The effects of coprecipitated silica were investigated in iron-based catalysts for Fischer-Tropsch Synthesis (FTS). Silica-containing catalysts exhibited micro pores (<10 nm) and large specific surface areas, while the silica-free catalyst had large pores (10-100 nm) and low specific surface area. Coprecipitated silica enhances the productivity of hydrocarbon for ITS, especially C5+ hydrocarbon selectivity. Silica-free and silica-containing iron catalyst showed high activity and stability over 100 h test, and exhibited little difference of the product selectivity (olefin/paraffin ratio) over the temperature range of 513-553 K. An iron catalyst has higher activity with the low H-2/CO ratio (0.4-1.0). Thus, an iron catalyst has the advantage in applications to coal-derived gas, as compared to the cobalt-based catalyst. (c) 2007 Elsevier B.V. All rights reserved.