Process for restoring membrane permeation properties
AssigneeMembrane Technology and Research, Inc.
InventorsIngo Pinnau, Lora G. Toy, Carlos G. Casillas
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Abstract
A process for restoring the selectivity of high-flee-volume, glassy polymer membranes for condensable components over less-condensable components or non-condensable components of a gas mixture. The process involves exposing the membrane to suitable sorbent vapor, such as propane or butane, thereby reopening the microvoids that make up the free volume. The selectivity of an aged membrane may be restored to 70-100% of its original value. The selectivity of a membrane which is known to age over time can also be maintained by keeping the membrane in a vapor environment when it is not in use.
Claims33
A process for at least partially restoring an original selectivity of a condensable component over another component of a gas stream, in a membrane in which said original selectivity has deteriorated, said membrane comprising a polymer characterized by a glass transition temperature T.sub.g of at least about 100 .degree. C. and a free volume V.sub.F of at least about 15%, said process comprising exposing said membrane to a vapor having a sorption capacity of at least about 0.1 g of said vapor per gram of said polymer and a kinetic molecular diameter of less than about 6.ANG..
A process for at least partially maintaining an original selectivity of a condensable component over another component of a gas stream, in a membrane in which said selectivity is known to deteriorate over time, said membrane comprising a polymer characterized by a glass transition temperature T.sub.g of at least about 100.degree. C. and a free volume V.sub.F of at least about 15%, said process comprising maintaining said membrane in an atmosphere comprising a vapor having a sorption capacity of at least about 0.1 g of said vapor per gram of said polymer and a kinetic molecular diameter of less than about 6.ANG..
Dependencies are inferred from the claim text.