Ionic liquids in separations

Ionic liquids are liquids composed completely of ions. In the past two decades, ionic liquids have been widely used as "green solvents" replacing traditional organic solvents for organic synthesis and catalysis. In addition, ionic liquids are playing an increasingly important role in separation science. In this Account, the application of ionic liquids in all areas of separation science including extractions, gas chromatography, and supported liquid membrane processes are highlighted.     

Ionic liquids as electrolytes

Salts having a low melting point are liquid at room temperature, or even below, and form a new class of liquids usually called room temperature ionic liquids (RTIL). Information about RTILs can be found in the literature with such key words as: room temperature molten salt, low-temperature molten salt, ambient-temperature molten salt, liquid organic salt or simply ionic liquid. Their physicochemical properties are the same as high temperature ionic liquids, but the practical aspects of their maintenance or handling are different enough to merit a distinction. The class of ionic liquids, based on tetraalkylammonium cation and chloroaluminate anion, has been extensively studied since late 1970s of the XX century, following the works of Osteryoung. Systematic research on the application of chloroaluminate ionic liquids as solvents was performed in 1980s. However, ionic liquids based on aluminium halides are moisture sensitive. During the last decade an increasing number of new ionic liquids have been prepared and used as solvents. The general aim of this paper was to review the physical and chemical properties of RTILs from the point of view of their possible application as electrolytes in electrochemical processes and devices. The following points are discussed: melting and freezing, conductivity, viscosity, temperature dependence of conductivity, transport and transference numbers, electrochemical stability, possible application in aluminium electroplating, lithium batteries and in electrochemical capacitors.     

Ionic liquids in electrochromic devices

The ionic liquid (PYR₁₄TFSI) has proved to be the key material to make a Li-ion conducting element of a complete electrochromic device, when interposed between transparent film electrodes like WO₃ and Li-charged V₂O₅. The key features of this ionic liquid and its mixtures with LiTFSI are the excellent transparency in the visible and NIR optical regions, the good ionic conductivity and the electrochemical compatibility with inorganic Li-intercalation oxide thin film electrodes used in electrochromic devices. The higher optical contrast found during WO₃ colouration with PYR₁₄TFSI-LiTFSI, compared to that in a conventional non-aqueous electrolyte like PC-LiTFSI, was attributed to the larger inertness of the former one (no decomposition reaction at the lowest electrode potential). This highly conductive ionic liquid has been incorporated into a polymer matrix (P(EO)₁₀LiTFSI), in order to obtain a transparent solid electrolyte with high Li ion conductivity and good mechanical stability. Finally this solid PYR₁₄TFSI-P(EO)₁₀LiTFSI transparent ion conductor was interposed between the same electrodes as above in order to yield a fully solid-state, Li-ion electrochromic device. This new solid electrolyte was able to transfer reversibly a Li ionic charge between 5 mC cm⁻² and 10 mC cm⁻² from the lithium storage electrode Li_xV₂O₅ to the WO₃ electrochromic electrode in less than 100 s at room T, darkening the device from an initial 80% to a final 30% transmittance (at 650 nm). Such a device has been tested first under various constant current conditions, and later under potentiostatic control using ±2 V steps. The latter method allows not only for a faster response of the electrochromic system, but provides also an easier life stability test of the device, which withstood 2000 cycles with little changes in its optical contrast.     

Ionic liquids as active pharmaceutical ingredients

Ionic liquids (ILs) are ionic compounds that possess a melting temperature below 100 °C. Their physical and chemical properties are attractive for various applications. Several organic materials that are now classified as ionic liquids were described as far back as the mid-19th century. The search for new and different ILs has led to the progressive development and application of three generations of ILs: 1) The focus of the first generation was mainly on their unique intrinsic physical and chemical properties, such as density, viscosity, conductivity, solubility, and high thermal and chemical stability. 2) The second generation of ILs offered the potential to tune some of these physical and chemical properties, allowing the formation of "task-specific ionic liquids" which can have application as lubricants, energetic materials (in the case of selective separation and extraction processes), and as more environmentally friendly (greener) reaction solvents, among others. 3) The third and most recent generation of ILs involve active pharmaceutical ingredients (API), which are being used to produce ILs with biological activity. Herein we summarize recent developments in the area of third-generation ionic liquids that are being used as APIs, with a particular focus on efforts to overcome current hurdles encountered by APIs. We also offer some innovative solutions in new medical treatment and delivery options.     

