Free radical theory in lignin oxidation depolymerization

Abstract

Depolymerized lignin could provide a renewable alternative to fossil resources. Oxidative depolymerization is a popular, mild, and environmentally friendly lignin depolymerization method. Studying the radical mechanisms of this reaction could provide insight into the orientation and selectivity of the products. In this review, we provide a comprehensive overview of the radicals in oxidative depolymerization of lignin, from the interaction mechanisms of the exogenous radicals generated from the chemical environment to the C-centered radicals generated from lignin. We also discuss the relationship between the radical attack site and depolymerization products. In the future, we hope that investigation of free radical theory in the lignin oxidative process will be more systematically and deeply developed for the high-value utilization of lignin resources.