Glycolysis Of PET Research Articles

PET Glycolysis to BHET Efficiently Catalyzed by Stable and Recyclable Pd-Cu/γ-Al2O3.

Glycolysis of poly(ethylene terephthalate) (PET) is a prospective way for degradation of PET to its monomer bis(hydroxyethyl) terephthalate (BHET), providing the possibility for a permanent loop recycling. However, most reported glycolysis catalysts are homogeneous, making the catalyst difficult to recover and contaminating the products. Herein, we reported on the Pd-Cu/γ-Al2O3 catalyst and applied it in the glycolysis of PET as catalyst. The formed structure gave Pd-Cu/γ-Al2O3 a high active surface area, which enabled these micro-particles to work more efficiently. The PET conversion and BHET yield reached 99% and 86%, respectively, in the presence of 5 wt% of Pd-Cu/γ-Al2O3 catalyst within 80 min at 160 °C. After the reaction, the catalyst can be quickly separated by filtration, so it can be easily reused without significant loss of reactivity at least five times. Therefore, the Pd-Cu/γ-Al2O3 catalyst may contribute to an economically and environmentally improved large-scale recycling of PET fiber waste.

Factorial Analysis and Thermal Kinetics of Chemical Recycling of Poly(ethylene terephthalate) Aided by Neoteric Imidazolium-Based Ionic Liquids.

Poly(ethylene terephthalate) (PET) waste accumulation poses significant environmental challenges due to its persistent nature and current management limitations. This study explores the effectiveness of imidazolium-based neoteric solvents [Emim][OAc] and [Bmim][OAc] as catalytic co-solvents in the glycolysis of PET with ethylene glycol (EG). Reaction thermal kinetics showed that both ionic liquids (ILs) significantly enhanced the depolymerization rate of PET compared to traditional methods. The use of [Emim][OAc] offered a lower activation energy of 88.69 kJ·mol-1, thus making the process more energy-efficient. The contribution of key process parameters, including temperature (T), plastic-to-ionic liquid (P/IL) mass ratio, and plastic-to-solvent (P/S) mass ratio, were evaluated by means of a factorial analysis and optimized to achieve the maximum PET conversion for both neoteric solvents. The relevance sequence for both ionic liquids involved the linear factors T and P/S, followed by the interaction factors T×P/S and T×P/IL, with P/IL being the less significant parameter. The optimal conditions, with a predicted conversion of 100%, involved a temperature of 190 °C, with a P/IL of 1:1 and a P/S of 1:2.5, regardless of the IL used as the catalytic co-solvent.

DFT study on the depolymerization of PET by Ca-catalyzed glycolysis reaction model

Poly(ethylene terephthalate) (PET) is the most common plastics produced for applications in food and drinking containers. It is degraded to valuable product by several methods. Glycolysis of PET gains bis(2-hydroxyethylene) terephthalate (BHET) as the main product utilized as plasticizer. Calcium catalysts, Ca2+ and Ca(OH)2∙2H2O were explored to study the mechanism of PET cleavage by DFT calculations at B3LYP/6-311++G** level. Two possible pathways, coordination, and non-coordination of ethylene glycol on the calcium in glycolysis reaction, have been investigated. In addition, poly(ethylene furanoate) (PEF), considered as a sustainable polymer with the similar functional properties, was chose for the comparison of conformational structures with PET. The understanding of the relationship between PET (and PEF) structures and calcium catalysts is useful for the future development of linear sustainable polyesters.

The Recyclable Dual-Functional Zeolite Nanocrystals Promoting the High Efficiency Glycolysis of PET

The Recyclable Dual-Functional Zeolite Nanocrystals Promoting the High Efficiency Glycolysis of PET

Efficient and eco-friendly UV-cured polyurethane coating: Harnessing thiol-yne systems for corrosion protection

