Preparation of Au-Pd/SiO2 catalyst with egg-shell structure and its application in p-CNB hydrogenation reaction

• Main Authors: Tzu-Hao Wang, 王祖皓
• Other Authors: Yu-Wen Chen
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/6gy93a

碩士 === 國立中央大學 === 化學工程與材料工程學系 === 105 === Nano-palladium catalyst has been reported to have high activity for hydrogenation reaction but selectivity of main product, p-chloroaniline (p-CAN), was low. In this study, gold-palladium bimetals were loaded on spherical silica to form the egg-shell catalyst and used different ratio of Au/Pd metal on silica to carry out the p-CNB hydrogenation reaction. All the catalysts were characterized by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS). The condition of hydrogenation reaction was room temperature as reaction temperature, 0.55MPa as H2 partial pressure and at 300 rpm stirring rate. The average particle size of Pd-Au/SiO2 fresh catalyst was smaller than that of Pd/SiO2 and the active metals were highly dispersed on SiO2 support surface. In the early stage of reaction, metals still maintained high dispersion. The main reason is adding gold as promoter can prevent metals from agglomeration and dispread Pd to single active site. However, after long time on the stream, metals agglomeration on silica surface and larger particle size were observed and resulted in decrease in active metals and lead to deactivation. Besides, the activity of catalyst was significantly decreased but selectivity of p-CAN was not obvious change in p-CNB hydrogenation reaction. Therefore, metals composition was not serious change after the reaction.