Catalytic performance of cobalt-silica catalyst for Fischer-Tropsch synthesis: Effects of reaction rates on efficiency of liquid synthesis

The model predicts the influence of reaction rates on the performance of the fixed bed FT reactor using an unpromoted Co/SiO2 catalyst at 503 K, 15 bar and 6 L gcat−1 h−1. As a result, the conversions of 91.57% and 97.26% were achieved for CO and H2, respectively, with the FT C5+ synthesis reaction rate of 7.81×10−5 mol gcat−1 s−1. The higher rate of C5+ formation was found by increasing FT reaction rates compared to the rate of lighter the hydrocarbons׳ formation. At the same condition, only 5.04% and 8.91% methane and C2-C4 selectivity respectively, were predicted; while the highest value of 86.05% liquid (C5+) selectivity was obtained in this case. It was concluded that the higher rate of conversion of H2 inside the pores filled with liquid products, compared to that of CO, caused an increase in the H2/CO ratio in the catalyst pores; and thus, a shift towards the formation of lighter hydrocarbons.