Uniformity dispersive, anti-coking core@double-shell-structured Co@SiO₂@C: Effect of graphitic carbon modified interior pore-walls on C₅₊ selectivity in Fischer-Tropsch synthesis

Highly dispersed Co nanoparticles with proper interaction with mesoporous support are benefit for the suppression of self-aggregation, which enhances its Fischer-Tropsch synthesis (FTs) activity. However, construct such Co based supported catalysts with high activity and stability in FTs by conventional mesoporous support, especially the common used mesoporous SiO₂, has proven challenging due to their undesirable hydrothermal stability and poor reducibility. Herein, we developed a unique core@double-shell Co@SiO₂@C structure with optimized interface of the mesoporous catalyst by introducing graphitic carbon layer which can weaken the interaction between metallic Co and silica. Transmission electron microscopy (TEM) images, together with Nitrogen adsorption-desorption characterization result, proved the well-defined core@double-shell structure of graphitic carbon modified catalyst. The Co@SiO₂@C-2 material produced after optimizing the calcination temperature to 600°C process large surface area and pore volume, and show higher CO conversion (62.2%) and C₅₊ selectivity (62.2%) than Co₃O₄@SiO₂ in a period of 100h. The significant improvement in the FTS performance of Co@SiO₂@C is not only attributed to a good synergistic effect by a combination of the Co dispersion and reducibility. The unique core@double-shell structure with graphitic carbon modified interior pore-walls also contributes to the formation of heavy hydrocarbon, as well as the protecting with the metallic Co particles away from oxidation and aggregation.