Effect of support properties on the performance of supported Pd catalysts in hydrodesulfurization

SiO₂, siliceous MCM-41 (Si-MCM-41), physical mixture of Si-MCM-41 and ZSM-5 (Z-MCM-41-M), and Z-MCM-41 composite obtained by coating MCM-41 on ZSM-5 zeolite particles were prepared and characterized by XRD, HRTEM, N₂ adsorption-desorption and NH₃-TPD. The performances of the supported Pd catalysts in hydrodesulfurization (HDS) were evaluated in a fixed-bed reactor with dibenzothiophene (DBT) as the model sulfur-containing molecule; the effect of support properties on the performance of supported Pd catalysts in HDS was then investigated. The results indicated that the performance in HDS of supported Pd catalysts are significantly influenced by the support properties. Although the specific surface has a minor influence on the HDS activity of the supported Pd catalysts, the hydrogenation (HYD) selectivity is probably related to the pore structure of support; the mesoporous structure is beneficial to the improvement of HYD selectivity. The acid supports can give the Pd catalysts higher HDS activity, owing to the hydrogen spillover effect. The Z-MCM-41 composite is an excellent support for noble metal Pd catalyst in HDS, which can be ascribed to the synergy of the mesoporous structure of MCM-41 and acidic properties of ZSM-5.