Tesis: "CO₂ hydrogenation"

1

Musadi, Maya Ramadianti. "Catalytic hydrogenation of CO₂ for sustainable transport". Thesis, University of Manchester, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505377.

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C02 emissions are one of the main causes of the greenhouse effect. Reactions between C02 and H2, such as methanol synthesis and methanation, could play an important role in reducing these emissions. The low methanol yield, both selectivity and conversion, is the main problem in the methanol synthesis. Methanation could be considered as another alternative process, because recent research showed that the yield in methanation'process is high, the conversion of C02 to C~ was nearly 100%. By using a combination of the Zero Emission Petrol Vehicle (ZEPV) concept, catalytic hydrogenation of CO2 and methanol to gasoline (MTG) process gasoline can be re-synthesised from recycle C02. The objectives of this thesis are to examine the methanol sY!lthesis behaviour in the lab scale tubular catalytic reactor, to investigate the effect of molecular Sieve 4A (MS 4A) on this synthesis and to analyse the feasibility study for a re-syn fuel refinery. First, methanol synthesis experiments were performed on a CuO/ZnO/AhOJ catalyst at 190- 2200 C, 1 bar, 3600 - 7200 h-I and H2/C02 = 3 - 4. The results indicated that methanol was produced from reaction between H2 and CO2 at those conditions. A maximum C02 conversion was reached at 1900 C, 1 bar, 3600 h-I and H2/C02 = 4. The numerical model results predicted that the initial rate of methanol synthesis increase sharply at pressures into 50 atm and is then relativ~ly constant at pressures above 50 atm. At 50 atm, the initial rate ratio is predicted to increase 35 - 45 times than the initial rate at 1 atm. The presence of water is one of the problems affecting the synthesis. Then to investigate the effect of adding a desiccant, methanol synthesis using a CuO/ZnO/AhOJ catalyst and a MS 4A were carried out at the conditions with the maximum CO2 conversion. The results showed that MS 4A adsorbed water hence the conversion of C02 increased from 1.13% to 2.12%. According to the numerical model, these conversions are predicted 35 - 45 times at pressure around 50 atm. Finally, material and energy balances were calculated for four possible chemical pathways for this re-synthesis (the direct CO2 hydrogenation, the Camere process, the methane to methanol process and the electrolysis process) to determine energy requirements in the re-syn fuel refineries. By using the ZEPV concept, some 70 MT/year of C02 from the combustion of about 22 MT/year of gasoline in around 30 million vehicles in UK can be liquefied at 70 bar and stored on board. This liquid C02 is available to be converted back to gasoline via methanol. The 30% conversion, which was obtained from combination of experiment and numerical model results, was applied for direct hydrogenation of CO2. For the other chemical pathways, the conversion used was based on previous studies. Carrying out this recycling in a set of geographically distributed 're-syn fuel' refineries using offshore wind energy has no further requirement for exploration of crude oil, no limitation of raw material and furthermore no cost penalty for the emitted carbon value. The economic analysis shows that the present (2008) forecourt price for the typical oil refinery (98 p/l) is lower than this forecourt price for the 're-syn fuel' refinery using the offshore wind energy (l09 p/l). By predicting that the wind energy cost will be reduced to as Iowa 2.5 plkWh in the future (2020), it is estimated that the forecourt price of gasoli~e from this futuristic sustainable resynthesis refinery would be decreased to 89 p/l. This forecourt price is cheaper than the current gasoline forecourt price from a typical conventional oil refinery. Based on this preliminary economic assessment, gasoline re-synthesis from recycled CO2 using offshore wind energy is both perfectly sustainable and almost competitive for today and will be cheaper than gasoline from crude oil in the future.

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2

Rennison, A. J. "CO hydrogenation on reduced solid solution catalysts". Thesis, University of Bath, 1987. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378000.

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3

Balakrishnan, Nianthrini. "Theoretical Studies of Co Based Catalysts on CO Hydrogenation and Oxidation". Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4434.

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CO hydrogenation and CO oxidation are two important processes addressing the energy and environmental issues of great interest. Both processes are carried out using metallic catalysts. The objective of this dissertation is to study the catalytic processes that govern these two reactions from a molecular perspective using quantum mechanical calculations. Density Functional Theory (DFT) has proven to be a valuable tool to study adsorption, dissociation, chain growth, reaction pathways etc., on well-defined surfaces. DFT was used to study the CO reduction reactions on promoted cobalt catalyst surfaces and CO oxidation mechanisms on cobalt surfaces. CO hydrogenation via Fischer-Tropsch Synthesis (FTS) is a process used to produce liquid fuels from synthesis gas. The economics of the Fischer-Tropsch process strongly depends on the performance of the catalyst used. The desired properties of a catalyst include selectivity towards middle distillate products such as diesel and jet fuel, higher activity and longer catalyst life. Catalysts are often modified by adding promoters to obtain these desirable properties. Promoters can influence the reaction pathways, reducibility, dispersion, activity and selectivity. In FTS, understanding the effect of promoters in the molecular scale would help in tailoring catalysts with higher activity and desired selectivity. Preventing deactivation of catalyst is important in FTS to increase the catalyst life. Deactivation of Co catalyst can occur by reoxidation, C deposition, sintering, formation of cobalt-support compounds etc. Designing catalyst with resistance to deactivation by the use of promoters is explored in this dissertation. The influence of promoters on the initiation pathways of CO hydrogenation is also explored as a first step towards determining the selectivity of promoted catalyst. The influence of Pt promoter on O removal from the surface of Co catalyst showed that Pt promoter reduced the activation barrier for the removal of O on both flat and stepped Co surfaces. An approximate kinetic model was developed and a volcano plot was established. The turn-over frequency (TOF) calculated based on the activation barriers showed that Pt promoted Co surface had a higher rate than unpromoted Co surface. The effect of Pt and Ru promoters on various pathways of C deposition on Co catalyst was studied to gain a mechanistic understanding. The promoters did not affect the subsurface C formation but they increased the barriers for C-C and C-C-C formation and also decreased the barriers for C-H formation. The promoters also influence the stabilities of C compounds on the Co surface suggesting that Pt and Ru promoters would decrease C deposition on Co catalysts. The effect of Pt promoter on unassisted and H-assisted CO activation pathways on Co catalyst was studied. Pt promoted Co surface followed H-assisted CO activation. Pt promoter decreased the activation barriers for CO activation pathways on Co catalyst thereby increasing the activity of Co catalyst. CO oxidation is a process used to prevent poisoning of fuel cell catalysts and reduce pollution of the atmosphere through exhaust gases containing CO. Expensive catalysts like Pt are widely used for CO oxidation which significantly increases the cost of the process and hence it is necessary to search for alternative lower cost catalysts. Understanding the mechanism of a reaction is the first step towards designing better and efficient catalyst. DFT is helpful in determining the basic mechanism and intermediates of reactions. The mechanism of CO oxidation on CoO catalyst was explored. Four possible mechanisms for CO oxidation on CoO catalyst were studied to determine the most likely mechanism. The mechanism was found to be a two-step process with activation barrier for formation of CO2 larger than the barrier for formation of the intermediate species.

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4

Nozonke, Dumani. "Iron modification of rhodium nano-crystallites for CO hydrogenation". Master's thesis, University of Cape Town, 2013. http://hdl.handle.net/11427/16858.

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The aim of this study was to investigate the effect of iron on alumina-supported well defined nano-sized rhodium crystallites on the activity and selectivity for CO hydrogenation. The objective was to prepare model catalysts with similar average crystallite size and narrow size distribution.

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5

Schweicher, Julien. "Kinetic and mechanistic studies of CO hydrogenation over cobalt-based catalysts". Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210036.

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During this PhD thesis, cobalt (Co) catalysts have been prepared, characterized and studied in the carbon monoxide hydrogenation (CO+H2) reaction (also known as “Fischer-Tropsch” (FT) reaction). In industry, the FT synthesis aims at producing long chain hydrocarbons such as gasoline or diesel fuels. The interest is that the reactants (CO and H2) are obtained from other carbonaceous sources than crude oil: natural gas, coal, biomass or even petroleum residues. As it is well known that the worldwide crude oil reserves will be depleted in a few decades, the FT reaction represents an attractive alternative for the production of various fuels. Moreover, this reaction can also be used to produce high value specialty chemicals (long chain alcohols, light olefins…).

Two different types of catalysts have been investigated during this thesis: cobalt with magnesia used as support or dispersant (Co/MgO) and cobalt with silica used as support (Co/SiO2). Each catalyst from the first class is prepared by precipitation of a mixed Co/Mg oxalate in acetone. This coprecipitation is followed by a thermal decomposition under reductive atmosphere leading to a mixed Co/MgO catalyst. On the other hand, Co/SiO2 catalysts are prepared by impregnation of a commercial silica support with a chloroform solution containing Co nanoparticles. This impregnation is then followed by a thermal activation under reductive atmosphere.

The mixed Co/Mg oxalates and the resulting Co/MgO catalysts have been extensively characterized in order to gain a better understanding of the composition, the structure and the morphology of these materials: thermal treatments under reductive and inert atmospheres (followed by MS, DRIFTS, TGA and DTA), BET surface area measurements, XRD and electron microscopy studies have been performed. Moreover, an original in situ technique for measuring the H2 chemisorption surface area of catalysts has been developed and used over our catalysts.

The performances of the Co/MgO and Co/SiO2 catalysts have then been evaluated in the CO+H2 reaction at atmospheric pressure. Chemical Transient Kinetics (CTK) experiments have been carried out in order to obtain information about the reaction kinetics and mechanism and the nature of the catalyst active surface under reaction conditions. The influence of several experimental parameters (temperature, H2 and CO partial pressures, total volumetric flow rate) and the effect of passivation are also discussed with regard to the catalyst behavior.

Our results indicate that the FT active surface of Co/MgO 10/1 (molar ratio) is entirely covered by carbon, oxygen and hydrogen atoms, most probably associated as surface complexes (possibly formate species). Thus, this active surface does not present the properties of a metallic Co surface (this has been proved by performing original experiments consisting in switching from the CO+H2 reaction to the propane hydrogenolysis reaction (C3H8+H2) which is sensitive to the metallic nature of the catalyst). CTK experiments have also shown that gaseous CO is the monomer responsible for chain lengthening in the FT reaction (and not any CHx surface intermediates as commonly believed). Moreover, CO chemisorption has been found to be irreversible under reaction conditions.

The CTK results obtained over Co/SiO2 are quite different and do not permit to draw sharp conclusions concerning the FT reaction mechanism. More detailed studies would have to be carried out over these samples.

Finally, Co/MgO catalysts have also been studied on a combined DRIFTS/MS experimental set-up in Belfast. CTK and Steady-State Isotopic Transient Kinetic Analysis (SSITKA) experiments have been carried out. While formate and methylene (CH2) groups have been detected by DRIFTS during the FT reaction, the results indicate that these species play no role as active intermediates. These formates are most probably located on MgO or at the Co/MgO interface, while methylene groups stand for skeleton CH2 in either hydrocarbon or carboxylate. Unfortunately, formate/methylene species have not been detected by DRIFTS over pure Co catalyst without MgO, because of the full signal absorption.

