Zeolite-Y encapsulated metal complexes of oxovanadium(VI), copper(II) and nickel(II) as catalyst for the oxidation of styrene, cyclohexane and methyl phenyl sulfide

Abstract

Oxovanadium(IV), copper(II) and nickel(II) complexes of Schiff base derived from salicylaldehyde and o-aminobenzyl alcohol (H2sal-oaba) have been encapsulated in the nano-pores of zeolite-Y by flexible ligand method and characterised by metal analysis, spectroscopic (IR and electronic) studies, scanning electron micrographs, thermal analysis and X-ray diffraction patterns. The encapsulated complexes abbreviated here as [VO(sal-oaba)(H2O)]-Y, [Cu(sal-oaba)(H2O)]-Y and [Ni(sal-oaba)(H2O)3]-Y catalyse the oxidation of styrene, cyclohexane and methyl phenyl sulfide using H2O2 as oxidant in good yield. Styrene catalysed by [VO(sal-oaba)(H2O)]-Y, [Cu(sal-oaba)(H2O)]-Y under optimised reaction conditions gave five reaction products namely, styrene oxide, benzaldehyde, 1-phenylethane-1,2-diol, benzoic acid and phenylacetaldehyde, while [Ni(sal-oaba)(H2O)3]-Y gave benzaldehyde selectively. In the presence of tert-butylhydroperoxide all catalysts gave styrene oxide in major yield, though overall conversion has been found low (10-30%). The oxidation products of cyclohexane are cyclohexanone and cyclohexanol. A maximum of 93.2% conversion of methyl phenyl sulfide has been achieved with [VO(sal-oaba)(H2O)]-Y using H2O2 as oxidant, where selectivity of sulfoxide was 96.9%. Other catalysts were inactive towards the oxidation of methyl phenyl sulfide while neat complex [VO(sal-oaba)] has been found to be equally active. © 2007 Elsevier B.V. All rights reserved.