Paramagnetic ionic liquids as “liquid fixed-bed” catalysts in flow application

The structural diversity of Ionic Liquids is well-known and widely used to generate solvents designed for special applications. Magnetic as well as catalytic properties have been described previously. To our best knowledge we report the first time about the combination of both, the magnetic and catalytic behaviour of imidazole based magnetic ionic liquids was used to establish a so-called liquid fixed-bed (LFB) in a micro-/meso-structured reactor. As proof of priciple the esterification of Ac2O with cyclohexanol was investigated by bubbling generated regular microdroplets of the reaction mixture through the magnetically fixed ionic liquid catalyst. With residence times of approx. 1.4 s a yield of 78.5% of the target ester molecule was achieved.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Paramagnetic ionic liquid [BMIM]Fe2Cl7 used as fixed liquid catalyst in micro-structured reactors for esterification reaction. ► Catalysts is fixed by external magnetic forces of NdFeB magnets. ► The magnetically fixed liquid forms a new type of a liquid fixed-bed (LFB) catalyst. ► The esterification of cyclohexanol with acetic acid gives 78.5% (GC) yield of the respective ester within 1.3 s. ► LFBs with additional functional groups or ligands opens-up new and unusual processing in continuous micro flow applications.