High-pressure solubility of carbon dioxide in imidazolium-based ionic liquids with anions [PF6] and [BF4]

The solubility of carbon dioxide in three ionic liquids (ILs) under supercritical fluid condition was measured at pressures up to 32 MPa and at temperatures of 313.15, 323.15, and 333.15 K in a high-pressure view cell. The imidazolium-derivative ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]), 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]), and 1-octyl-3-methylimidazolium tetrafluoroborate ([omim][BF₄]) were employed in this research. The effects of pressure, temperature, nature of anion and cation as well as the water content on the solubility of CO₂ in the ILs were investigated experimentally. The solubility of CO₂ in the IL was higher for the ILs with longer cationic alkyl group and for the ILs with lower anion polarity. The lower the water content or the lower the temperature as well as the higher the pressure, the higher was the solubility of CO₂.     

Critical properties and acentric factors of ionic liquids

Since most ionic liquids (ILs) decompose before reaching their critical state, the experimental measurement of their critical properties are not possible. In this study, the critical temperatures, critical pressures and acentric factors of ten commonly investigated ILs were determined by making an optimum fit of the calculated vapor-liquid equilibrium data of binary mixtures of CO₂+IL to the experimental values found in literature. For this purpose, the Peng-Robinson equation of state (PR EoS) and the differential evolution optimization method were used. The ILs considered were 1-ethyl-3-methylimidazolium hexafluorophosphate ([emim][PF₆]), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([emim][Tf₂N]), 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]), 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([bmim][Tf₂N]), 1-hexyl-3-methylimidazolium tetrafluoroborate ([hmim][BF₄]), 1-hexyl-3-methylimidazolium hexafluorophosphate ([hmim][PF₆]), 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide ([hmim][Tf₂N]), 1-octyl-3-methylimidazolium tetrafluoroborate ([omim][BF₄]) and 1-octyl-3-methylimidazolium hexafluorophosphate ([omim][PF₆]). To evaluate the ability of the determined parameters in predicting the phase behavior of systems other than the systems that were used for parameter optimization, both sets of parameters obtained in this work and that of Valderrama et al. were used to predict bubble-point pressures of CHF₃+[bmim][PF₆] (by using the PR EoS and the Soave-Redlich-Kwong equation of state. The bubble-point pressures of CO₂+IL systems optimized in this study by the PR EoS were also determined using the Soave-Redlich-Kwong equation of state (SRK EoS). In addition, liquid densities of pure ILs were predicted using a generalized correlation proposed by Valderrama and Abu-Shark. In all cases, the various predicted properties of these ten ILs, were in better agreement with the experimental data, using the critical properties and acentric factor obtained in this study, compared to the values suggested by Valderrama et al.     

Physical and electrochemical properties of 1-butyl-3-methylimidazolium bromide, 1-butyl-3-methylimidazolium iodide,and 1-butyl-3-methylimidazolium tetrafluoroborate

The density, viscosity, refractive index, heat capacity, heat of dilution, ionic conductivity, and electrochemical stability of 1-butyl-3-methylimidazolium bromide ([bmim][Br]), 1-butyl-3-methylimidazolium iodide ([bmim][I]), and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) were measured at room temperature or over a temperature range of 293.2 to 323.2 K. The density and refractive index values of [bmim][I] appeared to be the highest among three ionic liquids (ILs). However, the experimental viscosity values of [bmim][Br] were higher than those of [bmim][BF₄], while the heat capacities and heats of dilution of [bmim][BF₄] were higher than those of [bmim][Br]. The cyclic voltammogram of [bmim][br] and [bmim][BF₄] indicated electrochemical windows in the stability range from 2.7 V of [bmim][[Br] to 4.7 V of [bmim][BF₄].     

