dy(3)) and L(2)2RECH2SiMe3 (RE = Y(5), Er(6), Dy(7), Yb(8)), while reaction of Yb(CH2SiMe3)3(thf)2 with 2 equiv of HL(1) afforded the ytterbium dialkyl complex L(1)Yb(CH2SiMe3)2(thf)2 (4). Reactions of RE(CH2SiMe3)3(thf)2 with HL(3) gave the tris(heteroaryl) rare-earth metal complexes L(3)3RE (RE = Y(9), Er(10)). In the presence of cocatalysts, the rare-earth metal monoalkyl complexes initiated isoprene polymerization with a high activity (90% conversion of 1000 equiv of isoprene in 25 min) producing polymers with high regio- and stereoselectivity (1,4-cis polymers up to 99%).

  6. Current advances in precious metal core–shell catalyst design

    PubMed Central

    Wang, Xiaohong; He, Beibei; Hu, Zhiyu; Zeng, Zhigang; Han, Sheng

    2014-01-01

    Precious metal nanoparticles are commonly used as the main active components of various catalysts. Given their high cost, limited quantity, and easy loss of catalytic activity under severe conditions, precious metals should be used in catalysts at low volumes and be protected from damaging environments. Accordingly, reducing the amount of precious metals without compromising their catalytic performance is difficult, particularly under challenging conditions. As multifunctional materials, core–shell nanoparticles are highly important owing to their wide range of applications in chemistry, physics, biology, and environmental areas. Compared with their single-component counterparts and other composites, core–shell nanoparticles offer a new active interface and a potential synergistic effect between the core and shell, making these materials highly attractive in catalytic application. On one hand, when a precious metal is used as the shell material, the catalytic activity can be greatly improved because of the increased surface area and the closed interfacial interaction between the core and the shell. On the other hand, when a precious metal is applied as the core material, the catalytic stability can be remarkably improved because of the protection conferred by the shell material. Therefore, a reasonable design of the core–shell catalyst for target applications must be developed. We summarize the latest advances in the fabrications, properties, and applications of core–shell nanoparticles in this paper. The current research trends of these core–shell catalysts are also highlighted. PMID:27877695

  7. Current advances in precious metal core-shell catalyst design.

    PubMed

    Wang, Xiaohong; He, Beibei; Hu, Zhiyu; Zeng, Zhigang; Han, Sheng

    2014-08-01

    Precious metal nanoparticles are commonly used as the main active components of various catalysts. Given their high cost, limited quantity, and easy loss of catalytic activity under severe conditions, precious metals should be used in catalysts at low volumes and be protected from damaging environments. Accordingly, reducing the amount of precious metals without compromising their catalytic performance is difficult, particularly under challenging conditions. As multifunctional materials, core-shell nanoparticles are highly important owing to their wide range of applications in chemistry, physics, biology, and environmental areas. Compared with their single-component counterparts and other composites, core-shell nanoparticles offer a new active interface and a potential synergistic effect between the core and shell, making these materials highly attractive in catalytic application. On one hand, when a precious metal is used as the shell material, the catalytic activity can be greatly improved because of the increased surface area and the closed interfacial interaction between the core and the shell. On the other hand, when a precious metal is applied as the core material, the catalytic stability can be remarkably improved because of the protection conferred by the shell material. Therefore, a reasonable design of the core-shell catalyst for target applications must be developed. We summarize the latest advances in the fabrications, properties, and applications of core-shell nanoparticles in this paper. The current research trends of these core-shell catalysts are also highlighted.

  8. Next Generation Catalyst Engineering via Support Modification

    DTIC Science & Technology

    2016-01-21

    composition are independent of the amount of nitrogen present. After cycling to 1.1 V, low implantation dose (5- 15 s) resulted in poor stability while...Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 fuel cell, electrochemistry, electrocatalysis, carbon, platinum, nitrogen doping...focused on the development and characterization of nitrogen -doped catalysts in membrane electrode assemblies (MEAs) for single-cell acid and alkaline

  9. 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.

  10. 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.

  11. Copper catalysts for soot oxidation: alumina versus perovskite supports.

    PubMed

    López-Suárez, F E; Bueno-López, A; Illán-Gómez, M J; Adamski, A; Ura, B; Trawczynski, J

    2008-10-15

    Copper catalysts prepared using four supports (Mg- and Sr-modified Al2O3 and MgTiO3 and SrTiO3 perovskites) have been tested for soot oxidation by 02 and NOx/O2. Among the catalysts studied, Cu/SrTiO3 is the most active for soot oxidation by NOx/O2 and the support affects positively copper activity. With this catalyst, and under the experimental conditions used, the soot combustion by NOx/O2 presents a considerable rate from 500 degrees C (100 degrees C below the uncatalysed reaction). The Cu/ SrTiO3 catalyst is also the most effective for NOx chemisorption around 425 degrees C. The best activity of Cu/SrTiO3 can be attributed to the improved redox properties of copper originated by Cu-support interactions. This seems to be related to the presence of weakly bound oxygen on this sample. The copper species present in the catalyst Cu/SrTiO3 can be reduced more easily than those in other supports, and for this reason, this catalyst seems to be the most effective to convert NO into NO2, which explains its highest activity for soot oxidation.

  12. 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.

  13. Carbon nanotubes/tin oxide nanocomposite-supported Pt catalysts for methanol electro-oxidation.

    PubMed

    Li, Xingwei; Wei, Jiadi; Chai, Yuzheng; Zhang, Shuo

    2015-07-15

    Carbon nanotubes/tin oxide nanocomposite (MWCNTs-SnO2) was obtained via the hydrolysis of SnCl4 in the presence of multi-walled carbon nanotubes (MWCNTs) and subsequent calcinations. And carbon nanotubes/tin oxide nanocomposite-supported Pt catalysts (Pt/MWCNTs-SnO2) were prepared by in-situ liquid phase reduction using H2PtCl6 as a metal precursor. As-prepared catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM), and their catalytic performances were evaluated by chronoamperometry (CA) and cyclic voltammetry (CV). Desirable catalytic performance for methanol electro-oxidation was observed with a reduced size and an improved dispersion of Pt catalysts on the MWCNTs-SnO2 nanocomposite. The calcination temperature of MWCNTs-SnO2 nanocomposite was a key factor for controlling the catalytic performance of Pt/MWCNTs-SnO2 catalysts.

  14. 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.

  15. 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.

  16. Polyolefin-supported recoverable/reusable Cr(III)-salen catalysts.

    PubMed

    Bergbreiter, David E; Hobbs, Christopher; Hongfa, Chayanant

    2011-01-21

    The design of functional soluble polyolefins for use as supports for salen ligands and metal complexes is described. Examples and applications that use both polyisobutylene (PIB)- and polyethylene (PE(Olig))-bound recoverable/recyclable salen ligands/metal complexes are detailed. In the case of using PIB as a support, the polymer-bound complexes can be recovered through the use of latent biphasic or a thermomorphic mixed solvent systems. In the case of PE(Olig)-supported complexes, the thermomorphic PE(Olig)-bound salen species can be dissolved in "hot" solvents and quantitatively recovered as solids upon cooling to room temperature. Both the PIB- and PE(Olig)-bound salen catalysts were shown to catalyze the ring-opening of epoxides with various nucleophiles. Both sorts of polyolefin-bound catalysts can be recycled and reused with no observed loss in activity. However, limitations of catalyst concentration make chiral versions of these complexes uncompetitive in comparison to conventional chiral salen catalysts that can be used in neat substrate at higher concentration to produce high enantioselectivity in the ring-opening products. The preparation of a PIB-bound "half-salen" catalyst was also briefly examined.

  17. 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

    2016-09-07

    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.

  18. Characterization and catalytic performance of Co/SBA-15 supported gold catalysts for CO oxidation

    SciTech Connect

    Xu Xiuyan; Li Jinjun; Hao Zhengping . E-mail: zpinghao@mail.rcees.ac.cn; Zhao Wei; Hu Chun

    2006-02-02

    Cobalt-containing SBA-15 supported gold catalysts for low-temperature CO oxidation were prepared and characterized by N{sub 2} adsorption/desorption, X-ray diffraction, transmission electron microscopy, inductively coupled plasma-atom emission spectroscopy and X-ray photoelectron spectroscopy techniques. The effects of cobalt and gold content on the catalyst activity were investigated in detail. Among them, 2% Au/40% Co/SBA-15 shows the highest activity, its complete conversion temperature for CO is at 273 K. It was believed that both the dispersion of Co{sub 3}O{sub 4} and the high surface areas caused by SBA-15 contribute to the good activities of cobalt-containing SBA-15 supported gold catalysts. Furthermore, the strong metal-support interaction between gold and cobalt oxides is greatly related to the catalytic performance.

  19. 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

  20. Microbial recovery of metals from spent catalysts. Quarterly report, April--June, 1990

    SciTech Connect

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

    1990-12-31

    The second quarter of 1990 was one of peripheral progress on the project of reclaiming molybdenum and nickel from spent coal liquefaction catalysts. We defined some important parameters for future research and we were able to clear up ambiguities in some of the past approaches and the problems uniquely associated with the ability of T. ferrooxidans to leach both Ni{sup ++} and molybdate from spent, alumina supported catalyst from the Wilsonville pilot project. We were also able to show the T. ferrooxidans was very sensitive to molybdate and extremely sensitive to tungstate, but showed relatively little sensitivity for the related elements chromate, vanadate and for the catalyst associated metal, Ni{sup ++}. There appears to be no negative synergistic effects between Ni{sup ++} and molybdate for growth, which bodies well for processes to reclaim both these metals from spent coal liquefaction catalysts. We have shown that T. ferrooxidans is indeed capable of leaching molybdate and Ni{sup ++} from spent catalysts if the catalyst is washed extensively with both an organic solvent such as tetrahydrofuran to remove the oily contaminants and an aqueous acidic medium to remove readily solubilized N{sup ++} and molybdate. It is possible to extract into an acidic medium enough molybdate from THF washed spent catalyst within 24 hr to completely inhibit the growth of all tested T. ferrooxidans strains. The stage is now set for the development of a molybdate tolerant strain to be used for actual leaching of the spent catalyst. We are currently seeking simpler ways of pretreating the raw spent catalyst in order to make it more amenable to microbial leaching and possibly produce an economic and feasible technology.

  1. Support effects studied on model supported catalysts. Progress report, April 1, 1991--March 31, 1992

    SciTech Connect

    Gorte, R.G.

