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Catalytic oxidation of CO over ordered mesoporous platinum

Catalytic oxidation of CO over ordered mesoporous platinum
Catalytic oxidation of CO over ordered mesoporous platinum
Hexagonal phase mesoporous (H1Pt) was recently reported to have different catalytic properties compared to conventional platinum catalysts. To further investigate this observation the catalytic activity of H1Pt/Al2O3 for CO oxidation was compared with the activity of a corresponding catalyst prepared from Pt-black (Pt-black/Al2O3). The H1Pt/Al2O3 catalyst showed ignition at lower temperatures but extinction at higher temperatures compared to Pt-black/Al2O3. These observations were further supported by oxygen step-response experiments at constant temperature, where the H1Pt/Al2O3 catalyst showed ignition at lower oxygen concentrations when starting from a CO poisoned surface and extinction at higher O2 concentrations when starting from the high-reactive state. Furthermore, adsorption of CO on the catalysts was studied in situ using infrared spectroscopy in absence and presence of oxygen after pre-oxidation and pre-reduction, respectively. At 150 °C the H1Pt/Al2O3 sample showed activity for CO oxidation in the presence of oxygen regardless of pretreatment, whereas Pt-black/Al2O3 was inactive due to CO self-poisoning.

The differences observed in the low reactive state are suggested to be due to structural differences of the platinum surface in the catalysts resulting in a lower sensitivity of the H1Pt/Al2O3 catalyst towards CO self-poisoning and a higher capacity to activate oxygen, and thus a higher activity for CO oxidation. During the high reactive state, the observed higher sensitivity to the concentration ratio between CO and oxygen, and to the temperature is likely due to less optimal ratio between the sticking coefficients of the reactants on the H1Pt catalyst and to higher mass-transport limitations in its narrower pores during the initial stage of the extinction.

platinum, Pt/Al2O3, catalyst, CO oxidation, ignition, extinction
0021-9517
253-260
Saramat, Ali
05f5e6d8-0e07-4f9c-9eb0-feed942c9d80
Thormahlen, Peter
56a539a7-86c1-48b9-aba7-5ac5b8d8c9f0
Skoglungh, Magnus
1ff4345c-b735-4a46-a95d-7af9fabdb59d
Attard, George S.
3219075d-2364-4f00-aeb9-1d90f8cd0d36
Palmqvist, Anders E.C.
8f27a6c2-f7d5-45d2-9c4b-5359cf04da7a
Saramat, Ali
05f5e6d8-0e07-4f9c-9eb0-feed942c9d80
Thormahlen, Peter
56a539a7-86c1-48b9-aba7-5ac5b8d8c9f0
Skoglungh, Magnus
1ff4345c-b735-4a46-a95d-7af9fabdb59d
Attard, George S.
3219075d-2364-4f00-aeb9-1d90f8cd0d36
Palmqvist, Anders E.C.
8f27a6c2-f7d5-45d2-9c4b-5359cf04da7a

Saramat, Ali, Thormahlen, Peter, Skoglungh, Magnus, Attard, George S. and Palmqvist, Anders E.C. (2008) Catalytic oxidation of CO over ordered mesoporous platinum. Journal of Catalysis, 253 (2), 253-260. (doi:10.1016/j.jcat.2007.11.007).

Record type: Article

Abstract

Hexagonal phase mesoporous (H1Pt) was recently reported to have different catalytic properties compared to conventional platinum catalysts. To further investigate this observation the catalytic activity of H1Pt/Al2O3 for CO oxidation was compared with the activity of a corresponding catalyst prepared from Pt-black (Pt-black/Al2O3). The H1Pt/Al2O3 catalyst showed ignition at lower temperatures but extinction at higher temperatures compared to Pt-black/Al2O3. These observations were further supported by oxygen step-response experiments at constant temperature, where the H1Pt/Al2O3 catalyst showed ignition at lower oxygen concentrations when starting from a CO poisoned surface and extinction at higher O2 concentrations when starting from the high-reactive state. Furthermore, adsorption of CO on the catalysts was studied in situ using infrared spectroscopy in absence and presence of oxygen after pre-oxidation and pre-reduction, respectively. At 150 °C the H1Pt/Al2O3 sample showed activity for CO oxidation in the presence of oxygen regardless of pretreatment, whereas Pt-black/Al2O3 was inactive due to CO self-poisoning.

The differences observed in the low reactive state are suggested to be due to structural differences of the platinum surface in the catalysts resulting in a lower sensitivity of the H1Pt/Al2O3 catalyst towards CO self-poisoning and a higher capacity to activate oxygen, and thus a higher activity for CO oxidation. During the high reactive state, the observed higher sensitivity to the concentration ratio between CO and oxygen, and to the temperature is likely due to less optimal ratio between the sticking coefficients of the reactants on the H1Pt catalyst and to higher mass-transport limitations in its narrower pores during the initial stage of the extinction.

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More information

e-pub ahead of print date: 23 December 2007
Published date: 25 January 2008
Keywords: platinum, Pt/Al2O3, catalyst, CO oxidation, ignition, extinction

Identifiers

Local EPrints ID: 147791
URI: http://eprints.soton.ac.uk/id/eprint/147791
ISSN: 0021-9517
PURE UUID: d66e1e7c-9c36-4111-84e6-daf30becc2f3
ORCID for George S. Attard: ORCID iD orcid.org/0000-0001-8304-0742

Catalogue record

Date deposited: 27 Apr 2010 08:07
Last modified: 07 Aug 2019 00:52

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