Dissertations / Theses on the topic 'Synthetic Zeolites'
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Amin, S. "Surface barriers on synthetic zeolites." Thesis, University of Salford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291648.
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Sulaiman, Shamsul Kamal. "Preparation of synthetic zeolites from aluminosilicate materials." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.427789.
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Williams, C. D. "Use of synthetic zeolites as slow release agents." Thesis, University of Salford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.381713.
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Brace, Shelley. "Synthetic and structural studies of high silica MFI zeolites." Thesis, Keele University, 2017. http://eprints.keele.ac.uk/3778/.
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A systematic series of high-silica fluoride MFI zeolites were efficiently synthesised using a variety of shape and size structure directing agents. The effects of these structure directing agents on the zeolite synthesised have been studied by the complementary use of X-ray diffraction and solid state NMR. These 14N, 13C and 29Si NMR experiments yield information about the orientation of the structure directing agent within zeolite pores. They also identify covalently bonded fluoride in the form of pentacoordinated silicon whereby the first case of static and dynamic ordering of fluoride in the same zeolite is discovered by changing the structure directing agent. A two-dimensional solid state NMR experiment has also been used to study 13C isotopically labelled silicalite-1 synthesised using n-methyltributylammonium iodide. The double cross polarisation (DCP) experiment allows the distance to be determined between the structure directing agent and silicon framework for the first time in a zeolite system using NMR. This experiment has the potential to be replicated for silicalite-1 zeolites synthesised using alternate structure directing agents or for other zeolites systems.
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Kini, Gautam Chandrakanth. "Characterization of synthetic zeolites optimized for heavy metal uptake from wastewater." [Gainesville, Fla.] : University of Florida, 2006. http://purl.fcla.edu/fcla/etd/UFE0015769.
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Holmes, Amy Elizabeth. "Synthetic and atomic force microscopy studies of offretite/erionite family zeolites." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/synthetic-and-atomic-force-microscopy-studies-of-offretiteerionite-family-zeolites(476728ac-6294-44e9-9ac7-b2abcef04b0b).html.
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Several members of the ABC-6 zeolite family, namely offretite, zeolite T, ZSM-34 and zeolite L, were synthesised with a view to studying the effect of synthetic parameters on the resulting crystal properties. A range of procedures for producing offretite and ZSM-34 were tested, and crystals with the optimal morphology, purity, crystallinity and size identified. A standard procedure for synthesising zeolite T was used, before the effect of systematically altering the cation concentration, Si/Al ratio and water content in the synthesis mixture was studied, and the optimal composition identified. Ex-situ AFM was used to study the morphology of the resulting crystals, as well as to determine information about surface features, such as the shape and height of terraces. This information could be used to infer the growth mechanism for each crystal. The AFM studies of zeolite L were compared with those of previous studies and found to agree. For offretite, zeolite T and ZSM-34, 1.2 nm high terraces elongated along the length of the {100} face of the crystals were observed. Where the crystals exhibited a micro-crystalline morphology without distinct faces HR-SEM was used to study their morphology and terracing. In-situ AFM was used to study the dissolution of the crystals in basic media. In each case the terraces were observed to dissolve primarily length-wise. The dissolution of terraces on zeolite T was considered in particular detail. The terrace height was measured during dissolution, and three distinct measurements were observed, 1.2, 0.8 and 0.2 nm. These heights were related to framework features. Lateral force AFM measurements were used to show the relationship between decreased terrace height and increased lateral deflection, indicating that dissolving areas of crystal exhibited increased tip-sample friction. The rate of dissolution of terraces on zeolite T was also considered. It was found that dissolution rate increased with increasing NaOH concentration, and with increasing tip-sample force in the AFM. These observations allowed order of reaction for the dissolution process of zeolite T to be estimated at 2.54. A magnesium substituted aluminophosphate ABC-6 family zeotype material, MgAPO-CJ60, was also synthesised and analysed. Solid-state NMR was used to determine the distribution of aluminium and phosphorous within the framework, which was found to be non-random.
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Hui, Kwan San. "Recycling of coal fly ash : synthetic zeolite 4A and MCM-41 /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?MECH%202004%20HUI.
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Tian, Yuyang. "Synthesis and characterization of crystalline microporous materials : investigation of new synthetic routes." Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/6371.
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Conventionally, crystalline microporous materials such as zeolites and metal-organic frameworks (MOFs) are synthesized through the hydrothermal route or the trial-and-error approach. Other synthetic strategies may lead to the synthesis of microporous materials with new architectures or interesting properties. The general aim of this thesis is to investigate some new synthetic routes towards crystalline microporous materials. A top-down and post-synthesis method is reported in Chapter 4. Some zeolites are built up by layers and double-4-ring pillars. Germanium is preferentially located in the double-4-ring sites of a zeolite framework and is hydrolytically unstable. The idea of the top-down method is to disassemble these zeolites to the layer structures by dissolving the Ge-containing pillars and reassemble them to a new framework. This method is applied to the germanosilicate IWW and ITH zeolites for the first time. The effects of framework chemical compositions, Ge distributions and disassembling conditions on the top-down treatment process are investigated. The products obtained from the top-down treatment are characterised. An ionic liquid assisted strategy for the synthesis of zeolites is described in Chapter 5. The ionic liquid assisted strategy is a solvent free reaction. The raw materials are transformed to zeolites through a solid state reaction. The ionic liquids are first used as structure-directing agents (SDAs) in this solvent free reaction to replace the expensive quaternary ammonium hydroxide. A TON zeolite is synthesized using 1-ethyl-3-methylimidazolium bromide as the SDA. Moreover, the ionic liquid assisted strategy is considered as a “green chemistry” synthetic route due to the high yield of the zeolites and the minor production of waste water. Many aluminophosphates have been successfully synthesized through ionothermal routes. Most of them are synthesized using 1-alkyl-3-methylimidazolium based ionic liquids. A new ionic liquid, 1-(2-hydroxyl-ethyl)-3-methylimidazolium chloride ([HOEmim]Cl), is prepared and used for the ionothermal synthesis of aluminophosphate materials. A zeolite analogue with the CHA framework has been synthesized. At high synthetic temperatures, the products are large single crystals. The structures of the framework and the SDA are investigated by single crystal diffraction and other characterisation methods. Flexible MOF materials are usually synthesized by a trial-and-error approach. Recently a flexible MOF compound was synthesized using 5-sulfoisophthalic acid (SIP) as the ligand. It was proposed the sulfonate is weakly coordinated to the metal, which brings flexibility to the compound, and the carboxylate groups keep the framework intact. 2-sulfoterephthalic acid (STP) which also contains one sulfonate group and two carboxylate groups is believed to be an alternative ligand for the targeted synthesis of flexible MOFs. In Chapter 7, a MOF compound is synthesized using STP and 4, 4'-bipyridine (Bpy) as ligands to validate the proposed strategy can be generalized. Variable temperature single crystal diffraction analysis solves the structure and reveals a reversible structure transformation upon dehydration and rehydration.
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Rebedea, Irina. "An investigation into the use of synthetic zeolites for in situ land reclamation." Thesis, Liverpool John Moores University, 1997. http://researchonline.ljmu.ac.uk/5562/.
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This thesis describes an experimental study to determine the feasibility of using zeolite addition for the in situ treatment of soils contaminated with heavy metals. The aim of the present work was to examine the effectiveness of three synthetic zeolites to reduce plant available metal pools in contaminated soils. Three contaminated soils were studied, which are representative of typical contamination sites in the UK: Prescot, site of a copper refmery, Trelogan, an old lead/zinc mine spoil, and Gateacre, a sewage sludge treated field. The action of zeolites to reduce available metal concentrations in soils is due to their ion-exchange properties. To investigate the decrease of metal bioavailability by zeolites, laboratory and greenhouse trials were performed to clarify the mechanism of heavy metal fixation by synthetic zeolites and to quantify the effect of different zeolites for land remediation. For this approach, it was necessary to measure the metal concentration in the soil and the soil solution in zeolite-amended soils and to determine the zeolite specific isotherms of all the metals studied. Cation exchange studies involved exchanging the sodium form of the zeolites with different metals in solution, in order to determine the zeolite affinity for the metals copper, cadmium, zinc and lead. The resulting isotherms demonstrated that all three zeolites showed a preference for the heavy metal ions over sodium ions. The changes in metal speciation in zeolite-treated contaminated soils were evaluated using sequential extraction procedures. After incubation with synthetic zeolites, metals extracted with ammonium acetate were significantly decreased (31.4 % - 72.4 %) in amended soils compared to the controls. This decrease in heavy metal availability is extremely significant. The exchangeable metal fraction is the most available for uptake by plants. Long term soil solution experiments with zeolite-amended soils showed that the metal concentrations in the aqueous leachate were significantly reduced than in the leachate from the same substrates without zeolite addition. Greenhouse pot trials were carried out with sunflower (Helianthus annuus), maize (Zea mays), willows (Salix viminalis) and ryegrass (Lolium perenne) plants grown in zeolite amended contaminated soils. There were significant improvements in visual appearance and growth of plants from the zeolite-treated soils compared to the controls. In addition, metal content of plant tissues was reduced when compared to the controls. Optimum zeolite concentrations were noted for each zeolite. Zeolite P and 4A were more effective at reducing the phytotoxicity at 0.5% and 1%, whilst zeolite Y had to be added at 5% to achieve a similar effect. In order to link the laboratory test results and soil data to a pilot field scale, in which the actual soil and environmental conditions are required to give a complete evaluation of the proposal technique when applied to a given hazardous waste site, a field trial was initiated, at a copper contaminated site at B.I.C.C., Prescot to examine the effectiveness of zeolite amendments under field conditions. Zeolites P and 4A applied at 1% level proved to be an effective treatment for the remediation of the contaminated site, as indicated by improved plant growth and low metal concentrations in the water soluble fraction of the soil. The results show that zeolite addition, particularly zeolites P and 4A, provide an effective method for decreasing plant heavy metal bioavailability in polluted soils, under glasshouse and field conditions.
