Method for purifying monoethylene glycol

Abstract

The invention relates to a method for purifying and recovering monoethylene glycol (MEG) from a solution obtained by depolymerizing at least one polyester having at least one MEG unit. The solution is preferably obtained from enzymatic depolymerization of polyethylene terephthalate (PET) contained in a plastic article under alkaline conditions. The invention also relates to a process for recycling and recovering the monomers of a polymer-containing material (e.g., a plastic article) comprising at least one polyester (e.g., PET) having at least one MEG unit.

Description

Technical Field

[0001] The present invention relates to a method for purifying and recovering monoethylene glycol (MEG) from a solution obtained by depolymerization of at least one polyester having at least one MEG unit. Preferably, the solution is obtained by enzymatic depolymerization of polyethylene terephthalate (PET) contained in a plastic product under alkaline conditions. In addition, the present invention relates to a method for recycling a polymer-containing material (e.g. a plastic product) comprising at least one polyester having at least one MEG unit (e.g. PET) and recovering its monomers. The method of the present invention is particularly suitable for degrading plastic products comprising polyethylene terephthalate. Background Art

[0002] Plastics are cheap and durable materials, which can be used to manufacture various products (food packaging, textiles, etc.) that have purposes in a wide range of applications. Therefore, the production of plastics has increased sharply in the past decades. In addition, most of them are used for disposable applications for single use, such as packaging, agricultural films, disposable consumer goods or short-lived products discarded within one year of manufacturing. Due to the durability of the polymer involved, a large amount of plastics are deposited in landfills and natural habitats around the world, producing increasing environmental problems. For example, in recent years, polyethylene terephthalate (PET), an aromatic polyester produced by terephthalic acid and monoethylene glycol, has been widely used in the manufacture of several products for human consumption, such as food and beverage packaging (for example: bottle, the soft drink of convenient size, the pouch for food) or textiles, fabrics, mats, carpets, etc.

[0003] Different solutions, from plastic degradation to plastic recycling, have been investigated to reduce the environmental and economic impacts associated with the accumulation of plastic waste. Mechanical recycling technology remains the most commonly used technology, but it faces several disadvantages. In fact, it requires extensive and expensive sorting and leads to downgraded applications due to the overall loss of molecular weight during the process and the uncontrolled presence of additives in the recycled products. Current recycling technologies are also expensive. Therefore, recycled plastic products are usually non-competitive compared to virgin plastics.

[0004] Chemical and enzymatic recycling of plastic products has also been developed and described (e.g., WO2014 / 079844, WO2015 / 097104, WO2015 / 173265, WO2017 / 198786, and WO2020 / 094646). These technologies allow the chemical components of polymers to be recovered in the form of monomers and / or oligomers. Growing interest is focused on the optimal process development for hydrolyzing polyester waste (such as PET waste) to recover terephthalic acid (TA) and monoethylene glycol (MEG). Several recycling methods have been reported, including chemical recycling of polyester or recycling of polyester using hydrolytic enzymes. Methods for recovering TA have been described (e.g., WO2020 / 094661) and typically, purification of MEG is performed by distillation. The recovered monomers / oligomers can then be purified and used to remanufacture plastic products of equal quality to the original plastic products, so that this method leads to infinite recycling of plastics.

[0005] However, the depolymerization of polyesters such as PET (e.g., alkaline depolymerization of PET) has the disadvantage that it produces a large amount of dicarboxylates, byproducts (e.g., DEG, TEG) and other inorganic impurities in the reaction solution that are not completely removed during the TA purification process. Therefore, at the end of the process, the recovered monoethylene glycol (MEG) contains a large proportion of impurities, preventing its further reuse for the manufacture of high-quality and transparent plastic products.

[0006] An object of the present invention is to recover purified MEG from the depolymerization of polyester or polyester-containing materials. According to EP1160228, ethylene glycol (such as MEG) produced by the reaction of ethylene oxide with water is separated from an aqueous mixture with organic acids, salts and unidentified UV light absorbers. The applicability of the method disclosed in EP1160228 for recovering MEG from a depolymerization solution of a polyester (such as PET) is neither disclosed nor suggested in this document. In particular, the depolymerization solution of a polyester containing at least one MEG unit contains components different from those of the aqueous solution disclosed in EP1160228. The depolymerization solution may contain impurities, such as derivatives of other units of the depolymerized polymer, such as terephthalic acid or its salts when the polyester is PET, and / or heavy impurities.

[0007] By studying this problem, the inventors have surprisingly demonstrated that the implementation of a process comprising specific steps in a defined order allows obtaining high-purity MEG from a solution obtained by depolymerizing at least one polyester having at least one MEG unit. The purity of the MEG obtained is much higher than that obtained by classical distillation purification and can even be as high as the purity required in the existing specifications for petrochemical MEG. SUMMARY OF THE INVENTION

[0009] The present inventors have found that it is possible to establish a purification process for producing highly purified MEG suitable for repolymerization from the depolymerization of a polyester having at least one MEG unit. More specifically, the present inventors have developed a process that can recover high-purity MEG from the hydrolysis of a polyester having at least one MEG unit. Furthermore, the present inventors have found that the purification process can be implemented for purifying MEG from a solution obtained from the chemical and biological depolymerization of at least one polyester having at least one MEG unit.

[0010] The inventors are credited with determining a specific series of steps for obtaining highly purified MEG from a solution comprising ethylene glycol and salts as depolymerization products and which results in the removal of all undesirable impurities in the final MEG. The process of the invention allows the recovery of MEG monomers forming the original polymer of the polyester so that said monomers can be reprocessed to synthesize new polymers of the same or another type.

[0011] In this respect, it is an object of the present invention to provide a process for purifying monoethylene glycol (MEG) from a depolymerization solution of at least one polyester having at least one MEG unit, the process comprising the following steps:

[0012] a) subjecting the depolymerization solution to at least one evaporation-condensation step in order to obtain a bottom fraction and a condensed top fraction,

[0013] b) contacting the condensed top fraction obtained in step (a) with a resin to obtain a solution,

[0014] c) subjecting the solution obtained in step (b) to at least one distillation step to obtain a distillate, and

[0015] d) recovering purified MEG from the distillate obtained in step (c).

[0016] In one embodiment, the polyester having at least one MEG unit is selected from the group consisting of polyethylene terephthalate (PET), polyethylene adipate (PEA), polyethylene 2,5-furandicarboxylate (PEF) and polyethylene naphthalate (PEN). In a specific embodiment, the polyester having at least one MEG unit is PET.

[0017] In one embodiment, the depolymerization from which the depolymerization solution for carrying out the process of the invention is obtained is a biological or chemical depolymerization. In a preferred embodiment, the biological or chemical depolymerization is a hydrolysis, preferably a hydrolysis under alkaline conditions (i.e. alkaline enzymatic depolymerization or alkaline chemical depolymerization such as saponification), even more preferably an alkaline enzymatic depolymerization.

[0018] In a preferred embodiment, the depolymerization solution of at least one polyester having at least one MEG unit comprises at least MEG, water and heavy impurities, and may further comprise traces of acids and / or salts.

[0019] In one embodiment, the depolymerization solution of at least one polyester having at least one MEG unit is obtained by depolymerizing a reaction solution of at least one polyester having at least one MEG unit, the reaction solution comprising a dicarboxylate and MEG, and subjected to one or more steps selected from filtration, decolorization, precipitation and evaporation-concentration.

[0020] Advantageously, step (a) comprises a first evaporation-condensation step, and further comprises subjecting the bottom fraction obtained from the first evaporation-condensation step to a second evaporation-condensation step, wherein the condensed top fraction obtained from the second evaporation-condensation step is mixed with the condensed top fraction obtained from the first evaporation-condensation step, and wherein the mixed condensed top fraction is subjected to step (b).

[0021] In a preferred embodiment, the bottom fraction obtained from the first evaporation-condensation step is filtered before being subjected to the second evaporation-condensation step.

[0022] In a preferred embodiment, step (b) is performed by contacting the condensed top fraction obtained in step (a) with an ion exchange resin, preferably a strong anion exchange resin.

[0023] In a preferred embodiment, step (c) consists in two distillation steps.

[0024] In a specific embodiment, the depolymerization solution is obtained by enzymatic depolymerization of PET, wherein the pH of the reaction medium is adjusted to 6.5 to 9 by adding a base to the reaction medium. As described in WO2020 / 094661, the TA salt produced by the depolymerization is removed from the solution by precipitation and filtration to obtain a reaction solution to be subjected to the method of the present invention.

[0025] An object of the present invention is to provide a process for purifying MEG from a depolymerization solution of at least one polyester having at least one MEG unit, wherein the process comprises or consists in the following steps:

[0026] a) subjecting the depolymerization solution to at least one evaporation-condensation step, preferably two evaporation-condensation steps, both carried out in a thin-film evaporator, to obtain a bottom fraction and a condensed top fraction mixture,

[0027] b) contacting the condensed top fraction obtained in step (a) with a strong anion exchange resin to obtain a solution,

[0028] c) subjecting the solution obtained in step (b) to two distillations, and

[0029] d) recovering purified MEG from the distillate obtained in step (c).

[0030] Another object of the present invention is to provide a method for recycling a polymer-containing material (such as a plastic article) comprising at least one polyester having at least one MEG unit, the method comprising the following steps:

[0031] a.1) subjecting a polyester having at least one MEG unit to a depolymerization step to obtain a reaction solution comprising dicarboxylate, MEG and solid components,

[0032] b.1) filtering the reaction solution obtained in step (a.1) to remove solid components and obtain a filtrate,

[0033] c.1) purifying the filtrate obtained in step (b.1) to obtain a purified filtrate,

[0034] d.1) precipitating the dicarboxylic acid by acidifying the purified filtrate obtained in step (c.1) to obtain a slurry,

[0035] e.1) filtering the slurry obtained in step (d.1) to remove the precipitated dicarboxylic acid to obtain a filtrate,

[0036] f.1) subjecting the filtrate obtained in step (e.1) to at least one evaporation-concentration step to obtain a MEG concentrated solution,

[0037] g.1) purifying the MEG of the concentrated solution obtained in step (f.1) by the process according to the invention to obtain purified MEG.

[0038] Advantageously, in step (a.1), the depolymerization is a hydrolysis under alkaline conditions, preferably an alkaline enzymatic depolymerization. Advantageously, in step (c.1), the purification of the filtrate obtained in step (b.1) is carried out by one or more steps selected from ultrafiltration, adsorption on activated carbon, ion exchange resins and chromatography.

[0039] In one embodiment, the polymer-containing material comprising at least one polyester having at least one MEG unit is a plastic article comprising at least one polyester having at least one MEG unit. In a specific embodiment, when the polyester having at least one MEG unit is PET, the dicarboxylic acid is terephthalic acid (TA) and the dicarboxylate is a terephthalate salt.

[0040] Another object of the present invention is to use the purified MEG obtained by the process according to the invention for producing a polyester containing at least one MEG unit.

[0041] These and other objects and embodiments of the present invention will become more readily apparent following the detailed description of the invention including preferred embodiments thereof which are presented in general terms. DETAILED DESCRIPTION OF THE INVENTION

[0043] The present invention relates to a process for purifying monoethylene glycol (MEG) from a solution obtained by depolymerizing at least one polyester having at least one MEG unit and allowing the recovery of the MEG monomers forming the original polyester so that the monomers can be reprocessed to synthesize new polyesters.

[0044] The invention in particular allows to remove part or all, preferably all, of the remaining dicarboxylates (eg TA salts if the polyester is PET) and other inorganic impurities, as well as by-products such as diethylene glycol (DEG) and triethylene glycol (TEG) present in the solution obtained from the depolymerization process.

[0045] The present invention also relates to a recycling process for recycling polymer-containing materials, such as plastics, comprising at least one polyester having at least one MEG unit to produce and recover TA salts and purified MEG monomer.

