Mechanistic Investigation and Optimization of a Mixed-Oxide@Alkali Carbonate Redox Catalyst Platform for Enhanced Ethane Oxidative Dehydrogenation

Abstract Chemical looping oxidative dehydrogenation (CL-ODH) of ethane has emerged as a promising alternative for ethylene production, with the potential to mitigate the environmental and sustainability concerns associated with conventional steam cracking. The main challenge of CL-ODH is the design of active and selective redox catalysts to enhance ethane activation while minimizing the generation of by-products such as COx (CO and CO2). This study employs ab initio molecular dynamics (AIMD) simulations to investigate the formation and reactivity of oxygen species in mixed metal-oxides@Li2CO3 and Na2CO3 redox catalysts. Estimated reaction free energies are used as thermodynamic descriptors, while the computational insights are supplemented with experimental validations. Our analysis indicates that peroxide (O22–) and •OH radicals provide more favorable thermodynamic driving forces for ethane C–H activation at the outer carbonate surface than monatomic oxygen radical anion (O–) and superoxide (O2–). In addition, mechanistic investigations into COx formation reveal that the product water can interact with peroxide-derived species at the gas–carbonate interface to generate •OH radicals, consistent with prior experimental observations. In Li2CO3, •OH-mediated pathways retain favorable ethane C─H activation thermodynamics while reducing the driving force for selected COx-forming transformations relative to peroxide. These findings provide important mechanistic insights into the design and optimization of mixed-oxide@alkali carbonate core-shell redox catalysts for CL-ODH.