This report deals with the mathematical model of the transient behaviour of an existing ethane dehydrogenation furnace which is composed of two main sections: a preheating convection section and a radiant-heated section. The correlation of pressure drop with time has been found from the available data. The fractional carbon deposition and the multiplier coefficient of a pressure drop equation have been determined by the direct search optimization technique of Hooke and Jeeves. An optimal policy for the cyclic operation of the furnace was determined by considering plant temperature profile and hydrocarbon/ steam ration as parameters for maximizing average ethylene produced per day. The effect of temperature profile on the distribution of carbon deposited along the reactor was also predicted and discussed. / Thesis / Master of Engineering (ME)

The reaction barrier and heat of formation of the various dehydrogenation reactions involved in the steam reforming of ethane is a critical concern in the applications and understanding of these reactions. Focusing on Ir-based catalyst, we report a comprehensive reaction network of dehydrogenation of ethane on Ir(100) based on extensive density functional theory calculations performed on 10 C-H bond cleavage reactions, utilizing the Vienna Ab Initio Package codes. The geometric and electronic structures of the adsorption of C2Hx species with corresponding transition-state structures is reported. We found that the C-H bond in CH3C required the most energy to activate, due to the most stable four-fold hollow adsorption site configuration. Ethane can easily dissociate to CH3CH and CH2CH2 on Ir(100) and further investigation of surface temperature dependence will contribute to the research effort in this area. By using the degree of dehydrogenation of the reactant species as a variable to correlate the C-H bond cleavage barrier as well as reaction energy. DFT studies reveal that the surface Ir(100) to a great extent promotes ethane dehydrogenation when compared to other surfaces.

No description available.

[ES] La presente tesis doctoral se sitúa en el marco de la actual transición energética, que plantea la sustitución progresiva de materias primas de origen fósil por fuentes renovables, tanto para la obtención de productos químicos como para la producción de combustibles. En este contexto de transición paulatina a las renovables, y teniendo en cuenta los últimos pronósticos, las fuentes fósiles (fundamentalmente gas natural) y derivados de la biomasa, jugarán un papel fundamental durante el cambio. Se ha llevado a cabo un estudio sobre el empleo de óxidos metálicos (basados en bronces de wolframio o en óxido de níquel), como catalizadores para: i) la transformación de derivados de biomasa: de glicerol a acroleína/ácido acrílico; y de compuestos oxigenados de cadena corta presentes en efluentes acuosos (procedentes de tratamientos de extracción de bio-aceites de pirolisis) a combustibles; y ii) la transformación de componentes del gas natural, concretamente la obtención de etileno a partir de etano, mediante deshidrogenación oxidativa (ODH). El trabajo se presenta desde una perspectiva de la química de materiales, haciendo hincapié en las propiedades fisicoquímicas de los distintos sistemas catalíticos, empleando técnicas de caracterización convencionales e in situ, además de reacciones modelo (transformación de metanol y etanol), con el objetivo de entender las funciones catalíticas presentes en cada caso. Tanto para la transformación de glicerol en fase gas, como para la valorización de mezclas acuosas de compuestos oxigenados de cadena corta, se han utilizado catalizadores basados en bronces de wolframio. Se ha tratado de poner de manifiesto la gran versatilidad composicional y estructural (con el consiguiente control de las propiedades funcionales), que presentan este tipo de materiales. En este sentido, las propiedades ácidas y redox de catalizadores W-V-O pueden ser moduladas, para una misma concentración de vanadio, mediante el control de la relación de fases cristalinas (hexagonal y monoclínica) del óxido de wolframio. Este efecto se ha estudiado empleando la transformación aeróbica de metanol como reacción "test", y tiene una gran influencia en la deshidratación oxidativa de glicerol a ácido acrílico. A su vez, mediante la sustitución isomórfica de wolframio por niobio (en el sistema WO3-Nb2O5) es posible controlar la relación de centros ácidos de tipo Brönsted y Lewis en la superficie de los materiales. Por un lado, los catalizadores con una alta relación Brönsted/Lewis se han mostrado más efectivos en la deshidratación de glicerol a acroleína, mientras que los catalizadores con altas concentraciones de centros de tipo Lewis presentan altos rendimientos a productos de condensación de compuestos oxigenados de cadena corta. Adicionalmente se han estudiado las diferencias entre catalizadores (bien óxidos mixtos W-V-O o W-Nb-O) preparados mediante un método hidrotermal o mediante reflujo, así como el efecto de la utilización de