Ionic liquid application

The following subsections attempt to comment upon common impurities in commercial ionic liquid products and their significance for known ionic liquid applications. The aim is to help the reader to understand the significance of different impurities for their application. Since chloroaluminate ionic liquids are not produced or distributed commercially, we do not deal with them here. 

What is going to be the first area of broad, commercial ionic liquid application This is probably the question most frequently asked of everybody who is active in developing ionic liquid methodology. The answer is not easy to give. Some petrochemical processes are ready to be licensed or are in pilot plant development (as described in Section 5.2), but there is still some time needed to bring these applications on stream and to claim a broad replacement of existing technologies by ionic liquids in this area. For some non-synthetic applications, in contrast, the lead time from the first experiments to full technical realization is much shorter. 

An ionic liquid can be used as a pure solvent or as a co-solvent. An enzyme-ionic liquid system can be operated in a single phase or in multiple phases. Although most research has focused on enzymatic catalysis in ionic liquids, application to whole cell systems has also been reported (272). Besides searches for an alternative non-volatile and polar media with reduced water and orgamc solvents for biocatalysis, significant attention has been paid to the dispersion of enzymes and microorganisms in ionic liquids so that repeated use of the expensive biocatalysts can be realized. Another incentive for biocatalysis in ionic liquid media is to take advantage of the tunability of the solvent properties of the ionic liquids to achieve improved catalytic performance. Because biocatalysts are applied predominantly at lower temperatures (occasionally exceeding 100°C), thermal stability limitations of ionic liquids are typically not a concern. Instead, the solvent properties are most critical to the performance of biocatalysts. 

This study focuses firstly on the transfer of regeneration principles as they have been developed in the field of water-based electroplating and of purification options for ionic liquids as they are experienced in other fields of ionic liquid application. A number of purification procedures for fresh ionic liquids have already been tested on the laboratory scale with respect to their finishing in downstream processing. These include distillation, recrystallization, extraction, membrane filtration, batch adsorption and semi-continuous chromatography. But little is known yet about efficiency on the technical scale. Another important aspect discussed is the recovery of ionic liquids from rinse or washing water. 

Malhotra SV (2010) Ionic liquid applications pharmaceuticals, therapeutics, and biotechnology, ACS symposium series 1038. American Chemical Society, Washington, DC... 

Apart from the extensive use of ILs in catalysis and organic/inorganic synthesis [11,12] (see also Chapter 5 and Section 6.1) their advantages for materials chemistry, and especially for the synthesis of novel nanostructures, have been only gradually realized in recent years. This contribution will actualize a recent review [13] and aims to introduce this specific field of ionic liquid applications which undoubtedly promises great potential for future research and development. 

In 2002 we predicted that non-synthetic applications would have a great chance to be among the first technical ionic liquid applications. This assumption has held true as Chapter 9 clearly proves. Non-synthetic applications are particularly attractive due to their often much shorter development times. Usually, the improvement over existing technology is only based on one or very few specific properties of the ionic liquid, whereas, for most synthetic applications a complex mixture of physicochemical properties in dynamic mixtures has to be considered. This point is well illustrated by the fact that all liquid-liquid biphasic catalysis involves both a reaction and an extraction step. Hence, the ionic liquid catalyst solution has to ftilfil at the same time aU of the requirements to work as a superior reaction medium as well as its role as a suitable extraction medium. The result is a significantly more complex set of material requirements which prolongs the specific ionic liquid development and testing times. 

From this reasoning we can expect also for the years to come that non-synthetic applications will have a significant share of newly arising technical ionic liquid applications. 

At first sight, this may seem like a very simple question with a simple answer, yes. The problem is, of course, that many organic and inorganic ions are in chemical equilibrium with neutral species. Depending on the position of this equilibrium -and the latter is a function of temperature and pressure - even a pure ionic liquid may contain significant amounts of neutral molecules. Of course, this will greatly infiuence all properties of the substance. Volatility, viscosity, chemical reactivity etc. will greatly differ from the hypothetical mixture of the individual ions if free molecular species such as amines, phosphines, Bronsted-acids or acid esters form as neutral molecules in an equilibrium reaction under the conditions of the ionic liquid application. 

Kadokawa, J. Preparation of polysaccharide-based materials compatibilized with ionic liquids. In Ionic liquids, application and perspectives Kokorin, A., Ed. InTech Rijeka, 2011, pp 95-114. 

In gas chromatography, a column is coated with a thin layer of a hquid stationary phase and a sample is separated by the relative abilities of its components to dissolve in it from the gas phase. The greater the interactions with the stationary phase, the slower the transit of the sample through the column. Combination of Abraham s solvation parameter model (Eq. (2.1)) [104] with GC measurements has been used to determine the nature of ionic liquid-solute interactions [105-107]. Given the experimental setup, this technique is likely to be particularly appropriate for understanding what ionic liquid-solute interactions could be important in SILP and other related surface-supported ionic liquid applications. 

E. (2002) Ionic liquids applications in catalysis. Catal. Today, 74, 157-189. 

Ionic Liquid Applications in Pilot Plants and Industry... 

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