A Green and Efficient Synthesis of ZSM-5 Using NaY as Seed with Mother Liquid Recycling and in the Absence of Organic Template

A green and efficient route toward the synthesis of ZSM-5 is developed, which is characterized by using silica gel powder as silica source and NaY as seed, low synthesis H2O/SiO2 ratio, high zeolite yield, mother liquid recycling, and organic template free. ZSM-5 zeolite was synthesized with silica to alumina ratios from 30 to 70 under autogenous pressure using NaY as seed. By fine-tuning the chemical composition, ZSM-5 with high crystallinity was obtained. Compared with the conventional synthesis method using waterglass as silica source, this method considerably improves zeolite yield and silica source utilization. The synthesized samples were characterized by X-ray diffraction, nitrogen adsorption and desorption, scanning electron microscopy, X-ray fluorescence, NH3-temperature programmed desorption, and pyridine infrared spectrum analysis. Besides creating less waste, mother liquid recycling has a positive effect on crystallization rate and crystal morphology. Crystallization mechanisms for silica powder as silica source with and without mother liquid recycling were also discussed. Catalytic cracking results show that ZSM-5 prepared by this method is a promising catalytic material.