Unexpectedly large selectivities for olefin separations utilizing silver ion in ion-exchange membranes

Perfluorosulfonate ionomer membranes (Nafion) that have been ion-exchanged with silver(I) ion exhibit unexpectedly large selectivities for the separation of certain unsaturated hydrocarbon mixtures, such as styrene from ethylbenzene and linear C[sub 5]-C[sub 10] dienes from monoenes. Transmembrane fluxes increase linearly with the reciprocal of membrane thickness with no loss of selectivity for membrane thicknesses between 40 and 2.5 [mu]m. The large selectivities are due to competitive absorption of the hydrocarbons by the membranes. This effect cannot be predicted from single-component experiments or known complexation constants between the hydrocarbon and aqueous Ag(I). The unexpectedly large separation factors for the diene/monoene mixtures can be explained semiquantitatively by invoking the complexation of dienes to two Ag(I) ions. 44 refs., 9 figs., 7 tabs.