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[ES] En esta tesis se realiza un estudio de acidez de zeolita LTA con la relación Si/Al 5 y 40 utilizando la técnica de dispersión inelástica de neutrones (INS) en combinación con otras tecnicas como la modelización computacional y la espectroscopía de resonancia magnética nuclear (RMN). Las zeolitas son aluminosilicatos altamente cristalinos que forman parte de un grupo importante de los materiales funcionales. Las zeolitas son extremadamente útiles como catalizadores para muchas reacciones importantes con moléculas orgánicas. Las más importantes son craqueo, isomerización y síntesis de hidrocarburos. Las propiedades catalíticas de una zeolita dependen principalmente de su acidez y ésta depende de tres factores: el número totál de los sitios ácidos, sus fuerzas individuales y su localización individual, estando estos tres factores relacionados. Los parámetros geométricos definidos por localización de los sitios ácidos (es decir, la longitud y los ángulos de enlaces entre los átomos alrededor del sitio ácido) contribuyen de una manera importante a la fuerza ácida. En la literatura hay muchos trabajos de estudios de acidez en zeolita utilizando la espectrometría infrarroja (IR), sin embargo, con esta técnica es imposible medir las vibraciones de flexión (bending modes, 200-1200 cm-1), las bandas más sensibles al entorno local de los centros ácidos, ya que estas bandas se superponen con las bandas de vibración de la red de zeolite (300-1800 cm-1). En esta tesis se realiza un estudio de acidez utilizando la tecnica de INS, que nos permite medir principalmente los modos de vibración de los átomos de H y también nos permite medir todas las bandas de vibración (incluido el bending). Este estudio muestra que la combinación de la alta calidad de las muestras y la sensibilidad del instrumento utilizado permite detectar con alta precisión los sitios ácidos y obtener la información sobre su posición que a su vez nos perimte obtener la posición de los átomos de Al. Con el fin de interpretar los espectros INS se ha realizado un estudio computacional (cálculos ab-initio) con el objetivo de comparar los espectros cálculados con los resultados experimentales y definir el modelo que reproduce la posición mas probable de los centros ácidos en la muestra. / [CA] En aquesta tesi es realitza un estudi d'acidesa de zeolita LTA amb la relació Si / Al 5 i 40 utilitzant la tècnica de dispersió inelastica de neutrons (INS) en combinació d'altres tècniques com la modelització computacional i la espectroscòpia de ressonància magnètica nuclear (RMN ). Les zeolites són aluminosilicats altament cristal·lins que formen part d'un grup important dels materials funcionals. Les zeolites són extremadament útils com a catalitzadors per a moltes reaccions importants amb molècules orgàniques. Les més importants són craqueig, isomerització i síntesi d'hidrocarburs. Les propietats catalítiques d'una zeolita depenen principalment de la seva acidesa i aquesta depèn de tres factors: el nombre total dels llocs àcids, les seves forces individuals i la seva localització individual, estant aquests tres factors relacionats. Els paràmetres geomètrics definits per localització dels llocs àcids (és a dir, la longitud i els angles d'enllaços entre els àtoms al voltant del lloc àcid) contribueixen d'una manera important a la força àcida. En literatura hi ha molts treballs d'estudis d'acidesa en zeolita utilitzant l'espectrometria infraroja (IR), però és impossible mesurar les vibracions de flexió (bending modes, 200-1200 cm-1) amb aquesta tècnica ja que aquestes bandes es superposen amb les bandes de vibració de la xarxa de zeolita (300-1800 cm-1). La tècnica de dispersió inelastica de neutrons (Inelastic neutron scattering) ha estat utilitzada per estudiar l'acidesa de la zeolita LTA amb diferents relacions Si / Al (per tant diferents c.ontinguts de H en la zeolita). En aquesta tesi es realitza un estudi d'acidesa utilitzant la tècnica de INS, que ens permet mesurar principalment els modes de vibració dels àtoms d'H i també ens permet mesurar totes les bandes de vibració (inclòs el bending). Aquest estudi mostra que la combinació de l'alta qualitat de les mostres i la sensibilitat del instrument utilitzat permet detectar amb alta precisió els llocs àcids i obtenir la informació sobre la seva posició que en el seu lloc ens perimte obtenir la posició d'Al. Per tal de interpretar els espectres INS s'ha realitzat un estudi computacional (càlculs ab-initio) amb la comparació dels espectres calculats amb els resultats experimentals. / [EN] This thesis is dedicated to the study of acidity of LTA zeolites with Si/Al ratios 5 and 40 by using the technique of inelastic neutron scattering (INS) in combination with other techniques such as computational modeling and nuclear magnetic resonance (NMR) spectroscopy. Zeolites are crystalline and microporous aluminosilicates which form one of the most important groups of functional materials. Zeolites are widely used as solid acid catalysts for the wide range of important processes regarding organic molecules. The most important are cracking, isomerization reaction and synthesis of hydrocarbons. The catalytic properties of a zeolite depend strongly on its acidity, and