Liquid-Liquid Equilibrium Studies for Potential Solvents/Cosolvents for the Separation of Aromatics and Alkanes

Liquid-liquid equilibria (LLE) data for ternary systems of n-heptane + a solvent mixture + toluene were measured at 298.15 and 313.15 K and 101.3 kPa. The solvents investigated are mixtures of N-methylpyrrolidone and glycerol, with ratios of N-methylpyrrolidone to glycerol of 90:10, 70:30, and 50:50. LLE measurements were carried out using the direct analytical method, and the composition analysis was performed using gas chromatography. The effectiveness of the solvent mixtures of N-methylpyrrolidone and glycerol in extracting toluene from n-heptane was evaluated by determining the solvent selectivity and capacity and evaluating the extent of the two-phase region. All systems investigated were found to exhibit type I LLE behavior. The binodal curves were correlated to the Hlavatý β function and log γ equations. The tie-lines were correlated with the NRTL and UNIQUAC activity coefficient models. A comparison of the root-mean-square deviation (rmsd) showed that the NRTL model provided a better correlation for all systems.