Synthesis, Oxygen Permeation, and CO2-Tolerance Properties of Ce0.8Gd0.2O2-δ-Ba0.95La0.05Fe1-xNbxO3-δ Dual-Phase Membranes

A series of CO2-tolerant dual-phase dense oxygen permeable membranes of stoichiometry Ce0.8Gd0.2O2-delta-Ba0.95La0.05Fe1-xNbxO3-delta (CG-BLF1-xNx, x = 0, 0.025, 0.05, 0.10, and 0.15) were designed and prepared by the sol-gel method. Their stability regarding phase composition and structure, oxygen permeability, and CO2-tolerant property were investigated by X-ray diffraction (XRD), thermogravimetry and differential scanning calorimetry (TG-DSC), and temperature-programmed desorption of oxygen (O-2-TPD). Results of the materials characterization showed excellent chemical compatibility between CG and BLF1-xNx without the formation of any impurity phase after sintering at 1200 degrees C in air. The oxygen-permeation experiments showed that with increasing niobium content, the oxygen permeability of the CG-BLF1-xNx membranes decreased slightly, but the compositional and structural stability in CO2 atmosphere improved significantly. The 60 wt % CG-40 wt % BLF0.9N0.1 membrane showed simultaneously good oxygen permeability and excellent CO2 tolerance, and the oxygen-permeation flux reached 0.195 mL.cm(-2).min(-1) in pure CO2 atmosphere at 925 degrees C using a 1.0 mm thick membrane. This work demonstrates that CG-BLF1-xNx dual-phase membranes have great application potential for separating oxygen from highly concentrated CO2 atmosphere.