Gas solubility in long‐chain imidazolium‐based ionic liquids

The gas solubility in 1‐dodecyl‐3‐methylimidazolium [C₁₂MIM] based ionic liquids (ILs) was measured at temperatures (333.2, 353.2, and 373.2) K and pressures up to 60 bar for the first time. The popular UNIFAC‐Lei model was successfully extended to long‐chain imidazolium‐based IL and gas (CO₂, CO, and H₂) systems. The free volume theory was used to explain the gas solubility and selectivity in imidazolium‐based ILs by calculating the fractional free volume and free volume by the COSMO‐RS model. Furthermore, the excess enthalpy of gas‐IL system was concerned to provide new insights into temperature dependency of gas (CO₂, CO, and H₂) solubility in ILs. The experimental data, calculation, and theoretical analysis presented in this work are important in gas separations with ILs or supported ionic liquid membranes. © 2017 American Institute of Chemical Engineers AIChE J, 63: 1792–1798, 2017     

Development of ethanolamine‐based ionic liquid membranes for efficient CO2/CH4 separation

This study is focused on the development of ionic liquids (ILs) based polymeric membranes for the separation of carbon dioxide (CO₂) from methane (CH₄). The advantage of ILs in selective CO₂ absorption is that it enhances the CO₂ selective separation for the ionic liquid membranes (ILMs). ILMs are developed and characterized with two different ILs using the solution‐casting method. Three different blend compositions of ILs and polysulfone (PSF) are selected for each ILMs 10, 20, and 30 wt %. Effect of the different types of ILs such as triethanolamine formate (TEAF) and triethanolamine acetate (TEAA) are investigated on PSF‐based ILMs. Field emission scanning electron microscopy analysis of the membranes showed reasonable homogeneity between the ILs and PSF. Thermogravimetric analysis showed that by increasing the ILs loading thermal stability of the membranes improved. Mechanical analysis on developed membranes showed that ILs phase reduced the amount of plastic flow of the PSF phase and therefore, fracture takes place at gradually lower strains with increasing ILs content. Gas permeation evaluation was carried out on the developed membranes for CO₂/CH₄ separation between 2 bar to 10 bar feed pressure. Results showed that CO₂ permeance increases with the addition of ILs 10–30 wt % in ILMs. With 20–30 wt % TEAF‐ILMs and TEAA‐ILMs, the highest selectivity of a CO₂/CH₄ 53.96 ± 0.3, 37.64 ± 0.2 and CO₂ permeance 69.5 ± 0.6, 55.21 ± 0.3 is observed for treated membrane at 2–10 bar. The selectivity using mixed gas test at various CO₂/CH₄ compositions shows consistent results with the ideal gas selectivity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45395.     

Ionic Liquids‐Based Membranes for Carbon Dioxide Separation

Ionic liquids (ILs) have gained wide‐spread focus owing to its negligible vapor pressure, low heat capacity, high thermal stability, and structural diversity. The solubility and selectivity toward carbon dioxide has made ILs a unique platform that possess the potential in gas separations. In particularly, combining functional ILs with membranes and porous supports is an efficient way to design task‐specific materials for CO₂ separations. This minireview summarizes the developments and advances of ionic liquids‐based membranes for CO₂ separations in recent three years, with an emphasis on the strategy of incorporating ionic liquids and CO₂ separation performance.     

Computer‐aided design of ionic liquids as solvents for extractive desulfurization

Although ionic liquids (ILs) have been widely explored as solvents for extractive desulfurization (EDS) of fuel oils, systematic studying of the optimal design of ILs for this process is still scarce. The UNIFAC‐IL model is extended first to describe the EDS system based on exhaustive experimental data. Then, based on the obtained UNIFAC‐IL model and group contribution models for predicting the melting point and viscosity of ILs, a mixed‐integer nonlinear programming (MINLP) problem is formulated for the purpose of computer‐aided ionic liquid design (CAILD). The MINLP problem is solved to optimize the liquid‐liquid extraction performance of ILs in a given multicomponent model EDS system, under consideration of constraints regarding the IL structure, thermodynamic and physical properties. The top five IL candidates preidentified from CAILD are further evaluated by means of process simulation using ASPEN Plus. Thereby, [C₅MPy][C(CN)₃] is identified as the most suitable solvent for EDS. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1013–1025, 2018     

