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

Abstract

To provide an alkaline subcritical water composition, a water-containing composition, an apparatus, and a container that enable decomposition of polymers and the like while suppressing corrosion of the reaction apparatus.SOLUTION: The present invention provides an alkaline subcritical water composition, having a pH of 13.7 or less, and showing a potential of 400 mV or more at a current density exceeding 10 mA / cm2 in an anodic polarization curve measured using steel as the test electrode.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to basic subcritical water compositions, water-containing compositions, devices, and containers. [Background technology]

[0002] In recent years, the necessity of environmental conservation and building a resource-circulating society has been considered, and various researches have been conducted on the recycling of organic materials such as plastics. Among them, decomposition processing technology using subcritical water is used. For example, Patent Document 1 and Non-Patent Document 1 describe a method of decomposing a fluorine-containing polymer by reacting it in subcritical water containing a basic compound such as potassium hydroxide. [Prior art documents] [Patent documents]

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

[0004] [Non-Patent Document 1] Jin Hamaura et al., Eur. Polym. J. 182 (2023), 111724 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present 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 a reaction apparatus. [Means for solving the problem]

[0006] The present disclosure (1) relates to a method for treating a liquid having a pH of 13.7 or less, and a current density of 10 mA / cm in an anodic polarization curve using a steel material as a test electrode. 2The present invention relates to a basic subcritical water composition having a potential of 400 mV or more when the potential exceeds the critical potential.

[0007] The present disclosure (2) is the basic subcritical water composition of the present disclosure (1) having a temperature of 180°C or higher and lower than 250°C.

[0008] The present disclosure (3) is the basic subcritical water composition according to the present disclosure (1) or (2), in which the steel material contains 8 mass % or more of Ni.

[0009] The present disclosure (4) also discloses that in an anodic polarization curve at 180°C or higher and lower than 250°C and using a steel material as a test electrode, the current density is 10 mA / cm 2 The water-containing composition has a potential of 400 mV or more and 900 mV or less when the potential exceeds the threshold value.

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

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

[0012] The present disclosure (7) relates to an apparatus including a basic subcritical water composition in any combination with any of the present disclosures (1) to (3), or a water-containing composition in any combination with any of the present disclosures (4) to (6).

[0013] The present disclosure (8) relates to a container comprising a basic subcritical water composition in any combination with any of the present disclosures (1) to (3), or a water-containing composition in any combination with any of the present disclosures (4) to (6). Effect of the Invention

[0014] According to the present disclosure, it is possible to provide a basic subcritical water composition, a water-containing composition, an apparatus, and a container that can decompose a polymer or the like while suppressing corrosion of a reaction apparatus. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present disclosure will now be described in detail.

[0016] The present disclosure relates to an anodic polarization curve in which the pH is 13.7 or less and a steel material is used as a test electrode, and the current density is 10 mA / cm 2 The present disclosure relates to a basic subcritical water composition having a potential of 400 mV or more when the potential exceeds 100 mV. The basic subcritical water composition of the present disclosure has the above-mentioned configuration, and can be used in subcritical water treatment of various objects while suppressing corrosion of a reaction apparatus. For example, polymers and the like can be decomposed.

[0017] The basic subcritical water composition of the present disclosure contains subcritical water. Subcritical water is water in a liquid state that is pressurized to a temperature range exceeding 100°C and lower than the critical temperature of 374°C. Subcritical water has different physical properties from water at 100°C or lower. In particular, subcritical water in the range of 200°C to 300°C has a significantly reduced relative dielectric constant and exhibits almost the same lipid solubility as methanol or acetone at room temperature, and exhibits a lipid solubility of 10 at room temperature. -14 The ion product in mol / L is 10 -11 The concentration of hydrogen ions and hydroxide ions is on the order of mol / L, and is 30 times higher than that of water at room temperature. Therefore, it is known that subcritical water, particularly at 200°C to 300°C, exhibits a different reactivity from 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, even more preferably 240°C or less, even more preferably 235°C or less, and is preferably 180°C or more, more preferably 200°C or more, even more preferably 205°C or more, even more preferably 210°C or more, particularly preferably 215°C or more, especially more preferably 220°C or more, and especially preferably 225°C or more.

