Inductive effect of various seeds on the organic template-free synthesis of zeolite ZSM-5

Abstract

A comprehensive investigation into the effect of seed on the crystallization of ZSM-5 in the absence of template was performed by introducing seeds with different frameworks and pore structures into the gel mixture. It was found that the crystallization behavior of template-free ZSM-5 was strongly governed by three key factors in a synergetic way. Firstly, the common composite building units contained in the seed and product zeolites crucially promoted the nucleation and subsequent crystal growth of target zeolites. Secondly, the terminal TOH units on the surface of seed crystals strengthened their recognition capacity to the composite units formed in systems, which significantly accelerated the crystallization process. Thirdly, the external surface area provided by seeds offered specific sites for composite building units to attach to and pile up to form new zeolitic layer. Thus, in this work, ZSM-5 or ZSM-11 zeolites with terminal TOH were viewed as the preferable seeds to induce the formation of ZSM-5 in a short period (12–16 h) without template addition and the crystal size could be easily controlled just by using seeds with different external surface area.