The ε-Fe2C/Cu Interface Synergistically Boosts Highly Selective Fischer–Tropsch Synthesis toward Light Olefins

Traditional Fischer–Tropsch synthesis (FTS) on iron-based catalysts is limited by the Anderson–Schulz–Flory (ASF) distribution, with a maximum theoretical selectivity of 58% for the C2–C4 hydrocarbons, accompanied by substantial methane byproduct formation. Suppressing methane formation while enhancing light olefin selectivity is of great significance, however, it remains a major challenge in this field. Herein, we developed a series of Fe/Cux@Al2O3 surrounded catalysts, which in situ formed a unique ε-Fe2C/Cu interfacial structure during the FTS. The optimized Fe/Cu3.8@Al2O3 catalyst achieved 84.7% selectivity toward C2–C4 hydrocarbons, significantly exceeding the ASF distribution limit, with a low CH4 selectivity of 8.9% and an unprecedented light olefin selectivity of 62.3%. Further investigation and theoretical calculations revealed that in the FTS reaction, CO and H2 adsorbed and dissociated on the ε-Fe2C surface, leading to the formation of CHx and CnHm intermediates through hydrogenation and chain-growth processes. Meanwhile, H* dissociated on the Cu surface migrated to the adjacent ε-Fe2C sites via hydrogen spillover. The appropriate supply of H* regulated the hydrogenation and desorption of CHx and CnHm species, simultaneously suppressing CH4 formation and limiting long-chain hydrocarbons (C5+) production. This work provides valuable insights and strategies for designing advanced FTS catalysts for the highly selective production of light olefins from syngas.