Solubility Of Ionic Liquids Research Articles

Reducing CO2 using room-temperature ionic liquids

Ionic liquids—imidazolnium salts which are molten near room temperature—have been demonstrated for the low-temperature synthesis of metals and alloys, such as aluminum and titanium-aluminum alloys, and also for the recycling of aluminum composites and scrap. These processes help reduce CO 2 emissions from metallurgical processes. Similar approaches are being followed worldwide. A review on the use of ionic liquids in the electrodeposition of metals and semi-conductors was published in 2002. The interesting polar properties of these ionic liquids are being utilized in other applications of chemical synthesis as well. A. Fadeev and M. Meagher, who described the use of ionic liquids as extractants in biofuel production, noted that the room-temperature ionic liquids have potential as extractants in recovery of butyl alcohol from fermentation broth. Water solubility in ionic liquid is an important factor affecting selectivity of butyl alcohol extraction from aqueous solutions.

Ionic liquid‐assisted PDMS microchannel modification for efficiently resolving fluorescent dye and protein adsorption

Herein, a hybrid system consisting of ionic liquid (IL) and nonionic surfactant has been successfully developed for dynamic modification of PDMS microchips and analyte adsorption such as fluoresent dyes and proteins has been efficiently suppressed. Mutual authentication between microchip electrophoresis and confocal laser scanning microscope was carried out to characterize the multiple novel functions of the IL-containing system and a possible mechanism was raised. Soluble IL used herein not only played the role as supporting electrolyte, but also provided increased EOF in the PDMS microchannel compared with common electrolytes such as phosphate buffer. Due to the high ionic conductivity of IL, on-column field-amplified sample stacking effect was four-fold higher than that without IL. Furthermore, an excellent synergistic effect existed between IL and nonionic surfactant, which enhanced the ability of resolving analyte adsorption to PDMS surface, and was demonstrated in the sensitive and efficient determination of rhodamine B (with detection limit of 8 nM) and a well separated mixture of proteins.

Improving Carbon Dioxide Solubility in Ionic Liquids

Previously we showed that CO2 could be used to extract organic molecules from ionic liquids without contamination of the ionic liquid. Consequently a number of other groups demonstrated that ionic liquid/CO2 biphasic systems could be used for homogeneously catalyzed reactions. Large differences in the solubility of various gases in ionic liquids present the possibility of using them for gas separations. More recently we and others have shown that the presence of CO2 increases the solubility of other gases that are poorly soluble in the ionic liquid phase. Therefore, a knowledge and understanding of the phase behavior of these ionic liquid/CO2 systems is important. With the aim of finding ionic liquids that improve CO2 solubility and gaining more information to help us understand how to design CO2-philic ionic liquids, we present the low- and high-pressure measurements of CO2 solubility in a range of ionic liquids possessing structures likely to increase the solubility of CO2. We examined the CO2 solubility in a number of ionic liquids with systematic increases in fluorination. We also studied nonfluorinated ionic liquids that have structural features known to improve CO2 solubility in other compounds such as polymers, for example, carbonyl groups and long alkyl chains with branching or ether linkages. Results show that ionic liquids containing increased fluoroalkyl chains on either the cation or anion do improve CO2 solubility when compared to less fluorinated ionic liquids previously studied. It was also found that it was possible to obtain similar, high levels of CO2 solubility in nonfluorous ionic liquids. In agreement with our previous results, we found that the anion frequently plays a key role in determining CO2 solubility in ionic liquids.

