Synthesis of ZSM-5 via organotemplate-free and dry gel conversion method: Investigating the effects of experimental parameters.

ZSM-5 zeolite was successfully synthesized in an organic template-free system by a dry gel conversion (DGC) method. The influence factors, such as crystallization temperature, crystallization time, water content in the autoclave and the SiO 2 /Al 2 O 3 molar ratio in the dry gel, have been investigated systematically. A series of DGC-ZSM-5 zeolites were characterized by XRD, SEM, XRF, BET and NH 3 -TPD. The results showed that the high crystallinity of ZSM-5 could be obtained without organic template. The content of water in the autoclave and the SiO 2 /Al 2 O 3 molar ratio have a significant effect on the crystallinity and purity of DGC-ZSM-5. Furthermore, a possible formation mechanism was proposed based on the investigation of the crystallization process. Compared with the zeolite synthesized by hydrothermal method, the DGC-ZSM-5 zeolite not only exhibits much shorter crystallization time and smaller particle size, but also retains the synthesis gel SiO 2 /Al 2 O 3 molar ratio in the final materials. The crystallization process of ZSM-5 zeolite by a dry gel conversion method. Image 1 • Highly crystalline ZSM-5 was prepared without any organic template by a DGC method. • The prepared ZSM-5 zeolite needs shorter crystallization time. • The prepared ZSM-5 zeolite has higher acidic sites and smaller particle sizes. • External bulk water in the autoclave plays a crucial role in crystallization process. [ABSTRACT FROM AUTHOR]