Дисертації з теми "Catalytic reaction dynamics"
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Gelß, Patrick [Verfasser]. "The Tensor-Train Format and Its Applications : Modeling and Analysis of Chemical Reaction Networks, Catalytic Processes, Fluid Flows, and Brownian Dynamics / Patrick Gelß." Berlin : Freie Universität Berlin, 2017. http://d-nb.info/1140487140/34.
Повний текст джерелаYun, Thomas. "Fuel reformation and hydrogen generation in variable volume membrane batch reactors with dynamic liquid fuel introduction." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53550.
Повний текст джерелаPham, Van Tuyet. "The synthesis and reactions of chiral 1,3,2-oxazaphospholane derivations : kinetic and mechanistic studies of polyether omega-phase catalyzed reactions of potassium cyanide with benzyl bromide in non-polar, aprotic solvent toluene." Diss., Georgia Institute of Technology, 1987. http://hdl.handle.net/1853/27416.
Повний текст джерелаFusion, Joe. "The Role of Environmental Dynamics in the Emergence of Autocatalytic Networks." PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2458.
Повний текст джерелаKumar, Ankan. "Physical Models and Computational Algorithms for Simulation of Catalytic Monolithic Reactors." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1230142666.
Повний текст джерелаLarsson, Rikard. "Reversible Sulfur Reactions in Pre-Equilibrated and Catalytic Self-Screening Dynamic Combinatorial Chemistry Protocols." Licentiate thesis, Stockholm, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3917.
Повний текст джерелаLIN, PENG. "Enzyme cascade reactions on 3D DNA scaffold with dynamic shape transformation." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/265209.
Повний текст джерела新制・課程博士
博士(エネルギー科学)
甲第23437号
エネ博第424号
新制||エネ||81(附属図書館)
京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻
(主査)教授 森井 孝, 教授 佐川 尚, 教授 片平 正人
学位規則第4条第1項該当
Doctor of Energy Science
Kyoto University
DFAM
Vongvilai, Pornrapee. "Dynamic Covalent Resolution: Applications in System Screening and Asymmetric Synthesis." Doctoral thesis, Stockholm : Skolan för kemivetenskap, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-11200.
Повний текст джерелаRaymand, David. "Surface and Interface Studies of ZnO using Reactive Dynamics Simulation." Doctoral thesis, Uppsala universitet, Strukturkemi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-129304.
Повний текст джерелаLorenzo, Maria Ortega. "Complexities and dynamics of the enantioselective site in heterogeneous catalysis : tartaric acid and methylacetoacetate on Cu(110)." Thesis, University of Liverpool, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366724.
Повний текст джерелаZhang, Yang. "Dynamic Systems : Enzymatic Synthesis, Exchange Reactions and Applications in Materials Science." Doctoral thesis, KTH, Organisk kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-173480.
Повний текст джерелаQC 20150911
Warner, Madeleine. "Ruthenium-Catalyzed Hydrogen Transfer Reactions : Mechanistic Studies and Chemoenzymatic Dynamic Kinetic Resolutions." Doctoral thesis, Stockholms universitet, Institutionen för organisk kemi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-89263.
Повний текст джерелаAt the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 5: Mansucript.
Medeiros, Nicholas J. "Computational Fluid Dynamics Simulations of Radial Dispersion in Low N Fixed Bed Reactors." Digital WPI, 2015. https://digitalcommons.wpi.edu/etd-theses/1306.
Повний текст джерелаWang, Shujiang. "Insights into dynamic covalent chemistry for bioconjugation applications." Doctoral thesis, Uppsala universitet, Polymerkemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-329022.
Повний текст джерелаSilva, Mojica Ernesto. "Polymer-silica Hybrids for Separation of CO2 and Catalysis of Organic Reactions." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1398439043.
Повний текст джерелаHurley, Jeffrey S. "Phase transfer catalysis of deuterium exchange reactions : II kinetic and mechanistic studies of the thermal decomposition of glycolate and hedta in the presence of the sodium salts of hydroxide, nitrate, nitrite, aluminate and carbonate." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/30717.
Повний текст джерелаMills, Landon C. "IMPACT OF CONFORMATIONAL CHANGE, SOLVATION ENVIRONMENT, AND POST-TRANSLATIONAL MODIFICATION ON DESULFURIZATION ENZYME 2'-HYDROXYBIPHENYL-2-SULFINATE DESULFINASE (DSZB) STABILITY AND ACTIVITY." UKnowledge, 2019. https://uknowledge.uky.edu/cme_etds/105.
Повний текст джерелаLarsson, Rikard. "Dynamic Systems for Screening, Control and Identification of Protein-Ligand Interactions." Doctoral thesis, Stockholm : Kemi, Chemistry, Kungliga Tekniska högskolan, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4709.
Повний текст джерелаReocreux, Romain. "Biomass derivatives in heterogeneous catalysis : adsorption, reactivity and support from first principles." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEN019/document.
Повний текст джерелаMoving away from fossil ressources is currently being accompanied by the increasing exploitation of biomass.This shift requires the development of new processes, in particular in heterogeneous catalysis. Chemists are nowfacing two major challenges: (i) deoxygenate biomass (cellulose/lignin) to produce platform intermediates with aeel-known chemistry (ii) make catalysts resistant to water, ubiquitous within the context of biomass.Within a collaboration with experimentalists at the University of Ottawa, we have first studied the deoxygenationof lignin-like aromatics. From an ab initio (DFT) inspection, we have characterized and described the adsorptionof such aromatic oxygenates on Pt(111) with simple molecular descriptors. We have then investigated thedecomposition mechanism of anisole and 2-phenoxyethanol. For these two model compounds, we have showedthe significance of hydrogen and carbonaceous species to have the deoxygenation reaction proceed properly.Meanwhile, we have examined the stability, in water, of γ-alumina, a major support in heterogeneous catalysis.The necessity to perform ab initio molecular dynamics simulations makes the modeling of such a systemparticularly challenging computationally. The simulations have nevertheless enabled us to characterize thestructuration of liquid water in contact with alumina and the significance of solvation on surface aluminol groups.Using rare-event methods (constrained dynamics, metadynamics) we have eventually been able to probe thereactivity of alcohols and water with hydrated alumina. We have then identified the first steps of hydration andgained insights on how to limit them
Danielson, Thomas Lee. "Investigation of Static and Dynamic Reaction Mechanisms at Interfaces and Surfaces Using Density Functional Theory and Kinetic Monte Carlo Simulations." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/71296.
