Preparation, characterization and microstructural optimization of a thin γ-alumina membrane on a porous stainless steel substrate

In this work, a supported mesoporous (MEP) γ-Al2O3 membrane was synthesized on conventional α-Al2O3 substrates by sol–gel dip coating process. In the following, the preparation of a novel metallic–ceramic composite membrane was studied, which incorporated desirable properties of both ceramic membrane and porous metallic substrate. For this purpose, mesoporous alumina membrane layer was developed on a porous 316L stainless steel substrate. The substrate was prepared by loose powder sintering and modified by soaking–rolling and fast drying method. The prepared membranes were characterized using scanning electron microscope (SEM), field emission scanning electron microscope (FESEM), X-ray diffractometer (XRD) and N2-adsorption/desorption measurements (BET analyses). The results revealed that a defect-free γ-alumina membrane with 2.1 nm average pore size can be produced. Permeation tests with N2 gas revealed that the stainless steel substrate had 40 times more permeability than conventionally used alumina support. Additionally, single gas permeation of γ-alumina membrane for CO2 and N2 was compared. It was observed that CO2 could be separated from N2 by the MEP γ-Al2O3 membrane in high pressure permeation condition, where stainless steel presents superior mechanical strength than alumina as a substrate.