[0046] definition

[0047] In the context of the present invention, "polymer-containing material" or "polymer-containing product" refers to a product, such as a plastic article, which contains at least one polymer in crystalline, semi-crystalline or completely amorphous form. In a specific embodiment, the polymer-containing material refers to any article made of at least one plastic material, such as a plastic sheet, tube, rod, profile, shape, film, block, fiber, etc., which contains at least one polyester having at least one MEG unit, and possibly other substances or additives, such as plasticizers, minerals or organic fillers. In another specific embodiment, the polymer-containing material refers to a plastic compound or plastic preparation in the molten or solid state, which is suitable for the preparation of plastic articles. In another specific embodiment, the polymer-containing material refers to a textile, fabric or fiber containing at least one polymer. In another specific embodiment, the polymer-containing material refers to plastic waste or fiber waste containing at least one polymer. In particular, the polymer-containing material is a plastic article.

[0048] In the context of the present invention, the term "plastic article" or "plastic product" is used to refer to any article or product comprising at least one polymer, such as plastic sheets, tubes, rods, profiles, moldings, blocks, fibers, etc. Preferably, the plastic product is a manufactured product, such as rigid or flexible packaging (bottles, trays, cups, etc.), agricultural films, bags and sacks, disposables, etc., carpet waste, fabrics, textiles, etc. The plastic article may contain further substances or additives, such as plasticizers, minerals, organic fillers or dyes. In the context of the present invention, the plastic article may contain a mixture of semi-crystalline and / or amorphous polymers and / or additives.

[0049] "Polymer" refers to a chemical compound or mixture of compounds whose structure consists of multiple repeating units (ie, "monomers") connected by covalent chemical bonds. In the context of the present invention, the term "polymer" refers to such chemical compounds used in the composition of plastic articles.

[0050] A "recycling process" with respect to a plastic article refers to a process by which at least one polyester of the plastic article is degraded to produce at least one type of monomer and / or oligomer, which is recovered for reuse. Optionally, the monomer and / or oligomer is suitable for further repolymerization. In the context of the present invention, the plastic article comprises at least one polyester having at least one MEG unit, which polyester is depolymerized and produces at least MEG monomer.

[0051] The term "polyester" refers to a polymer containing ester functional groups in its backbone. The ester functional group is characterized by a carbon bonded to three other atoms: a single bond to carbon, a double bond to oxygen, and a single bond to oxygen. The single-bonded oxygen is bonded to another carbon. Depending on the composition of their backbone, polyesters can be aliphatic, aromatic, or semiaromatic. Polyesters can be homopolymers or copolymers.

[0052] The term "polyester having at least one MEG unit" refers to a polyester formed from MEG and a dicarboxylic acid monomer. Examples of polyesters having at least one MEG unit include polyethylene terephthalate (PET), polyethylene adipate, polyethylene 2,5-furandicarboxylate, and polyethylene naphthalate. Polyethylene terephthalate is a semiaromatic copolymer composed of two monomers: terephthalic acid and ethylene glycol. Polyethylene adipate is an aliphatic copolymer composed of adipic acid and ethylene glycol monomers. Polyethylene 2,5-furandicarboxylate is a semiaromatic copolymer composed of 2,5-furandicarboxylic acid and ethylene glycol monomers. Polyethylene naphthalate is a semiaromatic copolymer composed of naphthalene-2,6-dicarboxylic acid and ethylene glycol monomers.

[0053] As used herein, the term "dissolved" or "in dissolved form" refers to a compound that is dissolved in a liquid, as distinguished from an undissolved solid form.

[0054] The term "depolymerization" in relation to a solution obtained by depolymerizing at least one polyester having at least one MEG unit refers to a process by which the polyester having at least one MEG unit is depolymerized and / or degraded into smaller molecules such as monomers and / or oligomers and / or any degradation products. Depolymerization processes include chemical and biological depolymerization processes.

[0055] The expression "solution obtained from the depolymerization of at least one polyester having at least one MEG unit" or "depolymerization solution of at least one polyester having at least one MEG unit" or "solution of depolymerizing at least one polyester having at least one MEG unit", or even "depolymerization solution" refers to a solution directly produced or obtained at the end of a depolymerization step of said polyester or a solution produced or obtained after one or several treatment steps of a solution directly produced or obtained at the end of a depolymerization step of said polyester. The depolymerization solution according to the invention comprises components and / or impurities specific to the depolymerization process and is therefore different from any solution comprising MEG and obtained by a process different from depolymerization. The solution comprises MEG and other degradation products. As degradation products there may be mentioned, for example, other monomers, oligomers and / or salts thereof. Treatment steps may be carried out to remove part of the degradation products.

[0056] According to the present invention, "oligomer" refers to a molecule containing 2 to about 20 monomer units. As an example, oligomers that can be recovered from PET include mono-2-hydroxyethyl terephthalate (MHET), bis(2-hydroxyethyl) terephthalate (BHET), 1-(2-hydroxyethyl) 4-methyl terephthalate (HEMT), dimethyl terephthalate (DMT), diethylene glycol (DEG) and / or triethylene glycol (TEG).

[0057] The term "salt," when referring to an acid salt, refers to any compound formed when the hydrogen ions of an acid are partially or completely replaced by positive ions such as sodium, potassium, ammonium or metal ions.

[0058] The term "dicarboxylic acid" refers to a compound containing two carboxyl functional groups -COOH. It is represented by the formula HO2C-R-CO2H, where R can be aliphatic and / or aromatic, preferably aromatic. As examples, terephthalic acid, isophthalic acid, adipic acid, 2,5-furandicarboxylic acid and naphthalene 2,6-dicarboxylic acid are dicarboxylic acids. The dicarboxylic acid is usually derived from units other than MEG of the polyester. The dicarboxylic acid preferably has a molecular weight of 100 g / mol or more. In one embodiment, the dicarboxylic acid is different from oxalic acid.

[0059] When the replaceable hydrogen ions in a dicarboxylic acid are partially or completely replaced by positive ions such as sodium, potassium, ammonium or metal ions, a "dicarboxylate salt" is formed. "TA salt" or "terephthalate salt" is included in this definition. In the context of the present invention, TA salts may include disodium terephthalate C8H4Na2O4, dipotassium terephthalate C8H4K2O4, diammonium terephthalate C8H 12 N2O4, monosodium terephthalate C8H5NaO4, monopotassium terephthalate C8H5KO4 and / or monoammonium terephthalate C8H 10 NO4.

[0060] The term "monoethylene glycol" or "MEG" refers to the molecule represented by the formula C2H6O2 (HO-CH2-CH2-OH) recovered at the end of the purification process according to the invention.

[0061] When referring to a compound, the term "purification process" refers to a process in which the purity of the compound is increased. For example, the purity of the compound before the purification process may be less than 70%, less than 50%, or even less than 30%, relative to the total weight of the sample containing the compound to be purified. For example, the purity of the compound after the purification process may be higher than 80%, preferably higher than 90%, more preferably higher than 95%, and even more preferably higher than 99%, relative to the total weight of the sample containing the purified compound.

[0062] The "heating temperature" used in the present invention corresponds to the temperature of the heating medium used to transfer heat from a heat source such as steam directly or through a suitable heating device to the process medium that is then used in the process. The term "process temperature" or "bottom temperature" corresponds to the temperature of the bottom fraction inside the process medium (i.e., the solution obtained by depolymerizing at least one polyester having at least one MEG unit or the solution to be distilled). Due to the heat transfer, the heating temperature of the heating medium is generally higher than the processing temperature inside the process medium. In addition, when measuring the temperature, the tolerance error range can be + / -5°C, + / -4°C, + / -3°C, + / -2°C or + / -1°C.

[0063] "Ambient temperature" or "room temperature" refers to a temperature of 10°C to 30°C, in particular 20°C to 25°C.

[0064] Unless expressly stated otherwise, the expression "X to Y" includes boundaries. The expression means that the target range includes the X and Y values, as well as all values ​​from X to Y.

[0065] The process for purifying MEG according to the invention

[0066] An object of the present invention is to provide a process for purifying monoethylene glycol (MEG) from a depolymerization solution of at least one polyester having at least one MEG unit, said process comprising the following steps:

[0067] a) subjecting the depolymerization solution to at least one evaporation-condensation step in order to obtain a bottom fraction and a condensed top fraction,

[0068] b) contacting the condensed top fraction obtained in step (a) with a resin to obtain a solution,

[0069] c) subjecting the solution obtained in step (b) to at least one distillation step to obtain a distillate, and

[0070] d) recovering purified MEG from the distillate obtained in step (c).

[0071] The process can provide highly purified MEG from a solution obtained from depolymerization of at least one polyester having at least one MEG unit.

[0072] In fact, the inventors have surprisingly found that, thanks to the process of the invention, the purity of MEG recovered from the solution obtained from the depolymerization of polyester has been greatly improved to approach the purity of MEG of petrochemical origin. More specifically, this purification process allows the reuse of recovered monomers of MEG suitable for repolymerization in polyester chains.

[0073] Furthermore, the obtained MEG exhibits low color values ​​according to the APHA scale, in particular a low APHA index and / or a low APHA boiling point value. The APHA boiling point value can be obtained as an APHA index according to ASTM-5386 after heating the sample at 198° C. for 4 hours. The APHA index of the obtained MEG is preferably below 5, and / or the APHA boiling point value is preferably below 200, more preferably below 160, even more preferably below 50, in particular below 20.

[0074] Evaporation-condensation step (a)

[0075] The method for purifying MEG comprises a step (a) in which a solution obtained by depolymerizing at least one polyester having at least one MEG unit is subjected to at least one evaporation-condensation step to obtain a bottom fraction and a condensed top fraction. According to the present invention, an evaporation-condensation step refers to an evaporation step followed by a condensation step. In one embodiment, the evaporation-condensation of step (a) consists in one evaporation step and one condensation step.

[0076] The condensed top fraction corresponds to the fraction evaporated during the evaporation step, which is recovered at the top of the evaporator and condensed during the condensation step. The condensed top fraction generally comprises MEG as well as other volatile molecules such as water, DEG and TEG.

[0077] The bottom fraction corresponds to the fraction which remains at the bottom of the evaporator during the evaporation-condensation step.

[0078] Advantageously, said step allows the removal of salts from said condensed top fraction. More specifically, said step allows the recovery of heavy impurities, mainly salts and solid impurities, at the bottom of the evaporator. In one embodiment, when the polyester to be depolymerized is PET, the depolymerization process is alkaline hydrolysis, preferably enzymatic or chemical alkaline hydrolysis using NaOH. In this case, said step allows the recovery of most of the TA salts and other salts such as Na2SO4 at the bottom of the evaporator.

[0079] The evaporation step allows to separate one or more dissolved salts contained in the solution obtained by depolymerizing at least one polyester having at least one MEG unit. This step is carried out by heating the solution under vacuum until the desired evaporation rate is reached. The evaporation rate is the ratio of the amount evaporated to the amount supplied. Those skilled in the art know how to adjust the desired evaporation rate to avoid precipitated salts blocking the bottom of the evaporator. The salts are retained in the bottom fraction and MEG and other volatile molecules (such as water, DEG and TEG) are evaporated. The vapor enters the condensation step to produce a top fraction.

[0080] The separated salts can be selected, for example, from dicarboxylates, such as terephthalates and salts of other degradation products of polyesters. Among the degradation products of polyesters, for example, mono-2-hydroxyethyl terephthalate (MHET), bis(2-hydroxyethyl) terephthalate (BHET) and isophthalic acid (IPA) salts can be mentioned, which can be separated in the evaporation-condensation step (a).

[0081] The evaporation of the evaporation-concentration of step (a) can be carried out in any suitable evaporator, such as a thin film evaporator, a batch evaporator, a forced circulation evaporator or a flash evaporator, preferably in a thin film evaporator. Subsequently, the condensation of the evaporated top fraction can be carried out by passing the top fraction through a heat exchanger, preferably a tubular heat exchanger or a plate heat exchanger with a cooling medium having a temperature below 50° C. Preferably, the heat exchanger is a condensation unit, more preferably a water-cooled condensation unit.

