The methanol to propylene (MTP) process is industrially performed in a fixed-bed reactor with recycling of the condensate. It is well known that a coking pattern with distinct reaction zones develops along the reactor. In order to gain a better understanding of the deactivation processes occurring in industry, we have investigated the stability of ZSM-5 under MTP conditions as well as the nature of the coke deposits formed in a back-mixed Micro-Berty reactor (CSTR). In this way, a homogeneous deactivation of the zeolite is ensured.Comparison with results obtained in a typical plug-flow reactor (PFR) showed that the conversion decreases significantly faster in PFR than in CSTR for experiments performed at similar initial conversion (Figure 1). Interestingly, less coke is observed on the more deactivated PFR samples. Differences in burning temperature and heat of combustion among coke deposits in PFR and CSTR point to a different nature of the deactivating species. Accordingly, it is proposed that a different and faster deactivation pathway exists when a high local concentration of methanol is achieved, as it is the case for the first layers of active catalyst in PFR. Figure 1. Deactivation behavior in Micro-Berty reactor and plug-flow reactor at 723 K. In the inset: Coke deposition within 5 h reaction time. Support from the Clariant Produkte (Deutschland) GmbH in the framework of MuniCat is gratefully acknowledged.

Deactivation pathways during methanol to propylene (MTP) conversion over ZSM-5 catalysts

248th National Meeting (2014)

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