Condensation Reactions of Some Lignin Related Compounds at Relatively Low Pyrolysis Temperature

This research was supported by the 21st COE program “Establishment of Sustainable Energy System” from Ministry of Education, Culture, Sports, Science and Technology, Japan.

Abstract

Condensation reactions of some lignin related compounds were studied under the pyrolysis conditions (air/250°C/2 h). Guaiacol, methylguaiacol and methylveratrole were recovered almost quantitatively with small amount of radical coupling products derived from phenoxy and benzyl radicals. Side‐chains (C_α˭C_β, C_α‐OH) increased the condensation reactivity substantially. From the dimer structures, vinyl condensation and quinone methide mechanisms were indicated as important condensation pathways for these compounds. As for model compounds for the structures formed in lignin primary pyrolysis, coniferyl alcohol (from β‐ether structure) was very reactive, while 4,4′‐dihydroxy‐3,3′‐dimethoxystilbene (from β‐aryl structure) was stable.

Keywords:

• Lignin
• pyrolysis
• condensation
• lignin related compound
• mechanism

Notes

This research was supported by the 21st COE program “Establishment of Sustainable Energy System” from Ministry of Education, Culture, Sports, Science and Technology, Japan.