Integrated kinetic and reactor model for CO₂ splitting over Ni-based oxygen carriers in chemical looping combustion–CO₂ splitting applications

With rising atmospheric CO₂ concentrations, global temperatures are increasing, resulting in severe climate-change patterns. Carbon capture, utilization, and storage technologies can reduce emissions and extend the utility of fossil fuels during the energy transition. Although CO₂ is thermodynamically stable and difficult to convert, its transformation into CO enables use as a valuable feedstock for fuels and chemicals, such as light olefins and acetic acid. Chemical looping combustion (CLC) is a technology that produces energy while inherently separating CO₂. By integrating a CO₂ splitting (CDS) reaction into this process, the separated CO₂ can be effectively converted into CO. In this study, a reactor model for CO₂ splitting was developed as a foundational step toward a fully integrated CLC–CDS system. Thermogravimetric analysis confirmed that CO₂ splitting follows a dissociative adsorption mechanism with a reaction order of 0.52. Batch bubbling fluidized bed experiments indicated the oxygen-carrier kinetics are consistent with a nucleation and nuclei growth model, with an activation energy of 67.7 kJ/mol. This value was in close agreement with the DFT-derived activation energy (approximately 65.2 kJ/mol). The effects of gas and solid residence times were investigated in a continuous solid-flow bubbling fluidized bed reactor. Based on these findings, an n -th-order plug flow reactor model was established to predict CO₂-to-CO conversion. Overall, the proposed model provides valuable guidelines for the design and optimization of integrated CLC–CDS systems.