Promoting the Catalytic Ozonation of Toluene by Introducing SO into the α-MnO/ZSM-5 Catalyst to Tune Both Oxygen Vacancies and Acid Sites.

Mn-based catalysts hold the promise of practical applications in catalytic ozonation of toluene at room temperature, yet improvement of toluene conversion and CO selectivity remains challenging. Here, an innovative α-MnO/ZSM-5 catalyst modified with SO was successfully prepared, and both characterizations and density functional theory (DFT) calculations showed that SO introduction facilitated the formation of oxygen vacancies, Lewis and Brönsted acid sites, and active oxygen species and enhanced the adsorption ability of toluene on α-MnO/ZSM-5. Characterizations also showed that SO introduction made the catalyst possess larger specific surface area, superior reducibility, and stronger surface acidity. As a result, α-MnO/ZSM-5 with a S/Mn molar ratio of 0.019 exhibited the best toluene conversion and CO selectivity, 87 and 94%, respectively, after the reaction for 8 h at 30 °C under an initial concentration of 5 ppm toluene and 45 ppm ozone, relative humidity of 45%, and space velocity of 32,000 h, far superior to those of non-noble catalysts reported to date under comparable reaction conditions. The synergistic role of increased oxygen vacancies and acid sites of α-MnO/ZSM-5 modified with SO resulted in excellent toluene conversion and CO selectivity. The findings represented a critical step toward the rational design and synthesis of highly efficient catalysts for catalytic ozonation of toluene.