Liquid-liquid equilibrium of systems containing triolein + (fatty acid/ partial acylglycerols/ester) + ethanol: Experimental data and UNIFAC modeling

Abstract

The demand for biofuels, such as biodiesel, has a very powerful appeal nowadays. In some countries, such as Brazil, the biodiesel production by ethylic route has some advantages, since ethanol is a renewable alcohol produced in a large scale and at a competitive production cost. Besides being an alternative reactant, ethanol can be used as a solvent for extracting vegetable oils from seeds and also for deacidifying crude vegetable oil by liquid-liquid extraction. Such characteristics of ethanol suggest the need to investigate the ethylic route for biodiesel production. The comprehension of liquid-liquid equilibrium (LLE) is essential for the design and optimization of liquid-liquid extraction for deacidification processes of vegetable oils and for systems which correspond to the initial stage of transesterification reaction with ethanol. In this context, this study aimed to measure the liquid-liquid equilibrium data of ternary systems with pure fatty components containing triolein + (fatty acid or partial acylglycerols or ester) + ethanol at 45 °C. As the prediction of UNIFAC with literature parameters was poor, these ternary data were used to readjust the UNIFAC parameters. The global average deviation between experimental and calculated compositions decreased from 6.48% to 1.48%. The prediction capacity of the UNIFAC model with this new parameter set was evaluated in multicomponent systems related to biodiesel production. An improvement in the prediction of the LLE with these parameters was achieved in comparison to the results using the original UNIFAC parameters available in the literature.