Made available in DSpace on 2014-12-17T15:42:28Z (GMT). No. of bitstreams: 1 MariaJFC_TESE.pdf: 4007652 bytes, checksum: 7bb363c54641679d79bbff5c76de539f (MD5) Previous issue date: 2013-06-03 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The processing of heavy oil produced in Brazil is an emergency action and a strategic plan to obtain self-sufficiency and economic surpluses. Seen in these terms, it is indispensable to invest in research to obtain new catalysts for obtaining light fraction of hydrocarbons from heavy fractions of petroleum. This dissertation for the degree of Doctor of Philosophy reports the materials preparation that combine the high catalytic activity of zeolites with the greater accessibility of the mesoporosity, more particularly the HZSM-5/MCM-41 hybrid, done by synthesis processes with less environmental impact than conventional ones. Innovative methodologies were developed for the synthesis of micro-mesoporous hybrid material by dual templating mechanism and from crystalline zeolitic aluminosilicate in the absence of organic template. The synthesis of hybrid with pore bimodal distribution took place from one-single organic directing agent aimed to eliminate the use of organic templates, acids of any kind or organic solvents like templating agent of crystalline zeolitic aluminosilicate together with temperature-programmed microwave-assisted, making the experimental procedures of preparation most practical and easy, with good reproducibility and low cost. The study about crystalline zeolitic aluminosilicate in the absence of organic template, especially MFI type, is based on use of H2O and Na+ cation playing a structural directing role in place of an organic template. Advanced characterization techniques such as X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Highresolution Transmission Electron Microscopy (HRTEM), Adsorption of N2 and CO2, kinetic studies by Thermogravimetric Analysis (TGA) and Pyrolysis coupled to Gas Chromatography/Mass Spectrometry (Pyrolysis-GC/MS) were employed in order to evaluate the synthesized materials. Achieve the proposed objectives, has made available a set of new methodologies for the synthesis of zeolite and hybrid micro-mesoporous material, these suitable for catalytic pyrolysis of heavy oils aimed at producing light fraction / O processamento do petr?leo pesado produzido no Pa?s ? uma a??o emergencial e estrat?gica para obter a auto-sufici?ncia e super?vits econ?micos. Neste sentido, ? indispens?vel o investimento em pesquisas de novos catalisadores para obten??o de derivados leves a partir de fra??es pesadas do petr?leo. O trabalho de doutorado aqui reportado dedicouse ? prepara??o de materiais que combinem, numa ?nica estrutura, a elevada atividade catal?tica de ze?litas, com melhor acessibilidade de materiais mesoporosos, como a estrutura h?brida HZSM-5/MCM-41, utilizando processos de s?ntese com menor impacto ambiental que os convencionais. Metodologias inovadoras foram desenvolvidas para a s?ntese do catalisador h?brido micro-mesoporoso ou ze?lito-mesoporoso por mecanismo de direcionamento estrutural via duplo agente diretor org?nico e tamb?m a partir de estrutura zeol?tica sintetizada na aus?ncia total de direcionador org?nico. Esse ?ltimo, tamb?m chamado de s?ntese do h?brido com distribui??o bimodal de poros a partir de um ?nico agente diretor org?nico, visou eliminar o uso dos direcionadores org?nicos, ?cidos de qualquer natureza ou solventes org?nicos como molde estrutural da estrutura zeol?tica em conjunto com