Characterization of the superacidit Y in zeolite Y by 27Al mas and 1H/27Al trapdor NMR and FTIR: Corrrelation with catalytic activity

Abstract Two zeolites Y (Z1 and Z2) with a global Si/Al ratio of 4.3 and 16.2 respectively and presenting extra-framework Al species have been characterized by NMR and FTIR. The infrared spectrum of activated Z1 presents a band at 3601 cm −1 which is assigned to strong Bronsted acid sites. By quantitative measurements it is shown that the OH group at 3601 cm −1 corresponds to the TRAPDOR NMR band at 3.1 ppm associated with ionic extra-framework Al. This superacidity, confirmed by infrared measurement of pyridine desorption, has been correlated with the catalytic activity in the hydroisomerization of n-hepatane.