Hydrogenation of Cinnamaldehyde and Citral over Ru Supported Catalysts

Citral and cinnamaldehyde have been hydrogenated over a series of Ru catalysts supported on carbon and alumina. In the hydrogenation of citral selectivity to unsaturated alcohols remains constant regardless of the Ru particle size. In the hydrogenation of cinnamaldehyde, cinnamyl alcohol is instead preferentially formed on the larger Ru particles. Addition of tin to ruthenium decreases the catalytic activity but increases (up to 90%) the selectivity to unsaturated alcohols. It is suggested that the preferential hydrogenation of the C=O group occurs on sites associated with tin ions. The influence of the nature of the support and salt precursors is also discussed.