Повний текст джерелаPh. D.
Angelin, Marcus. "Discovery-Oriented Screening of Dynamic Systems: Combinatorial and Synthetic Applications." Doctoral thesis, KTH, Organisk kemi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12524.
Повний текст джерелаQC 20100628
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.
Повний текст джерелаPelissari, Daniel Cícero 1989. "Estudo da influência dos bicos injetores sobre o escoamento gás-sólido e as reações em um riser de FCC via CFD." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266017.
Повний текст джерелаDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: A aplicação de fluidodinâmica computacional (CFD) em estudos de otimização e projeto de novos equipamentos de processos industriais vem aumentando significativamente, uma vez que apresenta custo reduzido e possibilidade de avaliar equipamentos complexos e de extremas condições de operação. Dentre os processos mais estudados via CFD está o processo de craqueamento catalítico fluidizado (FCC), onde as frações pesadas do petróleo de baixo valor são convertidas em produtos de maior valor agregado, sendo uma das aplicações de fluidização gás-sólido mais importante na indústria de petróleo. O presente trabalho avaliou especificamente a zona de injeção do FCC, na qual a matéria-prima, alimentada por bicos injetores, se mistura a sólidos quentes (catalisador) e a vapor de fluidização. A performance desses dispersores de carga para garantir uma boa distribuição das gotículas de gasóleo com o catalisador é a chave para melhorar a eficiência do riser de FCC. Desta forma, o principal objetivo deste trabalho foi avaliar o efeito de diferentes designs, ângulos (30°, 45° e 60°) e configurações dos injetores sobre o escoamento gás-sólido e o desempenho do riser. Para tal, simulou-se um escoamento gás-sólido reativo tridimensional baseado em uma abordagem Eulerian-Eulerian. Nas simulações foram utilizados o modelo cinético de 12-lumps de Wu et al. (2009), modelo de turbulência k-? e modelo de arraste de Gidaspow. Foi observado que o design, o ângulo e a configuração dos bicos injetores exercem uma forte influência sobre a fluidodinâmica e a performance do riser, sendo o ângulo a variável que apresentou maior influência. Pôde-se observar que o design de bico tipo multi-orifícios (Caso 3) foi o que apresentou os melhores resultados, sendo a partir deste avaliados os ângulos, onde notou-se que o aumento do ângulo de 30° para 60° melhorou a mistura entre as fases e o rendimento. A análise dos arranjos foi realizada utilizando o design de bico do Caso 3 e o ângulo de 45°, e observou-se que o arranjo com bicos intercalados (Arranjo 2) apresentou uma mistura mais homogênea entre as fases e, consequentemente, uma melhor conversão e rendimento de produtos desejados. Em geral, os resultados obtidos no presente trabalho salientam a importância da utilização de geometrias mais detalhadas para os bicos, uma vez que influenciam a mistura entre as fases, a qual afeta o desempenho do riser
Abstract: The Computational Fluid Dynamic (CFD) application in industrial process optimization and new equipments design studies has increased significantly, once it presents low cost and the possibility of evaluating complex and extreme operating conditions equipments . Among the most widely studied processes via CFD is the fluidized catalytic cracking process (FCC), where the oil heavy fractions of low-value are converted into higher value-added products and which is one of the most important gas-solid fluidization applications in the oil industry . The present study specifically evaluated the FCC injection zone, in which the feedstock fed by nozzles, is mixed with hot solids (catalyst) and fluidization steam. The nozzles performance to guarantee a good gas oil droplets distribution with the catalyst is the key to improve the efficiency of FCC riser. Thus, the study main objective was to evaluate the different nozzles designs, angles (30 °, 45 ° and 60 °) and arrangements effect on the gas-solid flow and the riser performance. For this purpose, it was simulated a three-dimensional reactive gas-solid flow based on an Eulerian-Eulerian approach. In the simulations it was used the 12 lumps kinetic model by Wu et al. (2009), turbulence model k- ? and drag model Gidaspow. It was observed that the nozzle design, angle and configuration have a strong influence on fluid dynamics and on the riser performance, and the angle was the variable with the greatest influence. It can be observed that the nozzle design of multi-orifice type (Case 3) showed the best results, and that¿s why it was used to evaluate the angle, in which was noted that the angle increase of 30 ° to 60 ° improved phases mixing and the yield. The arrangement analysis was performed using Case 3 nozzle design and the design angle of 45 °, and it was observed that the arrangement with intercalated nozzles (Arrangement 2) showed a more homogeneous phases mixture and therefore a better conversion and desired product yield. In general, the results obtained in this work highlighted the importance of using more detailed geometries for the nozzles, since they influence the mixing of the phases, which affects the riser performance
Mestrado
Engenharia Química
Mestre em Engenharia Química
Lopes, Gabriela Cantarelli. "Estudo computacional da dinâmica do escoamento reativo em risers industriais de FCC." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266768.
