The effect of microwave radiation on the prepared 0.5Fe/ZSM-5 catalysts as a post-synthesis modification step was studied in the methanol-to-hydrocarbons process using the temperature-programmed surface reaction (TPSR) technique. This was achieved by preparing a series of 0.5Fe/ZSM-5 based catalysts under varying microwave power levels (0–700 W) and over a 10 s period, after iron impregnating the HZSM-5 zeolite (Si/Al = 30 and 80). Physicochemical properties were determined by XRD, SEM, BET, FT-IR, C3H9N-TPSR, and TGA techniques. It was found that microwave radiation induced few changes in the bulk properties of the 0.5Fe/ZSM-5 catalysts, but their surface and catalytic behavior were distinctly changed. Microwave radiation enhanced crystallinity and mesoporous growth, decreased coke and methane formation, decreased the concentration of Brønsted acidic sites, and decreased surface area and micropore volume as the microwave power level was increased from 0 to 700 W. From the TPSR profiles, it was observed that microwave radiation affects the peak intensities of the produced hydrocarbons. Application of microwave radiation shifted the desorption temperatures of the MTH process products over the HZSM-5(30) and HZSM-5(80) based catalysts to lower and higher values respectively. The MeOH-TPSR profiles showed that methanol was converted to DME and subsequently converted to aliphatic and aromatic hydrocarbons. It is reasonable to suggest that microwave radiation would be an essential post-synthesis modification step to mitigate coke formation and methane formation and increase catalyst activity and selectivity. / Chemical Engineering / M. Tech. (Chemical Engineering)

Cette étude se situe dans le cadre des recherches menées par le CEAEA sur la production massive d'hydrogène, sans émission de gaz à effet de serre, via un cycle thermo-chimique de décomposition de l'eau couplé à une source de chaleur à haute température d'origine nucléaire. Dans le cas particulier du cycle dit« Iode-Soufre», on doit extraire H2 à partir d'un mélange H2/HI/H20 très corrosif, opération pour laquelle des procédés membranaires ont été proposés. L'objectif de ce travail est le développement de membranes zéolithiques de type MFI susceptibles d'être utilisées dans ce contexte. Nous présentons les différents matériaux utilisés, la méthodologie de synthèse de couches minces de Silicalite-1 et de ZSM-5 synthétisée sans structurant organique, les techniques de caractérisation des membranes. Une étude cinétique nous a permis d'optimiser et de contrôler les conditions d'obtention de ces couches minces déposées sur des substrats tubulaires en Ti02 et plans en Al2O3-α. De nombreuses expériences de perméation ont été réalisées, pour des gaz simples (H2, He, Ar, N 2, C02, SF6) et des mélanges gazeux (H2/H20/Ar) et (H2/H20/HI/Ar). Les effets de la température, de la pression amont, de l'épaisseur et de la longueur de la couche mince ainsi que du gaz vecteur ont été étudiés en détail. Il apparaît que la présence de molécules d'H20 dans le système joue un rôle prépondérant sur la perméation des autres molécules. / In the general context of massive and "carbon free" hydrogen production studies, the aim of this work was the development of zeolitic MFI membranes for hydrogen extraction and separation. The methodology of synthesis, the membranes characterization techniques as well as the permeation experimental setup are presented. Optimization and control of the elaboration of Ti02 supported Silicalite-1 and template free ZSM-5 membranes have been reached. Details of the full kinetic study that we performed are given. Numerous permeation experiments, involving pure gas (H2, He, Ar, N2, C02, SF6) and mixtures (H2/H20/Ar) and (H2/H 20/HI/Ar) have been carried on. The effects of temperature, feed pressure, thickness and length of the membranes, as well as the role of the sweeping gas have been emphasized. In the case of gas mixtures, the presence of H20 molecules appears to be a predominant factor.

