Showing papers on "Ionic liquid published in 2007"
TL;DR: Hydrogenation of Alkenes and Arenes by Nanoparticles 2624 3.1.2.
Abstract: 2.5. Stabilization of IL Emulsions by Nanoparticles 2623 3. Hydrogenations in ILs 2623 3.1. Hydrogenation on IL-Stabilized Nanoparticles 2623 3.1.1. Hydrogenation of 1,3-Butadiene 2623 3.1.2. Hydrogenation of Alkenes and Arenes 2624 3.1.3. Hydrogenation of Ketones 2624 3.2. Homogeneous Catalytic Hydrogenation in ILs 2624 3.3. Hydrogenation of Functionalized ILs 2625 3.3.1. Selective Hydrogenation of Polymers 2625 3.4. Asymmetric Hydrogenations 2626 3.4.1. Enantioselective Hydrogenation 2626 3.5. Role of the ILs Purity in Hydrogenation Reactions 2628
1,996 citations
TL;DR: The catalytic conversion of sugars giving high yield to 5-hydroxymethylfurfural (HMF), a versatile intermediate, is reported, finding chromium (II) chloride to be uniquely effective, leading to the conversion of glucose to HMF with a yield near 70%.
Abstract: Replacing petroleum feedstocks by biomass requires efficient methods to convert carbohydrates to a variety of chemical compounds. We report the catalytic conversion of sugars giving high yield to 5-hydroxymethylfurfural (HMF), a versatile intermediate. Metal halides in 1-alkyl-3-methylimidazolium chloride are catalysts, among which chromium (II) chloride is found to be uniquely effective, leading to the conversion of glucose to HMF with a yield near 70%. A wide range of metal halides is found to catalyze the conversion of fructose to HMF. Only a negligible amount of levulinic acid is formed in these reactions.
1,831 citations
TL;DR: This study provides the first experimental evidence of the existence of nanoscale heterogeneities in neat liquid and supercooled RTILs, such as 1-alkyl-3-methyl imidazolium-based salts, using X-ray diffraction, showing a behavior that resembles the density one only below the glass transition, thus suggesting a complex behavior above this temperature.
Abstract: Room-temperature ionic liquids (RTILs) are organic salts that are characterized by low melting points. They are considered to possess a homogeneous microscopic structure. We provide the first experimental evidence of the existence of nanoscale heterogeneities in neat liquid and supercooled RTILs, such as 1-alkyl-3-methyl imidazolium-based salts, using X-ray diffraction. These heterogeneities are of the order of a few nanometers and their size is proportional to the alkyl chain length. These results provide strong support to the findings from recent molecular dynamics simulations, which proposed the occurrence of nanostructures in RTILs, as a consequence of alkyl chains segregation. Moreover, our study addresses the issue of the temperature dependence of the heterogeneities size, showing a behavior that resembles the density one only below the glass transition, thus suggesting a complex behavior above this temperature. These results will provide a novel interpretation approach for the unique chemical physi...
1,144 citations
TL;DR: The application of ionic liquids in all areas of separation science including extractions, gas chromatography, and supported liquid membrane processes are highlighted.
Abstract: Ionic liquids are liquids composed completely of ions. In the past two decades, ionic liquids have been widely used as “green solvents” replacing traditional organic solvents for organic synthesis and catalysis. In addition, ionic liquids are playing an increasingly important role in separation science. In this Account, the application of ionic liquids in all areas of separation science including extractions, gas chromatography, and supported liquid membrane processes are highlighted.
957 citations
TL;DR: The present paper demonstrates that both hardwoods and softwoods are readily soluble in various imidazolium-based ionic liquids (ILs) under gentle conditions, and offers a variety of new possibilities for its structural and macromolecular characterization, without the prior isolation of its individual components.
Abstract: The present paper demonstrates that both hardwoods and softwoods are readily soluble in various imidazolium-based ionic liquids (ILs) under gentle conditions. More specifically, a variety of ionic liquids can only partially dissolve wood chips, whereas ionic liquids such as 1-butyl-3-methylimidazolium chloride and 1-allyl-3-methylimidazolium chloride have good solvating power for Norway spruce sawdust and Norway spruce and Southern pine thermomechanical pulp (TMP) fibers. Despite the fact that the obtained solutions were not fully clear, these ionic liquids provided solutions which permitted the complete acetylation of the wood. Alternatively, transparent amber solutions of wood could be obtained when the dissolution of the same lignocellulosic samples was attempted in 1-benzyl-3-methylimidazolium chloride. This realization was based on a designed augmented interaction of the aromatic character of the cation of the ionic liquid with the lignin in the wood. After dissolution, wood can be regenerated as an ...
