Ultrasound induced morphology-controlled synthesis of Au nanoparticles decorated on Fe2O3/ZrO2 catalyst and their catalytic performance in Fischer-Tropsch synthesis

Abstract

Fischer-Tropsch synthesis (FTS) is a classical approach for the production of liquid fuel and organic chemicals from syngas (CO + H2). In this study, a surfactant-free sonochemical approach was employed to synthesize unique nanostructures of Fe2O3/ZrO2 composites with various Fe/Zr molar ratios (0.5, 1, and 2) and different nanocube (NC), nanorod (NR) and sphere-like (S-L) morphologies. Moreover, highly dispersed Au nanoparticles were sonochemically decorated on the Fe2O3/ZrO2 NC surface. The as-synthesized Fe2O3/ZrO2 NPs were evaluated as FTS catalysts. The obtained catalytic results demonstrated that the Fe/Zr molar ratio played important roles on the obtained FTS catalytic activity. Interestingly, when 2.5 wt% Au nanodot used as promoter to Fe2O3/ZrO2 nanocube catalyst, the CO conversion ratio was raised significantly, meanwhile, the methanation process was suppressed and the C5+ selectivity was quite increased to reach a maximum value of 79.5% at 270 °C. The significant enhancement in the catalytic activity of the Au-doped Fe2O3/ZrO2 NC composites catalyst is mostly attributed to the enhanced reducibility, the enriched catalyst surface with abundant electron density and the blocked hydrogenation on the surface of Fe active sites, and the dramatic increase in the pore size of the catalyst. Increasing the Au concentration in the catalyst to 5 wt% produced deactivated catalysts due to the particles aggregation and poisoning.