Phase equilibrium measurements and thermodynamic modeling of binary mixtures containing a diesel compound n-dodecane + biodiesel compounds: Ethyl dodecanoate and ethyl octanoate

The vapor pressures of two binary systems ethyl dodecanoate (1) + n-dodecane (2) and ethyl octanoate (1) + n-dodecane (2), were measured by means of a static apparatus at temperatures between 373.15 K and 453.15 K. The data were correlated with the Antoine equation. From these data, the molar excess Gibbs energies GE were obtained with Barker's method and fitted to the Redlich-Kister equation. The binary mixture (ethyl octanoate (1) + n-dodecane (2)) exhibits maximum azeotropic behavior. Positive values of the excess Gibbs energy are obtained for all the investigated constant temperatures and over the whole composition range. The data were also correlated by using Wilson equation and good results were obtained in the prediction of the total pressure and thermodynamic excess properties; however deviations were observed with respect to the experimental and predicted GE, using modified UNIFAC (Dortmund) group contribution model. Additionally, the NRTL model was applied to regress the experimental GE. The investigated systems were successfully represented by the NRTL model.