Formation of terephthalic acid esters

Abstract

To provide a process for the formation of terephthalate esters by the depolymerization of polyethylene terephthalate (PET) or poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate).SOLUTION: A depolymerization process for the formation of terephthalate esters of the formula (I) includes the step for bringing PET or poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) into contact with a solvent for swelling the polyester, an alcoholic solvent, and a sub-stoichiometric amount of an alkoxide.SELECTED DRAWING: None

Description

Technical Field

[0001] Cross-reference This patent application claims the benefit of U.S. Application No. 15 / 706,484, filed Sep. 15, 2017, which is incorporated herein by reference in its entirety.

[0002] The present disclosure relates to the formation of ester derivatives from polyesters, and more specifically to the formation of terephthalic acid esters from polyethylene terephthalate (PET) or poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG). The present disclosure also relates to the formation of dimethyl terephthalate (DMT). The present disclosure also relates to the formation of monoethylene glycol (MEG).

Background Art

[0003] The polyethylene terephthalate (PET) resin market has grown strongly as PET has replaced glass in carbonated soft drinks, bottled water, and food containers.

[0004] Dimethyl terephthalate (DMT) is primarily used in the production of polyethylene terephthalate (PET) for fibers, films, container plastics, and specialty plastic applications.

[0005] The largest polyester segment is the fiber market, where it is used to manufacture household fiber products such as clothing, sheets and curtains, carpets and rugs, and industrial products such as tire cords, seat belts, hoses, and ropes. PET films are used in electrical applications such as dielectric metal foil capacitors and for food packaging.

[0006] Growth in polyester has not been translated into demand for DMT. For most grades of polyester used in textile products and in food and beverage containers, it is more economical to use purified terephthalic acid rather than DMT.

SUMMARY OF THE INVENTION

[0007] Disclosed herein is a process for converting a polyester selected from the group consisting of polyethylene terephthalate and poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) to a terephthalate of formula (I):

[0008]

CHEMICAL

[0009] In certain embodiments of the process, R 1 or R 2 is methyl.

[0010] In certain embodiments of the process, the alcoholic solvent is selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, t-butanol, ethylene glycol, glycerol, cyclohexane-1,4-diyl dimethanol, phenol, benzyl alcohol, and any combination thereof.

[0011] In certain embodiments of the process, the alcoholic solvent is methanol.

[0012] In certain embodiments of the process, the solvent for swelling the polyester is selected from the group consisting of nonpolar solvents, polar aprotic solvents, polar protic solvents, and any combination thereof.

[0013] In certain embodiments of the process, the solvent for swelling the polyester is selected from the group consisting of DMSO, DMF, acetone, halogenated solvents, n-hexane, nitrobenzene, methanol, benzyl alcohol, benzaldehyde, and any combination thereof.

[0014] In certain embodiments of the process, the solvent for swelling the polyester is a halogenated solvent.

[0015] In certain embodiments of the process, the solvent for swelling the polyester is methanol.

[0016] In certain embodiments of the process, the ratio of the solvent for swelling the polyester to the alcoholic solvent is between about 0.1:1 and about 2:1 (w:w).

[0017] In certain embodiments of the process, the ratio of the solvent for swelling the polyester to the alcoholic solvent is between about 0.5:1 and about 1:1 (w:w).

[0018] In certain embodiments of the process, the alkoxide is selected from the group consisting of alkali metal alkoxides, alkaline earth metal alkoxides, metal alkoxides, ammonium alkoxides, and any combination thereof.

[0019] In certain embodiments of the process, the alkoxide is selected from the group consisting of sodium methoxide, potassium ethoxide, aluminum tri-n-propoxide, and tetrabutylammonium methoxide.

[0020] In certain embodiments of the process, the alkoxide is sodium methoxide.

[0021] In certain embodiments of the process, the alkoxide is generated in situ by adding an alkali metal, alkaline earth metal, or metal to an alcohol-based solvent.

[0022] In certain embodiments of the process, the ratio of polyester to alkoxide is between about 15:1 and about 125:1 (w:w).

[0023] In certain embodiments of the process, the ratio of polyester to alkoxide is between about 20:1 and about 25:1 (w:w).

[0024] In certain embodiments of the process, the ratio of polyester to alkoxide is between about 15:1 and about 60:1 (w:w).

[0025] In certain embodiments of the process, the ratio of polyester to alkoxide is between about 20:1 and about 50:1 (w:w).

[0026] In certain embodiments of the process, the process is carried out until a yield of about 80% of the terephthalate of formula (I) is achieved.

[0027] In certain embodiments of the process, the process is carried out without external heat.

[0028] In certain embodiments of the process, the process is carried out at a temperature between about 25°C and about 85°C.

[0029] In certain embodiments of the process, the process is carried out at a temperature between about 25°C and about 80°C.

[0030] In certain embodiments of the process, the process is carried out at atmospheric pressure.

[0031] In certain embodiments of the process, the polyester is polyethylene terephthalate.

[0032] In certain embodiments of the process, the process further comprises recovering monoethylene glycol (MEG).

[0033] In certain embodiments of the process, the polyester is in the form of polymer flakes and is part of the feedstock.

[0034] In certain embodiments of the process, the average polymer flake particle size is between 1 mm and 20 mm.

[0035] In certain embodiments of the process, the average polymer flake particle size is between 1 mm and 5 mm.

[0036] A process for converting polyethylene terephthalate to dimethyl terephthalate is also disclosed herein and includes a process of mixing polyethylene terephthalate into a mixture comprising: (a) a solvent for swelling the polyethylene terephthalate; (b) methanol; and, (c) a substoichiometric amount of alkoxide.

[0037] In certain embodiments of the process, the solvent for swelling polyethylene terephthalate is selected from the group consisting of halogenated solvents, DMSO, benzyl alcohol, methanol, and any combination thereof.

[0038] In certain embodiments of the process, the solvent for swelling polyethylene terephthalate is a halogenated solvent.

[0039] In certain embodiments of the process, the solvent for swelling polyethylene terephthalate is methanol.

[0040] In certain embodiments of the process, the ratio of polyethylene terephthalate to alkoxide is between about 20:1 and about 25:1 (w:w).

[0041] In certain embodiments of the process, the ratio of polyester to alkoxide is between about 15:1 and about 60:1 (w:w).

[0042] In certain embodiments of the process, the ratio of polyester to alkoxide is between about 20:1 and about 50:1 (w:w).

[0043] In certain embodiments of the process, the alkoxide is selected from the group consisting of sodium methoxide, potassium ethoxide, aluminum tri-n-propoxide, and tetrabutylammonium methoxide.

