La présente thèse s’inscrit dans un projet collaboratif de type CEFIPRA entre l’Inde (Dr. Ravi Kumar, Department of Metallurgical and Materials Engineering, Indian Institute of Technology-Madras (IIT Madras), Chennai) et la France (Dr. Samuel Bernard, Institut Européen des Membranes, CNRS, Montpellier). Les travaux de thèses se sont consacrés à la synthèse de céramiques de type non-oxyde autour de systèmes binaires (nitrure de silicium et nitrure de bore) et ternaires (Si-M-N, B-M-N (M=Ti, Zr, Hf)) à partir de précurseurs moléculaires et polymères, i.e., la voie polymères précéramiques ou PDCs. L’idée principale de ce travail est de former des structures nanocomposites à partir des systèmes ternaires dans lesquelles des nanocristaux de nitrures métalliques (M=Ti, Zr, Hf) se développent pendant la synthèse du nitrure de silicium et du nitrure de bore. Une caractérisation complète allant des polymères aux matériaux finaux a été conduite. Ces matériaux ont ensuite été préparés sous forme de composés mésoporeux (monolithes) en couplant la voie des polymères précéramiques à une approche de nanomoulage. Ces monolithes à haute surface spécifique et mésoporosité interconnectée ont alors été appliqués comme support de nanoparticules de platine pour l’hydrolyse du borohydrure de sodium pour générer de l’hydrogène. Les performances en tant que support de catalyseur ont été évaluées en termes de volume d’hydrogène libéré et de reproductibilité. Nous avons montré que les nanocomposites TiN/Si3N4 de surface spécifique très élevée présentent les meilleures performances grâce à l’activité catalytique du Si3N4 amorphe, de la présence de TiN nanométrique et de l’effet synergétique entre les nanoparticules Pt, le TiN nanostructuré et le Si3N4 amorphe. En preuve de concept, nous avons montré que ces structures nanocomposites étaient multifonctionnelles: elles peuvent être appliquées en tant que supports d’électro-catalyseurs et matériaux d’électrodes dans les piles à combustibles et les super-condensateurs, en particulier pour ceux contenant des matériaux lamellaires 2D et du carbone libre. / The thesis has been funded by a collaborative research partnership between Indian (Dr. Ravi Kumar, Department of Metallurgical and Materials Engineering, Indian Institute of Technology-Madras (IIT Madras), Chennai) and French institutes (Dr. Samuel Bernard, European Membrane Institute, CNRS, Montpellier), IFCPRA/CEFIPRA. It is focused on the synthesis, and characterization of binary (silicon nitride and boron nitride) and ternary (Si-M-N, B-M-N (M = Ti, Zr, Hf)) ceramics which are prepared through a precursor approach based on the Polymer-Derived Ceramics (PDCs) route. The idea behind the preparation of the ternary systems is to form nanocomposite structures in which metal nitrides (M = Ti, Zr, Hf) nanocrystals grow during the synthesis of silicon nitride and boron nitride. A complete characterization from the polymer to the final material is done. Then, these materials have been prepared as mesoporous monoliths coupling the PDCs route with a nanocasting approach to be applied as supports of platinum nanoparticles for the hydrolysis of liquid hydrogen carriers such as sodium borohydride. The performance as catalyst supports has been evaluated in terms of volume of hydrogen released and reproducibility. We showed that the very high specific surface area TiN/Si3N4 nanocomposites displayed the best performance because of the catalytic activity of amorphous Si3N4, the presence of nanoscaled TiN and the synergetic effect between Pt nanoparticles, nanoscaled TiN and amorphous Si3N4. Interesting, these materials are multi-functional as demonstrated as a proof of concept: they can be applied as electrocatalyst supports, electrode materials for fuel cells and supercapacitors, in particular those containing 2D layered materials and free carbon.

