Synthesis of MFI zeolites with improved crystallization rate and mesoporosity in the presence of CO 2-in-water emulsions

Abstract

In this work, we demonstrate a novel and efficient route for fast crystallization of MFI zeolites of silicalite-1 and ZSM-5 with enhanced silica condensation in the presence of CO 2-in-water microemulsions. Compared to the conventional synthesis method, this new technique needs a very short time for the crystallization of MFI zeolites (4–8 h) in the presence of compressed CO 2. Furthermore, the synthesis of MFI zeolites containing mesoporosity (mesoporous MFI zeolites) under compressed CO 2 condition does not require any organotemplate, which is of great economic importance to industrial application. Interestingly, ZSM-5 synthesized in the presence of compressed CO 2 possessed uniform chain-like crystal morphology, while silicalite-1 synthesized in the presence of compressed CO 2 exhibited monodispersed crystals as characterized by scanning electron microscopy (SEM). We have extended the CO 2-in-water microemulsions route to synthesize other zeolites such as TS-1, Beta and Y. This newly developed method opens a new avenue for the fast synthesis of template-free mesoporous zeolites.