Catalytic oxidation of lignin–acetoderivatives: a potential new recovery route for value-added aromatic aldehydes from acetoderivatives

Abstract

Catalytic wet air oxidation (CWAO) of lignin and phenolic composition of wastewater is a useful pathway towards the recovery of valuable compounds. In this study, bamboo lignin was catalytically oxidized to aromatic aldehydes and acetoderivatives; similarly acetovanillone and acetosyringone were oxidized to vanillin and syringaldehyde, respectively. A total product 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 was reported for the first time in the temperature range of 120–150 °C, with activation energies of 85.29 kJ mol⁻¹ and 120.7 kJ mol⁻¹, respectively. To date, CWAO breaks down the lignin polymer and toxic phenolic compounds reasonably and effectively, producing value-added aldehydes, which could become a potential new route for the recovery of value-added products.