Vapor Pressure of Water in Mixtures with Hydrophilic Ionic Liquids – A Contribution to the Design of Processes for Drying of Gases by Absorption in Ionic Liquids

The low water vapor pressures of mixtures of water with the ionic liquids (ILs), [EMIM][EtSO₄] and [BEIM][EtSO₄], indicate that a process of gas dehydration by absorption in ILs might be an alternative to the classical absorption process with triethylene glycol (TEG). The activity coefficient for an infinite dilution of water in the IL (x_IL → 1), which should be low for efficient dehydration, is only about 0.2 for [EMIM][EtSO₄] compared to 0.6 for triethylene glycol. In contrast to TEG, losses by evaporation are excluded with ILs as solvents, because they have a negligible vapor pressure. The number of separation stages needed for the absorption in the IL and for the subsequent regeneration of the water‐loaded IL is small, about six and eight, respectively. IL regeneration can be achieved by distillation of water out of the IL (e.g., at 120 °C) and stripping with ambient air, which is not possible in the case of TEG (chemical attack by O₂).     

Modified COSMO-UNIFAC model for ionic liquid–CO2 systems and molecular dynamic simulation

A new predictive molecular thermodynamic model (i.e., modified COSMO-SAC-UNIFAC) was first proposed and extended to predict the solubility of CO₂ in pure and mixed ionic liquids (ILs) at the temperatures down to 263.2 K. It is interesting to discover that with equimolar amounts, the solubility of CO₂ in such 1:1 IL pairs, that is, [A₁][B₁] + [A₂][B₂] and [A₁][B₂] + [A₂][B₁], was consistent at the same temperature and pressure in the case of exchanging their respective cations and anions. The molecular dynamic (MD) simulation for CO₂ + mixed ILs was performed to deeply analyze and explain this intriguing phenomenon. Not only the CO₂ gas drying experiment with the ILs ([C2mim][OAc], [C2mim][dca], and [C2mim][OAc] + [C2mim][dca]) as absorbents but also the corresponding process simulation and optimization were made to stress the effectiveness and applicability of the new thermodynamic model. Thus, this work ranges from molecular level to systematic scale.     

1‐Allyl‐3‐methylimidazolium halometallate ionic liquids as efficient catalysts for the glycolysis of poly(ethylene terephthalate)

Series of 1‐allyl‐3‐methylimidazolium halometallate ionic liquids (ILs) were synthesized and used to degrade poly(ethylene terephthalate) (PET) as catalysts in the solvent of ethylene glycol. One important feature of these new IL catalysts is that most of them, especially [amim][CoCl₃] and [amim][ZnCl₃], exhibit higher catalytic activity under mild reaction condition, compared to the traditional catalysts [e.g., Zn(Ac)₂], the conventional IL catalysts (e.g., [bmim]Cl), Fe‐containing magnetic IL catalysts (e.g., [bmim][FeCl₄]), and metallic acetate IL catalysts (e.g., [Deim][Zn(OAc)₃]). For example, using [amim][ZnCl₃] as catalyst, the conversion of PET and the selectivity of bis(hydroxyethyl) terephthalate (BHET) reach up to 100% and 80.1%, respectively, under atmospheric pressure at 175°C for only 1.25 h. Another important feature is that BHET can be easily separated from the catalyst and has a high purity. Finally, based on the experimental phenomena, in ‐situ infrared spectra, and experimental results, the possible mechanism of degradation with synthesized IL is proposed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The role of hydrogen-bond in solubilizing drugs by ionic liquids: A molecular dynamics and density functional theory study

The solvation mechanisms of aspirin and etomidate in four combinations of [Emim]⁺ and [BuGun]⁺ paired with [OAc]⁻ and [NTf₂]⁻ were systematically studied by molecular dynamics simulations and DFT calculations. It was shown that the favorable solvation of aspirin and etomidate correlated well with hydrogen-bond (H-bond) basicity of anions and the H-bond acidity of cations, respectively. Wherein, the H-bond between aspirin and [OAc]⁻ anion with high H-bond basicity possessed covalent feature, so ILs containing [OAc]⁻ anion has the best effective in solubilizing aspirin. However, H-bond interactions between etomidate and cations exhibited an electrostatic dominant, and moderate cation–anion interaction could weaken it. Accordingly, for etomidate, the best ILs solvent comprised a weakly interacting anion and a cation with strong H-bond acidity, that is, [BuGun][NTf₂]. This solvation difference was because aspirin with carboxyl group displayed strongly H-bond donating characteristic, whereas etomidate with no active hydrogen protons mainly formed H-bond with cations. Additionally, we found that π–π stacking interactions were of secondary importance for the solubilization of etomidate, but little for aspirin. These simulations will be helpful for experimental design new ILs to solubilize some drugs with aspirin-like or etomidate-like structures.     

