Separation On O2, N2, and SF6 Gas Using Carbon Molecular Sieve Hollow Fiber Membranes

摘要

At the present time, there is a growing interest in the development of gas separation membranes based on materials providing better selectivity, thermal stability and chemical stability than those already existing. Carbon molecular sieve (CMS) membranes are promising materials for membrane-based gas separation because of their excellent permeation and separation properties and thermal and chemical stability under harsh conditions, such as at high pressure and elevated high temperatures [1]. CMS membranes fabricated by pyrolysis of different polymeric materials are characterized by a very narrow microporosity (°3-5A), which allows very sharp discrimination between gas molecules having different sizes and shape. In particular, thermally stable polyimides acting as organic molecular sieves are excellent precursors for obtaining CMS membranes [2]. Polyimides are rigid, high melting, high Tg, thermally stable polymers formed by the condensation reactions dianhydrides with diamines. Because of their high thermal stabilities, polyimides are used in machined devices and other high temperature applications [3]. The separation of gas molecules with a molecular size under 4A by CMS membranes can be effectively achieved via a molecular sieve mechanism. The important factors determining the microstructure and gas separation properties of the CMS membranes are the choice of polymeric precursor and the pyrolysis conditions [4-5].