Doctorat en Sciences de l'ingénieur
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6

DAUBREGE, FRANCK. "Etude de la mise en regime des catalyseurs a base de cuivre et de cobalt destines a la synthese d'alcools superieurs a partir de co/h#2". Paris 6, 1990. http://www.theses.fr/1990PA066465.

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Les catalyseurs a base de cuivre et de cobalt (cu-co-al-zn) acalinises ou non, destines a la synthese d'alcools superieurs a partir du co/co#2/h#2, se caracterisent lors de leur phase initiale de fonctionnement par une methanation transitoire importante. A l'issue de cette mise en regime, le comportement du systeme catalytique evolue soit vers celui d'un catalyseur de synthese du methanol, soit vers celui d'un catalyseur de synthese d'hydrocarbures ou d'alcools c#1-c#6 en melange. L'objet de ce travail concerne l'etude des parametres reactionnels et structuraux qui regissent les transformations du systeme catalytique conduisant a de tels comportements. Pour cette etude, la preparation et la caracterisation par dx, stem, tpr et esca de systeme modeles a ete entreprise. Le comportement de ces systemes modeles, en synthese co/h#2 sous pression et vis-a-vis de reactions tests a ete examine. L'importance du rapport zn/co de surface sur l'orientation des selectivites en synthese co/h#2 a ete degage. Apres mise en regime, le comportement de ces systemes apparait lie au depot d'entites carbonnees et a la plus ou moins grande stabilite des listes bimetalliques cuivre-cobalt selon la formulation

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7

Yao, Libo. "Sustainable, energy-efficient hydrogenation processes for selective chemical syntheses". University of Akron / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=akron1626172267871778.

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8

Aoyama, Yoshimasa. "Hybridization of 4d Metal Nanoparticles with Metal-Organic Framework and the Investigation of the Catalytic Property". Kyoto University, 2020. http://hdl.handle.net/2433/254504.

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9

Ji, Qinqin. "The synthesis of higher alcohols from CO2 hydrogenation with Co, Cu, Fe-based catalysts". Thesis, Strasbourg, 2017. http://www.theses.fr/2017STRAF023/document.

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Le CO2 est une source de carbone propre pour les réactions chimiques, nombreux chercheurs ont étudié l'utilisation du CO2. Les alcools supérieurs sont des additifs de carburant propres. La synthèse des alcools supérieurs à partir de l'hydrogénation du CO a également été étudiée par de nombreux chercheurs, mais il existe peu de littératures sur la synthèse des alcools supérieurs à partir de l'hydrogénation du CO2, qui est une réaction complexe et difficile. Les catalyseurs utilisés pour la synthèse des alcools supérieurs nécessitent au moins deux phases actives et une bonne synergie. Dans notre étude, nous avons étudié les catalyseurs spinelle basés sur Co. Cu. Fe et l'effet des supports (CNTs et TUD-1) et celui des promoteurs (K, Na, Cs) à la réaction de HAS. Nous avons trouvé que le catalyseur CuFe-précurseur-800 est favorable pour la synthèse d'hydrocarbures en C2+ et d'alcools supérieurs. Dans l'hydrogénation du CO2, Co agit comme catalyseur de méthanisation plutôt que comme catalyseur FT, en raison du mécanisme de réaction différent entre l'hydrogénation du CO et celle du CO2. Afin d'inhiber la formation d'hydrocarbures de quantités importante, il est préférable de choisir des catalyseurs sans Co dans la réaction d'hydrogénation du CO2. En comparant les fonctions des CNT et du TUD-1, nous avons constaté que le CNT est un support parfait pour la synthèse de produits à longue chaîne (alcools supérieurs et hydrocarbures C2+). Le support TUD-1 est plus adapté à la synthèse de produits à un seul carbone (méthane et méthanol) .L'addition d'alcalis en tant que promoteurs conduit non seulement à augmenter la conversion de CO2 et H2, mais augmente également la sélectivité des produits visés fortement, des alcools supérieurs. Le catalyseur 0.5K30CuFeCNTs possède une productivités les plus élevées (370.7 g ∙ kg-1 ∙ h-1) d'alcools supérieurs à 350 ° C et 50 bar
CO2 is a clean carbon source for the chemical reactions, many researchers have studied the utilization of CO2. Higher alcohols are clean fuel additives. The synthesis of higher alcohols from CO hydrogenation has also been studied by many researchers, but there are few literatures about the synthesis of higher alcohols from CO2 hydrogenation, which is a complex and difficult reaction. The catalysts that used for higher alcohols synthesis need at least two active phases and goodcooperation. In our study, we tested the Co. Cu. Fe spinel-based catalysts and the effect of supports (CNTs and TUD-1) and promoters (K, Na, Cs) to the HAS reaction. We found that catalyst CuFe-precursor-800 is beneficial for the synthesis of C2+ hydrocarbons and higher alcohols. In the CO2 hydrogenation, Co acts as a methanation catalyst rather than acting as a FT catalyst, because of the different reaction mechanism between CO hydrogenation and CO2 hydrogenation. In order to inhibit the formation of huge amount of hydrocarbons, it is better to choose catalysts without Co in the CO2 hydrogenation reaction. Compared the functions of CNTs and TUD-1, we found that CNTs is a perfect support for the synthesis of long-chain products (higher alcohols and C2+ hydrocarbons). The TUD-1 support are more suitable for synthesis of single-carbon products (methane and methanol).The addition of alkalis as promoters does not only lead to increase the conversion of CO2 and H2, but also sharply increased the selectivity to the desired products, higher alcohols. The catalyst 0.5K30CuFeCNTs owns the highest productivities (370.7 g∙kg-1∙h-1) of higher alcohols at 350 °C and 50 bar

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10

FERREIRA, ELINER A. "Estudo das propriedades magnéticas e da microestrutura em imãs permanentes à base de Pr-Fe-B-Co-Nd obtidos pelos processos HD e HDDR". reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11694.

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11

Paredes-Nunez, Anaëlle. "Étude de la réaction d’hydrogénation du CO sur des catalyseurs à base de cobalt supporté par DRIFTS operando". Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1200.

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Notre dépendance à l'égard des combustibles fossiles et la diminution des ressources pétrolières nous imposent la recherche de sources renouvelables d'énergie et de produits chimiques. La synthèse Fischer-Tropsch permet de répondre à la demande en carburants propres et renouvelables grâce à l'utilisation de gaz de synthèse issu de la biomasse. L'objectif de ce travail est de contribuer à la compréhension du mécanisme de l'hydrogénation du CO sur des catalyseurs au cobalt et à l'identification du site actif par des études spectroscopiques DRIFTS operando. Ce système permet d'observer les différentes espèces adsorbées à la surface du catalyseur pendant la réaction : CO pontés et linéaires, formiates, carboxylates et hydrocarbures. Nos travaux ont montré qu'une fraction des formiates dits « rapides» peut expliquer la formation du méthanol dans nos conditions de réaction. L'ajout dans le mélange H2+CO d'un élément minéral typique de la biomasse, le chlore sous forme de trichloréthylène, a révélé que, l'activité diminuait. La bande des CO pontés étant la plus impactée et se déplaçant vers les hauts nombres d'onde, l'effet du chlore a été notamment associé à un effet électronique sur le cobalt. L'adsorption du chlore étant réversible, nous avons également étudié l'effet de l'étain. Ce métal n'adsorbe pas le CO dans nos conditions et peut s'adsorber à la surface du cobalt. L'étain empoisonne sélectivement la formation des CO pontés et limite fortement la chimisorption de l'hydrogène. Une relation linéaire entre la vitesse de formation des produits et la proportion de CO pontés est observée, révélant l'importance des CO pontés pour la réaction d'hydrogénation du CO
Our dependence on fossil fuels and the decrease of oil resources warrant the search for renewable energy sources and chemicals. Fischer-Tropsch synthesis enables meeting the requirements for cleaner and renewable fuels through the use of syngas obtained from biomass.The objective of this work was to contribute to the understanding of the mechanism of CO hydrogenation on cobalt-based catalysts and the identification of the active site by operando DRIFT spectroscopy. Different species were adsorbed on the surface of the catalyst under reaction conditions: bridged and linear CO, formates, carboxylates and hydrocarbons. Our resutls shows that so-called “fast formate” can account for the formation of methanol under our reaction conditions. The study of a typical biomass element, chlorine, revealed that the activity decreased under trichloroethylene,. The CO bridged band being the most affected band and shifting to higher wavenumber, the chlorine effect was partly associated with an electronic effect on cobalt. Chlorine adsorption being reversible, tin poisoning was also studied. This metal does not adsorb CO under our conditions. Tin addition to cobalt selectively poisons bridged CO and greatly limits the chemisorption of hydrogen. A linear relationship between the rate of formation of products and the proportion of CO bridged is observed, highlighting the importance of CO bridged

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12

Clark, Joshua Patrick. "A multinuclear solid state nuclear magnetic resonance investigation of the preparation of Co, Pt and Ni based hydrogenation catalyst systems". Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/106443/.

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It was known highly dispersed Co (HDC) catalysts for Fischer-Tropsch applications could be synthesised from either Co metal or CoCO3 precursors. Both synthesis routes were known to precipitate Co oxide nanoparticles from solution onto a support via Co(III) ammine complexes. The synthesis pathway was not known. Using solid state NMR and single crystal X-ray diffraction (XRD) a suite of Co(III) complexes have been characterised. The HDC catalyst synthesis from Co metal produced the Co(III) complex which was identified as [(Co(NH3)3)2(μ-OH)2(μ-CO3)](CO3)∙5H2O via single crystal XRD. The 59 Co solid state NMR then confirmed the precipitant from the CoCO3 route was the same complex. The characterisation of a suite of Co(III) complexes of differing oxo coordination has been obtained. It was observed that each oxo coordinating ligand increased the NMR chemical shift by ~800 ppm. For a single oxo coordination a disparity of ~1000 ppm was also observed due to effects from the anion, crystallographic water and type of oxo coordination. Spin-spin coupling with the 59 Co nucleus was observed to occur for bidentate carbonate and ammine ligands yielded ǀ2 J( 59 Co, 13 C)ǀ of 1-10 Hz and ǀ1 J( 59 Co, 15 N)ǀ of 56-75 Hz. The bonding of monodentate and bridging carbonate ligands was observed to be ionic in nature lacking the spin-spin coupling. It was hypothesised Co oxide nanoparticles precipitated from Werner’s complex, [Co((μ-OH)2Co(NH3)4)3](SO4)3∙9H2O. This was observed in the solid state NMR studies at 14518 ppm. From the time resolved 59 Co solution state NMR measurements of the HDC catalyst syntheses a resonance was observed at 14300 ppm. This was assigned to the central Co oxo coordinated environment of Werner’s complex. In conjunction with observations of chemical shifts coinciding with known precursors to Werner’s complex, it has been possible to suggest a reaction pathway. It was concluded that [Co(NH3)5CO3]+ and [Co(NH3)4CO3]+ eventually become Werner’s complex before precipitating out of solution as Co oxide nanoparticles. The study of Pt and Ni hydrogenation catalyst precursors on α-alumina, γ-alumina, silica and titania have been undertaken. From the Pt materials, it was observed oligomeric Pt oxide structures deposited on the supports. The 195 Pt NMR measurements of these oligomeric structures showed disorder due to a mix of hydroxyl and O bridges in addition to preferential orientations. These orientations were thought to arise from the formation of sheet like structures. All measurements were compared to PtO2, the 195 Pt measurement of which produced an axial symmetric lineshape due to chemical shift anisotropy yielding a Ω of 3916(100) ppm, κ of -1.00(8) and a δiso of 4607(100) ppm. Finally, 27 Al measurements of the γ-alumina support showed reactions with nitric acid occurred. This formed an aluminium nitrate species on the surface which was removed with heat treatment. It was also concluded AlO(V) sites were preferential binding points for the Pt oxide. The AlO(V) 27 Al NMR resonance was seen to disappear with heat treatment, it has been proposed AlO(V) converts to AlO(VI) with the addition of Al–O– Pt bonds.

