Phase Equilibria for Systems Containing Refined Soybean Oil plus Cosolvents at Different Temperatures

Investigation of mutual solubility between vegetable oil and five low-toxic cosolvents is assessed. Liquid-liquid equilibrium data were experimentally collected for systems containing refined soybean oil plus cosolvents composed of {(anhydrous ethanol, ethyl lactate, or dimethyl sulfoxide) plus water} and {(ethyl lactate or dimethyl sulfoxide) plus formic acid} at different temperatures. Compared with pure solvent-oil systems (previous results), it was observed that addition of water or formic acid decreases the mutual solubilities of cosolvent-oil systems. Low quantities of the oil were found in cosolvent-rich phases, and very poor solubility occurs for the system containing oil plus dimethyl sulfoxide plus water. Experimental data were satisfactorily correlated by the NRTL and UNIQUAC models, presenting global deviations lower than 0.29%. Furthermore, predictions using five different versions of the UNIFAC method (UNIFAC-LL, UNIFAC-DMD, UNIFAC-LBY, original UNIFAC with parameters of Hirata et al., and UNIFAC-NIST) agreed for some cases. However, results showed a necessity to improve the predictive capacity of the UNIFAC methods for fatty systems.