Correlation between the physicochemical properties and catalytic performances of micro/mesoporous CoCeO_x mixed oxides for propane combustion

A series of micro-mesoporous CoCeO_x catalysts have been successfully prepared using a double template combining sol-gel method. The catalytic performance of novel CoCeO_x catalysts are investigated and compared with pure Co₃O₄ and CeO₂ catalysts for total oxidation of propane. It is found that the Co₁Ce₁ catalyst shows the highest catalytic activity (T₅₀ = 217 °C) as well as a good reaction stability and water tolerance among the five catalysts. The Co₃O₄, CeO₂ and CoCeO_x catalysts are characterized using XRD, BET, Raman, XPS, H₂-TPR, O₂-TPD, HRTEM, HAADF-STEM and in situ DRIFTS. The results demonstrate that the larger BET surface area, smaller grain size, stronger reducibility and more active oxygen species of the Co₁Ce₁ catalyst are responsible for its outstanding catalytic performance among the five catalysts. Moreover, the synergistic effect between Co and Ce over CoCeO_x catalysts are probably relevant to the formation of Co_xCe_1−xO_2−σ solid solution. In addition, on the basis of the results of XPS, kinetic analysis and in situ DRIFTS, the surface Co³⁺ ions and active oxygen species are regarded as the major active sites of the CoCeO_x catalysts for total oxidation of propane, and then a scheme of reaction model based on Langmuir-Hinshelwood mechanism is suggested at last. It can be expected that the micro-mesoporous CoCoO_x catalysts are promising materials for VOCs removal, and the results in this research may also provide some new insights into the catalyst design and mechanism exploration for VOCs catalytic oxidation.