Effect of Sulfate on an Iron Manganese Catalyst for Fischer-Tropsch Synthesis

The effect of sulfate on Fischer-Tropsch synthesis performance was investigated in a slurry- phase continuously stirred tank reactor (CSTR) over a Fe-Mn catalyst. The physiochemical properties of the catalyst impregnated with different levels of sulfate were characterized by N2 physisorption, X-ray photoelectron spectroscopy (XPS), H2 (or CO) temperature-programmed reduction (TPR), Møssbauer spectroscopy, and CO2 temperature-programmed desorption (TPD). The characterization results indicated that the impregnated sulfate slightly decreased the BET surface area and pore volume of the catalyst, suppressed the catalyst reduction and carburization in CO and syngas, and decreased the catalyst surface basicity. At the same time, the addition of small amounts of sulfate improved the activities of Fischer- Tropsch synthesis (FTS) and water gas shift (WGS), shifted the product to light hydrocarbons (C1–C11) and suppressed the formation of heavy products (C12+). Addition of SO2−4 to the catalyst improved the FTS activity at a sulfur loading of 0.05–0.80 g per 100 g Fe, and S-05 catalyst gave the highest CO conversion (62.3%), and beyond this sulfur level the activity of the catalyst decreased.