Binary Mixtures Of Ionic Liquids Research Articles

Apparent molar properties of trioctylmethylammonium based ionic liquids in toluene and dodecane at T = (293.15 to 328.15) K

The structural variance ability of ionic liquids (ILs) provides an opportunity to fine tune the thermophysical properties for given application. For effective extraction of metal ion from water, the applied ILs should be hydrophobic and preferably containing non fluorinated anions. The hydrophobicity of ILs can be further manipulated by the addition of diluents. To understand extraction of metal ion using binary mixtures of ILs + diluent, it is utmost important to explore different types of interactions exist in the binary mixtures using thermophysical properties. For this purpose, we present experimentally measured data of densities, ρ and speeds of sound, u for binary solutions of aprotic ionic liquids (APILs) namely trioctylmethylammonioum bis-(2-ethylhexyl) phosphate [TOMA][DEHP], trioctylmethylammonioum bis-(2-ethylhexyl) diglycolamate [TOMA][DGA], trioctylmethylammonioum bis-(2-ethyhexyl)sulfosuccinate [TOMA][DEHS] in toluene and dodecane (diluents) at T = 293.15 K to 328.15 K. The apparent molar properties like volume Vϕ, isentropic compressibility Ks,ϕ and limiting expansivity Eϕ∞ were calculated and explained in terms of temperature, size of anion, and nature of solvent. The both Vϕ and Ks,ϕ were increased with rise in temperature and replacing toluene with dodecane whereas decreased with increase in concentration of APIL. The Redlich-Mayer type equation was used to correlate apparent molar volume, Vϕ∞ and apparent molar isentropic compressibility, Kϕ∞ at infinite dilution. The influence of interactions (IL-IL or IL-solvent) in studied binary mixtures was elucidated by Sv and Sk parameters. It was observed that ion-solvent interactions are dominating in APILs + toluene than in APILs + dodecane.

Assessing possible influence of structuring effects in solution on cytotoxicity of ionic liquid systems

During the last decades, micro-structuring phenomena, formation of polar domains and assembling of nano-scale heterogeneities in ionic liquids (ILs) have been discovered. Here we assess the influence of structuring effects in solution on biological activity of ionic systems. In the present work, we studied cytotoxicity of aqueous solutions of binary mixtures of common ILs and showed that it mostly did not comply with the concentration addition model thus suggesting the occurrence of toxicity-affecting interactions in the media. In most cases, antagonistic effects were observed in the studied systems. Micro-heterogeneous water structures were experimentally detected in the binary IL mixtures for the first time. By using a cytotoxicity assay, NMR spectroscopy and scanning electron microscopy, a novel research direction was explored dealing with a relationship between dynamic structuring effects in ILs and their cytotoxicity.

Structural Anomalies in Binary Mixtures of Ionic Liquid [Bmim]BF4 with Water Studied by EPR.

Ionic liquids (ILs) show a variety of unusual and intriguing properties on a molecular level. Recently, a new type of structural anomaly occurring in neat ILs near their glass transition temperatures (Tg) has been found. In particular, the coexistence of two types of IL environments was observed, one of which progressively suppresses the molecular mobility upon temperature increase within ∼(Tg-60 K) and Tg. To clarify the nature of these anomalies, their general characteristics, and potential for applications, in this work we investigated the molecular mobility in binary mixtures of IL [Bmim]BF4 with water using electron paramagnetic resonance spectroscopy and spin probes (stable nitroxides TEMPO-D18, (2,2,6,6-tetramethylpiperidin-1-yl)oxyl, and 14-carbamoyl-7-azadispiro[5.1.5.2]pentadeca-14-ene-7-oxyl). In a series of such mixtures with water content xH2O = 0.2-50 wt %, we detected similar anomalies to those found in neat IL (xH2O = 0). For xH2O < 2.5 wt %, the differences in manifestations of structural anomalies are negligible compared to those in neat ILs. In the range 2.5 ≤ xH2O < 5 wt %, an abrupt partial suppression of anomaly is observed, but further increase of the water content up to xH2O = 50 wt % has no impact on anomaly since, most plausibly, it leads only to the growth of the water-rich domains. Consequently, the observed structural anomalies are rather robust against the presence of water in ILs, which is beneficial for their potential applications.