this in turns depends on: the total number of acid sites, their individual strength, and their individual location. These three factors are strongly correlated. Geometric parameters that are defined by the location of the acid site (i.e., bond angles and lengths around the acid site) make a remarkable contribution to the acid strength. There are several studies, found in literatures, typically done by Infrared (IR) or Nuclear magnetic resonance (NMR) technique and dedicated to acidity of zeolites. However, the hydrogen bending modes (200-1200 cm-1), which are found to be more sensitive to local environment, cannot be observed by this technique, since these bands overlap with strong bands of the vibrations of zeolitic framework (300-1800 cm-1). INS technique used in this study allows to detect the bands of vibrations of hydrogen atoms in zeolites (including bending modes). Moreover, this study shows that the combination of an extremely high quality of the samples and the sensitivity of the instrument allows to detect with high precision the acid sites of both high-silica and low-silica zeolites and obtain information about their position. This in its turn gives us the possibility to obtain the aluminium location in zeolites. In order to fully understand the INS spectra we performed ab-initio calculations that allow to interpret the experimental bands and choose a structural model that reproduces the probable location of acid sites in the sample. / Lemishko, T. (2019). Inelastic neutron scattering study of Brønsted acidity in LTA zeolite [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/119966

Ce travail s’intéresse à l’étude de l’adsorption sélective du phénol dans des solutions d’hydrocarbures pour la purification des biocarburants issus de la biomasse de la 2ème génération. L’objectif de ce travail est de proposer, à l’aide d’une approche expérimentale et théorique, un adsorbant présentant à la fois une grande capacité d’adsorption du phénol, une sélectivité envers le phénol même en présence d’autres composés aromatiques ainsi qu’un bon pouvoir régénératif dans des conditions douces.Plusieurs familles d’adsorbants sont étudiées : des zéolithes Y et USY avec différents cations de compensation de charge (H+ et Na+) et différentes proportions de la surface micro et de mésoporeuse, des solides siliciques ayant des variables teneurs en groupement silanols et du charbon actif comme solide de référence. Les résultats d’adsorption montrent que dans les micropores des zéolithes, le phénol « interne » peut s’adsorber au nombre de 2 à 4 molécules par supercage, sans pouvoir entrer dans les cages sodalites. Dans la surface mésoporeuse des zéolithes USY et des solides siliciques, la quantité de phénol « externe » adsorbée dépend de la densité des silanols. En présence de toluène dans le mélange, les sites acides montrent une sélectivité importante envers l’adsorption du phénol, cette sélectivité est justifiée par une énergie d’interaction du phénol supérieure à celle du toluène sur ces sites. En revanche, l’adsorption du phénol sur le Na+ et les groupements silanols est affectée respectivement par la présence de faibles et de hautes teneurs en toluène. L’étude de la capacité de régénération des adsorbants met en évidence que les espèces phénoliques fortement liées sont formées sur les sites acides des zéolithes Y (H+Y, Na+Y et USY).Le meilleur compromis en termes de capacité d’adsorption de phénol, de sélectivité et de pouvoir régénératif est obtenu sur la zéolithe H+Y présentant un rapport Si/Al de 2,9. / This work focuses on the study of the selective adsorption of phenol from hydrocarbon solutions for the purification of 2nd generation biofuels. The objective of this work is to propose, using experimental and theoretical approaches, an adsorbent that can gather a good adsorption capacity of phenol, a selectivity towards phenol even in the presence of other aromatic compounds as well as good regeneration capacity under mild conditions.Several adsorbents were studied: Y and USY zeolites with different cations (H+ and Na+) and different proportions of micro and mesoporous surfaces, silica based solids presenting variable amount of silanol group and charcoal as a reference. The adsorption results show that, in the microporous of zeolites, the "internal" phenol can be adsorb to the number of 2 to 4 molecules per supercage, without being able to enter in the sodalite cages. In the mesoporous surface of the USY zeolites and the silica based solids, the amount of adsorbed "external" phenol depends on the density of the silanol groups. In the presence of toluene in the mixture, the acidic sites show a high selectivity towards phenol adsorption, this selectivity is justified by a higher interaction energy of phenol than toluene over these sites. Whereas, the adsorption of phenol over Na+ cation and over the silanol groups was respectively affected at low and high toluene levels. The study of the regeneration capacity of the adsorbents shows that the strongly bounded phenolic species are formed on the acidic sites of Y zeolites (H+Y, Na+Y and USY).The best compromise in terms of phenol adsorption capacity, selectivity and regeneration ability was obtained over the H+Y zeolite presenting a Si/Al ratio of 2.9.

