Preparation of dense La0. 5Sr0. 5Fe0. 8Cu0. 2O3− δ–(Li, Na) 2CO3–LiAlO2 composite membrane for CO2 separation

Dense La0.5Sr0.5Fe0.8Cu0.2O3−δ–(Li,Na)2CO3 and La0.5Sr0.5Fe0.8Cu0.2O3−δ–(Li,Na)2CO3–LiAlO2 composite membranes were prepared for CO2 separation. The La0.5Sr0.5Fe0.8Cu0.2O3−δ (LSFCu) was prepared via the combined EDTA–citrate complex sol–gel process according to a previous study and then used in the synthesis of the dual phase membrane. XRD characterisation of the La0.5Sr0.5Fe0.8Cu0.2O3−δ sample showed it is orthorhombic structure with space group , a=5.4784(5) Å, b=7.7456(7) Å, c=5.5014(5) Å, and V=233.44(4) Å3.

Dense composite membrane was obtained after carbonate treatment. Mixed CO2/N2, CO2/O2 and CO2/air gases were used for CO2 permeation experiments. At 750 °C, high CO2 permeation rate of 1.55 ml cm−2 min−1 was observed for the LSFCu–(Li,Na)2CO3–LiAlO2 composite membrane when 20% CO2/80% O2 mixture was used as the feed gas. Introduction of ~10 wt% LiAlO2 in the oxide–carbonate composite results in increased CO2 permeation rates which is likely due to the enhancement in surface reaction.

The dominant pathway for CO2 permeation in the LSFCu–(Li,Na)2CO3–LiAlO2 composite membrane was believed through the coherent interaction between O2− and ions. Increased oxygen partial pressure in the feed gas can facilitate CO2 permeation. Due to the low O2 concentration in real flue gases, potentially the LSFCu–(Li,Na)2CO3–LiAlO2 dual phase membrane will separate CO2 only which provides an alternative technology for CO2 separation.