Download or read book A spectroscopic characterization of the structure of supported metal catalysts written by Johannus Hubertus Anna Martens and published by . This book was released on 1988 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterization of Solid Materials and Heterogeneous Catalysts 2 Volume Set written by Michel Che and published by John Wiley & Sons. This book was released on 2012-05-14 with total page 1313 pages. Available in PDF, EPUB and Kindle. Book excerpt: This two-volume book provides an overview of physical techniques used to characterize the structure of solid materials, on the one hand, and to investigate the reactivity of their surface, on the other. Therefore this book is a must-have for anyone working in fields related to surface reactivity. Among the latter, and because of its most important industrial impact, catalysis has been used as the directing thread of the book. After the preface and a general introduction to physical techniques by M. Che and J.C. Vedrine, two overviews on physical techniques are presented by G. Ertl and Sir J.M. Thomas for investigating model catalysts and porous catalysts, respectively. The book is organized into four parts: Molecular/Local Spectroscopies, Macroscopic Techniques, Characterization of the Fluid Phase (Gas and/ or Liquid), and Advanced Characterization. Each chapter focuses upon the following important themes: overview of the technique, most important parameters to interpret the experimental data, practical details, applications of the technique, particularly during chemical processes, with its advantages and disadvantages, conclusions.

Download or read book Spectroscopic Characterization of Supported Metal Oxide Catalysts written by Michael Andrew Vuurman and published by . This book was released on 1992 with total page 167 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterization of the Structure Bonding Uniformity and Catalytic Properties of Supported Molecular Iridium Catalysts written by Adam Scott Hoffman and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Supported metal catalysts are widely applied in technology, and a class of such catalysts, supported single-site metal catalysts, is drawing increasing attention because of prospects for increased application and the opportunities for fundamental understanding afforded by such catalysts made to have nearly uniform structures. Elucidation of structure-catalytic activity relationships of supported metals is complicated by the heterogeneity of the metal bonding sites on almost all support surfaces, especially those that are amorphous or incorporate multiple phases. The research summarized in this dissertation was carried out with the goal of fundamental understanding of the structures, reactivities, and catalytic properties of supported single-site catalysts with relatively well-defined structures. The catalyst samples consisted of Ir(C2H4) 2 or Ir(CO)2 supported on MgO or HY zeolite. The catalysts were synthesized by chemisorbing Ir(C2H4)2(acac) or Ir(CO)2(acac) (acac is acetylacetonate) on the above-mentioned supports that had been treated at elevated temperatures to remove water, or, in the case of MgO, to generate unique surface sites for bonding of the metal. The samples were characterized by infrared spectroscopy, X-ray absorption spectroscopy (including X-ray absorption near edge structure and extended X-ray absorption fine structure (EXAFS) analysis), scanning transmission electron microscopy, X-ray diffraction, N2 adsorption, and thermogravimetric analysis. The samples were tested as catalysts for the ethylene hydrogenation reaction. The research yielded four main results. First, a spectroscopic cell was developed for characterization of supported ultra-low loading metal catalyst, second, infrared spectroscopy characterizing metal carbonyls elucidated the uniformity of the metal-support interaction, third, high-energy-resolution X-ray absorption spectroscopy was used to identify ligands not detectable with infrared, and finally a limiting case of the metal-support interaction is identified and characterized. A specific goal was to generate unique surface sites on MgO as a support for samples with iridium loadings as low as 0.01 wt%, to determine sites for preferential bonding of iridium to the support. For characterization of samples with low iridium loadings using X-ray absorption spectroscopy, a novel experimental X-ray absorption spectroscopy cell was designed and fabricated; it allows for investigation of samples in transmission or fluorescence detection modes at temperatures up to 300°C under flow or vacuum conditions. Infrared characterization of the [nu][subscript CO] bands of supported Ir(CO)2 showed that narrower full bands corresponded to higher degrees of uniformity of the supported metal species, with the most uniform being those on zeolites, as a consequence of high degree of crystallinity and uniformity of bonding sites. The results also include new synthesis techniques, such as those involving low synthesis temperatures, high Si:Al ration in the zeolites, and high degrees of support crystallinity resulting from treatments that lead to high degrees of bonding site uniformity. High-energy-resolution fluorescence detection X-ray absorption spectroscopy was used to detect the dynamic exchange of C2H4 and CO ligands on the single-site Ir under conditions for which the sensitivity of conventional infrared spectroscopy was insufficient. The improved resolution in the XANES region also identified specific, assignable, features to C2H4 and CO ligands making it a valuable technique for catalyst characterization. EXAFS analysis of samples consisting of Ir(C2H4)2 supported on MgO demonstrated a change in coordination with decreasing loading and a limiting case of tripodal iridium on the MgO surface. The tripodal species have low initial activity for ethylene hydrogenation relative to the corresponding bipodal species, but they are characterized by greater thermal stability and can be used stably as catalysts at temperatures as high as at least to 300°C in reductive atmospheres. The results show that various surface sites can be involved in the bonding metals to MgO and that these sites exhibit distinct properties.

