DEHYDRATION OF WATER ETHANOL MIXTURES BY PERVAPORATION USING MODIFIED POLY(VINYL ALCOHOL) MEMBRANE

Dehydration of organic compounds can be achieved economically with pervaporation process. For example, in an ethanol plant, applying a fermentation, distillation-pervaporation combined process has clear advantage against the pure distillation for saving energy. The purpose of this paper is to develop new membranes with high selectivity and acceptable permeation rate for the separation of alcohol/water systems. Novel composite membranes were prepared by casting an aqueous solution of poly(vinyl alcohol) and poly-(styrenesulfonic acid) in ultrathin film on a microporous polyacrylonitrile supporting membrane, evaporating the solvent, and heat-curing at 120-degrees-C for 2 h. The composite membranes were soaked in an aqueous solution of multi-valent metal salts and ionic cross-linked. The novel composite membranes were found to have high separation factor of 1000-2000, and also good permeation rate of 0.1-0.2 kg m-2 h-1 by pervaporation for 95 wt% ethanol aqueous solution at 60-degrees-C, and also 43 as separation factor for methanol/water system, 13900 as separation factor for iso-propanol/water system, 17900 as separation factor for t-butanol/water system using 95 wt% alcohol concentration at 60-degrees-C.