Ethylene and propylene are important chemical feedstocks for the production of polyethylene and polypropylene. Ethylene and propylene can be produced by various methods including steam cracking of liquefied natural gas (LNG), naphta or light olefin fractions. The methanol to olefin (MTO) process provides an alternative means of producing ethylene and propylene, where ZSM-5 is frequently used as catalyst due to its hydrophobicity, strong acidity, molecular sieve properties and low tendency towards coking, which makes ZSM-5 one the most popular zeolite catalysts in the industry. The oil crisis 1973 and the second oil crisis in 1978 caused the development of a commercial MTO process. Mobil Research and Development Corporation built a fixed-bed pilot plant to demonstrate the feasibility of the MTO as well as methanol-to-gasoline (MTG) process. When the oil price dropped again during the 1980’s, further developments of commercial processes were stopped for the time being. However, investigations on a bench scale are still pursued, and applications for patents are still submitted. During this study ZSM-5 was synthesized with a hydrothermal method, which produced agglomerated polycrystalline grains with characteristic ZSM-5 morphology and a Si/Al ratio of approximately 40. The synthesis time, synthesis temperature and aging time were varied while keeping all the other synthesis parameters constant in order to determine their influence on crystallite size. The synthesis time was varied between 12-72 hours, synthesis temperature was varied between 130-170°C and aging time between 30-90 minutes. Using SEM to determine crystal size, it was found that a variation in the aging time produced the largest crystallites (average of 21.6μm ± 10.8μm) while also having the largest influence on crystallite size followed by synthesis temperature (average of 13.1μm ± 4.9μm) and finally synthesis time (average of 5.7μm ± 0.4μm). In all cases XRD and SEM confirmed the formation of ZSM-5. To evaluate the as-synthesized ZSM-5 and compare it to a commercial ZSM-5 catalyst, Catalyst A using the MTO process, ZSM-5 was synthesized for 72 hours at 170°C with an aging time of 60 minutes before synthesis. The as-synthesized as well as Catalyst A’s agglomerated polycrystalline grains were sieved into three size fractions: smaller than 75μm, 75-150μm and 150-300μm. All six ZSM-5 fractions of ZSM-5 were used as catalysts for the MTO process in a fixed bed reactor at 400°C, atmospheric pressure and a 20wt% methanol to water feed. At 3.5 hours time on stream (TOS), the intermediate 75-150μm fraction had the highest light olefin selectivity for both the as-synthesized as well as Catalyst A, followed by the 150-300μm fraction and finally the smaller than 75μm fraction with the lowest light olefin selectivity. From this results it is clear that the as-synthesised ZSM-5 did not perform as well as Catalyst A. While the intercrystalline voids of the agglomerated ZSM-5 form second-order pores where self-diffusion is enhanced, the increased diffusional barriers created by the intercrystalline boundaries reduce the diffusion rate, promoting secondary reactions at the strong Brönsted acid sites thereby reducing ethylene and propylene selectivity. Coking reduces access to the Brönsted acid sites and plays a more influencial role for smaller crystallite sizes. Accordingly, the smaller than 75μm fraction had the lowest light olefin selectivity, while the 150-300μm fraction was probably least influenced by coking. The increased pathways for products and reagents in the 150-300μm fraction resulted in more secondary reactions taking place within this catalyst than the 75-150μm fraction explaining the superior performance of the 75-150μm fraction. Since the grain size determines the ratio of the external to the internal surface areas as well as the amount of intercrystalline boundaries in the catalyst, it follows that the catalytic activity and polycrystalline grain size ratio should actually be tailored when optimising the product distribution of the ZSM-5 catalysed MTO process. The as-synthesized ZSM-5 didn’t perform very well when compared to Catalyst A and modification of the synthesis method is recommended. / Thesis (MSc (Chemistry))--North-West University, Potchefstroom Campus, 2012.