o m?todo hidrot?rmico assistido por irradia??o via micro-ondas, tornando o procedimento experimental de prepara??o pr?tico e simples, com boa reprodutibilidade e menor custo. A metodologia de prepara??o da ze?lita MFI do tipo ZSM-5 utiliza H2O e c?tions Na+ no papel de direcionamento estrutural e compensa??o de cargas na estrutura. T?cnicas relevantes de caracteriza??o, como Difra??o de Raios-X (XRD), Espectroscopia no Infravermelho com Transformada de Fourier (FTIR), Microscopia Eletr?nica de Varredura (SEM), Microscopia Eletr?nica de Transmiss?o de Alta Resolu??o (HRTEM), Adsor??o de N2 e CO2, estudos cin?ticos via An?lises Termogravim?tricas (TGA) e Pir?lise acoplada ? Cromatografia Gasosa/Espectrometria de Massas (Pyrolysis-GC/MS), foram empregadas no intuito de avaliar os materiais sintetizados. Alcan?ados os objetivos propostos, disponibilizou-se um conjunto de novas metodologias para s?ntese de catalisadores zeol?ticos e h?bridos micromesoporosos, estes adequados para pir?lise catal?tica de ?leos pesados visando ? produ??o de derivados leves

Background Fatigue often occurs as long-term complication in chronically critically ill (CCI) patients after prolonged intensive care treatment. The Multidimensional Fatigue Inventory (MFI-20) has been established as valid instrument to measure fatigue in a wide range of medical illnesses. Regarding the measurement of fatigue in CCI patients, the psychometric properties of the MFI-20 have not been investigated so far. Thus, the present study examines reliability and validity of the MFI-20 in CCI patients. Methods A convenience sample of n = 195 patients with Critical Illness Polyneuropathy (CIP) or Myopathy (CIM) were recruited via personal contact within four weeks (t1) following the transfer from acute care ICU to post-acute ICU at a large rehabilitation hospital. N = 113 (median age 61.1 yrs., 72.6% men) patients were again contacted via telephone three (t2) and six (t3) months following the transfer to post-acute ICU. The MFI-20, the Euro-Quality of Life (EQ-5D-3 L) and the Structured Clinical Interview for the Diagnostic and Statistical Manual of mental disorders DSM-IV (SCID-I) were applied within this prospective cohort study. Results The internal consistency Cronbach’s α was adequate for the MFI-total and all but the subscale Reduced Motivation (RM) (range: .50–.91). Item-to-total correlations (range: .22–.80) indicated item redundancy for the subscale RM. Confirmatory Factor analyses (CFAs) revealed poor model fit for the original 5-factor model of the MFI-20 (t2/t3, Confirmatory Fit Index, CFI = .783/ .834; Tucker-Lewis Index, TLI = .751/ .809; Root Mean Square Error of Approximation, RMSEA = .112/ .103). Among the alternative models (1-, 2-, 3-factor models), the data best fit to a 3-factor solution summarizing the highly correlated factors General −/ Physical Fatigue/ Reduced Activity (GF/ PF/ RA) (t2/ t3, CFI = .878/ .896, TLI = .846/ .869, RMSEA = .089/ .085, 90% Confidence Interval .073–.104/ .066–.104). The MFI-total score significantly correlated with the health-related quality of life (range: −.65-(−).66) and the diagnosis of major depression (range: .27–.37). Conclusions In the present sample of CCI patients, a reliable and valid factor structure of the MFI-20 could not be ascertained. Especially the subscale RM should be revised. Since the factors GF, PF and RA cannot be separated from each other and the unclear factorial structure in the present sample of CCI patients, the MFI-20 is not recommended for use in this context.

