Plate-like MFI crystal growth achieved by guanidine compounds

Abstract

Plate-like MFI zeolite with a short b-axis length is highly desired for industrial applications, because the larger straight channels along the b-axis are a primary pathway for mass transfer. This work reports that guanidine compounds, such as tetramethylguanidine (TMG), dodecylguanidine hydrochloride (DGH), and polyhexamethylene biguanidine hydrochloride (PHMB), are more efficient for synthesizing these types of zeolites, needing neither a greater amount of water nor a longer crystallization period. Because of the modifiers used, the zeolite crystals with a thickness of 75–110 nm were obtained by crystallizing the gel with an H₂O/SiO₂ mole ratio of 14 at 170 °C for 12 h. Moreover, the incorporation of Al and Ti into the ZSM-5 and TS-1 frameworks was also increased by the modifiers.