Ionic liquids in catalysis

Room temperature ionic liquids and their mixtures—a review

Ionic liquids (ILs), considered to be a relatively recent magical chemical due their unique properties, have a large variety of applications in all areas of the chemical industries. The areas of application include electrolyte in batteries, lubricants, plasticizers, solvents and catalysis in synthesis, matrices for mass spectroscopy, solvents to manufacture nano-materials, extraction, gas absorption agents, etc. Non-volatility and non-flammability are their common characteristics giving them an advantageous edge in various applications. This common advantage, when considered with the possibility of tuning the chemical and physical properties of ILs by changing anion–cation combination is a great opportunity to obtain task-specific ILs for a multitude of specific applications. There are numerous studies in the related literature concerning the unique properties, preparation methods, and different applications of ILs in the literature. In this review, a general description of ILs and historical background are given; basic properties of ILs such as solvent properties, polarity, toxicology, air and moisture stability are discussed; structure of ILs, cation, anion types and synthesis methods in the related literature are briefly summarized. However, the main focus of this paper is how ILs may be used in the chemicals processing industries. Thus, the main application areas are searched and the basic applications such as solvent replacement, purification of gases, homogenous and heterogeneous catalysis, biological reactions media and removal of metal ions are discussed in detail. Not only the advantages of ILs but also the essential challenges and potentials for using ILs in the chemical industries are also addressed. ILs have become the partner of scCO 2 in many applications and most of the reported studies in the literature focus on the interaction of these two green solvents, i.e. ILs and scCO 2 . The chemistry of the ILs has been reviewed in numerous papers earlier. Therefore, the major purpose of this review paper is to provide an overview for the specific chemical and physical properties of ILs and to investigate IL–scCO 2 systems in some detail. Recovery of solutes from ILs with CO 2 , separation of ILs from organic solvents by CO 2 , high-pressure phase behavior of IL–scCO 2 systems, solubility of ILs in CO 2 phase, and the interaction of the IL–scCO 2 system at molecular level are also included.

A review of ionic liquids towards supercritical fluid applications

Chromatographic and spectroscopic methods for the determination of solvent properties of room temperature ionic liquids

Ionic liquids (ILs) are ambient temperature molten salts and have attracted considerable attention because of their unique properties such as nonflammability, negligible volatility, high ionic conductivity, and thermal stability. Here, we show that the combinations of macromolecules with ILs as solvents and additives could offer new progress, challenges, and opportunities in polymer materials science. Compatible binary systems, where ILs are solidified (gelled) by polymers, can be used as ion-conducting polymer electrolytes (ion gels). The ion transport in ion gels is found to be decoupled from the segmental motion of the polymers, leading to relatively high ionic conductivities even at their glass transition temperatures. The flexibility of the molecular design of ILs allows us to prepare many new ILs having electrochemical functionalities such as proton, electron, and lithium ion transport. The new ILs and their ion gels appear to be promising candidates as new materials for electrochemical applications...

Macromolecules in Ionic Liquids: Progress, Challenges, and Opportunities

Room-temperature ionic liquids are salts that are liquid at room temperature. Their use as catalysts and catalytic support has been studied extensively. However, there are very few measurements on their solubility and phase equilibria in common organic solvents. In this work, the liquid−liquid phase equilibria of mixtures of room-temperature ionic liquids, 1-alkyl-3-methylimidazolium hexafluorophosphate, [Rnmim][PF6] (1) where Rn = butyl, pentyl, hexyl, heptyl, and octyl, with butan-1-ol (2) over a composition range have been measured. The binodal coexistence curves of the mixtures were found to have an upper critical solution temperature (USCT) at x2 ≈ 0.9. The UCST decreases with increase in the length of the alkyl chain of the ionic liquid, with the UCST of the butyl at 373 K and that of the octyl at 326 K. Both the UCST and the composition at the UCST as a function of the 1-alkyl group chain length can be reasonably well predicted from theory on the basis of unimolecular quantum chemical calculations.

and Alexander V. Deev

Papers

Liquid−Liquid Equilibria of Room-Temperature Ionic Liquids and Butan-1-ol†