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SILVA, SUELANNY C. da. "Estudo da influência da temperatura nas propriedades magnéticas e na microestrutura nos imãs permanentes à base de Pr-Fe-B-Nb-Co obtidos com hidrogênio". reponame:Repositório Institucional do IPEN, 2007. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11612.

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Peng, Lu. "Metal Nanoparticles Wrapped on Defective Nitrogen-doped Graphitic Carbons as Highly Selective Catalysts for C02 Hydrogenation". Doctoral thesis, Universitat Politècnica de València, 2021. http://hdl.handle.net/10251/172329.

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[ES] Teniendo en cuenta el agotamiento de los combustibles fósiles y la creciente concentración de CO2 en la atmósfera, la hidrogenación de CO2 es una forma prometedora de convertir el CO2 en productos químicos y combustibles de carbono de alto valor añadido. Considerando la gran influencia del tamaño de partícula, la composición química, la naturaleza del soporte y las condiciones de operación sobre el comportamiento catalítico de los catalizadores, se han desarrollado una serie de catalizadores para la hidrogenación de CO2 basados en metales abundantes no nobles y polisacáridos naturales como precursores del grafeno. En la presente tesis doctoral, las especies metálicas soportadas sobre una matriz de carbono grafítico defectuosa, con diferentes tamaños de partículas, muestran diferente actividad catalítica y selectividad para la hidrogenación de CO2. Se prepararon, de forma controlada, nanopartículas de aleaciones de Co y Co-Fe soportadas en grafenos dopados con N defectuosos, con una amplia distribución de tamaño de nanopartículas, para la reacción de Sabatier, presentando una selectividad a metano superior al 90% con valores de conversión de CO2 superiores al 85%. En el caso de un solo metal, Co o Fe, y sus aleaciones en forma de "clusters" y pequeñas nanopartículas soportadas en el mismo material, la selectividad de la hidrogenación de CO2 cambia a CO, en lugar de metano, obteniéndose un valor del 98 % y alcanzando una conversión de CO2 del 56%. Conviene resaltar que, los catalizadores basados en "clusters" de aleaciones de metal con una carga de metal incluso por debajo del 0.2 % en peso, exhiben una mayor selectividad y rendimiento que los que tienen nanopartículas de aleaciones de Co-Fe más grandes que varían de 1 a 4 nm y una carga de metal más alta en una composición similar. Siguiendo la línea de investigación de hidrogenación de CO2, se desarrollaron una serie de nanopartículas de aleaciones de Co-Fe soportadas sobre grafenos dopados con N defectuosos con distribución de tamaño de nanopartículas controlada en el rango de 7-17 nm, obteniendo una selectividad hacia hidrocarburos C2+ alrededor del 45% y una conversión del CO2 cercana al 60%. Además, se realizó un estudio comparativo de la actividad catalítica de catalizadores similares basados en Co-Fe con promotores e inhibidores para la hidrogenación de CO2, observando su influencia en la conversión y selectividad de CO2. Finalmente, además de los catalizadores basados en Co-Fe, también se han preparado catalizadores basados en Cu-ZnO mediante un método de dos pasos. Estas nanopartículas de Cu-ZnO soportadas sobre grafeno defectuoso dopado con N exhiben una alta selectividad hacia la conversión de CO2 a metanol.
[CA] Tenint en compte l'esgotament dels combustibles fòssils i la creixent concentració de CO2 en l'atmosfera, la hidrogenació de CO2 és una forma prometedora de convertir el CO2 en productes químics i combustibles de carboni d'alt valor afegit. Considerant la gran influència de la grandària de partícula, la composició química, la naturalesa del suport i les condicions d'operació sobre el comportament catalític dels catalitzadors, s'han desenvolupat una sèrie de catalitzadors per a la hidrogenació de CO2 basats en metalls abundants no nobles i polisacàrids naturals com a precursors del grafé. En la present tesi doctoral, les espècies metàl·liques suportades sobre una matriu de carboni grafític defectuosa, amb diferents grandàries de partícules, mostren diferent activitat catalítica i selectivitat per a la hidrogenació de CO2. Es van preparar, de manera controlada, nanopartícules d'aliatges de Co i Co-Fe suportades en grafens dopats amb N defectuosos, amb una àmplia distribució de grandària de nanopartícules, per a la reacció de Sabatier, presentant una selectivitat a metà superior al 90% amb valors de conversió de CO2 superiors al 85%. En el cas d'un sol metall, Co o Fe, i els seus aliatges en forma de "clústers" i xicotetes nanopartícules suportades en el mateix material, la selectivitat de la hidrogenació de CO2 canvia a CO, en lloc de metà, obtenint-se un valor del 98% i aconseguint una conversió de CO2 del 56%. Convé ressaltar que, els catalitzadors basats en "clústers" d'aliatges de metall amb una càrrega de metall fins i tot per davall del 0.2% en pes, exhibeixen una major selectivitat i rendiment que els que tenen nanopartícules d'aliatges de Co-Fe més grans que varien d'1 a 4 nm i una càrrega de metall més alta en una composició similar. Seguint la línia d'investigació d'hidrogenació de CO2, es van desenvolupar una sèrie de nanopartícules d'aliatges de Co-Fe suportades sobre grafens dopats amb N defectuosos amb distribució de grandària de nanopartícules controlada en el rang de 7-17 nm, obtenint una selectivitat cap a hidrocarburs C2+ al voltant del 45% i una conversió del CO2 pròxima al 60%. A més, es va realitzar un estudi comparatiu de l'activitat catalítica de catalitzadors similars basats en Co-Fe amb promotors i inhibidors per a la hidrogenació de CO2, observant la seua influència en la conversió i selectivitat de CO2. Finalment, a més dels catalitzadors basats en Co-Fe, també s'han preparat catalitzadors basats en Cu-ZnO mitjançant un mètode de dos passos. Aquestes nanopartícules de Cu-ZnO suportades sobre grafé defectuós dopat amb N exhibeixen una alta selectivitat cap a la conversió de CO2 a metanol.
[EN] Considering the depletion of fossil fuels and the increasing atmospheric CO2 concentration, CO2 hydrogenation is a promising way to convert CO2 into value-added carbon-containing chemicals and fuels. Taking into account the significant influences of the particle size, chemical composition, nature of the support, and operation conditions on the catalytic performance of catalysts, a series of catalysts for CO2 hydrogenation have been developed based on the use of abundant non-noble metals and natural polysaccharides as graphene precursors. In the present PhD Thesis, metal species supported on defective graphitic carbon matrix with different particle sizes show different catalytic activity and selectivity for CO2 hydrogenation. Under effective control, Co and Co-Fe alloy nanoparticles wrapped on defective N-doped graphenes with a broad nanoparticle size distribution were prepared and performed for the Sabatier reaction, exhibiting a selectivity to methane over 90 % at CO2 conversion values over 85 %. In the case of single Co or Fe metal and their alloys in the form of clusters and small nanoparticles wrapped on the same support, the selectivity for CO2 hydrogenation shifts to CO, rather than methane, reaching a conversion of 56 % with 98 % CO selectivity. It is worth noting that the metal alloy clusters-based catalysts with the metal loading even below 0.2 wt.% exhibit a higher selectivity and better performance than the ones with larger Co-Fe alloy nanoparticles ranging from 1-4 nm and higher metal loading in a similar composition. Following the research line for CO2 hydrogenation, a series of Co-Fe alloy nanoparticles supported on defective N-doped graphenes with controlled nanoparticle size distribution in the range of 7-17 nm are developed, obtaining a selectivity towards C2+ hydrocarbons about 45% with a CO2 conversion close to 60%. In addition, a comparative catalytic activity of similar Co-Fe-based catalysts with promoters and poison has been studied for CO2 hydrogenation to observe their influence on CO2 conversion and selectivity. Finally, besides Co-Fe-based catalysts, Cu-ZnO-based catalysts have also been prepared by a two-step method. These Cu-ZnO nanoparticles supported on N-doped defective graphene exhibit a high selectivity for CO2 conversion to methanol.
Peng, L. (2021). Metal Nanoparticles Wrapped on Defective Nitrogen-doped Graphitic Carbons as Highly Selective Catalysts for C02 Hydrogenation [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/172329
TESIS

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15

Ralston, Walter Thomas. "Hydrogenation Reactions of CO and CO2| New Insights through In Situ X-ray Spectroscopy and Chemical Transient Kinetics Experiments on Cobalt Catalysts". Thesis, University of California, Berkeley, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10282649.

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The catalytic hydrogenations of CO and CO2 to more useful chemicals is not only beneficial in producing more valuable products and reducing dependence on fossil fuels, but present a scientific challenge in how to control the selectivity of these reactions. Using colloidal chemistry techniques, a high level of control over the synthesis of nanomaterials can be achieved, and by exploiting this fact a simple model system can be realized to understand the reaction of CO and CO2 on a molecular level. Specifically, this dissertation focuses on understanding cobalt materials for the conversion of CO and CO2 into more useful, valuable chemicals.

Colloidally prepared cobalt nanoparticles with a narrow size distribution were supported in mesoporous SiO2 and TiO2 to study the effect of the support on the Co catalyzed hydrogenation of CO and CO2. The 10nm Co/SiO2 and Co/TiO2 catalysts were tested for CO and CO2 hydrogenation at 5 bar with a ratio to hydrogen of 1:2 and 1:3, respectively. In addition, the effect of Co oxidation state was studied by using different reduction pretreatment temperatures (250°C and 450°C). The results showed that for both hydrogenation reactions, Co/TiO2 had a high activity at both reduction temperatures compared to Co/SiO2. However, unlike Co/SiO2 which showed higher activity after 450°C reduction, Co/TiO2 had a higher activity after reduction at 250°C. Through synchrotron x-ray spectroscopy, it was concluded that the TiO2 was wetting the Co particle at higher reduction temperatures and dewetting at lower reduction temperatures. In addition to the wetting, CoO was observed to be the surface species on Co/TiO2 catalyst after reduction at low temperatures, which catalyzed both CO and CO2 hydrogenation reactions with higher activity than the Co metal obtained after reduction at 450°C.

Classical steady-state measurements are limited in so much as they are often unable to provide information on individual reaction steps in complex reaction pathways. To attempt to circumvent this, a chemical transient kinetics (CTK) reactor was designed and built. Verification of the reactor was performed by evaluating a catalyst from the literature and confirming the results. A CoMgO catalyst was used to accomplish this, and our original findings show that at short time scales steric hindrances at the surface may push the product distribution towards olefinic rather than branched compounds.

