Selective Hydrogenation of Polyunsaturated Hydrocarbons using SCILL-Type Catalysts

In the last decades, ionic liquids have been discovered as a powerful tool for catalyst design. One more recent discovery is that heterogeneous catalyst performance can be changed by coating with a thin ionic liquid film. In this work, this so called Solid Catalyst with Ionic Liquid Layer (SCILL) concept was applied to two industrial relevant reactions, the partial hydrogenation of aromatics and the selective hydrogenation of acetylene in ethylene rich feeds. Partial hydrogenation of aromatics is of interest for the production of valuable intermediates for the synthesis route to nylon. While the industrial process relies on strong diffusion and solubility effects in a liquid phase process to overcome unfavourable reaction kinetics, it was here tried to transfer the process to the gas phase. Within this work, a particle size study on the reaction performance was carried out, using very small ruthenium nanoparticles down to 1.1 nm synthesised using a dendrimer templated approach. This revealed a so far unreported increase in selectivity to the intermediate for decreasing particles size. The application of an ionic liquid film to create solubility and adsorption effects on the catalyst surface proved successful when using imidazolium based ionic liquids. The addition of organic compounds as modifiers improved the selectivity greatly for the case of methanol. Acetylene hydrogenation is applied in the production of polymer grade ethylene, where it has to be removed from the product stream of cracking processes. The challenge here is to avoid the hydrogenation of the ethylene, which leads to loss of valuable product and thermal runaway due to the high exothermicity of the reaction. It was shown that the performance of an industrial Pd Ag alloy catalyst can be significantly increased by ionic liquid coating. The stable operation temperature range significantly increased while at the same time the formation of catalyst deactivating oligomers was greatly supressed. By investigating the catalysts behaviour under extreme conditions it was further possible to define the stable operation parameters for the process. Simulation of an industrial scale reactor revealed a superior performance of the SCILL catalyst in all aspects. Through the broader stable temperature range, it is furthermore possible to counter higher acetylene concentrations by increased temperatures without the threat of thermal runaway, making the SCILL catalyst also more versatile and efficient.