Platelike MFI Crystals with Controlled Crystal Faces Aspect Ratio

Zeolite crystals offering a short diffusion pathway through the pore network are highly desired for a number of catalytic and molecule separation applications. Herein, we develop a simple synthetic strategy toward reducing the thickness along the b-axis of MFI-type crystals, thus providing a short diffusion path along the straight channel. Our approach combines preliminary aging and a fluoride-assisted low-temperature crystallization. The synthesized MFI crystals are in the micrometer-size range along the a- and c-axis, while the thickness along the b-axis is a few tens of nanometers. The synthesis parameters controlling the formation of platelike zeolite are studied, and the factors controlling the zeolite growth are identified. The synthesis strategy works equally well with all-silica MFI (silicalite-1) and its Al- and Ga-containing derivatives. The catalytic activity of platelike ZSM-5 in the methanol-to-hydrocarbons (MTH) reaction is compared with a commercial nanosized ZSM-5 sample, as the platelike ZSM-5 exhibits a substantially extended lifetime. The synthesis of platelike MFI crystals is successfully scaled up to a kilogram scale.

Automated summary

A simple synthetic strategy was developed to reduce the thickness of zeolite crystals along the b-axis, providing a short diffusion path along the straight channel. The synthesized MFI crystals, with micrometer-size along the a- and c-axis and thickness in the tens of nanometers along the b-axis, showed good catalytic activity in the methanol-to-hydrocarbons reaction. The synthesis of platelike MFI crystals was successfully scaled up to a kilogram scale, demonstrating extended catalytic lifetime compared to commercial nanosized samples.