Synthesis and catalytic performance of a small crystal NaY zeolite with high SiO₂/Al₂O₃ ratio

Abstract

A small crystal NaY zeolite with a high SiO₂/Al₂O₃ ratio was successfully synthesized with seeding and without organic template, and the effects of the silicon source, aging time and Na₂O seeding content on the crystal size of NaY zeolite were investigated. The synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier-Transform Infrared (FT-IR) spectroscopy and N₂ adsorption-desorption. The results showed that the silicon source used to prepare seeding had a great effect on the crystal size of NaY zeolite, NaY zeolite with average size of 100 nm and SiO₂/Al₂O₃ ratio of 5.42 was obtained by using the seeding prepared with silica sol. Moreover, the crystal size of NaY zeolite decreased with an extension of the aging time and an increase of the Na₂O content of seeding. The catalytic performance of small crystal Y zeolite was evaluated in the hydrocracking of vacuum gas oil (VGO), the catalyst with smaller crystal Y zeolite presented higher VGO conversion and middle distillates selectivity than those with larger ones due to its higher surface area and more amount of mesoporous.