Glycolysis Process in Chemical Recycling of PET Bottles

Rapid and efficient depolymerization of colored polyester waste into recycled polyester using superheated steam and a decomposer. The colored polyester is contacted with superheated steam after adding a decomposer containing alkali, acid, salt, alcohol, or polyol. The decomposer removes dyes from the polyester before depolymerization. The superheated steam quickly decomposes the polyester into monomers without dissolution. The decomposer aids decomposition. The resulting dibasic acid and glycol can be purified for recycled polyester production.

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A method for depolymerizing polyethylene terephthalate (PET) using a catalyst with reduced environmental impact and that is readily available. The catalyst is a mixture of aluminum chloride and sodium chloride. The catalyst allows efficient depolymerization of PET into bis-2-hydroxyethyl terephthalate (BHET) using ethylene glycol as a solvent. The catalyst has lower environmental impact compared to traditional catalysts like zinc acetate. The aluminum chloride and sodium chloride can be easily prepared from readily available raw materials. This allows more sustainable and economical PET recycling from sources like post-consumer carpets with high contaminant levels.

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Recycling of polyethylene terephthalate (PET) waste into new PET using a two-step process that involves partial depolymerization followed by full depolymerization. The process reduces the amount of ethylene glycol and catalyst needed compared to conventional glycolysis. It also shortens the depolymerization time. The process involves mixing PET with ethylene glycol at 200-250°C for partial depolymerization. Then, contacting the partially depolymerized PET with ethylene glycol and catalyst at 170-200°C for full depolymerization. This yields bis(2-hydroxyethyl) terephthalate (BHET) with lower ethylene glycol and catalyst consumption, and shorter time compared to direct glycol

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Recycling terephthalate polyesters to improve the quality/properties. The recycling is carried out in a manner that reduces the overall energy consumption compared to gaseous methanol. The depolymerization is carried out in a manner that can be carried out in a continuous fashion.

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Method for producing high purity bis-2-hydroxyethyl terephthalate (BHET) from waste polyester through multi-stage depolymerization and separation. The method involves depolymerizing waste polyester using two-stage glycolysis reactions at lower temperatures, followed by ion exchange, distillation, and final distillation steps to remove impurities and unreacted glycols. This reduces contaminants like diethylene glycol esters that degrade BHET properties when recycling waste polyester. The resulting BHET has high purity and quality for use in polyester production.

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Enzymatic method for recycling post-consumer PET bottles by depolymerizing them into a more useful form for repolymerization. The method involves using enzymes to hydrolyze the PET into bisphenol A ethylene glycol terephthalate (BHET) esters. This is done by soaking the PET in ethylene glycol at 70°C with enzymes for several hours. The BHET esters can then be used as a feedstock for new PET production, avoiding the need for virgin petroleum-based terephthalic acid.

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Efficiently recycling polyester fibers like PET into high-purity monomer crystals for reuse. The recycling process involves reacting waste polyester fibers with methanol to produce dimethyl terephthalate (DMT). The DMT is then recrystallized. To purify the recrystallized DMT, it is mixed with a decolorizing solution containing an organic solvent like toluene and an adsorbent like activated carbon to remove impurities. The purified DMT is further reacted with a polyhydric alcohol like ethylene glycol to produce bis(hydroxyethyl) terephthalate (BHET). The BHET is also recrystallized to obtain high-purity crystals.

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Recycling a polyester material that can be recycled to form high-quality recycled polyester chips (r-PET). The recycling includes providing a recycled polyester fabric, using a chemical de-polymerization liquid to chemically depolymerize the recycled polyester fabric, so as to form a de-polymerization product containing BHET, dissolving the BHET in water to form a aqueous phase liquid, cooling the aqueous phase liquid from a dissolution temperature to a first crystallization temperature, so as to crystallize at least a part of the BHET, and cooling the aqueous phase liquid from the first crystallization temperature to a second crystallization temperature.

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Recycling of polyester waste like colored and opaque PET bottles to produce new polyester resin. The recycling method involves conditioning the feedstock containing colored and opaque PET by extruding and mixing it with ethylene glycol. This conditioning step improves the depolymerization efficiency by breaking down the polymer structure. The conditioned feed is then depolymerized in a reactor using a catalyst to produce monomers. The monomers are separated and purified to obtain a recycled polyester resin. The conditioning step is crucial for recycling high-impurity PET feedstocks like colored and opaque PET with high pigment content.

