L’objectif de notre travail, était l’étude de deux classes de catalyseurs dans la réaction d’oxydation totale de COV. L’application visée étant la destruction à basse température de ces traces de polluants dans l’air. Des oxydes mixtes Co3O4-CeO2 ont été préparés par co-précipitation. Avec l’oxyde mixte (% atomique Co/Ce = 1), nous avons obtenu les meilleures performances catalytiques et montré que la réactivité étaient exaltée par une forte mobilité des oxygènes de coeur. Des catalyseurs à base d’or (2wt%) et de palladium (1wt%) ont été déposés sur des supports oxydes comme la cérine et le titane afin de favoriser une interaction métal support, ou sur un support alumine. Des solides à base d’alumine dopée au cérium, manganèse, fer et titane ont également été préparés. Pour l’or, l’évolution des performances catalytiques en fonction du support ont été les suivantes: Au2%/Al2O3 < Au2%/TiO2 < Au2%/CeO2, alors que pour le palladium nous avons obtenu les tendances suivantes : Pd1%/CeO2 < Pd1%/Al2O3 < Pd1%/TiO2. Pour l’Au, l’interaction métal support a permis d’expliquer les différences de réactivité alors que pour le palladium, l’activité est liée aux sites actifs de palladium Pd0/PdO présents à la surface. Avec les systèmes dopés, les résultats ont montré que les meilleurs catalyseurs étaient le Au2%/Ce5%/Al2O3 et le Pd1%/Ce5%/Al2O3. Cette exaltation a été attribuée à la grande mobilité des oxygènes en raison d’un défaut de structure induit par l’insertion des ions Al3+ au sein du réseau de la cérine et une forte interaction des particules très bien dispersées / The aim of the work was to study two classes of catalysts for the complete oxidation of volatile organic compounds. The target application for air pollution control is the total abatement of VOC at low temperature. Mixed oxide Co3O4-CeO2, were prepared by co-precipitation method. Among them, the mixed oxide corresponding to Co/Ce atomic ratio close to 1, was the best performing. The participation of surface oxygen species and high bulk mobile oxygen were the factors determining the high activity of Co30Ce in the total oxidation of propylene and toluene. Au (2wt%) and Pd (1wt%) catalysts were prepared over typical reducible oxides, such as CeO2 and TiO2. For comparison, catalysts over Al2O3, were also prepared. Moreover, the effect on the activity of Au and Pd supported over Al2O3 doped by cerium, manganese, iron and titanium was investigated. The so prepared Au and Pd catalysts were compared in the total oxidation of propylene. It was found that the activity of gold catalysts supported over un-doped oxides varied in the order: Au2%/Al2O3 < Au2%/TiO2 < Au2%/CeO2, while a different trend was observed for palladium catalysts: Pd1%/CeO2 < Pd1%/Al2O3 < Pd1%/TiO2. For Au catalysts, the nature of the support and the extent of interaction with the support are the key factors in determining the activity, whilst for the Pd supported ones, the activity seems to be governed by the nature of Pd species, Pd0/PdO, present in the catalyst. Au2%/Ce5%/Al2O3 and Pd1%/Ce5%/Al2O3 appear the best samples. The enhanced catalytic performances were attributed to high-oxygen mobility due to a defective ceria structure induced by the insertion of Al3+ ions into the lattice and also strong metal-support interaction between nanoparticles highly dispersed

Catalytic combustion is an environmentally benign technologywhich has recently reached the stage of commercialization.Palladium is the catalyst of choice when considering gasturbines fuelled with natural gas because of its superioractivity for methane oxidation. Several fundamental issues arestill open and their understanding would result in animprovement of the technology. Hence, the work presented inthis thesis aims at the identification of some of theparameters which govern the combustion activity ofpalladium-based catalysts. The first part of this work gives a background to catalyticcombustion and a brief comparison with other existingtechnologies. Paper I reviews some of the issues related tomaterial development and combustor design. The second part of this thesis consists of an experimentalinvestigation on palladium-based catalysts. The influence ofthe preparation method onthe properties of these catalystmaterials is investigated in Paper II. Paper III examines theactivity of the following catalysts: Pd/Al2O3, Pd/Ba-Al2O3 andPd/La-Al2O3. Specific attention is given to the metal-supportinteraction which strongly affects the combustion activity ofpalladium. The effect of doping of the support by addition ofcerium is reported in Paper IV. Finally, the deactivation of combustion catalysts isconsidered. The various deactivation processes which may affecthigh temperature combustion catalysts are reviewed in Paper V.Paper VI focuses on the poisoning of supported palladiumcatalysts by sulphur species. Palladium exhibits a higherresistance to sulphur poisoning than transition metals.Nevertheless, the nature of the support material plays animportant role and may entail a severe loss of activity whensulphur is present in the fuel-air mixture entering thecombustion chamber. <b>Keywords</b>: catalytic combustion, gas turbine, methane,palladium, alumina, barium, lanthanum, oxidation, preparation,temperature-programmed oxidation (TPO), decomposition,reoxidation, X-ray photoelectron spectroscopy (XPS),metal-support interaction, deactivation, sulphur, poisoning.The cover illustration is a TEM picture of a 100 nm palladiumparticle supported on alumina

