Réactivité des suies diesel en atmosphères oxydantes

Abstract : The main objective of this thesis was to study the reactivity of diesel exhaust soot under oxidizing conditions. The two studied diesel soot are collected from the same motor bench. This survey appears in a project titled "modelling of a catalysed diesel particulate filter" in which several laboratories (LTAC Metz, LRS Paris VI and LCA Saint-Avold) had collaborated with an industrial partner (Renault SA).Firstly, the soot samples have been characterized by various analytic techniques in order to determine their structural and chemical characteristics as well as their thermal behaviour. We also put in evidence the existence of an interaction between soot and adsorbed compounds during thermal treatment in inert atmosphere (formation of a microporous carbonaceous layer).Concerning the reactivity of non catalysed soot under air, the kinetic parameters have been determined thanks to thermogravimetric analyses. The values obtained for the combustion of the carbonaceous matrix are near for all soot samples (Ea = 140-170 kJ.mol-1, n ~ 0.25, nO2 ~ 0.72). Nor the quantity of soluble organic fraction (SOF), volatile organic fraction (VOF), the mineral inclusions and the thermal treatment seems to influence the combustion process.the effect of a Pt/ZrO2-CeO2 catalyst on the oxidization of soot under air and under a mixture containing 10 % of oxygen and 700 ppm of NO2/Ar has been studied by thermogravimetry. For the catalysed reaction, the activation energy decreases and the order of the reaction of soot (n) increases. There is a change of reaction mechanism. In the case of the reaction under air, it seems that contact between soot and catalyst is necessary whereas in presence of NO2 the catalyst is active even without contact.Finally, the formation of the reaction intermediates (R-NOx) created during the reaction of soot with NO2 has been put forward by thermogravimetry. The nature of these compounds has been determined by infrared spectrometry in agreement with the literature results. Some possible formation and decomposition mechanisms of these species have been proposed thanks to the analysis of gases obtained during soot-NO2 reaction and the thermodesorption of the R-NOx and ROx formed.
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Salvatore Collura. Réactivité des suies diesel en atmosphères oxydantes. Autre. Université Paul Verlaine - Metz, 2004. Français. ⟨NNT : 2004METZ010S⟩. ⟨tel-01750163⟩

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