Download or read book Characterization of Competitive Oxidation Reactions Over a Model Pt Pd Al2O3 Diesel Oxidation Catalyst written by Karishma Vistasp Irani and published by . This book was released on 2009 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt: There has been a growing interest in using lean-burn engines due to their higher fuel economy and associated lower CO2 emissions. However, there are challenges in reducing NOX in an O2-rich (lean-burn) exhaust, and in low temperature soot oxidation. NOX storage/reduction (NSR) and selective catalytic reduction (SCR) are commercial NOX reduction technologies, and both are more efficient with levels of NO2 that are higher than those that are in engine exhaust (engine-out NO2 levels are ~10% of the total NOX). Therefore diesel oxidation catalysts are installed upstream of these technologies to provide NO2 through NO oxidation. The motivation behind this research project was two-fold. The first was to gain a better understanding of the effect of hydrocarbons on NO oxidation over a monolithic diesel oxidation catalyst. The second was to spatially resolve competitive oxidation reactions as a function of temperature and position within the same diesel oxidation catalyst (as that used in the first part). A technique known as spatially resolved capillary-inlet mass spectrometry (SpaciMS) was used to measure the gas concentrations at various positions within the catalyst. Diesel engine exhaust contains a mixture of compounds including NO, CO and various hydrocarbons, which react simultaneously over a catalyst, and each can influence the oxidation rates of the others. While studying the effect of hydrocarbons on NO oxidation in this project, propylene was found to have an apparent inhibition effect on NO oxidation, which increased with increasing propylene concentration. This apparent inhibition is a result of the NO2, as a product of NO oxidation, reacting with the propylene as an oxidant. Experiments with NO2 demonstrate a significant temperature decrease in the onset of NO2 reduction when propylene was present, which decreased further with increasing amounts of propylene, verifying NO2 as an oxidant. Similar results were observed with m-xylene and dodecane addition as well. The results also demonstrate that NO2 was consumed preferentially relative to O2 during hydrocarbon oxidation. With low inlet levels of O2, it was evident that the addition of NO2 had an apparent inhibition effect on propylene oxidation after the onset of NO2 reduction. This subsequent inhibition was due to the NO formed, demonstrating that C3H6 results in reduced NO2 outlet levels while NO inhibits C3H6 oxidation. The development of new models as well as validation of existing models requires the ability to spatially resolve oxidation reactions within a monolith. Spatially-resolved data will also give catalyst manufacturers insight into the location of active fronts, thereby directing the design of more efficient catalysts. In this research project, spatially resolving the oxidation reactions demonstrated that H2 and CO are oxidized prior to C3H6 and C12H26 and clearly show back-to-front ignition of the reductant species. An enhancement in NO oxidation was observed at the same time as dodecane oxidation light off, likely related to dodecane partial oxidation products.
