Development, performance and stability of sulfur-free, macrovoid-free BSCF capillaries for high temperature oxygen separation from air

► Replacement of polysulfone with cellulose acetate avoids sulfur contamination of the BSCF structure after calcination and sintering. ► Optimization of polymer solution/suspension leads to macrovoid-free capillaries. ► Sulfur contamination affects oxygen flux and activation energy of oxygen transport mechanism. ► Oxygen flux of 0.4 mm thick, sulfur-free, macrovoid-free BSCF capillaries is mainly limited by bulk diffusion. ► Post-operation analysis reveals evidence of kinetic demixing and decomposition.