Le développement d'outils numériques de prédiction de la durée de vie des polymères constitue un levier prometteur pour réduire les durées des processus de certification de ces matériaux dans le domaine automobile sans sacrifier leur fiabilité. Cette thèse s'applique à la modélisation de la photo-thermo-oxydation du polypropylène isotactique (iPP), laquelle est responsable de l'altération de ses propriétés mécaniques et d'aspect. L'approche adoptée consiste à coupler la cinétique des réactions de photo- et thermo-oxydation avec des phénomènes physiques, comme le transport du dioxygène et l'atténuation de la lumière UV dans l'épaisseur du matériau, pour décrire l'ensemble des évolutions physico-chimiques. Les propriétés aux échelles supérieures, sur lesquelles seront définis les critères de fin de vie, seront calculées a posteriori en appliquant les relations structure-propriété adéquates. Le principal enjeu était d'étendre le modèle cinétique de vieillissement thermique préexistant au vieillissement photo-thermique en prenant en compte les réactions d'amorçage photolytique. De lourdes campagnes d'essais de vieillissement et de caractérisation menées sur un iPP de référence, ainsi qu'une capitalisation exhaustive des données de la littérature d'autres iPPs, ont permis de mettre au point un modèle cinétique de photo-thermo-oxydation et de le généraliser à l'ensemble de la famille des iPPs dans de larges domaines de pression partielle d'oxygène (de 0.2 à 50 bars), de température (de 40 à 230°C) et d'exposition à la lumière UV (intensités et sources lumineuses variables) décrivant des conditions de vieillissements naturels et accélérés. La validation expérimentale du modèle a permis d'étayer l'approche cinétique et de montrer ses limites, mais aussi de révéler un certain nombre d'enjeux numériques. Le modèle a été conçu pour être un outil numérique évolutif qui permettra, à terme, d'optimiser la représentativité des méthodes d'essais de vieillissement et la performance des formulations commerciales d'iPP. L'ensemble de ces développements théoriques et numériques peut être appliqué à la photo-thermo-dégradation d'autres types de polymères, mais aussi dans d'autres champs d'application de la photochimie macromoléculaire telle que la photo-polymérisation UV.Mots-Clés : Polypropylène, photo-thermo-oxydation, contrôle par la diffusion d'oxygène, effet d'écran, modélisation cinétique, prédiction de durée de vie. / Developing numerical tools for polymer lifetime prediction constitutes a promising opportunity for shortening the duration of material certification procedures in the automotive industry without decreasing their reliability. This PhD thesis aims at modeling the photothermal oxidation of isotactic polypropylene (iPP), which is responsible for the alteration of both its mechanical and aspect properties. The adopted approach consists in coupling the kinetics of photo- and thermo-oxidation reactions with physical phenomena, such as oxygen transport and UV-light attenuation in the material thickness, in order to describe all the physico-chemical changes. Upper-scale properties, from which will be defined the end-of-life criteria, will be calculated afterwards by applying the suitable structure-property relationships. The main challenge was to extend the pre-existing kinetic model of thermal ageing to photothermal ageing by taking into account initiation reactions of photolysis. Heavy campaigns of ageing and characterization tests made on a reference iPP, as well as an exhaustive capitalization of literature data of other iPPs, have allowed elaborating a kinetic model of photothermal oxidation and to generalize it to the whole iPP family in large domains of oxygen partial pressure (from 0.2 to 50 bars), temperature (from 40 to 230°C) and UV-light exposure (variable intensities and light sources) describing both natural and accelerated ageing conditions. The experimental validation of the model has allowed substantiating the kinetic approach and showing its limitations, as well as highlighting some numerical issues. The model has been designed in order to be an upgradable numerical tool which will allow, at term, optimizing the representativeness of the ageing testing devices and the performance of commercial iPP formulations. All these theoretical and numerical developments are prone to be applied to the photothermal degradation of other types of polymer substrates, but also in other application fields of the macromolecular photochemistry such as UV-photopolymerization.Keywords: Polypropylene, photothermal oxidation, oxygen diffusion control, screen effect, kinetic modeling, lifetime prediction.

