Valorizing plastic toy wastes to flammable gases through CO2-mediated pyrolysis with a Co-based catalyst

Abstract

Toys are discarded due to their short life cycle. Unfortunately, development of sustainable disposal platform for toy has not gained particular concern. To establish a reliable disposal platform, this study employed a pyrolysis platform to valorize plastics into value-added fuels. To confer more environmentally resilient process, CO₂ was used as a feedstock to enhance the process efficiency from a perspective of the yield of flammable gases. To this end, waste toy brick (WTB) was used as a model compound. The exact types of plastics (polyacrylonitrile, polybutadiene, polystyrene, and polymethyl methacrylate) in WTB were experimentally determined. In pyrolysis of WTB, the complicated mixture of benzene derivatives was inevitably generated. To detoxify them by means of syngas (H₂/CO) production, catalytic pyrolysis was performed. Co catalyst effectively induced chemical bond scissions, leading to substantially enhanced H₂ formation. Also, the gas phase reactions (GPRs) between CO₂ and volatile compounds over Co catalyst expedited the production rate of CO, and such CO enhancement effectively offered a chance to mitigate toxic chemical generations. The synergistic contribution of CO₂ and Co catalyst enhanced syngas formation more than 25 times in reference to pyrolysis of WTB without Co catalyst. The GPRs also greatly prevented catalyst deactivation.

Keywords: ABS plastic; Circular economy; Plastic management; Polymethyl methacrylate; Syngas; Waste-to-energy.