Depolymerization Of Polyethylene Terephthalate Research Articles

Catalytic Glycolysis of Poly(ethylene terephthalate) Using Zinc and Cobalt Oxides Recycled from Spent Batteries

The chemical recycling of polyethylene terephthalate (PET) to bis(2-hydroxyethyl) terephthalate (BHET) was studied using recycled metal oxides. Recovered zinc (RZnO) and cobalt (RCoO) oxides were obtained after a biohydrometallurgical process to recycle spent alkaline and lithium-ion batteries (LIBs), respectively. Besides, a mixed oxide (Co/RZnO) was prepared by mechanical milling of 2.5 wt% of RCoO on RZnO. The structural, textural, and acidity properties of the catalysts were analyzed by XRD, XANES, SEM, TEM, FT-IR, SBET and pyridine-TPD. The depolymerization of PET (from soft-drink bottles) was carried out with ethylene glycol (EG) at 196 °C for 2 h, using PET/catalyst and PET/EG ratios of 100:1 and 1:8, respectively. The yields of the BHET monomer in the presence of RZnO, RCoO and Co/RZnO as catalysts were 50%, 10% and 80%, respectively. The highest catalytic activity of Co/RZnO could be attributed to the presence of weak and strong acid sites, its overall higher concentration of acid sites and a synergetic effect between Co3O4 and ZnO. The obtained BHET was characterized by DSC, FT-IR, 1H NMR and 13C NMR analyses, which confirmed the purity and structure of the monomer. Metal oxides obtained using spent alkaline and lithium-ion batteries as raw materials could be used as catalysts for waste PET treatment and pure BHET monomer synthesis.

Eco-friendly, Expeditious Depolymerization of PET in the Blend Fabrics by Using a Bio-based Deep Eutectic Solvent under Microwave Irradiation for Composition Identification

An eco-friendly, expeditious technique was developed for depolymerization of polyethylene terephthalate (PET) in blend fabric. A completely bio-based deep eutectic solvent (DES), glycerol-choline chloride (GC), could replace conventional toxic solvents commonly used in PET depolymerization. Microwave irradiation was used to facilitate the process with high energy efficiency. The PET portion in 65/35 and 50/50 PET/cotton blends was removed by GC containing 5% NaOH in less than 100 seconds of microwave irradiation. Various instrumental techniques such as FTIR, TGA, SEM, and XRD substantiated the removal of PET from the blend fabrics. The depolymerization mechanism was investigated by analyzing its dissolved residues by HPLC. Finally, a commercial sample with 45/55 PET/cotton was also examined to confirm that the test method developed could have practical application.

PET glycolysis optimization using ionic liquid [Bmin]ZnCl3 as catalyst and kinetic evaluation

Abstract In the present work, the depolymerization of polyethylene terephthalate (PET) was performed by the method of glycolysis with ethylene glycol. The process was carried out using a factorial design in the Box-Behnken optimization model, using a response surface methodology (RSM) in which three factors (time, temperature and mass ratio of ethylene glycol) were studied in three levels of variation (- 1, 0, +1) with two replicates of the center point, totalizing 15 experiments for which the yield of bis (2-hydroxyethyl) terephthalate (BHET) monomers formed in the process was chosen as response. In parallel, the Arrhenius kinetic test was used to determine the apparent activation energy (Ea) for the 1-butyl-3-methylimidazole trichlorozincate ([Bmin]ZnCl3) - catalyst used in the depolymerization process. The products of glycolysis obtained were characterized by spectroscopic techniques (FTIR), (1 H and 13C NMR), thermal analyses (TGA) and (DSC) and Mass Spectrometry LC-MS/MS hybrid Quadrupole-Orbitrap.

Functionalized 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD) as Novel Organocatalyst for Efficient Depolymerization of Polyethylene Terephthalate (PET) Wastes

Poly(ethyleneterephthalate) waste was efficiently depolymerized through glycolysis and aminolysis reactions in the presence of functionalized 1,5,7-triazabicyclo [4.4.0] dec-5-ene (TBD) catalyst. The new catalyst of monoamide-ester type, was synthesized through reaction of dimethylterephthalate (DMT) with TBD in refluxing benzene. It was developed as a consequence of the mechanistic investigations of the transesterification reaction of isosorbide with DMT. To test the stability of functionalized TBD compound towards possible amide bond breakage, reactions with primary and secondary glycols as well as primary amines were performed when only the carboxymethyl group reacted. Moreover, it was found that the depolymerization of poly(ethyleneterephthalate) wastes proceeds faster in the presence of this novel organocatalyst by comparison with the hygroscopic TBD precursor.

