Imidazolium Acetate Research Articles

Absorption of carbon dioxide in aqueous solutions of imidazolium ionic liquids with carboxylate anions

The solubility of carbon dioxide at atmospheric pressure in aqueous mixtures of 1,3-alkyl substituted imidazolium ionic liquids (ILs) containing carboxylic anions was studied. The ILs showed increased solubility of CO2 with decreasing water concentration. The relationship between the CO2 concentration in solution and the mole fraction of water in the ILs describes a sigmoidal curve. The regression constants of a logistic function were used to quantitatively assess the absorbent capacity and the effect of water on CO2 absorption. ILs containing the most basic anions, such as pivalate, propionate and acetate, had the best properties. It was observed that the impact of water on absorption primarily depended on the cation structure. The best absorption performance was observed for 1,3-dibutylimidazolium pivalate and 1-butyl-3-methyl imidazolium acetate.

Influence of water concentration in the viscosities and densities of cellulose dissolving ionic liquids. Correlation of viscosity data

The densities and viscosities of aqueous mixtures of two cellulose dissolving ionic liquids: 1-allyl-3-methylimidazolium chloride and 1-ethyl-3-methyl imidazolium acetate ionic liquids have been experimentally determined for water concentration up to approx. 35% water at atmospheric pressure and temperature range from (298.15 to 373.15)K. Molar excess volumes were calculated, resulting in negative values. Literature viscosity correlations were modified in order to describe the viscosity as a function of temperature and water concentration for both water concentrations lower than xH2O=0.4 and for all the water concentration range. These modified equations were applied to correlate viscosity of (water+ionic liquid) viscosity data for other 1-alkyl-3-methylimidazolium chloride ionic liquids as well as for (ethanol+1-ethyl-3-methyl imidazolium acetate) from literature obtaining a good reproducibility of the data.

Nanostructural Reorganization Manifests in Sui-Generis Density Trend of Imidazolium Acetate/Water Binary Mixtures.

Ionic liquids (ILs) are emerging as a novel class of solvents in chemical and biochemical research. Their range of applications further expands when a small quantity of water is added. Thus, the past decade has seen extensive research on IL/water binary mixtures. While the thermophysical properties of most of these mixtures exhibited the expected trend, few others have shown deviations from the general course. One such example is the increase in density of the 1-alkyl-3-methyl imidazolium acetate ([Rn mim][Ac])-based ILs with the addition of low to moderate concentrations of water. Although such a unique trend was observed for imidazolium cations of different tail lengths and also from independent experiments, the molecular basis of this unique behavior remains unknown. In this study, we examine the nanostructural reordering in [Rn mim][Ac] (n = 2-6) ILs due to added water by means of molecular dynamics simulations, and correlate the observed changes to the sui-generis density trend. Results suggest that the initial rise in density in these ILs mainly pertains to the water-induced increased spatial correlation among the polar components, where high basicity of the acetate anion plays a key role. At moderate water concentration, the density can rise further for ILs with longer cation tails due to hydrophobic clustering. Thus, while [emim][Ac]/water mixtures exhibit the density turnover at Xw = 0.5, [bmim][Ac] and [hmim][Ac] show the turnover at Xw = 0.7. The detailed understanding provided here could help the preparation of optimal IL/water binary mixtures for various biochemical applications.

Grafting chitosan with polyethylenimine in an ionic liquid for efficient gene delivery.

Modifying chitosan (CS) with polyethylenimine (PEI) grafts is an effective way to improve its gene transfection performance. However, it is still a challenge to conduct the grafting with fine control and high efficiency, particularly for the modification of water-insoluble CS. Herein, a novel method to graft CS with PEI (1.8 kDa, PEI-1.8) was developed by using ionic liquid 1-butyl-3-methyl imidazolium acetate ([BMIM]Ac) as a reaction solvent, water-insoluble CS as a reaction substrate and 1,1-carbonyldiimidazole (CDI) as a linking agent. The grafting reaction was greatly accelerated and the reaction time was largely shortened to 4 h by taking advantages of the good solubility of CS, the enhanced nucleophilicity of amino groups and the preferential stability of the activated complexes in the ionic liquid. The chitosan-graft-polyethylenimine (CS-g-PEI) products were characterized by 1H NMR, FTIR and GPC. PEI-1.8 was quantitatively grafted to CS through urea linkages, and the grafting degree (GD) was conveniently tuned by varying the molar ratios of PEI-1.8 to D-glucosamine units of CS in the range of 9.0 × 10-3 to 9.0 × 10-2. Compared with CS, the synthesized CS-g-PEI copolymers showed higher pDNA-binding affinity, which increased with the GD as shown in Agarose gel electrophoresis. The dynamic light scattering (DLS) experiment demonstrated that the CS-g-PEI/pDNA polyplexes had suitable particle sizes and proper ζ-potentials for cell transfection. The CS-g-PEI copolymer with a medium GD of 4.5% conferred the best gene transfection, with the efficiency 44 times of CS and 38 times of PEI-1.8 in HEp-2 cells. The cytotoxicity of CS-g-PEI was tested and found nearly as low as that of CS and much lower than that of PEI.

