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.

Catalytic Approaches to Tackle Mixed Plastic Waste Challenges: A Review

“…For example, monitor waste contains a multilayered plastic composition of high-impact polystyrene, poly(methyl methacrylate), and acrylonitrile butadiene styrene, PET, and polycarbonate (PC: 2.2%). 88 Plastic oil from monitor waste pyrolysis contained more than 50 chemical species, including a large quantity of methyl methacrylate, benzene derivatives, PAHs, and bisphenol A. Since this complicated chemical mixture is not suitable for industrial applications, it is suggested to convert it into value-added syngas.…”

“…Since this complicated chemical mixture is not suitable for industrial applications, it is suggested to convert it into value-added syngas. 88 Product distribution between plastic oil and gas from pyrolysis of PE/PP/PS/PET mixture is highly dependent on the pyrolysis temperature 73,74 and heating rate. 70 As the pyrolysis temperature and the heating rate increased, the yield of pyrolysis gas also increased.…”

Separation and Solvent Based Material Recycling of Polycarbonate from Electronic Waste

“…It has been reported that as much as 3.5 tons of CO 2 can be emitted into the atmosphere per ton of plastic incinerated. 15,16 Flame retardants are added to polymers to enhance their ability to resist combustion. Containing mainly phosphorus or halogenated compounds, they are added to plastic components near and around electrical wires, cables, and other sensitive equipment to ensure their safe usage.…”

“…When landfilled, the heavy metals as well as flame retardants commonly added to E-waste plastics often leach into the local environment, polluting the soil, water sources, and eventually the food chain. ,,− When incinerated for energy conversion, large amounts of CO 2 are released into the atmosphere, contributing to the ongoing global warming climate crisis. It has been reported that as much as 3.5 tons of CO 2 can be emitted into the atmosphere per ton of plastic incinerated. , …”

ACS Sustainable Chemistry & Engineering Virtual Special Issue: Thermal and Catalytical Chemical Conversions of Plastic Wastes for Sustainable Production of Energy, Fuels, and Chemicals

“…Energy and exergy efficiencies of this system are 51.75% and 45.22%, respectively. Jung et al 19 devised a reliable platform for treatment of complex plastic compounds in e-waste, which was used for catalytic pyrolysis of LCD monitor waste with a nickel catalyst to promote H 2 formation. Chari et al 20 calculated the climate change impact of −371 kg CO 2 per ton of mixed plastic wastes processed by hydrogen production process.…”