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Title: Au-0 nanocolloids as recyclable quasihomogeneous metal catalysts in the chemoselective hydrogenation of alpha,beta-unsaturated aldehydes and ketones to allylic alcohols
Authors: Mertens, Pascal ×
Poelman, H
Ye, Xingpu
Vankelecom, Ivo
Jacobs, Pierre
De Vos, Dirk #
Issue Date: Apr-2007
Publisher: Elsevier Science Publishers
Series Title: Catalysis Today vol:122 issue:3-4 pages:352-360
Abstract: In the catalytic hydrogenation of a,(3-unsaturated aldehydes and ketones, highly selective allylic alcohol formation can be achieved by application of Au-0 nanocolloids dispersed in amide solvents. The polyvinylpyrrolidone protected Au-0 nanoparticles prefer C=O reduction over C=C saturation and act as chemoselective quasi homogeneous metal catalysts in the hydrogenation of trans-2-butenal (crotonaldehyde), 2-methyl-2-propenal (methacrolein), 4-methyl-3-penten-2-one (mesityl oxide) and 3-methyl-3-penten-2-one. An extensive solvent screening revealed the superiority of amides as media for both synthesis and application of the Au-0 nanocolloids. In comparison with the widely used alcohol solvents, amides offer enhanced colloidal stability for the Au-0 nanosol and increased hydrogenation chemoselectivity. Control over the Au cluster formation provided the opportunity to investigate the size-dependency of the catalytic performance and to determine the optimum gold cluster size for a maximization of the allylic alcohol yields. The most successful Auo clusters, with a typical diameter of 7 nm and synthesized in N,Ndimethylformamide, lead to a crotyl alcohol selectivity of 73% at 93% crotonaldehyde conversion and a 58% allylic alcohol yield in the hydrogenation of mesityl oxide at a molar substrate/Au catalyst ratio of 200. Analogous Pt-0 and Ru-0 sols are more active than the Auo nanosols, but substantially less chemoselective for allylic alcohols. The Auo nanocolloids can be recycled efficiently by ultrafiltration over custom-made, crosslinked polyimide membranes. In the recycling experiments the gold nanodispersion was well retained by the solvent-resistant ultrafiltration membranes and the performance of the colloidal gold catalyst was satisfactorily preserved in successive hydrogenation runs. (C) 2007 Elsevier B.V. All rights reserved.
URI: 
ISSN: 0920-5861
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Centre for Surface Chemistry and Catalysis
Department of Materials Engineering - miscellaneous
× corresponding author
# (joint) last author

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