un soporte mesoporoso (KIT-6), sobre sus propiedades catalíticas en la transformación aeróbica en fase gaseosa de etanol y glicerol. Finalmente, en lo que concierne a la transformación de componentes del gas natural, se han empleado materiales basados en óxido de níquel (soportado sobre distintos óxidos y/o promovido con distintos metales) como catalizadores para la ODH de etano. En este caso el estudio se ha centrado fundamentalmente en dilucidar los efectos de promotores y soportes en la naturaleza y propiedades fisicoquímicas del óxido de níquel, los cuales dan lugar a un cambio drástico en sus propiedades catalíticas. Así, se ha observado que modificando la reducibilidad y las características superficiales del óxido de níquel es posible transformar un catalizador muy poco selectivo en la ODH de etano (como es el NiO, con una selectividad a etileno del 30 %) en uno de los catalizadores más selectivos para llevar a cab / [CA] Aquesta tesi doctoral es situa dins del marc de l'actual transició energètica, la qual planteja la substitució progressiva de les primeres matèries d'origen fòssil per fonts renovables, tant per a l'obtenció de productes químics com per a la producció de combustibles. En aquest context de transició gradual a les renovables, i tenint en compte els últims pronòstics, les fonts fòssils (principalment el gas natural) i els derivats de la biomassa, exerciran un paper fonamental durant aquest canvi. S'ha dut a terme un estudi sobre la utilització d'òxids metàl·lics (basats en bronzes de wolframi o en òxid de níquel), com a catalitzadors per a: i) la transformació de derivats de la biomassa: de glicerol a acroleïna/àcid acrílic; i de compostos oxigenats de cadena curta presents en efluents aquosos (procedents de tractaments d'extracció de bio-olis de la piròlisi) a combustibles; i ii) la transformació de components del gas natural, concretament l'obtenció d'etilè a partir d'età, mitjançant la deshidrogenació oxidativa. El treball es presenta des del punt de vista de la química de materials, posant l'accent en les propietats fisicoquímiques dels diferents sistemes catalítics, utilitzant tècniques de caracterització convencionals i in situ, a més de reaccions model, amb l'objectiu d'entendre les funcions catalítiques presents en cadascun dels casos. Tant per a la transformació del glicerol en fase gasosa com per a la valorització de les mescles aquoses de compostos oxigenats de cadena curta, s'han utilitzat catalitzadors basats en bronze de wolframi. S'ha intentat posar de manifest la gran versatilitat de composicions i estructures (amb el conseqüent control de les propietats funcionals) que presenten aquest tipus de materials. En aquest sentit, les propietats àcides i redox dels catalitzadors de W - V - O poden ser modulades, per a una mateixa concentració de vanadi, mitjançant el control de la relació de fases cristal·lines (hexagonal i monoclínica) de l'òxid de wolframi. Aquest efecte s'ha estudiat utilitzant la transformació aeròbica de metanol com a reacció "test", i presenta una gran influència en la deshidratació oxidativa de glicerol a àcid acrílic. Al mateix temps, mitjançant la substitució isomòrfica de wolframi per niobi (en el sistema WO3 - Nb2O5), és possible controlar la relació de centres àcids de tipus Brönsted i Lewis en la superfície dels materials. Per una part, els catalitzadors que presenten una relació Brönsted / Lewis alta s'han mostrat més efectius en la deshidratació de glicerol a acroleïna, mentre que els catalitzadors amb unes altes concentracions de tipus Lewis presenten alts rendiments a productes de condensació de compostos oxigenats de cadena curta. Addicionalment, s'han estudiat les diferències entre catalitzadors (ja siguin òxids mixtos W-V-O o W-Nb-O) preparats mitjançant un mètode hidrotermal o mitjançant un mètode de reflux, així com l'efecte que presenta la utilització d'un suport mesoporós (KIT-6), sobre les seves propietats catalítiques en la reacció de transformació aeròbica en fase gasosa d'etanol i glicerol. Finalment, pel que fa referència a la transformació de components del gas natural, s'han utilitzat materials basats en òxid de níquel (suportat sobre diferents òxids i/o promoguts amb diferents metalls) i catalitzadors per a la deshidrogenació oxidativa d'età. En aquest cas, l'estudi s'ha focalitzat principalment en dilucidar els efectes de promotors i suports en la naturalesa i propietats fisicoquímiques de l'òxid de níquel, els quals impliquen un canvi dràstic en les seves propietats catalítiques. Així doncs, s'ha observat que modificant la reductibilitat i les característiques superficials de l'òxid de níquel és possible transformar un catalitzador molt poc selectiu en la deshidrogenació oxidativa de l'età (com és el cas del NiO, amb una selectivitat a l'etilè del 30%) en un dels cata / [EN] The present doctoral thesis is set within the scope of the current energy transition, which considers the progressive substitution of non-renewable fossil sources by renewable feedstocks for the production of chemicals and