[0044] In certain embodiments of the process, the alkoxide is sodium methoxide.

[0045] In certain embodiments of the process, the ratio of the solvent for swelling polyethylene terephthalate to methanol is between about 0.5:1 and about 1:1 (w:w).

[0046] In certain embodiments of the process, the process is carried out until a yield of about 80% of dimethyl terephthalate is achieved.

[0047] In certain embodiments of the process, the process is carried out without external heat.

[0048] In certain embodiments of the process, the process is carried out at a temperature between about 25°C and about 85°C.

[0049] In certain embodiments of the process, the process is carried out at a temperature between about 25°C and about 80°C.

[0050] In certain embodiments of the process, the process is carried out at atmospheric pressure.

[0051] In certain embodiments of the process, the process further includes recovering monoethylene glycol (MEG).

[0052] In certain embodiments of the process, the polyethylene terephthalate is in the form of polymer flakes and is part of the feedstock.

[0053] In certain embodiments of the process, the average polymer flake particle size is between 1 mm and 20 mm.

[0054] In certain embodiments of the process, the average polymer flake particle size is between 1 mm and 5 mm.

[0055] Dimethyl terephthalate (DMT) prepared using the process described herein is also provided herein.

[0056] Monoethylene glycol (MEG) prepared using the process described herein is also provided herein.

[0057] Also provided herein is a reaction mixture comprising: (a) A polyester selected from polyethylene terephthalate and poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate); (b) A solvent for swelling the polyester; (c) An alcoholic solvent; and (d) A sub-stoichiometric amount of an alkoxide.

[0058] In certain embodiments of the reaction mixture, the alcoholic solvent is selected from the group consisting of methanol, ethanol, n-propanol, isopropanol, t-butanol, ethylene glycol, glycerol, cyclohexane-1,4-diyl dimethanol, phenol, benzyl alcohol, and any combination thereof.

[0059] In certain embodiments of the reaction mixture, the solvent for swelling the polyester is selected from the group consisting of nonpolar solvents, polar aprotic solvents, polar protic solvents, and any combination thereof.

[0060] In certain embodiments of the reaction mixture, the solvent for swelling the polyester is a halogenated solvent.

[0061] In certain embodiments of the reaction mixture, the solvent for swelling the polyester is methanol.

[0062] In certain embodiments of the reaction mixture, the alcoholic solvent is methanol.

[0063] In certain embodiments of the reaction mixture, the ratio of the solvent for swelling the polyester to the alcoholic solvent is between about 0.5:1 and about 1:1 (w:w).

[0064] In certain embodiments of the reaction mixture, the ratio of the polyester to the alkoxide is between about 15:1 and about 30:1 (w:w).

[0065] In certain embodiments of the reaction mixture, the ratio of polyethylene terephthalate to alkoxide is between about 20:1 and about 25:1 (w:w).

[0066] In certain embodiments of the reaction mixture, the ratio of polyester to alkoxide is between about 15:1 and about 60:1 (w:w).

[0067] In certain embodiments of the reaction mixture, the ratio of polyester to alkoxide is between about 20:1 and about 50:1 (w:w).

[0068] In certain embodiments of the reaction mixture, the alkoxide is selected from the group consisting of sodium methoxide, potassium ethoxide, aluminum tri-n-propoxide, and tetrabutylammonium methoxide.

[0069] In certain embodiments of the reaction mixture, the alkoxide is sodium methoxide.

[0070] In certain embodiments of the reaction mixture, the polyester is polyethylene terephthalate.

DETAILED DESCRIPTION OF THE INVENTION

[0071] Dimethyl terephthalate (DMT) is used in the production of polyesters including polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), and polybutylene terephthalate (PBT). Since DMT is volatile, it is an intermediate in some recycling schemes (e.g., from plastic bottles) for PET. Hydrogenation of DMT gives the diol 1,4-cyclohexanedimethanol, which is a useful monomer in the formation of polyester resins.

[0072] DMT has been manufactured in many ways. As is customary and still commercially valuable is the direct esterification of terephthalic acid. Alternatively, it is prepared by alternating steps of oxidation and methyl-esterification from paraxylene via methyl p-toluate. The process for manufacturing DMT from paraxylene and methanol consists of four main steps: oxidation, esterification, distillation, and crystallization. The mixture of paraxylene and p-toluic acid ester is oxidized with air in the presence of a transition metal catalyst (Co / Mn). The mixture of acids resulting from the oxidation is esterified with methanol to produce a mixture of esters. The crude ester mixture is distilled to remove all the resulting heavy-boiling substances and residues; the lighter esters are recycled to the oxidation section. Thereafter, the crude DMT is crystallized to remove DMT isomers, residual acids, and aromatic aldehydes.

[0073] Improvements in DMT production from PET recycling: Due to the increasing use of PET and PETG in the packaging and fiber (carpet and other textiles) industries, there is a need for an efficient, low-energy, high-yield, and cost-effective method for forming DMT from PET or PETG.

[0074] Polyester Described herein is a process for converting a polyester to an ester derivative; the process includes combining the polyester with a mixture including: (a) a solvent for swelling the polyester; (b) an alcohol-based solvent; and, (c) a sub-stoichiometric amount of an alkoxide.

[0075] In some embodiments, the polyester is selected from polyethylene terephthalate (PET), poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG), polyglycolide or polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone (PCL), polyhydroxybutyrate (PHB), polyethylene adipate (PEA), polybutylene succinate (PBS), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene naphthalate (PEN), Vectran®, Kutin, and any combination thereof.

[0076] In some embodiments, the polyester is polyethylene terephthalate (PET):

[0077]

Chemical formula

[0078] In some embodiments, the polyester is a terephthalic acid / ethylene glycol oligomer.

[0079] In some embodiments, the polyester is poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate (PETG):

[0080]

Chemical formula

[0081] In some embodiments, the polyester is polyglycolide or polyglycolic acid (PGA).

[0082]

Chemical formula

[0083] In some embodiments, the polyester is polylactic acid (PLA):

[0084]

Chemical formula

[0085] In some embodiments, the polyester is polycaprolactone (PCL):

[0086]

Chemical formula

[0087] In some embodiments, the polyester is polyhydroxybutyrate (PHB):

[0088]

Chemical formula

[0089] In some embodiments, the polyester is polyethylene adipate (PEA):

[0090]

Chemical formula

[0091] In some embodiments, the polyester is polybutylene succinate (PBS):

[0092]

Chemical formula

[0093] In some embodiments, the polyester is poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV):

[0094]

Chemical formula

[0095] In some embodiments, the polyester is polybutylene terephthalate (PBT):

[0096]

Chem.

