Perovskite-type halo-oxide La1-xSrxFeO3-delta X sigma (X=F, Cl) catalysts selective for the oxidation of ethane to ethene

The catalytic performance and characterization of perovskite-type halo-oxid e La1-xSxFeO3-deltaXsigma (X=F, Cl) as well as La1-x SrxFeO3-delta (x = 0-0 .8) for the oxidative dehydrogenation of ethane (ODE) to ethene have been i nvestigated. XRD results indicate that the catalysts had oxygen-deficient p erovskite structures and TGA results demonstrated that the F- and Cl-doped perovskites were thermally stable. Under the reaction conditions of C2H2/O- 2/N-2 = 2/1/3.7, temperature = 660 degrees C, and space velocity = 6000 mt h(-1) g(-1), C2H6 conversion, C2H4 selectivity, and C2H4 yield were, respec tively, 55.3, 45.1, and 24.9% over La0.6Sr0.4FeO3-0.048; 76.8, 62.1, and 47 .7% over La0.8Sr0.2FeO3-0.103F0.216; and 84.4, 68.4, and 57.6% over La0.6Sr 0.4FeO3-0.103Cl0.164. Over the two halo-oxide catalysts, with an increase i n space velocity, C2H6 conversion decreased, whereas C2H4 selectivity incre ased. 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 th e presence of halide ions in the perovskite lattices promotes lattice oxyge n mobility. It is apparent that the inclusion of F- or Cl- ions in La1-xSrx FeO3-delta can reduce the deep oxidation of C2H4 and thus enhance C2H4 sele ctivity. Based on the results of O-2-TPD and TPR studies, we suggest that t he oxygen species that desorbed at temperatures ranging from 590 to 700 deg rees 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 re gulating the oxygen vacancy density and the oxidation states of B-site cati ons by implanting halide ions into oxygen vacancies in perovskite-type oxid es (ABO(3)), one may obtain catalysts that are durable and selective for th e ODE reaction. (C) 2000 Academic Press.