Download or read book BIMETALLIC PLATINUM GOLD AND PLATINUM TIN CATALYSTS REACTIVITY ADSORPTION BEHAVIOR AND SURFACE COMPOSITION BIMETALLIC CATALYSTS written by KRISHNAN BALAKRISHNAN and published by . This book was released on 1991 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: partially reduced to a Sn (0) state. The interactions between platinum and an alumina-stabilized tin species (Sn (II), Sn (IV)) could explain the behavior of Pt-Sn/Al$\sb2$O$\sb3$ catalysts.
Download or read book PLATINUM GOLD AND PLATINUM TIN BIMETALLIC CATALYSTS CORRELATION BETWEEN MICROSTRUCTURE MISCIBILITY AND ACTIVITY written by AMIT SACHDEV and published by . This book was released on 1989 with total page 208 pages. Available in PDF, EPUB and Kindle. Book excerpt: microstructural information is vital in the interpretation of the catalytic reactivity trends.
Download or read book New Frontiers in Catalysis Parts A C written by L. Guczi and published by Elsevier. This book was released on 1993-04-20 with total page 2955 pages. Available in PDF, EPUB and Kindle. Book excerpt: These volumes comprise the proceedings of the major international meeting on catalysis which is held at 4 year intervals. The programme focussed on New Frontiers in Catalysis including nontraditional catalytic materials and environmental catalysis. The contributions cover a wide range of fundamental, applied, industrial and engineering aspects of catalysis. The extensive range of highly efficient industrial techniques for observing and characterizing catalytically important surfaces is evident.The programme covered the following sessions: Mechanism, theory, in situ methods; Catalytic reaction on atomically clean surfaces; Catalytic reaction on zeolites and related substances; New methods and principles for catalyst preparation; Hydrotreatment reactions (HDS, HDN); Characterization of catalysts, application of novel techniques; Selective oxidation; New catalytic aspects of heteropoly acids and related compounds; Reaction of hydrocarbons; Nontraditional catalytic materials; Fuel upgrading; Alkane activation; Acid-base catalysis; New selective catalytic reactons, fine chemicals; Environmental catalysis; Industrial catalysis, deactivation, reactivation; Synthesis from syngas; Electrocatalysis; Photocatalysis.The invited lectures and 433 papers included in these volumes present an update on all areas of catalysis and applications.
Download or read book Reactivity and Stability of Platinum and Platinum Alloy Catalysts Toward the Oxygen Reduction Reaction written by Sergio Rafael Calvo and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Density functional theory (DFT) is used to study the reactivity of Pt and Pt-M (M: Pd, Co, Ni, V, and Rh) alloy catalysts towards the oxygen reduction reaction (ORR) as a function of the alloy overall composition and surface atomic distribution and compared to that on pure Pt surfaces. Reactivity is evaluated on the basis of the adsorption strength of oxygenated compounds which are intermediate species of the four-electron oxygen reduction reaction, separating the effect of the first electron-proton transfer from that of the three last electron-proton transfer steps. It is found that most homogeneous distribution PtxM catalysts thermodynamically favor the dissociation of adsorbed OOH in comparison with pure Platinum and adsorb strongly O and OH due to the strong oxyphilicity of the M elements. On the other hand, in all cases skin Platinum surfaces catalysts do not favor the dissociation of adsorbed OOH and do favor the reduction of M-O and M-OH with respect to Platinum. Considering the overall pathway of the reactions to catalyze the ORR most of the skin Platinum monolayer catalysts provide more negative free energy changes and should behave at least in a similar way than Platinum in following order: Pt3V (skin Pt)> Pt3Co (skin Pt)> Pt3Ni (skin Pt)> Pt> PtPd (skin)> Pt4Rh (skin Pt)> PtPd3 (skin). In all cases, the reactivity is shown to be not only sensitive to the overall composition of the catalyst, but most importantly to the surface atomic distribution. Proposed electrochemical dissolution reactions of the catalyst atoms are also analyzed for the ORR catalysts, by computing the free energy changes of Platinum and bimetallic Pt-X (X: Co, Pd, Ni, and Rh) catalysts. It is found that Platinum is thermodynamically more stable than Pt-alloys in Pt3Co, Pt3Pd, Pt3Ni and Pt4Rh.