Extraction Behavior of Cu(II) Ion From Chloride Medium to the Hydrophobic Ionic Liquids Using 1,10-Phenanthroline

The study of liquid-liquid extraction of Cu(II) ion was carried out by using a series of hydrophobic ionic liquids; 1-butyl-3-methylimidazolium hexafluorophosphate ([C₄mimPF₆]), 1-hexyl-3-methylimidazolium hexafluorophospahate ([C₆mimPF₆]), 1-butyl-3-methylimidazolium bistrifluoromethylsulfonyl imide ([C₄mimNTf₂]) and 1-hexyl-3-methylimidazolium bistrifluoromethylsulfonyl imide ([C₆mimNTf₂]) as extraction phase. Cu(II) prefer to extract into [C₄mimPF₆] which is the less hydrophobic of ionic liquids. The extraction behavior of Cu(II) ion depends on the type of counterion and the extraction of Cu(II) ion in ionic liquid system proceeds via similar mechanism with a molecular organic solvent. From these results, it was proposed that the extraction of Cu complexes from chloride medium proceeds through ion pair mechanism.     

Desulfurization of Diesel Fuel by Extraction with Lewis-Acidic Ionic Liquid

Abstract

Ionic liquids were found to be highly selective for the extractive removal of aromatic sulfur compounds from fuels at room temperature. The efficiency of ionic liquids for the removal of aromatic sulfur compounds is dependent on the properties and structure of the ionic liquids. In this work, the Lewis-acidic ionic liquid 1-butyl-3-methylimidazolium tetrahalogenoferrate(III) ([BMIM] [FeCl₄]) was synthesized and demonstrated to be more effective for the removal of aromatic sulfur compounds from diesel over ionic liquids 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM] [BF₄]) because of its Lewis-acidic property. The ionic liquids favorably extracted organic compounds with a higher density of aromatic π-electrons. [BMIM][FeCl₄] ionic liquid can be regenerated through reextraction by hexane, and could be used in multiple steps for the removal of sulfur compounds from diesel.     

Surface tension and viscosity of 1-butyl-3-methylimidazolium iodide and 1-butyl-3-methylimidazolium tetrafluoroborate, and solubility of lithium bromide+1-butyl-3-methylimidazolium bromide in water

The surface tension and viscosity of 1-butyl-3-methylimidazolium iodide ([bmim][I]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF₄]) were measured over a temperature range of 298. 15 to 323.15 K. It was found that both the viscosity and surface tension decrease with increasing temperature and that the surface tension and viscosity values of [bmim][I] were higher than those of [bmim][BF₄]. Additionally, the solubility of lithium bromide (2)+1-butyl-3-methylimidazolium bromide ([bmim][Br]) (3) in water (1) was measured at three different mass ratios (w₂/w₃=4 and 7, w₃=0) by using a visual polythermal method. The solubility of the suggested systems was better than that of lithium bromide in water.     

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.     

Extraction of dioxouranium(VI) in small channels using ionic liquids

The extraction behaviour of dioxouranium(VI) from nitric acid solutions with tributylphosphate (TBP) dissolved (30%, v/v) in room temperature ionic liquids (viz. 1-butyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide, [C₄mim][NTf₂], 1-decyl-3-methylimidazolium bis{(trifluoromethyl)sulfonyl}amide, [C₁₀mim][NTf₂], and trihexyltetradecylphosphonium bis{(trifluoromethyl)sulfonyl}amide, [P_6 6 6 14][NTf₂]) was investigated. The experiments were performed in a capillary (0.5 mm internal diameter) made of Teflon, operated in the plug flow regime. The effects of ionic liquid type, initial nitric acid concentration, and residence time on dioxouranium(VI) extraction were studied. UV–vis spectroscopy was used for the determination of the dioxouranium(VI) concentration in the ionic liquid phase. For increasing [HNO₃]_aq,init, the %extraction decreased and then increased for [C₄mim][NTf₂], while for the other two ionic liquids it increased. The %extraction also increased with residence time in the channel. Overall mass transfer coefficients were about 0.2 s^–1 in all TBP/ionic liquid systems at the initial nitric acid concentration of 3 M when a 10 cm capillary was used.     

