Lignin behaviour during wood liquefaction—Characterization by quantitative 31P, 13C NMR and size-exclusion chromatography

A blend of spruce (Picea spp.) and fir (Abies spp.) sawdust was liquefied by an optimized technique in the presence of multifunctional alcohols and p-toluene sulfonic acid monohydrate as a catalyst. The lignin behaviour during wood liquefaction was studied at different reaction times. Samples prepared by the new separation procedure were characterized by quantitative 31P, 13C NMR and by size-exclusion chromatography. The final products showed increased molar masses indicating the condensation reactions between the lignin and the multifunctional alcohols. Aliphatic chains were found to be incorporated into the lignin network after liquefaction. The resulting polymer showed an increased content of aliphatic hydroxyl groups with respect to the starting material and a high degree of solubility in multifunctional alcohols.