Prediction of surface tension of the binary mixtures containing ionic liquid using heuristic approaches; an input parameters investigation

In this study, the effect of input parameters on the performance of the artificial neural network (ANN) has been investigated to predict the surface tension of the 33 non-ionic + ionic liquids binary mixture. To achieve this purpose, in this work, 8 various approaches for input parameters are considered. Physical properties such as temperature, reduced temperature, critical temperature, critical pressure, critical volume, molecular weight, acentric factor and critical compressibility factor as well as two different mixing rules have been used to prepare various input parameters approaches. The root mean square error (RMSE) of the most accurate approach, obtained for all 1537 data points regarding 33 binary mixtures, is 7.88 × 10−3. Furthermore, five different other intelligence methods such as ANFIS, ANFIS-ACO, ANFIS-DE, ANFIS-GA, and ANFIS-PSO have been applied to estimate the surface tension of the concerned binary mixtures based on the best input parameters. The comparison between the results of the ANN and five other methods show that the ANN method has the best accuracy.

Binary mixtures of ionic liquids based on EMIm cation and fluorinated anions: physico-chemical characterization in view of their application as low-temperature electrolytes

Binary mixtures of ionic liquids (ILs) consisting of 1-ethyl-3-methylimidazolium [EMIm]+ cation coupled with fluorinated anions: bis(fluorosulfonyl)imide [FSI]-, bis(trifluoromethanesulfonyl)imide [TFSI]- and tetrafluoroborate [BF4]-, were formulated to obtain ionic fluids which are liquid at low temperature and to understand their properties. The thermal behaviour of [EMIm][TFSI]x[FSI](1-x), [EMIm][FSI]x[BF4](1-x) and [EMIm][TFSI]x[BF4](1-x) mixtures with various molar ratios of IL components was investigated with differential scanning calorimetry (DSC). They exhibited reduced enthalpy of the phase transitions and lower melting temperature compared to the parent ILs, or only vitrification/devitrification occurring below −90 °C in some cases where x ranges from 0.5 to 0.8, 0.1 to 0.6 or 0.2 to 0.8 for [EMIm][TFSI]x[FSI](1-x), [EMIm][FSI]x[BF4](1-x) and [EMIm][TFSI]x[BF4](1-x), respectively. For the formulations showing solely a glass transition, considered to be prospective low-temperature electrolytes, the density, viscosity and conductivity values were determined in a wide temperature range. The density demonstrated linear temperature dependence, whilst the dynamic viscosity and ionic conductivity followed the Vogel-Tamman-Fulcher equation. The corresponding Walden plot for pure ILs and their mixtures revealed a high degree of ionicity classifying them as “good ionic liquids” even down to −25 °C. The [EMIm][FSI]x[BF4](1-x) mixtures with x ranging from 0.5 to 0.6 displayed the lowest viscosity and highest conductivity, indicating them as promising electrolytes for IL-based electrochemical capacitors operating at low temperature, down to at least −40 °C.

