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.     

Cation effect of ammonium imide based ionic liquids in alcohols extraction from alcohol-alkane azeotropic mixtures

During recent last years, outstanding properties of ionic liquids such as low melting point, large liquid range and negligible volatility have turned them into possible volatile organic solvents replacers to break alcohol-alkane azeotropic mixtures. On this basis, two ionic liquids, butyltrimethylammoniumbis(trifluoromethylsulfonyl)imide, [BTMA][NTf₂], and tributylmethylammoniumbis(trifluoromethylsulfonyl)imide, [TBMA][NTf₂], were studied through ternary liquid+liquid equilibrium (LLE) of {alkane(1) + alcohol (2) + IL(3)} at T = 298.15 K and atmospheric pressure in order to consider the effect of ionic liquid cation alkyl chain length on the extraction process.The ILs capability as azeotrope breakers was determined by the calculation of parameters such as solute distribution ratio, β, and selectivity, S and this capability was compared with other bis (trifluoromethylsulfonyl)imide based ionic liquids from literature. The consistency of tie-line data was ascertained by applying the Othmer–Tobias and Hand equations. Finally, the experimental LLE were correlated by the Non Random Two Liquid (NRTL) thermodynamic model.     

(Liquid + liquid) equilibria for the ternary mixtures (alkane + toluene + ionic liquid) at T = 298.15 K: Influence of the anion on the phase equilibria

(Liquid + liquid) equilibrium data for the ionic liquids 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [BMpyr][NTf₂], and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate, [BMpyr][TFO], with toluene, and heptane or cyclohexane were determined at T = 298.15 K and atmospheric pressure. In order to check if these ILs can be used as potential solvents for the extraction of toluene from aliphatic compounds, the ability of the ILs as solvents was evaluated in terms of selectivity and solute distribution ratio. The experimental data were correlated accurately with the Non Random Two-Liquid model.     

Densities and viscosities for ionic liquids mixtures containing [eOHmim][BF4], [bmim][BF4] and [bpy][BF4]

Densities and viscosities of binary ionic liquids mixtures, 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate ([eOHmim][BF₄]) + 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]), 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate ([eOHmim][BF₄]) + N-butylpyridinium tetrafluoroborate ([bpy][BF₄]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) + N-butylpyridinium tetrafluoroborate ([bpy][BF₄]) were measured over the entire mole fraction from T = (298.15 to 343.15) K. The excess molar volumes were calculated and correlated by Redlich–Kiser polynomial expansions. The viscosities for pure ionic liquids were analyzed by means of the Vogel–Tammann–Fulcher equation and ideal mixing rules were applied for the ILs mixtures.     

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.     

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.     

Effect of temperature on the physical properties of 1-butyl-3-methylimidazolium based ionic liquids with thiocyanate and tetrafluoroborate anions,and 1-hexyl-3-methylimidazolium with tetrafluoroborate and hexafluorophosphate anions

The effect of temperature on the physical properties of some ionic liquids was investigated. Density, refractive index, surface tension, dynamic and kinematic viscosities of 1-butyl-3-methylimidazolium based ionic liquids with thiocyanate and tetrafluoroborate, and 1-hexyl-3-methylimidazolium with tetrafluoroborate and hexafluorophosphate anions were measured at various temperatures (density from T = (278.15 to 363.15) K, refractive index from (293.15 to 343.15) K, surface tension from (283.15 to 333.15) K, dynamic viscosity from (283.15 to 368.15) K, and kinematic viscosity from (298.15 to 363.15) K). The volumetric properties for the ionic liquids were also calculated from the experimental values of the density at T = 298.15 K. The Vogel–Fulcher–Tammann (VFT) equation was applied to correlate experimental values of dynamic and kinematic viscosities as a function of temperature. As well, the relation between density and refractive index was correlated satisfactorily with several empirical equations such as Lorentz–Lorenz, Dale–Gladstone, Eykman, Oster, Arago–Biot, Newton and Modified–Eykman. Finally, the relation between surface tension and viscosity was investigated and the parachor method was used to predict density, refractive index and surface tension of the ionic liquids.     

