Physical and electrochemical properties of lithium-doped 1-butyl-3-methylimidazolium salts

Two well known room temperature ionic liquids (RTILs), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF₄]) and 1-butyl-3-methylimidazolium iodide ([BMIm][I]), were synthesized. Their physical properties such as reflective indices, densities, viscosities, heat capacities, and heats of dilution were measured. The overall properties of [BMIm][BF₄] obtained after two-step reactions were superior to those of the IL with a halide anion. The incorporation of lithium ions using lithium tetrafluoroborate (LiBF₄) in each IL was carried out and ionic conductivities as a function of temperature and Li ion concentration were investigated. The isothermal conductivity graph showed a parabolic curve shape suggesting that the maximum values exist at a specific concentration condition while they continuously increased as the temperature increased. The conductivities reached as high as 10⁻³ S·cm⁻¹.     

Electrochemical nucleation from molten salts—I. Diffusion controlled electrodeposition of silver from alkali molten nitrates

The electrodeposition of silver on platinum from solutions in the molten nitrate eutectic NaNO₃—KNO₃ has been studied using chronopotentiometry, cyclic voltammetry and the potential step technique. In each case, the early stages of metal deposition are shown to be controlled by a nucleation process. Similar results were also obtained from studies of electrodeposition from aqueous solution, ie of silver on platinum and graphite and of mercury on graphite. Unless allowance is made for the effects of nucleation, anomalous diffusion coefficients will be obtained. The potentiostatic growth transients are in accord with a process of instantaneous nucleation and subsequent hemispherical growth, although the observed concentration dependence is at variance with that predicted by existing theories.     

ARGET ATRP of acrylonitrile with ionic liquid as reaction medium and FeBr3/isophthalic acid as catalyst system

Atom transfer radical polymerization using activators regenerated by electron transfer (ARGET ATRP) of acrylonitrile with FeBr₃ and isophthalic acid (IA) as catalyst and ligand, ascorbic acid (VC) as reducing agent, and ethyl 2‐bromoisobutyrate as initiator was approached for the first time in the presence of air in 1‐dodecyl‐3‐methylimidazolium tetrafluoroborate ([C₁₂mim][BF₄]), 1‐octyl‐3‐methylimidazolium tetrafluoroborate ([C₈mim][BF₄]), and 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([C₄mim][BF₄]). The rate of polymerization in [C₁₂mim][BF₄] was considerably faster than in [C₈mim][BF₄] and [C₄mim][BF₄]. With an increase of VC concentration, both the monomer conversion and the molecular weight distribution showed a trend of increase. Polyacrylonitrile (PAN) with higher molecular weight at 166,250 and broader distribution at 1.34 was successfully prepared with PAN as macroinitiator via ARGET ATRP in [C₁₂mim][BF₄] in the presence of air. The resultant polyacrylonitrile fibers were obtained with the fineness at 1.15 dtex and the tenacity at 6.24 cN dtex^?1. Additionally, it was shown that [C₁₂mim][BF₄] could be recycled and reused after simple purification and had no effect on the living nature of polymerization. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

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.     

Fabrication of silver nanoparticles via self-regulated reduction by 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate

Silver nanoparticles exhibiting antimicrobial properties via self-regulated reduction were successfully prepared by using hydroxylated ionic liquids in an aqueous phase without additives. A new water-phase synthesis of silver nanoparticles using 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate ([HEMIm][BF₄]) and 1-(2′-hydroxyethyl)-2-methyl-3-dodecylimidazolium chloride ([C₁₂HEMIm][Cl]) was described. 1-(2-hydroxyethyl)-3-methylimidazolium tetrafluoroborate serves as both a reductant and a stabilizer in this fabrication. Furthermore, we presented the antimicrobial properties of the resulting silver nanoparticles through the minimal inhibitory concentrations (MIC) test.     

