Liquid raw material, method for preparing same, and method for preparing terephthalic acid using same

Abstract

The present invention relates to a liquid raw material, a method for preparing same, and a method for preparing terephthalic acid using same. The liquid raw material is obtained through alcoholysis of waste polyester and includes a specific compound.

Description

Liquid raw material, method for manufacturing the same, and method for manufacturing terephthalic acid using the same

[0001] The present invention relates to a liquid raw material obtained from waste polyester, a method for manufacturing said liquid raw material, and a method for manufacturing terephthalic acid using said liquid raw material.

[0002] Among the types of polymers, polyester resin is widely used as a material for beverage or food containers; various packaging films or sheets; or various interior and exterior materials such as panels, shelves, and partitions.

[0003] As the widespread use of polyester resins has resulted in an unmanageable annual global volume of polyester waste, interest in recycling waste polyester or regeneration processes utilizing waste polyester is increasing. Specifically, development is underway for processes that decompose (depolymerize) waste polyester to produce recycled polymerization raw materials, and further, to manufacture recycled polyester resin using these recycled polymerization raw materials.

[0004] As an example of the above process, recycled terephthalic acid (r-TPA), a recycled polymerization raw material, is produced by subjecting waste polyester to alcoholic decomposition and hydrolysis. However, this process consumes a significant amount of energy to recover by-products generated during the alcoholic decomposition reaction, and the hydrolysis reaction rate is not secured above the required level, which limits the ability to increase the yield of recycled terephthalic acid.

[0005] Therefore, there is a need for a technology that can produce recycled terephthalic acid at a high yield while lowering the energy consumed in the recycling process by improving the waste polyester recycling process.

[0006] The inventors have confirmed that by controlling the composition of the liquid raw material, which is a product obtained through the alcoholic decomposition of waste polyester, it is possible to reduce the energy required to recover by-products (e.g., ethylene glycol (EG)) generated during the alcoholic decomposition reaction process and to produce terephthalic acid of high purity in high yield.

[0007] Therefore, the objective of the present invention is to provide a liquid raw material capable of securing an optimal hydrolysis reaction rate while drastically reducing the energy required to recover by-products, and a method for manufacturing the same.

[0008] In addition, another objective of the present invention is to provide a method for manufacturing terephthalic acid using the above-mentioned liquid raw material.

[0009] To solve the above problem, the present invention provides a liquid raw material obtained through the alcohololysis of waste polyester and comprising a compound represented by the following chemical formulas 1 to 3:

[0010] [Chemical Formula 1]

[0011]

[0012] [Chemical Formula 2]

[0013]

[0014] [Chemical Formula 3]

[0015]

[0016] In the above chemical formulas 1 to 3,

[0017] R1, R2, and R3 are each independently alkyls having 4 or more carbon atoms, and

[0018] n is an integer greater than or equal to 1.

[0019] In addition, the present invention provides a method for manufacturing a liquid raw material comprising the step of alcoholizing waste polyester with an alcohol having 4 or more carbon atoms, and comprising a compound represented by Chemical Formula 1 to Chemical Formula 3.

[0020] The present invention also provides a method for producing terephthalic acid comprising the steps of: alcoholizing waste polyester with an alcohol having 4 or more carbon atoms to produce a liquid raw material; and hydrolyzing the liquid raw material, wherein the liquid raw material comprises a compound represented by Chemical Formula 1 to Chemical Formula 3.

[0021] Because the liquid raw material contains a specific compound in a specific ratio, the energy consumed to recover by-products (e.g., ethylene glycol, etc.) generated during the alcohol decomposition reaction process can be drastically reduced, and an optimized hydrolysis reaction rate can be secured. Specifically, the liquid raw material according to the present invention is easiest to purify, allows for efficient recovery of process chemicals such as alcohol (e.g., ethylene glycol), and can have excellent hydrolysis reactivity.

[0022] Therefore, when terephthalic acid is manufactured using the liquid raw material according to the present invention, high-purity terephthalic acid (regenerated terephthalic acid) can be manufactured in high yield even if the hydrolysis reaction is carried out for a relatively short time (e.g., within 4 hours).

[0023] The present invention will be described in detail below. Hereinafter, the present invention is not limited to the contents described below, but may be modified in various forms as long as the essence of the invention is not altered.

[0024] In this specification, the use of the word “comprising” is intended to specify certain characteristics, regions, steps, processes, elements, and / or components, and unless specifically stated otherwise, it does not exclude the presence or addition of other characteristics, regions, steps, processes, elements, and / or components.

[0025] All numbers and expressions indicating the amounts of components, reaction conditions, etc. described in this specification may be understood to be modified by the term "about" in all cases unless otherwise specified.

[0026] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0027]

[0028] Research on indirect hydrolysis is active as an alternative to direct hydrolysis, which converts waste polyester (e.g., waste polyethylene terephthalate (W-PET)) directly into regenerated terephthalic acid (r-TPA), but it requires two or more reaction steps, so it is necessary to improve process complexity and economic feasibility.

[0029] The biggest disadvantage of the aforementioned direct hydrolysis is that purification is virtually impossible. Generally, the easiest substances to purify are in a liquid state. This is because liquid substances can be purified through adsorption purification without the need for separate melting energy. Adsorption purification is the most common and economical method for removing colorants. However, terephthalic acid (TPA) is a substance that is difficult to melt as well as dissolve, making the application of an economical and efficient decolorization process nearly impossible.