Повний текст джерелаTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: O craqueamento catalítico fluido (FCC) é um dos processos de maior importância da indústria do refino de petróleo, já que converte as frações pesadas de baixo valor comercial provenientes de outros processos de refino, em produtos comercialmente mais importantes, como gasolina, GLP e diesel. Atualmente, com o aumento da demanda por combustíveis fósseis e a redução na extração de óleos convencionais, o aperfeiçoamento do processo de FCC tem se tornado essencial para as refinarias. Estudos empíricos sobre a dinâmica do escoamento em reatores industriais de FCC são raros, em parte devido às altas temperaturas e pressões presentes no interior desses reatores, o que dificulta a obtenção de dados, e em parte por causa da complexidade da operação, que envolve uma série de fenômenos simultâneos, como a vaporizacão da carga, reações heterogêneas, a expansão do leito devido ao craqueamento e a desativação das partículas de catalisador, por exemplo. Contudo, para que se possa melhorar a performance do processo, é necessário conhecer a dinâmica desse escoamento. Foi proposto então, neste estudo a simulação computacional de risers industriais de FCC, usando ferramentas de CFD. O nível de complexidade das simulações realizadas foi aumentado gradativamente e fenômenos como a adsorção das moléculas reagentes nos sítios ativos do catalisador e a vaporizacão da carga líquida, foram estudados separadamente, possibilitando a avaliação individual de sua influência sobre o processo em termos de variáveis globais. Para uma análise detalhada do escoamento, foram usados modelos tridimensionais e foram propostas configurações geométricas similares às encontradas em unidades típicas de FCC. Além disso, um estudo da sensibilidade das variáveis do escoamento ao uso de diferentes geometrias de saída para o reator foi realizado, tornando possível determinar as configurações que propiciam melhor rendimento para o processo. Em geral, os resultados fluidodinâmicos obtidos neste estudo ressaltam a importância da aplicação de modelos que representem os complexos fenômenos presentes no riser de FCC, já que estes influenciam consideravelmente as reações
Abstract: The fluid catalytic cracking (FCC) is one of the most important process in the oil refining industry. It converts heavy distillation fractions with low commercial value into lighter and valuable hydrocarbon products such as gasoline, diesel and LPG. With the increase in the fossil fuels demand and the reduction in the conventional oil extraction, the improvement of the FCC process has become essential for the refineries. Empirical studies on the dynamics of the flow in industrial FCC reactors are rarely found, partly due to high temperatures and pressures present in these reactors, which difficult the data obtaining, and in part because of the complexity of the operation, which involves several simultaneous phenomena, such as the feedstock vaporization, heterogeneous reactions, the bed expansion due to cracking and deactivation of the catalyst particles, for example. However, it is necessary to understand the flow in order to improve the performance of the process. Then, a numerical study of industrial FCC riser reactors using CFD tools was proposed in this work. The level of complexity of the simulations was increased gradually and phenomena such as the adsorption of reactant molecules in catalyst active sites and the vaporization of liquid feedstock, were studied individually, allowing the evaluation of each phenomena on the process. For a detailed analysis of the flow, three-dimensional models were used in these simulations and geometric configurations similar to those found in typical FCC units have been applied. Furthermore, a study of the sensitivity of the variables of the flow to the use of different geometries for the reactor outlet was developed, enabling the determination of the output configuration that provides a better yield for the process. Overall, the fluid dynamic results obtained in this study emphasize the importance of application of models that represent the complex phenomena present in the FCC riser, since they substantially influence the reactions
Doutorado
Desenvolvimento de Processos Químicos
Doutor em Engenharia Química
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.
Повний текст джерелаKong, Liang. "Bismuth oxybromide-based photocatalysts for solar energy utilisation and environmental remediation." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:c95ee3cc-b276-4c69-8b3f-eb60cc64e1c0.
Повний текст джерелаKulchat, Sirinan. "Dynamic covalent chemistry of C=N, C=C and quaternary ammonium constituents." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAF018/document.
Повний текст джерелаThis thesis describes the dynamic covalent chemistry (DCC) of imine/imine, Knoevenagel/imine, and Knoevenagel/Knoevenagel exchange. L-proline is shown to be an excellent organocatalyst to accelerate the formation of dynamic covalent libraries (DCLs). The interconversion between Knoevenagel derivatives of dimethylbarbituric acid and imines is found to occur rapidly in the absence of catalyst. A new class of DCC based on nucleophilic substitution (SN2/SN2’) component exchange between quaternary ammonium salts and tertiary amines is developed, by the use of iodide as a catalyst. The exchange reactions between pyridinium salts and a pyridine derivative generate dynamic ionic liquids. Finally, kinetic and thermodynamic selection of imine formation in a DCC is perfomed in aqueous solution and organic solvent
Ibargüen, becerra César. "Effet des forces de van der Waals sur la dynamique de l'azote et de l'hydrogène en interaction avec la surface de W(100)." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0261.
Повний текст джерелаAn important part of scientific literature is devoted to the heterogeneous elementary processes occurring at gas-solid interface due to their great importance and key role in many different domains and applications. Thus, interaction of gas atoms/molecules with surface reactions are of primary importance in the study of: heterogeneous catalysis, combustion of solid fuel and coal gasification, processes of corrosion, hydrogen storage in solid material, automotive and oil industry, plasma-wall interactions in the context of thermonuclear experimental reactor (ITER), atmospheric re-entries technologies and astrochemistry, to name some examples. When an atom or molecule impinges on a surface many different elementary processes can take place, which depends on factors such as: the collision energy of the projectile, the angle of incidence to the surface, the surface temperature, the initial state of the molecules, the transference of energy projectiles-surface, etc. All these factors determines the mechanisms of reaction and the dynamics of the processes. Experimental molecular beams (MB) and other experimental techniques are able to accurately control the initial state of the reactive and characterizing products of gas-surface reactions. However, in most of the case experimental techniques do not provide enough details about the mechanisms through which elementary processes occur. Consequently, theoretical models becomes essential to rationalize the description that in certain cases the experiments do not reach.The main goal of this thesis work is to propose an analyze of the dynamics of several elementary processes occurring on a W(100) surface, such as: the inelastic scattering of N2 and H2, the dissociative and non-dissociative adsorption of of H2 and the adsorption and absorption of H and N. Compared to previous studies, the novelty of this work resides in the taking into account of van der Waals long-distance interactions, which are essential to reach a good agreement between theoretical and experiment results, especially at low collision energy regime. To rationalize the non-adiabatic effects, the energy dissipation to lattice vibrations and electronic excitation are taken in to account by means of GLO and LDFA models respectively
Nascimento, Ana Paula Favaro 1982. "Estudo de adsorção de impurezas moleculares e caminhos de reação em nanofios de ouro." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277679.