Download or read book Construction and Reactivity of Pt Based Bi component Catalytic Systems written by Rentao Mu and published by Springer. This book was released on 2017-06-20 with total page 99 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, the author outlines the construction of active structure and modulation of catalytic reactivity of Pt-based bi-component catalysts, from the model systems to real supported catalysts. The thesis investigates the promotion effect of the second components on catalytic performance of Pt catalysts, and presents the reversible generation of the “sandwich-like” structure of Pt-Ni catalysts, containing both surface NiO1-X and subsurface Ni by alternating redox treatments at medium temperature. With the aid of single layer graphene, the dynamic process of chemical reactions occurring on the Pt(111) surface can be visualized using in-situ LEEM and DUV-PEEM techniques, the results of which are included here. The author reveals that the graphene layer exhibits a strong confinement effect on the chemistry of molecules underneath and the intercalated CO can desorb from the Pt surface around room temperature and in UHV, which may promote the CO oxidation confined under graphene.
Download or read book Gold platinum Single Crystal Catalysts written by Johann Wolfgang Adriaan Sachtler and published by . This book was released on 1982 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Supported Bimetallic Catalysts Derived from Platinum gold Phosphine Stabilized Cluster Compounds Their Preparation Characterization and Catalytic Activity written by Irina Vladimirovna Gubkina Graf and published by . This book was released on 1996 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Platinum tin Bimetallic Catalysts Supported on L zeolite written by Hui Wang and published by . This book was released on 1997 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bimetallic Catalysts written by John H. Sinfelt and published by Wiley-Interscience. This book was released on 1983-09-29 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents an account of the research on bimetallic catalysts. Focuses attention on the possibility of influencing the selectivity of chemical transformations on metal surfaces and preparing metal alloys in a highly dispersed state. Covers the validation and elucidation of the bimetallic cluster concept. Includes figures and tables.
Download or read book Platinum tin Bimetallic Catalysts Supported on L zZeolite written by Hui Wang and published by . This book was released on 1998 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Synthesis and Characterization of Bimetallic Platinum gold Catalysts written by Corina Mihut and published by . This book was released on 2002 with total page 410 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metals Abstracts written by and published by . This book was released on 1996 with total page 1650 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Controlled Surface Segregation Leads to Efficient Coke resistant Nickel platinum Bimetallic Catalysts for the Dry Reforming of Methane written by and published by . This book was released on 2015 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface composition and structure are of vital importance for heterogeneous catalysts, especially for bimetallic catalysts, which often vary as a function of reaction conditions (known as surface segregation). The preparation of bimetallic catalysts with controlled metal surface composition and structure is very challenging. In this study, we synthesize a series of Ni/Pt bimetallic catalysts with controlled metal surface composition and structure using a method derived from surface organometallic chemistry. The evolution of the surface composition and structure of the obtained bimetallic catalysts under simulated reaction conditions is investigated by various techniques, which include CO-probe IR spectroscopy, high-angle annular dark-field scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, extended X-ray absorption fine structure analysis, X-ray absorption near-edge structure analysis, XRD, and X-ray photoelectron spectroscopy. It is demonstrated that the structure of the bimetallic catalyst is evolved from Pt monolayer island-modified Ni nanoparticles to core-shell bimetallic nanoparticles composed of a Ni-rich core and a Ni/Pt alloy shell upon thermal treatment. As a result, these catalysts are active for the dry reforming of methane, and their catalytic activities, stabilities, and carbon formation vary with their surface composition and structure.
