Development of an effective High Temperature Fischer-Tropsch Synthesis (HTFTS) catalyst is of interest in process intensification that combines methane reforming with long chain hydrocarbon production. Literature indicates iron catalysts supported on mesoporous silica performed relatively well in high temperature applications. In this work, we investigated the effect of manganese promoter on iron catalysts for FTS at 430 °C as it was known from previous studies that manganese promotion could enhance the CO conversion with higher hydrocarbon yields. Also, the effect of temperature on FTS activity was evaluated by testing the base and promoted Fe/SBA-15 catalysts for temperature ranging from 370 to 430 °C. Incipient wetness impregnation method was used to prepare the catalysts. The catalysts used in this work were un-promoted iron (15 wt%) and Mn promoted (1.4, 2.8, 4.2, 5.6, 11.2 wt%) iron (15 wt%) catalysts supported on SBA-15. The catalysts were characterized using XRD, TPR, N2 Physisorption, and SEM. These catalysts were first activated in synthesis gas (H2: CO = 2:1) at 430 °C and then tested for their catalytic performance at the same temperature and atmospheric pressure. Prior work with SBA-15 supported iron catalysts showed that manganese promotion could improve the CO conversion when compared to copper and potassium. The main goal of this work was to study the effect of varying the manganese content on SBA-15 supported iron catalysts to determine the optimum loading of Mn along with the effect of temperature. It was found that CO conversion increases from 27% to74% with increasing the amount of manganese. The yield of CO2 increased substantially with higher Mn loadings. When different Mn promoted iron catalysts were compared, the catalysts with 2.8 wt% Mn loading showed the best performance in terms of the CO conversion and yield of C2+ hydrocarbons. Catalyst with 2.8 wt% of manganese loading yielded a CO conversion of 54%, with a methane yield of 17%, 32% (carbon) yield of C2- C4 and 9%(carbon) yields of C5+ hydrocarbon products, respectively. The effect of operating temperature on the catalytic performance of both the base catalyst 15Fe/SBA-15 and the promoted 2.8Mn/15Fe/SBA-15 catalyst was also examined. The unpromoted iron catalyst showed an improved catalytic activity at 400 °C with the total CO conversion of 38% and a higher yields of C5+ hydrocarbons. A significant decrease was also observed in the yields of CH4 and CO2. The methane and carbon dioxide yield increased from 11% and 8% to 25% and 40%, respectively, as the temperature increased from 400 to 450 °C. The catalyst with 2.8 wt% of manganese promotion gave better CO conversion and hydrocarbon product yields at 430 °C. Lower temperature showed negative effect on hydrocarbon product yield for manganese promoted catalysts.

Lewis acids (ZnCl2, CoCl2, NiCl2, TiCl4, and CdCl2) when supported on silica gel can effectively catalyze transesterification of organophosphotriesters. In anhydrous acetonitrile and in the presence of excess alcohol, such reactions follow pseudo-first-order kinetics. Progress and efficacy of these reactions were monitored by UV-vis and 31P NMR spectroscopy.

Thesis advisor: Chia-Kuang Tsung / Heterogeneous catalysis is a critical field for chemical industry processes, energy applications, and transportation, to name a few. In all avenues, control over the activity and selectivity towards specific products are of extreme importance. Generally, two separate methods can be utilized for controlling the active surface areas; a below and above the surface approach. In this dissertation, both approaches will be addressed, first starting with controlling the active sites from a below approach and moving towards control through sieving and gating effects above the surface. For the first part half, the control of the product selectivity is controlled by finely tuning the atomic structures of nanoparticle catalysts, mainly Au-Pd, Pd-Ni-Pt, and Pd Ni3Pt octahedral and cubic nanoparticle catalysts. Through these shaped core-shell, occasionally referred to as core@shell, particles the shape is maintained in order to expose and study certain crystal facets in order to obtain a more open or closed series of active sites. With the core shell particles, the interior core particle (Au and Pd) is used for the overall shape but also to expansively/compressively strain the outer shell layer. By straining the surface, the surface electronic structure is altered, by raising or lowering the d-band structure, allowing for reactants to adsorb more or less strongly as well as adsorb on different surface sites. For the below the surface projects, the synthesized nanoparticle catalyst are used for electrochemical oxidation reactions, such as ethanol and methanol oxidation, in order to study the effect of the core and shell layers on initial activity, metal migration during cycling, as well as particle stability and activity using different crystal structures. In particular, the use of core shell, alloyed, and intermetallic (ordered alloys) particles are studied in more detail. In the second half of this dissertation, control of the selectivity will be explored from the top down approach; in particular the use of metal organic framework (MOF) will be utilized. MOF, with its inherent size selective properties due to caging effects from the chosen linkers and nodes, is used to coat the surface of catalysts for gas, liquid, and electrochemical catalysis. By using nanoparticle catalyst, the use of MOF, more explicitly the robust zirconium based UiO-66, as a crystalline capping agent is first explored. By incorporating both the nanoparticle and UiO-66 amino functionalized precursors in the synthesis, the nanoparticles are formed first and followed by coating in