To see the other types of publications on this topic, follow the link: HDS catalysts.
Dissertations / Theses on the topic 'HDS catalysts'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 37 dissertations / theses for your research on the topic 'HDS catalysts.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Quilfen, Cyril. "Supercritical fluids synthesis, characterization and test of HDS catalysts : Assessment of criticality of metals contained in HDS catalysts." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0405/document.
Full textAbstract:
Dans un contexte environnemental où les législations concernant la teneur ensoufre présent dans les coupes pétrolières sont de plus en plus drastiques, le développementde nouveaux catalyseurs toujours plus actifs est donc nécessaire. Cette augmentation del´activité catalytique est possible à plusieurs niveaux dont, par exemple, par l´utilisation denouveaux procédés de synthèse tel que l´emploi de la voie fluides supercritiques. Dans unpremier temps, l´objectif est d´étudier les éléments utilisés pour préparer ces catalyseurs afind´avoir une vision plus large des réserves, des utilisations, des possibilités de substitutions…La criticité de ces éléments a donc été évaluée par le biais de plusieurs indicateurs. Dans unsecond temps, la compréhension de la synthèse de catalyseurs d´hydrodésulfuration (HDS) aété étudiée. Pour cela des expériences utilisant différents solvants et précurseurs métalliquesont été suivies via des analyses in situ Raman. Après avoir défini les résultats les plusprobants, le procédé de préparation de catalyseurs HDS assisté par le CO2 supercritique(scCO2) a été optimisé à travers une étude paramétrique. Pour cela, la température, lapression, le solvant d´imprégnation, le ratio entre CO2 et solvant d´imprégnation, le temps deréaction et le chargement en métaux ont été variés. Les matériaux obtenus ont ensuite étéfinement caractérisés (microscopie, DRX, Raman, ICP, microsonde) avant d´être activés parsulfuration et testés dans différentes réactions catalytiques (hydrogénation du toluène,hydrodésulfuration du dibenzothiophène et du 4,6-diméthyldibenzothiophène)In an environmental context where legislations concerning the sulfur content in oilare increasingly drastic, the research for new and ever more active catalysts is necessary. Thisincrease of the catalytic activity is possible at several levels, for example, with the use of novelsynthetic processes such as the use of the supercritical fluids route. In a first stage, theobjective is to study the elements used to prepare these catalysts in order to have a broaderview of the reserves, the uses, the possibility of substitutions ... The criticality of these elementshas therefore been evaluated by means of several indicators. In a second stage, theunderstanding of the synthesis of hydrodesulfurization catalysts (HDS) was studied. For thispurpose, experiments using different solvents and metallic precursors were followed by in situRaman analyses. After defining the most convincing results, the process for preparing HDScatalysts assisted by supercritical CO2 medium (scCO2) was optimized through a parametricstudy. For this, temperature, pressure, impregnation solvent, ratio of CO2 to impregnationsolvent, reaction time and metal loading were varied. The materials obtained were thencharacterized (microscopy, DRX, Raman, ICP, microprobe) before being activated bysulfidation and tested in various catalytic reactions (hydrogenation of toluene,hydrodesulfurization of dibenzothiophene and 4,6-dimethyldibenzothiophene)
2
Oliveira, De Souza Danilo. "Quick-EXAFS and hydrotreating catalysts : chemometrics contribution." Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10061/document.
Full textAbstract:
L’hydrodésulfuration (HDS) est un procédé catalytique utilisé pour éliminer le soufre des carburants. La demande mondiale de carburants propres a stimulé les recherches sur autour de ce procédé afin de mieux comprendre les mécanismes réactionnels et de produire des catalyseurs plus efficaces. Deux axes de recherches peuvent être dégagés : d’une part la formulation de nouvelles voies de synthèse permettant la production des catalyseurs plus efficaces et d’autre part la compréhension du processus catalytique au niveau moléculaire. La compréhension des transformations structurales du catalyseur au niveau moléculaire pendant la réaction ainsi que pendant la genèse de la phase active est une nécessité pour améliorer les propriétés des catalyseurs. Dans ce contexte, ce travail propose deux objectifs. En premier lieu, il présente nouvelle méthode de synthèse de catalyseurs d’HDS à base de CoMo supporté dans TiO2 par voie sol-gel. Dans un deuxième temps, le travail présente la mise-en-œuvre de la chimiometrie pour traiter des données in situ de spectroscopie d’absorption de rayons-X (XAS) qui permet d’obtenir des informations sur la structure moléculaire du catalyseur pendant son activation. Les installations synchrotron de dernière génération permettent en effet d’enregistrer des données expérimentales avec résolution temporelle de l’ordre de la seconde (Quick-EXAFS) et la chimiometrie fournit des outils d’analyse et d’interprétation pour extraire des informations sur les cinétiques de réaction et sur les transformations structurales menant à la formation de la phase active du catalyseurHydrodesulfurization (HDS) is catalytic process used to remove sulfur from petroleum feedstock. The world claim for clean fuel boosted scientists to get new insights on the catalytic reaction in order to understand the mechanisms of the process and, thus, produce catalysts that are more efficient. Such researches are based mainly in to lines: by one hand, in the formulation of new routes that lead to tailored catalysts and, by the other hand, in a better understanding of the catalytic process at the molecular and atomic level. Particularly, the later leads to an optimization of the formulation and better catalytic performance, for which is required further understanding of the molecular structure, its transformations during the reaction, the nature of active species and its genesis. In this picture, the goal of this work is twofold. First, to present a new route for produce HDS CoMo-based catalysts via one-pot sol-gel method, which revealed to have suitable macro- and microscopic properties making promising solids for further applications. Second, to adapt and use chemometrics method to treat in situ measurements, particularly, X-ray absorption spectra (XAS), to get new insights on the genesis of the catalytic active phase at the molecular level. XAS techniques is suitable to probe local atomic structure, and last generation synchrotron facilities provide conditions to perform such in situ experiments with very fast acquisition (Quick-EXAFS). Chemometrics provide a brand new scope on data analysis and interpretation for extract information on the kinetics of reaction and structure transformation that leads to the active phase of the catalysts
3
Babcock, Kenneth W. "Influence of mass transport limitations on kinetics of thiophene desulfurization for resids HDS catalyst in the fresh, spent, and regenerated states." Thesis, Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/11870.
Full text
4
Steiner, Petr. "Kinetic and Deactivation Studies of Hydrodesulfurization Catalysts." Doctoral thesis, Norwegian University of Science and Technology, Department of Chemical Engineering, 2002. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-94.
Full textAbstract:
Hydrodesulfurization is an important part of the hydrotreating process. More stringent regulations on the quality of fuels bring new requirements to the catalytic processes. The removal of sulfur has become a key issue in the oil refining and this work aims to address several aspects of the process.
Kinetic studies of the hydrodesulfurization reaction over conventional (molybdenum-based) and new (Pt/Y-zeolite) catalysts are reported. The hydrodesulfurization of both the real oil (light gas oil from Statoil Mongstad refinery) and model compounds (thiophene and dibenzothiophene) over a NiMo/γ-Al2O3 catalyst were studied. In a high-pressure study of the light gas oil, substituted alkyl-DBTs were found to be the most difficult to desulfurize and the order of reactivity was found to be DBT > 4-MDBT > 4,6-DMDBT. Steric hindrance together with electronic effects were identified as possible reasons for this behavior. The difference in reactivities of the individual compounds was found to decrease with the increasing reaction temperature. A gas chromatograph equipped with the atomic emission detector (GC-AED) was used for the analysis of the individual components of the oil.
The initial deactivation and the steady-state kinetics were studied during the HDS of thiophene at atmospheric pressure. Unpromoted Mo/γ-Al2O3, CoMo/γ-Al2O3, NiMo/γ-Al2O3, and phosphorus modified NiMo/γ-Al2O3 were used for the deactivation study, while NiMo/γ-Al2O3,CoMo/γ-Al2O3, and Pt/Y-zeolite (with three different pretreatments) were used for the steadystate study. Several experiments related to the deactivation of Mo/γ-Al2O3 and NiMo/γ-Al2O3 catalysts prepared with the chelating agent (NTA) were also performed and NTA was found to have no significant effect on the activity of the catalysts.
In the deactivation study, a fast initial decrease in the activity was observed on all the catalysts. However, nickel promoted catalysts were found to be more resistant to deactivation than unpromoted ones. The presence of phosphorus slightly increased the activity of the catalyst towards the thiophene HDS, but had no effect on the deactivation behavior. Several methods to regenerate the catalyst were investigated. During the resulfiding experiments, a difference between Mo/γ-Al2O3 and NiMo/γ-Al2O3 was observed. Deactivation of the Mo catalyst was more severe with increasing temperature, while for the NiMo catalyst the opposite behavior was observed. Carbon deposition on catalysts followed the similar trend: More carbon was observed on the Mo catalyst at higher temperatures, while the opposite is true for NiMo. The restoration of the activity of NiMo was complete, while the reactivation of the Mo catalyst was only partial. The results from the reactivation experiments with pure H2 and inert gas (helium) suggest that several mechanisms of the restoration of activity exist: Resulfiding of the desulfided active sites, hydrogenation and removal of the deposited carbonaceous species, and the desorption of the reactants and products from the active sites of the catalyst. Based on the observed results, the higher hydrogenation activity of nickel is assumed to be the reason for the behavior. Hydrogenation causes the faster removal of the deposited carbonaceous species and this leads to the conclusion that the desulfiding of the active sites and the adsorption of the reaction species is significantly less pronounced on the NiMo/γ-Al2O3 catalyst.
Characterization studies show differences between standard and NTA-based catalysts. The higher amount of carbon on the NTA catalysts is attributed to the presence of the carboncontaining precursor - NTA. The changes in the surface area and the pore volume were observed only during the sulfiding process. In the case of standard catalysts the surface area and the pore volume decreased, while for the NTA-based catalysts the opposite is true. No change in the surface area and the pore volume with the increasing time on stream indicates that the deactivation is not due to structural changes of the catalyst. The amount of sulfur was found to be constant during the time on stream for all the catalysts.
In the steady-state study of the HDS of thiophene, CoMo and NiMo catalysts were found to be equally active. The activity of the Pt/Y-zeolite catalyst was found to be comparable to conventional catalysts when based on the amount of active material, but a fast deactivation was observed. The product selectivities during the HDS of thiophene were found to be the same for all standard catalysts, but slightly different for the Pt/Y-zeolite catalyst. This was attributed to a higher hydrogenation activity of the Pt/Y-zeolite catalyst.
