Oxygen permeation properties of novel BaCo0.85Bi0.05Zr0.1O3−δ hollow fibre membrane

Abstract

In this work, we characterized and tested the oxygen permeation properties of BaCo 0.85 Bi 0.05 Zr 0.1 O 3-d (BCBZ) hollow fibre membranes fabricated by a combined phase inversion for spinning and sintering route using polyetherimide (PEI) as the polymer binder. The powder X-ray diffraction results showed that the BCBZ powder for spinning had to be calcined at around 950 °C to form a hexagonal phase structure, while the hollow fibre precursors were sintered at 1150–1200 °C to form the cubic perovskite structure for oxygen permeation. It displayed the highest oxygen flux of 7.3 cm 3 (STP) cm -2 min -1 at 950 °C under an air/He gradient. The theoretical correlation of the oxygen fluxes at different operating conditions showed that the oxygen permeation through BCBZ fibre was limited by surface exchange reactions. Carbon dioxide (CO 2 ) resistance of BCBZ hollow fibre was tested by exposing it to alternating different sweep gas containing helium (He), 20% CO 2 in He, 80% CO 2 in He, and pure He. Despite the significant reduction in oxygen fluxes upon subjected to CO 2 -containing sweep gases due to the strong CO 2 sorption on the membrane surface, no permanent damage on the membrane was detected and the original flux could be recovered at the end of the 105-h test once the sweep gas was switched back to helium. This result clearly highlights the high CO 2 resistance of BCBZ hollow fibre membrane due to the presence of Zr 4+ with higher acidity than Co 2+ in BCBZ perovskite lattice. High CO 2 tolerance enables the membrane use as membrane reactors for more advanced applications where the presence of CO 2 -containing atmosphere is unavoidable.