改性ZSM-5分子筛催化合成哌嗪

Synthesis of piperazine catalyzed by modified ZSM-5 zeolite

研究了不同金属离子改性得到的M-ZSM-5分子筛在以乙二胺(EDA)为原料合成哌嗪反应中的催化性能。通过NH3-TPD和BET法对催化剂进行表征,结果表明,经过离子交换后HZSM-5的骨架结构没有发生变化,仅仅是表面酸性发生了变化。重点考察了催化剂酸性对反应的影响,实验表明,提高弱酸和中强酸中心所占比例有利于哌嗪(PA)和三乙烯二胺(TEDA)生成。以Zn-ZSM-5和Zn/K-ZSM-5为催化剂,在常压,t=360℃,空速为0.25 g/(min.h),m(EDA)∶m(H2O)=4∶6的反应条件下,原料EDA的转化率分别为94.1%和82.6%;产物PA和TEDA的选择性分别为45.5%,42.1%和29.4%,50.1%。

The catalytic performance of modified ZSM-5 zeolite in the synthesis of piperazine from ethylenediamine （EDA） was studied. The catalysts were characterized by NH3-TPD and BET method. The results show that the frame structure of HZSM-5 has no change after ion exchange, but its surface acidity changed. The discussion was concentrated on the effect of the catalyst acidity on the reaction. The experimental results indicate that increasing the proportion of weak-strength acid and medium-strength acid is favorable for forming piperazine （PA） and triethylenediamine （TEDA）. Under the reaction conditions of atmospheric pressure, t = 360 ℃, space velocity =0. 25 g/（ min - h）, m （EDA） ： m （ H2 O） = 4 ： 6, the conversions of EDA are 94.1% and 82.6% respectively, the selectivity of PA and TEDA are 45.5%, 42.1% and 29.4%, 50. 1% respectively when Zn-ZSM-Sand Zn/K- ZSM-5 are used as catalysts.