A molten carbonate shell modified perovskite redox catalyst for anaerobic oxidative dehydrogenation of ethane

Acceptor-doped, redox-active perovskite oxides such as La_0.8Sr_0.2FeO₃ (LSF) are active for ethane oxidation to CO _x but show poor selectivity to ethylene. This article reports molten Li₂CO₃ as an effective "promoter" to modify LSF for chemical looping-oxidative dehydrogenation (CL-ODH) of ethane. Under the working state, the redox catalyst is composed of a molten Li₂CO₃ layer covering the solid LSF substrate. The molten layer facilitates the transport of active peroxide (O₂ ^2-) species formed on LSF while blocking the nonselective sites. Spectroscopy measurements and density functional theory calculations indicate that Fe⁴⁺→Fe³⁺ transition is responsible for the peroxide formation, which results in both exothermic ODH and air reoxidation steps. With >90% ethylene selectivity, up to 59% ethylene yield, and favorable heat of reactions, the core-shell redox catalyst has an excellent potential to be effective for intensified ethane conversion. The mechanistic findings also provide a generalized approach for designing CL-ODH redox catalysts.