Room temperature direct oxidation of benzene to phenol using hydrogen peroxide in the presence of vanadium-substituted heteropolymolybdates

Abstract

The liquid-phase direct catalytic oxidation of benzene to phenol was studied at room temperature using vanadium-substituted heteropolyacids as catalysts. Glacial acetic acid was employed as the solvent for the first time, while hydrogen peroxide was used as the oxidant. A yield of 26% and a selectivity of 91%, respectively, were obtained. The as-prepared phenol was separated by column chromatography and was characterized by infrared and mass spectrometry. The catalysts have been characterized by elemental analysis, thermal gravimetric analysis, infrared spectroscopy, UV–vis spectroscopy, X-ray diffraction, and 31P NMR and 51V NMR techniques. The effects of various reaction parameters, such as solvent, reaction temperature, reaction time and the amount of hydrogen peroxide used, were studied. The effects of different vanadium species on the catalytic performance were also studied. Glacial acetic acid was found to be the most suitable solvent among the solvents used in present work. An appropriate molar ratio of H 2O 2 to benzene of 1.7, and a favorable reaction time of 100 min were optimized. H 4PMo 11VO 40·13H 2O was found to be the most active in terms of turnover based on vanadium atom and the most stable catalyst.