Download or read book Mechanistic Studies of the Ethylbenzene Disproportionation onAcidic Zeolite Catalysts by in Situ Solid state NMR Spectroscopy written by Jun Huang and published by . This book was released on 2008 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mechanistic Studies of the Methanol to olefin Process on Acidic Zeolite Catalysts by in Situ Solid State NMR UV Vis Spectroscopy written by Yijiao Jiang and published by . This book was released on 2007 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mechanistic Studies of Transformations Over Zeolite Catalysts Probed by Novel Solid State NMR Methods written by Patrick William Goguen and published by . This book was released on 1997 with total page 412 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book In Situ Solid state Nuclear Magnetic Resonance Studies of Reactions in Zeolite Catalysts written by Eric Jon Munson and published by . This book was released on 1993 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Characterization and Design of Zeolite Catalysts written by Miki Niwa and published by Springer Science & Business Media. This book was released on 2010-08-17 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalysis and catalyst is a key technology to solve the problems in energy and environment issues to sustain our human society. We believe that comprehensive understanding of the catalysis and catalyst provides us a chance to develop a new catalyst and contributes greatly to our society. However, the ?eld of heterogeneous catalyst is dif?cultto study andstill stays behindmoredeveloped?elds ofchemistry such as organic and physical chemistries. This is a dilemma to the chemists who study the catalysis and catalyst. While we can accomplish the progress in the - dustrial application, the scienti?c understandingis not complete yet. A gap between the useful application and incomplete scienti?c understanding, however, becomes smaller and smaller in recent years. Because zeolites are ?ne crystals, and the structure is clearly known, the study on the catalysis using the zeolites is easier than those encountered in other catalysts such as metals and metal oxides. Very fortunately, zeolites provide us the strong acidity with the ?ne distribution which enables various useful catalytic reactions. When some metals and cations are loaded in close to the acid sites, these loadede- ments show extraordinarycharacters, and many catalytic reactions proceed thereon.
Download or read book Mechanistic Studies of the Vapor phase Beckmann Rearrangement on Solid Catalysts by in Situ Solid state NMR Spectroscopy written by Venkata Ramana Reddy Marthala and published by . This book was released on 2009 with total page 125 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Zeolites and Catalysis written by Jiri Cejka and published by John Wiley & Sons. This book was released on 2010-05-27 with total page 918 pages. Available in PDF, EPUB and Kindle. Book excerpt: This indispensable two-volume handbook covers everything on this hot research field. The first part deals with the synthesis, modification, characterization and application of catalytic active zeolites, while the second focuses on such reaction types as cracking, hydrocracking, isomerization, reforming and other industrially important topics. Edited by a highly experienced and internationally renowned team with chapters written by the "Who's Who" of zeolite research.
Download or read book Zeolite Catalysts written by Subhash Bhatia and published by CRC Press. This book was released on 2020-07-24 with total page 302 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presented in an easy-to-read form, this book on zeolite catalysis cover all aspects of the subject. It focuses on synthesis, structure, diffusion, deactivation, and industrial applications. This book is an ideal text for courses on catalysis or as a supplementary text for those studying applied or industrial chemistry. It is also a useful resource for anyone who works with zeolites as catalysts in the laboratory, pilot plants, or commercial installations.
Download or read book Deactivation And Regeneration Of Zeolite Catalysts written by Guisnet Michel and published by World Scientific Publishing Company. This book was released on 2011-02-21 with total page 360 pages. Available in PDF, EPUB and Kindle. Book excerpt: In chemical processes, the progressive deactivation of solid catalysts is a major economic concern and mastering their stability has become as essential as controlling their activity and selectivity. For these reasons, there is a strong motivation to understand the mechanisms leading to any loss in activity and/or selectivity and to find out the efficient preventive measures and regenerative solutions that open the way towards cheaper and cleaner processes. This book covers the fundamental and applied aspects of solid catalyst deactivation in a comprehensive way and encompasses the state of the art in the field of reactions catalyzed by zeolites. This particular choice is justified by the widespread use of molecular sieves in refining, petrochemicals and organic chemicals synthesis processes, by the large variety in the nature of their active sites (acid, base, acid-base, redox, bifunctional) and especially by their peculiar features, in terms of crystallinity, structural order and textural properties, which make them ideal models for heterogeneous catalysis. The aim of this book is to be a critical review in the field of zeolite deactivation and regeneration by collecting contributions from experts in the field which describe the factors, explain the techniques to study the causes and suggest methods to prevent (or limit) catalyst deactivation. At the same time, a selection of commercial processes and exemplar cases provides the reader with theoretical insights and practical hints on the deactivation mechanisms and draws attention to the key role played by the loss of activity on process design and industrial practice./a
Download or read book Molecular Transport and Reaction in Zeolites written by Nai Y. Chen and published by John Wiley & Sons. This book was released on 1996-12-17 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book examines the molecular dynamics that occur within zeolites. Our understanding of how these marvelous catalysts work has been greatly enhanced by the advent ot new tools such as NMR, scanning-transmission-electron microscopy, and sophisticated computer modelling. By combining recent findings and newly developed models with classical developments in the theory of diffusion, this book provides a complete picture of the physical chemistry of hydrocarbon transformation in zeolites. It should be an excellent guide to those involved in catalyst design.
