Pollution from automobile exhaust is one of the most major environmental problems because of increasing usage of engine technologies. Diesel and lean burn gasoline engines operate under oxygen rich (lean) conditions and they emit harmfull gases to the atmosphere (CO,CO2, NO, NO2). The control of NOx emission from exhaust has become a challenging issue in engine industry because of the worldwide environmental regulations. Therefore lean-burn NOx emission control technologies have been developed to reduce emission of harmfull gases from exhausts, and the NOx storage/reduction (NSR) catalysts is one of the most promising candidates to reduce the pollution caused by lean-burn engines. In NSR systems, NO from the emission is first oxidized to NO2 over noble metal sites (Pt, Rh, Pd) during lean-burn engine operation. After that NO2 is stored as nitrites and nitrates in alkali earth oxides (BaO,MgO, CaO) particles or monolayer which is well dispersed on a substrate (Gamma-Al2O3, TiO2, SiO2). Finally, stored NOx compound are broken into N2 and O2 on noble metal sites. The Pt/BaO/Gamma-Al2O3 system is one of the most popular subjects in literature both experimentally and theoretically since this system is known to be catalytically more active and ecient in interactions between NOx and Pt-BaO components are still not clearly explained. For this reason, in this thesis, the interaction between catalytic redox components, Pt and Rh, and the support material Gamma-Al2O3 and the eects of Pt and Rh in atomic and diatomic clusters forms on the adsorption of the NO2 molecule on the Gamma-Al2O3(100) surface have been investigated by using density functional theory (DFT).

A síntese de Fischer-Tropsch é um processo de conversão do gás de síntese (CO + H2) em hidrocarbonetos de cadeias longas. Os catalisadores clássicos para a hidrogenação do CO são, principalmente, o Fe e o Co suportados em diferentes óxidos. O desempenho catalítico do catalisador é influenciado pelo tamanho, dispersão e grau de redução das partículas metálicas. Estudos recentes mostram uma promissora aplicação de materiais à base de nanofibras de carbono na catálise heterogênea. Estes materiais apresentam algumas vantagens em relação aos suportes catalíticos tradicionais, tais como: uma baixa interação metal-suporte, elevada área superficial, ausência de poros fechados, alta condutividade térmica, elevada inércia química e hidrofobicidade. Neste trabalho foram fabricados suportes catalíticos macroscópicos à base de nanofibras de carbono, empregando o método de vapor deposição, a partir da decomposição do etano. Os catalisadores foram preparados pela impregnação incipiente do Co e de promotores na superfície do suporte. Foram empregados os metais nobres, Ir, Pt e Ru, como promotores catalíticos, com o objetivo de incrementar a redutibilidade e a atividade do catalisador. Todos os catalisadores foram caracterizados por Quimissorção de CO, Fisissorção de N2, Redução a Temperatura Programada (TPR), Espectroscopia Fotoeletrônica de Raios X (XPS) e Microscopia Eletrônica de Transmissão (MET). Os catalisadores foram, então, testados na síntese de Fischer-Tropsch, utilizando um reator de leito fixo e fluxo contínuo, com análise simultânea dos produtos gasosos e controle sistemático da temperatura, pressão e vazão dos reagentes. Finalmente, foram analisados os produtos líquidos obtidos na reação com objetivo de conhecer a influência dos promotores na seletividade dos hidrocarbonetos formados. / Fischer-Tropsch synthesis is a process of converting the syngas (CO + H2) to long-chain hydrocarbons. The traditional catalysts for the CO hydrogenation are Fe and Co supported on different oxides. Catalytic performance of the catalyst is influenced by size, dispersion and degree of reduction of metal particles. Recent studies show a promising application of materials based on carbon nanofibers in heterogeneous catalysis. These materials have some advantages compared to traditional catalyst supports, such as a low metal support interaction, high surface area, no closed pores, high thermal conductivity, high chemical resistance, and hydrophobicity. In this work, based on macroscopic carbon nanofiber catalyst supports have been manufactured by employing the method of chemical vapor deposition from ethane decomposition. Catalysts were prepared by incipient wetness impregnation of Co and promoters on the support surface. Noble metals, Ir, Pt and Ru were used as catalytic promoters, with the aim of increasing the reductibility and catalyst activity. All catalysts were characterized by CO Chemisorption, N2 Physisorption, Temperature Programmed Reduction (TPR), X-ray Photoelectron Spectroscopy (XPS), and Transmission Electron Microscopy (TEM). The catalysts were then tested in the Fischer-Tropsch synthesis using a fixed bed reactor, continuous flow, with simultaneous analysis of gaseous products and systematic temperature control, pressure, and flow rate of the reactants. Finally, the liquid products obtained in the reaction were analyzed in order to determine the influence of promoters on the selectivity of hydrocarbons formed.

