Basic subcritical water composition, water-containing composition, apparatus, and container

Abstract

The present invention provides a basic subcritical water composition, a water-containing composition, an apparatus, and a container that can decompose polymers and the like while suppressing corrosion of the reaction apparatus. [Solution] The pH is 13.7 or less, In the anodic polarization curve using steel as the test electrode, the current density was 10 mA / cm². 2 A basic subcritical water composition in which the potential is 400mV or higher when it exceeds a certain value.

Description

[Technical Field]

[0001] This disclosure relates to basic subcritical water compositions, water-containing compositions, apparatus, and containers. [Background technology]

[0002] In recent times, with the need for environmental conservation and the creation of a resource-recycling society being considered, various studies are being conducted on the recycling of organic materials such as plastics. Among these studies, decomposition technology using subcritical water is being employed. For example, Patent Document 1 and Non-Patent Document 1 describe a method of decomposing fluorine-containing polymers by reacting them in subcritical water containing basic compounds such as potassium hydroxide. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2021-155478 [Non-patent literature]

[0004] [Non-Patent Document 1] Jin Hamaura et al., Eur. Polym. J. 182 (2023), 111724 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] The purpose of this disclosure is to provide a basic subcritical water composition, a water-containing composition, an apparatus, and a container that can decompose polymers and the like while suppressing corrosion of the reaction apparatus. [Means for solving the problem]

[0006] This disclosure (1) describes a pH of 13.7 or less, in which a current density of 10 mA / cm² is observed in the anodic polarization curve using steel as the test electrode. 2This invention relates to a basic subcritical water composition in which the potential when it exceeds a certain value is 400 mV or higher.

[0007] Disclosure (2) is a basic subcritical water composition of Disclosure (1) having a temperature of 180°C or higher and less than 250°C.

[0008] Disclosure (3) is a basic subcritical water composition of Disclosure (1) or (2) wherein the steel material contains 8% by mass or more of Ni.

[0009] The present disclosure (4) also states that in an anodic polarization curve at a temperature of 180°C or higher and less than 250°C, and using steel as the test electrode, the current density is 10 mA / cm². 2 This invention relates to a water-containing composition in which the potential when it exceeds a certain value is between 400mV and 900mV.

[0010] Disclosure (5) is the water-containing composition of Disclosure (4) wherein the steel material contains 8% by mass or more of Ni.

[0011] Disclosure (6) is a water-containing composition of Disclosure (4) or (5) having a pH of 10 or more and 13.7 or less.

[0012] Disclosure (7) relates to an apparatus comprising a basic subcritical water composition in any combination with any of Disclosures (1) to (3), or a water-containing composition in any combination with any of Disclosures (4) to (6).

[0013] Disclosure (8) relates to a container comprising a basic subcritical water composition in any combination with any of Disclosures (1) to (3), or a water-containing composition in any combination with any of Disclosures (4) to (6). [Effects of the Invention]

[0014] According to this disclosure, it is possible to provide a basic subcritical water composition, a water-containing composition, an apparatus, and a container that can decompose polymers, etc., while suppressing corrosion of the reaction apparatus. [Modes for carrying out the invention]

[0015] Hereinafter, the present disclosure will be specifically described.

[0016] The present disclosure relates to a basic subcritical water composition having a pH of 13.7 or less and a potential of 400 mV or more when the current density exceeds 10 mA / cm 2 in the anodic polarization curve using a steel material as a test electrode. Since the basic subcritical water composition of the present disclosure has the above configuration, it can be used for subcritical water treatment of various objects while suppressing corrosion of the reaction device. For example, it can decompose polymers and the like.

[0017] The basic subcritical water composition of the present disclosure contains subcritical water. Subcritical water is water in a liquid state that exceeds 100°C and is in a temperature range lower than the critical temperature of 374°C when pressurized. Subcritical water has properties different from those of water at 100°C or lower. Particularly, in the range of 200°C to 300°C, the relative dielectric constant of subcritical water significantly decreases, showing almost the same lipophilicity as methanol or acetone at room temperature, or the ionic product that was 10 -14 mol / L becomes on the order of 10 -11 mol / L, and the concentrations of hydrogen ions and hydroxide ions become 30 times higher than those of water at room temperature. Therefore, it is known that subcritical water in the range of 200°C to 300°C shows reactivity different from that of water at room temperature. The temperature of the basic subcritical water composition of the present disclosure is preferably less than 250°C, more preferably 245°C or less, still more preferably 240°C or less, even more preferably 235°C or less, and preferably 180°C or more, more preferably 200°C or more, still more preferably 205°C or more, even more preferably 210°C or more, particularly preferably 215°C or more, particularly more preferably 220°C or more, and extremely preferably 225°C or more.