[0082] Depending on the content of the solution subjected to step (a), its volume and / or the type of evaporator used, step (a) may comprise or consist of one or several evaporation-condensation steps.

[0083] The person skilled in the art is able to adjust the evaporation conditions, such as temperature, pressure and / or evaporation rate, in particular depending on the sample to be evaporated and the evaporator used. For example, if the evaporation is carried out in a thin film evaporator, the evaporation rate is preferably limited to 90% by controlling the heating or process temperature during the evaporation to avoid the formation of dry areas on the exchanger surface.

[0084] According to the invention, the evaporation-condensation step is operated by controlling the process pressure (inside the process medium) and the heating temperature or process temperature simultaneously.

[0085] When the temperature of the heating medium is controlled, the heating temperature during evaporation is below 200°C, below 195°C, below 193°C, below 190°C, below 185°C, below 180°C, below 170°C, preferably below 195°C, and the pressure is 15 mbar absolute pressure or higher, for example 20 mbar absolute pressure or higher, such as 30 mbar absolute pressure or higher, such as 40 mbar absolute pressure or higher, such as 50 mbar absolute pressure or higher, such as 60 mbar absolute pressure or higher, such as 70 mbar absolute pressure or higher, such as 80 mbar absolute pressure or higher, such as 85 mbar absolute pressure or higher, such as 90 mbar absolute pressure or higher, such as 95 mbar absolute pressure or higher, such as 98 mbar absolute pressure or higher, such as 99 mbar absolute pressure or higher, such as 100 mbar absolute pressure or higher. The pressure may be 1000 mbar absolute or lower, such as 500 mbar absolute or lower, such as 300 mbar absolute or lower, such as 200 mbar absolute or lower. In some embodiments, the heating temperature during evaporation is below 200°C, below 195°C, below 193°C, below 190°C, below 185°C, below 180°C, below 170°C, preferably below 195°C, and the pressure is 50 mbar absolute to 1000 mbar absolute, preferably 50 mbar absolute to 500 mbar absolute, more preferably 50 mbar absolute to 300 mbar absolute, even more preferably 50 mbar absolute to 200 mbar absolute. In some embodiments, the evaporation of step (a) is operated at a heating temperature of 80°C-200°C, preferably 100°C-195°C, more preferably 120°C-193°C, even more preferably 140°C-193°C, and the pressure is 15 mbar absolute pressure or higher, such as 20 mbar absolute pressure or higher, such as 30 mbar absolute pressure or higher, such as 40 mbar absolute pressure or higher, such as 50 mbar absolute pressure or higher, such as 60 mbar absolute pressure or higher, such as 70 mbar absolute pressure or higher, such as 80 mbar absolute pressure or higher, such as 85 mbar absolute pressure or higher, such as 95 mbar absolute pressure or higher, such as 98 mbar absolute pressure or higher, for example 99 mbar absolute pressure or higher, for example 100 mbar absolute pressure or higher. The pressure can be 1000 mbar absolute pressure or lower, such as 500 mbar absolute pressure or lower, such as 300 mbar absolute pressure or lower, such as 200 mbar absolute pressure or lower.In some embodiments, the evaporation of step (a) is operated at a heating temperature of 80°C-200°C, preferably 100°C-195°C, more preferably 120°C-193°C, even more preferably 140°C-193°C, and the pressure is 50mbar absolute pressure-1000mbar absolute pressure, preferably 50mbar absolute pressure-500mbar absolute pressure, more preferably 5-300mbar absolute pressure, even more preferably 50-200mbar absolute pressure.

[0086] Alternatively, when controlling the temperature inside the process medium, the process temperature during evaporation is below 195°C, below 190°C, below 180°C, preferably below 170°C, more preferably 80°C-200°C, more preferably 100°C-175°C, and the pressure is 15 mbar absolute pressure or more, such as 20 mbar absolute pressure or more, such as 30 mbar absolute pressure or more, such as 40 mbar absolute pressure or more, such as 50 mbar absolute pressure or more, such as 60 mbar absolute pressure or more, such as 70 mbar absolute pressure or more, such as 80 mbar absolute pressure or more, such as 85 mbar absolute pressure or more, such as 90 mbar absolute pressure or more, such as 95 mbar absolute pressure or more, such as 98 mbar absolute pressure or more, such as 99 mbar absolute pressure or more, such as 100 mbar absolute pressure or more. The pressure may be 1000 mbar absolute or lower, such as 500 mbar absolute or lower, such as 300 mbar absolute or lower, such as 200 mbar absolute or lower, such as 100 mbar absolute or lower. In one embodiment, the process temperature during evaporation is below 195° C., below 190° C., below 180° C., preferably below 170° C., more preferably 80° C. to 200° C., more preferably 100° C. to 175° C., and the pressure is 50 mbar absolute to 1000 mbar absolute, preferably 50 mbar absolute to 500 mbar absolute, more preferably 50 mbar absolute to 300 mbar absolute, even more preferably 50 mbar absolute to 200 mbar absolute.

[0087] In one embodiment, the evaporation of the first evaporation-condensation step and / or the second evaporation-condensation step of step (a) is carried out under vacuum conditions, preferably at 15 mbar absolute pressure or higher, preferably at 15-500 mbar absolute pressure, for example 50-500 mbar absolute pressure, more preferably at 100 mbar absolute pressure.

[0088] In some embodiments, step (a) comprises 1, 2, 3, 4 or 5 evaporation-condensation steps. Preferably, step (a) comprises 1, 2, 3 or 4 evaporation-condensation steps, more preferably two evaporation-condensation steps.

[0089] In some embodiments, step (a) comprises or consists in an evaporation-condensation step. In some embodiments, step (a) comprises or consists in an evaporation-condensation step performed in a forced circulation evaporator.

[0090] When step (a) comprises more than one evaporation-condensation step, each evaporation-condensation step is carried out on the bottom fraction of the previous evaporation-condensation step. The condensed top fractions obtained after each condensation step are preferably mixed before carrying out step (b).

[0091] When step (a) comprises more than one evaporation-condensation step, the last evaporation-condensation step is preferably carried out in a thin film evaporator. In some embodiments, the first evaporation-condensation step is carried out in a forced circulation evaporator and the second evaporation-condensation step is carried out in a thin film evaporator. In some embodiments, the first and / or second evaporation-condensation step is carried out in a batch evaporator.

[0092] In another embodiment, in addition to the first evaporation-condensation step in step (a), step (a) comprises an additional evaporation-condensation step, wherein the bottom fraction obtained from the first evaporation-condensation step is subjected to a second evaporation-condensation step, and wherein the condensed top fractions obtained from the first and second evaporation-condensation steps are mixed before being subjected to step (b). The additional evaporation-condensation step increases the yield of recovered MEG.

[0093] In a specific embodiment, the bottom fraction obtained from the first evaporation-condensation step is filtered before being subjected to the second evaporation-condensation step. In particular, the evaporation of the second evaporation-condensation step is carried out in a thin film evaporator.

[0094] In one embodiment, the first and second evaporation-condensation steps are carried out in a thin film evaporator. In particular, the temperature of the additional evaporation is higher than the temperature of the first evaporation, and the two evaporations are carried out at the same pressure.

[0095] In a particular embodiment, step (a) consists of two evaporation-condensation steps, wherein the bottom fraction obtained from the first evaporation-condensation step is subjected to the second evaporation-condensation step, and wherein the condensed top fractions obtained from the first and second evaporation-condensation steps are mixed before being subjected to step (b).

[0096] In particular, the evaporation of the first evaporation-condensation step is carried out at a process temperature of 90°C-180°C, 100°C-170°C, 120°C-170°C, 90°C-150°C, 100°C-155°C, 110°C-140°C, 110°C-125°C, preferably 115°C-120°C, at an absolute pressure of 15 mbar or more, such as an absolute pressure of 15-500 mbar, such as an absolute pressure of 50-500 mbar, an absolute pressure of 50-300 mbar, preferably at a process temperature of 100 mbar. bar absolute pressure, and the evaporation of the second evaporation-condensation step is carried out at a pressure of 120°C-150°C, 120°C-155°C, 130°C-155°C, 130°C-150°C, 135°C-150°C, 135°C-145°C, at a pressure of 15 mbar absolute pressure or higher, such as 15 mbar absolute pressure-500 mbar absolute pressure, such as 50 mbar absolute pressure-500 mbar absolute pressure, preferably at a pressure of 100 mbar absolute pressure.

[0097] In a particular embodiment, step (a) consists of two evaporation-condensation steps, wherein:

[0098] (1) the evaporation in the first evaporation-condensation step is operated at a process temperature of 100° C. to 180° C., e.g., 110° C. to 135° C., preferably 110° C. to 125° C., more preferably 118° C., at a pressure of 15 mbar absolute or higher, e.g., 15-500 mbar absolute, preferably 50-500 mbar absolute, more preferably 50-120 mbar absolute, e.g., 80-120 mbar absolute; and

[0099] (2) The evaporation of the second evaporation-condensation is operated at a process temperature of 130° C. to 150° C., preferably 144° C., and at a pressure of 15 mbar absolute or higher, such as 15 to 500 mbar absolute, preferably 50 to 500 mbar absolute, more preferably 50 to 120 mbar absolute, such as 80 to 120 mbar absolute.

[0100] In a preferred embodiment, the evaporation step is carried out at a pressure of 100 mbar absolute. In a particular embodiment, both evaporations are carried out at the same pressure, preferably at a pressure of 100 mbar absolute.

[0101] In particular, the evaporation of the first evaporation-condensation step is carried out at a heating temperature of 150°C-180°C, 155°C-170°C, 160°C-170°C, at a pressure of 5 mbar absolute or higher, such as 5-500 mbar absolute, such as 50-500 mbar absolute, 50-300 mbar absolute, preferably 100 mbar absolute; and the evaporation of the second evaporation-condensation step is carried out at a heating temperature of 150°C-200°C, 155°C-195°C, preferably 165°C-195°C, at a pressure of 5 mbar absolute or higher, such as 5 mbar absolute-500 mbar absolute, such as 50 mbar absolute-500 mbar absolute, preferably 100 mbar absolute. Preferably, the two evaporation steps are carried out at the same absolute pressure of 100 mbar.

[0102] In a particular embodiment, step (a) consists of two evaporation-condensation steps, wherein:

[0103] (1) the evaporation in the first evaporation-condensation step is operated at a heating temperature of 155° C. to 170° C., preferably 160° C. to 170° C., at a pressure of 5 mbar absolute or higher, such as 5 mbar absolute to 500 mbar absolute, such as 50 mbar absolute to 500 mbar absolute, preferably 50 mbar absolute to 120 mbar absolute, such as 80 mbar absolute to 120 mbar absolute, and

[0104] (2) The evaporation of the second evaporation-condensation is operated at a heating temperature of 155°C-195°C, preferably 165°C-195°C, and at a pressure of 5 mbar absolute or higher, such as 5-500 mbar absolute, such as 50-500 mbar absolute, preferably 50-120 mbar absolute, such as 80-120 mbar absolute.

[0105] Advantageously, the condensed top fraction recovered from step (a) comprises at least 60% MEG, preferably at least 70% MEG, more preferably at least 80% MEG.

[0106] (b) a step of contacting the condensed top fraction obtained in step (a) with a resin

[0107] In this step, the condensed top fraction or the combined condensed top fractions of the previous step (a) is brought into contact with a resin, preferably passed through a resin, to obtain a solution.

[0108] The inventors have demonstrated that, even when the solution subjected to step (a) contains acidic compounds and / or trace substances, contacting the top fraction obtained in step (a) with a resin provides a solution containing MEG with a lower acidity. In a preferred embodiment, the condensed top fraction of step (a) is contacted with an ion exchange resin, preferably by an ion exchange resin, preferably a strong anion exchange resin. A person skilled in the art is able to select a suitable ion exchange resin to be implemented and to adjust the flow rate depending on the content of the top fraction obtained in step (a). Anion exchange resins can be mentioned under the trade name Anion exchange resins containing quaternary ammonium groups are commercially available, such as A500MBPlusOH or A860. Preferably, the ion exchange resin is A860. The anion exchange resin may be, for example, polyacrylic acid cross-linked with divinylbenzene anion exchange resin, or polystyrene cross-linked with divinylbenzene anion exchange resin. The use of anion exchange resins allows for higher purity and improves the UV transmittance of the purified MEG.

