Inhibitory effect of Zn<sup>2+</sup> on the chain‐initiation process of cumene oxidation
Zhicheng Chen, Yuhang Li, Yonghai Cao, Qiao Zhang, Hao Yu, Feng Peng
Abstract
Abstract Carbon nanotubes (CNTs) have excellent catalytic activity in liquid phase reaction, especially in aerobic oxidation of cumene. In previous work, the conversion of cumene was 41.8% and the selectivity of cumene hydroperoxide was 71.5%, which was catalyzed by CNTs. But a small amount of impurity Zn 2+ totally blocked up the aerobic oxidation of cumene that catalyzed by CNTs, which is an unexpected discovery. By analyzing the catalytic mechanism of CNTs, the inhibition effect of Zn 2+ is locked on the abstraction of H atom from cumene. The inhibition of Zn 2+ is confirmed in two effects by density functional theory calculations. First, due to the strongly coordination of active oxygen species (ROS) by Zn 2+ , the energy barrier of initial reaction increases to 1.90 eV, which is nearly 4 times higher than that of the only ROS promoted‐process. Second, the interaction of Zn 2+ and RO· or ROO· to inhibits the chain propagation reaction of free radicals. This work precisely demonstrates that the inhibition effect of Zn 2+ on initial reaction of cumene. The most significant thing is that the effect of metallic heteroatoms is not negligible in organic oxidation reaction.