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Author :
Publisher :
ISBN 13 :
Total Pages : 204 pages
Book Rating : 4.:/5 (916 download)
Download or read book New Insights Into the Oxidative Dehydrogenation of Propane and Ethane on Supported Vanadium Oxide Catalysts written by and published by . This book was released on 2009 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Asad Ahmad Khan
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (16 download)
Download or read book Oxidative Dehydrogenation (ODH) of Ethane to Ethene Over Supported Vanadium Containing Oxide Catalysts written by Asad Ahmad Khan and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Jordan G. Barr
Publisher :
ISBN 13 :
Total Pages : 216 pages
Book Rating : 4.:/5 (442 download)
Download or read book Oxidative Dehydrogenation of Propane to Propene Over Supported Vanadium Oxide Catalysts written by Jordan G. Barr and published by . This book was released on 2000 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Sameer Ali Al-Ghamdi
Publisher :
ISBN 13 :
Total Pages : 500 pages
Book Rating : 4.:/5 (16 download)
Download or read book Oxygen-free Propane Oxidative Dehydrogenation Over Vanadium Oxide Catalysts written by Sameer Ali Al-Ghamdi and published by . This book was released on 2013 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: Propane conversion to propylene has been the subject of intensive researches. This is due to the increasing demand for propylene. Current propylene production processes suffer from several limitations. Oxidative dehydrogenation (ODH) is a promising alternative technology for propylene production overcoming the drawbacks of current processes. However, selectivity control in ODH is still a challenge preventing it from an industrial application. This is due to the formation of undesired carbon oxides. Thus, the development of a selective catalyst is crucial for the commercialization of ODH. Vanadium oxide catalysts have been proposed as the most active and selective catalyst for propane ODH. Moreover, new reactor concepts such as fluidized-bed might also help to make the ODH a feasible alternative for olefins productionas, offering some outstanding advantages in comparison to conventional reactors. This dissertation provides fundamental understanding of structure-reactivity relationship of vanadium oxide catalyst for propane ODH in a fluidized-bed reactor using the lattice oxygen of vanadium oxide catalysts in the absence of gas-phase oxygen. Supported vanadium oxide catalysts with different vanadium loadings (5-10 wt %) supported on?-Al2O3 is used. The prepared catalysts are characterized using several techniques such as BET surface area, H2-TPR, NH3-TPD, O2 Chemisorption, Laser Raman Spectroscopy, Pyridine FTIR and XRD. Characterization of the catalysts reveals that monomeric VOx species are predominant at low vanadium loadings while polymeric VOx species increase with higher loadings until monolayer surface coverage is reached. Moreover, the catalysts display moderated acidity compared to that of the bare alumina due to the relative increase in the number of Brønsted acid sites. Successive-injections propane ODH experiments in the CREC Riser Simulator over partially reduced catalyst show good propane conversions (12%-15%) and promising propylene selectivity (68-86%) at 475-550 0C. Product selectivities are found to augment with the catalyst's degree of reduction suggesting that a certain degree of catalyst reduction is required for better propylene selectivity. Compared to average propylene yields of 5% and 15% obtained in FCC and steam cracking technologies, respectively, promising value of 7% was obtained in the present propane ODH study over vanadium oxide catalyst and under oxygen free conditions. Such result would encourage further investigation of propane ODH in the absence of molecular gas oxygen as promising alternative/supplementary technology for the production of propylene. A kinetic model relating reaction rate to the catalyst's degree of oxidation is proposed. Non- linear regression leads to model parameters with low confidence intervals, suggesting the adequacy of the proposed model in predicting the ODH reaction under the selected reaction conditions.
