Waste-to-Energy: Production of Fuel Gases from Plastic Wastes

Cheuk-Fai Chow; Chow-Shing Lam; Kai-Chung Lau; Cheng-Bin Gong

doi:10.3390/polym13213672

Waste-to-Energy: Production of Fuel Gases from Plastic Wastes

Polymers (Basel). 2021 Oct 25;13(21):3672. doi: 10.3390/polym13213672.

Authors

Cheuk-Fai Chow¹, Chow-Shing Lam², Kai-Chung Lau², Cheng-Bin Gong³

Affiliations

¹ Department of Science and Environmental Studies, The Education University of Hong Kong, 10 Lo Ping Road, Tai Po, Hong Kong, China.
² Department of Chemistry, City University of Hong Kong, Kowloon Tong, Hong Kong, China.
³ The Key Laboratory of Applied Chemistry of Chongqing Municipality, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China.

Abstract

A new mechanochemical method was developed to convert polymer wastes, polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC), to fuel gases (H₂, CH₄, and CO) under ball-milling with KMnO₄ at room temperature. By using various solid-state characterizations (XPS, SEM, EDS, FTIR, and NMR), and density functional theory calculations, it was found that the activation followed the hydrogen atom transfer (HAT) mechanism. Two metal oxidant molecules were found to abstract two separate hydrogen atoms from the α-CH and β-CH units of substrates, [-_βCH₂-_αCH(R)-]_n, where R = H in PE, R = _γCH₃ in PP, and R = Cl in PVC, resulting in a di-radical, [-_βCH^•-_αC^•(R)-]. Subsequently, the two unpaired electrons of the di-radical were recombined into an alkene intermediate, [-_βCH = _αC(R)-], which underwent further oxidation to produce H₂, CH₄, and CO gases.

Keywords: C-H bond activation; ball-milling; hydrogen atom transfer; polymer degradation.