Development of polyimide membrane for gas permeation

Abstract

Carbon molecular sieve (CMS) membranes were prepared using aromatic polyimide (P84) and polyvinylpyrrolidone (PVP) polymer blends. Spin coating of the polymer blends onto porous stainless steel substrate produced various polymeric membranes which were then pyrolysed at 400°C and 450°C under vacuum.

The characteristics of the carbon structures and the gas permeation properties of the CMS membranes were investigated in terms of the weight percentage of PVP and the final pyrolysis temperature. Scanning electron microscopy (SEM) was employed to examine the structural morphologies of the CMS membranes.

The results of this study indicated that the permeation rates of CO2 and O2 increased with the incremental content of PVP. This was due to the thermal labile PVP acting as a pore-forming agent in the CMS membranes during pyrolysis which provided an enhanced diffusional pathway through the CMS membranes for the gas molecules. Furthermore, increasing the pyrolysis temperature from 400°C to 450°C yielded increases in permeation rates of CO2 and O2. The selectivity of the CMS membranes was found to decrease with increasing weight percentage of PVP in the polymeric blend while the selectivity of the CMS membranes increased with final pyrolysis temperature.