[0030] The above liquid material can also be purified by distillation by utilizing the difference in boiling points between colored or colorless impurities. r-BHET, generated during the decomposition of waste polyester, undergoes repolymerization during distillation due to terminal hydroxyl groups, leading to an extreme reduction in yield; therefore, it is advantageous to have no terminal hydroxyl groups to facilitate distillation purification. Another product, r-DMT, is a material that can resolve the aforementioned repolymerization problem because it lacks terminal hydroxyl groups; however, since it is a solid at room temperature, purification methods such as distillation or adsorption require the consumption of separate melting energy or a third solvent, making it ultimately inefficient in terms of energy. Furthermore, methanol, the solvent used for the r-DMT reaction, vaporizes during the melting / dissolution process of r-DMT, causing an excessive increase in process pressure and potentially leading to safety issues; resolving this also requires excessive investment costs.

[0031] Intermediate materials generated during the decomposition of waste polyester can be converted into r-TPA through a hydrolysis reaction. During this process, the alcohol component substituted at the terminal end of the intermediate material is replaced by water to form r-TPA, while simultaneously generating alcohol as a byproduct. Since r-TPA, a raw material for recycled polymerization, is a major component of general-purpose polymers, ensuring economic viability is essential. Therefore, an extremely high recovery rate is required for the alcohol, a process chemical generated as a byproduct.

[0032] The most economical separation and recovery method for mixtures of liquids is phase separation. As a technique that utilizes the properties of two immiscible liquids, economic recovery is possible if the alcohol, a byproduct generated during the aforementioned hydrolysis process, does not mix with water.

[0033] Alcohols that have the above-mentioned advantages in purification and recovery, that is, alcohols suitable for forming intermediate-type substances that do not mix with water and do not have a hydroxyl group at the end, are mono-alcohols with more than butanol carbon atoms.

[0034] The process of manufacturing the above butanol-substituted intermediate material is carried out through a simple process of mixing an excess amount of butanol with waste polyester, adding an appropriate amount of catalyst, and heating to a temperature above a predetermined temperature (e.g., 180°C), at which time ethylene glycol (EG), one of the main components of waste polyester, is generated as a byproduct.

[0035] Since the above ethylene glycol (EG) is also an alcohol, recovery of ethylene glycol (EG) is essential because if it is not recovered during the manufacturing process of the above intermediate material, a reverse reaction occurs in which the intermediate material returns to its original state due to the ethylene glycol (EG).

[0036] In addition, the above intermediate material is converted into r-TPA through a hydrolysis reaction using water. Since the hydrolysis reaction uses an excess amount of water, the energy consumption can vary significantly depending on the reaction temperature determined by the characteristics (composition) of the raw material containing the intermediate material.

[0037] Considering these points, a raw material containing an intermediate material obtained from waste polyester must be in a liquid state and have a composition that facilitates the recovery of alcohols such as ethylene glycol (EG) and ensures a hydrolysis reaction rate. Accordingly, the present invention aims to provide a liquid raw material containing an intermediate material obtained from waste polyester, having a composition that facilitates the recovery of alcohols and ensures a hydrolysis reaction rate. This is explained in detail as follows.

[0038]

[0039] Liquid ingredients

[0040] The liquid raw material according to the present invention is obtained through the alcoholic decomposition of waste polyester and, by including specific compounds, can exhibit excellent hydrolysis reactivity while drastically lowering the recovery energy of alcohol as a byproduct. Specifically, the liquid raw material is obtained through the alcoholic decomposition of waste polyester using an alcohol having 4 or more carbon atoms and comprises compounds represented by the following chemical formulas 1 to 3:

[0041] [Chemical Formula 1]

[0042]

[0043] [Chemical Formula 2]

[0044]

[0045] [Chemical Formula 3]

[0046]

[0047] In the above chemical formulas 1 to 3,

[0048] R1, R2 and R3 are each independently alkyls with 4 or more carbon atoms, and n is an integer greater than or equal to 1.

[0049] Specifically, according to the present invention, R1, R2, and R3 may be identical or different from each other and may each independently be an alkyl having 4 to 13 carbon atoms (e.g., an alkyl having 4 to 12 carbon atoms, an alkyl having 4 to 10 carbon atoms, an alkyl having 4 to 8 carbon atoms, or an alkyl having 4 to 6 carbon atoms). Additionally, n may be an integer from 1 to 3.

[0050] For example, the above R1, R2, and R3 are each independently butyl, n-butyl, isobutyl, tert-butyl, sec-butyl, 1-methyl-butyl, 1-ethyl-butyl, pentyl, n-pentyl, isopentyl, neopentyl, tert-pentyl, hexyl, n-hexyl, 1-methylpentyl, 2-methylpentyl, 4-methyl-2-pentyl, 3,3-dimethylbutyl, 2-ethylbutyl, hexyl, 1-methylhexyl, 2-ethyl-1-hexyl, heptyl, n-heptyl, 1-methylheptyl, octyl, n-octyl, isooctyl, tert-octyl, 2-propylpentyl, n-nonyl, 2,2-dimethylheptyl, 1-ethyl-propyl, 1,1-dimethyl-propyl, isohexyl, 2-methylpentyl, It may be 4-methylhexyl, 5-methylhexyl, decanyl, undecanyl, dodecanyl, tridecanyl, or tetradecanyl.

[0051] The compound represented by Chemical Formula 1 included in the above liquid raw material is a di-alcoholic terephthalate (DATP) and may be a major intermediate substance that is converted into terephthalic acid (TPA) through a hydrolysis reaction described later. For example, the compound represented by Chemical Formula 1 may be dibutyl terephthalate (DBTP).

[0052] The compound represented by Chemical Formula 1 may be included in the liquid raw material in a relatively high amount. Specifically, according to the present invention, the content of the compound represented by Chemical Formula 1 may be 50 to 95 mol% based on the total molar amount of the liquid raw material. For example, the content of the compound represented by Chemical Formula 1 may be 50 to 93 mol%, 50 to 92 mol%, 50 to 90 mol%, 50 to 87 mol%, 51 to 85 mol%, 51 to 80 mol%, 51 to 76 mol%, 51 to 70 mol%, or 51 to 60 mol% based on the total molar amount of the liquid raw material. As the content of the compound represented by Chemical Formula 1 is within the above range, the recovery efficiency of alcohol can be maximized while ensuring hydrolysis reactivity. Specifically, while a high content of the compound represented by Chemical Formula 1 has advantages in recovering alcohol, the reduced affinity with water lowers hydrolysis reactivity, leading to increased energy consumption for restoring hydrolysis reactivity, and in some cases, there is a possibility that additives such as surfactants may need to be used artificially. Therefore, it is desirable that the content of the compound represented by Chemical Formula 1 be within the above range.

