Basis of permeability/selectivity tradeoff relations in polymeric gas separation membranes

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Gas separation properties of polymer membrane materials follow distinct tradeoff relations: more permeable polymers are generally less selective and vice versa. Robeson1 identified the best combinations of permeability and selectivity for important binary gas pairs (O2/N2, CO2/CH4, H2/N2, etc.) and represented these permeability/selectivity combinations empirically as αA/B = βA/BPA-λAB, where PA and PB are the permeability coefficients of the more permeable and less permeable gases, respectively, αA/B is selectivity (=PA/PB), and λA/B and βA/B are empirical parameters. This report provides a fundamental theory for this observation. In the theory, λA/B depends only on gas size. βA/B depends on λA/B, gas condensability, and one adjustable parameter.

Original languageEnglish
Pages (from-to)375-380
Number of pages6
Issue number2
Publication statusPublished - 26 Jan 1999
Externally publishedYes

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