Pt/CeO2 catalysts in selective hydrogenation of crotonaldehyde: high performance of chlorine-free catalysts

The hydrogenation of crotonaldehyde was conducted in gaseous phase, at atmo spheric pressure, on Pt/CeO2 catalysts prepared from metal precursors conta ining or not chlorine. The activities and selectivities were studied, at 25 3 K, as a function of the reduction temperature of the catalyst (473-993 K) . The Pt/CeO2 catalyst, prepared from tetraammineplatinum nitrate, led to 5 -20% crotyl alcohol selectivity when the catalyst was reduced at low temper ature (473-673 K), while increasing the reduction temperature up to 973 K, the crotyl alcohol selectivity reached more than 80%. Repeating a series of experiments after a re-calcination treatment at 673 K, the selectivity dec reased to only 40% after 473 K reduction to reach again more than 80% after 673 K reduction temperature. A phase transformation of Pt to CePt5 was obs erved by XRD analysis after 973 K reduction treatment. Differently on Pt/Ce O2 catalysts containing chlorine, prepared from either chloroplatinic acid or tetraammineplatinum chloride, the crotyl alcohol selectivity never excee ded 30% and did not form alloy up to 973 K reduction temperature. The main results are interpreted considering that the activity of CePt5 for C=C hydr ogenation is low compared to unmodified platinum catalyst and the activatio n of the carbonyl bond is induced by the presence of oxygen vacancies sites located at the interface between ceria and the metallic particles. The res ults are in good accordance with the information known at the present time on the metal-support interactions in Pt deposited on CeO2.