Superior performance of Cu-Ce binary oxides for toluene catalytic oxidation: Cu-Ce synergistic effect and reaction pathways
A series of Cu-Ce binary oxides were synthesized via a facile co-precipitation method for toluene catalytic oxidation. The physicochemical properties of these samples were characterized by BET, XRD, SEM, TEM, H 2 -TPR, O 2 -TPD, and XPS. It reveals that Cu 1 Ce 3 catalyst possesses a higher specific surface area, stronger Cu-Ce synergistic effect, and better low-temperature reducibility than other samples. Moreover, Cu 1 Ce 3 catalyst exhibited superior toluene oxidation activity with 99.10% toluene removal efficiency and 97.28% CO 2 selectivity at 200 °C, as well as satisfactory stability and moisture resistance. Therefore, Cu 1 Ce 3 catalyst indicates a huge potential for practical applications, such as coal-fired flue gas and spray coating industry. The reaction pathways for toluene catalytic oxidation over the Cu 1 Ce 3 catalyst were further illuminated by in-situ DRIFTs. In the main pathway, toluene molecules were firstly in contact with the interface lattice oxygen, then the abstraction of H atoms occurred on the methyl group, and benzyl alcohol is considered as the primary intermediate, during which the rate-determining step is the oxidation of benzyl alcohol. In the secondary pathway, a little proportion of toluene molecules were directly oxidized into benzoic acid by the chemisorbed oxygen species. In subsequent steps, all the intermediates were converted into CO 2 and H 2 O. At last, it is confirmed that the toluene oxidation over Cu 1 Ce 3 catalyst involves a Mars-van-Krevelen mechanism via this study.
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