Imidazolium-based alkylphosphate ionic liquids – A potential solvent for extractive desulfurization of fuel

N-ethyl-imidazolium-based alkylphosphate ionic liquid (IL), viz. N-ethyl- N-methyl-imidazolium dimethylphosphate ([EMIM][DMP]), N-ethyl- N-ethyl-imidazolium diethylphosphate ([EEIM][DEP]) and N-butyl- N-ethyl-imidazolium dibutylphosphate ([BEIM][DBP]) were demonstrated to be effective for the removal of aromatic sulfur compounds (S-compound) 3-methylthiophene (3-MT), benzothiophene (BT) and dibenzothiophene (DBT) from fuel oils in terms of sulfur partition coefficients ( K N ) at 298.15 K. It was shown that the extractive ability of the alkylphosphate ILs was dominated by the structure of the cation and followed the order [BEIM][DBP] > [EEIM][DEP] > [EMIM][DMP] for each S-compound studied with their K N -value being 1.72, 1.61 and 1.17, respectively for DBT. For a specified IL the sulfur selectivity followed the order DBT > BT > 3-MT with their K N -value being 1.61, 1.39 and 0.78, respectively for [EEIM][DEP]. The alkylphosphate ILs are insoluble in fuel while the fuel solubility in ILs varies from 20.6 mg(fuel)/g(IL) for [EMIM][DMP] to 266.9 mg(fuel)/g(IL) for [BEIM][DBP]. The results suggest that [EEIM][DEP] might be used as a promising solvent for the extractive desulfurization of fuel, considering its higher sulfur extractive ability, lower solubility for fuel and thus negligible influence on the constituent of fuel, and the ease of regeneration for the spent IL via water dilution process.

Reverse Micelles in Carbon Dioxide with Ionic‐Liquid Domains

Supercritical CO2 is an attractive green solvent. [1] However, CO2 is generally a poor solvent for high-molecular-weight or hydrophilic molecules, which rules out many potential applications. An effective way to solve this problem is to create reverse micelles or microemulsions with supercritical CO2 as the continuous phase. Many studies have been carried out on water-in-CO2 microemulsions and reverse micelles in supercritical CO2 with water domains. [2] Researchers have also investigated the applications of water-in-CO2 microemulsions, for example, for the extraction of biomolecules and metal ions, for the preparation of nanoparticles, and as media for chemical reactions. Room-temperature ionic liquids, which are organic salts with melting points below 100 8C, have attracted much attention. They can dissolve many organic and inorganic substances, and their properties are tunable to satisfy the requirements of a variety of tasks. Many ionic liquids can be considered as cleaner solvents than standard solvents because they are nonvolatile and often nontoxic or low toxic. Ionic liquids have potential applications in a range of areas, such as separations, chemical reactions, and materials synthesis. It was reported that ionic liquids could dissolve supercritical CO2, whereas the solubility of ionic liquids in supercritical CO2 was negligible. [10]

EFFECT OF IMIDAZOLIUM-BASED IONIC LIQUIDS ON THE PHOTOSYNTHETIC ACTIVITY AND GROWTH RATE OF SELENASTRUM CAPRICORNUTUM

Ionic liquids (ILs) are low-melting organic salts that are being researched intensively as possible environmentally friendly replacements for volatile organic solvents. Despite their nonmeasurable vapor pressure, some quantities of ILs soon will be present in effluent discharges because solubility of ILs in water is small, but far from negligible. Therefore, it is important to understand how ILs will influence aquatic ecosystems. In the present study, the toxic effects of imidazolium-based ILs (1-butyl-3-methylimidazolium cation associated with bromide [BMIM] [Br] and tetrafluoroborate [BMIM] [BF4]) to the freshwater green alga Selenastrum capricornutum were investigated. Two approaches were followed to quantify toxicity of these compounds: Analyses of photosynthetic activity and cell proliferation. The obtained data showed that the relative declines of growth rates generally were more pronounced than those of photosynthetic activity. The ecotoxicity of a range of common organic solvents also was examined. It was revealed that both imidazolium-based ILs studied were some orders of magnitude more toxic than methanol, isopropanol, and dimethylformamide. In addition, with respect to IL incorporating perfluorinated anion, EC50 values (concentrations which lead to a 50% reduction of the exposed organisms relative to control) of the previously prepared stock solution were significantly lower compared to those of the freshly made one. This might be due to hydrolytic effects of [BMIM][BF4] leading to fluoride formation, which was confirmed by ion chromatography analysis. This indicates that, after ILs are discharged into the aqueous system, they can become more toxic than expected by laboratory data with fresh ILs.

