Download or read book Low Temperature Water gas Shift Reaction Over Gold ferrochrome Catalysts written by Gaurav Narendra Vajani and published by . This book was released on 2011 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work consists of the investigation of gold-ferrochrome catalysts under low temperature water-gas shift reaction conditions. The goal of this research is the development of a kinetic model and understanding the deactivation mechanism of gold-ferrochrome catalyst during water-gas shift reaction. The motivation for studying these catalysts comes from the importance and need of water-gas shift for low temperature applications requiring highly active catalysts that remain stable for long term commercial use. Gold based catalysts supported on metal oxide supports show considerable promise but no kinetic models exist and very little is known about their stability. The first part involves the development of a kinetic model for low temperature water-gas shift over gold-ferrochrome catalysts. Using experimental measurement of kinetics, a power-law rate expression with a factor accounting for catalyst deactivation has been presented.^This is the first reported rate expression for gold-ferrochrome catalysts used for water-gas shift. The effect of various operating conditions on the reaction rate has been discussed. The second part investigates the cause of catalyst deactivation and a mechanism of deactivation of gold-ferrochrome catalyst has been proposed. Under various operating conditions, the catalyst loses its activity rapidly. Long term stability tests and adsorption measurements provide evidence for the loss of active sites. Two aspects of catalyst deactivation are studied: firstly, possible changes in the nature of support and gold particles and secondly, detailed investigation into catalyst deactivation by carbon deposition. Characterization of active and deactivated samples using microscopic and spectroscopic techniques provides qualitative insight into the cause of catalyst deactivation.^The degree of deactivation by sintering and carbon deposition has been quantified by exposing the catalyst to various environments. A novel technique for in-situ gravimetric analysis of the catalyst is developed using a tapered element oscillating microbalance and this helps shed light on the loss in catalytic activity and its relation to carbon deposition. Thermodynamic calculations provide validation for the phase of the support and ascertain the tendency of carbon deposition under low temperature water-gas shift conditions. Carbon deposition and sintering of gold, the main factors contributing to the deactivation of gold-ferrochrome have been discussed.

Download or read book Mechanistic Modeling of the High Temperature Water Gas Shift Reaction on Ferrochrome written by John Slocum Coleman and published by . This book was released on 2008 with total page 234 pages. Available in PDF, EPUB and Kindle. Book excerpt: ?Pub Inc This dissertation consists of investigations on ferrochrome, copper promoted ferrochrome, and gold on ferrochrome. The first investigation involved the examination of reaction mechanisms for water-gas shift over ferrochrome catalysts under high temperature operation. Mechanisms were developed to represent the two primary mechanism types presented in literature, namely the regenerative and associative mechanisms. Both mechanism types have been suggested within the literature based on the fit of rate expressions derived from them, and experimental characterizations have provided support for both mechanisms. Mechanistic kinetic modeling was performed and comparisons to experimentally available information were made between each of the mechanisms considering both mechanistic parameters and predicted behavior under reaction conditions. A combined mechanism was additionally proposed to provide both mechanistic pathways, and comparisons to each of the individual mechanisms were made. The results of the mechanistic kinetic modeling suggest that an associative mechanism does not accurately describe water-gas shift. Both the regenerative and combined mechanisms yield quantitatively and qualitatively similar predictions. The observations made during the mechanistic kinetic modeling were then used to develop a computational chemistry model of the active site for water-gas shift over ferrochrome. Cluster models representing potential active sites of the (100), (110), and (111) surfaces of magnetite were generated and compared using the enthalpy of localization for the surface oxygen species as a selection criterion. The cluster developed from the (111) surface showed the best qualitative agreement to the regenerative and combined mechanisms, suggesting the (111) surface of magnetite may be catalytically active. The combined mechanism as formulated for the mechanistic kinetic modeling of an unpromoted ferrochrome catalyst was then fit to experimental data generated for a copper promoted ferrochrome catalyst. While copper has been shown in the past to be an effective promoter for ferrochrome water-gas shift catalysts, the method of promotion is still unclear. The mechanistic kinetic study of a copper promoted ferrochrome catalyst suggested that copper acts as a substitutional promoter, modifying key parameters within the mechanistic model. The changes in the kinetic parameters caused by copper in the combined mechanistic model mirror predictions made using a "virtual" catalyst developed from the mechanistic model for an unpromoted ferrochrome. Finally, an experimental study of the preparation and performance of gold promoted low temperature ferrochrome catalysts was underataken. The key to active gold catalysts lies in the size of gold particles supported on the surface of the catalyst. The investigation of nanoparticles preparation techniques and their eventual attachment onto a ferrochrome support suggested that while monodisperse gold can be synthesized, the attachment onto the catalyst surface generates agglomerated clusters that are catalytically inactive. Traditional deposition-precipitation techniques yielded active low temperature catalysts. These catalysts were evaluated kinetically, and a rate expression for low temperature water-gas shift was developed. They were observed to deactivate appreciably under reaction conditions, and this aspect of their performance was also quantified.

Download or read book Gold Catalysts for the Low temperature Water gas Shift Reaction written by James Carter and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Heterogeneous Catalysis by Supported Gold Catalysts for the Low Temperature Water gas Shift Reaction written by Aluha James Lulizi and published by . This book was released on 2003 with total page 336 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Studies of the Water gas Shift Reaction Over Supported Gold and Platinum Catalysts written by Steven Taylor Evans and published by . This book was released on 2004 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Performance of Gold Catalysts for Low Temperature Water Gas Shift written by Stephen Roberts and published by . This book was released on 2001 with total page 162 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Activity and Stability of Nanostructured Gold cerium Oxide Catalysts for the Water gas Shift Reaction written by Qi Fu and published by . This book was released on 2004 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced low-temperature water-gas shift (LTS) catalysts of high activity and stability are under development to produce essentially CO-free hydrogen to feed PEM fuel cells for power generation. Materials based on nanocrystalline cerium oxide (ceria) are among the most promising LTS catalysts. Understanding the structural properties relationship with the WGS activity is fundamentally important in order to rational design the catalysts.