Les mousses solides, en polyuréthane, sont connues pour avoir des propriétés de transports intéressantes telles que des faibles pertes de charges engendrées ou une grande surface spécifique développée permettant une bonne évacuation de la chaleur. Cependant, elles ne sont pas utilisées en tant que support catalytique à cause des méthodes de déposition actuelles qui provoquent une altération de leurs propriétés mécaniques. Nous avons tout d’abord utilisé une nouvelle méthode de déposition basée sur la polydopamine(PDA), un polymère aux propriétés intéressantes, d’adhésion et de réduction. La PDA va venir recouvrir de manière homogène notre support puis va servir d’intermédiaire pour le dépôt de différentes phases active, qu’elles soient commerciales ou synthétisées in-situ. Par la suite, nos supports ont été employés dans plusieurs réactions, qu’elles soient monophasiques (liquide) ou bi-phasiques (gaz/liquide), afin de mettre en avant l’efficacité et la stabilité du dépôt de nos phases actives. De plus, il nous a été possible de déposer une phase active intéressante pour la production d’hydrogène. L’étude cinétique de cette réaction à basse température a été réalisée et a montré des résultats prometteurs pour le domaine des énergies renouvelables. Enfin, la dernière partie est consacrée à la mise en place de notre support structuré au sein d’un réacteur innovant, permettant d’utiliser les propriétés mécaniques du dit support afin d’améliorer les propriétés de transfert de matière / Solid foams, made with polyurethane, are well known for their interesting transport properties such as low pressure drop or high specific surface area. However, there are not used as catalytic support due to actual deposition method which causes an alteration of their mechanical properties. First, we used a new deposition method using polydopamine (PDA), a polymer with interesting adhesive and reducing properties. The PDA layer will cover homogenously our support then will act as intermediary for active phase deposition, whether they are commercially available or synthetized in-situ. Afterward, our supports were tested for several catalytic reactions, whether monophasic (liquid phase) or biphasic (gas/liquid) to show the active phase efficiency and stability. Furthermore, we successfully deposited a good active phase (cobalt) for hydrogen production. Kinetic study at low temperature were done and shown promising results for sustainable energy production. Finally, the last part was devoted to the use of our soft structured catalytic support within a new reactor, allowing to use its mechanical properties to improve mass transfer

Reverse Water Gas Shift Reaction (RWGS) är en attraktiv lösning för CO2-använding och minskning av utsläppen i atmosfären. Denna reaktion begränsas av termodynamiken och det finns problem med storskalig tillämpning. För att förbättra genomförandet av processen krävs utveckling av en effektiv katalysator. I mosats till typiska undersökningar som använder katalytiska metaller på en inert bärare, i denna undersökning användas en bimetallisk katalysator på en aktiv bärare.  RWGS-reaktionen studerades genom att använda Cu-Fe/CeO2-katalysator den K-promoterade motsvarigheten i olika mängder. Katalysatorerna testades i en fastbäddsreaktor. Katalysatorerna syntetiserades genom hydrotermisk metod och successiv impregnering av aktiva metaller. De framställda katalysatorerna analyserades med hjälp av BET-analys, H2-temperaturprogrammerad reduktion och röntgendiffraktion (XRD). Temperatur och H2/CO2 effekterna bedömdes. Experimentella resultat visade att Cu-Fe/CeO2 uppvisar avsevärd katalytisk aktivitet vid temperaturer högre än 500°C. Den CO2 omvandling med bimetalliska katalysatorn varierade mellan 24 % och 100 % avjämviktsvärdet med GHSV 360 000 h-1. Dessutom varierade CO selektivitet i intervallet mellan 70% och 95%. K-promoterad katalysator uppvisade lägre aktivitet antagligen på grund av partiell täckning av metalliska aktiva ytan, vilket resulterade i lägre omvandling (10%-~50% av jämviktsvärdet). Längre experiment (69-100 timmar) för de icke-promotoriserade katalysatorerna uppvisade inga avaktivering eller aktivitet/selektivitetsförlust i motsats till den K-promoterade katalysatorn som uppvisade en långsam aktivitetsavklingning troligen på grund av sintring. / Reverse Water Gas Shift Reaction (RWGS)is an attractive solution for CO2 utilizationand consecutive reduction of emissions in the atmosphere. This reaction is limited by thermodynamics while there are problems with its implementation at large scale. To improve the process implementation, development of an efficient and effective catalyst is required. Contrary to typical studies where catalytically active metals are deposited on inert supports, in this study the