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Stability of palladium-based catalysts during catalytic combustion of methane: The influence of water
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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2007 (English)In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 74, no 3-4, 242-250 p.Article in journal (Refereed) Published
Abstract [en]

The stability of methane conversion was studied over a Pd/Al2O3 catalyst and bimetallic Pd-Pt/Al2O3 catalysts. The activity of methane combustion over Pd/Al2O3 gradually decreased with time, whereas the methane conversion over bimetallic Pd-Pt catalysts was significantly more stable. The differences in combustion behavior were further investigated by activity tests where additional water vapor was periodically added to the feed stream. From these tests it was concluded that water speeds up the degradation process of the Pd/Al2O3 catalyst, whereas the catalyst containing Pt was not affected to the same extent. DRIFTS studies in a mixture of oxygen and methane revealed that both catalysts produce surface hydroxyls during combustion, although the steady state concentration on the pure Pd catalyst is higher for a fixed temperature and water partial pressure. The structure of the bimetallic catalyst grains with a PdO domain and a Pd-Pt alloy domain may be the reason for the higher stability, as the PdO domain appears to be more affected by the water generated in the combustion reaction than the alloy. Not all fuels that produce water during combustion will have stability issues. It appears that less strong binding in the fuel molecule will compensate for the degradation.

Place, publisher, year, edition, pages
2007. Vol. 74, no 3-4, 242-250 p.
Keyword [en]
palladium, platinum, bimetal, methane, catalytic combustion, stability, water, drifts
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-6563DOI: 10.1016/j.apcatb.2007.02.015ISI: 000248875000008Scopus ID: 2-s2.0-34447272007OAI: oai:DiVA.org:kth-6563DiVA: diva2:11309
Note
Uppdaterad från submitted till published: 20100916 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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