Supported Ionic Liquid Hollow Fiber Membranes for CO2/H2 Separation

Supported ionic liquid membranes continue to be of interest because of their excellent gas transport properties, although they have yet to find their way into commercial applications.  Taking advantage of unique features of hollow fibers and other cost benefits associated with them, supported ionic liquid hollow fiber membranes (SILHFMs) advance this technology into a practical form. In this study, hollow fiber supports were prepared from commercially available polyimide polymers with different porosities and internal morphologies. 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf₂N]) was selected as the ionic liquid. The internal fiber morphology was controlled in such a way to achieve an outer membrane separation layer with micro-porous structure. Gas permeance and selectivity for CO₂/H₂ separation were investigated from 37 to 200 °C and it was found that for this type of membrane both permeance and selectivity increase with increasing porosity. The highest porosity hollow fibers had gas transport properties that were similar to flat sheet supports. A modified resistance model was used to predict the transport properties and based on the co-permeance of gases with respect to the surface porosity of the fiber.