Elaboration of La0.8Sr0.2Fe0.7Ga0.3O3−δ/La0.8M0.2FeO3−δ (M = Ca, Sr and Ba) asymmetric membranes by tape-casting and co-firing

The performance of a catalytic membrane reactor (CMR), for partial oxidation of methane, mainly depends on the oxygen semi-permeation properties of the membrane and on its architecture. This paper presents the elaboration, by tape-casting lamination and co-firing process, of a membrane consisting of a crack free La0.8Sr0.2Fe0.7Ga0.3O3−δ (LSFG8273) dense thin film supported by a porous layer. In the porous layer, gallium must be eliminated due to its cost. In order to avoid membrane cracking during the sintering and under working conditions, the material of the porous support was chosen and adapted to have the same shrinkage during the co-firing and a thermal expansion coefficient similar to the dense membrane material. Two materials fulfil these conditions: La0.8Sr0.2FeO3−δ (LSF821) and La0.8Ba0.2FeO3−δ (LBF821). Asymmetric membranes lead to an enhancement of the oxygen semi-permeation flux compared to self-supported membranes, with suitable mechanical properties in working conditions. The porous layer has a beneficial influence on oxygen semi-permeation of the membrane. At working temperature, the limiting mechanism of oxygen transport through the membrane is the oxygen surface exchanges.