Accelerated crystallization of zeolites via hydroxyl free radicals

In the hydrothermal crystallization of zeolites from basic media, hydroxide ions (OH-) catalyze the depolymerization of the aluminosilicate gel by breaking the Si, Al-O-Si, Al bonds and catalyze the polymerization of the aluminosilicate anions around the hydrated cation species by remaking the Si, Al-O-Si, Al bonds. We report that hydroxyl free radicals (center dot OH) are involved in the zeolite crystallization under hydrothermal conditions. The crystallization processes of zeolites-such as Na-A, Na-X, NaZ-21, and silicalite-1-can be accelerated with hydroxyl free radicals generated by ultraviolet irradiation or Fenton's reagent.