Kirkwood-Buff integrals and structure factor for binary mixtures of ionic liquid with 1-alkanol

In this paper, we have tried to describe the factors affecting molecular interactions and structure of binary systems including 1-Hexyl-3-methylimidazolium Nitrate ([Hmim][NO3]) and 1-alkanol (1-hexanol, up to 1-decanol) using Kirkwood-Buff (KB) integrals and structure factor. Obtained results indicate that unlike molecules tend to form favorable interactions via forming hydrogen bonds or dipolar interactions and stay alongside, while an increase in the carbon chain of 1-alkanols reduces the strength of bonds and tendency of the unlike molecules to stay together. Moreover, the structure of mixtures was studied using the concentration-concentration structure factor, SCC(0). Results from the application of this parameter show that in all binary mixtures, heterocoordination is predominant, ordering occurs in solutions and fluctuations are less than random orientation. In addition, the chemical short-range order parameter α′, which is an important function to understand the complex formation and phase segregation in the liquid mixtures, was calculated and discussed for mentioned mixtures. For current binary mixtures, experimental data and theoretical investigations are novel and reported for the first time.

Physicochemical Characterization of Ionic Liquid Binary Mixtures Containing 1-Butyl-3-methylimidazolium as the Common Cation

Mixing ionic liquids (as well as mixing an inorganic salt in an ionic liquid) constitutes an easy, elegant methodology for obtaining new ionic materials. In this study, 3 ionic liquids (ILs) sharin...

Mesoscale Organization and Dynamics in Binary Ionic Liquid Mixtures.

The impact of mesoscale organization on dynamics and ion transport in binary ionic liquid mixtures is investigated by broad-band dielectric spectroscopy, dynamic-mechanical spectroscopy, X-ray scattering, and molecular dynamics simulations. The mixtures are found to form distinct liquids with macroscopic properties that significantly deviate from weighted contributions of the neat components. For instance, it is shown that the mesoscale morphologies in ionic liquids can be tuned by mixing to enhance the static dielectric permittivity of the resulting liquid by as high as 100% relative to the neat ionic liquid components. This enhancement is attributed to the intricate role of interfacial dynamics associated with the changes in the mesoscopic aggregate morphologies in these systems. These results demonstrate the potential to design the physicochemical properties of ionic liquids through control of solvophobic aggregation.

The excess molar volume and the molar surface Gibbs energy of the binary of the ether-functionalized ionic liquids [C22O1IM][TfO] with ethanol and isomeric propanols at T = (288.15–318.15) K

The density and surface tension for the binary mixtures of ionic liquid (ILs) [C22O1IM][TfO] with ethanol, 1-propanol and 2-propanol are measured across the entire range of mole fraction at T = (288.15–318.15) K. The excess molar volumes of the binary mixtures are calculated, the relationship between VE and the mole fraction and temperature are explored. Especially, the term, △VE/△T is proposed to describe the interaction between the solvent and solute quantificationally. The molar surface Gibbs energy of the binary mixtures are obtained based on the density and surface tension, and the interaction between the components in both liquid and surface phase of the binary mixture is discussed. And its applications are also explored, including the estimation of surface tension for the binary mixtures and the improvement of the traditional Eötvös equation. At the same time, the polarity of the binary mixtures of [C22O1IM][TfO] with alcohols is obtained.

Responsive Ionogel Surface with Renewable Antibiofouling Properties.

The synthesis of ionogels with a responsive, self-replenishing surface for combating biofouling is described. Ionogels are prepared by infiltrating poly(vinylidene fluoride-co-hexafluoropropylene) with binary mixtures of ionic liquids (IL): 1-octadecyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide ([C18 C1 im][NTf2 ], melting point Tm = 55 °C) and 1-hexyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide ([C6 C1 im][NTf2 ], Tm = -9 °C). The IL mixtures release spontaneously from the gel matrix and eventually crystallize on the surface. This leads to self-replenishment of the surface of ionogels even after mechanical damage. The incorporation of [C6 C1 im][NTf2 ] provides the antimicrobial efficacy of ionogels while the crystals of [C18 C1 im][NTf2 ] serve as a skeleton maintaining [C6 C1 im][NTf2 ] on the surface. By heating, the ionogel surface transforms from solid to liquid-infused state-the removal of biofilms/bacteria developed under a long time of colonization is facilitated. The antimicrobial efficacy is maintained even after several cycles of biofilm formation and detachment. This work provides an opportunity to apply ionogels as functional coatings with renewable antibiofouling properties.

