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Doory, Layla Kim. „Development of catalytic reactor designs for enhanced CO oxidation“. Thesis, University College London (University of London), 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.282799.
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Wang, Tongyu [Verfasser], Karsten [Akademischer Betreuer] Reuter und Sebastian [Akademischer Betreuer] Günther. „Shape and Catalytic Mechanism of RuO2 Particles at CO Oxidation Reaction Conditions: First-Principles Based Multi-Scale Modeling / Tongyu Wang. Betreuer: Karsten Reuter. Gutachter: Karsten Reuter ; Sebastian Günther“. München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1079001883/34.
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Neugebohren, Jannis. „Implementing Ion Imaging to Probe Chemical Kinetics and Dynamics at Surfaces“. Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2018. http://hdl.handle.net/11858/00-1735-0000-002E-E43B-1.
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Janák, Marcel. „Diagnostika polovodičů a monitorování chemických reakcí metodou SIMS“. Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-443241.
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Hmotnostná spektrometria sekundárnych iónov s analýzou doby letu (TOF-SIMS) patrí vďaka vysokej citlivosti na prvkové zloženie medzi významné metódy analýzy pevných povrchov. Táto práca demonštruje možnosti TOF-SIMS v troch odlišných oblastiach výskumu. Prvá časť práce sa zaoberá lokalizáciou defektov vysokonapäťových polovodičových súčiastok, ktorá je nevyhnutná k ich ďalšiemu skúmaniu metódou TOF-SIMS. Bola navrhnutá experimentálna zostava s riadiacim softvérom umožňujúca automatizované meranie záverného prúdu v rôznych miestach polovodičový súčiastok. Druhá časť práce sa zaoberá kvantifikáciou koncentrácie Mg dopantov v rôznych hĺbkach vzoriek AlGaN. Kvantifikácia je založená na metóde RSF a umožňuje charakterizáciu AlGaN heteroštruktúr určených na výrobu tranzistorov s vysokou elektrónovou mobilitou (HEMT) alebo na výrobu rôznych optoelektronických zariadení. Sada 12 AlGaN kalibračných vzoriek dopovaných Mg, určených na kvantifikáciu hĺbkových profilov, bola pripravená metódou iónovej implantácie. Posledná časť práce demonštruje možnosti metódy TOF-SIMS vo výskume heterogénnej katalýzy. Hlavným objektom nášho výskumu je dynamika oxidácie CO na oxid uhličitý na polykryštalickom povrchu platiny za tlakov vysokého vákua. V tejto práci prezentujem prvé TOF-SIMS pozorovanie časopriestorových vzorov v reálnom čase, ktoré vznikajú v dôsledku rôzneho pokrytia povrchu Pt reaktantmi. Výsledky TOF-SIMS experimentu boli porovnané s výsledkami podobného experiment v rastrovacom elektrónovom mikroskope (SEM).
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Wolff, Niklas von. „Reaction mechanisms of CO₂ activation and catalytic reduction“. Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS580.
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L’utilisation du dioxyde de carbone (CO₂) comme source de composés C1 pour la chimie fine est intéressante d’un point de vue économique et pour des raisons écologiques. Issu de l’oxydation de la matière carbonée, le CO₂ est un gaz non-toxique, abondant et peu coûteux. Sa transformation en produits chimiques présentant de hautes valeurs ajoutées est actuellement entravée par sa stabilité thermodynamique. Afin de développer de nouveaux processus et catalyseurs pour la réduction catalytique du CO₂, une compréhension détaillée des mécanismes réactionnels de l’activation et de la réduction de ce gaz est nécessaire. En utilisant comme catalyseurs des paires de Lewis frustrée (FLPs) contenant une base azotée liée à un ion silicénium, les influences respectives de l’adduit CO₂-FLP et du réducteur ont été déterminées expérimentalement et par calcul DFT dans le cadre de l’hydroboration du CO₂ en équivalent de méthanol. Une nouvelle réaction visant à la création de liaisons carbone–carbone par le transfert du fragment pyridyle de molécules de pyridylsilanes (C₅H₄N–SiMe₃) sur le CO₂ était également étudiée. Le mécanisme réactionnel de cette transformation a été établi sur la base de calculs théoriques. Nous avons montré le double rôle du CO₂ qui est à la fois un réactif et un catalyseur de la réaction de transfert du groupe pyridyle. La compréhension fine de cette réaction nous a permis de l’étendre à la formation de sulfones et sulfonamides qui sont des groupements chimiques essentiels dans le domaine pharmaceutique. En utilisant le SO₂ à la fois comme catalyseur et réactif, des silanes aromatiques et hétéro-aromatiques ont été transformés en sulfones correspondants en une seule étape. Finalement, nous avons trouvé un couplage croisé original, de type Hiyama, entre espèces aromatiques électrophiles et des espèces C(sp2)–Si nucléophiles en présence de SO₂The use of CO₂ as a C1 chemical feedstock for the fine chemical industry is interesting both economically and ecologically, as CO₂ is non-toxic, abundant and cheap. Nevertheless, transformations of CO₂ into value-added products is hampered by its high thermodynamic stability and its inertness toward reduction. In order to design new catalysts able to overcome this kinetic challenge, a profound understanding of the reaction mechanisms at play in CO₂ reduction is needed. Using novel N/Si+ frustrated Lewis pairs (FLPs), the influence of CO₂ adducts and different hydroborane reducing agents on the reaction mechanism in the catalytic hydroboration of CO₂ were investigated, both by DFT calculations and experiments. In a second step, the reaction mechanism of a novel reaction for the creation of C–C bonds from CO₂ and pyridylsilanes (C₅H₄N–SiMe₃) was analyzed by DFT calculations. It was shown that CO₂ plays a double role in this transformation, acting both as a catalyst and a C1-building block. The fine understanding of this transformation then led to the development of a novel approach for the synthesis of sulfones and sulfonamides. Starting from SO₂ and aromatic silanes/amine silanes, these products were obtained in a single step under metal-free conditions. Noteworthy, sulfones and sulfonamides are common motifs in organic chemistry and found in a variety of highly important drugs. Finally, this concept was extended to aromatic halides as coupling partners, and it was thus shown for the first time that a sulfonylative Hiyama reaction is a possible approach to the synthesis of sulfones
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Anantharaman, Bharthwaj. „Reaction mechanisms for catalytic partial oxidation systems : application to ethylene epoxidation“. Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32328.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2005.Includes bibliographical references.
With the rapid advances in kinetic modeling, building elementary surface mechanisms have become vital to understand the complex chemistry for catalytic partial oxidation systems. Given that there is selected experimental knowledge on surface species and a large number of unknown thermochemical, rate parameters, the challenge is to integrate the knowledge to identify all the important species and accurately estimate the parameters to build a detailed surface mechanism. This thesis presents computational methodology for quickly calculating thermodynamically consistent temperature/coverage-dependent heats of formation, heat capacities and entropies, correction approach for improving accuracy in heats of formation predicted by composite G3- based quantum chemistry methods, and detailed surface mechanism for explaining selectivity in ethylene epoxidation. Basis of the computational methodology is the Unity Bond Index- Quadratic Exponential Potential (UBI-QEP) approach, which applies quadratic exponential potential to model interaction energies between atoms and additive pairwise energies to compute total energy of an adsorbed molecule. By minimizing the total energy subject to bond order constraint, formulas for chemisorption enthalpies have been derived for surface species bound to on-top, hollow and bridge coordination sites with symmetric, asymmetric and chelating coordination structures on transition metal catalysts. The UBI-QEP theory for diatomics has been extended for polyatomic adsorbates with empirical modifications to the theory.
(cont.) Formulas for activation energies have been derived for generic reaction types, including simple adsorption, dissociation-recombination, and disproportionation reactions. Basis of the correction approach is the Bond Additivity Correction (BAC) procedures, which apply atomic, molecular and bond- wise modifications to enthalpies of molecules predicted by G3B3 and G3MP2B3 composite quantum chemistry methods available in Gaussian® suite of programs. The new procedures have improved the accuracy of thermochemical properties for open and closed shell molecules containing various chemical moieties, multireference configurations, isomers and degrees of saturation involving elements from first 3 rows of the periodic table. The detailed mechanism explains the selectivity to ethylene oxide based on the parallel branching reactions of surface oxametallacycle to epoxide and acetaldehyde. Using Decomposition Tree Approach, surface reactions and species have been generated to develop a comprehensive mechanism for epoxidation. As a result of these developments in the thesis, chemisorption enthalpies can now be estimated within 3 kcal/mol of experimental values for transition metal catalysts and enthalpies predicted by G3B3 and G3MP2B3 Gaussian methods can be corrected within 0.5 kcal/mol. Examples of heterogeneous reaction systems involving silver-catalyzed ethylene epoxidation demonstrate the effectiveness of the methodologies developed in this work.
by Bharthwaj Anantharaman.
Ph.D.
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Dhanasekaran, Venkatesan. „Oxide supported Au-Pd nanoparticles for CO oxidation reaction“. Thesis, Sorbonne Paris Cité, 2017. https://theses.md.univ-paris-diderot.fr/DHANASEKARAN_Venkatesan_1_va_20170629.pdf.
