Crosslinked Membrane And Polymer For Making Same And Method Of Using Membrane

Abstract

A composition of and a method of making high performance crosslinked membranes are described. The membranes have a high resistance to plasticization by use of crosslinking. The preferred polymer material for the membrane is a polyimide polymer comprising covalently bonded ester crosslinks. The resultant membrane exhibits a high permeability of CO 2 in combination with a high CO 2 /CH 4 selectivity. Another embodiment provides a method of making the membrane from a monesterified polymer followed by final crosslinking after the membrane is formed.

What is claimed is: 
     
         1 . A hollow fiber polymer membrane, comprising:
 a hollow fiber crosslinked polymer selected from the group consisting of polyimides, poyletherimides, polyethersulfones and polysulfones, having covalent ester crosslinks; and having a CO 2  permeance of at least 20 GPU and a CO 2 /CH 4  selectivity of greater than 20, at 35 degrees C. and a pressure of 100 psia.   
     
     
         2 . The hollow fiber polymer membrane of  claim 1  wherein the polymer has an average molecular weight of between 20,000 and 200,000. 
     
     
         3 . The hollow fiber polymer membrane of  claim 1  wherein the membrane material has an average molecular weight greater than the entanglement MW of the polymer. 
     
     
         4 . The hollow fiber polymer membrane of  claim 1  wherein:
 the polymer is made from the monomers A+B+C; where A is a dianhydride of the formula; 
 
       
         
           
           
               
               
           
         
         where X 1  and X 2  are the same or different halogenated alkyl group, phenyl or halogen; 
         where R 1 , R 2 , R 3 , R 4 , R 5 , and R 6  are H, alkyl, or halogen; 
         where B is a diamino cyclic compound without a carboxylic acid functionality; 
         where C is a diamino cyclic compound with a carboxylic acid functionality; 
         wherein the ratio of B to C is between 1:4 and 8:1. 
       
     
     
         5 . A method of making a crosslinked hollow fiber membrane comprising:
 preparing a polymer comprising a predetermined quantity of crosslinkable sites, the polymer selected from the group consisting of polyimides, poyletherimides, polyethersulfones and polysulfones, having covalent ester crosslinks having a CO 2  permeance of at least 20 GPU and a CO 2 /CH 4  selectivity of greater than 20, at 35 degrees C. and a pressure of 100 psi; and   forming a hollow fiber from the polymer.   
     
     
         6 . A process for producing hydrocarbon products comprising:
 separating two gases having different molecular sizes in a feedstream including these two gas components, the process including:   (a) providing a hollow fiber crosslinked polymer selected from the group consisting of polyimides, poyletherimides, polyethersulfones and polysulfones, having covalent ester crosslinks; and having a CO 2  permeance of at least 20 GPU and a CO 2 /CH 4  selectivity of greater than 20, at 35 degrees C. and a pressure of 100 psi and   (b) directing a feedstream including the first and second gas components to the feed side of the membrane and withdrawing a retentate stream depleted in the first gas component and withdrawing a permeate stream enriched in the first gas component from the permeate side of the membrane.   
     
     
         7 . A hollow fiber polymer membrane, comprising:
 a hollow fiber polymer membrane including a porous support layer and a skin layer which is supported by the support layer, the skin layer including a crosslinked polymer selected from the group consisting of polyimides, poyletherimides, polyethersulfones and polysulfones and having covalent ester crosslinks;   wherein the hollow fiber polymer membrane has a CO 2  permeance of at least 20 GPU and a CO 2 /CH 4  selectivity of greater than 20, at 35 degrees C. and a pressure of 100 psia.