Depolymerization method of polyethylene terephthalate (PET)

Abstract

The present disclosure relates to the formation of dimethyl terephthalate (DMT) and monoethylene glycol (MEG). The present invention also relates to the depolymerization of polyethylene terephthalate (PET) and the recovery of dimethyl terephthalate (DMT) and monoethylene glycol (MEG) by using sodium methoxide as a catalyst.

Description

[0001] Cross-references

[0002] This application claims the benefit of U.S. Provisional Application Serial No. 62 / 821,270, filed on March 20, 2019, which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to the formation of dimethyl terephthalate (DMT) and monoethylene glycol (MEG) from polyethylene terephthalate (PET). Background Art

[0004] The polyethylene terephthalate (PET) bottle resin market has been experiencing strong growth as PET resin has replaced glass in carbonated soft drinks, bottled water and food containers.

[0005] Dimethyl terephthalate (DMT) is primarily used to make polyethylene terephthalate (PET) for fibers, films, container plastics and specialty plastic applications.

[0006] The largest segment of the polyester industry is the fiber market, where it is used to make clothing, home textiles such as sheets and curtains, carpets and rugs, and industrial products such as tire cord, seat belts, hoses and ropes. PET film is used in electrical applications, such as dielectric metal foil capacitors, and for food packaging. Summary of the invention

[0007] Disclosed herein is a method for depolymerizing polyethylene terephthalate (PET) contained in a raw material to form dimethyl terephthalate (DMT) and monoethylene glycol (MEG); the method comprising:

[0008] (i) mixing a raw material comprising polyethylene terephthalate (PET) with a first portion of methanol;

[0009] combining to form a first mixture;

[0010] (ii) adding sodium methoxide to the first mixture;

[0011] (iii) mixing; and

[0012] (iv) adding a second portion of methanol to form a second mixture;

[0013] Dimethyl terephthalate (DMT) and monoethylene glycol (MEG) are thereby formed.

[0014] In some embodiments of the process for depolymerization of polyethylene terephthalate (PET), the amount of the first portion of methanol is from about 0.1 to about 0.5 kg / kg of feedstock.

[0015] In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the amount of the first portion of methanol is about 0.3 kg / kg of feedstock.

[0016] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 15 min to about 120 min.

[0017] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 60 minutes.

[0018] In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), step (i) is performed at a temperature of about 50°C to about 100°C.

[0019] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed at a temperature of about 60°C to about 90°C.

[0020] In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), step (i) is performed at a temperature of about 60°C.

[0021] In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), step (i) is performed at a temperature of about 80°C.

[0022] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed for about 10 min to about 120 min.

[0023] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed for about 30 min.

[0024] In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), step (iii) is performed at a temperature of about 40°C to about 100°C.

[0025] In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), step (iii) is performed at a temperature of about 85°C to about 90°C.

[0026] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), a second portion of methanol is provided to maintain a sodium methoxide concentration in the second mixture at about 0.2 wt-% to about 5.0 wt-%.

[0027] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), a second portion of methanol is provided to maintain a sodium methoxide concentration in the second mixture at about 0.5 wt-% to about 1.5 wt-%.

[0028] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), a second portion of methanol is provided to maintain a sodium methoxide concentration in the second mixture at about 0.7 wt-%.

[0029] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the second portion of methanol is provided in portions at predetermined times.

[0030] In some embodiments of the method of depolymerizing polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided about 1 min to about 60 min after the addition of the sodium methoxide.

[0031] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided about 30 min after the addition of the sodium methoxide.

[0032] In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the amount of the first portion of the second portion of methanol is from about 50 g / kg feedstock to about 100 g / kg feedstock.

[0033] In some embodiments of the method of depolymerizing polyethylene terephthalate (PET), the second portion of the second portion of methanol is provided about 30 min to about 90 min after the addition of the sodium methoxide.

[0034] In some embodiments of the method of depolymerizing polyethylene terephthalate (PET), the second portion of the second portion of methanol is provided about 60 min after the addition of the sodium methoxide.

[0035] In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the amount of the second portion of the second portion of methanol is from about 100 g / kg feedstock to about 200 g / kg feedstock.

[0036] In some embodiments of the method of depolymerizing polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided about 60 min to about 120 min after the addition of the sodium methoxide.

[0037] In some embodiments of the method of depolymerizing polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided about 90 minutes after the addition of the sodium methoxide.

[0038] In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the amount of the third portion of the second portion of methanol is from about 100 g / kg feedstock to about 200 g / kg feedstock.

[0039] In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), a second portion of methanol is provided continuously.

[0040] In some embodiments of the process for depolymerization of polyethylene terephthalate (PET), the second portion of methanol is continuously provided at a rate of about 50 g / h / kg of feedstock to about 100 g / h / kg of feedstock.

[0041] In some embodiments of the method of depolymerizing polyethylene terephthalate (PET), the ratio of sodium methoxide to polyethylene terephthalate (PET) is from about 1:2 to about 1:28 (mol / mol).

[0042] In some embodiments of the method of depolymerizing polyethylene terephthalate (PET), the ratio of sodium methoxide to polyethylene terephthalate (PET) is from about 1:5 to about 1:20 (mol / mol).

[0043] In some embodiments of the method of depolymerizing polyethylene terephthalate (PET), the ratio of sodium methoxide to polyethylene terephthalate (PET) is from about 1:10 to about 1:20 (mol / mol).

[0044] In some embodiments of the method of depolymerizing polyethylene terephthalate (PET), the ratio of sodium methoxide to polyethylene terephthalate (PET) is from about 1:10 to about 1:15 (mol / mol).

