Process for efficiently collecting terephthalic acid (TPA) in enzymatic degradation process of polyester

Abstract

The present application relates to a process for efficiently collecting terephthalic acid in an enzymatic decomposition process of a polyester containing terephthalic acid as a monomer.

Description

A process for efficiently recovering TPA (terephthalic acid) in a polyester enzyme decomposition process.

[0001] The present application relates to a process for efficiently recovering terephthalic acid (TPA) in a polyester enzymatic decomposition process containing terephthalic acid (TPA) as a unit.

[0002]

[0003] More than 400 million tons of new plastics are produced each year, and as environmental issues surrounding waste plastics are highlighted, efforts are being made to reduce production through regulations on disposable products and the use of plastic alternatives. However, in reality, the production volume continues to increase every year.

[0004] Polyethylene terephthalate (PET), which accounts for less than 10% of all plastics, is newly produced at approximately 360 million tons annually. Due to its primary use in disposable products, PET is considered the plastic with the shortest life cycle. Recycling of waste plastics includes mechanical recycling, pyrolysis, and chemical recycling, each of which is either commercialized or in the final stages of research toward commercialization. While each technology offers potential solutions to the plastic waste issue, none of the existing methods are perfect due to their impacts on quality, carbon neutrality, resource depletion, and eutrophication of marine and freshwater bodies.

[0005] To solve environmental problems caused by waste plastics, such as microplastics, greenhouse gas emissions, and resource depletion, a series of research results are being published on the use of enzymes to biologically decompose PET, a representative type of plastic, and unlike conventional recycling methods, the advantage of these enzymatic methods is that they enable PET to be converted into terephthalic acid (TPA) and ethylene glycol (EG), which can be used to create new polymers, enabling infinite regeneration. However, the process of recovering high-purity TPA with a high yield that can be repolymerized into PET from the reaction solution after decomposition is still complex and difficult, and this is an obstacle to securing the economic feasibility of technology to recycle waste plastics through biological decomposition of PET.

[0006] [Prior Art Literature]

[0007] (Patent Document 1) KR 10-2021-0091202 A

[0008] (Patent Document 2) EP 3877458 A1

[0009] (Patent Document 3) US 2022-0002516 A1

[0010] The present application relates to a process for efficiently recovering terephthalic acid in a polyester enzymatic decomposition process containing terephthalic acid as a unit.

[0011]

[0012] The purpose of the present application is to provide a method for producing terephthalic acid, which comprises the steps of enzymatically depolymerizing a polyester containing terephthalic acid as a unit while maintaining the pH in a reactor at 5 to 9; and the step of adding a base to the reactant after the end of the enzymatic reaction to maintain the pH at 9.0 or higher.

[0013]

[0014] The method of the present invention can increase the yield of terephthalic acid produced by enzymatic decomposition of a polyester containing terephthalic acid as a unit.

[0015]

[0016] This is explained in detail as follows. Meanwhile, each description and embodiment disclosed in this application can also be applied to each other description and embodiment. In other words, all combinations of the various elements disclosed in this application fall within the scope of this application. Furthermore, the scope of this application is not limited by the specific descriptions described below.

[0017] Furthermore, those skilled in the art will recognize or be able to ascertain, using only routine experimentation, numerous equivalents to the specific embodiments described in this application. Furthermore, such equivalents are intended to be encompassed by this application.

[0018] Additionally, numerous papers and patents are referenced and cited throughout this specification. The disclosures of these cited papers and patents are incorporated herein by reference in their entirety, thereby providing a clearer understanding of the technical field to which this application pertains and the content of this application.

[0019]

[0020] One aspect of the present application is a method for producing terephthalic acid, comprising the steps of enzymatically depolymerizing a polyester containing terephthalic acid as a unit; and the step of adding a base to the reactants to maintain the pH at 9.0 or higher.

[0021]

[0022] The term "polyester" refers to a polymer that contains an ester functional group in the main chain of its structure. For the purposes of this application, the polyester is a polyester that contains terephthalic acid as a unit.

[0023] In one embodiment, the polyester may be selected from polyethylene terephthalate, polyethylene terephthalate glycol (PETG), polyethylene co-isosorbide terephthalate (PEIT), polytrimethylene terephthalate (PTT), polybutylene adipate terephthalate (PBAT), polycyclohexylenedimethylene terephthalate (PCT), and polybutylene terephthalate (PBT).

[0024] The polyethylene terephthalate of the present invention is a semi-aromatic copolymer composed of two monomers, terephthalic acid and ethylene glycol. Terephthalic acid is produced by depolymerizing polyethylene terephthalate.

[0025] The method of the present application is characterized in that the yield of terephthalic acid is increased by including a step of adding a base to the reactant to maintain the pH at 9.0 or higher.

