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Afshar, Farniya Ali. "Development and performance analysis of autonomous catalytic micropumps". Doctoral thesis, Universitat Autònoma de Barcelona, 2014. http://hdl.handle.net/10803/284892.
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Uno de los principales retos de la ingeniería de nanomotores, además de las dificultades para fabricar objetos nanométricos complejos, es cómo proveerles de energía para que funcionen. La aplicación de campos externos es una forma común y fácil de impulsar motores relativamente grandes. Sin embargo, cuando el tamaño de los motores se hace más pequeño, la transferencia de energia desde la escala macroscópica a la nanoescala se vuelve más problemática. Por lo tanto, el desarrollo de sistemas a nivel de la nanoescala totalmente autónomos que puedan generar su propia energía para poder autopropulsarse es muy deseable. Los sistemas biológicos ofrecen numerosos ejemplos de micro/nano motores autónomos. El punto clave detrás de la eficiente maquinaria biológica es la conversión de energía química en movimiento direccional. Por lo tanto existe un alto interés en crear nuevos motores artificiales que puedan auto-impulsarse y realizar actividades autónomas de forma similar a la impresionante maquinaria molecular de los organismos vivos. Recientemente se ha comenzado una intensa actividad científica en el desarrollo de motores y sistemas de bombeo propulsados químicamente en base a la auto-generación local de gradientes.
El presente trabajo de investigación trata sobre el concepto de microsistemas de bombeo catalítico que fue reportado por primera vez en 2005. Un microsistema de bombeo catalítico es un sistema activo que tiene la capacidad de inducir fenómenos electrohidrodinámicos a partir de una reacción (electro)química sobre una micro/nano estructura bimetálica. Aunque los dispositivos catalíticos han sido objeto de investigaciones anteriores en el que sus aplicaciones nanotecnológicas han comenzado a demostrarse, el mecanismo de actuación quimio-mecánica ha sido menos estudiado. Esto es en parte debido a la compleja interrelación que existe entre las reacciones catalíticas y los fenómenos electro-hidrodinámicos. Como consecuencia de ello todavía hay una serie de preguntas sin resolver que requieren mayor investigación para establecer el rol desempeñado por los diferentes procesos y lograr una mejor comprensión del mecanismo detrás de ellos. Por lo tanto, en esta tesis doctoral se ha realizado una caracterización exhaustiva de la actuación quimio-mecánica para entender los principales factores fisicoquímicos que regulan el mecanismo de funcionamiento de microbombas bimetálicas de Au- Pt en presencia de peróxido de hidrógeno como combustible. Las investigaciones han sido solventadas no sólo con resultados experimentales sino también con simulaciones numéricas. Estos estudios fundamentales son relevantes no sólo para estos sistemas de bombeos catalíticos, sino también para micro/nanomotores o nanorobots suspendidos en fluidos o coloides activos autopropulsados. Los estudios se han extendido también a otras estructuras bimetálicas ( Au- Ag , Au- Ru , Au -Rh , Cu - Ag , Cu - Ni, Ni- Ru y Ni- Ag) y a dispositivos semiconductores/metálicos ( Si dopado p / Pt , Si dopado n / Pt) con la idea de evaluar sus potencialidades como sistemas de bombeo catalítico en presencia del mismo combustible químico. En el caso de los sistemas metal/semiconductor su funcionamiento se basa en la fotoactivación de reacciones catalíticas, lo que proporciona un valor añadido a estas bombas y permite el desarrollo de nuevos interruptores foto-electrohidrodinámicos. Estos logros pueden abrir nuevas y prometedoras líneas de investigación en el campo de los actuadores y nanomotores catalíticos. El trabajo de tesis describe también una de las posibles aplicaciones de estos dispositivos activos que está relacionada con el transporte y depósito de materia en lugares específicos de un sustrato guiado por los fenómenos electrohidrodinámicos locales. Eso permite fabricar superficies nanoestructuradas de forma autónoma con un gran impacto nanotecnológico en una amplia gama de campos.One of the main challenges in the engineering of nanomachines, besides the difficulties to fabricate complex nanometric objects, is how to power them. The application of external fields is a common and easy way to actuate relatively large machines. However, when the size of the machines becomes smaller, the transfer of power from the macroscopic scale to the nanoscale becomes problematic. Therefore, the development of fully autonomous nanoscale systems which can self-generate their required power is very desirable. Biological systems are the source of numerous examples of natural micro/nanoscale autonomous motors. The conversion of chemical energy into directional motion is the key point behind the high efficient nanofactory of biomolecular machines. Therefore there is a high interest to create novel artificial machines which can self-propel and perform autonomous activities in a similar way the impressive molecular machinery does in living organisms. Many research activities have recently focused on chemically powered motors and micropumps based on the local self-generation of gradients. The present research work deals with the catalytic micropump concept which was reported for the first time in 2005. A catalytic micropump is an active system which has the capability of triggering electrohydrodynamic phenomena due to an (electro)chemical reaction taken place on a micro/nano bimetallic structure. Although catalytic devices have been the subject of previous reports in which their nanotechnological applications have started to be demonstrated, the mechanism of the chemo-mechanical actuation has been less studied. That is in part due to the complex interrelation between the catalytic reactions and the electro-hydrodynamic phenomena. As a consequence there is still a number of intriguing questions that require further investigation for establishing the role played by the different processes and for achieving a better understanding of the mechanism behind them. Therefore, the research was focused on the full characterization of the chemomechanical actuation and the understanding of the main physicochemical factors governing the operating mechanism of Au-Pt bimetallic micropumps in presence of hydrogen peroxide fuel. The investigations were supported not only by experimental findings but also by numerical simulations. These fundamental studies are of high importance not only for catalytic micropumps but also for other autonomous micro/nano swimmers or active self-propelled colloids. The studies were also extended to other bimetallic structures (Au-Ag, Au-Ru, Au-Rh, Cu-Ag, Cu-Ni, Ni-Ru and Ni-Ag) and to semiconductor/metallic structures (p-doped Si/Pt, n-doped Si/Pt) to evaluate their potentialities as catalytic micropumps in presence of the same chemical fuel. In the last case photoactivation of the catalytic reactions can be accomplished which provides an added value to these pumps as novel photochemical-electrohydrodynamic switches. These achievements can open new and promising research activities in the field of catalytic actuators and nanomotors. The thesis work also describes one of the potential applications of these active devices which is related to the autonomous material guiding and self-assembly on particular locations of a sample. That allows fabricating nanostructured surfaces in an autonomous way with potential nanotechnological impact in a wide range of fields.
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Chawla, Neha. "The Catalytic Performance of Lithium Oxygen Battery Cathodes". FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3810.
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High energy density batteries have garnered much attention in recent years due to their demand in electric vehicles. Lithium-oxygen (Li-O2) batteries are becoming some of the most promising energy storage and conversion technologies due to their ultra-high energy density. They are still in the infancy stage of development and there are many challenges needing to be overcome before their practical commercial application. Some of these challenges include low round-trip efficiency, lower than theoretical capacity, and poor rechargeability. Most of these issued stem from the poor catalytic performance of the cathode that leads to a high overpotential of the battery. In this doctoral work, Li-O2 cathodes containing nanoparticles of palladium were used to alleviate this problem. Cathodes composed of palladium-coated and palladium-filled carbon nanotubes (CNTs) were prepared and investigated for their battery performance. The full discharge of batteries showed 6-fold increase in the first discharge of the Pdfilled over the pristine CNTs and 35% increase over their Pd-coated counterparts. The Pd-filled CNTs also exhibited improved cyclability with 58 full cycles of 500 mAh·g-1 at current density of 250 mA·g-1 versus 35 and 43 cycles for pristine and Pd-coated CNTs, respectively. The effect of encapsulating the Pd catalysts inside the CNTs proved to increase the stability of the electrolyte during both discharging and charging. Voltammetry, Raman spectroscopy, XRD, UV/Vis spectroscopy, and visual inspection of the discharge products using scanning electron microscopy confirmed the increased stability of the electrolyte due catalyst shielding. The electrochemical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on carbon nanotubes (CNT) cathodes with palladium (Pd) catalyst, Pd-coated CNT and Pd-filled CNT, have been evaluated in an ether-based electrolyte solution to develop a lithium oxygen (Li−O2) battery with a high specific energy. The electrochemical properties of CNT cathodes were studied using electrochemical impedance spectroscopy (EIS). The infrared spectroscopy and SEM are employed to analyze the reaction products adsorbed on the electrode surface of the Li-O2 battery developed using Pd-coated and Pd-filled CNTs as cathode and an ether based electrolyte. vii Studies in this dissertation conclude that the use of nanocatalysts composed of palladium improved the overall performance of the Li-O2 batteries, while shielding these catalysts from direct contact with the electrolyte prolonged the life of the battery by stabilizing the electrolyte.
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Gómez, Sanz Sara. "Exploiting carbon in enhancing the performance of catalytic materials". Thesis, University of Cambridge, 2014. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708360.
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Berger, Christine, Rainer A. Rakoczy, Roger Gläser y Jens Weitkamp. "Synthesis and catalytic performance of large zeolite Y crystals". Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-196408.
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Berger, Christine, Rainer A. Rakoczy, Roger Gläser y Jens Weitkamp. "Synthesis and catalytic performance of large zeolite Y crystals". Diffusion fundamentals 2 (2005) 82, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14418.
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Gomes, Flores Camila. "Synthesis and catalytic performance of metal-zeolite composite catalysts". Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1R010/document.