[0045] In some embodiments of the process for depolymerization of polyethylene terephthalate (PET), dimethyl terephthalate is obtained in a yield of at least about 90 mol%.

[0046] In some embodiments of the process for depolymerization of polyethylene terephthalate (PET), dimethyl terephthalate is obtained in a yield of at least about 95 mol%.

[0047] In some embodiments of the process for depolymerization of polyethylene terephthalate (PET), dimethyl terephthalate is obtained in a yield of at least about 99 mol%.

[0048] In some embodiments of the process for depolymerization of polyethylene terephthalate (PET), monoethylene glycol is obtained in a yield of at least about 80 mol%.

[0049] In some embodiments of the process for depolymerization of polyethylene terephthalate (PET), monoethylene glycol is obtained in a yield of at least about 85 mol%.

[0050] In some embodiments of the process for depolymerization of polyethylene terephthalate (PET), monoethylene glycol is obtained in a yield of at least about 90 mol%.

[0051] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the feedstock comprising polyethylene terephthalate (PET) is provided in the form of pellets.

[0052] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the average particle size is from about 0.1 mm to about 20 mm.

[0053] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the average particle size is from about 5 mm to about 10 mm.

[0054] In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the average particle size is at most about 6 mm.

[0055] In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the average particle size is at most about 8 mm. DETAILED DESCRIPTION

[0056] Dimethyl terephthalate (DMT) is used in the production of polyesters, including polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), and polybutylene terephthalate (PBT). Because DMT is volatile, it is an intermediate in certain PET recycling schemes, such as from plastic bottles. Hydrogenation of DMT yields the diol 1,4-cyclohexanedimethanol, which is a useful monomer in the formation of polyester resins.

[0057] DMT has been produced in a variety of ways. Traditionally and still of commercial value is the direct esterification of terephthalic acid. Alternatively, it is prepared from p-xylene via methyl p-toluate by alternating oxidation and methyl esterification steps. The method for producing DMT from p-xylene and methanol consists of four main steps: oxidation, esterification, distillation and crystallization. In the presence of a transition metal catalyst (Co / Mn), a mixture of p-xylene and p-toluic acid ester is oxidized with air. The acid mixture produced by oxidation is esterified with methanol to produce a mixture of esters. The crude ester mixture is distilled to remove all heavy boilers and the residues produced; the lighter esters are recycled to the oxidation section. The crude DMT is then crystallized to remove DMT isomers, residual acids and aromatic aldehydes.

[0058] Improvements in the production of DMT and MEG from PET recycling: Due to the growing use of PET in the packaging and fiber (carpet and other textiles) industries, there is a need for an efficient, low energy, high yield and cost-effective way to form DMT and MEG from PET.

[0059] raw material

[0060] A method is described herein for depolymerizing polyethylene terephthalate (PET) contained in a feedstock to form dimethyl terephthalate (DMT) and monoethylene glycol (MEG).

[0061] In some embodiments, the feedstock comprising polyethylene terephthalate further comprises contaminants such as additional polymers (e.g., polyethylene, polypropylene, polyvinyl chloride (PVC), polycarbonate (PC), polyvinylidene chloride (PVDC), and polyamide), paper, colorants, dirt, ethylene vinyl alcohol (EVOH), ethylene vinyl acetate (EVA), cellulose, glue, or any combination thereof. In some embodiments, the feedstock comprises about 5% to about 30% contaminants.

[0062] Mishra et al. (Kinetic and thermodynamic study of methanolysis of poly(ethylene terephthalate)waste powder Polym. Int. 52:337-342 (2003)) have shown that an increase in the particle size of PET flakes results in a decrease in depolymerization. Mishra et al. recorded 127.5 μm as the optimal particle size. A depolymerization method that allows the use of larger raw material particles is needed. In some embodiments, the raw material comprising polyethylene terephthalate (PET) is provided in the form of particles. In some embodiments, the average particle size is from about 0.1 mm to about 20 mm. In some embodiments, the average particle size is from about 5 mm to about 10 mm. In some embodiments, the average particle size is at most about 5 mm. In some embodiments, the average particle size is at most about 6 mm. In some embodiments, the average particle size is at most about 7 mm. In some embodiments, the average particle size is at most about 8 mm. In some embodiments, the average particle size is at most about 9 mm. In some embodiments, the average particle size is at most about 10 mm. In some embodiments, the average particle size is at most about 11 mm. In some embodiments, the average particle size is at most about 12 mm. In some embodiments, the average particle size is at most about 13 mm. In some embodiments, the average particle size is at most about 14 mm. In some embodiments, the average particle size is at most about 15 mm. In some embodiments, the average particle size is at most about 16 mm. In some embodiments, the average particle size is at most about 17 mm. In some embodiments, the average particle size is at most about 18 mm. In some embodiments, the average particle size is at most about 19 mm. In some embodiments, the average particle size is at most about 20 mm.

[0063] DMT

[0064] A method is described herein for depolymerizing polyethylene terephthalate (PET) contained in a feedstock to form dimethyl terephthalate (DMT) and monoethylene glycol (MEG).

