Cuprous-based composite ionic liquids for the selective absorption of CO: Experimental study and thermodynamic analysis

Three cuprous-based composite ionic liquids (ILs) [EimH][OAc]–xCuOAc (x = 0.5, 0.6, 0.7) were prepared and employed for efficient absorption of CO. It is shown that the cuprous composite IL [EimH][OAc]–0.6CuOAc exhibited the largest absorption capacity for CO (0.031 g/g at 293.15 K and 1 bar) and had a record CO/N₂ selectivity of 967, which is better than most of common ILs and solvents reported in the literature. The results of Fourier transform infrared (FTIR) spectra, electrospray ionization mass spectrometry (ESI-MS) analysis, and theoretical calculations reveal that such superior CO capacity mainly resulted from two kinds of chemical interaction between CO and the active anionic species [Cu(OAc)₂]⁻ in [EimH][OAc]–0.6CuOAc. Furthermore, a “deactivated IL model” was further proposed to accurately describe the absorption behavior of CO in [EimH][OAc]–0.6CuOAc, in which the thermodynamic parameters including Henry's law constants, reaction equilibrium constants, and absorption enthalpies were estimated by the correlation of the experimental solubilities of CO.     

Ab initio calculations of the interaction between thiophene and ionic liquids

The fundamental natures of the interaction between thiophene and ionic liquids of 1-n-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]⁺[PF₆]⁻) and 1-n-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]⁺[BF₄]⁻) were investigated using ab initio calculations and correlated with previous experimental results. The optimized structures show that the anions of the ionic liquids are situated outside the ring plane of the thiophene, with the fluorine atoms interacting with the hydrogen atoms of the thiophene, and the cation of the ionic liquids approaches the thiophene with its positively charged atoms approaching the negatively charged atoms of TS. It is concluded that thiophene molecules interact with the ionic liquids mainly via Coulombian attraction. Further analysis explained the results obtained from an absorption experiment that the molar ratios of the absorbed thiophene to the ionic liquids were approximately 3.5/1 and 2.4/1 for [BMIM]⁺[PF₆]⁻ and [BMIM]⁺[BF₄]⁻, respectively. The strong electron donation of the phosphorus atom to the fluorine atoms in the PF₆⁻ cluster is believed to be the major factor resulting in the higher molar ratio of thiophene/[BMIM]⁺[PF₆]⁻. The other factor is the difference of the compactness between the cation and the anion in the two ionic liquids.     

Aromatic sulfur‐nitrogen extraction using ionic liquids: Experiments and predictions using an a priori model

The tie‐line composition of three quaternary system namely 1‐ethyl‐3‐methylimidazolium acetate ([EMIM][OAc]) ([EMIM][OAc]) (1) + thiophene (2) + pyridine (3) + toluene (4), 1‐ethyl‐3‐methylimidazolium ethylsulphate ([EMIM][EtSO₄]) (1) + thiophene (2) + pyridine (3) + toluene (4), 1‐ethyl‐3‐methylimidazolium methylsulphonate ([EMIM][MeSO₃]) (1) + thiophene (2) + pyridine (3) + toluene (4) were experimentally determined at 298.15 K. The measured tie‐line data were successfully correlated with the nonrandom two liquid and UNIversal QUAsiChemical model prediction which gave less than 1% root mean square deviation (RMSD). [EMIM][MeSO₃] looks to be a promising solvent for the simultaneous separation having distribution ratios less than unity for both thiophene and pyridine. The quantum chemical‐based conductor like screening model for real solvent (COSMO‐RS) model was then used to predict the tie‐line composition of quaternary systems. COSMO‐RS gave the RMSD for the studied systems to be 8.41, 8.74, and 6.53% for the ionic liquids, respectively. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4806–4815, 2013     

Quantum chemical studies on the simultaneous interaction of thiophene and pyridine with ionic liquid