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Les nanoparticules (NPs) bimétalliques Au-Pd ont été étudiées pour leur activité catalytique dans la réaction d'oxydation du CO. La technique de préparation, la taille et la composition des nanoparticules ont un grand impact sur le comportement catalytique du système. Ici, des nanoparticules de 3 et 5nm de diamètre Au1-xPdx (x = 0, 0.25, 0.5, 0.75, 1) ont été utilisées pour étudier l'effet de la taille et de la composition. Les échantillons ont été synthétisés par nano-lithographie à base de micelles, technique bien adaptée pour obtenir des particules ayant une distribution en taille étroite. Afin d’obtenir une répartition homogène des micelles chargées en ions métalliques sur des substrats de SiO2/Si(001), nous avons eu recours à la méthode de « spin-coating » et obtenu une organisation quasi-hexagonales des micelles observable en SEM. Un plasma d'oxygène ou d'hydrogène a été utilisé pour éliminer le polymère, réduire les ions métalliques et permettre la formation de nanoparticules. Nous avons entrepris une approche systématique pour étudier l'effet du plasma sur la structure et la morphologie des NPs à l'aide des techniques de diffusion des rayons X. L'oxydation et l'activité catalytique des NPs Au1-xPdx pour l'oxydation du CO ont été étudiées à 300 °C et 0.5 bar dans le réacteur à flux XCAT disponible sur la ligne de lumière SixS du Synchrotron SOLEIL, France. Les mesures de l'activité d'oxydation du CO ont montré que les NPs préparées en utilisant le plasma d'oxygène présentent un taux de conversion en CO2 plus élevé que les NPs préparées à l'aide de plasma d'hydrogène pour une composition donnée. Les nanoparticules de Pd préparées avec du plasma d'O2 se sont révélées être le catalyseur le plus actif : aucun effet synergique n'a été observé pour les nanoparticules bimétalliques pour la réaction d'oxydation du COAu-Pd bimetallic nanoparticles (NPs) have been studied for their catalytic activity in CO oxidation reaction. The preparation technique, size and composition of the nanoparticles have great impact on the catalytic behaviour of the system. Here, 3 and 5nm diameter Au1-xPdx (x = 0, 0.25, 0.5, 0.75, 1) nanoparticles were employed to study the effect of size and composition. The samples were synthesized by micelle nanolithography, a technique well adapted to yield narrow size distribution of nanoparticles. To achieve monodisperse metal-loaded micelles on SiO2/Si(001) substrates we employed spin-coating and observe quasi-hexagonal ordered micelles in SEM. Oxygen or hydrogen plasma were used to remove the polymer, reduce the metal ions and enable nanoparticle formation. We made a systematic approach to study the effect of plasma on the structure and morphology of the NPs by means of surface x-ray scattering techniques. The oxidation behavior and CO oxidation activity of the Au1-xPdx NPs were studied at 300°C and 0.5 bar in the flow reactor XCAT available at the SixS Beamline, Synchrotron SOLEIL, France. The CO oxidation activity measurements showed that the NPs prepared using the oxygen plasma present higher CO2 conversion rate than the NPs prepared using hydrogen plasma for a given composition. The Pd nanoparticles prepared using O2 plasma were found to be the most active catalyst: no synergetic effects were observed for bimetallic nanoparticles for the CO oxidation reaction
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Nuhu, Abdullahi. „Catalytic reaction of CO and alcohols over supported gold catalysts“. Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54729/.
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Studies of CO, methanol and some higher alcohol oxidations over gold supported on TiO2 (Degussa), Y-AI2O3 and SiCh were investigated. The methods of preparation of catalysts used are deposition precipitation and incipient wetness impregnation. Several parameters have been investigated for CO oxidation over Au/TiO2 prepared by deposition precipitation, such as temperature programmed pulse flow reaction, isothermal and continuous flow CO oxidation, anaerobic CO reaction, calcination temperature, effect of moisture (in the presence of water, and methanol), kinetics and CO oxidation in the presence of hydrogen etc. The catalysts are demonstrated to have high activity even at room temperature. Gold supported on TiO 2 (Degussa) was characterized by BET surface area method, powder X-ray diffraction, SEM, EDAX, XPS, and Raman spectroscopy. The CO oxidation reaction studied on A11/Y-AI2O3 and Au/SiC catalysts prepared by deposition precipitation (DP) and incipient wetness impregnation (IW) methods showed that the A11/Y-AI2O3 catalyst prepared by DP method is much more active than A11/Y-AI2O3 and Au/SiC 2 prepared by the incipient wetness impregnation method. Presumably, the low performances of the IW catalysts are ascribed due to presence of chloride which leads to gold sintering in the catalyst. However, the performance of these catalysts with respect to CO oxidation was less than the Au/TiO 2 catalyst prepared by DP method. The characterization of the catalyst shows the BET surface area of A11/Y-AI2O3 and Au/SiCh catalysts to be 128 and 320m
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Wang, Jiamin. „Exploring Strategies to Break Adsorption-Energy Scaling Relations in Catalytic CO Oxidation“. Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/96537.
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An atomistic control of chemical bonds formation and cleavage holds the key to making molecular transformations more energy efficient and product selective. However, inherent scaling relations among binding strengths of adsorbates on various catalytic materials often give rise to volcano-shaped relationships between the catalytic activity and the affinity of critical intermediates to the surface. The optimal catalysts should bind the reactants 'just right', i.e., neither too strong nor too weak, which is the Sabatier's principle. It is extremely useful for searching promising catalysts, but also imposes serious constraints on design flexibility. Therefore, how to circumvent scaling constraints is crucial for advancing catalytic science. It has been shown that hot electrons can selectively activate the chemical bonds that are not responsive to phonon excitation, thus providing a rational approach beyond scaling limitation. Another emerging yet effective way to break the scaling constraint is single atom catalysis. Strong interactions of supported single atoms with supports dramatically affect the electronic structure of active sites, which reroutes mechanistic pathways of surface reactions. In my PhD research, we use CO oxidation reaction on metal-based active sites as a benchmark system to tailor mechanistic pathways through those two strategies 1) ultra-fast laser induced nonadiabatic surface chemistry and 2) oxide-supported single metal catalysis, with the aim to go beyond the Sabatier activity volcano in metal catalysis.Doctor of Philosophy
Catalysis is the process of increasing the chemical reaction rate by lowering down the activation barrier. There are three different types of catalysis including enzyme, homogeneous, and heterogeneous catalysis. Heterogeneous catalytic reactions involve a sequence of elementary steps, e.g., adsorption of reactants onto the solid surface, transformation of adsorbed species, and desorption of the products. However, the existing scaling relations among binding energies of reaction intermediates on various catalytic materials lead to volcano-shaped relationships, which show the reaction activity versus the binding energy of critical intermediates. The optimal catalysts should bind the reaction intermediates neither too strong nor too weak. This is the Sabatier's principle, which provides useful guidance for searching promising catalysts. But it also imposes the constraint on the attainable catalytic performance. How to break the constraint to further improve the catalytic activity is an emerging problem. The recent studies have shown that the hot surface electrons on the metal surfaces induced by the ultra-fast laser can selectively activate the chemical bonds, thus providing a rational approach beyond scaling constraints. Another way to break the scaling constraint is single atom catalysis. The metal oxides are frequently used as the support to stabilize the single metal atoms. The strong interaction between the single metal atoms and the support affects the electronic structure of the catalysts. Thereby catalytic reactions on the single metal atoms catalyst are very different from that on metal surfaces. In my PhD research, we use CO oxidation reaction as a benchmark system, to tailor reaction pathways through those two strategies on 1) Ru(0001) under ultra-fast laser pulse and 2) Ir single metal atoms supported on spinel oxides, to go beyond Sabatier activity volcano in metal catalysis.
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Lau, Ngai Ting. „Catalytic reduction of sulfur dioxide and nitric oxide /“. View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?CENG%202006%20LAU.
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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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Cerasari, Stefano. „Kinetic and nonlinear effects associated with the catalytic CO oxidation on Pt surfaces“. [S.l. : s.n.], 2000. http://www.diss.fu-berlin.de/2000/61/index.html.
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Fansuri, Hamzah. „Catalytic partial oxidation of propylene to acrolein : the catalyst structure, reaction mechanisms and kinetics /“. Curtin University of Technology, Department of Chemical Engineering, 2005. http://espace.library.curtin.edu.au:80/R/?func=dbin-jump-full&object_id=16386.
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Bismuth molybdates have long been known as active catalysts for selective oxidation of olefins. There are several phases of bismuth molybdates but only three of them are known to be active for partial oxidation of propylene to acrolein, namely, α, β, and γ bismuth molybdates. A significant amount of work has been carried out and reported in the literature, aiming to understand the reaction mechanisms so as to control the reaction process. It has been revealed that the oxidation reaction follows the redox mechanisms and lattice oxygen plays a key role as the main oxygen source for the reaction and controls the catalyst performance. The properties of the lattice oxygen are influenced by the bulk crystalline structure of the catalyst. Therefore, it is possible that the crystal structure influences the performance of the catalyst in promoting the partial oxidation reaction. However, there appears to be a lack of detailed reports in the literature on the relationship between the bulk crystal structure and the activity and selectivity of the catalyst for the partial oxidation reaction. The work reported in this thesis has been designed to achieve an improved understanding of the catalyst structure in relation to the activity and selectivity of the catalyst for the partial oxidation of propylene to acrolein.In order to fulfil the objectives of this study, several investigation steps have been taken, namely 1) acquiring and analysing the catalyst structural parameters under real reaction conditions as well as at room temperature by means of neutron diffraction and X-ray diffraction, 2) obtaining kinetics from experimentation using a packed-bed reactor operating under differential reactor mode so as to eliminate the mass diffusion effect, and 3) developing and proposing reaction mechanisms which contain events that occur on the crystalline structure of the catalysts, particularly lattice oxygen, during the reaction. Characterisation of the structure of the catalysts has been carried out by means of In-situ neutron diffraction, which has the ability to probe the crystal structure at atomic level. The structure is characterised under simulated reaction conditions to investigate the dynamics of the crystal structure, particularly lattice oxygen, during the reaction. The In-situ diffraction studies have uncovered the relationship between the crystal structure of bismuth molybdates and their selectivity and activity towards the catalytic partial oxidation of propylene to acrolein. The possible active lattice oxygen in the bismuth molybdate structures has been identified. The active lattice oxygen ions are responsible for maintaining redox balance in the crystal lattice and thus control the catalyst activity and selectivity. Mobile oxygen ions in the three bismuth molybdate crystal phases are different. The mobile oxygen ions are O(1), O(11), and O(12) in the α phase; O(3), O(11), O(16), and O(18) in the β phase; and O(1) and O(5) in the γ phase.
