Fast and deep oxidative desulfurization of dibenzothiophene with catalysts of MoO3-TiO2@MCM-22 featuring adjustable Lewis and Brønsted acid sites
The synthesis of high-performance and recyclable catalysts for oxidative desulfurization (ODS) from fuels has been a significant challenge. In this research, novel catalysts of MoO3-TiO2@MCM-22 with excellent catalytic performance were successfully prepared via a facile impregnation method. Results showed that the optimal catalyst at a Mo-Ti mass ratio of 1:4 (MT-1:4) exhibited the highest catalytic efficiency for ODS of dibenzothiophene (DBT) with a sulfur conversion of 99.96% within 15 min. Interestingly, the enhanced ODS activity was attributed to the synergistic effect between MoO3 and TiO2, which was achieved by adjusting the concentrations of Lewis and Brønsted acid sites on the surface of MCM-22. Catalyst MT-1:4 achieved the highest concentrations of Lewis and Brønsted acid sites and the largest combined index, resulting in the formation of peroxometallate complexes. Besides, the kinetic studies revealed that the ODS was a pseudo first-order reaction with an apparent activation energy of 48.9 kJ/mol. There was no significant reduction in catalytic activity after 8 successive cycles, which manifested the perfect reusability of catalyst MT-1:4 for the ODS system. Furthermore, a plausible ODS mechanism was proposed with MoO3-TiO2@MCM-22 catalyst. Therefore, the prepared MoO3-TiO2@MCM-22 exhibited favorable industrial application potential for ODS.