Co/SiO2 catalysts for Fischer–Tropsch synthesis; effect of Co loading and support modification by TiO2

The influence of cobalt loading and titania addition to the silica support on Fischer–Tropsch synthesis activity is investigated over two series of catalysts with Co loading of 6 wt% and 12 wt%. The pure silica support is prepared by sol–gel procedure in acid conditions. The modification by TiO2 is performed by grafting with titanium isopropoxide. The catalysts are prepared by wet-impregnation over amorphous SiO2 and over SiO2 modified by TiO2 (5 wt%). The samples, characterized by N2-adsorption–desorption analyses, X-ray diffraction (XRD), temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS), are tested in the low-temperature Fischer–Tropsch synthesis using the conditions of 483 K, 20 bar and H2/CO = 2.1. The improved conversion rate and the increased SC5+ of the titania containing catalysts are discussed in terms of the stronger interaction between cobalt and titania affecting the cobalt oxide reducibility.

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► Co3O4 crystallite sizes do not depend on the cobalt loading.
► Co3O4 particle sizes are smaller in the presence of grafted TiO2 over SiO2.
► Reducibility of cobalt oxides is hindered in the presence of TiO2 over SiO2.
► The catalytic performance of cobalt catalyst in FT reaction is improved by the presence of TiO2.