Download or read book Predicting the Effect of Catalyst Axial Active Site Distributions on a Diesel Oxidation Catalyst Performance written by Suad Al-Adwani and published by . This book was released on 2012 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt: Zone-coated diesel oxidation catalysts (DOCs) can be used to obtain overall improved performance in oxidation reaction extents. However, why this occurs and under what conditions an impact is expected are unknown. In order to demonstrate why these catalysts work better than their standard counterparts and how significant the improved performance is, the CO oxidation performance over a series of Pt-Pd/Al2O3 catalysts, each with a different distribution of precious metal down the length, while maintaining equivalent totals of precious metal, was modeled. Simulations with different flow rates, ramp rates, steady-state temperatures at the end of the ramp rate, different total precious metal loadings, and CO inlet values were compared. At conversions less than 50%, the most significant differences were noted when the temperature was ramped to just at the CO oxidation light-off point (a typical measure of 50% conversion/oxidation), with catalysts containing more precious metal at the downstream portions leading to better light-off conversion performance. However, in terms of cumulative emissions over a long period of time, a "front-loaded" design proved best. These results are readily explained by decreased CO poisoning and the propagation of the heat derived from the exotherm from the front to the rear of the catalyst. Also, although the trends were the same, regardless of change in the parameter, the impact of different distributions was more apparent under conditions where a catalyst would be challenged, i.e., at low temperature ramp rates, higher CO inlet concentrations, and lower amounts of total catalyst used. At higher ramp rates, the input heat from the entering gas stream played an increasingly important role, relative to conduction associated with the exotherm, dampening the effects of the catalyst distribution. Therefore, although catalysts that are zone-coated with precious metals, or any active sites, could prove better in terms of performance than homogeneously distributed active site catalysts, this improvement is only significant under certain reaction conditions. In a mixture of three reactants, CO, C3H6 and NO oxidation, it was found that a loading a larger amount of active sites in the catalyst middle, maintained better CO and C3H6 oxidation but not NO oxidation, which required the whole catalyst length. A faster light-off conversion was also related to higher amount of precious metal at the catalyst outlet. The CO conversion performance for a variety of distributed precious metal designs was evaluated as a function of exposure time to sulphur and the spatial accumulation profile of sulphur along the monolith length was predicted. The results illustrate that the sulphur accumulates near the catalyst inlet and decreases toward the outlet, resulting in shifting the reaction zones further toward the catalyst outlet. With sulfation, light-off temperatures (T50) increased and the time for back to front reaction propagation also increased. A back loaded catalyst resulted in the best light-off conversion compared to the other catalyst designs and a middle loaded catalyst maintained a higher overall conversion if sulphur poisoning takes place. These catalyst designs were also tested under thermal aging conditions by using a second order sintering model integrated with the CO oxidation reaction model. The spatial normalized dispersion profiles along the monolith showed that the catalyst outlet experienced significant damage relative to the inlet due to sintering. A front loaded catalyst design had the highest catalytic activity due its resistance to sintering.
Download or read book On the Performance of Oxidation Catalysts and SCR Catalysts in the Presence of Alkali Compounds Representative of Biofuel Contaminants written by Yiquan Xie and published by . This book was released on 2017 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to global lean exhaust gas and new emission regulations, exhaust after-treatment systems of diesel engines are getting more and more sophisticated and comprise a series of catalytic units. In the present work, two of these catalytic systems were studied, Diesel Oxidation Catalysts (DOC) and Selective Catalytic Reduction (SCR) catalysts. Particular attention is paid to their performance in the presence of alkali compounds when bio-diesel is utilized as the alternative fuel.Firstly, this thesis focuses on the catalytic behavior of the Diesel Oxidation Catalyst using different aging characteristics of road mileage in order to improve the efficiency of an ammonia SCR system on an after-treatment line composed by a DOC + DPF + SCR. The studied catalyst is a commercial diesel oxidation catalyst (Pt/Pd/Al2O3) provided by Continental. Hydrothermal aging under different conditions on carrots of monolith were performed. Also studied in the monolith form over the commercial DOC, the influence of the addition of different alkali metal species (K and Na) on the commercial DOC through catalytic tests performed on this structured catalyst under multicomponent (C3H6 / CO / NO / NO2) co-feeding conditions was explored. Aiming at investigating the effects of the presence of different alkali metal species on the DOC at the level of active phase, homemade bimetallic DOC is prepared and then different alkali metal species incorporated. Finally, encouraged by the evident influence of alkali compounds on DOCs, their impacts on the downstream SCR catalysts are also studied in this thesis. The studied SCR catalyst is a commercial V2O5-based catalyst provided by UMICORE company.
