Infinite Dilution In Ionic Liquids Research Articles

Amino Acid Ester based Phenolic Ionic Liquids as a Potential Solvent for the Bioactive Compound Luteolin: Synthesis, Characterization, and Food Preservation Activity

Ionic liquids (ILs) have gained great attention as potent solubilizing agents of poorly soluble bioactive compounds. The use of Luteolin (LUT) – a natural bioactive compound – is limited because of its poor aqueous solubility. To address this issue, this study reports potential ILs for effectively solubilizing LUT at ambient temperature. First, promising ILs were screened from a potential 180 ILs that were proposed by the combination of 20 standard amino acid ethyl esters cations and nine phenolic acids anions using the conductor-like screening model for real solvents (COSMO-RS); the activity coefficients of LUT at infinite dilution in ILs were used as the screening criteria. Four proline ethyl ester phenolate ILs (PEEP-ILs) composed of a biocompatible proline ethyl ester and bioactive phenolic acids (trans-ferulic, vanillic, p-coumaric, and 4-hydroxybenzoic acid) were selected and synthesized. The synthesized PEEP-ILs were characterized through 1H NMR, FT-IR, elemental analysis, TGA, and DSC. The experimental solubility of LUT in PEEP-ILs (60% IL in water) showed excellent solubility. Among the PEEP-ILs, proline ethyl ester ferulate (IL[ProEt][Fer]) exhibited the best LUT solubility, followed by ILs with p-coumarate (IL[ProEt][Cou]), vanillate (IL[ProEt][Van]), and 4-hydroxybenzoate (IL[ProEt][Ben]). 1H NMR assessment and COSMO-RS prediction confirmed that the ILs facilitated the solubilization of LUT through multiple hydrogen bonding, π − π, and cation − π interactions between the LUT and the ILs. The biocompatibility study revealed that PEEP-ILs were relatively harmless and low toxicity compared with conventional imidazolium, pyridinium, pyrrolidinium, piperidinium, and morpholinium-based ILs. The LUT dissolved in the newly-synthesized PEEP-ILs and demonstrated better organoleptic properties on red apple slices. These results indicate that PEEP-ILs can be potential green alternatives to conventional toxic solvents for dissolving poorly water-soluble bioactive natural preservatives.

Developing a new correlation for the aliphatic and aromatic hydrocarbon diffusion coefficients at infinite dilution in ionic liquids

In this work the Taylor dispersion technique has been used to measure the diffusion coefficients of n-heptane and toluene at infinite dilution in four ionic liquids, namely 1-ethyl-3-methylimidazolium thiocyanate ([emim][SCN]), 1-ethyl-3-methylimidazolium tricyanomethanide ([emim][TCM]), 1-butyl-3-methylimidazolium tricyanomethanide ([bmim][TCM]), and 1-butyl-4-methylpyridinium tricyanomethanide ([4bmpy][TCM]), at the range temperatures from (298.2–333.2) K. The hydrocarbon diffusion is faster at higher temperatures because of the lower ionic liquid viscosity, and toluene diffuses faster than n-heptane due to its smaller molecular volume. In addition, it is seen that the values of the n-heptane diffusion coefficients decrease with an increase in the molecular weight and molar volume of the ionic liquid. The same is observed for the diffusion coefficients of toluene in the most viscous ionic liquids ([bmim][TCM], [4bmpy][TCM] and [4empy][Tf2N]), but, conversely, they increase for the least viscous ionic liquids ([emim][SCN], [emim][DCA], and [emim][TCM]). This behavior suggests that the strength of the toluene-ionic liquid chemical interactions have a significant effect on diffusion. A new empirical correlation has been proposed as a variation of the Wilke-Chang equation. Two additional variables have been introduced in this correlation; the molar fraction of the maximum hydrocarbon solubility, to take into account the toluene-ionic liquid interactions, as well as the molar volume of the ionic liquid, because of the huge difference between them and the solute. This new correlation satisfactorily fits the experimental data with an average deviation of 9.6%.

