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Nanomaterials for high-temperature catalytic combustion
KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology.
2007 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [sv]

Katalytisk förbränning är en lovande teknik för användning vid kraftgenerering, särskilt för gasturbiner. Genom att använda katalytisk förbränning kan man nå mycket låga emissioner av kväveoxider (NOX), kolmonoxid (CO) och oförbrända kolväten (UHC) samtidigt, vilket är svårt vid konventionell förbränning. Förutom att man erhåller låga emissioner, kan katalytisk förbränning stabilisera förbränningen och kan därmed användas för att uppnå stabil förbränning för gaser med låga värmevärden.

Denna avhandling behandlar huvudsakligen högtemperaturdelen av den katalytiska förbränningskammaren. Kraven på denna del har visat sig svåra att nå. För att den katalytiska förbränningskammaren ska kunna göras till ett alternativ till den konventionella, måste katalysatorer med bättre stabilitet och aktivitet utvecklas.

Målet med denna avhandling har varit att utveckla katalysatorer med högre aktivitet och stabilitet, lämpliga för högtemperaturdelen av en katalytisk förbränningskammare för förbränning av naturgas.

En mikroemulsionsbaserad framställningsmetod utvecklades för att undersöka om den kunde ge katalysatorer med bättre stabilitet och aktivitet. Bärarmaterial som är kända för sin stabilitet, magnesia och hexaaluminat, framställdes med den nya metoden. Mikroemulsionsmetoden användes också för att impregnera de framställda materialen med de mer aktiva materialen perovskit (LaMnO3) och ceriumdioxid (CeO2). Det visade sig att mikroemulsionsmetoden kan användas för att framställa katalysatorer med bättre aktivitet jämfört med de konventionella framställningsmetoderna. Genom att använda mikroemulsionen för att lägga på aktiva material på bäraren erhölls också en högre aktivitet jämfört med konventionella beläggningsstekniker.

Eftersom katalysatorerna ska användas under lång tid i förbräningskammaren utfördes också en åldringsstudie. Som jämförelse användes en av de mest stabila materialen som rapporterats i litteraturen: LMHA (mangan-substituerad lantan-hexaaluminat). Resultaten visade att LMHA deaktiverade mycket mer jämfört med flera av katalysatorerna innehållande ceriumdioxid på hexaaluminat som framställts med den utvecklade mikroemulsionstekniken.

Abstract [en]

Catalytic combustion is a promising technology for 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 been 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. A microemulsion-based preparation method was developed for this purpose in an attempt to increase the stability and activity of the catalysts. Supports known for their stability, magnesia and hexaaluminate, were prepared using the new method. The microemulsion method was also used to impregnate the prepared material with the more active materials perovskite (LaMnO3) and ceria (CeO2). It was shown that the microemulsion method could be used to prepare catalysts with better activity compared to the conventional methods. Furthermore, by using the microemulsion to apply active materials onto the support a significantly higher activity was obtained than when using conventional impregnation techniques.

Since the catalysts will operate in the catalytic combustor for extended periods of time under harsh conditions, an aging study was performed. One of the most stable catalysts reported in the literature, LMHA (manganese-substituted lanthanum hexaaluminate), was included in the study for comparison purposes. The results show 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.

Place, publisher, year, edition, pages
Stockholm: KTH , 2007. , xii, 67 p.
Series
Trita-CHE-Report, ISSN 1654-1081 ; 2007:24
Keyword [en]
catalytic combustion, microemulsion, hexaaluminate, magnesia, perovskite, ceria, methane, gas turbine
Keyword [sv]
katalytisk förbränning, mikroemulsion, hexaaluminat, magnesia, perovskit, ceriumdioxid, metan, gasturbin
National Category
Chemical Process Engineering
Identifiers
URN: urn:nbn:se:kth:diva-4360ISBN: 978-91-7178-656-2 (print)OAI: oai:DiVA.org:kth-4360DiVA: diva2:11958
Presentation
2007-05-16, 593, Teknikringen 42, 100 44 Stockholm, 14:00
Supervisors
Note
QC 20101104Available from: 2007-05-08 Created: 2007-05-08 Last updated: 2010-11-04Bibliographically approved
List of papers
1. 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: 2017-12-14Bibliographically approved
2. 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: 2017-12-14Bibliographically approved
3. 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: 2017-12-14Bibliographically approved

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