CO2-stable and cobalt-free Ce0.8Sm0.2O2-δ-La0.8Ca0.2Al0.3Fe0.7O3-δ dual-phase hollow fiber membranes for oxygen separation

Abstract

In this work, 60 wt% Ce0.8Sm0.2O2-δ-40 wt% La0.8Ca0.2Al0.3Fe0.7O3-δ (SDC-LCAF) dual-phase oxygen permeable hollow fiber membrane precursors were prepared via a combined sol–gel and phase inversion technique. Dual-phase SDC-LCAF hollow fiber membrane with compatible fluorite and perovskite phases was obtained after sintering at 1450 °C. The chemical compatibility, thermal expansion, conductivity, oxygen permeation, CO2 tolerance, and short-term regenerative durability regarding the phase structure and composition were systematically studied. The oxygen flux of the SDC-LCAF dual-phase membrane was significantly increased compared to that of LCAF single phase membrane. At 950 °C, the oxygen flux of the SDC-LCAF hollow fiber membrane reached 1.84 mL min−1 cm−2 when both the He sweep and the air feed flow rates were 100 mL min−1, and the dual-phase membrane exhibited stable oxygen permeation fluxes in pure CO2 atmosphere. When pure CO2 was used as the sweep gas in a 225-h short-term stability test, the oxygen permeation fluxes decreased slightly because of the inhibiting effect of CO2 on oxygen surface-exchange reaction. Nevertheless, the ability of the SDC-LCAF membrane to recover the original oxygen permeation performance indicated that the membrane surface did not react irreversibly with CO2. The CO2 stability was not reflected in the LCAF single phase membrane, thus indicating the superior membrane stability following the incorporation of the SDC phase.