YBa2Cu3O7-delta X sigma (X = F and Cl): Highly active and durable catalysts for the selective oxidation of ethane to ethene

摘要

The catalytic performance and characterization of YBa2Cu3O7-delta and YBa2Cu3O7-deltaXsigma for the oxidative dehydrogenation of ethane (ODE) to ethene have been investigated. Under the reaction conditions of temperature = 680 degrees C, C2H6/O-2/N-2 molar ratio = 2/1/3.7, and contact time = 1.67 x 10(-4) h g ml(-1), YBa2Cu3O7-0.21F0.16 showed 84.1% C2H6 conversion, 81.8% C2H4 selectivity, and 68.8% C2H4 yield; YBa2Cu3O7-0.18Cl0.13 showed 92.5% C2H6 conversion, 72.0% C2H4 selectivity, and 66.6% C2H4 yield. The sustainable performance during a period of 40 h on-stream reaction at 680 degrees C demonstrated that the F- and Cl-doped catalysts are durable. X-ray powder diffraction results indicated that the undoped YBa2Cu3O7-delta and halide-doped YBa2Cu3O7-deltaXsigma were of triple-layered oxygen-deficient perovskite-type orthorhombic structure. The results of the X-ray photoelectron spectroscopy, thermal treatment, thermogravimetric analysis, and O-18(2)-pulsing studies indicated that the incorporation of halide ions into the YBa2Cu3O7-delta lattice enhanced the activity of lattice oxygen. According to the O-2 temperature-programmed desorption and temperature-programmed reduction results, we conclude that the oxygen species desorbed at 610-710 degrees C are active for the selective oxidation of ethane and those desorbed below 610 degrees C are active for the total oxidation of ethane; a suitable oxygen nonstoichiometry and Cu3+ concentration in YBa2Cu3O7-deltaXsigma, are required for the best catalytic performance of the catalysts. (C) low Academic Press. [References: 78]