EFFECTS OF MOLECULAR-STRUCTURE AND EQUIVALENT-WEIGHT ON FACILITATED TRANSPORT OF ALKENES IN AG(I)-PFSI MEMBRANES

Fluxes and separation factors are reported for the facilitated transpo rt of a variety of Cg alkenes and dienes through two Ag(I)-exchanged p olyfluorosulfonate ionomer membranes. For acyclic dienes, the largest separation factors are observed between those compounds with the great est difference in spacing of the double bonds, and those with complete ly external versus internal double bonds. For cases where the spacing of the double bonds is the same, the compound with at least one termin al double bond exhibited a higher flux. The trends in fluxes for cycli c dienes is quite different; 1,4-cyclohexadiene is transported more sl owly than cyclohexene while 1,3-cyclohexadiene is transported almost e ight times more rapidly than cyclohexene. Methyl-substituents on the c arbons comprising double bonds have minor effects on the transport pro perties. As anticipated, PFSI materials that contain more ion-exchange sites and absorb greater quantities of water exhibit slightly greater fluxes and separation factors for most alkene separations.