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

Background Fatigue often occurs as long-term complication in chronically critically ill (CCI) patients after prolonged intensive care treatment. The Multidimensional Fatigue Inventory (MFI-20) has been established as valid instrument to measure fatigue in a wide range of medical illnesses. Regarding the measurement of fatigue in CCI patients, the psychometric properties of the MFI-20 have not been investigated so far. Thus, the present study examines reliability and validity of the MFI-20 in CCI patients. Methods A convenience sample of n = 195 patients with Critical Illness Polyneuropathy (CIP) or Myopathy (CIM) were recruited via personal contact within four weeks (t1) following the transfer from acute care ICU to post-acute ICU at a large rehabilitation hospital. N = 113 (median age 61.1 yrs., 72.6% men) patients were again contacted via telephone three (t2) and six (t3) months following the transfer to post-acute ICU. The MFI-20, the Euro-Quality of Life (EQ-5D-3 L) and the Structured Clinical Interview for the Diagnostic and Statistical Manual of mental disorders DSM-IV (SCID-I) were applied within this prospective cohort study. Results The internal consistency Cronbach’s α was adequate for the MFI-total and all but the subscale Reduced Motivation (RM) (range: .50–.91). Item-to-total correlations (range: .22–.80) indicated item redundancy for the subscale RM. Confirmatory Factor analyses (CFAs) revealed poor model fit for the original 5-factor model of the MFI-20 (t2/t3, Confirmatory Fit Index, CFI = .783/ .834; Tucker-Lewis Index, TLI = .751/ .809; Root Mean Square Error of Approximation, RMSEA = .112/ .103). Among the alternative models (1-, 2-, 3-factor models), the data best fit to a 3-factor solution summarizing the highly correlated factors General −/ Physical Fatigue/ Reduced Activity (GF/ PF/ RA) (t2/ t3, CFI = .878/ .896, TLI = .846/ .869, RMSEA = .089/ .085, 90% Confidence Interval .073–.104/ .066–.104). The MFI-total score significantly correlated with the health-related quality of life (range: −.65-(−).66) and the diagnosis of major depression (range: .27–.37). Conclusions In the present sample of CCI patients, a reliable and valid factor structure of the MFI-20 could not be ascertained. Especially the subscale RM should be revised. Since the factors GF, PF and RA cannot be separated from each other and the unclear factorial structure in the present sample of CCI patients, the MFI-20 is not recommended for use in this context.

[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 / TESIS

Control and analysis of protein aggregation is an increasing challenge to biopharmaceutical research and development. Therefore it is important to understand the interactions, causes and analysis of particles in order to control protein aggregation to enable successful biopharmaceutical formulations. This work investigates the role of different non-ionic surfactants on protein conformational stability, as assessed by HSDSC, and on protein size stability as assessed by Dynamic Light Scattering (DLS), HIAC and MFI. BSA and IgG2 were used as model proteins. Thermal unfolding experiments indicated a very weak surfactant-immunoglobulin IgG2 interaction, compared to much stronger interactions for the BSA surfactant systems. The DLS results showed that BSA and IgG2 with different surfactants and concentration produced different levels of particle size growth. The heat treatment and aging of samples in the presence of Tween 20, Tween 80, Brij 35 and Pluronic F-68 surfactants led to an increase in the populations of larger particles for BSA samples, whereas IgG2 systems did not notably aggregate under storage conditions MFI was shown to be more sensitive than HIAC technique for measuring sub-visible particles in protein surfactant systems. Heat treatment and storage stress showed a significant effect on BSA and IgG2 protein sub-visible particle size stability. This work has demonstrated that both proteins with different Tween 20, Tween 80, Brij 35 and Pluronic F-68 concentrations, have different level of conformational and size stability. Also aging samples and heating stress bears the potential to generate particles, but this depends on surfactant type. Poor predictive correlations between the analytical methods were determined.

Control and analysis of protein aggregation is an increasing challenge to biopharmaceutical research and development. Therefore it is important to understand the interactions, causes and analysis of particles in order to control protein aggregation to enable successful biopharmaceutical formulations. This work investigates the role of different non-ionic surfactants on protein conformational stability, as assessed by HSDSC, and on protein size stability as assessed by Dynamic Light Scattering (DLS), HIAC and MFI. BSA and IgG2 were used as model proteins. Thermal unfolding experiments indicated a very weak surfactant-immunoglobulin IgG2 interaction, compared to much stronger interactions for the BSA surfactant systems. The DLS results showed that BSA and IgG2 with different surfactants and concentration produced different levels of particle size growth. The heat treatment and aging of samples in the presence of Tween 20, Tween 80, Brij 35 and Pluronic F-68 surfactants led to an increase in the populations of larger particles for BSA samples, whereas IgG2 systems did not notably aggregate under storage conditions MFI was shown to be more sensitive than HIAC technique for measuring sub-visible particles in protein surfactant systems. Heat treatment and storage stress showed a significant effect on BSA and IgG2 protein sub-visible particle size stability. This work has demonstrated that both proteins with different Tween 20, Tween 80, Brij 35 and Pluronic F-68 concentrations, have different level of conformational and size stability. Also aging samples and heating stress bears the potential to generate particles, but this depends on surfactant type. Poor predictive correlations between the analytical methods were determined.