On the Regular Behavior of a Binary Mixture of Ionic Liquids.

Binary mixtures of the ionic liquids 1-ethyl-3-methylimidazolium dicyanamide and tributyl(methyl)ammonium dicyanamide, [C2C1im]x[N4441](1-x)[N(CN)2], are studied by means of their excess properties (enthalpy and volume), their viscosity, and their Raman spectra. The mixtures exhibit positive values of excess volume VE and excess enthalpy HE. The plot of the logarithm of viscosity as a function of composition is consistent with the finding HE > 0. The excess thermodynamic properties of the ionic liquid mixtures are compared with well-known results for binary mixtures of (high-temperature) molten salts. The asymmetry of the curve HE versus composition is reproduced by considering the volumetric fraction of the [C2C1im]x[N4441](1-x)[N(CN)2] mixtures according to basic results of the theory of regular solutions. The anion totally symmetric stretching mode νs(C≡N) was used to probe the local environment around the anion in a Raman spectroscopy investigation of the [C2C1im]x[N4441](1-x)[N(CN)2] mixtures as a function of the composition. The Raman band shape (peak frequency and bandwidth) of the νs(C≡N) mode changes as expected from the fluctuation of concentration around the probe oscillator according to models for vibrational spectroscopy of liquid mixtures. This thermodynamic and spectroscopic study leads to the classification of the [C2C1im]x[N4441](1-x)[N(CN)2] mixture as a regular solution. The application of the regular solution equation for HE to other ionic liquid binary mixtures is discussed.

Liquid–Liquid Equilibria in Binary Mixtures of Dihydroxy Alcohols and Imidazolium-Based Ionic Liquids

Binary liquid–liquid equilibria (LLE) for mixtures of dihydroxy alcohols and three imidazolium-based ionic liquids (ILs) were measured. The dihydroxy alcohols were 1,3-propanediol, 1,4-butanediol, ...

Thermophysical characterization of sorbitol and 1–ethyl–3–methylimidazolium acetate mixtures

In this study, the solubility of a sugar alcohol (sorbitol) in 1–ethyl–3–methylimidazolium acetate was measured experimentally at various temperatures. Excess Gibbs energy models were utilized for modeling of solubility. Additionally, the thermophysical properties including density and viscosity of the binary mixtures of ionic liquid and sorbitol were measured. With the application of experimental data the apparent molar volumes at infinite dilution Vϕ0, the apparent molar isobaric expansibility Eϕ0 and Hepler's constants were calculated. It was found that sorbitol behaves as structure-breaker in the ionic liquid. Moreover, the applicability of local composition models for correlation of the experimental solubility and density data was further investigated. Additionally, Arrhenius–Andrade and Vogel–Tamman–Fulcher equations were applied for correlation of the viscosity measurements.

Effect of Isomerism on the Liquid–Liquid Phase Behavior of Mixtures of 1-Alkyl-3-methylimidazolium Bis((trifluoromethyl)sulfonyl)amide Ionic Liquids with Heptanol

Systematic investigations on the liquid–liquid phase behavior of binary mixtures of ionic liquids (IL) of the type 1-alkyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)amide (CxmimNTf2, x = 2, 4, 6, 8, and 10) with n-heptanol and its branched isomers 3-ethyl-3-pentanol and 2,4-dimethyl-3-pentanol have been performed. The phase diagrams were determined at atmospheric pressure in the temperature range (T) of 263–448 K by applying the cloud point method. The phase diagrams are analyzed in terms of well-established numerical concepts based on Ising criticality. The results are discussed, and trends and explanations for the shifts of the range of solubility are given. The systems show partial miscibility with upper critical solution temperatures. Comparing the solutions in branched alcohols with those in the linear isomer, the critical solution points are found to be remarkably shifted toward higher temperatures and lower IL contents. The trend becomes more pronounced for ILs with shorter alkyl side chains where also a change of the shape of the phase diagrams is observed.

