Abstract:The oxidative pyrolysis technology of biomass utilizes the exothermic oxidation reactions of organic materials to tackle the heating challenges associated with conventional large-scale anaerobic pyrolysis. This approach reduces investment costs and contributes to achieving the "dual carbon" goals. A significant challenge in biomass pyrolysis is the formation of heavy components in bio-oil (biomass pyrolysis oil), which are key precursors for coke formation during the heating process. However, the underlying mechanisms governing the evolution of these heavy components in bio-oil produced by oxidative pyrolysis remain unclear. Therefore, this study investigates the effect of oxygen on the heavy components in bio-oil during the pyrolysis of individual biomass components and their mixtures. The heavy components in the bio-oil were characterized using a Fourier transform ion cyclotron resonance mass spectrometer. The results showed that the bio-oil yields from oxidative pyrolysis of each component, both individually or in mixtures, were higher than from anaerobic pyrolysis. Specifically, the bio-oil yields from oxidative pyrolysis of cellulose, hemicellulose, and lignin were increased by 28%, 11%, and 17%, respectively, compared to anoxic pyrolysis. Regardless of whether oxidative or non-oxidative pyrolysis was utilized, interactions among the three components consistently led to a reduction in bio-oil yield. Under oxidative conditions, the molecular weight and oxygen content of heavy components in bio-oil from cellulose and lignin pyrolysis increased significantly, whereas those in bio-oil from hemicellulose pyrolysis decreased. This suggests that inducing oxygen enhances the depolymerization of cellulose and lignin, intensifying secondary polymerization reactions among volatile fractions. It also promotes homogeneous oxidation reactions of hemicellulose-derived products, resulting in the generation of more small molecules, water, and gases. Furthermore, interactions among the three components significantly inhibit bio-oil formation. The interaction between cellulose and hemicellulose, as well as between hemicellulose and lignin, enhances secondary polymerization among the components, promoting the formation of phenolic and lipid compounds in the heavy components of the bio-oil. On the other hand, the interaction between cellulose and lignin facilitates the conversion of high-molecular-weight heavy components into lower-molecular-weight compounds, enhancing lipid formation while inhibiting phenolic compound production. Additionally, the trends in the evolution of heavy components in bio-oil from oxidative co-pyrolysis of actual poplar, simulated poplar mixtures, and cellulose-lignin mixtures display similar patterns. This suggests that during the oxidative pyrolysis of actual poplar, the generation of heavy components is primarily driven by the interaction between cellulose and lignin. Close-