Ceria Based Composite Membranes for Oxygen Separation

Mixed ionic-electronic conducting membranes for oxygen gas separation are attracting a lot of interest due to their promising potential for the pure oxygen and the syngas production. Apart from the need for a sufficiently high oxygen permeation fluxes, the prolonged stability of these membranes under the large oxygen potential gradients at elevated temperatures is decisive for the future applications.

The gadolinium doped cerium oxide (CGO) based composite membranes are considered as promising candidates due to inherent stability of CGO phase. The CGO matrix is a main oxygen ion transporter; meanwhile the primary role of a secondary phase in this membrane is to compensate the low electronic conductivity of matrix at intended functioning conditions.

In this work thin film (15-20 μm) composite membranes based on CGO matrix and LSF electronic conducting phase were fabricated and evaluated. Composite thin film was deposited on tubular structural support made of porous MgO phase. Porous CGO layers (20 μm) were implemented as backbones for catalytic phase on both sides of a composite membrane (Fig. 1). 

During initial trials, the catalytic phase free CGO/LSF composite membranes demonstrated oxygen fluxes close to 1 ml×min×cm-2 at 900 °C and the oxygen driving force of log pO₂=-2.

Issues related to processing parameters and new results on performance of these asymmetric geometry CGO/LSF composite membranes will be presented.

 Figure 1. Cross-section of asymmetric CGO-LSF composite membrane.