SOLID-STATE CRYSTALLIZATION PROCESS AND MECHANISM OF B-AL-ZSM-5 ZEOLITE

Solid-stare crystallization process and mechanism of B-Al-ZSM-5 zeolit e from a dry gel of B2O3 . Al2O3 . SiO2 in the mixture of ethylamine a nd water vapour were studied by B-11, Al-27, Si-29, C-13 MAS NMR, XRD and IR. The extranetwork trigonal BO3 units in the gel play an importa nt role in the process of crystallization. The change of chemical envi ronment around Al atoms is complicated in the process of crystallizati on. Octahedral Al-O groups existing in the intermediate products do no t appear in both the initial gel and final product. Silicon is mainly present as hydroxyl compounds, and the extrastructural Si-O groups det ected in the process of crystallization disappear alter complete cryst allization. Ethylamine plays the role of both template and reactant. I t acts with the boron-, aluminum-, and silicon-hydroxyls through hydro gen bonding and promotes the crystallization process. The relative cry stallinity of the final B-Al-ZSM-5 product is about 93% as measured wi th B-11 MAS NMR and IR.