Correlation of the Solubilizing Abilities of 1-Butyl-1-methylpiperidinium Bis(trifluoromethylsulfonyl)imide and 1-Butyl-1-methylpyrrolidinium Tetracyanoborate

Chromatographic retention data were measured for a wide range of organic solutes on 1-butyl-1-methylpyrrolidinium tetracyanoborate ([BMPyrr]⁺[B(CN)₄]^?) and 1-butyl-1-methyl-piperidinium bis(trifluoromethylsulfonyl)imide ([BMPip]⁺[Tf₂N]^?) stationary phases at 323 K and 353 K. The measured retention factors were combined with published infinite dilution activity coefficient and gas-to-water partition coefficient data to yield gas-to-anhydrous ionic liquid (IL) and water-to-anhydrous IL partition coefficients. Both sets of partition coefficients were analyzed using the Abraham model. The derived Abraham model correlations describe the observed gas-to-IL (log₁₀ K) and water-to-IL (log₁₀ P) partition coefficient data to within average standard deviations of about 0.10 and 0.15 log₁₀ units, respectively.     

(Liquid + liquid) equilibrium for the ternary systems {heptane + toluene + 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide} and {heptane + toluene + 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide} ionic liquids

The (liquid + liquid) equilibrium (LLE) data for two systems containing heptane, toluene, and 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide ([mpim][Tf₂N]) or 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([amim][Tf₂N]) ionic liquids (ILs) were determined at T = 313.2 K and atmospheric pressure. The effect of a double bond in an alkyl side chain in the imidazolium cation was evaluated in terms of selectivity and extractive capacity. The results show a decrease of the amount of toluene and heptane dissolved in the IL with the allyl group. Thus, the distribution ratios of toluene and heptane of [mpim][Tf₂N] IL are higher than those of [amim][Tf₂N] IL. On the other hand, the separation factor of the [amim][Tf₂N] IL increases comparing to [mpim][Tf₂N] IL. The NRTL model was used to correlate satisfactorily the experimental LLE data for the two studied ternary systems.     

N-butylpyridinium bis-(trifluoromethylsulfonyl)imide ionic liquids as solvents for the liquid-liquid extraction of aromatics from their mixtures with alkanes: Isomeric effect of the cation

The liquid-liquid equilibria (LLE) of four ternary systems comprising toluene, heptane, and an ionic liquid with the cation N-butylpyridinium ([bpy]), or 2-methyl-N-butylpyridinium ([2bmpy]), or 3-methyl-N-butylpyridinium ([3bmpy]), or 4-methyl-N-butylpyridinium ([4bmpy]), and the anion bis-(trifluoromethylsulfonyl)imide ([Tf₂N]) were determined at 313.2 K and atmospheric pressure. The distribution ratios and the separation factor curves from the LLE data were plotted and compared to those for sulfolane. The results show no significant differences in the values of these parameters between [bpy][Tf₂N] and [2bmpy][Tf₂N], and between [3bmpy][Tf₂N] and [4bmpy][Tf₂N]. The experimental LLE data were satisfactorily correlated by means of the thermodynamic NRTL model.     

Infinite dilution activity coefficients and gas-to-liquid partition coefficients of organic solutes dissolved in 1-sec-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and in 1-tert-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

Inverse gas chromatography was used to measure infinite dilution activity coefficients and gas-to-liquid partition coefficients for 48 organic solute probes in either 1-sec-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide or 1-tert-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide in the temperature range from 323.15 to 373.15 K. Partial molar excess enthalpies of solution were calculated from the variation of the infinite dilution activity coefficients with temperature. Abraham model correlations were also derived from the experimental partition coefficient data. The derived Abraham model correlations describe the observed partition coefficients to within 0.11 log units.     

