A Comparative Study of the Performance of Symmetric and Asymmetric Mixed-conducting Membranes

According to the configuration, mixed-conducting membranes are classified as symmetric membranes and asymmetric membranes consisting of a thin dense layer and a porous support. In this study, these two kinds of SrCo_0.4Fe_0.5Zr_0.1O_3-δ oxide-based membranes were systematically compared in terms of oxygen permeability and chemical stability, and their differences were elucidated by means of the theoretical calculation. For the oxygen permeability, the asymmetric membrane was greater than the symmetric membrane due to the significant decrease of bulk diffusion resistance in the thin dense layer of the asymmetric membrane. In regard to the chemical stability, the increase of oxygen partial pressure on the asymmetric membrane surface at CH₄ side produced the stable time of over 1032 h in partial oxidation of methane at 1123 K, while the symmetric membrane was only of 528 h. This study demonstrated that the asymmetric membrane was a promising geometrical configuration for the practical application.