Separation of benzene and hexane by solvent extraction with 1-alkyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide ionic liquids: effect of the alkyl-substituent length

The influence of the alkyl-substituent chain in 1-alkyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide ionic liquids ([C(n)mim][NTf(2)], where n is the length of a linear alkyl chain) as solvents for the separation of benzene and hexane by liquid extraction was investigated. The liquid-liquid equilibrium (LLE) at 25 degrees C for the ternary systems ([C(n)mim][NTf(2)] + hexane + benzene), with n taking the values 4, 8, 10, and 12, were determined. These data were analyzed and compared to those previously reported for the system ([C(2)mim][NTf(2)] + hexane + benzene). The results show that short alkyl chains on the imidazolium cation of the ionic liquid lead to a better extractive separation of benzene and hexane, and reveal the influence of the relative degree of ordering in the ionic liquids on the extraction parameters.     

Determination of the diffusion coefficient of CO2 in the ionic liquid EMIM NTf2 using online FTIR measurements

Physical data concerning the absorption kinetics like the diffusion coefficients are important values for designing an economically working gas separation processes. Considering ionic liquids, which emerged in recent years as interesting alternative solvent media for versatile industrial purposes, usually only solubility data for gases are available if at all. Therefore in order to gain additional information such as diffusion coefficients of gases in ionic liquids, we established an efficient and easily assembled set-up based on time-resolved FTIR measurements. Applying this methodology, the diffusion coefficient of carbon dioxide in 1-ethyl-3-methyl-imidizolium bis[(trifluoromethyl)sulfonyl]amide (EMIM NTf₂) was determined at a temperature of 303 K.     

Hydrophobic, Highly Conductive Ambient-Temperature Molten Salts

New, hydrophobic ionic liquids with low melting points (<-30 degrees C to ambient temperature) have been synthesized and investigated, based on 1,3-dialkyl imidazolium cations and hydrophobic anions. Other imidazolium molten salts with hydrophilic anions and thus water-soluble are also described. The molten salts were characterized by NMR and elemental analysis. Their density, melting point, viscosity, conductivity, refractive index, electrochemical window, thermal stability, and miscibility with water and organic solvents were determined. The influence of the alkyl substituents in 1, 2, 3, and 4(5)-positions on these properties was scrutinized. Viscosities as low as 35 cP (for 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)amide (bis(triflyl)amide) and trifluoroacetate) and conductivities as high as 9.6 mS/cm were obtained. Photophysical probe studies were carried out to establish more precisely the solvent properties of 1-ethyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)amide). The hydrophobic molten salts are promising solvents for electrochemical, photovoltaic, and synthetic applications.     

Extraction of Lithium from Salt Lake Brine with Triisobutyl Phosphate in Ionic Liquid and Kerosene

Three ionic liquids(ILs), namely, 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-me- thylimidazolium bis[(trifluoromethyl)sulfonyl]imide and 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sul- fonyl]imide with the triisobutyl phosphate(TIBP) and kerosene system were respectively used to extract lithium ion from salt lake brine with a high concentration ratio of magnesium and lithium experimentally. Results indicate that the highest extraction selectivity for lithium was obtained with IL 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)- sulfonyl]imide. The effects of solution pH and phase ratio R(O/A) on the extractive step and the influence of acid concentration of the stripping solution and R(O/A) on the back extraction step were also investigated systematically. The single-step extraction efficiency of lithium ion was 83.71% under the optimal extraction conditions, and the single-step back extraction efficiency was 85.61% with a 1.0 mol/L HCl in 1.0 mol/L NaCl medium as stripping agent at R(O/A)=2. The liquid-liquid extraction mechanism and the complex of the ligand with lithium were proposed.     

Metal bis[trifluoromethyl)sulfonyl]amide complexes: highly efficient Friedel-Crafts acylation catalysts

A range of metal bis[(trifluoromethyl)sulfonyl]amide complexes, including many unreported ones, have been synthesised, most of which have been found to be excellent Friedel-Crafts acylation catalysts in the absence of solvent; these reactions have also been carried out in ionic liquids, which allow the catalysts to be recycled and reused.     

