There are many problems associated with the use of fossil fuels to produce fuels and chemicals, and lignocellulosic biomass stands as a promising alternative fuel/chemical feedstock. Large scale processing of biomass will likely take place in high temperature liquid water due to the low vapor pressure and polar nature of carbohydrates. However, little is known about the material stability of these catalysts in high temperature aqueous phase environments. This dissertation aims to investigate the structural integrity of some common catalytic materials under typical biomass reforming conditions. There are 3 main objectives of this study: 1) identify potentially stable candidates from commonly used materials, 2) understand the mechanism(s) by which these catalysts degrade, 3) design/modify catalysts in an effort to increase their hydrothermal stability. The two main materials investigated in this work are zeolites (faujasite, ZSM-5) and γ-Al2O3 as these are commonly used as catalysts and catalyst supports. A number of physicochemical techniques were used to characterize the materials as a function of treatment time at conditions relevant for biomass reforming. For zeolites, the major findings are that ZSM-5 framework is highly stable whereas faujasite stability depends on the Si/Al ratio, where silicon rich materials are less stable. For γ-Al2O3 based catalysts, it was found that the alumina support hydrates and undergoes a phase transformation to form crystalline boehmite (AlOOH) with a subsequent loss in surface area and Lewis acid sites. When metal particles are present on the support, the phase change kinetics are slowed. The role of metal precursor on the stability of γ-Al2O3 supported catalysts was also explored, and it was found that the precursor used in catalyst synthesis changes the boehmite formation kinetics and also affects alumina support dissolution. The final thrust aims to stabilize a Pt/γ-Al2O3 catalyst by depositing silicon on the catalyst surface. The silicon modification is effective in protecting the catalyst from boehmite formation upon exposure to hot liquid water while also stabilizing metal particles against sintering. Additionally, an increase in turnover number for hydrogen production via aqueous phase reforming of sorbitol was observed.

L’amélioration de la qualité de l’air est un enjeu majeur pour la santé et l’environnement. Le challenge pour les fabricants de convertisseurs catalytiques pour la dépollution automobile est d’optimiser leur formulation pour répondre aux normes réglementant les émissions polluantes se durcissant, tout en rentabilisant l’utilisation de métaux précieux dont les ressources s’épuisent. Dans cette thèse, un nouveau support catalytique MgAl2O4 méso-poreux a été synthétisé par atomisation d’un sol aqueux contenant un copolymère tri-blocs. Les nano-cristallites de MgAl2O4 en contact quasi-ponctuel permettent d’atteindre des taux de dispersion de la phase active Pt-Pd supérieurs à ceux d’un catalyseur d’oxydation Diesel commercialisé, pris comme référence par la société Renault. La phase active d’un catalyseur 2,5%m.PtPd(3:2)[450°C]/MgAl2O4[900°C] présente une stabilité hydrothermale similaire à celle ce dernier grâce aux ancrages chimiques (croissance épitaxiale, solutions solides) et mécaniques (marches atomiques, pores). Bien que la totalité des métaux précieux ne soit pas accessible (insertion, encapsulation) pour l’oxydation du CO, des HC et de NO, les performances catalytiques atteintes par ce catalyseur au cours de vieillissements hydrothermaux sont comparables à celle d’un DOC de référence. La conversion des HC est similaire à celle du DOC de référence et dépendante de la concentration locale des sites actifs. La conversion du CO est légèrement pénalisée car les particules sont de trop petite taille et à l’état oxydé. Enfin, ce catalyseur ne réduit pas les NOx, en revanche il assure une oxydation plus importante de NO en NO2 après vieillissement hydrothermal que le DOC de référence, ainsi que le stockage de NO2. Cela représente un avantage majeur pour le bon fonctionnement du filtre à particules situé en aval du DOC. / The improvement of air quality is a major issue for the health and the environment. The challenge for the manufacturers of catalytic converters for automotive depollution is to optimize their formulation to meet the standards regulating the polluting emissions hardening, while making a profitable use of the precious metals whose resources are becoming exhausted. In this thesis, a new, mesoporous, MgAl2O4, catalytic support was synthesized by atomization of an aqueous sol containing a tri-block copolymer. The MgAl2O4 nanocristallites in point contact enable to reach higher dispersion rates of the Pt-Pd active phase than those of a commercialized DOC taken as reference by Renault. The active phase of the 