The UV-curable coatings have received significant attention from researchers due to their excellent advantages in corrosion protection. However, there has not been much effort made to investigate the UV-curable thiol-yne system. This project aims to prepare effective and environmentally-friendly polyurethane coatings capable of being cured by UV light using thiol-yne systems. Utilizing the chain extender derived from the glycolysis of PET, the bis(2-hydroxyethyl) terephthalate (BHET) as a glycolysis product was synthesized via the glycolysis reaction. Polyurethanes (PUYNE: yne-terminated polyurethanes and PUSH: thiol-terminated polyurethanes) were synthesized by utilizing BHET, and by altering the quantity of the BHET, and PUX coatings were formed upon exposure to UV light. The impact of PUYNE molecular weight and the resulting amount of thiol-yne crosslinking on mechanical and thermal properties were evaluated, and corrosion resistance was examined with electrochemical impedance spectroscopy (EIS). PUX1, which had the lowest molecular weight and the highest number of thioether bonds, exhibited the superior corrosion resistance properties so that after 8 weeks of immersion in saline solution, the impedance modulus at 0.01 Hz was 1.43×108 Ω.cm2. This study provides insight into the application of thiol-yne systems in forming UV-cured coatings and their protective role in preventing corrosion.

Overcoming the Limitations of Organocatalyzed Glycolysis of Poly(ethylene terephthalate) to Facilitate the Recycling of Complex Waste Under Mild Conditions.

Although multiple methods have been reported in the literature for the chemical recycling of poly(ethylene terephthalate) (PET), large-scale depolymerization is not yet widely employed. The main reasons for the limited adoption of chemical recycling of PET are the harsh conditions required and the lack of selectivity. In this study, the organocatalytic glycolysis of PET mediated by organic bases at low temperatures is studied, and routes to avoid the deactivation of the catalyst are explored. It is shown that the formation of terephthalic acid by uncontrolled hydrolysis leads to issues which can be resolved using potassium tert-butoxide as a cocatalyst. Finally, complex PET waste obtained from a mechanical recycling plant was depolymerized under optimized conditions, obtaining bis(2-hydroxyethyl) terephthalate yields >90% in less than 15 min at only 100 °C. These results open the way to efficient recycling of PET-enriched waste streams under milder conditions.

One-pot synthesis of titanium isophthalate and highly active catalytic glycolysis of waste PET

The glycolysis of PET represents a pivotal approach to achieving high-value utilization following its disposal.

Envisioning a BHET Economy: Adding Value to PET Waste

Poly(ethylene terephthalate), the fifth most produced polymer, generates significant waste annually. This increased waste production has spurred interest in chemical and mechanical pathways for recycling. The shift from laboratory settings to larger-scale implementation creates opportunities to explore the value and recovery of recycling products. Derived from the glycolysis of PET, bis(2-hydroxyethyl) terephthalate (BHET) exhibits versatility as a depolymerization product and valuable monomer. BHET exhibits versatility and finds application across diverse industries such as resins, coatings, foams, and tissue scaffolds. Incorporating BHET, which is a chemical recycling product, supports higher recycling rates and contributes to a more sustainable approach to generating materials. This review illuminates the opportunities for BHET as a valuable feedstock for a more circular polymer materials economy.

Modeling of Poly(Ethylene Terephthalate) Homogeneous Glycolysis Kinetics.

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.

Catalytic Fabric Recycling: Glycolysis of Blended PET with Carbon Dioxide and Ammonia

Catalytic Fabric Recycling: Glycolysis of Blended PET with Carbon Dioxide and Ammonia

Degradation of Poly(ethylene terephthalate) Using Metal-Free 1,8-Diazabicyclo[5.4.0]undec-7-ene-Based Deep Eutectic Solvents as Efficient Catalysts

Poly(ethylene terephthalate) (PET) is glycolyzed to obtain bis(hydroxyethyl) terephthalate (BHET), and repolymerization produces new PET material, making this a sustainable recycling process. However, most studies have reported common metal-based catalysts, which typically have harsh synthetic conditions and are prone to negative environmental impacts. In this study, 1,8-diazabicyclo[5.4.0]undec-7-ene-based deep eutectic solvents (DBU-based DESs) effectively degraded PET to obtain BHET due to their high activity, low price, and accessible production properties. Under the optimized reaction conditions (DES 3.2 wt %, PET/ethylene glycol (EG) 1:3, 180 °C, 70 min), PET bottle flakes were completely degraded, and the yield of BHET achieved 83%. In addition, a possible degradation mechanism was postulated based on experimental data and calculations using density functional theory (DFT). The formation of hydrogen bonds between EG and DES and between PET and DES can promote glycolysis of PET, which in turn could facilitate the attack of hydroxyl oxygen in ethylene glycol (EG) on carbonyl carbon in PET.

