Role of the residual chlorides in platinum and ruthenium catalysts for the hydrogenation of α,β-unsaturated aldehydes

The gas-phase hydrogenation of crotonaldehyde has been performed over platinum and ruthenium catalysts supported over graphites with a tailored content in surface oxygen groups and prepared with different metal precursors. It is found that the selectivity to the unsaturated alcohol is independent of the amount of oxygen groups on the surface of the graphite supports. Notwithstanding this, their presence has an effect when a metal chloride precursor is used in the catalyst preparation since they act as anchoring sites of the chloride ions and the latter in residual amounts promote the hydrogenation of the carbonyl group. The addition of tin to platinum enhances also the selectivity to crotyl alcohol. (C) 2000 Elsevier Science B.V. All rights reserved.