Preparation of LSCF ceramic hollow-fiber membranes for oxygen production by a phase-inversion/sintering technique

A mixed oxide-electron conducting ceramic, La0.6Sr0.4Co0.2Fe0.8O3-alpha (LSCF), hollow-fiber membrane was prepared by a combined phase-inversion/sintering technique. The hollow-fiber membrane precursor was first spun from a starting solution containing 66.33 wt % LSCF powder, 6.63 wt % PESf binder, 0.5 wt % PVP additive, and 26.54 wt % NMP and then sintered at elevated temperatures between 1100 and 1280degreesC for 4 h to obtain membranes with a gastight property. The hollow-fiber membranes prepared show an asymmetric structure in which a spongelike material is sandwiched by fingerlike structures located at the outer and inner walls of the fibers. Oxygen permeation fluxes through the hollow-fiber membranes were measured under different temperatures and downstream oxygen partial pressures. The results indicated that the oxygen flux obtained from the hollow-fiber membrane is higher than that obtained from conventional LSCF disk-shaped or tubular membranes, most probably because of the reduced thickness and porous inner surface of the membranes prepared. The operating temperature plays a more important role in determining the oxygen permeation flux of LSCF membranes. Once the operating temperature is over 700degreesC, the oxygen permeation flux increases sharply as a result of an order-disorder transition of the oxygen vacancies.