Rhodium complexes containing chiral P-donor ligands as catalysts for asymmetric hydrogenation in non conventional media

Abstract  

Rhodium-catalysed asymmetric hydrogenation using P-donor ligands, such as new fluorinated (R)-BINOL and azadioxaphosphabicyclo[3.3.0]octane derivatives was carried out in different reaction media such as organic solvent (CH₂Cl₂), ionic liquid ([BMI][PF₆]), supercritical carbon dioxide (scCO₂) and [BMI][PF₆]/scCO₂ mixture. The best enantioselectivities were obtained in neat [BMI][PF₆], allowing a recycling up to ten times without activity loss. However, the enantioselectivity was lost due to ligand leaching. The ionic liquid phase containing rhodium molecular species was supported on functionalized multi-walled carbon nanotubes in order to improve the recycling, but unfortunately the asymmetric induction was lost upon catalyst immobilization.     

Efficient recovery of ionic liquid by electrodialysis in the acid hydrolysis process

Electrodialysis (ED) has been recently known as a highly effective technique to remove and recover ionic liquids from aqueous solution. When a conventional electrolyte solution for the ED process containing Na₂SO₄ was used, a recovery ratio of an acidic IL, 1-butyl-3-methylimidazolium hydrogen sulfate ([Bmim][HSO₄]), was 90%. On the other hand, the value clearly increased to 96% when we employed [Bmim][HSO₄] as the electrolyte solution. In an acid hydrolysis of bagasse using the IL under microwave irradiation, the recovery ratio maintains 96%, irrespective of reaction time. This demonstrates the applicability of the proposed ED system in biomass processing.     

CO2 absorption properties of Brønsted acid-base ionic liquid composed of N,N-dimethylformamide and bis(trifluoromethanesulfonyl)amide

The solubilities of CO₂ and the liquid densities in a Brønsted acid-base ionic liquid, [DMFH][Tf₂N], composed of N,N-dimethylformamide (DMF) and bis(trifluoromethanesulfonyl)amide (HTf₂N) have been investigated at high pressures and at different temperatures. The results were compared with those in DMF and a typical 1-butyl-3-methylimidazolium analogue with the same anion, [BMIM][Tf₂N]. The mole fraction scaled solubilities of CO₂ in the three liquids showed a slight increase in the following order, DMF < [DMFH][Tf₂N] < [BMIM][Tf₂N], whereas more remarkable difference was observed in the volume scaled concentrations of CO₂, [BMIM][Tf₂N] < [DMFH][Tf₂N] « DMF, mainly due to the bulkiness of liquid entities.     

1-丁基-3-甲基咪唑表面活性离子液体的界面膨胀流变行为研究

研究了1-丁基-3-甲基咪唑十二烷基硫酸盐([bmim][DS])和1-丁基-3-甲基咪唑二(2-乙基己基)磺基琥珀酸酯盐([bmin][AOT]两种表面活性离子液体在正庚烷/水界面的动态界面张力和膨胀特性。比较了[bmim][DS]或[bmin][AOT]和传统表面活性剂十二烷基硫酸钠(SDS)或二(2-乙基己基)磺基琥珀酸酯钠(Na[AOT])之间的膨胀弹性,并且考察了1-丁基-3-甲基咪唑阳离子之间静电相互作用对界面膜特性的影响。另外,通过对比[bmim][DS]和[bmim][AOT]在不同浓度下的膨胀弹性,验证了烷基链数量的改变对界面膨胀流变行为的影响。     

Electrochemical behavior of glassy carbon electrodes modified by multi-walled carbon nanotube/surfactant films in a buffer solution and an ionic liquid

