Preparation of NaY membrane in fluorine containing system

NaY zeolite membrane with high pervaporation performance was synthesized in fluorine containing system by the method of secondary hydrothermal growth. The crystallization of NaY zeolite and the pervaporation performance of NaY membrane synthesized in fluorine containing system were compared with those synthesized in fluorine-free system. Crystallization time and n(SiO₂)/n(Al₂O₃) of the system were also optimized. The as-synthesized NaY zeolite layers were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The results showed that the addition of NH₄F in synthesis system suppressed the formation of P-type zeolite, which was bedded in the zeolite membrane as the impurity phase. Five NaY zeolite membranes prepared under optimized synthesis conditions of n(SiO₂)/n(Al₂O₃) of 25, crystallization time of 6.5 h, showed a high average flux of (5.3±0.3) kg/(m²·h) and a good average separation factor of 63±3 for a mixture of water and ethanol with the mass ratio of 10/90 at 75°C, which were higher than those of NaY zeolite membranes prepared in fluorine-free system.