<p dir="ltr">Zeolites are microporous crystalline aluminosilicates that are widely used as catalysts for upgrading hydrocarbons and oxygenates to higher value chemicals and fuels. The substitution of tetrahedral Si⁴⁺ with Al³⁺ in a charge-neutral silica framework ([SiO_4/2]) generates anionic centers ([AlO_4/2]^-), which charge-compensate Brønsted acid protons (H⁺) that serve as active sites for catalysis. Brønsted acid sites in aluminosilicates of diverse topologies have similar acid strength, but can be located within varying intracrystalline (or internal) microporous environments (0.4‒2 nm diameter) or at extracrystalline (or external) surfaces and mesoporous environments (>2 nm diameter); yet, catalytic diversity exists, <i>even</i> for a fixed zeolite framework topology, because micropores impose constraints on molecular access to and from intracrystalline active sites and provide van der Waals contacts that influence the stabilities of reactive intermediates and transition states. Tailoring the material properties of a given zeolite framework for targeted catalytic applications requires strategies to design both the bulk crystallite properties (e.g., morphology, active site density) that influence intracrystalline diffusion and the secondary environments that surround active sites and influence intrinsic kinetics, and further necessitates molecular-level insights to elucidate the influences of bulk and active site properties on catalysis. In this work, we provide synthetic and post-synthetic strategies to respectively tune active site environments within varying micropore voids and at external surfaces of zeolites, and develop gas-phase toluene methylation and liquid-phase mesitylene benzylation as probe reactions to quantify the catalytic consequences of active site environments on aromatic alkylation catalysis.</p><p dir="ltr">The MFI framework (orthorhombic phase) consists of 12 crystallographic distinct tetrahedral-sites and 26 unique framework oxygen atoms located around channels (~0.55 nm diameter) or channel intersections (~0.70 nm diameter). The synthesis of MFI zeolites using the conventional tetra-<i>n</i>-propylammonium (TPA⁺) organic structure directing agent (OSDA) is known to place framework Al and their attendant H⁺ sites within the larger intersection environments, because electrostatic interactions are favorable between such locations of [AlO_4/2]^- and the quaternary N⁺ center in TPA⁺ that becomes positioned rigidly within channel intersections during crystallization. The methylation of toluene by dimethyl ether (DME; 403 K) on MFI-TPA zeolites of fixed active site densities (~2 Al per unit cell) result in <i>ortho</i>-xylene (<i>o</i>-X; ~65%) as the major product over <i>para</i>-xylene (<i>p</i>-X; ~27%) and <i>meta</i>-xylene (<i>m</i>-X; ~8%). In contrast, toluene methylation on MFI zeolites (~2 Al per unit cell) synthesized using non-conventional OSDAs, such as ethylenediamine (EDA) or 1,4-diazabicyclo[2.2.2]octane (DABCO), predominantly forms <i>p</i>-X (~75%) over <i>o</i>-X (~23%) and <i>m</i>-X (~2%). Within the subsets of MFI-TPA and MFI-EDA/DABCO zeolites, measured xylene formation rates and isomer selectivities are independent of crystallite sizes (0.1‒13 µm), toluene conversions (0.02‒2.0%) and external H⁺ content (up to 9% external H⁺ per total Al), indicating negligible effects of diffusion-enhanced secondary xylene isomerization reactions at intracrystalline or extracrystalline domains. The invariance of xylene isomer selectivity with reactant pressures (0.2‒9 kPa toluene, 25‒66 kPa DME) or methylating agent (1‒4 kPa methanol) indicate that differences in reactivity of toluene to form each xylene isomer reflects differences in the stabilities of their respective kinetically relevant transition states that share the same reactive intermediate. Measured xylene isomer formation rate constants and rate constant ratios, obtained from mechanism-derived rate expressions and interpreted using transition state theory formalisms, are used alongside density functional theory (DFT) calculations to reveal that intersection void environments (~0.70 nm diameter) similarly stabilize all three xylene transition states over