Heat capacities at 298.15 K of the extended [CnC1im][Ntf2] ionic liquid series

High-precision heat capacities at 298.15 K of the [C_nC₁im][Ntf₂] ionic liquid series were measured with an uncertainty of less than ±0.3%, using a drop heat capacity apparatus that was recently updated. The dependence of the $c_p^o$ values on the alkyl side chain length for the extended ionic liquid series [C_nC₁im][Ntf₂] (with n = 2 to 8, 10, and 12) displays a trend shift at [C₆C₁im][Ntf₂], which is taken as an evidence for percolation limit. Above this limit there is an increase in the methylene group contribution to the molar heat capacity which is in agreement with the higher molar absolute entropies change observed from the (liquid + vapor) equilibrium results. The obtained experimental results support the model that the ionic liquids tend to be segregated into a polar network and non-polar domains, being followed by an increase of the entropy contribution of the non-polar domains.     

Application of [EMpy][ESO4] ionic liquid as solvent for the liquid extraction of xylenes from hexane

Liquid–liquid equilibrium (LLE) data for the ternary systems {hexane + o-xylene + 1-ethyl-3-methylpyridinium ethylsulfate}, {hexane + p-xylene + 1-ethyl-3-methylpyridinium ethylsulfate}, and {hexane + m-xylene + 1-ethyl-3-methylpyridinium ethylsulfate} were determined at T = 298.15 K and atmospheric pressure. Selectivity, percent removal of aromatic, and solute distribution ratio, derived from the experimental equilibrium data, were used to determine if this ionic liquid can be used as a potential extracting solvent for the separation of xylenes from hexane. The consistency of tie-line data was ascertained by applying the Othmer–Tobias equation. The phase diagrams for the ternary systems are shown, and the tie-lines correlated with the NRTL model have been compared with the experimental data.     

Evaluation of [bmim][PF6] as an ionic solvent for the extraction of propylbenzene from aliphatic compounds

The evaluation of using 1-butyl-3-methylimidazolium hexaflurophosphate ionic liquid, [bmim][PF₆], as a solvent for the extraction of propylbenzene from aliphatic compounds was studied. The (liquid + liquid) equilibrium (LLE) for two ternary systems comprising {dodecane or tetradecane + propylbenzene + [bmim][PF₆]} were analysed at atmospheric pressure and two temperatures, (313 and 333) K. The consistency of the experimental tie line data was ascertained by applying the Othmer–Tobias correlation. The effect of temperature, n-alkane chain length and solvent to feed ratio upon solubility, distribution ratio, selectivity, and per cent removal of the aromatic were investigated. The experimental LLE data were correlated using the UNIQAC and NRTL models for the activity coefficient with estimation of new interaction parameters, using the simplex minimization method and a composition based objective function. The calculated results from both methods are considered satisfactory.     

(Liquid + liquid) equilibria of [C8mim][NTf2] ionic liquid with a sulfur-component and hydrocarbons

(Liquid + liquid) equilibrium (LLE) data for {1-methyl-3-octylimidazolium bis[trifluoromethylsulfonyl]imide + thiophene + n-dodecane} and {1-methyl-3-octylimidazolium bis[trifluoromethylsulfonyl]imide + thiophene + cyclohexane} ternary systems have been determined experimentally at 298.15 K. The compositions of the tie-lines ends have been obtained by gas chromatographic analysis of phases at equilibrium, being distribution coefficients and separation factors calculated from them. The experimental results have been correlated by means of the NRTL model but considerable deviations from experimental data were found.     

Solubility of CO2 in the ionic liquid [hmim][Tf2N]

New experimental results are presented for the total pressure above liquid mixtures of carbon dioxide and the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([hmim][Tf₂N]). The series of experiments were performed at preset temperature and liquid phase composition by means of a very precise high-pressure view-cell technique based on the synthetic method. A temperature range from (293.15 to 413.2) K was investigated where the maximum pressure reached approximately 10 MPa. Gas molalities in [hmim][Tf₂N] ranged up to about 4.7 mol · kg⁻¹. The (extended) Henry’s law is successfully applied to correlate the solubility pressures.     

