Download or read book Surface Science Studies of Olefin Oxidation on the Silver Surface written by Ashay Dileep Javadekar and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The constant urge of making industrial chemical processes economically viable and highly selective to desired products triggers much catalysis research. A broad goal of catalysis research is to design and develop new or improved catalysts for variety of processes. Direct oxidation (oxidation using O 2 To date, ethylene oxide (EO) and epoxybutene (EpB) are the only two epoxides that have been successfully manufactured at industrial levels by direct heterogeneous oxidation. Surface science studies of the mechanisms of these epoxidation processes have demonstrated the formation of reaction intermediates, or air) represents a major class of chemical processes utilizing heterogeneous catalysis. Ethylene epoxidation has 40-50% share in the total value of large volume chemicals produced by direct heterogeneous oxidation. Epoxidation remains one of the most important chemical reactions, but little is understood in terms of reaction mechanism. Most of the catalyst design and improvement in this area has been carried out by empirical approaches at industrial scale. Epoxidation also represents one of most active areas of surface science research, mainly due to the utility of surface science techniques to develop a molecular understanding of epoxidation processes. Understanding reaction mechanisms at a molecular level helps in creating a rational basis for design of more efficient and more selective epoxidation catalysts. The aim of the work included in this thesis is to develop molecular understanding of non-selective pathways in ethylene epoxidation and to isolate intermediates in the formation of epoxybutene on the Ag(111) surface. To date, ethylene oxide (EO) and epoxybutene (EpB) are the only two epoxides that have been successfully manufactured at industrial levels by direct heterogeneous oxidation. Surface science studies of the mechanisms of these epoxidation processes have demonstrated the formation of reaction intermediates, oxametallacycles, in epoxidation reaction sequences. In the case of ethylene oxide, epoxidation proceeds via formation of an oxametallacycle, produced by reaction of ethylene and atomic oxygen on the silver catalyst surface. This oxametallacycle then reacts via one transition state to form EO and another transition state to form acetaldehyde and combustion products. The difference in the activation barriers for these two branching reactions is very small and hence selectivity to EO depends on these two competing pathways. Initial experiments in the current study concentrate on UHV studies of 'path 2', the non-selective pathway in ethylene epoxidation. In surface science experiments examining the reactions of acetaldehyde on an oxygen precovered Ag(111) surface, formation of acetate species was observed. At acetaldehyde exposures sufficient to completely consume oxygen to form acetates, the acetate species decompose to reaction products, predominantly CO 2, at ~550 K. Hence, the acetate species are found to be stable from 300 K to 500 K, within the temperature range at which ethylene oxide production is typically carried out in industry. At lower acetaldehyde coverages producing an adsorbed layer containing both acetates and oxygen atoms, the acetate species decompose near room temperature to form only combustion products, CO 2 and H 2 O, providing a combustion route accessible at the temperatures employed in ethylene epoxidation. These experiments are the first evidence of formation of acetate species on the Ag(111) surface and serve to map out the pathway for complete combustion in ethylene oxidation on silver catalysts. In experiments with 1-epoxy-3-butene on Ag(111) surface, at a lower dosing temperature of 190 K, molecular desorption of EpB is observed. At a higher dosing temperature of 300 K, a high temperature state was observed desorbing at around 510 K, suggesting formation of an intermediate. The product analysis of the desorption spectra indicated formation of EpB, 2,5-dihydrofuran (2,5-DHF) and crotonaldehyde. These observations support the conclusions from steady state reactor experiments, where crotonaldehyde and 2,5-DHF were reported in the final products. In the reactor studies, the rate determining step of butadiene epoxidation was reported to be the desorption of the final EpB product and its isomers, which is also supported by formation of stable intermediate upto 510 K which reacted to form products like 2,5-DHF and crotonaldehyde. For studying promoter effects in UHV, a cesium deposition source capable of producing controlled and very minute Cs loadings was developed. In studying Cs deposition on Ag(111), it has been observed that Cs stays on the Ag(111) surface up to 700 K. This observation is certainly helpful to carry out further research of promoter effects on the reactivity of the intermediate in the EpB formation, as the intermediate in the EpB formation is stable on the surface up to 510 K. Surface science experiments of EpB on the Cs-promoted Ag(111) surface can potentially explain, at the molecular level, the increase in selectivity observed in butadiene oxidation on the CsCl promoted silver catalyst in steady state reactor experiments. The ultimate impact of this research would be demonstration of successful approaches for designing more efficient and more selective epoxidation catalysts.