Ionic liquid effects on the reaction of β-enaminones and tert-butylhydrazine and applications for the synthesis of pyrazoles

In order to evaluate the effect of a series of 10 different ionic liquids ([BMIM][BF₄], [BMIM][Br], [OMIM][BF₄], [BMIM][PF₆], [DBMIM][Br], [DBMIM][BF₄], [BMIM][OH], [BMIM][SCN], [HMIM][HSO₄] and [HMIM][CF₃CO₂]) the cyclocondensation reaction between 4-dimethylamino-1-phenyl-3-alken-2-ones (RC(O)CHCHNMe₂, where R = Ph, 4-Me-Ph, 4-F-Ph, 4-Cl-Ph, 4-Br-Ph, 4-NO₂-Ph, thien-2-yl, fur-2-yl, pyrrol-2-yl, pyrid-2-yl, hexyl, dimethoxymethyl) and tert-butylhydrazine was performed. The effects of each ionic liquid are discussed and the best yields for the cyclocondensation reaction studied were obtained using [BMIM][BF₄].     

Ionic liquid effects on the reaction of β-enaminones and tert-butylhydrazine and applications for the synthesis of pyrazoles

In order to evaluate the effect of a series of 10 different ionic liquids ([BMIM][BF₄], [BMIM][Br], [OMIM][BF₄], [BMIM][PF₆], [DBMIM][Br], [DBMIM][BF₄], [BMIM][OH], [BMIM][SCN], [HMIM][HSO₄] and [HMIM][CF₃CO₂]) the cyclocondensation reaction between 4-dimethylamino-1-phenyl-3-alken-2-ones (RC(O)CHCHNMe₂, where R = Ph, 4-Me-Ph, 4-F-Ph, 4-Cl-Ph, 4-Br-Ph, 4-NO₂-Ph, thien-2-yl, fur-2-yl, pyrrol-2-yl, pyrid-2-yl, hexyl, dimethoxymethyl) and tert-butylhydrazine was performed. The effects of each ionic liquid are discussed and the best yields for the cyclocondensation reaction studied were obtained using [BMIM][BF₄].     

4,4-Bipyridinium ionic liquids exhibiting excellent solubility for metal salts: Potential solvents for electrodeposition

Newly synthesised 4,4-bipyridinium based ionic liquids exhibit good metal coordinating abilities and are able to dissolve metal salts at high concentrations. The ability to capture metal salts into the ionic liquid media facilitates the application of ionic liquids in many areas such as metal extraction or electrochemistry. The ionic liquid n-butyl-4,4-bipyridinium bis(trifluoromethyl)sulfonylamide ([C₄Bipyr][Tf₂N]) exhibits a large liquidus range and a wide electrochemical window. The successful electrodeposition of Cu (II) to Cu (0) from a solution of Cu(NO₃)₂ in [C₄Bipyr][Tf₂N] shows the potential of this new type of ionic liquids for electrodeposition.     

Retention mechanism of some solutes using ionic liquids as mobile phase modifier in RP-high-performance liquid chromatography (HPLC)

Two kinds of ionic liquid, 1-Hexyl-3-methylimidazolium tetrafluoroborate ([Hmim][BF₄]) and 1-Methyl-3-octylimidazolium tetrafluoroborate ([Omim][BF₄]), were used as additives in the linear solvation energy relationships (LSERs) model to investigate the fundamental chemical interactions governing the retention of nine aromatic compounds in acetonitrile/water mobile phases on a C₁₈ column. The effects of the [Hmim][BF₄] and [Omim][BF₄] were compared and the ability of the LSERs to account for the chemical interactions underlying solute retention was shown. A comparison of predicted and experimental retention factors suggests that LSER formalism is able to reproduce adequately the experimental retention factors of the solutes studied in the different experimental conditions investigated.     

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].     

