Abstract The aim of the thesis was to find new information on the effect of BaO and oxygen storage capacity material on NOx reduction. A total of nine different kinds of Pd/Al2O3-based metallic monoliths were studied. Promoters such as oxygen storage capacity material (OSC material in our case Cex-1ZrxO2 mixed oxides) and stabilisers such as barium (BaO) were added into the catalyst alone or together to improve catalyst properties such as catalytic activity, selectivity, and thermal stability. The key aspects in this thesis can be divided into four parts. First, the behaviour of NO reduction and CO as well as C2H4 oxidation over Pd/Al2O3-based catalysts in rich, stoichiometric and lean conditions were studied. Secondly, the effect of BaO and the OSC material in NO reduction was considered. Thirdly, the preparation procedure, i.e. the addition order of BaO, OSC material, and Pd on the catalyst was considered. Finally, the effect of ageing on the behaviour of catalysts was investigated. Several characterization methods (in situ DRIFT, catalytic activity measurements, N2 physisorption, CO chemisorption, dynamic oxygen storage capacity measurements, and X-ray diffraction (XRD)) were utilised to find answers to the behaviour of these catalysts in the studied model reactions. The Rapid Ageing Hot in Laboratory (RAHLAB) method was used to age the catalyst. First, it was demonstrated that the CO and hydrocarbon oxidation and NO reduction reactions over the Pd/Al2O3-based catalyst behave differently. NO reduction and CO and hydrocarbon oxidation reactions were dependent on the reaction conditions and temperatures. Secondly, the effect of OSC and BaO on NO reduction was studied separately. In the case of OSC material, it was observed that the OSC material has an effect on NO reduction as well as on CO and C2H4 oxidation. In the case of BaO, it was observed that BaO has a positive effect on NO reduction as well as CO and C2H4 oxidation especially in rich conditions. Thirdly, the effects of the addition order of OSC and BaO on the catalyst was studied separately. It was shown that these have an effect on NO reduction, especially after ageing. First, on the fresh Pd/Al2O3 catalyst it was observed that the addition order of OSC on the catalyst has not an influence on catalyst performance. The effect of the BaO addition order on the Pd/OSC/Al2O3-based catalyst is found to be insignificant, especially, after the ageing process. Furthermore, it is observed that the effect of RAHLAB ageing was that the catalyst lost its catalytic activity, stability, and selectivity.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21122号 / 工博第4486号 / 新制||工||1697(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 田中 庸裕, 教授 陰山 洋, 教授 佐藤 啓文 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

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As renewable energy production becomes more prevalent, the challenge of producing renewable dispatchable fuel for the transportation sector remains unresolved. One promising approach is to produce hydrogen from solar energy with a two step thermochemical cycle which utilizes an oxygen storage material (OSM) to split water through two reversible reactions. Due to the strong coupling between reactor design, operational parameters, and OSM properties, the direct comparison of two OSMs is not straightforward. In order to guide the designs of OSMs for two-step thermochemical hydrogen production, a methodology is developed to model the max performance possible for a two-step thermochemical cycle. The novel contribution of this model considers the strong coupling between reactor operation, OSM properties, and reactor performance. Next, a method for screening and evaluating new OSMs which utilizes thermogravimetric analysis (TGA) is proposed. With this data, the modeling method previously developed is applied to determine maximum reactor efficiency possible with new materials. This allows many materials to be evaluated quickly, and facilitates further characterization new OSMs. Additionally, by comparing the predicted maximum efficiency of a new material with the efficiency of current ones, this method facilitates the comparison of two different OSMs on equal footing.