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Les zéolithes sont des solides cristallins microporeux avec un système de pores réguliers, qui ont trouvé de nombreuses applications dans les procédés industriels tels que le raffinage du pétrole, la synthèse organique, l'adsorption et la séparation. Une très petite taille des pores des zéolithes (~1 nm) impose des limitations diffusionelles pour des nombreuses réactions catalytiques. La performance catalytique des catalyseurs bifonctionnels à base de zéolites peut être améliorée en créant des zéolithes hiérarchisées et en contrôlant la localisation des espèces métalliques. L'imprégnation est une méthode efficace pour la préparation de catalyseurs bifonctionnels à base de cobalt-zéolite pour la production directe de carburants liquides à partir de gaz de synthèse. Dans les catalyseurs préparés par imprégnation, le cobalt occupe les sites cationiques dans les micropores de zéolite, ce qui diminue le nombre de sites acides disponibles pour l'isomérisation et le craquage des hydrocarbures. L'isolement des ions cobalt en sites cationiques réduit la réductibilité du catalyseur, rend difficile d’obtenir l’état métallique et diminue la quantité de sites actifs métalliques disponibles pour la synthèse Fischer Tropsch. Nous avons démontré que la présence des ions Na+ au lieu des ions H+ dans les sites cationiques de zéolite favorise le dépôt de cobalt à la surface externe, alors que les sites acides dans les micropores de la zéolite sont peu affectés. Une autre approche de cette thèse porte sur la synthèse de zéolithes hiérarchisées à plusieurs niveaux de méso- et microporosité en utilisant des agents structurants sacrificiels. Les zéolithes hiérarchisées synthétisées à l'aide de nanotubes de carbone contenant du cobalt présentaient une activité catalytique plus élevée, une sélectivité en méthane plus faible et une sélectivité plus importante en hydrocarbures isomérisés dans la synthèse Fischer-Tropsch. La stratégie de synthèse fondée sur les nanotubes de carbone comme agents structurants a été étendue à d'autres métaux comme le nickel et le magnésium. Cette nouvelle approche à la synthèse de composites métal-zéolite en utilisant des nanotubes de métal-carbone comme agents structurants sacrificiels augmente la mésoporosité et améliore la performance pour l’hydrogénation d’aromatiques et l’acylation d’anisoleZeolites are microporous crystalline solids with a regular pore system, which have found numerous applications in industrial processes such as oil refining, organic synthesis, adsorption and separation. Very small pore size of zeolites (~1 nm) imposes diffusional limitations for many catalytic reactions. The catalytic performance of metal zeolite bifunctional catalysts can be improved by creating hierarchical zeolites and by controlling localization of metal species within the zeolite crystals. Impregnation is an efficient method for the preparation of bi-functional cobalt-zeolite catalysts for the direct production of liquid fuels from syngas. In the catalysts prepared via impregnation, cobalt occupies the cation exchange positions in the zeolite micropores decreasing the number of acid sites available for hydrocarbon isomerization and cracking. Isolation of cobalt ions in cationic positions reduces catalyst reducibility, makes it difficult to achieve metallic state and decreases the amount available metal active sites for Fischer Tropsch synthesis. We found that the presence of Na+ instead of H+ ions in the exchange positions of the large pore Beta zeolite favored deposition of cobalt on the external surface of the zeolite, while the acid sites in the zeolite micropores were not much affected. The large pore cobalt Beta zeolite catalyst with cobalt species localized on the external surface and high concentration of acid sites in the zeolite crystals has showed enhanced catalytic performance in Fischer-Tropsch synthesis combined with hydrocarbon isomerization. Another approach of this thesis has addressed creating hierarchical zeolites with several levels of meso- and microporosity using sacrificial templates. Hierarchical zeolites synthesized using cobalt containing carbon nanotubes, as sacrificial hard templates exhibited higher catalytic activity, lower methane selectivity and higher selectivity to isomerized hydrocarbons in Fischer-Tropsch synthesis. The synthesis strategy based on metal carbon nanotubes as sacrificial templates has been extended to other metals such as nickel and magnesium. This new approach to the synthesis of metal-zeolite composite increases the mesoporosity and improves the catalytic performance in hydrogenation of aromatics and anisole acylation
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Medina, Molano Natalia Stefania. "Contribution of radioactivity to catalytic performance in heterogeneous media". Electronic Thesis or Diss., Université de Lille (2022-....), 2023. http://www.theses.fr/2023ULILR025.
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Afin d'établir des voies possibles d'utilisation de métaux nobles récupérées du combustible nucléaire tels que le 107Pd, la présente thèse vise à étudier l'effet du rayonnement dans trois applications différentes : la catalyse hétérogène, avec - comme réaction modèle - l'hydrogénation du cinnamaldéhyde (CNA) ; la photocatalyse, avec - comme réaction modèle - la décoloration de l'orange de méthyle (MO) et la régénération des catalyseurs, désactivés lors de la synthèse de l'hydroxyméthyl furfural. Des protocoles ont été élaborés pour répondre aux exigences de sécurité nucléaire : applicable en boîte à gant et sorbonne, selon le cas.Le rayonnement β émis par le 107Pd n'a montré aucun effet lors de l'hydrogénation du CNA, indépendamment des conditions de réaction. En revanche, la décoloration a été initié par la présence de la radiation β sur le catalyseur en substituant de la lumière visible. Une diminution de l'absorbance (au point isosbéstique) a été observée. Ce dernier corrélait avec la quantité de catalyseur radioactif, mettant en évidence l'activation par le rayonnement β. Enfin, la régénération du catalyseur à base de Pd a donné des résultats prometteurs après l'irradiation γ, montrant notamment une augmentation de la performance catalytique après irradiation du catalyseur désactivé. Par ailleurs, le catalyseur à base de Ru, bien que généralement peu performant, a montré une activité plus élevée que l'activité du catalyseur frais après irradiation par rayonnement This thesis aimed to identify applications of noble metals recovered from spent nuclear fuels such as 107Pd. To study the effect of the radiation three different applications were selected: heterogeneous catalysis, with the hydrogenation of cinnamaldehyde (CNA) as model reaction; photocatalysis, with the decolourisation of methyl orange (MO) as model reaction; and the regeneration of catalysts, deactivated with the synthesis of hydroxymethyl furfural. Protocols were developed for the synthesis of the catalysts and the performance testing in restricted nuclear environment, namely in glove box and for the implementation of the reactions in glove box and extractor column as appropriate.Regarding the results it was found that β-radiation did not show any effect on the hydrogenation of CNA independent of the applied reaction conditions. On the other hand, the decolourisation of MO was successfully activated by the β-radiation of the catalyst. A decrease in absorbance (at the isosbestic point) was observed and was correlated to the amount of the catalyst employed, evidencing the effect of the irradiation doses. Finally, the regeneration of the Pd-based catalyst showed promising results after γ-irradiation, notably with a partial recovery of the initial catalytic performance after -irradiation. Meanwhile, the Ru-based catalyst, although generally not performing well, showed increased activity compared to the fresh catalyst upon -irradiation
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Gomes, Flores Camila. "Synthesis and catalytic performance of metal-zeolite composite catalysts". Electronic Thesis or Diss., Université de Lille (2018-2021), 2019. http://www.theses.fr/2019LILUR010.
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Les zéolithes sont des solides cristallins microporeux avec un système de pores réguliers, qui ont trouvé de nombreuses applications dans les procédés industriels tels que le raffinage du pétrole, la synthèse organique, l'adsorption et la séparation. Une très petite taille des pores des zéolithes (~1 nm) impose des limitations diffusionelles pour des nombreuses réactions catalytiques. La performance catalytique des catalyseurs bifonctionnels à base de zéolites peut être améliorée en créant des zéolithes hiérarchisées et en contrôlant la localisation des espèces métalliques. L'imprégnation est une méthode efficace pour la préparation de catalyseurs bifonctionnels à base de cobalt-zéolite pour la production directe de carburants liquides à partir de gaz de synthèse. Dans les catalyseurs préparés par imprégnation, le cobalt occupe les sites cationiques dans les micropores de zéolite, ce qui diminue le nombre de sites acides disponibles pour l'isomérisation et le craquage des hydrocarbures. L'isolement des ions cobalt en sites cationiques réduit la réductibilité du catalyseur, rend difficile d’obtenir l’état métallique et diminue la quantité de sites actifs métalliques disponibles pour la synthèse Fischer Tropsch. Nous avons démontré que la présence des ions Na+ au lieu des ions H+ dans les sites cationiques de zéolite favorise le dépôt de cobalt à la surface externe, alors que les sites acides dans les micropores de la zéolite sont peu affectés. Une autre approche de cette thèse porte sur la synthèse de zéolithes hiérarchisées à plusieurs niveaux de méso- et microporosité en utilisant des agents structurants sacrificiels. Les zéolithes hiérarchisées synthétisées à l'aide de nanotubes de carbone contenant du cobalt présentaient une activité catalytique plus élevée, une sélectivité en méthane plus faible et une sélectivité plus importante en hydrocarbures isomérisés dans la synthèse Fischer-Tropsch. La stratégie de synthèse fondée sur les nanotubes de carbone comme agents structurants a été étendue à d'autres métaux comme le nickel et le magnésium. Cette nouvelle approche à la synthèse de composites métal-zéolite en utilisant des nanotubes de métal-carbone comme agents structurants sacrificiels augmente la mésoporosité et améliore la performance pour l’hydrogénation d’aromatiques et l’acylation d’anisoleZeolites are microporous crystalline solids with a regular pore system, which have found numerous applications in industrial processes such as oil refining, organic synthesis, adsorption and separation. Very small pore size of zeolites (~1 nm) imposes diffusional limitations for many catalytic reactions. The catalytic performance of metal zeolite bifunctional catalysts can be improved by creating hierarchical zeolites and by controlling localization of metal species within the zeolite crystals. Impregnation is an efficient method for the preparation of bi-functional cobalt-zeolite catalysts for the direct production of liquid fuels from syngas. In the catalysts prepared via impregnation, cobalt occupies the cation exchange positions in the zeolite micropores decreasing the number of acid sites available for hydrocarbon isomerization and cracking. Isolation of cobalt ions in cationic positions reduces catalyst reducibility, makes it difficult to achieve metallic state and decreases the amount available metal active sites for Fischer Tropsch synthesis. We found that the presence of Na+ instead of H+ ions in the exchange positions of the large pore Beta zeolite favored deposition of cobalt on the external surface of the zeolite, while the acid sites in the zeolite micropores were not much affected. The large pore cobalt Beta zeolite catalyst with cobalt species localized on the external surface and high concentration of acid sites in the zeolite crystals has showed enhanced catalytic performance in Fischer-Tropsch synthesis combined with hydrocarbon isomerization. Another approach of this thesis has addressed creating hierarchical zeolites with several levels of meso- and microporosity using sacrificial templates. Hierarchical zeolites synthesized using cobalt containing carbon nanotubes, as sacrificial hard templates exhibited higher catalytic activity, lower methane selectivity and higher selectivity to isomerized hydrocarbons in Fischer-Tropsch synthesis. The synthesis strategy based on metal carbon nanotubes as sacrificial templates has been extended to other metals such as nickel and magnesium. This new approach to the synthesis of metal-zeolite composite increases the mesoporosity and improves the catalytic performance in hydrogenation of aromatics and anisole acylation
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Zhang, Changlin. "RATIONAL DESIGN OF ELECTROCATALYSTS WITH ENHANCED CATALYTIC PERFORMANCE IN ENERGY CONVERSION". University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1478274856161346.
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Bayraktar, Oguz. "Effect of pretreatment on the performance of metal contaminated commercial FCC catalyst". Morgantown, W. Va. : [West Virginia University Libraries], 2001. http://etd.wvu.edu/templates/showETD.cfm?recnum=2071.
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Thesis (Ph. D.)--West Virginia University, 2001.Title from document title page. Document formatted into pages; contains xvi, 214 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 199-208).
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Garcia, Amaya Arias. "Investigation of the flow performance of automative close coupled catalyst on flow rigs and engines". Thesis, Coventry University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247185.
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Rickett, Gavin Leon. "The performance of supported noble metal catalysts in conditions of catalytic combustion". Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441326.
