Ionic industrial aspects

The aspects of medium engineering summarized so far were a hot topic in biocatalysis research during the 1980s and 1990s [5]. Nowadays, all of them constitute a well-established methodology that is successfully employed by chemists in synthetic applications, both in academia and industry. In turn, the main research interests of medium engineering have moved toward the use of ionic liquids as reaction media and the employment of additives. 

Recently a novel class of deep eutectic solvents based on choline chloride have been developed. These can be handled easily under environmental conditions and circumvent many problems that occur in aqueous solutions. They also offer the first economically viable liquids that can be used on an industrial scale. As the interest of electrochemists and classical electroplaters in ionic liquids has risen strongly in the last few years we decided, in 2006, to collect the key aspects of the electrodeposition from ionic liquids in the present book. The book has been written by a panel of expert authors during late 2006 and the first half of 2007 and thus describes the state of the art as of that point in time. 

Before going into the methods for radical reactions it most be said tlmt polycondensation or polyaddition have led to more industrial preparation. In this connection epoxy resins, the polyurethanes obtained from prepolymers and, more recently, more specialized polymers such as the PEB AC (ATOCHEM), amid-ether or polyimids (KHERIMIDE from RHONE POULENC must be mentioned). Moreover, it is interesting to note that the ionic methods (cationic or anionic ones) have not produced industrial products (except dihydroxy poly (dimethyl siloxanes), poly (tetrahydro-furanes)) but they have facilitated theoretical studies both on the analytical aspects and the materials we can obtain. 

Ionic Liquids Industrial Applications for Green Chemistry, Ed. R. D. Rogers and K. R. Seddon, ACS Symp. Ser., vol. 818, American Chemical Society, Washington D.C., 2002 Electrochemical Aspects of Ionic Liquids, ed. H. Ohno, Wiley-Interscience, Hoboken, 2005 Ionic Liquids The Front and Future of Material Development, ed. H. Ohno, CMC Press, Tokyo, 2003 H. Zhao, Chem. Eng. Comm., 2006, 193, 1660. 

The invention of new methods for catalyst recovery appear likely to further increase the attractiveness of SCCO2 as a reaction medium, potentially in partnership with a second phase such as water, ionic liquid, or PEG. Given the high price of chiral homogeneous catalysts and the particularly clean separations that can be obtained using the biphasic catalysis techniques described in Section 3.3, one can expect industrial interest in this aspect in particular. 

This chapter will walk through the various forms these catalytic resins take. The catalysts covered in this review fall into three classes, (i) transition metals covalently bonded to the polymer support through an organometallic bond, (ii) transition metals coordinated to the polymer support, typically in ionic form and (iii) transition metal clusters that are formed by precipitating metals into nanoparticles within the polymeric framework. Additionally, this chapter covers the synthetically useful and industrially practiced reactions catalyzed by transition metals loaded onto organic supports and comments on the mechanisms and reusability aspects of the processes [1]. 

While the purity of ionic liquids has already been discussed from the synthetic perspective in Section 2.2, the following section aims to highlight this aspect from the viewpoint of an industrial company aiming to apply ionic liquids in its processes and products. What exactly is purity. Most people would define purity by the actual content of the desired compound expressed in weight percent. Already, this is not an easy thing to do with ionic liquids. As salts they intrinsically consist of two compounds, a cation and an anion. For example a sample of [EMIMJCl might contain 5 wt.% of [EMIM][HS04] as impurity. This means the ionic liquid is 100 wt.% pure in terms of the cation [EMIM]+ and 95 wt.% pure in terms of the anion chloride. 

Ionic liquids are still in the research phase. Therefore, there are only a few industrial applications known (Fig. 20.3). However, there is a large field of potentially interesting applications (Table 20.3). Several pilots or industrial processes using ILs were publicly announced. There are few reviews which describe those applications in detail [1]. Most of the potential applications are as solvents or catalysts in many chemical reactions such as Diels-Alder, Friedel-Crafts reactions, and biocatalysis. Applications in other fields such as in separations, fluid applications, and analytical applications, are lower in numbers. There are now many companies who supply ionic liquids in gram scale to multi-ton scale. Some of the key suppliers are listed in Table 20.4. In this chapter, maiifly the applications in the pilot-plant and industrial phase will be discussed. Aspects of ionic liquid stability, cost, recycling, and waste disposal will be also discussed at the end of this chapter. 

The scope of applications of ionic liquids has been extended to many domains and now much broader than assumed. Following this tremendous development associated with the commercial availability of ILs, the industrial applicability of ILs rapidly appeared as an important aspect as demonstrated by the accelerating number of patents. However, despite of their significant benefits, their translation into viable industrial processes is far from being obvious and the industrialization of IL technologies is rather slow. For the industrial use of ILs, some major issues must be addressed such as purity, stability, toxicity, cost, waste disposal, and recycling which may be barriers to IL commercialization. Several pilot plants or industrial processes using ILs were publicly announced and some of them are considered in this section. 

For a successful application of ionic liquids in industrial processes, these aspects must be taken into consideration. However, the chance for a general substitution of... 

A. Christou, Reliability Aspects of Moisture and Ionic Contamination Diffusion Through Hybrid Encapsulants, in Proceedings of the Technical Program—International Microelectronics Conference (1978) p. 237, Industrial Scientific Conference Management, Inc., New York. Electric insulators and dielectrics Silicone/epoxy-polyurethane interpenetrating networks, moisture, and ion diffusion through potting compounds. 

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