Catalytic performance of mesoporous Mn-Co-Ti for o-xylene degradation: Mechanistic study under practical conditions

Abstract

Catalytic combustion of volatile organic compounds from industrial flue gases at low temperatures remains a challenge. Herein, we developed a mesoporous Mn-Co-Ti catalyst for o-xylene degradation by a solvothermal strategy. The optimized Mn_0.1Co-TiO₂ catalyst possessed a nanoflower structures with a surface area of 83.1 m²/g and mesoporous volume of 0.1191 cm³/g. Mn-doping modulated the electronic interactions between Mn and Co, which promoted the formation of MnCo₂O_4.5 phase and increased Co³⁺ and Mn⁴⁺ content of the catalyst. The Mn_0.1Co-TiO₂ catalyst had an improved reduction capacity from 170 to 644 °C, with a maximum H₂ consumption of 4.56 mmol/g. The Mn_0.1Co-TiO₂ catalyst achieved 50% o-xylene conversion at 193 °C at a GHSV of 60,000 h⁻¹, whereas the equivalent catalyst prepared by impregnation required 315 °C for 50% o-xylene conversion. In the presence of NO, the generated NO₂ accelerated o-xylene conversion because it promoted the generation of more Mn⁴⁺-O-Co³⁺ active sites and accumulation of intermediates such as maleate and acetate species. NH₃ and H₂O had slight inhibitory effects on o-xylene conversion, which were attenuated by abundant mesopores and redox ability of catalyst. SO₂ gas caused inactive sulfates and chemical deactivation on catalyst surface, thus leading to excessive formation of benzoquinone products.