investigation of a bimetallic (Fe-Cu) catalyst on an active support was carried out. In particular, the RWGS reaction was studied over Cu − Fe/CeO2 catalyst with and without potassium promotion by means of catalytic activity tests in a fixed bed reactor. The catalysts were synthesized by hydrothermal method and successive impregnation of active metals. All the materials were characterized by means of BET analysis, H2 temperature programmed reduction and x-ray diffraction. The effects of temperature and H2/CO2 molar ratio were assessed. Experimental results showed that Cu −Fe and exhibit considerable catalytic activity at temperatures greater than 500°C. CO2 conversions of 24% to 100% of the equilibrium conversion were achieved at gas hourly space velocities of 360 000 h−1. Selectivity for CO varied between 70-95% Potassium promotion plausibly results to a partial coverage of active sites, and thus leading to lower conversion (10%-~50% of the equilibrium value). Longer runs (69-100h) showed no signs of deactivation and activity/selectivity loss for the unpromoted catalysts, while the K-promoted catalyst exhibited a slow activity decay probably due to sintering.

No presente trabalho foi desenvolvido um suporte catalítico monolítico para fins aeroespaciais empregando a manufatura aditiva. Para tanto, foi proposta uma geometria que proporcione um escoamento turbulento, permitindo um maior contato entre o reagente e a superfície do catalisador, proporcionando menor perda de carga ao sistema. Esta nova estrutura foi obtida via manufatura aditiva, através da técnica de Sinterização Seletiva a Laser (SLS) indireta. Para utilizar a técnica SLS e material cerâmico, foi necessário desenvolver um revestimento sobre as partículas de alumina para promover a aderência entre as mesmas durante o processo de manufatura aditiva. Em seguida foram definidos, experimentalmente, os parâmetros de aplicação da técnica SLS para o compósito alumina/poliamida. Por fim, foi fabricado, via SLS, o suporte catalítico na forma monolítica. Após a confecção do suporte monolítico, foi desenvolvido um revestimento composto de pseudo-boemita e nitrato de alumínio e aplicado na superfície do monólito, a fim de expandir a área superficial específica do material. Este aumento da área específica favorece a dispersão da fase ativa, composta de óxidos de cobalto e manganês, na superfície do suporte. A caracterização do catalisador monolítico foi realizada a partir das técnicas de Adsorção de Nitrogênio, Análise Termogravimétrica, Microscopia Eletrônica de Varredura e Espectrometria de Emissão Ótica com Fonte de Plasma (ICP-OES). O desempenho do catalisador monolítico na decomposição do H2O2 concentrado foi analisado via teste de gota, monitorado por câmera de alta velocidade. Os bons resultados obtidos nesta reação apontam esta técnica de obtenção de suporte catalítico monolítico através da manufatura aditiva como uma metodologia promissora a ser empregada em sistemas catalíticos com elevada difusão de massa e calor, mas principalmente em sistemas propulsivos a monopropelente. / This work was developed by the additive manufacture monolithic catalytic support to apply aerospace applications. A geometry was proposed to implement a turbulent flow allowing a better contact with catalytic surface and reagent with a low pressure drop in the system. This new structure was obtained by additive manufacture through indirect Selective Laser Sintering (SLS) technique. Firstly, in order to use the SLS for the ceramic material was developed a coating on the alumina particles to promote a melting between them during addictive manufacturing process. Secondly, the printer parameters SLS was configurated into the alumina/polyamide particle. Finally, the monolithic catalytic support was built via SLS. After the monolithic support building, the pseudo-boehmite and aluminum nitrate coating was developed and applied on the monolithic surface to increase the specific superficial area of the material. This increasing of the specific surface area helps the spread of the active phase to made up of cobalt and manganese oxide in the support surface. The characterization of the monolithic catalyst was carried out using the nitrogen adsorption technique, thermogravimetric analysis, scanning electron microscopy and inductive coupled plasma with optical emission spectrometry. The monolithic catalytic performance in the H2O2 concentrated decomposition was analyzed via drop test monitored by the high-speed camera. The good results of this reaction and such a technique of monolithic catalytic support obtainment through the additive manufacture show that a promising methodology can be used in the catalytic system with high diffusion of mass and heat but mainly, in monopropellant propulsive system.