Author : Israel E. Wachs
Publisher : Springer Nature
ISBN 13 : 3031071255
Total Pages : 1109 pages
Book Rating : 4.0/5 (31 download)
Download or read book Springer Handbook of Advanced Catalyst Characterization written by Israel E. Wachs and published by Springer Nature. This book was released on 2023-06-12 with total page 1109 pages. Available in PDF, EPUB and Kindle. Book excerpt: Co-edited by world-renowned scientists in the field of catalysis, this book contains the cutting-edge in situ and operando spectroscopy characterization techniques operating under reaction conditions to determine a materials’ bulk, surface, and solution complex and their applications in the field of catalysis with emphasis on solid catalysts in powder form since such catalyst are relevant for industrial applications. The handbook covers from widely-used to cutting-edge techniques. The handbook is written for a broad audience of students and professionals who want to pursue the full capabilities available by the current state-of-the-art in characterization to fully understand how their catalysts really operate and guide the rational design of advanced catalysts. Individuals involved in catalysis research will be interested in this handbook because it contains a catalogue of cutting-edge methods employed in characterization of catalysts. These techniques find wide use in applications such as petroleum refining, chemical manufacture, natural gas conversion, pollution control, transportation, power generation, pharmaceuticals and food processing. fdsfds
Author : Ailing Qiao
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (138 download)
Download or read book Oxidative Dehydrogenation of Ethane to Ethylene Over Supported Vanadia and Ni-Nb-M-O Mixed Metal Oxide Catalysts written by Ailing Qiao and published by . This book was released on 2015 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Ailing Qiao
Publisher :
ISBN 13 :
Total Pages : 109 pages
Book Rating : 4.:/5 (922 download)
Download or read book Oxidative Dehydrogenation of Ethane to Ethylene Over Supported Vanadia and Ni-Nb-M-O Mided Metal Oxide Catalysts written by Ailing Qiao and published by . This book was released on 2013 with total page 109 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Alyssa Marie Love
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (124 download)
Download or read book Fundamental Studies on the Structure of Surface Oxide Sites on Supported Oxidative Dehydrogenation Catalysts written by Alyssa Marie Love and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The structure of metal oxide sites on supported metal oxide catalysts has a significant impact on the performance of the catalyst. For example, silica-supported vanadium oxide-a catalyst widely studied for the oxidative dehydrogenation of propane (ODHP) to propene-has a higher selectivity towards propene when the catalyst surface is comprised of primarily dispersed VOx surface species. Conversely, as the loading of vanadium oxide is increased beyond the monolayer coverage threshold, three-dimensional V2O5 particles begin to form which lower the catalyst selectivity towards propene (at higher propane conversions) in favor of COx combustion products. For this catalytic application and for other supported metal oxides, understanding the variables that maximize the dispersion of two-dimensional metal oxide species on a support surface is invaluable information to improve the preparation of these catalysts. This thesis describes the synthesis and detailed characterization of supported oxide catalysts for the oxidative dehydrogenation of catalysts. In this work, vapor-phase grafting techniques were used to investigate the chemical reactions that occur during the synthesis of silica-supported vanadium oxide ODH catalysts. By depositing the neat vanadium precursor, VO(OiPr)3, onto silica dehydrated at 700 degrees C (called V/SiO2(700)), the complexity of variables in the synthesis was significantly decreased (compared to incipient wetness). Key anchoring and restructuring reactions during the formation of vanadium oxide sites on silica were characterized with a combination of infrared (IR), Raman, solid-state nuclear magnetic resonance (NMR), and X-Ray absorption spectroscopic studies, in addition to thermogravimetric analysis-differential scanning calorimetry-mass spectrometry (TGA-DSC-MS), inductively coupled plasma (ICP) elemental analysis, etc. Afterwards, key synthesis variables (i.e., isopropanol solvent, H-bonded silanols and Na+ ions on the support surface) were incorporated into this grafting system to develop a more comprehensive model for the dispersion of vanadium oxide under wet impregnation conditions. Efforts to improve Raman sensitivity towards metal oxide surface sites with shell-isolated nanoparticle-enhanced Raman spectroscopy (SHINERS) are also addressed in this work. The methodology and characterization approach presented for the study of supported vanadium oxide catalysts was also applied to the study of promising new ODHP catalysts, including hexagonal boron nitride and silica-supported boron oxide catalysts.
