Different Types Of Ionic Liquids Research Articles

Solvatochromic parameters of imidazolium-, hydroxyammonium-, pyridinium- and phosphonium-based room temperature ionic liquids

Solvatochromic solvent parameters of different room temperature ionic liquids based on the imidazolium, hydroxyammonium, pyridinium and phosphonium cations, namely 1-butyl-3-methyl imidazolium hexafluorophosphate, 1-hexyl-3-methyl imidazolium hexafluorophosphate, 1-octyl-3-methyl imidazolium hexafluorophosphate, 1-octyl-3-methyl imidazolium tetrafluoroborate, N-octylpyridinium tetrafluoroborate, 2-hydroxyethylammonium formate, 2-hydroxypropylammonium formate, trihexyl-(tetradecyl)phosphonium chloride, trihexyl-(tetradecyl)phosphonium bromide, trihexyl-(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide and trihexyl-(tetradecyl)phosphonium dicyanamide were determined at 25°C using UV–Vis spectroscopy. Specifically, we have measured the Kamlet–Taft parameters: α (hydrogen-bond donor acidity), β (hydrogen-bond acceptor basicity), π* (dipolarity/polarizability) and the Reichardt's normalized polarity parameter, ETN.In previous works, we employed the Solvation Parameter Model to predict the partition coefficients for compounds of biological and pharmacological interest and to elucidate the chemical interactions involved in the partition process of different probe molecules between water and different types of ionic liquids. In this work, we have used the obtained solvatochromic solvent parameters to explain and understand the relative magnitudes of the chemical interactions obtained with the solvation parameter model.

Solubility of hydrogen sulfide in ionic liquids for gas removal processes using artificial neural networks

Artificial neural networks have been used for the correlation and prediction of solubility data of hydrogen sulfide in ionic liquids. The solubility of hydrogen sulfide is highly variable for different types of ionic liquids at the same temperature and pressure and its correlation and prediction is of special importance in the removal of hydrogen sulfide from flue gases for which effective and efficient solvents are required. Several network architectures were tested to finally choose a three layer network with 6, 10 and 1 neuron, respectively (6, 10, 1). Twelve binary hydrogen sulfide+ionic liquids mixtures were considered in the study. Solubility data (pressure, temperature, gas concentration in the liquid phase) for these systems were taken from the literature (392 data points for training and 104 data points for testing). The training variables are the temperature and the pressure of the binary systems being the target variable the solubility of hydrogen sulfide in the ionic liquid. Average absolute deviations are lower than 4.0% and the maximum individual absolute deviation in solubility is 12.6%. The proposed neural network model is a good alternative method for the estimation of solubility of hydrogen sulfide in ionic liquids for its use in process analysis, process design and process simulation.

Thermodynamic modeling of refrigerants solubility in ionic liquids using original and ϵ*-Modified Sanchez–Lacombe equations of state

Ionic liquids can dramatically improve the efficiency of absorption refrigeration processes due to their negligibly small vapor pressure; where the IL absorbs the refrigerant gas in one stage and subsequently releases the high-pressure gas upon addition of heat. In the current study, phase equilibrium data (P-T-x) of a diverse set of refrigerants in different types of ionic liquids are modeled with the aid of two equations of state based on lattice fluid theory, i.e. Sanchez–Lacombe and ϵ*-Modified Sanchez–Lacombe EOSs. The characteristic parameters of the pure components were determined from a database of 3086 experimental liquid density datapoints for 11 refrigerants and 12 ILs. According to the results obtained by considering the experimental data of 25 binary IL/refrigerant mixtures comprised of 88 isotherms with a total of 658 datapoints, both EOSs can successfully correlate the solubility data with AARDs of %5.773 and %5.771 for SL and ϵ*-Modified SL EOSs, respectively.

High-Efficient Oxidation–Extraction Desulfurization Process by Ionic Liquid 1-Butyl-3-methyl-imidazolium Trifluoroacetic Acid

A Brønsted acid ionic liquid (IL), [C4mim]TFA (1-butyl-3-methyl-imidazolium trifluoroacetic acid), was synthesized and used as an extractant and catalyst for oxidation desulfurization (ODS) of thiophene from model oil with hydrogen peroxide as the oxidant. The major factors of the reaction were investigated in detail. The effect of different types of ILs on oxidative and extractive desulfurization capacities of model oil was tested, which proved TFA– > HSO4– > COO– > AlCl4– > AcO–. The reaction heat caused by H2O2 dissolved in IL was determined by a calorimeter.