The mobile lattice oxygen ions are proposed to be the source of the oxidising oxygen responsible for the selective oxidation of propylene to acrolein. One common feature of all mobile oxygen ions, from a catalyst crystal structure point of view, is that they are all related to molybdenum ions rather than bismuth ions in the lattice. By modifying the physical and chemical environment of the molybdenum oxide polyhedra, it is possible to modify the catalyst selectivity and activity. The diffraction diagnoses have also shown that molybdenum oxide polyhedra in all bismuth molybdate are unsaturated. In contrast, the bismuth oxide polyhedra are over charged. The co-existence of molybdenum ions that are co-ordinately unsaturated with bismuth ions that are over valence-charged promote the formation of allyl radical such as those found in the partial oxidation of propylene to acrolein. The molybdenum ions become propylene-adsorbing sites while the bismuth ions are the active sites to attract hydrogen from the adsorbed propylene, leading to the formation of the allyl intermediate. Oxygen ions from the mobile lattice oxygen are a more moderate oxidant than molecular oxygen. With their mild activity, the partially oxidised products are the main products such as acrolein and formaldehyde when oxygen ions react with the allyl intermediate while more complete combustion products such as carbon oxides and organic acids become the side products.
Investigation into the kinetics and reaction mechanisms has revealed the aforementioned evidence to support the role of the mobile lattice oxygen ions in the partial oxidation of propylene to acrolein. The kinetic experiments have employed the power rate law to model the kinetic data. The model shows that the reaction orders in propylene and oxygen concentrations are a function of the reaction temperature. The reaction order in propylene increases with reaction temperature, from 0.6 at 300°C to 1.0 at 450°C for all the bismuth molybdate catalysts, while the reaction order in oxygen decreases from 0.6 at 300°C to 0 at 450°C. The activation energies are 99.7, 173, and 97.7 kJ.mol-1 for α-Bi2Mo3O12, β-Bi2Mo2O9, and γ-Bi2MoO6, respectively. The changes in reaction orders with respect to propylene and oxygen indicate that the reaction occurs through the redox mechanisms, using the mobile lattice oxygen. The structural dynamics identified earlier explains the decrease in the acrolein selectivity at high temperatures (ca above 390°C). At these temperatures, the mobile oxygen becomes more mobile and more active. As a result, as the mobility of the oxygen ions increase, their reactivity also increases. The increase in the oxygen reactivity leads to unselective, complete oxidation reaction, forming the complete oxidation products CO2 and H2O. The reduction-reoxidation of bismuth molybdate is controlled by the diffusion of oxygen ions in the lattice, because the reduction sites do not have to be adjacent to the oxidation sites. The oxygen diffusion rate is in turn controlled by how mobile the lattice oxygen ions are.
Hence, the mobile oxygen ions discussed earlier control the catalyst activity in catalysing the reaction of propylene partial oxidation. The examination of several reaction mechanism models has given further evidence that the propylene partial oxidation to acrolein occurs via the redox mechanism. In this mechanism, the rate of acrolein formation depends on the degree of fully oxidised sites in the bismuth molybdate. The oxidised sites affect the apparent reaction orders in propylene and oxygen and thus control the kinetics of partial oxidation of propylene to acrolein. The more easily the reduced catalysts are reoxidised, the more active the catalysts in converting propylene to acrolein. A set of reaction steps has been proposed, which adequately reassembles the reaction mechanism. Side product reactions are also identified and included in the mechanisms. The present thesis has revealed a much detailed insight into the role of lattice oxygen in the catalytic partial oxidation of propylene to acrolein over bismuth molybdates and established the relationship between structure and activity and selectivity of the catalyst. This work has laid a foundation for future catalyst design to be based on structural knowledge of the catalysts.
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Davó-Quiñonero, Arantxa. „Copper-based catalysts for the Preferential Oxidation of CO in H2-rich streams (CO-PROX reaction)“. Doctoral thesis, Universidad de Alicante, 2019. http://hdl.handle.net/10045/98737.
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The Preferential CO Oxidation (CO-PROX) is a promising catalytic strategy to remove CO residual content from H2-rich streams. Mixed copper and cerium oxide catalysts are materials that display an excellent performance towards COPROX reaction by means of synergistic interaction the copper and cerium-rich phases. Alternatively, mixed manganese oxides are proposed as active supports with very positive catalytic features when these are loaded with copper species. This Project Thesis comprises a detailed study on the implementation of copper oxide – manganese oxide catalysts in CO-PROX reaction and the establishment of a critical comparison with regards to the consolidated cerium-based catalysts.
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Gladh, Jörgen. „Ultrafast Probing of CO Reactions on Metal Surfaces : Changes in the molecular orbitals during the catalysis process“. Doctoral thesis, Stockholms universitet, Fysikum, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-132248.
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This thesis presents experimental studies of three different chemical reaction steps relevant for heterogeneous catalysis: dissociation, desorption, and oxidation. CO on single-crystal metal surfaces was chosen as the model systems. X-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES) provide information about the electronic structure, and were performed on CO/Fe to measure both a non-dissociative, and a pre-dissociative state. The measurement on the pre-dissociative state showed a π → π* excitation, which implies a partly broken internal π bond in the molecule. Ultrafast laser-induced reactions were used to examine the dynamic properties of desorption and oxidation. Here CO/Ru and CO/O/Ru were used as model systems. Desorption of CO from a Ru surface involve both hot electrons and phonons. In the case of CO oxidation from CO/O/Ru a pronounced wavelength dependence of the branching ratio between desorption and oxidation was observed. Excitation with 400 nm showed a factor of 3-4 higher selectivity towards oxidation than 800 nm. This was attributed to coupling to transiently excited, non-thermalized electrons. Finally, by performing optical pump/x-ray probe XAS and XES changes in the electronic structure during the reaction could be followed, both for desorption and oxidation. In the CO/Ru experiment, two different transient excitation paths were observed, one leading to a precursor state, and one where CO moves into a more highly coordinated site. Using selective excitation in XES, these were shown to coexist on the surface. In the oxidation experiment, probing the reacting species located near the transition state region in an associative catalytic surface reaction was demonstrated for the very first time.
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Luke, Ronald John Campbell. „The reversible electrochemical promotion of the catalytic oxidation of carbon monoxide over platinum supported yttria-stabilised zirconia“. Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243861.
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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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Utaka, Toshimasa. „Catalytic production of hydrogen from hydrocarbon and removal of CO by water gas shift reaction“. 京都大学 (Kyoto University), 2003. http://hdl.handle.net/2433/148865.
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Yan, Zhen. „Model catalytic studies of single crystal, polycrystalline metal, and supported catalysts“. [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-2455.
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Zell, Elizabeth Theresa. „Synthesis and Support Shape Effects on the Catalytic Activities of CuOx/CeO2 Nanomaterials“. Youngstown State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1525699148756394.
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Ono, Luis. „IN-SITU GAS PHASE CATALYTIC PROPERTIES OF METAL NANOPARTICLES“. Doctoral diss., University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3277.
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Recent advances in surface science technology have opened new opportunities for atomic scale studies in the field of nanoparticle (NP) catalysis. The 2007 Nobel Prize of Chemistry awarded to Prof. G. Ertl, a pioneer in introducing surface science techniques to the field of heterogeneous catalysis, shows the importance of the field and revealed some of the fundamental processes of how chemical reactions take place at extended surfaces. However, after several decades of intense research, fundamental understanding on the factors that dominate the activity, selectivity, and stability (life-time) of nanoscale catalysts are still not well understood. This dissertation aims to explore the basic processes taking place in NP catalyzed chemical reactions by systematically changing their size, shape, oxide support, and composition, one factor at a time. Low temperature oxidation of CO over gold NPs supported on different metal oxides and carbides (SiO2, TiO2, TiC, etc.) has been used as a model reaction. The fabrication of nanocatalysts with a narrow size and shape distribution is essential for the microscopic understanding of reaction kinetics on complex catalyst systems ("real-world" systems). Our NP synthesis tools are based on self-assembly techniques such as diblock-copolymer encapsulation and nanosphere lithography. The morphological, electronic and chemical properties of these nanocatalysts have been investigated by atomic force microscopy (AFM), scanning tunneling microscopy (STM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and temperature-programmed desorption (TPD). Chapter 1 describes briefly the basic principles of the instrumentation used within this experimental dissertation. Since most of the state-of-art surface science characterization tools provide ensemble-averaged information, catalyst samples with well defined morphology and structure must be available to be able to extract meaningful information on how size and shape affect the physical and chemical properties of these structures. In chapter 2, the inverse-micelle encapsulation and nanosphere lithography methods used in this dissertation for synthesizing uniformly arranged and narrow size- and shape-selected spherical and triangular NPs are described. Chapter 3 describes morphological changes on individual Au NPs supported on SiO2 as function of the annealing temperature and gaseous environment. In addition, NP mobility is monitored. Chapter 4 explores size-effects on the electronic and catalytic properties of size-selected Au NPs supported on a transition metal carbide, TiC. The effect of interparticle interactions on the reactivity and stability (catalyst lifetime) of Au NPs deposited on TiC is discussed in chapter 5. Size and support effects on the formation and thermal stability of Au2O3, PtO and PtO2 on Au and Pt NPs supported on SiO2, TiO2 and ZrO2 is investigated in chapter 6. Emphasis is given to gaining insight into the role of the NP/support interface and that played by oxygen vacancies on the stability of the above metal oxides. Chapter 7 reports on the formation, thermal stability, and vibrational properties of mono- and bimetallic AuxFe1-x (x = 1, 0.8, 0.5, 0.2, 0) NPs supported on TiO2(110). At the end of the thesis, a brief summary describes the main highlights of this 5-year research program.Ph.D.
Department of Physics
Sciences
Physics PhD
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Hughes, Dimitri. „Facilitated characterization of a catalytic partial oxidation fuel reformer using in situ measurements“. Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31646.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2010.Committee Co-Chair: Haynes, Comas; Committee Co-Chair: Wepfer, William; Committee Member: Jeter, Sheldon. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Ozensoy, Emrah. „Polarization modulation infrared reflection absorption spectroscopy for heterogeneous catalytic applications at elevated pressures“. Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/2201.
