Novel precipitated iron Fischer–Tropsch catalysts with Fe₃O₄ coexisting with α-Fe₂O₃

Abstract

The present study was undertaken to investigate the catalytic behavior of an industrial iron catalyst (Fe/Cu/K/SiO₂) prepared from ferrous sulfate precursor for Fischer–Tropsch (FT) synthesis, in which different amount of Fe₃O₄ coexist with α-Fe₂O₃. The catalyst samples were characterized by BET, XRD, H₂-TPR and Mössbauer effect spectroscopy (MES). The FT synthesis performance of the catalysts were carried out in a fixed bed reactor (FBR) under reaction conditions of 250 °C, 1.5 MPa, 2.0 nL/g-cat/h, and H₂/CO=2/1 for 200 h. The results from XRD and MES for the catalyst samples of pre- and post-reduction indicate that more iron carbides form in the catalysts that have lower Fe₃O₄ contents. H₂-TPR for the catalysts displays that Fe₃O₄ may facilitate the reduction of catalysts only when it was highly dispersed. FT reaction study in the FBR shows that the catalysts become more active with the decrease of Fe₃O₄ contents in the catalysts. However, the catalyst with certain amount of highly dispersed Fe₃O₄ exhibited high FT synthesis activity with CO conversion more than 75%. The catalyst also displayed much less olefins selectivity. A comparison of FTS performances of one of these catalysts with some known catalysts was also made in this paper.