Catalytic Oxidation of Propylene, Toluene, Carbon Monoxide, and Carbon Black over Au/CeO 2

Au/CeO2 solids were prepared by two methods: deposition-precipitation (DP) and impregnation (Imp). The prepared solids were calcined under air at 400°C. Both types of catalysts have been tested in the total oxidation of propylene, toluene, carbon monoxide, and carbon black. Au/CeO2-DP solids were the most reactive owing to the high number of gold nanoparticles and Au+ species and the low concentration of Cl- ions present on its surface compared to those observed in Au/CeO2-Imp solids

Etude de l'oxydation totale du propène sur des catalyseurs à base de zirconium modifiés par l'ajout du cuivre et/ou de l'yttrium

Des catalyseurs à base de cuivre et de zirconium ont été synthétisés par coprécipitation et par imprégnation. La performance catalytique a été testée pour la réaction d'oxydation totale du propène. Le cuivre améliore l'activité de la zircone et la sélectivité en CO2. Une caractérisation après test révèle une diminution de l'aire spécifique due au frittage. Ce frittage est associé à une transformation en surface de la phase quadratique de la zircone stabilisée par le cuivre en une phase monoclinique dans le cas des échantillons coprécipités et imprégnés sur oxyhydroxyde. L'introduction de l'yttrium à la zircone (1; 5 et 10% Y) a été réalisée pour mieux stabiliser cette phase quadratique. Dans ce cas, les oxydes mixtes sont plus actifs que la zircone. La meilleure activité de l'échantillon à 5% d'yttrium par rapport aux autres oxydes mixtes a été corrélée au plus grand nombre de défauts Zr3+. Le cuivre déposé sur ces oxydes mixtes a conduit à un effet de synergie entre le support et la phase active cuivre puisque c'est l'échantillon Cu/ZrO2 dopé à 5% d'yttrium qui possède la plus grande activité catalytique. Un mécanisme réactionnel de type rédox a permis d'expliquer les différences d'activitéCopper was introduced into zirconia by coprecipitation and impregnation methods. These samples were tested towards total propene oxidation reaction. Copper promotes the catalytic activity and the selectivity of the reaction towards CO2 formation. The characterization of the catalysts after the catalytic test showed a decrease of the specific area due to a sintering. This sintering transforms, on the surface, the stabilized tetragonal phase of zirconia into a monoclinic one in the case of the samples coprecipitated and impregnated with copper over oxyhydroxide (EPR measurements). Yttrium was introduced into zirconia (1; 5 and 10% mol. Y) in order to stabilize its metastable tetragonal phase. The mixed oxides were more active than zirconia. The best activity of the sample with 5% yttrium compared to the other mixed oxides was correlated to its greater number of Zr3+ defects. Copper impregnated over these oxides leads to a synergy effect between the supports and the active phase (copper) because the sample Cu/ZrO2 doped with 5% yttrium is the most active. Thus, a redox mechanism was proposed to explain the difference of activity.DUNKERQUE-BU Lettres Sci.Hum. (591832101) / SudocSudocFranceF

Bioinspired Cu-Mn hydroxyapatite materials for toluene total oxidation

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Formaldehyde total oxidation on manganese-doped hydroxyapatite: the effect of mn content

International audienceAn aqueous impregnation method using manganese (II) nitrate precursor, followed by calcination at 400 °C, was carried out for the preparation of manganese doped hydroxyapatite catalysts (MnxHap; x = Mn wt.%: 2.5, 5.0, 10, 20, and 30 based on MnO2). Methods of characterization including inductively coupled plasma spectroscopy (ICP), N2 physisorption, X-ray Diffraction (XRD), Fourier-Transform Transmission Infrared (FT-IR), Raman, and Thermal gravimetric analysis (TGA/MS) analysis were used for the identification of Mn species and its surrounding environment. Raman spectroscopy indicated the presence of the ε-MnO2 phase for Mn20Hap and Mn30Hap in agreement with the XRD results and the presence of β-MnOOH species for Mn5Hap and Mn10Hap. The formaldehyde total oxidation was investigated on these catalysts and it was shown that Mn5Hap was the most active catalyst, achieving a normalized rate of formaldehyde (HCHO) conversion into CO2 per mole of Mn of 0.042 h−1 at a temperature of 145 °C. The well dispersed oxidized manganese species on Hap with a medium Mn AOS (average oxidation state) were mainly responsible for this performance. Since HCHO was retained on the surface of all catalysts during the catalytic test, the combined Diffuse Reflectance Infrared Fourier Transform spectroscopy (DRIFT) experiment at room temperature and thermodesorption (TD)-FTIR identified formate species as their oxidation consumed surface OH groups. A stability test and moisture effect study showed that the presence of water vapor has a beneficial effect on the performances of the catalyst

Catalytic oxidation of toluene over copper-manganese binary oxides supported on hydroxyapatite: stability tests

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