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Nanosponge MFI zeolites functionalized with metal nanoparticles for catalysis
Laštovičková, Anna ; Mazur, Michal (advisor) ; Vyskočilová, Eliška (referee)
Metal nanoparticles immobilized at various supports have outstanding catalytic activity in hydrogenation reactions. Zeolites are used as supports, mainly due to their porous structure. In this work, metal nanoparticles were immobilized on MFI nanosponge zeolites. Zeolite nanosponges (pure silica and degallated) were impregnated with pure platinum and platinum mixed with rare-earth elements (cerium, lanthanum, and yttrium) to form alloys. The main aim of this work was to investigate the activity of bimetallic nanoparticles immobilized on zeolite nanosponges in hydrogenation of cinnamaldehyde. It is a versatile model reaction to investigate catalysts, due to the presence of three different reducible groups (C=C bond, C=O bond and benzene ring) in the cinnamaldehyde molecule. The objective was to focus on selectivity effects of various catalyst towards three possible products of cinnamaldehyde hydrogenation (hydrocinnamaldehyde, cinnamyl alcohol and hydrocinnamyl alcohol). The metal alloys evolution is more feasible on the degallated zeolites due to the defects in the structure called silanol nests. These defects stabilize bimetallic nanoparticles. Moreover, samples prepared with use of degallated support showed larger surface areas. Pure-silica zeolites impregnated with metals were also prepared for...
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Design and adaptation of electron microscope accessories for in-situ experiments
Drozd, Michal ; Mikulík, Petr (referee) ; Kolíbal, Miroslav (advisor)
Účinnost katalyzátoru v kombinaci s optimalizovanou reakcí a minimalizováním jeho množsví jsou klíčovými faktory při snižování investičních a provozních nákladů v rámci chemických procesů. Díky pokročilým experimentálním technikám mohou být katalyzátory dále zlepšovány. Jednou z těchto technik je in-situ elektronová mikroskopie. Tato práce se zabývá vývojem zařízení pro automatický ohřev vzorku, automatickým vpouštěním reaktantů a měřením parciálních tlaků v komoře mikroskopu. Dále je pomocí provedených experimentů srovnán přístup pomocí environmentálního rastrovacího mikroskopu, kde se využívá laserový ohřev vzorku s přístupem, který využívá skenovací elektronový mikroskop připojený k ultra vakuové komoře, kde se vzorek zahřívá pomocí průchodu elektrického proudu.
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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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Development of new pathways for syntheses of sesquiterpenoids
Topolovčan, Nikola ; Kotora, Martin (advisor) ; Dvořák, Dalimil (referee) ; Pour, Milan (referee)
This work consists of four consecutive parts, each dealing with syntheses of structurally diverse compounds. The syntheses were based on the methods within the domain of transition-metal catalyzed and/or mediated reactions with particular emaphasis on the application of organozirconium chemistry. 1. A method for synthesis of tricyclic condensed hydrocarbons possessing 5(6)-7-6(aryl) framework was developed. It is based on reaction of bicyclic zirconacyclopentenes, prepared by oxidative dimerization of enynes on a low-valent zirconocene species (Negishi's reagent), with ortho-halobenzaldehydes in the presence of various additives. The presence of two different centers of reactivity - the sp2 C-Zr and sp3 C-Zr bond - allowed sequential functionalization of each bond. Thanks to its higher nucleophilicity, the sp3 C-Zr bond reacted preferentially with the carbonyl carbon of the aldehyde yielding an oxazirconacycloheptene. The subsequent transmetallation of the remaining sp2 C-Zr bond with CuCl in the presence of other additives (catalysts) enabled an intramolecular cross-coupling reaction with the aryl halide moiety furnishing the desired tricyclic products in reasonable yields. The scope of the reaction with respect to differently functionalized reactants was assessed, as well as its mechanistic...
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Effect of silver in homogeneous gold catalysis
Motloch, Petr ; Roithová, Jana (advisor) ; Hocek, Michal (referee)
Gold catalysis has recently experienced a sustained upswing in interest from scientific community. The amount of new reactions catalysed by gold is so significant that little is known about mechanisms of most of these reactions. Research into mechanisms of (not only) gold catalysed reactions is therefore very significant area of interest and important to the continued improvement of gold catalysed reactions. Formation of cationic π-complexes is considered a first mechanistic step in reactions catalysed by gold(I). The bond dissociation energies of gas phase cationic π-complexes were investigated by mass spectrometry and theory calculations in this thesis. These complexes consisted of differently substituted unsaturated hydrocarbons (alkenes, alkynes, alkadienes and allenes) and complex cations of silver and gold containing second ligand (triphenylphosphine, acetonitrile). On the basis of the results obtained from this study, a possible origin of the "silver effect" in gold(I) catalysis is discussed. Key words catalysis, gold, silver, mass spectrometry, DFT calculations, reaction intermediates
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Synthesis of cycles using organocatalysis and catalysis with metal complexes
Hurný, David ; Veselý, Jan (advisor) ; Trnka, Tomáš (referee)
This thesis deals with an enantioselective synthesis of cyclic compounds by using a combination of organocatalysis and transition metal catalysis. The thesis deals mainly with usage of aminocatalyst for activation of aldehydes and copper catalyst for activation of terminal triple bond. The first part is focused on the preparation of starting compounds for cyclizations (α-oxoesters, α- substituted nitroalkanes and α-substituted aldehydes). The second part concerns carbocyclization itself and optimization of reaction conditions to achieve highly stereoselective reaction. Powered by TCPDF (www.tcpdf.org)
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Immobilization of protease V8 on magnetic particles for application to proteolytic cleavage of pepsin A
Čepa, Adam ; Pacáková, Věra (advisor) ; Tichá, Marie (referee)
This thesis is part of a long-standing research in the field of diagnosis of the stomach diseases, which is based on the gastric enzyme pepsin A mapping. It was found that a phosphorylation in the primary structure of this enzyme may serve as a marker of incipient stage of carcinogenesis. This thesis is focused on the immobilization of protease V8 isolated from microorganism Stafylococcus aureus to magnetic agarose beads. Protease V8 is a promising candidate for producing peptide maps of pepsin A. The influence of pH, temperature and reaction time on the enzyme to activity has been studied and the optimal conditions for hydrolytic catalysis of formation of peptide fragments of pepsin A.
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Redox and catalytic properties of modified papain
Lachmanová, Štěpánka ; Hudeček, Jiří (advisor) ; Zima, Jiří (referee)
Redox and Catalytic Properties of Modified Papain Endopeptidase papain could be modified by the organometallic complex [(η6 -C6H5(CH2)2NHCO(CH2)Cl)Ru(N^N)Cl]Cl, (N^N) = 1,10-phenanthroline (TB11), which binds to the free sulfhydryl group of cysteine in the active centre of protein. This modification influences the catalytic properties of papain. The redox properties of the TB11 complex in its free form and when it is bound to papain were studied by the polarographic and voltammetric methods. Modified endopeptidase is reduced in the adsorbed state. Therefore, a phase-sensitive AC voltammetry is used for studies of the electron transfer in the TB11 modified papain. This method gives suitable methodology for studying the electron transfer rates in the systems influenced by adsorption. Using this method the catalytic hydrogen evolution process was detected not only in the TB11, but also for TB11 covalently-attached to the papain molecule. The results help better understand the catalytic mechanism of the hydrogenation reactions in the presence of TB11 modified enzyme. Adsorption properties of papain at different substrates were studied by AFM measurement. The formation of a compact monolayer was proved for the gold substrate modified by a layer of 11-mercaptoundecanoic acid.
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