室温离子液体室

介绍了主要由烷基咪唑盐阳离子及氟阴离子组成的室温离子液体的制备、物理性质、化学性质及其在常温条件下的应用.     

Viscosity of linseed oil as a function of mineral spirits and temperature

The viscosities of raw linseed oil, boiled linseed oil, and combinations of raw or boiled linseed oil with mineral spirits were measured as a function of temperature. In general, the viscosity data for these solutions were found to follow the equation n=Be^E/RT, where n is viscosity, B is a constant, E is the activation energy of flow, and T is absolute temperature. The viscosity values interpolated from the regression equations at 25 C, 40 C, and 60 C were analyzed as a function of percent mineral spirits for raw and boiled linseed oils. The results suggest that linseed oilmineral spirits mixtures behave as ideal solutions.     

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].     

Dialkylimidazolium halide ionic liquids as dual function inhibitors for methane hydrate

Six dialkylimidazolium halide ionic liquids have been investigated for their potential application as novel gas hydrate inhibitors. Their effects on the equilibrium methane hydrate dissociation curve in a pressure range 105–205 bar and the induction time of methane hydrate formation at 114 bar and a high degree of supercooling, i.e., about 25 °C, are measured in a high-pressure micro-differential scanning calorimeter. Similar to dialkylimidazolium tetrafluoroborate investigated in our previous work, these ionic liquids are found to shift the equilibrium hydrate dissociation/stability curve to a lower temperature and, at the same time, retard the hydrate formation by slowing down the hydrate nucleation rate. To understand the performance of these ionic liquids in inhibiting the hydrate formation, the electrical conductivity and infrared spectra of ionic liquids are also obtained and analyzed.     

The structural organization in aqueous solutions of ionic liquids

The ¹H NMR combined with the local composition (LC) model has been employed to investigate the structural organization of two aqueous solutions of ionic liquids (ILs), namely 1‐ethyl‐3‐methylimidazolium tetrafluoroborate (EmimBF₄) and n‐butylammonium nitrate (N4NO₃). The correlation of chemical shifts using the LC model shows that the self‐association of IL plays the leading role, and water prefers to interact with IL rather than self‐association in IL‐rich region. Instead the network of water molecules is established in water‐rich region, because the self‐association of water predominates. Furthermore, the difference between the local and the bulk composition presents the turnover at x_(IL) (mole fraction of IL) close to 0.6 for EmimBF₄/water, which is in accordance with the change of excess function. Accordingly, it could be presumed that the excess properties for N4NO₃/water system should behave turnover at x_(IL) ≈ 0.55 since the local and the bulk exhibit maximal difference at this composition. © 2008 American Institute of Chemical Engineers AIChE J, 2009     

铁基离子液的水相合成工艺

目前铁基离子液在基础和应用研究方面得到广泛的关注。从合成铁基离子液的原料出发,通过调节不同原料配比,系统研究了在空气气氛和水环境条件下铁基离子液的合成过程及现象。探索了水相废液再循环使用合成铁基离子液的绿色零排放工艺,对比了无水和水相两种不同环境下产物铁基离子液的差异,以及可能的相互转化条件,为理解和推动铁基离子液的相关研究与应用提供基础参考。     

离子液体应用研究进展

由于离子液体具有较低的熔点、良好的导电性和可以忽略的蒸汽压等优点,引起了科学界和工业界的广泛瞩目.随着研究的日益深入,室温离子液体已经被开发和应用到诸多领域.对室温离子液体应用的研究进展进行了综述,详细介绍了离子液体在电化学、化学反应、分离过程以及在新材料等方面的应用.并对该领域的研究前景作了展望.     

近几年国内外离子液体气相色谱柱的进展

室温离子液体由于它具有十分特殊的性质,得到了各个领域广泛的应用,近几年在气相色谱中应用室温离子液体作固定相的研究成为气相色谱的热点,这主要是由于新开发出来的离子液体可以很好地满足气相色谱固定相的要求。对近几年室温离子液体在气相色谱中的应用做一简要综述。     

水介质中离子液体催化合成四氢喹唑啉

以1-丁基-3-甲基咪唑四氟硼酸盐作为催化剂，以芳香胺和2-氨基苯甲醛为原料，在水介质中通过环化缩合反应，合成了一系列四氢喹唑啉类衍生物。通过对模板反应条件的探究，确定了最优条件为：0.2 mmol 2-（1-吡咯烷基）苯甲醛（Ⅰa），0.4 mmol芳香胺（Ⅱa），30%（以Ⅰa物质的量为基准）的催化剂，1 mL H2O，90 ℃下反应6 h，可得到产率为81%的产物。同时探索了的反应底物普适性，以较好的底物范围合成了19种四氢喹唑啉类衍生物。     

