Catalytic performance of CoMo catalysts supported on mesoporous ZSM-5 zeolite-alumina composites in the hydrodesulfurization of 4,6-dimethyldibenzothiophene

Abstract

Composite materials (AZ-M-x) were prepared by mechanically mixing the mesoporous zeolite ZSM-5 (MZSM-5) and γ-Al2O3. This composite was employed as a support for CoMo catalysts (CoMoS/AZ-M-x). The CoMoS/AZ-M-x catalysts show high activity (TOF=2.1–3.0×10−3s−1) in the hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) as compared to the CoMo catalyst supported on γ-Al2O3 (CoMoS/γ-Al2O3, TOF=1.9×10−4s−1), and the HDS activity increased with the MZSM-5 content in the composites. In contrast, the HDS activity of a mixture of microporous ZSM-5 with γ-Al2O3 supported CoMo catalyst is similar to that of the CoMoS/γ-Al2O3 catalyst. Compared with microporous ZSM-5, introducing MZSM-5 into γ-Al2O3 improves the mesoporous structure of the composites, which benefits mass transfer of the reactant molecules. Furthermore, MZSM-5 in the composites modifies their surface properties with abundant acidic hydroxyl groups, which can weaken the Mo-support interaction, leading to modifications in the morphology of the MoS2 phases to form multi-stacked MoS2 active phases on the CoMoS/AZ-M-x catalysts.