Phase Equilibria in Triacylglycerols – Ethanol – Oleic Acid – Athyl Oleate Quasi-Quaternary System

Abstract

In order to use waste vegetable oils to produce biodiesel a possibility of reagents (sunflower oil and ethanol) mixture homogenization under the simultaneous effect of two cosolvents (oleic acid and ethyl oleate) was investigated. The possibility of action of oleic acid and ethyl oleate as cosolvents was analyzed with GSP model. For qualitative assessment of the intermolecular interaction parameter ξ was used. This parameter is a measure of the ratio between cross-association (solvation) energy A–B and self-association (association) energies A–A and B–B. It was shown that most important role at intermolecular interactions of oleic acid and ethyl oleate with triglycerides belonged to dispersion forces. Predominant contribution of hydrogen bonds in the interaction of oleic acid and ethyl oleate with ethanol was shown. The prediction of improving the effect of the cosolvents with temperature increasing was done, and it was confirmed by experimental results. The effect of oleic acid and ethyl oleate as cosolvents for homogenization of mixtures of sunflower oil and ethanol was investigated experimentally by studying the phase equilibria in the quasi-quaternary system triacylglycerols (sunflower oil) – ethanol – oleic acid – ethyl oleate at 30, 40, 50, 60 and 70 °C. The results of the experiments are presented in the form of phase diagrams of quasi-ternary boundary systems: triacylglycerols – oleic acid – ethanol and triacylglycerols – ethyl oleate – ethanol, and the phase diagrams of composition tetrahedron sections with five different ratios of components oleic acid: ethyl oleate. Generalization of the research results is presented in the form of polythermal phase diagram for the system triacylglycerols – ethanol – oleic acid – ethyl oleate. Solubility polytherms (from 30 to 70 °C) for the system triacylglycerols – ethanol – mixed cosolvent with different ratios of oleic acid and ethyl oleate were plotted.

Keywords

• biodiesel, waste vegetable oils, cosolvents, oleic acid, ethyl oleate, phase equilibrium, homogenization.