RU2458946C2 - Method for ethanolysis of poly(ethylene terephthalate) (pet) with formation of diethylene terephthlate (det) - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a method of processing polyethylene terephthalate wastes. The method involves ethanolysis of polyethylene terephthalate (PET), in which material containing PET reacts with ethanol. Ethylene glycol and an aromatic diethyl ester, such as diethyl isophthalate and/or diethyl terephthalate, are separated. PET or a terpolymer containing a terephthalate monomer and ethylene glycol monomers react with ethanol and ethanol, diethyl terephthalate, ethylene glycol and optionally diethyl isophthalate are separated. The separated diethyl components can undergo liquid-phase oxidation to obtain an aromatic carboxylic acid. Acetic acid can also be obtained via liquid-phase oxidation of the separated diethyl components. Aromatic carboxylic acid can be used to obtain polymers. The invention also describes apparatus for processing polyethylene terephthalate wastes. The apparatus includes a reactor, a distillation column operating at atmospheric pressure and a vacuum distillation column.

EFFECT: high efficiency of the method.

29 cl, 1 dwg, 8 tbl, 8 ex

Description

BACKGROUND OF THE INVENTION

The present invention provides a method for oxidizing aromatic ethyl esters and utilizing poly (ethylene terephthalate) (PET) and other polymers containing ethylene monomers and ester monomers, in particular aromatic ester monomers. The invention also provides a method for processing waste polymers containing PET and optionally other polymers. The present invention provides a method for isolating ethylene glycol and ethyl esters from polymer wastes and preparing polymers from them. The invention also provides raw materials with components from ethyl esters of aromatic acids to produce aromatic carboxylic acids and a method for producing acetic acid and aromatic carboxylic acids.

PET and other copolymers, for example polyethylene isophthalate (PEI), polyethylene naphthalate (PEN) and others, are commonly used in films, fibers, packaging and many other applications. The widespread use of such polymers has generated increased interest in the disposal of products made from them. Many white papers require or offer incentives for recycling polymers. In addition, consumers and the consumer-oriented business are increasingly interested in using or selling recycling products. The term "polymers" as used herein includes copolymers. As used herein, an “ester ethylene polymer” means a polymer containing at least ester monomers and ethylene monomers, which may contain other monomer components. The term “aromatic ester ethylene polymer” refers to an ester ethylene polymer in which the ester monomers contain one or more aromatic rings.

One way to utilize such polymer products is to mix polymer wastes with freshly prepared polymer. Unfortunately, polymer products and, consequently, polymer wastes often contain significant amounts of impurities, which significantly limit their processing capabilities. Often polymer wastes contain adhesives, metals, dyes and many other pollutants that make such wastes unsuitable for many processing methods. In some cases, the polymer products contain many different polymers or copolymers, which increase the difficulty of processing. For example, in the case of PET, it is believed that impurities of PEI and phthalic anhydride derivatives often make it impossible to process them. For products that include several different types of polymers, mixing waste and fresh polymer may not be acceptable. In addition, the mixing of waste and fresh product often leads to significant decomposition under the action of waste, which makes the resulting mixed polymer unsuitable for many processing methods.

An alternative processing method is methanolysis, in which PET is reacted with methanol to give dimethyl terephthalate (DMT) and ethylene glycol. Although methanolysis methods allow slightly larger amounts of impurities, these methods are extremely limited in their ability to dispose of contaminated products. In addition, products containing several different types of polymers are generally not suitable for methanolysis or significantly reduce the efficiency of methanolysis; examples are products containing a mixture of PET with polyvinyl chloride or other halogenated polymers or polymers containing a significant amount of metals. PET methanolysis has other significant disadvantages, including difficulties in separating DMT from ethylene glycol. In addition, the storage and handling of DMT may be difficult due to its high melting point.

Ethanolysis is the transesterification of PET with ethanol to form ethylene glycol and diethyl terephthalate (DET). The possibility of using other lower alcohols was mentioned in some patent sources on PET methanolysis; however, there is no information on the implementation of this method with ethanol. In addition, significant differences between the methanolysis of PET and its ethanolysis were not evaluated. There is also a lack of understanding of the appreciable advantages of PET ethanolysis compared to methanolysis. For example, DET can be converted to terephthalic acid (TA) by liquid phase oxidation on existing equipment to produce TA by liquid phase oxidation of para-xylene. In addition, DET has a lower melting point than DMT, so liquid phase operations, such as separation from liquid ethylene glycol, can be carried out more easily. The lower melting point of the resulting DET also facilitates its storage and handling compared to DMT.

Another method for processing PET is depolymerization. During depolymerization, the ester bond breaks and the polymer decomposes into monomeric components. It is usually desirable to purify the monomers. However, in existing depolymerization processes, such purification leads to the fact that recycling the polymer is more difficult and expensive than obtaining fresh polymer.

The reaction of PET with ethylene glycol to form bis (hydroxyethyl) terephthalate (BNET) is one way of processing PET by depolymerization. The purification methods of the obtained BNET monomer are limited since It has low volatility and polymerizes in PET at elevated temperatures. Such properties do not allow distillation of the BNET monomer, which means that during depolymerization by glycolysis only very pure PET raw materials can be used for processing. This severely limits the use of glycolysis as a recycling method for PET.

The authors found a method for processing waste polymers, in particular PET and other ester ethylene polymers, by ethanolisation with the formation of ethyl esters and ethylene glycol, oxidation of the obtained ethyl ester to carboxylic acid and acetic acid, from which PET and other polymers can be obtained.

Aromatic carboxylic acids, such as benzoic, phthalic, terephthalic, isophthalic, trimellitic, pyromellitic, trimesin and naphthalenedicarboxylic, are important intermediates in the synthesis of many chemical and polymeric substances. To obtain PET and PEI, terephthalic and isophthalic acids are used, respectively. Naphthalenedicarboxylic acid is used to produce PEN. Phthalic acid in the form of an anhydride is widely used to obtain plasticizers, dyes, fragrances, saccharin and many other chemical compounds.

Typically, aromatic carboxylic acids can be obtained by oxidation of the corresponding precursor, dimethyl aromatic hydrocarbon. For example, terephthalic acid is usually produced by the oxidation of para-xylene, and isophthalic acid by the oxidation of meta-xylene. Phthalic acid is obtained by the oxidation of ortho-xylene. Naphthalenedicarboxylic acid is usually obtained by oxidation of 2,6-dimethylnaphthalene.

An example of such a method can be found in US Pat. No. 2,833,816, incorporated herein by reference, which describes the liquid phase oxidation of xylene isomers to the corresponding benzenedicarboxylic acids in the presence of bromine and a cobalt-manganese catalyst. In the following example, US Pat. No. 5,103,933, incorporated herein by reference, discloses that liquid phase oxidation of dimethylnaphthalenes to naphthalenedicarboxylic acids can be carried out in the presence of bromine and a cobalt-manganese catalyst.

Typically, aromatic carboxylic acids are then purified. For example, a process comprising contacting a crude aromatic carboxylic acid with a catalyst and hydrogen in a reducing atmosphere is described in US Pat. Nos. 3,538,039, 4,892,972 and 5,362,908.

Subsequent purification methods typically include contacting a solution of the oxidation product — a crude aromatic carboxylic acid — with hydrogen and a catalyst under reducing conditions. The catalysts used for such purification usually contain one or more active hydrogenating metals, such as ruthenium, rhodium, palladium or platinum, on a suitable support — carbon or titanium oxide.

Used the term "aromatic hydrocarbon" means a molecule consisting of carbon atoms and hydrogen and containing one or more aromatic cycles, such as benzene or naphthalene cycle. For the purposes of this application, the term “aromatic hydrocarbon” includes those molecules that contain one or more heteroatoms, for example, oxygen or nitrogen atoms. “Methyl aromatic hydrocarbon” means an aromatic hydrocarbon molecule with one or more methyl groups connected to one or more aromatic rings. "Aromatic ethyl esters" means aromatic acid ethyl esters with one or more ethyl groups. The term "aromatic carboxylic acid" means an aromatic acid with one or more carboxyl groups.

The liquid phase oxidation of dimethyl aromatic hydrocarbons to aromatic carboxylic acids is usually carried out using a reaction mixture containing methyl aromatic hydrocarbons and a solvent in the presence of a molecular oxygen source. Typically, the solvent is C ₁ -C ₈ monocarboxylic acid, for example, acetic or benzoic acid, or mixtures thereof with water. Such methods typically include adding a certain amount of solvent, as the solvent is consumed, for example, as a result of combustion, side reactions, inefficient separation or other losses. Such solvent losses may be undesirable, and attempts are often made to minimize losses and to isolate the solvent as completely as possible to reduce the amount of solvent to be added.

A catalyst is also present in the oxidizing reaction mixture. Typically, the catalyst includes a promoter, for example bromine, and at least one suitable heavy metal. Suitable heavy metals include heavy metals with an atomic mass in the range of about 23-178. Examples include cobalt, manganese, vanadium, molybdenum, chromium, iron, nickel, zirconium, hafnium or lanthanide, for example cerium. Suitable forms of these metals include, for example, acetates, hydroxides and carbonates.

A molecular oxygen source is also introduced into the reaction mixture. Typically, gaseous oxygen is used as the source of molecular oxygen, which is bubbled or otherwise mixed with the liquid reaction mixture. Usually air is used to supply oxygen. Typically, 1.5 moles of O ₂ for each methyl group are needed to convert methyl aromatic hydrocarbon to the corresponding aromatic carboxylic acid, and one mole of H ₂ O is formed. For example, to convert one mole of dimethyl aromatic hydrocarbon into one mole of aromatic carboxylic acid, a minimum of 3.0 moles of O ₂ and two moles of H ₂ O are formed.

The authors found that aromatic ethyl esters can be a suitable raw material for the production of aromatic carboxylic acids and can even be used in the same or similar methods for producing aromatic carboxylic acids from methyl aromatic hydrocarbons. The use of aromatic ethyl esters is especially justified when the reaction solvent is acetic acid, because during oxidation, aromatic ethyl esters are oxidized to form the corresponding aromatic dicarboxylic acid and acetic acid. In cases where the solvent is acetic acid, the use of aromatic ethyl esters makes it possible to reduce the amount of added solvent or even not to add it at all.

When using methanolysis of PET to produce DMT and ethylene glycol, the resulting DMT is usually converted to TA and methanol by hydrolysis. Unfortunately, such hydrolysis requires special equipment both for the reaction itself and for the isolation of methanolysis by-products. Most often, TA is obtained by liquid-phase oxidation of para-xylene, but DMT cannot be used in such liquid-phase oxidation methods, because, among other reasons, methyl groups are converted to CO, CO ₂ , methyl acetate or other undesirable by-products. In contrast, DET can be used in liquid phase oxidation processes to convert para-xylene to TA.

SUMMARY OF THE INVENTION

The authors found that aromatic ethyl esters can be used as raw materials for the production of aromatic carboxylic acids. Aromatic ethyl esters, preferably including aromatic diethyl esters, can be used in liquid phase oxidation processes to produce aromatic carboxylic acids. This mechanism is especially applicable in the case of DET, diethyl isophthalate (DEI) and diethyl naphthalate (DEN), which can be used in existing xylene oxidation processes to produce terephthalic and isophthalic acids. Aromatic ethyl esters can also be used to produce acetic acid or even co-production of aromatic carboxylic acid and acetic acid. Aromatic ethyl esters can be isolated by processing polymers derived from aromatic carboxylic acids, and carboxylic acids can be used to make polymers, as disclosed in copyright patent applications entitled “Ethanolysis of PET and Preparation of Diethyl Terephthalate” and “Method for Utilization of PET”, both from December 29, 2005, incorporated herein by reference. In particular, ethanolysis can be used to separate DET and DEI from PET and PEI, respectively.

In some embodiments, the present invention provides a feed for producing an aromatic carboxylic acid comprising at least one aromatic ethyl ester, preferably an aromatic diethyl ester. Based on the entire aromatic carboxylic acid precursor, in order to obtain the desired aromatic carboxylic acid or acids, it is preferred that the feed contains at least about 1% by weight of at least one aromatic ethyl ester, more preferably at least about 5% by weight and still more preferably at least about 10 wt.% at least one aromatic ethyl ester. Preferably, the aromatic diethyl ester is DET, DEI, DEN, or a combination thereof. The feed may also include a dimethyl aromatic hydrocarbon, for example para-xylene.

In another embodiment, the invention provides a method for producing terephthalic acid, comprising oxidizing diethyl terephthalate to form terephthalic acid.

