The Effect of Hydrophobicity on Silica-Supported Cobalt Catalysts in Fischer-Tropsch Synthesis

This work focuses on the effect of surface hydrophobicity of SiO₂ gel supports on the catalytic performance of Co based catalysts in Fischer-Tropsch (FT) synthesis. SiO₂ supports of three different degrees of hydrophobicity were prepared with varying amount of dichlorodimethylsilane. Homogeneous deposition precipitation was used to load 10 wt% Co on each of the hydrophobic SiO₂ supports as well as on the hydrophilic SiO₂ support. The hydrophilic SiO₂ supported cobalt catalyst was used as a reference for this study. In this work, various catalyst characterization techniques were used i.e. BET, XRD, Fourier-Transform Infra-red (FTIR) spectroscopy, MAS NMR, water contact angle, zeta potential, H₂ chemisorption, temperature programmed reduction (TPR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and temperature programmed surface reaction (TPSR). FT experiment showed that hydrophobic SiO₂-supported Co catalysts showed better FT activity than the hydrophilic SiO₂-supported Co catalyst because the hydrophobicized SiO₂-support prevents the water produced during the FT reaction from adsorbing onto the cobalt active sites. Thus, there is higher number of cobalt active sites available on the hydrophobic SiO₂-supported Co catalysts which increases CO adsorption and dissociation and subsequently leads to higher catalytic performance during FT synthesis.