Le méthanethiol (MeSH) est un intermédiaire important dans la synthèse de la méthionine, un acide aminé largement utilisé dans l'industrie agro-alimentaire. Le marché étant en constante augmentation, il est indispensable d'optimiser la formation de MeSH à partir de méthanol (MeOH) et de sulfure d'hydrogène (H2S) en présence de K2WO4/Al2O3 (10,5 % massique). L'impact de paramètres clés, tels la conversion du méthanol, la température ou le rapport molaire H2S/MeOH a été étudié dans des conditions proches de celles du procédé. Un fort effet inhibiteur de l'eau, co-produit de la réaction, a été mis en évidence, aussi bien sur l'activité catalytique que sur les sélectivités des différents produits. En revanche, le dioxyde de carbone (CO2) et le monoxyde de carbone (CO), produits non valorisables, n'ont aucun impact sur les performances du catalyseur. Un schéma réactionnel complet a été établi rendant compte de la formation des différents produits de réaction. Un modèle cinétique faisant intervenir le formalisme de Langmuir-Hinshelwood, en accord avec les résultats expérimentaux, a été développé.La caractérisation du catalyseur K2WO4/Al2O3 a confirmé que le site actif est une paire acide-base, l'acidité étant apporté par le tungstène alors que le potassium génèrerait une basicité à la surface du matériau. A partir de ces observations, la mesure des performances catalytiques de solides à base de terres rares, présentant une acidité et une basicité plus fortes, montre que ceux-ci sont plus actifs que le catalyseur K2WO4/Al2O3, tout en conservant une sélectivité en MeSH similaire. / Methanethiol (MeSH) is a key intermediate involved in the synthesis of methionine, an essential amino acid widely used in food-processing industry. Given that methionine market is constantly growing, optimizing MeSH production from methanol (MeOH) and hydrogen sulfide (H2S) is of paramount importance. The impact of key parameters, such as MeOH conversion, temperature, or H2S/MeOH molar ratio has been studied in a range consistent with industrial conditions. A strong inhibiting effect of water (which is the co-product of the reaction) has been highlighted, both on catalytic activity and selectivities towards the different products. However, carbon dioxide (CO2) and carbon monoxide (CO), which are non-recoverable products, have no influence on catalytic performances. A complete reaction scheme accounting for the formation of the different reaction products has been proposed. A kinetic model using Langmuir-Hinshelwood formalism was developed, which affords precise estimation of experimental data.Characterization of K2WO4/Al2O3 catalyst confirmed that acid-base dual sites were the active sites responsible for MeSH formation. Acidity is mainly brought by tungsten species whereas potassium addition allows increasing the basicity of the catalyst. Based on these observations, the catalytic performances of rare-earth based oxides, which possess stronger acidity and basicity, have been measured. These materials exhibit significantly higher activity than K2WO4/Al2O3 catalyst, with similar MeSH selectivity.

Le réacteur à inversion de flux pour retenir et recycler la chaleur est une technologie efficace qui intègre la réaction chimique et la réutilisation de la chaleur dégagée lors de la réaction. Cette technologie a été considérablement commercialisée et industrialisée, vue l'amélioration de la productivité du réacteur et vue l'intensification du procédé qu'elle offrirait. Par analogie chaleur-matière, il a été voulu, par l'actuel travail de doctorat, évaluer la technologie d'inversion de flux et la combinaison de la réaction chimique et de la séparation et la rétention du catalyseur (matière) dans un seul réacteur adsorbeur multifonctionnel. La métathèse des oléfines qui utilise des catalyseurs moléculaires -qui ne sont pas/ ne peuvent pas être efficacement et parfaitement immobilisés et hétérogénéisés sur un support solide- peut être réalisée dans le réacteur adsorbeur à inversion de flux, qui prétend permettre de séparer, de recycler et de retenir les catalyseurs. La réaction cible dans cette thèse est l'homo-métathèse de l'oléate de méthyle. D'abord, un modèle cinétique pour décrire cette réaction et la transformation du réactif a été développé et proposé en suivant une approche micro-cinétique. Ensuite, ce modèle a été ajusté par rapport aux résultats expérimentaux pour optimiser et accéder aux paramètres cinétiques de la réaction. Le modèle cinétique, ainsi obtenu, permettra après son intégration dans le modèle du réacteur adsorbeur à inversion de flux, de prédire la conversion du réactif et sa concentration à la sortie. Le réacteur adsorbeur à inversion de flux, a été étudié et évalué, par la modélisation et par une étude théorique calculatoire, pour avoir une meilleure compréhension de son comportement, et aussi