Catalytic Removal of Benzene at Mild Temperature over Manganese Oxide Catalysts

Series of MnO_x catalysts were synthesized through oxalate route and calcined at facile temperatures. Characterizations through XRD, N₂-adsorption/desorption, HRTEM, C₆H₆-TPD, O₂-TPD, XPS, and H₂-TPR revealed that MnO_x calcined at 250 °C (N250) with a main crystal phase of Mn₂O₃ showed micro-mesopores and largest specific surface area, and therefore had a high adsorption capacity of C₆H₆. N250 also presented better oxygen mobility, rich surface adsorbed oxygen species (O_ads), and proper ratio of surface Mn⁴⁺/Mn³⁺. The starting temperature of H₂-TPR of N250 was the lowest among the obtained MnO_x samples. As a result, N250 exhibited the lowest T₉₀ value of 191 °C in C₆H₆ thermal catalytic oxidation (WHSV 60,000 mL g_cat.⁻¹ h⁻¹, initial C₆H₆ concentration 190 ppm) among all the catalysts, and this T₉₀ value is lower than those reported in many research. At last, a potential reaction pathway was proposed according to the results of in-situ FTIR measurement.