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Préparation de nanoparticules de rhodium(0) sur support mésoporeux assistée par des sels d'ammonium quaternaires : Application à la catalyse d'hydrogénation asymétrique d'arènes prochiraux

Abstract : This thesis aims to develop new catalysts combining Rh(0) nanoparticles with promising activities and the confinement effect of mesoporous materials for applications in asymmetric hydrogenation in water. Particles were prepared by the reaction of NaBH4 with RhCl3, directly, within silicic (SBA-15) or aluminosilicic (Al-SBA-15) mesostructured materials with assistance of quaternary ammonium salts. A first set of materials was obtained by testing 13 molecules of "free" stabilizing agents varying in chain length, polar head or counter-ion. In this case, structures including from 12 to 16 carbon atoms led to better metal dispersions. Strong electrostatic interactions with Al-SBA-15 have been highlighted for C16H33N(CH3)2(CH2CH2OH)+ Cl-. In a second step, equivalents ammonium salts were covalently grafted (via their carbon chain) on SBA-15 or Al-SBA-15 proceeding by nucleophilic attack of chloropropyl groups (co-condensation) by N,N-dimethylethanolamine. The conditions of implementation of the substitution reaction had to be optimized to minimize side reactions between the amine and the free silanol groups. Rh(0) nanoparticles of both series catalyze the hydrogenation of diphenylmethane at room temperature and under 1 bar of H2. Ammonium salts with asymmetric centers have also been studied leading to catalysts of ethylpyruvate and m-methylanisole hydrogenation working in water under 40 bar of H2 and affording slight enantiomeric excess.
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Submitted on : Friday, June 14, 2013 - 5:23:18 PM
Last modification on : Tuesday, December 14, 2021 - 3:56:10 AM
Long-term archiving on: : Sunday, September 15, 2013 - 4:12:34 AM

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  • HAL Id : tel-00834363, version 1

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Rita Sassine. Préparation de nanoparticules de rhodium(0) sur support mésoporeux assistée par des sels d'ammonium quaternaires : Application à la catalyse d'hydrogénation asymétrique d'arènes prochiraux. Génie des procédés. Université Pierre et Marie Curie - Paris VI, 2012. Français. ⟨NNT : 2012PA066053⟩. ⟨tel-00834363⟩

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2013