EP4353876A1 - Process for obtaining terephthalic acid and recovering sodium hydroxide from a sodium terephthalate solution produced from reused polyethylene terephthalate (pet) - Google Patents
Process for obtaining terephthalic acid and recovering sodium hydroxide from a sodium terephthalate solution produced from reused polyethylene terephthalate (pet) Download PDFInfo
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- EP4353876A1 EP4353876A1 EP21944450.2A EP21944450A EP4353876A1 EP 4353876 A1 EP4353876 A1 EP 4353876A1 EP 21944450 A EP21944450 A EP 21944450A EP 4353876 A1 EP4353876 A1 EP 4353876A1
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- European Patent Office
- Prior art keywords
- terephthalic acid
- sodium hydroxide
- solution
- sodium
- recovering
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- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 title claims abstract description 180
- KKEYFWRCBNTPAC-UHFFFAOYSA-N Terephthalic acid Chemical compound OC(=O)C1=CC=C(C(O)=O)C=C1 KKEYFWRCBNTPAC-UHFFFAOYSA-N 0.000 title claims abstract description 130
- 238000000034 method Methods 0.000 title claims abstract description 54
- VIQSRHWJEKERKR-UHFFFAOYSA-L disodium;terephthalate Chemical compound [Na+].[Na+].[O-]C(=O)C1=CC=C(C([O-])=O)C=C1 VIQSRHWJEKERKR-UHFFFAOYSA-L 0.000 title claims abstract description 42
- -1 polyethylene terephthalate Polymers 0.000 title claims description 8
- 229920000139 polyethylene terephthalate Polymers 0.000 title description 29
- 239000005020 polyethylene terephthalate Substances 0.000 title description 29
- 230000001476 alcoholic effect Effects 0.000 claims abstract description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 13
- 230000007062 hydrolysis Effects 0.000 claims abstract description 5
- 238000006460 hydrolysis reaction Methods 0.000 claims abstract description 5
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 claims description 15
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 6
- 229910052708 sodium Inorganic materials 0.000 claims description 6
- 239000011734 sodium Substances 0.000 claims description 6
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 claims description 4
- 238000011084 recovery Methods 0.000 claims description 4
- 239000012528 membrane Substances 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- BDERNNFJNOPAEC-UHFFFAOYSA-N propan-1-ol Chemical compound CCCO BDERNNFJNOPAEC-UHFFFAOYSA-N 0.000 claims description 2
- IISLNQNUYOZKNE-UHFFFAOYSA-N sodium;terephthalic acid Chemical compound [Na].OC(=O)C1=CC=C(C(O)=O)C=C1 IISLNQNUYOZKNE-UHFFFAOYSA-N 0.000 claims 1
- 239000006227 byproduct Substances 0.000 abstract description 7
- 238000004064 recycling Methods 0.000 abstract description 7
- 239000000243 solution Substances 0.000 description 36
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 15
- 238000006243 chemical reaction Methods 0.000 description 5
- 238000005868 electrolysis reaction Methods 0.000 description 5
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 3
- 230000005611 electricity Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 229910052938 sodium sulfate Inorganic materials 0.000 description 3
- 235000011152 sodium sulphate Nutrition 0.000 description 3
- 239000007787 solid Substances 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- WQDUMFSSJAZKTM-UHFFFAOYSA-N Sodium methoxide Chemical compound [Na+].[O-]C WQDUMFSSJAZKTM-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 238000001704 evaporation Methods 0.000 description 2
- 230000008020 evaporation Effects 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 150000004703 alkoxides Chemical class 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 230000000295 complement effect Effects 0.000 description 1
- 239000002537 cosmetic Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 239000003014 ion exchange membrane Substances 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- 229920000728 polyester Polymers 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000035484 reaction time Effects 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/14—Alkali metal compounds
- C25B1/16—Hydroxides
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B3/00—Electrolytic production of organic compounds
Definitions
- the present invention is related to obtaining terephthalic acid, and more particularly it is related to a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET.
- Terephthalic acid has various applications in the chemical, cosmetic, and even pharmaceutical industries.
- the most common way to obtain terephthalic acid is from oil.
- this way of obtaining it is not a good long-term viable option, because oil is a non-renewable resource.
- sodium hydroxide (NaOH) also has many applications in various industries, mainly in the chemical industry. It is known that sodium hydroxide can be obtained electrolytically using ion exchange membranes from aqueous solutions of sodium chloride. However, this industrial process typically only produces solutions of between 20 and 40 % sodium hydroxide and requires more operations to obtain it in a solid state.