Predictions of flavonoid solubility in ionic liquids by COSMO-RS: experimental verification, structural elucidation, and solvation characterization

Predictions of the solubility of flavonoids in a large variety of ionic liquids (ILs) with over 1800 available structures were examined based on COSMO-RS computation. The results show that the solubilities of flavonoids are strongly anion-dependent. Experimental measurement of the solubilities of esculin and rutin in 12 ILs with varying anions and cations show that predicted and experimental results generally have a good agreement. Based on the sound physical basis of COSMO-RS, the solubility changes of flavonoids were quantitatively associated with solvation interactions and structural characteristics of ILs. COSMO-RS derived parameters, i.e. misfit, H-bonding and van der Waals interaction energy, are shown to be capable of characterizing the complicated multiple interactions in the IL system effectively. H-bonding interaction is the most dominant interaction for ILs (followed by misfit and van der Waals interactions) to determine the solubility of flavonoids, and the anionic part has greater effect on the overall H-bonding capability of the IL. Based on basicity of anions, ILs were categorized into 3 groups, corresponding to the classification of the solubility of flavonoid. COSMO sigma-moment descriptors, which roughly denote the characteristic properties of the ILs, might be of general value to have a fast estimation for the solubilities of flavonoids as well as those compounds with massive moieties as H-bonding donors. The results obtained in this work may be important for achieving an improved understanding of IL solvations and the tailoring of the desired structures of ILs used as the media for efficient enzymatic esterification of flavonoids.

Influence of high pressure on solubility of ionic liquids: experimental data and correlation

The solid–liquid phase equilibrium (SLE) in binary mixtures that contain a room-temperature ionic liquid, IL, and an organic solvent: {1-ethyl-3-methylimidazolium tosylate, [EMIM][TOS] (1) + cyclohexane, or benzene (2)} and {1,3-dimethylimidazolium methylsulfate, [MMIM][CH3SO4] (1) + hexan-1-ol (2)} have been measured under very high pressures up to about 900 MPa at the temperature range from T = 328 to 363 K. The termostatted apparatus for the measurements of transition pressures from the liquid to the solid state was used. The pressure–temperature–composition relation of the high pressure solid–liquid phase equilibria polynomial based on the Yang model was satisfactorily used. The freezing and melting temperatures at a constant composition increase monotonously with pressure. The high pressure experimental results obtained at isothermal conditions (p–x) were interpolated to well known T–x diagrams. Additionally, the SLE of binary systems {[EMIM][TOS] (1) + cyclohexane, or benzene (2)} at normal pressure have been measured by a dynamic method from 270 K to the melting point of the IL. Experimental solubility results are compared with values calculated by means of the non-random, two-liquid equation (NRTL) utilizing parameters derived from SLE and liquid–liquid equilibria (LLE) results. The experimental results at high pressures were compared for every system to these at normal pressure. The paper includes thermophysical basic characterization of pure ionic liquids obtained via differential scanning calorimetry (DSC), temperatures and enthalpies of melting. The influence of the interaction between the IL and solvent on the solubility at 0.1 MPa and high pressure up to 900 MPa was discussed.

Obtaining high transesterification activity for subtilisin in ionic liquids

It is known that subtilisin shows poor transesterification activity in ionic liquids (ILs). The present work, taking subtilisin as the system, explores approaches for biocatalyst preparations, which are capable of yielding higher/adequate transesterification activity in these solvents. Of all the approaches tried, enzyme precipitated and rinsed with n-propanol (EPRP) gave the best results (about 10,000 times increase in initial rates in 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF 6]) over what is obtained with pH tuned lyophilized powders). In case of water soluble ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF 4]), pH tuned lyophilized subtilisin did not show any transesterification activity. EPRP, however, gave an initial rate (for transesterification) of 2.78 mmol mg − 1 h − 1 .