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Wang, Yi. "Synthesis and catalytic performance of hierarchical Zeolites supported Nickel-Tungsten hydrodesulfurization catalysts". Thesis, Lille 1, 2015. http://www.theses.fr/2015LIL10124/document.
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Des règles environnementales de plus en plus strictes imposent une concentration en soufre dans les carburants en-dessous de 10 à 15 ppm. Donc, des catalyseurs plus efficaces doivent être développés. Dans ce travail, des catalyseurs nickel-tungsten supportés sur zéolites Beta et Mordenite hiérarchisées ont été préparés et évaluées en hydrodésulfuration (HDS).Tout d'abord, des zéolites Beta hiérarchisées ont été obtenues par post-traitement et caractérisées par DRX, N2-sorption, SEM, TEM et RMN. En conséquence, la zéolite Beta hiérarchisée préparée par post-traitement base-acide présente une excellente activité dans les réactions en catalyse acide, en particulier pour la conversion de grosses molécules.Des catalyseurs NiW supportés sur Al2O3 (NiW/Al2O3), zéolite Beta commerciale et hierarchisée (NiW/HB et NiW/HB-M), zéolite Mordenite commerciale et hierarchisée (NiW/HM et NiW/HM-M) ont été préparés et caractérisés par XRD, N2-sorption, IR, TEM et XPS. L'activité en HDS du 4,6-DMDBT sur NiW/HM-M et NiW/HB-M est plus du double de celle du catalyseur à base d’alumine NiW/Al2O3. La désactivation de catalyseurs supportés sur zéolite Beta a été étudiée dans la réaction d’HDS du thiophène. Les résultats indiquent que le mélange des solides NiW/HB ou NiW/HB-M avec NiW/Al2O3 et l'utilisation de zéolite Beta après échange avec des ions Na+ comme support (NiW/NaB-M) améliorent remarquablement la capacité anti-désactivation des catalyseurs. En conséquence, les catalyseurs NiW/NaB-M et catalyseur mélangé conduisent à une activité catalytique supérieure à celle de NiW/HB-M et NiW/Al2O3More and more strict regulations were drawn up in many countries to limit the concentration of sulfur below 10 ppm or 15 ppm in transportation fuel oil. Therefore, more efficient catalysts have to be developed. In this work, hierarchical Beta and Mordenite zeolite supported nickel-tungsten catalysts were prepared and evaluated in hydrodesulfurization (HDS) reactions.Firstly, hierarchical Beta zeolite was prepared by post-treatment and characterized by XRD, N2-sorption, SEM/TEM and NMR techniques. As a result, hierarchical zeolite Beta prepared by base-acid treatment exhibited excellent catalytic activity in acid-catalytic reactions, especially towards large molecules. NiW catalysts supported on Al2O3, commercial Beta and Mordenite zeolites (HB and HM), and hierarchical Beta and Mordenite prepared by post treatment (HB-M and HM-M) were characterized by XRD, N2 sorption, IR, TEM and XPS. Zeolite supported catalysts exhibited higher catalytic performance in the HDS of 4,6-DMDBT, due to the strong acidity of the zeolitic support that supplied an additional isomerization reaction route. The use of hierarchical zeolite could further improve the isomerization ability of catalyst. As a result, the HDS activity of 4,6-DMDBT over NiW/HM-M and NiW/HB-M was more than twice as that of NiW/Al2O3. The deactivation of hierarchical Beta zeolite supported catalysts was studied in the HDS of thiophene. Interestingly, mixing NiW/HB or NiW/HB-M with NiW/Al2O3 and the utilization of Na+-exchanged Beta as support (NiW/NaB) improved remarkably the anti-deactivation ability of the catalysts. As a result, NiW/NaB-M and mixture catalyst gave superior catalytic activity than NiW/HB-M and NiW/Al2O3
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Jaf, Zainab. "Catalytic performance, Thermo-elastic, surfaces and coating properties of transition metal nitrides". Thesis, Jaf, Zainab (2018) Catalytic performance, Thermo-elastic, surfaces and coating properties of transition metal nitrides. PhD thesis, Murdoch University, 2018. https://researchrepository.murdoch.edu.au/id/eprint/42920/.
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Among transition metal nitrides (TMNs), refractory molybdenum nitrides have been deployed in a wide array of strategic industrial applications due to their remarkable mechanical electrical and catalytic properties. This dissertation has a two-fold aims; first to comprehensively report electronic, thermo-mechanical and electronic characteristics of the bulk and surfaces of molybdenum nitride, and secondly to construct robust mechanistic pathways for prominent catalysed reactions. Most parts of this thesis utilise the density functional theory (DFT) framework to acquire these two objectives. I have carefully benchmarked the accuracy of theoretically-obtained results against experimental quantities pertinent to investigated systems, most notably, lattice parameters of bulk phases, bulk modulus, surface relaxations, and chemical conversion values.
Atomic charge distributions and density of states enabled to illustrate the bonding nature of investigated phases of molybdenum nitrides. For instance, we found that the MoN phase largely exhibits a metallic character with strong Mo-N ionic bonds. Based on estimated Gibbs free energies, the cubic phase of molybdenum nitrides incurs higher thermodynamic stability than the hexagonal phase, with no detected phase transition in the selected T–P ranges, as experimentally observed. The elastic stiffness coefficients of MoN in the hexagonal structure indicated higher mechanical stability in reference to the cubic structure. The optical conductivity of both phases near zero-photon energy coincides well with their metallic character inferred by their corresponding density of states curves.
Motivated by the fact that, the hexagonal structure δ-MoN is a potential replacement for cubic boron nitride (c-BN) and diamond (ultra-incompressible materials), we elect to computationally study the electronic properties, thermodynamic stability phase diagram, and vacancy formation energies of all plausible atomic terminations of NiAs and WC-type configurations of δ3-MoN and δ-WN hexagonal phases, correspondingly. Various low Miller indices of surface terminations of δ3-MoN and δ-WN have been considered. Ab initio atomistic thermodynamic analysis predicts that N-terminated (111) and (100) slabs to be the most energetically favourable surface terminations amongst the explored surfaces of δ3-MoN and δ-WN, respectively. Evidenced by plotted density of states, bulk and surfaces of δ3-MoN and δ-WN display a metallic character. In terms of surface relaxation and reconstructions, most investigated surfaces experience mainly downward displacements of their topmost layers. Most notably, the relaxed Mo-termination in (111) and (100) surfaces of δ3-MoN, demonstrate significant reconstructions resulted in the first layer to be solely truncated with nitrogen atoms instead of molybdenum in the un-relaxed initial geometry. Nevertheless, no significant surface reconstruction has been noticed in most of considered δ-WN configurations. Calculated Bader’s electronic charges reveal charge transfer from Mo/W atoms to N atoms, largely retaining the ionic bond nature in their bulk phases. Moreover, computed vacancy formation energy calculations indicated that creation of surface nitrogen vacancies are a highly endothermic process.
After considering bulk and surface properties, mechanistic and kinetics aspects for several hydrogen-transfer involved reactions have been investigated. The selective hydrogenation of acetylene (ethyne), present in hydrocarbon feed into ethylene (ethene) plays a critical importance in petroleum unit operations. The dissociative adsorption of hydrogen over the γ-Mo2N surface preferentially occurs over the vacant nitrogen sites. Our calculated overall uptake rate of hydrogen molecules by the γ-Mo2N surface correlates very well with analogous experimental findings. Likewise, accessible energy barriers for hydrogen migration from a low energy site (N-vacant) to a higher energy site (atop N) accounts for the experimentally observed facile mobility of hydrogen atoms over surfaces of Mo2N. The constructed detailed mechanisms for the partial and full hydrogenation of C2H2 into C2H4 and C2H6; respectively, highlight several thermodynamic and kinetic factors that underline the selective occurrence of partial rather than full hydrogenation of alkynes over transitional metal nitrides in general. For instance, we demonstrate that a higher barrier for the initial hydrogenation step in the full hydrogenation route in comparison to the analogous step in partial hydrogenation pathway (17.4 kcal mol-1 versus 10.8 kcal mol-1) to contribute significantly in the selective occurrence of partial hydrogenation of alkynes cuts.
It is well-known that catalytic removal of the S-content from thiophenic compounds is an essential step in efforts aiming to diminish the environmental burdens of transportation fuels. We therefore investigate the hydrodesulfurization HDS mechanisms of thiophene C4H4S over γ-Mo2N catalyst via DFT calculations. We found that the thiophene molecule preferentially adsorbs in a flat mode over 3-fold fcc nitrogen hollow sites. The HDS mechanism may potentially proceed either unimolecularly (direct desulfurization) or via H-assisted reactions (hydrogenation). Due to a sizable activation barrier required for the first C−S bond scission, we predict that the direct desulfurization to contribute insignificantly in the HDS mechanism. Migration of adsorbed hydrogen atoms from the γ-Mo2N surface to the thiophene ring significantly reduces activation barrier required in the C−S bond scission. Estimated conversion values predict a 50-70% consumption of thiophene at temperature as low as 700 K and at low values of gas hourly space velocities. Our computed conversion values were in a qualitative agreement with analogous limited experimental estimates.
I also probed the reduction mechanism of p-chloronitrobenzene (p-CNB) to p-chloroaniline (p-CAN) over the γ-Mo2N (111) surface. Our findings display that, p-CNB prefers to be adsorbed over two distinct adsorption sites namely, hollow fcc and N-hollow hcp sites with relatively sizable adsorption energies. We establish that, the activation of nitro group proceeds through direct pathway along with forming several reaction intermediates. Most of these intermediaries reside in a significant well-depth in reference to the entrance channel. Central to the constructed mechanism is H-transfer steps from fcc and hcp hollow sites to the NO/-NH groups through modest reaction barriers. Our computed rate constant for the conversion of p-CNB correlates very well with the experimental finding at the temperature window of the catalytic tests. Plotted species profiles via a simplified kinetics model confirm the experimentally reported high selectivity toward the formation of p-CAN at relatively low temperatures.
In this dissertation, not only binary TMNs, but also ternary TMNs have been investigated in the form of Cr−Mo−N thin films. Closed field unbalanced magnetron sputtering ion plating (CFUMSIP) was deployed to fabricate the aforementioned films with different Mo contents. XRD results confirmed the face centered cubic (fcc) structure of pure CrN film. The incorporation of molybdenum (Mo) in the CrN matrix, however, was confirmed by both XRD and XPS analyses. The CrMoN coatings demonstrate various polycrystalline phases including CrN, γ-Mo2N, Cr with oxides layers of MoO3, CrO3, and Cr2O3. Microstructure results show that the grain size of Cr-Mo-N coatings increases with the increase of Mo content due to the formation of MoN phase, when Mo atoms interact with N atoms around the grain boundaries of CrN phase. The optical results revealed that, the synthesised coatings exhibit low reflection magnitudes in the visible region of the solar spectrum, introducing them as good antireflection surfaces. Mo-containing samples improved solar absorptance of about 76% was recorded in the wavelength range of 200 – 800 nm. However, low thermal emittance of about 20% was obtained at 2500 – 15000 nm. Measured experimental and DFT computed values exhibited absorption coefficients (α) with a matching trend, across the wavelength range of 200 to 800 nm.
