Industrial applications of ionic liquids

The potential to use Ionic Liquids (ILs) as novel solvents or fluids for a diverse range of applications has become increasingly rent as researchers in academia and try respond to challenges from atmospheric emissions and disposal of many common solvents by evaluating novel reaction media. The intrinsic non-volatile nature of ILs provides an opportunity to reduce, or even completely eliminate, hazardous and toxic emissions to the atmosphere, thus providing the promise for significant environmental benefits. In synthesis and catalysis, ILs have been used as solvents (or solvents and catalysts), with the greatest current effort on using the ILs as alternatives to VOCs. In contrast, electrochemical studies hove utills'ed the fact that ILs are liquid rather than solids to provide liquid electrolytes without needing to odd an additional solvent. is overview appraiso an appraisal of potential to use ILs in industrial applications, illustrating some areas where practical uses are being developed, and how, throuqh understanding ionic liquids in a conceptuo level, new opportunities ore continuing to evolve.

Purification of imidazolium ionic liquids for spectroscopic applications

Ionic liquids are often contaminated by colored impurities. These impurities can be problematic for spectroscopic studies or for monitoring organic reactions by UV/Vis spectroscopy. The effect of different purification methods on the optical quality of colored ionic liquids was studied and compared. Yellowish ionic liquids can partially be decolorized by treatment with active charcoal or by recrystallization. Our experiments show column liquid chromatography is not always a good technique to prepare spectrograde imidazolium halide ionic liquids. Colorless and UV-transparent ionic liquids were synthesized by a method that can exclude the need for further purification steps. (c) 2005 Elsevier B.V. All rights reserved.

Bridging the Gap between Ionic Liquids and Molten Salts: Group 1 Metal Salts of the Bistriflamide Anion in the Gas Phase

Fourier transform ion cyclotron resonance mass spectrometry experiments showed that liquid Group 1 metal salts of the bistriflamide anion undergoing reduced-pressure distillation exhibit a remarkable behavior that is in transition between that of the vapor-liquid equilibrium characteristics of aprotic ionic liquids and that of the Group 1 metal halides: the unperturbed vapors resemble those of aprotic ionic liquids, in the sense that they are essentially composed of discrete ion pairs. However, the formation of large aggregates through a succession of ion-molecule reactions is closer to what might be expected for Group I metal halides. Similar experiments were also carried out with bis{(trifluoromethyl)sulfonyl}amine to investigate the effect of H+, which despite being the smallest Group 1 cation, is generally regarded as a nonmetal species. In this case, instead of the complex ion-molecule reaction pattern found for the vapors of Group I metal salts, an equilibrium similar to those observed for aprotic ionic liquids was observed.

Ionic Liquids Containing Boron Cluster Anions

The combination of different boron cluster anions and some of the cations typically found in the composition of ionic liquids has been possible by straightforward metathetic reactions, producing new low melting point salts; the imidazolium cations have been systematically studied, [C(n)mim](+) (when [C(n)mim](+) = 1-alkyl-3-methylimidazolium; n = 2, 4, 6, 8, 10, 12, 14, 16, or 18). Melting points increase in the anionic order [Co(C2B9H11)(2)](-) =-34 degrees C). The salts [C(n)mim](2)[X] ([X](2-) = [B10Cl10](2-) or [B12Cl12](2-), n = 16 or 18) show liquid crystal phases between the solid and liquid states. Tetraalkylphosphonium salts of [B10Cl10](2-) have also been prepared. Physical properties, such as thermal stability, density, or viscosity, have been measured for some selected samples. The presence of the perhalogenated dianion [B12Cl12](2-) in the composition of the imidazolium salts renders highly thermally stable compounds. For example, [C(2)mim](2)[B12Cl12] starts to decompose above 480 degrees C in a dynamic TGA analysis under a dinitrogen atmosphere. Crystal structures of [C(2)mim][Co(C2B9H11)(2)] and [C(2)mim](2)[B12Cl12] have been determined. H-1 NMR spectra of selected imidazolium-boron cluster anion salts have been recorded from solutions as a function of the concentration, showing trends related to the cation-anion interactions.

Thermodynamic properties and atomistic structure of the dry amorphous silica surface from a reactive force field model

A force field model of the Keating type supplemented by rules to break, form, and interchange bonds is applied to investigate thermodynamic and structural properties of the amorphous SiO2 surface. A simulated quench from the liquid phase has been carried out for a silica sample made of 3888 silicon and 7776 oxygen atoms arranged on a slab similar to 40 angstrom thick, periodically repeated along two directions. The quench results into an amorphous sample, exposing two parallel square surfaces of similar to 42 nm(2) area each. Thermal averages computed during the quench allow us to determine the surface thermodynamic properties as a function of temperature. The surface tension turns out to be gamma=310 +/- 20 erg/cm(2) at room temperature and gamma=270 +/- 30 at T=2000 K, in fair agreement with available experimental estimates. The entropy contribution Ts-s to the surface tension is relatively low at all temperatures, representing at most similar to 20% of the surface energy. Almost without exceptions, Si atoms are fourfold coordinated and oxygen atoms are twofold coordinated. Twofold and threefold rings appear only at low concentration and are preferentially found in proximity of the surface. Above the glass temperature T-g=1660 +/- 50 K, the mobility of surface atoms is, as expected, slightly higher than that of bulk atoms. The computation of the height-height correlation function shows that the silica surface is rough in the equilibrium and undercooled liquid phase, becoming smooth below the glass temperature T-g.

