The enhanced catalytic performance of Mg2+-doped CuCr2O4 catalyst in ethane oxychlorination

Abstract

A series of novel spinel oxide catalysts, Cu1−xMgxCr2O4 (x = 0, 0.2, 0.4, 0.6, 0.8, and 1), for the ethane oxychlorination catalytic reaction were prepared by a sol–gel method, and X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Brunauer–Emmett–Teller, H2 temperature-programmed reduction, O2 temperature-programmed desorption, and X-ray photoelectron spectroscopy were used to characterize the catalysts. It was found that the enhanced catalytic performance could be attributed to A-site doping of Mg2+ in the CuCr2O4 catalysts. The addition of Mg2+ changes the preferred orientation of the crystal from CuCr2O4 (0 2 0) to Cu0.6Mg0.4Cr2O4 (1 2 1) and leads to lattice distortions and more surface defect oxygen species in Cu0.6Mg0.4Cr2O4. The Cu0.6Mg0.4Cr2O4 catalyst shows optical catalytic performance for ethane oxychlorination, with an average ethane conversion of 95.6% and a vinyl chloride selectivity of 50.2%. Density functional theory results showed that the Cu0.6Mg0.4Cr2O4 catalyst would enhance the adsorption ability of the crystal (1 2 1) plane for C2H6, C2H3Cl, and C2H4. C2H3Cl is preferentially desorbed in the conversion of reactant C2H6 on the (1 2 1) plane. It is evident that the difference in electron density between C2H3Cl and C2H4 on the planes contributes to the improvement of Cu0.6Mg0.4Cr2O4 selectivity.