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This dissertation focuses on bridging the pressure and complexity gap between heterogeneous catalysis and surface science by introducing new instrumental tools that can operate under catalytically relevant conditions (i.e. atmospheric pressures and temperatures higher than room temperature). Thus, some of the few detailed examples of the polarization modulation infrared reflection absorption spectroscopy (PM-IRAS) as an in situ vibrational spectroscopic tool for the elevated-pressure investigation of gas/solid interfaces on planar single crystal model catalyst systems were presented in this work. Furthermore, for the first time in the literature, PM-IRAS technique was applied to study complex multi-component model catalyst structures exhibiting three dimensional morphologies such as metal nanoparticles deposited on a metal-oxide thin film. In order to achieve a molecular understanding of the properties of CO+NO catalytic reaction at elevated temperatures and pressures on Pd based catalysts, adsorption trends of each of the reactant molecules were studied separately on Pd (111). The adsorption properties of CO/Pd (111) and NO/Pd (111) systems both under UHV conditions and at elevated pressures were discussed in a comparative manner to highlight the pressure dependent behavioral differences between these two probe molecules by emphasizing the risks of extrapolating UHV trends to elevated pressure regimes. CO+NO reaction mechanism and kinetics was also studied on Pd (111) by in situ PM-IRAS. Factors affecting the conversion and the selectivity of the Pd (111) model catalyst towards CO+NO reaction at elevated pressures were discussed. Formation of isocyanate containing species?? was also observed and the catalytic implications of this observation was elaborated. Finally, design and characterization of a complex model catalyst composed of supported Pd nano-particles was investigated using CO adsorption at elevated pressures. Catalytic activity of the defect sites on the supported Pd nano-particles towards CO dissociation was demonstrated and compared with Pd (111) to elucidate the significance of the surface morphology of the active sites in a catalytic reaction.
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Fragkopoulos, Ioannis. „Modelling of electrochemical promotion in heterogeneous catalytic systems“. Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/modelling-of-electrochemical-promotion-in-heterogeneous-catalytic-systems(af0e3881-75d7-40f1-88b9-32a6a6bb0be9).html.
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The subject of this work is the development of accurate frameworks to describe the electrochemical promotion of catalysis (EPOC) phenomenon. EPOC, also known as non-Faradaic electrochemical modification of catalytic activity (NEMCA), refers to the enhancement of the catalytic performance by application of current or potential in a catalyst/support system. Although this technology is of increasing interest nowadays in the field of modern electrochemistry and exhibits a great industrial potential, there are still just a few commercial applications, partly because the addressed phenomenon is not fully understood and has not been modelled to allow robust system design and control. For this purpose, a systematic multi-dimensional, isothermal, dynamic model is developed to address the EPOC phenomenon using the electrochemical oxidation of CO over Pt/YSZ as an illustrative system. The formulated model is based on partial differential equations (PDEs) accounting for the simulation of the mass and charge transport as well as the electrochemical phenomena taking place at the triple phase boundaries (TPBs, where the gas phase, the catalyst and the support are all in contact) implemented through a commercial finite element method (FEM) software (COMSOL Multiphysics). The constructed model is used in conjunction with experimental data for parameter estimation purposes, and a validated model is obtained. The results demonstrate that the effect in such a system is strongly non-Faradaic, with Faradaic rates 3 orders of magnidute lower than the non-Faradaic ones. The formulated model is extended to describe the various processes taking place in the electrochemically promoted CO combustion system at their characteristic length-scales. The proposed framework couples a macroscopic model simulating charge transport as well as electrochemical phenomena occuring at the TPBs implemented through a FEM-package and an in-house developed efficient implementation of the kinetic Monte Carlo method (kMC) for the simulation of reaction-diffusion micro-processes on the catalyst. Dynamic communication of macro- and micro-scopic models at the TPBs results in the construction of an integrated multi-scale system. Comparison between the multi-scale framework and a fully macroscopic model is carried out for several sets of operating conditions and differences between the two models steady-state outputs are presented and discussed. A detailed FEM/kMC model, regardless of accurately simulating the several phenomena at their appropriate length-scales, might not be suitable for large system simulations due to the high computational demand. To address this limitation, a computationally efficient coarse-graining methodology, the so-called gap-tooth method, is implemented. In this scheme the catalytic surface is efficiently represented by a small subset of the spatial domain (tooth) separated by gaps. While kMC simulations within each individual tooth (micro-lattice) are used to predict the corresponding evolution of the micro-processes, intelligent interpolation rules are employed to allow for the exchange (diffusion) of species between consecutive micro-lattices. A validated gap-tooth/kMC scheme is obtained and it is exploited for FEM/gap-tooth/kMC electrochemically promoted CO oxidation simulations achieving high computational savings.
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Hou, Liwei. „Metal oxide synthesis and its application in the heterogeneous catalytic oxidation processes, using H2O2 or peroxydisulfate as oxidant“. Thesis, Poitiers, 2013. http://www.theses.fr/2013POIT2271/document.
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Parmi les procédés avancés d'oxydation (AOPs), les procédés de type Fenton (réactif de Fenton: Fe2+/H2O2) et les procédés d'oxydation par le persulfate, sont décrits comme des procédés très performants. Le procédé Fenton est une voie prometteuse et attractive pour le traitement d'une large variété de composés organiques polluants, difficiles à traiter par les voies classiques de dépollution. Au cours du procédé Fenton, des radicaux hydroxyles, molécules à fort pouvoir oxydant capable de réagir avec pratiquement tous types de composés organiques et inorganiques, sont générés. De même, du fait de la structure similaire entre H2O2 et les ions peroxydisulfate, ces derniers peuvent se décomposer en radicaux sulfates (SO4-•), un autre type d'oxydant hautement réactif pouvant réagir avec les composés organiques. Cependant, les procédés Fenton et d'activation du peroxydisulfate classiques présentent plusieurs inconvénients. En effet, la solution doit être acidifiée avant la réaction, et des procédés complexes de purification / séparation sont nécessaires après réaction. Afin de contourner ces inconvénients, le développement de procédés de traitement hétérogènes est proposé pour le traitement de l'eau. Dans cette optique de développement de procédés économes, les oxydes de fer comme la magnétite sont proposés comme remplaçants des sels solubles de fer. Une utilisation de tels matériaux, à l'état solide, présente des avantages indéniables, dont la séparation aisée de l'espèce active après réaction par sédimentation ou filtration. Dans le cadre de ce travail de doctorat, différents types d'oxydes de fer, hématite ou magnétite, ont été synthétisés en milieu liquide ionique. La morphologie, les propriétés structurales, les rapports de surface FeII/FeIII, les surfaces spécifiques, les tailles de domaine cristallin, etc. ont été évaluées. Deux molécules différentes, la tétracycline (TC) et le phenol, couramment utilisées dans l'industrie chimique, ont été sélectionnées comme polluants modèles afin d'évaluer les performances des matériaux préparés pour leur élimination. Une partie importante du travail de doctorat a donc été l'étude des propriétés des matériaux pour l'élimination de polluants organiques par le procédé Fenton hétérogène. Les résultats montrent clairement que les principaux facteurs affectant les performances du procédé sont reliés aux propriétés de la phase active, du fait du caractère surfacique des réactions. La stabilité des systèmes catalytiques préparés est néanmoins une propriété cruciale également étudiée. Le manuscrit de doctorat met donc l'accent sur la conception de matériaux originaux destinés à une utilisation dans les procédés avancés d'oxydation dans l'eauFenton reaction (Fenton reagent: (Fe2+/H2O2)) and persulfate oxidation process, as advanced oxidation processes, are powerful oxidations used world around. Fenton reaction has been evidenced to be a promising and attractive treatment method for the degradation of a wide variety of hazardous organic pollutants, which are difficult to be treated using traditional soft treatment technologies. During Fenton process, free hydroxyl radicals (HO•), strong oxidant molecules capable of reacting with practically all types of organic and inorganic compounds, are generated. In the meanwhile, due to the similar structure between H2O2 and peroxydisulfate ions, peroxydisulfate ions can be decomposed to sulfate radicals (SO4-•), another kind of highly active oxidant that can react with organic compounds. However, the classical Fenton or peroxydisulfate activation processes present some disadvantages. Indeed, the solution needed acidification before carrying out the reaction and complex separation processes have to be applied after reaction. To overcome these drawbacks, heterogeneous catalytic oxidation processes were introduced for wastewater treatment. In this line, magnetite was evidenced as potential substituent to soluble iron ions, and it offers significant advantages such as an easy separation after reaction since the active material can be easily recovered by sedimentation or filtration for further used. In this PhD work, iron oxides, hematite and magnetite, were synthesized using an ionic liquid mediated process. The morphology, structural properties, FeII/FeIII surface ratios, specific surface areas (SSA), mean particle diameters, site densities, etc. were evaluated. Two different model pollutants (tetracycline (TC) and phenol), which are widely used chemicals all over the world, were selected to evaluate the performance of the prepared active materials. A significant part of the PhD study was then on the study of heterogeneous Fenton-like reaction for phenol and TC degradation. Experiments showed that the main factors affecting the heterogeneous Fenton-like system are related to the heterogeneous active phase properties, due to the surface reaction nature occurring over iron oxide surface. However, stability of this active phase, with progressive dissolution under reaction, is also a real challenge. This PhD manuscript, focusing on the design of highly active materials for advanced oxidation processes (AOPs), is constituted of five experiment result parts
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Siriwardane, Upali. „Systematic syntheses of iron-triad (Fe,Ru,Os) tetranuclear clusters by redox condensation reactions of [Ru(3);CO(11)) and [Os(3);CO(11)] trinuclear carbonylates; co-crystallization of ruthenium-osmium clusters /“. The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487264603216477.
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Kim, Sang Hoon. „Study of reaction mechanisms on single crystal surfaces with scanning tunneling microscopy“. Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2003. http://dx.doi.org/10.18452/14884.