UiO-66-NH2, where the amino group acts as an anchor, completely coating the particles. The full coating is tested through size selective alkene hydrogenations with the NP surface further tested by liquid phase selective aldehyde hydrogenations; the UiO-66-NH2 pores help to guide the reactant molecule in a particular orientation for the carbonyl to interact rather than the unsaturated C=C bond. This approach is taken for more complex hybrid structures for electrochemical proton exchange membrane fuel cell (PEMFC) conditions. Through the gating effects, the UiO-66 blocks the Pt surface active sites from poisonous sulfonate groups off of the ionomer membrane while simultaneously preventing aggregation and leaching of Pt atoms during electrochemical working conditions. / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Orientador: Mauricio Boscolo / Banca: Diogo Paschoalini Volanti / Banca: João Claudio Thoméo / Banca: José Clayston Melo Pereira / Banca: Adriana Paula Ferreira / Resumo: Os biocombustíveis são vistos como fontes sustentáveis para substituir os combustíveis fósseis, e o etanol é reconhecido como a principal alternativa. Uma maneira de aumentar a competitividade desse composto é o princípio de biorrefinaria, associando a produção de mais de um produto por processo. Os desafios estão associados ao desenvolvimento e desempenho de novos catalisadores capazes de produzir compostos de maior valor agregado. Os óxidos utilizados são derivados de HDLs e foram modificados com Cu, V, W, Ti, Sn e Zr. Os materiais foram caracterizados por diversas técnicas analíticas e, após a caracterização, foram empregados em reações em batelada a fim de converterem etanol em produtos de maior peso e valor. Em um segundo momento avalia'se a despolimerização da biomassa presente nas reações, e a metodologia de superfície de resposta para a maximização da reforma do etanol e dos produtos condensáveis. Por fim, um desses materiais sintetizados, foi testado em condições severas de tempo e temperatura a fim de avaliar os produtos formados e a robustez desse catalisador durante vários ciclos reacionais. Os produtos foram analisados por CG-FID e CG-MS e os resultados discutidos com base na literatura. A incorporação dos metais foi possível nas condições testadas e a modificação é capaz de apresentar um perfil diferente de conversão e reforma para cada metal modificador. Amaior conversão em produtos é do W-OMM (54,7%). Os produtos majoritários encontrados em todas as reações... / Abstract: Biofuels are seen as sustainable sources to replace fossil fuels and ethanol is recognized as the main alternative. To increase the competitiveness of this compound is the biorefinery principle, associating the production of more product per process. The challenges are development and performance of new catalysts for production of higher value compounds. The oxides used are derived from HDLs and were modified with Cu, V, W, Ti, Sn and Zr. The materials were characterized by various techniques, and after characterization, they were employed in batch reactions to convert ethanol. Secondly, the depolymerization of the biomass present in the reactions and the response surface methodology for maximizing the reforming of ethanol and condensable products are evaluated. Finally, one of these synthesized materials was tested under severe time and temperature conditions to evaluate the products formed and the robustness of this catalyst during reaction cycles. The products were analyzed by CG-FID and CG-MS and the results discussed based on the literature. The incorporation of the metals is possible under the tested conditions and the modification is able to present a different conversion and reforming profile for each modifier metal. The largest conversion in products and the best oxide for conversion is W-OMM(54.7%), with Sn-OMM (10.4%) being the worst. The major products found in all reactions were butanol and ethyl acetate. Modification with metals reveals that the Guerbet pathway ... / Doutor

No description available.

The unifying goal of this work is the design of a heterogeneous catalyst that can facilitate the energy intensive oxygen evolution reaction (OER) in water splitting, considered one of the ‘holy grails’ in catalytic science. In order for this process to be industrially feasible, an efficient catalyst composed of first row transition metal based materials must be used. To accomplish this, existing systems must be studied in order to determine which properties are important and subsequent creation and modification of new systems based on lessons learned must be employed. Birnessite, a 2D layered manganese dioxide, comprises the majority of the effort. In the studies leading to this work, this material was primarily studied by mineralogists with the majority focusing on structural characterization. However, the material’s moderate activity toward performing the OER has revived interest. In this work, we look to determine important species, the role dopants play in activity, and the function of the interlayer and surface chemistry. From these findings, an enhanced, earth abundant OER catalyst will be designed. We determine that Mn3+ in the system plays and important role in producing a catalytic species with large oxygen production capabilities. By increasing the amount of Mn3+ in the system via a simple comproportionation reaction by exposing the Mn4+ to Mn2+ ion, we increase the total turnover of birnessite 50-fold. Additionally, the addition of dopants to the system , both within and between the sheets, has a positive effect on the activity of birnessite. In particular, incorporation of cobalt into the lattice of birnessite brings the activity level on par to that of precious metal oxide catalysts due to the cobalt offering a deeper electron acceptor than