Effects of Synthesis Parameters on Organic Template-Free Preparation of Zeolite Y

Abstract

In this work, the effects of reaction conditions on the conventional hydrothermal synthesis and crystal growth kinetics of zeolites Y in aqueous sodium alkaline solutions without the use of organic templates were studied. For this purpose, a series of Y-type zeolites were synthesized at different reaction conditions such as various aging temperatures, crystallization temperatures, Na₂O contents of the initial gel and crystallization times using hydrothermal process. The prepared samples were well characterized by the X-ray diffraction (XRD) and N₂ adsorption–desorption techniques. The results prove that the Na₂O contents of the initial gel and synthesis temperature increase the rate of the Y and P zeolite crystallization. The effect of Na₂O and temperature on the synthesis of two different zeolite types (Y and P) with a constant initial synthetic composition under the organic template-free synthesis of zeolite Y was studied. In inappropriate conditions, the P-type zeolite was the major impurity obtained along with the Y-type zeolite. Also from the experimental results, the kinetic parameters for both zeolite Y and zeolite P were calculated. The kinetic study show that the activation energy for crystallization of both zeolites was enhanced by increasing the Na₂O content of the initial gel due to the structure-directing role of Na⁺ cation in the induction period and crystal growth step.