Synthesis of unsaturated polyester resin from waste cellulose and polyethylene terephthalate

Unsaturated polyester resin (UPRc) was synthesized from maleic anhydride (MA) and products of glycolysis. Oligo-polyethylene terephthalate (OPET) and oligo-cellulose (OC) were obtained by depolymerization of polyethylene terephthalate (PET) waste and paper waste, respectively, both with triethylene glycol in the presence of a catalyst. OC and OPET glycolyzed product and UPRc were characterized by gel permeation chromatography, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry and nuclear magnetic resonance (1H-RMN, 13C-RMN, HSQC). Measurements showed that the initial morphological integrity of OC changed due to incorporation of semicrystalline OPET in ploycondensation with MA. Results reflect the enhanced hydrophobicity and thermal stability of the cellulose as a consequence of esterification.

Ultrasmall Cobalt Nanoparticles as a Catalyst for PET Glycolysis: A Green Protocol for Pure Hydroxyethyl Terephthalate Precipitation without Water

Polyethylene terephthalate (PET) is a very stable polymer widely used in the modern world. Due to its stability, this polymer can remain in the environment for several years before its complete degradation. The glycolysis reaction of PET has emerged as a green approach to obtain the PET monomer, thus avoiding such environmental problems and adding value to this waste. In this work, PET waste was depolymerized by glycolysis using ultrasmall cobalt nanoparticles (1.5 wt %) as the catalyst for the production of bis-2-hydroxyethyl terephthalate (BHET). A capping agent (tannic acid, TA) and a borohydride reduction approach were used to obtain such ultrasmall cobalt nanoparticles (∼3 nm). A PET depolymerization yield of 96% was achieved within 3 h at 180 °C. The precipitation of 77% of pure BHET was achieved without the need for water. The remaining ethylene glycol solution containing the ultrasmall cobalt nanoparticle catalyst was reused five times for this glycolysis process, demonstrating the feasibility of ...

Depolymerization and Assimilation of Poly (Ethylene Terephthalate) By Whole-Cell Bioprocess

Now, biofunctionalization of synthetic polymers can be achieved through biocatalysts. Uniquely among the great enzyme, whole-cell biocatalysts provide a promising alternative for bioprocess. The bioprocess of depolymerization and assimilation of polyethylene terephthalate (PET) was investigated with whole-cell from aeromonas as biocatalyst in this investigation. The engineered aeromonas strain, which can grow with PET particle as sole carbon source and major energy, was employed as biocatalysts. The main products, such as terephtalic acid (TA), bis (2-hydroxyethyl terephthalate) (BHET) and benzoic acid (BA), muconic acid (MA), were recognized in whole-cell bioprocess of PET depolymerization. It showed that variation of these products was more complex than that in case of enzyme treatment, for the interaction of solid insoluble substrate, microbe cell and enzymes secreted by cells in this heterogeneous process. The result demonstrated that not only the ester bonds can be cleaved, but also the benzene ring can be decomposed in the process of whole-cell catalysis. And some of the intermediate products, which have inhibiting effect in enzyme catalysis process, can be utilized and further degraded in whole-cell bioprocess. Furthermore, assays by DSC showed that as degradation of PET progressed, crystallinity of PET granular increased by 1.81% due to preferential degradation of amorphous regions.

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

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-1 ) and biocompatible ionic liquid (IL), cholinium phosphate ([Ch]3 [PO4 ]), 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]3 [PO4 ] 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]3 [PO4 ] 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]3 [PO4 ]-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.

An overview on PET waste recycling for application in packaging

The most important thermoplastic is one of the polyethylene terephthalate (PET) individuals from the polyester group. Owing to its excellent physical and chemical properties, it has enormous applications in food and beverage packaging. One of the most effective ways to reduce the quantity of PET wastes is the route of recycling the wastes. Incessant hard work of researchers across the world has acquired incredible upgrades in the techniques involved in PET recycling. This paper reviews (a) the most viable methods that have emerged over the years for concoction reusing of PET with extraordinary accentuation on glycolytic depolymerization of PET with ethylene glycol; (b) the different process and late improvements towards expanding the monomer yield; and (d) effect of new innovations, for example, nanotechnology, on future improvements of compound reusing of PET and utilization of recycled PET in the packaging sector.

Development and Applications of Transesterification Reactions Catalyzed by N-Heterocyclic Olefins.

A novel method to utilize N-heterocyclic olefins (NHOs), the alkylidene derivatives of N-heterocycic carbenes, as organocatalysts to promote transesterification reactions has been developed. Because of their strong Brønsted/Lewis basicity, NHOs can enhance the nucleophilicity of alcohols for their acylation reactions with carboxylic esters. This transformation can be employed in industrially relevant processes such as the production of biodiesel, the depolymerization of polyethylene terephthalate (PET) from plastic bottles for recycling purposes, and the ring-opening polymerization of cyclic esters to form biodegradable polymers such as polylactide (PLA) and polycaprolactone (PCL).

