Abstract: The effects of Mo and Cu promoters on the properties of FeK/SiO₂ catalysts and their Fischer-Tropsch synthesis (FTS) performance were studied. The catalysts were characterized by N₂ adsorption, H₂ temperature-programmed reduction, X-ray diffraction, Mössbauer effect spectroscopy and X-ray photoelectron spectroscopy. The characterization results indicate that Mo addition inhibits the reduction and carburization of the catalysts, which is opposite to Cu promoter. When Mo and Cu are co-added, similar reduction and carburization behavior is observed as that of Cu promoter alone. FTS performance was tested at 280 ^oC, 1.5 MPa, 2 000 h^-1, and syngas H₂/CO = 2.0 in a fixed-bed reactor. The reaction results show that Mo addition decreases the FTS activity and improves the stability of heavy hydrocarbon (C₅₊) selec-tivity over the catalysts; Cu addition increases the activity but has no contribution to the stability of C₅₊ selectivity. For the co-promoted catalyst, stable selectivity to C₅₊ is obtained without sacrificing activity.

Key words: Fischer-Tropsch synthesis, iron-based catalyst, molybdenum promoter, copper promoter, heavy hydrocarbon selectivity