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.     

Effects of temperature and anion species on CO2 permeability and CO2/N2 separation coefficient through ionic liquid membranes

The permeability of carbon dioxide (CO₂) through imidazolium-based ionic liquid membranes was measured by a sweep gas method. Six species of ionic liquids were studied in this work as follows: [emim][BF₄], [bmim][BF₄], [bmim][PF₆], [bmim][Tf₂N], [bmim][OTf], and [bmim][dca]. The ionic liquids were supported with a polyvinylidene fluoride porous membrane. The measurements were performed at T = (303.15 to 343.15) K. The partial pressure difference between feed and permeate sides was 0.121 MPa. The permeability of the CO₂ increases with temperature for the all ionic liquid species. Base on solution diffusion theory, it can be explained that the diffusion coefficient of CO₂ in an ionic liquid affects the temperature dependence more strongly than the solubility coefficient. The greatest permeability was obtained with the [bmim][Tf₂N] membrane. The membrane of [bmim][PF₆] presents the lowest permeability.The separation coefficient between CO₂ and N₂ through the ionic liquid membranes was also investigated at the volume fraction of CO₂ at feed side 0.10. The separation coefficient decreases with the increase of temperature for the all ionic liquid species. The membrane of [emim][BF₄] and [bmim][BF₄] gives the highest separation coefficient at constant temperature. The lowest separation coefficient was obtained from [bmim][Tf₂N] membrane which presents the highest permeability of CO₂.     

The Synthesis of Anatase TiO2 Nanoparticles by Solvothermal Method using Ionic Liquid as Additive

The solvothermal reactions of Ti(OiPr)₄ in alcohol using ionic liquid as additive were investigated. In the presence of [BMIM][Cl], [BMIM][Br], [BMIM][NTf₂], [BMIM][SO₃Me], [BMIM][SO₄Me], or [BMIM][OTf] (BMIM = 1‐Butyl‐3‐methylimidazolium), pure anatase nanoparticles were obtained. The controlled hydrolysis of Ti(OiPr)₄ in the presence of ionic liquids to form titanium oxo clusters plays a key role in the formation of anatase nanostructures, and ionic liquids can be repeatedly used to synthesise anatase nanoparticles. However, in the presence of [BMIM][PF₆], [BMIM]₂[Ti(OH)₆] was obtained by an anion exchange reaction.     

Isotope effects on miscibility of 1-alkyl-3-methylimidazolium bis(trifluoromethyl)sulfonyl imides with aromatic hydrocarbons

The liquid–liquid miscibility temperatures as a function of composition and deuterium substitution have been experimentally determined for the binary mixtures of 1-decyl-3-methylimidazolium bis(trifluoromethyl)sulfonyl imide, [C₁₀MIM][NTf₂], and 1-dodecyl-3-methylimidazolium bis(trifluoromethyl)sulfonyl imide, [C₁₂MIM][NTf₂] with benzene and toluene and their deuterated forms. All systems exhibit upper critical solution temperatures (UCSTs) and better miscibility for ionic liquids with longer alkyl chain. The interchange of benzene for toluene results in worse miscibility for [C₁₀MIM][NTf₂] and better for [C₁₂MIM][NTf₂]. Deuteration of the aromatics leads to better miscibility in each case. The sign of the isotope effect is in agreement with expectations and its value seems to be seriously affected by the neighborhood of the hypercritical state.     

The “one-pot” synthesis of 2,5-diformylfuran,a promising synthon for organic materials in the conversion of biomass

The organic ionic oxidant 4-acetamido-2,2,6,6-tetramethyl-1-oxopiperidinium tetrafluoroborate, [Pip*(O)][BF₄], was found to be compatible with both classical organic solvents and the ionic liquids [BMIm][Cl]/[BMIm][BF₄] (BMIm is 1-butyl-3-methylimidazolium), which are essential in the conversion of cellulose biomass. A unique NMR monitoring procedure developed in our group was used to study the conversion of fructose to 2,5-diformylfuran in ionic liquids. This process can successfully be carried out in a “one-pot” fashion; [Pip*(O)][BF₄] efficiently oxidizes intermediate 5-hydroxymethylfurfural. The reaction is highly selective, giving 2,5-diformylfuran in 95% yield.     

