Transport and high-selectivity mechanisms of C 4 hydrocarbons through anhydrous Ag +-doped perfluorocarbon-type ion-exchange membranes

Abstract

Permeation experiments have been carried out for n-butane, but-1-ene and isobutene through anhydrous Ag ⁺-doped perfluorosulfonate membranes from an AgBF ₄ aqueous solution. The anhydrous Ag ⁺-doped perfluorosulfonate membranes are microporous and n-butane flows through the microporous channels in these membranes in the gas phase. On the other hand, the transport of but-1-ene and isobutene is mainly controlled by hydrodynamic surface flow. Both the permeability of alkenes and the ideal selectivity of alkene/alkane increased with the increase in upstream gas pressure. The highest ideal separation factor is 2500 for but-1-ene/ n-butane and 810 for isobutene/ n-butane, indicating that anhydrous Ag ⁺-doped PSM membranes are applicable for the separation of alkenes and alkanes. The ideal separation factor of 7.9 is also obtained for but-1-ene/isobutene.