In other embodiments, the invention provides a method for producing aromatic carboxylic acids, comprising the step of reacting with oxygen in the reaction zone of at least one aromatic ethyl ester, preferably an aromatic diethyl ester, in the presence of a solvent containing acetic acid. To obtain the desired aromatic carboxylic acid or acids from the precursor aromatic carboxylic acid, it is preferred that the feed in the reaction zone contains at least about 1 wt.% Of at least one aromatic ethyl ester, more preferably at least about 5 wt.% , even more preferably at least about 10 wt.%. Preferably, the aromatic diethyl ester is DET, DEI, DEN, or a combination thereof. The method may also include the step of reacting with oxygen in the reaction zone of at least one dimethyl aromatic hydrocarbon in the presence of a solvent. Preferably, the at least one dimethyl aromatic hydrocarbon is para-xylene. Preferably, a catalyst comprising at least one heavy metal is present in the reaction zone. Preferably, at least one heavy metal is cobalt or manganese. Preferably, the catalyst also contains a halogen compound, preferably bromine.

In some other embodiments, the invention provides a method for producing acetic acid, comprising the step of reacting in the reaction zone of at least one aromatic ethyl ester, preferably an aromatic diethyl ester, in the presence of oxygen and optionally water. Preferably, a catalyst comprising at least one heavy metal is present in the reaction zone. At least one heavy metal is preferably cobalt or manganese. It is also preferred that the catalyst also contains a halogen compound, preferably bromine. Preferably, the at least one aromatic diethyl ester is DET, DEI, DEN, or a combination thereof.

In other embodiments, the present invention provides a process for co-production of aromatic carboxylic acid and acetic acid, comprising reacting with oxygen in the reaction zone of a feed comprising an aromatic ethyl ester, preferably an aromatic diethyl ester. Preferably, the aromatic diethyl ester is DET, DEI, DEN, or a combination thereof. Optionally, at least one dimethyl aromatic hydrocarbon, preferably para-xylene, is present in the reaction zone. Preferably, a catalyst comprising at least one heavy metal is present in the reaction zone. At least one heavy metal is preferably cobalt or manganese. Preferably, the catalyst also contains a halogen compound, preferably bromine.

The authors found that recycling PET by ethanolysis can have significant advantages over other methods of disposal. Importantly, PET ethanolysis products are DET and ethylene glycol. The separation of DET and ethylene glycol from the reaction products and from each other is carried out differently than the separation of DMT and ethylene glycol, and this is more important. In addition, DET can be used in many existing plants producing TA by liquid-phase oxidation of para-xylene. In addition, DET has a significantly lower melting point than DMT, so DET can be easily processed, transported and / or stored as a melt rather than solid. In general, when working with the liquid phase at a given temperature, the use of ethanol, unlike methanol, allows you to work at a lower pressure to achieve the desired alcohol concentration in the liquid phase. Operating at lower pressure can result in significant energy savings.

The authors found that some types of PET contain impurities that catalyze the ethanolysis of PET. In addition, titanium, preferably in the form of an organic titanate, is an effective catalyst. The authors also found that ethanolysis of PET can be carried out so that it proceeds stably in the presence of water, which allows the use of fuel-grade ethanol.

In addition, the authors found that, unlike methanolysis processing methods, in which it is necessary to deactivate the catalyst after the reaction in order to avoid undesirable reverse reactions, including the reaction of DMT with ethylene glycol, ethanolysis catalysts can be maintained in an active state, and this will not adversely affect product isolation. This allows reuse of the catalyst without a reactivation step.

In one embodiment, the invention provides a method for processing poly (ethylene terephthalate). The method includes the steps of combining in the reaction zone of poly (ethylene terephthalate) with ethanol to form a reaction mixture; a reaction in the reaction mixture at a temperature of about 180 ° C-300 ° C to form a mixture of reaction products; the selection of a mixture of reaction products of the first fraction containing ethanol; isolating from the mixture of reaction products a second fraction containing ethylene glycol; and isolating from the mixture of reaction products a third fraction containing diethyl terephthalate.

Preferably, the stage of separation of the first fraction containing ethanol from the mixture of reaction products was carried out in the first separation zone, and the stage of separation of the second fraction containing ethylene glycol from the mixture of reaction products and separation of the third fraction containing diethyl terephthalate from the reaction mixture was carried out in the second zone separation.

Some options also include the steps of separating the second fraction into a first stream containing most of the diethyl terephthalate and a second stream containing ethylene glycol; returning at least a portion of the first stream to the second separation zone and recovering ethylene glycol from the second stream in the third separation zone. It is preferable to carry out the stage of separation of the second fraction by separating the layers of liquid phases. Optionally, the step of separating the second fraction may comprise the step of adding water to at least a portion of the second fraction. In some embodiments, the first separation zone includes a first distillation column, and the second separation zone includes a second distillation column. Preferably, the first distillation column operates at near atmospheric pressure and the second distillation column operates at a pressure below atmospheric. Optionally, at least a portion of the ethanol recovered with the first fraction is sent to the reaction zone.

In some embodiments, a catalyst is placed in the reaction zone and preferably selected from the group consisting of catalytically active impurities in PET, copper phthalocyanine, zinc acetate, cobalt acetate, manganese acetate, magnesium acetate, titanium (IV) isopropoxide or other organic titanates and combinations thereof . Optionally, water can be added to the reaction zone, for example, using fuel-grade ethanol. Preferably, in such embodiments, the catalyst contains titanium, preferably in the form of organic titanates.

Some options include the step of isolating from a mixture of reaction products a fourth fraction containing a catalyst and PET oligomers. Preferably, at least a portion of the fourth fraction is directed to the reaction zone.

Another embodiment of the invention provides apparatus for processing poly (ethylene terephthalate). The apparatus includes a reactor for the reaction of poly (ethylene terephthalate) with ethanol and the formation of a mixture of reaction products; an atmospheric evaporation chamber or distillation column for separating ethanol from the mixture of reaction products; and a vacuum distillation column for isolating diethyl terephthalate from the mixture of reaction products. Optionally, the apparatus may include a decantation vessel for collecting a portion of the mixture of reaction products.

Some options offer a method of producing diethyl terephthalate. Such a method includes the reaction steps of poly (ethylene terephthalate) and ethanol in the reaction zone to form a mixture of reaction products containing ethanol, poly (ethylene terephthalate), diethyl terephthalate and ethylene glycol; isolating from a mixture of reaction products a first fraction containing ethanol, a second fraction containing an azeotrope of diethyl terephthalate with ethylene glycol, and a third fraction containing diethyl terephthalate; isolating from the azeotrope a stream containing most of the diethyl terephthalate, and supplying at least a portion of the stream to the separation step. Preferably, the catalyst is in the reaction zone. More preferably, the catalyst is selected from the group consisting of catalytically active impurities in PET, copper phthalocyanine, zinc acetate, cobalt acetate, manganese acetate, magnesium acetate, titanium (IV) isopropoxide or other organic titanates and combinations thereof. In some embodiments, the invention provides a method for producing diethyl terephthalate and diethyl isophthalate. Such a process includes reaction steps in a reaction zone of ethanol with a feed comprising poly (ethylene terephthalate) and poly (ethylene isophthalate) to form a mixture of reaction products; isolating from a mixture of reaction products a first fraction containing ethanol; isolating a second fraction containing ethylene glycol from a mixture of reaction products; and isolating a third fraction containing diethyl terephthalate and diethyl isophthalate from a mixture of reaction products. Preferably, a catalyst is present in the reaction zone. More preferably, the catalyst is selected from the group consisting of catalytically active impurities in PET, copper phthalocyanine, zinc acetate, titanium (IV) isopropoxide or other organic titanates and combinations thereof. Optional presence of water in the reaction zone. The presence of organic titanates in the reaction zone is preferred. Preferably, the ethanol in the reaction zone is fuel grade ethanol.

The authors found that raw materials containing PET can be reacted with ethanol to form diethyl esters, which can be oxidized to aromatic carboxylic acids, which are then used to produce polymers. In particular, PET can be reacted with ethanol to form ethylene glycol and diethyl terephthalate, which can be sent to existing liquid phase oxidation processes to form terephthalic acid, used to make PET. This processing method is not sensitive to many impurities, which allows you to dispose of a wide range of PET waste. This processing method makes it possible to utilize PET and other polymers without fear of decomposition of the final polymer product.

In some embodiments, the invention provides a method for processing PET. The method includes reaction steps in a first reaction zone of a first portion of a feed containing PET with ethanol to form a first mixture of reaction products; isolating aromatic ethyl esters from the first mixture of reaction products; oxidation in the second reaction zone of a second portion of a feed containing at least a portion of aromatic ethyl esters to produce aromatic carboxylic acids; and a reaction in a third reaction zone of at least a portion of aromatic carboxylic acid and ethylene glycol to form a polymer containing PET. The first portion of the feed may contain at least 1000 ppm. by weight of polyvinyl chloride (calculated on PET). The second portion of the feed preferably includes precursors of the desired aromatic carboxylic acids in the form of dimethyl aromatic hydrocarbons. At least a portion of the first reaction product mixture can be contacted with an ion exchange resin to remove at least a portion of the soluble impurities contained in the first reaction product mixture. For ease of handling and processing, the first mixture of reaction products can be brought to a temperature of about 50-120 ° C.

Aromatic carboxylic acid can be purified prior to use to form polymers. Ethanol can be of fuel quality.

In other embodiments, the invention provides a method for producing PET from PET waste. The method includes reaction steps in a first reaction zone of a first portion of a feed containing PET with ethanol to form a first mixture of reaction products; isolating DET from the first reaction product mixture; reacting with oxygen at least a portion of the DET in the second reaction zone in the presence of a solvent containing low molecular weight carboxylic acid to form terephthalic acid; purification of at least a portion of the terephthalic acid in the hydrogenation reaction zone to form purified terephthalic acid; and obtaining PET from at least a portion of the purified terephthalic acid.

Brief Description of the Drawing

Figure 1 illustrates a variant of ethanolysis and isolation of products in accordance with a variant of the present invention.

Description of Preferred Options

The present invention provides methods and apparatus for processing PET by ethanolysis and producing DET. Ethanolysis is the transesterification of PET with ethanol to form ethylene glycol and DET. By ethanolysis, various types and qualities of PET can be disposed of, including, but not limited to, brown flakes, green flakes, blue flakes, colorless flakes, amber flakes, or mixtures thereof. The ability to use mixed PET flakes is an advantage because such mixed flakes are more readily available than pure flakes such as pure colorless flakes. In some embodiments, the recyclable PET is in the form of PET bags, which optionally can be ground and / or dissolved in a suitable solvent.

The present invention also provides raw materials for the production of aromatic carboxylic acids. Such raw materials include one or more aromatic ethyl esters. Aromatic ethyl esters can be used alone as a raw material, and in a preferred embodiment, one or more aromatic ethyl esters are used as a raw material component to produce aromatic carboxylic acids. Aromatic ethyl esters, in particular, are used as raw materials in liquid phase oxidation processes to produce aromatic carboxylic acids.

The present invention provides a process for processing PET and other polyesters by reacting polymer wastes with ethanol to form ethylene glycol and ethyl esters, which can be oxidized to the corresponding carboxylic acids. Carboxylic acids and optionally ethylene glycol isolated from ethanolysis products can be used to make polyesters.

In some embodiments, ethyl ester can be used as feed in existing oxidation processes to produce the corresponding carboxylic acids. For example, aromatic diethyl esters can be used in existing liquid phase oxidation processes to produce aromatic dicarboxylic acids from dimethyl aromatic hydrocarbons. Once converted to aromatic dicarboxylic acid, they can be used instead of or along with aromatic dicarboxylic acids, which are not obtained in the processing of polyesters. This allows you to use recyclables without fear of decomposition of the resulting final polyester, and then there is no need to modify existing polymerization methods to obtain polyesters from aromatic carboxylic acids.

Ethanolysis is the transesterification of a polyester with ethanol to form ethyl esters and ethylene glycol. Ethyl esters can be converted to the corresponding carboxylic acids, which can be used to make the polymer using the polycondensation reaction.

In specific embodiments of the processing method, a wide range of polyesters can be used, including many contaminated polyester wastes. In embodiments where PET waste is disposed of, a wide range of contaminated PET sources can be obtained, including, but not limited to, PET waste along with other polyesters, terpolymers, polyvinyl chloride, polyolefins, adhesives, heavy metals and many other impurities that are not suitable for other recycling methods.

When processing PET by ethanolysis, DET and ethylene glycol are obtained. Ethanolysis is the transesterification of a polyester with ethanol to form ethyl esters and DET. Various types and qualities of PET can be processed by ethanolysis, including, but not limited to, brown flakes, green flakes, blue flakes, colorless flakes, amber flakes, or mixtures thereof. The ability to use mixed PET flakes is an advantage because such mixed flakes are more readily available than pure flakes such as pure colorless flakes. In some embodiments, the recyclable PET is in the form of PET bags, which optionally can be ground and / or dissolved in a suitable solvent.