The electrochemical behavior of glassy carbon (GC) electrodes coated with multi-walled carbon nanotube (MWCNT)/surfactant films was studied in an ionic liquid and a phosphate buffer solution (pH = 6.86), using cyclic voltammetry. The dispersion of MWCNTs in different media was investigated by scanning and transmission electron microscopy. Cast films of MWCNT/zwitterionic dodecyldimethylamine oxide on a GC electrode show a typical redox couple in phosphate buffer solution, which is better than that of MWCNT/anionic sodium dodecyl sulfate and cationic alkyltrimethylammonium bromide. However in the ionic liquid, 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]), the GC electrode modified by MWCNT/cationic surfactant films shows a well-defined irreversible reduction of MWCNTs. The cyclic voltammograms clearly show that the surfactant hydrophilic group plays an important role in the electrochemical behavior of the MWCNTs. The electrolytes also have an important effect. In an ionic liquid, the strong binding of the ionic liquid cations with the MWCNTs may change the structure of the modified films and lead to changes of electrochemical behavior.     

Desulfurization of Real Fuel Oils by Extraction with Ionic Liquids

Aromatic 1-butyl-3-methylimidazolium dicyanamide ([C₄mim][N(CN)₂]) and 1-ethyl-3-methylimidazolium dicyanamide ([C₂mim][N(CN)₂]) ionic liquids are tested for their performance in the extractive desulfurization of real FCC gasoline and diesel fuel. [C₄mim][N(CN)₂] has proven to be more effective than [C₂mim][N(CN)₂] in removing sulfur from fuels and was thus selected to undergo a series of further tests. A competitive desulfurization efficiency of nearly 40% and 30% was realized with [C₄mim][N(CN)₂] for diesel fuel and gasoline, respectively, in a single extraction at <1 h, 25°C, and 1:1(w/w)IL:fuel. The influence of IL:fuel mass ratio, temperature, and multiple extractions on S-extraction efficiency is investigated, and the result tends to favor large-scale industrial application. This high efficiency obtained at low temperature, together with the insensitivity of the Nernst partition coefficient on desulfurization efficiency, is industrially favorable because not much energy and cost are required. The influence of mass ratios is not obvious, but to some degree, the Nernst partition coefficients depend on the mass ratio, suggesting that this extraction is not a completely physically-determined extraction. This work offers a significant contribution to the production of clean oils by extraction with ionic liquids.     

Electrochemical behavior of C60 films and C60/lipid films in ionic liquids

Cyclic voltammograms (CVs) of C₆₀ films and C₆₀ embedded in cast films of triple-tailed cationic surfactant solutions and salt-free zero-charged cationic/anionic (catanionic) surfactant vesicles on glassy carbon electrode in a typical room-temperature ionic liquid (RT-IL), 1-n-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]), were examined. CVs show typically electrochemical oxidation and reduction. The salt-free zero-charged catanionic surfactant bilayer vesicles were determined by freeze-fracture transmission electron microscopy (FF-TEM) images and small-angle X-ray scattering (SAXS) measurements. The cast films of the salt-free zero-charged catanionic surfactant vesicles incorporated C₆₀ molecules were employed to study the electrochemical properties in RT-ILs, which would open new fields for the bulk electronic properties of fullerenes or their derivatives in ionic liquids.     

Reverse atom transfer radical polymerization of methyl methacrylate in imidazolium ionic liquids

Reverse atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) employing 2,2-azobisisobutyronitrile (AIBN)/CuCl₂/bipyridine(bipy) as the initiating system was approached at 80 °C in two ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate ([C₄mim][BF₄]) and 1-dodecyl-3-methylimidazolium tetrafluoroborate ([C₁₂mim][BF₄]), respectively. The polymerization in [C₁₂mim][BF₄] proceeded in a well-controlled manner as evidenced by kinetic studies, end group analysis, chain extension, and block copolymerization results, but not in [C₄mim][BF₄] presumably due to poor solubility of PMMA in it. The kinetic study of reverse ATRP of MMA in recycled [C₁₂mim][BF₄] suggested that this ionic liquid could be re-used as reaction solvent after simple purification, without affecting the living nature of polymerization.     

