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Étude du dopage de catalyseurs de déshydrogénation oxydante de l’éthane et du propane

Abstract : The oxidative dehydrogenations of propane and ethane have been studied on alkaline earth oxides doped with neodymium oxide (AEO) and nickel oxide doped with different metal oxides. Two types of synthesis have been compared for the preparation of AEO+Nd samples. The characterization by XRD showed the formation of solid solutions with different defects (cationic vacancies, dislocations). The formation of agglomerates of neodymium has also been observed. The catalytic testing showed that the presence of neodymium oxide increases both the conversion of propane and the selectivity to propylene. The addition of neodymium oxide increases the basicity of the catalysts, which seems to be beneficial to the selectivity. The nickel oxide based catalysts are very efficient in the oxidative dehydrogenation of ethane. The study shows that there is no formation of extended solid solution. The addition of niobium and oxalates anions leads to the isolation of the active O- sites at the surface of the nickel oxide, which decreases the activity but strongly increases the selectivity to ethylene. Furthermore, it modifies textural properties of nickel oxide increasing its specific surface area leading to better conversions. However, the applicability of this type of catalysts stays under question because of a deactivation that has been evidenced with time on stream. The characterization of the fresh and deactivated catalysts by XRD, Raman, XPS, TEM, EDX and TPD of O2 showed that this deactivation is due to the slow and irreversible reduction of Ni3+ cations leading to a further decrease in number of the O- species. The formation of NiNb2O6 phase during the deactivation has been evidenced.
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Bistra Savova. Étude du dopage de catalyseurs de déshydrogénation oxydante de l’éthane et du propane. Autre. Université Claude Bernard - Lyon I, 2009. Français. ⟨NNT : 2009LYO10341⟩. ⟨tel-00687933⟩

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