- JP2004250544 refers to a process to recover terephthalic acid from a terephthalic acid polyester by electrolysis.
- the method uses an alcoholic solution of ethylene glycol, sodium sulfate and water as catholyte for electrolysis.
- this document does not consider the recovery of sodium hydroxide from a sodium terephthalate solution, so it is not suitable as a complement to the PET recycling process.
- Document JP11302208 describes a method for producing terephthalic acid and ethylene glycol from PET. The method involves putting PET in contact with sodium hydroxide in ethylene glycol and subsequently separating the sodium terephthalate produced.
- the method described in document JP11302208 requires reaching high temperatures of between 170 °C to 180 °C, which increases the cost of the process to recycle PET, because a large amount of energy and special equipment are needed for these temperatures to be reached, in addition to the fact that some acid is used to obtain terephthalic acid, for example sulfuric acid, thus obtaining sodium sulfate as a by-product.
- Another object of the present invention is to provide a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET that does not need to use large amounts of water and electricity.
- Another object of the present invention is to provide a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET that does not generate many byproducts.
- the present invention refers to a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET, which comprises the following steps:
- Figure 1 shows a scheme of the chemical reaction of a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET within the electrolytic cell in accordance with the present invention.
- a process has been found to obtain terephthalic acid and recover sodium hydroxide from a solution of sodium terephthalate produced from reused PET, which does not require large amounts of water or energy.
- one aspect of the present invention is a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET, which comprises the following steps:
- the alcoholic medium placed on the cathodic side of the electrolytic cell is methanol, ethanol, propanol, butanol, or a mixture thereof.
- sodium hydroxide is added to the alcoholic medium placed on the cathodic side of the electrolytic cell to obtain an alcoholic solution.
- the alcoholic solution with sodium hydroxide has a molarity of 0.25 M to 1 M.
- the electrolytic cell has a membrane or a diaphragm between the anodic side and the cathodic side.
- the electric current applied to the electrolytic cell has a density of between 0.1 to 0.5 Amperes/cm 2 .
- the applied electrical current is measured continuously to determine the number of Coulombs passing through the electrodes.
- electric current is applied to the electrolytic cell for a period of 50 to 70 minutes. Preferably, after the period the electrodes are removed.
- a cell could be designed that worked continuously.
- a solution of terephthalic acid is obtained from the anodic side of the electrolytic cell and sodium hydroxide and sodium alkoxide in an alcoholic solution are obtained from the cathodic side of the electrolytic cell.
- the solution from the anodic side, which contains precipitated terephthalic acid is filtered.
- the water-washed terephthalic acid is oven dried at a temperature of between 125 to 135°C.
- the terephthalic acid is dried in the oven for 50 to 70 minutes.
- the percentage of electronic efficiency of recovery of terephthalic acid relative to sodium terephthalate solution is 50 to 85 %.
- the sodium alkoxide is in an alcoholic solution and in a concentration of between 5 % to 30 % (m/V).
- sodium hydroxide is obtained by adding the stoichiometric amount of water.
- Solid sodium hydroxide is obtained by evaporation of the corresponding alcohol. It should be noted that the production of terephthalic acid and sodium hydroxide occurs simultaneously.
- Figure 1 shows a diagram of the chemical reaction of the process to obtain terephthalic acid and recover sodium hydroxide from a solution of sodium terephthalate produced from reused PET within the electrolytic cell according to the present invention.
- Figure 1 shows the anodic side, that is, the left side of figure 1 and the cathodic side, that is, the right side of figure 1 seen frontally.
- an aqueous solution of sodium terephthalate is introduced on the anodic side of said electrolytic cell and an alcoholic medium with sodium hydroxide is introduced on the cathodic side.
- a test was conducted to recover terephthalic acid and sodium hydroxide from a sodium terephthalate solution obtained from a PET hydrolysis process according to the present invention.
- the sodium terephthalate solution was prepared with 12 g of sodium terephthalate and 100 mL of water.
- 90 mL of a solution of methanol with sodium hydroxide were added on the cathodic side of the electrolytic cell.
- the solution was prepared with 1 g of NaOH and 100 mL of methanol.
- a platinum electrode was placed on the anodic side and a stainless-steel electrode on the cathodic side and the electrolytic cell was connected to a power source.
- the power source was turned on and the current was controlled and maintained for one hour at an electrical intensity of 0.4 to 0.6 Amperes.
