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Catalytic combustion of methane over bimetallic Pd-Pt catalysts: The influence of support materials
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: Applied Catalysis B: Environmental, ISSN 0926-3373, Vol. 66, 175-185 p.Article in journal (Refereed) Published
Abstract [en]

The effect of support material on the catalytic performance for methane combustion has been studied for bimetallic palladium-platinum catalysts and compared with a monometallic palladium catalyst on alumina. The catalytic activities of the various catalysts were measured in a tubular reactor, in which both the activity and stability of methane conversion were monitored. In addition, all catalysts were analysed by temperature-programmed oxidation and in situ XRD operating at high temperatures in order to study the oxidation/reduction properties.

The activity of the monometallic palladium catalyst decreases under steady-state conditions, even at a temperature as low as 470 degrees C. In situ XRD results showed that no decomposition of bulk PdO into metallic palladium occurred at temperatures below 800 degrees C. Hence, the reason for the drop in activity is probably not connected to the bulk PdO decomposition.

All Pd-Pt catalysts, independently of the support, have considerably more stable methane conversion than the monometallic palladium catalyst. However. dissimilanties in activity and ability to reoxidise PdO were observed for the various support materials. Pd-Pt supported on Al2O3 was the most active catalyst in the low-temperature region, Pd-Pt supported on ceria-stabilised ZrO2 was the most active between 620 and 800 degrees C, whereas Pd-Pt supported on LaMnAl11O19 was superior for temperatures above 800 degrees C. The ability to reoxidise metallic Pd into PdO was observed to vary between the supports. The alumina sample showed a very slow reoxidation, whereas ceria-stabilised ZrO2 was clearly faster

Place, publisher, year, edition, pages
2006. Vol. 66, 175-185 p.
Keyword [en]
palladium, platinum, bimetal, catalytic combustion, zirconia, alumina, hexaaluminate, ceria, yttria, methane
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-6561DOI: 10.1016/j.apcatb.2006.03.010ISI: 000238331300004Scopus ID: 2-s2.0-33646787467OAI: oai:DiVA.org:kth-6561DiVA: diva2:11307
Note

QC 20100916

Available from: 2006-12-11 Created: 2006-12-11 Last updated: 2017-06-13Bibliographically 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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