Determination and modelling of osmotic coefficients and vapour pressures of binary systems 1- and 2-propanol with CnMimNTf2 ionic liquids (n = 2, 3, and 4) at T = 323.15 K

The osmotic and activity coefficients and vapour pressures of binary mixtures containing 1-propanol, or 2-propanol and imidazolium-based ionic liquids with bis(trifluoromethylsulfonyl)imide as anion (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, C₂MimNTf₂, 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide, C₃MimNTf₂, and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, C₄MimNTf₂) were determined at T = 323.15 K using the vapour pressure osmometry technique. The experimental osmotic coefficients were correlated using the extended Pitzer model modified by Archer and the MNRTL model, obtaining standard deviations lower than 0.033 and 0.064, respectively. The mean molal activity coefficients and the excess Gibbs free energy for the mixtures studied were calculated from the parameters of the extended Pitzer model modified by Archer. Besides the effect of the alkyl-chain of the cation, the effect of the anion can be assessed comparing the experimental results with those previously obtained for imidazolium ionic liquids with sulphate anions.     

Densities and refractive indices of imidazolium- and phosphonium-based ionic liquids: Effect of temperature,alkyl chain length,and anion

A systematic study of densities and refractive indices of 17 room temperature ionic liquids is presented at four different temperatures ranging from 293 K to 333 K. The ionic liquids are grouped into four families: 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide, [C_nmim][Ntf₂], ionic liquids (with n = 2, 4, 6, 8, 10, 12, and 14); 1-alkyl-3-methylimidazolium hexafluorophosphate, [C_nmim][PF₆], ionic liquids (with n = 4, 6, 8); ionic liquids based on the trihexyl(tetradecyl)phosphonium cation, [P_{6 6 6 14}], combined with the anions bis(trifluoromethylsulfonyl)amide, [Ntf₂], acetate, [OAc], and triflate, [OTf]; and [C₄mim]-based ionic liquids combined with the anions [OAc], [OTf], methylsulfate [MeSO₄], and tetrafluoroborate [BF₄]. The data obtained were analysed to determine the effect of (i) temperature, (ii) the alkyl chain length of the 1-alkyl-3-methylimidazolium cation, and (iii) the nature of the anion. Different empirical models for the calculation of the densities of the ionic liquids were tested. Molar refractions were also calculated from the volumetric and refractive index data and the values were discussed with the aim of checking their utility in obtaining insights on the intermolecular forces and behaviour in solution of the different ionic liquids.     

Physical and electrochemical properties of low-viscosity phosphonium ionic liquids as potential electrolytes

A new group of room temperature ionic liquids based on triethylalkylphosphonium cations together with a bis(trifluoromethylsulfonyl)imide anion as a novel electrolyte is presented in this report. It was found that phosphonium ionic liquids showed lower viscosities and higher conductivities than those of the corresponding ammonium ionic liquids. Particularly, phosphonium ionic liquids containing a methoxy group, triethyl(methoxymethyl)phosphonium bis(trifluoromethylsulfonyl)imide and triethyl(2-methoxyethyl)phosphonium bis(trifluoromethylsulfonyl)imide, exhibited quite low viscosities (35 and 44 mPa s at 25 °C, respectively). Linear sweep voltammetry measured in neat phosphonium ionic liquids at a glassy carbon electrode indicated wide potential windows (at least −3.0 to +2.3 V vs. Fc/Fc⁺). Thermogravimetric analysis suggested that phosphonium ionic liquids were thermally stable up to nearly 400 °C, showing slower gravimetric decreases at high temperature compared to those of the corresponding ammonium ionic liquids.     

Characterization of SEI layer formed on high performance Si–Cu anode in ionic liquid battery electrolyte

Formation of the SEI layer on Si–Cu film electrode in the ionic liquid electrolyte of 1 M lithium bis(trifluoromethylsulfonyl)imide/1-methyl-1-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide (LiTFSI/MPP-TFSI) was investigated using ex-situ ATR FTIR and X-ray photoelectron spectroscopy. The SEI layer is found to be composed of organic and inorganic compounds that are the decomposition products of MPP cation and TFSI anion, and effectively passivate the electrode surface during initial cycling. Formation of a stable SEI layer leads to an excellent capacity retention 98% of the maximum discharge capacity, delivering discharge capacities of > 1620 mAhg^? 1 over 200 cycles. The data contribute to a basic understanding of SEI formation and composition responsible for the cycling performance of Si-based alloy anodes in ionic liquid electrolyte-based rechargeable lithium batteries.     

