Investigation of the crystallization of zeolite A from hydrogels aged under high pressure

Abstract

This paper investigates the influence of the aging of zeolite A hydrogel under high pressure on the synthesis of zeolite A. The effects of the aging pressure, aging time and type of gas are examined. The products are characterized by scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. The results indicate that high-pressure aging leads to an increase in the nucleation rate, facilitating the formation of zeolite A with high crystallinity, small particle sizes and narrow particle size distribution. The type of gas also exerts an influence on the synthesis of zeolite A, as hydrogels aged under high pressure in a gas with a higher solubility in water can produce zeolite A with smaller particle sizes. Thus, by adjusting the aging pressure and the type of gas used, the size of the resulting zeolite A can be controlled. The mechanism of the high-pressure aging is related to the interaction of the gel with the dissolved gas. An influence of the aging of hydrogels on the syntheses of zeolite Y, silicalite-1 and SAPO-34 is also observed.