Liquid–liquid equilibrium data and thermodynamic modeling for systems related to the production of ethyl esters of fatty acids from soybean soapstock acid oil

•We measured LLE for the ethanol-based biodiesel systems.•Soybean soapstock acid oil + FAEE + (ethanol + water) were measured.•Tie lines and binodal curves were measured for all systems.•The experimental data were well modeled using NRTL and UNIQUAC models.

We obtained liquid–liquid equilibrium (LLE) data for the systems involved in biodiesel production from a low-value feedstock, namely fatty acids from soybean soapstock acid oil (FA-SSAO), at 303.2 and 323.2 K. The systems studied were water + ethanol + FA-SSAO and water + ethanol + fatty acid ethyl esters (EE-SSAO). The mass fractions of the compounds in equilibrium in the two phases were determined analytically, whereas the binodal curves were obtained by the cloud-point method. The increase in temperature from 303.2 and 323.2 K slightly increased the miscibility of the EE-SSAO system. We found that ethanol is more soluble in water than in either FA-SSAO or EE-SSAO, and that an increase in ethanol content in either the FA-SSAO-rich phase or the EE-SSAO-rich phase enhances water solubility in these phases. The experimental data were satisfactorily modeled by the NRTL and UNIQUAC approaches.