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Ziel dieser Arbeit war, die Rastertunnelmikroskopie, die bereits zur Aufklärung von einfachen Reaktionsmechanismen eingesetzt wurde, für em kompliziertere Reaktionen anzuwenden. Die Oxidation von CO auf Pd(111) und auf einem RuO2-Film auf Ru(0001) wurde untersucht. Strukturelle Analysen ergeben mikroskopische Verteilungen der Adsorbate in den Überstrukturen von O und CO auf Pd(111) und RuO2. Dynamische und quantitative Analysen der Reaktionen liefern die Kinetik und die Mechanismen der Reaktionen direkt auf der mikroskopischen Ebene. O-Atome auf Pd(111) sind bei mittleren Bedeckungsgraden (0.10< theta mathrm O 135 K beweglich. Die Aktivierungsenergie der Diffusion (E * mathrm diff ) beträgt 0.54 pm 0.08 eV, der präexponentielle Faktor der Sprünge Gamma mathrm o beträgt 10 16 pm 3 s -1. Bei niedrigen Bedeckungen (theta mathrm CO sim 0) sind die CO-Moleküle auf Pd(111) schon bei T mathrm sample = 60 K sehr beweglich. Wenn man einen präexponentiellen Faktor von Gamma mathrm o = 10 13 s -1 annimmt, ergibt sich für E * mathrm diff von CO ein Wert von 0.15 eV. Adsorbiert CO auf der (2 times2) -O-Überstruktur bei T mathrm sample > 130 K, kommt es mit steigendem Bedeckungsgrad von CO zu Phasenübergängen, zunächst in eine ( sqrt 3 times Sqrt 3 ) R30 circ -O-Struktur, dann in eine (2 times1)-Struktur. Während der Phasenübergänge nimmt die Mobilität der O-Atome zu, was sich in einer Abnahme der E* mathrm diff um 10 bis 20 % (unter der Annahme von Gamma mathrm o = 10 16 s -1) im Vergleich zu einer CO-freien Oberfläche niederschlägt. Am Ende der Phasenübergänge entstehen aus einer fast völlig ungeordneten (O+CO)-Phase viele kleine (2 times1)-Inseln, die sich zu grösseren Inseln zusammenlegen. Die (2 times1)-Inseln sind bereits bei T mathrm sample = 136 K sehr reaktiv. Die quantitative Analyse der Abreaktion der (2 times1)-Inseln ergibt, dass die Reaktionsrate proportional zur Inselfläche und nicht zur Randlänge ist. Die Reaktionsordnung bezüglich theta mathrm(2 times1) ist sim 1. Unter der Annahme eines Vorfaktors k mathrm o von 10 13 s -1 wurde für diese Reaktion ein E* mathrm reac von 0.41 eV abgeschätzt. Für eine CO-Adsorption auf der (2 times2)-O-Überstruktur bei T mathrm sample < 130 K kommt es nicht zu einem Phasenübergang, sondern CO adsorbiert auf der (2 times2)-O-Struktur. Der RuO2-Film wurde bei Temperaturen zwischen 650 und 900 K auf der Ru(0001)-Probe aufgewachsen. Die Morphologie des Oxidfilms hängt stark von der Temperatur der Probe während des Wachstums Tprep ab. Bei Tprep sim 650 K ist die Morphologie überwiegend kinetisch bestimmt. Mit steigendener Temperatur bis Tprep = 900 K werden thermodynamische Effekte immer wichtiger. Die Dicke der Oxidschicht hängt nicht von Tprep ab und beträgt 7 AA bis 15 AA, was 2 bis 5 (Ru-O)-Monolagen entspricht. Die thermodynamische Stabilität der Morphologie ergibt sich aus Experimenten, in denen die Oxidschicht durch Heizen auf verschiedene Temperaturen partiell verdampft wurde. Der Film dampft nicht lageweise ab, sondern es entstehen Löcher in der ansonsten unverdampften Oxidschicht. Die Löcher haben eine charakteristische Form. Sie bilden Parallelogramme oder Rechtecke mit einer langen Achse in [001]-Richtung. Die Oberflächenenergie gamma 001 der einen Flanke der Löcher ist 2 bis 5 mal grösser als gamma bar110 der anderen Flanke. Beim Verdampfen des Films verbleiben die freigesetzten Ru-Atome des Oxids auf dem Substrat. Sie bilden dort eine komplizierte Morphologie von hexagonalen und runden Inseln. Die mikroskopischen Beobachtungen der chemischen Prozesse auf dem Film bestätigen die auf den makroskopischen Untersuchungen basierenden Modelle. Ein neuer Befund ist, dass die CO-Moleküle bei Raumtemperatur auf den Rulf -Reihen stabil adsorbieren, sobald die Ruzf -Reihen vollständig mit CO bedeckt sind. Der maximale Bedeckungsgrad theta mathrm CO1f ist 0.5, die COlf-Moleküle bilden lokal geordnete (2times1)-, c(2times2)- und (1times1)-Überstrukturen. Allerdings kommt es bei theta mathrm CO1f sim 0.5 zu einer langsamen Desorption. Wenn man ein k mathrm o von 10 16 s -1 annimmt, lässt sich ein E * mathrm des von 1.00 eV abschätzen. Unter der Annahme von Gamma mathrm o und k mathrm o von 10 13 s -1 lassen sich E* mathrm diff -Werte für O und CO zwischen 0.89 und 0.93 eV abschätzen, und für die Reaktion zwischen COlf und Olf ein Wert von E* mathrm reac sim 0.87 eV. Die Reaktionen zwischen Ozf und COlf, zwischen Olf und COzf sowie zwischen Olf und COlf verlaufen überwiegend statistisch. Manchmal wird eine leicht bevorzugte Reaktion quer zu den Rulf - und Ruzf -Reihen beobachtet. Unter steady-state-Bedingungen kann CO bei genügend grossem Partialdruck auf der Oberfläche adsorbieren. Unter steady-state-Bedingungen werden die gleichen COlf-Überstrukturen beobachtet wie in einer CO-Atmosphäre oder bei der Titration mit CO. Bei massiver Dosierung der Oxidoberfläche mit Oz und CO (sim 100 L) werden weisse Flecken beobachtet, die COlf ähnlich sind. Allerdings reagieren diese weder mit Oz noch mit CO, was auf einen anderen chemischen Zustand der RuO2-Oberfläche als den sauberen Zustand hinweist.Scanning Tunneling Microscopy has already been established as a tool for the investigation of simple reaction mechanisms. The aim of this thesis was to apply this technique to study emmore complicated reactions. The oxidation of CO on Pd(111) and on a RuO2 film grown on Ru(0001) was investigated. Structural analyses of the O, CO and (CO+O) adlayers on Pd(111) and on RuO2 reveal the microscopic distributions of the adsorbates on the surfaces. Dynamic and quantitative analyses of the reactions yield the reaction kinetics and the reaction mechanisms in a direct way at the microscopic level. O atoms on Pd(111) at intermediate coverages (0.10
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Emmerich, Thomas [Verfasser], Martin [Akademischer Betreuer] Muhler und Wolfgang [Akademischer Betreuer] Grünert. „Ceria- and zirconia-based materials for the catalytic oxidation of CO and soot / Thomas Emmerich. Gutachter: Martin Muhler ; Wolfgang Grünert“. Bochum : Ruhr-Universität Bochum, 2016. http://d-nb.info/1099703549/34.
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Cuzan, Olesea. „Synthesis and characterization of new transition metal complexes for catalytic oxidation and electrolytic proton reduction“. Thesis, Aix-Marseille, 2016. http://www.theses.fr/2016AIXM4356/document.
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De nos jours, la capacité à synthétiser de nouveaux catalyseurs métallique bioinspirés pour améliorer et élargir le spectre d'activité catalytique est d’une importance capitale pour une chimie respectueuse de notre environnement.Cette thèse se concentre sur la conception de nouveaux complexes de métaux de transition (cuivre et palladium) basés sur deux classes différentes de ligands organiques : les benzotriazolyle-phénolates et les phosphonates. La synthèse et la caractérisation de nouveaux composés a été réalisée par différentes méthodes physico-chimiques (électrochimie, EPR, UV-vis, IR, cristallographie aux rayons X) et la chimie théorique. La génération et la caractérisation des différentes espèces réduites et oxydées nous ont aidés dans la détermination des mécanismes possible. Les composés obtenus ont été utilisés avec succès comme catalyseurs dans divers procédés tels que: la production d'hydrogène, l'oxydation d'alcool et le clivage d'ADNNowadays, the ability to synthesize new bioinspired metal catalysts to improve and broaden the spectrum of catalytic activity is of paramount importance for sustainable chemistry respectful for our environment. This thesis is focused on the design of transition metal complexes (copper and palladium) based on two different classes of organic ligands: benzotriazolyl-phenolates and phosphonates.Different original complexes based on palladium and copper were synthetized from benzotriazolyl-phenolate and phosphonates ligands. The characterization of the new compounds was performed by different physical and physico-chemical methods (electrochemistry, EPR, UV-vis, IR, X-ray crystallography) and quantum chemistry. The generation and characterization of different reduced and oxidized species helped us in the possible mechanisms determination. The obtained compounds were successfully employed as catalysts in different processes as: hydrogen production, alcohol oxidation and DNA cleavage
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Zhang, Ziyin. „An Experimental Study of Catalytic Effects on Reaction Kinetics and Producer Gas in Gasification of Coal-Biomass Blend Chars with Steam“. Thesis, University of Canterbury. Chemical and Process Engineering, 2011. http://hdl.handle.net/10092/6204.
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The objective of this thesis is to experimentally investigate the performance of steam gasification of chars of pure coal (lignite, sub-bituminous), pure biomass (radiata pine, eucalyptus nitens) and their blends. The influences of gasification temperature, types of coal and biomass, coal-biomass blending ratio, alkali and alkaline earth metal (AAEM) in lignite, on specific gasification characteristics (producer gas composition and yield, char reactivity) were studied. In addition, synergistic effects in co-gasification of coal-biomass blend char were also investigated. This project is in accordance with objectives of the BISGAS Consortium.