fuels. In this context of gradual transition, and according to recent energy outlooks, fossil sources (especially natural gas) and biomass feedstocks will play a key role during the shift. A study on the use of metal oxides (based on tungsten bronzes or nickel oxides) as catalysts for different reactions has been conducted. Particularly, they have been studied as catalytic materials for: i) the transformation of biomass-derived feedstocks: glycerol transformation into acrolein/acrylic acid, and the transformation of short-chain oxygenates present in aqueous effluents (derived from extraction processes of pyrolysis bio-oils) into fuels; and ii) the valorization of natural gas components, i.e. the transformation of ethane into ethylene by oxidative dehydrogenation. The work is presented from a materials chemistry perspective, emphasizing the physicochemical characteristics of the different catalytic systems by using conventional and in situ characterization techniques and model reactions (gas phase methanol and ethanol transformation); with the aim of understanding the specific catalytic functionalities present in each case. For both gas phase glycerol transformation and the valorization of short-chain oxygenates aqueous mixtures, catalyst based on tungsten oxide bronzes have been used. The compositional and structural versatility of this structural types (with the subsequent control of their functional properties) will be highlighted. In this sense, the acid-redox properties of W-V-O catalysts can be modulated by controlling the crystalline phase composition in the materials (i.e. hexagonal and monoclinic polymorphs of tungsten oxide) at a fixed V concentration. This effect has been studied by using the gas-phase aerobic transformation of methanol as a surface test reaction. The concentration of the hexagonal and monoclinic polymorphs in the catalysts has also an important influence in the gas-phase transformation of glycerol into acrylic acid. Also, it is possible to control the Brönsted/Lewis acid nature of the surface by the isomorphic substitution of Nb for W in WO3-Nb2O5 system. On the one hand, catalysts showing a higher proportion of Brönsted acid sites are more effective in the glycerol dehydration to acrolein. On the other hand, materials with a higher concentration of Lewis acid sites display high yields to condensation products in the aqueous phase valorization of short chain oxygenates. Additionally, the differences between W-V-O and W-Nb-O catalysts prepared by both reflux and hydrothermal methods have been studied. Also the effect of adding a mesoporous KIT-6 silica as support on the catalytic performance in the gas phase transformation of ethanol and glycerol will be underlined. Considering the transformation of natural gas components, nickel oxide-based materials were chosen (either supported on different oxides and/or promoted with different metals) to perform the oxidative dehydrogenation (ODH) of ethane. In this case the study has been focused on elucidating the effects of both promoters and supports on the nature and physicochemical features of nickel oxide, which lead to a drastic change in the catalytic behavior of these materials. This way, it has been observed that by the modification of the reducibility and the chemical nature of nickel oxide, it is possible to transform an apparently non-selective catalyst in the ODH of ethane (like NiO, showing a selectivity to ethylene of ca. 30 %) into one of the most selective catalysts reported in the literature (presenting a selectivity to ethylene of ca. 90 %). / También me gustaría agradecerle al Prof. Avelino Corma, investigador principal del proyecto SEV-2012-0267, a través del cual he podido realizar mi tesis doctoral enel Instituto de Tecnología Química (SVP-2014-068669). / Delgado Muñoz, D. (2019). Catalytic valorization of natural gas and biomass-derived feedstocks by metal oxides [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/122298

Este trabalho tem como objetivo apresentar, através da modelagem de uma planta gásquímica e da identificação das tecnologias disponíveis, a versatilidade do uso do gás natural como insumo para a indústria química, visando à produção de metanol, amônia e hidrogênio, a partir da fração metano, bem como na indústria petroquímica a obtenção do eteno através da fração etano. Baseado nas pesquisas de mercado, determinou-se que dentre os produtos a serem obtidos a partir do metano, o metanol é o que apresenta o cenário interno mais crítico. Esta situação é refletida através do contínuo aumento da importação, sem que haja nenhuma sinalização deste déficit ser sanado, através da construção de novas unidades industriais. Por outro lado, o cenário da amônia se mostra estável e, ainda que haja um déficit na produção nacional, a situação atual não se mostra tão crítica, mesmo quando realizada a projeção da demanda até 2030. Analisando-se o cenário petroquímico, em poucos anos a produção de eteno atingirá o seu gargalo, e o maior entrave diagnosticado, para a expansão das