Patent ID: 6497747
Filing Date: 2002-12-24
Classification: B01D,C08G

Abstract:
A process for separating one or more gases from a mixture of gases comprising the step of bring the gaseous mixture into contact with a first side of a composite polyimide gas separation membrane, such that a portion of said gas mixture permeates to a second side of said membrane and a portion of said gas mixture is collected as a nonpermeate, the resulting gas mixture on said second side of said membrane being enriched in one or more components over that of the mixture on the first side of said membrane, wherein said composite gas separation membrane is formed by: (a) synthesizing a polyamic acid salt polymer in an aprotic solvent; (b) recovering said polyamic acid salt polymer from said aprotic solvent; c) forming a solution of said polyamic acid salt polymer in a coating solvent system; (d) applying said coating solvent system to a porous substrate to form a coating layer on said porous substrate; (e) solidifying said coating layer by drying, or by immersing the coated substrate into a nonsolvent or by a combination thereof to form a solidified coating layer; and (f) converting said polymeric acid salt coating layer into a polyimide layer, thus forming a composite polyimide gas separation membrane.