A comparative study on the selective hydrogenation of α,β unsaturated aldehyde and ketone to unsaturated alcohols on Au supported catalysts

The hydrogenation of trans,4-phenyl,3-buten,2-one (benzalacetone) and trans,3-phenyl, propenal (cinnamaldehyde) was carried out on Au supported on iron oxides catalysts. Commercial goethite (FeOOH), maghemite (γFe2O3) and hematite (αFe2O3) were used as supports. The catalytic activity of Au/Fe2O3 reference catalyst, supplied by the World Gold Council, was also investigated. Gold catalysts and the parent supports were characterized by BET, X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption of ammonia (NH3-TPD) and high resolution transmission electron microscopy (HRTEM). Among the catalysts investigated Au supported on FeOOH shows the highest activity and selectivity to UA in the hydrogenation of unsaturated carbonyl compounds whereas Au supported on αFe2O3 are the less active and selective catalysts. The catalytic activity and selectivity to unsaturated alcohols (UA) in the hydrogenation of benzalacetone and cinnamaldehyde are less influenced by the morphology of gold particles and are mainly influenced by the nature of the support. A correlation between the reducibility of the catalysts and the activity and selectivity to UA has been found. Increasing the reducibility of the catalysts both the activity and selectivity to UA increase. These results let us to argue that active and selective sites are formed by negative gold particles formed through the electron transfer from the reduced support to the metal.