Method for purifying terephthalic acid

Abstract

The method for purifying terephthalic acid of the present invention includes the steps of contacting crude terephthalic acid with graphite, activated carbon, and a molecular sieve to obtain a reaction mixture; stirring the reaction mixture for a first predetermined time; filtering the reaction mixture to obtain a reaction mixture filtrate; supplying graphite, activated carbon, and a molecular sieve to the reaction mixture filtrate; stirring the reaction mixture filtrate for a second predetermined time; filtering the reaction mixture filtrate to obtain a reaction product solution; and precipitating purified terephthalic acid from the reaction product solution.

Description

[Technical Field]

[0001] The following is a general description of the purification methods for terephthalic acid (TPA), specifically, the purification methods for terephthalic acid (TPA) at room temperature, including the application of graphite, activated carbon, and molecular sieves. [Background technology]

[0002] WO 2020 / 173961 (the entire disclosure of which, excluding definitions, disclaimers, disclaimers, and inconsistencies, is incorporated herein by reference) provides a method for alkaline hydrolysis of one or more plastic polymers to terephthalic acid (TPA) and / or ethylene glycol (EG) and / or other monomers that form one or more plastic polymers, the method comprising the steps of: a) contacting one or more plastic polymers with a metal oxide in solution in the presence of a base to obtain a reaction mixture; b) stirring the reaction mixture under UV light for a suitable period of time; c) recovering terephthalic acid, ethylene glycol and / or other monomers from the reaction mixture.

[0003] The process of WO 2020 / 173961 may produce terephthalic acid that contains impurities or is of a quality that requires further purification before further processing and use. Current methods for purifying TPA are energy intensive and economically inefficient.

[0004] Therefore, there is a need for improved methods for purifying TPA. Summary of the Invention

[0005] A method for purifying terephthalic acid according to one embodiment is described below, which includes contacting crude terephthalic acid with graphite, activated carbon, and a molecular sieve to obtain a reaction mixture, stirring the reaction mixture for a first predetermined time, filtering the reaction mixture to obtain a reaction mixture filtrate, supplying the reaction mixture filtrate with graphite, activated carbon, and a molecular sieve, stirring the reaction mixture filtrate for a second predetermined time, filtering the reaction mixture filtrate to obtain a reaction product solution, and precipitating purified terephthalic acid from the reaction product solution.

[0006] In some embodiments, the reaction mixture is stirred at pH 14.

[0007] In some embodiments, the reaction mixture filtrate is stirred at pH 7.

[0008] In some embodiments, graphite, activated carbon, and molecular sieves are provided for contact with crude terephthalic acid in a ratio of 1:6:2.

[0009] According to some embodiments, graphite, activated carbon, and molecular sieves are provided to the reaction mixture filtrate in a ratio of 1:6:2.

[0010] In some embodiments, purified terephthalic acid is precipitated from the reaction product solution using an acid.

[0011] In some embodiments, the acid is hydrochloric acid or sulfuric acid.

[0012] In some embodiments, the first predetermined time period is between 10 minutes and 120 minutes.

[0013] In some embodiments, the first predetermined period of time is 30 minutes.

[0014] In some embodiments, the second predetermined time period is between 10 minutes and 120 minutes.

[0015] In some embodiments, the second predetermined period of time is 30 minutes.

[0016] In some embodiments, the method is carried out at room temperature.

[0017] In some embodiments, the molecular sieve that contacts the crude terephthalic acid is zeolite 13X.

[0018] In some embodiments, the molecular sieve provided to the reaction mixture filtrate is zeolite 13X.

