Analysis of solvation in ionic liquids using a new linear solvation energy relationship

A new linear solvation energy relationship (LSER) equation, where the solute internal energy term has been incorporated into the traditional LSER equation, is used for the analysis of solvation in ionic liquids. Modeling results obtained using the new LSER equation indicate that all solute parameters (dispersion, polarity, hydrogen bonding, cavity formation, and solute internal energy) have approximately equal importance in the solvation of organic solutes in ionic liquids. The magnitude of dispersion interaction is stronger in ionic liquids than in aqueous solution, whereas hydrogen‐bonding interactions are stronger in water than in ionic liquids. This indicates that the solubility of polar compounds that contain bulky and aromatic groups can be enhanced in ionic liquids due to higher dispersion interactions in ionic liquids than in aqueous solution. On the other hand, the LSER equation without the solute internal energy term does not yield the meaningful solute–solvent interaction terms, indicating that the inclusion of a solute internal energy term is necessary to properly describe the solvation of organic solutes in liquid solvents. Copyright © 2004 Society of Chemical Industry     

The Correlation and Prediction of Butane/Water and Gas/Butane Partition Coefficients

It has been pointed out previously that the butane/water partition coefficient is a key parameter in the determination of extraction affinity. We have taken 43 such partition coefficients and have obtained a very satisfactory correlation with Abraham solvation parameters. Similarly, we have obtained a good correlation of 43 gas/butane partition coefficients. These correlations are general, and can be used to predict further values of the butane/water and gas/butane partition coefficient.     

Intermolecular dynamics, interactions, and solvation in ionic liquids

Ionic liquids can simultaneously assume multiple solvent roles, because they are strongly polar and polarizable solvents and binary solutions and frequently contain very hydrophobic components. When the cation and anion functional groups are tuned appropriately, ionic liquids can be used as designer solvents for a broad range of applications. In this Account, we discuss our spectroscopic studies on the intermolecular interactions, dynamics, solvation, transport, and friction in ionic liquids, as compared with information obtained from macroscopic experiments including viscometry and calorimetry.     

基于COSMO-SAC模型的离子液体萃取剂的选择

COSMO-SAC模型是计算无限稀释活度因子的一种有效方法,只需知道分子结构,即可进行有机物或离子液体的无限稀释活度因子计算。COSMO-SAC模型中最耗时的计算步骤是产生σ-图谱(σ-profile)的量子化学计算。利用Materials Studio软件中的DMol3模块,建立了包含32种离子液体阴离子和191种离子液体阳离子的σ-图谱数据库。利用σ-图谱数据库和COSMO-SAC模型,针对离子液体液液萃取过程,提出了离子液体萃取剂的计算机辅助分子设计方法。以乙醇-乙酸乙酯体系为研究对象,选择了适宜的离子液体萃取剂,采用乙醇-乙酸乙酯-离子液体三元体系的液液平衡文献数据进行了验证。     

Explaining Ionic Liquid Water Solubility in Terms of Cation and Anion Hydrophobicity

The water solubility of salts is ordinarily dictated by lattice energy and ion solvation. However, in the case of low melting salts also known as ionic liquids, lattice energy is immaterial and differences in hydrophobicity largely account for differences in their water solubility. In this contribution, the activity coefficients of ionic liquids in water are split into cation and anion contributions by regression against cation hydrophobicity parameters that are experimentally determined by reversed phase liquid chromatography. In this way, anion hydrophobicity parameters are derived, as well as an equation to estimate water solubilities for cation-anion combinations for which the water solubility has not been measured. Thus, a new pathway to the quantification of aqueous ion solvation is shown, making use of the relative weakness of interactions between ionic liquid ions as compared to their hydrophobicities.     

Photofading Kinetics and Thermodynamics of Some Azo Disperse Dyes in Amide Solvents under the Influence of Far Ultra–violet Radiation

The paper reports some kinetic measurements of photofading of some 4′-substituted 4–diethylaminoazobenzenes in formamide, N–methy/formamide, N, N–dimethy/formamide, N–methylacetamide and N, N–dimethyiacetamide. The observed Hammett p–values suggest a reductive pathway, as confirmed by the presence of anilines among the fading products. The free energies of solvation of the dyes in the various solvents have also been calculated by measuring the distribution coefficients of the dye between the amide solvent and n–hexane, as immiscible standard solvent. A fair linear correlation exists between the observed rate constants and the free energies of transfer, suggesting the possibility that photofading rate increases with increasing solvation of dye.     