2,5%m.PtPd(3:2)[450°C]/MgAl2O4[900°C] catalyst presents similar hydrothermal stability to that of the reference DOC thanks to chemical anchoring (epitaxial growth, solid solutions) and mechanical anchoring (atomic steps, pores). Although the totality of the precious metal content is not accessible (insertion, encapsulation) for CO, HC and NO oxidation, the catalytic performances reached by this catalyst during hydrothermal aging are comparable with that of the reference DOC. The conversion of the HC is similar to that of the reference DOC and depends on the local concentration of the active sites. The CO conversion rate is slightly penalized since the particles are too smalls and in an oxidized state. Lastly, this catalyst does not reduce NOx but ensures a more important oxidation of NO in NO2 after a hydrothermal aging than the reference DOC and also the storage of NO2 which have a positive impact on the proper functioning of the downstream diesel particulate filter.

Global warming along with the climate change derived from the World's demand for energy are among the greatest challenges to our society. To tackle climate change issue, research must focus on proposing practical approaches for carbon emissions reduction and environmental remediation. This thesis focuses on carbon dioxide separation mainly from flue gases (major sources of carbon dioxide emissions) using metal organic frameworks (MOFs) to reduce its impact on the global warming hence the climate change. MOFs are a class of crystalline porous adsorbents with structures that attract CO2 selectively and store it in their porous frameworks. Over the course of this PhD research, the fundamental aspects of these materials, as well as their practical applications, have been investigated. For example, the synthesis recipe of copper (II) benzene-1,3,5-tricarboxylate (CuBTC) MOF was improved to deliver a product of high yield ( > 89%) and free of by-product. Also, a mechanism study on the hydrothermal stability CuBTC MOF was carried out under simulated flue gas conditions and delivered the first experimental proof of the decomposition mechanism of CuBTC MOF caused by the water vapour. The fundamental understanding of the stability of materials then motivated the research into the development of a facile method of using an economic functional dopant (i.e. glycine) to strengthen the structure of CuBTC MOF (completely stable towards water vapour), as well as to improve the selectivity of resulting materials to CO2 (by 15% in comparison to the original CuBTC MOF). The suitability of the CuBTC MOF for fixed bed adsorption processes was also assessed using a combined experimental and process simulation method. In addition to the experimental approaches, molecular simulation based on grand canonical Monte Carlo method was also used to understand the effect of structural defects of MOFs on the CO2 adsorption isotherms.

A systematic silylation approach using mono-, di-, and trichlorosilanes with different alkyl chain lengths was employed to enhance the hydrothermal stability of zeolite Y. DRIFT spectra of the silylated zeolites indicate that the attachment of the silanes takes place at surface silanol groups. Regarding hydrothermal stability under aqueous-phase processing (APP) conditions, i.e., pH ≈ 2, 473 K and autogenous pressure, the selective silylation of the zeolite surface usingmonochlorosilanes has no considerable influence. By using trichlorosilanes, the hydrothermal stability of zeolite Y can be improved significantly as proven by a stability test in an aqueous solution of 0.2M levulinic acid (LA) and 0.6M formic acid (FA) at 473 K. However, the silylationwith trichlorosilanes results in a significant loss of total specific pore volume and total specific surface area, e.g., 0.35 cm3 g−1 and 507m2 g−1 for the silylated zeolite Y functionalized with n-octadecyltrichlorosilane compared to 0.51 cm3 g−1 and 788 m2 g−1 for the parent zeolite Y. The hydrogenation of LA to g-valerolactone (GVL) was conducted over 3 wt.-% Pt on zeolite Y (3PtY) silylated with either n-octadecyltrichlorosilane or methyltrichlorosilane using different reducing agents, e.g., FA or H2. While in the stability test an enhanced hydrothermal stability was found for zeolite Y silylated with n-octadecyltrichlorosilane, its stability in the hydrogenation of LA was far less pronounced. Only by applying an excess amount of methyltrichlorosilane, i.e., 10 mmol per 1 g of zeolite Y, presumably resulting in a high degree of polymerization among the silanes, a recognizable improvement of the stability of the 3 PtY catalyst could be achieved. Nonetheless, the pore blockage found for zeolite Y silylated with an excess amount of methyltrichlorosilane was reflected in a drastically lower GVL yield at 493 K using FA as reducing agent, i.e., 12 vs. 34% for 3PtY after 24 h.