The simultaneous interaction of thiophene and pyridine with different ionic liquids:1‐butyl‐1‐methylpyrrolidinium tetrafluoroborate([BPYRO][BF₄]),1‐butyl‐1‐methylpyrrolidinium hexafluoro‐phosphate ([BPYRO][PF₆]), 1‐butyl‐4‐methylpyridinium tetrafluoroborate ([BPY][BF₄]), 1‐butyl‐4‐methylpyridinium hexafluorophosphate ([BPY][PF₆]) and 1‐benzyl‐3‐methylimidazolium tetrafluoroborate ([BeMIM][BF₄]) were investigated using quantum chemical calculations. A three‐tier approach comprising of partial charges, interaction energies and sigma profile generation using conductor‐like screening model for real solvents (COSMO‐RS) was chosen to study the systems. A quantitative attempt based on the CH‐π interaction in ionic liquid; thiophene–pyridine complexes gave the interaction energies of ILs in the order: [BPY][BF₄] > [BPYRO][PF₆] > [BeMIM][BF₄] > [BPY][PF₆] > [BPYRO][BF₄]. An inverse relation was observed between the activity coefficient at infinite dilution predicted via COSMO‐RS–based model and interaction energies. The dominance of CH‐π interaction was evident from the sigma profiles of ionic liquid together with thiophene and pyridine. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Novel ionic liquids as reaction medium for ATRP of acrylonitrile in the absence of any ligand

Atom transfer radical polymerization (ATRP) of acrylonitrile (AN) with ethyl 2-bromoisobutyrate (EBiB) as the initiator was firstly approached in the absence of any ligand in three novel ionic liquids, 1-methylimidazolium acetate ([mim][AT]), 1-methylimidazolium valerate ([mim][VT]) and 1-methylimidazolium caproate ([mim][CT]), respectively. All the polymerizations in the ionic liquids proceeded in a well-controlled manner. The polymerization in [mim][AT] not only showed the best control of molecular weight and its distribution but also provided a rather rapid reaction rate with the molar ratio of [AN]:[FeBr₂]:[EBiB] at 200:2:1. The resulting polyacrylonitrile was successfully used as the macroinitiator to proceed the chain extension polymerization in [mim][AT]. After simple purification, all the ionic liquids and FeBr₂ could be recycled and reused and had no effect on the living nature of polymerization.     

基于COSMO-RS方法筛选离子液体分离乙酸乙酯-乙腈共沸物

采用COSMO-RS方法探究了不同离子液体在分离乙酸乙酯-乙腈共沸物系中的应用;通过预测值与实验值的对比,验证了COSMO-thermX预测离子液体分离效果的准确性。离子液体的选择性和不同离子液体对乙酸乙酯-乙腈近沸点处相对挥发度的影响为指标,计算和分析了17种阳离子和13种阴离子组成的221种离子液体对乙酸乙酯-乙腈共沸物系的分离效果的影响规律。结果表明,含有[OAc]^－和[Cl]^－的离子液体对于乙酸乙酯-乙腈混合物的分离具有更好的促进效果,而阳离子的变化对于乙酸乙酯-乙腈混合物分离的促进效果差异较小。应用表面电荷密度分布（σ-profile）进一步研究了阴离子[OAc]^－和[Cl]^－对共沸物的影响,研究发现,阴离子[OAc]^－和[Cl]^－对乙酸乙酯-乙腈的分离效果影响顺序为[OAc]^－>[Cl]^－;综合筛选结果,得出离子液体[BMIM][OAc]有望在乙酸乙酯-乙腈共沸混合物分离过程中成为一种高效的萃取剂。     

Solubilities of small hydrocarbons,viscosities of diluted tetraalkylphosphonium bis(2,4,4‐trimethylpentyl) phosphinates