Depuis la découverte de la piézoélectricité dans le quartz, les besoins en matériaux efficaces pour des applications technologiques piézoélectriques (PZ) et d’Optiques Non-Linéaires (ONL) ont considérablement augmenté. Les deux propriétés doivent présenter une stabilité thermique élevée dans une large gamme de température. Dans le cadre de ma thèse, les matériaux de type quartz BaXO2 (X=Zn ou Co) ont donc été étudiés car ils cristallisent dans le même groupe d’espace P3121 que le quartz-a l'un des matériaux les plus utilisés, principalement pour ses propriétés de PZ et d’ONL.Nous avons commencé ce travail par le composé BaZnO2 car il présenterait un coefficient de couplage électromécanique K11=35,7% supérieur à celui du quartz. Une étude combinée expériences/théorie a permis de i) caractériser la stabilité chimique et thermique jusqu’à 1273 K, et de ii) déterminer les propriétés diélectriques et vibrationnelles (IR-Raman) du matériau. Les propriétés ONL, calculées par DFT, seraient en outre supérieures à celles du quartz.Dans BaCoO2, le degré d’oxydation +II du Co en symétrie tétraédrique implique un ordre antiferromagnétique à température ambiante (TN =330 K). Associé à la structure type quartz, un couplage piézo-magnétique peut être envisagé. BaCoO2 a été caractérisé structuralement/vibrationnellement (résultats confrontés à la théorie) jusqu’à 1273 K et une capacité de stockage d’oxygène réversible exceptionnelle a pu être mise en évidence dans BaCoO2+x (0 ≤ x ≤ 1) par ATG, spectroscopie Raman et par diffraction de rayons X grâce à une séquence de transition topotactique. / Since the discovery of the piezoelectricity in quartz, the need of efficient materials for piezoelectric and non-linear optic technological applications has increased dramatically. Both properties have to exhibit a high thermal stability over a wide temperature range. In my thesis work, the BaXO2 quartz type structure materials (X = Zn or Co) have been studied since they crystallize in the same P3121/P3221 space group than quartz, which is still one of the most widely used minerals mainly due to its piezoelectric properties.We have started this work with the BaZnO2 compound since first-principles-based calculations predicted an electromechanical coupling, k_11=35.7%. Our combined experimental and theoretical study allowed i) to characterize the chemical and thermal stability of BaZnO2 up to 1273 K, and ii) to determine the dielectric and vibrational (IR-Raman) properties of the material. Additionally the non-linear optic responses are predicted to be one order of magnitude higher than those reported for quartz.In BaCoO2, the oxidation state of Co (+II) in a tetrahedral symmetry implies an antiferromagnetic order at room temperature ( T_N=330 K). Associated with the -quartz type structure, a piezo-magnetic coupling can be considered. BaCoO2 was structurally and vibrationally characterized up to 1273 K (as obtained results were confronted to theory) and an exceptional reversible oxygen storage capacity was pointed out in BaCoO_(2+δ )(0 < δ ≤ 1) based on thermogravimetric measurements, Raman spectroscopy and X-ray diffraction characterizations. The oxygen insertion/disinsertion mechanism is governed by a topotactic transition sequence.

