Direct synthesis of 3-picoline from 2-methylglutaronitrile over supported PdZn catalyst: promoting effects of Zn

The promotion effect of transition metal on the catalytic performance of a Pd catalyst for the direct synthesis of 3-picoline from 2-methylglutaronitrile was investigated. The PdZn/SiO2–Al2O3 catalysts with appropriate Zn/Pd molar ratio exhibited a high 3-picoline yield. Kinetic and mechanism analysis revealed a kinetically relevant step of dehydrogenation in 3-methyltetrahydropyridine to 3-picoline involving the bound of 3-methyltetrahydropyridine to a Zn site and dehydrogenation by a vicinal Pd site to form 3-picoline. Such synergy between Zn and Pd sites accounted for the observed superiority of PdZn catalysts in direct synthesis of 3-picoline.