[0065] In some embodiments, the DMT contains less than about 10% impurities (w / w). In some embodiments, the DMT contains less than about 9% impurities (w / w). In some embodiments, the DMT contains less than about 8% impurities (w / w). In some embodiments, the DMT contains less than about 7% impurities (w / w). In some embodiments, the DMT contains less than about 6% impurities (w / w). In some embodiments, the DMT contains less than about 5% impurities (w / w). In some embodiments, the DMT contains less than about 4% impurities (w / w). In some embodiments, the DMT contains less than about 3% impurities (w / w). In some embodiments, the DMT contains less than about 2% impurities (w / w). In some embodiments, the DMT contains less than about 1% impurities (w / w). In some embodiments, the DMT contains less than about 0.5% impurities (w / w). In some embodiments, the DMT contains less than about 0.4% impurities (w / w). In some embodiments, the DMT contains less than about 0.3% impurities (w / w). In some embodiments, the DMT contains less than about 0.2% impurities (w / w). In some embodiments, the DMT contains less than about 0.1% impurities (w / w).

[0066] In some embodiments, the DMT contains less than about 250 ppm of any metal, less than about 240 ppm of any metal, less than about 230 ppm of any metal, less than about 220 ppm of any metal, less than about 210 ppm of any metal, less than about 200 ppm of any metal, less than about 190 ppm of any metal, less than about 180 ppm of any metal, less than about 170 ppm of any metal, less than about 160 ppm of any metal, less than about 150 ppm of any metal, less than about 140 ppm of any metal, less than about 130 ppm of any metal, less than about 120 ppm of any metal, less than about 110 ppm of any metal, less than about 100 ppm of any metal, less than about 90 ppm of any metal, less than about 80 ppm of any metal, less than about 70 ppm of any metal, less than about 60 ppm of any metal, less than about 50 ppm of any metal, less than about 40 ppm of any metal, less than about 30 ppm of any metal, less than about 20 ppm of any metal, any metal, less than about 10 ppm of any metal, less than about 5 ppm of any metal, less than about 4 ppm of any metal, less than about 3 ppm of any metal, less than about 2 ppm of any metal, less than about 1 ppm of any metal, less than about 0.9 ppm of any metal, less than about 0.8 ppm of any metal, less than about 0.7 ppm of any metal, less than about 0.6 ppm of any metal, less than about 0.5 ppm of any metal, less than about 0.4 ppm of any metal, less than about 0.3 ppm of any metal, less than about 0.2 ppm of any metal, less than about 0.1 ppm of any metal, less than about 0.09 ppm of any metal, less than about 0.08 ppm of any metal, less than about 0.07 ppm of any metal, less than about 0.06 ppm of any metal, less than about 0.05 ppm of any metal, less than about 0.04 ppm of any metal, less than about 0.03 ppm of any metal, less than about 0.02 ppm of any metal, or less than about 0.01 ppm of any metal.

[0067] In some embodiments, the DMT contains less than about 10 ppm sodium methoxide, less than about 5 ppm sodium methoxide, less than about 4 ppm sodium methoxide, less than about 3 ppm sodium methoxide, less than about 2 ppm sodium methoxide, less than about 1 ppm sodium methoxide, less than about 0.9 ppm sodium methoxide, less than about 0.8 ppm sodium methoxide, less than about 0.7 ppm sodium methoxide, less than about 0.6 ppm sodium methoxide, less than about 0.5 ppm sodium methoxide, less than about 0.4 ppm sodium methoxide, less than about 0.3 ppm sodium methoxide, less than about 0.2 ppm sodium methoxide, less than about 0.1 ppm sodium methoxide, less than about 0.09 ppm sodium methoxide, less than about 0.08 ppm sodium methoxide, less than about 0.07 ppm sodium methoxide, less than about 0.06 ppm sodium methoxide, less than about 0.05 ppm sodium methoxide, less than about 0.04 ppm sodium methoxide, less than about 0.03 ppm sodium methoxide, less than about 0.02 ppm sodium methoxide, or less than about 0.01 ppm sodium methoxide.

[0068] In some embodiments, the DMT is obtained in a yield of about 50mol% to about 99mol%. In some embodiments, the DMT is obtained in a yield of about 60mol% to about 99mol%. In some embodiments, the DMT is obtained in a yield of about 70mol% to about 99mol%. In some embodiments, the DMT is obtained in a yield of about 80mol% to about 99mol%. In some embodiments, the DMT is obtained in a yield of about 85mol% to about 99mol%. In some embodiments, the DMT is obtained in a yield of about 90mol% to about 99mol%. In some embodiments, the DMT is obtained in a yield of at least about 50mol%. In some embodiments, the DMT is obtained in a yield of at least about 55mol%. In some embodiments, the DMT is obtained in a yield of at least about 60mol%. In some embodiments, the DMT is obtained in a yield of at least about 65mol%. In some embodiments, the DMT is obtained in a yield of at least about 70mol%. In some embodiments, the DMT is obtained in a yield of at least about 75 mol%. In some embodiments, the DMT is obtained in a yield of at least about 80 mol%. In some embodiments, the DMT is obtained in a yield of at least about 85 mol%. In some embodiments, the DMT is obtained in a yield of at least about 90 mol%. In some embodiments, the DMT is obtained in a yield of at least about 95 mol%.

[0069] In some embodiments, the DMT is obtained in a yield of at least about 99 mol%.

[0070] MEG

[0071] A method is described herein for depolymerizing polyethylene terephthalate (PET) contained in a feedstock to form dimethyl terephthalate (DMT) and monoethylene glycol (MEG).

