Abstract: The crystal transformation among ZSM-5, ZSM-57, and mordenite was studied under different conditions, such as SiO2/Al2O3 molar ratio, alkalinity, n-butylamine template, crystallization time, and temperature. The results showed that higher alkalinity and longer crystallization time were of benefit to mordenite; lower alkalinity and higher induction temperature of crystallization were in favor of ZSM-57 with low n(SiO2)/n(Al2O3) ratio; alkalinity was required to be adjusted accurately to synthesize ZSM-5 with low n(SiO2)/n(Al2O3) ratio, shortening of crystallization time, decrease in induction temperature of crystallization, and the addition of seed crystal were all in favor of ZSM-5 with low n(SiO2)/n(Al2O3) ratio. A slight change in the above conditions would result in the transformation among the three crystals, and two or more crystal phases could be observed in the products.

Key words: Zeolite ZSM-5, Zeolite ZSM-57, Mordenite, Crystal transformation