Industrial Aspects of Ionic Liquids

A growing number of scientists and engineers are attracted by the fascinating properties of ionic liquids (ILs) as they have begun the transition from curiosities 

The introduction oftetrafluoroborate [2] and hexafluorophosphate [3], based ionic liquids, and especially the development of their synthesis by means of metathesis from alkali salts [4], can be regarded as key steps toward commercial IL production. 

This commercial availability of ionic liquids has become an important factor for the success of ILs methodology, as can be seen in the rising number of publications on ionic liquids (about 60 in 1998 to more than 1400 in 2003). Besides Solvent Innovation [5], the first commercial supplier, a number of others now offer ILs as well, the majority based on imidazolium cations. 

During 2003 we saw the first published process based on ILs [6], In its BASIL process (see Section 5.3.2), BASF has disclosed the involvement of an imidazolium-based ionic-liquid in the production of alkoxyphenylphosphines. This constitutes an impressive demonstration that IL technology can result in significant financial savings. Another process said to be poised for licensing is the French Petroleum Institute s butene dimerization process, the Difasol process (see Section 5.3.1). Besides these, some more promising applications are currently under investigation, and are hoped to be disclosed in the near future. Notable examples of research areas are in electrochemistry (batteries), biocatalysis, and the application of ILs in extraction processes, e.g., the deep desulfurization of diesel oil. 

Before the scale-up of IL synthesis is attempted, a number of different criteria have to be considered. Quality of starting materials and products alike is a key factor. Furthermore, commercial availability and price of the starting materials have to be taken into account too. For the scale itself, aspects as the heat management (alkylation reactions are exothermic) and proper mass transport are crucial. 

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