HIGH SELECTIVITY POLYIMIDE MEMBRANE FOR NATURAL GAS UPGRADING AND HYDROGEN PURIFICATION

A polyimide polymer having hydroxyl and acetoxy function groups is provided together with a membrane made from the polymer. Also provided is a process for separating at least one gas from a mixture of gases using a polyimide membrane comprising a polyimide polymer with hydroxyl and acetoxy functional the process comprising: (a) providing the polyimide membrane comprising the polyimide polymer with hydroxyl and acetoxy functional groups which is permeable to the at least one gas; (b) contacting the mixture on one side of the polyimide membrane to cause said at least one gas to permeate the membrane; and (c) removing from the opposite side of the membrane a permeate gas composition comprising a portion of said at least one gas which permeated the polyimide membrane.