The inhibition effect of other sulfur compounds and aromatics on the high-pressure hydrodesulfurization of dibenzothiophene (DBT), the so-called “matrix effect” was studied. Thiophene and DMDS have the same inhibiting effect on the total conversion of DBT, but differences exist in the effect on the selectivities of the products at low concentrations. The results indicate that the inhibiting effect of H2S on the direct desulfurization route is stronger than the effect of thiophene on the hydrogenation pathway. In the study of aromatics, both toluene and naphthalene affect the total conversion of DBT. Naphthalene was found to be a much stronger inhibitor and inhibits mainly the direct desulfurization pathway, while the hydrogenation route is more affected by the presence of toluene.
5
Antunes, Florence Pereira Novais. "Determinação de propriedades e estruturas de catalisadores de sulfeto de molibdênio suportados em MgO por cálculos ab initio." Universidade Federal de Juiz de Fora, 2015. https://repositorio.ufjf.br/jspui/handle/ufjf/317.
Full textAbstract:
Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-01-04T13:12:06Z
No. of bitstreams: 1
florencepereiranovaisantunes.pdf: 6342982 bytes, checksum: b846018e0b6dd62bd5ea051a6710659a (MD5)Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-01-25T15:55:33Z (GMT) No. of bitstreams: 1 florencepereiranovaisantunes.pdf: 6342982 bytes, checksum: b846018e0b6dd62bd5ea051a6710659a (MD5)
Made available in DSpace on 2016-01-25T15:55:33Z (GMT). No. of bitstreams: 1 florencepereiranovaisantunes.pdf: 6342982 bytes, checksum: b846018e0b6dd62bd5ea051a6710659a (MD5) Previous issue date: 2015-06-03
CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Associada à redução das emissões veiculares, o principal processo de interesse no hidrotratamento é a hidrodessulfurização, HDS, na qual o átomo de enxofre presente nas moléculas organosulfuradas é adsorvido no catalisador e reage com hidrogênio, formando sulfeto de hidrogênio (H2S) e os hidrocarbonetos livres de heteroátomos. As reações de HDS são exotérmicas e irreversíveis, sendo que seu mecanismo envolve reações de hidrogenólise – quebra da ligação CS – e de hidrogenação – saturação das duplas ligações. Existem divergências na literatura sobre o mecanismo dessas reações. O interesse pela área de materiais relacionados às reações deste tipo e à catálise heterogênea está em constante expansão devido à possibilidade de produzir diversos tipos de materiais de grande aplicabilidade e custos menos onerosos. Os estudos sobre HDS buscam o desenvolvimento de catalisadores com maior capacidade para promover uma remoção mais efetiva do enxofre, além de esclarecimentos referentes ao seu mecanismo. Os catalisadores mais comumente usados são compostos que possuem estruturas de MoS2 como fase ativa. Apesar de possuir atividade catalítica na forma mássica, o MoS2 geralmente é suportado em uma superfície com extensa área como suporte, geralmente óxidos, sendo a γalumina a mais utilizada. Existem diversos estudos recentes reportando uso de outros tipos de óxidos, como TiO2, sílica, zeólitas, ZrO2, MgO e óxidos mistos. No presente trabalho, é feita a proposta de dois tipos de estruturas de catalisadores de sulfeto de molibdênio suportados em MgO, através de cálculos ab initio. É de aceitação geral, hoje em dia, que a atividade dos catalisadores de HDS está fundamentalmente ligada à existência de vacâncias aniônicas de enxofre, situadas, predominantemente, nas bordas dos cristalitos da fase ativa, já que o enxofre dos planos basais está muito fortemente ligado para permitir a formação destas vacâncias. Levandose em conta que a formação de vacâncias é uma etapa crucial para HDS, procuramos obter informações estruturais mais precisas que auxiliem no entendimento dessa etapa da reação. Para isso mostramos o estudo da formação de sítios coordenativamente insaturados na borda do sulfeto de molibdênio suportado em MgO. Além disso, discutimos a interação do sulfeto com o suporte, variando o número de camadas de sulfeto e a presença de átomo promotor de cobalto na borda. Com isso, procuramos fornecer informações estruturais de modelos teóricos de MoS2 suportado em MgO utilizando DFT a fim de contribuir com estudos nesse contexto. Para isso, foi calculada a energia de formação de vacâncias, diferença da densidade de cargas eletrônicas, pDOS e análise das cargas de Bader. Concluímos que tanto o suporte quanto o átomo promotor influenciam na formação de vacâncias na borda do sulfeto de molibdênio suportado em MgO. A influência dessas variáveis está em dependência com o tamanho da lamela, proporções de átomos de enxofre de borda e tipo de interação do sulfeto com o suporte. Em geral podemos afirmar que os dois agem de modo a diminuir a energia de formação de vacâncias, contribuindo para a melhora dessa etapa.
With respect to the reduction of pollutant emission of vehicles, the main process of hydrotreatment is the hydrodesulfurization, HDS, in which the sulfur atom of the organosulfur molecules is adsorved on the catalyst and reacts with hydrogen forming hydrogen sulfide (H2S) and heteroatomfree hydrocarbons. The HDS reactions are exothermic and irreversible and their mechanisms involve hydrogenolysis reactions – the break of CS bond – and the hydrogenation – saturation of double bonds. There are many divergences in the literature about the mechanism of these reactions. The interest about these types of reactions and the heterogenous catalysis in the material field is in constant expansion due to the possibility of producing several types of materials with great applicabilities and inferior costs. The studies about HDS seek the development of catalysts with a higher capacity to promote a more effective removal of sulfur besides the elucidation of their mechanisms. The catalysts more commonly used are compounds which possess MoS2 structures as the active phase. Even though it has catalytic activity in the bulk structure, the MoS2 is generally supported on a surface with an extended area, usually oxides such as alumina, which is the most utilized. There are many recent studies γ reporting the use of other types of oxides such as TiO2, silica, zeolites, ZrO2, MgO and mixed oxides. In this present work, a proposition of two types of catalyst structures of molybdenum sulfides supported on MgO is done by means of ab initio calculations. It is commonly accepted nowadays that the activity of HDS catalysts is greatly related to the existence of anionic vacancies of sulfur located majorly on the edges of the active phase, since the sulfurs of the basal planes are strongly bonded to permit the formation of these vacancies. Taking into account that the vacancy formation is a crucial step for HDS, we sought to obtain more precise structural information to assist the understanding of this reaction step. Thereby, we presented the study of the formation of the coordenative unsaturated sites on the edge of the molybdenum sulfide supported on MgO. Moreover, we discussed about the interaction between the sulfide and the support by varying the amount of the sulfide layers and the presence of the cobalt atom on the edge. Thereby, we sought to provide structural information on the theoretical models of MoS2 supported on MgO using DFT in order to contribute with studies in this context. In order to do that, we calculated the energy of the vacancy formation, the difference of the charge densities, pDOS and Bader charge analysis. We concluded that the support and the promoting atoms influence the formation of the vacancies on the edge of the molybdenum supported on MgO. The influence of these variables depends on the size of the layer, the proportions of the sulfur atoms on the edge and the type of the interaction of the sulfide on the support. In short, we can confirm that both act to decrease the energy of the vacancy formation, thus contributing to the improvement of this step.
6
Zanotello, Tatiane Cristina. "Adição de fósforo (P) em catalisadores NiMo, suportados em γ-Al2O3, Al2O3/TiO2 e TiO2 - efeito na hidrodessulfurização do tiofeno." Universidade Federal de São Carlos, 2013. https://repositorio.ufscar.br/handle/ufscar/4108.
Full textAbstract:
Made available in DSpace on 2016-06-02T19:56:49Z (GMT). No. of bitstreams: 1
4974.pdf: 3642452 bytes, checksum: 9983d14f77babcbd0c76cb3ef274c7c6 (MD5)
Previous issue date: 2013-02-18Universidade Federal de Sao Carlos
Mo, NiMo or NiMoP HDS catalysts were supported on Al2O3, Al2O3-TiO2 or TiO2. These supports were synthesized via sol-gel and in the case o TiO2 it was used a commercial sample. The active phases were introduced by impregnation. Supports and catalysts in the oxide form were characterized by X-ray diffraction (XRD), diffuse reflectance UV-Vis spectroscopy (DRSUV-Vis), thermogravimetric analyses (TG), temperature-programmed reduction with H2 (TPR-H2), N2 adsorption/desorption, energy dispersive X-ray spectroscopy (EDS), X-ray fluorescence (XRF), temperature-programmed desorption of NH3 (TPD-NH3), high resolution transmission electron microscopy (HRTEM) and evaluated at 300°C in the HDS of thiophene, used as a model molecule. Alumina presented a high specific surface area and meso/macroprous characteristics, allowing a high dispersion of the active phases, as was evidenced by XRD and DRSUV-VIS data. A HRTEM image of a NiMo/Al2O3 catalyst showed the presence of crystalline MoS2 whose activity was substantially promoted by the presence of Ni. The NiMo catalysts were active in the HDS of thiophene, however, the activity was enhanced significantly by the incorporation of P. This result corroborates the positive influence of P in the preparation of HDS catalysts. It was suggested that P must participate as promoter in the formation of the NiMoS phase during the sulfidation process of the Ni and Mo oxides. The supported NiMoP catalysts prepared in this work were more active than a commercial NiMoP/ Al2O3 catalyst, with this result validating the preparation procedures used here. The titania addition in the alumina framework led to NiMo catalysts possessing lower activity. That behavior was attributed to the formation of Ni and Mo sulfides without interaction diminishing the generation NiMoS phase, which is highly active in the HDS of sulfured organic compounds.
Catalisadores para hidrodessulfurização (HDS) contendo Mo, NiMo ou NiMo e o aditivo fósforo (P), foram suportados sobre Al2O3, Al2O3-TiO2 ou TiO2. A alumina e a alumina-titânia foram sintetizadas via sol-gel e, no caso da titânia pura, utilizada uma amostra comercial. A introdução dos sais precursores da fase ativa foi realizada via impregnação. Suportes e catalisadores na forma de óxidos foram caracterizados através de difração de raios X (DRX), espectroscopia por refletância difusa no ultravioleta visível (DRSUV-VIS), termogravimetria (TG), redução com hidrogênio à temperatura programada (RTP-H2), adsorção/dessorção de N2, espectroscopia de energia dispersiva de raios X (EDX), fluorescência de raios X (FRX), dessorção de amônia a temperatura programada (TPD-NH3), microscopia eletrônica de transmissão de alta resolução (HRTEM) e avaliados a 300⁰C na HDS do tiofeno. A alumina apresentou uma alta área superficial específica e características meso/macroporosa, possibilitando alta dispersão das fases ativas, conforme evidenciado por DRX e dados de DRSUV-VIS. A imagem de HRTEM do catalisador NiMo/Al2O3 mostrou a presença de MoS2 cuja atividade foi promovida substancialmente pela presença de Ni. Os catalisadores NiMo sobre os suportes utilizados foram ativos no HDS do tiofeno, entretanto, essa atividade foi melhorada pela incorporação de P. Esse resultado ratifica a influência positiva da utilização desse aditivo na preparação de catalisadores de HDS. O fósforo deve atuar como um promotor na formação de espécies NiMoS durante o processo de sulfetação dos óxidos de Mo e Ni. Os catalisadores NiMoP preparados neste trabalho apresentaram atividade específica superior à de um catalisador NiMoP/Al2O3 comercial, o que valida os procedimentos de preparação utilizados no trabalho. A adição de titânia na alumina durante a síntese sol-gel conduziu a catalisadores com menor atividade. Esse resultado foi atribuído à formação de sulfetos de Ni e Mo não interativos, com a consequente diminuição da formação da fase NiMoS de alta atividade no HDS de compostos organo-sulfurados.