电化学双电层电容器动态模拟：离子尺寸及扩散系数的优化

电化学双电层电容器的低能量密度限制了其在储能动力等领域的应用,而有机电解液作为提升器件能量密度的关键因素,研究其导电电解质的特性具有重要的意义。通过构建电化学双电层电容器的动态模型,模拟了电化学双电层电容器的循环伏安曲线,并定量探究和解析了离子溶剂化尺寸和扩散系数对电容性能的影响。模拟结果表明：在低扫描速率情况下,电容性能主要受控于双电层结构特性,比电容随着离子溶剂化尺寸的减小而增大,而离子扩散系数对其电容性能没有影响;在高扫描速率情况下,电容性能会受控于离子传质过程,比电容随着离子溶剂化尺寸和离子扩散系数的增大而增大。并基于模拟计算和分析结果提出了理性设计和优化电化学双电层电容器的策略。     

A theoretical model for the exchange of sodium ions between propylene carbonate and β-Al2O3

The passage of sodium ions from propylene carbonate into β-alumina and vise versa involves the crossing of a potential barrier which is due to the change of the solvation structure of the ions. This change occurs at the interface. In the present approach to calculation of the transfer coefficients both solvents are treated with the dielectric continuum model. The empirical parameters for the inner solvation shell of Wu and Friedmann[19] are used for propylene carbonate. In β-alumina the van der Waals diameter of sodium is used. This corresponds to the Stokes'[18] model of solvated ion structure in liquids and crystals. The two results for the work function calculation are then superimposed and the transfer coefficient is obtained in the usual way from the change of activation energy caused by an applied difference of electrochemical potential. The asymmetry of the dieletric constants and of the solvation shell structures leads to asymmetric transfer coefficients.     

用微扰理论状态方程计算电解质水溶液的活度系数

近年来,电解质溶液理论的研究日益活跃^[1]。因为理论模型能反映微观粒子参数与溶液结构和性质间的关系,参数物理意义明确,预测功能强。电解质溶液的原始模型中,忽略了离子－溶剂和溶剂－溶剂相互作用,而只考虑在溶剂平均场中离子之间的相互作用。这类模型不能反映溶液的本质和溶质－溶剂间的真实相互作用,因此很难推广到混合溶剂电解质溶液。用微扰理论研究电解质溶液的状态方程已经取得很大进展^[2]。硬球离子流体^[3]和离子－偶极^[4]模型流体的微扰理论处理结果已经成功地用于构筑实际电解质溶液的状态方程^[5]。作者采用微扰理论研究了电解质溶液的密度性质^[6],本文将进一步研究活度系数的计算问题。     

S-噻吗洛尔-D-酒石酸非对映体盐在有机溶剂中的溶解度测定和预测

实验测定了S-噻吗洛尔-D-酒石酸非对映体盐(S-TTS)在乙醇、正丙醇、丙酮、1,2-二氯乙烷和乙酸乙酯中的溶解度。在相同温度下,S-TTS在这些溶剂中的溶解度(s)顺序是:s(乙醇)>s(正丙醇)>s(丙酮)>s(1,2-二氯乙烷)>s(乙酸乙酯)。用四参数多项式、Apelblat方程、改进的Apelblat方程和λH方程关联了溶解度实验数据,以四参数多项式关联实验数据的结果最好,其相关系数(R2)>0.99,平均绝对相对偏差(AARD)(%)<4。提出了1,2,5-硫氮二茂基团、含手性碳次甲基基团(*CH)等新的基团相互作用参数,并用UNIFAC法预测了S-TTS在这5种溶剂中的溶解度,所得结果的平均绝对相对偏差(%)<53,并与用.H方程等的结果作了比较。     

Measurement and correlation of supercritical CO2 and ionic liquid systems for design of advanced unit operations

