(669f) Effects of a Supercritical Hexane Media on Fischer-Tropsch Reaction Performance with an Iron-Based Nanoscale Catalyst

The Fischer-Tropsch synthesis process is a promising way of converting syngas, which can be generated from a variety of carbonaceous feedstocks, into hydrocarbon fuels and chemicals. Difficulties with heat management, catalyst maintenance, and product selectivity all tend to contribute to the process producing less of the desired products. These issues, coupled with the process directly competing with the relatively volatilely-priced petroleum, make the economics of FTS challenging. While traditionally the challenges associated with FTS would be approached by methods such as more complex reactor design or significant recycle, research has shown that some alternative approaches are also available.

Supercritical fluids have tunable properties are intermediate between those of a gas and a liquid and are miscible with both gases and liquids. When used as a reaction medium for FTS, the enhanced transport properties of SCFs allow for single-phase, fixed bed operation with balanced mass and heat transfer. Since the initial work of the Fujimoto group, numerous groups have demonstrated the significant benefits a supercritical fluid reaction medium can bring to FTS. Specifically, Fischer-Tropsch synthesis conducted in a supercritical fluid media has been shown to give elevated olefin selectivity, elevated heavy product selectivity, reduced CH₄ and CO₂ selectivities, and improved activity maintenance.

Due to their high surface area, nanoscale catalysts are potentially very active for surface-catalyzed reactions such as Fischer-Tropsch synthesis. While nanoparticle catalysts require a support to reduce attrition and provide mechanical strength, a properly selected nanoscale catalyst and support can offer superior performance relative to more traditional catalysts. Specifically, iron-based catalysts supported on carbon nanotubes have been shown to be stable under FTS conditions, have superior activity, elevated olefin selectivity, and high throughput per volume.

The purpose of this work is to investigate the effect of a supercritical reaction media on Fischer-Tropsch synthesis conducted on an iron-based nanoscale catalyst. Specifically, the objective of this work is to investigate the effects of catalyst support and composition on FTS CO conversion, liquid product selectivity, CH₄ production, and CO₂ production.