Ethylene and propylene are important chemical feedstocks for the production of polyethylene and polypropylene. Ethylene and propylene can be produced by various methods including steam cracking of liquefied natural gas (LNG), naphta or light olefin fractions. The methanol to olefin (MTO) process provides an alternative means of producing ethylene and propylene, where ZSM-5 is frequently used as catalyst due to its hydrophobicity, strong acidity, molecular sieve properties and low tendency towards coking, which makes ZSM-5 one the most popular zeolite catalysts in the industry. The oil crisis 1973 and the second oil crisis in 1978 caused the development of a commercial MTO process. Mobil Research and Development Corporation built a fixed-bed pilot plant to demonstrate the feasibility of the MTO as well as methanol-to-gasoline (MTG) process. When the oil price dropped again during the 1980’s, further developments of commercial processes were stopped for the time being. However, investigations on a bench scale are still pursued, and applications for patents are still submitted. During this study ZSM-5 was synthesized with a hydrothermal method, which produced agglomerated polycrystalline grains with characteristic ZSM-5 morphology and a Si/Al ratio of approximately 40. The synthesis time, synthesis temperature and aging time were varied while keeping all the other synthesis parameters constant in order to determine their influence on crystallite size. The synthesis time was varied between 12-72 hours, synthesis temperature was varied between 130-170°C and aging time between 30-90 minutes. Using SEM to determine crystal size, it was found that a variation in the aging time produced the largest crystallites (average of 21.6μm ± 10.8μm) while also having the largest influence on crystallite size followed by synthesis temperature (average of 13.1μm ± 4.9μm) and finally synthesis time (average of 5.7μm ± 0.4μm). In all cases XRD and SEM confirmed the formation of ZSM-5. To evaluate the as-synthesized ZSM-5 and compare it to a commercial ZSM-5 catalyst, Catalyst A using the MTO process, ZSM-5 was synthesized for 72 hours at 170°C with an aging time of 60 minutes before synthesis. The as-synthesized as well as Catalyst A’s agglomerated polycrystalline grains were sieved into three size fractions: smaller than 75μm, 75-150μm and 150-300μm. All six ZSM-5 fractions of ZSM-5 were used as catalysts for the MTO process in a fixed bed reactor at 400°C, atmospheric pressure and a 20wt% methanol to water feed. At 3.5 hours time on stream (TOS), the intermediate 75-150μm fraction had the highest light olefin selectivity for both the as-synthesized as well as Catalyst A, followed by the 150-300μm fraction and finally the smaller than 75μm fraction with the lowest light olefin selectivity. From this results it is clear that the as-synthesised ZSM-5 did not perform as well as Catalyst A. While the intercrystalline voids of the agglomerated ZSM-5 form second-order pores where self-diffusion is enhanced, the increased diffusional barriers created by the intercrystalline boundaries reduce the diffusion rate, promoting secondary reactions at the strong Brönsted acid sites thereby reducing ethylene and propylene selectivity. Coking reduces access to the Brönsted acid sites and plays a more influencial role for smaller crystallite sizes. Accordingly, the smaller than 75μm fraction had the lowest light olefin selectivity, while the 150-300μm fraction was probably least influenced by coking. The increased pathways for products and reagents in the 150-300μm fraction resulted in more secondary reactions taking place within this catalyst than the 75-150μm fraction explaining the superior performance of the 75-150μm fraction. Since the grain size determines the ratio of the external to the internal surface areas as well as the amount of intercrystalline boundaries in the catalyst, it follows that the catalytic activity and polycrystalline grain size ratio should actually be tailored when optimising the product distribution of the ZSM-5 catalysed MTO process. The as-synthesized ZSM-5 didn’t perform very well when compared to Catalyst A and modification of the synthesis method is recommended. / Thesis (MSc (Chemistry))--North-West University, Potchefstroom Campus, 2012.

