Carbon molecular sieve membranes derived from thermally labile polymer containing blend polymers and their gas separation properties

Carbon molecular sieve (CMS) membranes were prepared by controlled pyrolysis of polyimide (PI)/polyvinylpyrrolidone (PVP) blends. The average d-spacing values calculated from wide-angle X-ray diffraction data were significantly increased with the amount of PVP. The pyrolytic CMS membranes showed the type I isotherm according to IUPAC classification from the nitrogen adsorption isotherm. From pure gas permeation experiments using He, CO2, O2, and N2, it was found that the existence of a thermally labile phase significantly affected the gas permeation performance of the final CMS membranes. The gas permeabilities through the CMS membranes were enhanced by the introduction of thermally labile polymer (PVP) and decreased as the final pyrolysis temperature increased. The CMS membrane derived from PI containing 10 wt.% PVP and pyrolyzed at 550 °C showed maximum gas permeability for O2 of 630 Barrers and O2/N2 selectivity of 10. For a CMS membrane pyrolyzed at 700 °C derived from a precursor containing 10% PVP, the gas permeability for O2 was 230 Barrers and O2/N2 selectivity was 14.