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Ag0 and Co0 nanocolloids as recyclable quasihomogeneous metal catalysts for the hydrogenation of α,β-unsaturated aldehydes to allylic alcohol fragrances

Paper ID Volume ID Publish Year Pages File Format Full-Text
43594 45978 2007 10 PDF Available
Title
Ag0 and Co0 nanocolloids as recyclable quasihomogeneous metal catalysts for the hydrogenation of α,β-unsaturated aldehydes to allylic alcohol fragrances
Abstract

The hydrogenation of the α,β-unsaturated aldehydes cinnamaldehyde (trans-3-phenyl-2-propenal), citral (3,7-dimethyl-2,6-octadienal) and leaf aldehyde (trans-2-hexenal) was investigated with metal colloids as quasihomogeneous catalysts in organic solvents. Using polyvinylpyrrolidone-stabilized Ag0 and Co0 nanoclusters, the carbonyl compounds were chemoselectively hydrogenated to the desired allylic alcohol fragrances. Particularly the Ag0 nanosols emerged as a worthwhile alternative for Pt or Ru based catalysts. Amides proved to be excellent solvents for the synthesis as well as for the application of the metal nanocolloids in the hydrogenation of α,β-unsaturated aldehydes. In the challenging hydrogenation of citral, a selectivity exceeding 70% towards the doubly unsaturated alcohol isomers (geraniol and nerol) was attained at 90% conversion using Ag0 nanocolloids dispersed in N,N-dimethylacetamide. Reactions were performed under mild conditions (2.0 MPa H2, 323 K) at a molar citral/silver ratio of 200/1. The addition of Lewis acid cations, such as Fe3+ or Zn2+ resulted in a further improvement of the catalytic activity and chemoselectivity. Finally, by application of membrane filtrations, an efficient separation of the metallic nanocolloids from the reaction mixtures was realized. In the recycling of the metal nanosols, the metal catalysts’ nanodispersion and performance were satisfactorily preserved.

Graphical abstractPolyvinylpyrrolidone-stabilized Ag0 and Co0 nanoclusters are successful quasihomogeneous catalysts for the chemoselective hydrogenation of α,β-unsaturated aldehydes to allylic alcohols. Particularly the Ag0 nanosols emerged as a worthwhile alternative for Pt and Ru based catalysts. Amides proved to be superior to the conventional alcohol solvents and emerged as excellent solvents for the synthesis and application of the colloidal metal catalysts. Finally, recycling of the colloidal catalysts by solvent-resistent nanofiltration (SRNF) with custom-made polyimide membranes proved practicable and a satisfactory preservation of the catalysts’ nanodispersion and performance was observed. Figure optionsDownload full-size imageDownload as PowerPoint slide

Keywords
Selective hydrogenation; Unsaturated aldehyde; Allylic alcohol; Quasihomogeneous catalyst; Colloidal catalyst; Silver; Cobalt; Cinnamaldehyde; Citral; Leaf aldehyde; Membrane; SRNF
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Ag0 and Co0 nanocolloids as recyclable quasihomogeneous metal catalysts for the hydrogenation of α,β-unsaturated aldehydes to allylic alcohol fragrances
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 325, Issue 1, 30 May 2007, Pages 130–139
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us