Role of lattice oxygen in the combustion of methane over PdO/ZrO{sub 2}: Combined pulse TG/DTA and MS study with {sup 18}O-labeled catalyst
- Swiss Federal Inst. of Technology, Zuerich (Switzerland)
The contribution of a redox mechanism involving lattice oxygen in the catalytic combustion of methane over PdO/ZrO{sub 2} catalysts, prepared from amorphous Pd-Zr alloys, has been studied by means of gas pulse methods, including a novel technique `pulse thermal analysis`, and using labeled catalysts containing Pd{sup 18}O. Special emphasis was devoted to the influence of the isotope exchange (scrambling) of reactants and products, especially O{sub 2} and CO{sub 2}, with the catalyst on the quantity of {sup 18}O-containing reaction products. Substantial amounts of H{sub 2}{sup 18}O and C{sup 18}O{sup 16}O were detected during pulses of a reactant mixture consisting of methane and {sup 16}O{sub 2} in a ratio 1:4 at 300 and 500{degree}C. The effect of the oxygen exchange of molecular oxygen with the solid phase proved to be negligible due to its low extent. At 300{degree}C, at least 20% of the CO{sub 2} formed originated from the redox mechanism involving lattice oxygen. At 500{degree}C, oxygen exchange of CO{sub 2} with the catalyst became predominant and precluded determining reliably the proportion of CO{sub 2} formed by the redox process. The results indicate that a substantial part of methane is oxidized via a redox process. Consequently, this reaction has to be taken into account when interpreting the catalytic behavior of palladium-based catalysts and explaining the structure-activity relations previously observed. 66 refs., 9 figs., 2 tabs.
- OSTI ID:
- 458663
- Journal Information:
- Journal of Physical Chemistry, Vol. 100, Issue 51; Other Information: PBD: 19 Dec 1996
- Country of Publication:
- United States
- Language:
- English
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