Author : Juan Mauricio Venegas
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (124 download)
Download or read book Mechanistic Insights on the Oxidative Dehydrogenation of Light Alkanes Catalyzed by Boron-based Catalysts written by Juan Mauricio Venegas and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Light olefins such as ethylene and propylene form the foundation of the modern chemical industry, with yearly production volumes well into the hundreds of millions of metric tons. Currently, these light olefins are mainly produced via energy-intensive steam cracking. Alternatively, oxidative dehydrogenation (ODH) of light alkanes to produce olefins allows for lower operation temperatures and extended catalyst lifetimes, providing valuable process efficiencies. This route has led to significant research interest due to the wide availability of natural gas from shale deposits. Advances in this area have still not yielded catalysts that are sufficiently selective to olefins for industrial implementation, and ODH still remains a holy grail of selective alkane oxidation research. Research into selective heterogeneous catalysts for the ODH of propane has led to the extensive use of vanadium oxide-based catalysts, and studies on the surface mechanism involved have been used to improve the catalytic activity of the material. Despite decades of research, however, selectivity towards propylene has not proven satisfactory at industrially-relevant conversions. In this thesis, I will present the serendipitous discovery and subsequent development of hexagonal boron nitride (hBN) and other boron-containing catalysts as selective ODH catalysts. Specifically, I will illustrate the evolution of our understanding of the chemical origin of the reactivity of these materials, which until our initial discovery were deemed chemically inert. By combining reactivity studies with spectroscopic characterization highlighted a unique interaction between boron and oxiygen that differs from that of metal oxides. This methodical characterization of catalytic activity and structural changes of hBN during ODH prompted us to zero in on oxidized boron species, not hBN itself, as the true catalyst of alkane oxidation. In turn, this discovery led us to describe a whole class of B-containing materials that share (and often improve upon) the catalytic performance of hBN. At this point, we decided to step away from material studies and instead improve our understanding on how the catalytic performance of hBN is affected by reactor operating parameters. In particular, we investigated the role of heat and mass transfer on catalytic performance. Unexpectedly, we were once again surprised by hBN when various experimental results during these efforts suggested the significance of gas phase chemistry on ODH performance. For example, we observed that upon dilution of hBN with an inert thermal conductor (to mitigate hotspot formation), the observed reactivity scales with total bed volume rather than hBN mass. Up until these studies, we expected all reactivity to stem from oxidized boron species, but these may be only a part of a more complex surface-gas phase reaction network. The final portion of this thesis presents our latest efforts to understand the role of each reactant on surface and gas phase reaction pathways. Within this work, we incorporate water into our reaction feeds to assess its influence as a source of gas phase radical species to carry out propane activation. Indeed, we observe significant rate enhancements by addition of water. This reactivity enhancement likely involves influencing reactive species concentrations primarily in the gas phase and, to a lesser extent, altering the surface composition during ODH. Overall, this thesis expands our understanding of B-based materials as ODH catalysts and highlights the importance of considering gas phase radical chemistry in future process development.