Повний текст джерелаTese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
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Resumo: A fabricação e o estudo de nanofios de ouro despertam grande interesse na comunidade científica, na tentativa de maior entendimento de efeitos quânticos de sistemas em escala reduzida, assim como na possibilidade de seu uso em aplicações tecnológicas. Uma vez que os nanofios de ouro apresentam propriedades surpreendentes quando dopados por impurezas atômicas fomos motivados a estudar como estas se formam. Devido ao fato de em escala nanoscópica o ouro apresentar atividade catalítica, consideramos que a presença de impurezas se deve a reação de pequenas moléculas em nanofios de Au. O estudo foi realizado por meio de cálculos abinitio via Teoria do Funcional da Densidade, usando o código computacional SIESTA. A metodologia para o estudo da estrutura eletrônica desses sistemas foi a de otimização de geometria e de dinâmica molecular ab initio. Nosso foco de estudo foi encontrar caminhos reacionais para a formação de impurezas atômicas de carbono ou de oxigênio nas cadeias atômicas lineares de nanofios monoatômicos. A análise se baseou na interação entre duas moléculas catalisada pelo nanofio, as moléculas consideradas em nosso estudo foram CO e O2. Um estudo extensivo e detalhado das possíveis reações foi feito. Dentre os vários caminhos estudados, uma reação sequencial onde uma molécula de O2 é adsorvida por apenas um dos seus oxigênios, inicia um processo, que seguido pela adsorção de uma molécula de CO, leva a formação de um complexo O2-CO ligado a cadeia atômica do nanofio. Nós mostramos situações onde este complexo fica ativado e reage formando uma molécula de CO2 que vai para a fase gasosa deixando o nanofio dopado com um átomo de oxigênio. Portanto este trabalho apresenta um caminho reacional para a formação de uma impureza atômica na cadeia atômica de um nanofio de ouro, uma questão que esperava uma solução a quase uma década.
Abstract: The manufacture and the study of gold nanowires weakened great interest of the scientific community in the quest for better understanding of the quantum effects in systems with reduced scales and also due to the possibility of their use in technological applications. Since gold nanowires present novel and surprising properties when doped with atomic impurities, this led us into the search to understand how these impurities can be produced. Due to the fact that gold in nanoscale presents catalytic activity, we considered the possibility of chemical reactions with small molecules in the presence of gold nanowires. The present study was performed with ab initio calculations based in the density functional theory as implemented by the SIESTA code. The methodology for the electronic structure studies was the geometry optimization using conjugated gradient method and abinitio molecular dynamics. Our focus was to find reaction paths to produce atomic impurities of carbon and oxygen in linear atomic chains of gold nanowires. The analysis was based in the reaction of two molecules catalized by the nanowire, the molecules considered in this study were CO and O2. An extensive and detailed study of possible pathways was undertaken. Among the various paths, a sequential reaction where only one O of a adsorbed O2 molecule attached to the nanowire, started the process, followed by the adsorption of a CO molecule nearby that formed an O2-CO complex attached to the atomic chain of the nanowire. We presented circumstances in which this complex becomes activated and evolves to form a CO2 molecule that goes into the gas phase leaving an atomic oxygen impurity attached to the linear chain. Therefore, this work presented a reactional path to the formation of an atomic impurity in the atomic chain of a gold nanowire, a question that waited an answer for almost ten years.
Doutorado
Física
Doutora em Ciências
Eley, Clive William. "The rational design of photocatalytic semiconductor nanocrystals." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:ee29c922-857c-432a-8316-a7e04c822b1d.
Повний текст джерелаBahroun, Sami. "Modélisation et approche thermodynamique pour la commande des réacteurs chimiques catalytiques triphasiques continus et discontinus." Phd thesis, Université Claude Bernard - Lyon I, 2010. http://tel.archives-ouvertes.fr/tel-00720906.
Повний текст джерела(7307489), Ishant Khurana. "Catalytic Consequences of Active Site Speciation, Density, Mobility and Stability on Selective Catalytic Reduction of NOx with Ammonia over Cu-Exchanged Zeolites." Thesis, 2019.
Знайти повний текст джерелаSelective catalytic reduction (SCR) of NOx using NH3 as a reductant (4NH3+ 4NO + O2 6H2O + 4N2) over Cu-SSZ-13 zeolites is a commercial technology used to meet emissions targets in lean-burn and diesel engine exhaust. Optimization of catalyst design parameters to improve catalyst reactivity and stability against deactivation (hydrothermal and sulfur poisoning) necessitates detailed molecular level understanding of structurally different active Cu sites and the reaction mechanism. With the help of synthetic, titrimetric, spectroscopic, kinetic and computational techniques, we established new molecular level details regarding 1) active Cu site speciation in monomeric and dimeric complexes in Cu-SSZ-13, 2) elementary steps in the catalytic reaction mechanism, 3) and deactivation mechanisms upon hydrothermal treatment and sulfur poisoning.