de l'influence des conditions opératoires sur le procédé (perte de catalyseur, conversion, productivité, etc.). Le design de réacteur qui a été proposé dans cette étude et ce travail est une colonne à lit fixe d'adsorbant, avec inversion de flux. Les résultats de simulation du réacteur adsorbeur à inversion de flux pour retenir et recycler les catalyseurs moléculaires ont montré l'intensification du procédé que peut offrir cette technologie en se référant à un réacteur continu conventionnel (réacteur tubulaire monophasique). Il a été montré aussi qu'il n'est pas possible d'atteindre un régime permanent, sans appoint et rajout du catalyseur pour compenser les pertes, dues aux phénomènes physiques indissociables au réacteur. Par la suite, un dispositif expérimental a été construit pour vérifier et valider les résultats de simulations ainsi obtenus, et aussi pour démonter, à l'échelle pilote, la faisabilité de la technologie d'inversion de flux avec adsorption pour séparer l'adsorbé et le retenir à l'intérieur de la colonne. Et similairement au réacteur à inversion de flux pour le recyclage et la réutilisation de la chaleur, le réacteur adsorbeur à inversion de flux pour séparer et recycler le catalyseur, peut lui aussi, avoir un comportement asymptotique sous certaines conditions opératoires, et s'approcher du fonctionnement du réacteur adsorbeur à contre-courant. Par la modélisation et le calcul numérique, il a été établi le domaine des conditions opératoires dans lesquelles, les réacteurs adsorbeurs à inversion de flux et à contre-courant sont équivalents. Le modèle asymptotique à contre-courant permet de calculer et de pré-dimensionner plus rapidement le réacteur à inversion de flux / The reverse flow reactor for heat trapping is an efficient technology that integrates the chemical reaction and the recovery of the heat of the reaction. This technology was widely commercialized and applied in industry because of the reactor productivity enhancement and the process intensification it offers. By heat-matter analogy, we wanted, in this thesis, to evaluate the reverse flow technique and the combination of the chemical reaction with the trapping and the recycling of the catalyst (matter) in one single multi-functional adsorber reactor. The metathesis of olefins that uses molecular catalysts -which are imperfectly immobilized and heterogeneized on the solid support- can be performed in the reverse flow adsorber reactor that claims to separate, recycle and trap the catalyst. The targeted reaction is the self-metathesis of methyl oleate. Thus, a kinetic model of the reaction was developed using a micro-kinetic approach. The obtained kinetic model was fitted to the experiences to get the kinetic parameters values. Then, the kinetic model can be integrated in the reverse flow adsorber reactor model to predict the conversion and the outlet methyl oleate concentration. The reverse flow reactor adsorber was evaluated and studied (by modeling and theoretical study) to have a better understanding of its behavior, and of the operating parameters influence on the process (catalyst leaching, conversion, productivity, etc.). A single fixed bed adsorption column is proposed as a design for the reverse flow adsorber reactor. The simulation results show the process intensification that offers the reverse flow adsorber reactor for catalyst trapping in comparison with a conventional continuous reactor (continuous flow tubular reactor). They also show that it is not possible to reach a stable operation and a permanent regime without catalyst makeup that compensate the leaching. Then, an experimental setup was built to verify, to validate the simulations results, and to demonstrate, at the pilot scale, the feasibility of the reverse flow technology to separate and to trap the adsorbate inside the adsorber. And similarly to the reverse flow reactor for heat trapping, the reverse flow adsorber reactor for catalyst trapping and separation can have an asymptotic behavior under certain operating conditions, and approaches the operation of a counter current adsorber reactor. By modeling and numerical calculation, it has been determined the operating conditions, at which, the reverse flow and the counter current adsorber reactors are equivalents. The counter current asymptotic model allow a rapid reverse flow reactor computing and pre-design

