Development and analysis of the Original UNIFAC-CI model for prediction of vapor–liquid and solid–liquid equilibria

Azizul Azri Mustaffa, Rafiqul Gani, Georgios Kontogeorgis

Research output: Contribution to journalJournal articleResearchpeer-review


In this work, we present a further development and analysis of the Original UNIFAC-CI models for the prediction of vapor–liquid equilibrium (VLE) and solid–liquid equilibrium (SLE) for a wide range of mixtures. Three sets of atom interaction parameters (AIPs) have been regressed. For the first two sets, only VLE experimental data were used in parameter estimation. In the first set, no weighting factors were used for each of the VLE data in the objective function when regressing the AIPs. However, for the second set, the AIPs have been regressed using the so-called QVLE quality factors obtained for each of the VLE data from a quality assessment algorithm (consistency tests) as weighting factors in the objective functions. For the third set of parameters, SLE and VLE data were used in the regression of AIPs. The result of the correlations in terms of deviations errors and predictions using these three sets of regressed parameters are presented, compared and discussed. The significance of adding the QVLE values and SLE systems in the regression of the AIPs are also highlighted. UNIFAC is a model that can be in principle used for both VLE and SLE (as well as other types of phase behavior) calculations. The range of applicability of the predictive UNIFAC-CI is investigated and it is shown to what extent the Original UNIFAC-CI model can successfully predict SLE especially when the needed parameters are missing.
Original languageEnglish
JournalFluid Phase Equilibria
Pages (from-to)24-44
Publication statusPublished - 2014


  • Connectivity index
  • Solid–liquid equilibrium
  • Vapor–liquid equilibrium
  • Atom interaction parameters


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