This work is concerning the study of model ceria based calalysts structure by methods of electron diffraction RHEED and photoelectron spectroscopy XPS. The influence of deposition conditions and substrate on the growth of epitaxial cerium oxide films on copper single crystals is described in detail. The work then describes the interaction of cerium and tin in model systems and the creation of SnCeOx mixed oxide and its structure. In the last chapter, the interaction of palladium with cerium and tin oxide layers is examined, and the creation of paladium bimetallic alloys is described. Powered by TCPDF (www.tcpdf.org)

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<p>The reprocessing of spent fuel is a key component in reducing the end waste from nuclear power plant operations and creating a sustainable closed fuel cycle. Central to this effort is the extraction and reprocessing of actinide materials to be recycled into fast or thermal reactors. Reprocessed actinides can contribute additional energy and may be partially transmuted in current thermal systems using mixed oxide fuels before being sent to fast reactors. The use of current thermal reactors as an intermediary step significantly reduces the fast reactor infrastructure needed to handle the spent fuel inventory in the long term, and also provides a source of additional energy from existing mined resources in the short term. An optimization of the fast and thermal systems in a closed fuel cycle reduces the end cycle waste to primarily fission products which have little residual value and manageable disposal and monitoring demands. The dissertation explores the design and analysis of an actinide transmutation solution utilizing a current thermal reactor design. The TRUMOX-30 CANDU-900 system defined herein uses a mixed oxide fuel containing 3.1% transuranic actinides extracted from 30 year cooled spent fuel from a prototypical Pressurized Water Reactor (PWR) and mixed with natural uranium. A significant constraint imposed on the design is that the actinide burning is to occur in an existing CANDU design without major changes or infrastructure replacement. Hence the standard CANDU design and analysis methodology was employed to produce and evaluate the system. The phased approach includes extensive neutron transport modeling of the lattice and control device super-cell configurations, which feed forward in to a detailed full core diffusion model of the TRUMOX-30 CANDU-900 design. Suitable fuel burnup and significant actinide conversion was achieved while remaining within the prescribed operational envelope of the CANDU reactor. The design was evaluated against existing operational constraints and limits, performing well and achieving the goal of actinide transmutation with no changes to the reactor design. This effort demonstrated the adaptation of a current CANDU-900 reactor as a platform for intermediary actinide transmutation which may form part of a sustainable and efficient fuel cycle.</p> / Doctor of Philosophy (PhD)

Les oxydes mixtes de cérium-zirconium sont au cœur de nombreux sujets de recherche. En effet, ces matériaux sont utilisés dans différents domaines d'application, et tout particulièrement en catalyse, dans les catalyseurs trois voies en automobile ou pour l'oxydation de polluants organiques. L'intérêt pour ce composé réside dans ses propriétés remarquables d'oxydoréduction, sa capacité de stockage de l'oxygène et sa résistance au frittage. En conséquence, un nombre important de méthodes de synthèse ont été mises au point et soulignent la grande sensibilité de cet oxyde mixte à la voie de préparation employée. Dans le cadre de ce travail deux grandes voies de synthèses ont été utilisées, la co-précipitation (milieu aqueux) et la dégradation des -dicétonates métalliques (milieu non aqueux). Ces synthèses ont été réalisées à l'aide de plusieurs techniques que sont (i) le chauffage à pression atmosphérique, (ii) le traitement hydrothermal, (iii) la sonolyse et (iv) la combinaison de la sonolyse et du traitement hydrothermal, de façon successive ou en simultané. Afin de pouvoir réaliser cette dernière méthode de synthèse innovante, un réacteur permettant de réaliser un traitement sonochimique en température et sous pression a été développé (réacteur sonothermal). L'activité chimique des ultrasons dans ces conditions