[0053] The compound represented by Chemical Formula 2 included in the above liquid raw material is a compound generated during the alcohololysis reaction of the waste polyester, and may be a compound having a structure in which one side is substituted with mono-alcohol and the other side is not substituted due to unreacted or reverse reaction (specifically, alcohol-ethylene terephthalate (AETP)). For example, the compound represented by Chemical Formula 2 may be butyl-ethylene terephthalate (BETP).

[0054] Since the compound represented by Chemical Formula 2 has an affinity for water and influences the hydrolysis reaction, controlling its content may be important. Specifically, the hydrolysis reaction described below proceeds more favorably when the affinity between the compound represented by Chemical Formula 1, which is the main intermediate substance, and water is greater. Accordingly, a high content of the compound represented by Chemical Formula 2, which has an affinity for water within the liquid raw material, has the advantage of lowering the temperature during the hydrolysis reaction. However, if the content of the compound represented by Chemical Formula 2 is too high, the energy required to recover alcohol (e.g., ethylene glycol (EG)) from an excess amount of water increases rapidly, which may result in a failure to achieve both economic efficiency and environmental friendliness. Therefore, it is necessary to optimize the content of the compound represented by Chemical Formula 2.

[0055] According to the present invention, the content of the compound represented by Formula 2 may be 5 to 50 mol% based on the total molar amount of the liquid raw material. For example, the content of the compound represented by Formula 2 may be 5 to 49 mol%, 7 to 49 mol%, 9 to 48 mol%, 10 to 48 mol%, 11 to 47 mol%, 13 to 47 mol%, 16 to 46 mol%, 20 to 46 mol%, or 30 to 45 mol% based on the total molar amount of the liquid raw material. As the content of the compound represented by Formula 2 is within the above range, terephthalic acid can be produced in a high yield while achieving economic efficiency and environmental friendliness.

[0056] The compound represented by Chemical Formula 3 included in the above liquid raw material may be a compound (e.g., a dimer) that remains as an unreacted residue during the alcohololysis reaction of the waste polyester. This compound represented by Chemical Formula 3 has a liquid state rather than a solid state within the liquid raw material due to the assistance of the compound represented by Chemical Formula 1 (the compound represented by Chemical Formula 3 is dissolved by the compound represented by Chemical Formula 1). Since a separate heating process is required to proceed with subsequent processes such as purification if it exists in a solid state, it is desirable that its content be relatively low.

[0057] According to the present invention, the content of the compound represented by Formula 3 may be 0.1 to 5 mol% based on the total molar amount of the liquid raw material. For example, the content of the compound represented by Formula 3 may be 0.3 to 5 mol%, 0.5 to 5 mol%, 0.8 to 5 mol%, 1 to 5 mol%, 1.5 to 5 mol%, 2 to 5 mol%, 2.5 to 5 mol%, 3 to 5 mol%, or 4 to 5 mol% based on the total molar amount of the liquid raw material. As the content of the compound represented by Formula 3 is within the above range, terephthalic acid having high purity can be produced while increasing the purification efficiency of the liquid raw material.

[0058] The compounds represented by the above chemical formulas 1 to 3 all exist in a liquid state within the liquid raw material, and as a result, the liquid raw material according to the present invention can be easily purified by various methods (e.g., distillation, adsorption, phase separation, etc.).

[0059] Meanwhile, the above liquid raw material may further include one or more selected from the group consisting of ethylene glycol and unreacted alcohol. Specifically, the above liquid raw material may include the ethylene glycol and not include the unreacted alcohol, or not include the ethylene glycol and include the unreacted alcohol, or include both the ethylene glycol and the unreacted alcohol.

[0060] The above ethylene glycol may refer to a byproduct generated by the alcoholic decomposition reaction of waste polyester, and the above unreacted alcohol may refer to residual alcohol remaining after alcohols with 4 or more carbon atoms introduced for the alcoholic decomposition reaction of waste polyester did not participate in the alcoholic decomposition reaction.

[0061]

[0062] Method for manufacturing liquid raw materials

[0063] The method for manufacturing a liquid raw material according to the present invention includes the step of alcoholizing waste polyester with an alcohol having 4 or more carbon atoms. The liquid raw material obtained through the alcoholization step comprises compounds represented by the following chemical formulas 1 to 3, and a detailed description thereof is omitted as it is identical to that described above.

[0064] [Chemical Formula 1]

[0065]

[0066] [Chemical Formula 2]

[0067]

[0068] [Chemical Formula 3]

[0069]

[0070] In the above chemical formulas 1 to 3,

[0071] R1, R2, and R3 are each independently alkyls having 4 or more carbon atoms, and

[0072] n is an integer greater than or equal to 1.

[0073] The above waste polyester may be waste polyester products that have been crushed or melted. Specifically, the above waste polyester may include one or more selected from the group consisting of waste polyethylene terephthalate fibers, waste polyethylene terephthalate containers, waste polyethylene terephthalate films, and polyester waste (Post Industrial Recycled material; PIR), and may be a product that has been crushed (Flake) or converted into a pellet form (Post-consumer recycled material, PCR). The above polyester waste (PIR) may refer to defective products or scraps generated during the molding process of films, fibers, containers, etc.