In this study, experiments were performed in a bench-scale gasifier at gasification temperatures of 850°C, 900°C and 950°C, respectively. Two types of coals (lignite and sub-bituminous) and two kinds of biomass (radiata pine and eucalyptus nitens) from New Zealand were selected as sample fuels. From these raw materials, the chars with coal-to-biomass blending ratios of 0:100 (pure coal), 20:80, 50:50, 80:20 and 100:0 (pure biomass), which were derived through the devolatilization at temperature of 900°C for 7 minutes, were gasified with steam as gasification agent. During the gasification tests, the producer gas composition and gas production were continuously analysed using a Micro gas chromatograph. When the gas production was undetectable, the gasification process was assumed to be completed and the gasification time was recorded. The gasification producer gas consisted of three main gas components: hydrogen (H2), carbon monoxide (CO) and carbon dioxide (CO2).
The results from gasification of chars of individual solid fuels (coal or biomass) confirmed that biomass char gasification was faster than coal char gasification. The influences of gasification temperatures were shown as: when gasification temperature increased, the H2 yield increased in coal char gasification but decreased in biomass char gasification. In the meantime, CO yields increased while CO2 yields decreased in both coal char and biomass char gasification. In addition, the char reactivity of all the pure fuel samples increased with elevated gasification temperatures.
The results from co-gasification of coal-biomass blend char exhibited that the syngas production rate, which is defined as the total gas production divided by the gasification completion time, was enhanced by an increase in gasification temperatures as well as an increase in the biomass proportion in the blend. The AAEM species played a significant catalytic role in both gasification of pure coal chars and co-gasification of coal-biomass blend chars. The presence of AAEM increased the producer gas yield and enhanced the char reactivity.
The positive synergistic effects of the coal-biomass blending char on syngas production rate only existed in the co-gasification of lignite-eucalyptus nitens blend chars. The other blend chars showed either insignificant synergistic effects or negative effects on the syngas production rate.
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Lang, Mason J. „CATALYTIC WASTE GASIFICATION: WATER-GAS SHIFT & SELECTIVITY OFOXIDATION FOR POLYETHYLENE“. Cleveland State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=csu1560982761165342.
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Lahr, David Louis. „Molecular oxygen adsorbates at a Au/Ni(111) surface alloy and their role in catalytic CO oxidation at 70 - 250 K“. Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36250.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2006.Includes bibliographical references.
Oxygen is observed to adsorb molecularly on 0.13 - 0.27 ML Au/Ni(1 111) surface alloys at 77 K, in stark contrast to dissociative adsorption on Ni and no adsorption on Au surfaces. Molecular 02 adsorbates on the Au/Ni(111) surface alloy are identified by their 0=0 vibrational modes at 790, 850 and 950 cm-', measured by electron energy loss spectroscopy. Possible Ni adsorption sites for the three types of molecularly adsorbed 02 are proposed. The dramatic change in Ni reactivity occurs within a narrow Au coverage range around 0.13 ML Au and arises from poorer overlap between the Ni d-band and the 02 LUMO as the Ni d-band shifts to lower energy with increasing Au content of the Au/Ni surface alloy. The amount of molecular adsorption as a function of Au coverage cannot be described by an analytical or simulated model based on Au atom proximity to Ni sites, suggesting the role of cooperative effects in 02 stabilization. Adsorbed molecular 02 dissociates between 110 to 150 K. No oxygen desorbs. At Au coverages greater than 0.27 ML, the energy of the Ni d-band is shifted sufficiently low to destabilize oxygen adsorption.
(cont.) Carbon monoxide is catalytically oxidized on the Au/Ni(111) surface alloy at 70 and 77 K via a Langmuir-Hinshelwood mechanism. Molecularly adsorbed 02 is identified as the reactant with adsorbed CO. The reaction probability at 77 K is 0.4. Atomically adsorbed O and CO do not react at 77 or 300 K. Between 108 and 125 K, CO reacts with either atomic O adsorbed on Au atoms or with molecularly adsorbed 02. Between 125-150 K, CO2 production coincides with 02 dissociation, suggesting a "hot atom" mechanism. The reactive potential energy surfaces likely have a late transition state. This work demonstrates that the nanoscale size of Au clusters and its associated quantum size effect are not the necessary feature that enables Au-catalyzed low temperature CO oxidation. Rather, this work strongly suggests that an adsorbed 02 species similarly stabilized at the perimeter of Au nanoparticles is the critical reactant in supported oxide systems.
by David Louis Lahr.
Ph.D.
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Liu, Yong [Verfasser], Ferdi [Gutachter] Schüth und Martin [Gutachter] Muhler. „Novel catalytic materials for glycerol utilization and CO oxidation / Yong Liu ; Gutachter: Ferdi Schüth, Martin Muhler ; Fakultät für Chemie und Biochemie“. Bochum : Ruhr-Universität Bochum, 2010. http://d-nb.info/1240476019/34.
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Vilekar, Saurabh A. „Catalytic and Electrocatalytic Pathways in Fuel Cells“. Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-dissertations/125.
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A fundamental understanding of the kinetics and mechanisms of the catalytic reaction steps involved in the process of converting a fuel into hydrogen rich stream suitable for a fuel cell, as well as the electro-catalytic reactions within a fuel cell, is not only conceptually appealing, but could provide a sound basis for the design and development of efficient fuel processor/fuel cell systems. With the quantum chemical calculations on kinetics of elementary catalytic reaction steps becoming rather commonplace, and with increasing information now available in terms of electronic structures, vibration spectra, and kinetic data (activation energy and pre-exponential factors), the stage is set for development of a comprehensive approach. Toward this end, we have developed a framework that can utilize this basic information to develop a comprehensive understanding of catalytic and electrocatalytic reaction networks. The approach is based on the development of Reaction Route (RR) Graphs, which not only represent the reaction pathways pictorially, but are quantitative networks consistent with the Kirchhoff's laws of flow networks, allowing a detailed quantitative analysis by exploiting the analogy with electrical circuits. The result is an unambiguous portrayal of the reaction scheme that lays bare the dominant pathways. Further, the rate-limiting steps are identified rationally with ease, based on comparison of step resistances, as are the dominant pathways via flux analysis. In fact, explicit steady-state overall reaction (OR) rate expression can also be derived in an Ohm's law form, i.e. OR rate = OR motive force/OR resistance of an equivalent electric circuit, which derives directly from the RR graph of its mechanism. This approach is utilized for a detailed analysis of the catalytic and electro-catalytic reaction systems involved in reformer/fuel cell systems. The catalytic reaction systems considered include methanol decomposition, water gas shift, ammonia decomposition, and methane steam reforming, which have been studied mechanistically and kinetically. A detailed analysis of the electro-catalytic reactions in connection to the anode and cathode of fuel cells, i.e. hydrogen electrode reaction and the oxygen reduction reaction, has also been accomplished. These reaction systems have not so far been investigated at this level of detail. The basic underlying principles of the RR graphs and the topological analysis for these reaction systems are discussed.
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Gottfried, Jörg Michael. „CO oxidation over gold adsorption and reaction of oxygen, carbon monoxide, and carbon dioxide on an Au(110)-(1x2) surface /“. [S.l. : s.n.], 2003. http://www.diss.fu-berlin.de/2003/133/index.html.
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Hejral, Uta Elisabeth [Verfasser], und Andreas [Akademischer Betreuer] Stierle. „Operando characterization of supported alloy nanoparticles during catalytic CO oxidation by surface sensitive x-ray diffraction / Uta Elisabeth Hejral ; Betreuer: Andreas Stierle“. Hamburg : Staats- und Universitätsbibliothek Hamburg, 2016. http://d-nb.info/1120623251/34.
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Wang, Jijin. „Sum frequency generation study of CO adsorbed on palladium single crystal and nanoparticles : adsorption and catalytic oxidation as a function of size“. Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00933675.
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The CO reaction on metals is of great interest experimentally and theoretically because it serves as a model system to understand molecular chemisorption and catalyzed reactions on metals. This thesis aims at progressing along the general trends of surface science: bridging the pressure and material gaps in the study of catalysts. Sum Frequency Generation (SFG) is at the heart of this work. It involves a nonlinear optical process with an IR pulse induced coherent first-order polarization up-converted by a visible pulse into a second-order polarization at the sum frequency. In this thesis it is used to record CO vibrational spectra on the Pd nanoparticles (NP)/MgO/Ag(100) to understand the adsorption and oxidation thanks to its specific advantages in surface science: sensitivity and surface selectivity. The questions proposed are the possible roles of the adsorption sites which only exist on the NPs, the effect of the size of NPs and the presence of oxygen on the CO adsorption and catalytic reactivity, the effect of adsorption of oxygen (from 'normal' - dissociative chemisorption to 'sub-surface'), the variation of reactivity of CO in the different sites when pressure and temperature increase. (1) We have studied CO adsorption on Pd(100) as a reference. Below a CO coverage of 0.5 ML SFG results confirm previous IRAS studies. Above 0.5 ML, we have observed in much more details than previously two vibrational bands assigned to CO at compressed and uncompressed bridge sites, of which we have measured the frequency and intensity and the decoherence time T₂ as a function of coverage. (2) Pd NP size effect on CO adsorption is studied (from Pd(100) to particles with about 300 atoms). At pressures below 10⁻³ mbar the CO spectra on a coalesced layer and on large NPs are dominated by the same bridge band as on Pd(100). The CO singleton frequency decreases with coverage, revealing the evolution of chemisorption with size. DFT calculations done at ENS Lyon reveal that the main mechanism is the strain induced by the substrate which increases the Pd-Pd bondlength, favors electron back donation to CO, weakens the CO bond and probably reinforce the CO-metal bond. (3) Because of a limit of our maximal temperature, we have to study the CO catalytic oxidation in an excess of oxygen to avoid self-poisoning by CO. The results strongly suggest that bridge sites are the key sites in catalysis in our experimental condition. However, while a fraction of bridge sites are more reactive on NPs, a large fraction of them seem less reactive with respect to Pd(100). The reactivity of CO on (100) facet decreases at smaller NP size. It emerges the ideal that the reaction proceeds by the most reactive sites, and that the other sites are only reservoir in reactivity, if the diffusion between sites are high enough. Oxygen modifies the adsorption of co-reactants. In the case of CO + O / Pd NPs / MgO, below 10⁻⁴ mbar oxygen does not seem to influence significantly CO adsorption; between 10⁻³ and 10⁻¹ mbar the spectroscopic signature of CO compression disappears, and above 1 mbar a new class of a top sites appears, suggesting that some oxygen species (perhaps "subsurface") favors CO adsorption on linear sites. A pump-probe experiment has been done to compare the effect of pump on different adsorption sites. All this confirms the interest of SFG vibrational spectroscopy for catalysis. An additional contribution of this thesis to SFG is the study of the spectro-temporal aspects of SFG emission. SFG spectra containing several bands are modeled in details based on an ODT/Au system and compared to experimental spectra, showing that in SFG spectra are affected by the spectro-temporal shape of the visible laser. The standard deconvolution method used in the literature is only approximate. Accurate spectro-temporal spectrum modeling is required to evaluate precisely the relative intensities when several bands are present.
