(2026) Energy Conversion and Management_CO₂-assisted control of H₂/CO ratio in plastic waste pyrolysis

Lee T.; Moon G.; Kim Y.-M.; Kwon E.E.
 

(Elsevier Ltd) Energy Conversion and Management ISSN: 1968904 Vol.350 Issue. Article No.120997 DOI: 10.1016/j.enconman.2025.120997

Plastic waste pyrolysis offers a promising route to produce precursors for chemical synthesis. Nonetheless, the compositional heterogeneity of pyrogenic products requires extensive separation and purification of platform chemicals, which critically limits the economic feasibility of circular valorization. To address this limitation, this study investigates carbon dioxide (CO₂)-mediated pyrolysis of plastic waste for producing syngas with a controllable hydrogen-to-carbon monoxide (H₂/CO) molar ratio. Plastic optical cable (POC) waste was selected as a model feedstock, and characterization revealed two main polymeric constituents: polymethyl methacrylate (PMMA) and poly(ethylene-co-vinyl acetate) (EVA). Conventional POC pyrolysis yielded a broad distribution of hydrocarbons (C₆-C₃₈), yet homogeneous interactions between CO₂ and the heavy molecular hydrocarbons derived from POC were limited. To promote these interactions, an isothermal catalytic bed containing a Ni-based catalyst was integrated downstream of the pyrolyzer. The catalytic bed facilitated the cracking of long-chain hydrocarbons into lighter species, which enhances their reactions with CO₂ and promotes CO formation. Increasing the catalytic bed temperature from 500 to 700 °C intensified CO₂ reactivity, leading to greater syngas yields and more effective modulation of its composition. The effect of CO₂ concentration (0–80 vol%) was also examined, revealing that higher CO₂ contents increased total syngas production while exponentially decreasing the H₂/CO molar ratio. The tunable H₂/CO ratio achieved via CO₂-assisted catalytic pyrolysis offers a promising platform for synthesizing fuels and chemicals, thereby contributing to the circular valorization of plastic waste. © 2025 Elsevier Ltd.

This work was supported by the National Research Foundation of Korea (NRF) grants funded by the Korean Government (MSIT) (grant numbers: RS-2024-00342766 and RS-2023-NR077231 ).