Effect of metal-support interaction during selective hydrogenation of cinnamaldehyde to cinnamyl alcohol on platinum based bimetallic catalysts

The ethylenic unsaturation of alpha-beta ethylenic aldehydes is much more reactive to catalytic hydrogen addition than the carbon-oxygen double bond, giving saturated aldehydes in a first step. Fortunately, in a liquid phase hydrogenation, the selectivity to the unsaturated alcohols may be improved by the choice of appropriate solvents and bimetallic catalysts. In this work much attention has been brought to the factors that allow to achieve the best possible selectivity to cinnamyl alcohol. An oxide known to give special metal-support interaction, namely TiO2, was chosen as our support. A careful study of the precursor reduction by TPR was a valuable guide to establish the final preparation for the active phase. The catalyst precursor was dried and reduced in an electric furnace under a flow of gas at atmospheric pressure. Compared to Pt, Pt-Sn and Pt-Fe on carbon, a monometallic Pt/TiO2 catalyst gives an excellent selectivity but a rather poor activity, Finally a selectivity to cinnamyl alcohol as high as 97% and a high activity are reached by using a bimetallic Pt-Fe/TiO2. This good selectivity has been attributed to the metal support interaction.