Made available in DSpace on 2014-12-17T15:41:53Z (GMT). No. of bitstreams: 1 JoseABLRA_DISSERT.pdf: 2347923 bytes, checksum: 6e0dcb6d004a500ef5b9305459cc4e95 (MD5) Previous issue date: 2010-05-27 / Mesoporous molecular sieves of MCM-41 type are considered as promising support for metal in the refining processes of petroleum-based materials as catalysts and adsorbents for environmental protection. In this work, mesoporous molecular sieves MCM-41 were modified with different rare earth ions (La, Eu e Yb) for the obtaining nanostrutured materials with catalytic properties. The catalysts were synthesized by the hydrothermal method at 100oC for 120 h, presenting, all the samples, in the gel of synthesis molar ratio Si/Ln = 50. The obtained materials after calcination at 500oC for 2 h were characterized by XRD, surface area BET, TG/DTG, FTIR, and hydrothermal stability at 700?C. The XRD analysis of the catalysts indicated that the materials containing rare earth presented characteristic hexagonal structure of the mesoporous materials of the type MCM-41. The TG curves showed that the decomposition of the structural template occurs in the materials at temperatures lower than 500oC. The samples presented variations as the specific superficial area, average diameter of pores and thickness of the silica wall, as a function of the nature of the rare earth impregnated in the mesoporous material. Hydrotermal stability was evaluated through the exposition of the materials to water vapour at 700?C. The thiophene adsorptions reach a maximum at 80% of conversion and incorporation of the rare earths showed influence in the process. Adsorption capacity followed the sequence: Yb-MCM-41 < La-MCM-41 < Eu-MCM-41 < MCM-41 / As peneiras moleculares mesoporosas do tipo MCM-41 s?o consideradas promissoras como suporte para metais em processos de refino de materiais a base de petr?leo, como catalisadores e como adsorventes para prote??o ambiental. Neste trabalho a peneira molecular mesoporosa tipo MCM-41 foi modificada com diferentes terras raras (La, Eu e Yb) para a obten??o de materiais nanoestruturados com propriedades catal?ticas. Os catalisadores foram sintetizados pelo m?todo hidrot?rmico a 100 oC por 120 horas, apresentando, todas as amostras, no gel de s?ntese raz?o molar Si/Ln = 50. Os materiais resultantes, ap?s calcina??o a 500 oC por 2 horas, foram caracterizados por: DRX, ?rea superficial pelo m?todo de BET, TG/DTG, FTIR e testes hidrot?rmicos a 700oC. As an?lises de DRX dos catalisadores indicaram que os materiais contendo as terras raras apresentaram estrutura hexagonal caracter?stica do material mesoporoso tipo MCM-41. As curvas TG mostraram que a decomposi??o do direcionador estrutural ocorre nos materiais em temperaturas inferiores a 500oC. As amostras apresentaram varia??es quanto ? ?rea superficial espec?fica, di?metro m?dio de poros e espessura da parede de s?lica, em fun??o da natureza da terra rara impregnada no material mesoporoso. A estabilidade hidrot?rmica foi avaliada atrav?s da exposi??o dos materiais a vapor d ?gua a 700oC. A adsor??o de tiofeno atingiu valores m?ximos de 80% e a incorpora??o das terras raras influenciaram no processo. A ordem crescente de capacidade de adsor??o seguiu a seguinte seq??ncia: Yb-MCM-41 < La-MCM-41 < Eu-MCM-41 < MCM-41