[0074] Considering the yield of terephthalic acid, the waste polyester may contain 50% by weight or more of polyethylene terephthalate (PET) based on the total weight of the waste polyester, and specifically, may contain 55% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more (e.g., 50 to 100% by weight, 60 to 97% by weight, 70 to 95% by weight, or 80 to 90% by weight).

[0075] The carbon number of the alcohol used for the alcoholic decomposition of the waste polyester may be 4 or more, 6 or more, 8 or more, 10 or more, or 12 or more. Specifically, the carbon number of the alcohol may be 4 to 13, 4 to 12, 4 to 10, 4 to 8, or 4 to 6. By performing alcoholic decomposition of the waste polyester using an alcohol having the above carbon number, alcoholic decomposition can be performed at a relatively lower temperature and pressure compared to conventional methods, and a liquid raw material containing only liquid components (compounds represented by Chemical Formulas 1 to 3) without containing solid components can be obtained. In addition, the reaction rate of the alcoholic decomposition can be increased.

[0076] According to the present invention, the reaction ratio of the waste polyester and the alcohol for the alcohol decomposition is not particularly limited, but may be a weight ratio of 1:1 to 10. Specifically, the weight ratio may be 1:1 to 8, 1:1 to 6, 1:1 to 5, 1:1 to 4, 1:1 to 3, or 1:1 to 2.

[0077] According to the present invention, the pseudo-alcohol decomposition may be performed at a temperature of 170 to 250 ℃ for 0.5 to 12 hours. Specifically, the pseudo-alcohol decomposition reaction may be performed at a temperature of 180 to 245 ℃, 185 to 240 ℃, 190 to 235 ℃, 195 to 230 ℃, 200 to 225 ℃, or 210 to 220 ℃ for 1 to 10 hours, 1.5 to 8 hours, 2 to 6 hours, 2.5 to 5 hours, 3 to 4.5 hours, or 3.5 to 4 hours. Meanwhile, the reaction pressure may be set according to the reaction temperature and / or reaction time of the pseudo-alcohol decomposition. Specifically, the pressure during the above alcohol decomposition reaction may be 1 to 40 bar, 2 to 35 bar, 5 to 30 bar, 7 to 25 bar, 9 to 20 bar, 10 to 17 bar, or 12 to 15 bar.

[0078] A catalyst may or may not be added to the above alcohol decomposition reaction. If the above alcohol decomposition reaction is a catalyst-free reaction in which no catalyst is added, the removal process for insoluble metals, etc., can be omitted, thereby enabling the production of high-purity terephthalic acid while ensuring environmental friendliness. Furthermore, if the above alcohol decomposition reaction is a catalyst-containing reaction in which a catalyst is added, the activity of the alcohol decomposition reaction is increased, thereby improving processability (economic efficiency).

[0079] As a catalyst introduced into the above alcohol decomposition reaction, metal acetate salts, alkali metal salts, or hydroxy salts may be used. Specifically, the catalyst is Li + , Na + , K + , or Cs + alkali metal ions, Be 2+ , Mg 2+ , Ca 2+ , or Ba 2+ alkaline earth metal ions, NH 4+ , and Zn 2+One or more cations selected from the group consisting of; and / or OH - , OR - , HCO3 - , CO3 2- , benzoate ion (C7H5O2 - It may include one or more anions selected from the group consisting of ), 4-alkoxycarbonylbenzoate ions, acetate ions, and terephthalate ions.

[0080] For example, the catalyst may include one or more selected from the group consisting of Zn(OAC)2, Co(OAc)2, Mn(OAc)2, Mg(OAc)2, Ca(OAc)2, Pb(OAc)2, Ba(OAc)2, LiOAc, NaOAc, KOAc, Pd(OAc)2, Zn(OAC)2·2H2O, Co(OAc)2·4H2O, Mn(OAc)2·4H2O, Mg(OAc)2·4H2O, Ti(OBu)4, Ti(OiPr)4, GeO2, Al(OiPr)3, Na2CO3, K2CO3, dibutyltin(IV) oxide, tin octosate, titanium phosphate, and terephthalic acid.

[0081] The amount of the catalyst added may be 10 to 10,000 ppm, 50 to 9,000 ppm, 100 to 8,000 ppm, 200 to 6,000 ppm, 300 to 4,000 ppm, 500 to 3,000 ppm, 700 to 2,000 ppm, 800 to 1,500 ppm, or 900 to 1,200 ppm, based on the total weight of the waste polyester.

[0082] The present invention allows for the easy production of a liquid raw material having a composition capable of exhibiting excellent hydrolysis reactivity while extremely lowering the recovery energy of alcohol byproducts by controlling the reaction conditions of alcohol decomposition in a process of producing a liquid raw material by decomposing waste polyester with an alcohol having 4 or more carbon atoms.

[0083] Meanwhile, the method for manufacturing a liquid raw material according to the present invention may further include a step of fractionally distilling the product obtained through the above alcohol decomposition step. The fractional distillation may be performed using a fractional distillation method that is generally known, thereby removing and recovering unreacted alcohol (e.g., butanol) and by-products (e.g., ethylene glycol). The recovered unreacted alcohol may be reused in the above alcohol decomposition step, and the recovered by-product, ethylene glycol, may be reused as a polymerization raw material for polyester or utilized in other processes, thereby ensuring processability (economic feasibility). By-products such as diethylene glycol may also be removed through such fractional distillation.

[0084] In addition, the method for manufacturing a liquid raw material according to the present invention may further include a step of adsorbing and purifying the product obtained through the alcohol decomposition step. Specifically, the adsorbing and purifying may be performed using one or more adsorbents selected from the group consisting of activated carbon, silica gel, alumina, zeolite, and activated clay, or through bed adsorption.

[0085] Specifically, the adsorbent may be activated carbon or a mixture of activated carbon and silica gel. For example, as the adsorbent, a mixture of activated carbon and silica gel mixed in a weight ratio of 1:0.5 to 1.5 or 1:0.8 to 1.2 may be used.