Solubilities of isobutane and cyclopropane in ionic liquids

In this work, we presented the solubilities of isobutane and cyclopropane in 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([HMIM][Tf₂N]) and trihexyl tetradecylphosphonium bis(2,4,4-trimethylpentyl) phosphinate ([P(14)666][TMPP]) from T = (302 to 344) K up to 1.16 MPa. Henry’s constants for isobutane and cyclopropane in [HMIM][Tf₂N] and [P(14)666][TMPP] were calculated from experimental results. Solubilities of isobutane and cyclopropane in [HMIM][Tf₂N] are apparently smaller than those in [P(14)666][TMPP]. The effects of temperature, pressure and the number of carbon atoms in the hydrocarbons on the solubility were investigated in detail. A modified Krichevsky–Kasarnovsky equation was successfully applied to correlate the experimental results. The mean absolute relative deviations and the maximum absolute relative deviations are less than (2.4 and 4.6)%, respectively.     

The Temperature Effect on the Transport Properties of 1-Alkyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide Ionic Liquids

The temperature dependences of specific and equivalent conductivities, viscosity, density, and crystallization temperature are determined for three 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([C _n MeIm] [Tf₂N], n = 2, 3, 4) ionic liquids saturated with water vapor at room temperature. It is established that in the area of positive temperatures, the relationship between viscosity and conductivity obeys the fractional Walden rule with exponents of 0.97, 0.92, and 0.92 for ionic liquids with ethyl-, propyl-, butylradicals, respectively. The temperature dependences of conductivity and viscosity are approximated using the Vogel–Fulcher–Tammann equation (R² > 0.999), and ideal glass transition temperatures T₀ are calculated for the investigated liquids. The obtained values of T₀ depend largely on the chosen range of temperatures. It is shown that [C₂MeIm][Tf₂N] occupies a separate position with regard to [C₃MeIm][Tf₂N] and [C₄MeIm][Tf₂N].     

Solubility of carbon dioxide in the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide

In this work, the phase behaviour of the binary system of carbon dioxide and the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([emim][Tf₂N]) has been studied experimentally. The equipment used for the experiments is the Cailletet set-up, based on visual observations of phase transitions of systems with constant overall composition. Results are reported for carbon dioxide concentrations ranging from 12.3 to 59.3 mol%, and within temperature and pressure ranges of 310–450 K and 0–15 MPa, respectively. The data reveal an extremely high capacity of the selected ionic liquid for dissolving CO₂ gas, for example, reaching up to about 60 mol% within the above-mentioned pressure and temperature range. Also, the solubility of CO₂ in the ionic liquid [emim][Tf₂N] is compared to the solubility of CO₂ in the ionic liquid [emim][PF₆], an ionic liquid that shares the same cation.     

Correlation of the Solubilizing Abilities of Hexyl(trimethyl)ammonium <Emphasis Type="Italic">bis</Emphasis>((Trifluoromethyl)sulfonyl)imide, 1-Propyl-1-methylpiperidinium <Emphasis Type="Italic">bis</Emphasis>((Trifluoromethyl)sulfonyl)imide,and 1-Butyl-1-methyl-pyrrolidinium Thiocyanate

Chromatographic retention data were measured for a wide range of organic solutes on 1-butyl-1-methylpyrrolidinium thiocyanate ([BMPyrr]⁺[SCN]⁻), hexyl(trimethyl)ammonium bis((trifluoromethyl)sulfonyl)imide ([HexM₃Am]⁺[(Tf)₂N]⁻), and 1-propyl-1-methylpiperidinium bis((trifluoromethyl)sulfonyl)imide ([PMPip]⁺[(Tf)₂N]⁻) stationary phases at 323 and 353 K. The measured retention factors were combined with published infinite dilution activity coefficient and gas-to-water partition coefficient data to yield gas-to-anhydrous ionic liquid (IL) partition coefficients and water-to-anhydrous IL partition coefficients. Both sets of partition coefficients were analyzed using the Abraham model. The derived Abraham model correlations describe the observed gas-to-IL and water-to-IL partition coefficient data to within average standard deviations of 0.116 and 0.156 log₁₀ units, respectively.     