Ce travail de thèse a porté sur l’étude des propriétés d’adsorption et de séparation en milieu humide par des polymères de coordination poreux. Nous avons utilisé les techniques de volumétrie d’adsorption, de séparation par chromatographie en phase gaz, de spectroscopie de fluorescence ainsi que et de la modélisation Monte Carlo afin de comprendre les mécanismes qui gouvernent l’adsorption de ces matériaux. Les molécules adsorbables étudiées sont l’eau et des vapeurs d’hydrocarbures linéaires (pentane et n-hexane), cycliques (cyclohexane et cyclohexène) et polycycliques (anthracène). Les adsorbants étudiés sont les Analogues de Bleu de Prusse (ABP) ainsi que deux matériaux organométalliques poreux de référence, le ZIF8 et le CuBTC. Parmi les résultats principaux apportés par ce travail, nous avons montré que les Analogues de Bleu de Prusse ont une stabilité hydrothermale remarquable leur conférant des propriétés d’adsorption en milieu humide très prometteuses. Parmi les ABP étudiés, le Co[CoIII(CN)6]0.66 ⊡0.33 .5.2H2O a montré des propriétés d’adsorption et de séparation très supérieures à celles d’autres ABPs. Par exemple, il a été possible de moduler sa balance hydrophobe/hydrophile par le contrôle de la coordination de l’eau sur le centre métallique insaturé, tout en préservant son caractère lipophile. Nous avons aussi montré que cet analogue de bleu de Prusse est capable de séparer des mélanges d’hydrocarbures secs ou très humides de façon répétée. Sur un aspect plus fondamental, nous avons montré que le confinement d’anthracène par le ZIF-8, qui est un composé organométallique poreux possédant des cavités de taille ajustée à celle du fluorophore, pouvait induire une extinction complète de certaines bandes d’absorption de celui-ci. / This PhD thesis is focused on the study of wet adsorption and separation properties by porous coordination polymers. We used adsorption volumetry, gas chromatography separation techniques, fluorescence spectroscopy techniques and Monte Carlo modeling to understand the mechanisms governing the adsorption of these materials. The adsorbable molecules studied are water and hydrocarbon vapors linear (pentane and n-hexane), cyclic (cyclohexane and cyclohexene) and polycyclic (anthracene). The adsorbents studied are the Prussian Blue Analogues (ABP) as well as two reference porous organometallic materials, ZIF8 and CuBTC. Among the main results provided by this work, we have shown that Prussian Blue Analogues have remarkable hydrothermal stability conferring them very promising wet adsorption properties. Among the ABPs studied, Co [CoIII (CN)6] 0.66 ⊡0.33 .5.2H2O showed adsorption and separation properties far superior to those of other ABPs. For example, it has been possible to modulate its hydrophobic / hydrophilic balance by controlling the coordination of water on the unsaturated metal center, while preserving its lipophilic character. We have also shown that this Prussian blue analogue is capable of separating mixtures of dry or very wet hydrocarbons repeatedly. On a more fundamental aspect, we have shown that the confinement of anthracene by ZIF-8, which is a porous organometallic compound with cavities of size adjusted to that of the fluorophore, could induce a complete extinction of certain absorption bands of this one.