7
Zavala, Sanchez Luz Adela. "Supported metal disulfide (TMS) catalysts for ultra-deep HDS : coupling of IR spectoscopy and microscopy for a deeper insight into active sites." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMC258.
Full textAbstract:
Ce travail de thèse a permis d’obtenir une caractérisation à l’échelle atomique des feuillets (Co)MoS2 et (Ni)WS2 de catalyseurs d’hydrotraitement supportés sur alumine et de déterminer l’impact d’un additif organique, l’acide citrique (CA). Dans cette étude des techniques avancées ont été mises en œuvre telles la caractérisation par adsorption de CO à basse température suivie par spectroscopie IR (IR/CO), des calculs DFT et des observations par microscopie électronique haute résolution en mode transmission et par STEM HAADF.Sur les catalyseurs non promu à base de W et de Mo, l’adsorption de CO permet de discriminer les sites des bords M- et des bords S- des feuillets de TMS. La détermination des coefficients d’extinction molaire des bandes liées au CO adsorbé permet de déduire la morphologie des feuillets. L’HR STEM HAADF confirme que l’addition de CA modifie la morphologie des feuillets TMS d’un triangle tronqué à une forme hexagonal.Sur les catalyseurs promus NiW et CoMo, la microscopie electronique montre que l’addition de CA diminue la taille des feuillets de TMS et conduit aussi à la création de petits clusters (<1 nm). L’analyse de particules isolées par HR STEM HAADF permet d’identifier la nature des atomes du bord du feuillet de TMS. Ainsi la microscopie et l’IR/CO mettent en évidence que au sein d’un même feuillet sulfure peuvent coexister des bords totalement promus, et partiellement promusThis work was focused on obtaining an atomic scale characterization of the (Co)MoS2 and (Ni)WS2 slabs of hydrotreating catalysts supported on alumina and to determine the impact of citric acid (CA) addition. In this study, advanced techniques were implemented such as low temperature CO adsorption followed by IR spectroscopy (IR/CO), DFT calculations and high resolution electron microscopy observations in transmission mode and by STEM HAADF.On the non-promoted W and Mo catalysts, CO adsorption makes it possible to discriminate between the sites of the M- and S- edges of the TMS slabs. The determination of the molar extinction coefficients of the adsorbed CO bands allows the morphology of the slabs to be deduced. HR STEM HAADF confirms that the addition of CA modifies the morphology of the TMS slabs from a truncated triangle to a hexagonal shape.On the promoted NiW and CoMo catalysts, electron microscopy shows that the addition of CA decreases the size of the TMS slabs and also leads to the creation of very small clusters (<1 nm). The analysis of isolated particles by HR STEM HAADF allows identifying the nature of the atoms on the edge of the TMS slabs. Thus microscopy and IR/CO show that within the same sulfide slabs, can coexist edges that are fully promoted and partially promoted
8
Lee, Yong-Kul. "Reactivity and Structure of Supported Nickel Phosphides (Ni2P) in Deep Hydrodesulfurization Catalysis." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/30228.
Full textAbstract:
This dissertation describes preparation and characterization of Ni2P catalysts and their application in deep hydrodesulfurization (HDS) of a model sulfur compound, 4,6-dimethyldibenzothiophene (4,6-DMDBT), one of the most refractory S-compounds. This topic is of great importance in addressing recently enacted environmental regulations limiting the sulfur content in fuels. The work carried out includes synthesis of Ni2P on different siliceous supports, SiO2, MCM-41, and ultra-stable Y zeolite (USY). It also includes determining the characteristics of the supported Ni2P catalysts with a wide range of techniques: X-ray powder diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and X-ray absorption fine structure (XAFS) spectroscopy. The use of these techniques allowed better understanding of the nature of the active sites as well as the effect of supports. Activity tests were conducted in the HDS of 4,6-DMDBT and the HDN of quinoline. The performance of the catalysts will be compared to that of a conventional sulfide hydrotreating catalyst, Ni-Mo-S/Al2O3. Investigation of the reaction mechanism in the hydrodenitrogenation (HDN) of 2-methylpiperidine together with in situ FT-IR measurements were conducted to understand how catalyst properties affect activity and selectivity.Ph. D.
9
Lesage, Clément. "Caractérisation par Quick-XAS operando du rôle de l’additif organique sur le mécanisme de sulfuration en phase liquide des catalyseurs d’hydrotraitement." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS565.
Full textAbstract:
Pour répondre aux normes environnementales relatives à la teneur en soufre des carburants pétroliers et optimiser l’éco-efficience des procédés d’hydrotraitement, un des leviers consiste à mettre au point des catalyseurs de plus en plus performants. Ces dernières années, l’amélioration des performances catalytiques a été possible notamment par l’ajout d’additifs organiques dont le rôle est d’améliorer la dispersion des phases oxydes sur le support catalytique et/ou de complexer les métaux pouvant conduire à leur sulfuration simultanée et favoriser ainsi la formation de catalyseurs plus actifs. Avant son utilisation, le catalyseur peut être activé selon deux méthodes. La première méthode en phase gaz (H₂S/H₂, 1 bar) a largement été utilisée en laboratoire pour étudier l’effet des additifs organiques. Cependant, la seconde méthode en phase liquide (Gazole/H₂/DMDS) sous pression (30 bar) et à 350°C est celle utilisée industriellement. Pour étudier en détail le mécanisme de sulfuration in situ en conditions industrielles des catalyseurs d’HDT additivés, une cellule d’analyse Quick-XAS permettant de reproduire ces conditions opératoires a été développée et validée sur la ligne ROCK du synchrotron SOLEIL. Le Quick-XAS est en effet une technique de choix pour caractériser la structure des phases actives formées pendant cette étape d’activation et ainsi mettre en évidence le rôle des additifs (acide citrique, triéthylène glycol et acide thioglycolique). Cette étude nous a permis d’apporter de nouvelles connaissances pour expliquer les modifications apportées à la phase active pendant la sulfuration en phase liquide et leur effet sur les performances catalytiques. En complément, le couplage des spectroscopies Raman et d’absorption des rayons X mises en œuvre sur les catalyseurs oxydes a permis une meilleure compréhension du rôle des additifs organiques étudiés dès l’étape de synthèse des solidesTo meet the environmental standards on the sulfur content in fuels and improve the eco-efficiency of hydrotreatment processes, one lever is to develop more and more efficient catalysts. In the last years, the improvement of catalytic performances has been made possible by the addition of organic additives whose role is to improve the dispersion of the oxide precursors on the support and/or create a complex with the metals, which could lead to a simultaneous sulfidation and to a more active catalyst. Before its use, the catalyst may be activated via two different methods. The first one with a gas mixture (H₂S/H₂, 1 bar), was largely used at the laboratory scale to study the effect of organic additives. However, the second activation method with a liquid phase (Gasoil/H₂/DMDS) under 30 bar at 350°C is the one used at the industrial scale. To study in situ the sulfidation mechanism of additivated HDT catalysts in industrial conditions, a Quick-XAS analytical cell was developed and validated on the ROCK beamline at the SOLEIL synchrotron. Quick-XAS is a technique of choice to characterize the formation of the active phase during the activation procedure and therefore evidence the role of organic additives (citric acid, triethyleneglycol, thioglycolic acid). This study has provided us with new knowledge to explain the changes observed in the active phase during liquid phase sulfidation and their effect on catalytic performance. In addition, coupling the Raman spectroscopy and the absorption spectroscopy to study the oxide phase has led to a better understanding of the role of the organic additives studied from the solid synthesis stage
10
Vasconcelos, SebastiÃo Junior Teixeira. "Catalysts from hydrotalcite dopped with copper in chemical transformation of glycerol." Universidade Federal do CearÃ, 2014. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=14604.
Full textAbstract:
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoThe hydrotalcites are a class of layered double hydroxides with important physical and chemical properties. The use of this class of compounds in catalysis of specific reactions also requires many studies. The literature has exploited these materials in catalytic reactions in liquid phase with glycerol, particularly in hydrogenolysis reactions. The gas phase reactions with glycerol usually make use of acid catalysts. Thus, both the liquid phase reactions involving catalysts derived from hydrotalcite-like gas phase reactions involving basic catalysts require further study. We developed a study to elucidating the combined effects of basic catalytic sites (MgO and amorphous aluminum oxide) and dehydrogenation (derived from copper oxides) in the hydrogenolysis reaction. The materials used were derived from hydrotalcite oxides, and oxides derivatives containing in its composition 2.5% copper (molar ratio) in relation to the metal network hydrotalcite (Mg and Al). The results obtained for the gas phase show an interrelationship between the sites and the major products of the reaction, acetol and acrolein. Was determined conditions under which one or another product is more favored, with conversions that can reach over 90% and selectivities that exceed 99%. In the liquid phase this interrelationship is more difficult to be demonstrated, given the complications arising from the greater contact time between catalyst and reactants to the point of the major products at the reaction gas phase includes both as reaction intermediates in the liquid phase. In the liquid phase, the predominant carbon chain compounds of higher alcohol and ester functional groups, cyclic compounds but also from various functional groups.
