Influence of water on the carbon dioxide absorption by 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide

The effect of the addition of water on the absorption of carbon dioxide by the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide was studied experimentally by measuring the low-pressure carbon dioxide solubility and the viscosity of the liquid solvent at temperatures from 303 to 323 K. Water is only partially miscible with the ionic liquid up to a mole fraction of 0.302 at 293 K, 0.321 at 303 K and 0.381 at 323 K. It was observed that the solubility of carbon dioxide decreases with the quantity of water from a mole fraction of 2.63 × 10-2 for the pure ionic liquid at 303.4 K to a value of 1.88 × 10-2, a reduction of 30% of the solubility, for a mole fraction of water of 0.28. The viscosity of the liquid solvent also decreases, up to 40% at 303 K, from 28.6 mPa s for the pure ionic liquid to 16.4 mPa s for a water mole fraction of 0.302.

Isolation and Characterisation of 1-Alkyl-3- Methylimidazolium Chloride Ionic Liquid-Tolerant and Biodegrading Marine Bacteria

The aim of this study was to isolate and identify marine-derived bacteria which exhibited high tolerance to, and an ability to biodegrade, 1-alkyl-3-methylimidazolium chloride ionic liquids. The salinity and hydrocarbon load of some marine environments may induce selective pressures which enhance the ability of microbes to grow in the presence of these liquid salts. The isolates obtained in this study generally showed a greater ability to grow in the presence of the selected ionic liquids compared to microorganisms described previously, with two marine-derived bacteria, Rhodococcus erythropolis and Brevibacterium sanguinis growing in concentrations exceeding 1 M 1-ethyl-3-methylimidazolium chloride. The ability of these bacteria to degrade the selected ionic liquids was assessed using High Performance Liquid Chromatography (HPLC), and three were shown to degrade the selected ionic liquids by up to 59% over a 63-day test period. These bacterial isolates represent excellent candidates for further potential applications in the bioremediation of ionic liquid-containing waste or following accidental environmental exposure.

The phase behaviour of 1-alkyl-3-methylimidazolium tetrafluoroborates; ionic liquids and ionic liquid crystals

Air- and water-stable 1-alkyl-3-methylimidazolium tetrafluoroborate salts with the general formula [C-mim][BF] (n = 0-18) have been prepared by metathesis from the corresponding chloride or bromide salts. The salts have been characterised by H NMR and IR spectroscopy, microanalysis, polarising optical microscopy and differential scanning calorimetry. Those with short alkyl chains (n = 2-10) are isotropic ionic liquids at room temperature and exhibit a wide liquid range, whereas the longer chain analogues are low melting mesomorphic crystalline solids which display an enantiotropic smectic A mesophase. The thermal range of the mesophase increases with increasing chain length and in the case of the longest chain salt prepared, [C-mim][BF], the mesophase range is ca. 150°C.

Oxygen solubility in ionic liquids based on 1-alkyl-3-methylimidazolium cations

This work presents the results of oxygen solubility in ionic liquids based on 1-alkyl-3-methylimidazolium cations. Solubility measurements have been carried out in gasometric apparatus at 22, 50 and 90 degrees C under atmospheric pressure. We report the Henry's constants. In general the occurrence of carbon-fluorine bonds and carbon-hydrogen bonds in ionic liquids (ILs) which can create hydrogen bonds with dissolved oxygen, significantly affects the growth of value of solubility constant K-H. Additionally, the stability of ILs towards molecular oxygen was tested. All ILs used in this study were stable in the presence of oxygen and free-radical initiator.

