Ozone treatment of surface of membrane to improve permselectivity

A surface-modified gas separation membrane having improved permselectivity properties for separating a mixture of gases as compared to an unmodified member, and further wherein said membrane is a hollow fiber membrane adapted for boreside feed, the surface-modified gas separation membrane produced by a process comprising the steps of:

• (a) providing a surface unmodified gas separation membrane;
• (b) providing a solution of a coating material, wherein said coating material is an organic material having at least one site of unsaturation;
• (c) contacting the surface unmodified gas separation membrane with the solution of the coating material;
• (d) coating said coating material on the surface unmodified gas separation membrane by passing a solution of the coating material through the bore of the hollow fiber membrane to produce a coated gas separation membrane;
• (e) optionally removing substantially all of the residual coating material from the surface of the coated gas separation membrane of step (d);
• (f) optionally removing substantially all of the solvent from the surface of the coated gas separation membrane of step (d) or (e) by contacting the surface with at least one anhydrous non-oxidizing gas;
• (g) heating the coated gas separation membrane of step (d), (e), or (f) at about 10° C. to about 150° C.;
• (h) contacting the heated coated gas separation membrane of step (g) with at least one oxidizing agent for a time effective to surface modify the gas separation membrane between about 5 minutes and 24 hours to produce the surface modified gas separation membrane having improved permselectivity, wherein the oxidizing agent is oxygen, ozone or combinations thereof;
• and
• (i) optionally contacting the surface oxidized gas separation membrane of step (h) with a non-oxidizing gas for a time effective to remove substantially all of the oxidizing gas to produce the surface modified gas separation membrane having improved permselectivity.