Controlling Crystal Transformation between Zeolite ZSM-5 and Mordenite without Organic Structure-Directing Agent

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• 作者：Xianliang HUANG ; Rongrong ZHANG ; Zhengbao WANG
• 关键词：ZSM-5 zeolite ; template-free ; mordenite ; crystal transformation ; controlling
• 刊名：Chinese Journal of Catalysis
• 出版年：2012
• 出版时间：July-August, 2012
• 年：2012
• 卷：33
• 期：7-8
• 页码：1290-1298
• 全文大小：697 K

文摘

Zeolite crystals were synthesized at a lower temperature (150¡ãC) by adding a nucleation solution prepared at higher temperature (190¡ãC) to the mother solution. The effects of the Na₂O/SiO₂ ratio, nucleation time of the nucleation solution, and the ratio of Na₂O/SiO₂ ratio in the mother solution on crystal transformation between ZSM-5 and mordenite were investigated. The transformation between zeolite ZSM-5 and mordenite could be controlled effectively by changing the overall Na₂O/SiO₂ ratio in the overall solution. A Na₂O/SiO₂ ratio of 0.18 formed a boundary between ZSM-5 and mordenite phases when the overall solution had a composition of xNa₂O:100SiO₂:2.5Al₂O₃:12SO₄^2?:4000H₂O. When the Na₂O/SiO₂ ratio was increased higher than 0.18 by altering the composition of the mother solution, the ZSM-5 product formed by nucleation at higher temperature (190¡ãC) could be transformed into mordenite crystals during crystallization at lower temperature (150¡ãC). When the Na₂O/SiO₂ ratio was ¡Ü 0.18, a product containing both ZSM-5 and mordenite crystals was obtained during nucleation at higher temperature that could be transformed into ZSM-5 crystals during crystallization at lower temperature. A precondition for crystal transformation between ZSM-5 and mordenite was that the crystallinity of the product formed during nucleation at higher temperature must be ¡Ü 30 % .