Investigation of Aging Mechanism of Pt‐ZSM‐5 Catalysts for Non‐Oxidative Propane Dehydrogenation

Abstract

A Pt‐ZSM5 catalyst, coked during propane dehydrogenation and regenerated with lean air, was studied by various in‐situ and ex‐situ methods. A newly developed isothermal ceramic flat‐bed reactor with inert surfaces is described and used in the experiments. Comparative measurements successfully demonstrated that temperature alone has no effect on the catalyst and that changes in conversion and selectivity are due to coke formation. Nuclear magnetic resonance (NMR) studies using triphenylphosphine probe molecules of activated and deactivated samples showed the localization of the Pt clusters inside and outside the zeolite pores. It was shown that the Pt clusters are mainly located inside the zeolites and that the mobilization of Pt by contact with oxygen leads to permanent aging.