Isobaric vapor–liquid equilibria for ethanol–water system containing different ionic liquids at atmospheric pressure

Isobaric vapor–liquid equilibrium (VLE) data for ethanol–water systems containing ionic liquids (ILs) 1-methyl-3-methylimidazolium dimethylphosphate ([MMIM][DMP]), 1-ethyl-3-methylimidazolium diethylphosphate ([EMIM][DEP]), 1-butyl-3-methylimidazolium bromide ([BMIM][Br]), 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]) and 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) at atmospheric pressure (101.32 kPa) were measured with a circulation still. The results showed that the VLE of ethanol–water systems in the presence of different ILs was obviously different from that of the IL-free system. All ILs studied showed a salting-out effect, which gave rise to a change of the relative volatility of ethanol, and even to an elimination of the azeotropic point. It was found that the salting-out effect followed the order of [BMIM][Cl] > [BMIM][Br] > [BMIM][PF₆] and [MMIM][DMP] > [EMIM][DEP], which was ascribed to the preferential solvation ability of the ions resulting from the dissociation of the IL.     

用[BMIM][Cu2Cl3]离子液体萃取脱除汽油中的硫化物

以不同的IL（ionic liquid）/油质量比,采用[BMIM][Cu2Cl3]（[BMIM]=1-butyl-3-methylimidazolium）对模型汽油和商品汽油进行单步和多步萃取脱硫实验;并合成几种具有不同阴离子和阳离子结构的离子液体,评价和比较了离子液体对商品汽油的萃取脱硫性能的影响。实验结果表明,具有较好的水稳定性和常温流动性的[BMIM] [Cu2Cl3]离子液体硫容较高,在IL/油质量比为1∶3时,经多步萃取后,油品中的硫质量分数降至20×10-6～30×10-6,累计脱硫率超过95%。汽油中其他组分对脱硫效果影响很小。[BMIM][Cu2Cl3]与汽油形成稳定的两相系统,分离方便。离子液体脱硫能力可以通过四氯化碳反萃取完全恢复。     

1-Butyl-3-methylimidazolium-based ionic liquids and an anionic surfactant: Excellent background electrolyte modifiers for the analysis of benzodiazepines through capillary electrophoresis

In this study, we found that adding 1-butyl-3-methylimidazolium-based ionic liquids (ILs) and sodium dodecyl sulfate (SDS) as modifiers in the background electrolyte (BGE) for capillary electrophoresis enhanced the separation of benzodiazepines. In particular, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([BMIM][NTf₂]) was the best IL additive for the separation system because its anionic moiety interacted favorably with the benzodiazepines. We added SDS because of its known effect on the separation of hydrophobic analytes. We optimized the separation conditions in terms of the concentrations of the IL, SDS, and organic solvent, the pH, and the BGE's ionic strength. The optimal BGE, containing 170 mM [BMIM][NTf₂] and 10 mM SDS, provided baseline separation, high efficiency, and satisfactory peak shapes for the benzodiazepines. The separation mechanism was based on heteroassociation between the anionic moiety of the IL and the benzodiazepines, with SDS improving the resolution of the separation. The limits of detection for the seven analytes ranged from 2.74 to 4.42 μg/mL. We subjected a urine sample to off-line solid phase extraction (SPE) prior to the analysis of its benzodiazepine content. Our experimental results reveal that the combination of [BMIM][NTf₂] and SDS provides adequate separation efficiency for its application to CE analyses of benzodiazepines after SPE concentration.     

Protein structure and dynamics in ionic liquids. Insights from molecular dynamics simulation studies

We present in this work the first molecular simulation study of an enzyme, the serine protease cutinase from Fusarium solani pisi, in two ionic liquids (ILs): 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]) and 1-butyl-3-methylimidazolium nitrate ([BMIM][NO(3)]). We tested different water contents in these ILs at room temperature (298 K) and high temperature (343 K), and we observe that the enzyme structure is highly dependent on the amount of water present in the IL media. We show that the enzyme is preferentially stabilized in [BMIM][PF6] at 5-10% (w/w) (weight of water over protein) water content at room temperature. [BMIM][PF6] renders a more nativelike enzyme structure at the same water content of 5-10% (w/w) as previously found for hexane, and the system displays a similar bell-shape-like dependence with the water content in the IL media. [BMIM][PF6] is shown to increase significantly the protein thermostability at high temperatures, especially at low hydration. Our analysis indicates that the enzyme is less stabilized in [BMIM][NO(3)] relative to [BMIM][PF6] at both temperatures, most likely due to the strong affinity of the [NO(3)]- anion toward the protein main chain. These findings are in accordance with the experimental knowledge for these two ionic liquids. We also show that these ILs "strip off" most of the water from the enzyme surface in a degree similar to that found for polar organic solvents such as acetonitrile, and that the remaining waters at the enzyme surface are organized in many small clusters.     