Correlation of ionic liquid viscosity using Valderrama-Patel-Teja cubic equation of state and the geometric similitude concept. Part II: Binary mixtures of ionic liquids

The general equation of state employed in direct form, and for the first time presented in Part I of this series, is extended to correlate and predict the viscosity of binary mixtures of ionic liquids. The extension, also done for the first time, considers the classical mixing and combining rules commonly used in studies on pressure-temperature-volume equations of state, including two cases: (i) with no-interaction parameter (predictive model); and (ii) with one adjustable interaction parameter (correlating model). Data on viscosity of binary mixtures of ionic liquids have been gathered from the literature, analyzed, and selected, to finally construct a database of consistent data to obtain a general model that relates viscosity with pressure, temperature and concentration. A total of 2520 data points distributed on 344 isotherms, for 32 mixtures were considered for analysis, with average absolute relative deviations below 6%. If no interaction parameter is used, the model is still capable of predicting the viscosity of a mixture using only properties of the pure components. Results show that the model is accurate enough, being simpler and more accurate than sophisticated multiparametric models.

Extractive separation of benzene and cyclohexane using binary mixtures of ionic liquids

The separation of benzene and cyclohexane is a challenging process in petrochemical industry due to their close boiling points. Solvent mixing is a useful technique to enhance the extraction performance of liquid–liquid extraction process. In this work, the performance of solvent mixtures involving two organic solvents (N,N-dimethylformamide and ethylene glycol) and four ionic liquids (ILs), namely, 1-ethyl-3-methylimidazolium thiocyanate (C2mimSCN), 1-ethyl-3-methylimidazolium dicyanamide (C2mimN(CN)2), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (C2mimTf2N) and 1-ethyl-3-methylimidazolium acetate (C2mimAc) was investigated for the extractive separation of benzene and cyclohexane. The mixing ratios of the binary solvents were optimized using the ideal mixing calculation and validated experimentally through liquid–liquid extraction process. Six new quaternary liquid–liquid equilibria for the mixed solvents with benzene and cyclohexane were investigated at 25 °C and 1 atm, with feed concentrations of benzene ranging from 10 to 50 wt%. Ethylene glycol was discovered a good solvent pair with C2mimTf2N that could lead to potential cost savings. At the optimized mixing fraction, the {C2mimTf2N + C2mimSCN} mixture demonstrated the highest extraction performance, which was superior to that of sulfolane. Additionally, the {C2mimSCN + C2mimN(CN)2} and {C2mimN(CN)2 + C2mimAc} mixtures were found to increase the selectivity while maintaining the benzene distribution ratio in relation to sulfolane. The ILs were not present in the raffinate layer of any of the systems, indicating the reliable performance of the ILs in terms of avoiding solvent cross-contamination. This work demonstrated the use of binary solvent mixtures as a new efficient and versatile method to enhance extraction performance.

Comprehensive models for density prediction of ionic liquid + molecular solvent mixtures at different temperatures

ABSTRACTTo present comprehensive models for density prediction of the binary mixtures of ionic liquids (ILs), the density data for 193 sets of ionic liquid + molecular solvents were collected from the literature and were analysed by Jouyban-Acree and Jouyban-Acree-van’t Hoff and their combined version with Abraham solvation parameters. To check the capability of the trained models for density prediction, the ‘leave many out’ cross-validation method was used and the obtained overall % ARD were 3.7, 8.7, 4.1 and 8.5 for Jouyban-Acree, Jouyban-Acree-van’t Hoff, Jouyban-Acree–Abraham and Jouyban-Acree-van’t Hoff-Abraham models, respectively. It was concluded that all predictive models have the excellent accuracy for density prediction of the studied mixtures but the Jouyban-Acree and Jouyban-Acree-Abraham with lower %ARD are better than other models. However, the Jouyban-Acree-van’t Hoff–Abraham models may be preferred due to the lack of necessity of density data for components 1 and 2.