Nonaqueous microemulsion-containing ionic liquid [bmim][PF6] as polar microenvironment

The phase behavior of toluene/Triton X-100 (TX-100)/1-butyl-3-methylimidazolium hexafluorophosphate([bmim][PF6]) was studied. It was demonstrated that the single-phase microemulsion area covered about 75% of the phase diagram at 25 °C. Electrical conductivities of the system with different w ([bmim][PF6]-to-TX-100 molar ratio) values were determined, and the results were used to locate the sub-regions of the single-phase microemulsion. The results showed that a transform from [bmim][PF6]-in-oil ([bmim][PF6]/O) microstructure via a bicontinuous region to an oil-in-[bmim][PF6] (O/[bmim][PF6]) microstructure occurred with the increase of Φ (weight fraction of TX-100 and [bmim][PF6] in the system). The aggregate size of the reverse microemulsions of [bmim][PF6]/O was determined using small-angle X-ray scattering. The results showed that the size of the reverse microemulsions depended markedly on the w values.     

Transimination reactions in [b-3C-im][NTf2] ionic liquid

Compared to conventional molecular solvents, the ionic liquid [b-3C-im][NTf(2)] was found to promote transimination reactions with up to ～100-fold rate enhancement. This rate effect observed at ambient temperature might be explained by the fact that the ionic liquid displays weak Lewis acidity with very low, if any, nucleophilicity and its imidazolium cation is expected to interact by associating with, and thus electrophilically activating, the C=N bond of the starting imine, leading to increased stabilization of the polar, charged intermediate species and ultimately, rapid product formation. Moreover, the presence of 1 mol% Sc(OTf)(3) in [b-3C-im][NTf(2)] further facilitates the transimination reactions studied.     

Vapor-liquid-liquid equilibria of pentafluoroethane and ionic liquid [bmim][PF6] mixtures studied with the volumetric method

In this article, we investigate vapor-liquid-liquid equilibria (VLLE) of binary systems using a simple volumetric method. Being different from the usual cloud-point method for the determination of liquid-liquid separation boundaries, the present volumetric method is able to determine the direct VLLE properties, such as equilibrium compositions, as well as molar volumes of the two liquid phases, by measuring only weights and volumes of liquid samples. The theory behind this method is described, and detailed error analyses for our simple apparatus are discussed by using well-established systems in the literature: water + 2-butanol and 1-butanol + 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]). Then, results for mixtures of [bmim][PF(6)] and pentafluoroethane (R-125) are provided, as well as those of the test systems above. As predicted in our earlier work, this binary system shows liquid-liquid separations in the R-125-rich side solutions with a lower critical solution temperature. In addition, we have found very large negative excess molar volumes in this system.     

酸性离子液体萃取/催化二苯并噻吩氧化脱硫反应的优化

ö以Brönsted酸性离子液体N-甲基-2-吡咯烷酮磷酸二氢盐(\[Hnmp\]H₂PO₄)为萃取剂和催化剂,双氧水为氧化剂,二苯并噻吩(DBT)溶于正辛烷为模型油,利用正交实验法优化了DBT氧化脱硫反应工艺。所优化的反应条件为：反应温度60℃,模型油与离子液体体积比为1∶1,氧/硫摩尔比为16, 氧化时间5h;在此条件下模型油脱硫率达99.8%,实际柴油脱硫率为64.3%。由正交实验极差可知,各因素对DBT脱硫率影响的大小依次为：反应温度＞反应时间＞氧/硫摩尔比＞剂油比;离子液体循环利用6次,脱硫率下降不明显。     

Ionic liquid [bmim][BF4] acts as solvent and promoter for synthesis of halo-containing N-arylphthalimides

A new synthetic process of N-arylphthalimide and halo-containing N-arylphthalimides through the reaction between phthalic anhydride and aromatic amines bearing halo groups in[bmim][BF_4]was described,ionic liquid[bmim][BF_4]acted as the dual role of solvent and promoter.     

