Étude de l'oxydation de solides carbonés ex-cellulose et de leurs interactions avec des sels de cuivre supportés

Abstract : This work was carried out inside the European Research Group (GDRE-CNRS) "Adsorbants carbonés et environnement". This fundamental study is devoted to the influence of some carbon physico-chemical properties (and especially carbon surface chemistry) on the preparation of supported-catalysts. Following the aim, it's necessary to have at one's disposal both functionnalized carbons and powerful analytical tools. Cellulose can be used as a well-defined carbonaceous precursor in order to prepare a great variety of supports in simple and reproducible conditions. The pyrolysis parameters were optimized, and the char obtained at 450 °C in a sealed reactor has the following characteristic ; a great content of elemental carbon (82%). Supplementary pretreatments at 250 °C were found to expand considerably the initially low specific surface area of the char. The solid surface chemistry was greatly modified by an oxidative post-treatment under air at 280 °C. Functionnal evolution during oxidation is mainly related to the progressive conversion of carboxyle goups into anhydrides structures. Acidic groups are beneficial in terms of rendering a more uniform distribution of the cooper precursor on the support during impregnation. The supported copper oxide is reduced during the activation under inert atmosphere at 400 °C in a two steps redox mechanism, in which carbon behaves as the reducing agent. Functionnal groups and low cooper loadings act like promoting factors for the reduction of the active phase. The connections between supports properties and active sites were further investigated with the help of a model reaction, the catalytic degradation of alcohols. The development of new methodologies for DRIFT spectroscopy has allowed us to monitor the functionnal evolution of the solids during oxidation, and also to study the interactions between cooper salts and the supports both during impregnation and activation
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Bruno Azambre. Étude de l'oxydation de solides carbonés ex-cellulose et de leurs interactions avec des sels de cuivre supportés. Chimie. Université Paul Verlaine - Metz, 2000. Français. ⟨NNT : 2000METZ033S⟩. ⟨tel-01775390⟩

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