unconfined surfaces (>2 nm diameter) without altering the established aromatic substitution patterns, while channel void environments (~0.55 nm diameter) preferentially destabilize bulkier <i>o</i>-X and <i>m</i>-X transition states thereby resulting in high intrinsic <i>p</i>-X selectivity. DFT calculations reveal that the ability of protonated DABCO complexes to reorient within MFI intersections and participate in additional hydrogen-bonding interactions with anionic Al centers during synthesis, facilitates the placement of Al in smaller channel environments that are less favored by TPA⁺. These molecular-level details, enabled by combining synthesis, characterization, kinetics and DFT, establish a mechanistic link between OSDA structure, active site placement and transition state stability, and provide active site design strategies orthogonal to crystallite design approaches that rely on complex reaction-diffusion phenomena.</p><p dir="ltr">For various reactions including toluene methylation at higher reaction temperatures (573‒773 K) and toluene conversions (>10%), extracrystalline H⁺ sites in MFI zeolites are reported to influence reactivity, selectivity, and deactivation behavior during catalysis in undesired ways. Post-synthetic chemical treatments to passivate external H⁺ sites on MFI zeolites result in unintended (but not always undesirable) changes to bulk structural properties and Al and H⁺ contents. The number of extracrystalline H⁺ sites is difficult to quantify using conventional spectroscopic or titrimetric methods, especially when present in dilute amounts on samples whose surfaces have been passivated. The systematic treatment of MFI zeolites (2.4, 5.7 and 7.1 Al per unit cell) using ammonium hexafluorosilicate (AHFS) at varying treatment duration times, AHFS concentrations and number of successive treatments resulted in MFI zeolites that retain their bulk structural properties and total Al and H⁺ contents, except for one parent MFI sample containing a significant amount of non-framework Al species. The benzylation of mesitylene by dibenzyl ether (363 K) occurs exclusively at external H⁺ sites because the bulky 1,3,5-trimethyl-2-benzylbenzene product is sterically prevented from forming at intracrystalline H⁺ sites. The intrinsic zero-order rate constant (per external H⁺) for mesitylene benzylation is extracted from rate measurements (per total Al) on a suite of untreated MFI samples with known amounts of external H⁺ sites (1‒15% external H⁺ per total Al) quantified using bulky 2,6-di-<i>tert</i>-butylpyridine base titrants. Measured zero-order rate constants on AHFS-treated MFI zeolites are used to quantify the extent to which AHFS treatments passivate external H⁺ sites, revealing efficacies that depend on the specific treatment conditions and the parent sample used. The developed kinetic methods demonstrate the utility of catalytic probes, when compared to stoichiometric probes based on spectroscopic or titration methods, in amplifying and quantifying dilute concentrations of external H⁺ sites on zeolites. The methods enable comparisons of the efficacy of various post-synthetic passivation strategies and permit rigorous assessments of the influence of external H⁺ during acid catalysis.</p><p dir="ltr">Overall, this work provides (post-)synthetic strategies to tune active site environments within intracrystalline micropores or at extracrystalline surfaces and develops quantitative kinetic probes that enable a molecular-level understanding of catalytic consequences of active site environments on aromatic alkylation reactions. Taken together, the methodology and findings of this study have broader implications in zeolite catalyst design for selectively upgrading traditional fossil feedstocks (crude oil and shale gas) and emerging feedstocks (biomass and waste plastics).</p>

