The oxidative coupling of methane over BaCO{sub 3}/LaOBr-catalysts of high ethylene yield
- Hong Kong Baptist Univ., Kowloon Tong (Hong Kong)
Tetragonal LaOBr is a better catalyst than La{sub 2}O{sub 3} for the oxidative coupling of methane (OCM), whereas BaCO{sub 3} is a good promoter for LaOBr. With contact time equal to 0.2 g s ml{sup -1} and a CH{sub 4}:O{sub 2}:N{sub 2}ratio of 1:1:12, a C{sub 2} yield of 26.3% with a C{sub 2}H{sub 4}/C{sub 2}H{sub 6} ratio of 4.3 could be achieved over the 50 mol% BaCO{sub 3}/LaOBr catalyst at 800{degrees}C. When the CH{sub 4}:O{sub 2}:N{sub 2} ratio was 0.5:1:12 and the contact time was 0.6 g s ml{sup -1}, the C{sub 2} yield became 18.9% and C{sub 2}H{sub 4} was the sole C{sub 2} product. Fixing the CH{sub 4}:O{sub 2}:N{sub 2} ratio to 2.6:1:12 and contact time to 0.6 g s ml{sup -1}, the C{sub 2}H{sub 4}/C{sub 2}H{sub 6} ratios over the LaOF, LaOBr, and 30 mol% BaCO{sub 3}/LaOBr catalysts were, respectively, 1.6, 3.3, and 11.3 at 800{degrees}C. The authors suggest that for a mixed catalyst like BaCO{sub 3}/LaOBr, nonstochiometric behavior is expected and defects such as O{sup -} centers and trapped electrons which would bring about the generation of surface dioxygen species could be present within the constituent structures of at the interfaces. The authors suggest that the direct interaction of CH{sub 4} with O{sub 2}{sup 2-} is an efficient way of producing carbene, and the coupling of carbene, rather than methyl radical, could be the major step for C{sub 2}H{sub 4} generation over these highly C{sub 2}H{sub 4} selective BaCO{sub 3}/LaOBr catalysts. 36 refs., 9 figs., 5 tabs.
- OSTI ID:
- 501850
- Journal Information:
- Journal of Catalysis, Vol. 163, Issue 2; Other Information: PBD: Oct 1996
- Country of Publication:
- United States
- Language:
- English
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