Selection of top layer materials for gas-liquid membrane contactors

Gas-liquid membrane contactors frequently suffer from wetting of the microporous membrane. Stabilization layers at the liquid side of the membrane potentially prevent this wetting. We applied such stabilized membranes to the separation of olefins and paraffins using AgNO3 solutions as absorption liquid. The stabilization material requires permeation of olefins at minimum counter transport of water. Appropriate selection of the top layer material is crucial in this application. This report describes the selection of potential top layer materials. Dense films of the selected materials were prepared and used to determine ethylene and ethane permeabilities, to perform pervaporation experiments with water and a 3.5M solution of silver nitrate in water, and to determine the swelling behavior of the dense films in water and in a 3.5M silver nitrate solution. Based on the characterization experiments, ethylene propylenediene terpolymer is the most appropriate candidate with the highest potential for application in a gas-liquid membrane contactor for the separation of paraffins and olefins. It has a relatively high olefin permeability (46.4 Barrer) and a corresponding low water vapor permeability and low swelling tendency in a 3.5M silver nitrate solution (1490 Barrer and 0.14 wt%, respectively). (C) 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 323-334, 2004.