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Hejral, Uta Elisabeth Verfasser], und Andreas [Akademischer Betreuer] [Stierle. „Operando characterization of supported alloy nanoparticles during catalytic CO oxidation by surface sensitive x-ray diffraction / Uta Elisabeth Hejral ; Betreuer: Andreas Stierle“. Hamburg : Staats- und Universitätsbibliothek Hamburg, 2016. http://nbn-resolving.de/urn:nbn:de:gbv:18-81945.
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Finer, Julia E. „Evaluation of the Effect of Dioxygen, Industrial Heterogeneous Palladium Catalyst, pH and Iron Content on the Generation of 3 High-Value Aldehydes from Corn Stover Lignin“. University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1397234827.
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Ross, Martin James. „Investigation into Catalytic Metallodrugs that Target Hepatitis C IRES RNA: Development, Characterization, and Mechanism“. The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440421045.
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Tanaka, Yohei. „Removal of CO by water gas shift reaction and catalytic production of hydrogen from dimethyl ether over Cu-based spinel-type oxide catalyst“. 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/144925.
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Kyoto University (京都大学)0048
新制・課程博士
博士(工学)
甲第11580号
工博第2526号
新制||工||1343(附属図書館)
23223
UT51-2005-D329
京都大学大学院工学研究科物質ｴﾈﾙｷﾞｰ化学専攻
(主査)教授 江口 浩一, 教授 井上 正志, 教授 垣内 隆
学位規則第4条第1項該当
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Herrera, Delgado Karla [Verfasser], und O. [Akademischer Betreuer] Deutschmann. „Surface Reaction Kinetics for Oxidation and Reforming of H2, CO, and CH4 over Nickel-based Catalysts / Karla Herrera Delgado. Betreuer: O. Deutschmann“. Karlsruhe : KIT-Bibliothek, 2014. http://d-nb.info/1056955864/34.
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Pfisterer, Jonas H. K. [Verfasser]. „Toward nanoscale reactivity mapping under electro-catalytic reaction conditions : Plasmon-enhanced vibrational spectroscopy of the electrochemical gold oxidation and gold oxide reduction / Jonas H. K. Pfisterer“. Mainz : Universitätsbibliothek Mainz, 2019. http://d-nb.info/1199377449/34.
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Zhao, Yanyan. „Dinuclear Heterogeneous Catalysts on Metal Oxide Supports:“. Thesis, Boston College, 2020. http://hdl.handle.net/2345/bc-ir:109003.
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Thesis advisor: Dunwei WangAtomically dispersed catalysts refer to substrate-supported heterogeneous catalysts featuring one or a few active metal atoms that are separated from one another. They represent an important class of materials ranging from single atom catalysts (SACs) and nanoparticles (NPs). The study of SACs has brought an attention of understanding the reaction mechanism at the molecular level. SACs is a promising field, however, there are still many challenges and opportunities in developing the next generation of catalysts. Catalysts featuring two atoms with well-defined structures as active sites are poorly studied. It is expected that this class of catalysts will show uniqueness in activity, selectivity, and stability. However, the difficulty in synthesizing such structures has been a critical challenge. I tackled this challenge by using a facile photochemical method to generate active metal centers consisting of two iridium metal atoms bridged by O ligands and bound to a support by stripping the ligands of the organometallic complex. My research also unveiled the structure of this dinuclear heterogeneous catalysts (DHCs) by integrating various characterization resources. Direct evidence unambiguously supporting the dinuclear nature of catalysts anchored on metal oxides is obtained by aberration-corrected scanning transmission electron microscopy. In addition, different binding modes have been achieved on two categories of metal oxides with distinguishable surface oxygen densities and interatomic distances of binding sites. Side-on bound DHCs was demonstrated on iron oxide and ceria where both Ir atoms are affixed to the surface with similar coordination environment. The binding sites on the OH-terminated surface of Fe2O3 and CeO2 anchor the catalysts to provide outstanding stability against detachment, diffusion and aggregation. The competing end-on binding mode, where only one Ir atom is attached to the substrate and the other one is dangling was observed on WO3. Evidence supporting the binding modes was obtained by in situ diffuse reflectance infrared Fourier transform spectroscopy. In addition, the synergistic effect between two adjacent Ir atoms and the uniqueness of different coordinative oxygen atoms around Ir atoms were investigated by a series of operando spectroscopy such as X-ray absorption spectroscopy and microscopy at atomic level under the reaction condition. The resulting catalysts exhibit high activities and stabilities toward H2O photo-oxidation and preferential CO oxidation. Density functional theory calculations provide additional support for atomic structure, binding sites modes on metal oxides, as well as insights into how DHCs may be beneficial for these catalytic reactions. This research has important implications for future studies of highly effective heterogeneous catalysts for complex chemical reactions
Thesis (PhD) — Boston College, 2020
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Chemistry
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Freitas, Kênia da Silva. „Eletrocatalisadores de ligas de platina dispersos em substratos de óxidos para a reação de oxidação de hidrogênio puro e na presença de CO“. Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/75/75131/tde-25082009-164210/.
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Neste trabalho são apresentados resultados dos estudos da reação de oxidação de hidrogênio puro realizados em eletrodos rotatório em camada ultrafina porosa e na presença de CO em células a combustível utilizando catalisadores formados por Pt dispersas em substratos de óxidos, tais como, Pt/RuO 2 -C, Pt/RhO 2 -C, Pt/WO 3 -C e em Pt/WC-C. As reações foram também estudadas em suporte puro, como, RhO 2 /C e WC/C em diferentes proporções atômicas. Este estudo teve como finalidade estudar as propriedades catalíticas destes materiais visando elucidar os mecanismos da reação de oxidação de hidrogênio (ROH) sobre estes catalisadores dispersos, possibilitando a obtenção de parâmetros cinéticos das reações. Em conjunto com as medidas eletroquímicas, foram realizados estudos sobre as propriedades eletrônicas e estruturais destes catalisadores, o que possibilita relacionar suas propriedades eletrônicas e estruturais com a cinética da HOR. Observou-se que a presença dos óxidos de Ru, Rh e WO 3 favorecem a diminuição do grau de recobrimento da Pt por CO, deixando mais sítios disponíveis a ROH, em consequência do esvaziamento da banda 5d da Pt, o que diminui a retro-doação de elétrons da Pt ao CO, diminuindo a força da ligação Pt-CO. Como observado, essas modificação eletrônicas observadas nos espectros de XANES não induziram a nenhuma mudança perceptível na cinética ou no mecanismo reacional. Para quase todos os catalisadores, a tolerância ao CO pode ser explicada tanto em termos do mecanismo eletrônico como do bifuncional evidenciado pela formação de CO 2 nas medidas de EMS.This work shows results of studies of the hydrogen oxidation reaction (HOR) pure in rotation in ultra porous layer and in the presence of CO in the fuel cell to the electrocatalysts of Pt alloy dispersed on oxide substrates such Pt/RuO 2 -C, Pt/RhO 2 -C, Pt/WO 3 -C, Pt/WC-C and pure materials, as RhO 2 /C and WC. The study of the catalytic properties of these materials to elucidate the mechanisms of hydrogen oxidation reaction on these dispersed catalysts, allowing the collection of kinetic parameters of reactions. Together with the electrochemical measurements were carried out studies on the structural and electronic properties of these catalysts, which allow relating their structural and electronic properties with the kinetics of the HOR. It was observed that the presence of oxides of Ru, Rh and WO 3 encourage the reduction of the degree of coating of Pt by CO, leaving more sites available to ROH, as a consequence of emptying of the Pt 5d band, which reduces the backdonation of electrons from Pt to CO by reducing the strength of Pt-CO binding. As noted, these changes observed in electronic spectra of XANES not led to any perceptible change in the kinetics or the reaction mechanism. For almost all catalysts, the CO tolerance can be explained in terms of the electronic effect and the bifunctional mechanism evidenced by the formation of CO 2 in the EMS.
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Brummer, Vladimír. „Zařízení pro zneškodňování odpadních plynů katalytickou oxidací“. Doctoral thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2017. http://www.nusl.cz/ntk/nusl-320159.
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This thesis deals with the design of the equipment and documentation for the design of equipment for the removal of volatile organic compounds (VOC) and carbon monoxide (CO) by catalytic oxidation and the selection of appropriate technological conditions for this technology. Introduction is devoted to familiarization with the field of the catalytic oxidation, used catalysts, catalyst supports and their active components. Advantages and disadvantages of the use of catalytic oxidation versus thermal incineration are outlined and currently applicable legislative terms for VOC and CO emissions are listed. In the next part of the thesis the fundamental mathematical tools and research findings available for catalytic reactor model designed primarily for monolithic catalysts are summarized. Presented kinetic model considers continuous reactor with plug flow of gas and adiabatic heating by oxidation reactions corrected for the heat loss of the reactor. The next chapter discusses the design of the new prototype of the catalytic oxidation pilot plant (i.e. the reactor incl. peripherals) primarily intended for monolithic catalysts and bulk catalysts in the form of the fixed bed. The basis for the design and sizing are material and energy balances in the ChemCAD for different intended use of the unit, from which boundary conditions of the unit operating parameters arises. Pilot plant has been designed and built, functionality tests was scheduled also with consecutive obtaining of experimental data not only for the reactor kinetic model. Results of the model for the catalytic combustion were in good agreement with measured data. The next part includes two industrial case studies of the catalytic oxidation process usage for the chemical industry. In particular it was dealt with a replacement of the non-catalytic combustion for the catalytic for VOC abatement from chemical production plants off-gas streams of the company Momentive Specialty Chemicals in Sokolov and German city Leuna. These case studies have brought many valuable experimental and technological knowledge from long-term pilot tests and also verification of design concept, thanks to which it was later possible to design a pilot unit for removal of pollutants in premises of NETME Centre and among other to economically evaluate the usage of catalytic oxidation for the off gas cleaning, in comparison with traditional combustion, in two completely different individual cases. This information was valuable and necessary for the verification of theoretical assumptions of the thesis on specific conditions of two different industrial productions. Based on acquired practical experience and theoretical background, guidelines for designing of devices for VOC and CO removal in the industry were developed.
