Chinese Journal of Catalysis ›› 2012, Vol. 33 ›› Issue (8): 1290-1298.DOI: 10.1016/S1872-2067(11)60400-2

• Research papers • Previous Articles     Next Articles

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

HUANG Xianliang, ZHANG Rongrong, WANG Zhengbao*   

  1. Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, Zhejiang, China
  • Received:2012-02-22 Revised:2012-04-12 Online:2012-08-01 Published:2012-08-01

Abstract: Zeolite crystals were synthesized at a lower temperature (150 °C) by adding a nucleation solution prepared at higher temperature (190 °C) 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: 12SO42-: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 °C) could be transformed into mordenite crystals during crystallization at lower temperature (150 °C). When the Na2O/SiO2 ratio was ≤ 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 ≤ 30%.

Key words: ZSM-5 zeolite, template-free, mordenite, crystal transformation, controlling