[0109] According to the present invention, this step is preferably carried out in a continuous mode at room temperature.

[0110] Distillation step (c)

[0111] According to the invention, the solution obtained in step (b) is subjected to at least one distillation step (c) to obtain a distillate. Step (c) is intended to separate the MEG monomer from the oligomers such as DEG and TEG present in the solution. In addition, this step allows the water content of the solution to be reduced.

[0112] As for the evaporation-condensation step, this step is operated by controlling the process pressure (inside the process medium) and the heating temperature or process temperature simultaneously.

[0113] Step (c) may comprise or consist of one or several distillation steps. In some embodiments, step (c) comprises 1, 2, 3 or 4 distillation steps.

[0114] The skilled person will know how to adjust the temperature and / or pressure to carry out the distillation. In particular, depending on the number of distillation steps to be carried out in step (c), the skilled person will know how to adjust the temperature and pressure of each distillation step so that the distillate contains MEG.

[0115] When the temperature of the heating medium is controlled, the heating temperature during the distillation step is lower than 250°C, lower than 220°C, lower than 200°C, and preferably lower than 190°C at a pressure of 15 mbar absolute pressure or more, such as 20 mbar absolute pressure or more, such as 22 mbar absolute pressure or more, such as 25 mbar absolute pressure or more, such as 27 mbar absolute pressure or more, such as 40 mbar absolute pressure or more, such as 50 mbar absolute pressure or more, such as 80 mbar absolute pressure or more, such as 90 mbar absolute pressure or more, such as 100 mbar absolute pressure or more, such as 120 mbar absolute pressure or more, such as 170 mbar absolute pressure or more, such as 180 mbar absolute pressure or more, such as 195 mbar absolute pressure or more, such as 200 mbar absolute pressure or more, such as 205 mbar absolute pressure. The pressure may be 1000 mbar absolute or lower, such as 500 mbar absolute or lower, such as 300 mbar absolute or lower, such as 220 mbar absolute or lower, such as 210 mbar absolute or lower, such as 205 mbar absolute or lower, such as 200 mbar absolute or lower. Preferably, the pressure is 15-300 mbar absolute, such as 20-250 mbar absolute. In some embodiments, the heating temperature during the distillation step is less than 250°C, less than 220°C, less than 200°C, preferably less than 190°C, and the pressure is 50-300 mbar absolute, preferably 100-250 mbar absolute. In some embodiments, the distillation step is operated at a heating temperature of 140°C-250°C, 150°C-250°C, 155°C-220°C, 160°C-250°C, 170°C-250°C, 160°C-220°C, preferably 170°C-210°C.

[0116] Alternatively, when controlling the temperature inside the process medium, the process temperature (bottom temperature) is 110°C-200°C, 125°C-180°C, 130°C-180°C, 135°C-175°C and the pressure is 15 mbar absolute pressure or higher, such as 20 mbar absolute pressure or higher, such as 22 mbar absolute pressure or higher, such as 25 mbar absolute pressure or higher, such as 27 mbar absolute pressure or higher, such as 40 mbar absolute pressure or higher, such as 50 mbar absolute pressure or higher, such as 80 mbar absolute pressure or higher, such as 90 mbar absolute pressure or higher, such as 100 mbar absolute pressure or higher, such as 120 mbar absolute pressure or higher, such as 150 mbar absolute pressure or higher, such as 170 mbar absolute pressure or higher, such as 180 mbar absolute pressure or higher, for example 195 mbar absolute pressure or higher, such as 200 mbar absolute pressure or higher, such as 205 mbar absolute pressure or higher. The pressure can be 1000mbar absolute pressure or lower, such as 500mbar absolute pressure or lower, such as 300mbar absolute pressure or lower, such as 220mbar absolute pressure or lower, such as 210mbar absolute pressure or lower, such as 205mbar absolute pressure or lower, such as 200mbar absolute pressure or lower. Preferably, the pressure is 15-300mbar absolute pressure, for example 20-250mbar absolute pressure. Preferably, the pressure is 15-300mbar absolute pressure. In some embodiments, the process temperature (bottom temperature) is 110°C-200°C, 125°C-180°C, 130°C-180°C, 135°C-175°C, and the pressure is 50-300mbar absolute pressure, preferably 100-250mbar absolute pressure.

[0117] In one embodiment, step (c) consists in a distillation step. In a specific embodiment, step (c) consists in a distillation step, wherein MEG is directly recovered via a side draw. Thus, when controlling the temperature inside the process medium, the distillation is carried out at a process temperature (bottom temperature) of 120°C to 190°C, preferably 130°C to 180°C, more preferably 140°C to 180°C and a pressure of 15 to 300 mbar absolute, such as 50 to 300 mbar absolute, preferably 90 to 210 mbar absolute, more preferably 100 mbar absolute. A person skilled in the art knows how to adjust the side draw to recover MEG.

[0118] In another embodiment, the solution obtained in step (b) is subjected to at least two separate distillation steps. In a specific embodiment, step (c) consists in two distillation steps, preferably wherein the pressure of the second distillation is lower than the pressure of the first distillation.

[0119] For example, when two distillation steps are performed:

[0120] (1) the first distillation is carried out at a temperature (bottom temperature) of 120° C. to 170° C., preferably 130° C. to 160° C. and a pressure of 100 to 300 mbar absolute pressure, preferably 140 to 230 mbar absolute pressure; and

[0121] (2) The second distillation is carried out at a temperature (bottom temperature) of 130° C. to 220° C., preferably 130° C. to 180° C., and a pressure of 50 to 300 mbar absolute pressure, preferably 90 to 210 mbar absolute pressure.

[0122] According to this particular embodiment of the invention:

[0123] - the first distillation allows the removal of water and light components in the top fraction, while MEG, DEG and TEG remain in the bottom fraction, and

[0124] - A second distillation carried out on the bottom fraction obtained from the first distillation allows the separation of MEG in the top fraction (distillate), while heavier components such as DEG and TEG remain in the bottom fraction. In this classical distillation, a distillate containing MEG is recovered at the top of the column.

[0125] In a preferred embodiment, step (c) comprises or consists in two separate distillation steps, wherein the first distillation is carried out under the same conditions as described above, and wherein the second distillation is a distillation with two sections, wherein MEG is recovered by side draw at the upper part of the column. "Distillation with two sections" means a specific arrangement of a distillation column by adding a supplementary upper section to the second distillation column, wherein the distillate containing MEG is not recovered at the very top of the column but in the upper part of the column. In this case, the final light materials (if any) are preferably purged at the very top of the column.

[0126] In this embodiment, the first distillation allows the removal of water and light components in the top fraction, while MEG, DEG and TEG remain in the bottom fraction, and the second distillation allows DEG, TEG and heavy components to remain in the bottom, MEG is extracted and recovered by a side draw located in the first upper part of the column, and the final lights (if present) are purged at the very top of the column.

[0127] Typically, when the second distillation is a distillation having two zones, it is carried out at a process temperature of 130-200° C., preferably 150-180° C., and at a pressure of 15-100 mbar absolute, preferably 20-90 mbar absolute.

[0128] As an example:

[0129] (1) the first distillation is carried out at a process temperature of 120°C to 195°C, preferably 150°C to 185°C and an absolute pressure of 15 to 300 mbar, preferably 100 to 230 mbar; and

[0130] (2) The second distillation is a distillation having two zones, and is carried out at a process temperature of 130° C. to 200° C., preferably 150° C. to 180° C., and at a pressure of 15 to 100 mbar absolute pressure, preferably 20 to 90 mbar absolute pressure.

[0131] In another embodiment, step (c) comprises or consists in three separate distillation steps, wherein the first and the third distillation are carried out under the same conditions as described above, and wherein the second distillation is a distillation with two zones as defined above.

[0132] In one embodiment, the distillation step of step (c) is carried out under vacuum conditions, preferably at an absolute pressure of 50-500 mbar.

[0133] A distillate comprising MEG may be recovered from the distillation column used to carry out step (c) by any suitable means. For example, the distillation may include a side draw suitable for recovering MEG.

[0134] In a preferred embodiment, the purification processes are carried out in the order from a) to d) and the MEG is recovered after distillation.

[0135] Step (c') Further steps

[0136] In one embodiment, the process of the present invention further comprises a step (c'), wherein before the recovery step (d), the distillate obtained in step c) is subjected to one or more steps selected from distillation, hydrogenation, dehydration and decolorization, preferably a distillation step and / or a decolorization step, wherein the decolorization step is preferably carried out by activated carbon adsorption.

[0137] This step (c') is optional and can be carried out on the distillate obtained in step (c) before carrying out the recovery step (d). It allows to increase the UV transmittance of the purified MEG.

[0138] According to the present invention, the distillate obtained in step c) may be further subjected to one or more steps selected from distillation, hydrogenation, dehydration or decolorization, preferably a distillation step and / or a decolorization step.

[0139] In one embodiment, the distillate obtained in step c) may be further subjected to a decolorization step, wherein the distillate is passed through an adsorbent. The adsorbent may be any adsorbent known to those skilled in the art, such as activated carbon, macroporous resins, preferably activated carbon. In particular, the step is preferably carried out at room temperature. Preferably, the method further comprises a step wherein the decolorization step is carried out by adsorption on activated carbon.

[0140] In another embodiment, the distillate obtained in step c) may be further subjected to a distillation step. The distillation is carried out under the same conditions (heating temperature or process temperature-pressure) as those specified in step (c).

[0141] In a specific embodiment, the distillate obtained in step c) may be further subjected to a distillation followed by a decolorization step.

[0142] According to the present invention, an object of the present invention is to provide a method for purifying MEG from a solution obtained by depolymerizing at least one MEG unit, wherein the method comprises or consists in the following steps:

[0143] a. subjecting the depolymerization solution to two evaporation-condensation steps, preferably wherein the second evaporation-condensation step is carried out in a thin film evaporator, more preferably wherein both evaporation-condensation steps are carried out in a thin film evaporator, to obtain a bottom fraction and a condensed top fraction mixture,

[0144] b. contacting the condensed top fraction obtained in step (a) with an anion exchange resin to obtain a solution,

[0145] c. subjecting the solution obtained in step (b) to two distillations to obtain a distillate, preferably wherein the second distillation is a distillation having two zones, and

[0146] d. Recovering purified MEG from the distillate obtained in step (c).

[0147] According to the present invention, another object of the present invention is to provide a method for purifying MEG from a solution obtained by depolymerizing at least one MEG unit, wherein the method comprises or consists in the following steps:

[0148] a. subjecting the depolymerization solution to two evaporation-condensation steps, preferably wherein the second evaporation-condensation step is carried out in a thin film evaporator, more preferably wherein both evaporation-condensation steps are carried out in a thin film evaporator, to obtain a bottom fraction and a condensed top fraction mixture,

[0149] b. contacting the condensed top fraction obtained in step (a) with an anion exchange resin to obtain a solution,

[0150] c. subjecting the solution obtained in step (b) to two distillations to obtain a distillate, preferably wherein the second distillation is a distillation having two zones,

[0151] c '. Optionally, subjecting the distillate obtained in step (c) to one or more additional steps selected from distillation, hydrogenation, dehydration or decolorization, preferably a distillation step and / or a decolorization step, to obtain a solution, and

[0152] d. Recovering purified MEG from the distillate obtained in step (c') or step (c).

[0153] When the second distillation is a distillation with two zones, preferably there is no additional step of step c'). A distillation step with two zones helps to obtain the same MEG purity without the further step of step c').

[0154] According to the present invention, the process can be carried out in discontinuous mode, ie under batch conditions, or in continuous mode, continuously from steps a) to c), more preferably steps a) to d). Continuous mode is preferred.

