Conversion of methyl radicals to methanol and formaldehyde over vanadium oxide catalysts
- Texas A&M Univ., College Station, TX (United States)
Methyl radicals, formed by the thermal decomposition of azomethane, react with V{sub 2}O{sub 5} to form methoxide ions. Infrared results confirm the presence of methoxide ions, and ESR spectra demonstrate that the reaction involves the reduction of V{sup 5+} to V{sup 4+}. The methoxide ions may either decompose to formaldehyde or react with water or surface protons to form methanol. In temperature-programmed reaction experiments, both methanol and formaldehyde reached a maximum concentration in the gas phase at 200- 250{degrees}C over V{sub 2}O{sub 5}, but over V{sub 2}O{sub 5}/SiO{sub 2}, the methanol and formaldehyde maxima were shifted to ca. 300 and 400{degrees}C, respectively. The production of CH{sub 3}OH at the lower temperature over V{sub 2}O{sub 5}/SiO{sub 2} suggests that methoxide ions may react with water or surface protons to form methanol more quickly than they decompose to formaldehyde. Nevertheless, in continuous flow experiments at 300 and 500{degrees}C, formaldehyde was the principal oxygenated product because of the rapid oxidation of CH{sub 3}OH at this temperature, and, in the case of pure V{sub 2}O{sub 5}, the direct conversion of methoxide ions to formaldehyde appears to compete favorably with their reaction with water. 20 refs., 5 figs., 5 tabs.
- OSTI ID:
- 476839
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 165; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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