Download or read book Spatial Temperature and Concentration Changes Following Heterogeneous Damage to a Model Diesel Oxidation Catalyst written by April Elizabeth Russell and published by . This book was released on 2010 with total page 83 pages. Available in PDF, EPUB and Kindle. Book excerpt: Infra-Red thermography and spatially-resolved capillary inlet mass spectrometry (SpaciMS) have been used to characterize propylene oxidation along a Pt/Al2O3 monolith-supported catalyst, before and after heterogeneous deactivation. The combined techniques clearly show reaction location, and therefore catalyst use, and how these change with thermal and sulphur degradation. Following the heterogeneous thermal aging, the reaction zones at steady state were broader and located farther into the catalyst relative to those observed with the fresh catalyst. As well, the time for the temperature and concentration waves to travel through the catalyst during back-to-front ignition increased. These effects were more pronounced with 1500 ppm propylene relative to 4500 ppm propylene. Such trends could not be detected based on standard catalyst-outlet measurements. The light-off behaviour was also impacted by the aging, resulting in complex changes to the temperature front propagation, depending on the propylene concentration. With each sulphur exposure step, light-off temperatures increased and the time for back-to-front ignition during temperature programmed oxidation changed pattern. With 1500 ppm propylene fed, the reaction zones established during steady-state operation shifted farther into the catalyst and increased slightly in width following sulphur treatment; at very high temperature and for 4500 ppm propylene, the reaction zones were very close to the catalyst inlet and virtually indistinguishable between catalyst sulphation states. However, at lower steady-state temperatures for the higher propylene concentration, the catalyst did experience delays in reaction light-off and light-off position moved downstream in the catalyst with sulphur damage.
Download or read book Catalysis written by James Spivey and published by Royal Society of Chemistry. This book was released on 2018-05-03 with total page 243 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalysts are required for a variety of applications. Industrialists and academics are increasingly challenged to find cost effective and environmentally benign catalysts to use. This volume looks at modern approaches to catalysis and critically reviews the extensive literature on areas such as catalysts derived from waste materials, determining the pore structure of activated carbon by nitrogen gas adsorption and a new tool to explore catalytic reaction mechanisms - the catalytic shock tube. With an emphasis on interdisciplinary content, this book is aimed at catalytic science and engineering research communities.
Download or read book Catalytic Hydrogenation written by L. Cervený and published by Elsevier. This book was released on 1986-08-01 with total page 705 pages. Available in PDF, EPUB and Kindle. Book excerpt: The collection of contributions in this volume presents the most up-to-date findings in catalytic hydrogenation. The individual chapters have been written by 36 top specialists each of whom has achieved a remarkable depth of coverage when dealing with his particular topic. In addition to detailed treatment of the most recent problems connected with catalytic hydrogenations, the book also contains a number of previously unpublished results obtained either by the authors themselves or within the organizations to which they are affiliated.Because of its topical and original character, the book provides a wealth of information which will be invaluable not only to researchers and technicians dealing with hydrogenation, but also to all those concerned with homogeneous and heterogeneous catalysis, organic technology, petrochemistry and chemical engineering.
Download or read book Environmental Catalysis written by John N. Armor and published by American Chemical Society. This book was released on 1994 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first comprehensive volume on the major aspects of environmental catalysis. Focuses on NO x removal, mobile engine emission controls, power plant emissions, control of volatile organic compounds, SO x emissions, and waste minimization. Overview chapters introduce each section and provide added perspective and coverage. Includes comprehensive technical reports on automotive and diesel emission control catalysis, NO x removal, and removal of chlorinated hydrocarbons from various process streams.