[0072] In some embodiments, the MEG contains less than about 10% impurities (w / w). In some embodiments, the MEG contains less than about 9% impurities (w / w). In some embodiments, the MEG contains less than about 8% impurities (w / w). In some embodiments, the MEG contains less than about 7% impurities (w / w). In some embodiments, the MEG contains less than about 6% impurities (w / w). In some embodiments, the MEG contains less than about 5% impurities (w / w). In some embodiments, the MEG contains less than about 4% impurities (w / w). In some embodiments, the MEG contains less than about 3% impurities (w / w). In some embodiments, the MEG contains less than about 2% impurities (w / w). In some embodiments, the MEG contains less than about 1% impurities (w / w). In some embodiments, the MEG contains less than about 0.5% impurities (w / w). In some embodiments, the MEG contains less than about 0.4% impurities (w / w). In some embodiments, the MEG contains less than about 0.3% impurities (w / w). In some embodiments, the MEG contains less than about 0.2% impurities (w / w). In some embodiments, the MEG contains less than about 0.1% impurities (w / w).

[0073] In some embodiments, the MEG is obtained at a yield of about 50mol% to about 99mol%. In some embodiments, the MEG is obtained at a yield of about 60mol% to about 99mol%. In some embodiments, the MEG is obtained at a yield of about 70mol% to about 99mol%. In some embodiments, the MEG is obtained at a yield of about 80mol% to about 99mol%. In some embodiments, the MEG is obtained at a yield of about 85mol% to about 99mol%. In some embodiments, the MEG is obtained at a yield of about 90mol% to about 99mol%. In some embodiments, the MEG is obtained at a yield of at least about 50mol%. In some embodiments, the MEG is obtained at a yield of at least about 55mol%. In some embodiments, the MEG is obtained at a yield of at least about 60mol%. In some embodiments, the MEG is obtained at a yield of at least about 65mol%. In some embodiments, the MEG is obtained at a yield of at least about 70mol%. In some embodiments, the MEG is obtained in a yield of at least about 75 mol%. In some embodiments, the MEG is obtained in a yield of at least about 80 mol%. In some embodiments, the MEG is obtained in a yield of at least about 85 mol%. In some embodiments, the MEG is obtained in a yield of at least about 90 mol%. In some embodiments, the MEG is obtained in a yield of at least about 95 mol%. In some embodiments, the MEG is obtained in a yield of at least about 99 mol%.

[0074] Sodium Methanol

[0075] A method is described herein for depolymerizing polyethylene terephthalate (PET) contained in a feedstock to form dimethyl terephthalate (DMT) and monoethylene glycol (MEG).

[0076] In some embodiments, the methods described herein include a catalytic amount of sodium methoxide. In some embodiments, the methods described herein include a substoichiometric amount of sodium methoxide.

[0077] As used herein, "substoichiometric amount" is used to indicate that the amount of material used is less than the stoichiometric amount. The term is used interchangeably with "catalytic amount" in this article. In some embodiments, the substoichiometric amount is less than or equal to about 95% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 90% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 85% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 80% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 75% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 70% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 65% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 60% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 55% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 50% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 45% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 40% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 35% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 30% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 25% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 20% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 15% of the stoichiometric amount. In some embodiments, the substoichiometric amount is less than or equal to about 10% of the stoichiometric amount.

[0078] As used herein, "stoichiometric amount" is intended to mean the amount of material used that is equal to the number of ester linkages present in the polyester.

[0079] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the ratio of sodium methoxide to polyethylene terephthalate (PET) is from about 1:2 to about 1:28 (mol / mol). In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the ratio of sodium methoxide to polyethylene terephthalate (PET) is from about 1:5 to about 1:20 (mol / mol). In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the ratio of sodium methoxide to polyethylene terephthalate (PET) is from about 1:10 to about 1:20 (mol / mol). In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the ratio of sodium methoxide to polyethylene terephthalate (PET) is from about 1:10 to about 1:15 (mol / mol).

[0080] Depolymerization method

[0081] A method for depolymerizing polyethylene terephthalate (PET) contained in a feedstock to form dimethyl terephthalate (DMT) and monoethylene glycol (MEG) is described herein; the method comprising:

[0082] (i) mixing a raw material comprising polyethylene terephthalate (PET) with a first portion of methanol;

[0083] combining to form a first mixture;

[0084] (ii) adding sodium methoxide to the first mixture;

[0085] (iii) mixing; and

[0086] (iv) adding a second portion of methanol to form a second mixture;

[0087] Dimethyl terephthalate (DMT) and monoethylene glycol (MEG) are thereby formed.

[0088] Step (i)

[0089] In some embodiments, the methods described herein include pre-treating the polyethylene terephthalate (PET) with a first portion of a methanol solvent to swell the polyethylene terephthalate (PET) prior to adding the sodium methoxide.

[0090] In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the first portion of methanol is about 0.1 to about 0.5 kg / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the first portion of methanol is about 0.2 to about 0.4 kg / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the first portion of methanol is about 0.1 to about 0.3 kg / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the first portion of methanol is about 0.3 to about 0.5 kg / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the first portion of methanol is about 0.1 kg / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the first portion of methanol is about 0.2 kg / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the first portion of methanol is about 0.3 kg / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the first portion of methanol is about 0.4 kg / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the first portion of methanol is about 0.5 kg / kg of raw material.

[0091] In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (i) is performed for about 15 min to about 120 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (i) is performed for about 15 min to about 90 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (i) is performed for about 15 min to about 60 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (i) is performed for about 30 min to about 120 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (i) is performed for about 60 min to about 120 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (i) is performed for about 45 min to about 90 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (i) is performed for about 45 min to about 60 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 60 min to about 90 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 15 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 20 min.

[0092] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 25 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 30 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 35 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 40 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 45 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 50 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 55 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 60 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 65 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 70 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 75 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 80 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 85 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 90 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 95 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 100 min.

[0093] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 105 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 110 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 115 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed for about 120 min.

