Controlling generation of benzenes and polycyclic aromatic hydrocarbons in thermolysis of polyvinyl chloride in CO₂

This study emphasizes the control of benzene derivatives and polycyclic aromatic hydrocarbons (PAHs) in thermolysis of polyvinyl chloride (PVC) using CO₂. To this end, the generation of benzenes and PAHs from the thermolysis of PVC in N₂ was characterized and all experimental findings from the thermolysis of PVC in N₂ were used as the reference value to configure the role of CO₂ in the thermolysis of PVC. The formation of hydrogen chloride (HCl) followed by the subsequent dechlorination in the thermolysis of PVC in N₂ resulted in the high yield of charring compounds, providing a favorable condition for forming benzene derivatives and PAHs. However, the thermal degradation of PVC in CO₂ showed the genuine thermal degradation patterns. For instance, despite the presence of the source for oxygen, the formation of CO at temperatures higher than 600 °C was observed in the thermolysis of PVC in CO₂, suggesting that some unknown reactions between hydrocarbons from the thermolysis of PVC and CO₂ are initiated to form CO. In addition to these unknown reactions, the enhanced thermal cracking induced by CO₂ was observed. Two identified roles of CO₂ during the thermolysis of CO₂ was only limited at temperatures higher than 600 °C. However, despite no precise description for the mechanistic role of CO₂ at this stage of study, the formation of benzene derivatives and PAHs was effectively controlled in the presence of CO₂ at temperatures higher than 480 °C. Thus, these empirical findings in this study are necessary to further be investigated in the future, which offers a great venue offering a new means for modifying and/or controlling the harmful chemical species.