A research group at DTU Chemistry shows, that zeolite recrystallization allows synthesis of extremely efficient gold nanoparticle catalysts
This latest research from DTU Chemistry could revive one of the oldest processes in the chemical industry, namely production of acetaldehyde from ethanol. This principle has the potential to apply to a range of new catalysts.
A group of researchers at DTU Chemistry and at the Max-Planck-Institute für Kohlenforschung has managed to oxidize ethanol effectively and selectively into acetaldehyde by use of a novel type of zeolite catalyst with encapsulated gold nanoparticles.
“This is likely to be a favourable, green alternative to the so-called Wacker process, which dominates the world’s current production of acetaldehyde. And hopefully this is just the beginning. This type of catalyst will in principle apply to a range of other reactions,” says Associate Professor Søren Kegnæs from DTU Chemistry. DTU has patented the new type of catalysts, and Søren Kegnæs and his group hope that industry will be interested in cooperation on this.
Gold nanoparticles
While most other attempts to encapsulate metal nanoparticles in zeolites have relied on expensive additives and complex procedures, this new approach is both simple and effective. Crystals of the zeolite silicalite-1 are modified by recrystallization, which creates intra-particle voids and mesopores. The recrystallization is performed in the present base and a surfactant, which protects the outer surface of the crystals. Since the zeolite crystals are porous, the base will penetrate into the crystals and begin to dissolve them from within. The trick is to stop the process at the right time when the inner voids have the optimal size. The voids will then be filled with a precursor solution containing a metal salt. The confined space provides ideal conditions for preparation of small and disperses gold nanoparticles inside the zeolite crystals.
A clever way to use bio-ethanol
To prove their creation of efficient catalysts, the researchers chose to catalyze the oxidation of ethanol into acetaldehyde.
“We chose the ethanol process because bio-ethanol receives large attention these years since it is a renewable resource,” Associate Professor Søren Kegnæs explains.
“If you want to use ethanol as the fuel you need to get rid of the water content, which will cost you a rather high amount of energy. It would thus be interesting to find alternative use of the bio-ethanol in which a high content of water is not a problem. This is the case for the production of acetaldehyde,” notes Søren Kegnæs. “Also, this revival of ethanol as a source for the production of acetaldehyde has some benefits in comparison with the use of ethylene, since ethylene is produced from crude oil which is a non-renewable resource.” The results are published in Angewandte Chemie, Oxidation of Bioethanol using Zeolite-Encapsulated Gold Nanoparticles.
International cooperation
Associate Professor Søren Kegnæs emphasizes the cooperation on this project between DTU Chemistry and the Max-Planck-Institute which was made possible by a grant from the Danish Council for Independent Research (FTP).
“The cooperation takes place in a very open atmosphere, with a high degree of sharing ideas and having students visit for shorter or longer periods of time.”
Søren Kegnæs
Associate Professor
DTU Chemistry, Center for Catalysis and Sustainable Chemistry
Tel: +45 4525 2402
skk@kemi.dtu.dk
