Abstract: A typical Fe-based catalyst for Fischer-Tropsch synthesis (FTS) was prepared by a combination method of continuous co-precipitation and spray-drying technology. The study was undertaken to investigate the iron phase transformation under different pretreatment conditions and the influence of phase structure on FTS activity of the catalyst in a stirred tank slurry reactor. N2 adsorption-desorption, X-ray diffraction, and Mössbauer effect spectroscopy were used to characterize the catalyst. It was found that α-Fe2O3 in the fresh catalyst was reduced first to Fe3O4 and then converted to iron carbides (FexC) in the syngas atmosphere. Increasing the reduction space velocity promoted the reduction and carburization of the catalyst. Higher reduction pressure facilitated the reduction of α-Fe2O3 to Fe3O4 but suppressed the carburization of magnetite. During FTS the catalytic activity decreased gradually with increasing magnetite content and decreasing iron carbide content.

Key words: Fischer-Tropsch synthesis, iron-based catalyst, syngas, iron oxide, iron carbide