Chemical looping oxidative dehydrogenation of ethane over Fe-Co/HZSM-5 redox catalyst

Abstract

Chemical looping oxidative dehydrogenation (CL-ODH) has been extensively investigated as a green strategy for light olefins production from alkanes/naphtha without thermodynamic equilibrium constraints. However, achieving high ethylene selectivity as well as promising ethane conversion at relatively low-temperature (≤600 °C) in CL-ODH of ethane is still challenging. Herein, we show that Fe-Co dual-metal oxides supported by HZSM-5 zeolite can be used as appropriate redox catalysts for low-temperature CL-ODH of ethane. By tuning the loading mass ratio of Fe: Co oxides on the HZSM-5 support, 87 % ethylene selectivity and 23 % ethane conversion can be attained at 600 °C and 4800 mL·h−1·g−1 with the best-performing sample, i.e., 8Fe-2Co/HZ5(200). The stability of this sample was then assessed across 100 redox cycles, no obvious coking was observed within the entire test. Comparison test and physicochemical characterization results showed that both sample acidity and the role of dual-metal oxides are pivotal for ethane ODH to yield ethylene, in which dual-metal oxides are responsible for low-temperature ethane activation while proper amount of medium-strong acidity is critical for ethylene selectivity as well as activity. Overall, the present work demonstrates the feasibility of using HZSM-5 supported Fe-Co dual-metal oxides as redox catalyst for low-temperature CL-ODH of ethane, and provides a facile way for redox catalyst design to balance sample activity and selectivity.