Liquid-Liquid Equilibria in Ternary and Quaternary Systems Present in Biodiesel Production from Soybean Oil at (298.2 and 333.2) K

Liquid-liquid equilibrium (LLE) data for soybean oil biodiesel (BIO-SO) + ethanol + glycerol and BIO-SO + ethanol + glycerol + sodium hydroxide systems at (298.2 and 333.2) K and atmospheric pressure (approximate to 95 kPa) were determined by gas chromatography and potentiometric titration. These systems occur in the biodiesel production process and present a biodiesel-rich (upper layer) and a glycerol-rich phase (bottom layer). The influence of temperature and NaOH in ethanol partition coefficient (K) and biodiesel selectivity (S) was studied. Results show that ethanol distributes preferably to the glycerol-rich phase and that biodiesel solubilizes more ethanol than glycerol. Increasing the temperature by 35 K causes an increase in K and S. Adding 1 wt % of NaOH in the system does not affect K but enhances S at 298.2 K and diminishes it at 333.2 K. The nonrandom two-liquid (NRTL) model was used for correlation LLE experimental data, presenting a root-mean-square deviation equal to 1.6 % for both ternary and quaternary systems. Data were submitted to the Ishida test, giving R-2 > 0.96 for all systems.