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Navarro-Fernandez, Oscar. "Synthesis, Activation and Catalytic Activity of N-Heterocyclic Carbene Bearing Palladium Catalysts". ScholarWorks@UNO, 2006. http://scholarworks.uno.edu/td/330.
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The syntheses and characterization of a series of (NHC)Pd(II) complexes (NHC = N-heterocyclic carbene) are described. A variety of architectures and precursors have been employed to lead to numerous air- and moisture-stable complexes. The use of those complexes as pre-catalysts in cross-coupling (Suzuki- Miyaura, Buchwald-Hartwig) and related (catalytic dehalogenation, £-ketone arylation) reactions is also discussed. A comparison of the activity of a variety of (NHC)Pd complexes as pre-catalysts for cross-coupling reactions was carried out. The results indicate that the activation of those pre-catalysts, leading to the catalytically active [(NHC)Pd(0)] species, was key in assuring high catalytic performance under mild reaction conditions. For the first series of complexes described, (NHC)Pd(allyl)Cl complexes, a better understanding of the process leading to the catalytically active species has permitted us to introduce simple modifications (alkyl or aryl groups at the allyl moiety) that dramatically alter the performance of the complexes by facilitating their activation, decreasing reaction times, catalyst loadings and even allowing reactions to be conducted at room temperature. Catalyst loadings as low as 0.05 mol% can be used for the Suzuki-Miyaura crosscoupling of aryl chlorides and aryl boronic acids at room temperature, leading to the synthesis of poly-ortho-substituted biaryls in excellent yields. This catalyst loading is the lowest ever used for this purpose. The system also allows for the first examples of coupling between aryl chlorides and alkenyl boronic acids at room temperature. When the temperature is raised to 80 ¢ XC for these reactions, a catalyst loading as low as 50 ppm can be used to effectively carry out Suzuki-Miyaura cross-couplings in remarkably short reaction times. As an added advantage, these complexes are air- and moisture-stable and can be prepared in a facile one-pot, multigram scale synthesis from commercially available starting materials in very high yields. The second series of complexes described revolves around the (NHC)Pd(acac)n framework. These complexes are also air- and moisture-stable and can be prepared in a one-step synthesis in high yields from commercially available materials. These complexes were tested forƒn £-ketone arylation and Buchwald-Hartwig amination reactions affording high yields of the desired products, in short reaction times and mild reaction conditions.
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Haimad, N. "A theoretical and experimental investigation of the flow performance of automotive catalytic converters". Thesis, Coventry University, 1997. http://curve.coventry.ac.uk/open/items/3f51aa95-571c-73d5-bee3-4b523cab0a1c/1.
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Considerable research is being carried out into the parameters that affect catalyst performance in order to meet the latest emission regulations. The conversion efficiency and the durability of automotive catalytic converters are significantly dependent on catalyst flow performance. Related investigations are commonly conducted using CFD techniques which represent an inexpensive and fast alternative to experimental methods. This thesis focuses on the flow performance of automotive catalytic converters using both experimental and computational techniques. The work describes the effects of inlet flow conditions on catalyst performance, the application of radial vanes to catalyst systems and the refinement of the CFD flow model which increases the accuracy of the predicted catalyst flow performance. the effects of inlet flow conditions on the flow maldistribution across the catalyst face and the total pressure loss through the system were assessed using a steady air flow rig. Tests were conducted over a range of Reynolds numbers typically encountered in automotive catalytic converters using a uniform and a fully-developed inlet flow condition. The results showed that the flow maldistribution significantly increases with Reynolds number notably in wide-angled diffusers. The catalyst flow performance is considerably improved when the inlet flow is uniform rather than fully-developed, the non-dimensional total pressure loss is reduced by 8% at Re=60000 and the flow maldistribution across the catalyst face is decreased by 12.5% and 15% respective Reynolds numbers of 30000 and 60000 when using a 60 degree diffuser. The total pressure loss through the system was found to be mostly associated with the monolith brick resistance. When the flow maldistribution is approximately 2, the pressure loss across the monolith brick represents 80% of the system pressure loss. The flow maldistribution across the catalyst face was improved by locating a system of radial splitters in the diffuser. The optimum flow performance was found to be a complex function of the vane design. A maximum improvement in the flow maldistrution indices M and Mi of 25% and 50% respectively was achieved at the expense of an increase in total pressure loss of 13.5% at Re = 60000. Both CFD and flow visualisation techniques were used as an aid to interpreting the flow field in the diffuser. Although a qualitative agreement was obtained using CFD, the flow maldistribution across the catalyst face was underpredected by up to 20%. The accuracy of the flow predictions was significantly improved by investigating the flow field in the monolith channels. Flow recirculation occurs in the channel entry length when the flow approaches the monolith channels at an angle which induces an additional implemented into four models of the flow through axisymmetric catalyst assemblies using various diffuser geometries and inlet flow conditions. By including the flow entrance effects in the porous media approach, the flow maldistribution was predicted within 8% instead of 15% when these effects are neglected. Further investigation of the flow in the monolith channels will be required to accurately model three-dimentional flows (racetrack catalysts) and to include various channel geometries and system flow rates.
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Gomes, Pedro Miguel Vidinha. "Strategies for the enhancement of the catalytic performance of cutinase in nonaqueous media". Doctoral thesis, Faculdade de Ciências e Tecnologia, 2007. http://hdl.handle.net/10362/9364.
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Deshpande, Nitish. "Catalytic Material Design: Design Factors Affecting Catalyst Performance for Biomass and FineChemical Applications". The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu154273906480973.
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sharafi, mona. "Bottom-Up Synthesis Of Macromolecules And Their Selective Catalytic Performance At The Nanoscale". ScholarWorks @ UVM, 2020. https://scholarworks.uvm.edu/graddis/1189.
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Finding sustainable ways to create complex, sequence-defined polymers is
essential for future advances in the fields of medicine, electronics, and energy. Thus,
inspired by how nature builds functional macromolecules, this account aims to discover
catalysts, which will facilitate the accurate replication of synthetic nanoscale structures. In
this regard, the comprehensive sight of the work described within this dissertation is to
resolve the following fundamental questions: i) How to generate large, preorganized
macromolecules which can behave as supramolecular hosts to tune the properties of
molecules present in the vicinity of them? ii) What shapes do sequence-defined
oligomers/polymers adopt in solution under various conditions? In what ways can local
polymer conformations be manipulated by binding to supramolecular hosts? iii) Can we
exploit the folding behavior of these polymers as a powerful tool to provide selective
reactivity at the nanoscale and enhance the replication accuracy? Various synthetic
approaches leading to the successful precise manufacturing of synthetic macromolecules
including molecular strips, large macrocycles and porous cages are described. A significant
portion of my PhD research was also focused on the framework of selective catalysis for
polymers functionalization and replication; a unique concept which hasn’t been reported
previously.
Selective catalysis at the molecular scale represents a cornerstone of chemical
synthesis. However, it still remains an open question how to elevate tunable catalysis to
larger length-scales, where nanoscale structures (e.g. whole polymer chains) act as the
substrates and get functionalized in a selective manner. The efficient synthesis of a
hydrazone-linked tetrahedron with large opening, which acts as a catalyst to sizeselectively
functionalize polydisperse polymer-mixtures is described in details.
Experimental and computational evidence are provided to support a dual catalytic effect
exerted by the molecular tetrahedron, which (i) helps to unfold the polymer substrates and
(ii) exposes the amino groups on the polymeric side chains to the 12 triglyme units of the
tetrahedron to accelerate aminolysis. I was able to demonstrate complete reversal of the
intrinsic size-selectivity for polymer functionalization with our tetrahedral cage as the
catalyst. This finding enable the possibility to engineer hydrolytically stable molecular
polyhedra as organocatalysts for size- and future site-selective, post-synthetic polymer
modification (inspired by post-translational protein modification).
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Hajar, Yasmine. "Effect of Electrochemical Promotion and Metal-Support Interaction on Catalytic Performance of Nano-catalysts". Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39701.
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In heterogeneous catalysis, promoting the activity of the catalytic metals is long known as an important method to make a process more efficient and viable. Noble metals have been promoted classically by a chemical coverage of an ionic solution on the surface of the catalyst or using inert support, e.g., silica or alumina, allowing an increase of the dispersion of the catalyst. Therefore, new methods of promotion needed to be better explored to improve the efficiency of metal and metal oxide catalysts. One way of enhancing the catalyst’s activity is to disperse the noble metal at the nanoscale using an active type of support that is ion-conducting. Not only lattice ions can be exchanged with the surface of the nanoparticles but it can also engage in the oxidation reaction on the surface, resulting in what is known as metal-support interaction (MSI). Another method of improving the catalytic activity is to polarize the catalyst, allowing ions to migrate from a solid electrolyte to the gas-exposed surface, in a phenomenon known as electrochemical promotion of catalysis (EPOC). The change in the ions concentration on the surface would change the adsorption energy of the gaseous reactants and enhance or supress the catalytic rate.
In this thesis, the effect of supporting nanoparticles of noble and non-noble metal (oxides) (Pt, Ru, Ir, Ni) was studied for the case of ionic and ionic-electronic conducting supports (CeO2, TiO2, YSZ). The enhancement in their catalytic rate was found and correlated to an electrochemical property, the exchange current density. Then, using isotopically-labeled oxygen, the oxygen exchange ability of the conductive oxides was evaluated when supporting Ir and Ru nanoparticles and correlated with the results from C3H8 isotopic oxidation reaction, which showed the extent of involvement of oxygen from the support as carried by the isotopically-labeled CO2 produced.
Following this, electrochemical promotion of catalysis experiments were performed for different reactant/catalyst systems (C2H4 - Pt, Ru; C3H8 - Pt; CH4 - Pd, Ni9Pd). In the first system, the main outcome was the functional equivalence found for the MSI and EPOC effect in promoting the catalysts as experiments were performed at different temperatures, reactants partial pressures and polarization values. In the case of C3H8/Pt, the novel dispersion of Pt on an intermediate supporting layer (LSM/GDC) was found as a feasible method to obtain long stability of the catalyst while electrochemically promoting the rate of reaction. For CH4 oxidation, the polarization of the Pd nanoparticles showed continuous oxidation of the bulk of the catalyst resulting in a continuous increase of the catalytic rate. The Ni9Pd synthesized in a way to form a core/double-shell layer of Ni/Pd resulted in an enhanced catalytic rate and enhanced stability compared to stand-alone Pd.