Made available in DSpace on 2016-06-02T19:55:27Z (GMT). No. of bitstreams: 1 3046.pdf: 22010317 bytes, checksum: 740eb3cb48c20a2e8fee311c2c3dd513 (MD5) Previous issue date: 2010-06-15 / Universidade Federal de Sao Carlos / Pt catalysts supported on CeO2-La2O3-Al2O3, with different mixed oxide compositions, and CeO2-ZrO2-Al2O3, prepared using three different routes, were synthesized by sol gel technique. The samples were characterized using thermal analysis, N2 adsorption, X-ray diffraction, diffusive reflectance spectroscopy, Fourier transform infrared spectroscopy of CO adsorption and high resolution transmission electronic microscopy. The Pt dispersion was determined from the data of cyclohexane dehydrogenation rate. In situ temperature programmed reduction and Xray absorption near edge structure using redox treatments were performed trying to find a better understanding for the sample behaviors in the reaction conditions. The catalysts were evaluated in the steam reforming and partial oxidation of methane. In the Pt/CeO2-La2O3-Al2O3 catalysts, the substitution of La for Ce caused a higher stability of CeIII in the alumina structure and higher metal electron density. The oxidation at high temperature caused the Pt agglomeration, on the other hand the reduction treatment lead to a support re-dispersion. The mixed oxides samples with elevated ceria content showed higher activity in the steam reforming and partial oxidation of methane. This behavior was attributed to the ability of promoting the gasification of coke. For the Pt/CeO2-ZrO2-Al2O3 samples, the solid solution between CeO2 and ZrO2 was dependent on the calcination temperature. Phase segregation was observed for the sample calcined at 950ºC, which decreased the catalytic activity. It was attributed to a smaller O* mobility in this sample. / Catalisadores de Pt suportados em óxidos mistos de CeO2-La2O3-Al2O3, com diferentes composições do óxido misto, e CeO2-ZrO2-Al2O3, preparados por três diferentes rotas de adição destes óxidos na alumina, foram sintetizados por meio da técnica sol gel. As amostras tiveram suas propriedades estruturais caracterizadas por meio de técnicas de análise térmica, adsorção de N2, difração de raios X, espectroscopia de refletância difusa, espectroscopia no infravermelho do CO adsorvido, medida de dispersão metálica aparente pela reação de desidrogenação do cicloexano e microscopia eletrônica de transmissão de alta resolução. Com o intuito de um maior esclarecimento dos comportamentos dos catalisadores quando submetidos a condições semelhantes à atmosfera de reação, estudos de oxiredução in situ foram realizados para as amostras e monitorados pelas técnicas de redução a temperatura programada e espectroscopia de alta resolução da borda de absorção. O desempenho catalítico dos catalisadores foi avaliado nas reações de reforma a vapor e oxidação parcial do metano. No que se refere às amostras de Pt/CeO2-La2O3-Al2O3 pode-se afirmar que a substituição do La pelo Ce ocasionou a maior estabilidade do CeIII na rede da alumina e a formação de sítios de Pt com maior densidade eletrônica. O tratamento de oxidação em alta temperatura ocasionou a aglomeração da fase ativa, enquanto que sob condições redutoras, os suportes a base de céria apresentaram um comportamento de re-dispersão. Os maiores valores de atividade nas reações de reforma a vapor e oxidação parcial do metano foram evidenciados para as amostras suportadas nos óxidos mistos com o maior teor de céria. Este resultado foi atribuído a maior interface entre metal-suporte o que proporcionou uma maior transferência de O* para a partícula de Pt, auxiliando na remoção de coque da superfície do catalisador. Para as amostras suportadas nos óxidos mistos de CeO2-ZrO2-Al2O3, a formação da solução sólida entre os óxidos de cério e zircônio demonstrou-se bastante depende da temperatura de calcinação do suporte, apresentando segregação de fases após a calcinação a 950 ºC, e diminuição na atividade catalítica na reação de oxidação parcial do metano em torno de 15%. Este comportamento foi relacionado à menor mobilidade de O* desta amostra, ocasionada pela a separação das fases em CeO2 e ZrO2.

