Handbook of Solvents - George Wypych - ChemTech - Ventech!

21.2 Ionic liquids 1459
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21.2 IONIC LIQUIDS
D.W. Rooney, K.R. Seddon
School of Chemistry, The Queen’s University of Belfast
Belfast, Northern Ireland
21.2.1 INTRODUCTION
The first question one would ask is “What is an ionic liquid?” Ionic liquids can be described,
in the crudest terms, as room temperature molten salts. The term “ionic liquid” could therefore
be applied to all molten salt systems such as cryolite (Na3AlF6) used in aluminum production
or even molten table salt (NaCl). However the use of the word “molten” conjures up
images of high temperature processes which are highly corrosive and difficult to design. In
contrast to this, the ionic liquids discussed here are generally benign solvents which can be
applied to a significant number of industrial processes leading to enhanced yields, greater
recyclability and processes with an overall reduced environmental impact. Therefore an
ionic liquid is normally described as a molten salts which is fluid at room temperature, or
close to room temperature (salts melting below 100 o C are often considered in this category).
One only has to look at recent patent publications to discover that these solvents are finding