Download or read book Selective Propene Oxidation on Mixed Metal Oxide Catalysts written by David William James and published by . This book was released on 2002 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Selective Propane Oxidation on Mixed Metal Oxide Catalysts written by David William James and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Metal Oxides in Heterogeneous Catalysis written by Jacques C. Vedrine and published by Elsevier. This book was released on 2018-01-11 with total page 620 pages. Available in PDF, EPUB and Kindle. Book excerpt: Metal Oxides in Heterogeneous Catalysis is an overview of the past, present and future of heterogeneous catalysis using metal oxides catalysts. The book presents the historical, theoretical, and practical aspects of metal oxide-based heterogeneous catalysis. Metal Oxides in Heterogeneous Catalysis deals with fundamental information on heterogeneous catalysis, including reaction mechanisms and kinetics approaches.There is also a focus on the classification of metal oxides used as catalysts, preparation methods and touches on zeolites, mesoporous materials and Metal-organic frameworks (MOFs) in catalysis. It will touch on acid or base-type reactions, selective (partial) and total oxidation reactions, and enzymatic type reactions The book also touches heavily on the biomass applications of metal oxide catalysts and environmentally related/depollution reactions such as COVs elimination, DeNOx, and DeSOx. Finally, the book also deals with future trends and prospects in metal oxide-based heterogeneous catalysis. Presents case studies in each chapter that provide a focus on the industrial applications Includes fundamentals, key theories and practical applications of metal oxide-based heterogeneous catalysis in one comprehensive resource Edited, and contributed, by leading experts who provide perspectives on synthesis, characterization and applications
Download or read book Investigation of M1 Phase Molybdenum Based Mixed Metal Oxide Catalysts for Selective Oxidation of Propane written by Xin Li and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Acrylic acid and acrylonitrile are important intermediates for producing a number of common chemicals and materials used in paints, adhesives, plastics, fibers, etc. Traditionally, their production has relied on propylene feedstocks, and replacing propylene with the cheaper and more abundant propane as the raw material has attracted a lot of research interest during the past two decades. Several promising catalysts have been discovered, and to date, Mo-V-Nb-Te-O mixed metal oxides are the most efficient for both propane oxidation to acrylic acid and ammoxidation to acrylonitrile. Two orthorhombic phases named M1 and M2 have been identified as the major components, and M1 is generally considered the key factor for propane activation. In particular, the [001] face of the M1 structure has been proposed to provide active centers and the valence distribution on [001] face is believed to play an important role in determining the reaction mechanism. However, the detailed mechanism is not fully understood. This has limited opportunities to further improve catalysts performance or design better catalysts by rational means. This absence can be related to the past failure of generating M1 phase alone in synthesis, and many catalysts studied previously were actually mixtures. Thus, in this work, we carried out investigations of the highly pure M1 catalyst focusing on the synthesis, catalytic behavior, and structural model development. The hydrothermal method has been shown to yield M1 phase with high purity at the expense of a more complicated procedure. The simple slurry method was used by us to synthesize catalyst samples. It is found that, besides M1 and M2, tellurium molybdate TeMo 5 O 16, V-substituted Mo 5 O 14 or (V, Mo) 5 O 14, and Mosubstituted V 2 O 5 or (Mo, V) 2 O 5 are also often formed together. The final phase composition can be significantly affected by nominal metal composition, slurry pH, calcination heating rate, etc. And the relative amount of each phase under different conditions can be directly correlated with respective V/Mo and Te/Mo ratios. Further, an additional purification step where the sample mixture is washed by H 2 O 2 solution was studied, and it is observed that concentrated hydrogen peroxide offers the most effective removal of undesired phases. A complete procedure for obtaining M1 phase in high purity has been developed. Synthesized M1 catalysts were characterized by EDS and XPS, and results suggest that the M1 structure shows high chemical flexibility and can contain vanadium to quite different levels depending on the nominal metal stoichiometry in the slurry. In particular, it is seen that the more vanadium in the slurry, the more vanadium in the final M1 structure. Additionally, no significant difference between the surface and the bulk was observed with respect to metal composition.
Download or read book Heterogeneous Catalysis of Mixed Oxides written by Makoto Misono and published by Elsevier Inc. Chapters. This book was released on 2013-02-28 with total page 87 pages. Available in PDF, EPUB and Kindle. Book excerpt: The chemistry of metal oxides, both single and mixed metal oxides, relevant to heterogeneous catalysis such as relationships among the composition, structure, and chemical properties of mixed oxides, is provided in perspective. The important chemical properties in heterogeneous catalysis are acid–base and reduction–oxidation (redox) properties, where ionic radii, electronegativity, valency, and tendency to form covalent bond of constituent elements are most influential. Structural factors such as lattice defects and nonstoichiometry are also relevant. Although the surface of metal oxides is different from the solid bulk and changes depending on various factors, the surface reflects more or less the solid bulk and the knowledge of bulk properties is useful to understand the catalysis of mixed oxides. In some cases, the solid bulk actually takes part in catalysis. Other fundamental features of metal oxide catalysis like synergistic effects of more than two different active sites (acid and base, acid and oxidation, etc.) are also discussed.
