Meta-diisopropylbenzene is reacted with propylene over the acid form of the molecular sieves SAPO-5, mordenite, offretite, beta, hexagonal and cubic faujasite (hex and FAU), L, SAPO-37, and an amorphous silica-alumina at temperatures around 463 K in a flow-type fixed-bed reactor. A small amount of cracking is observed. The main reactions of meta-diisopropylbenzene are isomerization and alkylation. This alkylation is proposed as a new test reaction to characterize the effective size of the voids in larger pore (12 T-atom rings or above) molecular sieves by measuring the amount ratio of formed 1,3,5- to 1,2,4-triisopropylbenzene. In most cases, this ratio increases with the increasing effective void size of the molecular sieves in the order: SAPO-5 < mordenite < offretite < beta < hex ≈ FAU < L < SAPO-37 < amorphous silica-alumina. Since samples with the FAU topology show lower selectivities to 1,3,5-triisopropylbenzene than the mesoporous, amorphous silica-alumina, pore curvature has an influence on alkylation selectivity even for voids of 13 A size. / Ph. D.

The heats of immersion in n-alcohols of zeolites NaY, 5A and ZSM-5 and the kinetics of the immersion process have been determined using a Calvet MS-70 microcalorimeter. The specific heat of immersion decreased non-linearly as a function of chain length of alcohol for NaY and 5A. In contrast, the specific heat of immersion passed through a maximum at n-pentanol for ZSM-S. The specific immersion time as a function of chain length of alcohol showed an apparent linear increase in the order 5A > ZSM-S > NaY. NaY showed almost no increase. The effects of sample evacuation temperature and butyl alcohol isomer bulk on the heats of immersion were also investigated. These results were interpreted in terms of molecular accessibility of the wetting liquid into the pores of the zeolites and in terms of the Si/Al ratio of the zeolites. The overall kinetics of immersion appears to be first order. / Master of Science

The first <i>in situ</i> ¹³C NMR monitoring of zeolite catalyzed reaction is described. The dehydration of 2-propanol over H-ZSM-5 was observed using solution type techniques. Although this produces broad lines, several mechanistic details were elucidated. This study indicates that: 1) the dehydration does not proceed through a cyclopropyl carbenium ion intermediate, 2) propene oligomerizes on the catalyst and reaches a steady state concentration before propene is desorbed, and 3) the 2-propanol flowing over the catalyst does not react with the oligomerized propene. / Master of Science

