<p>Cu-zeolites have received renewed attention as catalytic materials that facilitate partial methane oxidation (PMO) to methanol, with a variety of mononuclear, binuclear, and multinuclear Cu active site motifs that have been proposed in prior literature. Our approach to more precisely identify and probe the Cu structures that activate O₂ and reduce in CH₄relies on the synthesis of model supports with varying composition and well-defined Cu speciation, which also facilitates connections between experimental data and theoretical models. Chabazite (CHA) zeolites are high-symmetry frameworks that contain a single lattice tetrahedral site (T-site), in which Cu²⁺ ions exchange at paired Al sites in a six-membered ring (6-MR) while CuOH⁺ species exchange at isolated 6-MR Al sites, the latter of which can react to form binuclear O/O₂-bridged Cu structures. In this work, Cu-CHA zeolites were synthesized to contain predominantly Cu²⁺ (Z₂Cu) or CuOH⁺ (ZCuOH) species of varying density, or a mixture of Z₂Cu and ZCuOH sites. Z₂Cu and ZCuOH sites were quantified by titration of residual Brønsted acid sites with NH₃, which respectively exchange with 2:1 or 1:1 H⁺:Cu²⁺ stoichiometry. Stoichiometric PMO reaction cycles on Cu-zeolites involved high-temperature (723 K) activation in O₂, and then moderate-temperature (473 K) reduction in CH₄ and treatment in H₂O (473 K) to extract CH₃OH. <i>I</i><i>n-situ</i> UV-Visible spectroscopy under oxidizing (O₂, 723 K) and reducing (CO, 523 K; CH₄, 473 K; He, 723 K) conditions detected the presence of mononuclear and binuclear Cu site types, while <i>in-situ</i> Cu K-edge X-ray absorption spectroscopy after such treatments was used to quantify Cu(I) and Cu(II) contents and <i>in situ</i> Raman spectroscopy was used to identify the Cu structures formed. ZCuOH, but not Z₂Cu sites, are precursors to binuclear O/O₂-bridged Cu sites that form upon O₂ activation and subsequently produce methanol after stoichiometric PMO cycles, at yields (per total Cu) that increased systematically with ZCuOH site density. The fraction of Cu(II) sites that undergo auto-reduction in inert at high temperatures (He, 723 K) is identical, within experimental error, to the fraction that reduces in CH₄ at temperatures relevant for PMO (473 K), providing a quantitative link between the binuclear Cu site motifs involved in both reaction pathways and motivating refinement of currently postulated PMO reaction mechanisms. These Cu-CHA zeolites were also studied for other redox chemistries including the selective catalytic reduction (SCR) of NO_x with NH₃. <i>In situ </i>UV-Visible and X-ray absorption spectroscopies were used to monitor and quantify the transient partial reduction of Cu(II) to Cu(I) during exposure to NH₃ (473 K), in concert with titration methods that use NO and NH₃ co-reductants to fully reduce all Cu(II) ions that remain after treatment in NH₃ alone to the Cu(I) state, providing quantitative evidence that both Z₂Cu and ZCuOH sites are able to reduce in NH₃ alone to similar extents as a function of time. These findings provide new insight into the reaction pathways and mechanisms in which NH₃ behaves as a reductant of mononuclear Cu(II) sites in zeolites, which are undesired side-reactions that occur during steady-state NO_x SCR and that often unintendedly result in Cu(II) reduction prior to spectroscopic or titrimetric characterization. Overall, the strategy in this dissertation employs synthetic methods to control framework Al density and arrangement in zeolite supports to emphasize extra-framework Cu site motifs of different structure and at different spatial densities, and to interrogate these model materials using a combination of <i>in situ</i> spectroscopic techniques together with theory, in order to elucidate active site structure and proximity requirements in redox catalysis. This work demonstrates how quantitative reactivity and site titration data, brought together with an arsenal of tools available in contemporary catalysis research, can provide detailed mechanistic insights into transition metal-catalyzed redox cycles on heterogeneous catalysts.</p>

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 concentrées. / Zeolites 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.