Ce travail porte sur l’étude expérimentale de la réponse optique linéaire et non-linéaire de nanoparticules métalliques individuelles. Pour cela une technique optique originale en champ lointain, basée sur la modulation spatiale de l’échantillon, a été mise en place et combinée avec une technique pompe-sonde résolue en temps à l'échelle femtoseconde. Dans un premier temps nous nous sommes intéressés à la caractérisation optique de nanoparticules modèles formées par une nanosphère d’argent encapsulée dans une couronne de silice. Nous avons mis en évidence la conséquence principale du confinement quantique électronique sur la réponse optique des nanoparticules : l'élargissement de leur résonance plasmon de surface avec la réduction de la taille (proportionnel à l’inverse du rayon, pour des nanosphères). Cette étude détaillée n’avait jamais été réalisée, car elle nécessite des mesures sur des nanoparticules uniques (pour s'affranchir des effets d’élargissement inhomogène de la résonance dus aux dispersions en taille, géométrie et environnement) et de taille connue. Ceci a été possible grâce à la mesure quantitative de leur section efficace d'extinction et/ou à la corrélation directe de l'image optique du nano-objet avec son image par microscopie électronique. La deuxième partie de ce travail a été consacrée à l'étude de la réponse optique linéaire et non-linéaire résolue en temps de nanobâtonnets d’or. Ces systèmes sont particulièrement intéressants car leurs propriétés optiques peuvent être contrôlées en modifiant leur géométrie (rapport d’aspect en particulier). Leur spectre d'extinction et sa dépendance en polarisation ont tout d'abord été étudiés au niveau de l'objet individuel. La comparaison de cette réponse optique linéaire avec des modèles théoriques a permis d'obtenir des informations sur leur orientation et géométrie. La réponse optique non-linéaire ultrarapide du même nanobâtonnet a ensuite été mesurée par une technique pompe-sonde femtoseconde à très haute sensibilité. La nanoparticule étudiée étant totalement caractérisée optiquement, une mesure quantitative de sa non-linéarité a ainsi pu être réalisée, et son origine physique déterminée à partir d'un modèle théorique. / This work focuses on the experimental study of linear and nonlinear optical responses of single metal nanoparticles. For this, an original far field optical technique, based on the spatial modulation of the sample, was set-up and combined with a femtosecond time-resolved pump-probe technique. We have first investigated the optical properties of model nanoparticles, formed by a silver nanosphere coated with a silica shell. We have highlighted the main consequence of electronic quantum confinement on the optical response of a nanoparticle: the broadening of its localized surface plasmon resonance with size reduction (proportional to the inverse of the radius, for nanospheres). This detailed study had never been realized, because it requires measurements on single nanoparticles (to eliminate the influence of inhomogeneous effects on the resonance due to size, geometry and environment dispersions) and of known size. This was possible thanks to the quantitative measurement of extinction cross-section and / or correlation of the optical image of the nano-object with its electron microscopy image. The second part of this work has been devoted to the study of the linear and time-resolved non-linear optical responses of gold nanorods. These systems are particularly interesting because their optical properties can be controlled by changing their geometry (in particular their aspect ratio). First, the extinction spectrum and its polarization dependence have been studied on individual objects. Comparison of the linear optical response with theoretical models provides information on orientation and geometry of the nanorod. The ultrafast nonlinear optical response of the nanorod was then measured with a high sensitivity femtosecond pump-probe technique. The investigated nanoparticles being fully characterized optically, a quantitative measurement of their non-linearity could be achieved, and its physical origin determined using a theoretical model.

