Polyester recycling process with pre-reaction purification

Abstract

The depolymerization reaction of a polyester feed with an organic catalyst and an alcohol solvent produces (i) recycled monomers or oligomeric diesters from the polyester, (ii) an organic catalyst for reuse, and (iii) an alcohol solvent, which can also be reused. The presence of volatile impurities such as water, acetaldehyde, and organic solvents can interfere with the success of the depolymerization reaction. A pre-reaction distillation step removes volatile impurities from the polyester feed, resulting in an efficient depolymerization reaction with consistency from batch to batch. The polyester feed can be further treated with a water azeotrope to remove water from the polyester feed prior to the pre-reaction distillation.

Description

Technical Field

[0001] The present invention relates generally to recycling methods, and more specifically, to methods for recycling polyester-based materials that incorporate a distillation step. Background Technology

[0002] In chemical recycling methods, even very small amounts of impurities in the feed polymer can cause a significant reduction in the quality of the recycled product. These polymer impurities (including low molecular weight volatile impurities) can cause haze formation in otherwise transparent materials or degrade the performance of the packaging polymer. In food contact applications, acetaldehyde (AA), a degradation byproduct formed when polyethylene terephthalate (PET) is heated, can alter the taste of beverages placed in PET bottles containing only trace amounts of AA. While strong-flavored beverages such as cola can tolerate AA levels up to 8 ppm, tasteless beverages such as drinking water should have less than 3 ppm of AA. Similarly, in chemical processes, impurities carried in the reaction feed can cause the formation of undesirable byproducts. For example, materials processed in uncontrolled atmospheres can acquire varying amounts of water depending on the presence of variables in the storage or processing environment, such as humidity, temperature, and storage type. In the case of recycled materials and reagents, both PET and ethylene glycol (EG) are hygroscopic. Although PET absorbs less than 1% water, water is commonly used in the sorting and cleaning processes of recycling equipment from which PET is derived for chemical recycling. The presence of this water in the PET feed reduces the efficiency and effectiveness of PET chemical recycling methods. Summary of the Invention

[0003] In one aspect, the present invention relates to a method comprising: treating a material comprising polyester by distillation to remove volatile impurities from the material; depolymerizing the distilled material with an organic catalyst and an alcohol solvent; and recovering reaction products from the depolymerization, comprising monomers or oligoesters from the polyester, an organic catalyst for reuse, and an alcohol solvent as an unreacted byproduct of the depolymerization.

[0004] In another aspect, the present invention relates to a method comprising: removing water from a polyester-containing material by treating the material with a solvent that forms an azeotrope with water; treating the material by distillation to remove volatile impurities from the material; depolymerizing the distilled material with an organic catalyst and an alcohol solvent; and recovering the reaction product from the depolymerization, which comprises monomers or oligoesters from the polyester, an organic catalyst for reuse, and an alcohol solvent as an unreacted byproduct of the depolymerization.

[0005] In another aspect, the present invention relates to a method comprising: treating a material comprising polyethylene terephthalate (PET) using a distillation process to remove volatile impurities from the material; depolymerizing the distilled material with an amine organic catalyst and / or its carboxylate and an alcohol solvent; and recovering the reaction product from the depolymerization, which comprises di(2-hydroxyethyl) terephthalate (BHET) as a monomeric diester of PET, an amine organic catalyst for reuse, and any excess alcohol solvent.

[0006] Other aspects and / or embodiments of the invention will be provided in the detailed description of the invention set forth below, without limitation. Attached Figure Description

[0007] Figure 1 This is a photograph showing the results of a depolymerization reaction of a PET feed contaminated with water without prior distillation (Example 1).

[0008] Figure 2 This is a photograph showing the results of a depolymerization reaction of a PET feed contaminated with water, in conjunction with the pre-reaction distillation process described herein (Example 2).

[0009] Figure 3 These are photographs showing clean colored PET sheets before and after decolorization treatment with dichloromethane (DCM) (Example 3).

[0010] Figure 4A and 4B The results are H-NMR (d-DMSO) analysis of water and ethylene glycol (EG) content from distillates obtained from wet, dirty, mixed-color PET sheets after 34 minutes (Example 2). Figure 4A It is a superimposed NMR spectrum of water and EG content. Figure 4B This is a graph showing the mole fractions of water and EG in the distillate.

[0011] Figure 5 These are photographs showing mixed PET sheets of curbside dirt before and after purification treatment with dichloromethane (DCM) (Example 4).