    1991-11-01

    We are studying model catalysts in which the active phase is deposited onto flat oxide substrates in order to understand how a catalyst is affected by its support. We have examined the following growth and stability of titania overlayers which had been vapor deposited onto a Rh foil; the growth of Pt films on ZnO(0001)Zn and O(0001)O and compared the results to those obtained for Pt on {alpha}-Al{sub 2}O{sub 3}(0001). Samples were prepared by vapor deposition of Pt onto flat substrates in ultra high vacuum, and metal coverages were measured using a quartz-crystal, film thickness monitor; the structure and CO adsorption properties of Pt films vapor deposited onto a ZrO{sub 2}(100) crystal; the deposition of Rh on a ZrO{sub 2}(100) crystal; The absorption of NO on Pt particles supported on CeO{sub 2}, {alpha}-Al{sub 2}O{sub 3}(0001), and the Zn- and O-polar surfaces of ZnO(0001). We have investigated supported oxides in order to understand the acidic properties that have been reported for monolayer oxides. Our first studies were of amorphous, silicalumina catalysts. Finally, we have also begun to prepare model supported oxides in order to be able to used spectroscopic methods to characterize the sites formed on these materials. Our first studies were of niobia deposition on oxidized Al films and on an {alpha}-Al{sub 2}O{sub 3}(0001) crystal.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  3. Lewis acid double metal cyanide catalysts for hydroamination of phenylacetylene.

    PubMed

    Peeters, Annelies; Valvekens, Pieterjan; Vermoortele, Frederik; Ameloot, Rob; Kirschhock, Christine; De Vos, Dirk

    2011-04-14

    Double metal cyanides (DMCs) are highly active recyclable heterogeneous catalysts for hydroamination of phenylacetylene with 4-isopropylaniline. The best hydroamination yields are obtained with Zn-Co DMCs, especially if the particle size is decreased by a reverse emulsion synthesis technique.

  4. 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.

  5. 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.

  6. 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.

  7. 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

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    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. 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.

  10. 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.; ...

    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

  11. 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.

  12. 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.

  13. Development of supported palladium particles in Pd/C catalysts

    SciTech Connect

    Semikolenov, V.A.; Lavrenko, S.P.; Zaikovskii, V.I.

    1994-07-01

    A series of Pd/C catalysts characterized by different morphology of supported Pd particles is prepared by deposition from aqueous H{sub 2}PdCl{sub 4} solutions. The development of palladium particles on the surface of a carbonaceous support is studied by high-resolution electron microscopy. Soluble Pd compounds are shown to be involved in the development of supported particles in the course of catalyst reduction. A scheme that accounts for the formation of round-shaped particles, grapelike clusters, and Pd microcrystallites is proposed.

  14. A silica-supported, switchable, and recyclable hydroformylation-hydrogenation catalyst.

    PubMed

    Sandee, A J; Reek, J N; Kamer, P C; van Leeuwen, P W

    2001-09-05

    A homogeneous hydroformylation catalyst, designed to produce selectively linear aldehydes, was covalently tethered to a polysilicate support. The immobilized transition-metal complex [Rh(A)CO]+(1+)), in which A is N-(3-trimethoxysilane-n-propyl)-4,5-bis(diphenylphosphino)phenoxazine, was prepared both via the sol-gel process and by covalent anchoring to silica. 1+ was characterized by means of (31)P and (29)Si MAS NMR, FT-IR, and X-ray photoelectron spectroscopy. Polysilicate immobilized Rh(A) performed as a selective hydroformylation catalyst showing an overall selectivity for the linear aldehyde of 94.6% (linear to branched aldehyde ratio of 65). In addition 1-nonanol, obtained via the hydrogenation of the corresponding aldehyde, was formed as an unexpected secondary product (3.6% at 20% conversion). Under standard hydroformylation conditions, 1+ and HRh(A)(CO)(2)(1) coexist on the support. This dual catalyst system performed as a hydroformylation/hydrogenation sequence catalyst (Z), giving selectively 1-nonanol from 1-octene; ultimately, 98% of 1-octene was converted to mainly 1-nonanal and 97% of the nonanal was hydrogenated to 1-nonanol. The addition of 1-propanol completely changes Z in a hydroformylation catalyst (X), which produces 1-nonanal with an overall selectivity of 93%, and completely suppresses the reduction reaction. If the atmosphere is changed from CO/H(2) to H(2) the catalyst system is switched to the hydrogenation mode (Y), which shows a clean and complete hydrogenation of 1-octene and 1-nonanal within 24 h. The immobilized catalyst can be recycled and the system can be switched reversibly between the three "catalyst modes" X, Y, and Z, completely retaining the catalyst performance in each mode.

  15. 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 Shari; Hensley, Alyssa J.; 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.

  16. Kinetics of synthesizing polymer-supported quaternary ammonium catalysts.

    PubMed

    Wu, Ho-Shing; Lo, Chi-Wei

    2006-01-01

    This study attempted to synthesize the optimum quaterary ammonium poly(styrene-co-methylstyrene) catalyst using the combinatorial chemistry method. The catalyst was synthesized by a mix-split method. A phase-transfer catalyst library with 25 kinds of polystyrene-supported quaternary ammonium salt catalyst was the the result of the reaction of five kinds of chloromethylated crosslinked polystyrene with five tert-amines. The allylation of phenol and the oxidation of benzyl alcohol were used as the probing reaction to screen out the most active catalyst for the reaction using the iterative deconvolution method. The screening conditions included teritary amine and organic solvent. The structure of the most active catalyst in the allylation of phenol shows 20 mol % ring substitution and 0.177-0.25-mm pellet size activated with trihexylamine. For oxidation of benzyl alcohol, the reaction conditions of the most active catalyst included a resin of 20% ring substitution and pellet size of 0.177-0.25 mm, activated with triethylamine reacting in an organic solvent of n-hexane.

  17. 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.

  18. Carbon-supported Pd-Ir catalyst as anodic catalyst in direct formic acid fuel cell

    NASA Astrophysics Data System (ADS)

    Wang, Xin; Tang, Yawen; Gao, Ying; Lu, Tianhong

    It was reported for the first time that the electrocatalytic activity of the Carbon-supported Pd-Ir (Pd-Ir/C) catalyst with the suitable atomic ratio of Pd and Ir for the oxidation of formic acid in the direct formic acid fuel cell (DFAFC) is better than that of the Carbon-supported Pd (Pd/C) catalyst, although Ir has no electrocatalytic activity for the oxidation of formic acid. The potential of the anodic peak of formic acid at the Pd-Ir/C catalyst electrode with the atomic ratio of Pd and Ir = 5:1 is 50 mV more negative than that and the peak current density is 13% higher than that at the Pd/C catalyst electrode. This is attributed to that Ir can promote the oxidation of formic acid at Pd through the direct pathway because Ir can decrease the adsorption strength of CO on Pd. However, when the content of Ir in the Pd-Ir/C catalyst is too high the electrocatalytic activity of the Pd-Ir/C catalyst would be decreased because Ir has no electrocatalytic activity for the oxidation of formic acid.

  19. HREM study of structure of supported Pt catalysts

    NASA Astrophysics Data System (ADS)

    Yao, Ming-Hui; Smith, David J.; Kalakkad, Dinesh; Datye, Abhaya K.

    1993-03-01

    The surface structure and morphology of Pt catalysts supported on various oxides were studied by HREM profile imaging. An unstable Ti oxide overlayer and a stable crystalline monolayer on TiO2 supported Pt particles were observed after HTR at 923K. The overlayers could explain the SMSI in Pt/TiO2.

  20. Active Site Structures in Nitrogen-Doped Carbon-Supported Cobalt Catalysts for the Oxygen Reduction Reaction.

    PubMed

    Qian, Yingdan; Liu, Zheng; Zhang, Hui; Wu, Ping; Cai, Chenxin

    2016-12-07

    The catalytic mechanism and the nature of active sites are revealed for the oxygen reduction reaction (ORR) with new non-noble-metal nitrogen-doped carbon-supported transition-metal catalysts (metal-N-C catalyst). Specifically, new nitrogen-doped carbon-supported cobalt catalysts (Co-N-C catalysts) are made by pyrolyzing various ratios of the nitrogen-atom rich heterocycle compound, 1-ethyl-3-methyl imidazolium dicyanamide (EMIM-dca) and cobalt salt (Co(NO3)2). The ORR activity (JK at 0.8 V vs RHE, in 0.1 M KOH solution) of a typical catalyst in this family, Co15-N-C800, is 8.25 mA/mg, which is much higher than the ORR activity values of N-C catalysts (0.41 mA/mg). The active site in the catalyst is found to be the Co-N species, which is most likely in the form of Co2N. Metallic cobalt (Co) particles, Co3C species, and N-C species are not catalytically active sites, nor do these moieties interact with the Co-N active sites during the catalysis of the ORR. Increasing the Co salt content during the synthesis favors the formation of Co-N active sites in the final catalyst. Higher pyrolysis temperatures (e.g., a temperature higher than 800 °C) do not favor the formation of the Co-N active sites, but cause the formed Co-N active sites to decompose, which, therefore, leads to a lower catalytic activity. This reveals that the control of the parameters that affect the final structure is critical to catalyst performance and, therefore, the effective development of high-performance heteroatom-doped non-noble-metal ORR catalysts.

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

    DOE PAGES

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

    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.

  2. 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.

  3. 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.

  4. Support effects on hydrotreating activity of NiMo catalysts

    SciTech Connect

    Dominguez-Crespo, M.A. Arce-Estrada, E.M.; Torres-Huerta, A.M.

    2007-10-15

    The effect of the gamma alumina particle size on the catalytic activity of NiMoS{sub x} catalysts prepared by precipitation method of aluminum acetate at pH = 10 was studied. The structural characterization of the supports was measured by using XRD, pyridine FTIR-TPD and nitrogen physisorption. NiMo catalysts were characterized during the preparation steps (annealing and sulfidation) using transmission electron microscopy (TEM). Hydrogen TPR studies of the NiMo catalysts were also carried out in order to correlate their hydrogenating properties and their catalytic functionality. Catalytic tests were carried out in a pilot plant at 613, 633 and 653 K temperatures. The results showed that the rate constants of hydrodesulfurization (HDS), hydrodenitrogenation (HDN) and hydrodearomatizing (HDA) at 613-653 K decreased in the following order: A > B > C corresponding to the increase of NiMoS particle size associated to these catalysts.

  5. 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.

  6. CVD synthesis of boron nitride nanotubes without metal catalysts

    NASA Astrophysics Data System (ADS)

    Ma, R.; Bando, Y.; Sato, T.

