Insights into the intrinsic kinetics for efficient hydrodesulfurization of 4,6-dimethyldibenzothiophene over mesoporous CoMoS2/ZSM-5

The intrinsic kinetics of hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene (4,6-DMDBT) over mesoporous CoMoS2/ZSM-5 (CoMoS2/MZSM-5) was investigated by comparing the commercial CoMoS2/gamma-Al2O3. A pseudo-first-order kinetic model considering the direct desulfurization (DDS) and two detailed partial and full hydrogenation pathways was formulated with simple power law rate equations. The apparent rate constants of five lumped reactions on CoMoS2/MZSM-5 are 2-4 times larger than those of CoMoS2/gamma-Al2O3. With both catalyst system, the pre-exponential factor plays a dominant role in the reaction rate of DDS pathway showing equally high activation energies. The apparent activation energies show a critical effect on the reaction rate of two hydrogenation and subsequent desulfurization reactions. Furthermore, the Delplot analysis was applied to identify the reaction sequence of product formation and verify the reaction network. The HDS performance and reaction rates of individual reaction steps can be rationally linked to the morphology and available content of CoMoS phase as identified by HRTEM and XPS characterization. Thus, multi-stacked MoS2 nanocrystallites on CoMoS2/MZSM-5 provide more available sulfur vacancies to facilitate the DDS pathway, and catalyze efficiently the hydrogenation and subsequent desulfurization with the synergy of brim sites and sulfur vacancies.

Automated summary

The intrinsic kinetics of the hydrodesulfurization of 4,6-DMDBT was studied using CoMoS2/MZSM-5 catalyst and compared to CoMoS2/γ-Al2O3 catalyst. A kinetic model considering direct desulfurization and two hydrogenation pathways was established. The rate constants of reactions on CoMoS2/MZSM-5 were higher than those on CoMoS2/γ-Al2O3. Activation energies played a critical role in the reaction rates, and sulfur vacancies were found to facilitate the reaction.