Ionic-Liquid-Supported Synthesis: A Novel Liquid-Phase Strategy for Organic Synthesis

Soluble ionic liquids have recently been used as supports for catalyst/reagent immobilization and synthesis in homogeneous solution phase. The wide range of ionic liquid supports available makes their use as supports compatible with most common chemistries. The solubility properties of these ionic liquid supports can be tuned by the variation of cations and anions to make them phase separate from less polar organic solvents and aqueous media. The ionic-liquid-supported species can therefore be purified from the reaction mixture by simple washings. Ionic-liquid-supported catalysts and reagents have been prepared and used, and they are easily recovered and reused. Parallel and combinatorial libraries of small molecules have been synthesized. Ionic-liquid-supported synthesis (ILSS) has been applied to the preparation of oligopeptides and oligosaccharides. The comparison of ILSS with solid-phase synthesis, soluble-polymer-supported synthesis, and fluorous phase synthesis has been highlighted where applicable.

Extractive Desulfurization of Gasoline Using Imidazolium-Based Phosphoric Ionic Liquids

Sulfur partition coefficients for sulfur compounds 3-methylthiophene (3-MT), benzothiophene (BT), and dibenzothiophene (DBT) between phosphoric ionic liquids (ILs), namely, N-methyl-N-methylimidazolium dimethyl phosphate ([MMIM][DMP]), N-ethyl-N-methylimidazolium diethyl phosphate ([EMIM][DEP]), and N-butyl-N-methylimidazolium dibutyl phosphate (BMIM][DBP]), and gasoline were determined experimentally at 298.15 K over a wide range of sulfur content and compared with other IL extractants. The solubility of sulfur (as DBT, BT) in ILs aqueous solution at 298.15 K and varying water content was also measured. It was shown that the desulfurization ability of the ILs for each sulfur component (DBT, BT, 3-MT) followed the order of [BMIM][DBP] > [EMIM][DEP] ≫ [MMIM][DMP], and the sulfur removal selectivity for a specified IL followed the order of DBT > BT > 3-MT. The phosphoric ILs are insoluble in gasoline while the fuel solubility in ILs is noticeable and follows the order of [BMIM][DBP] ≫ [EMIM][DEP] > [MMIM][DMP]. Considering the relatively high sulfur removal ability, low fuel dissolvability, and small influence on the gasoline treated, [EMIM][DEP] might be used as a promising solvent for the desulfurization of gasoline via an extractive desulfurization (EDS) process. The sulfur components in the spent ILs could be conveniently separated via a water dilution process.

Rheological Behavior of Polyarylsulfone 1‐Butyl‐3‐Methylimidazolium Chloride Solutions

Polyarylsufone polymers are engineering thermoplastics that can only be dissolved in polar solvents. We found that polyarylsufone has good solubility in ionic liquid (IL) with IL being a new kind of green solvent; thus, ILs are potential substitutes for conventional molecular solvents. However, the thermodynamics in ionic liquids are different then those in conventional solvents, so ILs as solvents have attracted enormous attention recently. Rheological behavior is an important factor in polymer material processing. The rheological behavior of polyarylsulfone (PASF) in both N, N,‐dimethylacetamide (DMAc) and ionic liquid 1‐butyl‐3‐methylimidazolium chloride [(Bmim) Cl] were studied in this paper as a function of concentration for concentrated solutions. It is interesting that the rheological behavior of the PASF/(Bmim) Cl solution is very different from that of PASF/DMAc solutions. In DMAc, as concentration increases viscosity increases, while the rheological behavior of the PASF/(Bmim) Cl solution exhibits a maximum in the viscosity‐concentration plots.

