Comparative characterization of degraded lignin polymer from the organosolv fractionation process with various catalysts and alcohols

摘要

Triploid poplar was fractionated using mild organosolv process, and detailed characteristic elucidation of the lignin obtained was performed to determine the effects of various chemicals (sodium hydroxide, triethylamine, and formic acid) and solvents (methanol, ethanol, n-propanol, and n-butanol). Both nondestructive techniques (e.g., NMR technology) and degradation methods (e.g., alkaline nitrobenzene oxidation) were performed to comparatively evaluate the structural degradation of lignin molecules. The addition of acidic and basic catalysts improved the purity of lignin by acid hydrolysis and the cleavage of the ester groups and other types of lignin-carbohydrate interactions formed by polyoses and lignin under the basic conditions. A certain amount of aryl alkyl ether linkages (β-O-4) was cleaved during the fractionation process, whereas other carbon-carbon linkages were resistant to degradation. The formation of new carbon-carbon bonds led to the lignin fraction with obviously higher molecular weight and thermal stability, resulting from the induced carbon cation under the acidic condition.