The present thesis proposes to explore the potential of Zeolitic Imidazolate Framework ZIFs for CO2 capture applications in the conditions required by the Pressure Swing Adsorption separations process. Molecular modelling methods, combining Monte Carlo, Density Functional Theory and ab-initio simulations, were employed to mimic pure and mixture gas adsorption in ZIF materials. A transferable Force Field specifically developed for ZIFs materials is used to characterize a large variety of frameworks. Theses studies enable us to better understand the phenomena acting during adsorption process. Thereby several innovative modifications are proposed to enhance the ZIFs properties for CO2 capture and a series of hypothetical ZIFs are designed, characterized and compared to existing materials. The results cumulated during this thesis were then summarized to propose a first correlative model able to predict ZIF properties from a set of solids descriptors. This study enables to guide the structure design to optimize the ZIF properties.

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Made available in DSpace on 2014-12-17T15:42:29Z (GMT). No. of bitstreams: 1 MarcelaNB_TESE.pdf: 4650032 bytes, checksum: 4b8ec547749f785718e5f099093fa925 (MD5) Previous issue date: 2013-09-30 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Intensive use of machinery and engines burning fuel dumps into the atmosphere huge amounts of carbon dioxide (CO2), causing the intensification of the greenhouse effect. Climate changes that are occurring in the world are directly related to emissions of greenhouse gases, mainly CO2, gases, mainly due to the excessive use of fossil fuels. The search for new technologies to minimize the environmental impacts of this phenomenon has been investigated. Sequestration of CO2 is one of the alternatives that can help minimize greenhouse gas emissions. The CO2 can be captured by the post-combustion technology, by adsorption using adsorbents selective for this purpose. With this objective, were synthesized by hydrothermal method at 100 ?C, the type mesoporous materials MCM - 41 and SBA-15. After the synthesis, the materials were submitted to a calcination step and subsequently functionalized with different amines (APTES, MEA, DEA and PEI) through reflux method. The samples functionalized with amines were tested for adsorption of CO2 in order to evaluate their adsorption capacities as well, were subjected to various analyzes of characterization in order to assess the efficiency of the method used for functionalization with amines. The physic-chemical techniques were used: X- ray diffraction (XRD), nitrogen adsorption and desorption (BET/BJH), scanning electron microscopy (SEM), transmission electron microscopy (TEM), CNH Analysis, Thermogravimetry (TG/DTG) and photoelectron spectroscopy X-ray (XPS). The CO2 adsorption experiments were carried out under the following conditions: 100 mg of adsorbent, at 25 ?C under a flow of 100 ml/min of CO2, atmospheric pressure and the adsorption variation in time 10-210 min. The X-ray diffraction with the transmission electron micrographs for the samples synthesized and functionalized, MCM-41 and SBA-15 showed characteristic peaks of hexagonal mesoporous structure formation, showing the structure thereof was obtained. The method used was efficient reflux according to XPS and elemental analysis, which showed the presence of amines in the starting materials. The functionalized SBA -15 samples were those that had potential as best adsorbent for CO2 capture when compared with samples of MCM-41, obtaining the maximum adsorption capacity for SBA-15-P sample / A intensa utiliza??o de m?quinas e motores queimando combust?veis despeja na atmosfera imensas quantidades de di?xido de carbono (CO2), causando a intensifica??o do Efeito Estufa. As mudan?as clim?ticas que v?m ocorrendo no mundo est?o diretamente relacionadas ?s emiss?es de gases de efeito estufa, principalmente CO2, devido, sobretudo, ao uso excessivo de combust?veis f?sseis. A busca por novas tecnologias para minimizar os impactos ambientais decorrentes deste fen?meno vem sendo investigadas. O sequestro de CO2 ? uma das alternativas que pode ajudar a minimizar as emiss?es desses gases. O CO2 pode ser capturado pela tecnologia p?s-combust?o, atrav?s do processo de adsor??o, utilizando adsorventes seletivos para este fim. Com este objetivo, foram sintetizados, pelo m?todo hidrot?rmico a 100?C, materiais mesoporosos do tipo MCM-41 e SBA-15. Ap?s as s?nteses os materiais foram submetidos ? etapa de calcina??o e, posteriormente, funcionalizados com diferentes tipos de aminas (APTES, MEA, DEA e PEI), atrav?s do m?todo de refluxo. As amostras funcionalizadas com as aminas foram testadas nos ensaios de adsor??o de CO2 afim de avaliar suas capacidades de adsor??o, bem como, foram submetidas a diversas an?lises de caracteriza??o no intuito de avaliar a efici?ncia do m?todo utilizado para a funcionaliza??o com as aminas. As t?cnicas f?sico-qu?micas utilizadas foram: Difra??o de Raios-X (DRX), Adsor??o e Dessor??o de nitrog?nio (BET/BJH), Microscopia eletr?nica de varredura (MEV), Microscopia eletr?nica de transmiss?o (MET), An?lise elementar CNH, Termogravimetria (TG/DTG) e Espectroscopia fotoeletr?nica de Raios-X (XPS). Os ensaios de adsor??o de CO2 foram realizados nas seguintes condi??es: 100 mg de adsorvente, temperatura de 25 ?C sob fluxo de 100 mL/min de CO2, press?o atmosf?rica e com varia??o no tempo de adsor??o de 10 a 210 min. Os difratogramas de Raios-X juntamente com as micrografias eletr?nicas de transmiss?o para as amostras sintetizadas e funcionalizadas, MCM-41 e SBA-15, apresentaram os picos caracter?sticos da forma??o de estrutura mesoporosa hexagonal, evidenciando que a estrutura do mesmo foi obtida. O m?todo de refluxo utilizado foi eficiente segundo as an?lises de elementar e XPS, na qual, mostrou a presen?a das aminas nos materiais de partida. As amostras funcionalizadas de SBA-15 foram as que tiveram melhor potencial como adsorvente para captura de CO2 quando comparadas com as amostras de MCM-41, obtendo a m?xima capacidade de adsor??o para a amostra SBA-15-P