[0097] In some embodiments, the polyester is polytrimethylene terephthalate (PTT):

[0098]

Chem.

[0099] In some embodiments, the polyester is polyethylene naphthalate (PEN):

[0100]

Chem.

[0101] In some embodiments, the polyester is Vectran®:

[0102]

Chem.

[0103] In some embodiments, the polyester is cutin. Cutin is one of two waxy polymers that are the main components of the plant cuticle, covering all aerial surfaces of the plant. Cutin consists of omega-hydroxy acids and their derivatives, linked via ester bonds to form a polyester polymer. There are two main cutin monomer families, the C16 and C18 families. The C16 family consists mainly of 16-hydroxy palmitic acid and 9,16- or 10,16-dihydroxy palmitic acid. The C18 family consists mainly of 18-hydroxy oleic acid, 9,10-epoxy-18-hydroxy stearic acid, and 9,10,18-trihydroxy stearate. Tomato cutin consists of 16-hydroxy palmitic acid and 10,16-dihydroxy palmitic acid, where the 10-isomer is generally dominant. Tomato cutin is a transesterified polyester biopolymer. The significant proportion of secondary esters (esterification at the C-10 secondary hydroxyl) indicates that the polyester structure is highly branched.

[0104] In some embodiments, the polyester is in a feedstock that contains impurities such as additional polymers (e.g., polyethylene, polypropylene, polyvinyl chloride (PVC), paper, colorants, dust, ethylene vinyl alcohol (EvOH), polycarbonate (PC), polyvinylidene chloride (PVDC), ethylene vinyl acetate (EVA), adhesives, polyamides, or any combination thereof). In some embodiments, the feedstock contains between about 5% and about 20% impurities.

[0105] Mishra et al. (Kinetic and thermodynamic study of methanolysis of poly(ethylene terephthalate) waste powder Polym. Int. 52:337-342 (2003)) showed that an increase in the particle size of PET flakes causes a decrease in depolymerization. Mishra et al. recorded 127.5 μm as the optimal particle size. There is a need for a depolymerization process that allows the use of larger polymer flakes. In some embodiments, the feedstock includes polymer flakes. In some embodiments, the average particle size of the polymer flakes is between 1 mm and 20 mm. In some embodiments, the average particle size of the polymer flakes is between 1 mm and 15 mm. In some embodiments, the average particle size of the flakes is between 1 mm and 10 mm. In some embodiments, the average particle size of the polymer flakes is between 1 mm and 5 mm.

[0106] Ester derivative Described herein is a process for converting a polyester to an ester derivative; including the process of mixing a polyester into a mixture comprising: (a) a solvent for swelling the polyester; (b) an alcohol-based solvent; and, (c) a sub-stoichiometric amount of an alkoxide.

[0107] In some embodiments, the polyester is polyglycolide or polyglycolic acid (PGA), and the ester derivative is a 2-hydroxyacetate derivative. In some embodiments, the ester derivative is methyl 2-hydroxyacetate.

[0108] In some embodiments, the polyester is polylactic acid (PLA), and the ester derivative is a 2-hydroxypropanoate derivative. In some embodiments, the ester derivative is methyl 2-hydroxypropanoate.

[0109] In some embodiments, the polyester is polycaprolactone (PCL), and the ester derivative is a 6-hydroxyhexanoate derivative. In some embodiments, the ester derivative is methyl 6-hydroxyhexanoate.

[0110] In some embodiments, the polyester is polyhydroxybutyrate (PHB), and the ester derivative is a hydroxybutyrate derivative. In some embodiments, the ester derivative is methyl hydroxybutyrate.

[0111] In some embodiments, the polyester is polyethylene adipate (PEA), and the ester derivative is an adipate derivative. In some embodiments, the ester derivative is dimethyl adipate.

[0112] In some embodiments, the polyester is polybutylene succinate (PBS), and the ester derivative is a succinate derivative. In some embodiments, the ester derivative is dimethyl succinate.

[0113] In some embodiments, the polyester is poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), and the ester derivative is a hydroxybutyrate derivative, a hydroxyvalerate derivative, or a combination thereof. In some embodiments, the ester derivative is methyl hydroxybutyrate, methyl hydroxyvalerate, or a combination thereof.

[0114] In some embodiments, the polyester is polyethylene naphthalate (PEN), and the ester derivative is a naphthalate derivative. In some embodiments, the ester derivative is dimethyl naphthalate.

[0115] In some embodiments, the polyester is vectran, and the ester derivative is a naphthoate derivative, a benzoate derivative, or a combination thereof. In some embodiments, the ester derivative is methyl hydroxynaphthoate or methyl hydroxybenzoate.

[0116] In some embodiments, the polyester is chitin, and the ester derivative is a hydroxypalmitate or a dihydroxypalmitate derivative. In some embodiments, the ester derivative is methyl hydroxypalmitate or methyl dihydroxypalmitate.

[0117] In some embodiments, the polyester is polyethylene terephthalate (PET), poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) (PETG), polytrimethylene terephthalate (PTT), or polybutylene terephthalate (PBT), and the ester derivative is a terephthalate derivative. In some embodiments, the terephthalate derivative is a compound of formula (I):

[0118] [Chemical formula] wherein R 1 and R 2 are independently selected from the group consisting of hydrogen, C1-C6 alkyl, C1-C6 haloalkyl, C1-C6 hydroxyalkyl, optionally substituted C3-C8 cycloalkyl, optionally substituted (C1-C6 alkyl)(C3-C8 cycloalkyl), optionally substituted aryl, and optionally substituted (C1-C6 alkyl)(aryl); and one of R 1 or R 2 is not hydrogen.

[0119] In some embodiments of the compound of formula (I), R 1 and R 2is independently C1-C6 alkyl or C1-C6 hydroxyalkyl.

[0120] In some embodiments of the compound of formula (I), R 1 and R 2 are independently C1-C6 alkyl. In some embodiments of the compound of formula (I), R 1 and R 2 are independently methyl, ethyl, propyl, isopropyl, or butyl. In some embodiments of the compound of formula (I), R 1 and R 2 are independently methyl or ethyl. In some embodiments of the compound of formula (I), R 1 and R 2 is methyl. In some embodiments of the compound of formula (I), R 1 and R 2 is ethyl. In some embodiments of the compound of formula (I), R 1 and R 2 is not hydrogen.

[0121] In some embodiments of the compound of formula (I), R 1 and R 2 are independently C1-C6 hydroxyalkyl. In some embodiments of the compound of formula (I), R 1 and R 2 are independently hydroxyethyl or propanediol. In some embodiments of the compound of formula (I), R 1 and R 2 is hydroxyethyl. In some embodiments of the compound of formula (I), R 1 and R 2 is 2-hydroxyethyl. In some embodiments of the compound of formula (I), R 1 and R 2 is dihydroxypropyl. In some embodiments of the compound of formula (I), R 1 and R 2 is 2,3-dihydroxypropyl.