Tetraalkylphosphonium bis(2,4,4‐trimethylpentyl)phosphinates show large solubilities for methane, ethane, ethylene, and propane. In these ionic liquids, solubilities of ethane are larger than those of ethylene. Therefore, these ionic liquids may be useful solvents for separation of ethane and ethylene; because the vapor pressure of ethylene is higher than that of ethane, the relative volatility ethylene/ethane is enhanced. However, the viscosities of these ionic liquids are too high for an industrial process. Low‐viscosity 1‐butyl‐3‐H‐imidazolium acetate([BHMIM][AC]) is a suitable diluent for reducing the large viscosities of trihexyl tetradecylphosphonium bis(2,4,4‐trimethylpentyl) phosphinate ([P(14)666][TMPP]) and tetrabutylphosphonium bis(2,4,4‐trimethylpentyl) phosphinate ([P4444][TMPP]). Addition of 20 wt % [BHMIM][AC] gives a dramatic drop in the viscosities of these ionic liquids. Mixtures of [P(14)666][TMPP] or [P4444][TMPP] with 20 or 50 wt % [BHMIM][AC] show high solubilities for the four solutes when compared with those in other ionic liquids. In these mixtures, the solubility for ethane is higher than that for ethylene. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2607–2612, 2014     

萃取精馏分离甲醇-丁酮萃取剂的选择

为了解决工业生产中甲醇-丁酮共沸体系难分离的问题,本研究采用一步法合成了N-乙基吡啶溴盐([EPy][Br])、N-丁基吡啶溴盐([BPy][Br])和N-己基吡啶溴盐([HPy][Br])3种离子液体(IL),测定了101.3 kPa下这3种离子液体对甲醇-丁酮共沸物系的溶剂选择性,并考察了溶剂比对其选择性的影响,同时将离子液体的分离性能与有机溶剂进行了比较。实验结果表明:合成的3种离子液体都可提高甲醇对丁酮的相对挥发度,它们的选择性大小顺序为[EPy][Br]> [BPy][Br]> [HPy][Br],同时,它们的选择性随溶剂比的增加而增大,与常规有机溶剂相比,离子液体作为萃取剂具有显著优势。因此,可以选用[EPy][Br]作为分离甲醇-丁酮共沸物系的萃取剂。     

Recovery of Furfural from Aqueous Solution by Ionic Liquid Based Liquid–Liquid Extraction

Abstract

Liquid–liquid extraction with imidazolium based ionic liquids ([C₄mim][PF₆], [C₆mim][PF₆], and [C₈mim][PF₆]) is proposed for the separation of furfural or 5-methylfurfural from aqueous solution. Factors affecting the extraction of furfural or 5-methylfurfural have been studied. It was shown that the extraction equilibria can be achieved within 30 min and the process was less affected by the factors such as volume ratio and feed concentration. The partition coefficients of furfural and 5-methylfurfural decreased with increasing temperature. [C₆mim][PF₆] was found to have the best extraction ability among the three ionic liquids studied. Presence of small amount of NaCl or Na₂SO₄ in the aqueous phase results in the considerable increase in the partition coefficients of furfural because of the competitive hydration of the salts with furfural. A thermodynamic study revealed that the extraction process was driven mainly by hydrophobic interactions. Further experimental results indicated that furfural can be separated selectively from aqueous furfural/acetic acid mixtures.     

Selective Separation of Toluene/n‐Heptane by Supported Ionic Liquid Membranes with [Bmim][BF4]

Room‐temperature ionic liquids serve as alternative solvents for volatile organic compounds in liquid‐liquid extraction and liquid membrane separation. 1‐Butyl‐3‐methylimidazolium tetrafluoroborate ([Bmim][BF₄]) was applied for extraction and supported ionic liquid membranes (SILMs) to separate toluene and n‐heptane. A high separation factor of toluene was achieved due to the strong interaction between ionic liquid cations and toluene. The mass transfer performance of the SILM process was enhanced by higher operating temperature. With the increase of initial toluene concentration in the feed phase, the mass transfer flux and removal efficiency of the SILM process were improved, while the separation factor decreased. The mass transfer flux was growing with the increase of flow rate at both sides. The SILM process was stable over a long time period due to the high viscosity and low volatility of [Bmim][BF₄].     

