Evaluation of the oxidative conversion of benzothiophene and dibenzothiophene in a model fuel using DBD plasma and a TiO2/MCM-41 catalyst

Abstract

This study investigates the oxidative conversion of benzothiophene (BT) and dibenzothiophene (DBT) at room temperature using ozone generated by dielectric barrier discharge (DBD) plasma, with and without a synthesized TiO 2 /MCM-41 catalyst. Unlike most previous DBD-plasma-assisted ODS systems that rely on ionic liquid or organic solvent extraction, this process operates without any solvent in the reaction medium, offering a simpler approach to oxidizing refractory sulfur compounds. The catalyst was prepared by a two-step method and characterized by BET, XRD, SEM-EDX, XRF, and FTIR. Introducing TiO 2 onto mesoporous MCM-41 enhances the dispersion and accessibility of active sites. Furthermore, whereas most earlier reports have focused on overall sulfur removal (oxidation + extraction), this study provides a quantitative, time-resolved evaluation of the extent of oxidation for each sulfur compound using high-performance liquid chromatography (HPLC), offering a cost-effective alternative to conventional GC-MS. Selectivity tests with a benzene–toluene–xylene (BTX) mixture confirmed that the system selectively oxidizes sulfur compounds without attacking aromatic hydrocarbons. Without the catalyst, BT oxidation reached 99% within 10 min, whereas DBT oxidation reached only 18% after 120 min. Remarkably, adding only 0.05 g of TiO 2 /MCM-41 increased DBT oxidation to 97% within 60 min, representing a ~ 5.4-fold increase in the oxidation rate. The reactivity order was BT ≫ DBT. Overall, these findings demonstrate that the DBD plasma/TiO 2 /MCM-41 system enables efficient deep oxidation of refractory sulfur compounds under ambient, solvent-free conditions, providing a simpler and more economical alternative to existing catalytic plasma systems. Low-cost HPLC monitoring further enhances the practical viability of this method for routine ODS studies.