Physical and CO2-Absorption Properties of Imidazolium Ionic Liquids with Tetracyanoborate and Bis(trifluoromethanesulfonyl)amide Anions

Ionic liquids with tetracyanoborate ([TCB]^?) and bis(trifluoromethanesulfonyl)amide ([Tf₂N]^?) anions generally have low viscosities and high CO₂ capacities, and thus they are attractive solvents for CO₂-related applications. Herein, we have investigated physical and CO₂-absorption properties of 1-ethyl-3-methylimidazolium tetracyanoborate ionic liquid ([emim][TCB]) to discuss the anion effects of [TCB]^? in comparison with the previous results of [emim][Tf₂N]. The density, viscosity, electrical conductivity, and isobaric molar heat capacity were measured as a function of temperature at atmospheric pressure. [emim][TCB] has both lower density and isobaric molar heat capacity than [emim][Tf₂N]. [emim][TCB] shows superior transport properties (lower viscosity and higher electrical conductivity) compared to [emim][Tf₂N], whereas the Walden plots of molar conductivity against fluidity (reciprocal of viscosity) have smaller values in [emim][TCB] than in [emim][Tf₂N] at certain fluidities. The high-pressure CO₂ solubilities were also determined in [emim][TCB]. The mole fraction scaled solubility of CO₂ in [emim][TCB] is slightly larger than that in [emim][Tf₂N] at certain pressures and temperatures. The former ionic liquid shows much higher molarity scaled solubility of CO₂ than the latter because of the smaller molar volume. It is suggested that both anions have similar strength of intermolecular interaction with CO₂ and comparable changes in the solvent structure between neat and CO₂ solution, in view of the thermodynamic parameters of dissolution.     

Measurement of SO2 solubility in ionic liquids

Measurements of the solubility of sulfur dioxide (SO(2)) in the ionic liquids 1-n-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf(2)N]) and 1-n-hexyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide ([hmpy][Tf(2)N]) at temperatures from 25 to 60 degrees C and pressures up to 4 bar indicate that large amounts (up to 85 mol %) of SO(2) dissolve in ionic liquids by simple physical absorption.     

Coordination environment of [UO2Br4] in ionic liquids and crystal structure of [Bmim]2[UO2Br4]

The complex formed by the reaction of the uranyl ion, UO₂²⁺, with bromide ions in the ionic liquids 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([Bmim][Tf₂N]) and methyl-tributylammonium bis(trifluoromethylsulfonyl)imide ([MeBu₃N][Tf₂N]) has been investigated by UV–Vis and U L_III-edge EXAFS spectroscopy and compared to the crystal structure of [Bmim]₂[UO₂Br₄]. The solid state reveals a classical tetragonal bipyramid geometry for [UO₂Br₄]²⁻ with hydrogen bonds between the Bmim⁺ and the coordinated bromides. The UV–Vis spectroscopy reveals the quantitative formation of [UO₂Br₄]²⁻ when a stoichiometric amount of bromide ions is added to UO₂(CF₃SO₃)₂ in both Tf₂N-based ionic liquids. The absorption spectrum also suggests a D_4h symmetry for [UO₂Br₄]²⁻ in ionic liquids, as previously observed for the [UO₂Cl₄]²⁻ congener. EXAFS analysis supports this conclusion and demonstrates that the [UO₂Br₄]²⁻ coordination polyhedron is maintained in the ionic liquids without any coordinating solvent or water molecules. The mean U–O and U–Br distances in the solutions, determined by EXAFS, are, respectively, 1.766(2) and 2.821(2) Å in [Bmim][Tf₂N], and, respectively, 1.768(2) and 2.827(2) Å, in [MeBu₃N][Tf₂N]. Similar results are obtained in both ionic liquids indicating no significant influence of the ionic liquid cation either on the complexation reaction or on the structure of the uranyl species.     

Development of Abraham model IL-specific correlations for N-triethyl(octyl)ammonium bis(fluorosulfonyl)imide and 1-butyl-3-methylpyrrolidinium bis(fluorosulfonyl)imide

ABSTRACT

Abraham model correlations are derived for describing gas-to-ionic liquid and water-to-ionic liquid partition coefficients from published experimental data for solutes dissolved in both N-triethyl(octyl)ammonium bis(fluorosulfonyl)imide and 1-butyl-3-methyl-pyrrolidinium bis(fluorosulfonyl)imide. Derived Abraham model correlations describe the observed partition coefficient data to within 0.13 log units. As part of the current study the existing equation coefficients for the N-triethyl(octyl)ammonium cation were updated and reported for the first time were equation coefficients for the bis(trifluorosulfonyl)imide anion.     

