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 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 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.

The production of fuel and chemicals is expected to be based on renewable energies in the next few years. However, combustion causes CO2 emission. Its reduction is one of the main focuses to regulate greenhouse effect, as expected by the Kyoto protocol. One combustion technology which could reduce CO2 emissions is chemical-looping combustion coupled to a CO2 capture device. This technique involves the use of a bed-material, with a size between 100 and 500 µm, composed of an oxide supported by a porous ceramic. This oxide acts as an oxygen carrier and circulates from a reducing atmosphere reactor, where oxygen reacts with CO to produce CO2, to an oxidising reactor, where combustion occurs. In order to improve the reactivity of this carrier, a fluidized bed reactor is used and involves gas velocity. Attrition resistant granulates are therefore needed because of the high impacts occurring in the reactors. Moreover, large pore network is expected to improve the reactivity of the carrier because of the higher accessibility of the gas. Granulates studied for oxygen carrier supports are frequently based on γ-alumina, which is highly mesoporous. In order to understand the importance of microstructure, three different routes were studied with samples composed of macropores, mesopores and a sample composed of both type of pores. Pore size could be successfully tailored with addition of diatomite, composed of pores in the micrometer range. This thesis aims to describe the tailoring of microstructure with addition of diatomite and at understanding its influence on attrition resistance. To be able to verify the performance of the developed supports, impregnation of copper oxide and looping experiments were performed.

The production of fuel and chemicals is expected to be based on renewable energies in the next few years. However, combustion causes CO2 emission. Its reduction is one of the main focuses to regulate greenhouse effect, as expected by the Kyoto protocol. One combustion technology which could reduce CO2 emissions is chemical-looping combustion coupled to a CO2 capture device. This technique involves the use of a bed-material, with a size between 100 and 500 µm, composed of an oxide supported by a porous ceramic. This oxide acts as an oxygen carrier and circulates from a reducing atmosphere reactor, where oxygen reacts with CO to produce CO2, to an oxidising reactor, where combustion occurs. In order to improve the reactivity of this carrier, a fluidized bed reactor is used and involves gas velocity. Attrition resistant granulates are therefore needed because of the high impacts occurring in the reactors. Moreover, large pore network is expected to improve the reactivity of the carrier because of the higher accessibility of the gas. Granulates studied for oxygen carrier supports are frequently based on γ-alumina, which is highly mesoporous. In order to understand the importance of microstructure, three different routes were studied with samples composed of macropores, mesopores and a sample composed of both type of pores. Pore size could be successfully tailored with addition of diatomite, composed of pores in the micrometer range. This thesis aims to describe the tailoring of microstructure with addition of diatomite and at understanding its influence on attrition resistance. To be able to verify the performance of the developed supports, impregnation of copper oxide and looping experiments were performed.