Thermochemically stable ceramic composite membranes based on Bi2O3 for oxygen separation with high permeability

Abstract

Ceramic oxygen separation membranes can be utilized to reduce CO₂ emissions in fossil fuel power generation cycles based on oxy-fuel combustion. State-of-the-art oxygen permeable membranes based on Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3−δ (BSCF) offer high oxygen permeability but suffer from long-term instability, especially in the presence of CO₂. In this work, we present a novel ceramic composite membrane consisting of 60 vol% (Bi_0.8Tm_0.2)₂O_3−δ (BTM) and 40 vol% (La_0.8Sr_0.2)_0.99MnO_3−δ (LSM), which shows not only comparable oxygen permeability to that of BSCF but also outstanding long-term stability. At 900 °C, oxygen fluxes of 1.01 mL min⁻¹ cm⁻² and 1.33 mL min⁻¹ cm⁻² were obtained for membranes with thicknesses of 1.35 mm and 0.75 mm, respectively. Moreover, significant oxygen fluxes were obtained at temperatures down to 600 °C. A stable operation of the membrane was demonstrated with insignificant changes in the oxygen flux at 750 °C for approx. one month and at 700 °C with 50% CO₂ as the sweep gas for more than two weeks.