[0094] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is carried out at a temperature of about 25°C to about 100°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is carried out at a temperature of about 25°C to about 60°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is carried out at a temperature of about 25°C to about 80°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is carried out at a temperature of about 50°C to about 100°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is carried out at a temperature of about 60°C to about 90°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is carried out at a temperature of about 25°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed at a temperature of about 30°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed at a temperature of about 35°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed at a temperature of about 40°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed at a temperature of about 45°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed at a temperature of about 50°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed at a temperature of about 55°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed at a temperature of about 60°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed at a temperature of about 65°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed at a temperature of about 70°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed at a temperature of about 75°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed at a temperature of about 80°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed at a temperature of about 85°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed at a temperature of about 90°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (i) is performed at a temperature of about 95°C. In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), step (i) is performed at a temperature of about 100°C.

[0095] Step (iii)

[0096] In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 10 min to about 120 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 10 min to about 90 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 10 min to about 60 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 10 min to about 45 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 10 min to about 30 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 30 min to about 120 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 60 min to about 120 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 90 min to about 120 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 10 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 15 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 20 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 25 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 30 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 35 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 40 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed for about 45 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed for about 50 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed for about 55 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed for about 60 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed for about 65 min.In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 70 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 75 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 80 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 85 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 90 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 95 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 100 min. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is performed for about 105 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed for about 110 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed for about 115 min. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed for about 120 min.

[0097] In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is carried out at a temperature of about 40°C to about 100°C. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is carried out at a temperature of about 50°C to about 100°C. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is carried out at a temperature of about 60°C to about 100°C. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is carried out at a temperature of about 70°C to about 100°C. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is carried out at a temperature of about 80°C to about 100°C. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iii) is carried out at a temperature of about 85°C to about 90°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed at a temperature of about 40°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed at a temperature of about 45°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed at a temperature of about 50°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed at a temperature of about 55°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed at a temperature of about 60°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed at a temperature of about 65°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed at a temperature of about 70°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed at a temperature of about 75°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed at a temperature of about 80°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed at a temperature of about 85°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed at a temperature of about 90°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed at a temperature of about 95°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iii) is performed at a temperature of about 100°C.

[0098] Step (iv)

[0099] In some embodiments of the process for depolymerization of polyethylene terephthalate (PET), methanol is consumed during the depolymerization process to form dimethyl terephthalate (DMT).In some embodiments of the process for depolymerization of polyethylene terephthalate (PET), a second portion of methanol is added.

[0100] In some embodiments of the depolymerization method of polyethylene terephthalate (PET), a second portion of methanol is provided to maintain the sodium methoxide concentration in the second mixture at about 0.2 wt-% to about 5.0 wt-%. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), a second portion of methanol is provided to maintain the sodium methoxide concentration in the second mixture at about 0.2 wt-% to about 4.0 wt-%. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), a second portion of methanol is provided to maintain the sodium methoxide concentration in the second mixture at about 0.2 wt-% to about 3.0 wt-%. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), a second portion of methanol is provided to maintain the sodium methoxide concentration in the second mixture at about 0.2 wt-% to about 2.0 wt-%. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), a second portion of methanol is provided to maintain the sodium methoxide concentration in the second mixture at about 0.2 wt-% to about 1.5 wt-%. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), a second portion of methanol is provided to maintain a sodium methoxide concentration in the second mixture at about 0.5 wt-% to about 1.0 wt-%. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), a second portion of methanol is provided to maintain a sodium methoxide concentration in the second mixture at about 0.7 wt-%. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), a second portion of methanol is provided to maintain a sodium methoxide concentration in the second mixture at about 0.2 wt-%, about 0.3 wt-%, about 0.4 wt-%, about 0.5 wt-%, about 0.6 wt-%, about 0.7 wt-%, about 0.8 wt-%, about 0.9 wt-%, about 1 wt-%, about 1.1 wt-%, about 1.2 wt-%, about 1.3 wt-%, about 1.4 wt-%, about 1.5 wt-%, about 1.6 wt-%, about 1.7 wt-%, about 1.8 wt-%, about 1.9 wt-%, about 2 wt-%, about 2.1 wt-%, about 2.2 wt-%, about 2. 3wt-%, about 2.4wt-%, about 2.5wt-%, about 2.6wt-%, about 2.7wt-%, about 2.8wt-%, about 2.9wt-%, about 3wt-%, about 3.1wt-%, about 3.2wt-%, about 3.3wt-%, about 3.4wt-%, about 3.5wt-%, about 3.6wt-%, about 3.7wt-%, about 3.8wt-%, about 3.9wt-%, about 4wt-%, about 4.1wt-%, about 4.2wt-%, about 4.3wt-%, about 4.4wt-%, about 4.5wt-%, about 4.6wt-%, about 4.7wt-%, about 4.8wt-%, about 4.9wt-% or about 5wt-%.

[0101] In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 25°C to about 100°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 25°C to about 60°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 25°C to about 80°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 50°C to about 100°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 60°C to about 90°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 25°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 30°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 35°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 40°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 45°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 50°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 55°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 60°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 65°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 70°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 75°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 80°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 85°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 90°C. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 95°C.In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), step (iv) is performed at a temperature of about 100°C.

[0102] In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iv) is performed for a total time of about 1 hour to about 10 hours. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iv) is performed for a total time of about 1 hour to about 8 hours. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iv) is performed for a total time of about 1 hour to about 5 hours. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iv) is performed for a total time of about 4 hours to about 6 hours. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), step (iv) is performed for a total time of about 3 hours to about 7 hours.

