Aqueous‐Phase Hydrogenation of Saturated and Unsaturated Ketones and Aldehydes over Supported Platinum–Rhenium Catalysts

The hydrogenation rates of C=C and C=O bonds in methyl vinyl ketone and crotonaldehyde were measured over a series of silica-supported Pt-Re catalysts (1:1 atomic ratio of Pt/Re) in liquid water with H-2 (15psig) at 333K. The hydrogenation of methyl vinyl ketone did not produce any unsaturated alcohol because of the rapid hydrogenation of C=C relative to that of C=O. The addition of Re to Pt impacted the rate of C=C hydrogenation negatively in methyl vinyl ketone and crotonaldehyde, but promoted the selectivity of C=O hydrogenation in crotonaldehyde in which the unsaturated alcohol increased from 5% on Pt to 21% on Pt-Re. The addition of Re to Pt also promoted the rate of C=O hydrogenation in 2-butanone, whereas little effect was observed during the hydrogenation of butanal. The results of electron microscopy and H-2 chemisorption on the Pt-Re catalysts showed the increasing interaction between Pt and Re with the increasing metal weight loading, and results from rate measurements suggest that oxophilic Re can be used to promote the Pt-catalyzed hydrogenation of carbonyl groups in multifunctional molecules.