The methanol-to-olefins reaction is an important industrial process for the production of light olefins (C2-C4). Silicoaluminophosphates are the most common catalysts for this process with SAPO-34 (CHA), SAPO-18 (AEI) and their intergrowths being considered the most catalytically active and selective. Understanding the crystal growth of such materials is important for control of the structure and defect incorporation, which can have a large effect on the catalytic behaviour. In this thesis, the synthesis, characterisation, catalysis and crystal growth of such materials are investigated. A series of CHA/AEI intergrowth materials were synthesised by sequential increases in silicon content, where low silicon content led to formation of AEI and higher silicon content led to CHA and intergrowth formation. X-ray diffraction and MAS-NMR were used to quantify the amount of intergrowth and there was a strong correlation between both techniques. Atomic Force Microscopy (AFM) revealed the mechanism by which these intergrowth structures grow. There is competition at the surface between the spiral-growth and layer-growth mechanisms, which has a significant effect on the resulting intergrowth, as intergrowth formation is only permitted with a layer-growth mechanism. Intergrowth on screw dislocations is not allowed, and thus discrete blocks of pure-phase AEI or CHA form. These intergrowth materials were tested for their performance in the methanol-to-olefins reaction. With a higher level of silicon, the catalysts had a larger acid site density but equivalent acid strength. The conversion of methanol over the catalysts correlated with the acid site density, where a greater acid site density led to higher conversion and faster deactivation. The selectivity over time was similar for all catalysts, with a high selectivity to ethylene and propylene. However, at the same percentage conversion, the C2/C3 ratio showed a strong correlation to the cage shape. Catalysts with a higher ratio of AEI cages had a higher selectivity to C3 and C4 products than the other catalysts, owing to the larger size of the internal AEI cage compared to the CHA cage. The crystal growth mechanism on SAPO-18 was investigated in detail to interrogate the complex spiral pattern that forms on the surface. Spirals form in a triangular type pattern due to differences in growth rates in different crystallographic directions. Interlaced terraces were also present. The unit cell and the relative orientation of the AEI cages define the different growth rates. In-situ AFM was used to investigate the dissolution behaviour of SAPO-18 and SAPO-34. In both cases, dissolution occurred via classical step retreat. The similarity in the layer stacking in both materials led to equivalent structure dissolution in both cases. The 0.9 nm layers dissolved first to 0.7 nm (closed cages) then to 0.4 nm (unstable intermediates). Dissolution of SAPO-18 revealed unusual spiral dissolution pits near the core of the dislocations. CHA/AEI intergrowth materials were also prepared using a dual-template method, where two templates, morpholine for CHA and N,N-diisopropylethylamine for AEI, were combined during synthesis. The phase transition from CHA to AEI occurred at different molar ratios with different synthesis procedures. XRD modelling confirmed the synthesis of an intergrowth phase at a molar ratio of 70% morpholine and 30% DPEA. Changes in chemical shift in the 13C MAS-NMR were used to observe the different template interactions with the framework as the ratio of CHA and AEI cages changed.

