Conversion of toxic chemicals into flammable gases through the thermolysis of polyurethane foam using CO₂

Construction waste is considered an environmental problem because its landfilling/incineration treatment methods has noticeably increased the likelihood of releasing microplastics, leachates, air pollutants, and toxic gases into the environment. Nevertheless, an environmentally benign disposal protocol for building plastic waste has yet to be fully implemented. In this study, a cleaner and safer disposal platform for building plastic waste is suggested. Specifically, the thermo-chemical treatment of building insulator waste (BIW) was conducted using CO₂ as a key detoxifying agent. The BIW used in this study was composed of polyurethane foam (PUF), according to instrumental analyses. The thermal degradation of the PUF resulted in the dominant production of hazardous chemicals such as 4,4′-methylenedianiline (MDA) and its derivatives. The toxic compounds were transformed/detoxified into syngas (H₂/CO) through the catalytic pyrolysis of PUF over nickel-based catalysts. Using CO₂ as a detoxifying agent, MDA and its derivatives were further transformed into CO due to the homogeneous chemical reaction between CO₂ and toxic compounds. 78.4 wt% of toxic compounds were converted into syngas over the CO₂-mediated catalytic pyrolysis. Simultaneous reduction of toxic chemicals and production of value-added compounds propose that CO₂ has a great potential to be used as a reaction medium to suppress toxic chemical valorization. Thus, this study experimentally confirmed the technical viability of catalytic pyrolysis under CO₂ as a promising disposal platform for BIW, effectively suppressing the fate of toxic compounds.