Templated synthesis, evaluation and immobilization of metal nanoparticles for catalysis
Final Report Abstract
The aim of the project was to develop well-defined nanoparticles based on Ruthenium and investigate their catalytic performance. The synthetic methods and skills developed during the course of this project helped significantly to implement this technique in the groups of Reinout Meijboom and Marco Haumann. Based on the expertise gained, the Meijboom group was able to synthesize various other metal nanoparticles based on e.g. Au, Pd and Pt. Thus, a library of well-defined MNPs is available by now that can be utilized for reactions of interest, including oxidation reactions that are marked as an important future research area in Germany. In the test reactions 4-nitrophenol reduction and toluene hydrogenation the Ru-MNP proved to be stable when supported on the right carrier material. The well-defined size distribution of the as prepared MNPs was beneficial alone in achieving a threefold higher yield in hydrogenation compared to commercial catalysts with twice the activity. Such selectivity and activity enhancement can be exploited for other reactions in future projects. The coating of these MNPs with ionic liquids helped to improve the selectivity further, however, at the cost of activity. The influence of the ionic liquid cannot be related to modification of the local concentration at the catalyst surface alone. A more detailed understanding of such multiple parameters seems necessary. The combinations of templated nanoparticle synthesis and ionic liquid coating can result in additive improvement of the yield. While the commercial catalyst only yielded 0.1 % partially hydrogenated intermediate, the dendrimer derived G6-RuSil60 catalyst improved that yield by a factor of 15. Additional coating with [BMIM][NTf2] more than doubled the yield to 4.1 %. An interesting result was the drastic yield improvement upon methanol co-feeding in the gasphase. For the standard Ru/Al2O3 catalyst the yield increased by 250 % while for the SCILL catalyst this increase was still approx. 120 %. The exact reason is not clear as of yet but should be investigated in further studies. The reported yield of 7.5 % is the highest yield reported so far for continuous gas-phase hydrogenation of toluene. The methanol addition using dendrimer derived Ru-MNPs did not improve the yield further. The Fischer-Tropsch reaction was accelerated dramatically be the use of G6 derived MNPs, the exact reasons not clear at the moment. During the course of the project, additional coating with ionic liquids was not investigated in further detail.
Publications
- Preparation of Well-Defined Dendrimer Encapsulated Ruthenium Nanoparticles and Their Evaluation in the Reduction of 4 ‑ Nitrophenol According to the Langmuir − Hinshelwood Approach. Langmuir, 2013, 29, 13433 – 13442
N.C. Antonels, R. Meijboom
- Preparation of well-defined dendrimer encapsulated ruthenium nanoparticles and their application as catalyst and enhancement of activity when utilised as SCILL catalysts in the hydrogenation of citral. Catal. Commun. 2014, 57, 148 – 152
N.C. Antonels, R. Meijboom
(See online at https://doi.org/10.1016/j.catcom.2014.08.012)
