Catalytic Mechanism of Cu2+and Fe3+in Alkaline O2Oxidation of Lignin

Abstract

The catalytic mechanisms of Cu²⁺ and Fe³⁺ in the alkaline oxidation of lignin are discussed. Best aldehyde yields were obtained by using Cu²⁺ and Fe³⁺ as catalysts. Without these two ions present or in the absence of one or other of them, yields were lower. It is clear that Cu²⁺ and Fe³⁺ significantly influence the reactions. Cu²⁺, acting as the electron acceptor, accelerates the formation of the phenoxy radical, thus speeding up the radical reaction. In order to interpret the effect of Fe³⁺ on oxidative degradation of lignin and formation of aldehydes, formation of an intermediate, O₂-Fe³⁺-lignin complex and its catalytic mechanism have been proposed.