Galleria mellonella as a novel in vivo model for assessment of the toxicity of 1-alkyl-3-methylimidazolium chloride ionic liquids

The larval form of the Greater Wax Moth (Galleria mellonella) was evaluated as a model system for the study of the acute in vivo toxicity of 1-alkyl-3-methylimidazolium chloride ionic liquids. 24-h median lethal dose (LD50) values for nine of these ionic liquids bearing alkyl chain substituents ranging from 2 to 18 carbon atoms were determined. The in vivo toxicity of the ionic liquids was found to correlate directly with the length of the alkyl chain substituent, and the pattern of toxicity observed was in accordance with previous studies of ionic liquid toxicity in other living systems, including a characteristic toxicity ‘cut-off’ effect. However, G. mellonella appeared to be more susceptible to the toxic effects of the ionic liquids tested, possibly as a result of their high body fat content. The results obtained in this study indicate that G. mellonella represents a sensitive, reliable and robust in vivo model organism for the evaluation of ionic liquid toxicity.

Evaluation of the ionic liquids 1-alkyl-3-methylimidazolium hexafluorophosphate as a solvent for the extraction of benzene from cyclohexane : ( Liquid + liquid ) equilibria

In the catalytic hydrogenation of benzene to cyclohexane, the separation of unreacted benzene from the product stream is inevitable and essential for an economically viable process. In order to evaluate the separation efficiency of ionic liquids (ILs) as a solvent in this extraction processes, the ternary (liquid + liquid) equilibrium of 1-alkyl-3-methylimidazolium hexafluorophosphate, [Cnmim][PF6] (n = 4, 5, 6), with benzene and cyclohexane was studied at T = 298.15 K and atmospheric pressure. The reliability of the experimentally determined tie-line data was confirmed by applying the Othmer–Tobias equation. The solute distribution coefficient and solvent selectivity for the systems studied were calculated and compared with literature data for other ILs and sulfolane. It turns out that the benzene distribution coefficient increases and solvent selectivity decreases as the length of the cation alkyl chain grows, and the ionic liquids [Cnmim][PF6] proved to be promising solvents for benzene–cyclohexane extractive separation. Finally, an NRTL model was applied to correlate and fit the experimental LLE data for the ternary systems studied.

Efficient, halide free synthesis of new, low cost ionic liquids: 1,3-dialkylimidazolium salts containing methyl- and ethyl-sulfate anions

New low-cost ionic liquids containing methyl- and ethyl-sulfate anions can be easily and efficiently prepared under ambient conditions by the reaction of 1-alkylimidazoles with dimethyl sulfate and diethyl sulfate. The preparation and characterization of a series of 1,3-dialkylimidazolium alkyl sulfate and 1,2,3-trialkylimidazolium alkyl sulfate salts are reported. 1,3-Dialkylimidazolium salts containing at least one non-methyl N-alkyl substituent are liquids at, or below room, temperature. Three salts were crystalline at room temperature, the single crystal X-ray structure of 1,3-dimethylimidazolium methyl sulfate was determined and shows the formation of discrete ribbons comprising of two anion-cation hydrogen-bonded chains linked via intra-chain hydrogen-bonding, but little, or no inter-ribbon hydrogen-bonding. The salts are stable, water soluble, inherently 'chloride-free', display an electrochemical window of greater than 4 V, and can be used as alternatives to the corresponding halide salts in metathesis reactions to prepare other ionic liquids including 1-butyl-3-methylimidazolium hexafluorophosphate.

Ionic liquids as solvent and solvent additives for the synthesis of sol-gel materials

The ionic liquid (IL) 1-butyl-3-methylimidazolium chloride was used as a drying control chemical additive in the synthesis of silica sol-gel materials with and without methanol as a co-solvent. The resulting gels were characterized by using thermogravimetric analysis, differential scanning calorimetry, infrared spectroscopy and water sorption kinetics. Calcined gels were analyzed using scanning electron microscopy and nitrogen adsorption isotherms for surface area and pore volume determination. Non-calcined gels were monolithic and showed general cloudiness with lesser degrees observed at higher IL volumes. Calcinations resulted in the formation of powders with increased available surface area as the amount of IL volume was increased. This is consistent with an increase in respective pore volume but a general decrease in average pore size. The resulting materials exhibited conventional structural microdomains, in contrast to periodicity reported when other ionic liquids were used as templates.

