<p>Nanotechnology is a relatively new research topic that attracts increasing interest from scientists and engineers all over the world, due to its novel applications. The use of nanomaterials has extended to a broad range of applications, for example chemical synthesis, microporous media synthesis and catalytic combustion, contributing to achievement of improved or promising results. Microemulsion (ME) is considered a powerful tool for synthesis of nanomaterials, due to its unique properties. This thesis concentrates on the use of the ME as a catalyst synthesis route for obtaining metal nanoparticles for two challenging concepts: Hydrogen production by a membrane reactor and selective catalytic oxidation (SCO) of ammonia in gasified biomass.</p><p>Particularly for the scope of the fist concept presented in this thesis, palladium nanoparticles were synthesised from ME in order to be deposited on zeolite composite membranes to improve the H₂ / CO₂ separation (hydrogen production) ability. The membranes impregnated with Pd nanoparticles were then tested in a metal reactor for the permeance and selectivity towards H₂ and CO₂. Regarding the second concept, cerium-lanthanum oxide nanoparticles were prepared by conventional methods and from ME in order to be tested for their activity towards SCO of ammonia in gasified biomass.</p><p>The environmental importance of these two applications under investigation is great, since both are involved in processes contributing to the minimisation of the harmful exhaust gases released to the atmosphere from numerous industrial applications, such as the oil industry and heat-and-power production (for example combustion of natural gas or biomass in a gas turbine cycle). Regarding these applications, separation and capture of CO₂ from exhaust gases and oxidation of the fuel-bound ammonia in gasified biomass directly to nitrogen, minimising at the same time NO_xformation, are rated as very important technologies. The results obtained from this work and presented analytically in this thesis are considered successful and at the same time promising, since further research on the ME method can even lead to improvement of the current achievements.</p><p>The first part (Chapter 2) of the thesis gives a general background on the ME method and the applications in the two concepts under investigation. Additionally, it describes how the nanoparticles corresponding to the concepts were synthesised.</p><p>The second part (Chapter 3) of the thesis describes the different Pd-nanoparticle impregnation methods on the zeolite composite membranes and the results obtained form the permeation tests. In parallel with impregnation methods, various aspects that affect the Pd impregnation efficiency and the membrane performance such as duration, temperature and calcination conditions are discussed thoroughly.</p><p>The third and final part of the thesis (Chapter 4) concerns the preparation of the cerium-lanthanum oxide catalysts and the activity tests (under simulated gasified biomass fuel conditions) carried out in order to monitor the activity of these catalysts towards the SCO of ammonia. Additionally, a comparison of the activity between identical catalysts prepared by conventional methods and the ME method is discussed.</p>

Nanotechnology is a relatively new research topic that attracts increasing interest from scientists and engineers all over the world, due to its novel applications. The use of nanomaterials has extended to a broad range of applications, for example chemical synthesis, microporous media synthesis and catalytic combustion, contributing to achievement of improved or promising results. Microemulsion (ME) is considered a powerful tool for synthesis of nanomaterials, due to its unique properties. This thesis concentrates on the use of the ME as a catalyst synthesis route for obtaining metal nanoparticles for two challenging concepts: Hydrogen production by a membrane reactor and selective catalytic oxidation (SCO) of ammonia in gasified biomass. Particularly for the scope of the fist concept presented in this thesis, palladium nanoparticles were synthesised from ME in order to be deposited on zeolite composite membranes to improve the H2 / CO2 separation (hydrogen production) ability. The membranes impregnated with Pd nanoparticles were then tested in a metal reactor for the permeance and selectivity towards H2 and CO2. Regarding the second concept, cerium-lanthanum oxide nanoparticles were prepared by conventional methods and from ME in order to be tested for their activity towards SCO of ammonia in gasified biomass. The environmental importance of these two applications under investigation is great, since both are involved in processes contributing to the minimisation of the harmful exhaust gases released to the atmosphere from numerous industrial applications, such as the oil industry and heat-and-power production (for example combustion of natural gas or biomass in a gas turbine cycle). Regarding these applications, separation and capture of CO2 from exhaust gases and oxidation of the fuel-bound ammonia in gasified biomass directly to nitrogen, minimising at the same time NOx formation, are rated as very important technologies. The results obtained from