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Indexed by:期刊论文

Date of Publication:2013-12-01

Journal:MATERIALS CHARACTERIZATION

Included Journals:SCIE、EI、Scopus

Volume:86

Page Number:221-231

ISSN No.:1044-5803

Key Words:Zeolite NaY; Zeolite ANA; Zeolite SOD; Phase transformation; UV Raman

Abstract:The phase transformation mechanism of zeolite NaY under alkaline hydrothermal conditions was investigated by UV Raman spectroscopy, X-ray diffraction,. X-ray fluorescence and scanning electron microscopy techniques. The results revealed that the products and transformation rate are dependent on the alkalinities. All of the starting and resulting zeolites are constructed with the 4-ring and 6-ring secondary building units. The products have lower Si/Al ratio, higher framework density and smaller pore size, which are more stable under alkaline hydrothermal condition. During the phase transformation the fragments of faujasite are formed, then the fragments combine to form different zeolites depending on basicity. Zeolite NaY crystals are consumed as the reservoir for the transformation products during the recrystallization process. For the first time, a 4-membered ring intermediate was found at the early stage of the recrystallization process. A cooperative interaction of liquid and solid phases is required for inducing the phase transformation. (C) 2013 Elsevier Inc. All rights reserved.