Characterization of lignins from organosolv pulping according to the organocell process: Part 4. permanganate oxidation and thioacidolysis

Soluble and residual spruce lignins were subjected to permanganate oxidation and thioacidolysis to elucidate changes in lignin's structure during Organocell pulping. As expected degradation reactions known from soda pulping are dominant especially in stage 2, including extensive enol ether formation. The chemical effect of methanol appears to be restricted to a minor methylation of the α-C-atom which prevents quinone methide formation and thus suppresses subsequent condensation reactions. Other beneficial effects of methanol such as liquor diffusion into the chips and a better lignin solubility obviously contribute to the successful delignification of softwoods in Organocell pulping.