抄録
The vapor phase dehydrogenation of piperazine to pyrazine on palladium was examined by using a flow method and a pulse technique. When Pd supported on Al2O3 was used as the rare metal catalyst in a stationary process, the activity decreased in a few hours by carbon deposition, although a high initial activity was observed. In contrast, Pd (1%)-UO3 (5%)-Al2O3 continued a higher level yield of 65% at 400°. The effectiveness of the rare earth metal oxides as the catalyst support of Pd was in the order of CeO2> UO2≫ThO2. Dehydrogenation rates among six-membered saturated ring compounds were estimated as cyclohexane≃piperizine≪piperazine. The steric configuration significantly influenced the rate of dehydrogenation ; cis-2, 3-dimethylpiperazine was dehydrogenated faster than the trans isomer. From these results a geometrically plane intermediate structure of piperazines on Pd was suggested.