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Whitehead, Kate. "The application of synthetic zeolites for the removal of heavy metals from contaminated effluents." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/771884/.
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The aim of this research was to provide a comprehensive evaluation of the heavy metal removal performance of two synthetic zeolites, Zeocros CA150 and Zeocros CG180. Detailed laboratory investigations of the key parameters known to affect zeolitic ion exchange were performed with respect to lead, zinc, copper, cadmium and nickel by means of batch equilibrium tests. The study into the effect of contact time suggests that a near equilibrium state was reached within two hours. As metal hydroxide precipitation was minimal at pH 6.0 and the structural integrity of the zeolite was maintained, metal removal at this pH is predominantly by ion exchange rather than chemical precipitation. Fluctuations in both silicon and aluminium release from the zeolites suggest that partial dissolution may occur under mildly acidic conditions, an observation discussed elsewhere in the literature. Heavy metal removal decreased with increasing metal loading, with the zeolites exhibiting Significantly lower operating exchange capacities compared to the theoretical ones. Exchange capacities varied between 1.3-4.9 meq/g and 0.5-4.6 meq/g for CA 150 and CG180 respectively for the five metals studied. Throughout all of the experimental investigations, lead was removed preferentially (>99%) and nickel removal effiCiencies were the lowest «20%). The results from the mixed metal studies demonstrated that lead removal was the least affected by the presence of other heavy metals whereas cadmium, copper and zinc removal was suppressed in comparison to that from Single metal solutions. The presence of competing ions was not found to adversely affect lead removal by CA 150 and CG180, with copper and cadmium removal showing the most suppression in the presence of calcium, magnesium, potassium and sodium. Zinc uptake by both zeolites proved the most sensitive to the addition of hardness ions even under soft water conditions. The zeolites were also demonstrated to achieve up to 100% removal from real effluents, outperforming a natural zeolite, clinoptilolite. Overall, this research has demonstrated the considerable potential of these synthetic zeolites to selectively remove heavy metals from complex contaminated effluents, indicating their possible application as a tertiary technology for effluent treatment.
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Hart, R. "The potential use of synthetic faujasite zeolites as slow release ammonium and potassium fertilizers." Thesis, City University London, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375831.
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Simancas, Coloma Jorge. "Synthesis and Characterization of Zeolitic Materials Using Phosphorous Organic Structure Directing Agents." Doctoral thesis, Universitat Politècnica de València, 2021. http://hdl.handle.net/10251/171267.
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[ES] Las zeolitas son materiales cristalinos microporosos con canales y tamaños de poro de dimensiones moleculares. La estructura y composición de las zeolitas les confiere interesantes propiedades que permiten su aplicación en una amplia gama de aplicaciones industriales como adsorción, separación o catálisis. La síntesis de zeolitas es la etapa más importante para el control de la estructura y composición de las zeolitas y, por tanto, crítica para la optimización de sus propiedades.
Esta tesis se ha centrado en la síntesis de zeolitas utilizando compuestos que contienen fósforo (cationes fosfonio y aminofosfonio) como Agentes Directores de Estructura (P-ADE). El uso de compuestos fosforados influye en la cristalización y propiedades de las zeolitas obtenidas en comparación con las zeolitas obtenidas con cationes de amonio clásicos.
Los compuestos fosforados se eligieron debido a su diferente química y estabilidad con respecto a los cationes de amonio clásicos comúnmente usados en la síntesis de zeolitas. Estos aspectos se estudiaron con un estudio comparativo de diferentes cationes de amonio y fosforados.
Los compuestos de fósforo utilizados en este trabajo han dado lugar a nuevas estructuras cristalinas (ITQ-58 e ITQ-66) y han abierto nuevas vías de síntesis de zeolitas ya conocidas (RTH, IWV y DON), ampliando su gama de composiciones químicas.
La descomposición térmica de los P-ADE confinados dentro de las zeolitas da lugar a la formación de especies de fósforo extra-red que permanecen dentro de los canales y cavidades de las zeolitas. Estas especies modulan las propiedades ácidas y de adsorción de los materiales finales dependiendo de los tratamientos post-síntesis. En este trabajo se ha estudiado una ruta para la incorporación de cantidades controladas de fósforo durante la etapa de síntesis. Esto ha permitido controlar la adsorción y las propiedades ácidas en las zeolitas de poro pequeño, lo que no se puede lograr mediante metodologías de post-síntesis.[CA] Les zeolites són materials cristal·lins microporosos amb canals i mides de porus de dimensions moleculars. L'estructura i composició de les zeolites els confereix interessants propietats que permeten la seua aplicació en una àmplia gamma d'aplicacions industrials com adsorció, separació o catàlisi. La síntesi de zeolites és l'etapa més important per al control de l'estructura i composició de les zeolites i, per tant, crítica per a l'optimització de les seues propietats. Aquesta tesi s'ha centrat en la síntesi de zeolites utilitzant compostos que contenen fòsfor (cations fosfoni i aminofosfoni) com a agents directors d'estructura (P-ADE). L'ús de compostos fosforats influeix en la cristal·lització i propietats de les zeolites obtingudes en comparació amb les zeolites obtingudes amb cations d'amoni clàssics. Els compostos fosforats es van triar a causa de la seua diferent química i estabilitat pel que fa als cations d'amoni clàssics utilitzats en la síntesi de zeolites. Aquests aspectes s¿estudiaren amb un estudi comparatiu de diferents cations d'amoni i fosforats. Els compostos de fòsfor utilitzats en aquest treball han donat lloc a noves estructures cristal·lines (ITQ-58 i ITQ-66) i han obert noves vies de síntesi de zeolites ja conegudes (RTH, IWV i DO), ampliant la seua gamma de composicions químiques. La descomposició tèrmica dels P-ADE atrapats dins de les zeolites dona lloc a la for-mació d'espècies de fòsfor extra-xarxa que romanen dins dels canals i cavitats de les zeolites. Aquestes espècies modulen les propietats àcides i d'adsorció dels materials finals depenent dels tractaments post-síntesi. En aquest treball s'ha estudiat una ruta per la incorporació de quantitats controlades de fòsfor durant l'etapa de síntesi. Això ha permés controlar l'adsorció i les propietats àcides en les zeolites de porus petit, el que no es pot aconseguir mitjançant metodologies de post-síntesi.
[EN] Zeolites are microporous crystalline materials with channels and pore openings of molecular dimensions. The structure and composition of zeolites confers them interesting properties that allow their application in a wide range of industrial applications as adsorption, separation or catalysis. The synthesis of zeolites is the most important stage to control the structure and composition of zeolites, and thus, critical to optimize their properties. This thesis has been focused on the synthesis of zeolites using phosphorous containing compounds (phosphonium and aminophosphonium cations) as Organic Structure Directing Agents (P-OSDA). The use of these phosphorous compounds influence the crystallization and properties of the obtained zeolites compared to zeolites obtained with classical ammo-nium cations. Phosphorous compounds were chosen because of their different chemistry and stabil-ity properties respect to classical ammonium cations commonly used in the synthesis of zeo-lites. These aspects were studied in a comparative study with different ammonium and phosphorous cations. The phosphorous compounds used in this work have yielded new crystalline structures (ITQ-58 and ITQ-66) and opened new routes for the synthesis of already known zeolites (RTH, IWV and DON), widening their chemical composition range. The thermal decomposition of the P-OSDAs entrapped inside the zeolites yields to the formation of extra-framework phosphorus species that remain inside the channels and voids of the zeolites. These species modulate the adsorption and acid properties of the final materials depending on the post-synthesis treatments. In this work, a route for the incorporation of controlled amounts of phosphorus during the synthesis stage has been studied. This has allowed to control the adsorption and acid properties in small pores zeolites, which cannot be achieved by post-synthesis methodologies.
I wish to firstly acknowledge the Spanish Government for the necessary funding for the FPI pre-doctoral fellowship (BES-2013-062999). Also, this thesis would not have been possible without the infrastructures provided by the UPV and the CSIC staff, fused into the ITQ. Furthermore, I want to acknowledge the Microscopy Service of the UPV for their support in sample microscopy characterization
Simancas Coloma, J. (2021). Synthesis and Characterization of Zeolitic Materials Using Phosphorous Organic Structure Directing Agents [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/171267
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Zaitceva, Olesia. "Development of new synthetic tools for the preparation of coumarins and thiocoumarins." Thesis, Strasbourg, 2019. http://www.theses.fr/2019STRAF014.
