Accelerating Zeolite Crystallization under High External Hydrostatic Pressure

Abstract

Hydrostatic pressure, an often-overlooked parameter in the hydrothermal synthesis of zeolite, has been shown to influence crystallization significantly. This study systematically investigates the role of external hydrostatic pressure on the synthesis of two aluminosilicate zeolites: (1) MFI-type zeolites from clear and milky solutions and (2) FAU-type zeolites from an amorphous aluminosilicate precursor. Applying external hydrostatic pressure significantly accelerates zeolite formation in both systems. Utilizing a two-step heating protocol under autogenous conditions and high hydrostatic pressures (200 MPa for MFI and 800 MPa for FAU), we demonstrate that pressure application during the early synthesis stages dramatically enhances nucleation frequency. This leads to faster crystallization and smaller, more uniformly distributed crystals. Furthermore, the findings reveal the potential of hydrostatic pressure to control critical material properties, including crystal size, crystallinity, and nucleation frequency. By elucidating these effects, this study advances the fundamental understanding of zeolite crystallization mechanisms and provides more tools for the rational design of customized zeolites for catalytic and other applications.