Compositional engineering of Sr-substituted perovskite oxygen carriers for selective ethylene production via chemical looping oxidative dehydrogenation

Chemical looping oxidative dehydrogenation (CL-ODH) is a promising route for selective ethylene production, but its performance is highly dependent on the phase stability, oxygen reactivity, and defect chemistry of oxygen carriers, which remain difficult to control in bulk oxide systems. A series of Sr x Y 1-x FeO 3 (x = 0–0.3) perovskite oxygen carriers was investigated to clarify how A-site Sr substitution influences structural evolution, oxygen vacancy formation, redox behavior, surface basicity, and CL-ODH performance. Structural and surface analyses revealed that increasing Sr content induces lattice expansion and oxygen vacancy formation, accompanied by modification of surface acid–base properties and the formation of oxygen-deficient perovskite-related domains at higher substitution levels. Catalytic tests at 700 °C showed that Sr substitution alters reaction pathways. Pristine YFeO 3 exhibited the highest apparent ethane conversion but produced large amounts of CO x , CH 4 , and H 2 , indicating deep oxidation and cracking. In contrast, Sr-substituted compositions suppressed non-selective oxidation and enhanced ethylene selectivity, with the highest intrinsic selectivity observed at higher Sr contents. A carbon balance in the mid-90% range for all Sr-substituted samples enabled a reliable comparison of gas-phase selectivity. The observed performance trends indicate a conversion–selectivity trade-off arising from the interplay between lattice oxygen reactivity, oxygen vacancy concentration, and surface basicity. These results demonstrate that controlling oxygen vacancy concentration and lattice oxygen reactivity through A-site substitution is critical for achieving selective and stable CL-ODH performance and provide mechanistic insight into the design of bulk perovskite oxygen carriers.