Studies on cobalt catalyst supported on silica with different pore size for Fischer–Tropsch synthesis

Mesoporous molecular sieves (MCM-48, SBA-15 and SiO2) with different pore diameters have been used as supports of Co catalysts for Fischer–Tropsch (F–T) synthesis. The catalysts were characterized by N2 physisorption, X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption (H2 TPD) followed by pulse oxygen reoxidation and transmission electron microscopy (TEM). The catalytic performace for FT synthesis was tested with a fixed bed reactor. TEM and H2 TPD showed that the cobalt crystallite size formed on Co/SBA-15 with the pore diameter of 5.3 nm were the largest, and the ones formed on Co/MCM-48 with pore diameter of 2.6 nm were the smallest. The Co/SiO2 with the average pore diameter at 10.4 nm is most active for FTS. The Co/SBA-15 presented the highest selectivity to C5+. The activity of the three catalysts was affected by the reducibility of cobalt oxides and C5+ selectivity was determined by the cobalt crystallite size.