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: Delta nu OH center dot center dot center dot CO=411 cm(-1) and Delta nu OH center dot center dot center dot N2=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 (Delta nu OH center dot center dot center dot CO=ca. 380 cm(-1)) indicating that 3600 cm(-1) hydroxyls are the most acidic in all the zeolites.