A Bubbling Reactor Technology for Rapid Synthesis of Uniform, Small MFI-Type Zeolite Crystals

MFI-type zeolite is one important family of materials used in today’s industries as catalysts and adsorbents. Preparation of this type of zeolite material as uniform and pure crystals of sizes from tens of nanometer to hundred nanometer are not only desired by current catalytic and adsorption processes with enhanced reaction kinetics and/or selectivity, but also much needed by some new applications, such as CO2 capture and composite materials. However, it has been a major challenge in the zeolite synthesis field to prepare small crystals of MFI-type zeolite over a range of Si/Al ratio with very high throughput. In this work, a gas-bubbling flow reactor is used to conduct hydrothermal growth of the zeolite crystals with fully controllable Si/Al ratio and crystal sizes. Distinctive, uniform ZSM-5 crystals are successfully synthesized within two hours of reaction time, exceptionally short compared to the conventional synthesis process. The crystals are small enough to form a stable milk-like suspension in water. The Si/Al ratio can be controlled by adjusting the growth solution and conditions over a range from about 9 to infinity. Characterization of the prepared ZSM-5 by SEM/EDS, XRD, TEM, N2 adsorption/desorption, and NMR shows some interesting properties.