Gas–liquid mass‐transfer properties in CO2 absorption system with ionic liquids

The deficiency of mass‐transfer properties in ionic liquids (ILs) has become a bottleneck in developing the novel IL‐based CO₂ capture processes. In this study, the liquid‐side mass‐transfer coefficients (k_L) were measured systematically in a stirred cell reactor by the decreasing pressure method at temperatures ranging from 303 to 323 K and over a wide range of IL concentrations from 0 to 100 wt %. Based on the data of k_L, the kinetics of chemical absorption of CO₂ with mixed solvents containing 30 wt % monoethanolamine (MEA) and 0–70 wt % ILs were investigated. The k_L in IL systems is influenced not only by the viscosity but also the molecular structures of ILs. The enhancement factors and the reaction activation energy were quantified. Considering both the mass‐transfer rates and the stability of IL in CO₂ absorption system, the new IL‐based system MEA + [bmim][NO₃] + H₂O is recommended. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2929–2939, 2014     

Ecotoxicological risk profile of ionic liquids: octanol‐water distribution coefficients and toxicological data

BACKGROUND: A knowledge of the toxicity of ionic liquids (ILs) and their influence on aquatic ecosystems must be assessed before an accurate judgment of their environmental benefits and prior to their industrial application. In the present work, the overall octanol‐water distribution coefficients (D_ow) of imidazolium‐based ILs were measured using the slow‐stirring method. Biological tests were performed to establish the toxicity of some of these imidazolium‐based ILs and to relate it with the D_ow. RESULTS: The D_ow values of the ILs investigated are low and concentration dependent, indicating that these ILs, at low concentrations, will not accumulate or bioconcentrate in the environment. Moreover, it is shown that the most hydrophobic anions present higher D_ow and higher toxicity, which means lower EC₅₀ values (the concentration of IL needed to decrease the luminescence of the marine bacteria Vibrio fischeri by 50% compared with the control organism luminescence). CONCLUSIONS: A new and more accurate interpretation of the partition of ionic liquids between water and 1‐octanol is presented. The work included measurement of new D_ow data and the study of their relation with water solubility and EC₅₀ values. Copyright © 2011 Society of Chemical Industry     

Thermodynamic validation of 1‐alkyl‐3‐methylimidazolium carboxylates as task‐specific ionic liquids for H2S absorption

Solubilities of H₂S in five 1‐alkyl‐3‐methylimidazolium carboxylates ionic liquids (ILs) have been measured at temperatures from 293.15 to 333.15 K and pressures up to 350 kPa. It is shown that these ILs have significantly larger absorption capacities for H₂S than those common ILs reported in the literature. The solubility is found to increase dramatically with the increasing alkalinity of the anions and slightly with the increasing length of the alkyl chains on the cations. It is further demonstrated that the absorption isotherms are typically nonideal. With the assumption of complex formation between H₂S and ILs, a reaction equilibrium thermodynamic model is developed to correlate the experimental solubilities. The model favors a reaction mechanism of AB₂ type that two IL molecules interact with one H₂S molecule. Thermodynamic parameters such as Henry's law constants, reaction equilibrium constants, and heat of complex formation are also calculated to evaluate the absorption process of H₂S in these ILs. © 2012 American Institute of Chemical Engineers AIChE J, 59: 2227–2235, 2013     

Efficient capture of carbon dioxide with novel mass‐transfer intensification device using ionic liquids

A novel mass‐transfer intensified approach for CO₂ capture with ionic liquids (ILs) using rotating packed bed (RPB) reactor was presented. This new approach combined the advantages of RPB as a high mass‐transfer intensification device for viscous system and IL as a novel, environmentally benign CO₂ capture media with high thermal stability and extremely low volatility. Amino‐functionalized IL (2‐hydroxyethyl)‐trimethyl‐ammonium (S)?2‐pyrrolidinecarboxylic acid salt ([Choline][Pro]) was synthesized to perform experimental examination of CO₂ capture by chemical absorption. In RPB, it took only 0.2 s to reach 0.2 mol CO₂/mol IL at 293 K, indicating that RPB was kinetically favorable to absorption of CO₂ in IL because of its efficient mass‐transfer intensification. The effects of operation parameters on CO₂ removal efficiency and IL absorbent capacity were studied. In addition, a model based on penetration theory was proposed to explore the mechanism of gas–liquid mass transfer of ILs system in RPB. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2957–2965, 2013     