And lastly, to comprehend the ions’ effect in the electrochemical promotion and the non-Faradaic nature of the phenomena, density-functional theory (DFT) modeling was used to demonstrate the increase of the heat of adsorption of reactants depending on their electronegative/positive nature.
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Jiang, Lulu. "Catalytic Performance and Characterization of Zn-doped Cryptomelane-type Manganese Dioxide For Ethanol Oxidation". Miami University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=miami1352827354.
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Castro, Galnares Sebastián (Castro Galnares Wright Paz). "Calibration and performance of a selective catalytic reduction (SCR) bench rig for NOx̳ emissions control". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45785.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.In title on title page, double underscored "x" appears as subscript.
Includes bibliographical references (p. 15).
A laboratory test rig was designed and built to easily test SCR (Selective Catalytic Reduction) technology. Equipped with three 6 kW heaters, connections for liquid N2 and an assortment of test gases, and a connection with an MKS NOx Analyzer, the rig allows for a vast range of SCR test conditions, and can easily be adapted for degreening, aging, and the implementation of other technologies onto the rig. To calibrate the test rig, baseline parameterization of a Cu-based zeolite (aluminosilicate) core was performed, including a temperature sweep and an NO/NO2 concentration sweep, while always maintaining a 1:1 ratio between NOx and NH3 reductant. The catalyst was found to have a peak deNOx efficiency of 99.8% between 250 'C and 300 'C, and maintained 98% efficiency with NO/NO2 < 1, while minimizing pollutant N20 generation.
by Sebastián Castro Galnares.
S.B.
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Wang, Kai. "Fundamental Understanding of Catalytic Performance of Perovskite Oxides in Advanced Oxidation Processes for Water Remediation". Thesis, Curtin University, 2022. http://hdl.handle.net/20.500.11937/89453.
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Perovskite oxides emerge as a group of promising catalysts for advanced oxidation processes (AOPs) owing to their flexible compositions and rich properties. In this thesis, a series of perovskite oxides has been designed and investigated in two novel AOPs systems (peroxymonosulfate activation and in-situ AOPs) for water remediation. The fundamental understandings of the intrinsic effects of some important material properties, such as crystal structure, defect feature, and surface properties on catalytic performances have been unveiled.
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Fedock, John Andrew. "Low temperature polymer electrolyte fuel cell performance degradation". [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002565.
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Li, Chenwei [Verfasser]. "Synthesis, characterization and catalytic performance of cerium dioxide with different morphologies for HCl oxidation / Chenwei Li". Gießen : Universitätsbibliothek, 2018. http://d-nb.info/1160874883/34.
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Sanchez, Trujillo Felipe Juan. "Investigation of the catalytic performance of palladium-based catalysts for hydrogen production from formic acid decomposition". Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/117629/.
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The objective of this work is to present formic acid as a suitable compound to be used in a hydrogen economy. Catalytic decomposition of formic acid at mild conditions is evaluated as a model reaction for hydrogen generation, making emphasis on the productivity, reusability of the catalysts, and quantification of concomitant CO evolved from the reaction. Characterisation of the fresh and used catalysts is performed to study the activity/structure relationship and investigate the possible reasons for its deactivation. Computational calculations are used to support experimental data and correlate productivity and CO evolution with the elementary steps of the reaction and the most common surfaces of the catalyst. Synthesis of materials with different surface properties and preparation methods is a fundamental part of this work. In Chapter 3, a commercial Pd/C catalyst is used as a reference to establish the reaction conditions that lead to a kinetically limited reaction. Reusability tests and subsequent characterisation of the used catalyst in conjunction with computational studies are performed to investigate its stability. Continuous flow experiments are carried out as a preliminary test to improve the reusability. Following the identification of the main parameters and characteristics of the catalysts involved in formic acid decomposition, in Chapter 4, materials with different properties (graphitisation degree and acid/base surface functionalisation) are synthesised by two preparation methods (sol-immobilisation and impregnation) using carbon nanofibers as supports. Once the optimal preparation method is identified, a set of parameters are modified in Chapter 5 to investigate the effects it has on the structure and morphology of the catalysts. Besides this optimisation, two supports (activated charcoal and titania) are investigated and an initial study of bimetallic catalysts and its properties is explored. Chapter 6 presents the main consequences of these results and a set of possibilities to continue this research.
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Fan, Kaicai. "Development of High Performance Electrocatalyst for Water Splitting Application". Thesis, Griffith University, 2018. http://hdl.handle.net/10072/382229.
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With increasing global demand for energy, rapid depletion of fossil fuels and intensification of environmental concerns, exploring clean and sustainable energy carriers to replace fossil fuel is becoming critical. Among the various alternatives, hydrogen has been intensively regarded as a promising energy carrier to fulfill the increasing energy demand due to its large energy density per unit mass and eco-friendly production possibilities. However, hydrogen does not exist in molecular structure in nature, and it is essential to obtain efficient and sustainable H2 production technologies. Alkaline water electrolysis is an effective, clean and sustainable process to produce high-quality hydrogen. In this process, highly active electrocatalysts for the hydrogen evolution reaction (HER) are required to accelerate the sluggish kinetics and lower the overpotentials (η) for efficient hydrogen evolution. To date, a noble metal, platinum (Pt), is the state-of-art electrocatalyst for HER. However, exploration of alternative electrocatalysts with low cost and excellent electrocatalytic activity is of vital importance to realize large-scale hydrogen production through water electrolysis. Generally, an electrochemically active catalyst should have an optimal hydrogen adsorption free energy to allow efficient catalytic hydrogen adsorption/desorption. In alkaline solution, dissociation of water onto the electrocatalyst determines the overall HER efficiency.
This thesis focuses on rational design and synthesis of different earth-abundant electrocatalysts for electrocatalytic HER in alkaline media. Through facile anion or cation doping strategies, electrocatalysts with abundant accessible active sites, enhanced electronic conductivity and accelerated HER kinetics have been systematically fabricated, characterized and evaluated.
First, an efficient HER electrocatalyst in alkaline media was fabricated by incorporating sulfur atoms into a cobalt (hydro)oxide crystal structure. The resultant catalyst exhibits a remarkably enhanced HER activity with a low-overpotential of 119 mV at 10 mA/cm2 and an excellent durability. The results suggest that cobalt hydroxide benefits water adsorption and cleavage, while the negatively charged sulfur ligands facilitate hydrogen adsorption and desorption on the surface of electrocatalysts, leading to significantly promoted Volmer and Heyrovsky steps for HER in alkaline media.
Second, exploring bifunctional electrocatalysts which can simultaneously accelerate the HER and oxygen evolution reaction (OER) activities plays a key role in alkaline water splitting. Here, sulfur atoms were incorporated into the mixed transition metal hydroxide with high OER performance to render excellent HER activity. The enhanced catalytic activity towards HER was confirmed by a synergistic effect between the retained metal hydroxide host and the incorporated sulfur atoms. In addition, the full water splitting electrolyzer equipped with fabricated bifunctional electrocatalysts as anode and cathode materials exhibited remarkable overall water splitting performance comparable to that with benchmark Pt and RuO2 electrocatalysts.
The S/Se co-doped Co3O4 nanosheets on carbon cloth were fabricated by a facile room temperature chalcogen atom incorporation methodology and were applied as the electrocatalyst for HER in alkaline media. The sulfur and selenium atoms were homogeneously distributed on the surface by forming Co-S or Co-Se bonds which play a key role in the structural change in electrochemical activation. The obtained electrocatalysts demonstrated remarkably improved HER activity compared to that of the original Co3O4.
Finally, molybdenum doped cobalt hydroxide was fabricated with significantly accelerated HER kinetics. The introduced Mo sites not only effectively facilitate water dissociation process and desorption of the OHads intermediates, but also simultaneously optimize the hydrogen adsorption free energy. Therefore, the in situ-generated Mo-doped amorphous cobalt hydroxide exhibited a remarkable HER performance in alkaline media with an overpotential of only -80 mV at a current density of 10 mA/cm2.
This thesis innovatively explores strategies to improve the catalytic activity towards HER of metal (hydro)oxide in alkaline media. The surface foreign atom doping was demonstrated to manipulate the surface structure of catalysts, thus not only improving the water dissociation processes, but also facilitating the hydrogen adsorption/desorption on the catalysts. The demonstrated facile and effective strategies could be adopted for the fabrication of cost-effective and highly active catalysts for other important chemical reactions for energy conversion applications.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environment and Sc
Science, Environment, Engineering and Technology
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Takahashi, Masaru. "Solvothermal synthesis of Ga2O3-Al2O3 catalysts and their performance for selective catalytic reduction of NO with methane". 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/136136.
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Ma, Liang-Chih. "Palladium/Alloy-based Catalytic Membrane Reactor Technology Options for Hydrogen Production: A Techno-Economic Performance Assessment Study". Digital WPI, 2016. https://digitalcommons.wpi.edu/etd-dissertations/535.
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Hydrogen (H2) represents an energy carrier endowed with the potential to contribute to the design of a robust and reliable global energy system by complementing electricity as well as liquid fuels use in an environmentally responsible manner provided that the pertinent H2 production technologies (conventional and new ones) can reach techno-economically attractive performance levels in the presence of irreducible (macroeconomic, fuel market, regulatory) uncertainty. Indeed, the role of H2 in the global energy economy is widely recognized as significant in light also of fast-growing demand in the petrochemical and chemical processing sector as well as future regulatory action on greenhouse gas emissions. Pd and Pd/Alloy-based catalytic membrane reactor (CMR) modules potentially integrated into H2 production (HP-CMR) process systems offer a promising technical pathway towards H2 production with enhanced environmental performance in a carbon-constrained world. However, the lack of accumulated operating experience for HP-CMR plants on the commercial scale poses significant challenges. Therefore, any preliminary attempt to assess their economic viability is certainly justified. A comprehensive techno-economic performance assessment framework has been developed for HP-CMRs with CO2 capture capabilities. A functional Net Present Value (NPV) model has been developed first to evaluate the economic viability of HP-CMRs. The plant/project value of HP-CMR is compared to other competing technology options such as traditional coal-gasification and methane steam reforming-based hydrogen production plants with and without CO2 capture. Sources of irreducible uncertainty (market and regulatory) as well as technology risks are explicitly recognized and the effect of these uncertainty drivers on the plant’s/project’s value is taken into account using Monte-Carlo techniques. Therefore, more realistic distribution profiles of the plant’s economic performance outcomes are generated rather than single-point value estimates. It is shown that future regulatory action on CO2 emissions could induce appealing NPV-distribution profiles for HP-CMRs in the presence of uncertainty and technology risks. Finally, the valuation assessment is complemented with a sensitivity analysis for different representative values of the discount rate that span a reasonable range associated with business and financing risks. It apparently indicates that creatively structured financing mechanisms leading to a reduction of the cost of capital/discount rate could induce more appealing economic performance outcomes and valuation profiles. Furthermore, the proposed research work aims at the development of a methodological framework to assess the economic value of flexible alternatives in the design and operation of HP-CMR plants with carbon capture capabilities under the aforementioned sources of uncertainty. The main objective is to demonstrate the potential value enhancement associated with the long-term economic performance of flexible HP-CMR project investments by managing the uncertainty associated with future environmental regulations. Within the proposed context, promising design flexibility concepts for HP-CMR plants are introduced and operational as well as constructional flexibility options are identified and assessed. In particular, operational flexibility will be realized through periodic and temporary shutdowns of the carbon capture unit in response to regulatory uncertainties. Constructional flexibility will be realized by considering the installation of a carbon capture unit at three strategic periods: 1) installation in the initial design phase, 2) retrofitting at a later stage and 3) retrofitting with preinvestment. Monte Carlo simulations and financial analysis will be conducted in order to demonstrate that, in the presence of irreducible uncertainty, design flexibility options could lead to economic performance enhancement of HP-CMR plants by actively responding to the above sources of uncertainty as they get resolved over the plant’s lifetime.
