Oxidative pyrolysis characteristics and exothermic heat release effects of cellulose, hemicellulose, and lignin

Oxidative pyrolysis of biomass, which introduces controlled oxygen into the reaction, enables autothermal processes and addresses heat transfer challenges in large reactors. Oxygen promotes exothermic reactions and changes product composition. Given the unique chemistry of cellulose, hemicellulose, and lignin, their pyrolytic behaviors vary with oxygen levels. This study examines these variations. The results indicate that when 10 vol% of oxygen is introduced, for cellulose, the main impact is on the third (310–410 °C) and fourth (410–700 °C) stages of pyrolysis, where O 2 reacts with the produced sugars (reducing by 6.6 %) and biochar to generate CO, a small amount of CO 2 , and water; for hemicellulose, the main impact is on the fourth stage (340–850 °C), where O 2 reacts with the produced biochar to generate CO, a small amount of CO 2 , and water; for lignin, the main impact is on the second (190–410 °C) and third (410–850 °C) stages, where O 2 reacts with the produced phenolic monomers (reducing by 2.2 %) and biochar to generate CO 2 , a small amount of CO, and water. Cellulose and hemicellulose generate more CO in oxidative pyrolysis, whereas lignin produces more CO 2 , due to varying oxygen content. Furthermore, after the introduction of 10 vol% of oxygen, the pyrolysis process of both lignin and cellulose is advanced, with lignin reaching an exothermic peak value of 18.6 mW/mg, which is 5.3 mW/mg higher than that of cellulose and 11.2 mW/mg higher than that of hemicellulose, indicating that lignin releases the most heat, while hemicellulose releases the least.