[0086] The amount of the adsorbent added is not particularly limited, but based on the total weight of the product obtained through the alcohol decomposition step, it may be 0.1 to 20 weight%, 0.1 to 18 weight%, 0.2 to 15 weight%, 0.2 to 10 weight%, 0.3 to 5 weight%, or 0.3 to 2 weight%. As the amount of the adsorbent added is within the above range, insoluble impurities such as metals or impurities such as coloring agents and pigments derived from waste polyester can be effectively removed, thereby enabling the production of terephthalic acid with excellent purity and quality.

[0087] In addition, the method for manufacturing a liquid raw material according to the present invention may further include a step of concentrating the product obtained through the alcohol decomposition step (specifically, the product obtained through alcohol decomposition and adsorption purification). The concentration may be carried out by a commonly known concentration method, thereby removing and recovering unreacted alcohol (e.g., butanol) and by-products (e.g., ethylene glycol).

[0088] Specifically, the concentration can be performed by stirring the adsorbed purified product at a temperature of 55 to 115 ℃, 60 to 110 ℃, 65 to 105 ℃, or 75 to 100 ℃ for 1 to 5 hours, 1.5 to 4 hours, or 2 to 4 hours, followed by a filtration process.

[0089]

[0090] Method for manufacturing terephthalic acid

[0091] A method for producing terephthalic acid according to the present invention comprises the steps of: producing a liquid raw material by alcoholizing waste polyester with an alcohol having 4 or more carbon atoms; and hydrolyzing the liquid raw material, wherein the liquid raw material comprises a compound represented by the following chemical formulas 1 to 3.

[0092] [Chemical Formula 1]

[0093]

[0094] [Chemical Formula 2]

[0095]

[0096] [Chemical Formula 3]

[0097]

[0098] In the above chemical formulas 1 to 3,

[0099] R1, R2, and R3 are each independently alkyls having 4 or more carbon atoms, and

[0100] n is an integer greater than or equal to 1.

[0101] The description of the step of producing a liquid raw material comprising compounds represented by Chemical Formulas 1 to 3 by alcoholizing the above waste polyester with an alcohol having 4 or more carbon atoms is substantially the same as the description in the 'method for producing a liquid raw material' described above, so a detailed description thereof is omitted.

[0102] The step of hydrolyzing the above liquid raw material can be performed by reacting the above liquid raw material with water, and terephthalic acid (regenerated terephthalic acid) can be obtained as a reaction product.

[0103] The product obtained through the above hydrolysis (a product containing terephthalic acid, which is the result of the reaction) may contain a relatively high amount of ethylene glycol (EG) as a byproduct. Specifically, the content of ethylene glycol contained in the product may be 5 to 50 mol%, 6 to 50 mol%, 7 to 49 mol%, 10 to 49 mol%, 12 to 48 mol%, 15 to 47 mol%, 18 to 47 mol%, 20 to 46 mol%, or 25 to 46 mol% with respect to 100 mol% of terephthalic acid contained in the product. The fact that the content of ethylene glycol is within the above range means that the reaction rate of hydrolysis is fast, thereby enabling improved hydrolysis reactivity.

[0104] Specifically, in the above hydrolysis process, the ethylene glycol is produced by the decomposition of the compound represented by Chemical Formula 2 and / or the compound represented by Chemical Formula 3 contained in the liquid raw material. Since the reaction rate of hydrolysis is accelerated through the decomposition, the ethylene glycol is produced in a relatively large amount, so the degree of improvement in hydrolysis reactivity can be confirmed according to the content (amount produced) of the ethylene glycol.

[0105] Meanwhile, the above hydrolysis reaction may be carried out by adding water to the above liquid raw material and at a temperature of 180 to 280 ℃, 185 to 275 ℃, 190 to 270 ℃, 195 to 260 ℃, 200 to 250 ℃, 210 to 240 ℃, or 220 to 235 ℃ for 0.5 to 20 hours, 0.5 to 15 hours, 0.5 to 10 hours, 1 to 7 hours, 1 to 4 hours, or 1 to 2 hours.

[0106] The reaction ratio of the liquid raw material and the water is not particularly limited, but may be a weight ratio of 1:1 to 100. Specifically, the weight ratio may be 1:1 to 50, 1:1 to 30, 1:1 to 20, 1:1 to 10, 1:1 to 7, 1:1 to 5, or 1:1 to 3.

[0107] A catalyst may or may not be added to the above hydrolysis reaction. If the above hydrolysis reaction is a catalyst-free reaction in which no catalyst is added, the removal process for insoluble metals, etc., can be omitted, thereby enabling the production of high-purity terephthalic acid while ensuring environmental friendliness. Furthermore, if the above hydrolysis reaction is a catalyst-containing reaction in which a catalyst is added, the activity of the hydrolysis reaction is increased, thereby improving processability (economic efficiency).

[0108] As a catalyst introduced into the above hydrolysis reaction, metal acetate salts, alkali metal salts, or hydroxy salts may be used. Specifically, the catalyst is Li + , Na + , K + , or Cs + alkali metal ions, Be 2+ , Mg 2+ , Ca 2+ , or Ba 2+ alkaline earth metal ions, NH 4+ and Zn 2+ One or more cations selected from the group consisting of; and / or OH - , OR - , HCO3 - , CO3 2- , benzoate ion (C7H5O2 - It may include one or more anions selected from the group consisting of ), 4-alkoxycarbonylbenzoate ions, acetate ions, and terephthalate ions.

[0109] For example, the catalyst may include one or more selected from the group consisting of Zn(OAC)2, Co(OAc)2, Mn(OAc)2, Mg(OAc)2, Ca(OAc)2, Pb(OAc)2, Ba(OAc)2, LiOAc, NaOAc, KOAc, Pd(OAc)2, Zn(OAC)2·2H2O, Co(OAc)2·4H2O, Mn(OAc)2·4H2O, Mg(OAc)2·4H2O, Ti(OBu)4, Ti(OiPr)4, GeO2, Al(OiPr)3, Na2CO3, K2CO3, dibutyltin(IV) oxide, tin octosate, titanium phosphate, and terephthalic acid.