Ionic liquid mediated surface micropatterning of polymer blends

A polymer of intrinsic porosity (i.e., PIM‐1) has been blended with different ionic liquids (ILs) in order to evaluate the effect of the ILs on the microstructure of the polymer blend. [C₈MIM][Cl], [BMIM][DCa], [BMPyr][DCa], and [BMIM][Tf₂N] have been selected and were mixed with PIM‐1. Polymer blends containing up to 80 wt % of ILs were prepared by a casting method with chloroform as solvent. SEM images show that during the film formation a structuring of the surface appears depending on the nature and the concentration of ILs, with appearance of well‐defined microstructure in the case of [BMIM][Tf₂N] and [BMIM][DCa]. In the case of [BMIM][Tf₂N]/PIM‐1 film, the lower IL concentration induces the denser film with small micropatterns onto the surface. AFM analysis indicates that the ILs are well dispersed on the surface. X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and water contact angle measurements show that a gradient of IL concentration is observed across the film thickness. It is demonstrated that ILs are versatile co‐solvents for inducing controlled micropatterns in polymer membrane surfaces. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46109.     

Acidic protic ionic liquid-based deep eutectic solvents capturing SO2 with low enthalpy changes

With the aim of lowering energy consumption for gas regeneration, rational design of absorbents with low absorption enthalpy changes while retaining good gas solubility is of both scientific and practical significance. Herein, we demonstrated that acidic protic ionic liquid (APIL)-based deep eutectic solvents (DESs), which comprise N-ethylimidazole hydrochloride ([EimH]Cl) and ethylene glycol (EG), were able to reversibly absorb SO₂ with high solubility (11.60 mol kg⁻¹) and SO₂/CO₂ selectivity (655) at 293.2 K and 101.3 kPa. Meanwhile, [EimH]Cl/EG DESs exhibit very low enthalpy changes (Δ_rH_m) ranging from −27.1 to −25.6 kJ mol⁻¹, and thus ease of desorption at very mild temperature conditions (303.2 K) with desorption ratios up to 99.6%. Recycling experiments showed that no obvious loss in capacity was found after six absorption–desorption cycles, suggesting good regeneration performance of [EimH]Cl/EG DESs. Moreover, spectroscopic analysis revealed the charge-transfer interaction between [EimH]Cl/EG and SO₂.     

咪唑类离子液体混合物用于二氧化硫高效吸收

开发易制备、价格便宜、面向SO₂气体高效分离的离子液体（ILs），是当前ILs从实验探索迈向工业应用的难点与重大挑战。合成了不同摩尔比（3∶1、2∶1、1∶1、1∶2和1∶3）的1-乙基-3-甲基咪唑氯盐（[Emim][Cl]）和1-乙基-3-甲基咪唑乙酸盐（[Emim][OAc]）的离子液体混合物[Emim][Cl]_x[OAc]_1-x， 在测定其密度、黏度、热稳定性等基本物性数据的基础上，研究了[Emim][Cl]_x[OAc]_1-x混合物在不同温度和SO₂分压下的SO₂吸收能力。结果表明，[Emim][Cl]_x[OAc]_1-x能够有效地捕获SO₂。[Emim][Cl]与[Emim][OAc]之间存在协同促进作用，有利于实现SO₂高效吸收。[Emim][Cl]_0.33[OAc]_0.66混合液在1.0和0.2 atm（1 atm=101325 Pa）下捕获SO₂量分别为（1.34±0.08）和（0.74±0.05） g/g，与现有结果相比，混合物在SO₂捕获方面有明显优势。此外，这些离子液体混合物对二氧化硫的吸收和解吸具有良好的可逆性。     

Application of Room‐Temperature Aprotic and Protic Ionic Liquids for Oxidative Folding of Cysteine‐Rich Peptides

The oxidation of the conotoxin μ‐SIIIA in different ionic liquids was investigated, and the results were compared with those obtained in [C₂mim][OAc]. Conversion of the reduced precursor into the oxidized product was observed in the protic ILs methyl‐ and ethylammonium formate (MAF and EAf, respectively), whereas choline dihydrogenphosphate and Ammoeng 110 failed to yield folded peptide. However, the quality and yield of the peptide obtained in MAF and EAF were lower than in the case of the product from [C₂mim][OAc]. Reaction conditions (temperature, water content) also had an impact on peptide conversion. A closer look at the activities of μ‐SIIIA versions derived from an up‐scaled synthesis in [C₂mim][OAc] revealed a significant loss of the effect on ion channel Na_V1.4 relative to the buffer‐oxidized peptide, whereas digestion of either μ‐SIIIA product by trypsin was unaffected. This was attributed to adherence of ions from the IL to the peptide, because the disulfide connectivity is basically the same for the differentially oxidized μ‐SIIIA versions.     