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Tangale, N. P. "Zeolite based micro-mesoporous composites: synthesis, characterization and catalytic performance as heterogeneous catalyst for valorization of sugar". Thesis(Ph.D.), CSIR- National Chemical Laboratory, Pune, 2018. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/4576.
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Bock, Thorsten R. "Catalytic phosphonation of high performance polymers and POSS novel components for polymer blend and nanocomposite fuel cell membranes /". [S.l.] : [s.n.], 2007. http://www.freidok.uni-freiburg.de/volltexte/2881.
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Yoshida, Shosuke. "Engineering of a Type III Rubisco from a Hyperthermophilic Archaeon Aimed to Enhance Catalytic Performance at Ambient Temperatures". 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/57249.
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Kyoto University (京都大学)0048
新制・課程博士
博士(工学)
甲第13793号
工博第2897号
新制||工||1428(附属図書館)
26009
UT51-2008-C709
京都大学大学院工学研究科合成・生物化学専攻
(主査)教授 今中 忠行, 教授 青山 安宏, 教授 濵地 格
学位規則第4条第1項該当
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Aydemir, Bugce. "Synthesis Of Mesoporous Catalysts And Their Performance In Pyrolysis Of Polyethylene". Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612830/index.pdf.
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Plastic materials are widely used throughout the world due to their low prices and easy processing methods. A serious problem of environmental pollution is brought with the widespread use of these materials due to their non-biodegradabilty. For this reason, plastic materials are degraded into lower molecular weight liquid and gaseous products which are potential raw materials and fuels for petrochemical industry. The use of catalysts enhances the formation of more valuable hydrocarbons at lower reaction temperatures and residence times.
In this study, aluminum containing MCM-41 and tungstophosphoric acid (TPA) loaded SBA-15 materials were synthesized by impregnation of Al and TPA into hydrothermally synthesized MCM-41 and SBA-15, respectively to be used in catalytic degradation of polyethylene. Al was incorporated into MCM-41 framework with different Al/Si ratios using aluminum triisopropylate as the aluminum source and TPA was incorporated to the porous framework of SBA-15 with different W/Si ratios, using tungstophosphoric acid hydrate as the acid source.
From XRD analysis, it was observed that introducing acidic compounds did not cause deformations in the regularity and by EDS analysis, it was found out that at lower loadings, acidic compounds were introduced more effectively for MCM-41 materials. Nitrogen adsorption-desorption isotherms showed that the synthesized materials exhibited type IV isotherms. SEM and TEM pictures showed the hexagonal regularly ordered structure of SBA-15 and MCM-41 materials. FTIR analysis of the pyridine adsorbed synthesized materials revealed the existence of Lewis and Brønsted acid sites in the synthesized materials. From TGA analysis it was observed that aluminum impregnated MCM-41 samples reduced the temperature of the degradation reaction significantly and TPA loaded SBA-15 samples reduced activation energy of the reaction effectively. In the degradation reaction system, non-catalytic and catalytic degradation experiments of polyethylene were performed. In non-catalytic degradation and catalytic degradation reactions carried out using aluminum containing MCM-41 materials, selectivity of C3 and C4 hydrocarbon gases was high and in catalytic degradation reactions carried out using TPA impregnated SBA-15 materials, selectivity of ethylene was high. In the liquid analysis of non-catalytic degradation reactions, it was observed that the product distribution was mainly composed of hydrocarbons greater than C18. The use of aluminum loaded MCM-41 and TPA loaded SBA-15 materials resulted in a liquid product distribution in the range of C5-C14, which is the hydrocarbon range of gasoline fuel.
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Zhang, Zhihao. "The Development of Three Dimensional Porous Nickel Materials and their Catalytic Performance towards Oxygen Evolution Reaction in Alkaline Media". Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/40636.
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As the global energy crisis and environmental pollution problem continues, there is an increasing demand for clean and sustainable energy storage and conversion technologies, such as water-splitting electrolysis. Water electrolysis is a process of running an electrical current through water in separating the hydrogen and oxygen. Oxygen evolution reaction (OER) is a key reaction in this electrochemical process, and the electrochemical performance of these systems is usually hindered by the slow OER reaction kinetics. In order to achieve high energy conversion efficiency, the development of efficient OER catalysts is the key. To achieve that, abundant research is done by using noble metal oxides as catalyst, such as IrO2 and RuO2. However, considering their high cost, a cheap earth-abundant material with a high OER catalytic activity is required. Accordingly, this study has been focused on the synthesis of three dimensional porous structured Ni-based OER catalysts. First, a 3D porous Ni meso-foam was developed through a facile high-temperature one-pot synthesis method, and its catalytic activity towards OER was explored. Specifically, the as-synthesized Ni meso-foam material, referred to as raw NMF, has a wire-linked structure and high surface area. A reduction procedure was introduced to obtain reduced Ni meso-foam materials, referred to as NMF-H2. It was also oxidized in air at 600 ℃ to form a semi-hollow NiO crosslinking phase and subsequently reduced in H2 at 300℃, forming a regenerated porous Ni foam material, referred to as NMF-O2/H2. The composition and morphology of all materials were investigated by XRD and SEM, respectively. The SEM image reveals that, in the porous NMF-O2/H2, the cross-linked meso-wire structure was maintained, and the average pore size is between 0.5-5 μm. Electrochemical analysis show that the OER activity of the Ni foam catalysts follows NMF-O2/H2 > NMF-H2 > raw NMF. In addition to the NMF-based materials, a Ni/Ni(OH)2 layer-structured electrocatalyst, referred to as NiDHBT, was also developed using a dynamic hydrogen bubble templating (DHBT) method. First, the 3D-porous micro Ni/Zn nanoplatelets were constructed in a two-step DHBT deposition method. The Ni/Zn foil was used as a scaffold, featured with the open porous structure and high surface area, for the subsequent electrodeposition of Ni(OH)2. Then, the Zn was etched from the as-prepared Ni/Zn/Ni(OH)2 nanocomposite to obtain the NiDHBT. The catalytic performance of the NiDHBT toward OER reaction was evaluated, and the optimal catalysts developed from different electro deposition potentials were determined. On the recognition of the high catalytic activity of NMF-O2/H2 and NiDHBT, porous structured FeOx-Nickel meso-foam, referred to as Fe@NMF-O2/H2, and FeOx- Ni/Ni(OH)2 layered-structure materials, referred to as Fe@NiDHBT, was further developed to explore the benefits of FeOx deposition for its OER catalytic performance. The deposition of FeOx is achieved by physical mixing FeOx colloid with NMF-O2/H2 and NiDHBT, and the electrochemical performance of these materials was examined in 1 M KOH. Among the developed materials, the best performing catalyst is Fe@NiDHBT synthesized by loading FeOx colloid onto the NiDHBT support. The overpotential for Fe@NiDHBT to reach 10 mA·cm-2 is 247mV, and the corresponding Tafel slope is 48.10mV·dec-1. Therefore, it was concluded that the FeOx¬¬ loading modification is an effective strategy to improve the OER activity of Ni foam-based catalysts.
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Inayat, Amer [Verfasser] y Wilhelm [Akademischer Betreuer] Schwieger. "Open-cell Foams as Catalyst Support: A Description of Morphology, Fluid Dynamics and Catalytic Performance / Amer Inayat. Gutachter: Wilhelm Schwieger". Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2014. http://d-nb.info/1054342253/34.
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Lin, ChienShung. "Effect of wall thermal conductivity on the performance of Swiss roll combustors using ammonia pretreated Pt catalyst for catalytic reaction". Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Thesis/Spring2009/C_Lin_040609.pdf.
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Thesis (M.S. in mechanical engineering)--Washington State University, May 2009.Title from PDF title page (viewed on May 27, 2009). "School of Mechanical and Material Engineering." Includes bibliographical references (p. 45-47).
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Enachi, Andreea Verfasser], Marc D. [Akademischer Betreuer] Walter y Martin [Akademischer Betreuer] [Bröring. "Development of homogeneous Co and Ni (pre−)catalysts : synthesis, characterization, and catalytic performance / Andreea Enachi ; Marc D. Walter, Martin Bröring". Braunschweig : Technische Universität Braunschweig, 2021. http://d-nb.info/122547843X/34.
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Pinkas, Jiri. "Modification of cyclopentadienyl ligands in titanium and zirconium metallocene dichlorides : impact on their catalytic performance in polymerization and copolymerization of olefins". Dijon, 2004. http://www.theses.fr/2004DIJOS054.
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Väliheikki, A. (Ari). "Resistance of catalytic materials towards chemical impurities:the effect of sulphur and biomaterial-based compounds on the performance of DOC and SCR catalysts". Doctoral thesis, Oulun yliopisto, 2016. http://urn.fi/urn:isbn:9789526212845.
