Current Status of Impurities and Their Removal Technologies of Plastic Waste Pyrolysis Oil

Plastic waste pyrolysis oil (PWPO) holds significant potential as a core material for promoting circular economy. However, impurities in PWPO hinder its use as a feedstock for plastic production. Nitrogen, sulfur, oxygen, chlorine, and metallic materials are the most common impurities to steam cracking process, causing issues such as corrosion, fouling, coke formation, and catalytic deactivation. In this study, industrial thresholds (ITs) for each impurity in feedstock for industrial naphtha cracking center (NCCs) are presented, however ITs for certain metal impurities specific to PWPO currently are unavailable. The composition of PWPO is influenced by the type of plastic waste, with Cl, Cu, Si and Fe identified as major impurities. Among removal methods, chlorine removal has been the most extensively studied, typically achieved through catalytic or pretreatment processes. Oxygen removal using HZM-5 catalysts have been investigated, but nitrogen removal methods remain understudied for PWPO. Similarly, research on methods for removing metal impurities removal from PWPO is, to the best of our knowledge, sparse. This review examines recent advances in identifying PWPO impurities and their removal technology. To facilitate the effective use of PWPO, proper classification of the waste is of utmost importance. Additionally, further research is needed to establish ITs and develop purification methods that specifically targets PWPO.