[0122] In some embodiments of the compound of formula (I), R 1 and R 2 are independently optionally substituted (C1-C6 alkyl)(C3-C8 cycloalkyl). In some embodiments of the compound of formula (I), R 1 and R 2 are independently substituted (C1-C6 alkyl)(C3-C8 cycloalkyl). In some embodiments of the compound of formula (I), R 1 and R 2 is 4-(hydroxymethyl)cyclohexyl)methyl.

[0123] In some embodiments of the compound of formula (I), R 1 and R 2 are independently optionally substituted aryl. In some embodiments of the compound of formula (I), R 1 and R 2 is phenyl.

[0124] In some embodiments of the compound of formula (I), R 1 and R 2 are independently optionally substituted (C1-C6 alkyl)(aryl). In some embodiments of the compound of formula (I), R 1 and R 2 is benzyl.

[0125] In some embodiments, the ester derivative comprises less than about 10% impurities (w / w). In some embodiments, the ester derivative comprises less than about 9% impurities (w / w). In some embodiments, the ester derivative comprises less than about 8% impurities (w / w). In some embodiments, the ester derivative comprises less than about 7% impurities (w / w). In some embodiments, the ester derivative comprises less than about 6% impurities (w / w). In some embodiments, the ester derivative comprises less than about 5% impurities (w / w). In some embodiments, the ester derivative comprises less than about 4% impurities (w / w). In some embodiments, the ester derivative comprises less than about 3% impurities (w / w). In some embodiments, the ester derivative comprises less than about 2% impurities (w / w). In some embodiments, the ester derivative comprises less than about 1% impurities (w / w). In some embodiments, the ester derivative comprises less than about 0.5% impurities (w / w). In some embodiments, the ester derivative comprises less than about 0.4% impurities (w / w). In some embodiments, the ester derivative comprises less than about 0.3% impurities (w / w). In some embodiments, the ester derivative comprises less than about 0.2% impurities (w / w). In some embodiments, the ester derivative comprises less than about 0.1% impurities (w / w).

[0126] In some embodiments, the ester derivative comprises 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, 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.

[0127] Glycol Described herein is a process for converting a polyester to an ester derivative; the process includes combining the polyester with a mixture including: (a) A solvent for swelling the polyester; (b) An alcohol-based solvent; and, (c) A sub-stoichiometric amount of alkoxide.

[0128] In some embodiments, the process further includes the formation of glycol. In some embodiments, the glycol is monoethylene glycol (MEG) (or ethylene glycol). In some embodiments, the glycol is propylene glycol. In some embodiments, the glycol is butylene glycol.

[0129] In some embodiments, the glycol is obtained in a yield between about 80 and about 99 mol%. In some embodiments, the glycol is obtained in a yield between about 85 and about 99 mol%. In some embodiments, the glycol is obtained in a yield between about 90 and about 99 mol%. In some embodiments, the glycol is obtained in a yield of at least about 80 mol%. In some embodiments, the glycol is obtained in a yield of at least about 85 mol%.

[0130] In some embodiments, the glycol contains less than about 10% impurities (w / w). In some embodiments, the glycol contains less than about 9% impurities (w / w). In some embodiments, the glycol contains less than about 8% impurities (w / w). In some embodiments, the glycol contains less than about 7% impurities (w / w). In some embodiments, the glycol contains less than about 6% impurities (w / w). In some embodiments, the glycol contains less than about 5% impurities (w / w). In some embodiments, the glycol contains less than about 4% impurities (w / w). In some embodiments, the glycol contains less than about 3% impurities (w / w). In some embodiments, the glycol contains less than about 2% impurities (w / w). In some embodiments, the glycol contains less than about 1% impurities (w / w). In some embodiments, the glycol contains less than about 0.5% impurities (w / w). In some embodiments, the glycol contains less than about 0.4% impurities (w / w). In some embodiments, the glycol contains less than about 0.3% impurities (w / w). In some embodiments, the glycol contains less than about 0.2% impurities (w / w). In some embodiments, the glycol contains less than about 0.1% impurities (w / w).

[0131] In some embodiments, the glycol comprises 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, 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.

[0132] Alcohol-based solvent Described herein is a process for converting a polyester to an ester derivative; the process includes combining the polyester with a mixture including: (a) A solvent for swelling the polyester; (b) An alcohol-based solvent; and, (c) A sub-stoichiometric amount of alkoxide.

[0133] In some embodiments, the processes described herein include an alcohol-based solvent. In some embodiments, the alcohol-based solvent is a linear alcohol, a branched alcohol, a cyclic alcohol, or any combination thereof. In some embodiments, the alcohol-based solvent is selected from methanol, ethanol, n-propanol, isopropanol, t-butanol, ethylene glycol, glycerol, cyclohexane-1,4-diyl dimethanol, phenol, benzyl alcohol, and any combination thereof.

[0134] In some embodiments, the alcohol-based solvent is a linear C1-C4 alcohol. In some embodiments, the alcohol-based solvent is methanol, ethanol, propanol, butanol, or a combination thereof. In some embodiments, the alcohol-based solvent is methanol, ethanol, propanol, or a combination thereof. In some embodiments, the alcohol-based solvent is methanol. In some embodiments, the alcohol is ethanol. In some embodiments, the alcohol-based solvent is a branched C3-C4 alcohol. In some embodiments, the alcohol is t-butanol, s-butanol, i-butanol, i-propanol, or any combination thereof. In some embodiments, the alcohol-based solvent is a cyclic C3-C8 alcohol. In some embodiments, the alcohol-based solvent is cyclopropanol, cyclobutanol, cyclopentanol, cyclohexanol, cycloheptanol, cyclohexane-1,4-diyl dimethanol, or any combination thereof. In some embodiments, the alcohol-based solvent is cyclohexane-1,4-diyl dimethanol.

[0135] In some embodiments, the alcoholic solvent is a polyol. In some embodiments, the alcoholic solvent is selected from ethylene glycol, glycerol, and any combination thereof.

[0136] In some embodiments, the alcoholic solvent is selected from phenol, benzyl alcohol, and any combination thereof.

[0137] Solvent for swelling polyester Described herein is a process for converting a polyester into an ester derivative; including the process of mixing the polyester into a mixture comprising: (a) a solvent for swelling the polyester; (b) an alcoholic solvent; and, (c) a substoichiometric amount of alkoxide.