Author : Susannah L. Scott
Publisher : Springer Science & Business Media
ISBN 13 : 0387306412
Total Pages : 341 pages
Book Rating : 4.3/5 (873 download)
Download or read book Nanostructured Catalysts written by Susannah L. Scott and published by Springer Science & Business Media. This book was released on 2008-04-06 with total page 341 pages. Available in PDF, EPUB and Kindle. Book excerpt: With the recent advent of nanotechnology, research and development in the area of nanostructured materials has gained unprecedented prominence. Novel materials with potentially exciting new applications are being discovered at a much higher rate than ever before. Innovative tools to fabricate, manipulate, characterize and evaluate such materials are being developed and expanded. To keep pace with this extremely rapid growth, it is necessary to take a breath from time to time, to critically assess the current knowledge and provide thoughts for future developments. This book represents one of these moments, as a number of prominent scientists in nanostructured materials join forces to provide insightful reviews of their areas of expertise, thus offering an overall picture of the state-- the art of the field. Nanostructured materials designate an increasing number of materials with designed shapes, surfaces, structures, pore systems, etc. Nanostructured materials with modified surfaces include those whose surfaces have been altered via such techniques as grafting and tethering of organic or organometallic species, or through various deposition procedures including electro, electroless and vapor deposition, or simple adsorption. These materials find important applications in catalysis, separation and environmental remediation. Materials with patterned surfaces, which are essential for the optoelectronics industry, constitute another important class of surface-modified nanostructured materials. Other materials are considered nanostructured because of their composition and internal organization.
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.
Author :
Publisher :
ISBN 13 :
Total Pages : 5 pages
Book Rating : 4.:/5 (727 download)
Download or read book Effect of Catalyst Structure on Oxidative Dehydrogenation of Ethane and Propane on Alumina-supported Vanadia written by and published by . This book was released on 2001 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The catalytic properties of Al2O3-supported vanadia with a wide range of VOx surface density (1.4-34.2 V/nm2) and structure were examined for the oxidative dehydrogenation of ethane and propane. UV-visible and Raman spectra showed that vanadia is dispersed predominantly as isolated monovanadate species below (almost equal to)2.3 V/nm2. As surface densities increase, two-dimensional polyvanadates appear (2.3-7.0 V/nm2) along with increasing amounts of V2O5 crystallites at surface densities above 7.0 V/nm2. The rate constant for oxidative dehydrogenation (k1) and its ratio with alkane and alkene combustion (k2/k1 and k3/k1, respectively) were compared for both alkane reactants as a function of vanadia surface density. Propene formation rates (per V-atom) are (almost equal to)8 times higher than ethene formation rates at a given reaction temperature, but the apparent ODH activation energies (E1) are similar for the two reactants and relatively insensitive to vanadia surface density. Ethene and propene formation rates (per V-atom) are strongly influenced by vanadia surface density and reach a maximum value at intermediate surface densities ((almost equal to)8 V/nm2). The ratio of k2/k1 depends weakly on reaction temperature, indicating that activation energies for alkane combustion and ODH reactions are similar. The ratio of k2/k1 is independent of surface density for ethane, but increase slightly with vanadia surface density for propane, suggesting that isolated structures prevalent at low surface densities are slightly more selective for alkane dehydrogenation reactions. The ratio of k3/k1 decreases markedly with increasing reaction temperature for both ethane and propane ODH. Thus, the apparent activation energy for alkene combustion (E3) is much lower than that for alkane dehydrogenation (E1) and the difference between these two activation energies decreases with increasing surface density. The lower alkene selectivities observed at high vanadia surface densities are attributed to an increase in alkene adsorption enthalpies with increasing vanadia surface density. The highest yield of alkene is obtained for catalysts containing predominantly isolated monovanadate species and operated at high temperatures that avoid homogeneous reactions (
Author : Sang-Eon Park
Publisher : Elsevier
ISBN 13 : 0080472176
Total Pages : 626 pages
Book Rating : 4.0/5 (84 download)