La réponse optique de nanoparticules (NPs) de métaux nobles est dominée par une résonance géante diterésonance de plasmon de surface (RPS), très sensible à la taille, la morphologie et l’environnement diélectriquedes NPs. Elle est étudiée sur des NPs individuelles grâce à un dispositif de Spectroscopie à Modulation Spatiale(SMS) permettant d’accéder à leur section efficace d’extinction absolue sur un large domaine spectral (300-900nm) en corrélation avec leur morphologie observée indépendamment par microscopie électronique àtransmission (MET) ou à balayage (MEB).Mon travail de thèse a d’abord consisté à développer un nouveau dispositif afin de mesurer l’extinction et de ladiffusion d’un même nano-objet unique, donnant ainsi accès à des mesures quantitatives de la section efficace dediffusion moyennant une connaissance a priori du diagramme angulaire de répartition de la lumière diffusée.La seconde partie concerne des études optiques (expérimentales et théoriques) et structurales (MET ou MEB) denano-objets exotiques. Tout d’abord, une étude systématique réalisée sur un grand nombre de bipyramides d’orélaborées par voie chimique a montré que leur RPS, située dans le rouge, est extrêmement sensible à leurmorphologie et à leur environnement, ce qui en fait des candidats de choix pour des capteurs biologiques. Parailleurs, l‘émergence d’une RPS induite par couplage plasmonique a été mis en évidence sur des nano-antennesnanolithographiées à base de métaux de transition (Pd, Pt, Cr). Ces résultats ouvrent des perspectivesd’applications nouvelles en élargissant la plasmonique à des métaux aux propriétés chimiques très variées(photo-catalyse, magnéto-optique). / The optical response of noble metal nanoparticles (NPs) are known to be dominated by the Localized SurfacePlasmon Resonance (LSPR), which is highly sensitive to the size of the NPs, their shape and their environment.This optical response can be studied on single nanoparticles thanks to a highly sensitive setup based on theSpatial Modulation Spectroscopy (SMS) which gives access to their absolute extinction cross-section on a widespectral range (300–900 nm). Moreover, the morphology of the same objects studied in optics is characterized bya direct observation in Transmission or Scanning Electron Microscopy (TEM or SEM).In this work, a new setup allowing the measurement of both the extinction and the scattering of a single nanoobjecthas been developed. This technique allows a quantitative measurement of the scattering cross-sectionprovided the angular distribution of the scattered light by the NP is known.The second part is related to experimental and theoretical optical studies and morphological observationsthrough TEM and SEM of exotic nano-objects. First, a systematic study performed on a large number of goldbipyramids, chemically elaborated, has shown that the LSPR located in the red is highly sensitive to theirmorphology and to the environment. Thus, these objects can likely be used as biological sensors. In addition,emergence of a resonance induced by plasmon coupling has been evidenced on lithographed nano-antennasbased on transition metal (Pd, Pt, Cr) for which no LSPR is usually expected. This opens up prospects for novelapplications by extending the field of plasmonics to metals of various chemical properties (photocatalysis,magneto-optics).

Parmi les différents procédés chimiques, l'Oxydation en Voie Humide Catalysée (OVHC) apparaît comme une technique de choix pour le traitement des eaux usées à forte teneur en composés toxiques et peu biodégradables. Ce procédé, sous pression, est limité par la faible solubilité de l'oxygène. L'étape cruciale de la réaction est alors le transfert de l'oxygène jusqu'à la particule métallique via le support. Les phénomènes régissant ce transfert sont la composition des supports oxydes et l'interaction métal/support. L'objectif de ce travail est d'étudier l'influence de la teneur en CeO2, connue pour ses propriétés de transfert et de stockage d'oxygène, sur les propriétés de catalyseurs Ru/TiO2-x%CeO2 et Pt/TiO2-x%CeO2 en oxydation voie humide catalysée du phénol et de l'acide acétique.L'addition de cérine améliore les propriétés de stockage de l'oxygène des matériaux mais favorise (i) pour l'OVHC du phénol, la formation de polymères insolubles en solution et le dépôt d'espèces carbonées sur la surface catalytique, (ii) pour l'OVHC de l'acide acétique une carbonatation des supports. Il en résulte, dans les deux cas, une perte d'activité par blocage des sites catalytiques. Le platine s'avère plus actif que le ruthénium pour l'OVHC du phénol alors que l'inverse est observé dans le cas de l'acide acétique. / Among the different chemical processes, catalytic wet air oxidation (CWAO) appears to be a promising process for the treatment of wastewater containing high levels of toxic and poorly biodegradable compounds. This over pressure process is limited by the low oxygen solubility. The limiting step of reaction is the oxygen transfer to the metal particle through the support. Phenomena governing this transfer are the oxide support composition and the metal/support interaction. The objective of this work is to study the influence of the CeO2 content, known for its oxygen transfer and storage capacity, over the catalytic properties of Ru/TiO2-x%CeO2 and Pt/TiO2-x%CeO2 for catalytic wet air oxidation of phenol and acetic acid. The addition of ceria improves the oxygen storage capacity of materials but it enhances i) for CWAO of phenol, the formation of insoluble polymers in solution and the deposition of carbonaceous species on the catalytic surface, ii) for CWAO of acetic acid, the formation of carbonates on the support. In both cases an activity lost is due to the blocking of catalytic sites. Platinum is more active than ruthenium for CWAO of phenol while the opposite is observed in the case of acetic acid.