Correlation of solubility data of ammonia in ionic liquids for gas separation processes using artificial neural networks

Abstract Artificial neural networks have been used for the correlation and prediction of solubility data of ammonia in ionic liquids. This solubility of ammonia is highly variable for different types of ionic liquids at the same temperature and pressure, its correlation and prediction is of special importance in the removal of ammonia from flue gases for which effective and efficient solvents are required. Nine binary ammonia + ionic liquids mixtures were considered in the study. Solubility data (P–T–x) of these systems were taken from the literature (208 data points for training and 50 data points for testing). The training variables are the temperature and the pressure of the binary systems (T, P), being the target variable the solubility of ammonia in the ionic liquid (x). The study shows that the neural network model is a good alternative method for the estimation of solubility for this type of mixtures. Absolute average deviations were below 5.6%, for each isothermal data set and overall absolute average deviations were below 3.0%. Only in the range of low solubility (below 0.2 in mole fraction) did predicted solubility give deviations higher than 10%.

Application and mechanism of carrier facilitated carbohydrate extraction from aqueous solution

Recovery of carbohydrates from aqueous solution represents a problem due to their large, multivalent and flexible structure and their high hydrophilicity. Organic solvents as well as alternative solvents such as ionic liquids are able to extract carbohydrates from aqueous media by the aid of primary amines. The mechanism of the extraction process has been explored by using galactose and its corresponding O-methyl galactoside. The results indicate that the mechanism is based on formation of an adduct between the aldo-structure of the monosaccharide and the primary amine to provide a hemiaminal, which is extracted into the organic phase. The extraction rate can be influenced by variation of temperature, time, and the amount of amine and depends on the structure of the carbohydrate. The selectivity can also be tuned using different types of ionic liquids. This procedure opens the possibility to recover a carbohydrate selectively from a mixture of different carbohydrates.

Two-stage prediction of the effects of imidazolium and pyridinium ionic liquid mixtures on luciferase.

The predicted toxicity of mixtures of imidazolium and pyridinium ionic liquids (ILs) in the ratios of their EC50, EC10, and NOEC (no observed effect concentration) were compared to the observed toxicity of these mixtures on luciferase. The toxicities of EC50 ratio mixture can be effectively predicted by two-stage prediction (TSP) method, but were overestimated by the concentration addition (CA) model and underestimated by the independent action (IA) model. The toxicities of EC10 ratio mixtures can be basically predicted by TSP and CA, but were underestimated by IA. The toxicities of NOEC ratio mixtures can be predicted by TSP and CA in a certain concentration range, but were underestimated by IA. Our results support the use of TSP as a default approach for predicting the combined effect of different types of ILs at the molecular level. In addition, mixtures of ILs mixed at NOEC and EC10 could cause significant effects of 64.1% and 97.7%, respectively. Therefore, we should pay high attention to the combined effects in mixture risk assessment.

Catalytic Role of Ionic Liquids for Dissolution and Degradation of Biomacromolecules

Natural biomacromolecules constitute a diverse feedstock, including carbohydrate-based polysaccharides (cellulose, hemicellulose, starch, agarose, and Konjac glucomannan) together with lignin — extracted mainly from biomass — and other protein based polymers, namely keratin, chitin, chitosan, and silk fibroin. The complex and heterogeneous chemical structure of biomacromolecules makes them difficult to dissolve and disintegrate into simpler molecules for further applications. In this regard, ionic liquids are potential solvents for the dissolution and modification of long chain biopolymers. This provides a promising pretreatment technology and is known to allow adequate extraction of biopolymers from natural sources. This paper highlights the properties of ionic liquids for their use as versatile solvents. This review provides a critical outlook regarding the influence of several process parameters that govern the fractionation of biomacromolecules into their constituent elements and further pretreatment processes. The performance of different types of ionic liquids for processing of biomacromolecules, focusing on their pertinent capability as catalysts to enhance the rate of hydrolysis, also is discussed in this article.

Potential halophilic cellulases for in situ enzymatic saccharification of ionic liquids pretreated lignocelluloses

Ionic liquids (ILs) have been used as an alternative green solvent for lignocelluloses pretreatment. However, being a salt, ILs exhibit an inhibitory effect on cellulases activity, thus making the subsequent saccharification inefficient. The aim of the present study is to produce salt-tolerant cellulases, with the rationale that the enzyme also tolerant to the presence of ILs. The enzyme was produced from a locally isolated halophilic strain and was characterized and assessed for its tolerance to different types of ionic liquids. The results showed that halophilic cellulases produced from Aspergillus terreus UniMAP AA-6 exhibited higher tolerance to ILs and enhanced thermo stability in the presence of high saline conditions.

