Low-temperature Ionic Liquid Research Articles

Physicochemical properties of an N-decylpyridinium tetrachloroferrate ionic liquid

A low-temperature ionic liquid N-decylpyridinium tetrachloroferrate was synthesized. The temperature dependences of density and viscosity of the synthesized ionic liquid, as well as its thermal stability and magnetic properties were studied. The response of N-decylpyridinium tetrachloroferrate to magnetic field was visualized, and its structure was calculated at the DFT/B3LYB/6-31G(d,p) level of theory.

Spectroscopic study of solvation processes and ionic association in lithium salt solutions with ionic and aprotic solvents

The Raman spectra of the mixtures containing the low-temperature ionic liquid ethylmethylimidazolinium bis(trifluoromethanesulfonyl)imide (EMIIm), the salt component lithium bis(trifluoromethylesulfonyl)-imide (LiIm), and the aprotic solvent ethylene carbonate (EC) are studied. It is found that the addition of the lithium salt to the ionic liquid results in the formation of ion pairs or more complex cation-anion aggregates. Dilution of these systems with ethylene carbonate leads to the solvation of lithium ions.

Electrospun nanosized cellulose fibers using ionic liquids at room temperature

Aiming at replacing the noxious solvents commonly employed, ionic-liquid-based solvents have been recently explored as novel non-volatile and non-flammable media for the electrospinning of polymers. In this work, nanosized and biodegradable cellulose fibers were obtained by electrospinning at room temperature using a pure ionic liquid or a binary mixture of two selected ionic liquids. The electrospinning of 8 wt% cellulose in 1-ethyl-3-methylimidazolium acetate medium (a low viscosity and room temperature ionic liquid capable of efficiently dissolving cellulose) showed to produce electrospun fibers with average diameters within (470 ± 110) nm. With the goal of tailoring the surface tension of the spinning dope, a surface active ionic liquid was further added in a 0.10 : 0.90 mole fraction ratio. Electrospun cellulose fibers from the binary mixture composed of 1-ethyl-3-methylimidazolium acetate and 1-decyl-3-methylimidazolium chloride ionic liquids presented average diameters within (120 ± 55) nm. Scanning electron microscopy, X-ray diffraction analysis, nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric assays were used as core methods to evaluate the structural integrity, morphology and crystallinity of the raw, electrospun, and regenerated samples of cellulose. Moreover, the photoluminescence spectra of both raw and electrospun fibers were acquired, and compared, indicating that the cellulose emitting centers are not affected by the dissolution of cellulose in ionic liquids. Finally, the use of non-volatile solvents in electrospinning coupled to a water coagulation bath allows the recovery of the ionic fluid, and represents a step forward into the search of environmentally friendly alternatives to the conventional approaches.

Thermophysical properties of ionic liquids: Do we know how to measure them accurately?

Low temperature ionic liquids (LTILs) are innovative fluids for chemical and materials processing, and the recent explosion on their measurement, molecular interpretations and property prediction, allied to the first industrial processes that start to use them as environmentally friendly solvents and reaction fluids, raises a very important point to all the scientific and industrial community, for those that have been involved in the measurement of thermophysical properties of liquids. A careful analysis, assessing its quality, shows that there are discrepancies between data from different laboratories, and sometimes, from samples of different synthesis batches. Therefore a fundamental question must be raised: Do we know enough about the molecular constitution and properties of these fluids, to measure correctly their properties? And if we think we know, which types of care have we to take a priori? It is the purpose of this paper to analyze the main problems in the measurement of some thermophysical properties of RTILs (density, heat capacity; viscosity, thermal conductivity, and electrical conductivity), calling the attention to the uses and misuses of traditional equipment, with or without handling care.

Physical properties of the 1-butyl-3-methylimidazolium bromide—tantalum pentabromide low-temperature ionic liquid

The physicochemical properties (density, glass-transition temperature, viscosity, and specific conductivity) of the 1-butyl-3-methylimidazolium bromide-tantalum pentabromide low-temperature ionic liquid have been studied at concentrations of TaBr5 from 0 to 0.33 mol/kg of BMImBr. The dissolution of tantalum pentabromide in the BMImBr ionic liquid was accompanied by the formation of complex tantalum-containing anions and led to the formation of a highly polymerized structure of the liquid possessing thixo-tropic properties.

