Study of the Fischer–Tropsch synthesis on nano-precipitated iron-based catalysts with different particle sizes

Abstract

Nano iron-based catalysts with different particle sizes were prepared by a co-precipitated method and characterized by XRD, N₂ adsorption, SEM, Mössbauer spectroscopy, XPS, H₂-TPR, CO-TPD, H₂-TPD and TGA. The CO-TPD results revealed that large particle sizes of catalysts were not conducive to the adsorption of CO, and exhibited low activity of FTS. The decrease of catalyst particle size enhanced the interaction between Fe and Mn, and promoted the CO chemical adsorption and the formation of Fe₅C₂, but the hydrogenation reaction was inhibited as confirmed by H₂-TPD. When the particle size continued to decrease, Mössbauer spectroscopy showed that MnFe₂O₄ appeared in the catalyst phase, which hindered the reduction of catalysts and the adsorption of feed gas. Overall, the sample FeMnSm-600 showed the highest C_2–4 selectivity of 33% at the highest CO conversion of 79% during the reaction conditions of 300 °C, 1.0 MPa, 12 000 mL (g h)⁻¹, and H₂/CO = 2.