Characterization of nanosized material extracted from clear suspensions for MFI zeolite synthesis

The silica species contained in an aged clear suspension, which upon heatin g gives rise to the crystallization of Silicalite-l, were extracted with 80 % efficiency using a sequence of acidification, salting out, phase transfer into organic solvent, and freeze-drying methods. This silica powder was ch aracterized by X-ray scattering, transmission electron microscopy, atomic f orce microscopy, and Si-29 magic angle spinning nuclear magnetic resonance. These techniques gave evidence for the presence of a very specific morphol ogy, corresponding to slab shaped particles, with dimensions of 1.3 x 4.0 x 3.0 nm. The nanoslabs have the MFI structure with nine channel intersectio ns per particle, each containing a TPA cation. The identity of the extracte d nanoslabs with the species in suspension is evidenced with in situ and ex situ X-ray scattering.