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Nanotemplated High-Temperature Materials for Catalytic Combustion
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

Catalytic combustion is a promising technology for heat and power applications, especially gas turbines. By using catalytic combustion ultra low emissions of nitrogen oxides (NOX), carbon monoxide (CO) and unburned hydrocarbons (UHC) can be reached simultaneously, which is very difficult with conventional combustion technologies. Besides achieving low emission levels, catalytic combustion can stabilize the combustion and thereby be used to obtain stable combustion with low heating-value gases. This thesis is focused on the high-temperature part of the catalytic combustor. The level of performance demanded on this part has proven hard to achieve. In order to make the catalytic combustor an alternative to the conventional flame combustor, more stable catalysts with higher activity have to be developed.

The objective of this work was to develop catalysts with higher activity and stability, suitable for the high-temperature part of a catalytic combustor fueled by natural gas. Two template-based preparation methods were developed for this purpose. One method was based on soft templates (microemulsion) and the other on hard templates (carbon). Supports known for their stability, magnesia and hexaaluminate, were prepared using the developed methods. Catalytically active materials, perovskite (LaMnO3) and ceria (CeO2), were added to the supports in order to obtain catalysts with high activities and stabilities. The supports were impregnated with active materials by using a conventional technique as well as by using the microemulsion technique.

It was shown that the microemulsion method can be used to prepare catalysts with higher activity compared to the conventional methods. Furthermore, by using a microemulsion to apply active materials onto the support a significantly higher activity was obtained than when using the conventional impregnation technique. Since the catalysts will operate in the catalytic combustor for extended periods of time under harsh conditions, an aging study was performed on selected catalysts prepared by the microemulsion technique. The stability of the catalysts was assessed by measuring the activity before and after aging at 1000 C in humid air for 100 h. One of the most stable catalysts reported in the literature, LMHA (manganese-substituted lanthanum hexaaluminate), was included in the study for comparative purposes. The results showed that LMHA deactivated much more strongly compared to several of the catalysts consisting of ceria supported on lanthanum hexaaluminate prepared by the developed microemulsion method.

Carbon templating was shown be a very good technique for the preparation of high-surface-area hexaaluminates with excellent sintering resistance. It was found that the pore size distribution of the carbon used as template was a crucial parameter in the preparation of hexaaluminates. When a carbon with small pores was used as template, the formation of the hexaaluminate crystals was strongly inhibited. This resulted in a material with poor sintering resistance. On the other hand, if a carbon with larger pores was used as template, it was possible to prepare materials with hexaaluminate as the major phase. These materials were, after accelerated aging at 1400 C in humid air, shown to retain surface areas twice as high as reported for conventionally prepared materials.

Place, publisher, year, edition, pages
Stockholm: KTH , 2008. , xiii, 76 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2008:46
Keyword [en]
Carbon templating, Catalytic combustion, Ceria, Gas turbine, Hexaaluminate, Magnesia, Methane, Microemulsion, Perovskite
National Category
Chemical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-4800ISBN: 978-91-7415-019-3 (print)OAI: oai:DiVA.org:kth-4800DiVA: diva2:14033
Public defence
2008-06-13, D1, Huvudbyggnaden, Lindstedtsvägen 17, Stockholm, 10:00
Opponent
Supervisors
Note
QC 20100719Available from: 2008-06-04 Created: 2008-06-04 Last updated: 2010-07-19Bibliographically approved
List of papers
1. Recent developments in the application of nanoparticles prepared from w/o microemulsions in heterogeneous catalysis
Open this publication in new window or tab >>Recent developments in the application of nanoparticles prepared from w/o microemulsions in heterogeneous catalysis
2008 (English)In: Current Opinion in Colloid & Interface Science, ISSN 1359-0294, Vol. 13, no 4, 270-286 p.Article in journal (Refereed) Published
Abstract [en]

This paper reviews the use of microemulsions, especially the water-in-oil (w/o) microemulsions, for preparation of nanoparticles that are employed as catalyst components in heterogeneous catalytic reactions. The objective is to show the growing interest of using microemulsions in the preparation of different types of materials such as metals, single metal oxides or mixed metal oxides with a broad range of application in heterogeneous catalysis and also in electrocatalysis. In most cases, the catalytic material showed improved catalytic properties as a result of the special synthesis environment created by the microemulsions. Still, research is needed for a better understanding of such beneficial effects. In addition, this method needs improvements in order to produce, in an environmentally friendly way, a suitable amount of material for use in industrial-scale catalytic processes.

Keyword
microemulsion; heterogeneous catalysis; nanoparticles; catalyst preparation
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-8647 (URN)10.1016/j.cocis.2007.10.001 (DOI)000257565700010 ()2-s2.0-44949250032 (Scopus ID)
Note
QC 20100719Available from: 2008-06-04 Created: 2008-06-04 Last updated: 2010-07-19Bibliographically approved
2. Synthesis of barium hexaaluminate by co-precipitation in microemulsion
Open this publication in new window or tab >>Synthesis of barium hexaaluminate by co-precipitation in microemulsion
(English)In: Materials Chemistry and Physics, ISSN 0254-0584Article in journal (Other academic) Submitted
Keyword
barium hexaaluminate; reverse microemulsion; hydrothermal treatment; calcination
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-8648 (URN)
Note
QS 20120326Available from: 2008-06-04 Created: 2008-06-04 Last updated: 2012-03-26Bibliographically approved
3. Catalytic combustion of methane over perovskite supported on lanthanum hexaaluminate prepared through the microemulsion method
Open this publication in new window or tab >>Catalytic combustion of methane over perovskite supported on lanthanum hexaaluminate prepared through the microemulsion method
2007 (English)In: Studies in Surface Science and Catalysis, ISSN 0167-2991, Vol. 172, 465-468 p.Article in journal (Refereed) Published
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-8649 (URN)
Note
QC 20100716Available from: 2008-06-04 Created: 2008-06-04 Last updated: 2010-07-16Bibliographically approved
4. Stability of hexaaluminate-based catalysts for high-temperature catalytic combustion of methane
Open this publication in new window or tab >>Stability of hexaaluminate-based catalysts for high-temperature catalytic combustion of methane
2008 (English)In: Applied Catalysis B: Environmental, ISSN 0926-3373, E-ISSN 1873-3883, Vol. 84, no 1-2, 241-250 p.Article in journal (Refereed) Published
Abstract [en]

