Hydrodesulfurization of dibenzothiophene catalyzed by Pd supported on overgrowth-type MCM-41/HY composite

Siliceous MCM-41 (Si-MCM-41), aluminosilicate MCM-41 (Al-MCM-41) and two micro-mesoporous materials obtained either by physically mixing Si-MCM-41 with HY zeolite [MY(M)] or by overgrowing Si-MCM-41 over HY zeolite particles [MY(C)], were prepared and characterized by means of XRD, XRF and pyridine adsorbed FT-IR. The hydrodesulfurization (HDS) performances of the supported Pd catalysts were evaluated with dibenzothiophene (DBT) as the model sulfur-containing molecule. The results indicated that the HDS performances of Pd catalysts are significantly influenced by the pore structures and acid properties of the supports. Pd catalysts supported on the acidic supports showed enhanced stability as well as HDS and hydrogenation (HYD) activities. Among the catalysts studied, Pd/MY(C) exhibited the highest activity and stability in DBT HDS. Its enhanced HDS performance especially sulfur resistance may result from the unique core/shell structure of MY(C). The effect of the acid properties and pore structures of the supports on the HDS performances of Pd catalysts was discussed by considering formation of "electronic-deficient" Pd particles and an "auto-regeneration" mechanism involving spillover hydrogen. (C) 2009 Elsevier B.V. All rights reserved.