Mutual solubility measurements and correlations of imidazolium-based ionic liquid mixtures with alcohols

The mutual solubility of ionic liquids (ILs), 1-butyl-3-ethylimidazolium tetrafluoroborate, 1-butyl-3-propylimidazolium tetrafluoroborate, and 1,3-dibutylimidazolium tetrafluoroborate with alcohols, 1-propanol, 1-butanol, 1-pentanol, and 1-hexanol were measured at atmospheric pressure. Upper critical solution temperatures (UCSTs) were estimated from experimental results using a polynomial equation. The UCSTs increased as increasing the chain length of alcohol. On other hand, the decreasing UCSTs occurred when the alkyl chain length on the cation of ionic liquids increased. The (liquid + liquid) equilibrium data were correlated by the original UNIQUAC, extended UNIQUAC, and modified UNIQUAC models. The temperature dependence of the solubility of ILs in alcohols and alcohols in ILs is represented successfully using the UNIQUAC, extended UNIQUAC, and modified UNIQUAC models with a quadratic function of temperature for binary energy parameters.     

Influence of the ionic liquid structure on thiophene solubility

Binary liquid-liquid equilibria for 10 systems containing an ionic liquid with thiophene were measured by dynamic method in the temperature range from 283 K to the boiling point of thiophene. The influence of ionic liquid structure on solubility of thiophene is discussed in comparison with results taken from the literature. The solubility of thiophene in all investigated ionic liquids is high - below 0.31 ionic liquid mole fraction.     

Enhanced solubility and selective benzoylation of nucleosides in novel ionic liquid

Solubility and benzoylation study of both ribo- and deoxyribonucleosides is reported in a new ionic liquid MoeMIM·TFA; high selectivity for O-benzoylation is achieved.     

Non-catalytic liquid phase oxidation of alkenes with nitrous oxide. 1. Oxidation of cyclohexene to cyclohexanone

A very efficient way of alkenes oxidation to carbonyl compounds is discovered. It is based on remarkable ability of nitrous oxide to interact directly with the double C=C bonds of liquid alkene and to transfer its oxygen, without catalyst aid, to unsaturated carbon atom with nearly 100% selectivity. This oxidation method can be applied to a wide range of organic compounds including aliphatic, cyclic, heterocyclic alkenes and their numerous derivatives.     

反气相色谱测定双阳离子型离子液体的溶解度参数

采用反气相色谱法,于343.15 K到363.15 K温度下测定了双阳离子型离子液体1,10-双(N-甲基咪唑鎓)癸烷六氟磷酸盐［C10(MIM)2］［PF6］2的溶解度参数。以正辛烷、正十二烷、正十四烷和正十六烷为探针溶剂,计算了探针溶剂的特性保留体积(V0g)、摩尔吸收焓(ΔHS1)、无限稀释摩尔混合焓(ΔH∞1)、摩尔蒸发焓(ΔHv)、无限稀释活度系数(γ∞12)以及探针溶剂与［C10(MIM)2］［PF6］2的Flory-Huggins相互作用参数(χ∞12),测得该离子液体的溶解度参数(δ2)为15.01 (J\5cm~3)1/2。这一结果对研究离子液体的溶液性质和应用有指导作用。     

Study of the solubility of CO2, H2S and their mixture in the ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate: Experimental and modelling

New experimental results are presented for the solubility of carbon dioxide, hydrogen sulfide in the ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate ([C₈mim][PF₆]) at temperatures range from (303.15 to 353.15) K and pressures up to about 2 MPa. The solubility of the mixture of CO₂/H₂S in [C₈mim][PF₆] under various feed compositions were also measured at temperatures of (303.15, 323.15 and 343.15) K and the pressure up to 1 MPa. The solubility of carbon dioxide and hydrogen sulfide increased with increasing pressure and decreased with increasing temperature and the solubility of H₂S is about three times that of CO₂ in the particular ionic liquid studied. The measured data were correlated using extended Henry’s law included Pitzer’s virial expansion for the excess Gibbs energy, and the generic Redlich–Kwong cubic equation of state proposed for gas/ionic liquid systems. The correlations from the two models show quite good consistency with the experimental data for CO₂/IL and H₂S/IL binary mixtures within experimental uncertainties. For CO₂/H₂S/IL ternary mixtures, the RK model shows better correlation with the experimental values. We also studied the effect of cation alkyl chain length on the CO₂ and H₂S solubility by comparison of the experimental data of this study with those of previous reports. As the cation alkyl chain length became longer, the solubility of CO₂ and H₂S increased in the ionic liquid. Additionally, the influence of the anion on the solubility is studied by comparing the solubility of CO₂ and H₂S in [C₈mim][PF₆] with those in [C₈mim][Tf₂N]. As a result, CO₂ and H₂S have higher solubility in the IL with [Tf₂N]⁻ as the anion.     

