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Permeability of dense (homogeneous) cellulose acetate membranes to methane, carbon dioxide, and their mixtures at elevated pressures
Author(s) -
Houde A. Y.,
Krishnakumar B.,
Charati S. G.,
Stern S. A.
Publication year - 1996
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/(sici)1097-4628(19961226)62:13<2181::aid-app1>3.0.co;2-f
Subject(s) - carbon dioxide , methane , homogeneous , chemical engineering , cellulose acetate , membrane , permeability (electromagnetism) , cellulose , materials science , chemistry , organic chemistry , thermodynamics , biochemistry , physics , engineering
Mean permeability coefficients for CH 4 and CO 2 ( P̄ CH 4and P̄ CO 2) in cellulose acetate (CA, DS = 2.45) were determined at 35°C (95°F) and at pressures up to about 54 atm (800 psia). The measurements were made with pure CH 4 and CO 2 as well as with CH 4 /CO 2 mixtures containing 9.7, 24.0, and 46.1 mol % CO 2 . In the measurements with the pure gases, P̄ CH 4was found to decrease with increasing pressure, as expected from the “dual‐mode” sorption model. By contrast, P̄ CO 2passes through a minimum and then increases with increasing pressure, probably due to the plasticization (swelling) of CA by CO 2 . The values of P̄ CH 4and P̄ CO 2determined with the mixtures containing 9.7 and 24.0 mol % CO 2 decrease with increasing total pressure; this behavior is adequately described by the extended “dual‐mode” sorption model for mixtures. By contrast, the values of P̄ CH 4and P̄ CO 2obtained with the mixture containing 46.1 mol % CO 2 pass through a minimum and then increase as the total pressure is raised, probably also due to the plasticization of CA by CO 2 . The CO 2 /CH 4 selectivity (≡ P̄ CO 2/ P̄ CH 4) of the CA membrances decreases with increasing total pressure and, at constant pressure, decreases with increasing CO 2 concentration in the feed mixture. The effects of exposing the CA membranes to high‐pressure CO 2 prior to the permeability measurements (“conditioning” effects) on P̄ CH 4and P̄ CO 2have also been studied. © 1996 John Wiley & Sons, Inc.