centrais produtoras, está relacionado à disponibilidade do insumo. Dentro da abordagem técnica proposta, a modelagem da planta gás-química aponta ser viável concentrar a produção de amônia, metanol e hidrogênio no mesmo pólo e que, para estes produtos, a tecnologia atual encontra-se madura e em estágio avançado. Já a produção de eteno, a partir do etano, não deve estar diretamente vinculada, a princípio, à obtenção dos demais produtos, pelo alto volume de gás natural necessário para liberar a fração de etano ideal para a sustentabilidade do projeto. / This work has as objective to present, through the modeling of a gas-chemical plant and also, through the identification of the current available technologies, the versatility of the use of natural gas as a raw material for the chemical industry, aiming the production of methanol, ammonia and hydrogen, from the fraction methane, as well as in the petrochemical industry, the attainment of ethene from the ethane fraction. Based in a market research, it was determined that amongst the products to be obtained from methane, methanol is the product that presents the most critical internal scenario. This situation is reflected through the continuous increase of the importation; without it there is no signaling that this deficit can be overcome, unless new industrials units are constructed. On the other hand, the ammonia scenario is steady and, despite presenting a deficit in the national production, the current situation does not reveal to very so critical, carried through the projection of the demand up to 2030. Analyzing the petrochemical scene, in a few years the ethene production will reach its pass and the biggest diagnosed impediment is related to the availability of the feedstock. Considering the technique proposal, the modeling of the gas-chemical plant shows the viability of concentrating the production of ammonia, methanol and hydrogen in the same site and that, for these products, the current technologies are mature and very well developed. Already the ethene production, from ethane, does not have to be directly entailed, in principle, to the attainment of the other products, considering the high volume of natural gas necessary to liberate the necessary amount of ethane for the sustainable of the project.

Submitted by Deyse Queiroz (deysequeirozz@hotmail.com) on 2018-05-28T13:21:33Z No. of bitstreams: 1 CARLA ROCHA PORDEUS - DISSERTAÇÃO PPGSA PROFISSIONAL 2017..pdf: 2843883 bytes, checksum: 014b0d5482560187c558623c669ff0f6 (MD5) / Made available in DSpace on 2018-05-28T13:21:33Z (GMT). No. of bitstreams: 1 CARLA ROCHA PORDEUS - DISSERTAÇÃO PPGSA PROFISSIONAL 2017..pdf: 2843883 bytes, checksum: 014b0d5482560187c558623c669ff0f6 (MD5) Previous issue date: 2017 / O direito ao meio ambiente ecologicamente equilibrado foi consagrado constitucionalmente, atribuindo-se ao Poder Público e à coletividade o dever de defendê-lo e preservá-lo para as presentes e futuras gerações. Além do sistema de responsabilidades compartilhadas, alguns deveres foram incumbidos especificamente ao Poder Público.Dentre eles, destaca-se o de controlar a produção, a comercialização e o emprego de substâncias que comportem risco para a vida, a qualidade de vida e o meio ambiente. Os agrotóxicos, produtos da indústria química, são substâncias que devem ser controladas pelo Poder Público em virtude da magnitude dos danos que podem provocar. Como exemplo, cita-se os prejuízos causados pela ampla e irrestrita utilização do inseticida dicloro-difenil-tricloro-etano (DDT), substância hoje reconhecidamente carcinogênica. Sendo assim, com vistas a garantir o direito fundamental ao meio ambiente equilibrado, bem como direito social a alimentação adequada, este garantido no art. 6º da Constituição Federal de 1988, que contempla a garantia de alimento livre de agrotóxico, o ordenamento jurídico pátrio estabelece normas regulamentadoras do registro, da comercialização e do uso dos agrotóxicos, respeitada a distribuição de competências prevista na CF/88, decorrente do modelo federativo adotado. Ante o exposto, o presente trabalho cientifico tem por objetivo analisar tais normas,e ,notadamente, no âmbito da cidade de Sousa-PB, verificar se o Poder Legislativo municipal tem atuado no sentido de, dentro da competência suplementar que lhe é conferida, produzir as normas referentes ao uso e armazenamento de agrotóxicos, considerando a realidade e interesse local, demonstrando inicialmente o histórico acerca do uso de agrotóxicos no Brasil e no mundo; identificando os principais agrotóxicos e seus efeitos na saúde humana e no meio ambiente; e apontando, sob uma perspectiva jurídica a legislação que rege a matéria, além da competência para tratar da mesma de acordo com os entes da Federação (União, Estados e Municípios). Para tanto, realiza um levantamento bibliográfico e uma pesquisa documental, associados a informações coletadas junto à Câmara de Vereadores de Sousa, Vigilância Sanitária e Secretaria de Agricultura e Meio Ambiente do Município, necessárias à contextualização