Quantum chemical studies on the simultaneous interaction of thiophene and pyridine with ionic liquid

The simultaneous interaction of thiophene and pyridine with different ionic liquids:1‐butyl‐1‐methylpyrrolidinium tetrafluoroborate([BPYRO][BF₄]),1‐butyl‐1‐methylpyrrolidinium hexafluoro‐phosphate ([BPYRO][PF₆]), 1‐butyl‐4‐methylpyridinium tetrafluoroborate ([BPY][BF₄]), 1‐butyl‐4‐methylpyridinium hexafluorophosphate ([BPY][PF₆]) and 1‐benzyl‐3‐methylimidazolium tetrafluoroborate ([BeMIM][BF₄]) were investigated using quantum chemical calculations. A three‐tier approach comprising of partial charges, interaction energies and sigma profile generation using conductor‐like screening model for real solvents (COSMO‐RS) was chosen to study the systems. A quantitative attempt based on the CH‐π interaction in ionic liquid; thiophene–pyridine complexes gave the interaction energies of ILs in the order: [BPY][BF₄] > [BPYRO][PF₆] > [BeMIM][BF₄] > [BPY][PF₆] > [BPYRO][BF₄]. An inverse relation was observed between the activity coefficient at infinite dilution predicted via COSMO‐RS–based model and interaction energies. The dominance of CH‐π interaction was evident from the sigma profiles of ionic liquid together with thiophene and pyridine. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Effect of small amount of water on the dynamics properties and microstructures of ionic liquids

A series of systems of 1‐butyl‐3‐methylimidazolium acetate ([Bmim][Ac]), 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([Bmim][BF₄]), and 1‐butyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ([Bmim][Tf₂N]) with a small amount of water were simulated. Viscosities of systems were obtained by nonequilibrium molecule dynamics simulation and the results show that the viscosities change in different ways: for [Bmim][BF₄] and [Bmim][Tf₂N], viscosities decrease rapidly in the first stage, and then decrease slowly with the increase of water content. But for [Bmim][Ac], the viscosities increase first and then decrease. The unique phenomenon of [Bmim][Ac] can be attributed to the formation of chain‐like structure of anion???water???anion???. Hydrogen bond (HB) interaction between ion pairs is weakened, but the number of HB between water and anions increases with increase of water content. Besides, the microstructures of water in ionic liquids‐water systems were compared and found that the distribution of water is more concentrated in [Bmim][Tf₂N]‐H₂O system, while it is isotropy in [Bmim][Ac]‐H₂O system. © 2016 American Institute of Chemical Engineers AIChE J, 63: 2248–2256, 2017     

Physical and electrochemical properties of 1-(2-hydroxyethyl)-3-methyl imidazolium and N-(2-hydroxyethyl)-N-methyl morpholinium ionic liquids

Various ionic liquids (ILs) were prepared via metathesis reaction from two kinds of 1-(2-hydroxyethyl)-3-methyl imidazolium ([HEMIm]⁺) and N-(2-hydroxyethyl)-N-methyl morphorinium ([HEMMor]⁺) cations and three kinds of tetrafluoroborate ([BF₄]⁻), bis(trifluoromethanesulfonyl)imide ([TFSI]⁻) and hexafluorophosphate ([PF₆]⁻) anions. All the [HEMIm]⁺ derivatives were in a liquid state at room temperature. In particular, [HEMIm][BF₄] and [HEMIm][TFSI] showed no possible melting point from −150 °C to 200 °C by DSC analysis, and their high thermal stability until 380-400 °C was verified by TGA analysis. Also, their stable electrochemical property (electrochemical window of more than 6.0 V) and high ionic conductivity (0.002-0.004 S cm⁻¹) further confirm that the suggested ILs are potential electrolytes for use in electrochemical devices. Simultaneously, the [HEMMor]⁺ derivatives have practical value in electrolyte applications because of their easy synthesis procedures, cheap morpholinium cation sources and possibilities of high Li⁺ mobility by oxygen group in the morpholinium cation. However, [HEMMor]⁺ derivatives showing high viscosity usually had lower ionic conductivities than [HEMIm]⁺ derivatives.     

