Depolymerization of lignin by wet air oxidation

In the present study, effect of temperature (150–250 °C) and pressure (500–1500 psi) was investigated for depolymerization of lignin by wet air oxidation (WAO). Commercial alkali lignin was used as representative lignin material. The degradation/oxidation products of WAO treatments were identified to understand the potential value of the depolymerization products. Depolymerization efficiency of alkali lignin was also compared to lignin extracted from corn stover and eastern redcedar (cedar) under the same WAO condition. Isovanillic acid was found to be the main product of WAO at 150 °C and 1000 psi oxygen conditions. The higher temperature (200 and 250 °C) and higher oxygen pressure (1000 and 1500 psi) conditions led to formation of more oxidized products, mostly carboxylic acid-derived compounds. The results showed that alkali lignin was more vulnerable to depolymerization compared to the lignins extracted from corn stover and cedar.