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Influence of bases on heterogeneous Lewis acid catalyzed hydrogen transfer reactions
Veselá, Klára ; Přech, Jan (advisor) ; Bulánek, Roman (referee)
Heterogeneous Lewis acid zeolites catalyzed Meerwein-Ponndorf-Verley (MPV) reduction (transfer hydrogenation), where ketones and aldehydes are reduced to the corresponding alcohols. The hydrogen is taken from a secondary alcohol. These Lewis acid zeolite catalysts have a great advantage over homogenous catalysts as they are well separable from the reaction mixture and recyclable. Lewis acid zeolites are materials that contain incorporated tin or zirconium species, which act as Lewis acid sites. MPV reduction of citronellal provides citronellol as a product. However, the reaction of citronellal with 2- propanol also proceeds via a parallel reaction pathway providing isopulegol as the major product. Addition of pyridine (an organic base) to the reaction mixture switches the selectivity of the reaction, i.e., citronellol becomes the main product of the cited citronellal reaction with 2-propanol. It was investigated whether this phenomenon would also be observed for reactions with the addition of different bases. To answer these questions, Sn-BEA and Zr-BEA were prepared by hydrothermal synthesis. Impreg-Zr-BEA and impreg-Sn-BEA were prepared by postsynthesis metal incorporation. In addition, highly porous 2D Self-pillared pentasil zeolites containing tin and zirconium were hydrothermally synthesized....
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Aplications of hydrogenation catalysts prepared by reductive demetalation of zeolites
Kurucová, Svetlana ; Přech, Jan (advisor) ; Vyskočilová, Eliška (referee)
Hydrogenation reactions belong to the most important reactions in the chemical industry. They are needed for crude oil processing, production of pharmaceutical, polymers, chemical specialties, etc. Supported noble metal catalysts are commonly used industrial catalysts due to their high activity and selectivity. However, the high cost of production and recovery of noble metal catalysts is one of the disadvantages of their use. The application of transition metal catalysts containing Cu, Fe or Zn presents a more environmentally friendly alternative to currently used catalysts. In this work, we studied the catalytic activity of metal@zeolite composite catalysts containing CuFe and CuZn bimetallic nanoparticles, prepared by reductive demetallation in hydrogenation of -NO2, -C≡C-, -C=C- and -C=O groups. Reductive demetallation is a novel method for the synthesis of bimetallic nanoparticles encapsulated inside zeolite pores. The catalytic activity of the metal@zeolite composites prepared by reductive demetallation was compared with analogues synthesised by impregnation and ion exchange in the hydrogenation of p-nitrotoluene, 3-ethynylanisole and cinnamaldehyde. Metal@zeolite catalysts synthesised by reductive demetallation were active in the hydrogenation of all the cited groups: -NO2, -C≡C-, -C=C- and...
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Využití zeolitů v technológii vín révy vinné
Miklovičová, Kristína
This bachelor thesis has a theoretical-empirical character and its content is focused on the use of zeolites in the production technology of wine. The theoretical part defines the zeolite, its origin, composition and structure as well as the properties, the division of individual zeolites and their possible use in enology. This natural rock, characterized by their high absorption quality, is able to bind molecules to itself due to its porous structure. The empirical part analyses the effects of zeolites in the production technology of wine. Zeolite was applicated in the fermentation process of wine together with the yeasts. The experiment was performed with three variants of individual concentrations of zeolite and subsequently the sensory and chemical properties of wine were monitored. The experiment confirmed the reduction of thermolabile proteins after the application of zeolite, lower production of acetion and also lower concentration of polyphenol oxidase, thus preventing oxidation.
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Stabilization of metal nanoparticles in MWW zeolite for catalytic applications
Molitorisová, Sidónia ; Shamzhy, Mariya (advisor) ; Hronec, Mlan (referee)
Controlling both size of metal nanoparticles (MNPs) and acidobasic characteristics of the zeolite support is highly desirable for preparation of stable and active bifunctional catalysts. 2D-3D transformation of layered zeolite precursor into three-dimensional zeolite coupled with metal encapsulation is one of the most efficient synthetic strategies so far to achieve the appropriate metal dispersion and aggregative stability of MNPs within zeolite matrix. Nevertheless, the effect of support acidic characteristics on the properties of thus prepared metal@zeolite catalyst remained unrevealed, while the synthetic strategy itself requires further optimization to minimize the loss of metal component. This work addresses the influence of chemical composition of zeolite layered precursor on physical-chemical and catalytic properties of metal@zeolite catalysts prepared via 2D-3D transformation strategy, taken Pd@MCM-222D-3D system as a representative example. Both Si/Al ratio of MCM-22P layered precursor (e.g., Si/Al = 15, 20, 30) and Pd loading (e.g., 0.1, 0.3, 0.8 wt.%) were varied resulting in a set of nine Pd@MCM-222D-3D catalysts. In addition, three Pd@MCM-22impreg catalysts with the same metal loading (0.1 wt.%), but different Si/Al ratios of a support were synthesized via conventional impregnation...
