Gas-phase coupling of methyl radicals during the catalytic partial oxidation of methane

Journal Article · Tue Dec 08 23:00:00 EST 1987 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00259a059· OSTI ID:7200172

Campbell, K D; Morales, E; Lunsford, J H

It is generally accepted that the initial step in the catalytic oxidative coupling of methane involves the homolytic cleavage of a C-H bond. This results in the formation of surface OH species and CH/sub 3//sup ./ radicals which may undergo coupling to form ethane. A question arises as to whether the methyl radical coupling occurs on the surface or in the gas phase. Keller and Bhasin proposed a mechanism for the catalytic oxidative coupling of CH/sub 4/ in which the formation of C/sub 2/H/sub 6/ resulted from the surface coupling of adsorbed CH/sub 3/* radicals. In contrast to this mechanism, Lunsford and co-workers proposed that a homogeneous gas-phase coupling of CH/sub 3/* radicals, formed by the surface abstraction of H-atoms from CH/sub 4/, was the primary pathway for C/sub 2/H/sub 6/ formation. Evidence for the existence of gas-phase CH/sub 3//sup ./ radicals during the oxidative coupling of CH/sub 4/ has been obtained by Driscoll et al. with the use of a matrix isolation electron spin resonance (MIESA) technique and, more recently, by Jones et al. with use of the Paneth lead mirror technique. The modeling studies of Labinger and Ott and of Kimble and Kolts also support the role of gas-phase CH/sub 3//sup ./ radicals; however, the actual significance of these radicals in the formation of C/sub 2/H/sub 6/ has not been experimentally proven. In this communication of a lower limit for the rate of gas-phase CH/sub 3/* radical formation over a lithium-promoted MgO catalysts has been determined and this result is compared with the overall rate of C/sub 2/H/sub 6/ formation.

• Research Organization: Texas A and M Univ., College Station (USA)
• OSTI ID: 7200172
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:25; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKALINE EARTH METAL COMPOUNDS
ALKANES
ALKYL RADICALS
CATALYSIS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DATA
ETHANE
EXPERIMENTAL DATA
FLUIDS
GASES
HYDROCARBONS
INFORMATION
KINETICS
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
METHANE
METHYL RADICALS
NUMERICAL DATA
ORGANIC COMPOUNDS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
RADICALS
REACTION KINETICS
SYNTHESIS