Catalytic Oxidation of Lignin for the Production of Value-Added Aromatic Aldehydes

Catalytic wet air oxidation (CWAO) of lignin or phenolic composition in waste water is a useful pathway for the recovery of valuable compounds. In this study, bamboo lignin was catalytically oxidized to aromatic aldehydes and acetoderivatives, so was acetovanillone oxidized to vanillin. A total products yield of 9.5% from bamboo lignin, and a vanillin yield of 51% with greater than 90% selectivity from acetovanillone were achieved. The proposed reaction pathways suggest a two-step route towards the formation of value-added aromatic aldehydes from lignin via degradation of acetoderivatives. The kinetics study for the degradation of acetovanillone and formation of vanillin were reported for the first time over the temperature range of 120-150 °C, with the activation energies of 85.29 kJ/mol and 120.7 kJ/mol respectively. To date, CWAO breaks down the lignin polymer and toxic phenolic compounds reasonably and effectively, producing value-added aldehydes, which has a great potential to becoming a new route for the recovery of value-added products from lignin.