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The effects of several thermal and hydrothermal treatments of low soda Y zeolites of different lanthanum content have been investigated by infrared and X-ray powder methods. The absorption maxima of the framework vibrational bands shifted toward higher frequencies after steaming at 540 and 820°. The cationic and framework atom coordinates, interatomic distances, and angles of low and high lanthanum Y zeolites steamed at 540°were determined. The changes in location of infrared absorption maxima are attributed to partial framework dealumination. Observed unit cell shrinkage supports this assumption. The detection of a nonframework position at X -Y = Z = 0.028 in the structure of steamed, low-lanthanum Y has been attributed to nonframework aluminum. We conclude that steaming results in partial framework dealumination and possible structural rearrangement in the framework. These effects are more pronounced for low-lanthanum zeolites.

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