(1) We will show that nano sized samples of SAPO-34 synthesized by microwave heating presents much higher lifetime than standard-SAPO-34 synthesized by conventional hydrothermal method for the reaction of methanol to olefins. (2) We will stabilize the Nano SAPO-34 in the ways such as steaming with water or calcinated in H2 condition. (3) The treatment of mix alkali treatment with proper TPAOH/NaOH could make composites with mesopore and microporous structure in the zeolite ZSM-5 to reduce strong acid quantity and the change the selectivity of the main product. (4) Different 8MR zeolite show different selectivity and lifetime in the same condition in the reaction of methanol to olefins. / Li, Z. (2014). New micro and mesoporous materials for the reaction of methanol to olefins [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/44229

[ES] Las zeolitas tradicionalmente se han considerado silicoaluminatos microporosos formados por tetraedros TO4 (T = Si, Al) conectados entre sí, compartiendo átomos de oxígeno dando lugar a canales y cavidades de dimensiones moleculares. Debido al potencial que presentan como catalizadores en aplicaciones relevantes en la industria química y más recientemente en la industria medioambiental, ha habido un creciente interés en la síntesis de nuevos materiales zeolíticos. La incorporación de elementos diferentes al silicio y aluminio en su estructura (P, Ge, Fe, Ti, B etc.) ha dado lugar a la aparición de nuevos tamices moleculares zeolíticos, entre los que destacan los aluminofosfatos (AlPOs), siendo la primera familia de tamices moleculares con composiciones en las que no participa el silicio. El elevado número de nuevas estructuras de aluminofosfatos sintetizados, con tamaños de poro de hasta 13 Å, así como la facilidad con que el aluminio y el fósforo pueden ser sustituidos por otros elementos químicos, ha despertado un gran interés en estos materiales, al abrir un amplio rango de aplicaciones, especialmente en procesos de adsorción y catálisis. La presente tesis doctoral se centra en la síntesis de nuevos aluminofosfatos, empleando nuevas moléculas orgánicas como agentes directores de estructura, para su posterior aplicación como catalizadores en reacciones químicas de interés. En el Capítulo 1, se presenta una introducción general sobre las zeolitas y más concretamente los aluminofosfatos, su síntesis, propiedades y aplicaciones. En el Capítulo 2, se presentan los objetivos generales de este trabajo. En el Capítulo 3, se muestra la síntesis de los diferentes agentes directores de estructura orgánicos, así como de los principales materiales sintetizados, junto con los equipos de caracterización y procedimientos catalíticos utilizados. El Capítulo 4, se centra en la síntesis del primer aluminofosfato con estructura SAO (AlPO-SAO) y sus derivados incorporando silicio (SAPO-SAO) y germanio (GeAPO-SAO), siendo éste último, el primer germanoaluminofosfato tridimensional de poro grande descrito hasta la actualidad. La actividad catalítica de los catalizadores preparados es evaluada en la reacción de transposición de Beckmann y comparada con el material SAPO-37 (FAU). En el Capítulo 5, se estudian mediante síntesis de co-template los silicoaluminfosfatos erionita (ERI) y chabacita (CHA), ambos pertenecientes a la familia ABC-6, preparados a partir de dos nuevas familias de agentes directores de estructura orgánicos. En el Capítulo 6, se propone una nueva ruta de síntesis basada en la síntesis de co-template anterior, para la preparación del silicoaluminofosfato SAPO-34 empleando una mezcla de agentes directores de estructura orgánicos de tipo amina y tetraalquilfosfonio, estudiándose la naturaleza de las especies de fósforo localizadas en las cavidades de la estructura chabacita. Finalmente, se han evaluado las propiedades catalíticas del catalizador activado en distintas condiciones en el proceso de metanol a olefinas comparándolas con un material SAPO-34 sintetizado únicamente mediante un agente director de estructura orgánico nitrogenado. Por otra parte, se ha estudiado la estabilidad de todos los catalizadores en presencia de vapor de agua (100% steaming) a elevada temperatura. / [CA] Les zeolites tradicionalment s'han considerat silicoaluminats microporosos formats per tetraedres TO4 (T=Si, Al) connectats entre sí, compartint àtoms d'oxigen donant lloc a Canals i cavitats de dimensions moleculars. Degut al potencial que presenten com a catalitzadors en aplicacions rellevants en