a pu être mise en évidence lors de la sonolyse de l'eau (légère ou lourde) et de celle d'un hydrocarbure. Au cours de la préparation de (Ce,Zr)O2, des paramètres autres que le dispositif de synthèse ont été étudiés, comme la présence d'un surfactant ou la longueur de chaine du solvant. Ainsi, il a pu être démontré que, dans le cas de la voie aqueuse, l'utilisation du réacteur sonothermal a une réelle incidence sur la surface spécifique du matériau final en comparaison de la réalisation successive des traitements sonochimique et hydrothermal. Les oxydes présentant les propriétés structurales les plus intéressantes ont été sélectionnés afin d'être employé en tant que support de métal noble dans des catalyseurs de type Pt/(Ce,Zr)O2. L'évaluation de l'activité catalytique de ces matériaux, lors de l'oxydation catalytique à l'air humide de l'acide formique, a montré que celle-ci dépend non seulement du mode de synthèse de l'oxyde mixte, mais également de la voie de dépôt du platine et du couple méthode de dépôt du platine/méthode de synthèse du support. / Cerium-zirconium mixed oxides are at the heart of numerous research subjects. Indeed, these materials are used in different fields of application, and particularly in catalysis in three-way catalyst for automobile or for organic pollutant oxidation. The interest for this compound resides in its remarkable oxidoreduction properties, its oxygen storage capacity and its resistance to sintering. Consequently, numerous preparation methods have been developed and underline the high sensitivity of these oxides to the synthesis way. In the present work, two main synthesis have been employed, coprecipitation (aqueous medium) and  diketonate degradation (non-aqueous medium). These syntheses have been realized with several techniques which are (i) heating at atmospheric pressure, (ii) hydrothermal treatment, (iii) sonolysis and (iv) combination of sonolysis and hydrothermal treatments, in a successive or simultaneous way. In order to realize this last and innovative method, a reactor allowing sonochemical treatment under high temperature and pressure has been developed. Under these conditions, the ultrasounds chemical activity has been proved during light or heavy water or hydrocarbon sonolysis. During the (Ce,Zr)O2 preparation, other parameters than the synthesis technique have been studied such as the surfactant presence or the solvent chain length. Thus, it has been shown that, in the case of aqueous synthesis, the use of the sonothermal reactor has a real effect on the specific surface area of the material in comparison of successive realization of sonochemical and hydrothermal treatments. Oxides with the more interesting structural properties have been selected for being used as supports of noble metal in the Pt/(Ce,Zr)O2 catalysts. The evaluation of the catalytic activity of these materials, during the catalytic wet air oxidation of formic acid, showed that it not only depends on the synthesis method, but also on the platinum deposition method and the pair platinum deposition method/support synthesis method.

Partículas nanométricas de óxidos têm despertado um grande interesse devido a ampla gama de aplicações, por exemplo em catálise, óptica, sensores de gases, semicondutores, entre outros. Por isso, há vários estudos para uma grande variedade de óxidos com composição MO2, em função do tamanho e terminação da superfície. Também existe um grande interesse no estudo de óxidos mistos devido a possibilidade de combinar dois ou mais óxidos em escala nanométrica, com objetivo de controlar as propriedades físicas e químicas em função da composição. Neste trabalho, utilizou-se os metais Ce e Zr, uma vez que os óxidos desses elementos têm um grande potencial de aplicação na indústria como em células combustíveis, reações catalíticas entre outros. Os óxidos mistos Cem-nZrnO2mpossuem a capacidade de armazenar ou liberar oxigênio ao longo de reações químicas, e portanto, são largamente empregados em catalisadores de três-vias na indústria automobilística. Neste estudo foi empregada a teoria do funcional da densidade (DFT) com o funcional de troca-correlação proposto por Perdew, Burke e Ernzerhof (PBE). Investigou-se as propriedades estruturais, energéticas e eletrônicas dos clusters puros e então, selecionou-se quatro estruturas, as quais foram