PVC–activated carbon based matrices: A promising combination for pervaporation membranes useful for aromatic–alkane separations

Abstract

The separation of aromatic–aliphatic liquid mixtures is difficult perform in a satisfactory technico-economic manner by conventional methods, such as extractive distillation, azeotropic distillation, or liquid–liquid extraction. The separation by pervaporation (PV) of liquid toluene–heptane mixtures, selected as a model mixture, was performed with several dense membranes based on poly(vinylchloride) (PVC) as the starting material. Aiming to improve the performances of pure PVC films, i.e. high selectivity and very low flux, composite membranes were prepared by incorporating different percentages of activated carbon introduced as selective sorbent fillers for toluene. In this study, we report the results obtained with composite PVC membranes containing up to 40wt% Maxsorb SPD30. The transport properties of these membranes were characterized by measurements of isothermal sorption and by pervaporation of binary mixtures. It was found that the performances of certain composite membranes were significantly increased compared with pure PVC membranes. Under the same experimental conditions, the pervaporation toluene flux was seven times higher, whereas the toluene selectivity was only slightly decreased (the permeate enrichment decreased from 89 to 83wt% at 74°C). Thus, the combination PVC with activated carbon appears to be a promising method to obtain effective PV membranes for aromatic–alkane separations.