Les métaux nobles (Au, Ag, Pt, Ir, Pd et Ru) sont utilisés en salle blanche pour la réalisation de dispositifs électroniques ou peuvent être apportés par les équipements de fabrication (composants d’alliage par exemple). Il a été montré qu’ils pouvaient impacter fortement les dispositifs. Il est alors nécessaire de procéder au contrôle des équipements pour diagnostiquer au plus tôt une contamination. Or, il n’existe pas de technique industrielle pour leur suivi et ce à des niveaux d’au moins 5.109 at.cm-2 - recommandation ITRS. Il se pose la question de la pertinence de ces recommandations en fonction des types de dispositifs (SPAD notamment). Dans un premier temps, les travaux ont consisté à développer une technique physico-chimique pour l’analyse des métaux nobles sur silicium par VPD-DC-ICPMS. Enfin, leur dangerosité vis-à-vis des équipements et des dispositifs a été évaluée d’après leur comportement en température et le DCR généré sur SPAD. / Noble metals (Au, Ag, Pt, Ir, Pd and Ru) are used for the fabrication of microelectronics devices or can be brought by manufacturing tools (alloy components for example). It is well known that these impurities are detrimental to the efficiency of the devices. This implies a real and present need for control of their introduction in clean rooms to diagnose as soon as possible a contamination. Yet, there are no industrial technique for their follow-up at levels about 5.109 at.cm-2 - ITRS recommendations. The relevance of these recommendations according to the electronic device (SPAD in particular) could be questioned. At first, this study consisted in developing a physicochemical technique for the analysis of noble metals on Si wafers by VPD-DC-ICPMS. Then, their dangerousness towards tools and devices was established according to their behavior in temperature and the DCR generated on SPAD devices.

Functional nanomaterials are gaining attention due to their excellent shape and size dependent optical, electrical and catalytic properties. Synthesizing nanoparticles is no longer novel with the availability of a host of synthesis protocols for a variety of shapes and sizes of particles. What is currently needed is an understanding the fundamentals of shape and size controlled synthesis to produce functional nanomaterials that is simple and general. In addition to simple metallic nanostructures, synthesizing bimetallic and hybrid nanostructures are important for applications. Instead of trying to add functionality to the preformed nanomaterials, it is advantageous to look for cost effective and general synthetic protocols that can yield bimetallic, hybrid nanostructures along with the shape and size control. In this dissertation, a novel synthetic protocol for the synthesis of ultrfine single crystalline nanowires, metallic and bimetallic nanostructures and hybrid nanostructures has been investigated. The key point of the synthesis is that all different functional nanostructures are achieved by the use of noble metal intermediates in organic medium without phase transfer reagents. The roles of capping agents, oriented attachment and aggregation phenomenon have been studied in order to understand the formation mechanisms. Along with the synthesis, formation mechanisms, the optical and catalytic properties of the functional, noble metal, bimetallic and hybrid nanostructures have been studied. The entire thesis based on the results and findings obtained from the present investigation is organized as follows: Chapter I provides a general introduction to functional nanomaterials, their properties and some general applications, along with a brief description of conventional methods for size and shape-controlled synthesis. Chapter II deals with the materials and methods which essentially gives the information about the materials used for the synthesis and the techniques utilized to characterize the materials chosen for the investigation. Chapter III presents a novel method of for synthesizing noble metals nanostructures starting from an intermediate solid phase. The method involves the direct synthesis of noble metal intermediates in organic medium without the use of any phase transfer reagent. Controlled reduction of these intermediates leads to the formation of ultrafine nanocrystallite building blocks. Controlled aggregation of the nanocrystallites under different conditions leads to the formation of different nanostructures ranging from single crystalline nanowires to porous metallic clusters. In this chapter, the details of synthesis of the intermediate phase of gold are presented. This intermediate phase is the rocksalt phase of AuCl that has been experimentally realized for the first time. Manipulation of the AuCl nanocubes leads to the formation of a variety of nanostructures of Au starting from hollow cubes to extended porous structures. Mechanistic details of the formation of the intermediate and the nanostructures are presented in this chapter. Chapter IV deals with the symmetry breaking of an FCC metal (gold) by oriented attachment of metal