    2001-03-01

    An efficient CVD synthetic route for bulk quantities of boron nitride nanotubes (BN-NTs) was developed, where a B-N-O precursor generated from melamine diborate (C 3N 6H 6·2H 3BO 3) was employed as the precursor and no metal catalyst was used. The resultant tubes all show remarkable ordering of the concentric atomic layers and exhibit stoichiometric BN composition. It is commonly found that the nanotubes have bulbous tips showing B-N-O amorphous clusters encapsulated in BN cages. The amorphous clusters might play the catalytic role in the nanotube `tip-growth' process as the metal catalysts do in the metal-catalyzed CVD method.

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

    PubMed

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

    2016-06-06

    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.

  8. Density functional calculations in the automotive industry: Catalyst supports and hydrogen storage materials

    NASA Astrophysics Data System (ADS)

    Wolverton, Christopher

    2006-03-01

    In my talk, I will describe some uses of density functional theory (DFT) calculations in the research laboratory at Ford, and particularly highlight work that was inspired by, or performed in collaboration with Ken Hass. I begin with a discussion of past work on γ-Al2O3 catalyst support materials, but also discuss the current main focus of our group's activities: hydrogen storage materials. Catalyst Supports: In current three-way automotive catalysts, precious metals are often supported by the phase of aluminum oxide known as γ-Al2O3. Despite the ubiquitous nature of this oxide in current automobile catalysts, and a considerable amount of effort expended to understand this material, many questions about the phase stability and even crystal structure of γ-Al2O3 remain. DFT calculations have made significant progress in unraveling these unanswered questions, allowing one to construct realistic models of the supported catalysts materials. Hydrogen Storage Materials: One of the major bottlenecks to the widespread use of hydrogen-fueled vehicles is the ability to store sufficient energy on-board to enable vehicle attributes acceptable to customers. I will give a general introduction to the topic of hydrogen storage, and a broad survey of the various classes of hydrogen storage technologies, and point out some pros and cons associated with each class. Currently known technologies have insufficient usable energy densities, and I will describe how DFT calculations are aiding the search for improved high density storage materials.

  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. Development of polysilane-supported palladium/alumina hybrid catalysts and their application to hydrogenation.

    PubMed

    Oyamada, Hidekazu; Naito, Takeshi; Miyamoto, Shinpei; Akiyama, Ryo; Hagio, Hiroyuki; Kobayashi, Shū

    2008-01-07

    Novel immobilized Pd catalysts, polysilane-supported palladium/alumina hybrid catalysts, have been developed. The catalysts showed high catalytic activity for hydrogenation, and could be used in an organic solvent or under solvent-free conditions.

  11. Wet catalyst-support films for production of vertically aligned carbon nanotubes.

    PubMed

    Alvarez, Noe T; Hamilton, Christopher E; Pint, Cary L; Orbaek, Alvin; Yao, Jun; Frosinini, Aldo L; Barron, Andrew R; Tour, James M; Hauge, Robert H

    2010-07-01

    A procedure for vertically aligned carbon nanotube (VA-CNT) production has been developed through liquid-phase deposition of alumoxanes (aluminum oxide hydroxides, boehmite) as a catalyst support. Through a simple spin-coating of alumoxane nanoparticles, uniform centimer-square thin film surfaces were coated and used as supports for subsequent deposition of metal catalyst. Uniform VA-CNTs are observed to grow from this film following deposition of both conventional evaporated Fe catalyst, as well as premade Fe nanoparticles drop-dried from the liquid phase. The quality and uniformity of the VA-CNTs are comparable to growth from conventional evaporated layers of Al(2)O(3). The combined use of alumoxane and Fe nanoparticles to coat surfaces represents an inexpensive and scalable approach to large-scale VA-CNT production that makes chemical vapor deposition significantly more competitive when compared to other CNT production techniques.

  12. 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.

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

    DOEpatents

    Willigan, Rhonda R [Manchester, CT; Vanderspurt, Thomas Henry [Glastonbury, CT; Tulyani, Sonia [Manchester, CT; Radhakrishnan, Rakesh [Vernon, CT; Opalka, Susanne Marie [Glastonbury, CT; Emerson, Sean C [Broad Brook, CT

    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.

  14. 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.

  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. 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...

  17. 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...

  18. 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.

  19. Polyaniline and Perfluorosulfonic Acid Co-Stabilized Metal Catalysts for Oxygen Reduction Reaction.

    PubMed

    Ye, Bei; Cheng, Kun; Li, Wenqiang; Liu, Jing; Zhang, Jie; Mu, Shichun

    2017-06-06

    A proton (perfluorosulfonic acid, PFSA) and electron (polyaniline, PANI) conductor polymer costabilized Pt catalyst (Pt-PFSA/C@PANI) is synthesized to improve the long-term stability of polymer electrolyte membrane fuel cells (PEMFCs). The prepared catalyst not only displays comparable oxygen reduction reaction (ORR) activity, but significantly higher electrochemical stability than commercial porous carbon nanosphere supported Pt catalysts (Pt/C). This robust electrochemical property can be due to the result of PFSA and PANI. PANI as protector inhibits carbon nanospheres from corrosion of carbon supports in harsh chemical and electrochemical conditions. Meanwhile, PFSA wrapped Pt NPs (Pt@PFSA) can also anchor Pt NPs on C@PANI to avoid aggregation and detachment of Pt NPs, due to the increased metal-support interaction caused by the strong electrostatic attraction between PANI and PFSA with corresponding positive and negative charges. Significantly, after coating PANI on carbon supports (C@PANI), almost all micropores in the surface of carbon disappear, effectively avoiding the embedding of Pt nanopaticles into micropores. Furthermore, the triple-phase boundary toward ORR catalysis can be facilitated by PFSA as proton conductor (solid electrolyte). These are of benefit to increase utilization of Pt noble metals and ORR activity of our new catalysts.

  20. 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.

  1. 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. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. 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.

  3. Methods of making textured catalysts

    DOEpatents

    Werpy, Todd [West Richland, WA; Frye, Jr., John G.; Wang, Yong [Richland, WA; Zacher, Alan H [Kennewick, WA

    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.

  4. A Facile Molecular Precursor Route to Metal Phosphide Nanoparticles and Their Evaluation as Hydrodeoxygenation Catalysts

    DOE PAGES

    Habas, Susan E.; Baddour, Frederick G.; Ruddy, Daniel A.; ...

    2015-11-05

    Metal phosphides have been identified as a promising class of materials for the catalytic upgrading of bio-oils, which are renewable and potentially inexpensive sources for liquid fuels. Herein, we report the facile synthesis of a series of solid, phase-pure metal phosphide nanoparticles (NPs) (Ni2P, Rh2P, and Pd3P) utilizing commercially available, air-stable metal–phosphine complexes in a one-pot reaction. This single-source molecular precursor route provides an alternative method to access metal phosphide NPs with controlled phases and without the formation of metal NP intermediates that can lead to hollow particles. The formation of the Ni2P NPs was shown to proceed through anmore » amorphous Ni–P intermediate, leading to the desired NP morphology and metal-rich phase. This low-temperature, rapid route to well-defined metal NPs is expected to have broad applicability to a variety of readily available or easily synthesized metal–phosphine complexes with high decomposition temperatures. Hydrodeoxygenation of acetic acid, an abundant bio-oil component, was performed to investigate H2 activation and deoxygenation pathways under conditions that are relevant to ex situ catalytic fast pyrolysis (high temperatures, low pressures, and near-stoichiometric H2 concentrations). The catalytic performance of the silica-supported metal phosphide NPs was compared to the analogous incipient wetness (IW) metal and metal phosphide catalysts over the range 200–500 °C. Decarbonylation was the primary pathway for H2 incorporation in the presence of all of the catalysts except NP-Pd3P, which exhibited minimal productive activity, and IW-Ni, which evolved H2. The highly controlled NP-Ni2P and NP-Rh2P catalysts, which were stable under these conditions, behaved comparably to the IW-metal phosphides, with a slight shift to higher product onset temperatures, likely due to the presence of surface ligands. Most importantly, the NP-Ni2P catalyst exhibited H2 activation and

  5. A Facile Molecular Precursor Route to Metal Phosphide Nanoparticles and Their Evaluation as Hydrodeoxygenation Catalysts

    SciTech Connect

    Habas, Susan E.; Baddour, Frederick G.; Ruddy, Daniel A.; Nash, Connor P.; Wang, Jun; Pan, Ming; Hensley, Jesse E.; Schaidle, Joshua A.

    2015-11-05

    Metal phosphides have been identified as a promising class of materials for the catalytic upgrading of bio-oils, which are renewable and potentially inexpensive sources for liquid fuels. Herein, we report the facile synthesis of a series of solid, phase-pure metal phosphide nanoparticles (NPs) (Ni2P, Rh2P, and Pd3P) utilizing commercially available, air-stable metal–phosphine complexes in a one-pot reaction. This single-source molecular precursor route provides an alternative method to access metal phosphide NPs with controlled phases and without the formation of metal NP intermediates that can lead to hollow particles. The formation of the Ni2P NPs was shown to proceed through an amorphous Ni–P intermediate, leading to the desired NP morphology and metal-rich phase. This low-temperature, rapid route to well-defined metal NPs is expected to have broad applicability to a variety of readily available or easily synthesized metal–phosphine complexes with high decomposition temperatures. Hydrodeoxygenation of acetic acid, an abundant bio-oil component, was performed to investigate H2 activation and deoxygenation pathways under conditions that are relevant to ex situ catalytic fast pyrolysis (high temperatures, low pressures, and near-stoichiometric H2 concentrations). The catalytic performance of the silica-supported metal phosphide NPs was compared to the analogous incipient wetness (IW) metal and metal phosphide catalysts over the range 200–500 °C. Decarbonylation was the primary pathway for H2 incorporation in the presence of all of the catalysts except NP-Pd3P, which exhibited minimal productive activity, and IW-Ni, which evolved H2. The highly controlled NP-Ni2P and NP-Rh2P catalysts, which were stable under these conditions, behaved comparably to the IW-metal phosphides, with a slight shift to higher product onset temperatures, likely due to the presence of

  6. Reaction Engineering with Metal-Organic Framework Catalysts

    NASA Astrophysics Data System (ADS)

    Melkonian, Arek Viken

    To date, there has been no comprehensive attempt to perform and/or describe catalytic reactions in the gas phase that utilize metal-organic frameworks (MOFs) as catalysts. In addition, there has been no attempt to reaction engineer these MOF catalysts in order to determine their regimes of optimal catalytic activity and possible limitations to their use. A zinc-based MOF that has been post-synthetically modified with a homogeneous palladium catalyst, Pd(CH 3CN)2Cl2, is used to catalyze the hydrogenation of propylene. The catalyst is assembled in a packed-bed reactor under a continuous flow of reactants. The reaction is optimized with respect to isoreticular metalation, reactant flow rate, and reactor temperature. Maximum catalytic conversion is found at intermediate metalations of 40% and 60%, high hydrogen flow of 50 ccm, and intermediate reactor temperatures of 100 °C and 150 °C. The MOF-60 catalyst is exposed to a traditional catalyst poison, carbon monoxide (CO). It is found that the MOF is reversibly poisoned upon introduction of CO. Upon poisoning, catalytic conversions rates of 90%-100% are dramatically reduced to less than 10%-30%, depending on the CO flow rate and the reactor temperature. The CO poisoning is shown to be reversible, a similar effect as found with palladium on carbon (Pd/C). The time scale of poisoning and recovery is very fast for both the MOF catalyst and Pd/C (approximately 10-30 seconds). Other effects of temperature on the MOF-40 are also investigated. At fixed reactant flow, the temperature grid is partitioned into finer steps of 10 °C to determine the temperature that yields the highest catalytic conversion. It is found that conversion is nearly uniform in the range between the highest conversions, i.e., conversion plateaus between the optimum temperatures. The catalyst also exhibits a weak thermal hysteresis. There is no significant improvement in conversion with thermal cycling after alternating the reactor temperature between

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

    DOE PAGES

    Zhuang, Zhongbin; Giles, Stephen A.; Zheng, Jie; ...