(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 son materiales microporosos cristalinos formados por una red de tetraedros TO4 (T = Si, Al, Ti, ...) interconectados entre sí compartiendo átomos de oxígeno, que generan estructuras tridimensionales definidas por poros y cavidades de dimensiones moleculares. Su capacidad como tamices moleculares, junto con la gran diversidad de sólidos zeolíticos descritos en lo que respecta a topologías de poro, tipos de cavidades, composición química y propiedades texturales, hace de este tipo de materiales importantes catalizadores heterogéneos en procesos de gran interés para la industria química. La presente tesis doctoral busca la síntesis de zeolitas con propiedades fisicoquímicas y texturales controladas, especialmente en lo referente al tipo de cavidad catalítica, la distribución de los centros activos y el control del tamaño de cristal, para su posterior aplicación como catalizadores en reacciones de interés. La primera parte de este trabajo se centra en la síntesis de zeolitas de poro pequeño de estructura tipo CHA con una distribución homogénea de los centros ácidos de aluminio a lo largo de todo el cristal. Para ello, se ha combinado el uso de un agente director específico para dicha estructura con precursores cristalinos. El procedimiento utilizado permite la preparación del material con un tamaño de cristal nanométrico. Esta zeolita ha mostrado ser un catalizador eficiente y estable para el proceso de metanol a olefinas ligeras, alternativa de gran interés en la actualidad frente al uso del petróleo como precursor de ese tipo de compuestos. En la segunda parte de la tesis doctoral se presentan nuevos agentes directores de estructura orgánicos (ADEOs) de constitución sencilla, formados por una parte cíclica directora y una cadena alifática corta, que permiten la preparación de zeolitas clásicas (ZSM-5, Beta y MCM-22) en sus formas nanocristalinas. El control de las propiedades texturales, especialmente en lo que concierne al tamaño de cristal, implica importantes mejoras catalíticas en procesos con limitaciones de tipo difusional para reactivos y/o productos. En ese sentido, el desarrollo de métodos de síntesis eficientes que empleen moléculas directoras de bajo coste facilitaría el empleo real de las zeolitas nanocristalinas a nivel industrial. Finalmente, la última parte propone un nuevo paradigma en la preparación de zeolitas: la síntesis a medida de materiales zeolíticos para su uso como catalizadores en reacciones químicas preestablecidas. El principal objetivo es diseñar sólidos con un perfecto control de la cavidad catalítica, capaces de maximizar las interacciones con los estados de transición de la reacción objetivo, empleando mímicos de dichos intermedios de reacción como ADEOs. Esta táctica evitaría el procedimiento heurístico utilizado tradicionalmente en la búsqueda de la zeolita más activa para un determinado proceso químico. A modo de ejemplo, esta metodología novedosa de síntesis se ha aplicado en la preparación de catalizadores para la síntesis de adamantano y reacciones de cicloadición de tipo Diels-Alder. / [CA] Les zeolites són materials microporosos cristal·lins formats per una xarxa de tetraedres TO4 (T = Si, Al, Ti, ...) interconnectats entre si compartint àtoms d'oxigen, que generen estructures tridimensionals definides per porus i cavitats de dimensions moleculars. La seva capacitat com tamisos moleculars, juntament amb la gran diversitat de sòlids zeolítics descrits pel que fa a tipologies de porus, cavitats, composició química i propietats texturals, fa d'aquest tipus de materials importants catalitzadors heterogenis en processos de gran interès per la indústria química. La present tesi doctoral busca la síntesi de zeolites amb propietats fisicoquímiques i texturals controlades, especialment pel que fa al tipus de cavitat catalítica, la distribució dels centres actius i el control de la grandària de cristall, per a la seua posterior aplicació com a catalitzadors en reaccions d'interès. La primera part d'aquest treball se centra en la síntesi de la zeolita de porus petit CHA amb una distribució homogènia dels centres àcids d'alumini al llarg de tot el cristall. Per a això, s'ha combinat l'ús d'un agent director d'estructura orgànic (ADEO) específic per aquesta estructura amb precursors cristal·lins. El procediment utilitzat permet la preparació del material amb una grandària de cristall nanomètrica. Aquesta zeolita ha mostrat ser un catalitzador eficient i estable per al procés de metanol a olefines lleugeres, alternativa de gran interès en l'actualitat davant l'ús del petroli com a precursor d'aquest tipus de compostos. A la segona part de la tesi doctoral es presenten nous ADEOs de constitució senzilla, formats per una part cíclica directora i una cadena alifàtica curta, que permeten la preparació de zeolites clàssiques i de rellevància industrial (ZSM-5, Beta i MCM-22) en les seves formes nanocristal·lines. El control de les propietats texturals, especialment pel que fa a la grandària de cristall, implica