A comprehensive study of {γ-butyrolactone + 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide} binary mixtures

Density, electrical conductivity and viscosity of binary liquid mixtures of γ-butyrolactone, (GBL) with 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide, [pmim][NTf₂], were measured at different temperatures from (293.15 to 323.15) K and at atmospheric pressure (p = 0.1 MPa) over the whole composition range. Excess molar volumes have been calculated from the experimental densities and were fitted with Redlich–Kister’s polynomial equation. Other volumetric properties have been also calculated in order to obtain information about interactions between GBL and selected ionic liquid. All the results are compared with those obtained for binary mixtures of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [bmim][NTf₂], with GBL. From the viscosity measurements, the Angell strength parameter was calculated for pure ionic liquid indicating that [pmim][NTf₂] is a “fragile” liquid. Electrical conductivity results were discussed in the scope of Bahe–Varela theoretical model.     

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.     

PVT properties for binary ionic liquids of 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl)imide with anisole or acetophenone at pressures up to 50 MPa

Densities of pure 1-methyl-1-propylpiperidinium bis(trifluoromethylsulfonyl)imide, [C₃mpip][NTf₂], and its mixtures with anisole or acetophenone were measured with a high-pressure densimeter at temperatures from 298.15 K to 348.15 K and pressures up to 50 MPa. The Tait equation was employed to represent pressure effect on the isothermal densities. The experimental results reveal that the excess volumes of (anisole + [C₃mpip][NTf₂]) and (acetophenone + [C₃mpip][NTf₂]) are all negative over the entire experimental conditions. In addition to an empirical generalized equation, the density data were also correlated quantitatively with the Flory–Orwoll–Vrij (FOV) and the Schotte equations of state.     

Volumetric properties and enthalpies of solution of alcohols CkH2k+1OH (k = 1, 2, 6) in 1-methyl-3-alkylimidazolium bis(trifluoromethylsulfonyl)imide {[C1CnIm][NTf2] n = 2, 4, 6, 8, 10} ionic liquids

We present a study on the effect of the alkyl chain length of the imidazolium ring in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids, [C₁C_nIm][NTf₂] (n = 2 to 10), on the mixing properties of (ionic liquid + alcohol) mixtures (enthalpy and volume). We have measured small excess molar volumes with highly asymmetric curves as a function of mole fraction composition (S-shape) with more negative values in the alcohol-rich regions. The excess molar volumes increase with the increase of the alkyl-chain length of the imidazolium cation of the ionic liquid. The values of the partial molar excess enthalpy and the enthalpy of mixing are positive and, for the case of methanol, do not vary monotonously with the length of the alkyl side-chain of the cation on the ionic liquid – increasing from n = 2 to 6 and then decreasing from n = 8. This non-monotonous variation is explained by a more favourable interaction of methanol with the cation head group of the ionic liquid for alkyl chains longer than eight carbon atoms. It is also observed that the mixing is less favourable for the smaller alcohols, the enthalpy of mixing decreasing to less positive values as the alkyl chain of the alcohol increases. Based on the data from this work and on the knowledge of the vapour pressure of {[C₁C_nIm][NTf₂] + alcohol} binary mixtures at T = 298 K reported in the literature, the excess Gibbs free energy, excess enthalpy and excess entropy could be then calculated and it was observed that these mixtures behave like the ones constituted by a non-associating and a non-polar component, with its solution behaviour being determined by the enthalpy.     

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.     

Application of the PFV EoS correlation to excess molar volumes of (1-ethyl-3-methylimidazolium ethylsulfate + alkanols) at different temperatures

The experimental densities for the binary systems of an ionic liquid and an alkanol {1-ethyl-3-methylimidazolium ethylsulfate [EMIM]⁺ [EtSO₄]^? + methanol or 1-propanol or 2-propanol} were determined at T = (298.15, 303.15, and 313.15) K. The excess molar volumes for the above systems were then calculated from the experimental density values for each temperature. The Redlich–Kister smoothing polynomial was used to fit the experimental results and the partial molar volumes were determined from the Redlich–Kister coefficients. For all the systems studied, the excess molar volume results were negative over the entire composition range for all the temperatures. The excess molar volumes were correlated with the pentic four parameter virial (PFV) equation of state (EoS) model.     