Download or read book In Situ M ssbauer Spectroscopic Studies of Iron exchanged Y zeolite Catalysts for the Selective Catalytic Reduction with Ammonia and Direct Decomposition of Nitric Oxide written by Ralf Schmidt and published by . This book was released on 1991 with total page 460 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Zeolites in Catalysis written by Jiří Čejka and published by Royal Society of Chemistry. This book was released on 2017-06-07 with total page 547 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accessible references for researchers and industrialists in this exciting field, covering both developments and applications of catalysis.
Download or read book Mechanistic Investigations of Alkane Activation and Reaction on Zeolitic Catalysts written by Matthew Jarrod Truitt and published by . This book was released on 2006 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: Keywords: zeolites, alkanes, soild-state NMR.
Download or read book Solid State NMR Studies of Zeolite Catalysis and Investigation of Novel Microporous Titanosilicates written by A. Philippou and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Catalysis and Zeolites written by Jens Weitkamp and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 582 pages. Available in PDF, EPUB and Kindle. Book excerpt: Zeolites occur in nature and have been known for almost 250 years as alumino silicate minerals. Examples are clinoptilolite, mordenite, offretite, ferrierite, erionite and chabazite. Today, most of these and many other zeolites are of great interest in heterogeneous catalysis, yet their naturally occurring forms are of limited value as catalysts because nature has not optimized their properties for catalytic applications and the naturally occurring zeolites almost always contain undesired impurity phases. It was only with the advent of synthetic zeolites in the period from about 1948 to 1959 (thanks to the pioneering work of R. M. Barrer and R. M. Milton) that this class of porous materials began to playa role in catalysis. A landmark event was the introduction of synthetic faujasites (zeolite X at first, zeolite Y slightly later) as catalysts in fluid catalytic cracking (FCC) of heavy petroleum distillates in 1962, one of the most important chemical processes with a worldwide capacity of the order of 500 million t/a. Compared to the previously used amorphous silica-alumina catalysts, the zeolites were not only orders of magnitude more active, which enabled drastic process engineering improvements to be made, but they also brought about a significant increase in the yield of the target product, viz. motor gasoline. With the huge FCC capacity worldwide, the added value of this yield enhancement is of the order of 10 billion US $ per year.
Download or read book Structure and Reactivity of Zeolite and Carbon Supported Catalysts for the Oxidative Carbonylation of Alcohols written by Daniel Neal Briggs and published by . This book was released on 2010 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract Structure and Reactivity of Zeolite- and Carbon-Supported Catalysts for the Oxidative Carbonylation of Alcohols by Daniel Neal Briggs Doctor of Philosophy in Chemical Engineering University of California, Berkeley Professor Alexis T. Bell, Chair The oxidative carbonylation of alcohols to produce dialkyl carbonates is a process that takes place commercially in a slurry of cuprous chloride in the appropriate alcohol. While this process is chemically efficient, it incurs costs in terms of energy (for product separation) and materials attrition (due to the corrosive nature of the chloride anion) that can be alleviated in a gas-phase process. Efforts to develop a supported copper catalyst for making dialkyl carbonates have been undertaken, using carbons or oxidic supports (including zeolites). However, the activity, selectivity and stability of the supported catalysts are not yet competitive with the slurry process. Little is understood regarding the nature of the active species or the mechanism by which carbonates and byproducts are formed. Catalyst properties that lead to favorable activity and selectivity have not been clearly outlined. To improve supported catalysts for this process, we have carried out detailed investigations of the structure and catalytic behavior of zeolite- and carbon-supported Cu catalysts for the synthesis of dimethyl or diethyl carbonates. The aim of the work on Cu+-exchanged zeolites was to establish the effects of zeolite structure/chemical composition on the activity and selectivity of Cu-exchanged Y (Si/Al = 2.5), ZSM-5 (Si/Al = 12), and Mordenite (Si/Al = 10) for the oxidative carbonylation of methanol to DMC. Catalysts were prepared by solid-state ion-exchange of the H-form of each zeolite with CuCl, and were then characterized by FTIR and X-ray absorption spectroscopy (XAS). The XANES