Carbon dioxide as oxidant for the conversion of methane to ethane and ethylene using modified CeO{sub 2} catalysts
- Tohoku Univ., Sendai (Japan)
CaO-CeO{sub 2} is the most effective catalyst for the conversion at 850 C of CH{sub 4} to C{sub 2}H{sub 6} and C{sub 2}H{sub 4} by CO{sub 2} among a series of CeO{sub 2} catalysts modified with alkali and alkaline earth metal oxides. When the CaO-CeO{sub 2} catalyst is prepared in the range of Ca/Ce ratio 0.1--0.5 by impregnation method, there exist synergistic effects between the two components for the formation of C{sub 2} hydrocarbons, and the catalyst forms solid solution. It is thus suggested that the formation of solid solution is responsible for synergistic effects. The lattice oxygen of the CaO-CeO{sub 2} catalyst converts CH{sub 4} mainly to H{sub 2} and CO, and the presence of CO{sub 2} is indispensable for C{sub 2} formation. Both C{sub 2} selectivity and C{sub 2} yield increase remarkably with increasing partial pressure of CO{sub 2}, these values at 850 C reaching 75 and 4% at 70 kPa, respectively. Correlation of the results of kinetic analyses and CO{sub 2} TPD measurements indicates that the existence of the pool of the CO{sub 2} chemisorbed on the CaO-CeO{sub 2} catalyst accounts for high C{sub 2} selectivity and yield. The characterization of the binary catalyst show that bulk carbonates are not detectable during reaction and Ce{sup 3+} sites are formed at the outermost layer. It is speculated that these sites activate the chemisorbed CO{sub 2} to generate active oxygen species, which work for the conversion of CH{sub 4} to C{sub 2} hydrocarbons.
- OSTI ID:
- 687732
- Journal Information:
- Journal of Catalysis, Journal Name: Journal of Catalysis Journal Issue: 1 Vol. 186; ISSN 0021-9517; ISSN JCTLA5
- Country of Publication:
- United States
- Language:
- English
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