Overview of Activity Coefficient of Methanol at Infinite Dilution in Ionic Liquids and their Modeling using Group Contribution Model

A predictive model is developed by using a group contribution method for the estimation of the infinite dilution activity coefficient (IDAC) of methanol in ionic liquids (ILs). A simple van’t Hoff ...

Quantitative structure–activity relationships (QSARs) for estimation of activity coefficient at infinite dilution of water in ionic liquids for natural gas dehydration

Recently, ionic liquids (ILs) have been considered as alternative solvents to glycol in dehydration of natural gas. However, due to the unlimited structural variations and possible combinations of cations and anions of the ILs, selection of potential ILs for this separation process has been a difficult task. Activity coefficient at infinite dilution is one of the most important thermodynamic properties for preliminary selection of suitable liquid desiccants for water absorption and designing of the natural gas dehydration process. In this paper, COSMO-RS based quantitative structure–property/activity relationship (QSPR/QSAR) models were developed for prediction of activity coefficient of water at infinite dilution in ILs over various temperatures. COSMO-RS based descriptors were generated for 53 ILs (318 data points) at various temperatures. Multiple linear regressions were applied to develop the models. The accuracies of the models were verified by different statistical tests. The model provides a better understanding of the effect of the structural variations of ILs on their affinity for water.

Overview of Activity Coefficient of Thiophene at Infinite Dilution in Ionic Liquids and their Modeling Using COSMO-RS

Ionic liquids (ILs) gained a lot of attention, from both academe and industry, as alternative liquids for different types of applications. Chemical and physical characteristics can be designed with the large availability of cation and anions. Experimental measurement of all these systems is not practically feasible, hence requiring the use of a computational predictive model study. This work evaluates the prediction of the activity coefficient (γs∞) at infinite dilution in several classes of ILs using the conductor-like screening model for real solvents (COSMO-RS), a model based on unimolecular quantum chemistry calculations. Comparison of the experimental γs∞ value with COSMO-RS predicted data is carried out, and absolute average relative deviation was determined to be 24.1%, indicating that the COSMO-RS model presents a reliable prediction to determine γs∞ in a wide range of ILs. The observation also confirms that polarizability of ILs plays a crucial role in their interaction with thiophene. With respe...

Evaluation of the Conductor-like Screening Model for Real Solvents for the Prediction of the Water Activity Coefficient at Infinite Dilution in Ionic Liquids

Ionic liquids (ILs) have attracted great attention, from both industry and academia, as alternative fluids for very different types of applications. The large number of cations and anions allow a wide range of physical and chemical characteristics to be designed. However, the exhaustive measurement of all these systems is impractical, thus requiring the use of a predictive model for their study. In this work, the predictive capability of the conductor-like screening model for real solvents (COSMO-RS), a model based on unimolecular quantum chemistry calculations, was evaluated for the prediction water activity coefficient at infinite dilution, γw∞, in several classes of ILs. A critical evaluation of the experimental and predicted data using COSMO-RS was carried out. The global average relative deviation was found to be 27.2%, indicating that the model presents a satisfactory prediction ability to estimate γw∞ in a broad range of ILs. The results also showed that the basicity of the ILs anions plays an impo...

Vapor–Liquid Equilibria of Water + Alkylimidazolium-Based Ionic Liquids: Measurements and Perturbed-Chain Statistical Associating Fluid Theory Modeling

