Decomposition of methane and subsequent reaction of carbonaceous residues over Rh/Mo/Al{sub 2}O{sub 3} catalysts
- Univ. of Dundee (United Kingdom). Dept. of Chemistry
The role of a molybdenum addition to Rh/Al{sub 2}O{sub 3} catalysts has been studied in the decomposition of methane and subsequent hydrogenation reactions of the hydrocarbonaceous residues produced. Mo existed as a dispersed phase over the alumina support, which, following reduction, was present as exposed isolated Mo{sup 2+} ions and as a surface layer on Rh particles which reduced the latter`s propensity to adsorb CO. Methane underwent decomposition at 673 K to generate C{sub x}H and other hydrocarbonaceous species which blocked surface sites on Rh/Mo/Al{sub 2}O{sub 3} in the order bridging sites on Rh, Rh gem-dicarbonyl, Mo{sup 2+}, and Rh on-top sites. A further proportion of the coke generated was located on the alumina support surface. Subsequent hydrogenation of the coked Rh/Mo/Al{sub 2}O{sub 3} catalyst showed two maxima in product formation, the first between room temperature and 350 K and the second between 375 and 475 K, whereas methane was detected only at ca. 473 K for Rh/Al{sub 2}O{sub 3} in the absence of Mo. The presence of Mo in the Rh/Al{sub 2}O{sub 3} catalyst enhances the extent to which coke removal takes place in hydrogen at low temperatures, possibly by restricting the mobility, and thus the ageing, of the residues. Restructuring of the carbonaceous residues occurs in the presence of CO for Rh/Al{sub 2}O{sub 3} but is less significant for Rh/Mo/Al{sub 2}O{sub 3}.
- OSTI ID:
- 354389
- Journal Information:
- Journal of Catalysis, Vol. 184, Issue 1; Other Information: PBD: 15 May 1999
- Country of Publication:
- United States
- Language:
- English
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