da temática ora proposta. De forma que, conhecendo a realidade acerca da legislação regente do uso de agrotóxicos no município se possa delinear os caminhos para minimizar os impactos de tal prática no meio ambiente e na saúde coletiva. / The right to the ecologically balanced environment was constitutionally enshrined, and it was the responsibility of the public power and the community to defend and preserve it for present and future generations. In addition to the system of shared responsibilities, some duties were specifically entrusted to the Public Power. Among them, the most important is to control the production, commercialization and use of substances that present risks to life, quality of life and the environment. Agrochemicals, chemicals in the chemical industry, are substances that must be controlled by the government due to the magnitude of the damages they can cause. One example is the damage caused by the widespread and unrestricted use of the insecticide dichloro-diphenyl-trichloroethane (DDT), a substance known today as carcinogenic. Therefore, in order to guarantee the fundamental right to the balanced environment, as well as social right to adequate food, this guaranteed in art. 6, of the Federal Constitution of 1988, which provides for the guarantee of food free of pesticides, the legal order of the country establishes regulatory norms for the registration, commercialization and use of pesticides, respecting the distribution of competences set forth in CF / 88, resulting from the federative model adopted. In light of the above, the objective of this scientific work is to analyze such norms and, especially, within the city of Sousa-PB, to verify if the municipal Legislative Power has acted in the sense of, within the additional competence that is conferred on it, produce The rules regarding the use and storage of pesticides, considering local reality and interest, initially demonstrating the history about the use of pesticides in Brazil and in the world; Identifying the main pesticides and their effects on human health and the environment; And pointing out, from a legal perspective, the legislation that governs the matter, besides the competence to deal with it in agreement with the entities of the Federation (Union, States and Municipalities). To do so, it carries out a bibliographical survey and a documentary research, associated with information collected from the City Council of Sousa, Sanitary Surveillance and the Department of Agriculture and Environment of the Municipality, necessary to contextualize the theme proposed herein. So, knowing the reality about the legislation governing the use of pesticides in the municipality can outline the ways to minimize the impacts of such practice on the environment and collective health.

Recent studies have shown that ruthenium(III) acetylacetonate is acting as homogeneous catalyst in the hydrolysis of sodium borohydride. Although trimethlyphosphite is found to be a poison for the catalytic hydrolysis of sodium borohydride, a longer observation of the reaction in the presence of ruthenium(III) acetylacetonate and 2 equivalent trimethylphosphite shows an unexpected enhancement in the catalytic activity after an induction period. The same rate enhancement is observed when 2 equivalent triphenylphosphine is added into the reaction solution. Addition of 1 equivalent 1,2-bis(diphenylphosphino)ethane, dppe, into the solution shows similarly a rate enhancement in the hydrolysis of sodium borohydride catalyzed by ruthenium(III) acetylacetonate. The effect of 1,2-bis(diphenylphosphino)ethane on the catalytic activity of ruthenium(III) acetylacetonate in the hydrolysis of sodium borohydride was studied by varying mole ratio of dppe / Ru(acac)3, ruthenium concentration, substrate concentration and temperature. The highest enhancement in the rate of hydrolysis was obtained when 1 equivalent dppe was used and therefore, this mole ratio of dppe / Ru(acac)3 was used in the further studies. The rate of the reaction was found to be first order in catalyst concentration and zero order in substrate concentration. From the evaluation of rate constant versus temperature data, the activation parameters for the hydrolysis of sodium borohydride catalyzed by ruthenium(III) acetylacetonate plus 1 equivalent dppe were found to be Ea= 59 &plusmn / 2 kJ/mol, &amp / #8710 / H&amp / #8800 / = 60 &plusmn / 1 kJ.mol-1 and &amp / #8710 / S&amp / #8800 / = -50 &plusmn / 3 J.(mol.K)-1. A series of control experiments were performed to characterize the active catalyst. However, the only useful information could be obtained by comparison of the UV-vis electronic absorption spectra taken from the solution during the catalytic reaction, is that, ruthenium(III) is reduced to ruthenium(II) in the course of reaction. It was concluded that a ruthenium(II) species is formed as a transient and may be the active catalyst in the reaction. After the reaction, the only ruthenium species isolated from the solution was the ruthenium(III) acetylacetonate.