Lipase‐catalyzed acylation of konjac glucomannan in ionic liquids

A comparative study was made of lipase‐catalyzed acylation of konjac glucomannan (KGM) with vinyl acetate as the acyl donor in five ionic liquids (ILs) and also in the presence of the organic solvent tert‐butanol (t‐BuOH). An obvious enhancement in enzyme activity and stability was observed using ILs as the reaction media when compared with t‐BuOH. The maximum degree of substitution (DS) of the modified KGM in ILs and t‐BuOH under the conditions employed is 0.71 and 0.54, respectively. The water activity (a_w) of the reaction system affected the acylation of KGM to some extent. 1‐Butyl‐3‐methylimidazolium tetrafluoroborate (C₄MIm.BF₄) was the best IL medium for the reaction, and an a_w of 0.75 was optimum. It was also found that the nature of both the cation and the anion of ILs had an effect on the reaction. Candida antarctica lipase B immobilized on an acrylic resin (Novozym 435) displayed no acylation activity to KGM in 1‐butyl‐3‐methylimidazolium chloride (C₄MIm.Cl). The optimum reaction temperature for enzymatic acylation in ILs was shown to be 45‐55 °C. Enzymatic acylation of KGM in IL‐t‐BuOH co‐solvent systems was also investigated. When an appropriate amount of t‐BuOH was added to ILs, the DS of the modified KGM was enhanced. Additionally, the enzymatic acylation of KGM in all the media examined was shown to be regioselective, with acylation occurring predominantly at the C‐6‐OH. Copyright © 2006 Society of Chemical Industry     

Improved activity and stability of pseudomonas capaci lipase in a novel biocompatible ionic liquid, 1‐isobutyl‐3‐methylimidazolium hexafluorophosphate

BACKGROUND: Enzymes may exhibit enhanced activity, stability and selectivity in ionic liquids, depending on the properties of the liquid. The physical–chemical properties of ionic liquids, however, may be modified by altering the anion or cation in the ionic liquid. This feature is a key factor for realizing successful reactions. In this work, a new ionic liquid, 1‐isobutyl‐3‐methylimidazolium hexafluorophosphate (abbreviated as [i‐C₄mim][PF₆]), was synthesized and investigated as a novel medium for the transesterification reaction of 2‐phenylethanol with vinyl acetate catalyzed by pseudomonas capaci lipase. As contrasts, the reaction was also carried out in two reference solvents; the isomeric ionic liquid [i‐C₄mim][PF₆], 1‐butyl‐3‐methylimidazolium hexafluorophosphate (abbreviated as [C₄mim][PF₆]), and hexanes. RESULTS: As reaction medium, [i‐C₄mim][PF₆] was best among the three solvents. The initial reaction rate, the equilibrium conversion of 2‐phenylethanol and the half‐lifetime of the lipase in [i‐C₄mim][PF₆] medium were about 1.5, 1.2 and 3‐fold that obtained in [C₄mim][PF₆] medium, respectively. The lipase in [i‐C₄mim][PF₆] medium was recycled 10 times without substantial diminution in activity. CONCLUSION: The ionic liquid [i‐C₄mim][PF₆] has good biocompatibility, and can be used widely as green media in various biocatalysis reactions to improve the activity and stability of enzymes. Besides hydrophobicity and nucleophilicity, the spatial configuration of ionic liquids is also considered a key factor effecting the behaviour of the enzyme in ionic liquids. Copyright © 2008 Society of Chemical Industry     

Efficient Halogenation of Aromatic Systems Using N‐Halosuccinimides in Ionic Liquids

A simple, rapid and highly regioselective green protocol has been developed for the halogenation of aromatic systems with N‐halosuccinimides using room temperature ionic liquids (ILs) as novel and recyclable reaction media to produce the corresponding halogenated aromatic compounds in high to quantitative yields. N‐Halosuccinimides show enhanced reactivity in ionic liquids thereby reducing the reaction times dramatically and improving the yields substantially.     

Enhancement of activity and selectivity in lipase‐catalyzed transesterification in ionic liquids by the use of additives

BACKGROUND: Seven ionic liquids (ILs) based on 1-alkyl-3-methylimidazolium cation in combination with hexafluorophosphate and bis{(trifluoromethyl)sulfonyl}imide anions were tested as reaction media for lipase-catalyzed transesterification in low water conditions. With the aim of improving the activity and/or selectivity of the lipase, various treatments were applied to ionic liquid media such as equilibration with aqueous solutions of salts, NaHCO₃ or Na₂CO₃, or the addition of a catalytic amount of a non-reactive organic base to the reaction mixture, triethylamine. RESULTS: The treated ionic liquids were shown to be excellent media for lipase-catalyzed ester synthesis by transesterification compared with conventional organic solvents, such as n-hexane. All treatments were found to enhance the synthetic activity of the enzyme, the best results being achieved with the addition of triethylamine. The addition of a catalytic amount of this base to the ILs resulted in a significant increase in both the synthetic activity and selectivity values. For instance, the synthetic activity in [emim⁺][TfN₂⁻] was enhanced more than 12 times and the selectivity increased from 86% to 95% when triethylamine was used. CONCLUSION: These treatments could be easy-to-use approaches to improve the efficiency of enzymatic reactions in ionic liquids when the reaction does not proceed smoothly. Copyright © 2007 Society of Chemical Industry     

