Hydrodynamic surface flow and the swelling effect of C-2 and C-4 alkenes through anhydrous Ag+-doped perfluorocarbon type ion-exchange membranes

The transport mechanism was investigated for n-butane, 1-butene, ethane, an d ethene through anhydrous Ag+-doped PSM at various upstream gas pressures. 1-Butene and ethene molecules can be adsorbed and form multilayers on the Ag+ sites in the membrane. Their adsorption behavior can be described by th e BET n-layer adsorption theory. These adsorbed alkene molecules can also s well the surrounding polymer chains to a certain extent, causing resistance to the migration of these alkene multilayer molecules to decrease as the c oncentration of the adsorbed alkenes increases. The permeation behavior of 1-butene and ethene is mainly controlled by the hydrodynamic surface flow m echanism, and their fluxes are much higher than those of alkanes, especiall y at high upstream gas pressures. This leads to the high ideal selectivity of 1-butene/n-butane and ethene/ethane at relatively high pressure. It is a lso shown that the more C atoms present in the hydrocarbon molecules, the h igher will be the permselectivity of alkenes relative to their correspondin g saturated alkanes, which will be expected in the anhydrous Ag+-doped PSM. (C) 1999 Academic Press.