Physical properties of ionic liquids based on 1-alkyl-3-methylimidazolium cation and hexafluorophosphate as anion and temperature dependence

Densities ρ, speeds of sound u, and refractive indices n_D were measured from T = (278.15 to 343.15) K. Dynamic viscosities η were measured from T = (293.15 to 323.15) K. Surface tensions σ were determined from T = (288.15 to 313.15) K. The physical properties data were measured at atmospheric pressure. The coefficients of thermal expansion α_p of the ionic liquids were calculated from the experimental values of the density at several temperatures. The Parachor method was used to predict the densities, the refractive indices, and the surface tensions of the ionic liquids, and a comparison between experimental and predictive values was made at T = 298.15 K.     

Excess molar volumes and isentropic compressibility of binary systems {trioctylmethylammonium bis(trifluoromethysulfonyl)imide + methanol or ethanol or 1-propanol} at different temperatures

This paper reports measurements of densities for the binary systems of an ionic liquid and an alkanol at T = (298.15, 303.15, and 313.15) K. The IL is trioctylmethylammonium bis(trifluoromethylsulfonyl)imide [OMA]⁺[Tf₂N]^? and the alkanols are methanol, or ethanol, or 1-propanol. The speed of sound at T = 298.15 K for the same binary systems was also measured. The excess molar volumes and the isentropic compressibilities for the above systems were then calculated from the experimental densities and the speed of sound, respectively. Redlich–Kister smoothing polynomial equation was used to fit the excess molar volume and the deviation in isentropic compressibility data. The partial molar volumes were determined from the Redlich–Kister coefficients. For all the systems studied, the excess molar volumes have both negative and positive values, while the deviations in isentropic compressibility are negative over the entire composition range.     

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.     

Properties of ionic liquid HMIMPF6 with carbonates,ketones and alkyl acetates

The densities and refractive indices of the pure ionic liquid (IL) HMIMPF₆ were determined at temperature range from T =(278.15 to 318.15) K for density and from T = (288.15 to 318.15) K for refractive index. The coefficient of thermal expansion of HMIMPF₆ was calculated from the experimental values of density. The densities and refractive indices of binary mixtures involving dimethyl carbonate (DMC), diethyl carbonate (DEC), acetone, 2-butanone, 2-pentanone, methylacetate, ethylacetate, and butylacetate + HMIMPF₆ (1-hexyl-3-methylimidazolium hexafluorophosphate) have been measured at T = 298.15 K and atmospheric pressure. Excess molar volumes and changes of refractive index on mixing for the binary systems were calculated. The miscibility of IL with different organic solvents and (liquid + liquid) equilibrium (LLE) data of binary mixture HMIMPF₆ + DEC have been determined experimentally.     

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.     

Physico-chemical and excess properties of the binary mixtures of methylcyclohexane + ethanol, + propan-1-ol, + propan-2-ol, + butan-1-ol, + 2-methyl-1-propanol,or 3-methyl-1-butanol at T = (298.15, 303.15, and 308.15) K

Physico-chemical properties viz., density, viscosity, and refractive index at temperatures = (298.15, 303.15, and 308.15) K and the speed of sound at T = 298.15 K are measured for the binary mixtures of methylcyclohexane with ethanol, propan1-ol, propan-2-ol, butan-1-ol, 2-methyl-1-propanol, and 3-methyl-1-butanol over the entire range of mixture composition. From these data, excess molar volume, deviations in viscosity, molar refraction, speed of sound, and isentropic compressibility have been calculated. These results are fitted to the polynomial equation to derive the coefficients and standard errors. The experimental and calculated quantities are used to study the nature of mixing behaviours between the mixture components.     

Physicochemical properties of {1-methyl piperazine (1) + water (2)} system at T = (298.15 to 343.15) K and atmospheric pressure

Densities (ρ) and viscosities (η) of aqueous 1-methylpiperazine (1-MPZ) solutions are reported at T = (298.15 to 343.15) K. Refractive indices (n_D) are reported at T = (293.15 to 333.15) K, and surface tensions (γ) are reported at T = (298.15 to 333.15) K. Derived excess properties, except excess viscosities (Δη), are found to be negative over the entire composition range. The addition of 1-MPZ reduces drastically the surface tension of water. The temperature dependence of surface tensions is explained in terms of surface entropy (S^S) and enthalpy (H^S). The measured and derived properties are used to probe the microscopic liquid structure of the bulk and surface of the aqueous amine solutions.