The thermochemistry of solvation of imidazolium-based ionic liquids in benzene

ABSTRACT

The present work is devoted to the thermochemical study of solvation of ionic liquids (IL) in benzene. The solution enthalpies of 1-ethyl-3-methylimidazolium tricyanomethanide [EMIM][C(CN)₃], 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF₄], 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIM][PF₆], 1-octyl-3-methylimidazolium tetrafluoroborate [OMIM][BF₄], 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [EMIM][NTf₂], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [BMIM][NTf₂] and 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM][TfO] in benzene were measured. The solvation enthalpies of imidazolium-based IL were calculated. Molar refractions of imidazolium-based IL form literature data on density and refractive indexes of IL were also calculated. The linear correlation between solvation enthalpy and molar refraction of IL was observed. This correlation can be used to calculate the vaporization enthalpy of imidazolium-based IL from solution calorimetry data.     

Synthesis,physical, and thermodynamic properties of 1-alkyl-cyanopyridinium bis{(trifluoromethyl)sulfonyl}imide ionic liquids

Synthesis of new ionic liquids (ILs) viz. 1-butyl-3-cyanopyridinium bis{(trifluoromethyl)sulfonyl}imide, [BCN³Py][NTf₂], 1-hexyl-3-cyanopyridinium bis{(trifluoromethyl)sulfonyl}imide, [HCN³Py][NTf₂], 1-hexyl-4-cyanopyridinium bis{(trifluoromethyl)sulfonyl}imide, [HCN⁴Py][NTf₂], and 1-octyl-3-cyanopyridinium bis{(trifluoromethyl)sulfonyl}imide, [OCN³Py][NTf₂] were performed. The specific basic characterization of new compounds by NMR spectra, elementary analysis, water content and glass transition temperature as well as melting temperature, enthalpy of fusion and decomposition of compounds TG/DTA determined by the differential scanning calorimetry, DSC is presented. The heat capacity was measured at three temperatures (298.15, 323.15, and 353.15) K and at pressure 0.1 MPa. The effect of temperature on the density and viscosity is reported over the temperature range from (293.15 to 363.15) K and at 0.1 MPa. The density and viscosity correlation for these systems was provided by an empirical polynomial. From the density–temperature dependence, the isothermal expansion coefficient (volume expansivity), α, was calculated. The surface tension of pure ionic liquids was measured at 0.1 MPa at five temperatures (298.15, 308.15, 318.15, 328.15, and 338.15) K. The surface thermodynamic functions such as surface entropy and enthalpy, critical temperatures according to the Eötvös and Guggenheim definition and the total surface energy of the ILs studied were derived from the temperature dependence of the surface tension values. The parachor and speed of sound for pure ionic liquids were described within a range of temperature from (298.15 to 338.15) K. A qualitative analysis on these quantities in terms of molecular interactions is reported.     

Formation of metastable crystals of [C4mim][NTf2] and [C6mim][NTf2]

Heat capacities of crystalline 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C₄mim][NTf₂] and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C₆mim][NTf₂] in the range 80 K-T_fus were measured in an adiabatic calorimeter. Anomalies in the heat-capacity curves for the both compounds occurred near 240 K. Positions of the anomalies depended on thermal history of the samples. More stable crystals had higher heat capacities in the range 220-260 K. Below 200 K heat capacities of all the crystals of the same compound were indistinguishable.     

Thermodynamic properties and polymorphism of 1-alkyl-3-methylimidazolium bis(triflamides)

Heat capacities in a range of temperatures of (5 to 370) K, enthalpies and temperatures of phase transitions for 1-ethyl-3-methylimidazolium bis(triflamide) ([C₂mim][NTf₂]) and 1-octyl-3-methylimidazolium bis(triflamide) ([C₈mim][NTf₂]) have been determined by adiabatic calorimetry. [C₂mim][NTf₂] has been found to form four crystalline phases with different fusion temperatures. Formation of the phases can be controlled by the temperature of annealing during crystallization. [C₈mim][NTf₂] forms three sequences of crystalline modifications, each including two polymorphs. Based on results of the measurements, thermodynamic functions for the compounds under study have been calculated.A heat-capacity anomaly near T = 230 K reported earlier for [C₄mim][NTf₂] and [C₆mim][NTf₂] have been found in some crystalline modifications of both the studied compounds. The position of the anomaly depends on the temperature of annealing of the crystals.     