Porous inorganic solids including mesoporous silicas, zeolites and silicoalumnio-phosphates have been investigated as adsorbents for carbon dioxide, particularly in relation to uptake from flue gases at 0.1 bar and ca. 298 K, but also at higher pressures. The mesoporous silicas SBA-1 and SBA-2, with mesocages separated by narrower windows, have been prepared, calcined at various temperatures and also nitrided with ammonia at high temperature. Nitridation has resulted in framework nitrogen incorporation, but this gave only small increases in the uptake of CO₂ of these mesoporous silicas, which are very low (< 0.2 mmol g⁻¹) at flue gas conditions (0.1 bar, 298 K). A series of cationic forms of the small pore zeolites, chabazite, ZK-5 and Rho, have been prepared by exhaustive cation exchange (and pre-calcination of the as-prepared form of Rho). In addition, a series of ultrastabilised zeolite Rho samples has been prepared to investigate the influence of extra-framework aluminium species on CO₂ uptake. For comparison, the silicoaluminophosphate versions of ZK-5 (SAPO STA-14) and Rho (SAPO(RHO)) have been prepared. Adsorption on Li-, Na-, K- and Ca-forms of chabazite (Si/Al = 3.0) has been related to the crystal structures of their dehydrated forms, as determined by Rietveld refinement against powder X-ray diffraction data (PXRD). For Na- and K-chabazite the structure has been measured in situ by PXRD during CO₂ adsorption. Li-chabazite has the highest uptake from all chabazite cationic forms (4.3 mmol g⁻¹). PXRD of K-chabazite reveals cation migration from eight-membered ring sites to six-membered ring sites upon CO₂ adsorption. Na-chabazite shows partial transformation from rhombohedral to monoclinic symmetry upon prolonged evacuation at high temperature, with resultant non-Type I CO₂ adsorption behaviour. Li-, Na- and K-forms of ZK-5 (Si/Al = 4.16) show high CO₂ uptakes at 0.1 bar and 298 K (Li-ZK-5, 4.7 mmol g⁻¹, which is the highest of the solids measured here). Like all H-forms, H-ZK-5 shows weaker uptake. None of the ZK-5 forms show high selectivity for CO₂ over small hydrocarbons, because cations do not block eight-membered ring windows and the structures do not distort upon dehydration. Uptake of CO₂ on univalent cation forms of zeolite Rho has been studied at low (up to 1 bar) and high (up to 10 bar) pressures. All cationic forms (but not H-Rho) show distortion (Im3̅m to I4̅3m) upon dehydration. Forms of zeolite Rho in which cations occupy window sites in the eight-membered rings between α-cages show hysteresis in their CO₂ isotherms, the magnitude of which (Na⁺,NH₄⁺ < K⁺ < Cs⁺) correlates with the tendency of cations to occupy double eight-membered ring sites rather than single eight-membered ring sites. Additionally, reversible CO₂ uptake using the Zero Length Column method on fully and partially cation exchanged samples has been measured. In situ synchrotron PXRD of CO₂ adsorption on Na-Rho indicates Na cations remain in window sites on the time average, indicating CO₂ uptake must occur by a 'trapdoor mechanism' by which Na cations move away from the windows to allow CO₂ to adsorb. In addition, in situ PXRD reveals the adsorption sites of CO₂ bound cations. Adsorption of small hydrocarbons does not occur on Rho, even at high pressure, indicating that adsorption is selective, and depends on the degree of interaction with the adsorbate rather than simply on the molecular size. Na-Rho is therefore a selective adsorbent for CO₂ over CH₄ with selectivities of 150–25 at 1–9 bar and 298 K, predicted from the single component isotherms, and an uptake of 3.07 mmol g⁻¹ at 0.1 bar. High ‘selectivities' are also observed over K-, Cs- and Ca-forms, examples of a novel type of adsorption selectivity.

L'objectif de ce travail concerne l'étude de l'amorphisation sous pression (PIA) dans des aluminophosphates, qui présentent des coefficients de expansion thermiques négatif (NTE). La synthèse de ces aluminophosphates, leur stabilité en température (dilatation) ainsi que leur comportement sous pression (amorphisationant) été étudiés. Les aluminophosphates choisis pour réaliser cette étude sont AlPO4-54, premier tamis moléculaire uniforme ayant des pores (unidimensionnelles parallèles à l'axe c) de diamètre supérieur à 1 nm, et AlPO4-17, qui présente une porosité tridimensionnelle et le plus fort coefficient de dilatation thermique négatif connu dans les matériaux oxydes. Chaque matériau déshydrataté a été étudié par diffraction des rayons-X sous pression en cellule à enclume de diamants (CED). AlPO4-54 subit une transformation de phase vers AlPO4-8 sous pression avant l'amorphisation. Au contraire, AlPO4-17 qui s'amorphise à basses pressions, est extrêmement compressible et présente une instabilité élastique, avec valeur négative pour B0'. Des valeurs anormales (négatives) pour B0' sont rares et ont déjà été observées pour des cyanures et des MOF (metal organic framework). Cette instabilité semble être caractéristique des matériaux présentant une forte NTE, montrant le lien entre la NTE et la compressibilité anormale. L'influence de la basse température sur l'eau confinée dans les pores de la structure d'AlPO4-54•xH2O a été étudié par diffraction des rayons X et par spectroscopie Raman sur monocristal. Les résultats ont été comparés à des simulations Monte Carlo sur le matériau. Les résultats ont montré que les molécules d'eau en contact avec la surface de la structure du pore unidimensionnel sont plus ordonnées vers 173 K, alors que l'eau du centre du pore est restée dans un état de type verre (liquide) à toutes les autres températures étudiées. L'amorphisation d'AlPO4-54•xH2O a été suivie par diffraction des rayons X et par spectroscopie Raman in-situ sous pression dans une CED en utilisant huile de silicone et l'eau comme milieux transmetteurs de pression. Des analyses ex-situ des échantillons de la forme amorphe d'AlPO4-54•xH2O ont été réalisées par résonance magnétique nucléaire et spectroscopie d'absorption de rayons x au synchrotron Soleil (ligne LUCIA). L'analyse de la structure locale a révélé qu'un changement de coordinence est responsable pour la déstabilisation de la structure : deux molécules d'eau ont été contraintes à entrer dans la sphère de coordination de l'Al tétraédrique, devenant ainsi un site octaédrique. / The aim of this study is to investigate pressure-induced amorphisation (PIA) in negative thermal expansion (NTE) aluminophosphates. The aluminophosphates AlPO4-17 and AlPO4-54 are of particular importance, the first exhibits the highest known degree of negative thermal expansion for an oxide and the second exhibits the largest pores known for zeolites with a diameter of 12 Å. These materials exhibit unusual behavior upon compression due to the softening of a large number of low frequency modes leading to pressure-induced amorphisation. The pressure-induced amorphisation in the exceptional NTE material AlPO4-17 was studied by in situ X-ray powder diffraction. AlPO4-17 shows anomalous behavior under pressure with elastic instability and negative value of B0'. Anomalous compressibility behavior may be observed in other materials that exhibit strong NTE, indicating a link between these two physical properties due by low-energy lattice vibrations. The pressure-induced phase transition of the AlPO4-54 to AlPO4-8 and the consequent amorphisation of the final structure, was studied by X-ray diffraction in situ at high pressures. The freezing of nanoconfined water in the AlPO4-54•xH2O was studied by Single Crystal X-ray Diffraction and Raman spectroscopy experiments and were compared to Monte Carlo and Molecular Dynamics simulations. Results shows that, at the pore surface, the adsorbed layer of water molecules had a crystal-like orientational order, in contrast, a cylindrical core of glassy water in the pore center is present due to the frustration arising from the curvature. The effect of H2O on the (PIA) of AlPO4-54•xH2O was studied by in situ X-ray powder diffraction and Raman spectroscopy under high pressures. Ex situ analysis were used to investigate the local structure of pressure-amorphized microporous AlPO4-54•xH2O by nuclear resonance magnetic and by X-ray absorption spectroscopy at the synchrotron Soleil (beamline LUCIA) which shows that, upon increasing the pressure, two water molecules enters in the coordination sphere of IVAl, changing the coordination from 4- to 6-fold, which destabilizes the structure.