Comparing π-complexation capabilities of ionic liquids containing silver(I) and copper(I) ions by headspace single drop microextraction in combination with high-performance liquid chromatography

Selective π-complexation capabilities of silver(I) and copper(I) ions can be effectively facilitated in ionic liquids. To understand the effects of environmental factors that influence the π-complexation of these metal ions with analytes, techniques that employ small volumes of ionic liquid that can be readily analyzed are desired. In this study, headspace single drop microextraction coupled with HPLC is used to investigate a diverse set of environmental factors on the metal ion-mediated complexation with aromatic compounds in ionic liquid media. Silver(I) and copper(I) bis[(trifluoromethyl)sulfonyl]imide salts were both studied by dissolving them in the 1-decyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide ionic liquid and employing the mixture as extraction media for aromatic compounds. Water and acetonitrile within the sample solution were observed to interfere with the complexation of silver(I) ions and aromatic compounds, while ethylene glycol and triethylene glycol did not. The temperature and extraction times were optimized to fully facilitate the π-complexation capabilities of metal ions in ionic liquid media. Partition coefficients between the sample headspace and metal ion were determined using a three-phase equilibria model. Although no discernable difference in analyte partitioning between the headspace and ionic liquid solvent was observed, analyte partition coefficients to silver(I) ion tended to be greater compared to copper(I) ion.     

Tunable Lower Critical Solution Temperature of Poly(butyl acrylate) in Ionic Liquid Blends

We describe the lower critical solution temperature(LCST)-type phase behavior of poly(butyl acrylate)(PBA) dissolved in hydrophobic 1-alkyl-3-methylimidazolium bis{(trifluoromethyl) sulfonyl}amide ionic liquids(ILs). The temperature-composition phase diagrams of these PBA/ILs systems are strongly asymmetric with the critical composition shifted to low concentrations of PBA. As the molecular weight increases from 5.0×10~3 to 2.0×10~4, the critical temperature decreases by about 67 °C, and the critical composition shifts to a lower concentration.Furthermore, the LCST of PBA/ILs system increases as increasing the alkyl side chain length in the imidazolium cation. Using IL blends as solvents,the LCST of PBA can be tuned almost linearly over a wide range by varying the mixing ratio of two ionic liquids without modifying the chemical structure of the polymers.     

Extraction of Cupric Ions with Ionic Liquids Containing Polypyridine‐type Small Molecules or Peripherally Pyridine‐modified Dendrimers

The hydrophobic ionic liquid N‐butyl‐N‐methylpyrrolidinium bis((trifluoromethyl)sulfonyl)amide (BMP‐TFSA IL), which contains a series of flexible ionophores of polypyridine‐type small molecules or two rigid ionophores of peripherally pyridine‐modified PAMAM dendrimers, was used to extract cupric ions from aqueous solutions. The polypyridine‐type ionophores show good selectivity toward cupric ions at pH 2. The selectivity is affected by the spacing between the two amino groups. However, the pyridine‐modified dendrimers showed poor selectivity, although their extraction efficiency still depended on the pH of the aqueous solution. The ionic liquids that contained small molecular ionophores and their dendrimer analogs were reused after acid washing or electrochemical reduction. During acid washing, the nitrogen atoms of the ionophores were protonated to release the cupric ions into the aqueous phase, and the copper atoms were deposited onto the electrode surface during the electrochemical reduction accompanied by the regeneration of the ionophores.     

Direct methylation and trifluoroethylation of imidazole and pyridine derivatives

Direct methylation or trifluoroethylation of imidazole and pyridine derivatives using N-methyl bis((perfluoroalkyl)sulfonyl)imides or trifluoroethyl phenyliodonium bis((trifluoromethyl)sulfonyl)imide affords high yields of the corresponding salts. This methodology provides a simple route to a variety of room temperature ionic liquids (RTILs).     

