Design of asymmetric multilayer membranes based on mixed ionic–electronic conducting composites supported on Ni–Al foam substrate

This paper presents the results of research aimed at design of multilayer asymmetric oxygen separation membranes comprised of functionally graded by composition and porosity nanocomposite layers with mixed ionic–electronic conductivity (MIEC) and a high oxygen mobility supported on the compressed Ni–Al alloy foam substrate. Complex oxides with fluorite-like structure (Ce0.9Gd0.1O2−δ), perovskite-like structure La0.8Sr0.2Fe1−xNixO3−δ (x = 0.3–0.4) and spinel structure MnFe2O4 synthesized via polymerized precursors (Pechini) route were used for the preparation of these nanocomposites by ultrasonic dispersion of their mixtures in isopropanol with addition of polyvinyl butyral. Parameters characterizing their oxygen mobility and reactivity were estimated by oxygen isotope heteroexchange, weight loss transients, temperature-programmed reduction by CH4 and reoxidation by CO2. Membranes were prepared by successively supporting on one side of substrate macroporous–mesoporous–microporous-dense layers of MIEC nanocomposites finally covered by a porous layer of La–Ni–Pt/Pr0.3Ce0.35Zr0.35O2−x catalyst. Preliminary tests of this membrane in the lab-scale reactor in the process of methane selective oxidation/oxi-dry reforming into syngas demonstrated their oxygen permeability and performance promising for the practical application.