How can Ionic Liquids be recycled?
Recycling of Ionic Liquids is easy, when protonated cations are used. In this case the Ionic Liquids can be switched off by deprotonation. The resulting amine or imidazole is a conventional liquid which can be distilled for recycling or purification purpose. It is more difficult with the alkylated cations. Apart from a purification or recycling by a liquid-liquid extraction two principal distillations methods haven been reported. The first is the formation of distillable carbenes [WO 01/77081] the second is the back-alkylation of the anion [WO 01/15175; DE 10002420]. Imidazolium cations can be deprotonated by bases to form neutral carbenes. These carbenes are surprisingly stable and can be distilled. The Ionic Liquid can be recycled by further reaction of the carbene with an acid. This controlled decomposition reaction even allows for a recycling or purification process of the Ionic Liquid. In this case the Ionic Liquid is thermally cleaved. The neutral imidazole and alkylating agent a