Dramatic Change in Viscosities of Pure Ionic Liquids upon Addition of Molecular Solvents

Viscosities of binary mixtures of pyridinium based ionic liquids (1-butyl pyridinium tetrafluoroborate, [BP][BF₄], 1-butyl 3-methyl pyridinium tetrafluoroborate [3-MBP][BF₄], 1-butyl 4-methyl pyridinium tetrafluoroborate, [4-MBP][BF₄]), and phosphonium based ionic liquids, (tetrabutyl phosphonium alaninate, [TBP][Ala]; tetrabutyl phosphonium valinate, [TBP][Val]) with the molecular solvents, water, methanol and dichloromethane, have been measured at 298.15 K. A Brookfield ultra-rheometer was employed to measure the reported viscosities. The drop in viscosity in the close vicinity of pure ionic liquid is more prominent in polar solvents like water compared to less polar solvents. The temperature dependence of this observation was also studied for binary mixtures of [4-MBP][BF₄] with water in range of 298.15–323.15 K. The Vogel-Fulcher-Tamman (VFT) equation was employed to investigate the temperature dependence of the viscosities of pure pyridinium-based ionic liquids in the temperature range from 298.15–323.15 K.     

Extraction and high performance liquid chromatographic determination of 3-indole butyric acid in pea plants by using imidazolium-based ionic liquids as extractant

In this paper, imidazolium-based ionic liquids [C₄mim][PF₆], [C₆mim][PF₆], [C₈mim][PF₆], [C₆mim][BF₄] and [C₈mim][BF₄] were tested as extracting solvents for removal of 3-indole butyric acid (IBA) from aqueous media with subsequent determination using HPLC. Percent extraction of IBA was strongly affected by pH of aqueous phases and the chemical structures of ionic liquids (ILs). Extraction of IBA was quantitative in the pH values lower than pK_a of IBA. Considering both extraction and stripping efficiencies of IBA, [C₄mim][PF₆] was found to act more efficient than other studied ILs. Capacity of [C₄mim][PF₆] was 17.6 × 10⁻⁴ mmol IBA per 1.0 mL of IL. Ionic strength of aqueous phase and temperature had shown no serious effects on extraction efficiency of IBA. A preconcentration factor of 100 and a relative standard deviation of 1.16% were obtained. It was found that ionic liquid phase was reusable almost five times for extraction/stripping purposes. 3-Indole acetic acid showed interferential effect in the extraction step. In order to assess the applicability of the method, extraction and stripping of IBA from pea plants and some other samples were studied.     

Self‐assembly and lower critical solution temperature properties of supramolecular block copolymer/ionic liquid complexes depending on the alkyl chain length of imidazolium rings

We report the liquid crystalline (LC) assembly and lower critical solution temperature (LCST) properties of wedge‐shaped block copolymer (BCP)/1‐alkyl‐3‐methylimidazolium tetrafluoroborate ([C_nMIM][BF₄], n = 2, 4, 6) complexes ( 1 – 3 ) depending on the alkyl chain length of the ionic liquids (ILs). In contrast to the crystalline BCP, all of the ionic samples showed LC phases. 1 with [C₂MIM][BF₄] exhibited a hexagonal columnar phase, and 3 with [C₆MIM][BF₄] exhibited a gyroid phase. Interestingly, a temperature‐dependent transformation from columnar phase to gyroid phase was revealed for 2 with [C₄MIM][BF₄]. The phase difference may be explained by the supramolecular shape change that was dependent on the alkyl chain length of the ILs. The LCST behavior was characterized using the differential scanning calorimetry, turbidity observations, and the X‐ray diffraction techniques. Notably, the primary d‐spacing began to decrease at the clouding temperature (T_c). 3 showed the highest T_c at 130 °C, which is greater than the temperature of the order‐to‐disorder transition. The results demonstrate that the subtle variation in the IL structure affects the morphological and LCST properties. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 3587–3596     

The physicochemical properties of some imidazolium-based ionic liquids and their binary mixtures

The density, viscosity and conductivity of ionic liquids (ILs), 1-octyl-3-methylimidazolium tetrafluoroborate ([omim][BF4]), 1-octyl-3-methylimidazolium chloride ([omim][Cl]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim] BF4]), 1-hexyl- 3-methylimidazolium chloride ([hmim][Cl]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF6]), and the [omim][BF4] + [omim][Cl], [hmim][BF4] + [hmim][Cl], and [hmim][PF6] + [hmim][Cl] binary mixtures were studied at dif- ferent temperatures. It was demonstrated that the densities of both the neat ILs and their mixtures varied linearly with temper- ature. The density sensitivity of a binary mixture is between those of the two components. The excess molar volumes (VE) of [hmim][BF4] + [hmim][Cl] and [hmim][PF6] + [hmim][Cl] mixtures are positive in the whole composition range. For [omim][BF4] + [omim][Cl], the VE is also positive in the [omim][Cl]-rich region, but is negative in the [omim][BF4]-rich re- gion. The viscosity or conductivity of a mixture is in the intermediate of those of the two neat ILs. For all the neat ILs and the binary mixtures studied, the order of conductivity is opposite to that of the viscosity. The Vogel-Tammann-Fulcher (VTF) equations can be used to fit the viscosity and conductivity of all the neat ILs and the binary mixtures. The neat ILs and their mixtures obey the Fractional Walden Rule very well, and the values of the Walden slopes are all smaller than unit, indicating obvious ion associations in the neat ILs and the binary mixtures.     