- the electrolytic cell was connected to an ammeter that continuously measured and recorded the current that passed through the electrodes and in this way the amount of electricity in Coulombs that passed through the electrodes of the electrolytic cell was determined.
- the power source was turned off, the electrodes from each side of the electrolytic cell were removed and the solution from the anodic side was filtered, which contained precipitated terephthalic acid, sad precipitate was washed and the terephthalic acid washed, dried in the oven at 130° C for one hour and then weighed. On the cathodic side sodium methoxide was obtained. Adding water to this solution produces sodium hydroxide in methanol. Solid sodium hydroxide is obtained by evaporation of the corresponding alcohol.
- the temperatures of the two half-cells were measured, as well as the variations in current between the two electrodes of the electrolytic cell, to know the efficiency of the precipitated terephthalic acid obtained.
- Table 1 shows the results obtained: TABLE 1 Initial current (A) Time (min) Terephthalic acid weight (g) Amount of electricity (Coulombs) Electronic efficiency (%) 0.4252 60 0.331 1253 30.7 0.5397 60 0.70 1549 52.5 0.530 60 0.784 1411 64.6 0.521 60 0.837 1794 65.7
- the amount of terephthalic acid obtained is good considering the amount of mL of sodium terephthalate solution with which the reaction began. Furthermore, the mL of water used and the electrical energy necessary for the reaction represent a very low cost in relation to the cost at which terephthalic acid and sodium hydroxide can be sold.
- a test was conducted using different reaction times in a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET, according to the present invention.
- the purpose of this test is to see if there is variation in the efficiency of the process. From the results obtained, there is no significant difference.
- the process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET has been designed to not generate the by-products generated in the PET recycling process. Furthermore, the described method does not require large amounts of water or energy, and practically does not generate by-products, and it will be evident to any person skilled in the art that the embodiments of a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET as described above and illustrated in the drawing that accompanies it, are only illustrative but not limiting of the present invention, since numerous considerable changes in its details are possible without departing from the scope of the invention.
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- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
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- Metallurgy (AREA)
- Inorganic Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
A process for obtaining terephthalic acid and recovering sodium hydroxide from a sodium terephthalate solution produced from reused PET, which includes the following steps: i) placing a sodium terephthalate solution obtained from a PET hydrolysis process on the anodic side; ii) placing an alcoholic medium on the cathodic side of the electrolytic cell; iii) applying an electric current that circulates through the anodic side and the cathodic side of the electrolytic cell and; iv) recovering terephthalic acid and sodium hydroxide. The method has been designed to not generate the by-products generated in the PET recycling process, and thus have a "green" process. Furthermore, the method described does not require large amounts of water or energy.
Description
- The present invention is related to obtaining terephthalic acid, and more particularly it is related to a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET.
- In the chemical recycling process of polyethylene terephthalate, better known as PET, by-products are generated, and a large amount of sodium hydroxide (NaOH) is consumed. An example of this is described in document
MX271258 - Terephthalic acid has various applications in the chemical, cosmetic, and even pharmaceutical industries. The most common way to obtain terephthalic acid is from oil. However, this way of obtaining it is not a good long-term viable option, because oil is a non-renewable resource. On the other hand, sodium hydroxide (NaOH) also has many applications in various industries, mainly in the chemical industry. It is known that sodium hydroxide can be obtained electrolytically using ion exchange membranes from aqueous solutions of sodium chloride. However, this industrial process typically only produces solutions of between 20 and 40 % sodium hydroxide and requires more operations to obtain it in a solid state.
- Therefore, there is a need to develop a method that allows recovering the reagents consumed in the PET recycling process, such as sodium hydroxide.
- Among the solutions proposed in the state of the art is document
JP2004250544 - Document
JP11302208 JP11302208 - Because of the above, we have sought to eliminate the drawbacks presented by the methods for obtaining terephthalic acid currently used, developing a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET, without using large amounts of water and energy.
- Considering the defects of the prior art, it is an object of the present invention to provide a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from PET that allows the recovery of the hydroxide of sodium that is normally consumed in the PET recycling process.
- Another object of the present invention is to provide a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET that does not need to use large amounts of water and electricity.
- Finally, another object of the present invention is to provide a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET that does not generate many byproducts.
- These and other goals are achieved through a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET according to the present invention.
- A method of obtaining terephthalic acid and ethylene glycol and recovering sodium hydroxide consumed in the PET recycling process which does not require large amounts of water or energy has been invented. Thus, the present invention refers to a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET, which comprises the following steps:
- i) placing a sodium terephthalate solution obtained from a PET hydrolysis process on the anodic side in an electrolytic cell;
- ii) placing an alcoholic medium on the cathodic side of the electrolytic cell;
- iii) applying an electric current that circulates through the anodic side and the cathodic side of the electrolytic cell and;
- iv) recovering terephthalic acid and sodium hydroxide.
