On the dynamic nature of Mo sites for methane dehydroaromatization

The mechanism of methane activation on Mo/HZSM-5 is not yet fully understood, despite the great interest in methane dehydroaromatization (MDA) to replace aromatics production in oil refineries. It is difficult to assess the exact nature of the active site due to fast coking. By pre-carburizing Mo/HZ...

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Published in:Chemical science (Cambridge) Vol. 9; no. 21; pp. 4801 - 4807
Main Authors: Vollmer, Ina, van der Linden, Bart, Ould-Chikh, Samy, Aguilar-Tapia, Antonio, Yarulina, Irina, Abou-Hamad, Edy, Sneider, Yuri G., Olivos Suarez, Alma I., Hazemann, Jean-Louis, Kapteijn, Freek, Gascon, Jorge
Format: Journal Article
Language:English
Published: England Royal Society of Chemistry 2018
The Royal Society of Chemistry
Subjects:
Benzene
Carbon monoxide
Carburization (corrosion)
Carburizing
Catalysis
Chemical Sciences
Chemistry
Coke
Coking
Methane
Molecular chains
Molybdenum carbide
NMR
Nuclear magnetic resonance
Refineries
ISSN:2041-6520, 2041-6539
Online Access:Get full text
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Summary:The mechanism of methane activation on Mo/HZSM-5 is not yet fully understood, despite the great interest in methane dehydroaromatization (MDA) to replace aromatics production in oil refineries. It is difficult to assess the exact nature of the active site due to fast coking. By pre-carburizing Mo/HZSM-5 with carbon monoxide (CO), the MDA active site formation was isolated from coke formation. With this a clear 13 C NMR signal solely from the active site and not obscured by coke was obtained, and it revealed two types of likely molecular Mo (oxy-)carbidic species in addition to the β-Mo 2 C nanoparticles often mentioned in the literature. Furthermore, separating the active site formation from coking by pre-carburization helped us examine how methane is activated on the catalytic site by carrying out MDA using isotopically labelled methane ( 13 CH 4 ). Carbon originating from the pre-formed carbide was incorporated into the main products of the reaction, ethylene and benzene, demonstrating the dynamic behavior of the (oxy-)carbidic active sites.
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PMCID: PMC5982205
ISSN:2041-6520
2041-6539
DOI:10.1039/C8SC01263F