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     

Prediction and screening of solubility of pharmaceuticals in single‐ and mixed‐ionic liquids using COSMO‐SAC model

In this work, we investigated the prediction of solubility (x_d) of drug molecules in single‐ and mixed‐ionic liquid (IL) solutions using the COSMO‐SAC activity coefficient model. In particular, the effect of dissociation of IL on solubility is examined. The prediction accuracy is found to be 91% in x_d (root‐mean‐square deviation in ln x_d is 0.65) for a total of 442 data points with solubility ranging from 0.93 to 2.84 × 10^?4 (mole fraction) and temperature ranging from 248.9 to 488.3 K. The solubility of drug is found not sensitive to the treatment of dissociation of IL in the calculations. The method is used to determine the solubility of paracetamol in 2624 single IL made from combination of 82 cations and 32 anions. The solubility of paracetamol can vary by 4 orders of magnitude in different ILs, indicating that this is a powerful method for screening for solvents with desired solubility power. The solubility of a drug in binary IL solution can be significantly higher or lower than those in pure IL components. For the 3,441,376 binary IL mixtures, about 8% of the mixtures exhibit higher solubility for paracetamol and 6% exhibit lower solubility. Our results indicate that mixing ILs can be a viable approach for tuning drug solubility. © 2017 American Institute of Chemical Engineers AIChE J, 63: 3096–3104, 2017     

Computer‐aided design of tailor‐made ionic liquids

Ionic liquids (IL), with their negligible vapor pressure, have the potential to replace volatile organic solvents in several processes. They also exhibit other unique characteristics, such as high thermal stability, wide liquid range, and wide electrochemical window, which make them attractive for many important applications. In addition, millions of ILs can be formed through different combination of cations, anions, and other functional groups. Till now, majority of work on IL selection, for a given application, is guided by trial and error experimentation. In this article, we present a computer‐aided IL design framework, based on semiempirical structure‐property models and optimization methods, which can consider several IL candidates and design optimal structures for a given application. This powerful methodology has great potential to act as a knowledge‐based framework to aid synthetic chemists and engineers develop new ILs. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4627–4640, 2013     

Design and screening of ionic liquids for C2H2/C2H4 separation by COSMO‐RS and experiments

Ionic liquids (ILs) have been proposed as promising solvents for separating C₂H₂ and C₂H₄, but screening an industrially attractive IL with high capacity from numerous available ILs remains challenging. In this work, a rapid screening method based on COSMO‐RS was developed. We also present an efficient strategy to improve the C₂H₂ capacity in ILs together with adequate C₂H₂/C₂H₄ selectivity with the aid of COSMO‐RS. The essence of this strategy is to increase molecular free volume of ILs and simultaneously enhance hydrogen‐bond basicity of anions by introducing flexible and highly asymmetric structures, which is validated by a new class of tetraalkylphosphonium ILs featuring long‐chain carboxylate anions. At 298.1 K and 1 bar, the solubility of C₂H₂ in ILs reaches 0.476 mol/mol IL, very high for a physical absorption, with a selectivity of up to 21.4. The separation performance of tetraalkylphosphonium ILs to the mixture of C₂H₂/C₂H₄ was also evaluated. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2016–2027, 2015     

Ionic liquids for absorption and separation of gases: An extensive database and a systematic screening method

Ionic liquids (ILs) have attracted considerable attention in both the academic and industrial communities for absorbing and separating gases. However, a data‐rich and well‐structured systematic database has not yet been established, and screening for highly efficient ILs meeting various requirements remains a challenging task. In this study, an extensive database of estimated Henry's law constants of twelve gases in more than ten thousand ILs at 313.15 K is established using the COSMO‐RS method. Based on the database, a new systematic and efficient screening method for IL selection for the absorption and separation of gases subject to important target properties is proposed. Application of the database and the screening method is highlighted through case studies involving two important gases separation problems (CO₂ from CH₄ and C₂H₂ from C₂H₄). The results demonstrate the effectiveness of using the screening method together with the database to explore and screen novel ILs meeting specific requirements for the absorption and separation of gases. © 2017 American Institute of Chemical Engineers AIChE J, 63: 1353–1367, 2017     

Study on the extraction of dyes into a room‐temperature ionic liquid and their mechanisms

The investigation of liquid–liquid extraction of dyes is carried out by using ionic liquid—1‐butyl‐3‐methylimidazolium hexafluorophosphate ([BMIM][PF₆])—as extraction phase. The effects of its process parameters are studied in detail, such as extraction phase ratio, pH of the aqueous phase, and concentration of dicyclohexyl‐18‐crown‐6 (DCH‐18C6) in the organic phase. Important results are obtained as follows: acid dyes can be extracted with [BMIM][PF₆] quantitatively; the removal of reactive dyes is low; however, it can be greatly increased by the addition of DCH‐18C6. The pH value has a great impact on the removal of the acid dye and the reactive dye. However, it does not influence the extraction of the weak acid dye. It is found that the extraction process of acid dyes adopts the form of anion exchange and the soluble part of the ionic liquid plays an important role as counter‐ions. Copyright © 2007 Society of Chemical Industry     