L'objectif de la thèse est d'identifier les effets de l'acidité de catalyseurs sulfures supportés en hydrodésazotation (HDN) afin d'améliorer les performances catalytiques.Un modèle cinétique de Langmuir-Hinshelwood y compris le transfert de masse liquide-vapeur a été utilisé pour analyser les données cinétiques obtenues à partir de l'HDN de la quinoléine et de l'indole sur NiMo(P)/Al2O3 et NiMo(P)/ASA. Les résultats de la modélisation cinétique a montré que le NiMo(P)/ASA a favorisé l'hydrogénation du 1,2,3,4-tétrahydroquinoléine en decahydroquinoléine, qui est l'étape limitant de vitesse de l'HDN de la quinoléine. Cependant, l'effet de promotion du NiMo(P)/ASA pour les étapes d'hydrogénation de l'HDN de l'indole n'a pas été mis en évidence. En plus, le NiMo(P)/ASA a favorisé fortement les réactions d'élimination de l'atome d'azote. Les composés azotés adsorbent plus fortement sur NiMo (P)/ASA. La caractérisation par spectroscopie infrarouge de CO a suggéré que ces résultats pourraient être liés à la modification des propriétés électroniques de la phase NiMoS due à l'acidité plus élevée de l'ASA.La quinoléine est un fort inhibiteur pour l'HDN de l'indole alors que l'effet inhibiteur de l'indole sur l'HDN de la quinoléine était négligeable sur NiMo(P)/Al2O3 et plus important sur NiMo(P)/ASA. L'HDN d'un mélange de Straight Run et Coker Gazole a permis d'évaluer le mécanisme réactionnel et de comparer la réactivité vers HDN de différents composés. L'HDN des composés neutres a été inhibée par une adsorption forte des composés basiques. Les composés de type carbazole et quinoléine étaient réfractaires. Le NiMo(P)/ASA a probablement favorisé plus les craquages et montré une désactivation plus rapide que le NiMo(P)/Al2O3 / The thesis objective is to identify the support acidity effects of sulfide catalysts in hydrodenitrogenation (HDN) reactions in order to improve the HDN catalysts.Kinetic data obtained from quinoline and indole HDN, over NiMo(P)/Al2O3 and NiMo(P)/ASA catalysts were analyzed by a Langmuir-Hinshelwood kinetic model, including liquid-vapor mass transfer, in order to estimate kinetic and adsorption parameters. Kinetic modeling results indicated that the NiMo(P)/ASA catalyst favored the hydrogenation of 1,2,3,4-tetrahydroquinoline into decahydroquinoline, which is the rate limiting step of quinoline HDN. However, the promoting effect of the NiMo(P)/ASA in hydrogenation steps of indole HDN was not evidenced. In quinoline and indole HDN, the NiMo(P)/ASA showed a strong promoting effect in N-removal reactions. Nitrogen compounds adsorb more strongly over NiMo(P)/ASA. Characterization by Infra-Red spectroscopy of CO suggested that these results might be related to the modification of the electronic properties of promoted NiMoS phase due to higher acidity of ASA.The HDN of quinoline-indole mixture showed a strong inhibiting effect of quinoline on indole HDN whereas the inhibiting effect of indole on quinoline HDN was negligible over NiMo(P)/Al2O3 and more important over NiMo(P)/ASA. The HDN of a mixture of Straight Run and Coker Gas Oil allowed an access to the HDN mechanism and comparison of reactivity towards HDN of different compounds. The HDN of neutral compounds was inhibited by the stronger adsorption of basic compounds. Carbazole-type and quinoline-type compounds were refractory. The NiMo(P)/ASA likely favored more cracking reactions and as well showed a faster deactivation rate than the Al2O3 counter catalyst

[pt] A ustulação cloretante é um processo amplamente utilizado no âmbito da metalurgia extrativa, principalmente no que se diz respeito à obtenção de metais. Estudos demonstram que a partir de um agente cloretante gasoso e a incorporação no sistema de um agente redutor, tanto a cinética quanto a termodinâmica das reações são estimuladas. Neste contexto, compostos organoclorados, como CCl4 e C2Cl4, despontam como candidatos promissores à substituição do Cl2. O presente estudo realiza uma avaliação termodinâmica dos processos a partir de diagramas de especiação para o equilíbrio, assim como a modelagem de dados cinéticos associados à cloração do óxido de cobre (CuO - 923 K a 1173 K) e do pentóxido de tântalo (Ta2O5 - 1073 K a 1223 K), em atmosfera de C2Cl4 diluído em N2, mediante o emprego de equações já consolidadas no âmbito da modelagem de reações gás-sólido (núcleo não reagido, auto-catalítico e Avrami). Os modelos do núcleo não reagido com controle difusional pela camada de cinzas e controle químico, foram os dois que apresentaram ajustes de melhor qualidade. O modelo difusional apresentou energia de ativação global para o CuO de 71,5592 mais ou menos 10 kJ.mol(-1) e de 62,2606 mais ou menos 10 kJ.mol (-1) para o Ta2O5, enquanto que com controle químico, para o CuO, obteve-se o valor de 118,0049 mais ou menos 10 kJ.mol(-1) e para o Ta2O5 um valor de 119,131 mais ou menos 10 kJ.mol(-1). Valores consistentes com o que é apresentado na literatura, sendo superiores em modelos com premissa química do que em modelos difusionais. Aspectos físicos também foram considerados e mediante ao número de Reynolds encontrado (Re=0,26 – escoamento laminar), reforçou-se um controle de natureza mista possível para ambos os óxidos. / [en] Chloride roasting is a process widely used in the field of extractive metallurgy, especially with regard to obtaining