We examined the effect of the pore dimension of zeolites on the separation of gas mixtures using atomistic simulation methods. We studied two categories of the zeolites with small pores: pore modified silicalite for H₂/CH₄separation and small pore silica zeolites for CO₂/CH₄separation. The effect of pore modification of silicalite on the H₂/CH₄separation was examined. Under some degrees of surface modification, the CH₄flux was reduced much more than the H₂flux, resulting in high ideal selectivities. The use of small pore zeolites for CO₂/CH₄separations was studied. In DDR, we showed that CO₂diffusion rates are only weakly affected by the presence of CH₄, even though the latter molecules diffuse very slowly. Consequently, therefore, the permeance of CO₂in the equimolar mixtures is similar to the permeance for pure CO₂, while the CH₄permeance in the mixture is greatly reduced relatively to the pure component permeance. The calculated CO₂/CH₄separation selectivities are higher than 100 for a wide range of feed pressure, indicating excellent separation capabilities of DDR based membranes. Inspired by the observation in DDR we also examined the separation capabilities of 10 additional pure silica small pore zeolites for CO₂/CH₄separations. From these considerations, we predict that SAS, MTF and RWR will exhibit high separation selectivities because of their very high adsorption selectivities for CO₂over CH₄. CHA and IHW, which have similar pore structures to DDR, showed comparable separation selectivities to DDR because of large differences in the diffusion rates of CO₂and CH₄.

