Imidazolium-based Room Temperature Ionic Liquids Research Articles

Acoustic cavitation in 1-butyl-3-methylimidazolium bis(triflluoromethyl-sulfonyl)imide based ionic liquid

In this work, a comparison between the temperatures/pressures within acoustic cavitation bubble in an imidazolium-based room-temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium bis(triflluoromethyl-sulfonyl)imide ([BMIM][NTf2]), and in water has been made for a wide range of cavitation parameters including frequency (140–1000kHz), acoustic intensity (0.5–1Wcm−2), liquid temperature (20–50°C) and external static pressure (0.7–1.5atm). The used cavitation model takes into account the liquid compressibility as well as the surface tension and the viscosity of the medium. It was found that the bubble temperatures and pressures were always much higher in the ionic liquid compared to those predicted in water. The valuable effect of [BMIM][NTf2] on the bubble temperature was more pronounced at higher acoustic intensity and liquid temperature and lower frequency and external static pressure. However, confrontation between the predicted and the experimental estimated temperatures in ionic liquids showed an opposite trend as the temperatures measured in some pure ionic liquids are of the same order as those observed in water. The injection of liquid droplets into cavitation bubbles, the pyrolysis of ionic liquids at the bubble-solution interface as well as the lower number of collapsing bubbles in the ionic liquid may be the responsible for the lower measured bubble temperatures in ionic liquids, as compared with water.

Efficient removal of phenolic compounds from model oil using benzyl Imidazolium-based ionic liquids

Three benzyl imidazolium-based room temperature ionic liquids (RTILs) with various substituents namely allyl, benzyl, and vinyl were synthesized and used as solvents in liquid-liquid extraction for the removal of phenolic compounds from hexane as the model oil. The RTILs were characterized using 1H NMR, 13C NMR, FT-IR, and CHN elemental analyses. Their density and viscosity were also measured. Five main parameters were evaluated through the removal process; the effect of IL substituent, the phase volume ratio of IL and model oil, phase contact time, and temperature. IL containing allylic substituent showed outstanding performance with approximately 95% efficiency under selected optimized conditions. To ensure that the RTIL can be used as a solvent for the removal of phenol, various other types of model oil apart from hexane such as petroleum ether, heptane, and cyclohexane were also used. The RTIL exhibited good recyclability and negligible loss of mass even after six cycles. Further mechanistic interactions between RTIL and phenol were studied by 1H NMR and FT-IR.

THE INFLUENCE OF IONIC LIQUID TYPE, CONCENTRATION, AND SLUG SIZE ON HEAVY OIL RECOVERY PERFORMANCE

Recent studies show that Ionic Liquids (ILs) have the ability to improve oil recovery. In this experimental study, an imidazolium-based Room-Temperature Ionic Liquid (RTIL), 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]), was used to extract heavy oil (14 °API) from unconsolidated packed sand samples. The RTIL was injected as slug, with different concentrations and sizes. The [EMIM][OAc] results were compared with the efficiency of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][Tf2N]) and 1-dodecyl-3-methylimidazolium chloride ([DMIM][Cl]) ILs. The results indicate that the efficiency of IL depends mainly on the type of IL. A comparison with a well-known commercial surfactant (Sodium Dodecyl Sulfate, SDS) was performed, and the results confirmed the higher efficiency of the ionic liquids. Changes in Interfacial Tension (IFT), Surface Tension (SFT), and Zeta Potential (ZP) in the solution supported the recovery factor results. Finding the optimum concentration and slug size are significant factors in making the oil extraction process more economical.

Extraction behaviour of dioxouranium(VI) cation by two phosphorous-based liquid cation-exchangers in room-temperature ionic liquids

ABSTRACTExtraction of uranium with bis-(2-ethylhexyl) phosphonic acid (PC-88A) and bis(2,4,4-trimethylpentyl) phosphinic acid (Cyanex-272) was studied in several imidazolium-based room-temperature ionic liquids (RTILs), Cnmim·X (where n = 4, 6, 8 and X = PF6 and Tf2N). The extraction kinetics was slow and about 0.5–1 h equilibration time was required for most of the extraction systems, except in C8mim·PF6, where 2 h and 4 h were required to reach the equilibrium values for PC-88A and Cyanex-272, respectively. The extraction of UO22+ ion by the two ligands was significantly affected by the nature and the composition of the RTILs.