[0155] Step (d) of recovering MEG

[0156] According to the present invention, recovery of MEG means recovery of the distillate obtained in step (c) or the solution obtained in step (c') containing purified MEG. In other words, purified MEG is contained in liquid form in the distillate obtained at the end of step (c) or the solution obtained at the end of step (c'). Alternatively, recovery of MEG is carried out continuously during the distillation step of step (c) or (c') by using a side draw.

[0157] The MEG purification process according to the invention allows recovery of highly purified MEG. In one embodiment, the MEG obtained has a purity of at least 95%, preferably at least 99%, more preferably at least 99.9%.

[0158] Solution obtained by depolymerization or depolymerization solution

[0159] According to the invention, a solution obtained from the depolymerization of at least one polyester comprising at least one MEG unit refers to a solution obtained or produced from the chemical or biological depolymerization, preferably via hydrolysis, of said at least one polyester comprising at least one MEG unit.

[0160] Composition of the solution obtained by depolymerization (depolymerization solution)

[0161] The solution can include depolymerized and / or degraded molecules, such as monomer and / or oligomer and / or any degradation product and / or heavy impurities and / or trace acids and / or salts and / or water. More particularly, the solution can include monomers and / or salts and / or oligomers such as DEG and TEG and / or derivatives thereof, such as MEG and / or dicarboxylates such as terephthalates, isophthalic acid (IPA) salts, including terephthalic acid mono-2-hydroxyethyl ester (MHET) and / or terephthalic acid bis (2-hydroxyethyl) ester (BHET), dimethyl terephthalate (DMT) and / or heavy impurities and / or trace acids and / or water. The content of the depolymerization solution depends on the depolymerization method, such as hydrolysis, glycolysis, methanol decomposition, etc.

[0162] In a preferred embodiment, the solution is a homogeneous solution free of any residual solids.

[0163] The term "heavy impurities" refers to mainly dissolved non-volatile impurities such as heavy metals, antimony, copper, depolymerizing agents such as catalysts or enzymes.

[0164] "Trace acid" refers to the total amount of acid in a glycol sample titrated with an aqueous base (KOH or NaOH). Acidity is calculated as acetic acid equivalent (mg / kg). The test method is described in ASTM E 2679, which is particularly useful for determining low acidity levels. In the context of the present invention, the concentration of trace acid is equivalent to a concentration of less than 2 g KOH / kg, preferably less than 1100 mg KOH / kg, more preferably less than 700 mg KOH / kg, measured according to ASTM E 2679.

[0165] In one embodiment, the solution obtained from the depolymerization of at least one polyester comprising at least one MEG unit comprises MEG, at least one monomer chosen from dicarboxylic acids such as terephthalic acid (TPA) or isophthalic acid (IPA), at least one salt of such monomers, and / or salts such as Na2SO4 and / or oligomers such as mono-2-hydroxyethyl terephthalate (MHET).

[0166] In a specific embodiment, the solution obtained from the depolymerization of at least one polyester having at least one MEG unit comprises MEG, water, heavy impurities and optionally further comprises traces of acids and / or salts.

[0167] In a specific embodiment, the solution obtained from the depolymerization of at least one polyester having at least one MEG unit comprises MEG, water and heavy impurities and also salts, such as sodium sulfate salts, dicarboxylates and / or traces of acids.

[0168] In a specific embodiment, the solution obtained from the alkaline hydrolysis of at least one polyester comprising at least one MEG unit comprises MEG and / or heavy impurities and / or water and / or traces of acid and / or soluble salts such as sodium sulfate salts, dicarboxylates.

[0169] In a preferred embodiment, the solution obtained from the depolymerization of at least one polyester comprising at least one MEG unit is an aqueous concentrated solution of MEG as defined below.

[0170] In a particular embodiment, the solution obtained from the depolymerization of at least one polyester comprising at least one MEG unit comprises at least one MEG and heavy impurities.

[0171] In one embodiment, the solution obtained from depolymerizing PET comprises MEG, heavy impurities and terephthalate salts and eventually sodium sulfate salts and / or traces of acid.

[0172] In a preferred embodiment, the solution obtained from the depolymerization of at least one polyester comprising at least one MEG unit comprises at least 400 g / kg of MEG, at least 500 g / kg, at least 600 g / kg, at least 700 g / kg of MEG or at least 800 g / kg of MEG, based on the total weight of the solution. Preferably, the solution comprises at least 600 g / kg of MEG, preferably 700 g / kg of MEG.

[0173] The salt that can be present in the solution can be one or more of sodium, potassium or ammonium salts or mixtures thereof. For example, the salt can be selected from Na2SO4, K2SO4, (NH4)2SO4, NaCl, KCl, NH4Cl, Na2PO4, K2PO4, (NH4)2PO4, NaNO3, KNO3, NH4NO3 or mixtures thereof, and / or dicarboxylates.

[0174] In one embodiment, the dicarboxylate is selected from terephthalate, adipate, 2,5-furandicarboxylate and naphthalene-2,6-dicarboxylate. Preferably, the dicarboxylate is a TA salt.

[0175] In one embodiment, the solution comprises at least 5 g / kg of salt, preferably at least 10 g / kg, more preferably 20 g / kg of salt, based on the total weight of the aqueous solution. In one embodiment, the initial solution comprises at most 80 g / kg of salt, preferably at most 50 g / kg, more preferably at most 30 g / kg of salt, based on the total weight of the aqueous solution. Specifically, the initial solution comprises 5 g / kg-80 g / kg of salt, 10 g / kg-80 g / kg of salt, 10 g / kg-50 g / kg of salt.

[0176] Chemical or biological depolymerization steps

[0177] The depolymerization step of obtaining a solution subjected to the purification method of the present invention targets at least one polyester having at least one MEG unit. In one embodiment, the method of the present invention is implemented with a polymer-containing material, preferably a plastic product derived from a plastic waste collection and / or post-industrial waste and comprising at least one polyester having at least one MEG unit. More specifically, the method of the present invention can be used to degrade household plastic waste, including plastic bottles, plastic trays, plastic bags, plastic packaging, soft plastics and / or hard plastics, which are even contaminated by food residues, surfactants, etc. Alternatively or in addition, the method of the present invention can be used to degrade used fibers, such as fibers from fabrics, textiles, tires and / or industrial waste. More specifically, the method of the present invention can be used together with PET plastic waste and / or PET fiber waste.

[0178] In a particular embodiment, the polyester having at least one MEG unit is selected from the group consisting of polyethylene terephthalate (PET), polyethylene adipate (PEA), polyethylene furandicarboxylate (PEF) and polyethylene naphthalate (PEN). In a preferred embodiment, the polyester having at least one MEG unit is PET.

[0179] In particular, the depolymerization step is a chemical depolymerization or a biological depolymerization. In a preferred embodiment, the depolymerization to obtain the solution subjected to the process of the invention is a hydrolysis, preferably a hydrolysis under alkaline conditions, more preferably an alkaline enzymatic depolymerization or an alkaline chemical depolymerization such as saponification, even more preferably an alkaline enzymatic depolymerization.

[0180] In the context of the present invention, "hydrolysis" refers to the cleavage of ester bonds by OH ions in the presence of water, regardless of whether the reaction is biological or chemical depolymerization. For example, the hydrolysis of PET produces terephthalic acid (TA) and ethylene glycol (MEG). In a preferred embodiment, the hydrolysis is an alkaline hydrolysis, in which a base (or alkali) is used as a reactant to decompose the polyester in an aqueous medium. This base can be selected from NaOH, KOH, NH4OH or LiOH. As an example, the alkaline hydrolysis of PET produces terephthalic acid (TA) salts and ethylene glycol (MEG).

[0181] In one embodiment, the depolymerization step comprises contacting at least one polyester having at least one MEG unit with a depolymerization agent (ie, a chemical and / or biological depolymerization agent).

[0182] Advantageously, the depolymerization step comprising a depolymerization agent is carried out in a liquid medium, more advantageously an aqueous medium, as the initial reaction medium.

[0183] In one embodiment, the depolymerization of the polyester having at least one MEG unit is a chemical depolymerization, preferably a hydrolysis. Preferably, the chemical depolymerization is an alkaline chemical hydrolysis, such as a saponification.

[0184] In the context of the present invention, the term "chemical depolymerization" refers to a process by which at least one polyester having at least one MEG unit is depolymerized by contacting it with a reactant such as methanol or water, optionally in the presence of one or more chemical agents such as a catalyst. These processes are known as methanolysis and chemical hydrolysis, respectively. Other processes include glycolysis, aminolysis and ammonialysis. Methanolysis of PET produces dimethyl terephthalate (DMT) and monoethylene glycol (MEG).

[0185] In one embodiment, chemical depolymerization is carried out by hydrolysis. For example, chemical alkaline hydrolysis (also known as saponification) of PET produces terephthalate and ethylene glycol (MEG). During the saponification reaction, the polyester is reacted with a strong alkali metal base such as NaOH or KOH in the presence of water.

[0186] In one embodiment, the depolymerization step comprises contacting at least one polyester having at least one MEG unit with a chemical agent in an alkaline medium as a starting reaction medium, the alkaline medium comprising a base such as KOH, NaOH, NH4OH or LiOH.

[0187] In a particular embodiment, the depolymerizing agent is a chemical depolymerizing agent. In particular, the chemical agent is selected from metal catalysts, stable and non-toxic hydrosilanes (PMHS, TMDS) and other catalysts such as commercially available B(C6F5)3 and [Ph3C + ,B(C6F5)4 -] catalyst. In particular, the catalyst is selected from alkoxides, carbonates, acetates, hydroxides, alkali metal oxides, alkaline earth metals, calcium oxide, calcium hydroxide, calcium carbonate, sodium carbonate, iron oxide, zinc acetate, zeolites. In some embodiments, the catalyst used in the depolymerization method of the present invention comprises at least one of germanium compounds, titanium compounds, antimony compounds, zinc compounds, cadmium compounds, manganese compounds, magnesium compounds, cobalt compounds, silicon compounds, tin compounds, lead compounds and aluminum compounds. In particular, the catalyst comprises germanium dioxide, cobalt acetate, titanium tetrachloride, titanium phosphate, titanium tetrabutoxide, titanium tetraisopropoxide, titanium tetra-n-propoxide, titanium tetraethoxide, titanium tetramethoxide, titanium tetra(acetylacetonate) complex, titanium tetra(2,4-hexanedione) complex, titanium tetra(3,5-heptanedione) complex, titanium dimethoxybis(acetylacetonate) complex, titanium diethoxybis(acetylacetonate) complex, titanium diisopropoxybis(acetylacetonate) complex, titanium di-n-propoxybis(acetylacetonate) complex, titanium dibutoxybis(acetylacetonate) complex, titanium dihydroxybisglycolate, titanium dihydroxybisglycolate, titanium dihydroxybislactate, titanium dihydroxybis(2-hydroxypropionate), titanium lactate. , titanium octanediolate, titanium dimethoxybistriethanolamine, titanium diethoxybistriethanolamine, titanium dibutoxybistriethanolamine, hexamethyldititanate, hexaethyldititanate, hexapropyldititanate, hexabutyldititanate, hexaphenyldititanate, octamethyltrititanate, octaethyltrititanate, octapropyltrititanate, octabutyltrititanate, octaphenyltrititanate, hexaalkoxydititanate, zinc acetate, manganese acetate, methyl silicate, zinc chloride, lead acetate, sodium carbonate, sodium bicarbonate, acetic acid, sodium sulfate, potassium sulfate, zeolite, lithium chloride, magnesium chloride, ferric chloride, zinc oxide, magnesium oxide, calcium oxide, barium oxide, antimony trioxide and at least one of antimony triacetate. Alternatively, the catalyst is selected from nanoparticles. The chemical agent can be selected from any catalyst known to those skilled in the art that has the ability to degrade and / or depolymerize the target polymer.

