Hydrogenation of pyridine and its derivatives over supported nanometer noble metal catalysts

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 degrees C, p(H-2) = 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 approximate to 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.