    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

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

    SciTech Connect

    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. Here, owing to its high activity and low cost, our catalyst shows significant potential for use in low-cost, high-performance fuel cells.

  9. 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.

  10. 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

  11. Enhanced Hydrodeoxygenation of m -Cresol over Bimetallic Pt–Mo Catalysts through an Oxophilic Metal-Induced Tautomerization Pathway

    DOE PAGES

    Robinson, Allison; Ferguson, Glen Allen; Gallagher, James R.; ...

    2016-05-26

    Supported bimetallic catalysts consisting of a noble metal (e.g., Pt) and an oxophilic metal (e.g., Mo) have received considerable attention for the hydrodeoxygenation of oxygenated aromatic compounds produced from biomass fast pyrolysis. Here, we report that PtMo can catalyze m-cresol deoxygenation via a pathway involving an initial tautomerization step. In contrast, the dominant mechanism on monometallic Pt/Al2O3 was found to be sequential Pt-catalyzed ring hydrogenation followed by dehydration on the support. Bimetallic Pt10Mo1 and Pt1Mo1 catalysts were found to produce the completely hydrogenated and deoxygenated product, methylcyclohexane (MCH), with much higher yields than monometallic Pt catalysts with comparable metal loadingsmore » and surface areas. Over an inert carbon support, MCH formation was found to be slow over monometallic Pt catalysts, while deoxygenation was significant for PtMo catalysts even in the absence of an acidic support material. Experimental studies of m-cresol deoxygenation together with density functional theory calculations indicated that Mo sites on the PtMo bimetallic surface dramatically lower the barrier for m-cresol tautomerization and subsequent deoxygenation. The accessibility of this pathway arises from the increased interaction between the oxygen of m-cresol and the Mo sites in the Pt surface. This interaction significantly alters the configuration of the precursor and transition states for tautomerization. Lastly, a suite of catalyst characterization techniques including X-ray absorption spectroscopy (XAS) and temperature-programmed reduction (TPR) indicate that Mo was present in a reduced state on the bimetallic surface under conditions relevant for reaction. Overall, these results suggest that the use of bifunctional metal catalysts can result in new reaction pathways that are unfavorable on monometallic noble metal catalysts.« less

  12. Replacing precious metals with carbide catalysts for hydrogenation reactions

    DOE PAGES

    Ruijun, Hou; Chen, Jingguang G.; Chang, Kuan; ...

    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

  13. 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.

  14. 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

  15. Mullite-supported Rh catalyst: a promising catalyst for the decomposition of N2O propellant.

    PubMed

    Zhao, Xiangyun; Cong, Yu; Lv, Fei; Li, Lin; Wang, Xiaodong; Zhang, Tao

    2010-05-07

    A mullite-supported Rh catalyst with an unusual crystalline structure in favour of high-temperature reactions was applied for the first time to the catalytic decomposition of N(2)O propellants, and has shown a promising initial activity and thermal stability.

  16. 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.

  17. 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).

  18. Enhanced Fuel Cell Catalyst Durability with Nitrogen Modified Carbon Supports

    DTIC Science & Technology

    2013-02-12

    materials. enrichment in ruthenium with the N-modified samples as compared to the non-implanted commercial and in-house sputtered samples. Over- all we...found a major difference between commercial and sputtered samples with respect to their ruthenium compositions with the results summarized in Table I. In...commercial catalysts, surface ruthenium is distributed between metallic ruthenium (Ru(0), Ru(II), Ru(IV), ruthe- nium oxide RuO2 and hydrous ruthenium

  19. 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

  20. Sink effect in activated carbon-supported hydrodesulfurization catalysts

    SciTech Connect

    Laine, J.; Labady, M.; Severino, F.; Yunes, S.

    1997-03-01

    A synergistic effect has been proposed in previous papers, attempting to explain the higher activity of activated carbon-supported hydrodesulfurization (HDS) catalysts with respect to conventional alumina-supported catalysts, reported earlier. However, activated carbon characteristics can be strongly affected by the raw material and the method of activation. Thus, previous work using Ni-Mo catalysts supported on two different activated carbons (one prepared by {open_quotes}physical{close_quotes} and the other by {open_quotes}chemical{close_quotes} activation) showed different optimal Ni concentrations for higher HDS activity, such difference being attributed to the predominance of Topsoe`s Type I {open_quotes}NiMoS{close_quotes} phase in one carbon and the predominance of Type II in the other. Due to the lack of proper characterization of the activated carbon supported catalysts of the previous work, this paper presents further data suggesting that microporosity provided by the activated carbon may be the responsible for the above referred synergism. 12 refs., 1 fig., 3 tabs.

  1. Metal-Organic Framework-Derived Reduced Graphene Oxide-Supported ZnO/ZnCo2O4/C Hollow Nanocages as Cathode Catalysts for Aluminum-O2 Batteries.

    PubMed

    Liu, Yisi; Jiang, Hao; Hao, Jiayu; Liu, Yulong; Shen, Haibo; Li, Wenzhang; Li, Jie

    2017-09-05

    Aluminum-air battery is a promising candidate for large-scale energy applications because of its low cost and high energy density. Remarkably, tremendous efforts have been concentrated on developing efficient and stable cathode electrocatalysts toward the oxygen reduction reaction. In this work, a hydrothermal-calcination approach was utilized to prepare novel reduced graphene oxide (rGO)-supported hollow ZnO/ZnCo2O4 nanoparticle-embedded carbon nanocages (ZnO/ZnCo2O4/C@rGO) using a zeolitic imidazolate framework (ZIF-67)/graphene oxide/zinc nitrate composite as the precursor. The ZnO/ZnCo2O4/C@rGO hybrid exhibits remarkable electrocatalytic performance for oxygen reduction reaction under alkaline conditions and superior stability and methanol tolerance to those of the commercial Pt/C catalyst. Furthermore, novel and simple Al-air coin cells were first fabricated using the hybrid materials as cathode catalysts under ambient air conditions to further investigate their catalytic performance. The coin cell with the ZnO/ZnCo2O4/C@rGO cathode catalyst displays a higher open circuit voltage and discharge voltage and more sluggish potential drop than those of the cell with the ZnO/ZnCo2O4/C cathode catalyst, which confirms that rGO can enhance the electrocatalytic activity and stability of the catalyst system. The excellent electrocatalytic performance of the ZnO/ZnCo2O4/C@rGO hybrid is attributed to the prominent conductivity and high specific surface area resulting from rGO, the more accessible catalytic active sites induced by the unique porous hollow nanocage structure, and synergic covalent coupling between rGO sheets and ZnO/ZnCo2O4/C nanocages.

  2. Water-gas shift reaction on alumina-supported Pt-CeOx catalysts prepared by supercritical fluid deposition

    DOE PAGES

    Deal, Jacob W.; Le, Phong; Corey, C. Blake; ...

    2016-08-25

    Alumina-supported platinum catalysts, both with and without ceria, were prepared by supercritical fluid deposition and evaluated for activity for water-gas shift reaction. The organometallic precursor, platinum(II) acetylacetonate, was deposited from solution in supercritical carbon dioxide. Analysis of the catalysts by high resolution scanning transmission electron microscopy indicated that platinum was present in the form of highly dispersed metal nanoparticles. Pretreatment of the alumina-supported ceria in hydrogen prior to the deposition of the platinum precursor resulted in more platinum nucleated on ceria than non-pretreated alumina-supported ceria but varied in both particle size and structure. The ceria-containing catalyst that was not pretreatedmore » exhibited a more uniform particle size, and the Pt particles were encapsulated in crystalline ceria. Reaction rate measurements showed that the catalyst was more active for water-gas shift, with reaction rates per mass of platinum that exceeded most literature values for water-gas shift reaction on Pt-CeOx catalysts. The high activity was attributed to the significant fraction of platinum/ceria interfacial contact. We found that these results show the promise of supercritical fluid deposition as a scalable means of synthesizing highly active supported metal catalysts that offer efficient utilization of precious metals.« less

  3. 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.

  4. Hierarchical nanostructured hollow spherical carbon with mesoporous shell as a unique cathode catalyst support in proton exchange membrane fuel cell.

    PubMed

    Fang, Baizeng; Kim, Jung Ho; Kim, Minsik; Kim, Minwoo; Yu, Jong-Sung

    2009-03-07

    Hierarchical nanostructured spherical carbon with hollow macroporous core in combination with mesoporous shell has been explored to support Pt cathode catalyst with high metal loading in proton exchange membrane fuel cell (PEMFC). The hollow core-mesoporous shell carbon (HCMSC) has unique structural characteristics such as large specific surface area and mesoporous volume, ensuring uniform dispersion of the supported high loading (60 wt%) Pt nanoparticles with small particle size, and well-developed three-dimensionally interconnected hierarchical porosity network, facilitating fast mass transport. The HCMSC-supported Pt(60 wt%) cathode catalyst has demonstrated markedly enhanced catalytic activity toward oxygen reduction and greatly improved PEMFC polarization performance compared with carbon black Vulcan XC-72 (VC)-supported ones. Furthermore, the HCMSC-supported Pt(40 wt%) or Pt(60 wt%) outperforms the HCMSC-supported Pt(20 wt%) even at a low catalyst loading of 0.2 mg Pt cm(-2) in the cathode, which is completely different from the VC-supported Pt catalysts. The capability of supporting high loading Pt is supposed to accelerate the commercialization of PEMFC due to the anticipated significant reduction in the amount of catalyst support required, diffusion layer thickness and fabricating cost of the supported Pt catalyst electrode.

