Vapor Pressure Measurements and Predictions for Binary Systems Containing Ethyl Octanoate or Ethyl Dodecanoate as Biodiesels and n-Tetradecane as Petrodiesel Compound

Abstract

The present work falls within the research line focused on the phase equilibria of binary mixtures comprising typical compounds, widely present in biodiesel/petrodiesel blends. The study was performed by investigating the liquid–vapor equilibria and thermodynamic properties of two binary systems: ethyl octanoate (1) + n-tetradecane (2) and ethyl dodecanoate (1) + n-tetradecane (2) using experimental and computational methods. The experimental data of vapor pressures were measured through a static apparatus at nine temperatures from (373.15 K and 453.15 K) with an interval of 10 K. The obtained experimental data are used to determine the activity coefficients (γ_i) and excess molar Gibbs energies (G^E) of the investigated binary mixtures by applying the Redlich–Kister equation according to Barker’s method. Positive values of the excess molar Gibbs energy are obtained for all the investigated constant temperatures and over the whole composition range. The obtained G^E values were correlated by using two semi-predictive models (NRTL and Heil). The prediction displays agreement with the experimental data obtained with Barker’s method. The present work provides a set of thermodynamic data that may be very useful for the development of eco-friendly alternative biodiesel.