This thesis concerns catalytic combustion for gas turbineapplication using a low heating-value (LHV) gas, derived fromgasified waste. The main research in catalytic combustionfocuses on methane as fuel, but an increasing interest isdirected towards catalytic combustion of LHV fuels. This thesisshows that it is possible to catalytically combust a LHV gasand to oxidize fuel-bound nitrogen (NH3) directly into N2without forming NOX. The first part of the thesis gives abackground to the system. It defines waste, shortly describesgasification and more thoroughly catalytic combustion. The second part of the present thesis, paper I, concerns thedevelopment and testing of potential catalysts for catalyticcombustion of LHV gases. The objective of this work was toinvestigate the possibility to use a stable metal oxide insteadof noble metals as ignition catalyst and at the same timereduce the formation of NOX. In paper II pilot-scale tests werecarried out to prove the potential of catalytic combustionusing real gasified waste and to compare with the resultsobtained in laboratory scale using a synthetic gas simulatinggasified waste. In paper III, selective catalytic oxidation fordecreasing the NOX formation from fuel-bound nitrogen wasexamined using two different approaches: fuel-lean andfuel-rich conditions. Finally, the last part of the thesis deals with deactivationof catalysts. The various deactivation processes which mayaffect high-temperature catalytic combustion are reviewed inpaper IV. In paper V the poisoning effect of low amounts ofsulfur was studied; various metal oxides as well as supportedpalladium and platinum catalysts were used as catalysts forcombustion of a synthetic gas. In conclusion, with the results obtained in this thesis itwould be possible to compose a working catalytic system for gasturbine application using a LHV gas. <b>Keywords:</b>Catalytic combustion; Gasified waste; LHVfuel; RDF; Biomass; Selective catalytic oxidation; NH3; NOX;Palladium; Platinum; Hexaaluminate; Garnet; Spinel;Deactivation; Sulfur; Poisoning

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. / QC 20100916

<p>Catalytic combustion is a promising combustion technique in gas turbines, which results in ultra low levels of NO_x, CO and unburned hydrocarbons. Due to the low combustion temperature achieved in catalytic combustion almost no thermal NOx is formed. The focus in this thesis will be 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 with time during operation. The unstable activity will result in increasing difficulties to ignite the fuel. The objective of the work presented in this thesis has been to improve the catalytic performance of supported palladium catalysts, with focus on stabilizing the methane conversion.</p><p>The first part gives a general background to gas turbines and catalytic combustion.</p><p>The second part concerns the monometallic palladium catalysts; their behaviour during methane combustion is addressed.</p><p>The third part describes different bimetallic catalysts, which all have palladium as one of the active components. Results from the activity tests of methane combustion showed that it is possible to stabilize the activity by adding certain co-metals into the palladium catalyst. The morphology of the various bimetallic catalysts has been studied to gain a better understanding of the various combustion behaviours.</p><p>Finally, the influence of pressure on the catalytic performance is evaluated. The catalysts were tested under more realistic conditions for gas turbines, with elevated pressure, in a high-pressure test facility with a 100 kW fuel power.</p>

