Frederick Schwab

Ruthenium‐Catalyzed Selective Hydrogenation of Benzene to Cyclohexene in the Presence of an Ionic Liquid

The hydrogenation of benzene in organic phase leads rapidly to cyclohexane. A very simple catalyst system comprising only supported ruthenium in water with the addition of the ionic liquid 1 (R=Me) in the ppm range catalyzes the extremely difficult selective hydrogenation of benzene to cyclohexene. It is not necessary to add large amounts of salt (ZnSO₄) or other metals, which is otherwise done to control selectivity.

Simple selective hydrogenation of benzene to cyclohexene in the presence of sodium dicyanamide

A new catalyst system was used in the liquid phase hydrogenation of benzene to cyclohexene containing only an aqueous solution of Ru/La2O3 and a very small quantity of sodium dicyanamide (NaDCA). This additive considerably improves the catalyst performance compared to DCA based ionic liquids. The effects of the amount of NaDCA and metal loading of the catalyst were investigated and a high initial selectivity to cyclohexene of 70% was reached.

CHAPTER 6:Modification of Supports and Heterogeneous Catalysts by Ionic Liquids: SILP and SCILL Systems

The modification of catalysts with ionic liquids represents a development that combines both homogeneous and heterogeneous catalysis. This achievement is especially described by three different concepts: SILP, SCILL and nanoparticles in IL. SILP refers to the case where a metal complex is dissolved in an ionic liquid which is immobilised on an inert support material. SCILL includes the catalyst systems consisting of a heterogeneous catalyst which is coated by a thin layer of an ionic liquid, while metal nanoparticles in IL covers the cases where unsupported catalysts are highly dispersed in IL media. The most important step to a successful utilisation of these concepts is the determination of a suitable ionic liquid. Therefore, understanding the role of IL in each specific case is very important. Characteristic properties like solubility of reactants and gases, immiscibility with polar or non-polar solvents, coordinating or non-coordinating character can be adjusted by the choice of cation and anion.