Liquid-liquid equilibria for ternary systems containing ethylic palm oil biodiesel + ethanol + glycerol/water: Experimental data at 298.15 and 323.15 K and thermodynamic modeling

Several plant species have been proposed as source of oil for the transesterification reaction that generates the mixture of esters known as biodiesel; this biofuel has been considered as an energetic solution to the political, economic and environmental problems related to the use of petroleum-based fuels. The biodiesel process produces, stoichiometrically, 10% by volume of glycerol. Therefore, purification of the products after the reaction is mandatory. One of the most commonly used methods for biodiesel purification is washing with water. Nevertheless, the limited knowledge of the liquid-liquid equilibria of systems containing biodiesel + alcohol + different solvents have limited the understanding of phase separation and operating conditions of the biodiesel production and purification units, specially by the ethylic route. This work aims at the experimental determination and thermodynamic modeling of liquid-liquid equilibrium data in ternary systems containing ethylic palm oil biodiesel, ethanol and (glycerol or water) at temperatures of 298.15 and 323.15 K and atmospheric pressure. Densimetry and refractive index were the analytical techniques used for the determination of the phase compositions. The results confirmed the efficiency of washing as a method for recovering ethanol from the ester-rich phase generated at the end of the transesterification reaction. The thermodynamic modeling with the NRTL model showed good correlation with the experimental equilibrium data, especially at low and medium concentrations of ethanol.