Ionic liquids as porogens in the microwave-assisted synthesis of methacrylate monoliths for chromatographic application

Several imidazolium-based ionic liquids (ILs) with varying cation alkyl chain length (C₄–C₁₀) and anion type (tetrafluoroborate ([BF₄]⁻), hexafluorophosphate ([PF₆]⁻) and bis(trifluoromethylsulfonyl)imide ([Tf₂N]⁻)) were used as reaction media in the microwave polymerization of methacrylate-based stationary phases. Scanning electron micrographs and backpressures of poly(butyl methacrylate-ethylene dimethacrylate) (poly(BMA-EDMA)) monoliths synthesized in the presence of these ionic liquids demonstrated that porosity and permeability decreased when cation alkyl chain length and anion hydrophobicity were increased. Performance of these monoliths was assessed for their ability to separate parabens by capillary electrochromatography (CEC). Intra-batch precision (n = 3 columns) for retention time and peak area ranged was 0.80–1.13% and 3.71–4.58%, respectively. In addition, a good repeatability of RSD_{Retention time} = <0.30% and ∼1.0%, RSD_{Peak area} = <1.30% and <4.3%, and RSD_Efficiency = <0.6% and <11.5% for intra-day and inter-day, respectively exemplify monolith performance reliability for poly(BMA-EDMA) fabricated using 1-hexyl-3-methylimidazolium tetrafluoroborate ([C₆mim][BF₄]) porogen. This monolith was also tested for its potential in nanoLC to separate protein digests in gradient mode. ILs as porogens also fabricated different alkyl methacrylate (AMA) (C4–C18) monoliths. Furthermore, employing binary IL porogen mixture such as 1-butyl-3-methylimidazolium tetrafluoroborate ([C₄mim][BF₄]) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C₄mim][Tf₂N]) successfully decreased the denseness of the monolith, than when using [C₄mim][Tf₂N] IL alone, enabling a chromatographic run to be performed with 1:1 ratio produced baseline separation for the analytes. The combination of ILs and microwave irradiation made polymer synthesis very fast (∼10 min), entirely green (organic solvent-free) and energy saving process.     

Mixing and decomposition behavior of {[4bmpy][Tf2N] + [emim][EtSO4]} and {[4bmpy][Tf2N] + [emim][TFES]} ionic liquid mixtures

Mixing ionic liquids (ILs) has been revealed as a useful way to finely tune the properties of IL-based solvents. The scarce available studies on IL mixtures have shown a quasi-ideal behavior of their physical properties. In this work, we have performed a thermophysical characterization of two binary IL mixtures, namely {4-methyl-N-butylpyridinium bis(trifluoromethylsulfonyl)imide ([4bmpy][Tf₂N]) + 1-ethyl-3-methylimidazolium ethylsulfate ([emim][EtSO₄])} and {[4bmpy][Tf₂N] + 1-ethyl-3-methylimidazolium 1,1,2,2-tetrafluoroethanesulfonate [emim][TFES]}. Both binary IL mixtures have been recently proposed as promising solvents in the (liquid + liquid) extraction of aromatic hydrocarbons from mixtures with alkanes. Densities, viscosities, refractive indices, thermal stability, and specific heats of the {[4bmpy][Tf₂N] + [emim][EtSO₄]} and {[4bmpy][Tf₂N] + [emim][TFES]} IL mixtures have been measured as a function of both temperature and composition. Dynamic viscosities, refractive indices, and thermal stability of the {[4bmpy][Tf₂N] + [emim][EtSO₄]} mixture have exhibited strong deviations from the ideality, in contrast with the quasi-ideal properties of the {[4bmpy][Tf₂N] + [emim][TFES]} mixture and the behavior of the imidazolium and pyridinium-based IL mixtures studied hitherto. The reliability of predictive methods of the thermophysical properties of the mixtures has also been evaluated.     

