Molecular-level investigation on supported CrOx catalyst for oxidative dehydrogenation of propane with carbon dioxide
2022
Wang, Jian | Zhu, Min-Li | Song, Yong-Hong | Liu, Zhao-Tie | Wang, Li | Liu, Zhong-Wen
Although the supported CrOₓ is widely applied as an important industrial catalyst for oxidation processes (such as propane dehydrogenation), the molecular-level understanding of its catalytic mechanism is still limited. In this work, the oxidative dehydrogenation of propane with carbon dioxide (CO₂-ODP) was exploited as a probe reaction to investigate CrOₓ highly dispersed over dealuminated β zeolite (CrSiβ). It was revealed that the activity of the CrSiβ catalyst was dependent on the dispersion of Cr species and the content of initial highly-dispersed Cr⁶⁺ oxides. Namely, the oxygen of terminal Cr = O bonds in initial Cr⁶⁺ oxides could rapidly react with propane molecules, thus generating the coordinatively unsaturated Cr³⁺ oxides as active sites for the redox cycles of CO₂-ODP. In this redox cycle, the unsaturated Cr³⁺site takes an oxygen from a CO₂ molecule and then the activated oxygen reacts with propane to produce H₂O and propene. This finding is not only important for the molecular understanding of the CrOₓ catalytic properties, but also is beneficial for the rational design of more efficient CrOₓ catalysts for dehydrogenation reactions including CO₂-ODP.
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