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A process for depolymerizing recycled polyesters containing opaque polyethylene terephthalate (PET) to recover monomers. The process involves conditioning the feedstock, glycolysis at high temperature and pressure, separating the diols, and final separation of the monomers. The high temperature and short residence times prevent pigment catalysis and blockage. The diol separation removes impurities. This allows recycling of feedstocks with high opaque PET content that can't be filtered out.

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Method for preparing a high-purity, high-yield monomer from waste PET plastic, and using it to make thermoplastic polymers with improved properties. The process involves glycolysis of waste PET with ethylene glycol and a catalyst like zinc acetate or sodium bicarbonate at 180-200°C. This converts the PET into bis(hydroxyethyl) terephthalate (BHET) monomer. The BHET can then be used to make thermoplastic polymers like polyurethanes.

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Integrated process for recycling polyester like PET that allows recycling of opaque PET with high filler content. The process involves depolymerizing the feedstock using glycolysis, separating the diester fraction, purifying it, then condensing it with terephthalic acid and diol to make new PET. This allows extracting and recycling the valuable terephthalic acid and diester components from opaque PET, avoiding issues with clogging pigments. The process also involves treating the glycol and diol effluents to recover and recycle those as well.

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Enzymatic recycling of post-consumer PET plastic waste into new PET using glycolysis. The process involves breaking down the polyester structure of PET into bis-hydroxyethylene terephthalate (BHET) monomers using enzymes. The enzymatic glycolysis reaction is carried out on pretreated PET waste, such as ground-up bottles, to enrich the BHET content. The BHET-rich stream can then be repolymerized into new PET. The enzymatic recycling avoids using catalysts that could contaminate the recycled PET.

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Chemically recycling polyester waste, like colored textiles and containers, into colorless polyester for new products. The process involves depolymerizing the waste using glycol to make BHET. Centrifugation separates out impurities like dyes and fillers. This allows recycling polyester waste with up to 50,000 ppm colorants into new polyester products without the color. The centrifugation parameters (G force, temperature) optimize separation without BHET precipitation.

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Chemically recycling polyethylene terephthalate (PET) using microwave radiation to decompose PET into its active intermediates, forming bis(2-hydroxyethyl) terephthalate (BHET) monomer. The microwave radiation is used to heat a reaction mixture containing PET, ethylene glycol, catalyst, and microwave absorber. Adding small amounts of microwave absorbers like sodium chloride significantly reduces the energy consumption compared to using catalysts alone. The microwave absorbers optimize the reaction by lowering the temperature required to decompose PET.

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Chemical recycling method for plastic waste, particularly waste PET, that improves process efficiency and reaction efficiency compared to traditional solid-state depolymerization. The method involves melting the waste PET before depolymerization instead of feeding it as flakes. This allows the PET to depolymerize in a liquid state rather than solid, preventing clogging and yield issues caused by differences in reaction rates due to flake size.

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Chemical recycling of plastic waste, in particular waste PET, and to a method for producing BHET from waste PET. The method involves depolymerizing waste PET and a reaction solvent in the presence of a depolymerization catalyst, wherein the depolymerization reaction comprises converting the waste PET into PET.

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Chemically recycling polyethylene terephthalate (PET) waste to directly obtain low-viscosity polyols for making unsaturated esters and polyurethanes. The recycling process involves depolymerizing PET waste with excess glycols and a catalyst to form oligomers. Then, adding a chelating agent to recover residual glycols under reduced pressure while stopping the catalyst. This prevents polymerization and allows isolating low-viscosity polyols. The chelating agent removes the catalyst's function, controlling molecular weight.

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Recycling of transparent PET waste like bottles, textiles, and film into food-safe PET resin using chemical glycolysis. The process involves cleaning, drying, sorting, and extracting metals/non-PET fractions from the PET waste. Then, the cleaned PET is depolymerized into monomers using an extruder. The monomers are mixed and filtered to produce a food-grade PET resin suitable for contact with food.

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A process for producing antimony-free recycled polyester chips that enables recycling of waste polyester while avoiding environmental pollution from antimony catalysts. The process involves separating cotton from the polyester in waste cloth, crystallizing the resulting BHET, polymerizing the BHET into PET, and separating impurities during transesterification. This allows producing pure, antimony-free recycled polyester chips using a titanium catalyst instead of antimony.

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