*5.2.2 Synthesis of polymers*

The native lignin can be used for synthesis of several polymers. To do this, changes in the reactive sites such as phenol and hydroxyl groups like ligninphenolation is the mostly used process. Lignin-phenolation is carried out using methanol or ethanol in acidic medium, with a boiling point temperature of the tested solvent to make phenol-formaldehyde (PF) resins. Similarly, sulfur-mediated demethylation is a process to remove the methyl from the hydroxyl groups in lignin is economical and most significant reaction to synthesize phenol-formaldehyde resins [26].

## *5.2.3 Catalytic reactions*

There are feasibly many catalytic reactions for lignin modification; but the three important of them are oxidation, hydrogenolysis, and hydrodeoxygenation.
