Preparation of DESs/SG catalyst and its performance in the oxidative desulfurization

DESs/SG catalyst was prepared by supporting the proline-based deep eutectic solvent (DES) on the silica-gel (SG) matrix using a sol-gel method; the catalyst structure was characterized by FT-IR, XRD, SEM/EDS and N₂ adsorption-desorption. The results showed that the DESs were successfully incorporated into the silica-gel matrix, leading to a decrease in the surface area and pore volume, but an increase in the pore diameter. With hydrogen peroxide as oxidant, the catalytic performance of DESs/SG in the oxidative desulfurization of a model oil containing dibenzothiophene (DBT) was investigated; the effects of deep eutectic solvent loading, reaction temperature, n(H₂O₂)/n(S) ratio, catalyst amount, sulfur compound type and catalyst recycle times on the desulfurization efficiency were considered. The results indicated that under optimum desulfurization conditions, the desulfurization degrees for DBT, 4, 6-dimethyl-dibenzothiophene (4, 6-DMDBT) and benzothiophene (BT) over the DESs/SG catalyst were 97%, 96.5% and 46.4%, respectively; after recycling for 9 times, the DESs/SG catalyst still displayed a desulfurization degree of above 89.4%.