Preparation and characterization of Al2O3 hollow fiber membranes

α-Al2O3 hollow fibers were prepared by a phase-inversion method combined with the reaction bonded aluminum oxide (RBAO) process. Next, γ-Al2O3 membranes, which were fabricated by a sol-gel process, were cast on the outer surface of the hollow fiber supports. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), nitrogen isothermal absorption measurements and gas permeability testing were used to characterize the supports and γ-Al2O3 membranes. The results showed that the mechanical strength of hollow fiber supports is better than that of non-RBAO hollow fiber, and their porosity and mean pore size were 50.1% and 0.88 μm, respectively. SEM images of γ-Al2O3 membranes showed that the membranes were defect-free. The most concentrative pore diameter and the specific surface area of γ-Al2O3 membranes were about 4.5 nm and 228.9 m2/g, respectively. Gas permeability tests suggested that the γ-Al2O3 membranes possessed gas selectivity, and the separation factor for N2/Ar are 1.133 at 0.3 MPa and 1.139 at 0.4 MPa, respectively, which is slightly smaller than the value expected from the ideal Kundsen diffusion (α = 1.194).