Enzymatic Decomposition for PET Bottle Recycling

A process for degrading polyester-containing materials like plastic products using enzymes in acidic conditions. The process involves contacting the polyester-containing material with enzymes like PETase and MHETase at acidic pH between 3 and 6. The enzymes degrade the polyester into monomers and oligomers. The acidic conditions allow avoiding salt production and reducing base consumption. The process can be scaled up for industrial use. The degraded polyester products can be recovered and purified.

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Neutral hydrolysis method for waste polyester without waste liquid discharge. The method involves a two-step process: (1) alcohol treatment with ethylene glycol to partially depolymerize and dissolve impurities in the waste polyester, (2) hydrolysis in ethylene glycol to completely depolymerize and separate the polyester into pure terephthalic acid and ethylene glycol. This allows recycling the polyester without generating waste water. The alcohol treatment reduces polyester molecular weight and impurity content, making hydrolysis milder and more efficient.

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Improved process for depolymerizing PET plastic into BHET, which is a valuable chemical used to make new PET. The process involves converting PET into BHET using a specific solvent mixture in a reactive distillation column. The solvent is a mixture of ethanol and sodium ethoxide, prepared by reacting ethanol and sodium hydroxide in the distillation column. This solvent selectively breaks down the PET into BHET with less byproducts compared to traditional solvents. The BHET can then be purified and used to make new PET.

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A selective and efficient chemical recycling process for polyethylene terephthalate (PET) plastics that can recycle contaminated, colored, or heterogeneous PET waste that cannot be recycled through conventional mechanical processes. The chemical recycling uses a catalytic system with a base and an aprotic solvent to depolymerize the PET into its monomers by reacting with excess nucleophiles like alcohols or amines. This enables selective degradation of pure PET while avoiding degradation of contaminants like metals, fillers, or other polymers. The low temperature, catalytic conditions make it scalable and energy-efficient compared to harsh methods like radiation or microwaves.

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A PET hydrolase enzyme derived from bacteria that can degrade PET plastic into harmless soluble products. The hydrolase enzyme, named PpPETase from Pseudomonas paralcaligenes and ScPETase from Streptomyces calvus, can be used to break down PET into monohydroxyethyl terephthalate (MHET), terephthalic acid (TPA), and ethylene glycol (EG). The enzyme is isolated and expressed from bacteria, allowing it to be used in biotechnological applications like waste treatment to degrade PET plastics in an environmentally friendly way.

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A method to degrade polyethylene terephthalate (PET) plastic waste using a combined chemical-enzymatic process. The method involves dissolving PET in an organic solvent, adding a small amount of alkali, and pre-degrading the PET in solution at moderate temperature. The pre-degraded PET suspension is then enzymatically hydrolyzed to fully degrade the PET into monomers like terephthalic acid. This two-step process allows efficient bioconversion of high-crystallinity PET waste into valuable monomers using mild conditions and a trace amount of alkali.

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Method to recycle waste PET into higher value PETG/PCTG copolyester using mixed alcohol depolymerization followed by polycondensation. The recycling process involves alcoholysis of waste PET using a catalyst to break down the polymer into BHET/BHCT monomers and oligomers using a mixture of ethylene glycol (EG) and 1,4-cyclohexanedimethanol (CHDM). These depolymerization products are then polycondensed using a catalyst to make PETG/PCTG copolyester with properties like improved light transmittance, environmental friendliness, and heat resistance compared to virgin PET.

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A double depolymerization method for recycling waste polyester like PET that involves using two different depolymerization techniques in series to improve product yield and purity compared to single methods. The first step is an initial depolymerization using a method like alkaline hydrolysis or methanolysis to partially break down the polyester into monomers or oligomers. The second step is a final depolymerization using a different method like glycolysis or alcoholysis to fully depolymerize the partially broken polymer into monomers. This two-step process allows higher yields and better purification compared to using just one depolymerization method.

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A process for degrading plastic products containing polyesters like PET by enzymatic depolymerization at acidic pH without base addition. The process involves two steps: a preliminary step at pH 6.5-10 to reach high terephthalic acid concentration in the reaction medium, followed by main depolymerization at pH 4-6. The high terephthalic acid concentration in the medium allows acidic depolymerization without pH adjustment. Enzymes degrade the polyesters. The acidic depolymerization provides economic benefits by reducing base consumption and salt production.

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Recycling PET-based materials like disposable bottles, trays, fabrics, and insulation into terephthalate esters like dimethyl terephthalate (DMT) using a simple, room temperature process without pre-treatment. The method involves grinding the PET waste into chips, then reacting it with an alcohol like methanol or ethanol at atmospheric pressure and room temperature for less than an hour. The PET breaks down into terephthalate esters and the alcohol. This allows recycling of contaminated PET materials like fabrics with elastane or cotton blends.

