HYDROGENATION BEHAVIOR OVER SIO2-SUPPORTED LANTHANIDE PALLADIUM BIMETALLIC CATALYSTS WITH CONSIDERABLE HYDROGEN UPTAKE

Novel lanthanide-containing catalysts prepared by the use of dissolution of lanthanide metals in liquid ammonia have been studied. The hydrogenation of propene was carried out at 193-263 K over SiO2-supported lanthanide-palladium bimetallic catalysts (Ln-Pd/SiO2; Ln = Eu and Yb) obtained when the dissolved lanthanide in liquid ammonia reacted with 5 wt.% Pd/SiO2. Ln-Pd/SiO2 showed remarkable synergetic effects between the lanthanide and palladium metal involving considerable hydrogen uptake during the hydrogenation of propene. The rapid hydrogen uptake by Ln-Pd/SiO2 occurred at the start of the reaction, followed by the hydrogenation of propene with a definite induction period. The catalyst contained reactive hydrogen species which were able to efficiently hydrogenate the adsorbed propene. The kinetic studies indicated that the hydrogenation predominantly proceeds through a reaction path using hydrogen taken up by the catalyst. The presence of adsorbed propene on the catalyst surface was important to induce a promoting effect towards hydrogen uptake with subsequent hydrogenation of propene.