Research Progress in Increasing Phenolic Hydroxyl Content of Lignin

Lignin is an abundant renewable resource in nature, which contains a variety of functional groups, but it has not been effectively utilized because of its complex structure. Phenolic hydroxyl is small and has good reactivity, so the reactivity of lignin could be obviously increased by improving the phenolic hydroxyl content. This paper mainly introduced some methods of improving lignin′s phenolic hydroxyl content, including phenolic modification, deoxidization by catalyst, demethylation, ultrasonic processing and electrochemical process, and then discribed the reaction principle, the advantages and disadvantages of each method. Finally, put forward some suggestions for future research focus.