The effect of hydrophobicity on SiO2-supported Co catalysts in Fischer-Tropsch synthesis

Three different degrees of hydrophobized SiO2 supports were prepared by varying the amount of dichlorodimethylsilane used for the hydrophobization of hydrophilic SiO2 gel. Thereafter, 10 wt% Co was loaded on each SiO2 supports. The SiO2 supports and catalysts were characterized by BET, X-ray powder diffraction (XRD), Fourier-Transform Infrared (FTIR) spectroscopy, solid-state magic-angle spin nuclear magnetic resonance (MAS NMR), temperature-programmed reduction (TPR), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), water contact angle and zeta potential. The hydrophobized SiO2 enhanced the catalytic activity of the SiO2?supported Co catalysts because the hydrophobized SiO2 impedes the strong Co-SiO2 interaction, which aids the SiO2 supported Co catalysts to achieve highly reducible cobalt oxides. The hydrophobized SiO2?supported Co catalysts also created more active sites for the hydrogenation of CO due to the quick desorption of water molecules from the Co catalysts? active sites. Furthermore, it was observed that at a higher degree of hydrophobicity above the threshold, larger cobalt clusters were created, which decreased the reducibility of the cobalt oxides and subsequently caused a decline in the activity.

Automated summary

By varying the degree of hydrophobization of SiO2 supports, the catalytic activity of Co catalysts supported on SiO2 was enhanced, also promoting the hydrogenation of CO. It was observed that higher hydrophobicity resulted in larger cobalt clusters, decreasing the reducibility of cobalt oxides and leading to a decline in activity.