Separation of ethanol-water mixtures by vapor permeation through cellophane membrane.

Abstract

Vapor permeation (VaP) using cellophane membrane was compared with pervaporation (PV) for ethanol-water mixtures under isothermal conditions (Mode I). The selectivity of VaP was higher than that of PV through whole feed composition, while the permeation rate of VaP was lower than that of PV. It was observed that the membrane in PV was more swollen than in VaP. In the case (Mode II) which feed vapor was superheated in VaP under keeping downstream pressure constant, the selectivity increased remarkably and the permeation rate decreased. In another case (Mode III) which downstream temperature near the membrane was dropped and the temperature gradient was generated through the membrane in VaP, the permeation rate increased and the selectivity decreased. The influence of temperature to the permeation rate could be expressed by the Arrhenius' correlation only for Mode I. With regard to the influence of downstream pressure, the selectivity of Mode II showed only a slight decrease with downstream pressure, not so much decrease as the usual condition (Mode I).