Understanding the Nucleation and Crystal Growth of Zeolites: A Case Study on the Crystallization of ZSM-5 from a Hydrogel System Under Ultrasonication

For the preparation of zeolites, ultrasonication is an efficient pretreatment that homogenizes the reactant mixture prior to hydrothermal synthesis. However, very few studies directly employ ultrasonication during hydrothermal synthesis, and the effect of ultrasonication on zeolite crystallization has not been fully understood yet. Herein, we report the crystallization behavior of ZSM-5 zeolite in the presence of ultrasonication. We demonstrated that the crystallization time decreases with the irradiation power (97, 194, and 323 W), while the irradiation power also regulates the nucleation and crystal growth of ZSM-5 to produce crystals with different sizes. To understand the role of ultrasonication, the evolution of aluminosilicate particles was investigated in terms of morphology, compositions, and structural information. During the induction period, the incorporation of organic cations to the solid phase, which is essential to the nucleation of ZSM-5 in this system, was enhanced under 323 W irradiation. In addition, a relatively uniform fusion behavior of the aluminosilicate particles was observed in the ultrasonic system, which produced an abundance of tiny crystals. Finally, it was shown that the enhanced crystal growth rate under ultrasonication was possibly due to the increased amount of silanol groups on the crystal surface, which facilitated the condensation between aluminosilicate species.