Insight into the oxidative desulfurization mechanism of aromatic sulfur compounds over Ti-MWW zeolite: A computational study

The mechanism of aromatic sulfur compounds oxidized on Ti-MWW zeolite with H2O2 was studied by density functional theory. The results show that the adsorption capacity of solvents on Ti-η2-OOH decreases in the order of CH3COCH3> CH3OH > CH3CN > H2O. The energy barriers of thiophene on different active centers are in the order of Ti-η2-OOH-CH3CN < Ti-η2-OOH-CH3COCH3< Ti-η2-OOH-CH3OH < Ti-η2-OOH-H2O < Ti-η2-OOH < Ti-η1-OOH, showing a linear correlation with the Hirshfeld charge of Oα. The interaction energy calculations indicate that the polar solvent not only participates in the reaction but also plays a critical role in timely removing products. Moreover, the oxidative activation energies of four aromatic sulfur compounds follow the order: thiophene > benzothiophene > dibenzothiophene >4, 6-dimethyldibenzothiophene, confirming that Ti-MWW could provide sufficient space for the aromatic sulfur compounds with relatively large molecular size and has an excellent oxidation desulfurization performance. Our results address the controversy over the oxidation desulfurization reactivity of aromatic sulfur compounds by Ti-MWW in experimental studies and provide insights to further studies.