CATALYTIC PROPERTIES OF LOW-VALENT LANTHANIDE SPECIES INTRODUCED INTO Y-ZEOLITE

Low-valent ytterbium or europium species were introduced into Y-zeolites by impregnation from ytterbium or europium metal dissolved in liquid ammonia. The zeolites thus loaded with ytterbium or europium have a high catalytic activity for the isomerization of but-1-ene at 273 K, when they were heated under vacuum at ca. 500 K. Their catalytic activities are strongly influenced by the alkali-metal cations present in the Y-zeolite. The isomerization proceeds via an allylic carbanion-type intermediate. On the other hand, the zeolites heated under vacuum around 900 K are active for the hydrogenation of ethene at 273 K, and buta-1,3-diene at 323 K. The photoluminescence of europium supported on zeolites and temperature-programmed desorption spectra of gases desorbed from zeolites loaded with europium or ytterbium suggest that metal imides such as EuNH, and metal-like species may be formed by the zeolites under vacuum at ca. 500 and 900 K, respectively.