[0019] Other aspects and features will become apparent to those skilled in the art upon review of the following description of several exemplary embodiments. [Brief explanation of the drawings]

[0020] [Figure 1] The drawings accompanying this document are intended to illustrate various examples of the articles, methods, and apparatus herein. Figure 1 is a flow chart of a method for purifying terephthalic acid according to one embodiment. [Figure 2] FIG. 2 is a table detailing the chemical and physical properties of terephthalic acid produced using the method of FIG. 1 in accordance with an embodiment. [Figure 3] FIG. 3 is a table detailing the chemical and physical properties of terephthalic acid produced using the method of FIG. 1 according to another embodiment. [Figure 4] FIG. 4 is a table detailing the chemical and physical properties of terephthalic acid produced using the method of FIG. 1 according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] Various devices or processes are described below to illustrate examples of the claimed embodiments. No embodiment described below is intended to limit any claimed embodiment, and any claimed embodiment may encompass a process or device different from the process or device described below. No claimed embodiment is limited to a device or process having all the features of any device or process described below, or to features common to multiple or all of the devices described below.

[0022] Furthermore, although process steps, method steps, algorithms, or the like may be described (in the disclosure and / or claims) in a sequential order, such processes, methods, algorithms, or the like may be configured to operate in other orders. In other words, any order or sequence of steps described does not necessarily indicate that the steps must be performed in that order. Steps of processes described herein may be performed in any order practical. Additionally, some steps may be performed simultaneously.

[0023] Where a single device or article is described herein, it will be apparent that multiple devices / articles (whether or not cooperating) may be used in place of the single device or article. Similarly, where multiple devices or articles are described herein (whether or not cooperating), it will be apparent that a single device / article may be used in place of the multiple devices or articles.

[0024] Associated with the screw conveyor reactor system described herein is a method for decomposing plastic materials into terephthalic acid (TPA), ethylene glycol, and / or other monomers that form the plastic materials.

[0025] The method comprises the steps of: contacting one or more plastic polymers with a metal oxide in solution in the presence of a base to form a reaction mixture; stirring the reaction mixture under ultraviolet light for a suitable period of time; and recovering terephthalic acid, ethylene glycol and / or other monomers from the reaction mixture.

[0026] The process involves alkaline hydrolysis of polymers, including polyethylene terephthalate (PET), which can be performed at room temperature with relatively high efficiency compared to other methods for breaking down polymers into their constituent monomers.

[0027] In some embodiments, the solvent is ethanol or an ethanol-water mixture.

[0028] In some embodiments, the polymer is polyethylene terephthalate (PET).

[0029] In some embodiments, the metal oxide is TiO2.

[0030] In some embodiments, the base is NaOH.

[0031] In some embodiments, the initial pH of the reaction mixture is 14.

[0032] In some embodiments, the reaction mixture is stirred at room temperature.

[0033] After the terephthalic acid is recovered at the end of this process, it may be of low purity and may require further processing to obtain commercially useful terephthalic acid, which may be fed to a process requiring virgin terephthalic acid.

[0034] Commonly used methods for purifying TPA involve a recrystallization process, which requires heating at high temperatures (e.g., 200°C), is energy intensive, and involves the use of hazardous solvents such as dimethylformamide (DMF), which pose safety risks to workers and can require expensive, time-consuming, and complex procedures to handle and manage.

[0035] Described herein are methods for purifying TPA and other compounds. The systems and methods described herein are particularly applicable to purifying TPA produced by the room-temperature alkaline polymer hydrolysis process described above and in WO 2020 / 173961. In some embodiments, the TPA purification methods described herein can also be applied to TPA from other sources and to compounds other than TPA. By using sufficient amounts of three adsorbents and performing two adsorption steps under different pH conditions, the adsorbents can efficiently remove impurities present in impure PET-derived TPA. The methods described herein can consistently produce virgin TPA with up to 1% higher purity and up to 5% brighter whiteness. Additional pH adjustments may be performed when purifying compounds other than TPA.

[0036] Any of the methods described herein can be applied to the purification of other compounds, including low molecular weight (<200 g / mol) monomers, such as lactic acid. In other examples, water, such as wastewater, air, proteins, and other substances can be purified by the methods described herein.

[0037] 1, the flowchart shown therein outlines an embodiment of a TPA purification method 100. The method 100 includes steps 102, 104, 106, 108, 110, 112, and 114.

