Solid polymer electrolyte composite membranes for olefin/paraffin separation

Ethylene and propylene are produced in larger quantities than any other org anic compound. Production of these olefins requires separation of the olefi ns from the corresponding paraffins. Distillation is currently used but thi s is an extremely energy-intensive process due to the very low relative vol atility of the components. Previous studies have shown that facilitated tra nsport membranes can have high selectivity for olefin/paraffin separation. However, four problems have limited the commercial application of facilitat ed transport membranes: (i) poor mechanical stability, (ii) the difficulty in preparing thin, high-flux composite membranes, (iii) the requirement of a water-vapor-saturated feed to provide mobility for the olefin-selective c arrier, and (iv) poor chemical stability due to carrier poisoning. Solid po lymer electrolytes are a novel class of facilitated transport membranes for olefin/paraffin separation. These membranes solve the first three problems listed above. Solid polymer electrolyte membranes are based on rubbery, po lyether-based polymers containing a dissolved olefin-complexing metal salt. Solid polymer electrolyte composite membranes made from poly(ethylene oxid e) loaded with silver tetrafluoroborate showed an ethylene/ethane selectivi ty of up to 240 and an ethylene permeance of 8 x 10(-6) cm(3)(STP)/cm(2) s cmHg with a dry feed gas mixture. (C) 2001 Elsevier Science B.V. All rights reserved.