[0018] The water used to prepare the subcritical water is not particularly limited, and any water may be used, such as tap water, ion-exchanged water, distilled water, well water, etc., but ion-exchanged water and distilled water are preferred from the viewpoint of suppressing side reactions caused by the influence of coexisting salts, etc. The amount of water used may be enough to fully immerse the object to be treated, but care must be taken if the amount of water introduced into the sealed container for pressurization is extremely small, as the water will all turn into steam after heating and will not become 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, and cesium hydroxide, and among these, sodium hydroxide and / or potassium hydroxide are preferred. Here, potassium hydroxide is known to have a higher activity and higher basicity than sodium hydroxide in a concentrated solution. From this viewpoint, potassium hydroxide is the most preferred.

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

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

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

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

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

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

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

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

[0029] Examples of the steel material 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 basic subcritical water composition is preferably 10 or more, more preferably 11 or more, even more preferably 12 or more, and even more preferably 13 or more, and is preferably 13.6 or less, and more preferably 13.5 or less.

[0031] The present disclosure also describes an anodic polarization curve at 180° C. or higher and lower than 250° C. using a steel material as a test electrode, in which the current density is 10 mA / cm 2 The water-containing composition of the present disclosure has a potential of 400 mV or more and 900 mV or less when the potential exceeds 100 mV. The water-containing composition of the present disclosure has the above-mentioned configuration, and can be used to treat various objects while suppressing corrosion of a reaction device. For example, it can decompose polymers, etc.

[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, and even more preferably 235°C or less, and is 180°C or more, preferably 200°C or more, more preferably 205°C or more, even more preferably 210°C or more, even more preferably 215°C or more, particularly preferably 220°C or more, and even more preferably 225°C or more.

[0033] The water-containing composition of the present disclosure has a current density of 10 mA / cm in an anodic polarization curve using a steel material as a test electrode. 2 When the potential exceeds 400mV or more and 900mV or less, the current density is 10mA / cm2 or less in the anodic polarization curve using steel as the test electrode. 2 When the potential exceeds this value, it is preferably 450 mV or more, more preferably 500 mV or more, and even more preferably 550 mV or more.

[0034] In the water-containing composition of the present disclosure, the steel material may be any of those listed in the basic subcritical water composition of the present disclosure.

[0035] The water-containing compositions of the present disclosure preferably comprise subcritical water.

[0036] The water-containing 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. As the alkali metal hydroxide and the alkaline earth metal hydroxide, those exemplified in the basic subcritical water composition of the present disclosure can be used.

[0037] The concentration of the basic compound in the water-containing composition of the present disclosure can be in the same range as described for the basic subcritical water composition of the present disclosure.

[0038] The pH of the water-containing composition of the present disclosure is preferably 10 or more, more preferably 11 or more, even more preferably 12 or more, even more preferably 13 or more, and is preferably 13.7 or less, more preferably 13.6 or less, even more preferably 13.5 or less.

[0039] The basic subcritical water composition and water-containing composition of the present disclosure are preferably used in contact with the above-mentioned steel material. For example, it is more preferable to use them in contact with a container made of the above-mentioned steel material. They are also preferably used for treating an object (preferably subcritical water treatment) in a container made of the above-mentioned steel material. The basic subcritical water composition and water-containing composition of the present disclosure are unlikely to corrode the above-mentioned steel material even when they come into contact with the steel material.

