Elsevier

Journal of Membrane Science

Volume 62, Issue 2, 1 October 1991, Pages 165-185
Journal of Membrane Science

Correlation of separation factor versus permeability for polymeric membranes

https://doi.org/10.1016/0376-7388(91)80060-JGet rights and content

Abstract

The separation of gases utilizing polymeric membranes has emerged into a commercially utilized unit operation. It has been recognized in the past decade that the separation factor for gas pairs varies inversely with the permeability of the more permeable gas of the specific pair. An analysis of the literature data for binary gas mixtures from the list of He, H2, O2, N2, CH4, and CO2 reveals an upper bound relationship for these mixtures. The upper bound can be represented by a log-log plot of αij (separation factor = Pi/Pj) versus Pi (where Pi = permeability of the more permeable gas). Above the linear upper bound on the log-log plot, virtually no values exist. The slope of this line (n) from the relationship Pi=kαnij can be related to the difference between the gas molecular diameters Δdji (djdi) where the gas molecular diameter chosen is the Lennard-Jones kinetic diameter. This relationship yields linearity for a plot of −1/n versus Δdji, and the line passes through (0,0) for the x–y plot thus providing further verification of this analysis. These results indicate that the diffusion coefficient governs the separating capabilities of polymers for these gas pairs. As the polymer molecular spacing becomes tighter the permeability decreases due to decreasing diffusion coefficients, but the separation characteristics are enhanced.

References (75)

  • M. Langsam et al.

    Substituted propyne polymers. I. Chemical surface modification of poly[1-(trimethylsilyl)propyne] for gas separation membranes

    Gas. Sep. Purif.

    (1988)
  • M.S. Delaney et al.

    Oxygen/nitrogen transport in glassy polymers with oxygen-binding pendant groups

    J. Membrane Sci.

    (1990)
  • B. Gebben et al.

    Gas separation properties of a thermally stable and chemically resistant polytriazole membrane

    J. Membrane Sci.

    (1989)
  • D.R.B. Walker et al.

    Transport characteristics of a polypyrrolone for gas separation

    J. Membrane Sci.

    (1991)
  • T.H. Kim et al.

    Advanced gas separation membrane materials: Rigid aromatic polyimides

    Sep. Sci. Technol.

    (1988)
  • S.A. Stern et al.

    Structure/permeability relationship of polyimide membranes. Application to the separation of gas mixture

    J. Polym. Sci., Part B, Polym. Phys.

    (1989)
  • H.J. Bixler et al.

    Barrier properties of polymer films

  • C.E. Rogers et al.

    Separation by permeation through polymeric membranes

  • V.T. Stannett et al.

    Recent advances in membrane science and technology

    Adv. Polymer. Sci.

    (1979)
  • S. Pauly

    Permeability and diffusion data

  • J. Crank et al.
    (1968)
  • H.B. Hopfenberg
    (1974)
  • C.E. Rogers

    Permeability and chemical resistance

  • J. Comyn
    (1985)
  • P. Meares
    (1965)
  • J. Crank
    (1975)
  • S.T. Hwang et al.

    Gaseous transfer coefficients in membranes

    Sep. Sci.

    (1974)
  • S.T. Hwang et al.
    (1975)
  • P. Meares
    (1976)
  • S.A. Stern et al.

    The selective permeation of gases through polymers

    Ann. Rev. Mater Sci.

    (1981)
  • W.J. Koros et al.

    Transport properties

  • D.R. Lloyd

    Material Sciences of Synthetic Membranes

    (1985)
  • K. Toi et al.

    Gas sorption and transport in poly(phenylene oxide) and comparisons with other glassy polymers

    J. Appl. Polym. Sci.

    (1982)
  • G.J. van Amerongen

    Diffusion in elastomers

    Rubber Chem. Technol.

    (1964)
  • V.T. Stannett

    Simple gases

  • R.T. Chern et al.

    Material selection for membrane based gas separation

  • D.W. van Krevelen
    (1976)
  • Cited by (3015)

    View all citing articles on Scopus
    View full text