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Phase selection controlled by sodium ions in the synthesis of FAU/LTA composite zeolite

By Shenglin Liu and Longya Xu Qingxia Wang Sujuan Xie Linyan Hu

Abstract

Zeolite faujasite (FAU), Linde type A (LTA) and FAU/LTA composite have been synthesized using tetramethylammonium cation (TMA +) as template, by adjusting only the concentration of Na + ions in the initial solution (1.00 Al2 O3 4.36 SiO2 : 2.39 (TMA)2 O : β Na2 O : 249.00H2 O). Na + ions alter the phase composition of the product more than TMA+ or OH− ions. When Na2 O concentration [Na2 O] increases from 0.024 to 0.168, the product gradually changes from pure FAU to pure LTA via the formation of FAU/LTA composite with increasing LTA fraction. Interestingly, the induction periods of FAU and LTA in the FAU/LTA composite zeolite ([Na2 O] is 0.072) are both 13 h, quite different from the induction periods of their individual pure phases—45 h for FAU and 4 h for LTA. During the crystallization, the LTA/(FAU + LTA) fraction in the composite zeolite decreases in a nearly linear fashion. Scanning electron microscopy, thermogravimetry and differential thermal analysis indicate some difference between the properties of the FAU/LTA composite zeolite and of the mechanical mixture

Topics: FAU, LTA, Composite zeolite, crystallization, sodium concentration, Materials of engineering and construction. Mechanics of materials, TA401-492, Electrical engineering. Electronics. Nuclear engineering, TK1-9971, Technology, T, DOAJ:Materials, DOAJ:Technology and Engineering, Biotechnology, TP248.13-248.65
Publisher: National Institute for Materials Science
Year: 2009
OAI identifier: oai:doaj.org/article:23a4d41892b94b1390d35e8fae1f0f9a
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