Magnetic hollow micro-sized nanoaggregates for synergistically accelerating PET glycolysis

The glycolysis of PET catalyzed by hollow micro-sized nanoaggregates is a highly effective and sustainable way to tackle the escalating plastic waste problem and create a circular plastic economy.

Efficient glycolysis of PET catalyzed by a metal-free phosphazene base: the important role of EG−

A new kind of efficient metal-free catalyst phosphazene base (t-BuP2) was developed, which could achieve 100% conversion of PET and obtain comparable BHET yield (92.7%) to metal-based catalysts.

Amino Acid-Based Cholinium Ionic Liquids as Sustainable Catalysts for PET Depolymerization

Chemical recycling to monomers is one of the key strategies in tackling the issues deriving from persistent plastic pollution in the environment, and poly(ethylene terephthalate) (PET) is among the most used polymers in modern society. In this context, we herein describe the glycolysis of PET to bis-hydroxyethyl terephthalate (BHET), promoted by basic cholinium salts differing for the anions, also comprising amino acid anions. We investigated the optimal reaction conditions, finding that the best-performing catalyst is [Ch][Gly], in the presence of which a conversion of 85% and a yield of 51% are achieved at 150 °C after 6 h, from PET deriving from a clear water bottle. We used our protocol to carry out the glycolysis of PET deriving from different postconsumer waste, like opaque and colored bottles and food packages, finding that the performance is better in the former compared with the latter starting materials.

Metal ions immobilized on polymer ionic liquid as novel efficient and facile recycled catalyst for glycolysis of PET

Environmental pollution aroused by accumulation of waste PET has attracted worldwide attention. Metal chloride as Lewis acid catalyst has excellent catalytic performance in enormous organic reaction. However, the high solubility of the metal chloride in ethylene glycol and the residue of metal ions in the product will have an adverse impact on the subsequent process. In this work, polymer ionic liquid containing [NTf2]− which is insoluble in ethylene glycol at room temperature was synthesized and used to immobilize metal ions to catalyze glycolysis of PET. After reaction, the polymer ionic liquid-metal ion catalyst could be recovered at room temperature by simple filtration. PET conversion reached 95.4% and BHET yield reached 77.8% using PIL-Zn2+ as catalyst at 195 °C for 120 min. Ionic liquid was characterized by FT-IR, NMR and ESI-MS. Interaction between ionic liquid and metal ions was characterized by FT-IR. The interaction energy of polymer ionic liquid-metal ion complex is higher than that of ethylene glycol-metal ion complex by DFT calculation (Density functional calculation). The both content of metal ion in polymer ionic liquid-metal ion complex and catalytic performance of as-synthesized catalysts did not obviously decrease after the catalyst was reused for five times. This work mainly provided a way of recovering catalyst and promote development of glycolysis of PET.

Fabrication of magnetic bimetallic Co–Zn based zeolitic imidazolate frameworks composites as catalyst of glycolysis of mixed plastic

With the increasing awareness of environmental protection, the degradation of waste plastic has attracted more and more attention. In this study, the glycolysis of PET and PBT which are widely used in daily life were investigated using CoFe2O4@ZIF-8/ZIF-67 composite as catalyst. Moreover, the glycolysis of PET/PBT mixed plastic was also studied. The result showed that CoFe2O4@ZIF-8/ZIF-67 has ideally catalytic effect in glycolysis of plastic, especially in glycolysis of PET/PBT mixed plastic. PET/PBT (5 g), CoFe2O4@ZIF-8/ZIF-67 (0.05 g) and ethylene glycol (25 g) were at 200 °C for 60 min, plastic conversion is up to 100% and BHET yield reached 84.3%. The main product of glycolysis of PBT and PET/PBT was characterized and confirmed to be bis(hydroxyalkyl) terephthalate (BHET). The result of UPLC indicated that purity of main product of glycolysis of PET/PBT was 92%. The as-synthesized catalysts were characterized by XRD, FT-IR, SEM, TGA, N2 adsorption–desorption and VSM. The catalytic performance of catalysts was significantly influenced by external BET surface area. More importantly, the magnetic catalyst could be collected quickly by external magnetic field. The catalytic performance of CoFe2O4@ZIF-8/ZIF-67 did not obviously decrease and element content of Zn and Co in catalyst was just decreased by less than 10% after it was reused for five times.