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Pour la première fois la coumarine a été isolée à l’état naturel en 1820. Depuis, les scientifiques ont extraits plus d’une mille de combinaisons de coumarines et développé plusieurs voies de leur synthèses. Les coumarines sont largement utilisées en pharmacie, médecine, chimie optique et biochimie. Thiocoumarine quant à elle intervient dans les domaines similaires à celui de coumarine. Grâce à ce vaste champ d’applications de coumarines et un grand potentiel de thiocoumarines, nous avons décidé de mettre au point de nouvelles méthodes pour synthétiser ces composants. Le but principal de notre recherche se base sur le développement de méthodes de préparation de dérivés de coumarines et de thiocoumarines à partir de dérivés acétyléniques. La recherche se concentre sur deux méthodes principales : catalyse homogène avec un complexe de platine & catalyse hétérogène avec des zéolithes acides. Les résultats des travaux entrepris dans le cadre de cette thèse ont permis d’identifier des conditions pour la cyclisation de O- et S-aryl propinoates en coumarines et thiocoumarines. Alors que le complexe de Pt(II) (PPy)PtCl(MeCN) s’est avéré performant pour la cyclisation de O-aryl propinoates en coumarines, les zéolithes apparaissent comme des catalyseurs acides efficaces pour l’accès non seulement aux coumarines, mais aussi aux thiocoumarines, peu décrite dans la littératureThe first separation of coumarin was made in 1820, since then scientists extracted more than a thousand natural coumarins and came up with many ways to synthesize them. Coumarins have found application in pharmaceutics, medicine, optical chemistry and biochemistry. Thiocoumarins are poorly represented in the literature than coumarins, but find application in similar areas. Due to a wide range of applications of coumarins and great potential of thiocoumarins, we decided to search for effective methods for synthesizing these compounds. The main goal of our study relies on the development of new methods for preparing coumarin and thiocoumarin derivatives starting from acetylenic compounds. The work is divided into the development of two strategies: homogeneous catalysis with a platinum complex and parallel to heterogeneous catalysis with acidic zeolites. According to the results it was possible to reveal the conditions for the cyclization of O- and S- arylpropynoates to coumarins and thiocoumarins. Although it was shown that the Pt (II) complex (PyPhPtCl(MeCN)) acts to cyclize O-arylpropynoates into coumarins, zeolites (H-Y, H-USY) are effective acid catalysts for access not only to coumarins, but also to thiocoumarins
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Boruntea, Cristian-Renato. "Design, synthesis and characterization of small-pore zeolites for industrial environmental applications." Doctoral thesis, Universitat Politècnica de València, 2020. http://hdl.handle.net/10251/141094.
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[ES] El Proyecto de investigación aquí descrito se estructura en dos partes. La primera parte se centra en la investigación fundamental con el objetivo de crear un protocolo para la síntesis de zeolitas. La segunda parte se refiere al diseño, síntesis y caracterización de nuevas zeolitas, particularmente utiles para aplicaciones DeNOx,, pero también podría ser útil para aplicaciones MTO.
La investigación fundamental sugiere un Nuevo modelo de preparación de zeolitas utilizando otras zeolitas como simiente. Este proceso se llama transformación zeolita-zeolita o también conversión interzeolita. El alto rendimiento obtenido, la rápida cristalización y la mejor utilización y rendimiento de los materiales de partida se han tenido en cuenta para mejorar el proceso en base a un proyecto de doctorado financiado por una empresa. Este método se ha ilustrado utilizando varias zeolitas como semilla, entre otras FAU y CHA, para la preparación de las dos zeolitas objetivo: AEI y AFX.
En la segunda parte, la investigación se centra en el diseño de nuevas zeolitas de poro medio. Se han seleccionado tres zeolitas hipotéticas de una base de datos de 933611 estructuras. Esta selección se ha realizado utilizando descriptores específicamente diseñados en base a la aplicabilidad de estas zeolitas en procesos DeNOx zeolitas. A continuación se han buscado los agentes directores de estructura (ADE) más apropiados, con la ayuda de métodos computacionales, algunos de los cuales se han sintetizado posteriormente. El uso de dichos ADE en el gel de síntesis ha permitido la obtención de una zeolita cuya topología (ERI) ha sido identificada mediante análisis por PXRD, y cuya morfología y tamaño de cristal (particularmente pequeño) la hacen muy adecuada para su uso como catalizador en algunos procesos.
El trabajo de síntesis también reveló la aparición de una nueva zeolita de alta densidad, llamada 'paracelsio-K'. Este nuevo material se ha obtenido al explorar el espacio de fases que cristalizan al utilizar 1-methyl-DABCO como ADE. La síntesis de esta zeolita tiene un especial interés porque el ADE no se incorpora en los canales de la zeolita, pero más bien influyendo en la nucleación y cristalización. La caracterización reveló que la composición del material es próxima al mineral microcline, estructuralmente cercano al paracelsio, ambos feldespatos. A diferencia de los feldespatos el paracelsio-K contiene moléculas de agua en su interior (1 molécula por cavidad) y puede describirse como el material más simple de la familia de las zeolitas que contiene cadenas del tipo 'doble-cigüeñal'. Utilizando los elementos topológicos correspondientes a esta estructura es posible generar estructuras zeolíticas ya conocidas, como GIS, APC, MER, PHI, SIV y algunas otras zeolitas hipotéticas.[CAT] El Projecte d'investigació aquí descrit s'estructura en dos parts. La primera part se centra en la investigació fonamental amb l'objectiu de crear un protocol per a la síntesis de zeolites. La segona part es refereix al disseny, síntesis i caracterització de noves zeolites, particularment útils per a aplicacions DeNOx , però també podria ser útil per a aplicacions MTO. La investigació fonamental suggereix un nou model de preparació de zeolites utilitzant altres zeolites com a llavor. Aquest procés s'anomena transformació zeolita-zeolita o també conversió interzeolita. L'alt rendiment obtingut, la ràpida cristal·lització i la millor utilització i rendiment dels materials de partida s'han tingut en compte per millorar el procés en base a un projecte de doctorat finançat per una empresa. Aquest mètode s'ha il·lustrat utilitzant diverses zeolites com a llavor, entre altres FAU i CHA, per a la preparació de les dues zeolites objectiu: AEI i AFX. A la segona part, la investigació se centra en el disseny de noves zeolites de porus mitjà. S'han seleccionat tres zeolites hipotètiques d'una base de dades de 933.611 estructures. Aquesta selecció s'ha realitzat utilitzant descriptors específicament dissenyats sobre la base de l'aplicabilitat d'aquestes zeolites en processos DeNOx zeolites. A continuació s'han buscat els agents directors d'estructura (ADE) més apropiats, amb l'ajuda de mètodes computacionals, alguns dels quals s'han sintetitzat posteriorment. L'ús d'aquests ADE al gel de síntesi ha permès l'obtenció d'una zeolita la topologia (ERI) ha estat identificada mitjançant anàlisi per PXRD, i la morfologia i mida de vidre (particularment petit) la fan molt adequada per al seu ús com a catalitzador en alguns processos. El treball de síntesi també va revelar l'aparició d'una nova zeolita d'alta densitat, anomenada 'paracelsio-K'. Aquest nou material s'ha obtingut a explorar l'espai de fases que cristal·litzen en utilitzar 1-methyl-DABCO com ADE. La síntesi d'aquesta zeolita té un especial interès perquè el ADE no s'incorpora en els canals de la zeolita, però més aviat influint en la nucleació i cristal·lització. La caracterització va revelar que la composició del material és propera al mineral microcline, estructuralment proper al paracelsio, tots dos feldspats. A diferència dels feldspats el paracelsio-K conté molècules d'aigua al seu interior (1 molècula per cavitat) i pot descriure com el material més simple de la família de les zeolites que conté cadenes del tipus 'doble-cigonyal'. Utilitzant els elements topològics corresponents a aquesta estructura és possible generar estructures zeolítiques ja conegudes, com GIS, APC, MER, PHI, SIV i algunes altres zeolites hipotètiques.
[EN] The research project described herein is structured in two parts. The first part is focused on the fundamental research with the aim of creating a toolbox for zeolite preparation. The second part deal with the design, synthesis and characterization of novel zeolites particular useful for DeNOx applications, but could be also useful for MTO applications. The fundamental research is addressing a novel approach of preparing zeolites by using other zeolites as raw materials. This process is known as zeolite-to-zeolite transformation or interzeolite conversion. The high yield obtained, fast crystallization time and the better utilization of the raw materials (e.g. parent zeolite, organic structure directing agent (OSDA)), are important benefits of interzeolite conversion technic, which answer the objectives formulated for an industrial PhD project. The method has been exemplified by using various raw materials as parent zeolites, such as FAU and CHA for the preparation of two target small pore zeolites AEI and AFX. In the second part the focus has been on the design of novel small pore zeolites. Three hypothetical frameworks have been selected by narrowing down a database containing 933611 structures. The selection has been performed by using the general descriptors for the state-of-the-art DeNOx zeolites (e.g. CHA). This was followed by finding suitable OSDAs for the selected frameworks, by using computational methods. The usage of the theoretically predicted OSDAs in synthesis gels made possible the synthesis of a novel high-silica zeolite. PXRD analysis, revealed that the zeolite has the ERI framework topology. The obtained material has a distinct particle morphology and smaller crystallites, which are key parameters for various catalytic processes. The synthesis work revealed also a novel dense zeolite, named K-paracelsian. The new material has been obtained while exploring the phase space using 1-methyl-DABCO as OSDA. The synthesis of this zeolite is especially interesting in the sense that the OSDA is not being incorporated into the zeolite channels, but rather influencing the nucleation and crystallization. Further characterization revealed a material compositionally closely related to the mineral microcline and structurally closely related to the mineral paracelsian, both of which are feldspars. In contrast to the feldspars, K-paracelsian contains intrazeolitic water corresponding to one molecule per cage and can be described as the simplest endmember of a family of dense double-crankshaft zeolite topologies. By applying the identified building principle, a number of known zeolite frameworks (e.g. GIS, APC, MER, PHI, SIV) and hypothetical zeolite topologies can be constructed.
The authors thank Haldor Topsoe A/S and Innovation Fund Denmark for financial support under the Industrial PhD programme (Case no. 1355-0174B). We thank MINECO of Spain for funding (SEV-2016- 0683 and RTI2018-101033-B-100) and ASIC-UPV for the use of computational facilities. We also thank Prof. M. M. J. Treacy for assistance with the Database of Prospective Zeolite Structures.
Boruntea, C. (2020). Design, synthesis and characterization of small-pore zeolites for industrial environmental applications [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/141094
TESIS
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Barquist, Karna Nicole Larsen Sarah C. "Synthesis and environmental adsorption applications of functionalized zeolites and iron oxide/zeolite composites." [Iowa City, Iowa] : University of Iowa, 2009. http://ir.uiowa.edu/etd/334.