Orientador: Celso Valentim Santilli / Banca: Leila Aparecida Chiavacci Favorin / Banca: Eduardo Ferreira Molina / Resumo: Neste trabalho a metodologia sol-gel foi utilizada para a preparação de materiais híbridos orgânico-inorgânicos (HOI) à base de óxido de poli-etileno (PEO), ligado de forma covalente com o agente acoplador 3(isocianatopropil) - trietoxisilano (IsoTREOS) conjugados com um material zeolítico do tipo MFI, visando aplicações como catalisador para a reação de acetilação do glicerol e assim agregar valor a esse coproduto gerado na produção do biodiesel. O objetivo desta dissertação é demonstrar que o sinergismo entre híbridos do tipo siloxano-poliéter e as zeólitas pode ser explorado na produção de hidrogéis com atividade catalítica. As análises por Microscopia Eletrônica de Varredura (MEV) evidenciaram a homogeneidade na dispersão do material zeolítico na matriz híbrida Os difratogramas de raios-X apresentaram os picos característicos da estrutura cristalina da zeolita ZSM-5 após a conjugação com a matriz U-PEO. Os resultados de Calorimetria Diferencial de Varredura (DSC) revelaram que não ocorre uma mudança significativa na temperatura de transição vítrea (Tg), após a conjugação da matriz híbrida com a zeólita e revelaram uma diminuição do pico endotérmico associado à fusão dos domínios cristalinos do PEO1900, indicando uma possível interação matriz-zeólita. As análises por Espectroscopia no Infravermelho com Transformada de Fourier (FTIR) confirmaram a interação entre a matriz híbrida e a zeólita pelo deslocamento das bandas associadas ao oxigênio tipo éter não coordenado. Medid... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work the sol-gel methodology was used for the preparation of organic-inorganic hybrid (HOI) materials based on polyethylene oxide (PEO) - covalently bonded with the coupling agent 3 (isocyanatopropyl) triethoxysilane (IsoTREOS) conjugate with a zeolitic material of the MFI type, aiming at applications as catalyst for glycerol acetylation reaction and thus add value to this byproduct generated in biodiesel production. The objective of this dissertation is to demonstrate that the synergism between siloxane-polyether hybrids and zeolites can be explored in the production of catalytic activity hydrogels. Scanning Electron Microscopy (SEM) analyzes showed homogeneity in the dispersion of zeolite material in the hybrid matrix. XDR patterns showed the characteristic peaks of the ZSM-5 zeolite crystal structure after conjugation with the U-PEO matrix. Differential Scanning Calorimetry (DSC) results revealed that no significant change in glass transition temperature (Tg) occurs after conjugation of hybrid matrix with zeolite and revealed a decrease in endothermic peak associated with fusion of crystalline domains of PEO1900., indicating a possible matrix-zeolite interaction. Fourier Transform Infrared Spectroscopy (FTIR) analyzes confirmed the interaction between the hybrid matrix and zeolite by shifting the bands associated with uncoordinated ether oxygen. Small-angle X-ray Scattering (SAXS) measurements showed that the starting reagents in the solketal production reaction w... (Complete abstract click electronic access below) / Mestre

This thesis summarizes experimental results on mass transport of small hydrocarbons in micro-porous crystals obtained via interference microscopy (IFM). The transport process has been investigated in three difffferent materials with difffferent pore structures : the metal-organic framework Zn(tbip) with one-dimensional pores, a FER type zeolite with two-dimensional anisotropic pore structure and zeolite A, a LTA type material with isotropic three-dimensional pore structure. Mass transport is described in terms of diffffusivity and surface permeability, both derived from the detected transient concentration profiles. The results on intra-crystalline diffffusion are discussed under consideration of the influences of pore diameter and molecule diameter, which are both found to have a strong influence on the diffffusivity. Based on experimental results measured on the Zn(tbip) material, a new model for the description of surface barriers is developed and proved by experiment. It is demonstrated that the observed surface barrier is created by the total blockage of a large number of pore entrances at the surface and not by a homogeneous surface layer.

