Combined Chemical Activation and Fenton Degradation to Convert Waste Polyethylene into High‐Value Fine Chemicals

Abstract

Plastic waste is a valuable organic resource. However, proper technologies to recover usable materials from plastic are still very rare. Although the conversion/cracking/degradation of certain plastics into chemicals has drawn much attention, effective and selective cracking of the major waste plastic polyethylene is extremely difficult, with degradation of C-C/C-H bonds identified as the bottleneck. Pyrolysis, for example, is a nonselective degradation method used to crack plastics, but it requires a very high energy input. To solve the current plastic pollution crisis, more effective technologies are needed for converting plastic waste into useful substances that can be fed into the energy cycle or used to produce fine chemicals for industry. In this study, we demonstrate a new and effective chemical approach by using the Fenton reaction to convert polyethylene plastic waste into carboxylic acids under ambient conditions. Understanding the fundamentals of this new chemical process provides a possible protocol to solve global plastic-waste problems.

Depolymerization of lignin for biological conversion through sulfonation and a chelator-mediated Fenton reaction

“…Depolymerization of sulfonated PE, PSS, and LS by Fenton reactions has been demonstrated in prior work. 35–38 In the present work we show that depolymerization of PSS and LS proceeds efficiently with CMF reactions optimized to use low amounts of H 2 O 2 and we demonstrate bioavailability of some of the products. The molecular weight distribution of LS depolymerized by CMF does not contain as many resolved low molecular weight peaks as is typically reported for other depolymerization methods.…”

“…61 The presence of aromatic groups is not required for C–C bond cleavage in sulfonated polymers by the Fenton reaction, as sulfonated polyethylene can also be depolymerized with this method. 35 Together, these findings suggest that the positively-charged Fe ions, alone or in complex with DHB, associate strongly with negatively-charged sulfonic acid groups such that hydroxyl radical is generated in very close proximity to the polymer chain. Hydroxyl radicals are highly reactive and are believed to react within 1–5 molecular diameters of their site of formation in the crowded environment of living cells.…”

“…The method combines sulfonation with a chelator-mediated Fenton (CMF) reaction. Prior work has shown that the Fenton reaction can depolymerize sulfonated polyethylene, 35 sulfonated polystyrene, 36,37 and lignosulfonate (LS). 38 In the work of Areskogh, et al 38 the emphasis was on increasing the molecular weight of LS for polymeric applications, in contrast to the aim of the present work to depolymerize LS.…”

Sustainable chemical upcycling of waste polyolefins by heterogeneous catalysis

“…Thus, the premodification of polyolefin to hydrophilic is necessary. As a classic example, Chow et al 79 used the sulfonation process to connect the hydrophilic sulfonic acid group to the carbon atom on the chain. The sulfonic acid group then can coordinate with Fe ions to form PESO 3 -Fe, which accelerates the degradation of polyolefins by the Fenton reaction (Figure 7A).…”

“…The introduction of active functional groups (hydroxyl, carbonyl, amino, halogen atoms, etc.) 79,[114][115][116][117] into the olefin intermediate can upgrade polyolefins with higher value and specific performance. On the other hand, the functionalization can promote the polymers to be decomposed such as the sulfonation process in the aforementioned Fenton reaction (Figure 12).…”