Cooperative effect of NHPI and BmimBr for promoting cumene catalytic oxidation

Abstract

Cumyl hydroperoxide (CHP) is an important intermediate in phenol/acetone production; however, its long reaction time and low yield remain industrial challenges. In this study, an active and promising catalyst combination—NHPI + BmimBr ionic liquid (IL)—was developed for cumene oxidation under solvent-, transition-metal-salt-, and CHP-initiator-free conditions, which exhibited a synergistic catalytic effect and excellent catalytic performance. The cumene oxidation rate was accelerated by 33.3 %, leading to the rapid synthesis of a significant amount of the target product, CHP. DFT calculations demonstrated that NHPI undergoes hydrogen atom abstraction reaction through its interaction with BmimBr, forming PINO and carbene-Br radicals that can extract hydrogen. Additionally, EPR analysis demonstrated that both radicals are involved in the reaction. The nature of the synergistic effect was confirmed using theoretical and experimental approaches. The proposed catalyst eliminates the requirement of an initiator for IL and NHPI application, paving the way for the efficient production of CHP without solvents or initiators.