Task-Specific Organic Salts and Ionic Liquids Binary Mixtures: A Combination to Obtain 5-Hydroxymethylfurfural From Carbohydrates.

The increase in energy demand and depletion of fossil fuels are among major issues of modern society. Valorization and transformation of raw materials in products of industrial value represent a challenge. This justifies the growing interest of scientific research toward the identification of suitable media and methodologies able to pursue above goals, paying attention to matter of sustainability. On this subject, we studied sulfonic-acid functionalized diimidazolium salts as catalysts for the conversion of fructose and sucrose to 5-hydroxymethylfurfural (5-HMF) in an ionic liquid mixture. In general, using these salts allowed us to obtain 5-HMF in good yields from both substrates in mild conditions. Indeed, at 60°C and in the presence of 20 mol% of catalyst, 5-HMF yields of 60 and 30% were obtained from fructose and sucrose, respectively. The catalytic system was recycled and used up to six times observing no appreciable loss in yield for the first four cycles. Moreover, we gathered mechanistic information by in situ 1H NMR monitoring the dehydration of fructose. To dissect the role of acidity on the reaction, we determined the Hammett acidity function of each salt. Comparison of these results with yields and reactivity observed in the presence of related monocationic salts and with a dicationic salt bearing only one sulfonic acid group, allowed stating that the reactivity observed is the result of the combined action of acidity and structural features of the catalysts. Overall, the approach proposed here could contribute to pave the way to increase sustainability in the raw material valorization processes.

Ionic Liquid Binary Mixtures, Zeolites, and Ultrasound Irradiation: A Combination to Promote Carbohydrate Conversion into 5-Hydroxymethylfurfural

The efficient conversion of biomass into value-added compounds under mild and safer conditions is a cornerstone of present research efforts to meet the needs of the chemical industry with sustainable development. In this work, we studied the dehydration of fructose, glucose, and sucrose into 5-hydroxymethylfurfural (5-HMF), catalyzed by HY zeolite, in three ionic liquid mixtures differing for the cation, aromatic, or aliphatic. We investigated the effect of several operational parameters such as temperature, catalyst loading, zeolite counterion, solvent mixture, and added chloride. In the optimal experimental conditions, we obtained good conversions to 5-HMF especially for fructose and sucrose, 73% and 62%, using the relatively low temperatures of 80 and 120 °C, respectively. Interestingly, in the used experimental conditions, the solvent–catalyst systems can be reused for at least 6 cycles without loss in performance. We also investigated the dehydration of fructose under sonochemical activation, obtaini...

Green biocatalytic synthesis of biodiesel from microalgae in one-pot systems based on sponge-like ionic liquids

Abstract Binary mixtures of ionic liquids (ILs) have been used for developing one-pot systems suitable for the direct extraction and biocatalytic transformation of algal oil to biodiesel without prior isolation. These mixtures were based on the combination of sponge-like ionic liquids (e.g. 1-hexadecyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [C16mim][NTf2]) with the IL 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]), taking into account the excellent suitability to carry out the biocatalytic synthesis of biodiesel of the first one, and the ability for dissolving cellulosic biomass of the second. The extraction of oils was carried out by incubating the dry microalgae (Chlorella vulgaris or Chlorella protothecoides) in the appropriated IL binary mixture at 110 °C, which after being cooled at 60 °C allowed to be transformed to biodiesel by an immobilized lipase. This resulted in a fast and efficient biodiesel synthesis, e.g. up to 100% yield in 2 h at 60 °C. The subsequent cooling until room temperature and the iterative centrifugation of the resulting semi-solid systems at 20 and 18 °C led to the separation of the liquid algae biodiesel from the solid IL mixture, which was recovered and reused for further operation cycles.