this work and presented analytically in this thesis are considered successful and at the same time promising, since further research on the ME method can even lead to improvement of the current achievements. The first part (Chapter 2) of the thesis gives a general background on the ME method and the applications in the two concepts under investigation. Additionally, it describes how the nanoparticles corresponding to the concepts were synthesised. The second part (Chapter 3) of the thesis describes the different Pd-nanoparticle impregnation methods on the zeolite composite membranes and the results obtained form the permeation tests. In parallel with impregnation methods, various aspects that affect the Pd impregnation efficiency and the membrane performance such as duration, temperature and calcination conditions are discussed thoroughly. The third and final part of the thesis (Chapter 4) concerns the preparation of the cerium-lanthanum oxide catalysts and the activity tests (under simulated gasified biomass fuel conditions) carried out in order to monitor the activity of these catalysts towards the SCO of ammonia. Additionally, a comparison of the activity between identical catalysts prepared by conventional methods and the ME method is discussed. / QC 20101216

[ES] Las zeolitas son sólidos cristalinos microporosos con canales y cavidades de tamaños moleculares, que pueden presentar gran variedad de estructuras y composición química, lo que las hace útiles como catalizadores en gran variedad de procesos químicos. En la presente tesis doctoral, se han estudiado en profundidad las propiedades estructurales de zeolitas con estructura RTH y MFI pura sílice y aluminosilicato, utilizando fundamentalmente la técnica de resonancia magnética nuclear (RMN). Además, se han estudiado catalizadores zeolíticos tipo Ag-FAU para una reacción de interés medioambiental como la Oxidación Catalítica Selectiva de NH3 (NH3-SCO). En esta tesis, las zeolitas tipo MFI y RTH se han sintetizado utilizando tetraalquilamonios y tetralquilfosfonios como ADEs y HF como agente mineralizante. Los resultados referentes a la zeolita MFI pura sílice indican que el ADE utilizado afecta al orden local de la estructura, a la distribución de flúor y a la formación de defectos de red. En la síntesis de la zeolita tipo MFI aluminosilicato, se ha observado que el ADE utilizado y la relación Si/Al produce diferencias significativas en los espectros de RMN de 27Al, que se atribuyen normalmente a variaciones en la distribución del aluminio en diferentes sitios cristalográficos. Sin embargo, las diferencias desaparecen después de la calcinación, lo que cuestiona esta interpretación. La zeolita tipo RTH pura sílice se ha sintetizado con el catión iPr3MeP+ variando los tiempos y la temperatura de síntesis. Estos parámetros afectan tanto a la estructura local de los átomos de silicio como a la distribución del flúor en la zeolita. Se ha observado también la transformación de la estructura tipo STF a RTH durante la síntesis. La modificación con fósforo de zeolitas tipo aluminosilicato, que normalmente se realiza por impregnación, estabiliza el aluminio de la red en condiciones hidrotermales, lo que tiene importantes implicaciones en las aplicaciones industriales. En esta tesis, se han incorporado cantidades variables de fósforo en las zeolitas MFI y RTH aluminosilicatos utilizando mezclas de alquilamonios y alquilfosfonios como ADEs. Los resultados indican que el fósforo permanece en las zeolitas después de la calcinación estabilizando el aluminio de red. La caracterización detallada de las muestras ha permitido proponer las especies Al-P formadas, responsables de la estabilización de la red. Además, las zeolitas P-RTH y P-ZSM-5 se han utilizado como catalizadores para la reacción de metanol a olefinas. Por último, se ha estudiado la influencia de diferentes parámetros como la relación Ag/Al, la presencia de cationes alcalinos o la acidez Brønsted en zeolitas Ag-FAU y sus repercusiones en el comportamiento catalítico para la reacción de NH3-SCO. Los catalizadores se han caracterizado exhaustivamente antes, durante y después de la reacción, observándose que las partículas de plata metálica, que son los centros activos, se re-dispersan y oxidan en condiciones de reacción. / [CA] Les zeolites són sòlids cristal·lins i microporosos amb canals i cavitats de dimensions moleculars, que poden presentar una gran varietat d' estructures i composició química, això les fa molt interessants com a catalitzadors en un ampli nombre de reaccions químiques. En la present tesi doctoral, s'ha estudiat en profunditat les propietats estructurals de les zeolites amb estructura RTH i MFI pura sílice i amb sílici i alumini, utilitzant fonamentalment la tècnica de ressonància magnètica nuclear. A més, s'han estudiat catalitzadors basats en Ag-FAU zeolites per a una reacció d'interès mediambiental com es l' Oxidació Catalítica Selectiva d'amoníac (NH3-SCO). En aquesta tesi, les zeolites tipus MFI i RTH s'han sintetitzat amb l'ús de cations tetraalquilamoni i tetraalquilfosfoni i HF com agent mineralitzant. Els resultats obtinguts per a la zeolita MFI pura sílice mostren com l'ADE utilitzat juga un paper important en l'ordre local dels àtoms de silici, la