Download or read book Molecular Structure reactivity Relationships for Propane Oxidation Over Model Mixed Oxide Catalysts written by and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Mixed Mo-V-Sb-Nb and Mo-V-Te-Nb oxides were recently discovered as highly active and selective catalysts for the propane oxidation to propylene and oxygenates, i.e. acrolein and acrylic acid. Fundamental information is needed for understanding the bulk and surface molecular structure-activity/selectivity relationships and providing rules of rational design of improved mixed metal oxide catalysts for the selective oxidation of propane. The phase composition and catalytic activity of the model Mo-V-Sb-Nb-O system strongly depended on the synthesis route and composition. A number of distinct solid-state phases were observed in this system: Mo6V9O40, MoO3, rutile SbVO4 and the defect "Mo-V-Nb-O" phases. The kinetic studies indicated that the high selectivity to acrylic acid (2̃0 mol.%) was associated with the Mo6V9O40 and the defect "Mo-V-Nb-O" phases. The synthesis of these mixed Mo-V-Sb-Nb-O system was performed using combinatorial chemistry techniques to explore the utility of liquid phase automated synthesis for the reproducible preparation of these catalysts. This study indicated good reproducibility of phase compositions and catalytic properties and provided new insights into the transformation processes that occur in these oxides with time on stream. It was discovered in this research that the model mixed Mo-V-Te-O catalyst represents a simple model system for elucidating the molecular structure-activity/selectivity relationships in propane selective oxidation. This catalyst contains the two major crystalline phases proposed as active and selective for propane oxidation. This research elucidated the effect of the chemical composition, solution pH and thermal treatment on phase composition and catalytic performance. High resolution TEM study established the crystal structures of the hexagonal and orthorhombic phases in terms of their space groups, unit cell parameters, atomic coordinates and elemental compositions. In order to understand the role of the structure, morphology and composition of mixed Mo-V-Te-Nb-O system, novel synthesis approaches employing ordered arrays of colloidal polystyrene spheres (0.4 ưm) were successfully developed. These novel nanocrystalline catalysts with surface areas in the 80-110 m2/g range consisted of 20-50 nm particles of desirable catalytic phases and contained 6-20 nm pores. Kinetic studies demonstrated the acrylic acid yields exceeding 40 mol.% and approaching the commercial targets for the selective oxidation of propane to acrylic acid.
Download or read book Propene Oxidation on Mixed Metal Oxide Catalysts written by Elizabeth Jane Rowbotham and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 489 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 Toward a Molecular Level Understanding of Mixed Metal Oxide Oxidation Catalysts written by Andrew Getsoian and published by . This book was released on 2013 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: The selective oxidation and ammoxidation of light olefins comprises a 5 million ton per year industry, and is responsible for making possible products from nitrile rubber to Plexiglas to acrylic paint. The industrial catalyst of choice for such reactions is based on bismuth molybdate, and was first patented in the 1950s. In the intervening decades, a significant body of research has been done on bismuth molybdate-based catalysts, and yet a surprising amount is still not known about how these catalysts work. This Thesis has focused primarily on developing new methods for studying bismuth molybdates and related catalysts in order to gain new insight into the means by which the physical and electronic structures of the active sites in these catalysts give rise to their catalytic activity. The mechanism by which propene is oxidized on the (010) surface of Bi2Mo3O12 has been investigated using the RPBE+U variety of density functional theory (DFT). The location of the active site was determined, and the calculated barrier for the rate-determining step at this site found to be in good agreement with experimental results. Calculations revealed the essential roles of bismuth and molybdenum in providing the geometric and electronic structure responsible for catalytic activity at the active site, and suggested that catalytic activity could be further enhanced by substitution with a more reducible element. In order to accurately model substitution of an additional reducible element in to Bi2Mo3O12 using DFT, more sophisticated approaches than RPBE+U were required. Two more advanced density functionals, M06-L and HSE, were examined. The HSE functional was found to be too expensive for practical use on extended systems like bismuth molybdate catalysts. The accuracy of the M06-L functional for lattice constants