Estimation of viscosity of binary mixtures of ionic liquids and solvents using an artificial neural network based on the structure groups of the ionic liquid

A feed-forward neural network was constructed and tested to estimate the viscosities of binary mixtures of five different types of ionic liquids with various polar and non-polar solvents within a range of temperatures. The ionic liquids investigated had various anions and consisted of either the imidazolium, ammonium, pyridinium, pyrrolidinium, or isoquinolinium cations, with various cation alkyl side-chains. Together, a total of 1996 experimental data were collected from previously published literature and divided randomly into three different datasets: 1775 data points making up the training and validation datasets, and 221 data points selected as a test dataset. The molecular weight and group structure of the ionic liquid, the molecular weight and reduced boiling temperature of the solvent, and the molar composition, temperature, and pressure of the system were selected as the independent input variables. Results indicated that the network structure presented in this study is capable to estimate the viscosity of such nonideal binary mixtures, consisting of a range of ionic liquids and solvents, with an average relative error of 0.6%.

Combined use of hydroxypropyl-β-cyclodextrin and ionic liquids for the simultaneous enantioseparation of four azole antifungals by CE and a study of the synergistic effect

A CE method employing a dual system of hydroxypropyl-β-cyclodextrin (HP-β-CD) and ionic liquids (ILs) has been developed for the simultaneous enantioseparation of four azole antifungals for the first time. In this study, three different types of ILs were employed as modifiers and among them dodecyl trimethyl ammonium chloride was found to be the most effective. The effects of the concentration, cations, and anions of ILs on the enantioseparation were investigated. With the developed dual system, all the enantiomers were well separated in resolutions of 3.8, 3.5, 2.8, and 2.5 for miconazole, econazole, ketoconazole, and itraconazole, respectively. The interactions between dodecyl trimethyl ammonium chloride and HP-β-CD were also studied using a neutral polyacrylamide coated capillary and (1) H NMR spectroscopy to further explore the synergistic effect involved. It was found that ILs improved the enantioseparation not only by changing the EOF, but also by interactions with HP-β-CD that could change its ability of forming inclusion complex with the enantiomers.

Modeling and thermodynamic consistency of solubility data of refrigerants in ionic liquids

Phase equilibrium data of temperature, pressure and solubility (T-P-x) of hydrofluorocarbon-type refrigerants in different types of ionic liquids over wide ranges of temperatures and pressures are modeled and tested for thermodynamic consistency. Experimental data taken from the literature for nineteen binary mixtures refrigerant + ionic liquids with a total of forty eight isothermal data sets are considered in the study. The modified Peng–Robinson equation of state proposed by Kwak and Mansoori is used for correlating the P-T-x data and a flexible thermodynamic consistency method is applied to analyze the data. Modeling is found acceptable in all cases, meaning that deviations in correlating the data are low, proving at the same time the claimed flexibility of a well-founded model that uses simple van der Waals mixing rules. Thirty eight data sets resulted to be thermodynamically consistent, nine were found to be not-fully consistent and only one set was found to be thermodynamically inconsistent.

Effects of different ionic liquids on the electrospinning of a polyacrylonitrile polymer solution

ABSTRACTAdditives have been proven to be useful in improving electrospinnability and controlling fiber morphology through the modification of solution properties, including the conductivity, viscosity, and surface tension. In this study, the effects of adding small amounts of four different types of ionic liquids [i.e., 1‐butyl‐3‐methylimidazolium chloride (C4MIMCl), 1‐dodecyl‐3‐methylimidazolium chloride (C12MIMCl), 1‐ethyl‐3‐methylimidazolium bromide (C2MIMBr), and 1‐ethyl‐3‐methylimidazolium phosphate (C2MIM)3PO4] on the solution properties, electrospinning process, and characteristics of polyacrylonitrile (PAN) were investigated. The results show that the solution conductivities significantly increased with the addition of different ionic liquids with concentrations varying from 0.1 to 1.0 wt %, and the tendency depended on the structures of the ionic liquids. (C2MIM)3PO4 showed the highest conductivity value; this was followed by C2MIMBr, C4MIMCl, and C12MIMCl. The ionic liquids formed visible crystals; this made the fiber surfaces rough, and some fiber segments underwent partial aggregation. A regular varying tendency between the minimum mean diameter of the PAN/ionic liquid fibers and the structure of the ionic liquid was found. The PAN/N,N‐dimethylformamide (DMF)/(C2MIM)3PO4 solution showed the highest conductivity among the four systems with different ionic liquids added, and the thinnest minimum diameter of the PAN/(C2MIM)3PO4 fibers appeared with a relatively low ionic liquid concentration of 0.25 wt %, whereas the PAN/DMF/C12MIMCl solution had the lowest conductivity, and the minimum mean diameter of PAN/C12MIMCl fibers appeared at a relatively high ionic liquid concentration of 0.8 wt %. Although the conductivity of the PAN/DMF/C2MIMBr solution was higher than that of the PAN/DMF/C4MIMCl solution, the minimum mean diameters of the PAN/C2MIMBr and PAN/C4MIMCl fibers appeared at the same ionic liquid concentration of 0.5 wt % because of the similar ionic activities of C2MIMBr and C4MIMCl. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2359–2368, 2013

