PRELIMINARY SELECTION OF POLYMERIC ENTRAINERS FOR THE AZEOTROPIC DISTILLATION OF MTBE/METHANOL AND ETHANOL/WATER MIXTURES USING THE UNIFAC GROUP-CONTRIBUTION CALCULATIONS METHOD

In this work the UNIFAC group-contribution calculations method was used to determine relative volatility in the presence of selected polymeric entrainers at different weight fractions in ethanol/water and methyl tertiary butyl ether/methanol systems. To quantify the effect of the added polymers, the ratio of relative volatility with and without the polymer was calculated. The purpose of these calculations was to identify the systems that have ratios of relative volatility distinct from unity because they may indicate polymers with the ability to break the azeotrope. This information should guide the initial selection of potential polymers capable of breaking the azeotrope and thus save time and effort. The results of these calculations are reported. Because these polymers must be soluble in the system, solubility tests were performed and the results are reported. Comparison of these predictions with previously published experimental vapor-liquid equilibrium data for the same systems gave conflicting results: Some predictions were confirmed and others were not. Thus, the UNIFAC group-contribution calculations were not always reliable in predicting relative volatility. More accurate group-contribution methods would make the polymer design more reliable.