nanoparticles by the preferential removal of capping agent from certain facets and followed by the attachment of gold nanoparticles along those bare facets. This kind of oriented attachment leads to the formation of 1D nanostructures with high aspect ratios. In this chapter, the synthesis, characterisation, formation mechanism and optical properties of high aspect ratio, molecular scale single crystalline gold nanowires has been described. This represent the first ever successful method to produce ultrafine 1D metallic nanostructures approaching molecular dimensions. Chapter V deals with the formation of hybrid nanostructures by attaching the cubic intermediate phase to a substrate like carbon nanotubes followed by the reduction of the attached intermediates on the tubes. The Pt intermediates have been synthesized and attached on the wall of functionalized CNTs and reduced. The PtCNT nanocomposites been characterized by several spectroscopic and microscopic techniques. The electrocatalytic activity of these nanocomposites towards the methanol oxidation has also been investigated. The composites exhibit high catalytic activity and good long term performance. The presence of functional groups on the CNT surface overcomes some of the limitations of current single metal catalysts that suffer from CO poisoning. Chapter VI deals with the formation of palladium nanostructures ranging from nanoparticles to hierarchical aggregates by controlled aggregation of nanoparticles in an organic medium that is tuned by the dielectric constant of the system. A crystalline intermediate of palladium salt has been synthesized and this intermediate of palladium has been used as the precursor solution for the synthesis of palladium nanostructures. The formation mechanism of the nanoporous Pd cluster is investigated using the modified DLVO approach. The catalytic efficiency of the Pd nanostructures has been investigated using the reduction of pnitrophenol and electrocatalytic hydrogen storage as model reactions. Chapter VII discusses the possibility of achieving functional bimetallic alloys by simultaneous reduction of the cubic intermediate of two different metals with experimental evidences. The synergistic effect of the two different metals gives rise to better catalytic activity. This chapter mainly deals with the synthesis of bimetallic porous nanoclusters of goldpalladium and goldplatinum in an organic medium. Detailed microstructural and spectroscopic characterisation of the bimetallic nanoclusters has been carried out and their electrocatalytic performance, morphological stability also investigated.

Le développement de méthodes rapides, précises et ultra-sensibles pour la détection d'analytes cibles en solution est crucial pour la recherche et les applications potentielles en médecine ou biologie moléculaire. Une approche très prometteuse consiste à développer des nano-capteurs à partir de nano-objets métalliques (NOM) qui présentent une résonance d'extinction dans leur réponse optique. Cette résonance nommée résonance de plasmon de surface localisée (RPSL) peut être ajustée spectralement en jouant sur la nature, la morphologie et l'environnement du NOM. Mesurer des modifications sur la RPSL de nano-objets individuels en présence d'analytes cibles doit permettre de s'affranchir des effets de moyennes dans les mesures d'ensemble. De plus, cela ouvre la voie vers le développement d'échantillons micrométriques pour des tests multicibles sans étiquette (« label-free »).Dans ce travail on a développé un nouveau dispositif expérimental basé sur la technique de spectroscopie à modulation spatiale (SMS) permettant de sonder la réponse optique de NOM individuels en milieu liquide. En parallèle des méthodes de synthèse ont été mises au point pour obtenir des échantillons sondes stables permettant des mesures sur NOM unique, en particulier sur des bipyramides d'or qui présentent de nombreuses qualités intrinsèques faisant d'elles de bonnes candidates pour le « bio-sensing ».Des mesures ont été réalisées dans des environnements d'indice variable et les changements détectés sont en bon accord avec les simulations théoriques. De plus, de nombreuses études ont été réalisées pour comprendre l'influence des nombreux paramètres agissant sur la réponse optique des systèmes étudiés / Advances in the development of rapid, accurate and highly sensitive methods for detecting target analytes in solution will provide crucial tools for research and applications in medicine and molecular biology. One of the currently most promising approaches is the development of nanosensors based on the localized surface plasmon resonance (LSPR) of noble metal nano-objects (MNOs), which is an optical response that depends on their size, shape, composition and local environment. The ability to measure the modification of the reponse of a single MNO in the presence of a target analyte would allow each object to act as an independent probe with increased sensitivity as the signal would be isolated from the averaging effects of ensemble