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

Journal Article · Thu Dec 19 04:00:00 EST 1996 · Journal of Physical Chemistry

DOI:https://doi.org/10.1021/jp961903a· OSTI ID:458663

Mueller, C A; Maciejewski, M; Koeppel, R A; Tschan, R; Baiker, A ^[1]

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1. 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, Journal Name: Journal of Physical Chemistry Journal Issue: 51 Vol. 100; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

Related Subjects

10 SYNTHETIC FUELS
40 CHEMISTRY
CATALYSIS
CATALYSTS
COMBUSTION
DIFFERENTIAL THERMAL ANALYSIS
GRAVIMETRIC ANALYSIS
ISOTOPIC EXCHANGE
MASS SPECTRA
METHANE
OXYGEN 18
PALLADIUM OXIDES
REDOX REACTIONS
ZIRCONIUM OXIDES