Separation and recovery of cellulose and lignin using ionic liquids: a process for recovery from paper‐based waste

BACKGROUND: The production of paper makes use of cellulose and lignin as a raw material, and almost all cellulose and lignin production comes from raw wood materials, contributing to deforestation and resulting in potential environmental harm. It is therefore beneficial to develop technologies for cellulose and lignin recovery for re‐use and sustainability of resources. RESULTS: Three imidazolium based ionic liquids (ILs), 1‐(2‐cyanoethyl)‐3‐methylimidazolium bromide (cyanoMIMBr), 1‐propyl‐3‐methylimidazolium bromide (propylMIMBr) and 1‐butyl‐3‐methylimidazolium chloride (butylMIMCl), were synthesised by microwave technology and fully characterised by mass spectrometry, thermogravimetric differential scanning calorimetry, thin layer chromatography, nuclear magnetic resonance and Fourier transform infrared spectroscopies. Cellulose and lignin were soluble in all three ILs with solubility being greatest in cyanoMIMBr. Regeneration of cellulose and lignin was achieved from saturated solutions of cellulose in IL and lignin in IL for all three ILs. The ILs propylMIMBr and butylMIMBr have been used for the first time in the separation and recovery of cellulose and lignin and regeneration of the IL from a mixture of cellulose and lignin in IL. FTIR analysis confirms successful recovery. CONCLUSIONS: This work demonstrates the ability of ILs to separate and recover cellulose and lignin from a mixed system. Copyright © 2009 Society of Chemical Industry     

Recent trends in (ligno)cellulose dissolution using neoteric solvents: switchable,distillable and bio‐based ionic liquids

Recent years have witnessed the use of different ionic liquids for biomass processing, either at the level of lignocellulose pre‐treatment, to fractionate biomass in its main components, separating hemicellulose and lignin from cellulose, or directly in cellulose decrystallization by dissolving it in the ionic liquid and subsequent precipitation by adding anti‐solvents. Yet, most of the ILs employed in these strategies (e.g. imidazolium‐based solvents) are (still) expensive for such applications, and provide discussable ecological footprints. In an attempt to combine the highly useful generated knowledge with novel neoteric solvents with improved properties, economics, availability and ecology, several new trends have appeared in these areas during recent years. They comprise the use of switchable ILs, based on strong organic bases and CO₂, the application of distillable ILs, as well as the use of bio‐based and low‐cost ILs and deep‐eutectic‐solvents (DES), e.g. choline chloride‐based derivatives. Apart from other emerging uses, for all these solvents some preliminary applications in biomass processing involving pretreatments, cellulose dissolution and other applications have been successfully reported. This Minireview contextualizes these recent trends and discusses them with emphasis on future use of them in biorefineries and biomass valorization. © 2013 Society of Chemical Industry     

A controllability analysis of a pilot‐scale CO2 capture plant using ionic liquids

Nowadays there is a world concern on the impact and effect of large CO₂ atmospheric concentrations on human health. Fossil‐fuel combustion processes in power plants are among the major contributors to this issue. Hence, it becomes important to develop new clean and sustainable processes aimed to reduce the amount of CO₂ released to atmosphere by combustion processes in power plants. One of the best feasible manners to achieve this purposes lies in the use of a closed‐loop control system able to keep the amount of green‐house gases under specification even in the presence of unexpected scenarios. Of course, CO₂ capture has been extensively researched in the past. However, in this regard the industrial practice has consisted in using Amines leading to sustainability and safety issues. Hence, it makes sense to seek for new and potentially environmental friendly process design to address CO₂ reduction from power plants but applying a new type of sustainable stripping solvents. In this work we address the sustainable CO₂ reduction issue from a process control point of view applying a previous design proposed by our research team based on the deployment of Ionic Liquids (IL) as potential green solvents and developing an efficient and decentralized multiloop control system. We demonstrate that the closed‐loop system is able to maintain the CO₂ concentration levels under specification by testing in presence of several demanding scenarios. Overall, from an economic, sustainable and control point of view it looks feasible to replace the traditional amines‐based CO₂ capture process by other alternatives based on the application of IL as potential green solvents. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3298–3309, 2016     

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     

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     

Viscosity of ionic liquids: Database,observation, and quantitative structure‐property relationship analysis

