Heterogenization of Chloroaluminate Ionic Liquids on Mesocellular Foam Silica (MCF)

摘要

Ionic liquids consist of ions and exist in liquid state at ambient temperature. In other words, the ionic liquids can have both liquid and ionic characters. Because of these characteristic properties, the ionic liquids have rendered a new class of solvents with nonmolecular, ionic character. In addition, these unique properties of ionic liquids are attractive for the development of the catalytic processes and the environmentally friendly processes. In recent years, the halogenoaluminate(Ⅲ) and the closely related alkylhalogenoaluminate(Ⅲ) ionic liquids have been by far the most widely studied. The chloroaluminate ionic liquid (CIL) has been examined as one of the halogenoaluminate ionic liquids. The GIL is well known to be not only a versatile solvent like other ionic liquids but also an effective Lewis acid catalyst. The CIL has two advantages: first, it is easy to control its Lewis acidity and second, it is easily heterogenized to solid supports. The ionic liquids, if heterogenized, yield the so-called supported liquid phase (SLP) which can be very useful in organic synthesis. For this reason, the heterogenization of ionic liquids has been actively studied by many researchers. Compared to other well-known acid catalysts, e.g., silica alumina or zeolite, the heterogenized chloroaluminate ionic liquid bears some advantages. The most notable advantage may be the easily tuneable acidity. In this regard, it is important to select a suitable support material. The mesoporous materials have unique properties such as the large surface area, the large pore size and the regular pore shape and thus they can meet the conditions required as a support for the heterogenization of ionic liquids.