[0026]

[0027] In one embodiment, the method is characterized by comprising, after the step of depolymerizing the polyester by an enzyme, a step of adding a base to the reactant after the end of the enzyme reaction to maintain the pH at 9.0 or higher.

[0028] In one embodiment, the method comprises steps a) and b):

[0029] a) a step of enzymatically depolymerizing a polyester containing terephthalic acid as a unit while maintaining the pH in the reactor at 5 to 9; and

[0030] b) A step of adding a base to the reactant after the completion of the enzymatic reaction in step a) above to maintain the pH at 9.0 or higher.

[0031]

[0032] In one embodiment, the method comprises steps a) to c):

[0033] a) A step of enzymatically depolymerizing a polyester containing terephthalic acid as a unit;

[0034] b) a step of maintaining the pH at 9.0 or higher by adding a base to the reactant after the enzyme reaction in step a) is completed; and

[0035] c) A step of recovering terephthalic acid from the solution obtained in step b).

[0036]

[0037] In any one of the embodiments described above, the method comprises steps a) and b):

[0038] a) a step of enzymatically depolymerizing polyethylene terephthalate (PET) while maintaining the pH in the reactor at 5 to 9; and

[0039] b) A step of adding a base to the reactant after the completion of the enzymatic reaction in step a) above to maintain the pH at 9.0 or higher.

[0040]

[0041] In any one of the embodiments described above, the method comprises steps a) to c):

[0042] a) A step of enzymatically depolymerizing polyethylene terephthalate (PET);

[0043] b) a step of maintaining the pH at 9.0 or higher by adding a base to the reactant after the enzyme reaction in step a) is completed; and

[0044] c) A step of recovering terephthalic acid from the solution obtained in step b).

[0045]

[0046] In any one of the above-described embodiments, the reaction of step a) is carried out while maintaining the pH in the reactor at 5 to 9.

[0047] For example, the pH within the reactor may be less than 9.

[0048] For example, the pH within the reactor may be about 5 or more and less than 9.

[0049] For example, the pH within the reactor may be about 5.2 to 9, 5.4 to 8.95, 5.6 to 8.9, 5.8 to 8.85, 6 to 8.8, 6.2 to 8.75, 6.4 to 8.7, 6.6 to 8.65, 6.8 to 8.6, 7 to 8.55, 7.1 to 8.5, 7.2 to 8.45, 7.3 to 8.4, 7.4 to 8.35, 7.5 to 8.3, 7.6 to 8.25, 7.7 to 8.2, 7.8 to 8.15, 7.9 to 8.1, or 8 to 8.05.

[0050] In any one of the above-described embodiments, the enzymatic reaction of step a) is performed under a temperature condition of about 20°C to 80°C. For example, it may be performed under a temperature condition of about 30°C to 70°C, or about 40°C to 60°C.

[0051] In any one of the embodiments described above, the enzyme of step a) has PET decomposing enzyme activity at pH 5 to 9.

[0052] In any one of the embodiments described above, the enzyme of step a) comprises, consists essentially of, or consists of an amino acid sequence having at least 70%, 80%, 85%, 90%, 95%, 99%, or 100% homology or identity thereto, or consists essentially of or consists of the amino acid sequence represented by SEQ ID NO: 1.

[0053] With respect to PET degrading enzymes, the disclosures in US 2020-0048621 A1 and Three-directional engineering of IsPETase with enhanced protein yield, activity, and durability, Journal of Hazardous Materials, Volume 459, 2023, 132297, ISSN 0304-3894 are incorporated herein by reference in their entirety. For example, the enzyme may be Z1-PETase.

[0054] Meanwhile, in relation to the amino acid sequence in the present application, even if it is described as a polypeptide "comprising" the amino acid sequence described in a specific sequence number, a polypeptide "consisting of" the amino acid sequence described in a specific sequence number, or a polypeptide or protein "having" the amino acid sequence described in a specific sequence number, it is obvious that a protein having an amino acid sequence in which a portion of the sequence is deleted, modified, substituted, conservatively substituted, or added can also be used in the present application, as long as it has the same or corresponding activity as the polypeptide consisting of the amino acid sequence of the corresponding sequence number. For example, it may be a case in which the amino acid sequence has an addition of a sequence that does not alter the function of the protein at the N-terminus and / or C-terminus, a mutation that may occur naturally, a silent mutation thereof, or a conservative substitution, but is not limited thereto.