  5. Enantioselection on Heterogeneous Noble Metal Catalyst: Proline-Induced Asymmetry in the Hydrogenation of Isophorone on Pd Catalyst.

    PubMed

    Rodríguez-García, Laura; Hungerbühler, Konrad; Baiker, Alfons; Meemken, Fabian

    2015-09-23

    In the (S)-proline-mediated asymmetric hydrogenation of isophorone (IP) on supported Pd catalyst, excellent enantioselectivity is achieved, with an enantiomeric excess of up to 99%. The role of the heterogeneous catalyst has been the subject of a controversial debate, and the current mechanistic understanding cannot explain the observed enantioselectivity of this catalytic system. The lack of in situ information about the role of the heterogeneous catalyst has prompted us to investigate the surface processes occurring at the methanol-Pd catalyst interface using attenuated total reflection infrared spectroscopy. Time-resolved monitoring of the homogeneous solution and of the catalytic solid-liquid interface coupled with catalytic data provides crucial information on the catalytically relevant enantiodifferentiating processes. While the condensation of IP and the corresponding chiral product 3,3,5-trimethylcyclohexanone with the chiral amine is connected to the enantiodifferentiation, it was found that the crucial enantioselectivity-controlling steps take place on the metal surface, and the reaction has to be classified as heterogeneous asymmetric hydrogenation. The presented spectroscopic and catalytic results provide strong evidence for the existence of two competing enantioselective processes leading to opposing enantioselection. Depending on surface coverage of the Pd catalyst, the reaction is controlled either by kinetic resolution ((S)-pathway) or by chiral catalysis ((R)-pathway). Steering the hydrogenation on the (R)-reaction pathway requires sufficient concentration of IP-(S)-proline condensate, as this chiral reactive intermediate becomes the most abundant surface species, inhibiting the competing kinetic resolution. The unraveled (R)-reaction pathway emphasizes an intriguing strategy for inducing chirality in heterogeneous asymmetric catalysis.

  6. Transition-Metal Nitride Core@Noble-Metal Shell Nanoparticles as Highly CO Tolerant Catalysts.

    PubMed

    Garg, Aaron; Milina, Maria; Ball, Madelyn; Zanchet, Daniela; Hunt, Sean T; Dumesic, James A; Román-Leshkov, Yuriy

    2017-07-17

    Core-shell architectures offer an effective way to tune and enhance the properties of noble-metal catalysts. Herein, we demonstrate the synthesis of Pt shell on titanium tungsten nitride core nanoparticles (Pt/TiWN) by high temperature ammonia nitridation of a parent core-shell carbide material (Pt/TiWC). X-ray photoelectron spectroscopy revealed significant core-level shifts for Pt shells supported on TiWN cores, corresponding to increased stabilization of the Pt valence d-states. The modulation of the electronic structure of the Pt shell by the nitride core translated into enhanced CO tolerance during hydrogen electrooxidation in the presence of CO. The ability to control shell coverage and vary the heterometallic composition of the shell and nitride core opens up attractive opportunities to synthesize a broad range of new materials with tunable catalytic properties. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. 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.

  8. Continuous Production of Carbon-Supported Cubic and Octahedral Platinum-Based Catalysts Using Conveyor Transport System.

    PubMed

    Tsao, Kai-Chieh; Yang, Hong

    2016-09-01

    A conveyor transport system is developed for the continuous production of carbon-supported uniform Pt nanocubes, and Pt3 Ni nanocubes and octahedra in a single-reaction system under hot carbon monoxide environment. Oleylamine is critical for the high loading and even the dispersion of Pt nanocubes on a carbon support. The metal catalyst shows high performance in electrocatalytic oxidation of methanol.

  9. Particle size, precursor, and support effects in the hydrogenolysis of alkanes over supported rhodium catalysts

    SciTech Connect

    Coq, B.; Dutartre, R.; Figueras, F.; Tazi, T. )

    1990-04-01

    A series of Rh catalysts of widely varying dispersion has been prepared using {gamma}-alumina as support and Rh acetylacetonate (Rh(acac){sub 3}) as precursor. The hydrogenolyses of n-hexane (nH), methylcyclopentane (MCP), and 2,2,3,3-tetramethylbutane (TeMB) were investigated as model reactions. Clear dependence of turnover frequency on Rh particle size is observed for nH and MCP hydrogenolysis, but only slight changes of selectivities occur with these alkanes. By contrast, large modifications of both specific activity and selectivity appear when TeMB is reacted. TeMB hydrogenolysis is thus a reliable tool for studying modifications of the surface structure of rhodium particles. This probe was used to investigate the effects of precursor and support on rhodium catalysts. The effect of chlorine is appreciable and shifts the selectivity of TeMB hydrogenolysis toward that of large particles. This is attributed to a different morphology of the rhodium particles. When the effect of dispersion of the metal is taken into account, no support effect is observed when SiO{sub 2} or ZrO{sub 2} is used as support. The different properties of rhodium on MgO can also be attributed to a different morphology of the particles. For Rh/TiO{sub 2} prepared from RhCl{sub 3} {center dot} 3H{sub 2}O, the catalytic properties are similar to those of Rh/Al{sub 2}O{sub 3} of moderate dispersion whatever temperature is used for reduction. Rh/TiO{sub 2} prepared from Rh(acac){sub 3} and reduced at 573 and 773 K simulates the catalytic properties of particles smaller than indeed observed. This effect can be interpreted by a partial coverage of the Rh surface by TiO{sub x} species (SMSI). This SMSI effect disappears upon reduction at 873 K.

  10. 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.

  11. 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.

  12. Coupled Metal/Oxide Catalysts with Tunable Product Selectivity for Electrocatalytic CO2 Reduction.

    PubMed

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

    2017-08-30

    One major challenge to the electrochemical conversion of CO2 to useful fuels and chemical products is the lack of efficient catalysts that can selectively direct the reaction to one desirable product and avoid the other possible side products. Making use of strong metal/oxide interactions has recently been demonstrated to be effective in enhancing electrocatalysis in the liquid phase. Here, we report one of the first systematic studies on composition-dependent influences of metal/oxide interactions on electrocatalytic CO2 reduction, utilizing Cu/SnOx heterostructured nanoparticles supported on carbon nanotubes (CNTs) as a model catalyst system. By adjusting the Cu/Sn ratio in the catalyst material structure, we can tune the products of the CO2 electrocatalytic reduction reaction from hydrocarbon-favorable to CO-selective to formic acid-dominant. In the Cu-rich regime, SnOx dramatically alters the catalytic behavior of Cu. The Cu/SnOx-CNT catalyst containing 6.2% of SnOx converts CO2 to CO with a high faradaic efficiency (FE) of 89% and a jCO of 11.3 mA·cm(-2) at -0.99 V versus reversible hydrogen electrode, in stark contrast to the Cu-CNT catalyst on which ethylene and methane are the main products for CO2 reduction. In the Sn-rich regime, Cu modifies the catalytic properties of SnOx. The Cu/SnOx-CNT catalyst containing 30.2% of SnOx reduces CO2 to formic acid with an FE of 77% and a jHCOOH of 4.0 mA·cm(-2) at -0.99 V, outperforming the SnOx-CNT catalyst which only converts CO2 to formic acid in an FE of 48%.

  13. Nanoporous carbon supported metal particles: their synthesis and characterisation

    NASA Astrophysics Data System (ADS)

    Yang, Yunxia; Tang, Liangguang; Burke, Nick; Chiang, Ken

    2012-08-01

    In the current work, a simplified hard templating approach is used to synthesise metal (Ag, Rh, Ir and Pt) containing structured carbon. The target metals are first introduced into the NaY zeolite template by wetness impregnation. The metals are carried in the super cages of the zeolite and subsequently embedded in the final structures after the steps of carbonisation and the template removal. Scanning electron microscopy images have confirmed that the carbon structures produced by this method retain the morphology of the original template. Transmission electron microscopy reveals the presence of dispersed metal particles in all the carbon structures produced. The metal loadings in these templated structures can reach 35 wt% without significant losses of surface areas and pore volumes. Selected carbon supported metals are tested for their catalytic activity for the methanation of carbon monoxide. The finding suggested that this method is effective in preparing metal nanoparticles for use as catalysts.

  14. 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

  15. Bimetallic platinum group metal-free catalysts for high power generating microbial fuel cells

    NASA Astrophysics Data System (ADS)

    Kodali, Mounika; Santoro, Carlo; Herrera, Sergio; Serov, Alexey; Atanassov, Plamen

    2017-10-01

    M1-M2-N-C bimetallic catalysts with M1 as Fe and Co and M2 as Fe, Co, Ni and Mn were synthesized and investigated as cathode catalysts for oxygen reduction reaction (ORR). The catalysts were prepared by Sacrificial Support Method in which silica was the template and aminoantipyrine (AAPyr) was the organic precursor. The electro-catalytic properties of these catalysts were investigated by using rotating ring disk (RRDE) electrode setup in neutral electrolyte. Fe-Mn-AAPyr outperformed Fe-AAPyr that showed higher performances compared to Fe-Co-AAPyr and Fe-Ni-AAPyr in terms of half-wave potential. In parallel, Fe-Co-AAPyr, Co-Mn-AAPyr and Co-Ni-AAPyr outperformed Co-AAPyr. The presence of Co within the catalyst contributed to high peroxide production not desired for efficient ORR. The catalytic capability of the catalysts integrated in air-breathing cathode was also verified. It was found that Co-based catalysts showed an improvement in performance by the addition of second metal compared to simple Co- AAPyr. Fe-based bimetallic materials didn't show improvement compared to Fe-AAPyr with the exception of Fe-Mn-AAPyr catalyst that had the highest performance recorded in this study with maximum power density of 221.8 ± 6.6 μWcm-2. Activated carbon (AC) was used as control and had the lowest performances in RRDE and achieved only 95.6 ± 5.8 μWcm-2 when tested in MFC.

  16. Noble metal-free hydrogen evolution catalysts for water splitting.

    PubMed

    Zou, Xiaoxin; Zhang, Yu

    2015-08-07

    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.