<p>Avgasmängden som bensindrivna fordon tillåts släppa ut minskas hela tiden. Ett sätt att möta framtida krav, är att förbättra katalysatorns effektivitet. För att göra detta kan luft-bränsle-förhållandet regleras med avseende på syrelagringen i katalysatorn, istället för som idag, reglera mot stökiometriskt blandningsförhållande. Eftersom syrelagringen inte går att mäta med en givare behövs en modell som beskriver katalysatorns dynamiska egenskaper. Tre sådana modeller har undersökts, utvärderats och jämförts.</p><p>Två av modellerna har implementerats i Matlab/Simulink och anpassats till mätningar från en experimentuppställning. För att kunna observera syrelagringen online valdes slutligen en av modellerna ut, och implementerades i ett Extended Kalman filter.</p><p>Ytterligare arbete behöver läggas ner på den mest lovande modellen, och detsamma gäller för Kalmanfiltret, men på sikt förväntas resultaten kunna bli bra.</p> / <p>The legal amount of emissions that vehicles with spark ignited engines are allowed to produce are steadily reduced over time. To meet future emission requirements it is desirable to make the catalytic converter work in a more efficient way. One way to do this is to control the air-fuel-ratio according to the oxygen storage level in the converter, instead of, as is done today, always trying to keep it close to stoichiometric. The oxygen storage level cannot be measured by a sensor. Hence, a model describing the dynamic behaviors of the converter is needed to observe this level. Three such models have been examined, validated, and compared.</p><p>Two of these models have been implemented in Matlab/Simulink and adapted to measurements from an experimental setup. Finally, one of the models was chosen to be incorporated in an extended Kalman filter (EKF), in order to make it possible to observe the oxygen storage level online.</p><p>The model that shows best potential needs further work, and the EKF is working with flaws, but overall the results are promising.</p>

Point defects are an inherent part of crystalline materials and they influence important physical and chemical properties, such as diffusion, hardness, catalytic activity and phase stability. Increased understanding of point defects enables us to tailor the defect-related properties to the application at hand. Modeling and simulation have a prominent role in acquiring this knowledge. In this thesis thermodynamic and kinetic properties of point defects in metals and ceramics are studied using first-principles calculations based on density functional theory. Phenomenological models are used to translate the atomic level properties, obtained from the first-principles calculations, into functional materials properties. The next paragraph presents the particular problems under study. The formation and migration of vacancies and simple vacancy clusters in copper are investigated by calculating the energies associated with these processes. The structure, stability and electronic properties of the low-oxygen oxides of titanium, TiOx with 1/3 &lt; x &lt; 3/2, are studied and the importance of structural vacancies is demonstrated. We develop an integrated first-principles and Calphad approach to calculate phase diagrams in the titanium-carbon-nitrogen system, with particular focus on vacancy-induced ordering of the substoichiometric carbonitride phase, TiCxNy (x+y &lt; 1). The possibility of forming higher oxides of plutonium than plutonium dioxide is explored by calculating the enthalpies for nonstoichiometric defect-containing compounds and the analysis shows that such oxidation is only produced by strong oxidants. For ceria (CeO2) doped with trivalent ions from the lanthanide series we probe the connection between the choice of a dopant and the improvement of ionic conductivity by studying the oxygen-vacancy formation and migration properties. The significance of minimizing the dopant-vacancy interactions is highlighted. We investigate the redox thermodynamics of CeO2-MO2 solid solutions with M being Ti, Zr, Hf, Th, Si, Ge, Sn or Pb and show that reduction is facilitated by small solutes. The results in this thesis are relevant for the performance of solid electrolytes, which are an integral part of solid oxide fuel cells, oxygen storage materials in automotive three-way catalysts, nuclear waste materials and cutting tool materials. / QC 20100622

Avgasmängden som bensindrivna fordon tillåts släppa ut minskas hela tiden. Ett sätt att möta framtida krav, är att förbättra katalysatorns effektivitet. För att göra detta kan luft-bränsle-förhållandet regleras med avseende på syrelagringen i katalysatorn, istället för som idag, reglera mot stökiometriskt blandningsförhållande. Eftersom syrelagringen inte går att mäta med en givare behövs en modell som beskriver katalysatorns dynamiska egenskaper. Tre sådana modeller har undersökts, utvärderats och jämförts. Två av modellerna har implementerats i Matlab/Simulink och anpassats till mätningar från en experimentuppställning. För att kunna observera syrelagringen online valdes slutligen en av modellerna ut, och implementerades i ett Extended Kalman filter. Ytterligare arbete behöver läggas ner på den mest lovande modellen, och detsamma gäller för Kalmanfiltret, men på sikt förväntas resultaten kunna bli bra. / The legal amount of emissions that vehicles with spark ignited engines are allowed to produce are steadily reduced over time. To meet future emission requirements it is desirable to make the catalytic converter work in a more efficient way. One way to do this is to control the air-fuel-ratio according to the oxygen storage level in the converter, instead of, as is done today, always trying to keep it close to stoichiometric. The oxygen storage level cannot be measured by a sensor. Hence, a model describing the dynamic behaviors of the converter is needed to observe this level. Three such models have been examined, validated, and compared. Two of these models have been implemented in Matlab/Simulink and adapted to measurements from an experimental setup. Finally, one of the models was chosen to be incorporated in an extended Kalman filter (EKF), in order to make it possible to observe the oxygen storage level online. The model that shows best potential needs further work, and the EKF is working with flaws, but overall the results are promising.

