Facile Synthesis of Size-Controlled ZSM-22 Zeolite along the [001] Direction via Two-Step Crystallization

A facile method was developed to precisely control the particle size of nanosized ZSM-22 zeolite with a range of 80–850 nm via a two-step crystallization procedure. Based on the ZSM-22 crystallization process, inhibiting or promoting the crystal growth and the fusion of nanocrystals are crucial to obtain specific sized ZSM-22. For this purpose, the crystallization process of ZSM-22 was quenched after 12 h to obtain abundantly viable ZSM-22 nanocrystals formed on the aluminosilicate amorphous particles. In the recrystallization process, the viable nanocrystals continued to crystallize and the dissolved amorphous particles released Si and Al species as nutrients. After further simplifying the procedures, some additives were used at the very beginning of the recrystallization procedure. Not only small crystals can be formed but also the crystal length of ZSM-22 along the [001] direction varies from 80 to 850 nm. We have systematically investigated the influencing factors such as alkali metal cations and the alkalinity of the synthesis system on the mechanism of ZSM-22 zeolite nucleation and growth and the morphology and yield of products. We report a facile synthetic route for size-controlled nanosized ZSM-22 by decoupling its nucleation and growth processes for the first time.