Material selection considerations for gas separation processes

Advantages and disadvantages associated with common membrane types used in gas separation operations are reviewed. Comparisons between dense‐walled and several different types of asymmetric structures are made. In addition to overall membrane structure, the molecular natures of different membrane material types are treated. Tradeoffs between the use of rubbery and glassy polymers are considered first, followed by a treatment of the optimization of glassy membrane permeability and permselectivity properties. Material optimization principles are defined in terms of the basic thermodynamic solution and kinetic transport properties of polymers, and applications of these principles are illustrated for a modified poly(phenylene oxide) and a homologous series of polyimides derived from pyromellitic dianhydride.