Sustainable Valorization of E-Waste Plastic through Catalytic Pyrolysis Using CO2

Abstract

A massive amount of waste of electrical and electronic equipment (E-waste) is being discarded as a solid waste. A valorization platform for the organic part in E-waste has not been fully matured, while metallic compounds have been properly recycled. In these respects, a reliable disposal platform for complex plastic compounds in E-waste is developed in this study. Using a pyrolysis platform, the complicated plastic mixture in E-waste was valorized into value-added products. To deliberate a more environmentally benign process, CO2 was used as a cofeedstock. As a model E-waste, LCD monitor waste (LMW) was tested. The exact types of plastics in LMW (polyacrylonitrile, polybutadiene, polystyrene, poly(methyl methacrylate), polyethylene terephthalate, and polycarbonate) and their mass fractions were determined. From pyrolysis of LMW, the heterogeneous mixture of liquid (toxic) hydrocarbons was generated. To selectively convert/detoxify hydrocarbon into syngas (H2/CO), catalytic pyrolysis was applied. A Ni catalyst led to chemical bond scissions, improving H2 formation. When CO2 was fed as a cofeedstock, volatile hydrocarbons were further turned into CO through chemical reactions between CO2 and hydrocarbons. This synergistic effect of CO2 and Ni catalyst improved syngas formation more than 15 times. CO2 also greatly extended the stability of a catalyst, effectively preventing coke formation.