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Barquist, Karna Nicole. "Synthesis and environmental adsorption applications of functionalized zeolites and iron oxide/zeolite composites." Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/334.
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Silicalite-1 crystals and hollow tube structures were synthesized and functionalized with amine and sulfur containing groups. The adsorption behavior of metal ions (Pb2+, CrO4-) in aqueous solution was investigated on nanocrystalline zeolites functionalized with amines and thiols. Nanocrystalline zeolites with a diameter of 30-50 nm and external surface areas around 100 m2/g were functionalized with 3-aminopropyltriethoxysilane (3-APTES) and 3-mercaptopropyltrimethoxysilane (3-MPTMS). The materials were characterized by 29Si magic angle spinning nuclear magnetic resonance spectroscopy and x-ray diffraction. The adsorption of metal ions from aqueous solutions of Pb (NO3)2 and Na2Cr2O7 was measured by inductively coupled plasma-atomic emission spectroscopy. The effects of various conditions such as pH and concentration were studied to optimize adsorption. Adsorption on functionalized mesoporous silica (MS) was conducted for comparison to the functionalized zeolites.
Magnetic zeolite/iron composites were prepared using nanoscale and commercial faujasite zeolites. The composites were functionalized with amine groups to facilitate chromate adsorption under acidic conditions. The materials were characterized using nitrogen adsorption, scanning electron microscopy, thermogravametric analysis, FTIR spectroscopy, and Mossbauer spectroscopy. The adsorption of chromium was evaluated using inductively coupled plasma-optical emission spectroscopy (ICP/OES) to monitor solution chromium quantitatively. The removal of the composites with a magnet was demonstrated. The materials were then evaluated for the adsorption of Cr6+ using ICP-OES to detect chromium.
Iron containing zeolite composites were prepared using nanoscale faujasite zeolites. The composites were functionalized with amine groups and Fe ions to facilitate arsenate(As V) adsorption under a variety of pH conditions. The materials were characterized using nitrogen adsorption, X-ray diffraction, thermogravametric analysis and FTIR spectroscopy, and Mossbauer spectroscopy. The adsorption of arsenic was evaluated using inductively coupled plasma-optical emission spectroscopy (ICP/OES) to monitor solution concentration quantitatively. The removal of the composites with a magnet was demonstrated. Kinetics and pH dependence of the adsorption were studied.
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Cornelius, Mero-Lee Ursula. "The role of aluminium content in the control of the morphology of fly ash based hierarchical zeolite X." University of the Western Cape, 2015. http://hdl.handle.net/11394/5232.
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>Magister Scientiae - MScCoal is the main source of electricity in South Africa, the combustion of which produces a large amount of waste (coal fly ash) annually. The large-scale generation of coal fly ash places major strain on landfills and the material is toxic in nature. The high silicon and aluminium content in fly ash makes it a suitable starting material for zeolite synthesis. Utilisation of fly ash as a starting material for zeolite synthesis alleviates an environmental burden by converting a waste product to an industrially applicable material. In this study, hierarchical zeolite X was synthesised from coal fly ash via the fusion method. The clear fused fly ash (FFA) extract (with molar composition 0.12 Al·14.6 Na·1.00 Si·163 H₂O) served as the synthesis solution for hydrothermal treatment. The influence of synthesis parameters (such as Si/Al ratio, aluminium source, hydrothermal temperature and stirring) on hierarchical zeolite X formation was studied to determine the cause behind the formation of this material. Synthesised zeolites and starting materials (Arnot coal fly ash and fused fly ash) were characterised by various analytical techniques such as XRD and SEM-EDS to determine the phase purity, morphology and elemental composition (framework Si/Al ratio) of these materials. The synthesis of hierarchical zeolite X under hydrothermal conditions was found to be highly sensitive to the aluminium content of the synthesis solution. The hierarchical morphology of zeolite X was formed preferentially in relatively aluminium-deficient (i.e. high Si/Al ratio) synthesis environments under stirred hydrothermal conditions of 90 °C for 16 hours. In the case of sodium aluminate addition, octahedral shaped zeolite X crystals were formed in relatively low Si/Al ratio synthesis environments, which was attributed to the presence of excess sodium cation content in the synthesis solution. Selected hierarchical zeolites (D2 and E2) were characterised further to gain more insight into the properties of this material. HR-TEM and FTIR revealed that hierarchical zeolite D2 and E2 exhibited the typical structural features of zeolite X. Zeolite D2 and E2 contained both micropores and mesopores and had a high BET surface area of 338-362 m²/g. These zeolites also exhibited appreciable solid acidity (0.81-1.12 mmol H/g zeolite). These properties make hierarchical zeolite X a favourable material for application in catalysis or adsorption. Overall, the formation of zeolite X with hierarchical morphology was proposed to be linked to the presence of zeolite P1 structural units in the framework of the zeolite.
National Research Foundation
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Folifac, Leo. "Performance of zeolite ZSM-5 synthesised from South African fly ash in the conversion of methanol to hydrocarbons." Thesis, Cape Peninsula University of Technology, 2018. http://hdl.handle.net/20.500.11838/2751.
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Thesis (Master of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2018.Zeolites have found applications as heterogeneous or solid catalyst in the petrochemical and refining industries. Zeolite ZSM-5 in particular is a highly siliceous solid catalyst with a porous network that consists of medium pore structure (pore openings 5-5.5 A). The solid catalyst (ZSM-5) is well known for its high temperature stability and strong acidity, which makes it an established catalyst used for different petrochemical processes such as Methanol-To-Gasoline (MTG), isomerisation, disproportionation, and cracking. Unlike in the past, the synthesis of zeolite ZSM-5 from other sources that contains silica (Si) and alumina (Al) with the addition of a template (TPBr) as a structure-directing agent is eminent. Its synthesis can be achievable from coal fly ash that is a waste material and a cheap source of Si and Al. Coal fly ash is a waste material that is produced during the combustion of coal to generate electricity. The elemental composition of coal fly ash consists of mostly SiO2 and Al2O3 together with other significant and trace elements. Zeolite ZSM-5 catalyst synthesised from coal fly ash by previous authors required an excessive amount of additional source of silica even though the XRD spectra still show the presence of quartz and mullite phase in the final products. These phases prevented the use of fly ash (solid) as a precursor to synthesise zeolite ZSM-5 products. However, the synthesis of high purity zeolite ZSM-5 products by extracting silica and alumina from South African fly ash and then using it with small amounts of fumed silica was investigated This aim was achieved by fusing fly ash (FA) with sodium hydroxide (NaOH) under hydrothermal condition set at 550 oC for 1 hour 30 minutes. The quartz and mullite phase observed by previous authors was digested by the fusion process. Thereafter, the treatment of fused fly ash filtrate (FFAF) with concentrated H2SO4 (98-99%), precipitated silica and removed Al that therefore increased the Si/Al ratio from 1.97 in fly ash (FA) to 9.5 in the silica extract (named fused fly ash extract). This route was designed to improve the quality of the final products and reduced the amount of fumed silica added to the synthesis mixture prior to hydrothermal synthesis. In this line of investigation, the process of adding fumed silica to the hydrothermal gel was optimised. H-FF1 with a Si/Al ratio of 9.5 was synthesised using the silica extract without the addition of fumed silica. Its XRD, SEM and relative crystallinity results proved that H-FF1 was inactive and hence was not further characterised and utilised in the conversion of methanol to hydrocarbons (MTH). Purer phase zeolite ZSM-5 products (H-FF2 and H-FF3) that were synthesised from silica extract with the addition of small amounts of fumed silica were characterised and successfully used in the methanol to hydrocarbons (MTH) reaction. The synthesised ZSM-5 products had different Si/Al ratio, different morphology, crystal size, BET surface area, and relative crystallinity as well as different trends in the MTH reaction. It was also observed that H-FF2 and H-FF3 (pure phase) solid catalyst deactivated faster than the commercial H-ZSM-5 in the MTH reaction. However, the MTH conversion over H-FF2 competed with that of the commercial H-ZSM-5 within 3 hours of time on stream (TOS) but later deactivated at a faster rate. This was caused by the large crystal size and reduced BET surface area of H-FF2 when compared to the commercial H-ZSM-5. However, H-FF2 performed better than H-FF3 on stream (MTH reaction) due to its smaller crystal size and higher BET. This study has successfully utilised a route that synthesised high purity zeolite ZSM-5 products from the South African fused fly ash extract (FFAE) with the addition of small amounts of fumed silica. The properties of the synthesised zeolite ZSM-5 products (H-FF2 and H-FF3) were similar to that of the commercial H-ZSM-5 as well as active in the MTH reaction. This promoted the utilisation of a waste material (coal fly ash) to synthesise highly siliceous zeolite ZSM-5 products that avoided the presence of mineral phases from fly ash in the final products.
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Liu, X. "Gallosilicate zeolites." Thesis, University of Cambridge, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377222.
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Khodabandeh, Shervin Davis Mark E. Davis Mark E. "Synthesis of alkaline-earth zeolites /." Diss., Pasadena, Calif. : California Institute of Technology, 1997. http://resolver.caltech.edu/CaltechETD:etd-01102008-150302.
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Bessa, Raquel de Andrade. "Synthesis and characterization of composite magnetic zeolites using kaolin for softening water." Universidade Federal do CearÃ, 2016. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=17007.
