核壳MFI/CHA分子筛的合成及催化性能

Synthesis and Catalytic Activity of Core-Shell MFI/CHA Zeolites

采用二次生长法(外延法)在ZSM-5(MFI型)晶体颗粒表面外延生长SAPO-34(CHA型)磷酸硅铝分子筛壳层,合成了MFI/CHA型核壳分子筛材料。并利用X射线衍射(XRD)、扫描电镜(SEM)、能量色散射线光谱(EDS)和傅里叶变换红外(FTIR)光谱对其进行了表征。结果表明,核相ZSM-5的预处理步骤对于成功合成此核壳型分子筛材料十分关键。通过研究晶化温度和晶化时间对MFI/CHA核壳型沸石分子筛合成的影响推测出MFI/CHA壳层生长的晶化机理,并考察在甲醇芳构化中的择形催化作用。

MFI/CHA core- shell zeolites were synthesized by a two- step hydrothermal synthesis strategy（epitaxial growth）. The growth of silicoaluminophosphate SAPO-34 fabricates crystalline layers over ZSM-5 nanocrystal crystallites. The samples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, energy-dispersive X-ray spectrometry（EDS）, and Fourier transform infrared（FTIR）spectroscopy. The analyses indicate that the pretreatment step of the core phase was an important step during the synthesis. The growth kinetics of the MFI/CHA core-shell zeolites were investigated by analyzing the products obtained with different secondary crystallization times and temperatures. The core-shell zeolite shows good shape-selective catalytic performance for converting methanol to aromatic compounds.