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

摘要

Time-resolved C-13, Na-23, Al-27, and Si-29 MAS NMR has been applied insitu for monitoring the hydrothermal synthesis of zeolite BEA. Isotopic labelling with Si-29 and C-13 isotopes has been used to follow the fate of siliceous species and structure directing agent (((CH3)-C-13-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.