[0012] Figure 6 These are photographs of five distillation fractions of mixed PET flakes from roadside dirt treated with DCM (Example 4).

[0013] Figure 7 yes Figure 6 NMR results of the five distillation fractions. Detailed Implementation Plan

[0014] The following description sets forth preferred aspects and / or embodiments of the invention currently considered to be protected by the claims. Any substitutions or modifications in function, purpose, or structure are intended to be covered by the appended claims. As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly indicates otherwise. The terms “comprising,” “including,” and / or “containing,” as used in the specification and the appended claims, specify the presence of a explicitly stated component, element, feature, and / or step, but do not exclude the presence or addition of one or more other components, elements, features, and / or steps.

[0015] Volatile catalyst (VolCat) chemical recycling methods are described in US 9,255,194B2 by Allen et al. and US 9,914,816B2 by Allen et al. In one embodiment, the VolCat method depolymerizes a polyester in a reactor at a temperature equal to or above the boiling point of the alcohol using an alcohol solvent and an organic catalyst. In another embodiment, the boiling point of the organic catalyst is at least 50°C lower than that of the alcohol solvent, and depolymerization is carried out at a temperature higher than that of the alcohol solvent. In yet another embodiment, the boiling point of the organic catalyst is at least 50°C lower than that of the alcohol solvent, and depolymerization is carried out at a temperature higher than that of the organic catalyst. In yet another embodiment, the polyester feed and alcohol solvent are heated to a reaction temperature of approximately 200-250°C before the introduction of the organic catalyst. The reaction products from VolCat depolymerization are monomers and / or oligoesters from the polyester, along with the recovered organic catalyst and excess alcohol solvent, the former intended for reuse in recycled polyester products and the latter also potentially for reuse in subsequent depolymerization reactions.

[0016] In another embodiment, the VolCat reaction is carried out in a chemical reactor, which may be a pressure reactor, such as an autoclave or extrusion reactor, or a non-pressurized reactor, such as a round-bottom flask. In another embodiment, the depolymerization reaction, which may be pressurized or non-pressurized, and one or more optional purification steps for the monomer product are carried out in a batch and / or continuous flow manner. In another embodiment, the depolymerized polyester monomer product, whether obtained in a batch process or by continuous flow, can be purified using a solvent in which the monomer product has limited solubility. Alcohols and / or water are non-limiting examples of such purification solvents. When using alcohols for purification, the alcohol can be unreacted alcohol from the depolymerization reaction or a newly introduced clean alcohol. In another embodiment, the recovered monomer product obtained from the VolCat reaction can be used to produce new polymer materials.

[0017] In another embodiment, the polyester is selected from polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), polypropylene terephthalate (PTT), polyethylene furanate (PEF), and combinations thereof. In another embodiment, the alcohol solvent is a glycol and / or a diol solvent. In another embodiment, the alcohol solvent is selected from 1,2-ethylene glycol (EG), 1,3-propanediol (trimethylenediol), 1,4-butanediol (tetramethylenediol), 1,5-pentanediol (pentanediol), and combinations thereof. In another embodiment, the organic catalyst is an amine organic catalyst and / or its carboxylate. In another embodiment, the amine of the amine organic catalyst and / or its carboxylate is a tertiary amine. In another embodiment, the amine organic catalyst and / or its carboxylate is selected from triethylamine (TEA), tetramethylethylenediamine (TMEDA), pentamethyldiethylenetriamine (PMDETA), trimethyltriazacyclononane (TACN), 4-(N,N-dimethylamino)pyridine (DMAP), 1,4-diazabicyclo[2.2.2]octane (DABCO), N-methylimidazole (NMI), and combinations thereof. In another embodiment, the amine organic catalyst and / or its carboxylate is TEA and / or its carboxylate.

[0018] In one embodiment, the polyester feed comprises terephthalate, and the recovered depolymerization product comprises terephthalate monomer. In another embodiment, the polyester feed comprises PET, and the recovered polyester monomer product is bis(2-hydroxyethyl) terephthalate (BHET). In yet another embodiment, the polyester feed comprises PET, the alcohol is EG, the amine organic catalyst is TEA and / or its carboxylate, and the recovered reaction product comprises unreacted EG, TEA, and BHET.

[0019] This paper describes a modified VolCat process that includes pre-reaction distillation, performed during or after heating the polyester feed and alcohol solvent, just before the addition of an organic catalyst to the reaction mixture. Pre-reaction distillation: (i) removes volatile impurities from the polyester feed; (ii) improves product purity after the completion of the VolCat process; (iii) eliminates the need for pre-drying the feed before introducing it into the reactor; and (iv) produces consistent reaction times that do not require adjustment between batches or during operation of the flow process.