in birnessite alone. In conjunction with these studies, the role of the interlayer species and catalyst confinement has demonstrated the ability to greatly enhance a catalyst’s ability to perform the OER by ordering and orienting the water around the active confined catalyst. Combining confinement effects with the cobalt-doped birnessite sheets resulted in further enhancement in the material’s OER capabilities. This system mimics that of an enzyme where the cobalt-doped birnessite sheets facilitate greater electron-hole transfer to the interlayer active site, where the confinement effects enhance electron transfer kinetics and water organization for O-O bond formation. Additionally, metal chalcogenide OER catalysts were explored with mattagamite phase cobalt pertelluride. Through the work, we determine the formation of a Te-Co-O heterostructure as the catalytically active phase, where the metallic nature of the cobalt pertelluride facilitates charge mobility between the electrode and catalyst’s cobalt oxide surface functioning as the active OER species. / Chemistry

Yes / Coprecipitation method was used to prepare non-stoichiometric pristine copper and iron layered double hydroxide (LDH) doped with zirconium and embedded with reduced graphene oxide. The composite materials (ZrRGOCuFe LDHs) were studied for the photodegradation of methylene blue (MB) dye as a model contaminant from an aqueous solution. These composites were fully characterized by X-rays diffraction (XRD), Scanning electron microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), Photoluminescence (PL), Raman spectroscopy and Electrochemical Impedance Spectroscopy (EIS). The results of Raman, Photoluminescence and Electrochemical Impedance Spectroscopy revealed the presence of oxygen defects level in the composites. Such defects are believed to be essential for boosting the catalytic potential of the composites. The secondary pollution manifested by transition metal ions is usually tackled by inducing heterogeneous catalysis. Herein, pristine CuFe LDH has been doped with Zr and RGO moieties to realize heterogeneous catalysis within ZrRGOCuFe LDH dopants. An admirable band ranging between 1.74 and 2.0 eV was obtained for the doped materials. The remarkable photodegradation efficiency of 95.2% was achieved by using heterogeneous photocatlyst Zr0.6RGOCuFe LDH within 75 min at a pH of 7, photocatalyst dosage of 1.0 g/L and methylene blue dye solution of 10 ppm under visible light irradiation. The total organic content (TOC) analysis has revealed removal of 92% organic content. Moreover, the catalyst has the potentia to maitain sufficient stability and reusability capacity even after three successive cycles. The reaction kinetics and proposed photocatalytic mechanism were also explained in detail.

[ES] Se ha desarrollado un método de síntesis "verde" de compuestos metal orgánicos en medio acuoso, a temperatura y presión ambientes, fácilmente escalable y con tiempos de cristalización muy cortos (10 min). El método se ha aplicado con éxito a la síntesis de trimesatos de metales divalentes isoreticulares y con fórmula general M3(BTC)2·12 H2O (M = Ni2+, Co2+, Cu2+ y Zn2+; BTC = trimesato). La estructura de estos materiales presenta dos tipos de centros metálicos ("puente" y "ter-minales") en proporción 2 a 1, ambos con coordinación octaédrica y unidos a 4 moléculas de H2O y a dos oxígenos carboxilato del ligando. Usando este método de síntesis, se han preparado también series de compuestos bimetálicos isoreticulares de Co-Ni y Co-Zn en todo el rango de concentraciones, así como compues-tos de Mn-Ni con una concentración máxima de Mn2+ del 50%. Mediante la combinación de difracción de rayos X (en polvo y de monocristal) y microscopía EDX/SEM se ha demostrado que los compuestos bimetálicos forman verdaderas disoluciones sólidas (no meras mezclas de fases) y que los iones metálicos se dis-tribuyen homogéneamente en todo el cristal. Además, el análisis detallado de la variación de los parámetros de celda con la composición en compuestos Co-Ni y Co-Zn aporta fuertes evidencias de que los iones Co2+ ocupan preferentemente las posiciones "terminales". Se ha evaluado la actividad de los compuestos preparados como catalizadores para la oxidación aeróbica de cumeno (CM) a cumeno hidroperóxido (CHP). El com-puesto monometálico de Co2+, Co-BTC, presentó una elevada actividad, aunque la selectividad a CHP obtenida fue relativamente baja (69%), ya que los iones Co2+ catalizan también la descomposición del CHP formado. Una buena estrategia para optimizar esta selectividad consistió en aislar los iones Co2+ en una matriz de Ni-BTC (que es inerte tanto para la oxidación de CM como para la descomposición de CHP). Así, al disminuir la concentración de iones Co2+ en compuestos bimetálicos Co-Ni se observó un aumento de la selectividad a CHP de hasta el 91% para el material con un 5% de Co. Se ha calculado que estadísticamente el 73% de los iones Co2+ en este material se encuentran aislados, por lo que la des-composición/sobreoxidación del CHP se ve muy limitada. Usando una variación del método de síntesis, se han obtenido también compuestos isoreticulares de Co2+ en los que los ligandos trimesato se han reemplazado parcialmente por ligandos isoftálico o 5-aminoisoftálico. Al utilizar estos com-puestos como catalizadores para la oxidación aeróbica de CM, se ha observado que la introducción de este segundo ligando (y en particular del 5-aminoisoftálico) en la red metal-orgánica facilita la descomposición del CHP formado y aumenta la selectividad final a 2-fenil-2-propanol (PP). Esto se ha atribuido a la creación de defectos puntuales en la red del material, que presentan una mayor actividad para la descomposición de CHP. Siguiendo con la oxidación de CM como reacción modelo, se ha