Catalytic oxidation of native lignin to phenolic monomers: Insight into aldehydes formation and stabilization

The catalytic oxidation of lignin into phenolic monomers with aldehydes as the main products is very attractive but the yield of desired monomers is still limited. The aim of this work is to investigate the reaction pathway for the conversion of lignin to aldehydes and aldehydes stabilization in alkaline media. Studies on pure aldehydes stability revealed that over-oxidation to carboxylic acids and condensation are crucial factors of limited yield. A chemical protection method using aniline as the capping agent was applied to the depolymerization of real lignin and achieved the theoretical maximum monomer yield within 30 min at 160 °C.