Investigation Of Novel Inorganic Membrane Material With High Oxygen Permeation And Stability

Inorganic dense oxygen permeation membrane is ceramic membrane, which has a mixed oxygen ionic and electronic conductivity. The membrane can separate oxygen with 100% selectivity, without additional electronic power. Because of their potential applications in separating oxygen from air or involving oxygen reaction, inorganic dense oxygen permeation membranes have attracted much attentions. In order to practical applications, the inorganic dense oxygen permeation membrane should not only have the high oxygen permeability, but also have excellent structural stability. However, as far as now, the high oxygen permeation flux and excellent structural stability are traded off. When the inorganic dense oxygen permeation membrane has a high oxygen permeation flux, it often corresponds to a poor structure stability, and vice versa. In order to solve the problem, we design and develop a novel membrane material, and apply them in methane partial oxidation and combustion reaction.(1) Through bifunctional doping, we design a novel Ba Bi0.05Co0.8Ta0.15O3-δ membrane, which have high oxygen permeation and excellent structural stability. At 950 oC, the oxygen permeation of 0.5 mm disk membrane can reach 3.57 ml/min.cm2, showing a high oxygen permeability. Meanwhile, the oxygen permeation flux of disk membrane maintains 2.2 ml/min.cm2 without any decrease during 280 h operation. The results of XRD and SEM indicate that the spent membrane still keeps perovskite structure, which can prove the feasibility of bifunctional doping. We provide a new idea for designing material.(2) We design a novel A-site deficient membranes based on(Pr0.9La0.1)1.9(Ni0.74Cu0.21Ga0.05)O4+δ using the defect theory. The oxygen permeation flux is improved obviously, from 0.35 ml/min.cm2 to 0.83 ml/min.cm2. Also, the deficient(Pr0.9La0.1)1.9(Ni0.74Cu0.21Ga0.05)O4+δ membrane excellent structural stability, although at the intermediate temperature. A stable oxygen permeation flux of 0.25, 0.13, 0.07 ml/min.cm2 is achieved during 285 h at 800, 775 and 750 oC without any decay, which showed reasonable stable structure.(3) Dense U-shaped Ba Co0.7Fe0.2Ta0.1O3-δ hollow-fiber membranes are prepared through a phase inversion spinning process. The result of thermal cycling performance proves the feasibility of U-shaped, which can effectively avoid the damage of the membrane at varying temperatures. Meanwhile, the oxygen permeation improved obviously. At 975 oC, the oxygen permeation of U-shaped Ba Co0.7Fe0.2Ta0.1O3-δ hollow-fiber membranes can reach 7.73 ml/min.cm2 under air/He atmosphere. During 250 h operation, the oxygen permeation flux of membrane maintains 4.26 ml/min.cm2 without any decrease.(4) The U-shaped Ba Co0.7Fe0.2Ta0.1O3-δ hollow-fiber membrane reactor was constructed for partial oxidation of methane(POM) successfully. At 875 oC, the oxygen permeation flux of U-shaped Ba Co0.7Fe0.2Ta0.1O3-δ hollow-fiber membrane reactor can reach 20 ml/min.cm2, with 96% methane conversion and 99% CO selectivity.(5) The U-shaped Ba Co0.7Fe0.2Ta0.1O3-δ hollow-fiber membrane reactor was constructed for combustion reaction of methane successfully. At 975 oC, the oxygen permeation flux of U-shaped Ba Co0.7Fe0.2Ta0.1O3-δ hollow-fiber membrane reactor can reach 2.2 ml/min.cm2, with 100% methane conversion and 100% CO2 selectivity, which shows an excellent properties.