aplicadas na construção dos clusters de óxidos mistos de céria-zircônia. Por meio dos estudos de eletronegatividade de Mulliken, verificou-se que os clusters de zircônia apresentam uma tendência maior em atrair elétrons, quando comparados aos clusters de céria. Observou-se também que as estruturas de mais baixa energia de céria e zircônia apresentam diferentes números de coordenação (CN), no caso 4 e 3 NNN (vizinhos mais próximos), respectivamente. Isso se deve ao fato de tais estruturas não serem esféricas e também aos diferentes tamanhos atômicos de Ce e Zr. Além disso, notou-se que há uma maior compactação dos clusters de menor energia se comparados aos de maior energia, tanto para o céria quanto para zircônia, obteve-se os seguintes valores de diâmetro 1 nm e 2 nm para essa variação da energia relativa. Com esses resultados tem-se que há uma propensão dos clusters mistos, manterem propriedades semelhantes dos cluster puros, devido a similaridade entre o comportamento das estruturas de céria e da zircônia, os quais foram os agentes geradores dos clusters mistos. Observou-se que as propriedades estruturais dos cluster puros como CN, dav, &sigma; e raio, mantiveram-se com a mesmas tendências nos clusters mistos. Para a obtenção do cluster mais estável analisou-se a energia de formação dos sistemas, sendo que a configuração mais favorável de ser formada é a Ce0,27Zr0,73O2, a qual considerou-se a estrutura pGMC representativa das configurações estudadas. Levando-se em consideração os resultados obtidos, na análise de formação dos clusters mistos delimitou-se a região de maior probabilidade de formação de clusters mistos estáveis entre 25% a 60%, de cério na composição. / Oxide nanomaterials have aroused great interest due to their application in several fields, such as in catalysis, optics, gas sensors, semiconductors, among others. Therefore, there are several studies for a wide variety of oxides with composition, and MO2, depending on the size and surface termination. There is also great interest in the study of mixed oxides due to the possibility of combining two or more oxides on a nanometric scale, in order to control their physical and chemical properties. In this work the metals Ce and Zr were used, since the oxides of these elements have a promising application in the industry as in fuel cells, catalytic reactions among others. The mixed oxides Cem-nZrnO2m present the ability to store or release oxygen during chemical reactions and therefore are widely used in three-way catalysts in the automotive industry. In this study, we used density functional theory (DFT) with PBE for the exchange-correlation functional. To investigate the structural, electronic and energetic properties of clusters, four selected structures were applied to build up the mixed ceria-zirconia oxides. Through the Mulliken electronegativity studies, it was found that zirconia clusters have a greater tendency to attract electrons, than the ceria clusters. Also observed that the lowest energy structures of ceria and zirconia have different coordination numbers, 4 and 3 NNN (Number of Nearest Neighbours), respectively. This is due to the fact that such structures are not spherical and have different atomic sizes. In addition, it was noted that there is a higher compaction of the clusters of lower energy compared to higher energy, for both ceria and zirconia, it was obtained the following values of diameter 1 nm and 2 nm for this variation of relative energy change. These results show that there is a trend in which mixed clusters have similar properties of the pure cluster, due to the similarity between the behavior of the structures of ceria and zirconia, which were the generating agents of the mixed clusters. It was observed that the structural properties of the pure clusters like CN, dav, &sigma; and cluster radii, remained with the same trends in the mixed clusters. To obtain the most stable clusters we analyzed the formation energy of the systems, the most favorable configuration to be obtained is Ce0,27Zr0,73O2, which was considered the representative pGMC structure of the studied configurations. Taking into consideration the results, obtained in the analysis of the formation of the mixed clusters, delimited the higher probability of formation of mixed stable clusters between 25% to 60%, of cerium in composition.

