Effect of SiO2 support particle sizes on the performance of FeZn catalysts in VR slurry-phase hydrocracking

In order to gain insight into the influence of SiO₂ support particle size on the vacuum residue (VR) slurry-phase hydrocracking performance of Fe-based catalysts, a series of FeZn/SiO₂ catalysts with varying SiO₂ particle sizes were prepared. Characterization results show that the surface area and pore volume of the FeZn/SiO₂ catalysts increase with the reduction of SiO₂ particle sizes. The metals Fe and Zn species on FeZn/SiO₂-S catalyst are more readily reducible via H₂-TPR analysis. Notably, FeZn/SiO₂-S catalyst presents higher metal dispersion and a greater degree of sulfurization compared to the other catalysts by XRD and XPS. Hydrocracking results demonstrate that the FeZn/SiO₂-S catalyst achieves the lowest coke and gas yields (11.9 wt% and 0.4 wt%), respectively, and the highest VR conversion among these catalysts. The superior performance of the FeZn/SiO₂-S catalyst in VR slurry-phase hydrocracking is ascribed to its enhanced hydrogenation activity, deriving from the higher dispersion and sulfurization of metals species. This suppresses the aggregation of polycyclic aromatic hydrocarbons in VR and the over-cracking of intermediate products. Additionally, the increased mesopore associated with smaller SiO₂ particles facilitates to the diffusion of large VR molecules, further promoting the hydrocracking reaction.