Volumetric and compressibility behaviour of ionic liquid, 1-n-butyl-3-methylimidazolium hexafluorophosphate and tetrabutylammonium hexafluorophosphate in organic solvents at T = 298.15 K

Density and speed of sound measurements have been made on the systems containing the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) and some organic solvents having a wide range of dielectric constants. Similar studies have been carried out for tetrabutylammonium hexafluorophosphate ([TBA][PF₆]), which has common anion ([PF₆]⁻) with the studied ionic liquid. For the systems investigated, the apparent molar volumes and apparent molar isentropic compressibilities were determined and fitted to the Redlich–Mayer and the Pitzer equations from which the corresponding limiting values were obtained. These limiting values were used to obtain some information about ion–solvent interactions. Furthermore, using the ionic limiting apparent volume values for [TBA]⁺ from the literature and limiting apparent molar volume for the ionic liquid and [TBA][PF₆] obtained in this work, the ionic limiting apparent molar volume values for the cation [BMIM]⁺ in different organic solvents were also estimated.     

Oleic acid as the capping agent in the synthesis of noble metal nanoparticles in imidazolium-based ionic liquids

This paper reports the synthesis and automatic separation of solvent dispersible silver and platinum nanoparticles in 1-butyl-3-methylimidazolium bis(triflylmethyl-sulfonyl) imide ([BMIM][Tf2N]) ionic liquid (IL) using oleic acid as the major capping agent.     

Liquid-liquid extraction of lysozyme using a dye-modified ionic liquid

An affinity-dye, Cibacron Blue 3GA (CB), derivatized organic salt [BMIM]3[CB] was synthesized for lysozyme extraction. This compound was formed by mixing an ionic liquid (IL) [BMIM][Cl] and the silver salt of CB. Liquid-liquid extractions of lysozyme from the aqueous and [BMIM]3[CB] in [BMIM][PF6] solutions were examined in this study. The transfer of lysozyme from the aqueous phase to the IL phase decreased while the pH of the aqueous phase increased. An extraction higher than 90% was observed at pH 4. Under a high ionic strength, the lysozyme would transform back from the IL phase into the aqueous phase. Lysozyme molecules were almost quantitatively recovered from the IL phase to the aqueous solutions of 1M KCl under pH 9-11. It appeared that the extraction was specific for lysozyme in contrast to cytochrome c, ovalbumin, and bovine serum albumin. The extraction efficiency of the IL phase remained essentially the same after eight cycles of extraction.     

Ionic liquid-induced changes in the properties of aqueous sodium dodecyl sulfate solution: effect of acidic/basic functional groups

The effects of ionic liquids 1-(2-aminoethyl)-3-methylimidazolium chloride ([MimAE]Cl), 1-carboxylmethyl-3-methylimidazolium chloride ([MimCM]Cl), 1-(2-hydroxylethyl)-3-methylimidazolium chloride ([MimHE]Cl), and 1-ethyl-3-methylimidazolium chloride ([Emim]Cl) on the physicochemical properties of aqueous sodium dodecyl sulfate (SDS) solutions were studied. Compared with [Emim]Cl, the presence of amino group can further facilitate the micellization of SDS, while the opposite result is observed as carboxyl group is imparted. No obvious changes in critical micelle concentration (CMC) and $ {\gamma_{\mathrm{CMC}}} $ values are induced by the neutral hydroxyl group. Only the addition of [MimAE]Cl drastically increases the micellar size. Significant decrease in CMC and increase in micellar size were observed with decreasing pH of [MimAE]Cl solution. The increase in pH of [MimCM]Cl solution results in a slight increase in CMC and decrease in micellar size. ¹H NMR spectra revealed the amino groups are adsorbed at the micellar surface, while the carboxyl groups/carboxylate ions and hydroxyl groups tend to point towards bulk water.     

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.     

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.     

