Chemoselective hydrogenation of the C=O group in unsaturated aldehydes over clay-supported platinum catalysts

The preparation and application of a series of clay-supported platinum catalysts are described. Most of these catalysts were found to be more selective in the hydrogenation of α,β-unsaturated aldehydes than the carbon, alumina and silica supported samples. The best results were obtained with cinnamaldehyde using Pt/K-10 with almost exclusive formation of cinnamyl alcohol under mild experimental conditions. Using these new catalysts the selectivities of the unsaturated alcohol also increased in the case of citral hydrogenation. These results confirm the beneficial role of the support, which was interpreted in terms of surface acidity, pointing out the necessity of the Lewis acid sites near the platinum crystallites. These sites are responsible for the enhanced adsorption of the reactant molecules by the C=O moiety.