| Fischer-Tropsch (F-T) synthesis is a process used to convert coal-derived syngas to hydrocarbon liquids and waxes. A slurry phase bubble-column reactor (SBCR) is the preferred type due to improved heat and mass transfer and operational simplicity in terms of catalyst loading and discharge. A potential disadvantage in the SBCR is the attrition of the catalyst, which can cause difficulty with the catalyst/wax separation, resulting in gradual loss of catalyst from the reactor. In this work, two approaches have been evaluated to measure the strength and attrition resistance of Fe F-T catalysts: uniaxial compaction and ultrasonic fragmentation. The ultrasonic fragmentation method has been found to be more sensitive to the differences between different materials, which are not seen by the uniaxial compaction method. The ultrasonic fragmentation approach was applied to spray-dried Fe F-T catalysts containing precipitated silica. Silica was used as the binder because it provided a morphology that was conducive to creating interlocking forces that held the catalyst particles together. The addition of silica improved the attrition resistance of Fe F-T catalysts significantly, compared to the unsupported Fe catalyst. Process variables, such as calcination, were investigated to determine their effects on the strength and morphology of these catalysts. Aside from developing attrition resistant precipitated Fe F-T catalysts, a novel approach to the synthesis of Fe F-T catalyst particles encapsulated in a spray-dried mesoporous silica has been developed. This approach makes use of a liquid-crystal template mechanism to create a silica framework whereby nanosized Fe F-T catalyst particles are trapped inside this matrix. Other process variables, such as surfactant and Fe/Si ratio, were investigated to determine their effects on the strength and morphology of these catalysts. In addition, reduction studies coupled with X-ray diffraction analysis were performed to determine the extent of reducibility for the precipitated and encapsulated catalysts, and to understand the effect of processing on reducibility. Results show that the encapsulated Fe F-T catalyst containing 40 wt.% iron oxide is the most successful catalyst synthesized in this work, both because of its high strength and extent of reducibility. |