Electrochemical formation of a cesium–tin alloy in an amide-type ionic liquid

Electrochemical formation of cesium–tin alloys in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) containing 0.5 M CsTFSA has been studied. Cathodic decomposition of BMPTFSA on a platinum electrode was suppressed by addition of CsTFSA, suggesting that Cs⁺ accumulated on the electrode surface and hindered the reduction of BMPTFSA. Multiple cathodic current peaks were observed on a tin electrode in the ionic liquid. Energy-dispersive X-ray analysis and X-ray diffraction results suggested formation of cesium–tin alloys after potentiostatic cathodic reduction on the tin electrode at room temperature.     

1-Alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids as solvents in the separation of azeotropic mixtures

(Liquid + liquid) equilibrium data for the ionic liquids 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMim][NTf₂], 1-propyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [PMim][NTf₂], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [BMim][NTf₂], and 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [HMim][NTf₂], mixed with ethanol and heptane were studied at T = 298.15 K and atmospheric pressure. The ability of these ionic liquids as solvents for the extraction of ethanol from heptane was evaluated in terms of selectivity and solute distribution ratio. Moreover, density and refractive index values over the miscible region for the ternary mixtures were also measured at T = 313.15 K. Finally, the experimental data were correlated with the Non Random Two Liquids (NRTL) and UNIversal QUAsi Chemical (UNIQUAC) thermodynamic models, and an exhaustive comparison with available literature data of the studied systems was carried out.     

An SFG/DFG investigation of CN− adsorption at an Au electrode in 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl) amide ionic liquid

In this paper we report an SFG/DFG investigation of the adsorption of CN^? – used as a probe molecule to study the electrochemical double-layer structure – at a polycrystalline Au electrode in 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl) amide ([BMP][TFSA]) room-temperature ionic liquid (RTIL). The adsorption of CN^? yielded single SFG and DFG bands in the range from ca. 2125 to 2135 cm^?1, exhibiting a Stark tuning of ca. 3 cm^?1 V^?1. Vibrational resonances – corresponding to modes of the RTIL coadsorbed with CN^?, were found in the range from ca. 1200 to 1500 cm^?1. The study of the double-layer structure was complemented by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements, from which the differential double-layer capacity (C_DL) was estimated.     

Solubility of erythromycin in ionic liquids

(Solid + liquid) and (liquid + liquid) phase equilibria of binary mixtures containing various ionic liquid and erythromycin were studied. The solubility of erythromycin in 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, or 1-decyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, or trihexiltertadecilphosphonium chloride, or butyltrimethylammonium bis(trifluoromethylsulfonyl)imide, or methyltrioctylammonium bis(trifluoromethylsulfonyl)imide, or 1-butyl-1-methyl-pyrrolidinium bis(trifluoromethylsulfonyl)imide has been measured by a dynamic method, in a wide range of temperatures from (284 to 358) K, at atmospheric pressure. The activity coefficients of erythromycin in ionic liquids were calculated and their comparison with ideal solution was discussed. The experimental data were correlated successfully by means of the semi-empirical Grant equation.     

Liquid–liquid miscibility and volumetric properties of aqueous solutions of ionic liquids as a function of temperature

The volumetric properties of seven {water + ionic liquid} binary mixtures have been studied as a function of temperature from (293 to 343) K. The phase behaviour of the systems was first investigated using a nephelometric method and excess molar volumes were calculated from densities measured using an Anton Paar densimeter and fitted using a Redlich–Kister type equation. Two ionic liquids fully miscible with water (1-butyl-3-methylimidazolium tetrafluoroborate ([C₁C₄Im][BF₄]) and 1-ethyl-3-methylimidazolium ethylsulfate ([C₁C₂Im][EtSO₄])) and five ionic liquids only partially miscible with water (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C₁C₂Im][NTf₂]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C₁C₄Im][NTf₂]), 1-butyl-3-methylimidazolium hexafluorophosphate ([C₁C₄Im][PF₆]), 1-butyl-3-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C₁C₄Pyrro][NTf₂]), and butyltrimethylammonium bis(trifluoromethylsulfonyl)imide ([N₄₁₁₁][NTf₂])) were chosen. Small excess volumes (less than 0.5 cm³ · mol^?1 at 298 K) are obtained compared with the molar volumes of the pure components (less than 0.3% of the molar volume of the pure ionic liquid). For all the considered systems, except for {[C₁C₂Im][EtSO₄] + water}, positive excess molar volumes were calculated. Finally, an increase of the non-ideality character is observed for all the systems as temperature increases.     