measurements. Furthermore it would allow the development of micrometric, functionalized multiprobe samples for multitarget label-free assays.In this work, a novel experimental setup based on the spatial modulation spectroscopy (SMS) technique has been developed to measure the optical response of individual nano-objects in a liquid environment. In parallel, a new technique has also been developed to elaborate stable probes for measurements with the new setup, with a focus on gold bipyramids due to numerous qualities that make them excellent candidates for biosensing probes. The setup has been used to measure the response of individual objects in environments of different real refractive indices and the detected changes have been shown to be in good agreement with theoretical calculations. Numerical studies have also been performed to investigate the influence on the optical response of numerous factors encountered in the studied systems

[ES] En este trabajo estudiamos dos reacciones catalíticas relevantes para la industria y la localización del anión fluoruro en la zeolita RTH, sintetizada en medio fluoruro. El capítulo 3 es el primer capítulo de resultados, donde se estudia la reducción quimioselectiva del nitroestireno en las superficies Ni(111), Co(111), Cu(111) y Pd(111). El mecanismo generalmente aceptado de esta reacción está basado en el esquema propuesto por Haber en 1898, en el que la reacción puede transcurrir por dos rutas, la directa y la de condensación. En este capítulo exploramos ambas rutas, y observamos que la ruptura de los enlaces N-O y la consecuente formación de enlaces metal-O está más favorecida que la formación de enlaces N-H en las superficies Ni(111) y Co(111), debido al carácter oxofílico de ambos metales. Las etapas más lentas involucran la formación de enlaces N-H. En las superficies de metales nobles como Pt(111) y Pd(111) se observa el comportamiento contrario. La superficie Cu(111) es un caso intermedio comparado con los metales nobles y no nobles. Además, el nitroestireno interactúa con los átomos de Cu de la superficie solo a través de grupo nitro, con lo cual es un candidato ideal para alcanzar selectividades cerca del 100%. Sin embargo, la superficie Cu(111) no es capaz de activar la molécula de H2. En este sentido, proponemos un catalizador bimetálico basado en Cu, dopado con otro metal capaz de activar al H2, tales como el Pd o el Ni. En los capítulos 4 y 5 se ha estudiado la reducción catalítica selectiva de los óxidos de nitrógeno (SCR, en inglés) con amoníaco. Usando métodos de DFT, hemos encontrado rutas para la oxidación de NO a NO2, nitritos y nitratos con energías de activación relativamente bajas. También, hemos encontrado que la reducción de Cu2+ a Cu+ requiere la participación simultánea de NO y NH3. Posteriormente, hemos estudiado la influencia del NH3 en este sistema con métodos de dinámica molecular. El NH3 interacciona fuertemente con el Cu+ de forma que dos moléculas de este gas son suficientes para romper la coordinación del catión Cu+ con los oxígenos del anillo 6r, y formar el complejo lineal [Cu(NH3)2]+. Además, los cationes Cu2+ pueden ser estabilizados fuera de la red mediante la formación del complejo tetraamincobre(II). Debido a la presencia de los cationes Cu+ y Cu2+ coordinados a la red de la zeolita, aparecen bandas en la región entre 800-1000 cm-1 del espectro infrarrojo. El análisis de las frecuencias IR de varios modelos con Cu+ y Cu2+ coordinados al anillo 6r, o formando complejos con amoniaco indica que cuando los cationes Cu+ y Cu2+ están coordinados a los oxígenos del anillo 6r aparecen vibraciones entre 830 y 960 cm-1. Frecuencias en esta zona también se obtienen en los casos en que NO, NO2, O2 y combinaciones de dos de ellos están adsorbidos en Cu+ y Cu2+. Sin embargo, cuando los cationes Cu+ y Cu2+ están fuera del anillo (no hay enlaces entre los cationes de cobre y los oxígenos del anillo 6r) no se obtienen vibraciones de IR en esta región del espectro. Estos resultados indican que con el seguimiento del espectro IR durante la reacción SCR es posible determinar si los cationes Cu+ y Cu2+ están coordinados o no al anillo de 6r en las etapas de oxidación y reducción. Por último, hemos simulado el desplazamiento químico de 19F, δiso,, en la zeolita sintetizada RTH. El análisis del δiso de los distintos modelos utilizados nos ha permitido reconocer la simetría del material sintetizado, el cual pertenece al grupo espacial P1 y la nueva celda unidad ha sido confirmada experimentalmente por difracción de rayos X. Finalmente, hemos asignado la señal experimental que aparece en el espectro de 19F a -67.2_ppm, al F- localizado en un sitio T2, el cual es a su vez la posición más estable. Además, la señal a -71.8 ppm se ha asignado al anión F- localizado en un sitio T4. / [CA] En aquest treball estudiem dues reaccions catalítiques rellevants per a la indústria i la localització de l'anió fluorur en la zeolita RTH, sintetitzada al mig fluorur. El capítol 3 és el primer capítol de resultats, on s'estudia la reducció quimioselectiva