Pt and Pt-alloy catalysts and their properties for the liquid-phase hydrogenation of cinnamaldehyde

The selective hydrogenation of alpha,beta -unsaturated aldehydes to the corresponding unsaturated alcohol is not only of general interest in fine chemical and pharmaceutical intermediate production but also of specific relevance to the perfume and flavouring industries. A number of Pt/graphite catalysts have been prepared with metal loadings in the range 5-10 wt.% metal on graphite and with added cobalt in the composition range 5-99.5 mol%. These catalysts have been characterised using temperature programmed reduction (TPR) and have been compared with a commercial 5% (w/w) Pt/graphite catalyst for the hydrogenation of cinnamaldehyde in toluene and biphasic toluene/aqueous solutions containing a range of bases or potassium based salts. The reactions were carried out in a stirred reactor in the pressure range 4-11 bar absolute, in the temperature range 298-373 K, and with the concentration of cinnamaldehyde in the range 0.038-0.303 kmol/m(3). The presence of strong bases was found to enhance both catalyst activity and selectivity to cinnamyl alcohol. (C) 2001 Elsevier Science B.V. All rights reserved.