950 citations
TL;DR: In this paper, the characteristics of dye-sensitized solar cells using an ionic liquid as the electrolyte and compare them with the response of a solvent-containing electrolyte cell were analyzed.
Abstract: In this work, we study the characteristics of dye-sensitized solar cells using an ionic liquid as the electrolyte and compare them with the response of a solvent-containing electrolyte cell. Impedance spectroscopy is used to derive the key circuit elements determining the photovoltaic performance of the cell. On the basis of this data, photocurrent voltage curves are calculated and compared with experimental results.
881 citations
TL;DR: In this article, the authors present an alternative approach for the processing of lignocellulosic materials that relies on their solubility in solvent systems based on the ionic liquid (IL) 1-n-butyl-3-methylimidazolium chloride ([C4mim]Cl).
805 citations
TL;DR: Ionothermal synthesis, the use of ionic liquids as both solvent and template (structure-directing agent), has been used to prepare zeolites and inorganic-organic hybrids such as metal-organic frameworks.
Abstract: Ionothermal synthesis, the use of ionic liquids as both solvent and template (structure-directing agent), has been used to prepare zeolites and inorganic-organic hybrids such as metal-organic frameworks. The underlying properties of the ionothermal method are discussed, and it is compared with traditional hydrothermal preparative methods. The materials resulting from ionothermal synthesis are described, and any structural features that can be related to the ionic liquid used as the solvent are discussed. Future areas of potential interest are also considered.
761 citations
TL;DR: 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 liquid previously studied, and it was found that it was possible to obtain similar, high levels of CO2solubility in nonfluorous ionic fluids.
Abstract: 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 solubilit...
704 citations
699 citations
TL;DR: The objective of the present review is to discuss different aspects of the use of ILs in carbohydrate chemistry, in particular, dissolution and functionalization of simple sugars, cyclodextrins, cellulose, starch, and chitin/chitosan.
TL;DR: Ionic liquids can serve as solvents for lanthanide-mediated organic reactions, and there are several examples of high reactivity and selectivity.
Abstract: Ionic liquids are solvents that consist entirely of ions. These nonvolatile and nonflammable solvents offer interesting opportunities for lanthanide and actinide chemistry. They can replace the organic phase in solvent extraction systems and can be used as nonaqueous electrolytes for electrodeposition of metals. Ionic liquids could find applications in the nuclear fuel cycle. Lanthanide coordination compounds or lanthanide-containing nanoparticles can be obtained via ionothermal or microwave-assisted synthesis in ionic liquids. Lanthanide-doped ionogels are a new type of luminescent hybrid materials. Ionic liquids can serve as solvents for lanthanide-mediated organic reactions, and there are several examples of high reactivity and selectivity.
TL;DR: In this article, a coin cell assembled with microporous activated carbon and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PYR14TFSI) ionic liquid as the electrolyte was cycled for 40,000 cycles without any change of cell resistance.
TL;DR: Measurements of the solubilities of CO2, CH4, C2H 6, C 2H 4, O2, and N2 in 1-hexyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide are described and focus is placed on efforts to tailor ionic liquids to enhance the solUBilities of some gases, with particular emphasis on carbon dioxide.
Abstract: The solubilities of gases in ionic liquids are important in evaluating ionic liquids as solvents for reactions involving permanent gases, as gas storage media, and as solvents for gas separations Gas solubilities are also important in developing methods to separate solutes from ionic liquid solutions Here we describe our measurements of the solubilities of CO2, CH4, C2H6, C2H4, O2, and N2 in 1-hexyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide and compare these results to our previous investigations In addition, focus is placed on efforts to tailor ionic liquids to enhance the solubilities of some gases, with particular emphasis on carbon dioxide
TL;DR: In this article, the authors examined the application of select ionic liquids (ILs) as aprotic green solvents for lignin and found that up to 20 wt% Lignin can be dissolved in [hmim][CF3SO3], [mmim][MeSO4] and [bmim][meSO4].
