Separation of toluene from cyclic hydrocarbons using 1-butyl-3-methylimidazolium methylsulfate ionic liquid at T = 298.15 K and atmospheric pressure

In this paper the extraction of toluene from cyclic hydrocarbons (cyclohexane, or methylcyclohexane, or cyclooctane, or cyclohexene) was analyzed by liquid extraction with 1-butyl-3-methylimidazolium methylsulfate ionic liquid, [BMim][MSO₄], as solvent. The experimental (liquid + liquid) equilibrium (LLE) data were determined at T = 298.15 K and atmospheric pressure. Solubility curves were obtained by the cloud point method and tie-line compositions were determined by density measurement. An analysis of the influence of different cyclic hydrocarbons on the extraction was performed.The effectiveness of the extraction of toluene from cyclic hydrocarbons was evaluated by means of the solute distribution ratio and selectivity values. The degree of consistency of the experimental LLE data was ascertained using the Othmer–Tobias and Hand equations. The experimental data for the (liquid + liquid) equilibria of the ternary systems were correlated with the Non-Random Two-Liquid (NRTL) and UNIversal QUAsi-Chemical (UNIQUAC) thermodynamic models.     

Application of the Bahe's pseudolattice-theory to water—1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF4) mixtures at 298.15 K: Part I. Autoprotolysis constants

The autoprotolysis constants (K_s) of water - 1-butyl-3-methylimidazolium tetrafluoroborate (bmimBF₄) mixtures were determined at 298 K over the composition range of 0 to 77.43 vol.% bmimBF₄ using potentiometric method with a glass electrode. A slight increase in the autoprotolysis constant was observed when the salt was added to the water. The value of the ionic product of the medium then decreases as the bmimBF₄ content increases from about 20 vol.%. The acid-base properties of these media were perfectly described by Bahe's approaches that were completed by Varela et al. concerning structured electrolyte solutions with large short-range interactions.     

Densities and volumetric properties of binary mixtures of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate with benzaldehyde at T = (298.15 to 313.15) K

The densities of the binary mixtures formed by 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF₄] with aromatic compound (benzaldehyde) have been determined over the full range of compositions at the temperature range from (298.15 to 313.15) K and at atmospheric pressure using a vibrating-tube densimeter (DMA4500). Excess molar volumes $(V_{\text{m}}^{\text{E}})$ have been obtained from these experimental results, and been fitted by the fourth-order Redlich–Kister equation. In addition, partial molar volumes, apparent molar volumes, and partial molar volumes at infinite dilution have been calculated for each component. Our results show $V_{\text{m}}^{\text{E}}$ decreases slightly when temperature increases in the systems studied. The results have been interpreted in terms of ion–dipole interactions and structural factors of the ionic liquid and these organic molecular liquids.     

Temperature dependence of the microstructure of 1-butyl-3-methylimidazolium tetrafluoroborate in aqueous solution

Many applications of ionic liquids (ILs) are closely related with their microstructure in mixtures. For example, morphology and pore size of the MCM-41 prepared in aqueous ILs are greatly dependent on the aggregation behavior of the ILs in water. Therefore, the study on the microstructure of ILs in aqueous solutions is of great importance. In this work, ¹H NMR, dynamic light scattering and attenuated total reflection infrared spectroscopy have been used to investigate the temperature effect on the structures of aqueous 1-butyl-3-methylimidazolium tetrafluoroborate ([C₄mim][BF₄]) solutions. It was shown that the size of the IL aggregates becomes larger with decreasing temperature. When the system temperature is below the upper critical solution temperature (UCST) of the binary mixture at about 4 °C, the aggregate size of the IL is larger than 1000 nm. Additionally, the two-dimensional IR results reveal that at low IL concentrations, H₂O can interact with [BF₄]⁻ prior to the CH groups of the imidazolium ring, whereas cation and anion of the IL tend to form aggregate at high IL concentrations. With the decrease of temperature, the interactions between cation and anion of the IL become stronger, but those between the IL and water become weaker, thereby resulting in the growth of the aggregate of cation with anion of the IL. This result may give a reasonable explanation for the origin of the UCST behavior of aqueous [C₄mim][BF₄] solution.     

Liquid structures of 1-butyl-3-methylimidazolium tetrafluoroborate and carbon dioxide mixtures by X-ray diffraction measurements

X-ray diffraction measurements for the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF₄], mixed with CO₂ were carried out at high pressures using our developed polymer cell. The intermolecular distribution functions obtained for [BMIM][BF₄]–CO₂ mixtures showed that CO₂ molecules are preferentially solvated to the [BF₄]⁻ anion. The similar preferential solvation was previously observed in analogous 1-btuyl-3-methylimidazolium hexafluorophosphate, [BMIM][PF₆], with a different anion, which is in harmony with the present results in [BMIM][BF₄]–CO₂.     

