UV-raman and NMR spectroscopic studies on the crystallization of zeolite A and a New Synthetic Route

Limin Ren, Caijin Lie, Fengtao Fan, Qiang Guo, Desheng Liang, Zhaochi Feng, Can Li, Shougui Li, Feng Shou Xiao

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44 Scopus citations

Abstract

UV-Raman and NMR spectroscopy, combined with other techniques, have been used to characterize crystallization of zeolite A. In situ UV-Raman spectroscopy shows that the starting gel for crystallization of zeolite A contains a lot of four-ring (4R) building units and the appearance of six-ring (6R) building blocks is the signal for crystal formation. 29Si NMR spectroscopy results suggest that the starting gel is double four-ring (D4R) rich and during crystallization of zeolite A both α and β cages appear. 27Al NMR spectroscopy results indicate the absence of Al (2Si) species in the starting gel, suggesting the absence of single 4R building units in the starting gel. Furthermore, composition analysis of both solid and liquid samples shows that the solid rather than liquid phase predominates for the crystallization of zeolite A. Therefore, it is proposed that the crystallization of zeolite A mainly occurs in the solid phase by self-assembly or rearrangement starting from the zeolite building units mainly consisting of D4R. The essential role of D4R is directly confirmed by successful conversion from a solution of D4R to zeolite A in the presence of NaCl, and the importance of solid phase is reasonably demonstrated by the successful synthesis of zeolite A from a dry aluminosilicate gel. By considering that the solid phase has a major contribution to crystallization, a novel route was designed to synthesizing zeolite A from the raw materials water glass (Na2SiO3 in aqueous solution) and NaAlO2, without additional water and NaOH; this route not only simplifies synthetic procedures, but reduces water consumption.

Original languageEnglish (US)
Pages (from-to)6162-6169
Number of pages8
JournalChemistry - A European Journal
Volume17
Issue number22
DOIs
StatePublished - May 23 2011

Keywords

  • NMR spectroscopy
  • UV-Raman spectroscopy
  • crystal growth
  • synthesis design
  • zeolites

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