Influence of Textural Properties of Co@SiO₂ Catalysts on the Performance of Fischer–Tropsch Synthesis

Cobalt core-shell catalysts are advanced materials for Fischer-Tropsch synthesis, which enhance catalytic performance. This study explores the impact of pore diameter on the performance of mesoporous silica-coated cobalt oxide core-shell catalysts (Co@SiO₂), maintaining a constant shell thickness while varying the porosity. The synthesis method successfully yields a core-shell morphology with a centralized core, an average core diameter ranging from 30 to 34 nm, a total diameter between 97 and 103 nm, and a SiO₂ shell thickness of 32.5-34.5 nm. Textural characterization shows a specific surface area from 236 to 771 m²/g, with average pore diameters between 3.5 and 11.8 nm. The results indicate a significant change in the distribution of products, exhibiting more expressive selectivity in the range of C₁₉-C₂₄ and C₂₅-C₂₉ hydrocarbons with the core-shell catalyst and C₃₀₊ hydrocarbons with the supported catalyst. It also demonstrates that a decrease in pore diameter of the silica shell leads to significant changes in product distribution. Specifically, a reduction in the pore size from 9.2 nm (Co@SiO₂_0.03) to 3.5 nm (Co@SiO₂_0.09) results in a 17% increase in selectivity toward the C₁₉-C₂₄ fraction and a concomitant 24% decrease in the C₂₅-C₂₉ fraction. Furthermore, the silica shell provided a protective effect on the active phase, with no evidence of sintering observed in the spent encapsulated catalysts.