| Autor: |
El Kabouss, Kaoutar, Kacimi, Mohamed, Ziyad, Mahfoud, Ammar, Souad, Ensuque, Alain, Piquemal, Jean-Yves, Bozon-Verduraz, François |
| Zdroj: |
Journal of Materials Chemistry; 2006, Vol. 16 Issue: 25 p2453-2463, 11p |
| Abstrakt: |
Impregnation of calcium hydroxyapatite by a solution of Co(ii) nitrate followed by calcination at 823 K gives rise to various species, depending on the cobalt content. At low cobalt content (0.2 wt%), the cobalt species are isolatedsix-coordinated Co2+ions. For Co content ≥0.4 wt%, the presence of tetrahedral Co2+and octahedral Co3+species is attested by UV–visible–NIR spectroscopy, magnetic measurements and XPS data. Magnetic data at low temperature suggest the formation of clustered CoxOyentities. For Co content ≥1.7 wt%, Co3O4nanocrystals are generated, as evidenced by XRD and magnetic measurements.In the presence of oxygen, the butan-2-ol conversion produces only butan-2-one. The most active catalysts are the cobalt poorest samples which contain only isolated Co2+ions. Oxidative dehydrogenation of ethane gives a similar trend. Upon increasing the cobalt loading above 0.9 wt%, the specific dehydrogenation activity of Co2+ions decreases because the nature of the sites changes and the basic properties are lowered. Relationships between the nature of the sites and the catalytic performances are proposed. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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