Effects of Ag on morphology and catalytic performance of iron catalysts for Fischer–Tropsch synthesis

Abstract

Fe₃O₄ nanoparticles with pore size of 12.4 nm were synthesized and employed as catalyst for Fischer–Tropsch (FT) synthesis. The as-prepared Fe₃O₄ catalyst achieved a CO conversion of 98.3% while yielding higher than 50 wt% gasoline range (C₅–C₁₁) hydrocarbons after FT reaction for 48 h. Furthermore, highly activated Ag-doped composites were designed through a one-pot solvothermal method, and then porous core/shell materials were obtained. Interestingly, active metal oxide (Fe₃O₄) nanoparticles were interspersed on the surface of the Ag promoter. Importantly, pores could enhance the dispersion of metal particles and facilitate heat and mass transfer. The addition of Ag promoter decreased the selectivity to CH₄ and enhanced the yield of C₂–C₄ olefins. In particular, 0.8Ag/Fe₃O₄ displayed high CO conversion (96.4%) and optimum selectivity to C₂–C₄ olefins (28.3 wt%) while yielding a low selectivity to CH₄ (12.1 wt%), as well as a good selectivity to C₅–C₁₁. More importantly, 0.8Ag/Fe₃O₄ showed the highest catalytic activity (>1.6 × 10⁻⁴ mol_co g_Fe⁻¹ s⁻¹) and the best total hydrocarbon yield (5.25 × 10⁻³ g_HC g_Fe⁻¹ s⁻¹).