Abstract: Carbon coated mesoporous SBA-15, named SBA-15C, was obtained from as-synthesized SBA-15 after graphitization in inert gas. With SBA-15 and SBA-15C as supports and cobalt nitrate aqueous solution as precursor, the supported cobalt-based catalyst samples were prepared by a wet impregnation method. The catalyst samples were characterized by X-ray diffraction, N₂ physisorption, temperature-programmed reduction, and NH₃ microcalorimetric adsorption. The results suggested that upon doping the inner walls of SBA-15 with carbon, the hexagonal ordered mesoporous framework was retained while the surface area decreased a little and the thickness of pore wall increased. The supported cobalt-based catalyst retained the mesoporous characteristics with decreased surface area and pore volume. The average particle size of Co₃O₄ on SBA-15C was smaller than that on SBA-15, which suggested that the existence of carbon improved the dispersion of Co₃O₄ particles. However, the modification of SBA-15 with carbon films did not seem to increase the reducibility of Co₃O₄. Both Co/SBA-15 and Co/SBA-15C exhibited high selectivity for C₅₊ hydrocarbons (~80%), but Co/SBA-15C showed higher stability in the F-T synthesis reactions.

Key words: SBA-15 zeolite, pore wall modification, cobalt-based catalyst, Fischer-Tropsch synthesis