Understanding Polymorphic Control of Pharmaceuticals Using Imidazolium-Based Ionic Liquid Mixtures as Crystallization Directing Agents

Imidazolium-based room temperature ionic liquids (RTILs) were tested to assess their ability to control molecular polymorphic behavior. Mixtures of RTILs with distinct cation/anion combinations revealed promising capabilities in directing the crystallization process toward less stable polymorphs. In our tests, gabapentin (GBP) neuroleptic drug was used as a case study, as it is a well know polymorphic active pharmaceutical ingredient. For the first time, pure “bulk” GBP Form IV, a highly unstable polymorph, was isolated through RTILs. Forms were maintained over time, once they were kept soaked, opening new perspectives for the method presented here. Molecular dynamics (MD) simulations clearly supported the results. In this work the polymorphic behavior of GBP is controlled recurring to the use of different pure imidazolium-based RTILs or mixtures, as crystallization solvents. Molecular dynamics simulations clearly supported the results showing that specific H(acidic(C4/C6mim))···O(carboxylate) interaction...

Ionic Liquid Induced Enhancement in the Stickiness of Sticky Dissociative Electroreductive C[sbnd]Cl Bond Cleavage: A Key to Eco-Green Detoxification of Chloroacetonitrile

Detailed voltammetric investigations that demonstrate the potential of 1-butyl-3-methyl imidazolium tetrafluoroborate ([BMIM][BF4]), a commonly used room-temperature ionic liquid (RTIL), to enhance the stickiness in the sticky dissociative electrodetoxification pathway for chloroacetonitrile are presented. Convolution analysis of the voltammetric data in light of the Marcus-Hush formulation reveals that electroreductive cleavage of the CCl bond of chloroacetonitrile (ClCH2CN) in [BMIM][BF4] follows a sticky dissociative pathway like that in conventional organic solvents. Interestingly the interaction energy between Cl̄ and CNCH2 (radical) in [BMIM][BF4] is observed to be almost ten times higher than that reported for the same species in N,N-dimethylformamide (DMF). This RTIL-induced enhancement in the interaction energy among the electrochemically generated fragments reduces the kinetic barrier and hence the overpotential required for heterogeneous electroreduction of ClCH2CN. The lower overpotential that implies lesser energy consumption for the electroreduction and the green features of [BMIM][BF4] jointly support the use of imidazolium-based RTILs for eco-green electrodetoxification of halohydrocarbons like chloroacetonitrile.

Room-temperature ionic liquids modified zeolite SSZ-13 membranes for CO2/CH4 separation

A new modification strategy using precursors of silanized imidazolium-based room temperature ionic liquids (RTILs) has been developed for surface modification of zeolite membranes by the gentle liquid-phase silanization reaction. The advantage of RTILs in selective adsorption of CO2 could enhance the CO2-selective separation for the RTILs-modified membranes. The parameters, such as the precursor and the anion type of RTILs were optimized. Characterizations including Fourier transform infrared spectroscopy, field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy, showed that silanized imidazolium-based RTILs were grafted on the surface of SSZ-13 crystals and membrane. Carbon dioxide/methane selectivity of the modified membranes was strongly depended on the type of the balanced anion of RTILs. Single-gas permeation for H2, CO2, N2, CH4, C2H6 and i-C4H10 and mixture CO2/CH4 separation through the fresh and modified membranes were investigated. When [TESPMIM][BF4] precursor was used, the average CO2 permeance of three modified membranes decreased by only 44% (average CO2 permeance of 1.0×10−7molm−2s−1Pa−1) and CO2/CH4 selectivity increased by a factor of 7 (average CO2/CH4 selectivity of 87) for an equilmolar CO2/CH4 mixture at room temperature compared with those of the fresh membranes.

Facilitated Ion Transport in Smectic Ordered Ionic Liquid Crystals.

A novel ionic mixture of an imidazolium-based room-temperature ionic liquid containing ethylene-oxide-functionalized phosphite anions is fabricated, which, when doped with lithium salt, self-assembles into a smectic-ordered ionic liquid crystal through Coulombic interactions between the ion species. Interestingly, the smectic order in the ionic-liquid-crystal ionogel facilitates ionic transport.