Use of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate in countercurrent chromatography

Room temperature ionic liquids (RTIL) are molten salts that are liquids at room temperature. Their liquid state makes them possible candidates as solvents in countercurrent chromatography (CCC), which uses solvents as both the mobile and stationary phases. The study focuses on 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM PF₆), an easy to synthesize and purify RTIL whose melting point is –8°C. It is shown that BMIM PF₆ behaves like a solvent of significant polarity (comparable with that of ethanol). The ternary phase diagram water–acetonitrile–BMIM PF₆ is given, because it was necessary to add acetonitrile to reduce the ionic liquid viscosity. The 40:20:40% w/w water–acetonitrile–BMIM PF₆ biphasic liquid system was found to be appropriate as a biphasic liquid system for CCC. Different aromatic solutes, including bases, acids, and neutral compounds, were injected into the CCC column to estimate their distribution constants between the ionic liquid-rich phase and the aqueous phase. The resulting K_il/w constants were compared with the corresponding literature octanol–water partition coefficients, K_o/w. The important drawbacks in the use of RTIL in CCC are clearly pointed out: high viscosity producing pressure build-up, UV absorbance limiting the use of the convenient UV detector, and non-volatility precluding the use of the evaporative light-scattering detector for continuous detection.     

Influence of the alkyl group on thermophysical properties of carboxylic acids in 1-butyl-3-methylimidazolium thiocyanate ionic liquid at various temperatures

In the present study, influence of the alkyl group and temperature on the interactions between the carboxylic acid and ionic liquid (IL) mixtures were discussed in term of density and sound velocity measurements. The IL used in this study was 1-butyl-3-methylimidazolium thiocyanate ([BMIM]⁺[SCN]⁻). The density (ρ), and sound velocity (u), of the IL, acetic acid, propionic acid, and their corresponding binary systems {[BMIM]⁺[SCN]⁻ (x₁) + acetic or propionic acid (x₂)} have been measured at T = (293.15, 298.15, 303.15, 308.15 and 313.15) K and at p = 0.1 MPa. The excess molar volumes, $V_{\text{m}}^{\text{E}}$, isentropic compressibility, κ_s, and deviation in isentropic compressibility, Δκ_s, were calculated using experimental density and sound velocity data, respectively. The Redlich–Kister polynomial equation was used to fit the excess/deviation properties. These results are useful for describing the intermolecular interactions that exist between the IL and carboxylic acid mixtures.     

Isothermal (vapour + liquid) equilibrium and thermophysical properties for (1-butyl-3-methylimidazolium iodide + 1-butanol) binary system

Experimental isothermal (vapour + liquid) equilibrium (VLE) data are reported for the binary mixture containing 1-butyl-3-methylimidazolium iodide ([bmim]I) + 1-butanol at three temperatures: (353.15, 363.15, and 373.15) K, in the range of 0 to 0.22 liquid mole fraction of [bmim]I. Additionally, refractive index measurements have been performed at three temperatures: (293.15, 298.15 and 308.15) K in the whole composition range. Densities, excess molar volumes, surface tensions and surface tension deviations of the binary mixture were predicted by Lorenz–Lorentz (n_D-ρ) mixing rule. Dielectric permittivities and their deviations were evaluated by known equations. (Vapour + liquid) equilibrium data were correlated with Wilson thermodynamic model while refractive index data with the 3-parameters Redlich–Kister equation by means of maximum likelihood method. For the VLE data, the real vapour phase behaviour by virial equation of state was considered. The studied mixture presents S-shaped abatement from the ideality. Refractive index deviations, surface tension deviations and dielectric permittivity deviations are positive, while excess molar volumes are negative at all temperatures and on whole composition range. The VLE data may be used in separation processes design, and the thermophysical properties as key parameters in specific applications.     

Separation of toluene from alkanes using 1-ethyl-3-methylpyridinium ethylsulfate ionic liquid at T = 298.15 K and atmospheric pressure

In this paper, the separation of toluene from aliphatic hydrocarbons (heptane, or octane, or nonane) was analyzed by solvent extraction with 1-ethyl-3-methylpyridinium ethylsulfate ionic liquid, [EMpy][ESO₄]. Liquid?liquid equilibrium (LLE) data for the ternary systems {heptane (1) + toluene (2) + [EMpy][ESO₄] (3)}, {octane (1) + toluene (2) + [EMpy][ESO₄] (3)}, and {nonane (1) + toluene (2) + [EMpy][ESO₄] (3)} were obtained by measurements at T = 298.15 K and atmospheric pressure. The selectivity, % removal of aromatic, and solute distribution ratio, obtained from experimental equilibrium results, were used to determine the ability of [EMpy][ESO₄] as a solvent. The degree of consistency of the experimental LLE values was ascertained using the Othmer–Tobias and Hand equations. The experimental results for the ternary systems were correlated with the NRTL model. Finally, the results obtained were compared with other ionic liquids and other solvents.     

