Optimization and Kinetic Evaluation for Glycolytic Depolymerization of Post-Consumer PET Waste with Sodium Methoxide

Javed, Saqib; Fisse, Jonas; Vogt, Dieter

doi:10.3390/polym15030687

Cited by 11 publications

(7 citation statements)

References 46 publications

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“…This indicates that equilibrium has been reached in the reaction and since the conversion of the dimer to the BHET monomer is a reversible process, polymerization can occur generating dimers or oligomers [ 45 ]. Therefore, extending the reaction after equilibrium has been reached causes the reaction to shift backwards, increasing the amount of dimer with a slight loss of the BHET monomer [ 46 ]. Figure 6 b refers to the NMR results for glycolyzed samples extracted at different reaction times.…”

Section: Resultsmentioning

confidence: 99%

Improving the Sustainability of Catalytic Glycolysis of Complex PET Waste through Bio-Solvolysis

Amundarain,

López-Montenegro,

Fulgencio-Medrano

et al. 2024

Polymers

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This work addresses a novel bio-solvolysis process for the treatment of complex poly(ethylene terephthalate) (PET) waste using a biobased monoethylene glycol (BioMEG) as a depolymerization agent in order to achieve a more sustainable chemical recycling process. Five difficult-to-recycle PET waste streams, including multilayer trays, coloured bottles and postconsumer textiles, were selected for the study. After characterization and conditioning of the samples, an evaluation of the proposed bio-solvolysis process was carried out by monitoring the reaction over time to determine the degree of PET conversion (91.3–97.1%) and bis(2-hydroxyethyl) terephthalate (BHET) monomer yield (71.5–76.3%). A monomer purification process, using activated carbon (AC), was also developed to remove the colour and to reduce the metal content of the solid. By applying this purification strategy, the whiteness (L*) of the BHET greatly increased from around 60 to over 95 (L* = 100 for pure white) and the Zn content was significantly reduced from around 200 to 2 mg/kg. The chemical structure of the purified monomers was analyzed via infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC), and the composition of the samples was measured by proton nuclear magnetic resonance (1H-NMR), proving a high purity of the monomers with a BHET content up to 99.5% in mol.

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Section: Resultsmentioning

confidence: 99%

Improving the Sustainability of Catalytic Glycolysis of Complex PET Waste through Bio-Solvolysis

Amundarain,

López-Montenegro,

Fulgencio-Medrano

et al. 2024

Polymers

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“…An important task for further study of homogeneous glycolysis both in solution and in melt is the development of its kinetic model, which takes into account the conditions of the process. The currently existing models take into account only the reactions of ester groups of PET and the resulting products of glycolysis with ethylene glycol, as well as reverse reactions [ 36 , 41 ]. This approach does not take into account the interaction of PET ester groups with terminal hydroxyl groups formed during the reaction.…”

Section: Introductionmentioning

confidence: 99%

Modeling of Poly(Ethylene Terephthalate) Homogeneous Glycolysis Kinetics

et al. 2023

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Polymer composites with various recycled poly(ethylene terephthalate)-based (PET-based) polyester matrices (poly(ethylene terephthalate), copolyesters, and unsaturated polyester resins), similar in properties to the primary ones, can be obtained based on PET glycolysis products after purification. PET glycolysis allows one to obtain bis(2-hydroxyethyl) terephthalate and oligo(ethylene terephthalates) with various molecular weights. A kinetic model of poly(ethylene terephthalate) homogeneous glycolysis under the combined or separate action of oligo(ethylene terephthalates), bis(2-hydroxyethyl) terephthalate, and ethylene glycol is proposed. The model takes into account the interaction of bound, terminal, and free ethylene glycol molecules in the PET feedstock and the glycolysis agent. Experimental data were obtained on the molecular weight distribution of poly(ethylene terephthalate) glycolysis products and the content of bis(2-hydroxyethyl) terephthalate monomer in them to verify the model. Homogeneous glycolysis of PET was carried out at atmospheric pressure in dimethyl sulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP) solvents with catalyst based on antimony trioxide (Sb2O3) under the action of different agents: ethylene glycol at temperatures of 165 and 180 °C; bis(2-hydroxyethyl) terephthalate at 250 °C; and oligoethylene terephthalate with polycondensation degree 3 at 250 °C. Homogeneous step-by-step glycolysis under the successive action of the oligo(ethylene terephthalate) trimer, bis(2-hydroxyethyl) terephthalate, and ethylene glycol at temperatures of 250, 220, and 190 °C, respectively, was also studied. The composition of products was confirmed using FTIR spectroscopy. Molecular weight characteristics were determined using gel permeation chromatography (GPC), the content of bis(2-hydroxyethyl) terephthalate was determined via extraction with water at 60 °C. The developed kinetic model was found to be in agreement with the experimental data and it could be used further to predict the optimal conditions for homogeneous PET glycolysis and to obtain polymer-based composite materials with desired properties.

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“…This not only reduces the purity of the BHET monomer but also harms the quality of the recycled PET. Consequently, efforts to develop glycolysis catalysts have shifted their focus from heavy metal salts to environmentally benign materials, e.g., light metal salts. , The application of sodium-based salts was reported by López-Fonseca et al to find an environmentally friendly alternative to zinc acetate. At 196 °C, they reported up to 66% BHET yield using sodium carbonate as a catalyst for PET glycolysis.…”

Section: Introductionmentioning

confidence: 99%

Kinetic Investigation for Chemical Depolymerization of Post-Consumer PET Waste Using Sodium Ethoxide

Javed

Fisse

Vogt

2023

Ind. Eng. Chem. Res.

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Reaction kinetics provides significant insights into the reaction rate and mechanism to control a chemical reaction. In the present work, the detailed kinetics of glycolytic depolymerization of post-consumer polyethylene terephthalate (PET) waste in the presence of sodium ethoxide (EtONa) was investigated. The glycolysis experiments were conducted in a batch reactor over a temperature range of 160 to 197 °C. The confirmation of the product, the bis(2-hydroxyethyl)terephthalate monomer, was carried out using nuclear magnetic resonance spectroscopy, high-performance liquid chromatography, differential scanning calorimetry, and X-ray diffraction techniques. Investigations on the influence of particle size and temperature showed that conversion increased with a decrease in particle size and increasing temperature. Equilibrium conversions were found at different temperatures, and a van 't Hoff plot was used to confirm that the depolymerization reaction is endothermic. Gibbs' free energy was used to calculate the ceiling temperature (T C = 156 °C). Three kinetic models were tested for their applicability. It was found that the EtONa-catalyzed glycolysis of PET follows a first-order reversible reaction kinetic model at higher temperatures (170−197 °C). However, a heterogeneous shrinking core mechanism was applicable in a lower temperature range (160−170 °C). The kinetic evaluation revealed that the PET glycolysis reaction consists of heterogeneous and homogeneous mechanisms depending upon the depolymerization stages at various temperatures.

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Optimization and Kinetic Evaluation for Glycolytic Depolymerization of Post-Consumer PET Waste with Sodium Methoxide

Cited by 11 publications

References 46 publications

Improving the Sustainability of Catalytic Glycolysis of Complex PET Waste through Bio-Solvolysis

Improving the Sustainability of Catalytic Glycolysis of Complex PET Waste through Bio-Solvolysis

Modeling of Poly(Ethylene Terephthalate) Homogeneous Glycolysis Kinetics

Kinetic Investigation for Chemical Depolymerization of Post-Consumer PET Waste Using Sodium Ethoxide

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