Download or read book Applications Of X ray Photoelectron Spectroscopy To Catalytic Studies From Routine Analysis To Cutting edge Surface Characterization written by Spyridon Zafeiratos and published by World Scientific. This book was released on 2023-07-04 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt: X-ray photoelectron spectroscopy (XPS) has become a standard practice technique, and automated XPS facilities can be found in industry and in universities all over the world. This transformed XPS from an advanced characterization method for dedicated research, to a rather standard analysis technique of surface analysis. The catalyst's surface state is probably the most prominent factor that influences the catalytic performance. It is therefore no surprise that XPS has become an indispensable tool in studies of solid catalysts. It has been directly used to investigate issues such as the surface composition of the active catalyst and reaction and deactivation mechanisms.The objective of this book is to provide a comprehensive overview of the current status and future perspectives of X-ray photoelectron spectroscopy dedicated to catalytic applications, including thermal catalysis, electrocatalysis, and photo(electro)catalysis. The book contains 13 chapters, starting with the necessary introduction of the technique background, including basic phenomena and instrumentation aspects. The second part of the book focuses on the presentation of long-established applications of the technique, such as XPS studies of model catalysts. Finally, the book describes relatively recent developments of this method for cutting-edge surface characterization mainly using synchrotron X-ray radiation.

Download or read book Investigation of Reactions of Complex Epoxides on Silver 110 written by Adrienne Claire Lukaski and published by ProQuest. This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct oxidation processes, such as ethylene epoxidation to ethylene oxide, have been researched extensively due to the uniqueness of this process and to the commercial significance of the epoxide product. Despite the importance of epoxide production, the mechanistic details of olefin epoxidation remained obscure until recently and the majority of significant advances in Ag catalyst development occurred primarily through empirical methods. Recent surface science studies of ethylene oxide on Ag(111) have identified an oxametallacycle as the active intermediate in ethylene epoxidation; expansion of the epoxide ring to incorporate surface silver atoms forms the oxametallacycle species. Oxametallacycles have been isolated by ring-opening ethylene oxide on Ag(111) and Ag(110), 1-epoxy-3-butene on Ag(111) and Ag(110), styrene oxide on Ag(111) and Ag(110) and isoprene oxide and propylene oxide on Ag(110). Surface science techniques and Density Functional Theory (DFT) were used in this study to investigate the interactions of styrene oxide and isoprene oxide with the Ag(110) surface, as well as the interactions of ethylene oxide and propylene oxide with the clean and O-covered Ag(110) surfaces. TPD experiments demonstrate that the styrene oxide ring opens at the substituted carbon, and DFT calculations indicate that the phenyl ring of the resulting oxametallacycle is oriented nearly parallel to the Ag(110) surface. Interaction of the phenyl group with the silver surface stabilizes this intermediate relative to that derived from the mono-olefin epoxide, ethylene oxide. During TPD, the oxametallacycle undergoes ring closure to reform styrene oxide and isomerization to phenylacetaldehyde at 505 K on Ag(110). Styrene oxide-derived oxametallacycles exhibit similar ring-closure behavior on the Ag(111) surface. Isoprene oxide also forms a strongly bound oxametallacycle intermediate on the Ag(110) surface. The oxametallacycle undergoes ring-closure to reform isoprene oxide in two peaks at 320 and 460 K when synthesized by epoxide adsorption at low temperatures. Epoxide doses at higher surface temperatures (ca. 300 K) lead to isomerization of the oxametallacycle and desorption of the aldehyde isomer, 2-methyl-2-butenal, in a single peak at 460 K. This work represents the first demonstration of a surface oxametallacycle species derived from an allylic epoxide. Similar to oxametallacycles derived from the non-allylic epoxides, isoprene oxide ring opens at the carbon bound to the unsaturated vinyl and methyl substituent groups to form a linear oxametallacycle on the Ag(110) surface. The structure of the isoprene oxide-derived oxametallacycle resembles that formed from ring-opening its non-allylic counterpart, 1-epoxy-3-butene, on Ag(110), according to DFT calculations. Following adsorption at 250 K on both clean and O-covered Ag(110), ethylene oxide ring-opens to form a stable oxametallacycle. On the clean Ag(110) surface, the oxametallacycle reacts to reform the parent epoxide at 280 K during TPD, while the aldehyde isomer, acetaldehyde, is observed at higher oxametallacycle coverages. In the presence of coadsorbed oxygen atoms, a portion of the oxametallacycles dissociate to release ethylene. However, of those that react to form oxygen-containing products, the fraction forming ethylene oxide is similar to that on the clean surface. The acetaldehyde product of oxametallacycle reactions combusts via formation of acetate species; the acetates react to form CO 2 at temperatures as low as 360 K on the O-covered surface. No evidence was observed for other combustion channels. This work provides experimental evidence for the connection of oxametallacycles to combustion via acetaldehyde formation, as well as to ring-closure to form ethylene oxide. Adsorption of propylene oxide at 120 K with subsequent flash of the surface to 230 K prior to TPD leads to the formation of a stable oxametallacycle on both the clean and O-covered Ag(110) surfaces; the oxametallacycle then undergoes ring-closure to reform propylene oxide at 250 K during TPD. The selectivity to propylene oxide decreases at higher oxametallacycle coverages where acetone and allyl alcohol are formed; carbon dioxide is also formed near 250, 350, and 450 K from reactions of the oxametallacycle and its products on the O-covered surface. At higher oxametallacycle coverages, additional higher temperature desorptions are observed at 300 and 400 K; the product distributions in these peaks are the same as that in the 250 K peak. Similar to reactions of ethylene oxide on the O-covered Ag(110) surface, the same fraction of oxametallacycle species reacts to form propylene oxide in the presence of co-adsorbed oxygen as that on the clean surface, although the coverage of oxametallacycles is 10-20% higher on the O-covered surface. The principal effects of co-adsorbed oxygen are to increase the capacity of the surface and to open an additional combustion pathway to CO 2 . The oxametallacycle undergoes combustion through a propionaldehyde species. This work represents the first time that an oxametallacycle has been linked to propylene oxide production.

