Impact of Fe@Mn–hydrophobically modified SiO2 interaction strength on Fischer-Tropsch synthesis performance and CO2 selectivity

• A series of Fe-based catalyst combined with hydrophobically modified SiO 2 were investigated for FTS. • The addition of hydrophobic SiO 2 markedly improved the catalytic stability of Fe@Mn. • Core-shell structure of Fe@Mn@SiO 2 -c demonstrated the strongest interaction and the lowest CO 2 selectivity. • A decrease in H 2 O concentration in the surface microenvironment of active sites suppresses WGS activity. A series of hydrophobically modified MnO 2 -coated Fe 3 O 4 (Fe@Mn) catalysts were prepared to investigate the effect of the interaction strength between Fe@Mn and hydrophobically modified SiO 2 (SiO 2 -c) on their physicochemical properties, FTS performance and CO 2 selectivity, including granule mixing of Fe@Mn and SiO 2 -c (Fe@Mn+SiO 2 -c (g)), powder mixing of Fe@Mn and SiO 2 -c (Fe@Mn+SiO 2 -c (p)) and core-shell structure of Fe@Mn@SiO 2 -c. The interaction between Fe@Mn and SiO 2 -c evolves and strengthens with the structural progression from physically mixed to core-shell configurations. Contact angle measurements indicate that Fe@Mn@SiO 2 -c exhibits superior hydrophobicity compared to Fe@Mn+SiO 2 -c (g/p). Fe@Mn+SiO 2 -c (g/p) maintains a CO 2 selectivity comparable to that of Fe@Mn, while exhibiting significantly enhanced stability. Although Fe@Mn@SiO 2 -c shows a relatively lower CO conversion, it achieves the lowest CO 2 selectivity alongside a higher selectivity for light olefins. The study reveals that the altered surface microenvironment of Fe@Mn@SiO 2 -c is the key factor in suppressing the water-gas shift (WGS) reaction activity during FTS, thereby reducing CO 2 selectivity. This work elucidates the underlying mechanism by which the interaction mode between the Fe-based catalyst and the hydrophobic material influences the FTS performance, particularly the CO 2 selectivity. The strongly interacting Fe@Mn@SiO 2 -c exhibited reduced CO conversion but significantly lower CO 2 selectivity, while the physical mixture with weaker interaction did not suppress CO 2 selectivity but markedly enhanced catalyst stability.