Depolymerization of corn cobs using the CO2/lithium bromide trihydrate system for low molecular weight lignin with high antioxidant activity

Biomass as a green renewable energy source has the potential to become a significant energy source in the future due to the depletion of fossil fuels. Herein, carbon dioxide was employed to enhance the acidic pretreatment of corn cobs with lithium bromide trihydrate (LBTH) system to extract low molecular weight lignin with high antioxidant activity. The main factors that have an influence on the degradation of carbohydrates and lignin in corn cobs were examined, such as the amount of CO 2 and the reaction temperature during the treatment with the CO 2 /LBTH system. The results showed that the extraction yield rate of low molecular weight lignin and the total conversion of corn cobs were 81.6% and 83.5%, respectively, under the operating conditions of 76.2 g CO 2 concentration at 100 °C for 4 h during the treatment of CO 2 /LBTH system. Specifically, the CO 2 /LBTH system promoted the breakdown of the β- O -4 aryl ether bond of lignin, resulting in the production of low molecular weight lignin with improved hydroxyl content and antioxidant activity. To transform inexpensive biomass resources into lignin with a high value-added, the CO 2 /LBTH system is thus of strategic and practical relevance. Graphical abstract