Direct hydroxylation of benzene with hydrogen peroxide over pyridine–heteropoly compounds

The hybrid catalysts, pyridine (Py) modified molybdovanadophosphates with Keggin structure Pyn–PMo(12−m)VmO40 (n = 1–3, m = 1–3), were prepared and characterized by FT-IR. Among various catalysts, Py1–PMo10V2O40 exhibited the highest yield of phenol (20.5%) with the selectivity of phenol of 98.0% at 353 K for 5 h in the direct hydroxylation of benzene to phenol with H2O2 in the acetic acid and acetonitrile (volume ratio 1:1) mixed solvent. Pyridine plays an important role in the promotion of the catalytic activities, mostly due to the electronic interaction between pyridine and heteropolyacid together with the more remarkable pseudo-liquid-phase behavior. The influences of the reaction temperature, the amount of H2O2, the amount of Py1–PMo10V2O40 and the reaction time on the yield of phenol were investigated to obtain the optimal reaction conditions for phenol formation.