Ionic liquids combined with supercritical fluid technology hold great promise as working solvents for developing compact processes. Ionic liquids, which are organic molten salts, typically have extremely low volatility and high functionality, but possess high viscosities, surface tensions and low diffusion coefficients, which can limit their applicability. CO₂, on the other hand, especially in its supercritical state, is a green solvent that can be used advantageously when combined with the ionic liquid to provide viscosity and surface tension reduction and to promote mass transfer. The solubility of CO₂ in the ionic liquid is key to estimating the important physical properties that include partition coefficients, viscosities, densities, interfacial tensions, thermal conductivities and heat capacities needed in contactor design. In this work, we examine a subset of available high pressure pure component ionic liquid PVT data and high pressure CO₂-ionic liquid solubility data and report new correlations for CO₂-ionic liquid systems with equations of state that have some industrial applications including: (1) general, (2) fuel desulfurization, (3) CO₂ capture, and (4) chiral separation. New measurements of solubility data for the CO₂ and 1-butyl-3-methylimidazolium octyl sulfate, [bmim][OcSO₄] system are reported and correlated. In the correlation of the CO₂ ionic liquid phase behavior, the Peng-Robinson and the Sanchez-Lacombe equations of state were considered and are compared. It is shown that excellent correlation of CO₂ solubility can be obtained with either equation and they share some common characteristics regarding interaction parameters. In the Sanchez-Lacombe equation, parameters that are derived from the supercritical region were found to be important for obtaining good correlation of the CO₂-ionic liquid solubility data.     

Measurement and correlation of supercritical CO2 and ionic liquid systems for design of advanced unit operations

Ionicliquids combined with supercritical fluid technology hold great promise as working solvents for developing compact processes. Ionic liquids, which are organic molten salts, typically have extremely low volatility and high functionality, but possess high viscosities, surface tensions and low diffusion coefficients, which can limit their applicability. CO₂, on the other hand, especially in its supercritical state, is a green solvent that can be used advantageously when combined with the ionic liquid to provide viscosity and surface tension reduction and to promote mass transfer. The solubility of CO₂ in the ionic liquid is key to estimating the important physical properties that include partition coefficients, viscosities, densities, interfacial tensions, thermal conductivities and heat capacities needed in contactor design. In this work, we examine a subset of available high pressure pure component ionic liquid PVT data and high pressure CO₂ - ionic liquid solubility data and report new correlations for CO₂-ionic liquid systems with equations of state that have some industrial applications including: (1) general, (2) fuel desulfurization, (3) CO₂ capture, and (4) chiral separation. New measurements of solubility data for the CO₂ and 1-butyl-3-methylimidazolium octyl sulfate, [bmim][OcSO₄] system are reported and correlated. In the correlation of the CO₂ ionic liquid phase behavior, the Peng-Robinson and the Sanchez-Lacombe equations of state were considered and are compared. It is shown that excellent correlation of CO₂ solubility can be obtained with either equation and they share some common characteristics regarding interaction parameters. In the Sanchez-Lacombe equation, parameters that are derived from the supercritical region were found to be important for obtaining good correlation of the CO₂-ionic liquid solubility data.     

Study of dissolution of cellulose in ionic liquids by computer modeling

Computer modeling of the geometry and electronic structure of the solvent and its complexes with water and cellobiose allowed: explaining the decrease in the dissolving power of an ionic liquid in the presence of water using data on the electronic structure of the molecules; determining the overall mechanism of solvation of cellulose by ionic liquids and other organic solvents; calculating the change in the energy information of a solvate complex of the elementary cellulose unit with 1-butyl-3-methylimidazolium chloride, which was-20.64 kcal/mole. __________ Translated from Khimicheskie Volokna, No. 2, pp. 51–54, March–April, 2007.     

Solution studies of metal sulfonate ionomers IV: Effects of cosolvents

Previous studies have shown that metal sulfonated ionomers display unusual solution behavior. Typically, inomers, such as metal sulfonated EPDM or sulfonated polystyrene, are readily dissolved in mixed solvents, such as hydrocarbons plus alcohols. Such mixed solvents can provide unusual viscosity-temperature behavior due to the strong inter-or intramolecular interactions of the ionic groups. This paper is concerned with studies directed at a variety of polar cosolvents, including amines, alcohols, acids, amides, and esters, in interactions with zinc sulfonated ethylene propylene diene monomer (sulfo-EPDM). Within various classes of compounds the structural effects of such cosolvents on the solution viscosities of sulfonate ionomers have been elucidated. Generally, amines and alcohols have been found to be the most effective cosolvents. Amines appear to form a specific complex with zinc and can virtually eliminate ion pair association at extremely low levels. Within a homologous series, those compounds of shortest hydrocarbon chain length provide the most effective solvation of the ionic groups of sulfonated EPDM. The effect of structure of the amines or alcohols on solution viscosity has shown the efficiency of cosolvent interaction proceeding as normal > iso > secondary > tertiary in the alcohol series. These results are interpreted as a consequence of the cosolvent solvating the ionic groups wherein the more bulky cosolvents are least effective in solvating the metal cations.     

