Download or read book Chemistry of Oxygenates on Transition Metal Surfaces written by and published by . This book was released on 1991 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Goal is to understand the requirements for and competition between activation of C-H, C-C, and C-O bonds in the synthesis and decomposition of oxygenates on transition metal surfaces. Efforts during the past year was devoted primarily to the role of activation of?-CH bonds in decarbonylation of higher oxygenates on surfaces of metals such as Rh and Pd; studies were completed of more than a dozen C1-C3 oxygenates on Rh(111), and progress was made with reagents for which?-CH scission is blocked. It is shown that alcohols and aldehydes do not react via a common pathway on on Rh(111). Ethanol and acetaldehyde are formed from CO + H2 by parallel routes on Rh catalysts which do not contain interacting supports or oxide promoters; i.e., the two compounds result from CO insertion into different metal-hydrocarbon bonds. Aldehydes decarbonylate via?-CH scission to form acyl, followed by C-C scission to release an alkyl ligand; this ligand undergoes hydrogenation and dehydrogenation steps. Alcohols form surface alkoxides, but these do not dehydrogenate further to the aldehydes, they release CO + H2 but no volatile hydrocarbon. These results indicate that?-CH scissors to form a surface oxametallacycle intermediate; supporting evidence is spresented for this intermediate. Chemistry of alcohols blocked to different extends at the?-position was also studied; complete blocking (CF3CH2OH) forces the reaction to follow the aldehyde-acyl path, while partial substitution at the? position (branched alcohols) favors the oxametallacycle pathway. (DLC).
Download or read book Chemistry of Oxygenates on Transition Metal Surfaces written by and published by . This book was released on 1991 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: Goal is to understand the requirements for and competition between activation of C-H, C-C, and C-O bonds in the synthesis and decomposition of oxygenates on transition metal surfaces. Efforts during the past year was devoted primarily to the role of activation of [beta]-CH bonds in decarbonylation of higher oxygenates on surfaces of metals such as Rh and Pd; studies were completed of more than a dozen C1-C3 oxygenates on Rh(111), and progress was made with reagents for which [beta]-CH scission is blocked. It is shown that alcohols and aldehydes do not react via a common pathway on on Rh(111). Ethanol and acetaldehyde are formed from CO + H2 by parallel routes on Rh catalysts which do not contain interacting supports or oxide promoters; i.e., the two compounds result from CO insertion into different metal-hydrocarbon bonds. Aldehydes decarbonylate via [alpha]-CH scission to form acyl, followed by C-C scission to release an alkyl ligand; this ligand undergoes hydrogenation and dehydrogenation steps. Alcohols form surface alkoxides, but these do not dehydrogenate further to the aldehydes, they release CO + H2 but no volatile hydrocarbon. These results indicate that [beta]-CH scissors to form a surface oxametallacycle intermediate; supporting evidence is spresented for this intermediate. Chemistry of alcohols blocked to different extends at the [beta]-position was also studied; complete blocking (CF3CH2OH) forces the reaction to follow the aldehyde-acyl path, while partial substitution at the [beta] position (branched alcohols) favors the oxametallacycle pathway. (DLC).
Download or read book Transition Metal Oxides written by H.H. Kung and published by Elsevier. This book was released on 1989-04-01 with total page 299 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book the author presents an up-to-date summary of existing information on the structure, electronic properties, chemistry and catalytic properties of transition metal oxides. The subjects covered in the book can be divided into three sections. The first (chapters 1 to 3) covers the structural, physical, magnetic, and electronic properties of transition metal oxides. Although the emphasis is on surface properties, relevant bulk properties are also discussed. The second section (chapters 4 to 7) covers surface chemical properties. It includes topics that describe the importance of surface coordinative unsaturation in adsorption, the formation of surface acidity and the role of acidity in determining surface chemical properties, the nature and reactivities of adsorbed oxygen, and the surface chemistry in the reduction of oxides. The third section (chapters 8 to 14) is on the catalytic properties. Various catalytic reactions including decomposition, hydrogenation, isomerization, metathesis, selective oxidation, and reactions involving carbon oxides are discussed. Emphasis is placed more on reaction mechanisms and the role of catalysts than on kinetics and processes. Chapters on the preparation of oxide catalysts and on photo-assisted processes are also included. Whenever appropriate, relationships between various topics are indicated. Written for surface physicists, chemists, and catalytic engineers, the book will serve as a useful source of information for investigators and as a comprehensive overview of the subject for graduate students.
