MOLECULAR MODELING OF PERVAPORATION SEPARATION OF BINARY-MIXTURES WITH POLYMERIC MEMBRANES

Results of detailed molecular dynamics simulations on the interfaces b etween the following amorphous polymers and feed mixtures are reported : poly(dimethyl siloxane) (PDMS) and 90:10 wt% water-ethanol, poly(vin yl alcohol) (PVA) and 90:10 wt% ethanol-water, and poly(methyl phenyl siloxane) (PMPhS) and 20:80 wt% benzene-n-heptane. The simulation resu lts reflect important features of the respective pervaporation process es. In the case of PDMS/wates-ethanol the technically relevant enrichm ent of the permeate stream with ethanol can be anticipated already fro m the interface behaviour during the early stages of sorption and abso rption of feed molecules, while for the PVA/ethanol-water system the t echnically utilised depletion of the retentate stream from water molec ules is observable. Here the solubility related enrichment factor for water in the membrane is about 4. For the system PMPhS/benzene-n-hepta ne, on the other hand, a relatively low solubility related enrichment factor for benzene in the membrane of about 2 could be predicted. Ther efore, an enrichment of the majority component n-heptane is to be expe cted in the respective retentate stream. (C) 1998 Elsevier Science B.V .