Abstract: This study examined the application of select ionic liquids (ILs) as aprotic green solvents for lignin. Dissolution experiments were carried out employing lignin isolated from pine kraft pulp. Up to 20 wt% lignin could be dissolved in [hmim][CF3SO3], [mmim][MeSO4] and [bmim][MeSO4]. For the [bmim]+‐containing ionic liquids, the order of lignin solubility for varying anions was: [MeSO4]−>Cl−∼Br−⋙[PF6]−, indicating that the solubility of lignin was principally influenced by the nature of the anions. Ionic liquids containing large, non‐coordinating anions [PF4]− and [PF6]− were unsuitable as a solvent for lignin. 13C nuclear magnetic resonance (NMR) analyses of lignin and model compounds showed that 13C signals using ionic liquid as a solvent were shifted up‐field by δ 0.1 to 1.9 ppm in comparison to 13C NMR data acquired using dimethyl sulfoxide (DMSO) as the solvent.
TL;DR: Unique phase behavior of the resulting hydrophobic ionic liquids and water mixture is found; the mixture is clearly phase separated at room temperature, but the solubility of water in this IL increases upon cooling, to give a homogeneous solution.
Abstract: The preparation of ionic liquids derived from amino acids, and their properties, are outlined Since amino acids have both a carboxylic acid residue and an amino group in a single molecule, they can be used as either anions or cations These groups are also useful in their ability to introduce functional group(s) Twenty different natural amino acids were used as anions, to couple with the 1-ethyl-3-methylimidazolium cation The salts obtained were all liquid at room temperature The properties of the resulting ionic liquids (AAILs) depend on the side groups of the amino acids involved These AAILs, composed of an amino acid with some functional groups such as a hydrogen bonding group, a charged group, or an aromatic ring, had an increased glass transition (or melting) temperature and/or higher viscosity as a result of additional interactions among the ions Viscosity is reduced and the decomposition temperature of imidazolium-type salts is improved by using the tetrabutylphosphonium cation The chirality of AAILs was maintained even upon heating to 150 degrees C after acetylation of the free amino group The amino group was also modified to introduce a strong acid group so as to form hydrophobic and chiral ionic liquids Unique phase behavior of the resulting hydrophobic ionic liquids and water mixture is found; the mixture is clearly phase separated at room temperature, but the solubility of water in this IL increases upon cooling, to give a homogeneous solution This phase change is reversible, and separation occurs again by raising the temperature a few degrees It is extraordinary for an IL/water mixture to display such behavior with a lower critical solution temperature Some likely applications are proposed for these amino acid derived ionic liquids
TL;DR: In this article, the authors focus on the reactivity of ionic liquids, as opposed to reactivity in ionic liquid, although discussion of the latter is often included where it aids understanding of the former.
TL;DR: In this article, a drop-shape analysis technique and 1H NMR measurements were used to monitor the adsorption at the aqueous solution-air interface and selfaggregation behavior of room-temperature ionic liquids (ionic liquids) of the 1-alkyl-3-methylimidazolium family of cations, [Cnmim]+, with different linear alkyl chain lengths, CnH2n+1 (½n = 1-7), and different counter-ions, namely [CNMim]Cl (n
TL;DR: Eutectic mixtures of zinc chloride and donor molecules such as urea and acetamide are described and it is proposed that these constitute a new class of ionic liquids that fit well to the Hole theory model recently proposed.
Abstract: Eutectic mixtures of zinc chloride and donor molecules such as urea and acetamide are described and it is proposed that these constitute a new class of ionic liquids. FAB-MS analysis shows that the liquids are made up of metal-containing anions and cations in which the donor is coordinated to the cation. Data on the viscosity, conductivity, density, phase behaviour and surface tension are presented and these are shown to be significantly different to other related ionic liquids that incorporate quaternary ammonium salts. The conductivity and viscosity are comparable with other ionic liquids and the data fit well to the Hole theory model recently proposed.
TL;DR: The processing of carbon nanotubes with ionic liquids is not accompanied by the disruption of the pi-conjugated nanotube structure and does not require solvents; therefore it can readily be scaled up.
Abstract: A serendipitous finding that ionic liquids gel with carbon nanotubes has opened a new possibility of ionic liquids as modifiers for carbon nanotubes. Upon being ground into ionic liquids, carbon nanotube bundles are untangled, and the resultant fine bundles form a network structure. This is due to the possible specific interaction between the imidazolium ion component and the pi-electronic nanotube surface. The resultant gelatinous materials, consisting of highly electroconductive nanowires and fluid electrolytes, can be utilized for a wide variety of electrochemical applications, such as sensors, capacitors, and actuators. Ionic liquids allow for noncovalent and covalent modifications of carbon nanotubes and fabrication of polymer composites with enhanced physical properties. The processing of carbon nanotubes with ionic liquids is not accompanied by the disruption of the pi-conjugated nanotube structure and does not require solvents; therefore it can readily be scaled up. This article focuses on new aspects of ionic liquids for designer soft materials based on carbon nanotubes.
