CO₂-tolerant oxygen-permeable perovskite-type membranes with high permeability

There is a desire for CO₂-tolerant oxygen-permeable membranes for CO₂ capture based on the oxyfuel process. Here we report a general doping strategy for developing CO₂-tolerant SrFeO_3-δ-based oxygen-permeable membranes. To combine excellent CO₂ tolerance and high permeability, two novel CO₂-tolerant oxygen-permeable membranes of SrFe_0.9Ta_0.1O_3-δ (SFT) and SrFe_0.8Sb_0.2O_3-δ (SFS) have been developed based on this doping strategy. Both SFT and SFS oxides possessed high phase stability especially in a pure CO₂ atmosphere for 96 h at 1173 K. The high CO₂-tolerant properties were mainly associated with high acidity, high valence and appropriate ionic radius of the Ta or Sb cation and high average metal bond energy of SFT or SFS oxide. Both SFT and SFS disk membranes (1 mm-thick) with low oxygen permeation activation energies exhibited high oxygen permeation fluxes of 0.3 and 0.22 ml min^-1 cm^-2, respectively, which were unchanged during the long-term operation (130 h) under air/CO₂ gradient at 1173 K. Furthermore, the highest oxygen permeation flux of 1.15 ml min^-1 cm^-2 through the SFT multichannel hollow fiber (MHF) membrane at 1173 K under air/CO₂ gradient can meet the requirement of commercial application in the oxyfuel process. The present results would give guidance for the design of CO₂-tolerant SF-based membranes.