Modified UNIFAC Dortmund

To reduce the weaknesses of UNIFAC, the modified UNIFAC method was developed [55]. The main differences compared to original UNIFAC are  

For fitting the temperature-dependent group interaction parameters of modified UNIFAC, in contrast to original UNIFAC, besides VLE data the following data are also used  

The various thermodynamic properties deliver different important information for fitting reliable temperature-depondent parameters. The contributions can be summarized as follows  

For fitting the parameters simultaneously to the different types of data, weighting factors are used for the different contributions to the objective function  

The modifications of modified UNI FAC compared to original UNI FAC are summarized below. The combinatorial part is calculated using the following slightly modified empirical equation  

---

Two modified versions of the UNIFAC model, based on temperature-dependent parameters, have come into use. Not only do they provide a wide temperature range of applicability, but also they allow correlation of various kinds of property data, including phase equilibria, infinite dilution activity coefficients, and excess properties. The most recent revision and extension of the modified UNIFAC (Dortmund) model is provided by Gmehling et al. [Ind. Eng. Chem. Res. 41 1678-1688 (2002)]. An extended UNIFAC model called KT-UNI-FAC is described in detail by Kang et al. [Ind. Eng. Chem. Res. 41 3260-3273 (2003)]. Both papers contain extensive literature citations. 

Lohmann J, Job R, and GmehlingJ. From UNIFAC to Modified UNIFAC (Dortmund). IndEng Chem Res 2001 40 957-964. 

Jakob, A., H. Grensemann, J. Lohmann, and J. Gmehling. 2006. Further development of modified UNIFAC (Dortmund) Revision and extension 5. Industrial and Engineering Chemistry Research. 45, 7924. 

Wittig, R. Lohmann, J. Joh, R. Horstmann, S. Gmehiing, J. Vapor-hquid equiUbtia and enthalpies of mixing in a temperature range from 298.15 to 413.15 K for the further development of modified UNIFAC (Dortmund) Ind. Eng. Chem. Res. 2001,40, 5831-5838... 

With regards to the issue indicated above with the VTPR method, researchers have tried to develop this method by using an enormous database available for modified UNIFAC Dortmund. It was foimd that the coefficients of activity from the VTPR model using the Dortmund data bank differed from those ultimately obtained by VTPR using UNIFAC (Do) ... 

Model equations eorrespond to the modified UNIFAC (Dortmund) model. The aetivity eoeffieient of solute (yj) is ealeulated eonsidering a eombinatorial (y ) and a residual (y ) eontributions ... 

Nebig, S. Boelts, R. Gmehling, J. Measurement of vapor-liquid equilibria (VLE) and excess enthalpies (HE) of binary systems with 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and prediction of these properties and. gamma..inf using modified UNIFAC (Dortmund). Fluid Phase Equilib. 2007, 258, 168-178. 

LOH 01] Lohmann J., Joh R., Gmehling J., From UNIFAC to modified UNIFAC (Dortmund) , Industrial Engineering Chemistry Research, vol. 40, pp. 957-964,2001. 

---