[0038] The methods described herein may be carried out as a batch operation, preferably in a reaction vessel equipped with an agitator and a plug-drain filter. In some examples, the methods described herein may be carried out as a batch operation in a series configuration of multiple reaction vessels. In some examples, the methods described herein may be adapted to be carried out as a continuous process.

[0039] In step 102, crude terephthalic acid is contacted with graphite, activated carbon, and molecular sieves. The crude terephthalic acid may be sourced from the product of a polymer recycling process, such as the ambient temperature alkaline polymer hydrolysis process described in WO 2020 / 173961. In some examples, the contacting process in step 102 may be carried out in a reaction vessel.

[0040] In some examples, such crude terephthalic acid may contain impurities such as dyes (e.g., azo dyes such as Pigment Yellow 13, Sudan Black B, Sudan Red G, or anthraquinones such as Disperse Red 11), solid pigments (e.g., carbon black), isomeric monomers (e.g., phthalic acid, isophthalic acid, etc.), as well as molecules that may be present as impurities in PET (e.g., benzoic acid, p-toluic acid, bisphenol A, 4-carboxybenzaldehyde), metal ions (e.g., chromium, iron, nickel, antimony, sodium, titanium, aluminum, barium, calcium, cobalt, manganese, molybdenum, lithium, potassium, zinc), and / or other impurities.

[0041] The graphite provided in step 102 may include amorphous, crystalline, or flake graphite having a purity of 99% and a particle size range of 5-30 μm (micrometers). In other examples, graphite of different purity levels, morphologies, and particle sizes may alternatively be provided.

[0042] In some examples, the graphite of step 102 has a crystallite height of 60-100 nm, an interlayer distance of 0.25-0.35 nm, a D90 particle size of 5-30 μm, and a BET specific surface area of ​​10-15 μm.2 / g, an ash content of less than 0.05%, and individual metals generally less than 2 ppm.

[0043] The activated carbon provided in step 102 has a surface area of ​​500 to 1500 m 2 / g and may include granular activated carbon having a particle size of less than 1 mm.

[0044] In other examples, activated carbon having different purity levels, morphologies, surface areas, and particle sizes can alternatively be provided. In some examples, the activated carbon of step 102 has a grinding fineness of 70% by weight (less than 40 μm), an Iodine Index of 900-1500 mg / g, and an Iodine Index of 800-1500 μm. 2 / g of surface area.

[0045] The molecular sieve provided in step 102 may comprise an aluminosilicate crystalline molecular sieve, such as Zeolite 13X molecular sieve, which has an average pore size of 9 Angstroms and is capable of adsorbing molecules with a kinetic diameter of less than 9 Angstroms.

[0046] In some examples, the molecular sieve of step 102 has a diameter of 3-5 μm and an average surface area of ​​700 m 2 / g。 In other examples, other molecular sieves having similar compositions and / or specifications may be provided instead. In other examples, other molecular sieves having different compositions and / or specifications may be provided instead.

[0047] The graphite, activated carbon, and molecular sieve provided in step 102 may be provided in a mass ratio of 1:6:2, respectively, of graphite, activated carbon, and molecular sieve. In other examples, the graphite, activated carbon, and molecular sieve may be provided in other ratios.

[0048] In some examples, crude terephthalic acid is dissolved in water to form M-TPA (the "M" may be derived from the hydrolysis process). + or K +M-TPA may be provided in the form of a metal such as tungsten (representing a metal such as tungsten) at a concentration near its maximum solubility in solution (about 13 wt %) at pH 14. In some examples, after step 102, the total solution of 210 L contains 3 kg of activated carbon, 1 kg of zeolite 13X, and 0.5 kg of graphite.