Electrochemical properties of the system of Ag—1-butyl-3-methylimidazolium bromide low-temperature ionic liquid—silver bromide

The methods of potentiometry, electrochemical impedance spectroscopy, cyclic voltammetry, and gravimetry were used to study the electrochemical behavior of a silver electrode in low-temperature ionic liquids of BMImBr and BMImBr—AgBr, and also the process of cathodic reduction of Ag(I) compounds out of a BMImBr—AgBr melt. It is shown that an AgBr film is formed on the silver surface and its properties are determined by the ionic liquid composition. It is found that the process of silver electrodeposition from a BMImBr—AgBr binary alloy occurs irreversibly, at a high current efficiency (up to 100%) and a good quality of the deposit at low current densities. At 70°C, the transfer coefficients of the cathodic process (α = 0.56 and 0.16) and diffusion coefficients (D Ag(I) = 0.48 × 10−7 cm2/s and 3.3 × 10−7 cm2/s) of silver-containing ions are determined in ionic liquids with the AgBr concentration of 0.81 and 1.53 mol/kg BMImBr, accordingly.

Electroconductivity of low-temperature ionic liquid 1-butyl-3-methylimidazolium bromide-silver bromide. Effects of AgBr concentration and temperature

The effects of temperature and component ratio to electroconductivity of ionic liquid BMImBr — (1.5 to 1.88 mol %) Ag Br were studied. At 10 mol % AgBr concentration, the properties of ionic liquid were stabilized and the values of specific electroconductivity χ, viscosity-corrected specific electroconductivity χη, and equation coefficients of the temperature curve of χ changed insignificantly. The diffusion coefficient of silver complex ion was calculated: DAg + p = 1.07 × 10−7 cm2s−1.

Low-Temperature Production of Ti-Al Alloys Using Ionic Liquid Electrolytes: Effect of Process Variables on Current Density, Current Efficiency, and Deposit Morphology

Application of novel low-temperature ionic liquid electrolytes for the extraction of Ti-Al alloys was investigated. The study was focused on the production of Ti-Al alloys from AlCl3-1-butyl-3-methyl imidazolium chloride (BmimCl) (molar ratio of AlCl3 and BmimCl is 2:1) at different temperatures between 70 °C and 125 °C ± 3 °C. The Ti-Al alloys were deposited on titanium sheet (>99.9 wt pct) cathodes at various voltages between 1.5 and 3.0 V. Titanium sheet was used as the anode and its dissolution served the source of Ti ion in the electrolyte. Morphology and composition of deposited Ti-Al alloys were investigated using a scanning electron microscope (SEM) with energy-dispersive spectroscopy (EDS) and an inductively coupled plasma–optical emission spectrometer (ICP-OES). The phase analysis was carried out using X-ray diffraction (XRD). This study was focused to determine the effect of process variables such as applied voltage and temperature on cathode current density, current efficiency, composition, and morphology of Ti-Al alloys. The Ti-Al alloys containing about 13 to 25 atom pct Ti were produced with a current efficiency of about 79 to 87 pct. This study shows that uniform and fine particle size with high titanium content Ti-Al alloy was obtained in the voltage range of 1.5 to 2.0 V and temperature between 70 °C to 100 °C.

The physicochemical properties of the low-temperature ionic liquid silver bromide-1-butyl-3-methylimidazolium bromide

The physicochemical properties of the low-temperature ionic liquid based on 1-butyl-3-methylimidazolium bromide (BMImBr) and silver bromide were studied. Differential scanning calorimetry, Fourier transform IR spectroscopy, densimetry, viscometry, and conductometry measurements were performed to determine the dependences of the parameters under study on the concentration of AgBr. It was shown that the temperature and concentration behavior of the physicochemical properties of BMImBr-AgBr melts characterized the interaction between the system components with the formation of complex particles.