  17. Pyrometallurgical Recovery of Platinum Group Metals from Spent Catalysts

    NASA Astrophysics Data System (ADS)

    Peng, Zhiwei; Li, Zhizhong; Lin, Xiaolong; Tang, Huimin; Ye, Lei; Ma, Yutian; Rao, Mingjun; Zhang, Yuanbo; Li, Guanghui; Jiang, Tao

    2017-09-01

    As an important secondary resource with abundant platinum group metals (PGMs), spent catalysts demand recycling for both economic and environmental benefits. This article reviews the main pyrometallurgical processes for PGM recovery from spent catalysts. Existing processes, including smelting, vaporization, and sintering processes, are discussed based in part on a review of the physiochemical characteristics of PGMs in spent catalysts. The smelting technology, which produces a PGM-containing alloy, is significantly influenced by the addition of various collectors, such as lead, copper, iron, matte, or printed circuit board (PCB), considering their chemical affinities for PGMs. The vaporization process can recover PGMs in vapor form at low temperatures (250-700°C), but it suffers high corrosion and potential environmental and health risks as a result of involvement of the hazardous gases, mainly Cl2 and CO. The sintering process serves as a reforming means for recycling of the spent catalysts by in situ reduction of their oxidized PGMs components. Among these processes, the smelting process seems more promising although its overall performance can be further improved by seeking a suitable target-oriented collector and flux, together with proper pretreatment and process intensification using an external field.

  18. Pyrometallurgical Recovery of Platinum Group Metals from Spent Catalysts

    NASA Astrophysics Data System (ADS)

    Peng, Zhiwei; Li, Zhizhong; Lin, Xiaolong; Tang, Huimin; Ye, Lei; Ma, Yutian; Rao, Mingjun; Zhang, Yuanbo; Li, Guanghui; Jiang, Tao

    2017-07-01

    As an important secondary resource with abundant platinum group metals (PGMs), spent catalysts demand recycling for both economic and environmental benefits. This article reviews the main pyrometallurgical processes for PGM recovery from spent catalysts. Existing processes, including smelting, vaporization, and sintering processes, are discussed based in part on a review of the physiochemical characteristics of PGMs in spent catalysts. The smelting technology, which produces a PGM-containing alloy, is significantly influenced by the addition of various collectors, such as lead, copper, iron, matte, or printed circuit board (PCB), considering their chemical affinities for PGMs. The vaporization process can recover PGMs in vapor form at low temperatures (250-700°C), but it suffers high corrosion and potential environmental and health risks as a result of involvement of the hazardous gases, mainly Cl2 and CO. The sintering process serves as a reforming means for recycling of the spent catalysts by in situ reduction of their oxidized PGMs components. Among these processes, the smelting process seems more promising although its overall performance can be further improved by seeking a suitable target-oriented collector and flux, together with proper pretreatment and process intensification using an external field.

  19. Dry reforming of methane on a highly-active Ni-CeO2 catalyst: Effects of metal-support interactions on C–H bond breaking

    SciTech Connect

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

    2016-05-04

    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 C1s XPS region. As a result, the reforming of methane proceeds in a clean and efficient way.

  20. Dry reforming of methane on a highly-active Ni-CeO2 catalyst: Effects of metal-support interactions on C–H bond breaking

    SciTech Connect

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

    2016-05-04

    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 C1s XPS region. As a result, the reforming of methane proceeds in a clean and efficient way.

  1. Synthesis of carbon-supported copper catalyst and its catalytic performance in methanol dehydrogenation

    NASA Astrophysics Data System (ADS)

    Shelepova, Ekaterina V.; Vedyagin, Aleksey A.; Ilina, Ludmila Yu.; Nizovskii, Alexander I.; Tsyrulnikov, Pavel G.

    2017-07-01

    Carbon-supported copper catalyst was prepared by incipient wetness impregnation of Sibunit with an aqueous solution of copper nitrate. Copper loading was 5 wt.%. Temperature of reductive pretreatment was varied within a range of 200-400 °C. The samples were characterized by transmission electron microscopy, X-ray diffraction analysis, X-ray photoelectron and X-ray absorption spectroscopies. Catalytic activity of the samples was studied in a reaction of methanol dehydrogenation. Silica-based catalyst with similar copper loading was used as a reference. It was found that copper is distributed over the surface of support in the form of metallic and partially oxidized particles of about 12-17 nm in size. Diminished interaction of copper with support was supposed to be responsible for high catalytic activity.

  2. Highly efficient nonprecious metal catalyst prepared with metal-organic framework in a continuous carbon nanofibrous network.

    PubMed

    Shui, Jianglan; Chen, Chen; Grabstanowicz, Lauren; Zhao, Dan; Liu, Di-Jia

    2015-08-25

    Fuel cell vehicles, the only all-electric technology with a demonstrated >300 miles per fill travel range, use Pt as the electrode catalyst. The high price of Pt creates a major cost barrier for large-scale implementation of polymer electrolyte membrane fuel cells. Nonprecious metal catalysts (NPMCs) represent attractive low-cost alternatives. However, a significantly lower turnover frequency at the individual catalytic site renders the traditional carbon-supported NPMCs inadequate in reaching the desired performance afforded by Pt. Unconventional catalyst design aiming at maximizing the active site density at much improved mass and charge transports is essential for the next-generation NPMC. We report here a method of preparing highly efficient, nanofibrous NPMC for cathodic oxygen reduction reaction by electrospinning a polymer solution containing ferrous organometallics and zeolitic imidazolate framework followed by thermal activation. The catalyst offers a carbon nanonetwork architecture made of microporous nanofibers decorated by uniformly distributed high-density active sites. In a single-cell test, the membrane electrode containing such a catalyst delivered unprecedented volumetric activities of 3.3 A ⋅ cm(-3) at 0.9 V or 450 A ⋅ cm(-3) extrapolated at 0.8 V, representing the highest reported value in the literature. Improved fuel cell durability was also observed.

  3. Inverse oxide/metal catalysts in fundamental studies and practical applications: A perspective of recent developments

    DOE PAGES

    Rodriguez, José A.; Liu, Ping; Graciani, Jesús; ...

    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

  4. Inverse oxide/metal catalysts in fundamental studies and practical applications: A perspective of recent developments

    SciTech Connect

    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 the 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.

  5. Inverse oxide/metal catalysts in fundamental studies and practical applications: A perspective of recent developments

    SciTech Connect

    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 the 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.

  6. 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

  7. 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.

  8. 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.

  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. 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

  11. 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.

  12. Gold-supported cerium-doped NiOx catalysts for water oxidation

    DOE PAGES

    Ng, Jia Wei Desmond; García-Melchor, Max; Bajdich, Michal; ...

    2016-04-29

    Here, 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-coordinatedmore » 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.« less

  13. Gold-supported cerium-doped NiOx catalysts for water oxidation

    SciTech Connect

    Ng, Jia Wei Desmond; García-Melchor, Max; Bajdich, Michal; Chakthranont, Pongkarn; Kirk, Charlotte; Vojvodic, Aleksandra; Jaramillo, Thomas F.

    2016-04-29

    Here, 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.

  14. Non-precious metal catalysts prepared from precursor comprising cyanamide

    DOEpatents

    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. Catalytic oxidation of benzene in the gas phase over alumina-supported silver catalysts.

    PubMed

    Einaga, Hisahiro; Ogata, Atsushi

    2010-04-01

    Catalytic properties of Ag/Al(2)O(3) for complete oxidation of benzene with ozone at 295-373 K were studied and compared with those of Mn/Al(2)O(3). At the reaction temperature of 295 K, the Ag/Al(2)O(3) catalysts showed selectivity to CO(x) (ca. 80%) higher than that of the oxide of metals in the first transition series (Fe, Mn, Co, Ni, Cu) supported on Al(2)O(3), which had selectivities of 28-62%. The catalyst showed gradual deactivation from accumulation of byproduct compounds on the catalyst surface. FTIR studies revealed that the byproduct compounds consisted of easily decomposable species and hardly decomposable species. The rate for benzene oxidation linearly increased with Ag loadings (approximately 15 wt %) and was not improved at higher loading levels. The ratios of ozone decomposition to benzene oxidation and ozone decomposition to CO(x) selectivity were evaluated to be 7.5 and 80%, respectively, and they were independent of benzene conversion. The Ag/Al(2)O(3) catalyst showed steady-state activities at a reaction temperature of 313-373 K, and the conversion increased with the increase in the reaction temperature. The presence of water vapor in the reaction gas inhibited the catalyst deactivation, and steady-state activity was obtained at a reaction temperature of 295 K, while it did not affect the activities for benzene oxidation but improved the CO(2) selectivity.

  16. Metal-silicate catalysts: Single site, mesoporous systems without templates

    SciTech Connect

    Barnes, Craig E.; Sharp, Katherine; Albert, Austin A; Abbott, Joshua; Peretich, Michael E; Fulvio, Pasquale; Ciesielski, Peter N.; Donohoe, Bryon S.

    2015-06-01

    The textural properties of a family of silicate and mixed metal-silicate materials prepared by a nonaqueous sol-gel reaction involving the cubic silicate Si8O20(SnMe3)8 and metal chlorides MCl4 (M = Si, Ti, Zr) cross-linking reagents are described. Nitrogen adsorption isotherm data is presented and surface area and pore size distribution analyses for several examples of these materials are developed and correlated with the ratio of cross-linking reagent and the cubic silicate building block at the time of synthesis. Significant surface area and pore size distributions that shift to higher pore diameters are observed as the ratio of cross-linking reagent-to-cubic building block increases. A simple strategy for simultaneously controlling the porosity of these matrices while homogeneously dispersing identical metal centers on their surfaces for next generation catalysts is described.

  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. Texture of Mo-containing hydrodesulfurization catalysts on different supports

    SciTech Connect

    Krasnopol'skaya, S.M.; Lur'e, M.A.; Kurets, I.Z.; Rak, V.S.; Belyaeva, V.A.; Shmidt, F.K.

    1988-10-01

    The thermal desorption of nitrogen was used to investigate the texture of molybdenum-containing hydrodesulfurization catalysts, synthesized on the basis of ..gamma..-Al/sub 2/O/sub 3/ and a genetic mixture of mountain cork (palygorskite) and montmorillonite. Their activity in the hydrogenolysis of thiophene has been determined. It has been shown that in the preparation of the oxide or sulfide forms the texture of the contact, containing the natural support, changes more strongly than that based on aluminum oxide. Elimination of the oxidizing calcination stage produces sulfide forms of the catalysts with a larger specific surface, porosity, and higher catalytic activity. A stronger effect is obtained on the natural support.

