The Effect of Mn Content on Catalytic Activity of the Co–Mn–Ce Catalysts for Propane Oxidation: Importance of Lattice Defect and Surface Active Species
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Composite oxide catalysts with Co/Mn/Ce molar ratio of 3:x:2(x = 1, 3, 5 and 7) have been successfully prepared by co-precipitation method. The crystal phase structure, elemental valence, oxygen vacancy and reductivity of the catalysts were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), H2 temperature program reduction(H2-TPR) and in situ DRIFTs. The results demonstrated that when x = 1, the Co–Mn–Ce catalyst had the smallest grain size and oxygen vacancy. A flow reactor experimental system was used to analyze the effect of Mn content on light-off temperature (T10) and complete oxidation temperature (T90) of propane oxidation over Co–Mn–Ce catalysts under anhydrous condition and 5% vol of water vapor. The results showed that when x = 1, the catalyst exhibits the highest activity (T10 = 200 °C, T90 = 307 °C) and water tolerance among the four catalysts. It indicated that when x = 1, the incorporation of Mn content can improve the ability of Co–Mn–Ce catalysts for propane oxidation. Based on the Langmuir–Hinshelwood theory, the surface chemical reaction pathway of propane oxidation was constructed and it revealed that the major active sites of Co–Mn–Ce catalysts mainly depend on surface oxygen vacancy and the surface active species (Mn4+,Oads).
KeywordsComposite oxide catalysts Propane Catalytic oxidation Oxygen vacancy Light-off temperature
This work is supported by the National Natural Science Fund (51676090) and the National Engineering Laboratory Open Fund for Mobile Source Pollution Emission Control Technology (NELMS2018A18) for financial supports.
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Conflict of interest
The authors declare no conflict of interest.