Supported transition metals oxides and N-hydroxyphthalimide as binary catalytic systems for the liquid-phase oxidation of cumene

The heterogeneous catalysts based on single active component such as V2O5, MnOx and CuOx and bi-components V2O5-MoO3 V2O5-WO3 and V2O5-SbOx supported onto TiO2, TiO2-SiO2 and Al2O3-SiO2 was prepared and characterized. The aerobic liquid-phase oxidation of cumene (RH) in the presence of binary catalytic system containing N-hydroxyphthalimide (NHPI) and supported V, Mn and Cu oxides has been studied. It was observed that catalytic activities of the mono metallic systems decreases in order V2O5 ≈ MnOx > CuOx, bi-metallic catalysts showed no catalytic activities. The effect of catalytic system composition comprising MnOx or VOx and NHPI, AIBN on the oxidation rate was studied. The major oxidations product was cumene hydroperoxide, whereas dimethyl phenyl carbinol and acetophenone were found as minor ones. The reactions scheme that summarizes the oxidation chemistry identifying the related role of heterogeneous initiation and homogeneous propagation and termination steps for oxidation of cumene via free-radical mechanism are presented.