  19. Synthesis, characterization, and activity of Co/Fe alumina/silica supported Ft catalysts and the study of promoter effect of ruthenium

    NASA Astrophysics Data System (ADS)

    Esumike, Sunday Azubike

    The alumina and hybrid alumina-silica FT catalyst were prepared by one-step solgel/oil-drop methods using metal-nitrate-solutions (method-I), and nanoparticle-metaloxides (method-2). The nanoparticle-metal-oxides did not participate in solubility equilibria in contrast to metal nitrate in method-1 causing no metal ion seepage; therefore, method-2 yields higher XRF metal loading efficiency than method-1. The thermal analysis confirmed that the metal loading by method-1 and method-2 involved two different pathways. Method-1 involves solubility equilibria in the conversion of metal-nitrate to metal- hydroxide and finally to metal-oxide, while in method-2 nanoparticle-metal-oxide remained intact during sol-gel-oil-drop and calcination steps. The alumina supported catalysts were dominated by gamma-alumina PXRD peaks in alumina catalysts while amorphous alumino-silicate phase was the bulk of hybrid alumina-silica catalysts. The presence of cobalt oxides (CoO, Co3O4) and iron oxides (FeO, Fe2O3) phases are confirmed in the catalysts prepared by method-1 and method-2. The PXRD analysis indicated weak peak intensities in catalysts with 5 wt. % total metal loading. PXRD pattern confirmed alloy formation in the bimetallic catalysts (CoFe2O4) on alumina support phase gamma-A12 O3. The surface area and pore diameter of hybrid alumina-silica granules (301 - 372 m2/g and 7.3 nm) showed better values than the alumina granules (251 - 256 m2/g and 6.5 nm). The support pore diameter of both types of granules is within the mesoporous range (1 - 50 nm). The morphology of all the catalysts is preserved upon metal loading and heat treatments. The surface characteristics of the sol-gel-oil-drop method prepared catalysts indicate there was no significant pore blockage of the support below 10 wt % total metal loading. The CO conversion of the FT catalysts was measured to screen catalytic active metals and determine the optimum temperatures of the FT reaction for the alumina catalysts. The

  20. Carbon supports from natural organic materials and carbon-supported palladium catalysts

    SciTech Connect

    Kuznetsov, B.N.

    2007-07-15

    Experimental data are presented concerning the influence of preparation conditions on the pore structure of carbon supports obtained from different types of plant biomass, thermally expanded graphites, and chemically modified anthracites, on the distribution and particle size of supported palladium, and on the activity of the supported catalyst in the liquid-phase hydrogenation of hex-1-ene and cyclohexene.

  1. 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.

  2. 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%). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Metal-Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations.

    PubMed

    Zhang, Teng; Manna, Kuntal; Lin, Wenbin

    2016-03-09

    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.

  4. Fundamental studies of hydrogen interaction with supported meta and bimetallic catalysts

    SciTech Connect

    Bhatia, Sandeep

    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.

  5. 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.

  6. A Tandem Catalyst with Multiple Metal Oxide Interfaces Produced by Atomic Layer Deposition.

    PubMed

    Ge, Huibin; Zhang, Bin; Gu, Xiaomin; Liang, Haojie; Yang, Huimin; Gao, Zhe; Wang, Jianguo; Qin, Yong

    2016-06-13

    Ideal heterogeneous tandem catalysts necessitate the rational design and integration of collaborative active sites. Herein, we report on the synthesis of a new tandem catalyst with multiple metal-oxide interfaces based on a tube-in-tube nanostructure using template-assisted atomic layer deposition, in which Ni nanoparticles are supported on the outer surface of the inner Al2 O3 nanotube (Ni/Al2 O3 interface) and Pt nanoparticles are attached to the inner surface of the outer TiO2 nanotube (Pt/TiO2 interface). The tandem catalyst shows remarkably high catalytic efficiency in nitrobenzene hydrogenation over Pt/TiO2 interface with hydrogen formed in situ by the decomposition of hydrazine hydrate over Ni/Al2 O3 interface. This can be ascribed to the synergy effect of the two interfaces and the confined nanospace favoring the instant transfer of intermediates. The tube-in-tube tandem catalyst with multiple metal-oxide interfaces represents a new concept for the design of highly efficient and multifunctional nanocatalysts.

  7. Covalent triazine framework supported non-noble metal nanoparticles with superior activity for catalytic hydrolysis of ammonia borane: from mechanistic study to catalyst design† †Electronic supplementary information (ESI) available: 11B NMR spectra, XRD patterns, results of BET and ICP, XPS spectra, TOF values and activation energies E a of the non-noble metal catalysts, time versus volume of H2, catalytic activities and TEM images of 5% Co/CNT, 3% Co/CNT, 1% Co/CNT, the plot of hydrogen generation rate versus the concentration of Co and AB, kinetic isotope effect and TEM image of 5% Co/CTF-1 after reaction. See DOI: 10.1039/c6sc02456d Click here for additional data file.

    PubMed Central

    Li, Zhao; Liu, Lin; Chen, Weidong; Zhang, Miao; Wu, Guotao; Chen, Ping

    2017-01-01

    Development of non-noble metal catalysts with similar activity and stability to noble metals is of significant importance in the conversion and utilization of clean energy. The catalytic hydrolysis of ammonia borane (AB) to produce 3 equiv. of H2, as an example of where noble metal catalysts significantly outperform their non-noble peers, serves as an excellent test site for the design and optimization of non-noble metal catalysts. Our kinetic isotopic effect measurements reveal, for the first time, that the kinetic key step of the hydrolysis is the activation of H2O. Deducibly, a transition metal with an optimal electronic structure that bonds H2O and –OH in intermediate strengths would favor the hydrolysis of AB. By employing a covalent triazine framework (CTF), a newly developed porous material capable of donating electrons through the lone pairs on N, the electron densities of nano-sized Co and Ni supported on CTF are markedly increased, as well as their catalytic activities. Specifically, Co/CTF exhibits a total turnover frequency of 42.3 molH2 molCo –1 min–1 at room temperature, which is superior to all peer non-noble metal catalysts ever reported and even comparable to some noble metal catalysts. PMID:28451227

  8. Spectroscopic evidence for origins of size and support effects on selectivity of Cu nanoparticle dehydrogenation catalysts

    SciTech Connect

    Witzke, M. E.; Dietrich, P. J.; Ibrahim, M. Y. S.; Al-Bardan, K.; Triezenberg, M. D.; Flaherty, D. W.

    2016-12-12

    Selective dehydrogenation catalysts that produce acetaldehyde from bio-derived ethanol can increase the efficiency of subsequent processes such as C–C coupling over metal oxides to produce 1-butanol or 1,3-butadiene or oxidation to acetic acid. Here, we use in situ X-ray absorption spectroscopy and steady state kinetics experiments to identify Cuδ+ at the perimeter of supported Cu clusters as the active site for esterification and Cu0 surface sites as sites for dehydrogenation. Correlation of dehydrogenation and esterification selectivities to in situ measures of Cu oxidation states show that this relationship holds for Cu clusters over a wide-range of diameters (2–35 nm) and catalyst supports and reveals that dehydrogenation selectivities may be controlled by manipulating either.

  9. 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.

  10. 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.

  11. Method of inducing surface ensembles on a metal catalyst

    DOEpatents

    Miller, Steven S.

    1989-01-01

    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.

  12. 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.

  13. 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

    2016-06-08

    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.

  14. Effect of support and pre-treatment conditions on Pt-Sn catalysts: application to nitrate reduction in water.

    PubMed

    Soares, Olívia Salomé G P; Jardim, Erika O; Reyes-Carmona, Alvaro; Ruiz-Martínez, Javier; Silvestre-Albero, Joaquín; Rodríguez-Castellón, Enrique; Orfão, José J M; Sepúlveda-Escribano, Antonio; Pereira, Manuel Fernando R

    2012-03-01

    The effect of the support (activated carbon or titanium dioxide) on the catalytic activity and selectivity to nitrogen of Pt-Sn catalysts in nitrate reduction was studied. The effects of the preparation conditions and the Pt:Sn atomic ratio were also evaluated. It was observed that the support plays an important role in nitrate reduction and that different preparation conditions lead to different catalytic activities and selectivities. Generally, the catalysts supported on activated carbon were less active but more selective to nitrogen than those supported on titanium dioxide. The monometallic Pt catalyst is active for nitrate reduction only when supported on titanium dioxide, which is explained by the involvement of the support in the reaction mechanism. The catalysts were characterized by different techniques, and significant changes on metal chemical states were observed for the different preparation conditions used. Only metallic Pt and oxidized Sn were observed at low calcination and reduction temperatures, but some metallic Sn was also present when high temperatures were used, being also possible the formation of Pt-Sn alloys.

  15. Recyclable porous polymer-supported copper catalysts for Glaser and Huisgen 1,3-diolar cycloaddition reactions.

    PubMed

    Sun, Qi; Lv, Zhonfei; Du, Yuyang; Wu, Qinming; Wang, Liang; Zhu, Longfeng; Meng, Xiangju; Chen, Wanzhi; Xiao, Feng-Shou

    2013-11-01

    A family of polymer-attached phenanthrolines was prepared from solvothermal copolymerization of divinylbenzene with N-(1,10-phenanthroline-5-yl)acrylamide in different ratios. The polymer-supported copper catalysts were obtained through typical impregnation with copper(II) salts. The polymers and supported copper catalysts have been characterized by N2 adsortion, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TG); they exhibit a high surface area, hierarchical porosity, large pore volume, and high thermal and chemical stabilities. The copper catalyst has proved to be highly active for Glaser homocoupling of alkynes and Huisgen 1,3-diolar cycloaddition of alkynes with benzyl azide under mild conditions at low catalyst loading. The heterogeneous copper catalyst is more active than commonly used homogeneous and nonporous polystyrene-supported copper catalysts. In particular, the catalyst is easily recovered and can be recycled at least ten times without any obvious loss in catalytic activity. Metal leaching was prevented due to the strong binding ability of phenanthroline and products were not contaminated with copper, as determined by ICP analysis.

  16. Phase-Transfer Activation of Transition Metal Catalysts.

    PubMed

    Tuba, Robert; Xi, Zhenxing; Bazzi, Hassan S; Gladysz, John A

    2015-11-02

    With metal-based catalysts, it is quite common that a ligand (L) must first dissociate from a catalyst precursor (L'n M-L) to activate the catalyst. The resulting coordinatively unsaturated active species (L'n M) can either back react with the ligand in a k-1 step, or combine with the substrate in a k2 step. When dissociation is not rate determining and k-1 [L] is greater than or comparable to k2 [substrate], this slows the rate of reaction. By introducing a phase label onto the ligand L and providing a suitable orthogonal liquid or solid phase, dramatic rate accelerations can be achieved. This phenomenon is termed "phase-transfer activation". In this Concept, some historical antecedents are reviewed, followed by successful applications involving fluorous/organic and aqueous/organic liquid/liquid biphasic catalysis, and liquid/solid biphasic catalysis. Variants that include a chemical trap for the phase-labeled ligands are also described. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. 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.

