PREPARAÇÃO DE MEMBRANAS A BASE DE PEROVSKITAS PARA A OXIDAÇÃO PARCIAL DO METANO

• Autor(a) principal: Souza, Helena Prudêncio de
• Data de Publicação: 2006
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal Fluminense (RIUFF)
• Texto Completo: https://app.uff.br/riuff/handle/1/20962
• topic: Membrana seletiva ao oxigênio: Condução do oxigênio, Perovskita, Reação de oxidação parcial do metano.; Metano; Oxidação; Reação de oxidação; Selective membrane to the oxygen; Conduction of the oxygen, Perovskita, Reaction of partial oxidation of the methane; CNPQ::CIENCIAS EXATAS E DA TERRA::QUIMICA::QUIMICA ORGANICA

The partial substitution of A site cations by La on the membranes Sr1-xAxCo0,5FeO3-? with x= 0,0; 0,2 and 0,6 were prepared by solid-state reaction and combustion synthesis. The membranes were characterized by d by X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) and were examine the evolution of the membrane under the reactor conditions of the partial oxidation of methane. The powders membrane showed sodium carbonate, a perovskite phase (SrFe1--xCoxO3-?), intergrowth (Sr4Fe6-xCoxO13-?) and spinel phase (Fe,Co3O4) with variations. The membrane SrCo0,5FeO3-? prepared by solid-state reaction, the interface (Sr4Fe6-xCoxO13-?) is the dominant phase along with appreciable amount of perovskite phase (SrFe1--xCoxO3-?). The particle size of the powder increased on the membrane with ligant glycol poly etilene a 1150oC/2h. The scanning electron microscope (SEM) with an energy dispersive spectrometer (EDS) the membrane SrCo0,5FeO3-? (SCF-OS) showed perovskite phase SrCoxFe1-xO3-?, for the x<0,5 correspond of the spherical grains and plate-like grains Sr4Fe6O13+? . Under the reactor conditions of the partial oxidation of methane the membrane showed low conversion and high selectivity CO2. The interface phase didn t avoid a cobalt reduction, hence didn t promote the partial oxidation of methane. The membrane prepared by combustion synthesis, SrCo0,5FeO3-? (SCFCS) were sintered to dense at 1150oC/2h, with ligant glycol poly etielene. The phase dominant was perovskite SrFeO3-? that through a scanning electron microscope (SEM), corresponding the spherical grains and the plate-like grains Sr4Fe6-xCoxO13+? for x=2, an intergrowth. The cobalt in the intergrowth decrease when the membrane under conditions of the partial oxidation of methane. The substitution of La for Sr in the membrane Sr1-xAxCo0,5FeO3-?, for x=0,2 e 0,6 de La only occurred independent of the lanthanum concentration and looked with transformation intergrowth for the perovskite phase.The increase in x avoids the high cristalinity of the perovskite phase, without need the higher temperature. On the membranes with x=0,2 for the La the composition of the spherical grains were LaxSr1-xFeO3-? and plate-like grains Sr4-xLaxFe4Co2O13+? for x<0,8. In the solid state reaction and combustion the membrane with x=0,6, the spherical grains was LaxSr1-xFeO3-? and plate-like grains Sr4-xLaxFe4Co2O13+? for x<2,4. The conversion in the membranes with La was low and selectivity CO2 showed alter with reaction time. Only with x=0,6 of the La didn t contribute membrane, in the partial oxidation catalytic of the methane reaction. Generally, the substitution Co by Fe occurred in the part iron oxides, membranes with La avoided a reduction of the cobalt that didn t contribute for the partial oxidation catalytic of the methane reaction.