A Modified UNIFAC (Dortmund) Model. 3. Revision and Extension

Abstract

The group contribution method Modified UNIFAC (Dortmund) is a well-known model for the reliable prediction of phase equilibria (VLE, LLE, SLE of eutectic systems, azeotropic data and γ∞) and excess properties (hE). Compared to the original UNIFAC method, Modified UNIFAC (Dortmund) provides a much better description of the temperature dependence of the activity coefficients, and a more reliable presentation of the real behavior of phase equilibria in the dilute region; in addition, it also leads to better results for asymmetric mixtures (i.e., those involving molecules of very different size). Nevertheless, the parameters published previously sometimes give poor results, especially at high (>140 °C) and low (<0 °C) temperatures. To overcome these weaknesses, solid−liquid equilibria (SLE) of eutectic systems and enthalpies of mixing (hE) at high temperatures have been included additionally in the database used for fitting the required group interaction parameters in order to ensure reliable results at low and high temperatures. This paper contains details of 78 new or revised pairs of group interaction parameters for Mod. UNIFAC (Do) covering a large temperature range.