Recycling of poly(ethylene terephthalate) – A review focusing on chemical methods

Geyer, Björn; Lorenz, Günter; Kandelbauer, Andreas

doi:10.3144/expresspolymlett.2016.53

Cited by 197 publications

(122 citation statements)

References 227 publications

(228 reference statements)

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“…Betaine shows the lowest efficiency in terms of both the conversion of PET and the yield of BHET. [Ch][Lys] was reported to be a good IL for biomass pretreatment; its ability to degrade PET is 100 % after 4 h at 180 °C; however, the yield of BHET for [Ch][Lys] is only 42.7 %. This distinction of the performance of [Ch][Lys] might be attributable to the fact that the hydrogen bonding between the [Ch][Lys] ion pairs is stronger than that between [Ch][Lys] and PET.…”

Section: Resultsmentioning

confidence: 99%

Solubilization and Upgrading of High Polyethylene Terephthalate Loadings in a Low‐Costing Bifunctional Ionic Liquid

et al. 2018

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The solubilization and efficient upgrading of high loadings of polyethylene terephthalate (PET) are important challenges, and most solvents for PET are highly toxic. Herein, a low-cost (ca. $1.2 kg ) and biocompatible ionic liquid (IL), cholinium phosphate ([Ch] [PO ]), is demonstrated for the first time to play bifunctional roles in the solubilization and glycolytic degradation of PET. A high loading of PET (10 wt %) was readily dissolved in [Ch] [PO ] at relatively low temperatures (120 °C, 3 h) and under water-rich conditions. In-depth analysis of the solution revealed that high PET solubilization in [Ch] [PO ] could be ascribed to significant PET depolymerization. Acid precipitation yielded terephthalic acid as the dominant depolymerized monomer with a theoretical yield of approximately 95 %. Further exploration showed that in the presence of ethylene glycol (EG), the [Ch] [PO ]-catalyzed glycolysis of PET could efficiently occur with approximately 100 % conversion of PET and approximately 60.6 % yield of bis(2-hydroxyethyl)terephthalate under metal-free conditions. The IL could be reused at least three times without an apparent decrease in activity. NMR spectroscopy analysis revealed that strong hydrogen-bonding interactions between EG and the IL played an important role in the activation of EG and promotion of the glycolysis reaction. This study opens up avenues for exploring environmentally benign and efficient IL technology for solubilizing and recycling postconsumer polyester plastics.

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Section: Resultsmentioning

confidence: 99%

Solubilization and Upgrading of High Polyethylene Terephthalate Loadings in a Low‐Costing Bifunctional Ionic Liquid

et al. 2018

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“…[1,2] Biocatalysts, particularly esterase enzymes, offer potentiala lternatives for degradingP ET under safer conditions (Figure 1a). [1,2] Biocatalysts, particularly esterase enzymes, offer potentiala lternatives for degradingP ET under safer conditions (Figure 1a).…”

Section: Introductionmentioning

confidence: 99%

Acceleration of Enzymatic Degradation of Poly(ethylene terephthalate) by Surface Coating with Anionic Surfactants

et al. 2018

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Enzymatic degradation of poly(ethylene terephthalate) (PET) is promising because this process is safer than conventional industrial approaches. Recently, a cationic PET hydrolase (PETase) was identified from Ideonella sakaiensis. Pre‐incubation of a low‐crystallinity PET film with anionic surfactants prior to initiating the reaction was found to improve PETase activity 120‐fold. After 36 h at 30 °C, the film thickness decreased by 22 %. The binding of surfactants to the film makes the surface anionic, thereby attracting the cationic PETase. Mutagenesis of PETase showed that the surface cationic region formed by R53, R90, and K95, which are located on the same side as the substrate binding pocket, was crucial for efficient acceleration of activity by the anionic surfactant. Thus, surfactant bound on PET aligns the orientation of the active site to the surface, resulting in efficient hydrolysis. We believe that this approach using PETase could be further improved by designing surfactant molecules for the more efficient enzymatic PET degradation.

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“…Recycling of PET through depolymerization has been extensively studied and reviewed due to the large volumes of PET bottles, which are creating a fast-growing waste problem (Al-Sabagh et al 2016;Chen et al 2011;Dutt and Soni 2013;George and Kurian 2014;Geyer et al 2016;Paliwal and Mungray 2013;Sinha et al 2010). There are three main chemical degradation methods for PET; hydrolysis (acid, neutral, or alkaline), alcoholysis (Oakley et al 1993), and glycolysis (Viana et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Development of an efficient route for combined recycling of PET and cotton from mixed fabrics

et al. 2017

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Most textile waste is either incinerated or landfilled today, yet, the material could instead be recycled through chemical recycling to new high-quality textiles. A first important step is separation since chemical recycling of textiles requires pure streams. The focus of this paper is on the separation of cotton and PET (poly(ethylene terephthalate), polyester) from mixed textiles, so called polycotton. Polycotton is one of the most common materials in service textiles used in sheets and towels at hospitals and hotels. A straightforward process using 5-15 wt% NaOH in water and temperature in the range between 70 and 90°C for the hydrolysis of PET was evaluated on the lab-scale. In the process, the PET was degraded to terephthalic acid (TPA) and ethylene glycol (EG). Three product streams were generated from the process. First is the cotton; second, the TPA; and, third, the filtrate containing EG and the process chemicals. The end products and the extent of PET degradation were characterized using light microscopy, UV-spectroscopy, and ATR FT-IR spectroscopy, as well as solution and solid-state NMR spectroscopy. Furthermore, the cotton cellulose degradation was evaluated by analyzing the intrinsic viscosity of the cotton cellulose. The findings show that with the addition of a phase transfer catalyst (benzyltributylammonium chloride (BTBAC)), PET hydrolysis in 10% NaOH solution at 90°C can be completed within 40 min. Analysis of the degraded PET with NMR spectroscopy showed that no contaminants remained in the recovered TPA, and that the filtrate mainly contained EG and BTBAC (when added). The yield of the cotton cellulose was high, up to 97%, depending on how long the samples were treated. The findings also showed that the separation can be performed without the phase transfer catalyst; however, this requires longer treatment times, which results in more cellulose degradation.

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Recycling of poly(ethylene terephthalate) – A review focusing on chemical methods

Cited by 197 publications

References 227 publications

Solubilization and Upgrading of High Polyethylene Terephthalate Loadings in a Low‐Costing Bifunctional Ionic Liquid

Solubilization and Upgrading of High Polyethylene Terephthalate Loadings in a Low‐Costing Bifunctional Ionic Liquid

Acceleration of Enzymatic Degradation of Poly(ethylene terephthalate) by Surface Coating with Anionic Surfactants

Development of an efficient route for combined recycling of PET and cotton from mixed fabrics

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