[0049] The three components added in step 102 capture impurities through an adsorption process. Activated carbon can remove dyes by utilizing its large internal pores to adsorb them. Zeolite 13X's pores are relatively small compared to activated carbon, allowing it to capture organic molecules with small molecular weights. The graphite surface allows for non-chemical, soft bonding between organic matter and metal ions. By changing the pH from alkaline to neutral, the surface charge of the adsorbent changes from negative to neutral or from positive to neutral-negative, facilitating the adsorption of organic molecules with slight negative or positive regions in their molecules, in addition to heavy metals.

[0050] The reaction mixture is stirred for a first predetermined period of time in step 104. The reaction mixture can be stirred in a reaction vessel having an integral stirring element or using a similar device.

[0051] The reaction mixture may be stirred for a period ranging from 10 minutes to 120 minutes. In some instances, the reaction mixture may be stirred for 60 minutes in step 104. In other instances, the reaction mixture may be stirred for a different period of time.

[0052] In step 104, the reaction mixture may be stirred at an alkaline pH. Prior to stirring, a pH adjuster, such as HCl, NaOH, or other compound, may be added to the reaction mixture to adjust the pH of the reaction mixture. In some examples, the reaction mixture may be stirred at a pH of 14.

[0053] In step 106, the reaction mixture is filtered to obtain a reaction mixture filtrate. In some examples, the reaction mixture may be filtered through a plug-drain filter connected to or integral with the reaction vessel in which steps 102 and / or 104 were performed. The filter can separate the solid components of the reaction mixture from the liquid components. The filter may have a pore size slightly smaller than the diameter of the smallest solid component of the reaction mixture. For example, if the diameter of the smallest solid particle is 5 μm (micrometers), the filter may have a pore size of 4 μm.

[0054] After filtration, the reaction mixture filtrate can be fed to another vessel for further processing.

[0055] In some embodiments of the methods described herein, steps 102-106 can each be divided into multiple substeps performed sequentially. For example, in step 102, only one of the graphite, activated carbon, and molecular sieve can be provided, after which the mixture can be stirred and filtered (similar to steps 104 and 106). After filtration, another of the graphite, activated carbon, and molecular sieve (e.g., one not yet provided in the method) can be provided, after which the mixture can be stirred and filtered (similar to steps 104 and 106). After the second filtration, another of the graphite, activated carbon, and molecular sieve (e.g., the last not yet provided in the method) can be provided, after which the mixture can be further stirred and finally filtered (similar to steps 104 and 106) to produce the reaction mixture filtrate referred to in step 106.

[0056] In some examples, steps 102-106 can each be divided into two substeps, where two of the graphite, activated carbon, and molecular sieve can be provided in a first substep and the remaining material can be provided in a second substep. In some examples, the second substep can occur before the first substep.

[0057] In some examples, steps 102-106 can each be divided into three substeps, where one of the graphite, activated carbon, and molecular sieve can be provided in a first substep, one of the remaining two materials can be provided in a second substep, and the remaining third material can be provided in a third substep. In some examples, the first, second, and third substeps can be performed in any order.

[0058] In some examples, steps 102-106 can be performed using a staged column filtration system.

[0059] In step 108, graphite, activated carbon, and molecular sieves are provided to the reaction mixture filtrate. The graphite provided in step 108 may include amorphous, crystalline, or flake graphite having a purity of 99% and a particle size range of 5 to 30 μm (micrometers). In other examples, graphite of different purity levels, morphologies, and particle sizes may alternatively be provided.

[0060] In some examples, the graphite of step 108 has a crystallite height of 60-100 nm, an interlayer distance of 0.25-0.35 nm, a D90 particle size of 5-30 μm, and a BET specific surface area of ​​10-15 μm. 2 / g, an ash content of less than 0.05%, and individual metal contents generally less than 2 ppm.

[0061] The activated carbon provided in step 108 has a surface area of ​​500 to 1500 m 2 / g and particle size less than 1 mm. In other examples, activated carbon of different purity levels, shapes, surface areas, and particle sizes may be provided instead.

[0062] In some examples, the activated carbon of step 108 has a grinding fineness of 70% by weight (less than 40 μm), an iodine index of 900-1500 mg / g, and an iodine index of 800-1500 m 2 / g of surface area.

