Pervaporation with chitosan membranes: separation of dimethyl carbonate/methanol/water mixtures

This study deals with the separation of binary dimethyl carbonate (DMC)/methanol, DMC/water, and methanol/water mixtures as well as ternary DMC/methanol/water mixtures by pervaporation using chitosan membranes. It is relevant to the manufacturing of DMC, where the energy intensive extractive distillation or pressure swing distillation is used conventionally for the separation of the reaction mixtures. Chitosan membranes were prepared by solution casting, followed by alkaline treatment. The effects of feed composition and operating temperature on the separation performance were investigated, and the membrane properties under the experimental conditions that are of interest to the manufacturing of DMC were evaluated. It was demonstrated that the membrane exhibited good performance for the DMC/methanol separation as well as the dehydration of DMC. The membrane also showed the capability of dehydrating methanol, but with a lower permselectivity. For the separation of ternary DMC/methanol/water mixtures, the interactions among the permeating components were shown to have a significant effect on the membrane performance. (C) 2002 Elsevier Science B.V. All rights reserved.