ZnO nanofluids: Green synthesis, characterization, and antibacterial activity

Zinc oxide nanoparticles have been synthesized by microwave decomposition of zinc acetate precursor using an ionic liquid, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide, [bmim][NTf2] as a green solvent. The structure and morphology of ZnO nanoparticles have been characterized using X-ray diffraction and transmission electron microscopy. The ZnO nanofluids have been prepared by dispersing ZnO nanoparticles in glycerol as a base fluid in the presence of ammonium citrate as a dispersant. The antibacterial activity of suspensions of ZnO nanofluids against (E. coli) has been evaluated by estimating the reduction ratio of the bacteria treated with ZnO. Survival ratio of bacteria decreases with increasing the concentrations of ZnO nanofluids and time. The results show that an increase in the concentrations of ZnO nanofluids produces strong antibacterial activity toward E. coli. (C) 2010 Elsevier B.V. All rights reserved.

Facile in situ synthesis of nanofluids based on ionic liquids and copper oxide clusters and nanoparticles

Two stable nanofluids comprising of mixed valent copper(_I,_II) oxide clusters (<1 nm) suspended in 1-butyl-3-methylimidazolium acetate, [C(₄)mim][OAc], and copper(_II) oxide nanoparticles (<50 nm) suspended in trioctyl(dodecyl) phosphonium acetate, [P-₈₈₈₁₂][OAc], were synthesised in a facile one-pot reaction from solutions of copper(_II) acetate hydrate in the corresponding ionic liquids. Formation of the nanostructures was studied using ¹³C NMR spectroscopy and differential scanning calorimetry (DSC). From a solution of Cu(OAc)₂ in 1-ethyl-3-methylimidazolium acetate, [C₂mim][OAc], crystals were obtained that revealed the structure of [C₂mim][Cu₃(OAc)₅(OH)₂(H₂O)]center dot H₂O, indicating the formation of copper hydroxo-clusters in the course of the reaction. Synthesised nanostructures were studied using transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Physical properties of the prepared IL-nanofluids were examined using IR and UV-VIS spectroscopy, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and densitometry. 

Microwave Irradiation for the Facile Synthesis of Transition-Metal Nanoparticles (NPs) in Ionic Liquids (ILs) from Metal-Carbonyl Precursors and Ru-, Rh-, and Ir-NP/IL Dispersions as Biphasic Liquid-Liquid Hydrogenation Nanocatalysts for Cyclohexene

Stable chromium, molybdenum, tungsten, manganese, rhenium, ruthenium, osmium, cobalt, rhodium, and iridium metal nanoparticles (MNPs) have been reproducibly obtained by facile, rapid (3 min), and energysaving 10 W microwave irradiation (MWI) under an argon atmosphere from their metal–carbonyl precursors [Mx(CO)y] in the ionic liquid (IL) 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]). This MWI synthesis is compared to UV-photolytic (1000 W, 15 min) or conventional thermal decomposition (180–2508C, 6–12 h) of [Mx(CO)y] in ILs. The MWIobtained nanoparticles have a very small (<5 nm) and uniform size and are prepared without any additional stabilizers or capping molecules as long-term stable M-NP/IL dispersions (characterization by transmission electron microscopy (TEM), transmission electron diffraction (TED), and dynamic light scattering (DLS)). The ruthenium, rhodium, or iridium nanoparticle/IL dispersions are highly active
and easily recyclable catalysts for the biphasic liquid–liquid hydrogenation of cyclohexene to cyclohexane with activities of up to 522 (mol product)(mol Ru)1h1 and 884 (mol product)(molRh)1h1 and give almost quantitative conversion within 2 h at 10 bar H2 and 908C. Catalyst poisoning experiments with CS2 (0.05 equiv per Ru) suggest a heterogeneous surface catalysis of RuNPs.

