Phase Diagrams for Liquid-Liquid Equilibrium of Neopentyl Glycol plus Sodium Formate plus Water

Phase diagrams for the ternary (neopentyl glycol + sodium formate + water) system were measured. Phase equilibrium data were obtained at different temperatures of 333.15, 343.15, and 353.15 K. The effect of temperature on the liquid-liquid phase equilibrium was studied and the length, and slope of the tie-line at different temperatures for the conjugate phase were investigated. It was found that the tie-line length decreases and the two-phase area is slightly reduced by increasing temperature. The three fitting parameters of the Merchuk and Pirdashti equations were obtained with the temperature dependence expressed in the linear form, respectively. Compared with the Pirdashti equation, the binodal curves were described satisfactorily with the Merchuk equation, further, the plait points at various temperatures were estimated by extrapolation. The Othmer-Tobias and Hand models were used for the correlation of the phase equilibrium behavior. The correlation coefficients of the models were obtained for the corresponding temperatures. The results showed that it was well fitted with the Othmer-Tobias model by contrast with the Hand model.