[0110] The amount of the catalyst added may be 50 to 5,000 ppm, 70 to 4,500 ppm, 100 to 4,000 ppm, 150 to 3,000 ppm, 200 to 2,000 ppm, 250 to 1,000 ppm, 300 to 800 ppm, 350 to 700 ppm, 400 to 600 ppm, 450 to 650 ppm, or 500 to 600 ppm, based on the total weight of the liquid raw material.

[0111] Through this hydrolysis reaction, solid terephthalic acid (regenerated terephthalic acid) can be obtained in high yield, and the obtained terephthalic acid can be usefully used in the manufacture of general-purpose polymers (e.g., polyester).

[0112] The terephthalic acid produced through the above alcohol decomposition step and the above hydrolysis step can exhibit a high yield. Specifically, based on performing the above hydrolysis reaction for 4 hours, the yield of the terephthalic acid can be 70% or more, 72% or more, 74% or more, 76% or more, 78% or more, 80% or more, 85% or more, or 90% or more.

[0113] Meanwhile, the method for producing terephthalic acid according to the present invention may further include the steps of filtering, washing, and drying the product obtained through the hydrolysis. Specifically, the product may be cooled to a temperature such that water does not vaporize (e.g., room temperature to less than 100°C) to obtain a solution in the form of a slurry, filtered to obtain a solid filtrate, and then the obtained solid filtrate may be washed and vacuum dried to obtain solid terephthalic acid.

[0114] The above washing may be performed using a mixture of alcohols with 4 or more carbon atoms and / or water, protic solvents such as isopropanol or acetic acid, or non-protic solvents such as acetone, dichloromethane, chloroform, tetrahydrofuran (THF), or toluene. Through such washing, residual pigments or impurities generated by pigment decomposition during hydrolysis, particularly yellow impurities, can be effectively removed, thereby improving the yellowness or color characteristics of terephthalic acid. In addition, by using water for the washing, inorganic salts can be removed, thereby improving the quality of the terephthalic acid produced.

[0115] The present invention will be explained in more detail through the following examples. However, the following examples are merely illustrative of the present invention and do not limit the scope of the present invention.

[0116]

[0117] [Example 1-1]

[0118] 1 kg of waste polyethylene terephthalate (waste PET) and 1 L of 1-butanol as the alcohol were introduced into a first high-pressure reactor with a capacity of 7 L, and Zn(OA) was used as an alcohol decomposition catalyst. C 1000 mg of )2·2H2O (1000 ppm relative to the total weight of the waste PET) was added.

[0119] Afterwards, all connections of the first high-pressure reactor were closed to maintain a seal, and the temperature was raised to 220°C over 1 hour. Then, the alcohol decomposition reaction was carried out by stirring while maintaining a temperature of 220°C and a pressure of 14 bar for 4 hours.

[0120] After the above alcohol decomposition reaction was completed, the liquid raw material was cooled to room temperature. The components and their content of the obtained liquid raw material were analyzed using NMR (JEOL analytical instrument), and as a result, it was confirmed that the product contained a compound of Formula 1 (DBTP) in which R1 is (CH2)3CH3, residual ethylene glycol (EG), unreacted 1-butanol, a compound of Formula 2 (BETP) in which R2 is (CH2)3CH3, and a compound of Formula 3 (Dimer) in which R3 is (CH2)3CH3. Subsequently, 5 g of activated carbon was added to the liquid raw material as an adsorbent for purification, and the used activated carbon was removed by vacuum filtration.

[0121] Subsequently, the purified liquid raw material was placed into a separate flask, and the excess unreacted 1-butanol and residual ethylene glycol (EG) were recovered using a fractional distillation apparatus to obtain a concentrated liquid raw material. Subsequently, the obtained liquid raw material was used in a hydrolysis reaction.

[0122]

[0123] [Examples 1-2]

[0124] A liquid raw material was obtained in the same manner as in Example 1-1 above, except that 2 L of 1-butanol was used as the alcohol.

[0125]

[0126] [Examples 1-3]

[0127] A liquid raw material was obtained in the same manner as in Example 1-1 above, except that 3 L of 1-butanol was used as the alcohol.

[0128]

[0129] [Examples 1-4]

[0130] A liquid raw material was obtained in the same manner as in Example 1-1, except that 4 L of 1-butanol was used as the alcohol.

[0131]

[0132] [Examples 1-5]

[0133] A liquid raw material was obtained in the same manner as in Example 1-1 above, except that 8 L of 1-butanol was used as the alcohol.

[0134]

[0135] [Comparative Example 1-1]

[0136] 4 L of 1-butanol was added as the alcohol to the liquid raw material (concentrated liquid raw material obtained through primary alcohol decomposition) obtained by the same method as in Example 1-1, and the mixture of the liquid raw material and 1-butanol was introduced into a first high-pressure reactor with a capacity of 7 L. At this time, Zn(OA) was used as the alcohol decomposition catalyst. C There was no additional input of )2·2H2O.

[0137] Afterwards, all connection parts of the first high-pressure reactor were closed to maintain a seal, and the temperature was raised to 220°C over 1 hour. Then, the second alcohol decomposition reaction was carried out by stirring while maintaining a temperature of 220°C and a pressure of 14 bar for 4 hours.

[0138] After the above secondary alcohol decomposition reaction was completed, the liquid raw material was cooled to room temperature. The components and their content of the obtained liquid raw material were analyzed using NMR (JEOL analytical instrument), and as a result, it was confirmed that the compound of Formula 1 (DBTP) in which R1 is (CH2)3CH3, residual ethylene glycol (EG), unreacted 1-butanol, compound of Formula 2 (BETP) in which R2 is (CH2)3CH3, and compound of Formula 3 (Dimer) in which R3 is (CH2)3CH3 were included.

