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 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 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 Heterogeneous Catalysis of Mixed Oxides written by M. Misono and published by Newnes. This book was released on 2013-02-28 with total page 193 pages. Available in PDF, EPUB and Kindle. Book excerpt: Mixed oxides are the most widely used catalyst materials for industrial catalytic processes. The principal objective of this book is to describe systematically the mixed oxide catalysts, from their fundamentals through their practical applications. After describing concisely general items concerning mixed oxide and mixed oxide catalysts, two important mixed oxide catalyst materials, namely, heteropolyacids and perovskites, are taken as typical examples and discussed in detail. These two materials have several advantages: 1. They are, respectively, typical examples of salts of oxoacids and double oxide, that is, the two main categories of mixed oxides in solid state chemistry. 2. Both exhibit excellent catalytic performance in nearly crystalline state and are used in several industrial applications. 3. They have studied for many years. In addition, metal oxides functioning as a catalyst support (carrier) are included. Although the supports are very important in practical applications, and tremendous progress has been made in the past decades, few systematic reviews exist. It is notable that heteropolyacids and perovskite exhibit unique performance when used as a support. Fundamental catalytic science and technology and solid state chemistry necessary is presented for the proper understanding of mixed oxide catalysts as well as for R&D. For the latter, the concept of design of practical catalysts is very important. This is considered throughout the book. Systematically describes design principles of mixed oxide catalysts Shows how catalysis and solid-state chemistry of metal oxides are inter-related Covers all useful basic concepts of mixed oxide catalysis

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 2008-12-23 with total page 887 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 Handbook Of Advanced Methods And Processes In Oxidation Catalysis From Laboratory To Industry written by Daniel Duprez and published by World Scientific. This book was released on 2014-07-24 with total page 1035 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers a comprehensive overview of the most recent developments in both total oxidation and combustion and also in selective oxidation. For each topic, fundamental aspects are paralleled with industrial applications. The book covers oxidation catalysis, one of the major areas of industrial chemistry, outlining recent achievements, current challenges and future opportunities. One distinguishing feature of the book is the selection of arguments which are emblematic of current trends in the chemical industry, such as miniaturization, use of alternative, greener oxidants, and innovative systems for pollutant abatement. Topics outlined are described in terms of both catalyst and reaction chemistry, and also reactor and process technology.

Download or read book Developing Enhanced Mixed Metal Oxide Catalysts for Electrocatalytic Water Oxidation Using Insights from X ray Absorption Spectroscopy written by Linsey C. Seitz and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Efficient and economic conversion of renewable energy sources is critical for development of technologies that can shift global energy dependence away from fossil fuels. Increased global energy consumption along with heightened awareness of environmental, health, and political issues with fossil fuels are driving the need for alternative technologies. Wind and sun provide more than enough energy to meet the growing energy demand, provided that challenges with intermittency, scale, and cost-effectiveness can be overcome. These obstacles can be mitigated through development of highly active catalysts using abundant and inexpensive materials to convert solar and wind energy into fuels and chemicals. One promising method of converting solar energy into fuel is by splitting water to produce hydrogen and oxygen. This can be achieved using a monolithic photoelectrochemical (PEC) water splitting device which combines photon-absorbing semiconductors with catalysts that drive the respective reactions or a photovoltaic/electrolyzer system which separates these two components. The first part of this thesis presents a model to quantify loss mechanisms in PEC water splitting based on the current state of materials research and calculate maximum solar-to-hydrogen (STH) conversion efficiencies. Results of this model indicate that a major limitation to the efficiency of solar-driven electrochemical water splitting is the oxygen evolution reaction (OER) which requires significant overpotential beyond the thermodynamic redox potential to proceed. The remainder of this dissertation focuses on understanding the interaction between metals in mixed metal oxide catalysts for the OER using electrochemical and advanced spectroscopic techniques towards the development of highly active and stable catalysts. Mixed metal oxide catalysts provide a robust platform for tuning binding energies of OER reaction intermediates to the catalyst surface, thereby affecting activity, through controlled material composition and geometry. We investigate two distinct mixed metal oxide catalyst systems using X-ray absorption spectroscopy (XAS) to probe local geometric and electronic structure and correlate the results with changes in activity. XAS is a synchrotron based technique which provides elemental-specific information by exciting electronic transitions from core to valence orbitals at various elemental edges. XAS studies at the Co K and L edges for a cobalt titanium oxide (CoTiOx) catalyst system identify stabilization effects on the Co oxidation state and overall structure from varying amounts of Ti precursor used during material synthesis. XAS before and after catalyst exposure to OER conditions indicate that catalysts with the least long range order become most oxidized and exhibit the highest activities. Similarly, in situ XAS at the Mn K and Au LIII edges reveal that there is a charge transfer at interfacial sites between manganese oxide (MnOx) and gold (Au) under OER conditions which coincides with significantly increased OER activity compared to MnOx without Au. Our results indicate that Au facilitates stabilization of more oxidized phases of Mn at lower overpotentials, thereby allowing for earlier onset of OER and higher activity. Lastly, we present an investigation of a novel mixed metal oxide catalyst, strontium iridium oxide (SrIrO3) which has the highest reported activity for any known OER catalyst. While it depends on use of Ir, a precious metal, its remarkably high activity compared to rutile IrO2 reduces the Ir loading necessary to achieve similar current densities. In summary, this dissertation explores a broad spectrum of catalysts for the oxygen evolution reaction and uses advanced material characterization methods to draw correlations between the structure, oxidation state, and catalytic activity for these materials. This work provides fundamental insight towards improving efficiency of electrochemical water oxidation processes for the conversion of renewable energy sources to fuels and chemicals.

