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Synthesis of the violet fragrances on MFI zeolite catalysts
Domenová, Alica ; Mazur, Michal (advisor) ; Kadam, Shashikant Arun (referee)
Zeolites are porous aluminosilicates widely used in acid catalysis due to their properties, such as Brønsted and Lewis acidity, thermal stability, and defined pore structure providing shape selectivity. Zeolites can be synthesized as nanolayered crystals that can be further modified by pillaring. These architectures are more open, thus can lead to novel applications of zeolites in catalysis. One of the acid-catalyzed reactions where 3D standard zeolites were shown to be active catalysts is cyclization of pseudoionone. This reaction is used for the synthesis of α-, β- , and γ-ionones, important organic compounds used in medicine and fragrance industries mainly as violet fragrances. Up to date, there are no reports on the catalytic activity of layered zeolites in ionone synthesis, however, these open structures have a potential to be utilized in such reactions due to the improved reactant diffusion through the catalyst. In this work, catalytic performance of the materials based on MFI zeolite layers was investigated in the conversion of pseudoionone-to-ionones. Catalysts were synthesized using hydrothermal crystallization followed by post-synthesis modification via pillaring. Structure and textural properties of the catalysts were thoroughly characterized using X-ray diffraction and nitrogen...
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The effect of reaction conditions and type of active sites on the kinetics of heterogeneously catalysed formylation of amines
Olšovská, Adéla ; Veselý, Ondřej (advisor) ; Kubička, David (referee)
Formamides are valuable compounds in pharmaceutical production and organic synthesis; however, their common synthesis methods suffer from number of drawbacks including low reaction rate and contamination with heavy metals leached from a catalyst. According to several articles, these problems could be overcome by using zeolite-based catalysts. Nevertheless, the mentioned articles provide somewhat conflicting results and also lack a clear description of which centres in zeolites are catalytic active. Therefore, we prepared a set of zeolite-based catalysts commonly described in the literature (zeolite Beta ion exchanged to H+ and Cu2+ form) in order to test them as catalysts and clarify their catalytic behaviour and nature of the active sites. We chose formylation of N-methylaniline by formic acid as the model reaction for our research and performed a series of experiments under varying conditions (solvents, concentration of reactants, temperature). In contrast to the published articles, none of the investigated materials demonstrated significant catalytic activity in our experiments. Moreover, we found that the often pronounced catalyst: zeolite Beta ion-exchanged into the copper form, is unstable in the presence of formic acid, which causes leaching of copper into the reaction mixture. At the same...
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