Molecular dynamics simulations of the aqueous interface with the [BMI][PF6] ionic liquid: Comparison of different solvent models

We report a Molecular Dynamics (MD) study of the interface between water and the hygroscopic room temperature Ionic Liquid "IL" [BMI][PF6] (1-butyl-3-methyl-imidazolium hexafluorophosphate), comparing the TIP3P, SPC/E and TIP5P models for water and two IL models where the ions are +/-1 or +/-0.9 charged. A recent MD study (A. Chaumont, R. Schurhammer and G. Wipff, J. Phys. Chem. B, 2005, 109, 18964) showed that using TIP3P water in conjunction with the IL(+/-1) model led to water-IL mixing without forming an interface, whereas a biphasic system could be obtained with the IL(+/-0.9) model. With the TIP5P and SPC/E models, the juxtaposed aqueous and IL phases are found to remain distinct for at least 20 ns. The resulting IL humidity, exaggerated with the IL(+/-1) model, is in better agreement with experiment using the IL(+/-0.9) model. We also report demixing simulations on the "randomly mixed" liquids, using the IL(+/-0.9) model for the ionic liquid. With the three tested water models, the phases separate very slowly ( approximately 20 ns or more) compared to "classical" chloroform-water mixtures (less than 1 ns), leading to biphasic systems similar to those obtained after equilibration of the juxtaposed liquids. The characteristics of the interface (size, polarity, ion orientation, electrostatic potential) are compared with the different models. Possible reasons why, among the three tested water models, the widely-used TIP3P model exaggerates the inter-solvent mixing, are analyzed. The difficulty in computationally and experimentally equilibrating water-IL mixtures is attributed to the slow dynamics and micro-heterogeneity of the IL and to the different states of water in the IL phase.     

Improvement of carbon paste-based enzyme electrode using a new ionic liquid [Pmim][PF6] as the binder

A new carbon ionic liquid electrode (CILE) has been constructed using a low melting point (39?°C) hydrophobic ionic liquid (IL) 1-propyl-3-methylimidazolium hexafluorophosphate ([Pmim][PF₆]) as the binder. Both cyclic voltammetry and electrochemical impedance spectroscopy demonstrate that, in addition to the composition optimization of the IL/graphite composite, heating the composite at a temperature a little higher than the melting point of [Pmim][PF₆] can also lower the background current and enhance the mechanical strength of the CILE. The heated CILE is more sensitive than the traditional carbon paste electrode for the detection of H₂O₂. Glucose oxidase (GOx) can be easily entrapped in the bulk IL/graphite composite. Heating the GOx-modified CILE (GOx-CILE) at the melting point of [Pmim][PF₆] does not lower the catalytic activity of GOx. As compared with n-octylpyridinium hexafluorophosphate (melting point 65?°C) as the binder, [Pmim][PF₆]-based CILE is much better in signal-to-noise ratio. Under the optimum conditions, the [Pmim][PF₆]-based GOx-CILE has a linear amperometric response to glucose over a concentration range of 2.0–26?mM with the detection limit as low as 0.39?mM. It follows that choosing an IL with a melting point of ca. 40?°C as a binder to fabricate enzyme-entrapped CILEs is a good strategy for the enhancement of the performance of the electrode.     

Anomalous diffusion of water in [BMIM][TFSI] room-temperature ionic liquid

We have studied the self-diffusion properties of butyl-methyl-imidazolium bis(trifluoromethylsulfonyl)-imide ([BMIM][TFSI]) + water system. The self-diffusion coefficients of cations, anions, and water molecules were determined by pulsed field gradient NMR. These measures were performed with increased water quantity up to saturation (from 0.3 to 30 mol %). Unexpected variations have been observed. The self-diffusion coefficient of every species increases with the quantity of water but not in the same order of magnitude. Whereas very similar evolutions are observed for the anion and cation, the increase is 25 times greater for water molecules. We interpret our data by the existence of phase separation at microscopic scale.     

Solubility of tetrafluoromethane in the ionic liquid [hmim][Tf2N

Experimental results for the solubility of tetrafluoromethane (CF4, R14) in the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([hmim][Tf2N]) are presented for temperatures between 293.3 and 413.3 K, at pressures (gas molalities) up to 9.6 MPa (0.22 mol kg-1). The experimental results were determined with a high-pressure view-cell technique operating on the synthetic method. The experimental data were used to determine Henry's constant of tetrafluoromethane in [hmim][Tf2N]. The results for the Henry's constant (at zero pressure) are correlated (on the molality scale) within the experimental uncertainty (i.e., about 1.1%) by ln(k(0)(H,CF4)/MPa) = 7.537 - 893.8/(T/K) - 0.003977(T/K). Henry's law was also extended to describe the gas solubility at higher pressures. Furthermore, a cubic equation of state was used to correlate the gas solubility over the entire range of experimentally investigated temperature and pressure. Both methods proved suited for a reliable correlation of the new experimental data.     