Fast proton conductor under anhydrous condition synthesized from 12-phosphotungstic acid and ionic liquid

In this study, we synthesized a molecular hybrid conductor electrolyte using PWA ([H₃PW₁₂O₄₀·nH₂O]) and [1-butyl-3-methylimidazole][bis-(fluoromethanesulfonyl) amide] ([BMIM][TFSI]) ionic liquid. The [BMIM][TFSI] ionic liquid can interact with the strongly acidic PWA. The hybrids were hydrophilic, and included some water molecules in the structure of the hybrids. The water molecules remained up to 80 °C, contributing to improve conductivity under an anhydrous N₂ atmosphere. The conductivity of PWA-[BMIM][TFSI] hybrid under anhydrous conditions increased from 10⁻⁴ S/cm to 0.04 S/cm at 60 °C. The conductivity of the hybrids at each temperature was higher than that of pure PWA and [BMIM][TFSI] under anhydrous condition. It can be due to the protonic carriers.     

Interfacial properties between ionic-liquid-based electrolytes and lithium-ion-battery separator

For lithium salts, ionic liquids (ILs) are promising alternatives to conventional solvents in lithium-ion batteries (LIBs) due to a more favorable high-voltage operating window, and due to improved safety through reduction of flammability. Toward better understanding of wetting properties of IL-based electrolytes on a LIB separator, wetting properties affect electrochemical performance, experimental studies were made to determine the influence of solvent, lithium-salt type and salt concentration. Surface tensions and advancing contact angles were measured for two pure ILs ([C₄C₁im][BF₄] and [C₄C₁im][OTf]) and for four IL/alkylcarbonate solvent blends (1:1 mass ratio, [C₄C₁im][BF₄]/PC, [C₄C₁im][BF₄]/DMC, [C₄C₁im][OTf]/PC, and [C₄C₁im][OTf]/ DMC) with several concentrations of a lithium salt (LiClO₄, LiPF₆, and LiTFSI). A significant improvement of wettability of pure ILs was observed by adding DMC, while adding PC with surface tension higher than that of pure ILs is detrimental to wetting behavior. Contact angles decrease by adding LiTFSI but show almost no change upon addition of LiPF₆ or LiClO₄. Surface tensions follow the same trend as that for contact angles. Incorporation of TFSI⁻ anion gives favorable separator wettability. Estimates were made for interfacial properties of the separator (dispersive and polar components of the surface free energy for solid-vapor, for liquid–vapor, and for solid–liquid interfacial free energy).     

Nucleation and crystal growth in gold electrodeposition from acid solution Part I: Soft gold

The initial stages of gold electrodeposition on a gold electrode were studied in a proprietary bath (Renovel N) using linear sweep voltammetry and chronoamperometry. Tafel plots with two different slopes were obtained, indicating that the mechanism for gold deposition depends on potential. An inhibition phenomenon was observed during gold electrocrystallization. Experimental current-time transients were analysed using nonlinear least-squares approximations by various models of nucleation and crystal growth. The electrodeposition mechanism changes from three-dimensional progressive at lower overpotentials to three-dimensional instantaneous at higher overpotentials. Moreover, additional two-dimensional progressive or a secondary three-dimensional progressive processes take place in certain potential ranges. It was shown that the outward growth rate of the substrate's base plane displays a linear Tafel relationship whereas the vertical growth rate of gold crystals decreases at more negative potentials due to an inhibition process.     

The effects of Li salts on the performance of a polymer actuator based on single-walled carbon nanotube-ionic liquid gel

The effects of Li salts (Lithium tetrafluoroborate (Li[BF₄]) and Lithium bis(trifluoromethanesulfonyl)imide (Li[TFSI])) on the electrochemical and electromechanical properties of an actuator using a polymer-supported single-walled carbon nanotube (SWCNT)-ionic liquid (IL) gel electrode were investigated. The ionic conductivities of the gel electrolyte layers with molar ratios of Li[BF₄]/1-ethlyl-3-methylimidazolium tetrafluoroborate (EMI[BF₄]) = 0.1 and 0.5, and Li[TFSI]/1-ethlyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (EMI[TFSI]) = 0.1 and 0.3 were higher than those containing only EMI[BF₄] and only EMI[TFSI], respectively. We found a large capacitance value 65-96 F/g at a slow sweep rate 1 mV s⁻¹. The actuator containing Li salt/IL performed much better than that containing only IL. It is considered that the higher ionic conductivity of the gel electrolyte layer containing Li salt/IL produces the quick response actuator, and that the large capacitance gives a large generated strain.     

