Highly selective and direct oxidation of cyclohexane to cyclohexanone over vanadium exchanged NaY at room temperature under solvent-free conditions

Abstract

Vanadium exchanged zeolite Y has been synthesized by simple ion-exchange on NaY and resulting V–Y material has been employed as a heterogeneous catalyst for highly selective and direct one-pot liquid phase oxidation of cyclohexane to cyclohexanone under solvent-free conditions at room temperature. The catalyst (V–Y) has been thoroughly characterized by powder X-ray diffraction (PXRD), N2 sorption, transmission electron microscopic (TEM), Fourier transform infrared (FT IR), UV–visible, X-ray photoelectron spectroscopic (XPS) and atomic absorption spectroscopic (AAS) analyses. The selective oxidation reaction proceeds smoothly over this V-containing heterogeneous catalyst in the presence of tert-butylhydroperoxide (TBHP) as oxidant and the progress of the reaction has been monitored thoroughly by gas chromatographic (GC) and gas chromatography coupled with mass spectrometric (GC–MS) analyses. The recycling efficiency of the V–Y catalyst has been tested by conducting the catalytic reaction repeatedly with the recovered catalyst, where almost retention of the original catalytic activity and selectivity after five reaction cycles has been observed. The effect of oxidant amounts on the catalytic reaction has been studied. Mechanistic pathway for the catalytic reaction over this inexpensive, non-air sensitive, eco-friendly and reusable vanadium exchanged zeolite has been proposed, suggesting future potential of V–Y in solvent-free liquid phase selective oxidation reactions under very mild conditions.