Continuing work on the CTK, two distinct particle sizes of Co nanoparticles were synthesized and tested under atmospheric conditions (H2:CO = 2:1) on the transient reactor. 4.3 nm Co and 9.5 nm Co were supported on MCF-17 to study the previously observed size effect, where Co nanoparticles lose activity at smaller sizes. It was found that indeed, the 4.3 nm Co are less active because they contain less CO dissociation sites, which are necessary for populating the surface with carbon monomers and spurring subsequent chain growth. The specific CO dissociation site was identified as the Co (221) step, of which larger Co particles have more and smaller Co particles have less.

To investigate the nature of the MnO / Co3O4 interface, an in situ study using synchrotron radiation was undertaken. A sample of 6nm MnO nanoparticles loaded on mesoporous Co3O4 was studied with ambient pressure x-ray photoelectron spectroscopy, soft x-ray absorption spectroscopy at the Mn and Co L edges, and scanning transmission x-ray microscopy. X-ray measurements show that under reducing conditions of CO + H2, the MnO nanoparticles wet the Co surface until it is completely covered by a layer of MnO. Through the combination of techniques, it is shown that the system is catalytic active at the low pressures studied, and that the nature of the interface between MnO and Co3O4 is highly dependent on the temperature and gaseous environment it is prepared in. (Abstract shortened by ProQuest.)

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Li, Liwei. "Density functional theory study of alcohol synthesis reactions on alkali-promoted Mo2C catalysts". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53456.

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As an important chemical raw material, alcohols can be used as fuels, solvents and chemical feedstocks to produce a variety of downstream products. With limited fossil fuel resources, alcohol synthesis from syngas reactions can be a potential alternative to the traditional petroleum based alcohol synthesis. Among many catalysts active for syngas to alcohol processes, alkali promoted Mo2C has shown promising performance. More interestingly, the alkali promoter was found to play an important role in shifting the reaction selectivity from hydrocarbons to alcohols. However, limited understanding of the mechanism of this alkali promoter effect is available due to the complexity of syngas reaction mechanism and low content of alkali added to the catalysts. In this thesis, we performed a comprehensive investigation of the alkali promoter effect with density functional theory (DFT) calculations as our primary tool. We first examine various Mo2C surfaces to determine a representative surface structure active to alkali adsorption. On this particular surface, we develop a syngas reaction network including relevant reaction mechanisms proposed in previous literature. With energetics derived from DFT calculations and a BEP relation, we predict the syngas reaction selectivity and find it to be in excellent agreement with experimental results. The dominant reaction mechanism and selectivity determining steps are determined from sensitivity analysis. We also propose a formation mechanism of alkali promoters on Mo2C catalysts that shows consistency between experimental IR and DFT computed vibrational frequencies. Finally, the effect of alkali promoters on the selectivity determining steps for syngas reactions are investigated from DFT calculations and charge analysis. We are able to rationalize the role of alkali promoters in shifting the reaction selectivity from hydrocarbons to alcohols on Mo2C catalysts.

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Zhang, Long. "In-Situ Infrared Studies of Adsorbed Species in CO₂ Capture and Green Chemical Processes". University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1481213980572202.

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Zanella, Specia Rodolfo. "Nouvelle méthode de préparation de nanoparticules d'or supportées sur TiO2, caractérisation et propriétés catalytiques pour des réactions d'oxydation et d'hydrogénation". Paris 6, 2003. http://www.theses.fr/2003PA066343.

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Endot, N. B. "Selective hydrogenation of 5-hydroxymethylfurfural (HMF) to 2, 5-dimethylfuran (DMF) over Ru, Ni, and Co mono and bimetallic catalysts supported on carbon and carbon nanotube". Thesis, University of Liverpool, 2017. http://livrepository.liverpool.ac.uk/3008300/.

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The main objective of this thesis is to develop better catalysts for the hydrogenation of 5- hydroxymethylfurfural, HMF into high quality liquid fuel 2, 5- dimethylfuran (DMF) or partly hydrogenating compounds. This could be achieved by exploiting the support effect and using CNTs to improve activity and developing mono- and bimetallic systems utilising less expensive metals like Nickel, Cobalt or Iron compared to noble metals like ruthenium and rhodium. Succeeding at this could be an economic incentive for the scale-up production of DMF. In addition, we envisaged the opportunity to be able to produce the metal catalyst and support in one simple step using a sugar and the metal salt and we studied the utilisation of carbon synthesised hydrothermally from glucose as a catalyst support using microwave techniques. The physical and chemical properties of the catalysts were characterised using such techniques as X-ray diffraction (XRD), temperature programmed reduction (TPR), inductively coupled plasma emission spectroscopy (ICP), hydrogen and carbon monoxide chemisorption, transition electron microscopy (TEM) and x-ray photoelectron spectroscopy (XPS). Hydrogenation of HMF to DMF was examined over monometallic and bimetallic Ru, Ni and Co supported on carbon and CNT at 150 °C (20 bar of H2). Among the monometallic catalysts supported on carbon, Ru catalysts exhibited the highest DMF yield up to 80 % in 3 hours followed by Ni and Co catalyst. This is because Ni and Co are not as good as Ru in the hydrogenolysis step in order to get to DMF. As a comparison to carbon, CNT as a support shows a remarkable improvement in the HMF conversion and DMF yield in a shorter reaction time. The effect is consistence for all the catalysts. A control test with only CNT showed a negligible activity which confirms that the enhancement is due to the presence of metal catalyst. HMF conversion of 100 % with 84 % DMF yield in 1 hr was achieved over 5 wt % Ru/CNT. The improvement of reactivity is attributed to the electronic effect of CNT derived from the curvature shape of CNT. This consequently enhanced the electron density of metal thus improving the adsorption of C=O bonds resulting in higher reactivity. We found that the promoting effect of the CNT support was universal to all catalyst tested, so that reasonably good Co and Ni catalysts could be obtained, particularly for the initial step of the reaction. The bimetallic system of RuCo and RuNi with specific molar ratios showed a significant improvement in reactivity compared to their monometallic counterparts, particularly considering the lower loading used. High yield of DMF was obtained even at low Ru content in a bimetallic catalyst without losing much DMF yield. 3.5 % RuCo/C 1:5 (0.6 % Ru) and 3.2 % RuNi 1:3 (0.7 % Ru) have better specific DMF yield as compared to 5% Ru/C and 5 % Ru/CNT. 4.2 % RuCo/CNT 1:2 with only 0.2 % loading of Ru showed the highest specific DMF yield. This finding is a positive outcome in order to reduce the dependent on the expensive noble metal without compromising the activity and the yield of desired product, in our case DMF. This proved the synergistic effect of this system. The only difference when different supports were used was that CNT improved the reaction rates however this is also lead to the formation of ring hydrogenation and ring opening products. Carbon has lower reaction rate however it gives better DMF yield. Finally, we demonstrated that one step microwave assisted synthesis of carbon supported catalysts is a promising technique to simultaneously synthesise catalyst as well as hydrothermal carbon in a shorter amount of time compared to the conventional hydrothermal and incipient wetness impregnation method.

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20

Boudouvas, Denis. "Effet du potassium sur un catalyseur composite Fe-Co-C en synthèse d'hydrocarbures". Grenoble INPG, 1989. http://www.theses.fr/1989INPG0092.

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Etude de la promotion par le potassium du catalyseur composite fe-co-c, c'est-a-dire de l'amelioration de son activite catalytique et de sa selectivite en alcenes. L'addition de potassium est realisee soit par impregnation par une solution aqueuse de k#2co#3, soit par la formation intermediaire d'un compose d'insertion avec le carbone de formule kc#3#2. L'evolution de la selectivite des catalyseurs promus et non promus par le potassium est etudiee a des conversions en monoxyde de carbone analogues a celles d'un procede industriel. Des tests catalytiques a faible conversion et des mesures de chimisorption de gaz reagissants sont effectues

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21

Deronzier, Thierry. "Développement d'une nouvelle voie de synthèse de catalyseurs métalliques autosupportés (nanomousses) : étude des propriétés structurales et catalytiques". Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10184.

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L’or, habituellement considéré comme catalytiquement inactif, fait preuve d’une activité étonnante pour diverses réactions d’oxydation pourvu qu’il soit supporté sur un oxyde approprié. Ces dix dernières années, des méthodes de synthèse par dissolution sélective du composé le moins noble d’un alliage métallique (dealloying) ont permis l’obtention de catalyseurs d’or nanoporeux. Ces catalyseurs font preuve d’une très forte activité catalytique vis-à-vis de la réaction d’oxydation du monoxyde de carbone. Cependant, des études plus récentes semblent montrer que cette activité est due aux impuretés présentes dans les catalyseurs, qui sont imputables aux limitations de la méthode de synthèse utilisée. Dans cette étude, un catalyseur nanoporeux d’or pur a été obtenu par oxydation spontanée d’un alliage AuZr à température ambiante puis dissolution sélective totale de ZrO2 dans HF. Ce catalyseur démontre des caractéristiques structurales et morphologiques similaires à celles des échantillons obtenus par dealloying. Leur évaluation catalytique a été réalisée par réaction d’oxydation du CO et en PrOx : les résultats montrent que l’or pur nanoporeux n’est pas catalytiquement actif. La préparation de catalyseurs AgAu selon la même méthode a permis l’obtention de catalyseurs de différentes teneurs en argent, proches des résidus obtenus par dealloying. L’impact de la présence de l’impureté d’argent sur la catalyse est avéré : elle permet d’exacerber l’activité de l’or à température ambiante par synergie des deux éléments. Cependant, l’effet promoteur de l’hydrogène disparaît en PrOx et l’impact de la concentration d’argent est faible lors de l’oxydation du CO. Une étude exploratoire sur les nanomousses NiPd a été menée en parallèle. Le palladium, qui présente le meilleur compromis activité/sélectivité pour les hydrogénations sélectives, voit son activité exacerbée lorsqu’il est déposé à la surface d’un monocristal de Nickel. Cet effet n’existe pas pour des nanoparticules Pd/Ni supportées. Un catalyseur NiPd a donc été préparé dans cette étude selon la méthode des nickels de Raney® afin de combiner les propriétés des monocristaux et des nanoparticules
Gold, generally considered as catalytically inactive, demonstrates a surprising activity toward several oxidation reactions when supported on a proper oxide. New synthesis ways have been developed for ten years to obtain nanoporous gold catalysts based on selective dissolution of the less noble component of a metallic alloy (dealloying). These catalysts exhibit very high activity towards the carbon monoxide oxidation reaction. However recent studies seem to reveal that this activity could be due to impurities inherent to dealloying. In this study a very pure nanoporous catalyst was obtained by spontaneous oxidation of a AuZr alloy at room temperature; a total selective dissolution of ZrO2 was then carried out in HF. Its structural and morphological characteristics proved to be similar to the dealloyed catalysts ones. The evaluation of its catalytic properties by CO oxidation showed that pure nanoporous gold was not catalytically active. Besides bimetallic AgAu catalysts were prepared following the same preparation method with three silver concentrations chosen close to the residual impurities concentrations obtained by dealloying. Their catalytic properties proved to be impacted by silver impurities: gold activity was emphasized at room temperature by synergy between the two elements. However, the promotional effect of hydrogen disappeared in PrOx and the role of silver concentration was low for CO oxidation. In parallel an exploratory study was carried out on NiPd nanofoams. The catalysts were prepared following the Raney® nickel method to improve the palladium activity towards the selective hydrogenation reaction. The results showed a slight increase of the catalytic activity

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22

Barrios, Medina Alan Josue. "Synthèse Directe d'Oléfines Légères par des Réactions d'Hydrogénation du CO et du CO2". Electronic Thesis or Diss., Centrale Lille Institut, 2021. http://www.theses.fr/2021CLIL0030.

