Fischer-Tropsch Synthesis: The effect of hydrophobicity on silica-supported iron catalysts

Abstract This work focuses on the effect of surface hydrophobicity of SiO2 supports on the performance of SiO2-supported Fe catalysts during Fischer–Tropsch synthesis (FTS). Three different hydrophobized SiO2 supports were synthesized by varying the amount of the dichlorodimethylsilane used for the hydrophobization of the hydrophilic mesoporous SiO2 gel. Fe metal of approximately 9 wt% was loaded on the hydrophilic SiO2, and three hydrophobized SiO2 supports by homogeneous deposition precipitation. The wholly hydrophobized SiO2 surface improved the catalytic activity of Fe catalysts because the hydrophobized SiO2 increased the reducibility of the iron oxide and inhibited readsorption of water over the surface of the Fe catalyst, therefore creating more available active sites for the adsorption of CO. Also, hydrophobized SiO2 decreased the CH4 selectivity and C2–C4 selectivity and increased C5+ selectivity of the Fe catalysts due to the promotion of chain growth by the hydrophobized SiO2. Furthermore, the hydrophobized SiO2 decreased the CO2 selectivity of the Fe catalysts because the hydrophobized SiO2 hindered the readsorption of water over the surface of the Fe catalysts, which leads to the inhibition of water gas shift reaction and subsequently the hindering of the CO2 formation.