<p>Catalytic combustion is an environmentally benign technologywhich has recently reached the stage of commercialization.Palladium is the catalyst of choice when considering gasturbines fuelled with natural gas because of its superioractivity for methane oxidation. Several fundamental issues arestill open and their understanding would result in animprovement of the technology. Hence, the work presented inthis thesis aims at the identification of some of theparameters which govern the combustion activity ofpalladium-based catalysts.</p><p>The first part of this work gives a background to catalyticcombustion and a brief comparison with other existingtechnologies. Paper I reviews some of the issues related tomaterial development and combustor design.</p><p>The second part of this thesis consists of an experimentalinvestigation on palladium-based catalysts. The influence ofthe preparation method onthe properties of these catalystmaterials is investigated in Paper II. Paper III examines theactivity of the following catalysts: Pd/Al2O3, Pd/Ba-Al2O3 andPd/La-Al2O3. Specific attention is given to the metal-supportinteraction which strongly affects the combustion activity ofpalladium. The effect of doping of the support by addition ofcerium is reported in Paper IV.</p><p>Finally, the deactivation of combustion catalysts isconsidered. The various deactivation processes which may affecthigh temperature combustion catalysts are reviewed in Paper V.Paper VI focuses on the poisoning of supported palladiumcatalysts by sulphur species. Palladium exhibits a higherresistance to sulphur poisoning than transition metals.Nevertheless, the nature of the support material plays animportant role and may entail a severe loss of activity whensulphur is present in the fuel-air mixture entering thecombustion chamber.</p><p><b>Keywords</b>: catalytic combustion, gas turbine, methane,palladium, alumina, barium, lanthanum, oxidation, preparation,temperature-programmed oxidation (TPO), decomposition,reoxidation, X-ray photoelectron spectroscopy (XPS),metal-support interaction, deactivation, sulphur, poisoning.The cover illustration is a TEM picture of a 100 nm palladiumparticle supported on alumina</p>

<p>This thesis concerns catalytic combustion for gas turbineapplication using a low heating-value (LHV) gas, derived fromgasified waste. The main research in catalytic combustionfocuses on methane as fuel, but an increasing interest isdirected towards catalytic combustion of LHV fuels. This thesisshows that it is possible to catalytically combust a LHV gasand to oxidize fuel-bound nitrogen (NH3) directly into N2without forming NOX. The first part of the thesis gives abackground to the system. It defines waste, shortly describesgasification and more thoroughly catalytic combustion.</p><p>The second part of the present thesis, paper I, concerns thedevelopment and testing of potential catalysts for catalyticcombustion of LHV gases. The objective of this work was toinvestigate the possibility to use a stable metal oxide insteadof noble metals as ignition catalyst and at the same timereduce the formation of NOX. In paper II pilot-scale tests werecarried out to prove the potential of catalytic combustionusing real gasified waste and to compare with the resultsobtained in laboratory scale using a synthetic gas simulatinggasified waste. In paper III, selective catalytic oxidation fordecreasing the NOX formation from fuel-bound nitrogen wasexamined using two different approaches: fuel-lean andfuel-rich conditions.</p><p>Finally, the last part of the thesis deals with deactivationof catalysts. The various deactivation processes which mayaffect high-temperature catalytic combustion are reviewed inpaper IV. In paper V the poisoning effect of low amounts ofsulfur was studied; various metal oxides as well as supportedpalladium and platinum catalysts were used as catalysts forcombustion of a synthetic gas.</p><p>In conclusion, with the results obtained in this thesis itwould be possible to compose a working catalytic system for gasturbine application using a LHV gas.</p><p><b>Keywords:</b>Catalytic combustion; Gasified waste; LHVfuel; RDF; Biomass; Selective catalytic oxidation; NH3; NOX;Palladium; Platinum; Hexaaluminate; Garnet; Spinel;Deactivation; Sulfur; Poisoning</p>