Liquid Phase Behavior in Systems of 1-Butyl-3-alkylimidazolium bis{(trifluoromethyl)sulfonyl}imide Ionic Liquids with Water: Influence of the Structure of the C5 Alkyl Substituent

In the present paper a study of the liquid phase behavior in aqueous systems of imidazolium-based ionic liquids (ILs) with the bis{(trifluoromethyl)sulfonyl}imide anion is addressed. To highlight the influence of the C5 alkyl side group structure on their properties, a series of ILs with linear, branched, and cyclic substituents was studied. As was already shown in our previous work, very subtle changes in the cation structure at the molecular scale can have a significant and unexpected impact on the bulk properties. Therefore, in this work, the mutual solubilities of 1-butyl-3-alkylimidazolium bis{(trifluoromethyl)sulfonyl}imide ionic liquids and water were studied, both experimentally and by modeling, at atmospheric pressure as a function of temperature from 293.15 to 328.15 K. The solubilities of the ionic liquids in water are very low, typically around 10^?5 mole fraction units and were measured by a direct analytical method, making use of UV–Vis spectrophotometry. The solubilities of water in the ionic liquids were found to be around 0.20 mole fraction units and were measured using the cloud-point method. In addition to the experimental data, the liquid–liquid equilibria in the systems were modeled using the COSMO-RS methodology. Phase diagrams and the critical solution points were also estimated by applying the universal scaling laws based on the 3D Ising model, taking into account the non-linearity of the diameter and crossover to mean-field behavior.     

Various metal nanoparticles produced by accelerated electron beam irradiation of room-temperature ionic liquid

Various metal nanoparticles including base metal were produced by a brief accelerated electron beam irradiation of 1-alkyl-3-methylimidazolium bis((trifluoromethyl)sulfonyl)amide room-temperature ionic liquid without a stabilizing agent, which is usually employed so as to prevent aggregation.     

Evidence for lower critical solution behavior in ionic liquid solutions

Lower critical solution temperatures (LCST)-type of phase diagrams, including the presence of closed loops, have been encountered for the first time in binary and quasi-binary liquid solutions of ionic liquids. Furthermore, the results constitute the first experimental support for the existence of a theoretically postulated, but never encountered, special kind of type VII phase diagram. Two distinct mechanisms are involved in the appearance of demixing upon temperature increase. These findings underlie the presence of specific, oriented interactions between the ionic liquid, 1-alkyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide, [Cnmim][NTf2], and trichloromethane, as well as aggregation phenomena.     

Effect of Phosphonium Ionic Liquids on the Extraction of Rare-Earth Elements(III) with 2,2′-Oxybis(N,N-dioctylacetamide) from Nitric Acid Solutions

Russian Journal of General Chemistry - New phosphonium ionic liquids, alkyldiphenylethylphosphonium bis[(trifluoromethyl)sulfonyl]imides (Alk = C4H9, C8H17, and C12H25) have been synthesized. The...     

微波辅助合成有机膦功能化离子液体及对稀土离子的萃取

用微波辐射法,合成了5个含有机膦氧基团的离子液体：1-丙基-3-(3-二苯基氧膦基)丙基咪唑双(三氟甲基磺酰基)亚胺盐([PImC3P(O)Ph2][Tf2N])、1-己基-3-(3-二苯基氧膦基)丙基咪唑双(三氟甲基磺酰基)亚胺盐([HImC3P(O)Ph2][Tf2N])、1-丙基-3-(3-苯基乙氧基氧膦基)丙基咪唑双(三氟甲基磺酰基)亚胺盐([PImC3P(O)Ph(OEt)][Tf2N])、1-己基-3-(3-苯基乙氧基氧膦基)丙基咪唑双(三氟甲基磺酰基)亚胺盐([HImC3P(O)Ph(OEt)][Tf2N])和(3-苯基乙氧基氧膦基)丙基三乙胺双(三氟甲基磺酰基)亚胺盐([TENC3P(O)Ph(OEt)][Tf2N])。 用31P NMR、1H NMR、13C NMR、MS及FT-IR对产物结构进行了表征。 研究了这类离子液体对稀土Nd(III)的萃取性能。 结果表明,这类功能化离子液体可作为单一组分萃取稀土而无需加入有机稀释剂,离子液体结构对萃取效率影响很大,相同条件下季铵盐型结构的离子液体[TENC3P(O)Ph(OEt)][Tf2N]对稀土Nd(Ⅲ)的萃取效率最高。 稀土溶液pH值对萃取效率影响显著,近中性条件下(pH=6.63),对稀土Nd(Ⅲ)的萃取率最高。 用pH=1.00的盐酸溶液可以较好的从离子液体相反萃Nd(Ⅲ),反萃率可达94%。     