Adsorption of ionic liquids from aqueous effluents by activated carbon

The separation of imidazolium-based ionic liquids (ILs) from aqueous solution by adsorption has been investigated using a commercial activated carbon (AC) as adsorbent. Equilibrium experiments were carried out for obtaining the adsorption isotherms of ILs on AC at different temperatures. The influence of both cation and anion was analyzed by studying 17 different ILs. The role of the surface chemistry of the adsorbent was also examined using ACs modified by oxidative and thermal treatments. The incorporation of IL on the AC surface was studied by N₂ adsorption-desorption measurements and elemental analysis. In addition to this, a COSMO-RS computational approach was developed to estimate molecular and thermodynamic properties of the solvent-adsorbate-adsorbent system, which allowed us to analyze the adsorption mechanism from a molecular point of view. The results of this work indicate that the adsorption with AC is an affordable environmental application to remove hydrophobic ILs from water streams, proposing the use of acetone for adsorbent regeneration. It has also been demonstrated that the adsorption of refractory hydrophilic ILs can be improved by modifying the amount and nature of oxygen groups on the AC surface, particularly by including hydroxyl groups to promote hydrogen-bonding interactions with the basic groups of hydrophilic ILs.     

Recovery of ionic liquids from dilute aqueous solutions by electrodialysis

Ionic liquid/s (IL/ILs) are ideal solvents for many separation processes, such as cellulose dissolution, extraction of heavy metal ions and coal liquefaction residues, etc. During the above processes, ILs would inevitably remain in effluents. Due to their high costs and potential detrimental impacts on environment, it is extremely important to recycle ILs from dilute aqueous solutions. Electrodialysis (ED) was used for primary separation and recycling ILs. In order to evaluate the performance of ED process, the effects of initial concentration, applied voltage and initial volume of the dilute solutions on the overall current efficiency (η), recovery ratio (R) and concentration ratio (ω) were investigated. Among these experimental results, the highest recovery ratio could reach 85.2% and the highest overall current efficiency could reach 80.9%. The ED energy consumption is also discussed and the highest specific energy consumption (R_e) could reach about 1350 g/kW h. The effects of IL cation and anion sizes on concentrating process are also evaluated. The experimental results indicate that ED is an effective method to concentrate IL aqueous solutions.     

Octanol/water partition coefficients of ionic liquids

BACKGROUND: Room temperature ionic liquids (ILs) are attractive alternatives to environmentally unfriendly volatile organic solvents. Partitioning is one of the most important and fundamental properties of a chemical, and the octanol/water partition coefficient is widely used to measure the tendency of a chemical to cross biological membranes. However, there is very limited information on the concentration dependence of the partition coefficients of ILs. This study investigated the octanol/water partitioning of 1‐butyl‐3‐methylimidazolium ([bmim]) ILs containing either hexafluorophosphate ([PF₆]) or bis[(trifluoromethyl)sulfonyl]amide ([Tf₂N]) over a wide range of IL concentrations of three to five orders of magnitude. RESULTS: It was found that the apparent partition coefficients of the ILs increased with increasing IL concentration. A model based on the ionic nature of ILs was proposed to explain this behaviour, and the results showed a good fit with the experimental data. The intrinsic partition coefficients and dissociation constants of the ILs were determined using the equations from the proposed model. The differences in the intrinsic partition parameter values between the two ILs showed a good correlation with other physicochemical properties. CONCLUSIONS: The present study clearly shows that the octanol/water partition coefficients of ILs increase with increasing IL concentration owing to the formation of ion pairs. By using the proposed partition model, it was possible to determine the intrinsic partition coefficients of ILs, and it was found that the apparent partition coefficients of ILs converge to the intrinsic partition coefficients of the ionic species and ion pairs of ILs with decreasing and increasing IL concentration respectively. Copyright © 2008 Society of Chemical Industry     

Viscosity of ionic liquids using the concept of mass connectivity and artificial neural networks

Artificial neural networks (ANN) and the concept of mass connectivity index are used to correlate and predict the viscosity of ionic liquids. Different topologies of a multilayer feed forward artificial neural network were studied and the optimum architecture was determined. Viscosity data at several temperatures taken from the literature for 58 ionic liquids with 327 data points were used for training the network. To discriminate among the different substances, the molecular mass of the anion and of the cation, the mass connectivity index and the density at 298 K were considered as the independent variables. The capabilities of the designed network were tested by predicting viscosities for situations not considered during the training process (31 viscosity data for 26 ionic liquids). The results demonstrate that the chosen network and the variables considered allow estimating the viscosity of ionic liquids with acceptable accuracy for engineering calculations. The program codes and the necessary input files to calculate the viscosity for other ionic liquids are provided.     

Application of room temperature ionic liquids to Li batteries

Novel electrolyte materials, room temperature ionic liquids (RTILs) were applied to the Li battery system and their characteristics in Li-metal batteries are discussed, partly reviewing authors work in the past. Quaternary ammonium (QA) cation-imide RTIL was focused on because of the excellent stability in cathodic environment of Li. Li/LiCoO₂ cell performance and Li cycling efficiency using the selected QA-imide RTIL was almost satisfactory. In addition, thermal stability of selected QA-imide RTIL with the charged positive electrode and Li was the advantage for Li battery. On the other hand, further improvement in the conducting properties is required with balanced approach for both electrochemical stability and thermal stability in order to use the RTIL electrolyte practically in batteries.     