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Baggalútar are well-rounded spheroids that typically measures 16-18 mm in size and have a brownreddish appearance. They can be found in the Hvalfjörður bay in SW Iceland. There are manydescriptions in literature and on the internet that Baggalútar are volcanic spherulites formed by quartzor cristobalite spheres growing out of a common centre and there is also a broadly accepted consensusof this theory. However, despite this consensus that Baggalútar are volcanic spherulites there exist nodetailed investigation of their origin. The aim of the thesis is to investigate what Baggalútar is exactlyand how they form. This is achieved by using a combination of petrographic observations with apolarization microscope, mineral chemistry from electron microprobe analysis and measurements oftheir magnetic properties. The results are compared with different geological and anthropological spheroids, spherulites,nodules and concretions. The petrographic observations show that they predominantly consist of finegrained basaltic tephra (groundmass) together with zeolites infilling voids. Analyses of mineralchemistry indicate that the groundmass consists of augitic pyroxene, plagioclase, and two differentoxides where one classifies as titanomagnetite. The magnetic measurements support this by showing aCurie temperature at approximately 460-470 °C which is likely to be titano-magnetite. Although thedifferent geological and anthropological processes that typically results spheroidal shapes have somesimilarities that could explain the formation of baggalútar, most of these can be excluded for differentreasons. The internal textures of baggalútar strongly indicate that the shape is controlled by externalfactors, like weathering or erosion from beach outcrops. This could explain the spherical shape of asingle baggalút, but it fails to explain the spheroidal shapes of individual baggalútar joined together inclusters. / Baggalútar är väl rundade sfäroider som vanligtvis mäter 16–18 mm i storlek och har ett brunt rödaktigtutseende. De hittas i Hvalfjörðurbukten i SW Island. Det finns många beskrivningar i litteraturen ochpå internet som säger att Baggalútar är vulkaniska sfäruliter som bildas av kvarts- eller kristobalitsfärersom växer fram ur ett gemensamt centrum och det finns också en allmänt accepterad konsensus omdenna teori. Men trots denna konsensus om att Baggalútar är vulkaniska sfäruliter finns det ingendetaljerad undersökning av deras ursprung. Syftet med avhandlingen är att undersöka exakt vadBaggalútar är och hur de bildas. Detta uppnås genom att använda en kombination av petrografiskaobservationer med ett polarisationsmikroskop, mineralkemi från elektronmikrosondanalys ochmätningar av deras magnetiska egenskaper. Resultaten jämförs med olika geologiska och antropologiska sfäroider, sfäruliter, noduler ochkonkretioner. De petrografiska observationerna visar att de till övervägande del består av finkornigbasaltisk tefra (grundmassa) tillsammans med zeoliter som fyller ut tomrum. Analyser av mineralkemivisar att grundmassan består av augitisk pyroxen, plagioklas och två olika oxider där den enaklassificeras som titanomagnetit. De magnetiska mätningarna stödjer detta genom att visa en Curietemperatur på cirka 460–470 °C som sannolikt är titanomagnetit. Även om de olika geologiska ochantropologiska processerna som vanligtvis resulterar i sfäroida former har vissa likheter som kanförklara bildandet av baggalútar, kan de flesta av dessa uteslutas av olika anledningar. Baggalútars inretexturer indikerar starkt att formen styrs av yttre faktorer, som väderpåverkan eller erosion frånstrandhällar. Detta kan förklara den sfäriska formen av en enda baggalút, men det misslyckas med attförklara de sfäriska formerna av individuella baggalútar i sammanfogade kluster.

Comparative studies over micro-/mesoporous Cu-containing zeolites ZSM-5 prepared by top-down treatment involving NaOH, TPAOH or mixture of NaOH/TPAOH (tetrapropylammonium hydroxide) were conducted. The results of the catalytic data revealed the highest activity of the Cu-ZSM-5 catalyst both in the absence and presence of water vapor. The physico-chemical characterization (diffuse reflectance UV-Vis (DR UV-Vis), Fourier transform infrared (FT-IR) spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, temperature-programmed desorption of NOx (TPD-NOx), and microkinetic modeling) results indicated that the microporous structure of ZSM-5 effectively stabilized isolated Cu ion monomers. Besides the attempts targeted to the modification of the textural properties of the parent ZSM-5, in the next approach, we studied the effect of the co-presence of sodium and copper cations in the microporous H-ZSM-5. The presence of co-cation promoted the evolution of [Cu–O–Cu]2+ dimers that bind NOx strongly with the desorption energy barrier of least 80 kJ mol−1. Water presence in the gas phase significantly decreases the rate of ammonia oxidation, while the reaction rates and activation energies of NH3-SCR remain unaffected.

