Pervaporation of multi component aromatic/aliphatic mixtures through copolyimide membranes

Industrial applications of aromatic/aliphatic separations by pervaporation require the investigation of multi component mixtures. In this work a multi component aromatic/aliphatic mixture was applied as feed. The aromatic feed components were not only mononuclear but also di- and trinuclear. Different membranes based on 6FDA-4MPD/DABA copolyimides were investigated. The copolyimide composition was varied concerning the number of cross-linking sites. For the preparation of cross-linked membranes different cross-linking agents were used. Additionally pre-treatment of the membranes was investigated. The pervaporation conditions were varied concerning the permeate as well as feed pressure, feed temperature, and feed composition. Experiments were carried out at 100 degrees C and 150 degrees C, a permeate pressure of 25 mbar and 250 mbar respectively was applied and the feed pressure was 1bar or rather 12 bar. In the course of the measurements acceptable fluxes between 1,9 kg . mu m . m(-2). h(-1) and 23,6 kg . mu m . m(-2) . h(-1) were found. Enrichment factors for all aromatics over aliphatic components in the range of beta(arom).= 1,3 and beta(arom).= 2,3 were reached. That means in some cases a doubling of the aromatics concentration was achieved.