[0188] At the end of the alkaline chemical depolymerization step, a "reaction solution" is obtained, which comprises monomers of MEG and dicarboxylates, such as terephthalates.

[0189] In another embodiment, the depolymerization of the polyester having at least one MEG unit is a biological depolymerization, preferably a hydrolytic depolymerization, more preferably an enzymatic depolymerization. Preferably, the biological depolymerization is an alkaline enzymatic depolymerization.

[0190] The term "biodepolymerization" refers to a process for depolymerizing at least one polyester having at least one MEG unit by contacting at least one polyester having at least one MEG unit with a biological agent capable of degrading the polyester. The biodepolymerization is performed by hydrolysis. In a preferred embodiment, the hydrolysis is an alkaline hydrolysis. As an example, the bioalkaline hydrolysis of PET produces terephthalic acid (TA) salts and ethylene glycol (MEG).

[0191] In a particular embodiment, the depolymerizing agent is a biological depolymerizing agent. In particular, the biological depolymerizing agent is an enzyme (i.e., a depolymerizing enzyme). In this case, biological depolymerization is referred to as enzymatic depolymerization. Alternatively or in addition, the biological depolymerizing agent is a microorganism that expresses and secretes the depolymerizing enzyme. Preferably, the enzyme is capable of degrading polyester, more preferably a polyester object of the present invention having at least one MEG unit. As an example, a depolymerizing enzyme as an enzyme is capable of degrading PET into monomeric forms, i.e., TA, MEG, mono-2-hydroxyethyl terephthalate (MHET) and / or bis(2-hydroxyethyl) terephthalate (BHET).

[0192] In one embodiment, the enzyme is selected from esterases. In a preferred embodiment, the enzyme is selected from lipases or cutinases. In a particular embodiment, the plastic article is contacted with at least two different depolymerases.

[0193] In a particular embodiment, when the target polyester is PET, the depolymerase is an esterase. Specifically, the depolymerase is a cutinase, preferably a cutinase produced by a microorganism selected from the group consisting of Thermobifida cellulosityca, Thermobifida halotolerans, Thermobifida fusca, Thermobifida alba, Bacillus subtilis, Fusarium solani pisi, Humicola insolens, Sirococcus conigenus, Pseudomonas mendocina, Thielavia terrestris, Saccharomonospora viridis, and Thermomonospora curvata, or any functional variant thereof. In another embodiment, the cutinase is selected from a metagenomic library, such as the LC-cutinase described in Sulaiman et al., 2012, or the esterase described in EP3517608, or any functional variant thereof, including the depolymerases listed in WO2018 / 011284, WO2018 / 011281, WO2020 / 021116, WO2020 / 021117, WO2020 / 021118 and WO 2021005198. In another specific embodiment, the depolymerase is a lipase preferably produced by Ideonella sakaiensis, or any functional variant thereof, including the depolymerases listed in WO2021005199. In another specific embodiment, the depolymerase is a cutinase produced by Humicola insolens, such as A0A075B5G4 mentioned in Uniprot, or any functional variant thereof. In another embodiment, the depolymerase is selected from commercial enzymes such as Novozym 51032 or any functional variant thereof. In one embodiment, the enzyme is selected from enzymes having PET degradation activity (PETase) and / or enzymes having MHET degradation activity (MHETase).

[0194] In another embodiment, the depolymerizing agent is a microorganism expressing and secreting a depolymerase. In the context of the present invention, the enzyme can be secreted in the culture medium or to the cell membrane of the microorganism, wherein the enzyme can be anchored. The microorganism can be a natural synthetic depolymerase, or it can be a recombinant microorganism, wherein a recombinant nucleotide sequence encoding a depolymerase has been inserted using, for example, a vector. For example, the nucleotide molecule encoding the target depolymerase is inserted into a vector, such as a plasmid, a recombinant virus, a phage, an episome, an artificial chromosome, etc. The transformation of the host cell and the culture conditions suitable for the host are well known to those skilled in the art. According to the present invention, several microorganisms and / or several enzymes can be used together or sequentially used to depolymerize the different types of polymers contained in the same plastic or different plastics.

[0195] In a specific embodiment, when the target polyester is PET, the depolymerization step is carried out at a temperature of 20°C-90°C, preferably 30°C-80°C, more preferably 40°C-75°C, more preferably 50°C-75°C, and even more preferably 60°C-75°C. In addition, the depolymerization step is preferably carried out at a pH of 5-11, preferably 7-9, more preferably 7-8.5, and even more preferably 7-8. In one embodiment, the depolymerization step is carried out at a pH of 6.5-9, preferably 6.5-8.5, more preferably 7-8, and even more preferably 7.5-8.5. Alternatively, the depolymerization step can be carried out under industrial and / or composting conditions.

[0196] In one embodiment, the depolymerization of the polyester having at least one MEG unit is obtained by biodepolymerization, wherein the pH of the reaction medium is adjusted to 6.5-9 by adding a base to the reaction medium. Any base known to those skilled in the art can be used. In particular, the base is selected from sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH) or ammonia (NH4OH). Advantageously, the base is sodium hydroxide (NaOH). The time required for the depolymerization step may vary depending on the polyester itself (ie, source, its composition, etc.), the type and amount of the depolymerizing agent used, and various process parameters (ie, temperature, pH, other reagents, etc.). Those skilled in the art can easily adjust the depolymerization process step parameters. Examples of the method are described in WO2014 / 079844, WO2015 / 097104, WO2015 / 173265, WO2017 / 198786, WO2020 / 094661 and WO2020 / 094646.

[0197] At the end of the alkaline biodepolymerization step, a "reaction solution" is obtained, which comprises monomers and / or oligomers of MEG and / or dicarboxylates such as terephthalates such as DEG or TEG and / or derivatives thereof including mono-2-hydroxyethyl terephthalate (MHET) and / or dimethyl terephthalate (DMT) and / or colorants and / water. In a specific embodiment, the reaction solution for depolymerizing at least one polyester having at least one MEG unit comprises dicarboxylates and MEG and undepolymerized polyester such as PET. In a preferred embodiment, the reaction solution for depolymerizing at least PET comprises terephthalate, MEG and undepolymerized PET.

[0198] In some embodiments, the reaction solution obtained at the end of the depolymerization step is used as the solution obtained from the depolymerization of at least one polyester having at least one MEG unit in the purification process according to the invention. In an alternative embodiment, the reaction solution obtained at the end of the depolymerization step is subjected to one or several preliminary steps of the purification process as disclosed in the following sections to obtain a solution obtained from the depolymerization of at least one polyester having at least one MEG unit for use in the purification process according to the invention.

[0199] Optional preliminary steps of the purification process

[0200] The reaction solution obtained at the end of the depolymerization step can be subjected to one or more steps before carrying out the purification method according to the invention. For example, said steps allow the removal of any solid residues, the purification of the dicarboxylate and / or the decolorization of the reaction solution. Specific examples of said pre-steps can be found in WO2020 / 094661.

[0201] In one embodiment, before entering the MEG purification method of the present invention, the "reaction solution" can be subjected to one or more steps selected from the group consisting of filtration, purification of the filtrate, precipitation and evaporation-concentration. Preferably, the reaction solution can be subjected to one or more steps selected from the group consisting of filtration, decolorization, precipitation and evaporation-concentration.

[0202] In one embodiment, the solution obtained by depolymerizing at least one polyester having at least one MEG unit is obtained by depolymerizing at least one polyester having at least one MEG unit, the reaction solution comprising a dicarboxylate and MEG, and subjected to one or more steps selected from filtration, decolorization, precipitation and evaporation-concentration.

[0203] - filter

[0204] Filtration refers to the separation of solid undepolymerized polyester (such as PET) from the liquid phase of the reaction medium (including dissolved dicarboxylic acid salts, such as TA salts, and MEG). The filtration threshold and other filtration conditions, such as the optional presence of filter aids, can be adjusted by a person skilled in the art. Alternatively, the separation of undepolymerized polyester can also be carried out by centrifugation or any other method known to a person skilled in the art.

[0205] The filtrate containing dissolved dicarboxylate salts such as TA salts as well as the desired MEG is retained.

[0206] - Purification of filtrate

[0207] The filtrate can be purified by subjecting it to one or more steps selected from ultrafiltration, decolorization, passing through an ion exchanger and chromatography. Preferably, the filtrate is decolorized by adsorption on activated carbon. Any other equivalent method known to those skilled in the art can be used.

[0208] - The dicarboxylic acid is precipitated by acidifying the solution and then filtering

[0209] Acid precipitation refers to precipitating dicarboxylic acids such as TA by adding acid to the reaction solution to form a slurry. The acid can be selected from inorganic acids such as sulfuric acid, hydrochloric acid, phosphoric acid or nitric acid, organic acids such as acetic acid and mixtures thereof. Alternatively, it can be precipitated by acidification through CO2 overpressure. This operation is followed by filtration to remove the precipitated dicarboxylic acids. Finally, the filtrate contains MEG and MEG with soluble residual salts (such as sodium sulfate). Any other method for removing salts can be easily implemented by those skilled in the art.

[0210] For example, the filtrate containing the dicarboxylate salt, such as TA salt, may be subjected to all or some of the following steps:

[0211] 1. purifying the filtrate by subjecting the solution to one or more steps selected from ultrafiltration, carbon adsorption, subjecting to ion exchange resins and chromatography; and / or

[0212] 2. Precipitate the dicarboxylic acid (e.g. TA) contained in the purified filtrate by acidification with an inorganic acid (which may be selected from the following: sulfuric acid, chloric acid, phosphoric acid or nitric acid) or with an organic acid (e.g. acetic acid) or a mixture thereof. The solution may also be acidified by CO2 overpressure. This step also includes the dissolution, precipitation of the salt produced simultaneously with the dicarboxylic acid (e.g. TA); and / or

[0213] 3. Filtering the solution containing the precipitated dicarboxylic acid (such as TA) to recover the dicarboxylic acid (such as TA) in solid form and a filtrate containing MEG and soluble residual salts (such as sodium sulfate). Therefore, before the process of the present invention, at least 80%, preferably at least 90%, more preferably 95%, and even more preferably greater than or equal to 98% of the dicarboxylic acid (such as TA) is removed from the reaction medium.

[0214] - Evaporation-concentration step to obtain concentrated MEG solution

[0215] The purpose of this step is to remove most of the dissolved salts, such as sodium sulfate, from the above solution and obtain a concentrated solution of MEG.

[0216] The evaporation-concentration step refers to the operation of dehydrating by heating the filtrate under vacuum. Once the desired pressure (vacuum) is reached, the water evaporates and the remaining salt, such as sodium sulfate, crystallizes. The crystallized salt is then filtered out to obtain a concentrated solution (filtrate) of MEG and a filter cake of crystallized salt. The filter cake can be washed with water, the washing water is combined with the filtrate, and then returned to the evaporator. The washing operation can be repeated several times by washing the filter cake again, merging it with the filtrate, and the mixture is subjected to the evaporation-concentration step again. Advantageously, the washing operation is repeated three times to extract the maximum amount of salt while minimizing the loss of MEG.

[0217] Finally, an aqueous concentrated solution of MEG is obtained.

[0218] For the following steps, this aqueous concentrated solution of MEG is referred to as the solution obtained from the depolymerization.

[0219] Process for recycling a polymer-containing material comprising at least one polyester having at least one MEG unit

[0220] Another object of the present invention is to provide a method for recycling a polymer-containing material (such as a plastic article) comprising at least one polyester having at least one MEG unit, the method comprising the following steps:

[0221] a.1) subjecting the polyester to a depolymerization step to obtain a reaction solution comprising dicarboxylate, MEG and solid components,

[0222] b.1) filtering the reaction solution obtained in step (a.1) to remove solid components and obtain a filtrate,

[0223] c.1) purifying the filtrate obtained in step (b.1), preferably by one or more steps selected from ultrafiltration, activated carbon adsorption, ion exchange resin and chromatography to obtain a purified filtrate,

[0224] d.1) precipitating the dicarboxylic acid by acidifying the purified filtrate obtained in step (c.1) to obtain a slurry,

[0225] e.1) filtering the slurry obtained in step (d.1) to remove the precipitated dicarboxylic acid to obtain a filtrate,

[0226] f.1) subjecting the filtrate obtained in step (e.1) to at least one evaporation-concentration step to obtain a MEG concentrated solution,

[0227] g.1) purifying the MEG of the concentrated solution obtained in step (f.1) by the process according to the invention to obtain purified MEG.

