Pervaporation of binary water–alcohol and methanol–alcohol mixtures through microporous methylated silica membranes: Maxwell–Stefan modeling

The transport of pure water and methanol and the selective pervaporation of binary mixtures of water or methanol in alcohols (ethanol, isopropanol, butanol) are studied for two methylated microporous silica membranes as a function of feed composition (0–15 vol% water or methanol) at 60 °C. Flux data show interaction effects between the polar components in the feed. Alcohol molecules block water and methanol transport, whereas water and methanol block or enhance the alcohol transport. A simplified Maxwell–Stefan model is set up to predict fluxes from pure component pervaporation data and from literature adsorption coefficients. The Vignes equation is used to describe the concentration dependency of the mutual diffusion coefficient. The model allows a good quantitative prediction of the ethanol–water, isopropanol–water and ethanol–methanol mixtures, but needs improvement for the isopropanol–methanol and for the butanol mixtures either in water or in methanol.