Download or read book The Structure and Activity of Supported Metal Catalysts II Crystallite Size and CO Chemisorption on Platinum silica Catalysts Reprinted from Journal of Catalysis Vol 7 No 4 April 1967 written by T. A. Dorling and published by . This book was released on 1967 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Structure and Activity of Supported Metal Catalysts I Crystallite Size and Specific Activity for Benzene Hydrogenation of Platinum silica Catalysts Reprinted from Journal of Catalysts Vol 5 No 1 February 1966 written by T. A. Dorling and published by . This book was released on 1966 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Influence of Metal support Interactions and Crystallite Size on the Adsorption and Catalytic Behavior of Platinum Catalysts written by Bishwajit Sen and published by . This book was released on 1987 with total page 804 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Reactivity and Characterization of Supported Noble Metal Catalysts written by Keishla R. Rivera-Dones and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalytically driven processes account for over ninety percent of industrial chemical manufacturing today. Developments in manufacturing processes are largely driven by continued improvements in catalytic materials, which aim to increase production volumes while minimizing costs along with safety and environmental hazards. In order to achieve these goals, however, a rational approach in catalyst design must be pursued that aims to understand and build upon the fundamental structural, electronic, and chemical properties governing catalytic performance. To that purpose, the work presented in this dissertation makes use of kinetic experiments, theoretical models, and advanced characterization techniques to generate a fundamental understanding of noble metal surfaces employed in a variety of catalytic reaction systems. In Chapter 2, we discuss the use of N2 physisorption, CO chemisorption, and NH3 temperature programed desorption to evaluate the effect of support acidity on the reactivity profiles of various zeolite-supported Pt and Pt-Sn catalysts for the non-oxidative coupling of methane to ethylene and aromatics. Reactivity studies for Pt-Sn/H-ZSM-5 catalysts at 973 K showed that, while all catalysts produced ethylene as the primary product, increasing support acidity led to an increase in naphthalene selectivity at the expense of benzene selectivity. Volcano-shaped profiles observed for the generation of aromatic products suggest that the formation of a reactive hydrocarbon pool on acidic support surfaces could be responsible for the oligomerization of ethylene. Notably, the Pt-Sn/H-ZSM-5 (SiO2:Al2O3 = 50) catalyst was found to be comparable to the state-of-the-art Mo/H-ZSM-5 catalysts in terms of carbon product generation and resistance to coke formation. In Chapter 3, x-ray absorption spectroscopy (XAS) was used to highlight the effect of local electronic and structural environments in specially synthesized metallic catalysts. The local coordination and nearest-neighbor distance of Pd species were evaluated to understand metal dispersion and the effect of catalyst support on the extent of bimetallic particle formation in Pd, AgPd, CuPd, and AuPd catalysts synthesized by controlled surface reactions (CSR) for a variety of amination, hydrodechlorination, and hydrogenation reactions. Near-edge structure analyses were also used on these Pd catalysts, as well as on a set of Mo-containing multi-metallic catalysts prepared by atomic layer deposition (ALD) for synthesis gas conversion, to understand catalyst reducibility along with potential support and hydrogen spillover effects on the extent of metal reduction. Chapter 4 evaluates the effects of catalyst support and pretreatment conditions on the hydrogenation of acetone over SiO2-, Al2O3-, and ZSM-5-supported platinum catalysts. Pt/ZSM-5 catalysts were found to have specific conversion rates and turnover frequencies that were 2 - 3 orders of magnitude higher than those observed over Pt/SiO2 and Pt/Al2O3 catalysts, regardless of zeolite acidity or pretreatment conditions. For Pt/ZSM-5 catalysts, the higher activity was achieved by increasing calcination and decreasing reduction temperatures, likely due to the effects of these treatments on the morphology of the platinum particles. CO-FTIR measurements showed a shift to higher frequencies of the Pt-CO band in Pt/ZSM-5 catalysts compared to Pt/SiO2, which alluded to the interactions between Pt and the porous zeolite structure as a source of the activity enhancements observed. Chapter 5 introduces the use of transient kinetics studies and theoretical modeling to explore the importance of surface coverage effects in the hydrogenation of acetone over platinum. Transient models based on steady-state microkinetics using static and dynamic inclusion of surface coverage via the Langmuir and Bragg-Williams approximations, respectively, predicted notable differences in the decay profiles of the most abundant reactive intermediate (MARI) from the catalytic surface. Experimental studies using steady-state isotopic transient kinetic analysis (SSITKA) methods served to validate the theoretical predictions for transients induced by complete acetone removal from or its substitution in the reactant feed and provided tangible evidence for the importance of surface coverage effects in understanding the reactivity of platinum catalysts for acetone hydrogenation. Lastly, Chapter 6 addresses possible future research directions in the field of transient kinetics studies.
