Selective hydrogenation of alfa,beta unsaturated ketone on Au supported on MgO catalysts

The selective hydrogenation of alfa,beta unsaturated carbonyl compounds to the correspondingunsaturated alcohols (UA) is an important reaction in the manufacture of fragrances in the perfumeiy industries. The classical hydrogenation metal catalysts show none or low selectivity towards the hydrogenation of C=O bond. In the hydrogenation of alfa,beta unsaturated aldehydes, the selectivity of the metal catalysts can be irnproved by addition of promoters such as Fe(III) and Sn(II), and/ or by electron donating ligand effects from the support. Otherwise the hydrogenation of unsanirated ketones by gaseous hydrogen in the presence of prornoted noble metal catalysts always lead to the hydrogenation of the C=C bond . Milone e co. reported that the selective hydrogenation of alfa,beta unsaturated aldehydes and ketones to the corresponding unsaturated alcohols, with molecular H2, can be achieved on Au supported on a mixture of iron oxy-hydroxide catalysts. In particular they found that the selectivity toward the formation of the unsaturated alcohol increases wilh the reducibility of the support. Negatively charged gold nanoparticles as a consequence of an electron transfer mechanisrn from the reduced support to the metal has been proposed as active and selective sites. ln literature it is reported that the oxidation rate of CO in presence of Au/MgO catalysts enhances with the increase of F center formed on annealed magnesium oxide. Taking into account these data, the aim of this work is to investigate the behaviour of Au/MgO system in the reaction of hydrogenation of benzalacetone. Au/MgO catalysts were prepared by DP with NaOH and by DP with urea, in accordance with the method developed by Zanella. Different urea concentration and the presence of magnesium citrate has been also evaluated. Particularly lhe influence of the preparation method on Au deposited yield (determined by XRF analysis) and the preliminary results of the reaction of hydrogenation of benzalacetone will be presented. A detailed characterization of the catalysts by means of TPR, TGA, TEM, XRD and BET surface area will be also reported.