Group Contribution Method for the Prediction of the Infinite Dilution Activity Coefficient of Non-Electrolyte Organic Compounds in Water


Bruce Mollera, Jürgen Rareya,b,c,* , Deresh Ramjugernatha

a School of Chemical Engineering, University of Kwa-Zulu Natal, Durban 4041, RSA

b DDBST GmbH, Industriestr. 1, 26121 Oldenburg, FRG

c Industrial Chemistry, Carl von Ossietzky University Oldenburg, 26111 Oldenburg, FRG

*(corresponding author, tel.: +49 441 798 3846, fax: +49 441 798 3330, email: rarey@ddbst.de)

19.8.2012: Being prepared for publication

The infinite dilution activity coefficient () plays an important role when determining the phase equilibrium behaviour of compounds which are strongly diluted. Since water is the most used solvent in industry it stands to reason that in water is an important property. There are a fair amount of methods available in literature for the prediction of the activity coefficient in (theoretically) any solvent such as the group contribution methods (UNIFAC, Mod. UNIFAC etc.) and quantum chemical methods (COSMO-RS, COSMO-SAC etc.). While these methods are good for smaller less complicated solutes they tend to fail for larger more complicated solutes. In this paper a method is proposed which treats the infinite dilution activity coefficient in waster as a pure component property and fits it to a simple group contribution scheme. The relative mean deviation (%) for the training set is 7.3 % for 630 compounds and 9.1 % for the test set which contained 25 compounds.

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