Au-Pd@SiO2 catalyst with egg-shell structure and its application in reaction
| Autor: | Chia-Yin Ho, 何嘉茵 |
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| Rok vydání: | 2018 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 106 Nano-sized palladium and gold catalysts have high activity for hydrogenation reaction. Since very small amount of metals are used, usually metals are deposited on the support. SiO2 is used for the reaction since it can resist in acidic condition. In liquid phase hydrogenation, pore diffusion is always a rate-limiting step. It is desired to deposit metals on the shell of SiO2 beads. The objective of this study was to develop a method to prepare bimetallic catalyst with core-shell structure. Three different pathways were used to prepare the egg-shell catalysts. All the egg-shell catalysts were characterized by optical microscope, X-ray diffraction, transmission electron microscopy, high resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Liquid phase hydrogenation of p-chloronitrobenzene to p-chloroaniline was used as the test reaction. The reaction was carried out at 298K, 0.6 MPa partial pressure of H2 and 300 rpm of stirring rate in a batch reactor. In order to obtain the kinetic data, powder catalysts were also prepared and tested for reaction. The results show that increasing the concentration of NaOH in preparation process increased the thickness of the shell. The average particle size of the metals wass in nanosize and all metals were homogeneously dispersed in the shell of catalysts. The egg-shell catalyst made by method 1 had the smallest thickness of shell had the highest selectivity of p-chloroaniline. On the other hand, the powder catalysts had a higher activity, but selectivity of p-chloroaniline was not significantly different compared with the egg-shell catalysts. The catalysts with lower Pd loadings and higher Au loadings had high activity and selectivity. It suggests that adding gold can effectively increase the selectivity of p-CAN. In this study, the catalyst with egg-shell structure was successfully prepared which can be applied in industry for various reactions. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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