As hidrotalcitas sÃo uma classe de hidrÃxidos duplos lamelares com importantes propriedades fÃsico-quÃmicas. O emprego desta classe de compostos na catÃlise de reaÃÃes especÃficas requer, ainda, muitos estudos. A literatura tem explorado estes materiais na catÃlise das reaÃÃes com glicerol em fase lÃquida, principalmente, em reaÃÃes de hidrogenÃlise. As reaÃÃes em fase gasosa com glicerol normalmente fazem uso de catalisadores Ãcidos, de modo. Deste modo, tanto as reaÃÃes em fase lÃquida envolvendo catalisadores derivados da hidrotalcita como reaÃÃes em fase gasosa envolvendo catalisadores bÃsicos requerem maiores estudos. Desenvolveu-se um estudo com vistas a elucidaÃÃo dos efeitos combinados de sÃtios catalÃticos bÃsicos (MgO e Ãxidos de alumÃnio amorfo) e desidrogenante (Ãxidos derivados do cobre) na reaÃÃo de hidrogenÃlise. Os materiais empregados foram Ãxidos derivados da hidrotalcita, e Ãxidos derivados contendo em sua composiÃÃo 2,5% cobre (proporÃÃo molar) em relaÃÃo aos metais da rede hidrotalcita (Mg e Al). Os resultados obtidos para a fase gasosa evidenciam uma inter-relaÃÃo entre os sÃtios e os produtos majoritÃrios da reaÃÃo, acetol e acroleina. Determinou-se condiÃÃes em que um ou outro produto à mais favorecido, com conversÃes que podem chegar a mais de 90% e seletividades que superam 99%. Em fase lÃquida esta inter-relaÃÃo à mais difÃcil de ser evidenciada, dadas as complicaÃÃes originadas pelo maior tempo de contato entre catalisador e reagentes a tal ponto dos produtos majoritÃrios verificados na reaÃÃo fase gasosa figurarem como intermediÃrios da reaÃÃo em fase lÃquida. Na fase lÃquida, predominam compostos de maior cadeia carbÃnica dos grupos funcionais Ãlcool e Ãster, mas tambÃm compostos cÃclicos de grupos funcionais diversos.
11
Illesinghe, Jayamini P. M. "Synthesis and use of nitrogen heterocycles in metal mediated reactions." Monash University, School of Chemistry, 2004. http://arrow.monash.edu.au/hdl/1959.1/9637.
Full text
12
Hantzer, Sylvain. "Nouveaux materiaux pour la reaction d'hydrodesulfuration (hds)." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13120.
Full textAbstract:
Nouveau modele de phase active obtenu par interpretation des resultats de rmn du **(59)co et de microscopie electronique haute resolution pour des catalyseurs d'hydrotraitement a base de sulfure de molybdene et de cobalt. Application a d'autres systemes : nire, core, rhre et rhmo. Etude de l'empoisonnement par la porphyrine de catalyseur nimo/al::(2)o::(3)
13
Dumeignil, Franck. "CATALYSE ET ENVIRONNEMENT : DEVELOPPEMENT ET AMELIORATION DE PROCEDES D'HDN & HDS / ETUDE DU COMPORTEMENT DES PHASES ACTIVES IN SITU." Habilitation à diriger des recherches, Université des Sciences et Technologie de Lille - Lille I, 2005. http://tel.archives-ouvertes.fr/tel-00098387.
Full textAbstract:
Les gouvernements et l'opinion publique ont maintenant nettement pris conscience de l'absolue nécessité d'utiliser plus rationnellement et parcimonieusement les énergies fossiles, et plus particulièrement les carburants commerciaux. On distingue deux aspects essentiels à cette problématique : l'aspect écologique avec la nécessité de proposer des carburants plus ‘propres' (au travers notamment du couple interdépendant désulfuration/déazotation), et l'aspect énergétique avec la nécessité d'économiser au maximum les carburants fossiles tout en développant l'utilisation de nouvelles sources d'énergie alternatives, ce deuxième aspect étant aussi étroitement lié à la nécessité de diminuer les émissions de CO2 afin d'enrayer l'effet de serre.Dans ce contexte, les travaux de recherche effectués en France et au Japon présentés dans cet exposé portent essentiellement sur l'amélioration des procédés de désulfuration/déazotation des coupes pétrolières. En outre, des travaux de recherche plus récemment entamés constituent une ouverture vers le développement des nouvelles technologies en rapport avec l'utilisation de l'hydrogène comme nouveau vecteur d'énergie du 21ème siècle.
De nouvelles techniques de caractérisation in situ des phases actives ont été mises au point afin d'avoir une meilleure connaissance des modes de fonctionnement des catalyseurs d'hydrotraitement, ce qui a permis de mieux cibler les stratégies à mettre en œuvre pour leur amélioration. Les catalyseurs d'hydrotraitement ont été améliorés grâce à l'utilisation de nouveaux supports pour les phases actives conventionnelles à base de MoS2. De plus, les performances de nouvelles phases actives à base de métaux nobles ont aussi été évaluées. Enfin, de nouvelles technologies de purification de ces coupes pétrolières à basse consommation d'énergie ont été développées, i) la biodéazotation à l'aide d'une nouvelle bactérie, et ii) l'oxy-désulfuration/oxy-déazotation, lesquelles se sont montrées particulièrement efficaces.
Par ailleurs pour répondre à la demande croissante d'hydrogène tout en valorisant des déchets particulièrement réfractaires aux procédés de recyclage, un procédé de production d'hydrogène par réformage à la vapeur de déchets de PVC est en cours d'élaboration. Parallèlement, nous tentons actuellement de comprendre le mode de stockage/déstockage de l'hydrogène dans les oxydes mixtes (technologie propre au LCL) à l'aide de diverses techniques de caractérisations physico-chimiques.
14
Teoh, Euneace Ching Mei. "Synthesis of amino acids by metal-catalysed reactions." Monash University, School of Chemistry, 2004. http://arrow.monash.edu.au/hdl/1959.1/9633.
Full text
15
Leung, Yin-Ling. "Surface studies of planar model HDN catalysts." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ34576.pdf.
Full text
16
Baubet, Bertrand. "Influence de la morphologie 2D de la phase active sur la sélectivité des catalyseurs sulfures en HDS des essences." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10067.
Full textAbstract:
Ce travail de thèse étudie l’influence de la morphologie des feuillets de sulfure de molybdène sur la sélectivité des catalyseurs d’hydrotraitement. Les feuillets de phase active présentent en effet deux types de bords appelés « M-edge » et « S-edge » susceptibles de conduire à des réactivités différentes. Le changement de la morphologie 2D des feuillets pourrait modifier les proportions de bords M et S exposés et ainsi les propriétés catalytiques des catalyseurs sulfures. Pour cela, des catalyseurs non promus (Mo) et promus (CoMo), supportés sur alumine ont été préparés par imprégnation à sec puis sulfurés dans des conditions variées (gaz et température). Des tests catalytiques en hydrodésulfuration (HDS) sélective des essences de FCC (sélectivité HDS/HYD) ont ensuite permis d’évaluer l’impact de la morphologie en s’appuyant sur des modèles géométriques construits à partir de calculs DFT et de caractérisations expérimentales (TEM, IR (CO), TPR, XPS). Les résultats obtenus pour les catalyseurs de type Mo semblent ainsi confirmer l’influence de la morphologie 2D sur la sélectivité HDS/HYD, le bord M paraissant être le plus sélectif pour les catalyseurs non promus. Ils mettent également en évidence l’importance de la réductibilité plus ou moins marquée des bords sur les propriétés catalytiques, notamment sur le bord M. Le changement des conditions de sulfuration semble donc affecter la morphologie des particules mais également les propriétés chimiques propres à chaque bord. En ce qui concerne les catalyseurs promus, la variation des conditions de sulfuration semble agir essentiellement au niveau de la répartition du promoteur entre les bords M et S. Cependant, les interactions avec le support paraissent constituer un frein aux effets de promotion. Dans ce contexte, les sulfurations à haute température sous H2S pur permettent d’obtenir des gains significatifs en activité et sélectivité. Ces résultats semblent dus à de faibles interactions avec le support et une décoration privilégiée du bord S qui pourrait favoriser la réaction d’HDS et limiter la réaction d’HYD. Au final, les interprétations effectuées en terme de morphologie 2D tendent à confirmer que ce paramètre peut constituer un axe de développement intéressant pour les catalyseurs d’hydrotraitement. L'optimisation des conditions de sulfuration permettraient bien de faire varier la morphologie et le taux de décoration du promoteur des catalyseurs, améliorant ainsi significativement l'activité et la sélectivitéThis thesis examines the influence of the morphology of particles of molybdenum sulfide on selectivity of hydrotreating catalysts. Nanoparticles of active phase present two types of edges called “M-edge” and “S-edge” which may lead to different reactivities. The change in morphology of the 2D sheets could change the proportions of M and S edges exposed and thus the catalytic properties of sulfide catalysts. For this, non-promoted (Mo) and promoted (CoMo) catalysts, supported on alumina were prepared by dry impregnation and sulfide in various conditions (gas and temperature). Catalytic tests in selective hydrodesulfurization (HDS) of FCC gasoline (selectivity HDS /HYD) were then used to assess the impact of the morphology based on geometrical models which were constructed with DFT calculations and experimental characterizations (TEM, IR (CO), TPR, XPS). The results for Mo catalysts seem to confirm the influence of the 2D morphology selectivity HDS / HYD, M-edge appearing to be the most selective for non-promoted catalysts. They also highlight the importance of the reducibility more or less pronounced of the edges on the catalytic properties, especially on the M-edge. The different conditions of sulfidation seem to affect the morphology of the particles but also the specific chemical properties at each edge. Regarding to the promoted catalysts, the different conditions of sulfidation appear to act primarily at the distribution of the promoter between the M and S edges. However, interactions with the carrier appear to constitute an obstacle to promoting effects. In this context, sulfidations at high temperature in pure H2S lead to obtain significant gains in activity and selectivity. These results appear to be due to weak interactions with the carrier and to the presence of the promoter on the S-edge which could promote the HDS reaction and limit the HYD reaction. Finally, the interpretations made in terms of 2D morphology tend to confirm that this parameter can be an interesting line of development for hydrotreating catalysts. Optimization of the sulfidation conditions could effectively allow to vary the morphology and the rate of decoration of promoted catalysts which significantly improve the activity and selectivity
17
Catherin, Nelly. "Selective ring opening of naphthenes over bifunctional catalysts in the presence of H2S." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1246.