Polymer electrolytes based on poly(ethylene glycol) dimethyl ether and the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate: Preparation, physico-chemical characterization, and theoretical study

Polymer electrolytes based on poly(ethylene glycol) dimethyl ether (PEGdME) and the ionic liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF₆) have been prepared and characterized by different techniques. Coordination of the IL by the polymer occurs mainly in the amorphous phase. This finding was correlated with previous theoretical investigations of a similar model for polymer electrolytes based on poly(ethylene oxide), PEO, and IL. It has been obtained ionic conductivity σ ∼ 10⁻³ S cm⁻¹ for the polymer electrolyte with 35 wt% of IL at 100 °C. The same order of magnitude for σ was obtained by molecular dynamics simulation of PEO/IL. This work demonstrates consistency between experimental and theoretical results for polymer electrolytes containing ionic liquids.     

疏水性离子液体用于萃取酚类物质

测定了苯酚、苯基酚、苯二酚等几种不同取代基的酚类物质在疏水性离子液体[bmim]PF6(1-丁基-3-甲基咪唑六氟磷酸盐)和[dmim]PF6(1-癸基-3-甲基咪唑六氟磷酸盐)与水两相中的分配系数. 实验结果表明,萃取过程很快可以达到平衡. 与传统有机溶剂相比,分配系数处在同一个数量级. 分配系数随温度升高而降低,离子液体对不同取代基的酚类萃取能力有很大差异,咪唑基团上取代烷基链的长度对不同酚类物质的分配系数有很大影响,因此可以通过调节离子液体结构使其适用于不同成分的含酚废水.     

Electropolymerization of benzotriazole in room temperature ionic liquid [bmim]PF<Subscript>6</Subscript>

The electropolymerization of benzotriazole on an Au electrode was investigated via cyclic voltammetry and chronoamperometry in a room temperature ionic liquid medium, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim]PF₆) containing glacial acetic acid. The chronoamperometric investigation revealed that the instantaneous nucleation predominated the potentiostatic electropolymerization of benzotriazole at the oxidation peak potential. Scanning electron microscopy indicated that the polymer film was compact and relatively smooth and infrared spectroscopy suggested the polymer chains were formed mainly via coupling of the unsaturated nitrogen atoms. The polymer was found to be highly electroactive, showing a quasi-reversible and stable pair of redox peaks centering at 0.9 V versus Ag/AgCl in 0.1 mol L⁻¹ H₂SO₄.     

Room temperature ionic liquids in electrosynthesis and spectroelectrochemical characterization of poly(para-phenylene)

Room temperature ionic liquids (RTILs) were used in electrochemical polymerization and in doping studies (oxidation and reduction) of poly(para-phenylene) (PPP). Cyclic voltammetry was used simultaneously with Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy. Electropolymerization and doping of PPP were done by potential scanning in acetonitrile (ACN + 0.1 M TBAPF₆), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF₆]) and butylmethylpyrrolidinium bis (trifluoromethylsulfonyl) imide ([BMP][Tf₂N]). The cyclic voltammograms recorded during polymerization of the PPP film indicate that the best film growth was achieved in [BMIM][PF₆]. The films made in [BMP][Tf₂N] were more stable than films made in ACN (0.1 M TBAPF₆). Results from p-doping studies show that doping can be made at higher potentials in RTILs than in ACN (0.1 M TBAPF₆). It was also found that n-doping can be performed in RTILs at higher negative potentials (−2.2 V) than in ACN (0.1 M TBAPF₆) (−1.8 V). The best n-doping response was achieved in [BMP][Tf₂N]. Also, n-doping in [BMIM][PF₆] was better than in ACN (0.1 M TBAPF₆). The in situ ATR-FTIR spectroscopy was used to study p- and n-doping of PPP films. During both p- and n-doping the spectra indicated formation of infrared active vibration bands (IRAV) in the wavenumber region 1600-800 cm⁻¹. The obtained IRAV bands correlate to the theoretical modes calculated by Zerbi and co-workers according to the effective conjugation coordinate theory (ECC). All these results indicate that RTILs are good solvents in spectroscopic and electrochemical studies of conducting polymers.