Ionic liquids future research

The potential improvements that ionic liquids may impart to conducting polymers have been widely discussed - increased doping levels, smoother films, increased conductivity, decreased over-oxidation and improved electrochemical stability and so on. However, the research to date in this area has only just begun to investigate these hypotheses and demonstrate any material advantages in the use of ionic liquids future directions in this area must focus on some of these issues in addition to simply demonstrating the use of new ionic liquids for conducting polymer synthesis. 

Research in ionic liquid methodology is still young and there is still a lot to explore. Prevention of fundamental research on some new families of ionic liquids by exploitation of an IP position would simply kill off a lot of future possibilities. 

Obviously, with the development of the first catalytic reactions in ionic liquids, the general research focus turned away from basic studies of metal complexes dissolved in ionic liquids. Today there is a clear lack of fundamental understanding of many catalytic processes in ionic liquids on a molecular level. Much more fundamental work is undoubtedly needed and should be encouraged in order to speed up the future development of transition metal catalysis in ionic liquids. 

In the author s group, much lower-melting benzenesulfonate, tosylate, or octyl-sulfate ionic liquids have recently been obtained in combination with imidazolium ions. These systems have been successfully applied as catalyst media for the biphasic, Rh-catalyzed hydroformylation of 1-octene [14]. The catalyst activities obtained with these systems were in all cases equal to or even higher than those found with the commonly used [BMIM][PF6]. Taking into account the much lower costs of the ionic medium, the better hydrolysis stability, and the wider disposal options relating to, for example, an octylsulfate ionic liquid in comparison to [BMIM][PF6], there is no real reason to center future hydroformylation research around hexafluorophosphate ionic liquids. 

In this book we have decided to concentrate on purely synthetic applications of ionic liquids, just to keep the amount of material to a manageable level. FFowever, we think that synthetic and non-synthetic applications (and the people doing research in these areas) should not be treated separately for a number of reasons. Each area can profit from developments made in the other field, especially concerning the availability of physicochemical data and practical experience of development of technical processes using ionic liquids. In fact, in all production-scale chemical reactions some typically non-synthetic aspects (such as the heat capacity of the ionic liquid or product extraction from the ionic catalyst layer) have to be considered anyway. The most important reason for close collaboration by synthetic and non-synthetic scientists in the field of ionic liquid research is, however, the fact that in both areas an increase in the understanding of the ionic liquid material is the key factor for successful future development. 

We are far here from aiming to advise anybody about future research projects. The only message that we would like to communicate is that a chemical reaction is not necessarily surprising or important because it somehow works as well in an ionic liquid. One should look for those applications in which the specific properties of the ionic liquids may allow one to achieve something special that has not been possible in traditional solvents. If the reaction can be performed better (whatever you may mean by that) in another solvent, then use that solvent. In order to be able to make that judgement, it is imperative that we all include comparisons with molecular solvents in our studies, and not only those that we loiow are bad, but those that are the best alternatives. 

Taking into account the much lower costs of the ionic medium, the better stability against hydrolysis and the wider disposal options related to, for example, an octylsulfate or a tosylate ionic liquid in comparison to BMIM PF6], there is no real reason to centre future hydroformylation research around hexafluorophosphate ionic liquids. 

The ionic liquid investment could be further reduced if future research enables the application of ammonium based alkylsulfate or arylsulfonate ionic liquids. For these systems bulk prices around 15 /kg are expected. Ammonium based alkylsulfate or arylsulfonate ionic liquids usually show melting points slightly above room temperature but clearly below the operating temperature of the hydroformylation reaction. Therefore these systems may be less suitable for the liquid-liquid biphasic process in which the ionic liquid may be involved in process steps at ambient temperature (e.g. phase separation or liquid storage). In contrast, for the SILP catalyst a room temperature ionic liquid is not necessarily required as long as the film becomes a liquid under the reaction conditions. Assuming an ammonium based SILP catalyst, the capital investment for the ionic liquid for the industrial SILP catalyst would add up to 105,000 . 

Of course, there is still a large amount of research to be done to develop further the very preliminary character of the above described economic evaluation of an ionic liquid hydroformylation process. Only on the basis of more detailed data it will be possible to decide whether we will see an industrial hydroformylation plant using ionic liquids in the future. 

Thermomorphic solvent systems are at a relatively yoimg stage of development. Compared to ionic liquids or supercritical CO2 there is much less experience available. Large-scale applications are unknown at present. There are a lot of options for the future but these will depend on further research in the area. 

An Oven/iew of a Rapidly Expanding Area in Chemistry Exploring the future in chemical analysis research, Ionic Liquids in Chemical Analysis focuses on materials that promise entirely new ways to perform solution chemistry. It provides a broad overview of the applications of ionic liquids in various areas of analytical chemistry, including separation science, spectroscopy, mass spectrometry, and sensors. 

The reactions that have been observed so far in ionic liquids represent the tip of the iceberg. In the future, research will involve efforts to optimize such phenomena as the relative solubilities of the reactants and products, the reaction kinetics, the liquid range of the solvent, the cost of the solvent, the intrinsic catalytic behavior of the... 

Obviously, it can not be the aim of this contribution to repeat or summarise the above mentioned reviews again. In contrast, a few selected recent developments in different areas of ionic liquid research should be highlighted which are believed to be of some general relevance for the future development of ionic liquids and their application in synthetic chemistry. 

While impressive progress has been made in the development of stable, non-volatile electrolyte formulations, the conversion yields obtained with these systems are presently in the 7-10% range, i.e., below the 11.1% reached with volatile solvents. Future research efforts will be dedicated to bridge the performance gap between these systems. The focus will be on hole conductors and solvent-free electrolytes such as ionic liquids. The latter are a particularly attractive choice for the first commercial modules, due to their high stability, negligible vapor pressure and excellent compatibility with the environment. 

In addition to this, related areas such as liquid CO2 and C02-expanded solvents should not be overlooked. Many additives and complex modifiers are being used to facilitate reactions in SCCO2 and perhaps the use of a small amount of organic solvent (perhaps from a bio-feedstock) could be justified in order to reduce the cost of a process and therefore lead to its uptake by industry. In addition to this, continued research into biphasic systems C02-water, C02-ionic liquids, CO2-PEG/surfactants and CC -solids (including heterogeneous catalysts) is needed to deliver pure products and reduced cost to future end-users of this technology. 

The intercalation of ionic liquids containing paramagnetic anions into materials with layer (e.g., graphite) or porous (e.g., zeolite) structures and research concerning transport properties under the magnetic field are both promising areas for future exploration. 

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