Time-Resolved In Situ MAS NMR Monitoring of the Nucleation and Growth of Zeolite BEA Catalysts under Hydrothermal Conditions.

Time-resolved 13 C, 23 Na, 27 Al, and 29 Si MAS NMR has been applied in situ for monitoring the hydrothermal synthesis of zeolite BEA. Isotopic labelling with 29 Si and 13 C isotopes has been used to follow the fate of siliceous species and structure directing agent ((13 CH3 -CH2 )4 NOH). 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 so on and for the design of novel outstanding materials for different applications.