Acid-based organosolv lignin extraction from wheat straw: Kinetic and structural analysis

Abstract

Optimizing the pretreatment of lignocellulosic biomass is essential to obtain high purity fractions, and particularly a lignin polymer which can be easily used for further high-value applications. To better understand the changes in the chemical structure of lignin during its extraction and its kinetics, wheat straw was pretreated at mild conditions (105 °C, atmospheric pressure) in an organic acid-based organosolv medium. Lignin, collected for extraction times 0 to 3h30, was analyzed by different techniques (GPC, GC-FID and 31 P NMR) to determine its chemical structure and to quantify the modifications which could occur during the organosolv pretreatment (phenolic and total hydroxyl groups content, molecular weight, fragments condensation, esterification). The kinetics of lignin extraction was successfully assessed with the potential degree of delignification model. • Pretreatment of wheat straw in an acetic and formic acid based organosolv medium. • Providing new insights of organosolv lignin extraction mechanisms at atmospheric pressure. • Chemical characterization of lignin fragments over time. • Successful application of potential degree of delignification kinetic model.