and geometries, reaction energies and barriers, electronic structures, and non-covalent interactions was investigated, and compared results from the RPBE+U method. The M06-L functional was found to be superior to RPBE+U for lattice constants, reaction energies, and non-covalent interactions, and as good as or better than RPBE+U for electronic structures. Use of the M06-L functional was therefore determined to be preferable to use of RPBE+U for use in the study of substituted bismuth molybdate catalysts. Calculations employing the M06-L functional were combined with physical characterization using diffuse reflectance UV-VIS, x-ray photoelectron, and x-ray near edge absorption spectroscopies in order to understand the effect of substitution of vanadium for molybdenum on the activation energy for propene oxidation in catalysts of formula Bi1-x/3V1-xMoxO4. In these catalysts, substitution of vanadium for molybdenum has been observed to lower the apparent activation barrier for propene oxidation. It was found that the lower activation barrier for propene oxidation over mixed vanadate-molybdate catalysts is a consequence of the smaller difference between the catalyst conduction band edge energy and the energy level of the highest occupied molecular orbital in propene. The lower conduction band edge energy in mixed vanadate-molybdate catalysts is related to the energies of and degrees of mixing between the V 3d and Mo 4d orbitals comprising the conduction band. Both of these observations suggest general principles that may be of relevance to a variety of mixed metal oxide catalyst systems. An improved procedure for synthesizing bismuth molybdate and bismuth vanadate catalysts was also developed. This procedure involved a two step templating process: a structured mesoporous carbon was templated from KIT-6 or MCM-48 mesoporous silica, and the structured mesoporous carbon in turn used as a template during synthesis of the metal oxide catalyst. Catalysts produced by the double templating process had surface areas of 14-17 m2/g, a large improvement on the
Download or read book Selective Oxidation by Heterogeneous Catalysis written by Gabriele Centi and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 519 pages. Available in PDF, EPUB and Kindle. Book excerpt: Selective Oxidation by Heterogeneous Catalysis covers one of the major areas of industrial petrochemical production, outlining open questions and new opportunities. It gives keys for the interpretation and analysis of data and design of new catalysts and reactions, and provides guidelines for future research. A distinctive feature of this book is the use of concept by example. Rather than reporting an overview of the literature results, the authors have selected some representative examples, the in-depth analysis of which makes it possible to clarify the fundamental, but new concepts necessary for a better understanding of the new opportunities in this field and the design of new catalysts or catalytic reactions. Attention is given not only to the catalyst itself, but also to the use of the catalyst inside the process, thus evidencing the relationship between catalyst design and engineering aspects of the process. This book provides suggestions for new innovative directions of research and indications on how to reconsider the field of selective oxidation from different perspectives, outlining that is not a mature field of research, but that new important breakthroughs can be derived from fundamental and applied research. Suggestions are offered on how to use less conventional approaches in terms of both catalyst design and analysis of the data.
Download or read book Nanostructured Catalysts written by Christian Hess and published by Royal Society of Chemistry. This book was released on 2011-07-22 with total page 453 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book gives a comprehensive up-to-date summary of the existing information on the structural/electronic properties, chemistry and catalytic properties of vanadium and molybdenum containing catalysts. It discusses the importance of nanoscience for the controlled synthesis of catalysts with functional properties and introduces the necessary background regarding surface properties and preparation techniques, leading from a textbook level to the current state of knowledge. Then follows an extensive survey and analysis of the existing open and patent literature - an essential knowledge source for the development of the new generation of partial oxidation catalysts. Important examples from current research on partial oxidation reactions are reviewed from experts in the field. The next chapter discusses the importance of 2- and 3-dimensional model systems for a fundamental understanding of the structure of transition metal oxide catalysts and its correlation to reactivity. Finally, an outlook on research opportunities within the area of partial oxidation reactions is presented.
