Microstructure, strength and CO ₂ separation characteristics of α -alumina supported γ -alumina thin film membrane

In this work, a mesoporous γ-Al2O3 membrane was synthesised on an α-Al2O3 substrate by a sol–gel dip coating process. The membranes were characterised using SEM, field emission SEM, X-ray diffractometry and N2 adsorption/desorption measurements (Brunauer–Emmett–Teller analyses). The characterisation results revealed that a flawless γ-alumina membrane layer with 3·5 μm thickness and 2·1 nm average pore size was achieved. Subsequent separation tests indicated that CO2 could be separated from N2 by the mesoporous γ-Al2O3 membrane. In spite of the difficulties of the separation, the optimised microstructure achieved for the prepared membrane led to desirable and regular permeation behaviour. It was also observed that separation could be more efficient in high pressure permeation conditions. The prepared substrate fulfilled the required strength and permeability for the thin γ-Al2O3 membrane film under these conditions. Accordingly, an optimised completely ceramic membrane structure, applicable for CO2 separation applications, was achieved.