[0228] In particular, the step (g.1) comprises the following steps:

[0229] a) subjecting the solution obtained in step (f.1) to at least one evaporation-condensation step to obtain a bottom fraction and a condensed top fraction,

[0230] b) contacting the condensed top fraction obtained in step (a) with a resin to obtain a solution,

[0231] c) subjecting the solution obtained in step (b) to at least one distillation step to obtain a distillate, and

[0232] d) recovering purified MEG from the distillate obtained in step (c).

[0233] Steps d.1) and e.1) are particularly important for obtaining a MEG concentrated solution containing a small amount of salts, preferably substantially free of salts, such as TA salts produced by the depolymerization, so as to obtain MEG with desired properties. Here, "substantially free" means that the MEG concentrated solution obtained in step f.1) contains 3 wt.% or less of salts, such as 1 wt.% or less, such as 0.8 wt.% or less, such as 0.7 wt.% or less, such as 0.6 wt.% or less, such as 0.5 wt.% or less, based on the total weight of the solution.

[0234] In one embodiment, the MEG concentrated solution obtained in step f.1) comprises 65 wt.% or more MEG, such as 68 wt.% or more, such as 70 wt.% or more, such as 75 wt.% or more, such as 80 wt.% or more, based on the total weight of the solution.

[0235] In one embodiment, the MEG concentrated solution obtained in step f.1) comprises 65 wt.% or more MEG and DEG, such as 68 wt.% or more, such as 70 wt.% or more, such as 75 wt.% or more, such as 80 wt.% or more, based on the total weight of the solution.

[0236] All embodiments disclosed above with respect to the process for purifying MEG from a solution obtained by depolymerizing at least one polyester having at least one MEG unit also apply to step (g.1) of the process for recycling a polymer-containing material comprising at least one polyester having at least one MEG unit. In a preferred embodiment, the polyester having at least one MEG unit is PET. In some embodiments, in step c), the solution obtained from step (b) is subjected to two distillations, the second of which is a distillation having two sections.

[0237] The depolymerization step of step a.1) is performed as described in the above section, ie a chemical or biological depolymerization step. Preferably, the depolymerization step a.1) is performed by chemical or biological depolymerization under alkaline conditions.

[0238] In a preferred embodiment, the depolymerization step a.1) is a hydrolysis under alkaline conditions. In another preferred embodiment, it is a biological depolymerization step, i.e. an enzymatic depolymerization. Alternatively, the depolymerization step a.1) is a chemical hydrolysis under alkaline conditions, such as saponification.

[0239] In one embodiment, the polymer-containing material comprising at least one polyester having at least one MEG unit is a plastic article.

[0240] In a particular embodiment, when the polyester having at least one MEG unit is PET, the dicarboxylic acid is terephthalic acid (TA) and the dicarboxylate is terephthalate. In this case, the solid component removed in step (b.1) comprises undepolymerized PET.

[0241] According to the invention, the filtration of steps b.1) and e.1), the purification of the filtrate of step c.1), the precipitation by acidification of step d.1) and / or the evaporation-concentration of step f.1) are carried out as described in the above sections, i.e. as preliminary steps of the purification process of the invention. In a preferred embodiment, the process for recycling a polymer-containing material comprising at least one polyester having at least one MEG unit is carried out in the order of a.1) to g.1).

[0242] Applications and uses of purified MEG

[0243] According to the invention, the recovered MEG can be reused for the synthesis of polymers, in particular polyesters comprising at least one MEG unit as described above. A person skilled in the art can easily adapt the process parameters to the monomers / oligomers and polymers to be synthesized.

[0244] Another object of the present invention is to provide a polyester comprising at least one MEG unit, preferably PET, polymerized from MEG purified by the process of the present invention.

[0245] In one embodiment, the recovered MEG can be reused as antifreeze.

[0246] In one embodiment, the recovered MEG can be used as a desiccant in the gas industry.

[0247] The invention also relates to the use of the purified MEG obtained by the process according to the invention for producing polyesters containing at least one MEG unit.

[0248] Polyester containing at least one MEG unit

[0249] Another object of the present invention is to provide a polyester comprising at least one MEG unit, wherein the MEG is a purified MEG obtained by the process according to the present invention.

[0250] The following examples are intended to illustrate but not to limit the disclosed embodiments. Specific implementation plan

[0251] Example A: Process according to the invention for recycling plastic articles comprising polyester

[0252] Experimental part:

[0253] A-Pre-step: Preparation and conversion of PET waste

[0254] In Example A1, ground PET trays containing >98% PET were used. They were dry-mixed with 1% by weight of citric acid in powder form (Orgater exp 141 / 183 from Adeka), based on the total weight of the composition, and then extruded using a twin-screw extruder Leistritz ZSE 18MAXX, which includes nine consecutive heating zones (Z1-Z9) and a head (Z10), wherein the temperature can be independently controlled and adjusted in each zone, thereby producing an extruded foaming composition. The screw speed was set to 110 rpm and the total flow rate was set to 4 kg / h. The molten polymer arrived in a screw head (Z10) comprising a punch plate with a 3.5 mm hole and was immediately immersed in a 2 m long cold water bath (10° C.). The resulting extrudate was granulated into 2-3 mm solid particles.

[0255] The particles are then subjected to steps B to D.

[0256] In Examples A2 and A3, washed and colored flakes from PET bottle waste containing >98% PET were micronized to a fine powder of <500 μm size using an Ultra Centrifugal Mill ZM200 system.

[0257] The powder is then subjected to steps B to D.

[0258] B-Enzymatic depolymerization of PET waste (step a1)

[0259] The degradation process was carried out in a 1000 L reactor (800 L usable volume) using a variant of LC-cutinase (Sulaiman et al., Appl Environ Microbiol. 2012 Mar). Such a variant (hereinafter referred to as "LCC-ICCIG") corresponds to the enzyme of SEQ ID N°1 with the following mutations F208I+D203C+S248C+V170I+Y92G and was expressed in Trichoderma reesei.

[0260] At the beginning of the degradation process, the converted PET waste was added at a concentration of 150 g / kg, based on the total weight of the reaction medium, and LCC-ICCIG was added at a concentration of 1 mg / g PET. During all depolymerization steps, the stirring speed was adjusted to 130 rpm, the temperature was adjusted to 60° C. and the pH of the reaction medium was adjusted to pH 8±0.05 by adding 25% NaOH solution.

[0261] The depolymerization rate was monitored by measuring the amount of NaOH added to the reaction medium to neutralize the terephthalic acid (TA) produced by the depolymerization.

[0262] The depolymerization rate after 48 hours was 98%.

[0263] At the end of the depolymerization, the reaction solution contained TA salt as dicarboxylate, MEG and undepolymerized PET in the form of solid components.

[0264] Preliminary steps in the C-MEG purification process: Removal of undepolymerized PET and terephthalic acid (TA) and sodium sulfate salt

[0265] - Filtering (step b1)

[0266] The reaction solution was then filtered to separate the solid phase of the reaction solution in the reactor (mainly residual undepolymerized PET waste) from the liquid phase of the reaction solution (containing dissolved TA salts and MEG).

[0267] The solid components removed from the fluid are removed. The filtrate containing the dissolved TA salts as well as the desired MEG is retained.

[0268] - Purification of the filtrate by adsorption on activated carbon (step c1)

[0269] The filtrate containing dissolved TA salts and MEG was purified by passing the filtrate through an activated carbon 1 L column at room temperature.

[0270] - Precipitation of TA by acidification of the solution (step d1) followed by filtration (step e1)

[0271] The purified filtrate was then acidified by adding 98% sulfuric acid to precipitate TA in solution until a final pH of 2.7-3 was reached.

[0272] As a result, TA precipitate was formed and then filtered out from the slurry.

[0273] Finally, the filtrate contains MEG with dissolved residual salts such as sodium sulfate.

[0274] - Evaporation-concentration step to obtain concentrated MEG solution (step f1)

[0275] A first evaporation stage was carried out by heating the product to 80° C. while stirring and by gradually placing the evaporator under vacuum until a pressure of about 300 mbar absolute was reached until crystals appeared.

[0276] The resulting slurry is cooled overnight to allow the remaining dissolved sodium sulfate to crystallize. The sodium sulfate crystals formed are filtered and then washed. The wash water and the filtrate containing MEG are then returned to the evaporator for the next stage.

[0277] These operations (evaporation / filtration / washing of sodium sulfate crystals) were repeated three times to extract the maximum amount of dissolved salts.

[0278] D-Method for purifying MEG (step g1)

[0279] Example A1 - Process for purifying MEG produced by enzymatic depolymerization of PET trays

[0280] As mentioned in the previous section, the "concentrated solution of MEG" obtained after the evaporation-concentration step will be referred to as "solution" hereinafter.

[0281] The composition of the solution entering the process of the present invention is shown in Table 1.

[0282] Main Ingredients Quantity (quality) water 31.5％ MEG 65.4％ DEG & Recombinant 2.6％ <![CDATA[Dry matter containing Na2SO4 salt and heavy impurities]]> 0.5％

[0283] Table 1: Composition of the concentrated solution of MEG entering the process for purifying MEG.

[0284] The solution is subjected to the method of the present invention, the method comprising the steps of:

[0285] (a) Evaporation-condensation step

[0286] The evaporation step is carried out on a continuous wiped film evaporator made of glass. The evaporator is heated with hot oil circulating in a double jacket. The product is fed continuously into the evaporator.

[0287] The evaporation of the solution was carried out in two stages with different conditions as described in Table 2. The top fraction from the first evaporation stage was condensed to obtain a first condensate, while the bottom fraction was subjected to a second evaporation stage. The top fraction obtained from the second evaporation step was also condensed to obtain a second condensate.

[0288] Finally, the first and second condensates are combined.

[0289] Evaporation conditions: 1st Evaporation Stage Second evaporation stage Process pressure (mbar absolute pressure) 100 100 Heating temperature(℃) 161-165 188-193

[0290] Table 2: Conditions for two-step evaporation

[0291] The heating temperature corresponds to the temperature of the hot oil circulating in the double jacket.

[0292] Condensation is performed using a water-cooled condensing unit.

[0293] (b) Contact with resin

[0294] The condensate obtained from step (a) was then passed at room temperature through a 50 mm diameter / 500 mm high glass column loaded with 375 g of OH-form PUROLITE A 860. The flow rate was set so that the velocity in the column was 1 m / h.

[0295] (c) Distillation

[0296] The solution obtained from step (b) was subjected to two consecutive distillation steps using a glass column distillation, ie, 0.16 inch pro-pak distillation packing with a height of 1200 mm (3*400 mm).

[0297] The boiler of the column is heated with hot oil which circulates in the double jacket of the boiler.

[0298] The conditions for the two distillation steps are described in Table 3.

[0299] The column was fed with 1.3 kg / h.

[0300] 1st distillation step Second distillation step Process pressure (mbar absolute pressure) 205 100 Bottom temperature(℃) 153 136 Heating temperature(℃) 175 200 Reflux ratio 1 1

[0301] Table 3: Conditions for the two distillation steps.

[0302] The heating temperature corresponds to the temperature of the hot oil circulating in the double jacket.

[0303] (d) Recovery of purified MEG

[0304] The distillate containing purified MEG recovered from the process of the present invention has the characteristics described in Table 4. The results are compared with the required specification values ​​for MEG used in the production of PET and plastic bottles. These specification values ​​can be found in the material data sheets of commercial monoethylene glycol polyester grades.

[0305]

[0306] Table 4: Analysis of MEG purified by the method of the present invention

[0307] In summary, the process according to the invention leads to a purity greater than 99.9%, which is similar to the purity of MEG of petrochemical origin used commercially for the production of PET and plastic bottles. Furthermore, the process of the invention allows to meet other specified specification values ​​as shown in Table 4.

[0308] Example A2 - Process for purifying MEG produced by enzymatic depolymerization of PET bottles

[0309] For this example, the composition of the solution entering the purification section is shown in Table 5.

[0310] Main Ingredients Quantity (quality) water QSP MEG 80.8％ DEG & Recombinant 3％ Dry matter (salt) <1％

[0311] Table 5: Composition of the concentrated solution of MEG entering the purification section.

[0312] The solution is subjected to the method of the present invention, the method comprising the steps of:

[0313] (a) Evaporation-condensation step

[0314] The evaporation step was carried out on a batch stainless steel evaporator. The 100 L evaporator was equipped with a stirrer and heated with hot oil circulating in a double jacket.

[0315] Evaporation was performed as described in Example A1 using the conditions disclosed in Table 6 below.

[0316] 1st Evaporation Stage Second evaporation stage Process pressure (mbar absolute pressure) 200 75 Bottom temperature(℃) 164 136 Heating temperature(℃) 170 170

[0317] Table 6: Conditions for the two evaporation steps.

[0318] The heating temperature corresponds to the temperature of the hot oil circulating in the double jacket.

[0319] Condensation was carried out using a water-cooled tube condenser.

[0320] (b) Contact with resin

[0321] The deacidification step was carried out in an 8 L glass column loaded with 3.5 l of PUROLITE A860 in OH-form. The condensate obtained in step (a) was continuously fed into the column at room temperature at a set flow rate so that the velocity in the column was 0.8 m / h.

[0322] (c) Distillation

[0323] Two distillation runs were performed using glass column distillation. The column used to perform these experiments had the following characteristics:

[0324] -Diameter: 50mm

[0325] - Filling: Sulzer filler BX

[0326] - Useful filling height: 1000mm per section

[0327] The boiler of the column is heated with hot oil which circulates in the shell of the falling film evaporator.

[0328] The conditions for the two distillation steps are described in Table 7.

[0329] 1st distillation step Second distillation step Process pressure (mbar absolute pressure) 150 130 Heating temperature(℃) 207-210 205 Bottom temperature(℃) 143.5 140 Reflux ratio 0.2 0.07

[0330] Table 7: Conditions for the two distillation steps.

[0331] The heating temperature corresponds to the temperature of the hot oil circulating in the double jacket.

[0332] (c') Purification step

[0333] The distillate from the previous step (c) was subjected to an additional refining step. The step was carried out in a 2.5 cm diameter glass column loaded with activated carbon. It was continuously fed into the column at room temperature. The flow rate was set to 0.6 l / h so that the velocity in the column was 1.2 m / h.

[0334] (d) Recovery of purified MEG

[0335] The purified MEG recovered from the process of the invention was analyzed and had the characteristics described in Table 8. As in Example A1, the results were compared with the required specification values ​​for MEG of petrochemical origin classically used for the production of PET and plastic bottles.

[0336]

[0337] Table 8: Analysis of MEG purified by the method of the present invention

[0338] In summary, the process for purifying MEG according to the invention results in a purity greater than 99.9%, which is similar to MEG of petrochemical origin classically used for the production of PET and plastic bottles. Furthermore, the process of the invention allows to meet other specified specification values ​​as shown in Table 8.

[0339] In addition, transparent bottles have been successfully produced using MEG purified according to the present invention and TA purified from the depolymerization process as described in WO2014 / 079844, WO2015 / 097104, WO2015 / 173265, WO2017 / 198786, WO2020 / 094661 and WO2020 / 094646.

[0340] Example A3 - Process for purifying MEG produced by enzymatic depolymerization of PET bottle flakes, comprising a distillation having two sections

[0341] The composition of the solution entering the process of the present invention is shown in Table 9.

[0342] Main Ingredients Quantity (quality) water QSP MEG 81％ DEG About 4% Heavy components About 2% <![CDATA[Dry matter containing Na2SO4 salt and heavy impurities]]> <1％

[0343] Table 9: Composition of the concentrated solution of MEG entering the process for purifying MEG.

[0344] The solution is subjected to the method of the present invention, the method comprising the steps of:

[0345] (a) Evaporation-condensation step

[0346] The evaporation step is carried out in a continuous 0.5 m 2 The evaporation is carried out on a wiped film evaporator made of stainless steel. The evaporator is heated with steam circulating in a double jacket. The product is fed continuously into the evaporator.

[0347] The evaporation of the solution was carried out in two stages with different conditions as described in Table 10. The top fraction from the first evaporation stage was condensed to obtain a first condensate, while the bottom fraction was subjected to a second evaporation stage. The top fraction obtained from the second evaporation step was also condensed to obtain a second condensate.

[0348] Finally, the first and second condensates are combined.

[0349] Evaporation conditions: 1st Evaporation Stage Second evaporation stage Process pressure (mbar absolute pressure) 100 65 Heating temperature(℃) 161-165 150-160 Feed flow rate (kg / hr) 40 23

[0350] Table 10: Conditions for two-step evaporation

[0351] The heating temperature corresponds to the temperature of the steam circulating in the double jacket.

[0352] Condensation is performed using a water-cooled condensing unit.

[0353] (b) Contact with resin

[0354] The condensate obtained from step (a) was then passed at room temperature through a tall glass column loaded with PUROLITE A860 in OH-form. The flow rate was set so that the velocity in the column was 1 m / h.

[0355] (c) Distillation

[0356] The setup for two consecutive distillations was based on Example A2, with the introduction of a supplementary upper section on the second distillation, so that the MEG was collected via a side draw.

[0357] The column boiler is heated with hot oil or steam circulating in a double jacket.

[0358] The conditions for the two distillation steps are described in Table 11.

[0359] 1st distillation step Second distillation step Process pressure (mbar absolute pressure) 205 100 Bottom temperature(℃) 153 169 Distillate temperature (℃) 60 132 Reflux ratio 0.2 0.5

[0360] Table 11: Conditions for the two distillation steps.

[0361] (d) Recovery of purified MEG

[0362] The distillate containing purified MEG recovered from the process of the present invention has the characteristics described in Table 12. The results are compared with the required specification values ​​for MEG used in the production of PET and plastic bottles. These specification values ​​can be found in the material data sheets of commercial monoethylene glycol polyester grades.

[0363]

[0364] Table 12: Analysis of MEG purified by the method of the present invention

[0365] In addition, the recovered purified MEG exhibits an alpha-boiling point value of less than 20. Such specification can be easily measured by one skilled in the art. For example, the alpha boiling point can be measured according to the ASTM D-5386 method after heating the sample at 198°C for 4 hours.

[0366] In summary, the process according to the invention results in a purity greater than 99.9%, which is similar to the purity of MEG of petrochemical origin used commercially for the production of PET and plastic bottles. Furthermore, the process of the invention allows to meet other specified specification values ​​as shown in Table 12.

Claims

1. A method for purifying monoethylene glycol (MEG) from a depolymerization solution of at least one polyester having at least one MEG unit, the method comprising the following steps: a) subjecting the depolymerization solution to at least one evaporation-condensation step in order to obtain a bottom fraction and a condensed top fraction, b) contacting the condensed top fraction obtained in step (a) with a resin to obtain a solution, c) subjecting the solution obtained in step (b) to at least one distillation step to obtain a distillate, and d) recovering purified MEG from the distillate obtained in step (c).

2. The process according to claim 1, further comprising a step (c'), wherein before the recovery step (d), the distillate obtained in step c) is subjected to one or more steps selected from distillation, hydrogenation, dehydration and decolorization, preferably a distillation step and / or a decolorization step, wherein the decolorization step is preferably carried out by adsorption on activated carbon.

3. The method according to claim 1 or 2, wherein the polyester having at least one MEG unit is selected from the group consisting of polyethylene terephthalate (PET), polyethylene adipate (PEA), polyethylene 2,5-furandicarboxylate (PEF) and polyethylene naphthalate (PEN), preferably the polyester is PET.

4. The method according to any one of claims 1 to 3, wherein the depolymerization is a biological depolymerization, preferably a hydrolytic depolymerization, more preferably an enzymatic depolymerization, even more preferably an alkaline enzymatic depolymerization.

5. The method according to any one of claims 1 to 3, wherein the depolymerization is a chemical depolymerization, preferably a hydrolysis, more preferably an alkaline chemical hydrolysis such as saponification.

6. The method according to any one of claims 1 to 5, wherein the depolymerization solution is a reaction solution for depolymerizing at least one polyester having at least one MEG unit, the reaction solution comprising a dicarboxylate and MEG, and subjected to one or more steps selected from filtration, decolorization, precipitation and evaporation-concentration.

7. The process according to any one of claims 1 to 6, wherein the evaporation of the evaporation-condensation of step (a) is carried out in a thin film evaporator, a batch evaporator, a forced circulation evaporator or a flash evaporator, preferably in a thin film evaporator.

8. The process according to any one of claims 1 to 7, wherein step (a) comprises an additional evaporation-condensation step, wherein the bottom fraction obtained from the first evaporation-condensation step is subjected to a second evaporation-condensation step, and wherein the condensed top fractions obtained from the first and second evaporation-condensation steps are mixed before being subjected to step (b).

9. The process according to claim 8, wherein the bottom fraction obtained from the first evaporation-condensation step is filtered before being subjected to the second evaporation-condensation step and / or wherein the evaporation of the second evaporation-condensation step is carried out in a thin film evaporator.

10. The process according to any one of claims 1 to 9, wherein step (b) is performed by passing the condensed top fraction obtained in step (a) through an ion exchange resin, preferably a strong anion exchange resin.

11. The process according to any one of claims 1 to 10, wherein the evaporation of the first and / or the second evaporation-condensation step of step (a) and / or the distillation step of step (c) are carried out under vacuum conditions, preferably at a pressure of 15-500 mbar absolute, more preferably at a pressure of 100 mbar absolute.

12. The method according to any one of claims 1 to 11, wherein the method comprises or consists in the following steps: a) subjecting the depolymerization solution to at least one evaporation-condensation step, preferably two evaporation-condensation steps, both carried out in a thin-film evaporator, to obtain a bottom fraction and a condensed top fraction mixture, b) contacting the condensed top fraction obtained in step (a) with a strong anion exchange resin to obtain a solution, c) subjecting the solution obtained in step (b) to a double distillation, the second distillation optionally being a distillation with two zones, and d) recovering purified MEG from the distillate obtained in step (c).

13. A method for recycling a polymer-containing material comprising at least one polyester having at least one MEG unit, the method comprising the steps of: a.1) subjecting the polyester having at least one MEG unit to a depolymerization step, preferably hydrolysis under alkaline conditions, preferably enzymatic depolymerization, to obtain a reaction solution comprising dicarboxylate, MEG and solid components, b.1) filtering the reaction solution obtained in step (a.1) to remove solid components and obtain a filtrate, c.1) purifying the filtrate obtained in step (b.1) by one or more steps selected from ultrafiltration, activated carbon adsorption, ion exchange resin and chromatography to obtain a purified filtrate, d.1) precipitating the dicarboxylic acid by acidifying the purified filtrate obtained in step (c.1) to obtain a slurry, e.1) filtering the slurry obtained in step (d.1) to remove the precipitated dicarboxylic acid to obtain a filtrate, f.1) subjecting the filtrate obtained in step (e.1) to at least one evaporation-concentration step to obtain a MEG concentrated solution, g.1) purifying the MEG of the concentrated solution obtained in step (f.1) by a method according to any one of claims 1 to 12 to obtain purified MEG.

14. The method of claim 13, wherein the polyester having at least one MEG unit is PET, the dicarboxylic acid is terephthalic acid (TA), and the dicarboxylate is terephthalate.

15. Use of purified MEG obtained by the process according to any one of claims 1 to 12 for the production of polyesters containing at least one MEG unit.

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