Structure and properties of eucalyptus lignin extracted with benzenesulfonic and p-toluenesulfonic acids under mild conditions

Abstract

Acid hydrotrope is a novel solvent used for biomass refining, because it can effectively separate lignocellulose for value-added utilization of products. In this case, eucalyptus was fractionated using benzenesulfonic acid (BA) and p-toluenesulfonic acid (p-TsOH) as acid hydrotropes at a low temperature (80 °C) and in a short time (20 min). Results showed that both BA and p-TsOH efficiently liberated lignin from the raw material, with the highest lignin removal rates of 82.90% and 79.60%, respectively. The extracted lignin had high purities (> 98.50%), medium molecular weights (4390–5440) and excellent homogeneities (PDI ≤ 2.15). Under the same acid mass fraction conditions, BA showed better lignin removal, smaller molecular weight and higher purity of extracted lignin. 2,2-Diphenyl-1-pyridylhydrobenzyl test showed that the lignin extracted by BA had more powerful antioxidant activity. The acid hydrotrope fractionation of eucalyptus exhibited the advantages of rapid delignification under mild conditions, providing a reference for separation and utilization of lignin from lignocellulose.