Photophysics and dynamics of a β-carboline analogue in room temperature ionic liquids

Room temperature ionic liquids are rapidly emerging as a new class of media that are ideally suited for various applications including carrying out chemical reactions. In the present article, we report the photophysics of a β-carboline analogue, namely, 3-acetyl-4-oxo-6,7-dihydro-12H indolo-[2,3-a] quinolizine (AODIQ), in three room temperature ionic liquids (RTILs), 1-butyl-3-methylimidazolium methyl sulfate ([BMIM][MeSO(4)]), 1-butyl-3-methylimidazolium octyl sulfate ([BMIM][C(8)SO(4)]) and 1-ethyl-3-methylimidazolium methyl sulfate ([EMIM][MeSO(4)]). Out of these, [BMIM][C(8)SO(4)] is a typical RTIL that forms micellar aggregates above a critical micellar concentration (CMC). Steady state absorption, steady state and time resolved fluorescence techniques are used to probe the properties of these systems. The investigation reveals that the photophysics of AODIQ is modified significantly in the micelle-forming RTIL as compared to that in the other two. A comparative study with the fluorophore in [BMIM][C(8)SO(4)] and a conventional anionic surfactant of a similar hydrophobic chain length from the sodium-n-alkyl sulfate series, viz., sodium octyl sulfate (S(8)S), reveals that the fluorophore experiences a more constrained environment in the RTIL micelle as compared to the conventional anionic micelle.     

Revealing long-range density fluctuations in dialkylimidazolium chloride ionic liquids by dynamic light scattering

In this study, the structures and dynamics of ionic liquids of 1-allyl-3-methylimidazolium chloride ([AMIM][Cl]) and 1-n-butyl-3-methylimidazolium chloride ([BMIM][Cl]) were studied by dynamic light scattering with polarized and depolarized geometries in the temperature range from 300 to 400 K. The temperature range covered supercooled and liquid states for [BMIM][Cl] and covered the liquid state for [AMIM][Cl]. The results show that for these ionic liquids at all chosen temperatures only one ultraslow relaxation is observed in the polarized component of dynamic light scattering, however, the ultraslow relaxation is not observed in the depolarized component. The ultraslow relaxation exhibited several typical features of the "cluster" mode generally found in glass-forming liquids and polymer melts, such as diffusive, strongly scattering-vector-dependent, and nearly exponential characters, which thus corresponded to long-range density fluctuations. The physical origin for long-range density fluctuations was the existence of heterogeneities with large characteristic length scales in these ionic liquids. It was further considered that molecules of these ionic liquids not only tended to aggregate to form dynamic clusters but also possibly formed dynamic networks in the supercooled state and the heterogeneities could exist even at temperatures higher than the melting points.     

Concentration-dependent dual behavior of hydrophilic ionic liquid in changing properties of aqueous sodium dodecyl sulfate

Modifying physicochemical properties of aqueous surfactant solutions in favorable fashion by addition of environmentally benign room-temperature ionic liquids (ILs) has enormous future potential. Due to its unusual properties, an IL may demonstrate a unique role in altering the properties of aqueous surfactant solutions. Changes in the properties of aqueous sodium dodecyl sulfate (SDS), an anionic surfactant, upon addition of a common and popular "hydrophilic" ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate [bmim][BF4] are presented. Addition of low concentrations of [bmim][BF4] (i.e., 相似文献   

Ionic liquid-induced unprecedented size enhancement of aggregates within aqueous sodium dodecylbenzene sulfonate

Physicochemical properties of aqueous micellar solutions may change in the presence of ionic liquids (ILs). Micelles help to increase the aqueous solubility of ILs. The average size of the micellar aggregates within aqueous sodium dodecylbenzene sulfonate (SDBS) is observed by dynamic light scattering (DLS) and transmission electron microscopy (TEM) to increase in a sudden and drastic fashion as the IL 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]) is added. Similar addition of [bmim][PF(6)] to aqueous sodium dodecyl sulfate (SDS) results in only a slow gradual increase in average aggregate size. While addition of the IL [bmim][BF(4)] also gives rise to sudden aggregate size enhancement within aqueous SDBS, the IL 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF(4)]), and inorganic salts NaPF(6) and NaBF(4), only gradually increase the assembly size upon their addition. Bulk dynamic viscosity, microviscosity, dipolarity (indicated by the fluorescent reporter pyrene), zeta potential, and electrical conductance measurements were taken to gain insight into this unusual size enhancement. It is proposed that bmim(+) cations of the IL undergo Coulombic attractive interactions with anionic headgroups at the micellar surface at all [bmim][PF(6)] concentrations in aqueous SDS; in aqueous SDBS, beyond a critical IL concentration, bmim(+) becomes involved in cation-π interaction with the phenyl moiety of SDBS within micellar aggregates with the butyl group aligned along the alkyl chain of the surfactant. This relocation of bmim(+) results in an unprecedented size increase in micellar aggregates. Aromaticity of the IL cation alongside the presence of sufficiently aliphatic (butyl or longer) alkyl chains on the IL appear to be essential for this dramatic critical expansion in self-assembly dimensions within aqueous SDBS.     