Download or read book Ultra low Temperature Water gas Shift Reaction with Supported Ionic Liquid Phase SILP Catalysts written by Sebastian Werner and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book WATER GAS SHIFT KINETICS OVER IRON OXIDE CATALYSTS AT MEMBRANE REACTOR CONDITIONS written by and published by . This book was released on 2002 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt: The kinetics of water-gas shift were studied over ferrochrome catalysts under conditions with high carbon dioxide partial pressures, such as would be expected in a membrane reactor. The catalyst activity is inhibited by increasing carbon dioxide partial pressure. A microkinetic model of the reaction kinetics was developed. The model indicated that catalyst performance could be improved by decreasing the strength of surface oxygen bonds. Literature data indicated that adding either ceria or copper to the catalyst as a promoter might impart this desired effect. Ceria-promoted ferrochrome catalysts did not perform any better than unpromoted catalyst at the conditions tested, but copper-promoted ferrochrome catalysts did offer an improvement over the base ferrochrome material. A different class of water-gas shift catalyst, sulfided CoMo/Al2O3 is not affected by carbon dioxide and may be a good alternative to the ferrochrome system, provided other constraints, notably the requisite sulfur level and maximum temperature, are not too limiting. A model was developed for an adiabatic, high-temperature water-gas shift membrane reactor. Simulation results indicate that an excess of steam in the feed (three moles of water per mole of CO) is beneficial even in a membrane reactor as it reduces the rate of adiabatic temperature rise. The simulations also indicate that much greater improvement can be attained by improving the catalyst as opposed to improving the membrane. Further, eliminating the inhibition by carbon dioxide will have a greater impact than will increasing the catalyst activity (assuming inhibition is still operative). Follow-up research into the use of sulfide catalysts with continued kinetic and reactor modeling is suggested.

Download or read book High temperature Water gas Shift Reaction Over Cr free Fe Al Catalysts Promoted with First Row Transition Metals written by Sittichai Natesakhawat and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Investigation of Supported Gold Catalysts for the Water Gas Shift Reaction written by Ratchaneekorn Pilasombat and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Catalysis By Gold written by Geoffrey C Bond and published by World Scientific. This book was released on 2006-08-15 with total page 383 pages. Available in PDF, EPUB and Kindle. Book excerpt: Gold has traditionally been regarded as inactive as a catalytic metal. However, the advent of nanoparticulate gold on high surface area oxide supports has demonstrated its high catalytic activity in many chemical reactions. Gold is active as a heterogeneous catalyst in both gas and liquid phases, and complexes catalyse reactions homogeneously in solution. Many of the reactions being studied will lead to new application areas for catalysis by gold in pollution control, chemical processing, sensors and fuel cell technology. This book describes the properties of gold, the methods for preparing gold catalysts and ways to characterise and use them effectively in reactions. The reaction mechanisms and reasons for the high activities are discussed and the applications for gold catalysis considered./a

Download or read book Performance of Gold Reference Catalysts in the Water Gas Shift Reaction written by Yatish Surendra Daya and published by . This book was released on 2007 with total page 164 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Low Temperature Carbon Monoxide Oxidation Over Gold Supported on Iron Oxide Catalysts written by Chien Sze and published by . This book was released on 1995 with total page 310 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Water gas Shift Reaction in Nonisothermal Conditions Over an Iron Oxide chromium Oxide Catalyst written by Riitta L. Keiski and published by . This book was released on 1991 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book High Temperature Water Gas Shift Catalysts written by S. Benny and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The high-temperature (HT) Water Gas Shift (WGS) reaction has considerable technological relevance for lowering CO content during the conversion of natural gas or liquid hydrocarbons to hydrogen. Conventional HT-WGS catalysts based on oxides of iron and chromium are well established industrially. However, it is crucial to remove any impurities present such as Cr6+, S or N during the catalytic process. In particular, Cr6+ is regarded as a Class I carcinogen and its presence is restricted by EU legislation. Even though Cr6+ is reduced during the catalytic process, caution must still be taken to eliminate any further impurities. Hence, it is desirable to identify alternative promoters and develop a Cr-free HT-WGS catalyst. This thesis presents results obtained using atomistic simulation techniques to investigate the effect of Cr3+ and possible alternative dopants in three important iron oxide materials, Hematite ([alpha]-Fe2O3), Maghemite ([gamma]-Fe2O3) and Magnetite (Fe3O4). The starting point is to develop an understanding of the structural properties and distribution of Cr3+ on the bulk and surface material of hematite. The critical stage of understanding the role of Cr3+ provides the basis from which criteria for novel dopants can be assessed. Al3+ and Mn3+ are proposed as the promising candidates on the basis of this study. The research has been extended to other complex iron oxides, such as maghemite and magnetite. In summary, the role of chromium in the HT-WGS reaction has been investigated to establish criteria for effective, alternative promoter dopants. This investigation has provided a detailed insight into the atomic level behaviour of Cr3+, Mn3+, Al3+ impurities in three major iron oxide phases. The alternative dopants predicted in this study have been the subject of parallel experimental studies conducted by Johnson Matthey. The results of this study are already benefiting the design of more efficient iron-oxide catalysts for the HT-WGS reaction.