la industria química i més recentment en la industria mediambiental, hi ha hagut un creixent interès en la síntesis de nous materials zeolítics. La incorporació d'elements diferents al silici i alumini en la seua estructura (P, Ge, Fe, Ti, B etc.) ha donat lloc a l'aparició de nous tamisos moleculars zeolítics, entre els que destaquen els aluminofosfats (AlPOs), siguent la primera família de tamisos moleculars amb composicions en les que no participa el silici. L'elevat nombre de noves estructures d'aluminofosfats sintetitzats, amb tamany de porus de fins a 13 Å, així com la facilitat amb que l'alumini i el fòsfor puguen ser substituïts per altres elements químics, ha despertat un gran interès en estos materials, a l'obrir un ampli rang d'aplicacions, especialment en processos d'adsorció i catàlisi. La present tesi doctoral es centra en la síntesi de nous aluminofosfats, emprant noves molècules orgàniques com agents directors d'estructura, per a la seua posterior aplicació com a catalitzadors en reaccions químiques d'interès. Al Capítol 1, es presenta una introducció general sobre les zeolites i més concretament els aluminofosfats, la seua síntesi, propietats i aplicacions. Al Capítol 2, es presenten els objectius generals d'este treball. Al Capítol 3, es mostra la síntesis dels diferents agents directors d'estructura orgànics, així com dels principals materials sintetitzats, junt amb els equips de caracterització i procediments catalítics utilitzats. El Capítol 4, es centra en la síntesi del primer aluminofosfat amb estructura SAO (AlPO-SAO) i els seus derivats incorporant silici (SAPO-SAO) i germani (GeAPO-SAO), siguent este últim, el primer germanoaluminofosfat tridimensional de porus gran descrit fins l'actualitat. L'activitat catalítica dels catalitzadors preparats és avaluada en la reacció de transposició de Beckmann i comparada amb el material SAPO-37 (FAU). Al Capítol 5, s'estudien mitjançant síntesi de co-template els silicoaluminofosfats eritonita (ERI) i chabazita (CHA), ambdós pertanyents a la família ABC-6, preparats a partir de dos noves famílies d'agents directors d'estructura orgànics. Al Capítol 6, es proposa una nova ruta sintètica basada en la síntesi de co-template anterior, per a la preparació del silicoaluminofosfat SAPO-34 emprant una mescla d'agents directors d'estructura orgànics de tipus amina i tetraalquilfosfoni, estudiant-se la natura de les espècies de fòsfor localitzades en les cavitats de l'estructura chabazita. Finalment, s'han avaluat les propietats catalítiques del catalitzador activat en diverses condicions en el procés de metanol a olefines comparant-les amb un material SAPO-34 sintetitzat únicament mitjançant un agent director d'estructura orgànic nitrogenat. Per altra banda, s'ha estudiat l'estabilitat de tots els catalitzadors en presència de vapor d'aigua (100% steaming) a elevada temperatura. ¿ / [EN] Zeolites have traditionally been considered as microporous silicoaluminates formed by TO4 (T= Si, Al) tetrahedras connected, sharing oxygen atoms, giving rise to channels and cavities of molecular dimensions. Due to their potential as catalysts in relevant applications in the chemical industry, and more recently in the environmental industry, there has been a growing interest in the synthesis of new zeolitc. The incorporation of elements other than silicon and aluminum in their structure (P, Ge, Fe, Ti, B, etc) has led to appearance of new zeolitic molecular sieves, among which the aluminophosphates (AlPOs) stand out, being the first family of molecular sieves with compositions in which silicon does not participate. The high number of new structures of synthesized AlPOs, with pore sizes up to 13 Å, along with the ease in which the aluminum and phosphorus can be substituted by other chemical elements, has awakened a great interest in these materials, opening a wide range of applications, especiallly in adsorption and catalysis processes. This doctoral thesis focuses on the synthesis of new aluminophosphates, using new organic molecules as structure directing agents, for their further application as catalysts in chemical reactions of interest. In Chapter 1, a general introduction about zeolites and, more specifically, aluminophosphates, as well as their synthesis, properties and applications are presented. In Chapter 2, the general objectives of this work are presented. In Chapter 3, the synthesis of the different organic structure agents is shown. Furthermore, the main