Superior separation of hemicellulose-derived sugars from eucalyptus with tropic acid pretreatment

• Hemicellulose derived sugars were separated using tropic acid pretreatment. • The yield of hemicellulose-derived total sugars was 85.78%. • The degradation of xylose in the hydrolysate was inhibited. • Separation of hemicellulose increased from 68.29% to 79.74%. Organic acid pretreatments can efficiently separate biomass-based hemicellulose and selectively produce hemicellulose-derived sugars. In this study, hemicellulose is separation as xylose, oligosaccharides in the tropic acid-catalyzed hydrothermal pretreatment of eucalyptus. The maximum yield of hemicellulose-derived sugars (85.78%) with 71.25% xylose selectivity (based on the total xylose in raw material) was achieved in the hydrolysate under optimal conditions (5% TA, 160 ℃, 80 min). The yield of hemicellulose-derived sugar and the separation yield of hemicellulose increased by 11.06% and 11.45% compared with glycolic acid pretreatment in the similar severity factor. The separation yield of cellulose and lignin was decreased by 4.23% and 0.98%, respectively. This resulted in residual solids with higher biological stability (higher fiber crystallinity index, higher thermal stability, and higher lignin content). Therefore, higher hemicellulose separation selectivity and rich hemicellulose-derived sugars were obtained using TA pretreatment. The work would bring up a new method for biomass refining.