Lignin Depolymerization to Dicarboxylic Acids with Sodium Percarbonate

Lignin depolymerization to dicarboxylic acids (DCAs) by the one-step Fenton oxidation process results in poor yield and significant amounts of residual solids. A process based on the use of sodium percarbonate on bagasse lignin depolymerization was conducted at 60-300 degrees C, for 1-6 h. This approach resulted in significantly higher DCA yields (predominantly oxalic, malonic, and succinic acids), without the formation of char, when compared to the acidic H2O2/chalcopyrite process. This was in part due to the effectiveness of the alkaline reaction medium in suppressing the thermal degradation of DCAs during processing. It was determined that increasing the alkaline content of the reaction mixture further significantly improved DCA yield. When applying this process at 200 degrees C for 3 h, using 1 M NaOH (in addition to 0.6 M sodium percarbonate) increased DCA yield by 85%. The process developed was applied to the lignin model compounds; guaiacol, vanillic acid, and p-hydroxybenzoic acid. It was demonstrated that the degradation pathways and product ratios of these compounds differed, implying an influence of lignin monomer ratio 'on the DCA product range. DCAs produced from this process have the potential to be used in the industrial production of green insecticides, fungicides, and disinfectants.