Effects of the CO/CO2 Ratio in Synthesis Gas on the Catalytic Behavior in Fischer–Tropsch Synthesis Using K/Fe–Cu–Al Catalysts

Abstract

The catalytic behavior of a K/Fe–Cu–Al catalyst has been investigated together with carbon deposition by variation of the CO2/(CO + CO2) ratios in H2-sufficient feed gas during the Fischer–Tropsch synthesis (FTS). Both fresh and used catalysts were characterized by means of X-ray diffraction, temperature-programmed decarburization, thermogravimetric analysis, and elemental analysis. Under H2-sufficient and CO2-abundant conditions [H2/(2CO + 3CO2) = 1, and CO2/(CO + CO2) ≥ 0.5], CO2 in the feed gas was consumed for hydrocarbon production. The COx conversion to hydrocarbons increased with the temperature, pressure, and CO content in the feed gas. Under high-pressure reaction conditions, carbon deposition was significantly reduced, as compared to that at low pressures. Overall, conditions involving a high CO2/(CO + CO2) ratio, temperature, and pressure are beneficial for both CO2 utilization and prevention of carbon deposition in the FTS using Fe catalysts.