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

The catalytic behavior of a K/Fe–Cu–Al catalyst has been investigated together with carbon deposition by variation of the CO 2 /(CO + CO 2 ) ratios in H 2 -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 H 2 -sufficient and CO 2 -abundant conditions [H 2 /(2CO + 3CO 2 ) = 1, and CO 2 /(CO + CO 2 ) ≥ 0.5], CO 2 in the feed gas was consumed for hydrocarbon production. The CO x 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 CO 2 /(CO + CO 2 ) ratio, temperature, and pressure are beneficial for both CO 2 utilization and prevention of carbon deposition in the FTS using Fe catalysts.