No presente trabalho foi desenvolvido um suporte catalítico monolítico para fins aeroespaciais empregando a manufatura aditiva. Para tanto, foi proposta uma geometria que proporcione um escoamento turbulento, permitindo um maior contato entre o reagente e a superfície do catalisador, proporcionando menor perda de carga ao sistema. Esta nova estrutura foi obtida via manufatura aditiva, através da técnica de Sinterização Seletiva a Laser (SLS) indireta. Para utilizar a técnica SLS e material cerâmico, foi necessário desenvolver um revestimento sobre as partículas de alumina para promover a aderência entre as mesmas durante o processo de manufatura aditiva. Em seguida foram definidos, experimentalmente, os parâmetros de aplicação da técnica SLS para o compósito alumina/poliamida. Por fim, foi fabricado, via SLS, o suporte catalítico na forma monolítica. Após a confecção do suporte monolítico, foi desenvolvido um revestimento composto de pseudo-boemita e nitrato de alumínio e aplicado na superfície do monólito, a fim de expandir a área superficial específica do material. Este aumento da área específica favorece a dispersão da fase ativa, composta de óxidos de cobalto e manganês, na superfície do suporte. A caracterização do catalisador monolítico foi realizada a partir das técnicas de Adsorção de Nitrogênio, Análise Termogravimétrica, Microscopia Eletrônica de Varredura e Espectrometria de Emissão Ótica com Fonte de Plasma (ICP-OES). O desempenho do catalisador monolítico na decomposição do H2O2 concentrado foi analisado via teste de gota, monitorado por câmera de alta velocidade. Os bons resultados obtidos nesta reação apontam esta técnica de obtenção de suporte catalítico monolítico através da manufatura aditiva como uma metodologia promissora a ser empregada em sistemas catalíticos com elevada difusão de massa e calor, mas principalmente em sistemas propulsivos a monopropelente. / This work was developed by the additive manufacture monolithic catalytic support to apply aerospace applications. A geometry was proposed to implement a turbulent flow allowing a better contact with catalytic surface and reagent with a low pressure drop in the system. This new structure was obtained by additive manufacture through indirect Selective Laser Sintering (SLS) technique. Firstly, in order to use the SLS for the ceramic material was developed a coating on the alumina particles to promote a melting between them during addictive manufacturing process. Secondly, the printer parameters SLS was configurated into the alumina/polyamide particle. Finally, the monolithic catalytic support was built via SLS. After the monolithic support building, the pseudo-boehmite and aluminum nitrate coating was developed and applied on the monolithic surface to increase the specific superficial area of the material. This increasing of the specific surface area helps the spread of the active phase to made up of cobalt and manganese oxide in the support surface. The characterization of the monolithic catalyst was carried out using the nitrogen adsorption technique, thermogravimetric analysis, scanning electron microscopy and inductive coupled plasma with optical emission spectrometry. The monolithic catalytic performance in the H2O2 concentrated decomposition was analyzed via drop test monitored by the high-speed camera. The good results of this reaction and such a technique of monolithic catalytic support obtainment through the additive manufacture show that a promising methodology can be used in the catalytic system with high diffusion of mass and heat but mainly, in monopropellant propulsive system.