Abstract: 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.

Key words: FAU, zeolite, adsorption, aromatics