A comparative study of the oxides of lanthanum, cerium, praseodymium, and samarium as catalysts for the oxidative dehydrogenation of methane in the presence and absence of carbon tetrachloride
- Univ. of Waterloo, Ontario (Canada)
The catalytic oxidative coupling of methane to ethane and ethene has been investigated on the rare earth oxides, i.e., La[sub 2]O[sub 3], CeO[sub 2], Pr[sub 6]O[sub 11], and Sm[sub 2]O[sub 3]. Addition of a small amount of tetrachloromethane (TCM) to the reactant stream improves the catalytic activity of these oxides. In particular, the praseodymium catalyst yields high selectivity to the C[sub 2] compounds comparable to La[sub 2]O[sub 3] or Sm[sub 2]O[sub 3] when TCM is present in the feedstream. The X-ray diffraction patterns for these catalysts after the reaction with TCM show the presence of the oxychlorides in the catalysts except for the cerium catalyst, for which the selectivity to C[sub 2] compounds is very low even in the presence of TCM. The oxychlorides can be generated on La[sub 2]O[sub 3], Sm[sub 2]O[sub 3], or Pr[sub 6]O[sub 11] by preheating under a stream including TCM. The product distribution of the reaction with these catalysts in the absence of TCM is similar to that with the oxides in the presence of TCM, while Pr[sub 6]O[sub 11] pretreated with TCM is unstable with no TCM in the feedstream. It appears that the improvement of the activity of the rare earth catalysts with TCM in the feedstream is primarily due to the formation of the oxychlorides during the reaction. 49 refs., 6 figs., 5 tabs.
- OSTI ID:
- 6259545
- Journal Information:
- Journal of Catalysis; (United States), Journal Name: Journal of Catalysis; (United States) Vol. 139:2; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ALKANES
ALKENES
CARBON TETRACHLORIDE
CATALYSIS
CATALYSTS
CATALYTIC EFFECTS
CERIUM COMPOUNDS
CERIUM OXIDES
CHALCOGENIDES
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
CHLORINATED ALIPHATIC HYDROCARBONS
CHLORINE COMPOUNDS
COHERENT SCATTERING
COUPLING
DEHYDROGENATION
DIFFRACTION
ETHANE
ETHYLENE
HALOGEN COMPOUNDS
HALOGENATED ALIPHATIC HYDROCARBONS
HETEROGENEOUS CATALYSIS
HYDROCARBONS
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
METHANE
ORGANIC CHLORINE COMPOUNDS
ORGANIC COMPOUNDS
ORGANIC HALOGEN COMPOUNDS
OXIDATION
OXIDES
OXYCHLORIDES
OXYGEN COMPOUNDS
OXYHALIDES
PRASEODYMIUM COMPOUNDS
PRASEODYMIUM OXIDES
RARE EARTH COMPOUNDS
SAMARIUM COMPOUNDS
SAMARIUM OXIDES
SCATTERING
X-RAY DIFFRACTION
YIELDS