The processing of PET by ethanolysis can be carried out continuously or batchwise to obtain DET and ethylene glycol, or semi-batch. An example of a semi-batch process is the batch ethanolysis of PET with the continuous separation of products — DET and ethylene glycol — from a periodically formed reaction mixture. PET and ethanol are introduced into the ethanolysis reaction zone in the presence of a suitable catalyst. The resulting mixture of reaction products is separated to isolate the products. This separation can be carried out in many ways known to specialists in this field. However, it is preferred that the separation include distillation to isolate ethanol, DET and ethylene glycol.

PET, usually in the form of used products or waste flakes, is preferably first dissolved in any solvent. Any solvent that does not adversely affect the ethanolysis reaction may be used. However, it is preferred that the solvent is ethanol and / or bottoms of a distillation residue from a second separation zone. In one embodiment, the solvent is part of a mixture of reaction products obtained from the reaction zone. It is not necessary to filter the dissolved feed from PET to remove impurities, such as adhesives, which may be present in some feeds. The PET feed is reacted with ethanol in the reaction zone in the presence of a suitable catalyst. Ethanol can be combined with PET feed in the reaction zone in upflow from the reaction zone or used as a combination thereof.

The catalyst can be introduced into the reaction zone, combined with PET feedstock, combined with ethanol, combined with a solvent, it can also be in the return liquid bottoms stream, or it can be introduced by a combination of these options.

Raw materials containing PET may include other polymers and impurities, for example PEI, PEN, polyvinyl chloride, polyolefins, heavy metals, dyes, plasticizers and many other compounds that are often used to obtain products from PET or in connection with PET. Typically, ethanolysis of PET, as described herein, is less sensitive to the presence of such polymers and impurities than many other PET processing methods. An advantage is the fact that some other polymers are converted during ethanolysis to the corresponding ethyl esters, which can be converted to the corresponding carboxylic acids and then esterified and polymerized to form polymers. In some embodiments, at least a portion of the other polymers present with PET are reacted with ethanol to form aromatic ethyl esters. Such aromatic ethyl esters can be oxidized to aromatic carboxylic acids, which can be esterified and polymerized and the polymers recovered.

The ethanol used for ethanolysis may be industrial ethanol, however, the authors found that it is efficient to use fuel-grade ethanol. Fuel ethanol usually contains more water than industrial ethanol, and usually it contains methylated alcohol (usually a hydrocarbon or hydrocarbon compound). In some embodiments of the invention, para-xylene can be used as methylated spirits. In such embodiments, nqpa-xylene can be isolated from the reaction products and then mixed with DET. Such variants are particularly suitable for use in a liquid phase oxidation process for converting para-xylene to TA. Although the exact composition of fuel-grade ethanol varies, fuel ethanol may contain about 0.25-2.0 vol.% Water, but usually contains about 1 vol.% Water and about 1-5 vol.% Denatured alcohol. Fuel ethanol may also contain other compounds, for example traces of metal compounds, gums and methanol. Although different laws may contain different specifications for fuel-grade ethanol, it is anticipated that these options will not have a significant effect on the ethanolysis of PET, as described herein. An example of technical specifications for fuel ethanol commonly used in the United States is ASTM D 4806 (Standard Specification for Denatured Fuel Ethanol for Mixing with Kerosene for Use in Spark-ignited Automobile Engines).

The authors found that ethanolysis can be effectively carried out, despite the presence of water, methylated spirits and other compounds in fuel ethanol. The authors found that ethanolysis, as shown here, can be carried out efficiently using ethanol containing up to about 5 wt.% Water. The use of fuel-grade alcohol is very attractive because fuel alcohol is an easily accessible consumer product. In addition, ethanol is considered an environmentally friendly and renewable resource. Many laws encourage the use of products such as ethanol.

The reaction zone may include one or more reactors, which allows sufficiently good mixing of recyclable PET, ethanol and catalyst; for example, it may be stirred tank reactors, ideal displacement reactors, batch reactors, or combinations thereof.

The ethanolysis reaction is preferably carried out at a temperature of at least about 180 ° C, more preferably at least about 195 ° C. Although lower temperatures can be used, the conversion will be low. It is preferable to conduct the reaction at a temperature not exceeding about 300 ° C, more preferably not higher than about 250 ° C. Although higher temperatures can be used, such higher temperatures can lead to the formation of an undesirable amount of by-products, for example diethyl ether.

The ethanolysis reaction can be carried out at pressures below atmospheric, for example 80 kPa, or at atmospheric pressure. It is preferable to carry out ethanolysis at a pressure above atmospheric, more preferably at a pressure of at least about 200 kPa, more preferably at least about 1000 kPa, more preferably at least about 2000 kPa. It is preferable to carry out ethanolysis at a pressure not higher than about 6000 kPa, more preferably not higher than about 5000 kPa. The values given are approximate and the pressure can vary significantly during the reaction, especially if ethanolysis is carried out in a closed batch reactor. For example, in a closed batch system, the pressure usually falls during the reaction. Although pressure depends on temperature, a wide range of conditions under which ethanol and PET waste remain in the liquid phase allows temperature and pressure to be controlled independently of each other.

The mixture of reaction products is then separated to isolate reaction products, including ethanol, DET and ethylene glycol, and optionally DEI, DEN and other desired components. During separation, other components can be isolated if desired. Examples of such components include para-xylene, if present, other reacted and non-polymers, or desired compounds that may be present in PET. As shown above, part of the mixture of reaction products can be used as a solvent for raw materials containing PET. In some embodiments of the continuous processes, part of the reaction product mixture is removed, but additional reaction components are added. To maintain effective continuous operation, some of the reaction mixture can also be removed by blowing.

Separation can be carried out by crystallization, distillation, filtration, separation of liquid phases, extraction with a solvent or other known separation methods, or using a combination of separation methods. Preferably, the separation includes a first separation zone for separating ethanol, a second separation zone for separating DET and ethylene glycol, and a third separation zone for separating purified ethylene glycol. Separation may optionally include one or more purification steps to remove one or more components from the reaction products. In one embodiment, the first and second separation zones include distillation and separation of the liquid phases. Liquid phase separation is not effective for isolating DMT in the methanolysis process, because DMT usually melts at about 140-142 ° C and mixes with ethylene glycol at higher temperatures.

It is preferable to separate to isolate at least a first fraction containing mainly ethanol and light reaction by-products, a second fraction containing a majority of ethylene glycol, a third fraction containing mainly DET, and a fourth fraction containing high boiling and non-volatile components. In a preferred embodiment, the first fraction is isolated in the first reaction zone, and the second, third and fourth fractions are isolated in the second separation zone. However, fractions can be isolated in parts or a combination of fractions can be isolated. In addition, parts of the fractions can be isolated at different stages of separation. For example, during the separation, part of the first fraction, which contains mainly ethanol and light by-products, can be isolated at one point, and the other part of the first fraction can be isolated by distillation. Separation equipment may be part of more than one separation zone. In one embodiment, a portion of the first fraction, containing mainly ethanol and light by-products, is isolated in the evaporation chamber of the first separation zone, and another part of the first fraction is isolated in a distillation column, which is part of the first separation zone and part of the second separation zone.

Preferably, the separation includes distillation. The distillation can be carried out in one or more distillation columns - part of the first separation zone - with the formation of the first fraction containing mainly ethanol and light reaction by-products. It is preferable to use one or more distillation columns, parts of a second separation zone, to separate a second portion containing mainly ethylene glycol, a third fraction containing mainly DET, and a fourth fraction containing high boiling compounds. In one embodiment, the first separation zone includes a distillation column that operates at or near atmospheric pressure, and the second separation zone includes a distillation column that operates below atmospheric pressure. In another embodiment, the separation includes a distillation column, which is at least part of the first separation zone and at least part of the second separation zone. Preferably, in such an embodiment, at least a portion of a first fraction containing mainly ethanol and light reaction by-products, a second fraction containing a large part of ethylene glycol, a third fraction containing mainly DET, and a fourth fraction containing high boiling and non-volatile compounds.

All or part of the ethanol recovered by separation can be returned to the ethanolysis reaction. Such recycling is carried out by using ethanol recovered by separation as a solvent for recyclable PET. Such reuse can also be accomplished by feeding ethanol recovered by separation as an upward stream in the ethanolysis reaction zone or directly to the ethanolysis reaction zone. In one embodiment, the first fraction containing mainly ethanol and light reaction by-products is isolated in the first separation zone, all or part of the first fraction is selected to remove at least part of the light by-products from the first fraction, preferably by condensation or other known separation methods, and at least a portion of the ethanol of the first fraction is returned for use in the ethanolysis reaction or as a solvent for PET. Optionally, before using in the ethanolysis reaction or as a solvent for PET, all or part of the first fraction should be subjected to other treatments and / or stored and / or mixed with ethanol from another source. In one embodiment, all or part of the ethanol from the first fraction can be introduced into the reaction zone using the heat of this ethanol from the first fraction to heat the PET to the reaction temperature.

Ethylene glycol isolated by separation, preferably in the second fraction obtained in the second separation zone, is mainly in the form of an ethylene glycol-DET azeotrope ("EG-DET azeotrope"). Although the concentration of DET in the EG-DET azeotrope varies depending on the separation method used and its handling, usually the EG-DET azeotrope contains less than 10 wt.% DET. At temperatures above the melting point of DET (44 ° C, 1 atmosphere) and below the boiling point of ethylene glycol (196-198 ° C), the azeotrope is separated into a first layer enriched in DET and a second layer enriched in ethylene glycol.

The first layer enriched with DET can be separated by a known method of separation of liquid phases, such as decantation, and it is preferable to return to the separation more preferably in the second separation zone. Optionally, the first layer can be sent directly to the storage of the resulting DET. The second layer enriched in ethylene glycol can then be purified by distillation or other methods in the third separation zone, where ethylene glycol is isolated, and the remainder of the second layer can be returned to the separation. If the remainder of the second layer is returned, then the place to which it is returned depends on the separation method or methods used in the third separation zone. For example, if distillation is used in the third separation zone, an ethylene glycol stream and an ethylene glycol azeotrope stream with DET are formed, and it is better to combine the azeotrope stream with the second fraction from the second separation zone. If separation methods such as filtration, crystallization or distillation are used to separate ethylene glycol from the second layer, it is preferable to return the remainder of the second layer to the second separation zone. Other separation methods, for example, solvent extraction or azeotropic distillation, may require further processing of the remainder of the second layer and / or the isolated ethylene glycol. The EG azeotrope with DET may also contain diethylene glycol, which is mainly contained in the layer enriched in ethylene glycol, and it is preferable to clean it in the third separation zone. A small portion of diethylene glycol remains in the DET-rich layer, and it is preferable to return it to separation with DET.

Methanolysis processes typically form an ethylene glycol azeotrope with DMT, which contains about 15 wt.% DMT. As noted above, liquid phase separation methods are not effective for isolating DMT and ethylene glycol, and other methods are generally used, typically more complex and often more energy intensive.

In one embodiment, water is used to intensify the separation of the ethylene glycol mixture with DET. DET can be isolated from a mixture of ethylene glycol and DET by adding water, followed by separation of the liquid phases. Adding water increases the concentration of DET in the first layer and lowers the concentration of DET in the second layer. A liquid phase separation method, for example decantation, can be used to separate the first layer, which is preferably returned to the second separation zone or optionally sent to the storage of the resulting DET. The volume of water used to intensify the separation is found in the second layer and can be separated further.

In another embodiment, a hydrocarbon, preferably para-xylene, is used to intensify the separation. The addition of such a hydrocarbon increases the concentration of DET in the first layer and lowers the concentration of DET in the second layer. If hydrocarbon is used to intensify the separation, the hydrocarbon will be predominantly in the first layer and will be processed together with the first layer. In this case, an additional separation can be made. Para-xylene has the advantage that, if desired, it can be left with the resulting DET and used in the liquid phase oxidation reaction to produce TA, as described herein. In addition, a certain amount of para-xylene can be used to facilitate the work with the obtained DET by lowering the melting point of the DET. In some embodiments, both water and para-xylene are used to intensify the separation.

The first layer is not always necessarily a lighter layer. For example, if water is used to intensify separation, the first layer will be heavier. On the contrary, if napa-xylene is used to intensify the separation, the first layer will be lighter.