Molecular-Level Kinetic Modeling of the Gasification of Common Plastics

A molecular-level kinetic model was developed for the gasification of common plastics, including polyethylene (PE), polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polystyrene (PS). Model development was divided into three steps: molecular characterization of the feed, generation of a pathway-level reaction network, and creation of the material balance differential equations (DEs). The structure of all polymers was modeled as linear with known repeat units. For PE, PVC, and PET, Flory–Stockmayer statistics were used to describe the initial polymer size distribution. PS was described using a two-parameter γ distribution. The parameters of all polymer size distributions were tuned using data from the literature. The chemistry of plastic gasification contains depolymerization, pyrolysis, and gasification reactions. The initial depolymerization of PE and PET was modeled using random-scission and Flory–Stockmayer statistics. A statistical method was created extending random scission to a genera...

Effect of the modified silica Nanofiller on the Mechanical Properties of Unsaturated Polyester Resins Based on Recycled Polyethylene Terephthalate

Unsaturated polyester resin (UPe)-based nanocomposites and fumed silica Aerosil R812S, R805 and R816, and R200 modified with phenyl terminal group, R200NPh, were prepared. UPe resins were synthesized from maleic anhydride and products of glycolysis, obtained by polyethylene terephthalate depolymerization with dipropylene glycol in the presence of tetrabutyl titanate catalyst. The obtained unsaturated polyesters were characterized by acid, hydroxyl, and iodine values and by FTIR and NMR analysis. The microstructural analysis of the prepared nanocomposites, performed by using transmission electron microscopy, confirmed that silica nanoparticles formed chain-like aggregates in the polymer matrix. The presence of modified silica nanoparticles had no influence on the glass transition temperature and thermal stability of polyester matrix. The tensile modulus, stress at break, and hardness of cured products increased with increasing silica content. The impact strength of cured samples was not influenced by the silica content. POLYM. COMPOS., 38:538–554, 2017. © 2015 Society of Plastics Engineers

PET Depolymerization Catalyzed by Sulfates under Microwave Irradiation

Different sulfates were used as the catalysts of polyethylene terephthalate (PET) depolymerization under microwave of 250 watts, in which ZnSO4presented the best catalysis in this reaction, and the depolymerization degree (DPD) of PET was reached to 90 %. It was found that the depolymerization was occurred simultaneously on the surface and the internal parts of PET chips by the observation of scanning electron microscope (SEM) images. In addition, DPD increased with the improvement of the polarization forces of these sulfates.

Catalytic depolymerization of polyethylene terephthalate in hot compressed water

Zinc acetate (Zn(Ac)2) catalyzed depolymerization of polyethylene terephthalate (PET) in hot compressed water (HCW) was carried out in a batch autoclave reactor, as a potential method for chemical recycling of waste PET. The effects of the ratio of Zn(Ac)2 to PET (0–3%), temperature (220–300°C), and reaction time (5–60min) were investigated. The optimal conditions for complete catalytic depolymerization of PET were temperature 240°C, pressure 3.2MPa, reaction time 30min, and Zn(Ac)2/PET ratio 1.5%. The main products of catalytic depolymerization were identified and quantified as terephthalic acid and ethylene glycol by Fourier-transform infrared spectroscopy, high-performance liquid chromatography, gas chromatography/mass spectrometry, and gas chromatography. The maximum yield of terephthalic acid reached 90.5%. The phase behavior of PET with or without a catalyst in water during heating and cooling was studied in a fused-silica capillary reactor. According to the phase change data, the temperature of PET dissolution in HCW to form a homogeneous aqueous solution was decreased by adding Zn(Ac)2.

Effect of Support Size on the Catalytic Activity of Metal-Oxide-Doped Silica Particles in the Glycolysis of Polyethylene Terephthalate

Zinc oxide (ZnO) and cerium oxide (CeO2) nanoparticles were deposited on the surface of preformed silica spheres with diameters ranging from 60 to 750 nm. Ultrasonic irradiation was employed to promote the deposition of the metal oxide nanoparticles on the surface of silica. Silica-supported zinc oxide or cerium oxide was used as a catalyst in the glycolysis of polyethylene terephthalate, one of the key processes in the depolymerization of polyethylene terephthalate. The effect of the support size on the catalytic activity was studied in terms of monomer yield, and the monomer concentration was analyzed via high-performance liquid chromatography (HPLC). The morphologies and surface properties of the catalysts were characterized using a scanning electron microscope, a transmission electron microscope, and a BET surface area analyzer, while the monomer was characterized via HPLC and nuclear-magnetic-resonance spectroscopy. Both the zinc oxide and cerium oxide deposited on a smaller support showed better distribution and less aggregation. The high specific surface area of the smaller support catalysts provided a large number of active sites. The highest monomer yield was obtained with a catalyst of 60-nm silica support.

