Effects of polymer binders on separation performance of the perovskite-type 4-bore hollow fiber membranes

Most perovskite oxides are commonly recognized as less tolerance to sulfur and sulfur-containing species. In a hollow fiber fabrication, polymer binders (sulfur-containing polyether sulphone (PES) and sulfur-free polyetherimide (PEI)) are expected to have different impacts on the membrane performance in terms of both permeability and stability. In this study, BaCo_0.7Fe_0.22Nb_0.08O_3-δ (BCFN) 4-bore hollow fibers using PES and PEI as binders were prepared by a phase inversion and sintering technique. The sintering behavior, mechanical strength, crystal structure, morphology, composition, oxygen permeation and long-term stability were investigated systematically. Formation of sulfate was identified on the surface and in the bulk of the membrane fabricated via the PES route. The sulfur poisoning was confirmed taking place during not only the sintering stage but also the operation stage. The sulfur-containing PES contributed to a lower oxygen permeation flux than the sulfur-free PEI and also a severe degradation of permeation flux that there was more than 65% decrease over the original value within the first 100 h at 650 °C. Membrane fabricated via the PEI route can operate for more than 300 h without obvious degradation.