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Low-temperature oxidation of carbon monoxide and methane over alumina and ceria supported platinum catalysts

Applied Catalysis B: Environmental, ISSN: 0926-3373, Vol: 101, Issue: 3, Page: 669-675
2011
  • 84
    Citations
  • 0
    Usage
  • 71
    Captures
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    Mentions
  • 0
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Metric Options:   Counts1 Year3 Year

Metrics Details

  • Citations
    84
    • Citation Indexes
      84
  • Captures
    71

Article Description

The ignition and extinction processes for total oxidation of CO, CH 4 and CO + CH 4 mixture in oxygen excess over Pt/Al 2 O 3 and Pt/CeO 2 catalysts with the platinum phase distributed either homogeneously or heterogeneously (i.e., locally high platinum concentration) in the support have been studied by temperature programmed oxidation experiments. Following the preparation methods by Arnby et al. [42], the samples have the same Pt load and dispersion. Generally the catalytic activity follows the order: Pt/CeO 2 (heterogeneous) > Pt/CeO 2 (homogeneous) > Pt/Al 2 O 3 (heterogeneous) > Pt/Al 2 O 3 (homogeneous) as indicated by lower ignition and/or extinction temperatures. For Pt/Al 2 O 3, the addition of NO 2 to the reactant stream increases the rate of oxidation of CO in the pre-ignition regime although the light-off temperature T 50 is shifted towards higher temperatures (except for low CO concentrations). In the case of the Pt/CeO 2, the CO conversion generally decreases. For CH 4 oxidation in the presence of NO 2, the conversion increases for Pt/Al 2 O 3 and decreases for Pt/CeO 2. The addition of CO 2 in the reactant stream has minor influence on CO oxidation over Pt/Al 2 O 3 while for Pt/CeO 2, T 50 is shifted towards higher temperatures. For the simultaneous oxidation of CO and CH 4, a reverse hysteresis for methane oxidation is observed, i.e., the extinction process occurs at higher temperature than the corresponding ignition process. The improved activity for CO oxidation over samples with heterogeneous Pt distribution is likely due to less tendency towards CO self-poisoning through the development of steeper concentration gradients in the Pt containing regions in the porous support material. The significant increase of activity for both reactions over ceria-supported Pt is here assigned to highly active sites at the platinum–ceria boundary but also, to some extent, the oxygen storage and release function and dynamics of the transport of oxygen in the Pt/CeO 2 system.

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