Maleic acid as a dicarboxylic acid hydrotrope for sustainable fractionation of wood at atmospheric pressure and ≤100 °C: mode and utility of lignin esterification

Maleic acid for wood fractionation at atmospheric pressure to result in carboxylated lignin with minimal condensation, light color, and to facilitate processing of fractionated solids. 2D ¹H–¹³C HQSC and HMBC analyses confirmed lignin esterification.