The characterization of BaCO{sub 3}-modified LaOF catalysts for the OCM reaction
- Hong Kong Baptist Univ., Kowloon (Hong Kong); and others
In this paper, BaCO{sub 3} is reported to be a good promoter for rhombohedral LaOF. With the addition of 5-20 mol% BaCO{sub 3}, methane conversion at 800{degrees}C was increased by ca. 40% with only slight loss in C{sub 2} selectivity. At CH{sub 4}: O{sub 2}: N{sub 2} = 2.6: 1:12 and a contact time of 0.6 g s ml{sup -1}, the methane conversion was 36.1%, while the C{sub 2} selectivity was 45.3%, giving a C{sub 2} yield of 16.4% over the 10 mol% BaCO{sub 3}/LaOF catalyst at 800{degrees}C. Comparing to LaOF, there was a 30% increase in C{sub 2} yield. Moreover, similar to the case of BaCO{sub 3}/LaOBr, the C{sub 2}H{sub 4}/C{sub 2}H{sub 6} ratio was enhanced by the presence of 5-20 mol% BaCO{sub 3}. The loaded barium was found to remain on the surface of the catalyst. XRD, O{sub 2}-TPD, and CO{sub 2}-TPD studies revealed that the BaCO{sub 3}/LaOF catalysts changed greatly in composition, surface site basicity, and active site concentration during OCM reaction. In situ Raman studies disclosed that at 700{degrees}C under CH{sub 4}/O{sub 2} (2.6/1), O{sub 2}-species were present on the 210 mol% BaCO{sub 3}/LaOF catalyst, while none was observed on LaOF. The authors conclude that the enhancement in methane conversion over the 5-20 mol% BaCO{sub 3}/LaOF catalysts was due to the generation of surface BaCO{sub 3} clusters on LaOF, which could decompose at the temperature range (700-850{degrees}C) adopted for OCM reaction to give BaO entities capable of activating O{sub 2} to adsorbed O{sub 2}{sup 2-}. 38 refs., 10 figs., 1 tab.
- OSTI ID:
- 563475
- Journal Information:
- Journal of Catalysis, Vol. 167, Issue 2; Other Information: PBD: 15 Apr 1997
- Country of Publication:
- United States
- Language:
- English
Similar Records
Oxidative coupling of methane over a Sr-promoted La{sub 2}O{sub 3} catalyst supported on a low surface area porous catalyst carrier
Elementary reactions in the oxidative coupling of methane over Mn/Na{sub 2}WO{sub 4}/SiO{sub 2} and Mn/Na{sub 2}WO{sub 4}/MgO catalysts