Modeling of liquid–liquid equilibrium of systems relevant for biodiesel production using Backtracking Search Optimization

• Backtracking Search Optimization is used for liquid–liquid equilibrium modeling of biofuels mixtures.
• The closure equation is used to improve the performance of Backtracking Search Optimization.
• NRTL model offers the best performance for LLE data modeling of tested biofuels systems.

In this paper, the liquid–liquid equilibrium of thirty ternary systems relevant for biodiesel production was modeled using the NRTL and UNIQUAC equations and the Backtracking Search Optimization algorithm (BSOA). Performance of this new optimization method for liquid–liquid equilibrium (LLE) parameter estimation, with and without the application of the closure equations, has been analyzed and compared with those obtained using the genetic algorithm (GA) and harmony search algorithm (HAS). Results on the estimation of the interaction parameters of local composition models showed that BSOA with the closure equations can provide promising results in tested biofuel systems. The use of closure equations improves the performance of BSOA for LLE parameter estimation in biofuels mixtures. However, the selection in the parameter elimination using closure equation is relevant for obtaining the best results in LLE data modeling. Finally, NRTL offers the best performance for LLE data modeling of tested ternary systems and this model is attractive for process system engineering in biodiesel production and purification.