DET is isolated by separation, preferably as a first portion of a third fraction from the second separation zone. Although the separation is usually carried out so that the third fraction from the second separation zone contains at least 95 wt.% DET, preferably at least 97 wt.% DET, it is necessary to further separate the third fraction for purification of DET, for example, by filtration, distillation or crystallization. For example, the isolated DET may contain small amounts of diethylene glycol (DEG), ethylene glycol, or both of these compounds, and may also contain water. To clean the DET, a liquid phase separation method can be used. If water is present in the isolated DET, regardless of whether it was used to intensify the liquid separation of the liquid phases or not, the isolated DET can optionally be dehydrated to remove water. In addition, PET may contain, for example, isophthalate, which may be present in the feed together with PET and which may be converted to DEI by ethanolysis. If DEI is present in the reaction product mixture, it is usually isolated as a small impurity in combination with DET, preferably in a third fraction. You can optionally separate DEI from DET using known separation methods, such as crystallization or distillation. However, the DEI may be partially stored in the received DET.

The remainder of the reaction product mixture, preferably isolated as a fourth fraction from the second separation zone, contains an active catalyst, reaction by-products and other high boiling compounds. Typically, in methanolysis methods, either only the obtained DMT, or DMT and ethylene glycol are distilled off during the methanolysis reaction, or the catalyst is deactivated, which stops the reaction and avoids undesired reactions during the separation. It is better when the catalyst present in the remainder of the reaction product mixture is an active catalyst suitable for catalysis of the ethanolysis reaction. Preferably, at least a portion of the remainder of the mixture of reaction products is returned for use in the reaction zone. Such recycling can be accomplished by adding at least a portion of the residue to the reaction zone or to an upward stream in the reaction zone, for example, to dissolve the PET. Optionally, at least a portion of the residue can be treated to form a catalyst recycle stream with a higher concentration of catalyst and returned for use in the reaction zone.

At any stage, the feed or mixture of reaction products can be purified to reduce the content of undesirable impurities. Cleaning can be carried out in one or several stages, and can be carried out in stages and in different ducts. It is preferable to clean the mixture of reaction products before or after any separation zone. In one embodiment, the mixture of reaction products is purified after separation of the first fraction in the first separation zone. In another embodiment, at least a portion of the fourth fraction recovered in the second separation zone is cleaned. In another embodiment, the mixture of reaction products is purified after separation of the first fraction in the first separation zone and also at least part of the fourth fraction in the second separation zone. The cleaning may include bypass lines so that all or part of the raw material to be cleaned can be allowed to bypass all or part of the cleaning. Such by-pass lines are especially convenient if you use different PET waste with different impurities to bypass unnecessary cleaning areas.

Since DET has a melting point of about 44 ° C at 1 atm, the reaction products can be kept in the melt and many cleaning methods can be effectively applied. The purification methods used will depend on the nature of the impurities that are intended to be removed by purification, and include centrifugation, distillation, solvent extraction, filtration, ion exchange, adsorption, or other methods. For example, if PET waste contains insoluble impurities, such as polyolefins, polyvinyl chloride, aluminum, paper, glass, dirt or other insoluble materials, then filtration or centrifugation is suitable. If soluble metals, such as antimony, which are present in the PET waste as polymerization catalysts, need to be removed, then methods such as ion exchange or activated carbon treatment are suitable. A combination of methods can be used for cleaning. It is preferable to purify the reaction products during separation.

In particular, to remove soluble metals, it is possible to purify the mixture of reaction products using ion exchange resins. Ion exchange is the reversible exchange of ions between a solid (an ion-exchange substance is also called an ion-exchange resin) and a liquid or melt in the absence of a permanent change in the structure of the solid. Typically, traditional ion-exchange resins consist of a cross-linked polymer matrix with a relatively uniform distribution of ion-active centers over the structure. As a rule, ion-exchange materials are available in the form of spheres or sometimes granules of a specific size and uniformity for the needs of a particular application. Ion exchange materials have limited thermal stability. Typically, ion exchange materials are limited to temperatures up to 150 ° C and often their use is severely limited to lower temperatures. Suitable ion exchange resins for purification are commercially available and include DOWEX resins suitable for removing heavy metals, including antimony. The particular ion exchange resin used depends on many factors, including the nature of the undesirable impurities that are expected to be removed using the ion exchange resin.

Soluble metals can be part of the polymer due to the use of these metals as catalysts for polymerization processes. Typically, ion exchange resins are not suitable for use at high temperatures, such as in methanolysis processes. However, the ethanolysis reaction and reaction products can be maintained at temperatures acceptable for ion exchange resins. For example, reaction products can be maintained at temperatures of 44-100 ° C. Purification using ion exchange resins is particularly suitable for the removal of soluble heavy metals, such as antimony, which may be present in raw materials along with PET. In addition, centrifugal purification is particularly suitable for removing insoluble halogenated compounds such as polyvinyl chloride. The ability to process PET raw materials containing soluble heavy metals and / or insoluble halogenated polymers dramatically expands the range of available PET-based raw materials, which allows the processing of a much wider range of PET-based products than was possible using methanolysis and other existing processing methods .

Ion exchange resins can also be used to remove HCl, which is present in the reaction product mixture if polyvinyl chloride is present in the PET waste feed. The ability to use ion exchange resins to remove HCl makes it possible to dispose of raw materials from PET waste with much higher concentrations of polyvinyl chloride than in commonly used processing methods. In some embodiments, the invention provides a method for processing PET waste in the form of a feed containing more than 1000 ppm. by weight of polyvinyl chloride (calculated on PET). In other embodiments, the invention provides a method for processing PET waste containing more than 1250 ppm. by weight or even 1500 ppm by weight of polyvinyl chloride (calculated on PET).

Ethanolysis reaction catalysts include known transesterification catalysts. Suitable catalysts include copper acetate, cobalt acetate, manganese acetate, magnesium acetate, titanium, and combinations thereof. The catalytically active metals are preferably in the form of acetates or, in the case of titanium, in the form of titanium (IV) isopropoxide or other organic titanates and combinations thereof. However, it was unexpectedly found that impurities present in mixed PET flakes, for example dyes and metal compounds, can be effective catalysts for ethanolysis of PET. Such impurities present in PET flakes, which are used in the catalysis of ethanolysis, are referred to herein as “catalytically active impurities”. It has been found that brown flakes contain especially necessary amounts and types of catalytically active impurities. In one embodiment, the ethanolysis reaction catalyst comprises catalytically active impurities. In another embodiment, at least a portion of the remainder of the reaction product mixture contains catalytically active impurities, and it is advantageous to use them as a catalyst for the ethanolysis reaction.

Surprisingly, copper phthalocyanine can be used as a suitable catalyst for the ethanolysis reaction. When using copper phthalocyanine as a catalyst, it is preferred that its concentration is at least about 3 ppm. by weight (based on PET flakes). In another embodiment, PET waste flakes containing brown, blue, or green PET, or a combination thereof, are conveniently used as raw materials with PET and at least a portion of the reaction catalyst. However, the presence of water in an ethanolysis reaction, for example as a result of the use of fuel-grade ethanol, can reduce the effectiveness of catalytically active impurities, including copper phthalocyanine. It has also been found that titanium is a suitable catalyst even in the presence of fuel-grade ethanol, preferably in the form of an organic titanate such as titanium (IV) isopropoxide. If fuel ethanol is used or another water source is present in the reaction zone, it is preferred that at least a portion of the catalyst is titanium, preferably in the form of an organic titanate. If titanium is used as a catalyst, usually in the form of organic titanate, titanium is usually present in the reaction zone in an amount of about 5-5000 ppm. calculated on the mass of PET in the reaction zone.

Figure 1 illustrates a variant in which the ethanolysis reaction is carried out in a batch mode, and the separation method is carried out in a continuous mode.

In FIG. 1, PET waste is fed to a batch reactor R1 in a reaction zone where two parallel batch reactors are located. In Figure 1, a batch reactor R1 is illustrated for loading raw materials, and a batch reactor R2 for unloading products. The PET-containing feed is mixed with ethanol from an ethanol tank and with ethanol of the first fraction F1 from the first separation zone. A portion of the first fraction is evaporated from the reaction product mixture V1, a second portion of the first fraction is isolated from the first distillation column V4, and the remainder of the first fraction is isolated from the second distillation column V5. A suitable catalyst from the catalyst tank is fed to a batch reactor R1. The reaction can take place in one reaction vessel, while another is emptied and the feed is loaded into it. The ethanolysis reaction proceeds in a loaded reaction vessel, preferably at an initial pressure of about 200-1000 kPa and an initial temperature of about 70-100 ° C. As the reaction proceeds, the temperature in the vessel rises to about 180-260 ° C and the pressure rises to about 1500-5000 kPa. The reaction vessel is maintained at this pressure and temperature for about 0.25-5.0 hours, after which the temperature is lowered until the pressure becomes about 10-500 kPa, after which the mixture of reaction products is fed into intermediate tank V2, which is part of the first separation zones.

As shown in FIG. 1, a portion of the first fraction F1 containing ethanol and light by-products in the reaction product mixture is vaporized in the evaporation chamber V1 and ethanol is condensed into the second batch reactor R1, which is charged or ethanol is returned to the ethanol tank. This allows you to keep the intermediate tank V2 in relatively mild conditions, preferably at a pressure close to atmospheric, and a temperature of about 50-100 ° C. Such conditions make it possible to maintain a mixture of reaction products in the liquid phase and minimize the reverse reaction of DET with ethylene glycol. Such an intermediate tank with mild conditions cannot be implemented in the methanolysis process, because the conditions necessary to maintain DMT in the liquid phase would cause an unwanted back reaction between DMT and ethylene glycol.

Figure 1 shows that part of the mixture of reaction products is returned to the reaction zone F4, in this case, to the reactor R1, which is filled. In this embodiment, the mixture of reaction products is continuously fed from the intermediate tank to the purification zone V3. Cleaning may include bypass lines so that all or part of the reaction product mixture from the intermediate tank can be bypassed all or part of the treatment line. Examples of cleaning methods that can be used include, but are not limited to, filtration, centrifugation, ion exchange, and adsorption on activated carbon or clays. The choice of cleaning method will depend on the nature of the PET waste material used. For example, if PET waste contains insoluble impurities such as polyolefins, polyvinyl chloride, aluminum, paper, glass, dirt, or other insoluble materials, filtration or centrifugation is suitable. If soluble metals, such as antimony, which are present in the PET waste as polymerization catalysts, need to be removed, then methods such as ion exchange or activated carbon treatment are suitable. A combination of methods can be used for cleaning.

As shown in figure 1, the mixture of reaction products from the purification zone V3 is fed to the first distillation column V4, which is part of the first separation zone. The first distillation column V4 operates at or near atmospheric pressure. A second portion of the first fraction F1, containing mainly ethanol and light reaction by-products, is isolated from the first distillation column V4.

In figure 1, after the first distillation column V4, the mixture of reaction products is fed to the second distillation column V5, which is part of the first separation zone and part of the second separation zone. The second distillation column V5 operates at a pressure below atmospheric. Four fractions are isolated from the second distillation column V5: the remaining part of the first fraction F1, containing mainly ethanol and light reaction by-products, the second fraction F2, containing the main part of ethylene glycol, the third fraction F3, containing mainly DET, and the fourth fraction F4, containing high boilers connections.

The remainder of the first fraction is combined with other portions of the first fraction and the first fraction is refrigerated, the condensed ethanol is returned to the ethanol tank, and the remainder of the first fraction is removed by blowing.

As shown in FIG. 1, the second fraction F2 is sent to a decantation tank V6 for separating the liquid phases, where the second fraction F2 forms a first layer L1 enriched in DET and a second layer L2 enriched in ethylene glycol. Water from tank V7 is added to the second fraction F2 to increase the concentration of DET in the first layer and lower the concentration of DET in the second layer L2. The liquid from the first layer L1 is returned to the second distillation column V5 or alternatively to the reservoir V9 for storing the obtained DET or both tanks, and the liquid from the second layer L2 is sent to the third separation zone V8. The third fraction F3 is sent to reservoir V9 to store the resulting DET. A portion of the fourth fraction F4 is returned for use in the reaction zone and the remainder of the fourth fraction is removed by blowing.

As shown in figure 1, the second layer L2 is sent to the third separation zone V8, from which ethylene glycol is isolated and sent to the container for the obtained ethylene glycol V10.

The resulting ethyl ester can then be converted to carboxylic acid. Preferably, the ethyl ester is an aromatic ethyl ester, more preferably an aromatic diethyl ester. Puff ethyl ester can be oxidized by reaction with oxygen to form the corresponding carboxylic acid and acetic acid.

