The effect of Mn on the performance of MCF-supported highly dispersed iron catalysts for Fischer–Tropsch synthesis

Abstract

The effect of the Mn promoter in supported iron-based catalysts with different atomic ratios of Mn : Fe : Cu = x : 268 : 18 (x = 0, 9, 27, and 55) using mesoporous silica foam (MCF) as the carrier was evaluated in Fischer–Tropsch synthesis (FTS). High-dispersion iron catalysts with an iron content of up to 30 wt% were prepared using a co-impregnation method. The surface composition and physicochemical properties were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and N₂-physisorption. The introduction of Mn in supported catalysts at a Mn : Fe atomic ratio of 9 : 268 led to the formation of ferric oxide for calcined catalysts; meanwhile, the carbonization of metallic iron was decreased and the reducibility of catalysts was decreased as well, which may be because of the enhanced FeMn interaction. Additionally, the yield of C₅₊ hydrocarbons could be effectively increased by the Mn promoter; the MCF-supported iron catalyst with an optimal Mn : Fe ratio of 9 : 268 showed the highest C₅₊ selectivity and the lowest CH₄ selectivity.