The influence of the distribution of catalyst activity on the resistan
ce against poisoning is studied. For a constant amount of catalyst the
location and width of the active zone is analyzed experimentally. Sev
eral methods for pellet preparation are described. The results demonst
rate that for a model experimental system the optimal distribution is
a thin active layer inside the pellet. This coincides with our previou
s theoretical results which are summarized in this paper.