离子液体催化烷基化反应的研究进展

烷基化反应是工业生产合成中间体的重要反应,而离子液体良好的催化活性可以解决一些合成工艺的环保问题,因而成为近年来绿色化学的研究热点。文章综述了离子液体的常规制备方法以及其在催化烷烃、芳烃和酚类等烷基化反应中的应用。文献研究表明,离子液体能显著提高烷基化反应的选择性和产率,并可反复多次回收利用。     

Ionic liquids for CO2 electrochemical reduction

Electrochemical reduction of CO₂ is a novel research field towards a CO₂-neutral global economy and combating fast accelerating and disastrous climate changes while finding new solutions to store renewable energy in value-added chemicals and fuels. Ionic liquids (ILs), as medium and catalysts (or supporting part of catalysts) have been given wide attention in the electrochemical CO₂ reduction reaction (CO₂RR) due to their unique advantages in lowering overpotential and improving the product selectivity, as well as their designable and tunable properties. In this review, we have summarized the recent progress of CO₂ electro-reduction in IL-based electrolytes to produce higher-value chemicals. We then have highlighted the unique enhancing effect of ILs on CO₂RR as templates, precursors, and surface functional moieties of electrocatalytic materials. Finally, computational chemistry tools utilized to understand how the ILs facilitate the CO₂RR or to propose the reaction mechanisms, generated intermediates and products have been discussed.     

离子液体--走向工业化的绿色溶剂

介绍了离子液体的种类、特性及其合成方法。论述了离子液体作为溶剂或催化剂的优点及其在化学反应、分离过程、电化学及其他领域中的应用,离子液体在这些领域的应用已取得许多良好的实验结果。指出离子液体在太阳电池、双电层电容器等电化学方面的应用大有前途,还可用于高离子导电聚合物、万能润滑剂的制备以及纤维素的溶解等应用领域。但是离子液体走向工业化应用尚存在成本高、黏度大、物理性质和毒性数据的缺乏等问题。     

离子液体在烷基化反应中的应用

介绍了离子液体在烷基化反应中的种类,性质,有关离子液体在烷烃与烯烃的烷基化反应,芳香烃的烷基化反应及其他的烷基化合成反应中作用及应用的研究进展。     

离子液体在萃取中的应用研究

离子液体具有特殊的物理化学性质,通过选择不同的阳离子和阴离子改变离子液体的物理化学性质,因此离子液体可以取代传统的有机分子溶剂应用于不同的分离过程.本文综述离子液体萃取金属离子、有机化合物、生物分子,脱硫,脱氮及气体分离等的最近研究进展.     

Ionic liquids enhanced performance of PVC gels actuator

Stimulated devices are highly demanded for actuators and artificial muscles in the recent era but susceptible to low deformation at an applied voltage. In the present work, ionic liquids (ILs) based gel films were prepared from the polyvinyl chloride (PVC), dibutyl adipate (DBA), 1-butyl, 3-methimidazolium chloride, and 1-pentyl-3-methylimidazolium hexafluorophosphate by a simple solvent evaporation method. The structural, morphological, optical, and mechanical properties of the composite PVC/ILs gel were characterized by Fourier-transform infrared spectroscopy (FTIR), Large Angle X-ray scattering (LAXS), UV–visible (UV–vis) absorption spectroscopy, scanning electron micrpscopy (SEM) and elemental mapping. We found that the displacement of plasticized PVC gels-based actuator was 0.1 mm with the response time of 0.33 s at an induced voltage of 1000 V. The loading of 0.02% of IL (fluorides) with PVC gel showed maximum deformation of 0.16 mm with a relatively rapid response time of 0.2 s. These high deformation and response time values of IL fluoride-based gels are dramatically higher than reported PVC gels. Likewise, the loading of IL fluorides in the PVC gel showed a high elongation value at the break of about 377%. This work suggests that the flexible gel based on IL fluorides and PVC could be a potential candidate for the fabrication of high-performance artificial muscles and tunable soft actuators.     