We have demonstrated that Cu in Cu-SSZ-13 speciates as two distinct isolated sites, nominally divalent CuII and monovalent [CuII(OH)]+ complexes exchanged at paired Al and isolated Al sites, respectively. This Cu site model accurately described a wide range of zeolite chemical composition, as evidenced by spectroscopic (Infrared and X-ray absorption) and titrimetric characterization of Cu sites under ex situ conditions and in situ and operando SCR reaction conditions. Monovalent [CuII(OH)]+ complexes have been further found to condense to form multinuclear Cu-oxo complexes upon high temperature oxidative treatment, which have been characterized using UV-visible spectroscopy, CO-temperature programmed reduction and dry NO oxidation as a probe reaction. Structurally different isolated Cu sites have different susceptibilities to H2 and He reductions, but are similarly susceptible to NO+NH3 reduction and have been found to catalyze NOx SCR reaction at similar turnover rates (per CuII; 473 K) via a CuII/CuI redox cycle, as their structurally different identities are masked by NH3 solvation during reaction.
Molecular level insights on the low temperature CuII/CuI redox mechanism have been obtained using experiments performed in situand in operando coupled withtheory. Evidence has been provided to show that the CuII to CuI reduction half-cycle involves single-site Cu reduction of isolated CuII sites with NO+NH3, which is independent of Cu spatial density. In contrast, the CuI to CuII oxidation half-cycle involves dual-site Cu oxidation with O2 to form dimeric Cu-oxo complexes, which is dependent on Cu spatial density. Such dual-site oxidation during the SCR CuII/CuI redox cycle requires two CuI(NH3)2sites, which is enabled by NH3solvation that confers mobility to isolated CuI sites and allows reactions between two CuI(NH3)2 species and O2. As a result, standard SCR rates depend on Cu proximity in Cu-SSZ-13 zeolites when CuI oxidation steps are kinetically relevant. Additional unresolved pieces of mechanism have been investigated, such as the reactivity of Cu dimers, the types of reaction intermediates involved, and the debated role of Brønsted acid sites in the SCR cycle, to postulate a detailed reaction mechanism. A strategy has been discussed to operate either in oxidation or reduction-limited kinetic regimes, to extract oxidation and reduction rate constants, and better interpret the kinetic differences among Cu-SSZ-13 catalysts.
The stability of active Cu sites upon sulfur oxide poisoning has been assessed by exposing model Cu-zeolite samples to dry SO2 and O2 streams at 473 and 673 K, and then analyzing the surface intermediates formed via spectroscopic and kinetic assessments. Model Cu-SSZ-13 zeolites were synthesized to contain distinct Cu active site types, predominantly either divalent CuII ions exchanged at proximal framework Al (Z2Cu), or monovalent [CuIIOH]+ complexes exchanged at isolated framework Al (ZCuOH). SCR turnover rates (473 K, per Cu) decreased linearly with increasing S content to undetectable values at equimolar S:Cu ratios, consistent with poisoning of each Cu site with one SO2-derived intermediate. Cu and S K-edge X-ray absorption spectroscopy and density functional theory calculations were used to identify the structures and binding energies of different SO2-derived intermediates at Z2Cu and ZCuOH sites, revealing that bisulfates are particularly low in energy, and residual Brønsted protons are liberated at Z2Cu sites as bisulfates are formed. Molecular dynamics simulations also show that Cu sites bound to one HSO4- are immobile, but become liberated from the framework and more mobile when bound to two HSO4-. These findings indicate that Z2Cu sites are more resistant to SO2poisoning than ZCuOH sites, and are easier to regenerate once poisoned.
The stability of active Cu sites on various small-pore Cu-zeolites during hydrothermal deactivation (high temperature steaming conditions) has also been assessed by probing the structural and kinetic changes to active Cu sites. Three small-pore, eight-membered ring (8-MR) zeolites of different cage-based topology (CHA, AEI, RTH) have been investigated. With the help of UV-visible spectroscopy to probe the Cu structure, in conjunction with measuring differential reaction kinetics before and after subsequent treatments, it has been suggested that the RTH framework imposes internal transport restrictions, effectively functioning as a 1-D framework during SCR catalysis. Hydrothermal aging of Cu-RTH results in complete deactivation and undetectable SCR rates, despite no changes in long-range structure or micropore volume after hydrothermal aging treatments and subsequent SCR exposure, highlighting beneficial properties conferred by double six-membered ring (D6R) composite building units. Exposure aging conditions and SCR reactants resulted in deleterious structural changes to Cu sites, likely reflecting the formation of inactive copper-aluminate domains. Therefore, the viability of Cu-zeolites for practical low temperature NOx SCR catalysis cannot be inferred solely from assessments of framework structural integrity after aging treatments, but also require Cu active site and kinetic characterization after aged zeolites are exposed to low temperature SCR conditions.
(5930264), Arthur J. Shih. "Synthesis and Characterization of Copper-Exchanged Zeolite Catalysts and Kinetic Studies on NOx Selective Catalytic Reduction with Ammonia." 2019.
Знайти повний текст джерелаAlthough Cu-SSZ-13 zeolites are used commercially in diesel engine exhaust after-treatment for abatement of toxic NOx pollutants via selective catalytic reduction (SCR) with NH3, molecular details of its active centers and mechanistic details of the redox reactions they catalyze, specifically of the Cu(I) to Cu(II) oxidation half-reaction, are not well understood. A detailed understanding of the SCR reaction mechanism and nature of the Cu active site would provide insight into their catalytic performance and guidance on synthesizing materials with improved low temperature (< 473 K) reactivity and stability against deactivation (e.g. hydrothermal, sulfur oxides). We use computational, titration, spectroscopic, and kinetic techniques to elucidate (1) the presence of two types of Cu2+ ions in Cu-SSZ-13 materials, (2) molecular details on how these Cu cations, facilitated by NH3 solvation, undergo a reduction-oxidation catalytic cycle, and (3) that sulfur oxides poison the two different types of Cu2+ ions to different extents at via different mechanisms.