Download or read book Oxide Surfaces written by and published by Elsevier. This book was released on 2001-05-21 with total page 677 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book is a multi-author survey (in 15 chapters) of the current state of knowledge and recent developments in our understanding of oxide surfaces. The author list includes most of the acknowledged world experts in this field. The material covered includes fundamental theory and experimental studies of the geometrical, vibrational and electronic structure of such surfaces, but with a special emphasis on the chemical properties and associated reactivity. The main focus is on metal oxides but coverage extends from 'simple' rocksalt materials such as MgO through to complex transition metal oxides with different valencies.
Download or read book Adsorption and Catalysis on Transition Metals and Their Oxides written by Vsevolod F. Kiselev and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 453 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book deals with adsorption and catalysis on the surface of transition elements and their compounds, many of which are in teresting because of their particular electronic structure. The authors have worked through a vast body of experimental evi dence on the structure and properties of surfaces of transition metals and relevant oxides. Consideration is given mostly to simple (as opposed to mixed) oxides of transition elements, to common metals and to the adsorption of simple gases. A great deal of attention is paid to the nature of active surface sites responsible for chemisorption and catalytic transformations. The description relies mainly on the simplified ligand-field theory, which, however, proves quite satisfactory for predicting the adsorptive and catalytic activity of species. In many cases simple systems were explored with the aid of novel techniques, and it is only for such systems that the mechanism of the ele mentary act of adsorption and catalysis can be given adequate treatment. The present monograph has emerged from our earlier work in Russian, which appeared in the Khimiya Publishing House (Mos cow) in 1981. This English edition has, however, been revised completely to broaden its scope and to include more recent a chievements. For fruitful discussions the authors are grateful to A.A.
Download or read book Oxygen Complexes and Oxygen Activation by Transition Metals written by Arthur Martell and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 341 pages. Available in PDF, EPUB and Kindle. Book excerpt: This monograph consists of manuscripts, summary statements, and poster abstracts submitted by invited speakers and poster contributors who participated in the symposium "Oxygen Complexes and Oxygen Activation by Transition Metals," held March 23-26, 1987, at Texas A&M University. This meeting was the fifth annual international symposium sponsored by the Texas A&M Industry-University Cooperative Chemistry Program (IUCCP). The co chairmen of the conference were Professors Arthur E. Martell and Donald T. Sawyer of the Texas A&M University Chemistry Department. The program was developed by an academic-industrial steering committee consisting of the co-chairmen and members appointed by the sponsoring chemical companies Dr. James F. Bradzil, The Standard Oil Company, Ohio; Dr. Jerry R. Ebner, Monsanto Company; Dr. Craig Murchison, Dow Chemical Company; Dr. Donald C. Olsen, Shell Development Company; Dr. Tim R. Ryan, Celanese Chemical Company; and Dr. Ron Sanderson, Texaco Chemical Company. The subject of this conference reflects the intense interest that has developed in academic institutions and industry on several aspects of dioxygen chemistry. These include the formation of dioxygen complexes and their applications in facilitated transport and oxygen separation; homo geneous and heterogeneous catalysis of oxidation; and oxygenation of organic substrates by molecular oxygen. The conference differs in two respects from several other symposia on dioxygen chemistry held during the past few years. First, there is extensive industrial participation, especially with respect to oxygen activation.
Download or read book Electronic Structure and Reactivity of Metal Surfaces written by E. Derouane and published by Springer Science & Business Media. This book was released on 2013-03-09 with total page 636 pages. Available in PDF, EPUB and Kindle. Book excerpt: Imagine that a young physicist would approach a granting agen cy and propose to contribute to heterogeneous catalysis by studying the heat conductivity of gases in contact with a hot filament. How would he be received now? How would he have been treated sixty years ago ? Yet, more than sixty years ago, Irving Langmuir, through his study of heat transfer from a tungsten filament, uncovered most of the fundamental ideas which are used to-day by the scientific com munity in pure and applied heterogeneous catalysis. Through his work with what were for the first time "clean" metal surfaces, Langmuir formulated during a period of a little over ten years un til the early thirties, the concepts of chemisorption, monolayer, adsorption sites, adsorption isotherm, sticking probability, cata lytic mechanisms by way of the interaction between chemisorbed spe cies, behavior of non-uniform surfaces and repulsion between adsor bed dipoles. It is fair to say that many of these ideas constituting the first revolution in surface chemistry have since been refined through thousands of investigations. Countless papers have been pu blished on the subject of the Langmuir adsorption isotherm, the Langmuir catalytic kinetics and the Langmuir site-exclusion adsorp tion kinetics. The refinements have been significant. ThE original concepts in their primitive or amended form are used everyday by catalytic chemists and chemical engineers allover the world in their treatment of experimental data, design of reactors or inven tion of new processes.