Influence of ionic liquid composition on the stability of polyvinyl chloride‐based ionic liquid inclusion membranes in aqueous solution

Membrane technology has gained significant importance with the incorporation of ionic liquids into their structure. This work shows the influence of ionic liquid composition on the stability of PVC‐based polymer ionic liquid inclusion membranes (PILIMs) in aqueous solution. Among the ILs investigated, those membranes which contain between 20 and 30%_w/w of the least soluble, [OMIM⁺][PF₆^?] and [OMIM⁺][Ntf₂^?], exhibit losses of IL lower than 10%. For both ILs, the amount immobilized was maximum for the membranes with 30%_w/w of IL (0.0838 and 0.0832 g, respectively). On the contrary, the ionic liquid loss increases as its solubility in water increase, reaching 99.52% when PILIMs are prepared with 70%_w/w of [OMIM⁺][BF₄^?]. The results demonstrate that the stability of PILIMs depends on the solubility of the IL in the surrounding phase and the specific interaction between the IL and the polymeric support for PVC‐to‐IL ratios higher than 30%_w/w. © 2016 American Institute of Chemical Engineers AIChE J, 63: 770–780, 2017     

High Regioselective Diels–‐Alder Reaction of Myrcene with Acrolein Catalyzed by Zinc‐Containing Ionic Liquids

The ambient zinc‐containing ionic liquids, MX‐ZnCl₂, functioning as both Lewis acid catalyst and green solvent, are employed for a high regioselective Diels–Alder reaction of myrcene with acrolein for the first time, where MX is either 1‐butyl‐3‐methylimidazolium chloride (BmimCl), 1‐ethyl‐3‐methylimidazolium bromide (EmimBr), N‐butylpyridinium bromide (BPyBr), or N‐ethylpyridinium bromide (EtPyBr). Compared with the analogous reaction performed over a ZnCl₂ catalyst in the conventional solvent dichloromethane, higher regioselectivity of the ‘para’ cycloadduct and excellent yield were achieved at shorter reaction time in these ionic liquids with optimized molar compositions of MX and ZnCl₂. These moisture‐insensitive ionic liquids can be easily separated from reaction products after simple washing with hexane, allowing their reuse with no obvious loss in activity.     

11α hydroxylation of 16α, 17‐epoxyprogesterone in biphasic ionic liquid/water system by Aspergillus ochraceus

BACKGROUND: The improved efficiency of steroid biotransformation using the biphasic system is generally attributed to the positive effect on the solubility of substrate in aqueous media. A promising alternative for the application of organic solvents in biphasic systems is the use of ionic liquids (ILs). This study aims to investigate the applicability of the biphasic ILs/water system for 11α hydroxylation of 16α, 17‐epoxyprogesterone (HEP) by Aspergillus ochraceus. RESULTS: Of the seven ILs tested, [C₃mim][PF₆] exhibited the best biocompatibility, with markedly improved biotransformation efficiency. In the [C₃mim][PF₆]‐based biphasic system, substrate conversion reached 90% under the condition in which buffer pH, volume ratio of buffer to ILs, cell concentration, and substrate concentration were 4.8, 10/1, 165 g L^?1 and 20 g L^?1, respectively. This is more efficient than that of the monophasic aqueous system. The effects of the cations and anions of these ILs on the 11α hydroxylation of 16α, 17‐epoxyprogesterone (HEP) by A. ochraceus is also discussed. CONCLUSION: The above results showed that IL/water biphasic system improved the efficiency of 11α hydroxylation of 16α, 17‐epoxyprogesterone (HEP) by A. ochraceus, thus suggesting the potential industrial application of ILs‐based biphasic systems for steroid biotransformation. © 2012 Society of Chemical Industry     

Synthesis of Polyoxymethylene Dimethyl Ethers Catalyzed by Pyrrolidinonium‐Based Ionic Liquids

Polyoxymethylene dimethyl ethers (PODE_n) are widely applied as diesel additives in engines. Ionic liquids (ILs) replace traditional liquid acids as catalysts in chemical processes. A series of pyrrolidinonium‐based Brønsted acidity ILs were synthesized, investigated, and employed as catalysts for the synthesis of PODE_n from methylal and trioxane for the first time. The Hammett function values were measured to uncover the connection between catalytic performance and acidity‐activity of the ILs considered. The optimal experimental conditions for the synthesis of PODE_n were determined. The maximum values of both the conversion of raw material and the selectivity of PODE_3–8 were obtained with 1‐octyl‐2‐pyrrolidinonium trifluoromethanesulfonate ([NOP][TFO]) as the catalyst. [NOP][TFO] provides greater selectivity of PODE_3–4 than the traditional catalysts such as H₂SO₄ and CF₃SO₃H.     

