Une nouvelle classe de catalyseurs hétérogènes au palladium et au platine pour la chimie organique de synthèse
|Abstract:||The heterogeneous palladium/platinum (Pd/Pt) catalysts studied are part of a new range of heterogeneous catalysts developed at SiliCycle Inc for fine chemicals and pharmaceutical chemistry. These catalysts are synthesized from Pd/Pt nanoparticles (NPs) sequestered in the mesoporous cages of hydrophobic organosilicon support MeSiO₁, ₅. The hydrophobic nature of the catalysts is generated by the presence of the methyl groups of the methyltriethoxysilane silane (MTES) used as a monomer in the synthesis of the support. These heterogeneous catalysts, stable in air and moisture, have been found to be very reactive in many chemical reactions, especially under mild conditions of temperature and pressure, for example in carboncarbon coupling reactions, in hydrogenation reactions or in hydrosilylation reactions. The problem is that these catalysts proved to be reactive only for low metal contents (0.5 wt% Pd and 2.0 wt% Pt) and that their catalytic activity decreases considerably in the reusability test at high temperature and high pressure. Under these conditions the catalysts are no longer reusable. The main objective of this thesis is to make improvements to this class of hydrophobic catalysts in order to further increase their catalytic activity and their selectivity. Thus, novel heterogeneous catalytic materials stable to air and moisture have been developed. These catalysts are characterized by better mechanical resistence and stability of Pd/Pt NPs to sintering with high reuse capability under mild conditions, but also at high temperatures and pressures. Their catalytic activity has been evaluated in green applications with high industrial impact. The catalytic activity of Pd catalysts was evaluated in the hydrogenation of squalene to squalane, a fully saturated hydrocarbon, easily adopted by cosmetic formulators for its remarkable properties such as its high stability to oxidation, rancidity and heat. The catalytic activity of the Pt catalysts was evaluated in the hydrosilylation reaction, one of the most important methods for the synthesis of organosilicon compounds and particularly for the industrial scale production of organosilanes by addition of Si-H bonds to double bonds. First, the organosilicon support was doped with Al₂O₃ units. The new catalyst with Pd/Pt NPs encapsulated in the mesoporous cages of an organosilicic support doped with Al₂O₃ units, Pd⁰/MeSiO₁, ₅-Al₂O₃ and Pt⁰/MeSiO₁, ₅-Al₂O₃, have shown a high stability in air and humidity.|
|Document Type:||Thèse de doctorat|
|Open Access Date:||23 September 2019|
|Collection:||Thèses et mémoires|
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