Download or read book Theoretical Studies of Transition Metal Surfaces as Electrocatalysts for Oxygen Electroreduction written by Eduardo J. Lamas and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In the last few years the quest towards a hydrogen based economy has intensified interest for effective and less expensive catalysts for fuel cell applications. Due to its slow kinetics, alternative catalysts for the oxygen electroreduction reaction are actively researched. Platinum alloys with different transition metals (for example: Ni, Co and Fe) have shown improved activity over pure Pt. The design of a Pt-free catalysts is also highly desirable, and different alternatives including metalloporphyrins and Pd-based catalysts are being researched. Pd-based catalysts constitute an attractive alternative to Pt alloys in some fuel cell applications, not only because of lower costs but also because of the lower reactivity of Pt alloys towards methanol, which is important for improved methanol crossover tolerance on direct methanol fuel cells. In this work we apply density functional theory (DFT) to the study of four catalysts for oxygen electroreduction. The electronic structure of these surfaces is characterized together with their surface reconstruction properties and their interactions with oxygen electroreduction intermediates both in presence and absence of water. The energetics obtained for the intermediates is combined with entropy data from thermodynamic tables to generate free energy profiles for two representative reaction mechanisms where the cell potential is included as a variable. The study of the barriers in these profiles points to the elementary steps in the reaction mechanisms that are likely to be rate-determining. The highest barrier in the series pathway is located at the first proton and charge transfer on all four catalytic surfaces. This is in good agreement with observed rate laws for this reaction. The instability of hydrogen peroxide on all surfaces, especially compared with the relatively higher stability of other intermediates, strongly points at this intermediate as the most likely point where the oxygen bond is broken during oxygen reduction. This adds to the argument that this path might be active during oxygen electroreduction. A better understanding behind the reaction mechanism and reactivities on these representative surfaces will help to find systematic ways of improvement of currently used catalysts in the oxygen electroreduction reaction.
Download or read book Transition Metal Catalysis in Aerobic Alcohol Oxidation written by Francesca Cardona and published by Royal Society of Chemistry. This book was released on 2015 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book deals with the search for environmentally benign procedures for the oxidation of alcohols and gives an overview of their transition-metal-catalyzed aerobic oxidation.
Download or read book Theoretical Aspects of Transition Metal Catalysis written by Gernot Frenking and published by Springer Science & Business Media. This book was released on 2005-06-23 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: Transition metal catalysis belongs to the most important chemical research areas because a ubiquitous number of chemical reactions are catalyzed by transition metal compounds. Many efforts are being made by industry and academia to find new and more efficient catalysts for chemical processes. Transition metals play a prominent role in catalytic research because they have been proven to show an enormous diversity in lowering the activation barrier for chemical reactions. For many years, the search for new catalysts was carried out by trial and error, which was costly and time consuming. The understanding of the mechanism of the catalytic process is often not very advanced because it is difficult to study the elementary steps of the catalysis with experimental techniques. The development of modern quantum chemical methods for calculating possible intermediates and transition states was a breakthrough in gaining an understanding of the reaction pathways of transition metal catalyzed reactions. This volume, organized into eight chapters written by leading scientists in the field, illustrates the progress made during the last decade. The reader will obtain a deep insight into the present state of quantum chemical research in transition metal catalysis.
Download or read book Oxygen in Catalysis written by Adam Bielanski and published by CRC Press. This book was released on 1990-11-29 with total page 496 pages. Available in PDF, EPUB and Kindle. Book excerpt: A description of catalytic systems commonly used as model systems in the laboratory and as industrial catalysts in large-scale operations, and a discussion of the mechanisms operating in these reactions. Attempts to describe the elementary steps by quantum chemical methods are also shown, as are rec
Download or read book First principles Studies of the Reactivity of Oxygen on Transition Metal Surfaces written by Ye Xu and published by . This book was released on 2004 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computational Catalysis written by Aravind Asthagiri and published by Royal Society of Chemistry. This book was released on 2014 with total page 277 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents a comprehensive review of the methods and approaches being adopted to push forward the boundaries of computational catalysis.