Download or read book Energy Research Abstracts written by and published by . This book was released on 1981 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Encyclopedia of Surface and Colloid Science written by P. Somasundaran and published by CRC Press. This book was released on 2006 with total page 1084 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Third World Congress on Oxidation Catalysis written by S.T. Oyama and published by Elsevier. This book was released on 1997-09-12 with total page 1277 pages. Available in PDF, EPUB and Kindle. Book excerpt: The overall theme of the 3rd World Congress is "Atom Efficient Catalytic Oxidations for Global Technologies". This theme was chosen to stimulate the participants to report their findings with an emphasis on conserving valuable material in their catalytic transformations, as well as conserving energy, in an environmentally responsible manner. Progress towards this stated goal is substantial as evidenced by the tremendous response of the community in their participation of quality publications complied in these Proceedings of the Congress. The subjects presented span a wide range of oxidation reactions and catalysts. These include the currently important area of lower alkane oxidation to the corresponding olefins, unsaturated aldehydes, acids and nitriles. The four featured lectures and seven plenary lectures constitute the general background and overview of the subject matter at hand. The 104 contributed papers and 13 poster manuscripts, summarized in this compendium, probe new avenues to achieve catalytically efficient oxidation reactions for the future needs of mankind in a global environment.

Download or read book Iron Catalysis Design And Applications written by Jose M Palomo and published by World Scientific. This book was released on 2021-03-15 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt: Iron Catalysis: Design and Applications is an exciting new book that takes readers inside the world of iron catalysis guided by international catalysis expert, Dr Jose M Palomo. Iron is the most abundant metal in the planet, cost-effective, environmentally friendly, with an easily manipulated remediation process. In the last few years the use of this nonprecious metal has gained extraordinary attention particularly for its potential as a catalyst in different areas. This book compiles a series of chapters describing the most significant advances in the last few years since the design of different iron catalysts and nanocatalysts and iron-containing artificial and natural enzymes. The chapters also cover its application in different areas of interest such as organic synthesis, environmental remediation, enzyme-like activities or the creation of novel types of electrodes for battery design.