Hydrogen fluoride capture by imidazolium acetate ionic liquid

Extraction of hydrofluoric acid (HF) from oils is a drastically important problem in petroleum industry, since HF causes quick corrosion of pipe lines and brings severe health problems to humanity. Some ionic liquids (ILs) constitute promising scavenger agents thanks to strong binding to polar compounds and tunability. PM7-MD simulations and hybrid density functional theory are employed here to consider HF capture ability of ILs. Discussing the effects and impacts of the cation and the anion separately and together, we evaluate performance of imidazolium acetate and outline systematic search guidelines for efficient adsorption and extraction of HF.

Integrating Ultra‐Thermal‐Sensitive Fluids into Elastomers for Multifunctional Flexible Sensors

An ultra-thermal-sensitive conductive fluid composed of 1-octyl-3-methyl imidazolium acetate is integrated into different designed elastomers for the rapid and precise detection of multiple physical parameters, such as epidermal temperature, near-infrared light, and pressure force. The liquid sensor not only detects temperature and pressure simultaneously but also realizes the signal separation through different sensing mechanism. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Dissolution Model of Ball Milled Rice Straw Particles in 1-Ethyl-3-Methyl Imidazolium Acetate at Elevated Temperature

In Asia, rice straw residue left in fields after harvest is often burned which causes air pollution or anaerobically digested in the rice patty moist soil to yield methane a greenhouse gas. Effective and efficient process strategies are needed to convert straw into fuels and feedstock’s which do not harm the environment. As a result, this study was undertaken to liquefy Japanese rice straw (RS) an abundant agricultural residue into a liquid after pre-treatment by ball-milling at various temperatures and develop a bioprocess model. Specifically, RS was ball milled into 75-100 μm size particles at temperatures of 60°C, 25°C, and -196°C (cryogenically) and dissolved by heating in 1-ethyl-3- methylimidazolium acetate [Emim][OAc] at different temperatures between 120° 140° and 160°C to understand the interactions between the process parameters. The milled RS powder particles were characterized by FTIR, XRD, BET analyzer and dissolution follow using optical microscopy. The particle dissolution was analyzed by measuring the particle light intensity ratio and particle cross-sectional area as a function of heating time. Higher milling temperature leads to amorphization of the RS cellulose accelerating dissolution. Measurement of the particle light intensity ratio was used to estimate the rice straw particles dissolution endpoint. A particle dissolution model indicated that ball milling temperature and [Emim][OAc] heating temperature strongly interacts influencing the dissolution time. To dissolve RS in [Emim][OAc] quickly, it important to reduce the crystallinity of the cellulose and increase the particle surface area by milling at higher temperature. It is believed this model would have applications to other biomass dissolution processes.

Elucidating the conformational energetics of glucose and cellobiose in ionic liquids.

A major challenge for the utilization of lignocellulosic feedstocks for liquid fuels and other value added chemicals has been the recalcitrant nature of crystalline cellulose to various hydrolysis techniques. Ionic liquids (ILs) are considered to be a promising solvent for the dissolution and conversion of cellulose to simple sugars, which has the potential to facilitate the unlocking of biomass as a supplement and/or replacement for petroleum as a feedstock. Recent studies have revealed that the orientation of the hydroxymethyl group, described via the ω dihedral, and the glycosidic bond, described via the φ-ψ dihedrals, are significantly modified in the presence of ILs. In this study, we explore the energetics driving the orientational preference of the ω dihedral and the φ-ψ dihedrals for glucose and cellobiose in water and three imidazolium based ILs. It is found that interactions between the cation and the ring oxygen in glucose directly impact the conformational preference of the ω dihedral shifting the distribution towards the gauche-trans (GT) conformation and creating an increasingly unfavorable gauche-gauche (GG) conformation with increasing tail length. This discovery modifies the current hypothesis that intramolecular hydrogen bonding is responsible for the shift in the ω dihedral distribution and illuminates the importance of the cation's character. In addition, it is found that the IL's interaction with the glycosidic bond results in the modification of the observed φ-ψ dihedrals, which may have implications for hydrolysis in the presence of ILs. The molecular level information gained from this study identifies the favorable IL-sugar interactions that need to be exploited in order to enhance the utilization of lignocellulosic biomass as a ubiquitous feedstock.

