Enhancing oxygen permeation through hierarchically-structured perovskite membrane elaborated by freeze-casting

Abstract

[EN] Innovative asymmetric oxygen-transport membrane architectures were prepared by combining freeze-casting and film deposition techniques. Freeze-casting enabled to optimize the gas transport through the support by creating a hierarchical porosity while a dense top-layer of 30 µm was coated over this support by screen printing. The versatility of this technique was demonstrated by preparing highly porous bodies made of fast ionic conductors, e.g. perovskites and doped ceria fluorites, with a large number of applications in catalysis, electrochemistry and gas separation. Permeation tests using an all- La0.6Sr0.4Co0.2Fe0.8O3-d; asymmetric membrane proved the beneficial effect of such porous supports over the O2 fluxes with a maximum value of 6.8 ml.min-1.cm-2 at 1000 ºC, markedly above the results achieved so far with conventional preparation techniques. Gas permeance study through the porous freeze-cast support showed that the particular pore structure allows the gaseous transport resistance to be minimized. The related pressure drop is found to be very low in comparison with conventional porous supports, e.g. tape-cast supports, with for example only 0.59 bar.mm -1 with argon at 800 ºC for an inlet flow of 400 mL.min -1.cm-2. Finally, the stability of the asymmetric membrane has been evaluated under CO 2atmosphere during 48 hours and at 900ºC. The membrane is found to be stable without deactivation nor decrease in the O2 permeation flux.