metals. Studies show that from a gaseous chlorinating agent and the incorporation of a reducing agent in the system, both the kinetics and the thermodynamics of the reactions are stimulated. In this context, organochlorine compounds, such as CCl4 and C2Cl4, stand out as promising candidates for the replacement of Cl2. The present study performs a thermodynamic evaluation of the processes from speciation diagrams for equilibrium, as well as the modeling of kinetic data associated with the chlorination of copper oxide (CuO - 923 K to 1173 K) and tantalum pentoxide (Ta2O5 - 1073 K to 1223 K), in an atmosphere of C2Cl4 diluted in N2, using equations already consolidated in the context of gas-solid reaction modeling (shrinking core, auto-catalytic and Avrami). The models of the shrinking core with diffusional control by the ash layer and chemical control, were the two that presented better quality adjustments. The diffusional model showed global activation energy for the CuO of 71.5592 plus-minus 10 kJ.mol (-1) and 62.2606 plus-minus 10 kJ.mol (-1) for Ta2O5, while with chemical control, for CuO, 118.0049 plus-minus 10 kJ.mol (-1) was obtained and for Ta2O5 a value of 119,131 plus-minus 10 kJ.mol (-1). Values consistent with what is presented in the literature, being higher in models with chemical premise than in diffusion models. Physical aspects were also considered and, based on the Reynolds number found (Re = 0,26 - laminar flow), a control of mixed nature possible for both oxides was reinforced.

<div>To compensate for their sessile existence, plants synthesize and emit a wide diversity of volatile organic compounds (VOCs) that serve important biological functions pertaining to defense, reproduction, and plant-plant signaling. In addition to their importance in plant secondary metabolism, VOCs are used as fragrances, flavoring agents, and therapeutics. Plant metabolic engineering has successfully been implemented towards the design of value-added plants with enhanced defense, improved aroma and flavor, and increased production of specialty chemicals. However, rational design requires rigorous characterization of the mechanisms controlling metabolic fluxes in a network. Thus, the major aims of this dissertation are to study biological and physical mechanisms controlling the synthesis and emission of plant VOCs. This dissertation focuses on (i) modeling 2-phenylethanol biosynthesis in Arabidopsis and (ii) characterization of the biophysical properties of flower cuticles with respect to the emission of VOCs.</div><div><br></div><div>2-Phenylethanol (2-PE) is a naturally-occurring aromatic volatile with properties that make it a candidate oxygenate for petroleum-derived gasoline. In plants, 2-PE biosynthesis competes with the phenylpropanoid pathway for the common precursor L-phenylalanine (Phe). The phenylpropanoid pathway directs up to 30% of fixed carbon towards the production of lignin, a major constituent of plant cell walls that renders biomass recalcitrant to pretreatment techniques impeding the economical production of biofuels. An initial genetic engineering approach was proposed, whereby a portion of the carbon flux towards lignin production is diverted towards the biosynthesis 2-PE. Transgenic Arabidopsis thaliana expressing enzymes catalyzing the biosynthetic steps from Phe to 2-PE were generated. Excised stems from transgenic Arabidopsis were supplied 13C6-ring labeled Phe, and isotopic enrichment of downstream metabolites were quantified to calculate fluxes. By combining flux measurements with predictions from a kinetic model of the Phe metabolic network, we hypothesized that 2-PE biosynthesis in transgenic Arabidopsis was limited by endogenous pools of cytosolic Phe. Multiple independent genetic strategies were proposed based on model-guided predictions, such as inducing Phe hyper-accumulation, reduction of the activity of the competing phenylpropanoid pathway, and sequestering the 2-PE biosynthesis pathway in plastids. Combining kinetic modeling with time-course in vivo metabolomics led to successful rational engineering of 2-PE accumulating plants.</div><div><br></div><div>The plant cuticle is the physical interface between the flower and its surrounding environment. Passage of VOCs through the cuticle is driven solely by diffusion and is thus dependent on the cuticle physicochemical properties. Wax compounds in the cuticular matrix self-assemble into a multiphase system of crystalline and amorphous regions, where their relative amounts and arrangements govern VOC diffusion. To investigate the effect of wax composition on the crystallinity and permeability of the cuticle, we characterized the cuticular waxes of Petunia hybrida petals using GC-MS, FTIR, DSC, and XRD. Petal waxes were found to be enriched with long-chain hydrocarbons forming semi-crystalline waxes localized