Dialkylphosphate-Based Ionic Liquids as Solvents to Extract Toluene from Heptane

Abstract

In this work, the ability of ionic liquids (ILs) 1,3-dimethylimidazolium dimethylphosphate ([MMIM]-[DMP]), 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]), and 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][DBP]) as alternative solvents used in liquid removal of toluene from its combination with heptane was studied. The liquid−liquid equilibrium (LLE) data in relation to ternary systems {toluene + heptane + [MMIM]-[DMP], [EMIM][DEP], or [BMIM][DBP]} calibrated at T = 298.2 K and atmospheric pressure. The LLE results studied in relation to ternary systems were fitted by the thermodynamic nonrandom two-liquid (NRTL) model. The toluene solute distribution ratios and toluene/heptane selectivities, derived from the experimental LLE data, were compiled and analyzed to determine the extraction capacity of the studied ILs. ■ INTRODUCTIONThe separation of toluene and heptane is a difficult and complicated process because of the formation of azeotrope. For the toluene and heptane system, liquid−liquid extraction is a common industrial separation process in which conventional organic compounds such as sulfolane, N-methyl pyrrolidone, or dimethyl sulfoxide 1,2 are used as solvents. However, the disadvantage of these solvents is that they are not environmentally friendly.Over the past decade, ionic liquids (ILs) have received considerable attention for their use as possible replacements for the conventional organic solvents in liquid−liquid extraction because of their notable properties. 3−5 Currently, few publications in relation to the liquid−liquid extraction of toluene from heptane using ILs as solvents have been investigated. Meindersma et al. 6 evaluated the separation of toluene from heptane using sulfolane and 1-alkyl-3-methylimidazolium methylsulfate ([AMIM][MeSO 4 ]) ILs. Larriba et al. 7 investigated the effect of the length of alkyl substituent chain of 1-alkyl-3-methylimidazolium thiocyanate and 1-alkyl-3-methylimidazolium dicyanamide ([AMIM][DCA]) ILs, in the separation of toluene and heptane. Corderíet al. 8 investigated the separation of toluene from heptane using the IL 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]). Ebrahimi et al. 9 studied the LLE data in relation to the ternary system containing bis(trifluoromethylsulfonyl)imide-based ILs with toluene + heptane. In this work, three dialkylphosphate-based ILs, [MMIM]-[DMP], [EMIM][DEP], and [BMIM][DBP], were studied as solvents for the liquid removal of toluene from heptane. Subsequently, the experimental LLE data generated were measured for the ternary systems {toluene + heptane + [MMIM][DMP], [EMIM][DEP], or [BMIM][DBP]} at T = 298.2 K and atmospheric pressure. The NRTL 10 model was used to fit the experimental results for the ternary systems studied. The capacity of the investigated ILs as solvents in the extraction process was analyzed by applying the toluene solute distribution ratios and toluene/heptane selectivities. ■ EXPERIMENTAL SECTION Materials. Toluene with purity of 99.5 % (mass; Sinopharm Chemical Reagent Co., Ltd., Shan...

Comparison of Ionic Liquids to Conventional Organic Solvents for Extraction of Aromatics from Aliphatics

“…Effect of the anion on the (a) selectivity and (b) distribution factor in mole fraction basis and (c) distribution factor in mass fraction basis versus composition of toluene in the upper raffinate phase for the heptane + toluene + [emim] + cation-based ionic liquids systems. Solid symbols, 298.15 K; open symbols, 313.15 K. (Solid black square) [Tf 2 N] − ; (open black square) [Tf 2 N] − ; (solid blue circle) [DEP] − ; (solid green diamond) [OAc] − ; (open orange triangle) [CH 3 SO 3 ] − ; (open purple star) [CF 3 SO 3 ] − ; (cross) [CHF 2 CF 2 SO 3 ] − ; (solid red inverted triangle) [ESO 4 ] − ; (open red inverted triangle) [ESO 4 ] − ; (×) [SCN] − ; (asterisk) [DCA] − ; (dash) [TCM] − ; and (black square with line) sulfolane …”

“…Liquid–liquid phase equilibrium, capacity, and selectivity have been reported for several combinations of aliphatics and aromatics using ionic liquids as the extraction solvent. Among the ionic liquids studied, the cations used are mostly imidazolium ,− and pyridinium. ,,,− A few studies use pyrrolidinium, ammonium, ,, morpholinium, and other cations, , while the most investigated ionic liquid anion is bis­(trifluoromethylsulfonyl)­imide ([Tf 2 N] − ). In addition, aromatic extractions have been performed with ionic liquid mixtures in an attempt to improve both selectivity and capacity. − In some cases, infinite dilution activity coefficients of aromatic and aliphatic compounds in ionic liquids have been used as a first pass evaluation of the suitability of a particular ionic liquid for aliphatic–aromatic separation. …”

Hydrocarbon Extraction with Ionic Liquids

“…Garci ́a et al 214 used [EMIM][Tf 2 N] to separate a toluene/ heptane system at 313.2 K, demonstrating that the IL had a lower selectivity of toluene/heptane than SUL and a higher distribution coefficient of toluene. Cai et al 215…”

Promising Thiolanium Ionic Liquid for Extraction of Aromatics from Aliphatics: Experiments and Modeling

“…Thermophysical properties of these ILs have been previously characterized, and all have densities significantly greater than n -heptane and toluene and decomposition temperatures above 550 K. − Systems of [bthiol]­[Tf 2 N] and n -heptane with o , m , and p -xylene were also measured to test the behavior of different aromatics. One reason ILs are of great interest is that the IL mole fraction in the n -heptane-rich phase is reported as negligible; − ,− however, to assess the feasibility of a commercial process, it is important to know this composition, no matter how small. For this reason, a nuclear magnetic resonance (NMR) method was developed to better quantify this number.…”