Este trabalho tem como objetivo apresentar, através da modelagem de uma planta gásquímica e da identificação das tecnologias disponíveis, a versatilidade do uso do gás natural como insumo para a indústria química, visando à produção de metanol, amônia e hidrogênio, a partir da fração metano, bem como na indústria petroquímica a obtenção do eteno através da fração etano. Baseado nas pesquisas de mercado, determinou-se que dentre os produtos a serem obtidos a partir do metano, o metanol é o que apresenta o cenário interno mais crítico. Esta situação é refletida através do contínuo aumento da importação, sem que haja nenhuma sinalização deste déficit ser sanado, através da construção de novas unidades industriais. Por outro lado, o cenário da amônia se mostra estável e, ainda que haja um déficit na produção nacional, a situação atual não se mostra tão crítica, mesmo quando realizada a projeção da demanda até 2030. Analisando-se o cenário petroquímico, em poucos anos a produção de eteno atingirá o seu gargalo, e o maior entrave diagnosticado, para a expansão das centrais produtoras, está relacionado à disponibilidade do insumo. Dentro da abordagem técnica proposta, a modelagem da planta gás-química aponta ser viável concentrar a produção de amônia, metanol e hidrogênio no mesmo pólo e que, para estes produtos, a tecnologia atual encontra-se madura e em estágio avançado. Já a produção de eteno, a partir do etano, não deve estar diretamente vinculada, a princípio, à obtenção dos demais produtos, pelo alto volume de gás natural necessário para liberar a fração de etano ideal para a sustentabilidade do projeto. / This work has as objective to present, through the modeling of a gas-chemical plant and also, through the identification of the current available technologies, the versatility of the use of natural gas as a raw material for the chemical industry, aiming the production of methanol, ammonia and hydrogen, from the fraction methane, as well as in the petrochemical industry, the attainment of ethene from the ethane fraction. Based in a market research, it was determined that amongst the products to be obtained from methane, methanol is the product that presents the most critical internal scenario. This situation is reflected through the continuous increase of the importation; without it there is no signaling that this deficit can be overcome, unless new industrials units are constructed. On the other hand, the ammonia scenario is steady and, despite presenting a deficit in the national production, the current situation does not reveal to very so critical, carried through the projection of the demand up to 2030. Analyzing the petrochemical scene, in a few years the ethene production will reach its pass and the biggest diagnosed impediment is related to the availability of the feedstock. Considering the technique proposal, the modeling of the gas-chemical plant shows the viability of concentrating the production of ammonia, methanol and hydrogen in the same site and that, for these products, the current technologies are mature and very well developed. Already the ethene production, from ethane, does not have to be directly entailed, in principle, to the attainment of the other products, considering the high volume of natural gas necessary to liberate the necessary amount of ethane for the sustainable of the project.