Synthesis,physical, and thermodynamic properties of 1-alkyl-cyanopyridinium bis{(trifluoromethyl)sulfonyl}imide ionic liquids

Synthesis of new ionic liquids (ILs) viz. 1-butyl-3-cyanopyridinium bis{(trifluoromethyl)sulfonyl}imide, [BCN³Py][NTf₂], 1-hexyl-3-cyanopyridinium bis{(trifluoromethyl)sulfonyl}imide, [HCN³Py][NTf₂], 1-hexyl-4-cyanopyridinium bis{(trifluoromethyl)sulfonyl}imide, [HCN⁴Py][NTf₂], and 1-octyl-3-cyanopyridinium bis{(trifluoromethyl)sulfonyl}imide, [OCN³Py][NTf₂] were performed. The specific basic characterization of new compounds by NMR spectra, elementary analysis, water content and glass transition temperature as well as melting temperature, enthalpy of fusion and decomposition of compounds TG/DTA determined by the differential scanning calorimetry, DSC is presented. The heat capacity was measured at three temperatures (298.15, 323.15, and 353.15) K and at pressure 0.1 MPa. The effect of temperature on the density and viscosity is reported over the temperature range from (293.15 to 363.15) K and at 0.1 MPa. The density and viscosity correlation for these systems was provided by an empirical polynomial. From the density–temperature dependence, the isothermal expansion coefficient (volume expansivity), α, was calculated. The surface tension of pure ionic liquids was measured at 0.1 MPa at five temperatures (298.15, 308.15, 318.15, 328.15, and 338.15) K. The surface thermodynamic functions such as surface entropy and enthalpy, critical temperatures according to the Eötvös and Guggenheim definition and the total surface energy of the ILs studied were derived from the temperature dependence of the surface tension values. The parachor and speed of sound for pure ionic liquids were described within a range of temperature from (298.15 to 338.15) K. A qualitative analysis on these quantities in terms of molecular interactions is reported.     

分子模拟研究气体在室温离子液体中的溶解度

在作者先前建立的分子力场基础上, 采用Widom粒子插入法预测了CO₂、N₂、O₂、Ar及CH₄等5种气体在多种咪唑类离子液体中的溶解度, 包括2种侧链长度的阳离子和3种阴离子. 首先考察了256个离子对组成的体系中溶质分子插入次数对计算结果的影响, 在此基础上计算了不同温度下气体在1-丁基-3-甲基咪唑的四氟化硼盐([bmim][BF₄])和六氟化磷盐([bmim][PF₆])中的溶解度. 计算结果正确反映了CO₂气体溶解度的变化趋势, 在[bmim][BF₄]中溶解度的模拟结果与实验值符合很好, 且明显优于Pádua等的模拟结果；在[bmim][PF₆]中的溶解度较实验值偏高, 精度与文献模拟结果相当；并预测了较高温度下CO₂气体在[bmim][BF₄]和[bmim][PF₆]中的溶解度. 计算结果也正确地反映了5种气体在[bmim][PF₆]中溶解度实验值的相对大小. 另外考察了常温下几种气体在不同室温离子液体中的溶解度, 模拟结果表明气体在含有较长碳链和双-三氟甲基磺酰胺阴离子(Tf₂N^－)的离子液体中溶解度较大.     

Liquid-liquid interfacial tension of equilibrated mixtures of ionic liquids and hydrocarbons