evaluado la actividad catalítica de compuestos isoreticulares de cobalto con ligandos bispirazolato funcionalizados con distintos grupos (CoBPZ, CoBPZ-NO2 y CoBPZ-NH2). En este caso se ha observado una clara influencia del ligando utilizado sobre la acti-vidad catalítica y la selectividad a CHP o PP del material. Mientras que el Co-BPZ presenta una baja conversión de CM y una elevada selectividad a CHP, Co-BPZ-NH2 presenta las características opuestas: una elevada velocidad de reacción pero una baja selectividad a CHP. En este último caso, el producto mayoritario forma-do es el PP. Por último, el estudio de MOFs de cationes divalentes como catalizadores de oxidación se ha completado con una reacción de síntesis de quinazolina mediante acoplamiento oxidativo de bencilamina y 2-aminoacetofenona usando TBHP co-mo oxidante. Como catalizadores para esta reacción se ha utilizado el trimesato de / [CA] S'ha desenvolupat un mètode de síntesi "verda" de compostos metall orgànics en medi aquós, a temperatura i pressió ambients, fàcilment escalable i amb temps de cristal·lització molt curts (10 min). El mètode s'ha aplicat amb èxit a la síntesi de trimesats de metalls divalents isoreticular i amb fórmula general M3(BTC)2·12 H2O (M = Ni2+, Co2+, Cu2+ y Zn2+; BTC = trimesat). L'estructura d'aquests materials presenta dos tipus de centres metàl·lics ("pon" i "terminals") en una proporció de 2 a 1, ambdós amb coordinació octaèdrica i units a 4 molècules d'aigua i a 2 oxígens carboxilat del lligand. Emprant aquest mètode de síntesi, s'han preparat també sèries de compostos bimetàl·lics isoreticular de Co-Ni i Co-Zn en tot el rang de concentracions, així com compostos de Mn-Ni amb una concentració màxima de Mn2+ del 50%. Mitjançant l'ús combinat de difracció de raigs X (en pols i de monocristall) i microscòpia EDX/SEM s'ha demostrat que els compostos bimetàl·lics formen vertaderes dissolucions sòlides (no simples mescles de fase) i que els ions metàl·lics es distribueixen homogèniament en tot el cristall. A més, l'anàlisi detallat de la variació dels paràmetres de cel·la amb la composició de compostos Co-Ni i Co-Zn aporta fortes evidències de que els ions Co2+ ocupen preferentment les posicions "terminals". S'ha avaluat l'activitat dels compostos preparats com a catalitzador per a l'oxidació aeròbica de cumè (CM) a cumè hidroperòxid (CHP). El compost monometàl·lic de Co2+, Co-BTC, presenta una elevada activitat, encara que la selectivitat a CHP obtinguda és relativament baixa (69%), ja que els ions Co2+ catalitzen també la descomposició del CHP format. Una bona estratègia per optimitzar aquesta selectivitat consisteix en aïllar els ions Co2+ en una matriu de Ni-BTC (que és inert tant per a l'oxidació de CM com per a la descomposició de CHP). Així, a mesura que disminueix la concentració d'ions Co2+ en compostos bimetàl·lics Co-Ni s'observa un augment de la selectivitat a CHP de fins el 91% per al material amb un 5% de cobalt. S'ha calculat que estadísticament el 73% dels ions Co2+ d'aquest material es troben aïllats, de manera que la descomposició/sobreoxidació del CHP es veu molt limitada. Emprant una variació del mètode de síntesi, s'han obtingut també compostosisoreticulars de Co2+ en els que els lligands trimesat s'han reemplaçat parcialment per lligands isoftàlic o 5-aminoisoftàlic. Quan aquest compostos s'usen com a catalitzadors per a l'oxidació aeròbica de CM, sobserva que la introducció d'aquest segon lligand (i en particular del 5-aminoisoftàlic) en la xarxa metallorgànica es facilita la descomposició del CHP format i augmenta la selectivitat final a 2-fenil-2-propanol (PP). Això s'ha atribuït a la creació de defectes puntuals en la xarxa del material, que presenten una major activitat per a la descomposició del CHP. Seguint amb l'oxidació de CM com a reacció model, s'ha avaluat l'activitat catalítica de compostosisoreticulars de cobalt amb lligands bispirazolat funcionalitzats amb distints grups (CoBPZ, CoBPZ-NO2 i CoBPZ-NH2). En aquest cas s'ha observat una clara influència del lligand utilitzat sobre l'activitat catalítica i la selectivitat a CHP o PP del material. Mentre que el CoBPZ presenta una baixa conversió de CM i una elevada selectivitat a CHP, CoBPZ-NH2 presenta les característiques oposades: una elevada velocitat de reacció però una baixa selectivitat a CHP. En aquest últim cas, el producte majoritari format és el PP. Per últim, l'estudi de MOFs amb cations divalent como a catalitzadors d'oxidació s'ha completat amb una reacció de síntesi de quinazolina mitjançant acoblament oxidatiu de benzilamina i 2-aminoacetofenona emprant TBHP como a oxidant. Com a catalitzadors per aquesta reacció s'ha utilitzat el trimesat de coure, HKUST-1, així com materials isoreticular amb lligands mixtes obtinguts reemplaçant pa / [EN] A "green" synthesis method has been developed for the preparation of metal organic frameworks in aqueous media, which is easily scalable, at room tempera-ture, ambient pressure and very short crystallization times (10 min). This method has been successfully applied to the synthesis of isoreticular divalent metal trimesates of general formula M3(BTC)2·12 H2O (M = Ni2+, Co2+, Cu2+ y Zn2+; BTC = trimesate). The structure of these compounds features two types of metal centers ("bridging" and "terminal") in a 2 to 1 ratio, both with octahedral coordina-tion and linked to 4 water molecules and 2 carboxylate oxygens of the ligand. Using this method, two series of bimetallic isoreticular compounds of Co-Ni and Co-Zn have also been prepared in all range of compositions, as well as bimetallic Mn-Ni compounds up to a maximum concentration of 50% of Mn2+. A combined X-ray diffraction (powder and single crystal) and EDX/SEM has shown that these bimetallic compounds form true solid solutions (not simple mixture of