2020 journal article

Depolymerization of Lignin into Monophenolics By Ferrous/ Persulfate Reagent Under Mild Conditions

ChemSusChem, 10.

author keywords: β -O-4 cleavage; Box-Behnken model; free radical reaction; lignin depolymerization; phenolic monomers
topics (OpenAlex): Lignin and Wood Chemistry; Biochemical and biochemical processes; Enzyme-mediated dye degradation
Source: ORCID
Added: November 14, 2020

Abstract This study aimed to use a persulfate together with transition metal ions as the reagent to effectively depolymerize lignin into monophenolic compounds under mild conditions (ambient pressure, temperature <100 °C). The Box‐Behnken experimental design in combination with the response surface methodology was applied to obtain optimized reaction conditions. The results showed that this reagent could depolymerize up to 99 % of lignin dimers to mainly veratraldehyde. This reaction also successfully depolymerized industrial lignins with a high yield of phenolic oils and monophenolic compounds. Quantum chemistry calculations using the density functional theory level indicated that the persulfate free radical attacks C β to break the β‐O‐4 bond of lignin through a five‐membered ring mechanism. This mechanism using persulfate free radicals has a lower activation barrier than that using hydroxyl radicals. Gel permeation chromatography and 2D‐NMR spectroscopy demonstrated the effective cleavage of the β‐O‐4 bonds of lignin after depolymerization.