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La catalyse solide acide a été pendant longtemps l'objet d'activité de recherche intense, en particulier pour l'industrie pétrochimique. Aujourd'hui, les catalyseurs solides acides sont de plus en plus étudiés dans d'autres domaines et en particulier dans celles liées à la «chimie verte» et à la valorisation des bioressources, telles que la synthèse de biodiesel et la transformation des polysaccharides. L’objectif de la thèse est d’étudier le potentiel des matériaux poreux sulfonés ayant une porosité contrôlée dans des réactions catalysées par un acide en condition eau surchauffé telle que l'hydrolyse de la cellobiose. Dans une première partie, nous décrivons la préparation et la caractérisation des organosilicates mésoporeux périodiques sulfonés de type SBA-15, SBA-1 et KIT-6 par co-condensation de 1,4-bis (triéthoxysilyl) benzène (BTEB). Les matériaux ont été acidifiés suivant des voies différentes à l'aide de 3-mercaptopropyltriméthoxysilane (MPTMS)/H2O2 ou d'acide chlorosulfonique (ClSO3H). Leur propriété acide a été étudiée par adsorption d’NH3 suivie par calorimétrie et par la réaction de déshydratation d'isopropanol (IPA) comme réaction modèle en phase gazeuse. Contrairement à notre attente, l'adsorption d’NH3 suivie par calorimétrie a mis en évidence l'hétérogénéité de la force des sites suggérant la présence de sites distincts de la sulfonation. Les solides sulfonés avec l'acide chlorosulfonique ont une activité équivalente à celle de la résine sulfonée, Amberlyst 15, mais ils sont moins stables en raison de la libération des espèces de soufre. Les catalyseurs préparés en utilisant un groupement mercapto-propyle suivie d’une oxydation sont moins acides et ils ont donné des niveaux d'activité plus basse dans la réaction de déshydratation d'IPA. Pour l'hydrolyse de la cellobiose, de bonnes performances ont été obtenues à 150°C, mais, ces matériaux se sont montrés instables dans des conditions hydrothermales avec une lixiviation totale de soufre réalisant alors la réaction en phase homogène. Un lavage dans l'eau surchauffée des matériaux contenant des groupements propyles-SO3H conduit à une diminution de leur efficacité dans l'hydrolyse de la cellobiose, mais un gain de stabilité a été obtenu, permettant le recyclage de ces matériaux. Dans une deuxième partie, des répliques carbonées sulfonées par l’acide chlorosulfonique ou l’acide sulfurique ont été synthétisé. La sulfonation par l’acide sulfurique suivi par un lavage dans l’eau bouillante puis un prétraitement thermique à 300°C sous azote, de ces matériaux aboutissent au meilleur catalyseur en termes d’activité/stabilité. / Catalysis with solid acids has been for a long time the subject of intense research activities, especially for the petrochemical industry. Nowadays, solid acid catalysts are more and more studied in other areas and particularly in those related to “green chemistry” and bioresources valorization such as biodiesel synthesis and now polysaccharides transformations. The present work aimed to investigate the potential of acidic ordered mesoporous materials with a controlled local environment of the acid sites for applications in acid catalyzed reactions in hot water such as cellobiose hydrolysis. First we described the synthesis of periodic mesoporous organosilicas SBA-15, SBA-1 and KIT-6 types, from the condensation of 1,4-Bis(triethoxysilyl)benzene. The material was sulfonated using 3-mercaptopropyltrimethoxysilane further oxidized with H2O2 or chlorosulfonic acid to give Brønsted solid acids which were fully characterised. Their acidic properties were studied by calorimetry of NH3 adsorption and in the model reaction of gas phase isopropanol dehydration. The calorimetry of NH3 adsorption has evidenced the heterogeneity of the acid strength distribution suggesting the presence of distinct sites of sulfonation contrary to our expectation. For gas phase isopropanol (IPA) dehydration, the solids sulfonated with the chlorosulfonic acid exhibited an activity equivalent to that of the sulfonated resin, Amberlyst 15, but were less stable due to sulphur species release, assumed to be sulfonated silanols. The acidic organosilicas obtained via H2O2 oxidation of the mercapto-propyl group are less acidic catalysts, showing a low activity for gas phase IPA dehydration. In the hydrolysis reaction, the solids were active at 150 °C however sulfur leaching analysis showed that the reaction preceded mainly homogeneously, especially for the material acidified with chlorosulfonic acid. A hot washing pre-treatment applied to the catalysts containing the sulfonated propyl groups, led to a decrease of their hydrolysis activity but along with a gain of stability allowing recycling. Second we described the synthesis of ordered mesoporous carbon and their sulfonation with chlorosulfonic acid or sulfuric acid. Sulfonation of carbon replicas with sulfuric acid followed by washing in hot water and thermal pretreatment at 300°C under nitrogen, lead to the best catalyst in terms of activity / stability.

