Mechanism of Propylene Epoxidation via O2 with Co‐Oxidation of Aldehydes by Metalloporphyrins

Abstract

Propylene epoxidation by O2 plus acrolein in the presence of metalloporphyrins were investigated. According to the difference in initiation time and the reaction rate, a hypothesis metalloporphyrins or its center ion played a principal role in the initiation of reaction (redox reaction) rather than in the catalysis of PO generation reaction have been proposed, which was verified by the cyclic voltammogram of metalloporphyrins and UV/Vis spectra of samples in the time course study. Furthermore, the propylene epoxidation experiments using aldehydes easier to be initiated and corresponding blank control without metalloporphyrins were also investigated, and the results showed the same conclusion. On the other hand, the mechanism that the active species are peroxyacyl radical and peroxy acid was proposed through density function theory calculations, and in peroxyacyl radical path the intermediate generation process was the free radical addition of propylene by peroxyacyl radical. Moreover, optimum reaction paths were also carried out by computational calculations, the results showed that peroxyacyl radical was with higher activity than peroxy acid. As for peroxyacyl radical, the main addition site was the C1 of propylene, which was proved by the condensed Fukui function.