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

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 (C-5-C-11) 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 C-2-C-4 olefins. In particular, 0.8Ag/Fe3O4 displayed high CO conversion (96.4%) and optimum selectivity to C-2-C-4 olefins (28.3 wt%) while yielding a low selectivity to CH4 (12.1 wt%), as well as a good selectivity to C-5-C-11. More importantly, 0.8Ag/ Fe3O4 showed the highest catalytic activity (>1.6 x 10(-4) mol(co) g(Fe)(-1) s(-1)) and the best total hydrocarbon yield (5.25 x 10(-3) g(HC) g(Fe)(-1) s(-1)).