Consistency test of solubility data of ammonia in ionic liquids using the modified Peng–Robinson equation of Kwak and Mansoori

Phase equilibrium data of temperature, pressure and solubility (T–P–x) of ammonia in different types of ionic liquids over wide ranges of temperatures and pressures are modeled and tested for thermodynamic consistency. The modified Peng–Robinson equation of state proposed by Kwak and Mansoori is used for correlating the isothermal PX data and a flexible thermodynamic consistency method applied to analyze forty seven isothermal P–x data available in the open literature. Modeling is found acceptable in all cases, meaning that deviations in correlating the data are low, proving at the same time the claimed flexibility of a well-founded model that uses simple van der Waals mixing rules. For all cases, the thermodynamic consistency method gives a clear conclusion about consistency or inconsistency of a set of experimental T–P–x data based on the established criteria.

Design and performance evaluation of ionic liquid-based microwave-assisted simultaneous extraction of kaempferol and quercetin from Chinese medicinal plants

An ionic liquid-based microwave-assisted extraction (IL-MAE) technique has been successfully developed for the simultaneous effective extraction of quercetin and kaempferol from Toona sinensis and Rosa chinensis which are Chinese medicinal plants. Twenty different types of ionic liquids (ILs) with different cations and anions have been synthesized and investigated. Several significant operating parameters of IL-MAE were optimized by a series of single factor experiments and orthogonal design L9 (34) experiments, respectively. Compared with ionic liquid-based maceration extraction (IL-ME), ionic liquid-based heat extraction (IL-HE) and ionic liquid-based ultrasound-assisted extraction (IL-UAE), the optimized approach was demonstrated as the optimal technique with the highest extraction efficiency and the shortest extraction time. Reversed phase high performance liquid chromatography (RP-HPLC) with ultraviolet-detection (UV-DAD) was employed for the simultaneous analysis of kaempferol and quercetin. The results indicated that the extraction amounts of quercetin from Toona sinensis extracted using [Bmim]Br and from Rosa chinensis extracted using [Omim]Br were 176.5 mg g−1 with RSD 1.2% and 134.3 mg g−1 with RSD 0.63%. And the extraction amounts of kaempferol from Toona sinensis extracted using [Bmim]Br and from Rosa chinensis extracted using [Omim]Br were 16.12 mg g−1 with RSD 0.24% and 9.070 mg g−1 with RSD 0.15%. The developed approach for analyzing quercetin was linear between the concentrations of 32.10 mg L−1 to 233.3 mg L−1 in Toona sinensis and 25.70 mg L−1 to 160.5 mg L−1 in Rosa chinensis with the regression coefficients (R) of 0.9998 and 0.9999, respectively. And for kaempferol, the developed approach was linear between the concentrations of 0.73 mg L−1 to 23.20 mg L−1 in Toona sinensis and 0.19 mg L−1 to 15.00 mg L−1 in Rosa chinensis with the regression coefficients (R) of 0.9993 and 0.9996, respectively. The recoveries of quercetin extracted by the developed methods were 96.76–104.1% in Toona sinensis and 98.40–103.3% in Rosa chinensis, and the recoveries of kaempferol were 95.75–106.3% in Toona sinensis and 98.55–102.9% in Rosa chinensis with the RSDs of lower than 3.0%. The LODs were 1.87–2.26 μg mL−1. The microstructures and chemical structures of these two researched samples before and after different extraction procedures were also investigated.

Shifts in the temperature of maximum density (TMD) of ionic liquid aqueous solutions

This work investigates for the first time shifts in the temperature of maximum density (TMD) of water caused by ionic liquid solutes. A vast amount of high-precision volumetric data--more than 6000 equilibrated (static) high-precision density determination corresponding to ∼90 distinct ionic liquid aqueous solutions of 28 different types of ionic liquid--allowed us to analyze the TMD shifts for different homologous series or similar sets of ionic solutes and explain the overall effects in terms of hydrophobic, electrostatic and hydrogen-bonding contributions. The differences between the observed TMD shifts in the -2 < t/°C < 4 range and salting-in or salting-out effects produced by the same type of ions in aqueous solutions at higher temperatures are discussed taking into account the different types of possible solute-water interactions that can modify the structure of the aqueous phase. The results also reveal different insights concerning the nature of the ions that constitute typical ionic liquids and are consistent with previous results that established hydrophobic and hydrophilic scales for ionic liquid ions based on their specific interactions with water and other probe molecules.

