NMR Evidence for Specific Germanium Siting in IM-12 Zeolite - Université Claude Bernard Lyon 1 Accéder directement au contenu
Article Dans Une Revue Chemistry of Materials Année : 2014

NMR Evidence for Specific Germanium Siting in IM-12 Zeolite

N. Kasian
  • Fonction : Auteur
A. Tuel
E. Verheyen
  • Fonction : Auteur
C. E. A. Kirschhock
  • Fonction : Auteur
F. Taulelle
  • Fonction : Auteur
J. A. Martens
  • Fonction : Auteur

Résumé

Ge-rich ITQ-13 and ITQ-22 zeolites were degermanated by acid leaching of as-made still containing organic template and calcined forms. These two zeolites could be almost completely degermanated without modifying the framework structure. This behavior is different from IM-12 zeolite, which undergoes framework transformation from UTL to OKO type upon degermanation. All three zeolite types contain double four-ring (D4R) units populated by germanium atoms. The UTL to OKO transformation involves the elimination of Germanate 4 rings (Ge 4R) from double four-ring (D4R) units connecting the layers. The differences of Si and Ge atom siting in D4R units in the three zeolites were probed using F-19 MAS NMR after post synthetic incorporation of fluoride and H-1-Si-29 CP/MAS NMR. In IM-12, NMR suggests that Ge atoms are all located in one of the faces of D4R units and form 4Rs that connect Si-rich layers together. In the degermanation process, the 4 Ge atoms of the Ge 4Rs are dislodged simultaneously, in excellent agreement with earlier EXAFS data. In ITQ-13 and ITQ-22 zeolites, Ge distributions are more complex, leading a progressive degermanation of the framework and to the presence of Si-O-Si bridges that prevents the structure from collapsing upon Ge extraction. Data suggest that IM-12 is unique in the family of Ge-containing zeolites.
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Dates et versions

hal-01149272 , version 1 (06-05-2015)

Identifiants

Citer

N. Kasian, A. Tuel, E. Verheyen, C. E. A. Kirschhock, F. Taulelle, et al.. NMR Evidence for Specific Germanium Siting in IM-12 Zeolite. Chemistry of Materials, 2014, 26 (19), pp.5556-5565. ⟨10.1021/cm502525w⟩. ⟨hal-01149272⟩
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