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

Abstract

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.