[0103] Sequential addition

[0104] In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the second portion of methanol is provided sequentially at a predetermined time in step (iv). In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the second portion of methanol is provided in portions at a predetermined time in step (iv). In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the second portion of methanol is provided in one, two, three, four, five, six, seven, eight, nine or ten portions. In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the second portion of methanol is provided in one, two, three, four or five portions. In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the second portion of methanol is provided in one, two or three portions. In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the second portion of methanol is provided in two or three portions. In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the second portion of methanol is provided in two portions. In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the second portion of methanol is provided in three portions. In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the second portion of methanol is provided in four portions. In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the second portion of methanol is provided in five portions. In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the second portion of methanol is provided in six portions. In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the second portion of methanol is provided in seven portions. In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the second portion of methanol is provided in eight portions. In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the second portion of methanol is provided in nine portions. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the second portion of methanol is provided in ten portions.

[0105] In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the mixture is mixed between each addition.

[0106] In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided about 1 min to about 60 min after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided about 15 min to about 45 min after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided about 1 min after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided about 5 min after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided about 10 min after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided about 15 min after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided at about 20 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided at about 25 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided at about 30 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided at about 35 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided at about 40 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided at about 45 minutes after the addition of sodium methoxide. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided about 50 minutes after the addition of sodium methoxide. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided about 55 minutes after the addition of sodium methoxide. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the first portion of the second portion of methanol is provided about 60 minutes after the addition of sodium methoxide.

[0107] In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the first portion of the second portion of methanol is about 10 g / kg of raw material to about 100 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the first portion of the second portion of methanol is about 50 g / kg of raw material to about 100 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the first portion of the second portion of methanol is about 50 g / kg of raw material to about 80 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the first portion of the second portion of methanol is about 10 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the first portion of the second portion of methanol is about 20 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the first portion of the second portion of methanol is about 30 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is about 40 g / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is about 50 g / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is about 60 g / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is about 70 g / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is about 80 g / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the first portion of the second portion of methanol is about 90 g / kg raw material. In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the amount of the first portion of the second portion of methanol is about 100 g / kg of feedstock.

[0108] In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of the second portion of methanol is provided at about 30 minutes to about 90 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of the second portion of methanol is provided at about 45 minutes to about 75 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of the second portion of methanol is provided at about 30 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of the second portion of methanol is provided at about 35 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of the second portion of methanol is provided at about 40 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of the second portion of methanol is provided at about 45 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of the second portion of methanol is provided at about 50 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of the second portion of methanol is provided at about 55 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of the second portion of methanol is provided at about 60 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of the second portion of methanol is provided at about 65 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of the second portion of methanol is provided at about 70 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of the second portion of methanol is provided at about 75 minutes after the addition of sodium methoxide. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), a second portion of the second portion of methanol is provided at about 80 minutes after the addition of sodium methoxide. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), a second portion of the second portion of methanol is provided at about 85 minutes after the addition of sodium methoxide. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), a second portion of the second portion of methanol is provided at about 90 minutes after the addition of sodium methoxide.

[0109] In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the second portion of the second portion of methanol is about 100 g / kg of raw material to about 200 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the second portion of the second portion of methanol is about 100 g / kg of raw material to about 150 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the second portion of the second portion of methanol is about 100 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the second portion of the second portion of methanol is about 110 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the second portion of the second portion of methanol is about 120 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the second portion of the second portion of methanol is about 130 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the second portion of the second portion of methanol is about 140g / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the second portion of the second portion of methanol is about 150g / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the second portion of the second portion of methanol is about 160g / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the second portion of the second portion of methanol is about 170g / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the second portion of the second portion of methanol is about 180g / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the second portion of the second portion of methanol is about 190g / kg raw material. In some embodiments of the method for depolymerization of polyethylene terephthalate (PET), the amount of the second portion of the second portion of methanol is about 200 g / kg of feedstock.

[0110] In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 60 min to about 120 min after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 90 min to about 120 min after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 60 min to about 90 min after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 60 min after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 65 min after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 70 min after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 75 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 80 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 85 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 90 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 95 minutes after the addition of sodium methoxide. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 100 minutes after the addition of sodium methoxide. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 105 min after the addition of sodium methoxide. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 110 min after the addition of sodium methoxide. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 115 min after the addition of sodium methoxide. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the third portion of the second portion of methanol is provided at about 120 min after the addition of sodium methoxide.

[0111] In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the third portion of the second portion of methanol is about 100 g / kg of raw material to about 200 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the third portion of the second portion of methanol is about 100 g / kg of raw material to about 150 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the third portion of the second portion of methanol is about 100 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the third portion of the second portion of methanol is about 110 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the third portion of the second portion of methanol is about 120 g / kg of raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the third portion of the second portion of methanol is about 130 g / kg of raw material. In some embodiments of the method for depolymerizing polyethylene terephthalate (PET), the amount of the third portion of the second portion of methanol is about 140 g / kg of feedstock.

[0112] In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the third portion of the second portion of methanol is about 150 g / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the third portion of the second portion of methanol is about 160 g / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the third portion of the second portion of methanol is about 170 g / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the third portion of the second portion of methanol is about 180 g / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the third portion of the second portion of methanol is about 190 g / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the amount of the third portion of the second portion of methanol is about 200 g / kg raw material.

[0113] Continuous addition

[0114] In some embodiments of the process for depolymerization of polyethylene terephthalate (PET), a second portion of methanol is continuously provided in step (iv).

