Oxidative depolymerization of lignin in ionic liquids

ChemSusChem. 2010 Jun 21;3(6):719-23. doi: 10.1002/cssc.200900242.

Abstract

Beech lignin was oxidatively cleaved in ionic liquids to give phenols, unsaturated propylaromatics, and aromatic aldehydes. A multiparallel batch reactor system was used to screen different ionic liquids and metal catalysts. Mn(NO(3))(2) in 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [EMIM][CF(3)SO(3)] proved to be the most effective reaction system. A larger scale batch reaction with this system in a 300 mL autoclave (11 g lignin starting material) resulted in a maximum conversion of 66.3 % (24 h at 100 degrees C, 84x10(5) Pa air). By adjusting the reaction conditions and catalyst loading, the selectivity of the process could be shifted from syringaldehyde as the predominant product to 2,6-dimethoxy-1,4-benzoquinone (DMBQ). Surprisingly, the latter could be isolated as a pure substance in 11.5 wt % overall yield by a simple extraction/crystallization process.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Benzaldehydes / chemical synthesis
  • Benzoquinones / chemical synthesis*
  • Catalysis
  • Ionic Liquids / chemistry
  • Lignin / chemistry*
  • Oxidation-Reduction

Substances

  • Benzaldehydes
  • Benzoquinones
  • Ionic Liquids
  • 2,6-dimethoxy-1,4-benzoquinone
  • syringaldehyde
  • Lignin