Study of [EMim][ESO4] ionic liquid as solvent in the liquid-liquid extraction of xylenes from their mixtures with hexane

The aim of this work is to determine if the ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate is a good solvent for the separation of xylenes and hexane by liquid extraction. With this purpose, liquid-liquid equilibrium (LLE) data for the ternary systems {hexane + o-xylene, or m-xylene, or p-xylene + 1-ethyl-3-methylimidazolium ethylsulfate} were determined at T = 298.15 K and atmospheric pressure. Selectivity and solute distribution ratio, derived from the experimental equilibrium data, were calculated and used to determine if this ionic liquid can be used as a potential solvent for the extraction of xylenes from their mixtures with hexane. The experimental LLE data for the ternary systems were correlated using the NRTL and UNIQUAC models.     

A new type of microemulsion containing task-special ionic liquid [NH2ebim][BF4]

The formation of microemulsions in the presence of cyclohexane, Triton X-100, n-butanol, water, and task-special ionic liquid (TSIL) (1-2-aminoethyl-3-butylimidazolium tetrafluoroborate) was studied at 25°C. The phase behavior of this ternary system was investigated. Three subregions (namely, water-in-oil phase, bicontinuous phase, and oil-in-water phase) were identified in the single-phase region by dynamic light scattering (DLS) technique and electrical conductivity measurement. Microstructures of microemulsions with different water contents have been predicted by using dissipative particle dynamics (DPD) simulation. It was found that the DPD simulations successfully reproduce the experimental results in the article. The location of TSIL in the microemulsions was predicted by DPD simulation further. The result indicates that TSIL is more easy to locate in the surfactant and cosurfactant layer and has amphiphilicity, which provides us new insights into the potential applications of TSIL-based microemulsions in separation and new nano-scale material preparation because of the interaction of TSIL with some special components at the interface of oil and water.     

Structure of [C4mpyr][NTf2] room-temperature ionic liquid at charged gold interfaces

The structure of 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C(4)mpyr][NTf(2)]) room-temperature ionic liquid at an electrified gold interface was studied using neutron reflectometry, cyclic voltammetry, and differential capacitance measurements. Subtle differences were observed between the reflectivity data collected on a gold electrode at three different applied potentials. Detailed analysis of the fitted reflectivity data reveals an excess of [C(4)mpyr](+) at the interface, with the amount decreasing at increasingly positive potentials. A cation rich interface was found even at a positively charged electrode, which indicates a nonelectrostatic (specific) adsorption of [C(4)mpyr](+) onto the gold electrode.     

Chiral quaternary alkylammonium ionic liquid [Pro-dabco][BF4]: as a recyclable and highly efficient organocatalyst for asymmetric Michael addition reactions

A novel series of chiral quaternary ammonium ionic liquids have been synthesized and shown to be very effective catalysts for the asymmetric Michael addition reactions of ketones and aldehydes to nitroolefins with excellent yields (up to 100%), diastereoselectivities (syn/anti = 99:1), and enantioselectivities (up to 97%). The catalytic system, an ionic liquid organocatalyst in [Bmim][BF₄], could be reused five times without a significant loss in catalytic activity or stereoselectivity.     

Evaluation of the ionic liquids 1-alkyl-3-methylimidazolium hexafluorophosphate as a solvent for the extraction of benzene from cyclohexane: (Liquid + liquid) equilibria

In the catalytic hydrogenation of benzene to cyclohexane, the separation of unreacted benzene from the product stream is inevitable and essential for an economically viable process. In order to evaluate the separation efficiency of ionic liquids (ILs) as a solvent in this extraction processes, the ternary (liquid + liquid) equilibrium of 1-alkyl-3-methylimidazolium hexafluorophosphate, [C_nmim][PF₆] (n = 4, 5, 6), with benzene and cyclohexane was studied at T = 298.15 K and atmospheric pressure. The reliability of the experimentally determined tie-line data was confirmed by applying the Othmer–Tobias equation. The solute distribution coefficient and solvent selectivity for the systems studied were calculated and compared with literature data for other ILs and sulfolane. It turns out that the benzene distribution coefficient increases and solvent selectivity decreases as the length of the cation alkyl chain grows, and the ionic liquids [C_nmim][PF₆] proved to be promising solvents for benzene–cyclohexane extractive separation. Finally, an NRTL model was applied to correlate and fit the experimental LLE data for the ternary systems studied.     

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。