[0018] The water used for the preparation of subcritical water is not particularly limited, and any water such as tap water, ion-exchanged water, distilled water, well water, etc. may be used. However, from the viewpoint of suppressing side reactions due to the influence of coexisting salts and the like, ion-exchanged water and distilled water are preferably mentioned. Regarding the amount of water to be used, it is only necessary that the object to be treated is sufficiently immersed. However, caution is required because if the amount of water introduced into the sealed container for pressurization is extremely small, all of it will become steam after heating and will not reach the state of subcritical water.

[0019] The basic subcritical water composition of the present disclosure preferably contains at least one basic compound selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides.

[0020] Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, cesium hydroxide, etc. Among these, sodium hydroxide and / or potassium hydroxide are preferable. Here, it is known that potassium hydroxide has a higher activity and higher basicity than sodium hydroxide in a concentrated solution. From such a viewpoint, it can be said that potassium hydroxide is most preferable.

[0021] Examples of the alkaline earth metal hydroxide include calcium hydroxide, barium hydroxide, etc.

[0022] The concentration of the basic compound in the above basic subcritical water composition is preferably 0.5 M or less, more preferably 0.45 M or less, still more preferably 0.40 M or less, still more preferably 0.35 M or less, and preferably 0.01 M or more, more preferably 0.05 M or more, still more preferably 0.10 M or more, still more preferably 0.15 M or more. As is well known to those skilled in the art, the unit "M" means mol / L.

[0023] In the anodic polarization curve using a steel material as a test electrode, the basic subcritical water composition of the present disclosure has a current density of 10 mA / cm 2The potential is 400mV or higher when it exceeds this value. In the anodic polarization curve using steel as the test electrode, the current density is 10mA / cm². 2 When the potential exceeds a certain value, it is preferably 450mV or higher, more preferably 500mV or higher, even more preferably 550mV or higher, and preferably 900mV or lower.

[0024] The above anodic polarization curve is measured using a potentiostat with a potential sweep rate of 20 mV / min, in accordance with JIS G0577.

[0025] The above steel material preferably contains at least one selected from the group consisting of Ni, Cr, and Fe.

[0026] The above steel material preferably contains 8% by mass or more of Ni, more preferably 15% by mass or more, and even more preferably 70% by mass or more. There is no particular upper limit, but it is usually 90% by mass.

[0027] The above steel material preferably contains 10% by mass or more of Cr, more preferably 20% by mass or more, more preferably 40% by mass or less, and more preferably 30% by mass or less.

[0028] The above steel material preferably contains 5% by mass or more of Fe, more preferably 20% by mass or more, even more preferably 40% by mass or more, and preferably 80% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less.

[0029] Examples of the above-mentioned steel materials include SUS310S, SUS304L, and NCF600.

[0030] The basic subcritical water composition of the present disclosure has a pH of 13.7 or less. The pH of the above basic subcritical water composition is preferably 10 or more, more preferably 11 or more, still more preferably 12 or more, still more preferably 13 or more, and preferably 13.6 or less, more preferably 13.5 or less.

[0031] The present disclosure also relates to a water-containing composition at a temperature of 180°C or more and less than 250°C, and in an anodic polarization curve using a steel material as a test electrode, when the current density exceeds 10 mA / cm 2 and the potential is 400 mV or more and 900 mV or less. Since the water-containing composition of the present disclosure has the above configuration, it can be used for treating various objects while suppressing the corrosion of the reaction apparatus. For example, it can decompose polymers and the like.

[0032] The temperature of the water-containing composition of the present disclosure is less than 250°C, preferably 245°C or less, more preferably 240°C or less, still more preferably 235°C or less, and also 180°C or more, preferably 200°C or more, more preferably 205°C or more, still more preferably 210°C or more, still more preferably 215°C or more, particularly preferably 220°C or more, and extremely preferably 225°C or more.

[0033] In the anodic polarization curve of the water-containing composition of the present disclosure using a steel material as a test electrode, when the current density exceeds 10 mA / cm 2 the potential is 400 mV or more and 900 mV or less. In the anodic polarization curve using a steel material as a test electrode, when the current density exceeds 10 mA / cm 2 the potential is preferably 450 mV or more, more preferably 500 mV or more, and still more preferably 550 mV or more.

[0034] In the water-containing composition of the present disclosure, as the above steel material, those mentioned in the basic subcritical water composition of the present disclosure can be used.