[0055] For example, the PET degrading enzyme may comprise an amino acid sequence having at least 70%, 80%, 85%, 90%, 95%, 99%, or 100% homology or identity thereto with the Z1-PETase. Meanwhile, as an example, in the sequence of the PET degrading enzyme of the present application, the amino acid corresponding to amino acid 121 from the N-terminus of the PET degrading enzyme (IsPETase) sequence derived from Ideonella sakaiensis is glutamic acid, the amino acid corresponding to amino acid 186 is histidine, the amino acid corresponding to amino acid 242 is threonine, the amino acid corresponding to amino acid 246 is aspartic acid, the amino acid corresponding to amino acid 233 is cysteine, the amino acid corresponding to amino acid 282 is cysteine, the amino acid corresponding to amino acid 181 is valine, the amino acid corresponding to amino acid 180 is valine, the amino acid corresponding to amino acid 37 is aspartic acid, the amino acid corresponding to amino acid 132 is glutamic acid, the amino acid corresponding to amino acid 224 is glutamic acid, the amino acid corresponding to amino acid 171 is cysteine, and the amino acid corresponding to amino acid 193 is glutamic acid, the amino acid corresponding to amino acid 224 is glutamic acid, the amino acid corresponding to amino acid 171 is cysteine, and the amino acid corresponding to amino acid 193 is glutamic acid. The amino acid corresponding to the amino acid may be cysteine.

[0056] In any one of the embodiments described above, the enzyme is used at about 0.01% to 5% (w / w) per polyester medium.

[0057]

[0058] In this application, the term "about" may be used before a specific numerical value. As used herein, the term "about" encompasses not only the exact number described after the term, but also a range that is or is nearly that number. Whether a number is or is nearly the specific number described can be determined based on the context in which it is presented. For example, the term "about" may refer to a range of -10% to +10% of a numerical value. In another example, the term "about" may refer to a range of -5% to +5% of a given numerical value. However, this is not a limitation.

[0059]

[0060] In any one of the embodiments described above, the method comprises a step of separating the reactants into solid and liquid after step a) and before performing step b).

[0061] The high-liquid separation method is not particularly limited, and any method known in the art can be used.

[0062] As an example, the method may include a step of centrifuging the reactants to separate solid and liquid before performing step b) after step a).

[0063] For example, the enzyme used in step a) above can be removed in the solid-liquid separation step.

[0064]

[0065] In any one of the embodiments described above, the method comprises a step of decolorizing the reactants after step a) and before performing step b).

[0066] The decolorization method may include solvent treatment and adsorption processes, but is not particularly limited, and any method known in the art may be used.

[0067]

[0068] In any one of the above-described embodiments, the reactant of step b) is obtained by further including a step of physically removing the enzyme or inactivating the enzyme after step a).

[0069]

[0070] In any one of the above-described embodiments, in the step of adding a base to the reactant of step b) to maintain the pH at 9.0 or higher, the pH may be maintained above 9.

[0071] The upper limit of the above pH is not particularly limited, but may be, for example, about 13 or less, 12.5, 12, 11.5, or 11 or less.

[0072]

[0073] In any one of the embodiments described above, the base of step b) is selected from NaOH, ammonia, Ca(OH)2 and KOH.

[0074] The ammonia may be introduced in a gaseous state or an aqueous solution state, but is not limited thereto. When ammonia gas is introduced, the ammonia may dissolve in the water present in the reactor to form an aqueous solution.

[0075] In any one of the above-described embodiments, step b) is performed at a temperature condition of about 25°C to 100°C. For example, the temperature condition may be about 25°C to 95°C, 25°C to 90°C, 25°C to 85°C, 30°C to 80°C, 30°C to 75°C, 30°C to 70°C, 35°C to 65°C, 35°C to 60°C, 35°C to 55°C, 40°C to 100°C, 40°C to 95°C, 40°C to 90°C, 40°C to 85°C, 40°C to 80°C, 45°C to 75°C, 45°C to 70°C, 45°C to 65°C, 45°C to 60°C, or 45°C to 55°C.

[0076] In any one of the above-described embodiments, step b) is performed for 30 minutes or more.

[0077] The execution time of the above step b) can be appropriately adjusted within a range that can increase the recovery rate of terephthalic acid. For example, the above step b) can be performed for 30 minutes or more, 1 hour or more, 1.5 hours or more, or 2 hours or more.

[0078]

[0079] In any one of the above-described embodiments, step c) may include a step of crystallizing terephthalic acid by adding acid to the solution obtained from step b) to adjust the pH to 3 or lower.

[0080] The above acid is not particularly limited, but may be selected from H2SO4, HCl, H3PO4, and NaNO3.

[0081] In any one of the above-described embodiments, the pH of step c) may be appropriately adjusted within a range capable of precipitating terephthalic acid. For example, the pH may be 1 to 2.

[0082]

[0083] In any one of the embodiments described above, the method further comprises a step of filtering the solution containing terephthalic acid after step c). The filter cutoff can be applied by a person skilled in the art. After the filtering step, terephthalic acid is recovered from the solution, and the remaining retentate can be recycled to the reactor so that the remaining terephthalic acid can be precipitated.

[0084] In any one of the embodiments described above, the solution containing a salt of terephthalic acid may be subjected to a concentration step in which water contained in the solution is removed and terephthalic acid precipitation can be induced.

