Effect of the pore size of Co/SBA-15 isomorphically substituted with zirconium on its catalytic performance in Fischer-Tropsch synthesis

Cobalt catalysts supported on a series of mesoporous SBA-15 materials isomorphically substituted with zirconium (Zr/Si atomic ratio=1/20) with different pore sizes (5.7 nm,7.8 nm,11.6 nm,17.6 nm) have been synthesized.The catalysts were characterized by transmission electron microscopy,29 Si solid state magic angle spinning (MAS)NMR,N2 adsorption-desorption measurements,X-ray powder diffraction,X-ray photoelectron spectroscopy,H2-temperature programmed reduction,H2-temperature programmed desorption and O2 titrations.The results indicated that larger pore size led to weaker interactions between cobalt and the supports which lowered the temperature of both reduction steps (Co3O4 → CoO and CoO→ Co0).The catalytic performances of the catalysts in Fischer-Tropsch synthesis (FTS) were tested in a fixed bed reactor.It was found that the FTS catalytic activity and product selectivity depended strongly on the pore size of the catalysts.The catalyst with a pore size of 7.8 nm showed the best FTS activity,and the catalyst with a pore size of 17.6 nm showed the highest selectivity to C12-C20 and C20+ hydrocarbons.