Curable Imidazolium Poly(ionic liquid)/Ionic Liquid Coating for Containment and Decontamination of Toxic Industrial Chemical-Contacted Substrates

A curable, imidazolium-based room-temperature ionic liquid (RTIL) coating system has been developed for the containment and decontamination of toxic industrial chemical-contacted surfaces. The curing times and mechanical properties of this poly(RTIL)/RTIL platform, which is based on alcohol–isocyanate step-growth polymerization chemistry, can be tuned by modifying the structures of the step-growth monomers, the stoichiometric ratio of linear (diol, A2) to cross-linking (triol, A3) RTIL monomers used, and the amount of free RTIL in the formulation. When applied to painted steel and rubber test substrates contacted with o-dichlorobenzene (o-DCB) (a polychlorinated biphenyl simulant), a 50:50 (A2:A3) step-growth alcohol-RTIL monomer mixture cross-linked with a stoichiometric amount of a commercial di-isocyanate monomer (B2) and containing 43 wt % free RTIL in the coating, reduced the o-DCB vapor amount by 96–99% compared to the uncoated, o-DCB-contacted control samples. This peelable, flexible, solid coating also removed by sorption up to >99% of the o-DCB liquid applied to the substrates after 24 h of contact.

Structure and Dynamics of Bio-Membranes and their Hydration Water in Water Solution of Room Temperature Ionic Liquids: An Experimental and Computational Study

The molecularly thin layer of water in direct contact with bio-molecules in a physiological environment plays a major role in determining their properties and functions. In this context, water is a shorthand notation for “water electrolyte solution”, since almost without exception a variety of ions dissolved in water are needed to ensure the stability of bio-systems, greatly contributing to their complex behaviours.In recent years, the development of compounds of the so-called room-temperature ionic liquid (RTIL) family has enormously expanded the number of ionic systems that could be used to modify the properties of the interfacial water, and thus to affect the behaviour of bio-systems.Our study concerns the microscopic mechanisms underlying RTIL effects on biosystems (e.g. phospholipid bilayers, proteins, and nucleic acids) through their hydration water, and relies on the combination of neutron scattering and molecular dynamics (MD) simulations.We present the results for the interaction of imidazolium-based RTILs with phospholipid bilayers [1,2]. Neutron reflectometry and MD simulations confirm the tendency of cations to be absorbed into the lipid phase, enhancing the penetration of water into the bilayer. Neutron scattering and MD reveal apparent changes in the relaxation time of water in close contact of the lipid head upon addition of RTILs, that reflect phase changes in the structure and dynamics of the system.[1] A. Benedetto, et al. J. Phys. Chem. B, 2014, 118, 12192.[2] A. Benedetto, et al. J. Chem. Phys., 2015, 142, 124706.

CO<sub>2</sub> Capture at Room Temperature and Ambient Pressure: Isomer Effect in Room Temperature Ionic Liquid/Propanol Solutions

A CO2 capture system without supercritical CO2 was optimized for mixtures of hydrophobic room temperature ionic liquids (RTILs) and propanol. We tested RTILs using bis(trifluoromethanesulfonyl)imide, TFSI-, anion and four quaternary ammonium cations, two quaternary phosphonium cations, and one imidazolium cation. The addition of 2-propanol into the RTILs clearly promoted the capture of normal CO2(nCO2) at ambient temperature and pressure. When combined with 2-propanol, the most efficient RTILs for nCO2 capture were N-butyl-N,N,N-trimethylammonium TFSI-. This enhancement of nCO2 capture was not observed in RTIL mixtures with 1-propanol or in propanol mixtures containing other phosphonium- and imidazolium-based RTILs. The torsion angle of TFSI-, which was calculated using density functional theory, is thought to be related to high nCO2 capture efficiently.

Titanium deposition from ionic liquids - appropriate choice of electrolyte and precursor.

