Binodal curves of systems involved in the production of soybean oil biodiesel and castor oil biodiesel were obtained at different temperatures by the titration method under isothermal conditions. The measurements allow the analysis of the mutual solubility of the compounds present after the transesterification reaction and supply data for the process of separation and purification of biodiesel. The systems studied were soybean oil biodiesel + glycerol + ethanol at temperatures of (298.15, 333.15, and 343.15) K, soybean oil biodiesel + ethanol + water at temperatures of (298.15 and 323.15) K, and castor oil biodiesel + ethanol + glycerol to 333.15 K. The highest levels of biodiesel were obtained at 298.15 K, although small changes in temperature did not significantly affect the system behavior. The two-phase region for the system of ethanol + biodiesel + glycerol at 333.15 K using soybean oil as raw material was bigger than the two-phase region using castor oil, which allows us to separate higher amounts of biodiesel after the transesterification reaction at the stage of interest.

In this work, ternary liquidÀliquid equilibrium (LLE) data for the castor oil biodiesel (BIOÀCO) þ ethanol þ glycerol and quaternary LLE data for biodiesel (BIOÀCO) þ ethanol þ glycerol þ NaOH systems at (298.2 and 333.2) K and atmospheric pressure (≈ 95 kPa) were determined by gas chromatography. The influence of temperature and catalyst in the phase diagrams were studied. Ethanol partition coefficients and biodiesel selectivities were calculated. Results showed that ethanol distributed slightly more to the glycerol phase and that biodiesel solubilizes preferentially ethanol than glycerol. LLE experimental data were correlated with the NRTL model, presenting root-mean-square deviations < 1.3 %. Hand and Othmer-Tobias correlations were used to test the data quality, which presented R 2 > 0.98 for all systems.

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 (≈ 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 glycerolrich 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.

In this work, experimental liquid-liquid equilibrium data for the ternary system water + acrylic acid + 4-methyl-2-pentanone were determined at 298.15 K and atmospheric pressure. The experimental data were also compared with the values correlated by the NRTL and UNIQUAC models. Good quantitative agreement was obtained with these models. In general, the average deviations from the NRTL model are slightly greater than those from the UNIQUAC model. The reliability of the experimental tie-line data was confirmed by using the Othmer-Tobias correlation. Distribution coefficients and selectivity were evaluated for the immiscibility region.

Liquid–liquid equilibrium (LLE) data for the soybean oil biodiesel (BIO-SO) + ethanol + water and castor oil biodiesel (BIO–CO) + ethanol + water systems at (298.2 and 333.2) K and atmospheric pressure were determined by gas chromatography and volumetric Karl Fischer titration. The degree of consistency of the experimental LLE data was ascertained by applying the Hand and Othmer-Tobias correlations. Ethanol distribution coefficients and water selectivity were evaluated for the immiscibility region. The experimental data were also compared with the values correlated by the NRTL and UNIQUAC activity coefficient models. For all systems studied, the average deviations found for the UNIQUAC model are larger than those found for the NRTL model.