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 CO2 and the reaction temperature during the treatment with the CO2/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 CO2 concentration at 100 degrees C for 4 h during the treatment of CO2/LBTH system. Specifically, the CO2/LBTH system promoted the breakdown of the beta-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 CO2/LBTH system is thus of strategic and practical relevance.