Kinetic analysis of crystallization of zeolite beta synthesized by direct heating

To quantitatively investigate the initial crystallization of zeolite beta synthesized by direct heating, the extent of the reaction was precisely evaluated by X-ray diffraction measurements and Rietveld structural refinement, and a kinetic analysis of crystallization was performed using the Avrami-Erofe'ev equation. The activation energy for crystallization was lower than that for hydrothermal synthesis. Reaction and synthesis time curves revealed that the initial zeolite beta crystallization consisted of three stages. The first was an induction period with nucleation by the generation of building units and the formation of an initial coordinated structure. The second stage was crystal growth by a diffusion-controlled reaction, and the third stage involved slowing down of crystallization by the limitation of dehydrocondensation. These stages could be analyzed by calculation of the rate constant and Avrami exponent for each stage.

Automated summary

In this study, the initial crystallization of zeolite beta synthesized by direct heating was quantitatively investigated using X-ray diffraction and Rietveld structural refinement, along with a kinetic analysis using the Avrami-Erofe'ev equation. The activation energy for crystallization was found to be lower than that for hydrothermal synthesis. The crystallization process of zeolite beta was identified to consist of three stages: induction period with nucleation, crystal growth by diffusion-controlled reaction, and slowing down of crystallization due to dehydrocondensation limitation.