[0139] Subsequently, the above liquid raw material was placed into a separate flask, and the excess unreacted 1-butanol and residual ethylene glycol (EG) were recovered using a fractional distillation apparatus, respectively, to obtain a concentrated liquid raw material (secondarily concentrated liquid raw material). Subsequently, the obtained liquid raw material was used in a hydrolysis reaction.

[0140]

[0141] The NMR analysis results of each liquid raw material in Examples 1-1 to 1-5 and Comparative Example 1-1 are shown in Table 1 below.

[0142]

[0143] Waste PET : 1-Butanol (weight ratio) DBTP : BETP : Dimer (mole%) Alcohol decomposition reaction conditions Example 1-11 : 15 1 : 44 : 5 220 ℃ / 4 hours Example 1-21 : 275 : 22 : 3 Example 1-31 : 383 : 15 : 2 Example 1-41 : 486 : 12 : 2 Example 1-51 : 893 : 6 : 1 Comparative Example 1-11 : 4 → Concentration → 1 : 497 : 2.9 : 0.1

[0144] Referring to Table 1 above, it can be confirmed that as the alcohol decomposition reaction according to the present invention is carried out, a liquid raw material is obtained in which the content of each of DBTP, BETP, and Dimer is controlled within the range of the present invention.

[0145]

[0146] [Example 2-1]

[0147] 60 g of the concentrated liquid raw material of Example 1-1 and 240 g of water were introduced into a second high-pressure reactor with a capacity of 600 ml, and Zn(OA) was used as a hydrolysis catalyst. C 30 mg of )2·2H2O (500 ppm relative to the total weight of the concentrated liquid raw material) was added.

[0148] Subsequently, the temperature of the second high-pressure reactor was raised to 230°C, and the hydrolysis reaction was carried out for 1 hour while maintaining the temperature at 230°C. Afterward, the reaction was cooled to 90°C to obtain a hydrolysis product in the form of a slurry. The solid obtained by filtering the hydrolysis product in the form of a slurry was washed with butanol and water at 90°C and vacuum dried to obtain 15.5 g of terephthalic acid (TPA) (yield: 42%). In addition, after filtering the hydrolysis product in the form of a slurry, the aqueous layer of the filtrate was collected and analyzed by GC (Gas Chromatography) to quantify the content of ethylene glycol (EG) contained in the hydrolysis product.

[0149]

[0150] [Example 2-2]

[0151] 27.7 g of terephthalic acid (TPA) (yield: 75%) was obtained by the same method as in Example 2-1 above, except that the hydrolysis reaction time was adjusted to 2 hours.

[0152]

[0153] [Examples 2-3]

[0154] 29.9 g of terephthalic acid (TPA) (yield: 81%) was obtained by the same method as in Example 2-1 above, except that the hydrolysis reaction time was adjusted to 4 hours.

[0155]

[0156] [Examples 2-4]

[0157] 8.8 g of terephthalic acid (TPA) (yield: 24%) was obtained by the same method as in Example 2-1, except that the concentrated liquid raw material of Example 1-2 was used.

[0158]

[0159] [Examples 2-5]

[0160] 21.2 g of terephthalic acid (TPA) (yield: 58%) was obtained by the same method as in Example 2-1, except that the hydrolysis reaction time was adjusted to 2 hours while using the concentrated liquid raw material of Example 1-2.

[0161]

[0162] [Examples 2-6]

[0163] 29.2 g of terephthalic acid (TPA) (yield: 80%) was obtained by the same method as in Example 2-1, except that the hydrolysis reaction time was adjusted to 4 hours while using the concentrated liquid raw material of Example 1-2.

[0164]

[0165] [Example 2-7]

[0166] 5.4 g of terephthalic acid (TPA) (yield: 15%) was obtained by the same method as in Example 2-1, except that the concentrated liquid raw material of Example 1-3 was used.

[0167]

[0168] [Examples 2-8]

[0169] 16.3 g of terephthalic acid (TPA) (yield: 45%) was obtained by the same method as in Example 2-1, except that the hydrolysis reaction time was adjusted to 2 hours while using the concentrated liquid raw material of Example 1-3.

[0170]

[0171] [Example 2-9]

[0172] 29.0 g of terephthalic acid (TPA) (yield: 80%) was obtained using the same method as in Example 2-1, except that the hydrolysis reaction time was adjusted to 4 hours while using the concentrated liquid raw material of Example 1-3.

[0173]

[0174] [Example 2-10]

[0175] Except for using the concentrated liquid raw material of Examples 1-4 above, 2.5 g of terephthalic acid (TPA) (yield: 7%) was obtained in the same manner as in Example 2-1 above.

[0176]

[0177] [Example 2-11]

[0178] 12.3 g of terephthalic acid (TPA) (yield: 34%) was obtained by the same method as in Example 2-1, except that the hydrolysis reaction time was adjusted to 2 hours while using the concentrated liquid raw material of Examples 1-4.

[0179]

[0180] [Example 2-12]

[0181] 28.3 g of terephthalic acid (TPA) (yield: 78%) was obtained by the same method as in Example 2-1, except that the hydrolysis reaction time was adjusted to 4 hours while using the concentrated liquid raw material of Examples 1-4.

[0182]

[0183] [Example 2-13]

[0184] 1.8 g of terephthalic acid (TPA) (yield: 5%) was obtained by the same method as in Example 2-1, except that the concentrated liquid raw material of Examples 1-5 was used.

[0185]

[0186] [Example 2-14]

[0187] 10.1 g of terephthalic acid (TPA) (yield: 28%) was obtained by the same method as in Example 2-1, except that the hydrolysis reaction time was adjusted to 2 hours while using the concentrated liquid raw material of Examples 1-5.

