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Biomass oxidative pyrolysis introduces restricted oxygen into the reaction zone, realizing autothermal pyrolysis to address the heat supply challenges inherent in large-scale applications. However, heavy components (＞200 Da) in bio-oil are critical precursors that lead to coke formation upon heating, which hinders the utilization of bio-oil. In this study, the conventional and oxidative pyrolysis experiments of cellulose, hemicellulose , and lignin in a fix-bed reactor were conducted at temperatures ranging from 300 °C to 800 °C, aiming to investigate the evolution of heavy components in bio-oil during biomass oxidative pyrolysis. The results showed that the addition of oxygen promoted the generation of bio-oil. Compared to conventional pyrolysis, the addition of oxygen mostly increased the yields of cellulose-oil, hemicellulose-oil, and lignin-oil by 28.21 %, 10.94 %, and 16.84 %, respectively. Further comprehensive analysis revealed that oxygen promoted the depolymerization of three components at a lower temperature range (＜ 500 °C). With increasing temperatures, oxygen enhanced the polymerization of volatiles from cellulose and lignin, where oxygen, acting as a binder, promoted the generation of phenolic compounds of heavy components in lignin-oil. Conversely, as the temperature increased, oxygen enhanced the oxidative decomposition of volatiles from hemicellulose , inhibiting the generation of heavy components in hemicellulose-oil. To sum up, this study presented a global evolution route of heavy components in bio-oil during oxidative pyrolysis of three components.
Xiong et al. (Sat,) studied this question.