Conceptual process design of extractive distillation processes for ethylbenzene/styrene separation

In the current styrene production process the distillation of the close-boiling ethylbenzene/styrene mixture to obtain an ethylbenzene impurity level of 100 ppm in styrene accounts for 75–80% of the energy requirements. The future target is to reach a level of 1–10 ppm, which will increase the energy requirements for the distillation even further. Extractive distillation is a well-known technology to separate close-boiling mixtures up to high purities. The objective of this study was to investigate whether extractive distillation using ionic liquids (ILs) is a promising alternative to obtain high purity styrene. Three ILs were studied: [3-mebupy][B(CN)₄], [4-mebupy][BF₄], and [EMIM][SCN]. Extractive distillation with sulfolane and the current conventional distillation process were used as benchmark processes. The IL [4-mebupy][BF₄] is expected to outperform the other two ILs with up to 11.5% lower energy requirements. The operational expenditures of the [4-mebupy][BF₄] process are found to be 43.2% lower than the current distillation process and 5% lower than extractive distillation with sulfolane extractive distillations. However, the capital expenditures for the sulfolane process will be about 23% lower than those for the [4-mebupy][BF₄] process. Finally, the conclusion can be drawn from the total annual costs that all studied extractive distillation processes outperform the current distillation process to obtain high purity styrene, but that the ILs evaluated will not perform better than sulfolane.     

Extractive Desulfurization of Fuel Oils with Thiazolium-Based Ionic Liquids

A new class of green solvents, known as ionic liquids (ILs), has recently been the subject of intensive research on the extractive desulfurization of fuel oils because of the limitation of the traditional hydrodesulfurization method in catalytically removing thiophenic sulfur compounds. In this work, four thiazolium-based ILs, that is, 3-butyl-4-methylthiazolium dicyanamide ([BMTH][DCA]), 3-butyl-4-methylthiazolium thiocyanate ([BMTH][SCN]), 3-butyl-4-methylthiazolium hexafluorophosphate ([BMTH][PF₆]), and 3-butyl-4-methylthiazolium tetrafluoroborate ([BMTH][BF₄]), are synthesized. The extractive capability of these ILs in removing thiophene (TS) and dibenzothiophene (DBT) from model fuel oils is investigated. [BMTH][DCA] and [BMTH][SCN] present better extractive desulfurization capability than [BMTH][BF₄] and [BMTH][PF₆], which may be ascribed to the additional π?π interaction between –C≡N (in [BMTH][DCA] and [BMTH][SCN]) and thiophenic ring (in TS and DBT); DBT in diesel fuel is more efficiently extracted than TS in gasoline. [BMTH][DCA] offers the best desulfurization results, where 64% and 45% sulfur removal are obtained for DBT and TS, respectively, at IL:oil mass ratio of 1:1, 25°C, 20 min. [BMTH][DCA] is thus selected to systematically investigate the effects of temperature, IL:oil mass ratio, initial sulfur content, multiple-extraction, and IL regeneration on desulfurization. The mutual solubility of [BMTH][DCA] with fuel oil is also determined. It is observed that the desulfurization capability is not too sensitive to temperature and initial sulfur content, which is desired in industrial application; the sulfur contents in gasoline and diesel fuel are reduced from 558 ppm to 20 ppm (after 5 cycles) and from 547 ppm to 8 ppm (after 4 cycles), respectively. This work may show a new option for deep desulfurization of fuel oils.