Download or read book Fundamental Research in Homogeneous Catalysis written by M. Tsutsui and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 247 pages. Available in PDF, EPUB and Kindle. Book excerpt: The objective of this workshop on homogeneous catalysis was to identi fy opportunities for the solution of energy problems and industrial produc tion problems by homogeneous catalysis. The first day of the workshop was devoted to plenary lectures on frontier areas in homogeneous catalysis which set the tone for the workshop. On succeeding days of the workshop, the participants were divided into five working groups for discussion of various aspects of homogeneous catalysis. Each of the five workshops engaged in extensive discussions and then formulated a rough draft of their report and recommendations. The reports of the working groups were presented at a plenary session and suggestions for changes and revisions were made. These minor revisions were incorporated into the working group report by the Co-Chairmen of the working groups. This workshop on homogeneous catalysis was sponsored by the Na tional Science Foundation (United States) and by the National Research Council (Italy). Additional financial support was provided by Montedison, E.N.I., and S.I.R. We wish to thank Mr. William M. Tsutsui for typing and assisting in the editorial work. The Robert A. Welch Foundation Grant A-420 partial ly supported the time spent by M. Tsutsui for the organization of the work shop and the editorial work of the proceedings. Organizing Committee, December, 1976 C. Casey G. P. Chiusoli J. Halpern M. Tsutsui, Co-Editor R. Ugo, Co-Editor v CONTENTS In troduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IX . . . . . . . . . . . .

Download or read book The Chemical Physics of Solid Surfaces and Heterogeneous Catalysis written by David Anthony King and published by . This book was released on 1982 with total page 494 pages. Available in PDF, EPUB and Kindle. Book excerpt: This series of volumes is a unique summary of the present state of understanding of solid surfaces. The physical basis of chemisorption and heterogeneous catalysis is presented as a well-developed science with contributions from an international panel of chemists, physicists and metallurgists. The books are destined to become a fundamental and indispensable reference source for all those studying the nature of solid surfaces and catalysis.

Download or read book Catalysis at Surfaces written by I.M. Campbell and published by Springer Science & Business Media. This book was released on 1988-08-31 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text provides a balanced introduction to the principles and techniques of heterogeneous catalysis. Beginning with the basic chemistry and physics of catalysis, the book goes on to pay particular attention to the contribution that surface science is making to our understanding of catalysis. It concludes with chapters devoted to carefully chosen examples of real catalytic systems, including catalytic action by enzymes and industrial processes based on solid catalysis. Looking to the future, the book introduces many novel types of catalysis.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1992 with total page 1572 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dissertation Abstracts International written by and published by . This book was released on 2001 with total page 682 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Surface Studies of Oxidation written by Ahmad Ali Audi and published by . This book was released on 2003 with total page 760 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Mechanisms in Homogeneous and Heterogeneous Epoxidation Catalysis written by S. Ted Oyama and published by Elsevier. This book was released on 2011-10-13 with total page 524 pages. Available in PDF, EPUB and Kindle. Book excerpt: The catalytic epoxidation of olefins plays an important role in the industrial production of several commodity compounds, as well as in the synthesis of many intermediates, fine chemicals, and pharmaceuticals. The scale of production ranges from millions of tons per year to a few grams per year. The diversity of catalysts is large and encompasses all the known categories of catalyst type: homogeneous, heterogeneous, and biological. This book summarizes the current status in these fields concentrating on rates, kinetics, and reaction mechanisms, but also covers broad topics including modeling, computational simulation, process concepts, spectroscopy and new catalyst development. The similarities and distinctions between the different reaction systems are compared, and the latest advances are described. Comprehensive listing of epoxide products Broad comparison of turnover frequencies of homogeneous, hetergeneous, main-group, biomimetic and biological catalysts Analysis of the general strengths and weaknesses of varied catalytic systems Detailed description of the mechanisms of reaction for classical and emerging catalysts

Download or read book Fossil Energy Update written by and published by . This book was released on 1981 with total page 820 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Surface Reactions written by R.J. Madix and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 291 pages. Available in PDF, EPUB and Kindle. Book excerpt: A treatment of the important aspects of physical chemistry on metal surfaces, including selective oxidation, desulfurization, cyclization, metal-organic chemical vapor deposition, alkane activation and hydrogen dissociation dynamics. Case studies focus on on the chemistry of selected systems, rather than the techniques, to convey the excitement of recent developments.

Download or read book Bulletin of the Academy of Sciences of the USSR Division of Chemical Science written by and published by . This book was released on 1962-04 with total page 604 pages. Available in PDF, EPUB and Kindle. Book excerpt: