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Author: Publisher: ISBN: Category : Languages : en Pages : 5
Book Description
A serious engineering problem that needs to be addressed in the scale-up of slurry-phase, Fischer-Tropsch reactors is attrition of the precipitated iron catalyst. Attrition, which can break down the catalyst into particles too small to filter, results from both mechanical and chemical forces. This study examines the chemical causes of attrition in iron catalysts. A bench-scale, slurry-phase CSTR is used to simulate operating conditions that lead to attrition of the catalyst. The average particle size and size distribution of the catalyst samples are used to determine the effect of slurry temperature, reducing gas, gas flow rate and time upon attrition of the catalyst. Carbon deposition, a possible contributing factor to attrition, has been examined using gravimetric analysis and TEM. Conditions affecting the rate of carbon deposition have been compared to those leading to attrition of the precipitated iron catalyst.
Author: Publisher: ISBN: Category : Languages : en Pages : 5
Book Description
A serious engineering problem that needs to be addressed in the scale-up of slurry-phase, Fischer-Tropsch reactors is attrition of the precipitated iron catalyst. Attrition, which can break down the catalyst into particles too small to filter, results from both mechanical and chemical forces. This study examines the chemical causes of attrition in iron catalysts. A bench-scale, slurry-phase CSTR is used to simulate operating conditions that lead to attrition of the catalyst. The average particle size and size distribution of the catalyst samples are used to determine the effect of slurry temperature, reducing gas, gas flow rate and time upon attrition of the catalyst. Carbon deposition, a possible contributing factor to attrition, has been examined using gravimetric analysis and TEM. Conditions affecting the rate of carbon deposition have been compared to those leading to attrition of the precipitated iron catalyst.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
This work has shown that the kaolin binder that has been used in commercial Fischer-Tropsch Synthesis catalysts doe not offer any significant attrition resistance. This is due in part to its morphology (plate-like) and to its particle size being much greater than the primary crystallite size of the iron oxide catalyst. From a microscopic examination of these catalysts, it appears that if the nanoscale attrition of the iron catalyst is to be avoided, the iron must be well dispersed on the binder, and the binder must provide an interlocking microstructure that provides strength and stability to the 30-70[mu]m agglomerates. The study of Fe/SiO[sub 2] catalysts has shown that co-precipitation of the iron and silica leads to formation of an amorphous glassy phase which is difficult to reduce even at 723K. On the other hand, when the iron was precipitated on a preformed silica, 25-40% of the iron could be reduced and carbided. The supported iron catalyst, after reduction, formed 15-20 nm iron carbide particles that look very similar to those on the unsupported catalyst. The major difference is these nanometer sized particles are anchored on a support and therefore would not be expected to breakup further and contribute to the fines generated as catalyst attrition proceeds. However, since only a fraction of the silica-supported iron can be reduced to the active carbide phase, our present efforts are devoted to moderating the Fe/SiO[sub 2] interaction by introducing an interfacial oxide phase. We are also studying the role of added Cu on the ease of reducibility of Fe/SiO[sub 2]. The implication of this work is that other binder materials should be explored that have a morphology that can strengthen the agglomerates and minimize the Fe-SiO[sub 2] interfacial reactions. This work is presently underway in our laboratory.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
An attrition resistant precipitated bulk iron catalyst is prepared from iron oxide precursor and a binder by spray drying. The catalysts are preferably used in carbon monoxide hydrogenation processes such as Fischer-Tropsch synthesis. These catalysts are suitable for use in fluidized-bed reactors, transport reactors and, especially, slurry bubble column reactors.
Author: G.A. Fuentes Publisher: Elsevier ISBN: 008052866X Category : Technology & Engineering Languages : en Pages : 711
Book Description
Catalyst Deactivation 1997 focused on 9 key topical areas: carbon deposition and coke formation, chemicals, environmental catalysis, modeling, petroleum processing, poisoning, syngas conversion, techniques, and thermal degradation. All of these areas were well represented at the meeting; moreover, several review articles were presented that provide perspectives on new research and development thrusts. The proceedings of the meeting are organized with six review and award articles at the front of the volume followed by topical articles a keynote, 5-6 oral, and 2-3 poster papers. A list of authors is provided at the end of the book. It should be emphasized that all of the papers were ranked and reviewed by members of the Scientific Committee.
Author: Jose M Palomo Publisher: World Scientific ISBN: 1786349639 Category : Science Languages : en Pages : 350
Book Description
Iron Catalysis: Design and Applications is an exciting new book that takes readers inside the world of iron catalysis guided by international catalysis expert, Dr Jose M Palomo. Iron is the most abundant metal in the planet, cost-effective, environmentally friendly, with an easily manipulated remediation process. In the last few years the use of this nonprecious metal has gained extraordinary attention particularly for its potential as a catalyst in different areas. This book compiles a series of chapters describing the most significant advances in the last few years since the design of different iron catalysts and nanocatalysts and iron-containing artificial and natural enzymes. The chapters also cover its application in different areas of interest such as organic synthesis, environmental remediation, enzyme-like activities or the creation of novel types of electrodes for battery design.
Author: Publisher: ISBN: Category : Languages : en Pages : 6
Book Description
The results of this work indicate that magnetite is not catalytically active for Fischer-Tropsch Synthesis (FTS) in precipitated, unsupported iron catalysts, but the formation of the carbide phase is necessary to obtain FTS activity. The transformation of magnetite to carbide, though essential to obtain FTS activity, also causes the catalyst to break down. This can lead to severe problems during operation in a commercial slurry phase reactor. The results presented here imply that activation and attrition are simultaneous and complementary processes. In another study, we show that the catalyst can also under go attrition on a micron scale which is caused by lack of strength of the forces binding the catalyst primary particles in the agglomerates. Both these processes can make wax separation and product recovery extremely difficult. In this study, we have also shown that H2 reduction of this catalyst to metallic iron is detrimental to subsequent catalyst activity and causes a loss of surface area due to sintering of the iron crystallites. Reduction to metallic Fe also causes impurities such as S to segregate to the surface causing a complete loss of FTS activity. It has been shown that even submonolayer amounts of S can cause a dramatic decrease in FTS activity, hence reduction to metallic Fe should be avoided during activation of these catalysts. We have shown, however, that a mild H2 reduction to magnetite does not lead to S segregation to the surface, and is therefore acceptable.
Author: J. Oudar Publisher: CRC Press ISBN: 9780824773380 Category : Science Languages : en Pages : 356
Book Description
Deactivation and Poisoning of Catalysts presents the most current research in the area of heterogeneous catalysis. It focuses on the chemically induced effects associated with bonded surface species that cause catalyst activity decline -- and in some cases a change in catalyst specificity. In addition, this volume examines poisoning of dispersed metal catalysts ... the thermodynamics of sulfur-metal and carbon-metal interactions ... model poisoning reactions on single crystals ... deactivation in petroleum refining and petrochemical processes ... coking of metal catalysts ... and more. The new approaches and solutions to catalyst deactivation and poisoning presented in this guide are invaluable to all heterogeneous catalysis specialists, including chemical and petroleum engineers, and surface, synthetic, physical, and industrial chemists. Book jacket.
Author: Victor Hugo Carreto Vazquez Publisher: ISBN: Category : Languages : en Pages :
Book Description
This thesis describes results of a study aimed at developing and evaluating attrition resistant iron catalysts prepared by spray drying technique. These catalysts are intended for Fischer-Tropsch (F-T) synthesis in a slurry bubble column reactor (SBCR). One of the major challenges associated with the use of SBCR for this purpose is the problem of catalyst/wax separation. If the catalyst particles break up into smaller ones during the F-T synthesis, these small particles (>5-10 [mu]m in diameter) will cause problems with the catalyst/wax separation. Several research groups have worked on development of attrition resistant spray-dried iron catalysts, and methodology to measure and predict their attrition behavior. However, these attrition tests were not conducted under conditions representative of those encountered in a SBCR. In this work, the attrition behavior of six spray-dried catalysts and two precipitated catalysts was evaluated under slurry reaction conditions in a stirred tank slurry reactor (STSR). Spray-dried catalysts used in this study were prepared at Texas A & M University (TAMU) and at Hampton University (HU), employing different preparation procedures and silica sources (potassium silicate, tetraethyl orthosilicate or colloidal silica). The attrition properties of F-T catalysts were determined by measuring particle size distribution (PSD) of catalysts before and after F-T synthesis in the STSR. This provides a direct measure of changes in particle size distribution in the STSR, and accounts for both physical and chemical attrition effects. Also, scanning electron microscopy (SEM) was used to investigate the mechanism of attrition - erosion vs. fracture, and to obtain morphological characteristics of catalysts. Spray dried 100Fe/3Cu/5K/16SiO2 catalyst (WCS3516-1), prepared from wet precursors using colloidal silica as the silica source, was the best in terms of its attrition strength. After 337 hours of F-T synthesis in the STSR, the reduction in the average particle size and generation of particles less than 10 [mu]m in diameter were found to be very small. This indicates that both particle fracture and erosion were insignificant during testing in the STSR. All other catalysts, except one of the spray dried catalysts synthesized at Hampton University, also had a good attrition resistance and would be suitable for use in slurry reactors for F-T synthesis.
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Author: G.A. Fuentes
Author: Jose M Palomo
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Author: J. Oudar
Author: Victor Hugo Carreto Vazquez
Author: Dragomir B. Bukur