L'objectif de ce travail de thèse est la compréhension de l'impact des propriétés acido-basiques des supports oxydes sur l'interaction métal-support ainsi que les effets du milieu réactionnel sur les propriétés structurales, électroniques, thermodynamique et réactives des catalyseurs métalliques hyper-dispersés. Le catalyseur modèle choisi est un agrégat monométallique de platine déposé sur alumine qui est la référence des études fondamentales pour permettre des progrès dans la compréhension de ce système complexe. La mise en œuvre de calculs dans le formalisme de la théorie de la fonctionnelle de la densité, réalisés à partir de modèles moléculaires périodiques, a permis de déterminer l'état de surface du catalyseur pour des conditions de température et de pression représentatifs de l'expérience. L'influence de la taille des particules conjointement à la présence de chlore sur la stabilité thermodynamique des agrégats de Pt supportés sur alumine-γ a démontré une stabilisation significative des agrégats Pt3 lors de la migration d'espèces de surface (H, OH et Cl) sur la particule. La reconstruction d'une morphologie biplanaire (la plus stable en absence d'hydrogène) vers une morphologie cuboctaédrique pour les forts taux de recouvrement en hydrogène sur les particules de Pt supportées a été démontrée et permet d'expliquer plusieurs observations expérimentales encore mal comprises. L'impact du milieu réactionnel sur la rupture C-C et C-H à partir de l'éthane sur l'agrégat Pt13 supporté sur alumine- γ a été démontré. Les résultats obtenus permettent de mieux comprendre l'importance des conditions de température et de pression du milieu réactionnel (notamment du rapport P(H2)/P(C2H6)) sur la stabilité des intermédiaires réactionnels. Ces résultats sont en accord avec les observations expérimentales et permettent de mettre en évidence que l'optimum de pression en hydrogène est relativement élevé dans le cas des réactions de reforming catalysées par du Pt seul. / The aim of this work is the understanding of the impact of acido-basic properties of oxide supports on the metal-support interaction as well as on the effects of reactive conditions on the structural, electronic, thermodynamic and reactive properties of hyper-dispersed metallic catalysts. The chosen model catalyst is a monometallic platinum cluster supported on alumina which is the reference of fundamental studies to improve the understanding of this complex system. DFT calculations were performed from periodic models to determine the surface state of the catalyst under representative experimental temperature and pressure. The influence of nano-clusters' size combined with the presence of chlorine on the thermodynamic stability of supported Pt clusters on γ-alumina demonstrated a significant stabilization of Pt3 clusters with the migration of surface species (H, OH and Cl) on the particle. The morphology reconstruction from biplanar (the most stable in absence of hydrogen) to a cuboctahedral morphology for the high hydrogen coverages on the supported Pt13 cluster is demonstrated and explains several experimental observations still controversial. The impact of the reactive conditions on the C-C and C-H bond scission from ethane on the Pt13 cluster supported on γ-alumina was demonstrated. Results helps to better understand the importance of temperature and pressure conditions in the reactive medium (notably the P(H2)/P(C2H6) ratio) on the stability of reactive intermediates. These results are in agreement with experimental observations and highlight that the optimum of hydrogen pressure is relatively high in the case of catalytic reforming reactions catalyzed by Pt only.

<p>The present work is focused on the synthesis of small-scale (modular processes) to produce olefins from light alkane resources in shale gas.</p> <p>Olefins, which are widely used to produce important chemicals and everyday consumer products, can be produced from light alkanes - ethane, propane, butanes etc. Shale gas is comprised of light alkanes in significant proportion; and is available in abundance. Meanwhile, shale gas wells are small sized in nature and are distributed over many different areas or regions. In this regard, using shale gas as raw material for olefin production would require expensive transportation infrastructure to move the gas from the wells or local gas gathering stations to large central processing facilities. This is because existing technologies for natural gas conversions are particularly suited for large-scale processing. One possible way to take advantage of the abundance of shale resource for olefins production is to place small-sized or modular processing plants at the well sites or local gas gathering stations.</p> <p>In this work, new process concepts are synthesized and studied towards developing simple technologies for on-site and modular processing of light alkane resources in shale gas for olefin production. Replacing steam with methane as diluent in conventional thermal cracking processes is proposed to eliminate front-end separation of methane from the shale gas processing scheme. Results from modeling studies showed that this is a promising approach. To eliminate the huge firebox volume associated with thermal cracking furnaces and allow for a compact cracking reactor system, the use of electricity to supply heat to the cracking reactor is considered. Synthesis efforts led to the development of two electrically powered reactor configurations that have improved energy efficiency and reduced carbon footprints over and compare to conventional thermal cracking furnace configurations.</p> <p>The ideas and results in the present work are radical in nature and could lead to a transformation in the utilization of light alkanes, natural gas and shale resources for the commercial production of fuels and chemicals.</p>