碱处理对ZSM-5分子筛多级孔道结构和扩散性能的影响

以氢氧化钠水溶液处理ZSM-5分子筛，调变分子筛内部孔道结构。使用“零长柱”(ZLC)方法研究不同碱处理时间下环己烷探针分子在ZSM-5分子筛中扩散系数的变化；使用Ar吸附-脱附手段表征碱处理前后样品中微孔和介孔体积、孔径分布变化；并结合透射电镜(TEM)表征研究了不同碱处理扩孔程度下ZSM-5分子筛中介孔的变化和孔道的连通情况，建立表征多级孔分子筛中孔道的连通性和定量评价扩孔效果的方法。结果表明：碱处理反应增加了ZSM-5分子筛中的介孔体积并改善了探针分子的扩散性能；随着碱处理时间增加，介孔中孔径大于10 nm的孔道比例逐渐提高，进一步改善了孔道间的连通性。

Impact of Alkali Treatment on Hierarchical Pore Structure and Diffusion Properties of ZSM-5 Zeolites

The pore structure of ZSM-5 zeolites was modulated with sodium hydroxide solution. The diffusivity of cyclohexane in ZSM-5 zeolites and the correlation between diffusivity and NaOH desilication time were studied by zero length column (ZLC) method. The pore volume and pore size distribution of micropores and mesopores of ZSM-5 zeolites were characterized by Ar adsorption-desorption method, and transmission electron microscopy (TEM) was used to study the structure and connectivity of mesopores in ZSM-5 zeolite with different NaOH desilication time. These experimental results show that the volume and connectivity of mesopores are increasing along with alkali treatment time, which increases the diffusivity of cyclohexane in ZSM-5 zeolites. With the increasing of NaOH desilication time, the proportion of mesoporous channels larger than 10 nm gradually increases, and these larger mesopores further improve the diffusivity of zeolites.