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L'hydrogénation du CO et du CO2 sont une voie intéressante de conversion des matières premières non pétrolières et renouvelables tels que la biomasse, le plastique et les déchets organiques, en carburant et en produits chimiques. L'activité, la sélectivité vers la production d’oléfines légères et la stabilité sont des défis majeurs de ces réactions sur les catalyseurs à base de fer. Dans cette thèse, nous avons synthétisé différents catalyseurs à base de fer pour l'hydrogénation du CO et du CO2 afin d'obtenir des catalyseurs hautement sélectifs, actifs et stables. Pour l'hydrogénation du CO, SiO2 a été utilisée comme support tandis que pour la réaction d'hydrogénation du CO2, les catalyseurs supportés par de la ZrO2 ont présenté les résultats les plus encourageants. Les résultats sont appuyés sur l'expérimentation à haut débit (EHD) pour identifier parmi 27 promoteurs les plus efficaces pour la synthèse de FT en évaluant également les différentes tendances de sélectivité en la réaction FT. Les tests EHD nous ont permis d'identifier clairement Sn, Sb, Bi et Pb comme les promoteurs les plus prometteurs afin d'obtenir des catalyseurs de Fe avec une plus grande activité. Après, nous nous sommes concentrés sur l'étude des promoteurs Sb et Sn, sur la performance catalytique des catalyseurs à base de fer supportés sur SiO2, en utilisant une combinaison de techniques avancées et in-situ. Les images MET du catalyseur FeSn/SiO2 activé ont montré des nanoparticules de Sn hautement dispersées sur le support de silice. D'autre part, le catalyseur FeSb/SiO2 activé a montré une morphologie coeur-coquille. Plus petite quantité de dépôt de carbone détectée est cruciale pour une meilleure stabilité des catalyseurs promus par Sn- et Sb dans la réaction FT. Finalement, nous nous sommes concentrés sur l'identification des promoteurs pour les catalyseurs de fer supportés sur ZrO2 pour la réaction d’hydrogénation du CO2. Nous avons observé une nette augmentation de la vitesse de réaction pour les catalyseurs promus par le K et le Cs. L’EHD a clairement montré que la présence de K est essentielle pour obtenir une plus grande sélectivité en oléfines légères. En plus, le Mo, Cu, Cs, Ce et Ga ont été identifiés comme des promoteurs capables d’augmenter encore la sélectivité en oléfines. Le travail effectué au cours de cette thèse a permis de concevoir de nouveaux catalyseurs pour la réaction d'hydrogénation du CO et du CO2 qui pourraient être facilement mis en oeuvre au niveau industriel. Les catalyseurs étudiés pour les deux réactions ont montré une amélioration de trois aspects clés : l'activité, la sélectivité et la stabilité
CO and CO2 Hydrogenation are an attractive way to convert non-petroleum and renewable feedstocks such as biomass, plastic and organic waste into fuels and chemicals. Activity, selectivity to light olefins and stability are major challenges of these reactions over Fe catalysts. In this thesis, we synthesized different iron-based catalysts for both CO and CO2 hydrogenation in order to get highly selective, active and stable catalysts. For CO hydrogenation SiO2 was used as support while for CO2 hydrogenation reaction ZrO2 supported catalysts presented the most encouraging results. We relied on High Throughput Experimentation (HTE) to identify among 27 promoters the most efficient ones for FT synthesis at the same time that different selectivity trends were evaluated. HTE tests allowed us to clearly identify Sn, Sb, Bi and Pb as the most promising promoters in order to obtain Fe catalysts with higher activity in FT synthesis. Then, we focused on studying the strong promoting effects of Sb and Sn on the catalytic performance of SiO2 supported iron Fischer Tropsch catalysts using a combination of advanced and in-situ techniques. TEM in the activated FeSn/SiO2 catalyst showed highly dispersed Sn nanoparticles on the silica support. On the other hand, activated FeSb/SiO2 catalyst showed a core-shell morphology. Additionally, smaller amount of carbon deposition detected is crucial for better stability of the Sn- and Sb-promoted catalysts in FT reaction. Finally, we focused on the identification of efficient promoters for ZrO2 supported iron catalysts in CO2 hydrogenation reaction. We observed the most pronounced increase in the reaction rate for the K and Cs promoted catalysts. HTE clearly showed that the presence of K was essential to achieve higher light olefin selectivity. Additionally, Mo, Cu, Cs, Ce and Ga were identified as possible promoters to further increase the selectivity of CO2 hydrogenation to this fraction. The work performed during this thesis allowed to design new catalysts for CO and CO2 hydrogenation reaction that could be easily implemented at industrial level. Catalysts studied for both reactions showed improvement three key aspects: activity, selectivity, and stability

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23

Chew, Ly May [Verfasser], Martin [Gutachter] Muhler y Wolfgang [Gutachter] Grünert. "Catalytic hydrogenation of CO_2 and CO to short-chain hydrocarbons over iron nanoparticles supported on functionalized carbon nanotubes / Ly May Chew ; Gutachter: Martin Muhler, Wolfgang Grünert ; Fakultät für Chemie und Biochemie". Bochum : Ruhr-Universität Bochum, 2015. http://d-nb.info/1204257035/34.

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Silva, Suelanny Carvalho da. "Estudo da influência da temperatura nas propriedades magnéticas e na microestrutura nos ímãs permanentes à base de Pr-Fe-B-Nb-Co obtidos com hidrogênio". Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/85/85134/tde-24102011-104115/.

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Pós magnéticos foram produzidos utilizando o processo de hidrogenação, desproporção, dessorção e recombinação (HDDR). A primeira parte deste trabalho envolveu o estudo do efeito da adição de Co na liga Pr14FebalCoxB6Nb0.1 (x= 0, 4, 8, 10, 12, 16) variando a de temperatura de dessorção/ recombinação de 800° a 900°C, com o objetivo de otimização do tratamento HDDR. A liga Pr14Fe80B6 foi utilizada como padrão. As ligas foram tratadas termicamente a 1100°C por 20 horas para eliminação do Fe- exixtente na liga em estado bruto de fusão. A temperatura de dessorção/ recombinação afetou a microestrutura e as propriedades magnéticas dos ímãs moldados com polímeros. A liga com baixa adição de cobalto (4 at.%) exigiu a temperatura de reação mais alta (880°C) entre os demais ímãs. As temperaturas ótimas para as ligas com 8 at.% Co e 10 at.% Co foram 840°C e 820°C, respectivamente. Ligas com altas concentrações de cobalto (12 at.% and 16 at.%) foram processadas a 840°C. A temperatura de dessorção/ recombinação que apresentou alta anisotropia nas ligas Pr14Fe80B6 e Pr14Fe79,9B6Nb0,1 foi de 820°C. O ímã que apresentou melhor remanência (862mT) foi processado com a liga Pr14Fe67,9Co12B6Nb0,1. Cada liga apresentou uma temperatura de reação otimizada e exibiu uma microestrutura particular, de acordo com a composição. A segunda parte deste trabalho envolveu a caracterização, dos pós HDDR de Pr14Fe80B6, que foram analisadas por difração de raios X com fonte síncrotron para a identificação e quantificação de fases cristalinas, e ainda para a determinação do tamanho médio de cristalitos da fase principal. A microscopia eletrônica de varredura (MEV) foi utilizada para revelar a morfologia dos pós HDDR.
Fine magnetic powders were produced using the hydrogenation disproportionation desorption and recombination (HDDR) process. The first stage in this work involved an investigation of the effect of the Co content and range of desorption/ recombination temperatures between 800 and 900°C with the purpose of optimizing the HDDR treatment for Pr14Fe80B6 and Pr14FebalCoxB6Nb0,1 (x= 0, 4, 8, 10, 12, 16) alloys. The cast alloys were annealed at 1100°C for 20 hours for homogenization. The processing temperature (desorption/ recombination) affected the microstructure and magnetic properties of the bonded magnets. The alloy with low cobalt content (4 at.%) required the highest reaction temperature (880°C) to yield anisotropic bonded magnets. The optimum temperature for alloys with 8 at.% Co and 10 at.% Co were 840°C and 820°C, respectively. Alloys with high cobalt content (12 at.% and 16 at.%) were processed at 840°C. The optimum desorption temperature for achieving high anisotropy for Pr14Fe80B6 and Pr14Fe79,9B6Nb0,1 was 820°C. The best remanence (862mT) was achieved with the Pr14Fe67,9B6Co12Nb0,1 magnet, processed at 840°C. Each alloy required an optimum reaction temperature and exhibited a particular microstructure according to the composition. The second stage of the work involved the characterization, for each temperature, of the Pr14Fe80B6 HDDR powder processed using X-ray diffraction analysis. The samples of the HDDR material were studied by synchrotron radiation powder diffraction using the Rietveld method for cell refinement, phase quantification and crystallite sizes determination. Scanning electron microscopy (SEM) has also been employed to reveal the morphology of the HDDR powder.

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25

Chafik, Abdelghani. "Influence de terres rares (La, Ce) sur les propriétés de systèmes catalytiques Métal-Carbone (Métal : Fe, Co, Ni) dans la conversion d'oxydes de carbone". Poitiers, 1988. http://www.theses.fr/1988POIT2309.

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26

Quezada, Maxwell Josias. "Hydrogénation catalytique de CO₂ en méthanol en lit fixe sous chauffage conventionnel et sous plasma à DBD ZSM-5 surface modification by plasma for catalytic activity improvement in the gas phase methanol-to-dimethylether reaction". Thesis, Normandie, 2020. http://www.theses.fr/2020NORMIR12.

