Use of Glycerol + 2-Methylpentane-2,4-diol Liquid Mixtures in the Separation of Toluene from n-Heptane via Liquid-Liquid Extraction

The use of 2-methyl-2,4-pentanediol as a potential cosolvent to glycerol was studied in order to investigate its impact on solvent capacity in the separation of toluene from n-heptane via liquid-liquid extraction. To this end, quaternary liquid-liquid equilibrium (LLE) data were experimentally measured for the system n-heptane + toluene + glycerol + 2-methyl-2,4-pentanediol at 298.2 and 313.2 K and 0.1 MPa. The measurements were conducted in a double-walled glass cell using the direct analytical method, and phase compositions were analyzed via gas chromatography. The data were correlated using the NRTL and UNIQUAC models, which were able to suitably represent the tie-line compositions. At different molar ratios of solvent to cosolvent, the selectivity and solvent capacity were calculated and compared to that of using pure glycerol. It was ascertained that the pseudo-ternary systems possess type I or type II behaviors depending on the molar ratio of glycerol to 2-methyl-2,4-pentanediol. It was observed that solvent capacity is not appreciatively improved for molar ratios that exhibit type II behavior; however, significant increases in capacity were noted for high molar ratios producing a type I system.