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Spatial and temporal study of zeolite formation

In this study the crystal growth kinetics of EMT type zeolite from an organic-template free system was investigated in detail by methods that provide short and long range structural information. TEM study revealed that the initial gel particles exhibit a core–shell structure. The core is abundant in mesopores with mother liquor trapped inside. The aluminosilicate shell is dense, impermeable to fluids, and contains a few mesocavities. Our findings clearly demonstrate that the inception of zeolite nucleation is occurring in the shell of the gel particles, at extremely thin surface zone. Hence, the external surface area of the primary gel particles is of vital importance in the nucleation process and directs the overall kinetics of zeolite formation. The main finding of the presented results is that zeolite properties, such as size and level of aggregation, can be controlled by proper engineering of the initial gel particles. The mechanism observed in the crystallization of EMT-type zeolite could be generalized for aluminosilicate zeolites formed from alkali-metal-rich hydrogel systems.

zeolite; nucleation; core-shell; amorphous phase

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