Full textAbstract:
L'ouverture sélective de cycle (OSC) d'hydrocarbures polycycliques vise à augmenter le nombre de cétane des carburants diesel. OSC efficace peut être atteint par l'hydroconversion sur des catalyseurs bifonctionnels métal noble/fonction acide. La décaline et, à plus faible mesure, le perhydroindane, le butylcyclohexane et la tétraline, ont été utilisés comme molécules modèles pour l'étude des l'OSC de sulfures de métaux de transition (TMSs) supportés sur zéolithes ou silice-alumine amorphe dans un réacteur à lit fixe sous haute pression (5 MPa) avec une concentration élevée d'H2S dans la charge réactionnelle (1 %). Les nombreux produits d'hydroconversion ont été identifiés grâce à la chromatographie gazeuse bidimensionnelle, qui nous a permis de mieux comprendre les mécanismes de réaction. Ce travail a consisté à l'étude de la nature et la charge du SMT et la nature du support. Comparé à la zéolithe seule, le catalyseur RuSx/HY (qui sert de référence) est plus stable et dix fois plus actif avec une sélectivité en produits d'ouverture proche des 30% à 240 °C. Les produits les plus abondants restent les produits d'isomérisation, ce qui suggère que l'acidité du support domine le schéma réactionnel. Quant à l'ajout de TMS, leur rôle est d'activer l'hydrogène, de favoriser les réactions d'hydrogénation/déshydrogénation et limiter le cokage des sites acides. NiSx/HY est aussi performant que les catalyseurs à base de Ru, Ir ou Rh et un effet de synergie est observé pour les catalyseurs ternaires Ni-Ru et Ni-Rh. Toutefois, comparé aux métaux nobles comme l'Ir et le Ru étudiés sans H2S, les catalyseurs sulfures sont quasiment non-hydrogénolysants. Enfin, la zéolithe HY présente des performances proches a la H-Beta mais avec moins de craquageThe selective ring opening (SRO) of polycyclic hydrocarbons aims at increasing the cetane numbers of diesel fuels. Efficient SRO can be achieved through hydroconversion over bifunctional noble metal/acid catalysts. Decalin and, to lower extents, perhydroindan, butylcyclohexane and tetralin, have been used as model molecules to investigate the SRO performances of transition metal sulfides (TMSs) supported on zeolites or amorphous silica-alumina in a high-pressure (5 MPa) flow-fixed bed reactor with a high concentration of H2S in the reactant feed (1 %). The numerous hydroconversion products have been identified using comprehensive two-dimensional chromatography for various levels of reactant conversions, which allowed us to gain insight into the reaction mechanisms. The presence, loading and nature of the TMS, and the nature of the support, have been investigated. With respect to the bare HY zeolite, RuSx/HY (which served as our reference) is more stable and ten times more active, with a ring-opening selectivity of up to 30 % at 240 °C. The most abundant products are skeletal-isomerization ones, which suggests that the acidic support dominates the reaction scheme. The TMS role is to activate hydrogen, catalyze hydrogenation/ dehydrogenation and prevent the coking of acidic sites. NiSx/HY performs similarly to Ru, Ir and Rh-based catalysts, and a synergetic promoting effect is observed for Ni-Ru and Ni-Rh combinations. However, with respect to noble metals such as Ir and Ru under H2S-free conditions, the sulfide counterparts appear much less (if not) hydrogenolytic. As compared to HY, the H-Beta support shows similar performance but promotes cracking
18
Lec, Jean-Christophe. "Les thioltransférases, des agents doubles impliqués dans le métabolisme du sulfure d’hydrogène : de la catalyse aux rôles physiologiques." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0305.
Full textAbstract:
Les 3-mercaptopyruvate sulfurtransférases (3-MST) et les thiosulfate sulfurtransférases (TST) sont des enzymes ubiquitaires de la famille des thioltransférases à domaine rhodanèse qui catalysent le transfert d’un atome de soufre d’un substrat donneur vers un substrat accepteur via un intermédiaire Cys-persulfure. Les 3-MST sont impliquées dans la formation de sulfure d’hydrogène (H2S), un gazotransmetteur toxique à forte concentration, alors que les TST interviendraient dans son élimination. L’objectif de mon projet était de décrypter les mécanismes moléculaires impliquant ces thioltransférases afin de mieux comprendre leurs rôles physiologiques. Pour cela, le mécanisme catalytique et les spécificités de substrats des enzymes humaines (3-MST, TSTD1 et Rhodanèse) et d’Escherichia coli (3-MST et GlpE) ont été caractérisés grâce à la mise au point de méthodes spécifiques permettant l’étude de chacune des étapes du mécanisme (fluorescence, stopped-flow, sonde H2S) et par une étude des relations structure-fonction menée en collaboration pour les aspects chimie théorique et cristallographie RX. J’ai montré que le site actif de ces enzymes est adapté à la catalyse d’un transfert de S0 à partir de composés soufrés non activés. De plus, le mécanisme de formation de l’intermédiaire persulfure ne dépend pas de l’enzyme mais du substrat donneur. En effet, la rupture de la liaison C-S du 3-mercaptopyruvate requiert la déprotonation des fonctions thiols du substrat et de la Cys essentielle, fonction assurée par la boucle catalytique CysX5 qui constitue un véritable site de reconnaissance thiolate, et l’intervention concomitante d’une molécule d’eau comme catalyseur acide. En présence de thiosulfate, hormis l’activation de la Cys seule la neutralisation des charges négatives du substrat est indispensable à la réaction de transfert de soufre. Enfin, et de façon inattendue, la 3-MST humaine pourrait être impliquée dans l’élimination cytosolique du sulfite, un composé toxique pour les cellules. Quant aux deux TST mitochondriales humaines, elles pourraient intervenir à la fois dans la signalisation cellulaire H2S-dépendante, via la production d’espèces polysulfure, et dans l’élimination d’H2S3-mercaptopyruvate sulfurtransferases (3-MSTs) and thiosulfate sulfurtransferases (TSTs) are ubiquitous enzymes that belong to the rhodanese sulfurtransferase family and catalyze the transfer of a sulfur atom from a donor to an acceptor substrate via a cysteine-persulfide intermediate. While 3-MSTs are involved in the biogenesis of hydrogen sulfide (H2S), a gasotransmitter known to be toxic at high concentration, TSTs are likely responsible of its degradation. My project mainly focused on deciphering the sulfurtransferase-dependent molecular mechanisms to better define their physiological functions. To address these questions, their catalytic mechanisms and substrate specificities were investigated. This was achieved through the development of kinetic approaches (fluorescence, stopped-flow, H2S specific probe) to study each step of the reaction catalyzed by human (3-MST, TSTD1 and Rhodanese) and Escherichia coli (3-MST, GlpE) enzymes and structure-function relationship studies performed in collaboration for the theoretical chemistry and the X-ray crystallography parts. Here, I show that the active site of these enzymes is optimized to perform an efficient S0 transfer from non-activated sulfur compounds. Moreover, the mechanisms leading to formation of the persulfide intermediate do not depend on the enzyme but rather on the donor substrate. Indeed, the cleavage of the carbon-sulfur bond of 3-mercaptopyruvate critically depends on the CysX5 catalytic loop acting as a thiolate hole to favor the deprotonation of the essential Cys and the substrate, and on a water-mediated protonation step. In the presence of thiosulfate, the Cys activation mode remains unchanged and the reaction of sulfur transfer is only driven by the neutralization of the negative charges of the substrate. In addition, we propose a new physiological function for the human 3-MST in the cytoplasmic elimination of sulfite, a toxic compound for the cells. Finally, the two human mitochondrial TSTs are likely to be involved in the H2S-mediated cellular signaling, through the formation of polysulfide entities, but also in H2S catabolism
19
Thompson, Scott Damon 1976. "Electrodeposition of platinum-based catalysts for polymer electrolyte membrane fuel cells." Monash University, School of Physics and Materials Engineering, 2003. http://arrow.monash.edu.au/hdl/1959.1/5668.
Full text
20
Jackson, Dominic. "Organic functionalisation of hexagonal mesoporous silica." Thesis, University of York, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341112.
Full text
21
Szakal, Andrea L. Bevilacqua Philip C. "The hepatitis delta virus (HDV) ribozyme as a model for RNA catalysis and folding." [University Park, Pa.] : Pennsylvania State University, 2008. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-2700/index.html.
Full text
22
Krebs, Emmanuel. "Modélisation moléculaire ab initio des effets de morphologie en catalyse par les sulfures." Paris 6, 2008. http://www.theses.fr/2008PA066174.
Full textAbstract:
L'un des procédés catalytiques du raffinage du pétrole, essentiel pour l'obtention de carburants propres (essence) vise à sélectivement hydrodésulfurer (HDS) les molécules soufrées (thiophènes) en évitant l’hydrogénation des molécules oléfiniques (HydO), afin de préserver l’indice d’octane des essences. La phase active des catalyseurs d'HDS est composée d'une phase disulfure de molybdène (MoS2), promue par du Co ou du Ni, et appelée "Co(Ni)MoS". La compréhension à l'échelle moléculaire de l’origine de la sélectivité HDS/HydO est l'enjeu de cette thèse. A l'aide de la modélisation moléculaire ab initio couplé à des modèles thermodynamiques, nous étudions premièrement la nature des sites actifs et la morphologie des phases Co(Ni)MoS en milieu réactionnel (HDS). Nous proposons, ensuite, une interprétation de la sélectivité HDS/HydO basée sur l'adsorption sélective de deux réactifs modèles (thiophénique et oléfinique) en fonction des conditions d'HDS. Le rôle clef des promoteurs est mis en évidence. Une interprétation électronique de l'adsorption des molécules est fournie.
23
Lima, Rubens William dos Santos. "Hidrodesoxigenação de bio-óleos utilizando catalisadores de níquel e molibdênio suportados em sílica mesoporosa SBA-15." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-07112017-153010/.