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     

油酚分离过程离子液体萃取溶剂的多尺度筛选

离子液体作为萃取溶剂已广泛用于油酚混合物的分离,但由于阴阳离子的可调控性,不同离子液体的性质差异较大,快速筛选得到具有应用前景的离子液体至关重要。针对间甲酚-异丙苯分离体系,采用COSMO-RS模型考察不同阴阳离子结构对离子液体分离性能的影响,并通过分子间相互作用能进行分析。在此基础上,提出一种多尺度的离子液体筛选方法,该方法包含无限稀释热力学性质计算、物性估算、相平衡关系计算和过程性能评价。该多尺度方法从分子尺度到单级平衡尺度,再到多级平衡尺度对离子液体进行逐步筛选。结果表明,1-乙基吡啶硫氰酸盐([C₂py][SCN])和1-乙基吡啶双氰胺盐([C₂py][DCA])是最终筛选得到的两种更具有油酚分离应用前景的离子液体。     

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).     

Thermodynamic Modeling of Imidazolium-Based Ionic Liquids with the [PF6]− Anion for Separation Purposes

There is an increased interest in developing accurate tools to relate the physicochemical properties of ionic liquids (ILs) to their microscopic structure as this information is needed to speed up the design of new ionic liquids for chemical and industrial processes. Molecular models can be used for this purpose. We explore here the extended capabilities of a model previously developed in the context of soft-SAFT, by Andreu and Vega in 2007 to reproduce the thermodynamic behavior of imidazolium hexafluorophosphate-based ([C_nmim][PF₆]) ionic liquids. The molecular parameters optimized in the previous work have been used here in a transferable manner; some new members of the [C_nmim][PF₆] family have also been added, as new recent experimental data has been published. The interfacial tensions have been calculated using a Density Gradient Approach and the results have been compared with available experimental data. The solubility of carbon monoxide and hydrogen in those ILs has been studied in the range of temperatures and pressures of application for separation processes. Binary mixtures with other imidazolium ionic liquids with different anions have been calculated, in a predictive manner. Finally, calculations of mixtures of ionic liquids with water also show very good agreement with experimental data. This work highlights the importance of using a simple but robust thermodynamic model, including the right level of interactions, to accurately describe the properties of these highly non-ideal systems.     

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.     

Liquid–liquid extraction of hydroxytyrosol,tyrosol, and oleuropein using ionic liquids

ABSTRACT

Hydroxytyrosol (HT), tyrosol (TY), and oleuropein (OL) are valuable compounds that can be obtained from olive oil production waste. This study implemented liquid–liquid extraction to obtain HT, TY, and OL from model solutions using two organic solvents, namely, ethyl acetate and n-butyl acetate, and three ionic liquids (ILs), namely, [P_6,6,6,14][Tf₂N], [P_6,6,6,14][DCA], and [omim][Tf₂N]. [P_6,6,6,14][DCA] showed the best performance, with extraction efficiencies of 92%, 96%, and 83% for HT, TY, and OL, respectively. [omim][Tf₂N] showed the highest selectivity in the extraction of TY. Comparisons of the results of a proposed mathematical model with experimental data yielded errors lower than 0.5%.     