Made available in DSpace on 2014-12-17T15:41:45Z (GMT). No. of bitstreams: 1 MariaJFCpdf.pdf: 4931245 bytes, checksum: 45a7ea893d17f478c73adf56787579aa (MD5) Previous issue date: 2008-12-22 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The present work reports the study of nanoporous structures, aiming at their use in research directed to the current demand of the petroleum industry to value heavy oil. Initially, two ways were chosen for the synthesis of porous structures from the molecular sieves of type Si-MCM-41. In the first way, the structure MCM-41 is precursory for heteroatom substitutes of silicon, generating catalyst of the type Al-MCM-41 from two different methods of incorporation of the metal. This variation of the incorporation method of Aluminum in the structure of Si-MCM-41 was carried out through the conventional procedure, where the aluminum source was incorporated to the gel of synthesis, and the procedure post-synthesis, where the Aluminum source was incorporated in catalyst after the synthesis of Si-MCM-41. In the second way, the MCM-41 acts as a support for growth of nanocrystals of zeolite embedded in their mesoporous, resulting in hybrid MCM-41/ZSM-5 catalyst. A comparative analysis was carried through characterizations by XRD, FTIR, measures of acidity through n-butylamine adsorption for TGA, SEM-XRF and N2 adsorption. Also crystalline aluminosilicate with zeolitic structure MFI of type ZSM-5 was synthesized without using organic templates. Methodologies to the preparation of these materials are related by literature using conventionally reactants that supply oxides of necessary silicon and aluminum, as well as a template agent, and in some cases co-template. The search for new routes of preparation for the ZSM-5 aimed at, above all, the optimization of the same as for the time and the temperature of synthesis, and mainly the elimination of the use of organic templates, that are material of high cost and generally very toxic. The current study is based on the use of the H2O and Na+ cations playing the role of structural template and charge compensation in the structure. Characterizations by XRD, FTIR, SEM-XRF and N2 adsorption were also conducted for this material in order to compare the samples of ZSM-5 synthesized in the absence of template and those used industrially and synthesized using structuring / O presente trabalho relata o estudo de estruturas nanoporosas, visando o uso em pesquisas que atendam a atual demanda da ind?stria do petr?leo, de valorizar ?leos pesados. Inicialmente, optou-se por duas vertentes para a s?ntese de estruturas porosas a partir da peneira molecular do tipo Si-MCM-41. Na primeira vertente, a estrutura MCM-41 ? precursora para hetero?tomos substituintes do sil?cio, gerando catalisadores do tipo Al-MCM-41 a partir de dois diferentes m?todos de incorpora??o do metal. Essa varia??o do m?todo de incorpora??o do Alum?nio na estrutura do Si-MCM-41 se deu atrav?s do procedimento convencional, no qual a fonte de alum?nio foi incorporada ao gel de s?ntese e do procedimento p?s-s?ntese, no qual a fonte de Alum?nio foi incorporada ao catalisador ap?s a s?ntese do Si-MCM-41. Na segunda vertente, o MCM-41 age como suporte para o crescimento de nanocristais de ze?lita embutidos nos seus mesoporos, resultando no catalisador h?brido MCM-41/ZSM-5. Uma an?lise comparativa foi realizada atrav?s de caracteriza??es por XRD, FTIR, medidas de acidez atrav?s de dessor??o de n-butilamina por TGA, SEM-XRF e Adsor??o de N2. Tamb?m foi sintetizado um aluminossilicato cristalino com estrutura zeol?tica MFI do tipo ZSM-5, na aus?ncia total de direcionador org?nico. Metodologias relacionadas ? prepara??o desses materiais s?o relatadas pela literatura utilizando-se convencionalmente reagentes que forne?am os ?xidos de sil?cio e de alum?nio necess?rios, bem como um agente direcionador, e em alguns casos at? co-direcionadores. A busca por novas rotas de prepara??o para a ZSM-5 visou, sobretudo, a otimiza??o da mesma no que se refere ao tempo e ? temperatura de s?ntese, e principalmente a elimina??o do uso dos direcionadores org?nicos, que s?o materiais de alto custo e geralmente muito t?xicos. O atual estudo se baseia na utiliza??o da H2O e dos c?tions Na+ desempenhando o papel de direcionamento estrutural e compensa??o de cargas na estrutura. Caracteriza??es por XRD, FTIR, SEM-XRF e Adsor??o de N2 tamb?m foram realizadas para esse material, a fim de comparar as amostras de ZSM-5 sintetizadas na aus?ncia do direcionador e aquelas utilizadas industrialmente e sintetizadas utilizando estruturantes