Kinetics of Catalyst Coking in the Hydrogenation of Nitrobenzene to Aniline-Investigations in an Isothermal Catalytic Wall Reactor

摘要

A Catalytic Wall Reactor operated under insothermal conditions was used to study both the steady state kinetics as well as the deactivation kinetics of the vapour phase hydrogenation of nitrobenzene to aniline using a palladium catalyst supported on lapha-alumina. The activity of the catalyst declined with time on stream due to coke formed form nitrobenzene parallel to the main reaction. Axial coke profiles were measured by total carbon analysis of subseqeunt wall segments. By fitting the measured coke profils at diffeent reaction conditions a coke fromation kinetic was determined. In order to get a sufficient fit it had to be differentiated between coke on the active site and coke on the support. The coke content on the active site was correlated with the activity function of both the main reaction as well as the coke formation reaction. Concerning the deactivation of the main reactio it was found that the mechanism of the main reaction changes with proceeding coking.