Catalysis Letters, Vol.67, No.2-4, 183-192, 2000
Halogenated La1.6Sr0.4CuO4 catalysts active for ethane selective oxidation to ethene
The catalytic performances and characterization of the catalysts La1.6Sr0.4CuO3.852, La1.6Sr0.4CuO3.857F0.143, and La1.6Sr0.4 CuO3.856Cl0.126 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 La1.6Sr0.4CuO4-delta 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 La1.6Sr0.4CuO3.857F0.143 and 79.6% C2H6 conversion, 74.6% C2H4 selectivity, and 59.4% C2H4 yield over La1.6Sr0.4CuO3.856Cl0.126 under the reaction conditions of C2H6/O-2/N-2 molar ratio 2/1/3.7, temperature 660 degrees C, and space velocity 6000 ml h(-1) g(-1). With the rise in space velocity, C2H6 conversion decreased, whereas C2H4 selectivity increased. Life studies showed that the two catalysts were durable within 60 h of on-stream ODE reaction. Based on the results of X-ray photoelectron spectroscopy, O-2 temperature-programmed desorption, and C2H6 and C2H6/O-2/N-2 (2/1/3.7 molar ratio) pulse studies, we conclude that (i) the inclusion of halide ions in the La1.6Sr0.4CuO4-delta lattice could promote lattice oxygen mobility, and (ii) the O- species accommodated in oxygen vacancies and desorbed below 600 degrees C favor ethane complete oxidation whereas the lattice oxygen species desorbed in the 600-700 degrees C range are active for ethane selective oxidation to ethene. By regulating the oxygen vacancy density and Cu3+/Cu ratio in the K2NiF4-type halo-oxide catalyst, one can generate a durable catalyst with good performance for the ODE reaction.
Keywords:ethane oxidative dehydrogenation;C2H4 generation;ODE reaction;K2NiF4-type halo-oxide catalyst;La1.6Sr0.4CuO4-delta X sigma (X = F;Cl);XPS characterization;superconducting cuprate material