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Etude de catalyseurs Pt-Pd supportés sur spinelle MgAl2O4 pour la dépollution automobile : synthèse, stabilité hydrothermale et perfomances catalytiques

Abstract : The improvement of air quality is a major issue for the health and the environment. The challenge for the manufacturers of catalytic converters for automotive depollution is to optimize their formulation to meet the standards regulating the polluting emissions hardening, while making a profitable use of the precious metals whose resources are becoming exhausted. In this thesis, a new, mesoporous, MgAl2O4, catalytic support was synthesized by atomization of an aqueous sol containing a tri-block copolymer. The MgAl2O4 nanocristallites in point contact enable to reach higher dispersion rates of the Pt-Pd active phase than those of a commercialized DOC taken as reference by Renault. The active phase of the 2,5%m.PtPd(3:2)[450°C]/MgAl2O4[900°C] catalyst presents similar hydrothermal stability to that of the reference DOC thanks to chemical anchoring (epitaxial growth, solid solutions) and mechanical anchoring (atomic steps, pores). Although the totality of the precious metal content is not accessible (insertion, encapsulation) for CO, HC and NO oxidation, the catalytic performances reached by this catalyst during hydrothermal aging are comparable with that of the reference DOC. The conversion of the HC is similar to that of the reference DOC and depends on the local concentration of the active sites. The CO conversion rate is slightly penalized since the particles are too smalls and in an oxidized state. Lastly, this catalyst does not reduce NOx but ensures a more important oxidation of NO in NO2 after a hydrothermal aging than the reference DOC and also the storage of NO2 which have a positive impact on the proper functioning of the downstream diesel particulate filter.
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https://tel.archives-ouvertes.fr/tel-01216468
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Solène Le Bras. Etude de catalyseurs Pt-Pd supportés sur spinelle MgAl2O4 pour la dépollution automobile : synthèse, stabilité hydrothermale et perfomances catalytiques. Génie chimique. Université de Limoges, 2015. Français. ⟨NNT : 2015LIMO0053⟩. ⟨tel-01216468⟩

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