on petal surfaces. A ternary system of wax compounds was proposed as a model for petal cuticles to investigate the effect of wax composition on cuticle crystallinity and permeability. Atomistic simulations of VOC displacement in waxes of varying chemical composition were performed at 298 K and 1 bar under NPT conditions to estimate diffusivities. Wax anisotropy was found to be highly dependent on the elongation of methylene chains, restricting the molecular diffusion path. Changes in crystalline symmetry were found to have measurable effects on VOC diffusion. Simulations of compositional variants of the model cuticle shows that changes in relative crystallinity exert differential control on the dynamics of VOC emissions.</div><div><br></div><div>To directly determine the effect of the cuticle on VOC emissions in petunia flowers, the wax exporter PhABCG12 was silenced using RNA interference, resulting in flowers with thinner cuticles. However, VOC emissions were found to have significantly decreased in transgenic flowers relative to the wild-type control. Dewaxing wild-type and transgenic petunia revealed that the cuticle serves as a site of VOC build-up during emission, and deficient coverage limits the extent to which compounds can accumulate. In addition, the cuticle was found to impart differing levels of mass transfer resistance for certain VOCs, suggesting that the cuticle controls the dynamics of VOC emissions. Taken together, petal cuticles provide an additional layer of regulation in emission of VOCs from plants.</div><div><br></div>

Les oxydes d’azotes (NOx) sont un des groupes majeurs de polluants primaires émis dans l’atmosphère, principalement par les transports et l’industries, dont leur réduction constitue un enjeu sociétal crucial. Afin de répondre à l’évolution de normes environnementales plus exigeantes, la diminution des NOx est notablement explorée via la réaction clef de Réduction Catalytique Sélective par l’ammoniac (NH3-RCS) en employant des catalyseurs à base de cuivre et de fer. Le développement maîtrisé et perfectionné de cette solution requiert une profonde compréhension du système catalytique et ce à différentes échelles. Cette étude vise ainsi à développer un modèle cinétique multi-sites pour la représentation des performances NH3-RCS, par l’exploration des propriétés physico-chimiques, de surface et catalytiques d’une série de catalyseurs zéolitiques microporeux (Chabazite) supportant le cuivre. Cette série de catalyseurs imprégnés, échangés et « One-pot » permit la profonde caractérisation de différentes configurations de sites actifs dont les impacts sur les comportements catalytiques furent étudiés et identifiés selon différentes conditions opératoires. Ainsi, le modèle permit de prendre en considération, via la distinction selon leur nature, de 5 sites majeurs : la compétition d’adsorption, l’impact de l’eau, la formation et décomposition d’intermédiaires clefs et un schéma réactionnel précis, de représenter les activités des différents catalyseurs. De plus, l’étude In-situ de la surface de ces catalyseurs via spectrométrie infra-rouge à réflexion diffuse (DRIFT) fut complémentaire à la compréhension des dynamiques de surface et l’identification des mécanismes du procédé catalytique / The reduction of atmospheric pollution from stationary and mobile engines is a serious challenge associated with stringent environmental regulations. For nitrogen oxides (NOx) abatement in particular, the selective catalytic reduction using urea or ammonia (urea- or NH3-SCR) over copper- and iron-based catalysts is one of most effective and economic technologies. In this respect, revisiting after-treatment systems by a deep comprehension of the catalyst behavior at different scale may significantly improve their eco- and health-friendliness. This study targets the development of a multi-site kinetic model using a series of copper chabazite-based catalysts, as a selected model SCR catalyst. To qualify these materials as beyond-state-of-the-art catalysts and to better understand the impact on different active site configurations, three catalysts were synthetized by different preparation methods (impregnation, ionic exchange and one-pot), finely characterized by different techniques and their ability to abate NOx via the ubiquitous NH3-SCR reaction was extensively assessed under several operating conditions. Each catalyst behavior was quantified and associated to their respective main active sites (five different configurations described). The diffusion, water impact, adsorption competition between key reactants and storage sites were also ones of the main points spotlighted in this study. In-situ characterization of these catalysts was also performed, using Diffuse Reflectance Infrared Fourier-Transform Spectroscopy (DRIFTS) to understand the surface dynamical properties of the catalyst, and to unveil the mechanistic of the catalytic processes

