Hydroxyl Groups of Exceptionally High Acidity in Desilicated Zeolites Y

The desilication of dealuminated zeolite Y in NaOH/tetrabutylammonium hydroxide mixtures produces hierarchical zeolite Y containing a micropore system as well as mesopores of significant volume and surface. IR studies evidenced that a new kind of hydroxyls was formed if desilication was realized above 318 K. This new kind of acidic hydroxyls is characterized by IR band at 3600 cm −1 . IR studies showed, that these new hydroxyls showed extremely high acidity. This was evidenced by very high frequency shifts of IR bands of OH interacting with probe molecules: CO and N 2 :Δ ν O H · · · C O =411 cm −1 andΔ ν O H · · · N 2=164 cm −1 , resp. These frequency shift are the highest in all the chemistry of zeolites including very strongly acidic dealuminated mazzite and steamed zeolite USY ( Δ ν O H · · · C O =ca. 380 cm −1 ) indicating that 3600 cm −1 hydroxyls are the most acidic in all the zeolites.