Simple But Tricky: Investigations of Terephthalic Acid Purity Obtained from Mixed PET Waste

Cosimbescu, Lelia; Merkel, Daniel R.; Darsell, Jens T.; Petrossian, Gayaneh

doi:10.1021/acs.iecr.1c02604

Cited by 32 publications

(39 citation statements)

References 28 publications

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“…Powdered, virgin PET for model reactions was purchased from Goodfellow Corporation (Coraopolis, PA). TPA was obtained from mixed-waste PET, composed of colored, clear, and opaque yellow bottles whose labels and caps were not removed, via basic hydrolysis, and the study is reported in detail elsewhere …”

Section: Methodsmentioning

confidence: 99%

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Kevlar-like Aramid Polymers from Mixed PET Waste

et al. 2022

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This work describes the synthetic approaches, spectroscopic and thermal characterization of aramid polymers prepared from waste polyethylene terephthalate (PET) via sustainable and scalable processes. Direct depolymerization of PET with aliphatic diamines under melt conditions resulted in decomposition without substantial formation of any aramid polymer. The Higashi–Ogata methodology or direct polycondensation of terephthalic acid (TPA) derived from PET waste and p -phenylenediamine, resulted in oligomerization and formation of aramids with a low degree of polymerization. The highest molecular weight polymers were obtained via the acid chloride of TPA, the traditional method. A proprietary solvent enabled the dissolution of most polymers and subsequent size exclusion chromatography analysis in the same solvent. We emphasize that although the soluble polymer compounds are prepared via the traditional route, they are novel. The apparent molecular weights of the soluble polymers ranged between 10–35 kDa ( M n ) and 28–81 kDa ( M w ). All analogues were prepared with commercially available diamines and diamine combinations. The obtained solid powders were dissolved in D 2 SO 4 and analyzed spectroscopically to qualitatively evaluate the degrees of polymerization, while the solids were characterized via thermogravimetric analysis and differential scanning calorimetry. Many reaction conditions were employed to improve the solution polycondensation reaction, and it was found that addition of pyridine (2 eq) to the NMP reaction medium was crucial in preventing the precipitation of the polymer. Contrary to conventional wisdom, CaCl 2 did not play a crucial role in the molecular weight increase of the polymer when oxydianiline was used. Our data indicated that the temperature and absence of CaCl 2 provided a boost in molecular weight. Both room temperature and 0 °C reactions generated similar polymers as suggested by nuclear magnetic resonance; however, the cold conditions enhanced gel formation, an important attribute in the future processing of these materials to obtain fibers. All analogues had a high degradation temperature at 5 and 10% weight loss ( 5% and T 10% ), above 400 °C, along with high percent char values. A glass transition ( T g ) was not detected in any of the analogues prepared.

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Section: Methodsmentioning

confidence: 99%

“…TPA was obtained from mixed-waste PET, composed of colored, clear, and opaque yellow bottles whose labels and caps were not removed, via basic hydrolysis, and the study is reported in detail elsewhere. 9 2.2. Synthesis.…”

Section: Methodsmentioning

confidence: 99%

Kevlar-like Aramid Polymers from Mixed PET Waste

et al. 2022

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“…While this paper has focused on mechanical recycling, depolymerization of PET and chemical recycling continue to be active areas of research. Recently, investigators at the Pacific Northwest National Laboratory depolymerized PET bottles with mixed waste of pigments, labels, adhesives, and polypropylene rings . At relatively mild conditions, and using no catalyst, the chopped PET was converted in both ethylene glycol and ethanol in water to generate 97–98% pure terephthalic acid monomer.…”

Section: Resultsmentioning

confidence: 99%

“…Recently, investigators at the Pacific Northwest National Laboratory depolymerized PET bottles with mixed waste of pigments, labels, adhesives, and polypropylene rings. 82 At relatively mild conditions, and using no catalyst, the chopped PET was converted in both ethylene glycol and ethanol in water to generate 97−98% pure terephthalic acid monomer. Examples of other research have examined chemical recycling as pyrolysis of HDPE 83 and pyrolysis and gasification of polypropylene.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Recycling of Plastics in the United States: Plastic Material Flows and Polyethylene Terephthalate (PET) Recycling Processes

Smith

Rao

Riegerix

2022

ACS Sustainable Chem. Eng.

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As efforts are made toward establishing a circular economy that engages in activities that maintain resources at their highest values for as long as possible, an important aspect is understanding the systems which allow recycling to occur. In this article a common plastic, polyethylene terephthalate, i.e., PET or plastic #1, has been studied because it is recycled at relatively high rates in the U.S. as compared to other plastics. A material flow analysis is described for PET resin showing materials collected, reclaimed for flake, and converted into items with recycled content. Imports/exports, reclaimer residue, and disposal with mismanaged waste are all shown for U.S. flows of PET. Barriers to recycling PET exist in the collecting, sorting, reclaiming, and converting steps, and this article describes them, offers some solutions, and suggests some research that chemists and engineers could focus on to improve the systems. This effort also models sorting at material recovery facilities (MRF) and reclaimers, with detailed descriptions of the material streams involved, to characterize the resource use and emissions from these operations that are key processes in the recycling system. Example results include greenhouse gas intensities of 8.58 kg CO2 equiv per ton of MRF feed and 103.7 kg CO2 equiv per ton of reclaimer PET bale feed. The results can be used in system analyses for various scenarios and as inputs in economic input-output and life cycle assessments.

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“…A significant finding in Figure is that the presence of PP or cellulose during PET hydrolysis does not increase the amount of byproducts in the solids containing the TPA. Cosimbescu et al studied the byproducts from hydrolysis (with ethylene glycol or ethanol as co-solvents) of pure PET and mixed waste (PET bottles with caps). Their analyses indicated 97–98% purity (based on proton peak areas from NMR) of the TPA irrespective of the components in the initial mixture.…”

Section: Resultsmentioning

confidence: 99%

Effect of Cellulose and Polypropylene on Hydrolysis of Polyethylene Terephthalate for Chemical Recycling

Subramanya

Savage

2022

ACS Eng. Au

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We examined the hydrolysis of polyethylene terephthalate (PET) with added polypropylene or cellulose and measured the yield of the terephthalic acid (TPA) monomer recovered. The TPA yield from hydrolysis at 250 °C for 30 min nearly doubled from 40 to 75% with the addition of polypropylene (PP). It increased to 55% with the addition of cellulose. There were no statistically significant increases in TPA yield from hydrolysis with the added plastic or biomass at 300 or 350 °C. The solid material recovered from the hydrolytic depolymerization, after first recovering water-and dichloromethane-soluble compounds, was largely TPA, and the amounts of the other reaction products present with it were largely the same irrespective of the presence or absence of PP or cellulose in the reactor. The TPA yield was affected strongly by the reaction time, reaction temperature, and PET type (fiber-reinforced pellet vs chips from a water bottle). The addition of PP or cellulose to the reactor reduces the influence of reaction time on TPA yield from PET hydrolysis.

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Simple But Tricky: Investigations of Terephthalic Acid Purity Obtained from Mixed PET Waste

Cited by 32 publications

References 28 publications

Kevlar-like Aramid Polymers from Mixed PET Waste

Kevlar-like Aramid Polymers from Mixed PET Waste

Recycling of Plastics in the United States: Plastic Material Flows and Polyethylene Terephthalate (PET) Recycling Processes

Effect of Cellulose and Polypropylene on Hydrolysis of Polyethylene Terephthalate for Chemical Recycling

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