Effects of Cu and K on Co-precipitated FeMn/SiO2 Catalysts for Fischer-Tropsch Synthesis

The effects of copper and potassium on the activity and selectivity of coprecipitated Fe-Mn/SiO2 catalysts for Fischer-Tropsch synthesis (FTS) were studied in a slurry phase continuous stirred tank reactor. The reduction and adsorption behaviors of the catalysts were investigated using temperature-programmed reduction/temperature-programmed desorption (TPR/TPD) methods. It was found that copper improves the reduction of the catalyst in H2 or CO. Potassium improves the reduction of the catalyst in CO, whereas it suppresses the reduction of the catalyst in H2. Copper enhances the H2 adsorption, whereas potassium has no influence on the H2 adsorption. In the FTS reaction, copper shortens the induction period required for reaching the steady state activity, whereas potassium prolongs the induction period. The potassium promoter increases the activity and decreases the selectivity of methane. The promotion effects of Cu and K on the activity and selectivity is more obvious than that of Cu, that is, the activity is higher and the methane selectivity is lower on the doubly promoted catalyst.