Osmotic and activity coefficients in the binary solutions of 1-butyl-3-methylimidazolium chloride and bromide in methanol or ethanol at T = 298.15 K from isopiestic measurements

Osmotic coefficients of the binary solutions of two room-temperature ionic liquids (1-butyl-3-methylimidazolium chloride and bromide) in methanol and ethanol have been measured at T = 298.15 K by the isopiestic method. The experimental osmotic coefficient data have been correlated using a forth-order polynomial in terms of (molality)^0.5, with both, ion interaction model of Pitzer and electrolyte non-random two liquid (e-NRTL) model of Chen. The values of vapor pressures of above-mentioned solutions have been calculated from the osmotic coefficients. The model parameters fitted to the experimental osmotic coefficients have been used for prediction of the mean ionic activity coefficients of those ionic liquids in methanol and ethanol.     

Physical properties of the ternary system (ethanol + water + 1-butyl-3-methylimidazolium methylsulphate) and its binary mixtures at several temperatures

In this paper, we report experimental densities, dynamic viscosities, and refractive indices and their derived properties of the ternary system (1-butyl-3-methylimidazolium methylsulphate + ethanol + water) at T = 298.15 K and of its binary systems 1-butyl-3-methylimidazolium methylsulphate with ethanol and with water at several temperatures T = (298.15, 313.15, 328.15) K. These physical properties have been measured over the whole composition range and at 0.1 MPa. Excess molar volumes, viscosity deviations, and excess free energy of activation for the binary systems at the abovementioned temperatures, were calculated and fitted to the Redlich–Kister equation to determine the fitting parameters and the root-mean-square deviations and for the ternary systems were calculated and fitted to Cibulka, Singh et al., and Nagata and Sakura equations. The ternary excess properties were predicted from binary contributions using geometrical solution models. Refractive indices were measured from T = 298.15 K over the whole composition range for the binary and ternary systems. The results were used to calculate deviations in the refractive index.     

Evidence of change in the molecular organization of 1-n-butyl-3-methylimidazolium tetrafluoroborate ionic liquid solutions with the addition of water

Physico-chemical properties of ionic liquids like density, viscosity, conductivity, surface tension and excess molar volume are strongly dependent on their concentration in aqueous solutions. 1-n-Butyl-3-methylimidazolium tetrafluoroborate/water solutions, at 25 °C, shows two clearly distinguished behaviors, corresponding to a water-rich and a salt-rich region, with distinct physico-chemical properties. It is shown that [BMIm][BF₄] exhibits surfactant properties. The results obtained are discussed in terms of the interactions between cations and anions of the ionic liquid and the water molecule. IR studies show that the addition of water modifies the organization of the ionic liquid molecules. The data collection reported is helpful for a variety of different technological applications and in particular for electrochemical applications, as capacitors, batteries and fuel cells among others.     

Osmotic coefficients of binary mixtures of 1-butyl-3-methylimidazolium methylsulfate and 1,3-dimethylimidazolium methylsulfate with alcohols at T = 323.15 K

Measurements of osmotic coefficients of BMimMSO₄ (1-butyl-3-methylimidazolium methylsulfate) and MMimMSO₄ (1,3-dimethylimidazolium methylsulfate) with ethanol, 1-propanol, and 2-propanol at T = 323.15 K are reported in this work. Vapour pressure and activity values for the binary systems studied are obtained from experimental results. The osmotic coefficients are correlated using the extended Pitzer model modified by Archer and the modified NRTL (MNRTL) model. The standard deviations obtained with both models are lower than 0.013 and 0.060, respectively. The parameters obtained with the extended Pitzer model of Archer are used to calculate the mean molal activity coefficients and the excess Gibbs free energy of the binary mixtures.     

Thermophysical properties of the binary mixtures (1,8-cineole + 1-alkanol) at T = (298.15 and 313.15) K and at atmospheric pressure

This work presents the measurements of the density, speed of sound, refractive index and enthalpy of binary mixtures containing {1,8-cineole + 1-alkanol (ethanol, 1-propanol, 1-butanol, and 1-pentanol)} at two temperatures (298.15 and 313.15) K and atmospheric pressure. The determination of excess molar volume, speed of sound deviation, refractive index deviation, molar refraction, molar refraction deviation, excess isentropic compressibility, and excess molar enthalpy are also given. Redlich–Kister equation was used to fit these derivate properties. The experimental data of the constituent binaries were analysed to discuss the nature and strengths of intermolecular interactions. Eventually some models, SAFT and PC-SAFT for density, Free Length and Collision Factor for speed of sound, Gladstone-Dale Arago-Biot for refractive index, and UNIFAC for excess molar enthalpy, among others, were successfully applied.     

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.     

Mutual solubilities of selected solvents and 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate

1-(2-Hydroxyethyl)-3-methylimidazolium tetrafluoroborate ([HYDEMIM][BF₄]) ionic liquid was characterised by infrared spectroscopy, nuclear magnetic resonance, ultraviolet-visible spectra and thermogravimetric analysis. Mutual mass fraction solubilities of the 12 selected solvents (ethanol, 1-propanol, 1-butanol, benzene, toluene, o-xylene, m-xylene, p-xylene, ethylbenzene, dichloromethane, chloroform and carbon tetrachloride) and [HYDEMIM][BF₄] in the temperature range from 283.16 to 353.61?K were measured using a cloud-point method. Measured solubility value S was correlated as a function of temperature by a second-order polynomial.