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Computational modelling of a laboratory burner using FLUENT code
Broukal, Jakub ; Vondál, Jiří (referee) ; Hájek, Jiří (advisor)
Tato diplomová práce je zaměřena na porovnání různých turbulentních a chemických modelů na příkladu volné metanové trysky ústící do vzduchu. Nejprve je uveden teoretický úvod k modelům, následován CFD (Ansys Fluent) simulacemi plamene pomocí vybraných modelů. Jako součást práce je provedeno a vyhodnoceno experimentální měření. V závěru jsou experimentální výsledky porovnány s nasimulovanými daty.
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The role of boron oxide in oxidative dehydrogenation of hydrocarbons
Stoklasa, Jan ; Rubeš, Miroslav (advisor) ; Grajciar, Lukáš (referee)
Hexagonal boron nitride appears to be a suitable catalyst for the oxidative dehydrogenation of hydrocarbons. With its high selectivity towards alkenes and low production of carbon monoxide and dioxide, this catalyst emerges as an ideal candidate for this process. Literature references indicates that a radical mechanism seems probable, as evidenced by the dependence on the reactor shape and catalytic volume. The exact mechanism is still under investigation, and the focus of this study is to describe the initial steps of the reaction and investigate poorly defined boron oxide (BOx) species. It has been found that during the reaction of the catalyst surface model with the O2H radical, two types of complexes are observed - dispersive and covalently bound. By monitoring the interaction energies, it was discovered that both types are energetically very close to each other, with a low barrier for transition between them. When the surface interacts with the propyl radical, only dispersive complexes were observed.
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Theoretical Investigation of ethanol dehydration catalyzed by acid sites in zeolites
Vacek, Jaroslav ; Nachtigall, Petr (advisor) ; Uhlík, Filip (referee)
Zeolites are a group of aluminosilicate minerals with catalytic properties. They may be used for many industrial applications such as catalytic cracking of oil. Zeolites are also capable of converting ethanol to diethylether and ethylen. This reaction is known as dehydration of ethanol. The reaction is potentially interesting as a way of converting ethanol to more valuable molecules. An experimental study (Shashikant A. Kadam, Mariya V. Shamzhy, 2018) has proven that diethylether is the preferred product when the temperatures are low and the partial pressure of ethanol is high. Ethylen is more significant product with higher temperature and lower partial pressure of ethanol. Aim of this thesis is to determine the mechanism of dehydration of ethanol. Furthermore it was attempted to explain the behavior of the reaction under different circumstances. The research was done in silico using the methods of computational chemistry. Such methods give information on the geometry and the energy of systems of molecules. Thus computational chemistry can be used to investigate the relational path and activation energy of the studied reaction. This thesis is a theoretical study of dehydration of ethanol catalysed by a zeolite.
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Catalytic synthesis of polyanilines
Bláha, Michal ; Vohlídal, Jiří (advisor) ; Omastová, Mária (referee) ; Trchová, Miroslava (referee)
This Ph.D. thesis is dealing with catalytic polymerization of aniline (ANI) and partially also of substituted anilines with FeCl3/H2O2 catalyst system, in which according to obtained results both active species, Fe3+ and HO , participate in the overall polymerization mechanism, creating a synergic system. The Fe3+ /H2O2 catalyst system, also called Fenton's system can considerably lower contamination of forming neat polyanilines (PANIs) by side-products characteristic of stoichiometric polymerization. However, catalytically prepared PANIs exhibit reduced conductivity related most probably to side reactions involving radicals generated as integral components of the FeCl3/H2O2 system. Catalytic polymerization of ANI with FeCl3/H2O2 system was found to be the reaction of approx. 2nd order with respect to ANI and gives PANIs of a good quality only when [H2O2] in the reaction mixture was kept low, i.e., at under- stoichiometric ratios [H2O2]/[ANI]. At over-stoichiometric ratio [H2O2]/[ANI], PANIs of lowered conductivity, worse spectroscopic characteristics and increased size of PANI nanostructures were obtained; nevertheless, these PANIs were not over-oxidized to pernigraniline state. The reaction-time profiles of the open-circuit potential of reaction mixtures exhibited an inflection related to the...
