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Abstract: La0.6Sr0.4Co0.8Fe0.2O3−α (LSCF) hollow fibre membranes with an asymmetric structure consisting of a central porous layer and two dense surface layers were prepared using a mixture of 50% ethanol+50% NMP as the internal coagulant. Using the resultant hollow fibre, the influence of CO2 as the sweep gas on the oxygen permeation behavior of the LSCF membranes has been investigated. The membranes before and after permeation test were characterized by XRD, SEM and EDX. The oxygen permeation fluxes of the LSCF membrane decreased with increasing the CO2 concentration in sweep gas. The significant poisoning effect of CO2 on the oxygen permeation through the LSCF perovskite membranes was mainly due to the chemical adsorption of CO2 to the membrane surface with a result that the oxygen vacancy sites were occupied by the oxygen atoms of CO2. The reaction between the LSCF membrane material and the adsorbed CO2 to form carbonates caused Sr segregation and corrosion on the membrane surface during the permeation process. Operated in pure CO2 as sweep gas for more than 100h at 900°C or above, the LSCF hollow fibre still displayed a stable performance. Although some areas of the membrane have been etched with a thickness about 1.4μm, no sign of membrane collapsing or failure exists. [Copyright &y& Elsevier]

Abstract: BaCe0.95Tb0.05O3−δ (BCTb) proton conducting perovskite powders were first synthesized via an EDTA–CA complexing method. Ni–BCTb cermet membranes were then fabricated by pressing a mixture of the BCTb and Ni powders in a weight ratio of 1:1 at 10MPa, followed by sintering at 1400°C for 10h. The properties of the BCTb powders and the Ni–BCTb membranes were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and conductivity measurement using a 4-probe method. The electrical conductivity of the Ni–BCTb membranes approaches to 400Scm−1 at room temperature but decreases with increasing temperatures. The maximum hydrogen permeation flux through the asymmetric Ni–BCTb membrane with a 90μm separation top layer integrated with a porous substrate has reached up to 0.914mL(STP)cm−2 min−1 at 850°C when using the 50% H2/N2 mixture feed and He as the sweep gas, respectively. The surface exchange reaction kinetics takes a controlling effect on the hydrogen permeation through the membrane. The long-term operation test indicates that the Ni–BCTb cermet membranes are not sufficiently stable for hydrogen permeation due to the phase decomposition of the BCTb perovskite. [Copyright &y& Elsevier]