Red mud is the waste from alumina production, contain high amount of residual alkaline, aluminate and some metals oxide such as iron oxide, silicon oxide, titanium oxide...; in which aluminum and silica proportions could be used for zeolite synthesis. The zeolite was synthesized by the hydrothermal method for obtaining RM-ZeO-Si which was signed for Si added and RM-ZeO- Si- Al for both Si and Al added. The obtained zeolites were then characterized by the XRD, EDX, SEM, BET and FT-IR methods. The results indicate that the synthesized zeolite is likely the new kind one with one surfur atom in the crystaline unit and has general formula of Na8(Al6Si6O24)S.4H2O. We tested the ability of ammonium and nitrite adsorption of the synthesized zeolites and found that the synthesized zeolites had very high adsorption capacity of both cation ammonium and anion nitrite; but the adsorption mechanism of each was different. Adsorption mechanism of ammonium was suggested as predominant ion exchange between ammonium cation in solution and sodium cation in zeolite crystals; while nitrite adsorbed on surface material by electrostatic attractive force between nitrite anion and electropositive surface of iron oxide particles. / Bùn đỏ là chất thải từ quá trình sản xuất nhôm, chứa lượng lớn kiểm, oxit nhôm và một số oxit khác như sắt oxit, silic oxit, titan oxit…trong đó tỷ lệ nhôm và silic có thể sử dụng để tổng hợp zeolit. Vật liệu zeolit được tổng hợp bằng phương pháp thủy nhiệt, thêm Si được ký hiệu là RMZeO- Si; vật liệu thêm đồng thời Si, Al được ký hiệu là RM- ZeO-Si/Al. Vật liệu zeolit tổng hợp được phân tích đặc trưng cấu trúc bằng các phương pháp XRD, EDX, SEM, BET và FT-IR. Các kết quả phân tích cho thấy vật liệu zeolit tổng hợp có điểm mới khác biệt so với các zeolit thông thường bởi trong cấu trúc phân tử có chứa nguyên tử S, công thức phân tử của zeolit là Na8(Al6Si6O24)S.4H2O. Kết quả khảo sát hấp phụ ban đầu cho thấy vật liệu có khả năng hấp phụ với cả ion amoni và nitrit, cơ chế hấp phụ khác nhau. Quá trình hấp phụ cation amoni là do quá trình trao đổi ion giữa cation amoni với cation natri trong tinh thể zeolit, còn quá trình hấp phụ nitrit trên bề mặt vật liệu do tương tác tĩnh điện giữa nitrit với các cấu tử oxit sắt.

Molecular dynamics (MD) simulation studies were considered in this study in the fields of phosphonium based ionic liquids (PBILs) and heterogeneous (solid/liquid) zeolite systems. A new generation of ionic liquids (ILs) called phase-separable ionic liquids (PSILs) are able to dissolve cellulose and lignin, a necessary step, for conversion of biomass to fuels and chemicals with co-solvents and are immiscible with water or saline solutions. Molecular simulations on these systems will provide insights of phase behavior and dissolution phenomenon. The knowledge of interfacial phase behavior of ionic liquids/solvent systems is critical for materials discovery for designing efficient dissolution processes. Transition zone from miscible to immiscible behavior was observed for alkyl chain lengths varying from 6 to 8. Emulsion phase was observed for [P8888]+ ion. Result from molecular dynamics (MD) simulations shows excellent agreement with experimental data for both chloride and acetate anions. These contributions will be helpful in modeling PBILs system for cellulose dissolution, liquid-liquid extraction and biomass studies. Another important aspect in biofuel conversion is glucose isomerization step using zeolites. Zeolites are crystalline solids that have wide applications in industrial areas for its hydrocarbon conversion, adsorption of molecules. In this study, we report MD simulation studies on glucose solution diffusion into zeolite structure as a function of temperature and pressure. Development of united-atom force field for PBILs, for phosphonium cation with anions of chloride and acetate, is considered in this study. Force field parameterization was considered for these ionic liquids with a variation of alkyl chain length in phosphonium ion with chloride and acetate anions. Performance of force field parameters was analyzed by calculating properties such as density and viscosity at various temperature and compared with available experimental data. Efficient algorithm techniques were developed in molecular simulations that will reduce computational load in calculating non-bonded interactions. We introduce theory of local sample (TLS) in calculating non-bonded interactions acting on atoms. Another algorithmic improvement in MD simulations is calculating force acting on atoms based on previous time steps, that achieves up to 50 % reduction in computational time

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