The integration of new CO2 capture and storage technologies in energy generation processes has led to the development and research in oxy-fuel combustion. In this technology, the carbon footprint is reduced if the fuel comes from a renewable source such as bio-oil (pyrolysis oil derived from biomass). This is a subject of growing interest. In this manuscript, we show bio-oil characterization using advanced techniques to elucidate the presence of oxygenated groups and aromatic compounds. We report that the presence of CO2 present in oxy-fuel environments modifies the thermal behavior of pyrolysis oils derived from sugarcane. At temperatures between 400°C and 700°C under CO2 atmosphere, there is evidence of reactions induced by the presence of CO2 modifying the behavior of carbonization reactions as crosslinking, aromatization, and condensation. The presence of CO2 likely induced a pH reduction. The chemical composition of char samples obtained at 400 °C and 700 °C were analyzed using FTIR and Thermal Analysis. These analyzes, allowed to elucidate the role of CO2 in carbonization. It was found that the cleavage of functional groups corresponding to the oligomers of lignin present in the bio-oil is strongly influenced by the presence of CO2. The presented results show that in CO2 atmospheres several new functional groups were observed in the char after carbonization processes. The phenomena observed were explained by the interactions of carbon dioxide with the oxygenated compounds in the solid phase formation at temperatures close to 400 °C.