Radiometric,potentiometric and conductometric measurements of the solubility and solubility product of europium trifluoride

The solubility and solubility product of europium trifluoride were measured by radiometric, potentiometric and conductometric methods. There are significant differences in the values of both solubility and solubility product obtained by the three different techniques. Due to reasons discussed in the text, radiometric values seem to be more acceptable than the others. The thermodynamic functions such as ΔH⁰, ΔG⁰ and ΔS⁰ for the dissolution process were also measured. The positive values of ΔH⁰ and ΔG⁰ and the negative value of ΔS⁰ are indicative of the slight solubility of EuF₃. The dependence of solubility on pH and also on the fluoride concentration has also been studied. It was confirmed that europium forms a monofoluoride complex in aqueous solution. The stability constant of this complex was estimated.     

二氰胺1-羟乙基-3-甲基咪唑离子液体的合成及对糖类化合物的溶解性能

根据离子液体结构-性能的关系,设计合成了一种新的低熔点、低黏度的功能化离子液体二氰胺1-羟乙基-3-甲基咪唑[Hemim][N(CN)2],并在298.2～353.2K的温度范围内测定了α-D-木糖、α-D-葡萄糖、D-果糖、蔗糖、D-乳糖、麦芽糖、棉子糖和木聚糖在该离子液体中的溶解度,计算了糖类化合物在离子液体中的标准溶解热力学参数.实验结果表明,除木聚糖外其他糖类化合物在[Hemim][N(CN)2]中均具有较高的溶解度,且其溶解度随着温度的升高显著增大.木聚糖属于多聚糖,溶解度较小,但温度效应非常明显.糖类化合物的溶解热力学参数SΔGo、TΔSSo和ΔHSo均为正值,且ΔHSoTΔSSo,说明溶解为焓控制过程.红外光谱结果表明,在溶解过程中木聚糖的氢键受到了一定程度的破坏,但它的结构并未发生明显的变化.     

Monte Carlo simulations of gas solubility in the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate

The Henry's constants of water, carbon dioxide, ethane, ethene, methane, oxygen, and nitrogen are computed in the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]) using test particle insertion and expanded ensemble Monte Carlo methods. The partial molar enthalpy and partial molar entropy of solvation are also computed for water, carbon dioxide, and oxygen. The results from the simulations are compared against experimental data from the literature. In addition, the accuracy and precision of the two methods in determining the Henry's constant are examined. Local organization of the ionic liquid around a solute molecule is analyzed, and the interactions responsible for the experimentally observed solubility trends are identified.     

Experimental measurements and prediction of liquid densities for n-alkane mixtures

We present experimental liquid densities for n-pentane, n-hexane and n-heptane and their binary mixtures from (273.15 to 363.15) K over the entire composition range (for the mixtures) at atmospheric pressure. A vibrating tube densimeter produces the experimental densities. Also, we present a generalized correlation to predict the liquid densities of n-alkanes and their mixtures. We have combined the principle of congruence with the Tait equation to obtain an equation that uses as variables: temperature, pressure and the equivalent carbon number of the mixture. Also, we present a generalized correlation for the atmospheric liquid densities of n-alkanes. The average absolute percentage deviation of this equation from the literature experimental density values is 0.26%. The Tait equation has an average percentage deviation of 0.15% from experimental density measurements.     

Surface tension measurements of imidazolium-based ionic liquids at liquid–vapor equilibrium

A series of high quality 1-alkyl-3-methylimidazolium-based ionic liquids are synthesized and used for studying their surface tension. The capillary rise method is used for measuring the surface tension of I⁻, Cl⁻, PF₆⁻, and BF₄⁻ salts in the temperature range 298–393 K. The capillary apparatus is evacuated and sealed under vacuum. The experimental results show that surface tension of these compounds depend systematically on temperature.     

The molecular and ionic solubility of nickel dimethylglyoximate

Values are reported for the solubility product constant and the ionization constant of nickel(II) dimethylglyoximate in aqueous solution. The solubility of nickel dimethylglyoximate in the investigated pH range from 2 to 9 is accounted for by the species Ni⁺² and Ni(HDx)₂; there is no evidence for the existence of a significant amount of NiHDx⁺.The extraction constant

has been calculated from the ionization constants of Ni(HDx)₂ and H₂Dx and the molecular solubilities of the former in water and chloroform.     