Full textAbstract:
Uma das desvantagens dos bio-óleos precursores do biodiesel é a alta carga de compostos oxigenados que diminuem seu poder de combustão, reduzindo sua eficiência e inviabilizando seu uso em larga escala. Nesse contexto, o processo de hidrodesoxigenação (HDO) é relevante, dado que elimina esses compostos através de uma reação catalítica e, portanto, aumenta o poder calorífico do combustível. Neste trabalho, estudou-se a HDO do guaiacol (2-metoxifenol) como composto modelo dos bio-óleos derivados da biomassa e avaliou-se o desempenho de catalisadores de Ni e Mo no processo. Estudou-se a performance de um catalisador suportado em SBA-15 - um material mesoporoso de sílica de alta área superficial - em comparação a de um catalisador tradicional suportado em gama-alumina. Para tal, utilizou-se um sistema contínuo em fase gasosa e reator de leito fixo. Utilizaram-se técnicas de caracterização de catalisadores, como adsorção de N2, MEV, MET, DRX, TPR-H2, FTIR, TPO-O2, Raman e TGA. Através das análises DRX e MET, comprovou-se que se formaram partículas de NiO e MoO3 de menor tamanho e mais dispersas no caso do catalisador de SBA-15, devido à menor interação com o suporte e maior área superficial, o que resultou em um grau de redução de 91,6 % deste catalisador, em comparação a 73,4 % do outro, analisados por TPR-H2. Os testes catalíticos mostraram que o catalisador de NiMo/SBA-15 supera o de alumina em termos de conversão no intervalo de 200 a 300 °C, com ciclohexeno e ciclohexano como principais produtos, em face à maior seletividade a catecol e fenol no NiMo/?-Al2O3. A 300 °C, o catalisador suportado em sílica alcançou taxas de 66,5 % para a HDO e 35,3 % HDA (hidrodesaromatização), enquanto o de alumina obteve somente 30,8 e 2,7 %, respectivamente. Finalmente, comprovou-se que o SBA-15 teve uma taxa de desativação por coque de 1,14 mgcoque gcat-1 h-1, 31 % menor que a taxa do catalisador de alumina, cujos depósitos foram de carbono grafítico bem estruturado e irreversível. Em vista dos resultados obtidos, esta dissertação apresenta as rotas e mecanismos de reação do guaiacol nos catalisadores estudados, conhecimento que é relevante para o desenvolvimento e aprimoramento de futuros catalisadores da HDO.A key disadvantage of the bio-oils precursors of biodiesel is the high load of oxygenated compounds that reduce their heat of combustion, dropping their efficiency and making them unfeasible on a large scale. In light of that, the hydrodeoxygenation process (HDO) is relevant, since it eliminates these compounds through a catalytic reaction, thus increasing the calorific value of the fuel. In this work, the HDO of guaiacol (2-methoxyphenol) as a model compound of the bio-oils derived from biomass was studied and the performance of Ni-Mo catalysts was evaluated. A catalyst supported on SBA-15 - a high surface area mesoporous silica material - was compared to a traditional gamma-alumina-supported catalyst. For this purpose, a continuous gas phase setup with fixed bed reactor was employed. The catalysts properties were identified by N2 adsorption, SEM, TEM, XRD, H2-TPR, FTIR, O2-TPO, Raman and TGA techniques. Through XRD and TEM, it was verified that smaller and more dispersed NiO and MoO3 particles were formed in the case of the SBA-15 catalyst, due to the lower interaction with the support and the greater surface area, which resulted in a degree of reduction of 91.6% for this catalyst, as opposed to 73.4% for the other one, both analyzed by H2-TPR. The catalytic tests showed that the NiMo/SBA-15 outperforms the alumina catalyst in terms of conversion in the range of 200 to 300 °C, with cyclohexene and cyclohexane as main products, in contrast with major selectivity to catechol and phenol on NiMo/?-Al2O3. At 300 °C, the silica-supported catalyst achieved rates of 66.5% for HDO and 35.3% for HDA (hydrodearomatization), whereas alumina reached only 30.8 and 2.7%, respectively. Finally, it was shown that the SBA-15 catalyst had a coke deactivation rate of 1.14 mgcoke gcat-1 h-1, 31% lower than the alumina catalyst, whose coke deposits consisted of well-structured irreversible graphitic carbon. In view of the results, this dissertation proposes the routes and reaction mechanisms of guaiacol on the studied catalysts, knowledge that is pertinent for the development and improvement of future HDO catalysts.
24
Duong-Viet, Cuong. "Synthesis and processing of nitrogen-doped carbon nanotubes as metal-free catalyst for H2S selective oxidation process." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAF029/document.
Full textAbstract:
Les nanotubes de carbone (NTCs) dopés avec différents hétéroéléments tels que l'oxygène et l'azote connaissent un intérêt croissant dans le domaine de la catalyse hétérogène comme leur utilisation en tant que catalyseur sans métaux. L'objectif de cette thèse consiste à la synthèse et la caractérisation de matériaux catalytiques à base de NTC dopés à l'azote supportés sur du carbure de silicium SiC par voie in situ (CVD) et ex-situ méthodes. Une autre approche a été utilisée pour la fonctionnalisation de la surface des nanotubes de carbone et basées sur l'utilisation d'un agent oxydant (HNO3) en phase gazeuse. Ce procédé d'oxydation crée non seulement des défauts sur la surface des nanotubes de carbone mais également décore leur surface avec des groupes fonctionnels oxygénés. Les NTCs dopés à l'oxygène et à l'azote ainsi synthétisés ont été caractérisés par différentes techniques (XPS, MEB, MET, BET, ATG). Ces catalyseurs carbonés présentent des performances remarquables en termes d'activité et de sélectivité en soufre, et une très grande stabilité sous flux en fonction du temps dans la réaction d'oxydation partielle de l'H2S en soufre élémentaire, et ce, même à vitesse spatiale de gaz élevée (WHSV) et faible rapport O2/H2S. L'influence des différentes propriétés physico-chimiques et les défauts présents sur la surface des NTC sur les performances catalytiques ont été étudiée et discutée dans le cadre de ce travailCarbon nanotubes (CNTs) containing different doping such as oxygen and nitrogen composites have received more and more scientific attention as metal-free catalyst in the field of heterogeneous catalysis. The aim of this thesis is related to the synthesis and characterization of nitrogen-doped CNTs decorated on SiC support using both in-situ (CVD with NH3) and ex-situ (N@C) methods. Other approach was employed for the surface functionalization of CNTs is based on the use of oxidative agent (HNO3) in gas phase. This oxidation process not only creates defects on the CNTs surface but also decorates their surface with oxygenated functional groups. The as-synthesized oxygen- and nitrogen-doped CNTs are characterized by different techniques (XPS, SEM, TEM, BET, TGA). The carbon based catalysts exhibit outstanding performances in term of activity and sulfur selectivity, and very high stability with time on stream in the partial oxidation of H2S into elemental sulfur even at high gas space velocity (WHSV) and low O2-to-H2S molar ratio. The influence of the physical-chemical properties and defects present on the CNTs surface on the catalytic performance was thoroughly investigated and discussed within the framework of this work
25
Michaux, Olivier. "Etude de la réactivité des sulfures métalliques pour la réaction d'hydrodésulfuration (HDS) une application de la RMN du métal solide à la catalyse." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb375996435.
Full text
26
Michaux, Olivier. "Etude de la reactivite des sulfures metalliques pour la reaction d'hydrodesulfuration (hds) : une application de la rmn du metal solide a la catalyse." Université Louis Pasteur (Strasbourg) (1971-2008), 1986. http://www.theses.fr/1986STR13073.
Full textAbstract:
Proposition d'un nouveau modele de surface active grace a l'utilisation de la rmn du cobalt 59 et a l'activite des sulfures de tous les metaux de transitions. Proposition d'un nouveau modele pour l'empoisonnement des catalyseurs hds par le vanadium
27
Berro, Youssef. "Élaboration de formulations catalytiques optimisées pour la valorisation de la biomasse par une approche combinée Théorie/Expérience." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0137.
Full textAbstract:
La valorisation de la lignine par pyrolyse produit des bio-huiles à haute teneur en oxygène. Ces bio-huiles sont valorisées par hydrodésoxygénation (HDO) pour obtenir des molécules non-oxygénées. Notre étude vise à élaborer de nouvelles catalyseurs en combinant les calculs de la théorie de la fonctionnelle de la densité (DFT) et les études expérimentales. L'HDO peut se faire suivant l'hydrogénation du cycle aromatique avant la rupture C-O (HYD) ou la rupture directe du C-O, désoxygénation directe (DDO). Le Fe/silice montre une bonne activité et sélectivité en aromatiques. Ainsi, nous développons ce type des catalyseurs afin de favoriser la voie DDO, augmenter la production d’aromatiques et limiter la consommation d’H2. Les énergies d'adsorption du phénol et de molécules inhibitrices sur les surfaces de silice, ayant différentes densités et types de silanols, ont été obtenues par DFT. Trois modes d'interaction du phénol ont été étudiés: O-perpendiculaire, π-plat et O-plat. Sur la silice amorphe, des énergies d'adsorption plus élevées ont été mises en évidence pour le mode O-plat, et une interaction spécifique de 120 kJ/mol (liaison C-Si et déformation du phénol) est observée. La compétition du CO est négligeable sur toutes les surfaces, ce qui rend la silice plus attractive que les catalyseurs sulfurés. Par conséquent, ces résultats motivent la synthèse de catalyseurs sur silice avec une densité de silanol allant de 2 à 4 OH/nm2. Des "Single Atom Catalysts SACs" de Fe/silice ont été élaborés en utilisant des tensioactifs non-ioniques/métalliques. La distribution des atomes de fer dans les micelles mixtes P123/CTAF permet la dispersion fine de ces atomes sur les mésopores de la silice. L'absence d'agrégats de fer a été confirmée par les mesures synchrotrons PDF, RMN, magnétiques, et STEM. Les calculs DFT+U ont confirmé que ces atomes sont principalement du Fe(III) à haut spin. Cette méthode augmente le nombre de sites actifs, ce qui améliore la performance catalytique. Cependant, les résultats catalytiques n’ont pas été satisfaisants à cause de la difficulté à réduire le Fe(III).Les catalyseurs Fe et bimétalliques Fe-Cu synthétisés par imprégnation ou co-précipitation avec décomposition thermale d'urée ont été testés pour l’HDO du guaiacol. Fe-Cu/SiO2 présente une meilleure performance (90% conversion, 70% sélectivité) que les catalyseurs Fe car l’incorporation de cuivre facilite la réduction du ferLignin pyrolysis produces oxygenated bio-oils with poor fuel efficiency. Hence, they are upgraded through hydrodeoxygenation (HDO) leading to the production of oxygen-free molecules and water as by-product. Our objective is to elaborate new catalysts for HDO by combining Density Functional Theory (DFT) calculations with experimental studies. HDO includes two deoxygenation routes: hydrogenation of aromatic ring before C-O cleavage (HYD) or direct C-O cleavage - Direct DeOxygenation (DDO). Fe@silica catalysts show a good activity and selectivity toward aromatics. Thus, our work focused on designing such catalysts that promote DDO in order to increase aromatics production under lower H2 pressure. The adsorption energies of phenol and inhibitors (CO and water) over silica surfaces, having various silanol densities and types, were computed by DFT. Three interaction modes were investigated: “perpendicular O-int”, “flat π-int”, and “flat O-int”. For amorphous silica, the highest adsorption energies were found for the “flat O-int” mode, and a specific interaction of 120 kJ/mol (with a C-Si bond and phenol deformation) was observed for surfaces with a silanol density between 2 and 3.3 OH/nm2. CO competitive adsorption is negligible for all silica surfaces, which make them more attractive than conventional sulfide catalysts. Hence, these results motivated the synthesis of silica-supported catalysts with a silanol density between 2 and 4 OH/nm2. Single iron atom catalysts (SACs) supported on silica were elaborated using non-ionic/metallic surfactants. Iron distribution within mixed P123/CTAF micelles, used as templates, allows the fine dispersion of those atoms within silica mesopores. The lack of iron clusters was confirmed by synchrotrons PDF, STEM mapping, magnetic and NMR measurements. DFT+U calculations confirmed that those atoms are predominately present as high spin Fe(III). This method increases the number of active sites, which improves the catalytic performance. However, the results of catalytic tests were unsatisfactory due to the difficulty of Fe(III) reduction. Metallic (Fe & Cu) and bimetallic (Fe-Cu) catalysts, synthesized by simple impregnation or through the co-precipitation method with thermal decomposition of urea, were tested for guaiacol HDO conversion. Results proved that bimetallic Fe-Cu have a better performance (90% conversion, 70% selectivity) than Fe-based catalysts since Cu incorporation facilitates the reduction of Fe(III)
28
Tahri, Abdelali. "Propriétés électriques et réactivité du molybdate de nickel NiMoO4 synthétisé par réaction solide-solide : étude de la réduction (H2) et de la sulfuration (H2S/H2) par thermogravimétrie." Dijon, 1991. http://www.theses.fr/1991DIJOS018.
