Coking Mechanism and the Distribution of Agglomeration Products in High-Silica MFI-Type Zeolites
G. V. ECHEVSKY, O. G. ECHEVSKAYA
Boreskov Institute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
egv@catalysis.ru
Ключевые слова: coke formation, MFI-type zeolites, carbenium mechanism, zeolites stability
Страницы: 20-31
Аннотация
Currently there is no agreement among the researchers worldwide about the mechanism of MFI-type zeolites deactivation due to coke accumulation in the areas of coke localization. This problem does not allow answering the question about the stability of these zeolites and their resistance to the reversible deactivation by coke. Our research provides the solution to this problem using physical and chemical methods: the electron paramagnetic resonance, X-ray photoelectron spectroscopy, thermal analysis and catalytic method of methanol conversion into hydrocarbons. We show that the key mechanism of coke formation is carbenium mechanism. Deactivation of zeolites occurs mainly due to the coke accumulation on the external surface of crystals of MFI-type zeolites. The contribution of “hydrocarbon pool” mechanism is negligibly small compared to the contribution of the carbenium mechanism of olefin formation by the dehydration reaction. This understanding allows increasing the stability of MFI type zeolites to coke formation by removing the acidic centres from the external surface of the crystals.
DOI: 10.15372/KhUR2023435
EDN: EWJRUK
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