phases) and that both ions distribute homogeneously throughout the crystal. A detailed analysis of the variation of cell parameters with the composition strongly sug-gests that Co2+ ions occupy preferentially the "terminal" positions of the frame-work. The materials obtained with the above method have been evaluated as catalysts for the aerobic oxidation of cumene (CM) to cumene hydroperoxide (CHO). The monometallic Co2+ compound, Co-BTC, showed a high catalytic activity, but a relatively low selectivity to CHP 69%), since the Co2+ ions can also catalyze the decomposition of the formed CHP. A good strategy to optimize the CHP selectivity consisted in isolating the Co2+ ions into a Ni-BTC (which is inert for both CM oxidation and CHP decomposition). In this way, as the concentration of Co2+ ions in the bimetallic Co-Ni compound decreases, a parallel increase of the CHP selec-tivity was observed, up to 91% for the material with 5% of Co. In this compound, 73% of the total Co2+ ions are statistically isolated, so that decomposi-tion/overoxidation of CHP is unlikely to occur. By using a variation of the above synthesis method, additional isoreticular Co2+ compounds have been prepared in which the trimesate ligands have been partially replaced by either isophthalic or 5-aminoisophthalic. When these compounds were used as catalysts for the aerobic oxidation of cumene, we observed that the introduction of this second ligand (in particular in the case of 5-aminoisophthalic) into the framework facilitates decomposition of CHP and in-creases the final selectivity to 2-phenyl-2-propanol (PP). This has been attributed to the progressive creation of point defects in the framework, having a higher activity for CHP decomposition. Following with the aerobic oxidation of CM as model reaction, we evaluated the catalytic activity of isoreticular cobalt compounds having bispyrazolate ligands bearing differnent functional groups (CoBPZ, CoBPZ-NO2 and CoBPZ-NH2). In this case, there is a clear influence of the ligand used on the catalytic activity of the material and the obtained selectivity to CHP or PP. While CoBPZ showed a low CM conversion and high CHP selectivity, the opposite properties are obtained for the Co-BPZ-NH2: i.e., a high reaction rate but a low CHP selectivity. In this latter case, the major product of the reaction was PP. Finally, the evaluation of divalent MOFs as oxidation catalysts has been complet-ed by addressing the synthesis of quinazoline through the oxidative coupling reaction of benzylamine and 2-aminoacetophenone using TBHP as oxidant. As catalysts for this reaction we have used a copper trimesate, HKUST-1, as well as isoreticular mixed-ligand compounds obtained by partially replacing trimesate ligands by 5-hydroxyisophthalic (OH-isophthalic). / Nowacka, AE. (2019). Divalent Metal Organic Frameworks as Heterogeneous Oxidation Catalysts [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/129872

[EN] The present thesis focuses on the rationalization of the zeolite synthesis for catalysis by understanding the nature of active sites and their microenvironments, together with their influence on the mechanisms of catalyzed reactions. In the first part of the thesis, efforts have been put on attempting to achieve the regioselective locating of active sites in zeolite catalyst and, more specifically, on tunning acid site locations in zeolite framework. The development of a zeolite synthesis strategy and an indicator that can describe the aluminum distribution in the zeolite framework is important to evaluate if the final objective has been achieved. In this part, in order to evaluate aluminum distribution in MFI framework, an indicator based on monomolecular and bimolecular mechanisms of n-hexene catalytic cracking was proposed. First, several ZSM-5 samples were synthesized, which have been reported in the literature to have different aluminum distributions. These samples were characterized to be analogous in physicochemical properties and, then, tested in the n-hexene cracking to justify the usefulness of the indicator proposed in this work. Using 27Al MAS NMR, the aluminum locations were proved to be different, which was also reflected by the indicator in this thesis, justifying its applicability to evaluate aluminum locations. Afterward, this indicator has been employed to check the zeolite synthesis methodology that could potentially lead to different aluminum distribution in zeolite frameworks. Then, a boron-assisted synthesis is proposed considering that boron and aluminum may have competitive positioning in ZSM-5 framework. Then, and by means of DFT calculations, we have studied if the unit cell of MFI shows different stabilities when substituted by aluminum and/or boron in different T positions. It has been found that boron location is less favored when introduced in 10-ring channels of the MFI framework, while aluminum shows no preference for positioning among all the T-sites. ZSM-5 samples with different Si/Al and Si/B were synthesized and their physicochemical properties as well as the relative proportion of paired and isolated states of aluminum was characterized. Characterization includes n-hexene cracking, for which the samples showed different preference toward monomolecular and bimolecular reactions. Finally, once the materials were proved to have different aluminum distribution, they were employed in methanol-to-propene (MTP) reactions to show the influence of aluminum distribution on an industry-relevant reaction where the spatial confinement has an important impact. Indeed, the samples with aluminum preferentially positioned in 10-ring channel favored more monomolecular cracking and less bimolecular side reactions such as oligomerization and hydrogen transfer, giving higher propene yield and lower amount