(403f) Template-Free Synthesis of Porous Zeolite NaY Particles with Hierarchical Nanostructures and Controllable Sizes

Hierarchical porous particles aggregated from primary Na-form zeolite Y nanocrystals were hydrothermally synthesized using a three-stage variable-temperature program without adding any organic additives, pore-generating agents and seeding crystals. The as-synthesized samples were characterized using powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray spectrometer (EDXS), Nitrogen sorption, particle size analysis and Fourier-Transform Infrared (FT-IR) spectroscopy. The significantly broadened diffraction peaks associated with FAU structure indicated that primary crystals were very small. SEM images showed that the zeolite particles are composed of very uniform zeolite NaY nanocrystals in the size range of 20-80 nm. TEM investigation revealed the intergrowth and random packing characteristics of the primary zeolite NaY nanocrystals. FAU structure of the as-synthesized samples was further conformed by FT-IR results. Interestingly, the particle sizes of the aggregates could be easily controlled by varying the alkalinity of the precursor without afterwards notably changing the primary sizes of zeolite NaY nanocrystals. Nitrogen sorption results showed the zeolite aggregates have microporosity and meso/macroporosity, and have large surface area arising from primary zeolite NaY nanocrystals. The hierarchical porous zeolite particles are mechanically strong, and they remain intact after ultrasonication for several hours.