Pervaporation separation of methanol from methanol/tert-amyl methyl ether mixtures with a commercial membrane

Tertiary ethers have attracted much attention as octane boosters, due to their pollution reduction and excellent blending capabilities. Although much research has been done in the area of pervaporation, not much attention has been given to the separation of organic-organic mixtures with commercially available membranes. In this study, the pervaporation and sorption characteristics of a commercial PVA-based membrane with methanol/tert-amyl methyl ether (TAME) mixtures were investigated by varying the feed composition and the feed temperature, and measuring quantities such as flux and selectivity. The membrane was found to be highly methanol selective, with the separation factor varying between 30 and 175, and a flux of 1-4 kg m(-2) h(-1). The flux was found to increase with an increase in temperature and with an increase in weight fraction methanol in the feed. The selectivity decreased with an increase in weight fraction methanol in the feed and increased with an increase in temperature. Sorption data showed that there was only a minor difference in the sorption of both molecules at equilibrium, indicating a diffusion-controlled transport mechanism. Deviation coefficients showed that the plasticisation of TAME has a retarding effect on methanol permeation, and that methanol has an enhancing coupling effect on TAME. Approximated diffusion coefficients confirmed diffusion-controlled transport mechanism and explained why the methanol partial flux was so much higher than that of TAME. It was finally shown that pervaporation can easily be used to break the azeotrope of methanol and TAME, and that the membrane shows potential for being used in an industrial hybrid distillation-pervaporation system. (C) 2002 Elsevier Science B.V. All rights reserved.