Many zeolites are deployed in various industrial processes owing to their robust catalytic performance and hydrothermal stability. Reactions in zeolites are catalyzed via framework aluminum. The Si/Al ratio is a metric that describes the relative aluminum content in zeolites. However, several researchers noted that the proximity of aluminum in the framework could impact the catalyst output [1–3]. In this work, the influence of paired acid sites is examined in ZSM-22. The 1-dimensional nature of ZSM-22 allows for direct assessment of aluminum proximity without the influence of channel intersection. Theoretical investigations via static density functional theory (DFT) optimization calculations on isolated and paired BAS in ZSM-22 revealed a potential increase in deprotonation potential energy (DPE), indicating a weaker acid with closer aluminum sites. One specific paired model, however, suggested stronger acid behavior, likely due to unfavorable proton-proton interactions influenced by proximity and orientation. Additionally, ammonia adsorption calculations inferred improved adsorption by isolated models, possibly due to unfavorable ammonium-proton interactions in the paired models. Reaction state calculations of ethylene and propylene oligomerization suggested enhanced stabilization of reactant molecules in paired sites. The synthesis of ZSM-22 showed sensitivity to precursor ratios and conditions, but pure samples were successfully achieved through iterative optimization. Catalytic testing of ethylene oligomerization with these samples, classified by their Si/Al ratios and unique fractions of paired acid sites, showed a correlation between higher fractions of paired BAS and increased catalytic activity and selectivity. Samples with higher fractions of paired BAS displayed a higher activity and selectivity for heavier hydrocarbons, explained by the enhanced adsorption capacity of paired BAS for larger reactant molecules, prompting further oligomerization and enhanced catalytic activity. Our findings demonstrate the impact of BAS proximity in dictating the activity and selectivity in ZSM-22 and provide valuable insights for designing more efficient industrial zeolite-based catalysts.

Commercially available 4,4′-dichlorodiphenylsulfone (DCDPS) was successfully disulfonated with fuming sulfuric acid to yield 3,3′-disodiumsulfonyl-4,4′-dichlorodiphenylsulfone (SDCDPS). Subsequently, DCDPS and SDCDPS were systematically reacted with 4,4′-biphenol under nucleophilic step polymerization conditions to generate a series of high molecular weight, film-forming, ductile, ion conducting copolymers. These were converted to the acid form and investigated as proton exchange membranes for fuel cells. Hydrophilicity increased with the level of sulfonation. However, water sorption increased gradually until about 50 mole percent SDCDPS was incorporated, and thereafter showed a large increase to yield water soluble materials for the 100% SDCDPS system. Atomic force microscopy (AFM) confirmed that the morphology of the copolymers displayed continuity of the hydrophilic phase at 60 mole percent SDCDPS. Conductivity measurements in the 40-50 mole percent SDCDPS range, where excellent mechanical strength was maintained, produced values of 0.1 S/cm or higher which were comparable to the control, Nafion™. These compositions also show a high degree of compatibility with heteropolyacids such as phosphotungstic acid. These inorganic compounds provide a promising mechanism for obtaining conductivity at temperatures well above the boiling point of water and membrane compositions containing them are being actively pursued. The water soluble 100% SDCDPS system was further investigated by successfully functionalizing the endgroups to afford aromatic amines via appropriate endcapping with m-aminophenol. Oligomers and polymers from 5-30 kg/mole number average molecular weight were synthesized and well characterized by NMR spectroscopy, endgroup titrations and size exclusion chromatography. The diamino-telechelic sulfonated segment was reacted with several dianhydrides and diamines to produce multiblock, hydrophobic polyimide-hydrophilic sulfonated polyarylene ether copolymers. Both ester-acid and amic acid synthesis routes were utilized in combination with spin-casting and bulk imidization. A series of tough, film-forming segmented copolymers was prepared and characterized. AFM measurements demonstrated the generation of quite well defined, nanophase-separated morphologies which were dependent upon composition as well as aging in a humid environment. Characterizations of the segmented copolymers for conductivity, and water and methanol sorption were performed and comparisons to state-of-the-art perfluorinated Nafion™ systems were made. It is concluded that the segmented or block systems have the potential to enhance certain desirable PEM characteristics in fuel cells, particularly those related to swelling, retention of mechanical strength at elevated temperatures, and critical adhesion issues in membrane electrode assemblies. / Ph. D.

Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico / A viabilidade econÃmica da produÃÃo do biodiesel depende do uso do glicerol, subproduto com estrutura multifuncional, considerado matÃriaâprima bio-renovÃvel, de grande potencial para ser transformado a combustÃveis ou produtos quÃmicos de maior valor agregado. Com o intuito de contribuir para o desenvolvimento dessa linha de pesquisa, foi realizado estudo do potencial catalÃtico da γ-Al2O3 modificada com Ãxido de molibdÃnio e promotores (Cu, Ni ou Co), na reaÃÃo de desidrataÃÃo do glicerol a intermediÃrios quÃmicos com aplicaÃÃo industrial. A estratÃgia foi sintetizar esferas de Al2O3 por mÃtodo hÃbrido, as quais apresentam interessantes propriedades estruturais, texturais e quÃmicas para em seguida impregnar com precursores dos metais via mÃtodo nÃo-convencional (Pechini). A composiÃÃo dos materiais foi escolhida com o objetivo de avaliar o efeito bifuncional causado pela combinaÃÃo das propriedades Ãcido/bÃsicas e redox de catalisadores de molibdÃnio suportado em alumina. Para fins comparativos foi testado catalisador comercial Ni-Mo/Al2O3 com elevada acidez e porosidade. Os catalisadores foram caracterizados por: ICP-OES, FRX, TGA/DTA, DRX, MEV, IV, TPR-H2, TPD-CO2, isotermas de adsorÃÃo/dessorÃÃo de N2, e acidez atravÃs de adsorÃÃo de piridina. O desempenho dos catalisadores foi avaliado na desidrataÃÃo do glicerol, sob fluxo de N2 ou H2, a 1atm e 250ÂC. As mudanÃas na atividade e seletividade devido à troca do gÃs de arraste estÃo associadas a alteraÃÃes nas propriedades Ãcido/redox dos catalisadores, como sugerido pelas medidas de acidez e TPR-H2. AcroleÃna foi o principal produto observado para todos os catalisadores, porÃm a amostra contendo cobre (CuMoAl), mostrou maior atividade catalÃtica e superior seletividade a Ãlcool alÃlico, bem como produÃÃo do 1-propanol; o que està associado a transferÃncia de hidrogÃnio. Essa seletividade concorda com resultados de TPR-H2, que mostram maior influÃncia do cobre sobre a reduÃÃo do Ãxido de molibdÃnio, quando comparado aos promotores (Co ou Ni). Ao final sÃo propostos passos reacionais envolvidos na conversÃo do glicerol a Ãlcool alÃlico. / The economic viability of biodiesel production depends of the use of glycerol, by-product with multifunctional structure, considered a bio-renewable feedstock of great potential to be transformed to fuel or higher value-added chemicals products. In order to contribute to the development of this research area, study was carried out in order to explore the catalytic potential γ-Al2O3 modified with molybdenum oxide and promoter (Cu, Ni or Co) in the glycerol dehydration reaction to chemical intermediates with industrial application was performed. The strategy was to synthesize Al2O3 spheres by hybrid method with interesting structural, textural and chemical properties for then impregnating with precursors of metals via unconventional method (Pechini). The material composition was chosen with the aim of evaluating the bifunctional effect caused by the combination of acid-base and redox properties of molybdenum catalysts supported on alumina. For comparison was evaluated commercial Ni-Mo/Al2O3 catalyst with high acidity and porosidade. The catalysts were characterized for: ICP-OES, XRF, TGA/DTA, XRD, SEM, IR, H2-TPR, TPD-CO2, N2 adsorption/desorption isotherms, and acidity measurements through pyridine adsorption. The catalytic performance was evaluated in the glycerol dehydration under N2 or H2 flow at atmospheric pressure and 250ÂC. The modification in the activity and selectivity due to the change of carrier gas are attributed to the changes of acid/redox properties of the catalyst, as suggested by acidity measurements and TPR-H2. Acrolein was the main product observed for all catalysts, but the cupper containing catalyst (CuMoAl) showed higher catalytic activity and, and superior selectivity to allyl alcohol, as well as the production of 1-propanol, which is due to the hydrogen transfer. This selectivity agrees with H2-TPR results, which show stronger effect of the copper over the molybdenum oxide reduction, if compared to the others promoter (Co or Ni). At the end it is proposed the reaction steps mechanism for the glycerol conversion to allyl alcohol.

