ABSTRACT
This chapter reviews carbon molecular sieve (CMS) membranes as a promising material for use in gas separation processes. Polymers such as cellulose derivatives, polyacrylonitrile, polyimides, phenolic resins, polyfurfuryl alcohol, polyvinylidene chloride and polyphenylene oxide have been used as precursors to produce CMS membranes. Kapton is a polyimide obtained by curing the polyamic acid prepared by condensation of pyromellitic dianhydride with oxydianiline. Because both Kapton and its precursor polyamic acid are available commercially, they are frequently used as starting materials for CMS membranes. Matrimid and P84 + 20% methylenediamine are commercially available polyimides that are sometimes used as precursors of CMS membranes. These polyimides can be conveniently cast into any form because they are soluble in various solvents. Phenolic resins have been used as precursors to prepare CMS membranes. Heat treatment of phenolic resin films at temperatures of around 900–1000°C produced CMS membranes that showed high permselectivities for mixtures of gases with molecular sizes smaller than 0.4 nm.