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Abstract Exhaust gas emissions, e.g. nitrogen oxides (NOx), hydrocarbons (HCs) and carbon monoxide (CO), are harmful to human health and the environment. Catalysis is an efficient method to decrease these emissions. Unfortunately, the fuels and lubricant oils may contain chemical impurities that are also present in exhaust gases. Thus, catalytic materials with high activity and chemical resistance towards impurities are needed in the abatement of exhaust gas emission. In this thesis, the aim was to gain new knowledge about the effects of chemical impurities on the behaviour and activity of the catalysts. To find out these effects, the impurities existing in the exhaust gas particulate matter after combustion of biofuels and fossil fuels were analysed. The studied zeolite (ZSM-5), cerium-zirconium mixed oxides (CeZr and ZrCe) and silicon-zirconium oxide (SiZr) based catalysts were also treated with impurities to simulate the poisoning of the catalysts by, e.g. potassium, sodium, phosphorus and sulphur, using gas or liquid phase treatments. Several characterization techniques were applied to find out the effects of impurities on catalysts’ properties. The activity of catalysts was tested in laboratory-scale measurements in CO and HC oxidation and NOx reduction using ammonia (NH3) and hydrogen (H2) as reductants. The results revealed that the CeZr based catalysts had a high activity in NOx reduction by NH3 and moderate activity by H2. Sulphur was proven to enhance the activity of CeZr catalysts in NOx reduction. This is due to an increase in chemisorbed oxygen after the sulphur treatment on the catalyst surface. Instead, in HC and CO oxidation reactions, sulphur had a negligible impact on the activity of the SiZr based diesel oxidation catalyst. Thus, both CeZr and SiZr based catalysts can be utilized in exhaust gas purification when sulphur is present. ZSM-5 based catalysts were proven to be resistant to potassium and sodium. Alternatively, the activity of SiZr based catalysts decreased due to phosphorus. Thus, the removal of biomaterial-based impurities from the exhaust gases is needed to retain high catalyst activity in the exhaust gas after-treatment systemTiivistelmä Pakokaasupäästöissä olevat typen oksidit (NOx), hiilivedyt (HCs) ja hiilimonoksidi (CO) ovat haitallisia ihmisten terveydelle ja ympäristölle. Katalyysi on tehokas menetelmä vähentää näitä päästökomponentteja. Polttoaineet ja voiteluöljyt sisältävät epäpuhtauksia, jotka siirtyvät myös pakokaasuihin. Tästä johtuen pakokaasupäästöjen hallinnassa tarvitaan katalyyttimateriaaleja, joilla on hyvä vastustuskyky myrkyttymistä vastaan. Tavoitteena oli saada uutta tietoa kemiallisten epäpuhtauksien vaikutuksesta katalyyttien toimintaan. Biopolttoaineiden sisältämät mahdolliset epäpuhtaudet selvitettiin analysoimalla fossiilisen ja biopolttoaineen palamisessa muodostuvia partikkeleita ja vertaamalla niitä polttoaineiden hivenaineanalyysiin. Tutkimuksessa käytetyt zeoliitti (ZSM-5), cerium-zirkonium-sekaoksidi (CeZr) ja pii-zirkonium-oksidipohjaiset (SiZr) katalyytit käsiteltiin epäpuhtauksilla (kalium, natrium, fosfori ja rikki) kaasu- ja nestefaasissa. Tutkimuksessa käytettiin useita karakterisointitekniikoita, joiden avulla selvitettiin epäpuhtauksien vaikutuksia katalyyttien ominaisuuksiin. Katalyyttien toimintaa testattiin laboratoriomittakaavan kokeissa CO:n ja HC-yhdisteiden hapetuksessa sekä NOx:ien pelkistyksessä käyttäen ammoniakkia (NH3) tai vetyä (H2) pelkistimenä. Tulokset osoittavat, että CeZr-pohjaisten katalyyttien aktiivisuus NOx:ien pelkistyksessä oli hyvä käytettäessä pelkistimenä NH3:a ja kohtalainen käytettäessä vetyä. Rikki paransi CeZr-katalyyttien aktiivisuutta NOx:ien pelkistyksessä, mikä johtui kemiallisesti sitoutuneen hapen osuudesta katalyyttien pinnoilla. Vastaavasti hiilivetyjen ja CO:n hapetusreaktioissa rikki ei vaikuttanut SiZr-pohjaisten dieselhapetuskatalyyttien aktiivisuuteen. Sekä CeZr- ja SiZr-pohjaisia katalyytteja voidaan siten käyttää rikkiä sisältävien pakokaasujen puhdistuksessa. SiZr-pohjaisten katalyyttien aktiivisuus laski fosforin vuoksi. ZSM-5-pohjaiset katalyytit olivat vastustuskykyisiä kaliumille ja natriumille. Kestäviä katalyyttejä on siten kehitettävä, mikäli biopolttoaineiden sisältämien epäpuhtauksien poistaminen polttoaineista ei ole mahdollista
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Keuler, Johan Nico. "Optimising catalyst and membrane performance and performing a fundamental analysis on the dehydrogenation of ethanol and 2-butanol in a catalytic membrane reactor". Thesis, Link to the online version, 2000. http://hdl.handle.net/10019.1/1277.
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Chen, Shuo. "Effect of metal dispersion on the catalytic performance of monometallic Ni/SBA-15 and Cu/SBA-15 catalysts in the hydroconversion of HMF". Thesis, Lille, 2019. http://www.theses.fr/2019LIL1R008.
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La production d'additifs pour les carburants, d’indices d'octane élevés, à partir des molécules biosourcées telles que le 5-hydroxyméthylfurfural (HMF) est le sujet de nombreuses études. Les catalyseurs à base de Pt, de Pd et de Ru sont décrits comme particulièrement actifs dans la réaction de conversion du HMF en 2,5-diméthylfurane (DMF) et en 2,5-diméthyltétrahydrofurane (DMTHF). Cependant leur substitution dans les formulations catalytiques est souhaitable compte tenu de leur coût élevé et de leur faible disponibilité. Les éléments de substitution peuvent être certains métaux de transition (par exemple Cu ou Ni), plus abondants, mais généralement moins actifs. Mes travaux de recherche ont donc portés sur la préparation de catalyseurs, à base de métaux de transition, actifs et sélectifs pour l'hydrogénation du HMF en des molécules pouvant être incorporées dans les carburants. Les phases actives étudiées au cours de mon doctorat reposent sur les métaux de transition Ni et Cu. Ces phases actives ont été supportées sur des silices mésoporeuses de type SBA-15. L'étude est divisée en deux parties distinctes, en fonction du métal étudié. La première partie du doctorat présente les résultats obtenus avec des catalyseurs monométalliques Ni supportés. Dans un premier temps, l'optimisation des paramètres de réaction pour l'hydroconversion sélective du HMF en DMF et en DMTHF a été réalisée en utilisant un catalyseur préparé par la méthode d'imprégnation à humidité naissante d’une solution du précurseur nitrate (Chapitre 3). Les paramètres de réaction optimisés incluent la température de réaction, la pression de dihydrogène, le rapport molaire HMF/Ni et le temps de réaction. Une étude cinétique préliminaire a également été réalisée. L’effet de la dispersion et de la taille des particules métalliques de Ni sur les performances catalytiques des catalyseurs Ni/SBA-15 a été étudié sur des matériaux préparés par la méthode d’infiltration à l'état fondu des précurseurs nitrates (Chapitre 4). Le niveau de dispersion du nickel a été modifié en utilisant des supports SBA-15 contenant des porosités d’interconnexion différentes et obtenues à différentes températures de synthèse. Les résultats montent que le catalyseur Ni/SBA-15, préparé par la méthode simple IWI, permet d’atteindre des rendements élevés en DMF et DMTHF dans des conditions réactionnelles optimales. Le niveau de dispersion du Ni, tel qu’observé à partir des matériaux obtenus par infiltration des sels fondus, a quant à lui un effet significatif sur l'activité catalytique du catalyseur. La deuxième partie de mes travaux de recherche porte sur les propriétés catalytiques des catalyseurs monométalliques à base de Cu/SBA-15 préparés par différentes méthodes, et présentant des états de division de la phase Cu différents (Chapitre 5). Les modes de synthèse appliqués incluent la méthode d’imprégnation à humidité naissante (IWI), la méthode d'autocombustion in situ (ISAC) et la méthode de déposition par précipitation (DP). La première partie de l’étude a donc portée sur l'optimisation des conditions de réaction pour l'hydroconversion sélective du HMF en DMF (avec le catalyseur Cu/SBA-15 préparé par la méthode ISAC). Les paramètres de réaction optimisés, comme dans le cadre de l’étude avec Ni/SBA-15, ont été la température de réaction, la pression de dihydrogène, le rapport molaire HMF/Cu et le temps de réaction. La réutilisation du catalyseur a également été étudiée, et une étude cinétique de la transformation du HMF sur Cu menée. Cette partie démontre que l’activité du Cu pour la conversion sélective du HMF en DMF dépend principalement de l’état de dispersion du Cu. L'utilisation de la méthode DP a conduit à un catalyseur Cu/SBA-15 hautement divisé, ce qui a permis d’atteindre des rendements élevs en DMFThe production of fuel additives, having high octane numbers, from biosourced molecules such as 5-hydroxymethylfurfural (HMF), is the subject of many studies. The Pt, Pd and Ru-based catalysts are described as particularly active in the conversion reaction of HMF to 2,5-dimethylfuran (DMF) and to 2,5-dimethyltetrahydrofuran (DMTHF). However, their substitutions in the catalytic formulations are desirable in view of their high cost and low availability. The substitution elements can be transition metals (for example Cu or Ni), which are more abundant, but generally less active. My research has focused on the preparation of catalysts, based on transition metals, active and selective for the hydrogenation of HMF into molecules that can be incorporated into fuels. The active phases studied during my Ph.D. are based on Ni and Cu transition metals. These active phases were supported on mesoporous silica of SBA-15 type. The study is divided into two distinct parts, depending on the metal studied.The first part of the Ph.D. presents the results obtained with Ni supported monometallic catalysts. In a first step, the optimization of the reaction parameters for the selective hydroconversion of HMF to DMF and DMTHF was carried out using a catalyst prepared by the incipient wetness impregnation (IWI) of the nitrate precursor solution (Chapter 3). Optimized reaction parameters include reaction temperature, dihydrogen pressure, HMF/Ni molar ratio, and reaction time. A preliminary kinetic study was also performed. The effect of the dispersion and size of Ni metal particles on the catalytic performance of Ni/SBA-15 catalysts was studied on materials prepared by the melt infiltration (MI) method of nitrate precursors (Chapter 4). The level of dispersion of the nickel was modified using SBA-15 supports containing different interconnection porosities, obtained at different synthesis temperatures. The results show that the Ni/SBA-15 catalyst, prepared by the simple IWI method, achieves high yields of DMF and DMTHF under optimal reaction conditions. The level of Ni dispersion, as observed from the materials obtained by infiltration of molten salts, has a significant effect on the catalytic activity of the catalyst.The second part of my research focuses on the catalytic properties of Cu/SBA-15 monometallic catalysts prepared by different methods, and having different Cu phase division degree (Chapter 5). The methods of preparation applied include the IWI method, the in situ autocombustion method (ISAC) and the deposition-precipitation method (DP). The first part of the study therefore focused on the optimization of the reaction conditions for the selective hydroconversion of HMF to DMF (over the Cu/SBA-15 catalyst prepared by the ISAC method). Optimized reaction parameters, as for Ni/SBA-15, were reaction temperature, hydrogen pressure, HMF/Cu molar ratio, and reaction time. The reuse of the catalyst was also studied, and a kinetic study of the transformation of HMF on Cu/SBA-15 conducted. This part demonstrates that the activity of Cu for the selective conversion of HMF to DMF depends mainly on the state of dispersion of Cu. The use of the DP method led to a highly divided Cu/SBA-15 catalyst, which made it possible to achieve high yields of DMF
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Mercier, Anne-Gaelle. "Etude et réalisation de couches actives de PEFMC architecturées". Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENI050.