Characterization and interfacial properties of the surfactant ionic liquid 1-dodecyl-3-methyl imidazolium acetate for enhanced oil recovery

Formulations of ionic liquids and alkalis are promising for enhanced oil recovery.

An abnormal N-heterocyclic carbene-carbon dioxide adduct from imidazolium acetate ionic liquids: the importance of basicity.

In the reaction of 1-ethyl-3-methylimidazolium acetate [C2C1Im][OAc] ionic liquid with carbon dioxide at 125 °C and 10 MPa, not only the known N-heterocyclic carbene (NHC)-CO2 adduct I, but also isomeric aNHC-CO2 adducts II and III were obtained. The abnormal NHC-CO2 adducts are stabilized by the presence of the polarizing basic acetate anion, according to static DFT calculations and ab initio molecular dynamics studies. A further possible reaction pathway is facilitated by the high basicity of the system, deprotonating the initially formed NHC-CO2 adduct I, which can then be converted in the presence of the excess of CO2 to the more stable 2-deprotonated anionic abnormal NHC-CO2 adduct via the anionic imidazolium-2,4-dicarboxylate according to DFT calculations on model compounds. This suggests a generalizable pathway to abnormal NHC complex formation.

Magnetic nanoparticles supported imidazolium-based ionic liquids as nanocatalyst in microwave-mediated solvent-free Biginelli reaction

The magnetic Fe3O4 nanoparticles supported imidazolium-based ionic liquids (MNPs–IILs), namely 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium hydrogen sulfate (MNPs–IIL–HSO4), 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium acetate (MNPs–IIL–OAc) and 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium chloride (MNPs–IIL–Cl) were used as efficient new catalysts for the one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-ones under microwave irradiation and solvent-free conditions in excellent yields. Utilization of easy reaction conditions, catalyst with high catalytic activity and good reusability, and simple magnetically work-up, makes this green protocol as an interesting option for the economic synthesis of Biginelli compounds. Microwave technology as an eco-friendly green synthetic approach has gradually been used in this organic procedure. Combining the advantages of microwave irradiation and magnetically nanocatalyst, this method provides an efficient and much improved modification of the original Biginelli reaction. We believe that this procedure appears to have a broad scope with respect to variation in the 3,4-dihydropyrimidin-2(1H)-ones (thiones). we have developed a rapid, effective, validated and environmental-friendly method for the synthesis of dihydropyrimidinones (thiones) using Fe3O4 nanoparticles immobilized imidazolium salt catalyst in microwave irradiation and solvent-free conditions. Reduced reaction times, high turnover frequency, high yields of products, absence of solvent and recyclability of catalyst make our catalyst a valuable system addition to previously reported methods. This green methodology should be amenable to construct new substituted dihydropyrimidinones scaffolds with potential biological applications.

Degradation of polylactide using basic ionic liquid imidazolium acetates

AbstractImidazolium acetate ionic liquids show high efficiency in the degradation of polylactides (PLA): degradation degree of PLA can reach almost 100 % in imidazolium acetate ionic liquids at 170°C and 1 h under atmospheric pressure, while the degradation degree of PLA remains close to 0 % using neutral 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim]BF4) and acidic ionic liquids at the same reaction conditions. With the increase of both the amount of acetate ionic liquid and the reaction temperature, the degradation degree of PLA increases. The structure of ionic liquids affects the degradation behavior of PLA: for cations, the proton from the C-2 position on the imidazolium ring is involved in the degradation of PLA; the degradation of PLA increases with the increase of the alkyl side-chain length of imidazolium cations; for anions, moderate basicity of the acetate ion contributes to the high activity of the imidazolium acetate ionic liquids in the degradation of PLA.

Uranyl(VI) Complexes in and from Imidazolium Acetate Ionic Liquids: Carbenes versus Acetates?