[pt] O sulfato de magnésio está presente em diversos rejeitos industriais e de mineração. Ele e seus derivados poderiam ser reaproveitados em várias áreas industriais, deixando de ser um rejeito para se tornar parte de um processo. Seu óxido, MgO, pode ser utilizado em algumas funções, como regulador de pH, dependendo de sua reatividade. Devido a isto sua formação deve ocorrer em temperaturas abaixo das temperaturas de decomposição do MgSO4. Assim sendo este trabalho avaliou aspectos da decomposição do MgSO4 através de dois artigos. O artigo 1 (Thermodynamics Simulations and Kinetics Modeling of the Thermal Decomposition of MgSO4.7H2O: Part 1 – Reducing Agent Effect), avaliou o efeito cinético da utilização do carbono, através de quatro diferentes agentes redutores, na decomposição térmica do MgSO4.7H2O, enquanto que o artigo 2 (Thermodynamics Simulations and Kinetics Modeling of the Thermal Decomposition of MgSO4.7H2O: Part 2 – Hydration Effect) analisou as influências da taxa de aquecimento dos ensaios e do grau de hidratação do sulfato de magnésio utilizado. Os ensaios termogravimétricos realizados ao longo destes artigos, utilizaram amostras com massa de aproximadamente 10 mg de mistura (sulfato + agente redutor) e estas misturas tiveram uma relação estequiométrica de 1:1. Os experimentos realizados no artigo 1, utilizaram como agentes redutores agentes redutores, carvão vegetal, coque verde, coque breeze e grafite. No artigo 2, os sulfatos analisados foram o anidro, o monohidratado e o heptahidratado e as taxas de aquecimento utilizadas foram de 5 K.min(-1) , 10 K.min(-1) , 15 K.min(-1) e 20 K.min(-1) . Todos os dados obtidos dos ensaios termogravimétricos foram processados através de modelagem matemática para se obter os dados cinéticos. No artigo 1 a utilização dos agentes redutores se mostrou eficiente reduzindo a energia de ativação da decomposição do sulfato de magnésio de 22,731 kJ.mol(-1) (sulfato puro) para 340,391 kJ.mol(-1) (coque verde), 196,120 kJ.mol(-1) (grafite), 191,100 kJ.mol(-1) (coque breeze) e 162,302 kJ.mol(-1) (carvão vegetal). No artigo 2, a taxa de aquecimento não se mostrou como um fator determinante para a decomposição do MgSO4, já em relação a hidratação do sulfato de magnésio, os resultados indicaram que uma pequena parcela de H2O no sistema pode influenciar positivamente a decomposição, visto que os valores de Ea médio foram de 404,5 KJ.mol(-1) (mono), 407 KJ.mol(-1) (anidro) e 433,3 KJ.mol(-1) (hepta). / [en] Magnesium sulfate is present in several industrial and mining wastes. It and its derivatives could be reused in various industrial areas, ceasing to be a waste to become part of a process. Its oxide, MgO, can be used in some functions, as a pH regulator, depending on its reactivity. Due to this, its formation must occur at temperatures below the decomposition temperatures of MgSO4. Therefore, this work evaluated aspects of the decomposition of MgSO4 through two articles. Article 1 (Thermodynamics Simulations and Kinetics Modeling of the Thermal Decomposition of MgSO4.7H2O: Part 1 – Reducing Agent Effect), evaluated the kinetic effect of using carbon, through four different reducing agents, on the thermal decomposition of MgSO4.7H2O, while article 2 (Thermodynamics Simulations and Kinetics Modeling of the Thermal Decomposition of MgSO4.7H2O: Part 2 – Hydration Effect) analyzed the influences of the heating rate of the tests and the degree of hydration of the magnesium sulfate used. The thermogravimetric tests carried out throughout these articles used samples with a mass of approximately 10 mg of the mixture (sulfate + reducing agent) and these mixtures had a stoichiometric ratio of 1:1. The experiments carried out in article 1 used reducing agents, charcoal, green coke, breeze coke, and graphite as reducing agents. In article 2, the sulfates analyzed were anhydrous, monohydrate, and heptahydrate and the heating rates used were 5 K.min(-1) , 10 K.min(-1) , 15 K.min(-1) , and 20 K.min(-1). All data obtained from thermogravimetric tests were processed through mathematical modeling to obtain kinetic data. In article 1, the use of reducing agents proved efficient, reducing the activation energy of magnesium sulfate decomposition from 22.731 kJ.mol(-1) (pure sulfate) to 340.391 kJ.mol(-1) (green coke), 196.120 kJ.mol(-1) (graphite), 191,100 kJ.mol(-1) (coke breeze) and 162,302 kJ.mol(-1) (charcoal). In article 2, the heating rate was not shown to be a determining factor for the decomposition of MgSO4, in relation to the hydration of magnesium sulfate, the results indicated that a small portion of H2O in the system can positively influence the decomposition since the average Ea values were 404.5 KJ.mol(-1) (mono), 407 KJ.mol(-1) (anhydrous) and 433.3 KJ.mol(-1) (hepta).