materials synthesized, together with the characterization equipment and catalytic procedures used are also displayed. Chapter 4 focuses on the synthesis of the first aluminophosphate with SAO structure (AlPO-SAO) and its derivatives incorporating silicon (SAPO-SAO) and germanium (GeAPO-SAO), being the latter the first three-dimensional large pore germaniumaluminophosphate reported until now. The catalytic activity of the prepared catalysts is evaluated in the Beckmann transposition reaction and compared with the SAPO-37 (FAU) material. In Chapter 5, erionite (ERI) and chabazite (CHA) silicoaluminophosphates, both belonging to the ABC-6 family, prepared from two new families of organic structures directing agentes, are studied by co-template synthesis. In Chapter 6, a new synthesis route based on the previous co-template synthesis is proposed for the preparation of the silicoaluminophosphate SAPO-34 using a mixture of organic structure directing agents of amine and tetraalkylphosphonium type, studying the nature of the phosphorus species located of the cavities chabazite structure. Finally, the catalytic properties of the catalysts activated under different conditions have been evaluated in the methanol process, comparing them with a SAPO-34 material synthesized only using a nitrogenous organic structure directing agent. On the other hand, the stability of all catalysts in the presence of water steam (100% steaming) at elevated temperatures has been studied. / González Camuñas, N. (2022). Síntesis, caracterización y aplicaciones catalíticas de aluminofosfatos y silicoaluminofosfatos zeolíticos obtenidos empleando nuevos agentes directores de estructura [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/184308

[ES] Toda esta disertación ha utilizado la química computacional como herramienta fundamental para el análisis científico. Por ello, en el Capítulo 2 se explican los modelos y métodos teóricos sobre este tema. La primera parte del capítulo se centra en los fundamentos de la química cuántica y, en concreto, se explica con detalle la Teoría del Funcional de la Densidad la cual constituye la base de los métodos computacionales aplicados. En esta sección, las nociones básicas del método Hartree-Fock sirven de prólogo a la DFT. El Capítulo 3 presenta los primeros resultados de este trabajo correspondientes a la reacción de metanol a olefinas catalizada por diferentes zeolitas con cavidades de poro pequeño. Esta reacción es un proceso industrial relevante que produce olefinas de cadena corta como eteno (C2=), propeno (C3=) y buteno (C4=) a escala industrial a partir de la biomasa. El sistema catalítico comprende tanto la estructura inorgánica de la zeolita que contiene los sitios ácidos Brønsted como las especies orgánicas confinadas, que forman la "hydrocarbon pool" y producen olefinas ligeras mediante pasos sucesivos de metilación y craqueo. Hemos centrado nuestros esfuerzos en comprender la naturaleza de la "hydrocarbon pool", una molécula de benceno polimetilada, y sus mecanismos de reacción para poder discernir entre ellos e identificar los catalizadores adecuados para mejorar la producción de propeno o eteno en función de la topología de cada cavidad zeolitica. Hemos podido identificar el grado de metilación de la "hydrocarbon pool" como el factor clave para potenciar el mecanismo de la ruta "paring", donde el propeno es el producto mayoritario, o el mecanismo de la ruta "side-chain", siendo el eteno el producto predominante. Este hallazgo nos permite establecer una relación entre la estabilización de los dos intermedios clave y la selectividad experimental observada con un alto grado de correlación. En el Capitulo 4 presentamos una nueva herramienta para el estudio de reacciones competitivas catalizadas por zeolitas. Utilizando un cribado computacional rápido con "force fields" para los intermedios clave de la reacción y un detallado estudio mecanístico usando la teoría del funcional de la densidad somos capaces de reconocer y cuantificar sutiles diferencias en la estabilización de intermedios y estados de transición dentro de huecos microporosos similares, aproximándonos así al nivel de reconocimiento molecular de las enzimas. Con estas herramientas somos capaces de seleccionar como catalizador una zeolita que obstaculice el mecanismo "alkyl-transfer" reduciendo la producción de eteno no deseado y potenciando al mismo tiempo el mecanismo "diaryl-mediated pathway". También somos capaces de obstaculizar la