High Performance Membranes for Removal of Carbon Dioxide from Natural Gas

40005 November 8, 1996 Membrane Technology and Research, Inc. About 17% of domestic raw natural gas requires processing to remove carbon dioxide, but current techniques suffer from a number of problems. Membrane separation offers promise; however, most of the membrane plants installed for this application have been based on cellulose acetate membranes, which have a carbon dioxide/methane selectivity of 20. If membranes could be made with selectivities of 40 or more, membrane separation would be a far more competitive carbon dioxide separation technique. While a number of designer polymers have been produced with selectivities in this range, they have not been incorporated into useful membrane systems because the materials are too costly and it is difficult to form these polymers into very thin but robust membranes. This project will develop improved membranes by chemically modifying the surface layer of an existing membrane which already has a very high carbon dioxide pressure-normalized flux and a fair carbon dioxide/methane selectivity of 15. The target performance is a membrane with a selectivity of 40, while maintaining an acceptable pressure-normalized flux. Phase I will evaluate the feasibility of the surface-treatment approach. Phase II will optimize the process and produce prototype modules. Anticipated Results/Potential Commercial Applications as described by the awardee: The new membrane modules would make membranes far more competitive with amine absorbers and other conventional technology in the natural gas processing industry. Significant cost savings could be achieved by natural gas processors, with consequent benefits to users.