Les systèmes à énergies renouvelables couplés à un stockage hydrogène apportent des solutions nouvelles et innovantes à l'alimentation électrique des milieux peu ou non électrifiés. Le concept de batterie H2 qui équipe ce type de système est une forme de stockage originale qui apporte l'autonomie et l'indépendance électrique pour des longues durées (typiquement stockage saisonnier). Le fonctionnement de cette batterie H2 est le suivant : un électrolyseur produit des gaz (H2 et O2) avec les surplus d'énergie de la source renouvelable ; l'hydrogène, voire l'oxygène, est ensuite stocké dans des réservoirs pour être utilisé ultérieurement grâce à une pile à combustible lorsque la source renouvelable est insuffisante. Dans cette étude, nous nous intéresserons spécifiquement au couplage entre des générateurs photovoltaïques avec une batterie H2/O2 pour l'alimentation d'un site isolé sans interruption. Ces travaux de recherche s'inscrivent dans le projet ANR PEPITE (ANR-PanH 2007-2012) et ont été menés en partenariat avec HELION Hydrogen Power, le CEA Liten et l'Université de Corse. Le projet est également labellisé par les pôles de compétitivité CAPENERGIES et TENERRDIS. Tout d'abord, une réflexion générale s'appuyant sur les propriétés d'une batterie H2/O2 démontre la nécessité d'introduire une batterie (ici au plomb) pour garantir un fonctionnement instantané et sans interruption. Puis, une étude qualitative sur les architectures électriques possibles (bus de tension DC, AC…) a été menée pour s'achever sur une étude quantitative réalisée spécifiquement pour le projet PEPITE. Parallèlement à cela, différentes stratégies de gestions énergétiques ont été proposées afin d'utiliser les deux stockages dans les meilleures conditions, de limiter leur vieillissement ainsi que les pertes. Deux bancs d'essais à échelle réduite (un premier à bus DC et un second à bus AC) ont été réalisés au sein du laboratoire LAPLACE afin de valider les études et de préparer le prototype final qui sera testé sur le site de HELION Hydrogen Power au cours de l'été 2011. / Renewable energy systems coupled to a hydrogen storage bring new and innovative solutions to supply power to environments with little or no electricity. The concept of H2 battery which is a part of such system is a form of storage that gives autonomy and electric independence for long periods (typically seasonal storage). The operation of this H2 battery is this: an electrolyser produces gases (H2 and O2) with the extra energy from the renewable source. Hydrogen or oxygen is then stored in tanks for later use with a fuel cell when the renewable source becomes insufficient. In this study, we focus specifically on the coupling between photovoltaic arrays with a H2/O2 battery to supply power to a remote site without interruption. This work is part of the PEPITE Project, partially funded by the french National Research Agency (ANR-Panh 2007-2011) and was conducted in partnership with HELION Hydrogen Power, CEA-Liten and the University of Corsica. The project is also accredited by the CAPENERGIES and TENERRDIS clusters. First, a general discussion based on the properties of a H2/O2 battery demonstrates the need to introduce a secondary battery (lead in our case) to ensure an instant and uninterrupted operation. Then, a qualitative study on the possible electrical architectures (DC bus or AC bus) was conducted and resulted in a quantitative study conducted specifically for the PEPITE project. At the same time, various energy management strategies have been proposed to use both storage in the best conditions, limiting their losses and aging. Two small scale bench tests (one with a DC bus and a second with an AC bus) were performed in the LAPLACE laboratory to validate our strategies and prepare the final prototype which will be tested on the site of HELION Hydrogen Power during the summer of 2011.