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Partículas nanométricas de óxidos têm despertado um grande interesse devido a ampla gama de aplicações, por exemplo em catálise, óptica, sensores de gases, semicondutores, entre outros. Por isso, há vários estudos para uma grande variedade de óxidos com composição MO2, em função do tamanho e terminação da superfície. Também existe um grande interesse no estudo de óxidos mistos devido a possibilidade de combinar dois ou mais óxidos em escala nanométrica, com objetivo de controlar as propriedades físicas e químicas em função da composição. Neste trabalho, utilizou-se os metais Ce e Zr, uma vez que os óxidos desses elementos têm um grande potencial de aplicação na indústria como em células combustíveis, reações catalíticas entre outros. Os óxidos mistos Cem-nZrnO2mpossuem a capacidade de armazenar ou liberar oxigênio ao longo de reações químicas, e portanto, são largamente empregados em catalisadores de três-vias na indústria automobilística. Neste estudo foi empregada a teoria do funcional da densidade (DFT) com o funcional de troca-correlação proposto por Perdew, Burke e Ernzerhof (PBE). Investigou-se as propriedades estruturais, energéticas e eletrônicas dos clusters puros e então, selecionou-se quatro estruturas, as quais foram aplicadas na construção dos clusters de óxidos mistos de céria-zircônia. Por meio dos estudos de eletronegatividade de Mulliken, verificou-se que os clusters de zircônia apresentam uma tendência maior em atrair elétrons, quando comparados aos clusters de céria. Observou-se também que as estruturas de mais baixa energia de céria e zircônia apresentam diferentes números de coordenação (CN), no caso 4 e 3 NNN (vizinhos mais próximos), respectivamente. Isso se deve ao fato de tais estruturas não serem esféricas e também aos diferentes tamanhos atômicos de Ce e Zr. Além disso, notou-se que há uma maior compactação dos clusters de menor energia se comparados aos de maior energia, tanto para o céria quanto para zircônia, obteve-se os seguintes valores de diâmetro 1 nm e 2 nm para essa variação da energia relativa. Com esses resultados tem-se que há uma propensão dos clusters mistos, manterem propriedades semelhantes dos cluster puros, devido a similaridade entre o comportamento das estruturas de céria e da zircônia, os quais foram os agentes geradores dos clusters mistos. Observou-se que as propriedades estruturais dos cluster puros como CN, dav, &sigma; e raio, mantiveram-se com a mesmas tendências nos clusters mistos. Para a obtenção do cluster mais estável analisou-se a energia de formação dos sistemas, sendo que a configuração mais favorável de ser formada é a Ce0,27Zr0,73O2, a qual considerou-se a estrutura pGMC representativa das configurações estudadas. Levando-se em consideração os resultados obtidos, na análise de formação dos clusters mistos delimitou-se a região de maior probabilidade de formação de clusters mistos estáveis entre 25% a 60%, de cério na composição. / Oxide nanomaterials have aroused great interest due to their application in several fields, such as in catalysis, optics, gas sensors, semiconductors, among others. Therefore, there are several studies for a wide variety of oxides with composition, and MO2, depending on the size and surface termination. There is also great interest in the study of mixed oxides due to the possibility of combining two or more oxides on a nanometric scale, in order to control their physical and chemical properties. In this work the metals Ce and Zr were used, since the oxides of these elements have a promising application in the industry as in fuel cells, catalytic reactions among others. The mixed oxides Cem-nZrnO2m present the ability to store or release oxygen during chemical reactions and therefore are widely used in three-way catalysts in the automotive industry. In this study, we used density functional theory (DFT) with PBE for the exchange-correlation functional. To investigate the structural, electronic and energetic properties of clusters, four selected structures were applied to build up the mixed ceria-zirconia oxides. Through the Mulliken electronegativity studies, it was found that zirconia clusters have a greater tendency to attract electrons, than the ceria clusters. Also observed that the lowest energy structures of ceria and zirconia have different coordination numbers, 4 and 3 NNN (Number of Nearest Neighbours), respectively. This is due to the fact that such structures are not spherical and have different atomic sizes. In addition, it was noted that there is a higher compaction of the clusters of lower energy compared to higher energy, for both ceria and zirconia, it was obtained the following values of diameter 1 nm and 2 nm for this variation of relative energy change. These results show that there is a trend in which mixed clusters have similar properties of the pure cluster, due to the similarity between the behavior of the structures of ceria and zirconia, which were the generating agents of the mixed clusters. It was observed that the structural properties of the pure clusters like CN, dav, &sigma; and cluster radii, remained with the same trends in the mixed clusters. To obtain the most stable clusters we analyzed the formation energy of the systems, the most favorable configuration to be obtained is Ce0,27Zr0,73O2, which was considered the representative pGMC structure of the studied configurations. Taking into consideration the results, obtained in the analysis of the formation of the mixed clusters, delimited the higher probability of formation of mixed stable clusters between 25% to 60%, of cerium in composition.

Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-05-04T13:40:00Z No. of bitstreams: 1 webertonreisdocarmo.pdf: 10785206 bytes, checksum: 2f8475c0ec8915c5f59c44191ffae7a0 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-05-17T13:31:07Z (GMT) No. of bitstreams: 1 webertonreisdocarmo.pdf: 10785206 bytes, checksum: 2f8475c0ec8915c5f59c44191ffae7a0 (MD5) / Made available in DSpace on 2017-05-17T13:31:07Z (GMT). No. of bitstreams: 1 webertonreisdocarmo.pdf: 10785206 bytes, checksum: 2f8475c0ec8915c5f59c44191ffae7a0 (MD5) Previous issue date: 2016-02-26 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / A catálise heterogênea desempenha um importante papel no desenvolvimento de tecnologias ambientais sustentáveis, abrangendo vários setores industriais. Normas cada vez mais rigorosas em relação às emissões de gases poluentes impõem melhorias nos processos empregados pela indústria. Baseado neste fato, a melhoria na preparação de catalisadores de hidrotratamento tem ganhado atenção de vários grupos de pesquisa devido à necessidade de produzir combustíveis mais limpos contendo menos impurezas, como os compostos de enxofre. Dependendo da finalidade, o processo de desenvolvimento de um catalisador pode consistir na produção de um novo catalisador sem nenhum dado disponível a seu respeito, ou o processo pode ter como objetivo melhorar um catalisador já conhecido. Nesse trabalho, tentamos contribuir com a melhora na atividade de um catalisador já conhecido alterando os suportes no qual esse catalisador é disperso. Para isso foram sintetizados compostos de hidrotalcitas do tipo MgZnAl-carbonato que foram usados como precursores dos suportes. Após a calcinação a 500 °C os suportes foram obtidos, e impregnados com sais de cobalto e molibdênio. Esses materiais foram calcinados com o objetivo de se obter os óxidos de cobalto e molibdênio dispersos sobre a superfície dos suportes para posterior sulfetação e ativação. Essa etapa final aconteceu in situ, onde logo após procedeu-se à avaliação catalítica para HDS de tiofeno e HID de cicloexeno. Os precursores foram preparados a partir de diferentes rotas sintéticas tais como: coprecipitação, hidrólise de uréia e coprecipitação assistida por ultrassom. Para todas as sínteses a variação da razão molar de Mg2+ /Zn2+, y, ocorreu nas quantidades de 5, 10, 15, 20, 25, 50, 75 e 100 mol%. Esses materiais foram caracterizados a partir de diferentes técnicas analíticas, onde foi possível constatar a formação da fase cristalina característica de compostos do tipo hidrotalcita com carbonato na região interlamelar. As análises de ICP-AES e CHN sugeriram um maior controle estequiométrico para as amostras obtidas por ultrassom e coprecipitação. A decomposição térmica das amostras de hidrotalcitas das diferentes séries, Znys, foi avaliada por difração de raios X in situ variando-se a temperatura no intervalo de 100 a 1000 °C, onde observou-se um comportamento térmico muito parecido para as amostras obtidas por diferentes rotas sintéticas contendo a mesma quantidade de zinco. Adicionalmente, o estudo da termodecomposição mostrou que as amostras formam uma fase amorfa próximo de 400 °C e que essa fase associada ao tamanho do cristalito é responsável pelo alargamento dos picos na região de médio ângulo no difratograma. A influencia da substituição dos cátions de Mg2+ por Zn2+ e da metodologia de síntese nas propriedades texturais dos óxidos mistos derivados da termodecomposição das hidrotalcitas foi estudada pela adsorção e dessorção de N2, bem como por microscopia eletrônica de varredura, onde constatou-se que a forma de obtenção dos precursores influência nas propriedades físico-químicas dos suportes. A avaliação catalítica dos materiais mostrou que todos aqueles testados são ativos para a hidrodessulfurização de tiofeno e hidrogenação de cicloexeno e ainda, quando comparado com o catalisador convencional suportado em alumina as amostras Zn5uCoMoS, Zn15cCoMoS se mostraram mais seletivas nas reações de hidrogenação e hidrodessulfurização. Em relação ao catalisador comercial todos os catalisadores da série ZnysCoMoS obtidos neste trabalho se mostraram mais seletivos, com destaque para o catalisador Zn5cCoMoS que além