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 (h E). 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 (h E) 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.

The group contribution method modified UNIFAC (Dortmund) has become very popular because of its large range of applicability and the reliable results predicted for vapor-liquid equilibria, solid-liquid equilibria, activity coefficients at infinite dilution, azeotropic data, and excess enthalpies over a wide temperature range. However, in a few cases, especially at high and low temperatures, poor results are obtained. To overcome this problem, the modified UNIFAC (Dortmund) parameters have been refitted to an extended database. Additionally, new groups for different amides, used as selective solvents, have been introduced. Altogether, 43 new or revised pairs of group interaction parameters for modified UNIFAC (Dortmund) are given.

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