Measurement of activity coefficients at infinite dilution for hydrocarbons in imidazolium-based ionic liquids and QSPR model

The separations of olefin/paraffin, aromatic/aliphatic hydrocarbons or olefin isomers using ionic liquids instead of volatile solvents have interested many researchers. Activity coefficients γ ^∞ at infinite dilution of a solute in ionic liquid are generally used in the selection of solvents for extraction or extractive distillation. In fact, the measurement of γ ⁻⁸ by gas-liquid chromatography is a speedy and cost-saving method. Activity coefficients at infinite dilution of hydrocarbon solutes, such as alkanes, hexenes, alkylbenzenes, styrene, in 1-allyl-3-methylimidazolium tetrafluoroborate ([AMIM][BF₄]) and 1-butyl-3-methyl imidazolium hexafluorophosphate ([BMIM][PF₆]), 1-isobutenyl-3-methylimidazolium tetrafluoroborate ([MPMIM][BF₄]) and [MPMIM][BF₄]-AgBF₄ have been determined by gas-liquid chromatography using ionic liquids as stationary phase. The measurements were carried out at different temperatures from 298 to 318 K. The separating effects of these ionic liquids for alkanes/hexane, aliphatic hydrocarbons/benzene and hexene isomers have been discussed. The hydrophobic parameter, dipole element, frontier molecular orbital energy gap and hydration energy of these hydrocarbons were calculated with the PM3 semi-empirical quantum chemistry method. The quantitative relations among the computed structure parameters and activity coefficients at infinite dilution were also developed. The experimental activity coefficient data are consistent with the correlated and predicted results using QSPR models.     

Study of the influence of the soluble organic fraction of an exhaust diesel soot by a linear solvation energy relationship approach

Two samples of soot are studied in the present work. The results obtained on a virgin diesel soot (VDS) are compared to those obtained on the corresponding material after removal of its soluble organic fraction (SOF). The adsorption properties of both materials towards organic compounds are investigated by gas chromatography (GC) using the linear solvation energy relationship (LSER) equation of Abraham [Chem Soc Rev 1993;22:73-83]. This approach allows each material to be characterized in terms of five quantitative molecular interaction parameters. The results show the large influence of the SOF in the adsorption process of gaseous organic compounds. This study reveals that the extracted diesel soot (EDS) can interact through molecular interactions similar to those obtained on fullerenes or graphite.     

Solvation and phase separation in ABA block copolymers

A conceptual scheme is presented for classifying the phase behavior of ABA block copolymers and solvents. The effect of solvent fraction ?_S on microphase separation is described for macroscopically homogeneous systems, but more attention is focused on the limits of solubility. A “miscibility map” is developed in terms of solubility parameters δ_A, δ_B, and δ_S and used to define regions of macrophase separation, complete miscibility, and partial miscibility. Combined with known triblock molecular structure, the miscibility map can be used to predict the character of solvated systems and guide the selection of solvents for special purposes. A survey of reports in the literature shows qualitative consistency with this treatment. New observations are reported on solvation of a polystyrene–polybutadiene–polystyrene polymer in numerous solvents; these are used to infer microstructural information and define the miscibility map more realistically.     

Thermodynamic modeling of CO2 solubility in ionic liquid ([C n -mim] [Tf2N]; n=2, 4, 6, 8) with using Wong-Sandler mixing rule, Peng-Rabinson equation of state (EOS) and differential evolution (DE) method

Environmental and safety regulations are creating increasing interest in ionic liquids which have been used as alternative solvents for a wide range of industrial applications. Knowing the phase equilibrium of these materials is very important. In this study, the solubility of CO₂ in ionic liquid 1-alkyl-3 methylimidazolium bis (trifluoromethylsulfonyl) imide ([C _n -mim][Tf₂N]; n=2, 4, 6, 8) was probed with the Peng-Robinson (PR) equation of state (EOS) and Wong-Sandler mixing rule and van Laar model for excess Gibbs free energy. The differential evolution (DE) optimization method was applied to optimize the binary interaction parameter and activity coefficients. Moreover, binary interaction parameters and activity coefficients were presented as mathematical correlations that for various materials have depended on temperature. Our results showed that average absolute derivations of our proposed model were less than other existing models, and by using the aforesaid method better prediction could be achieved.