[0063] The molecular sieve provided in step 108 may comprise an aluminosilicate crystalline molecular sieve, such as Zeolite 13X molecular sieve, which has an average pore size of 9 Angstroms and is capable of adsorbing molecules having a kinetic diameter of less than 9 Angstroms.

[0064] In some examples, the molecular sieve of step 108 has a diameter of 3-5 μm and an average surface area of ​​700 m 2 / g。 In other examples, other molecular sieves having similar compositions and / or specifications may be provided instead. In other examples, other molecular sieves having different compositions and / or specifications may be provided instead.

[0065] The graphite, activated carbon, and molecular sieve provided in step 108 may be provided in a mass ratio of 1:6:2, respectively, of graphite, activated carbon, and molecular sieve. In other examples, the graphite, activated carbon, and molecular sieve may be provided in other ratios, for example, as described above with reference to step 108.

[0066] The reaction mixture filtrate is stirred for a second predetermined period of time in step 110. The reaction mixture filtrate can be stirred in a reaction vessel having an integral stirring element or using a similar device.

[0067] The reaction mixture filtrate may be stirred for a period ranging from 10 minutes to 120 minutes. In some examples, the reaction mixture filtrate may be stirred for 30 minutes in step 110. In other examples, the reaction mixture filtrate may be stirred for a different period of time.

[0068] In step 110, the reaction mixture filtrate may be stirred at a neutral pH. Prior to stirring, a pH adjuster, such as HCl, NaOH, or other similar compounds, may be added to the reaction mixture to adjust the pH of the reaction mixture filtrate. In some examples, the reaction mixture may be stirred at a pH of 7.

[0069] In step 112, the reaction mixture filtrate is filtered to obtain a reaction product solution. In some examples, the reaction mixture filtrate may be filtered using a plug-drain filter connected to or integrated into the reaction vessel in which any one of steps 102-110 was performed. The filter can separate the solid components of the reaction mixture filtrate from the liquid components. The filter may have a pore size slightly smaller than the diameter of the smallest solid component of the reaction mixture. For example, if the smallest solid particle (e.g., a graphite particle) has a diameter of 5 μm, the filter may have a pore size of 4 μm.

[0070] After filtering the reaction mixture filtrate in step 112, the reaction product solution can be fed to another vessel for further processing or returned to the same vessel.

[0071] In some embodiments of the methods described herein, steps 108-112 can each be divided into multiple substeps performed sequentially. For example, in step 102, only one of the graphite, activated carbon, and molecular sieve may be provided, after which the mixture may be agitated and filtered (similar to steps 110 and 112). After filtration, another of the graphite, activated carbon, and molecular sieve (e.g., one not yet provided in the method) may be provided, after which the mixture may be agitated and filtered (similar to steps 110 and 11). After the second filtration, another of the graphite, activated carbon, and molecular sieve (e.g., the last not yet provided in the method) may be provided, after which the mixture may be further agitated and finally filtered (similar to steps 110 and 11) to produce the reaction product solution referred to in step 112.

[0072] In some examples, steps 108-112 can each be divided into two substeps, where two of the graphite, activated carbon, and molecular sieve can be provided in a first substep and the remaining material can be provided in a second substep. In some examples, the second substep can occur before the first substep.

[0073] In some examples, steps 108-112 can each be divided into three substeps, where one of the graphite, activated carbon, and molecular sieve can be provided in a first substep, one of the remaining two materials can be provided in a second substep, and the remaining third material can be provided in a third substep. In some examples, the first, second, and third substeps can be performed in any order.

[0074] In some examples, steps 108-112 can be performed using a staged column filtration system.

[0075] In step 114, purified terephthalic acid is precipitated from the reaction product solution. In some examples, the purified terephthalic acid can be precipitated by adding an acid to the reaction product solution. In some examples, the acid can include hydrochloric acid or sulfuric acid. In other examples, any other suitable acid can be used to facilitate precipitation.