distribució de fluor i la formació de defectes zeolítics. En la síntesi de la zeolita MFI aluminosilicat, s'ha observat que la natura dels ADEs i la relació Si/Al produeix diferències significatives a l'espectre de 27Al de RMN, normalment associades a una localització diferent de l'alumini. Però eixes diferències desapareixen amb la calcinació de les zeolites. La zeolita RTH pura sílice ha sigut sintetitzada amb el catió iPr3MeP+ modificant les condicions de síntesi (temps i temperatura). Els resultats mostren que l'ordre local dels àtoms de l' estructura zeolítica o la distribució de fluor es veu influenciada per aquests paràmetres. També s'ha pogut observar que en determinades condicions de síntesi es produeix la transformació de la estructura tipus STF en RTH en el procés de síntesi. La modificació amb fòsfor de les zeolites que contenen alumini, que normalment es realitza per impregnació, estabilitza l'alumini de l'estructura zeolítica en condicions hidrotermals, la qual cosa té una importància crucial per a les aplicacions industrials d'aquests materials. En aquesta tesi, s'han incorporat quantitats creixents de fòsfor a les zeolites RTH i MFI aluminosilicats utilitzant mescles d'alquilamonis i alquilfosfonis com ADEs. Els resultats indiquen que tot el fòsfor introduït roman a la zeolita després de la calcinació, estabilitzant l'alumini en la zeolita. La caracterització dels materials ha permès proposar les espècies Al-P formades a l'interior de les zeolites, que són les responsables de l'alta estabilitat hidrotermal de l'alumini a l'estructura zeolítica. A més, les zeolites RTH i MFI modificades amb fòsfor han sigut utilitzades com a catalitzadors en la reacció de metanol a olefines (MTO). Per últim, s'ha estudiat la influència de alguns paràmetres com la relació Ag/Al, la presència de cations alcalins o centres àcids de BrØnsted als catalitzadors tipus Ag-FAU i les seues repercussions per a la reacció de NH3-SCO. Els catalitzadors s'han caracteritzat abans, durant i després de la reacció i els resultats mostren que les nanopartícules de plata metàl·lica són el centre actiu de la reacció i que es re-dispersen i oxiden en condicions de reacció. / [EN] Zeolites are microporous crystalline solids containing channels and cavities of molecular dimensions, which can present different structures and chemical composition, making them especially interesting as catalysts in several chemical processes. In this doctoral thesis, we have deeply studied the structural properties of pure silica and aluminosilicate RTH- and MFI-type zeolites mainly using nuclear magnetic resonance (NMR) spectroscopy. Moreover, we have studied the properties of Ag-FAU zeolites as catalysts for the selective catalytic oxidation of ammonia (NH3-SCO), which is a reaction of great interest for the environmental. Here, zeolites RTH and MFI have been synthesized in the presence of tetraalkilammonium and phosphonium cations as OSDAs and in fluoride media. The results obtained for the MFI zeolites show that the OSDAs has a strong influence on the local order of the framework, the fluorine distribution and the formation of siloxy/silanol defects. The results for the aluminosilicate MFI-type (ZSM-5) zeolite show that the shape of the 27Al NMR spectrum changes depending on both the OSDA and the Si/Al ratio, which is usually attributed to a different Al sitting in the zeolite. These differences disappear after the calcination of the zeolites, questioning the classical interpretation. RTH-type zeolite has been synthesized using the iPr3MeP+ cation varying the synthesis conditions (time and temperature). The results show that these parameters affect the local environment of the silicon atoms and the fluorine distribution inside the zeolite. It has been also possible to identify the zeolitic transformation of the STF structure into the RTH-type during the synthesis. The introduction of phosphorus in the aluminosilicate zeolites, usually done by the impregnation procedure, stabilizes the framework aluminium under steam conditions, with important implications in industrial processes. In this doctoral thesis, we have varied the P/Al molar ratios using the dual-template synthesis technique. All phosphorus from the P-based OSDAs remain inside the zeolites after the thermal/hydrothermal treatments. The exhaustive characterization of the materials has allowed us to propose the Al-P species formed inside the zeolites responsible of the aluminium stabilization. Moreover, some phosphorus modified RTH and MFI zeolites were tested in the methanol to olefins (MTO) reaction. Finally, we have studied the influence of different parameters such as the Ag/Al ratio, the alkali cations or the presence of BrØnsted acid sites in the Ag-FAU zeolites and its implications in the NH3-SCO reaction. The Ag-FAU catalysts have been deeply characterized before, during and after the catalytic tests, identifying the Ag0 specie, which is the active centre for this reaction, and that metal particles are re-dispersed and oxidized under reaction conditions. / Martínez Ortigosa, J. (2021). Caracterización estructural de zeolitas por Resonancia Magnetica Nuclear y su aplicación como catalizadores [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/165576