The abundant oxygen vacancies of the Co–Ce mixed oxides towards catalytic combustion toluene

A series of catalysts (Co3O4/Beta-60, CeO2/Beta-60, CoCeOx/Beta-60) were prepared by constant volume impregnation method and were applied to the catalytic oxidation toluene. The characterization results showed that some Co ions were embedded into the lattice of CeO2 to form CoCeO2-δ solid solution that promoted the formation of a large number of oxygen vacancies and generation of active oxygen species for the deep oxidation of toluene. The mobility of active oxygen species and reducibility for CoCeOx/Beta-60 were both improved. Therefore, CoCeOx/Beta-60 showed the superior catalytic performance, the conversion of toluene was 90% when the temperature was 307 °C. The combination between the zeolite carrier and the active components endowed the supported catalyst with excellent stability. Additionally, the in situ DRIFTS results displayed that the oxidation of toluene over CoCeOx/Beta-60 followed the MvK mechanism and L-H mechanism. Adsorbed toluene could be oxidized by not only active adsorbed oxygen on oxygen vacancies but also the lattice oxygen species. However, gaseous oxygen was paramount importance for the total oxidation of toluene for the reason that the gaseous oxygen could be activated through the oxygen vacancies generated to fill the active oxygen species after the depletion of active adsorbed oxygen and lattice oxygen. The study systematically reviewed the data for the catalytic combustion of toluene, aiming to provide new avenues for the preparation and application of catalysts with excellent catalytic activity.