The Liquid-Phase Hydrogenation of Benzonitrile over a Nickel Catalyst.

The kinetics of liquid-phase hydrogenation of benzonitrile in the presence of a reduced nickel catalyst were studied at temperatures ranging from 70 to 100°C. The initial concentrations of benzonitrile in 250 ml methanol varied from 25 to 50g.Under given conditions, the absorption rate of hydrogen was first order in catalyst concentration. It was independent of the partial pressure of hydrogen and of the concentration of benzonitrile over a relatively low conversion range. The activation energy was calculated to be 8.8 Kcal/mol.The reactions to form Schiff-bases and secondary amines became evident when the absorption rate of hydrogen was low. Such reactions were markedly accelerated when the hydrogenation reaction was interrupted.Hydrogenation of benzonitrile was also studied in the presence of n-butylamine. The results indicated that when the absorption rate of hydrogen was high, the amine was involved in the formation of Schiff-bases as well as secondary amines only to a very slight extent. Upon interruption of the hydrogenation reaction, however, the presence of amine gave rise to the formation of mixed Schiff-bases.