Nanocomposite silver polymer electrolytes as facilitated olefin transport membranes

Solid-state silver polymer electrolyte membranes containing AgNO₃ dissolved in poly(2-ethyl-2-oxazoline) (POZ) as an olefin carrier are not efficient for the separation of olefin/paraffin mixtures (selectivity ∼1). The addition of fumed silica nanoparticles into the POZ/AgNO₃ complex membranes, however, resulted in a surprisingly significant enhancement of the permeance and selectivity (higher than 80) for propylene/propane mixtures. These enhancements are explained in terms of the silver ion activity in olefin coordination. FT-IR, X-ray photoelectron spectroscopy (XPS) and FT-Raman demonstrate that the silver ion activity continuously increases by Lewis acid-base interactions upon incorporation of the silica nanoparticles up to 0.1 mole ratio of silica, above which it abruptly decreases. Furthermore, the structural change of polymer electrolyte membranes took place by the presence of nanoparticles, supported by the T_g measurement.