The activation of hydrocarbon C-H bonds over transition metal oxide catalysts: A FTIR study of hydrocarbon catalytic combustion over MgCr{sub 2}O{sub 4}
- Universita P.le Kennedy, Geneva (Italy)
- Northeastern Univ., Boston, MA (United States)
The interaction of light hydrocarbons (methane, ethane, propane, propene, n-butane, isobutane, 1-butene, benzene, and toluene) with the oxidized surface of the spinel MgCr{sub 2}O{sub 4} (an active hydrocarbon combustion catalyst) has been investigated by FTIR spectroscopy in the temperature range 300-773 K. This interaction results in the reduction of the catalyst and the production of oxygen-containing adsorbed species. These species have been identified by comparison with the spectra of oxygen-containing species (alcohols, aldehydes, ketones, carboxylic acids, carbon oxides) directly adsorbed on the surface. It has been concluded that every hydrocarbon reacts at its weakest C-H bond on Cr{sup n+}=O (n = 5 or 6) surface sites giving rise by hydrogen abstraction and C-O bond formation to alkoxy groups. These species are further oxidized to carbonyl compounds and/or carboxylate anions and, finally, carbon oxides. The earlier intermediates (alkoxides, carbonyl compounds) are detectable only with the most reactive hydrocarbons (propane, n-butane, isobutane, propene, 1-butene, toluene), while with the least reactive hydrocarbons (methane and benzene), because of their two high activation temperature, only the final intermediates are detectable (carbonates, carboxylates). Molecular-level mechanism for C-H cleavage and hydrocarbon catalytic combustion are proposed. 47 refs., 11 figs., 1 tab.
- OSTI ID:
- 75807
- Journal Information:
- Journal of Catalysis, Vol. 151, Issue 1; Other Information: PBD: Jan 1995
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
01 COAL, LIGNITE, AND PEAT
02 PETROLEUM
03 NATURAL GAS
MAGNESIUM COMPOUNDS
CATALYTIC EFFECTS
CHROMATES
ALKANES
COMBUSTION
ALKENES
CATALYSTS
REACTION INTERMEDIATES
CHEMICAL ACTIVATION
ABSORPTION SPECTROSCOPY
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE 0400-1000 K
TEMPERATURE RANGE 0273-0400 K