Thermodynamic properties of the N-octylquinolinium bis{(trifluoromethyl)sulfonyl}imide

This work is a continuation of our wide ranging investigation on quinolinium based ionic liquids (ILs). The study includes specific basic characterisation of the synthesized compounds N-octylquinolinium bromide, [OQuin][Br] and N-octylquinolinium bis{(trifluoromethyl)sulfonyl}imide [OQuin][NTf₂] by NMR spectra, elementary analysis and water content. Differential scanning calorimetry (DSC) measurements gave us properties of the pure [OQuin][NTf₂] i.e. melting and glass-transition temperatures, the enthalpy of fusion as well as heat capacity at the glass transition. Densities and viscosities were determined as a function of temperature. The temperature-composition phase diagrams of 10 binary mixtures composed of organic solvent dissolved in the IL: {[OQuin][NTf₂] + aromatic hydrocarbon (benzene, or thiophene, or toluene, or ethylbenzene, or n-propylbenzene), or an alcohol (1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol, or 1-dodecanol)} were measured at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from (250 to 370) K. For mixtures with benzene and alkylbenzenes, the immiscibility gap in the liquid phase in a low mole fraction of the IL was observed with upper critical solution temperature (UCST) higher than the boiling point of the solvent. In the system with thiophene, the immiscibility gap is lower and UCST was measured. For binary mixtures with alcohols, complete miscibility in the liquid phase was observed for 1-butanol and 1-hexanol. In the systems with longer chain alcohols, the immiscibility gap with UCST was noted. Typical behaviour for ILs was observed with an increase of the chain length of an alcohol the solubility decreases. The well-known NRTL equation was used to correlate experimental (solid + liquid), SLE and (liquid + liquid), LLE phase equilibrium data sets.     

1-Alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids as solvents in the separation of azeotropic mixtures

(Liquid + liquid) equilibrium data for the ionic liquids 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMim][NTf₂], 1-propyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [PMim][NTf₂], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [BMim][NTf₂], and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [HMim][NTf₂], mixed with ethanol and heptane were studied at T = 298.15 K and atmospheric pressure. The ability of these ionic liquids as solvents for the extraction of ethanol from heptane was evaluated in terms of selectivity and solute distribution ratio. Moreover, density and refractive index values over the miscible region for the ternary mixtures were also measured at T = 313.15 K. Finally, the experimental data were correlated with the Non Random Two Liquids (NRTL) and UNIversal QUAsi Chemical (UNIQUAC) thermodynamic models, and an exhaustive comparison with available literature data of the studied systems was carried out.     

Radiation-induced darkening of ionic liquid [C4mim][NTf2] and its decoloration

The radiation effect on a hydrophobic room-temperature ionic liquid (RTIL), 1-butyl-3-methyl-imidazolium bis[(trifluoromethyl)sulfonyl]imide ([C₄mim][NTf₂]), was studied by γ-irradiation under nitrogen atmosphere. Accompanied by color darkening and increase of light absorbance in a wide wavelength range, a distinct absorption peak at around 290 nm for irradiated [C₄mim][NTf₂] appeared when acetonitrile was used as solvent, and the intensity of the peak enhanced with increasing dose. The spectrophotometric study on the irradiated RTILs containing 1,3-dialkylimidazolium cations associated with different inorganic anions revealed that the peak is ascribed to the radiolysis products of the [C₄mim]⁺. And the wavelength of the peak was affected by alkyl chain length on imidazolium cation, while the intensity of the peak was influenced by anions. With incorporating a little amounts of oxidants, such as KMnO₄ and HNO₃ into irradiated [C₄mim][NTf₂], the intensity of the peak at 290 nm decreased obviously and the decoloration of [C₄mim][NTf₂] occurred, suggesting that the peak at 290 nm is assigned to the colored species and the species can be oxidized.     

