A new model for acid sites in dealuminated Y zeolites

摘要

Infrared and MAS NMR spectroscopies of a series of progressively sodium exchanged Y zeolites were used to study the influence of dealumination on Brosted acidity. Dealumination of Y zeolite introduces extraframework phase in the structure of the zeolite. This extraframework phase can be located in the sodalite cages or in the supercages of the zeolite structure. Two types of extraframework phases can be observed, so-called amorphous and cationic. These two types of aluminium species in two different locations create four different perturbations of the Brosted acid site. A new model is proposed for the Brosted sites in the supercage of USY, explaining the influence of extraframework phase on Brosted acidity.