Perfluorosulfonated ionomer (PSI) membranes were used to investigate the separation of olefin/paraffin mixtures by means of silver-based facilitated transport of olefins. Pentene and pentane were used as model compounds and separation factors as high as 33 were obtained. Influence of linear C-3-C-6 alcohols and ketones on the separation of the pentene/pentane mixtures was investigated. The presence of oxygenates increases the fluxes of olefins and paraffins, resulting in lower selectivity for hydrocarbon separation.