Perovskite membranes oxygen flux

Table 4.1 Comparison of oxygen permeation performance of BSCF5582 membranes in different geometries with other most studied A Sr, ByCo 0 i based perovskite membranes. All flux values and sweep gas flow rates are quoted at standard temperature and pressure (STP) s C) ... 

As noted before, the membrane performance could be affected by the presence of H2O, CO2 or other volatile hydrocarbons in the gas phase of both compartments. As laid down in patent literature [1-3], the oxygen fluxes through Mg-, Ca-, Sr-, and Ba-doped perovskites deteriorated over time, roughly 30-50% over a time period of about 100 h, if the air used as feed gas contained several percent of H2O and amounts of CO2 on a hundreds of ppm level. It was claimed, that either no deterioration is found or the fluxes can be restored to their initial values if the temperature is raised above certain critical values, 500°C for magnesium, 600°C for calcium, 700°C for strontium and 810°C for barium. Though no explanation was given, it is possible that carbonate formation took place. One may further note that the tendency for carbonate formation increases at lower temperatures. 

A SEM micrograph of a co-sintered multilayer reactor is presented in Fig. 6.8 no delamination or interfacial reaction can be observed on the membrane. These co-sintered multilayer reactors, only based on perovskite materials, present higher oxygen flux than dense 1 mm thick membranes in an air/argon gradient. 

With optimized perovskite compositions even much higher fluxes in the range of 6 to 7 cm /cm min could be obtained recently [306]. The oxygen flux is not a linear inverse relationship to membrane thickness, because for thin membranes (about 0.3 mm) surface reactions become rate limiting. But even... 

A material for which the chemical stability in the presence of CO2 and SO2 has been extensively studied is BSCF, as it is one of the membrane materials with the highest flux. The presence of CO2 causes a reversible decline in oxygen flux. Even at concentrations of 500 ppm CO2 (ambient air), a slight decrease in the oxygen permeation rate is observed [34]. This decrease is caused by the formation of carbonates of alkaline earth metals on the exposed surface of the membrane. The carbonate formation of perovskite materials AB03 g in the presence of CO2 can be expressed as follows [72] ... 

Luo, H.X., Wei, Y.Y., Jiang, H.Q. et al. (2010) Performance of a ceramic membrane reactor with high oxygen flux Ta-containing perovskite for the partial oxidation of methane to syngas. Journal of Membrane Science, 350, 154-160. 

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