In this study titanium isopropoxide was dissolved in 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (BMITFSI) and further in a custom-made guanidinium-based ionic liquid (N11N11NpipGuaTFSI). Electrochemical investigations were carried out by means of cyclic voltammetry (CV) and the initial stages of metal deposition were followed by in situ scanning tunneling microscopy (STM). For BMITFSI we found one large cathodic reduction peak at a potential of -1.2 V vs. Pt, corresponding to the growth of monoatomic high islands. The obtained deposit was identified as elemental titanium by Auger Electron Spectroscopy (AES). Furthermore, we found a corresponding anodic peak at -0.3 V vs. Pt, which is associated with the dissolution of the islands. This observation leads to the assumption that titanium deposition from the imidazolium-based room-temperature ionic liquid (RTIL) proceeds in a one-step electron transfer. In contrast, for the guanidinium-based RTIL we found several peaks during titanium reduction and oxidation, which indicates a multi-step electron transfer in this alternative electrolyte.

A Refined All-Atom Potential for Imidazolium-Based Room Temperature Ionic Liquids: Acetate, Dicyanamide, and Thiocyanate Anions.

A refined set of potential parameters for 1-alkyl-3-methylimidazolium based room temperature ionic liquids with anions such as acetate, dicyanamide, and thiocyanate has been obtained. Site charges of ions were derived through the density-derived electrostatic and charge partitioning (DDEC/c3) method utilizing periodic density functional theory calculations of these liquids. Intermolecular structure and dynamics, in particular, the collective quantities predicted by the refined force field, match experimental results quantitatively.

Room temperature ionic liquid electrolytes for redox flow batteries

Redox flow batteries (RFBs) usually contain aqueous or organic electrolytes. The aim of this communication is to explore the suitability of room temperature ionic liquids (RTILs) as solvents for RFBs containing metal complexes. Towards this aim, the electrochemistry of the metal acetylacetonate (acac) complexes Mn(acac)3, Cr(acac)3, and V(acac)3 was studied in imidazolium-based RTILs. The V2+/V3+, V3+/V4+, and V4+/V5+ redox couples are quasi-reversible in 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide, [C2C1Im][N(Tf2)]. The Mn(acac)3 and Cr(acac)3 voltammetry, on the other hand, is irreversible in [C2C1Im][N(Tf2)] at glassy carbon (GC) but the rate of the Mn2+/Mn3+ reaction increases if Au electrodes are used. Charge–discharge measure- ments show that a coulombic efficiency of 72% is achievable using a V(acac)3/[C2C1Im][N(Tf2)]/GC cell.

Modification of the photophysics of 3-hydroxyflavone in aqueous solutions of imidazolium-based room temperature ionic liquids: a comparison between micelle-forming and non micelle-forming ionic liquids

Fluorometric techniques have been exploited to study the photophysical behaviour of an ESIPT probe, 3HF, in two imidazolium-based room temperature ionic liquids, one micelle-forming and the other non micelle-forming.

Strong electronic polarization of the C60 fullerene by imidazolium-based ionic liquids: accurate insights from Born-Oppenheimer molecular dynamic simulations.

Fullerenes are known to be polarizable due to their strained carbon-carbon bonds and high surface curvature. The electronic polarization of fullerenes is steadily of practical importance because it leads to non-additive interactions and, therefore, to unexpected phenomena. For the first time, hybrid density functional theory (HDFT) powered Born-Oppenheimer molecular dynamics (BOMD) simulations have been conducted to observe electronic polarization and charge transfer phenomena in the C60 fullerene at finite temperature (350 K). The non-additive phenomena are fostered by the three selected imidazolium-based room-temperature ionic liquids (RTILs). We conclude that although charge transfer appears nearly negligible in these systems, electronic polarization is indeed significant, leading to a systematically positive effective electrostatic charge on the C60 fullerene: +0.14e in [MMIM][Cl], +0.21e in [MMIM][NO3], and +0.17e in [MMIM][PF6]. These results are, to a certain extent, unexpected and provide a motivation for considering novel C60-RTILs systems. HDFT BOMD is a powerful tool for investigating electronic effects in RTIL and fullerene containing nuclear-electronic systems.