High-pressure phase equilibria of {carbon dioxide (CO2) + n-alkyl-imidazolium bis(trifluoromethylsulfonyl)amide} ionic liquids

Ionic liquids (ILs) and carbon dioxide (CO₂) systems have unique phase behavior that has been applied to applications in reactions, extractions, materials, etc. Detailed phase equilibria and modeling are highly desired for their further development. In this work, the (vapor + liquid) equilibrium, (vapor + liquid + liquid) equilibrium, and (liquid + liquid) equilibrium of n-alkyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)amide ionic liquids with CO₂ were measured at temperatures of (298.15, 323.15, 343.15) K and pressure up to 25 MPa. With a constant anion of bis(trifluoromethylsulfonyl)amide, the n-alkyl chain length on the cation was varied from 1-ethyl-3-methyl-imidazolium ([EMIm][Tf₂N]), 1-hexyl-3-methyl-imidazolium ([HMIm][Tf₂N]), to 1-decyl-3-methyl-imidazolium ([DMIm][Tf₂N]). The effects of the cation on the phase behavior and CO₂ solubility were investigated. The longer alkyl chain lengths increase the CO₂ solubility. The Peng–Robinson equation of state with van der Waals 2-parameter mixing rule with estimated IL critical properties were used to model and correlate the experimental data. The models correlate the (vapor + liquid) equilibrium and (liquid + liquid) equilibrium very well. However, extrapolation of the model to much higher pressures (>30 MPa) can results in the prediction of a mixture critical point which, as of yet, has not been found in the literature.     

Cation effect of ammonium imide based ionic liquids in alcohols extraction from alcohol-alkane azeotropic mixtures

During recent last years, outstanding properties of ionic liquids such as low melting point, large liquid range and negligible volatility have turned them into possible volatile organic solvents replacers to break alcohol-alkane azeotropic mixtures. On this basis, two ionic liquids, butyltrimethylammoniumbis(trifluoromethylsulfonyl)imide, [BTMA][NTf₂], and tributylmethylammoniumbis(trifluoromethylsulfonyl)imide, [TBMA][NTf₂], were studied through ternary liquid+liquid equilibrium (LLE) of {alkane(1) + alcohol (2) + IL(3)} at T = 298.15 K and atmospheric pressure in order to consider the effect of ionic liquid cation alkyl chain length on the extraction process.The ILs capability as azeotrope breakers was determined by the calculation of parameters such as solute distribution ratio, β, and selectivity, S and this capability was compared with other bis (trifluoromethylsulfonyl)imide based ionic liquids from literature. The consistency of tie-line data was ascertained by applying the Othmer–Tobias and Hand equations. Finally, the experimental LLE were correlated by the Non Random Two Liquid (NRTL) thermodynamic model.     

Ethanol extraction from its azeotropic mixture with hexane employing different ionic liquids as solvents

In this work, the ionic liquids 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [EMim][NTf₂], 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [BMim][NTf₂], 1-butyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide, [BMpy][NTf₂], 1-butyl-3-methylpyridinium trifluoromethanesulfonate, [BMpy][TfO], have been investigated for their use as solvents in extraction processes for the ethanol removal from its azeotropic mixture with hexane. Therefore, the experimental determination of the liquid + liquid equilibrium for the ternary systems {hexane (1) + ethanol (2) + [EMim][NTf₂] (3)}, {hexane (1) + ethanol (2) + [BMim][NTf₂] (3)}, {hexane (1) + ethanol (2) + [BMpy][NTf₂] (3)} and {hexane (1) + ethanol (2) + [BMpy][TfO] (3)} was carried out at T = 298.15 K and atmospheric pressure. Classical parameters such as selectivity and solute distribution ratio, derived from the tie-line data, were calculated and afterwards, the structural influence of the ionic liquids on the extraction process was analyzed. Finally, the experimental LLE data were correlated by means of the NRTL and UNIQUAC models.     

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.     

Hydrogen gas yields in irradiated room-temperature ionic liquids

Yields of H₂ produced by electron beam irradiation were investigated in a series of room-temperature ionic liquids comprising 1-hexyl-3-methylimidazolium, 1-hexyl-4-(dimethylamino)pyridinium, 1-butyl-1-methylpyrrolidinium, triethylammonium or trioctyl(tetradecyl)phosphonium cations associated with bis(trifluoromethylsulfonyl)imide anion. The G(H₂) values ranged from 2.6×10⁻⁸ mol/J for the imidazolium and pyridinium-based ionic liquids to 2.5×10⁻⁷ mol/J for the phosphonium liquid. These results correlate well with yields of gaseous hydrogen in studies of nonionic aliphatic and aromatic organic compounds.     

Additive free electrodeposition of nanocrystalline aluminium in a water and air stable ionic liquid

This paper shows for the first time that nanocrystalline aluminium can be electrodeposited without any additives in the ionic liquid 1-butyl-1-methyl pyrrolidinium bis(trifluoromethylsulfonyl)imide saturated with AlCl₃. The advantages of this ionic liquid compared to chloroaluminate ionic liquids, which were intensively investigated in the past, are that it is water and air stable, easy to purify as well as it is easy to dry to water contents below 1 ppm. Interestingly, this ionic liquid shows biphasic behaviour above a concentration of AlCl₃ of 1.6 mol/L. A significant current loop attributed to nucleation was found for bulk deposition of aluminium at room temperature on gold, whereas at 100 °C there is no nucleation loop. The deposits obtained are generally uniform, dense, shining and adherent to the substrate with crystallites in the nanosize regime. At 100 °C, the quality of the deposit is even better with an average size of the crystallites of 34 nm.     