[0076] The acid provided in step 114 may have a concentration of 98% if sulfuric acid is provided. The acid provided in step 114 may have a concentration of 33% if hydrochloric acid is provided. Other suitable acids provided will have equivalent concentrations ranging from 1 to 98%.

[0077] After the purified terephthalic acid is precipitated from the reaction product solution, the purified terephthalic acid may be separated from the solution by some means (e.g., filtration). In some examples, the purified terephthalic acid may be subjected to additional processing steps (e.g., heating, vacuum drying, or other processing steps). For example, the purified terephthalic acid may be subjected to a grinding process to produce purified terephthalic acid in the form of a free-flowing powder. Such a free-flowing powder may be transferred to a storage medium and vacuum-sealed or otherwise stored.

[0078] The purified terephthalic acid extracted by application of method 100 can be applied to subsequent chemical processes or applications where virgin quality terephthalic acid is required.

[0079] Referring now to Figure 2, Figure 2 shows a table 200 detailing the specifications for purified terephthalic acid produced using the method 100 described herein. The specifications detailed in table 200 include the impurity concentrations and characteristics of two samples of purified terephthalic acid. The samples can be compared to a PTA standard, as shown in Figure 2.

[0080] Referring now to Figure 3, Figure 3 shows a table 300 detailing the specifications for purified terephthalic acid produced using the method 100 described herein. The specifications detailed in table 300 include the concentrations of impurities in a sample of purified terephthalic acid. The sample can be compared to the listed standards, as shown in Figure 3.

[0081] Referring now to Figure 4, Figure 4 shows a table 400 detailing the specifications for purified terephthalic acid produced using the method 100 described herein. The specifications detailed in table 400 include the concentrations of impurities in a sample of purified terephthalic acid. The sample can be compared to the listed standards, as shown in Figure 4.

[0082] While the above description provides one or more example devices, methods, or systems, it will be understood that other devices, methods, or systems may be included within the scope of the claims as interpreted by one of ordinary skill in the art.

Claims

1. 1. A method for purifying terephthalic acid, comprising: contacting crude terephthalic acid with graphite, activated carbon, and molecular sieves to obtain a reaction mixture; stirring the reaction mixture for a first predetermined period of time; filtering the reaction mixture to obtain a reaction mixture filtrate; providing graphite, activated carbon, and molecular sieves to the reaction mixture filtrate; stirring the reaction mixture filtrate for a second predetermined period of time; filtering the reaction mixture filtrate to obtain a reaction product solution; and precipitating purified terephthalic acid from the reaction product solution A method comprising:

2. The reaction mixture is stirred at pH 14. The method of claim 1.

3. Stirring the reaction mixture filtrate at pH 7.

3. The method according to claim 1 or 2.

4. providing graphite, activated carbon, and molecular sieves in a ratio of 1:6:2 for contact with the crude terephthalic acid; The method according to any one of claims 1 to 3.

5. Feed the reaction mixture filtrate with graphite, activated carbon, and molecular sieves in a ratio of 1:6:2; The method according to any one of claims 1 to 4.

6. Precipitating the purified terephthalic acid from the reaction product solution using an acid. The method according to any one of claims 1 to 4.

7. The acid is hydrochloric acid or sulfuric acid. The method of claim 6.

8. The first predetermined time is 10 minutes to 120 minutes. The method according to any one of claims 1 to 7.

9. the first predetermined time period is 30 minutes; The method of claim 6.

10. The second predetermined time is 10 minutes to 120 minutes. The method according to any one of claims 1 to 9.

11. the second predetermined time is 30 minutes; The method of claim 10.

12. carried out at room temperature, The method according to any one of claims 1 to 11.

13. The molecular sieve that contacts the crude terephthalic acid is zeolite 13X. The method according to any one of claims 1 to 12.

14. The molecular sieve provided to the reaction mixture filtrate is zeolite 13X. The method according to any one of claims 1 to 13.

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