Direct extraction of biphasic organosolv lignin for producing aromatic aldehydes via alkaline oxidation

• Published in: Journal of the Taiwan Institute of Chemical Engineers 2024-05, Vol.158, p.105009, Article 105009
• Main Authors: Ishimaru, Hiroya, Yoshikawa, Takuya, Higuchi, Yudai, Nakasaka, Yuta, Yoshida, Akihiro, Sonoki, Tomonori, Masuda, Takao
• Format: Article
• Language: English
• Subjects: Alkaline oxidation; Aromatic aldehydes; Biphasic organosolv lignin; Liquid-liquid extraction
• ISSN: 1876-1070; 1876-1089
• DOI: 10.1016/j.jtice.2023.105009

•Aromatic aldehydes were obtained from organosolv lignin via alkaline oxidation.•Direct extraction method was developed to recover the lignin in 1-butanol phase.•Oxidation of willow-derived lignin yielded 14 C-mol% of aromatic aldehydes.•N-heptane soluble fraction selectively contained the lighter oxidized products. Lignin can be a sustainable source of aromatic compounds, whereas the utilization is limited because of its complex three-dimensional structure. Organosolv method is promising for the valorization of lignin because of its mild conditions as compared with industrial pulping processes. Aromatic aldehydes, widely used in various industries, are obtained by catalytic oxidation of lignin. Organosolv treatment of various types of lignocellulose in water/1-butanol solvent was conducted using a batch type reactor. During the solvent removal from 1-butanol phase containing organosolv lignin, the concentrated lignin was denatured, which was evaluated by measuring particle size distribution and thermal decomposition behavior of the lignin. The recovery procedure of lignin was improved, and the extraction of organosolv lignin from 1-butanol phase to alkaline solution was developed. The improved extraction method definitely showed a higher yield of aromatic compounds regardless of the type of lignocellulose, yielding 14 C-mol% of aromatic aldehydes after alkaline oxidation of willow-derived lignin. After the alkaline oxidation reaction, a simple solvent fractionation was applied for refining the oxidized products. The solvent fractionation of the oxidized products was achieved using ethyl acetate and n-heptane. n-Heptane-soluble fraction selectively contained the lighter fraction with maintaining the content of aromatic compounds.