Comparative study of catalytic activity of Pd loaded hydroxyapatite and fluoroapatite in butan-2-ol conversion and methane oxidation |
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Authors: | Zouhair Boukha, Mohamed Kacimi, Mahfoud Ziyad, Alain Ensuque,Fran ois Bozon-Verduraz |
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Affiliation: | aFaculté des Sciences, Laboratoire de Physico-chimie des Matériaux et Catalyse, Département de Chimie, Avenue Ibn Battouta, B.P. 1014, Rabat, Morocco bITODYS, UMR-CNRS 7086, Université Denis Diderot, Paris 7, 2 place Jussieu, Paris, France |
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Abstract: | Palladium loaded calcium-hydroxyapatite, Pd(z)/CaHAp, and calcium-fluoroapatite, Pd(z)/CaFAp, were synthesised and characterised by TEM, XRD, IR and UV–vis–NIR spectroscopies. Introduction of palladium does not change the structure of CaHAp and CaFAp. The average size of PdO particles was found to be around 4–5 nm on Pd(1)/CaHAp but larger (6–7 nm) on Pd(1)/CaFap. The acid–base properties of the supports and of the catalysts were studied using butan-2-ol conversion. On CaHAp and CaFAp, the butenes yield (dehydration reaction) is very low either in the absence or in the presence of oxygen. The methyl ethyl ketone yield (dehydrogenation reaction) is significant only in the presence of oxygen and higher over CaFAp. Conversely, the performances of Pd(z)/CaHAp are better than those of Pd(z)/CaFAp below 180 °C. Above 180 °C, buta-2-ol combustion is favoured on Pd/CaHAp but not on Pd/CaFAp. In methane oxidation, Pd(z)/CaHAp showed also a much larger activity than Pd(z)/CaFAp. On 2 wt% Pd loaded CaHAp, the methane oxidation reaches a conversion of almost 100% at 350 °C, which is comparable with the performance of conventional Pd/Al2O3 catalysts. The reducibility of PdO under methane–oxygen mixtures is lower on Pd(z)/CaHAp. For both reactions, the lower activity of Pd(z)/CaFAp is related to its higher acidity, resulting from the substitution of OH− by F−, and to the larger PdO particle size. |
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Keywords: | Calcium-hydroxyapatite Calcium-fluoroapatite Palladium and palladium oxide Methane combustion Butan-2-ol conversion TEM UV–vis–NIR IR spectroscopy |
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