Perspective on Lignin Oxidation: Advances, Challenges, and Future Directions.

Lignin valorization has gained increasing attention over the past decade. Being the world's largest source of renewable aromatics, its valorization could pave the way towards more profitable and more sustainable lignocellulose biorefineries. Many lignin valorization strategies focus on the disassembly of lignin into aromatic monomers, which can serve as platform molecules for the chemical industry. Within this framework, the oxidative conversion of lignin is of great interest because it enables the formation of highly functionalized, valuable compounds. This work provides a brief overview and critical discussion of lignin oxidation research. In the first part, oxidative conversion of lignin models and isolated lignin streams is reviewed. The second part highlights a number of challenges with respect to the substrate, catalyst, and operating conditions, and proposes some future directions regarding the oxidative conversion of lignin.