[0138] In some embodiments, the process described herein includes a process of pretreating the polyester with a solvent for swelling the polyester prior to the addition of the alcohol-based solvent and the alkoxide. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 5 minutes to about 60 minutes prior to the addition of the alcohol-based solvent and the alkoxide. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 5 minutes to about 40 minutes prior to the addition of the alcohol-based solvent and the alkoxide. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 5 minutes to about 20 minutes prior to the addition of the alcohol-based solvent and the alkoxide. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 5 minutes to about 10 minutes prior to the addition of the alcohol-based solvent and the alkoxide. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 5 minutes. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 10 minutes. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 15 minutes. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 20 minutes. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 25 minutes. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 30 minutes. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 35 minutes. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 40 minutes. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 45 minutes. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 50 minutes. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 55 minutes. In some embodiments, the pretreatment with the solvent for swelling the polyester is carried out for about 60 minutes.

[0139] In some embodiments, the processes described herein include a process of pretreating the polyester with a solvent for swelling the polyester simultaneously with the addition of an alcohol-based solvent and an alkoxide.

[0140] In some embodiments, the solvent for swelling the polyester is selected from nonpolar solvents, polar aprotic solvents, polar protic solvents, and any combination thereof.

[0141] In some embodiments, the solvent for swelling the polyester is selected from dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), acetone, halogenated solvents, n-hexane, nitrobenzene, methanol, benzyl alcohol, benzaldehyde, and any combination thereof. In some embodiments, the solvent for swelling the polyester is selected from DMSO, halogenated solvents, and any combination thereof. In some embodiments, the solvent for swelling the polyester is DMSO. In some embodiments, the solvent for swelling the polyester is a halogenated solvent. In some embodiments, the solvent for swelling the polyester is a chlorinated solvent. In some embodiments, the solvent for swelling the polyester is dichloromethane, dichloroethane, tetrachloroethane, chloroform, carbon tetrachloride, trichloroethane, or any combination thereof. In some embodiments, the solvent for swelling the polyester is dichloromethane. In some embodiments, the solvent for swelling the polyester is methanol.

[0142] In some embodiments, the ratio of the solvent for swelling the polyester to the alcohol-based solvent is between about 0.1:1 and about 2:1 (w:w). In some embodiments, the ratio of the solvent for swelling the polyester to the alcohol-based solvent is between about 1:1 and about 2:1 (w:w). In some embodiments, the ratio of the solvent for swelling the polyester to the alcohol-based solvent is between about 0.1:1 and about 2:1 (w:w), or between about 0.2:1 and about 2:1 (w:w), or between about 0.3:1 and about 2:1 (w:w), or between about 0.4:1 and about 2:1 (w:w), or between about 0.5:1 and about 2:1 (w:w), or between about 0.6:1 and about 2:1 (w:w), or between about 0.7:1 and about 2:1 (w:w), or between about 0.8:1 and about 2:1 (w:w), or between about 0.9:1 and about 2:1 (w:w), or between about 1:1 and about 2:1 (w:w), or between about 1:2 and about 2:1 (w:w), or between about 1:3 and about 2:1 (w:w), or between about 1:4 and about 2:1 (w:w), or between about 1:4 and about 2:1 (w:w), or between about 1:6 and about 2:1 (w:w), or between about 1:7 and about 2:1 (w:w), or between about 1:8 and about 2:1 (w:w), or between about 1:9 and about 2:1 (w:w), or between about 0.5:1 and about 1.5:1 (w:w), or between about 0.5:1 and about 1.5:1 (w:w), or between about 0.5:1 and about 1.5:1 (w:w), or between about 1:1 and about 1.5:1 (w:w). In some embodiments, the ratio of the solvent for swelling the polyester to the alcohol-based solvent is between about 0.5:1 and about 1:1 (w:w).

[0143] Alcoholate Described herein is a process for converting a polyester to an ester derivative; including the process of mixing a polyester into a mixture comprising: (a) a solvent for swelling the polyester; (b) an alcoholic solvent; and, (c) a substoichiometric amount of alcoholate.

[0144] In some embodiments, the processes described herein include adding a substoichiometric amount of alkoxide. In some embodiments, the processes described herein include adding a catalytic amount of alkoxide.

[0145] As used herein, the term "substoichiometric amount" is used to indicate that the amount of material used is less than the stoichiometric amount. The term is used interchangeably herein with "catalytic amount." In some embodiments, the substoichiometric amount is about 95% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 90% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 85% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 80% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 75% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 70% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 65% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 60% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 55% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 50% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 45% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 40% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 35% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 30% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 25% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 20% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 15% or less of the stoichiometric amount. In some embodiments, the substoichiometric amount is about 10% or less of the stoichiometric amount.

[0146] "Stoichiometric amount", as used herein, is used to indicate that the amount of material used is equivalent to the number of ester bonds in the polyester.

[0147] In some embodiments, the alkoxide comprising an alkoxide anion and a cation is selected from alkali metal alkoxides, alkaline earth metal alkoxides, metal alkoxides, ammonium alkoxides, and any combination thereof. In some embodiments, the alkoxide anion is a C1-C4 alkoxide anion. In some embodiments, the alkoxide anion is selected from methoxide, ethoxide, n-propoxide, n-butoxide, t-butoxide, sec-butoxide, iso-butoxide, iso-propoxide, and combinations thereof. In some embodiments, the alkoxide anion is methoxide, ethoxide, or any combination thereof. In some embodiments, the alkoxide anion is methoxide. In some embodiments, the cation is lithium, sodium, potassium, magnesium, calcium, strontium, barium, zinc, aluminum, or ammonium. In some embodiments, the alkoxide is sodium methoxide, potassium ethoxide or aluminum tri-n-propoxide. In some embodiments, the ammonium alkoxide is a tetraalkylammonium alkoxide. In some embodiments, the ammonium alkoxide is tetrabutylammonium alkoxide. In some embodiments, the alkoxide is sodium methoxide, potassium ethoxide, aluminum tri-n-propoxide, or tetrabutylammonium methoxide.

[0148] In some embodiments, the alkoxide is generated in situ by adding an alkali metal, alkaline earth metal, or metal to an alcohol-based solvent.