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CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorThe present work deals about the synthesis and characterization of magnetic zeolites obtained by hydrothermal route using kaolin from Brazilian Northeast as silicon and aluminum source. By means of the X-ray diffraction technique it was possible to identify zeolite LTA and zeolite P1 as major crystalline phases for each synthesis, with low intensity peaks referent to unreacted quartz present in the kaolin used, which is in accordance to the. FTIR spectra; the nanoparticles were identified as magnetite, with low intensity peaks referent to goethite. In scanning electron microscopy, however, it was not possible to morphologically identify these minor components, while the zeolites showed well defined morphologies, presenting unchanged morphology when in the composites form, but with nanoparticles dispersed over their surface, as expected. From transmission electron microscopy it was observed that the nanoparticles were of ca. 50 nm. Magnetic measurements indicated magnetite presence with superior diameter to critical diameter to superparamagnetic particles and remanent magnetization. Thermogravimetric analyses showed for the composites, lower mass loss than compared to the pure zeolites what may be associated to the improvement of its thermal stability. Granulometric distribution indicated nanoparticles agglomeration in variable sizes, while zeolites formed agglomerates of ca. 10 Âm. Water softening was accomplished by using both zeolites, with high efficiency on Ca2+ removal and similar behavior between the zeolite and its respective composite, being the best result observed for zeolite A, with efficiency of 97,95%, reaching equilibrium in the first contact minutes. The dependence on mass studies also showed that zeolite A and its composite presented the best efficiency, whereas zeolite P achieved the same removal levels using corresponding zeolite masses (45 mg). This way, the proposed method for zeolites synthesis proved to be efficient, so that the use of a magnet is capable to attract them, leading their excellent separation from the aqueous medium with its ionic exchange capacity unaffected.
O presente trabalho trata da sÃntese e caracterizaÃÃo de zeÃlitas magnÃticas obtidas por impregnaÃÃo de nanopartÃculas de magnetita a zeÃlitas A e P, sintetizadas por mÃtodo hidrotÃrmico utilizando caulim branco do Nordeste brasileiro como fonte de silÃcio e alumÃnio. Por meio da tÃcnica de difraÃÃo de raios-X foi possÃvel identificar como fases cristalinas majoritÃrias a zeÃlita LTA e P1 para cada sÃntese, com picos de baixa intensidade referentes a quartzo, resistente ao processo tÃrmico de tratamento prÃvio do caulim, bem como nos espectros de infravermelho; as nanopartÃculas foram identificadas como magnetita, havendo ainda indÃcios da presenÃa de goethita em pequena quantidade. Nas anÃlises de microscopia eletrÃnica de varredura, entretanto, nÃo foi possÃvel identificar esses componentes minoritÃrios morfologicamente; enquanto que a morfologia das zeÃlitas mostrou-se bem definida, sem alteraÃÃes apÃs a formaÃÃo dos compÃsitos, apenas com nanopartÃculas espalhadas em sua superfÃcie, como desejado. A partir da microscopia eletrÃnica de transmissÃo, pÃde-se observar melhor a variaÃÃo de tamanho das nanopartÃculas, em mÃdia de 50 nm. Medidas magnÃticas das amostras com essa propriedade indicaram a presenÃa de magnetita com diÃmetro superior ao diÃmetro crÃtico para partÃculas superparamagnÃticas e magnetizaÃÃo remanente. As anÃlises termogravimÃtricas mostraram que a adiÃÃo das nanopartÃculas Ãs zeÃlitas diminuiu sua perda de massa diante do aumento de temperatura e as anÃlises de distribuiÃÃo granulomÃtrica indicaram a aglomeraÃÃo das nanopartÃculas em tamanhos variÃveis, enquanto que as zeÃlitas formaram aglomerados de aproximadamente 10 Âm. Os ensaios de abrandamento de Ãguas mostraram alta eficiÃncia das zeÃlitas em remover Ca2+, com comportamento similar entre a zeÃlita e o seu respectivo compÃsito, encontrando para a zeÃlita A o maior percentual de remoÃÃo, de 97,95 %, atingindo equilÃbrio nos primeiros minutos de aplicaÃÃo. Os estudos de massa tambÃm mostraram a eficiÃncia da zeÃlita A e de seu compÃsito, tendo a zeÃlita P se aproximado dos mesmos nÃveis de remoÃÃo em massas referentes a 45 mg de zeÃlita. Assim, o mÃtodo proposto para sÃntese das zeÃlitas magnÃticas mostrou-se eficiente, de modo que a utilizaÃÃo de um Ãmà à capaz de atraÃ-las facilitando a separaÃÃo do meio apÃs a aplicaÃÃo em meio aquoso e sua capacidade de troca iÃnica nÃo foi afetada.
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Kibby, Sarah A. M. "Applications of zeolites to organic synthesis." Thesis, University of Edinburgh, 1990. http://hdl.handle.net/1842/10989.
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The application of zoelites as catalysts for a number of organic, liquid-phase, acid-promoted reactions is discussed with reference to zeolite acidity and structure on product yield and selectivity. The zeolites described are predominantly high silica materials including Nu-2, ZSM-5, Nu-10 and EU-1 structures. Examination of the Claisen rearrangement of allyl phenyl ether has shown that it is promoted by zeolites relative to the thermal reaction and that the extent of conversion increases with zeolite acidity. In addition to the expected products, 2-allylphenol and the cyclic 2-methyldihydrobenzofuran, small quantities of the para-product, 4-allylphenol are detected over H-Nu-2 and (Cu(II),H)-Y zeolites. 4-Allylphenol is not detected in the thermal rearrangement and its formation in the present work is attributed to an intermolecular mechanism via ether cleavage. Also examined is the Fries rearrangement of phenyl acetate and phenyl benzoate. The product selectivity is compared with that over Nafion-H, an acidic, non-porous, perfluorinated ion-exchange resin. Both rearrangements are more para-selective when performed in the presence of zeolites. In the rearrangement of phenyl acetate a number of by-products in addition to the expected 2- and 4-hydroxyacetophenones are observed. The aldol self-condensation of acetophenone to yield β-methylchalcone and of acetophenone and benzaldehyde to yield chalcone is promoted by H-Nu-2 zeolite. The ring closure of 2-benzoylbenzoic acid to anthraquinone takes place quantitatively over H-Nu-2. The cyclisation is monitored by i.r. to completion and the product isolated by extraction or sublimation. Of those zeolites examined, H-Nu-2 is likely to be most widely applicable as a catalyst in organic synthesis because of its relatively large pore dimensions, high silica content (thermal stability) and high acidity.
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Severance, Michael A. "Nanocrystalline Zeolites: Synthesis, Mechanism, and Applications." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1387817713.
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Ronchi, Laura. "Synthesis of Hydrophobic Zeolites for Energetic Applications." Thesis, Mulhouse, 2017. http://www.theses.fr/2017MULH0678/document.
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Les zéolithes sont des solides microporeux cristallins largement utilisés en adsorption, catalyse, échange ionique et comme tamis moléculaires. Les zéolithes hydrophobes purement siliciques (zéosils) peuvent être utilisées pour le stockage et l’absorption de l’énergie mécanique par intrusion d’eau à haute pression. En fonction du système “zéosil-eau”, lorsque la pression est relâchée (extrusion), le système peut restituer, dissiper ou absorber l’énergie mécanique fournie pendant la compression (intrusion) et donc, il peut montrer un comportement de type ressort, amortisseur ou pare-chocs. Récemment, il a été remarqué que l’intrusion de solutions salines peut améliorer considérablement les performances énergétiques de ces systèmes par une augmentation de la pression d’intrusion. Pendant ce travail, l’intrusion d’eau et de solutions de LiCl a été étudiée pour différentes zéosils pour mieux comprendre la relation qui existe entre la structure des zéosils (dimension des pores, type et dimensionnalité du système poreux) et le comportement ou les performances énergétiques du système “zéosil-liquide intrusé”.Les expériences avec des zéosils qui présentent une structure à cage ont confirmé une pression d’intrusion plus faible par rapport à celles observées par les zéosils ayant une structure à canaux. La pression d’intrusion augmente fortement avec la concentration de LiCl pour les zéosils caractérisés par de petites ouvertures des pores, spécialement pour ceux qui ont des cages, tandis que cette augmentation est plus faible lorsque de grandes ouvertures de pores sont présentes. Il a été aussi montré une influence de la concentration du sel sur le comportement, probablement, due à la nature particulière des solutions très concentréesZeolites are microporous crystalline solids widely used in adsorption, catalysis, ion exchange and molecular sieving. Hydrophobic pure-silica zeolites (zeosils) can be used for mechanical energy absorption and storage by high pressure intrusion-extrusion of water. Depending on the “zeosil-water” system, when the pressure is released (extrusion), the system is able to restore, dissipate or absorb the supplied mechanical energy during the compression step (intrusion) and therefore to display a spring, shock absorber or bumper behavior. Recently, it was found that the use of aqueous salt solutions could considerably improve the energetic performances of such systems by an increase of the intrusion pressure.In this work the intrusion of water and LiCl solutions was studied for different zeosils in order to understand the relationship between the structure of zeosils (pore size, pore system type and dimensionality) and the behavior or the energetic performances of “zeosil-liquid” systems. The experiments with cage-type zeosils confirmed a lower intrusion pressure in comparison with channel-type ones. The intrusion pressure strongly increases with the LiCl content for the zeosils with small pore openings, particularly, for the cage-type ones, while for larger pores this increase is less important. An influence of salt concentration on the behavior of “zeosils-liquid” systems probably due to the particular nature of highly concentrated solutions was also shown
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Herreros, Bruno. "Silicoglycolates in zeolite synthesis." Thesis, University of Cambridge, 1995. https://www.repository.cam.ac.uk/handle/1810/273044.
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Schmidt, Iver. "Design of nanoporous materials for light alkane transformation." Thesis, University of Liverpool, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369114.
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Nearchou, Antony. "Zeolites fit for a crown." Thesis, University of Bath, 2019. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.767594.