Download or read book Carbon Dioxide Utilization for Global Sustainability written by Sang-Eon Park and published by Elsevier. This book was released on 2004-10-27 with total page 626 pages. Available in PDF, EPUB and Kindle. Book excerpt: Addressing global environmental problems, such as global warming is essential to global sustainability. Continued research leads to advancement in standard methods and produces new data. Carbon Dioxide Utilization for Global Sustainability: Proceedings of the 7th ICCDU (International Conference on Carbon Dioxide Utilization) reflects the most recent research results, as well as stimulating scientific discussions with new challenges in advancing the development of carbon dioxide utilization. Drawing on a wealth of information, this well structured book will benefit students, researchers and consultants looking to catch up on current developments in environmental and chemical engineering. * Provides comprehensive data on CO2 utilisation* Contains up-to-date information, including recent research trends* Is written for students, researchers and consultants in environmental and chemical engineering
Author : Michel Boudart
Publisher : Elsevier
ISBN 13 : 1483183971
Total Pages : 263 pages
Book Rating : 4.4/5 (831 download)
Download or read book Kinetics of Chemical Processes written by Michel Boudart and published by Elsevier. This book was released on 2014-05-16 with total page 263 pages. Available in PDF, EPUB and Kindle. Book excerpt: Kinetics of Chemical Processes details the concepts associated with the kinetic study of the chemical processes. The book is comprised of 10 chapters that present information relevant to applied research. The text first covers the elementary chemical kinetics of elementary steps, and then proceeds to discussing catalysis. The next chapter tackles simplified kinetics of sequences at the steady state. Chapter 5 deals with coupled sequences in reaction networks, while Chapter 6 talks about autocatalysis and inhibition. The seventh chapter describes the irreducible transport phenomena in chemical kinetics. The next two chapters discuss the correlations in homogenous kinetics and heterogeneous catalysis, respectively. The last chapter covers the analysis of reaction networks. The book will be of great use to students, researchers, and practitioners of scientific disciplines that deal with chemical reaction, particularly chemistry and chemical engineering.
Author : Frank Klose
Publisher :
ISBN 13 : 9783939665595
Total Pages : 275 pages
Book Rating : 4.6/5 (655 download)
Download or read book Structure Activity Relations of Supported Vanadia Catalysts and the Potential of Membrane Reactors for the Oxidative Dehydrogenation of Ethane written by Frank Klose and published by . This book was released on 2008 with total page 275 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Jun Yang
Publisher :
ISBN 13 :
Total Pages : 214 pages
Book Rating : 4.:/5 (34 download)
Download or read book Vanadium Oxide-zirconia Catalyst for Propoane Oxidative Dehydrogenation written by Jun Yang and published by . This book was released on 1998 with total page 214 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Jean-Marie Basset
Publisher : Springer Science & Business Media
ISBN 13 : 9400929714
Total Pages : 340 pages
Book Rating : 4.4/5 (9 download)
Download or read book Surface Organometallic Chemistry: Molecular Approaches to Surface Catalysis written by Jean-Marie Basset and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt: Surface organometallic chemistry is a new field bringing together researchers from organometallic, inorganic, and surface chemistry and catalysis. Topics ranging from reaction mechanisms to catalyst preparation are considered from a molecular basis, according to which the "active site" on a catalyst surface has a supra-molecular character. This. the first book on the subject, is the outcome of a NATO Workshop held in Le Rouret. France, in May. 1986. It is our hope that the following chapters and the concluding summary of recommendations for research may help to provide a definition of surface organometallic chemistry. Besides catalysis. the central theme of the Workshop, four main topics are considered: 1) Reactions of organometallics with surfaces of metal oxides, metals. and zeolites; 2) Molecular models of surfaces, metal oxides, and metals; 3) Molecular approaches to the mechanisms of surface reactions; 4) Synthesis and modification of zeolites and related microporous solids. Most surface organometallic chemistry has been carried out on amorphous high-surf ace-area metal oxides such as silica. alumina. magnesia, and titania. The first chapter. contributed by KNOZINGER. gives a short summary of the structure and reactivity of metal oxide surfaces. Most of our understanding of these surfaces is based on acid base and redox chemistry; this chemistry has developed from X-ray and spectroscopic data, and much has been inferred from the structures and reactivities of adsorbed organic probe molecules. There are major opportunities for extending this understanding by use of well-defined (single crystal) oxide surfaces and organometallic probe molecules.
