Experimental Investigation of Liquid–Liquid Extraction of Toluene + Heptane or Toluene + Hexane Using Deep Eutectic Solvents

Abstract

In this work, the selective separation of toluene from mixtures of toluene + heptane or toluene + hexane was investigated using the newly emerging family of solvents, namely, deep eutectic solvents (DESs), as the extracting agent. The liquid–liquid equilibria (LLE) of these systems were measured at a temperature of 303.2 K and a pressure of 85 kPa. The DESs considered were made of choline chloride as the hydrogen bond acceptor (HBA) and phenol as the hydrogen bond donor (HBD), at the two different HBA–HBD molar ratios of 1:3 and 1:4. The experimental liquid–liquid equilibrium data, along with the selectivities and distribution coefficients, were reported for each set of equilibrium data and also compared with other ternary systems in the literature containing toluene + heptane or toluene + hexane and various solvents. The experimental results revealed that the studied DESs in this work have the potential to be utilized in the separation of toluene from either hexane or heptane at low concentrations of toluene. The experimental LLE data was also modeled using the nonrandom two-liquid (NRTL) model. The values of the root-mean-square deviations of the NRTL results with respect to experimental values indicated acceptable agreement, suggesting NRTL as a potential model for such systems.

Aqueous mixture viscosities of phenolic deep eutectic solvents

“…Figure 2 shows the significant effect of water on viscosity depression in both systems, where by adding only 10% (molar basis) of water to the investigated DESs, the viscosity can decrease by almost 25%. The experimental density values of neat DES1 and DES2 at the investigated temperatures, as well as DES2+ water systems at the investigated temperatures and compositions, are available in earlier studies by our group [5,26]. 24, these negative values show that the mixture viscosity is less than the molar arithmetic average viscosities of the pure DES and water.…”

“…They were introduced by Guo et al in 2013 [23] by proposing choline chloride + phenol mixtures at five different molar compositions (1:2 -1:6). After their introduction, this category of phenolic DESs, at different molar ratios, was considered for the various applications of CO2 capture [24,25], liquid-liquid extraction, [26,27] and utilization in solar cells [28]. Up to now, only two studies have been devoted to investigating the physical properties of this family of DESs in mixtures with other components.…”

A Review of the Use of Eutectic Solvents, Terpenes and Terpenoids in Liquid–liquid Extraction Processes

“…In the separation of hydrocarbons, the NRTL thermodynamic model has been successfully used in the correlation of the ternary liquid-liquid equilibria obtained in the separation with eutectic solvents of benzene and toluene from cyclohexane [57,58], BTEX from n-octane [54], toluene from n-hexane, n-heptane or n-octane [51,52,62,63], ethylbenzene from n-octane [64], ethylbenzene from styrene [65], thiophene from n-hexane and n-octane, pyridine and toluene from n-hexane [82], pyridine or benzothiazole from n-hexane, n-heptane and n-octane [83,84] and tetralin from dodecane [85]. On the other hand, the UNIQUAC model was simultaneously used with the NRTL model in the correlation of equilibria in the separation of toluene, quinoline and iodine from n-heptane [61,86] and in the extraction of benzene from thiophene and cyclohexane from hexadecane [59].…”

Pyridine Ionic Liquid-Based Deep Eutectic Solvents Selectively Separating Toluene from Alkanes

“…At present, organic solvents are used as extractants for the separation of aromatic/alkane mixtures, such as sulfolane, N -methyl pyrrolidine (NMP), N -formyl morpholine (NFM), dimethyl sulfoxide (DMSO), ethylene glycols, or propylene carbonate. − However, the toxicity, volatility, selectivity, and separation performance of organic solvents limit their development. In recent years, ionic liquids (ILs) and deep eutectic solvents (DESs) with designable structures and adjustable properties have become a hot spot for the design and development of new functionalized solvents due to their low volatility, low toxicity, high stability, and so forth. − Among them, DESs have become a potential choice of extractants for aromatic/alkane separation due to the advantages of simple synthesis process, easy availability of raw materials, and so forth. − …”