In der vorliegenden Arbeit wurden unter Anwendung unterschiedlicher Präparationstechniken vanadiumdotierte Metalloxide bzw. –oxofluoride synthetisiert, umfassend charakterisiert und in katalytischen, selektiven Oxidationsreaktionen (ODH von Propan und Methanoloxidation) getestet. Die Festkörper- und oberflächenchemischen Eigenschaften wurden generell mittels CHN-Analyse, ICP-OES, XRD, Raman-, FTIR-, MAS-NMR- und ESR-Spektroskopie, Py-PAS, TPD und Tieftemperatur-Stickstoffadsorption untersucht. Ergänzend kamen an ausgewählten Proben der temperaturprogrammierte Sauerstoffisotopenaustausch und Adsorptionsuntersuchungen von Methanol zum Einsatz. Als katalytische Testreaktionen dienten die oxidative Dehydrierung von Propan und die selektive Methanoloxidation. Unabhängig von der angewendeten Synthesemethode zeigte sich, dass die Festkörpereigenschaften sowohl durch den Vanadiumgehalt, als auch wesentlich durch die Art des Wirtsgitters beeinflusst werden. Es konnte nachgewiesen werden, dass eine hohe Sauerstoffaustauschaktivität und das Vorhandensein Brønsted-saurer Zentren auf den Katalysatoroberflächen die Aktivierung der Edukte in den hier untersuchten katalytischen Reaktionen begünstigen. In Bezug auf die Selektivität zu den Zielprodukten Propen bzw. Formaldehyd sind diese Eigenschaften allerdings nachteilig, da an derartigen Zentren immer die Produkte der Totaloxidation (CO und CO2) gebildet werden. Besonders bemerkenswert ist das Verhalten der vanadiumdotierten Aluminiumoxofluoride. Diese Phasen wurden mit einer neuen Methode synthetisiert und enthalten fast ausschließlich Lewis-saure Zentren. Die Matrix wird zudem maßgeblich durch die Fluoridionen bestimmt, sodass die Sauerstoffmobilität und –austauschaktivität sehr gering sind. Dadurch reagieren sie, trotz einer relativ hohen katalytischen Aktivität, außerordentlich selektiv in den hier untersuchten selektiven Oxidationsreaktionen. / In this thesis, vanadium containing metal oxides and oxyfluorides were prepared, thoroughly characterised and tested as catalysts in selective oxidation reactions. Bulk and surface properties of all samples were studied by means of CHN-analysis, ICP-OES, XRD, Raman-, FTIR-, MAS-NMR- und ESR-spectroscopy, Py-PAS, TPD and BET-adsorption. Moreover, the oxygen isotope exchange behaviour and the methanol adsorption properties of selected samples were analysed in order to correlate the surface properties with the catalytic behaviour of the materials. Irrespective of the preparation technique applied, the properties of the solids strongly depend on the host lattice as well as on the vanadium content. It has been clearly revealed that a high oxygen exchange activity and the presence of Brønsted acid sites on the catalyst surface promote the activation of the educts in selective oxidation reactions. The enhanced activity, however, is generally accompanied by a low selectivity towards the desired products propylene and formaldehyde, respectively. The low selectivity is caused by the high concentration of catalytically active sites leading to the formation of carbon oxides as total oxidation products of propane and methanol. A very promising catalytic behaviour was observed with vanadium-doped aluminium oxyfluorides. The oxyfluorides were prepared by a new method and contain almost exclusively Lewis-acid sites. The matrix is mainly determined by the fluoride anions resulting in a reduced oxygen mobility and exchange activity. Hence, the vanadium-doped aluminium oxyfluorides exhibit a relatively high catalytic activity accompanied by an excellent selectivity in the oxidation reaction of propane and methanol.