[0040] The basic subcritical water composition and water-containing composition of the present disclosure can be used for treating various objects, and can be preferably used for subcritical water treatment, and is suitable for decomposing 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 polyester (including liquid crystal polyester), and polycarbonate (PC); polyacetal (POM) resin; polyether resins such as polyphenylene oxide (PPO), modified polyphenylene ether, and polyether ether ketone (PEEK); polyamide imide (PAI) resins such as polyamino bismaleimide; 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). Further, fluororesins such as ethylene [Et] / TFE copolymer [ETFE], polyvinyl fluoride [PVF], polyvinylidene fluoride [PVdF], etc. are also included. The above-mentioned nylon MXD6 is a crystalline polycondensate obtained from metaxylenediamine [MXD] and adipic acid. Among them, polycondensation systems such as polyester resins and epoxy resins are preferred because they are easily depolymerized, and polyester resins are more preferred. Furthermore, it may be an oligomer constituting a polymer, or an oligomer to which a functional group has been added. By using the basic subcritical water composition and water-containing composition of the present disclosure, the decomposition of the above-mentioned polymers and the like can be promoted.

[0042] Next, a method of decomposing a polymer by reacting it in the basic subcritical water composition and water-containing composition of the present disclosure will be described. For example, water, the polymer to be treated, and a basic compound as necessary are added to a pressure vessel of a size according to the amount of the 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 may be sealed in. Examples of such gas include air, argon, and nitrogen. The degree of pressurization may 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 the present disclosure may be generated in the pressure vessel during the decomposition reaction. The heating temperature is less than 250°C, but is preferably 245°C or less, more preferably 240°C or less, and even more preferably 235°C or less, and is 180°C or more, preferably 200°C or more, more preferably 205°C or more, even more preferably 210°C or more, even more preferably 215°C or more, particularly preferably 220°C or more, and even more preferably 225°C or more. When the pressure vessel itself is equipped with a heating means, the heating means may be used for heating, and when 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 may be about 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 may be about 0.1 to 22 MPa.

[0044] The aqueous solution after the decomposition reaction contains the monomers and hydrocarbon compounds that constitute the polymer. The decomposition method may include a recovery step of recovering the generated monomers and hydrocarbon compounds after the decomposition step. By including the recovery step, the decomposition method can make effective use of resources.

[0045] The decomposition method preferably includes a crushing step of crushing the polymer into crushed particles having a maximum linear length of 3 mm or less before the decomposition step. By including the crushing step in the decomposition method, the polymer can be easily decomposed.

[0046] The grinding method is not particularly limited, but examples thereof include freeze grinding, disk milling, hammer milling, stone mill type grinding machine, jet milling, and the like.

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

[0048] The maximum linear length of the pulverized particles of the polymer is preferably 3 mm or less, more preferably 2 mm or less, even more preferably 1 mm or less, and even more preferably 500 μm or less. Also, 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 polymer is within the above range, the polymer is more easily decomposed.

[0049] The maximum linear length was determined by observing 100 or more secondary particles using SEM images, measuring the major axis of each secondary particle, and determining the largest major axis among the secondary particles as the maximum linear length.

[0050] The present disclosure also relates to an apparatus comprising the above-mentioned basic subcritical water composition or the above-mentioned water-containing composition.

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

[0052] In the apparatus of the present disclosure, a portion that comes into contact with the basic subcritical water composition and the water-containing composition is preferably made of the above-mentioned steel material. The apparatus of the present disclosure also preferably includes a container of the present disclosure described below.

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

[0054] The basic subcritical water composition and water-containing composition of the present disclosure can be used to treat various objects while suppressing corrosion of a reaction apparatus, and can preferably be used for subcritical water treatment, and therefore the container of the present disclosure is suitable as a container used for subcritical water treatment.Furthermore, the basic subcritical water composition and water-containing composition of the present disclosure can decompose a polymer or the like while suppressing corrosion of a reaction apparatus, and therefore the container of the present disclosure is particularly suitable as a container used for decomposing a polymer or the like.

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

[0056] Although the embodiments have been described above, it will be understood that various changes in form and details are possible without departing from the spirit and scope of the claims. EXAMPLES

[0057] Next, the present disclosure will be described with reference to examples, but the present disclosure is not limited to these examples.

