Kinetic study of the crystallization of ZSM-5 under organic template-free conditions

Abstract

Here, the ZSM-5 zeolite was prepared under organic template-free conditions at different reaction temperatures and initial gel compositions using a hydrothermal process. A kinetic study of the synthesis of Zeolite was performed based on crystal growth. The crystallinity degree of the prepared samples was calculated from the PXRD and FT-IR results and then the crystallization curves were obtained. From these curves, the kinetic parameters were computed. The obtained results showed that by increasing the Na⁺ content of the initial gel composition, the activation energy for the crystal growth was reduced and as a result, the crystallization rate of ZSM-5 zeolite was enhanced due to the structure-directing role of Na⁺ cation. The activation energy of the induction step, transition step and crystal growth step are 122.8, 46.2, and 48.5 kJ/mol respectively for the molar ratios of 29Na₂O:63SiO₂:Al₂O₃:2400H₂O:16H₂SO₄ and 141.0, 70.4, and 80.8 kJ/mol respectively for the molar ratios of 16Na₂O:31SiO₂:Al₂O₃:2400H₂O:16H₂SO₄.

Keywords:

• Crystal growth
• hydrothermal process
• kinetic study
• template-free synthesis
• ZSM-5

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors of this work appreciate the financial support of the Iran National Science Foundation (INSF) (Project No.: 97003551).