- The novel aspects that are considered characteristic of the present invention will be particularly established in the attached claims. However, some embodiments, characteristics, and some objects and advantages thereof will be better understood in the detailed description, when read in relation to the attached drawing, in which:
Figure 1 shows a scheme of the chemical reaction of a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET within the electrolytic cell in accordance with the present invention. - A process has been found to obtain terephthalic acid and recover sodium hydroxide from a solution of sodium terephthalate produced from reused PET, which does not require large amounts of water or energy.
- Thus, one aspect of the present invention is a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET, which comprises the following steps:
- i) placing a sodium terephthalate solution obtained from a PET hydrolysis process on the anodic side in an electrolytic cell;
- ii) placing an alcoholic medium on the cathodic side of the electrolytic cell;
- iii) applying an electric current that circulates through the anodic side and the cathodic side of the electrolytic cell and;
- iv) recovering terephthalic acid and sodium hydroxide.
- In a preferred embodiment of the present invention, the alcoholic medium placed on the cathodic side of the electrolytic cell is methanol, ethanol, propanol, butanol, or a mixture thereof. Preferably, sodium hydroxide is added to the alcoholic medium placed on the cathodic side of the electrolytic cell to obtain an alcoholic solution. Preferably, the alcoholic solution with sodium hydroxide has a molarity of 0.25 M to 1 M.
- In another preferred embodiment of the present invention, the electrolytic cell has a membrane or a diaphragm between the anodic side and the cathodic side. Preferably, the electric current applied to the electrolytic cell has a density of between 0.1 to 0.5 Amperes/cm2. Preferably, the applied electrical current is measured continuously to determine the number of Coulombs passing through the electrodes. Preferably, electric current is applied to the electrolytic cell for a period of 50 to 70 minutes. Preferably, after the period the electrodes are removed. However, a cell could be designed that worked continuously.
- In a preferred embodiment of the present invention, a solution of terephthalic acid is obtained from the anodic side of the electrolytic cell and sodium hydroxide and sodium alkoxide in an alcoholic solution are obtained from the cathodic side of the electrolytic cell. Preferably, the solution from the anodic side, which contains precipitated terephthalic acid, is filtered. Preferably, the water-washed terephthalic acid is oven dried at a temperature of between 125 to 135°C. Preferably, the terephthalic acid is dried in the oven for 50 to 70 minutes. Preferably, the percentage of electronic efficiency of recovery of terephthalic acid relative to sodium terephthalate solution is 50 to 85 %. Preferably, the sodium alkoxide is in an alcoholic solution and in a concentration of between 5 % to 30 % (m/V). In case of alkoxide formation, sodium hydroxide is obtained by adding the stoichiometric amount of water. Solid sodium hydroxide is obtained by evaporation of the corresponding alcohol. It should be noted that the production of terephthalic acid and sodium hydroxide occurs simultaneously.
- For a better understanding,
Figure 1 shows a diagram of the chemical reaction of the process to obtain terephthalic acid and recover sodium hydroxide from a solution of sodium terephthalate produced from reused PET within the electrolytic cell according to the present invention.Figure 1 shows the anodic side, that is, the left side offigure 1 and the cathodic side, that is, the right side offigure 1 seen frontally. Initially, in the electrolytic cell, an aqueous solution of sodium terephthalate is introduced on the anodic side of said electrolytic cell and an alcoholic medium with sodium hydroxide is introduced on the cathodic side. Then, a reaction occurs in which, from the oxidation of water at the anode, the protons produced react with the terephthalate ion, terephthalic acid (H2TF) is precipitated and oxygen (O2) is released. Simultaneously, on the cathodic side, sodium alkoxide (RONa) and hydrogen gas (H2) are produced. - The present invention will be better understood from the following examples, which are presented solely for illustrative purposes to allow a full understanding of the preferred embodiments of the present invention, without implying that there are no other non-illustrated embodiments that can be put into practice based on the detailed description above.
- A test was conducted to recover terephthalic acid and sodium hydroxide from a sodium terephthalate solution obtained from a PET hydrolysis process according to the present invention.