of alkanes and aromatics. The second part of the thesis focuses on rationalizing the synthesis of zeolites with cavities for catalyzing “a priory” selected reaction. More specifically, zeolite synthesis was carried out using OSDAs that mimic the transition state (TS) or a relevant intermediate in the target reaction. Ethylbenzene production by transalkylation between diethylbenzene and benzene was selected as the reaction to be catalyzed. A potential reaction TS was established and a diaryldimethylphosphonium OSDA was synthesized that mimicks the transition state in the diaryl-mediated mechanism of transalkylation between benzene and diethylbenzene. Then, the OSDA successfully led to the formation of the largepore zeolite ITQ-27. This ITQ-27 was tested in the reaction of transalkylation between benzene and diethylbenzene. The catalytic performance of this material was benchmarked to be superior than other commercially employed zeolites, such as USY, mordenite or Beta with similar physicochemical properties. Finally, Methanol to olefins (MTO) reaction was chosen as another target catalytic system, where the reaction pathways are more complicated than transalkylation between benzene and diethylbenzene but nevertheless they have been well established in the literature. Thus, several OSDAs were synthesized mimicking the intermediates and transition states of the paring pathway, which produces more propene and butenes, which are highly demanded among all products. The OSDAs led to formation of several cage-based small pore zeolites, such as CHA, RTH and AEI. All the zeolites obtained were tested in MTO reactions to evaluate their catalytic activity and gave high selectivity toward light olefins, which appeared to selectively depend on the zeolite tested. The tendency of each structure toward certain product distributions was related to the reaction mechanism by establishing a structure-reactivity correlation, when the experiment results were combined with theoretical calculations. It is proposed that different shape of the cavities stabilize different precursor intermediates present in the paring or side-chain pathways and this indicates the reaction preference between each pathway and therefore the product distributions. A linear correlation was obtained between the shape of cavities and the C3 = /C2 = molar ratios being possible. In this way, ITQ-3 (ITE structure) was predicted that should also give higher selectivity toward paring pathway, which has been demonstrated experimentally / [ES] La presente tesis se centra en la racionalización de la síntesis de zeolitas para su aplicación como catalizadores mediante la comprensión de la naturaleza de los sitios activos y sus microambientes, junto con su influencia en los mecanismos de las reacciones catalizadas. En la primera parte de la tesis, se han realizado esfuerzos para intentar lograr la ubicación regioselectiva de los sitios activos en el catalizador zeolítico y, más específicamente, en la ubicación controlada de sitios ácidos en la red cristalina de la zeolita. El desarrollo de una estrategia de síntesis adecuada junto con un indicador que pueda describir la distribución de aluminio en la red de la zeolita es importante para evaluar si se ha logrado el objetivo final. En esta parte, para evaluar la distribución de aluminio en la red de la zeolita MFI, se ha propuesto un indicador basado en los mecanismos monomoleculares y bimoleculares asociados a la reacción de craqueo catalítico de n-hexeno. En primer lugar, se sintetizaron varias muestras de ZSM-5, que según la literatura tienen diferentes distribuciones de aluminio. Estas muestras se caracterizaron por ser análogas en propiedades fisicoquímicas y, posteriormente, se analizaron en la reacción de craqueo de n-hexeno para justificar la utilidad del indicador propuesto en este trabajo. A partir de RMN MAS de 27Al se demostró que las ubicaciones de aluminio eran diferentes, lo que también se reflejó en el indicador propuesto en esta tesis, lo que justifica su aplicabilidad para evaluar distribuciones de aluminio. Posteriormente, este indicador se ha empleado para verificar la nueva metodología de síntesis de zeolitas que podría conducir a una distribución de aluminio diferente en sus estructuras cristalinas. En este sentido, se propone la síntesis de la zeolita ZSM-5 asistida por boro, considerando que el boro y el aluminio podrían tener un posicionamiento competitivo en la estructura MFI. Mediante cálculos de DFT, se ha estudiado si la celda unidad de MFI muestra diferente estabilidad cuando se introduce aluminio y/o boro en diferentes posiciones cristalográficas T. Se ha encontrado que la ubicación del boro está menos favorecida cuando se introduce en los canales de 10 miembros de la estructura MFI, mientras que el aluminio no muestra preferencia por el posicionamiento entre todos los sitios T. Se sintetizaron muestras de ZSM-5 con diferentes Si/Al y Si/B y se caracterizaron sus propiedades fisicoquímicas, así como la proporción relativa de estados emparejados y aislados de aluminio. La caracterización incluye el craqueo de n-hexeno, para el cual las muestras mostraron una preferencia diferente hacia las reacciones monomoleculares y bimoleculares. Finalmente, una vez demostrada la distinta distribución de aluminio en los materiales sintetizados, estos catalizadores se estudiaron en la reaccióde metanol a propeno (MTP) para mostrar la influencia de la distribución de aluminio en una reacción relevante a nivel industrial, donde el confinamiento espacial tiene un impacto importante. De hecho, las muestras con aluminio posicionadas preferentemente en un canal de 10 miembros favorecen reacciones de craqueo monomolecular frente a reacciones secundarias bimoleculares, como por ejemplo reacciones de oligomerización y de