[0058] The values ​​in the examples were measured by the following methods.

[0059] (1) Measurement of corrosion initiation potential The anodic polarization curve was measured according to JIS G0577. The potential was swept from the natural potential by a potentiostat at a potential sweep rate of 20 mV / min, and the current density was 10 mA / cm. 2 The potential at which this was reached was determined as the corrosion initiation potential.

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

[0061] Example 2 NCF600 was used as the test electrode, and an aqueous solution of potassium hydroxide adjusted to pH 13 was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 230°C. The voltage was increased at a potential sweep rate of 20 mV / min using a potentiostat, and the current density was 10 mA / cm. 2 The potential when the potential exceeded the limit was confirmed. The results are shown in Table 1.

[0062] Example 3 The test electrodes were made of SUS310S (Ni: 19.00-22.00 mass%, Cr: 24.00-26.00 mass%), and a potassium hydroxide aqueous solution adjusted to pH 13 was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 200°C. The voltage was increased at a potential sweep rate of 20 mV / min using a potentiostat, and the current density was increased to 10 mA / cm. 2 The potential when the potential exceeded the limit was confirmed. The results are shown in Table 1.

[0063] Example 4 The test electrode was made of SUS310S, and an aqueous solution of potassium hydroxide adjusted to pH 13.3 was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 200°C. The voltage was increased at a potential sweep rate of 20 mV / min using a potentiostat, and the current density was 10 mA / cm. 2 The potential when the potential exceeded the limit was confirmed. The results are shown in Table 1.

[0064] Example 5 The test electrode was made of SUS310S, and an aqueous solution of potassium hydroxide adjusted to pH 13 was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 230°C. The voltage was increased at a potential sweep rate of 20 mV / min using a potentiostat, and the current density was 10 mA / cm. 2 The potential when the potential exceeded the limit was confirmed. The results are shown in Table 1.

[0065] Comparative Example 1 NCF600 was used as the test electrode, and an aqueous solution of potassium hydroxide adjusted to pH 14 was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 230°C. The voltage was increased at a potential sweep rate of 20 mV / min using a potentiostat, and the current density was 10 mA / cm. 2 The potential when the potential exceeded the limit was confirmed. The results are shown in Table 1.

[0066] Comparative Example 2 NCF600 was used as the test electrode, and an aqueous solution of potassium hydroxide adjusted to pH 14 was placed in a container, pressurized to 0.8 MPa with argon gas, and then heated to 250°C. The voltage was increased at a potential sweep rate of 20 mV / min using a potentiostat, and the current density was 10 mA / cm. 2 The potential when the potential exceeded the limit was confirmed. The results are shown in Table 1.

[0067] Comparative Example 3 NCF600 was used as the test electrode, pure water was placed in a container, and the container was pressurized to 0.8 MPa with argon gas, and then heated to 200°C. The voltage was increased at a potential sweep rate of 20 mV / min using a potentiostat, and the current density was 10 mA / cm. 2 The potential when the potential exceeded the limit was confirmed. The results are shown in Table 1.

[0068] [Table 1]

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

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

[0071] [Table 2]

Claims

1. The pH is 13.7 or less, In the anodic polarization curve using steel as the test electrode, the current density was 10 mA / cm ２ The basic subcritical water composition has a potential of 400 mV or more when the potential exceeds 100 mV.

2. The basic subcritical water composition according to claim 1, which is heated at 180°C or higher but lower than 250°C.

3. The basic subcritical water composition according to claim 1 or 2, wherein the steel material contains 8 mass % or more of Ni.

4. In the anodic polarization curve using a steel material as the test electrode at 180°C or higher and lower than 250°C, the current density is 10 mA / cm ２ The water-containing composition has a potential of 400 mV or more and 900 mV or less when the potential exceeds the threshold.

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

6. 6. The water-containing composition according to claim 4, 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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