del nitroestireno en les superfícies Ni(111), Co(111), Cu(111) i Pd(111). El mecanisme generalment acceptat d'aquesta reacció està basat en l'esquema proposat per Haver-hi en 1898, en el qual la reacció pot transcórrer per dues rutes, la directa i la de condensació. En aquest capítol explorem totes dues rutes, i observem que la ruptura dels enllaços N-O i la conseqüent formació d'enllaços metall-O està més afavorida que la formació d'enllaços N-H en les superfícies Ni(111) i Co(111), a causa del caràcter oxofílico de tots dos metalls. Les etapes més lentes involucren la formació d'enllaços N-H. En les superfícies de metalls nobles com Pt(111) i Pd(111) s'observa el comportament contrari. La superfície Cu(111) és un cas intermedi comparat amb els metalls nobles i no nobles. A més, el nitroestireno interactua amb els àtoms de Cu de la superfície sol a través de grup nitre, amb la qual cosa és un candidat ideal per a aconseguir selectivitats prop del 100%. No obstant això, la superfície Cu(111) no és capaç d'activar la molècula d'H2. En aquest sentit, proposem un catalitzador bimetàl·lic basat en Cu, dopat amb un altre metall capaç d'activar a l'H2, com ara el Pd o el Ni. En els capítols 4 i 5 hem estudiat la reducció catalítica selectiva dels òxids de nitrogen (SCR, en anglés) amb amoníac. Usant mètodes de DFT, hem trobat rutes per a l'oxidació de NO a NO2, nitrits i nitrats amb energies d'activació relativament baixes. També, hem trobat que la reducció de Cu2+ a Cu+ requereix la participació simultània de NO i NH3. Posteriorment, hem estudiat la influència del NH3 en aquest sistema amb mètodes de dinàmica molecular. El NH3 interacciona fortament amb el Cu+ de manera que dues molècules d'aquest gas són suficients per a trencar la coordinació del catió Cu+ amb els oxígens de l'anell 6r, i formar el complex lineal [Cu(NH3)2]+. A més, els cations Cu2+ poden ser estabilitzats fora de la xarxa mitjançant la formació del complex tetraamincobre(II). A causa de la presència dels cations Cu+ i Cu2+ coordinats a la xarxa de la zeolita, apareixen bandes a la regió entre 800-1000 cm-1 de l'espectre infraroig. L'anàlisi de les freqüències IR de diversos models amb Cu+ i Cu2+ coordinats a l'anell 6r, o formant complexos amb amoníac indica que quan els cations Cu+ i Cu2+ estan coordinats als oxígens de l'anell 6r apareixen vibracions entre 830 i 960 cm-1. Freqüències en aquesta zona també s'obtenen en els casos en què NO, NO2, O2 i combinacions de dues d'ells estan adsorbidos en Cu+ i Cu2+. No obstant això, quan els cations Cu+ i Cu2+ estan fora de l'anell (no hi ha enllaços entre els cations de coure i els oxígens de l'anell 6r) no s'obtenen vibracions d'IR en aquesta regió de l'espectre. Aquests resultats indiquen que amb el seguiment de l'espectre IR durant la reacció SCR és possible determinar si els cations Cu+ i Cu2+ estan coordinats o no a l'anell de 6r en les etapes d'oxidació i reducció. Finalment, hem simulat el desplaçament químic de 19F, δiso, en la zeolita sintetitzada RTH. L'anàlisi del δiso dels diferents models utilitzats ens ha permés reconéixer la simetria del material sintetitzat, el qual pertany al grup espacial P1 i la nova cel·la unitat ha sigut confirmada experimentalment per difracció de raigs X. Finalment, hem assignat el senyal experimental que apareix en l'espectre de 19F a -67.2 ppm, al F- localitzat en un lloc T2, el qual és al seu torn la posició més estable. A més, el senyal a -71.8 ppm s'ha assignat a l'anió F- localitzat en un lloc T4. / [EN] In this work, we have studied two heterogeneous catalytic reactions and the localization of the fluoride anion in the as-made RTH framework, synthesized in fluoride medium. The first results, included in chapter 3, correspond to the chemoselective reduction of nitrostyrene on different metal surfaces, i.e, Ni(111), Co(111), Cu(111) and Pd(111). Until very recently, the reduction of the nitro group was explained on the basis of the general mechanism proposed by Haber in 1898 where the reaction can follow two routes, the direct and condensation route. We have explored the relevant elementary steps of both routes and found that because of the oxophilic nature of Ni and Co, the steps involving the dissociation of N-O bonds and formation of metal-O bonds are significantly favored compared with the other steps on both metal surfaces. In addition, the most demanding steps in terms of energy involve the formation of N-H bonds. These findings are in contrast to those of noble metals such as Pt and Pd, where the opposite behavior is observed. The behavior of Cu(111) lies in between the aforementioned cases, and also no chemical bonds between the carbon atoms of the aromatic ring of nitrostyrene and the Cu(111) surface is formed. For this reason, it might be an ideal candidate to achieve nearly 100 % selectivity. However, the Cu(111) surface does not seem to activate the H2 molecule. In this regard, we propose a bimetallic Cu-based catalyst whose surface is doped with atoms of a H2-activating metal, such as Ni or Pd. On another matter, we have