title: Phase selection controlled by sodium ions in the synthesis of FAU/LTA composite zeolite.
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 Al2O34.36 SiO2: 2.39 (TMA)2O : β Na2O : 249.00H2O). Na+ions alter the phase composition of the product more than TMA+or OH-ions. When Na2O concentration [Na2O] 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 ([Na2O] 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.
authors.affiliation: State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People's Republic of China; Graduate University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
authors.forename: Linyan
authors.initials: L
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People's Republic of China.
authors.forename: Sujuan
authors.initials: S
authors.lastname: Xie
authors.affiliation: State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People's Republic of China.
authors.forename: Qingxia
authors.initials: Q
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People's Republic of China.
authors.forename: Shenglin
authors.initials: S
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, People's Republic of China.
authors.forename: Longya
authors.initials: L
authors.lastname: Xu
keywords: Composite zeolite; FAU; LTA; crystallization; sodium concentration