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Taylor, Ann Elizabeth. "Microwave synthesis and occlusion reactions of zeolites." Thesis, University of Birmingham, 2007. http://etheses.bham.ac.uk//id/eprint/79/.
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The work presented in this volume covers two distinct fields of zeolite chemistry. The first section of this thesis is dedicated to the synthesis of zeolites A (LTA), X (FAU), Y, (FAU) and rho (RHO) in a microwave oven. Results have demonstrated that when zeolitic gels are heated in a microwave oven they yield zeolite crystals far quicker than when heated in a conventional oven. This is in part a consequence of the rapid heating of the zeolitic gel caused by the microwave radiation, however, this alone is not responsible for such dramatic reductions in synthesis times. An examination of the effect of reagents on the crystallisation of zeolites in a microwave oven is undertaken. The other portion of this thesis focuses on the ion exchange and occlusion reactions undergone by zeolites A (LTA), ZK-4 (LTA) and rho (RHO) in the presence of monovalent metal nitrates. In some cases non-framework peaks are seen in the powder X-ray diffraction patterns of occluded samples. These peaks are attributed to the formation of a superlattice within the zeolite cavities. Particular attention is given to the structural identification of the silver nitrate superlattice formed within zeolite A.
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Shah, Rashed. "Zeolite-Modified Fischer-Tropsch Synthesis." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10738.
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The improvement of the gasoline selectivity and quality with the addition of HZSM-5 to the Fe-FT process is evident from literature. The catalytic performance of the combined Fe-FT/HZSM-5 system has been observed to decline with time-on-stream, attributed to the migration of alkali from the Fe-FT catalyst tothe HZSM-5 zeolite. The catalytic performance of the combined Fe-FT/HZSM-5system has, however, been observed to considerably decline with time-on-stream, aphenomenon which has been attributed to the migration of alkali from the Fe-FT catalyst to he HZSM-5 zeolite. The objective of this study is to characterize and confirm the reported performance of the Fe-FT and combined Fe-FT/HZSM-5 catalyst systems in a stirred from top internal recycle reactor under typical high temperature FT conditions.
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Guarino, Bertholini Marita. "Innovative applications of natural zeolites." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/96581/1/Marita_Guarino%20Bertholini_Thesis.pdf.
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This project focused on the application of zeolite in wastewater treatment in its natural and modified forms. Hydraulic conductivity properties, landfill leachate treatment and manufacture of a novel hybrid zeolite product were the main foci. Significant gaps were revealed in hydraulic conductivity testing methods and have been explored. Sodium form zeolites showed good selectivity and acceptable efficiency for ammonia removal from landfill leachate on column studies. The production of hybrid zeolite was proven to be scalable and critical parameters, such as stirring and temperature were defined, as well as limitations and performance of the novel material.
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Healey, Adam Michael. "Synthesis and characterisation of potential high capacity ion exchange materials." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299518.
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Naydenov, Valeri. "Structured molecular sieves : synthesis, modification and characterization /." Luleå, 2003. http://epubl.luth.se/1402-1544/2003/39.
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Forbes, Neil R. "Synthesis of zeolites in the presence of diethanolamine." Thesis, Imperial College London, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268138.
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Williams, Jennifer Jean. "The modelling, synthesis and mechanical properties of zeolites." Thesis, University of Exeter, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438377.
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Petushkov, Anton. "Synthesis and characterization of nanocrystalline and mesoporous zeolites." Diss., University of Iowa, 2011. https://ir.uiowa.edu/etd/1057.
Full textAbstract:
Mesoporous aggregates of nanocrystalline zeolites with MFI and BEA frameworks have been synthesized using a one-pot and single structure directing agent method. The effect of different reaction conditions, such as temperature, time, pH and water content, on the particle size, surface area and mesopore volume has been studied. Nanocrystalline and mesoporous ZSM-5, β and Y zeolites were modified with different transition metals and the resulting single- and double metal containing catalyst materials were characterized. Nanocrystalline Silicalite-1 zeolite samples with varying particle size were functionalized with different organosilane groups and the cytotoxic activity of the zeolite nanocrystals was studied as a function of particle size, concentration, organic functional group type, as well as the type of cell line. Framework stability of nanocrystalline NaY zeolite was tested under different pH conditions. The synthesized zeolites used in this work were characterized using a variety of physicochemical methods, including powder X-ray diffraction, Solid State NMR, nitrogen sorption, electron microscopy, Inductively Coupled Plasma - Optical Emission Spectroscopy and X-ray Photoelectron Spectroscopy.
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Kuhn, Raquel Cristine. "Purificação de oligossacarideos utilizando coluna de leito fixo de zeolitas." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/256546.
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Orientador: Francisco Maugeri FilhoDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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Resumo: Os frutooligossacarídeos (FOS) são considerados ingredientes naturais de alimentos devido aos efeitos benéficos na proliferação de bifidobactérias no cólon humano, sendo classificados como prebióticos. Estudos recentes demonstram que a separação cromatográfica de monossacarídeos e misturas de dissacarídeos pode melhorar através da utilização de zeólitas Y, sendo também promissoras na separação de oligossacarídeos. Neste estudo, colunas com zeólitas foram utilizadas na separação de oligossacarídeos. A enzima produtora dos frutooligossacarídeos foi isolada de Rhodotorula sp., produzindo seletivamente GF2 (kestose), GF3 (nistose) e GF4 (frutofuranosilnistose). O rendimento de frutooligossacarídeos produzidos foi de 52% quando foi utilizada sacarose 50% como substrato. A separação dos frutooligossacarídeos foi realizada através de coluna empacotada com zeólitas Y trocadas com íons Ba2+. A eficiência de separação foi utilizada como critério para caracterizar a separação. Efeitos de temperatura (400C a 500C), quantidade de amostra injetada (1 a 3 mL), vazão (0,08 a 0,12 mL.min-1) e composição do desorvente (etanol 40 a 60%) foram analisados, através de um planejamento experimental fracionário, onde a vazão se mostrou significativa. O estudo de separação dos açúcares demonstrou que a condição mais favorável para a separação foi com duas colunas em série com etanol 60% como desorvente, temperatura de 500C, vazão de 0,08 mL.min-1 e quantidade de amostra injetada de 1 mL. Os valores de eficiência de separação foram de 0,60 para oligossacarídeos e glicose, 1,00 para oligossacarídeos e frutose, 0,22 para oligossacarídeos e sacarose, 0,43 para glicose e frutose, 0,82 para glicose e sacarose e 1,23 para frutose e sacarose
Abstract: Fructooligosaccharides (FOS) are nowadays considered natural food ingredients because of their beneficial effects in proliferating bifidobactéria in human colon; FOS are classified as prebiotics. Some recent studies show that the chromatographic separation of monosaccharides and a mixture of the disaccharides can be improved by using Y-zeolites, being promising in the separation of oligosaccharides. In this study, a column packed with zeolite was used to study the separation of oligosaccharides. The enzyme, which produces FOS from sucrose, was isolated from Rhodotorula sp., produced selectively GF2 (kestose), GF3 (nystose) and GF4 (frutofuranosyl nystose). The final yield of FOS was 52% when 50% sucrose was used as substrate. For the separation of fructooligosaccharides was used column packed with Ba2+ - exchanged Y zeolites. Efficiency of separation was used as a criterion to characterize the effectiveness of the separation. Effects of temperature (400C a 500C), amount of mixture injection (1 a 3 mL), flow rate (0,08 a 0,12 mL.min-1) and desorbent composition (ethanol 40 a 60%) were investigated, the according to a fractionary fatorial design; the flow rate was a significant factor under the response of efficiency of separation. The study of separation of sugars showed that the most favorable conditions for this separation were with utilization of two columns in series with ethanol 60% as desorbent, temperature of 500C, flow rate of 0,08mL.min-1 and amount of mixture injection of 1 mL. The values for the separation efficiency were 0,60 for oligosaccharides-glucose, 1,00 for oligosaccharides-fructose, 0,22 for oligosaccharides-sucrose, 0,43 for glucose-fructose, 0,82 for glucose-sucrose and 1,23 for fructose-sucrose
Mestrado
Mestre em Engenharia de Alimentos
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Hill, Susan Jane. "The synthesis of transition metal substituted aluminophosphate molecular sieves using tetrahalometallates." Thesis, University of Wolverhampton, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337315.
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Warrender, Stewart James. "Structure direction in the formation of zeolitic materials." Thesis, University of St Andrews, 2007. http://hdl.handle.net/10023/376.