La conception de solides à la fois stables en conditions hydrothermales, mais aussi capables de convertir des composés biosourcés en molécules plateformes dans un même lit catalytique, représente un défi majeur en science des matériaux.Dans ce contexte, des oxydes mixtes binaires et ternaires de silice dopée avec les éléments W, Ti, Zr, Nb, Ta et Mg (3 à 20%at.) ont été élaborés via la méthode non conventionnelle de synthèse Sol-Gel Non Hydrolytique (SGNH). Cette méthode permet d’obtenir des oxydes mixtes très homogènes et de moduler finement leurs propriétés via les paramètres de synthèse.Les solides sont majoritairement amorphes et mésoporeux. Les analyses en MET-EDS, FTIR et ToF-SIMS indiquent que les éléments dopants sont bien dispersés dans la silice et que les oxydes mixtes présentent majoritairement une homogénéité allant jusqu’à l’échelle nanométrique voire atomique.Les molécules sondes NH3 et CO révèlent la présence des sites acides de forces faible et moyenne, majoritairement de type Lewis pour l’ensemble des matériaux. La densité de sites acides peut être promue via : l’amélioration du degré d’homogénéité entre les oxydes, l’élaboration d’oxydes mixtes ternaires et l’augmentation de la teneur en éléments dopants.La caractérisation des solides par la réaction modèle de conversion du mélange cyclopentanol/cyclohexanone en phase gaz montre que la majorité des matériaux catalysent à la fois des réactions de déshydratation et de transfert d’hydrogène (réduction MPVO).Après traitement hydrothermal en phase gaz à 400°C, les solides conservent de bonnes textures, en particulier les oxydes mixtes ternaires et dopés à haute teneur.Cette étude montre la versatilité de la méthode de synthèse SGNH et son potentiel pour mettre au point des oxydes mixtes binaires et ternaires très homogènes. Les oxydes mixtes ternaires, contenant 20% d’éléments dopants et contenant du Nb, du Zr ou du Ta sont particulièrement prometteurs pour les applications visées. / The design of new heterogeneous catalysts with good hydrothermal stability that are able to transform bio-based components into building blocks in one single catalytic process is a main challenge in material science.In this context, binary and ternary mixed oxides of silica doped with W, Ti, Zr, Nb, Ta et Mg (3 to 20%at.) have been produced with the non-conventional Non-Hydrolytic Sol-Gel (NHSG) synthesis method. This method enables to obtain highly homogeneous mixed oxides and to finely shape the properties of the material with the synthesis parameters.The solids are mostly amorphous and mesoporous. TEM-EDS, FTIR and ToF-SIMS analysis indicate that the doping elements are highly dispersed in the silica and that most of the mixed oxides display nanometric or atomic scale homogeneity.The NH3 and CO bases show the presence of mostly Lewis weak and medium strength acid sites for these materials. The acid sites density can be improved through: increasing mixed oxide homogeneity, preparing ternary mixed oxides, increasing doping element content.The conversion of the mixture cyclopentanol/cyclohexanone in the gas phase shows that the majority of the materials perform both dehydration and hydrogen transfer reactions (MPVO reduction).After steaming at 400°C, the solids maintain good textures, particularly ternary mixed oxides and mixed oxides containing high dopant content.This study shows the versatility of the NHSG synthesis method and its applicability in order to design binary and ternary mixed oxides. The ternary mixed oxides containing 20%at. of doping elements with Nb, Zr and Ta are promising for the conversion of bio-based compounds.