Solubilities in Ionic Liquids and Molten Salts from a Simple Perturbed-Hard-Sphere Theory

In recent years, several publications have provided solubilities of ordinary gases and liquids in ionic liquids. This work reports an initial attempt to correlate the experimental data using a perturbed-hard-sphere theory; the perturbation is based on well-known molecular physics when the solution is considered as a dielectric continuum. For this correlation, the most important input parameters are the hard-sphere diameters of the solute and of the cation and anion that constitute the ionic liquid. In addition, the correlation uses the solvent's density and the solute's polarizability and dipole and quadrupole moments, if any. Dispersion-energy parameters are obtained from global correlation of solubility data. Results are given for 20 solutes in several ionic liquids at normal temperatures; in addition, some results are given for gases in two molten salts at very high temperatures. Because the theory used here is much simplified and because experimental uncertainties (especially for gaseous solutes) are ...

Synthesis of Symmetrical Organic Carbonates via Significantly Enhanced Alkylation of Metal Carbonates with Alkyl Halides/Sulfonates in Ionic Liquid

[reaction: see text] We report a new phosgene-free method for the synthesis of symmetrical organic carbonates via alkylation of metal carbonate with various alkyl halides and sulfonates in 1-n-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF6], as an ecofriendly reaction media. Alkylation of metal carbonate in various ionic liquids with 1-bromo-3-phenylpropane (1a) as a model reactant has thoroughly been investigated. Potassium and cesium carbonates appeared to be the most suitable metal carbonate due to their high solubility in ionic liquids. Besides good to excellent yields, this simple and convenient methodology is devoid of highly toxic and harmful chemicals such as phosgene and carbon monoxide, which is an additional advantage.

Anion Effects on Gas Solubility in Ionic Liquids

This work presents the results of solubility measurements for a series of gases in 1-n-butyl-3-methyl imidazolium tetrafluoroborate and 1-n-butyl-3-methyl imidazolium bis(trifluoromethylsulfonyl) imide. The gases considered include benzene, carbon dioxide, nitrous oxide, ethylene, ethane, oxygen, and carbon monoxide. Carbon dioxide and oxygen solubilities are also reported in methyl-tributylammonium bis(trifluoromethylsulfonyl) imide, butyl-methyl pyrrolidinium bis(trifluoromethylsulfonyl) imide, and tri-isobutyl-methyl phosphonium p-toluenesulfonate. We report the associated Henry's constants and enthalpies and entropies of absorption. In general, benzene, followed by carbon dioxide and nitrous oxide, have the highest solubilities and strongest interactions with the ionic liquids, followed by ethylene and ethane. Oxygen had very low solubilities and weak interactions. Carbon monoxide had a solubility below the detection limit of our apparatus. Ionic liquids with the bis(trifluoromethylsulfonyl) imide anion had the largest affinity for CO(2), regardless of whether the cation was imidazolium, pyrrolidinium, or tetraalkylammonium. These results suggest that the nature of the anion has the most significant influence on the gas solubilities.

Examination of the Potential of Ionic Liquids for Gas Separations

:Ionic liquids have received increasing interest in recent years for “green” synthesis and separations because they have essentially no vapor pressure. We have begun an investigation of the potential of ionic liquids for gas separations, including the removal of carbon dioxide from stack gas generated in coal-fired power plants. In this paper, we report results from measurements of the permeance of nitrogen and carbon dioxide in supported ionic liquid membranes. Preliminary results for a porous alumina membrane saturated with l-butyl-3-methyl imidazolium bis[trinuoromethylsulfonyl] amide yielded a CO2 : N2 selectivity of 127. Using previously reported measurements of CO2 solubility in ionic liquids (1) and the measured membrane transport characteristics, a preliminary economic analysis of a separation process based on supported ionic liquid membranes has been performed. A comparison of cost estimates for this membrane-based separation to cost estimates reported for carbon dioxide removal using a conventional amine scrubbing operation shows that, with continued technology development, an ionic liquid membrane process may potentially be economically competitive with amine scrubbing. A preliminary cost estimate for an ionic liquid scrubber indicates that an ionic liquid absorption process shows less favorable economics than a supported ionic liquid membrane or an amine scrubber. However, results indicate that a more comprehensive technical and economic assessment is warranted.