Ce travail vise à évaluer les performances de matériaux à base de silice et à rationaliser leur synthèse en fonction des propriétés d’adsorption recherchées (capacité et/ou sélectivité) en combinant des approches expérimentales et la modélisation de dynamique moléculaire. Ces matériaux devaient idéalement présenter une capacité d’adsorption CO2 mais également une sélectivité CO2 /CH4 élevées. Les différentes étapes de ce travail ont été :- la synthèse et la fonctionnalisation des matériaux de silice,- leur caractérisation texturale et chimique,- la détermination des capacités d’adsorption du CO2, de leur sélectivité CO2/CH 4 ,- les caractérisations par différentes techniques spectroscopiques et microscopiques des échantillons pour essayer de localiser l’adsorption du CO2 et mesurer sa mobilité,- l’identification microscopique par modélisation moléculaire des facteurs physico-chimiques influant sur l’adsorption préférentielle du CO2 et sa diffusivité dans le matériau hôte ainsi que sur le rôle du caractère hydrophile/hydrophobe du matériau de silice par le biais de sa fonctionnalisation.Ces objectifs ont nécessité la préparation de matériaux à surfaces spécifiques élevées par le biais d’un procédé sol-gel simple. Ces matériaux ont été modifiés afin d’obtenir un taux de fonctionnalisation par des groupements -CH3 suffisant pour modifier le caractère hydrophile du matériaux tout en conservant une surface spécifique suffisante. L’influence de la taille des pores a également été sondée.Les capacités d’adsorption des gaz sous pression ont été réalisées pour les gaz purs mais également sur des mélanges CO2/CH4 dans différentes proportions. La sélectivité CH 4 /CO 2 , souvent estimée à partir des isothermes des corps purs et/ou la méthode IAST, a dans ce cas été déterminée à partir de la mesure directe des isothermes des mélanges de gaz. Il est apparu que l’eau joue un rôle crucial sur les capacité et sélectivités d’adsorption. Ce paramètre est l’un de ceux qui a été étudié à travers les simulations de dynamiques moléculaires. L’influence de l’introduction de groupements hydrophobes a également été exploré.Les résultats obtenus par dynamique moléculaire sont dans l’ensemble en bon accord avec les données expérimentales. Ces deux approches parallèles expérience/théorie ont mis en évidence la sélectivité de l’un des matériaux pour des applications où l’effluent gazeux est peu chargé en CO 2 . / This work aims to evaluate the performance of silica-based materials and to rationalize their synthesis according to their desired adsorption properties (capacity and/or selectivity) by combining experimental approaches and the management of the molecular animal. These materials are ideally suited for CO2 adsorption capacity but also CO2/ CH4 selectivity. The different stages of this work were:- the synthesis and functionalization of the silica materials,- their textural and chemical characterization,- the determination of CO2 adsorption capacities, of their CO2/ CH4 selectivity.- the characterizations by various spectroscopic and microscopic techniques of tests to try to locate the adsorption of CO2 and to measure its mobility,- microscopic identification by the factor of physic-Factors influence the preferential adsorption of CO2 and its diffusivity in the role of hydrophilic / hydrophobic character in silica by functional.These objectives required the preparation of high specific surface materials through a simple sol-gel process. These materials have been modified in order to obtain a degree of functionalization with -CH3 groups sufficient to modify the hydrophilic nature of the material while maintaining a sufficient specific surface area. The influence of pore size was also probed.The adsorption capacities of the gases under pressure were carried out for pure gases but also on CO2/ CH4 mixtures in different proportions. The CH4/ CO2 selectivity, often estimated from the pure body isotherms and / or the IAST method, was in this case determined from the direct measurement of the isotherms of the gas mixtures. It has become apparent that water plays a crucial role in adsorption capacity and selectivity. This parameter is one of those studied through molecular dynamics simulations. The influence of the introduction of hydrophobic groups has also been explored.The results obtained by molecular dynamics are on the whole in good agreement with the experimental data. These two parallel experience / theory approaches have highlighted the selectivity of one of the materials for applications where the gaseous effluent is little loaded with CO2.

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