离子液体[BMIM]Br与[BMIM][BF4]配比浓度对Br-离子电荷转移的调节

利用X射线吸收精细结构光谱(XAFS)及紫外吸收光谱两种方法, 分析了离子液体1-丁基-3-甲基咪唑溴盐([BMIM]Br)中逐渐掺入1-丁基-3-甲基咪唑四氟硼酸盐([BMIM][BF₄])时, Br^-阴离子与咪唑阳离子之间氢键作用及电荷偏移量的改变. 随着[BMIM][BF₄]加入量增多, Br 元素XAFS近边(XANES)显示吸收峰降低, 吸收边位置向低能端位移0.9 eV; 扩展边(EXAFS)算出径向结构显示Br 与近邻原子间平均配位数降低、平均键长增长; 紫外光谱也有明显蓝移减色效应. 这些结果都表明Br₄^-的掺入改变了Br^-与阳离子间的电荷偏移量, 负电荷更多地转移到Br^-上, 量化计算的数据同样支持该结论.     

离子液体预处理对羊毛蛋白酶水解性能的影响

利用一种新型绿色溶剂--离子液体1-丁基-3-甲基咪唑氯盐(1-butyl-3-methylimidazolium chloride,[BMIM]Cl)对羊毛进行预处理,从而提高蛋白酶对羊毛的水解效率.系统研究了[BMIM]Cl预处理对蛋白酶处理后羊毛减量率、碱溶解度、蛋白质释放速率、氨基酸组成的影响,并从表面形态、表面润湿性能和纤维晶体结构等方面探讨了[BMIM]Cl对蛋白酶水解的促进作用机理.结果表明:羊毛经过[BMIM]Cl处理后,纤维减量率从2.68%提高到4.47%,碱溶解度达到11.6%,水解液中蛋白质浓度的变化显示[BMIM]Cl预处理使得蛋白质释放速率快速增加;羊毛纤维中低硫和部分高硫氨基酸百分比的降低进一步证实[BMIM]Cl预处理对蛋白酶水解起到了全面促进作用.SEM、润湿接触角以及WAXD测试结果显示预处理破坏了纤维鳞片层,增加了表面润湿性能,并且使得纤维结晶度下降,从而提高了蛋白酶对纤维的可及度,有利于酶解速率的提高.     

Thermodynamic studies of ionic interactions in aqueous solutions of imidazolium-based ionic liquids [Emim][Br] and [Bmim][Cl

Experimental measurements of density at different temperatures ranging from 293.15 to 313.15 K, the speed of sound and osmotic coefficients at 298.15 K for aqueous solution of 1-ethyl-3-methylimidazolium bromide ([Emim][Br]), and osmotic coefficients at 298.15 K for aqueous solutions of 1-butyl-3-methylimidazolium chloride ([Bmim][Cl]) in the dilute concentration region are taken. The data are used to obtain compressibilities, expansivity, apparent and limiting molar properties, internal pressure, activity, and activity coefficients for [Emim][Br] in aqueous solutions. Experimental activity coefficient data are compared with that obtained from Debye-Hückel and Pitzer models. The activity data are further used to obtain the hydration number and the osmotic second virial coefficients of ionic liquids. Partial molar entropies of [Bmim][Cl] are also obtained using the free-energy and enthalpy data. The distance of the closest approach of ions is estimated using the activity data for ILs in aqueous solutions and is compared with that of X-ray data analysis in the solid phase. The measured data show that the concentration dependence for aqueous solutions of [Emim][Br] can be accounted for in terms of the hydrophobic hydration of ions and that this IL exhibits Coulombic interactions as well as hydrophobic hydration for both the cations and anions. The small hydration numbers for the studied ILs indicate that the low charge density of cations and their hydrophobic nature is responsible for the formation of the water-structure-enforced ion pairs.     

