Investigation of AFeO3 (A=Ba, Sr) Perovskites for the Oxidative Dehydrogenation of Light Alkanes under Chemical Looping Conditions

Chemical looping-oxidative dehydrogenation (CL-ODH) of light alkanes: bulk AFeO₃ (A=Ba, Sr) perovskites exhibited promising CL-ODH performance to produce light C₂−C₃ olefins using tunable lattice oxygen. Performance degradation was attributed to the transformations of perovskite to reduced phases particularly brownmillerite A₂Fe₂O₅. Catalytic activity was fully restored upon exposure to air at an elevated temperature.

Abstract

Oxidative dehydrogenation (ODH) of light alkanes to produce C₂−C₃ olefins is a promising alternative to conventional steam cracking. Perovskite oxides are emerging as efficient catalysts for this process due to their unique properties such as high oxygen storage capacity (OSC), reversible redox behavior, and tunability. Here, we explore AFeO₃ (A=Ba, Sr) bulk perovskites for the ODH of ethane and propane under chemical looping conditions (CL-ODH). The higher OSC and oxygen mobility of SrFeO₃ perovskite contributed to its higher activity but lower olefin selectivity than its Ba counterpart. However, SrFeO₃ perovskite is superior in terms of cyclic stability over multiple redox cycles. Transformations of the perovskite to reduced phases including brownmillerite A₂Fe₂O₅ were identified by X-ray diffraction (XRD) as a cause of performance degradation, which was fully reversible upon air regeneration. A pre-desorption step was utilized to selectively tune the amount of lattice oxygen as a function of temperature and dwell time to enhance olefin selectivity while suppressing CO₂ formation from the deep oxidation of propane. Overall, SrFeO₃ exhibits promising potential for the CL-ODH of light alkanes, and optimization through surface and structural modifications may further engineer well-regulated lattice oxygen for maximizing olefin yield.

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