Download or read book Properties of Supported Metal Catalysts Progress Report April 1 June 30 1979 Al2O3 supported Pt written by and published by . This book was released on 1979 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The preparation and characterization of supported platinum catalysts has been extended to a series of alumina-supported catalysts similar to the previously investigated platinum--silica series. Characterization has been carried out via hydrogen chemisorption, hydrogen--oxygen titration, hydrogenolysis of methylcyclopropane and deuterium exchange with cyclopentane. In all, some twenty catalysts, with platinum percentage exposed ranging from 4.1 to 103% have been prepared and characterized. As was the case for the silica supported platinum, the specific conditions of catalyst pretreatment have been found to affect substantially the structure sensitive behavior in all cases. In addition, the thermal conditions employed in catalyst preparation affect the nature of structure sensitive behavior, which was not the case for Pt/SiO2. Substantial effort has been devoted to the development of a suitable system for making x-ray measurements in controlled atmospheres. Several of the Pt/SiO2 catalysts have been investigated in hydrogen atmospheres, with the curious result that the apparent loading of metal detected in hydrogen is lower than that determined in air (which agreed with the value determined in preparation).
Download or read book Metal support Interactions in Catalysis Sintering and Redispersion written by Scott A. Stevenson and published by . This book was released on 1987 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt: Very Good,No Highlights or Markup,all pages are intact.
Download or read book The Structure and Activity of Supported Metal Catalysts Lecture Given at Royal Institute of Chemistry Symposium Catalysis Theory and Practice London April 1967 written by Ronald Laidlaw Moss and published by . This book was released on 1967 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characterization and Reaction Studies of Silica Supported Platinum and Rhodium Model Catalysts written by Matthew James Lundwall and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The physical and catalytic properties of silica supported platinum or rhodium model catalysts are studied under both ultra high vacuum (UHV) and elevated pressure reaction conditions (>1torr). Platinum or rhodium nanoparticles are vapor deposited onto a SiO2/Mo(112) surface and characterized using various surface analytical methods. CO chemisorption is utilized as a surface probe to estimate the concentration of various sites on the nanoparticles through thermal desorption spectroscopy (TDS) and infrared reflection absorption spectroscopy (IRAS) along with microscopy techniques to estimate particle size. The results are compared with hard sphere models of face centered cubic metals described as truncated cubo-octahedron. Results demonstrate the excellent agreement between chemisorption and hard sphere models in estimating the concentration of undercoordinated atoms on the nanoparticle surface. Surfaces are then subjected to high pressure reaction conditions to test the efficacy of utilizing the rate of a chemical reaction to obtain structural information about the surface. The surfaces are translated in-situ to a high pressure reaction cell where both structure insensitive and sensitive reactions are performed. Structure insensitive reactions (e.g. CO oxidation) allow a method to calculate the total active area on a per atom basis for silica supported platinum and rhodium model catalysts under reaction conditions. While structure sensitive reactions allow an estimate of the types of reaction sites, such as step sites ([less than or equal to]C7) under reaction conditions (e.g. n-heptane dehydrocyclization). High pressure structure sensitive reactions (e.g. ethylene hydroformylation) are also shown to drastically alter the morphology of the surface by dispersing nanoparticles leading to inhibition of catalytic pathways. Moreover, the relationships between high index single crystals, oxide supported nanoparticles, and high surface area technical catalysts are established. Overall, the results demonstrate the utility of model catalysts in understanding the structure-activity relationships in heterogeneous catalytic reactions and the usefulness of high pressure reactions as an analytical probe of surface morphology.
