Synthesis of β-picoline from 2-methylglutaronitrile over supported noble metal catalysts I. Catalyst activity and selectivity Original Research Article

Silica-supported palladium, rhodium and platinum were active catalysts in the production of β-picoline by the vapour phase hydrogenation of a technical mixture of 2-methylglutaronitrile and 2-ethylsuccinonitrile, whereas NiSiO2 and RuSiO2 showed no appreciable activity. On the fresh Pd, Rh and Pt catalysts, β-picoline was obtained in a good yield and the complete conversions pointed to extremely high reaction rates. Accordingly, transport limitations due to film and pore diffusion were observed. Activity and selectivity of the catalysts decreased with time on stream, while catalyst stability decreased in the order Pt > Pd > Rh. A large number of by-products was formed, mainly from hydrogenolysis or intermolecular imine-amine condensation. Pt catalysts displayed the highest hydrogenolysis activity, Pd catalysts tended to condensations, while the behaviour of Rh containing catalysts was in between those of Pd and Pt catalysts. Stability and selectivity were influenced by the nature of the substrate, metal dispersion, basicity of the support and average metal ensemble size. The presence of 2-ethylsuccinonitrile in the feed led to the formation of pyrroles and polymers, but was not responsible for the observed deactivation, which was due to coke deposits formed by highly reactive intermediates.