- In the test, 90 mL of sodium terephthalate solution were added in the anodic side in an electrolytic cell. The sodium terephthalate solution was prepared with 12 g of sodium terephthalate and 100 mL of water. On the cathodic side of the electrolytic cell, 90 mL of a solution of methanol with sodium hydroxide were added. The solution was prepared with 1 g of NaOH and 100 mL of methanol.
- Then, a platinum electrode was placed on the anodic side and a stainless-steel electrode on the cathodic side and the electrolytic cell was connected to a power source. The power source was turned on and the current was controlled and maintained for one hour at an electrical intensity of 0.4 to 0.6 Amperes. The electrolytic cell was connected to an ammeter that continuously measured and recorded the current that passed through the electrodes and in this way the amount of electricity in Coulombs that passed through the electrodes of the electrolytic cell was determined. After one hour the power source was turned off, the electrodes from each side of the electrolytic cell were removed and the solution from the anodic side was filtered, which contained precipitated terephthalic acid, sad precipitate was washed and the terephthalic acid washed, dried in the oven at 130° C for one hour and then weighed. On the cathodic side sodium methoxide was obtained. Adding water to this solution produces sodium hydroxide in methanol. Solid sodium hydroxide is obtained by evaporation of the corresponding alcohol.
- During the test, the temperatures of the two half-cells were measured, as well as the variations in current between the two electrodes of the electrolytic cell, to know the efficiency of the precipitated terephthalic acid obtained.
- Table 1 shows the results obtained:
TABLE 1 Initial current (A) Time (min) Terephthalic acid weight (g) Amount of electricity (Coulombs) Electronic efficiency (%) 0.4252 60 0.331 1253 30.7 0.5397 60 0.70 1549 52.5 0.530 60 0.784 1411 64.6 0.521 60 0.837 1794 65.7 - As can be seen in the results obtained, the amount of terephthalic acid obtained is good considering the amount of mL of sodium terephthalate solution with which the reaction began. Furthermore, the mL of water used and the electrical energy necessary for the reaction represent a very low cost in relation to the cost at which terephthalic acid and sodium hydroxide can be sold.
- A test was conducted using different reaction times in a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET, according to the present invention. The purpose of this test is to see if there is variation in the efficiency of the process. From the results obtained, there is no significant difference.
- The experiments were conducted in the same cell and under the same conditions as in Example 1, except that there was variation in the electrolysis duration times. Table 2 shows the results obtained.
TABLE 2 Time (hr) Charge quantity (Coul) Weight of the terephthalic acid obtained (g) Electronic efficiency (%) 1 1753 0.93 68 2 2877 2.13 86 2 2193 1.45 79 3 4860 2.66 64 - As can be seen in the previous table, the electrolysis that lasted the longest was the one in which a greater amount of terephthalic acid was obtained.
- A test was conducted using different electrical currents in a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET, according to the present invention. The purpose of this test is to observe variation in the efficiency of obtaining terephthalic acid. The experiments were conducted in the same cell and under the same conditions as in Example 1, except that there was variation in the amount of current during electrolysis. Table 3 shows the results obtained.
TABLE 3 Electric current (A) Time (hr) Weight of the terephthalic acid obtained (g) Electronic efficiency (%) 0.6 1 1.26 68 0.36 1 0.69 62 0.49 1 0.75 63 1.7 1 2.74 52 - According to the above, the process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET has been designed to not generate the by-products generated in the PET recycling process. Furthermore, the described method does not require large amounts of water or energy, and practically does not generate by-products, and it will be evident to any person skilled in the art that the embodiments of a process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET as described above and illustrated in the drawing that accompanies it, are only illustrative but not limiting of the present invention, since numerous considerable changes in its details are possible without departing from the scope of the invention.
- Therefore, the present invention should not be considered restricted except as required by the prior art and by the scope of the appended claims.
Claims (12)
- A process for obtaining terephthalic acid and recovering sodium hydroxide from a sodium terephthalate solution produced from reused PET characterized in that it comprises the following steps: i) placing a sodium terephthalate solution obtained from a PET hydrolysis process on the anodic side; ii) placing an alcoholic medium on the cathodic side of the electrolytic cell; iii) applying an electric current that circulates through the anodic side and the cathodic side of the electrolytic cell and; iv) recovering terephthalic acid and sodium hydroxide.
- The process for obtaining terephthalic acid and recovering sodium hydroxide from a sodium terephthalate solution produced from reused PET according to claim 1, further characterized in that the alcoholic medium placed on the cathodic side of the electrolytic cell is methanol, ethanol, propanol, butanol, or a mixture thereof.