The industrial application of ionic liquids (ILs) requires the knowledge of their physical properties and phase behavior. This work addresses the experimental determination of the vapor–liquid equilibria (VLE) of binary systems composed of water + imidazolium-based ILs. The ILs under consideration are 1-butyl-3-methylimidazolium trifluoromethanesulfonate, 1-butyl-3-methylimidazolium thiocyanate, 1-butyl-3-methylimidazolium tosylate, 1-butyl-3-methylimidazolium trifluoroacetate, 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium methanesulfonate, and 1-butyl-3-methylimidazolium acetate, which allows the evaluation of the influence of the IL anion through the phase behavior. Isobaric VLE data were measured at 0.05, 0.07, and 0.1 MPa for IL mole fractions ranging between 0 and 0.7. The observed increase in the boiling temperatures of the mixtures is related with the strength of the interaction between the IL anion and water. The Perturbed-Chain Statistical Associating Fluid Theory (PC-SAFT) was further used to describe the obtained experimental data. The ILs were treated as molecular associating species with two association sites per IL. The model parameters for the pure fluids and the binary interaction parameter kij between water and ILs were determined by a simultaneous fitting to pure-IL densities, water activity coefficients at 298.15 K and VLE data at 0.1 MPa. Pure-IL densities, water activity coefficients, and VLE data were well described by PC-SAFT in broad temperature, pressure, and composition ranges. The PC-SAFT parameters were applied to predict the water activity coefficients at infinite dilution in ILs, and a satisfactory prediction of experimental data was observed.

Solubility of Sugars and Sugar Alcohols in Ionic Liquids: Measurement and PC-SAFT Modeling

Biorefining processes using ionic liquids (ILs) require proper solubility data of biomass-based compounds in ILs, as well as an appropriate thermodynamic approach for the modeling of such data. Carbohydrates and their derivatives such as sugar alcohols represent a class of compounds that could play an important role in biorefining. Thus, in this work, the pure IL density and solubility of xylitol and sorbitol in five different ILs were measured between 288 and 339 K. The ILs under consideration were 1-ethyl-3-methylimidazolium dicyanamide, 1-butyl-3-methylimidazolium dicyanamide ([bmim][DCA]), Aliquat dicyanamide, trihexyltetradecylphosphonium dicyanamide, and 1-ethyl-3-methylimidazolium trifluoroacetate. Comparison with the literature data was performed, showing good agreement. With the exception of [bmim][DCA], the solubility of these sugar alcohols in the other ILs is presented for the first time. The measured data as well as previously published solubility data of glucose and fructose in these ILs were modeled by means of PC-SAFT using a molecular-based associative approach for ILs. PC-SAFT was used in this work as it has shown to be applicable to model the solubility of xylitol and sorbitol in ILs (Paduszyński; et al. J. Phys. Chem. B 2013, 117, 7034-7046). For this purpose, three pure IL parameters were fitted to pure IL densities, activity coefficients of 1-propanol at infinite dilution in ILs, and/or xylitol solubility in ILs. This approach allows accurate modeling of the pure IL data and the mixture data with only one binary interaction parameter k(ij) between sugar and the IL or sugar alcohol and the IL. In cases where only the pure IL density and activity coefficients of 1-propanol at infinite dilution in ILs were used for the IL parameter estimation, the solubility of the sugars and sugar alcohols in the ILs could be predicted (k(ij) = 0 between sugar and the IL or sugar alcohol and the IL) with reasonable accuracy.

Ionic liquids: Solubility parameters and selectivities for organic solutes

Ionic liquids (ILs) are innovative solvents for chemical processing. In this work, a database on activity coefficients of organic solutes at infinite dilution in ILs was collected from literature sources. The activity coefficients have been correlated by activity coefficient model for the regular solution and have been used to estimate the solubility parameter of ILs. The solubility parameters of ILs have been further correlated based on a concept of the group contribution method. Through the analysis of the database and the prediction results of selectivities, it was shown here that as compared with conventional organic solvents, higher selectivity can be achieved by using ILs as working solvents for separation of alkane/aromatic, aromatic/aromatic hydrocarbon mixtures via extraction or supported liquid membrane. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3034–3041, 2013

Extension of the UNIFAC Model for Ionic Liquids

The UNIFAC model has recently become very popular for ionic liquids (ILs) because of its applicability for prediction of thermodynamic properties. This work is a continuation of our studies on the extension of group parameters of the UNIFAC model to systems with ILs. The new IL groups for 33 main groups and 53 subgroups were added into the current UNIFAC parameter matrix. The parameters of group surface area and volume for ILs were obtained by the COSMO calculation, while the group binary interaction parameters, anm and amn, were obtained by means of correlating the activity coefficients of solutes at infinite dilution in ILs at different temperatures exhaustively collected from literature by the end of 2011. The predicted results of UNIFAC model are more accurate than those of the COSMO-RS model so that it can be used for identifying the general relationship between molecular structure of ILs and separation performance for the separation of liquid mixtures with ILs.