Screening of ionic liquids as entrainers for the separation of 1-propanol + water and 2-propanol + water mixtures using COSMO-RS model

The COSMO-RS model was used to screen potential ionic liquids for the separation of aqueous azeotropic mixtures 1-propanol?+?water and 2-propanol?+?water. A combination of 22 cations (involving imidazolium, pyridinium, pyrrolidinium, quinolinium, and ammonium) and 36 anions were investigated. The anions chloride [Cl] and dihydrogen phosphate [H₂O₄P] were found to strongly influence the vapor liquid equilibrium behavior, whereas the ammonium-based cations diethanol ammonium [(Et)₂AMM]⁺ and tetra methyl ammonium [M₄AMM]⁺ were the most promising cations. In addition, the study of mixing enthalpy and excess Gibbs free energy confirmed that the molecular interaction of ionic liquids with water was found to be much larger than that with alcohols 1-propanol and 2-propanol, indicating the presence of a strong hydrogen bonding between the ionic liquids and water. Further, the addition of ionic liquids to the alcohol–water mixture reduces the activity coefficient of water and increases the relative volatility of the mixture, facilitating easier separation. Ionic liquids [(Et)₂AMM][Cl], [(Et)₂AMM][H₂O₄P], [M₄AMM][Cl], and [M₄AMM][H₂O₄P] are expected to be effective entrainers for the separation of the industrially important 1-propanol?+?water and 2-propanol?+?water systems.     

Phase equilibria and structural properties of thiophene/[Bmim][BF4]: A molecular insight from monte carlo simulations

The phase equilibria of thiophene in 1‐butyl‐3‐methylimidazolium tetrafluoroborate ([Bmim][BF₄]) is calculated by Monte Carlo simulation in Gibbs ensemble using a united atom force field. The liquid density of studied ionic liquid and the vapor pressure of thiophene in [Bmim][BF₄] were compared with corresponding experimental data reported in the literature, and a good agreement was obtained. In order to describe the solubility of thiophene in this ionic liquid, we have calculated the radial distribution functions and spatial distribution functions of thiophene/IL mixtures to study the interaction of thiophene with cations and anions of [Bmim][BF₄] in the liquid phase. The local composition concept in fluid was also examined to give further insight into the liquid structure. The results show that thiophene is well organized around the terminal carbon atom of the butyl or methyl chain attached to the imidazolium ring of cations and tends to adopt a symmetrically distribution on the anions. © 2014 American Institute of Chemical Engineers AIChE J, 60: 3916–3924, 2014     

The functionalized ionic liquid-stabilized palladium nanoparticles catalyzed selective hydrogenation in ionic liquid

The functionalized ionic liquid (2,3-dimethyl-1-[3-N,N-bis(2-pyridyl)-propylamido] imidazolium hexafluorophosphate, [BMMDPA][PF₆]) stabilized and modified palladium nanoparticles were obtained by reducing palladium(II) complex with molecular hydrogen. The as-synthesized palladium nanoparticles have been characterized by different methods. It was demonstrated that the Pd nanoparticles were very efficient catalysts for the selective hydrogenation of the CC bonds of various functionalized alkenes under mild conditions in neat ionic liquid (1-n-butyl-2,3-dimethylimidazolium hexafluorophosphate, [BMMIM][PF₆]). An efficient separation of the products from reaction mixture (ionic liquid phase) was realized and the catalyst’s nano-dispersion and high performance could be preserved.     

Oxidation desulfurization of fuel using pyridinium-based ionic liquids as phase-transfer catalysts

In this work, several ionic liquids based on pyridinium cations are prepared. The ionic liquids are employed as phase-transfer catalysts (PTCs) for phase-transfer catalytic oxidation of dibenzothiophene (DBT) dissolved in n-octane. The partition coefficients of DBT between ionic liquids and n-octane are investigated. Then H₂O₂-formic acid is used as an oxidant and ionic liquids are used as PTCs. The reaction turns to be heterogeneous and desulfurization rate of DBT increased apparently. When IL ([BPy]HSO₄) is used as PTC, and the condition are: temperature is 60 °C, time is 60 min, H₂O₂/sulfur molar ratio (O/S) is 4, the desulfurization rate reaches the maximum (93.3%), and the desulfurization of the real gasoline is also investigated, 87.7% of sulfur contents are removed under optima reaction conditions. The PTC [BPy]HSO₄ can be recycled for five times without significant decrease in activity.