Insight into modified CeMn based catalysts for efficient degradation of toluene by in situ infrared

Trace activated carbon (AC) and diatomaceous earth (DE) were used as structural promoters to be incorporated into Ce-Mn-based solid-solution catalysts by the redox precipitation method. The modified catalysts exhibit superior reducibility, with abundant Ce³⁺, Mn³⁺and reactive oxygen species, which are facilitated to the migration of oxygen and the generation of oxygen vacancies. In particular, the catalytic combustion temperatures of 90 % toluene (3000 ppm) on Ce₁Mn₃Ox-AC/DE were 84 °C (dry) and 123 °C (10 vol% H₂O), respectively. The role of lattice oxygen and adsorbed oxygen was revealed by in situ DRIFTS. Additionally, in situ DRIFTS was employed to verify that the degradation of toluene by Ce₁Mn₃Ox-AC/DE satisfied the Langmuir-Hinshelwood (L-H) mechanism and the Mars-Van Krevelen (MvK) mechanism. The possible reaction pathway was elucidated (toluene → benzyl alcohol → benzoic acid → maleic anhydride → CO₂ + H₂O). Furthermore, final products attributed to toluene oxidation were detected by in situ DRIFTS at 50 °C in the absence of oxygen, confirming that the catalyst possessed outstanding performance at low temperatures beyond mere adsorption.