[0020] Examples of volatile impurities that may be present in polyester feed and removed by pre-reaction distillation include, but are not limited to, water, acetaldehyde (AA), acetaldehyde acetal (e.g., acetaldehyde ethylene acetal), organic solvents used to purify polyester feed, other unwanted organic materials, and combinations thereof. As mentioned earlier, AA is a degradation product formed when polyester products are heated. Removing AA early in the recycling process is an important step because its content tends to increase during recycling. Examples of organic solvents that may be present in polyester feed include, but are not limited to, dichloromethane (DCM), which is used to remove color from polyester feed. Figure 3 , 5 The solvent used is hexafluoro-2-propanol (HFIPA), which is used as a polyester solvent; and a solvent that forms an azeotrope with water. In one embodiment, the polyester feed can be treated with a solvent that forms an azeotrope with water before pre-reaction distillation to help remove residual water from the polyester feed. The application of water azeotropes is particularly effective when the polyester feed contains >50 ppm of water. Examples of water azeotropes that can be used to treat polyester feeds include, but are not limited to, diethyl ether, alkanes, aromatics, and combinations thereof. Examples of alkanes include, but are not limited to, heptane, octane, nonane, and decane. Examples of aromatics include, but are not limited to, toluene and xylene. This azeotrope is then removed from the polyester feed by pre-reaction distillation.

[0021] The VolCat process is designed to recycle the organic catalyst at the end of the depolymerization process. Pre-reaction distillation improves the purity of the reaction products by removing volatile impurities (such as solvents used to purify the feed) and preventing them from being carried into the reaction, which could otherwise be entrained by the organic catalyst during recovery. In the VolCat process, early removal of volatile impurities eliminates or minimizes the burden of post-reaction purification steps.

[0022] For the original VolCat method, the low-grade polyester sample was purified in a separate unit operation by energy-intensive drying of the input material in an oven before the reaction began. The pre-reaction distillation purification step eliminates the need for drying the sample and uses the already required reaction mixture for a heating step to advantageously distill off unwanted volatiles.

[0023] The presence of impurities in the polyester feed of the VolCat reaction can adversely affect the reaction rate by influencing the performance of the organocatalyst. For example, impurities in the polyester feed may (i) increase the depolymerization time; (ii) partially deactivate the organocatalyst, leading to reduced depolymerization of the feed; and / or (iii) completely deactivate the organocatalyst. When the organocatalyst is partially deactivated, unreacted polyester will be introduced into the product stream. Figure 1Pre-reaction distillation removes impurities from the feed, mitigating the complexity caused by partial or incomplete depolymerization; thus, it allows the VolCat process to operate smoothly and consistently. Figure 2 ).

[0024] Figure 1 The VolCat method was applied to dirty, mixed-color PET sheets contaminated with water, resulting in filter clogging due to incomplete depolymerization of PET (Example 1). Figure 2 The incorporation of pre-reaction distillation into dirty, mixed-color PET sheets with the same water contamination resulted in significantly improved VolCat depolymerization (Example 2). Pre-reaction distillation produced very little residue, leading to improved filtration and purity of the reaction products.

[0025] Figure 3 The image shows the decolorization of clean colored PET sheets after DCM treatment. Figure 4A and 4B The H-NMR analysis data of the distillate obtained during a 34-minute time period during pre-reaction distillation of wet, dirty, mixed-color flakes are shown (Example 2). Figure 4A The measurements of water and EG in the distillate are shown. Figure 4B The superimposed H-NMR data of the distillate are shown, revealing the mole fractions of residual water and EG over time. Figure 4A and 4B The data showed that the amount of water in the distillate decreased as the temperature in the reactor increased, and that the amount of water in the sample was effectively removed by heating for 25 minutes.