importants millores catalítiques en processos amb limitacions de tipus difusional per reactius i / o productes. En aquest sentit, el desenvolupament de mètodes de síntesi eficients que empren molècules directores de baix cost facilitaria l'ocupació real de les zeolites nanocristal·lines a nivell industrial. Finalment, l'última part proposa un nou paradigma en la preparació de zeolites: la síntesi a mida de materials zeolítics per al seu ús com a catalitzadors en reaccions químiques preestablides. El principal objectiu és dissenyar sòlids amb un perfecte control de la cavitat catalítica, capaços de maximitzar les interaccions amb els estats de transició de la reacció objectiu, emprant mímics d'aquests intermedis de reacció com ADEOs. Aquesta tàctica evitaria el procediment heurístic utilitzat tradicionalment en la recerca de la zeolita més activa per a un determinat procés químic. A tall d'exemple, aquesta metodologia nova de síntesi s'ha aplicat en la preparació de catalitzadors per a la síntesi de adamantà i reaccions de cicloadició de tipus Diels-Alder. / [EN] Zeolites are crystalline microporous materials formed by interconnected TO4 tetrahedra (T = Si, Al, Ti, ...), which create three-dimensional structures defined by pores and cavities of molecular dimensions. Their capacity as molecular sieves, together with the fine-tune control of their properties, including pore topology, cavities, chemical composition or textural properties, among others, make zeolites essential heterogeneous catalysts for industrially-relevant chemical processes. This doctoral thesis seeks the synthesis of zeolites with controlled physicochemical and textural properties, especially focusing on the type of the catalytic cavity, the distribution of the active sites and the control of the crystal size, for their application as heterogeneous catalysts in reactions of interest. The first part of this work attempts the synthesis of the small pore CHA zeolite with a homogeneous distribution of the acidic aluminium centres through the entire crystals. For this, the use of a specific organic structure-directing agent (OSDA) for this zeolite has been combined with crystalline precursors. The procedure described allows the preparation of the high-silica CHA material with a nanometric crystal size. This zeolite performs as an efficient and stable catalyst for the transformation of methanol to light olefins process, which has been proposed as an attractive alternative to the petroleum-based route to obtain these products. In the second part of this thesis, new simple OSDAs combining a directing cyclic part and a short aliphatic chain have been proposed for the preparation of classical and industrially-relevant zeolites (ZSM-5, Beta and MCM-22) in their nanocrystalline forms. The control of textural properties, especially with regard to crystal size, implies significant catalytic improvements in processes with diffusion limitations for reagents and/or products. In this sense, the development of efficient synthesis methods employing low-cost OSDA molecules would facilitate the actual use of nanocrystalline zeolites in industry. Finally, the last part proposes a new paradigm in the preparation of zeolites: the customized synthesis of zeolitic materials for their use as catalysts in pre-established chemical reactions. The main objective is the design of solids with a perfect control of the catalytic cavity, capable of maximizing interactions with the transition states of the target reaction, using mimics of the reaction intermediates as OSDAs. This technique would avoid the heuristic procedure traditionally used in the search of active zeolites for target chemical processes. As an example, this novel synthesis methodology has been applied in the preparation of catalysts for the synthesis of adamantane and cycloaddition reactions, as Diels-Alder. / Gallego Sánchez, EM. (2019). SÍNTESIS DE ZEOLITAS CON PROPIEDADES TEXTURALES Y DE CONFINAMIENTO ADECUADAS PARA SU USO COMO CATALIZADORES EN REACCIONES QUÍMICAS DE INTERÉS INDUSTRIAL [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/134015

In this thesis, geometry is used as a basis for conducting experiments aimed at growing and arranging inorganic minerals on curved interfaces. Mineralisation is directed using crystalline and liquid-crystalline metallic soaps and surfactant/water systems as templates.¶ A review of the history, syntheses, structure and liquid crystallinity of metallic soaps and other amphiphiles is presented as a foundation to understanding the interfacial architectures in mesostructured template systems in general.