Hydrogenation of Aniline with Ruthenium-Palladium and Ruthenium-Platinum Alloy Catalysts Supported on Activated Carbon

Abstract

Hydrogenation of aniline with Ru-Pd and Ru-Pt alloy catalysts supported on activated carbon was investigated under an atmospheric pressure of hydrogen in the temperature range from 30° to 60° C. Under these conditions the pure Ru and pure Pd catalysts had very low activity for this reaction, but the alloy catalysts of these metals were active and in these alloy series a maximum activity appeared at about 25 atom% of Ru content. At the maximum point the activity was about 15 times as great as that of the pure Pd catalyst which was prepared by the same method as these alloy catalysts. The selectivity for cyclohexylamine increased by 15 mol% as compared with that of pure Pd at the composition of 25% Ru. In order to study the influence of the amino group of aniline on the hydrogenation of the benzen ring, benzene was hydrogenated with these alloy catalysts. For this reaction a maximum activity appeared at about 75 atom% of Ru content. On Ru-Pt alloy series, the hydrogenation of aniline did not show a maximum activity and the activity decreased greately when Ru was added to Pt. On this Ru-Pt series, the selectivity for cyclohexylamine changed almost linearly between the both pure metals. The hydrogenation of benzene with this alloy series was also studied. This alloy catalysts had higher activity than that of the pure metal when the reaction was carried out at 30° C. On both Ru-Pd and Ru-Pt alloy series, the compensation effect for the hydrogenation of aniline was recognised except the pure Ru catalyst. The activity and selec-tivity of the catalysts which were prepared by the deposition of a small amount of Ru on Pd or Pt metal surface, were also investigated.