[0026] Figure 5 The image shows mixed PET flakes of roadside dirt before and after DCM treatment. Figure 6 Six distillation fractions from pre-reaction distillation of mixed PET sheets taken from the same roadside dirt are shown (Example 4). Table 1 shows the HPLC UV absorption percentages (λ = 250 nm) of the reaction products (BHET and mother liquor) after VolCat depolymerization as described in Examples 1 and 2. (See Table 1 and...) Figure 1 and 2 As shown, the reaction product obtained by depolymerization of VolCat from dirty mixed PET sheets distilled before the reaction (Example 2); Figure 2 The reaction product obtained by depolymerization of VolCat without pre-reaction distillation is compared to that obtained in Example 1. Figure 1Higher purity and higher yield are observed. Table 1 shows that for the sample prepared using the pre-reaction distillation step (Example 2), a higher proportion of the desired BHET and dimer products and less carboxylic acid hydrolysis products can be seen. Table 2 (Example 5) shows that pre-reaction distillation has no discernible effect on the pore volume and porosity of the VolCat monomer or oligoester reaction products. Table 2 further shows that the monomer and / or oligoester reaction products from the VolCat reaction with or without pre-reaction distillation have higher pore volumes and comparable porosities than commercially available monomer and / or oligoester reaction products.

[0027] Table 1

[0028]

[0029] Figure 7 The superimposed NMR spectra of the five distillation fractions of Example 4 are shown in the figure. Figure 6 The early fractions (fractions 2 and 3) mainly contained DCM, ethylene glycol acetaldehyde, and water. Fraction 5, collected at 130°C, completely removed the undesirable ethylene glycol acetaldehyde and DCM. Fractions 6 and 7, collected at 160°C and 170°C respectively, had completely removed the water, and the fractions were primarily unreacted EG.

[0030] Various aspects and / or embodiments of the invention have been described for illustrative purposes, but are not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein has been chosen to best explain the principles, practical application, or technical improvements of the described aspects and / or embodiments relative to technology available in the market, or to enable others skilled in the art to understand the aspects and / or embodiments disclosed herein.

[0031] experiment

[0032] The following examples are provided to give those skilled in the art a complete disclosure of how to prepare and use the aspects and embodiments of the invention described herein. While efforts have been made to ensure accuracy regarding variables such as amounts, temperatures, etc., experimental errors and biases should be taken into account. Unless otherwise stated, parts are parts by weight, temperatures are in degrees Celsius, and pressures are at or near atmospheric pressure. Unless otherwise stated, all components are commercially available.

[0033] Example 1

[0034] Depolymerization reaction of PET feedstock contaminated with water

[0035] 1005g of dirty mixed-color PET flakes, containing visible water residue from the water-cooled cutting process, was used. PET and 4506g of EG were added to an 8L stainless steel Parr reactor with stirring. This reactor was connected to a closed distillation column with pressure regulation at the end and an addition burette containing 26.3g of TEA and 25g of EG. The reaction was heated to 220°C, and the TEA / EG mixture was added by pressurizing to 30psi. The reaction was carried out at this temperature for 1.5 hours. TEA was distilled off by first opening the valve of the distillation column and then slowly reducing the pressure to induce distillation. Distillation produced a two-phase liquid, found to be TEA and a large amount of water; the total weight of the distilled sample was measured to be 46g. Further distillation was performed until a total of 118g was recovered. The reaction solution was cooled to 80-85°C, at which point filtration with a filter aid was attempted, but unsuccessful due to the pasty nature of the crystals formed during the reaction, and redissolution was not achieved. Filtration was terminated after repeated attempts to scrape the pasty material from the surface of the filter aid. The remaining solution was further cooled to allow crystallization. In addition to the contaminants on the filter cake, approximately 40g of primarily recovered polyolefin clumps remained. The next day, the slurry was broken up, and a paste-like substance containing some product crystals and recovered polyolefins was scraped from the surface of the filter cake. Figure 1 As shown.

[0036] Example 2

[0037] Pre-reaction distillation and depolymerization of water-contaminated PET sheet feed

[0038] 1004 g of dirty mixed-color PET flakes, containing visible water content residue from a water-cooled cutting process, was used. PET and 4500 g of EG were added to an 8 L stainless steel Parr reactor with stirring. This reactor was connected to a distillation column via a Firestone valve with N2 flow and an addition burette containing 26.3 g of TEA and 25 g of EG. The reaction mixture was heated to 220 °C while collecting the distillate until the distillate temperature reached approximately 180 °C. The distillate was sampled within 34 minutes and analyzed by H-NMR in d-DMSO solvent to track the disappearance of water. Figure 4A and 4BIt was found that water was effectively removed from the sample by heating for 25 minutes. To proceed with the reaction, the valve to the column and the pressure regulator were closed, and the TEA / EG mixture was added to the reaction by pressurizing to 30 psi. The reaction was carried out at this temperature for 1.5 hours. TEA was distilled off by first opening the valve of the distillation column and then slowly reducing the pressure to induce distillation. Distillation produced a single-phase liquid, which was found to be TEA with no discernible water. The reaction solution was cooled to 80-85°C and easily filtered using diatomaceous earth as a filter aid. Approximately 41 g of sample, mainly composed of polyolefins, was recovered as a clump, in addition to contaminants on the filter cake. The reaction sequence was repeated twice more using the same filter aid, with no difficulty in filtration. After the third test, as... Figure 2 As shown, crystals form in the container after filtration with the filter aid, but there is no obvious residue. Use with... Figure 2 The same filter aid was used in both subsequent filtration processes without difficulty.

