Decomposition of a phenolic lignin model compound over organic N-bases in an ionic liquid

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 beta-O-4 linkage is dominant among lignins. Base-mediated cleavage of the beta-O-4 bond in a lignin model compound, guaiacylglycerol-beta-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 beta-O-4 bond. N-bases of varying basicity and structure were used at temperatures up to 150 degrees 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% beta-O-4 ether bond cleavage, and the higher activity is probably associated with the exposed nature of the N-atoms.