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Characterisation and microstructure of Pd and bimetallic Pd-Pt catalysts duirng methane oxidation
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
2007 (English)In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 245, no 2, 401-414 p.Article in journal (Refereed) Published
Abstract [en]

The catalytic oxidation of methane was studied over Pd/Al2O3 and Pd-Pt/Al2O3. It was found that the activity of Pd/Al2O3 gradually decreases with time at temperatures well below that of PdO decomposition. The opposite was observed for Pd-Pt/Al2O3, of which the activity decreases slightly with time. Morphological studies of the two catalysts showed major changes during operation. The palladium particles in Pd/Al2O3 are initially composed of smaller, randomly oriented crystals of both PdO and Pd. In oxidising atmospheres, the crystals become more oxidised and form larger crystals. The activity increase of Pd-PuAl2O3 is probably related to more PdO being formed during operation. The particles in Pd-Pt/Al2O3 are split into two different domains: one with PdO and the other likely consisting of an alloy between Pd and Pt. The alloy is initially rich in palladium, but the composition changes to a more equalmolar Pd-Pt structure during operation. The ejected Pd is oxidised into PdO, which is more active than its metallic phase. The amount of PdO formed depends on the oxidation time and temperature.

Place, publisher, year, edition, pages
2007. Vol. 245, no 2, 401-414 p.
Keyword [en]
palladium, platinum, bimetal, methane, TEM, PXRD, TPO, XPS, stability, catalytic combustion
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-6562DOI: 10.1016/j.jcat.2006.10.029ISI: 000243798400016Scopus ID: 2-s2.0-33845951166OAI: oai:DiVA.org:kth-6562DiVA: diva2:11308
Note

QC 20100916

Available from: 2006-12-11 Created: 2006-12-11 Last updated: 2017-12-14Bibliographically 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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