Rational design of double salt ionic liquids as extraction solvents: Separation of thiophene/n-octane as example

Although double salt ionic liquids (DSILs) offer significant advantages over classical two-ion ionic liquids as separation solvents, relevant studies are still scarce and a systematic DSIL selection method is thus highly desirable. In this contribution, a rational method for designing DSILs as extraction solvents is proposed and exemplified by the thiophene/n-octane separation. The effects of additional degrees of freedom for DSIL design (i.e., double cations and/or anions and the ion ratio) on the thermodynamic properties are first analyzed by COSMO-RS. Then, a multilevel DSIL design method combining the prediction of infinite dilution thermodynamic properties, the estimation of physical properties, the evaluation of phase equilibrium behavior, and the experimental validation is proposed. By applying this method, [C₂MIm][OAc] _x[NO₃]_1-x (x = [0, 1]) and [C₂MIm][OAc] _x[SCN]_1-x (x = [0.70, 1]) are identified as promising DSIL solvents for the thiophene/n-octane separation. Correspondingly, the liquid–liquid equilibria of {DSILs + thiophene + n-octane} with the designed DSILs are experimentally studied.     

High capacity absorption of SO2 using imidazole ionic liquid mixtures

The capture of sulfur dioxide (SO₂) with readily available and cost-effective ionic liquids (ILs) is one of the challenges for the application of ILs. Here, we synthesized the ILs mixtures with different molar ratios (3∶1, 2∶1, 1∶1, 1∶2, and 3∶1) of 1-ethyl-3-methylimidazolium chloride ([Emim][Cl]) and 1-ethyl-3-methylimidazolium acetate ([Emim][OAc]) to study their SO₂ absorption capacities. The SO₂ solubilities in these mixtures were investigated under different conditions. The SO₂ absorption capacities of [Emim][Cl]_x[OAc]_1-x at different temperatures and SO₂ partial pressure were measured. The results show that ILs can effectively capture SO₂. There exists a synergistic promotion effect between [Emim][Cl] and [Emim][OAc], resulting in quite high SO₂ absorption capacity. The [Emim][Cl]_0.33[OAc]_0.66 mixture can capture SO₂ (1.34±0.08) and (0.74±0.05) g/g at 1.0 and 0.2 atm(1 atm=101325 Pa), respectively. Comparing with the reported data, [Emim][Cl]_x[OAc]_1-x mixtures show obvious advantage for SO₂ capture. In addition, these ionic liquid mixtures have good reversibility for the absorption and desorption of sulfur dioxide.     

Extractive Desulfurization of Fuel Oils with Dicyano(nitroso)methanide-based Ionic Liquids

The inability of traditional hydrodesulfurization (HDS) to effectively remove aromatic sulfur compounds such as thiophene (TS) and dibenzothiophene (DBT) has called for alternative methods to be studied, among which extractive desulfurization using ionic liquids (ILs) has attracted increasing interest. In this work, we prepared a new IL, 1-butyl-3-methylimidazolium dicyano(nitroso)methanide ([C₄mim][dcnm]), and investigated its extractive desulfurization for both model oils and real FCC gasoline, where model diesel fuel was composed of n-hexane and droplets of DBT and model gasoline was composed of n-hexane, toluene and droplets of TS. Other three [dcnm]-based ILs, 1-ethyl-3-methylimidazolium dicyano(nitroso)methanide ([C₂min][dcnm]), N-ethyl-N-methylpyrrolidinium dicyano(nitroso)methanide ([C₂mpyr][dcnm]), and N-butyl-N-methylpyrrolidinium dicyano(nitroso)methanide ([C₄mpyr][dcnm]), were also comparatively investigated. These [dcnm]-based ILs have low viscosity which favors the mass transfer and reduces the extractive equilibrium time, also are fluorine-free which avoids the corrosion by hydrogen fluoride from anion decomposition that occurs generally in fluorine-containing ILs. The desulfurization ability follows the order [C₄min][dcnm] > [C₄mpyr][dcnm] > [C₂min][dcnm] > [C₂mpyr][dcnm]. Typically, [C₄min][dcnm] is capable of removing 66% DBT and 53% TS from their respective model oils after one cycle (initial 500 ppm S, 25°C, 15 min, mass ratio of IL:oil 1:1), and < 10 ppm S-content can be obtained after 4 cycles. It was observed interestingly that the S-content in real FCC gasoline can be reduced from initial 250 ppm to < 30 ppm after 6 cycles using [C₄min][dcnm] as extractive reagent, which is better than some previous results for real feedstocks. Mutual solubility, extractive temperature, IL:oil mass ratio, multiple extraction, initial S-content, and regeneration were also studied. These dcnm-based ILs are competitive extractive reagents compared with some other ILs to remove those aromatic S-compounds from fuel oils.     