Transport properties in ionic liquids and ionic liquid mixtures: the challenges of NMR pulsed field gradient diffusion measurements

Pulsed field gradient NMR is a powerful method for the measurement of diffusion coefficients in liquids and solids and has begun to attract much attention in the ionic liquids field. However, aspects of the methodology as traditionally applied to solutions may not be uniformly applicable in these more viscous and chemically complex systems. In this paper we present data which shows that the Pulsed Gradient Spin Echo (PGSE) method in particular suffers from intrinsic internal gradients and can produce apparent diffusion coefficients which vary by as much as 20% for different 1H nuclei within a given molecule--an obvious anomaly. In contrast, we show that the Pulsed Gradient Stimulated Echo method does not suffer from this problem to the same extent and produces self-consistent data to a high degree of accuracy (better than 1%). This level of significance has allowed the detection, in this work, of subtle mixing effects in [C(3)mpyr][NTf(2)] and [C(4)mpyr][NTf(2)] mixtures.     

Synthesis,characterization, and application of silica supported ionic liquid as catalyst for reductive amination of cyclohexanone with formic acid and triethyl amine as hydrogen source

A silica supported ionic liquid was synthesized and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, X-ray diffraction, N2 adsorption-desorption, and thermogravimetric analysis. All these techniques, especially SEM results indicated the presence of well-defined spherical particles having diameters larger than the pristine silica particles, confirming the successful immobilization of the ionic liquid. The prepared silica supported ionic liquid was used in the reductive amination of cyclohexanone under different conditions with different azeo-tropic mixtures of formic acid and triethyl amine as a hydrogen source. The catalyst showed effi-cient catalytic performance and excellent yields of N-cyclohexyl amine derivatives in the range of 58%to 84%at 30 °C. After completion of the reaction, the catalyst was easily recovered by simple filtration and reused for another five cycles without any significant impact on product yields. The obtained catalytic performance indicates that the present catalyst is green, very active, and reusable for the reductive amination of cyclohexanone.     

离子液体[bmim][dca]的微波辅助合成及其对几种糖的溶解性能

以N-甲基咪唑为母体,在微波辐射下经两步法合成了一种功能化离子液体溴化1-正丁基-3-甲基咪唑双氰胺盐([bmim][dca])。采用单因素试验法优化了合成条件:[bmim]Br与Na[N(CN)2]的摩尔比1∶1.1,丙酮作溶剂,微波功率800W,微波反应温度50℃,反应时间1h。在此条件下,[bmim][dca]收率可达85.2%。并通过IR对目标产物进行了分析和表征。通过溶解度测试得知,离子液体[bmim][dca]对蔗糖、葡萄糖和β-环糊精有良好的溶解能力,其中对β-环糊精的溶解效果最好。     

Interfacial tension and electrocapillary measurements of the room temperature ionic liquid/aqueous interface

The surface and aqueous interfacial tensions for a series of water-immiscible room-temperature ionic liquids (RTILs) have been measured. The RTILs used in this study were based on 1-alkyl-3-methylimidazolium cations (Cnmim, n=6, 8, 10, and 12) and bis(perfluoromethylsulfonyl)imide (BMSI) and bis(perfluoroethylsulfonyl)imide (BETI) anions. It was found that the surface tensions of the RTILs increased with an increasing cation chain length similar to the behavior of n-alkanes. Interfacial tensions of the RTILs with aqueous solutions, however, were found to decrease with the cation chain length, which has been attributed to the increased surface activity of the longer chain cations. We have also demonstrated the first use of electrocapillary measurements to study the polarizable RTIL/aqueous interfaces. From the electrocapillary data, the potential of zero charge (PZC) for these RTIL/aqueous interfaces was determined, as well as the relative surface excess charge and capacitance. The PZC was found to be dependent upon the structure of the anions and cations with PZC values ranging from -357 mV for C6mimBETI and -161 mV for C10mimBMSI. The electrocapillary results also show that the cations of the RTIL are becoming increasingly surface-active as the alkyl chain on the cation is lengthened, thereby modulating the interfacial potential.     

Catalytic oxidation of cyclohexene to cyclohexanone by a triple system in acidic aqueous acetonitrile medium

The catalytic oxidation of cyclohexene to cyclohexanone using Pd(OAc)2/HQ/FePc was investigated in an acidic aqueous solution of acetonitrile. The role of each component of this system in the oxidation of cyclohexene was explored by means of UV-VIS, IR, XPS spectroscopy and cyclic voltammetry, respectively. Based on the experimental results, the mechanism of the oxidation of cyelohexene catalyzed by Pd(OAc)2/HQ/FePc was elucidated.