Polyelectrolyte membranes for aromatic–aliphatic hydrocarbon separation by pervaporation

Different types of membranes based on polyelectrolytes were developed for the separation of aromatic–aliphatic hydrocarbon mixtures by pervaporation (PV). For that purpose, composite membranes with different polyelectrolytes, soluble either in water (sulfoethylcellulose) or in ethanol (custom-made copolymers of methyl methacrylate (MMA) and methacrylic acid [3-sulfo-propyl ester] potassium salt) were prepared by an interfacial reaction with oppositely charged ionic surfactants. The latter copolymer could also be cross-linked with Co2+ ions. Both membrane types show a clear enrichment of aromatic components (toluene or benzene) in the course of the PV process (from 20 wt.% in the feed to about 55 wt.% in the permeate). The fluxes are in the range of 1 kg/hm2 at a feed temperature of 80 °C. The separation of a benzene/cyclohexane mixture was also successful at 50 °C. In all cases, higher fluxes were obtained with benzene/cyclohexane feed mixtures than with toluene/heptane mixtures. Also, in multi-component feed mixtures, benzene exhibit the better permeate rates.