Stir bar sorptive extraction of diclofenac from liquid formulations: A proof of concept study

A new stir bar sorptive extraction (SBSE) technique coupled with HPLC-UV method for quantification of diclofenac in pharmaceutical formulations has been developed and validated as a proof of concept study. Commercially available polydimethylsiloxane stir bars (Twister (TM)) were used for method development and SBSE extraction (pH, phase ratio, stirring speed, temperature, ionic strength and time) and liquid desorption (solvents, desorption method, stirring time etc) procedures were optimised. The method was validated as per ICH guidelines and was successfully applied for the estimation of diclofenac from three liquid formulations viz. Voltarol (R) Optha single dose eye drops, Voltarol (R) Ophtha multidose eye drops and Voltarol (R) ampoules. The developed method was found to be linear (r=0.9999) over 100-2000 ng/ml concentration range with acceptable accuracy and precision (tested over three QC concentrations). The SBSE extraction recovery of the diclofenac was found to be 70% and the LOD and LOQ of the validated method were found to be 16.06 and 48.68 ng/ml, respectively. Furthermore, a forced degradation study of a diclofenac formulation leading to the formation of structurally similar cyclic impurity (indolinone) was carried out. The developed extraction method showed comparable results to that of the reference method, i.e. method was capable of selectively extracting the indolinone and diclofenac from the liquid matrix. Data on inter and intra stir bar accuracy and precision further confirmed robustness of the method, supporting the multiple re-use of the stir bars. (C) 2010 Elsevier B.V. All rights reserved.

Computational Verification of Two Universal Relations for Simple Ionic Liquids. Kinetic Properties of a Model 2:1 Molten Salt

Two semianalytical relations [Nature, 1996, 381, 137 and Phys. Rev. Lett. 2001, 87, 245901] predicting dynamical coefficients of simple liquids on the basis of structural properties have been tested by extensive molecular dynamics simulations for an idealized 2:1 model molten salt. In agreement with previous simulation studies, our results support the validity of the relation expressing the self-diffusion coefficient as a Function of the radial distribution functions for all thermodynamic conditions such that the system is in the ionic (ie., fully dissociated) liquid state. Deviations are apparent for high-density samples in the amorphous state and in the low-density, low-temperature range, when ions condense into AB(2) molecules. A similar relation predicting the ionic conductivity is only partially validated by our data. The simulation results, covering 210 distinct thermodynamic states, represent an extended database to tune and validate semianalytical theories of dynamical properties and provide a baseline for the interpretation of properties of more complex systems such as the room-temperature ionic liquids.

Effect of hydrophobic nanopatches within an ionic surface on the structure of liquids

The structures of liquid water and isopropanol have been studied as a function of the size of a hydrophobic patch present in a model hydrophilic surface via molecular dynamics simulations. A significant anisotropy extending into the first few solvent layers is found over the patch which suggests implications for many real-world systems in which nanoscale heterogeneity is found.

A kinetic study of the liquid-phase hydrogenation of citral on Au/TiO2 and Pt-Sn/TiO2 thin films in capillary microreactors

The kinetics of the liquid-phase hydrogenation of citral (3,7-dimethyl-2,6-octadienal) on Au/TiO2 and Pt-Sn/TiO2 thin films was studied in the temperature range 313-353 K and citral concentrations of 0.25-10.0 mol m(-3). The thin films were deposited onto the inner walls of silica capillaries with internal diameter of 250 mu m. First-order dependence on hydrogen pressure and near zero order dependence on citral concentration were observed for the initial rate of citral hydrogenation over the Pt-Sn/TiO2 and Au/TiO2 thin films. The Au/TiO2 catalyst prevents citronellal formation. The highest yield of unsaturated alcohols was obtained on the Pt-Sn/TiO2 film at a reaction temperature of 343 K, liquid residence time of 30 min and a citral conversion of 99%. (C) 2011 Elsevier B.V. All rights reserved.

Validation of Speciation Techniques: A Study of Chlorozincate(II) Ionic Liquids

The speciation of chlorozincate(II) ionic liquids, prepared by mixing 1-octyl-3-methylirnidazolium chloride, [C(8)mim]Cl, and zinc(II) chloride in various molar ratios, chi zncl(2), was investigated using Raman spectroscopy and differential scanning calorimetry; the Gutmann acceptor number, which is a quantitative measure of Lewis acidity, was also determined as a function of the composition. These results were combined with literature data to define the anionic speciation; in the neat liquid phase, the existence of cl(-), [ZnCl4](2-), [Zn2Cl6](2-), [Zn3Cl8](2-), and [Zn4Cl10](2-) anions was confirmed. From two chlorozincate(H) ionic liquids with [C(2)mim](+) cations (chi zncl(2) = 0.33 and chi zncl(2) = 0.50), crystals have been obtained, revealing the structures of [C(2)mim)(2)[ZnCl4] and [C(2)mim](2)[Zn2Cl6] forming three-dimensional hydrogen-bond networks. The compound [C(2)mim](2){Zn4Cl10} was crystallized from the chi zncl(1) = 0.75 composition, showing an open-framework structure, with the first example of zinc in a trigonal-bipyramidal chloride coordination. Reinvestigation of the electrospray ionization mass spectrometry of these systems demonstrated that it is an unreliable technique to study liquid-phase speciation.