Download or read book Selective Oxidation Over Mixed Metal Oxide Catalysts written by and published by . This book was released on 2010 with total page 73 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Mesoporous and Macroporous Mixed Metal Oxide MoVTeNbOx Catalysts for Propane amm Oxidation written by and published by . This book was released on 2008 with total page 189 pages. Available in PDF, EPUB and Kindle. Book excerpt: Approximately 5 million metric tons of acrylonitrile are produced worldwide annually for the manufacture of acrylic fibers, copolymers and reinforced carbon fibers. There is currently intense commercial interest in developing a new catalytic process for acrylonitrile production via propane ammoxidation employing multicomponent mixed metal oxides, which would replace the existing propylene ammoxidation technology. This new technology is expected to lower the production cost by 30% as compared to the existing process because of the lower cost of propane and increased production of valuable co-products, such as acetonitrile. The key to the success of this important technology is the development of novel mixed metal oxide catalysts that can selectively ammoxidize propane to acrylonitrile. Recent developments in macroscale and mesoscale structure-directed self-assembly offer many attractive possibilities for the molecular design of novel catalytic mixed metal oxides. The present work describes the development of novel synthesis approaches for macroporous and mesoporous mixed metal MoVTe(Sb)NbOx catalysts displaying ordered porous structures, high surface areas, flexible compositions and improved thermal stability for propane ammoxidation. This research began with systematic exploration of synthesis of mesoporous Nb2O5 oxides as a departure point in the subsequent synthesis of mixed M-Nb-O (M=Mo, V, Te, Sb) oxides employing Nb2O5 as the major component or the catalytic support. Nb2O5 was chosen for this study as the most stable metal oxide possessing the highest Tammann temperature among all constituent metal oxides (MoOx, VOx, TeOx and SbOx). Thermally stable (up to 500 °C) and well-defined two-dimensional hexagonal mesostructured niobium oxides were obtained possessing the surface areas of up to 210 m2/g. The pore size of mesoporous niobium oxides was for the first time tuned in a wide range from 4.6 to 21 nm by varying synthesis conditions. As compared with previous studies, mesoporous niobium oxides with tunable pore sizes obtained in this work possessed more attractive pores structures which make them promising as catalytic supports or a major component in the synthesis of improved MoVTeNbOx catalysts for selective (amm)oxidation of propane. Thermally stable mesoporous binary (Nb-M-O, M=Mo, V, or Sb), multicomponent (MNbOx, M=Mo+V+Te) and supported (M/Nb, M=Mo+V+Te+Nb) mixed metal oxide catalysts were for the first time synthesized by evaporation-induced self-assembly and incipient-wetness impregnation techniques. These mixed metal oxide phases displayed good thermal stability of amorphous inorganic wall (up to 400°C), large pore sizes (5-23 nm), high surface areas (up to 232 m2/g) and flexible inorganic wall compositions. Improved dispersion of active components in the Nb2O5 matrix and over the Nb2O5 support was observed. However, the desirable M1 phase was not observed in the products of thermal transformation of these mesoporous mixed metal oxides probably due to insufficient thickness of inorganic walls in these phases. In order to investigate nucleation of the catalytic M1 phase and further improve the thermal stability of the ordered porous structure, MoVTeNbOx phases displaying both macroporous and mesoporous structures were prepared by a dual templating approach employing colloidal arrays of polystyrene spheres and non-ionic surfactants. The MoVTeNbOx phases possessing such dual porosity were obtained after polystyrene spheres and non-ionic surfactants were removed in a low temperature calcination step. These hierarchical MoVTeNbOx phases displaying bimodal pore structure transformed into macroporous rutile phase possessing nanocrystalline inorganic walls at high temperature. These MoVTeNbOx rutile phases possessed high surface areas (70 m2/g), desirable pore architectures, robust nanocrystalline inorganic walls and enhanced thermal stability (up to 600 °C). Although these macroporous MoVTeNbOx rutile catalysts displayed lower activity in propane ammoxidation and lower acrylonitrile selectivity in propane ammoxidation as compared to the active and selective M1 phase, the novel synthesis method reported in these studies represents a promising general approach to design novel complex mixed metal oxides for a wide range of applications in selective oxidation catalysis.
Download or read book Advanced Materials in Catalysis written by Frank Bolz and published by Elsevier. This book was released on 2013-10-22 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced Materials in Catalysis is a collection of materials that discusses various catalysts. The book presents the physical and chemical properties that indicate that a particular class of materials may be of catalytic interest. The text first covers bimetallic catalysts, and then proceeds to examining the catalytic properties of compounds such as graphite intercalation compounds; oxides with the scheelite structure; and synthetic layered silicates and aluminosilicate. The book also covers reduction catalysts, biological catalysts, and monolithic catalyst supports. The selection will be of great use to students and practitioners of chemistry, particularly those who are involved in research studies that investigate materials problems in catalysis.
Download or read book Selective Oxidation of Propene written by Alexis T. Bell and published by . This book was released on 2013 with total page 63 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Yield Enhancement Effects of Mixed Metal Oxide Catalysts for Propene Oxidation written by Mark G. White and published by . This book was released on 1979 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bismuth written by Ying Zhou and published by BoD – Books on Demand. This book was released on 2018-06-20 with total page 231 pages. Available in PDF, EPUB and Kindle. Book excerpt: Bismuth (Bi) is a post-transition metal element with the atomic number of 83, which belongs to the pnictogen group elements in Period 6 in the elemental periodic table. As a heavy metal, the hazard of Bi is unusually low in contrast to its neighbors Pb and Sb. This property, along with other typical characteristics like strong diamagnetism and low thermal conductivity, makes Bi attractive in industrial applications. There are more than 100 commercial bismuth products, from pharmaceutical to industrial catalysts. Based on the wide applications of Bi materials, this book goes further and mainly focuses on the potential uses of Bi-based materials, which consist of nine chapters. In addition, a special chapter concerning the defect in bismuth is also presented.
