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°C and 150°C, a permeate pressure of 25 mbar and 250 mbar respectively was applied and the feed pressure was 1 bar or rather 12 bar. In the course of the measurements acceptable fluxes between 1,9 kg · µm · m-2 · h-1 and 23,6 kg · µm · m-2 · h-1 were found. Enrichment factors for all aromatics over aliphatic components in the range of βarom.=1,3 and βarom.=2,3 were reached. That means in some cases a doubling of the aromatics concentration was achieved. [ABSTRACT FROM AUTHOR]