Catalytic pyrolytic platform for scrap tires using CO₂ and steel slag

This study specifically examined CO₂-cofeeding pyrolysis of scrap tire (ST) to enhance H₂ generation. Thus, volatile pyrolysates (syngas and pyrolytic oil) from the thermolysis of ST in N₂ and CO₂ were compared to elucidate the mechanistic roles of CO₂. To this end, laboratory scale of pyrolysis of ST from N₂ and CO₂ was conducted in this study. The gaseous effluents from a pyrolyzer showed that enhanced CO evolution only from CO₂-cofeeding pyrolysis of ST. Moreover, a substantial decrease in the formation of benzene derivatives (BDs) including polycyclic aromatic hydrocarbons (PAHs) was discovered from CO₂-cofeeding pyrolysis of ST. Those findings offered that CO₂ could improve pyrolysis of ST by modifying the pyrogenic products, and those enhanced pyrolysis behaviors were ascribed to the homogeneous interaction between CO₂ and pyrolysates from the pyrolysis of ST (more CO generation). To advance the identified roles of CO₂, catalytic pyrolysis of ST in CO₂ was carried out using steel slag (SS) as a catalyst. In the presence of SS, the effectiveness of CO₂ on pyrolysis of ST was dramatically enhanced (~400% enhancement at 400 °C). Therefore, this study experimentally justified that the utilization of SS could alleviate the environmental burdens by adopting CO₂ in pyrolysis of ST. Also, the CO enhancement by CO₂ likely leads to the H₂ enhancement when the water-gas-shift (WGS) reaction was also conducted. All experimental findings from this study suggested that the use of CO₂ in pyrolysis of ST could be a breakthrough to enhance H₂ formation.