Halogenated La_1.6Sr_0.4CuO₄ catalysts active for ethane selective oxidation to ethene

The catalytic performances and characterization of the catalysts La_1.6Sr_0.4CuO_3.852, La_1.6Sr_0.4CuO_3.857F_0.143, and La_1.6Sr_0.4 CuO_3.856Cl_0.126 have been investigated for the oxidative dehydrogenation of ethane (ODE) to ethene. X-ray diffraction results indicated that the three catalysts have a single-phase tetragonal K₂NiF₄-type structure. The incorporation of fluoride or chloride ions in the La_1.6Sr_0.4CuO_4-δ lattice can significantly enhance C₂H₆ conversion and C₂H₄ selectivity. We observed 83.2% C₂H₆ conversion, 76.7% C₂H₄ selectivity, and 63.8% C₂H₄ yield over La_1.6Sr_0.4CuO_3.857F0.143 and 79.6% C₂H₆ conversion, 74.6% C₂H₄ selectivity, and 59.4% C₂H₄ yield over La_1.6Sr_0.4CuO_3.856Cl_0.126 under the reaction conditions of C₂H₆/O₂/N₂ molar ratio 2/1/3.7, temperature 660°C, and space velocity 6000 mlh^-1 g^-1. With the rise in space velocity, C₂H₆ conversion decreased, whereas C₂H₄ selectivity increased. Life studies showed that the two catalysis were durable within 60 h of on-stream ODE reaction. Based on the results of X-ray photoelectron spectroscopy, O₂ temperature-programmed desorption, and C₂H₆ and C₂H₆/O₂/N₂ (2/1/37 molar ratio) pulse studies, we conclude that (i) the inclusion of halide ions in the La_1.6Sr_0.4CuO_4-δ lattice could promote lattice oxygen mobility, and (ii) the O^- species accommodated in oxygen vacancies and desorbed below 600°C favor ethane complete oxidation whereas the lattice oxygen species desorbed in the 600-700°C range are active for ethane selective oxidation to ethene. By regulating the oxygen vacancy density and Cu³⁺/Cu ratio in the K₂NiF₄-tyDe halo-oxide catalyst, one can generate a durable catalyst with good performance for the ODE reaction.