On the role of zinc nanometric clusters in preparation of ZnNaY zeolite by ion exchange

Dehydration of Zn2+ exchanged NaY zeolite was studied by means of DRIFT spectra of adsorbed dihydrogen and carbon monoxide as molecular probes. Unlike alkaline earth forms of faujasites dehydration of ZnY zeolite at moderately high temperatures results in the formation of bridging protons and nanometric ZnO or mixed hydroxylated ZnO microclusters instead of bridging hydroxy groups and MeOH+ cations. After subsequent dehydration at above 573 K the zinc oxide clusters interact with acidic protons resulting in Zn2+ ions localized at S-II sites. These sites adsorb hydrogen in its molecular form. Heterolytic dissociative adsorption does not take place even at elevated temperatures.