¶ In this study, a range of metallic soaps of varying chain length and cation type are synthesised and characterised to find potentially useful templates for mineral growth. These include alkaline-earth, transition metal, heavy metal and lanthanide soaps. These are systematically characterised using a variety of analytical techniques, including chemical analyses, x-ray diffraction (XRD) infrared spectroscopy (IR) and differential scanning calorimetry (DSC). Their molecular and crystal structures are studied using transmission electron microscopy (TEM), cryo-TEM, electron diffraction (ED), electron paramagnetic spin resonance (EPR), absorption spectroscopy (UV-VIS), high resolution laser spectroscopy, atomic force microscopy (AFM), nuclear magnetic resonance spectroscopy, scanning electron microscopy (SEM), electron dispersive x-ray analysis (EDXA), thermal gravimetric analysis (TGA) and magnetic measurements. Models for the molecular and crystal structures of metallic soaps are proposed. The soaps are predominantly lamellar crystalline or liquid crystalline lamellar rotor phases with tilted and/or untilted molecular constituents. These display evidence of varying degrees of headgroup organisation, including superstructuring and polymerisation. A single crystal structure is presented for a complex of pyridine with cobalt soap. Simple models for their structure are discussed in terms of their swelling properties in water and oils. Experiments are also presented to demonstrate the sorbent properties of aluminium soaps on oil spills.¶ The thermotropic liquid crystallinity of alkaline earth, transition metal, heavy metal and lanthanide soaps is investigated in detail. This is done to assess their suitability as templates, and to document their novel thermotropic behaviour, particularly the relatively unknown lanthanide soaps. Liquid crystalline behaviours are studied using high-temperature XRD (HTXRD), hot-stage optical microscopy and DSC. Models for a liquid crystalline phase progression from crystals to anisotropic liquids are discussed in terms of theories of self-assembly and interfacial curvature. The terminology required for this is drawn from various nomenclature systems for amphiphilic crystals and liquid crystals. General agreement with previous studies is reported for known soaps, while liquid crystallinity is demonstrated in the lanthanide and some non-lanthanide soaps for the first time. A general phase progression of crystalline lamellar through liquid crystalline lamellar to non-lamellar liquid crystalline is discussed in terms of models concerned with the molecular and crystal structures of the soaps and their phase transitions via headgroup and chain re-arrangements.¶ Experiments aimed at guiding growth of metal sulfides using metallic soaps as templates are described, and a model for this growth is discussed. Metal sulfides have been successfully grown by reacting crystalline and liquid crystalline transition metal and heavy metal soaps with H2S gas at room temperature and at elevated temperature. These have been characterised using XRD, TEM, ED and IR. Sulfide growth is demonstrated to be restricted and guided by the reacting soap template architecture. Zinc, cadmium, indium and lead soaps formed confined nanoparticles within the matrix of their reacting soap template. In contrast, curved and flat sheet-like structures, some resembling sponges were found in the products of sulfided iron, cobalt, nickel, copper, tin and bismuth soaps. A model to explain this behaviour is developed in terms of the crystal and liquid crystal structures of the soaps and the crystal structures of the metal sulfide particles.¶ Liquid crystalline iron soaps have been subjected to controlled thermal degradation yielding magnetic iron oxide nanoparticles. Some XRD and TEM evidence has been found for formation of magnetic mesostructures in heat-treated iron soaps. Models for the molecular and liquid crystalline structure of iron soaps, their thermotropic phase progression and eventual conversion to these magnetic products are discussed. Systematic syntheses of mesoporous silicates from sheeted clays are discussed.¶The templates that have been used are cationic surfactants and small, organic molecular salts. Experiments are reported where a cooperative self-assembly of surfactant/water/kanemite plus or minus salt and oils yields 'folded sheet materials' (FSM'S). Templating of kanemite has also been achieved using cobalt cage surfactants. A theoretical prediction of the specific surface areas and specific volumes of homologous sets of FSM's gave excellent agreement with measured values. The geometry and topology of the mesostructures are discussed. A theoretical model is also discussed regarding the curvature found in the sheets of natural clays , and results of templating clays and silica using metallic soaps are presented. Experiments and a model for low temperature nucleation and growth of microporous silicalite-1 are described in terms of silica templating by water clathrates.¶ Finally, the problem of finding minimal surface descriptions of crystal networks is addressed. Combinatoric methods are used to disprove the existence of possible embeddings of type I and II clathrate networks in non-self intersecting periodic minimal surfaces. The crystal network of the clathrate silicate, melanophlogite is successfully embedded in the WI-10 self-intersecting surface. Details of a previously unreported, genus-25 periodic surface with symmetry Im3m are discussed.