Differential Capacitance of the Electrical Double Layer in Imidazolium-Based Ionic Liquids: Influence of Potential, Cation Size, and Temperature

The interfaces formed at glassy carbon electrodes in three low-temperature ionic liquids (1-methyl-3-ethylimidazolium chloride, emimCl; 1-methyl-3-butylimidazolium chloride, bmimCl; and 1-methyl-3-hexylimidazolium chloride, hmimCl) were investigated by cyclic voltammetry and impedance spectroscopy. The potential dependence of the differential double layer capacitance was measured at several temperatures between 80 and 140 °C, and the temperature response was found to be broadly similar to that obtained with high-temperature molten salts. The differential capacitance/potential curves have a minimum and two side branches. The minimum corresponds to the point of zero charge. The differential capacitance increases in the order hmimCl < bmimCl < emimCl because the double layer is thinner when imidazolium (Rmim) cations with shorter alkyl chain lengths are used. The impedance spectra and capacitance curves indicate that cations are adsorbed at the open-circuit potential and that their surface excess concentrati...

Electrochemical activation and dehalogenation of freons in low-temperature ionic liquids

The effect of various factors (the nature of the medium and the electrode material, the electronic structure of the Freons, etc.) on the electrochemical activation and dehalogenation of a series of Freons [F113 (CF2ClCFCl2), F13B1 (CF3Br), F114B2 (CF2BrCF2Br), and F113B2 (CFClBrCF2Br)] in various low-temperature ionic liquids (LTIL) [1-butyl-3-methylimidazolium, 1-butyl-1-methylpyrrolidinium, and trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imides and 1-butyl-3-methylimidazolium hexafluorophosphate, tetrafluoroborate, and trifluoroacetate] at various electrodes (glassy carbon, Pt, Ag) was studied. It was established in particular that the investigated processes are affected substantially by the electrical conductivity and viscosity of the medium. With decrease of the latter the peak potential in the cyclic voltammetry of the electrochemical reduction of the Freons is shifted toward less negative values while the current increases. It was found that a silver cathode has a specific effect on the electrochemical activation of the Freons in the LTILs, and this may be due to the formation of complexes Ag⋯Hal⋯Rf between the Freons and silver atoms on the electrode surface, in which cleavage of the C—Hal bond is facilitated. Such processes are compared with the processes realized in the traditional solvent dimethylformamide.

New ceramic–carbon composites for electrodes for electrochemical capacitors

A new class of composite materials is introduced. Fine powders of silica, titania, Y-modified zirconia, and three types of alumina were pressed and sintered to form porous monoliths with relatively uniform pore structure. Carbon was then deposited in the pores of such monoliths by thermal decomposition of dichloromethane, cyclohexene, and glucose. The structure of the carbon deposit was studied by low-temperature nitrogen adsorption and by thermal analysis. The composite materials were used as electrodes in electrochemical capacitors with 1-ethyl-3-methylimidazolium trifluoromethylsulfonate (a low-temperature ionic liquid) as the electrolyte. High capacitances were observed for glucose-derived materials, which had high specific surface areas.

Efficient and Convenient Procedure for Protection of Hydroxyl Groups to the THP, THF and TMS Ethers and Oxidation of these Ethers to Their Aldehydes or Ketones in [BPy]FeCl4 as a Low Cost Room Temperature Ionic Liquid.

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Efficient and Convenient Procedure for Protection of Hydroxyl Groups to the THP, THF and TMS Ethers and Oxidation of these Ethers to their Aldehydes or Ketones in [BPy]FeCl4 as a Low Cost Room Temperature Ionic Liquid

Abstract Alcohols were converted to the corresponding THP, THF or TMS ethers in high to excellent yields in 1-n-butylpyridinium chloroferrate media as a stable and low cost room temperature ionic liquid. In addition, oxidation of these ethers to their aldehydes or ketones without any overoxidation reactions in this ionic liquid was also performed.

