La0.7Sr0.3FeO3−α perovskite hollow fiber membranes for oxygen permeation and methane conversion

Abstract

Gas-tight La0.7Sr0.3FeO3−α (LSF) perovskite hollow fiber membranes were fabricated by the phase inversion/sintering technique using self-made ceramic powder. The permeation and reaction properties of the LSF membrane were investigated systematically by using He, CO2, H2 and CH4 as the sweep or reactive gas, respectively. The experimental results indicate that the cobalt-free LSF hollow fiber membrane exhibits good stability when exposed in inert gases like He and weak acid gases like CO2 but is not stable in a reducing environment. Continuous and severe segregation may occur when the LSF membrane is operated in H2 and CH4 atmosphere. The oxygen permeation rate is highly dependent on the formation rate of oxygen vacancies on the membrane sweeping side surface. Compared to He as the sweep gas, the use of CO2 restrained the oxygen permeation due to the strong chemical adsorption on the membrane surface. However, the LSF membrane still suffers from the reaction with H2 and CH4 to form porous debris on the membrane surface, which may initially promote the oxygen flux but will finally result in membrane leaking or even breakage. When using H2 or CH4 as the sweep gas, the oxygen in the air feed can be depleted completely by permeating through the membrane. Although the LSF membrane exhibits a kind of catalytic activity to the partial oxidation of methane into syngas with a maximum CO yield of 1.2%, additional catalyst is required to avoid the deep oxidation of the products so that high syngas yields can be achieved.