TY - JOUR
T1 - Structural characterization of pure Na-nephelines synthesized by zeolite conversion route
AU - Dimitrijevic, Radovan
AU - Dondur, Vera
AU - Vulic, Predrag
AU - Markovic, Smilja
AU - Macura, Slobodan
PY - 2004/10
Y1 - 2004/10
N2 - Using the zeolite thermally induced transformation route and starting from Na-LTA, Na-FAU and Na-GIS zeolites as precursors, we synthesized pure sodium nephelines (ps-Ne) with Si/Al ratios between 1.0 and 1.5 (ps-Ne LTA , ps-Ne FAU , ps-Ne GIS ). By X-ray diffraction analysis of intermediaries, we found that ps-Ne LTA and ps-Ne FAU were obtained as polymorphous transformation products from carnegieite phases and ps-Ne GIS was synthesized directly from amorphous zeolite precursor. Stoichiometric ps-Ne LTA {Na 8 [Al 8 Si 8 ] 16 O 32 } and non-stoichiometric ps-Ne FAU {(Na 7.20 □ 0.80 ) 8 [Al 7.20 Si 8.80 ] 16 O 32 } and ps-Ne GIS {(Na 6.41 □ 1.59 ) 8 [Al 6.41 Si 9.59 ] 16 O 32 } were obtained at temperatures 900-1200 °C. The crystal structures of these ps-Ne-s were refined in the P6 3 space group, from X-ray powder data using the Rietveld method. Mean T-O bond lengths decreases almost linearly with increasing the Si/Al ratio. These changes are induced by short-range order-disorder of Si, Al cations through the T G and T S sites. The increase of short-range disorder over T-sites, is followed and confirmed by 29 Si MAS NMR and IR spectroscopy. Comparison of the Si/Al ordering of synthesized ps-Ne structures with the published data shows inverse segregation of framework cations (Si; T1=T4 and Al; T2=T3). That is probably a consequence of applied synthesis route.
AB - Using the zeolite thermally induced transformation route and starting from Na-LTA, Na-FAU and Na-GIS zeolites as precursors, we synthesized pure sodium nephelines (ps-Ne) with Si/Al ratios between 1.0 and 1.5 (ps-Ne LTA , ps-Ne FAU , ps-Ne GIS ). By X-ray diffraction analysis of intermediaries, we found that ps-Ne LTA and ps-Ne FAU were obtained as polymorphous transformation products from carnegieite phases and ps-Ne GIS was synthesized directly from amorphous zeolite precursor. Stoichiometric ps-Ne LTA {Na 8 [Al 8 Si 8 ] 16 O 32 } and non-stoichiometric ps-Ne FAU {(Na 7.20 □ 0.80 ) 8 [Al 7.20 Si 8.80 ] 16 O 32 } and ps-Ne GIS {(Na 6.41 □ 1.59 ) 8 [Al 6.41 Si 9.59 ] 16 O 32 } were obtained at temperatures 900-1200 °C. The crystal structures of these ps-Ne-s were refined in the P6 3 space group, from X-ray powder data using the Rietveld method. Mean T-O bond lengths decreases almost linearly with increasing the Si/Al ratio. These changes are induced by short-range order-disorder of Si, Al cations through the T G and T S sites. The increase of short-range disorder over T-sites, is followed and confirmed by 29 Si MAS NMR and IR spectroscopy. Comparison of the Si/Al ordering of synthesized ps-Ne structures with the published data shows inverse segregation of framework cations (Si; T1=T4 and Al; T2=T3). That is probably a consequence of applied synthesis route.
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U2 - 10.1016/j.jpcs.2004.03.005
DO - 10.1016/j.jpcs.2004.03.005
M3 - Article
AN - SCOPUS:3142693482
SN - 0022-3697
VL - 65
SP - 1623
EP - 1633
JO - Journal of Physics and Chemistry of Solids
JF - Journal of Physics and Chemistry of Solids
IS - 10
ER -