A short note on the use of an equation of state (EOS) based approach to modelling the thermodynamics of biodiesel systems

• Fuel surrogates for biodiesels, from six different vegetable oils, were presented.
• Preliminary attempt to use an EOS for biodiesel phase equilibrium predictions.
• Equation of State Binary interaction parameters, for biodiesels, were regressed.
• Predictions were made for VLE and LLE, using the new interaction parameters.
• The predicted results compared unsatisfactorily to experimental data.

An initial attempt to adapt the Peng–Robinson EOS, with Huron–Vidal mixing rules, for the prediction of phase equilibrium in the production of biodiesel is described in this work. Six vegetable oils and methanol were chosen to constitute the feedstock. In order to describe the chemical composition of the vegetable oils, a fuel surrogate technique was employed. In regressing the binary interaction parameters for the equation of state, it was found that the necessary binary phase equilibrium data were seldom available in the literature. Thus, the EOS was formulated as a predictive model in which the KT-UNIFAC method was used to assist in generating binary interaction parameters. The EOS was subsequently tested by computing phase equilibrium and then comparing the results to the small amount of available experimental data. It was found that the predictions ranged from less than satisfactory to very good.