The efficient valorization of lignin is crucial if we are to replace current petroleum‐based feedstock and establish more sustainable and competitive lignocellulosic biorefineries. Pulp and paper mills and second‐generation biorefineries produce large quantities of low‐value technical lignin as a by‐product, which is often combusted on‐site for energy recovery. This Review focuses on the conversion of technical lignins by oxidative depolymerization employing heterogeneous catalysts. It scrutinizes the current literature describing the use of various heterogeneous catalysts in the oxidative depolymerization of lignin and includes a comparison of the methods, catalyst loadings, reaction media, and types of catalyst applied, as well as the reaction products and yields. Furthermore, current techniques for the determination of product yields and product recovery are discussed. Finally, challenges and suggestions for future approaches are outlined.

Zirconia-supported vanadium–copper catalysts (VCux:yZr) were used for the oxidative depolymerization of softwood LignoBoost Kraft lignin (LB). Various VCux:yZr catalysts were prepared (x:y = 0:1, 1:4, 1:2, 3:4, 1:1, and 1:0) by incipient wetness impregnation, and reactions were performed in alkaline water at 150 °C under an O2 pressure of 5 bar for 10 min. 1H–13C HSQC NMR spectroscopy was used for product identification and quantification. The most promising catalyst was VCu1:2Zr, giving a total monomer yield of 9 wt% and the highest selectivity for vanillin (59%). This catalyst was characterized before and after use by N2 physisorption, XRD, TGA, SEM-EDS, and XPS. Cleavage of the main interunit linkages in LB, including the β-O-4 bonds and recalcitrant C–C bonds, was also observed. The findings of this study demonstrate the potential of the V–Cu/ZrO2 catalyst system in the production of value-added aromatics from technical lignin under relatively mild conditions. This would contribute to the more sustainable use of an underutilized side-stream in forest-based industries, provided catalyst reuse can be successfully demonstrated.