Perovskite-Type Halo-oxide La1−xSrxFeO3−δXσ (X=F, Cl) Catalysts Selective for the Oxidation of Ethane to Ethene

Abstract

The catalytic performance and characterization of perovskite-type halo-oxide La1−xSrxFeO3−δXσ (X=F, Cl) as well as La1−x SrxFeO3−δ (x=0–0.8) for the oxidative dehydrogenation of ethane (ODE) to ethene have been investigated. XRD results indicate that the catalysts had oxygen-deficient perovskite structures and TGA results demonstrated that the F- and Cl-doped perovskites were thermally stable. Under the reaction conditions of C2H6/O2/N2=2/1/3.7, temperature=660°C, and space velocity=6000 mL h−1 g−1, C2H6 conversion, C2H4 selectivity, and C2H4 yield were, respectively, 55.3, 45.1, and 24.9% over La0.6Sr0.4FeO3−0.048; 76.8,62.1, and 47.7% over La0.8Sr0.2FeO3−0.103F0.216semi; and 84.4, 68.4, and 57.6% over La0.6Sr0.4FeO3−0.103Cl0.164. Over the two halo-oxide catalysts, with an increase in space velocity, C2H6 conversion decreased, whereas C2H4 selectivity increased. Both La0.8Sr0.2FeO3−0.103F0.216 and La0.6Sr0.4FeO3−0.103Cl0.164 were durable within 40 h of onstream ODE reaction. XPS results suggested that the presence of halide ions in the perovskite lattices promotes lattice oxygen mobility. It is apparent that the inclusion of F− or Cl− ions in La1−xSrxFeO3−δ can reduce the deep oxidation of C2H4 and thus enhance C2H4 selectivity. Based on the results of O2-TPD and TPR studies, we suggest that the oxygen species that desorbed at temperatures ranging from 590 to 700°C over the La0.8Sr0.2FeO3−0.103F0.216 and La0.6Sr0.4FeO3−0.103Cl0.164 catalysts are active for the selective oxidation of ethane to ethene. By regulating the oxygen vacancy density and the oxidation states of B-site cations by implanting halide ions into oxygen vacancies in perovskite-type oxides (ABO3), one may obtain catalysts that are durable and selective for the ODE reaction.