Chemical Looping-Based Oxidative Dehydrogenation of Ethane and Successive CO2 Activation on Fe-Modified CeZrOx Mixed-Metal Oxides

초록

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 degrees 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.

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