Study of the behaviour of the azeotropic mixture ethanol–water with imidazolium-based ionic liquids

In this work, experimental data of isobaric vapour–liquid equilibria for the ternary system ethanol + water + 1-hexyl-3-methylimidazolium chloride ([C₆mim][Cl]) and for the corresponding binary systems containing the ionic liquid (ethanol + [C₆mim][Cl], water + [C₆mim][Cl]) were carried out at 101.300 kPa. VLE experimental data of binary and ternary systems were correlated using the NRTL equation. In a previous work [N. Calvar, B. González, E. Gómez, A. Domínguez, J. Chem. Eng. Data 51 (2006) 2178–2181], the VLE of the ternary system ethanol + water + [C₄mim][Cl] was determined and correlated, so we can study the influence of different ionic liquids in the behaviour of the azeotropic mixture ethanol–water.     

Effect of ionic liquid organizing ability and amine structure on the rate and mechanism of base induced elimination of 1,1,1-tribromo-2,2-bis(phenyl-substituted)ethanes

The kinetics of the elimination reaction of 1,1,1-tribromo-2,2-bis(phenyl-substituted)ethanes into the corresponding 1,1-dibromo-2,2-bis(phenyl-substituted)ethenes induced by amines were studied in three room temperature ionic liquids ([BMIM][BF₄], [BMIM][PF₆], [BdMIM][BF₄]). In order to have information about reagent-ionic liquid interactions, the reaction was carried out over the temperature range (293.1-313.1 K). To study the effect of the amine on the rate and occurrence of the elimination reaction, several primary, secondary and tertiary amines with different structure (cyclic and acyclic), basicity and steric requirements were used. The data collected show that the reaction occurs faster in ionic liquids than in other conventional solvents. Furthermore, ionic liquids seem to be able to induce, for the studied reaction, a shift of mechanism from E1_cb (in MeOH) versus E2 (in ionic liquid).     

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.     

Evaluation and comparison of global scalar properties for the simultaneous interaction of ionic liquids with thiophene and pyridine

Ab initio studies were carried out with mixtures containing ionic liquid with thiophene and pyridine for studying the simultaneous interaction. Global scalar properties such as HOMO/LUMO energies, HOMO–LUMO energy gap, chemical hardness, chemical potential, electronegativity, global hardness, global softness and electrophilicity index were determined for clusters containing ionic liquids with thiophene and pyridine. Ionic liquids containing: 1-butyl-3-methylpyrrolidinium [BUMPYR], 1-benzyl-3-methyimidazolioum [BeMIM] and 1-butyl-3-methylpyridinium [BUMPY] cations combined with inorganic anions containing fluorine ([BF₄] and [PF₆]) were studied in this work. [BeMIM][BF₄] (1-benzyl-3-methyimidazolioum tetrafluoroborate) with a HOMO–LUMO energy gap of 0.1882 Hartrees was found to be the most effective IL. Further a ranking based on all the mentioned scalar parameters also pointed out [BeMIM][BF₄] to be the most desirable IL. The overall ranking after taking into considerations all factors followed: [BeMIM][BF₄] > [BUMPYR][BF₄] > [BUMPY][PF₆] > [BUMPY][BF₄] > [BUMPYR][PF₆]. To validate the findings, infinite dilution activity coefficients were predicted using the quantum chemical based COSMO-RS methodology which gave the same trend as observed using scalar properties.     

Thermodynamic modeling of hydrogen sulfide solubility in ionic liquids using modified SAFT-VR and PC-SAFT equations of state

Equations of state based on the statistical associating fluid theory for potentials of variable range (SAFT-VR) and the perturbed chain statistical associating fluid theory (PC-SAFT) have been used to model the PVT behavior of ionic liquids and the solubility of H₂S in six imidazolium-based ionic liquids. The studied systems included [bmim][PF6], [hmim][PF6], [bmim][BF4], [hmim][BF4], [bmim][NTF2] and [hmim][NTF2] at various temperatures and pressures.For pure components, parameters of the models have been obtained by fitting the models to experimental data on liquid densities; the average relative deviation between the calculated and experimental densities for ionic liquids is less than 2.42% in the PC-SAFT model and 5.44% in the SAFT-VR approach, the latter which incorporates the square-well potential for short-range interactions. In both models an additional term has been added to account for dipole-dipole interactions between solute molecules resulting from the permanent charges on the chain molecules of the solvents. The model parameters have also been correlated as functions of the molecular weight of the solvents. For binary mixtures of ionic liquids and H₂S, the association interactions between H₂S molecules and between the ionic liquids and H₂S molecules have also been taken into account in both approaches, using binary interaction coefficients. The results show an average deviation of less than 5% in the calculation of the mole fraction of H₂S in the ionic liquids. The effect of inclusion of the polar term has been studied for binary systems in both models.     