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     

Enhanced stability of <Emphasis Type="Italic">Candida antarctica</Emphasis> lipase B in ionic liquids

The activity and stability of lipase from Candida antarctica were investigated in the kinetic resolution of (R,S)-1-phenylethanol with vinyl acetate using ionic liquids (ILs) as reaction media. Among ILs tested, the highest activity of lipase was observed in [Edmim][Tf₂N]. In hydrophobic ILs such as [Edmim][Tf₂N], [Emim][Tf₂N] and [Pmim] [PF₆], lipase could retain its activity after 5 times reuse, while the activity of lipase in hydrophilic ILs and organic solvents was drastically decreased. The activities of lipase in [Edmim][Tf₂N], [Emim][Tf₂N] and [Pmim][PF₆] were also well maintained after 1 day incubation at 80 °C. The lipase suspended in [Edmim][Tf₂N] could be successfully reused 6 times without loss of activity.     

High pressure solubility of CO2 in non-fluorinated phosphonium-based ionic liquids

High pressure solubility of carbon dioxide in three phosphonium-based ionic liquids has been measured experimentally. A synthetic method was used to measure vapor–liquid, vapor–liquid–liquid and liquid–liquid equilibria of carbon dioxide in the ionic liquids trihexyltetradecylphosphonium bromide [thtdp][Br], trihexyltetradecylphosphonium dicyanamide [thtdp][dca] and trihexyltetradecylphosphonium bis(2,4,4-trime-thylpentyl)phosphinate [thtdp][phos] for a temperature range of 271–363 K and up to 90 MPa. Furthermore, the densities and viscosities of these ILs have been measured in a temperature range of 293–363 K. The solubility of carbon dioxide in these ILs is (on mole fraction basis) significantly larger than most of the commonly used fluorinated imidazolium ionic liquids. The latter statement, however, does not hold for the [Br] and [dca] based IL if the solubility is compared on molality (mole/mass solvent) basis, where the solubility differences among physical ILs tends to vanish indicating a strong molecular weight effect. The solubility of carbon dioxide in [thtdp][phos], both on mole fraction and molality basis, is among the highest compared to all the other physical ILs reported so far in the literature. The Peng–Robinson equation of state in combination with Wong–Sandler mixing rules incorporating the NRTL Gibbs excess energy model was applied to represent the experimental data with acceptable accuracy.     

Ionic liquids for highly efficient methyl chloride capture and dehydration

A new methyl chloride (CH₃Cl) capture and dehydration process using two ionic liquids (ILs) was designed and systematically studied. ILs [EMIM][Ac] and [EMIM][BF₄] were screened out as CH₃Cl capture and drying absorbents through the COSMO-RS model. The result of solubility experiment suggests [EMIM][Ac] has an excellent solvent capacity for CH₃Cl at mild operation conditions. The bench-scale CH₃Cl absorption experiments further confirmed the outstanding CH₃Cl capture ability of [EMIM][Ac]. Besides, the water content of outlet gas can be decreased to 452 ppm (mass fraction) using [EMIM][BF₄] in the dehydration experiment. The industrial-scale CH₃Cl capture and dehydration process was simulated and optimized. Compared to the benchmarked triethylene glycol process, IL process has higher product purity (99.99 wt%), and lower energy consumption. The quantum chemical calculations clearly revealed the relationship between hydrogen bond and separation performance. This study provides a decision-making basis for designing green process associated with volatile organic compounds.     

