CO2 conversion to CO by reverse water gas shift and dry reforming using chemical looping†

Abstract

Chemical looping technology provides an efficient means of sustainable CO₂ conversion to the important chemical intermediate of CO or syngas by changing conventional co-feeding of reactant into alternating feeding. It presents the important benefits of simplified gas separation, improved selectivity, and more independently adjusted operation conditions compared to those of conventional reactions. Oxygen carriers (OCs) are pivotally important for the performance of chemical looping processes. Herein, recent advances of OCs for two representative chemical looping CO₂ conversion technologies to CO are reviewed systematically: reverse water gas shift chemical looping (RWGS-CL) and dry reforming of methane by chemical looping (DRM-CL). The influence of composition along with surface and bulk structures of these OCs on conversion, selectivity, and lattice oxygen reactivity, are discussed to obtain better design and optimisation strategies for the tailored OCs. Moreover, modified Ellingham diagrams that exhibit the thermodynamic properties for potential metal oxides for the effective screening of active OCs of DRM-CL and RWGS-CL are proposed, yielding valuable insights not only into RWGS-CL and DRM-CL but also into other distinct chemical looping processes involving into the same reactions. Finally, a summary and prospects are presented for some challenges and future research orientation for CO₂ conversion to CO via chemical looping.