Hierarchical porous ZSM-5-promoted FeSiMn catalyst for gasoline selectivity via Fischer–Tropsch synthesis: effect of acid sites

Abstract

With the growing global energy crisis and environmental problems, the Fischer–Tropsch synthesis (FTS) is considered as a direct route for producing cleaner fuels. Moreover, Fe-based catalysts are suitable for the production of traditional gasoline-based products (C₅–C₁₁). Specially, zeolites with acid sites are commonly employed for hydrocracking the heavy hydrocarbons during the FTS reaction, and the amount of acid sites is crucial for modifying the product selectivity. In this work, heterogeneous porous ZSM-5 samples with different amounts of acid sites were physically mixed with the chestnut-shaped FeSiMn catalyst. It was found that the C₅–C₁₁ selectivity was enhanced over the FeSiMn + ZSM-5(26) and FeSiMn + ZSM-5(17) catalysts in comparison to the bare FeSiMn catalyst. The NH₃-TPD results indicated that the C₅–C₁₁ selectivity increased from 38.8 wt% (FeSiMn + ZSM-5(26)) to 53.5 wt% (FeSiMn + ZSM-5(17)) with the amount of weak and medium acid sites increasing from 0.169 to 0.563 mmol g⁻¹. Benefiting from ZSM-5(17), the FeSiMn + ZSM-5(17) catalyst could effectively facilitate the C₁₂₊ hydrocracking reaction. The FTS performance indicates that FeSiMn + ZSM-5(17) possesses outstanding catalytic activity and enhanced C₅–C₁₁ productivity due to the appropriate interaction between active particles and ZSM-5(17).