transferencia de hidrógeno, dando un mayor rendimiento a propeno y una menor cantidad de alcanos y compuestos aromáticos. La segunda parte de la tesis se centra en racionalizar la síntesis de zeolitas con cavidades para catalizar una reacción seleccionada "a priori". Más específicamente, la síntesis de zeolita se llevó a cabo utilizando agentes directores de estructura orgánicos (ADEO) que mimetizan el estado de transición (ET) o el intermedio relevante en la reacción objetivo. La producción de etilbenceno por transalquilación entre dietilbenceno y benceno se ha seleccionado como una reacción objetivo a catalizar. Se estableció el ET determinante de la reacción y se sintetizó un ADEO tipo diarildimetilfosfonio que mimetiza el estado de transición del mecanismo de la reacción de transalquilación entre benceno y dietilbenceno. Dicho ADEO permitió la cristalización de la zeolita de poro grande ITQ-27, cuyo comportamiento catalítico se estudió en la reacción de transalquilación entre benceno y dietilbenceno. La actividad catalítica de la zeolita ITQ-27 se mostró claramente superior al de otras zeolitas empleadas comercialmente, como USY, mordenita o Beta, todas ellas con propiedades fisicoquímicas similares a la ITQ-27. Finalmente, la reacción de metanol a olefinas (MTO) se eligió como otro sistema catalítico objetivo, donde los mecanismos de reacción son mucho más complicados que en el caso de la reacción de transalquilación entre benceno y dietilbenceno, pero, sin embargo, están bien establecidos en la literatura. Se sintetizaron varios ADEOs que mimetizan los intermedios y los estados de transición de la ruta “paring”, que produce más propeno y butenos, y que son posiblemente los productos más demandados. Dichos ADEOs mímicos permitieron la formación de varias zeolitas de poro pequeño basadas en cavidades, como las zeolitas CHA, RTH y AEI. Todas las zeolitas obtenidas se probaron en la reacción MTO para evaluar su actividad catalítica, obteniéndose una alta selectividad hacia distintas olefinas ligeras, cuya selectividad depende de la forma y tamaño de la cavidad de cada zeolita. La tendencia de cada estructura hacia ciertas distribuciones de productos se ha relacionado con el mecanismo de reacción, pudiendo establecer una correlación estructura-reactividad al combinar los resultados experimentales con cálculos teóricos. / [CA] La present tesi es centra en la racionalització de la síntesi de zeolites per a la seva aplicació com a catalitzadors mitjançant la comprensió de la naturalesa dels centres actius i els seus microambientes, juntament amb la seva influència en els mecanismes de les reaccions catalitzades. A la primera part de la tesi, s'han realitzat esforços per intentar aconseguir la ubicació regioselectiva dels centres actius en el catalitzador zeolític i, més específicament, en la ubicació controlada de centres àcids en la xarxa cristal·lina de la zeolita. El desenvolupament d'una estratègia de síntesi adequada juntament amb un indicador que descriga la distribució d'alumini a la xarxa de la zeolita és important per avaluar si s'ha aconseguit l'objectiu final. En aquesta part, per avaluar la distribució d'alumini a la xarxa de la zeolita MFI, s'ha proposat un indicador basat en els mecanismes monomoleculares i bimoleculars associats a la reacció de craqueig catalític de n-hexé. En primer lloc, es van sintetitzar diverses mostres de ZSM-5, que segons la literatura tenen diferents distribucions d'alumini. Aquestes mostres es van caracteritzar per ser anàlogues en propietats fisicoquímiques i, posteriorment, es van analitzar en la reacció de craqueig de nhexéper justificar la utilitat de l'indicador proposat en aquest treball. A partir dels espectres de RMN MAS de 27Al es va demostrar que les ubicacions d'alumini eren diferents, el que també es va reflectir en l'indicador proposat en aquesta tesi, justificant la seva aplicabilitat per avaluar distintes distribucions d'alumini. Posteriorment, aquest indicador s'ha emprat per verificar la nova metodologia de síntesi de zeolites que podria conduir a una distribució d'alumini diferent al llarg de les seves estructures cristal·lines. En aquest sentit, s’ha proposat la síntesi de la zeolita ZSM-5 assistida per bor, considerant que el bor i l'alumini podrien tenir un posicionament competitiu en l'estructura MFI. Mitjançant càlculs de DFT, s'ha estudiat si la cel·la unitat de MFI mostra diferent estabilitat quan s’introdueix alumini i/o bor en diferents posicions cristal·logràfiques T. S'ha trobat que la ubicació dels àtoms de bor està menys afavorida als canals de 10 membres de la estructura MFI, mentre que l'alumini no mostra preferència pel posicionament entre tots els llocs T. Es van sintetitzar mostres de ZSM-5 amb diferents relacions de Si/Al i Si/B i es van caracteritzar les seves propietats fisicoquímiques, així com la proporció relativa d'estats aparellats i aïllats d'alumini. La caracterització inclou la reacció de craqueig de n-hexé, on les mostres van mostrar una preferència diferent cap a les reaccions monomoleculares i bimoleculars. Finalment, un cop demostrada la diferent distribució d'alumini en els materials sintetitzats, aquests catalitzadors es van estudiar a la reacció de metanol a propè (MTP) per mostrar la influència de la distribució d'alumini en una reacció rellevant a nivell industrial, on el confinament espacial té un impacte important. De fet, les mostres amb alumini posicionades preferentment en un canal de 10 membres afavoreixen reaccions de craqueig monomolecular enfront de reaccions secundàries bimoleculars, com ara reaccions d'oligomerització i de transferència d'hidrogen, donant un major rendiment a propè i una menor quantitat d'alcans i compostos aromàtics. La segona part de la tesi es centra en racionalitzar la síntesi de zeolites amb cavitats