From Lignin to Chemicals: An Expedition from Classical to Modern Catalytic Valorization Technologies

For the transition towards greener biorefineries with reduced waste, valorization of lignin to drop-in chemicals instead of their combustion for energy purposes is a key issue for future processes. In this context, lignin should be extracted from lignocellulosic biomass (LCB) and fragmented into smaller units, followed by catalytic funneling to fine chemicals. In this review, we report on the classical approaches for lignin valorization from LCB: thermal treatments, solvolytic valorization, acid-catalyzed process, and base-catalyzed process. We also provide the reader with the modern approach of lignin valorization that led to an integrated LCB biorefinery. The performance of different solid catalysts in lignin-first approach via reductive or oxidative catalytic fractionation at different conditions is discussed in detail.