Full textAbstract:
Structure direction in the formation of zeolitic materials has been investigated through the parallel approaches of structural and synthesis studies. The structures of gallosilicates TNU-6 and TNU-7 have been solved from powder X-ray diffraction. TNU-6 (P6₃, a = b = 10.5078(1)Å, c = 8.5277(1)Å) is found to possess a stuffed tridymite-like structure isostructural with BaFeGaO₄. Evidence from electron diffraction, single crystal and high-resolution powder X-ray diffraction suggests the presence of a √3a superstructure, analogous to the related KAlGeO₄ phase, arising from a subtle variation in tilt of tetrahedral units. The structure of TNU-7 consists of an ordered 1:1 intergrowth of alternating sheets of mazzite and mordenite (Pmmn, a = 7.5721(1)Å, b = 17.0739(2)Å, c = 25.8438(5)Å). The crystallisation field of TNU-7 is found to lie between those of mazzite and mordenite, suggesting that this is an example of a ‘boundary phase’ - phase selectivity being governed strongly by the presence and quantity of Ga in the synthesis gel. The distribution of extra-framework Na⁺ cations in the as-made material, and Cs⁺ and Sr²⁺ in ion-exchanged samples, suggests a higher extra-framework charge per T-site associated with the mazzite region of the structure, indicating the possible existence of compositional zoning, consistent with the preference to form mazzite at high Ga gel-content. The structures and synthesis conditions for both TNU-6 and TNU-7 suggests a cooperative effect between Ga and extra-framework species in directing the formation of these phases. The structure of the novel aluminosilicate TNU-9 has been confirmed by energy minimisation and powder neutron diffraction studies (C2/m, a = 28.177(2)Å, b = 20.030(1)Å, c = 19.464(1)Å, β = 92.311(4)º ). Monte Carlo-Simulated Annealing studies have been employed to investigate the favoured location of the 1,4-bis(N- methylpyrrolidinium)butane template molecule within the complex pore system. Remarkably, three (possibly four) different positions are assumed by the structure-directing agent, forming head-to-middle and head-to-head motifs between constituent framework aluminosilicate sheets. TNU-9 crystallises in a very narrow gel composition window suggesting a strong cooperative effect between organic and inorganic gel components. Structure direction of phosphate-based materials (aluminophosphates, magnesium aluminophosphates and silicoaluminophosphates) has been investigated through co-templating synthesis studies. In particular, the structure-directing activity of Cu²⁺ (and to a lesser extent Ni²⁺) complexes of the azamacrocyles cyclam and cyclen, and related derivatives, is investigated in the presence of additional amines (dipropylamine, diisopropylamine, tetraethylammonium hydroxide, diisopropylethylamine). Complexes of a selection of linear polyamines, and also cobalticinium are studied for comparison. Although added primarily as pH moderators, the additional amines are also found to influence the crystallisation and hence provide effective routes to the synthesis of transition metal-containing materials with potential catalytic application. The ‘strength’ of the structure-directing ability of the additional amines is found to vary depending on the identity of the primary structure-directing agent, with behaviour ranging from passive pH moderator to dominating structure-directing agent. The outcome of syntheses is also highly dependent on inorganic gel composition. Through appropriate combination of structure-directing agent and additional amine, mixed Cu²⁺/Ni²⁺-containing MgAPO and SAPO STA-6 (SAS) and STA-7 (SAV) materials have been synthesised for the first time, as well as a low Si form of SAPO STA-7 (with and without Cu²⁺). Also, the combination of cyclam, tetraethylammonium hydroxide and HF has been found to produce a SAPO analogue of STA-7 possessing silicate islands. In addition, transition metal-containing materials possessing the AEL, AFI, CHA, UT-6 and LEV topologies have also been synthesised via this approach. Elemental analysis, UV-Vis, ESR and NMR spectroscopy are employed to confirm the presence of the desired complex in selected samples, while X-ray diffraction and ESR spectroscopy are employed to investigate the environment of extra-framework transition metal species, post calcination, in MgAPO STA-6, SAPO STA-6 and STA-7, MgAPO-18, and MgAPO-5.
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Nouar, Farid. "Design, Synthesis and Post-Synthetic Modifications of Functional Metal-Organic Materials." Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1725.
Full textAbstract:
Porous solids are a class of materials of high scientific and technological significance. Indeed, they have the ability to interact with atoms, ions or molecules not only at their surface but also throughout the bulk of the solid. This ability places these materials as a major class involved in many applications such as gas storage and separation, catalysis, drug delivery and sensor technology.
Metal-Organic Materials (MOMs) or coordination polymers (CPs) are crystalline compounds constructed from metal ions or clusters and organic components that are linked via coordination bonds to form zero-, one-, two or three-periodic structures. Porous Metal-Organic Materials (MOMs) or Metal-Organic Frameworks (MOFs) are a relatively new class of nanoporous materials that typically possess regular micropores stable upon removal of guests. An extraordinary academic and industrial interests was witnessed over the past two decades and is evidenced by a fantastic grow of these new materials. Indeed, due to a self-assembly process and readily available metals and organic linkers, an almost infinite number of materials can, in principle, be synthesized. However, a rational design is very challenging but not impossible. In theory, MOMs could be designed and synthesized with tuned functionalities toward specific properties that will determine their potential applications.
The present research involves the design and synthesis of functional porous Metal-Organic Materials that can be used as platforms for specific studies related to many applications such as for example gas storage and particularly hydrogen storage. In this manuscript, I will discuss the studies performed on existing major Metal-Organic Frameworks, namely Zeolite-like Metal-Organic Frameworks (ZMOFs) that were designed and synthesized in my research group. My research was also focused on the design and the synthesis of new highly porous isoreticular materials based on Metal-Organic Polyhedra (MOP) where desirable functionality and unique features can be introduced in the final material prior and/or after the assembly process. The use of hetero-functional ligands for a rational design toward binary or ternary net will also be discussed in this dissertation.
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Tamer, Nadir Hakan. "Synthesis And Characterization Of Zeolite Beta." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/12607433/index.pdf.
Full textAbstract:
Zeolite beta has been synthesized using hydrothermal methods. In order to synthesize zeolite beta an aqueous gel having a molar batch composition of 2.2 Na2O∙
Al2O3&
#8729
x SiO2&
#8729
4.6 (TEA)2O&
#8729
444 H2O was utilized. The synthesis parameters were SiO2/Al2O3 ratio (20 &
#8804
x &
#8804
50) and crystallization time (6 &
#8804
t &
#8804
16 days). Pure zeolite beta was crystallized from the experiments which were performed with the batch composition having SiO2/Al2O3 of 20 and 30 in 6 to 16 days period. For SiO2/Al2O3 of 20 and 30, the highest yield was obtained for 12 days. Therefore, the rest of the experiments, in which SiO2/Al2O3 was 40 and 50, were carried out keeping the synthesis time constant (12 days). Pure zeolite beta was also synthesized for SiO2/Al2O3 of 40 and 50. The highest yield and the most crystalline zeolite beta sample were obtained from the experiment performed at SiO2/Al2O3 of 50 with a synthesis time of 12 days. The morphology and crystal size of the zeolite beta samples were identified by using scanning electron microscope (SEM). It was observed that, zeolite beta samples had spheroidal morphology with the crystal size of about 0.5 &
#956
m. According to the thermogravimetric analyses (TGA), it was found that template molecules and moisture constituted nearly 18 % by weight of the zeolite beta samples. The surface area of the calcined zeolite beta sample was determined by N2 adsorption and was found to be 488 m2/g. Gravimetric sorption analyses yield that, the limiting sorption capacity of Na-Beta for methanol, ethanol, isopropanol and n-butanol at 0°
C was about the same with a value of 0.25 cm3/g. For o-xylene, m-xylene and p-xylene that value was 0.21 cm3/g, 0.22 cm3/g and 0.24 cm3/g, respectively.
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Molina, Aurora De La Trinidad. "Synthesis of zeolites and their utilisation in waste treatment." Thesis, University of Leeds, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405726.
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Rossin, Joseph A. "Synthesis, characterization and reactivity of transition metal containing zeolites." Diss., Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/76271.
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Transition metal containing zeolites (zeolite A and ZSM-5) were prepared by addition of various transition metal containing substrates to zeolite synthesis gels. Crystal growth data were recorded in order to determine the influence of the transition metal species on the rate of crystal growth. X-ray diffraction, oxygen adsorption, FTIR and SEM were utilized to evaluate crystal purity. X-ray photoelectron spectroscopy (XPS), chemical analysis and electron microprobe analysis were performed in order to ascertain the position (intrazeolitic versus surface) and homogeneity of the transition metal. It was concluded that intrazeolitic transition metals were produced by the novel procedure presented in this work.
1-Hexene hydroformylation by rhodium zeolite A showed intrazeolitic rhodium to migrate to the external surface of the zeolite. However, in the presence of a solution and surface rhodium poison, intrazeolitic rhodium was found to hydroformylate 1-hexene exclusively to heptanal.
Ruthenium containing zeolite A was evaluated under CO-hydrogenation conditions. No migration of intrazeolitic ruthenium to the external surface of the zeolite was observed over the course of the reaction. The product distribution obtained for this catalyst did not follow a log normal behavior. Also, loss of zeolite crystallinity was observed following the reaction.
Cobalt ZSM-5 was evaluated under CO-hydrogenation conditions. No migration of cobalt to the external surface of the zeolite occurred. XPS analysis of the catalyst following various stages of the reaction indicated that intrazeolitic cobalt was not reduced to the zero valent state. Consequently, the non-zero valent cobalt was not capable of hydrogenating carbon monoxide.Ph. D.
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Li, Yunxiang. "Modification of zeolites and synthesis of SAPO-templated carbon." Doctoral thesis, Stockholms universitet, Institutionen för material- och miljökemi (MMK), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-141834.
Full textAbstract:
Zeolites are crystalline aluminosilicates with diverse structures and uniform porosities. They are widely used as catalysts, adsorbents and ion-exchangers in industry. Direct or post modifications optimize the performance of zeolites for different applications. In this thesis, IZM-2 and TON-type zeolites were synthesized, modified and studied. In addition, FAU-type zeolite and silicoaluminophosphate (SAPO) molecular sieves were applied as templates for the preparation of microporous carbons. In the first part of this thesis, the IZM-2 zeolite with an unknown structure was synthesized. We focused on the increasing the secondary porosity and the varied framework compositions upon post modifications. The structure determination of this IZM-2 zeolite was hindered by the small size of crystals. In the second part of this thesis, the synthesis composition was directly modified in order to increase the crystal sizes. IZM-2 crystals were enlarged by excluding the aluminium atoms from the framework. The micropores of the obtained pure-silica polymorphs were activated by ion-exchanging alkali-metal ions with protons. Typically, TON-type zeolites that are synthesized at hydrothermal conditions under stirring have needle-shaped crystals. In the third part of this thesis, snowflake-shaped aggregates were produced by using static hydrothermal conditions for the synthesis of TON-type zeolites. The effects of synthesis parameters on the growth and morphology of crystals were discussed in detail. In the last part of this thesis, microporous carbons with a structural regularity were prepared by chemical vapour deposition (CVD) of propylene using a silicoaluminophosphate (SAPO-37) template. Compared to the conventional zeolite templates, the SAPO template could be removed under mild conditions, without using hydrofluoric acid, and the generated carbons had a large specific surface area and a high fraction of ultrasmall micropores.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.