desproporción de dietilbenceno, una ruta no deseada del mecanismo "diaryl-mediated pathway" que conduce a la producción de trietilbenceno, mientras que se favorece la transalquilación de dietilbenceno aumentando el rendimiento obtenido de etilbenceno. en la primera sección del Capítulo 5, estudiamos la afinidad energética de cationes alquilamonio comercialmente disponibles con ligeras diferencias en sus grupos alquilo, TEA, MTEA y DMDEA, para la síntesis de CHA y sus efectos sobre la calidad del material obtenido. Evaluamos las energías de interacción entre la zeolita y el catión de diferentes combinaciones de agentes directores y cationes Na+ con métodos DFT periódicos pudiendo distinguir pequeños efectos de estabilización causados por ligeras diferencias estructurales entre moléculas que repercuten en la estructura final sintetizada. Durante la segunda sección del Capítulo 5, identificamos las características estructurales de diferentes agentes directores de estructura para la síntesis de AEI que mejoran las probabilidades de dispersión del Al en posiciones tetraédricas distintas de T1 obteniendo un catalizador AEI diferente de los sintetizados clásicamente. / [CA] Tota aquesta dissertació utilitza la química computacional com eina fonamental per a l'anàlisi científica. Per això, en el Capítol 2 s'expliquen els models i mètodes teòrics sobre aquest tema. La primera part del capítol es centra en els fonaments de la química quàntica i, en concret, s'explica amb detall la Teoria del Funcional de la Densitat la qual constitueix la base dels mètodes computacionals aplicats. En aquesta secció, les nocions bàsiques del mètode Hartree-Fock serveixen de pròleg a la DFT. El Capítol 3 presenta els primers resultats d'aquest treball corresponents a la reacció de metanol a olefines catalitzada per diferents zeolites amb cavitats de porus petit. Aquesta reacció és un procés industrial rellevant que produeix olefines de cadena curta com etè (C2=), propè (C3=) i butè (C4=) a escala industrial a partir de la biomassa. El sistema catalític comprèn tant l'estructura inorgànica de la zeolita que conté els llocs àcids Brønsted com les espècies orgàniques confinades, que formen la "hydrocarbon pool" i produeixen olefines lleugeres mitjançant passos successius de metilació i craqueig. Hem centrat els nostres esforços en comprendre la naturalesa de la "hydrocarbon pool", una molècula de benzè polimetilada, i els seus mecanismes de reacció per a poder discernir entre ells i identificar els catalitzadors adequats per millorar la producció de propè o etè en funció de la topologia de cada cavitat zeolitica. Hem pogut identificar el grau de metilació de la "hydrocarbon pool" com el factor clau per a potenciar el mecanisme de la ruta "paring", on el propè és el producte majoritari, o el mecanisme de la ruta "side-chain", sent l'etè el producte predominant. Al Capítol 4 presentem una nova eina per a l'estudi de reaccions competitives catalitzades per zeolites. Utilitzant un cribratge computacional ràpid amb "force fields" per als intermedis clau de la reacció i un detallat estudi mecanístic amb la teoria del funcional de la densitat som capaços de reconèixer i quantificar subtils diferències en l'estabilització d'intermedis i estats de transició dins de buits microporosos similars, aproximant-nos així al nivell de reconeixement molecular dels enzims. en la primera secció del Capítol 5, estudiem l'afinitat energètica de cations alquilamoni comercialment disponibles amb lleugeres diferències als seus grups alquil, TEA, MTEA i DMDEA, per a la síntesi de CHA i els seus efectes sobre la qualitat del material obtingut. Avaluem les energies d'interacció entre la zeolita i el catió entre diferents combinacions d'agents directors i cations Na+ amb mètodes DFT periòdics podent distingir petits efectes d'estabilització causats per lleugeres diferències estructurals entre molècules que repercuteixen en l'estructura final sintetitzada. Durant la segona secció del Capítol 5, identifiquem les característiques estructurals de diferents agents directors d'estructura per a la síntesi d'AEI que milloren les probabilitats de propagació de l'Al a través de posicions tetrahedriques diferents de T1 obtenint un catalitzador AEI diferent dels sintetitzats clàssicament. / [EN] Computational chemistry has been used as the fundamental tool during the whole work. Therefore, the theoretical models and methods on this subject are explained in Chapter 2. The first part