Mixed matrix membranes (MMMs) consisting of a polymer bulk phase and an inorganic dispersed phase have the potential to provide a more selective membrane because they incorporate the selectivity of a zeolite dispersed phase while maintaining the ease of use of a polymer membrane. A critical problem in MMM applications is control over the polymer-zeolite interface adhesion during fabrication which can detrimentally impact membrane performance. In this work, MgOxHy (1≤x≤2, 0≤y≤2) nanostructures have been grown on pure-silica MFI and aluminosilicate LTA zeolites through four surface deposition techniques: Grignard decomposition reactions, solvothermal and modified solvothermal depositions, and ion-exchange induced surface crystallization. The structural properties of the surface nanostructures produced by each of the four methods were thoroughly characterized for their morphology, crystallinity, porosity, surface area, elemental composition, and these properties were used to predict the method’s suitability for use in composite membranes. The nanostructured zeolites were used in mixed matrix membranes (MMMs) at two MMMs weight loadings. The dispersion, mechanical properties, and CO₂/CH₄ gas separation properties were measured MMMs made with each method of functionalized LTA. All functionalization methods improve adhesion with the polymer observable by microscopy, the dispersion of particles, and the elastic modulus and hardness of the membrane. Gas permeation measurements prove the quality and effectiveness of the Ion Exchange membrane for CO₂/CH₄ separation by its significant increase in selectivity over the pure polymer. Lastly, the interface between the two materials was studied by probing the interfacial polymer mobility using NMR spin-spin relaxation measurements and mechanical mapping of membrane cross sections. It was shown that the nanostructures have both steric and chemical interactions with the polymer. Mapping of the elastic modulus indicated that functionalization methods that resulted in poorer zeolite coverage also disrupted the mechanical properties of the membrane at the interface of the materials. The investigations in this thesis provide detailed structure-property relationships of surface-modified molecular sieves and nanocomposite membranes fabricated using these materials, allowing a rational approach to the design of such materials and membranes.

Thesis (Ph.D.)--Mechanical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Graham, Samuel; Committee Co-Chair: Nair, Sankar; Committee Member: Grover - Gallivan, Martha; Committee Member: McDowell, David; Committee Member: Schelling, Patrick; Committee Member: Zhang, Zhuomin

Tesis por compendio / [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. / [CA] 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]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/141094 / Compendio

L’objectif de ce travail est de préparer des polymères composites antimicrobiens, utilisant de l’acide polylactique (PLA) et/ou du caoutchouc naturel époxydé et incluant des particules d’argent insérées dans des matrices zéolites (AgZ), agissant en tant que composé actif. Un des verrous contrôlant l’activité antibactérienne des matériaux synthétisés est relié à l’étude de l’absorption de l’eau. En effet la mise en œuvre de composites PLA antibactériens rencontre le problème du caractère faiblement hydrophile de PLA, induisant une faible efficacité antimicrobienne. Ainsi afin d’amplifier l’activité antibactérienne des composites AgZ/PLA, une solution prometteuse consiste à introduire un second polymère hautement polaire et flexible. Le caoutchouc naturel époxydé a été ainsi sélectionné pour être associé au composite AgZ/PLA et le taux d’absorption d’eau mesuré témoigne d’un accroissement notable. La morphologie et la distribution des particules AgZ a été étudiée. L’accroissement remarquable du caractère antibactérien des composites ENR/AgZ/PLA a été démontré ; ainsi des tests menés sur S. aureus montrent que la croissance bactérienne a été inhibée à hauteur de 98-99%. L’étude a aussi été menée en fonction de la proportion de caoutchouc et des particules AgZ. De plus les composites ENR/AgZ/PLA possèdent une plus haute résistance à l’impact comparés à l’emploi de PLA pur, suggérant ainsi que ces nouveaux composites pourront constituer des matériaux de choix pour des applications à la fois antibactériennes et nécessitant une résistance à l’impact forte. / The aim of this work is to prepare antibacterial polymers composites, involving especially poly(lactic acid) (PLA) and epoxidized natural rubber (ENR) in the presence of silver-substituted zeolites (AgZ) as an active ingredient. Herein, the key to control the antibacterial activity of the composites which is the water absorption characteristic was thoroughly studied. In general, the fabrication of antibacterial PLA composites encounters with the problem relating to the poor hydrophilicity of PLA which is the cause of antibacterial ineffectiveness. To enhance the antibacterial activity of the composites, blending with the second polymer having high polarity and flexibility is a promising way to produce the antibacterial AgZ/PLA composite. Herein, epoxidized natural rubber (ENR) was selected to blend with AgZ/PLA composites and the increase in the water absorption percentage could be observed. The morphology as well as the AgZ distribution in the composites were also investigated. The remarkable enhancement of antibacterial activity of ENR/AgZ/PLA composites was observed because more than 98-99% inhibition of S. aureus growth was found. Furthermore, the effects of rubber content and amount of AgZ on the antibacterial activity of the composites were investigated. Moreover, the ENR/AgZ/PLA composites possessed the higher impact resistance compared to neat PLA, suggesting that the improved composites might be a choice in applications at which both antibacterial activity and impact resistance property are of great importance.