Regulation mechanism of CO2 on Cr6+ in CrOx-based catalysts for ethane oxidative dehydrogenation

To elucidate the active sites and reaction mechanism of CrO x /ZrO 2 catalysts in CO 2 -assisted oxidative dehydrogenation (CO 2 -ODH) of ethane, a combination of multiple characterization techniques, DFT calculations, and in situ FTIR spectroscopy was employed. Results reveal the coexistence of isolated and polymeric Cr 6+ species on the catalyst surface, with catalytic activity exhibiting a strong positive correlation with the content of polymeric Cr 6+ , confirming its role as the key active component. Further investigation uncovers a distinct and strong electronic interaction between CrO x and ZrO 2 that facilitates the formation and stabilization of polymeric Cr 6+ . This interaction is absent in CrO x /CeO 2 and CrO x /TiO 2 systems, offering a theoretical rationale for the rational design of catalyst supports. Mechanistically, CO 2 plays a dual role: it participates in both ethane ODH and the RWGS reaction, and reoxidizes coordinatively unsaturated Cr 3+ to Cr 6+ , thereby enhancing reaction stability. This work elucidates the CO 2 -ODH pathway and the regulatory role of CO 2 , offering new insights into the design of active sites in CrO x -based catalysts. However, pronounced catalyst deactivation currently limits industrial application, highlighting the need for future efforts to focus on improving catalyst stability.