[0149] In some embodiments, the ratio of polyester to alkoxide is between about 15:1 to about 125:1 (w:w), or between about 15:1 to about 100:1 (w:w), or between about 15:1 to about 80:1 (w:w), or between about 15:1 to about 60:1 (w:w), or between about 15:1 to about 40:1 (w:w), or between about 15:1 to about 25:1 (w:w), or between about 15:1 to about 20:1 (w:w), or between about 20:1 to about 25:1 (w:w), or between about 20:1 to about 50:1 (w:w), or between about 30:1 to about 60:1 (w:w), or between about 40:1 to about 70:1 (w:w), or between about 50:1 to about 80:1 (w:w), or between about 60:1 to about 90:1 (w:w), or between about 20:1 to about 125:1 (w:w), or between about 40:1 to about 125:1 (w:w), or between about 60:1 to about 125:1 (w:w), or between about 80:1 to about 125:1 (w:w), or between about 100:1 to about 125:1 (w:w). In some embodiments, the ratio of polyester to alkoxide is between about 20:1 to about 25:1 (w:w).

[0150] Reaction time Described herein is a process for converting a polyester to an ester derivative; including the process of combining the polyester with a mixture comprising: (a) a solvent for swelling the polyester; (b) an alcoholic solvent; and, (c) a substoichiometric amount of an alkoxide.

[0151] In some embodiments, the mixing of the polyester with the solvent, alkoxide, and alcoholic solvent for swelling the polyester is carried out for a sufficient period of time. In some embodiments, the mixing of the polyester with the solvent, alkoxide, and alcoholic solvent for swelling the polyester is carried out until a yield of about 70% of the desired ester is reached. In some embodiments, the mixing of the polyester with the solvent, alkoxide, and alcoholic solvent for swelling the polyester is carried out until a yield of about 75% of the desired ester is reached. In some embodiments, the mixing of the polyester with the solvent, alkoxide, and alcoholic solvent for swelling the polyester is carried out until a yield of about 80% of the desired ester is reached. In some embodiments, the mixing of the polyester with the solvent, alkoxide, and alcoholic solvent for swelling the polyester is carried out until a yield of about 85% of the desired ester is reached. In some embodiments, the mixing of the polyester with the solvent, alkoxide, and alcoholic solvent for swelling the polyester is carried out until a yield of about 90% of the desired ester is reached. In some embodiments, the mixing of the polyester with the solvent, alkoxide, and alcoholic solvent for swelling the polyester is carried out until a yield of about 95% of the desired ester is reached.

[0152] In some embodiments, the mixing of the polyester with the solvent, alkoxide, and alcoholic solvent for swelling the polyester is carried out for between about 10 minutes and 5 hours, or between about 10 minutes and 4 hours, or between about 10 minutes and 3 hours, or between about 10 minutes and 2 hours, or between about 20 minutes and 2 hours, or between about 30 minutes and 2 hours, or between about 40 minutes and 2 hours, or between about 30 minutes and 1 hour, or between about 30 minutes and 1.5 hours. In some embodiments, the mixing of the polyester with the solvent, alkoxide, and alcoholic solvent for swelling the polyester is carried out for about 10 minutes, or about 15 minutes, or about 20 minutes, or about 25 minutes, or about 30 minutes, or about 35 minutes, about 40 minutes, or about 45 minutes, or about 50 minutes, or about 60 minutes, or about 70 minutes, or about 80 minutes, about 90 minutes, or about 100 minutes, or about 110 minutes, about 120 minutes, or about 130 minutes, or about 140 minutes, about 150 minutes, or about 160 minutes, or about 170 minutes, or about 180 minutes. In some embodiments, the mixing of the polyester with the solvent for swelling the polyester, alkoxide, and alcoholic solvent is carried out for about 1 hour, or about 2 hours, or about 3 hours, or about 4 hours, or about 5 hours.

[0153] Temperature Described herein is a process for converting a polyester to an ester derivative; including the process of mixing the polyester into a mixture comprising: (a) a solvent for swelling the polyester; (b) an alcoholic solvent; and, (c) a substoichiometric amount of an alkoxide.

[0154] In some embodiments, the process disclosed herein is carried out at ambient temperature. In some embodiments, the ambient temperature is 25 ± 5°C.

[0155] In some embodiments, the processes disclosed herein are performed without external heat. In some embodiments, the process is exothermic and the temperature of the reaction mixture rises to at least 30 °C, at least 35 °C, at least 40 °C, at least 45 °C, at least 50 °C, at least 55 °C, or at least 60 °C. In some embodiments, no external heat source is used to raise the temperature of the reaction mixture.

[0156] In some embodiments, the processes disclosed herein are performed with external heat. In some embodiments, the processes disclosed herein are performed with external heat between about 25 °C and about 100 °C, between about 25 °C and about 85 °C, or between about 25 °C and about 80 °C, or between about 25 °C and about 60 °C, between about 40 °C and about 60 °C, or between about 40 °C and about 50 °C, or between about 30 °C and about 50 °C. In some embodiments, the processes disclosed herein are performed at about 26 °C, about 27 °C, about 28 °C, about 29 °C, about 30 °C, about 31 °C, about 32 °C, about 33 °C, about 34 °C, about 35 °C, about 36 °C, about 37 °C, about 38 °C, about 39 °C, about 40 °C, about 41 °C, about 42 °C, about 43 °C, about 44 °C, about 45 °C, about 46 °C, about 47 °C, about 48 °C, about 49 °C, about 50 °C, about 51 °C, about 52 °C, about 53 °C, about 54 °C, about 55 °C, about 56 °C, about 57 °C, about 58 °C, about 59 °C, about 60 °C, about 61 °C, about 62 °C, about 63 °C, about 64 °C, about 65 °C, about 66 °C, about 67 °C, about 68 °C, about 69 °C, about 70 °C, about 71 °C, about 72 °C, about 73 °C, about 74 °C, about 75 °C, about 76 °C, about 77 °C, about 78 °C, about 79 °C, about 80 °C, about 81 °C, about 82 °C, about 83 °C, about 84 °C, about 85 °C, about 86 °C, about 87 °C, about 88 °C, about 89 °C, about 90 °C, about 91 °C, about 92 °C, about 93 °C, about 94 °C, about 95 °C, about 96 °C, about 97 °C, about 98 °C, about 99 °C, or about 100 °C.

[0157] Pressure In some embodiments, the processes disclosed herein are conducted at atmospheric pressure. In some embodiments, the processes disclosed herein are conducted at elevated pressure. In some embodiments, the processes disclosed herein are conducted at a pressure between approximately atmospheric pressure and about 220 psi, or between approximately atmospheric pressure and about 200 psi, or between approximately atmospheric pressure and about 150 psi, or between approximately atmospheric pressure and about 100 psi, or between approximately atmospheric pressure and about 50, or between about 20 psi and about 150 psi, or between about 50 and about 100 psi. In some embodiments, the processes disclosed herein are conducted at about 14 psi, about 15 psi, about 16 psi, about 17 psi, about 18 psi, about 19 psi, about 20 psi, about 30 psi, about 40 psi, about 50 psi, about 60 psi, about 70 psi, about 80 psi, about 90 psi, about 100 psi, about 110 psi, about 120 psi, about 130 psi, about 140 psi, about 150 psi, about 160 psi, about 170 psi, about 180 psi, about 190 psi, about 200 psi, about 210 psi, or about 220 psi.

