Degradation of three β-O-4 lignin model compounds via organic electrolysis and elucidation of the degradation mechanisms

Yoshiyuki Uruma, Tomohiro Yamada, Tsubasa Kojima, Tianyuan Zhang, Chen Qu, Moe Ishihara, Takashi Watanabe, Kan Wakamatsu, Hirofumi Maekawa

Woody biomass comprising cellulose, hemicellulose, and lignin has been the focus of considerable attention as an alternative energy source to fossil fuel for various applications. However, lignin has a complex structure, which is difficult to degrade. Typically, lignin degradation is studied using beta- O-4 lignin model compounds as lignin contains a large number of beta- O-4 bonds. In this study, we investigated the degradation of the following lignin model compounds via organic electrolysis: 2-(2-methoxyphenoxy)-1- (4-methoxyphenyl)ethanol 1a, 1-(3,4-dimethoxyphenyl)-2-(2-methoxyphenoxy)-1,3-propanediol 2a, and 1-(4-hydroxy-3-methoxy phenyl)-2-(2-methoxyphenoxy)-1,3-propanediol 3a. The electr olysis was conducted for 2.5 h at a constant current of 0.2 A using a carbon electrode. Various degradation products such as 1-phenylethane-1,2-diol, vanillin, and guaiacol were identified upon separation via silica-gel column chromatog. The degradation reaction mechanisms were elucidated using electrochem. results as well as d. functional theory calculations The results suggest that the organic electr olytic reaction can be used for the degrad ation reaction of a lignin model with beta-O-4 bonds.

RSC Adv.

13

26

17991

18000

10.1039/d3ra02486e