Download or read book Modern Heterogeneous Oxidation Catalysis written by Noritaka Mizuno and published by John Wiley & Sons. This book was released on 2009-11-18 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: Filling a gap in the current literature, this comprehensive reference presents all important catalyst classes, including metal oxides, polyoxometalates, and zeolites. Readers will find here everything they need to know -- from structure design to characterization, and from immobilization to industrial processes. A true must-have for anyone working in this key technology.

Download or read book Key Structural Factors of Group 5 Metal Oxide Clusters for Base Catalytic Application written by Shun Hayashi and published by Springer Nature. This book was released on 2020-08-08 with total page 92 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides detailed information on the base catalysis of group 5 (Nb, Ta) metal oxide clusters by elucidating how the structural factors such as constituent metals, counter cations, and local structures of base sites affect their catalysis. Uniquely, it reveals the effects of key structural factors at the molecular level by combining experimental and theoretical approaches. The findings presented here provide rational design principles for base catalysis and will foster the development of promising catalysts for solving current and future energy and environmental problems.

Download or read book Kinetics of Heterogeneous Catalytic Reactions written by Michel Boudart and published by Princeton University Press. This book was released on 2014-07-14 with total page 241 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a critical account of the principles of the kinetics of heterogeneous catalytic reactions in the light of recent developments in surface science and catalysis science. Originally published in 1984. The Princeton Legacy Library uses the latest print-on-demand technology to again make available previously out-of-print books from the distinguished backlist of Princeton University Press. These editions preserve the original texts of these important books while presenting them in durable paperback and hardcover editions. The goal of the Princeton Legacy Library is to vastly increase access to the rich scholarly heritage found in the thousands of books published by Princeton University Press since its founding in 1905.

Download or read book Preparation of Mixed Metal Oxide Catalysts for VOC Total Oxidation written by Parag Shah and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Polymeric and Self Assembled Hydrogels written by Xian Jun Loh and published by Royal Society of Chemistry. This book was released on 2013 with total page 275 pages. Available in PDF, EPUB and Kindle. Book excerpt: The only book to give a complete picture of current hydrogel research, covering all the major applications as well as the fundamental principles behind them.

