Coke relocation and Mo immobilization in donut-shaped Mo/HZSM-5 catalysts for methane dehydroaromatization

Cheng, Ming; Cruchade, Hugo; Pinard, Ludovic; Dib, Eddy; Liu, Honghai; Wang, Jiujiang; Liu, Xinmei; Yan, Zi-Feng; Qin, Zhengxing; Mintova, Svetlana

doi:10.1039/d3ta05418g

Cited by 1 publication

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“…In the context of methane dehydro-aromatization (MDA), most attention has focused on studying coking and deactivation mechanisms in Mo-embedded zeolite catalysts. Donutshaped Mo/HZSM-5 catalysts, designed with a lower diffusion pathway, were shown to improve catalyst stability by shifting the location of coke from micropores to mesopores [9]. Kosinov et al investigated the carbonaceous species formed during Mo/zeolite-catalyzed MDA and related the distinction between hard and soft coke to their location within pores and on the external surface, respectively [10].…”

Section: Introductionmentioning

confidence: 99%

Coke Formation and Regeneration during Fe-ZSM-5-Catalyzed Methane Dehydro-Aromatization

Karpe,

Veser

2024

Catalysts

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Coke formation poses a significant obstacle in the direct conversion of methane into valuable chemicals such as ethylene, benzene, and hydrogen via methane dehydro-aromatization (MDA). At the elevated temperatures necessary for this reaction, coke is the thermodynamically favored product, causing rapid catalyst deactivation and hence necessitating frequent catalyst regeneration. Successful industrial implementation of MDA requires the advancement of catalyst regeneration processes and a comprehensive understanding of coke formation to enhance catalyst performance. Here, we examined the types of coke generated during MDA over a Fe-ZSM-5 catalyst and their impact on deactivation. By combining reactivity studies using catalysts with carefully controlled coke populations with the characterization of the catalyst via XRD, H2-TPR, and pyridine FTIR, we find that soft coke is formed at the Brønsted acid sites, resulting in loss of selectivity, while hard coke is formed at the metal sites causing a loss of activity. While soft coke can be removed at low regeneration temperatures, the removal of hard coke requires harsh conditions which compromise catalyst stability. An investigation into the use of CO2 as an alternative, mild oxidant for catalyst regeneration, however, shows that the mild oxidation strength of CO2 requires even higher regeneration temperatures and hence irreversible loss of Brønsted acid sites.

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Section: Introductionmentioning

confidence: 99%

Coke Formation and Regeneration during Fe-ZSM-5-Catalyzed Methane Dehydro-Aromatization

Karpe,

Veser

2024

Catalysts

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Coke relocation and Mo immobilization in donut-shaped Mo/HZSM-5 catalysts for methane dehydroaromatization

Abstract: Molybdenum-modified HZSM-5 catalysts are widely used for methane dehydroaromatization (MDA) but suffer from rapid deactivation due to coke formation.

Cited by 1 publication

References 48 publications

Coke Formation and Regeneration during Fe-ZSM-5-Catalyzed Methane Dehydro-Aromatization

Coke Formation and Regeneration during Fe-ZSM-5-Catalyzed Methane Dehydro-Aromatization

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