- The process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET according to claim 1, further characterized in that in the alcoholic medium placed on the cathodic side of the cell electrolytic, sodium hydroxide is added to obtain an alcoholic solution.
- The process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET according to claim 3, further characterized in that the alcoholic solution with sodium hydroxide has a molarity of 0.25 M to 1M.
- The process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET according to claim 1, further characterized in that the electrolytic cell has a membrane or a diaphragm between the anodic side and the cathodic side.
- The process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET in accordance with claim 1, further characterized in that the electric current applied to the electrolytic cell has a density of between 0.1 to 0.5 Amperes/cm2.
- The process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET in accordance with claim 1, further characterized in that, on the anodic side of the electrolytic cell, a solution of sodium terephthalic acid is obtained, and on the cathodic side of the electrolytic cell, sodium hydroxide and sodium alkoxide in an alcoholic solution are obtained.
- The process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET in accordance with claim 7, further characterized in that the solution on the anodic side, which contains precipitated terephthalic acid, is filtered.
- The process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET according to claim 7, further characterized in that the terephthalic acid washed with water is dried in the oven at a temperature of between 125 to 135 °C.
- The process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET in accordance with claim 7, further characterized in that the percentage of electronic efficiency of the recovery of terephthalic acid is 50 to 85 %.
- The process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET in accordance with claim 7, further characterized in that the sodium alkoxide is in an alcoholic solution and in a concentration between 5 % and 30 % (m/V).
- The process for obtaining terephthalic acid and recovering sodium hydroxide from a solution of sodium terephthalate produced from reused PET in accordance with claim 7, further characterized in that the obtaining of terephthalic acid and sodium hydroxide is produced simultaneously.
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PCT/IB2021/055081 WO2022259026A1 (en) | 2021-06-09 | 2021-06-09 | Process for obtaining terephthalic acid and recovering sodium hydroxide from a sodium terephthalate solution produced from reused polyethylene terephthalate (pet) |
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EP4353876A1 true EP4353876A1 (en) | 2024-04-17 |
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EP21944450.2A Pending EP4353876A1 (en) | 2021-06-09 | 2021-06-09 | Process for obtaining terephthalic acid and recovering sodium hydroxide from a sodium terephthalate solution produced from reused polyethylene terephthalate (pet) |
Country Status (4)
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EP (1) | EP4353876A1 (en) |
CN (1) | CN117858981A (en) |
CA (1) | CA3221682A1 (en) |
WO (1) | WO2022259026A1 (en) |
Family Cites Families (8)
Publication number | Priority date | Publication date | Assignee | Title |
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US4093528A (en) * | 1977-03-10 | 1978-06-06 | Suntech, Inc. | Terephthalic acid process |
US5290404A (en) * | 1990-10-31 | 1994-03-01 | Reilly Industries, Inc. | Electro-synthesis of alcohols and carboxylic acids from corresponding metal salts |
US5780704A (en) * | 1992-06-04 | 1998-07-14 | Mitsui Chemicals, Inc. | Process for treating plastic product |
FR2697839B1 (en) * | 1992-11-09 | 1995-01-13 | Inst Francais Du Petrole | Improved process for recovering alkali metal terephthalate and alkylene glycol from polyalkylene terephthalates. |
FR2767131B1 (en) * | 1997-08-06 | 1999-10-22 | Tredi | PROCESS FOR THE RECOVERY OF TEREPHTHALIC ACID AND, IF APPROPRIATE, SODA FROM A SODIUM POLYTEREPHTHALATE SOLUTION |
JPH11302208A (en) | 1998-04-22 | 1999-11-02 | Akira Oku | Recovery of terephthalic acid and ethylene glycol from polyethylene terephthalate |
JP2004250544A (en) | 2003-02-19 | 2004-09-09 | Kansai Tlo Kk | Method for recovering terephthalic acid from poly(terephthalic acid ester) |
CZ301118B6 (en) * | 2006-09-08 | 2009-11-11 | Ústav chemických procesu Akademie ved CR | Chemical recycling process of waste polyethyleneterephthalate |
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2021
- 2021-06-09 WO PCT/IB2021/055081 patent/WO2022259026A1/en active Application Filing
- 2021-06-09 CN CN202180101442.3A patent/CN117858981A/en active Pending
- 2021-06-09 CA CA3221682A patent/CA3221682A1/en active Pending
- 2021-06-09 EP EP21944450.2A patent/EP4353876A1/en active Pending
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WO2022259026A1 (en) | 2022-12-15 |
CN117858981A (en) | 2024-04-09 |
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