A New Theoretical Approach for Predicting Excess Properties of Alkanol/Alkane Mixtures

Quasichemical models and association theories have successfully been applied in literature to describe the excess Gibbs energy GE and the excess enthalpy HE of alkanol/alkane mixtures. These theories, however, are unable to predict the excess volume VE because of the restriction to the rigid lattice model. A derivation of a new approach based on a partition function is given in this work which combines the Kretschmer‐Wiebe association model with an equation of state developed by Flory et al. for nonpolar molecules of chainlike structure. The combined model contains two adjustable mixing parameters. It leads to a simultaneous description of GE, HE, and VE which is in good agreement with experimental GE and HE data of alkanol/alkane mixtures tested for mixtures of ethanol, propanol, hexanol, octanol, decanol, and dodecanol + hexane and nonane respectively. Experimental data of VE of the different alkanol/alkane systems ranging from strong positive over S‐shaped to negative concentration dependence are described correctly in qualitative respect. In some cases even quantitative agreement can be obtained.