1-Ethyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide as solvent for the separation of aromatic and aliphatic hydrocarbons by liquid extraction – extension to C7- and C8-fractions

Abstract

The ionic liquid 1-ethyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide ([C 2 mim][NTf 2 ]) was tested as solvent for the separation of aromatic and aliphatic hydrocarbons containing 7 or 8 carbon atoms (the C 7 -and C 8 -fractions). The liquid-liquid equilibria (LLE) of the ternary systems (heptane), at 25 • C, were experimentally determined. The performance of the ionic liquid as the solvent in such systems was evaluated by means of the calculation of the solute distribution ratio and the selectivity. The results were compared to those previously reported for the extraction of benzene from its mixtures with hexane by using the same ionic liquid, therefore analysing the influence of the size of the hydrocarbons. It was found that the ionic liquid is also good for the extraction of C 7 -and C 8 -fraction aromatic compounds, just a greater amount of ionic liquid being needed to perform an equivalently efficient separation than for the C 6 -fraction. It is also discussed how [C 2 mim][NTf 2 ] performs comparably better than the conventional solvent sulfolane. The original 'Non-Random Two-Liquid' (NRTL) equation was used to adequately correlate the experimental LLE data.

Liquid–liquid equilibria for ternary systems of {cyclohexane+aromatic compounds+1-ethyl-3-methylpyridinium ethylsulfate}

“…This model was not originally developed for systems that involve electrolytes, but nevertheless it has been widely used in the modelling of both LLE and vapour-liquid equilibria (VLE) in a variety of electrolyte systems, usually leading to good correlations for systems containing ILs. Also several authors used this model to describe their measurements of LLE with ILs [3][4][5][6][7][10][11][12][13][14].…”

“…However, these organic solvents are generally toxic, volatile, and flammable, causing harm effect to the environment. Nowadays [2][3][4][5][6][7][8][9][10][11][12][13][14][15], the ionic liquids are an attractive alternative to replace these organic solvents while improving performance and causing less damage to the environment and human health. Nevertheless, there are few publications concerning extraction of aromatic hydrocarbons from mixtures of aromatic and cycloalkanes using ionic liquids [9,10,15].…”

Measurement and correlation of liquid–liquid equilibria for ternary systems {cyclooctane+aromatic hydrocarbon+1-ethyl-3-methylpyridinium ethylsulfate} at T=298.15K and atmospheric pressure

“…However, in recent years the number of researchers working in this field has increased. Maduro and Aznar [1] studied the separation of aromatics (benzene, toluene, or m-xylene) from aliphatics (nonane, or undecano) using 1-butyl-3-methylimidazolium hexafluorophosphate; Domanska et al studied the effect of the ionic liquid cation on the ternary system {hexane + p-xylene + IL} at T = 298.15 K [6], and the separation of aromatic hydrocarbons from alkanes using an ammonium ionic liquid [7]; Arce et al [8][9][10][11] analyzed the separation of aromatics from alkanes using bis{(trifluoromethyl)sulfonyl}amide ionic liquids as solvents; Abu-Eishah and Dowaidar [12] investigated the separation of cyclohexane form aromatic compounds (benzene, or toluene, or ethylbenzene, or +o-xylene) using 4-methyl-N-butypyridinium tetrafluoroborate ionic liquid as solvent at T = 303.15 K; Wang et al [13] studied the liquid-liquid equilibria for the systems {benzene + cyclohexane + 1-methyl-3-methylimidazolium dimethylphosphate or 1-ethyl-3-methylimidazolium diethylphosphate}; Letcher and Reddy [14] presented a comparative study of two ionic liquids (1-hexyl-3-methylimidazolium tetrafluoroborate, and 1-hexyl-3-methylimidazolium hexafluorophosphate) as solvents in the separation of benzene from alkanes (heptane, dodecane, and hexacane); Pereiro and Rodríguez [15] carried out a investigation about the application of the ionic liquid Ammoeng 102 for aromatic/aliphatic hydrocarbon separation; and, García et al [16,17] reported LLE data for the separation of benzene from hexane using 1-butyl-3-methylimidazolium methylsulfate and 1-ethyl-3-methylimidazolium ethylsulfate ionic liquids at three temperatures and atmospheric pressure.…”

Ionic Liquid–Liquid Chromatography: A New General Purpose Separation Methodology

“…Most hydrophobic ionic liquids are very poorly soluble in water phases, but water has appreciable solubility in the ionic liquid phase. Thus, if the mobile phase in CCC is water, then product isolation is simply a matter of evaporating the water phase [40,124,125,129,[141][142][143][144].…”

“…This requires both experience and a database of ionic liquid properties [147][148][149]. For the separations discussed here (Table 4), the biphasic combinations of ionic liquids and molecular solvents were chosen based on previous research into ionic liquid phase behaviour and solvent extraction studies (also see Section 3.4) [40,42,124,125,129,[141][142][143]149]. One of the simple ways to find and select biphasic system consisting of ionic liquids and other solvents is demonstrated in Fig.…”