Core-Shell-Structured Co-Z@TiO₂ Catalysts Derived from ZIF-67 for Efficient Production of C₅₊ Hydrocarbons in Fischer-Tropsch Synthesis

The core-shell-structured Co-Z@TiO₂(N₂+O₂) catalyst, which was prepared by subsequent pyrolysis and calcination from precursor ZIF-67 coated by amorphous TiO₂, was applied in Fischer-Tropsch synthesis (FTS). Compared with Co-Z@TiO₂ catalyst, which was directly calcinated in air (Co-Z@TiO₂(O₂)) or pyrolyzed in N₂ (Co-Z@TiO₂(N₂)), the Co-Z@TiO₂(N₂+O₂) catalyst showed better dispersion, easier reducibility, and optimal metal cobalt particle size (8.4 nm) due to the intermediate pyrolysis treatment and core-shell structure. The Co-Z@TiO₂(N₂+O₂) catalyst exhibited high cobalt time yield (14.84 μmol_CO·g_Co^-1·s^-1), high selectivity to C₅₊ (81.5%), and low selectivity to low carbon hydrocarbon (CH₄ (12.7%) and C₂-C₄ (5.8%)). The core-shell structure could enhance diffusion limitations to transform intermediate products into heavier hydrocarbons. After 110 h of evaluation, the Co-Z@TiO₂(N₂+O₂) catalyst still maintained good catalytic performance and cobalt particle size distribution.