Patent ID: 8241501

Claim:
A process for separating at least one gas or liquid from a mixture of gases or liquids using a polymer membrane made from subjecting aromatic polyimide membranes first to a thermal treatment step followed by a crosslinking step wherein said aromatic polyimide membranes comprise at least one aromatic polyimide polymer comprising cross-linkable functional groups in a polymer backbone of said aromatic polyimide polymer and pendent —OH or —SH functional groups ortho to a heterocyclic imide nitrogen within said aromatic polyimide polymer wherein said polymer membrane is a cross-linked polybenzoxazole or polybenzothiazole polymer membrane and wherein said aromatic polyimide polymer has a structure represented by a plurality of first repeating units of a formula (I), wherein said formula (I) is: where —X 1 — of said formula (I) is or mixtures thereof, —X 2 — of said formula (I) is either the same as —X 1 — or is selected from or mixtures thereof, —X 3 — of said formula (I) is or mixtures thereof, —Z—, —Z′—, and —Z″— are independently —O— or —S—, and —R— is or mixtures thereof, said process comprising: a) providing said polymer membrane that is permeable to at least one gas or liquid; b) contacting a mixture of gases or liquids on one side of the said polymer membrane to cause at least one gas or liquid to permeate the said membrane; and c) removing from an opposite side of the said membrane a permeate gas or liquid composition that is a portion of said at least one gas or liquid that permeated the said membrane.