In situ DRIFT spectroscopy study into the reaction mechanism of toluene over CeMo catalysts

The CeMo catalysts were prepared via different method and employed for the catalytic combustion of toluene. The influence of different preparation methods on CeMo samples for toluene oxidation was revealed. The toluene catalytic oxidation efficiency followed an order of CeMo-HT > CeMo-CP > CeMo-Sg. The long-term test indicated that the CeMo-HT possessed outstanding thermal stability. The excellent catalytic activity of CeMo-HT could be reasonably attributed to the smallest grain size, the highest number of low valence Ce 3+ ions and O sur species. CeMo-HT catalyst prepared by the hydrothermal method possessed the richer oxygen vacancies, which promoted the deep oxidation of toluene, and effectively reduced the production of intermediates. However, CeMo-HT (aged) possessed poorer oxygen vacancies, and generated more by-products. Additionally, the two reaction pathways of the toluene were inferred. In pathway I for CeMo-HT (aged): toluene → benzyl alcohol → benzaldehyde → benzoic acid →carbonate → CO 2 and H 2 O. In pathway II for CeMo-HT: toluene → phenol → benzoquinone → maleic anhydride → CO 2 and H 2 O. Series of CeMo catalysts were synthesized via hydrothermal, precipitation and sol-gel methods. In situ DRIFTS combined with GC-MS were introduced to explored the process of toluene oxidation, confirmed of Ce 3+ /(Ce 3+ +Ce 4+ ) and O Sur /O total played an important role. • CeMo-HT sample exhibited best catalytic activity and stability for toluene oxidation. • Superb activity was attributed to high Ce 3+ / Ce 4+ and high O Sur /O total . • The oxygen vacancies were simply modulated by the preparation method. • Benzoic acid and phenol were key intermediates in toluene catalysis by in situ infrared analysis.