Coating of heterogenous catalysts

In heterogeneous catalysis the activity stems mainly from defects (e.g. corner atoms, site atoms, ad atoms) within the crystal structure of the catalyst. The controlled synthesis of these materials is still a black art in many cases. Furthermore, these highly active sites are very susceptible toward poisoning (sulfur, CO, oxygenates, etc.), thus requiring elaborate and expensive pre purification processes.
The SILP concept can be extended to the modification of existing heterogeneous catalysts by coating these non uniform surfaces with an ionic liquid film that acts as a diffusion barrier for poisons or competing substrates as depicted in the following scheme.

Schematic representation of extension of the SILP concept to coated heterogeneous catalysts

The use of these coated catalysts in hydrogenation reactions has been reported recently. Raney Nickel catalysts could be stored in air after coating with ionic liquids, a fact that might improve the handling of these catalysts. Beneficial effects of ionic liquid coating of Nickel catalysts have been observed in the hydrogenation of cyclooctadiene at the CVT, Universität Bayreuth.