In Situ Bulk Structural Investigation of Mo 5 O 14 Type Mixed Metal Oxide Catalysts for Partial Oxidation Reactions PDF Download

Author: Eva Rödel
Publisher:
ISBN:
Category :
Languages : en
Pages : 162

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Author: Andrew Getsoian
Publisher:
ISBN:
Category :
Languages : en
Pages : 150

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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

Author: Shun Hayashi
Publisher: Springer Nature
ISBN: 9811573484
Category : Science
Languages : en
Pages : 92

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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.

Author:
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Category : Crystallography
Languages : en
Pages : 644

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Author: S. David Jackson
Publisher: John Wiley & Sons
ISBN: 9783527318155
Category : Science
Languages : en
Pages : 916

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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.

Author: Ehsan Moharreri
Publisher:
ISBN:
Category : Electronic dissertations
Languages : en
Pages :

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Transition metal oxide-based systems as catalysts for oxidative reactions are studied. Utilizing aerobic oxygen as a cost-efficient and benign oxidant is explored for alcohol oxidation reactions. A detailed magnetic study is performed to understand the active phases of manganese oxide catalysts. The role of a well-known homogeneous copper oxide catalyst in an oxidation reaction is explored for making alcohols from aliphatic hydrocarbons. Finally, virtual screening techniques are explored in a preliminary study for materials discovery. In chapter I, aerobic transformation of alcohols is studied by mesoporous manganese oxide and cobalt oxide species. Catalyst optimization, characterization and substrate scope experimentation is performed for self-esterification of alcohols and aldehydes. In chapter II, a comprehensive magnetic characterization of mesoporous manganese oxide species is provided. While conventional methods do not lead to definitive phase determination, magnetic transitions and spin eco NMR techniques prove the mixed phase of meso MnOx materials. In chapter III, a synthetic copper complex is studied. The complex was modeled after the active site of particulate methane monooxygenase (pMMO). A detailed study of the complex structure, reaction medium and by- products showed that an important side reaction interfered with hydrocarbon oxidation. The nitrile solvent decomposes to amide by nucleophilic interactions from hydrogen peroxide. In the final chapter, preliminary computational screening tools are introduced. Extraction of geometrical features of molecular structures and evaluation of total energy with machine learning algorithms are performed and the ground work for application of such work to crystalline materials is proposed.

Author: Matthew M. Mench
Publisher: Academic Press
ISBN: 0123869366
Category : Technology & Engineering
Languages : en
Pages : 474

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For full market implementation of PEM fuel cells to become a reality, two main limiting technical issues must be overcome- cost and durability. This cutting-edge volume directly addresses the state-of-the-art advances in durability within every fuel cell stack component. [...] chapters on durability in the individual fuel cell components -- membranes, electrodes, diffusion media, and bipolar plates -- highlight specific degradation modes and mitigation strategies. The book also includes chapters which synthesize the component-related failure modes to examine experimental diagnostics, computational modeling, and laboratory protocol"--Back cover.

Author: Chuhyon John Eom
Publisher:
ISBN:
Category :
Languages : en
Pages : 123

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The structure-property relationship is a foundational concept of materials science and engineering. Tuning the catalytic properties of materials by varying their structural properties like stoichiometry and crystal facets have been integral to advances in electrocatalysis. Traditionally, these studies rely on ex situ, bulk structural characterizations to describe catalytic properties. Catalysis, however, occurs on a dynamic catalytic surface sensitive to its local environment. This dissertation uses in situ spectroscopy of metal oxide electrocatalysts to better capture the intricacies of such catalyst structure-property relationships. La2/3S1/3rMnO3 films are grown using molecular beam epitaxy for a controlled study on the effects of surface and sub-surface structure of metal oxides on the oxygen reduction reaction (ORR) catalysis. Ambient pressure X-ray photoelectron spectroscopy of the films show that the surface and sub-surface structures control the balance between electronic benefits vs. parasitic surface reactions for the ORR. The low atomic number group of an amorphous cobalt oxide catalyst in a phosphate network (CoPi) is studied using home-built stimulated Raman spectroscopy (SRS). In situ SRS reveals previously unreported phosphate motifs in CoPi under oxygen evolution reaction conditions. Isotopic studies show that the phosphate structure is intimately linked to the aqueous environment with implications for the catalyst microstructure and deposition. Extensions of the dissertation on the in situ spectroscopy of a quinone electrochemical systems is discussed in the end.

Author: Jacques C. Vedrine
Publisher: Elsevier
ISBN: 0128116323
Category : Technology & Engineering
Languages : en
Pages : 620

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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

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Category : Aeronautics
Languages : en
Pages : 602

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Lists citations with abstracts for aerospace related reports obtained from world wide sources and announces documents that have recently been entered into the NASA Scientific and Technical Information Database.