title: Molybdenum Speciation and its Impact on Catalytic Activity during Methane Dehydroaromatization in Zeolite ZSM-5 as Revealed by Operando X-Ray Methods.
abstract: 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 CH4 into metastable MoCx Oy species, which are primarily responsible for C2 Hx /C3 Hx formation. Further carburization leads to MoC3 clusters, whose presence coincides with benzene formation. Both sintering of MoC3 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 CH4 as a source for platform chemicals.
authors.affiliation: Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot, OX11 0FA, UK.|Chemistry Department, University College London, Gordon Street, London, WC1H 0AJ, UK.
authors.forename: Inés
authors.initials: I
authors.lastname: Lezcano-González
authors.affiliation: Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584, CG Utrecht, The Netherlands.
authors.forename: Ramon
authors.initials: R
authors.lastname: Oord
authors.affiliation: European Synchrotron Radiation Facility, 71, Avenue des Martyrs, CS40220, 38043, Grenoble Cedex 9, France.
authors.forename: Mauro
authors.initials: M
authors.lastname: Rovezzi
authors.affiliation: European Synchrotron Radiation Facility, 71, Avenue des Martyrs, CS40220, 38043, Grenoble Cedex 9, France.
authors.forename: Pieter
authors.initials: P
authors.lastname: Glatzel
authors.affiliation: Central Laser Facility, STFC, Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK.
authors.forename: Stanley W
authors.initials: SW
authors.lastname: Botchway
authors.affiliation: Inorganic Chemistry and Catalysis, Debye Institute for Nanomaterials Science, Utrecht University, Universiteitsweg 99, 3584, CG Utrecht, The Netherlands. B.M.Weckhuysen@uu.nl.
authors.forename: Bert M
authors.initials: BM
authors.lastname: Weckhuysen
authors.affiliation: Research Complex at Harwell, Rutherford Appleton Laboratory, Didcot, OX11 0FA, UK. Andrew.Beale@ucl.ac.uk.|Chemistry Department, University College London, Gordon Street, London, WC1H 0AJ, UK. Andrew.Beale@ucl.ac.uk.
authors.forename: Andrew M
authors.identifier: http://orcid.org/0000-0002-0923-1433
authors.initials: AM
authors.lastname: Beale
keywords: X-ray techniques; heterogeneous catalysis; methane; molybdenum; zeolites