离子液体在萃取分离中的研究应用

阐述了离子液体在萃取分离中的应用进展。重点介绍了离子液体在萃取分离有机物、金属离子和生物分子方面的应用研究,并对离子液体与超临界CO2相结合的萃取分离方法的研究作了简单介绍。     

Ionic liquids as new solvents of natural polymers

The study conducted led to the following conclusions: — Ionic liquids based on the 1-butyl-3-methylimidazolium cation are not solvents for most synthetic polymers, but dissolve natural polymers characterized by a large number of H bonds in the supramolecular structure up to high concentrations. — The dissolving power of IL based on the 1-butyl-3-methylimidazolium cation is a function of the nature of the anion and the value of the negative charge on its electron-donor sites: IL with an acetate anion dissolve natural polymers better than liquids with a chloride anion. — An increase in the length and number of hydrophobic alkyl radicals in the imidazolium cation increases the hydrophoby of the IL and is accompanied by a decrease in the dissolving power with respect to natural polymers. The charge distribution in the imidazolium cation is a function of the length and number of alkyl radicals, determines the strength of the cation—anion bond, and the dissolving power of the IL changes proportionally to this strength. — Incorporation of proton-donor diluents decreases the dipole moment and value of the negative charge of the IL anion, which results in loss of the dissolving power of the binary mixture. — Aprotic diluents can be incorporated in these IL, and the change in the dissolving power of the binary mixture will be a function of the donor capacity of the aprotic diluent: a smaller decrease in the dissolving power is observed for the binary mixture in which the diluent has a lower donor number and more weakly competes with the IL for formation of hydrogen bonds with the polymer. Translated from Khimicheskie Volokna, No. 3, pp. 75–80, May–June, 2008.     

离子液体在金属离子萃取方面的应用

介绍了离子液体/盐双水相的成相原理,离子液体萃取金属离子的萃取机理和萃取体系;综述了离子液体在碱金属和碱土金属、过渡金属、稀土及镧系锕系等金属离子萃取方面的应用研究进展;展望了离子液体在萃取方面的发展.     

离子液体及其在有机合成中的应用

简要介绍了离子液体的组成和制备方法，归纳了离子液体的优越性质，综述了离子液体作为催化剂和绿色溶剂在催化加氢、Diels-Alder反应等有机合成反应中的应用，提出离子液体解决了催化剂的回收问题，避免了挥发性溶剂对环境的污染，实现了有机合成的绿色化。展望了离子液体在日化及其相关行业合成中的应用前景。     

Ionic liquids for coal dissolution,extraction and liquefaction

Coal is the most abundant fossil fuel. Direct combustion of low- and medium-rank coals causes alarming environmental impacts. Therefore, it is crucial for coal to undergo pretreatments before its efficient utilization [such as coal to liquid (CTL) processes]. Conventional pretreatment methods suffer from several limitations including the use of volatile organic solvents, environmental hazards, strong reaction conditions (e.g. high temperature and pressure), consumption of large quantities of nonrecoverable chemicals (e.g. bases used in aqueous alkaline digestion), or being only effective for specific coals. On the other hand, coal pretreatment by nonvolatile ionic liquids (ILs) could lead to partial coal dissolution/swelling and structure disruption, which is a critical step before coal liquefaction, hydrogenation, pyrolysis or the inhibition of oxidation/combustion. In addition, ILs are suitable solvents for extracting sulfur compounds from coal, asphaltenes from Direct Coal Liquefaction Residues (DCLR) and phenolic compounds from coal tar. This review will discuss these aspects of coal pretreatments by ILs, and identify how ILs could lead to a cleaner and more efficient utilization of coal resources. © 2020 Society of Chemical Industry     

离子液体及其应用的研究新进展(续完)

叙述了离子液体在化学反应、分离过程、功能材料、电化学、石油化工和色谱等各个方面中的应用研究进展.     

离子液体介质中绿色催化研究新进展

综述了近年来离子液体在超临界CO2、生物催化、不对称催化3个方面的应用进展,阐明离子液体具有独特的物理化学性质,在许多化工过程中能代替传统的有机溶剂,真正实现环境友好及“绿色催化”,展望了离子液体的发展方向。