[0039] Example 3

[0040] Pre-reaction distillation and depolymerization of clean, colored PET sheet feed

[0041] 2.5 kg of clean, colored PET flakes were added to a 22 L reactor. 12 L of DCM was added to the reactor and gently stirred. The DCM turned dark almost immediately. Aliquots of the DCM were taken out every hour for 6 hours, and then analyzed after 24 hours. After 24 hours, the PET flakes were filtered from the DCM and dried. Figure 3 The images show PET sheets before and after DCM decolorization treatment.

[0042] Under stirring, 1004 g of pretreated clean colored PET flakes and 4500 g of EG were added to an 8 L stainless steel Parr reactor, which was connected to a distillation column with a Firestone valve supplying N2 flow and an addition burette containing 53 g of TEA and 25 g of EG. The reaction was heated to 220 °C while collecting the distillate until the distillate temperature reached approximately 180 °C. The reactor was heated from ambient temperature to 180 °C over approximately 30 minutes. Distillate fractions were collected at the following temperature intervals: 64.8 °C, 130 °C (at which point water begins to distill), 165 °C (separation into two phases), and 180 °C. To proceed with the reaction, the valves and pressure regulators of the distillation column were closed. When the reaction reached 220 °C, the TEA / EG mixture was added by pressurizing the sample chamber to 30 psi. The reaction was carried out at this temperature for 1.5 hours. TEA was distilled off by first opening the valves of the distillation column and then slowly reducing the pressure to induce distillation. Distillation yielded a single-phase liquid, identified as TEA, with no identifiable water. The reaction solution was cooled to 80-85°C, at which point it passed easily through a filter aid. The product filtered readily, showing no residual unreacted flakes or paste. Crystallization of the polyester reaction product BHET proceeded as usual.

[0043] Example 4

[0044] Pre-reaction distillation and depolymerization of roadside dirty mixed PET flake feed

[0045] 2.5 kg of dirty, roadside PET flakes were added to a 22 L glass reactor along with 12 L of DCM and gently stirred at room temperature. Upon addition to the flakes contained in the flask, the DCM immediately absorbed a surprising amount of color—even before stirring. DCM samples were removed at 1, 2, and 3 hours. Skimming off the less dense material from the liquid surface revealed PE, PP, and aluminum foil. The remaining PET flakes were filtered. Much of the dirt and grime initially on or within the dirty PET was released into the DCM liquid and easily filtered out, and the clean PET flakes were easily recovered. Almost no colored material or color residue in the form of polyolefins remained in the resulting product. Figure 5 Images of a portion of the sheet before and after the process are shown.

[0046] The depolymerization method described in Example 3 was repeated using pretreated roadside grime mixed PET sheets. The reaction was heated to 220°C while collecting the distillate until the distillate temperature reached approximately 170°C. Distillate fractions were collected at the following temperatures: 41°C, 50°C, 60°C, 130°C, 160°C, and 170°C. Figure 6 And obtain NMR readings for each fraction. Figure 7The reactor was then sealed to isolate the distillation column, and catalyst addition, reaction conditions, and BHET product recovery were carried out as usual.

[0047] Example 5

[0048] Porosity and pore volume of monomer products

[0049] Porosity and pore volume measurements were calculated for the BHET monomer products obtained from conventional VolCat depolymerization of PET and VolCat depolymerization of PET in the case of pre-reaction distillation. Table 2 shows the test results. Two Aldrich BHET monomers were tested simultaneously and are included in Table 2 for comparison with commercial products. Porosity and pore volume measurements were determined by mercury intrusion porosimetry according to ASTM D 4404-10 (where the sample is pre-degassed under vacuum at 25°C for 16 hours) at a contact angle of 140° (Particle Testing Authority, 4356 Communications Dr., Norcross, GA30093).