Electroacoustics and electroosmosis in low temperature ionic liquids

The electroacoustic method made it possible to study electrokinetic phenomena at high ionic strengths. Interestingly, the ζ potential does not cease at ionic strengths as high as 3 M in aqueous systems. Here, we show that also in low temperature ionic liquids the electrokinetic phenomena do exist. Dispersions of anatase in 1-alkyl-3-methylimidazolium (alkyl = butyl, hexyl, octyl or decyl) trifluoromethanesulfonates, hexafluorophosphates, and mixed tetrafluoroborate-chloride ionic liquids were studied. These ionic liquids are molten salts at room temperature, and they can be considered as about 3 M salt solutions in the absence of solvent. The electrokinetic potential of anatase determined by means of the electroacoustic method was negative for all ionic liquids studied, although for a few ionic liquids the standard deviation in a series of 20 consecutive measurements was higher than the absolute value. Absorption of moisture by the ionic liquids has rather insignificant effect on the electrokinetic potential of anatase. Electroosmosis in specimens of porous alumina saturated with ionic liquids was studied, and the electrokinetic charge of alumina was also negative.

Low-temperature ionic liquids immobilized in porous alumina

The pores in an aluminum oxide matrix can be completely filled with 1-alkyl-3-methylimidazolium tetrafluoroborates, hexafluorophosphates, triflates, and bis(trifluoromethylsulfonyl)imides. This possibility can be utilized to produce solid electrolytes for batteries and fuel cells.

Electroacoustics in low-temperature ionic liquids

Titanium dioxide was used as a model colloid to demonstrate the possibility of obtaining reliable values of the electrophoretic mobility in low-temperature ionic liquids. Mobilities as low as −0.98±0.16×10−10 and −1.25±0.33×10−10m2V−1s−1 were found in dry and wet 1-butyl-3-methylimidazolium triflate, respectively. These values are lower by two orders of magnitude than typical mobilities in stable aqueous dispersions due to a high viscosity of the ionic liquids.

Electroacoustics in low-temperature ionic liquids

Titanium dioxide was used as a model colloid to demonstrate the possibility of obtaining reliable values of the electrophoretic mobility in low-temperature ionic liquids. Mobilities as low as −0.98±0.16×10 −10 and −1.25±0.33×10 −10 m 2 V −1 s −1 were found in dry and wet 1-butyl-3-methylimidazolium triflate, respectively. These values are lower by two orders of magnitude than typical mobilities in stable aqueous dispersions due to a high viscosity of the ionic liquids.

Review: Current studies on some physical properties of ionic liquids

As a novel substituting solvent for organic solvents, low-temperature ionic liquids have attracted much attention as good media in organic synthesis and other chemical processes. Better understanding of physical properties of ionic liquids are very helpful in exploring reaction mechanisms and controlling reaction outputs. This review summarises current studies on several physical properties (melting point, vapor pressure and stability, polarity, miscibility, density, viscosity) that are important for organic reactions.

Thermal stability of low temperature ionic liquids revisited

The range of thermal stability of low temperature ionic liquids published in the literature (often >400 °C) is severely overrated. The decomposition temperature calculated from fast TGA scans in a protective atmosphere does not imply a long-term thermal stability below that temperature. Even at temperatures as low at 200 °C, 1-alkyl-3-methylimidazolium phosphates (alkyl = C4–C10) and 1-decyl-3-methylimidazolium triflate showed a slow, but appreciable mass loss. On the other hand, 1-butyl-3-methylimidazolium triflate was stable at 200 °C. The carbonization occurred in most studies salts irrespectively of the nature of the anion (hexafluorophosphate, triflate), but the salts with a shorter side chain (C4) did not show changes in their color after conditioning for 10 h at 200 °C in air. 1-Butyl-3-methylimidazolium triflate shows extremely good wettability against aluminum oxide and silver at elevated temperatures. Addition of silica (amorphous or quartz) accelerates the thermal decomposition of 1-alkyl-3-methylimidazolium phosphates and triflates at 200 °C, while the effect of other ceramic powders (titania, alumina) is less significant.