Kinetics of neutral hydrolytic depolymerization of PET (polyethylene terephthalate) waste at higher temperature and autogenious pressures

AbstractNeutral hydrolytic depolymerization of PET (Polyethylene terephthalate) waste was studied using 0.5‐L high pressure autoclave at the temperatures 100, 150, 200, 230, and 250°C at autogenious pressures 15, 80, 230, and 451 psi (pound per square inch) and time intervals of 60, 90, 120, and 150 min, respectively. The obtained terephthalic acid (TPA) was characterized by measuring its acid value and recording FTIR spectra. Depolymerization of the PET by neutral hydrolysis was found to be first order with velocity constant in the order of 10−2 min−1. Energy of activation and frequency factor were obtained by slope and intercept of Arrhenius plot, which were found to be 99.58 KJ mole−1 and 2.9 × 108 min−1respectively. Effect of temperature on rate of depolymerization reaction was also studied and optimized: rate of reaction increased drastically on increase in temperature from 150 to 200°C. Modified shrinking core model based on acid values focused the light on depolymerization of the PET into TPA by fragmentation due to formation of pores and cracks. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Polyethylene Terephthalate Chemical Recycling in the Melted State

In this work the results of research on polyethylene terephthalate depolymerization by the chemical recycling method in the fused state with use of alkalis are submitted. The potential of terephthalic acid and ethylene glycol reception from polymer with addition of alkalis in the melt is shown. It is established that calcium hydroxide is the optimal reagent for performing the depolymerization reaction. This method of chemical recycling does not have the demands of high temperature and pressure, it is realized in a short time and it results in products with the high cleanliness.

Recycling of waste PET into useful textile auxiliaries

Polyethylene terephthalate (PET) waste fibers were initially depolymerized using a glycolysis route in the presence of sodium sulfate as a catalyst, which is a commonly used chemical and ecofriendly as compared to heavy metal catalysts. Good yield of the pure monomer bis(2-hydroxyethylene terephthalate) (BHET) was obtained. Further, to attempt its reuse, the purified BHET was converted to different fatty amide derivatives to obtain quaternary ammonium compounds that have a potential for use as softener in the textile finishing process. The products were characterized by infrared spectroscopy. Application of these synthesized compounds was carried out on cotton fabric; they were evaluated for performance and were found to give good results. The chemicals used during depolymerization and reuse of PET are inexpensive and comparatively less harmful to the environment, and thus offer advantages in the chemical recycling of polyester waste fibers.

Polymer Concrete from Marble Wastes and Recycled Poly(ethylene terephthalate)

A polymer concrete (PC) was synthesized by mixing styrenated polyester (SP) and marble wastes as fillers. The unsaturated polyester (UP) used was prepared from the reaction of oligomers obtained from the depolymerization of polyethylene terephthalate (PET) soft drink bottles with maleic anhydride and adipic acid. The UP was then mixed with the styrene monomers at a ratio of 60: 40% by weight to obtain the SP used for the synthesis of the PC. The aim of this work is to study the suitability of the prepared PC to be used as polymer based building materials. Using marble and PET soft drink bottle wastes for the preparation of the PC affects the environment positively, by avoiding the accumulation of these wastes. Saving the raw materials of polymer and fillers for other applications is another economical advantage of preparing the PC from the recycled PET and marble waste. Mechanical integrity of the PC was studied as blocks prepared under different experimental conditions. Chemical resistance and water absorption were also followed to evaluate the durability of the products obtained. In addition, the flammability of the SP and the PC prepared was also studied. Based on the data obtained, it could be concluded that the PC under consideration has good chemical resistance for 20% Na2CO3, 10% Noah, tap water, ground water and sea water. Besides the acceptable chemical resistance, the prepared PC shows low apparent porosity, low water absorption, and small open pores.

Kinetics and thermodynamics of hydrolytic depolymerization of poly(ethylene terephthalate) at high pressure and temperature

AbstractHydrolytic depolymerization of PET (polyethylene terephthalate) waste in excess of water was studied using a 0.5‐L stirred high‐pressure autoclave at temperatures of 100, 150, 200, and 250°C and at 200, 300, 400, 500, 700, and 800 psi (pounds per square inch) pressure. Velocity constants of hydrolysis were calculated from the experimental data obtained. Maximum depolymerization (91.38%) of PET into monomer was obtained at 250°C and 800 psi. pressure. However, the maximum rate of reaction was recorded at 200°C and 500 psi temperature and pressure, respectively. The energy of activation and frequency factor were calculated, as 64.13 KJ/g mol and 7.336 × 104 min−1, respectively, for higher pressure and temperature conditions. It was also reported that the hydrolytic depolymerization is first order with the velocity constant 1.773 × 10−2 min−1 at 250°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3305–3309, 2003