Abstract

Lignin depolymerization is a necessary process step in utilizing the carbohydrates in biomass and in potentially converting the lignin into a chemical feedstock. Lignin contains several aryl-alkyl ether linkages and the β-O-4 linkage is dominant among lignins. Base-mediated cleavage of the β-O-4 bond in a lignin model compound, guaiacylglycerol-β-guaiacyl ether, is reported. Ionic liquids have shown promise in a variety of biomass processes and this study explores the potential to use an ionic liquid solvent (1-butyl-2,3-dimethylimidazolium chloride) and non-aqueous bases in cleaving the β-O-4 bond. N-bases of varying basicity and structure were used at temperatures up to 150°C. The cleavage reaction was not found to be catalytic. Among all the tested N-bases, 1,5,7-triazabicyclo[4.4.0]dec-5-ene was the most active, leading to more than 40% β-O-4 ether bond cleavage, and the higher activity is probably associated with the exposed nature of the N-atoms.