Aerobic oxidation of cumene to cumene hydroperoxide catalyzed by metalloporphyrins

A protocol for the aerobic oxidation of cumene to cumene hydroperoxide (CHP) catalyzed by metalloporphyrins is reported herein. Typically, the reaction was performed in an intermittent mode under an atmospheric pressure of air and below 130°C. Several important reaction parameters, such as the structure and concentration of metalloporphyrin, the air flow rate, and the temperature, were carefully studied. Analysis of the data obtained showed that the reaction was remarkably improved by the addition of metalloporphyrins, in terms of both the yield and formation rate of CHP while high selectivity was maintained. It was discovered that 4 or 5 h was the optimal reaction time when the reaction was catalyzed by monomanganese-porphyrin ((p-Cl)TPPMnCl) (7.20 × 10−5 mol/l) at 120°C with the air flow rate being 600 ml/min. From the results, we also found that higher concentration of (p-Cl)TPPMnCl, longer reaction time and higher reaction temperature were all detrimental to the production of CHP from cumene. Studies of the reaction kinetics revealed that the activation energy of the reaction (E) is around 38.9 × 104 kJ mol−1. The low apparent activation energy of the reaction could explain why the rate of cumene oxidation to CHP in the presence of metalloporphyrins was much faster than that of the non-catalyzed oxidation.