微波辅助Ni-B/SiO2非晶态催化剂的制备及其在硝基苯加氢中催化性能的研究

采用微波辐射干燥浸渍法获得的Ni2 /SiO2,再由液相KBH4还原制备Ni-B/SiO2非晶态催化剂,在液相硝基苯加氢反应中,该催化剂对苯胺的选择性为100%,催化活性显著高于由传统加热法制备的Ni-B/SiO2.根据XRD、XPS、SEM和氢吸附等表征,两种催化剂具有相似的活性中心本质,催化性能的不同主要归因于分散度的区别.与传统加热法相比,微波加热具有受热均匀以及增强Ni2 与载体SiO2相互结合力的特点,导致Ni-B/SiO2(MW)分散度增加,并能减少催化反应过程中活性相的脱落流失,延长催化剂使用寿命.

Microwave-Assisted Preparation of Ni-B/SiO2 Amorphous Catalyst and its Catalytic Performance in Nitrobenzene Hydrogenation

The microwave irradiation was employed to treat the catalyst precursor (Ni~ 2 /SiO_ 2 ) obtained via impregnation, which resulted in the Ni-B/SiO_ 2 amorphous catalyst through chemical reduction by aqueous KBH_ 4 solution. During liquid phase nitrobenzene hydrogenation, the as-prepared catalyst exhibited 100% selectivity toward aniline and its activity was much higher than that of the corresponding traditional Ni-B/SiO_ 2 amorphous catalyst obtained without microwave irradiation. According to various characterizations, such as XRD, XPS, SEM and hydrogen chemisorption etc., both two kinds of catalysts displayed similar active sites, and thus the hydrogenation activity was mainly dependent on the catalyst dispersion degree. The treatment with the microwave irradiation resulted in the higher dispersion, possibly owing to the uniform heating model and strong interaction between metallic ions and the support. Such strong interaction also inhibited the leaching of active phase during liquid phase catalytic hydrogenation, which may be beneficial to the catalyst lifetime.