Degradation of Lignin by Pyrolysis

Fast pyrolysis is an efficient technique for thermal degradation of lignin to bio-oils containing bio-phenols for the synthesis of adhesives, resins, and polymers. Lignin has a complex structure, and hence a large number of pyrolytic components are generated during the pyrolysis process. The composition of the pyrolytic products depends on the type of lignin, temperature, types of catalyst, and the design of the pyrolysis reactor. It was suggested that the pyrolysis of lignin consists of two steps. In the first step, by thermal cracking of the lignin macromolecule, vapor of monomeric phenolic compounds is formed during the vapor condensation process, followed by re-oligomerization of the monomeric compounds, forming pyrolysis oils comprising remarkable amounts of dimeric and other oligomeric products. However, the precise mechanism of the pyrolysis of lignin is not clear due to the complexity of the process.