Abstract: The highly dispersed supported noble metal catalysts were prepared and their catalytic performance for hydrogenation of pyridine was investigated. The results indicated that the 5%Ru/C catalyst exhibited the highest activity compared with Pd/C, Pt/C and Ir/C. The order of catalyst activity was Ru/C>Pd/C>Pt/C>Ir/C. Under the optimum reaction conditions of 100 ℃, p(H2)=3.0 MPa, and Ru/pyridine molar ratio=2.5/1?000, pyridine could be completely converted to piperidine with a 100% selectivity over 5%Ru/C. Furthermore, the activity and selectivity of 5%Ru/C did not decrease significantly after 5 cycle runs. The activity of bimetallic catalysts Ru-Pd/C and Ru-Ir/C was slightly lower than that of Ru/C, whereas the activity of Ru-Co/C was much lower than that of Ru/C. The reduced 5%Ru/C catalyst was characterized by high resolution transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The results showed that ruthenium was reduced to zero valence and the average particle diameter of Ru crystallites was smaller than 5 nm. The hydrogenation reactivity of pyridine and its derivatives was in the order pyridine≈2-methylpyridine>2,6-dimethylpyridine>3-methylpyridine>4-methylpyridine>3,5-dimethylpyridine>2-methoxy-pyridine, indicating that the electron factor played an important role in the reaction process.

Key words: ruthenium, activated carbon, supported catalyst, pyridine, hydrogenation, piperidine, methylpyridine