Liquid–liquid miscibility and volumetric properties of aqueous solutions of ionic liquids as a function of temperature

The volumetric properties of seven {water + ionic liquid} binary mixtures have been studied as a function of temperature from (293 to 343) K. The phase behaviour of the systems was first investigated using a nephelometric method and excess molar volumes were calculated from densities measured using an Anton Paar densimeter and fitted using a Redlich–Kister type equation. Two ionic liquids fully miscible with water (1-butyl-3-methylimidazolium tetrafluoroborate ([C₁C₄Im][BF₄]) and 1-ethyl-3-methylimidazolium ethylsulfate ([C₁C₂Im][EtSO₄])) and five ionic liquids only partially miscible with water (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C₁C₂Im][NTf₂]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C₁C₄Im][NTf₂]), 1-butyl-3-methylimidazolium hexafluorophosphate ([C₁C₄Im][PF₆]), 1-butyl-3-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C₁C₄Pyrro][NTf₂]), and butyltrimethylammonium bis(trifluoromethylsulfonyl)imide ([N₄₁₁₁][NTf₂])) were chosen. Small excess volumes (less than 0.5 cm³ · mol^?1 at 298 K) are obtained compared with the molar volumes of the pure components (less than 0.3% of the molar volume of the pure ionic liquid). For all the considered systems, except for {[C₁C₂Im][EtSO₄] + water}, positive excess molar volumes were calculated. Finally, an increase of the non-ideality character is observed for all the systems as temperature increases.     

Thermodynamic properties of the N-butylisoquinolinium bis(trifluoromethylsulfonyl)imide

A new isoquinolinium ionic liquid (IL) has been synthesised as a continuation of our work with quinolinium-based ionic liquids (ILs). The work includes specific basic characterization of synthesized compounds: N-isobutylquinolinium bromide, [BiQuin][Br] and N-isobutylquinolinium bis{(trifluoromethyl)sulfonyl}imide [BiQuin][NTf₂] by NMR spectra, elementary analysis and water content. The basic thermal properties of the pure [BiQuin][NTf₂], i.e. melting and glass-transition temperatures, the enthalpy of fusion as well as heat capacity at glass transition have been measured using a differential scanning microcalorimetry technique (DSC). Densities and viscosities were determined as a function of temperature. The temperature-composition phase diagrams of 8 binary mixtures composed of organic solvent dissolved in the IL: {[BiQuin][NTf₂] + aromatic hydrocarbon (benzene, or toluene, or ethylbenzene, or n-propylbenzene), or an alcohol (1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol)} were measured at ambient pressure. A dynamic method was used over a broad range of mole fraction and temperature from (270 to 320) K. For all the binary systems with benzene and alkylbenzenes, the eutectic diagrams were observed with an immiscibility gap in the liquid phase existing at low mole fraction of the IL with a very high upper critical solution temperature (UCST). For mixtures with alcohols, complete miscibility was observed for 1-butanol and also an immiscibility gap with UCST in the liquid phase for the remaining alcohols. The typical dependence was observed that with increasing chain length of an alcohol, the solubility decreases. The well-known NRTL equation was used to correlate experimental (solid + liquid), SLE and (liquid + liquid), LLE phase equilibrium data sets.     

Synthesis of copolyimides based on room temperature ionic liquid diamines

Block copolyimides based on aromatic dianhydrides and diamines copolymerized with diamino room temperature ionic liquid (RTIL) monomers were synthesized over a range of compositions. Specifically, two diamino RTILs, 1,3‐di(3‐aminopropyl) imidazolium bis[(trifluoromethyl)sulfonyl] imide ([DAPIM] [NTf₂]) and 1,12‐di[3‐(3‐aminopropyl) imidazolium] dodecane bis[(trifluoromethyl) sulfonyl] imide ([C₁₂ (DAPIM)₂] [NTf₂]₂) were synthesized using a Boc protection method. The two RTILs were reacted with 2,2‐bis(3,4‐carboxylphenyl) hexafluoropropane dianhydride (6FDA) to produce 6FDA‐RTILs oligomers that formed the RTIL component for the block copolyimides. The oligomers were reacted with 6FDA and m‐phenylenediamine (MDA) at oligomer concentration from 6.5 to 25.8 mol % to form block copolyimides. Increasing the concentration of the 6FDA‐RTIL oligomer in the block copolyimides resulted in a decrease in the thermal degradation temperature, glass transition temperature and an increase in the density. The gas permeability of the RTIL based block copolyimide decreased but the ideal permeability selectivity for CO₂/CH₄ gas pair increased relative to the pure 6FDA‐MDA. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4036–4046, 2010     