Group contribution lattice fluid equation of state (GCLF EOS) for ionic liquids

This work focuses on the extension of group parameters and application of the group-contribution lattice-fluid equation of state (GCLF EOS) for the systems with ionic liquids (ILs). The new group parameters ekk and Rkk for ILs in GCLF EOS were obtained by means of correlating the liquid density of pure ILs at different temperatures, while the group binary interaction parameters αmn were obtained by means of correlating the activity coefficients of solutes at infinite dilution in ILs at different temperatures, which were exhaustively collected from references. New IL groups were added into the current parameter matrix. It was verified that GCLF EOS for ILs can be used for predicting liquid densities of pure ILs or the mixture of IL and solute, vapor–liquid equilibria (VLE) and liquid–liquid equilibria (LLE) at finite concentration, as well as identifying the structure–property relation in separation science. This is the first work for us to extend the predictive GCLF EOS to the systems with ILs.

Activity Coefficients of Organic Solutes at Infinite Dilution in Ionic Liquids. 1. 1-Hexyl-3-Methylimidazolium Hexafluorophosphate and 1-Octyl-3-Methylimidazolium Hexafluorophosphate and Their Application to Alkane/Aromatic and Aromatic/Aromatic Hydrocarbon Separation

Activity coefficients at infinite dilution, γi,3∞, for organic solutes (alkanes, alkenes, alkyl benzenes, alcohols, chloromethanes, acetonitrile, ethyl acetate, dioxane, tetrahydrofuran, and acetone) in 1-hexyl-3-methylimidazolium hexafluorophosphate [HMIM][PF6] and 1-octyl-3-methylimidazolium hexafluorophosphate [OMIM][PF6] have been determined using gas–liquid chromatography at temperatures from 303.15 to 363.15 K with the ionic liquids as the stationary phase. The partial molar excess enthalpies at infinite dilution of the ionic liquids were calculated for the solutes from the temperature dependence of the experimental activity coefficients at infinite dilution. The solubility parameters of ionic liquids were also determined by the regular solution theory. The selectivities of various ionic liquids for the alkane/aromatic hydrocarbon and aromatic/aromatic were summarized from literature and calculated from γi,3∞.

UNIFAC Model for Ionic Liquids

This work focuses on the extension of group parameters of the UNIFAC model to systems with ionic liquids. The new group parameters for ionic liquids were obtained by means of correlating the activity coefficients of solutes at infinite dilution in ionic liquids at different temperatures. The group parameters for 12 main groups and 24 subgroups were added into the current UNIFAC parameter matrix. It was verified that the new group parameters can be used not only for predicting the vapor−liquid equilibria of the systems with ionic liquids at finite concentration, but also for screening the suitable ionic liquids in separation processes. Since there have been only a limited number of functional groups for ionic liquids included in the UNIFAC model, the future development of this predictive model will still require much more accurate experimental data.

Measurement of Activity Coefficients at Infinite Dilution in Ionic Liquids Using the Dilutor Technique

Activity coefficients at infinite dilution have been measured with the dilutor technique for 20 solutes (alkanes, alkenes, cyclic hydrocarbons, aromatic hydrocarbons, ketones, alcohols, and water) in the ionic liquids 1-methyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and 1-ethyl-3-methylimidazolium ethylsulfate. The measurements were carried out in the temperature range between 293.15 K and 333.15 K. The selectivities at infinite dilution ( = / ) for the separation of aliphatics from aromatics and n-hexane from 1-hexene are presented and discussed. From the results it can be concluded that the ionic liquids investigated show different advantages compared to those of the entrainers actually used for the separation of aliphatic from aromatic hydrocarbons by extractive distillation or extraction.