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Recycling of polyethylene terephthalate (PET) waste into new PET using a two-step process that involves partial depolymerization followed by complete depolymerization. This reduces the time and ethylene glycol required compared to direct depolymerization. The partial depolymerization step involves heating PET with excess ethylene glycol to 200-250°C to produce partially depolymerized PET. This intermediate is then depolymerized with ethylene glycol and catalyst at 170-200°C to form bis(2-hydroxyethyl) terephthalate (BHET). The BHET is purified and polymerized to regenerate PET.

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Chemical-biological integrated method to efficiently recycle PET into high-value products using a catalyst like betaine instead of heavy metal catalysts in the initial glycolysis step. The method involves glycolyzing PET in ethylene glycol with betaine as a catalyst to produce oligomers. These oligomers are then enzymatically hydrolyzed to monomers and platform chemicals. The betaine-catalyzed glycolysis prevents pH drops that inhibit enzymatic hydrolysis. This integrated approach allows efficient recycling of PET into valuable chemicals without adverse impacts on subsequent biological steps.

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Improved method for depolymerization of polyethylene terephthalate (PET) plastics to recycle them into the starting material ethylene glycol. The method involves using alkali metal alkoxides like sodium ethoxide or potassium ethoxide obtained by reactive distillation of ethanol and alkali metal hydroxide, instead of pure ethoxide, as the catalyst for PET depolymerization. The reactive distillation step allows in situ formation of the catalyst by reacting ethanol with alkali metal hydroxide in the distillation column. This provides a catalyst-rich environment for PET depolymerization without separate catalyst addition. The reactive distillation also enables simultaneous separation of ethanol and ethylene glycol byproduct.

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A method for recycling polyethylene terephthalate (PET) plastic that involves depolymerizing it using an electrolysis cell with an alkali metal glycolate solution. The PET is reacted with the glycolate solution to produce bis-2-hydroxyethyl terephthalate (BHET) at high yields. The method involves using an electrolysis cell with alkali metal glycolate solution instead of acid to depolymerize PET. The cell contains an alkali metal glycolate solution made by electrolysis. This method allows recycling PET into BHET with higher yields and less waste compared to other methods.

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Process for depolymerizing PET plastics into BHET using sodium or potassium glycolate obtained by reactive distillation. The process involves reacting glycol with alkali metal alcoholate like sodium or potassium ethoxide in a reactive distillation column. This produces a crude product stream containing glycolate, water, alcohol, and unreacted alcoholate. The glycolate can then be separated and used for depolymerizing PET to BHET. The reactive distillation provides higher yields of BHET compared to using glycolate directly. After depolymerization, the BHET can be polymerized again into PET if desired. This provides a recycling loop for PET plastics.

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Recycling of polyethylene terephthalate (PET) plastics by depolymerization to dimethyl terephthalate (DMT) using mild reaction conditions and catalysts. The process involves treating crushed PET waste with excess methanol, a guanidine or squid-based organic base, and a second base like an inorganic base or oxide ether. The reaction conditions are mild (25-80°C) compared to traditional methods. This allows selective depolymerization without structural changes or degradation products. The DMT can then be filtered and washed without further purification.

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Selective depolymerization of waste polyester like PET using aqueous metal salts to produce depolymerized monomers and oligomers. This allows recycling of waste plastics into new polymers without significant degradation. The process involves heating waste polyester in metal salt solution to break down the polymer. The depolymerized products can then be polymerized again to make renewable polyesters. The metal salt residue is removed. This selective depolymerization avoids the energy-intensive separation steps of conventional methods.

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Method for producing high purity recycled bis(2-hydroxyethyl) terephthalate (BHET) from waste polyester using a multi-stage depolymerization process. The method involves depolymerizing waste polyester twice, first at high temperature and then at lower temperature, followed by ion exchange, distillation, and final distillation steps. This reduces impurities like diethylene glycol esters compared to single stage depolymerization. The recycled BHET has >96% BHET content and <2% diethylene glycol esters.

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Recycling polyester-based materials like PET by incorporating a distillation step before depolymerization to improve product purity and consistency. The process involves treating the polyester feed with distillation to remove volatile impurities like water and acetaldehyde. This distilled feed is then depolymerized using an organic catalyst and alcohol solvent to produce monomeric or oligomeric diesters. The distillation step removes impurities that degrade product quality and avoids the need for pre-drying the feed. It also enables consistent reaction times without adjustment between batches.

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Using specific esterases to degrade polyester plastics like PET under acidic conditions between pH 3 and 6. The esterases have improved activity and thermal stability compared to the parent enzyme at these pH levels. The modified esterases contain specific amino acid substitutions like T11E, R12D, S13E, F90A, Y92G, W155A, T157S, Q182D, F208M, N204D, N204E, S206D, N211D, S212F, N213P, V219I, Y220M, Q237D, N241E, N243E, L247T, V170I,

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