<p>Katalytisk förbränning är en lovande teknik för användning vid kraftgenerering, särskilt för</p><p>gasturbiner. Genom att använda katalytisk förbränning kan man nå mycket låga emissioner av kväveoxider</p><p>(NOX), kolmonoxid (CO) och oförbrända kolväten (UHC) samtidigt, vilket är svårt vid</p><p>konventionell förbränning. Förutom att man erhåller låga emissioner, kan katalytisk förbränning stabilisera</p><p>förbränningen och kan därmed användas för att uppnå stabil förbränning för gaser med låga</p><p>värmevärden. Denna avhandling behandlar huvudsakligen högtemperaturdelen av den katalytiska</p><p>förbränningskammaren. Kraven på denna del har visat sig svåra att nå. För att den katalytiska förbränningskammaren</p><p>ska kunna göras till ett alternativ till den konventionella, måste katalysatorer</p><p>med bättre stabilitet och aktivitet utvecklas.</p><p>Målet med denna avhandling har varit att utveckla katalysatorer med högre aktivitet och stabilitet,</p><p>lämpliga för högtemperaturdelen av en katalytisk förbränningskammare för förbränning av naturgas.</p><p>En mikroemulsionsbaserad framställningsmetod utvecklades för att undersöka om den kunde ge</p><p>katalysatorer med bättre stabilitet och aktivitet. Bärarmaterial som är kända för sin stabilitet, magnesia</p><p>och hexaaluminat, framställdes med den nya metoden. Mikroemulsionsmetoden användes också</p><p>för att impregnera de framställda materialen med de mer aktiva materialen perovskit (LaMnO3) och</p><p>ceriumdioxid (CeO2). Det visade sig att mikroemulsionsmetoden kan användas för att framställa katalysatorer</p><p>med bättre aktivitet jämfört med de konventionella framställningsmetoderna. Genom att</p><p>använda mikroemulsionen för att lägga på aktiva material på bäraren erhölls också en högre aktivitet</p><p>jämfört med konventionella beläggningsstekniker.</p><p>Eftersom katalysatorerna ska användas under lång tid i förbräningskammaren utfördes också en</p><p>åldringsstudie. Som jämförelse användes en av de mest stabila materialen som rapporterats i litteraturen:</p><p>LMHA (mangan-substituerad lantan-hexaaluminat). Resultaten visade att LMHA deaktiverade</p><p>mycket mer jämfört med flera av katalysatorerna innehållande ceriumdioxid på hexaaluminat som</p><p>framställts med den utvecklade mikroemulsionstekniken.</p> / <p>Catalytic combustion is a promising technology for power applications, especially gas turbines.</p><p>By using catalytic combustion ultra low emissions of nitrogen oxides (NO_X), carbon monoxide (CO)</p><p>and unburned hydrocarbons (UHC) can be reached simultaneously, which is very difficult with conventional</p><p>combustion technologies. Besides achieving low emission levels, catalytic combustion can</p><p>stabilize the combustion and thereby be used to obtain stable combustion with low heating-value</p><p>gases. This thesis is focused on the high temperature part of the catalytic combustor. The level of</p><p>performance demanded on this part has been proven hard to achieve. In order to make the catalytic</p><p>combustor an alternative to the conventional flame combustor, more stable catalysts with higher activity</p><p>have to be developed.</p><p>The objective of this work was to develop catalysts with higher activity and stability, suitable</p><p>for the high-temperature part of a catalytic combustor fueled by natural gas. A microemulsion-based</p><p>preparation method was developed for this purpose in an attempt to increase the stability and activity</p><p>of the catalysts. Supports known for their stability, magnesia and hexaaluminate, were prepared using</p><p>the new method. The microemulsion method was also used to impregnate the prepared material with</p><p>the more active materials perovskite (LaMnO₃) and ceria (CeO₂). It was shown that the microemulsion</p><p>method could be used to prepare catalysts with better activity compared to the conventional</p><p>methods. Furthermore, by using the microemulsion to apply active materials onto the support a</p><p>significantly higher activity was obtained than when using conventional impregnation techniques.</p><p>Since the catalysts will operate in the catalytic combustor for extended periods of time under</p><p>harsh conditions, an aging study was performed. One of the most stable catalysts reported in the</p><p>literature, LMHA (manganese-substituted lanthanum hexaaluminate), was included in the study for</p><p>comparison purposes. The results show that LMHA deactivated much more strongly compared to</p><p>several of the catalysts consisting of ceria supported on lanthanum hexaaluminate prepared by the</p><p>developed microemulsion method.</p>

Catalytic combustion is a promising combustion technique in gas turbines, which results in ultra low levels of NOx, CO and unburned hydrocarbons. Due to the low combustion temperature achieved in catalytic combustion almost no thermal NOx is formed. The focus in this thesis will be 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 with time during operation. The unstable activity will result in increasing difficulties to ignite the fuel. The objective of the work presented in this thesis has been to improve the catalytic performance of supported palladium catalysts, with focus on stabilizing the methane conversion. The first part gives a general background to gas turbines and catalytic combustion. The second part concerns the monometallic palladium catalysts; their behaviour during methane combustion is addressed. The third part describes different bimetallic catalysts, which all have palladium as one of the active components. Results from the activity tests of methane combustion showed that it is possible to stabilize the activity by adding certain co-metals into the palladium catalyst. The morphology of the various bimetallic catalysts has been studied to gain a better understanding of the various combustion behaviours. Finally, the influence of pressure on the catalytic performance is evaluated. The catalysts were tested under more realistic conditions for gas turbines, with elevated pressure, in a high-pressure test facility with a 100 kW fuel power.

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. / 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. / QC 20101104