Kinetics of the Hydrogenation of Benzene on a Nickel Catalyst supported on Kieselguhr

Abstract

The kinetics of the catalytic hydrogenation of benzene on a commercial nickel catalyst (dp=2.65mm) was studied by a differential type of flow reactor.
The conversion of benzene is 5-8% for ordinary runs, and the maximum deviation of the catalyst temperature in the bed is less than 8°C.
Initial rates of reaction without cyclohexane and the rate for reactants containing some cyclohexane were measured at atmospheric pressure over the following range of conditions.
Temperature: 140, 160, 180, 200 and 220 [°C]
Partial pressure: p_H=0.4-0.9, p_B=0.1-0.6 p_O=0-0.5 [atm.]
Flow rate: 26-31 [gr/cm²hr.]
Twelve different mechanisms were presented, and checked by comparing experimental data of initial rates with the characteristic curve of the modified rate equation
As a result, the most plausible rate-controlling step was found to be in the surface reaction between one adsorbed benzene molecule and three adsorbed hydrogen molecules on the same type of active sites.
The final equation recommended for the vapor-phase hydrogenation of benzene on a nickel catalyst is as follows;