Production and Characterization of Synthetic Diesel Fuel from Coal via Fischer–Tropsch Indirect Liquefaction

This study investigates the production of synthetic diesel fuel from coal through indirect liquefaction using Fischer–Tropsch synthesis. A series of experiments was performed, starting with coal gasification in a vertical reactor at 1270°C and 22 bar to produce synthesis gas containing approximately 51.4% of carbon monoxide and 43.7% of hydrogen. After purification, the synthesis gas underwent catalytic conversion in a high-pressure reactor using a cobalt–zirconia catalyst. Under baseline conditions of 227°C and 25 bar, the average liquid product yield was 12.6 kg over 6 hours, with the diesel and kerosene fractions of 57.4% and 31.2%, respectively. Increasing the pressure to 30 bar enhanced the diesel fraction to 61.8% and improved the total liquid yield by 7.5%. The resulting synthetic diesel exhibited superior properties compared to petroleum-derived fuel, including a cetane number of 72, sulfur content below 2 mg/kg, and aromatic hydrocarbons limited to 3.2%. Stability tests conducted over 180 days confirmed excellent oxidation resistance. These findings demonstrate that indirect coal liquefaction can deliver high-quality diesel fuel with significant potential to reduce environmental impacts and enhance energy security. The cobalt–zirconia catalyst was prepared in-house as a bulk CoO–ZrO₂ granulate and pre-reduced in situ before synthesis. Under 225–230 °C and 25–30 bar, the system consistently delivered 57.4–61.8 wt% diesel within the liquid products with stable operation. The process configuration is compatible with pre-combustion CO₂ capture units, providing a clear pathway for integrating CCS in future scale-up.