Used the term "aromatic hydrocarbon" means a molecule consisting of carbon atoms and hydrogen and containing one or more aromatic cycles, such as benzene or naphthalene cycle. For the purposes of this application, an “aromatic hydrocarbon" includes such molecules with one or more heteroatoms, such as oxygen or nitrogen atoms. “Methyl aromatic hydrocarbon” means an aromatic hydrocarbon molecule with one or more methyl groups connected to one or more aromatic rings. "Aromatic ethyl esters" means aromatic acid ethyl esters containing one or more ethyl groups. As used herein, the term “aromatic carboxylic acid” means an aromatic acid with one or more carboxyl groups.

The authors found that aromatic ethyl esters are used as raw materials or components of raw materials for the production of aromatic carboxylic acids. In one embodiment, the present invention provides raw materials for the production of aromatic carboxylic acids. Such a feed contains one or more aromatic ethyl esters. Aromatic ethyl esters can be used on their own as such raw materials. In a preferred embodiment, one or more aromatic ethyl esters are used as feed components to produce aromatic carboxylic acids. Aromatic ethyl esters are particularly suitable as raw materials for liquid phase oxidation processes to produce aromatic carboxylic acids.

Aromatic carboxylic acids for which the invention is applicable contain carboxylated groups containing one or more aromatic rings, which can be obtained by the reaction of gaseous or liquid reagents in a liquid-phase system. Examples of aromatic carboxylic acids for which the invention is particularly applicable are terephthalic acid, phthalic acid, isophthalic acid, trimellitic acid and naphthalenedicarboxylic acids.

According to this invention, the feed contains one or more aromatic ethyl esters. The particular aromatic ethyl ester or combination of used aromatic ethyl esters will depend on which aromatic carboxylic acids are the desired products. For a specific aromatic carboxylic acid, the corresponding precursor — aromatic ethyl ester — constitutes all of the feed or is a component thereof. For example, for terephthalic acid, diethyl terephthalate is used as all or part of the feed. For isophthalic or phthalic acids, diethyl isophthalate or diethyl phthalate, respectively, is used as all or part of the raw material. In one embodiment, more than one aromatic ethyl ester is optionally used as the entire feedstock or its components to produce more than one aromatic carboxylic acid.

In one embodiment, the feed used to produce an aromatic carboxylic acid comprises at least one aromatic ethyl ester and at least one methyl aromatic hydrocarbon. For example, to obtain terephthalic acid, the feed may contain para-xylene and diethyl terephthalate. As another example, for the co-production of terephthalic acid and isophthalic acid, it is preferred that the feed is para-xylene, diethyl terephthalate and one or both of meta-xylene and diethyl isophthalate. To obtain naphthalenedicarboxylic acids, it is preferred that the feed contains at least one component, diethylnaphthalate and at least one component, dimethylnaphthalene.

The ratios of the components in the feed are not critical to this invention. However, it is preferred that the feed contains at least 1% by weight of aromatic ethyl esters (based on all aromatic carboxylic acid precursors to produce the desired aromatic carboxylic acid or acids). More preferably, the feed contains at least 5 wt.% Aromatic ethyl esters, more preferably at least 10 wt.% Aromatic ethyl esters. Although the feed may contain up to 100% by weight of aromatic ethyl esters (based on all aromatic carboxylic acid precursors to produce the desired aromatic carboxylic acid or acids), it is preferred that the feed contains less than 100% by weight of aromatic esters. The feed may contain significantly less than 100 wt.% Aromatic ethyl esters, for example less than 50 wt.% Or even less than 30 wt.% Aromatic ethyl esters. Optionally, the proportion of aromatic ethyl esters can be selected and / or set so as to maintain the desired concentration and composition of the solvent in the reaction zone.

To obtain aromatic carboxylic acids, it is preferable to use relatively pure substances and more preferably a feedstock in which the total content of the feed components (including all precursors of the desired acid or acids) is at least about 95 wt.% And more preferably at least 98 wt.% or even higher.

The liquid phase oxidation of aromatic ethyl esters to aromatic carboxylic acids can be carried out in a batch mode, continuous mode or semi-continuous mode. The oxidation reaction proceeds in the reaction zone, which may contain one or more reactors. The reaction zone may include mixing vessels or pipelines, where the components are combined and carry out the oxidation reaction. The reaction mixture is formed by mixing components including a feed, a solvent and a catalyst, optionally with a promoter, usually bromine. In continuous or semi-continuous mode, the components of the reaction mixture are preferably combined in a mixing vessel before being fed to the oxidation reactor, however, the reaction mixture can also be prepared in the oxidation reactor.

Solvents containing aqueous carboxylic acid, for example benzoic acid, and especially lower alkyl monocarboxylic (e.g. C ₁ -C ₈ ) acetic acid, are preferred, as they are minimally oxidized under typical oxidation reaction conditions used to produce aromatic carboxylic acids, and can enhance the catalytic effects of oxidation. Specific examples of suitable carboxylic acid solvents include acetic acid, propionic acid, butyric acid, benzoic acid, and mixtures thereof. Ethanol and other additional solvents that are oxidized to monocarboxylic acids under the conditions of the oxidation reaction can also be used as such and in combination with carboxylic acids, obtaining good results. Of course, in order to achieve high efficiency of the whole process and minimize the number of separation stages, it is preferable to use as a solvent a mixture of monocarboxylic acids and such an additional solvent so that the additional solvent can also be oxidized to the monocarboxylic acid with which it is used.

Typically, the proportion of solvent in the reaction zone is reduced either due to burnout (oxidation) of the solvent, or due to losses associated with inefficient isolation. In some industrial operations, such losses can be up to 2 wt.% Solvent or even 4 wt.% Or higher. Because of this, another solvent, commonly called an additional solvent, is introduced into the method for compensating for solvent losses. The present invention may be beneficial if the solvent contains acetic acid, as oxidation of aromatic ethyl esters leads to acetic acid. In cases where the solvent includes acetic acid, when using aromatic ethyl esters, you can reduce the amount of additional solvent or even not add it at all. In one embodiment, the proportion of aromatic ethyl esters in the feed is selected based on the amount of acetic acid added to the reaction zone during the oxidation of the aromatic ethyl esters in order to achieve the desired reduction or approximation to the amount of additional acetic acid.

The catalysts used in this invention include substances that effectively catalyze the oxidation of an aromatic ethyl ester to an aromatic carboxylic acid. Preferably, the catalyst is dissolved in the bulk of the liquid phase oxidation reaction to promote contact between the catalyst, oxygen and liquid feed; however, a heterogeneous catalyst or catalyst components may also be used. The catalyst includes at least one suitable heavy metal, for example a metal with an atomic mass in the range of about 23-178. Examples of suitable heavy metals include cobalt, manganese, vanadium, molybdenum, chromium, iron, nickel, zirconium, hafnium, or cerium-type lanthanides. Suitable forms of these metals include, for example, acetates, hydroxides and carbonates. The catalyst preferably includes cobalt compounds alone or in combination with one or more compounds of manganese, cerium, zirconium or hafnium.

Typically, the catalyst may contain a promoter that is used to enhance the oxidative activity of the catalytically active metal, preferably without contributing to the formation or increase in the concentration of undesirable by-products, and preferably in such a form that it dissolves in the liquid reaction mixture. Typically, halogen compounds are used as a promoter, for example, hydrogen halides, sodium halides, potassium halides, ammonium halides, halogenated hydrocarbons, halogenated carboxylic acids and other halogenated compounds. It is preferable to use bromine compounds as a promoter. Suitable bromine compounds include bromanthracenes, Br ₂ , HBr, NaBr, KBr, NH ₄ Br, benzyl bromide. bromoacetic acid, dibromoacetic acid, tetrabromoethane, ethylene dibromide, bromoacetyl bromide or mixtures thereof.

The oxidation reaction is carried out in a reaction zone comprising at least one oxidation reactor. The oxidation reactor may consist of one or more reaction vessels. Suitable oxidation reactors allow the mixing of liquid and gaseous reactants and the removal of gaseous products to control the course of the reaction. Types of reactors that can be used include, but are not limited to, stationary stirred tank reactors and flow-through ideal displacement reactors. Typically, the oxidation reactors are a column with one or more devices for mixing and distributing oxygen in a liquid boiling reaction mixture. Typically, the devices for mixing are one or more blades mounted on a rotating or otherwise moving rod. For example, the blades may be located on a rotating central vertical rod. Reactors can be made from materials that are stable at specific temperatures, pressures and reagents. Typically, suitable oxidation reactors are made from inert materials, such as titanium, or lined with materials such as titanium or glass to increase resistance to corrosion and other aggressive factors. For example, titanium and glass or other suitable corrosion-resistant materials are typically used for reactors and other equipment for producing terephthalic acid from diethyl terephthalate and optionally para-xylene using a solvent containing acetic acid and a catalytic system, which may include a bromide promoter, under typical reaction conditions due to the corrosive effect of the acid solvent and certain reaction products, for example methyl bromide.

The molecular oxygen source is also fed to the reaction zone, preferably to the oxidation reactor. Typically, a gaseous molecular oxygen source is used as the oxidizing gas. It is convenient to use air as a source of molecular oxygen. Oxygen enriched air, pure oxygen, or other gaseous mixtures, usually containing molecular oxygen in an amount of at least about 10 vol%, are also used. It is important to note that as the molecular oxygen content in the oxygen source increases, the requirements for the compressor and the handling of inert gases in the effluent decrease. The source of molecular oxygen can be introduced into the reaction zone at one or more places and is usually introduced so as to promote contact between molecular oxygen and other reagents. Typically, an oxidizing gas is introduced into the lower part of the reactor and distributed by means of stirring devices, such as one or more blades mounted on a rotating rod. The molecular oxygen content in the oxidizing gas varies, but usually remains in the range of about 5-100 vol.% Molecular oxygen. In order to avoid the formation of potentially explosive mixtures, an oxidizing gas is usually added so that the unreacted oxygen content in the vapor space above the liquid reaction mixture is below the ignition limit. Maintaining the oxygen content in the exhaust gas below the ignition limit depends on the method and rate of oxygen supply, the reaction rate (which depends on the reaction conditions) and the exhaust gas outlet. Typically, the oxidizing gas is supplied in an amount corresponding to these operating parameters, so that the overhead from the reactor contains about 0.5-8 vol.% Oxygen (calculated on the basis without solvent).

The ratios of raw materials, catalyst, oxygen and solvent are not critical for this invention and vary not only depending on the choice of raw materials and the target product, but also on the choice of equipment and operating parameters. The mass ratio of solvent to feedstock is usually in the range of from about 1: 1 to about 30: 1. Typically, an oxidizing gas is used, at least in a stoichiometric amount based on the feed, but not in such a large amount that the unreacted oxygen content in the vapor space above the liquid reaction mixture exceeds the ignition limit. The advantage is that for the oxidation of aromatic ethyl esters to aromatic carboxylic acids, the stoichiometric oxygen demand is lower than the oxidation of methyl aromatic hydrocarbons to aromatic carboxylic acids. For example, to oxidize one mole of dimethylaromatic hydrocarbons into one mole of the corresponding aromatic dicarboxylic acids, a minimum of 3 moles of O ₂ is required and two moles of H ₂ O are formed. A by-product of H ₂ O is often undesirable, and further processing should be performed to remove this by-product from other components solvent before it is recycled. In contrast, the required stoichiometric amount of O ₂ for the oxidation of one mole of aromatic diethyl esters into one mole of the corresponding aromatic dicarboxylic acid is only 2 moles of O ₂ . A side product of oxidation is acetic acid, which can be used as a solvent and, therefore, can not be removed. Although oxygen is typically supplied to the reaction zone in an amount greater than stoichiometric, the use of aromatic ethyl esters instead of methyl aromatic hydrocarbon in the feed or part thereof reduces the overall oxygen demand to produce the desired amount of aromatic carboxylic acid. In cases where the rate of production of aromatic carboxylic acid is limited by oxygen demand, the use of aromatic ethyl esters instead of methyl aromatic hydrocarbons can increase the rate of formation of aromatic carboxylic acids.

Typically, the catalysts are used in concentrations such that the amount of catalytically active metal based on the weight of the feed from aromatic hydrocarbon and solvent is more than about 100 ppm. by weight, preferably more than about 500 ppm by weight and less than about 10,000 ppm by weight, preferably less than about 7000 ppm by weight, more preferably less than about 5000 ppm by weight. Preferably, the halogen promoter, more preferably bromine, is present in such an amount that the atomic ratio of halogen to catalytically active metal is greater than about 0.1: 1, preferably more than about 0.2: 1 and less than about 4: 1, preferably less than about 1: 1 . Most preferably, the atomic ratio of halogen to catalytically active metal is in the range of about 0.25: 1 to about 1: 1.

