Permeability of dense (homogeneous) cellulose acetate membranes to methane, carbon dioxide, and their mixtures at elevated pressures
✍ Scribed by A. Y. Houde; B. Krishnakumar; S. G. Charati; S. A. Stern
- Publisher
- John Wiley and Sons
- Year
- 1996
- Tongue
- English
- Weight
- 1012 KB
- Volume
- 62
- Category
- Article
- ISSN
- 0021-8995
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✦ Synopsis
Mean permeability coefficients for CHI and COz (PcH, and pco2) 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 CHI and COP as well as with CH4/C02 mixtures containing 9.7, 24.0, and 46.1 mol % COP. In the measurements with the pure gases, PCH, was found to decrease with increasing pressure, as expected from the "dual-mode'' sorption model. By contrast, Pco2 passes through a minimum and then increases with increasing pressure, probably due to the plasticization (swelling) of CA by COP The values of pcH, and pco2 determined with the mixtures containing 9.7 and 24.0 mol % COP decrease with increasing total pressure; this behavior is adequately described by the extended "dualmode" sorption model for mixtures. By contrast, the values and pco2 obtained with the mixture containing 46.1 mol % COz pass through a minimum and then increase as the total pressure is raised, probably also due to the plasticization of CA by COz. The COz/ CH, selectivity ( = p c O 2 / p c H , ) of the CA membranes decreases with increasing total pressure and, at constant pressure, decreases with increasing CO, concentration in the feed mixture. The effects of exposing the CA membranes to high-pressure CO, prior to the permeability measurements ("conditioning" effects) on pcH, and pco, have also been studied.