Vapor pressure measurement for water,methanol, ethanol,and their binary mixtures in the presence of an ionic liquid 1-ethyl-3-methylimidazolium dimethylphosphate

Vapor pressure data were measured for water, methanol and ethanol as well as their binary mixtures with an ionic liquid (IL) 1-ethyl-3-methylimidazolium dimethylphosphate ([EMIM][DMP]) at varying temperature and IL-content ranging from mass fraction of 0.10–0.70 by a quasi-static method. The vapor pressure data for the IL-containing binary systems were correlated using NRTL equation with average absolute relative deviation (ARD) within 0.0076, and the binary NRTL parameters was used for predicting the vapor pressure of the IL-containing ternary systems with reasonable accuracy. In addition, the infinite activity coefficients of solvents in [EMIM][DMP] and isobaric vapor–liquid equilibrium for IL-containing ternary systems at 101.325 kPa and mass fraction of IL being 0.5 were predicted with the regressed NRTL parameters. The results indicate that ionic liquid [EMIM][DMP] can depress the volatility of the solvents of water, methanol and ethanol but to a varying degree, leading to the variation of relative volatility of a solvent and even removal of azeotrope for water–ethanol mixture.     

A "counter-charge layer in generalized solvents" framework for electrical double layers in neat and hybrid ionic liquid electrolytes

Room-temperature ionic liquids (RTILs) have received significant attention as electrolytes due to a number of attractive properties such as their wide electrochemical windows. Since electrical double layers (EDLs) are the cornerstone for the applications of RTILs in electrochemical systems such as supercapacitors, it is important to develop an understanding of the structure-capacitance relationships for the EDLs of these systems. Here we present a theoretical framework termed "counter-charge layer in generalized solvents" (CGS) for describing the structure and capacitance of the EDLs in neat RTILs and in RTILs mixed with different mass fractions of organic solvents. Within this framework, an EDL is made up of a counter-charge layer exactly balancing the electrode charge, and of polarized generalized solvents (in the form of layers of ion pairs, each of which has a zero net charge but has a dipole moment--the ion pairs thus can be considered as a generalized solvent) consisting of all RTILs inside the system except the counter-ions in the counter-charge layer, together with solvent molecules if present. Several key features of the EDLs that originate from the strong ion-ion correlation in RTILs, e.g., overscreening of electrode charge and alternating layering of counter-ions and co-ions, are explicitly incorporated into this framework. We show that the dielectric screening in EDLs is governed predominantly by the polarization of generalized solvents (or ion pairs) in the EDL, and the capacitance of an EDL can be related to its microstructure with few a priori assumptions or simplifications. We use this framework to understand two interesting phenomena observed in molecular dynamics simulations of EDLs in a neat IL of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF(4)]) and in a mixture of [BMIM][BF(4)] and acetonitrile (ACN): (1) the capacitance of the EDLs in the [BMIM][BF(4)]/ACN mixture increases only slightly when the mass fraction of ACN in the mixture increases from zero to 50% although the dielectric constant of bulk ACN is more than two times higher than that of neat [BMIM][BF(4)]; (2) the capacitance of EDLs near negative electrodes (with BMIM(+) ion as the counter-ion) is smaller than that near positive electrodes (with BF(4)(-) as the counter-ion) although the closest approaches of both ions to the electrode surface are nearly identical.     

Combination effects of cation and anion of ionic liquids on the cadmium metal-organic frameworks in ionothermal systems

The effects of cation and/or anion of two groups of ionic liquids ([EMI]X and [PMI]X, where EMI = 1-ethyl-3-methylimidazolium; PMI = 1-propyl-3-methylimidazolium; X = Cl, Br, and I) on the ionothermal reactions between Cd(NO 3) 2.4H 2O and 1,3,5-benzenetricarboxylic acid (H 3BTC) were studied. Three different Cd-BTC metal-organic frameworks, [EMI][Cd2(BTC)Cl2](1), [EMI][Cd(BTC)](2), and [PMI][Cd(BTC)](3), were formed into crystalline phases. 1 was obtained from reactions in [EMI]Cl, while the same reactions with Cl replaced by Br or I produced a known compound 2. The replacement of EMI(+) by PMI(+) produced 3, irrespective of the nature of X.