Dehydrogenation of Ethane via the Mars-van Krevelen Mechanism over La_0.8Ba_0.2MnO_3-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 La_0.8Ba_0.2MnO_3-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.