Location of cations in synthetic zeolites–X and –Y. Part 5.—The cation distribution in Ca–Y, Ca–X and La–Y in the ultimate stages of dehydration

Abstract

The structures of a series of Ca–Y samples, pretreated under varying conditions (temperature and deep bed) were studied using t.g.a., i.r. and X-ray powder techniques. Ca–Y and La–Y samples were studied for comparison. The distribution of cations and water molecules at room temperature (hydrated and dehydrated) and dehydrated at 423 K was similar, i.e. Ca²⁺ on site I′ and II, and H₂O on site II′. Higher dehydration temperatures result in a gradual removal of oxygen species from site II′ and a subsequent increase in the site I and II population. Deep bed treatment and subsequent dehydration at 623 K did not result in appreciable differences in cation location. No single stoichiometry could be assigned to the sodalite cage complex. For La–Y, a La₂O₃ oxide was formed at 623 K, but destroyed at 973 K.