Efficient Aerobic Oxidation Of Cumene And P-Menthane To Hydrocarbon Hydroperoxides(ROOH) In The Presence Of Metalloporphyrins

Metalloporphyrins, which resemble the important enzyme cytochrome P450 structurally, are among the most heavily investigated enzyme-mimic systems. Though previous works have shown that hydrocarbons can be oxidized to produce alcohols, ketones and acids in the presence of metalloporphyrins, producing hydroperoxides directly from hydrocarbons with metalloporphyrin catalysts is still rare. For this reason, in this work, we attempted the oxidation of p-menthane and cumene to produce p-menthane hydroperoxide(PMHP) and cumene hydroperoxide(CHP) with air in the presence of metalloporphyrins at atmospheric pressure. Different factors in the reaction were studied, such as effect of various of metalloporphyrins catalysts, effect of the concentration of the catalyst, effect of the flow rate of air and effect of the temperature. And the reaction mechanism was also studied here.Analysis of the data obtained showed that the reaction was greatly improved by the addition of metalloporphyrins, in terms of both the yield and formation rate of CHP while high selectivity was maintained.An efficient and selective protocol for the aerobic oxidation of cumene to CHP catalyzed by metalloporphyrins is reported herein. It was discovered that 4 or 5 hours was the optimal reaction time when the reaction was catalyzed by (p-Cl)TPPMnCl(7.20×10-5mol/L) at 120℃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. As metalloporphyrin is the catalyst, all the data from the reaction suggests zero-order kinetics for the initial reaction stages. Studies of the reaction kinetics revealed that the activation energy of the reaction (E) is around 11.40×103cal·mol-1, and the pre-exponential factor (Z) is about 1.85×104mol-0.5·l0.5·s-1.When metalloporphyrins were used as catalyst in the reaction of oxidation of p-menthane to PMHP, 120℃and about 4h reaction are the optimum choices in the presence of (p-Cl)TPPMnCl (6.0×10-5mol/L) under an atmospheric pressure of air. Furthermore, the yield of PMHP is increased remarkably when the reaction is carried out under programmed temperature comparing to the constant temperature. When the reaction is carried out at 120℃for 4h, and then reduced the temperature to 110 oC, another 4h later, the yield of PMHP is 24.3%, which is higher than that of the reaction at a constant temperature of 120℃or 110℃for 8h.