Download or read book Selective Catalytic Reduction of NOx written by Oliver Kröcher and published by MDPI. This book was released on 2018-12-14 with total page 281 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a printed edition of the Special Issue "Selective Catalytic Reduction of NOx" that was published in Catalysts
Download or read book In situ Characterization of Heterogeneous Catalysts written by José A. Rodriguez and published by John Wiley & Sons. This book was released on 2013-04-17 with total page 488 pages. Available in PDF, EPUB and Kindle. Book excerpt: Helps researchers develop new catalysts for sustainable fueland chemical production Reviewing the latest developments in the field, this bookexplores the in-situ characterization of heterogeneous catalysts,enabling readers to take full advantage of the sophisticatedtechniques used to study heterogeneous catalysts and reactionmechanisms. In using these techniques, readers can learn to improvethe selectivity and the performance of catalysts and how to preparecatalysts as efficiently as possible, with minimum waste. In-situ Characterization of Heterogeneous Catalysts featurescontributions from leading experts in the field of catalysis. Itbegins with an introduction to the fundamentals and thencovers: Characterization of electronic and structural properties ofcatalysts using X-ray absorption fine structure spectroscopy Techniques for structural characterization based on X-raydiffraction, neutron scattering, and pair distribution functionanalysis Microscopy and morphological studies Techniques for studying the interaction of adsorbates withcatalyst surfaces, including infrared spectroscopy, Ramanspectroscopy, EPR, and moderate pressure XPS Integration of techniques that provide information on thestructural properties of catalysts with techniques that facilitatethe study of surface reactions Throughout the book, detailed examples illustrate how techniquesfor studying catalysts and reaction mechanisms can be applied tosolve a broad range of problems in heterogeneous catalysis.Detailed figures help readers better understand how and why thetechniques discussed in the book work. At the end of each chapter,an extensive set of references leads to the primary literature inthe field. By explaining step by step modern techniques for the in-situcharacterization of heterogeneous catalysts, this book enableschemical scientists and engineers to better understand catalystbehavior and design new catalysts for green, sustainable fuel andchemical production.
Download or read book The Microkinetics of Heterogeneous Catalysis written by J. A. Dumesic and published by Wiley-VCH. This book was released on 1993-04-20 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt: Defines the emerging field of catalytic reaction synthesis in the search for new catalysts and catalytic processes. Illustrates how experimental data from diverse sources can be consolidated to form a quantitative description of the essential chemistry taking place on the catalyst surface. Elucidates the possible relationships between catalyst kinetic properties and surface chemical bonding properties. Offers examples of microkinetic analysis and catalytic reaction synthesis for a variety of catalytic reactions over metals, oxides, and zeolite catalysts. Illustrates the underlying strategy used to formulate a microkinetic model, calibrate the model to the existing experimental data, and assess the critical aspects of the essential surface chemistry involved in the catalytic process.
Download or read book Methane Conversion written by D.M. Bibby and published by Elsevier. This book was released on 1988-03-01 with total page 759 pages. Available in PDF, EPUB and Kindle. Book excerpt: This proceedings volume comprises the invited plenary lectures, contributed and poster papers presented at a symposium organised to mark the successful inauguration of the world's first commercial plant for production of gasoline from natural gas, based on the Mobil methanol-to-gasoline process. The objectives of the Symposium were to present both fundamental research and engineering aspects of the development and commercialization of gas-to-gasoline processes. These include steam reforming, methanol synthesis and methanol-to-gasoline. Possible alternative processes e.g. MOGD, Fischer-Tropsch synthesis of hydrocarbons, and the direct conversion of methane to higher hydrocarbons were also considered.The papers in this volume provide a valuable and extremely wide-ranging overview of current research into the various options for natural gas conversion, giving a detailed description of the gas-to-gasoline process and plant. Together, they represent a unique combination of fundamental surface chemistry catalyst characterization, reaction chemistry and engineering scale-up and commercialization.
Download or read book Perovskites and Related Mixed Oxides written by Pascal Granger and published by John Wiley & Sons. This book was released on 2016-02-23 with total page 1050 pages. Available in PDF, EPUB and Kindle. Book excerpt: This comprehensive handbook and ready reference details all the main achievements in the field of perovskite-based and related mixed-oxide materials. The authors discuss, in an unbiased manner, the potentials as well as the challenges related to their use, thus offering new perspectives for research and development on both an academic and industrial level. The first volume begins by summarizing the different synthesis routes from molten salts at high temperatures to colloidal crystal template methods, before going on to focus on the physical properties of the resulting materials and their related applications in the fields of electronics, energy harvesting, and storage as well as electromechanics and superconductivity. The second volume is dedicated to the catalytic applications of perovskites and related mixed oxides, including, but not limited to total oxidation of hydrocarbons, dry reforming of methane and denitrogenation. The concluding section deals with the development of chemical reactors and novel perovskite-based applications, such as fuel cells and high-performance ceramic membranes. Throughout, the contributions clearly point out the intimate links between structure, properties and applications of these materials, making this an invaluable tool for materials scientists and for catalytic and physical chemists.
