CO2-tolerant alkaline-earth metal-free single phase membrane for oxygen separation

A novel CO2-tolerant alkaline-earth metal-free single phase membrane based on (Nd0.9La0.1)2Ni0.74Cu0.21Ga0.05O4+δ (NLNCG) was successfully prepared though a sol-gel route. The oxygen permeation and the stability of the NLNCG under CO2 are investigated in detail. At 975 °C, when helium is used as the sweep gas, the oxygen permeation flux of 0.53 ml/min cm2 (STP) is obtained. When the sweep gas is changed from helium to CO2, the oxygen permeation flux is reduced to 0.48 ml/min cm2 (STP). Only a slight decrease of the oxygen permeation flux through the NLNCG membrane is observed. During the 420 h operation with CO2 as the sweep gas at 975 °C, a steady oxygen permeation flux through the NLNCG membrane of 0.53 ml/(min cm2) is obtained. From XRD and SEM characterizations, it is found that the spent membrane still maintains the perfect K2NiF4-type phase structure and intact microstructure without any carbonate indicating that the NLNCG membrane shows an excellent stability under CO2 atmosphere.