Dehydrogenation of Ethane via the Mars–van Krevelen Mechanism over La0.8Ba0.2MnO3−δ Perovskites under Anaerobic Conditions

Dehydrogenation of ethane over perovskite oxide catalysts was investigated using the redox of perovskites and H2O as an oxidizing agent. The La0.8Ba0.2MnO3−δ (LBMO) perovskite showed a high catalytic activity for dehydrogenation of ethane. Periodic dry (without H2O)–wet (with H2O) operation tests revealed that dehydrogenation of ethane in the presence of H2O over LBMO proceeded via the Mars–van Krevelen (MvK) mechanism. Under the wet condition with D2O instead of H2O, D2 formation was verified, demonstrating that reactive lattice oxygens in LBMO contributed to the dehydrogenation reaction and that they were regenerated by water. Isotopic transient tests with H2 18O and in situ X-ray absorption fine structure measurements revealed that the reduction and oxidation of Mn in LaMnO3 and LBMO occurred under the reaction atmosphere and that the partial replacement of the La sites with Ba improved the redox ability of Mn, resulting in its high activity. Furthermore, temperature-programmed reduction under H2 elucidated that the reduction of Mn3+ to Mn2+ was promoted by Ba doping. The LBMO perovskite showed the very high activity for dehydrogenation of ethane in the presence of H2O via the MvK mechanism by virtue of the high redox properties of Mn.