[0035] The water-containing composition disclosed herein preferably contains subcritical water.

[0036] The water-containing composition of this disclosure preferably contains at least one basic compound selected from the group consisting of alkali metal hydroxides and alkaline earth metal hydroxides. The alkali metal hydroxides and alkaline earth metal hydroxides listed in the basic subcritical water composition of this disclosure can be used.

[0037] The concentration of the basic compound in the water-containing composition of this disclosure may be within the same range as described in the basic subcritical water composition of this disclosure.

[0038] The pH of the water-containing composition disclosed herein is preferably 10 or higher, more preferably 11 or higher, even more preferably 12 or higher, even more preferably 13 or higher, and also preferably 13.7 or lower, more preferably 13.6 or lower, and even more preferably 13.5 or lower.

[0039] The basic subcritical water composition and water-containing composition of this disclosure are preferably used in contact with the steel materials described above. For example, they are more preferably used in contact with a container made of the steel materials described above. They are also preferably used for treating objects (preferably subcritical water treatment) in a container made of the steel materials described above. The basic subcritical water composition and water-containing composition of this disclosure are less likely to corrode the steel materials even when in contact with them.

[0040] The basic subcritical water composition and water-containing composition of this disclosure can be used to treat various objects, preferably in subcritical water treatment, and are suitable for the decomposition of polymers and the like.

[0041] Examples of polymers include polyolefin resins such as polyethylene and polypropylene; polyamide [PA] resins such as nylon 6, nylon 11, nylon 12, nylon 46, nylon 66, nylon 610, nylon 612, and nylon MXD6; polyester resins such as polyethylene terephthalate [PET], polybutylene terephthalate [PBT], polyarylate, aromatic polyesters (including liquid crystal polyesters), and polycarbonate [PC]; polyacetal [POM] resins; polyether resins such as polyphenylene oxide [PPO], modified polyphenylene ether, and polyether ether ketone [PEEK]; polyamide-imide [PAI] resins such as polyaminobismaleimide; polysulfone resins such as polysulfone [PSF] and polyethersulfone [PES]; vinyl polymers such as ABS resin and poly-4-methylpentene-1 (TPX resin), as well as polyphenylene sulfide [PPS], polyketone sulfide, polyetherimide, and polyimide [PI]. Furthermore, fluororesins such as ethylene [Et] / TFE copolymer [ETFE], polyvinyl fluoride [PVF], and polyvinylidene fluoride [PVdF] can also be mentioned. The above nylon MXD6 is a crystalline polycondensate obtained from metaxylenediamine [MXD] and adipic acid. Among these, polycondensate systems such as polyester resins and epoxy resins are preferred because they are easily depolymerized, and polyester resins are more preferred. Alternatively, the material may be an oligomer that constitutes the polymer, or an oligomer to which a functional group has been added. The basic subcritical water composition and water-containing composition of this disclosure can be used to accelerate the decomposition of the above-mentioned polymers, etc.

[0042] Next, a method for decomposing a polymer by reacting it in the basic subcritical water composition and water-containing composition of this disclosure will be described. For example, water, the polymer to be treated, and a basic compound as needed are added to a pressure vessel of a size appropriate to the amount of polymer to be treated, and the inside of the pressure vessel is pressurized and sealed. To pressurize the inside of the pressure vessel, a gas can be sealed inside. Examples of such gases include air, argon, and nitrogen. The degree of pressurization can be about 0.5 MPa, but is not particularly limited.

[0043] The pressure vessel that has undergone the above process is heated to initiate the decomposition reaction. The basic subcritical water composition and water-containing composition of this disclosure may be generated inside the pressure vessel during the above decomposition reaction. The heating temperature is less than 250°C, but is preferably 245°C or lower, more preferably 240°C or lower, even more preferably 235°C or lower, and also 180°C or higher, preferably 200°C or higher, more preferably 205°C or higher, even more preferably 210°C or higher, even more preferably 215°C or higher, particularly preferably 220°C or higher, and especially preferably 225°C or higher. If the pressure vessel itself is equipped with a heating means, it may be heated using that heating means; if the pressure vessel itself is not equipped with a heating means, the entire pressure vessel may be heated in an autoclave or oven. The reaction time can be approximately 1 minute to 100 hours, and may be 1 hour to 100 hours, but is preferably 1 minute to 1 hour, and more preferably 1 to 30 minutes. The reaction pressure can be approximately 0.1 to 22 MPa.