The oxidation of an aromatic ethyl ester to an aromatic carboxylic acid is carried out under an oxidation reaction. The reaction is carried out at temperatures sufficient to carry out the oxidation reaction and obtain the product of the desired purity with limited burn-out of the solvent. The heat released during oxidation is removed to maintain the necessary reaction conditions. Typically, the heat of reaction is dissipated by boiling the reaction mixture and removing the generated vapors from the reaction zone. Typically, a suitable temperature is greater than about 120 ° C, preferably about 140 ° C, and is below about 250 ° C, preferably below about 230 ° C. For some aromatic acids, for example terephthalic and naphthalenedicarboxylic acids, temperatures of about 145-230 ° C. are preferred. At temperatures below about 120 ° C, the oxidation reaction usually proceeds too slowly and leads to an insufficiently pure product and undesirably low conversion. For example, the oxidation of DET to terephthalic acid at a temperature below about 120 ° C may require more than 4 hours before practical completion. The resulting terephthalic acid may need significant additional processing due to the high content of impurities. At temperatures above 250 ° C there is a significant loss of solvent due to its burnout.

The pressure in the reaction vessel is chosen high enough to maintain a practically liquid phase in the vessel containing the feed and the solvent. Typically, pressures of about 5-40 kg / cm ² are suitable, although preferred pressures for specific methods vary depending on the composition of the feed and solvent, temperatures and other factors, but usually they are about 10-30 kg / cm ² . The contact time in the reaction vessel may vary in accordance with this performance and conditions in the range of about 20-150 minutes for different methods. In processes such as the oxidation of aromatic diethyl esters to terephthalic or isophthalic acid using acetic acid and water as a solvent for the reaction mixture, the solids content can reach up to about 50 wt.% Of the liquid reaction mass, more often it is usually about 10 -35 wt.%. For specialists in the field of production of aromatic acids, it is essential that the preferred conditions and operating parameters vary depending on different products and methods and can be within or even outside the intervals indicated above.

The overhead steam from the reactor usually contains a solvent and, if methyl aromatic hydrocarbons are present, also water. The advantage is that when replacing all or part of the methyl aromatic hydrocarbon in the feed with aromatic ethyl esters, the formation of excess water is reduced and thereby the need for treatment, use or removal of excess water is reduced. For example, in the liquid phase oxidation of para-xylene with the formation of terephthalic acid, approximately 2 moles of excess water are formed per 1 mol of the obtained terephthalic acid. In contrast, with liquid phase oxidation of DET with the formation of terephthalic acid, little excess water may or may not form at all. The overhead gas may also contain unreacted gaseous oxidizing gas, unreacted components of the feed, gaseous reaction by-products such as carbon oxides, evaporated reaction by-products such as methyl bromide, catalyst, or a combination thereof. If air is used as the oxidizing gas, the steam overhead usually contains solvent, water, unreacted feed components, monoethyl aromatic hydrocarbons, excess oxygen (if any), carbon oxides, nitrogen gas, and reaction by-products.

The overhead steam from the reactor may optionally be processed to return some components to the reaction zone. Typically, the overhead steam from the reactor is at high pressure and temperature, and its energy can be used preferably after treating the steam to return the solvent and unreacted components of the feed to the reaction zone. Such processing may include highly efficient separation, as described, for example, in US Pat. No. 5,723,656 to Abrams, which is incorporated herein by reference. This highly efficient separation helps reduce solvent loss and the amount of additional solvent used in the reaction by returning the reaction solvent (excluding water) and unreacted aromatic ethyl esters to the reaction zone. Highly efficient separation also makes it possible to practically retain water in the vapor phase, which is important for energy recovery.

Energy can be disposed of in the form of heat by heat exchange with another substance, for example water, to form steam, which can then be used in other parts of the method, in other methods, or both. Energy can also be disposed of in the form of work, for example, using an expander or other device to turn work into energy. Energy can be disposed of as heat or as work, either sequentially or in parallel. Recycled energy can be used to compensate for energy costs in this method or in other methods, stored, returned to the grid or use any combination of use for the necessary purposes.

Depending on the specific components of the raw material and solvent catalyst used, the overhead steam overhead of the reactor may contain corrosive compounds or other compounds that adversely affect energy recovery equipment. For example, when using bromine as a promoter in the liquid phase oxidation of DET to terephthalic acid, methyl bromide may be present in the overhead vapor stream of the reactor.

The overhead steam overhead of the reactor can be processed by another method or a combination of methods. For example, the overhead steam in the reactor, preferably after another treatment to isolate the solvent and unreacted components of the feed, can be treated to remove corrosive or combustible substances. Although any treatment can be used to remove corrosive or combustible substances, preferably without significant condensation of liquid water, it is preferable to subject the overhead steam to the reactor by thermal oxidation, more preferably catalytic thermal oxidation. The treated overhead steam overhead of the reactor is preferably sent to a catalytic oxidation apparatus in which the treated overhead steam overhead from the reactor is contacted with a suitable catalyst at high temperature and pressure in the presence of air or another source of molecular oxygen, and then the corrosive and combustible by-products are catalytically oxidized less corrosive or environmentally friendly substances. It is not necessary to apply preheating before such treatment by catalytic oxidation. Preheating can be accomplished by any suitable method, such as using a heat exchanger, direct injection of water vapor, or other methods known in the art.

Such catalytic oxidation treatment can be used to reduce or remove corrosive alkyl bromides. In addition, residual solvent that may be present can be removed by such catalytic oxidation treatment. In order to reduce the load on the catalytic oxidation unit, it is preferable to treat the overhead steam overhead of the reactor to remove a significant portion of the solvent. A high concentration of the reaction solvent in the catalytic oxidation stream would lead to an unacceptably high temperature rise in the catalytic oxidation unit. In addition, burning a reaction solvent that could be returned to oxidation would be economically disadvantageous.

Oxidation catalysts for such catalytic oxidation are commercially available from, for example, Engelhard Corp. or AlliedSignal Inc. Typically, such oxidation catalysts contain transition elements of the periodic system (IURAC), for example metals of group VIII. The preferred metal for catalytic oxidation treatment is platinum. Such catalytically active metals are used as oxide-type composites. Typically, the support for such catalytically active metals may be less catalytically active or inert. The carrier may be contained in the composite. Typical catalyst supports include mullite, spinel, sand, silica, alumina, aluminosilicate, titanium oxide, zirconia, alpha alumina, gamma alumina, delta alumina, eta alumina and their composites. Such catalytic oxidation catalysts can be used in any convenient configuration, of any shape or size, for contacting the oxidation promoting components with a stream that undergoes catalytic oxidation. For example, the catalyst may be in the form of tablets, granules, rings, spheres, etc.

Other optional methods for treating the overhead steam overhead of a reactor include passing through a scrubber to remove acidic inorganic substances such as bromine or hydrogen bromide. Hydrogen bromide and bromide are formed during the catalytic oxidation of alkyl bromides and organic impurities.

In a specific embodiment, the invention is used to oxidize in a boiling liquid phase a feed containing DET and para-xylene to terephthalic acid and isophthalic acid. The feed and solvent are continuously fed into the reaction zone, which is a reaction vessel. A catalyst and promoter, each preferably dissolved in a solvent, are also fed into the reaction vessel. A preferred solvent is acetic acid or aqueous acetic acid with a preferred solvent to feed ratio of from about 2: 1 to about 5: 1. The catalyst preferably contains cobalt in combination with manganese, cerium, zirconium, hafnium, or any combination thereof, as well as a bromine source. The catalyst is taken in amounts providing a content of about 600-3500 ppm. by weight of catalytically active metals based on the weight of aromatic hydrocarbon and solvent. Most preferably, the promoter is present in such an amount that the atomic ratio of bromine to catalytically active metal is from about 0.2: 1 to about 1.5: 1. The oxidizing gas, which is most preferably air, is fed into the reaction vessel at a rate effective to obtain a ratio of at least about 3-5.6 moles of molecular oxygen per mole of aromatic hydrocarbon in the feed so that the overhead vapor stream of the reactor contains about 0.5- 8 vol.% Oxygen (calculated on the basis of without solvent).

In such a specific embodiment, the reaction vessel is preferably maintained at a temperature of about 150-226 ° C and a pressure of about 5-40 kg / cm ² . Under such conditions, the contact of oxygen with the components of the feed in the liquid phase leads to the formation of crystals of solid terephthalic acid, usually in finely divided form. Under such conditions, the contact of oxygen and diethyl hydrocarbons in the liquid phase leads to the formation of acetic acid and crystals of solid terephthalic acid. The solids content of the boiling liquid suspension typically ranges from 40% by weight, and preferably from about 20-35% by weight, and the water content is usually from about 5-20% by weight, based on the weight of the solvent. Boiling the liquid mass to control the heat of reaction generated causes the evaporation of volatile components of the liquid mass, including the solvent and reaction water, along with the evaporation of by-products, unreacted components of the feed. Unreacted oxygen and vaporizing liquid components are released from the liquid into the reaction space above the liquid phase. Other substances, such as nitrogen and other inert gases present in the air, which is used as an oxidizing gas, carbon oxides and evaporating by-products, such as methyl acetate and methyl bromide, may also be present in the overhead steam stream of the reactor.

In this embodiment, the aromatic dicarboxylic acid obtained in the reaction, suspended or dissolved in part of the liquid mass, is removed from the vessel. The product stream can be processed by conventional methods to separate the components and isolate the aromatic carboxylic acid contained therein, usually by crystallization, separation of liquid and solid, and drying. As usual, a suspension of a solid product in a liquid is centrifuged, filtered, or both methods are applied in one or more stages. A soluble product dissolved in the liquid phase can be isolated by crystallization. A liquid containing water, a solvent, unreacted feed, and often also one or more liquid catalysts, a promoter, and intermediate reaction products can be returned to the reaction vessel. The formation of terephthalic acid from DET can proceed more slowly than the conversion of para-xylene to terephthalic acid. However, unreacted DET, which leaves the reaction zone either with the overhead vapor stream of the reactor, or together with the products, can be isolated together with the solvent and returned to the reaction zone, thereby increasing the effective contact time of the DET so that the slower reaction proceeds efficiently.

In such an embodiment, the resulting aromatic dicarboxylic acid isolated from the liquid can be used or stored as such, or it can be cleaned or treated differently. Purification is necessary to remove by-products and impurities that may be present together with the isolated aromatic dicarboxylic acid. For aromatic dicarboxylic acids, such as terephthalic and isophthalic acids, the purification preferably includes hydrogenation of the oxidation product, usually dissolved in water or another aqueous solvent, at elevated temperature and pressure in the presence of a catalyst containing a hydrogenation-active metal such as ruthenium, rhodium, platinum or palladium, typically supported on coal, titanium oxide, or other suitable chemically stable supports or supports for a catalytically active metal. Cleaning methods are known, for example, from US patents 3584039, 4782181, 4626598 and 4892972.

An advantage is that the use of aromatic ethyl esters can reduce the formation of certain impurities. For example, a notable impurity in crude terephthalic acid (derived from para-xylene) is 4-carboxybenzaldehyde (4-CBA), an intermediate in the formation of terephthalic acid from para-xylene. Great efforts are often expended in order to reduce the content of 4-CBA in terephthalic acid. In contrast, 4-CBA is not an intermediate in the formation of terephthalic acid from DET. DET can be used in raw materials to reduce the formation of 4-CBA as an impurity in the resulting terephthalic acid.

If the purification is carried out using water as a solvent, washing with water to remove the residual oxidation solvent from the solid aromatic carboxylic acid may be an alternative to drying. Such washing can be accomplished using suitable solvent replacement devices, such as filters, as described in US Pat. Nos. 5,679,846 and 5,175,355. Optionally, all or part of the mother liquor from the cleaning steps can be sent, directly or indirectly, to a high-efficiency separation apparatus or to another treatment. For example, if one or more distillation columns are used for highly efficient separation, all or part of the mother liquor can be used as reflux for one or more of these highly efficient distillation columns.

Typically, the oxidation mother liquor is separated from the resulting crude aromatic carboxylic acid using separation methods known in the art, for example, filtration, centrifugation, or a combination of known methods. It is preferable to return at least a portion of the mother liquor, and in industrial operations, a significant portion of the mother liquor is usually returned. For example, such a mother liquor can be returned directly or indirectly to an oxidation reactor or to a highly efficient separation apparatus. Such recycling is particularly desirable in the production of terephthalic acid from raw materials containing DET and para-xylene. The mother liquor can be separated from the obtained purified aromatic carboxylic acid by similar methods and the mother liquor can be returned after treatment with or without treatment for use in other stages of this method or in other methods.

