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Vanadium species in new catalysts for the selective oxidation of methane to formaldehyde: Activation of the catalytic sites |
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| Authors: | H. Launay S. Loridant D.L. Nguyen A.M. Volodin J.L. Dubois J.M.M. Millet |
| Affiliation: | aIRCELYON, Institut de Recherches sur la Catalyse et l’Environnement de Lyon, CNRS, Université Claude Bernard Lyon I, UMR5256, 2 Avenue Albert Einstein, Villeurbanne F-69626 cedex, France bBoreskov Insitute of Catalysis, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia cArkema, Centre de Recherches Rhône-Alpes, rue Henri Moissan, BP 63, F-69493 Pierre-Bénite cedex, France |
| Abstract: | New vanadium oxide supported on mesoporous silica catalysts for the oxidation of methane to formaldehyde were investigated by infrared and Raman spectroscopies to identify and characterize the molecular structure of the most active and selective catalytic sites. In situ and operando experiments have been conducted in order to understand the redox and hydroxylation/dehydroxylation processes of the vanadium species. (SiO)2VO(OH) species were identified in these catalysts in reaction conditions and shown to undergo a deprotonation at 580 °C under vacuum, leading to a site giving a photoluminescence band at 550 nm attributed to reverse radiative decay from the excited triplet state: (V4+–O−)* (V5+O2−). An activation mechanism of vanadium monomeric species with electrophilic oxygen species is proposed. |
| Keywords: | Supported vanadium oxide Mesoporous silica Heterogeneous catalysis Methane oxidation Formaldehyde Operando Raman spectroscopy In situ IR spectroscopy Hydroxylated monomeric vanadium species Electrophilic oxygen species |
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