Catalytic Friedel–Crafts allylation using Zn(II) triflimidate

The activity of various metallic triflates and triflimidates in the Friedel–Crafts allylation of activated aromatic rings was examined. Zinc bis(trifluoromethylsulfonyl)amide was proved to be a good catalyst in the model reaction with anisole and prenyl acetate. The Friedel–Crafts allylation reaction of various aryl derivatives with allyl acetates was efficiently catalysed under mild conditions, using 3 mol% of Zn(NTf₂)₂ as the catalyst, without solvent, at 100 °C. The desired ortho and para mono-allylated products were selectively obtained in good yields. The para isomer was always favoured.     

Effect of the pressure on the viscosities of ionic liquids: Experimental values for 1-ethyl-3-methylimidazolium ethylsulfate and two bis(trifluoromethyl-sulfonyl)imide salts

A new falling-body viscometer has been implemented to measure viscosity of liquids in a temperature range from (313.15 to 363.15) K at pressures up to 150 MPa. The accuracy of the viscometer was verified after comparing experimental results of squalane with previous literature data finding an average absolute deviation lower than 1.5%. With this device, we have measured viscosity values for three ionic liquids: 1-ethyl-3-methylimidazolium ethylsulfate, 1-butyl-1-methylpyrrolidinium bis(trifluoro-methylsulfonyl)imide and 1-(2-methoxyethyl)-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide within the temperature and pressure ranges noted above. The experimental values were correlated as a function of temperature and pressure with four different equations. In addition, we have analysed the pressure–viscosity derived properties for these fluids and for other five ionic liquids using literature values.     

Effect of the temperature on the physical properties of pure 1-propyl 3-methylimidazolium bis(trifluoromethylsulfonyl)imide and characterization of its binary mixtures with alcohols

In this paper, physical properties of a high purity sample of the ionic liquid 1-propyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [PMim][NTf₂], and its binary mixtures with methanol, ethanol, 1-propanol, and 2-propanol were measured at atmospheric pressure. The temperature dependence of density, refractive index and speed of sound (293.15 to 343.15) K and dynamic viscosity (298.15 to 343.15) K were studied at atmospheric pressure by conventional techniques for the pure ionic liquid. For its mixtures with alcohols, density, speed of sound, and refractive index were measured at T = 298.15 K over the whole composition range. The thermal expansion coefficient of the [PMim][NTf₂] was calculated from the experimental results using an empirical equation, and values of the excess molar volume, excess refractive index, and excess molar isentropic compressibility for the binary systems at the above mentioned temperature, were calculated and fitted to the Redlich–Kister equation. The heat capacity of the pure ionic liquid at T = 298.15 K was determined using DSC.     

(Liquid + liquid) equilibrium for the ternary systems {heptane + toluene + 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide} and {heptane + toluene + 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide} ionic liquids

The (liquid + liquid) equilibrium (LLE) data for two systems containing heptane, toluene, and 1-methyl-3-propylimidazolium bis(trifluoromethylsulfonyl)imide ([mpim][Tf₂N]) or 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([amim][Tf₂N]) ionic liquids (ILs) were determined at T = 313.2 K and atmospheric pressure. The effect of a double bond in an alkyl side chain in the imidazolium cation was evaluated in terms of selectivity and extractive capacity. The results show a decrease of the amount of toluene and heptane dissolved in the IL with the allyl group. Thus, the distribution ratios of toluene and heptane of [mpim][Tf₂N] IL are higher than those of [amim][Tf₂N] IL. On the other hand, the separation factor of the [amim][Tf₂N] IL increases comparing to [mpim][Tf₂N] IL. The NRTL model was used to correlate satisfactorily the experimental LLE data for the two studied ternary systems.     

Electrical,optical and photoelectrochemical studies on a solid PEO-polymer electrolyte doped with low viscosity ionic liquid

Solid polymer electrolyte (PEO:KI:I₂) membranes doped with low viscosity (34 cP at 25 °C) ionic liquid EMImTFSI (1-ethyl 3-methylimidazolium bis(trifluoromethylsulfonyl)imide) showing plasticizing effect as well as improved dye sensitized solar cell efficiency have been reported first time. Apart from ionic conductivity enhancement due to large number of free charge carriers provided by ionic liquid (IL) it assist in reducing cystallinity of polymer electrolyte matrix which was confirmed by polarized optical microscopy (POM). Cyclic voltammetry was carried out to study the reactions of iodide, iodine and IL in polymer electrolyte matrix.