Thermodynamic excess properties of ternary alcohol-hydrocarbon systems. Simplified method for predicting enthalpies from binary data

Abstract

Two general equations for estimation of excess enthalpies of ternary systems consisting of an alcohol and two hydrocarbons from observed excess properties of the various binary combinations have been developed. The first expression is based on the Kretschmer-Wiebe association model and takes the form $$\Delta \overline H _{ABC}^{ex} = h_A x_A K_A (\phi _{A1} - \phi _{A1}^o ) + Q_{ABC}$$ where $$\begin{gathered} Q_{ABC} = (x_A + x_B )(\phi _A + \phi _B )(\Delta \overline H _{AB}^{ex} )_{phys}^ \bullet + (x_A + x_C )(\phi _A + \phi _C )(\Delta \overline H _{AC}^{ex} )_{phys}^ \bullet \hfill \\ + (x_B + x_C )(\phi _B + \phi _C )(\Delta \overline H _{BC}^{ex} )_{phys}^ \bullet \hfill \\ \end{gathered}$$ \((\Delta \overline H _{ij}^{ex} )_{phys}^ \bullet\) represents the physical interactions in each of the individual binary systems, and the term involving φ A1 o represents the chemical contributions (caused by self-association) to the excess enthalpies of mixing. The second predictive expression is based on the Mecke-Kempter association model and is given by $$\Delta \overline H _{ABC}^{ex} = - h_A x_A [In(1 + K_A \phi _A )/K_A \phi _A - In(1 + K_A )/K_A ] + Q_{ABC}$$ where the first term (contained within brackets) represetns the chemical contributions to the enthalpies of mixing. The predictions of both expressions are compared with experimental data for the excess enthalpies of six ternary systems.