Glycolysis of polyethylene terephthalate: Magnetic nanoparticle CoFe2O4 catalyst modified using ionic liquid as surfactant

The catalytic effect of nanoparticles was significantly affected by its size and surface property. In this work, a series of ionic liquids were synthesized and used as surfactant to modify CoFe2O4 MNP. XRD, FT-IR, TEM and VSM were performed to characterize modified CoFe2O4. The modified CoFe2O4 MNP with average size of 7 nm was obtained and it was so well dispersed in ethylene glycol that ethylene glycol based magnetic fluid was obtained. Modified CoFe2O4 MNP was used as catalyst for glycolysis of PET and showed excellent catalytic effect. The influence of ionic liquids surfactant and experimental factors on glycolysis were investigated. Under optimal condition, PET (5 g), catalyst (CoFe2O4/C10-OAC, 0.1 g) and EG (25 g) at 195 °C for 2.5 h, the PET conversion was 100% and BHET yield was 95.4%. More importantly, this catalyst can be collected by external magnetic field and its catalytic effect did not obviously decrease after it was reused for ten times. This work provided a new type of highly efficient catalyst of glycolysis of PET.

Selective Chemical Upcycling of Mixed Plastics Guided by a Thermally Stable Organocatalyst.

Chemical recycling of plastic waste represents a greener alternative to landfill and incineration, and potentially offers a solution to the environmental consequences of increased plastic waste. Most plastics that are widely used today are designed for durability, hence currently available depolymerisation methods typically require harsh conditions and when applied to blended and mixed plastic feeds generate a mixture of products. Herein, we demonstrate that the energetic differences for the glycolysis of BPA-PC and PET in the presence of a protic ionic salt TBD:MSA catalyst enables the selective and sequential depolymerisation of these two commonly employed polymers. Employing the same procedure, functionalised cyclic carbonates can be obtained from both mixed plastic wastes and industrial polymer blend. This methodology demonstrates that the concept of catalytic depolymerisation offers great potential for selective polymer recycling and also presents plastic waste as a "greener" alternative feedstock for the synthesis of high added value molecules.

Polyurethane resin derived from polyol of palm olein and recycled poly(ethylene terephthalate)

PurposePoly(ethylene terephthalate) (PET) waste from soft drink bottles was incorporated into palm olein alkyd to produce new polyol for use in polyurethane resins as surface protection on metal surfaces.Design/methodology/approachAlkyd was prepared from palm olein, glycerol and phthalic anhydride. PET underwent simultaneous glycolysis and transesterification reactions with the alkyd. Varying the amount of PET has led to polyols with different viscosities. Polyurethane resins were produced by reacting the polyols with toluene diisocyanate. The resins were coated on mild steel panels and cured. Performances of the cured films were tested.FindingsThe polyurethanes (PU) resin cured to a harder film with better thermal stability. Films showed excellent adhesion properties, while higher content of PET exhibited higher pencil hardness, better water, salt, acid and alkali resistance.Research limitations/implicationsOther vegetable oils could also be used. The alkyd structure could be changed by formulation to have different functionality and the ability to incorporate higher amount of PET waste. Rate of glycolysis of PET could be increased by higher amount of ethylene glycol.Practical implicationsThis method has managed to use waste PET in producing new polyol and PU resins. The cured films exhibit good mechanical and chemical properties, as well as excellent adhesion and thermal stability.Social implicationsThe non-biodegradable PET has created environmental pollution problems connected to littering and illegal landfilling. It has become necessary to pay greater attention to recycling PET bottles for obtaining valuable products.Originality/valueThis approach is different from the earlier reports, where PET was recycled to recover the raw materials.

Glycolysis of PET Using 1,3-Dimethylimidazolium-2-Carboxylate as an Organocatalyst

The use of 1,3-dimethylimidazolium-2-carboxylate as an organocatalyst for the glycolysis of waste PET, poly(ethylene terephthalate), is reported for the first time. Post-consumer PET was completely...