Chemical Looping-Based Oxidative Dehydrogenation of Ethane and Successive CO₂Activation on Fe-Modified CeZrOx Mixed-Metal Oxides

Fe-modified CeZrOx bimetal oxides with 5–7 wt % Fe revealed higher catalytic activity for chemical looping-based dehydrogenation of ethane (CL-ODH), with successive activation of carbon dioxide due to the abundant lattice oxygen species. Optimal Fe modification on the Ce–Zr solid solution (Ce_0.5Zr_0.5O₂phase) with 5 wt % Fe was responsible for enhanced selectivity to C₂H₄(10.7% yield of C₂H₄at 600 °C with a turnover frequency (TOF) value of 0.049 s^–1). This was carried out by oxidative dehydrogenation of ethane with successive CO₂activation to form CO by a reverse Boudouard reaction or oxidation of partially reduced active metal oxides (oxygen-vacant sites), which was attributed to the enhanced thermal stability of Fe(x)CeZrOx catalysts. An excessive amount of iron oxides above 7 wt % Fe on the Ce–Zr bimetal oxides led to thermal agglomeration of iron oxides, resulting in an increased COx byproduct formation during C₂H₆dehydrogenation (reduction step), which was attributed to the larger amount of surface-adsorbed oxygen species possessing electrophilic nature and promoting facile deep oxidation reactions. Optimizing the surface iron content, along with the selective formation of thermally stable Ce_0.5Zr_0.5O₂solid solution phases having a larger amount of active lattice oxygen species, was found to be crucial for enhanced catalytic activity and stability in chemical looping-based ODH reactions.