Download or read book Acidity and Basicity written by Eike Brunner and published by Springer Science & Business Media. This book was released on 2008-02-20 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first handbook on zeolites and other microporous materials. It is an up-to-date, highly sophisticated collection of information for those who deal with zeolites in industry or at academic institutions as well as being a guide for newcomers.
Download or read book Catalytic Reactors written by Basudeb Saha and published by Walter de Gruyter GmbH & Co KG. This book was released on 2015-12-18 with total page 399 pages. Available in PDF, EPUB and Kindle. Book excerpt: Catalytic Reactors presents several key aspects of reactor design in Chemical and Process Engineering. Starting with the fundamental science across a broad interdisciplinary field, this graduate level textbook offers a concise overview on reactor and process design for students, scientists and practitioners new to the field. This book aims to collate into a comprehensive and well-informed work of leading researchers from north America, western Europe and south-east Asia. The editor and international experts discuss state-of-the-art applications of multifunctional reactors, biocatalytic membrane reactors, micro-flow reactors, industrial catalytic reactors, micro trickle bed reactors and multiphase catalytic reactors. The use of catalytic reactor technology is essential for the economic viability of the chemical manufacturing industry. The importance of Chemical and Process Engineering and efficient design of reactors are another focus of the book. Especially the combination of advantages from both catalysis and chemical reaction technology for optimization and intensification as essential factors in the future development of reactors and processes are discussed. Furthermore, options that can drastically influence reaction processes, e.g. choice of catalysts, alternative reaction pathways, mass and heat transfer effects, flow regimes and inherent design of catalytic reactors are reviewed in detail. Focuses on the state-of-the-art applications of catalytic reactors and optimization in the design and operation of industrial catalytic reactors Insights into transfer of knowledge from laboratory science to industry For students and researchers in Chemical and Mechanical Engineering, Chemistry, Industrial Catalysis and practising Engineers
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.
Download or read book Water Gas Shift Reaction written by Panagiotis Smirniotis and published by Elsevier. This book was released on 2015-06-11 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt: Water Gas Shift Reaction: Research Developments and Applications outlines the importance of hydrogen as a future fuel, along with the various hydrogen production methods. The book explains the development of catalysts for Water Gas Shift (WGS) reaction at different temperatures and steam/CO ratios, and also discussing the effect of different dopants on the WGS activity of iron oxide and the promotion and inhibition roles of the dopants on the WGS activity of iron oxide are explained. In addition, the book describes extensive characterization of modified ferrite catalysts, especially with Mossbauer spectroscopy and its advantage in understanding properties of metal doped ferrite catalysts, the exact dopant location, and its effect on electron hopping capability and WGS activity of Fe redox couple. - Outlines the importance of the Water Gas Shift Reaction and its application for hydrogen production - Provides detailed information on potential catalysts, their development, and their pros and cons, giving the reader insights on how modified ferrite catalysts work at different temperatures and different steam to CO ratios - Reviews hydrogen technology, its current importance, and production methods - Presents a clear presentation of the topics with many graphics and tables - Offers basic and advanced knowledge of catalysts characterization instrumental techniques
Download or read book Catalyst Preparation written by John Regalbuto and published by CRC Press. This book was released on 2016-04-19 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text explores the optimization of catalytic materials through traditional and novel methods of catalyst preparation, characterization, and monitoring for oxides, supported metals, zeolites, and heteropolyacids. It focuses on the synthesis of bulk materials and of heterogeneous materials, particularly at the nanoscale. The final chapters examine pretreatment, drying, finishing effects, and future applications involving catalyst preparation and the technological advances necessary for continued progress. Topics also include heat and mass transfer limitations, computation methods for predicting properties, and catalyst monitoring on laboratory and industrial scales.