Lanthanum hexaaluminate with a nominal composition of LaAl11O18 Was used to support 20 wt.% of LaMnO3 and CeO2. LaAl11O18 was prepared through co-precipitation of metal nitrates within the water phase of an isooctane/CFAB/1-butanol microemulsion. The stabilities of the prepared catalysts were assessed by measuring the activities for combustion of methane before and after aging at 1000 degrees C for 100h in air with 10 vol.% H2O. The activities were compared with LaMnAl11O19, due to its well-documented stability. It was shown that by using hydrothermal treatment of the microemulsion, a significantly higher surface area was obtained for the LaAl11O18. For LaMnO3, the reference support (Al2O3) was shown to be superior to LaAl11O18 as support, both in terms of activity and stability. Reactions between LaMnO3 and support were observed for all supports included in the study. For CeO2, LaAl11O18 was superior to Al2O3 as support. Deactivations of the CeO2 catalysts were linked to crystal growth of CeO2. LMHA deactivated strongly during aging; LaMnO3 on Al2O3 and several of the catalysts with CeO2 supported on LaAl11O18 showed a much more stable behavior.

Keyword
Catalytic combustion; Hexaaluminate; Methane; LaMnO3; CeO2; Microemulsion
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-7062 (URN)10.1016/j.apcatb.2008.04.002 (DOI)000260728300031 ()2-s2.0-52049125463 (Scopus ID)
Note
QC 20100719. Uppdaterad från submitted till published (20100719).Available from: 2007-05-08 Created: 2007-05-08 Last updated: 2010-07-19Bibliographically approved
5. Microemulsion synthesis of MgO-supported LaMnO3 for catalytic combustion of methane
Open this publication in new window or tab >>Microemulsion synthesis of MgO-supported LaMnO3 for catalytic combustion of methane
2006 (English)In: Catalysis Today, ISSN 0920-5861, E-ISSN 1873-4308, Vol. 117, no 4, 484-490 p.Article in journal (Refereed) Published
Abstract [en]

Catalysts with 20% LaMnO3 supported on MgO have been prepared via CTAB-1-butanol-iso-octane-nitrate salt microemulsion. The preparation method was successfully varied in order to obtain different degrees of interaction between LaMnO3 and MgO as shown by TPR and activity tests after calcination at 900 degrees C. Activity was tested on structured catalysts with 1.5% CH4 in air as test gas giving a GHSV of 100,000 h(-1). The activity was greatly enhanced by supporting LaMnO3 on MgO compared with the bulk LaMnO3. After calcination at 1100 degrees C both the surface area and TPR profiles were similar, indicating that the preparation method is of little importance at this high temperature due to interaction between the phases. Pure LaMmO(3) and MgO were prepared using the same microemulsion method for comparison purposes. Pure MgO showed an impressive thermal stability with a BET surface area exceeding 30 m(2)/g after calcination at 1300 degrees C. The method used to prepare pure LaMnO3 appeared not to be suitable since the surface area dropped to 1.1 m(2)/g already after calcination in 900 degrees C.

Keyword
catalytic combustion; methane; LaMnO3; MgO; microemulsion
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-7060 (URN)10.1016/j.cattod.2006.06.014 (DOI)000241085000014 ()2-s2.0-33748466713 (Scopus ID)
Note
QC 20100716Available from: 2007-05-08 Created: 2007-05-08 Last updated: 2011-09-28Bibliographically approved
6. High-surface-area lanthanum hexaaluminates by carbon templating
Open this publication in new window or tab >>High-surface-area lanthanum hexaaluminates by carbon templating
(English)Article in journal (Other academic) Submitted
Keyword
carbon templating; lanthanum hexaaluminate; carbon xerogel; activated carbon; catalytic combustion
National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-8652 (URN)
Note
QS 20120326Available from: 2008-06-04 Created: 2008-06-04 Last updated: 2012-03-26Bibliographically approved
7. Preparation of hexaaluminate
Open this publication in new window or tab >>Preparation of hexaaluminate
2008 (English)Patent (Other (popular science, discussion, etc.))
Abstract [en]

A method for preparing a hexaaluminate. The method comprises the steps of a) providing a porous template material, wherein pores having a pore size of about 5-200 nm form at least about 50% of the total pore volume; b) impregnating the material with a liquid comprising metal elements corresponding to the elements of said hexaaluminate to provide an impregnated material; c) drying the impregnated material to provide a dried material; d) optionally, repeating at least once step b), using the dried material, and step c); e) calcining the dried material in an inert atmosphere to provide a calcined material; and f) recovering the hexaaluminate by removing template material from the calcined material. A composition obtainable by such a method. A catalyst composition comprising a hexaaluminate, wherein the composition has an average surface area of at least about 9 m2/g after ageing of the composition in a moist high-temperature atmosphere. A supported catalyst comprising such a composition. Use of such a composition as a catalyst in a high-temperature application.

National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-8653 (URN)
Patent
EP 2119671A1
Note

QS 2015

Available from: 2008-06-04 Created: 2008-06-04 Last updated: 2015-01-21Bibliographically approved

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