Formation of uranyl(VI)-N-heterocyclic carbene complexes from 1-alkyl-3-methylimidazolium acetate ionic liquid carbene sources was investigated by theoretical methods, combining classical molecular dynamics ab initio molecular dynamics and static DFT calculations. The interaction between the UO2(2+) cation and the acetate anion was found to be very strong, in accordance with the hard and soft acids and bases principle. The calculations, however, indicate that the preference of the acetate anions to coordinate monodentately, together with the Coulombic repulsion between these anionic ligands, provides accessible sites for the carbene in the corresponding uranyl-acetato complexes. According to the calculations the carbene is bound to the uranium atom of the [UO2(OAc)3](-) complex with significant strength; ΔE value of -79.4 kJ mol(-1) was obtained. Comparison with the analogous, but experimentally confirmed, reaction between the present ionic liquid and CO2 indicates that this binding strength should be enough for the reaction to occur. The analogous aqua complexes exhibit lower stability, showing that traces of moisture should not prohibit the reaction via competitive coordination. The results obtained suggest a mild and very convenient method for preparing carbene complexes of metals in general, including those with the uranyl cation, which have been so far limited to a few exotic examples.

Ultrasound mediation for one-pot multi-component synthesis of amidoalkyl naphthols using new magnetic nanoparticles modified by ionic liquids

The ionic liquid 1-methyl-3-(3-trimethoxysilylpropyl) imidazolium acetate was immobilized on the Fe3O4 nanoparticles (MNPs-IL-OAc) and used as an efficient new heterogeneous nanocatalyst for the one-pot multi-component synthesis of 1-amidoalkyl-2-naphthols under ultrasound irradiation. The advantages of present combined method are the use of a low scale catalyst, easier work-up procedure, waste-free, green and efficient synthetic entry to excellent yield of products in a high reusability and a short reaction time.

Influence of ionic-liquid incubation temperature on changes in cellulose structure, biomass composition, and enzymatic digestibility

Varying ionic liquid, 1-ethyl 3-methyl imidazolium acetate, pretreatment incubation temperature on lignocellulosic biomass substrates, corn stover, switchgrass and poplar, can have dramatic effects on the enzymatic digestibility of the resultant regenerated biomass. In order to delineate the chemical and physical changes resulting from the pretreatment process and correlate changes with enzymatic digestibility, X-ray powder and fiber diffraction, 13C cross polarization/magic angle spinning nuclear magnetic resonance spectroscopy, and compositional analysis was completed on poplar, corn stover and switchgrass samples. Optimal pretreatment incubation temperatures were most closely associated with the retention of amorphous substrates upon drying of regenerated biomass. Maximal glucan to glucose conversion for 24 h enzyme hydrolysis was observed for corn stover, switchgrass and poplar at ionic liquid incubation temperatures of 100, 110 and 120 °C, respectively. We hypothesize that effective pretreatment temperatures must attain lignin redistribution and retention of xylan for optimal enzyme digestibility.

Effects of ionic liquid mixtures on lipid extraction from Chlorella vulgaris

In this study, pre-biodiesel-production lipid extraction from microalgae (Chlorella vulgaris) was performed. The yield-enhancing effects of ionic liquid blends on the lipid extraction were investigated. The initial fatty acids content of the C. vulgaris was 292.2 mg/g cell. The lipid extraction yield using single ionic liquids was compared with the yield obtained with organic solvents and ionic liquid mixtures, respectively. The yield by hexane–methanol solvent was 185.4 mg/g cell. Among the 12 ionic liquids, 1-ethyl-3-methyl imidazolium acetate, 1-ethyl-3-methyl imidazolium diethylphosphate, 1-ethyl-3-methyl imidazolium tetrafluoroborate, and 1-ethyl-3-methyl imidazolium chloride showed high (>200.0 mg/g cell) lipid extraction yields. Although the yields of 1-ethyl-3-methyl imidazolium ethyl sulfate and 1-ethyl-3-methyl imidazolium thiocyanate were only 60.5 and 42.7 mg/g cell, respectively, the yield for their mixture (weight ratio of 1:1) was improved to 158.2 mg/g cell. Similarly, whereas the lipid extraction yield of 1-ethyl-3-methyl imidazolium hydrogen sulfate was just 35.2 mg/g cell, that for its mixture with 1-ethyl-3-methyl imidazolium thiocyanate (weight ratio of 1:1) was boosted to 200.6 mg/g cell. Overall, the synergistic effects of the ionic liquid mixtures with different anions improved the lipid extraction yield of C. vulgaris.

Comparison of different ionic liquids pretreatment for barley straw enzymatic saccharification.

