Free radical chemistry in heterogeneous catalysis: How important is it?
- Texas A&M Univ. College Station, TX (United States)
The initial step in a number of catalytic hydrocarbon oxidation reactions, and even in acid-catalyzed reactions, can be attributed to radical formation. These surface radicals may either be neutral or cationic species. Although surface radicals have been identified both by direct ESR spectroscopy and by spin trapping, in situ studies of gas-phase radicals that emanate from the surface have provided the most definitive evidence for their role in catalysis. Most notable is the involvement of methyl radicals in the oxidative coupling of methane. In addition, such radicals may be intermediates in the reduction of nitric oxide. The CH{sub 3}{sm_bullet} radicals may react in the gas phase or with the surface. In the latter case, they function as strong reducing agents, and with CH{sub 3}{sm_bullet} radicals, methoxide ions are observed on the surface of reducible metal oxides. These methoxide ions are intermediates in the production of methanol and formaldehyde. The involvement of radicals on metal surfaces is less direct; however, evidence for the formation of hydrogen atoms from H{sub 2} on supported Pd has recently been reported by Miles and co-workers at Cardiff.
- OSTI ID:
- 370702
- Report Number(s):
- CONF-960376--
- Country of Publication:
- United States
- Language:
- English
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