[0115] In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of methanol is continuously provided at a rate of about 50 g / h / kg raw material to about 100 g / h / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of methanol is continuously provided at a rate of about 50 g / h / kg raw material to about 90 g / h / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of methanol is continuously provided at a rate of about 50 g / h / kg raw material to about 80 g / h / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of methanol is continuously provided at a rate of about 50 g / h / kg raw material to about 70 g / h / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of methanol is continuously provided at a rate of about 50 g / h / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of methanol is continuously provided at a rate of about 60 g / h / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of methanol is continuously provided at a rate of about 70 g / h / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of methanol is continuously provided at a rate of about 80 g / h / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of methanol is continuously provided at a rate of about 90 g / h / kg raw material. In some embodiments of the depolymerization method of polyethylene terephthalate (PET), the second portion of methanol is continuously provided at a rate of about 100 g / h / kg raw material.

[0116] Certain terms

[0117] The section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0118] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood in the art to which the claimed subject matter belongs. In the event that there are multiple definitions for terms herein, the definitions in this section shall prevail.

[0119] It should be understood that the general description and detailed description are exemplary and illustrative only and are not intended to limit any subject matter claimed. In this application, unless otherwise specifically stated, the use of the singular includes the plural. It must be noted that the singular forms "a", "an", and "the" used in this specification and the appended claims include plural referents unless the context clearly indicates otherwise. In this application, the use of "or" means "and / or" unless otherwise stated. In addition, the use of the term "includes" and other forms such as "comprises", "contains", and "has" is not restrictive.

[0120] Unless the context requires otherwise, throughout the specification and claims, the word "comprise" and variations thereof, such as "include" and "comprising", should be interpreted as having an open inclusive meaning, i.e., "including but not limited to". In addition, the headings provided herein are for convenience only and are not intended to interpret the scope or meaning of the claimed invention.

[0121] As used in this specification and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. It should also be noted that the term "or" is generally employed in its sense including "and / or" unless the context clearly dictates otherwise.

[0122] As used herein, the term "about" or "approximately" means within 10%, preferably within 10%, and more preferably within 5% of a given value or range.

[0123] As used herein, ambient temperature is a colloquial expression of the typical or preferred indoor (climate-controlled) temperature that people are generally accustomed to. It represents a small range of temperatures in which the air feels neither hot nor cold, which is approximately 21°C. In some embodiments, the ambient temperature is 25±5°C. In some embodiments, the ambient temperature is 18°C. In some embodiments, the ambient temperature is 19°C. In some embodiments, the ambient temperature is 20°C. In some embodiments, the ambient temperature is 21°C. In some embodiments, the ambient temperature is 22°C. In some embodiments, the ambient temperature is 23°C. In some embodiments, the ambient temperature is 24°C. In some embodiments, the ambient temperature is 25°C. In some embodiments, the ambient temperature is 26°C. In some embodiments, the ambient temperature is 27°C. In some embodiments, the ambient temperature is 28°C. In some embodiments, the ambient temperature is 29°C. In some embodiments, the ambient temperature is 30°C.

[0124] As used in this specification and the appended claims, depolymerization refers to a process of breaking down a polymer into its starting materials. It is essentially the opposite of polymerization. In some embodiments, depolymerization is achieved by methanolysis.

[0125] As used herein, the term "mol" when referring to PET is the molar amount and is calculated using the molecular weight of the "PET" unit, 192.17 g / mol.

[0126] Definitions of standard chemical terms may be found in references including, but not limited to, Carey and Sundberg "Advanced Organic Chemistry 4th Edition," Vol. A (2000) and Vol. B (2001), Plenum Press, New York.

[0127] Example

[0128] The following examples are intended to illustrate but not to limit the disclosed embodiments.

[0129] Example 1: Depolymerization of PET using sequential methanol addition

[0130] 3.00 kg of methanol were added to a 25 L reactor containing 10.00 kg of raw material (PET fines). The medium was stirred and heated to 60° C. for 1 hour. The temperature was then raised to 85° C., after which sodium methoxide (30 kg / t raw material) was added. The portioned addition of methanol was carried out as follows: 710 g was added 30 min after the addition of sodium methoxide, 1.21 kg was added after another 30 min, and the last 1.21 kg was added after another 30 min. After the addition of sodium methoxide, the reaction medium was stirred at 85° C. for a total of 8-10 h. The reaction yields were: 97% for DMT and 95% for MEG.

[0131] Example 2: PET Depolymerization with Partial Methanol Removal and Sequential Methanol Addition

[0132] 6.00 kg of methanol was added to a 25 L reactor containing 10.00 kg of raw material (PET fines). The medium was stirred and heated to 60° C. for 1 hour. Then 3 kg of liquid was discharged and the temperature was raised to 85° C., after which sodium methoxide (30 kg / t raw material) was added. The portioned addition of methanol was carried out as follows: 1.21 kg was added 30 min after the addition of sodium methoxide, 1.21 kg was added after another 30 min, and the last 1.21 kg was added after another 30 min. After the addition of sodium methoxide, the reaction medium was stirred at 85° C. for a total of 8-10 h. The reaction yields were: 87% for DMT and 83% for MEG.

[0133] Example 3: PET Depolymerization with Partial Methanol Removal and Single Methanol Addition

[0134] 6.00 kg of methanol was added to a 25 L reactor containing 10.00 kg of raw material (PET fines). The medium was stirred and heated to 60 ° C for 1 hour. Then 2.2 kg of liquid was discharged and the temperature was raised to 85 ° C, after which sodium methoxide (30 kg / t raw material) was added. After 30 min, 2.3 kg of methanol was added. After the addition of sodium methoxide, the reaction medium was stirred at 85 ° C for a total of 8-10 hours. The reaction yield of DMT was 80%, and the reaction yield of MEG was 93%.