Phase equilibria study of the binary systems (ionic liquid + thiophene): Desulphurization process

(Solid + liquid) equilibria (SLE) and (liquid + liquid) equilibria (LLE) for the binary systems: {ionic liquid (IL) N-butyl-4-methylpyridinium tosylate (p-toluenesulfonate) [BM⁴Py][TOS], or N-butyl-3-methylpyridinium tosylate [BM³Py][TOS], or N-hexyl-3-methylpyridinium tosylate [HM³Py][TOS], or N-butyl-4-methylpyridinium bis{(trifluoromethyl)sulfonyl}imide [BM⁴Py][NTf₂], or 1,4-dimethylpyridinium tosylate [M^1,4Py][TOS], or 2,4,6-collidine tosylate [M^2,4,6Py][TOS], or 1-ethyl-3-methylimidazolium thiocyanate [EMIM][SCN], or 1-butyl-3-methylimidazolium thiocyanate [BMIM][SCN], or 1-hexyl-3-methylimidazolium thiocyanate [HMIM][SCN], or triethylsulphonium bis(trifluoromethylsulfonyl)imide [Et₃S][NTf₂] + thiophene} have been determined at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from (270 to 390) K. In the case of systems (pyridinium IL, or sulphonium IL + thiophene) the mutual immiscibility with an upper critical solution temperature (UCST) was detected at the very narrow and low mole fraction of the IL. For the binary systems containing (imidazolium thiocyanate IL + thiophene), the mutual immiscibility with the lower critical solution temperature (LCST) was detected at the higher mole fraction range of the IL. The basic thermal properties of the pure ILs, i.e. melting and glass-transition temperatures as well as the enthalpy of fusion have been measured using a differential scanning microcalorimetry technique (DSC). The well-known NRTL equation has been used to correlate experimental SLE/LLE data sets.     

Diffusion Coefficients of Imidazolium Based Ionic Liquids in Aqueous Solutions

Diffusion coefficients of the ionic liquids [C₂MIM][EtSO₄], [C₄MIM][OcSO₄], [C₂MIM][NTf₂] and [C₄MIM][NTf₂] in water at high dilution have been measured using the Taylor dispersion technique. Data on the diffusion coefficients have been obtained for each solute at six temperatures between 288 and 313 K. The data have been fitted by the Arrhenius equation and activation energies of diffusion have been determined. Effective radii of the ionic liquid molecules have also been obtained using the Stokes–Einstein relationship.     

Thermophysical properties and phase equilibria study of the binary systems {N-hexylquinolinium bis(trifluoromethylsulfonyl)imide + aromatic hydrocarbons,or an alcohol}

The new quinolinium ionic liquid has been synthesised as a continuation of our work with quinolinium-based ionic liquids (ILs). The work includes specific basic characterisation of synthesized compounds: N-hexylquinolinium bromide, [HQuin][Br] and N-hexylquinolinium bis{(trifluoromethyl)sulfonyl}imide [HQuin][NTf₂] by NMR spectra, elementary analysis and water content. The basic thermal properties of the pure [HQuin][NTf₂] i.e. melting and glass-transition temperatures, the enthalpy of fusion as well as heat capacity have been measured using a differential scanning microcalorimetry technique (DSC) and thermal analysis instrument (TA). Densities and viscosities were determined as a function of temperature. Phase equilibria for the binary systems: {[HQuin][NTf₂]) + aromatic hydrocarbon (benzene, or toluene, or ethylbenzene, or n-propylbenzene), or an alcohol (1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol)} have been determined at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from (270 to 320) K. For all the binary systems with benzene and alkylbenzenes, the eutectic diagrams were observed with immiscibility gap in the liquid phase beginning from (0.13 to 0.28) mole fraction of the IL with very high an upper critical solution temperature (UCST). For mixtures with alcohols, the complete miscibility was observed for 1-butanol and immiscibility with UCST in the liquid phase for the remaining alcohols. The typical dependence was observed, that with increasing chain length of an alcohol the solubility decreases. The well-known NRTL equation was used to correlate experimental (solid + liquid), SLE and (liquid + liquid), LLE phase equilibria data sets. For the systems containing immiscibility gaps, (IL + an alcohol) parameters of the LLE correlation were used to the prediction of SLE.     