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L’objectif de cette thèse est de contribuer à l’optimisation de la production de méthanol par hydrogénation de CO₂ en synthétisant des nouveaux catalyseurs sous forme d’extrudés pour un usage industriel. Six catalyseurs à base de Cu et ZnO supportés sur de l’alumine et des ZSM-5 ont été préparés et testés. A 36 bar et sous chauffage conventionnel, le CuZnO/Al₂O₃ a montré le meilleur rendement en méthanol. Un procédé industriel basé sur ce catalyseur a été proposé et optimisé. L’influence de l’extraction de l’eau et du méthanol du milieu réactionnel en utilisant deux réacteurs en série au lieu d’un a été étudié et il a été trouvé que cela augmente le rendement en méthanol considérablement. Sous plasma à DBD et à 1 bar, le Cu/Al₂O₃ donne des meilleures conversions de CO₂, alors que le CuZnO/ZSM-5 montre des meilleurs rendements en méthanol. Cela a été attribuée à la conductivité ionique et à la constante diélectrique des matériaux
The objective of this thesis is to contribute to the optimisation of the production of methanol by hydrogenation of CO₂ by synthesising new catalysts in the form of extrudates for industrial use. In this regard, six Cu-ZnO based catalysts supported on alumina and ZSM-5 were prepared and tested. At 36 bar and under conventional heating, the CuZnO/Al₂O₃ showed the best methanol yield. An industrial process based on this catalyst has been proposed and optimised. The influence of extracting water and methanol from the reaction medium using two reactors in series instead of one was investigated and it was found to increase methanol yield considerably. Tests at atmospheric pressure and under DBD plasma showed that the Cu/Al₂O₃ gives better CO₂ conversions, while the CuZnO/ZSM-5 showed better methanol yields. This was attributed to the ionic conductivity and the dielectric constant of the catalysts

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27

Duran, Martinez Laura Elizabeth. "Dévelοppement et οptimisatiοn d'un prοcédé de prοductiοn de mοlécules d'intérêt par hydrοgénatiοn du CΟ2 à partir d'hydrοgène renοuvelable". Electronic Thesis or Diss., Normandie, 2024. http://www.theses.fr/2024NORMIR21.

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La transition des combustibles fossiles vers les sources d’énergie renouvelables est de plus en plus urgente en raison de leur contribution significative au changement climatique mondial. L'augmentation des niveaux de dioxyde de carbone dans l'atmosphère souligne le besoin critique d'alternatives durables. La conversion du CO₂ en molécules à valeur ajoutée (vecteurs énergétiques) offre une solution prometteuse pour réduire la dépendance aux combustibles fossiles. Cette thèse explore le potentiel de l'hydrogénation catalytique du CO₂ pour produire des produits chimiques à valeur ajoutée tels que le méthane, le méthanol et le di-méthyl éther (DME). Ces procédés offrent non seulement un moyen de réduire les émissions de CO₂, mais également une voie vers une production de carburant durable. La recherche explore divers processus catalytiques, en mettant particulièrement l'accent sur la catalyse thermique en raison de son efficacité supérieure et de sa pertinence pour une mise en œuvre industrielle. L'hydrogénation du CO₂ en une seule étape pour produire du DME est le cas étudié. Des expériences préliminaires ont été menées dans un réacteur à lit fixe de laboratoire pour mieux comprendre la performance des catalyseurs. Différents catalyseurs ont été testés pour la synthèse du DME. Étant donné que les réactions impliquées dans l'hydrogénation du CO₂ pour produire du DME comprennent la synthèse du méthanol à partir de CO₂ suivie de la déshydratation du méthanol, un mélange de catalyseurs a été réalisé pour la synthèse directe du DME. Pour le mélange de poudres, deux catalyseurs CuO/ZnO/Al₂O₃ (CZA), l'un commercial et l'autre développé, ont été testés pour la synthèse du méthanol, et deux zéolites CZA (HY et HZSM-5) ont été testées pour la déshydratation du méthanol. Le mélange physique de CZA-C avec HZSM-5 a été choisi pour une analyse plus approfondie. L'effet de la température, de la pression, du rapport molaire d'alimentation (H₂/CO₂) et de la vitesse spatiale horaire des gaz (GHSV) ont été évalués pour le développement de la cinétique de la synthèse du DME. Un modèle cinétique de Langmuir-Hinshelwood pour la synthèse du méthanol a été proposé, ainsi qu'une nouvelle relation pour la déshydratation du méthanol en DME, car la réaction n'est pas à l'équilibre. Un réacteur à Profil Optimal de Température (POT) intégrant le modèle cinétique développé a été étudié pour un contrôle précis de la température afin de maximiser la conversion du CO₂. Les simulations et optimisations ont confirmé que des temps de séjour plus longs, en ajustant la masse des catalyseurs, sont plus efficaces pour une conversion plus élevée du CO₂. Un avantage minimal (<1%) a été identifié en termes de conversion du CO₂ pour le réacteur POT par rapport à un réacteur isotherme. Cependant, la productivité combinée de DME et de méthanol a montré une meilleure performance (>4,4%) par rapport au réacteur isotherme. Un réacteur multitubulaire POT avec température de refroidissement variable, comprenant 958 tubes, a atteint une conversion du CO₂ de 34,18 % et un taux de production combiné de méthanol et de DME de 30,84 mol.h⁻¹ par tube, approchant l'équilibre thermodynamique sans recirculation
The transition from fossil fuels to renewable energy sources is becoming increasingly urgent due to their significant contribution to global climate change. The rising levels of carbon dioxide in the atmosphere highlight the critical need for sustainable alternatives. Converting CO₂ into value-added molecules (energy carriers) offers a promising solution to reduce reliance on fossil fuels. This thesis explores the potential of the catalytic hydrogenation of CO₂ to produce value-added chemicals such as methane, methanol, and dimethyl ether (DME). These processes not only offer a means to reduce CO₂ emissions but also provide a path toward sustainable fuel production. The research explores various catalytic processes, with a particular emphasis on thermal catalysis due to its higher efficiency and suitability for industrial implementation. The one-step CO₂ hydrogenation to DME is the case of study. Preliminary experiments were conducted into a laboratory fixed bed reactor to better understand catalyst performance. Different catalysts were tested for DME synthesis. Since the reactions that take place into CO₂ hydrogenation to DME comprise the methanol synthesis from CO₂ followed by methanol dehydration, a mixture of catalysts was done for the direct DME synthesis. For the powder mixture, two different CuO/ZnO/Al₂O₃ (CZA) catalysts, one commercial and one developed, were tested for methanol synthesis and two CZA zeolites (HY and HZSM-5) were tested for methanol dehydration. The physical mixture of CZA-C plus HZSM-5 was chosen for further analysis. The effect of temperature, pressure, feed molar ratio (H₂/CO₂) and gas hourly space velocity (GHSV) were assessed for the development of the kinetics of DME synthesis. A Langmuir–Hinshelwood kinetic model for methanol synthesis was proposed, along with a novel relationship for methanol dehydration to DME, since the reaction is not at equilibrium. An Optimal Temperature Profile (OTP) reactor integrating the kinetic model developed was studied for precise temperature control to maximise CO₂ conversion. Simulations and optimisations confirmed that longer residence times by adjusting catalysts mass is more effective for higher CO₂ conversion. A minimal advantage (<1%) was identified in terms of CO₂ conversion for the OTP reactor over an isothermal reactor. However, the combined productivity of DME and methanol had a better performance (>4.4%) over the isothermal reactor. An OTP multi-tubular reactor with variable coolant temperature, comprising 958 tubes, achieved 34.18% CO₂ conversion and a combined methanol and DME production rate of 30.84 mol.h⁻¹ per tube, approaching to thermodynamic equilibrium without recirculation

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28

Zhong, Song-Zheng y 鍾松政. "Co hydrogenation over supported FE, CO and Pt catalysts". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/26113583026942292851.

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LIAO, HONG-ZHANG y 廖宏章. "Application of nickel boride on CO hydrogenation". Thesis, 1987. http://ndltd.ncl.edu.tw/handle/99920456375661206105.

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30

Shadravan, Vahid. "Catalytic hydrogenation of CO and CO₂ in the presence of light hydrocarbons". Thesis, 2018. http://hdl.handle.net/1959.13/1393112.

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Research Doctorate - Doctor of Philosophy (PhD)
Carbon oxides emission, as by-products of many industrial synthetic hydrocarbon processes, causes serious environmental issues and negatively affects commercialisation of some new processes (e.g. OCM). Thus, producing CO and CO₂ (CO_x) free (or with minimal amount of CO_x) synthetic hydrocarbon streams is necessary to facilitate commercialization of these new processes as large scale industrial plants. Moreover, due to the significant environmental effect of CO_x, it is critical to develop processes to convert CO_x and reduce their emission into the atmosphere. In this thesis, catalytic hydrogenation of CO_x in the presence of light hydrocarbons (methane, C₂-C₃ alkane and alkene) was studied. The feasibility of converting CO_x (where the residual concentration of both CO and CO₂ in the product gas stream are less than 1 ppm) without reducing the inlet concentration of feed hydrocarbons was initially investigated over a bench-mark hydrogenation catalyst (Ni/Al₂O₃). It is found that the inlet species were consumed and converted in different temperature ranges. For feed compositions containing CO_x and C₁-C₃, the consumption of carbon monoxide, carbon dioxide and C₂/C₃ paraffins was observed and their maximum conversion was attained over different temperature ranges, in the following order: CO (150 – 250 °C) < CO₂ (250 – 350 °C) < C₂/C₃ paraffins (275 – 400 °C). Moreover, Olefins were converted under all reaction conditions at lower temperatures (below 150 °C) due to the hydrogenation reaction which resulted in the formation of saturated hydrocarbons. Furthermore, the studies on CO_x hydrogenation in the presence of light hydrocarbons were extended to the development of catalysts to enhance the total outlet concentration of light hydrocarbons in a CO_x-free product stream. The effect of different transition metals (i.e. Fe, Co, Cu, Cr, Mn, Zn, Ru, Rh, Ag and Cd) on the catalytic performance of a Ni/Al₂O₃ catalyst was studied. Different and distinct promoting or inhibiting influence was observed (e.g. maximum C₂-C₄ yield of production increased from 6% for Ni/Al₂O₃ to 12% for Ni-Mn/Al₂O₃). The characteristics of partially charged active sites of the catalysts were studied by employing different techniques (i.e. in situ NO-FTIR, CO-/H₂-TPD and chemisorption). It is found that the addition of transition metals to Ni/Al₂O₃ markedly changed the structure of the active sites on the primary catalyst. For example, addition of copper resulted in increasing the ratio of Carbon-accepting to Oxygen-accepting sites (i.e. NO linear/bent adsorption increased from 7.70 for Ni/Al₂O₃ to 24.89 for Ni-Cu/Al₂O₃), which is probably increased the chance of linear CO adsorption that needs higher temperature for C – O cleavage. In contrast, by adding manganese to Ni/Al₂O₃ catalyst the ratio of electron accepting to donating sites balanced on the catalyst surface. Thus, most probably the number active carbon and hydrogen species increased on the surface. Promoting effect of manganese on Ni/Al₂O₃ was further investigated. Catalyst activity measurements as well as various characterisation techniques (such as XRD, CO and H₂ chemisorption, in situ NO-FTIR and TPR) were performed for a series of Ni-Mn/Al₂O₃ catalysts with different nickel and manganese contents. It is considered that there is an optimum amount of Mn added (i.e. bi-metallic Ni-Mn/Al2O3 catalyst with 8 wt% of nickel and 4 wt% of manganese) to the primary catalyst which enhanced the catalyst activity and selectivity. Moreover, the more hydrogen amount in the feed stream improved the catalyst activity for CO_x hydrogenation and selectivity toward C₂-C4 production (i.e. maximum C₂-C₄ yield of production increased from 1.5% for ~9.5 kPa H2 to 6.5% for ~37.8 kPa H2 in the feed stream over Ni/Al₂O₃). According to investigation of the catalysts’ electronic properties with different Ni and Mn contents, changes in catalytic activity (for CO_x hydrogenation) and selectivity (for light hydrocarbons formation) can be interpreted as being due to the effect of different electronic structure of the catalysts with variety of Ni/Mn ratios. The electrostatic properties of crystalline nickel and nickel-manganese particles was studied by computational methods (i.e. KS-DFT). Finally, this study continued on investigating the catalytic hydrogenation of CO_x in an industrial gas mixture containing light hydrocarbons. Complete removal of CO_x present in an ethane offgas (ExxonMobil refinery, Altona, VIC) via catalytic hydrogenation (over Ni-Mn/Al₂O₃) was studied. The effects of adding extra hydrogen and pre-treatment of the feed stream on the process was analysed. It is found that the addition of hydrogen gas into the feed reduced the concentration of CO and CO₂ to below the detection limits. By adding 25% and 40% of extra H₂ to the feed stream no CO_x were detected in the outlet. Moreover, pre-treatment of the offgas using molecular sieves to remove water vapour from the feed gas stream did not affect COx hydrogenation at low temperatures (below 300 °C). However, pre-treatment resulted in a significant reduction in CO and CO₂ concentrations at temperatures above 300 °C. The results also confirmed the saturate gas plant ethane offgas can considerably deactivate the Ni-Mn/Al₂O₃ catalyst. The effect of ethane and ethylene in the feed gas stream on catalytic hydrogenation of low concentration CO and CO₂ has also been investigated. Ethane addition did not influence the hydrogenation of CO_x at 180 °C while it inhibited the hydrogenation reaction at 320 °C. On the other hand, ethylene addition inhibited CO and CO₂ hydrogenation at both 180 °C and 320 °C.