per catalitzar una reacció seleccionada "a priori". Més específicament, la síntesi de zeolita es va dur a terme utilitzant agents directors d'estructura orgànics (ADEO) que mimetitzen l'estat de transició (ET) o l'intermedi rellevant en la reacció objectiu. La producció de etilbenzèper transalquilació entre dietilbenzè i benzè s'ha seleccionat com una reacció objectiu a catalitzar. Es va establir l'ET determinant de la reacció i es va sintetitzar un ADEO tipus diarildimetilfosfoni que mimetitza eixe estat de transició. Eixe ADEO va permetre la cristal·lització de la zeolita de porus gran ITQ-27, i el seu comportament catalític es va estudiar en la reacció de transalquilación entre benzè i dietilbenzè. L'activitat catalítica de la zeolita ITQ-27 es va mostrar clarament superior a la d'altres zeolites emprades comercialment, com la USY, mordenita o Beta, totes elles amb propietats fisicoquímiques similars a la ITQ-27. Finalment, la reacció de metanol a olefines (MTO) es va triar com un altre sistema catalític objectiu, on els mecanismes de reacció són molt més complicats que en el cas de la reacció de transalquilació entre benzè i dietilbenzè, però que, al mateix temps, estan ben establerts en la literatura. Es van sintetitzar diversos ADEOs que mimetitzen alguns dels intermedis i dels estats de transició de la ruta "paring", que produeix més propè i butens, i que són possiblement els productes més demandats. Aquests ADEOs mímics van permetre la formació de diverses zeolites de porus petit basades en cavitats, com les zeolites CHA, RTH i AEI. Totes les zeolites obtingudes es van provar en la reacció MTO per avaluar la seva activitat catalítica, obtenint una alta selectivitat cap a diferents olefines lleugeres, on la selectivitat cap a cada olefina lleugera depèn de la forma i mida de la cavitat de cada zeolita. La tendència de cada estructura cap a certes distribucions de productes s'ha relacionat amb el mecanisme de reacció, i s´ha pogut establir una correlació estructura-reactivitat al combinar els resultats experimentals amb càlculs teòrics. / Li, C. (2020). Rationalize the synthesis of zeolite catalysts by understanding reaction mechanism [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/147115

At present, more than 80% of the world’s energy consumption and production of chemicals is originated from the use of fossil resources. There is a tremendous growing interest in utilising biomass molecules for energy provision due to their carbon neutrality. Lower alcohols such as methanol and ethanol if produced from biomass as transportation fuels as well as platform chemicals, can become strategically important for many energy/chemically starved countries. Currently, they are synthesised by indirect and inefficient processes. We show for the first time in this thesis study that ethylene glycol, the simplest representative of biomass-derived polyols, can be directly converted to these two lower alcohols by selective hydrogenolysis over modified Raney Ni and Cu catalysts in hydrogen atmosphere. This work provides essential information that may lead to the development of new catalysts for carbohydrate activation to methanol, a novel but important reaction concerning the important biomass conversion to transportable form of energy. Modification of electronic structure and the adsorption properties of Raney catalysts have therefore been achieved by blending with second metal(s). It is found that the activity and selectivity of this reaction can be significantly affected by this approach. In contrast, there is no subtle effect on methanol selectivity despite a great variation in the d-band centre positions of metal catalysts which show a distinctive effect on other products. Our result suggests that methanol is produced on specific surface sites independent from the other sites at an intrinsic rate and will not be converted to other products by the d-band alteration. On the other hand, it is reported in this thesis that a dramatic improvement in the combined selectivity to methanol/ethanol reaching 80% can be obtained over a Pd/Fe₃O₄ catalyst under relatively milder conditions (20 bar and 195 oC). This direct production of the non-enzymatic bio-alcohols is established over a carefully prepared co-precipitated Pd/Fe₃O₄ catalyst which gives a metallic phase of unexpectedly high dispersion ranging from small clusters to individual metal adatoms on defective iron oxide to give the required metal-support interaction for the novel synthesis. It is demonstrated that the small PdFe clusters on iron oxide surface provide the active species responsible for methanol production. In addition, a related Rh/Fe₃O₄ catalyst synthesised by co-precipitation is also shown to be selective for CO₂ and H₂ production from a direct methane-oxygen oxidation reaction. As a result, 2.7% conversion of methane with selectivity ratio of CO₂/H₂ = 4 in a mixed gas feed stream of CH₂/O₂ = 30 at 300 ^oC is obtained. The reaction is operated in a kinetically controlled regime at 300^oC, where the CO formation from reverse water gas shift reaction is greatly suppressed. It is evident that the Rh/Fe₃O₄ acts as an interesting bifunctional catalyst for this reaction. This catalyst firstly gives a high dispersion of Rh which is expected to deliver a higher surface energy with enhanced activity. The Rh metal surface provides catalytically active sites for dissociation of methane to adsorbed hydrogen and carbon atoms effectively, and active oxygen on metal surface readily catalyses the carbon atoms to CO. Following these elementary reactions, the surface oxygen from Fe₃O₄ subsequently converts it to CO₂ selectively at the metal-support interface. As a result, the novel study of catalytic biomass conversion and the discoveries of new catalysts are reported in this thesis.