Toluene oxidation over Co 3+ -rich spinel Co 3 O 4 : Evaluation of chemical and by-product species identified by in situ DRIFTS combined with PTR-TOF-MS

Series of Co -rich spinel Co O catalysts were synthesized and evaluated by toluene catalytic oxidation. An outstanding activity was achieved over Co O -N utilizing Co(NO ) ·6H O as precursor (T = 211 °C, T = 217 °C at conditions: 1000 ppm(v), WHSV = 60 000 mL g h ). Results of comparative characterizations demonstrated that such excellent performance was mainly attributed to large surface area, high reducibility at low temperature, high abundance of Co ions and structure defects, as well as highly active surface oxygen. The results of in situ DRIFTS revealed that in the air or N atmosphere, the by-products were almost the same. The reaction pathway of toluene oxidation can be described as follow: transformation of toluene from benzyl alcohol, benzaldehyde, benzoate, benzene, phenol, benzoquinone, maleic acid and to final products, which were fully confirmed by PTR-TOF-MS. Besides, ring opened by-products, such as acetone, acetic acid, acetaldehyde, etc. were also detected. In this work, the combination of in situ DRIFTS and PTR-TOF-MS provided a promising approach for further understanding of the mechanism of VOCs elimination.