Copper was exchanged onto H-SSZ-13 samples with different Si:Al ratios (4.5, 15, and 25) via liquid-phase ion exchange using Cu(NO3)2 as the precursor. The speciation of copper started from the most stable Cu2+ coordinated to two anionic sites on the zeolite framework to [CuOH]+ coordinated to only one anionic site on the zeolite framework with increasing Cu:Al ratios. The number of Cu2+ and [CuOH]+ sites was quantified by selective NH3 titration of the number of residual Brønsted acid sites after Cu exchange, and by quantification of Brønsted acidic Si(OH)Al and CuOH stretching vibrations from IR spectra. Cu-SSZ-13 with similar Cu densities and anionic framework site densities exhibit similar standard SCR rates, apparent activation energies, and orders regardless of the fraction of Z2Cu and ZCuOH sites, indicating that both sites are equally active within measurable error for SCR.
The standard SCR reaction uses O2 as the oxidant (4NH3 + 4NO + O2 -> 6H2O + 4N2) and involves a Cu(I)/Cu(II) redox cycle, with Cu(II) reduction mediated by NO and NH3, and Cu(I) oxidation mediated by NO and O2. In contrast, the fast SCR reaction (4NH3 + 2NO + 2NO2 -> 6H2O + 4N2) uses NO2 as the oxidant. Low temperature (437 K) standard SCR reaction kinetics over Cu-SSZ-13 zeolites depend on the spatial density and distribution of Cu ions, varied by changing the Cu:Al and Si:Al ratio. Facilitated by NH3 solvation, mobile Cu(I) complexes can dimerize with other Cu(I) complexes within diffusion distances to activate O2, as demonstrated through X-ray absorption spectroscopy and density functional theory calculations. Monte Carlo simulations are used to define average Cu-Cu distances. In contrast with O2-assisted oxidation reactions, NO2 oxidizes single Cu(I) complexes with similar kinetics among samples of varying Cu spatial density. These findings demonstrate that low temperature standard SCR is dependent on Cu spatial density and requires NH3 solvation to mobilize Cu(I) sites to activate O2, while in contrast fast SCR uses NO2 to oxidize single Cu(I) sites.
We also studied the effect of sulfur oxides, a common poison in diesel exhaust, on Cu-SSZ-13 zeolites. Model Cu-SSZ-13 samples exposed to dry SO2 and O2 streams at 473 and 673 K. These Cu-SSZ-13 zeolites were synthesized and characterized to contain distinct Cu active site types, predominantly either divalent Cu2+ ions exchanged at proximal framework Al sites (Z2Cu), or monovalent CuOH+ complexes exchanged at isolated framework Al sites (ZCuOH). On the model Z2Cu sample, SCR turnover rates (473 K, per Cu) catalyst decreased linearly with increasing S content to undetectable values at equimolar S:Cu molar ratios, while apparent activation energies remained constant at ~65 kJ mol-1, consistent with poisoning of each Z2Cu site with one SO2-derived intermediate. On the model ZCuOH sample, SCR turnover rates also decreased linearly with increasing S content, yet apparent activation energies decreased monotonically from ~50 to ~10 kJ mol-1, suggesting that multiple phenomena are responsible for the observed poisoning behavior and consistent with findings that SO2 exposure led to additional storage of SO2-derived intermediates on non-Cu surface sites. Changes to Cu2+ charge transfer features in UV-Visible spectra were more pronounced for SO2-poisoned ZCuOH than Z2Cu sites, while X-ray diffraction and micropore volume measurements show evidence of partial occlusion of microporous voids by SO2-derived deposits, suggesting that deactivation may not only reflect Cu site poisoning. Density functional theory calculations are used to identify the structures and binding energies of different SO2-derived intermediates at Z2Cu and ZCuOH sites. It is found that bisulfates are particularly low in energy, and residual Brønsted protons are liberated as these bisulfates are formed. These findings indicate that Z2Cu sites are more resistant to SO2 poisoning than ZCuOH sites, and are easier to regenerate once poisoned.
(11150073), Abhijit D. Talpade. "Pyrolysis based processing of biomass and shale gas resources to fuels and chemicals." Thesis, 2021.
Знайти повний текст джерелаBera, Anupam. "Thermal and Femtosecond Laser-Induced CO2-Surface Chemistry on Supported Iron-Oxide Based Nanoparticle Surfaces under UHV." Thesis, 2018. https://etd.iisc.ac.in/handle/2005/4874.
Повний текст джерелаPradhan, Kuldeep. "Simulation of fluid catalytic cracker." Thesis, 2012. http://ethesis.nitrkl.ac.in/4134/2/June_Kuldeep_Finally.pdf.
Повний текст джерелаLin, Jiaxing. "Multiple Electron and Electronic Energy Transfer Dynamics Relevant to Light Harvesting and Catalytic Reactions." Diss., 2015. http://hdl.handle.net/10161/11373.
Повний текст джерелаElectronic excitation energy transfer (EET) and electron transfer (ET) are of the fundamental importance to biochemical processes and solar energy conversion. The goal of this thesis is to develop and apply theoretical and computational tools to understand the mechanisms and kinetics of EET and ET in selected molecular systems with the aim to control and boost their efficacy. Specifically, this thesis focuses on three subjects: (1) computational study of energy transfer and its pathways in Ruthenium based metal organic frameworks (MOFs), (2) developing a general analytical model to describe the kinetics of energy transfer/electron transfer in condensed media, and (3) developing theoretical frameworks to describe multiple electron/exciton transfer processes.