Recently, application of ionic liquids due to their special solvency properties as a promising method of pretreatment for lignocellulosic biomass has received much attention. Chemical stability, temperature stability, non-flammability, low vapor pressure, wide liquidus range, and non-toxicity are among those unique properties. These solvents are also known as green solvents due to non-toxicity and low vapor pressure. The present study was set to compare the effect of five different ionic liquids namely, 1-ethyl-3-methyl imidazolium acetate, 1-ethyl-3-methyl imidazolium diethyl phosphate, 1-butyl-3-methyl imidazolium chlorides, 1,3-dimethyl imidazolium dimethyl phosphate, and 1-butyl-3-methylimidazolium-trifluoromethane sulfonate on barley straw in bioethanol production process. The performance of ionic liquids was evaluated based on the change observed in chemical structure, crystallinity index, and cellulose digestibility. Overall, 1-ethyl-3-methyl imidazolium acetate was found most effective in pretreating barely straw for bioethanol production. To the best of our knowledge, the present study reports different ionic liquids; some for the first time, for barely straw pretreatment.

Comparison of direct solvents for regenerated cellulosic fibers via the lyocell process and by means of ionic liquids

AbstractBecause new technology using ionic liquids (ILs) for cellulose processing enables the spinning of cellulose with various techniques, the resulting fiber property profiles differ significantly, depending on the process parameters. ILs are thermally stable, nontoxic, environmentally friendly solvents and dissolve cellulose directly; this leads to a high flexibility in the complete process chain for man‐made cellulosics. A comparison of the manufacture of cellulosic fibers according to the Lyocell process and by means of ILs is presented. The rheological behavior of the spinning dopes, the structures, and the physical textile properties of the prepared fibers were determined. The fibers spun from solutions of cellulose in N‐methyl morpholin‐N‐oxide monohydrate, 1‐ethyl‐3‐methyl imidazolium acetate, and 1‐ethyl‐3‐methyl imidazolium diethyl phosphate were compared. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Enzymatic hydrolysis from carbohydrates of barley straw pretreated by ionic liquids

AbstractBACKGROUND: Lignocellulosic biomass offers many potential advantages in comparison with the traditionally used sugars or starchy biomass since it is very widely available and does not compete with food and feed production. The abundance and high carbohydrates content of barley straw make it a good candidate for bioethanol production in Europe. Since biomass must be pretreated before enzymatic hydrolysis to improve the digestibility of both the cellulose and the hemicellulose biomass, the use of ionic liquids (IL) has been proposed as an environment‐friendly pretreatment of biomass.RESULTS: Different pretreatment conditions were investigated to determine the effects of the experimental conditions (temperature and time) on the enzymatic digestibility of pretreated material. The pretreatment of barley straw with 1‐ethyl‐3‐methyl imidazolium acetate treatment resulted in up to a 9‐fold increase in the cellulose conversion and a 13‐fold increase in the xylan conversion when compared with the untreated barley straw.CONCLUSION: Ionic liquid pretreatment of barley straw at 110°C for 30 min, followed by enzymatic hydrolysis, leads to a sugar yield of 53.5 g per 100 g raw material. It is then ready available for conversion into ethanol and is equivalent to more than 86% from potential sugars. The increase in saccharification was possible due to rupture of the lignin–hemicellulose linkages by treatment with 1‐ethyl‐3‐methyl imidazolium acetate. © 2012 Society of Chemical Industry

Enhancement of enzymatic digestibility of oil palm empty fruit bunch by ionic-liquid pretreatment

In this study, 4-methylmorpholine N-oxide (NMMO) and four ionic liquids were compared to determine the most suitable type for use in pretreatment of oil palm empty fruit bunch (EFB) to enhance enzymatic digestibility and obtain maximal fermentable sugar (glucose). Four types of ionic liquids, namely, 1-ethyl-3-methyl imidazolium acetate ([Emim]OAc), 1-butyl-3-methyl imidazolium chloride ([Bmim]Cl), tributyl methyl ammonium methylsulfate (MTBS), and 1-ethyl-3-methyl imidazolium diethylphosphate ([Emim]DEP), were used. The effects of pretreatment temperature and time on the enzymatic digestibility of EFB were examined. Among NMMO and four ionic liquids, NMMO and [Emim]OAc, showing high enzymatic digestibility, were found to be most effective for EFB pretreatment. The enzymatic digestibility of NMMO-pretreated EFB increased as pretreatment temperature and time increased. After [Emim]OAc pretreatment, the crystallinity index of EFB decreased, due to the conversion of crystalline cellulose to amorphous cellulose, and the enzymatic digestibility thereby was increased to 96.6% at 110 °C for 2 h.