[0044] The aqueous solution after the decomposition reaction contains monomers and hydrocarbon compounds that constituted the polymer. The above decomposition method may include a recovery step after the decomposition step in which the generated monomers and hydrocarbon compounds are recovered. By including the above recovery step, the above decomposition method makes it possible to make effective use of resources.

[0045] The above decomposition method preferably includes a grinding step before the decomposition step in which the polymer is ground into pulverized particles with a maximum straight length of 3 mm or less. Including the grinding step in the above decomposition method makes it easier to decompose the polymer.

[0046] While there are no particular limitations on the grinding method, examples include freeze grinding, disc milling, hammer milling, stone mill type grinding, and jet milling.

[0047] The grinding temperature is preferably -200°C or higher, and more preferably 90°C or lower. More preferably 40°C or lower, and even more preferably 0°C or lower.

[0048] The maximum linear length of the pulverized particles of the above polymer is preferably 3 mm or less, more preferably 2 mm or less, even more preferably 1 mm or less, and especially preferably 500 μm or less. Furthermore, it is preferably 10 μm or more, more preferably 30 μm or more, and even more preferably 100 μm or more. When the average particle size of the pulverized particles of the above polymer is within the above range, the polymer becomes even easier to decompose.

[0049] The maximum straight line length mentioned above was determined by observing over 100 secondary particles using SEM imaging and measuring the major axis of each secondary particle. The largest major axis among these was defined as the maximum straight line length.

[0050] This disclosure also relates to an apparatus comprising the basic subcritical water composition described above, or the water-containing composition described above.

[0051] The basic subcritical water composition and water-containing composition of this disclosure can be used to treat various substances while suppressing corrosion of the reaction equipment, and is preferably used for subcritical water treatment. Therefore, the apparatus of this disclosure is suitable as an apparatus for subcritical water treatment. Furthermore, since the basic subcritical water composition and water-containing composition of this disclosure can decompose polymers and the like while suppressing corrosion of the reaction equipment, the apparatus of this disclosure is particularly suitable as an apparatus for decomposing polymers and the like.

[0052] In the apparatus of this disclosure, it is preferable that the parts that come into contact with the basic subcritical water composition and the water-containing composition are made of the steel material described above. The apparatus of this disclosure may also preferably include the container of this disclosure, which will be described later.

[0053] This disclosure also relates to a container comprising the basic subcritical water composition described above, or the water-containing composition described above.

[0054] The basic subcritical water composition and water-containing composition of this disclosure can be used to treat various substances while suppressing corrosion of the reaction equipment, and can preferably be used for subcritical water treatment; therefore, the container of this disclosure is suitable as a container for subcritical water treatment. Furthermore, since the basic subcritical water composition and water-containing composition of this disclosure can decompose polymers and the like while suppressing corrosion of the reaction equipment, the container of this disclosure is particularly suitable as a container for decomposing polymers and the like.

[0055] The container of this disclosure is preferably made of the steel material described above.

[0056] Although embodiments have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of the claims. [Examples]

[0057] The present disclosure will now be explained with reference to examples, but the present disclosure is not limited to such examples.

[0058] Each value in the examples was measured by the following method.

[0059] (1) Measurement of corrosion initiation potential The anodic polarization curve was measured in accordance with JIS G0577. A potentiodynamic method was used, sweeping from the natural potential at a potential sweep rate of 20 mV / min using a potentiostat, with a current density of 10 mA / cm². 2 The potential at which this value was reached was defined as the corrosion initiation potential.

[0060] (Example 1) NCF600 (Ni: 72.00% by mass or more, Cr: 14.00-17.00% by mass, Fe: 6.00-10.00% by mass) was used as the test electrode. A potassium hydroxide aqueous solution prepared to pH 13.5 was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 230°C. The pressure was increased using a potentiostat at a potential sweep rate of 20 mV / min, and the current density was 10 mA / cm². 2 The potential was checked when it exceeded a certain value. The results are shown in Table 1.

[0061] (Example 2) An NCF600 test electrode was used, and a potassium hydroxide aqueous solution prepared to pH 13 was placed in a container. The solution was pressurized to 0.8 MPa with argon gas, and then heated to 230°C. A potentiostat was used to increase the pressure at a potential sweep rate of 20 mV / min, resulting in a current density of 10 mA / cm². 2 The potential was checked when it exceeded a certain value. The results are shown in Table 1.

