Abstract
In recent years, various novel and greener methodologies have been developed using ionic liquids (ILs). In these reactions, IL has played multiple roles like catalyst, solvent, and catalyst support. In some cases, it was observed that IL enables efficient catalytic reactions in comparison with conventional molecular solvents. On the other hand, although a number of catalytic reaction processes in which ILs are used have been established in industry, there were also some unexpected problems, such as unintelligible aberrance or degradation of so-called task-specific ILs occurring in reaction processes and on the pilot plant scale. Also, several urgent questions regarding the fundamental aspects of ILs particularly toxicity and greener preparation methods need to be clarified. Several industrial applications of ILs are also discussed.