NATURE OF ACTIVE SITES ON ZEOLITES .8. RARE EARTH Y ZEOLITE

The catalytic activity for o-xylene isomerization and the acidity, as measured by infrared studies of chemisorbed pyridine, of rare earth Y zeolite have been investigated. The zeolite is shown to be a Brönsted acid after calcination at 480 °C but Lewis acidity is also observed after 700 °C calcination. The Brönsted acid sites are believed to be hydroxyl groups similar to those observed in hydrogen and alkaline earth Y zeolites. The hydroxyl groups believed to be associated with rare earth cations are nonacidic with respect to a base of the strength of pyridine. The Brönsted acid site concentration and catalytic activity are intermediate between those of magnesium and hydrogen Y zeolites. There is a good correlation between the Brönsted acidity and catalytic activity of the three zeolites. Hence, Brönsted acid sites seem to be important in zeolite catalysis, but other types of sites may also play an important role. © 1969.