Download or read book Supported Metals in Catalysis written by James Arthur Anderson and published by World Scientific. This book was released on 2012 with total page 581 pages. Available in PDF, EPUB and Kindle. Book excerpt: With contributions from experts in supported metal catalysis, from both the industry and academia, this book presents the latest developments in characterization and application of supported metals in heterogeneous catalysis. In addition to a thorough and updated coverage of the traditional aspects of heterogeneous catalysis such as preparation, characterization and use in well-established technologies such as Naphtha reforming, the book also includes emerging areas where supported metal catalysis will make significant contributions in future developments, such as fuel cells and fine chemicals synthesis. The second edition of Supported Metals in Catalysis comes complete with new and updated chapters containing important summaries of research in a rapidly evolving field. Very few other books deal with this highly pertinent subject matter, and as such, it is a must-have for anyone working in the field of heterogeneous catalysis.

Download or read book Synthesis Characterization and Performance of Supported Molecular Catalysts written by Erjia Guan and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Metals are dominant catalysts, being used in forms ranging from simple atomically dispersed (single-site) metal complexes to few-atom clusters to nanoparticles to bulk metals. Investigations of atomically dispersed metal complexes are drawing wide attention because their well-defined structures facilitate fundamental understanding of catalysis as well as offering new catalytic properties. In this work, we extend the field of atomically dispersed supported metal catalysts to dinuclear clusters to build a bridge between atomically dispersed metal complexes and few-atom clusters. Thus, the research extends the subject of atomically dispersed supported catalysts to supported metal pair-site catalysts, which have heretofore been little investigated because of their instability, lack of uniformity, and difficulty of precise synthesis. A separate, collaborative project reported on here includes characterization by in-situ X-ray absorption spectroscopy of the structures of single-site supported metals present as promoters in complex catalysts that contain metal nanoparticles for selective hydrogenation of nitroarenes. Iridium and rhodium pair-site catalysts supported on MgO were synthesized and characterized with infrared (IR) and X-ray absorption spectroscopies and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM), supported by density functional theory (DFT) calculations done by collaborators. In-situ IR and X-ray absorption near edge structure (XANES) spectra were used to characterize the structural changes of the pair-sites under various treatment conditions, including ligand substitution reactions involving CO and hydrogen. Catalytic properties for ethylene hydrogenation and H-D exchange in the H2 + D2 reaction were tested and compared with those of single-site iridium and rhodium analogues as well as few-atom clusters of these metals supported on MgO. The pair-site catalysts on MgO activated by removal of ligands facilitate H2 dissociation much more rapidly than their single-site analogues and catalyze ethylene hydrogenation one to two orders of magnitude faster than their single-site analogues on MgO. The pair sites are active for ethylene hydrogenation even after being partially poisoned by CO, and, in contrast, the analogous single-site catalysts are fully poisoned. The results provide understanding of the roles of neighboring metal sites and the effects of ligands on pair sites catalysts, opening opportunities for synthesis of stable pairs of various metals on various supports. The benefits of such stable metal pair sites may extend to numerous reactions other than those investigated in this work. The single-site promoters investigated in this work are Sn cations on TiO2 supports that incorporate noble metal nanoparticle catalysts. These catalysts decidedly outperform the comparable unpromoted supported metals for hydrogenation of nitroarenes substituted with various reducible groups. X-ray absorption spectroscopy at the Sn K edge was used to characterize the structural changes in the single-site Sn in the catalysts as influenced by H2 and by nitrobenzene at 353 K and 1 atm. The changes in Sn–O coordination numbers and distances give evidence that the high activity and selectivity of these catalysts result from the creation of oxygen vacancies on the TiO2 surface associated with single-site Sn sites that lead to efficient, selective activation of the nitro group (in contrast to the other reducible group) coupled with reaction involving hydrogen atoms activated on the nearby metal nanoparticles.

Download or read book Metal Oxide Catalysis 2 Volume Set written by S. David Jackson and published by John Wiley & Sons. This book was released on 2008-11-24 with total page 916 pages. Available in PDF, EPUB and Kindle. Book excerpt: With its two-volume structure, this handbook and ready reference allows for comprehensive coverage of both characterization and applications, while uniform editing throughout ensures that the structure remains consistent. The result is an up-to-date review of metal oxides in catalysis. The first volume covers a range of techniques that are used to characterize oxides, with each chapter written by an expert in the field. Volume 2 goes on to cover the use of metal oxides in catalytic reactions. For all chemists and engineers working in the field of heterogeneous catalysis.

Download or read book Dispersed Metal Cluster Catalyts by Design written by and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 ligands on the metals and their reactions; EXAFS spectroscopy and high-resolution STEM to determine cluster framework structures and changes resulting from reactant treatment and locations of metal atoms on support surfaces; X-ray diffraction crystallography to determine full structures of cluster-ligand combinations in the absence of a support, and TEM with tomographic methods to observe individual metal atoms and determine three-dimensional structures of catalysts. Electronic structure calculations were used to verify and interpret spectra and extend the understanding of reactivity beyond what is measurable experimentally.

