Synthesis and application of colloidal nanocrystals of the MFI-type zeolites

The colloidal dispersion containing the nanosized zeolites with the MFI topology has been successfully prepared. A pre-aging process of the mother gel at 80 °C for 24 h before the crystallization was important for the formation of the nanosized zeolites. We have also found that silicalite-1 nanocrystals av. 62 nm in size were formed by the addition of acidic amino acids into the mother gel. The particle size of the zeolites can be controlled ranging from 62 to 530 nm by changing the amount of water, aging process, crystallization time and temperature and the addition of organic molecules. Furthermore, nanosized titanium silicalite-1 (TS-1) with the size of 50–130 nm has been successfully synthesized by the addition of a Ti source into the synthesis gel of the silicalite-1 nanocrystals. The nanosized TS-1 exhibits a higher catalytic activity in the epoxidation of cyclohexene than the microsized ones. Finally, we demonstrate the preparation of thin films of the silicalite-1 and TS-1 nanocrystals onto a silicon substrate by a dip-coating technique.

Graphical abstractThe colloidal dispersion containing the nanosized zeolites with the MFI topology including silicalite-1 av. 62 nm in size and TS-1 av. 100 nm in size, has been successfully prepared. Fabrication of the multilayer and monolayer films of silicalite-1 and TS-1 nanocrystals has also been attained by a dip-coating technique using the colloidal dispersion of the nanosized zeolites.Figure optionsDownload full-size imageDownload high-quality image (62 K)Download as PowerPoint slideResearch highlights► Colloidal nanocrystals of silicalite-1 av. 62 nm in size and TS-1 av. 100 nm in size were successfully prepared. ► Te TS-1 nanocrystals showed a higher catalytic activity in the epoxidation of cyclohexene than micro-sized TS-1. ► Multilayer and monolayer films of the silicalite-1 and TS-1 nanocrystals were also prepared.