[0158] Stirring Described herein is a process for converting a polyester to an ester derivative; including the process of combining the polyester with a mixture comprising: (a) a solvent for swelling the polyester; (b) an alcoholic solvent; and, (c) a substoichiometric amount of an alkoxide.

[0159] In some embodiments, the processes disclosed herein are conducted without stirring. In some embodiments, the processes disclosed herein are conducted with enhanced stirring. In some embodiments, a stirred batch reactor is used to provide stirring. In some embodiments, a continuous reactor is used to provide stirring.

[0160] Specific terms The headings of the paragraphs used in this specification are for the sole purpose of organization only and are not to be construed as limiting the described subject matter.

[0161] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which the claimed subject matter belongs. In the case where there are multiple definitions for terms in this specification, the definition in this section shall prevail. It should be understood that the general description and the detailed description are merely exemplary and explanatory and are not limited to any content. In this application, the use of the singular form includes the plural form unless otherwise specified. As used in this specification and the appended claims, it should be noted that the singular forms "a", "an", and "the" include plural referents unless the context clearly indicates otherwise. In this application, the use of "or" means "and / or" unless otherwise specified. Further, the use of the term "including" is not limited, like other forms such as "include", "includes", and "included".

[0162] Unless the context requires otherwise, throughout this specification and the following claims, the words "comprise", "comprises", "comprising", and variations thereof are to be construed in an open inclusive sense, i.e., "including, but not limited to". Further, the headings provided in this specification are for convenience only and do not interpret the scope or meaning of the claimed invention.

[0163] As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless otherwise expressly stated. Also, it should be noted that the term "or" is generally used in the sense that it includes "and / or" unless the context clearly dictates otherwise.

[0164] As used herein, the terms "about" or "approximately" mean within 10% of a given value or range, preferably within 10%, and more preferably within 5%.

[0165] As used herein, ambient temperature is an informal expression for a typical or preferred indoor (air-conditioned) temperature, a temperature that people are generally accustomed to. The temperature represents a small range of approximately 21°C, which is the temperature of the atmosphere that does not feel hot or cold. 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.

[0166] As used in this specification and the appended claims, depolymerization refers to a method of decomposing a polymer into its starting materials. Depolymerization is essentially the opposite of polymerization. In some embodiments, depolymerization is achieved by glycolysis, methanolysis, or hydrolysis, respectively classified by the reactants used for depolymerization, such as glycol, methanol, or water.

[0167] The definitions of standard chemical terms include, but are not limited to, Carey and Sundberg “ADVANCED ORGANIC CHEMISTRY 4TH ED” Vols. A (2000) and B (2001), Plenum Press, New York, and may be found in reference materials as well.

[0168] The following terms, as used herein, have the following meanings unless otherwise defined.

[0169] “Alkyl” refers to a straight or branched hydrocarbon chain radical attached to the rest of the molecule by a single bond. For example, a straight-chain alkyl containing up to 4 carbon atoms is called a straight-chain C1-C4 alkyl, and similarly, a straight-chain alkyl containing up to 3 carbon atoms is a straight-chain C1-C3 alkyl. Straight-chain alkyls include straight-chain C1-C4 alkyls, straight-chain C1-C3 alkyls, straight-chain C1-C2 alkyls, straight-chain C2-C3 alkyls, and straight-chain C2-C4 alkyls. Representative alkyls include methyl, ethyl, propyl, and butyl. Branched alkyls containing 3 and 4 carbon atoms are called branched C3-C4 alkyls. The group of representative branched alkyls includes, but is not limited to, t-butyl, sec-butyl, isobutyl, and isopropyl. Unless specifically stated otherwise herein, alkyl is optionally substituted with oxygen, halogen, -CN, -CF3, OH, -OMe, NH2, or -NO2. In some embodiments, alkyl is optionally substituted with oxygen, halogen, -CN, -CF3, OH, or -OMe. In some embodiments, alkyl is optionally substituted with halogen.

[0170] “Halo” or “halogen” refers to bromo, chloro, fluoro, or iodo. In some embodiments, the halogen is fluoro or chloro. In some embodiments, the halogen is fluoro.

[0171] "Haloalkyl" refers to an alkyl radical as defined above which is substituted by one or more halo atoms as described above, for example, trifluoromethyl, difluoromethyl, fluoromethyl, trichloromethyl, 2,2,2-trifluoroethyl, 1,2-difluoroethyl, 3-bromo-2-fluoropropyl, 1,2-dibromoethyl, etc.

[0172] As set forth above, "hydroxyalkyl" refers to an alkyl radical which is substituted by one or more -OH groups, for example, hydroxymethyl, hydroxyethyl, hydroxypropyl, propanediol, etc.

[0173] "Cycloalkyl" is stable and refers to a partially or fully saturated, monocyclic, or polycyclic carbocyclic ring, which may include fused or bridged ring systems. Representative cycloalkyls include, but are not limited to, cycloalkyls having 3 to 15 carbon atoms (C3-C15 cycloalkyl), 3 to 10 carbon atoms (C3-C10 cycloalkyl), 3 to 8 carbon atoms (C3-C8 cycloalkyl), 3 to 6 carbon atoms (C3-C6 cycloalkyl), 3 to 5 carbon atoms (C3-C5 cycloalkyl), or 3 to 4 carbon atoms (C3-C4 cycloalkyl). In some embodiments, the cycloalkyl is a 3- to 6-membered cycloalkyl. In some embodiments, the cycloalkyl is a 5- to 6-membered cycloalkyl. Monocyclic cycloalkyls include, for example, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl. Polycyclic cycloalkyls or carbocyclics include, for example, adamantyl, norbornyl, decalinyl, bicyclo[3.3.0]octane, bicyclo[4.3.0]nonane, cis-decalin, trans-decalin, bicyclo[2.1.1]hexane, bicyclo[2.2.1]heptane, bicyclo[2.2.2]octane, bicyclo[3.2.2]nonane, and bicyclo[3.3.2]decane, and 7,7-dimethyl-bicyclo[2.2.1]heptanyl. Partially saturated cycloalkyls include, for example, cyclopentenyl, cyclohexenyl, cycloheptenyl, and cyclooctenyl. Unless specifically stated otherwise herein, cycloalkyl is optionally substituted with oxo, halogen, methyl, ethyl, -CN, -CF3, OH, -OMe, NH2, or -NO2. In some embodiments, cycloalkyl is optionally substituted with oxo, halogen, methyl, ethyl, -CN, -CF3, OH, or -OMe. In some embodiments, cycloalkyl is optionally substituted with halogen.

