Deactivation mechanisms of palladium in methylcyclopentane conversion

Abstract

Pd/mordenite (Mor) catalysts are deactivated by a combined sintering–coking mechanism in methyl-cyclopentane conversion. Coke formation and particle size growth have been evaluated from micrographs taken before and after reaction. The extent of coking and agglomeration is dependent on the zelite proton concentration. Temperature programmed oxidation (TPO) of coke shows the typical profiles of coke on metal (C_M) and on acid (C_H+) sites. While a used Pd/HMor catalyst has more total coke than a used Pd/NaMor catalyst, the relative amount of coke on acid sites with respect to coke on metal sites (C_H+/C_M) for both catalysts was found to be almost the same. This observation is attributed to the relative proton concentration and Pd dispersion in HMor and NaMor. With the same Pd metal loading, Pd particles are much smaller in HMor than in NaMor due to highly favoured proton anchoring in the former.