Influence of ZrO2 crystal structure on the catalytic performance of Fe-Ni catalysts for CO2-assisted ethane dehydrogenation reaction

• The exposed crystal faces showed significant impact on the catalytic performance. • Fe 1.5 Ni 0.5 /ZrO 2 -M catalyst exhibits an ethylene selectivity of > 80.5%. • The monoclinic ZrO 2 has higher O v density and stronger metal-support interaction. • O v and Fe 2+ -O-Zr 3+ sites promote CO 2 activation through C=O bond cleavage. The catalytic reaction of ethane with CO 2 promotes the value-added conversion of natural gas and the resource utilization of greenhouse gases. In this work, the CO 2 -assisted ethane dehydrogenation reaction characteristics on Fe 1.5 Ni 0.5 /ZrO 2 (M, T, Mix) catalyst with different crystal plane structure were studied through catalyst activity test, catalytic reaction kinetics study and catalyst characterization analysis. It is found that the exposed crystal faces of the ZrO 2 -supported catalyst has a significant effect on the CO 2 -assisted ethane oxidative dehydrogenation reaction. The monoclinic phase Fe 1.5 Ni 0.5 /ZrO 2 -M catalyst exhibits the largest conversion of ethane (21.8%) and CO 2 (25.2%) and the maximum selectivity to C 2 H 4 (80.5%). Monoclinic phase of ZrO 2 selectively exposes the ( −1 1 1) and (1 1 1) low-index surfaces with higher oxygen vacancy (O v ) density and stronger metal-support interaction, which leads to the formation of more Fe x Zr 1-x O 2 structures with high catalytic activity. The reductive oxygen vacancy O v and Fe 2+ -O-Zr 3+ sites promote the activation of CO 2 through the cleavage of C=O bond to supplement O* species. The O* species on the oxidative Fe 3+ -O-Zr 4+ site are captured and combined with H* species derived from the selective cleavage of ethane C–H bond to generate H 2 O.