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Highly selective menthol synthesis by one-pot transformation of citronellal using Ru/H-BEA catalysts

Plößer, Jutta and Lucas, Martin and Claus, Peter (2014):
Highly selective menthol synthesis by one-pot transformation of citronellal using Ru/H-BEA catalysts.
In: Journal of Catalysis, pp. 189-197, 320, ISSN 00219517, [Online-Edition: http://dx.doi.org/10.1016/j.jcat.2014.10.007],
[Article]

Abstract

The one-pot transformation of citronellal to menthol requires a combined cyclization–hydrogenation step for which Ru/H-BEA catalysts were identified as highly active and selective catalysts. After identifying zeolite H-BEA as the most promising heterogeneous catalyst for the cyclization of citronellal to the intermediate isopulegol, bifunctional metal/H-BEA catalysts were investigated in the one-pot transformation of citronellal to menthols. Using Pd undesired defunctionalization prevailed, while using Pt and Ru, the formation of menthols predominated. Finally, for Ru/H-BEA catalysts, the effect of catalyst composition (Si:Al ratio, Ru content) and reaction conditions (temperature, hydrogen pressure, and solvent) was investigated to diminish citronellal hydrogenation, dimerization, and defunctionalization. Accordingly, with a 1%Ru/H-BEA-25 catalyst (Ru particle size = 1 nm) in dioxane at 15 bar hydrogen pressure and 373 K, a very high selectivity to menthols of 93% at nearly full conversion was obtained. The catalyst is also highly diastereoselective producing 79% of the desired (±)-menthol.

Item Type: Article
Erschienen: 2014
Creators: Plößer, Jutta and Lucas, Martin and Claus, Peter
Title: Highly selective menthol synthesis by one-pot transformation of citronellal using Ru/H-BEA catalysts
Language: English
Abstract:

The one-pot transformation of citronellal to menthol requires a combined cyclization–hydrogenation step for which Ru/H-BEA catalysts were identified as highly active and selective catalysts. After identifying zeolite H-BEA as the most promising heterogeneous catalyst for the cyclization of citronellal to the intermediate isopulegol, bifunctional metal/H-BEA catalysts were investigated in the one-pot transformation of citronellal to menthols. Using Pd undesired defunctionalization prevailed, while using Pt and Ru, the formation of menthols predominated. Finally, for Ru/H-BEA catalysts, the effect of catalyst composition (Si:Al ratio, Ru content) and reaction conditions (temperature, hydrogen pressure, and solvent) was investigated to diminish citronellal hydrogenation, dimerization, and defunctionalization. Accordingly, with a 1%Ru/H-BEA-25 catalyst (Ru particle size = 1 nm) in dioxane at 15 bar hydrogen pressure and 373 K, a very high selectivity to menthols of 93% at nearly full conversion was obtained. The catalyst is also highly diastereoselective producing 79% of the desired (±)-menthol.

Journal or Publication Title: Journal of Catalysis
Volume: 320
Divisions: 07 Department of Chemistry
07 Department of Chemistry > Fachgebiet Technische Chemie
07 Department of Chemistry > Fachgebiet Technische Chemie > Technische Chemie II
Date Deposited: 29 Jan 2015 16:22
Official URL: http://dx.doi.org/10.1016/j.jcat.2014.10.007
Identification Number: doi:10.1016/j.jcat.2014.10.007
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