A CHARACTERIZATION STUDY OF THE SURFACE-ACIDITY GENERATED ON THE CALCINATION AND REDUCTION OF A RANGE OF Y-ZEOLITES

Zeolite acidity, in the form of Bronsted acid sites generated on calcining or reducing a range of Y zeolites, was probed by infrared spectroscopy and the use of Hammett indicators. In particular, the acidity of a range of reduced NiY zeolites was characterized and correlated with reduction temperature and metal loading. The nature of the alkali metal co-cation (Li+, Na+, K+, Rb+, or Cs+ is shown to influence both the acid strength and the location of the Bronsted sites. Acid strength decreases in the order NiLiY > NiNaY > NiKY > NiRbNaY > NiCsNaY. Exchange of Ce3+ ions into NiY generates additional protonic acidity. Ni2+ reduction levels are inferred from the infrared data. The effect of the adsorption of three bases (ammonia, pyridine, and quinoline) onto the zeolite surface on the level of acidity was also considered. © 1990.