碱处理多级孔ZSM-5的酸性及吸附扩散性能研究

不同条件下用NaOH处理ZSM-5分子筛，得到了不同孔径分布的微-介孔多级ZSM-5分子筛，运用 XRD、N2吸附-脱附、SEM、NH3-TPD和Py-FTIR等方法对其进行表征。采用智能重量分析仪（IGA）等考察了改性后的分子筛与苯分子之间吸附扩散性能及其与酸量及吸附位的构效关系。结果表明，碱处理不会改变分子筛整体的晶相结构，但是碱处理会一定程度破坏分子筛的结晶度。碱改性会形成微-介多级孔分子筛，并能调变分子筛的酸量。调变后酸量相对大的多级孔ZSM-5分子筛有更多的吸附位，吸附量也会相应增大。此外，苯在多级孔ZSM-5上的传质性能不仅与多级孔ZSM-5分子筛的吸附位有关，还与孔结构有关。介孔含量越多，多级孔体系贯通性越好，苯的传质性能越好，越有利于多级孔ZSM-5活性位的吸附及其催化性能的提高。

PROPERTIES OF ADSORPTION,DIFFUSION AND ACIDITY OF ALKALI TREATED ZSM-5 WITH HIERARCHICAL PORE STRUCTURE

A series of hierarchical micro-meso-pore structure ZSM-5 zeolites were synthesized by NaOH treatment. The structural and acidity properties of as-synthesized zeolites were characterized by XRD, N2 adsorption, SEM, NH3-TPD, and Py-FTIR. The adsorption and diffusion performances of benzene on the treated ZSM-5 zeolites were investigated by an Intelligent Gravimetric Analyzer (IGA). The structure-activity relationship of hierarchical ZSM-5 zeolites was related with the mass transfer, adsorption sites, and acid amount. It is found that the structure of ZSM-5 zeolites is not changed by suitable alkali treatment except crystallinity. After alkali treatment, the meso and micro-porous structures are formed in the hierarchical ZSM-5 zeolites. The acidity of hierarchical ZSM-5 zeolites is improved, which produces more adsorption sites and thus increases the adsorption of benzene on the hierarchical ZSM-5. The adsorption performance of benzene on hierarchical ZSM-5 not only is correlated with the acidity, but also with pore structure of ZSM-5. As a result, the connectivity in the meso-porous ZSM-5 is improved with the increasing of meso-porous in hierarchical ZSM-5, which contributes to the adsorption of active sites and catalytic performance of the treated ZSM-5.