Assessment of CO2 stability and oxygen flux of oxygen permeable membranes

Oxygen permeation measurements on Ba0.5Sr0.5Co0.8Fe0.2O3-? (BSCF), SrCo1-xNbxO3-? (SCN; x=0.1, 0.2), Sr(Co0.8Fe0.2)1-yTiyO3-? (SCFT; y=0.1, 0.2, 0.4), La2NiO4 (L2N), Ca0.5Sr0.5Fe0.2Mn0.8O3-? (CSFM) and the dual phase material Ce0.8Sm0.2O1.9+Ag (CS+Ag) were carried out using CO2/N2 mixtures as sweep gas. A breakdown of the O2 permeation was observed for BSCF and SCN even at low CO2 concentrations. A protective layer of Ce0.8Gd0.2O1.9 on BSCF shifts the permeation breakdown to higher CO2 concentrations but was insufficient for pure CO2 sweep. SCFT samples show a stable O2 permeation with CO2 sweep, but only at temperatures of at least 900°C. The O2 permeation for CO2 sweep drops down with time, especially at lower temperatures. The time dependency was fitted by a logarithmic regression to predict the total loss of the O2 permeation. An excellent stability against CO2 was found only for L2N, CSFM and Cs+Ag. However, the O2 permeation values amounted to less than one order of magnitude below BSCF.