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Schilling, Christian Michael [Verfasser], Christian [Akademischer Betreuer] Hess, Rolf [Akademischer Betreuer] Schäfer und Rolf Jürgen [Akademischer Betreuer] Behm. „Operando Spectroscopy and DFT Modeling of Gold/Ceria Catalysts for CO Oxidation and Water-Gas Shift Reaction / Christian Michael Schilling ; Christian Hess, Rolf Schäfer, Rolf Jürgen Behm“. Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2018. http://d-nb.info/1163013528/34.
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Fernández, Villanueva Estefanía. „Theoretical Study of the Geometrical, Electronic and Catalytic properties of Metal Clusters and Nanoparticles“. Doctoral thesis, Universitat Politècnica de València, 2020. http://hdl.handle.net/10251/135277.
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[ES] Dado su tamaño subnanométrico, los clusters metálicos están regidos por el confinamiento cuántico, lo que les hace más "moleculares" y menos "metálicos". En consecuencia, manifiestan propiedades que difieren con respecto a las de partículas más grandes del mismo elemento, y que a menudo son ventajosas para la catálisis de reacciones específicas. Además, su menor tamaño los hace más económicos, con una mayor superficie expuesta. Todo ello hace que los clusters sean opciones muy interesantes en catálisis, y su estudio, síntesis y aplicación ha crecido continuamente desde su descubrimiento en los años 90.
Esta tesis se ha centrado principalmente en el cobre, del que se presenta, en primer lugar, un estudio fundamental sobre la disociación de oxígeno por clusters de diferentes tamaños. Después, se explora computacionalmente la catálisis de las oxidaciones de CO y propeno, confirmando que los clusters de Cu5 (o inferior) son prometedores para reacciones de oxidación. Las dos reacciones utilizadas son buenos ejemplos de la aplicación potencial en industria, sea para reducir emisiones de CO o para producir epóxido de propeno, que es un intermedio importante en la producción de plásticos y adhesivos, entre otros. Además, también se estudió la influencia de dos soportes en los clusters de cobre y su capacidad de oxidación: N-grafeno como un sistema más inerte y ceria como uno que puede participar activamente en reacciones de oxidación.
Finalmente, se incluyen otros dos estudios más específicos, sobre la capacidad de los clusters de Pt3 y Pd3 para catalizar reaciones de acoplamiento C-C como la reacción de Heck, importante para la síntesis de productos de la química fina, y sobre la reacción CO + NO en clusters de Pt, motivado por su uso potencial como catalizadores para la conversión de esas especies en los menos perjudiciales CO2 y N2 en motores de combustión interna.[CAT] Atès que són de grandària subnanomètrica, els clusters metàl·lics estan regits pel confinament quàntic, el qual els fa més "moleculars" i menys "metàl·lics". En conseqüència, manifesten propietats que són diferents a les de partícules més grans del mateix element, i que sovint són avantatjoses per a la catàlisi de reaccions específiques. A més a més, la seua menor grandària fa que siguen més econòmics, amb una major superfície exposada. Així, els clusters són una opció molt interesant en catàlisi, i el seu estudi, síntesi i aplicació ha cres-cut contínuament des del seu descobriment als anys 90. Aquesta tesi s'ha centrat principalment en el coure, del qual es presenta, en primer lloc, un estudi fonamental sobre la dissociació de l'oxígen per clusters de diferents grandàries. Després, s'explora computacionalment la catàlisi de les oxidacions de CO i de propè, confirmant que els clusters de Cu5 (o inferior) són prometedors per a reaccions d'oxidació. Les dues reaccions utilitzades són bons exemples de l'aplicació potencial en indústria, siga per reduir emissions de CO o per produir epòxid de propè, que és un intermedi important en la producció de plàstics i adhesius, entre altres. A més, també es va estudiar la influència de dos suports en els clusters de coure i la seua capacitat d'oxidació: N-grafè com a un sistema més inert i cèria com a un que pot participar activament en reaccions d'oxidació. Finalment, s'inclouen altres dos estudis més específics, sobre la capacitat dels clusters de Pt3 y Pd3 per catalitzar reaccions d'acoblament C-C com la reacció de Heck, important per a la síntesi de productes de la química fina, i sobre la reacció CO + NO als clusters de Pt, motivat pel seu ús potencial com a catalitzadors per a la conversió d'eixes espècies en els menys perjudicials CO2 i N2 als motors de combustió interna.
[EN] Due to their subnanometric size, metal clusters belong to the regime affected by quantum confinement, which makes them more "molecular" and less "metallic". As a result, they exhibit properties that differ with respect to those of larger particles of the same element, and which are often advantageous in the catalysis of specific reactions. Besides, their smaller size makes them more economic and with a higher surface exposed. All of this renders metal clusters very interesting options for catalysis, and their study, synthesis and application has steadily increased since their discovery in the 90s. In this work we have largely focused on copper, of which a fundamental study on the oxygen dissociation by clusters of different sizes is first presented. Then, the catalysis of the CO and propene oxidation reactions is theoretically explored, confirming that Cu5 (or smaller) clusters are promising systems for oxidation reactions. The two reactions used are good examples of the potential application in industry, either to reduce CO emissions or to produce propene epoxide, an important intermediate in the production of plastics and adhesives, among others. In addition, the influence of two supports in the copper clusters and their oxidation capability is explored: on N-graphene as a more inert system and on ceria as one that can actively participate in oxidation reactions. Finally, two other more specific studies are included, regarding the capability of Pt3 and Pd3 clusters to undergo C-C coupling reactions such as the Heck reaction, important for the synthesis of many products of fine chemistry, and regarding the CO + NO reaction on Pt clusters, motivated by their potential use as catalysts for the conversion of those species in less harmful CO2 and N2 in internal combustion engines.
En primer lugar me gustaría agradecer al Ministerio de Economía y Competitividad de España (MINECO) por la financiación de esta tesis mediante el programa Severo Ochoa (SVP-2013-068146), incluyendo los costes adicionales de mi estancia de investigación (EEBB-I-17-12057).
Fernández Villanueva, E. (2019). Theoretical Study of the Geometrical, Electronic and Catalytic properties of Metal Clusters and Nanoparticles [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/135277
TESIS
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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 matériauxThe 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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Djeffal, Lemya. „Développement de matériaux à base d'argiles pour l'oxydation catalytique de polluants organiques par des réactions de type Fenton“. Thesis, Littoral, 2013. http://www.theses.fr/2013DUNK0354.
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Dans ce travail, nous nous sommes intéressés à la synthèse et à la caractérisation de matériaux à base d'argiles naturelles en provenance d'Algérie et de Tunisie, pouvant être utilisés en tant que catalyseurs dans l'oxydation de polluants organiques par les réactions Fenton et photo-Fenton. Nous avons également optimisé les paramètres réactionnels (quantité de catalyseur, concentration en polluant...) dans le but d'améliorer les performances catalytiques de ces derniers. En effet, l'oxydation de polluants organiques récalcitrants par des réactions de type Fenton est considérée comme l'une des techniques les plus performantes parmi les procédés d'oxydation avancée (POA). Elle permet d'aboutir dans certains cas au stade ultime de l'oxydation qui est la minéralisation (transformation en CO₂ et H₂O). La caractérisation des argiles à l'état brut par différentes techniques physico-chimiques montre qu'en plus des matériaux argileux, il existe quelques oxydes métalliques dans toutes les argiles étudiées, avec des proportions plus ou moins variées. En particulier, la smectite a montré une contenance assez importante en fer. Les argiles synthétisés montrent une très bonne performance catalytique en un minimum de temps (2 heures de réaction). Le catalyseur à base de smectite calciné à 450°C et tamisé donne le meilleur rendement catalytique. Cette activité peut être expliquée par la forte teneur en fer ainsi qu'à la combinaison entre le choix de la taille des particules et la température de calcination de la smectite. La caractérisation de ce catalyseur a montré que ce matériau mésoporeux contenait une quantité de fer (III) stabilisée dans la structure par le fait de la calcinationIn this study, we are interested to the synthesis and charaterization of materials based on natural clays from Algeria and Tunisia, usable as catalysts in the oxidation of organic pollutants by the Fenton's and photo-Fenton's reaction. We have also optimized the reaction parameters (amount of catalyst, concentration of pollutant...) in order to improve the catalytic performance of these catalysts. Indeed, the oxidation of recalcitrant organic pollutants by Fenton-type reactions is regarded as one of the most effective method amongst the advanced oxidation process (AOPs). It can lead in some cases to the total mineralization of pollutants (conversion into CO₂ and H₂O). The caracterization of the raw clays various physicochemical methods shows that, in addiction to clay minerals, there are some metallic oxides in all studied clays, with varied proportions. Especially, smectite showed a fairly significant iron capacity. The synthesized clays show a good catalytic performance in minimum of time (2 hours of reaction). The smectite catalyst, sieved and calcined at 450°C gives the best performance. This activity can be explained by the high content of iron as well as the combination of the choice of particle size and the calcination temperature of the smectite. The caracterization of this catalyst, showed that this mesoporous material contains an amount of iron (III) stabilized in the structure by the fact of calcination