Download or read book Catalytic Properties of Platinum and Tungsten Carbide based Bimetallic Surfaces written by Michael P. Humbert and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Bimetallic surfaces often possess catalytic properties that differ from those of their parent metals, often resulting in activities and/or selectivities higher than those achievable with a monometallic catalyst. In addition, it is possible that the properties of bimetallic catalysts can be tuned by controlling their composition. In a fuel cell, for example, modifying Pt with small amounts of Au has the ability to stabilize the Pt while maintaining the activity of unmodified Pt. However, while increasing the amount of Au improves the stability, it does so at the expense of the activity of the underlying Pt. A plethora of additional examples can be given, and it is the wide range of applications that these materials may impact that has been the driving force behind the study of their properties. One class of bimetallic catalysts that has received a great deal of attention is Pt modified by 3d transition metals. A novel low-temperature cyclohexene hydrogenation pathway was found on Ni-modified Pt. Specifically, subsurface Ni modification of Pt(111) resulted in the improved catalytic activity. In order to determine the driving force behind the improvement in activity on Pt-Ni-Pt(111), a study of the interaction of hydrogen and cyclohexene with these surfaces was performed. From these results it was hypothesized that a weaker hydrogen binding energy (HBE) and cyclohexene binding energy were responsible for the novel properties of the Pt-Ni-Pt(111) surface. However, results on Pt-Co-Pt(111) seemed to conflict with this hypothesis as this surface had a weaker HBE and cyclohexene BE than did Pt-Ni-Pt(111), yet the activity on Pt-Ni-Pt(111) remained higher. The aim of this work was to explain this apparent discrepancy. By extending the Ni and Co-modified Pt(111) results to Fe and Cu-modified Pt(111), a volcano plot was found that related hydrogenation activity to the binding energy of cyclohexene. Further, Pt-Ni-Pt(111) had a binding energy near the optimal value. Thus, while the binding energy of hydrogen and cyclohexene on Pt-Co-Pt(111) was lower than that on Pt-Ni-Pt(111), it was too low such that Co modification of Pt led to lower activity than Ni modification. A similar result held for the case of acrolein hydrogenation, for which it was found that Pt-Ni-Pt(111) also provided an optimal binding energy to promote hydrogenation. In addition to the obvious impact of these results, the ability to correlate hydrogenation activity to a value which can be determined from density functional theory calculations leaves open the possibility to predict a priori additional surfaces which may possess attractive catalytic properties. While these results were promising, it was important to determine if Pt surfaces more relevant to industrial catalysts possessed the same activity improvement through modification with Ni. To that end, the single crystal studies were extended to polycrystalline Pt. As on Pt(111), Ni modification of Pt foil increased the activity toward hydrogenation. However, it was found that subsurface Ni was not necessary to promote this reaction since the Ni-Pt-Pt foil surface was also active toward this pathway. This was hypothesized to be due to the decreased binding energy of cyclohexene on the Ni-Pt-Pt(100) facet, or due the ability of Ni to form an alloy with Pt defect sites at lower temperatures than on Pt(111). Thus, the importance of considering the effect of the presence of multiple crystal facets, step edges, grain boundaries, and other defects was demonstrated. While, it was found that subsurface Ni-modification of polycrystalline Pt was not necessary for the production of cyclohexane from cyclohexene, subsurface Ni was necessary for the production of benzene, which was attributed to the lower binding energy of the benzene intermediate on Pt-Ni-Pt foil. Similar results were found for the hydrogenation of acrolein on Nimodified Pt foil. Specifically, surface and subsurface Ni enhanced the C=C hydrogenation pathway while subsurface Ni was required to hydrogenate the C=O moiety. Finally, it was desired to utilize the Pt-like properties of WC to replace the bulk Pt in Pt-Ni-Pt to arrive at an analogous Pt-Ni-WC surface. The reaction pathways of cyclohexene and acrolein were studied on this surface with the result that the activities and selectivities for cyclohexene and acrolein hydrogenation were similar on the Pt-Ni-Pt and Pt-Ni-WC surfaces. This led to the conclusion that it may indeed be feasible to replace the bulk Pt while producing a cheaper, more stable alternative.
