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.