无模板剂预晶化液添加法合成ZSM-5分子筛

Synthesis of Aggregate ZSM-5 Zeolite with Nucleation Gel in the Absence of Organic Template

研究了旋转烘箱中无模板剂条件下,预晶化液添加对合成ZSM-5分子筛的影响。系统研究了预晶化液加入量对合成分子筛晶化速率及颗粒大小的影响。采用X射线衍射,扫描电镜,N2吸附-脱附,和激光粒度分布等分析方法对合成的ZSM-5分子筛样品的物化性能进行了表征。结果表明,预晶化液的添加可以明显加快分子筛的晶化速率,预晶化液添加量为33.3wt%时达到最大结晶度的合成时间由未添加时的48 h减少到24 h。添加预晶化液的母液在150℃晶化24 h时所得ZSM-5分子筛团聚体的颗粒大小随着预晶化液加入量的增大而增大,由5.5μm增大到26.3μm。团聚体颗粒的比表面积比未添加预晶化液得到的分子筛(292 m2.g-1)有了不同程度的提高,如添加量为33.3wt%时为394 m2.g-1。对预晶化液添加法合成ZSM-5分子筛团聚体颗粒的生长机理进行了讨论。

The effect of nucleation gel on the preparation of aggregate ZSM-5 zeolite was studied under rotating autoclaves free from the organic structure-directing agent. The influence of the nucleation gel on the crystallization rate and particle size was investigated in detail. The physieoehemical properties of the products were characterized by using XRD, SEM, and N2 adsorption. The results indicate that the crystallization rate of the ZSM-5 zeolite is increased by the addition of the nucleation gel. The crystallization time with 33.3wt% nucleation gel is 24 h while that without nucleation gel is 48 h. When 33.3wt% nucleation gel is added, after crystallization at 150 ℃ for 24 h, the average size of the aggregate is increased from 5.5μm to 26.3 μm, and the specific surface area is increased from 292 m2· g-1 to 394 m2·g-1. The mechanism for the crystal growth of the aggregate zeolite ZSM-5 without organic template by the nucleation gel method is also discussed in this work.