Gas drying with ionic liquids

The gas drying technology with ionic liquids (ILs) was systematically studied ranging from the molecular level to industrial scale. The COSMO‐RS model was first used to screen the suitable IL and provide theoretical insights at the molecular level. Toward CO₂ gas dehydration, we measured the CO₂ solubility in single [EMIM][Tf₂N] and in the [EMIM][Tf₂N] + H₂O mixture, as well as the vapor‐liquid equilibrium (VLE) of [EMIM][Tf₂N] + H₂O system, to justify the applicability of UNIFAC model. Based on the thermodynamic study, the rigorous equilibrium (EQ) stage mathematical model was established for process simulation. The gas drying experiment with IL was also performed and the water content in gas product can be reduced to 375 ppm. It was confirmed that a less flow rate of absorbent, a higher CO₂ recovery ratio and a much lower energy consumption can be achieved with IL than with the conventional triethylene glycol (TEG). © 2017 American Institute of Chemical Engineers AIChE J, 64: 606–619, 2018     

Influence of ionic liquids under controlled water activity and low halide content on lipase activity

Room-temperature ionic liquids (ILs) can be used as reaction media for nonaqueous biocatalysis. However, the purity of ILs should be considered to understand the influence of ILs on enzyme activity. The major impurities in ILs are water and halide. In the transesterification of benzyl alcohol with vinyl acetate, the optimal water activities for lipases in [Omim][Tf₂N] were similar to those in organic solvents. The chloride impurity in [Omim][Tf₂N] seriously influenced the activity of lipase. In this work, the effect of ILs on lipase activity was investigated under controlled initial water activity and low halide content. The activity of lipase was highly dependent upon the anion structure of ILs. The initial reaction rate of lipases followed the order [Tf₂N]⁻>[PF6]⁻>[TfO]⁻>[SbF₆]⁻≈[BF₄]⁻. All tested lipases showed the highest activities in ILs containing [Tf₂N] anion. Particularly, [AAIM][Tf₂N] was shown as a suitable reaction medium for biocatalysis. Lipozyme IM showed the highest activity in this IL among tested ILs. Thermal stability of lipase was also investigated. The higher thermal stability of Novozym 435 was obtained in hydrophobic and water-immiscible ILs such as [Bmim][Tf₂N], [Edmim][Tf₂N], and [Bmim][PF₆].     

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     

Effect of Ionic Liquids on Surface and Aggregation Properties of Non-ionic Surfactant Triton™ X-100 in Aqueous Media

The effect of the hydrophilic ionic liquids (ILs) 1-butyl-2,3-dimethylimidazolium bromide [bdmim][Br] and 1-hexyl-2,3-dimethylimidazolium bromide [hdmim][Br] on the aggregation and surface active behaviour of the non-ionic surfactant Triton? X-100 (TX-100) was studied in aqueous media. Several aggregation properties of TX-100 + IL/water systems, such as critical micelle concentration (CMC), surface active parameters, aggregation number (N _agg) and aggregate size, were determined by surface tension, fluorescence and dynamic light scattering (DLS) techniques. It was found that the average micellar size and aggregation number decrease, whereas the CMC increases with increasing concentration of ILs. Interestingly, the CMC value of TX-100 is reduced slightly below 0.5 wt% of both the ILs in the medium. At higher wt% of IL in the system the CMC increases. It was demonstrated that ILs [bdmim][Br] and [hdmim][Br] can be judiciously used at different wt% for modifying the physico-chemical properties of TX-100.     

Extraction of polycyclic aromatic hydrocarbons from fluid catalytic cracking diesel with ionic liquids

Ionic liquids (ILs) as promising green solvents were first proposed to extract polycyclic aromatic hydrocarbons (PAHs) from fluid catalytic cracking (FCC) diesel. The COSMO-RS model was used for preliminary screening of IL extractants. The liquid–liquid equilibrium (LLE) experiments were performed to show that the IL [BMIM][BF₄] has a high selectivity for the model oil system. Further, the LLE experimental results show that the solubility of 1-methylnaphthalene in [BMIM][BF₄] is relatively low, while the IL exhibits a high selectivity of n-hexadecane to 1-methylnaphthalene. This means that the use of [BMIM][BF₄] can obtain the high-purity products when considering the almost nonvolatility of IL. Compared to the benchmark process, the multistage countercurrent–reflux extraction process can improve the PAHs purity by about 2% at the expense of 5.06% total annual cost and 6.42% energy consumption, rendering the use of IL to extract PAHs from FCC diesel more feasible in industry.