Screen-printed electrode-based electrochemical detector coupled with in-situ ionic-liquid-assisted dispersive liquid–liquid microextraction for determination of 2,4,6-trinitrotoluene

A novel method is reported, whereby screen-printed electrodes (SPELs) are combined with dispersive liquid–liquid microextraction. In-situ ionic liquid (IL) formation was used as an extractant phase in the microextraction technique and proved to be a simple, fast and inexpensive analytical method. This approach uses miniaturized systems both in sample preparation and in the detection stage, helping to develop environmentally friendly analytical methods and portable devices to enable rapid and onsite measurement. The microextraction method is based on a simple metathesis reaction, in which a water-immiscible IL (1-hexyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide, [Hmim][NTf₂]) is formed from a water-miscible IL (1-hexyl-3-methylimidazolium chloride, [Hmim][Cl]) and an ion-exchange reagent (lithium bis[(trifluoromethyl)sulfonyl]imide, LiNTf₂) in sample solutions. The explosive 2,4,6-trinitrotoluene (TNT) was used as a model analyte to develop the method. The electrochemical behavior of TNT in [Hmim][NTf₂] has been studied in SPELs. The extraction method was first optimized by use of a two-step multivariate optimization strategy, using Plackett–Burman and central composite designs. The method was then evaluated under optimum conditions and a good level of linearity was obtained, with a correlation coefficient of 0.9990. Limits of detection and quantification were 7 μg L^?1 and 9 μg L^?1, respectively. The repeatability of the proposed method was evaluated at two different spiking levels (20 and 50 μg L^?1), and coefficients of variation of 7 % and 5 % (n?=?5) were obtained. Tap water and industrial wastewater were selected as real-world water samples to assess the applicability of the method.

Investigations on the Physicochemical and Radiolytic Degradation Properties of Tri-<Emphasis Type="Italic">n</Emphasis>-butylphosphate–Ionic Liquid in the Presence of Nitric Acid

Tri-n-butylphosphate (TBP) in an ionic liquid (IL) has been proposed as a suitable alternative for the solvent extraction of actinides from nitric acid solutions. This paper reports the detailed investigations on the physicochemical and hydrodynamic properties of the solvent system containing TBP in 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C₄mim][NTf₂]) IL. The properties such as density, viscosity, phase separation time (PST), etc., were measured for irradiated and unirradiated solvent phases composed of TBP, [C₄mim][NTf₂] and 1.1 mol·L^–1 TBP in [C₄mim][NTf₂]. The results are compared with the values obtained in acid-equilibrated IL phases. ATR–FTIR spectroscopy and dynamic light scattering measurement of the IL phase were employed to characterize the interactions among the IL, TBP and nitric acid medium, and the aggregate size of the adduct formed in the IL phase.     

Effect of temperature and composition on the density,viscosity, surface tension,and thermodynamic properties of binary mixtures of N-octylisoquinolinium bis{(trifluoromethyl)sulfonyl}imide with alcohols

Density and viscosity were determined for the binary mixtures containing the ionic liquid N-octylisoquinolinium bis{(trifluoromethyl)sulfonyl}imide ([C₈iQuin][NTf₂]) and 1-alcohol (1-butanol, 1-hexanol, and 2-phenylethanol) at five temperatures (298.15, 308.15, 318.15, 328.15, and 338.15) K and ambient pressure. The density and viscosity correlations for these systems were tested by an empirical second-order polynomial and by the Vogel–Fucher–Tammann equation. Excess molar volumes were described by the Redlich–Kister polynomial expansion. The density and viscosity variations with compositions were described by polynomials. Viscosity deviations were calculated and correlated by the Redlich–Kister polynomial expansions. The surface tensions of pure ionic liquid and binary mixtures of [C₈iQuin][NTf₂] with 1-hexanol were measured at atmospheric pressure at three temperatures (298.15, 308.15, and 318.15) K. The surface tension deviations were calculated and correlated by the Redlich–Kister polynomial expansion. The surface thermodynamic functions such as surface entropy and enthalpy were derived from the temperature dependence of the surface tension values. The critical temperature, parachor, and speed of sound for pure ionic liquid were described. A qualitative analysis on these quantities in terms of molecular interactions is reported. The obtained results indicate that ionic liquid interactions with alcohols are strong dependent on the special trend of packing effects and hydrogen bonding of this ionic liquid with hydroxylic solvents. As previously observed, an increase by a 1-alcohol carbon chain length leads to lower interactions on mixing.     

