Transient kinetic studies of partial oxidation of CH{sub 4}
- State Univ. of New York, Amherst, NY (United States)
The kinetics of methane oxidation over Ni/La{sub 2}O{sub 3} at low temperatures (450-700{degrees}C), atmospheric pressure, and a residence time of 3.8 ms was studied by the pulse-transient analysis method. The transient response curves revealed that CO{sub 2} generation is delayed in comparison to that of CO, hence that CO is the primary product and CO{sub 2} is only subsequently generated from CO. The generation of C and O species over the surface of the catalyst during CH{sub 4}/O{sub 2} pulses and the desorption of CO were much faster than the generation of CO; hence the reaction between the surface carbon species and the surface O species constitutes the rate-controlling step. High CH{sub 4} conversions and almost 100% CO selectivities were obtained for small pulses of 45 {mu}l of CH{sub 4}/O{sub 2} over freshly reduced catalysts, with He as the carrier gas; over the unreduced catalyst the CH{sub 4} conversion and CO selectivity were low. The experimental data also indicated that the CH{sub 4} conversion and CO selectivity decreased when the surface of the reduced catalyst was oxidized. The results demonstrated that Ni atoms, obtained by the reduction of the catalyst, constitute the active sites in CH{sub 4} partial oxidation. One concludes that the CH{sub 4} conversion depends on its dissociation, whereas the CO selectivity is largely dependent on the strength of O species binding to the catalyst. Over the reduced catalyst, the O species oxidize with difficulty, because of their strong binding to Ni atoms, CO to CO{sub 2}, whereas over the unreduced catalyst (which contains Ni oxide), the oxygen species easily oxidize, because they are weakly adsorbed, CO to CO{sub 2}. 25 refs., 12 figs., 3 tabs.
- OSTI ID:
- 223987
- Journal Information:
- Journal of Catalysis, Vol. 158, Issue 1; Other Information: PBD: Jan 1996
- Country of Publication:
- United States
- Language:
- English
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