PVDF-HFP/이온성 액체 겔 분리막 제조 및 기체 투과도 측정

It is well known that CO2 can be dissolved easily in imidazolium-based room temperature ionic liquids (RTILs). Because of the high CO2 solubility in RTILs, membranes containing RTILs can separate easily gas mixtures such as CO2/N2 and CO2/CH4. In this study, we prepared poly(vinylidene fluoride)-hexafluoropropyl copolymer (PVDF-HFP) gel membranes with several RTILs and measured permeabilities of several gases. When the anion of ionic liquids was tetrafluoroborate(BF4 - ), both CO2 permeability and selectivities decreased as the carbon number of the cation increased. When the cation of ionic liquids was 1-ethyl-3-methylimidazolium(emim), CO2 permeability of gel membranes containing bis(trifluoro- methane)sulfoneimide(Tf2N - ) anion was double compared to those containing tetrafluoroborate(BF4 - ) anion. However, CO2/N2 and CO2/CH4 selectivities of the Tf2N - case were decreased, whereas the H2 selectivity was almost the same for two cases.

Interfacial ionic ‘liquids’: connecting static and dynamic structures

It is well known that room temperature ionic liquids (RTILs) often adopt a charge-separated layered structure, i.e. with alternating cation- and anion-rich layers, at electrified interfaces. However, the dynamic response of the layered structure to temporal variations in applied potential is not well understood. We used in situ, real-time x-ray reflectivity to study the potential-dependent electric double layer (EDL) structure of an imidazolium-based RTIL on charged epitaxial graphene during potential cycling as a function of temperature. The results suggest that the graphene–RTIL interfacial structure is bistable in which the EDL structure at any intermediate potential can be described by the combination of two extreme-potential structures whose proportions vary depending on the polarity and magnitude of the applied potential. This picture is supported by the EDL structures obtained by fully atomistic molecular dynamics simulations at various static potentials. The potential-driven transition between the two structures is characterized by an increasing width but with an approximately fixed hysteresis magnitude as a function of temperature. The results are consistent with the coexistence of distinct anion- and cation-adsorbed structures separated by an energy barrier (∼0.15 eV).

Distributed polarizability models for imidazolium-based ionic liquids.

Quantum chemical calculations are used to derive distributed polarizability models sufficiently accurate and compact to be used in classical molecular dynamics simulations of imidazolium-based room temperature ionic liquids. Two distributed polarizability models are fitted to reproduce the induction energy of three imidazolium cations (1,3-dimethyl-, 1-ethyl-3-methyl-, and 1-butyl-3-methylimidazolium) and four anions (tetrafluoroborate, hexafluorophosphate, nitrate, and thiocyanate) polarized by a point charge located successively on a grid of surrounding points. The first model includes charge-flow polarizabilities between first-neighbor atoms and isotropic dipolar polarizability on all atoms (except H), while the second model includes anisotropic dipolar polarizabilities on all atoms (except H). For the imidazolium cations, particular attention is given to the transferability of the distributed polarizability sets. The molecular polarizability and its anisotropy rebuilt by the distributed models are found to be in good agreement with the exact ab initio values for the three cations and 23 additional conformers of 1-ethyl-3-methyl-, 1-butyl-3-methyl-, 1-pentyl-3-methyl-, and 1-hexyl-3-methylimidazolium cations.

“Brick-and-mortar” synthesis of free-standing mesoporous carbon nanocomposite membranes as supports of room temperature ionic liquids for CO2−N2 separation

Free-standing mesoporous carbon−graphitic carbon nanocomposite membranes with controllable pore size (7.3−11.3nm) were synthesized by the “brick-and-mortar” method, carbon black (CB) as “bricks” and soft-templated phenolic resin-based mesoporous carbon (MC) as the “mortar”. Immobilization of imidazolium-based room temperature ionic liquids ([Cnmim][Tf2N], n=2, 4, and 6) in the MC−CB membranes produced a series of supported ionic liquid membranes (SILMs) that are permselective for separation of CO2−N2 gas pair. Strong capillary forces resulting from the well-developed mesoporosity of the MC−CB membranes greatly enhanced the stability of the supported ionic liquids. This enabled the SILMs to operate under transmembrane pressures as high as 1000kPa without degrading their separation performance. This makes it possible to apply SILMs to high-pressure CO2 capture and separation processes, where high transmembrane pressure would greatly increase the permeate flux through the membranes.