portion of the XAS data showed that all of the copper is present as Cu+ cations, and analysis of the EXAFS portion of the data shows the Cu+ cations have a Cu-O coordination number of ̃2.1 on Cu-Y and ̃2.7 on Cu-ZSM-5 and Cu-MOR. Dimethyl carbonate (DMC) was observed as the primary product when a mixture of CH3OH/CO/O2 was passed over Cu-Y, whereas dimethoxy methane was the primary product over Cu-ZSM-5 and Cu-MOR. The higher activity and selectivity of Cu-Y for the oxidative carbonylation of CO is attributed to the weaker adsorption of CO on the Cu+ cations exchanged into Y zeolite. In situ infrared observations reveal that under reaction conditions, adsorbed CO is displaced by methoxide groups bound to the Cu+ cations. The kinetics of DMC synthesis suggests that the rate-limiting step in the formation of this product is the insertion of CO into Cu-OCH3 bonds. The yield of DMC is observed to decline with methanol conversion due very likely to the hydrolysis of DMC to methanol and carbon dioxide. Next, the investigation turned to the synthesis of diethyl carbonate (DEC) by oxidative carbonylation of ethanol, using catalysts prepared by the dispersion of CuCl2 and PdCl2 on amorphous carbon. Catalysts were characterized extensively by XRD, XAFS, SEM and TEM with the aim of establishing their composition and structure after preparation, pretreatment, and use. It was observed that after preparation and pretreatment in He at 423 K, copper is present almost exclusively as Cu(I), most likely in the form of [CuCl2]- anions, whereas palladium is present as large PdCl2 particles. Catalysts prepared exclusively with copper or palladium chloride are inactive for DEC synthesis, indicating that both components must be present together. Evidence from XANES and EXAFS suggests that the DEC synthesis may occur on [PdCl2-x][CuCl2]x species deposited on the surface of the PdCl2 particles. As-prepared catalysts exhibited an increase in DEC synthesis activity and selectivity with time on stream, but then reached a maximum activity and selectivity, followed by a slow decrease in DEC activity. The loss of DEC activity was accompanied by a loss in Cl from the catalyst and the appearance of paratacamite. Further work was undertaken on carbon-supported catalysts, building on insights regarding the active species, this time with activated carbon or carbon nanofibers as the support. The objectives of this last study were to establish the effects of carbon support structure and pretreatment on the dispersion of the catalytically active components and, in turn, on the activity and selectivity of the catalyst for DEC synthesis. At the same surface loading of CuCl2 and PdCl2, partially oxidized carbon nanofibers resulted in a higher dispersion of the active components and a higher DEC activity than could be achieved on activated carbon. Catalyst characterization revealed that nearly atomic dispersion of CuCl2 and PdCl2 could be achieved on the edges of the graphene sheets comprising the carbon nanofibers. Over oxidation of the edges or their removal by heat treatment of the nanofibers resulted in a loss of catalyst activity. The loss of catalyst activity with time on stream could be overcome by the addition of ppm levels of CCl4 to the feed. While catalysts prepared with CuCl2 alone were active, a five-fold increase in activity was realized by using a PdCl2/CuCl2 ratio of 1/20. It was proposed that the Pd2+ cations interact with [CuCl2]- anions to form Pd[CuCl2]2 complexes that are stabilized through dative bonds formed with oxygen groups present at the edges of the graphene sheets of the support. A mechanism for DEC synthesis was outlined and a role for the Pd2+ cations as part of this mechanism was proposed.
Download or read book An Analysis of Commerical Zeolite Catalysts by Multinuclear NMR written by and published by . This book was released on 1990 with total page 67 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work involves studying two commercial hydrocracking catalysts by solid state multinuclear NMR silicon 29 and aluminum 27 with the goal of developing a method of determining the fraction zeolite in the catalysts. The zeolite fraction is known to be one of the faujasite zeolites type X or Y. The clay matrix of the catalyst is assumed to be kaolinite. Fresh, air-exposed commercial hydrocracking catalysts were provided by Phillips Petroleum. Sample 33351-86 was known to be a physical mixture of a Y zeolite and a clay matrix. The other catalyst, 33351-20, was composed of a faujasite zeolite grown within a clay matrix. Both were suspected of being about 20 wt % zeolite. Nothing is known about the state of pretreatment or cation exchange. A portion of each catalyst was calcined in a porcelain crucible in air at 500°C for two hours with a hour heating ramp preceding and a two hour cooling ramp following calcination. 64 refs., 21 figs., 8 tabs.
