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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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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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Preparation of polyacetylenes with N-benzylidene-2-hydroxyaniline groups
Zhernakova, Yulia ; Sedláček, Jan (advisor) ; Vyskočilová, Eliška (referee)
The following monoethynylated N-benzylidene-2-hydroxyanilines were prepared: N-(4- ethynylbenzylidene)-2-hydroxyaniline, N-(3-ethynylbenzylidene)-2-hydroxyaniline, N-(4- ethynylbenzylidene)-2-hydroxy-5-nitroaniline and N-(3-ethynylbenzylidene)-2-hydroxy-5- nitroaniline, which differed in the position of the ethynyl group on the benzylidene ring and the substitution of the hydroxyaniline ring. Monoethynylated N-benzylidene-2- hydroxyanilines were used as the monomers for the chain-growth coordination homo- and copolymerization. The homopolymerization resulted in linear polyacetylene homopolymers with N-benzylidene-2-hydroxyaniline substituents. The copolymerization with multiethynylarene-type cross-linkers provided densely cross-linked copolymeric polyacetylene networks. The linear units of the networks carried N-benzylidene-2- hydroxyaniline substituents, the interconnection between the chains of the networks being realized by arene links. The texture parameters of the prepared networks significantly depended on the type of comonomers used. The highest specific surface area values (~530 m2 /g) were achieved with networks prepared by copolymerization of N-(4- ethynylbenzylidene)-2-hydroxyaniline or N-(3-ethynylbenzylidene)-2-hydroxyaniline,with 4,4'-diethynylbiphenyl used as a cross-linker. Selected...
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