Full textAbstract:
Le molybdate de nickel NiMoO4 a été synthétisé par réaction solide-solide à partir des oxydes pulvérulents NiO et MoO3. La conductivité électrique du molybdate de nickel a été mesurée sur des céramiques dans le domaine de température 400-800° C. L'existence de deux variétés polymorphiques a et b-NiMoO4 est confirmée. La température de transition (T=690°C) correspond au changement de symétrie du molybdène qui passe de site Oh à Td. Le transport électrique pour les deux variétés a lieu selon un mécanisme classique de conduction par bande. La variété b-NiMoO4 se comporte comme un semiconducteur de type p dans le domaine 450-650°C avec une énergie d'activation de 1,3 eV. La variété a-NiMoO4 présente deux régimes de conduction : 1) dans son domaine métastable de température (450-650°C), c'est un semiconducteur de type p (Ea=1,3 eV), 2) à plus haute température (t>700°C), c'est un semiconducteur de type n avec une énergie d'activation plus grande (Ea=1,87 eV). L'étude cinétique de la réaction de sulfuration et l'analyse de produits de réaction nous a permis de proposer un mécanisme de sulfuration de ce molybdate qui peut se résumer ainsi : oxyde > oxysulfure > sulfure. L'étude cinétique de la réaction de réduction montre que la réduction par l'hydrogène des deux variétés a et b-NiMoO4 obéit à la loi 1-(1-alpha)1/3 = kt qui traduit un mécanisme contrôlé par une progression d'interface en symétrie sphérique. L'analyse par spectroscopie de photoélectrons XPS (ou ESCA) des produits de la sulfuration et de la réduction de NiMoO4 confirme l'existence d'un oxysulfure et permet de mettre en évidence du nickel métallique non décelé par diffraction des rayons X.
29
Elangwe, Emilia N. "Site Directed Mutagenesis, Expression and Enzymatic Studies of the 60 kDa Human HIV-TAT 1 Interactive Protein, TIP60." Digital Archive @ GSU, 2009. http://digitalarchive.gsu.edu/chemistry_theses/21.
Full textAbstract:
Tip60 is a 60 kDa nuclear protein which exists in three isoforms, belongs to the MYST/HAT family of proteins and was discovered after its interaction with the Human HIV-1 Tat. As a nuclear protein, Tip60 can act as a coactivator or repressor. To understand the HAT action of Tip60, two possible catalytic models exist; the ping-pong and the ternary complex formation models. In correlation with the exploration of HAT catalytic action, mutations of a Cys to Ala and a Glu to Gln on Esa1 (yeast homolog of Tip60 and MYST/HAT prototype), was reported to show wild type-like and decreased acetylating properties, respectively. In this work, Tip60 HAT action was explored. In Tip60, the Cys in the active site is important for acetylation of the H4(1-20) substrate and the Glu showed semi loss in acetylating the H4(1-20) peptide substrate. These data highlight a unique mechanism of Tip60 catalysis.
30
Dussault, Laurent. "Etude physico-chimique d'oxydes mixtes issus d'hydroxydes doubles lamellaires. : Application à la synthèse de nanofilaments de carbone." Phd thesis, Université de Pau et des Pays de l'Adour, 2005. http://tel.archives-ouvertes.fr/tel-00421914.
Full textAbstract:
Les Hydroxydes Doubles Lamellaires (HDL) présentent de nombreux domaines d'application en rapport avec leur structure lamellaire et la diversité de leur de composition. Ce travail souligne les potentialités des HDL lorsqu'ils sont utilisés comme précurseurs d'oxydes mixtes pouvant intervenir en catalyse hétérogène acido-basique ou d'oxydo-réduction.La première partie du mémoire concerne l'étude d'une série d'oxydes à base de nickel, cuivre, magnésium et aluminium, obtenus par calcination des HDL précurseurs à 450°C. La caractérisation structurale et l'étude de l'acido-basicité des oxydes mixtes en fonction de leur composition ont été réalisées. Elles s'appuient sur l'utilisation complémentaire de différentes méthodes analytiques physico-chimiques donnant accès à des informations concernant à la fois la structure, la composition et la morphologie des cristaux obtenus(DRX, ATG, analyse chimique, SPX...), ou permettant la caractérisation de leurs propriétés acido-basiques (adsorption de molécules sondes suivie par microcalorimétrie et SPX).
La seconde partie du travail est consacrée à l'utilisation des oxydes mixtes obtenus après calcination à 800°C pour la synthèse de nanofilaments de carbone à partir de la décomposition catalytique du méthane. Après une étude détaillée des oxydes mixtes, les nanofilaments produits ont été caractérisés à l'aide de différentes techniques, notamment la microscopie électronique à transmission. Les données physico-chimiques obtenues ont mis en évidence les relations entre les caractéristiques du catalyseur (composition, mode de synthèse, propriétés...) et le type des nanofilaments (tubes, fibres) obtenus.
31
Shih, Yu-Chia, and 施又嘉. "Applications of the Bimodal Catalysts in HDS Process." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/mavg2q.
Full textAbstract:
碩士國立成功大學
化學工程學系碩博士班
90
Abstract Most of the researches in the hydrodesulfurization (HDS) reaction of the residual oil were focused on a single catalyst pellet with a single pore diameter and uniform activity profile, or on simulating the amounts of desulfurization and the optimal pore diameters under isothermal condition. However, in the industrial applications, the outlet concentration of the sulfur-containing molecules is usually fixed in the HDS process by increasing the temperature of reactor to compensate for the deactivation of catalysts. In recent years, bimodal catalysts are of quite potential in the application of hydrodesulfurization (HDS). In this study, the mathematical model of a fixed bed for HDS of the residual oil with bimodal catalysts was established. A set of representative parameters of HDS and HDM was adopted according to the data from the published papers. These parameters was set as the standard operating condition. System parameters include the ratio of the mesopore diameter to the micropore diameter, the average diameter and the percentage of the mesopore and micropore, Thiele Modulus Φ, the residence time of residual oil in the fixed bed reactor, the outlet concentration of the sulfur-containing molecules, and the upper limiting temperature. This study uses the average diameter of the mesopore and micropore to simulate the bimodal catalysts. The simulation results show that the amounts of desufurization decrease at first, then increase as the percentage of mesopore increases at the diameter ratio of the mesopore to micropore equals to 3. The amounts of desulfurization increase with the increasing diameter of the micropores for a constant diameter of the mesopores. The faster the rate of desulfurization, the lower the initial temperature of the fixed bed reactor and the longer the age of catalysts. Decreasing the flow rate of residual oil or increasing the upper limiting temperature can prolong the life of catalysts. Furthermore, packing catalysts with larger pores in the upper-stage of reactor will have a better performance on both desulfurization and demetallation in a two-stage reactor.
32
Chi, Ren-Hai, and 紀仁海. "A Study of Vanadium-Based Catalysts for H2S Oxidation to Sulfur." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/21894111098884362738.
Full textAbstract:
碩士東海大學
化學工程學系研究所
86
This thesis studied several catalysts for the selective oxidation of hydrogen sulfide to sulfur, including magnesium vanadate catalysts and rare earth orthovanadate catalysts ( REVO4; RE = Ce, Y, La, Sm ). We also investigated the effect of Sb2O4 additive on the catalytic properties of the above catalystsfor the selective oxidation of H2S. In addition, BET, TPR, SEM, XRD and ESCA were used to characterize the catalysts in order to have better understanding of the catalytic performance. The above catalysts were prepared by slurry method in the solution of citrate acid . Experimental results indicated that the catalytic activity and selectivity decrease in the following order for the magnesium vanadate catalysts: MgV2O6>Mg2V2O7>Mg3V2O8. As to the REVO4 catalysts, the catalytic activity decreased in the following order: YVO4>CeVO4>LaVO4>SmVO4, but the CeVO4 had the best selectivity. Antimony oxide was mechanically mixed with magnesium vanadate catalysts and rare earth orthovanadate catalysts. It was found that antimony oxide improved sulfur selectivity but no new phase occurred. From the ESCA results, V+4 could have been oxidized to V+5. The phenomena can be explained with the remote-control mechanism. After calcination of the mechanical mixtures, an increase in the H2S conversion, sulfur yield and selectivity was observed
33
Danilovic, Nemanja. "Anode materials for sour natrual gas solid oxide fuel cells." Phd thesis, 2010. http://hdl.handle.net/10048/1008.
Full textAbstract:
Novel anode catalysts have been developed for sour natural gas solid oxide fuel cell (SOFC) applications. Sour natural gas comprises light hydrocarbons, and typically also contains H2S. An alternative fuel SOFC that operates directly on sour natural gas would reduce the overall cost of plant construction and operation for fuel cell power generation. The anode for such a fuel cell must have good catalytic and electrocatalytic activity for hydrocarbon conversion, sulfur-tolerance, resistance to coking, and good electronic and ionic conductivity.
The catalytic activity and stability of ABO3 (A= La, Ce and/or Sr, B=Cr and one or more of Ti, V, Cr, Fe, Mn, or Co) perovskites as SOFC anode materials depends on both A and B, and are modied by substituents. The materials have been prepared by both solid state and wet-chemical methods. The physical and chemical characteristics of the materials have been fully characterized using electron microscopy, XRD, calorimetry, dilatometry, particle size and area, using XPS and TGA-DSC-MS. Electrochemical performance was determined using potentiodynamic and potentiostatic cell testing, electrochemical impedance analysis, and conductivity measurements.
Neither Ce0.9Sr0.1VO3 nor Ce0.9Sr0.1Cr0.5V0.5O3 was an active anode for oxidation of H2 and CH4 fuels. However, active catalysts comprising Ce0.9Sr0.1V(O,S)3 and Ce0.9Sr0.1Cr0.5V0.5(O,S)3 were formed when small concentrations of H2S were present in the fuels. The oxysuldes formed in-situ were very active for conversion of H2S. The maximum performance improved from 50 mW cm2 to 85 mW cm2 in 0.5% H2S/CH4 at 850 oC with partial substitution of V by Cr in Ce0.9Sr0.1V(O,S)3 . Selective conversion of H2S offers potential for sweetening of sour gas without affecting the hydrocarbons.