also investigated the selective catalytic reduction of nitrogen oxides (SCR-NOx) and the main results are presented in the following two chapters, 4 and 5. By using static DFT methods, we found pathways for the oxidation of NO to NO2, nitrites and nitrates with relatively low activation energies. We also found, in agreement with experimental reports, that the reduction of Cu2+ to Cu+ requires the simultaneous participation of NO and NH3. Later, molecular dynamics simulations allowed us to assess the influence of NH3. The strong interaction of NH3 with the Cu+ cation is evidenced by its ability to detach Cu+ from the zeolite framework and form the mobile linear complex [Cu(NH3)2]+. Cu+ is no longer coordinated to the zeolite framework in the presence of two NH3 molecules. This observation and the fact that the T-O-T vibrations of the framework produce bands in the 800-1000 cm-1 region of the IR spectrum when perturbed by the coordination of Cu+ and Cu2+ cations, indicate that bands in the 800-1000 cm-1 regions should be observed when both copper cations are bonded to the framework oxygens. Finally, we have also studied NMR properties of the as-made pure silica RTH framework, aiming at locating the compensating fluoride anion. The calculation of the 19F chemical shift in different T sites and comparison with the experimental NMR spectra shows that the as-made RTH belongs to the P-1 space group with 16 Si, 32 O atoms, one fluoride anion and one OSDA cation. These results have been confirmed experimentally by XRD. In addition, we have assigned the experimental signal of 19F at -67.2 ppm to the fluoride anion in a T2 site, which in turn is the most stable location found, and the signal of -71.8 ppm to a fluoride anion sitting in a T4 site. / My acknowledgements to “La Caixa foundation” for the financial support through “La Caixa−Severo Ochoa” International PhD Fellowships (call 2015), to the Spanish Supercomputing Network (RES), to the Centre de Càlcul de la Universitat de València, to the Flemish Supercomputer Center (VSC) of Ghent University for the computational resources and technical support, and to the Spanish Government through the MAT2017-82288-C2-1-P programme / Millan Cabrera, R. (2021). Computational study of heterogeneous catalytic systems. Kinetic and structural insights from Density Functional Theory [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/161934

L’industrie produit de grandes quantités d’effluents aqueux qu’il convient de traiter. Des traitements alternatifs aux procédés biologiques doivent être développés pour certains effluents toxiques et/ou non biodégradables. L’oxydation en voie humide catalytique repose sur l’action de l’oxygène sur les polluants en phase aqueuse à haute température et haute pression. Préalablement à cette étude, des catalyseurs au Ru ou Pt supportés sur ZrO2 ou TiO2très actifs et très stables pour l’OVHC de polluants modèles et de quelques effluents réels ont été développés. Ce travail a examiné ces catalyseurs sur d’autres effluents réels : un effluent provenant d’une unité de production de membranes contenant du glycérol et du DMF, uneffluent de sauce de couchage provenant de l’industrie papetière et un concentrât de lixiviatde décharge. Les catalyseurs se sont révélés très actifs et stables pour la minéralisation du glycérol, mais une forte lixiviation a été observée lors de l’OVHC du DMF du fait de la présence d’amines. L’oxydation de l’effluent de sauce de couchage permet de minéraliser la charge organique, facilitant le recyclage de la charge minérale, avec une amélioration accrue de la biodégradabilité du surnageant en présence des catalyseurs. Enfin, l’ajout de catalyseurs lors de l’OVH du concentrât de lixiviat de décharge permet d’améliorer sa minéralisation et d’éliminer totalement les ions ammonium / Industries produce huge volumes of effluents which need to be treated before disposal.Alternative treatments to the more classical biological techniques are required in the case oftoxic and/or non biodegradable effluents. The wet air oxidation (WAO) and catalytic wet airoxidation (CWAO) are based on the reaction of an oxidant (oxygen) with the pollutants in aqueous phase at high temperature and pressure. Ru or Pt catalysts supported on zirconium and titanium oxides were previously shown to be highly active and stable in the CWAO of awide range of model compounds and real complex effluents. These catalysts were evaluated in the CWAO of problematic effluents: one containing glycerol and DMF, one paper coatingslip effluent and one concentrated landfill leachate. The catalysts showed high activity and stability in the CWAO of glycerol, while the metal leached upon DMF CWAO due to the presence of amines. WAO leads to the partial mineralization of the organic load in paper coating slip, allowing an easy separation recycling of mineral pigments, with an improved biodegradability of the supernatant with the use of a catalyst. The use of a catalyst upon landfill leachate WAO leads higher COT conversion and complete ammonia elimination