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The effect of platinum distribution in monolithic catalysts on the oxidation of CO and hydrocarbons

Karl Arnby (Institutionen för kemi- och bioteknik, Teknisk ytkemi ; Kompetenscentrum katalys (KCK)) ; Johan Assiks (Institutionen för kemi- och bioteknik, Teknisk ytkemi ; Kompetenscentrum katalys (KCK)) ; Per-Anders Carlsson (Institutionen för kemi- och bioteknik, Kemisk reaktionsteknik ; Kompetenscentrum katalys (KCK)) ; Anders Palmqvist (Institutionen för kemi- och bioteknik, Teknisk ytkemi ; Kompetenscentrum katalys (KCK)) ; Magnus Skoglundh (Institutionen för kemi- och bioteknik, Teknisk ytkemi ; Kompetenscentrum katalys (KCK))
Journal of Catalysis (0021-9517). Vol. 233 (2005), 1, p. 176-185.
[Artikel, refereegranskad vetenskaplig]

Monolithic Pt/gamma-Al2O3 catalysts were prepd. by depositing of the platinum phase, either homogeneously or heterogeneously (i.e., local high platinum concn.), in the washcoat. The influence of the platinum distribution on the ignition and extinction processes for oxidn. of CO, propene, and propane, resp., was investigated by both temp.-programmed and oxygen step-response flow-reactor expts. In addn., in situ XANES spectroscopy was used to follow changes in the chem. state of platinum during propane oxidn. For samples with heterogeneous platinum distribution, the results show an improved low-temp. activity for CO oxidn., whereas no clear improvement is obsd. for oxidn. of propene or propane. Comparison of the results for CO and hydrocarbon oxidn. shows that the improved activity cannot be explained by thermal effects. Moreover, calcns. indicate that the enhanced activity for CO oxidn. can be due to mass-transfer phenomena. This could not be confirmed by our expts., however. Instead, the improved activity for CO oxidn. can be due to varying platinum particle size between the samples. Furthermore, the oxidn. of propane is shown to be highly influenced by the oxygen concn., showing an activity max. for gas compositions close to the stoichiometric. High oxygen levels result most probably in a predominantly oxygen-covered surface, which inhibits the reaction and, as supported by the in situ XANES experiments, passivates the surface by forming platinum oxide.

Nyckelord: Environmental catalysis, Total oxidation, Low-temperature activity, CO, Propane, Propene, Platinum, Alumina, Platinum oxide, Mass transport, Heat transport, Structure sensitivity, XANES spectroscopy



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Denna post skapades 2006-01-19. Senast ändrad 2017-09-14.
CPL Pubid: 11797

 

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Institutioner (Chalmers)

Institutionen för kemi- och bioteknik, Teknisk ytkemi (2005-2014)
Kompetenscentrum katalys (KCK)
Institutionen för kemi- och bioteknik, Kemisk reaktionsteknik (2005-2014)

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