Extraction of Metal Ions from Aqueous Solutions Using Imidazolium Based Ionic Liquids

This article represents a step towards how to choose an ionic liquid as the solvent to improve metal ion (Ag⁺ and Pb²⁺) extraction. The liquid-liquid solvent extraction is proposed with the following imidazolium ionic liquids (ILs): 1-ethyl-3-ethylimidazolium, or 1-butyl-3-ethylimidazolium, or 1-hexyl-3-ethylimidazolium bis{(trifluoromethyl)sylfonyl}imide [EEIM][NTf₂], or [BEIM][NTf₂], or [HEIM][NTf₂], or 1-butyl-3-ethylimidazolium hexafluorophosphate [BEIM][PF₆], or 1-hexyl-3-ethylimidazolium hexafluorophosphate [HEIM][PF₆] and the popular 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF₆] for comparison. The effect of anion type (NTf₂⁻ versus PF₆⁻) and the effect of structural components of an ionic liquid including alkyl chain length at the cation and the ethyl substituent instead methyl at the cation, on the extraction and re-extraction processes by using dithizone as a metal chelator, were studied at 296 K. Dithizone was employed to form neutral metal-dithizone complexes with heavy metal ions to extract them from aqueous solution into the ILs. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users. Presented at the 236th ACS National Meeting, August 17–21, Philadelphia, USA.     

Separation of aromatic hydrocarbons from alkanes using ammonium ionic liquid C2NTf2 at T = 298.15 K

(Liquid + liquid) equilibrium data are presented for four ternary systems of an alkane, or aromatic compound and ethyl(2-hydroxyethyl)dimethylammonium bis{(trifluomethyl)sulfonyl}imide (C₂NTf₂) at 298.15 K: [hexane + benzene + C₂NTf₂], [hexane + p-xylene + C₂NTf₂], and [hexane, or octane + m-xylene + C₂NTf₂]. The separation of aromatic hydrocarbons (benzene, or p-xylene, or m-xylene) from aliphatic hydrocarbons (hexane, or octane) is investigated by extraction with the ammonium ionic liquid. Selectivities and distribution ratios are discussed for these mixtures at constant temperature. The data were analysed and compared to those previously reported for other ionic liquids and especially for the system {hexane + benzene + [EMIM][NTf₂]}. The nonrandom two liquid NRTL model was successfully used to correlate the experimental tie-lines and to calculate the phase compositions of the ternary systems.     

Ethanol extraction from its azeotropic mixture with hexane employing different ionic liquids as solvents

In this work, the ionic liquids 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMim][NTf₂], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [BMim][NTf₂], 1-butyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide, [BMpy][NTf₂], 1-butyl-3-methylpyridinium trifluoromethanesulfonate, [BMpy][TfO], have been investigated for their use as solvents in extraction processes for the ethanol removal from its azeotropic mixture with hexane. Therefore, the experimental determination of the liquid + liquid equilibrium for the ternary systems {hexane (1) + ethanol (2) + [EMim][NTf₂] (3)}, {hexane (1) + ethanol (2) + [BMim][NTf₂] (3)}, {hexane (1) + ethanol (2) + [BMpy][NTf₂] (3)} and {hexane (1) + ethanol (2) + [BMpy][TfO] (3)} was carried out at T = 298.15 K and atmospheric pressure. Classical parameters such as selectivity and solute distribution ratio, derived from the tie-line data, were calculated and afterwards, the structural influence of the ionic liquids on the extraction process was analyzed. Finally, the experimental LLE data were correlated by means of the NRTL and UNIQUAC models.