Chlorinated plastics offer unique opportunities and challenges in upcycling

Al Alshaikh, Ali; Bara, Jason E.

doi:10.1002/pi.6621

Cited by 4 publications

(1 citation statement)

References 83 publications

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“…Importantly, this effect of polymer has been found to be independent of leached chemicals and particle size/shape, with an independent effect of leached chemicals and particle size/shape also demonstrated. Furthermore, chlorinated polymers like PVC pose unique challenges, including in end-of-life management, compared to other plastics [ 65 ].…”

Section: Introductionmentioning

confidence: 99%

Impacts associated with the plastic polymers polycarbonate, polystyrene, polyvinyl chloride, and polybutadiene across their life cycle: A review

Seewoo,

Wong,

Mulders

et al. 2024

Heliyon

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Section: Introductionmentioning

confidence: 99%

Impacts associated with the plastic polymers polycarbonate, polystyrene, polyvinyl chloride, and polybutadiene across their life cycle: A review

Seewoo,

Wong,

Mulders

et al. 2024

Heliyon

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Catalytic Upcycling of Polyolefins

Sun,

Dong,

Gao

et al. 2024

Chem. Rev.

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The large production volumes of commodity polyolefins (specifically, polyethylene, polypropylene, polystyrene, and poly(vinyl chloride)), in conjunction with their low unit values and multitude of short-term uses, have resulted in a significant and pressing waste management challenge. Only a small fraction of these polyolefins is currently mechanically recycled, with the rest being incinerated, accumulating in landfills, or leaking into the natural environment. Since polyolefins are energy-rich materials, there is considerable interest in recouping some of their chemical value while simultaneously motivating more responsible end-of-life management. An emerging strategy is catalytic depolymerization, in which a portion of the C−C bonds in the polyolefin backbone is broken with the assistance of a catalyst and, in some cases, additional small molecule reagents. When the products are small molecules or materials with higher value in their own right, or as chemical feedstocks, the process is called upcycling. This review summarizes recent progress for four major catalytic upcycling strategies: hydrogenolysis, (hydro)cracking, tandem processes involving metathesis, and selective oxidation. Key considerations include macromolecular reaction mechanisms relative to small molecule mechanisms, catalyst design for macromolecular transformations, and the effect of process conditions on product selectivity. Metrics for describing polyolefin upcycling are critically evaluated, and an outlook for future advances is described.

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PVC Modification through Sequential Dehydrochlorination–Hydrogenation Reaction Cycles Facilitated via Fractionation by Green Solvents

Alshaikh,

Ezendu,

Ryoo

et al. 2024

ACS Appl. Polym. Mater.

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Polyvinyl chloride (PVC) is the third most produced plastic worldwide. However, it is also among the least recycled plastics, and research in PVC upcycling appears to lag behind that of other commodity plastics, as processing PVC waste can be more challenging. The C–Cl bond which distinguishes PVC among common polyolefins imparts unique properties but also causes difficulties when PVC is heated and/or in the presence of chemical agents. Generally, PVC has a propensity to undergo elimination reactions (via dehydrochlorination) forming conjugated CC bond sequences (“polyenes”) in the backbone via the release of HCl, thus complicating efforts for the thermomechanical reprocessing of PVC. We have found that these polyenes can be hydrogenated to aliphatic segments (i.e., −(CH2) n −) and this process can be repeated over multiple cycles. These strategies are enabled using “green” solvents, specifically acetone and ethyl acetate (EtOAc), which can leach lower molecular weight fractions of PVC from both virgin PVC and commercial samples containing plasticizers and other additive(s). The recovered PVC extracts (“PVCe”) were subjected to a reaction with NaOH in THF to produce a partially dehydrochlorinated PVC (DHPVC) that maintains the solubility of the parent PVCe. The obtained DHPVC is then treated with H2/[RhCl(PPh3)3] (i.e., Wilkinson’s catalyst) in EtOAc at 60 °C and 60 psi. The hydrogenated DHPVC [H2-DHPVC] obtained exhibits the solubility of PVCe, while the polyene segments in DHPVC have been fully deconjugated, as evidenced by UV–vis and FTIR spectra. H2-DHPVC also showed a slight reduction in the glass transition temperature (T g) compared to PVC or DHPVC from which it was obtained. The mild conditions allow for multiple cycles of dehydrochlorination–hydrogenation to be performed without degradation through oxidation or cross-linking causing insolubility. Furthermore, the methods presented are amenable to large-scale processing.

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Chlorinated plastics offer unique opportunities and challenges in upcycling

Cited by 4 publications

References 83 publications

Impacts associated with the plastic polymers polycarbonate, polystyrene, polyvinyl chloride, and polybutadiene across their life cycle: A review

Impacts associated with the plastic polymers polycarbonate, polystyrene, polyvinyl chloride, and polybutadiene across their life cycle: A review

Catalytic Upcycling of Polyolefins

PVC Modification through Sequential Dehydrochlorination–Hydrogenation Reaction Cycles Facilitated via Fractionation by Green Solvents

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