Accelerated Crystallization Kinetics of MFI Zeolite via Imidazolium-Based Synthesis

Abstract

Ionic liquids (ILs), known for their low melting points and vast array of possible combinations of cations and anions, serve as an ideal template for zeolite synthesis. MFI zeolite, with the distinct three-dimensional porous network, has attracted wide interest in petrochemical processes and environmental applications. In this study, we used 1-butyl-3-methylimidazolium (BMIM)-based ILs for MFI-type zeolite synthesis, successfully achieving a highly crystallized MFI-type crystal within 18 h. To highlight the benefits of using ILs, ZSM-5 zeolite synthesized using the conventional template, tetrapropylammonium hydroxide, was prepared for comparative analysis. Parameters including ion variations, aging duration, and aluminate content on crystal phase growth were explored. Furthermore, seed-assisted synthesis was carried out to verify the impact of the IL on the nucleation step. The mechanism underlying the accelerated crystallization process was subsequently elucidated, revealing that the inclusion of BMIM in the synthesis gel significantly contributed to rapid nucleation. This was followed by the immediate formation of amorphous particles. These particles then experienced inward growth, culminating in the development of well-crystallized particles. This discovery underscores the promising potential of ILs for efficient zeolite synthesis.