de mais seletivo, apresentou-se mais eficiente para a hidrodessulfurização de tiofeno quando comparado ao catalisador comercial. Ainda, a partir dos resultados, o que se observa é que a atividade catalítica e a seletividade dos catalisadores são muito sensíveis a pequenas mudanças no procedimento de preparação empregado para a obtenção dos suportes, uma vez que catalisadores com composições químicas muito próximas apresentaram diferentes propriedades catalíticas. / The heterogeneous catalysis plays an important role in the development of environmentally sustainable technologies, including multiple industries sectors. An increasingly stringent standard for pollutant emissions imposes an enhancement in these processes. Based on this fact, improvement in the preparation of hydrotreating catalysts is gaining attention from several research groups because of the need to produce cleaner fuels, as lower amounts of impurities such as sulfur compounds. Depending on the purpose, the development process of a catalyst may consist in an extreme situation, as the development of a new catalyst where no data is available about it, or the process may consist in improving a catalyst already known. In this work, we try to contribute to the improvement of a known catalyst already, altering the support in which it is dispersed. To these purposes hydrotalcites like MgZnAl-CO32- compounds were synthesized. After calcination at 500 °C supports were obtained and impregnated as salts of cobalt and molybdenum. These materials were calcined to obtain oxides of cobalt and molybdenum dispersed on the surface of the supports for subsequent sulfidation and activation. This final stage was made in situ, where soon after occurred the catalytic evaluation for HDS of thiophene and HID of cyclohexene. The precursors were prepared from different synthetic routes such as coprecipitation, urea hydrolysis, and coprecipitation assisted by ultrasound. For all synthesis, the ratio between divalent metallic cations (Zn2+ and Mg2+), y, was tested at 5, 10, 15, 20, 25, 50, 75 and 100 mol%. These materials were studied with different analytical techniques, where the formation of the typical compounds of the phase hydrotalcite with carbonate in the interlayer region can be seen. The analysis of ICP-AES and CNH suggested greater control of stoichiometry in samples obtained by ultrasound and co-precipitation. Thermal decomposition of hydrotalcites samples from different series, Znys were investigated by X-ray diffraction in situ, where varying the temperature range of 100 to 1000 °C, we observed a very similar thermal response to the samples obtained by different synthetic routes but with the same zinc content. Furthermore, the study showed that thermodecomposition of the samples formed an amorphous phase around 400 °C and that the phase associated with the crystallite size is responsible by peak broadening in the region of the middle angle diffraction. The influence of the zinc content and synthesis methodology on the physicochemical properties of mixed oxide derivatives from the hydrotalcite precursor MgZnAl-HT was evaluated through the adsorption/desorption of N2 and scanning electron microscopy (SEM), where it was observed that precursors synthesis variables influence on the physicochemical properties of the supports. The catalytic evaluation of the materials showed that all of them were active for hydrodesulfurization of thiophene and hydrogenation of cyclohexene. Samples Zn5uCoMoS and Zn15cCoMoS were selectivity in the hydrogenation and hydrodesulfurization reactions than the conventional catalyst supported in alumina. Regarding the commercial catalyst, all catalysts of the ZnysCoMoS series obtained in this study were more selective, highlighting the Zn5cCoMoS catalyst which in addition to more selective presented itself more efficient for hydrodesulfurization of thiophene as compared to the commercial catalyst. Thus, from the results it was observed that the catalytic activity and selectivity of the catalysts are sensitive to small changes in preparation procedures used to obtain the supports, since catalysts with very similar chemical compositions showed different catalytic properties.

