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Molybdenum Speciation and its Impact on Catalytic Activity during Methane Dehydroaromatization in Zeolite ZSM‐5 as Revealed by Operando X‐Ray Methods
Author(s) -
LezcanoGonzález Inés,
Oord Ramon,
Rovezzi Mauro,
Glatzel Pieter,
Botchway Stanley W.,
Weckhuysen Bert M.,
Beale Andrew M.
Publication year - 2016
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201601357
Subject(s) - zeolite , catalysis , chemistry , calcination , molybdenum , benzene , methane , butane , spectroscopy , inorganic chemistry , photochemistry , organic chemistry , physics , quantum mechanics
Combined high‐resolution fluorescence detection X‐ray absorption near‐edge spectroscopy, X‐ray diffraction, and X‐ray emission spectroscopy have been employed under operando conditions to obtain detailed new insight into the nature of the Mo species on zeolite ZSM‐5 during methane dehydroaromatization. The results show that isolated Mo–oxo species present after calcination are converted by CH 4 into metastable MoC x O y species, which are primarily responsible for C 2 H x /C 3 H x formation. Further carburization leads to MoC 3 clusters, whose presence coincides with benzene formation. Both sintering of MoC 3 and accumulation of large hydrocarbons on the external surface, evidenced by fluorescence‐lifetime imaging microscopy, are principally responsible for the decrease in catalytic performance. These results show the importance of controlling Mo speciation to achieve the desired product formation, which has important implications for realizing the impact of CH 4 as a source for platform chemicals.