Download or read book Metal Oxide supported Cluster Catalysts Derived from Organometallic Precursors written by Felix ShangChung Lai and published by . This book was released on 2003 with total page 1092 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Catalyst Characterization Science written by Marvin L. Deviney and published by . This book was released on 1985 with total page 640 pages. Available in PDF, EPUB and Kindle. Book excerpt: Highlights the rapid evolution of the surface science of catalysts. Focuses on multi-technique strategies for studying catalytic reactions and catalytic materials. Discusses new developments in electron microscopy, laser-induced desorption, magnetic methods, and new vibrational characterization techniques.

Download or read book Quantitative Spectroscopic Characterization of Surface Metal Oxide Catalytic Active Sites written by Hanjing Tian and published by . This book was released on 2006 with total page 420 pages. Available in PDF, EPUB and Kindle. Book excerpt: A quantitative spectroscopic method was successfully developed by the combination of Raman spectroscopy (both UV and Visible excitation) and UV/Vis Diffuse Reflectance Spectroscopy (DRS). This method has the potential ability to quantitatively characterize the structure of surface species and intermediates, as well as reaction mechanism of supported molybdena and vanadia catalysts in real time and under various conditions (ambient, dehydrated and reaction condition). It was found that the edge energy values of molybdena and vanadia coordination are LIEANERLY degree with the degree of polymerization, this linear relationship could be used to quantitatively determine surface structure of metal oxide. In this approach, for the first time, the surface concentration of monomeric/polymeric VO4 species on supported vanadia catalysts can be measured; and the turnover frequency of monomic/polymeric VO4 on propane oxidative dehydration can be separately determined. The results concluded V-O-support bond is the active site for the propane oxidative dehydration. In this approach, for the first time, the surface structure of Mo/HZSM5 will be assigned as isolated MoO4 and the surface Al-(MoO 4)3 is the active site for methane activation.

Download or read book Spectroscopy in Catalysis written by J. W. Niemantsverdriet and published by John Wiley & Sons. This book was released on 2007-09-24 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: Superbly organized and of great pedagogic value, 'Spectroscopy in Catalysis' describes the most important modern analytical techniques used to investigate catalytic surfaces. These include electron, ion, and vibrational spectroscopy, mass spectrometry, temperature-programmed techniques, diffraction, and microscopy. With the focus on practical use, rather than theory, each chapter presents current applications to illustrate the type of information that the technique provides and evaluates its possibilities and limitations, allowing selection of the best catalyst and the correct technique to solve a given problem. This third edition includes significant new developments and case studies, with all the chapters updated by way of recent examples and relevant new literature. For students and for everyone who wants a digestible introduction to catalyst characterization. From reviews of the previous editions: 'This is a truly valuable book ... very useful for industrial practitioners who need to be aware of the type of information that can be obtained from modern surface spectroscopies .... The book has a superb pedagogic value...' Journal of Catalysis '... this is an excellent text on spectroscopies in catalysis and I highly recommend it for ... introductory courses on heterogeneous catalysis or as a general introductory monograph.' Journal of the American Chemical Society

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 Characterization of the Metal support Interface in Supported Metal and Metal Complex Catalysts written by and published by . This book was released on 1991 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report discusses work on the characterization by extended x-ray absorption fine structure spectroscopy, structures formed on the surface of partially dehydroxylated magnesium oxides by adsorption of (HRe(CO)5).

Download or read book Spectroscopic Characterization of Heterogeneous Catalysts Methods of surface analysis written by J. L. G. Fierro and published by Elsevier Publishing Company. This book was released on 1990 with total page 402 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface spectroscopic techniques / J.L.G. Fierro -- Electronic structure and composition of surfaces / J. Alvarez, M.C. Asensio -- Surface groups on oxides / B.A. Morrow -- Characterization of catalyst structures by extended x-ray absorbtion spectroscopy / J.C. Conesa, P. Esteban, H. Dexpert, D. Bazin -- Characterisation of heterogeneous catalysts by Mössbauer spectroscopy / F.J. Berry.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1991 with total page 1460 pages. Available in PDF, EPUB and Kindle. Book excerpt: Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.

Download or read book Spectroscopic Characterization of Monometallic and Bimetallic Model Catalysts written by Kai Luo and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Monometallic and bimetallic model catalysts on either refractory metal singlecrystals as planar surfaces or oxide supports as nano-size clusters have been systematically studied using X-ray photoemission spectroscopy (XPS), low energy ion scattering spectroscopy (LEIS), low energy electron diffraction (LEED), infrared reflection absorption spectroscopy (IRAS), and temperature programmed desorption (TPD) under ultra-high vacuum (UHV) conditions. Of particular interest in this investigation is the characterization of the surface composition, morphology, and electronic/geometric structure of the following catalysts: Au/TiOx, Au-Pd/Mo(110), Au- Pd/SiO2, Cu-Pd/Mo(110), and Sn/Pd(100). Structure-reactivity correlations during surface-alloy formation and adsorption-desorption processes were explained in terms of ensemble and ligand effects. Prospects of translating the accumulated atomic-level information into more efficient 'real world' catalysts were discussed.