Nitration of sulfate lignin under homogeneous conditions studied by electron spectroscopy

Abstract

The nitration of sulfate lignin by nitric acid in an aqueous-dioxane medium under homogeneous conditions was studied. The method proposed makes it possible to synthesize nitrated lignin with the content of one nitro group per 1.5–2 phenylpropane units. At low consumptions of nitric acid, the nitration starts after an induction period, the duration of which decreases with increasing temperature. The presence of the induction period is related to redox transformations forming nitrous acid that nitrosates lignin.