低硅X分子筛的合成研究

为了合成结晶度较高的纯低硅X分子筛，系统研究了合成体系的硅铝比n(SiO₂)/n(Al₂O₃)]、碱硅比n(Na₂O+K₂O)/n(SiO₂)]、水碱比n(H₂O)/n(Na₂O+K₂O)]、钾碱比n(K₂O)/n(Na₂O+K₂O)]及老化温度、晶化温度对产物性质的影响规律，采用X射线衍射、甲苯动态吸附、X射线荧光光谱、固体核磁共振、扫描电镜对产物进行表征。结果表明：随着合成体系硅铝比、碱硅比、水碱比、钾碱比、老化温度、晶化温度的升高，所得低硅X分子筛的结晶度和合成产物的甲苯吸附容量均呈先升高后降低趋势；合成体系优选的硅铝比为2.05、碱硅比为3.25、水碱比为17、钾碱比为0.23、老化温度为50~80 ℃、晶化温度为95 ℃，所得低硅X分子筛的形貌为0.5~1.5 μm晶粒聚集的球体，硅铝比为2.0，不含非骨架铝。

SYNTHESIS OF X ZEOLITE WITH LOW SILICA TO ALUMINA RATIO

In order to synthesize pure low silicon X zeolite with high crystallinity, the effects of n(SiO₂)/n(Al₂O₃), n(Na₂O+K₂O)/n(SiO₂),n(H₂O)/n(Na₂O+K₂O)and n(K₂O)/n(Na₂O+K₂O) as well as aging and crystallization temperature on the properties of the products were systematically investigated. The products were characterized by X-ray diffraction, dynamic adsorption of toluene, X-ray fluorescence spectrum, solid state nuclear magnetic resonance, and scanning electron microscopy. The results showed that with the increase of n(SiO₂)/n(Al₂O₃),n(Na₂O+K₂O)/n(SiO₂),n(H₂O)/n(Na₂O+K₂O)，n(K₂O)/n(Na₂O+K₂O), aging temperature and crystallization temperature, the crystallinity and toluene adsorptive capacity of the synthesized low silicon X zeolite was increased firstly and then decreased. Under the optimum conditions covering a n(SiO₂)/n(Al₂O₃) of 2.05, a n(Na₂O+K₂O)/n(SiO₂) of 3.25, a n(H₂O)/n(Na₂O+K₂O) of 17, a n(K₂O)/n(Na₂O+K₂O) of 0.23, an aging temperature of 50－80 °C, and a crystallization temperature of 95 °C, the low silicon X zeolite with high crystallinity degree can be obtained. The low silicon X zeolite with a n(SiO₂)/n(Al₂O₃)of 2.0 without non-framework Al, shows sphere morphorology with a diameter of 0.5－1.5 μm.