sketches the fundamentals of quantum chemistry and specifically explains the Density Functional Theory that constitutes the basis of the computational methods applied. In this section, basic notions of the Hartree-Fock method serve as prologue for DFT after which more practical aspects are elucidated. Chapter 3 presents the first results of this work corresponding to the methanol to olefins reaction catalysed by different small-pore cage-like zeolites. This reaction is a relevant process that produces short chain olefins such as ethene, propene and butene at industrial scale from biomass. The catalytic system comprises both the zeolite inorganic framework containing the Brønsted acid sites and the confined organic species, that form the hydrocarbon pool and produce light olefins by successive methylation and cracking steps. Our efforts are focused on understanding the nature of the hydrocarbon pool, a polymethylated benzene molecule, and its reaction mechanisms in order to be able to discern between them and identify the proper catalysts to enhance propene or ethene production based on each zeolite cavity topology. We have been able to identify the hydrocarbon pool methylation degree as the key factor to enhance paring route mechanism where propene is the predominant product, or side-chain mechanism, with ethene being the predominant product. This finding enables us to establish a relation between the stabilization of the two key intermediates and the experimental selectivity observed with a high degree of correlation. In Chapter 4 we present a new tool for the study of competing reactions catalyzed by zeolites. Using a fast computational screening with force fields for the key intermediates of the reaction and a detailed density functional theory mechanistic study we are able to recognize and quantify subtle differences in the stabilization of intermediates and transition states within similar microporous voids, thus approaching the level of molecular recognition of enzymes. With these tools we are able to select a zeolite catalyst that hinders alkyl-transfer mechanism reducing the production of non-desired ethene while enhancing the diaryl-mediated pathyways mechanism. Once we discard the non-desired mechanism, we are also able to hinder the diethylbenzene disproportionation, a non-desired route of the diaryl-mediated pathways that leads to triethylbenzene production, while favouring diethylbenzene transalkylation increasing the obtained yield of ethylbenzene. To close this chapter, the theoretical results are compared with experimental selectivities obtained for eight candidate zeolites obtaining a good correlation between theory and experiment. in the first section of Chapter 5, we study the energetic affinity of commercially available alkylammonium cations with slight differences on their alkyl chain groups, as TEA, MTEA and DMDEA, for CHA synthesis and its effects on the quality of the material obtained. We evaluate the host-guest interaction energies of different combinations of OSDAs and Na+ cations with periodic DFT methods being able to distinguish small stabilization effects caused by slight structural differences between molecules that have an impact on the final structure synthesized. On the other hand, we present a new theoretical methodology to address Al positioning prediction in SSZ-39 zeolite with the AEI framework. During the second section of Chapter 5, we identify the structural features of different OSDAs for AEI synthesis that improve the probabilities of spreading Al through different T-site positions other than T1 obtaining an AEI catalyst different from the classically synthesized. / Vull agrair al Instituto de Tecnología Química per la concessió d’un contracte predoctoral, a la Red Española de Supercomputación (RES), al Centre de Càlcul de la Universitat de València, al Flemish Supercomputer Center (VSC) de la Ghent University pels recursos computacionals i el suport tècnic, a la Unió Europea i al Gobierno de España pel finançament d’aquest projecte a traves dels programes ERC-AdG-2014- 671093 (SynCatMatch) “Severo Ochoa” (SEV-2016-0683, MINECO) i dels projectes MAT2017-82288-C2-1-P i PID2020-112590GB-C21 (AEI/FEDER, UE), i al CSIC pel finançament de la estada al CMM a través del projecte i- Link (LINKA20381). / Ferri Vicedo, P. (2023). Ab initio design of efficient zeolite catalysts for methanol and hydrocarbons conversion [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/193493