Abstract: Synthesis of low-silica zeolite DFT and GIS were conducted with ethylene diamine as liquid phase and fluoride ion as mineralizing agent.Factors that affect the crystallization of low-silica zeolites,such as the dosage of hydrofluoric acid (HF) and mole ratio n(SiO₂)/n(Al₂O₃),were examined.Results showed that suitable molar compositions of the solid phase gels for low-silica zeolites DFT and GIS are n(HF)∶n(SiO₂)∶n(Al₂O₃)∶n(H₂O)=0.5∶1.0∶0.5∶5.0 and n(HF)∶n(SiO₂)∶n(Al₂O₃)∶n(H₂O)=2.5∶1.0∶0.5∶5.0,respectively.The results of elemental analyses as well as TG analyses confirmed that di-protonated ethylene diamine plays structure-directing and negative charge-compensating roles in the formation of zeolites DFT and GIS.The results also showed that the HF concentration displays a remarkable influence on the product type.Lower dosage of HF is preferable to form zeolite DFT,while increasing of the dosage of HF is preferable to form zeolite GIS.

Key words: low-silica zeolite, synthesis, vapor phase