It is understood that by-products, for example aromatic monoethyl esters, can form during the reaction. Some by-products will enter the vapor phase and they will be treated as part of the overhead steam of the reactor, some by-products will remain in the mother liquor, and some by-products will be present in the resulting aromatic carboxylic acid. The same by-products may be present in more than one of these streams. Such by-products or part thereof can be isolated and, if desired, returned to the reaction zone or blown off either after isolation or as part of a purge stream. Preferably, the by-products can be oxidized to form either aromatic carboxylic acids or a solvent that is returned to the reaction zone.

In addition to using the resulting aromatic carboxylic acids, aromatic diethyl esters can also be used in oxidation processes to produce excess acetic acid, which can be returned or sold, or used in other methods. Acetic acid is a highly demanded product of mass consumption, and the possibility of obtaining it as an additional product can be especially attractive. In one embodiment, the invention provides a method for producing acetic acid, either to reduce solvent loss, or to produce an excess of acetic acid. In this embodiment, aromatic ethyl esters are used in the liquid phase oxidation process of the type described.

Aromatic carboxylic acids can be used to make polymers. Although there are many methods for preparing polymers from carboxylic acids, generally carboxylic acids can be used in a condensation reaction with ethylene glycol to form an ethylene glycol ester molecule and an aromatic acid followed by polymerization. For example, terephthalic acid can be reacted with ethylene glycol to form PET. In another example, naphthalenedicarboxylic acid can be reacted with ethylene glycol to form PEN. Typically, condensation reactions are carried out with heating and in the presence of an acid catalyst. Water generated as a by-product is removed from the reaction, for example by distillation, to stimulate the reaction and minimize the reverse reaction.

In one embodiment, PET is formed from terephthalic acid and ethylene glycol. In the first stage of the reaction, an ester is formed from an acid and two ethylene glycol molecules. In a second step, the ester is heated to a temperature of about 210-290 ° C. under low pressure. It is known that many catalysts can be used to catalyze a polymerization reaction. Preferably, the catalyst includes antimony compounds, for example antimony (III) oxide. In this second stage, PET is formed and a portion of ethylene glycol is regenerated. Typically, ethylene glycol is removed and returned to the reaction.

In another embodiment, at least a portion of the ethylene glycol used to form the polymer is prepared by ethanolysis.

Alternatively, aromatic carboxylic acid can be converted to methyl ether and reacted with ethylene glycol to transesterify with alcohol to form an aromatic acid ester molecule with ethylene glycol, which is then polymerized. In this reaction, a by-product is formed - methanol, which is removed to stimulate the reaction.

Molecules of aromatic acid ester with ethylene glycol are optionally purified either prior to polymerization, or between polymerization steps, or both. In addition, other monomers or oligomers can be introduced into the polymerization process to produce polymer, terpolymers, etc.

The present invention has been described above and in the examples below with reference to specific options, but it is clear that you can make changes to the described apparatus and method, which would remain within the scope of the invention. For example, you can add devices such as heat exchangers, preheaters, additional refrigerators, reboilers, energy recovery devices and other equipment used in industry, without deviating from the scope of the invention. As another example, additional steps can be carried out, such as treating various streams to remove impurities or to change the physical or chemical properties of the streams without departing from the scope of the invention.

The following are non-limiting examples that illustrate various embodiments of the present invention.

In examples 1-5, unless otherwise indicated, the ethanolysis reaction was carried out in a 2 L Parr reactor. Reagents were loaded into the reactor, the reactor was closed and purged with nitrogen. Unless otherwise noted, the reactor was first pressurized to 40 psi (approximately 276 kPa), the stirrer was turned on, and the reactor was held at 200 ° C. for 2 hours. After 2 hours, the heating was turned off and the reactor was allowed to cool to room temperature overnight (with continuous stirring). After this, stirring was stopped and the reaction products were separated by distillation. Ethanol was isolated by distillation with stirring under ordinary pressure and the remaining reaction product was subjected to vacuum distillation. Vacuum distillation was carried out at about 27 "-29" RT. Art.

EXAMPLE 1

300 g of PET flakes of the types shown in Table 1 were reacted with ethanol at a weight ratio of ethanol and PET of 3: 1 according to the procedure described above. Ethanol contained 0.0734 wt.% Water. No further catalyst was added. Both mixed flakes and pure colorless flakes were obtained from NAPCOR, the National Association for PET Container Resources. The blended flakes contained about 55% by weight of brown flakes, and the rest were mainly green, amber and colorless PET flakes. The original bottle-grade resin was obtained from Wellman Inc. in the form of product No. 61802. The theoretical maximum percentage of DET and ethylene glycol in the reaction mixture was 28.86 wt.% And 8.06 wt.%, Respectively.

TABLE 1 DET and ethylene glycol isolated from various PET flakes Experience Used cereal DET isolated, wt.% Ethylene glycol, wt.% one Mixed 22.3 6.25 2 Mixed 25.2 6.54 3 Bottle grade resin 0.53 0.21 four Pure Colorless Clean 1.06 0.45 5 Brown 24.16 5.41 6 Amber 0.80 0.37 7 Mixed w / o brown 2.8 0.51 8 Pure colorless w / brown * 25.21 6.0 * 45 wt.% Pure colorless and 55% brown

The results of experiments 1 and 2 in table 1 showed that even in the absence of a catalyst, the mixed flakes contained catalytically active impurities catalyzing the ethanolysis reaction. Experiments 3-8 showed that catalytically active impurities were contained mainly in brown flakes. The authors were surprised to find that copper phthalocyanine, the pigment commonly used in brown PET, is a particularly effective catalyst for the ethanolysis reaction.

EXAMPLE 2

300 g of pure colorless PET flakes were reacted with 900 g of ethanol as described above in the presence of titanium in the form of organic titanate. As a source of titanium, TYZOR TPT, DuPont organic titanate, was used. Ethanol contained 0.0734 wt.% Water. Organic titanate was added based on 1000 ppm. by weight (based on PET) of titanium. The results are shown in table 2, experiment 9. Experiment 10 was carried out according to the above method using 200 g of pure colorless PET flakes and 600 g of ethanol. Organic titanate was added in an amount corresponding to 17.6 ppm. by weight (based on PET). The results are shown in table 2.

TABLE 2 DET and ethylene glycol obtained using organic titanate Experience Titanium DET isolated, wt.% Ethylene glycol, wt.% 9 1000 ppm by weight ppmw 25.61 6.24 10 17.6 ppm by weight 25.19 6.36

Table 2 illustrates the effectiveness of organic titanate in the catalysis of ethanolysis of PET. Even the very small amount used in experiment 10 was effective.

EXAMPLE 3

Ethanolysis was carried out as described above, without catalyst, using mixed PET flakes, as described in Example 1, and ethanol containing 0.0734 wt.% Water. The ethanol: PET ratio was 3: 1 and no further catalyst was added. After distillation of the reaction product, as described above, still bottoms were used as a catalyst for further ethanolysis reactions. An additional ethanolysis reaction was carried out using 600 g of ethanol containing 0.0734 wt.% Water, 162 g of pure colorless PET flakes and 38 g of bottoms. No additional catalyst was used. The results are shown in table 3.

TABLE 3 Distillation residues as an ethanolysis catalyst Experience PET DET highlighted Ethylene glycol isolated eleven 162 g pure colorless PET 38 g bottoms distillation distillation bottoms 24.3 wt.% 5.51 wt.%

Table 3 shows that the catalytically active impurities present in the mixed cereal feed remained active during the distillation and recycling of some bottoms could be used to efficiently catalyze the ethanolysis of PET. From a comparison of experiment 4 in table 1 and experiment 11 in table 3, the effectiveness of bottoms in catalysis of the ethanolysis reaction is especially clearly visible.

EXAMPLE 4

Additional tests were performed to determine the effect of water on the ethanolysis reaction. The ethanolysis reaction was carried out according to the method described above, and the results are shown in table 4, which shows the concentration of water used in ethanolysis (wt.%). For experiments 12-17, mixed flakes were used as the PET source (as described above), they were mixed with ethanol in an ethanol: PET ratio of 3: 1. For experiment 17, 300 g of mixed flakes were dried in a vacuum oven, removing approximately 1.78 g of water. For experiment 18, pure colorless flakes were used as PET raw material, 20 ppm was added to them. by weight of titanium (based on PET) in the form of organic titanate.

TABLE 4 The effect of the concentration of water in ethanol Experience Water in ethanol, wt.% DET isolated, wt.% Ethylene glycol, wt.% 12 0.0734 25.2 6.54 13 6.98 0.05 0 fourteen 1.06 2.8 0.95 fifteen 0.50 10.09 2.16 16 0.29 16.4 4.46 17 0.29 25.0 6.1 eighteen 1.06 21.4 5.99

The results shown in table 4 show that the effectiveness of catalytically active impurities in the catalysis of ethanolysis of PET is sensitive to the presence of water. Even about 1 wt.% Water in fuel ethanol significantly reduces the effectiveness of catalytically active impurities. However, it is surprising that organic titanate proved to be an effective catalyst even when using ethanol of fuel quality (about 1 wt.% Water). The ability to use fuel ethanol is especially important because fuel-grade ethanol is an easily accessible consumer product in many regions. In addition, due to the affinity of ethanol for water, the assumption of a certain amount of water in ethanol greatly facilitates the transport and handling of it.

EXAMPLE 5

It has been found that water can be used to facilitate the separation of the liquid phases of DET and ethylene glycol. 200 g of mixed PET flakes (as described above), 600 g of ethanol (with 0.0734 wt.% Water) and 0.133 g of zinc acetate were loaded into a 2-liter Parr reactor, heated to 220 ° C, stirred for 2 hours and cooled. Ethanol was removed from the product mixture by distillation at atmospheric pressure, followed by vacuum distillation of the remaining volatile impurities. The entire overhead after vacuum distillation was collected in one fraction and its mass was determined to be 207 g. In a cabinet heated to 58 ° C, this fraction formed two liquid layers. The liquid layers were analyzed and the results are shown under the numbers 19a (lower layer) and 19b (upper layer) in table 5 below. Then water (41 g) was added, the mixture was shaken and allowed to separate into two layers. The layers were analyzed and the results are shown in Table 5 under the numbers 20a (lower layer) and 20b (upper layer).

TABLE 5 Liquid separation Experience DET, wt.% Ethylene glycol, wt.% Diethylene glycol, wt.% Water, wt.% 19a 95.69 3.94 0.27 0 19b 4.29 87.3 4.79 0 20a 96.03 0.77 0.28 2.92 20b 0.45 51.9 3.09 50.74

As shown in table 5, water promotes the separation of the liquid phases of DET and ethylene glycol. The amount of ethylene glycol in the lower layer decreased significantly, and the amount of DET in the lower layer increased slightly. It is important that the bulk of the water remained in the upper layer along with the bulk of ethylene glycol. Since water is mainly located in the upper layer, it can be sent together with ethylene glycol for further purification, and the lower layer can be returned to distillation or isolated as the final DET product.

EXAMPLE 6

It was found that para-xylene can be used to facilitate the removal of DET from the ethylene glycol-rich fraction from the extraction separation of liquid phases. In a Parra reactor, 800 g of mixed PET flakes (as described above), 2400 g of ethanol (with 0.0734 wt.% Water) and 80 mg of titanium (IV) isopropoxide were loaded in several portions, heated to 200 ° C, stirred for 2 hours and cooled. From each portion, ethanol was removed from the mixture of reaction products by atmospheric distillation followed by vacuum distillation of the remaining volatile impurities. The entire overhead from vacuum distillation in the form of several portions was collected and combined into one fraction, the mass of which was 947 g. This fraction was processed in four stages. In stage 1, in a cabinet at 70 ° C, this fraction formed two liquid layers. The lower layer was enriched in DET, and the upper layer was enriched in ethylene glycol. The upper layer weighing 208 g was separated. In step 2, 50 g of water was added to the top layer isolated in step 1. The addition of water led to the formation of two layers, of which the upper layer is enriched in ethylene glycol and has a mass of 214.6 g, and the lower layer is enriched in DET and has a mass of 43.4 g. The upper layer from stage 2 was separated, its composition is shown in table 6 (extraction 0). At stage 3, part of the upper layer of stage 2 weighing 139 g was mixed with an equal mass of para-xylene and the mixture was shaken and allowed to separate into two layers at 70 ° C. It was found that the lower layer was enriched with ethylene glycol, it was separated. The composition of this lower layer, selected in stage 3, is shown in table 6 (extraction 1). At stage 4, the lower layer of stage 3 was mixed with an equal weight of fresh para-xylene, allowed to separate into two layers and the lower layer (rich in ethylene glycol) was separated. The composition of the lower layer selected in stage 4 is shown below in table 6 (extraction 2).