Epoxy resins cured with ionic liquids as novel supports for metal complex catalysts

In this work, the application of an epoxy resin cured with ammonium ionic liquids as a support for palladium complex catalyst is reported. Supports based on epoxy resin were obtained as a result of the use of ionic liquids: didecyldimethylammonium tetrafluoroborate [d₂m₂am][BF₄], 1-methyltheobromine tetrafluoroborate [mthb][BF₄], didecyldimethylammonium theobrominate [d₂m₂am][thb], didecyldimethylammonium theophyllinate [d₂m₂am][thp] as cross-linking agents. The characterization of polymeric supports and heterogenized palladium catalysts has involved research methods like time-of-flight secondary ion mass spectrometry (TOF-SIMS), infrared spectroscopy (IR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS). The activity and stability during long-term use of the investigated catalytic systems were tested in a model Heck reaction. The influence of the type of ILs used as epoxy hardeners on the catalytic properties of epoxy-supported palladium catalysts is discussed.     

PVT properties of imidazolium-, phosphonium-, pyridinium- and pyrrolidinium-based ionic liquids using critical point constants

Song and Mason equation of state (EOS) with a simple modification has been extended to modelling PVT properties of ionic liquids (ILs). The considered ILs are [C₁mim][MeSO4], [C₁mim][CH₃OC₂H₅SO₄], [C₁mim][(CH₃)₂PO₄], [C₂mim][MeSO4], [C₂mim][BF₄], [C₂mim][SCN], [C₂eim][NTf₂], [C₄mim][C(CN)₃], [C₄mim][CF₃SO₃], [C₄mim][SCN], [C₅mim][NTf₂], [C₈mim][NTf₂], [(C₆H₁₃)₃P(C₁₄H₂₉)][Cl], [(C₆H₁₃)₃P(C₁₄H₂₉)][NTf₂], [(C₆H₁₃)₃P(C₁₄H₂₉)][Ac], [C₃mpyr][NTf₂], [C₄mpyr][NTf₂] and [Py][C₂H₅OC₂H₄SO₄]. Three temperature-dependent parameters in the proposed EOS have been scaled as functions of reduced temperature with the use of the law of corresponding states. It is shown that the knowledge of just critical temperature and critical density is sufficient to predict the PVT properties of these ILs. The overall average absolute deviation of calculated densities from literature values for 1347 data points of 18 ILs was found to be 0.58%. The predicted density of ILs from proposed EOS has been compared with those obtained by other literature work. Moreover, we indicate that the Zeno line regularity can well be predicted by proposed model for ILs.     

Viscosities for Ionic Liquid Binary Mixtures with a Common Ion

At present, there is a considerable amount of work devoted to the study of the thermophysical properties of pure ionic liquids, which contrasts with the few data available for their mixtures. One of the most appealing characteristics of ionic liquids is the capability of subtly changing the chemical structure of the cation and anion in order to design appropriate solvents for specific applications. Mixtures of ionic liquids increase enormously this specificity, due to the unlimited combinations that arise from mixing two or more ionic liquids. In this context, the study of the thermophysical properties of these mixtures is revealed as a fundamental task. In this work the viscosities of the ionic liquid binary mixtures with a common ion ([C₆mim] + [C₂mim])[BF₄], ([C₆mim] + [C₄mim])[BF₄], [C₄mim]([BF₄] + [MeSO₄]) and [C₄mim]([PF₆] + [BF₄]) were determined within the temperature range (298.15–308.15) K. The temperature dependence of the viscosity for pure liquids is analyzed by means of the Vogel-Tammann-Fulcher equation and several mixing rules are applied for the mixtures.     

Thermodynamic analysis for solubility of pimelic acid in ionic liquids

Based on the solubilities of pimelic acid in ionic liquids [EMIM][HSO₄], [PMIM]Br, [i-PMIM][HSO₄], [BMIM]Br, and [BMIM][HSO₄], dissolution enthalpy and dissolution entropy at different temperatures have been calculated. The experimental data of solubilities are correlated with the modified Apelblat equation. The thermodynamic properties of pimelic acid in ionic liquids were discussed. The solubilities correlated by the model are in good agreement with experimental data.     

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.