[0085]

[0086] Hereinafter, this application will be described in more detail through examples and experimental examples. However, these examples and experimental examples are intended to exemplify this application and the scope of this application is not limited to these examples and experimental examples.

[0087]

[0088] Example 1. Decomposition of PET through enzymatic reaction

[0089] A 3 L reactor was charged with 2,000 g of water, 80 g of waste PET, and 0.08 g of PET-degrading enzyme. The weight ratio of water: waste PET: PET-degrading enzyme was 1:0.04:0.001. The PET enzyme used was Z1-PETase, described in Three-directional engineering of IsPETase with enhanced protein yield, activity, and durability, Journal of Hazardous Materials, Volume 459, 2023, 132297, ISSN 0304-3894.

[0090] The reaction temperature was set to 50°C and pH to 8, and ammonia gas was added to maintain the pH and the mixture was continuously stirred for 48 hours.

[0091] Unreacted substances were removed from the reaction solution obtained from the above reaction using a centrifuge. When the unreacted waste PET was washed with sufficient water and dried, the weight was as follows.

[0092] Control Experimental Example 1 Experimental Example 2 Unreacted waste PET weight (g) 22.52121

[0093] Example 2. Increase in terephthalic acid (TPA) recovery through pH adjustment.

[0094] In Example 1, a step was performed to remove unreacted waste PET using a centrifuge and adjust the pH of the remaining reaction solution.

[0095] The substances added to the filtered reactant during pH adjustment and the adjusted pH are as follows, and the temperature of the pH adjustment step was set to 60℃ and maintained for 2 hours.

[0096] Control experiment example 1 Experiment example 2 pH pH adjustment step None 9.3 9.3 Substance used Ammonia water NaOH

[0097] 10 g of activated carbon was added to the above reaction mixture, stirred at 50°C for 3 hours, and then filtered. Sulfuric acid was slowly added to the filtrate to adjust the pH to 2.0, thereby precipitating crystals.

[0098] The above decision was vacuum filtered, washed with 300 g of water, and then dried at 60°C.

[0099] The moisture content of the filtered crystals before drying and the amount of TPA obtained after drying are shown in the table below.

[0100] Control Experimental Example 1 Experimental Example 2 Moisture content of crystals before drying (%) 565656 TPA obtained after drying (g) 43.248.248.2 TPA content obtained after drying (%) * 82.599.599.5

[0101] * TPA content obtained after drying (%) = Pure TPA excluding impurities after drying (g) / TPA obtained after drying (g)

[0102]

[0103] From the above description, those skilled in the art will understand that the present application can be implemented in other specific forms without altering its technical concept or essential characteristics. In this regard, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. The scope of this application should be interpreted to include all changes or modifications derived from the meaning and scope of the following claims and their equivalents, rather than the detailed description above.

Claims

1. a) A step of enzymatically depolymerizing a polyester containing terephthalic acid as a unit while maintaining the pH in the reactor at 5 to 9; b) a step of adding a base to the reactant after the completion of the enzymatic reaction in step a) above to maintain the pH at 9.0 or higher; and c) a step of recovering terephthalic acid from the solution obtained in step b); A method for producing terephthalic acid, comprising:

2. A method for producing terephthalic acid in the first paragraph, wherein the base of step b) is selected from NaOH, ammonia, Ca(OH)2, and KOH.

3. A method for producing terephthalic acid, wherein step b) is performed at a temperature of 25°C to 100°C in the first paragraph.

4. A method for producing terephthalic acid, wherein step b) is performed for 30 minutes or more in the first paragraph.

5. A method for producing terephthalic acid, comprising a step of separating the solid and liquid reactants before performing step b) in the first paragraph.

6. A method for producing terephthalic acid, wherein the solid-liquid separation in paragraph 5 is performed by centrifuging the reactant.

7. A method for producing terephthalic acid, comprising a step of decolorizing the reactant before performing step b) after step a) in the first paragraph.

8. A method for producing terephthalic acid in the first paragraph, wherein the enzyme of step a) has PET decomposition enzyme activity at pH 5 to 9.

9. A method for producing terephthalic acid in the first paragraph, wherein the polyester is selected from among polyethylene terephthalate (PET), polyethylene terephthalate glycol (PETG), polyethylene co-isosorbide-terephthalate (PEIT), polytrimethylene terephthalate (PTT), polybutylene adipate terephthalate (PBAT), polycyclohexylenedimethylene terephthalate (PCT), and polybutylene terephthalate (PBT).

10. A method for producing terephthalic acid, wherein step c) comprises a step of crystallizing terephthalic acid by adding acid to the solution obtained from step b) to adjust the pH to 3 or lower.

11. A method for producing terephthalic acid in claim 10, wherein the acid is selected from H2SO4, HCl, H3PO4, and NaNO3.