Catalysis over supported nickel. Effect of support at low metal levels on benzene hydrogenation

Abstract

The effect of the support at low metal levels on the kinetics of the hydrogenation of benzene to cyclohexane have been studied over a series of nickel catalysts. Two different supports, silica and silica-alumina, were used, and the nickel concentration was varied in the 1–10 % range. Kinetic studies were made in a differential flow reactor at temperatures in the range 70–200°C. The activity and apparent activation energies decreased with decreasing nickel content. At the lower metal levels the nickel supported on silica-alumina was less active per unit area of nickel than was nickel supported on silica. The difference between the specific activity of the nickel on the two supports increased as the metal level decreased, indicating that the effect of the support is strongest at lower metal levels. The results do not support the contention that the effect of nickel concentration on catalyst activity results from the fact that a minimum nickel crystallite size is necessary for benzene hydrogenation.