Depuis les années 70, les oxydes mixtes de type hexaaluminate suscitent un intérêt certain pour les réactions catalytiques du fait de leur stabilité thermique élevée qui leur confère un fort potentiel pour les réactions à haute température. Cependant, la majorité des procédés de synthèse adoptés pour la préparation de ces derniers nécessite au moins une étape de traitement thermique à haute température afin d'achever le processus de cristallisation. Ainsi, les hexaaluminates préparées par voie chimique classique présentent des tailles de particules larges et des aires spécifiques réduites (< 20 m2 g-1). Dans le cadre de ce travail, l'optimisation des paramètres et des conditions de synthèse pour la préparation d'hexaaluminate nanocristalline de grande aire spécifique a fait l'objet d'une étude détaillée. Le broyage réactif s'est révélé être une méthode de synthèse efficace, et des aires spécifiques très élevées ont été obtenues (> 70 m2 g-1). Il a été observé que la nature et la concentration du métal de transition inséré dans la structure influence fortement les propriétés redox et la mobilité d'oxygène de ces solides. Cependant, pour une même composition chimique, les propriétés redox et la mobilité de l'oxygène sont conditionnées par les propriétés structurales et texturales. L'étude des propriétés catalytique des hexaaluminates en oxydation de CH4 et de CO a montré que l'activité de ces derniers résulte d'un équilibre complexe entre les propriétés texturales et structurales, l'état de la surface (nature et concentration des sites redox), et les propriétés de réductibilité et de mobilité d'oxygène. / Since the beginning of the 1970's, hexaaluminate mixed oxides gained were studied as active materials for catalytic reaction at high temperature, e.g. catalytic combustion. Their abilities to maintain phase stability and high surface area are considered of a great interest. Unfortunately, most of the reported chemical synthesis methods for hexaaluminate preparation involve at least one calcination step at high temperature (> 1100 °C) to crystallize the desired pure phase, which leads to crystal growth and unavoidable surface reduction.The catalytic performance of hexaaluminate materials depends essentially to the structural and textural properties i.e. surface area, crystal size, and phase purity. Thus the first part of this study was dedicated to the development of an original synthesis route, the "Activated Reactive Synthesis" process that is evidenced as a promising top down approach to generate nanostructured hexaaluminate with high surface area. Values of surface areas obtained were largely higher (>77 m2 g-1) to those reported for hexaaluminates prepared by conventional routes (~ 20 m2 g-1). The nature of the transition metal Mn+ inserted in the hexaaluminate structure, as well as its concentration, plays a key role on the redox behaviours and the oxygen transfer properties. Nevertheless, for a same chemical composition, the redox properties and oxygen mobility was found to be dependent to the structural and textural properties. Activities of hexaaluminate materials in oxidation reaction of CO and CH4 is reported to depend on a complex balance between structural and textural properties, surface state, reducibility, and oxygen mobility in the bulk.