[0174] "Aryl" refers to a radical derived from a hydrocarbon ring system containing hydrogen, 6 to 30 carbon atoms, and at least one aromatic ring. The aryl radical can be a monocyclic, bicyclic, tricyclic, or tetracyclic ring system, which can include fused or bridged ring systems. In some embodiments, aryl is a 6- to 10-membered aryl. In some embodiments, aryl is a 6-membered aryl. Aryl radicals include, but are not limited to, aryl radicals derived from the hydrocarbon ring systems of anthrylene, naphthylene, phenanthrylene, anthracene, azulene, benzene, chrysene, fluoranthene, fluorene, as-indacene, s-indacene, indane, indene, naphthalene, phenalene, phenanthrene, pleiadene, pyrene, and triphenylene. In some embodiments, aryl is phenyl. Unless specifically stated otherwise herein, aryl may be optionally substituted, for example, with halogen, amino, nitrile, nitro, hydroxyl, alkyl, alkenyl, alkynyl, haloalkyl, alkoxy, aryl, cycloalkyl, heterocycloalkyl, heteroaryl, etc. In some embodiments, aryl is optionally substituted with halogen, methyl, ethyl, -CN, -CF3, OH, -OMe, NH2, or -NO2. In some embodiments, aryl is optionally substituted with halogen, methyl, ethyl, -CN, -CF3, OH, or -OMe. In some embodiments, aryl is optionally substituted with halogen.

[0175] As used herein, the term "mol" when referring to PET is the number of moles and is calculated using the molecular weight of the "PET" unit, which is 192.17 g / mol.

Examples

[0176] The following examples illustrate, but are not intended to limit, the disclosed embodiments.

[0177] Example 1: Polyethylene terephthalate (1000 g) was introduced into the reactor. Dichloromethane (500 g) was added, and the mixture was stirred for about 40 minutes at room temperature and atmospheric pressure. Then, sodium methoxide and methanol were added to the reaction mixture, stirred for 120 minutes, and heated (see the table below for details of the amounts, times, and temperatures).

[0178] Thereafter, the reaction mixture was filtered, and the filter cake was washed with methanol. Then, the filter cake was melted and filtered at 140 °C to remove any unreacted substances. Thereafter, the filtered dimethyl terephthalate was distilled at 200 °C under vacuum. The liquid recovered from the filtration was distilled to recover the solvent and monoethylene glycol.

[0179] [Table 1]

[0180] Example 2: Polyethylene terephthalate (1000 g) was introduced into the reactor. DMSO (500 g) was added, and the mixture was stirred for about 40 minutes at room temperature and atmospheric pressure. Then, sodium methoxide (45 g) and methanol (550 g) were added to the reaction mixture, stirred and heated at 55 °C for 120 minutes.

[0181] Thereafter, the reaction mixture was filtered, and the filter cake was washed with methanol. Then, the filter cake was melted and filtered at 140 °C to remove any unreacted substances. Thereafter, the filtered dimethyl terephthalate was distilled at 200 °C under vacuum. The liquid recovered from the filtration was distilled to recover the solvent and monoethylene glycol.

[0182] Dimethyl terephthalate was obtained in a yield of 89%.

[0183] Example 3: PET (10,000 g) was treated with methanol (6,000 g) at 60 °C for 1 hour. Thereafter, the methanol was discharged. After the discharge, the reactor was heated to rise from 60 °C to 70 °C, and sodium methoxide (25 wt% in methanol) was added. Thirty minutes after the addition of sodium methoxide, the remaining amount of methanol was added. The reaction was stopped 3 hours after the addition of sodium methoxide. The reaction mixture was then cooled to room temperature and filtered to separate MEG, sodium methoxide, and residual methanol from DMT and unreacted substances. Trials 1 and 2 could not be filtered even when different solid-liquid separation methods (centrifugation, press filter, vacuum filter, or pressure filter) were used, but filtration was successful for Trials 3 to 5. Since filtration was not possible, the distillation of MEG was followed by the distillation of methanol, and then the distillation of DMT from the reaction mixture was attempted in a rotary evaporator. After the recovery of methanol, the reaction mixture changed to a paste, and the distillation of MEG and DMT from it was not possible due to side reactions with impurities.

[0184] After solid-liquid separation, for Trials 3 to 5. Residual methanol and MEG were recovered from the liquid phase into two different fractions using a rotary evaporator. DMT was successfully recovered from the solid phase using a thin-film evaporator.

[0185] The following table shows the recovery of DMT and MEG using different amounts of sodium methoxide.

[0186]

Table 2

Claims

1. A process for converting a polyester selected from polyethylene terephthalate and poly(ethylene glycol-co-1,4-cyclohexanedimethanol terephthalate) into dimethyl terephthalate, said process comprising: (i) mixing said polyester with methanol for swelling said polyester; and (ii) mixing said polyester with a mixture containing an alcohol and a sub-stoichiometric amount of methoxide, wherein the ratio of said polyester to said methoxide is from 20:1 to 125:1 (w / w). The process achieving a yield of at least 70% of dimethyl terephthalate within 2 hours.

2. The process according to claim 1, wherein said methoxide is selected from the group consisting of calcium methoxide, potassium methoxide, sodium methoxide, and any combination thereof.

3. The process according to claim 2, wherein said methoxide is sodium methoxide.

4. The process according to claim 1, wherein the ratio of said polyester to said methoxide is from 40:1 to 125:1 (w / w).

5. The process according to claim 4, wherein the ratio of said polyester to said methoxide is from 60:1 to 125:1 (w / w).

6. The process according to claim 4, wherein the ratio of said polyester to said methoxide is from 80:1 to 125:1 (w / w).

7. The process according to claim 1, achieving a yield of at least 80% of dimethyl terephthalate.

8. The process according to claim 7, achieving a yield of at least 90% of dimethyl terephthalate.

9. The process according to claim 8, achieving a yield of at least 95% of dimethyl terephthalate. **Claim 10** The process according to claim 1, wherein the alcohol is methanol. **Claim 11** The process according to claim 1, carried out at a pressure of less than 120 psi. **Claim 12** The process according to claim 1, carried out at a pressure of less than 100 psi. **Claim 13** The process according to claim 1, carried out at a pressure of atmospheric pressure to 50 psi. **Claim 14** The process according to claim 1, carried out at a pressure of 50 to 100 psi.

Images