FISCHER-TROPSCH SYNTHESIS IN SUPERCRITICAL PHASE CARBON DIOXIDE

Author

Derek Michael Perry, Southern Illinois University CarbondaleFollow

Date of Award

12-1-2009

Degree Name

Master of Science

Department

Mechanical Engineering

First Advisor

Mondal, Kanchan

Abstract

The Fischer-Tropsch (FT) synthesis reaction is an increasingly valuable tool that produces very clean alternative fuels for the transportation and other industries. By utilizing a ready supply of syngas (H2 and CO mixture) from coal, natural gas, or a biomass source, the catalyzed reaction looks to be a promising alternative which could potentially end dependency on imported petroleum. The supercritical phase FT synthesis reaction has shown, in numerous other studies, to possess superior heat transfer capabilities, high desorption rates from the catalyst surface (enhancing catalyst life), and overall high mass transfer rates of hydrocarbon products, when compared with conventional gas and liquid phase results. Prior studies at SIUC have shown that the use of supercritical CO2 as a medium for the Fischer-Tropsch (FT) synthesis reaction enhances reaction rates while suppressing excess CO2 production. This phenomena was observed in gas phase batch reactions, meaning never before has a continuous flow FT synthesis with analysis of the liquid product distribution been attempted while using CO2 as the supercritical-phase medium. This project verifies the conclusions in a continuous flow mode, allowing for the collection and analysis of a liquid fraction. Additionally, this study evaluates the changes in the liquid product distribution for a variation of operating pressures including supercritical-phase reaction conditions, using pressures of 350, 800, 1000, and 1200psi and temperatures of 250, 300, and 350°C. The findings show that the influence of carbon dioxide enhance product distribution to yield a higher diesel fraction (C13 to C15), when compared to results without carbon dioxide as a medium, which favor gasoline fraction (C7 to C9). The findings also illustrate that operating in the supercritical region enhances product distribution, but depending on the solvent density, could potentially produce large amounts of oxygenates (alcohols, ketones) in the product distribution.