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Study of microstructure of autoclaved aerated concrete with using of secondary raw materials
Martanová, Jana ; Suchý, Peter (referee) ; Kulísek, Karel (advisor)
Autoclaved aerated concrete is a used building material, especially for its thermal insulating properties. During autoclaving, an aerated concrete microstructure produces crystalline CSH phases, primarily tobermorite. The ingoing substances are calcium oxide and silica. In addition to commonly used raw materials, secondary raw materials rich in silicon dioxide can be used for production. The use of secondary raw materials gives the opportunity for the construction industry to be more environmentally friendly. Another benefit is the reduction of financial costs. The work explores the influence of individual secondary raw materials on the microstructure. High-temperature fly ash, fluid fly ash, cinder, ground glass and zeolite were used The raw materials were mixed with unalloyed lime at a molar ratio of calcium oxide to silicon dioxide of 0.73 and 1.0. Autoclaving capsules were used to synthesize tobermorite under laboratory conditions. Autoclave was performed at 170 °C and 190 °C with hydrothermal durations of 4, 8 and 16 hours. The most important influence on the microstructure was high-temperature fly ash, on the contrary, the greatest influence on the mechanical properties is attributed to the ground glass.
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Theoretical investigation of microporous materials for adsorption and catalysis
Položij, Miroslav ; Nachtigall, Petr (advisor) ; Bludský, Ota (referee) ; Cwiklik, Lukasz (referee)
Theoretical investigation of microporous materials for adsorption and catalysis Microporous materials are defined by a presence of pores with diameter smaller than 2 nm. They comprise a large variety of materials from amorphous materials to very well defined crystalline materials like zeolites or metal organic frameworks. Microporous materials are industrially very important group of materials used for adsorption, gas capture, molecular sieving, or heterogeneous catalysis. Zeolites are by far the most important group of microporous materials due to their use as catalysts for the petroleum cracking. One of the main limitations of the zeolite use in catalysis is their limited pore size. This obstacle can be solved by use of hierarchical zeolites with a secondary mesopore network which allows overcoming the diffusion problems. The aims of this study can be divided into two parts. In the first part, the structures of two-dimensional and hierarchical zeolites were investigated theoretically to identify the structure of new materials and to obtain reliable models to study the hierarchical zeolites. In the second part, the catalytic properties of several microporous materials were modelled to explain their experimental activity. The results of this thesis were used to identify the structure of a large...
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Immobilization of heavy metals in the cement matrix with the admixture of natural zeolite
Semerádová, Nikol ; Bayer, Patrik (referee) ; Vyšvařil, Martin (advisor)
Heavy metals released to the natural ecosystem constitute significant risks not only for organisms, but also for water supplies in the nature. There are a number of analytical methods for the determination of heavy metals. Each of them is suitable for different element and its character. Since the results of the analysis are applied during the solidification and stabilization, it is necessary to ensure the highest correlation between hazardous waste and solidification medium for maximum inhibition of toxic ions. This work investigates the stabilization of heavy metals binders based on cement base with admixture of the natural zeolite and its possible use for the solidification of heavy metals in soluble form.
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Cleaning effect of unconventional filtration materials
Fialová, Tereza ; Hynánková,, Eva (referee) ; Kriška-Dunajský, Michal (advisor)
Constructed wetlands and the soil filters are water treatment devices using the filter material that in most cases consists of natural river gravel, coarse sand or crushed stone. Master´s thesis deals with the research of cleaning effect of unconventional filtration materials, or more precisely with examination to load real waste water in a filtration column, to prove their ability to be used as an alternative medium that can ensure better cleaning effect. For the research work following metallurgical industry materials were used: fine slag and coarse slag 8-16 mm, materials from the natural character: zeolite, keramzit, a plastic material: PUR-foam. Also the traditional materials of fine gravel and coarse gravel were tested to compare the cleaning efficiency. Both the hydraulic and the cleaning efficiency of all above mentioned materials were tested. The examined hydraulic parameters are particularly porosity, hydraulic conductivity and suspended solids, turbidity and oxidation-reduction potential of both the inflow and outflow of the filter columns were determined. Accredited laboratory set the inflow and outflow of the filter columns BOD5, CODCr, total phosphorus, total nitrogen, nitrite, nitrate, ammonia and dissolved oxygen. By evaluating the results of the measurements it is determined which materials are suitable to be applied in the constructed wetlands and the soil filters. This filtration column was modeled by program HYDRUS and the result was compared with real results.
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Possibities to increase the frost resistance of brick body
Keršner, Štěpán ; Šveda,, Mikuláš (referee) ; Sokolář, Radomír (advisor)
This thesis, which comprises of a theoretical and a practical part, deals with possible means of increasing ceramic body frost resistance. The current state of research in the field of ceramic body frost resistance is summarized in the theoretical part. The practical part is divided into two sections. In the first section, the influence of firing temperature (820 °C and 1020 °C) and duration (2, 4 and 6 hours) on frost resistance and several other parameters is assessed by means of experiment, using a specimen of brick body made of mixes currently used in roof tile production by TONDACH Šlapanice and TONDACH Dolní Jirčany factories. In the second section of the practical part, two modifications are introduced of the mixture currently used in roof tile production in the TONDACH Šlapanice factory – GE clay and zeolite supplements were added, the effects of which are verified by means of experiment using specimens fired in a kiln designated for ceramic masonry blocks and alternatively in a kiln used for firing TONDACH Šlapanice roof tiles.
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