Fast synthesis of hierarchical nanosized pure Si-Beta zeolite via a steam-assisted conversion method

A hierarchical nanosized pure Si-Beta zeolite was firstly prepared via a micro-zone synchronous crystallization method by steam-assisted conversion taking inorganic silicon sources as raw material. Neither zeolite seeds nor fluoride mineralizing agent was required, only a bit of organic template agent (TEAOH/SiO2 = 0.05) was sufficient for constructing a self-sustaining plate-like nanosized aggregation with high surface area (631.09 m2/g) and pore volume (0.7 cm3/g) after 24 h period, much less than reported (TEAOH/SiO2≥0.54, 7–21 d). The pure Si-Beta zeolite also had a superior hydrophobicity than that of hydrothermal synthesis due to the advantage of micro-zone mass transfer. All the properties of resulting samples were investigated by comprehensive characterizations, including X-ray diffraction, scanning and transmission electron microscopy, nitrogen adsorption-desorption, water adsorption, Flourier transform infrared and solid state 29Si nuclear magnetic resonance. Importantly, a "micro-zone synchronous crystallization" mechanism was proposed to explain the formation of mesoporous structure and intrinsic micropores, so as to providing the theoretical guidance for one-step synthesis of hierarchical Beta and other zeolites.