A study of catalysts and mechanisms in synthesis reactions
- Texas A and M Univ., College Station, TX (USA). Dept. of Chemistry
The role of surface-generated gas phase radicals is best illustrated in the catalytic oxidative dimerization of methane to ethane. We previously demonstrated that methyl radicals, formed on the surface of lithium-promoted magnesium oxide (Li{sup +}/MgO) and sodium- promoted calcium oxide (Li{sup +}/CaO) emanate into the gas phase where they couple to form ethane, which in turn is dehydrogenated to ethylene. The reactions of radicals with metal oxide surfaces is a largely unexplored area of surface chemistry, therefore it was of interest to determine first the relative activities of metal oxides with methyl radicals and ultimately the specific activities of selected oxides. Moreover, it was found that a very reactive surface could be modified by the addition of an alkali metal carbonate, and that such modifications caused a profound effect on the catalytic properties of the oxide. Other systems, such as NaMnO{sub 4}/MgO have been examined to determine whether the coupling even occurs in the gas phase. This mixed-metal oxide is a selective oxidative dimerization catalyst, but it is ineffective in generating gas phase radicals. As a complementary technique to the matrix-isolation electron spin resonance (MIESR) system that was developed in our laboratory, a laser-induced fluorescence (LIF) spectrometer is being employed to study OH{center dot} radicals that are formed during the oxidation of CH{sub 4}. In addition to coupling, the surface-generated CH{sub 3}{center dot} radicals become involved in chain-branching reactions which yield OH{center dot} radicals. An extended goal of the project is to determine the vibrational and rotational temperatures of the radicals relative to the temperature of the surface.
- Research Organization:
- Texas A and M Univ., College Station, TX (USA). Dept. of Chemistry
- Sponsoring Organization:
- DOE/ER
- DOE Contract Number:
- FG05-88ER13829
- OSTI ID:
- 5730800
- Report Number(s):
- DOE/ER/13829-2; ON: DE89017805
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
400201* -- Chemical & Physicochemical Properties
ALKANES
ALKYL RADICALS
CATALYSTS
CATALYTIC EFFECTS
CERIUM COMPOUNDS
CERIUM OXIDES
CHALCOGENIDES
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
DOCUMENT TYPES
FLUORESCENCE
HYDROCARBONS
KINETICS
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
LUMINESCENCE
METHANE
METHYL RADICALS
ORGANIC COMPOUNDS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PROGRESS REPORT
RADICALS
RARE EARTH COMPOUNDS
REACTION KINETICS
YTTERBIUM COMPOUNDS
YTTERBIUM OXIDES