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31

Dong, Laura Beth. "Polystyrene hydrogenation in supercritical CO₂-decahydronaphthalene using porous catalysts". 2010. http://www.lib.ncsu.edu/theses/available/etd-01132010-100457/unrestricted/etd.pdf.

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32

GIU, JIN-SHAN y 邱金山. "Characterization of CoFe and CuFe bimetallic catalyst on CO hydrogenation". Thesis, 1987. http://ndltd.ncl.edu.tw/handle/17345487778031920412.

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33

Ying-ChiLin y 林英吉. "The application of Bimetallic catalysts for CO2 / CO hydrogenation reaction". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/p38fx9.

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34

Jiang, Wan-Lan y 江挽瀾. "Effect of addition of Mn to Fe catalyst for CO hydrogenation". Thesis, 1986. http://ndltd.ncl.edu.tw/handle/60475855729158071676.

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35

You, Wen-Wen y 游汶玟. "Selective hydrogenation of cinnamaldehyde in liquid-phase over Ag-Co catalysts". Thesis, 2013. http://ndltd.ncl.edu.tw/handle/41313903520903663669.

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碩士
桃園創新技術學院
材料應用科技研究所
101
The Ag-Co catalysts were prepared by chemical reduction with sodium borohydride. Physical and surface properties of catalysts were characterized by techniques of BET, XRD, TGA, DSC, SEM-EDS, TEM and AFM. The catalytic behaviors of catalysts were explored by the selective hydrogenation of cinnamaldehyde in liquid phase. The factors affecting the activity and selectivity of catalysts included the preparation conditions of catalysts, reaction conditions, phenomena of overall hydrogenation and promoter effect. The Ag catalyst was much less active than CoB under the basis of same metal content. Replacing a part of Ag by Co during the preparation could promote significantly the activity of Ag catalyst. The optimal molar ratio of Ag/Co in Ag-Co catalysts was 6/4. Ag-Co(6/4) catalyst was not only as active as CoB catalyst, but also the selectivity to cinnamyl alcohol (unsaturated alcohol) was higher under the same conversion. Silver itself has good activity in hydrogenation. The main reason for the low activity of Ag catalyst resulted from its low value of surface area, owing to the aggregation of silver metal. Replacing a small amount of Ag in catalyst by Co could significantly reduce the particle size of Ag, increase the surface area of catalyst, and the thermal stability was better than those of CoB and Ag catalysts. Ag-Co(6/4) catalyst could effectively hydrogenate cinnamaldehyde to unsaturated alcohol under 120 C and 120 psig. The adsorption strength of cinnamaldehyde molecules on Ag catalyst was much less than those on Group VIII metals. Therefore, the adsorption strength of the C=O bond with strong dipole was much greater than the C=C bond, the C=O bond was thus predominately reduced to form cinnamyl alcohol. A high selectivity of unsaturated alcohol about 93% was reached at the complete conversion over Ag-Co(6/4).

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36

ZHANG, YU-JIN y 張玉金. "Influence of mltal-support interaction on the CO adsorption and hydrogenation". Thesis, 1989. http://ndltd.ncl.edu.tw/handle/69815388031751477386.

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37

Chu, Chih-Yang y 朱智陽. "Effect of thermal treatment on the Nickle species and CO hydrogenation". Thesis, 1994. http://ndltd.ncl.edu.tw/handle/76577341770808776852.

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38

Lin, Jhe-yi y 林哲逸. "Studies on the CO poison and cyclic hydrogenation of the ZK60 alloy". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/11205346784817166724.

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碩士
逢甲大學
材料科學所
100
In this study, the ZK60 (Mg-5.7Zn-0.57Zr) alloy was severely deformed by equal channel angular pressing (ECAP) with route BA and 12 passes. Then, we used drilling machine to get small scraps, and added various contents of alloying elements to the scraps in ball milling for 20hr to prepare the alloy powders. The powders were used to analyze various hydrogen storage properties. Experimental results show that the hydrogen storage capacity of the ZK60 alloy is only 4.13wt% after 60 mins hydrogen absorption, and its hydrogen absorption rate is very slow. In order to improve the hydrogen storage properties, we added various amounts of activated carbon to the ZK60 alloy during ball milling. It is found that the hydrogen storage capacity and its absorption rate are obviously enhanced with the carbon addition. The alloy with addition of 5wt% activated carbon had the highest hydrogen storage capacity that reaches 6.16wt%. Therefore, we fixed activated carbon content at 5wt%, and added various amounts of vanadium and/or palladium during ball milling for the study of hydrogen storage properties. The results show that the alloys with 5C0.5V, 5C0.5Pd, and 5C0.5V0.75Pd additives, respectively, exhibited better hydrogenation kinetics. The maximum hydrogen storage capacity of the alloys with 5C0.5V additives reaches 7.01wt%. It is found that the addition of palladium during ball milling can effectively enhance hydrogen absorption rate. The hydrogen storage capacity can reach 61%~71% in the first minute as compared with that for 60 minutes hydrogen absorption, and it can reach 90% in the first 3 mins hydrogen absorption. Bseides, the addition of palladium has also a positive effect on cyclic hydrogenation. For the study of the cyclic hydrogenation and poison effect, the alloys with 5C0.5V and 5C0.5V0.75Pd additives were used for the cyclic test. The results show that the decrease percentage of the hydrogen storage capacity of the alloy with 5C0.5V additives is 54.59% after 300 cyclic test. However, the counterpart of the alloy with 5C0.5V0.75Pd additives is only 14.40% under the same condition. It means that the addition of palladium can effectively improve the properties on cyclic hydrogenation. For the hydrogen absorption capacity, the alloy with 5C0.5V0.75Pd is poisoned more seriously than that with 5C0.5V in the CO poison cyclic test. For the hydrogen absorption rate under poison condition, the catalytic effect of the palladium is good when CO concentration is less than 100ppm, but becomes worse when CO concentration is over 200ppm.

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39

Sikhwivhilu, Lucky Mashudu. "Titania derived nanotubes and nanoparticles : catalyst supports in hydrogenation, oxidation and esterification reactions". Thesis, 2009. http://hdl.handle.net/10539/5953.

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Nanotubular titanates were synthesized by a simple methodology using a commercial TiO2 (Degussa P25 containing anatase and rutile phases) and a base (KOH) solution. Prior to the removal of KOH, the samples of TiO2 were aged for three different time intervals (0, 2 days, 61 days). The freshly prepared synthetic samples were characterized for their structural and morphological properties by BET, XRD, Raman, TEM, HRTEM, EDX and SEM. Both TEM and SEM analysis revealed that ageing time influenced the tubular structure and morphology of the new materials. Raman and surface analysis data also showed that ageing time affected both the structural and surface properties of TiO2. The XRD results showed that the crystallinity of the TiO2 decreased with increasing ageing time. Energy dispersive Xray spectroscopy (EDX) showed that the tubes derived from TiO2 are comprised of potassium, titanium and oxygen. Catalysts A, B and C were prepared by the addition of 1 wt% Pd (wet impregnation) to the titanate formed after ageing of the TiO2 in KOH for 0, 2 and 61 days, respectively. The catalysts were tested for the vapour phase hydrogenation of phenol in a fixed-bed micro reactor within the temperature range of 165 to 300oC under atmospheric pressure. Of the three catalysts, catalyst B showed the best activity (conversion 97%) and total selectivity to cyclohexanone (99%). In contrast, catalyst C, which showed a moderate activity favoured selectivity to cyclohexanol. These results are attributed to differences in surface morphologies between the two catalysts B and C, associated with the surface area and a change in the surface acid-base properties. Catalyst B also showed a higher resistance towards deactivation and maintained a higher total selectivity to cyclohexanone than did catalyst C. A hydrothermal treatment of NaOH and TiO2 was employed to prepare two materials, TiO2-B and TiO2-C with relatively small crystallite size and large specific surface area. The hydrogenation of phenol was used to evaluate the activity of the catalysts Pd/TiO2-B and Pd/TiO2-C. The reaction proceeds in a single step and involves the formation of a partially hydrogenated product, namely cyclohexanone. The larger surface area catalyst (Pd/TiO2-C, 89 m2/g) showed better activity and selectivity to cyclohexanone than its counterpart (Pd/TiO2-B, 45 m2/g). The catalyst activity showed significant dependency on the surface area whereas the selectivity was greatly influenced by surface basicity. Titania derived nanotubes synthesized by treating P25 Degussa TiO2 with a concentrated KOH solution and aged for 2 days was used as a catalyst support for the hydrogenation of o-chloronitrobenzene (O-CNB) with Pd as the active phase. The vapour-phase hydrogenation of O-CNB was carried out in ethanol at 250 oC and atmospheric pressure over a Pd/TiO2 derived nanotube catalyst (Pd/TiO2-M). Pd/TiO2-M gave complete conversion (100%) of O-CNB with a selectivity to orthochloroaniline (O-CAN) of 86 %. The stability of the Pd/TiO2 catalyst was tested over 5 hours during which time the conversion slowly dropped to 80 % (selectivity 93 %) due to poisoning. TPR analysis revealed the existence of a strong palladium-support interaction and this was found to be crucial to the overall activity of the catalyst. It has been found that gold supported on potassium titanate, KTiO2(OH) can, under some circumstances, exhibit a superior performance for the oxidation of carbon monoxide, relative to that obtained with titania as a support. It appears that the dispersions of gold on the two types of support are sufficiently similar that other factors are responsible for the improved activity noted. It may be that the higher basic character and detailed structural features of the titanate surface play a role. The effect of the addition of alkali metal ions on the anatase to rutile transformation of titanium dioxide (P25 Degussa) was investigated using X-ray diffraction, Raman spectroscopy, and surface area measurements. Both Li and Cs ions accelerated the anatase to rutile transformation whereas Na and K ions did not show any effect. Furthermore, the effect was more pronounced after addition of the Li ions so that the transformation temperature dramatically decreased from ~800 oC for commercial TiO2 to ~600 oC. The surface area of the TiO2 material decreased with sintering due to the increase in crystalline size. Moreover, the acceleration of the transformation occurred at lower temperatures and at higher Li content. Mesoporous nanocrystalline TiO2 (HSA TiO2) was prepared by hydrothermal treatment of TiO2 with NaOH. The material was very amorphous and underwent the phase transformation from amorphous to anatase phase and subsequently from anatase to rutile phase with sintering. The anatase to rutile transformation was delayed after doping and grain growth was inhibited. After sintering at 800 oC the material (HSA TiO2) still contained a significant amount of the anatase phase. The complete transformation only occurred at ~1000 oC. The esterification of benzoic acid and butyric acid with propanol over alkali metal ions supported on TiO2 was investigated. K/TiO2-D showed the highest conversion for both benzoic acid and butyric acid. The selectivity to propylbenzoate and propylbutyrate was influenced by the basic nature of the catalysts. Butyric acid was found to be more reactive than benzoic acid. The difference in reactivity was explained in terms of steric and inductive effects. The differences in boiling points and pH values were also considered.

