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

Abstract

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.

Hydrocarbon Extraction with Ionic Liquids

“…The IL selection criteria for separating aromatics from aliphatic hydrocarbon mixtures include the distribution coefficients of aromatics and selectivity toward aromatics/aliphatics. Toluene/ n -heptane is a typical representative system for which liquid–liquid extraction methods are commonly used to separate toluene from heptane. ,− Arce et al used [EMIM]­[Tf 2 N] as an extraction solvent to separate toluene in a toluene/ n -heptane system at 298.15 K, and the IL’s performance as a solvent was evaluated by calculating the solute distribution ratio and selectivity. No IL was observed in the upper equilibrium phase of any contact line with heptane and toluene in the system, but a small amount of IL was detected in the upper phase of some equilibrium mixtures of octane and ethylbenzene in the system.…”

“…Extraction agent selection is undoubtedly a key factor in achieving efficient liquid–liquid extraction. Generally, organic solvents with high boiling points are used as extraction agents, such as sulfolane (SUL), N -methyl­pyrrolidone (NMP), dimethyl sulfoxide (DMSO), glycols, N -formyl­morpholine, and silicone oil. − Among them, SUL is widely used in aromatic hydrocarbon extraction due to its special properties . However, these solvents have unavoidable drawbacks, including (i) being partially dissolved in hydrocarbons, causing secondary pollution of products; (ii) inevitable volatile losses; and (iii) poor thermal stability resulting in solvent degradation during regeneration processes.…”