Controllably Confined ZnO on USY Zeolites (USY@ZnO/Al2 O3 ) as Efficient Lewis Acid Catalysts for Baeyer-Villiger Oxidation.

Abstract

A ZnAl-LDHs (layered double hydroxides) phase was readily formed on the surface of a USY zeolite through a distinctive in situ growth method that benefitted from the interaction of the added Zn source and aluminum species extracted from the Al-rich USY zeolite crystals. The migration of aluminum and simultaneous interaction with the external Zn source took place in one pot to form a ZnAl-LDHs phase coated on the surface of the USY crystals. Upon calcination, the ZnAl-LDHs phase was transformed into a ZnO/Al2 O3 composite that was still firmly anchored on the USY zeolite, without sacrificing the core-shell structure. The resultant USY@ZnO/Al2 O3 materials gave rise to unique Lewis acidity and hierarchical porosity, which endowed the catalyst with promising performance in the Baeyer-Villiger oxidation of ketones with H2 O2 or bulky tert-butyl hydroxide as an oxidant.