Templated synthesis, evaluation and immobilization of metal nanoparticles for catalysis

• Applicant: Professor Dr. Marco Haumann
• Subject Area: Technical Chemistry
• Term: from 2010 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 157334871

Many important homogeneous catalysts are used in industry in biphasic systems or by fixation on supports, the bridge between these two approaches is now being built through the use of nanoparticles (NPs; sometimes called giant clusters, nanoclusters, or colloids) whose activity is very high under mild conditions because of their very large surface area. This frontier domain is sometimes called "semiheterogeneous". Contrary to classic heterogeneous catalysts, these NPs are synthesized by the bottom-up approach from molecular precursors including a metal salt, a molecular stabilizer, and a reducing agent. Recent work has highlighted the importance of the nanoparticle approach to heterogeneous catalysis. By synthesizing a variety of sizes of nanoparticles the influence of size on activity and selectivity can be investigated. However up to now the synthesis of well-defined metal nanoparticles is - despite reporting of the contrary - still an elusive and novel field. One of the most successful ways of synthesizing well-defined, mono-disperse metallic nanoparticles is the templated synthesis of these particles. In order to pre-define and pre-determine the structure more cleariy, a monomolecular, mono-disperse (polymeric) template would be necessary. From the above follows that dendritic macromolecules would be ideal templates for the synthesis of extremely well-defined metal nanoparticles. Ionic liquids offer unique properties, which make them highly attractive in various fields of applications. Their ionic nature facilitates the stabilization of metal nanoparticles and can help to prevent sintering of these small particles during catalytic reactions. It is known that the catalytic activity is strongly depending on the size of the nanoparticle applied. In this approach the synthesis of nanoparticles with a defined and very narrow size distribution should be achieved by using dendritic structures as templates or nanoreactors for the particle formation. The thus prepared nanoparticles will be tested in ionic liquid systems with respect to their catalytic performance. Initial evaluation of a homogeneous system (i.e. nanoparticles in an ionic liquid) would give preliminary results on the size-activity relationships of these particles. Subsequent immobilization of the ionic liquid phase on a support would result in a heterogeneous system which will additionally be evaluated for activity and long term stability. The main focus of research would be on two reactions, namely the hydrogenation of simple aromatic molecules (e.g. toluene) and the Fischer-Tropsch reaction. In both reactions, the combination of defined nanoparticles and ionic liquids should lead to highly active and more selective catalysts.

• DFG Programme: Research Grants
• International Connection: South Africa
• Participating Person: Professor Dr. Reinout Meijboom