Luminescence of LaF3:Ln(3+) Nanocrystal Dispersions in Ionic Liquids

Ionic liquids were used as solvents for dispersing luminescent lanthanide-doped LaF3:Ln(3+) nanocrystals (Ln(3+) = Eu3+ and Nd3+). To increase the solubility of the inorganic nanoparticles in the ionic liquids, the nanocrystals were prepared with different stabilizing ligands, i.e., citrate, N,N,N-trimethylglycine (betaine), and lauryldimethylglycine (lauryl betaine). LaF3:5%Ln(3+) :betaine could successfully be dispersed in 1-butyl-1-methylpyrrolidinium bis(tiifluoromethylsulfonyl)imide [C(4)mpyr][Tf2N], 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate [C(4)mpyr][TfO], and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [C(4)mim][Tf2N] but only in limited amounts. Red photoluminescence was observed for the europium(III)-containing nanoparticles and near-infrared luminescence for the neodymium(III)-containing systems.

Kinetic model for the hydrolysis of lignocellulosic biomass in the ionic liquid, 1-ethyl-3-methyl-imidazolium chloride†

The kinetics of the acid-catalysed hydrolysis of cellobiose in the ionic liquid 1-ethyl-3-methylimidazolium chloride, [C(2)mim]Cl, was studied as a model for general lignocellulosic biomass hydrolysis in ionic liquid systems. The results show that the rate of the two competing reactions, polysaccharide hydrolysis and sugar decomposition, vary with acid strength, and that for acids with an aqueous pK(a) below approximately zero, the hydrolysis reaction is significantly faster than the degradation of glucose, thus allowing hydrolysis to be performed with a high selectivity in glucose. In tests with soluble cellulose, hemicellulose (xylan), and lignocellulosic biomass (Miscanthus grass), comparable hydrolysis rates were observed with bond scission occurring randomly along the biopolymer chains, in contrast to end-group hydrolysis observed with aqueous acids.

Volumetric properties and enthalpies of solution of alcohols CkH2k+1OH (k = 1, 2, 6) in 1-methyl-3-alkylimidazolium bis(trifluoromethylsulfonyl)imide {[C1CnIm][NTf2] n = 2, 4, 6, 8, 10} ionic liquids

We present a study on the effect of the alkyl chain length of the imidazolium ring in 1-alkyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquids, [C1CnIm][NTf2] (n = 2 to 10), on the mixing properties of (ionic liquid + alcohol) mixtures (enthalpy and volume). We have measured small excess molar volumes with highly asymmetric curves as a function of mole fraction composition (S-shape) with more negative values in the alcohol-rich regions. The excess molar volumes increase with the increase of the alkyl-chain length of the imidazolium cation of the ionic liquid. The values of the partial molar excess enthalpy and the enthalpy of mixing are positive and, for the case of methanol, do not vary monotonously with the length of the alkyl side-chain of the cation on the ionic liquid – increasing from n = 2 to 6 and then decreasing from n = 8. This non-monotonous variation is explained by a more favourable interaction of methanol with the cation head group of the ionic liquid for alkyl chains longer than eight carbon atoms. It is also observed that the mixing is less favourable for the smaller alcohols, the enthalpy of mixing decreasing to less positive values as the alkyl chain of the alcohol increases. Based on the data from this work and on the knowledge of the vapour pressure of {[C1CnIm][NTf2] + alcohol} binary mixtures at T = 298 K reported in the literature, the excess Gibbs free energy, excess enthalpy and excess entropy could be then calculated and it was observed that these mixtures behave like the ones constituted by a non-associating and a non-polar component, with its solution behaviour being determined by the enthalpy.

Enhanced antimicrobial activities of 1-alkyl-3-methyl imidazolium ionic liquids based on silver or copper containing anions

We have developed a series of 1-alkyl-3-methylimidazolium tetrachlorocuprate(II) and dibromoargentate(I) ionic liquids with enhanced antimicrobial activity when compared with 1-alkyl-3-methylimidazolium chloride ionic liquids. These new ionic liquids proved to be effective against a range of pathogenic bacteria and fungi.