Synthesis of some new polyhydrazides by direct polycondensation in ionic liquid and their metallization through transition metal complexation

A series of new polyhydrazides has been synthesized via direct polycondensation of benzofuro[2,3‐b]benzofuran‐2,9‐dicarboxylic acid (BBDA) with dihydrazides in ionic liquids (ILs) as a new class of solvents, which have interesting properties, such as nonvolatility, high ionic concentration, good thermal stability, and nonflammability. Direct polycondensation is successfully proceeded in ILs and triphenyl phosphite (condensing agent) without any additional extra components, such as LiCl and pyridine, using in similar reactions in ordinary (IL can act as both solvent and catalyst). The polyhydrazides have been obtained in quantitative yield and their intrinsic viscosities ranged from 0.21 to 0.47 dL g^?1. The polyhydrazides were characterized by means of IR, ¹H‐NMR, inherent viscosity (η_inh), solubility test, TGA, DSC, CHN analysis, and ultraviolet λ_max. They could be thermally converted into the corresponding poly(1,3,4‐oxadiazole)s approximately in the region of 210–330°C, as evidenced by the TGA thermograms. The polymers were readily soluble in several organic polar solvents, such as DMAc, N,N‐dimethylformamide, dimethylsulfoxide, N‐methyl‐2‐pyrrolidone and could be cast into flexible films. The polymer were metallized via complexation with various transition metal. The complexes were investigated by X‐ray diffraction, IR, and UV spectrophotometry. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Antimicrobial properties and thermal stability of polycarbonate modified with 1‐alkyl‐3‐methylimidazolium tetrafluoroborate ionic liquids

Four water immiscible ionic liquids (ILs): 1‐hexyl‐3‐methylimidazolium tetrafluoroborate, 1‐heptyl‐3‐methylimidazolium tetrafluoroborate, 1‐octyl‐3‐methylimidazolium tetrafluoroborate and 1‐dodecyl‐3‐methylimidazolium tetrafluoroborate have been synthesized. Polycarbonate (PC) films containing ILs were prepared by solvent casting from methylene chloride solutions. Scanning electron microscopy measurements showed the high homogeneity of PC/IL films with the IL content up to 4 wt %. The tendency to IL aggregation was observed for polymeric films with higher IL content (5%). PC/IL composites were found to have the reduced thermal decomposition temperature under both an air and a nitrogen atmosphere in comparison with the neat PC. The effect of IL content on the antimicrobial activity of PC films against Escherichia coli bacteria was studied. Pronounced antimicrobial efficacy was revealed for PC/IL films for all studied ILs starting from 3 wt % of IL. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40050.     

1‐Butyl‐3‐methylimidazolium Tetrafluoroborate ([Bmim]BF4) Ionic Liquid: A Novel and Recyclable Reaction Medium for the Synthesis of vic‐Diamines

Aziridines undergo ring opening smoothly with various arylamines in 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([bmim]BF₄) or 1‐butyl‐3‐methylimidazolium hexafluorophosphate ([bmim]PF₆) ionic liquids under mild and neutral conditions to afford the corresponding vicinal‐diamines in excellent yields with high regioselectivity. The recovered activated ionic liquids are recycled for four to five runs with no loss of activity.     

Structure‐based model for prediction of electrical conductivity of pure ionic liquids

A structure‐based method was proposed to estimate the electrical conductivity of ionic liquids covering wide ranges of temperature (238.15–484.1 K) and electrical conductivity (0.0001524–19.3 S/m) based on experimental data collect from literature from 1998 to 2015. The influences of temperature and ion structure on electrical conductivity were also discussed. The mean absolute percentage error between the calculated and literature data was 6.02%, with 6.12% for the training set (1978 data points, 177 ILs) and 5.10% for the test set (217 data points, 11 ILs). © 2016 American Institute of Chemical Engineers AIChE J, 62: 3751–3762, 2016