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Journal of inclusion phenomena

, Volume 3, Issue 2, pp 143–149 | Cite as

On the structures of X- and Y-type zeolites. Structural changes within the cavities of Na-Y during dehydration and contrasts with Na-X systems

  • Brian Beagley
  • John Dwyer
  • Frank R. Fitch
  • M. Ali Zanjanchi
Article

Abstract

Samples of dehydrated and partially dehydrated Na-Y were examined by X-ray diffraction methods revealing the progressive structural changes which occur as water is removed and the different behaviour compared with Na-X. The differences between Na-Y and Na-X reflect the reduced Al content of Na-Y and the consequential lower average capability of each framework oxygen atom for balancing cation charges. In the small-pore region of Na-Y, the total number of Na atoms remains relatively constant during dehydration (ca. 15 per unit cell compared withca. 18 in Na-X); unlike Na-X, Na-Y, has no site I atoms. Significant dehydration of the small-pore region, and the change from low to high site II occupancy, do not occur until the total water content of the sample is less than that which pertains under atmospheric conditions. In the 12-ring regionn of Na-Y, [Na(H2O)2]+ units are observed at an intermediate level of dehydration, possibly linked by water molecules astride the site III region to networks in adjacent 12-rings. There is no build-up, as in Na-X, of Na at site III, and site IIB (=III′) is (at least partially) occupied by H2O rather than Na. Further dehydration progressively removes H2O but there is little rearrangement of Na atom positions, except the build-up in site II which accounts for much of the loss of Na from the mobile phase.

Key words

Zeolite Y zeolite X crystal structure faujasite dehydration 

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Copyright information

© D. Reidel Publishing Company 1985

Authors and Affiliations

  • Brian Beagley
    • 1
  • John Dwyer
    • 1
  • Frank R. Fitch
    • 1
  • M. Ali Zanjanchi
    • 1
  1. 1.Department of ChemistryUniversity of Manchester Institute of Science and TechnologyManchesterU.K.

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