长链烷基咪唑类离子液体型表面活性剂的聚集行为

采用微波辐射法合成了咪唑类离子液体1-烷基-3-甲基咪唑氯盐[C_nMim]Cl (n=12,14,16),测定了[C_nMim]Cl的电导率及表面张力。结果表明,随着烷基链长度的增加,临界胶束浓度(CMC)与最小表面张力(γCMC)减小,[C_(16)Mim]Cl的表面活性最好。胶束化热力学参数(ΔG_(mic)⁰、ΔH_(mic)0、ΔH_(mic)⁰、ΔS_(mic)0、ΔS_(mic)⁰)表明,[C_(12)Mim]Cl的胶束化是熵驱动;而对于[C_(14)Mim]Cl与[C_(16)Mim]Cl的胶束化而言,25℃为焓驱动,超过35℃为熵驱动。     

功能化离子液体杂多酸盐催化丁二酸铵水溶液直接酯化

将磺酸功能化离子液体有机阳离子与Keggin结构的杂多酸(HPAs)阴离子结合,合成一系列磺酸功能化离子液体杂多酸盐(HPA-ILs),并对其结构进行了表征。将合成的杂多酸盐作为催化剂应用于丁二酸铵水溶液与正丁醇的直接酯化。与HPAs、H₂SO₄、[MIMPS]HSO₄和Nafion^®NR-50 resins等传统催化剂相比,HPA-ILs表现出更好的催化性能,并以 [MIMPS]₃PMo₁₂O₄₀作催化剂,详细探讨并确定了本反应的最佳工艺条件。在丁二酸铵质量分数为50%,催化剂质量分数为1.0%(以丁二酸铵计),醇铵摩尔比为5:1,反应时间为12 h,反应温度为130℃,真空度为0.02 MPa时,最佳酯收率达89.7%。催化剂重复使用6次后,酯收率仍保持在85%以上。     

咪唑类室温离子液体中有序聚集体的组装及应用

综述了近五年来国内外有关咪唑类室温离子液体作溶剂组装有序聚集体(如胶束、溶致液晶、微乳液等)的研究新进展,对比分析了离子型、非离子型和聚合物表面活性剂在离子液体和传统水溶液中组装聚集体的形态、结构、尺寸及机理方面的异同。同时,简要介绍了新型聚集体特别是离子液体微乳液的应用,并展望了这一研究的发展趋势。     

Viscosity of coal-derived liquids

A coal-derived liquid was separated into toluene insolubles, asphaltene and pentane soluble oil by conventional solvent analysis. The asphaltene was separated further into an acid-neutral and a basic component by a previously reported procedure from our laboratory. The viscosities of liquids reconstituted from toluene insolubles, asphaltenes, acid-neutral asphaltene or basic asphaltene in the pentane soluble oil were determined. The logarithm of the viscosity ratio is a linear function of concentration for each of the solutes. On a weight basis, the toluene insolubles produce about twice the viscosity as the asphaltenes. The viscosity of mixtures of acid-neutral and basic asphaltene in pentane soluble oil is greater than either component determined separately, presumably due to complex formation. The variation of the reduced specific viscosity with concentration indicates that aggregation of the asphaltene and toluene insoluble fractions plays a significant role in the viscosity of coal-derived liquids.     

Self-assembly of carbon nanotube films from room temperature ionic liquids

A novel method for the assembly of thin, uniform transparent and conductive films of single-walled carbon nanotubes (SWCNTs) on glass substrates is described. This process involves the initial transfer of a temporary suspension of SWCNTs in room temperature ionic liquid to the surface of water and the subsequent transfer of the SWCNT film onto a glass substrate. The average sheet resistance of the films was determined by four point probe measurements to be 1.52 and 4.13 kΩ/sq, with an average optical transparency of 50% and 63%, respectively.     

Microstructure of room temperature ionic liquids at stepped graphite electrodes

Molecular dynamics simulations of room temperature ionic liquid (RTIL) [emim][TFSI] at stepped graphite electrodes were performed to investigate the influence of the thickness of the electrode surface step on the microstructure of interfacial RTILs. A strong correlation was observed between the interfacial RTIL structure and the step thickness in electrode surface as well as the ion size. Specifically, when the step thickness is commensurate with ion size, the interfacial layering of cation/anion is more evident; whereas, the layering tends to be less defined when the step thickness is close to the half of ion size. Furthermore, two‐dimensional microstructure of ion layers exhibits different patterns and alignments of counterion/co‐ion lattice at neutral and charged electrodes. As the cation/anion layering could impose considerable effects on ion diffusion, the detailed information of interfacial RTILs at stepped graphite presented here would help to understand the molecular mechanism of RTIL‐electrode interfaces in supercapacitors. © 2015 American Institute of Chemical Engineers AIChE J, 61: 3022–3028, 2015