TL;DR: A review of ionic liquid toxicity research can be found in this article, where the authors highlight the development of degradable and bio-renewable ionic liquids, as well as their potential applications.
Abstract: The dramatic growth in ionic liquid research over the past decade has resulted in the development of a huge number of novel ionic liquids, as well as many associated applications. The perceived environmentally friendly nature of ionic liquids, which results from their negligible vapor pressure, is now under scrutiny since although they will not evaporate into air, it is not possible to guarantee that they will never enter the environment. Toxicity research studies including ecotoxicity, have recently received broad attention and the commonly accepted notion that ionic liquids have low toxicity has been shown to be incorrect. This review attempts to highlight the progress of ionic liquid toxicity research, as well as the development of degradable and bio-renewable ionic liquids.
TL;DR: It was found that both the pC20 and the Picmc values were somewhat lower than those for typical cationic surfactants, alkyltrimethylammonium bromides, and comparable to typical anionic surfactant, sodiumAlkyl sulfates.
Abstract: Aqueous solutions of three kinds of surface active ionic liquids composed of the 1-alkyl-3-methylimidazolium cation have been investigated by means of surface tension and electrical conductivity measurements at room temperature (298 K). The surface tension measurements provided a series of parameters, including critical micelle concentration (cmc), surface tension at the cmc (γcmc), adsorption efficiency (pC20), and effectiveness of surface tension reduction (Πcmc). In addition, with application of the Gibbs adsorption isotherm, maximum surface excess concentration (Γmax) and minimum surface area/molecule (Amin) at the air−water interface were estimated. The effect of sodium halides, NaCl, NaBr, and NaI, on the surface activity was also investigated. It was found that both the pC20 and the Πcmc were rather larger than those reported for traditional ionic surfactants and the cmc values were somewhat lower than those for typical cationic surfactants, alkyltrimethylammonium bromides, and comparable to typica...
TL;DR: A perspective on the relations between inorganic and organic cation ionic liquids (ILs), including members with melting points that overlap around the borderline 100 degrees C, and a basis for assessing their relation to aprotic ILs by means of a Gurney-type proton-transfer free energy level diagram.
Abstract: We give a perspective on the relations between inorganic and organic cation ionic liquids (ILs), including members with melting points that overlap around the borderline 100 °C. We then present data on the synthesis and properties (melting, boiling, glass temperatures, etc.) of a large number of an intermediate group of liquids that cover the ground between equimolar molecular mixtures and ILs, depending on the energetics of transfer of a proton from one member of the pair to the other. These proton-transfer ILs have interesting properties, including the ability to serve as electrolytes in solvent-free fuel cell systems. We provide a basis for assessing their relation to aprotic ILs by means of a Gurney-type proton-transfer free energy level diagram, with approximate values of the energy levels based on free energy of formation and pKa data. The energy level scheme allows us to verify the relation between solvent-free acidic and basic electrolytes, and the familiar aqueous variety, and to identify neutral...
TL;DR: In this article, the influence of different head groups, functionalised side chains and anions of ionic liquids on the marine bacteria Vibrio fischeri, the limnic green algae Scenedesmus vacuolatus and the fresh water plant Lemna minor was investigated.
TL;DR: This approach is demonstrated here with the field of energetic ionic liquids (EILs), which utilizes this design flexibility to find safe synthetic routes to ILs with high energy content and targeted physical properties.
Abstract: In this Account of the small portion of the recent research in ionic liquids (ILs) by the Rogers Group, we fast forward through the first evolution of IL research, where ILs were studied for their unique set of physical properties and the resulting potential for tunable “green solvents”, to the second evolution of ILs, where the tunability of the cation and anion independently offers almost unlimited access to targeted combinations of physical and chemical properties. This approach is demonstrated here with the field of energetic ionic liquids (EILs), which utilizes this design flexibility to find safe synthetic routes to ILs with high energy content and targeted physical properties.
TL;DR: In this paper, the solvation force profiles for three room-temperature ionic liquids (ILs), EAN, propylammonium nitrate (PAN), and 1-ethyl-3-methylimidazolium acetate (C2mimAc) confined between Si3N4 tips and mica, silica, and graphite have been measured using an atomic force microscope.
