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Influence of molar ratio on Pd-Pt catalysts for methane combustion
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
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2006 (English)In: Journal of Catalysis, ISSN 0021-9517, Vol. 243, no 1, 14-24 p.Article in journal (Refereed) Published
Abstract [en]

The catalytic oxidation of methane was investigated over six catalysts with different palladium and platinum molar ratios. The catalysts were characterised by TEM, EDS, XPS, PXRD and temperature-programmed oxidation. The results suggest that in the bimetallic catalysts, an alloy between Pd and Pt was formed in close contact with the PdO phase, with an exception for the Pt-rich catalyst, where no PdO was observed. It was found that the molar ratio between palladium and platinum clearly influences both the activity and the stability of methane conversion. By adding small amounts of platinum into the palladium catalyst, improved activity was obtained in comparison with the monometallic palladium catalyst. However, higher amounts of platinum are required for stabilising the methane conversion. The most promising catalysts with respect to both activity and stability were Pd67Pt33 and Pd50Pt50. The platinum-rich catalyst showed very poor activity for methane conversion.

Place, publisher, year, edition, pages
2006. Vol. 243, no 1, 14-24 p.
Keyword [en]
palladium, platinum, bimetal, methane, catalytic oxidation, TEM, XRD, TPO, XPS, stability
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-6560DOI: 10.1016/j.jcat.2006.06.019ISI: 000241205200003Scopus ID: 2-s2.0-33748630212OAI: oai:DiVA.org:kth-6560DiVA: diva2:11306
Note
QC 20100916Available from: 2006-12-11 Created: 2006-12-11 Last updated: 2010-09-16Bibliographically approved
In thesis
1. Bimetallic Palladium Catalysts for Methane Combustion in Gas Turbines
Open this publication in new window or tab >>Bimetallic Palladium Catalysts for Methane Combustion in Gas Turbines
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Catalytic combustion is a promising combustion technology for gas turbines, which results in ultra low emission levels of nitrogen oxides (NOx), carbon monoxide (CO) and unburned hydrocarbons (UHC). Due to the low temperature achieved in catalytic combustion almost no thermal NOx is formed. This thesis is concentrated on the first stage in a catalytic combustion chamber, i.e. the ignition catalyst. The catalyst used for this application is often a supported palladium based catalyst due to its excellent activity for methane combustion. However, this type of catalyst has a serious drawback; the methane conversion decreases severely with time during operation. The unstable activity will result in increasing difficulties to ignite the fuel. The parameters that govern the poor stability and other features of the palladium catalysts are discussed in the thesis.

The objective of the work is to improve the catalytic performance of supported palladium catalysts, with focus on stabilising the methane conversion. A large number of different bimetallic palladium catalysts have been evaluated, where the influence of co-metals, molar ratio and support material is addressed. Results from the activity tests of methane combustion showed that it is possible to stabilise the activity by adding certain co-metals into the palladium catalyst. An extensive characterisation study has been carried out on the various bimetallic catalysts in order to gain a better understanding of how their morphology and physicochemical properties determine the various patterns of combustion behaviour.

The environment inside a gas turbine combustor is very harsh for a catalyst. Since the stability of the catalyst is of great importance for ignition catalysts, it is essential to evaluate the risk of deactivation. In this work special emphasis has been given to thermal deactivation, water inhibition and sulphur poisoning. It was found that a bimetallic Pd Pt catalyst is significantly more tolerant to the various deactivation processes investigated than the monometallic palladium catalyst.

Finally, the influence of pressure on the catalytic performance has been investigated. The catalysts were assessed at more realistic conditions for gas turbines, in a high-pressure test facility with 100 kW fuel power.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 80 p.
Series
Trita-KET, ISSN 1104-3466 ; R231
Keyword
activity, bimetal, catalytic combustion, DRIFTS, EDS, gas turbine, methane, morphology, palladium, platinum, pressure, PXRD, stability, TEM, TPO, XPS
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-4222 (URN)91-7178-529-9 (ISBN)978-91-7178-529-9 (ISBN)
Public defence
2006-12-15, D3, Lindstedtsvägen 5, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100916Available from: 2006-12-11 Created: 2006-12-11 Last updated: 2010-09-16Bibliographically approved

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