Ionic liquids are possible alternative solvents for the separation of aromatic and aliphatic hydrocarbons by liquid-liquid extrac- tion. Interfacial tension is an important property to consider in the design of liquid-liquid extraction processes. In this work, the liquid-liquid interfacial tension and the mutual solubility at 25 °C have been measured for a series of biphasic, equilibrated mixtures of an ionic liquid and a hydrocarbon. In particular, the ionic liquids 1-alkyl-3-methylimidazolium bis(trifluorome- thanesulfonyl)imide (with the alkyl substituent being ethyl, hexyl or decyl), 1-ethyl-3-methylimidazolium ethylsulfate, and 1-ethyl-3-methylimidazolium methanesulfonate have been selected, as well as the hydrocarbons benzene, hexane, ethylben- zene, and octane. The selected sets of ionic liquids and hydrocarbons allow the analysis of the influence of a series of effects on the interfacial tension. For example, the interfacial tension decreases with an increase in the length of the alkyl substituent chain of the cation or with an increase of the degree of charge delocalisation in the anion of the ionic liquid. Also, the interfa- cial tension with the aromatic hydrocarbons is markedly lower than that with the aliphatic hydrocarbons. A smaller effect is caused by variation of the size of the hydrocarbon. Some of the observed trends can be explained from the mutual solubility of the hydrocarbon and the ionic liquid.     

Magnetic ionic liquids as non-conventional extraction solvents for the determination of polycyclic aromatic hydrocarbons

This work describes the applicability of magnetic ionic liquids (MILs) in the analytical determination of a group of heavy polycyclic aromatic hydrocarbons. Three different MILs, namely, benzyltrioctylammonium bromotrichloroferrate (III) (MIL A), methoxybenzyltrioctylammonium bromotrichloroferrate (III) (MIL B), and 1,12-di(3-benzylbenzimidazolium) dodecane bis[(trifluoromethyl)sulfonyl)]imide bromotrichloroferrate (III) (MIL C), were designed to exhibit hydrophobic properties, and their performance examined in a microextraction method for hydrophobic analytes. The magnet-assisted approach with these MILs was performed in combination with high performance liquid chromatography and fluorescence detection. The study of the extraction performance showed that MIL A was the most suitable solvent for the extraction of polycyclic aromatic hydrocarbons and under optimum conditions the fast extraction step required ∼20 μL of MIL A for 10 mL of aqueous sample, 24 mmol L⁻¹ NaOH, high ionic strength content of NaCl (25% (w/v)), 500 μL of acetone as dispersive solvent, and 5 min of vortex. The desorption step required the aid of an external magnetic field with a strong NdFeB magnet (the separation requires few seconds), two back-extraction steps for polycyclic aromatic hydrocarbons retained in the MIL droplet with n-hexane, evaporation and reconstitution with acetonitrile. The overall method presented limits of detection down to 5 ng L⁻¹, relative recoveries ranging from 91.5 to 119%, and inter-day reproducibility values (expressed as relative standard derivation) lower than 16.4% for a spiked level of 0.4 μg L⁻¹ (n = 9). The method was also applied for the analysis of real samples, including tap water, wastewater, and tea infusion.     

Binary ionic liquid mixtures as gas chromatography stationary phases for improving the separation selectivity of alcohols and aromatic compounds

Binary mixtures of two ionic liquids (ILs), 1-butyl-3-methylimidazolium chloride (BMIM-Cl) and 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide (BMIM-NTf2), have been studied for the first time as gas chromatographic stationary phases. The two ILs differ only in the nature of the associated anion. The solvation parameter model was used to examine the change of solvation interactions with the IL stationary phase composition. The hydrogen bond basicity increased linearly as the stationary phase was enriched with the BMIM-Cl IL. The retention factor of short-chained alcohols increased by as much as 1100% when performing the separation on a column containing an IL mixture of 25% BMIM-NTf2/75% BMIM-Cl compared to that of the neat BMIM-NTf2 IL column. By tuning the composition of the IL-stationary phase, the separation selectivity and resolution factors of alcohols and aromatic compounds were improved. A reversal of elution order was observed for specific classes of analytes with enhancements in the stationary phase hydrogen bond basicity.     

Extraction of rare earth elements with phosphoryl-containing lariat crown ether in the presence of ionic liquids

Interfacial distribution of rare earth elements (REE) La, Ce, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y between aqueous solutions of their nitrates and solutions of the lariat crown ether 1,4,10,13-tetraoxa-7,16-diaza(diphenylphosphinylmethyl)cyclooctadecane in dichloroethane was studied in the presence of the ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate and 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide. The stoichiometry of extracted complexes was determined; the effect of HNO₃ concentration in the aqueous phase and the nature of extractant and ionic liquid on the extraction efficiency of REE(III) was considered.