Oxidative Catalytic\nFractionation of Lignocellulose\nEnhanced by Copper–Manganese-Doped CeO<sub>2</sub>

Oxidative catalytic fractionation (OCF) represents an\nefficient\napproach to valorize lignocellulose for coproduction of monophenols\nand cellulose. To achieve an adequate monophenol yield, lignin oxidation,\ntypically, requires high O<sub>2</sub> pressure and an excess of Cu\ncatalysts (the Cu dosage is approximately 3–5 mol equiv relative\nto the aromatic units in lignin). However, these conditions are relatively\nharsh for cellulose, resulting in severe decomposition to aliphatic\nacids. To address the trade-off between the monophenol yield and cellulose\nproduction, we develop an enhanced OCF using a CuMnCeO<sub>2</sub> solid solution as the catalyst. Under relatively mild conditions\n(specifically, 0.1 MPa O<sub>2</sub>), 28.7 wt % monophenols were\nreleased from birch, using catalytic amounts of Cu (the Cu dosage\nwas about 0.03 mol equiv relative to the aromatic units in lignin).\nMeanwhile, up to 83.9% of cellulose was collected as a solid pulp.\nThe synergistic effect between doped metals (Cu and Mn) and oxygen\nvacancies was found to be crucial for enhanced lignin oxidation under\nmild conditions with minimized cellulose loss. The abundant surface\noxygen vacancies facilitated oxygen activation by well-dispersed Cu\nand Mn species, while the strong interaction between these metals\nenhanced the catalyst’s reducibility. Key intermediates such\nas β-vinyl aryl ethers and byproduct glycolic acid were identified\nby model experiments, confirming that lignin oxidation primarily followed\na 1,2-dioxetane homolysis mechanism. Overall, this enhanced OCF demonstrates\nthe potential viability of lignin oxidation in practical biorefinery\napplications.