Performance of hierarchical ZSM-5 supported cobalt catalyst in the Fischer-Tropsch synthesis

Uniform ZSM-5 nanoparticles (around 180 nm) were synthesized by steam assisted crystallization method (SAC), which have a hierarchically porous structure, composed of abundant open mesopores from the stacking of ZSM-5 particles and micropores in the ZSM-5 crystallites. The hierarchical ZSM-5 supported cobalt catalyst, with a cobalt loading of 15%, was then prepared through incipient impregnation and used in Fischer-Tropsch synthesis (FTS). The hierarchical ZSM-5 support and Co-based catalyst were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N₂ sorption. The results indicate that the hierarchical ZSM-5 supported cobalt catalyst performs excellently in FTS, since the mesoporous structure in the hierarchical ZSM-5 support can enhance the mass transfer of the reaction products and the acid sites on the microporous ZSM-5 framework can promote the hydrocracking of long chain hydrocarbon products. In comparison with the cobalt catalysts supported on bulk ZSM-5 and commercial ZSM-5, the hierarchical ZSM-5 supported cobalt catalyst exhibits much higher activity in FTS, lower selectivity to CH₄, and higher selectivity to C_5-20 hydrocarbons (68.9%).