Varnish removal from paintings using ionic liquids

The possibility of replacing volatile and toxic organic solvents by ionic liquids (ILs) could contribute to safer procedures for conservation and restoration. This study introduces the use of ILs in varnish removal from paintings. The efficacy of this new procedure was assessed by applying different types of ILs in mock-ups of several painting materials and varnishes. The removal of IL residues from the surface of paintings was assessed mainly by FTIR-ATR. The application of ILs to a real painting is illustrated.

Synthesis of Different Types of Ionic Liquids Using Conventional and Novel Methods

Ionic liquids (ILs) have recently attracted significant attention from academic and industrial sources. This is because, while their vapor pressures are negligible, many of them are liquids at room temperature and can dissolve a wide range of polar and non polar organic and inorganic molecules. Ionic liquids are not new; some of them have been known for many years, for instance [EtNH3]- [NO3], which has a melting point of 12 °C, was first described in 1914, For some time, it has been proposed that these ionic liquids provide a useful extension to the range of solvents that are available for synthetic chemistry. There are two basic methods for the preparation of ionic liquids: metathesis of a halide salt with, for instance, a silver, group 1 metal or ammonium salt of the desired anion and acid base neutralization reactions. To ensure the purity and completion of reaction of the ionic liquids, they were used the molecular solvents like acetonitrile, tetrahydro- furan and may be other appropriate solvents. In this Account, we discuss the progress of our laboratory in understanding the synthesis of different types of ionic liquids using conventional, cost effective and novel methods in which molecular solvents are replaced by ionic liquid itself.

Ionic liquid‐based microwave‐assisted extraction for the determination of flavonoid glycosides in pigeon pea leaves by high‐performance liquid chromatography‐diode array detector with pentafluorophenyl column

In this study, an ionic liquid-based microwave-assisted extraction (ILMAE) followed by high-performance liquid chromatography-diode array detector with a pentafluorophenyl column for the extraction and quantification of eight flavonoid glycosides in pigeon pea leaves is described. Compared with conventional extraction methods, ILMAE is a more effective and environment friendly method for the extraction of nature compounds from herbal plants. Nine different types of ionic liquids with different cations and anions were investigated. The results suggested that varying the anion and cation had significant effects on the extraction of flavonoid glycosides, and 1.0 M 1-butyl-3-methylimidazolium bromide ([C4MIM]Br) solution was selected as solvent. In addition, the extraction procedures were also optimized using a series of single-factor experiments. The optimum parameters were obtained as follows: extraction temperature 60°C, liquid-solid ratio 20:1 mL/g and extraction time 13 min. Moreover, an HPLC method using pentafluorophenyl column was established and validated. Good linearity was observed with the regression coefficients (r(2)) more than 0.999. The limit of detection (LODs) (S/N = 3) and limit of quantification (LOQs) (S/N = 10) for the components were less than 0.41 and 1.47 μg/mL, respectively. The inter- and intraday precisions that were used to evaluate the reproducibility and relative standard deviation (RSD) values were less than 4.57%. The recoveries were between 97.26 and 102.69%. The method was successfully used for the analysis of samples of pigeon pea leaves. In conclusion, the developed ILMAE-HPLC-diode array detector using pentafluorophenyl column method can be applied for quality control of pigeon pea leaves and related medicinal products.

Ionic liquid modified poly(2,6-dimethyl-1,4-phenylene oxide) for CO2 separation

Ionic liquid modified poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) was synthesized by introducing imidazolium-based, pyridinium-based, and ammonium-basd ionic liquid groups to the methyl position of PPO. Membranes were prepared from the different types of ionic liquid modified PPO (IPPO), and the permeability of CO2 and N2 in these membranes was characterized. For having the CO2-philic ionic liquid groups in the structure, the CO2 solubility of the IPPO is better than that of PPO, while the CO2 diffusivity in the IPPO is proportional to glass transition temperatures. The adsorption and desorption of CO2 in the IPPO were also investigated, and the results manifest that the adsorption and desorption of CO2 in IPPO are completely reversible, which makes the polymer promising as solid adsorbent materials for CO2 separation.