Study of Pure-Silica ZSM-5 Zeolite Growth From Solutions

Si-ZSM-5 syntheses from transparent mixtures containing tetrapopylammonium hydroxide (TPAOH), tetraethylorthosilicate (TEOS) and water have been widely studied as a model system for understanding zeolite growth process. The simple composition and aqueous media of these mixtures facilitate the use of many in/exit situ techniques, including Light/ X-ray scattering, calorimetry, electron microscopy [1-6]. One finding from these investigations is the presence of silica nanoparticles (3-5nm) during the whole synthesis of ZSM-5 zeolite. However, definitive structure and role of these particles in zeolite formation is still not well understood. Another important yet unresolved question is how TPA cations interact with these silica precursor particles and ultimately direct zeolite phase. We will summarize our studies in quantification of these organic-inorganic interactions via Pulse-Field gradient NMR and scattering techniques. These results for a series of TPA-silica mixtures before and upon heating will provide several insights on zeolite formation directed by organic molecules. Reference

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