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Les piles à combustible de type PEMFC constituent un maillon essentiel du cycle utilisant l'hydrogène comme vecteur d'énergie afin de permettre l'utilisation des énergies renouvelables. Cependant, leur développement connaît encore des limitations en termes de performances initiales, de coût et de durabilité. Cette thèse se concentre sur les couches actives des électrodes dont le catalyseur, souvent du platine, peut représenter jusqu'à 25% du coût global. Un des enjeux a ainsi été de mieux comprendre le fonctionnement de ces électrodes, qui peut être inhomogène, afin d'améliorer la distribution du platine dans la couche active et optimiser son utilisation. Pour cela, des électrodes « architecturées », c'est-à-dire avec des chargements en platine variables au sein de la couche active, ont été réalisées grâce à la flexibilité de deux procédés d'impression : le jet d'encre et la sérigraphie. Une adaptation de la formulation des encres catalytiques et des paramètres d'impression a permis la mise en œuvre de ces deux procédés et la réalisation de couches actives présentant une large gamme de chargements en catalyseur (0,05mgPt/cm² à 0,5mgPt/cm²). Différentes distributions de platine ont été étudiées et comparées à des couches actives uniformes: dans le plan d'une part, à l'échelle dent/canal de la plaque bipolaire et à l'échelle entrée/sortie, et dans l'épaisseur d'autre part. Les architectures ont permis de mettre en évidence différentes contributions de la couche active suivant sa localisation sous la plaque bipolaire et ainsi de proposer des modifications de sa structure qui peuvent être réalisées grâce aux procédés d'impression. Par ailleurs, la durabilité des structures les plus pertinentes a été évaluée par des essais de longue durée qui ont montré qu'il est possible de réduire la pente de dégradation par la modification de la distribution du platinePEM fuel cells stand for an essential link in the cycle using hydrogen as an energy carrier.However, their development is still limited by initial performance, costs and durability.This study focuses on the electrode catalyst layer which contains most of the time platinum, anexpensive catalyst that can represent 25% of the overall cost of a system. Thus, one of the issues hasbeen to provide a better understanding of electrode operating, which can be heterogeneous. The aim ofthis study is particularly to enhance platinum distribution in the catalyst layer to optimize itsutilization.Architectured electrodes, that is to say with variable platinum loading inside the catalyst layerhave been developed thanks to the flexibility of two printing processes : inkjet printing and screenprinting. The adjustment of catalyst ink formulation and printing parameters enabled to fabricatecatalyst layers with a wide range of platinum loading, from 0,05mgPt/cm² to 0,5mgPt/cm². Severalplatinum distributions were compared to uniform catalyst layers at different scales: the scale of ribsand channels and of gas inlet and oultet of bipolar plate, as well as through the catalyst layer thickness.Electrodes architecture enabled to point out different contribution of catalyst layers according to itslocalizing under the bipolar plate and to suggest modifications of its structure that provide an increaseof performance.Otherwise, the estimation of lifetime of several architectures thanks to ageing tests in loadcycling mode showed that these structures enabled to reduce their performance decay rate
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Langfeld, Kirsten [Verfasser] y Reinhard [Akademischer Betreuer] Schomäcker. "Impact of Synthesis Methods and Oxidizing Agents on the Catalytic Performance of Various Catalysts in the Oxidative Coupling of Methane / Kirsten Langfeld. Betreuer: Reinhard Schomäcker". Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2012. http://d-nb.info/1021219967/34.
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Àlvarez, Castro Helver Crispiniano 1984. "Análise de variáveis de processo via CFD visando aperfeiçoamento de performance em riser de FCC". [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266067.
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Orientador: Milton MoriTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-26T06:44:29Z (GMT). No. of bitstreams: 1 AlvarezCastro_HelverCrispiniano_D.pdf: 5280150 bytes, checksum: 96fb29e2849d11c06890186cb8af2f51 (MD5) Previous issue date: 2014
Resumo: Conversão de matéria-prima e rendimento são estudados através de um modelo 3D que simula o principal reator do processo de craqueamento catalítico fluidizado (FCC). Fluidodinâmica computacional (CFD) é usada como técnica com abordagem Euleriana-Euleriana para prever o comportamento do riser da FCC. O modelo considera 12 grupos com desativação do catalisador dada por coque e envenenamento por nitritos alcalinas e adsorção aromático policíclico para estimar o comportamento cinético, o qual partindo de uma determinada matéria prima, se craquea a diversos produtos. Composições diferentes para matérias-primas foram consideradas. Para validação o modelo foi comparado com dados experimentais em condições de operação industrial. O modelo é capaz de representar com precisão a geração de produtos para as diferentes condições de operação consideradas. Todas as condições consideradas foram resolvidos usando o solver Ansys CFX 14.0. As diferentes variáveis do processo de operação e efeitos hidrodinâmicos do riser industrial de craqueamento catalítico fluidizado (FCC) foram avaliadas. As previsões do modelo são apresentados e comparadas; conversão e produtos são apresentados. Recomendações para criar condições para obter maior rendimento do produto no processo industrial foram dadas
Abstract: Feedstock conversion and yield products are studied through a 3D model simulating the main reactor of the fluid catalytic cracking (FCC) process. Computational Fluid Dynamic (CFD) is used with Eulerian-Eulerian approach to predict the fluid catalytic cracking behavior. The model considers 12 lumps with catalyst deactivation by coke and poisoning by alkaline nitrides and polycyclic aromatic adsorption to estimate the kinetic behavior which, starting from a given feedstock, produces several cracking products. Different feedstock compositions are considered. The model is compared with sampling data at industrial operation conditions. The simulation model is able to represent accurately the products behavior for the different operating conditions considered. All the conditions considered were solved using a solver Ansys CFX 14.0. The different operation process variables and hydrodynamic effects of the industrial riser of a fluid catalytic cracking (FCC) are evaluated. Predictions from the model are shown and comparison with experimental conversion and yields products are presented; recommendations are drawn to establish the conditions to obtain higher product yields in the industrial process
Doutorado
Engenharia de Processos
Doutor em Engenharia Química
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Liu, Yiwei. "The catalytic performance and characterization of BaO- and BaX2(X=F, Cl, Br)-promoted Ln2O3(Ln=Y, Er, Nd) catalysts for the oxidative coupling of methane". HKBU Institutional Repository, 1998. http://repository.hkbu.edu.hk/etd_ra/176.
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Wang, Xingli [Verfasser], Peter [Akademischer Betreuer] Strasser, Frédéric [Gutachter] Jaouen y Peter [Gutachter] Strasser. "Copper-based nanostructured catalysts for efficient and selective CO2 electroreduction – synthesis, catalytic performance, and mechanistic analysis / Xingli Wang ; Gutachter: Frédéric Jaouen, Peter Strasser ; Betreuer: Peter Strasser". Berlin : Technische Universität Berlin, 2020. http://d-nb.info/1209601494/34.
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Soiné, Robert Paul. "An analysis of the performance of a South African stainless steel manufacturer in localising the demand for corrosion resistant steels within the Eastern Cape catalytic converter industry". Thesis, Port Elizabeth Technikon, 2004. http://hdl.handle.net/10948/200.
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Commercial decisions are been made with respect to the competitive advantage of manufacturing catalytic converters in South Africa. This thesis identifies those factors relating to the sourcing of stainless steel and the impact it has of securing future business in a competitive environment. The catalytic converter industry requires the support of a stainless steel plant that provides high quality products at a competitive price, while keeping abreast with international developments.
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Ballentine, Michael Drake. "Imidazolium Ionic Liquids as Multifunctional Solvents, Ligands, and Reducing Agents for Noble Metal Deposition onto Well-Defined Heterostructures and the Effect of Synthetic History on Catalytic Performance". TopSCHOLAR®, 2018. https://digitalcommons.wku.edu/theses/2101.
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1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM]Tf2N) was investigated as a multifunctional solvent, ligand, and reducing agent for platinum deposition onto well-defined CdSe@CdS nanorods. Platinum deposition was carried out thermally and photochemically using Pt(acac)2 as the metal precursor. Thermal deposition was investigated in [BMIM]Tf2N with and without addition of a sacrificial reducing agent, and product topology was compared with the products obtained from polyol reduction using 1,2-hexadecanediol, oleic acid, and oleylamine in diphenyl ether. Photochemically induced platinum deposition was carried out at room temperature in [BMIM]Tf2N, and product topology was compared with the photodeposition products obtained from a toluene dispersion. Thermal deposition of platinum in ionic liquid showed rods of broken morphology and small platinum nanoparticles speckled across the rods’ surface, while photodeposition of platinum exhibited particles decorated throughout the nanorod surface but larger in size than those exhibited by thermal means. Photocatalytic
reduction of methylene blue was studied using these Pt-CdSe@CdS heterostructured nanoparticles, and catalytic performance was correlated with topology and synthetic history. Initial findings of catalytic performance suggest that there in an advantage of depositing platinum nanoparticles onto the CdSe@CdS in the ionic liquid system. Methylene blue dye was degraded using each system and the results show and there is an increased performance of the nanorods synthesized in the ionic system.
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Hussain, Amir [Verfasser], Lahore Hector Marcelo [Akademischer Betreuer] Fernandez, Alexander [Gutachter] Lerchl, Majid Majeed [Gutachter] Akbar y Ana [Gutachter] Azevedo. "Performance of a Stirred Catalytic Basket Reactor for the production of Bio-ethanol / Amir Hussain ; Gutachter: Alexander Lerchl, Majid Majeed Akbar, Ana Azevedo ; Betreuer: Hector Marcelo Fernandez Lahore". Bremen : IRC-Library, Information Resource Center der Jacobs University Bremen, 2021. http://d-nb.info/1238897932/34.
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Kaddour, Mirvat. "ALTERNATIVE PROPULSION FOR AIRCRAFT OF GENERAL AVIATION CATEGORY". Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2016. http://www.nusl.cz/ntk/nusl-239859.
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Letecká doprava jako všechny ostatní dopravy podílí na produkci emisí skleníkových plynů, což je hlavní důvod změn klimatu. Disertační práce je zaměřena na možnost využití alternativního zdroje energie (paliva, motor) v letectví, aby se snížily emise produkované letadel. Oblast,na která již pracuje je všeobecné letectví, zejména letadel kategorie LSA a VLA. Tři možnosti, alternativní zdroj energie, budou diskutovány. První používá LPG palivo, další je elektrické motory, a poslední přidání katalyzátoru a výfukového systému. U každého z nich bude uvedeno výhody a nevýhody, hlavní změnu pohon letadla nebo výfukového systému a různé výkonnosti letadla v důsledku těchto změn.