Effect of Mn doping on the structure and oxidative desulfurization properties of Co-V-O binary metal oxides
Sulfur dioxide emitted from combustion of sulfur-containing aromatic compounds in fuels is a major contributor to atmospheric pollution. Oxidative desulfurization (ODS) has become a crucial complement to hydrodesulfurization (HDS) due to its mild reaction conditions and high efficiency in removing refractory aromatic sulfides. Metal doping is an effective strategy to modulate the electronic structure of catalysts and enhance catalytic performance. In this study, Mn-doped Co-V-O metal oxide (Mn-Co-V-O) was synthesized via a reflux method followed by high-temperature calcination. The structure, morphology, and surface chemical composition were characterized by FT-IR, XRD, SEM, XPS, and UV-vis DRS. The ODS performance toward dibenzothiophene (DBT) was evaluated using molecular oxygen as a green oxidant. Results indicated that Mn doping significantly enhanced the ODS activity compared to undoped Co-V-O. Under optimized conditions (110 °C, 0.03 g catalyst, 150 mL/min O2 flow, 20 mL model oil), a direct DBT removal rate of 81.6% was achieved. When combined with extraction, the desulfurization rate increased to 98.0%. Mechanistic studies revealed that Mn doping increased the surface oxygen vacancy concentration, facilitating oxygen activation to generate superoxide radicals (·O2−). Radical trapping experiments confirmed that ·O2− was the key active species responsible for selective oxidation of DBT to DBTO2. This study provides a reference for designing efficient metal oxide catalysts for deep oxidative desulfurization.