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Co and Mo Co-doped Fe2O3 for Selective Ethylene Production via Chemical Looping Oxidative Dehydrogenation

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journal contribution
posted on 2021-06-04, 15:38 authored by Xin Tian, Chaohe Zheng, Fanxing Li, Haibo Zhao
In this study, we investigate Co and/or Mo doped Fe2O3 (CoxMo1–x/Fe2O3, x = 0, 0.2, 0.3, 0.4, and 1) as redox catalysts for chemical looping oxidative dehydrogenation (CL-ODH) of ethane. Under the cyclic redox reaction mode, the five as-prepared samples behave differently toward ethane conversion. Among the five redox catalysts, CoFe2O4 (x = 1) is highly reactive and tends to overoxidize ethane into CO2, while Mo/Fe2O3 (x = 0) exhibits promising ethylene selectivity but inferior H2 removal capability. By tuning the molar ratio of Co/(Co + Mo), 87.4% ethylene selectivity at 56.2% ethane conversion can be achieved by the Co0.3Mo0.7/Fe2O3 (x = 0.3) redox catalyst at 825 °C and 6000 h–1. C2H6-TPR results show that the selectivity of Co0.3Mo0.7/Fe2O3 alters as the ODH reaction proceeds due to the dynamic change of surface properties of the redox catalyst in the reaction. XPS results indicate that a relatively low Fe content as well as a high Mo content at the near-surface of the redox catalyst is beneficial for its ethylene selectivity in CL-ODH of ethane. DFT calculations reveal that Co cations in the Co0.3Mo0.7/Fe2O3 structure are responsible for the activity and H2 combustion capability of the redox catalyst, while Mo plays a key role in tuning the ethylene selectivity.