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Metal-Free Photochemical Degradation of Lignin-Derived Aryl Ethers and Lignin by Autologous Radicals through Ionic Liquid Induction

  • Kang, Ying
  • Lu, Xingmei
  • Zhang, Guangjin
  • Yao, Xiaoqian
  • Xin, Jiayu
  • Yang, Shaoqi
  • Yang, Yongqing
  • Xu, Junli
  • Feng, Mi
  • Zhang, Suojiang
Publication Date
Aug 08, 2019
Institutional Repository of Institute of Process Engineering, CAS (IPE-IR)
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The degradation of lignin into aromatic products is very important, but harsh conditions and metal-based catalysts are commonly needed to cleave the inert bonds. Herein, an efficient self-initiated radical photochemical degradation for lignin-derived aryl ethers through ionic liquids (ILs) induction is demonstrated. The C-C/C-O bonds can be cleaved efficiently through free-radical-mediated reaction in the binary-ILs system 1-propenyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] imide [PMim][NTf2] and the Bronsted acid 1-propylsulfonic-3-methylimidazolium trifluoromethanesulfonate ([PrSO(3)HMim][OTf]) under ambient conditions. [PMim][NTf2] initiates the reaction by promoting the cleavage of the C-beta-H bond, and [PrSO(3)HMim][OTf] catalyzes the subsequent C-O-C bond fragmentation. Furthermore, alkyl, hydroxyl, and peroxy radicals are detected, which suggests degradation based on a photochemical free-radical process. Additionally, alkali lignin could also be degraded in the IL system. This work sheds light on sustainable biomass utilization through a self-initiated radical photochemical strategy under metal-free and mild conditions.

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