Download or read book Synthesis and Characterization of Pt and Pd Overlayer Catalysts for Aqueous Phase Reforming of Lactose and Hydrodeoygenation of Guaiacol and Anisole written by Qinghua Lai and published by . This book was released on 2016 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt: Supported bimetallic overlayer catalysts, Ni@Pt, Co@Pt, Ni@Pd, and Mo@Pt have been prepared by the directed deposition synthesis technique. The single crystal and computational studies have predicted that formation of Pd or Pt overlayer on Ni, Co or Mo base metal would cause a negative shift of d-band center of surface Pd or Pt, resulting in reduced binding strength for adsorbed species. The hydrogen chemisorption, ethylene hydrogenation descriptor reaction, XRD, H2-TPR, XAS and TEM studies were employed to characterize the catalysts. The alumina supported Ni@Pt and Co@Pt overlayer catalysts have been studied for aqueous phase reforming (APR) of lactose. Silica alumina supported Ni@Pt, Ni@Pd, and Mo@Pt catalysts have been investigated for hydrodeoxygenation (HDO) of lignin derived bio-oils. The H2 chemisorption and ethylene hydrogenation descriptor showed that alumina supported Ni@Pt and Co@Pt overlayer catalysts had reduced adsorption strength compared to a Pt only catalyst, which agrees with the computational prediction. XAS results showed that overlayer catalysts exhibited higher white line intensity than Pt catalyst, indicating a negative d-band shift for the Pt overlayer. Lactose APR studies showed that lactose could be used as feedstock to produce H2 and CO under desirable reaction condition. The Pt active sites of alumina supported Ni@Pt and Co@Pt overlayer catalysts showed significantly enhanced H2 production selectivity and activity when compared with that of a Pt only catalyst. The single deposition overlayer with the largest d-band shift showed the highest H2 activity. Silica alumina supported Ni@Pd, Ni@Pt, and Mo@Pt overlayer catalysts also showed the reduced adsorption strength compared to the Pd or Pt only catalyst. The TEM images of Ni@Pd overlayer catalyst provided evidence for a core/shell type structure. The H2-TPR results demonstrated the close interaction between Pt and Mo species for Mo@Pt overlayer catalysts. Guaiacol and anisole hydrodeoxygenation results showed that Pd and Pt active sites of overlayer catalysts showed significantly enhanced deoxygenation activity compared with that of Pd or Pt only catalyst. Further studies showed that guaiacol and anisole could be completely deoxygenated over the silica alumina supported metal catalysts at high W/F, yielding benzene, toluene, and xylenes as major products.
Download or read book Strong Metal support Interactions written by R. T. K. Baker and published by . This book was released on 1986 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 The Structure and Activity of Supported Metal Catalysts written by and published by . This book was released on 1967 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Surface Organometallic Chemistry Molecular Approaches to Surface Catalysis written by Jean-Marie Basset and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface organometallic chemistry is a new field bringing together researchers from organometallic, inorganic, and surface chemistry and catalysis. Topics ranging from reaction mechanisms to catalyst preparation are considered from a molecular basis, according to which the "active site" on a catalyst surface has a supra-molecular character. This. the first book on the subject, is the outcome of a NATO Workshop held in Le Rouret. France, in May. 1986. It is our hope that the following chapters and the concluding summary of recommendations for research may help to provide a definition of surface organometallic chemistry. Besides catalysis. the central theme of the Workshop, four main topics are considered: 1) Reactions of organometallics with surfaces of metal oxides, metals. and zeolites; 2) Molecular models of surfaces, metal oxides, and metals; 3) Molecular approaches to the mechanisms of surface reactions; 4) Synthesis and modification of zeolites and related microporous solids. Most surface organometallic chemistry has been carried out on amorphous high-surf ace-area metal oxides such as silica. alumina. magnesia, and titania. The first chapter. contributed by KNOZINGER. gives a short summary of the structure and reactivity of metal oxide surfaces. Most of our understanding of these surfaces is based on acid base and redox chemistry; this chemistry has developed from X-ray and spectroscopic data, and much has been inferred from the structures and reactivities of adsorbed organic probe molecules. There are major opportunities for extending this understanding by use of well-defined (single crystal) oxide surfaces and organometallic probe molecules.
Download or read book Supported Metal Catalysts written by J. Hartley and published by . This book was released on 1969 with total page 25 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Understanding and Controlling Metal Support Interactions in Nanocrystalline Bimetallic Catalysts written by Robert J. Davis and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The objectives of this research are to: 1) determine the catalytic behavior of model Pd and Rh catalysts on unpromoted and ceria-promoted supports, for the reduction of NO and N2O with CO, 2) determine the microstructures of the catalysts both before and after reaction in order to understand the catalytic behavior, and 3) understand the role of the metal/support interface in the catalytic process. The research examined the influence of Pd particle size and ceria loading on catalytic reaction for the NO+CO reaction. Dihydrogen chemisorption, temperature-programmed desorption (TPD) of NO, and high-resolution transmission electron microscopy (HRTEM) were used to characterize the catalyst samples. It was found that when ceria is used to promote Pd particles, the activity for NO+CO was a maximum for 2-nm-sized Pd particles. The maximum in activity results from a balance between the Pd/ceria interface, which enhances NO dissociation, and the close-packed planes of the Pd particles that facilitate product formation and/or desorption. The variations in apparent reaction orders and results from TPD were consistent with the idea that NO dissociation is promoted on very small particles (1 nm) and by the addition of ceria. Characterization of the catalysts by HRTEM showed that the ceria was typically present in the form of small crystallites from 3-7 nm in diameter, deposited near Pd particles, rather than as a thin film on the alumina support. This occurred whether the ceria was deposited before or after the Pd particles.
Download or read book Structure of Metallic Catalysts written by John Russell Anderson and published by . This book was released on 1975 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physical and Chemical Characterization of Iron titania Model Supported Catalysts written by Bruce John Tatarchuk and published by . This book was released on 1981 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt:
