Chemical Looping-Based Oxidative Dehydrogenation of Ethane and Successive CO₂ Activation on Fe-Modified CeZrO<i>x</i> 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 (Ce0.5Zr0.5O2 phase) with 5 wt % Fe was responsible for enhanced selectivity to C2H4 (10.7% yield of C2H4 at 600 °C with a turnover frequency (TOF) value of 0.049 s–1). This was carried out by oxidative dehydrogenation of ethane with successive CO2 activation 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 C2H6 dehydrogenation (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 Ce0.5Zr0.5O2 solid 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.