Download or read book Multiscale Modeling of Oxidation and Reduction Chemistry on Transition Metal Oxides written by Minkyu Kim (Ph. D. in chemical engineering) and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Transition metal catalysts, including platinum, palladium, and etc., are widely used in oxygen rich applications such as catalytic combustion of natural gas in lean gas turbine, exhaust gas remediation in automobiles and power generation. Under such processes, several different oxygen phases can potentially grow on the surface. The reactivity of such oxygen phases can be dramatically different and therefore there is a need to understand both the oxygen phase that exists under reaction conditions and the reactivity of such oxygen phases. To understand reactivity and stability of important transition metal oxide surfaces including PdO(101), RuO2(110), and IrO2(110), we investigated surface chemistry including thermal reduction, CO and alkane oxidation over those surfaces by using multiscale modeling approach compared with surface science experiments. This approach is based on developing kinetic Monte Carlo (kMC) models based on DFT calculations of the elementary steps occurring on the surface. The DFT based kMC simulations allow us to elucidate the role of various mechanisms on the overall reactivity of the surfaces under low and ambient pressures, and reaction conditions.
Download or read book Mechanistic Studies for Catalytic Transformation of Small Oxygenates on Transition Metals written by Suyash Singh and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past century, heterogeneous catalysis has played a central role in the development of efficient chemical processes for the conversion of fossil resources to fuels and chemicals, and identification of new, sustainable routes to upgrade renewable carbon sources that minimize the ecological footprint. More recently, unprecedented advances in electronic structure theory and related computational methods have provided a major thrust to the efforts that utilize density function theory (DFT) calculations for developing fundamental atomic-level understanding of these processes, and subsequently designing new and improved catalysts. In this dissertation, a combined theoretical and experimental approach is presented to study the reaction mechanisms for the catalytic conversion of formic acid (FA) and propylene oxide on transition metals. An iterative methodology comprising of DFT calculations, reaction kinetics measurements, and mean-field microkinetic modeling is employed to determine the nature of active sites on supported catalysts, explain the experimentally observed trends, and obtain predictions for the surface environment under reaction conditions. A detailed analysis of the DFT derived thermochemistry and kinetics parameters over a wide range of transition metal surfaces is performed to identify the key reactivity descriptors for FA decomposition on transition metal catalysts, and develop semi-empirical linear correlations that are then used to develop a microkinetic modeling based framework for the identification and design of improved (active and selective) bimetallic alloy catalysts. Finally, the possible utilization and applications of these methods and ideas in other key chemical transformations are proposed, and suggestions for future work are included.
Download or read book The Chemistry of Transition Metal Carbides and Nitrides written by S.T. Oyama and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 565 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book arose from a symposium titled 'Transition Metal Carbides and Nitrides: Preparation, Properties, and Reactivity' organized by Jae Sung Lee, Masatoshi Nagai and myself. The symposium was part of the 1995 Congress of Pacific Rim Chemical Societies, held in Honolulu, Hawaii between December 17-22, 1995. The meeting was the first major conference to exclusively address the theme of metal carbides and nitrides, and brought together many of the major researchers in the field. Over 50 scientists and engineers reported their latest findings in five sessions of presentations and discussions. The book closely follows the topics covered in the conference: Theory of bonding Structure and composition Catalytic properties Physical properties New methods of preparation Spectroscopy and microscopy The book is unique in its coverage. It provides a general introduction to the properties and nature of the materials, but also covers their latest applications in a wide variety of fields. It should thus be of interest to both experts and nonexperts in the fields of material science, solid-state chemistry, physics, ceramics engineering, and catalysis. The first chapter gives an overview, and many of the chapters provide summaries of advanced topics. All contributions were peer-reviewed.
Download or read book Quantum Chemistry Approaches to Chemisorption and Heterogeneous Catalysis written by F. Ruette and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 379 pages. Available in PDF, EPUB and Kindle. Book excerpt: The development of "high-tech" materials in contemporary industries is deeply related to a detailed understanding of specific surface properties of catalysts which make particular reactions possible. But this understanding presupposes that there exists a body of theory capable of explaining situations not easily accessible to experimental methods and of relating experimental findings among themselves and with theoretical constructs. For these reasons, theoretical developments in surface physics and surface chemistry of transition metal compounds have been of paramount importance in promoting progress in catalysis, electronic devices, corrosion, etc. Although a great variety of spectroscopic methods for analyzing solids and surfaces at molecular scale have been introduced in recent years, nevertheless, many questions about the adsorption sites and intermediates, the effect of promoters, the poisoning of active sites, the nature of segregation of impurities, the process of surface reconstruction, the mechanisms of reactions, etc. have remained unanswered simply because of the great complexity of surface phenomena. It is in this sense that quantum mechanical method- combined with experimental data - may shed some light on the microscopic properties of new surface materials.