In the study of energy transfer in Ruthenium based MOFs, we found that the excitation transport kinetics was well described by a Dexter (exchange) triplet-to-triplet incoherent multi-step hopping mechanism. The sensitive distance dependent rate for Dexter energy transfer in different MOF structures establishes unique energy transport pathways. For example, both one- and three-dimensional exciton-hopping networks were found in mixed Ru/Os MOFs. As such, Dexter energy transfer may potentially be helpful for spatially directing excitation energy along specific direction, for example, towards reaction centers, and an amenable for designing high efficiency energy transfer materials.
Significant amount EET processes happen in condense media and the nature of energy migration kinetics depends heavily on the donor (D) and acceptor (A) distribution in the media, especially for organic photovoltaic devices. The EET in the condense phase allow us to study the impact of ordered, partially ordered, and disordered DA distribution on the solar energy harvesting efficiency. To better account for the EET in condense phase, we developed a general analytical model for the description of the time-dependent luminescence decay emphasizing on the actual D-A spatial distribution. Applications of the developed model have been made to investigate the long-range excitation energy transfer in disordered polymer systems. By fitting the experimental transient luminescence spectra, we found that the derived EET kinetics showed better agreement with experimental observed luminescence decay both in short and long times, a significant improvement over the earlier models by Inokuti and Hirayama. Our model is more reliable in a wide range of time and acceptor density and can also be used for electron transfer.
The frontiers of ET and EET are moving from single particle one-step reactions to coupled multi-particle and multi-step processes. To understand the leading features that mediate the two-electron transfer in catalysis, we developed a two-electron transfer superexchange model that focuses on the roles of these features including (1) the one- and two-electron virtual intermediate states that mediate the ET, (2) the number of virtual intermediates with system size, and (3) the multiple classes of pathways interferes. Key questions, including how bridge structure and energetics influence multi-electron superexchange and interference between singly- and doubly-oxidized (or reduced) bridge virtual states are investigated. We found that even simple linear donor-bridge-acceptor systems have pathway topologies that resemble those seen for one-electron superexchange through bridges with multiple parallel pathways. The simple model two-electron transfer systems studied here exhibit a richness that is amenable to experimental exploration by manipulating the multiple pathways, pathway crosstalk, and changes in the number of donor and acceptor species. The features that emerge from these studies may assist in developing new strategies to deliver multiple electrons in condensed phase redox systems, including multiple-electron redox species, multi-metallic/multi-electron redox catalysts, and multi-exciton excited states.
Finally, to understand the role of structural and environmental disorder on incoherent ET, we developed a perturbative model based on the kinetic master equation to examine incoherent ET in non-equilibrium and non-Markovian regime. The developed method provides an effective way to explicitly investigate how a general (non-Gaussian) fluctuation in ET rate can modify the ET kinetics. Applications of this method have been made to study the ET kinetics for donor-bridge-acceptor systems with the structural and environmental fluctuations. Changing in ET kinetics with structural fluctuations of different nature was examined. Dominant fluctuation characters that significantly boost or reduce ET rate were identified. These findings may be helpful in designing efficient ET materials and provide strategies in modulating ET rate.
Dissertation
LUO, Yuan-Hong, and 羅元宏. "Simulation analysis of non-linear dynamics in heterogeneous catalytic reactions: from multiple steady states to chaos." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/56pn4t.
Повний текст джерела國立聯合大學
化學工程學系碩士班
106
A chemical reaction network existing multiple steady states may occur interesting nonlinear dynamic behaviors, such as limit cycle, period-doubling, period-adding, chaos and so on. In this research, we analyze three different reaction networks involving heterogeneous catalysis operated in a continuously stirred tank reactor (CSTR) with isothermal condition. Under the assumption of mass action law, the concentration variation with time for each component can be described by a set of nonlinear ordinary differential equations. Analyze the reaction network by the chemical reaction network toolbox (CRNT). If the system has the possibility to admit multiple steady states, a set of reaction rate constants and two corresponding steady states can be obtained. Then, the reaction rate constants and one of the steady states are input to Matcont for bifurcation analysis. By changing the reaction rate constants and the initial concentrations, some bifurcations can be found, such as Bogdanov-Takens (BT), zero Hopf (ZH), generalized Hopf (GH), period-doubling (PD) and so on. Numerical analysis is implemented by making small changes on parameters near the bifurcation ZH and PD to find Torus and chaos. The dynamic results are plot in the phase diagram. The Lyapunov exponent, Poincare map and power spectrum density are applied to determine chaos and explore its dynamic behavior.
(10971108), Yangjie Li. "REACTION ACCELERATION AT INTERFACES STUDIED BY MASS SPECTROMETRY." Thesis, 2021.
Знайти повний текст джерелаVarious organic reactions, including important synthetic reactions involving C–C, C–N, and C–O bond formation as well as reactions of biomolecules, are known to be accelerated when the reagents are present in confined volumes such as sprayed or levitated microdroplets or thin films. This phenomenon of reaction acceleration and the key role of interfaces played in it are of intrinsic interest and potentially of practical value as a simple, rapid method of performing small-scale synthesis. This dissertation has three focusing subtopics in the field of reaction acceleration: (1) application of reaction acceleration in levitated droplets and mass spectrometry to accelerate the reaction-analysis workflow of forced degradation of pharmaceuticals at small scale; (2) fundamental understanding of mechanisms of accelerated reactions at air/solution interfaces; (3) discovery the use of glass particles as a `green' heterogeneous catalysts in solutions and systematical study of solid(glass)/solution interfacial reaction acceleration as a superbase for synthesis and degradation using high-throughput screening.