Recovery of amino acids by imidazolium based ionic liquids from aqueous media

In this paper, imidazolium based ionic liquids [C4mim][PF6], [C6mim][PF6], [C6mim][BF4] and [C8mim][BF4] were used as alternative solvents for the recovery of some amino acids (L-tryptophan, L-phenylalanine, L-tyrosine, L-leucine and D-valine) from aqueous media. The experimental results shown that logarithm of partition coefficients, log (PIL/W), of the amino acids correlate well with the hydrophobicity of the amino acids, indicating the importance of the hydrophobic effect of amino acids as a driving force for their partition into a particular ionic liquid. The partition coefficients are found to be strongly affected by pH of aqueous phases and the water solubility in ionic liquids. They decrease steeply with increasing pH in the range of pH < pK1, but increase with increasing solubility of water in ionic liquid phases. The higher extraction degree at low pHs has been interpreted by the strong electrostatic interactions between cationic form of the amino acids and anion of the ionic liquids. The importance of anionic nature and the alkyl chain length on the cation of ionic liquids have also been examined. It is noted that ionic liquid with BF4− anion has much higher extraction efficiency for the amino acids than those with PF6− anion because of the stronger effective charge in BF4−. It seems likely that there is no correlation between the partition coefficients of the amino acids and the polarity of the ionic liquids. Preliminary results indicated that [C6mim][BF4] and [C8mim][BF4] ionic liquids may be adapted to liquid-liquid recovery process of some amino acids from aqueous media, and L-tryptophan can be effectively separated from fermentation broth in a multiple step process using [C6mim][BF4] as an extractant.

Measuring the solubilities of ionic liquids in water using ion-selective electrodes

Polyvinyl chloride-plasticized membrane ion-selective electrodes (ISE) based on conventional ion-exchangers have been proposed as a cheap universal tool to measure the solubilities of ionic liquids (ILs) in water. They are applicable for ILs with a wide range of solubilities in water, since the linear range of a potentiometric response spans several orders of magnitude. As an example, we have fabricated and tested ISEs for widely used alkylimidazolium ionic liquids. The aqueous solubilities of four typical ILs have been determined at 21 degrees C: 0.075 +/- 0.001 mol l(-1) (1-butyl-3-methylimidazolium, BMIm, hexafluorophosphate); 0.018 +/- 0.001 mol l(-1) (BMIm bis(triflylimide)); 0.054 +/- 0.007 mol l(-1) (1-butyl-2,3-dimethylimidazolium, BDMIm, hexafluorophosphate); 0.014 +/- 0.001 mol l(-1) (BDMIm bis(triflylimide)).

Effect of Organic Cosolvents on the Solubility of Ionic Liquids in Supercritical CO2

The solubilities of ionic liquids (ILs) 1-butyl-3- methylimidazolium hexafluorophosphate ([bmim][PF6]) and 1-butyl-3- methylimidazolium tetrafluoroborate ([bmim][BF4]) in supercritical (sc) CO2 with and without organic cosolvents were determined at 40.0 °C and 15.0 MPa. The mole fraction of a cosolvent was up to 0.3. The solubilities of the ILs in sc CO2 + polar cosolvent mixtures increased dramatically as the cosolvent concentration exceeded 10 mol %, but the solubility was extremely low when the concentration of the cosolvent was lower than 10 mol %. The effect of a cosolvent on the solubility of the ILs in sc CO2 depends mainly on its polarity. The stronger the polarity of a cosolvent, the larger the effect. The ability of the mixed cosolvent to enhance the solubility is intermediate between the two pure cosolvents.

Carbon Monoxide Solubility in Ionic Liquids: Determination, Prediction and Relevance to Hydroformylation.

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