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Firth, Daniel Sean. "A manifold destiny : advancing the frontiers of the ADOR process." Thesis, University of St Andrews, 2017. http://hdl.handle.net/10023/15664.
Full textAbstract:
This thesis deals with the various attempts to expand the ADOR (Assembly, Disassembly, Organisation and Reassembly) process. This includes the use of the ADOR process to incorporate new elements into a zeolite framework, the expansion of the ADOR process to other germanosilicate frameworks, and the first ever synthesis of a new ADORable germanosilicate and its subsequent daughters. Chapter 4 deals with the expansion of the ADOR process to the already known ADORable zeolite UTL, using the organisation and reassembly steps to incorporate Al and P, resulting in the formation of a zeolite-AlPO hybrid with distinct silicate layers connected by AlPO based s4r linkages. The material was shown to contain Al and P species and was unstable to acidic medium, atypical of the wholly silica zeolite frameworks produced by the ADOR process. MAS NMR studies showed the presence of both tetrahedral P and Al species in the material and that the presence of Si-OH groups was limited. Indicating that the layers had been reconnected with Al and P now present, forming a zeolite-AlPO hybrid. 29 Si-enriched materials were synthesised to confirm the presence of P-O-Si bonds, through 2D MAS NMR correlation experiments; however, results were limited due to the lack of signal strength. Chapter 5 deals with attempts to expand the ADOR process by applying the ADOR process to other already known germanosilicates. It was found that the non-ideal ADORable candidates NUD-1 and ITQ-33 were unable to undergo a controlled disassembly process, primarily due to their high Ge content and distribution of d4r/d3r. The zeolites ITQ-38 and IM-20 showed more promise. Both could undergo disassembly to form a layered material, which could then be organised and reassembled to form new materials. However, these materials were shown to not form perfect daughter zeolites and had a high degree of disorder. This was associated with the complexity of the ADOR process and the many factors that play a role in each step. Chapter 6 deals with the use of a family of SDAs (with the same biphenyl backbone) to synthesise new ADORable zeolites. The synthesis of the SDAs and their use in various zeolite syntheses was discussed. The potential of these SDAs for the synthesis of new zeolites was then evaluated. The investigations were relatively successful with the successful formation of an ADORable zeolite, which was already known, UTL. However, the suitability of such SDAs also put into question, due to their instability under hydrothermal conditions. Chapter 7 discussed the first successful a priori synthesis of a parent germanosilicate and its daughter zeolites by the ADOR process. The successful synthesis of an ADORable zeolite (SAZ-1) was conducted with the use of an imidazolium-naphthalene based SDA. Investigations were first conducted into changing the synthesis condition, exploring the impact of these changes on the resulting products, and optimising the synthesis conditions to favour the formation of the new zeolite SAZ-1. These investigations led to the new zeolite framework SAZ-1, which showed similarities to the zeolites NUD-2 and CIT-13, which were developed simultaneously by other institutions. The properties of the SAZ-1 framework were discussed and were found to be highly suitable for the ADOR process. SAZ-1 was then successfully disassembled, organised, and reassembled to form two new daughter zeolites SAZ-2 and SAZ-3. The alumination of SAZ-1P to form aluminated SAZ-2 and SAZ-3 was also attempted. Both zeolites showed an increase in catalytic activity, compared to the typical pure-silica daughter zeolites. The layers of SAZ- 1P were also able to undergo the same shifting process as seen for the ‘unfeasible' zeolites IPC-9 and IPC-10, but the resultant products were not as ordered as these previous examples. This in addition to the previous work highlighted some of the non-ideal properties of SAZ-1 compared to other ADORable zeolites, like UTL.
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Gilbert, Darren J. "Synthesis and processing using supercritical fluids." Thesis, University of Nottingham, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388317.
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Carleen, Bradford J. "Hydrothermal Synthesis Process for the Production of Silicalite-1 Crystal Aggregate Packing Particles." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-theses/137.
Full textAbstract:
Methyl Tertiary-Butyl Ether (MTBE) contamination of groundwater and surface waters has become a relevant environmental and public safety concern in recent years. This anthropogenic compound is now persistent at low concentrations in several valuable ground and surface water locations within the United States due largely to the widespread production of MTBE for use as a fuel oxygenate in conjunction with negligent underground storage practices during the 1980's and 1990's. Though there are several treatment strategies for the remediation of MTBE spill sites, the most efficient strategy may be adsorption of MTBE by a packed column of silicalite-1 adsorbent. Effective adaption of this technology requires cheap production of silicalite-1 sorbent packing particles on the order of 3 millimeters diameter. This work entails the development of a new synthesis process which results in sufficient in-situ crystallization of silicalite-1 aggregates within a 3 millimeter spherical amorphous silica gel source. The crystal aggregates sizes can be tuned from 5 to 70 µm, depending on synthesis parameters, and the finished silicalite-1 aggregate particle takes the shape of the amorphous gel source. These aggregate particles, when containing a small amorphous core, should be suitable for packed adsorption column applications. Multiple hydrothermal synthesis experiments were performed by batch methods featuring silica gel spheres as the sole silica source for the batch. Zeolite nucleation and crystal growth were demonstrated throughout the amorphous bead. Synthesis parameters were optimized both for short synthesis times, optimal mechanical properties, and cost effectiveness. The influence of product crystal size on particle hardness was also investigated. The packing production process is sufficiently ready for supporting pilot scale adsorption studies.
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Cetinturk, Gurtepe Irde. "Synthesis Of Binderless Tubular Zeolite X Macrobodies." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612789/index.pdf.
Full textAbstract:
Zeolites are microporous crystallines with well defined structures. Zeolites are used in variety of applications because of their properties such as high temperature stability, ion-exchange capacity, adsorption capacity and stability to harsh conditions. Some major applications of zeolites are ion-exchange, catalysis, adsorption and separation.
Synthetic zeolites are normally produced as fine crystalline powder. Prior to their use, the powder is usually formed into spheres, tablets and extrudates by addition binder. Since binders present in the zeolite can block the pores and decrase the adsorption properties, preparation binderless zeolite agglomerates with high mechanical stability has great technological importance.
Objective of the study is to synthesize binderless zeolite X tubular macrobodies by using the developed methods for the synthesis of zeolite A bars and tubes. Main steps of the study are synthesis of the tubular binderless zeolite X macrobodies, characterization of the macrobodies, determination the effect of hydrogel composition on zeolite phase and analyzing effect of time on the crystallinity of macrobodies.
Experimental method for synthesizing the binderless tubular zeolite X macrobodies includes the following stepspreparing hydrogel by mixing sodium aluminate and sodium silicate solutions, filtration of the hydrogel, paste preparation from solid phase of the hydrogel, extrusion of green tubes from paste, calcination of green tubes and crystallization of calcined tubes in filtered liquid of the hydrogel. In this study, synthesis of binderless tubular pure zeolite X macrobodies with high crystallinity was achieved. Micropore volume and BET surface area of the zeolite X tubular macrobody IÇ
S-18, which has 99.9 % crystallinity were determined as 0.178 cm3/g and 631.2 m2/g, respectively. Pure zeolite X, pure zeolite A and zeolite A, X mixtures were obtained after the crystallization of the calcined extrudates which were obtained from different hydrogel compositions. Ternary diagram which was based on the hydrogel compositions and the obtained zeolite phases was plotted.
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Onder, Aylin. "Synthesis Of Zeolite Membranes In Flow System." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614815/index.pdf.
Full textAbstract:
Zeolite membranes are formed as a thin zeolitic layer on the supports. They are usually synthesized by hydrothermal methods in batch systems. In this study, MFI and SAPO-34 type zeolite membranes were produced on macroporous tubular alumina supports in a recirculating flow system at elevated temperatures for the first time in the literature. During the synthesis, the synthesis mixture is flown between the reservoir and the membrane module which includes the support material.
The synthesis temperatures were 180°C and 220°
C, and the corresponding system pressures were approximately 20 and 30 bars for MFI and SAPO-34, respectively. The CH4 and n-C4H10 single gas permeances were measured through MFI membranes and the performance of membranes was investigated in the separation of equimolar CH4/n-C4H10 mixtures. The best MFI membrane had a CH4 single gas permeance of 1.45x10-6 mol/m2-s-Pa and CH4/n-C4H10 ideal selectivity of 35 at 25oC. The membranes preferentially permeated n-C4H10 in the separation of mixtures. The n-C4H10/CH4 separation selectivity was 43.6 with a total permeance of approximately 0.8x10-6 mol/m2-s-Pa at 25oC. The ideal selectivities of CO2/CH4 of SAPO-34 membrane synthesized in stagnant medium were 227, and >
1000 at 220 and 200oC, respectively. Formation of amorphous structure and the additional secondary phases (impurities) were observed on SAPO-34 membranes synthesized in recirculating flow system. The results showed that it is possible to produce SAPO-34 and high quality MFI membranes by a recirculating flow system operating at elevated temperature.
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Burkett, Sandra Louise Davis Mark E. "Mechanisms of structure direction in zeolite synthesis /." Diss., Pasadena, Calif. : California Institute of Technology, 1995. http://resolver.caltech.edu/CaltechETD:etd-11102005-104907.
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Sandström, Linda. "Zeolite membranes for efficient synthesis of biofuels /." Luleå : Luleå university of technology, 2009. http://pure.ltu.se/ws/fbspretrieve/3283415.
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