Abstract
Bimodal porous Ru/SiO2 catalysts for the Fischer-Tropsch reaction were prepared by modifying the surface of macro-porous silica with Ru–SiO2 prepared by the alkoxide method. The Ru particle size estimated by H2 adsorption increased with the pore size of the macro-porous silica, whereas the Ru crystallite size evaluated by XRD line broadening did not show much variation. The bimodal catalysts showed high and stable activity in the slurry phase under the reaction conditions of T = 493-503 K, P = 1 MPa, H2/CO = 2/1, and W/F = 5 g-catal.h/mol, with reduction in the used amounts of the expensive alkoxide. Selectivity for higher hydrocarbons increased with increasing pore diameter of the catalysts, which can be explained in terms of diffusivity of the slurry solvent and/or the products in the pores, and the effect of the Ru particle size depending on the macro-pore size of the catalysts.
