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Contribution to Understanding the Mechanism of SDA-Free, Seed-Induced Synthesis of Sub-Micrometer Sized ZSM-5 Zeolites

The seed-induced crystallization system has been adopted for the synthesis of sub-micrometer sized zeolite ZSM-5 in the absence of organic structure directing agent (SDA). The structural (phase purity), particulate (sizes and morphology) and chemical compositions (framework Si/Al ratios) of the crystalline end products could be well controlled via the batch alkalinity, excess of sodium ions, and aging of the reaction mixtures. More importantly, the crystallization mechanism has also been revealed as a typical linear, size-independent growth process on the surface of silicalite-1 seed nanocrystals embedded in the gel matrix without the formation of new nuclei either on the surface of growing seed crystals or in the gel matrix. The critical processes happened during crystallization have also been characterized by different methods and evaluated by population balance modeling approach.

Zeolite ZSM-5; Sub-micrometer sized; Crystallization; SDA-free; Seed-induced

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