[0050] Table 2

[0051]

[0052] * Manufactured by Aldrich in 2008; porosity and pore volume were tested simultaneously with IBM samples. ** Manufactured by Aldrich in 2001; porosity and pore volume were tested simultaneously with IBM samples.

Claims

1. A method comprising: Materials containing polyester are treated by distillation to remove volatile impurities from the materials; Materials depolymerized and distilled using organic catalysts and alcohol solvents; as well as The depolymerization recovery reaction product comprises monomers or oligoesters from the polyester, the organic catalyst for reuse, and the alcohol solvent as an unreacted byproduct of the depolymerization, wherein the volatile impurities are selected from water, acetaldehyde, acetaldehyde acetal, organic solvents and combinations thereof, wherein the organic solvent is selected from dichloromethane (DCM), hexafluoro-2-propanol (HFIPA), diethyl ether, alkanes, toluene, xylene and combinations thereof, wherein the organic catalyst is an amine organic catalyst and / or its carboxylate, and wherein the alcohol solvent is a diol and / or a diol.

2. The method according to claim 1, wherein the amine organic catalyst and / or the amine of its carboxylate is a tertiary amine.

3. The method according to claim 1, wherein the amine organic catalyst and / or its carboxylate is triethylamine and / or its carboxylate, and the alcohol solvent is ethylene glycol.

4. The method according to any one of the preceding claims, wherein the monomer or oligomeric diester has a pore volume in the range of 1 mL / g to 1.5 mL / g.

5. A method comprising: Water is removed from a material containing polyester by treating it with a solvent that forms an azeotrope with water. The material is treated by distillation to remove volatile impurities from it; Materials depolymerized and distilled using organic catalysts and alcohol solvents; as well as The depolymerization recovery reaction product comprises monomers or oligoesters from the polyester, the organic catalyst for reuse, and the alcohol solvent as an unreacted byproduct of the depolymerization, wherein the volatile impurities are selected from acetaldehyde, acetaldehyde acetal, organic solvents and combinations thereof, wherein the organic solvent is selected from dichloromethane (DCM), hexafluoro-2-propanol (HFIPA), diethyl ether, alkanes, toluene, xylene and combinations thereof, wherein the organic catalyst is an amine organic catalyst and / or its carboxylate, and wherein the alcohol solvent is a diol and / or a diol.

6. The method of claim 5, wherein the material contains >50 ppm of water.

7. The method according to claim 5 or 6, wherein the amine organic catalyst and / or the amine of its carboxylate are tertiary amines.

8. The method according to claim 5 or 6, wherein the amine organic catalyst and / or its carboxylate is triethylamine and / or its carboxylate, and the alcohol solvent is ethylene glycol.

9. The method according to claim 5 or 6, wherein the monomer or oligomeric diester has a pore volume in the range of 1 mL / g to 1.5 mL / g.

10. A method comprising: Materials containing polyethylene terephthalate (PET) are treated with a distillation process to remove volatile impurities from the material; Materials depolymerized and distilled using amine organic catalysts and / or their carboxylates and alcohol solvents; and The depolymerization recovery reaction product comprises di(2-hydroxyethyl) terephthalate (BHET) as a monomeric diester of PET, an amine organic catalyst for reuse, and any excess alcohol solvent, wherein the volatile impurities are selected from water, acetaldehyde, acetaldehyde acetal, organic solvents and combinations thereof, wherein the organic solvents are selected from dichloromethane (DCM), hexafluoro-2-propanol (HFIPA), diethyl ether, alkanes, toluene, xylene and combinations thereof, and wherein the alcohol solvent is a diol and / or a diol.

11. The method of claim 10, wherein the material contains >50 ppm of water.

12. The method of claim 11, wherein a solvent that forms an azeotrope with water is added to the material prior to processing the material using the distillation process.

13. The method according to any one of claims 10-12, wherein the amine organic catalyst and / or the amine of its carboxylate are tertiary amines.

14. The method according to any one of claims 10-12, wherein the amine organic catalyst and / or its carboxylate is triethylamine and / or its carboxylate, and the alcohol solvent is ethylene glycol.

15. The method according to any one of claims 10-12, wherein the BHET has a pore volume in the range of 1 to 1.5 mL / g.

16. The method according to claim 1, 5 or 10, wherein the distillation is performed during or after heating the material comprising polyester and alcohol solvent, before the addition of the organic catalyst.

17. The method of claim 16, wherein the distillation is performed during or after heating the material comprising the polyester and alcohol solvent, just before the addition of the organic catalyst.

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