Linear free energy relationship correlations for the solubilising characterisation of room temperature ionic liquids containing 1-hexyloxymethyl-3-methylimidazolium and 1,3-dihexyloxymethylimidazolium cations

Gas-to-room temperature ionic liquid (RTIL) partition coefficients have been compiled from the published literature for solutes dissolved in 1-hexyloxymethyl-3-methylimidazolium bis(trifluoromethylsulphonyl)imide, {[HxomMIm]⁺[(Tf)₂N]^?}, and in 1,3-dihexyloxymethylimidazolium bis(trifluoromethylsulphonyl)imide, {[(Hxom)₂Im]⁺[(Tf)₂N]^?}. These partition coefficients are converted into water-to-RTIL partition coefficients using the corresponding gas-to-water partition coefficients. Both sets of partition coefficients are analysed using the Abraham model with cation-specific and anion-specific equation coefficients. The equation coefficients are reported for the 1-hexyloxymethyl-3-methylimidazolium and 1,3-dihexyloxymethylimidazolium cations. The calculated cation coefficients can be combined with our previously determined nine sets of anion-specific equation coefficients to yield expressions capable of predicting the partition coefficients of solutes in 18 different RTILs.     

Solubility of CO2 in the ionic liquid [hmim][Tf2N]

New experimental results are presented for the total pressure above liquid mixtures of carbon dioxide and the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf₂N]). The series of experiments were performed at preset temperature and liquid phase composition by means of a very precise high-pressure view-cell technique based on the synthetic method. A temperature range from (293.15 to 413.2) K was investigated where the maximum pressure reached approximately 10 MPa. Gas molalities in [hmim][Tf₂N] ranged up to about 4.7 mol · kg⁻¹. The (extended) Henry’s law is successfully applied to correlate the solubility pressures.     

Laser-induced fluorescence and infrared spectroscopic studies on the specific solvation of tris(1-(2-thienyl)-4,4,4-trifluoro-1,3-butanedionato)europium(III) in an ionic liquid

The extraction constant and the two-phase stability constant (K_D,Mβ₃) of tris(2-thenoyltrifluoroacetonato)europium(III) between 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C₄mim][Tf₂N]) as an ionic liquid and an aqueous phase were determined by considering the extraction equilibria including anionic tetrakis(2-thenoyltrifluoroacetonato)europate(III). Specific solute-solvent interactions between the neutral Eu(III) chelate and [C₄mim][Tf₂N] molecules were revealed from the relationships between the distribution constant of the enol form of 2-thenoyltrifluoroacetone (Htta) as a proton chelate and the distribution constant (K_D,M) of the neutral Eu(III) chelate because the [C₄mim][Tf₂N] system gave the high K_D,Mβ₃ value compared with those in conventional molecular solvents such as benzene and 1,2-dichloroethane. The coordination environment of Eu³⁺ in the neutral Eu(III) chelate in [C₄mim][Tf₂N] was investigated by time-resolved laser-induced fluorescence spectroscopy and infrared absorption spectroscopy. Both methods consistently indicated that not only the Eu(III) chelate extracted but also Eu(tta)₃(H₂O)₃ synthesized as a solid crystal were almost completely dehydrated in [C₄mim][Tf₂N] saturated with water. Consequently, the higher K_D,M or extractability of the neutral Eu(III) chelate in the [C₄mim][Tf₂N] system can be ascribed to the dehydration of the Eu(III) chelate, which is caused by the specific solvation with [C₄mim][Tf₂N] molecules.     

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.     

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.     

Application of novel room temperature ionic liquids in flexible supercapacitors

This paper studied application of different types of room temperature ionic liquids (RTILs) into flexible supercapacitors. Typical RTILs including 1-buthyl-3-methyl-imidazolium [BMIM][Cl], trioctylmethylammonium bis(trifluoromethylsulfonyl)imide [OMA][TFSI] and triethylsulfonium bis(trifluoromethylsulfonyl)imide ([SET₃][TFSI]) were studied. [SET₃][TFSI] shows the best result as electrolyte in electrochemical double-layer (EDLC) supercapacitors with very high specific capacitance of 244 F/g at room temperature, overceiling the performance of conventional carbonate electrolyte such as dimethyl carbonate (DMC) with more stable performance and much larger electrochemical window.