  18. Metal-organic framework catalysts for selective cleavage of aryl-ether bonds

    DOEpatents

    Allendorf, Mark D.; Stavila, Vitalie

    2017-08-01

    The present invention relates to methods of employing a metal-organic framework (MOF) as a catalyst for cleaving chemical bonds. In particular instances, the MOF results in selective bond cleavage that results in hydrogenolyzis. Furthermore, the MOF catalyst can be reused in multiple cycles. Such MOF-based catalysts can be useful, e.g., to convert biomass components.

  19. Reduction of carbon dioxide by hydrogen on metal-carbon catalysts under supercritical conditions

    NASA Astrophysics Data System (ADS)

    Bogdan, V. I.; Koklin, A. E.; Kozak, D. O.; Kustov, L. M.

    2016-12-01

    The reduction of carbon dioxide with hydrogen on metal-carbon (Ru, Rh, Ir) catalysts is investigated under supercritical conditions for the first time. High selectivity (close to 100%) toward methanation with good stability of catalytic activity is observed for Ru- and Rh-containing catalyst, while the preferred reduction to CO is observed for Ir/C catalyst.

  20. 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.

  1. 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.

  2. Morphological effect of lanthanum-based supports on the catalytic performance of Pt catalysts in crotonaldehyde hydrogenation

    NASA Astrophysics Data System (ADS)

    Hou, Fengjun; Zhao, Huahua; Zhao, Jun; Yang, Jian; Yan, Liang; Song, Huangling; Chou, Lingjun

    2016-03-01

    Rod-like and particle-like La2O2CO3 and La2O3 were obtained via morphology-preserved thermal transformation of the La(OH)3 precursors. La2O2CO3- and La2O3-supported Pt catalysts were prepared by impregnation method and tested in the liquid-phase crotonaldehyde hydrogenation reaction. The textural and physicochemical properties of the samples were studied by a series of techniques including XRD, TG-DSC, N2 adsorption-desorption, TEM and HRTEM, IR spectrum, H2-TPD, and H2-TPR. Even after 600 °C reduction, Pt particles of about 0.8-2.8 nm interplayed with support surface to form Pt-doped interface, thereby preventing the catalysts from migration and affording a high dispersion of platinum. The specific exposed crystal-facets and surface oxygen species depending on the shape of the support affected the preferential deposition of Pt species and the metal-support interaction. Thus, Pt catalysts performed different physicochemical properties and catalytic performance relying on the morphology and structure of the supports. During the cycle experiment, severe deactivation was observed for NP-supported catalysts with an increased selectivity due to the aggregation and growth of Pt particles. Meantime, the NR-supported catalysts retained relatively high reactivity as a consequence of the crystal-facet confinement of rod-shaped lanthanum supports.

  3. The synthesis of metal nanoparticulate catalysts within functional microgel particles

    NASA Astrophysics Data System (ADS)

    Kaliva, Maria; Pavlopoulou, Eleni; Christodoulakis, Konstantinos; Vamvakaki, Maria; Anastasiadis, Spiros H.

    2012-02-01

    Electrostatically and sterically stabilized polymer microgel particles have been prepared containing either amino (poly(2-(diethylamino)ethyl methacrylate), PDEA) or carboxylic acid (poly(acrylic acid), PAA; poly(methacrylic acid), PMMA) functional groups. The PDEA, PAA and PMAA particles can be used for the incorporation of a large variety of metal nanoparticulate catalysts due to their functional amine and carboxylic acid groups; Pd, Ru and Ni nanoparticles have been synthesized. The more polar PAA microgels were designed as the nanocatalyst carrier system in aqueous reaction media while the less polar PMAA particles were prepared as the metal nanoparticle template for use in catalytic reactions that take place in organic solvents. The sterically and electrostatically stabilized microgel particles possess surface functional groups that can potentially interact with the microchannel walls of microfluidic catalytic reactors.

  4. 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

  5. Titanium cobalt nitride supported platinum catalyst with high activity and stability for oxygen reduction reaction

    NASA Astrophysics Data System (ADS)

    Xiao, Yonghao; Zhan, Guohe; Fu, Zhenggao; Pan, Zhanchang; Xiao, Chumin; Wu, Shoukun; Chen, Chun; Hu, Guanghui; Wei, Zhigang

    2015-06-01

    We describe a facile route to the development of novel robust non-carbon titanium cobalt nitride (Ti0.9Co0.1N) used as a support for Pt, and the catalyst exhibits high activity and stability for the oxygen reduction reaction (ORR). XRD and TEM results show that the synthesized Ti0.9Co0.1N is formed as a single-phase solid solution with high purity. The XPS measurements verified the strong metal/support interaction between Pt nanoparticles (NPs) and the Ti0.9Co0.1N support. Most importantly, Ti0.9Co0.1N supported Pt catalyst (Pt/Ti0.9Co0.1N) exhibits a much higher mass activity and durability than that of the commercial JM Pt/C electrocatalyst for ORR. The accelerated durability test (ADT) reveals that the novel Ti0.9Co0.1N support can dramatically enhance the durability of the catalyst and maintain the electrochemical surface area (ECSA) of Pt. Pt/Ti0.9Co0.1N shows great improvement in ECSA preservation, with only 35% of the initial ECSA drop even after 10 000 ADT cycles. The experimental data indicate that the electronic structure of Pt can be modified by Co doping, and there exists a strong interaction between Pt and the Ti0.9Co0.1N support, both of them are playing an important role in improving the activity and durability of the Pt/Ti0.9Co0.1N catalyst.

  6. Metal and precursor effect during 1-heptyne selective hydrogenation using an activated carbon as support.

    PubMed

    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.

  7. 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.

  8. 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

  9. Highly aligned vertical GaN nanowires using submonolayer metal catalysts

    DOEpatents

    Wang, George T [Albuquerque, NM; Li, Qiming [Albuquerque, NM; Creighton, J Randall [Albuquerque, NM

    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.

  10. Oxidation of CO and Methanol on Pd-Ni Catalysts Supported on Different Chemically-Treated Carbon Nanofibers

    PubMed Central

    Calderón, Juan Carlos; Rios Ráfales, Miguel; Nieto-Monge, María Jesús; Pardo, Juan Ignacio; Moliner, Rafael; Lázaro, María Jesús

    2016-01-01

    In this work, palladium-nickel nanoparticles supported on carbon nanofibers were synthesized, with metal contents close to 25 wt % and Pd:Ni atomic ratios near to 1:2. These catalysts were previously studied in order to determine their activity toward the oxygen reduction reaction. Before the deposition of metals, the carbon nanofibers were chemically treated in order to generate oxygen and nitrogen groups on their surface. Transmission electron microscopy analysis (TEM) images revealed particle diameters between 3 and 4 nm, overcoming the sizes observed for the nanoparticles supported on carbon black (catalyst Pd-Ni CB 1:2). From the CO oxidation at different temperatures, the activation energy Eact for this reaction was determined. These values indicated a high tolerance of the catalysts toward the CO poisoning, especially in the case of the catalysts supported on the non-chemically treated carbon nanofibers. On the other hand, apparent activation energy Eap for the methanol oxidation was also determined finding—as a rate determining step—the COads diffusion to the OHads for the catalysts supported on carbon nanofibers. The results here presented showed that the surface functional groups only play a role in the obtaining of lower particle sizes, which is an important factor in the obtaining of low CO oxidation activation energies. PMID:28335315

  11. Oxidation of CO and Methanol on Pd-Ni Catalysts Supported on Different Chemically-Treated Carbon Nanofibers.

    PubMed

    Calderón, Juan Carlos; Rios Ráfales, Miguel; Nieto-Monge, María Jesús; Pardo, Juan Ignacio; Moliner, Rafael; Lázaro, María Jesús

    2016-10-18

    In this work, palladium-nickel nanoparticles supported on carbon nanofibers were synthesized, with metal contents close to 25 wt % and Pd:Ni atomic ratios near to 1:2. These catalysts were previously studied in order to determine their activity toward the oxygen reduction reaction. Before the deposition of metals, the carbon nanofibers were chemically treated in order to generate oxygen and nitrogen groups on their surface. Transmission electron microscopy analysis (TEM) images revealed particle diameters between 3 and 4 nm, overcoming the sizes observed for the nanoparticles supported on carbon black (catalyst Pd-Ni CB 1:2). From the CO oxidation at different temperatures, the activation energy Eact for this reaction was determined. These values indicated a high tolerance of the catalysts toward the CO poisoning, especially in the case of the catalysts supported on the non-chemically treated carbon nanofibers. On the other hand, apparent activation energy Eap for the methanol oxidation was also determined finding-as a rate determining step-the COads diffusion to the OHads for the catalysts supported on carbon nanofibers. The results here presented showed that the surface functional groups only play a role in the obtaining of lower particle sizes, which is an important factor in the obtaining of low CO oxidation activation energies.

  12. 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

    2013-02-07

    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.

  13. 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.

  14. 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.

  15. High-efficiency palladium catalysts supported on ppy-modified C60 for formic acid oxidation.

    PubMed

    Bai, Zhengyu; Yang, Lin; Guo, Yuming; Zheng, Zhi; Hu, Chuangang; Xu, Pengle

    2011-02-14

    A facile preparation of polypyrrole-modified fullerene supported Pd nanoparticles catalyst is introduced; electrochemical measurements demonstrate that the obtained Pd/ppy-C(60) catalyst shows a good electrocatalytic activity and stability for the oxidation of formic acid.

  16. 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.

  17. Influence of various carbon nano-forms as supports for Pt catalyst on proton exchange membrane fuel cell performance

    NASA Astrophysics Data System (ADS)

    Bharti, Abha; Cheruvally, Gouri

    2017-08-01

    In this study, we discuss the influence of various carbon supports for Pt on proton exchange membrane (PEM) fuel cell performance. Here, Pt supported on various carbon nano-forms [Pt/carbon black (Pt/CB), Pt/single-walled carbon nanotubes (Pt/SWCNT), Pt/multi-walled carbon nanotubes (Pt/MWCNT) and Pt/graphene (Pt/G)] are synthesized by a facile, single step, microwave-assisted, modified chemical reduction route. Their physical, chemical and electrochemical characteristics pertaining to oxygen reduction reaction (ORR) catalytic activity and stability in PEM fuel cell are studied in detail by various techniques and compared. The study shows that the different carbon supports does not significantly affect the Pt particle size during synthesis, but leads to different amount of defective sites in the carbon framework which influence both the availability of active metal nano-catalysts and metal-support interaction. In-situ electrochemical investigations reveal that the different carbon supports influence both ORR catalytic activity and stability of the catalyst. This is further corroborated by the demonstration of varying polarization characteristics on PEM fuel cell performance by different carbon supported Pt catalysts. This study reveals MWCNT as the most suitable carbon support for Pt catalyst, exhibiting high activity and stability for ORR in PEM fuel cell.

  18. 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 per