Perovskites La0.75Sr0.25Cr0.5X0.5O3, (henceforth referred to as LSCX, X=Ti, Mn, Fe, Co) are active for conversion of H2, CH4 and 0.5% H2S/CH4. The order of activity in the different fuels depends on the substituent element: CH4, X=Fe>Mn>Ti; H2,X = Fe>Mn>Ti; and 0.5% H2S/CH4, X = Fe>Ti>Mn. The electrocatalytic activity for methane oxidation in a fuel cell correlates with ex-situ temperature programmed catalytic activity. A process is proposed to explain the difference in catalyst order and enhanced activities in H2S/CH4 as fuel compared to CH4 alone. The maximum power density of 250 mW cm2 was attained using a fuel cell with a composite anode, LSCFe-GDC | YSZ(0.3 mm) | Pt, operated at 850 oC (GDC is Ce0.9Gd0.1O3, a good mixed conductor under reducing conditions).Materials Engineering
34
Chan, Pui Yik Peggy Chemical Sciences & Engineering Faculty of Engineering UNSW. "Design and verification of catalytic membrane reactor for H2 recovery from H2S." 2007. http://handle.unsw.edu.au/1959.4/40550.
Full textAbstract:
Hydrogen sulfide is toxic by-product of many petroleum, petrochemical and mineral treatment operations. Due to the increasing stringent environment regulations, toxic H2S must be completely removed from industrial waste gases before venting to the atmosphere. The H2S decomposition reaction is a well known thermodynamically limited reaction. Alumina membrane fixed bed catalytic reactors offer the potential for improved conversions at reduced operating temperature due to product separation and catalyst activity. A theoretical and experimental work dealing with a packed bed membrane reactor is the subject of this thesis. A tubular alumina membrane reactor possessing thermal and corrosion resistance has been developed. A multicomponent permeation study indicated that the fluxes of gases could be quantitatively described as a combination of Knudsen diffusion and viscous flow through the porous alumina membrane. The catalytic decomposition of hydrogen sulfide to hydrogen and sulfur was conducted in membrane reactor incorporating a commercial porous alumina membrane in combination with catalytic function of bimetallic RuMo sulfide catalyst. The obtained results demonstrate the possibility of achieving conversion above the equilibrium conversion. The reaction rate is equal to the intrinsic rate since both internal/external mass transfer and heat transfer resistance are negligible for the size of catalyst particles considered. Results obtained with this system have shown a maximum of 2.3 times the equilibrium conversion at the operating temperature 983K, which was equivalent to the conversion at operating temperature 1200K in a conventional fixed bed reactor. The conversion enhancement was significant for the operation with high sweep to feed molar ratio. The reactor configuration of membrane reactor appeared to have an influence on its performance. Comparative experimental and simulation study showed that the cocurrent mode gave slightly higher conversion over counter-current mode. Mathematical models were developed for the reactor, based on plug flow behavior. Simulation had been performed in order to validate the model against experimental data. Reactor optimization was carried out using the validated model. The simulation results from the non-isothermal model were in reasonable agreement with the experimental data. On the other hand, the isothermal model which neglected heat effects that took place in the reactor, has leaded to over-predicted conversion. This study also illustrated that predictive simulations could be used to explore the effects of recycle operation; the optimization study showed that the alumina membrane reactor permitting retentate recycle, could achieve up to 48.6% conversion, corresponding to 6 folded of the equilibrium conversion. The simulations provide a logical methodology for experimental planning and design. To further elucidate the effect of reactor configuration, operation conditions and permeation parameters on the performance of membrane reactors, a high permselective Pt-composite MR model was developed. Comparison of alumina MR and Pt-composite MR was carried out via computer simulation. Porous membrane reactor with higher permeability but lower Permselectivity can attain comparable conversion as the composite membrane reactor with higher permselectivity but lower permeability. Ptcomposite MR was more superior to alumina MR without recycle. Retentate recycle in alumina MR is shown to outperform the Pt-composite MR. Alumina MR was therefore considered as potential candidate for industrial H2S treatment.
35
Huang, Jia-Yang, and 黃嘉洋. "Synthesis, Characterization, and Enhancement of Desulfurization Efficiencies of Desulfurized Catalysts in H2S-containing Syngas of a Gasifier." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/81661061170329849940.
Full textAbstract:
碩士元智大學
化學工程與材料科學學系
104
The increasing world population has caused the serious environmental pollutions that require paying more attention. In 1970 s, European countries and United States started to study the pollutions from coal power generation plants, and try to improve these problems. Nowadays, flue gas desulfurization (FGD) is the most important equipment for sulfur oxide removal, and it needs to be set up in every coal power generation plants. Dry desulfurization in medium-high temperature is the most favorable technology. Metal oxides are used as absorbents to remove sulfurs that show more thermal efficiencies than traditional cold washing method. Above all the metal oxides, zinc oxide is the most famous one, which has excellent thermal property. Until now, zinc oxide is improved by adding titanium to form zinc-titanium absorbent. Titanium has the ability to stabilize the crystal phase of zinc oxide, but doesn’t participate with absorption. Catalyst synthesis experiments mainly co-precipitation method. These as-synthesized metal oxides for desulfurization including Zn2TiO4, ZnFe2O4, CuO/Al2O3, CeO2/Al2O3 and CuO-CeO2/Al2O3 have been investigated and confirmed by XRD and JCPDS-ICDD database. Morphologies of catalysts indicated that particle size distributed between 30-95 nm. Additionally, nitrogen isotherms of some catalysts have the adsorption-desorption hysteresis loop that revealed their unique pore shape (capillary and slit-type pores). The highest surface value was 148 m2/g (CeO2/Al2O3), and the minimum value was 2.3 m2/g (CeO2-CuO/Al2O3). TGA curves shown that the catalytic pyrolysis temperature was located in the range of 600-1,000oC, which can be applied to the medium-high environment. The desulfurization efficiencies of various catalysts were CuO-CeO2/Al2O3>ZnFe2O4>Zn2TiO4>CeO2/Al2O3>CuO/Al2O3 after 5 times cyclic tests under 500oC and 1atm with GHSV=10,000 h-1 and H2S inlet concentration of 10,000 ppm by using 1.5 g catalysts. By analyzing the concentration of residual H2S in off-gases with FT-IR and UV, the desulfurization efficiencies of various catalysts were CuO-CeO2/Al2O3>ZnFe2O4>Zn2TiO4>CeO2/Al2O3>CuO/Al2O3. Above all as-synthesized catalysts, CuO-CeO2/Al2O3 has the highest desulfurization efficiencies as 95.2%, and can catalyze H2S 463.3 mg per kilogram catalyst after 5 times cyclic tests. These research results provided the important reference for practical desulfurization equipments in medium-high temperature range in the future.
36
Lin, Yan-Ting, and 林彥廷. "Preparation PtRu/HCS anode catalyst and alkaline composite PVA polymer membrane and their applications on alkaline methanol fuel cell." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/13605060968679681942.
Full textAbstract:
碩士明志科技大學
化學工程系碩士班
103
In this work, the alkaline composite polyer membrane and PtRu/HCS (Hollow carbon spheres, denoted as HCS) composite anode catalyst were prepared for alkaline direct methanol fuel cell (so-called ADMFCs). The comporents of the composite polymer membranes are comprised of polyvinyl alcohol (PVA) polymer matrix, Quanternary ammonium silica precursor (deroted as QASP), which is used as an anion exchange filler. The QASP precusor is synthesized by using Glycidyltrimethyl ammonium chloride (denoted as GTMAC) and (3-Aminopropyl)trimethoxysilane (denoted as AMPTS). The PVA polymer and QASP, (3-(Trimethylammonium)propyl-functionalized silica gel chloride (so-called TMAPFS) are blended to form the PVA/QASP/TMAPFS anion exchange membrane (denoted as QPVA-QSiO2). Furthermore, we fabricated the nano-PET nonwoven by an electrospinning process. The organic-inorganic PVA/QASP/TMAPFS-PET (denoted as QPVA-QSiO2/QPET) composite polymer membrane is formed by using QPVA-QSiO2 and QPET Nonwoven matrix. In addition, we also prepared hollow carbon spheres (HCS) composite carbon matrix, and its size is around 100-150 nm. The HCS carbon matrixs are synthesize by using glucose and SDS surfactant through a hydrothermal process. The SDS surfactant is used to as a morphology forming agent. The HCS with the high surface area can load with much high amount of PtRu catalysts. The PtRu/HCS catalyst was prepared by using a microwave heating process. The raw material includes ethylene glycol as a reducing agent and PtRu salts.Finally, we used the QPVA-QSiO2 or QPVA-QSiO2/QPET anion exchenge polymer membrane with as-prepared 50wt.% PtRu/HCS catalyst on ADMFC, and their electrochemical performances are systematically evaluated. According to the experimental results, we found that the ionic conductivity of the QPVA-QSiO2/QPET membranes are 5.35×10-2 S cm-1 and 6.59×10-2 S cm-1 at 30℃ and 70℃, respectively. The composite membrane also exhibited excellent thermal stability.We also discovered that the ADMFC with QPVA-QSiO2/QPET membrane and 50wt.% PtRu/HCS-1wt.%MWCNTs anode catalyst shows the best electrochemical performance at 70℃, its P.D. can reach ca. 77.54 mWcm-2. By comparing the literature data, we found that the performance of ADMFC with QPVA-QSiO2/QPET membrance is much batter than those of ADMFC cell with QPVA/Al2O3 membrane (P.D.= 35.13 mW cm-2) and ADMFC cell with QPVA-QSiO2 membrance (P.D.= 18.33 mW cm-2).
37
Chiu, Feng-Yu, and 邱夆昱. "(I) Synthesis of benzimidazole linked indoline derivative by acid catalyst(II) One-pot synthesis of derivative of ellipticine which has the activity against Mycobacterium tuberculosis." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/3snnw5.
Full textAbstract:
碩士國立交通大學
應用化學系碩博士班
105
This thesis has two parts: The first part is about synthesis of benzimidazole linked indoline derivatives from C-2-linked-o-aminobenzyl benzimidazole by acid catalyst. This method can apply to various funtional groups. There is no published paper refer to benzimidazole linked indoline derivatives, so we hope these heterobicyclic molecules can show more bioactivity and also hope this thesis can open a new page for research of drugs. The second part is about One-pot synthesis of derivative of ellipticine which has the activity against Mycobacterium tuberculosis. We hope we can improve its activity of anti-TB by changing different funtional groups to study the structure–activity relationship.