[0188]

[0189] [Example 2-15]

[0190] 26.7 g of terephthalic acid (TPA) (yield: 74%) was obtained using the same method as in Example 2-1, except that the hydrolysis reaction time was adjusted to 4 hours while using the concentrated liquid raw material of Examples 1-5.

[0191]

[0192] [Comparative Example 2-1]

[0193] 1.1 g of terephthalic acid (TPA) (yield: 3%) was obtained by the same method as in Example 2-1, except that the concentrated liquid raw material of Comparative Example 1-1 was used.

[0194]

[0195] [Comparative Example 2-2]

[0196] 6.1 g of terephthalic acid (TPA) (yield: 17%) was obtained using the same method as in Example 2-1, except that the hydrolysis reaction time was adjusted to 2 hours while using the concentrated liquid raw material of Comparative Example 1-1.

[0197]

[0198] [Comparative Example 2-3]

[0199] 24.8 g of terephthalic acid (TPA) (yield: 69%) was obtained by the same method as in Example 2-1, except that the hydrolysis reaction time was adjusted to 4 hours while using the concentrated liquid raw material of Comparative Example 1-1.

[0200]

[0201] The yields of terephthalic acid (TPA) and the content of ethylene glycol (EG) in Examples 2-1 to 2-15 and Comparative Examples 2-1 to 2-3 were summarized and are shown in Table 2 below.

[0202]

[0203] Liquid Raw Material Hydrolysis Reaction Time (h) TPA Yield (%) EG Content (Molar%) Example 2-1 Example 1-1 14 240 Example 2-2 27 546 Example 2-3 48 146 Example 2-4 Example 1-2 12 421 Example 2-5 25 824 Example 2-6 48 024 Example 2-7 Example 1-3 11 512 Example 2-8 24 516 Example 2-9 48 016 Example 2-10 Example 1-4 178 Example 2-11 23 413 Example 2-12 47 813 Example 2-13 Example 1-5 155 Example 2-14 22 87 Example 2-15 47 47 Comparative Example 2-1 Comparative Example 1-1 131 Comparative Example 2-2 2173 Comparative Example 2-3 4693 *TPA Yield = (Moles of TPA obtained / Total moles of compounds of Formulas 1, 2, and 3 contained in the liquid raw material) × 100 *TPA Production Ratio: 1 mol of TPA produced per 1 mol of compound of Formula 1; 1 mol of TPA produced per 1 mol of compound of Formula 2; 2 mol of TPA produced per 1 mol of compound of Formula 3 *EG Content: Mole% of EG relative to 100 mol% of obtained TPA (Moles of EG produced relative to the theoretical moles of TPA produced)

[0204] Referring to Table 2 above, it can be confirmed that terephthalic acid (TPA) is obtained in a relatively short time with a high yield (specifically, the yield of terephthalic acid (TPA) is 70% or more through a hydrolysis reaction within 4 hours) by hydrolyzing a liquid raw material having the composition according to the present invention (see Examples 2-1 to 2-15).

Claims

1. It is obtained through the alcoholic decomposition of waste polyester, and A liquid raw material comprising a compound represented by the following chemical formulas 1 to 3: [Chemical Formula 1] [Chemical Formula 2] [Chemical Formula 3] In the above chemical formulas 1 to 3, R1, R2, and R3 are each independently alkyls having 4 or more carbon atoms, and n is an integer greater than or equal to 1.

2. In Paragraph 1, A liquid raw material having a content of the compound represented by the above chemical formula 1 of 50 to 95 mol% based on the total molar amount of the liquid raw material.

3. In Paragraph 1, A liquid raw material having a content of the compound represented by the above chemical formula 2 of 5 to 50 mol% based on the total molar amount of the liquid raw material.

4. In Paragraph 1, A liquid raw material having a content of the compound represented by the above chemical formula 3 of 0.1 to 5 mol% based on the total molar amount of the liquid raw material.

5. In Paragraph 1, A liquid raw material in which, in the above chemical formulas 1 to 3, R1, R2, and R3 are each independently an alkyl having 4 to 13 carbon atoms, and n is an integer from 1 to 3.

6. A step of alcoholizing waste polyester with an alcohol having 4 or more carbon atoms, and A method for manufacturing a liquid raw material comprising a compound represented by the following chemical formulas 1 to 3: [Chemical Formula 1] [Chemical Formula 2] [Chemical Formula 3] In the above chemical formulas 1 to 3, R1, R2, and R3 are each independently alkyls having 4 or more carbon atoms, and n is an integer greater than or equal to 1.

7. In Paragraph 6, A method for manufacturing a liquid raw material, wherein the above alcohol decomposition is performed at a temperature of 170 to 250 ℃.

8. In Paragraph 6, A method for preparing a liquid raw material, wherein the above alcohol decomposition is performed for 0.5 to 12 hours.

9. In Paragraph 6, A method for manufacturing a liquid raw material, wherein the reaction ratio of the waste polyester to the alcohol is a weight ratio of 1:1 to 10.

10. A step of producing a liquid raw material by alcoholizing waste polyester with an alcohol having 4 or more carbon atoms; and The above includes a step of hydrolyzing the liquid raw material, A method for producing terephthalic acid, wherein the above liquid raw material comprises a compound represented by the following chemical formulas 1 to 3: [Chemical Formula 1] [Chemical Formula 2] [Chemical Formula 3] In the above chemical formulas 1 to 3, R1, R2, and R3 are each independently alkyls having 4 or more carbon atoms, and n is an integer greater than or equal to 1.

11. In Paragraph 10, A method for producing terephthalic acid, wherein the content of ethylene glycol contained in the product obtained through the above hydrolysis is 5 to 50 mol% with respect to 100 mol% of terephthalic acid contained in the product.

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