A BPDA-ODA polyimide film was formed on the outer surface of a porous alumina support tube (outside diameter, 2.4 mm; inside diameter, 1.8 mm; void fraction, 0.48; average pore size, 140 nm). It was imidized and then carbonized at 500–900°C. Defects usually generated during carbonization were completely avoided by optimizing temperature profiles. Carbonization above 600°C remarkably increased the permeance of He, CO2, CH4, N2, and C2H6 without losing the high permselectivity of the polyimide. The ultimate micropore volume determined by CO2 sorption was also increased to 0.36 × 10‒3 from 0.16 × 10‒3 m3, kg‒1. However, the micropore volume was not a dominant factor. The increase in permeance, which was mainly controlled by effective diffusivity of permeating species in the membrane, was dependent on pore-size distribution. The CO2 permeance and CO2/CH4 permselectivity of the carbonized membrane were 10‒7 mol•m‒2•s‒1•Pa‒1 and 100, respectively, at 30°C.
All Science Journal Classification (ASJC) codes
- Chemical Engineering(all)
- Industrial and Manufacturing Engineering