[0062] (Example 3) A SUS310S (Ni: 19.00-22.00% by mass, Cr: 24.00-26.00% by mass) test electrode was used. A potassium hydroxide aqueous solution prepared to pH 13 was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 200°C. The pressure was increased using a potentiostat at a potential sweep rate of 20 mV / min, resulting in a current density of 10 mA / cm². 2 The potential was checked when it exceeded a certain value. The results are shown in Table 1.

[0063] (Example 4) A SUS310S test electrode was used, and a potassium hydroxide aqueous solution prepared to pH 13.3 was placed in a container. The solution was pressurized to 0.8 MPa with argon gas, and then heated to 200°C. A potentiostat was used to increase the pressure at a potential sweep rate of 20 mV / min, resulting in a current density of 10 mA / cm². 2 The potential was checked when it exceeded a certain value. The results are shown in Table 1.

[0064] (Example 5) A SUS310S test electrode was used, and a potassium hydroxide aqueous solution prepared to pH 13 was placed in a container. The solution was pressurized to 0.8 MPa with argon gas, and then heated to 230°C. A potentiostat was used to increase the pressure at a potential sweep rate of 20 mV / min, resulting in a current density of 10 mA / cm². 2 The potential was checked when it exceeded a certain value. The results are shown in Table 1.

[0065] (Comparative Example 1) An NCF600 was used as the test electrode. A potassium hydroxide aqueous solution prepared to pH 14 was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 230°C. The pressure was increased using a potentiostat at a potential sweep rate of 20 mV / min, and the current density was 10 mA / cm². 2 The potential was checked when it exceeded a certain value. The results are shown in Table 1.

[0066] (Comparative Example 2) An NCF600 was used as the test electrode. A potassium hydroxide aqueous solution prepared to pH 14 was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 250°C. The pressure was increased using a potentiostat at a potential sweep rate of 20 mV / min, and the current density was 10 mA / cm². 2 The potential was checked when it exceeded a certain value. The results are shown in Table 1.

[0067] (Comparative Example 3) An NCF600 was used as the test electrode. Pure water was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 200°C. The pressure was increased using a potentiostat at a potential sweep rate of 20 mV / min, resulting in a current density of 10 mA / cm². 2 The potential was checked when it exceeded a certain value. The results are shown in Table 1.

[0068] [Table 1]

[0069] (Example 6) 100 mg of PET film (Toray Industries, Ltd., "Lumirror Film") and 20 ml of potassium hydroxide aqueous solution prepared to pH 13.5 were placed in an inner cylinder, and the inner cylinder was placed in a pressure vessel, which was then closed. After replacing the atmosphere inside the pressure vessel with nitrogen, it was placed in an electric furnace and heated to 230°C. Once the internal temperature of the pressure vessel reached 230°C, the reaction was allowed to proceed for 1 minute. The reaction pressure was set to 2.8 MPa. After the reaction was complete, the electric furnace was stopped, the pressure vessel was removed from the electric furnace, and cooled by forced air. The remaining film after processing was collected, washed with pure water, dried, and its weight was measured to calculate the remaining amount. The results are shown in Table 2.

[0070] (Examples 7-9, Comparative Example 4) In Example 6, the reaction was carried out in the same manner as in Example 6, except that instead of the potassium hydroxide aqueous solution prepared to pH 13.5, a potassium hydroxide aqueous solution prepared to the pH listed in Table 2 or pure water was used, and the reaction temperature, reaction pressure, and reaction time were changed as shown in Table 2. The amount of remaining film was then calculated. The results are shown in Table 2.

[0071] [Table 2]

Claims

1. The pH is 13.7 or lower. In the anodic polarization curve using steel as the test electrode, the current density is 10 mA / cm². ２ A basic subcritical water composition in which the potential is 400 mV or higher when it exceeds a certain value.

2. The basic subcritical water composition according to claim 1, wherein the temperature is 180°C or higher and less than 250°C.

3. The steel material is a basic subcritical water composition according to claim 1 or 2, containing 8% by mass or more of Ni.

4. In an anodic polarization curve taken at temperatures between 180°C and 250°C, using steel as the test electrode, the current density is 10 mA / cm². ２ A water-containing composition whose potential when it exceeds a certain value is between 400 mV and 900 mV.

5. The water-containing composition according to claim 4, wherein the steel material contains 8% by mass or more of Ni.

6. The water-containing composition according to claim 4 or 5, wherein the pH is 10 or more and 13.7 or less.

7. An apparatus comprising the basic subcritical water composition according to claim 1 or 2, or the water-containing composition according to claim 4 or 5.

8. A container comprising the basic subcritical water composition according to claim 1 or 2, or the water-containing composition according to claim 4 or 5.

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