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Preparation of cyclic derivatives of amino acids using a combination of organocatalysis and metal catalysis
Měrka, Pavel ; Veselý, Jan (advisor) ; Rýček, Lukáš (referee)
This diploma thesis is focused on the combination of enantioselective organocatalysis and transition metal catalysis. In the experimental part of the work, the optimization of reaction conditions with respect to the reaction yields, enantioselectivity and diastereoselectivity was solved. The applicability of the reaction was verified on various substrates. The second part of the work is focused on the study of the mechanism of the reaction using the methods of quantum chemistry. The kinetics of the reaction were monitored by NMR spectroscopy and the mechanism of the reaction was investigated by quantum chemistry methods. Keywords: aminocatalysis, palladium, synergistic catalysis, reaction mechanism, DFT
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Theoretical Investigation of ethanol dehydration catalyzed by acid sites in zeolites
Vacek, Jaroslav ; Nachtigall, Petr (advisor) ; Uhlík, Filip (referee)
Zeolites are a group of aluminosilicate minerals with catalytic properties. They may be used for many industrial applications such as catalytic cracking of oil. Zeolites are also capable of converting ethanol to diethylether and ethylen. This reaction is known as dehydration of ethanol. The reaction is potentially interesting as a way of converting ethanol to more valuable molecules. An experimental study (Shashikant A. Kadam, Mariya V. Shamzhy, 2018) has proven that diethylether is the preferred product when the temperatures are low and the partial pressure of ethanol is high. Ethylen is more significant product with higher temperature and lower partial pressure of ethanol. Aim of this thesis is to determine the mechanism of dehydration of ethanol. Furthermore it was attempted to explain the behavior of the reaction under different circumstances. The research was done in silico using the methods of computational chemistry. Such methods give information on the geometry and the energy of systems of molecules. Thus computational chemistry can be used to investigate the relational path and activation energy of the studied reaction. This thesis is a theoretical study of dehydration of ethanol catalysed by a zeolite.
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Theoretical studies of catalysts for Suzuki-Miyaura reaction
Měrka, Pavel ; Uhlík, Filip (advisor) ; Srnec, Martin (referee)
This thesis is focused on theoretical study of Suzuki-Miyaura cross- coupling reaction catalyzed by palladium complex with phosphinopherrocene li- gand. The aim of this work is to provide basic image of the catalytic cycle with newly prepared coordination compounds of palladium. Bromobenzene and phe- nyltriolborate were chosen as the model reagent. DFT method M06-2X was used for characterization of molecular goemetries of intermediates and most important transition states for all parts of catalytic cycle.
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Research of gold catalyzed reactions
Jašíková, Lucie ; Roithová, Jana (advisor) ; Polášek, Miroslav (referee) ; Starý, Ivo (referee)
The main focus of the current dissertation thesis is research of gold catalyzed reactions. I was using mass spectrometry as the primary research technique. I complemented the results with infrared multiphoton dissociation spectroscopy, nuclear magnetic resonance spectroscopy and quantum chemical calculations. I have investigated the interaction of the gold(I) cation with unsaturated hydrocarbons in the first part of my thesis. Secondly, I have studied gold(I) or silver(I) affinity to gold acetylides. In the last part, I have investigated the reaction mechanism of a gold mediated addition of methanol to alkynes. I found out that the gold(I) cation interacts stronger with gold acetylides than with nonactivated triple CC bonds. I showed that the complexes containing two gold atoms represent the key intermediates in the mechanism of addition of methanol to alkynes and that the ligand on the gold catalyst plays a fundamental role in the determination of the mechanism. Powered by TCPDF (www.tcpdf.org)
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Mechanism of copper mediated oxidative coupling of naphthols
Schröpferová, Tereza ; Roithová, Jana (advisor) ; Polášek, Miroslav (referee)
The 2,2'-disubstituated 1,1'-binaphthyls (BINOLs) are important ligands in enantioselective synthesis . The major approach for their preparation is based on transition-metal-mediated oxidative C-C coupling of 2-substituted naphtalenes. This diploma thesis examined the mechanism of the coupling reaction in the gas phase using mass spectrometry with electrospray ionization. The aim of this thesis was to compare the selectivity of the copper(II)- catalyzed coupling reaction of 2-naphthol and its derivative with an electron-withdrawing group, to detect possible reaction intermediates, and to determine the origin of the preference of the cross-coupling. The electron-withdrawing group of naphthol slows down the coupling reaction which enabled us to detect the reaction intermediates. The intermediates in the reaction of 2-naphthol were not observed, because the coupling reaction proceeds too quickly. Hence, we have observed only complexes of the coupling products. The preferential cross coupling was explaned on the basis of an interplay between the probability of the formation of binuclear copper complexes and the reactivity of such complexes.
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