Comparative study of catalytic activity of Pd loaded hydroxyapatite and fluoroapatite in butan-2-ol conversion and methane oxidation
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- 作者：Zouhair Boukha ; Mohamed Kacimi ; Mahfoud Ziyad ; Alain Ensuque ; Franç ; ois Bozon-Verduraz
- 关键词：Calcium-hydroxyapatite ; Calcium-fluoroapatite ; Palladium and palladium oxide ; Methane combustion ; Butan-2-ol conversion ; TEM ; UV– ; vis– ; NIR ; IR spectroscopy
- 刊名：Journal of Molecular Catalysis A: Chemical
- 出版年：2007
- 出版时间：1 June 2007
- 年：2007
- 卷：270
- 期：1-2
- 页码：205-213
- 全文大小：1063 K
文摘
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.