Production of Methyl p‑Hydroxycinnamate by Selective Tailoring of Herbaceous Lignin Using Metal-Based Deep Eutectic Solvents (DES) as Catalyst

• Published in: Industrial & engineering chemistry research Vol. 59; no. 39; pp. 17328 - 17337
• Main Authors: Li, Zhang-min, Long, Jin-xing, Zeng, Qiang, Wu, Yuan-hao, Cao, Ming-long, Liu, Si-jie, Li, Xue-hui
• Format: Journal Article
• Language: English
• Published: American Chemical Society 30-09-2020
• Subjects: Kinetics, Catalysis, and Reaction Engineering
• ISSN: 0888-5885; 1520-5045
• DOI: 10.1021/acs.iecr.0c01307

Catalytic conversion of lignin to versatile aromatic compounds is attracting increasing attention. However, it is highly desirable but challenging to produce a specific chemical with high yield through lignin depolymerization in a one-pot process because of the complex structure of the lignin molecule (mainly composed of H, G, and S units). In this study, a series of metal-based deep eutectic solvents (M-DESs) were prepared and used for the catalytic tailoring of lignin H units to produce value-added methyl p-hydroxycinnamate (MPC). In particular, M-DES ChCl­[FeCl3]2 showed excellent catalytic performance for the selective production of MPC as the sole product with high yield and selectivity (105.8 mg g–1 and 74.1%, respectively). Extensive characterizations using 2D HSQC NMR, 13C NMR, and GPC demonstrated that MPC was obtained from the selective tailoring of p-coumaric acid (pCA) units via the cleavage of ester bonds in lignin. Furthermore, M-DES ChCl­[FeCl3]2 also exhibited efficiency to other herbaceous lignins, and showed excellent recyclability. Therefore, this work provides an effective strategy for the valorization of lignin.