Study On The Direct Hydroxylation Of Benzene To Phenol Catalyzed By Sodium Metavanadate

The one-step catalytic hydroxylation of benzene to phenol involves the direct activation of C-H bond of benzene ring, which is one of the most difficult problems both in synthetic chemistry and green chemistry. In order to realize this goal, the design and preparation of effective catalysts are key issues. In this thesis, the direct catalytic hydroxylation of benzene to phenol was studied.Based on the previous work and literature, the homogenous liquid-phase direct catalytic oxidation of benzene to phenol was performed at room temperature in acetonitrile solvent using sodium metavanadate as the catalyst and hydrogen peroxide as the oxidant. The effects of various reaction parameters, such as acidity of the system, reaction temperature, reaction time and the amount of hydrogen peroxide used, were studied. The optimized experimental conditions are as the following: 0.2 mmol NaVO3, 1 mL (11.3 mmol) benzene, 15 mL acetonitrile, pH around 1, 2 mL (19.4 mmol) H2O2 (30%), reaction time of 13 h, and without stirring. Under these conditions, a phenol yield of 13.5% with a selectivity of 94% is obtained.The variation of vanadium species during the reaction was studied by in situ 51V-NMR method. It was found that vanadium species existed as VO2+ before the reaction. In the presence of hydrogen peroxide, VO2+ species might be transferred to peroxovanadate species, such as VO(O2)2, VO(O2), which oxidized benzene to phenol exerting the catalytic performance. A catalytic cycle involving the above...