Solid-state crystallization process and mechanism of B-Al-ZSM-5 zeolite *

Solid-state crystallization process and mechanism of B-Al-ZSM-5 zeolite from a dry gel of B2O3. A12O3 • SiO2 in the mixture of ethylamine and water vapour were studied by11B,27Al,29Si,13C MAS NMR, XRD and IR. The extranetwork trigonal BO3 units in the gel play an important role in the process of crystallization. The change of chemical environment around Al atoms is complicated in the process of crystallization. Octahedral Al-O groups existing in the intermediate products do not appear in both the initial gel and final product. Silicon is mainly present as hydroxyl compounds, and the extrastructural Si-O groups detected in the process of crystallization disappear after complete crystallization. Ethylamine plays the role of both template and reactant. It acts with the boron-, aluminum-, and silicon-hydroxyls through hydrogen bonding and promotes the crystallization process. The relative crystallinity of the final & A1-ZSM-5 product is about 93% as measured with11B MAS NMR and IR.