Reaction acceleration in confined volumes could enhance analytical methods in industrial chemistry. Forced degradation is critical to probe the stabilities and chemical reactivities of therapeutics. Typically performed in bulk followed by LC-MS analysis, this traditional workflow of reaction/analysis sequence usually requires several days to form and measure desirable amount of degradants. I developed a new method to study chemical degradation in a shorter time frame in order to speed up both drug discovery and the drug development process. Using the Leidenfrost effect, I was able to study, over the course of seconds, degradation in levitated microdroplets over a metal dice. This two-minute reaction/analysis workflow allows major degradation pathways of both small molecules and therapeutic peptides to be studied. The reactions studied include deamidation, disulfide bond cleavage, ether cleavage, dehydration, hydrolysis, and oxidation. The method uses microdroplets as nano-reactors and only require a minimal amount of therapeutics per stress condition and the desirable amount of degradant can be readily generated in seconds by adjusting the droplet levitation time, which is highly advantageous both in the discovery and development phase. Built on my research, microdroplets can potentially be applied in therapeutics discovery and development to rapidly screen stability of therapeutics and to screen the effects of excipients in enhancing formulation stabilities.
My research also advanced the fundamental understanding of reaction acceleration by disentangles the factors controlling reaction rates in microdroplet reactions using constant-volume levitated droplets and Katritzky transamination as a model. The large surface-to-volume ratios of these systems results in a major contribution from reactions at the air/solution interface where reaction rates are increased. Systems with higher surface-active reactants are subject to greater acceleration, particularly at lower concentrations and higher surface-to-volume ratios. These results highlight the key role that air/solution air/solution interfaces play in Katritzky reaction acceleration. They are also consistent with the view that reaction increased rate constant is at least in part due to limited solvation of reagents at the interface.
While reaction acceleration at air/solution interfaces has been well known in microdroplets, reaction acceleration at solid/solution interfaces appears to be a new phenomenon. The Katritzky reaction in bulk solution at room temperature is accelerated significantly by the surface of a glass container compared to a plastic container. Remarkably, the reaction rate is increased by more than two orders of magnitude upon the addition of glass particles with the rate increasing linearly with increasing amounts of glass. A similar phenomenon is observed when glass particles are added to levitated droplets, where large acceleration factors are seen. Evidence shows that glass acts as a ‘green’ heterogeneous catalyst: it participates as a base in the deprotonation step and is recovered unchanged from the reaction mixture.
Subsequent to this study, we have systematically explored the solid/solution interfacial acceleration phenomena using our latest generation of a high-throughput screening system which is capable of screening thousands of organic reactions in a single day. Using desorption electrospray ionization mass spectrometry (DESI-MS) for automated analysis, we have found that glass promotes not only organic reactions without organic catalysts but also reactions of biomolecules without enzymes. Such reactions include Knoevenagel condensation, imine formation, elimination of hydrogen halide, ester hydrolysis and/or transesterification of acetylcholine and phospholipids, as well as oxidation of glutathione. Glass has been used as a general `green' and powerful heterogeneous catalyst.
Rau, Jui-Yeh, and 饒瑞曄. "Dynamic variation and influence factors on the simultaneous removal of NO, SO2 and fly ash using a fluidized-bed catalytic reactor." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/62231053641304676522.
Повний текст джерела國立中興大學
環境工程學系所
98
In this study, a fluidized-bed catalytic reactor was applied for the removals of NO, SO2 and fly ash in a simulated condition of coal-fired power plant flue gas. The objectives of this study are included three parts. First, the modified and selected of catalyst, AC supports were modified by different solutions and impregnated with Cu, and analyzed their properties. Second, the removals of single pollutant such as NO, SO2, and fly ash by fluidized-bed catalytic reactor was studied. Finally, the activity of the catalyst for simultaneous removals of NO, SO2, and fly ash was investigated. Experimental results indicated that AC supports pretreated by HNO3 (AC-N) and H2SO4 (AC-S) increased the amounts of phenol and carboxylic acid groups, and further increased the dispersion and decreased the crystallite sizes of Cu active phases (20~100 nm). The activities of the CuO/AC catalysts on different pretreated AC supports follow the sequence of AC-N > AC-S > AC. The removal efficiency of NO can be improved by the adsorption capacity of NH3 when both phenol and carboxylic acid groups increased on the surface of the catalysts. The removal efficiencies of apart from NO, SO2 and fly ash are about 57%, 84% and 74%, respectively. However, the removal efficiencies of NO and SO2 were decreased to 9-17% after exposure to a concentration 1000 mg m-3 of fly ash. When the operating time was increased, the surface of the catalyst was covered by these fly ashes and resulted in the deactivation of the catalyst. For an average size of 4 (fine) and 40 (coarse) μm SiO2 and Al2O3 the activities of catalysts for simultaneous removals of NO, SO2, and particles were inhibited with increasing concentration of fly ash. The results of BET and SEM analyses verified meso- and macro-pore volume of the catalyst were obstructed by 4 μm SiO2. However, Al2O3 may become a part of catalyst bed material, and less likely to plug the catalyst surface. The removal efficiency of fly ash was increased with the increased in H2O content, but the activities of catalysts for simultaneous removals of SO2 and particles were inhibited. As the H2O content increased, the particle size distribution (PSD) of fine particles shifted to the coarse particles. The results of BET analyses show the particles obstruction phenomenon of the catalyst volume was lessened with increased H2O content. The aggregation phenomenon of fine particles shifted to the coarse particles may cause increase H2O content content in fluidized-bed catalytic reactor.
Blatnik, Michael T. "Optimization of Mixing in a Simulated Biomass Bed Reactor with a Center Feeding Tube." 2013. https://scholarworks.umass.edu/theses/1108.
Повний текст джерела