Claims

1. A method for depolymerizing polyethylene terephthalate (PET) contained in a raw material to form dimethyl terephthalate (DMT) and monoethylene glycol (MEG); include: (i) mixing a feedstock comprising polyethylene terephthalate (PET) with a first portion of methanol at a temperature of 50° C. to 100° C. to form a first mixture; (ii) after step (i), adding sodium methoxide to the first mixture; (iii) mixing at a temperature of 40°C to 100°C; and (iv) adding a second portion of methanol to form a second mixture; Dimethyl terephthalate (DMT) and monoethylene glycol (MEG) are thereby formed.

2. The method according to claim 1, wherein the amount of the first portion of methanol is 0.1 to 0.5 kg / kg of raw material.

3. The method according to claim 1, wherein the amount of the first portion of methanol is 0.3 kg / kg of raw material.

4. The method according to any one of claims 1 to 3, wherein step (i) is performed for 15 min to 120 min.

5. The method according to any one of claims 1 to 3, wherein step (i) is performed for 60 min.

6. The method according to any one of claims 1 to 3, wherein step (i) is carried out at a temperature of 60°C to 90°C.

7. The method according to any one of claims 1 to 3, wherein step (i) is carried out at a temperature of 60°C.

8. The method according to any one of claims 1 to 3, wherein step (i) is carried out at a temperature of 80°C.

9. The method according to any one of claims 1 to 3, wherein step (iii) is performed for 10 min to 120 min.

10. The method according to any one of claims 1 to 3, wherein step (iii) is performed for 30 min.

11. The method according to any one of claims 1 to 3, wherein step (iii) is carried out at a temperature of 85°C to 90°C.

12. The process according to any one of claims 1 to 3, wherein the second portion of methanol is provided to maintain a sodium methoxide concentration in the second mixture in the range of 0.2 wt-% to 5.0 wt-%.

13. The process according to any one of claims 1 to 3, wherein the second portion of methanol is provided to maintain a sodium methoxide concentration in the second mixture in the range of 0.5 wt-% to 1.5 wt-%.

14. The process according to any one of claims 1 to 3, wherein the second portion of methanol is provided so as to maintain a sodium methoxide concentration in the second mixture at 0.7 wt-%.

15. The method according to any one of claims 1-3, wherein the second portion of methanol is provided in portions at predetermined times.

16. The method of claim 15, wherein the first portion of the second portion of methanol is provided 1 min to 60 min after the addition of sodium methoxide.

17. The method of claim 16, wherein the first portion of the second portion of methanol is provided 30 min after the addition of the sodium methoxide.

18. The method of claim 16, wherein the amount of the first portion of the second portion of methanol is 50 g / kg to 100 g / kg of feedstock.

19. The method of claim 15, wherein the second portion of the second portion of methanol is provided 30 min to 90 min after the addition of the sodium methoxide.

20. The method of claim 15, wherein the second portion of the second portion of methanol is provided 60 min after the addition of the sodium methoxide.

21. The method of claim 19, wherein the amount of the second portion of the second portion of methanol is 100 g / kg to 200 g / kg of the feedstock.

22. The method of claim 15, wherein the third portion of the second portion of methanol is provided 60 min to 120 min after the addition of the sodium methoxide.

23. The method of claim 15, wherein the third portion of the second portion of methanol is provided 90 min after the addition of the sodium methoxide.

24. The method of claim 22, wherein the amount of the third portion of the second portion of methanol is 100 g / kg to 200 g / kg of the feedstock.

25. The process of any one of claims 1-3, wherein the second portion of methanol is provided continuously.

26. The method of claim 25, wherein the second portion of methanol is continuously provided at a rate of 50 g / h / kg feedstock to 100 g / h / kg feedstock.

27. The method of any one of claims 1-3, wherein the ratio of sodium methoxide to polyethylene terephthalate (PET) is 1:2 to 1:28 (mol / mol).

28. The method of any one of claims 1-3, wherein the ratio of sodium methoxide to polyethylene terephthalate (PET) is 1:5 to 1:20 (mol / mol).

29. The method of any one of claims 1-3, wherein the ratio of sodium methoxide to polyethylene terephthalate (PET) is 1:10 to 1:20 (mol / mol).

30. The method of any one of claims 1-3, wherein the ratio of sodium methoxide to polyethylene terephthalate (PET) is 1:10 to 1:15 (mol / mol).

31. The process of any one of claims 1-3, wherein the dimethyl terephthalate is obtained in a yield of at least 90 mol%.

32. The process of any one of claims 1-3, wherein the dimethyl terephthalate is obtained in a yield of at least 95 mol%.

33. The process of any one of claims 1-3, wherein the dimethyl terephthalate is obtained in a yield of at least 99 mol%.

34. The process of any one of claims 1-3, wherein the monoethylene glycol is obtained in a yield of at least 80 mol%.

35. The process of any one of claims 1-3, wherein the monoethylene glycol is obtained in a yield of at least 85 mol%.

36. The process of any one of claims 1-3, wherein the monoethylene glycol is obtained in a yield of at least 90 mol%.

37. The method of any one of claims 1-3, wherein the feedstock comprising polyethylene terephthalate (PET) is provided in pellet form.

38. A method according to claim 37, wherein the average particle size is from 0.1 mm to 20 mm.

39. The method of claim 37, wherein the average particle size is 5 mm to 10 mm.

40. The method of claim 37, wherein the average particle size is at most 6 mm.

41. The method of claim 37, wherein the average particle size is at most 8 mm.