Study of CO₂ permeation in Zn²⁺‐modified Al₂O₃‐carbonate membrane

Abstract

Molten carbonate-based membranes for CO 2 capture have received attentions because of their high CO 2 selectivity, potential energy-saving capability and environmental friendliness. Zn 2+ -modified Al 2 O 3 /carbonates membranes with the enhanced CO 2 permeability have been developed in this work. Interfaces of LiAlO 2 were formed on the surface of Al 2 O 3 due to the carbonates incorporation. Microstructural and interfacial characterisation of the membrane revealed that the outermost LiAlO 2 layer was due to the reactions between Li 2 CO 3 and ZnAl 2 O 4 , resulting in the dissolution of ZnO in the molten carbonate. CO 2 permeability of 0.5% ZnAl 2 O 4 /Al 2 O 3 /carbonates reached 9.12 × 10 −12 mol.m −1 s −1 Pa −1 at 700 • C, higher than that of Al 2 O 3 /carbonates, because of the dissolved ZnO. With the increase of ZnAl 2 O 4 , CO 2 permeability was decreased. The dissolved ZnO in the molten carbonates could enhance the ionic conductivity, whereas a higher amount of ZnO than its solubility will attenuate its effects on CO 2 permeation.