Viscosity data for ionic liquids (ILs) are needed for the theoretical study on viscosity or for the design/development of industrial process that involves ILs; understanding the relationship between ionic structure and viscosity is also desired to more rationally design and synthesize ILs with ideal viscosity. A database for the viscosity of pure ILs and their binary/ternary mixtures with molecular compounds is created by performing a comprehensive collection from published scientific literature sources worldwide covering the period from 1970 to 2009. In this database, there are 5046 data entries, 696 ILs, 306 cations, and 138 anions. Following the database, a direct observation of the effects of ionic structure along with temperature, pressure, and impurity on the viscosity is summarized, and a quantitative structure‐property relationship (QSPR) correlation is performed to understand the viscosity at a micro‐electronic or molecular level. Through direct observation and QSPR, the relationship between ILs structure and viscosity is addressed. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Global phase behavior of imidazolium ionic liquids and compressed 1,1,1,2‐tetrafluoroethane (R‐134a)

Novel processes involving ionic liquids with refrigerant gases have recently been developed. Here, the complete global phase behavior has been measured for the refrigerant gas, 1,1,1,2‐tetrafluoroethane (R‐134a) and 1‐n‐alkyl‐3‐methyl‐imidazolium ionic liquids with the anions hexafluorophosphate [PF₆], tetrafluoroborate [BF₄] and bis(trifluoromethylsulfonyl)imide [Tf₂N] from ～0°C to 105°C and to 33 MPa. All of the systems studied were Type V from the classification scheme of Scott‐van Konynenburg with regions of vapor‐liquid equilibrium, miscible/critical regions, vapor‐liquid‐liquid equilibrium, and upper and lower critical endpoints (UCEP and LCEP). The effect of the alkyl chain length has been investigated, for ethyl‐([EMIm]), n‐butyl‐([BMIm]), and n‐hexyl‐([HMIm]). With increasing chain length, the temperature of the lower critical end points increases and pressure at the mixture critical points decrease. With a common cation, the temperature of the LCEP increased and the mixture critical point pressures decreased in the order of [BF₄], [PF₆], and [Tf₂N]. © 2008 American Institute of Chemical Engineers AIChE J, 2009     

Production of silk fibroin nanoparticles using ionic liquids and high‐power ultrasounds

Biopolymeric nanoparticles have attracted great research interest in the last few years due to their multiple applications. This article describes how high‐power ultrasounds are capable of enhancing the dissolution process of silk proteins in ionic liquids (ILs) and how silk fibroin nanoparticles (SFNs) can be obtained directly from the silk/ionic liquid solution (SIL) by rapid desolvation in polar organic solvents. The silk fibroin integrity is highly preserved during the dissolution process, as confirmed by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) of the SIL. These regenerated SFNs are insoluble in water and other common organic solvents and are indistinguishable from the classical SFNs with respect to their diameter (180 ± 5 nm), Zeta potential (?25 ± 3 mV), high degree of β‐sheet and low cytotoxicity. Large amounts of silk can be turned into biomaterials directly from the SIL solution for use in a wide range of applications, while the ILs can be recovered from the coagulant solution under reduced pressure and reused without loss of their solvent properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41702.     

Evaluation of thermophysical data,COSMO-SAC predictions,and feed simplifications for aromatic extraction process simulation using ionic liquid [EMIM][NTf2]

Ionic liquids (ILs) are promising alternatives to conventional solvents for selective separation of aromatics from hydrocarbon mixtures, and their implementations depend on economic feasibility demonstrated by process simulation. Prior process modeling studies typically assume simplified hydrocarbon feeds or use the COSMO-SAC predictive model. Our goal is to evaluate how feed simplifications and COSMO-SAC predictions impact process modeling. We collect experimental data for 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]) from the ILThermo database to regress UNIQUAC model binary interaction parameters for 17 hydrocarbons. We find that feed simplifications tend to significantly underpredict process energy requirements and fail to reveal important details in the extractive distillation section of the process. COSMO-SAC predictions underpredict activity coefficient of aliphatics in [EMIM][NTf2] by a large margin, which leads to lower aromatic-aliphatic selectivities and overprediction of process energy requirements. It is significant enough to lead to the conclusion of process infeasibility in the case of [EMIM][NTf2].     

Simultaneous extraction and purification of myricetin from Chamaecyparis obtusa by multi‐phase extraction with ionic liquid‐modified mesoporous MCM‐41

BACKGROUND: Multi‐phase extraction is a novel method for the simultaneous extraction and separation of myricetin from Chamaecyparis obtusa . In this research, an amino ionic liquid‐modified MCM‐41 was used as the sorbent and the sample was packed with it into a cartridge. A fixed volume of solvent was then use to extract the target compound with several repetitions and to remove the myricetin to the sorbent. The washing and elution of solvent were investigated. RESULTS: FT‐IR and element contents tests confirmed that the ionic liquid groups were successfully immobilized on MCM‐41. 0.184 mg myricetin was extracted with five repetitions of 1.0 mL methanol. Then 2.0 mL n‐hexane and water were removed all the interference and 1.0 mL methanol was purified 0.1 mg myricetin from 0.2 g ionic liquid‐modified MCM‐41. CONCLUSION: Base on a comparison with traditional extraction methods, the low deviation error (3.16%), small amount of solvent required, highly selective separation and stability of the proposed method justify continuing its development. Copyright © 2011 Society of Chemical Industry