Download or read book Catalysis by Gold written by Geoffrey Colin Bond and published by World Scientific. This book was released on 2006 with total page 383 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gold has traditionally been regarded as inactive as a catalytic metal. However, the advent of nanoparticulate gold on high surface area oxide supports has demonstrated its high catalytic activity in many chemical reactions. Gold is active as a heterogeneous catalyst in both gas and liquid phases, and complexes catalyse reactions homogeneously in solution. Many of the reactions being studied will lead to new application areas for catalysis by gold in pollution control, chemical processing, sensors and fuel cell technology. This book describes the properties of gold, the methods for preparing gold catalysts and ways to characterise and use them effectively in reactions. The reaction mechanisms and reasons for the high activities are discussed and the applications for gold catalysis considered. Sample Chapter(s). Chapter 1: Introduction to Catalysis (892 KB). Contents: Introduction to Catalysis; The Physical and Chemical Properties of Gold; Physical Properties and Characterisation of Small Gold Particles; Preparation of Supported Gold Catalysts; Chemisorption of Simple Molecules on Gold; Oxidation of Carbon Monoxide; The Selective Oxidation of Carbon Monoxide; Selective Oxidation; Reactions Involving Hydrogen; The WaterOCoGas Shift; Reactions of Environmental Importance; Catalysis by Soluble and Supported Gold Compounds; Miscellaneous Reactions Catalysed by Gold; Commercial Applications. Readership: Postgraduate level researchers in academia and industry, as well as general readers."
Download or read book Synthesis and Characterization of Nickel Platinum and Cobalt Platinum Pseudomorphic Overlayer Catalysts Intended for Aqueous Phase Reforming of Lactose written by Michael D. Skoglund and published by . This book was released on 2013 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt: Alumina supported bimetallic overlayer Re@Pd, Ni@Pt, and Co@Pt (core@shell) catalysts have been synthesized using the directed deposition technique. Single crystal and first principles computational studies have indicated that the formation of an overlayer atop a base metal can have an electronic effect on the surface overlaying metal that ultimately can increase or decrease binding energies for adsorbed species such as H2 and CO. In order to detect electronic modifications of the overlaying Pd or Pt metal several characterization techniques were employed. These techniques include: hydrogen and carbon monoxide chemisorption, an ethylene hydrogenation descriptor reaction, and X-ray absorption spectroscopy. Non-structured bimetallic alloy catalysts were also examined for the Ni and Co systems and when compared to overlayer catalysts exhibited notably different behavior. To determine if changes in catalytic behavior previously reported for Re@Pd overlayer catalyst was not caused by particle size effects, samples were made with different metal loading, dispersion, and particle size. Particle size effects have long been known to play a role in catalytic behavior as smaller particles tend to have more unsaturated, highly reactive, metal sites (e.g., corners, kinks, and edges). It was found that the 7 wt% Re@Pd (~6 nm particle size) demonstrated similar reductions in quality and strength of hydrogen adsorption as were seen for the smaller particle 2 wt% Re@Pd (~3 nm particle size) counterpart. Ethylene hydrogenation activity also proved consistent when normalized based on active Pd sites. Results indicate that the formation of a Pd overlayer was the reason for observed changes in adsorption and hydrogenation activity and the effect cannot be merely attributed to particle size effects. Aqueous phase reforming (APR) has proven capable of reforming a feed into H2 under moderate pressures and temperatures. Because the APR reaction produces H2 and CO products, a catalyst that has a decrease in product adsorptions strength should make for an ideal APR catalyst. Ni@Pt and Co@Pt catalyst have demonstrated a decrease in hydrogen and carbon monoxide adsorption strength and have shown a reduction in ethylene hydrogenation activity when compared to a pure Pt catalyst. XAS studies have shown that overlayer catalysts demonstrate near edge absorption characteristics dissimilar to that of bimetallic catalyst of similar loading indicating that overlayer synthesis is not merely creating a bimetallic alloy. Successive overlayer depositions resulted in an increase in both Pt-M coordination number and interatomic distance indicating that multiple depositions could be depositing multiple overlayers of platinum. However, even with multiple layers deposited, overlayer catalytic activity remains different than that of non-structured bimetallic alloys and is in line with single crystal and computational predictions for overlayer catalyst systems.
Download or read book The Structure and Surface Compositions of Supported Pt Ru Bimetallic Catalysts written by Bahman Rejai-Dehkordi and published by . This book was released on 1989 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:
