Abstract: High purity zeolite ZSM-5 was synthesized by two-step method with coal fly ash pretreated by alkaline fusion and centrifugal extraction and hydrothermal method, the effects of alkali/ash and roasting temperature on the quantity of silicon aluminium dissolution were discussed, the influences of alkalinity, crystallization time, crystallization temperature and the Si/Al ratio on synthesis of zeolites were investigated.The results show that the highest silicon aluminium dissolution quantity obtained at 680 ℃, alkali/ash=2.3 and the high purity ZSM-5 zeolite synthesized at SiO2/Na2O=7, SiO2/Al2O3=45, crystallization time of 68 h and crystallization temperature of 180 ℃.

Key words: High purity zeolite ZSM-5 was synthesized by two-step method with coal fly ash pretreated by alkaline fusion and centrifugal extraction and hydrothermal method, the effects of alkali/ash and roasting temperature on the quantity of silicon aluminium dissolution were discussed, the influences of alkalinity, crystallization time, crystallization temperature and the Si/Al ratio on synthesis of zeolites were investigated.The results show that the highest silicon aluminium dissolution quantity obtained at 680 ℃, alkali/ash=2.3 and the high purity ZSM-5 zeolite synthesized at SiO2/Na2O=7, SiO2/Al2O3=45, crystallization time of 68 h and crystallization temperature of 180 ℃.