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Effect of Ce-doping on Rh/ZrO2 catalysts for partial oxidation of methane
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: Applied Catalysis A: General, ISSN 0926-860X, E-ISSN 1873-3875, Vol. 326, no 1, 8-16- p.Article in journal (Refereed) Published
Abstract [en]

The partial oxidation of methane over supported (ZrO2, CeO2-ZrO2) rhodium catalysts was investigated at atmospheric pressure. The effect of temperature, CH4/O-2 ratio, catalyst composition and pre-treatment was studied. Ceria doping of the support material resulted in significant improvements concerning the methane conversion and syngas selectivity, which could be related to a higher noble metal dispersion on the Rh/CeO2-ZrO2 catalyst. In addition, the light-off temperature was decreased by 128 degrees C when using CeO2-ZrO2, as support. X-ray photoelectron spectroscopy revealed the presence of different Rh oxidation states depending on catalyst composition and pre-treatment. A stabilization of partially oxidized (Rh delta+) species by ceria could be detected. An active and stable catalyst behavior could be observed for Rh/CeO2-ZrO2, irrespectively of catalyst pre-treatment, whereas an activation period was required for stabilizing the activity of the Rh/ZrO2 catalyst. The activity tests indicate that the indirect reaction mechanism, consisting of methane combustion followed by steam and dry reforming, prevails under the experimental conditions studied.

Place, publisher, year, edition, pages
2007. Vol. 326, no 1, 8-16- p.
Keyword [en]
partial oxidation of methane, Rh catalysts, catalytic combustion, ceria, XPS
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-6640DOI: 10.1016/j.apcata.2007.03.019ISI: 000247812600002Scopus ID: 2-s2.0-34249299771OAI: oai:DiVA.org:kth-6640DiVA: diva2:11404
Note
QC 20110125.Uppdaterad från submitted till published(20110125) Available from: 2006-12-15 Created: 2006-12-15 Last updated: 2017-12-14Bibliographically approved
In thesis
1. Development of catalysts for natural gas-fired gas turbine combustors
Open this publication in new window or tab >>Development of catalysts for natural gas-fired gas turbine combustors
2006 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Due to continuously stricter regulations regarding emissions from power generation processes, further development of existing gas turbine combustors is essential. A promising alternative to conventional flame combustion in gas turbines is catalytic combustion, which can result in ultralow emission levels of NOx, CO and unburned hydrocarbons. The work presented in this thesis concerns the development of methane oxidation catalysts for gas turbine combustors. The application of catalytic combustion to different combustor concepts is addressed in particular.

The first part of the thesis (Paper I) reports on catalyst development for fuel-lean methane combustion. Supported Pd-based catalysts were investigated at atmospheric pressure. The effect on catalytic activity of diluting the reaction mixture with water and/or carbon dioxide was studied in order to simulate a combustion process with exhaust gas recirculation. The catalytic activity was found to decrease significantly in the presence of water and CO2. However, modifying the catalyst by changing support material can have a considerable impact on the performance.

In the second part of this thesis (Papers II-IV), the development of rhodium catalysts for fuel-rich methane combustion is addressed. The effect of catalyst composition, oxygen-to-fuel ratio and catalyst pre-treatment on the methane conversion and the product gas composition was studied. An experimental investigation at elevated pressures of partial oxidation of methane/oxygen mixtures in exhaust gas-rich environments was also conducted. The most suitable catalyst identified for fuel-rich catalytic combustion of methane, i.e. Rh/Ce-ZrO2, showed benefits such as low light-off temperature, high activity and enhanced hydrogen selectivity.

In the final part of the thesis (Paper V), a numerical investigation of fuel-rich catalytic combustion is presented. Measurements and predictions were compared for partial oxidation of methane in exhaust gas diluted mixtures at elevated pressures. The numerical model was validated for several Rh-based catalysts. The key parameter controlling the catalytic performance was found to be the noble metal dispersion.

Place, publisher, year, edition, pages
Stockholm: KTH, 2006. 67 p.
Series
Trita-KET, ISSN 1104-3466 ; R232
Keyword
AZEP, catalytic combustion, CPO, methane oxidation, palladium, rhodium, support effect
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-4239 (URN)91-7178-543-4 (ISBN)978-91-7178-543-5 (ISBN)
Public defence
2006-12-19, D2, D, Lindstedtsvägen 5, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20110125Available from: 2006-12-15 Created: 2006-12-15 Last updated: 2011-01-25Bibliographically approved

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