Time-resolved in situ MAS NMR monitoring of the nucleation and growth of zeolite BEA catalysts under hydrothermal conditions
Time-resolved 13C, 23Na, 27Al and 29Si MAS NMR has been applied in situ for monitoring the hydrothermal synthesis of zeolite BEA. Isotopic labelling with 29Si and 13C isotopes has been used to follow the fate of silicious species and structure directing agent ((13CH3-CH2)4NOH). Two mechanistic pathways, namely, solution mediated and solid-solid hydrogel rearrangement have been distinguished for two synthesis procedures studied. The mechanisms of structure directing behavior of TEA+ cations in two reaction pathways have been elucidated. The results show that multinuclear MAS NMR can serve as a superior tool for monitoring hydrothermal synthesis of various solids including zeolites, zeotypes, mesoporous materials, metal organic frameworks and etc. and for the design of novel outstanding materials for different applications.
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