Oxidative dehydrogenation of ethane and subsequent CO₂ activation on Ce-incorporated FeTiO_x metal oxides

The Ce-incorporated FeTiO_x catalysts were investigated for an oxidative dehydrogenation (ODH) of C₂H₆ (reduction step) and successive CO₂ activation to CO (oxidation step) through redox chemical looping (CL-ODH) cycles of those partially reducible metal oxides via mutual phase changes between Fe²⁺/Fe³⁺ and Ti³⁺/Ti⁴⁺ species. A higher lattice oxygen mobility with less surface electrophilic oxygen natures on an optimal FeCeTiO_x(1) (Fe/Ce molar ratio = 1.0) was responsible for an enhanced cyclic stability. The lattice expansion by Ce-incorporation into the Fe/TiO₂ structures not only enhanced charge transport rates but also generated thermally stable trigonal ilmenite FeTiO₃ phases. These larger oxygen storage capacity of CeO₂ on the FeCeTiO_x(1) also revealed an excellent 5-times cyclic stability with a stable C₂H₄ formation rate and C₂H₄ selectivity of 84.1% for a reduction step of ethane as well as an excellent CO₂ activation to CO at 600 °C for an oxidation step (named as CL-ODH). Those superior catalytic performances on the FeCeTiO_x(1) were attributed to the partial formation of FeTiO₃ phases, which caused an improved lattice oxygen mobility by CeO₂ contribution with its higher oxygen storage nature and facile redox property. The large amount of non-stoichiometric surface oxygens at a higher Fe/Ce ratio above 2 mainly caused an enhanced CO₂ byproduct formation by the full oxidation of C₂H₆. The synergy effects on the FeCeTiO_x(1) were attributed to facile redox properties of lattice oxygen vacant sites by partially forming the strongly interacted stable FeTiO₃ phases with its resistance to coke depositions.