Polyelectrolyte membranes for aromatic-aliphatic hydrocarbon separation by pervaporation

Abstract

New types of membranes based on polyelectrolytes were developed for the separation of aromatic/aliphatic hydrocarbon mixtures by pervaporation. For that purpose composite membranes with different polyelectrolytes, soluble either in water (sulfoethylcellulose) or in ethanol (custom-made copolymers of methyl methacrylate 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 Co++ ions. Both membrane types show a significantly enrichment of aromatic components (toluene or benzene) in the course of the pervaporation 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.