Synthesis of stable and low-CO₂ selective ε-iron carbide Fischer-Tropsch catalysts.

Abstract

The Fe-catalyzed Fischer-Tropsch (FT) reaction constitutes the core of the coal-to-liquids (CTL) process, which converts coal into liquid fuels. Conventional Fe-based catalysts typically convert 30% of the CO feed to CO₂ in the FT unit. Decreasing the CO₂ release in the FT step will reduce costs and enhance productivity of the overall process. In this context, we synthesize phase-pure ε(')-Fe₂C catalysts exhibiting low CO₂ selectivity by carefully controlling the pretreatment and carburization conditions. Kinetic data reveal that liquid fuels can be obtained free from primary CO₂. These catalysts displayed stable FT performance at 23 bar and 235°C for at least 150 hours. Notably, in situ characterization emphasizes the high durability of pure ε(')-Fe₂C in an industrial pilot test. These findings contribute to the development of new Fe-based FT catalysts for next-generation CTL processes.