Abstract: Solvation force profiles for three room-temperature ionic liquids (ILs), ethylammonium nitrate (EAN), propylammonium nitrate (PAN), and 1-ethyl-3-methylimidazolium acetate (C2mimAc) confined between Si3N4 tips and mica, silica, and graphite have been measured using an atomic force microscope. The measurements reveal oscillatory behavior in all cases, with the size of the oscillations corresponding to the physical dimension of the ion pair. The surface charge and roughness and the orientation of cations at the interface are critical determinants of solvation layer formation in ILs. The greatest number of solvation layers is observed for EAN on highly charged, atomically smooth mica. Fewer and more compressible layers are observed for PAN due to its increased molecular flexibility. The lower surface charge and increased roughness of silica produces fewer solvation layers for both EAN and PAN compared to mica. For the EAN− and PAN−graphite systems, any attractive interaction with the substrate is due to the ...
TL;DR: In this paper, the critical properties, the normal boiling temperatures, and the acentric factors of ionic liquids have been determined using an extended group contribution method based on the well-known concepts of Lydersen and of Joback and Reid.
Abstract: The critical properties, the normal boiling temperatures, and the acentric factors of ionic liquids have been determined using an extended group contribution method based on the well-known concepts of Lydersen and of Joback and Reid. The critical properties of ionic liquids cannot be experimentally determined in many cases since most of these compounds start to decompose as the temperature approaches the normal boiling point. However, for the development of thermodynamic models either for pure components or for mixtures containing ionic liquids, the critical properties and other physical parameters are required. The so-called group contribution methods have been commonly used to estimate the critical properties of many substances for which these properties are not available, but no attempt has been made to estimate the critical properties of ionic liquids, as presented in this study. The method does not require any additional data besides the knowledge of the structure of the molecule and its molecular weight. Since experimental critical properties of ionic liquids are not available, the accuracy of the method is checked by calculating the liquid densities of the ionic liquids considered in the study. The results show that the values determined for the critical properties, for the normal boiling temperatures, and for the acentric factors are accurate enough for engineering calculations, for generalized correlations, and for equation of state methods, among other applications.
TL;DR: Standard free energies of aggregation DeltaGom of various ILs derived using the refractive index/concentration profiles were found comparable to those of classical ionic surfactants.
Abstract: Self aggregation of the ionic liquids, 1-butyl-3-methylimidazolium chloride [C4mim][Cl], 3-methyl-1-octylimidazolium chloride [C8mim][Cl], 1-butyl-3-methylimidazolium tetrafluoroborate [C4mim][BF4], N-butyl-3-methylpyridinium chloride [C4mpy][Cl], in aqueous solution has been investigated through 1H nuclear magnetic resonance (NMR) and steady-state fluorescence spectroscopy. Aggregation properties were determined by application of mass action theory to the concentration dependence of 1H NMR chemical shifts. Aggregation properties showed fairly good agreement with the previously reported results obtained from small angle neutron scattering, conductivity, and surface tension measurements. A detailed analysis of chemical shifts of water and various protons in ILs has been employed to probe the aggregate structure. Fluorescence spectroscopy provided important information about the critical aggregation concentration (cac) and the microenvironment of the aggregates. We could also observe a break point quite con...
15 Oct 2007
TL;DR: The influence of water content in the surface tension was studied for several ILs as a function of the temperature as well as afunction of water mole fraction, for the most hydrophobic IL investigated, [omim][PF(6)], and one of the more hygroscopic IL, [bmim][ PF(6].
Abstract: This work addresses the experimental measurements of the surface tension of eight imidazolium based ionic liquids (ILs) and their dependence with the temperature (288–353 K) and water content. The set of selected ionic liquids was chosen to provide a comprehensive study of the influence of the cation alkyl chain length, the number of cation substitutions and the anion on the properties under study. The influence of water content in the surface tension was studied for several ILs as a function of the temperature as well as a function of water mole fraction, for the most hydrophobic IL investigated, [omim][PF6], and one of the more hygroscopic IL, [bmim][PF6]. The surface thermodynamic functions such as surface entropy and enthalpy were derived from the temperature dependence of the surface tension values.
TL;DR: Metal nanoparticles with a small diameter and narrow size distribution that can be prepared by H(2) reduction of metal compounds or decomposition of organometallic species dissolved in ionic liquids (ILs) are catalysts for reactions under multiphase conditions.
Abstract: Metal nanoparticles (MNPs) with a small di- ameter and narrow size distribution can be prepared by H2 reduction of metal compounds or decomposition of organometallic species dissolved in ionic liquids (ILs). MNPs dispersed in ILs are catalysts for reactions under multiphase conditions. These soluble MNPs possess a pronounced surfacelike rather than single-site like cata- lytic properties. In other cases the MNPs are not stable and tend to aggregate or serve as reservoirs of mononu- clear catalytically active species.