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Gas separations utilizing glassy polymer membranes at sub-ambient temperatures

  • US 5,837,032 A
  • Filed: 02/10/1995
  • Issued: 11/17/1998
  • Est. Priority Date: 01/30/1991
  • Status: Expired due to Fees
First Claim
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1. A method of separating component gases in a gas mixture, which method comprises:

  • A. contacting a first side of a gas separation membrane, the membrane comprising a discriminating layer or region of a glassy polymer, with the gas mixture while maintaining a difference in chemical potential from the first side of the membrane to a second side of the membrane, such that at least one first component gas of the gas mixture selectively permeates relative to at least one second component gas in the gas mixture from the first side of the membrane through the membrane to the second side of the membrane, wherein said contacting occurs at a temperature of -5°

    C. or lower, with the proviso that said permeation of gas occurs at or above the freezing point of any liquid present in the gas mixture, wherein said membrane is selected so that, when using a mixture of 80 mole percent nitrogen and 20 mole percent oxygen as a feed at 30°

    C. with a pressure of 30 psia on the first side of the membrane and a vacuum of less than 1 mm Hg on the second side of the membrane, the permeability of oxygen in barrers is less than 2000 and has the following relationship to oxygen/nitrogen selectivity;

    ##EQU6## B. recovering at least one of the permeate gas or rejected non-permeate gas, with the proviso that cellulose triacetate polymer membranes are excluded.

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