Synthesis of nanosized Silicalite-1 in F−media

• Nanosized Silicalite-1 with high crystallinity was synthesized in fluoride media.
• Fluorine source, F/SiO2 ratio, reaction condition and silica source were studied.
• Content of Si–OH in the surface of silica source affects the size and crystallinity.

This paper reports on the successful crystallization of monodisperse, highly crystalline, nanosized zeolite Silicalite-1 crystals in fluoride media by using an active silica gel as silica source and tetrapropylammonium fluoride as structure directing agent. The synthesis procedure is hydrothermal dynamic crystallization. The silica/water ratio and synthesis temperature were reduced to optimize the number of crystal nuclei and control the rate of crystallization for obtaining nanosized zeolite crystals. Meanwhile, F− ions were used to partly replace OH− ions in the synthesis system to obtain zeolite products with high crystallinity. Analytical results of XRD-, SEM-, Dynamic Light Scanning- (DLS) IR-, Simultaneous Thermal Analysis- (STA) and N2 adsorption and desorption experiments show that the average particle size of zeolite Silicalite-1 product is about 45 nm and shows high crystallinity. The F− containing Silicalite-1 zeolite sample was compared with an industrial ZSM-5 zeolite sample and it shows obvious advantages in both reduced particle size and enhanced crystallinity.

A nanosized F-containing Silicalite-1 zeolite with high crystallinity and high thermal stability was synthesized by dynamic hydrothermal synthesis and the main factor was the concentration of Si–OH in the surface of silica source.Figure optionsDownload as PowerPoint slide