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 μmolCO·gCo–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.