Table 6 Ethylene glycol extraction with para-xylene Extra
nation DET (wt.%) Ethylene glycol (wt.%) Diethylene glycol (wt.%) Water (wt.%) para-Xylene (wt.%) 0 0.50 79.18 1.93 18.4 0 one 0.0037 77.49 1.85 20.5 0.118 2 <0.001 77.62 1.79 20.5 0.114

As shown in table 6, with para-xylene extraction, the DET is effectively removed from the ethylene glycol enriched layer. It is expected that the composition of the glycol-rich layer after extraction with a hydrocarbon such as para-xylene will be sufficiently pure to allow further purification of ethylene glycol to the purity of the polyester by conventional distillation methods.

EXAMPLE 7

Periodic liquid-phase oxidation reactions were carried out in 71 ml of a titanium batch reactor connected to a shaking device to mix the contents of the reactor. The components of the feed were loaded into this reactor, as shown in Table 6 below, as well as a catalyst solution containing 0.1 wt.% Co + Mn (as acetates) and HBr at a Co / Mn / Br molar ratio of 1/1/1. The solvent loaded in comparative experiment A and experiments 21 and 22 was a mixture of 80 wt.% Benzoic acid and water (20 wt.%). The solvent in experiment 23 was a mixture of 80 wt.% Acetic acid and 20 wt.% Water. An air pressure of 4.3 mol 02 per mole of charged para-xylene was created in the reactor. Then, the indicated temperatures were established in the reactor with internal stirring. The reactor was kept at this temperature for the indicated minutes, cooled to 25 ° C, then both gas and a suspension of products were taken for analysis. For analysis of the entire product, high pressure liquid chromatography (HPLC) was used. The formation of acetic acid was determined by gas chromatography. The yield of acetic acid was determined by acetate in comparative experiment A (introduced with catalytically active metals) adjusted for the loss of acetic acid in the form of carbon oxides. The results (including comparative experiment A) are shown in table 7.

TABLE 7 Periodic Liquid Phase Oxidation Reactions BUT 21 22 23 Reactor loading Det 0.0000 0.1200 0.1200 0.1200 para-xylene 0.5100 0.5000 0.5100 0.5100 Water 1.51 1.53 1.50 1.51 Acetic acid 7.50 Benzoic acid 7.52 7.51 7.51 0 Temperature (° F) 383 383 390 390 Minutes @ Pace twenty twenty thirty thirty Moth O ₂ / mol aromatic. hydrocarbon 4.261 4.331 4.246 4.261 Product (wt.%) TA 1.00 8.05 7.1 7.85 6.75 4-CBA 1.122 0.049 0.047 0.023 0.018 Benzoic acid 1.244 87.2 71.5 78.1 <0.001 n-toluic acid 1.428 0.026 0.031 0.005 0.004 Det 0 0.771 0.617 0.704 MET 0 0.298 0.357 0.275 Mol.% Converted ethyl groups N / a 33.9 53.5 70.2 A mole of the formed HOAc groups / mole conversion. ethyl groups N / a 52.2 59.6 (not determined)

In experiments with benzoic acid, the total amount of acetic acid formed can be determined as a solvent, which can be determined at low concentrations in the presence of a solvent, benzoic acid. These results show that in experiment 21, 33.9% of the ethyl groups in the DET were converted during the reaction. This can be determined by the concentration of residual DET and MET in the product. The amount of acetic acid in the product showed that 52.2% of the converted ethyl groups are manifested in the total formation of acetic acid. In experiment 22, at a slightly elevated temperature (390 ° F compared to 383 ° F) and for a longer reaction period (30 min compared to 20 min), the conversion of ethyl groups increased to 53.5% and the selectivity of acetic acid formation increased to 59.6 %

In experiment 23, due to the use of acetic acid as a solvent, it was not possible to accurately determine the increase in the content of acetic acid in the reactor. However, a conversion of 70% of the ethyl groups contained in DET and MET indicates an increase in conversion in the case of this solvent.

As follows from the data of table 7, the use of DET as a raw material did not adversely affect the production of terephthalic acid and in experiments 22 and 23 led to a significantly lower formation of 4-CBA. Example 6 shows that DET can replace all or part of para-xylene, commonly used as a raw material in the liquid phase production of terephthalic acid.

EXAMPLE 8

Semi-continuous liquid phase oxidation was carried out with stirring in a 2-liter pressure reactor made of titanium. Only solvent and catalyst were charged into this unit, pressure was created with nitrogen and heated to the indicated reaction temperature with stirring at a speed of 1000 rpm. Then, a mixture of raw materials from 20 wt.% DET and 80 wt.% Para-xylene was added to the reactor at a rate of 333 g in 80 minutes. At this time, a gas stream containing 21 wt.% O ₂ in nitrogen was supplied from the bottom of the reactor, and gas discharged from the reactor was passed through a refrigerator to return the condensed solvent to the reactor and non-condensable gaseous components were removed. After adding all the raw materials from DET and para-xylene, the gas was again replaced with nitrogen, the installation was cooled, the product was collected and analyzed as in the previous example. The results are shown in table 8.

TABLE 8 Semicontinuous Liquid Phase Oxidation Reactions 24 25 The loading of the reactor (the solvent contained 880 ppm Co and Co / Mn / Br in a molar ratio of 1/1/1) Det 67 67 n-Xylene 266 266 Acetic acid 0 884 Benzoic acid 884 0 Water 130 130 Reactor Temperature (° F) 385 385 % conversions (DET + MET) 60.2 51.7

Product (wt.%) TA 37.0 31,0 4-CBA 0.03 0.080 Benzoic acid (CBA) 58.8 0.135 n-toluic acid <0.001 0.051 n-Toluyl aldehyde <0.001 <0.001 Det 0.788 0.993 MET 1.25 1.33

Table 8 shows that DET can be successfully used as part of the feedstock in the liquid phase oxidation process of para-xylene to terephthalic acid with a low content of 4-CBA with a conversion of the DET / MET mixture of more than 60% per pass.

Claims (29)

1. A method of processing waste poly (ethylene terephthalate), comprising the steps of:
a) the reaction of the starting product with ethanol at a temperature of from 180 ° C to 300 ° C for 0.25-5.0 hours in the presence of a catalyst selected from the group consisting of catalytically active impurities of polyethylene terephthalate - compounds of copper and organic titanium, zinc, cobalt, manganese, magnesium, titanium and their combinations, with the formation in the reaction zone of a mixture of reaction products, including ethanol, ethylene glycol and diethyl terephthalate;
b) separating the reaction product mixture and isolating therefrom a first fraction containing isolated ethanol, a second fraction containing ethylene glycol and a third fraction containing diethyl terephthalate. 2. The method according to claim 1, in which the ethanol at the stage of mixing with the starting product with the formation of the reaction mixture is ethanol of fuel quality. 3. The method according to claim 1, in which the stage of separation from the mixture of reaction products of the first fraction containing the separated ethanol is carried out in the first separation zone, and the stage of separation from the mixture of reaction products of the second fraction containing ethylene glycol, and the separation of the reaction products of the third fraction containing diethyl terephthalate is carried out in a second separation zone. 4. The method according to claim 3, further comprising the steps of:
c) separating the second fraction into a first stream containing a major portion of diethyl terephthalate and a second stream containing ethylene glycol;
d) returning at least a portion of the first stream to the second separation zone; and
e) recovering ethylene glycol from a second stream in a third separation zone. 5. The method of claim 4, wherein the step of separating the second fraction further comprises the step of adding water to at least a portion of the second fraction. 6. The method of claim 5, wherein the step of separating the second fraction further comprises the step of adding n-heptane, para-xylene, or both of them, to at least a portion of the second fraction. 7. The method according to claim 3, in which the first separation zone includes a first distillation column operating at near atmospheric pressure, and the second separation zone includes a second distillation column operating at a pressure below atmospheric. 8. The method according to claim 3, in which at least a portion of the separated ethanol in the first fraction is in the reaction zone. 9. The method according to claim 1, in which the catalyst is titanium. 10. The method according to claim 9, in which the ethanol at the stage of mixing with the starting product with the formation of the reaction mixture is ethanol of fuel quality. 11. The method according to claim 1, further comprising the step of isolating a fourth fraction containing a catalyst from the reaction product mixture, at least a portion of the fourth fraction being sent to the reaction zone. 12. The method according to claim 1, in which at least part of the mixture of reaction products is subjected to separation into solid and liquid products to remove at least part of the undesirable impurities. 13. The method according to claim 1, in which at least a portion of the mixture of reaction products is subjected to ion exchange to remove at least a portion of undesirable impurities. 14. Equipment for the processing of poly (ethylene terephthalate) waste, including:
a) a reactor for reacting the starting material with ethanol and forming a mixture of reaction products;
b) a distillation column operating at atmospheric pressure to isolate ethanol from the mixture of reaction products and return at least a portion of the ethanol recovered directly or indirectly to the reaction zone; and
c) a vacuum distillation column for separating diethyl terephthalate from a mixture of reaction products. 15. The apparatus of claim 14, further comprising a device for separating solid and liquid products to remove at least a portion of insoluble unwanted impurities from at least a portion of the reaction product mixture. 16. The apparatus of claim 14, further comprising an ion exchange resin for removing at least a portion of soluble unwanted impurities from at least a portion of the mixture of reaction products. 17. A method of producing diethyl terephthalate from waste poly (ethylene terephthalate), comprising the steps of:
a) the reaction of the starting product with ethanol at a temperature of from 180 ° C to 300 ° C for 0.25-5.0 hours in the presence of a catalyst selected from the group consisting of catalytically active impurities of polyethylene terephthalate - organic copper compounds of titanium, zinc, cobalt , manganese, magnesium and their combinations, with the formation in the reaction zone of a mixture of reaction products, including ethanol, polyethylene terephthalate, diethyl terephthalate and ethylene glycol;
b) separating from the reaction product mixture the first fraction containing ethanol, the second fraction containing an azeotrope of diethyl terephthalate with ethylene glycol, and the third fraction containing diethyl terephthalate. 18. The method according to 17, in which water is present in the reaction zone. 19. The method according to 17, further comprising the steps of:
c) isolating from the azeotrope a stream containing the bulk of diethyl terephthalate by separating the liquid phases at a temperature above the melting point of diethyl terephthalate; and
d) supplying at least a portion of the stream from step (c) to a separation in step (b). 20. The method according to claim 19, further comprising the step of separating at least a portion of the insoluble undesirable impurities from the mixture of reaction products. 21. The method according to claim 19, further comprising the stage of separation by ion exchange of at least part of the soluble unwanted impurities from the mixture of reaction products. 22. The method according to 17, in which the catalyst is titanium (IV) isopropoxide. 23. A method of producing diethyl terephthalate and diethyl isophthalate, comprising the steps of:
a) a reaction in the reaction zone of ethanol with a feed containing terperephthalic acid terpolymer, isophthalic acid and ethylene glycol, at a temperature of from 180 ° C to 300 ° C for 0.25-5.0 hours in the presence of a catalyst selected from the group consisting of catalytically active impurities of polyethylene terephthalate - compounds of copper and organic titanium, zinc, cobalt, manganese, magnesium and their combinations, with the formation of a mixture of reaction products;
b) isolating from a mixture of reaction products a first fraction containing ethanol;
c) recovering from the mixture of reaction products a second fraction containing ethylene glycol; and
d) isolating from the mixture of reaction products a third fraction containing diethyl terephthalate and diethyl isophthalate. 24. The method according to item 23, in which the ethanol in the reaction zone is ethanol of fuel quality. 25. A method for processing poly (ethylene terephthalate) waste, comprising the steps of:
a) a reaction in a first reaction zone of a first feedstock containing polyethylene terephthalate with ethanol to form a first mixture of reaction products;
b) recovering aromatic ethyl esters from the first mixture of reaction products;
c) oxidation in the second reaction zone of a second feed containing at least a portion of aromatic ethyl esters to form an aromatic carboxylic acid;
d) a reaction in the third reaction zone of at least a portion of aromatic carboxylic acid and ethylene glycol to form a polymer comprising polyethylene terephthalate, wherein the reaction in all zones is carried out at a temperature of from 180 ° C to 300 ° C for 0.25-5.0 hours 26. The method according A.25, in which the first raw material contains at least 1000 ppm by weight of polyvinyl chloride calculated on the basis of polyethylene terephthalate. 27. The method of claim 26, wherein at least a portion of the first reaction product mixture is contacted with an ion exchange resin to remove at least a portion of soluble impurities present in the first reaction product mixture. 28. The method of claim 25, wherein the ethanol is fuel grade ethanol. 29. The method according A.25, in which the second raw material contains a precursor of aromatic carboxylic acid is dimethyl aromatic hydrocarbon.