Studies on precipitated iron catalysts for Fischer–Tropsch synthesis

The silica-containing precipitated iron catalysts had higher STY (C5+ hydrocarbon productivity), but were more difficult to be reduced with syngas (mixtures of hydrogen and carbon monoxide) than the silica-free precipitated iron catalyst. The results suggested that the added silicate suppresses the crystal growth of hematite from the structure of catalyst precursor. X-ray diffraction (XRD) studies of catalysts after activation under various conditions revealed that the presence of iron carbide (CFe2.5) was related to the active sites in the FT reaction, and that the relative quantity of iron carbide (CFe2.5) to magnetite (Fe3O4) was closely related to the number of active sites available for FT synthesis. The effects of copper on the silica-containing precipitated iron catalyst were to enhance the activity and the rate of reduction, as judged from the XRD and TPR studies.