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40

Shih, Wen-Cheng. "Heterogeneous CO Oxidation and Homogeneous Anthracene Hydrogenation Catalyzed by Gold, Silver and Alloys Nanoparticles". 2007. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-3007200701113000.

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41

Shih, Wen-Cheng y 施文塵. "Heterogeneous CO Oxidation and Homogeneous Anthracene Hydrogenation Catalyzed by Gold, Silver and Alloys Nanoparticles". Thesis, 2007. http://ndltd.ncl.edu.tw/handle/92526739475641924875.

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博士
臺灣大學
化學研究所
95
The heterogeneously catalytic CO Oxidation with Au-Ag alloy deposited on inert and acidic mesoporous aliminosilicate MCM-41 support, prepared by either one-pot or two-step procedure, has been investigated in terms of the experimental kinetics, in-situ DRIFTS, O2 pulse adsorption, O2-TPD and theoretical reaction modeling. For one-pot/3:1 Au-Ag/MCM-41 alloy catalyst, the unexpectedly high catalytic activity at 80oC may be associated with the non-dissociative and non-competitive adsorption Langmuir-Hinshelwood model between CO and O2 species in intimate proximity on the alloy surface. The small activation energy, negligible surface coverage and desorption with raising temperature for both CO and O2 may give rise to the unusual behavior in reaction rate above 80oC. At higher temperature, the different reaction behavior and/or active site for CO oxidation could be altered, which may behave like supported monometallic metal catalyst. For two-step/5:1 Au-Ag/MCM-41 catalyst, the high catalytic activity at 80oC could be due to non-dissociative and non-competitive or competitive Langmuir-Hinshelwood model between adsorbed CO on Au and O2 on Ag in close proximity of Au-Ag alloy surface as the RDS. The decrease in CO conversion with the increasing temperature could be caused by either desorption of both CO and O2 or dissociative adsorption for O2 on the Au-Ag alloy surface. Anthracene hydrogenation in aqueous micellar solutions at room temperature is homogeneously catalyzed by ionic-surfactant-protected Au and Ag nanoparticles with well-controlled particle sizes. A remarkable size-dependence of catalytic activity is derived. The difference in the optical property of meal nanoparticles could be related to the charging of their surfaces, indicating that both the metal nanoparticles play a role as the nanoelectrode storing electrons from hydrides. The behavior about the electron transfer-relaying effects of metal nanoparticles is proposed for the hydrogenation reaction.

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42

Pai, Yun-Chieh y 白芸潔. "Investigation of the Hydrogenation Effects upon Co/Pd Multilayers Using X-ray Absorption Spectroscopy". Thesis, 2017. http://ndltd.ncl.edu.tw/handle/ydz8km.

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Ndou, Dakalo Lorraine. "Catalytic evaluation of Ru(II) and Co(II) salicylaldimine complexes for transfer hydrogenation of acetophenone". Thesis, 2017. http://hdl.handle.net/10539/23597.

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A Dissertation submitted to the Faculty of Science, University of the Witwatersrand, in partial fulfilment of the requirements for the degree of Master of Science, 2017
N-(aryl) salicylaldimine ligands were prepared by the condensation of salicylaldehyde and aniline, 2,6 – dimethylaniline, 2,6 – diisopropylaniline and N,N-diethyl-p-phenylenediamine to give the desired ligands in good yields (70 - 93 % yield). The synthesised ligands were characterised by NMR spectroscopy, FTIR spectroscopy, ESI mass spectrometry and elemental analysis. The purity of these ligands was determined by determining the meting points. Co(II) and Ru(II) complexes were prepared from Co(OAc)2.4H2O and [RuCl2(η6-p cymene)]2 to afford the N-(aryl) salicylaldiminato complexes Co1 – Co4 and Ru1 – Ru4 with yields in the range 60 – 66 % and 90 – 97 %, respectively. These complexes were characterised by NMR spectroscopy, FTIR, ESI mass spectrometry, elemental analysis and TGA. The purity of these complexes was also determined by determining the melting point. The transfer hydrogenation of acetophenone was studied using 2-propanol as the hydrogen source and KOH as the base with the Ru (II) and Co (II) complexes as catalyst precursors. The catalytic activity of these complexes was evaluated using 1H-NMR and GC - MS. Preliminary studies were performed for 6 h at 82 oC and the conversion was evaluated using 1H-NMR. Due to the low catalytic activity of these complexes, the reaction time was increased to 48 h. Increasing the reaction time resulted in improvements in the conversion of the complexes. The catalysis was also evaluated at various temperatures to study the effect it has on the activity of the complexes. Temperature was found to not have a significant effect on the conversion. The ruthenium complexes were found to be active towards the transfer hydrogenation of acetophenone but the cobalt complexes were observed to have no catalytic activity in the transfer hydrogenation of acetophenone. The ruthenium complexes were investigated in an ionic liquid – organic biphasic system with the aim of separating the metal complexes in order to reuse the catalysts. Toluene was the organic phase and [BMIM]BF4 was the ionic liquid which afforded a biphasic system. Three cycles were performed and the performance of Ru1 – Ru3 decreased with each cycle but Ru4 behaved differently as the performance increased with each cycle.
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44

Chang, I.-Hsiu y 張溢修. "Promotion of Hydrogenation Characteristics for Li3N by Addition of Pd-Ni and Pd-Co Catalysts". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/21971304037413900760.

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碩士
國立中央大學
材料科學與工程研究所
97
Hydrogen is viewed as one kind of promising clean fuel of the future. The refueling method, the hydrogen storage, and the handling facilities are critical factors in the development of a hydrogen technology for transportation. An effective hydrogen storage technology is required to make this source of energy economically viable. Li3N is a potential hydrogen storage material owing to its high theoretical H2 capacity (10.4 wt%). In this study, the Pd, Pd-Ni and Pd-Co alloy catalysts were used to modify Li3N to enhance its hydrogenation kinetics. The hydrogenation properties were investigated by a technique of temperature programmed reduction (TPR). The identification of phase structures of materials before and after hydrogenation was carried out by the X-ray powder diffraction (XRD) method. The hydrogenation curves by TPR measurements displayed that the initial hydrogenation temperature (Ti) for Li3N was about 450 K. A following desorption peak starting at 660 K indicates that the hydride formed was not stable. For the modified Li3N, the Ti and absorption capacity was both changed by catalyzing with Pd-Ni and Pd-Co alloy catalysts. The hydrogenation kinetics of Li3N was promoted due to the spillover of hydrogen from alloy catalysts to Li3N and their Ti was lower than that of unmodified Li3N. Moreover, the Li3N hydride formed was stabilized by the PdxNi100-x PdxCo100-x modification and no hydrogen desorption peak was observed at high temperature. When 1:1 ratio of materials and catalysts is used, Pd15Ni85 and Pd15Co85 can decrease the Ti from 450 to 440 K and 370 K, respectively. In the case of Li3N : Pd15Ni85 = 1:4, the Ti of PdNi and PdCo modified Li3N further decreases to 420 K and 360 K and the their hydrogenation capacity is 107 % and 58 % of Li3N, respectively. As a result, the hydrogenation kinetic could effectively be promoted by addition of Pd15Ni85 and Pd15Co85 alloy catalysts.

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45

Lie, Leon y 賴亮全. "HYDROGENATION PROPERTIES OF SUBSTITUTIONAL LaNi5-BASED ALLOYS AND BALL MILLED Zr-Mn-V-Co-Ni AMORPHOUS ALLOY". Thesis, 1996. http://ndltd.ncl.edu.tw/handle/86730752730734215619.

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Al, Dakhil Abdullah. "Synthesis and Application of PN3P Cobalt Pincer Complex for Selective Hydrogenation of Nitriles to Secondary Imines and α -Alkylation of Nitriles with Alcohols". Thesis, 2018. http://hdl.handle.net/10754/628071.

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Pincer complexes moieties have attracted much attention in the past years. They have been proved that they are highly active catalysts in many different known transition metal-catalyzed organic reaction and some unpredictable organic transformation. In this thesis, we will use PN3P Cobalt pincer complex in two different applications. The first application is the unpresented Cobalt-catalyzed hydrogenation of nitriles to secondary imines. The selective hydrogenation of nitriles into secondary imines is a very challenging task and the catalysts play a very important role in the reaction and the selectivity. Herein in the thesis, we report the first selective hydrogenation of nitriles to secondary imines catalyzed by a well-defined and accessible PN3P cobalt pincer complex. Our results show different selectivity compared with the known PNP cobalt catalytic system during the nitriles hydrogenation. A set of aliphatic and aromatic nitriles are hydrogenated to the secondary imine under relatively mild conditions. The second application is the alkylation of nitriles with alcohols using PN3P cobalt pincer complex. The alcohol is being used here as alkylating agent in state of using toxic alkyl halides or excess amount of base to avoid any salt waste. The cobalt pincer complex work as catalyst for transformation that undergoes alkylation via hydrogen transfer pathways. The beauty of this reaction that it is delver water as the only byproduct. A different nitriles and alcohol are tolerated in this reaction.

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47

Alberico, Elisabetta [Verfasser]. "Optically active [(η6-arene)Cr(CO)3]-based [(eta6-arene)Cr(CO)3-based] diphosphines : synthesis and application in asymmetric homogeneous hydrogenation / vorgelegt von Elisabetta Alberico". 2003. http://d-nb.info/970879490/34.

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Strotman, Neil Adham. "I. Stereochemistry of cyclopropane formation involving group (IV) organometallic complexes : II. Slower stoichiometric and faster catalytic reduction of aldehydes by the PPh₃ substituted hydroxycyclopentadienyl ruthenium hydride [2,5-Ph₂-3,4-Tol₂([eta]⁵-C₄COH)]Ru(CO)(PPh₃)H: a highly complex chemoselective catalyst for hydrogenation of aldehydes over ketones /". 2005. http://catalog.hathitrust.org/api/volumes/oclc/70792586.html.

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