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 Catalysis rising stars in china written by Yulian He and published by Frontiers Media SA. This book was released on 2023-03-16 with total page 119 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Metal Oxide Promotion of Cobalt Based Fischer Tropsch Synthesis Catalysts written by Gregory Robert Johnson and published by . This book was released on 2015 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt: Synthetic fuel production by means of Fischer-Tropsch synthesis (FTS) involves the catalytic hydrogenation of CO over Co-based catalysts. Often, these catalysts incorporate performance-enhancing additives known as promoters. Although not catalytically active for FTS by themselves, promoters can alter the structural and electronic properties of the active Co metal so as to improve catalyst activity, selectivity, or stability. Elements that form metal oxides have been studied for their ability to increase CO consumption rates and shift the product distribution toward higher molecular weight. Despite several decades of study of such elements, there remains limited understanding of the connections between these promotional effects and element properties. Accordingly, this dissertation focuses on clarifying the chemical basis for the effects of metal oxide promotion and making connections to periodic trends. To understand the importance of physical contact between the promoter and the Co, the influence of Co-Mn spatial association on the magnitude of Mn promotional effects was investigated. Elemental maps obtained by STEM-EDS revealed that different catalyst pretreatment methods could control how closely associated the promoter and Co were at the nanoscale. By relating these results to catalytic reaction data, it was determined that higher extents of contact between the two elements were correlated with higher selectivities toward C5+ hydrocarbons. This work was extended to the elements Ce, Gd, La, and Zr, which are among the most commonly studied metal oxide-forming promoters. The presence of the promoter element suppressed methane formation and increased the FTS chain propagation probability, but the sensitivity of these effects toward promoter loading was different for each element. Elements that deposited preferentially onto the Co nanoparticles led to rapid shifts in the product distribution as the promoter loading increased, whereas elements that dispersed over the entire catalyst surface resulted in more gradual changes. For all promoters, the product selectivities became insensitive to loading when the loading reached a quantity nearly equivalent to that which would form a half monolayer of the promoter on the Co nanoparticle surface. These trends are characteristic of the formation of active sites along the interface between the Co and the promoter that exhibit improved product selectivity. Structurally, the oxidation states and local coordination environments of the promoters were consistent with highly dispersed oxides. No evidence for the formation of bimetallic alloys or large promoter-containing crystallites was detected by either X-ray absorption spectroscopy or X-ray diffraction. These data suggest that small promoter oxide moieties decorate the surface of the Co metal nanoparticles so as to form metal-metal oxide interfaces. Under this model, the promotional effects increase in magnitude as the fraction of Co active sites that are adjacent to the promoter increases. When the Co surface is sufficiently covered by the promoter so that the fraction of active sites that are along the perimeter of the promoter moieties is nearly unity, the catalyst performance ceases to improve as a function of promoter loading. Guided by this reasoning, the catalytic properties of the promoted catalysts were investigated using samples in which the fraction of sites that were promoted was near unity. Measurements of reaction kinetics were conducted to assess the impact of metal oxide promotion on the rate parameters governing FTS. The rates of CO consumption for both unpromoted and metal oxide-promoted catalysts followed a Langmuir-Hinshelwood rate law for which H-assisted CO dissociation is assumed to be the rate determining step. Each promoter increased the apparent rate constant and the CO adsorption constant that appear within the rate law. Thus, metal oxide promotion appears both to facilitate the cleavage of the C-O bond and to enhance the extent of CO adsorption onto the catalyst. This finding was reinforced by CO temperature programmed desorption experiments and an evaluation of the effects of Mn promotion on the rate of CO disproportionation. Owing to the appearance of the CO adsorption constant in the numerator and denominator of the rate law, it is possible for promoted catalysts to have both higher and lower turnover frequencies than unpromoted catalysts depending on the chosen operating pressure. As a consequence, an optimal promoter can be found for maximizing the turnover frequency at a given operating pressure. However, product selectivity, which is largely determined by the availability of adsorbed H, is invariably improved by a higher CO adsorption constant because it decreases the ratio of adsorbed H to CO on the Co surface. Strong correlations between catalyst performance and the Lewis acidity of the promoter oxide suggest that Lewis acid-base interactions between the promoter and the adsorbed CO are the cause for the observed metal oxide promotional effects. Much of the experimental data presented in this work favors the hypothesis that CO can interact simultaneously with Co through the C atom and with the promoter cation through the O atom. These chemical interactions, in which the promoter serves as a Lewis acid, weaken the bond between C and O. Experimental evidence for this effect was observed in the lower activation barrier for CO hydrogenation over the ZrO2-promoted catalysts and the appearance of adsorbed carbonyl species on the MnO-promoted catalyst with severely redshifted C-O stretching frequencies measured by in situ infrared spectroscopy. These results provide insight into the chemical mechanism by which metal oxides affect the reaction and identify Lewis acidity of the promoter as the relevant descriptor for quantitatively predicting metal oxide-based promotional effects over Co FTS catalysts.

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: