PROCESS FOR PURIFYING A TEREPHTHALATE ESTER BY ADSORPTION AND REGENERATION OF THE ADSORBENT

Abstract

The invention relates to a method for purifying a phthalic ester feedstock, comprising: a) an adsorption step by contacting the phthalic ester feedstock with at least one adsorbent from at least one fixed bed, said at least one adsorbent being a fresh adsorbent or a regenerated adsorbent, at a temperature between 60 and 150°C; then b) a regeneration step comprising contacting, at a temperature between 90 and 450°C, a regeneration fluid with said at least one adsorbent contained in said fixed bed or at least one of said fixed beds, to obtain a regenerated adsorbent. Figure 1 to be published

Description

Title of the invention: METHOD FOR PURIFYING A TEREPHTHALATE ESTER BY ADSORPTION AND REGENERATION OF THE ADSORBENT technical field

[0001] The invention relates to an efficient and economical method for purifying a terephthalate ester, in particular a terephthalate diester, such as dimethyl terephthalate (or dimethyl terephthalate, also known as DMT) or bis-(2-hydroxyethyl) terephthalate (BHET), by adsorption. More particularly, the invention relates to a method for purifying a feed comprising a terephthalate ester, in particular a diester terephthalate diester, by contacting said feed with at least one adsorbent, and regenerating said adsorbent(s), preferably in situ. The said purification process can advantageously be integrated into a more global process, for example as a purification step of a terephthalate diester obtained by depolymerization by glycolysis in the presence of a diol compound, of a polyester filler including in particular polyester terephthalate (PET), thus participating in the recycling of "plastics". Previous technique

[0002] Chemical recycling of polyester, in particular polyethylene terephthalate (PET), has been the subject of much work aimed at decomposing polyester recovered as waste into monomers which can again be used as a filler in a polymerization process.

[0003] Many polyesters are derived from material collection and sorting systems. In particular, polyester, and especially PET, can come from the collection of bottles, trays, films, resins, and / or fibers composed of polyester (such as textile fibers or tire fibers). Polyester from collection and sorting systems is called recyclable polyester.

[0004] Recyclable PET can be classified into four main categories:

[0005] - clear PET, consisting mainly of colorless transparent PET (generally at less 60% by weight) and azure transparent PET, which contains no pigments and can be used in mechanical recycling processes,

[0006] - dark or colored PET (green, red, etc.), which can generally contain up to 0.1% by weight of colorants or pigments but remains transparent, or translucent;

[0007] - opaque PET, which contains a significant amount of pigments at levels typically varying between 0.25 and 5.0% by weight to opacify the polymer. Opaque PET is increasingly used, for example, in the manufacture of food containers, such as milk bottles, in the composition of cosmetic, phytosanitary or dye bottles;

[0008] - multilayer PET, which comprises layers of polymers other than PET or A layer of recycled PET sandwiched between layers of virgin PET (i.e., PET that has not undergone recycling), or an aluminum film, for example. Multilayer PET is used after thermoforming to make packaging such as trays.

[0009] Collection systems, which feed into recycling systems, are structured differently depending on the country. They evolve to maximize the amount of plastic recovered from waste, depending on the nature and quantity of the waste streams and the sorting technologies. The recycling process for these streams generally includes an initial flake-forming stage during which raw packaging bales are washed, purified and sorted, shredded, then purified and sorted again to produce a flake stream containing generally less than 5% by mass of "macroscopic" impurities (glass, metals, other plastics, wood, paperboard, mineral elements), for example less than 1% by mass of "macroscopic" impurities, preferably less than 0.2% by mass of "macroscopic" impurities, and even more preferably less than 0.05% by mass.

[0010] The clear PET flakes can then undergo an extrusion-filtration step to produce extrudates that can then be reused by blending them with virgin PET to make new products (bottles, fibers, films). A vacuum solid-state polymerization (SSP) step is often necessary for food applications. This type of recycling is called mechanical recycling.

[0011] Dark (or colored) PET flakes are also mechanically recyclable. However, the coloring of the extrudates formed from the colored streams limits their uses: dark PET is most often used to produce fibers or packaging strips. Therefore, the market opportunities are more limited compared to those of light-colored PET.

[0012] The presence of opaque PET containing significant amounts of pigments in PET to be recycled poses problems for recyclers because opaque PET alters the mechanical properties of the recycled PET. Opaque PET is currently collected with colored PET and ends up in the colored PET stream. Given the increasing uses of opaque PET, the levels of opaque PET in the colored PET stream to be recycled are currently between 5-20% by weight and tend to increase further. Within a few years, it will be possible to reach opaque PET levels in the colored PET stream exceeding 20-30% by weight. However, it has been shown that beyond 10-15% opaque PET in colored PET streams, the mechanical properties of the recycled PET are altered (see "Impact of the development of white opaque PET on the recycling of PET packaging," preliminary note from COTREP). 5 / 12 / 13) and prevent recycling into fibers, the main outlet for colored PET in the industry.

[0013] Dyes are natural or synthetic substances, soluble in the material into which they are introduced, particularly in polyester, and used to color said material. Dyes commonly used are of various types and often contain heteroatoms, for example of type O and N, and conjugated unsaturations, such as quinone, methine, azo groups, or molecules like pyrazolone and quinophthalone.

[0014] Pigments, for their part, are finely divided substances, insoluble in the material into which they are introduced, particularly in polyester, and used to color and / or opacify said material. The main pigments used to color and / or opacify polyesters, particularly PET, are metal oxides such as TiO2, CoA12O4, Fe2O3, silicates, polysulfides, and carbon black. Pigments are generally in the form of particles with a size often between 0.1 and 10 µm, and predominantly between 0.4 and 0.8 µm. The complete removal of pigments, necessary for recycling opaque PET, is technically difficult, particularly by filtration, because pigments are extremely clogging.

[0015] Recycling colored and opaque PET is therefore extremely delicate.

[0016] US patent application 2006 / 0074136 describes a depolymerization process by Glycolysis of colored PET, particularly PET recovered from green colored PET bottles, in the presence of ethylene glycol. Following depolymerization, the resulting effluent is purified, either directly or after filtration, by adsorption onto activated carbon at a temperature above 170°C, then by extraction of residual colorants, particularly yellow colorants, by contact with an alcohol or glycol-type solvent, followed by crystallization of the BHET in the extraction solvent by lowering the temperature. The BHET is then separated by filtration. French patent application FR 3053691 describes a process for depolymerizing a polyester filler comprising opaque PET and, in particular, 0.1 to 10% by weight of pigments, by glycolysis in the presence of ethylene glycol. A purified bis-(2-hydroxyethyl) terephthalate (BHET) effluent is obtained after specific separation and purification steps by adsorption.

[0017] Adsorption is indeed often used to purify the monomer BHET diester. For example, patent application WO22108071 proposes a BHET purification process comprising introducing activated carbon into a BHET solution in water and then filtering the suspension to separate the activated carbon from the purified aqueous BHET solution. Patent FR3105234, on the other hand, proposes purification by adsorption of a BHET effluent in solution in a diol-type solvent, the solution passing through at least one fixed bed of at least one adsorbent comprising activated carbon is preferred. In application FR3124185, the raw BHET feedstock is dissolved in water and then the solution passes through at least one fixed bed of at least one adsorbent, preferably including activated carbon.

[0018] However, purification by adsorption generally implies a more or less rapid saturation of the adsorbent, in particular the adsorbent bed, and therefore a loss of adsorption efficiency. It is therefore necessary to anticipate:

[0019] - to discharge the saturated or used adsorbent and recharge the bed with fresh adsorbent (that is, nine);

[0020] - to discharge the used adsorbent, to regenerate it ex-situ and to recharge the bed by the regenerated adsorbent; or

[0021] - to regenerate the used adsorbent in-situ, i.e. without discharging it.

[0022] Ex-situ or in-situ regeneration offers the advantage of limiting the replacement of saturated or used adsorbent with fresh adsorbent, thus contributing to making the adsorption purification process as environmentally responsible as possible. Another benefit of ex-situ and in-situ regeneration lies in the reduction of raw material costs for the adsorption purification process, particularly the cost of purchasing adsorbents. In-situ regeneration offers other advantages, notably limiting manual operations and shortening the downtime of the adsorption unit (or column), whereas ex-situ regeneration involves additional costs related to the transport and storage of the material.

[0023] Patent FR3105234 and application FR3124185 mention the possibility of regenerating in-situ the adsorbent used for purification, without specifying any particular operating or implementation conditions.

[0024] The present invention seeks to improve the process of purifying a phthalic ester stream by adsorption, in particular by introducing an efficient and preferably economical regeneration step for the adsorbent. The present invention thus aims to provide an economical and as environmentally friendly as possible process for purifying a phthalic ester stream by adsorption, for example, from the depolymerization of polyester-based waste, particularly polyethylene terephthalate (PET), advantageously by introducing an efficient regeneration step for the adsorbent. Summary of the invention

[0025] The present invention relates to a method for purifying a phthalic ester feedstock, comprising:

[0026] a) an adsorption step by contacting said phthalic ester charge with at least one adsorbent contained in at least one fixed bed, said adsorption step a) being carried out at a temperature between 60 and 150°C, to obtain an effluent purified phthalate ester; then

[0027] b) a regeneration step comprising bringing a regeneration fluid into contact with said at least one adsorbent contained in said fixed bed or at least one of said fixed beds, said contacting in regeneration step b) being carried out at a temperature between 90 and 450°C, to obtain a regenerated adsorbent in said fixed bed or at least one of said fixed beds at the end of the regeneration step;

[0028] in step a), said at least one adsorbent being a fresh adsorbent or said regenerated adsorbent.

[0029] An advantage of the present invention lies in obtaining a purified phthalic ester effluent, and very advantageously in the form of a colorless or almost colorless liquid to the eye or a white solid to the eye, continuously and in a simple and economical manner.

[0030] The process according to the invention makes it possible to continuously purify a crude stream of phthalic esters, and in particular a crude stream of phthalic esters obtained after depolymerization, notably by glycolysis, of polyester waste typically comprising colored, opaque, or even multi-layered PET, and therefore consequently pigments and dyes. The process according to the invention makes it possible to purify such a stream while limiting the risk of clogging of the purification unit by adsorption and avoiding shutdowns of said unit that could be due to saturation of the adsorbent. Another advantage of the process according to the invention is that it makes it possible to maximize the adsorption capacity of said adsorbent.

[0031] The process according to the invention also makes it possible to reduce the consumption of adsorbent and more broadly to control the production costs of purified phthalic esters, while ensuring continuous production of said purified phthalic esters.

[0032] The process according to the invention is very flexible and can easily be integrated downstream of any polyester depolymerization process such as PET, and in particular opaque and / or colored PET, as a purification step for the phthalic diester effluent obtained directly from the depolymerization reaction or after intermediate separation steps. For example, the process according to the invention can easily be integrated as a decolorization step in the process described in French patent application FR 3053691. Description of the embodiments

[0033] According to the invention, the expressions "between ... and ..." and "between ... and ..." are equivalent and mean that the limit values ​​of the interval are included in the range of values ​​described. If this is not the case and the limit values ​​are not included in the range described, such clarification will be provided by the present invention.

[0034] In accordance with the invention, the different parameter ranges for a given step, such as pressure ranges and temperature ranges, can be used alone or in combination. For example, in the context of the present invention, a preferred pressure range can be combined with a more preferred temperature range.

[0035] In the following, particular embodiments of the invention are described. They can be implemented separately or in combination with each other, without limitation of combinations where technically feasible.

[0036] According to the present invention, the pressures are absolute pressures and are given in absolute MPa (or abs. MPa).

[0037] According to the invention, times and durations are expressed in hours (h), minutes (min) and / or seconds (sec).

[0038] The terms "upstream" and "downstream" are to be understood in relation to the general flow of the fluid(s) or flow in question in the process.

[0039] According to the invention, the term "phthalic ester" is any ester, and particularly any ester of phthalic acid, terephthalic acid, or isophthalic acid, advantageously having the chemical formula: X-O2C-(Aro)-CO2-Y, with n-(Aro)- = -(C6H4)- representing an aromatic ring, and X, Y being identical or preferably different groups selected from alkyl groups preferably comprising between 1 and 6 carbon atoms (i.e., C1-C6), hydroxyalkyl groups preferably comprising between 2 and 12 carbon atoms (i.e., C2-C12), preferably between 2 and 4 carbon atoms (C2-C4), and hydroxyalkyl ether groups preferably comprising between 2 and 12 carbon atoms (i.e., in C2-C12), preferably between 2 and 6 carbon atoms (C2-C6).For example, the term "phthalic ester" can refer to dimethyl terephthalate (DMT), bis(2-hydroxyethyl) terephthalate (BHET), 2-(2-hydroxyethoxy) ethyl 2-hydroxyethyl terephthalate (BHET-deg) or mixtures thereof.

[0040] According to the invention, polyethylene terephthalate or poly(ethylene terephthalate), also simply called PET, has a basic unit comprising a terephthalic acid diester, with the following formula repetition:

[0041] Classically, PET is obtained by polycondensation of terephthalic acid (PTA), or dimethyl terephthalate (DMT), with ethylene glycol.

[0042] According to the invention, the term "monomer" or "diester monomer" advantageously designates the repeating unit of a polyester polymer, and defines a diester of a dicarboxylic acid, preferably of an aromatic dicarboxylic acid and preferably Primarily terephthalic acid, and a diol comprising preferably between 2 and 12 carbon atoms, preferably between 2 and 4 carbon atoms, the preferred diol being ethylene glycol. Preferably, the term "monomer" or "diester monomer" refers to bis(2-hydroxyethyl) terephthalate (BHET) or dimethyl terephthalate (DMT).

[0043] The term "oligomer" typically refers to a small polymer, generally consisting of 2 to 20 repeating elementary units. According to the invention, the term "ester oligomer" or "BHET oligomer" refers to a terephthalate ester oligomer, comprising between 2 and 20, preferably between 2 and 5, repeating elementary units of formula -[O-CO-(C6H4)-CO-O-C2H4]-, with -(C6H4)- an aromatic ring.

[0044] According to the invention, the terms "diol" and "glycol" are used interchangeably and refer to compounds comprising two hydroxyl groups (-OH), and preferably comprising between 2 and 12 carbon atoms, preferably between 2 and 4 carbon atoms. The preferred diol is ethylene glycol, also called monoethylene glycol or MEG.

[0045] The diol or solvent diol streams, possibly involved in the steps of the process of the invention, thus comprise a diol, preferably ethylene glycol (or MEG), in a quantity greater than 40% by weight, preferably greater than 50% by weight, preferably greater than or equal to 60% by weight, of the total weight of the diol stream considered.

[0046] Similarly, a mono-alcohol, ether, ester, ketone or aldehyde solvent comprises at least 40% by weight, preferably at least 50% by weight, preferably at least 60% by weight, of mono-alcohol, ether, ester, ketone or aldehyde relative to the total weight of the solvent in question.

[0047] The term "dye" defines a substance soluble in polyester material and used to color it. The dye may be of natural or synthetic origin.

[0048] According to the invention, the term "pigment," more particularly coloring and / or opacifying pigment, defines a finely divided substance, insoluble in particular in polyester material. Pigments are in the form of solid particles, generally ranging in size from 0.1 to 10 pm, and predominantly between 0.4 and 0.8 pm. They are often mineral in nature. Pigments generally used, particularly for opacification, are metal oxides such as TiO2, CoAl2O4, Fe2O3, silicates, polysulfides, and carbon black.

[0049] The present invention thus relates to a method for purifying a phthalic ester filler, preferably comprising a terephthalic diester such as bis-(2-hydroxyethyl) terephthalate and / or dimethyl terephthalate, said filler being in particular obtained from the depolymerization of a polyester filler comprising PET, including:

[0050] a) an adsorption step during which the impurities of the phthalic ester filler are advantageously adsorbed onto an adsorbent implemented in at least one fixed bed, until the adsorbent is saturated; and

[0051] b) a regeneration step during which the adsorption capacity of the adsorbent is at least partially recovered and at the end of which the adsorbent is ready to be put back into operation.

[0052] More particularly, the present invention relates to a method for purifying a phthalic ester feedstock, preferably comprising a terephthalic diester, preferably comprising bis-(2-hydroxyethyl) terephthalate, the method preferably comprising:

[0053] a) an adsorption step by contacting said phthalic ester feedstock with at least one adsorbent contained in at least one fixed bed, said at least one adsorbent being a fresh adsorbent or a regenerated adsorbent advantageously obtained at the end of regeneration step b), said adsorption step a) being carried out at a temperature between 60 and 150°C and preferably at a pressure between 0.1 and 1.0 MPa, to obtain a purified phthalic ester effluent; then

[0054] b) a regeneration step comprising bringing a regeneration fluid into contact with said at least one adsorbent contained in said fixed bed or at least one of said fixed beds, to obtain a regenerated adsorbent in said fixed bed or at least one of said fixed beds at the end of the regeneration step,

[0055] said contact in step b) of regeneration being carried out at a temperature between 90 and 450°C, preferably between 150 and 400°C, and preferably between 250 and 350°C, preferably at a pressure between 0.1 and 7.0 MPa, in particular between 0.1 and 3.0 MPa and more particularly between 0.2 and 2.5 MPa, preferably for a duration between 0.5 and 200 hours, and preferably at a surface velocity between 0.01 and 5.00 cm / s,

[0056] the regeneration fluid being preferably an oxygenated solvent, more particularly chosen from water with at least one surfactant added, diols, esters, ethers, aldehydes, ketones, and mixtures thereof; most particularly chosen from diols preferably comprising at least 2 carbon atoms, preferably between 2 and 4 carbon atoms; monoalcohols preferably comprising between 1 and 6 carbon atoms; esters preferably comprising between 2 and 6 carbon atoms; ethers, in particular linear or cyclic ethers, and preferably comprising between 2 and 6 carbon atoms; aldehydes preferably comprising between 3 and 6 carbon atoms; ketones preferably comprising between 3 and 6 carbon atoms; and mixtures thereof; preferably the regeneration fluid being a diol preferably comprising at least 2 carbon atoms, preferably typically between 2 and 4 carbon atoms, and most preferably a diol comprising 2 carbon atoms such as ethylene glycol,

[0057] advantageously, in step b), the regeneration fluid circulating through said at least one adsorbent in such quantity that the volume ratio between the volume of said regeneration fluid and the volume of said at least one adsorbent in contact with said regeneration fluid is preferably between 1 and 50, preferably between 5 and 30, preferably between 5 and 20,

[0058] possibly, said regeneration step b) also comprising a waiting phase, at the end of the active regeneration phase, during which the circulation of the regeneration fluid is stopped in said fixed bed or at least one of said fixed beds, the latter or these is / are then put in reserve (or in standby) before being put back into operation (i.e. being put back into operation in the adsorption step a).

[0059] According to a preferred embodiment, the purification process uses at least two fixed beds, in particular between two and ten fixed beds, or even between two and six fixed beds, of at least one adsorbent, and:

[0060] the adsorption step a) employs at least one fixed bed of said at least one adsorbent, said at least one fixed bed employed in step a) being called the operating fixed bed, and simultaneously the regeneration step, in particular employed in situ, employs at least one fixed bed of said at least one adsorbent, said at least one fixed bed employed in step b) being called the regenerating fixed bed, said at least one regenerating fixed bed being distinct from said at least one operating fixed bed and the sum of the number of operating fixed beds and the number of regenerating fixed beds being equal to the total number of fixed beds employed by the purification process, said regeneration fluid circulating through said at least one regenerating fixed bed in the same or opposite direction, preferably opposite, to that of the phthalic ester charge circulating in said at least one fixed bed when it is in operation.When the adsorption step (a) employs several fixed beds of at least one adsorbent, said fixed beds in operation function in series, particularly in lead-lag, and when the regeneration step (b) employs several fixed beds, said fixed beds in regeneration are in series, particularly in lead-lag. In this preferred embodiment, the fixed bed in operation or the first fixed bed in operation of the series of fixed beds in operation advantageously switches to step (b) and becomes the fixed bed in regeneration or the last fixed bed in regeneration of the series of fixed beds in regeneration, and simultaneously the fixed bed in regeneration, possibly in standby phase, or the first fixed bed in regeneration of the series of fixed beds in regeneration, possibly in standby phase, switches to step (a) and becomes the fixed bed in operation or the last fixed bed in operation of the series of fixed beds in operation.

[0061] Charge

[0062] The process according to the invention is fed by a phthalic ester charge, possibly called a crude charge.

[0063] The phthalic ester filler advantageously comprises a terephthalic diester, for example bis-(2-hydroxyethyl) terephthalate (BHET) and / or dimethyl phthalate (DMT), preferably bis-(2-hydroxyethyl) terephthalate. Preferably, the phthalic filler comprises at least 70.0% by weight, preferably at least 85.0% by weight, preferably at least 95.0% by weight, preferably at least 99.0% by weight of phthalic ester, preferably terephthalic diester, preferably bis-(2-hydroxyethyl) terephthalate (BHET), 100.0% by weight representing the maximum of phthalic ester in the filler.

[0064] The phthalic ester filler may also include impurities, preferably soluble in the diester monomer. These impurities may also be called residual impurities. Examples include colorants, typically used to color polyester polymeric material, and organic or inorganic salts. More specifically, colorant-type impurities may represent up to 1% by weight (i.e., less than 1% by weight), preferably up to 0.1% by weight, preferably up to 0.05% by weight, of the total weight of the phthalic ester filler, and in particular at least 1 ppm by weight of the total weight of the phthalic ester filler.

[0065] The phthalic ester charge may also include mixtures of phthalic esters, for example mixtures of BHET and / or DMT with mono- or diesters of dicarboxylic acid, preferably of phthalic acid such as terephthalic acid or isophthalic acid, and of at least one monomer, dimer or trimer of diol, in particular ethylene glycol, and preferably comprising between 2 and 36 carbon atoms, preferably between 2 and 8 carbon atoms, such as diethylene glycol. These are, for example, mixtures of BHET with mono-(2-hydroxyethyl) terephthalate or MHET, bis-(2-hydroxyethyl) isophthalate or BHEI, 2-(2-hydrohydroxyethyl)ethyl 2-hydroxyethyl terephthalate or BHET-deg. The phthalic ester charge may thus comprise BHET and up to 15.0% wt%, preferably up to 10.0% wt%, preferably up to 5.0% wt%, other dicarboxylic acid esters, in particular BHET-deg, BHEI and / or MHET.

[0066] The phthalic ester filler may further optionally include a solvent, such as a mono-alcohol, in particular methanol or ethanol, or a diol, more particularly ethylene glycol. The phthalic ester filler may in particular include up to 50.0% by weight preferably, up to 30.0% by weight, preferably up to 15.0% by weight, preferably up to 5.0% by weight, preferably up to 1.0% by weight and most preferably up to 0.1% by weight, of solvent, and more particularly of a diol such as ethylene glycol, or only traces of solvent and in particular less than 500 ppm by weight of solvent, preferably diol and in particular ethylene glycol. The phthalic ester filler may also be solvent-free.

[0067] According to a preferred embodiment of the invention, the phthalic ester filler is obtained from a depolymerization process of a polyester filler, in particular a polyester waste filler comprising PET, typically colored and / or opaque PET, and optionally multi-layer PET. More particularly, the phthalic ester filler may be obtained directly or indirectly from the depolymerization, in the presence of a diol, preferably ethylene glycol, of a polyester filler comprising colored and / or opaque PET.The term "indirect issue" means that the depolymerization process includes pre-purification steps for the reaction effluent obtained after the depolymerization reaction in the presence of diol. These steps might include, for example, a separation step for excess diol used in glycolysis or generated during depolymerization, and / or a separation step for heavy impurities such as incompletely converted oligomers, and / or a separation step for ionic species, for example, by passing the effluent through ion-exchange resins. The term "direct issue" means that the depolymerization process does not include such pre-purification steps.

[0068] According to a very particular embodiment of the invention, the phthalic ester feedstock that powers the purification process according to the invention is obtained from a depolymerization process such as that described in French patent application FR 3053691, in which the purification process according to the invention replaces the described decolorization step. More particularly, the phthalic ester feedstock that powers the purification process according to the invention can be a pre-purified monomer effluent, obtained from a depolymerization step by glycolysis followed by a diol separation step and then a separation step of the effluent rich in liquid monomers, as described in French patent application FR 3053691.

[0069] Purification process

[0070] Advantageously, the purification process according to the invention comprises:

[0071] a) an adsorption step for impurities included in the phthalic ester feedstock, by contacting said phthalic ester feedstock, preferably mixed with an adsorption solvent, with at least one adsorbent contained in at least one fixed bed, to obtain a purified phthalic ester effluent; and

[0072] b) a regeneration step by contacting said at least one adsorbent, preferably saturated (or worn), contained in the fixed bed or at least one of the fixed beds, with a regeneration fluid preferably selected from oxygenated, organic or aqueous solvents, and more particularly from water to which at least one surfactant has been added, diols, monoalcohols, esters, ethers, aldehydes, ketones and their mixtures, at a temperature between 90 and 450°C, preferably between 150 and 400°C, and preferably between 250 and 350°C.

[0073] Preferably, the purification process according to the invention uses at least two fixed beds, in particular between two and ten fixed beds, and more particularly between two and six fixed beds, of at least one adsorbent. Preferably, each of said at least two fixed beds of at least one adsorbent is placed, advantageously individually, in an adsorber or a column (called an adsorption column). Said at least two fixed beds of at least one adsorbent used by the purification process can be distributed, in particular when step b) is carried out in situ, as follows:

[0074] - at least one fixed bed, in particular between one and five fixed bed(s), more particularly linked between one and three fixed bed(s), for example one, two or three fixed bed(s), implemented in step a) of adsorption and called fixed bed(s) in operation (or in line); and simultaneously

[0075] - at least one fixed bed, in particular between one and five fixed bed(s), more particularly linked between one and three fixed bed(s), for example one, two or three fixed bed(s), implemented in step b) of regeneration and called fixed bed(s) in regeneration;

[0076] and such that: said at least one fixed bed in regeneration is distinct from said at least one fixed bed in operation and the sum of the number of fixed beds in operation and the number of fixed beds in regeneration is equal to the total number of fixed beds implemented by the purification process.

[0077] Thus, for example, when the purification process uses two fixed beds of adsorbent, a first fixed bed of adsorbent is in operation, i.e., implemented in step a) of adsorption, while simultaneously, the second fixed bed of adsorbent is regenerating, i.e., implemented in step b) of regeneration. Such operation of the two fixed beds of adsorbent is called "swing," after the established English term. In this embodiment, when the adsorbent of the fixed bed in operation (or in line) is worn out (i.e., saturated with impurities), said fixed bed, in particular the adsorber containing said fixed bed, is then isolated, while said fixed bed in regeneration, in particular the adsorber containing the fixed bed in regeneration (or in reserve), is simultaneously brought online (or into operation).The spent adsorbent from the isolated fixed bed is then regenerated so that it can be put back into operation once the other fixed bed is in turn isolated. Thus, each fixed bed is successively operated and implemented in step b) of regeneration; and at any given time, one of the two beds is operating while the other is simultaneously implemented in step b. According to another embodiment, the purification process can implement four fixed beds of adsorbent, three fixed beds are operating while the fourth fixed bed is regenerating. According to yet another embodiment, the purification process can implement... four fixed beds of adsorbent, one fixed bed is in operation while the other three fixed beds are regenerating (or waiting).

[0078] Advantageously, the combination of at least two fixed beds implemented by the process makes it possible to overcome, in particular, clogging and / or potentially rapid saturation of the adsorbent. The presence of at least two fixed beds of adsorbent facilitates the regeneration of said adsorbent, advantageously without stopping the adsorption unit, or even the process, thus reducing the risks of clogging, avoiding unit shutdowns due to adsorbent saturation, controlling costs and limiting adsorbent consumption, while ensuring continuous production of a purified phthalic ester effluent.

[0079] Most advantageously, step b) of regeneration includes an active regeneration phase which corresponds to the contact of the adsorbent of said at least one fixed bed being regenerated with said regeneration fluid, and whose duration is advantageously less than or equal to the duration of step a) of adsorption. In other words, the regeneration (i.e. the active regeneration phase) of the adsorbent in the fixed bed or each fixed bed is carried out for a duration equal to or shorter than the duration of the adsorption phase (i.e. step a), and more particularly the saturation time of the adsorbent of the fixed bed considered), preferably the regeneration of the adsorbent is faster than the adsorption phase (i.e. step a).Step b) of regeneration may also include a standby phase, following the active regeneration phase, during which at least one regenerating fixed bed or at least one of the regenerating fixed beds, in which the adsorbent is regenerated, is put on standby (or in reserve). During the standby phase of step b), the circulation of the regeneration fluid is stopped in said regenerating fixed bed or at least one of said regenerating fixed beds, which is / are then put on standby (or in reserve) before being put back into operation (i.e., being put back into operation in step a) of adsorption).When step b) of regeneration employs several fixed beds of at least one adsorbent, the waiting phase includes bypassing the circulation of the regeneration fluid in at least one fixed bed in regeneration of the series, preferably in the first fixed bed in the series of fixed beds in regeneration, then if necessary the second, and so on up to all the fixed beds in regeneration if required.

[0080] When the adsorption step a) employs several fixed beds of at least one adsorbent, in particular between two and five, for example two or three fixed beds of at least one adsorbent, said fixed beds preferably operate in series and in particular in a lead-lag configuration. The term "lead-lag" here means that the fixed beds in the series are implemented in step a) with staggered start times relative to each other, the first fixed bed The first fixed bed in the series of operating fixed beds (or head bed) is the oldest in operation, meaning it has the longest implementation period in step a) (the earliest start date in step a) compared to the other operating beds. It is also the first in the series of operating fixed beds to switch over first in step b) of regeneration. This is because when the adsorbent in the head fixed bed (i.e., the first fixed bed in the series of operating fixed beds) is worn out (or saturated), this first fixed bed in the series is isolated, specifically its supply of phthalic ester charge is stopped, and it undergoes step b) of regeneration. The worn adsorbent it contains is then regenerated.At the end of regeneration step b), the fixed bed will then be put back into operation (or into operation) in the last position in the series of operating fixed beds, and so on. This combination of at least two fixed beds of adsorbent in series in adsorption step a), particularly operating in "lead-lag" in adsorption step a), advantageously maximizes the adsorption capacity of said adsorbent.

[0081] When regeneration step b) employs several fixed beds of at least one adsorbent, in particular between two and five, for example two or three fixed beds of at least one adsorbent, said fixed beds in regeneration preferably operate in series and in particular in lead-lag.The Anglo-Saxon term "lead-lag" here means that the fixed beds in regeneration of the series are implemented in step b) with a staggered start of implementation in time relative to each other, the first fixed bed in the series of fixed beds in regeneration being the oldest fixed bed in regeneration, i.e., whose implementation in step b) is the longest (the start of implementation in step b) furthest in time) relative to the other beds in regeneration of the series; it is also the first of the series of fixed beds in regeneration that will switch first to the adsorption step a), advantageously in last position of the fixed beds in operation, and the first fixed bed previously in operation which includes the saturated (or used) adsorbent will be implemented in step b) and positioned in last position of the series of fixed beds in regeneration.This embodiment of step b), in lead-lag mode of the fixed beds in regeneration (preferably between 2 and 5, for example 2 or 3 fixed beds in regeneration), allows for efficient or even improved regeneration, particularly in situ, of said at least one adsorbent. This embodiment thus makes it possible to maximize the adsorption capacity of the adsorbent during the subsequent adsorption step.

[0082] Thus, advantageously, when said at least one adsorbent of said at least one fixed bed implemented in step a) is saturated, the fixed bed in operation or the first fixed bed in operation of the series of fixed beds in operation switches to step b) of regeneration and becomes the fixed bed in regeneration or the last fixed bed in regeneration generation of the series of fixed beds in regeneration, and simultaneously the fixed bed in regeneration or the first fixed bed in regeneration of the series of fixed beds in regeneration switches to step a) and becomes the fixed bed in operation or the last fixed bed in operation of the series of fixed beds in operation.

[0083] The purification process according to the invention advantageously uses at least one adsorbent and preferably up to five different adsorbents, preferably in said fixed bed or in each of said fixed beds. In a very particular embodiment, the purification process uses one or two different adsorbents, preferably in said fixed bed or in each of said fixed beds. According to the invention, adsorbents are said to be different when their nature and / or composition and / or particle size and / or textural characteristics, such as pore volume, is / are different. Preferably, different adsorbents are of different natures. It can indeed be advantageous to combine several different adsorbents, particularly those of different natures, in order to optimize the removal of impurities from the phthalic ester charge, in particular dyes and / or salts, impurities whose nature can be very varied.Indeed, when phthalic ester filler originates from the depolymerization of polyester waste, such as PET packaging waste or plastic bottles, it can contain a very large number of colored and / or opaque PET particles and therefore a very large number of different coloring compounds. The coloring of the phthalic ester filler can also result from the degradation or transformation of compounds contained in the polyester waste during the various stages of a depolymerization process from which the phthalic ester filler may originate.

[0084] Preferably, said at least one adsorbent is selected from activated carbons, aluminas, clays, and mixtures thereof. The activated carbons are, for example, derived from petcoke, coal, or any other fossil source, or from biomass such as wood, coconut, or any other biomass source. Different raw materials can also be mixed to obtain activated carbons that can be used as adsorbents. The clays can be layered double hydroxides or natural or processed clays such as those known to those skilled in the art as bleaching earths. Preferably, at least one adsorbent comprises an activated carbon.Thus, when the purification process uses only one type of adsorbent, said adsorbent is activated carbon, and when it uses two or more different adsorbents, one adsorbent is activated carbon and the other(s) is / are another activated carbon, alumina, and / or clay, preferably activated carbon and / or clay. According to a highly preferred embodiment, the purification process of the invention uses one adsorbent, and said adsorbent is activated carbon. Preferably, each adsorbent used has a pore volume (Vp), determined by mercury porosimetry, greater than or equal to [value missing]. 0.25 ml / g, preferably greater than or equal to 0.40 ml / g, preferably greater than or equal to 0.50 ml / g, and preferably less than or equal to 5 ml / g.

[0085] Advantageously, said at least one adsorbent used in step a) may be:

[0086] i) a fresh adsorbent, or mixture of adsorbents, i.e. from a preparation process of said at least one adsorbent (external to said purification process) and being used in an adsorption step for the first time; or

[0087] ii) a regenerated adsorbent, or mixture of regenerated adsorbents, advantageously obtained at the end of step b) of regeneration.

[0088] Preferably, in step a) of adsorption, the phthalic ester filler is mixed with an adsorption solvent, upstream of contact with said at least one adsorbent contained in said at least one fixed bed in operation. The quantity of adsorption solvent introduced is very advantageously adjusted so that the phthalic ester filler represents preferably between 20 and 90% by weight, preferably between 30 and 80% by weight, most preferably between 40 and 75% by weight, and even more preferably between 40 and 60% by weight, of the total weight of the mixture consisting of the phthalic filler and the adsorption solvent. The adsorption solvent is advantageously chosen from: water, monoalcohols preferably comprising 1 to 6 carbon atoms (C1-C6), diols preferably comprising at least 2 carbon atoms (C2+), preferably 2 to 4 carbon atoms (C2-C4). Preferably, the adsorption solvent is water.The addition of an adsorption solvent, preferably water, advantageously in the proportions indicated, contributes advantageously to improving adsorption and thus helps to effectively remove at least some of the impurities present in the phthalic ester charge.

[0089] Advantageously, the adsorption step (a) is carried out at a temperature between 60 and 150°C, preferably between 70 and 120°C, preferably between 75 and 110°C, and preferably at a pressure between 0.1 and 1.0 MPa, preferably between 0.1 and 0.8 MPa, preferably between 0.1 and 0.5 MPa. Most advantageously, each adsorber in the adsorption step (a) is operated with a residence time preferably between 20 minutes and 40 hours, preferably between 1 and 30 hours, preferably between 1 and 20 hours. The residence time is defined here as the ratio between the internal volume of the adsorber considered and the volumetric flow rate of the phthalic ester feedstock or the mixture consisting of the phthalic ester feedstock and the adsorption solvent.

[0090] Preferably, the adsorption is implemented in traversed fixed bed mode (or fixed bed), that is to say in at least one fixed bed adsorber of adsorbent(s), in particular at least one column of adsorbent(s), preferably operating in ascending or descending mode, preferably in descending mode.

[0091] Said adsorption step a) thus makes it possible to obtain, advantageously continuously, a purified phthalic ester effluent. Optionally, said purified phthalic ester effluent can then be sent to a crystallization section in which crystals of the phthalic ester initially present in the phthalic feed, for example from BHET, are formed and then separated and dried.

[0092] During the adsorption step a), said at least one adsorbent contained in the fixed bed(s) in operation becomes loaded with impurities until it is saturated (or worn out).The said at least one spent absorbent from the said at least one fixed bed in operation or from at least one of the fixed beds in operation, advantageously from the fixed bed(s) in operation implemented in step a) for the longest time in the series of fixed beds in operation (which is / are advantageously the first fixed bed(s) in the series of fixed beds in operation) can then be regenerated during step b); the fixed bed which contains the said at least spent absorbent then switches to the regeneration step b) and simultaneously the said at least one fixed bed in regeneration or at least one of the fixed beds in regeneration, advantageously the fixed bed(s) in regeneration maintained in regeneration for the longest time (i.e. preferably the first fixed bed(s) in regeneration of the series) then switches to step a) and becomes in operation.

[0093] During regeneration step b), the flow of phthalic ester charge or of the mixture of phthalic ester charge and adsorption solvent advantageously no longer passes through said at least one fixed bed in regeneration.

[0094] Regeneration consists of bringing the saturated adsorbent into contact with a hot regeneration fluid, i.e., at a high temperature or at least higher than the operating temperature of step a) adsorption, so as to promote the desorption of impurities in order to recover a regenerated adsorbent whose adsorption capacity is advantageously at least partially restored. The desorption of impurities is achieved efficiently, both by increasing the temperature and by the competitive adsorption of the regeneration fluid.

[0095] The regeneration of the adsorbent in the fixed bed(s) is advantageously faster or as long, in terms of time, as the adsorption step (a). Thus, the regeneration step (b) advantageously comprises an active regeneration phase, which corresponds to a phase during which a regeneration fluid is brought into contact with said at least one adsorbent contained in said at least one fixed bed being regenerated, said active phase having a duration less than or equal to the duration of the adsorption step (a), preferably less than the duration of step (a). At the end of the active regeneration phase of step (b), the adsorbent contained in said at least one fixed bed being regenerated is regenerated and can be put back into operation. The regeneration step (b) may also comprise a waiting phase, following the active regeneration phase, during which said at least one fixed bed being regenerated or at least one fixed beds in regeneration are put on hold (or in reserve), before switching to step a).

[0096] The regeneration fluid is advantageously a liquid, under the operating conditions of the contact in said step b). The regeneration fluid is preferably an oxygenated, aqueous, or organic solvent. More particularly, the regeneration fluid is chosen from water with at least one surfactant added, diols, monoalcohols, esters, ethers, aldehydes, ketones, and mixtures thereof.

[0097] According to one embodiment of the invention, the regeneration fluid is water to which at least one surfactant has been added, preferably a surfactant. This at least one surfactant increases the affinity of impurities for the regeneration fluid, particularly for water. The water to which the additives have been added therefore comprises at least one surfactant at a weight content typically less than 10% by weight, preferably less than 5% by weight of the surfactant(s) relative to the total weight of the water to which the additives have been added. This at least one surfactant is chosen by a person skilled in the art based on their knowledge and, in particular, on the concept of hydrophilic-lipophilic balance, or HLB for "Hydrophilic-Lipophilic Balance" according to the Anglo-Saxon terminology. Preferably, said at least one surfactant of the added water used as a regeneration fluid has an HLB greater than 12, preferably between 12 and 20.Preferably, said at least one surfactant is selected from anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants, most preferably from anionic and nonionic surfactants. For example, said at least one surfactant is selected from: polysorbates, in particular polysorbate 20 (or polyoxyethylene sorbitan monolaurate), polysorbate 80 (or polyoxyethylene sorbitan monooleate), polysorbate 40 (polyoxyethylene sorbitan monopalmitate); stearates such as calcium stearate, sodium stearate; oleates such as sodium oleate, potassium oleate; stearyl alcohol; sodium dodecyl sulfate; ammonium dodecyl sulfate; Poloxamers; quaternary ammonium salts.

[0098] According to another embodiment of the invention, the regeneration fluid is an oxygenated organic solvent, preferably selected from: diols preferably comprising at least 2 carbon atoms (i.e., C2+), preferably between 2 and 4 carbon atoms (i.e., C2-C4); mono-alcohols preferably comprising between 1 and 6 carbon atoms (i.e., C1-C6); esters preferably comprising between 2 and 6 carbon atoms (i.e., C2-C6); ethers, in particular linear or cyclic, and preferably comprising between 2 and 6 carbon atoms (i.e., C2-C6); aldehydes preferably comprising between 3 and 6 carbon atoms (i.e., C3-C6); ketones preferably comprising between 3 and 6 carbon atoms (i.e. C3-C6), and their mixtures.

[0099] Preferably, the regeneration fluid is a diol, preferably comprising at least 2 carbon atoms, preferably between 2 and 4 carbon atoms and most preferably a diol comprising 2 carbon atoms such as ethylene glycol.

[0100] Advantageously, the quantity of regeneration fluid required, expressed as a volume of regeneration fluid per volume of adsorbent in contact with said regeneration fluid, is between 1 and 50, preferably between 5 and 30 and even more preferably between 5 and 20.

[0101] The active phase of regeneration step b) is advantageously carried out at a temperature between 90 and 450°C, preferably between 150 and 400°C, and preferably between 250 and 350°C, and preferably at a pressure between 0.1 and 7.0 MPa, in particular between 0.1 and 3.0 MPa and more particularly between 0.2 and 2.5 MPa. Preferably, regeneration step b) is carried out for a duration between 0.5 and 200 hours, and preferably at a surface velocity between 0.01 and 5.00 cm / s. The surface velocity (or linear velocity) is the velocity in the empty adsorber, i.e. without adsorbent; It corresponds advantageously to the volumetric flow rate (Qv) of the fluid feeding the adsorber, i.e. of the regeneration fluid in step b), with respect to the surface area (S) of the section of the adsorber (i.e. surface velocity = Qv / S).

[0102] Step b) of regeneration can be carried out in situ, i.e. directly in the adsorber(s) comprising said at least one fixed bed in regeneration and implemented in step b), or ex situ, i.e. in a unit external to the process, after unloading the spent adsorbent from the fixed bed(s) implemented in step b). Preferably, step b) of regeneration is carried out in situ.

[0103] Advantageously, the regeneration fluid flows through said at least one fixed bed in regeneration in the same or opposite direction, preferably opposite, to that of the phthalic ester charge flowing in said at least one fixed bed when it is in operation.

[0104] According to a preferred embodiment of the invention, the regeneration step b) employs several fixed beds, preferably between 2 and 5, for example 2 or 3 fixed beds, advantageously in series and particularly in a lead-lag configuration. Thus, most preferably, in step b), particularly when carried out in situ (i.e., in the same unit as in step a), the regeneration fluid flows through several regenerating fixed beds, preferably in the opposite direction to the flow of the phthalic ester charge or the mixture consisting of the phthalic ester charge and the adsorption solvent through said fixed beds when they are used in step a), the newly implemented fixed bed in step b) being positioned at the end of the series of regenerating fixed beds. This embodiment allows for regeneration, by particular in situ, effective, or even improved, of said at least one adsorbent, and advantageously allows maximizing the adsorption capacity of the adsorbent.

[0105] Said regeneration step b) advantageously comprises an active regeneration phase, which corresponds to a phase during which a regeneration fluid is brought into contact with said at least one adsorbent contained in said at least one fixed bed being regenerated. Said regeneration step b) may further comprise a waiting phase, following the active regeneration phase, during which the circulation of the regeneration fluid is stopped in said at least one fixed bed being regenerated or in at least one of the fixed beds being regenerated. Said fixed bed(s) being regenerated in which the circulation of the regeneration fluid is stopped is / are thus put into reserve (or standby) before being put back into operation (i.e., being implemented in adsorption step a).When the regeneration stage employs several fixed beds, the waiting phase includes bypassing the regeneration fluid circulation in at least one regenerating fixed bed of the series, preferably in the first fixed bed of the series of regenerating fixed beds, then if necessary the second, then the third, and so on up to all regenerating fixed beds if required.

[0106] During step b), and more particularly during the active phase of step b), e, the regeneration fluid recovered from the outlet of said at least one fixed bed undergoing regeneration is typically laden with impurities. It can optionally be treated, for example by distillation, so that it can be reused in the purification process, or even in a more comprehensive process in which the purification process according to the invention is integrated.

[0107] Indeed, the purification process according to the invention can be integrated as a purification step for a stream comprising at least one phthalic ester, such as bis-(2-hydroxyethyl) terephthalate (BHET), in a recycling process for a polyester feedstock comprising, in particular, polyethylene terephthalate (PET), said recycling process comprising a depolymerization step for the polyester, and in particular for the PET, more particularly a depolymerization step by glycolysis. For example, the purification process according to the invention can be integrated into the process described in French patent application FR 3053691, as a decolorization step for the pre-purified monomer effluent, resulting from a depolymerization step by glycolysis followed by a diol separation step and then a separation step for the effluent rich in liquid monomers.

[0108] The process according to the invention makes it possible to continuously and efficiently purify a crude stream of phthalic esters, and in particular a crude stream of phthalic esters obtained after depolymerization, notably by glycolysis, of polyester waste typically comprising colored, opaque, or even multi-layered PET and therefore consequently pigments and dyes. The process according to the invention allows for the purification of such a stream while limiting the risk of clogging of the adsorption unit and preventing downtime of said unit that could be caused by adsorbent saturation. Another advantage of the process according to the invention is that it maximizes the adsorption capacity of said adsorbent. The process according to the invention also reduces adsorbent consumption and, more broadly, controls the production costs of purified phthalic esters, while ensuring efficient and continuous purification of said phthalic esters.

[0109] The following figures and examples illustrate the invention without limiting its scope. List of figures [Fig 1]

[0110] Figure 1 illustrates an embodiment of the purification process according to the invention, in which the process employs two fixed-bed columns, C1 and C2, each containing the same adsorbent, preferably activated carbon, and preferably operating in a swing configuration. The solid arrows represent the feed to be treated, for example, a mixture of bis-(2-hydroxyethyl) terephthalate and water, said mixture being, in particular, at 90°C. The dashed arrows represent the regeneration fluid, for example, ethylene glycol, at 300°C. Figure 1a shows a first phase of the process: the feed to be treated is sent to the fixed-bed column C1, which is in operation, while the fixed-bed column C2 is either in reserve or undergoing regeneration.The regeneration fluid in C2 is introduced in the opposite direction to the feed in CL. Phase 2, shown in Figure 1b), begins when the adsorbent in the fixed-bed column Cl reaches saturation: the feed to be treated is then sent to the fixed-bed column C2, which is then in operation, while the fixed-bed column Cl is in regeneration, or in reserve. When the adsorbent in the fixed-bed column C2 is saturated, phase 1 starts again, and so on. [Fig 2]

[0111] Figure 2 illustrates another embodiment of the purification process according to the invention, in which the process employs four fixed-bed columns, C1 to C4, each containing the same adsorbent, preferably activated carbon. Three of these columns operate in lead-lag mode during the adsorption step (a), and the fourth is in regeneration mode. The solid arrows represent the feedstock to be treated, for example, a mixture of bis-(2-hydroxyethyl) terephthalate and water, said mixture being, in particular, at 90°C. The dashed arrows represent the regeneration fluid, for example, ethylene glycol, at 300°C.

[0112] During a first phase (Figure 2a), the charge to be treated passes through the fixed-bed column Cl, then C2 and then C3, said fixed-bed columns Cl, C2, C3 being then in function During operation, the fixed-bed column C4 is either in reserve or undergoing regeneration. The regeneration fluid is introduced into C4 in the opposite direction to that of the feed to be treated. In phase 2 (Figure 2b), the newly regenerated fixed-bed column, C4, is placed last in the series of operating fixed-bed columns to ensure better purification. Simultaneously, the most saturated columns are placed closest to the feed inlet. The same logic applies to phases 3 and 4 (Figure 2c and Figure 2d, respectively).

[0113] When the adsorbent of the fixed bed column C4 is saturated, phase 1 starts again, and so on. [Fig 3]

[0114] Figure 3 illustrates another embodiment of the purification process according to the invention, in which the process employs three fixed-bed columns, C1, C2, and C3, each containing the same adsorbent, preferably activated carbon, one of which is in regeneration mode and the other two operating as lead-lag during regeneration step b). The solid arrows represent the feedstock to be treated, for example, a mixture of bis-(2-hydroxyethyl) terephthalate and water, said mixture being, in particular, at 90°C. The dashed arrows represent the regeneration fluid, for example, ethylene glycol, at 300°C.

[0115] In a first phase (Figure 3a), the feed to be treated passes through the fixed-bed column C1, while the regeneration fluid flows through C3 and then C2. The regeneration fluid is introduced in the opposite direction to that of the feed. In phase 2 (Figure 3b), the fixed-bed column C1 containing the spent adsorbent is positioned as far as possible from the inlet of the regeneration fluid, in order to optimize regeneration efficiency and, in particular, to optimize the desorption of impurities. The fixed-bed column C3, previously located first in the series of fixed-bed columns undergoing regeneration, switches to operation, i.e., switches to the adsorption step a).The same logic applies to phase 3 (Figure 3c): the fixed bed column C3, now containing the spent adsorbent, switches to regeneration step b) and is placed furthest from the regeneration fluid inlet, and the fixed bed column C2, previously located in the first position in the series of fixed bed columns in regeneration, switches to operation, i.e. switches to adsorption step a).

[0116] When the adsorbent of the fixed bed column C3 is saturated, phase 1 starts again, and so on. EXAMPLES

[0117] In the following examples, the steps leading to obtaining the raw BHET charge are identical and described below.

[0118] A polyester filler comprising in particular 20% by weight of opaque PET is derived Collection and sorting channels are established for processing. Four kg / h of flakes of the polyester filler, comprising 20% ​​by weight of opaque PET which itself contains 6.2% by weight of TiO2 pigment, are heated to 250°C and then injected with 11.5 kg / h of ethylene glycol (MEG) into a first stirred reactor maintained at 250°C, then into a second and third stirred reactor maintained at 220°C. The reactors are maintained at a pressure of 0.4 MPa. The residence time, defined as the ratio of the liquid volume in the reactor to the sum of the liquid volumetric flow rates entering the reactor, is set at 20 min in the first reactor and 2.1 h in the second and third reactors.At the outlet of the third reactor, the reaction effluent consists of 67.7% by weight of diol composed predominantly of ethylene glycol (MEG) (i.e. comprising 95% by weight or more of MEG), 25.8% by weight of diester monomer composed predominantly of bis-(2-hydroxyethyl) terephthalate (BHET) (i.e. comprising 95% by weight or more of BHET), 0.32% by weight of TiO2, and 6.1% by weight of heavy compounds containing, among other things, dimers and / or oligomers.

[0119] The diol present in the reaction effluent is separated by evaporation in a series of two flash flasks at temperatures ranging from 180°C to 120°C and pressures from 0.04 MPa to 0.004 MPa, followed by a scraped-film evaporator operated at 175°C and 0.0005 MPa. Following this evaporation step, a MEG-rich stream of 10.46 kg / h and a BHET-rich liquid stream of 5.02 kg / h are recovered. The BHET-rich liquid stream, corresponding to the liquid monomer effluent, consists of 79.6 wt% BHET diester monomer, 0.6 wt% MEG, 1.0 wt% TiO2, and 18.8 wt% heavy compounds containing, among other things, BHET dimers.

[0120] The BHET-rich liquid stream is then injected into a short-path evaporator, also known as short-path distillation, operated at a pressure of 20 Pa. Hot oil at 215°C evaporates the BHET, which is then condensed in the short-path evaporator at 130°C to produce a BHET liquid stream as the short-path evaporator distillate, at a flow rate of 3.8 kg / h. The residence time in the short-path evaporator is 1 min. The BHET liquid stream recovered from the short-path evaporator corresponds to the crude BHET, which is the feedstock for the purification processes described in Examples 1 and 2 below. It consists of 99% by weight of BHET diester monomer and is free of any trace of TiO2.A heavy residue with a flow rate of 1.19 kg / h is also recovered as a residue from the short-path evaporator and comprises 16.7 wt% of BHET diester monomer, 79.2 wt% of BHET oligomers and 4.1 wt% of TiO2. Example 1 (compliant):

[0121] The crude BHET obtained is compressed to 0.15 MPa and feeds a section of The mixture is also supplied with a water flow. The water supply rate is adjusted so that the raw BHET represents 50% of the mixture's weight (raw BHET + water). This mixing section is operated at 90°C, at a pressure of 0.15 MPa.

[0122] In a first phase, an adsorption step is carried out: the resulting mixture (crude BHET + water) feeds a column filled with an adsorbent (i.e., a fixed bed of adsorbent). The adsorption section is operated at 90°C, at a pressure of 0.15 MPa. The column is then energized (i.e., it is in operation). The adsorbent used to fill the column is an activated carbon consisting of cylindrical extrudates 0.8 mm in diameter, reference ROY 0.8 from Cabot Norit.

[0123] The residence time is set at 40 minutes in a column. The linear velocity (or surface velocity) in an empty drum is 2.4 cm / min.

[0124] The effluent composed of BHET at 50% by weight in the mixture (BHET+water) is collected at the column outlet over time.

[0125] The system is left running until colored effluents appear at the outlet of the second column in adsorption mode. The activated carbon contained in the column is then considered to be used up.

[0126] In parallel, during this same first phase, a regeneration step is carried out in a second column of the same volume as the operating column and containing spent activated carbon (the same quantity of spent activated carbon as the quantity of activated carbon in the operating column). This second column has previously undergone an adsorption step carried out in a previous phase according to the same protocol as that described for the adsorption step above. Regeneration is performed by heating the second column to 300°C and circulating 15 volumes of ethylene glycol (relative to the volume of the column to be regenerated) in the direction of fluid flow opposite to that of the mixture (crude BHET + water) carried out during the adsorption step performed in a previous step.

[0127] The ethylene glycol effluent obtained at the outlet of the column during the regeneration step The regeneration process is colored, with the intensity of the observed color decreasing with the amount of regeneration ethylene glycol eluted. The color of the effluent at the column outlet reflects the desorption of colored species present on the spent Tadsorbent. At the end of the regeneration step, the activated carbon is then considered regenerated.

[0128] In a second phase, the first column, i.e., the column in operation (or in adsorption mode) in the first phase, switches to regeneration mode, and simultaneously the second column, which contains the regenerated adsorbent, switches to adsorption mode. Regeneration in the first column is carried out under the same conditions as those described for the first phase above, i.e., by heating the spent adsorbent to 300°C and circulating 15 volumes Ethylene glycol (relative to the volume of the column to be regenerated) is added in the opposite direction of fluid flow to that of the (crude BHET + water) mixture in the first column during the first phase (i.e., when it was in adsorption mode). Simultaneously, adsorption in the second column is carried out under the same conditions as those described above for the adsorption step in the first column, that is, with the same (BHET + water) mixture to be decolorized, same temperature, same flow rate, and same direction of flow (i.e., a direction of flow opposite to that of the ethylene glycol flow during regeneration). The direction of flow is thus opposite to that of the regeneration phase.

[0129] The BHET-water effluent collected at the outlet of the second column, which is in adsorption mode during the second phase, does not have any color.

[0130] The use of ethylene glycol as a regeneration solvent makes it possible to regenerate the spent adsorbents generated during the purification by adsorption of a BHET-water mixture. Example 2 (non-compliant):

[0131] The crude BHET obtained is mixed with water as described in Example 1.

[0132] The mixture (crude BHET + water) is sent to an adsorption unit identical to that described in Example 1 to undergo an adsorption step during a first phase, under the same conditions as those described in Example 1 in the adsorption step of the first phase. During this adsorption step, the said first column containing new (or fresh) Cabot Norit ROY 0.8 activated carbon is positioned in adsorption mode for the treatment of the mixture (raw BHET + water) at 90°C, 0.15 MPa, with a residence time of 40 minutes per column and at a linear velocity (or surface velocity) in empty drum of 2.4 cm / min.

[0133] As in Example 1, a second column contains spent activated carbon obtained from an adsorption step in a previous phase and conducted under conditions identical to those described above. In parallel with the adsorption step, during this first phase, a regeneration step is carried out in the second column to regenerate the spent adsorbent. Regeneration is performed at 200°C by circulating 15 volumes of water (relative to the volume of the columns to be regenerated) in the opposite direction of fluid flow to that used during the adsorption of the previous phase. The aqueous effluent obtained from the column outlet during regeneration is colorless, indicating the non-desorption of the dyes present on the spent adsorbent in the second column.

[0134] In a second phase, the first column, initially in adsorption in the first phase, switches to regeneration, and simultaneously the second column, in which regeneration by water circulation was implemented during the first phase, switches to adsorption. The regeneration in the first column is then The second column is operated under the same conditions as those described above during the first phase, i.e., by heating the spent adsorbent to 200°C and circulating 15 volumes of water (relative to the volume of the column to be regenerated) in the opposite direction of fluid flow to that of the (raw BHET + water) mixture used during the adsorption step in the first phase. Adsorption in the second column is carried out under the same conditions as those described above for the adsorption step in the first column during the first phase (identical in examples 1 and 2, i.e., with the same BHET-water mixture to be decolorized, same temperature, same flow rate, and same direction of flow, i.e., a direction of flow opposite to that of the water flow during regeneration).

[0135] The BHET-water effluent obtained at the outlet of the second column, which is in operation (in adsorption) during the second phase, is colored, which means that the regeneration of the used adsorbent, carried out by water circulation in example 2, has not worked.

[0136] The use of water as a regeneration solvent does not allow the regeneration of spent adsorbents generated during the purification by adsorption of a BHET-water mixture.

Claims

Claims

1. A method for purifying a phthalic ester feedstock, comprising: a) an adsorption step by bringing said phthalic ester feedstock into contact with at least one adsorbent contained in at least one fixed bed, said adsorption step a) being carried out at a temperature of between 60 and 150°C, to obtain a purified phthalic ester effluent; then b) a regeneration step comprising bringing a regeneration fluid into contact with said at least one adsorbent contained in said fixed bed or at least one of said fixed beds, said contacting of regeneration step b) being carried out at a temperature of between 90 and 450°C, to obtain a regenerated adsorbent in said fixed bed or at least one of said fixed beds at the end of the regeneration step; in step a), said at least one adsorbent being a fresh adsorbent or said regenerated adsorbent.

2. Method according to claim 1, in which the phthalic ester filler comprises a terephthalic diester, preferably bis-(2-hydroxyethyl) terephthalate, in particular resulting from the depolymerization of a polyester filler comprising PET.

3. Method according to claim 1 or 2, using at least two fixed beds, in particular between two and ten fixed beds, or even between two and six fixed beds, of at least one adsorbent.

4. Method according to one of the preceding claims, in which step a) of adsorption is carried out at a temperature between 70 and 120°C, preferably between 75 and 110°C, and preferably at a pressure between 0.1 and 1.0 MPa, preferably between 0.1 and 0.8 MPa, preferably between 0.1 and 0.5 MPa.

5. Method according to one of the preceding claims, in which the regeneration step b) is carried out at a temperature between 150 and 400°C, and preferably between 250 and 350°C, and preferentially at a pressure between 0.1 and 7.0 MPa, in particular between 0.1 and 3.0 MPa and more particularly between 0.2 and 2.5 MPa.

6. Method according to one of the preceding claims, in which the regeneration fluid is an oxygenated solvent, more particularly chosen from water with the addition of at least one surfactant, diols, monoalcohols, esters, ethers, aldehydes, ketones and mixtures thereof; in particular chosen from diols comprising preferably at least 2 carbon atoms, preferably between 2 and 4 carbon atoms; mono-alcohols preferably comprising between 1 and 6 carbon atoms; esters preferably comprising between 2 and 6 carbon atoms; ethers, in particular linear or cyclic and preferably comprising between 2 and 6 carbon atoms; aldehydes preferably comprising between 3 and 6 carbon atoms; ketones preferably comprising between 3 and 6 carbon atoms; and mixtures thereof.

7. Method according to one of the preceding claims, in which the regeneration fluid is a diol preferably comprising at least 2 carbon atoms, preferably between 2 and 4 carbon atoms and very preferably a diol comprising 2 carbon atoms such as ethylene glycol.

8. Method according to one of the preceding claims, in which, in step b), the regeneration fluid circulates through said at least one adsorbent in an amount such that the volume ratio between the volume of the regeneration fluid and the volume of said at least one adsorbent brought into contact with said regeneration fluid is between 1 and 50, preferably between 5 and 30, more preferably between 5 and 20.

9. Method according to one of the preceding claims, in which the regeneration step b) comprises an active phase, an active regeneration phase during which the regeneration fluid is brought into contact with said at least one adsorbent contained in said at least one fixed bed in regeneration, and a waiting phase at the end of the active regeneration phase and during which the circulation of the regeneration fluid is stopped.

10. A method according to one of the preceding claims, wherein said regeneration fluid circulates through said fixed bed or said at least one of said fixed beds in regeneration step b) in a direction opposite to that of the phthalic ester feed circulating in said fixed bed or said at least one of said fixed beds in adsorption step a).

11. Method according to one of the preceding claims, in which step b) of regeneration is carried out in situ.

12. Method according to one of the preceding claims, implementing at least two fixed beds of at least one adsorbent, and in which: step a) implements at least one fixed bed of at least one adsorbent, said at least one fixed bed implemented in step a) being called a fixed bed in operation, and when step a) of adsorption implements several fixed beds of at least one adsorbent, said fixed beds in operation being in series; and simultaneously step b) uses at least one fixed bed of at least one adsorbent, said at least one fixed bed used in step b) being called a fixed bed in regeneration, and when step b) of regeneration uses several fixed beds of at least one adsorbent, said fixed beds in regeneration being in series, said at least one fixed bed in regeneration being distinct from said at least one fixed bed in operation and the sum of the number of fixed beds in operation and the number of fixed beds in regeneration being equal to the total number of fixed beds implemented by the purification process, said regeneration fluid circulating through said at least one fixed bed in regeneration in a direction identical or opposite, preferably opposite, to that of the phthalic ester feed circulating in said at least one fixed bed when the latter is in operation, in which the fixed bed in operation or the first fixed bed in operation in the series of fixed beds in operation switches to regeneration step b) and becomes the fixed bed in regeneration or the last fixed bed in regeneration in the series of fixed beds in regeneration, and simultaneously the fixed bed in regeneration or the first fixed bed in regeneration in the series of fixed beds in regeneration switches to adsorption step a) and becomes the fixed bed in operation or the last fixed bed in operation in the series of fixed beds in operation.

13. Method according to one of claims 11 and 12, in which the adsorption step a) uses between one and five fixed bed(s) of at least one adsorbent, for example one, two or three fixed bed(s) of at least one adsorbent.

14. Method according to one of claims 11 to 13, in which the regeneration step b) uses between one and five fixed bed(s) of at least one adsorbent, for example one, two or three fixed bed(s) of at least one adsorbent.

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