Radiolysis of lignin: Prospective mechanism of high-temperature decomposition

The range of the radiation-thermal processes resulting in conversion of lignin into monomeric phenols is considered. Statistically the most probable places of macromolecule ionization are aromatic units. Release of phenolic products from a lignin macromolecule is the multistage process beginning via fragmentation of primary cation-radicals. Reactions of electrons and small radicals with macromolecules, also as degradation of cation-radicals, result in formation of phenoxyl radicals. Macroradicals possess lower heat stability in comparison with macromolecules. Thermal decomposition of macroradicals leads to release of monohydric and dihydric phenols. The probability of benzenediols formation increases in the presence of alkanes. As noted, partial transformation of lignin into charcoal is inevitable. - Highlights: • High-temperature radiolysis converts lignin into mono- and dihydric phenols. • Multipath formation of phenoxyl macroradicals takes place. • Light phenols are eliminated via thermal fragmentation of macroradicals. • Presence of alkanes intensifies benzenediols formation.