No description available.

[pt] A industrialização e a crescente preocupação com o meio ambiente geram, cada vez mais, a busca por fontes de energia que emitam menos gases efeito estufa. A biomassa, devido a sua grande ocorrência ao redor do mundo e a sua diversidade, é uma forte alternativa aos combustíveis fósseis. Sua gaseificação gera um combustível gasoso chamado syngas. A problemática no manejo dos resíduos sólidos urbanos (RSU) e a grande disponibilidade do bagaço de cana-de-açúcar no Brasil fizeram deles tipos de biomassa de interesse para este trabalho. Objetivou-se simular no MATLAB® a gaseificação cocorrente de biomassa com ar a partir de uma abordagem cinética. O modelo foi validado com dados da literatura e aplicado à simulação da co-gaseificação de RSU e bagaço de cana-de-açúcar, na qual a razão de co-gaseificação (RCG) representou a percentagem de RSU na biomassa de entrada. Um planejamento composto central com 3 fatores e 3 níveis foi realizado, resultando em 27 ensaios variando os fatores RCG, umidade da biomassa e razão de equivalência. Foram criados modelos polinomiais para a composição do syngas obtido, o PCI do syngas, a eficiência energética do processo e a soma das frações molares de CO e H2 em base úmida. Os modelos foram considerados robustos, com valores de R2 e R2 ajustado variando de 0,96082 a 0,99345 e 0,94007 a 0,98998, respectivamente. O impacto dos fatores escolhidos nas respostas foi analisado, e os modelos de eficiência energética e soma das frações molares de CO e H2 foram maximizados. O caso otimizado, com RCG 7,98 porcento, umidade 5,00 porcento e razão de equivalência 0,18, resultou em um syngas de composição 3,72 porcento H2O, 29,68 porcento CO, 7,87 porcento CO2, 19,07 porcento H2 e 0,80 porcento de CH4 em mol, correspondendo a um PCI de 6,56 MJ/Nm3 e uma eficiência energética de 37,66 porcento. Por fim, o processo demonstrou bom potencial para geração de um gás rico em CO e H2. / [en] Industrialization and growing environmental concern are increasingly leading to the search for energy sources that emit less greenhouse gases. Biomass, due to its great accessibility around the world and its diversity, is a strong alternative to fossil fuels. Its gasification produces a gaseous fuel called syngas. The urban solid waste (MSW) management problems and the wide availability of sugarcane bagasse in Brazil made them types of biomass of interest for this work. This work aimed to model biomass gasification in MATLAB ® for a downdraft gasifier and air as gasifying agent, using a kinetic approach. The model was validated with experimental and numerical data from the literature and was then applied to MSW and sugarcane bagasse co-gasification simulation, in which co-gasification ratio (CGR) represented MSW percentage in the incoming biomass. A central composite design of experiments with 3 factors and 3 levels was carried out, resulting in 27 tests varying CGR, biomass moisture and equivalence ratio. Polynomial models were created for syngas composition, syngas LHV, process energy efficiency and sum of CO and H2 molar fractions on a wet basis. The models were considered robust, with values of R2 and adjusted R2 ranging from 0,96082 to 0,99345 and 0,94007 to 0,98998, respectively. The impact of each chosen factor was investigated, and the energy efficiency and sum of CO and H2 molar fractions models were maximized. The optimized case, with CGR 7,98 percent, biomass moisture 5,00 percent and equivalence ratio 0,18, resulted in a syngas composition of 3,72 percent H2O, 29,68 percent CO, 7,87 percent CO2, 19,07 percent H2 and 0,80 percent CH4 in molar basis, corresponding to a LHV of 6,56 MJ/Nm3 and an energy efficiency of 37,66 percent. By the end, the process showed great potential to produce a syngas rich in CO and H2.